U.S. patent application number 10/291067 was filed with the patent office on 2003-07-03 for display unit and methods of displaying an image.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Bird, William E., Mueller, Bruno.
Application Number | 20030122844 10/291067 |
Document ID | / |
Family ID | 38832945 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030122844 |
Kind Code |
A1 |
Mueller, Bruno ; et
al. |
July 3, 2003 |
Display unit and methods of displaying an image
Abstract
The present invention provides a method of displaying an image
on a display device having first and second sides, said image
including an light restricting silhouette pattern having a
plurality of first transparent or translucent areas, and at least
one design layer having at least one color, said at least one
design layer being visible from one side of said display device and
substantially less visible from the other side, said image being
substantially transparent or translucent as viewed from the other
side, comprising the steps: 1) providing at least a definition of
said design layer to a computer; 2) generating a computerized
version of said design layer with the computer; 3) outputting the
computerized version of said design layer to said display device,
the computerized version of said design layer being modified to
subdivide said design layer into a plurality of second discrete
transparent or translucent areas and other areas, and 4) displaying
said modified design layer and said silhouette pattern with said
first and second transparent areas being in registry. Articles
produced in accordance with the method are also described.
Printers, raster image processing methods and systems, computer
graphics systems are described for producing the article.
Inventors: |
Mueller, Bruno;
(Duesseldorf, DE) ; Bird, William E.; (Winksele,
BE) |
Correspondence
Address: |
Office of Intellectual Property Counsel
3M Innovative Properties Company
PO Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
38832945 |
Appl. No.: |
10/291067 |
Filed: |
November 8, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10291067 |
Nov 8, 2002 |
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09202281 |
Dec 11, 1998 |
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6507413 |
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09202281 |
Dec 11, 1998 |
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PCT/US96/09888 |
Jun 14, 1996 |
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Current U.S.
Class: |
345/589 ;
345/592; 345/629; 358/1.9; 358/530 |
Current CPC
Class: |
Y10T 428/24851 20150115;
G06K 15/00 20130101; B44C 1/17 20130101; Y10T 428/24322 20150115;
B44F 1/10 20130101; B41J 3/546 20130101; Y10T 428/24876 20150115;
G06K 15/023 20130101; Y10T 428/162 20150115; Y10T 428/24736
20150115; B41J 3/407 20130101; Y10T 428/24868 20150115 |
Class at
Publication: |
345/589 ;
358/1.9; 345/592; 345/629; 358/530 |
International
Class: |
G06T 011/40; H04N
001/50; H04N 001/56; G06K 015/00; G06F 015/00; G09G 003/00; G06T
011/00 |
Claims
What is claimed is:
1. A method of printing comprising the steps of controlling the
ratio of transmission optical density to reflective optical density
at any area of an image graphic by use of computer software and
printing the image onto a substrate.
2. An imaged graphic having at least one area where the ratio of
transmission optical density to reflective optical density has been
controlled by by use of computer software during printing of the
image onto a substrate.
3. A method of displaying an image on a display device having first
and second sides, said image including an light restricting
silhouette pattern having a plurality of first transparent or
translucent areas, and at least one design layer having at least
one color, said at least one design layer being visible from one
side of said display device and substantially less visible from the
other side, said image being substantially transparent or
translucent as viewed from the other side, comprising the steps: 1)
providing at least a definition of said design layer to a computer;
2) generating a computerized version of said design layer with the
computer, 3) outputting the computerized version of said design
layer to said display device, the computerized version of said
design layer being modified to subdivide said design layer into a
plurality of second discrete transparent or translucent areas and
other areas, and 4) displaying said modified design layer and said
silhouette pattern with said first and second transparent areas
being in registry.
4. An article can have a conformable substrate and comprise: a
colorant receptor layer and a light restricting layer on said
substrate, said light restricting layer having a plurality of first
transparent or translucent areas.
5. An article having a conformable substrate and comprising: a
colorant receptor layer and a light restricting layer on said
substrate, said light restricting layer having a plurality of first
transparent or translucent areas.
6. An article comprising a polymeric substrate and a light
restricting layer and a design layer on said substrate, said design
layer including at least one color layer, said light restricting
layer being subdivided into a plurality of first transparent or
translucent areas, said design layer being subdivided into a
plurality of second transparent or translucent areas, and said
first and second transparent areas being in registry.
7. A printer for receiving a print file includes color separated
image data, light restricting layer data and transparency data, and
for printing the color separated image and the light restricting
layer data including transparent areas in both the color-separated
layer and the light restricting layer in accordance with the
transparency data.
8. A raster image processing method for raster image processing of
a print file including color separated image data, light
restricting layer data and transparency data, comprising operating
on said print file to generate raster image bitmaps for said color
separated image data and said light restricting layer data, and
introducing said transparency data into said raster image bitmaps
for said color separated image data and said light restricting
layer data so that the transparent areas in said color separated
image raster bitmap and said light restricting layer bitmap are in
registry.
9. A graphics computer based system for creating graphics images
including color separated layers and light restricting layers,
comprises first input means for image data, means for generating
color separated image data from said image data, means for
generating light restricting layer data, second input means for
transparency data, and means for outputting a display file
including said color separated image data, said light restricting
layer data and said transparency data.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a display unit, and in
particular to a display unit for displaying images viewable from
two sides, whereby the image as perceived from one side can be
different from the image perceived from the other side and the
display unit is transparent or translucent when viewed from one of
the sides.
[0002] The invention also relates to a method of displaying such an
image as well as printers suitable for displaying a printed image
and raster image processing (RIP) systems for preparing the data
before display, particularly before printing.
BACKGROUND OF THE INVENTION
[0003] Display devices with differing images on each side and being
transparent or translucent from one of the sides are known from a
variety of documents including EP-A-0170472 which describes a panel
comprising a light permeable material and a silhouette pattern,
comprising any arrangement of light restricting material which
subdivides the panel into a plurality of discrete light restricting
areas and/or a plurality of discrete transparent or translucent
areas, characterized in that a design is superimposed on or forms
part of said silhouette pattern so that said design is visible from
one side of the panel only, and wherein said design is less
perceptible from said one side of the panel as the level of
illumination transmitted through the panel from said other side
increases. A number of different vision effects are obtainable from
different panels falling within the above definition. Thus clarity
of vision can be maintained from the one side to the other side
with the exception of the area covered by the design with clarity
of vision through the whole of the panel from the other side to the
one side. Visibility from the one side to the other side can be
totally or partially obstructed while there is clarity of vision
through the whole of the panel from the other side to the one side,
in other words a unidirectional vision effect is obtained Clarity
of vision is obtainable from the one side to the other side except
in the area of the design while visibility from the other side to
the one side is totally or partially obstructed. Vision from either
side can be totally or partially obstructed. In all cases through
vision can be obtained in either direction through the panel when
the level of illumination perceived through the panel from the far
side of the panel sufficiently exceeds the illumination reflected
from the near side of the panel. The transparent areas typically
have dimensions ranging from 0.5 to 3 mm.
[0004] EP-A-0170472 and EP-00118638 describe methods of producing
both the silhouette pattern and also the imposed design. The
methods as described may be summarized as either sequential
printing of the silhouette and/or the design using screen
lithographic or similar ink printing processes with as exact a
registration as can be obtained or a method in which a mask is
applied and the printing processes are carried out through the mask
onto the substrate. When the mask is removed, the silhouette
pattern and image remain on the substrate only in the areas which
the mask or stencil allow the ink to penetrate.
[0005] EP-A-0234121 describes further methods of printing such an
image. The printing methods are limited to those including inks.
Again a mask is described which is subsequently removed taking with
it unwanted portions of the silhouette pattern and image.
[0006] U.S. Pat. No. 5,396,559 describes a security device for use
on identification cards, monetary documents, and the like using a
reference pattern and a message pattern each having the appearance
of a random pattern of dots. The reference pattern is a dense
pattern of randomly positioned dots, and the message pattern is a
modulated version of the reference pattern in which the dots of the
reference pattern are slightly repositioned by an amount depending
on the gray value or color value of a message image at each dot
location. The message image is decrypted and becomes visible with a
range of gray values when it is viewed through a film transparency
of the reference pattern. The dot pattern may be printed, embossed
or recorded as a photograph or a hologram. Decryption of the
message image may be accomplished by viewing through a contact
mask, superposition of images of the message pattern and reference
pattern, by viewing the message pattern through a mask positioned
at a real image of the reference pattern, or like means.
[0007] Japanese patent application Kokai 1 (1993)-57863 describes a
production of an image including transparent sections for areas of
the image. A method is described in which a decorative sheet is
prepared by registration printing in the order of a rear pattern
layer, a covering ink layer and a front pattern layer on a
transparent plastic sheet in such manner that a plurality of small
transparent portions remain in the image. No description is made as
to how the registration printing should be carried out.
[0008] Japanese patent application Kokai I(1989)-69397 describes a
method of producing a transparent plastic or glass substrate with a
printed layer including a plurality of holes. The method includes
printing the image onto a second substrate, perforating the image
and second substrate and then transferring the image only from the
second substrate to the transparent plastic or glass substrate.
SUMMARY OF THE INVENTION
[0009] The present invention provides a method of displaying an
image on a display device having first and second sides, said image
including a light restricting silhouette pattern having a plurality
of first transparent or translucent areas, and at least one design
layer having at least one colour, said at least one design layer
being visible from one side of said display device and
substantially less visible from the other side, said image being
substantially transparent or translucent as viewed from the other
side, comprising the steps:
[0010] 1) providing at least a definition of said design layer to a
computer;
[0011] 2) generating a computerized version of said design layer
with the computer;
[0012] 3) outputting the computerized version of said design layer
to said display device, the computerized version of said design
layer being modified to subdivide said design layer into a
plurality of second discrete transparent or translucent areas and
other areas, and
[0013] 4) displaying said modified design layer and said silhouette
pattern with said first and second transparent areas being in
registry.
[0014] The present invention also includes an article having a
conformable substrate, comprising: a colorant receptor layer and a
light restricting layer on said substrate, said light restricting
layer having a plurality of first transparent or translucent
areas.
[0015] The present invention also includes an article comprising: a
polymeric substrate having a composition comprising vinyl chloride
resin, optional acrylic resin, optional plasticizer, and optional
stabilizer, wherein the composition is formed on a polymeric
release liner having smoothness of a Sheffield value of from about
1 to about 10, and a light restricting layer and a design layer on
said substrate, said design layer including at least one color
layer, said light restricting layer being subdivided into a
plurality of first transparent or translucent areas, said design
layer being subdivided into a plurality of second transparent or
translucent areas, and said first and second transparent areas
being in registry.
[0016] The present invention further includes a printer for
receiving a print file including color separated image data, light
restricting layer data and transparency data, and for printing the
color separated image and the light restricting layer data
including transparent areas in both the color-separated layer and
the light restricting layer in accordance with the transparency
data.
[0017] The invention further includes a raster image processing
method for raster image processing of a print file including color
separated image data, light restricting layer data and transparency
data, comprising: operating on said print file to generate raster
image bitmaps for said color separated image data and said light
restricting layer data, and introducing said transparency data into
said raster image bitmaps for said color separated image data and
said light restricting layer data so that the transparent areas in
said color separated image raster bitmap and said light restricting
layer bitmap are in registry.
[0018] The invention includes in addition a raster image processing
system for raster image processing of a print file including color
separated image data, light restricting layer data and transparency
data, comprising: means operating on said print file to generate
raster image bitmaps for said color separated image data and said
light restricting layer data, and means introducing said
transparency data into said raster image bitmaps for said color
separated image data and said light restricting layer data so that
the transparent areas in said color separated image raster bitmap
and said light restricting layer bitmap are in registry.
[0019] The invention also includes a graphics computer based system
for creating graphics images including color separated layers and
light restricting layers, comprising: first input means for image
data, means for generating color separated image data from said
image data, means for generating light restricting layer data,
second input means for transparency data, and means for outputting
a display file including said color separated image data, said
light restricting layer data and said transparency data.
[0020] The present invention may provide conformable articles
including transparent areas in images, methods of providing the
same and printers, computer graphics systems and raster image
processing systems and methods for producing images on the articles
at low cost.
[0021] The present invention may provide conformable articles
including transparent areas in images, methods of providing the
same and printers, computer graphics systems and raster image
processing systems and methods for producing images on the articles
which allow variability in image not previously achieved. The
invention with its embodiments and advantages will be described
with reference to the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 shows a schematic cross section of a display unit in
accordance with the present invention;
[0023] FIG. 2 shows a block diagram of a display system in
accordance with the present invention.
[0024] FIG. 3 a complex image including transparent areas in
accordance with the present invention.
[0025] FIGS. 4A and B show characters and shapes defined by
transparent areas in accordance with the present invention.
[0026] FIG. 5 the graying effect of conventional light colored
window graphics as seen in the prior art.
[0027] FIG. 6 shows a schematic cross-section view of a second
embodiment of a display unit in accordance with the present
invention.
[0028] FIG. 7 shows a cross-section view backlight for use with the
second embodiment of the present invention.
[0029] FIG. 8 shows a schematic cross-section view of a third
embodiment of a display unit in accordance with the present
invention.
[0030] FIG. 9 is a cross-section through a printed substrate in
accordance with the present invention.
[0031] FIG. 10 is a cross-section through another printed substrate
in accordance with the present invention.
[0032] FIG. 11 is a cross-section view of a printing substrate in
accordance with a seventh embodiment of the present invention.
[0033] FIG. 12 is a cross-sectional view of a of a printing
substrate in accordance with an eighth embodiment of present
invention.
[0034] FIG. 13 is a cross-sectional view of a printing substrate of
a tenth embodiment of the present invention.
[0035] FIG. 14 illustrates a cross-sectional view of a durable,
optically clear, transparent layer of the eleventh embodiment of
the present invention prepared on a polymeric release layer.
[0036] FIG. 15 illustrates a cross-sectional view of the durable,
optically clear, transparent layer of the eleventh embodiment
during a lamination step.
[0037] FIG. 16 illustrates a cross-sectional view of the durable,
optically clear, transparent layer of the eleventh embodiment in
combination with an imaged substrate.
[0038] FIG. 17 illustrates a cross-sectional view of the durable,
optically clear, transparent layer of the present invention in
combination with an imaged substrate as a modification as a twelfth
embodiment of the invention.
[0039] FIG. 18 is a block diagram of the components of a printing
system in accordance with embodiments fourteen to sixteen of the
present invention.
[0040] FIG. 19A is a cross-section and 19B is a top view of a
printed substrate for use with embodiments fourteen to sixteen of
the present invention.
[0041] FIG. 20 is a schematic drawing of a printing head in
accordance with the fifteenth embodiment of the present
invention.
[0042] FIG. 21 is a schmatic drawing of a printer in accordance
with another embodiment of the present invention.
DEFINITIONS
[0043] As used in this application:
[0044] "colorant" means any material that imparts color to another
material or mixture and maybe either, dyes or pigments;
[0045] "colorant receptor layer" means any layer on a printing
substrate which is provided for the purpose of transferring
colorants to the substrate.
[0046] "durable" means the substrates used in the present invention
are capable of withstanding the wear and tear associated with
signage and may be 2 to 5 years in exterior environments;
[0047] "plastic" means a material that is capable of being shaped
or molded with or without application of heat and include
thermoplastics types, thermosets types, both of which may be
flexible, semi-rigid or rigid, brittle or ductile;
[0048] "smear-resistant" as used in this application means
resistant of the ink jet ink to smear as described in the following
test, printing an image with black lines, allowing a minimum of
five minutes time to dry, rubbing the line with the pad of the
finger with a light to moderate pressure, such as might be used
during normal handling of images, and observing whether spread of
the line occurs;
[0049] "durable" means the substrates useful in the present
invention are capable of withstanding the wear and tear associated
with signage and may be used 2 to 5 years in exterior
environments;
[0050] "conformable" means the substrates in a direct print film
are capable of conforming to uneven surfaces and retaining such
conformation during use without significant force applied per unit
area of the film. Typically the conformable substrate can be
adhered with hand pressure and conform to a surface having periodic
or compound irregularities, such as a rivet or welded ridge on the
exterior metallic surface of a tractor trailer, without the
substrate lifting from the surface. Preferably, a conformable
substrate in a direct print film exhibits a yield point and/or
permanent strain when subjected to a maximum tensile stress of
about 3.5.times.10.sup.7 N/m.sup.2 (5000 lb./square inch) at room
temperature according to ASTM D638-94b (1994), when the caliper
used for the test includes the total cross-sectional thickness of
the substrate, the thickness of the adhesive, and the thicknesses
of any further layers such as ink receptor, conductive or
dielectric layers. More preferably, the maximum tensile stress
limit is about 1.4.times.10.sup.7 N/m.sup.2 to provide more
conformable films. Most preferably, the maximum tensile stress
limit is about 7.times.10.sup.6 N/m.sup.2 to provide even more
conformable films. Conformability of the films still require
internal integrity. Desirably, the minimum tensile stress limit is
about 6.9.times.10.sup.4 N/m.sup.2 (10 lb./square inch) and
preferably the minimum tensile stress limit is about 1.7.times.105
N/m.sup.2 (25 lb./square inch).
[0051] Testing Methods
[0052] Bulk Powder Resistivity: "The Application of ZELEC ECP in
Static Dissipative Systems" (Du Pont Chemicals, Deepwater, N.J.
September 1992)
[0053] Specific Resistance: "Tego Conduct S Resistivity Measurement
and Apparatus" (available from Esprit Chemical Company, Rockland,
Md.) Surface Resistance: ASTM D 4496-87 and ASTM D 257-93 published
by American Society for Testing and Materials.
[0054] Color Shift: ASTM D 2244-93 published by American Society
for Testing and Materials.
[0055] Color Density: "Reflective Optical Density on a Status T
Method"" under the requirements of ANSI/ISO 5/3-1984, ANSI PH2.
18-1985 published by the Graphic Communications Association of
Arlington, Va. Reflected optical density is measured using
techniques well known to those in the printing industry. Examples
herein were evaluated with a Gretag SPM50 densitometer from Gretag
Limited, CH-8105 Regensdorf, Switzerland. Other instruments will
give similar comparisons, but not necessarily the same values.
"Color Density" is the measure of the intensity of the individual
primary colors on a recording medium to form the latent image and
is important to films of the present invention because color
density has a major impact upon the perceived aesthetics of the
image on the recording medium. By comparison, transmission optical
density may be measured using an optical densitometer such as a
Macbeth TD 904.
[0056] Sheffield: Sheflield method measurement described in TAPPI
Test T 538 om-88 published by the Technical Association of the Pulp
and Paper Industry of Atlanta, Ga.
[0057] The disclosures of the Testing Methods are incorporated
herein by reference.
[0058] Embodiments of the Invention
[0059] The figures are intended for illustrative purposes only.
Certain dimensions may have been exaggerated to improve
clarity.
[0060] FIG. 1 shows a schematic cross section through a display
unit of the kind used with the present invention. A display
includes a first silhouette pattern 2, comprising an arrangement of
light restricting material which subdivides the panel into a
plurality of discrete light restricting areas 5 and/or a plurality
of discrete transparent or translucent areas 6. The light
restricting areas 5 have light transmission reducing properties.
These may be, in one extreme, completely opaque, i.e. the optical
density in transmission is infinite. Transmission optical density
TOD (which is to be distinguished from reflection optical density,
ROD) is defined by the formula: 1 TOD = log 10 ( I i I t ) ,
[0061] where I.sub.i is the intensity of the incident light on the
sample material and I.sub.t is the intensity of the transmitted
light passing through the material. The present invention accepts
that the light restricting layer 5 may not be perfectly opaque but
may allow some light to transmit. It is preferred if the TOD of the
light restricting layer is greater than 1, preferably greater than
2, more preferably greater than 2.5 and most preferably 3 or
greater.
[0062] The translucent or transparent areas 6 allow light to pass
through. In one extreme the transparent areas 6 transmit all light
and reflect or scatter no light, i.e. a TOD of infinity and a ROD
of infinity, where the optical density in reflection is given by: 2
ROD = log 10 ( I 1 I R ) ,
[0063] I.sub.R being the reflected light intensity.
[0064] The present invention accepts that the
translucent/transparent areas 6 may not be perfect light
transmitters, i.e. they may absorb and/or reflect and/or scatter
some light. It is preferred if the TOD of the transparent or
translucent areas have an ROD of less than 1, preferably less than
0.5. The translucent areas 6 should differ in optical density from
the light restricting areas 5 by a sufficient amount to make a
clear visual difference. The TOD difference between areas 5 and 6
should preferably be greater than 0.3. According to the present
invention the areas 6 are preferably transparent, more preferably
optically clear.
[0065] The pattern of light restricting 5 and/or
transparent/translucent areas 6 may be any array of pixels, for
example, a pattern of parallel lines, dots, circles, squares, etc.
which may be arranged in a regular array, in the form of a design,
in an irregular array or in a random way. The transparent areas 6
may have any dimension depending upon the display device used, and
may be diameters typically in the range of 0.1 mm to 8 mm,
preferably 0.2 mm to 3 mm. The ratio of the transparent areas 6 to
light restricting areas 5 may be chosen as desired but is typically
0.3 to 3, usually about 1, i.e. 50% Of the surface area is covered
by transparent areas 6. In accordance with the present invention
the silhouette pattern 2 may be provided by any spatial light
modulator or filter which comprises a plurality of discrete light
restricting areas 5 and/or a plurality of discrete transparent or
translucent areas 6. The spatial light modulator or filter 2 may be
a silhouette pattern similar to that described in EP-A-0170472 or a
pattern created by the back-light of a liquid crystal (LCD) display
device or any other appropriate display device.
[0066] Substantially coextensive with the spatial light modulator
or filter 2 is placed a display device 3 and/or a display device 4.
Display device 3 or 4 can display an image which may be a full
color image represented schematically by the four layers 7-10,
7'-10' and the image is divided into transparent or translucent
areas 6 and colored design areas 7-10,7'-10' so that the
transparent or translucent areas 6 of the spatial light modulator
or filter 2 are aligned (in registry) with the translucent or
transparent areas 6 of display device 3, 4. The display device 3 or
4 may be a printed image, for instance, in accordance with
EP-A-0170472 or similar, or may be a LCD or LED display device
which is capable of displaying a monochrome or full color image. At
least one of display device 3 or 4 may be a black or dark colored
pattern.
[0067] The display unit 1 may be self-standing or may be laminated
to a substrate such as a transparent sheet of glass-like or
polymeric material. The glass or polymeric sheet may be laminated
to the display device 3, the display device 4 or may be interposed
between any of the layers 7-10,7'-10' or between display device 3
and silhouette pattern 2 or between silhouette pattern 2 and
display device 4. The substrate may be the window of a car, bus or
building or may be a flexible polymeric sheet. When the display
device 3 or 4 is black or a dark color and is located next to the
transparent sheet 1, the dark display device 3, 4 may be partly or
completely provided by tinting the transparent sheet as taught in
EP Patent No. 0 133 761.
[0068] FIG. 2 shows a schematic block diagram of the first
embodiment of the present invention. A suitable graphics image for
display purposes is generated in image generation means 12. The
image may be generated using computer 13 and special software
developed for production of graphic images such as Adobe
Photoshop.TM., Adobe Illustrator.TM., Corel-Draw.TM., Aldus.RTM.
Pagemaker.TM., Quark Xpress.TM. or similar. The image generation
means 12 may be a scanner with which all or part of picture
information from an image, a picture or photograph is converted
point by point into electrical signals to be stored in computer 13
as digital data.
[0069] Once the graphics image has been stored in computer 13 as a
matrix of digital data which include sufficient data to determine
the luminosity and color of each pixel of information, the data may
be prepared such that it may be displayed with a plurality of
transparent areas 6 within the graphics image.
[0070] In accordance with the present invention this may be done in
several different ways:
[0071] Method 1. The color-separated layers of data (conventionally
CMYK, cyan, magenta, yellow and black or if the black layer is not
used: CMY) may be modified to include no color data representing
the transparent areas 6 in each of the layers. This modification to
the data may be done in computer 13 but the invention is not
limited thereto. The pattern of transparent areas 6 may be provided
by overlaying the transparent areas 6 as areas of "no-color" onto
the graphics image within computer 13. The no-color data may be
stored as raster or pixel data. In general there is no need to
modify the half-tone algorithms as disclosed for instance in U.S.
Pat. Nos. 5,253,084; 5,258,832; 5,264,926; or 4,758,886 used to
create the full color image. However, if small diameters of the
transparent areas are used (<0 5 mm) it may be advisable to
select the size of the transparent areas 6 and their spacing so
that they are not a multiple of the size of halftone cells in order
to avoid rhythmic color shifts. With small size transparent areas
6, method 2 is preferred. The translucent/transparent areas 6 may
be a regular, irregular, or random array of dots, lines, squares,
circles, polygons, or similar, or a separate array of these
representing a design or image. Both the size and the distribution
of the transparent areas 6 may be varied through the image.
[0072] As shown in FIG. 3 the transparent areas 6 may be a complex
and attractive design 5, 6, 11 which has image portions 22 which
may be light restricting and a transparent design portion 23 made
up of transparent/translucent areas 6 surrounded by image areas
which may be light restricting areas 5. The transparent areas 6 may
have differing diameters and shapes in order to represent the
detail of the design correctly. It is understood that on the
reverse face of the design 22, 23, a fill color image 3 or 4 may be
displayed. The representation of the filigree patterns of the fern
leaves in a plurality of transparent areas 6 which are in registry
through multiple layers of printing requires exact printing of
small size repetitive transparent areas 6 separated by
substantially opaque regions 5 in order to create a vivid and clear
design.
[0073] Method 2. The data representing the transparent areas is
stored in a separate layer--a "T" layer--in computer 13. A display
output file from computer 13 includes the color separated primary
printing color layers, CMYK or CMY layers, plus the T layer. As
will be described later, the information in the T layer may be used
in different ways For instance, where Raster Image Processing (RIP)
is carried out, the data of the T layer may be introduced into each
of the CMYK layers in the final raster bitmap during or immediately
after the RIP. Introducing this data into the raster bitmap has the
advantages that small repetitive structure distortion may be
reduced and the registration of the final image may be improved, as
each color separated bitmap has the identical positions of the
transparent areas. Alternatively the T layer may bypass the RIP and
be used by a display control circuit to control the display 3,4 in
such a way that the transparent areas 6 are generated. For
instance, where the display device 3,4 is a printer, the
transparent areas 6 may be generated by activating or deactivating
the printer head during printing in accordance with the T layer
data.
[0074] Method 3. Method 3 is a modification of method 2 and uses a
separate transparent data layer T. The difference lies in the form
of the data. In accordance with method 3, transparency data is
stored in the same way as dot matrices are stored, except instead
of a dot representing a colored dot in the final display the dot
represents a transparent area 6. All the techniques of word
processing and graphics software can be duplicated in the inverse:
instead of colored dots on a white background, the data represents
a transparent areas in a light restricting background. For
instance, the data may be stored as transparent fonts. Thus a
letter such as "I" is stored in the computer as a character which
includes a predetermined array of transparent areas 6 as shown
schematically in FIG. 4A. When in the "T" mode, i.e. when
generating the data for the transparency layer T, the key stroke
"I" stores the array of transparent areas 6 shown in FIG. 4A.
Similarly transparency graphic programs can be used to create
designs in transparent areas. Thus straight lines or shapes may be
generated. Graphic elements: a rectangle and a line of transparent
dots, are shown schematically in FIG. 4B.
[0075] Method 4 is a modification to method 1 in which the
silhouette layer 2 is included in addition to the CMYK or CMY
layers. The silhouette layer 2 may generally be included as a light
colored spot color, in particular, white. It contains the
transparency data in registry with the transparency data in each of
the CMY or K layers.
[0076] Method 5 is a modification of method 2 in which the
silhouette layer 2 is included in addition to the CMYK or CMY
layers. The silhouette layer 2 may generally be included as a light
colored spot color. In preparing the silhouette layer 2 for
display, the same methods (e.g. RIP) may be used as described for
the CMYK or CMY layers.
[0077] Method 6 is a modification of method 3 in which the
silhouette layer 2 is included in addition to the CMYK or CMY
layers. The silhouette layer 2 may generally be included as a light
colored spot color. In preparing the silhouette layer 2 for
display, the same methods (e.g. RIP) may be used as described for
the CMYK or CMY layers.
[0078] Method 7 is a modification to method 4 in which the image of
display device 4 is included in addition to the first image of
display device 3 and the silhouette layer 2. The second image may
generally be included as further CMYK or CMY layers. These contain
the transparency data in registry with the transparency data in all
of the other layers.
[0079] Method 8 is a modification of method 4 in which the image of
display device 4 is included in addition to the first image of
display device 3 and the silhouette layer 2. In preparing the
second image 4 for display, the same methods (e.g. RIP) may be used
as described for the CMYK or CMY layers of the first image 3.
[0080] Method 9 is a modification of method 6 in which the image of
display device 4 is included in addition to the first image of
display device 3 and the silhouette layer 2. In preparing the
second image 4 for display, the same methods (e.g. RIP) may be used
as described for the CMYK or CMY layers of the first image 3.
[0081] For Methods 1-9, the image is output to a display device 14
which, in accordance with the present invention, may be a direct
display device similar to an LCD or LED display, an indirect
printing device 16-19, or a direct printing device 20, 21.
[0082] The method of displaying the data depends upon the method of
storing the data.
[0083] Methods 1, 2 and 7. As these methods have the transparency
data stored in each of the layers of the CMYK or CMY data, the CMYK
or CMY data can be handled as in conventional display devices
provided these can display the number of layers for the particular
method.
[0084] Methods 2, 3 5, 8 and 9 include a separate "T" layer, which
may be processed by display devices according to the present
invention. On some existing graphics software it may be possible to
specify a transparent spot color or to specify a spot color of any
desired color but modify the display device so that it displays
this spot color as transparent. In accordance with this
application, devices capable of processing data according to
methods 2,3,5,6,7,9 are called transparency layer display devices
or TLD devices.
[0085] When the display device 3 or 4 of FIG. 1 is viewed from the
front and the level of illumination on that side is high, the
transparent areas 6 appear dark, normally black. If the image to be
displayed is simply provided with transparent areas 6 without
modification to the colors of the image, this image appears
uniformly darker than the original. This is particularly noticeable
when the display device 3,4 is placed adjacent to the same image in
which there are no transparent areas 6. This can occur when the
display device 3,4 covers the window of a vehicle and the graphics
continue onto the body of the vehicle. This is shown in FIG. 5
(Prior Art) which a photocopy of a photograph of a train in which
large white lettering has been applied over the side of the train.
The white lettering passes over windows which have been covered
with conventional punched film window graphics. The gray appearance
of the window areas 54 in comparison to the adjacent areas 52 on
the body of the train can be clearly seen. Hue changes can also
occur in the arrangement such described with respect to FIG. 3 in
which full color portions 22 of the image may be adjacent to
portions 23 with transparent areas 6.
[0086] The following embodiment of the present invention provides a
solution to this problem.
[0087] The technique of undercolor removal is known in printing and
photography (see for example "The Reproduction of Color in
Photography, Printing & Television", Fountain Press, UK, Second
Impression 1988). Instead of printing or displaying dark areas of
the image with a combination of the three traditional colors Cyan,
Magenta and Yellow, using undercolor removal the black component of
the color is provided separately, e.g. by using separate black
toners or inks. In accordance with the present embodiment of the
invention this technique is used in a novel way. When preparing the
data for display, the computer graphics program of computer 13 of
FIG. 2 carries out undercolor removal in the normal way, however,
the apparent dark color of the transparent areas 6 is taken into
account in the undercolor removal. For example, if 50% of the image
area is provided by transparent areas 6, a color with a black
component of 50+X % will be displayed with only a black component
of X %. The color displayed is the true color as the remaining 50%
black is provided by the transparent areas 6 which appear black.
For a color with less than 50% black, no black is displayed. This
results in some darkening of the color with respect to the original
but the total effect is still improved. To prevent differences in
hue between light colored areas of the image with and without
transparent areas 6, the light colored areas of the image which do
not have the transparent areas 6 (e.g. outside window areas or area
22 of FIG. 3) are provided with additional black--in effect
undercolor addition. With the example given above, if a color only
has a 10% black component, this component is removed as completely
as possible from this color in the areas of the transparent areas
6. In parts of the image without transparent areas 6, this same
color has 40% black added so as to match the hues throughout the
image.
[0088] It is accepted that with some of the embodiments of the
present invention the display device 4 may be partly visible from
the other side of the silhouette layer 2, i.e. viewed from the side
of display device 3. This may be due to the fact that the
silhouette layer 2 can not be produced (e.g. by some kinds of
printing methods) with such opacity that the display device 4 is
totally isolated optically. When display device 4 has a dark color,
the result of a light restricting but not opaque silhouette layer 2
is that all the colors of display device 3 become darker. In
accordance with the present invention, any darkening of the image
displayed on display device 3 is also compensated for by undercolor
correction, or if this is not possible, by increasing the black
content of any part of the image 3 which lies outside the area
where there are transparent areas 6.
[0089] A further method of compensating for the darkening effect of
the transparent areas 6, is to partly metallize these areas. This
has the effect of reducing transmission but provides a gain in
reflected white light from the image 3. To achieve metallization,
the whole area of the substrate may be partly metallized using
techniques known for two way mirrors.
[0090] A direct or simultaneous display device 15 in accordance
with the present invention is a display device which displays at
least the image directly from the electrical output of the computer
13 and combines this with the silhouette pattern 2 so that the
transparent areas 6 of the silhouette layer 2 are in registry with
the transparent areas of the image. Such a direct display device 15
in accordance with a second embodiment of tile present invention is
shown schematically in FIG. 6. A conventional LCD display 24 is
addressed by an addressing unit 28 which is connected to the
computer 13 in the conventional way e.g. by means of cable and
connector 29. The LCD array 24 may form part of a window. Behind
the LCD array 24 is placed a back-light or reflector 25 which has a
light source 26 connected to a suitable power supply (not shown) by
cable and connector 27. The back-light 25 produces illumination in
the form of strips, squares, circles or similar shapes separated by
areas of transparent material such as to produce the silhouette
pattern 2 as shown in FIG. 1. An example of such a back-light 25 is
shown schematically in FIG. 7. The back-light 25 consists of a
series of optical fibers 30 producing distributed light separated
by transparent areas 31 which may be a transparent material such as
optically clear acrylic resin. The optical fibers 30 are modified
so that they distribute the light from the light source 26 and emit
the light in a distributed way along their length in a direction
perpendicular to the plane of the back-light 25 towards the LCD
display 24. This may be done by introducing an irregularity 32
called an optical element such as a slit, on the surface of each
fiber 30 away remote from the LCD display 24. Such optical fibers
30 including optical elements 32 for producing a distributed series
of cones of light are described in the article entitled "Control of
light output from plastic optical fiber with optical elements" by
Mary Poppendieck and David Brown, published at the International
Congress and Exposition of the Engineering Society for Advancing
Mobility Land Sea Air and Space, Feb. 26-29 1996.
[0091] When the optical elements 32 are arranged on the side of
each optical fiber 30 which is remote from the LCD display 24 then
the individual cones of light are reflected towards the LCD display
24 such as to illuminate parts, e.g. strips or rectangles of the
LCD display 24. As explained in the above mentioned article, the
spacing of optical elements 32 along the fiber 30 may be arranged
so that the spacing of the elements 32 is closer together or
intrude deeper into the fiber dependent upon the distance from the
light source 26. In this way, a uniform extraction of light along
the length of the fiber 30 may be achieved.
[0092] Further descriptions of how to produce a back light from
optical fibers are given in U.S. Pat. Nos. 5,226,105; 4,907,132;
4,885,663; 4,845,596; 4,519,017; 4,234,907; 5,432,876, 5,187,765;
and 5,005,931; all of which are incorporated herein by
reference.
[0093] The LCD display 24 is driven by the computer 13 via cable
and connector 29 and addressing unit 28 so that only those liquid
crystal cells of LCD display 24 which are illuminated by the
optical fibers 30 are addressed with data of the image 3 or 4 of
FIG. 1 of the present application prepared in accordance with
method 2 or 3 above. When the transparent areas are small, it is
preferred if the introduction of the transparent areas in the data
is delayed until immediately before display. For instance, the
output data file for the image on the display device is first
prepared in the computer 13. Then the transparent areas 6 are
introduced. It has been found that, particularly when the
transparent areas 6 are small and are in a regular array,
introducing the transparent areas at an earlier stage may result in
distortion of these areas, when the image is manipulated by other
algorithms, e.g. filters.
[0094] The under color removal mentioned above is carried out
allowing for the percentage of transparent areas 6 in the image 3,4
to be displayed. In the areas of the LCD display 24 which are
opposite the transparent areas 31 of back-light 25, the computer 13
outputs the relevant data so that the LCD display 24 is transparent
in these areas. Thus the image 3,4 displayed on LCD display 24
consists of areas of the image 3 or 4 illuminated by optical fibers
30 separated by transparent areas 31. When viewed from the front of
the LCD display 24, a full image 3 or 4 may be seen separated by
the transparent areas 6 which appear dark when the general
illumination on the back-side of the LCD display 24 is lower than
the general illumination on the front side of the LCD display 24.
On the other hand, when viewed from the back of the LCD display 24,
the display device 25 has transparent areas 31 separated by opaque
areas provided by the back of the optical fibers 30.
[0095] In accordance with a modification of the second embodiment
the back-light 25 may be provided by a series of LED units 33
separated by transparent areas 34 as shown in FIG. 8 schematically.
The LED elements 33 may be formed in lines or squares or circles or
in similar shapes and are arranged so that the light emitted from
the LED elements 33 is projected towards the LCD display 24. Thus
the LED elements 33 illuminate those parts of LCD display 24 which
contain image data fed to the LCD display 24 via connector and
cable 29 and addressing unit 28 from the computer 13. The data
output from the computer 13 provides transparent areas in the LCD
display 24 which are in registry with the transparent areas 34 of
the back-light 25 shown in FIG. 8.
[0096] Alternatively, the display device 14 in accordance with a
third embodiment of the present invention may be an indirect
printing device 16-19.
[0097] An indirect printing device in accordance with the present
invention is a printing method with which there is sequential
colorant transfer of individual color-separated images from
intermediate image carriers to the printing substrate. Typically
this requires a set of color-separated, i.e. single primary color,
intermediate image substrates 17 which are used in printing device
18 to produce the final printed image 19. The intermediate imaged
substrates 17 are produced from the computer output data in the
intermediate imaging device 16. Such an indirect printing method
may be for example lithographic or screen printing.
[0098] With reference to lithographic printing, the imaged
substrates 17 may be a series of imaged polyester lithographic
plates, suitable for lithographic printing on a printing press 18.
The lithographic substrates 17 may be generated directly from the
information from the computer 13 in a suitable imaging device 16.
The set of lithographic substrates 17 may be used to print
sequentially all or part of the image 4, silhouette pattern 2 and
image 3 of FIG. 1 in accordance with the present invention. For
instance, as shown schematically in FIG. 9, the image 4 may be a
pattern of black 42 on a transparent sheet 41 in registry with an
light restricting white silhouette pattern 43 onto which is printed
in registry a full 4-color image 44-47 leaving transparent areas
48. Data preparation may be performed by any of the methods 7 to 9
above. Thus, a total of 6 plates 17 maybe necessary: black, white,
cyan, magenta, yellow and black. An individual plate 17 may be used
several times for each color in order to obtain sufficient depth of
color or opacity of the printed layer 42-47. Where a dark tinted
transparent sheet 41 is used it may be possible to omit the first
black layers and use only five color layers: white, cyan, magenta,
yellow and optionally black. Data preparation may then be made in
accordance with any of the methods 4 to 6 above. In order to obtain
good registration between the various lithographic substrates 17,
they may be produced by a method described in co-pending European
patent application EP 95106746.1 filed on May 4, 1995 which is
incorporated herein by reference.
[0099] After preparation of the intermediate imaged substrates 17
from the image data, the final prints 19 are produced in printers
18 in the conventional way on clear films. The printing films used
for all the embodiments of the present invention involving printing
are conformable due to the conformable nature of the substrates
selected and the conformable adhesive layer contacting one major
surface of the substrate.
[0100] An alternate sequence of color layers 42-47 may be printed
as shown schematically in FIG. 10. The order of the layers 42 to 47
is reversed and the last color printed is the black layer 42. As
applied to a window substrate, transparent substrate 41 may now
form the outer layer or overlaminate of the sheeting 40. An
adhesive layer 50 may be applied optionally to the printed side of
sheeting 40 in order to secure the sheeting 40 to a window or
similar. Adhesive layer 50 may be any of the adhesives mentioned
below with reference to overlaminates. It is preferred if the
transparent substrate 41 of FIGS. 9 and 10 is the optically clear
vinyl sheeting in accordance with the eleventh embodiment of the
present invention. It is also preferred if the adhesive layer 50 is
optically clear, preferably an acrylic pressure sensitive
adhesive.
[0101] Although it is preferable to use a pressure-sensitive
adhesive, any adhesive that is particularly suited to the
particular substrate selected and end-use application can be used
on the sheeting 41. Such adhesives are those known in the art any
may include adhesives that are aggressively tacky adhesives,
pressure sensitive adhesives, repositionable and/or positionable
adhesives, hot melt adhesives and the like Pressure sensitive
adhesives are generally described in Satas, Ed., Handbook of
Pressure Sensitive Adhesives 2nd Ed. (Von Nostrand Reinhold 1989),
the disclosure of which is incorporated by reference.
[0102] Also, as indicated in FIG. 10, any errors in registration
between the printed layers 42-47 may be compensated for by making
the transparent areas 48 in the silhouette pattern, i.e. the white
layer 43, slightly smaller than in the colored layers 44 to 47.
Similarly, the transparent areas 48 in the black layer 42 may be
made slightly smaller than the areas 48 in the white layer 43. By
this means, missregistration of the colored layers will not
encroach into the transparent area 48, similarly missregistration
of the white layer 43 will also not encroach into the transparent
areas 48 of black layer 42.
[0103] The intermediate imaged substrates 17 may also be a set of
screens for a screen printing device 18. The output from computer
13 is then fed to an automatic screen producing device 16 as is
known to a skilled person in screen printing techniques. The final
image 19 is produced by sequential printing of the colors using the
screens 17 and conventional screen printing techniques.
[0104] A major disadvantage with indirect printing methods is that
the intermediate imaged substrates 17 are located in a printing
device 18 in sequence and the maintenance of exact registration
between the various layers of images 3 and 4 and silhouette pattern
2 of FIG. 1 is difficult or requires time consuming proofing and
adjustment. Some improvement may be obtained by using a full color
laser printer. In this case the intermediate imaged substrates 17
are provided by the imaged semi-conductive drums used to print
substrates 19 by means of the attraction of toner to the charged
electrostatic areas of the drum. Providing six or more drums
requires a special printer which is expensive, or in the
alternative, using the same drum six times may make exact
registration difficult. The AGFA Chromapress.TM. electrostatic
printing system supplied by AGFA-Gevaert NV, Mortsel, Belgium, may
be an indirect printer in accordance with the present invention.
The system includes 8 electrostatic printer drums arranged as a
series of four drums on each side of the substrate to be printed.
The printing drums are controlled by a computer graphics system
suitable for producing the modified images in accordance with the
present invention. This system is designed for printing onto paper
but could be modified to print onto clear films, especially
optically clear polyester films of the type known for overhead
transparencies.
[0105] It is preferred in accordance with fourth to sixteenth
embodiments of the method of the present invention if the display
device 14 is a direct printing device 20. In accordance with the
present invention a direct printing device is capable of deposition
of colorants of a full color image directly to a single printing
substrate. The printing substrate may be the final printed article
or an intermediate substrate. Hence a direct printing method is one
which does not make use of a set of intermediate imaged substrates
17 which must be used in sequence in order to print a substrate 19
in a printer 18. A direct printing device 20 in accordance with the
present invention is able to convert the signals from the computer
13 into a full color, image on a substrate 21 or a single
intermediate substrate used for transferring the image, e.g. a
decal, in order to produce, for example, the sheeting 40 shown
schematically in FIG. 9 or 10.
[0106] Such direct printing methods may include but are not limited
to, ink-jet including bubble jet and spark jet, thermal and
piezoelectric impulse jet, thermal transfer including sublimation
or mass thermal transfer or electrostatic or electrophotographic
printing methods. In accordance with the present invention a direct
printing method may also be the electrostatic transfer method known
as ScotchPrint.TM. Electronic Graphics System available from
Minnesota Mining and Manufacturing Company in which an
electrostatic image is first created on special electrostatic paper
and then is transferred in a single operation to a transparent
substrate 21. The distinction between the ScotchPrint.TM. process
described above and the indirect printing methods such as screen
printing or lithographic printing is that the transfer of the image
is carried out with a single substrate and is in full color whereas
the indirect printing methods make use of a set of color separated
imaged substrates 17 in order to generate a full color image. The
registration of electrostatic printing may be considerably better
than that of an indirect printer method, independent of whether the
transfer process is used.
[0107] An example of a printing process used in the present
invention comprises feeding the material 41 in either sheet form or
dispensed from a roll into a printer, printing a desired color
image and silhouette pattern 42-47 in accordance with the present
invention, retrieving the image from the printer and, optionally,
overlaminating the image with a film 50 to protect the receptor
coatings and image from water, scratching and other potential
sources of damage to the image, and then removing the release
liner, and affixing the printed image to a transparent substrate
for viewing.
[0108] It is preferred if the direct printing method has good local
registration. An example of good local registration printing is
that produced by a conventional high quality ink-jet printer which
prints relatively local areas of full color. Thus, very high
quality registration can be obtained locally on the receptor
medium. As very high definition is required around each small
transparent area in the image, good local registration may be
advantageous and some distortion of the complete image over long
distances may be tolerated. On the other hand, electrostatic
printers have distances of several centimeters between each color
station so that full color printing is not carried out as locally
as ink jet printers, even with single pass machines.
[0109] Many factors may affect the local registration of printing.
Ink jet printers move the substrate a distance of 2-3 mm between
colors, whereas a single pass electrostatic printer moves the
substrate between 100 and 150 mm and a thermal transfer printer
such as the Summagraphics Summachrome.TM. Imaging system prints the
whole area before changing color. Tests have indicated that the
amount of movement between color changes is not a reliable guide to
the degree of local registration.
[0110] Printers are often characterized by "dots per inch" or DPI.
Tests have indicated that DPI is a better guide but not an
infallible one for the choice of printer in accordance with the
present invention as can be seen from Table 1 below.
[0111] Warp or distortion or thermal expansion/contraction of the
substrate 21 or of intermediate substrates 17 may also affect or
reduce the theoretical level of local registration.
[0112] It has been determined that the degree of local registration
can be determined practically by printing a special test image
which includes a special full color image with a regular array of
transparent circles of different diameters in the image When the
diameter of a transparent area drops below a certain value, the
errors in printing registration are such that individual
transparent areas are reduced significantly in diameter.
[0113] The special test image is preferably constructed of all the
layers to be printed and each layer being printed at 100% color.
Each layer includes the pattern of transparent circles with
decreasing diameter in registration with every other layer. As an
example, layers of the colors black, white, magenta, yellow, cyan
and black are printed at 100% color intensity sequentially, each
layer including the array of transparent circles. As the colors are
at 100%, any missregistration will be easily visible as the
respective color encroaching into the transparent areas and
reducing their diameters.
[0114] In accordance with the present application, the "local
registration index" (LRI) of the printing method/printer involved,
is defined as the transparent area diameter in mm at which the
diameter of a substantial number of the transparent areas in the
printed image has reduced to 50% of its intended diameter in any
direction. Typical values are given in Table 1 for some commercial
printers. Actual values of LRI depend on the accuracy of setting up
the printer and of calibration. It is advantageous if the printer
in accordance with the present invention has a local registration
index (LRI) better than (i.e. less than) 1.0 mm and preferably less
than 0.6 mm and more preferably about 0.3 mm when printing 4 or
more colors.
1TABLE 1 LRI print Printer Type (mm) quality DPI Encad Novajet
Thermal Ink jet 0.6 excellent 360 SummaChrome .TM., Thermal
transfer .about.0.4* excellent 406 Summagraphics Corp. DesignJet
.TM. HP750C Thermal Ink jet .about.0.4* excellent 360 Hewlet
Packard Corp. Xerox 8954 Electrostatic 0.7 good 200 multipass 3M
Scotchprint .TM. 9512 Electrostatic, one 0.6 good 400 pass Raster
Graphics Inc. Electrostatic, 1.0 good 200 DCS 5400 multi-pass *The
quality of printing was very good that it was difficult to
determine the limit due to extraneous effects probably introduced
by the graphics software.
[0115] Generally, the silhouette pattern 2 includes an light
restricting light colored or white layer or metallic silvery or
gold layer which faces the display device 3 and/or the display
device 4 of FIG. 1. In accordance with the present invention, this
light restricting light colored layer 2 may be printed using light
colored, silver metallic or white ink or toner depending on the
printing method used. A white spot color is preferred. "Light
restricting" means that the deposited layer has a transmission
optical density (TOD) of at least 1.0, preferably of at least 2.0,
more preferably of 2.5 and most preferably of 3.0 or greater. The
software required for computer graphics using computer 13 in
accordance with the present invention is modified so that areas of
white are printed with the white toner or ink as a spot color,
whereas the transparent areas are "printed" as "no ink" areas.
[0116] To prepare the data for the graphics design, the image 3,4
may be first created and stored in computer 13 including data for a
light restricting layer 43. Under-color removal in accordance with
the invention may be carried out on the image data as described
above. The image is normally stored as color separated layers or
planes of data for each primary printing color. Each of the planes
represents the data for one color, e.g. black, cyan, magenta or
yellow or a spot color. With conventional equipinent, data
preparation method 7 is used and tile following is created: a 100%
black or dark colored plane of data representing layer 42 as the
first image 4 within the graphics software. This may be created as
a spot color layer. Next, a 100% white, silver or light colored
plane of data representing light colored layer 43 as the light
restricting layer 2 is produced. Finally, the data for layers 44-47
as the full color graphics image 3 is generated. The black and
white layers 42, 43 are preferably specified as spot colors. This
results typically in producing 6 sets or planes of data: one for
the black layer 42, one for the white layer 43 and four for layers
44-47 of magenta, yellow, cyan and black used for a full-color
print. However, the invention is not limited thereto. Where a good
quality process black may be produced, i.e. a black from a mixture
of cyan, magenta and yellow, the final black layer 47 may be
omitted. Where a tinted substrate is used the first black or dark
layer 42 may be omitted. One or more of the layers 42-47 may be
applied as a plurality of layers. For instance, the white layer 43
may be stored as a series of planes of data representing white
layer 43 in order to obtain sufficient opacity in the final
print.
[0117] The array of transparent areas 48 may be generated within
computer 13 and the image data modified by introducing the
transparent areas 48 into each of the layers of data representing
the printed layers 42-47 by overlaying or other technique.
Typically for printing devices 16-21, "EPS" Separation files are
constructed from the modified image including the transparent areas
48 and these files are communicated to the relevant intermediate
imaging device 16 or printer 20. Alternatively and preferably, the
introduction of the transparent areas 48 into the data to be
printed is delayed to the last possible step before creation of the
intermediate imaging substrates 17 or printing to form printed
images 21. This is best achieved using data preparation methods
5,6,8, or 9 in which a separate T layer is output from the computer
13. The T layer data is introduced into the CMYK layer data and the
silhouette layer data when the output data from the computer 13 is
raster image processed into raster bitmaps of the various print
layers 42-47. This has the advantage that operating on the data
with algorithms, e.g. to prepare print files, change scale, change
from Macintosh format to DOS format, is carried out before small
scale repetitive structures such as the transparent areas 48 are
introduced into the image data. Due to truncation errors, small
scale repetitive structures in digital data may suffer distortions
when operated on by algorithms. Such distortions may appear as
rhythmic changes of size or shape or loss of part of the image.
[0118] To protect the printing, a transparent overlaminate 49 may
be used which is preferably optically clear. It is preferred if the
overlaminate 49 is the optically clear sheeting in accordance with
the eleventh embodiment of the present invention.
[0119] In this application, overlaminate layer 49 refers to any
clear material that can be adhered to the surface of any existing
coated or uncoated sheet material. "Overlamination" refers to any
process of achieving this adherence, particularly without the
entrapment of air bubbles, creases or other defects that might
spoil the appearance of the finished article or image
[0120] The deleterious effects of ambient humidity may be slowed by
the overlamination of a transparent protective coat or sheet herein
referred to as an overlaminate. Overlamination has the further
advantage that the images are protected from scratching, splashes,
and the overlaminate can supply a high gloss finish or other
desired surface finish or design, and provide a degree of desired
optical dot-gain. The overlaminate layer 49 may also absorb
ultraviolet radiation or protect the underlayers and image from
deleterious effects of direct sunlight or other sources of
radiations. Overlamination is, for example, described in U.S. Pat.
No. 4,966,804.
[0121] After printing an image or design of the present invention,
the image is preferably overlaminated with a transparent colorless
or nearly colorless material 49. Suitable overlaminate layers 49
include any suitable transparent plastic material bearing on one
surface an adhesive. The adhesive of the overlaminate layer 49
could be a hot-melt or other thermal adhesive or a
pressure-sensitive adhesive. The surface of the overlaminate layer
49 can provide high gloss or matte or other surface texture.
Preferred overlaminate layers 49 are designed for external graphics
applications and include materials such as those commercially
available from 3M Company as Scotchprint.TM. 8910 Exterior
Protective Film, 8911 Exterior Protective Film, and 8912 Exterior
Protective Film. However, other films are available or could be
fabricated and the invention is not limited to those
exemplified.
[0122] In the absence of the use of a clear, transparent
overlaminate, a protective clear coat of a vinyl/acrylic material
may be applied, such as Product Nos. 3920, 8920, 9720, 66201, and
2120 protective coatings from the Commercial Graphics Division of
Minnesota Mining and Manufacturing Co. of St. Paul, USA to protect
the durable, imaged substrate. Such coating may be performed by
some printers at the end of the image printing process.
[0123] Pressure sensitive adhesives useful for layer 41 can be any
conventional pressure sensitive adhesive that adheres to both layer
41 and to the surface of the item upon which the sheeting 40 having
the permanent, accurate image is destined to be placed. Pressure
sensitive adhesives are generally described in Satas, Ed., Handbook
of Pressure Sensitive Adhesives 2nd Ed (Von Nostrand Reinhold
1989), the disclosure of which is incorporated by reference.
Pressure sensitive adhesives are commercially available from a
number of sources. Particularly preferred are acrylate pressure
sensitive adhesives commercially available from Minnesota Mining
and Manufacturing Company of St. Paul, Minn. and generally
described in U.S. Pat. Nos. 5,141,790, 4,605,592, 5,045,386, and
5,229,207.
[0124] Non-limiting further examples of pressure sensitive
adhesives useful with the present invention include those adhesives
described in U.S. Pat. Nos. Re. 24,906 (Ulrich); 2,973,826; Re.
33,353; 3,389,827;4,112,213; 4,310,509; 4,323,557; 4,732,808;
4,917,929; and 5,296,277 (Wilson et al.) and European Publication 0
051 935, the disclosures of which are incorporated by reference
herein. A presently preferred adhesive is an acrylate copolymer
pressure sensitive adhesive formed from a 90/10 weight percent
monomer ratio of 2-methylbutyl acrylate/acrylic acid in a 65/35
heptane/acetone solvent system (39-41% solids) and having an
inherent viscosity of about 0.7-0.85 dl/g.
[0125] Thickness of adhesive 318 can range from about 0.012 mm to
about 1 mm with a thickness of about 0.025 mm (1 mil) being
preferred.
[0126] The adhesive may be protected with an optional liner (not
shown) which can be constructed from any conventional release liner
known to those skilled in the art for image graphic media
Non-limiting examples include Polyslik.TM. release liners
commercially available from Rexam Release of Oak Brook, Ill. and
polyester liners such as a 0.096 mm polyethylene terephthalate film
with a matte backside coating on one major surface and on the other
major surface, a vanadium oxide/surfactant/sulfopolyester
antistatic primer coating and a condensation cure silicone exterior
coating. These antistatic coatings are generally described in U.S.
Pat. No. 5,427,835 (Morrison et al.), the disclosure of which is
incorporated by reference herein. Ideally the liner is optically
flat. The liner preferably has a Sheffield value between 1 and
10.
[0127] Non-limiting examples of further release liners include
silicone coated Kraft paper, silicone coated polyethylene coated
paper, silicone coated or non-coated polymeric materials such as
polyethylene or polypropylene, as well as the polymeric materials
coated with polymeric release agents such as silicone urea,
urethanes, and long chain alkyl acrylates, such as defined in U.S.
Pat. No. 3,957,724; 4,567,073; 4,313,988; 3,997,702; 4,614,667;
5,202,190; and 5,290,615; the disclosures of which are incorporated
by reference herein.
[0128] In accordance with the present invention the transparent
areas in the printing may be introduced after the RIP. The printer
20 or the intermediate imaging device 16 may be a "TLD" device
configured to introduce the transparent areas of the image. For
instance when printer 20 is an inkjet printer, the printer may be
configured so that no printing is carried out for the whole width
of a printing substrate at regular intervals. This produces a
series of parallel transparent areas.
[0129] Alternatively the printing head may be deactivated a
repeated number of times to produce a distribution of square or
rectangular transparent areas. If the printer 20 is an
electrostatic printer, portions of each printing head may be
missing or deactivated, which produces a series of longitudinal
transparent areas. Portions of the heads may be deactivated in
sequence to introduce square or rectangular transparent areas.
[0130] A TLD printer in accordance with the present invention may
be created by control of the printer 20 using the T layer data.
After raster image processing, the raster bit maps may be operated
on by a further algorithm using the T layer data which changes the
raster bit map such that transparent areas are produced when
printed. Such a modification may be done by a hard-wired circuit in
the printer 20 or by software run on a local processor in printer
20. Alternatively, the T layer data may be used to control the
printing head directly. For instance, for an ink jet printer the
print signals going to the printing head may be suppressed in
accordance with the T layer data to produce transparent areas at
the required positions.
[0131] In accordance with the fourth embodiment of the present
invention the silhouette pattern 2 and images 3 or 4 are printed
using ink-jet or bubble jet printing methods. Ink-jet printing
includes a variety of procedures including thermal ink-jet printing
and piezo-electric ink-jet printing. All these methods have in
common that discrete quantities of ink are sprayed from fine
nozzles towards a receptor sheet. Recently, wide format printers
have become commercially available, and therefore the printing of
larger articles such as large engineering drawings, blueprints and
color posters and signs has become feasible. Suitable receptor
sheeting for non-durable use may be transparent polyester marking
film 8501/8501H, supplied by Minnesota Mining and Manufacturing
Company. The optically clear, flexible vinyl substrate in
accordance with the eleventh embodiment is particularly preferred.
The formation of accurate inkjet images is provided by a variety of
commercially available printing techniques. A suitable large format
printer, including warranted clear films and inks is the Hewlett
Packard HP Design Jet 750C or 755CM printer, supplied by Hewlett
Packard Corporation of Palo Alto, Calif., USA, however, may other
brands are available. Non-limiting examples include thermal inkjet
printers such as DeskJet brand, PaintJet brand, Deskwriter brand,
DesignJet brand, and other printers commercially available from
Hewlett Packard Corporation as well as piezo type inkjet printers
such as those from Seiko-Epson, spray jet printers and continuous
inkjet printers. To perform the invention, additional cartridges
should be added to the printing head in addition to the usual four
colors, cyan, magenta, yellow and black. To print a black layer 42
and a white layer 43 of FIGS. 9 or 10, at least an additional white
station and black station are required. To obtain good opacity two
or more white or black cartridges may be added to the printing
head.
[0132] From the test results shown in Table 1, it can be seen that
ink jet printing provides highly accurate local registration
printing. Pigmented ink jet printing inks are available from the
Commercial Graphics Division of Minnesota Mining and Manufacturing
Company (3M). Generally, pigmented ink jet inks from 3M a
water-based pigmented ink which comprises a suspension of
commercially available pigment particles and a dispersant of a
formula of 1
[0133] wherein R is an alkyl, aryl, or aralkyl group obtained by
the removal of primary amino groups from alkyl, aryl, or aralkyl
amines;
[0134] m=1 to 6;
[0135] R.sup.3 and R.sup.4 are hydrogen or lower alkyl;
[0136] R.sup.5 is the residue of the nitrogen reactive compound
selected from the group consisting of acylating reagents, carbamoyl
halides, sulfamoyl halides, alkylating reagents, alkylating
(epoxide) reagents, iso(thio)cyanates, sulfonating reagents, and
aziactone reagents;
[0137] wherein R.sup.20 and R.sup.21 are independently, alkyl,
aryl, or aralkyl groups, or a cation selected from the group
consisting of a proton, lithium, sodium, potassium, ammonium, or
tetraalkyl ammonium.
[0138] Pigments for ink jet inks use the standard colors of cyan,
magenta, yellow, and black.
[0139] For black inks, carbon black can be used as the black
pigment. The selection of carbon blacks suitable for use with the
present invention is based primarily upon considerations of surface
oxidation (high "volatiles" preferred), and the degree of blackness
(also called jetness) of the pigment. Pigments that are acidic or
surface-treated provide suitable interaction sites for strong
dispersant adsorption. Pigments having a high surface oxide content
are more hydrophilic, and thereby much easier to disperse. Pigments
with a high degree of blackness or jetness provide a high quality
printed image.
[0140] For yellow inks, the use of nickel azo yellow pigment offers
several advantages. First, such pigments provide inks which are
highly durable in outdoor environments. Second, such pigments
contain nickel ions which may be able to form complex bonds with
the novel dispersants. Lastly, such pigments are believed to offer
a high degree of thermal conductivity. As a result, if particle
deposition onto a heater element does occur during the jetting
process, the deposited film will not significantly reduce the
heating efficiency of the ink, thereby allowing proper bubble
formation. For magenta inks, a primary consideration is
lightfastness, since it is very desirable to produce graphic images
that are adapted to outdoor applications. Quinacridone magenta
pigment is known to have excellent lightfastness, and therefore, is
one preferred magenta pigment.
[0141] For cyan inks, the considerations above, (i.e.,
lightfastness, durability, etc.), apply as well. As a variety of
satisfactory properties may be found using copper phthalocyanine as
a cyan pigment, inks comprising such pigments are one preferred
embodiment.
[0142] Preferably, pigmented ink jet inks can be prepared with
dispersants of the following formula. 2
[0143] Specific compositions of suitable dispersants are given in
the Table below.
2 Ex R* R.sup.3 R.sup.4 R.sup.5 R.sup.6 R.sup.7 R.sup.8 R.sup.9
R.sup.10 R.sup.11 n a R H H H CH.sub.3 CH.sub.3 C.sub.4H.sub.9 Na
Na H 2 0 b R H H H CH.sub.3 CH.sub.3 C.sub.8H.sub.17 Na Na H 2 0 c
R H H H CH.sub.3 CH.sub.3 C.sub.12H.sub.25 Na Na H 2 0 d R H H H
CH.sub.3 CH.sub.3 C.sub.18H.sub.37 Na Na H 2 0 e R H H H CH.sub.3
CH.sub.3 CH.sub.2CH.sub.2CH.sub.6CH.sub.5 Na Na H 2 0 f
C.sub.6H.sub.5CH.sub.2CH.sub.2 H H H CH.sub.3 CH.sub.3
C.sub.4H.sub.9 Na Na H 3 0 g N(CH.sub.2CH.sub.2).sub.3 H H H
CH.sub.3 CH.sub.3 C.sub.4H.sub.9 Na Na H 3 0 h R H H H CH.sub.3
CH.sub.3 R** C.sub.2H.sub.3 C.sub.2H.sub.5 H 2 0 j R H H H CH.sub.3
CH.sub.3 R*** C.sub.2H.sub.5 C.sub.2H.sub.5 H 2 0 *The aspartic
ester used in the preparation of the dispersant of examples a-e, h
and j was Desmophen .TM. XP 7059E, available from the Bayer
Corporation, Pittsburgh, PA. Desmophen .TM. XP 7059E contains a
short chain alkyl group. **The amine used in the ring opening
reaction to prepare dispersant of Example h was Jeffamine .TM.
M-600 [O-(2-aminopropyl)-O'-(m- ethoxyethyl)polypropylene glycol
500] (available from Fluka Chemical Corp. Ronkonkoma, NY). ***The
amine used in the ring opening reaction to prepare dispersant of
Example j was Jeffamine .TM. M-1000
[O-(2-aminopropyl)-O'-(2-methoxyethyl)copoly(ethylene, propylene
glycol 900] (available from Fluka Chemical Corp. Ronkonkoma,
NY).
[0144] In the practice and the field of the fifth embodiment, the
groups which are not directly involved in the reaction steps
forming the compounds of the present invention may be substituted
to meet desired physical property requirements in the final
dispersants. This is not only allowable, but may be highly
desirable or essential in the formation of tailored dispersants.
Where individual substituents may tolerate such broad substitution;
they are referred to as groups. For example, the term "alkyl group"
may allow for ester linkages or ether linkages, unsubstituted
alkyls, alkyls with such useful substitution as halogen, cyano,
carboxylic ester, sulfonate esters or salts, and the like. Where
the term "alkyl" or "alkyl moiety" is used, that term would include
only unsubstituted alkyls such as methyl, ethyl, propyl, butyl,
cyclohexyl, isooctyl, dodecyl, etc.
[0145] In addition to the pigments and dispersants described above,
the inks will comprise primarily water as a pigment suspension
agent. Such inks will typically also include further additives to
provide various properties. For example, an alcoholic polyol, may
be employed to control the drying rate of the ink. Suitable
alcoholic polyols include, for example, polyalkylene glycols such
as polyethylene glycol and polypropylene glycol, alkylene glycols
whose alkylene group has 2-6 carbon atoms, such as ethylene glycol,
propylene glycol, butylene glycol, triethylene glycol,
1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene
glycol; glycerol; and lower alkyl ethers of alcoholic polyols such
as ethylene glycol monomethyl or monoethyl ether, diethylene glycol
methyl or ethyl ether, and triethylene glycol monomethyl or
monoethyl ether. A surfactant, useful for wetting and reducing the
surface tension of the ink system, can be provided as well. In
addition to the above, other ink additives commonly known in the
art may also be used. These include, water-soluble organic
cosolvents, humectants, biocides, fungicides, defoamers, corrosion
inhibitors, viscosity modifiers, pH buffers, penetrants,
sequestering agents, and the like. Current compounding technology
for the processing of pigment dispersions employs numerous
processing technologies. One such technology makes use of
ultrasonic energy to achieve mixing and particle
deflocculation.
[0146] Another technology makes use of media mills, such as ball
mills, sand mills or attritors. Media mills achieve acceptable
pigment dispersions by subjecting the pigment mixture to high
intensity microshearing and cascading which breaks down
agglomerations of the pigment particles. However, media mill
processing systems often suffer from disadvantages including media
wear product contamination.
[0147] Additionally, if the flow rate in a media mill is raised
beyond a certain level, the resulting grinding and dispersion
becomes uneven, and much of the material leaves the system without
being sufficiently processed.
[0148] Problems associated with media milling systems can be
overcome, at least in part, using homogenizers and emulsifiers.
These systems generally function by forcing a premix of solids and
liquids to collide against a surface, or to collide against itself.
Unfortunately such high pressure devices are considered to be
unsuitable for processing pigment dispersions due to the abrasive
nature of the pigment particles and the relatively large size of
pigment agglomeration structures which can plug narrow gaps through
which such systems force the mixture being treated. Such clogging
can be avoided, at least in part, by filtration or preprocessing to
reduce the size of pigment agglomerations and to ensure sufficient
dispersion of the pigment prior to use of high pressure
processing.
[0149] In still another processing method, the pigment dispersion
can be forced through a series of small nozzles having diameters on
the order of about 150 micrometers to about 1000 micrometers. Such
systems must be able to withstand very high pressures at high fluid
velocities. Three different configurations for such systems may be
used: a) a "wedge" configuration with orifices of decreasing
diameter, b) a "wedge" configuration within which the orifices have
cavitation enhancement devices, and c) an "impinging jet"
configuration in which the dispersion stream is split into at least
two elements, each stream is passed through an orifice to create a
jet, and the jet streams are recombined by impinging them against
each other. Each of these systems has been found to yield
satisfactory results when processing water-based pigmented
inks.
[0150] After the ink has been processed using either of the "wedge"
configurations or the "impinging jet" configuration at a
concentration of about 15 % by weight, it is diluted with an
additional amount of deionized water and diethylene glycol to
produce a final ink concentration of about 4% concentration with a
given diethylene glycol-to-water ratio. In the dilution step, the
dispersion is mixed using a shear mixer (available, for example,
from Silverson Machines Inc., East Longmeadow, Mass.) at moderate
speed while water and diethylene glycol are sequentially added. The
addition of diethylene glycol is carried out slowly to prevent
flocculation of the dispersion.
[0151] Following the dilution step, the ink is filtered using, for
example, a 5 micron Whatman Polycap 36 HD cartridge type filter
(available from Arbor Technology, Ann Arbor, Mich.). A pump, such
as a Masterflex peristaltic pump (available from Barnant Co.,
Barrington, Ill.) can be used to feed the ink through the filter. A
flow rate of about 120 milliliters per minute with a back pressure
of about 3 psi is preferred. Further examples of suitable inks are
given in the co-pending US patent application also owned by
Minnesota Mining and Manufacturing Co. having attorney docket
number 52146USA4A, Ser. No. 08/556,336 and a PCT application ______
which claims priority therefrom, both of which are incorporated
herein by reference.
[0152] In accordance with the present invention the display device
4 of FIG. 1 may be a black or dark layer. This layer faces towards
the inside of a bus or building window to which the graphic has
been applied. It is preferable that this black layer is uniform and
that the graphic is durable, in particular water resistant.
[0153] Another ink jet formulation replaces the dispersants
previously described with water-soluble silicone polymers such as
poly(dimethylsiloxane)-g-poly(acrylate)s as additives in
water-based pigmented inks for ink jet printing, particularly
thermal ink jet printing. Further information about these ink jet
formulations can be found in copending, coassigned PCT patent
application serial no. ______ incorporated herein by reference.
[0154] Not only the inks but also the ink jet printing substrate is
preferably durable. In accordance with the seventh and eighth
embodiments, suitable durable receptor sheetings for durable ink
jet printed graphic products of the present invention will now be
described. Advantageously the articles of the seventh and eighth
embodiments accept pigment-based ink jet inks when the substrate is
comprised of weatherable plastic materials, allowing for heat and
light stable image constructions under such circumstances as are
found in exterior signing environments.
[0155] Referring to FIG. 11 an ink jet printing sheet (101) of the
present invention is illustrated comprising (a) an image receiving
layer (111-112) on (b) a substrate (110), wherein the sheet may
optionally have (c) a layer of adhesive (113) coated or laminated
to the substrate (110) on the surface away from the image receiving
layer (111-112). The adhesive layer (113) may or may not be backed
with release liner (114). In this embodiment (FIG. 11), the image
receiving layer (111-112) comprises at least two layers, wherein
one layer is a protective penetrant layer (112) and one layer is an
ink jet receptor layer (111).
[0156] Once the ink jet printing sheet has been imaged with ink jet
ink (shown as patches of dried ink containing pigment particles)
(115) using an ink jet printing process, the printed sheet (101)
may be overlaminated with a transparent protective layer (116). The
transparent protective layer (116) may be a transparent plastic
sheet bearing on one side a pressure-sensitive adhesive or hot-melt
(thermal) adhesive, or a clear coat, or a processing technique that
will affect the surface of the printed sheet (101).
[0157] Both ink jet receptor layer (111) and protective penetrant
layer (112) have particles (117) and (118), respectively, that
contribute to the performance of the printed sheet.
[0158] Typically, a release liner (114) comprises a paper or
plastic or other suitable sheet material coated or otherwise
treated with a release material such as a silicone or fluorocarbon
type material on at least one surface in contact with adhesive
layer such that adhesive layer adheres to release layer but is
easily removed from the release liner when desired so that the
adhesive layer is exposed.
[0159] Briefly, in one aspect of the seventh embodiment of the
present invention, an ink jet printing sheet is provided comprising
a substrate and an image receiving layer contacting the substrate,
wherein the image receiving layer comprises of at least one
protective penetrant layer of one composition and at least one ink
jet receptor layer of a second composition, and wherein the ink jet
receptor layer contains dispersed particles or particulates of a
size that causes protrusions from the protective penetrant layer.
Optionally, on the side of the substrate opposite from the image
receiving layer, in sequential order, is an adhesive layer and a
release liner.
[0160] An advantage of the seventh embodiment is an ink jet
printing sheet wherein the substrate and adhesive are durable for
periods of several years in an exterior environment where the
materials and images can be exposed to rain, sun, and such
variations in temperature as are found in exterior environments and
on surfaces in exterior environments. Typically, the articles of
the present invention have some flexibility such that it may be
adhered onto surfaces having some curvature or non uniformity e.g.
windows with screw heads or rivets, without easily ripping the
material or cracking or delamination of the image receiving layers,
overlaminating layers, other coatings or image or "tenting" of the
material over the protrusion.
[0161] The ink jet printing sheet provides useable images using
both dye-based and pigment-based ink jet inks suitable for use, for
example, in wide-format ink jet printers wherein both narrow or
wide images can be made by ink jet printing process The resultant
printed sheet is easily handleable without easy smearing of the
image and can be applied, when an adhesive layer is part of the ink
jet printing sheet, to a window, vehicle side or other surface
using techniques well known in the art without use of other devices
such as spray adhesives.
[0162] Finally, the articles of the seventh embodiment maintain
other desirable properties of an ideal ink jet printing sheet, such
as, dye bleed resistance and low background color. Good color
saturation and density are also observed in the printed images. The
printed articles do not curl excessively on exposure to humidity or
during the ink jet printing process, and printed images exhibit
quick ink drying times following printing with good image
sharpness.
[0163] Ink jet printing sheets are commercially available from the
Commercial Graphics Division of 3M. Ink jet printing sheets are
also described in PCT Publication WO 96/08377, which is
incorporated by reference herein.
[0164] Further embodiments are described in co-pending U.S. patent
application Ser. No. 08/554,256 and its corresponding PCT patent
application from claiming priority therefrom, both of which are
incorporated herein by reference.
[0165] In accordance with the present invention and shown
schematically in FIGS. 1, 7 and 8, six or seven layers of ink may
be printed with close registration to each other. It is preferable
if the inks are quick drying. The eighth embodiment of the present
invention addresses quick drying receptor materials for ink jet
printers. Further, ink receptor layers are not perfectly and a
method of improving the transparency would be preferable.
[0166] The eighth embodiment may provide in one aspect an inkjet
recording medium comprising a hydrophilic, microporous, polymeric
membrane having opposing major surfaces and a non-porous
hygroscopic layer residing on at least one major surface of the
membrane.
[0167] The hygroscopic layer provides a means for receiving an
inkjet image and retaining dyes and pigments contained in the
ink.
[0168] The hydrophilic, microporous, polymeric membrane provides a
means for durably supporting the hygroscopic layer containing the
inkjet image and also a means for diffusing the solvents contained
in the inks from the dyes and pigments retained in the hygroscopic
layer.
[0169] The combination of the hygroscopic layer and the
hydrophilic, microporous, polymeric membrane provides the means for
rapidly producing a precise inkjet image in a durable medium.
[0170] For purposes of this invention, "hydrophilic" means that the
contact angle of the liquid on the surface is less than 90 degrees.
For purposes of this invention, "hygroscopic" means the layer is
capable of being wet by a water-based blend of solvents and
surfactants used in inkjet inks, and the water-based blend is
absorbed by the layer. For purposes of this invention, "microporous
polymeric membrane" means a polymer film that contains an
interconnecting void structure. For purposes of this invention,
"non-porous layer" means a layer that does not contain an
interconnecting void structure. For purposes of this invention,
"hydrophilic microporous polymeric membrane" means a polymer film
whereby the capillary and surface tension forces of the water-based
liquids, such as a blend of solvents and surfactants, will cause
the liquid to be absorbed, i.e., to enter the pores of the
membrane. Preferably, the membrane will absorb water with less than
one atmosphere of pressure. For the purposes of this invention,
"precise" means that dot spread resulting from applying an ink jet
drop to the sheet is below a level at which the resolution of the
image is adversely affected. Examples without precise imaging might
show image bleed, uneven edges, or mottled colors.
[0171] In an eighth embodiment of the invention, inkjet recording
medium 210 of FIG. 12 is comprised of a hydrophilic, microporous,
polymeric membrane 212 having a hygroscopic layer 214 thereon. The
layer 214 can be coated on or laminated to the membrane 212 using
techniques known to those skilled in the art of coating or
laminating of multiple layered constructions. Non-limiting examples
of coating or laminating techniques include notched bar coating,
curtain coating, roll coating, extrusion coating, gravure coating,
calendering, and the like.
[0172] Hydrophilic, microporous, polymeric membrane 212 is
hydrophilic and receptive of aqueous solvents typically used in
inkjet formulations. Microporous membranes are available with a
variety of, pore sizes, compositions, thicknesses, and void
volumes. Microporous membranes suitable for this invention
preferably have adequate void volume to fully absorb the inkjet ink
discharged onto the hydrophilic layer of the inkjet recording
medium. It should be noted that this void volume must be accessible
to the inkjet ink. In other words, a microporous membrane without
channels connecting the voided areas to the hygroscopic surface
coating and to each other (i.e., a closed cell film) will not
provide the advantages of this invention and will instead function
similarly to a film having no voids at all.
[0173] Void volume is defined in ASTM D792 as the (1-Bulk
density/Polymer density)*100. If the density of the polymer is not
known, the void volume can be determined by saturating the membrane
with a liquid of known density and comparing the weight of the
saturated membrane with the weight of the membrane prior to
saturation. Typical void volumes for hydrophilic, microporous,
polymeric membrane 212 range from 10 to 99 percent, with common
ranges being 20 to 90%.
[0174] Void volume combined with membrane thickness determines the
ink volume capacity of the membrane. Membrane thickness also
affects the flexibility, durability, and dimensional stability of
the membrane. Membrane 212 can have a thickness ranging from about
0.01 mm to about 0.6 mm (0.5 mil to about 30 mils) or more for
typical uses. Preferably, the thicknesses are from about 0.04 mm to
about 0.25 mm (about 2 mils to about 10 mils).
[0175] The liquid volume of typical inkjet printers is
approximately 40 to 140 picoliters per drop. Typical resolution is
118 to 283 drops per centimeter. High resolution printers supply
smaller dot volumes. Actual results indicate a deposited volume of
1.95 to 2.23 microliters per square centimeter with each color.
Solid coverage in multicolor systems could lead to as high as 300%
coverage (using undercolor removal) thus leading to volume
deposition of 5.85 to 6.69 microliters per square centimeter.
[0176] Hydrophilic, microporous, polymeric membrane 212 has a pore
size that is less than the nominal drop size of the inkjet printer
in which the inkjet recording medium is to be used. The pore size
may be from 0.01 to 10 micrometers with a preferred range of from
0.5 to 5 micrometers with pores on at least one side of the
sheet.
[0177] The porosity, or voided aspect, of membrane 212 need not go
through the entire thickness of the membrane, but only to a
sufficient depth to create the necessary void volume. Therefore,
the membrane may be asymmetric in nature, such that one side
possesses the aforementioned properties, and the other side may be
more or less porous or non-porous. In such a case, the porous side
must have adequate void volume to absorb the liquid in the ink that
is passed through the hygroscopic layer 214.
[0178] Non-limiting examples of hydrophilic, microporous, polymeric
membranes include polyolefins, polyesters, polyvinyl halides, and
acrylics with a micro-voided structure. Preferred among these
candidates are a microporous membrane commercially available as
"Teslin" from PPG Industries as defined in U.S. Pat. No. 4,833,172
and hydrophilic microporous membranes typically used for
microfiltration, printing or liquid barrier films as described in
U.S. Pat. Nos. 4,867,881, 4,613,441, 5,238,618, and 5,443,727,
which are all incorporated by reference as if rewritten herein.
Teslin microporous membrane has an overall thickness of
approximately 0.18 mm, and the void volume has been measured
experimentally to be 65.9%. The ink volume capacity of the membrane
is thus 11.7 microliters per square centimeter. Therefore, this
membrane has sufficient void volume combined with thickness to
fully absorb the ink deposited by most inkjet printers, even at
300% coverage, without considering the amount retained in the
hygroscopic layer.
[0179] Membrane 212 can optionally also include a variety of
additives known to those skilled in the art. Non-limiting examples
include fillers such as silica, talc, calcium carbonate, titanium
dioxide, or other polymer inclusions. To obtain clarity these
fillers may be milled until their particle size is below the
wavelength of light. It can further include modifiers to improve
coating characteristics, surface tension, surface finish, and
hardness.
[0180] Hygroscopic layer 214 can be a coated layer or laminated
layer on that portion of membrane 212 upon which the inkjet image
is to be formed. Thus, layer 214 need not cover completely the
membrane 212. Nor need layer 214 cover both sides of membrane 212.
Layer 214 preferably lies substantially on the surface of membrane
212 and does not contact the inner pore surfaces of the membrane.
Depending on the ultimate purpose for the medium 210, at least one
side of membrane 212 may be covered at least in part by layer 214
and the other side may be scaled or coated with another material,
such as an anti-static coating, adhesive, barrier layer, strength
enhancing layer, etc.
[0181] Layer 214 can be constructed from a variety of naturally
occurring or synthetically constructed materials known to those
skilled in the art for providing an ink receptive surface.
Non-limiting examples of the materials used for forming layer 14
include polyvinyl alcohol, polyvinyl pyrrolidone, cellulose
derivatives such as carboxymethyl cellulose, polyethylene oxide,
water soluble starches and gums. In addition, inorganic fillers
such as silica, talc, calcium carbonate, titanium dioxide can be
beneficial to enhance handling, strength, wetting, or control
viscosity. Mordants, such as in U.S. Pat. Nos. 5,354,813 and
5,403,955 and color stabilizers can also be included.
[0182] Of these materials, hygroscopic, polymeric coatings are
preferred due to ease of manufacturing and performance to provide
an ink receptive surface for receiving and permanently contacting
and retaining dyes and pigments in a precise inkjet image. Of these
coatings, poly(N-vinyl lactams), polyethylene oxides, methyl and
propyl cellulose derivatives, and poly(vinyl alcohols) are
particularly preferred.
[0183] Hygroscopic layer 214 may be formed on membrane 212 using a
number of techniques, including coating, laminating, or
co-extrusion. When a hydrophilic coating solution is applied to the
membrane, solution viscosity and concentration will affect the
performance of the resulting inkjet recording medium. For example,
low viscosity coating solutions coated on membranes with very high
porosity and/or large pore size tend to fill the pores, resulting
in a coated membrane that is saturated with hygroscopic polymer and
has little or no coating on the surface. Membranes coated in such a
manner do not meet the requirements of this invention because the
imaged medium usually exhibits lower image density and contrast and
can dry more slowly.
[0184] Preferably, medium 210 after imaging can have the pore
structure of membrane 212 collapsed to provide transparency by a
post treatment such as heating or calendering, such as disclosed in
U.S. Pat. No. 5,443,727.
[0185] Further embodiments are given in co-pending U.S. patent
application Ser. No. 08/614,986 and a PCT patent application
claiming priority therefrom, both of which are incorporated herein
by reference.
[0186] Ninth and tenth embodiments of a direct printing method in
accordance with the present invention relate to electrostatic
printing. The term "electrostatic" is used for recording processes
in which a recording head is utilized to impose an electrostatic
pattern upon a recording medium, and in which a toner material is
subsequently attracted to, and affixed to the electrostatic
pattern. Processes of this type are employed for preparing
engineering graphics, artwork for advertisements, displays and the
like.
[0187] In a typical electrostatic imaging process, a recording head
which includes a linear array of a plurality of separately
chargeable electrodes, generally referred to as "nibs", is scanned
across a recording medium, and the nibs are selectively energized
to impose an electrostatic pattern upon the medium. The charged
medium is contacted with a toner, which typically comprises a
liquid containing a pigment or dye thereon. Excess toner is removed
from the medium, leaving toner only in the charged areas. The toner
is subsequently dried or otherwise fixed to produce a permanent
image. The process can be utilized for single color or full color
graphics and can be completed in a single pass across the medium or
in multiple passes across the medium.
[0188] The recording medium is an important component of the
electrostatic imaging system. The medium must be able to accept,
retain, and discharge the electrostatic pattern. The medium must
also be compatible with the toner system employed as well as the
particular imaging hardware, such as a single or multiple pass
electrostatic printer.
[0189] In accordance with the ninth embodiment of the present
invention electrostatic printing of media requires the printing of
electrostatic images on a dielectric paper construction followed by
transfer of that image to polymer films. Such conventional
electrostatic imaging is disclosed in U.S. Pat. No. 5,114,520 (Wang
et al.).
[0190] The dielectric paper construction typically comprises a
paper or paper-like substrate, a conductive layer coated on a major
surface of the substrate, a dielectric layer coated over the
conductive layer, and a release layer coated above, beneath, or
with the dielectric layer to assure that the image received above
the dielectric layer can be transferred to the final substrate upon
application of heat and pressure. A commercially available example
of this transfer process and the products to accomplish that
process is the Scotchprint.TM. Electronic Graphics System available
from Minnesota Mining and Manufacturing Company of St. Paul, Minn.
which is one direct printing method in accordance with the present
invention. A further suitable system for carrying out the present
invention is the printer DCS 5400 and associated inks, including
white and silver spot colors for the silhouette layer 2, available
from Raster Graphics Inc., San Jose, Calif., USA.
[0191] Both single pass and multipass electrostatic printers may be
used. Multipass printers have a single printing head and feed the
appropriate primary color to the head in each pass. In accordance
with the present invention the sequence of toners may be used to
print the sequence of colors described with reference to FIGS. 9
and 10: an initial dark layer 42, a light colored light restricting
layer 43 and CMYK layers 44 to 47 or vice versa. Single pass
machines have presently four or five printing heads arranged
parallel to each other in the longitudinal printing direction. In
accordance with the present invention conventional single pass
machines may be modified to run multipass. For instance, a four
head electrostatic printer may be modified to apply the dark layer
42 including printing registration marks along the longitudinal
edges of the printing substrate, and three identical layers of the
light restricting layer 43 on top of each other to increase the
opacity of this layer. In the second pass, the CMYK image layers 44
to 47 are applied using the registration marks to maintain
registration. Alternatively, a five head electrostatic printer may
be used to print the dark layer 42, the light restricting layer 43
and then CMY image layers 44 to 46 in one pass, using process (CMY)
black instead of the final black station. Due to the considerable
under color removal in accordance with the present invention, a
separate black (K, layer 47) is often not necessary.
[0192] A preferred transparent printing substrate, to which the
image is transferred from the electrostatic paper, is the optically
clear vinyl sheeting of the eleventh embodiment. Transfer of the
image from the electrostatic paper to the transparent substrate in
the laminator may result in some reduction of optical clarity of
the printing substrate in the transparent areas. This can be
corrected by running the printed substrate through the laminator
again after transfer of the image using an optically flat sheet as
a former such as polyester sheet. Polyester does not soften at
laminator temperatures so that there is no transfer of the image to
the polyester. One aspect of the tenth embodiment of the present
invention is the construction of a film for the direct printing of
electrostatic images.
[0193] In one aspect, the direct print film comprises a durable,
conformable, polymeric substrate having a conductive layer prepared
from a coating solution comprising conductive pigment and organic
solvent. Preferably, the conductive pigment in the conductive layer
has a bulk powder resistivity ranging from about 2 to about 15
Ohm-cm.
[0194] "Bulk powder resistivity" means electrical resistivity of
the bulk powder used in the conductive pigment according to the
following test described by E.I.
[0195] DuPont, one of the commercial suppliers of conductive
pigments. As described in Capano et al., "The Application of ZELEC
ECP in Static Dissipative Systems" (Du Pont Chemicals, Deepwater,
N.J. September 1992), a cylindrical cell, with electrodes at the
top and bottom is used to make bulk powder resistivity
measurements. A weighed amount of powder is placed into the cell
and then pressed with a laboratory press into a pellet. The
resistance between the two electrodes is then measured as a
function of the pressure applied and the thickness of powder
pellet. The bulk powder resistivities of Du Pont conductive
pigments commonly range from about 2 Ohm-cm to about 20 Ohm-cm
according to this test. Another supplier of conductive pigments,
Goldschmidt A. G. of Essen, Germany, identifies bulk powder
resistivity as "specific resistance" and employs a test method
available from Esprit Chemical Company of Rockland, Md. For
purposes of this application, the property of "bulk powder
resistivity" includes the concept of the property of "specific
resistance".
[0196] In another aspect, the direct print film comprises a
durable, conformable, polymeric substrate having on a major surface
a conductive layer coated thereon, and a dielectric layer coated on
the conductive layer, wherein the dielectric layer includes spacer
particles and abrasive particles. Spacer particles, which are
generally of a lower hardness than abrasive particles and/or have a
more rounded configuration than abrasive particles, function to
provide a roughness that maintains a relatively small gap between
the imaging head of the electrostatic printer and the remaining
surface of the direct print film. Abrasive particles function to
provide abrasivity to contact the imaging head of the electrostatic
printer in order to clean oxidation and other unwanted debris from
the imaging head.
[0197] Optionally, the direct print film has a field of pressure
sensitive adhesive coated on the other major surface of the direct
print film, protected by a release liner. The field of pressure
sensitive adhesive permits the direct application of the film
having an image printed thereon to be adhered to a final
location.
[0198] An advantage of the present invention is the ability to
eliminate manufacturing steps for the preparation of electrostatic
images on a final substrate.
[0199] An electrostatic direct printing film can have a surface
resistance in its conductive layer of about 2.times.10.sup.5 to
about 3.times.10.sup.6 Ohms/.quadrature. and can have a surface
resistance in its dielectric layer of greater than about
1.times.10.sup.8 Ohms/.quadrature.. This difference in surface
resistance results in clear, crisp images generated by the
electrostatic printer.
[0200] "Surface Resistance" is the measure of D-C resistance of
moderately conductive materials according to ASTM Test Designations
D 4496-87 and D 257-93.
[0201] Referring to FIG. 13, a typical construction of a film of
the present invention 310 comprises a substrate film 312 having on
a major surface thereof, a conductive layer 314 and a dielectric
layer 316. On the opposite major surface of film substrate 312
resides optional pressure sensitive adhesive 318 protected by a
release liner 320.
[0202] For electrostatic imaging on film 310, a conductive coating
layer 314 is provided from an organic solvent-based conductive
coating solution on the upper major surface of film substrate 312,
which can be any substrate described above for prior embodiments.
Electronically conductive layers employ a plurality of particles of
a transparent, electrically conductive material such as antimony
doped tin oxide or the like, disposed in a polymeric matrix.
Conductive layer 314 is prepared from a solution of a conductive
formulation that generally comprises a binder, conductive pigments,
dispersant, and organic-based solvent, the latter of which is
removed during the manufacturing process. The weight percent of
solids to organic solvent in the conductive formulation can range
from about 10 to about 40, with about 25 weight percent being
presently preferred for ease of application to film substrate
312.
[0203] After coating of conductive formulation on film substrate
312 and evaporation or other removal of organic solvent, the
thickness or caliper of the conductive layer 314 can range from
about 2 to about 5 .mu.m with about 3 .mu.m being presently
preferred.
[0204] Non-limiting examples of binders include acrylics,
polyester, and vinyl binders. Among acrylic binders, carboxylated
acrylate binders and hydroxylated acrylate binders are useful for
the present invention, such as those commercially available from
Allied Colloids of Suffolk, Va. such as "Surcol SP2" carboxylated
acrylate binder and "Surcol SP5 hydroxylated acrylate binder. Among
some of the polyesters materials which can be employed as binders
are materials sold by Goodyear of Akron, Ohio under the brand
"Vitel", of which grades PE222 and PE200 are particularly suitable
for use in the present invention. Also vinyl resins such as "UCAR"
"VAGD" brand resins from Union Carbide of Danbury, Conn. can also
be useful.
[0205] Conductive pigments can include antimony-containing tin
oxide pigments or other pigments such as indium doped tin oxide,
cadmium stannate, zinc oxides, and the like.
[0206] Non-limiting examples of antimony-containing tin oxide
conductive pigments include those pigments disclosed in U.S. Pat.
No. 5,192,613 (Work, III et al.), U.S. Pat. No. 4,431,764
(Yoshizumi); U.S. Pat. No. 4,965,137 (Ruf); U.S. Pat. No. 5,269,970
(Ruf et al.); and in product literature for "Tego S" pigments
commercially available from Goldschmidt AG of Essen, Federal
Republic of Germany and "Zelec" pigments commercially available
from DuPont of Wilmington, Del. Generally particle size should be
reduced by a milling process particularly when the Goldschmidt Tego
S conductive pigment is employed. Pigments are preferably milled
until the particle size is smaller than the wavelength of visible
light. Scattered transmittance of conductive layer 314 should be
10% or lower.
[0207] Particle size of the conductive pigments in the conductive
layer 314 can range from about 0.02 to about 0.4 .mu.m. Below about
0.02 .mu.m particle size, the conductive pigment is too easily
imbibed with solvent action, whereas at greater than 0.4 .mu.m, the
conductive layer 314 may affect transparency.
[0208] Preferably, the average particle size can range from about
0.05 .mu.m to about 0.2 .mu.m, with particles of about 0.1 .mu.m
being most preferred.
[0209] The bulk powder resistivity can range from about 2 to about
15 Ohm-cm with about 2 to about 10 Ohm-cm being preferred and about
6 to about 7 Ohm-cm being presently preferred. With the DuPont
pigments, the bulk powder resistivity can be about 2-5 Ohm-cm for
"Zelec 3410-T" pigments and 4-15 Ohm-cm for "Zelec 2610-S" found
acceptable for the present invention. The bulk powder resistivity
has been found to be important in controlling the final appearance
of the image on the direct print film because materials that are
too resistive require the use ol a larger amount of conductive
pigment can cause an objectionable amount of background color in
the final image.
[0210] The "Tego S" particles are identified to have a specific
resistance of 10, which is believed to compute to about bulk powder
resistivity of about 10.
[0211] A variety of surfactant materials can be employed as
dispersants for the conductive layer 314 in the present invention,
including nonionic and anionic dispersants In general, anionic
dispersants are most preferred, although the invention is not
limited thereto. One particularly preferred anionic dispersant is a
material branded "Lactimon" dispersant from BYK-Chemie USA
Corporation of Wallingford, Conn. Also commercially available from
BYK-Chemie USA Corporation is a nonionic dispersant is branded
"Anti Terra U" dispersant.
[0212] Non-limiting examples of solvents for the conductive
formulation include ethyl acetate and ethanol.
[0213] Formulations of the conductive layer 14 require a weight
ratio from about 5:1 to about 1:1 of pigment:binder with a
preference of a weight ratio of 3:1 pigment:binder. When "Tego S"
conductive pigment is employed, the weight ratio can range from
about 3.0:1 to about 4.7:1 pigment: binder. When the DuPont "Zelec"
conductive pigment is employed, the weight ratio can range from
about 1:1 to about 4:1 pigment:binder.
[0214] When the pigment to binder ratio falls below 1:1, there is
inadequate bulk conductivity of layer 314. When the weight ratio of
pigment:binder exceeds about 5:1, there is insufficient cohesive
strength of the layer 314 on film substrate 312.
[0215] Dielectric layer 316 can be coated on conductive layer 314
to provide the electrostatic capacitance required for electrostatic
imaging.
[0216] The dielectric layer 316 is of relatively high electrical
resistivity and contributes to the performance of film 310 for
direct printing of images electrostatically. In addition to
providing the interface of film 10 with the recording head and
toner, dielectric layer 316 covers and protects conductive layer
314 and provides the top surface for film 310.
[0217] Dielectric layer 316 is coated on layer 314 from a
dielectric formulation that comprises particulate matter of both
spacer particles and abrasive particles, preferably in particular
ratios dispersed in a binder.
[0218] Both the spacer particles and the abrasive particles should
be selected with consideration to the refractive index thereof, so
as to provide index matching to the remainder of dielectric layer
316 and film 310. In this manner, film 310 has a uniform
transparent appearance. The spacer particles can be fabricated from
a material having sufficient rigidity to withstand coating and
handling, but need not be highly abrasive. Non-limiting examples of
materials useful as spacer particles include relatively soft
materials such as a polymer or a mineral or relatively hard
materials such as silica or glass, provided that such relatively
hard materials have a relatively rounded configuration. More
particularly, useful spacer particles can be made from synthetic
silicas, glass micro beads, natural minerals, polymeric materials
such as polypropylene, polycarbonate, fluorocarbons or the
like.
[0219] Typically spacer particles have an average size ranging from
about 1 to about 15 .mu.m, and preferably below about 10 .mu.m. In
general, spacer particles will be present in a distribution of
sizes, although it is most preferred that the particles remain in a
size range of about 3-10 .mu.m. To improve transparency particle
sizes may be reduced to 0.4 .mu.m or below.
[0220] One particularly preferred group of spacer particle
materials comprise amorphous silica, of which is most preferred the
synthetic, amorphous silicas sold by the W. R. Grace Corporation
under the brand "Syloid 74". These materials have an average
particle size of approximately 3.5-7.5 .mu.m as measured on a
Coulter apparatus and an average particle size of 6-10 .mu.m as
measured on a Malvern analyzer. One specific member of this group
of materials comprises "Syloid 74 X-Regular" particles which have
an average particle size of 6.0 as measured on a Coulter
apparatus.
[0221] Abrasive particles useful for dielectric layer 316 of the
present invention are provided to assure that the performance of
spacer particles and abrasive are effectively decoupled so as to
provide an optimized dielectric medium.
[0222] The abrasive particles will generally be harder than the
spacer particle material chosen and will usually have a more
irregular configuration or texture than the spacer particle
material. Among some of the preferred abrasive materials are silica
materials such as microcrystalline silica and other mined or
processed silicas, as well as other abrasives such as carbides and
the like.
[0223] The abrasive particles generally have the same size range as
the spacer particles, typically in the range of about 1 to about 15
.mu.m and preferably less than 10 .mu.m.
[0224] One particularly preferred group of abrasive materials
comprises mined, microcrystalline silica sold under the brand
"Imsil" by Unimin Specialty Minerals, Inc. of Elko, Ill. These
materials comprise 98.9% silica with minor amounts of metal oxides.
One grade having particular utility comprises "Imsil A-10" which
has a median particle size of 2.2 .mu.m, and range of particle
sizes such that 99% of the particles have a size less than 10 .mu.m
and 76% of the particles have a size of less than 5 .mu.m
[0225] The proportion of spacer particles to abrasive particles are
such that the spacer particles are present in a larger amount.
Preferably, the ratios of spacer to abrasive particles fall within
the range of about 1.5:1 to about 5.1. Most preferably, the ratio
of spacer to abrasive particles is approximately 3:1.
[0226] The spacer particles and abrasive particles are disposed is
a binder which generally comprises a polymeric resin. The resin
should be of fairly high electrical resistivity, and should be
compatible with both types of particles and the toner. The resin
should have sufficient durability and flexibility to permit it to
function in the electrostatic imaging process and should be stable
in ambient atmospheric conditions and transparent.
[0227] There are large number of resins that meet these criteria.
One preferred group of materials are the acrylic copolymers of the
type commercially available from Rohm and Haas of Philadelphia, Pa.
under the brand "Desograph-E342-R".
[0228] A coating mixture to prepare dielectric layer 316 can employ
solvents such toluene into which the binder, spacer particles, and
abrasive particles can be added as solids. The range of total
solids in the coating mixture can be from 10 to about 35 and
preferably about 15 to 25 weight percent of the total coating
mixture. Of the total solids, the binder solids can comprise from
about 93 to about 78 and preferably 82 weight percent. Of the total
solids, the particles solids (preferably in a 3:1 spacer:abrasive
mixture) can comprise from about 7 to about 22 and preferably 18
weight percent.
[0229] The particle solids for the coating mixture can be blended
by ball milling for approximately two hours at room temperature.
Under these conditions, there is no significant reduction in
particle morphology, and the ball milling process only serves to
mix and disperse the particles. Other processes could be
employed.
[0230] There is a conflict between the need for surface roughness
for good printing and a need for a smooth surface to provide good
transparency. Surface roughness is desired to provide topography
for deposition of toner particles is based on a Sheffield
measurement method described in TAPPI Test T 538 om-88 published by
the Technical Association of the Pulp and Paper Industry of
Atlanta, Ga., incorporated herein by reference. For printing, the
dielectric layer 316 should have a surface roughness ranging from
about 50 to about 200 Sheffield units and preferably from about 80
to about 180 with 140 being presently preferred. On the other hand,
a surface with less than 10 Sheffield units is preferred for
transparent, particularly optically clear areas in the print.
According to the present invention it is preferred to print onto a
surface of 50 to 80 Sheffield units (lower end of the acceptable
range) and then to subject the finished print to a post-print
callendering process using an optically flat former such as an
optically clear polyester film.
[0231] Referring again to FIG. 13, a pair of electroconductive
ground stripes 322 and 324 can be provided in order to aid in the
prevention of "leading edge fog" by providing an avenue for
residual charge to be eliminated from the ground plane. These
stripes 322 and 324 ranging from about 0.76 to about 2.54 mm wide
are applied to dielectric layer 316 at opposing lateral edges of
film 310.
[0232] Stripes 322 and 324 can be made from a conductive ink sold
under the brand "Multifilm, Conductive Black Ink 9093E20J" from
Raffli and Swanson of Wilmington, Mass. and are configured to
permeate dielectric layer 316 at such lateral edges of film in
order to provide an electrical ground to the conductive layer
312.
[0233] Thus, a film 310 of the present invention can have in
sequential order, a release liner 320 comprising from about 0.07 to
about 0.15 mm (about 3 to about 6 mils) thickness, a field of
pressure sensitive adhesive 318 comprising about 0.03 mm (about 1
mil) thickness, a film substrate 312 comprising from about 0.05 to
about 0.10 mm (about 2 to about 4 mils) thickness, a conductive
coating layer 314 comprising from about 1 to about 5 micrometers
(0.04-0.2 mils), a dielectric layer 316 comprising from about 2 to
about 4 micrometers (0.08-0.16 mils) thickness, and a pair of
electroconductive ground stripes 322 and 324 at lateral edges of
film 310 that permeate layer 316 to layer 314.
[0234] A preferred method of constructing films of the present
invention comprises a modular construction, but can comprise a
sequential construction. In the sequential construction, beginning
with release liner 320, each of the layers 318, 316, 314 and 312
are built on top of release liner 320.
[0235] Preferably, the method of the present invention employs a
modular construction wherein the first step is the casting of a
film organosol onto a temporary release liner, preferably an
optically flat release liner in accordance with the eleventh
embodiment of the present invention, followed by fusing the
organosol to form a substrate 312 according to techniques known to
those skilled in the art. In an independent module, the field of
pressure sensitive adhesive 318 is cast on release liner 320,
preferably an optically flat liner in accordance with the eleventh
embodiment of the present invention and the techniques described
later. Then, the module of film substrate 312 on the temporary
liner is joined with the module of field of pressure sensitive
adhesive 318 on liner 318 and the temporary liner is discarded.
[0236] Alternatively, one can employ a commercially available
pressure sensitive adhesive-backed polymeric film in substitution
for the above described modular construction.
[0237] Conductive layer 314 can be coated on film substrate 312
using any technique known to those skilled in the art, preferably a
wire bar coating technique as known to those skilled in the art.
The # wire bar of from about 6 to about 40 is used to achieve the
1-5 micrometer thickness described as suitable for layer 314, with
a #10 wire bar being useful for DuPont conductive particles and a
#12 to #40 wire bar being useful for Tego conductive particles. The
wire bar coating process step can operate at a line speed ranging
from about 9 meters per minute to about 19 meters per minute and
preferably about 12 meters per minute (40 feet per minute).
[0238] Dielectric layer 316 is coated on conductive layer 14
according to coating techniques known to those skilled in the art,
preferably a reverse gravure coating of the dielectric layer 316
onto conductive layer 314. In those instances where a wire bar is
utilized, the total solids are preferably about 16 weight percent.
Where a reverse gravure process is employed, the total solids are
preferably about 25 weight percent. The ruling mill cylinder having
a theoretical "lay down" factor of about 0.031 mm to about 0.078 mm
is used to achieve the 1.5-5 micrometer thickness described as
suitable for layer 316 with 3 micrometer thickness being preferred.
The reverse gravure coating process step can operate at a line
speed ranging from about 1.5 to about 62 meters per minute, and
preferably about 15 meters per minute. The reverse gravure can
operate at a roll ratio ranging from about 0.5 to about 1.5, and
preferably about 1.0.
[0239] When ground stripes 322 and 324 are employed, such stripes
can be applied to lateral edges of film 310 using techniques known
to those skilled in the art, preferably an offset gravure or
flexographic coating of stripes 322 and 324. Stripes 322 and 324
permeate layer 316 at such lateral edges to create a ground path
from stripes 322 and 324 to layer 314. The offset gravure or
flexographic coating process step can operate at a line speed
ranging from about 12 meter per minute to about 31 meters per
minute, and preferably about 15 meters per minute (50 feet per
minute).
[0240] After imaging, film 310 can be protected with overlaminate
films as has been described previously. The overlaminating film of
the eleventh embodiment of the present invention is particularly
preferred.
[0241] Films 310 of the present invention can provide an average
color density as measured according to a "Reflective Optical
Density of a Status T Method" under the requirements of ANSI/ISO
5/3-1984, ANSI PH2. 18-1985 published by the Graphic Communications
Association of Arlington, Va. of from about 1.0 to about 1.6 O.D.
Units. Preferably, the average color density ranges from about 1.3
to about 1.5 O.D. Units. These values show that films 310 of the
present invention has an excellent color imaging capability after
electrostatic printing directly onto film 310 using electrostatic
printers otherwise used for the processes described in Wang et al.
and Chou et al. above.
[0242] Before calendering, films 310 of the present invention can
provide a 60.degree. Gloss from about 10 to about 30. 60.degree.
Gloss can be measured as described in ASTM D2457-90 (1990). After
post-print calendering, transparent areas of film 310 may have a
60.degree. Gloss of 100 to 150. Further embodiments are given in
co-pending U.S. patent application Ser. No. 08/581,324 which is
incorporated herein by reference.
[0243] Sheeting for overlaminates and printable substrates for use
in the embodiments in accordance with the present invention are
preferably flexible, weather resistant and optically clear. A
suitable substrate is a vinyl sheeting in accordance with an
eleventh embodiment of the present invention. Optionally the
sheeting may be provided with an optically clear adhesive.
[0244] While the optically clear, transparent overlaminates and
printing substrates known in the art and mentioned above are quite
acceptable for large format graphics uses, vinyl-based optically
clear, transparent overlaminate and printing substrate films remain
extremely elusive to achieve.
[0245] One aspect of the eleventh embodiment of the present
invention is an inexpensive, durable, optically clear, transparent
layer formed on a polymeric release liner that has preferred
surface properties to permit the layer of the present invention to
have optical clarity within acceptable ranges.
[0246] This layer in accordance with the eleventh embodiment of the
invention comprises a composition comprising vinyl chloride resin,
optional acrylic resin, optional plasticizer, and optional
stabilizer, wherein the composition is formed on a polymeric
release liner having thickness values from about 0.05 mm (0.002
inches) to about 0.12 mm (0.005 inches).
[0247] The method of forming the layer comprises the steps of:
forming the optically clear, transparent layer having two major
surfaces from an organosol on a first polymeric release liner
having a thickness ranging from about 0.05 mm (0.002 inches) to
about 0.127 mm (0.005 inches); optionally adhering a field of
pressure sensitive adhesive to a second release liner; and
optionally laminating the field of pressure sensitive adhesive to
an exposed major surface of the optically clear, transparent layer;
and optionally removing the first polymeric release liner.
[0248] An advantage of the eleventh embodiment is the ability of
the durable, optically clear, transparent layer to provide
stabilization and protection from abrasion and ultraviolet light
degradation. As shown in FIG. 9, the printing layers 42 to 47 on
printing substrate 41 may be protected by an overlaminate 49 which
may be the overlaminate in accordance with the eleventh embodiment.
However, the vinyl layer in accordance with the eleventh embodiment
may also be the printing substrate and overlaminate 41 of FIG. 10
which is adhered to a substrate such as a glass window by adhesive
50 with the image 42-47 therebetween. Therefore, the present
invention not only includes printing on to the vinyl layer in
accordance with the eleventh embodiment but also includes a method
of protecting an image in accordance with the present invention,
comprising the steps of forming a layer of the eleventh embodiment
on a polymeric release liner; and laminating the layer of the
eleventh embodiment over the image.
[0249] FIG. 14 shows a preparation composite 410 comprising a
durable, optically clear, transparent layer 412 of a thermally
processable organosol composition on a polymeric release liner 414
having smooth surface properties helpful in the formation of the
optical clarity properties of layer 412.
[0250] Liner 414 can be made-from a polymeric release liner
material known to those skilled in the art that has a surface
roughness, measured according to Haggerty Sheffield (see above), of
from about 1 to about 10 Sheffield units. Selection of the liner
414 should recognize the nature of the surface of liner 414
contacting layer 412 will determine the appearance of the outer
surface of layer 412 on the durable, imaged substrate. Non-limiting
examples of release liners include silicone coated polyester, urea
alkyd coated polyester, and the like. Particularly preferred for
release liner 414 is a urea alkyd coated polyester having a urea
polymer coating comprising a polyurea alkyd formulation of 0.005 mm
caliper on a 0.07 mm polyester film.
[0251] Release liner 414 can have a gloss ranging from about 100 to
about 150 and preferably from about 120 to about 140. Gloss is
measured by a Gardner 60.degree. Glossmeter using published
techniques known to those skilled in the art such as ASTM Standard
No. D523.
[0252] Durable, optically clear, transparent layer 412 comprises a
thermally processable composition containing vinyl chloride,
optional additional thermally processable resins, an optional
plasticizer, and an optional stabilizer where the layer can be
prepared from an organosol with a sufficient melt temperature to be
thermally processable to cause layer 412 to form on the polymeric
release liner 414 without causing harm to the surface of liner 414
responsible for formation of the optical clarity properties of the
layer 412.
[0253] Vinyl chloride is an industrial chemical commercially
available from many sources throughout the world. Preferably, the
vinyl chloride useful in the present invention is a vinyl chloride
resin comprising Geon vinyl chloride resin commercially available
from B. F. Goodrich Chemical Company of Cleveland, Ohio.
[0254] When used as another, but optional resin, in the formation
of layer 12, acrylic resin is readily available as an industrial
chemical commercially available from many sources throughout the
world. Desirably, the acrylic resin useful in layer 12 comprises
from about 75,000 to about 125,000 number average molecular weight.
Preferably, the acrylic resin useful in the present invention is an
acrylic resin comprising Elavacite acrylic resin having about
100,000 molecular weight commercially available from ICI Resins of
Wilmington, Del.
[0255] Optionally, the composition for layer 412 comprises a
plasticizer to aid in the formation of layer 12 and its transfer to
a durable, imaged substrate. Non-limiting examples of plasticizer
include 1,4-butylene glycol; adipic acid; butyloctyl phthalate;
hydrocarbon resins; di(2-ethylhexyl) azelate; dibutyl azelate;
dihexyl azelate; and the like. Particularly preferred for a
plasticizer, if present in the composition of layer 12, is Vikoflex
7170 plasticizer commercially available from ATOChem of
Philadelphia, Pa.
[0256] Optionally, the composition for layer 412 comprises a
stabilizer to aid in the formation of layer 412, provide
ultraviolet resistance, and assist transfer to a durable, imaged
substrate. Non-limiting examples of stabilizer include Hal-Lub,
Hal-Base, Hal-Carb, Hal-Stab brand hindered amine light stabilizers
commercially available from Hal-stab Company of Hammond, Ind.;
Nuostabe V1923 brand ultraviolet light stabilizer commercially
available from Witco of Greenwich, Conn.; Cosorb brand ultraviolet
light stabilizer commercially available from 3M Company of St.
Paul, Minn.; and Tinuvin brand HAL stabilizers commercially
available from Ciba-Geigy Corp. of Greensboro, N.C. Particularly
preferred for a stabilizer, if present in the composition of layer
12, is Tinuvin 1130 and Tinuvin 292 HAL stabilizers from Ciba-Geigy
or Nuostabe V1923 stabilizer.
[0257] The layer 412 can have a composition ranging from about 40
to about 60 weight percent of vinyl chloride, from about 10 to
about 30 weight percent acrylic resin, from about 0 to about 33
weight percent plasticizer, and from about 0 to about 10 weight
percent stabilizer.
[0258] Desirably, layer 412 can have composition ranging from about
45 to about 55 weight percent of vinyl chloride, from about 15 to
about 30 weight percent acrylic resin, from about 0 to about 20
weight percent plasticizer, and from about 0 to about 8 weight
percent stabilizer.
[0259] Preferably, layer 412 can have composition ranging from
about 47 to about 60 weight percent of vinyl chloride, from about
16 to about 27 weight percent acrylic resin, from about 10 to about
21 weight percent plasticizer, and from about 2 to about 6 weight
percent stabilizer.
[0260] Composition for layer 412 can be prepared by dissolving the
ingredients into solvents such as ketones and aromatics, preferably
Di-isobutyl ketone, mineral spirits, methyl ethyl ketone, methyl
isobutyl ketone and toluene, more preferably in equal parts of such
solvents. Layer 412 is knife or gravure coated on liner 414 with a
dry coating weight ranging from about 0.70 to about 1.10 g to yield
a dry thickness of from about 0.04 ml (0.0015 inches) to about 0.08
mm., (0.0030 inches). Preferably, liner 414 has a thickness ranging
from about 0.5 mm (0.002 inches) to about 1 mm and layer 412 has a
thickness ranging from about 0.5 mm (0.002 inches) to about 1
mm.
[0261] After coating, layer 412 is dried on liner 414 to remove
solvents at a temperature ranging from about 90.degree. C. to about
120.degree. C. for about 2 minutes, then it is fused in an oven for
30 seconds to 60 seconds at 175.degree. C. to 205.degree. C.
Composite 410 is then stored until usage, optionally, but
preferably as a portion of a lamination with a field of pressure
sensitive adhesive (PSA) and a second release liner protecting the
PSA field.
[0262] FIG. 15 illustrates a laminated composite 420, formed from
the lamination of a PSA field 416 (protected by second release
liner 418) laminated to a major surface of layer 412 opposite
polymeric release liner 414.
[0263] Field 416 and liner 418 are combined in a separate step
prior to lamination according to techniques well known to those
skilled in the art.
[0264] Field 416 can be any conventional pressure sensitive
adhesive that has optical clarity at least as good as and
preferably better than the optical clarity properties of layer 412.
Non-limiting examples of such adhesives include polyacrylates,
polyvinyletliers, natural rubber, silicone, rubber, styrene
butadiene, cis-polybutadiene, styrene-isoprene block copolymers.
Preferably, adhesives used include vinyl acrylic blends having a
weight percent ratio ranging from about 50/50 to about 90/10 and
preferably about 75/25 and a viscosity of 1100-1500 centipoise.
[0265] Field 416 can have a laminated thickness of from about 0.013
mm to about 0.05 mm, and preferably from about 0.015 to about 0.03
mm.
[0266] Release liner 418 can be made from a release liner material
known to those skilled in the art. Preferably, the release liner
material 418 has a surface roughness, measured according to
Haggerty Sheffield of from about 5 to about 40 Sheffields.
Selection of the liner 418 will affect the appearance of layer 412
and PSA field 16 during storage and prior to usage, which may be
material to customer preference for the layer of the present
invention. Non-limiting examples of release liners include silicone
coated polyester, silicone coated paper, urea alkyd coated
polyester, urea alkyd coated paper, and the like. Particularly
preferred for release liner 418 is a silicone coated polyester
commercially available from Rexani Release of Oak Brook, Ill.
having a silicone coating of 0.005 mm caliper on a 0 07 mm
polyester film.
[0267] Release liner 418 can have a gloss ranging from about 80 to
about 130 and preferably from about 100 to about 130. Gloss is
measured by a Gardner 60.degree. Glossmeter using published
techniques known to those skilled in the art such as ASTM Standard
No. D523.
[0268] After lamination of PSA field 416 to layer 412, first
polymeric release liner 414 can be removed prior to storage and
use.
[0269] FIG. 16 illustrates the cross-sectional appearance of final
composite 430 composed of layer 412 having PSA field 416 adhered to
a major surface thereof and also adhered to a substrate 422 having
an image 424 on the major surface thereof to which field 416 is
adhered. Layer 412 and PSA field 416 contact a major surface of
substrate 422 without enveloping substrate 422. Preferably,
substrate 422 has image 424 on one major surface and a field 424 of
adhesive (not shown) on the opposing major surface. Image 424 is
formed in accordance with the present invention.
[0270] Image 424 can comprise dyes, pigments, or combinations of
both from toners, inks, or paints, all as known to those skilled in
the art, in particular those described in embodiments of the
present invention.
[0271] Preferably, image 424 comprises compositions capable of
withstanding processing temperatures of at least about 100.degree.
C., and preferably at least about 105.degree. C. This film surface
is receptive to most inks, pigments, toners, dyes, and paints.
[0272] Substrate 422 can be any transparent substrate known to
those skilled in the art of image graphics. Non-limiting examples
include transparent glass, transparent acrylic sheets and
transparent polycarbonate sheets. Substrate 422 may be the window
of a building or vehicle.
[0273] Layer 412 and PSA field 416 are transferred from liner 418
on composite 420 to image 424 and substrate 422 by application of
pressure of a range sufficient to adhere PSA field 416 to substrate
422 and preferably from about 1 kg. to about 5 kg.
[0274] Layer 412 and PSA field 416 can have a combined caliper of
from about 0.05 mm (0.002 inches) to about 0.13 mm when adhered to
image 424 and substrate 422. Preferably, the caliper ranges from
about 0.10 mm to about 0.13 mm
[0275] After layer 412 and PSA field 416 are applied to image 424
and substrate 422, liner 18 can be removed, rolled, and can be
recycled for later use.
[0276] Machinery conventionally used in the formation of durable
imaged substrates can be used for the pressure sensitive transfer
of layer 412 to substrate 422. Non-limiting examples of machinery
include laminators such as Scotchprint.TM. 9540 and 9542 brand
laminators from 3M Company.
[0277] FIG. 17 illustrates a twelfth embodiment of the present
invention where an image 426 is placed on layer 412 of composite
410 prior to adhering of PSA field 416. Transfer layer 412 and PSA
field 416, with image 426 between layer 412 and PSA field 416, is
adhered to a substrate 422 (with or without a second image 424 as
seen in FIG. 17) to become final composite 430. In this embodiment,
an electrostatic imaging transfer process can be used such as the
Scotchprint.TM. Electronic Imaging system and electrostatic imaging
paper, such as No. 8601 image transfer paper, both commercially
available from Minnesota Mining and Manufacturing Co. St. Paul,
USA, to place a 4-color design and silhouette pattern layer toner
image from the electrostatic paper onto layer 412. Optionally, a
PSA field 416 is adhered and the liner 414 is pealed away leaving
image 426 on layer 412 for lamination transfer to a desirable
durable film. Alternatively, any of the printing methods of the
embodiments of the present invention, e.g. ink-jet or thermal
transfer, may be used to print the image onto layer 412. Thermal
mass transfer printing in accordance with the thirteenth embodiment
is particularly preferred.
[0278] Use of layer 412 provides abrasion and ultraviolet light
protection to image 424, image 426, or both, and substrate 422.
[0279] Abrasivity for layer 412 of the present invention before the
image 424 wears away ranges from about 500 to about 2000 cycles
with CS-10 abrasion wheels commercially available from Taber
Industries of Tonowanda, N.Y. and preferably from about 500 to
about 1000 cycles, depending the type of substrate used
[0280] Layer 412 provides protection to image 424 and substrate 422
without detracting from the appearance of the image. Layer 418 is
optically clear, transparent as determined by visual perception.
Preferably, optical clarity gives acceptable vision when measured
with a standard vision test with and without the film between one's
eyes and the vision chart.
[0281] A protective clear layer was prepared on an urea alkyd
coated polyester having a urea polymer coating comprising a
polyurea alkyd formulation of 0.005 mm caliper on a 0.07 mm
polyester film from the following components.
[0282] 46.7 weight percent Geon 178 vinyl resin (B. F. Goodrich,
Cleveland, Ohio); 17.9 weight percent Elvacite acrylic resin (ICI
Resins, Wilmington, Del.), 17.2 weight percent Vikoflex 7170
plasticizer (ATOChem, Philadelphia, Pa.); 2.3 weight percent
Tinuvin 292 HAL stabilizer (Ciba-Geigy, Greensboro, N.C.), 2.3
weight percent Nuostabe V1923 stabilizer (Witco, Greenwich, Conn.)
and 13 6 weight percent of a solvent system of two parts of
di-isobutyl ketone and one part mineral spirits.
[0283] A layer was knife coated on the liner with a wet thickness
of 0.127 mm and dried to remove solvents at a temperature of
120.degree. C. for 2 minutes, and then fused in an oven for 45
seconds at 175.degree. C. to a dry thickness of about 0.05 mm.
[0284] An adhesive was prepared from the following components:
3 VYHH (Union Carbide, Danbury, CT) 69 parts Acryloid B82 (Rohm and
Haas, Philadelphia, PA) 17 parts Paraplex G62 (C. P. Hall, Bedford
Park, IL) 14 parts
[0285] The components were dissolved in a solvent mixture comprised
of equal parts xylol, methyl ethyl ketone and methyl isobutyl
ketone to yield a final solution viscosity of 1100-1600 centipoise.
A field of solution was knife coated at 0.076 mm wet thickness on a
silicone coated polyester release liner having a silicone coating
of 0.005 mm caliper on a 0.07 mm polyester film (Rexam Release,
Chicago, Ill.) and dried at 120.degree. C. for 2 minutes to obtain
a dry thickness of 0.0025 mm.
[0286] The layer on liner from Example 9 was then contacted to the
adhesive field from Example 10 to produce the laminate as seen in
FIG. 15, applying a pressure of about 2.3 Kg/cm.sup.2.
[0287] In accordance with a thirteenth and particularly preferred
embodiment of the present invention, the display device 20,21 of
the present invention is a thermal transfer, including thermal mass
transfer or sublimation printer. In thermal mass transfer printing
a donor sheet or "ribbon" is placed in contact with a receptor
sheet and the donor sheet is heated in an imagewise manner (usually
from the back) by a localized thermal print head. The imagewise
distribution of heat (and pressure, if necessary) causes an
imagewise transfer of material from the donor sheet to the receptor
sheet. The material transferred is usually a binder containing
colorant (e.g. a dye, pigment or mixture of the two). The binder is
a thermally softenable material (e.g. a wax or a resin), which
releases from a carrier layer on the donor sheet and transfers and
adheres to the receptor sheet. The thermal head typically consists
of a matrix of minute heating elements, each of which can be
addressed individually, normally with highly controlled pulses of
current being passed through resistors which comprise the heating
elements. Recently, large format thermal mass transfer printers
have become commercially available with good local registration,
e.g. the SummaChrome.TM. Imaging system (406 DPI) from
Summagraphics Corporation, USA., or the GerberScientific
Products/Gerber Edge Graphtec Corp. USA/GC 1300 system (400 DPI),
or Roland Digital Group ColorCamm PNC-5000 system (360 DPI). Such
systems can be addressed directly by the computer 13 of the present
invention.
[0288] Thermal sublimation printers differ from thermal mass
transfer printers in that the donor ribbon does not contact the
receptor sheet. The term "sublimation" refers to the fact that the
colorant layer on the donor ribbon vaporizes and condenses onto the
receptor sheet without going through an intermediate liquid state.
By controlling the number of current pulses sent to each cell of
the thermal printing head, the heat generated can be controlled
which, in turn, determines the amount of sublimation and hence, the
color density at that location. An example of a sublimation printer
is the Rainbow.TM. series of printers supplied by Minnesota Mining
and manufacturing Co., St. Paul, USA. These printers are typically
small format.
[0289] Ribbons and printing methods for thermal transfer printing
of light restricting including opaque silver metallic, white opaque
and brilliant durable colors are known, for example, from U.S. Pat.
No. 5,409,883 and U.S. Pat. No. 5,312,683 as well as U.S. Pat. No.
5,472,932 which are all incorporated herein by reference. The light
restricting white and silver metallic ribbons known from U.S. Pat.
No. 5,409,883 and U.S. Pat. No. 5,312,683 are preferred to print
the light restricting light colored silhouette pattern 2 in
registry with the colored image 3,4 of the present invention onto a
suitable substrate. The optical density of the white light
restricting layer should be at least 1, preferably at least 2, more
preferably at least 2 5 and most preferably 3.
[0290] Extremely smooth, optically clear substrates having a very
flat surface are preferred as the transfer process is sensitive to
surface errors and the final sheeting should restrict vision as
little as possible. The clear vinyl sheeting in accordance with the
eleventh embodiment of the present invention is particularly
preferred. Thermal transfer colorants used in thermal transfer
ribbons are advantageous as commercially available ribbons provide
UV light and moisture resistant images in full color.
[0291] For example, the SummaChrome.TM. Imaging system (406 DPI)
from Summagraphics Corporation, USA includes a printer with eight
stations for up to eight different ribbons each of which can be
conveyed to the thermal printing head individually and in any
order. Four of these ribbons may be the conventional black,
magenta, yellow and cyan ribbons with four other ribbons being spot
colors, in particular at least an light restricting light colored
ribbon, such as metallic silver or white ribbons as mentioned
above. Resin based ribbons are preferred as they provide good
scratch resistant prints with good weatherability and durability.
Trials with the SummaChrome.TM. Imaging system have demonstrated
very good local registration between multiple layers of different
colored ribbons (see Table 1) resulting in exact registration
printing down to transparent area diameters of less than 1 mm.
[0292] The substrate for thermal transfer printing may be
commercially available, clear, particularly optically clear films
such as the transparent marking film VM 4414 from Minnesota Mining
and Manufacturing Co., St. Paul, USA or commercially available
optically clear polyester films. Particularly preferred are the
optically clear vinyl films in accordance with the eleventh
embodiment of the present invention. In order to give adequate
mechanical stability to the vinyl film, it is preferably supplied
in a laminate form with a polyester film with optional pressure
sensitive adhesive between the vinyl and the polyester.
[0293] In accordance with the fourteenth to sixteenth embodiments
of the present invention the TLD device 14 in accordance with the
present invention may be a combination of direct printers 60, 70 or
a combination of direct printer types in a printer 80.
[0294] The fourteenth to sixteenth embodiments of the present
invention provide printed substrates of exceptional quality
providing transparent areas 6 with optical clarity and free of
printing aids and also colored images of the highest quality.
[0295] As shown schematically in FIG. 18, the output of computer 13
which includes both CMYK image data as well as T-layer data is
supplied to printer 60 and optionally also to printer 70. Printer
60 is used to print a special silhouette pattern 2 onto a
conformable, translucent or transparent, preferably optically clear
substrate. The vinyl substrate of the eleventh embodiment is
particularly preferred. The output print 62 from printer 60 is fed
to printer 70 which may be a separate printer or a printing head
integrated with the printing head of printer 60. The final full
color image 3 including transparent areas 6 is produced by printer
80 as a final print 72.
[0296] Referring to FIGS. 19A and 19B, the transparent substrate
63, which may be any of the translucent, transparent and/or
optically clear substrates mentioned in the previous embodiments,
particularly the optically clear, conformable substrate of the
eleventh embodiment, is printed with layers 64 to 66 in registry
leaving transparent areas 67 in accordance with the transparency
data from the T layer. Printer 60 is preferably a thermal transfer
printer as described with reference to the thirteenth embodiment.
Layer 64 is a dark colored layer equivalent to layer 42 of FIG. 9
or 10. Layer 65 is a light colored silhouette layer and preferably
has a transmission optical density of at least 1, preferably at
least 2, more preferably at least 2,5 and most preferably at least
3. The white and metallic ribbons described in U.S. Pat. Nos.
5,312,683 and 5,409,883 are preferred. Layer 66 is a colorant
receptor layer printed at the same time as layer 65 or printed as a
separate layer.
[0297] Certain general principles about colorant receptor layers
are described in U.S. Pat. No. 5,472,932. In accordance with the
present invention, layer 66 may be an ink jet image receptor layer,
for instance as described with reference to the seventh embodiment
of the present invention including both a penetrant layer and an
ink receiving layer. Alternatively, layer 66 may be the hygoscopic
layer of the eighth embodiment and the substrate 63 may be the
microporous layer of the same embodiment. Alternatively, layer 66
may be the conductive and dielectric layers of the tenth
embodiment. Conductivity is maintained by providing a continuous
path in layer 66 about the transparent areas 67 as best shown in
FIG. 19B. The ribbons for printer 60 may be produced by embedding
the particular type of colorant receptor layer in a suitable resin
or wax.
[0298] As the colorant receptor layer 66 is placed in registry with
the light colored layer 65, there is no need for layer 66 to be
transparent. This has the advantage that receptor layer 66 may be
better optimized for acceptance of the inks or toners. In
particular the particle size limitations required in the ninth
embodiment may be relaxed. For the conductive layer, the particle
range may be extended to 0.02 to 10 .mu.m. Also the surface
roughness may be increased to 200 Sheffield units without affecting
the clarity of the transparent areas 67.
[0299] The pigments, particles and other materials required for the
colorant receptor layer 66 may be incorporated into a suitable
binder for transferring to layer 65 by heat and pressure as is
known for thermal transfer printing.
[0300] Printed substrate 62 may be transferred to a second printer
70. When printer 70 is an electrostatic printer, the substrate 62
may be printed directly in the printer 70 as described in the tenth
embodiment of the present invention. Surprisingly, the transparent
areas 67, which contain no dielectric and conductive layer, do not
receive charge and do not take up toner. Hence, there is no need to
provide printer 70 with the T layer data. This method of printing
should be distinguished over European Patent No. EP 0234121 and
U.S. Pat. No. B1 4,925,705 in which a mask is used and subsequently
removed. In accordance with this embodiment no mask is used.
[0301] The fifteenth embodiment of the present invention will be
described with reference to FIG. 20. Substrate 62 is prepared as
described above whereby layer 66 is an ink jet ink receptor layer.
The substrate 62 is printed in a modified ink jet printer 70. As
shown in FIG. 20 the printer 70 may include a conventional four
color ink jet printing head 76 which runs on a guide 71 across the
width of the substrate 62. Associated with head 76 is a continuous
tape having closely spaced registration marks. A sensor (not shown)
in head 76 detects the marks on tape 77 and sends reference
position data of the head 76 to the printer control circuit (not
shown). Attached to the head 76 is a light source 78 which may be a
laser and which provides a narrow beam of light directed
substantially perpendicular to the substrate 62. On the other side
of substrate 62 is mounted a head 74 on a further guide 73. head 74
is driven synchronously with head 76 by means of synchronized
stepper motors or DC servomotors as is known in the art.
Alternatively a mirror may be placed in the position of guide 73
and both head 74 and light source 78 may be mounted on the head 76.
Head 74 includes a light sensor 75. When the light beam from light
source 78 passes through transparent region 67 of substrate 62, the
sensor 75 sends a signal 79 to the control circuit of the printer.
The control circuit modifies the print signal 69 to head 76 so that
printing is only carried out in registry with layers 63 to 66.
[0302] A sixteenth embodiment of the present invention will be
described with reference to FIG. 21. Items with the same reference
numbers are identical to those of the fourteenth and fifteenth
embodiments. The printer 80 includes a thermal transfer printer 84,
86 to 89 and an ink jet printer 85, 90 to 93 combined in a single
head. Thermal transfer printer 84,86 to 89 includes two or more
ribbons, 88,89 which print layers 64 to 66 onto substrate 62. The
ribbons are held in ribbon carriers 86,87. The thermal printer
prints layers 64 to 66 on top of each other and in the width of one
pass of the ink jet printer 85. Under control of the printer
control circuit, the ink jet printer 85 then prints a full color
image in registry with the patterned layers 64 to 66 using CMYK
cartridges 90 to 93. The combined printing head may be mounted on a
guide 81 supported by supports 82, 83 at each end and may traverse
the width of substrate 62 as is conventional for ink jet printers.
A registration mark tape such as 77 of FIG. 20 may be used to
improve registry as is conventional in ink jet printers.
Alternatively, the printing head may be stationary and the
substrate 62 is moved in the X-Y directions by means of a known X-Y
plotter drive.
[0303] As the ink jet printer does not print in areas where there
are no layers 64 to 66, these areas do not require ink receptor
layers. The transparent areas 67 may therefore be maintained
optically clear.
[0304] While some embodiments of the invention have been described,
the invention is not limited thereto. For example, various ways of
identifying the invention include the following.
[0305] A method of displaying an image on a display device having
first and second sides, said image including an light restricting
silhouette pattern having a plurality of first transparent or
translucent areas, and at least one design layer having at least
one color, said at least one design layer being visible from one
side of said display device and substantially less visible from the
other side, said image being substantially transparent or
translucent as viewed from the other side, comprises the steps:
[0306] 1) providing at least a definition of said design layer to a
computer;
[0307] 2) generating a computerized version of said design layer
with the computer,
[0308] 3) outputting the computerized version of said design layer
to said display device, the computerized version of said design
layer being modified to subdivide said design layer into a
plurality of second discrete transparent or translucent areas and
other areas, and
[0309] 4) displaying said modified design layer and said silhouette
pattern with said first and second transparent areas being in
registry.
[0310] The method also can have a display device be an LCD display.
The method can have the first step include providing a definition
of a silhouette layer to the computer, the second include
generating a computerized version of said silhouette layer, and the
third step includes outputting the computerized versions of said
silhouette layer and said design layer, the computerized version of
said silhouette layer being modified to subdivide said silhouette
layer into the plurality of said first discrete transparent or
translucent areas. The method can have third step include
introducing the plurality of said second discrete transparent or
translucent areas into said computerized version of said design
layer using the computer. The method can have the third step
include introducing the plurality of said first discrete
transparent or translucent areas into said computerized version of
said silhouette layer using the computer. The method can have said
display device be a printer. The method can have the printer be a
direct or indirect printer. The method can have the printer be a
local exact registry printer. The method can have the local
registry index of the printer be smaller than 1 mm, preferably
smaller than 0.6 mm and most preferably smaller than 0.4 mm. The
method can have said computerized version of said design layer
include data of color-separated layers of said design layer. The
method can have said computerized versions of said design layer and
said silhouette layer include data of said first transparent or
translucent areas as separate transparency data. The method can
have said display device be a transparent layer display device.
[0311] An article can have a conformable substrate and comprise: a
colorant receptor layer and a light restricting layer on said
substrate, said light restricting layer having a plurality of first
transparent or translucent areas.
[0312] The article can have a conformable substrate, further
comprising: said colorant layer having a plurality of second
transparent or translucent areas, and said first transparent or
translucent areas being in registry with second transparent or
translucent areas. The article can have colorant receptor layer
include a conductive layer suitable for electrostatic printing. The
article can have said receptor layer include a dielectric layer
suitable for electrostatic printing. The article can have said
conductive layer include a conductive pigment comprising particles
of antimony intimately mixed with tin oxide. The article can have
the particles be antimony doped tin oxide. The article can have
said conductive layer have a surface resistance ranging between
2.0.times.10.sup.5 to about 3.times.1O.sup.6 Ohms/.quadrature.. The
article can have the dielectric layer comprise spacer particles and
abrasive particles with the ratio of spacer particles to abrasive
particles present within the range of about 1.5:1 to about 5:1. The
article can have colorant receptor layer include a conductive layer
suitable for electrostatic printing. The article can have said
receptor layer include a dielectric layer suitable for
electrostatic printing. The article can have said substrate be a
vinyl-containing polymeric substrate. The article can have said
colorant receptor layer include an ink receiving layer suitable for
ink jet printing The article can have said colorant receptor layer
include an ink receiving layer suitable for ink jet printing. The
article can have said substrate include a hydrophilic, microporous,
polymeric membrane and said colorant receptor layer includes a
hygroscopic layer. The article can have the pore structure of the
membrane be collapsed to provide transparency by a post treatment
after imaging such as heating or calendering. The article can
further comprise a protective penetrant layer and said ink
receiving layer containing dispersed particles of a size that
causes protrusions from the protective layer. The article can
comprise a protective penetrant layer and said ink receiving layer
containing dispersed particles of a size that causes protrusions
from the protective layer. The article can be durable. The article
can have said substrate be transparent, preferably optically
clear.
[0313] An article can comprise a polymeric substrate having a
composition comprising vinyl chloride resin, optional acrylic
resin, optional plasticizer, and optional stabilizer, wherein the
composition is formed on a polymeric release liner having
smoothness of a Sheffield value of from about 1 to about 10, and a
light restricting layer and a design layer on said substrate, said
design layer including at least one color layer, said light
restricting layer being subdivided into a plurality of first
transparent or translucent areas, said design layer being
subdivided into a plurality of second transparent or translucent
areas, and said first and second transparent areas being in
registry.
[0314] The article can further comprise acrylic resin. The article
can have the amount of vinyl chloride resin range from about 49 to
about 72 weight percent; the amount of acrylic resin ranges from
about 9 to about 33 weight percent; the amount of plasticizer
ranges from about 0 to about 25 weight percent; and wherein the
stabilizer ranges from about 0 to about 8 weight percent. The
article can have the amount of vinyl chloride resin range from
about 55 to about 65 weight percent; the amount of acrylic resin
ranges from about 16 to about 27 weight percent; and the
composition includes an amount of plasticizer ranging from about 10
to about 16 weight percent; and an amount of stabilizer the ranging
from about 2 to about 6 weight percent. The article can have said
substrate be transparent, preferably optically clear.
[0315] A printer for receiving a print file includes color
separated image data, light restricting layer data and transparency
data, and for printing the color separated image and the light
restricting layer data including transparent areas in both the
color-separated layer and the light restricting layer in accordance
with the transparency data.
[0316] The printer can be an electrostatic printer, an ink jet
printer, or a thermal transfer printer. The electrostatic printer
can include a linear array of a plurality of separately chargeable
electrodes, and said printer prints said transparency data by
selectively controlling ones of the separately chargeable
electrodes. The ink jet printer includes a plurality of ink jet
heads and said printer prints said transparency data by selectively
controlling ones of said ink jet heads. The thermal mass transfer
printer can print said light restricting layer and a further
printer device to print said color separated image data.
[0317] A raster image processing method for raster image processing
of a print file including color separated image data, light
restricting layer data and transparency data, can comprise
operating on said print file to generate raster image bitmaps for
said color separated image data and said light restricting layer
data, and introducing said transparency data into said raster image
bitmaps for said color separated image data and said light
restricting layer data so that the transparent areas in said color
separated image raster bitmap and said light restricting layer
bitmap are in registry.
[0318] The raster image processing method can have said color
separated image raster bitmap and said light restricting layer
bitmap are first created and then said transparent areas are
introduced.
[0319] A raster image processing system for raster image processing
of a print file including color separated image data, light
restricting layer data and transparency data, comprises means
operating on said print file to generate raster image bitmaps for
said color separated image data and said light restricting layer
data, and means introducing said transparency data into said raster
image bitmaps for said color separated image data and said light
restricting layer data so that the transparent areas in said color
separated image raster bitmap and said light restricting layer
bitmap are in registry.
[0320] The raster processing system can be hard-wired. The raster
processing system can include a programmable digital processor.
[0321] A graphics computer based system for creating graphics
images including color separated layers and light restricting
layers, comprises first input means for image data, means for
generating color separated image data from said image data, means
for generating light restricting layer data, second input means for
transparency data, and means for outputting a display file
including said color separated image data, said light restricting
layer data and said transparency data.
[0322] The graphics computer based system can further comprise
storage means for storing a plurality of standard transparency data
templates.
[0323] The claims follow.
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