U.S. patent application number 12/348932 was filed with the patent office on 2009-06-11 for glass substrate with protective glass, process for producing display device using glass substrate with protective glass, and silicone for release paper.
This patent application is currently assigned to ASAHI GLASS COMPANY, LIMITED. Invention is credited to Toshihiko HIGUCHI.
Application Number | 20090148682 12/348932 |
Document ID | / |
Family ID | 38923182 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090148682 |
Kind Code |
A1 |
HIGUCHI; Toshihiko |
June 11, 2009 |
GLASS SUBSTRATE WITH PROTECTIVE GLASS, PROCESS FOR PRODUCING
DISPLAY DEVICE USING GLASS SUBSTRATE WITH PROTECTIVE GLASS, AND
SILICONE FOR RELEASE PAPER
Abstract
To provide a glass substrate with protective glass which
suppresses formation of microscopic scratches on the back surface
of the glass substrate in the production process for a display
device, and which prevents a strength decrease in the process or
formation of etch pits after a chemical etching treatment; a
process for producing a display device by using the glass substrate
with protective glass; and silicone for release paper for the glass
substrate with protective glass. A glass substrate with protective
glass, which comprises a glass substrate and a protective glass
substrate laminated on each other, and which is characterized in
that the glass substrate and the protective glass substrate are
laminated by a resin layer having removability.
Inventors: |
HIGUCHI; Toshihiko;
(Chiyoda-ku, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ASAHI GLASS COMPANY,
LIMITED
Chiyoda-ku
JP
|
Family ID: |
38923182 |
Appl. No.: |
12/348932 |
Filed: |
January 6, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2007/063591 |
Jul 6, 2007 |
|
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12348932 |
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Current U.S.
Class: |
428/213 ;
156/247; 428/425.6; 428/426; 428/428; 428/441; 428/442;
525/371 |
Current CPC
Class: |
C03C 27/10 20130101;
G02F 2201/50 20130101; Y10T 428/31663 20150401; Y10T 428/1476
20150115; Y10T 428/31601 20150401; Y10T 428/31649 20150401; B32B
17/10036 20130101; C09D 183/04 20130101; Y10T 428/31645 20150401;
B32B 7/06 20130101; Y10T 428/2495 20150115; B32B 17/10972 20130101;
B32B 7/12 20130101; G02F 1/133302 20210101 |
Class at
Publication: |
428/213 ;
428/426; 428/442; 428/441; 428/425.6; 428/428; 525/371;
156/247 |
International
Class: |
B32B 17/10 20060101
B32B017/10; B32B 7/00 20060101 B32B007/00; C08L 83/04 20060101
C08L083/04; B32B 37/00 20060101 B32B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2006 |
JP |
2006-191388 |
Claims
1. A glass substrate with protective glass, which comprises a glass
substrate and a protective glass substrate laminated on each other,
and which is characterized in that the glass substrate and the
protective glass substrate are laminated by a resin layer having
removability.
2. The glass substrate with protective glass according to claim 1,
wherein the resin layer having removability is fixed on a surface
of the protective glass substrate.
3. The glass substrate with protective glass according to claim 1,
wherein the resin layer having removability is an acrylic resin
layer, a polyolefin resin layer, a polyurethane resin layer or a
silicone resin layer.
4. The glass substrate with protective glass according to claim 3,
wherein the silicone resin layer is a silicone resin layer having
releasability and non-adhesive property, or a silicone resin layer
having releasability and slight adhesive property.
5. The glass substrate with protective glass according to claim 4,
wherein the silicone resin layer having releasability and
non-adhesive property, or the silicone resin layer having
releasability and slight adhesive property, further has low
silicone migration property.
6. The glass substrate with a protective glass according to claim
4, wherein the silicone resin layer having releasability and
non-adhesive property, or the silicone resin layer having
releasability and slight adhesive property, is a layer made of a
cured product of silicone for release paper.
7. The glass substrate with protective glass according to claim 6,
wherein the cured product of silicone for release paper, is a
crosslinked product of a linear polyorganosiloxane having vinyl
groups at both terminals and/or in its side chain, and a
methylhydrogen polysiloxane having hydrosilyl groups in its
molecule.
8. The glass substrate with protective glass according to claim 7,
wherein before curing, the cured product of silicone for release
paper has a molar ratio of hydrosilyl groups of the methylhydrogen
polysiloxane to vinyl groups of the linear polyorganosiloxane being
from 1.3/1 to 0.7/1.
9. The glass substrate with protective glass according to claim 1,
wherein the thickness of the glass substrate is less than 1.0 mm,
and the total thickness of the protective glass substrate and the
resin layer having removability is at least 0.1 mm.
10. The glass substrate with protective glass according to claim 1,
wherein the difference between the linear expansion coefficient of
the glass substrate and the linear expansion coefficient of the
protective glass substrate is at most 15.times.10.sup.-7/.degree.
C.
11. A process for producing a display device by using a glass
substrate with protective glass, which comprises a step of forming
a resin layer having removability on a protective glass substrate,
a step of laminating a glass substrate on the resin layer-formed
surface of the protective glass substrate, a step of carrying out a
prescribed treatment for producing a display device on the glass
substrate, and a step of separating the glass substrate from the
protective glass substrate.
12. The process for producing a display device by using a glass
substrate with protective glass according to claim 11, wherein the
resin layer having removability is an acrylic resin layer, a
polyolefin resin layer, a polyurethane resin layer or a silicone
resin layer.
13. The process for producing a display device by using a glass
substrate with protective glass according to claim 12, wherein the
silicone resin layer is a silicone resin layer having releasability
and non-adhesive property, or a silicone resin layer having
releasability and slight adhesive property.
14. The process for producing a display device by using a glass
substrate with protective glass according to claim 13, wherein the
silicone resin layer having releasability and non-adhesive
property, or the silicone resin layer having releasability and
slight adhesive property, is a layer made of a cured product of
silicone for release paper.
15. The process for producing a display device by using a glass
substrate with protective glass according to claim 14, wherein the
cured product of silicone for release paper, is a crosslinked
product of a linear polyorganosiloxane having vinyl groups at both
terminals and/or in its side chain, and a methylhydrogen
polysiloxane having hydrosilyl groups in its molecule.
16. The process for producing a display device by using a glass
substrate with protective glass according to claim 15, wherein
before curing, the cured product of silicone for release paper has
a molar ratio of hydrosilyl groups of the methylhydrogen
polysiloxane to vinyl groups of the linear polyorganosiloxane being
from 1.3/1 to 0.7/1.
17. The process for producing a display device by using a glass
substrate with protective glass according to claim 11, wherein the
step of forming a resin layer having removability on the protective
glass substrate, includes applying silicone for release paper on
the protective glass substrate, followed by curing the silicone for
release paper.
18. The process for producing a display device by using a glass
substrate with protective glass according to claim 17, wherein the
silicone for release paper contains a linear polyorganosiloxane
having vinyl groups at both terminals and/or in its side chain, a
methylhydrogen polysiloxane having hydrosilyl groups in its
molecule, and a platinum catalyst.
19. The process for producing a display device by using a glass
substrate with protective glass according to claim 18, wherein in
the silicone for release paper, the molar ratio of hydrosilyl
groups of the methylhydrogen polysiloxane to vinyl groups of the
linear polyorganosiloxane is from 1.3/1 to 0.7/1.
20. The process for producing a display device by using a glass
substrate with protective glass according to claim 17, wherein the
silicone for release paper contains substantially no non-reactive
silicone.
21. The process for producing a display device by using a glass
substrate with protective glass according to claim 17, wherein
application of the silicone for release paper is carried out by a
die coating method, a spin coating method or a screen printing
method.
22. The process for producing a display device by using a glass
substrate with protective glass according to claim 17, wherein the
silicone for release paper is heat-cured at a temperature of from
50 to 250.degree. C.
23. The process for producing a display device by using a glass
substrate with protective glass according to claim 11, wherein the
step of laminating a glass substrate on the resin layer-formed
surface of the protective glass substrate, is carried out by using
vacuum pressing or vacuum lamination.
24. Silicone for release paper for a glass substrate with
protective glass, which is to be used for laminating the glass
substrate and the protective glass substrate.
25. The silicone for release paper according to claim 24, which
contains a linear polyorganosiloxane having vinyl groups at both
terminals and/or in its side chain, a methylhydrogen polysiloxane
having hydrosilyl groups in its molecule, and a platinum
catalyst.
26. The silicone for release paper according to claim 25, wherein
the molar ratio of hydrosilyl groups of the methylhydrogen
polysiloxane to vinyl groups of the linear polyorganosiloxane is
from 1.3/1 to 0.7/1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a glass substrate to be
used for a display device such as a liquid crystal display or an
organic EL display, more specifically, a laminated body of a glass
substrate and a back-protective glass substrate, to be used for
producing a display device by using such a glass substrate, a
process for producing a display device by using the laminate, and
silicone for release paper for the glass substrate with protective
glass.
BACKGROUND ART
[0002] A process for producing a liquid crystal display device
(LCD) generally comprises a step of forming an array on a glass
substrate, a step of forming a color filter on a glass substrate
different from the above glass substrate, a step of bonding the
glass substrate having an array formed thereon with the glass
substrate having a color filter formed thereon (an array/color
filter bonding step), a step of injecting liquid crystal and a step
of sealing the injection inlet. In each of the steps, since a back
surface of the glass substrate, namely, an opposite surface from
the surface on which an array or a color film is to be formed, is
directly contacted with a carrier jig, a hotplate, etc., whereby
microscopic scars are formed on its surface, which causes a
strength decrease of the glass substrate itself.
[0003] In the field of a medium or small sized liquid crystal
display (LCD), an organic EL display device (OLED), particularly, a
portable display device such as a mobile, a digital camera or a
cellular phone, weight saving and reduction in thickness of a
display device have been important objects, and since the reduction
in thickness of the glass substrate has been progressed, the
strength decrease of the glass substrate originated from such a
step has especially been a serious problem.
[0004] Further, in order to make a glass substrate thinner, a step
of carrying out a chemical etching treatment on a glass substrate
to make the substrate thickness thin after the array/color filter
bonding step, has been widely applied, but in a case where if
microscopic scars formed in the above step are present on the glass
substrate, pits (etch pits) having a diameter of from tens to
hundreds .mu.m will be formed on the glass substrate surface after
the chemical etching treatment, which would lead to optical
defects.
[0005] Therefore, in order to overcome the above problem, a process
for producing a display device has been suggested, wherein a
prescribed treatment for producing a display device is carried out
in such a state that a glass substrate is bonded with another
protective glass substrate, and after the completion of the
treatment, the glass substrate and the protective glass substrate
are separated (e.g. Patent Documents 1 to 6).
[0006] In these processes for producing a display device, a method
for laminating and fixing the glass substrate and the protective
glass substrate on each other may, for example, be a method of
fixing them by means of electrostatic adsorptivity or vacuum
adsorptivity caused between the glass substrates (e.g. Patent
Document 1), a method of fixing both ends of the glass substrates
by means of glass frit (e.g. Patent Document 2), a method of is
fusing the two glass substrates by irradiating the vicinity of the
edge surfaces of peripheral portions with laser beams (e.g. Patent
Document 3), and a method of disposing a removable adhesive or
adhesive sheet over the entire surfaces of the glass substrates,
and fixing them by the adhesive force (e.g. Patent Documents 4 to
6).
[0007] These methods have latent problems which may adversely
affect a display device to be produced.
[0008] That is, by the method of fixing the glass substrates by
means of electrostatic adsorptivity or vacuum adsorptivity, the
method of fixing both ends of the glass substrates by means of
glass frit, or the method of fusing the two glass substrates by
irradiating the vicinity of edge surfaces of peripheral portions
with laser beams, it is difficult to avoid inclusion of bubbles or
convex defects due to foreign matters such as dust in the process
of laminating and closely bonding the glass substrates without any
interlayer, and accordingly it is difficult to obtain a glass
substrate laminate having a smooth surface.
[0009] In the case of the method of disposing a removable adhesive
or adhesive sheet over the entire surface of the glass substrates,
it is easy to avoid inclusion of bubbles as compared with the case
of directly laminating the glass substrates, and it is considered
that convex defects due to foreign matters are less likely to
occur. However, it is difficult to separate the glass substrate and
the protective glass substrate, and the glass substrate may be
broken at the time of separation. Further, remaining of the
adhesive on the glass substrate after the separation is also
problematic. Further, the display device production process
comprises a step which requires treatment at high temperature, such
as a step of firing an insulating film or an alignment film in a
process for producing a liquid crystal display device. Therefore,
heat resistance is required for the adhesive or adhesive sheet, to
be used for the display device, but a method which satisfies both
heat resistance and removability has not been proposed yet.
[0010] Patent Document 1: JP-A-2000-241804
[0011] Patent Document 2: JP-A-58-3-54316
[0012] Patent Document 3: JP-A-2003-216068
[0013] Patent Document 4: JP-A-8-86993
[0014] Patent Document 5: JP-A-9-105896
[0015] Patent Document 6: JP-A-2000-252342
DISCLOSURE OF THE INVENTION
Objects to be Solved by the Invention
[0016] In order to solve the above problems of conventional
techniques, the present invention has objects to provide a glass
substrate with protective glass which suppresses formation of
microscopic scars on a back-surface of a glass substrate in a step
of producing a display device, and which prevents a strength
decrease of the glass substrate in the step or prevents formation
of etch pits by chemical etching treatment; a process for producing
a display device by using the glass substrate with protective
glass; and silicone for release paper for the glass substrate with
protective glass.
Means to Accomplish the Objects
[0017] In order to accomplish the above objects, the present
invention provides a glass substrate with protective glass
(hereinafter, in the present invention, referred to as a glass
substrate with protective glass of the present invention), which
comprises a glass substrate and a protective glass substrate
laminated on each other, and which is characterized in that the
glass substrate and the protective glass substrate are laminated by
a resin layer having removability.
[0018] The resin layer having removability is preferably fixed on a
surface of the protective glass substrate.
[0019] The resin layer having removability is preferably an acrylic
resin layer, a polyolefin resin layer, a polyurethane resin layer
or a silicone resin layer.
[0020] The silicone resin layer is preferably a silicone resin
layer having releasability and non-adhesive property, or a silicone
resin layer having releasability and slight adhesive property.
[0021] The silicone resin layer having releasability and
non-adhesive property, or the silicone resin layer having
releasability and slight adhesive property, further preferably has
low silicone migration property.
[0022] The silicone resin layer having releasability and
non-adhesive property, or the silicone resin layer having
releasability and slight adhesive property, is preferably a layer
made of a cured product of silicone for release paper.
[0023] The cured product of silicone for release paper, is
preferably a crosslinked product of a linear polyorganosiloxane
having vinyl groups at both terminals and/or in its side chain, and
a methylhydrogen polysiloxane having hydrosilyl groups in its
molecule.
[0024] Before curing, the cured product of silicone for release
paper preferably has a molar ratio of hydrosilyl groups of the
methylhydrogen polysiloxane to vinyl groups of the linear
polyorganosiloxane being from 1.3/1 to 0.7/1.
[0025] In the glass substrate with protective glass of the present
invention, the thickness of the glass substrate is preferably less
than 1.0 mm, and the total thickness of the protective glass
substrate and the resin layer having removability is preferably at
least 0.1 mm.
[0026] In the glass substrate with protective glass of the present
invention, the difference between the linear expansion coefficient
of the glass substrate and the linear expansion coefficient of the
protective glass substrate is preferably at most
15.times.10.sup.-7/.degree. C.
[0027] Further, the present invention provides a process for
producing a display device by using a glass substrate with
protective glass (hereinafter referred to as "a process for
producing a display device of the present invention"), which
comprises a step of forming a resin layer having removability on a
protective glass substrate, a step of laminating a glass substrate
on the resin layer-formed surface of the protective glass
substrate, a step of carrying out a prescribed treatment for
producing a display device on the glass substrate, and a step of
separating the glass substrate from the protective glass
substrate.
[0028] In the process for producing a display device of the present
invention, the resin layer having removability is preferably an
acrylic resin layer, a polyolefin resin layer, a polyurethane resin
layer or a silicone resin layer.
[0029] The silicone resin layer is preferably a silicone resin
layer having releasability and non-adhesive property, or a silicone
resin layer having releasability and slight adhesive property.
[0030] The silicone resin layer having releasability and
non-adhesive property, or the silicone resin layer having
releasability and slight adhesive property, is preferably a layer
made of a cured product of silicone for release paper.
[0031] The cured product of silicone for release paper, is a
crosslinked product of a linear polyorganosiloxane having vinyl
groups at both terminals and/or in its side chain, and a
methylhydrogen polysiloxane having hydrosilyl groups in its
molecule.
[0032] In the silicone for release paper, the molar ratio of
hydrosilyl groups of the methylhydrogen polysiloxane to vinyl
groups of the linear polyorganosiloxane is preferably from 1.3/1 to
0.7/1.
[0033] In the process for producing a display device of the present
invention, a step of forming a resin layer having removability on a
back-protective glass substrate, preferably includes applying
silicone for release paper on the protective glass substrate,
followed by curing the silicone for release paper.
[0034] The silicone for release paper preferably contains a linear
polyorganosiloxane having vinyl groups at both terminals and/or in
its side chain, a methylhydrogen polysiloxane, and a platinum
catalyst.
[0035] The silicone for release paper preferably contains
substantially no unreactive silicone.
[0036] The application of the silicone for release paper is
preferably carried out by a die coating method, a spin coating
method or a screen printing method.
[0037] The silicone for release paper is preferably heat-cured at a
temperature of from 50 to 250.degree. C.
[0038] The step of laminating a glass substrate on the resin
layer-formed surface of the protective glass substrate, is
preferably carried out by using vacuum pressing or vacuum
lamination.
[0039] Further, the present invention provides a silicone for
release paper for a glass substrate with protective glass, which is
to be used for laminating the glass substrate and the
back-protective glass substrate.
[0040] The silicone for release paper of the present invention
preferably contains a linear polyorganosiloxane having vinyl groups
at both terminals and/or in its side chain, a methylhydrogen
polysiloxane having a hydrosilyl groups in its molecule, and a
platinum catalyst.
[0041] In the silicone for release paper of the present invention,
the molar ratio of hydrosilyl groups of the methylhydrogen
polysiloxane to vinyl groups of the linear polyorganosiloxane is
preferably from 1.3/1 to 0.7/1.
EFFECTS OF THE INVENTION
[0042] The glass substrate with protective glass of the present
invention comprises a glass substrate and a protective glass
substrate laminated on each other by a resin layer having
removability, whereby by pressure bonding them by means of rolls or
a press, it is possible to easily laminate the both substrates.
Especially, when the glass substrate and the protective glass
substrate were laminated by using a vacuum lamination method or a
vacuum pressing method, inclusion of bubbles is suppressed, and
adhesion properties are good. Further, even when a foreign matter
such as dust is included at the interface of the laminated layers,
convex defects of the glass substrates are unlikely to occur by
deformation of the resin layer having flexibility.
[0043] Further, when lamination of the glass substrate and the
protective glass substrate is carried out by a vacuum lamination
method or a vacuum pressing method, even if very small bubbles
remain, the bubbles will not grow by heating, whereby convex
defects are less likely to occur in the glass substrate.
[0044] Furthermore, when a silicone resin layer having
releasability and non-adhesive property, or a silicone resin layer
having releasability and slight adhesive property, is used as the
resin layer having removability, bubbles are hardly included
particularly at the time of lamination, and even when bubbles are
included, the bubbles are easily removed by carrying out press
bonding by means of rolls or a press, and the heat resistance is
also good.
[0045] The glass substrate with protective glass of the present
invention comprises a glass substrate and a protective glass
substrate laminated via a resin layer having removability, and the
back surface of the glass substrate (an opposite surface from a
surface on which an array or a color filter is formed) is not
directly contacted to a carrier jig or a hotplate, in a step of
forming a display device, whereby there is no concern that
scratches are formed on the back surface of the glass substrate in
the step. Further, the back surface of the glass substrate is
contacted with a flexible resin layer having removability, which is
fixed on the surface of the protective glass substrate, whereby it
is possible to easily separate the laminate into the glass
substrate and the protective glass substrate, and during the
separation into the glass substrate and the protective glass
substrate, no scratches are formed on the back surface of the glass
substrate, and the glass substrate is unlikely to be broken.
[0046] Therefore, it is possible to significantly suppress the
decrease in strength of the glass substrate after the protective
glass substrate is removed and to suppress the etch pit formation
when a chemical etching treatment is carried out afterwards.
[0047] In the process for producing a display device of the present
invention, when a step of laminating the glass substrate on a
surface of the protective glass substrate where the resin layer
having removability is formed, by using vacuum pressing or vacuum
lamination, it is possible to suppress inclusion of bubbles into
the resin layer. As a result, there is an advantage that in a step
of forming transparent electrodes of e.g. ITO under a vacuum
atmosphere, it is possible to suppress formation of defects
originated from air bubbles included in the resin layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 is a cross-sectional schematic view illustrating a
glass substrate with protective glass produced in Example 1.
[0049] FIG. 2 is a cross-sectional schematic view illustrating the
relation between a jig and the glass substrate with protective
glass 1 shown in FIG. 1, during a peel test (1).
[0050] FIG. 3 is a cross-sectional schematic view illustrating the
relation between a jig and the glass substrate with protective
glass 1 shown in FIG. 1 during a shear strength test.
MEANINGS OF SYMBOLS
[0051] 1: Glass substrate with protective glass [0052] 11: Glass
substrate [0053] 12: Protective glass substrate [0054] 13: Silicone
resin layer [0055] 20, 21, 25, 26, 30 and 31: Polycarbonate
member
BEST MODE FOR CARRYING OUT THE INVENTION
[0056] Now, the glass substrate with protective glass will be
described.
[0057] The glass substrate with protective glass of the present
invention comprises a glass substrate and a protective glass
substrate laminated on each other, and is characterized in that the
glass substrate and the protective glass substrate are laminated by
a resin layer having removability.
[0058] Here, the resin layer having removability is preferably
fixed on a surface of the protective glass substrate. That is, the
removability of the resin layer is preferably exhibited by the
relation with the glass substrate.
[0059] The glass substrate is a glass substrate for a display
device such as LCD or OLED and has a thickness of from 0.1 mm to
0.7 mm. The thickness of the glass substrate is preferably from 0.4
mm to 0.7 mm for such a reason that such a glass substrate is easy
to handle at the time of producing a display device by using the
glass substrate, and that the glass substrate rarely breaks when it
is handled. When the glass substrate is made thin by carrying out a
chemical etching treatment, from a glass substrate having a
thickness of from 0.4 mm to 0.7 mm, a glass substrate having a
thickness of from 0.1 mm to 0.4 mm may be obtained.
[0060] Further, the display device as an object of the present
invention is a medium or small sized display device which is to be
used mainly for a mobile terminal such as a cellular phone or PDA,
or a digital camera. The display device is mainly LCD or OLED, and
LCD includes TN-type, STN-type, FE-type, TFT-type and MIM-type.
[0061] Characteristics required for the glass substrate, such as
the heat shrinkage ratio, surface shape and chemical resistance,
vary depend on the type of a display device. Accordingly, the glass
substrate may be made of alkali glass. However, alkali-free glass
is preferred since the heat shrinkage ratio is small.
[0062] In the present invention, the glass substrate is preferably
one having a small heat shrinkage ratio. In the case of glass, the
linear expansion coefficient defined in JIS R3102 (1995) is used as
an index for heat expansion and heat shrinkage. The glass substrate
preferably has the linear expansion coefficient of at most
50.times.10.sup.-7/.degree. C., more preferably at most
45.times.10.sup.-7/.degree. C., more preferably at most
40.times.10.sup.-7/.degree. C., more preferably at most
30.times.10.sup.-7/.degree. C., more preferably at most
20.times.10.sup.-7/.degree. C.
[0063] The protective glass substrate is laminated on the glass
substrate for a purpose of preventing formation of scars on the
back surface of the glass substrate in the step. Here, the back
surface of the glass substrate is a surface opposite from a surface
on which an array or a color filter is to be formed, in a
production step of LCD, and it is a surface which is directly
contacted with a carrier jig, a hotplate, etc. The thickness of the
protective glass substrate is not particularly limited, but it is
preferably a thickness for a laminate with the glass substrate to
be transported by the current production line. For example, the
current production line is designed to transport a substrate having
a thickness of 0.5 mm, whereby when the thickness of the glass
substrate is 0.3 mm, the thickness of the protective glass
substrate is preferably 0.2 mm combined with the thickness of the
resin layer having removability. The most common current production
line is one designed to transport a glass substrate having a
thickness of 0.7 mm. In such a case, when the substrate thickness
of the glass substrate is 0.4 mm, the substrate thickness of the
protective glass substrate is preferably 0.3 mm as combined with
the thickness of the resin layer having removability. However, the
production line is not limited to one designed to transport a glass
substrate having a thickness of 0.5 mm or 0.7 mm, but it is
sometimes designed to transport a glass substrate having a
thickness other than such a thickness. For example, there is a case
where the line is designed to transport a glass substrate having a
thickness of less than 0.5 mm, and there is also a case where the
line is designed to transport the glass substrate having a
thickness of more than 0.7 mm, e.g. 1.1 mm. In such a case, when
the thickness of the glass substrate is 0.7 mm, the thickness of
the protective glass substrate is preferably 0.4 mm as combined
with the thickness of the resin layer having removability.
[0064] Taking the thickness of the resin layer having removability
which will be described later, into a consideration, the thickness
of the protective glass substrate is preferably from 0.1 to 0.8 mm
as combined with the thickness of the resin layer having
removability.
[0065] Further, the protective glass substrate is one to prevent
scratches to be formed on the back surface of the glass substrate,
and its material is not particularly limited. Namely, it may be
either alkali glass or alkali-free glass. However, the linear
expansion coefficient of the protective glass substrate is
preferably substantially the same as the linear expansion
coefficient of the glass substrate. When the linear expansion
coefficient of the protective glass substrate is larger than the
linear expansion coefficient of the glass substrate, in a heating
step in the production process for a display device, expansion of
the protective glass substrate is suppressed by the glass substrate
with protective glass, whereby the glass substrate with protective
glass will have warpage. On the other hand, when the linear
expansion coefficient of the protective glass substrate is smaller
than the linear expansion coefficient of the glass substrate, by
the expansion of the glass substrate, the glass substrate is peeled
from the resin layer having removability, such being
disadvantageous.
[0066] In the present specification, the case where the linear
expansion coefficients are substantially the same, does not mean
that the linear expansion coefficient of the glass substrate
completely matches with the linear expansion coefficient of the
protective glass substrate, and there may be some difference
between them. The difference in the linear expansion coefficient
between the glass substrate and the protective glass substrate is
preferably at most 35.times.10.sup.-7/.degree. C., more preferably
at most 25.times.10.sup.-7/.degree. C., further preferably at most
15.times.10.sup.-7/.degree. C.
[0067] Further, since the protective glass substrate has an object
to protect the back surface of the glass substrate, its size is
preferably equal to or larger than the size of the glass
substrate.
[0068] When the glass substrate with protective glass of the
present invention is to be produced, a resin layer having
removability is formed on a protective glass substrate, and then, a
glass substrate is laminated on the resin layer-formed surface of
the protective glass substrate. More specifically, they are
laminated so that the resin layer-formed surface of the protective
glass substrate and the back surface of the glass substrate face
each other.
[0069] In the present specification, "a resin layer having
removability" means a resin layer having proper flexibility so that
it can follow micro-irregularities of the glass substrate.
Specifically, it is possible to use either a resin layer having
releasability and proper adhesive property (slight adhesive
property) or a resin layer having releasability and non-adhesive
property.
[0070] The resin layer having removability is preferably an acrylic
resin layer, a polyolefin resin layer, a polyurethane resin layer
or a silicone resin layer.
[0071] Among them, the resin layer having removability is
particularly preferably a silicone resin layer having releasability
and non-adhesive property, or a silicone resin layer having
releasability and slight adhesive property.
[0072] The silicone resin layer having releasability and
non-adhesive property is a silicone resin layer having proper
flexibility, and it is not one to fix the glass substrate by
adhesive force, like an adhesive, but it is one to fix the glass
substrate by a force attributable to a Van der Waals force between
the faced solid molecules, namely, a bonding strength.
[0073] On the other hand, the silicone resin layer having
releasability and slight adhesive property is one to fix the glass
substrate by a certain level of adhesive force in addition to the
above bonding strength. Further, the silicone resin layer having
releasability and non-adhesive property, and the silicone resin
layer having releasability and slight adhesive property, will be
generally referred to as "a silicone resin layer having
releasability and weak adhesive property".
[0074] Specifically, the silicone resin layer having releasability
and weak adhesive property fixes the glass substrate by a bonding
strength or by a bonding strength and a slight adhesive force,
whereby a force to slide the glass substrate and the protective
glass substrate in parallel to the interface of the laminated
layer, namely, a shear force, shows a high value. Therefore, the
glass substrate will not be displaced from the protective glass
substrate in the production process for a display device.
Accordingly, there will be no such a trouble that the substrates
are separated by such displacement.
[0075] With respect to the shear force of the silicone resin layer
having releasability and weak adhesive property, since the glass
substrate will not be displaced from the protective glass substrate
during the production process for a display device, in a shear
strength test which will be described later, the load when glass is
peeled off is preferably at least 0.1 kg wt/cm.sup.2, particularly
at least 0.3 kg wt/cm.sup.2, further preferably at least 0.5 kg
wt/cm.sup.2.
[0076] However, in a case where the thicknesses of both the glass
substrate and the protective glass substrate are large, for
example, when the thickness of a thinner substrate between the
glass substrate and the protective glass substrate, is at least 0.7
mm, the property of the resin layer to follow the shapes of the
substrates decreases, whereby the force to fix the glass substrate
may be insufficient by only a bonding strength. In such a case, it
is preferred to use a silicone resin layer having releasability and
slight adhesive property. The silicone resin layer having
releasability and slight adhesive property has relatively low
peeling force, preferably at most 0.8 kg wt/cm.sup.2.
[0077] In the case of the silicone resin layer having releasability
and slight adhesive property, a glass substrate is fixed by a
proper adhesive force in addition to a bonding strength, whereby
even if the thicknesses of both the glass substrate and the
protective glass substrate are large, the force to fix the glass
substrate will not be insufficient. Besides, the peeling force is
at most 0.8 kg wt/cm.sup.2, whereby the force required to peel the
glass substrate from the protective glass substrate, namely, the
peeling force, is low, and it is possible to easily separate the
protective glass substrate from the glass substrate after a
prescribed treatment to produce a display device on the glass
substrate, is carried out.
[0078] On the other hand, due to the releasability and weak
adhesive property of the silicone resin layer, the force to peel
the glass substrate from the protective glass substrate in a
perpendicular direction, namely, the peeling force, is low.
Therefore, it is possible to easily separate the protective glass
substrate from the glass substrate after a prescribed treatment for
producing a display device on the glass substrate, is carried
out.
[0079] With respect to the peeling force of the silicone resin
layer having releasability and weak adhesive property, from the
viewpoint that the protective glass substrate can easily be
separated from the glass substrate, the load to peel the protective
glass substrate in a peel test (1), which will be described later,
is preferably at most 2 kg wt/cm.sup.2, particularly preferably at
most 1 kg wt/cm.sup.2, further preferably at most 0.8 kg
wt/cm.sup.2. When a flexible substrate capable of roll-to-roll such
as a resin film, is used as the protective glass substrate, the
peeling force should be evaluated by a peel test with an angle such
as a 90.degree. peel test or a 180.degree. peel test. However, in a
peel test for glass substrates having a certain level of rigidity,
it is necessary to evaluate the peeling force by a testing method
such as the peel test (1) (namely, a 0.degree. peel test).
Therefore, even when the peeling force is evaluated, it is
preferably in the above range by a testing method such as the peel
test (1).
[0080] Specific modes of the silicone resin layer having
releasability and non-adhesive property, and the silicone resin
layer having releasability and slight adhesive property, will be
described later. With respect to the silicone resin layer having
releasability and non-adhesive property, its surface energy is
preferably from 16 to 21 erg/cm.sup.2 (unit), for a reason that air
bubbles included at the time of lamination, can easily be removed,
and the protective glass substrate can easily be separated from the
glass substrate.
[0081] The silicone resin layer having releasability and weak
adhesive property is excellent in heat resistance, whereby even
after a heating treatment, e.g. after heating at a temperature of
300.degree. C. in atmosphere for 1 hour, it is possible to exhibit
the above characteristics such that the peeling force is low, while
the shear force is high.
[0082] Hereinafter, in the present specification, the silicone
resin layer having releasability and weak adhesive force, will be
generally referred to as "a silicone resin layer of the present
invention" when it shows the common characteristics.
[0083] Since the silicone resin layer of the present invention, has
proper flexibility, bubbles are less likely to be included at the
time of lamination, and even if bubbles are included, since the
surface of the resin layer is non-adhesive or slightly adhesive,
the bubbles can easily be removed by pressure bonding by means of
rolls, press or the like.
[0084] The silicone resin layer of the present invention is
preferably a cured product of a silicone for release paper. The
silicone for release paper comprises, as the chief agent, a
silicone containing a linear dimethyl polysiloxane in its molecule
which is particularly excellent in release properties among
silicones. The silicone for release paper contains the chief agent
and a crosslinking agent and is fixed on the surface of the
substrate by curing by means of a catalyst, a photopolymerization
initiator or the like. The cured coating film of the silicone for
release paper has excellent release properties and appropriate
flexibility.
[0085] When the silicone for release paper having such properties
is used as the silicone resin layer of the present invention, a
silicone resin layer having appropriate flexibility and having
releasability and non-adhesive properties can be obtained.
[0086] The silicone for release paper can be classified by the
curing mechanism into a condensation reaction silicone, an addition
reaction silicone, an ultraviolet-curable silicone and an electron
beam-curable silicone. Any of these can be used in the present
invention. However, most preferred is an addition reaction silicone
from such a viewpoint that the curing reaction is easily carried
out, and a silicone resin layer of the present invention is easily
formed when the cured coating film is formed, and from the
viewpoint of heat resistance of the cured product. Further, it is
possible to ascertain to some extent whether or not the silicone
for release paper is contained in the resin layer by IR (infrared
spectroscopy) or from the strength or adhesive property of the
resin layer.
[0087] The addition reaction silicone comprises the chief agent
made of a linear polyorganosiloxane having vinyl groups at both
terminals and/or in its side chain, and a crosslinking agent made
of methylhydrogen polysiloxane having hydrosilyl groups in its
molecule, and it undergoes a heat curing reaction in the presence
of a platinum catalyst.
[0088] The linear polyorganosiloxane having vinyl groups at both
terminals and/or in its side chain, is a compound which can be
represented by either one of the following formulae.
##STR00001##
wherein each of m and n is an integer and may be 0. When m is 0,
the linear polyorganosiloxane will have vinyl groups at both
terminals. When m is an integer of at least 1, the linear
polyorganosiloxane will have vinyl groups at both terminals and in
its side chain.
##STR00002##
wherein m in the formula is an integer of at least 2, and n is an
integer and may be 0. In such a case, the linear polyorganosiloxane
will have vinyl groups in its side chain.
[0089] The methylhydrogen polysiloxane having hydrosilyl groups in
its molecule is a compound represented by the following
formula.
##STR00003##
wherein a in the formula is an integer, and b is an integer of at
least 1.
[0090] Further, a part of methyl groups at a terminal of the
methylhydrogen polysiloxane may be a hydrogen atom or a hydroxyl
group.
[0091] In the addition reaction silicone, the chief agent made of
the linear polyorganosiloxane having vinyl groups at both terminals
and/or in its side chain, and a crosslinking agent made of
methylhydrogen polysiloxane having hydrosilyl groups in its
molecule, is such that the molar ratio of the hydrosilyl groups to
the vinyl groups is preferably from 0.7/1 to 1.3/1, particularly
preferably from 0.8/1 to 1.2/1.
[0092] If the molar ratio of the hydrosilyl groups to the vinyl
groups exceeds 1.3/1, the peeling force after the heat treatment
increases, and the removability may be deteriorated. Further, if
the molar ratio of the hydrosilyl groups to the vinyl groups is
less than 0.7/1, the crosslink density of a cured product
decreases, whereby the chemical resistance, etc., may have a
problem. The reason why the peeling force after the heating
treatment increases when the molar ratio of the hydrosilyl groups
to the vinyl groups exceeds 1.3/1, is not apparent, but it is
considered that some kind of reaction between unreacted hydrosilyl
groups in the cured product and silanol groups at the glass
surface, by the heating treatment, is involved.
[0093] The catalyst to be used for heat curing reaction is
preferably a platinum catalyst, and as the platinum catalyst, a
known one may be used. Specifically, it may, for example, be
chloroplatinic acid such as tetrachloroplatinic(II) acid or
hexachloroplatinic(IV) acid, an alcohol compound of chloroplatinic
acid, an aldehyde compound or a complex salt of chloroplatinic acid
with an olefin.
[0094] The amount of the platinum catalyst used is preferably from
0.1 to 20 parts by mass, more preferably from 1 to 10 parts by
mass, per 100 parts by mass of the silicone for release paper.
[0095] The structures of silicone for release paper to be used for
forming a silicone resin layer having releasability and
non-adhesive property and to be used for forming a silicone resin
layer having releasability and slight adhesive property, are not
substantially different. Specifically, depending on the level of
the crosslink density in a resin cured product to be obtained by
heat-curing the silicone for release paper, a silicone resin layer
may be separated into a case of having releasability and
non-adhesive property or into a case of having releasability and
slight adhesive property. More specifically, when the crosslink
density in a resin cured product is large, a resin cured product
will have adhesive property.
[0096] From such a viewpoint, it may be said that in the above
linear polyorganosiloxane, when vinyl groups contained in its side
chain increase, a resin cured product to be obtained will have
adhesive property.
[0097] The silicone for release paper may be a solvent, emulsion or
solventless form, and any form can be used. However, in view of
productivity, safety and environmental properties, the solventless
form is preferred. In the case of using the solventless form,
bubbles are less likely to remain in the resin layer since a
solvent which causes bubbles at the time of heat curing,
ultraviolet curing or electron beam curing is not contained.
[0098] The silicone resin layer of the present invention may be
formed by only one silicone for release paper or may be formed by
two or more silicones for release paper. In a case where it is
formed by two or more silicones for release paper, it may be a
silicone resin layer having a multilayer structure in which the two
or more silicones for release paper are laminated with each other,
or may be a mixed silicone resin layer containing the two or more
silicones for release paper in one layer.
[0099] With respect to the silicone resin layer of the present
invention, it is preferred that components in the silicone resin
layer are less likely to migrate to the glass substrate when the
glass substrates are separated, that is, the resin layer preferably
has low silicone migration property.
[0100] The degree of easiness of migration of components in the
silicone resin layer, can be judged by employing the residual
adhesion ratio of the silicone resin layer as an index. The
residual adhesion ratio of the silicone resin layer can be measured
by the following method.
Method for Measuring Residual Adhesion Ratio
[0101] A standard adhesive tape (CELLOTAPE (trade mark) CT405A-15
(manufactured by NICHIBAN Co., Ltd.)) with a width of 15 mm is
bonded to the surface of the silicone resin layer manually and
heated at 70.degree. C. for 20 hours in the air. After a lapse of
20 hours, the standard adhesive tape is peeled from the silicone
resin layer. The peeled standard adhesive tape is bonded to the
surface of a clean glass substrate (e.g. AN100 (manufactured by
Asahi Glass Company, Limited)), and then the 180.degree. peel
strength (300 mm/min) is measured (peel strength (A)).
[0102] The same standard adhesive tape as above is bonded to the
surface of a clean glass substrate (e.g. AN100 (manufactured by
Asahi Glass Company, Limited)) manually and then left at room
temperature in the air for 20 hours. After a lapse of 20 hours, the
standard adhesive tape is peeled from the surface of the glass
substrate. The peeled standard adhesive tape is bonded to the
surface of a glass substrate (e.g. AN100 (manufactured by Asahi
Glass Company, Limited)), and the 180.degree. peel strength (300
mm/min) is measured (peel strength (B)).
[0103] The residual adhesion ratio is determined from the following
formula. Further, when there is no migration whatsoever, the
residual adhesion ratio is 100%.
Residual adhesion ratio(%)=peel strength(A)/peel
strength(B).times.100
[0104] The silicone resin layer of the present invention preferably
has a residual adhesion ratio obtained by the above measuring
method of at least 95%, more preferably at least 98%. When the
residual adhesion ratio is at least 95%, it is considered that
migration of components in the resin layer from the silicone resin
layer to the glass substrate surface is very low. Therefore, since
components in the silicone resin layer are less likely to migrate
to the surface of the glass substrate after separation, bonding
failure or the like is less likely occur when a polarizing plate or
the like is bonded to the surface of glass substrate.
[0105] To obtain a silicone resin layer having low silicone
migration property, a silicone for release paper containing no
components having high migration properties may be used. A
non-reactive silicone is blended in some cases so that the silicone
for release paper has releasability. In such a case, as the
non-reactive silicone, a linear dimethylpolysiloxane having a very
high molecular weight or a relatively low molecular weight linear
dimethylpolysiloxane having compatibility with the cured coating
film lowered by introducing a phenyl group or a higher alkyl group,
is used. Since such a non-reactive silicone is a component having
high migration property, the silicone for release paper used in the
present invention preferably has a non-reactive silicone content of
at most 5 mass %, and it more preferably contains substantially no
non-reactive silicone.
[0106] In the present invention, specifically, a suitable silicone
for release paper may, for example, be KNS-320A, KS-847 (each
manufactured by Shin-Etsu Silicones), TPR6700 (manufactured by GE
Toshiba Silicone), a combination of vinyl silicone "8500"
(manufactured by Arakawa Chemical Industries, Ltd.) and
methylhydrogen polysiloxane "12031" (manufactured by Arakawa
Chemical Industries, Ltd.), a combination of vinyl silicone "11364"
(manufactured by Arakawa Chemical Industries, Ltd.) and
methylhydrogen polysiloxane "12031" (manufactured by Arakawa
Chemical Industries, Ltd.), or a combination of vinyl silicone
"11365" (manufactured by Arakawa Chemical Industries, Ltd.) and
methylhydrogen polysiloxane "12031" (manufactured by Arakawa
Chemical Industries, Ltd.).
[0107] The suitable thickness of a resin layer having removability,
which includes the above silicone resin layer, is controlled by a
thinner thickness between the glass substrate and the protective
glass substrate. As the substrate thickness increases, the boding
strength of the resin layer to both substrates decreases, whereby
in order to secure sufficient bonding strength to both substrates,
the resin layer is needed to be thickened. Further, the most
preferred thickness of the resin layer may vary depending on the
level of flexibility or adhesive property of the resin layer to be
used.
[0108] In general, the thickness of the resin layer having
removability is preferably from 1 to 100 .mu.m. If the thickness of
the resin layer is thinner than 1 .mu.m, the bonding strength of
the resin layer to both substrates may be insufficient. Further,
when foreign matters are included, convex defects are likely to
form. On the other hand, when the thickness exceeds 100 .mu.m, it
takes time for curing of the resin, such being economically
disadvantageous.
[0109] The thickness of a resin having removability is more
preferably from 5 to 30 .mu.m. When the thickness of the resin
layer is from 5 to 30 .mu.m, even if thicknesses of the glass
substrate and the protective glass substrate are large, for
example, the thickness of the thinner substrate between the glass
substrate and the protective glass substrate is at least 0.5 mm,
the bonding strength of the resin layer to both substrates will
unlikely be insufficient. The thickness of the resin layer having
removability is further preferably from 15 to 30 .mu.m.
[0110] A process for forming the resin layer having removability on
the protective glass substrate is not particularly limited, and it
is suitably selected from known methods. When the silicone for
release paper is used for the resin layer having removability, the
silicone for release paper is applied on a surface of the
protective glass substrate, and then the silicone for release paper
is cured before glass is laminated.
[0111] As a method of applying the silicone for release paper, a
known method may be used. Specifically, it may, for example, be a
spray coating method, a die coating method, a spin coating method,
a dip coating method, a roll coating method, a bar coating method,
a screen printing method or a gravure coating method. Such a
coating method can properly be selected depending upon the type of
the silicone for release paper. For example, in a case where the
silicone for release paper is a solventless type, the die coating
method, the spin coating method or the screen printing method is
suitable. Among them, the screen printing method is preferred for a
reason that the yield of a liquid is suitable, and it is possible
to form a resin layer in a uniform thickness over the entire
surface of the glass substrate.
[0112] In a case where the silicone for release paper is a
solventless type, its amount to be applied is preferably from 1
g/m.sup.2 to 100 g/m.sup.2.
[0113] In the case of an addition reaction silicone, a mixture of
the silicone for release paper containing the chief agent and the
crosslinking agent, with a catalyst, is applied on the protective
glass substrate by any one of the above methods, and then
heat-cured. The heat-curing conditions vary depending upon the
amount of the catalyst blended, and for example, when 2 parts by
mass of a platinum catalyst is blended per 100 parts by mass of the
silicone for release paper, the mixture is heat-cured in atmosphere
at a temperature of from 50.degree. C. to 250.degree. C.,
preferably from 100.degree. C. to 200.degree. C. for from 5 to 60
minutes, preferably from 10 to 30 minutes.
[0114] In order to obtain a silicone resin layer having low
silicone migration property, it is preferred that the curing
reaction proceeds as far as possible so that unreacted silicone
components will not remain in the silicone resin layer. By
heat-curing under the above condition, unreacted silicone
components will not remain in the silicone resin layer. If the
heating time is too long, or if the heating temperature is too high
as compared with the above conditions, oxidative decomposition of
the silicone resin will take place simultaneously, and low
molecular weight silicone components will form, thus increasing the
silicone migration property.
[0115] Thus, it is preferred that the curing reaction proceeds as
far as possible so that unreacted silicone components will not
remain in the silicone resin layer, also to obtain favorable
releasability after heat treatment.
[0116] The shape of a resin layer to be formed on the protective
glass substrate is not particularly limited as long as the glass
substrate is not displaced from the protective glass substrate when
the production process for a display device is carried out by using
the glass substrate with protective glass. Therefore, it is not
necessary to form the resin layer on the entire surface of the
protective glass substrate, and the resin layer may be formed on a
part of the surface of the protective glass substrate. However, if
the resin layer is formed at a random position on the surface of
the protective glass substrate, the bonding strength of the resin
layer to the glass substrate may be deteriorated. Further, in a
state where the glass substrate is laminated on the resin
layer-formed surface of the protective glass, if there is a space
in the resin layer when the laminate is viewed from a side, it is
not possible to use a vacuum lamination method or a vacuum pressing
method. Therefore, when the resin layer is formed on a part of the
surface of the protective glass substrate, it is preferred to form
the resin layer so that the resin layer has a circular form (a
doughnut-like circular form) having some width, on the surface of
the protective glass substrate. In a case where such a resin layer
is formed, when the silicone for release paper is used for the
resin layer having removability, the silicone for release paper may
be screen-printed in a dot form as to draw a circle having some
width, on the surface of the protective glass substrate.
[0117] After the resin layer having removability is formed on the
protective glass substrate, the glass substrate is laminated on the
resin layer-formed surface of the protective glass substrate. When
the silicone for release paper is used for the resin layer having
removability, the silicone for release paper applied on the
protective glass substrate is heat-cured to form a silicone resin
layer, and then, the glass substrate is laminated on the silicone
resin-formed surface of the protective glass substrate. More
specifically, they are laminated so that the resin layer-formed
surface of the protective glass substrate and the back surface of
the glass substrate face each other.
[0118] By heat-curing the silicone for release paper, a silicone
resin cured product will be chemically bonded to the protective
glass substrate, and by an anchor effect, the silicone resin layer
will be bonded to the protective glass substrate. By these actions,
the silicone resin layer is "fixed" on the protective glass
substrate. Further, when the glass substrate is subjected to
lamination after the heat-curing, such a glass substrate can easily
be peeled.
[0119] The procedure to laminate the glass substrate on the surface
of the protective glass substrate with the resin having
removability formed, can be carried out by using a known process.
For example, in a normal pressure environment, the glass substrate
is laminated on the resin-formed surface, and then, the laminate
may be pressure bonded by using rolls or a press. By pressure
bonding by rolls or a press, the resin layer and the glass
substrate are more closely bonded to each other. Further, by
pressure bonding by rolls or a press, the bubbles included in the
resin layer can easily be removed.
[0120] However, from the viewpoint of suppressing inclusion of
bubbles or securing suitable bonding, it is preferred to use a
vacuum lamination method or a vacuum pressing method. By laminating
in a vacuum atmosphere, even if very small bubbles remain, the
bubbles will not grow by heating, whereby convex defects of the
glass substrate less likely to form.
[0121] When the glass substrate is to be laminated on the resin
layer-formed surface of the protective glass substrate, it is
necessary to sufficiently clean the surface of the glass substrate
and to laminate it in an environment of a high cleanness.
[0122] Extremely small foreign matters may be absorbed in the resin
layer by deformation of the resin layer having flexibility, and
they may not influence the bonding property of the surface of the
glass substrate with protective glass after the lamination.
However, depending on their amounts or sizes, the bonding property
of the laminate may be deteriorated.
[0123] Now, the process for producing a display device of the
present invention will be described. In the process for producing a
display device of the present invention, after the glass substrate
with protective glass of the present invention is formed by the
above procedure, prescribed treatment to produce a display device
on the glass substrate of the glass substrate with protective glass
is carried out. In the present specification, prescribed treatment
to produce a display device, widely includes various treatments
carried out in the production process when a display device such as
an LCD or an OLED is produced. Specific examples of treatments
carried out include, with reference to production of an LCD as an
example, a step of forming an array on the glass substrate, a step
of forming a color filter on a glass substrate different from the
above glass substrate, a step of bonding the glass substrate on
which the array is formed and the glass substrate on which the
color filter is formed (an array/color filter bonding step). As a
treatment carried out in these steps, specifically, for example,
washing with pure water, drying, film deposition, resist coating,
exposure, developing, etching and removal of resist may, for
example, be mentioned. Further, as a step carried out after the
array/color filter bonding step, a step of reduction in thickness
of the glass substrate by a chemical etching treatment, a liquid
crystal injection step and a step of sealing the inlet carried out
after the treatment may be mentioned, and treatment carried out in
these steps is also included.
[0124] However, all of these treatments do not need to be carried
out in a state of the glass substrate with protective glass. For
example, from the viewpoint of handling efficiency, it is preferred
that until the array/color filter bonding step, the respective
steps are carried out in a state of the glass substrate with
protective glass, and then, after separating the glass substrate
from the back surface of the protective glass substrate, the liquid
crystal injection step is carried out. Further, when the chemical
etching treatment is carried out after the array/color filter
bonding step is carried out, the glass substrate and the back
surface of the protective glass substrate need to be separated
before the chemical etching treatment is carried out.
[0125] Here, in the process for producing a display device of the
present invention, both of a glass substrate on which an array is
to be formed and a glass substrate on which a color filter is to be
formed, may not be a glass substrate with protective glass. For
example, it is possible to bond a glass substrate with protective
glass on which an array is formed and an ordinary glass substrate
on which a color filter is formed, or it is possible to bond an
ordinary glass substrate on which an array is formed and a glass
substrate with protective glass on which a color filter is
formed.
[0126] Further, with reference to production of an OLED as an
example, steps of forming an organic EL structure on the glass
substrate with protective glass include various steps such as a
step of forming a transparent electrode, a step of evaporating a
hole injection layer, a hole transport layer, an
electroluminescence layer, an electron transport layer, etc., and a
sealing step, and as treatments carried out in these steps,
specifically, for example, film deposition treatment, evaporation
treatment and treatment to bond a sealing plate may be
mentioned.
[0127] After the above prescribed treatment is carried out, the
glass substrate and the protective glass substrate are separated.
The separation may be carried out by peeling manually, but it is
possible to more easily carry out peeling by providing a start of
peeling at the edge portion by e.g. a blade of a razor or by
injecting air into the interface of the laminate. On the peeled
protective glass substrate, the resin layer having removability is
still present as it was formed, whereby it is possible to use the
protective glass substrate again, for a laminate with another glass
substrate.
[0128] After the glass substrate and the protective glass substrate
are separated, a display device having a glass substrate can be
obtained via required and desired steps. The steps carried out
include, in the case of an LCD, for example, a step of reduction in
thickness of the glass substrate by a chemical etching treatment, a
separation step into cells having a desired size, a step of
injecting liquid crystal and then sealing the inlet, a step of
bonding a polarizing plate and a module forming step. In the case
of an OLED, in addition to these steps, a step of assembling the
glass substrate on which an organic EL structure is formed and an
opposing substrate, is included.
[0129] Further, the present invention also provides silicone for
release paper, which is used for lamination of the protective glass
substrate and the glass substrate, and which is for the glass
substrate with protective glass.
EXAMPLES
Example 1
[0130] The protective glass substrate (AN100, manufactured by Asahi
Glass Company, Limited) having 400 mm.times.300 mm.times.0.3 mm
thick and having a linear expansion coefficient of
38.times.10.sup.-7/.degree. C., was cleaned by e.g. purified water
washing and UV washing, and then, a mixed product (application
amount 30 g/m.sup.2) of 100 parts by mass of a non-solvent addition
reaction type silicone for release paper (KNS-320A, viscosity: 400
cs, manufactured by Shin-Etsu Silicone) and 2 parts by mass of a
platinum type catalyst (CAT-PL-56, manufactured by Shin-Etsu
Silicone), was applied on the above protective glass substrate by a
screen printing machine, and was heat-cured at 180.degree. C. for
30 mins in the atmospheric air to obtain a silicone resin layer of
20 .mu.m thick.
[0131] A surface of a glass substrate (AN100, manufactured by Asahi
Glass Company, Limited) having 400 mm.times.300 mm.times.0.4 mm
thick and having a linear expansion coefficient of
38.times.10.sup.-7/.degree. C., which is to be contacted with the
silicone resin layer, was cleaned by e.g. purified water washing,
and UV washing, and then, a silicone-resin-layer-formed surface of
the protective glass substrate and the glass substrate were
laminated by a vacuum press at room temperature, to obtain a glass
substrate with protective glass (a glass substrate 1 with
protective glass) of the present invention. FIG. 1 is at
cross-sectional view of the glass substrate 1 with protective glass
obtained in such a manner. As shown in FIG. 1, the glass substrate
1 with protective glass comprises a glass substrate 11 and a
protective glass substrate 12 laminated on each other by a silicone
resin layer 13.
[0132] In the glass substrate 1 with protective glass, the glass
substrate 11 is bonded to the silicone resin layer 13 without
having formation of bubbles, and it had no convex defects and had
suitable smoothness.
[0133] The formed glass substrate 1 with protective glass was
evaluated as follows.
(1) Simple Peel Test
[0134] The glass substrate 1 with protective glass was set so that
the glass substrate 11 became upside, and the glass substrate 11
was fixed by using a jig. With such a state, the protective glass
substrate 12 was peeled downward manually, and it was easily
peeled. Further, with respect to the glass substrate 1 with
protective glass after it was heat treated at 300.degree. C. for 1
hour in an atmosphere, the peel test was also carried out, and the
protective glass substrate 12 was easily peeled and had suitable
heat resistance.
(2) Peel Test (1) (Before Heating)
[0135] A test was carried out by a jig shown in FIG. 2. Further,
for convenience of a Figure, the side length of the jig is shown
shorter than the actual one.
[0136] The glass substrate 1 with protective glass was cut into a
size of 50 mm.times.50 mm, and on surfaces of both glass substrates
(the glass substrate 11 and the protective glass substrate 12) of
the glass substrate 1 with protective glass, polycarbonate members
20 and 21, having 50 mm.times.50 mm.times.5 mm thick were bonded
with an adhesive for epoxy two-pack glass. Further, on each surface
of the polycarbonate members 20 and 21 bonded on glass substrates,
each of polycarbonate members 25 and 26, having 50 mm.times.50
mm.times.5 mm thick, was bonded. The position where each of the
polylcarbonate members 25 and 26 bonded was, as shown in FIG. 2, at
the most left end of each polycarbonate members 20 and 21 in a
horizontal direction, and at a parallel position is each
polycarbonate members 20 and 21 in a vertical direction.
[0137] The glass substrate 1 with protective glass having
polycarbonate members 20, 21 and 25, 26 bonded thereon, was set as
to have the protective glass substrate 12 downside. The
polycarbonate member 25 on a side of the glass substrate 11 was
fixed, and when the polycarbonate member 26 on a side of the
protective glass substrate 12 was peeled downward in a
perpendicular direction at a rate of 300 mm/min, the protective
glass substrate 12 was peeled when a load of 13.8 kg wt (0.55 kg
wt/cm.sup.2) was applied. No breakage was formed on the protective
glass substrate 12 or the glass substrate 11.
(3) Peel Test (1) (After Heating)
[0138] A peel test (1) (after heating) was carried out in the same
manner as in the peel test (1) (before heating) except that instead
of using the glass substrate 1 with protective glass in the peel
test (1) (before heating), a glass substrate 1 with protective
glass after being heat-treated at 300.degree. C. for 1 hour in an
atmosphere after lamination was used. The protective glass
substrate 12 was peeled when a load of 45 kg wt (1.8 kg
wt/cm.sup.2) was applied. No breakage was formed on the protective
glass substrate 12 or the glass substrate 11.
[0139] Further, this heat treatment is almost the same as the heat
treatment which is carried out when liquid crystal is formed.
(4) Shear Strength Test
[0140] A test was carried out by a jig shown in FIG. 3. Further,
for convenience of the Figure, the side length of the jig is shown
shorter than the actual one.
[0141] The glass substrate 1 with protective glass was cut into a
size of 25 mm.times.25 mm, and on surfaces of both glass substrates
(the glass substrates 11 and 12) of the glass substrate 1 with
protective glass, polycarbonate members 30 and 31, having 25
mm.times.50 mm.times.3 mm thick were bonded with an epoxy two-pack
adhesive for glass. The area for bonding was set as 25 mm.times.25
mm. Further, the areas for bonding were an area covering the
protective glass substrate 12 and a right half portion of the
polycarbonate member 31, and an area covering the glass substrate
11 and a left half portion of the polycarbonate member 30.
[0142] The polycarbonate member 30 bonded on the glass substrate 11
was fixed, and the polycarbonate member 31 bonded on the protective
glass substrate 12 was pulled at a pulling rate of 0.5 mm/min in a
lateral direction in FIG. 3 (in a length direction of the
polycarbonate members 30 and 31). The protective glass substrate 12
was peeled when a load of 13 kg wt (2.1 kg wt/cm.sup.2) was
applied. No breakage was formed on the protective glass substrate
12 or the glass substrate 11. Further, the shear strength test was
carried out with respect to the glass substrate 1 with protective
glass after being heat-treated at 300.degree. C. for 1 hour in an
atmosphere after lamination, but the same value was obtained.
(5) Measuring Residual Adhesion Ratio
[0143] By using the measuring method described in the above "method
for measuring residual adhesion ratio", the residual adhesion ratio
of a silicone resin layer formed by the above procedures, was
measured, and the residual adhesion ratio was 106%.
Example 2
[0144] The glass substrate with protective glass (a glass substrate
2 with protective glass) of the present invention was obtained by
carrying out the same procedures as in Example 1 except that the
substrate thickness of the protective glass substrate was 0.4
mm.
[0145] In the glass substrate 2 with protective glass, the glass
substrate was bonded to the silicone resin layer without forming
bubbles, and it had no convex defects and had suitable
smoothness.
[0146] When the simple peel test was carried out on the glass
substrate 2 with protective glass, it was easy to peel the back
surface protective glass substrate. Further, with respect to the
glass substrate 2 with protective glass after being heat-treated at
300.degree. C. for 1 hour in an atmosphere, the simple peel test
was carried out, and it was easy to peel the back surface
protective glass substrate, and the heat resistance was also
suitable.
[0147] Further, in the same manner as in Example 1, with respect to
the glass substrate 2 with protective glass, the peel test (1)
(before heating), peel test (1) (after heating) and the shear
strength test were carried out, and in each test, the protective
glass substrate was peeled when a load of 13.8 kg wt (0.55 kg
wt/cm.sup.2), a load of 45 kg wt (1.8 kg wt/cm.sup.2) and a load of
13 kg wt (2.1 kg wt/cm.sup.2) were applied, respectively.
[0148] In the same manner as in Example 1, the residual adhesion
ratio of the silicone resin layer formed by the above procedures,
was measured, and the residual adhesion ratio was 106%.
Example 3
[0149] The protective glass substrate (AN100, manufactured by Asahi
Glass Company, Limited) having 400 mm.times.300 mm.times.0.2 mm
thick and having a linear expansion coefficient of
38.times.10.sup.-7/.degree. C. was cleaned by e.g. purified water
washing and UV washing, and then, a mixed product (application
amount 20 g/m.sup.2) of a linear polyorganosiloxane having vinyl
groups at both terminals (tradename "8500", manufactured by Arakawa
Chemical Industries, Ltd.), methylhydrogen polysiloxane having
hydrosilyl groups in its molecule (tradename "12031" manufactured
by Arakawa Chemical Industries, Ltd.), and a platinum catalyst
(tradename CAT12070", manufactured by Arakawa Chemical Industries,
Ltd.), was applied on the above protective glass substrate by a
screen printing machine, and was heat-cured at 180.degree. C. for
30 minutes in an atmosphere to obtain a silicone resin layer of 20
.mu.m thick.
[0150] Here, the mixing ratio of the linear polyorganosiloxane to
methylhydrogen polysiloxane was adjusted so that the molar ratio of
the hydrosilyl groups to the vinyl groups became 1/1. The platinum
catalyst was added in an amount of 5 parts by mass per 100 parts by
mass of the total of the linear polyorganosiloxane and
methylhydrogen polysiloxane.
[0151] The glass substrate (AN100, manufactured by Asahi Glass
Company, Limited) having 400 mm.times.300 mm.times.0.5 mm thick and
having a linear expansion coefficient of
38.times.10.sup.-7/.degree. C. had its surface to be contacted with
the silicone resin layer, cleaned by e.g. purified water washing
and UV washing, and then, the silicone resin layer-formed surface
of the protective glass substrate and the glass substrate were
bonded to each other at room temperature by vacuum pressing to
obtain the glass substrate with protective glass (a glass substrate
3 with protective glass) of the present invention.
[0152] In the glass substrate 3 with protective glass, the glass
substrate was bonded to the silicone resin layer without forming
bubbles, and it had no convex defects and had suitable
smoothness.
[0153] When the simple peel test was carried out on the glass
substrate 3 with protective glass, it was easy to peel the
protective glass substrate. Further, with respect to the glass
substrate 3 with protective glass after being heat-treated at
300.degree. C. for 1 hour in an atmosphere, the simple peel test
was carried out, and it was easy to peel the protective glass
substrate, and the heat resistance was also suitable.
[0154] Further, in the same manner as in Example 1, with respect to
the glass substrate 3 with protective glass, the peel test (1)
(before heating), the peel test (1) (after heating) and the shear
strength test were carried out, and in each test, the protective
glass substrate was peeled when a load of 12 kg wt (0.47 kg
wt/cm.sup.2), a load of 12 kg wt (0.47 kg wt/cm.sup.2) and a load
of 12 kg wt (1.9 kg wt/cm.sup.2), were applied, respectively.
[0155] In the same manner as in Example 1, the residual adhesion
ratio of the silicone resin layer formed by the above procedures,
and the residual adhesion ratio was 105%.
Example 4
[0156] A glass substrate with protective glass (a glass substrate 4
with protective glass) was obtained by carrying out the same
procedures as Example 3 except that the substrate thickness of the
protective glass was adjusted as 0.4 mm, and that the substrate
thickness of the glass substrate was adjusted as 0.7 mm.
[0157] In the glass substrate 4 with protective glass, the glass
substrate was bonded with the silicone resin layer without forming
bubbles, and it had no convex defects and had suitable
smoothness.
[0158] When the simple peel test was carried out on the glass
substrate 4 with protective glass substrate, it was easy to peel
the protective glass substrate. Further, with respect to the glass
substrate 4 with protective glass after being heat treated at
300.degree. C. for 1 hour in an atmosphere, the simple peel test
was carried out, and it was easy to peel the protective glass
substrate, and the heat resistance was also suitable.
[0159] Further, in the same manner as in Example 1, with respect to
the glass substrate 4 with protective glass, the peel test (1)
(before heating), peel test (1) (after heating) and the shear
strength test were carried out, and in each test, the protective
glass substrate was peeled when a load of 12.0 kg wt (0.47 kg
wt/cm.sup.2), a load of 12 kg wt (0.47 kg wt/cm.sup.2) and a load
of 12 kg wt (1.9 kg wt/cm.sup.2) were applied, respectively.
[0160] In the same manner as in Example 1, the residual adhesion
ratio of the silicone resin layer formed by the above procedures,
was measured, and the residual adhesion ratio was 105%.
Example 5
[0161] In this Example of the present invention, an LCD is produced
by using the glass substrate 1 with protective glass obtained in
Example 1. Two glass substrates 1 with protective glass are
prepared, and a step for forming an array is carried out for one of
them to form an array on a surface of the glass substrate. For the
other one, a step for forming a color filter is carried out to form
a color filter on a surface of the glass substrate. The glass
substrate 1 with protective glass on which an array is formed, and
the glass substrate 1 with protective glass on which a color filter
is formed, are bonded to each other, and then, a start for peeling
is provided at the edge portion by a blade of a razor, and each
protective glass substrate is separated. On the surface of the
glass substrate after the separation, there are no scratches which
might lead to a strength decrease. Then, the glass substrate is cut
and segmentalized into 28 cells having 51 mm.times.38 mm, and then,
a liquid crystal injection step and a step of sealing the injection
inlet are carried out to form liquid crystal cells. For formed
liquid crystal cells, a step of attaching a polarizing plate is
carried out, and continuously, a module formation step is carried
out to obtain an LCD. The LCD obtained in such a manner has no
problem with respect to its characteristics.
Example 6
[0162] In this Example of the present invention, an LCD is produced
by using the glass substrate 3 with protective glass obtained in
Example 3. Two glass substrates 3 with protective glass are
prepared, and a step for forming an array is carried out for one of
them to form an array on a surface of the glass substrate. For the
other one, a step for forming a color filter is carried out to form
a color filter on a surface of the glass substrate. The glass
substrate 3 with protective glass on which an array is formed, and
the glass substrate 3 with protective glass on which a color filter
is formed, are bonded to each other, and then, a start for peeling
is provided at the edge portion by a blade of a razor, and each
protective glass substrate is separated. On the surface of the
glass substrate after the separation, there are no scratches which
might lead to a strength decrease. Then, by a chemical etching
treatment, each thickness of the glass substrates is adjusted as
0.3 mm. On the surface of the glass substrate after the chemical
etching treatment, there is no formation of etch pits which might
be an optically problem. After that, the glass substrate is cut and
segmentalized into 28 cells having 51 mm.times.38 mm, and then, a
liquid crystal injection step and a step of sealing the injection
inlet are carried out to form a liquid crystal cell. For formed
liquid crystal cells, a step of attaching a polarizing plate is
carried out, and continuously, a module formation step is carried
out to obtain an LCD. The LCD obtained in such a manner has no
problem with respect to its characteristics.
Example 7
[0163] In this example of the present invention, the glass
substrate 2 with protective glass obtained in Example 2 and an
alkali-free glass substrate having a thickness of 0.7 mm are used
to produce an LCD. The glass substrate 2 with protective glass is
prepared, and a step of forming a color filter is carried out to
form a color filter on a surface of the glass substrate 2 with
protective glass. On the other hand, for the alkali-free glass
substrate (AN-100, manufactured by Asahi Glass Company, Limited)
having a thickness of 0.7 mm, a step of forming an array is carried
out to form an array on a surface of the alkali-free glass
substrate having a thickness of 0.7 mm. The glass substrate 2 with
protective glass on which a color filter is formed, and the
alkali-free glass substrate having a thickness of 0.7 mm, on which
an array is formed, are bonded to each other, and then, a start for
peeling is provided at the edge portion by a blade of a razor,
whereby the protective glass substrate is separated from the glass
substrate 2 with protective glass. On the surface of the glass
substrate after the separation, there are no scratches which might
lead to a strength decrease. Then, a glass substrate/alkali-free
glass substrate attachment is segmentalized into 28 cells having 51
mm.times.38 mm by a razor cutter or scrub/break method. And then, a
liquid crystal injection step and a step of sealing the inlet are
carried out to form liquid crystal cells. For formed liquid crystal
cells, a step of attaching a polarizing plate is carried out, and
continuously, a module formation step is carried out to obtain an
LCD. The LCD obtained in such a manner has no problem with respect
to its characteristics.
Example 8
[0164] In this Example of the present invention, by using the glass
substrate 3 with protective glass obtained in Example 3, an OLED is
produced. By carrying out a step of forming a transparent
electrode, a step for forming an auxiliary electrode, a step of
vapor depositing a hole injection layer, a hole transport layer, a
luminous layer, an electron transport layer, etc., and a step of
sealing them, an organic EL structure is formed on the glass
substrate of the glass substrate 3 with protective glass. Then, the
protective glass substrate is separated. On the surface of the
glass substrate after the separation, there are no scratches which
might lead to a strength decrease. Then, the glass substrate is cut
by using a razor cutter or a scrub/break method, and segmentalized
into 40 cells having 41 mm.times.30 mm, and then, the glass
substrate on which the organic EL structure is formed, and the
facing substrate, are assembled, and a module formation step was
carried out to produce an OLED. The OLED obtained in such a manner
has no problem with respect to its characteristics.
Comparative Example 1
[0165] An LCD is obtained by carrying out the same procedures as
Example 5 except that instead of the glass substrate 1 with
protective glass, a glass substrate (AN100, manufactured by Asahi
Glass Company, Limited) having 400 mm.times.300 mm.times.0.4 mm
thick and having a linear expansion coefficient of
38.times.10.sup.-7/.degree. C., is used.
[0166] On the surface of the glass substrate after the array/color
filter bonding step, many scratches are formed, which might lead to
a strength decrease.
Comparative Example 2
[0167] An LCD is obtained by carrying out the same procedures as
Example 6 except that instead of the glass substrate 3 with
protective glass, a glass substrate (AN100, manufactured by Asahi
Glass Company, Limited) having 400 mm.times.300 mm.times.0.5 mm
thick and having a linear expansion coefficient of
38.times.10.sup.-7/.degree. C., is used.
[0168] On the surface of the glass substrate after the array/color
filter bonding step, many scratches are formed, which might lead to
a strength decrease. Further, on the surface of the glass substrate
after a chemical etching treatment, there is formation of etch pits
having a depth of 20 .mu.m, which are recognized as optical
defects.
INDUSTRIAL APPLICABILITY
[0169] The glass substrate with protective glass obtained by the
present invention, may be used as a glass substrate for various
display devices.
[0170] The entire disclosure of Japanese Patent Application No.
2006-191388 filed on Jul. 12, 2006 including specification, claims,
drawings and summary is incorporated herein by reference in its
entirety.
* * * * *