U.S. patent application number 12/452275 was filed with the patent office on 2010-06-03 for image display device and production method thereof.
This patent application is currently assigned to Sony Chemical & Information Device Corporation. Invention is credited to Yusuke Kamata, Yoshihisa Shinya, Tomoyuki Toyoda.
Application Number | 20100134713 12/452275 |
Document ID | / |
Family ID | 40259705 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100134713 |
Kind Code |
A1 |
Toyoda; Tomoyuki ; et
al. |
June 3, 2010 |
Image Display Device and Production Method Thereof
Abstract
An image display device, and a production method thereof are
provided, which are capable of suppressing warping of a protective
panel formed from a plastic as much as possible. In an image
display device having a liquid crystal display panel 1 and a
transparent protective panel 2 formed from a plastic which are
arranged facing each other via a cured resin, an outer dimension of
the protective panel 2 is made larger than an outer dimension of
the liquid crystal display panel 1, curing of a resin composition 4
is carried out in a state where a peripheral edge of the protective
panel 2 is fixed with a fixing jig 5, and the peripheral edge of
the protective panel 2 is fixed with the fixing jig 5 even after
the curing of the resin composition 4. Alternatively, the outer
dimension of the protective panel 2 is substantially equal to an
outer dimension of the liquid crystal display panel 1, this outer
dimension is substantially equal to an inner dimension of a case 8
of the liquid crystal display panel 1 and the protective panel 2,
and the curing of the resin composition 4 is carried out in a state
where the resin composition 4 is in contact with substantially the
whole face of the protective panel 2.
Inventors: |
Toyoda; Tomoyuki; (Tochigi,
JP) ; Shinya; Yoshihisa; (Tochigi, JP) ;
Kamata; Yusuke; (Tochigi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
Sony Chemical & Information
Device Corporation
Tokyo
JP
|
Family ID: |
40259705 |
Appl. No.: |
12/452275 |
Filed: |
July 16, 2008 |
PCT Filed: |
July 16, 2008 |
PCT NO: |
PCT/JP2008/062866 |
371 Date: |
December 23, 2009 |
Current U.S.
Class: |
349/58 ; 349/122;
445/24 |
Current CPC
Class: |
G02F 1/133311 20210101;
G02F 1/133325 20210101; G02F 2201/503 20130101; G02F 1/1333
20130101; G02F 1/13332 20210101; G02F 2201/50 20130101; G02F
1/133331 20210101; G02F 2202/28 20130101; G02F 2201/54 20130101;
G02F 1/133308 20130101 |
Class at
Publication: |
349/58 ; 349/122;
445/24 |
International
Class: |
G02F 1/1333 20060101
G02F001/1333; H01J 9/20 20060101 H01J009/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2007 |
JP |
2007-186360 |
Jan 11, 2008 |
JP |
2008-005027 |
Apr 10, 2008 |
JP |
2008-102051 |
Claims
1. An image display device comprising an image display panel and a
transparent protective panel formed from a plastic which are
arranged facing each other via a cured resin, wherein an outer
dimension of the protective panel is made larger than an outer
dimension of the image display panel, and a peripheral edge of the
protective panel is fixed with a fixing jig.
2. The image display device according to claim 1, wherein the
protective panel has a shielding part on a peripheral edge thereof
with the shielding part being fixed with the fixing jig.
3. The image display device according to claim 1, comprising a case
serving as the fixing jig.
4. The image display device according to claim 3, wherein an upper
face of the peripheral edge of the protective panel is held by the
case.
5. The image display device according to claim 3, wherein a lower
face of the peripheral edge of the protective panel is fixed and
supported by the case.
6. The image display device according to claim 1, wherein a
substantially whole face of the image display panel is adhered to
the cured resin.
7. An image display device comprising an image display panel and a
transparent protective panel formed from a plastic which are
arranged facing each other via a cured resin, wherein an outer
dimension of the protective panel is substantially equal to an
outer dimension of the image display panel, the outer dimension is
equal to an inner dimension of a case of the protective panel and
the image display panel, and a substantially whole face of the
protective panel is adhered to the image display panel by the cured
resin.
8. The image display device according to claim 1, wherein the
protective panel is formed from a polymethyl methacrylate.
9. The image display device according to claim 1, wherein the cured
resin is obtained by curing a resin composition having a curing
shrinkage ratio of 5% or lower by UV-ray irradiation, and has a
storage modulus at 25.degree. C. of 1.times.10.sup.7 Pa or
lower.
10. The image display device according to claim 9, wherein the
resin composition contains at least one kind of polymer selected
from the group consisting of a polyurethane acrylate, a
polyisoprene-based acrylate or an ester thereof, a hydrogenated
terpene resin, and a butadiene polymer; at least one kind of
acrylate monomer selected from the group consisting of isobornyl
acrylate, dicyclopentenyl oxyethyl methacrylate, and 2-hydroxybutyl
methacrylate; and a photopolymerization initiator.
11. The image display device according to claim 1, wherein the
image display panel is a liquid crystal display panel.
12. A method for producing an image display device comprising the
steps of arranging an image display panel and a transparent
protective panel formed from a plastic to face each other via a
resin composition, and curing the resin composition, wherein an
outer dimension of the protective panel is made larger than an
outer dimension of the image display panel, and the resin
composition is cured in a state where a peripheral edge of the
protective panel is fixed with a fixing jig.
13. The method for producing an image display device according to
claim 12, wherein the protective panel has a shielding part on the
peripheral edge thereof, and the resin composition is cured in a
state where the shielding part is fixed with the fixing jig.
14. The method for producing an image display device according to
claim 12, wherein a case is used as the fixing jig.
15. The method for producing an image display device according to
claim 14, wherein the resin composition is cured while an upper
face of the peripheral edge of the protective panel is held by the
case.
16. The method for producing an image display device according to
claim 14, wherein the resin composition is cured while a lower face
of the peripheral edge of the protective panel is fixed with the
case.
17. A method for producing an image display device comprising the
steps of arranging an image display panel and a transparent
protective panel formed from a plastic to face each other via a
resin composition, and curing the resin composition, wherein an
outer dimension of the protective panel is made substantially equal
to an outer dimension of the image display panel, the outer
dimension is made substantially equal to an inner dimension of a
case of the protective panel and the image display panel, and the
resin composition is cured in the case in a state where a
substantially whole face of the protective panel is in contact with
the resin composition.
18. The method for producing an image display device according to
claim 12, wherein the resin composition is cured by UV-ray
irradiation.
19. The method for producing an image display device according to
claim 12, wherein the resin composition has a curing shrinkage
ratio of 5% or lower and a cured resin thereof has a storage
modulus at 25.degree. C. of 1.times.10.sup.7 Pa or lower.
20. The method for producing an image display device according to
claim 19, wherein the resin composition contains at least one kind
of polymer selected from the group consisting of a polyurethane
acrylate, a polyisoprene-based acrylate or an ester thereof, a
hydrogenated terpene resin, and a butadiene polymer; at least one
kind of acrylate monomer selected from the group consisting of
isobornyl acrylate, dicyclopentenyl oxyethyl methacrylate, and
2-hydroxybutyl methacrylate; and a photopolymerization initiator.
Description
TECHNICAL FIELD
[0001] The present invention relates to an image display device
having an image display panel such as a liquid crystal display
panel, and a method for producing such an image display device.
More specifically, the present invention relates to an improved
image display device, and production method thereof, in which a
cured resin is arranged between an image display panel and a
transparent protective panel.
BACKGROUND ART
[0002] In an image display device such as a liquid crystal display
device, to prevent the image display panel from being damaged and
to protect the surface thereof, a transparent protective panel such
as a glass panel or a plastic panel is arranged on the front face
of the image display panel. More specifically, for example, the
protective panel is mounted inside a case with a slight gap with
respect to the image display panel, by arranging a spacer or the
like between the image display panel and the protective panel at
the peripheral edge of the image display panel.
[0003] However, when such a configuration is employed, the gap
between the image display panel and the protective panel scatters
light, resulting in decreased contrast and luminance. This leads to
the problem that image quality is harmed. Furthermore, in a
configuration in which a gap is present, reflection occurs at the
interface between the protective panel and air due to their
different refractive indices, which leads to visibility problems,
especially outdoors.
[0004] Based on such circumstances, it has been proposed to fill a
resin between the image display panel and the protective panel. For
example, in the liquid crystal display device described in Patent
Document 1, a spacer is arranged on the periphery of a polarizing
plate which is pasted on the surface of a liquid crystal display
panel, and a surface protective glass is mounted on an upper
portion of the spacer. Furthermore, the surface protective glass is
mounted on the liquid crystal display panel by filling an adhesive
so that air bubbles do not enter between the polarizing plate and
the surface protective glass.
[0005] Patent Document 2 also describes an image display device in
which an image display panel and a protective panel are closely
adhered via at least one or more layers of a transparent adhesive
material. Patent Document 2 describes that excellent impact
resistance can be realized by having a predetermined relationship
between the thickness of the transparent adhesive material and the
dynamic viscoelastic properties measured based on frequency
dispersion. [0006] [Patent Document 1] Japanese Patent Application
Laid-Open No. 2005-55641 [0007] [Patent Document 2] Japanese Patent
Application Laid-Open No. 2003-29644
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0008] However, from the perspective of production costs and impact
resistance, it is better to use a plastic panel than a glass panel
for the protective panel. Glass panels cost comparatively more than
plastic panels, and also have weaker impact resistance. Therefore,
the use of a plastic panel formed from polymethyl methacrylate
(PMMA), which is a kind of acrylic resin, as a protective panel is
being investigated.
[0009] However, the use of a plastic panel as a protective panel
leads to problems with the protective panel warping, which becomes
a cause of display quality deterioration. For example, if a resin
composition is filled between the image display panel and the
plastic panel and is cured, the image display panel is subjected to
stresses such as the internal stress generated due to volume
shrinkage during the curing of the resin composition, the external
stress generated by the plastic panel warping due to changes in the
environment temperature, and the residual stress of during molding
that the plastic panel itself has. When such internal, external, or
residual stresses are applied on the image display panel, if the
image display panel is a liquid crystal display panel, the cell gap
of the liquid crystal layer fluctuates in the order of nanometers,
which becomes a cause for the occurrence of image unevenness. In
particular, while in some cases the size of the protective panel is
made larger than the size of the image display panel, and a
shielding part is provided on the peripheral portion of the
protective panel, in such cases the tendency for image unevenness
to occur is pronounced. Furthermore, in extreme cases, the
peripheral portion of the protective panel can warp upwards,
causing light leakage and the like to occur.
[0010] To suppress volume shrinkage of the resin composition filled
between the image display panel and the protective panel, it has
even been tried to use a resin composition having a low curing
shrinkage ratio and a low elastic modulus. However, when a plastic
panel is used for the protective panel, the fact remains that the
results cannot always be said to be sufficient. This is because
plastic panels such as a polymethyl methacrylate panel tend to warp
from changes in the environment temperature (especially when
exposed to high temperatures). Therefore, the resin composition
tends to become hot and warp not only when the resin composition
filled between the image display panel and the protective panel
undergoes thermal curing, but even when such resin composition is
cured by UV-ray irradiation. In addition, warping also tends to
occur from the high temperatures even after curing.
[0011] The present invention was proposed in consideration of such
problems in the conventional art. It is an object of the present
invention to provide a configuration of an image display device
capable of suppressing warping of a protective panel formed from a
plastic as much as possible, and to provide a method for producing
the image display device.
Means for Solving the Problems
[0012] To achieve the above objects, a first image display device
according to the present invention is an image display device
comprising an image display panel and a transparent protective
panel formed from a plastic which are arranged facing each other
via a cured resin, wherein an outer dimension of the protective
panel is made larger than an outer dimension of the image display
panel, and a peripheral edge of the protective panel is fixed with
a fixing jig.
[0013] A first method for producing an image display device
according to the present invention is a method for producing an
image display device comprising the steps of arranging an image
display panel and a transparent protective panel formed from a
plastic to face each other via a resin composition, and curing the
resin composition, wherein an outer dimension of the protective
panel is made larger than an outer dimension of the image display
panel, and the resin composition is cured in a state where a
peripheral edge of the protective panel is fixed with a fixing
jig.
[0014] A second image display device according to the present
invention is an image display device comprising an image display
panel and a transparent protective panel formed from a plastic
which are arranged facing each other via a cured resin,
[0015] wherein an outer dimension of the protective panel is
substantially equal to an outer dimension of the image display
panel, the outer dimension is equal to an inner dimension of a case
of the protective panel and the image display panel, and
substantially the whole face of the protective panel is adhered to
the image display panel by the cured resin.
[0016] A second method for producing an image display device
according to the present invention is a method for producing an
image display device comprising the steps of arranging an image
display panel and a transparent protective panel formed from a
plastic to face each other via a resin composition, and curing the
resin composition, wherein an outer dimension of the protective
panel is substantially made equal to an outer dimension of the
image display panel, the outer dimension is substantially made
equal to an inner dimension of a case of the protective panel and
the image display panel, and curing the resin composition in the
case in a state where substantially the whole face of the
protective panel is in contact with the resin composition.
[0017] In the present invention, the expression "an outer dimension
of the protective panel is larger than an outer dimension of the
image display panel" refers to the image display panel being
included within the protective panel when in a plan view the
protective panel and the image display panel are superimposed.
Advantages of the Invention
[0018] As described above, when the size of the protective panel is
larger than the size of the image display panel, the occurrence of
warping at the peripheral edge of the protective panel is
pronounced. Therefore, in the first image display device or the
method for producing the same according to the present invention,
the resin composition is cured by UV-ray irradiation in a state
where the peripheral edge of the protective panel is fixed using a
fixing jig, and the peripheral edge is also fixed with the fixing
jig even after the curing. Consequently, the resin composition can
be cured in a state where warping of the protective panel is
corrected, and a state in which the protective panel is not warped
can be maintained.
[0019] On the other hand, in the second image display device or the
second method for producing the same according to the present
invention, the focus is on the size of the protective panel, the
size of the image display panel, and the size of the case thereof.
The resin composition is cured in a state where the outer dimension
of the protective panel, the outer dimension of the image display
panel, and the inner dimension of the case thereof are made
substantially equal. Then, the resin composition is cured in a
state where substantially the whole face of the protective panel is
in contact with the resin composition. Consequently, the resin
curing are not carried out in a state where the peripheral edge of
the protective panel is open. In addition, just by fitting the
protective panel and the image display panel in the case with the
resin composition interposed therebetween, warping upwards of the
protective panel can be suppressed from the side face (face in
contact with the case) of the protective panel. Consequently, the
resin can be uniformly cured over the whole face of the protective
panel without having to take any particular fixing measures for the
protective panel, and the occurrence of warping can be
suppressed.
[0020] The conventional art completely fails to describe the idea
of suppressing the occurrence of warping in the protective panel by
making the outer dimension of the protective panel, the outer
dimension of the image display panel, and the inner dimension of
the case thereof substantially equal. For example, in the invention
described in the above Patent Document 1, a surface protection
glass is used, and absolutely no consideration is given to warping
of a plastic panel. The invention of Patent Document 2 is directed
to an image display device having a comparatively large screen of
about 32 to 100 inches. Since the size of the protective panel is
smaller than the size of the display panel, and the configuration
is different from that of the present invention, the protection
configuration of the image display panel cannot be produced by the
simple operation of just superimposing the protective panel and the
image display panel via the resin composition and fitting the
resultant structure in the case.
[0021] Therefore, according to the first and second image display
devices of the present invention, even though the protective panel
is formed from a plastic, warping of the protective panel can be
reliably suppressed, and a highly reliable image display can be
obtained in which image unevenness and the like do not occur.
Furthermore, according to the method for producing an image display
device according to the present invention, such an image display
device can be provided.
[0022] Furthermore, according to the first and second image display
devices of the present invention, since a cured resin is arranged
between the protective panel and the image display panel,
advantageous effects from such configuration can also be obtained.
For example, reflection at the interface with the protective panel
can be suppressed, and sufficient outdoor visibility can also be
ensured. In addition, because the cured resin is arranged between
the protective panel and the image display panel, compared with
when a gap is provided between these panels, sufficient impact
resistance and the like can be ensured even if the clearance
between the protective panel and the image display panel is thin.
Therefore, the present invention is also useful in making the
device thinner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic diagram of a panel configuration of a
liquid crystal display device according to an embodiment of the
present invention.
[0024] FIG. 2 is a schematic cross-sectional diagram illustrating a
pasting step of a protective panel according to the embodiment
illustrated in FIG. 1.
[0025] FIG. 3 is a schematic diagram of a panel configuration of a
liquid crystal display device according to another embodiment of
the present invention.
[0026] FIG. 4 is a schematic cross-sectional diagram illustrating a
pasting step of a protective panel according to the embodiment
illustrated in FIG. 3.
[0027] FIG. 5 is a schematic cross-sectional diagram illustrating a
pasting step of a protective panel in a liquid crystal display
device according to another embodiment of the present
invention.
[0028] FIG. 6 is a schematic cross-sectional diagram illustrating
warping of a protective panel.
DESCRIPTION OF THE REFERENCE NUMERALS
[0029] 1 Liquid crystal display panel [0030] 2 Protective panel
[0031] 2a Shielding part [0032] 3 Cured resin [0033] 4 Resin
composition [0034] 5, 6 Fixing jig [0035] 5a Holding part [0036] 7
Adhesive tape [0037] 8 Case
BEST MODE FOR CARRYING OUT THE INVENTION
[0038] Embodiments of the image display device and production
method thereof to which the present invention is applied will now
be described with reference to the drawings using a liquid crystal
display device as an example. In the drawings, same-numbered
reference numerals represent the same or a similar structural
element.
[0039] FIG. 1 is a schematic diagram of a panel configuration of a
liquid crystal display device according to an embodiment of a first
aspect of the present invention. This liquid crystal display device
is used in a mobile phone, a portable game device or the like. The
liquid crystal display device includes a liquid crystal display
panel 1 for displaying images and a protective panel 2 for
protecting the surface of the liquid crystal display panel 1. The
liquid crystal display panel 1 and the protective panel 2 are
arranged facing each other via a cured resin 3. Furthermore, the
liquid crystal display panel 1 and protective panel 2 are
respectively adhered with substantially the whole face of the
surface or the back face of the cured resin 3. Consequently, the
liquid crystal display device has improved visibility and impact
resistance.
[0040] In the liquid crystal display panel 1, a liquid crystal
layer LC is formed such that a liquid crystal material is
sandwiched between a pair of substrates 11 and 12. Images are
displayed by controlling the orientation of the liquid crystal
material in this liquid crystal layer LC. More specifically,
provided on the pair of substrates 11 and 12 are a not-illustrated
color filter and black matrix, pixel electrodes and counter
electrodes, as well as drive transistors and the like. A polarizing
plate is pasted on the surface and back face of the pair of
substrates 11 and 12. Image display is performed by controlling the
drive of each pixel by an active matrix system, for example. A gap
g between the pair of substrates 11 and 12 is a so-called cell
gap.
[0041] Furthermore, in this image display device, a shielding part
2a is formed on the peripheral edge of the protective panel 2. The
outer dimension W2 of the protective panel 2, which includes the
shielding part 2a, is slightly larger than the outer dimension W1
of the liquid crystal display panel 1, so that the shielding part
2a protrudes towards the exterior side from the interior side of
the peripheral edge of the liquid crystal display panel 1. Light
leakage from the peripheral portion of the liquid crystal display
panel 1 can be reliably shielded by the shielding part 2a.
[0042] Thus, when the peripheral edge of the protective panel 2
protrudes from the peripheral edge of the liquid crystal display
panel 1, if the resin composition is simply arranged between these
panels, and the protective panel 2 and the liquid crystal display
panel 1 are pasted by curing the resin composition, as illustrated
in FIG. 6, the cured resin 3 warps upwards especially at the
peripheral portion of the protective panel 2 due to the internal
stress (arrow A) generated during the curing of the resin
composition and the external stress (arrow B) generated on the
peripheral portion when the protective panel 2 warps due to changes
in the environment temperature. Consequently, these stresses are
applied on the upper face of the liquid crystal display panel 1.
When such stresses are applied on the liquid crystal display panel
1, the gap g between the substrates 11 and 12 of the liquid crystal
display panel 1 fluctuates in the order of nanometers between the
center portion and the peripheral portion, for example, which may
cause image unevenness to occur.
[0043] However, in the present embodiment, the curing of the resin
composition is carried out in a state where the upper face of the
shielding part 2a of the protective panel 2 (i.e., the face of the
protective panel 2 on the opposite side of the liquid crystal
display panel 1) is held on the liquid crystal display panel 1 side
by a fixing jig 5. This prevents the protective panel 2 from
warping during the curing, so that as little stress as possible is
applied on the liquid crystal display panel 1. Furthermore, as
illustrated in FIG. 1, even after the resin composition is cured,
the upper face of the shielding part 2a continues to be held and
fixed with the fixing jig 5. Therefore, according to the present
embodiment, the peripheral edge of the protective panel 2 can be
maintained in a state free from warping. A method for pasting the
protective panel according to the present embodiment will now be
described.
[0044] FIG. 2 illustrates the pasting step of the protective panel
2 in the method for producing the liquid crystal display device of
the present embodiment. In this step, first, a resin composition 4
is coated between the liquid crystal display panel 1 and the
protective panel 2. In this case, the resin composition 4 may be
coated on the upper face of the liquid crystal display panel 1 and
the protective panel 2 is then superimposed thereon. Conversely,
the resin composition 4 may also be coated on the protective panel
2 side, and then the protective panel 2 is flipped over and is
superimposed on the liquid crystal display panel 1.
[0045] Examples of the resin composition 4 to be used may include
thermosetting and photocurable (for example, UV-ray curable) resin
compositions. However, from the perspective of avoiding a
high-temperature state during curing as much as possible, it is
preferred to use a UV-ray curable or similar photocurable resin
composition. In the present embodiment, a UV-ray curable resin
composition is used as the resin composition 4.
[0046] Furthermore, the resin composition 4 is prepared so as to
have a curing shrinkage ratio of preferably 5% or less, more
preferably 4.5% or less, even more preferably 4.0% or less, and
most preferably 0 to 2%. By doing so, the internal stress that
builds up in the cured resin 3 during curing of the resin
composition 4 can be reduced, and the generation of distortion at
the interface between the cured resin 3 and the liquid crystal
display panel 1, or at the interface between the cured resin 3 and
the protective panel 2, can be prevented.
[0047] In addition, the resin composition 4 is prepared so that the
storage modulus (25.degree. C.) of the cured resin 3 is preferably
1.times.10.sup.7 Pa or less, and more preferably of
1.times.10.sup.3 Pa to 1.times.10.sup.6 Pa. By doing so, the stress
that is applied on the liquid crystal display panel 1 after the
curing of the resin composition 4 can be reduced.
[0048] The magnitude of the internal stress that builds up in the
cured resin 3 during curing of the resin composition 4 can be
evaluated based on the average surface roughness of the cured resin
obtained by dropping the resin composition onto a flat plate and
curing the dropped resin composition. In practice, the distortion
generated at the interface with the liquid crystal display panel 1
and the protective panel 2 can be ignored if, for example, a cured
resin has an average surface roughness of 6.0 nm or less,
preferably 5.0 nm or less, and more preferably from 1 to 3 nm. In
this evaluation, the cured resin can be obtained by dropping 2 mg
of the resin composition onto a glass plate forming the substrate
of a liquid crystal display panel or an acrylic plate forming a
protective panel and curing the resin composition by UV-ray
irradiation to a 90% or higher cure ratio. In such a case, the
average surface roughness of the glass plate or the acrylic plate
is usually 1.0 nm or less. Therefore, the resin composition 4 used
in the present invention is a resin composition which when dropped
onto the glass plate or acrylic plate forming the substrate of a
liquid crystal display panel and then cured, yields a cured resin
having an average surface roughness in the above-described
range.
[0049] The resin composition 4 also has to have excellent optical
properties. For example, regarding the refractive index, it is
preferred that the refractive index of the cured resin 3 formed by
curing the resin composition 4 and the refractive indices of the
liquid crystal display panel 1 and the protective panel 2 are
equal. For example, if the substrate 11 of the liquid crystal
display panel 1 is formed from optical glass, the refractive index
(nD) is 1.49 to 1.50, and if the substrate is formed from hardened
glass, the refractive index is about 1.55. Furthermore, if the
protective panel 2 is formed from an acrylic resin, this refractive
index (nD) is 1.51 to 1.52. Accordingly, the refractive index (nD)
of the cured resin 3 is preferably 1.45 or more to 1.55 or less,
and more preferably 1.51 or more to 1.52 or less.
[0050] In addition, regarding transparency, if the cured resin 3 is
100 .mu.m thick, the transmittance of light in the visible
wavelength region is preferably 90% or higher.
[0051] Examples of resin compositions which satisfy the above
conditions include a resin composition containing at least one kind
of polymer selected from a polyurethane acrylate, a
polyisoprene-based acrylate or an ester thereof, a hydrogenated
terpene resin, a butadiene polymer and the like; at least one kind
of acrylate monomer selected from isobornyl acrylate,
dicyclopentenyl oxyethyl methacrylate, 2-hydroxybutyl methacrylate
and the like; and a photopolymerization initiator such as
1-hydroxycyclohexyl-phenyl-ketone. In this case, the kind and
proportion of the polymer and the acrylate monomer are adjusted so
that the values for the curing shrinkage ratio, storage modulus,
and optical properties fall within the above-described ranges. The
protective panel 2 is often provided with a function for cutting
light in the UV region to protect the liquid crystal display panel
1 against UV rays. Therefore, it is preferred to combine the
photopolymerization initiator with a photopolymerization initiator
that can cure even in the visible region (for example, trade name:
SpeedCure TPO, manufactured by Nihon SiberHegner KK).
[0052] When coating the resin composition 4 on the liquid crystal
display panel 1 or the protective panel 2, a spacer is formed on
the periphery of the liquid crystal display panel 1, for example,
before the coating of the resin composition 4 is carried out.
Obviously, the spacer may be omitted. Although the thickness of the
coated resin composition 4 is arbitrary, preferably the coating is
carried out so that the layer thickness of the cured resin 3 will
be about 50 .mu.m to 200 .mu.m.
[0053] After the coating of the resin composition 4, the liquid
crystal display panel 1 and the protective panel 2 are superimposed
over each other with the resin composition 4 interposed
therebetween. Here, the protective panel 2 is a transparent panel
made of a plastic. For example, an acrylic resin panel or the like,
such as a polymethyl methacrylate panel, may be used. Furthermore,
in the present embodiment, the protective panel 2 has on its
peripheral edge a shielding part 2a which shields light. The
shielding part 2a may be formed by pasting a light-shielding tape
or by printing a light-shielding coating.
[0054] The outer dimension of the protective panel 2 is larger than
the outer dimension of the liquid crystal display panel 1.
Therefore, when these panels are superimposed, the peripheral edge
of the protective panel 2 protrudes from the peripheral edge of the
liquid crystal display panel 1. If the joining with the protective
panel 2 is carried out by simply irradiating UV rays in this state
to cure the resin composition 4, the problem of warping of the
protective panel 2 arises. Thus, in the present embodiment, as
illustrated in FIG. 2, the resin composition 4 is cured in a state
where the peripheral edge of the protective panel 2 is fixed using
the fixing jig 5 so as to be held from the upper face of the
protective panel 2.
[0055] More specifically, the fixing jig 5 may have, for example, a
frame shape capable of housing in its interior the liquid crystal
display panel 1 and the protective panel 2, in which the upper end
portion is folded over to form an eaves-shaped holding part 5a. The
resin composition 4 is cured by UV-ray irradiation in a state where
the upper face of the peripheral edge of the protective panel 2,
which serves as the shielding part 2a, is held by this holding part
5a. Consequently, since the curing of the resin composition 4 is
carried out in a state in which the warping of the protective panel
2 is corrected, the flatness of the protective panel 2 is
maintained. Furthermore, even when the resin composition is cured
by UV-ray irradiation, in actual practice, the protective panel 2
is exposed to heat rays. However, as long as the shielding part 2a
is fixed with the holding part 5a, the warping will not expand even
if the protective panel 2 becomes hot.
[0056] Moreover, while the fixing jig 5 may be a dedicated jig used
only during the curing of the resin composition 4, the case housing
the liquid crystal display panel 1 on which the protective panel 2
is pasted may also be used for this purpose. The above-described
held state can be obtained by forming the eaves-shaped holding part
5a in the case of the liquid crystal display device into which the
liquid crystal display panel 1 and the like is to be mounted, and
mounting the liquid crystal display panel 1 in the case. In this
case, the case can be used as is, and the mounting of the liquid
crystal display panel 1 is completed simultaneously with the
completion of the curing of the resin composition 4. More
specifically, the liquid crystal display device has the exact same
structure as the state illustrated in FIG. 2. Furthermore, in this
case, the upper face of the protective panel 2 continues to be
supported and fixed with the case even after the curing of the
resin composition 4, whereby the warping of the protective panel 2
over time can also be prevented.
[0057] The thus-produced liquid crystal display device is a highly
reliable liquid crystal display device in which warping of the
protective panel 2 is reliably suppressed, and display unevenness
and the like does not occur. Furthermore, since the cured resin 3
is filled between the protective panel 2 and the liquid crystal
display panel 1, outdoor visibility can be sufficiently ensured,
and impact resistance can also be ensured.
[0058] FIG. 3 is a schematic diagram of a panel configuration of an
image display device according to another embodiment of the first
aspect of the present invention. This image display device differs
from the image display device illustrated in FIG. 1 in that the
lower face of the peripheral edge of the protective panel 2 formed
from a plastic, that is, the face on the liquid crystal display
panel 1 side of the protective panel 2, is adhered and fixed to the
upper end face of a fixing jig 6. Other features are formed in the
same manner as the image display device illustrated in FIG. 1.
[0059] The pasting method of the protective panel 2 in this
embodiment is, similar to as described above, to coat the liquid
crystal display panel 1 with the resin composition 4 and then
superimpose the protective panel 2 over the liquid crystal display
panel 1 with the resin composition 4 interposed therebetween. At
this stage, as illustrated in FIG. 4, a frame-shaped fixing jig 6
having roughly the same outer dimension as the protective panel 2
is used. The peripheral edge of the protective panel 2 is fixed
with the upper end face of this fixing jig 6. For example, the
protective panel 2 is adhesively fixed by pasting an adhesive tape
7 on the upper end face of the fixing jig 6. If the resin
composition 4 is cured by carrying out the UV-ray irradiation in
this state, similar to in the embodiment of FIG. 1, the warping of
the protective panel 2 can be reliably suppressed.
[0060] In the present embodiment too, the fixing jig 6 may be a
dedicated jig used only during the curing of the resin composition
4, or the case housing the liquid crystal display panel 1 may also
be used for this purpose. In the latter case, the liquid crystal
display device has the exact same structure as the state
illustrated in FIG. 3.
[0061] FIG. 5 is a schematic diagram of a method for producing a
panel configuration of a liquid crystal display device according to
an embodiment of a second aspect of the present invention. The
present embodiment is characterized in that the outer dimension of
the protective panel 2 is made substantially the same as the outer
dimension of the liquid crystal display panel 1, the outer
dimensions of these panels are made substantially the same as the
inner dimension of the case 8 thereof, and the curing of the resin
composition 4 is carried out in a state where the resin composition
4 is in contact with substantially the whole surface of the
protective panel 2. Furthermore, in the present embodiment also,
the method is the same as that of the above embodiments according
to the first aspect of the present invention as far as the coating
of the resin composition 4. Thus, such a description is omitted
here.
[0062] As described above, after coating the resin composition 4 on
the liquid crystal display panel 1, the protective panel 2 is
superimposed thereon. However, as illustrated in FIG. 5, at this
stage the outer dimension of the protective panel 2 is made
substantially the same as the outer dimension of the liquid crystal
display panel 1. Consequently, the whole face of the protective
panel 2 contacts the resin composition 4, and is in a so-called
"warping margin-less" state. In this state, the liquid crystal
display panel 1 and the protective panel 2 are housed in the case
8. Here, the inner dimension of the case 8 is set to be
substantially the same as the outer dimension of the protective
panel 2 and the liquid crystal display panel 1, and so that the
protective panel 2 superimposed on the liquid crystal display panel
1 fits precisely in the case 8. In this state, if the curing of the
resin composition 4 is carried out by irradiating UV rays, the
warping of the protective panel 2 can be simply and reliably
suppressed. This is because there are no protruding portions of the
protective panel 2 where warping becomes pronounced, and the
warping upwards of the protective panel 2 is suppressed by the case
8 which abuts a side face of the protective panel 2. Furthermore,
in the present embodiment, the shielding part has to be separately
provided.
[0063] Although embodiments of the present invention were described
above, the present invention is obviously not limited to those
embodiments. Various modifications may be made to the embodiments
discussed above without departing from the scope of the present
invention. For example, the shielding part may be omitted on the
peripheral edge of the protective panel. Furthermore, while the
above-described embodiments all apply the present invention in a
liquid crystal display device, the present invention may also be
applied in a device other than a liquid crystal display device. For
example, the present invention may also be applied in an organic EL
display device, a plasma display and the like.
EXAMPLES
[0064] Next, more specific examples of the present invention will
be described based on experiment results.
Example 1
[0065] A protective panel was pasted on a liquid crystal display
panel according to the method illustrated in FIG. 2 to produce a
liquid crystal display device. The used protective panel was a
transparent plastic panel formed from polymethyl methacrylate
(PMMA). A case housing the liquid crystal display panel was used as
a fixing jig. An upper face of a light shielding part formed on a
peripheral edge of the protective panel was held and fixed with
forming an eaves-shaped holding part on this case.
[0066] The resin composition to be arranged between the liquid
crystal display panel and the protective panel was prepared by
kneading in a kneader 70 parts by weight of an ester compound
formed from a maleic anhydride adduct of a polyisoprene polymer and
2-hydroxyethyl methacrylate, 30 parts by weight of dicyclopentenyl
oxyethyl methacrylate, 10 parts by weight of 2-hydroxybutyl
methacrylate, 30 parts by weight of a hydrogenated terpene resin,
140 parts by weight of a butadiene polymer, 4 parts by weight of a
photopolymerization initiator, and 0.5 parts by weight of a visible
region photopolymerization initiator.
[0067] The curing shrinkage ratio of this resin composition was
1.8%, and the storage modulus (25.degree. C.) of the cured resin
obtained by curing this resin composition was 1.times.10.sup.4 Pa.
Furthermore, the average surface roughness of the cured resin
obtained by dropping 2 mg of the resin composition onto a glass
plate for a liquid crystal cell, and curing the resin composition
by UV-ray irradiation at a cure ratio of 90% or higher, was 2.7 nm.
In addition, the transmittance in the visible region of a 100
.mu.m-thick cured resin formed from the above resin composition was
measured by a UV-Visible Spectrophotometer (model name: V-560,
manufactured by JASCO Corporation) to be 90% or higher.
[0068] For the storage modulus, the elastic modulus (Pa)
(25.degree. C.) was measured at a measurement frequency of 1 Hz
using a viscoelastometer (model name: DMS6100, manufactured by
Seiko Instruments Inc.).
[0069] The curing shrinkage ratio was determined by measuring the
specific gravities of the uncured resin solution and the cured
solid using an electronic densimeter (model name: SD-120L,
manufactured by Mirage), and calculating the difference between
them from the following equation.
Curing shrinkage ratio (%)=(Cured product specific gravity-Resin
solution specific gravity)/Cured product specific
gravity.times.100
[0070] The average surface roughness was determined by measuring
the distortion (Ra: average surface roughness) in a given region
(2.93 mm.times.2.20 mm) of a glass plate surface using a
three-dimensional non-contact surface roughness meter manufactured
by Zygo Corporation.
[0071] According to the present example, a liquid crystal display
device could be obtained which had hardly any warping of the
protective panel, no display unevenness, and excellent outdoor
visibility and impact resistance.
Example 2
[0072] A liquid crystal display device was produced in the same
manner as in Example 1, except that the resin composition to be
arranged between the liquid crystal display panel and the
protective panel was changed as follows. In the present example
too, a liquid crystal display device could be obtained which had
hardly any warping of the protective panel, no display unevenness,
and excellent outdoor visibility and impact resistance.
[0073] More specifically, the resin composition in the present
example was prepared by kneading in a kneader 100 parts by weight
of an ester compound formed from a maleic anhydride adduct of a
polyisoprene polymer and 2-hydroxyethyl methacrylate, 30 parts by
weight of dicyclopentenyl oxyethyl methacrylate, 10 parts by weight
of 2-hydroxybutyl methacrylate, 30 parts by weight of a
hydrogenated terpene resin, 210 parts by weight of a butadiene
polymer, 7 parts by weight of a photopolymerization initiator, and
1.5 parts by weight of a visible region photopolymerization
initiator.
[0074] The curing shrinkage ratio of this resin composition was
1.0%, and the storage modulus (25.degree. C.) of a cured resin
obtained by curing this resin composition was 4.times.10.sup.3 Pa.
Furthermore, the average surface roughness of the cured resin
obtained by dropping 2 mg of the resin composition onto a glass
plate for a liquid crystal cell, and curing the resin composition
by UV-ray irradiation at a cure ratio of 90% or higher, was 1.5 nm.
In addition, the transmittance in the visible region of a 100
.mu.m-thick cured resin formed from this resin composition was
measured by a UV-Visible Spectrophotometer (model name: V-560,
manufactured by JASCO Corporation) to be 90% or higher.
Example 3
[0075] A liquid crystal display device was produced in the same
manner as in Example 1, except that the resin composition to be
arranged between the liquid crystal display panel and the
protective panel was changed as follows. In the present example
too, a liquid crystal display device could be obtained which had
hardly any warping of the protective panel, no display unevenness,
and excellent outdoor visibility and impact resistance.
[0076] More specifically, the resin composition in the present
example was prepared by kneading in a kneader 70 parts by weight of
an ester compound formed from a maleic anhydride adduct of a
polyisoprene polymer and 2-hydroxyethyl methacrylate (trade name:
UC-203, manufactured by Kuraray Co., Ltd.), 30 parts by weight of
dicyclopentenyl oxyethyl methacrylate (trade name: FA512M,
manufactured by Hitachi Chemical Co., Ltd.), 10 parts by weight of
2-hydroxybutyl methacrylate (trade name: Light Ester HOB,
manufactured by Kyoeisha Chemical Co., Ltd.), 30 parts by weight of
a hydrogenated terpene resin (trade name: Clearon P-85,
manufactured by Yasuhara Chemical Co., Ltd.), 35 parts by weight of
a butadiene polymer (trade name: Polyoil 110, manufactured by Zeon
Corporation), 5 parts by weight of a photopolymerization initiator
trade name Irgacure 184D, manufactured by Ciba Specialty Chemicals
Inc.), and 2 parts by weight of a visible region
photopolymerization initiator (trade name Speed Cure TPO,
manufactured by Nihon SiberHegner KK).
[0077] The curing shrinkage ratio of this resin composition was
3.8%, and the storage modulus (25.degree. C.) of a cured resin
obtained by curing this resin composition was 4.times.10.sup.5 Pa.
Furthermore, the average surface roughness of the cured resin
obtained by dropping 2 mg of the resin composition onto a glass
plate for a liquid crystal cell, and curing the resin composition
by UV-ray irradiation at a cure ratio of 90% or higher, was 5.0 nm.
In addition, the transmittance in the visible region of a 100
.mu.m-thick cured resin formed from this resin composition was
measured by a UV-Visible Spectrophotometer (model name: V-560,
manufactured by JASCO Corporation) to be 90% or higher.
Example 4
[0078] A liquid crystal display device was produced using the same
protective panel as in Example 1, by pasting the protective panel
on the liquid crystal display panel according to the method
illustrated in FIG. 3. The used resin composition was also the same
as that in Example 1.
[0079] In the present example too, a liquid crystal display device
could be obtained which had hardly any warping of the protective
panel, no display unevenness, and excellent outdoor visibility and
impact resistance.
Example 5
[0080] A liquid crystal display device was produced using the same
protective panel as in Example 1, by pasting the protective panel
on the liquid crystal display panel according to the method
illustrated in FIG. 3. The used resin composition was the same as
that in Example 2.
[0081] In the present example too, a liquid crystal display device
could be obtained which had hardly any warping of the protective
panel, no display unevenness, and excellent outdoor visibility and
impact resistance.
Example 6
[0082] A liquid crystal display device was produced using the same
protective panel as in Example 1, by pasting the protective panel
on the liquid crystal display panel according to the method
illustrated in FIG. 3. The used resin composition was the same as
that in Example 3.
[0083] In the present example too, a liquid crystal display device
could be obtained which had hardly any warping of the protective
panel, no display unevenness, and excellent outdoor visibility and
impact resistance.
Example 7
[0084] A liquid crystal display device was produced using the same
protective panel as in Example 1, by carrying out the resin curing
during the pasting of the protective panel according to the method
illustrated in FIG. 5. The used resin composition was the same as
that in Example 1. In the present example too, a liquid crystal
display device could be obtained which had hardly any warping of
the protective panel, no display unevenness, and excellent outdoor
visibility and impact resistance.
Example 8
[0085] A liquid crystal display device was produced using the same
protective panel as in Example 1, by carrying out the resin curing
during the pasting of the protective panel according to the method
illustrated in FIG. 5. The used resin composition was the same as
that in Example 2. In the present example too, a liquid crystal
display device could be obtained which had hardly any warping of
the protective panel, no display unevenness, and excellent outdoor
visibility and impact resistance.
Example 9
[0086] A liquid crystal display device was produced using the same
protective panel as in Example 1, by carrying out the resin curing
during the pasting of the protective panel according to the method
illustrated in FIG. 5. The used resin composition was the same as
that in Example 3. In the present example too, a liquid crystal
display device could be obtained which had hardly any warping of
the protective panel, no display unevenness, and excellent outdoor
visibility and impact resistance.
* * * * *