U.S. patent application number 12/450232 was filed with the patent office on 2010-02-11 for image display device.
This patent application is currently assigned to Sony Chemical & Information Device Corporation. Invention is credited to Yusuke Kamata, Yoshihisa Shinya.
Application Number | 20100033661 12/450232 |
Document ID | / |
Family ID | 39863965 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100033661 |
Kind Code |
A1 |
Shinya; Yoshihisa ; et
al. |
February 11, 2010 |
IMAGE DISPLAY DEVICE
Abstract
A thin image display device is provided which is free from
display defects caused by the deformation of an image display part
and can display high brightness and high contrast images. The image
display device includes an image display part 2, a
light-transmitting protective part 3 arranged on the image display
part, and a cured resin layer 5 interposed between the image
display part 2 and the protective part 3. The cured resin layer 5
has a light transmittance in the visible region of 90% or more and
a refractive index (nD) of 1.45 or more and 1.55 or less.
Inventors: |
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: |
39863965 |
Appl. No.: |
12/450232 |
Filed: |
April 9, 2008 |
PCT Filed: |
April 9, 2008 |
PCT NO: |
PCT/JP2008/057024 |
371 Date: |
September 17, 2009 |
Current U.S.
Class: |
349/122 |
Current CPC
Class: |
G02F 2201/50 20130101;
C08F 290/067 20130101; C08L 51/003 20130101; G02F 1/133331
20210101; C08L 2203/20 20130101; G02F 1/133308 20130101; G02F
2202/023 20130101; G02F 1/133502 20130101; G02F 2202/28 20130101;
G02F 1/1335 20130101 |
Class at
Publication: |
349/122 |
International
Class: |
G02F 1/1333 20060101
G02F001/1333 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2007 |
JP |
2007-102252 |
Jul 17, 2007 |
JP |
2007-186360 |
Jan 11, 2008 |
JP |
2008-005027 |
Claims
1. An image display device, comprising an image display part and a
light-transmitting protective part arranged on the image display
part, wherein the image display device further comprises a cured
resin layer arranged between the image display part and the
protective part, and the cured resin layer has a light
transmittance in a visible region of 90% or more and a refractive
index (nD) of 1.45 or more and 1.55 or less.
2. The image display device according to claim 1, wherein the cured
resin layer has a storage modulus at 25.degree. C. of
1.0.times.10.sup.7 Pa or less.
3. The image display device according to claim 2, wherein the cured
resin layer has a storage modulus at 25.degree. C. of
1.times.10.sup.3 Pa to 1.times.10.sup.6 Pa.
4. The image display device according to claim 1, wherein the cured
resin layer is a cured product of a resin composition having a
curing shrinkage ratio of 5% or less.
5. The image display device according to claim 4, wherein the cured
resin layer is a cured product of a resin composition having a
curing shrinkage ratio of 4.0% or less.
6. The image display device according to claim 1, wherein the cured
resin layer has a thickness of 50 to 200 .mu.m.
7. The image display device according to claim 1, wherein the cured
resin layer has a refractive index (nD) of 1.51 or more and 1.52 or
less.
8. The image display device according to claim 1, wherein the cured
resin layer is a cured product of a photocurable resin composition
containing at least one kind of polymer selected from the group
consisting of a polyurethane acrylate, a polyisoprene 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, dicyclopentenyloxyethyl
methacrylate and 2-hydroxybutyl methacrylate; and a
photopolymerization initiator.
9. The image display device according to claim 1, wherein the image
display part is a liquid crystal display panel.
10. The image display device according to claim 1, wherein the
protective part is formed from an acrylic resin.
11. The image display device according to claim 1, wherein the
protective part is formed from an optical glass.
12. A resin composition for forming a cured resin layer that is
arranged between an image display part of an image display
apparatus and a light-transmitting protective part, the resin
composition having a curing shrinkage ratio of 5.0% or less, a
cured resin formed by curing the resin composition having a
transmittance in the visible region of 90% or higher and the resin
composition having a refractive index (nD) of 1.45 or more and 1.55
or less and a storage modulus at 25.degree. C. of
1.0.times.10.sup.7 Pa or less.
13. The resin composition according to claim 12, wherein the curing
shrinkage ratio is 4.0% or less.
14. The resin composition according to claim 12, wherein the
storage modulus at 25.degree. C. is 1.times.10.sup.3 Pa to
1.times.10.sup.6 Pa.
15. A cured resin layer arranged between an image display part of
an image display apparatus and a light-transmitting protective
part, the cured resin layer having a transmittance in the visible
region of 90% or higher and a refractive index (nD) of 1.45 or more
and 1.55 or less.
16. The cured resin layer according to claim 15, having a storage
modulus at 25.degree. C. of 1.times.10.sup.7 Pa or less.
17. The cured resin layer according to claim 16, wherein the
storage modulus at 25.degree. C. is 1.times.10.sup.3 Pa to
1.times.10.sup.6 Pa.
18. The cured resin layer according to claim 15, being a cured
product of a resin composition having a curing shrinkage ratio of
5% or less.
19. The cured resin layer according to claim 18, being a cured
product of a resin composition having a curing shrinkage ratio of
4.0% or less.
20. The cured resin layer according to claim 15, the refractive
index (nD) is 1.51 or more and 1.52 or less.
Description
TECHNICAL FIELD
[0001] The present invention relates to an image display device
such as a liquid crystal display device (LCD) used, for example, in
a cellular phone, and in particular to an image display device that
includes a transparent protective part arranged on an image display
part and a cured resin layer arranged between the image display
part and the protective part.
BACKGROUND ART
[0002] One conventional example of such an image display device is
a liquid crystal display device 101 shown in FIG. 4.
[0003] This liquid crystal display device 101 includes a
transparent protective part 103 made of, for example, glass or
plastic on a liquid crystal display panel 102, as shown in FIG.
4.
[0004] In this display device, to protect the surface of the liquid
crystal display panel 102 and a polarizing plate (not shown), a
spacer 104 is arranged between the liquid crystal display panel 102
and the protective part 103 to form a gap 105 between the liquid
crystal display panel 102 and the protective part 103.
[0005] However, the gap 105 present between the liquid crystal
display panel 102 and the protective part 103 causes light
scattering, and this results in a reduction in contrast and in
brightness. In addition, the presence of the gap 105 also makes it
difficult to produce thinner display panels.
[0006] In view of the above problems, a technique has been proposed
in which the gap between the liquid crystal display panel and the
protective part is filled with a resin (for example, Patent
Document 1). However, the stress during cure shrinkage of the cured
resin causes deformation of optical glass plates sandwiching the
liquid crystal of the liquid crystal display panel. This results in
display defects such as irregularities in the orientation of the
liquid crystal material.
[Patent Document 1] Japanese Patent Application Laid-Open No.
2005-55641.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0007] The present invention has been made in view of the problems
in the conventional technologies. It is an object of the present
invention to provide a thin image display device which is free from
display defects caused by the deformation of an image display part
and can display high brightness and high contrast images.
Means for Solving the Problems
[0008] To achieve the above object, the present inventors have
conducted extensive studies and found that as the difference in
refractive index (.DELTA.nD) between the protective part and gap of
an image display device increases, the brightness and contrast of
the image display device are lowered due to the scattering and
attenuation of image light from the image display part. This
results in a reduction in visibility. To avoid this problem, the
present inventors have found that it is effective to arrange a
cured resin layer having a certain refractive index between the
image display part and the protective part. Thus, the present
invention has been completed.
[0009] The inventors have also found that the internal stress
accumulated during curing of a resin composition can be
approximated by the product of the storage modulus after curing and
the curing shrinkage ratio. Therefore, it is preferable to use, as
the resin composition arranged between the image display part and
the protective part, a resin composition that has a certain curing
shrinkage ratio and yields a cured product having a certain storage
modulus.
[0010] Accordingly, the present invention provides an image display
device, comprising an image display part and a light-transmitting
protective part arranged on the image display part, wherein
[0011] the image display device further comprises a cured resin
layer arranged between the image display part and the protective
part, and
[0012] the cured resin layer has a light transmittance in a visible
region of 90% or more and a refractive index (nD) of 1.45 or more
and 1.55 or less.
[0013] Preferably, in the present invention, the cured resin layer
has an elastic modulus at 25.degree. C. of 1.0.times.10.sup.7 Pa or
less.
[0014] Preferably, in the present invention, the cured resin layer
is a cured product of a resin composition having a curing shrinkage
ratio of 5% or less.
[0015] Preferably, in the present invention, the cured resin layer
has a refractive index (nD) of 1.51 or more and 1.52 or less.
[0016] In the present invention, the image display part may be a
liquid crystal display panel.
[0017] In the present invention, the protective part may be formed
from an acrylic resin.
[0018] In the present invention, the protective part may be formed
from an optical glass.
EFFECTS OF THE INVENTION
[0019] In the present invention, the cured resin layer arranged
between the image display part and the protective part has a light
transmittance of 90% or more and a refractive index (nD) of 1.45 or
more and 1.55 or less and more preferably, for example, 1.51 or
more and 1.52 or less. In this manner, as compared to the case in
which air having a refractive index of 1.0 is arranged
therebetween, the differences in refractive index at the interface
of the image display part and the interface of the protective part
are smaller, so that the scattering and attenuation of image light
from the image display part can be reduced. Therefore, according to
the present invention, the brightness and contrast of the displayed
image can be increased, whereby the visibility can be improved.
[0020] In the present invention, the use of a resin composition
having a curing shrinkage ratio of 5% or less and yielding a cured
product having a storage modulus at 25.degree. C. of
1.0.times.10.sup.7 Pa or less can minimize the influence of the
stress during cure shrinkage of the resin on the image display part
and the protective part. Therefore, almost no distortion occurs in
the image display part and the protective part.
[0021] Accordingly, a high brightness and high contrast image can
be displayed without display defects.
[0022] In particular, when the image display part is a liquid
crystal display panel, display defects such as irregularities in
the orientation of the liquid crystal material can be reliably
prevented, so that a high quality image can be displayed.
[0023] Moreover, in the present invention, the gap between the
image display part and the protective part is filled with the cured
resin. This provides high impact resistance.
[0024] In addition, an image display device thinner than the
conventional example in which a gap is formed between the image
display part and the protective part can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a cross-sectional view illustrating the main part
of an embodiment of an image display device according to the
present invention.
[0026] FIG. 2 is a cross-sectional view illustrating the main part
of another embodiment of the image display device according to the
present invention.
[0027] FIG. 3 is a cross-sectional view illustrating the main part
of another embodiment of the image display device according to the
present invention.
[0028] FIG. 4 is a cross-sectional view illustrating the main part
of a conventional display device
DESCRIPTION OF REFERENCE NUMERALS
[0029] 1 image display device, 2 display part, 3 protective part, 4
spacer, 5 cured resin, 6 and 7 polarizing plate
BEST MODE FOR CARRYING OUT THE INVENTION
[0030] Hereinafter, preferred embodiments of the present invention
will be described in detail with reference to the drawings. In the
drawings, the same reference numerals denote the same or like
elements.
[0031] FIGS. 1 and 2 are cross-sectional views illustrating the
main parts of embodiments of an image display device according to
the present invention. The display device 1 of each embodiment
includes: an image display part 2 that is connected to a driving
circuit (not shown) and displays an image in a predetermined
manner; and a light-transmitting protective part 3 that is arranged
so as to face the image display part 2 with a predetermined
distance therebetween, as shown in FIGS. 1 and 2.
[0032] No particular limitation is imposed on the image display
device, and the image display device can be applied to various
applications. Examples of the image display device include liquid
crystal display devices for a cellular phone, a portable game
device, and the like. The image display part 2 of each embodiment
may be the liquid crystal display panel of such a liquid crystal
display device.
[0033] When the image display part 2 is a liquid crystal display
panel, polarizing plates 6 and 7 are provided on the surfaces of
the liquid crystal display panel, as shown in FIG. 2.
[0034] When the body of the liquid crystal display panel is formed
from an optical glass, the refractive index (nD) thereof is
generally 1.49 to 1.50. Some tempered glass has a refractive index
(nD) of about 1.55.
[0035] The protective part 3 is a plate-, sheet-, or film-like
light-transmitting member having substantially the same size as the
size of the display part 2. For example, optical glass or plastic
(an acrylic resin, such as polymethyl methacrylate, or the like)
can be suitably used as the light-transmitting member. An optical
layer such as an anti-reflective film, a shielding film, or a
viewing angle control film may be formed on the front or rear
surface of the protective part 3.
[0036] When the protective part 3 is formed from an acrylic resin,
the refractive index (nD) thereof is generally 1.51 to 1.52.
[0037] The protective part 3 is arranged on the display part 2
through a spacer 4 provided on a peripheral part of the display
part 2. The spacer 4 has a thickness of about 0.05 to about 1.5 mm,
so that the distance between the surfaces of the image display part
2 and the protective part 3 is maintained at about 1 mm.
[0038] To improve the brightness and contrast, a frame-like
shielding part (not shown) is provided on the peripheral part of
the protective part 3.
[0039] A cured resin layer 5 is arranged between the image display
part 2 and the protective part 3. This cured resin layer 5 has a
light transmittance in the visible region of 90% or more.
Preferably, the cured resin layer is formed so as to have a
thickness of 50 to 200 .mu.m.
[0040] Preferably, the cured resin layer 5 has a refractive index
(nD) substantially the same as those of the image display part 2
and the protective part 3. More specifically, the refractive index
(nD) is 1.45 or more and 1.55 or less, and preferably 1.51 or more
and 1.52 or less. In this manner, the brightness and contrast of
the image light from the image display part 2 can be increased, so
that the visibility can be improved.
[0041] The cured resin layer 5 has a storage modulus at 25.degree.
C. of preferably 1.0.times.10.sup.7 Pa or less, and more preferably
1.times.10.sup.3 to 1.times.10.sup.6 Pa. Typically, even when the
main resin component constituting the curable resin composition is
the same, if a remaining resin component or monomer component to be
used is different, the cured resin formed by curing such a curable
resin composition may have a storage modulus (25.degree. C.)
exceeding 1.times.10.sup.7. Such a cured resin layer is not
preferred.
[0042] The cured resin layer 5 is a cured product of a resin
composition having a curing shrinkage ratio of preferably 5% or
less, more preferably 4.5% or less, and still more preferably 4.0%
or less, and most preferably 0 to 2%. In this manner, the internal
stress that builds up in the cured resin layer when the curable
resin composition is cured can be reduced, and the occurrence of
distortion at the interface between the cured resin layer 5 and the
liquid crystal display panel 2 or the protective part 3 can be
prevented. Therefore, when the resin composition is arranged
between the liquid crystal display panel 2 and the protective part
3 and then cured, the cured product can reduce light scattering at
the interface between the cured resin layer 5 and the liquid
crystal display panel 2 or the protective part 3. This can improve
both the brightness of the displayed image and the visibility.
[0043] The magnitude of the internal stress that builds up in the
cured product of a resin composition during curing can be evaluated
by the average surface roughness of the cured resin obtained by
dropping the resin composition onto a flat plate and curing the
dropped resin composition. For example, 2 mg of a resin composition
is dropped onto a glass or acrylic plate and cured by irradiation
with UV light to a cure ratio of 90% or more. When the average
surface roughness of the resultant cured resin is 6.0 nm or less,
the interfacial distortion caused by the cured product of the
curable resin composition arranged between the liquid crystal
display panel 2 and the protective part 3 is practically
negligible. With the curable resin composition used in the present
invention, the average surface roughness can be preferably 6.0 nm
or less, more preferably 5.0 nm or less, and still more preferably
1 to 3 nm. Therefore, the distortion at the interfaces of the cured
resin is practically negligible.
[0044] Any glass plate used for sandwiching the liquid crystal of a
liquid crystal cell or used as the protective plate of a liquid
crystal cell may be preferably used as the above glass plate. Any
acrylic plate used as the protective plate of a liquid crystal cell
may be preferably used as the above acrylic plate. The average
surface roughness of such glass and acrylic plates is typically 1.0
nm or less.
[0045] It is preferable from the viewpoint of improving
productivity that the resin composition forming the cured resin
layer 5 is a photocurable resin composition. To prepare the resin
composition such that the cured resin layer 5 has a refractive
index (nD) of 1.51 or more and 1.52 or less, the monomer of the
resin composition is selected.
[0046] Preferred examples of such a resin include a resin
composition containing: at least one kind of polymer, such as a
polyurethane acrylate, a polyisoprene acrylates or an ester
thereof, a hydrogenated terpene resin, and a butadiene polymer; at
least one kind of acrylate monomer, such as isobornyl acrylate,
dicyclopentenyloxyethyl methacrylate, and 2-hydroxybutyl
methacrylate; and a photo polymerization initiator such as
1-hydroxy-cyclohexyl-phenyl-ketone.
[0047] The protective part 3 often has a UV cut function to protect
the display part 2 from UV light. In such a case, it is preferable
to use, as the photo polymerization initiator, a photo
polymerization initiator that can initiate curing in the visible
region (for example, trade name: SpeedCure TPO, product of Nihon
SiberHegner K.K.).
[0048] In a method of producing the image display device 1 of each
embodiment, for example, the spacer 4 and a projecting bank portion
(not shown) are first provided on the peripheral part of the image
display part 2, and a predetermined amount of the above-described
photocurable resin composition is dropped to the inner region
surrounded by the spacer 4 and the projecting bank portion.
[0049] Then, the protective part 3 is placed on the spacer 4 of the
image display part 2, and the gap between the display part 2 and
the protective part 3 is completely filled with the resin
composition.
[0050] Subsequently, the resin composition is irradiated with UV
light through the protective part 3 to thereby cure the resin
composition. In this manner, the target image display device 1 is
obtained.
[0051] In this image display device 1, since the refractive index
of the cured resin layer 5 is substantially the same as that of the
protective part 3, the brightness and contrast can be increased, so
that the visibility can be improved.
[0052] Since the influence of the stress during cure shrinkage of
the resin on the image display part 2 and the protective part 3 can
be minimized, almost no distortion occurs in the image display part
2 and the protective part 3. Therefore, no deformation occurs in
the image display part 2, so that a high brightness and high
contras image can be displayed without display defects.
[0053] Moreover, since the gap between the image display part 2 and
the protective part 3 is filled with the cured resin layer 5, high
impact resistance is obtained.
[0054] In addition, the image display device 1 can be produced
thinner than the conventional example in which a gap is provided
between the image display part and the protective part.
[0055] The present invention can be embodied in other various
forms. For example, an image display device 1 having no spacers 4
may be produced as shown in FIG. 3. In this case, the
above-described photocurable resin composition is applied to a base
2, and the protective part 3 is placed on the applied resin
composition. The resin composition is cured with light in the same
manner as described above.
[0056] Moreover, the present invention is applicable not only in
the liquid crystal display device described above, but also in
various panel displays such as an organic EL, a plasma display
apparatus and the like.
EXAMPLES
[0057] Hereinafter, the present invention will be specifically
described by way of Examples and Comparative Examples, but the
invention is not limited to the following Examples.
Example 1
[0058] 50 Parts by weight of polyurethane acrylate (trade name:
UV-3000B, manufactured by Nippon Synthetic Chemical Industry Co.,
Ltd.), 30 parts by weight of isobornyl acrylate (trade name: IBXA,
manufactured by Osaka Organic Chemical Industry Ltd.), 3 parts by
weight of a photopolymerization initiator (trade name: IRGACURE
184, manufactured by Ciba Specialty Chemicals Inc.), and 1 part by
weight of a photopolymerization initiator (trade name: SpeedCure
TPO, manufactured by Nihon SiberHegner K.K.) were kneaded using a
kneader to prepare a resin composition of Example 1.
Example 2
[0059] 70 Parts by weight of an ester compound formed from a maleic
anhydride adduct of polyisoprene polymer and 2-hydroxyethyl
methacrylate, 30 parts by weight of dicyclopentenyloxyethyl
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 photo
polymerization initiator for visible light were kneaded using a
kneader to prepare a resin composition of Example 2.
Example 3
[0060] 100 Parts by weight of an ester compound formed from a
maleic anhydride adduct of polyisoprene polymer and 2-hydroxyethyl
methacrylate, 30 parts by weight of dicyclopentenyloxyethyl
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
photopolymerization initiator for visible light were kneaded using
a kneader to prepare a resin composition of Example 3.
Example 4
[0061] 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 photopolymerization initiator (trade name SpeedCure
TPO, manufactured by Nihon SiberHegner K.K.) were kneaded using a
kneader to prepare a resin composition of Example 4.
Comparative Example 1
[0062] 50 Parts by weight of polybutadiene acrylate (trade name:
TE-2000, manufactured by Nippon Soda Co., Ltd.), 20 parts by weight
of hydroxyethyl methacrylate (trade name: Light Ester HO,
manufactured by Kyoeisha Chemical Co., Ltd.), 3 parts by weight of
a photopolymerization initiator (Irgacure 184, manufactured by Ciba
Specialty Chemicals Inc.), and 1 part by weight of a
photopolymerization initiator (trade name: SpeedCure TPO,
manufactured by Nihon SiberHegner K.K.) were kneaded using a
kneader to prepare a resin composition of Comparative Example
1.
Comparative Example 2
[0063] 50 parts by weight of polyurethane acrylate (trade name:
UV-3000B, manufactured by Nippon Synthetic Chemical Industry Co.,
Ltd.), 30 parts by weight of tricyclodecane dimethanol acrylate
(trade name: NK Ester LC2, manufactured by Shin-nakamura Chemical
Co., Ltd.), 3 parts by weight of a photopolymerization initiator
(Irgacure 184, manufactured by Ciba Specialty Chemicals Inc.), and
1 part by weight of a photopolymerization initiator (trade name:
SpeedCure TPO, manufactured by Nihon SiberHegner K.K.) were kneaded
using a kneader to prepare a resin composition of Comparative
Example 2.
Comparative Example 3
[0064] 50 parts by weight of polybutadiene acrylate (trade name:
TE-2000, manufactured by Nippon Soda Co., Ltd.), 20 parts by weight
of isobornyl acrylate (trade name: IBXA, manufactured by Osaka
Organic Chemical Industry Ltd.), 3 parts by weight of a
photopolymerization initiator (Irgacure 184, manufactured by Ciba
Specialty Chemicals Inc.), and 1 part by weight of a
photopolymerization initiator (trade name: SpeedCure TPO,
manufactured by Nihon SiberHegner K.K.) were kneaded using a
kneader to prepare a resin composition of Comparative Example
3.
Evaluation 1
[0065] The resin compositions prepared in Examples 1 to 4 and
Comparative Examples 1 to 3 were measured for light transmittance,
storage modulus, curing shrinkage ratio, surface roughness,
refractive index, and brightness as follows. The results are shown
in Table 1.
[Preparation of Samples]
[0066] The resin compositions prepared in Examples 1 to 4 and
Comparative Examples 1 to 3 were dropped onto a 100 .mu.m-thick
white glass plate so as to have a predetermined thickness. The
glass plates were conveyed onto a UV conveyer to obtain cured
products of the resins having a predetermined thickness. These
serve as samples for measuring light transmittance, storage
modulus, and curing shrinkage ratio.
[Light Transmittance]
[0067] The light transmittance in the visible region was measured
for each sample (the cured resin thickness of 100 .mu.m) using an
UV-visible spectrophotometer (V-560, manufactured by JASCO
Corporation) and was found to be 90% or more for all the
samples.
[Storage Modulus]
[0068] The storage modulus (Pa) (25.degree. C.) was measured for
each sample at a measurement frequency of 1 Hz using a
viscoelastometer (DMS 6100, manufactured by Seiko Instruments
Inc.).
[Curing Shrinkage Ratio]
[0069] The specific gravities of the uncured resin solution and the
cured solid product were measured using an electronic densimeter
(SD-120L, manufactured by Mirage Co., Ltd.), and the curing
shrinkage ratio (%) was calculated by the following equation based
on the difference in the specific gravities between the uncured
resin solution and the cured solid product.
Curing shrinkage ratio (%)={(Cured product specific gravity-Resin
solution specific gravity)/(Cured product specific
gravity)}.times.100 [Equation 1]
[Surface Roughness]
[0070] 2 mg of each resin composition was dropped onto a glass
plate for a liquid crystal cell. Then, the distortion (Ra: average
surface roughness) in a predetermined region (2.93 mm.times.2.20
mm) of a glass plate surface caused by the internal stress during
UV curing was measured using a three-dimensional non-contact
surface roughness meter manufactured by Zygo Corporation.
[Refractive Index]
[0071] Each resin composition was interposed between two releasing
PET films and formed into a film shape using a spacer having a
thickness of 100 .mu.m. This was conveyed on a UV conveyer to cure
the resin between the films. Subsequently, the releasing PET films
were removed. The cured resin was cut into pieces of appropriate
size, and the cut pieces were used as samples.
[0072] The sample of each cured resin was measured for refractive
index using a refractometer (Model-3, manufactured by ATAGO Co.,
Ltd.).
[Brightness]
[0073] The image display device shown in FIG. 2 and including a
protective part made of an acrylic resin (refractive index
(nD)=1.52) was produced using each resin composition. Then, a black
pattern was displayed on the image display part in the presence of
an external light source (500 to 600 lux), and the brightness
(brightness distribution) of the displayed black pattern was
measured. The measurement of the brightness of the black pattern
determines the quality of the contrast.
TABLE-US-00001 TABLE 1 Storage Curing Average surface Transmittance
modulus shrinkage roughness Refractive Brightness (%) (Pa) ratio
(%) (nm) index (nD) (cd/m.sup.2) Example 1 90 or more 1 .times.
10.sup.6 4.5 5.5 1.47 10 or less Example 2 90 or more 1 .times.
10.sup.4 1.8 2.7 1.52 10 or less Example 3 90 or more 4 .times.
10.sup.3 1.0 1.5 1.52 10 or less Example 4 90 or more 4 .times.
10.sup.5 3.8 5.0 1.52 10 or less Comparative 90 or more 2 .times.
10.sup.7 5.6 12.4 1.49 Uneven* Example 1 Comparative 90 or more 3
.times. 10.sup.8 4.3 36.5 1.49 Uneven* Example 2 Comparative 90 or
more 5 .times. 10.sup.8 5.6 64.2 1.50 Uneven* Example 3 *Uneven:
measurement was difficult due to unevenness in brightness.
[0074] As is clear from Table 1, in Examples 1 to 4, the storage
modulus was 4.times.10.sup.3 to 1.times.10.sup.6 Pa, and the curing
shrinkage ratio was 1.0 to 4.5%. Therefore, the average surface
roughness Ra was 1.5 to 5.5 nm, and almost no distortion occurred.
The results were satisfactory. However, in Comparative Example 1
(Ra=12.4 nm), Comparative Example 2 (Ra=36.5 nm), and Comparative
Example 3 (Ra=64.2 nm), Ra was large. This indicates that the
interface between the resin and the glass plate was deformed due to
the internal stress during curing of the resin.
[0075] Moreover, in Example 1, the refractive index of the cured
resin was substantially the same as that of the acrylic plate used
as the protective part, so that no light scattering occurred.
Therefore, the value of the brightness was found to be good, i.e.,
10 cd/m.sup.2 or less.
Example 5
[0076] 50 Parts by weight of polyisoprene methacrylate (trade name:
UC-203, manufactured by Kuraray Co., Ltd.), 10 parts by weight of
hydroxybutyl methacrylate (trade name: LIGHT-ESTER HOB,
manufactured by Kyoeisha Chemical Co., Ltd.), 20 parts by weight of
a low-molecular weight polybutadiene polymer (trade name: Polyoil
110, manufactured by ZEON corporation), 4 parts by weight of a
photopolymerization initiator (trade name: IRGACURE 184,
manufactured by Ciba Specialty Chemicals Inc.), and 1 part by
weight of a photopolymerization initiator (trade name SpeedCure
TPO, manufactured by Nihon SiberHegner K.K.) were kneaded using a
kneader to prepare a resin composition of Example 5.
Example 6
[0077] 50 Parts by weight of polyisoprene methacrylate (trade name:
UC-203, manufactured by Kuraray Co., Ltd.), 20 parts by weight of
hydroxybutyl methacrylate (trade name: LIGHT-ESTER HOB,
manufactured by Kyoeisha Chemical Co., Ltd.), 20 parts by weight of
a low-molecular weight polybutadiene polymer (trade name: Polyoil
110, manufactured by ZEON corporation), 4 parts by weight of a
photopolymerization initiator (trade name: IRGACURE 184,
manufactured by Ciba Specialty Chemicals Inc.), and 1 part by
weight of a photopolymerization initiator (trade name SpeedCure
TPO, manufactured by Nihon SiberHegner K.K.) were kneaded using a
kneader to prepare a resin composition of Example 6.
Example 7
[0078] 50 Parts by weight of polyisoprene methacrylate (trade name:
UC-203, manufactured by Kuraray Co., Ltd.), 20 parts by weight of
hydroxybutyl methacrylate (trade name: LIGHT-ESTER HOB,
manufactured by Kyoeisha Chemical Co., Ltd.), 15 parts by weight of
a low-molecular weight polybutadiene polymer (trade name: Polyoil
110, manufactured by ZEON corporation), 4 parts by weight of a
photopolymerization initiator (trade name: IRGACURE 184,
manufactured by Ciba Specialty Chemicals Inc.), and 1 part by
weight of a photopolymerization initiator (trade name SpeedCure
TPO, manufactured by Nihon SiberHegner K.K.) K.K.) were kneaded
using a kneader to prepare a resin composition of Example 7.
Evaluation 2
[0079] The resin compositions prepared in Examples 1 and 5 to 7
were measured for light transmittance, storage modulus, curing
shrinkage ratio, surface roughness, refractive index, and
brightness in the same manner as in Evaluation 1. The results are
shown in Table 2.
[0080] Note that, in the brightness measurement, an acrylic plate
or a glass plate shown in Table 2 was used as the protective
part.
TABLE-US-00002 TABLE 2 Storage Curing Average surface Refractive
index (nD) Transmittance modulus shrinkage roughness Refractive of
protective part Brightness (%) (Pa) ratio (%) (nm) index (nD)
material (cd/m.sup.2) Example 5 90 or more 1 .times. 10.sup.6 or
less 4.5 or less 5.5 or less 1.51 Acrylic plate 1.52 10 or less
Example 6 90 or more 1 .times. 10.sup.6 or less 4.5 or less 5.5 or
less 1.49 Glass plate 1.49 10 or less Example 7 90 or more 1
.times. 10.sup.6 or less 4.5 or less 5.5 or less 1.50 Glass plate
1.50 10 or less Example 1 90 or more 1 .times. 10.sup.6 or less 4.5
or less 5.5 or less 1.47 Glass plate 1.49 10 or less
[0081] As shown above, also in Examples 5 to 7, the values of the
light transmittance, storage modulus, and curing shrinkage ratio
were similar to those in Example 1, and the average surface
roughness was 5.5 nm or less. Therefore, the magnitude of
distortion in the glass or acrylic plate used as the protective
part was small. Moreover, in Examples 1 and 5 to 7, since the
refractive index of the cured resin was substantially the same as
that of the acrylic or glass plate used as the protective part,
practically acceptable brightness was achieved.
INDUSTRIAL APPLICABILITY
[0082] The present invention is useful as image display devices,
such as liquid display devices, and the like.
* * * * *