Patent Application
20080151163
The present invention contains subjects related to Japanese Patent Application JP 2006-343236 filed in the Japan Patent Office on Dec. 20, 2006, the entire contents of which being incorporated herein by reference.
1. Field of the Invention
The invention relates to an optical compensation panel, a method for manufacturing an optical compensation panel and a liquid crystal display device. In particular, the invention relates to an optical compensation panel having a first optical compensation layer, a second optical compensation layer and an adhesive layer for bonding the first optical compensation layer and the second optical compensation layer so as to face each other; a method for manufacturing the same; and a liquid crystal display device in which this optical compensation panel is disposed so as to face at a surface of a liquid crystal panel.
2. Description of the Related Art
A liquid crystal display device has a liquid crystal panel in which a liquid crystal layer is sealed between a pair of substrates. In the liquid crystal display device, the liquid crystal panel modulates light which has been irradiated from a liquid source, and displaying of an image is carried out by the modulated light. In comparison with CRT (cathode ray tube), such a liquid crystal display device has advantages such as slim type, lightweight and low electric power consumption. For that reason, the liquid crystal display device is used as a direct-view-type display device in electronic appliances such as personal computers, mobile phones and digital cameras and is also used as a projection-type display device such as projectors.
In the direct-view-type liquid crystal display device, the size of a display surface of the liquid crystal panel is a screen size as it is. For that reason, in performing displaying on a large-sized screen, in the direct-view-type liquid crystal display device, a large-sized liquid crystal panel is used. Alternatively, the display surface of an image is made large by coupling plural liquid crystal panels. Accordingly, in order to perform displaying on a large-sized screen in the direct-view-type liquid crystal display device, there is a possibility that the cost of the device becomes high.
On the other hand, in the projection-type liquid crystal display device, an image is displayed on a large-sized screen by irradiating a small-sized liquid crystal panel with light from a light source and enlarging and projecting the light which has transmitted through the liquid crystal panel by a lens. For that reason, in the projection-type liquid crystal display device, the device can be manufactured more cheaply than the direct-view-type liquid crystal display device.
This projection-type liquid crystal display device is roughly classified into a single-plate type and a three-plate type. In the single-plate type, the three primary colors are decomposed spatially or in terms of time by using one liquid crystal panel, thereby displaying an image on a screen. On the other hand, in the three-plate type, respective images of the three primary colors are displayed on three liquid crystal panels, respectively. Thereafter, the images of the three liquid crystal panels are combined into one image by using an optical system such as a prism, and the combined image is enlarged and projected, thereby displaying on a screen.
In such a liquid crystal display device, a TN mode is the mainstream. In the TN mode, since a pre-tilt component of a liquid crystal which is inclined at an angle of from 2 degrees to 8 degrees, there is a possibility that the contrast is reduced. Concretely, since the phase of a long-axis direction component of a liquid crystal molecule is delayed due to the anisotropy of a refractive index of the liquid crystal caused due to the pre-tilt component, incident light of linearly polarization becomes elliptical polarization due to the matter that a phase difference is generated between a slow-axis direction component and a fast-axis direction component by this liquid crystal molecule. Thus, there is a possibility that such a fault is generated.
For that reason, a reduction of the contrast of the image by the pre-tilt component is optically compensated by using an optical compensation panel, thereby realizing a high contrast.
The optical compensation panel is, for example, formed due to the matter that a pair of optical compensation layers are bonded by an adhesive layer. When these optical compensation layers compensate the phase difference, an image of the liquid crystal display device is displayed in a high contrast, and the image quality is enhanced (see, for example, JP-A-2006-184872, JP-A-2005-70771, JP-A-2004-245925 and JP-A-2004-46097). Here, for example, when a photopolymerization initiator photopolymerizes a photopolymerization material such as monomers upon irradiation with light, the adhesive layer is formed.
However, in the case where the optical compensation panel becomes high in temperature, there is a possibility that separation is generated between respective layers configuring the optical compensation panel or a possibility that respective layers are deformed to generate photoelastic birefringence. Thus, there may be the case where optical compensation cannot be sufficiently realized, and displaying with high contrast cannot be achieved, resulting in a reduction of the image quality.
As shown in
For that reason, when layer-to-layer separation is generated, there may be the case where optical compensation cannot be sufficiently realized, and displaying with high contrast cannot be achieved, resulting in a reduction of the image quality. In particular, in a projection-type liquid crystal display device, since the density of light to be irradiated on a liquid crystal panel is high, such a fault is actualized.
Accordingly, it is desirable to provide an optical compensation panel capable of displaying an image with high contrast, a method for manufacturing an optical compensation panel and a liquid crystal display device.
An optical compensation panel according to an embodiment of the invention is an optical compensation panel having a first optical compensation layer, a second optical compensation layer and an adhesive layer for bonding the first optical compensation layer and the second optical compensation layer so as to face each other, wherein the adhesive layer is made of a photopolymerization material, photopolymerization of which is started by a photopolymerization initiator upon irradiation with light, with the photopolymerization initiator being contained in an amount of from 2 to 5% by weight relative to the photopolymerization material in starting the photopolymerization, and the adhesive layer is formed so as to have a rate of change in glass transition temperature of the adhesive layer falling within 150% and a rate of change in weight of the adhesive layer falling within 5% before and after an annealing treatment.
A method for manufacturing an optical compensation panel according to an embodiment of the invention is a method for manufacturing an optical compensation panel including the step of bonding a first optical compensation layer and a second optical compensation layer by an adhesive layer so as to face each other, wherein the adhesive layer is made of a photopolymerization material, photopolymerization of which is started by a photopolymerization initiator upon irradiation with light, with the photopolymerization initiator being contained in an amount of from 2 to 5% by weight relative to the photopolymerization material in starting the photopolymerization, and the adhesive layer is formed so as to have a rate of change in glass transition temperature of the adhesive layer falling within 150% and a rate of change in weight of the adhesive layer falling within 5% before and after an annealing treatment.
The liquid crystal display device according to an embodiment of the invention is a liquid crystal display device including a liquid crystal panel having optical compensation panels disposed on a surface thereof to be irradiated with light so as to face each other, wherein the optical compensation panel has a first optical compensation layer, a second optical compensation layer and an adhesive layer for bonding the first optical compensation layer and the second optical compensation layer so as to face each other; and the adhesive layer is made of a photopolymerization material, photopolymerization of which is started by a photopolymerization initiator upon irradiation with light, with the photopolymerization initiator being contained in an amount of from 2 to 5% by weight relative to the photopolymerization material in starting the photopolymerization, and the adhesive layer is formed so as to have a rate of change in glass transition temperature of the adhesive layer falling within 150% and a rate of change in weight of the adhesive layer falling within 5% before and after an annealing treatment.
According to embodiments of the invention, not only the adhesive layer is formed so as to contain the photopolymerization initiator in an amount of from 2 to 5% by weight relative to the photopolymerization material, but the adhesive layer is formed so as to have a rate of change in glass transition temperature of the adhesive layer falling within 150% and a rate of change in weight of the adhesive layer falling within 5% before and after an annealing treatment.
According to embodiments of the invention, an optical compensation panel capable of displaying an image with high contrast, a method for manufacturing an optical compensation panel and a liquid crystal display device can be provided.
Embodiments according to the invention is hereunder described.
As shown in
The respective parts of the liquid crystal display device 500 of the present embodiment are hereunder described successively.
The light source 501 has a lamp 501a and a reflector 501b. The lamp 501a is, for example, configured by using a metal halide lamp and emits white light in a radial manner. The reflector 501b has a reflecting surface, and this reflecting surface reflects the light from the lamp 501a and emits the light from an opening thereof in parallel to an optical axis.
The first lens array 503 has a configuration in which plural lenses are arranged in a matrix manner and divides the light from the light source 501 into plural light fluxes.
The first reflecting mirror 504 reflects the light which has transmitted through the first lens array 503 and polarizes it toward the second lens array 505.
The second lens array 505 has a configuration the same as in the first lens array 503, in which plural lens are arranged in a matrix manner, and emits the light from the first reflecting mirror 504 into the first dichroic mirror 511.
The first dichroic mirror 511 separates the light from the second lens array 505 such that lights of blue component B and green component G are reflected, whereas light of red component R is transmitted. The transmitted light of red component R is emitted into the second reflecting mirror 512, and the reflected lights of blue component B and green component G are emitted into the second dichroic mirror 521.
The second reflecting mirror 512 reflects and polarizes the light of red component R which has transmitted through the first dichroic mirror 511, thereby making it incident into the first liquid crystal panel 541R via the first condenser lens 551R.
The second dichroic mirror 521 separates the lights of blue component B and green component G which have been reflected by the first dichroic mirror 511 such that the light of blue component B is transmitted, whereas the light of green component G is reflected. The reflected light of green component G is emitted into the second liquid crystal panel 541G via the second condenser lens 551G. On the other hand, the light of blue component B transmits through the first relay lens 531 and is then emitted into the third reflecting mirror 532.
The first relay lens 531 receives the light from the second dichroic mirror 521 and emits it into the third reflecting mirror 532. The first relay lens 531 is provided for the purpose of enhancing the use efficiency of the light of blue component B having a longer optical path length than the lights of other colors.
The third reflecting mirror 532 reflects and polarizes the light of blue component B and emits it into the fourth reflecting mirror 534 via the second relay lens 533.
The second relay lens 533 receives the light from the third reflecting mirror 532 and emits it into the fourth reflecting mirror 534. Similar to the foregoing first relay lens 531, the second relay lens 533 is provided for the purpose of enhancing the use efficiency of the light of blue component B having a longer optical path length than the lights of other colors.
The fourth reflecting mirror 534 reflects and polarizes the light of blue component B from the third reflecting mirror 532 and emits it into the third liquid crystal panel 541B via the third condenser lens 551B.
Each of the first, second and third liquid crystal panels 541R, 541G and 541B is disposed so as to face at the incident surface of the dichroic prism 561.
The first liquid crystal panel 541R is, for example, of an active matrix type and has a TFT substrate (not illustrated), an opposing substrate thereto (not illustrated) and a liquid crystal layer (not illustrated). The first liquid crystal panel 541R receives the light to be irradiated from the light source 501 via the respective parts from the opposing substrate side and then emits it into the TFT substrate side via the liquid crystal layer, thereby displaying an image. Here, as shown in
Similar to the first liquid crystal panel 541R, the second liquid crystal panel 541G is of an active matrix type and has a TFT substrate (not illustrated), an opposing substrate thereto (not illustrated) and a liquid crystal layer (not illustrated). The second liquid crystal panel 541G receives the light to be irradiated from the light source 501 via the respective parts from the opposing substrate side and then emits it into the TFT substrate side via the liquid crystal layer, thereby displaying an image. Here, as shown in
Similar to the first liquid crystal panel 541R and the second liquid crystal panel 541G, the third liquid crystal panel 541B is of an active matrix type and has a TFT substrate (not illustrated), an opposing substrate thereto (not illustrated) and a liquid crystal layer (not illustrated). The third liquid crystal panel 541B receives the light to be irradiated from the light source 501 via the respective parts from the opposing substrate side and then emits it into the TFT substrate side via the liquid crystal layer, thereby displaying an image. Here, as shown in
The dichroic prism 561 combines the lights of components of respective colors which have transmitted through the first, second and third liquid crystal panels 541R, 541G and 541B to produce a color image and emits the produced color image into the projection lens unit 571.
The projection lens unit 571 enlarges and projects the produced color image by the dichroic prism 561, thereby displaying it on a screen 580.
A detailed structure of each of the optical compensation panels 544R, 544G and 544B is hereunder described.
As shown in
Also, the optical compensation panels 544R, 544G and 544B are formed such that a retardation to the normal direction is not more than 80 nm. This is because by making this retardation fall within this range, an optical compensation characteristic with respect to the liquid crystal panel is favorable.
The respective parts of the optical compensation panels 544R, 544G and 544B are hereunder described successively.
As shown in
As shown in
As shown in
As shown in
As shown in
In the present embodiment, the adhesive layer 41 is made of a photocurable adhesive material and is formed by photopolymerizing a photopolymerization material by a photopolymerization initiator upon irradiation with light. Here, the photopolymerization initiator is contained in an amount of from 2 to 5% by weight relative to the photopolymerization material in starting the photopolymerization. The adhesive layer 41 is formed so as to have a rate of change in glass transition temperature of the adhesive layer 41 falling within 150% and a rate of change in weight of the adhesive layer 41 falling within 5% before and after an annealing treatment (storing for 200 hours under an atmosphere at 100° C.). Also, it is preferable that before and after the foregoing annealing treatment, a rate of shrinkage is not more than 0.5% and a rate of change in elastic modulus falls within 20%.
Concretely, it is preferable that the adhesive layer 41 is made of an acrylic polymer such as polymethacrylate and polycyanomethacrylate or a urethane based polymer. This is because a polymer adhesive prepared from an acrylic polymer or a urethane based polymer also has a high transmittance, and therefore, it is excellent in optical characteristics such as light transmission and optical isotropy. Besides, epoxy based polymers, polyester elastomers and carbonate based polymers are preferable.
When before and after an annealing treatment (storing for 200 hours under an atmosphere at 100° C.), the rate of change in glass transition temperature of the adhesive layer 41 exceeds 150%, the adhesive layer 41 is cured, and therefore, separation is easily generated. For that reason, in the present embodiment, a material of the adhesive layer 41 is properly selected and used such that before and after an annealing treatment, the rate of change in glass transition temperature of the adhesive layer 41 is not more than 150%. Also, when before and after an annealing treatment (storing for 200 hours under an atmosphere at 100° C.), the rate of change in weight of the adhesive layer 41 exceeds 5%, a change in volume of the adhesive layer 41 is large, and therefore, separation is easily generated. For that reason, in the present embodiment, a material of the adhesive layer 41 is properly selected and used such that before and after an annealing treatment, the rate of change in weight of the adhesive layer 41 falls within 5%.
In the present embodiment, the polymerization initiator is a compound which generates a radical upon irradiation with ultraviolet light. Examples of the polymerization initiator which is favorably used include 2-hydroxy-2-methyl-1-phenylpropan-1-one, hydroxycyclohexyl phenyl ketone, methyl phenyl glyoxylate, benzyl dimethyl ketal, Michler's ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide. Besides, a photopolymerization initiation aid such as amines can be used jointly. Examples of this photopolymerization initiation aid such as amines, which can be used, include 2-dimethylaminoethyl benzoate, dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate and isoamyl p-dimethylaminobenzoate.
The manufacturing method of each of the foregoing optical compensation panels 544R, 544G and 544B is hereunder described successively.
First of all, as shown in
Here, a polyimide film is coated on one surface of the first protective substrate 11, and the polyimide film is then subjected to an orientation treatment upon irradiation with light, thereby forming the oriented film 21. Thereafter, a photosensitive liquid crystal film composed of an ultraviolet-curable liquid crystal material or the like is coated on the oriented film 21 by, for example, a spin coating method. Then, the photosensitive liquid crystal film is cured upon irradiation with ultraviolet light, thereby forming the first optical compensation layer 31.
Next, as shown in
Here, a polyimide film is coated on one surface of the second protective substrate 12, and the polyimide film is then subjected to an orientation treatment upon irradiation with light, thereby forming the oriented film 22. Thereafter, a photosensitive liquid crystal film composed of an ultraviolet-curable liquid crystal material or the like is coated on the oriented film 22 by, for example, a spin coating method. Then, the photosensitive liquid crystal film is cured upon irradiation with ultraviolet light, thereby forming the second optical compensation layer 32.
Next, as shown in
Here, a coating solution of an adhesive material in which a photopolymerization initiator is contained in an amount of from 2 to 5% by weight relative to a photopolymerization material such as acrylic monomers and urethane based monomers is coated on the surface of the first protective substrate 11 on which the first optical compensation layer 31 is formed.
Furthermore, this adhesive layer 41 is formed so as to have a rate of change in glass transition temperature of the adhesive layer falling within 150% and a rate of change in weight of the adhesive layer falling within 5% before and after an annealing treatment.
Thereafter, the surface of the first protective substrate 11 on which the first optical compensation layer 31 is formed and the surface of the second protective substrate 12 on which the second optical compensation layer 32 is formed are stuck so as to face each other. Then, for example, by irradiating light from the side of the second protective substrate 12, the coating solution of an adhesive material as coated is photopolymerized and cured.
Then, after each of the optical compensation panels 544R, 544G and 544B had been thus manufactured, as shown in
Examples according to an embodiment of the invention are hereunder described.
In Example 1, in order to form each of the optical compensation panels 544R, 544G and 544B as shown in
Next, the first optical compensation layer 31 was formed. Here, the first optical compensation layer 31 was formed by using a liquid crystal polymer.
Then, the second optical compensation layer 32 was formed in the same manner as in the first optical compensation layer 31.
Next, the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other by the adhesive layer 41. Here, the adhesive layer 41 was formed by coating with a coating solution containing a monomer component and a polymerization initiator in a proportion of 2 wt % relative to the weight of the monomer component, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other by the adhesive layer 41. Here, three monomers of an acrylic monomer A, an acrylic monomer B and a urethane based monomer C were used as the monomer component, and two kinds of a photopolymerization initiator A and a photopolymerization initiator B were used as the polymerization initiator. Also, in this Example 1, two samples were prepared.
Different from Example 1, in Example 2, a coating solution containing a monomer component and a polymerization initiator in a proportion of 3 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Example 2 is identical with Example 1, except for this point.
Different from Example 1, in Example 3, a coating solution containing a monomer component and a polymerization initiator in a proportion of 4 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Example 3 is identical with Example 1, except for this point.
Different from Example 1, in Example 4, a coating solution containing a monomer component and a polymerization initiator in a proportion of 5 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Example 4 is identical with Example 1, except for this point.
Different from Example 1, in Comparative Example 1, a coating solution containing a monomer component and a polymerization initiator in a proportion of 1 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Comparative Example 1 is identical with Example 1, except for this point.
Different from Example 1, in Comparative Example 2, a coating solution containing a monomer component and a polymerization initiator in a proportion of 6 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Comparative Example 2 is identical with Example 1, except for this point.
Different from Example 1, in Comparative Example 3, a coating solution containing a monomer component and a polymerization initiator in a proportion of 7 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Comparative Example 3 is identical with Example 1, except for this point.
Different from Example 1, in Comparative Example 4, a coating solution containing a monomer component and a polymerization initiator in a proportion of 8 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Comparative Example 4 is identical with Example 1, except for this point.
Different from Example 1, in Comparative Example 5, a coating solution containing a monomer component and a polymerization initiator in a proportion of 10 wt % relative to the weight of the monomer component was prepared. Then, the adhesive layer 41 was formed by coating this coating solution in the same manner as in Example 1, and the first optical compensation layer 31 and the second optical compensation layer 32 were bonded to each other. This Comparative Example 5 is identical with Example 1, except for this point.
Evaluation results regarding the foregoing Examples and Comparative Examples are hereunder described.
Table 1 shows the results obtained by evaluating the Examples and Comparative Examples according to an embodiment of the invention.
As shown in Table 1, (1) rate of change in glass transition temperature, (2) rate of change in weight and (3) separation state were measured.
With respect to the “rate of change in glass transition temperature”, a glass transition point of the adhesive layer 41 was measured by the DMA method with respect to each of the foregoing optical compensation panels before and after an annealing treatment (storing for 200 hours under an atmosphere at 100° C.) . Here, the glass transition temperature was measured by setting up a sample size at 5 mm×5 mm×1 mm in thickness and regulating a temperature rise rate at 5° C./min. As shown in Table 1, with respect to each of the samples in which the adhesive layer 41 was formed at a glass transition temperature before the annealing treatment at from 36° C. to 43° C., a glass transition temperature after the annealing treatment was measured. By dividing the glass transition temperature of the adhesive layer 41 after the annealing treatment by the glass transition temperature of the adhesive layer 41 before the annealing treatment, a rate of change in glass transition temperature was calculated in terms of a percentage.
Also, with respect to the “rate of change in weight”, a weight of each of the foregoing optical compensation panels was measured before and after an annealing treatment by using an electronic force balance. Here, the sample size was set up at 70 mm×10 mm×1 mm in thickness. A value obtained by differentiating 100 from a percentage value as calculated by dividing a weight of the adhesive layer 41 after an annealing treatment (storing for 200 hours under an atmosphere at 100° C.) by a weight of the adhesive layer 41 before the annealing treatment was calculated as a rate of change in weight.
Also, with respect to the “separation state”, whether separation of the adhesive layer 41 was generated (designated as “yes”) or not generated (designated as “no”) was judged through observation by a polarizing microscope. Here, with respect to the case where a panel was prepared and annealed under the same condition as in the measurement of physical properties, the observation and judgment were carried out.
As shown in
On the other hand, as shown in
Also, as shown in
Furthermore, as shown in
In the light of the above, in this embodiment according to the invention, when the adhesive layer 41 is formed, the photopolymerization initiator is contained in an amount of from 2 to 5% by weight relative to the photopolymerization material in starting the photopolymerization. Also, this adhesive layer 41 is formed so as to have a rate of change in glass transition temperature of the adhesive layer falling within 150% and a rate of change in weight of the adhesive layer falling within 5% before and after an annealing treatment.
For that reason, in this embodiment according to the invention, the generation of layer-to-layer separation can be prevented from occurring due to the matter that the polymerization initiator of the adhesive layer 41 is vaporized under a high-temperature atmosphere, whereby the weight and volume of the adhesive layer 41 decrease. Accordingly, in this embodiment, since the optical compensation panels 544R, 544G and 544B are able to sufficiently realize optical compensation, not only an image with high contrast can be displayed, but the image quality can be enhanced.
In carrying out the invention, the invention is not limited to the foregoing embodiment, but various modified embodiments can be employed.
For example, while the projection type liquid crystal display device of a three-plate type has been described in the foregoing embodiment, it should not be construed that the invention is limited thereto. The invention can also be applied to, for example, a projection type liquid crystal display device of a single-plate type.
Also, for example, a substrate in which a pixel switching element such as TFT is formed may be used as the substrate which configures an optical compensation panel.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-343236 | Dec 2006 | JP | national |
