JPH07209637A - Filter for liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide a filter for a liq. crystal display element capable of enlarging the visual angle of the liq. crystal display screen, capable of reducing the shadow of the opaque part of the element, capable of being conveniently produced, and having no fear of producing moire flinges by mounting the filter on the emitted light side of the element. CONSTITUTION:A composition (1) contg. >=2 kinds of photopolymerizable monomers or oligomers having a different refractive index each other, a composition (2) contg. the photopolymerizable monomers or oligomers having a different refractive index before or after curing or a composition (3) contg. the photopolymerizable monomers or oligomers and a compd. having a different refractive index from that of the monomer or oligomer and which is not photopolymerized, is formed into a film. This filter for a liq. crystal display element consists of a light scattering plate obtained by irradiating the film composition with UV.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter for a liquid crystal display device, which can be mounted on a liquid crystal display device to widen a viewing angle and reduce deterioration of image quality due to an opaque portion of the device. It is a thing.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device has characteristics of thinness, light weight and high image quality, and is greatly expected as a display device capable of competing with a CRT. The driving principle is TN,
STN, ferroelectric, polymer dispersed type, etc. have been devised, and multi-color, high-definition liquid crystal displays, etc. are on the market.

Further, with the demand for a large screen and the development of high-definition technology, an enlarged projection image display device using a liquid crystal projector is becoming popular. Furthermore, in the virtual reality display device that makes images appear on the computer as if something actually exists by improving the computing processing speed of the computer, the liquid crystal display device is a goggle-like display device worn on the head. Is used.

The liquid crystal display device currently used is T
Most of the driving principles are N and STN, but these driving principles show that the brightness and the contrast of the image are different from each other when viewed from the upper and lower angles and / or the left and right angles with respect to the display screen. Since it is remarkably reduced, there is a problem that the viewing angle that can satisfy the image quality is narrow.
Regarding this viewing angle characteristic, a method for improving it has been studied for many years. As a method for improving this, for example, a method of correcting the pretilt angle of liquid crystal molecules using a liquid crystal alignment division technique has been studied, but a large increase in manufacturing cost cannot be avoided because the manufacturing process becomes complicated. Also, as a simple method, there is a method of mounting a diffusion sheet on a liquid crystal display panel to scatter light at a wide angle, but since the transmittance of the diffusion sheet is generally 80% or less, the brightness of the liquid crystal display screen is lowered. Resulting in. Further, the effect of enlarging the viewing angle is more effective as the angular distribution of light scattered by the diffusion sheet is wider, but the scattered light angle distribution of the diffusion sheet currently used is narrow,
A sheet with a wide scattering angle is required. Liquid crystal display devices based on other driving principles are currently in the development stage and have not yet achieved sufficient commercial performance.

Further, the liquid crystal display element has opaque portions such as bus electrodes and TFTs formed around the pixels. Especially in the case of a display device that magnifies a liquid crystal display screen such as a liquid crystal projector or a virtual reality display device, these opaque portions are enlarged and projected to cast a shadow on the display screen, which significantly deteriorates the image quality. . Regarding this problem, Japanese Patent Laid-Open No.
No. 232460 and Japanese Unexamined Patent Publication No. 5-273540 propose a method of providing a phase grating on a light emitting side substrate of a transmissive liquid crystal display device. These bend the light that has passed through the pixels of the liquid crystal display element due to the diffraction effect of the light that the phase grating has, and bring the light into the shaded portion caused by the opaque portion, thereby suppressing the deterioration of the image quality. As a phase grating,
A morphology modulation type phase grating obtained by a photolithography method and a refractive index modulation type phase grating obtained by a method in which monomers having different refractive indexes are distributed in a resin and then polymerized are exemplified. Due to the regular structure of the phase grating, moiré fringes are likely to occur, and it is necessary to improve the accuracy during manufacturing.

[0006]

It is an object of the present invention to increase the viewing angle of a liquid crystal display screen and reduce the shadow of the opaque portion of the liquid crystal display device by mounting the liquid crystal display device on the light emission side. , There is no risk of moire fringes on the screen,
Another object is to provide a filter that is easy to manufacture.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have formed a specific photopolymerizable composition in the form of a film,
Then, it was found that a filter composed of a light-scattering plate formed by irradiating this film-shaped composition with ultraviolet rays satisfies the above-mentioned object,
The present invention has been reached. That is, the present invention is as follows.

(1) Light obtained by forming a composition containing two or more kinds of photopolymerizable monomers or oligomers having different refractive indexes into a film and then irradiating the film composition with ultraviolet rays. A filter for a liquid crystal display device, characterized by comprising a scattering plate.

(2) From a light-scattering plate obtained by forming a composition containing a photopolymerizable monomer or oligomer having a different refractive index before and after curing in the form of a film, and then irradiating the film-like composition with ultraviolet rays. A filter for a liquid crystal display device, characterized in that (3) Obtained by forming a composition containing a photopolymerizable monomer or oligomer and a compound having a refractive index different from these and having no photopolymerization property into a film, and then irradiating the film composition with ultraviolet rays. A filter for a liquid crystal display device, which comprises a light scattering plate.

Specific examples of the photopolymerizable monomer used in the above (1) invention include tetrahydrofurfuryl acrylate, ethyl carbitol acrylate, dicyclopentenyloxyethyl acrylate, phenyl carbitol acrylate, nonylphenoxyethyl acrylate. , 2-hydroxy-3-phenoxypropyl acrylate, ω-hydroxyhexanoyloxyethyl acrylate, acryloyloxyethyl succinate, acryloyloxyethyl phthalate, tribromophenoxyethyl acrylate, isobornyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, and methacrylates corresponding to these acrylates, and N-vinyl Examples include rupyrrolidone and N-acryloylmorpholine.

Specific examples of the photopolymerizable oligomer used in the above (1) invention include polyol polyacrylate, modified polyol polyacrylate, isocyanuric acid skeleton polyacrylate, melamine acrylate,
Examples thereof include polyacrylates having a hydantoin skeleton, polybutadiene acrylates, epoxy acrylates and urethane acrylates.

In the above-mentioned invention (1), the photopolymerizable monomer and oligomer are different in refractive index from each other.
More than one seed is used. Examples of the combination include two types selected from monomers, a combination of one type of monomer and one type of oligomer, two types selected from oligomers, or a combination of one or more types of monomers or oligomers added to these combinations. . Among these combinations, it is preferable that at least two of them have a difference in refractive index of 0.01 or more.

Specific examples of the photopolymerizable monomer or oligomer having a different refractive index before and after curing used in the invention (2) include triethylene glycol diacrylate, polyethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, hydrogenated dicyclopentadienyl diacrylate, ethylene oxide modified bisphenol A
Diacrylate, trimethylolpropane triacrylate, pentaerythritol hexaacrylate, trisacryloxyisocyanurate, polyfunctional epoxy acrylate, polyfunctional urethane acrylate, and corresponding methacrylates and divinylbenzene, triallyl isocyanurate, diethylene glycol. Examples include bisallyl carbonate.

In the invention (2), the difference in refractive index before and after curing of the photopolymerizable monomer or oligomer having different refractive indexes before and after curing is preferably 0.01 or more.

Specific examples of the photopolymerizable monomer or oligomer used in the above (3) invention are selected from those listed as those used in the above (1) or (2) invention. One kind or two or more kinds are used.
Specific examples of the non-photopolymerizable compound used in the above (3) invention include polymers such as polystyrene, polymethylmethacrylate, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, nylon, and organic halogen compounds. , Organosilicon compounds, plasticizers,
Examples include plastic additives such as stabilizers. The difference in refractive index between the at least one photopolymerizable monomer or oligomer used in the invention (3) and the compound having no photopolymerizable property is preferably 0.01 or more.

A photopolymerization initiator is preferably used in the composition containing the photopolymerizable monomer or oligomer in the inventions (1) to (3) in order to improve the curability. As a photopolymerization initiator, for example, benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, diethoxyacetophenone, benzyl dimethyl ketal, 2-hydroxy-2-methylpropiophenone, 1-hydroxy. Examples thereof include cyclohexyl phenyl ketone.

In the composition containing the photopolymerizable monomer or oligomer in the inventions (1) to (3), 0.01% of a filler having an average particle size of 0.05 to 20 μm is used.
It is also possible to add 5 to 5 parts by weight or to add an ultraviolet absorber.

In the above inventions (1) to (3), the composition containing a photopolymerizable monomer or oligomer is coated on a substrate or enclosed in a cell to form a film. It Then, the film-shaped composition is irradiated with ultraviolet rays to be photopolymerized and cured to obtain a light scattering plate.

The light source used in the photopolymerization emits a light ray that contributes to the photopolymerization, and a lamp emitting an ultraviolet ray is one of the preferable light sources. It is most preferable to use parallel rays such as sunlight as the light rays, but if the light source is spherical or the ratio of the length of the lamp in the major axis direction to the length in the minor axis direction is 2: 1 or less, it is equivalent. It can exert its performance.

The thickness of the filter comprising the light-scattering plate of the present invention is not particularly limited, but it is 10 μm in order to exhibit the light-scattering ability.
It is preferably m or more. The thickness of the light scattering plate is preferably 10 to 300 μm in the case of a single layer, and is preferably the thickness of the single layer multiplied by the number of layers in the case of forming a multilayer.

The filter comprising the light-scattering plate of the present invention is produced by utilizing the fact that when a composition containing a specific photopolymerizable monomer or oligomer is irradiated with ultraviolet rays, it undergoes photopolymerization curing while causing phase separation. According to this method, a filter made of a smooth refractive index modulation type light scattering plate having a domain interval of 1 to 20 μm can be manufactured without using a mask during ultraviolet irradiation. Since this phase separation has a continuous interface, when light is transmitted to the obtained filter, reflection does not occur at the interface and the light transmittance is not reduced.This filter has a regular structure unlike the phase grating. Since it does not have any moire fringes, it does not occur. Further, this filter has a simple manufacturing method and is suitable for mass production because it has only a step of irradiating the film-shaped composition with ultraviolet rays without using a mask during manufacturing.

When the filter comprising the light scattering plate of the present invention is mounted on the light emission side of the liquid crystal display element, it is preferable that the filter is interposed between the outer surface of the element and the transparent base material to form a laminated body. As the transparent substrate used for this laminate,
It is not particularly limited as long as it is transparent, but examples thereof include polycarbonate resin, methacrylic resin, PET resin, polystyrene resin, and transparent glass. Further, these transparent substrates can be subjected to at least one treatment selected from an antireflection treatment, an antiglare treatment and a hard coat treatment on the outer surface. Furthermore, the method for laminating the transparent substrate and the light scattering plate is not particularly limited, and a known method can be used.

When mounting a filter composed of a light scattering plate on the light emission side of the liquid crystal display element, it is preferable that the filter is brought into close contact with the screen as much as possible. At that time, for example, a polarizing plate used on the outside of the liquid crystal panel and a light scattering plate may be integrated, and the light scattering plate may be directly attached to the liquid crystal display element for use.

Further, the liquid crystal used in the liquid crystal display element suitable for mounting the filter comprising the light scattering plate of the present invention and the driving method thereof are simple matrix driving using TN and STN type liquid crystal, TN. Type liquid crystal using T
All methods such as FT method active matrix driving can be mentioned.

As an example, FIG. 2 shows the structure of a TFT drive direct view type liquid crystal display element. In the case of a direct-viewing type liquid crystal display element, the light emitted from the backlight 1 passes through the polarizing plate 2, the TFT substrate 3, the liquid crystal cell 4, the color filter 5, the counter substrate 6, and the polarizing plate 7 and is emitted. It comes into my eyes. T
In the case of an FT drive liquid crystal display element, the TN mode is often used. In the TN mode, since the twist angle of the liquid crystal is 90 degrees, the viewing angle is only about 30 degrees. FIG. 3 shows an example of the TFT substrate. On the TFT substrate, the TFT element 8 and the TFT
A source bus electrode 9 and a gate bus electrode 10 for supplying a voltage to the element are arranged. FIG. 4 shows an example of the color filter. The color filter has pixels 12 for expressing colors in the liquid crystal display element and light leakage between the pixels to prevent TF.
A light shielding portion (black matrix) 13 for suppressing reflection of external light by the T element and the bus electrode is patterned. Therefore, the light emitted from the backlight is blocked by the opaque portions such as the TFT element 8, the bus electrodes 9, 10 and the light shielding portion 13 and the image becomes rough.

FIG. 1 shows the construction of a direct-viewing type liquid crystal display device in which a filter 14 comprising the light scattering plate of the present invention is mounted on the light exit side of the polarizing plate 7 on the observer side.

In the case of a liquid crystal projector, a light source lamp is arranged instead of the backlight 1 in FIG. 1 and a projector screen is arranged at the position of the observer.

[0028]

EXAMPLES The contents of the present invention will be described below based on examples. Example 1 40 parts of polyether urethane acrylate (refractive index 1.460) having an average molecular weight of about 6000 obtained by the reaction of polypropylene glycol, hexamethylene diisocyanate and 2-hydroxyethyl acrylate was added to 2,4,6-tri Bromphenyl acrylate 30 parts, 2
-Hydroxy-3-phenoxypropyl acrylate 3
0 part (refractive index 1.526) and 2 as a photopolymerization initiator
A photopolymerizable composition was prepared by adding and mixing 1.5 parts of -hydroxy-2-methylpropiophenone. The composition was applied on a glass plate to a thickness of about 130 μm to form a film of the photopolymerizable composition. The film-shaped body and the glass plate were combined with a lamp opening of 5 cm × 5 cm, a lamp input of 120 W / cm, a conveyor speed of 0.4 m / min. A liquid crystal display element filter made of a light scattering plate was produced by photopolymerization using the conveyor type ultraviolet irradiation device.

The scattered light intensity angle distribution of the liquid crystal display element filter was measured using a scattered light intensity angle distribution measuring device manufactured by Shimadzu Corporation. A schematic diagram of the device is shown in FIG. The incident angle θ with respect to the normal direction of the liquid crystal display element filter 14
The light 20 incident on is scattered by the liquid crystal display element filter 14 and is emitted. By measuring the angular distribution of the scattered light with a light intensity detector, the light scattering characteristics of the liquid crystal display element filter can be measured. FIG. 6 shows the light scattering characteristics when light having a wavelength of 550 nm is incident on the filter for a liquid crystal display element in this embodiment. Reference numerals 15 to 18 are intensity distributions of scattered light of light having incident angles of 0, 5, 10, and 15 degrees, respectively. With respect to the scattering angle φ, the straight transmitted light direction with respect to each incident light is set to 0 °, and the normal direction emitted light side from the straight transmitted light is set to a positive angle. The incident light from the normal direction to the liquid crystal display element filter gives scattered light intensity angle distribution characteristics having a Gaussian distribution with a half value width of about 8 degrees as shown in FIG. On the other hand, the incident light from 15 degrees to the normal direction is 1
As shown in FIG. 8, a straight transmitted light and a scattered light intensity angle distribution characteristic having a maximum at a scattering angle of about 27 degrees are given. In other words, the light incident at the normal direction of 15 degrees is reflected by the liquid crystal display element filter 1
4 scatters about 27 degrees.

Therefore, in FIG. 1 showing a structure in which the liquid crystal display element filter of the present invention is mounted on the direct-viewing type liquid crystal display element, the light passing through the outgoing light side polarizing plate 7 passes through the liquid crystal display element filter 14. As a result, they are scattered and bent toward the wide angle side. The light emitted from the liquid crystal display element has a higher contrast as it is closer to the normal direction of the liquid crystal display element. Therefore, if the light emitted in the vicinity of the normal direction is scattered to the wide angle side by the filter for the liquid crystal display element, it becomes a wide angle. The contrast on the side is improved. Further, since the emitted light is scattered, the light wraps around the shadow portion due to the opaque portion of the liquid crystal display element to make the shadow portion inconspicuous, so that the image quality can be improved.

In the case of a liquid crystal projector, by arranging a light source lamp unit instead of the backlight 1 of FIG. 1 and a projector screen at the position of the observer, it is possible to produce the effect of reducing the shadow of the opaque portion. Become. Also in this case, similarly to the case of the direct-view type liquid crystal display element, the image quality can be improved by scattering the emitted light by the filter for the liquid crystal display element and causing the light to come around and illuminate the shaded portion of the opaque portion.

[0032]

When the filter comprising the light scattering plate of the present invention is used, the viewing angle of the liquid crystal display screen can be widened, the shadow of the opaque portion can be reduced, and moire fringes are not generated. Further, the method for manufacturing this light scattering plate is simple.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a TFT drive direct-viewing type liquid crystal display device equipped with a liquid crystal display device filter of the present invention in an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a conventional TFT drive direct view type liquid crystal display element.

FIG. 3 is a plan view of a TFT substrate.

FIG. 4 is a plan view of a color filter.

FIG. 5 is a schematic view showing a scattered light angle distribution characteristic measuring method of a filter for a liquid crystal display element.

FIG. 6 is a graph showing scattered light intensity angle distribution characteristics of a filter for a liquid crystal display element.

[Explanation of symbols]

1. Backlight 2. Polarizing plate 3. TFT substrate 4. Liquid crystal cell 5. Color filter 6. Counter substrate 7. Polarizing plate 8. TFT element 9. Source bus electrode 10. Gate bus electrode 11. Pixel electrode 12. Pixel 13. Light-shielding part (black matrix) 14. Filter for liquid crystal display device 15. A spectrum showing a scattered light angle distribution when light is incident on a filter for a liquid crystal display element from a normal direction. 16. A spectrum showing a scattered light angle distribution when light is incident on the liquid crystal display element filter at an angle of 5 degrees with respect to the normal direction. 17. Liquid crystal display element filter with 10 in the normal direction
A spectrum showing the angular distribution of scattered light when light is incident from the angle of degrees. 18. 15 in the direction of the normal to the liquid crystal display element filter
A spectrum showing the angular distribution of scattered light when light is incident from the angle of degrees. 19. Detector. 20. Incident light. 21. Scattered light. 22. Straight transmitted light. 23. Angle of incidence. 24. Scattering angle.

Claims (3)

[Claims] 1. Light scattering obtained by forming a composition containing two or more kinds of photopolymerizable monomers or oligomers having different refractive indexes into a film, and then irradiating the film composition with ultraviolet rays. A filter for a liquid crystal display element, which is composed of a plate. 2. A light-scattering plate obtained by forming a composition containing a photopolymerizable monomer or oligomer having a different refractive index before and after curing into a film, and then irradiating the film-like composition with ultraviolet rays. A filter for a liquid crystal display device, which is characterized in that 3. A composition containing a photopolymerizable monomer or oligomer and a compound having a refractive index different from these and having no photopolymerizability is formed into a film, and then the film composition is irradiated with ultraviolet rays. A filter for a liquid crystal display element, comprising a light-scattering plate obtained as described above.