JPH07261164A - Substrate for liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a substrate for a liquid crystal display device which is increased in an apparent opening rate and with which the effective utilization of incident rays on this liquid crystal display device is possible. CONSTITUTION:The main parts of this substrate 1 for the liquid crystal display device are composed of a glass substrate 11, light shielding films 12 which are respectively formed in the parts corresponding to the parts between the respective picture elements on this substrate 11, color filter layers 13R, 13G, 13B of red, green and blue which are respectively formed in the parts corresponding to the respective picture element parts, plural microlenses 14 which are disposed in the parts corresponding to the respective picture element parts and a flattening layer 15 which covers these parts. Not only the rays made incident toward the respective picture element parts but also the rays made incident toward the parts between the picture elements are refracted in the direction toward the centers of the picture element parts by the microlenses and, therefore, the bright screen display capable of utilizing the entire part of the incident rays is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a liquid crystal display device, and more particularly to an improvement of a substrate for a liquid crystal display device in which the apparent aperture ratio is increased and the light rays incident on the liquid crystal display device can be effectively used. Is.

[0002]

2. Description of the Related Art A liquid crystal display device is mainly composed of a pair of substrates each of which is provided with an electrode capable of applying a voltage for each pixel and at least one of which is transparent, and a liquid crystal substance enclosed between these substrates. The liquid crystal substance is configured to change the orientation state of the liquid crystal substance for each picture element by applying a voltage between the electrodes to control the plane of polarization of the light transmitted through the liquid crystal substance, and at the same time, the polarizing film prevents the transmission / non-transmission of the light. The screen is controlled by controlling the transparency, and is widely used in home or business displays, video cameras, input / output devices, and the like.

Further, by applying a color filter substrate having a color filter layer on a transparent substrate to one of the above substrates, it is possible to colorize the screen display.

The color filter substrate a is
As shown in FIG. 2, a transparent substrate a1 and a plurality of color filter layers a which are respectively provided in the portions corresponding to the respective picture element portions and which color the transmitted light transmitted through the respective picture element portions into corresponding colors.
3R, a3G, a3B and these color filter layers a
3R, a3G, a3B, a light-shielding film a2 provided in a gap portion (corresponding to a portion between pixels), and a flattening layer a4 provided on the color filter layers a3R, a3G, a3B.
The main part is constituted by and, and the transparent electrode b and the alignment film (not shown) are respectively disposed on the surface of the flattening layer a4 and applied as the color filter substrate.

[0005]

By the way, when a voltage is applied between a pair of electrodes for screen display, the voltage application state between adjacent picture elements tends to be unstable, and thus the picture elements are likely to become unstable. The orientation of the liquid crystal substance corresponding to the inter-site portion is likely to be disturbed. Due to this, the transmittance of the transmitted light that passes through the inter-picture element regions also becomes unstable, which is likely to cause deterioration in the contrast between the picture elements and the color purity. Therefore, as described above, a method has been adopted in which the light-shielding film a2 is provided in the inter-pixel portion of the transparent substrate a1 to prevent light transmission through this portion to improve the contrast and color purity of the display screen.

However, the existence of the light-shielding film a2 makes it impossible to effectively utilize the incident light beam, which causes a problem of reducing the brightness of the display screen. For example, when an aperture ratio (%) is defined as a ratio of an area X ′ of a portion (light-transmittable portion) where the light shielding film a2 does not exist in the screen display area and a total area X of the screen display area, the TFT ( An active matrix drive type liquid crystal display device using a thin film transistor has an extremely low aperture ratio of about 40 to 50%, and a simple matrix drive type liquid crystal display device using STN (super twisted nematic) liquid crystal. In this case, the aperture ratio is at most about 70 to 80%. Therefore, only about 50 to 80% of the incident light rays are used for screen display, and there is a problem that the brightness of the display screen is reduced accordingly.

Therefore, a method of arranging a strong light source such as a fluorescent lamp on the back side of the liquid crystal display device to increase the brightness of the display screen is usually adopted. However, since such a strong light source consumes a large amount of power, it is difficult to drive the portable light source for a long time at the destination, and the liquid crystal display device is large and heavy, which makes the portable light source difficult.

The present invention has been made by paying attention to such a problem, and the problem is that the apparent aperture ratio is increased and the light rays incident on the liquid crystal display device can be effectively used. It is to provide a substrate for a display device.

[0009]

That is, the invention according to claim 1 is, between a pair of substrates in which electrodes for applying a voltage are arranged for each picture element and at least one of which is transparent, and between these substrates. An encapsulating liquid crystal substance is provided, and it is premised on a substrate for a liquid crystal display device that changes the orientation state of the liquid crystal substance for each picture element by applying a voltage between the electrodes to display a screen. A plurality of microlenses formed of a high refractive index material, each of which is provided in a portion corresponding to a picture element portion, focuses transmitted light passing through each picture element portion toward the center of each picture element portion, and the microlenses And a flattening layer which is made of a material having a lower refractive index and which covers a plurality of microlenses and flattens the surface thereof.

According to the first aspect of the invention, not only the light rays incident on the respective picture element portions of the transparent substrate but also the light rays incident on the inter-picture element portions are processed by the microlenses. Since the light is refracted toward the center of the portion, the entire incident light beam can be used for screen display. Therefore, the apparent aperture ratio is increased, and it is possible to improve the brightness of the display screen without causing a decrease in contrast between the picture elements.

Here, a material having a refractive index of 1.50 or more can be applied as the high refractive index material forming the microlens, and a refractive index of 1.48 can be used as the low refractive index material forming the planarizing layer. The following can be applied: The invention according to claim 2 relates to the invention in which the refractive indexes of these materials are specified.

That is, the invention according to claim 2 is premised on the substrate for a liquid crystal display device according to claim 1, and the high refractive index material constituting the microlens has a refractive index of 1.50 or more. In addition, the low-refractive-index material forming the flattening layer has a refractive index of 1.48 or less.

As the high refractive index material, a material having a high light transmittance and a high refractive index and a material having a small wavelength dispersion are preferable. As such a material, for example, an alcohol solution of silicon alkoxide is used as a base, and a metal (for example, titanium, zirconium,
Alternatively, a solution obtained by mixing an alcohol solution containing tantalum), coating or printing it on a portion corresponding to each picture element portion on the transparent substrate, and then baking it to react the silicon alkoxide with a metal can be applied.

Further, it is also possible to apply an organic resin having a refractive index of 1.50 or more as the high refractive index material. As such an organic resin, for example, a polycarbonate resin, a polystyrene resin, an acrylic epoxy resin, a fluorene acrylic resin, a polyimide resin, an aliphatic condensed polycyclic compound (containing a bromine atom or a sulfur atom in its chemical structure, Can also be applied.

Next, as the shape of the microlens, it is desirable that the surface thereof forms a part of a spherical surface.
In this case, the microlens has the function of a spherical lens, and the entire incident light rays incident on the respective picture element portions and the incident light rays incident on the inter-pixel portions are directed toward the center of each picture element portion. Can be refracted to. In addition, in order to increase the aperture ratio to enable a brighter screen display and to increase the yield and productivity of microlenses, its surface should be a shape that forms a part of the cylindrical side surface (kamaboko shape). Is also possible. In this case, the microlens has the function of a cylindrical lens, and the entire incident light rays incident on the respective pixel portions and the incident light rays incident on the inter-pixel portions are directed in the axial direction of the cylindrical lens. It becomes possible to refract.

As a method of forming a microlens using the above organic resin, for example, a method of forming by printing can be used. In addition, the organic resin is composed of a photosensitive resin, and the photosensitive resin is applied onto a transparent substrate to form a film, which is exposed / developed to selectively select a portion corresponding to each pixel portion of the transparent substrate. It is also possible to apply a method in which the remaining photosensitive resin is melted and then deformed into a microlens shape by the surface tension of the remaining photosensitive resin. Also,
The organic resin is applied on a transparent substrate to form a coating film, and a photosensitive resin is further applied on the organic resin coating film to form the coating film, and at the same time, exposure / development is performed to cause a side etching phenomenon during the development. Is used to process the photosensitive resin coating into a microlens shape, and then dry etching is performed to control the etching amount of the organic resin coating according to the film thickness of the photosensitive resin coating to make the organic resin coating microscopic. A method of molding into a lens shape can also be applied.

When a microlens is formed by applying a printing method, in order to improve the printability of the organic resin, fine powder of inorganic transparent pigment, fine powder of organic resin, A fine powder dispersion aid, a surfactant, a silane coupling agent, and the like can be added and mixed.
Further, when the fine powder of the inorganic transparent pigment or the fine powder of the organic resin has optical anisotropy, light rays refracted and incident on the inside of these optically anisotropic fine powders are polarized and separated, and each polarized light has its refractive index. May progress at a speed according to the above and may cause coloring of the emitted light. Therefore, in order to avoid such a coloring phenomenon, a material having optical isotropy such as equiaxed crystal or amorphous is desirable as the fine powder. Further, in order to improve the fluidity of the fine powder, the surface thereof may be coated with an organic resin or subjected to a surface reaction treatment with alcohol, amine or organic acid.

Next, when this substrate for a liquid crystal display device is applied to a transmissive liquid crystal display device, the fine powder of the inorganic transparent pigment or the fine powder of the organic resin is the refractive index of the organic resin forming the microlens. It is desirable to have a refractive index substantially equal to that, so that light reflection from the surface can be prevented and incident light can be efficiently used to display a bright screen.

On the other hand, when the liquid crystal display device substrate is applied to a reflection type liquid crystal display device, the fine particles of the inorganic transparent pigment or the fine particles of the organic resin are the refractive index of the organic resin forming the microlens. Those having different refractive indexes are desirable, whereby the light reflectance on the surface of the fine powder is increased, and the scattering due to this light reflection can be utilized to increase the viewing angle of the display screen. The inventions according to claims 3 and 4 are made from such technical reasons.

That is, the invention according to claim 3 is premised on the substrate for a liquid crystal display device according to claim 1 or 2, and the high refractive index material constituting the microlens is an organic resin and this organic resin. And a fine powder having a refractive index substantially equal to that of the fine powder dispersed therein,
The invention according to claim 4 is characterized in that the high-refractive-index material constituting the microlens contains an organic resin and fine powder dispersed in the organic resin and having a different refractive index. is there.

The material of the fine powder according to claim 3 or 4 is, for example, fine powder obtained by crushing commercially available optical glass. Since such optical glass is commercially available in a wide range from low refractive index of 1.4 to high refractive index of 2.0, it is possible to obtain an appropriate refractive index from these commercially available optical glasses. It is possible to select and use the one.

Next, as the material forming the above-mentioned flattening layer according to the present invention, a material having a lower refractive index is more preferable.
An organic silicate having a refractive index of 1.46 to 1.48, or a fluorine resin having a refractive index of 1.30 to 1.45 can be used. The invention according to claims 5 and 6 relates to the invention in which the material of the planarizing layer is specified based on this reason.

That is, the invention according to claim 5 is based on the substrate for a liquid crystal display device according to any one of claims 1 to 4, and the low-refractive-index material constituting the planarizing layer is an organic silicate. On the other hand, the invention according to claim 6 is characterized in that the low-refractive-index material forming the planarizing layer is a fluororesin.

The organic silicate according to claim 5 is, for example, MOF PCF manufactured by Tokyo Ohka Kogyo Co., Ltd.
Series (refractive index 1.46 to 1.48) etc. are available,
Examples of the fluorine-based resin according to claim 6 include tetrafluoroethylene-hexafluoropropylene copolymer (refractive index of about 1.34) and fluorine-based acrylic resin (refractive index of 1.34 to 1.40). Can be applied.

The flattening layer fills the steps between the microlenses and flattens the transparent electrodes and the alignment film provided on the flattening layer to prevent display unevenness and response unevenness. However, it is also possible to further improve the flatness of the surface of the flattening layer by interposing another transparent resin layer between the flattening layer and the microlens. The device substrate is a liquid crystal display device (for example, ST
It is suitable as a substrate of a display device to which N liquid crystal is applied.

Next, as the transparent substrate according to the present invention, in addition to a glass plate, a plastic film, a plastic board or the like can be used. Further, when the transparent substrate is provided with a color filter layer for coloring the transmitted light transmitted through each of the picture element portions into a corresponding color, color display of the liquid crystal display device becomes possible. The invention according to claim 7 is based on such a technical reason.

That is, the invention according to claim 7 is premised on the substrate for a liquid crystal display device according to any one of claims 1 to 6, and the transparent substrate is provided at each portion corresponding to each picture element portion. It is characterized by comprising a plurality of color filter layers for coloring the transmitted light transmitted through the picture element portion into corresponding colors.

As the color filter layer according to the seventh aspect, a layer containing a transparent resin binder and a colorant mixed in the transparent resin binder as a main component can be used. As such a transparent resin binder,
In order to prevent light reflection at the interface with the transparent substrate and to efficiently utilize the incident light, it is preferable that the transparent substrate has a refractive index substantially the same as that of the transparent substrate, for example, acrylic resin, acrylic epoxy resin, epoxy resin, polyester resin. , A poamide resin, a urethane resin, a polyimide resin, or a copolymer resin thereof can be used, and an epoxy resin to which a melamine resin is added can also be used. Further, these resins may be thermosetting resins, ultraviolet curing resins, electron beam curing resins, or resins using these curing methods together.

Next, a dye or a pigment can be applied as the colorant, and when a pigment is applied, an organic pigment in the form of fine particles having high transparency is preferable. As such a pigment, for example, the following red pigments, green pigments, and blue pigments of the three primary colors of light can be used.

In both cases, C.I. I. Number (Color In
dex No.).

"Red pigment" CI No. 97, 122, 14
9, 168, 177, 180, 192, 215 "green pigment" CI No. 7, 36 "blue pigment" CI No. 15, a mixture of 15 and 1, a mixture of 15 and 4, a mixture of 15 and 6, 22, 60, 64. Further, the color pigment is not limited to the above-mentioned red pigment, green pigment, and blue pigment, and it is also possible to use three complementary color pigments of cyan, magenta, and yellow. Further, these pigments may be coated with an organic resin or surface-treated with a surface treatment agent. As the surface treatment agent, for example, a coupling agent, alcohol, amine, organic acid or the like can be used.

The color filter layer may contain, in addition to the transparent resin and the colorant, a dispersion aid or a surfactant for uniformly dispersing the colorant in the form of fine particles in the transparent resin. . As a method of forming the color filter layer, a printing method such as a gravure offset printing method can be applied. It is also possible to use a photolithography method. That is, a colored photosensitive resin composition is prepared by mixing a transparent photosensitive resin with a coloring agent, and the colored photosensitive resin composition is applied onto a transparent substrate, and then exposed and developed to form each image on the transparent substrate. In this method, a colored photosensitive resin composition layer is selectively formed on each of the parts corresponding to the base part. Alternatively, it may be formed by a method in which a transparent resin is mixed with a colorant and electrodeposition is performed.

When the microlens is made of a material having a large wavelength dispersion, the optical path length of the transmitted light transmitted through the picture element portion of each color is changed by changing the thickness of the color filter layer for each color. Can be uniformly arranged.

When the transparent substrate has a color filter layer, another transparent resin layer is provided on this color filter layer to fill the irregularities caused by the color filter layer, thereby flattening the surface of the flattening layer. Can be further improved.

Further, in the liquid crystal display device substrate according to the present invention, it is possible to provide a light-shielding film for preventing light transmission between the picture elements in order to further improve the contrast of the display screen. The light-shielding film may be provided at a position in contact with the transparent substrate, or may be provided so as to fill the concave portion existing in the gap between the adjacent microlenses.

Next, the liquid crystal display device substrate according to the present invention can be used as an electrode plate of a liquid crystal display device by providing a transparent electrode and an alignment film on the flattening layer.
If the transparent electrode is composed of an ITO thin film, this IT
Since the O thin film has a high refractive index (about 1.9 to 2.1), an antireflection layer having an intermediate refractive index may be provided between the flattening film and the ITO thin film. As the antireflection layer, for example, a thin film of an oxide such as silicon dioxide,
Alternatively, an organic resin layer having a refractive index of about 1.4 to 1.5 can be used. Moreover, these oxide thin films and 1.4-
It is also possible to arrange an organic resin layer having a refractive index of about 1.5 on the transparent electrode to prevent light reflection on the surface of the transparent electrode.

[0037]

According to the substrate for a liquid crystal display device according to the invention described in claims 1 to 7, the transmitted light which is respectively provided at the portion corresponding to each picture element portion on the transparent substrate and which is transmitted through each picture element portion is respectively generated. A plurality of microlenses, which are made of a material having a high refractive index and are made of a material having a refractive index lower than those of the microlenses, are formed so as to flatten the surface. Since it has a flattening layer, the light rays incident on each pixel portion of the transparent substrate as well as the light rays incident on the inter-pixel portion are directed toward the center of each pixel portion by the microlens. Since it is refracted toward, the entire incident light beam can be used for screen display.

Further, according to the substrate for a liquid crystal display device of the fourth aspect, the high refractive index material forming the microlenses has an organic resin and a refractive index different from that dispersed in the organic resin. Since the fine powder is contained, the light reflectance on the surface of the fine powder is increased, and it is possible to increase the viewing angle of the display screen by utilizing the scattering due to the light reflection.

[0039]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Substrate 1 for liquid crystal display device according to this embodiment
Is a glass substrate 11 having a thickness of 0.7 mm as shown in FIG.
A light-shielding film 12 provided on the glass substrate 11 at a portion corresponding to each pixel portion, and a red color provided on a portion corresponding to each pixel portion on the glass substrate 11,
Green and blue three color filter layers 13R, 13
G, 13B (however, the thickness of the red color filter layer 13R is 1.2 μm, the thickness of the green color filter layer 13G is 1.15 μm, and the blue color filter layer 13G
Has a thickness of 1.1 μm), and a plurality of microlenses (convex lenses) 14 each having a thickness of 2.5 μm provided in the central portion of the glass substrate 11 corresponding to each pixel portion.
And a flattening layer 15 for covering the plurality of microlenses 14 and flattening the surface thereof, the main part of which is formed, and on the flattening layer 15, an I of 0.2 μm in thickness is formed.
A transparent electrode 2 made of TO is provided. In the figure,
x indicates an optical path of a light ray that passes through the microlens 14.

The refractive index for a light beam having a wavelength of 450 nm is 1.68, the refractive index for a light beam having a wavelength of 540 nm is 1.66, and the refractive index for a light beam having a wavelength of 610 nm is 1.
The microlens 14 is composed of a resin composition in which a polyimide resin of 65 is mixed with an optical glass fine powder (barium crown glass) having a refractive index of about 1.66 and a particle size of about 0.1 μm or less, In addition, the microlens 14 has a gentle spherical surface shape with a film thickness of about 2.5 μm at the center thereof.

On the other hand, the flattening layer 15 has a refractive index of 1.4.
The color filter layers 13R, 13 are composed of a UV-curable fluorine compound-modified acrylic resin of 0.
It is formed so that the total thickness of G, 13B, the microlens 14 and the flattening layer 15 is about 5 μm.

The substrate 1 for liquid crystal display device according to this embodiment is manufactured by the following method.

First, a red photosensitive resin made of a mixture of an acrylic transparent photosensitive resin and a red pigment is applied on a glass substrate 11 provided with a light shielding film 12 to form a film, and exposure / development is performed. Then, the red color filter layer 13R was formed by selectively leaving the coating film on a portion of the glass substrate 11 corresponding to each red pixel portion.

Subsequently, a green color filter layer 13G and a blue color filter layer 13B were sequentially formed by the same method.

Next, optical glass fine powder is mixed with the above-mentioned polyimide resin to form an ink, which is printed by the gravure offset printing method on each part corresponding to each picture element part on the glass substrate 11 and is heated and melted. A plurality of microlenses 14 were formed by being deformed into the above shape by the surface tension.

Further, 3% by weight of a photopolymerization initiator is mixed with an acrylate-based monomer modified with a fluorine-based compound, and the microlens 14 is coated without solvent and coated so that the surface becomes flat. In order to prevent the inhibition of polymerization due to the above, the above flattening layer 15 was formed by irradiating with ultraviolet rays in a nitrogen atmosphere and curing. The transparent electrode 2 is formed by continuously sputtering the surface of the flattening layer 15 without plasma-treating the flattening layer 15 in the vacuum chamber.

Then, when the liquid crystal display device was assembled by applying the liquid crystal display device substrate 1 according to this embodiment, it was about 15 as compared with the case where the conventional liquid crystal display device substrate shown in FIG. 2 was used. % A bright display screen was obtained.

[0049]

According to the inventions according to claims 1 to 7, not only the light rays incident on the respective picture element portions of the transparent substrate but also the light rays incident on the inter-picture element portions are separated by the microlenses. Since the light is refracted toward the center of the pixel portion, the entire incident light beam can be used for screen display.

Therefore, the apparent aperture ratio is increased, and the brightness of the display screen can be improved.

Further, according to the invention of claim 4, the apparent aperture ratio is increased, the brightness of the display screen can be improved, and the viewing angle of the display screen can be increased.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display device substrate according to an embodiment.

FIG. 2 is a cross-sectional view of a substrate for a liquid crystal display device according to a conventional example.

[Explanation of symbols]

 1 substrate for liquid crystal display device 11 glass substrate 12 light-shielding film 13R color filter layer 13G color filter layer 13B color filter layer 14 microlens 15 flattening layer 2 transparent electrode

Claims (7)

[Claims] 1. A pair of substrates, each of which is provided with an electrode to which a voltage can be applied for each pixel, at least one of which is transparent, and a liquid crystal substance enclosed between these substrates, wherein a voltage is applied between the electrodes. In the substrate for a liquid crystal display device in which the orientation state of the liquid crystal substance is changed for each picture element by applying a voltage, the picture element portion is provided on the transparent substrate at a position corresponding to each picture element portion. A plurality of microlenses made of a high-refractive index material and a plurality of microlenses made of a material having a lower refraction index than the microlenses are formed by converging the transmitted light in the central direction of each picture element portion. And a flattening layer for flattening the surface thereof. 2. The high refractive index material forming the microlens has a refractive index of 1.50 or more, and the low refractive index material forming the flattening layer has a refractive index of 1.48 or less. The substrate for a liquid crystal display device according to claim 1, which has. 3. The high refractive index material constituting the microlenses contains an organic resin and fine powder dispersed in the organic resin and having a refractive index substantially equal to that of the organic resin. 2. The substrate for liquid crystal display device according to 2. 4. The high refractive index material constituting the microlenses contains an organic resin and fine powder dispersed in the organic resin and having a refractive index different from that of the organic resin. A substrate for a liquid crystal display device as described above. 5. The low-refractive-index material forming the flattening layer is an organic silicate.
3. The substrate for liquid crystal display device according to 3 or 4. 6. The low refractive index material forming the flattening layer is a fluorine-based resin.
Alternatively, the substrate for a liquid crystal display device according to item 4. 7. The transparent substrate is provided with a plurality of color filter layers which are respectively provided at the portions corresponding to the respective picture element portions and which color the transmitted light transmitted through the respective picture element portions into corresponding colors. The substrate for a liquid crystal display device according to claim 1, 2, 3, 4, 5, or 6.