JPH07225306A - Color filter substrate for liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the color filter substrate which makes a bright screen display by increasing the apparent aperture rate. CONSTITUTION:This color filter substrate 1 has its principal part formed of a transparent substrate 11, a color filter layer 12 consisting of pixels 12R, 12G, and 12B of red, green, and blue provided at pixel positions on the transparent substrate, and an overcoat layer 13 which is provided covering the color filter layer 12 to flatten the surface; and the respective pixels of the color filter layer 12 each have a spherical surface which is thick in its center and thin at its peripheral part. A light beam which is made incident on between pixels is also refracted to the center of the pixel, not to mention a light beam which is made incident on each pixel, so all the incident light beams can be utilized for the screen display, which becomes bright.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color filter substrate for a liquid crystal display device, and more particularly to an improvement of a color filter substrate having an increased apparent aperture ratio and effective use of light rays incident on the liquid crystal display device. Is.

[0002]

2. Description of the Related Art A liquid crystal display device comprises a pair of electrode plates provided with electrodes capable of applying a voltage for each pixel, and a liquid crystal substance enclosed between the electrode plates, which constitutes a main part thereof. By applying a voltage between the electrodes, the alignment state of the liquid crystal substance is changed for each pixel to control the plane of polarization of the light that passes through this liquid crystal substance, and the polarizing film controls the transmission / non-transmission of the liquid crystal display. It is widely used for home or commercial displays, video cameras, input / output devices, and the like.

Also, by applying a color filter substrate having a color filter layer provided on a transparent substrate to one of the electrode plates, the screen display can be colored. The color filter substrate a is shown in FIG.
As shown in FIG. 3, each of the picture elements a3R, a3R, a3R, a3G, a3B corresponding to each pixel is formed on the transparent substrate a1.
A color filter layer a3 that colors transmitted light that passes through 3G and a3B to corresponding colors, respectively, and a light shield provided at a portion between the picture elements a3R, a3G, and a3B of the color filter layer a3 (corresponding to a portion between pixels). The film a2 and the overcoat layer a4 provided on the color filter layer a3 constitute a main part, and this overcoat layer a4
A transparent electrode c and an alignment film (not shown) are provided on the surface of the electrode and applied as the electrode plate.

[0004]

By the way, when a voltage is applied between a pair of electrode plates for screen display, the voltage application state between adjacent pixels is likely to be unstable, so that the inter-pixel region The orientation of the above liquid crystal substance corresponding to (3) is likely to be disturbed. Further, due to this, the transmittance of the transmitted light that passes through the inter-pixel portion also becomes unstable, which is likely to cause the deterioration of the contrast between pixels and the color purity. Therefore, as described above, the method of providing the light-shielding film a2 between the pixels of the transparent substrate a1 to prevent light transmission through this portion to improve the contrast and color purity of the display screen has been adopted.

However, since the existence of the light-shielding film a2 makes it impossible to effectively utilize the incident light beam, there is a problem that the brightness of the display screen is lowered. 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 device difficult to carry.

The present invention has been made by paying attention to such a problem. 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 filter substrate.

[0008]

That is, the invention according to claim 1 is such that a color filter layer composed of a plurality of picture elements and coloring transmitted light passing through each picture element with a corresponding color is provided on a transparent substrate. Based on the provided color filter substrate for liquid crystal display device, each picture element of the color filter layer is composed of a microlens for converging transmitted light passing through each picture element in the central direction of each picture element. It is characterized by that.

According to the first aspect of the invention, not only the light rays incident on the picture elements of the color filter layer but also the light rays incident on the inter-picture element portions are directed toward the center of each picture element. Since the light beam is refracted toward, the entire incident light beam can be used for screen display. As a result, the apparent aperture ratio is increased, so that it is possible to improve the brightness of the display screen without causing a decrease in contrast between pixels. Since each picture element in the color filter layer has a function of converging transmitted light, the manufacturing cost of the liquid crystal display device is much higher than that of the case where a microlens is molded separately from the color filter and incorporated in the liquid crystal display device. It is possible to make it cheap.

Each of the picture elements for converging the transmitted light in the central direction is mainly composed of a transparent resin having a refractive index of 1.5 or more and a colorant, and has a convex surface in cross section and a smooth surface shape. Is available. The invention according to claim 2 relates to the invention in which the structure of the picture element is specified.

That is, the invention according to claim 2 is premised on the color filter substrate for a liquid crystal display device according to claim 1, and the microlenses forming each picture element of the color filter layer have a refractive index of 1. It is characterized in that it has 5 or more transparent resins and a colorant as main components and has a convex surface in cross section and a smooth surface shape.

As the transparent resin constituting the microlens, one having a higher refractive index is preferable, and for example, acrylic resin, acrylic epoxy resin, epoxy resin, polyester resin, polyamide resin, urethane resin, polyimide resin, or a combination thereof. A polymer resin or a mixture of an epoxy resin and a melamine resin can be used. Further, since it is necessary to mold each picture element into a shape having a convex cross section and a smooth curved surface, it is desirable to use a curable resin. As such a resin, for example,
Examples of the resin include a thermosetting type resin, an ultraviolet ray curing type resin, and an electron beam curing type resin.

Further, a dye or a pigment can be applied as the colorant, and when the 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 pigment, green pigment, and blue pigment can be used.

Both are 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. Incidentally, 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.

When a pigment is applied as a colorant,
In order to easily and accurately form the shape of each picture element in the color filter layer, the lower the pigment content in the color filter layer is, the more preferable it is, and the more preferable content is 50% by weight or less, more preferably 40% by weight or less.

The color filter layer composed of a plurality of picture elements contains, in addition to the transparent resin and the colorant, a dispersion aid and a surfactant for uniformly dispersing the colorant in the form of fine particles in the transparent resin. It may be one.

The shape of the picture element in the color filter layer is preferably such that the surface thereof forms a part of a spherical surface. In this case, each of the picture elements of the color filter layer has a function of a spherical lens, and the entire incident light rays incident on the respective picture elements and the incident light rays directed toward the inter-picture element portion are defined by the respective picture elements. It becomes possible to refract in the central direction. Further, in order to increase the aperture ratio to enable a brighter screen display and to increase the yield and productivity of the color filter layer, the surface thereof has a shape (kamaboko shape) which constitutes a part of the cylindrical side surface. It is also possible. In this case, each picture element of the color filter layer has the function of a cylindrical lens, and the entire incident light ray incident on each picture element and the incident light ray incident on the inter-pixel area are defined by the cylindrical lens. It becomes possible to refract in the axial direction.

In such a color filter layer composed of a plurality of picture elements, for example, a colored resin layer containing a transparent resin and a colorant as a main component is formed at a pixel portion on a transparent substrate. After melting by heating and deforming into a gently curved surface shape with a convex section by the action of its surface tension,
It can be formed by a method of curing the transparent resin of the deformed colored resin layer and preventing the transparent resin from deforming when heated again. When the colored resin layer is formed in a matrix shape corresponding to the shape of an electrode formed in a matrix shape and the formed resin layer is heated and melted after the formation, a surface element forms a spherical surface due to the action of the surface tension. In addition, when the colored resin layer is formed in a stripe shape corresponding to the electrode shape formed in a stripe shape, and when the colored resin layer is heated and melted after formation, the surface tension causes the surface to become one of the side surfaces of the cylinder. It becomes a picture element of the shape (kamaboko shape) that constitutes the part.

As a method of forming the colored resin layer on the pixel portion on the transparent substrate, for example, a printing method such as a gravure offset printing method can be applied. In this case, the printed and formed colored resin layer has an irregular shape. Has a convex cross section.
Then, by heating and melting this, it is possible to shape the surface shape into a gently curved surface.

As a method of forming the colored resin layer on the pixel portion, a photolithography method can be used. 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 develop a colored photosensitive resin on a pixel portion. It is a method of selectively forming a resin composition layer.

As a method for curing the transparent resin, heat curing, ultraviolet curing, electron beam curing or the like can be applied depending on the type of the transparent resin to be applied.

Further, in the color filter layer composed of a plurality of picture elements, after a colored resin layer containing a transparent resin and a colorant as a main component is formed at a pixel portion on a transparent substrate, dry etching or a liquid developer ( For example, it is also possible to perform a development treatment with an alkaline developer or a solvent developer, and control the etching amount or the development amount depending on the site to mold the surface having a convex cross section and a gently curved surface.

When wavelength dispersion occurs in these color filter layers (a phenomenon in which the refractive index varies depending on the wavelength of transmitted light), the optical thickness is adjusted by adjusting the film thickness according to the color of the color filter layer. It is possible to make the film thickness (film thickness x refractive index) uniform.

Further, in this technical means, it is not necessary to provide a light-shielding film between the picture elements, but even if it is provided, the brightness of the display screen is not affected.

Next, the color filter substrate according to the invention of claim 1 or 2 can be used as an electrode plate of a liquid crystal display device by directly providing a transparent electrode and an alignment film on the color filter layer. Since the liquid crystal display device can be manufactured at low cost by applying the color filter substrate having such a structure, it is suitable as a color filter substrate for an inexpensive display device such as a game machine.

On the other hand, a transparent and flat surface overcoat layer may be provided on the color filter layer, and a transparent electrode and an alignment film may be provided on the surface to be used as an electrode plate of a liquid crystal display device. . In this case, since the transparent electrode and the alignment film are provided on a flat surface, the alignment property and the responsiveness of the liquid crystal substance are improved, so that the uneven response and the uneven display can be prevented and a high quality screen display can be realized. . However,
In order to maintain the light beam focusing performance of each pixel in the color filter layer, the overcoat layer needs to have a refractive index smaller than that of the color filter layer. The invention according to claim 3 is made for such a technical reason.

That is, the invention according to claim 3 is based on the color filter substrate for a liquid crystal display device according to claim 1 or 2, and has a refractive index smaller than that of the color filter layer on the color filter layer. An overcoat layer having a flat surface is provided, and the invention according to claim 4 is based on the color filter substrate for a liquid crystal display device according to claim 3, wherein the overcoat layer is It is characterized by being composed of a fluorine-based resin.

Since the transparent electrode provided on the overcoat layer generally has a large refractive index (IT having a typical ITO as a transparent electrode has a refractive index of 2.0 to 2.1), The light reflectance at the interface with the overcoat layer is extremely high. Therefore, in order to reduce the light reflectance and enable a bright screen display, it is possible to dispose an organic resin layer or a SiO ₂ thin film having an intermediate refractive index between the _two .

In the invention according to claims 1 to 4, a glass plate can be applied as the transparent substrate.
You may use a plastic film, a plastic board, etc.

[0031]

According to the inventions according to claims 1 and 2, each picture element of the color filter layer is constituted by a microlens for converging transmitted light passing through each picture element in the central direction of each picture element. , Not only the light rays incident on each pixel of the color filter layer, but also the light rays incident on the inter-pixel area are refracted toward the center of each pixel, so that the entire incident light ray is displayed on the screen. It can be used for.

On the other hand, according to the inventions of claims 3 to 4,
An overcoat layer having a smaller refractive index than the color filter layer and a flat surface is provided on the color filter layer. By providing a transparent electrode or an alignment film on the overcoat layer, the orientation and response of the liquid crystal substance can be improved. Since the property is improved, it is possible to prevent the uneven response and the uneven display.

[0033]

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

Color filter substrate 1 according to this embodiment
Is a glass substrate 11 having a thickness of 0.7 mm as shown in FIG.
And the pixel portion on the glass substrate 11 (the glass substrate 11
And a color filter layer 12 composed of three color picture elements 12R, 12G, and 12B of three colors of red, green, and blue. The overcoat layer 13 which covers and has a flat surface forms a main part of the overcoat layer 13, and the IT is formed on the overcoat layer 13.
A transparent electrode 2 made of O is provided.

The red picture element 12R has a refractive index of 1.
57 is composed of a colored transparent resin in which 31% by weight (solid content ratio) of an organic red pigment is dispersed in a fine particle state in a thermosetting type epoxy resin, and the film thickness in the central portion is about 2.45 μm. The peripheral surface has a gentle spherical surface shape with a thickness of about 0.5 μm. Further, the green picture element 12G contains 25% by weight (solid content ratio) of the epoxy resin.
It is composed of a colored transparent resin in which the organic green pigment of (1) is dispersed in the form of fine particles, and the film thickness at the center is about 2.
It has a smooth spherical surface shape of 55 μm and a peripheral thickness of about 0.5 μm. Also, the blue picture element 12B
Is made of a colored transparent resin in which 16% by weight (solid content ratio) of an organic blue pigment is dispersed in a fine particle state in the epoxy resin, and the thickness of the central portion thereof is about 2.60 μm.
m and the peripheral portion has a thickness of about 0.5 μm and has a gentle spherical surface shape. In addition, the above-mentioned overcoat layer 1
3 is made of an ultraviolet-curing type fluorine compound-modified acrylic resin having a refractive index of 1.40, and the total thickness of the color filter layer 12 and the overcoat layer 13 is about 4
It is formed to have a thickness of μm. In addition, the transparent electrode 2
Has a thickness of 0.14 μm.

The color filter substrate 1 is manufactured by the following method.

First, a printing ink composed of a mixture of the epoxy resin and a red pigment is gravure offset printed on the red pixel portion of the glass substrate 11 and is heated and melted so that the surface thereof has the above-described shape. Then, heating was continued and cured to form a red picture element 12R. Then, in the same manner, the green picture elements 12 are sequentially
G and blue picture elements 12B were respectively formed.

Next, a photopolymerization initiator was mixed in an amount of 3% by weight with an acrylate-based monomer modified with a fluorine-based compound, and the solvent was used without solvent from the red picture element 12R, the green picture element 12G and the blue picture element 12B. The above-mentioned color filter layer 12 was coated and applied so as to have a flat surface, and was irradiated with ultraviolet rays in a nitrogen atmosphere to be cured to prevent polymerization inhibition by oxygen, thereby forming an overcoat layer 13. The transparent electrode 2 is formed by plasma-treating the surface of the overcoat layer 13 in a vacuum chamber and then continuously sputtering the film without taking it out of the vacuum chamber.

When the liquid crystal display device is assembled by applying the color filter substrate 1 according to this embodiment,
It was possible to obtain a display screen that is approximately 30% brighter than when the conventional color filter substrate shown in FIG. 2 is used.

[0040]

According to the inventions of claims 1 and 2, a light ray incident on each picture element of the color filter layer and a light ray incident on a portion between picture elements are directed toward the center of each picture element. Since it is refracted toward, 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.

On the other hand, according to the inventions of claims 3 to 4,
By providing the transparent electrode or the alignment film on the overcoat layer formed on the color filter layer, the alignment property and the responsiveness of the liquid crystal substance are improved, so that it is possible to prevent the response unevenness and the display unevenness.

Therefore, it has an effect of enabling a bright and high quality display screen.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a color filter substrate according to an example.

FIG. 2 is a sectional view of a color filter substrate according to a conventional example.

[Explanation of symbols]

 1 Color Filter Substrate 2 Transparent Electrode 11 Glass Substrate 12 Color Filter Layer 13 Overcoat Layer 12R Picture Element 12G Picture Element 12B Picture Element

Claims (4)

[Claims] 1. A color filter substrate for a liquid crystal display device, wherein a color filter layer comprising a plurality of picture elements and coloring the transmitted light passing through each picture element with a corresponding color is provided on a transparent substrate. A color filter substrate for a liquid crystal display device, characterized in that each picture element of the filter layer is composed of a microlens that focuses transmitted light passing through each picture element toward the center of each picture element. 2. A microlens constituting each picture element of the color filter layer has a transparent resin having a refractive index of 1.5 or more as a main component and a colorant as a main component, and has a convex surface in section, and a surface shape which is gentle. The color filter substrate for a liquid crystal display device according to claim 1. 3. A color filter for a liquid crystal display device according to claim 1, wherein an overcoat layer having a smaller refractive index than the color filter layer and a flat surface is provided on the color filter layer. substrate. 4. The color filter substrate for a liquid crystal display device according to claim 3, wherein the overcoat layer is made of a fluororesin.