JPH07281168A - Liquid crystal color filter - Google Patents

Abstract

PURPOSE:To attain high brightness without increasing the power consumption of backlight by providing a fine convex lens on one surface of a transparent substrate in a liquid crystal color filter provided with a color filter layer on another surface of the transparent substrate. CONSTITUTION:The liquid crystal color filter has a structure provided with the color filter layers 2a, 2b, 2c on one surface of the transparent substrate 1 composed of a glass, a plastic film or the like and the fine convex lens 3 on another surface of the transparent substrate. A black matrix 4 is provided on the boundary part of each of the color filter layers 2a, 2b, 2c. The light passing through the transparent substrate 1 is collected at the focus F by the fine convex lens 3 and then, extremely bright color display is enabled. The color filter layers 2a, 2b, 2c are colored layers formed by photolithography or printing method conventionally used and having l-3mum thickness. And the fine convex lens is formed preferably from a printed transparent ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal color filter used in a color liquid crystal display.

[0002]

2. Description of the Related Art A liquid crystal display (LCD), which is a typical flat panel display, has advantages such as light weight, power saving, and thin shape, and replaces a conventional CRT (CRT) with a personal computer. It is used in a wide range of fields such as electronic desk calculators, clocks, and televisions.

Further, the liquid crystal display is changing from the conventional monochrome display to the color display, and the full color display of the liquid crystal display is achieved by the active matrix drive system,
Especially, the thin film transistor (TFT) driving system is rapidly expanding. Full color LCD displays are red, green, and patterned for each pixel.
The liquid crystal is driven as an optical shutter for three transmission color filters of blue.

FIG. 3 shows a liquid crystal display device based on the active matrix driving method. This device comprises a thin film transistor (TF) on a transparent substrate 10 such as glass.
T) 11, drive electrode (ITO film) 12, alignment film 1
3, liquid crystal layer 14, alignment film 15, common electrode (ITO film) 1
6. Red, green and blue color filter layers 18a, 18 covered with the overcoat layer 17
b, 18c and a transparent substrate 19 such as glass are provided in this order, and each pixel is independently controlled by a thin film transistor. Each color filter layer 18a, 18b,
A black matrix 22 is provided at the boundary of 18c, and polarizing plates (polarizing films) 20 and 21 are arranged on the front surface and the back surface, respectively.

Unlike a fluorescent tube, such a liquid crystal display device does not have a function of self-coloring. Therefore, in most cases, a transmissive type is used in which a light emitter called a backlight is placed on the back surface of the liquid crystal. In this case, the light of the backlight is first attenuated by the polarizing plate 20, further passes through the liquid crystal layer 14, the color filter layers 18a, 18b and 18c, and when passing through the final polarizing plate 21, 5% of the original light is emitted. It decays below. Therefore, increase the contrast of the image,
A strong backlight is required to obtain a bright screen, but it has a disadvantage of consuming a large amount of power.

Therefore, various methods for improving the screen brightness of a liquid crystal display have been conventionally studied. For example, a light guide plate printed with dots so that light is evenly scattered on an acrylic resin plate is used as a backlight, and a light diffusion plate made of polycarbonate or a prism sheet is further installed on the light guide plate. Technology has been developed for efficiently collecting light emitted from a liquid crystal display, and liquid crystal displays based on this method have also been produced.

Further, the color filter layers 18a, 18
In order to improve the light transmittance of b and 18c as much as possible,
Improvements are being made to make the dispersion of the pigment extremely small, and to make the line width of the black matrix as small as possible to increase the aperture ratio (JP-A-60-12).
9738 publication). However, the conventional improvement of the color filter has a limit to greatly improve the screen brightness, and the improvement is about 10 to 30% at most.

An object of the present invention is to provide a liquid crystal color filter capable of greatly improving the screen brightness.

[0009]

Means and Actions for Solving the Problems As a result of intensive studies conducted by the present inventors to solve the above problems and improve the screen brightness of a liquid crystal display, the other surface of a transparent substrate provided with a color filter layer on one surface When a lens function having a function of collecting light is provided in, it is possible to efficiently collect light, and a new fact that a very bright liquid crystal display can be obtained was found, and the present invention was completed. .

That is, the liquid crystal color filter of the present invention is characterized in that a color filter layer is provided on one surface of a transparent substrate, and a fine convex lens is provided on the other surface of the transparent substrate. FIG. 1 is a sectional view showing an example of a liquid crystal color filter of the present invention. As shown in the figure, the liquid crystal color filter of the present invention has a structure in which color filter layers 2a, 2b, 2c are provided on one surface of a transparent substrate 1 made of glass, a plastic film or the like, and fine convex lenses 3 are provided on the other surface. Have. Each color filter layer 2a, 2
A black matrix 4 is provided at the boundary between b and 2c.

As described above, according to the present invention, since the fine convex lens 3 is provided on the other surface of the transparent substrate 1, as shown in FIG. 2, light (shown by an arrow) passing through the transparent substrate 1 is fine. Since the convex lenses 3 gather at the focal point F, an extremely bright color display is possible. The color filter layers 2a, 2b and 2c have a thickness of 1 to 3 μm formed by a photolithography method or a printing method which have been conventionally used.
It is a colored layer of m. Each color filter layer 2a, 2b,
Pixels formed by the 2c array usually have 50 per side.
It is about 300 μm.

The fine convex lens 3 is preferably made of printed transparent ink. That is, since a printed pattern generally has a property of naturally forming a convex lens shape by the surface tension of the ink, a fine convex lens can be easily manufactured by printing at low cost. further,
By adjusting the viscosity and surface tension of the transparent ink, the curvature of the lens can be well controlled.

The transparent ink is made of a transparent resin,
Various solvents, transparent extender pigments, etc. can be used depending on the printability. As the resin, the material is not particularly limited, but printability, transparency, adhesiveness,
In terms of strength, thermosetting acrylic resin, epoxy resin,
Thermosetting resins such as polyester resin, phenol resin, urethane resin and melamine resin, heat resistant resins such as silicone resin and fluororesin, UV curable resin, electron beam curable resin and the like can also be used.

Examples of the extender pigment having high transparency include fine powder barium sulfate powder, silica powder, calcium carbonate powder and the like. Examples of the solvent usable in the present invention include cetyl alcohol, stearyl alcohol, oleyl alcohol, octyl alcohol, decyl alcohol, lauryl alcohol, tridecyl alcohol (tridecanol), n-butyl alcohol, cyclohexyl alcohol, and 2-methylcyclohexyl. Higher boiling higher alcohols such as alcohols or mixtures of C ₁₀ -C ₁₅ alkyl alcohols; methyl cellosolve, ethyl cellosolve, butyl cellosolve,
Alkyl ethers such as butyl carbitol, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate; aromatic hydrocarbons such as toluene, xylene and tetralin; ketones such as cyclohexanone, methylcyclohexanone, isophorone and diacetone alcohol However, the present invention is not limited thereto, and may be appropriately selected in consideration of printability (ink transfer property, etc.), workability, and the like. When higher alcohols are used, butyl carbitol (diethylene glycol monobutyl ether), butyl cellosolve, ethyl carbitol, which has a faster drying rate than this, is used in consideration of the drying property and fluidity of the ink.
Alcohols or esters such as butyl cellosolve acetate, butyl carbitol acetate, and terpineol may be used together. The amount of the solvent added may be appropriately determined in consideration of the solubility or dispersibility of the components such as the mixed resin used, workability, printability, etc., and is usually 5 to 80% by weight, preferably the total amount of the ink. 15-50% by weight
It is a degree.

The viscosity of the transparent ink is about 1 to 10,000.
Suitably it is P, preferably about 500-5,000 P. The surface tension of the transparent ink is 10 to 70 dyn /
Suitably it is cm, preferably 20 to 50 dyn / cm. As a printing method for producing the fine convex lens 3,
Various printing methods can be adopted, but since it is necessary to increase the thickness of the ink film to some extent, for example, screen printing or intaglio offset printing is suitable. However, even in the case of a waterless lithographic offset having a thin ink film thickness in one printing, the desired fine convex lens 3 can be obtained by repeating printing several times.

The shape of the fine convex lens 3 to be printed is not particularly limited, and examples thereof include a stripe shape and a dot shape. In general, it can be said that intaglio printing is suitable for stripe-shaped printing and screen printing is suitable for dot-shaped printing. The size of the transparent ink print pattern for forming the fine convex lens 3 is appropriately determined according to the size of the pixel, but is generally 10 to 3000 μm in width, preferably 50 to obtain a good light-collecting effect.
~ 300μm stripe pattern or diameter 10 ~ 3
000 μm, preferably 50 to 300 μm dot pattern, and the ratio of the line width or diameter to the maximum film thickness (film thickness / line width or diameter, hereinafter this ratio is referred to as aspect ratio) is in the range of 0.02 to 1. Preferably.

That is, when the width of the stripe pattern or the diameter of the dot pattern exceeds 3000 μm, the display becomes unclear, so-called display unevenness occurs. on the other hand,
Even if the width of the stripe pattern or the diameter of the dot pattern is less than 10 μm, the effect is not significantly changed, but it is very difficult to faithfully reproduce the shape by the current printing method.

The smaller the width of the stripe pattern and the smaller the diameter of the dot pattern are, the better, and it is preferable that there is no image unevenness within a predetermined range according to the line width of each pixel of red, green and blue. A good light collection effect can be obtained. Specifically, for the line width 100 of each pixel,
The width of the stripe pattern and the diameter of the dot pattern are about 5
It is a ratio of 0 to 300, preferably about 100 having the same width. Usually, for a pixel whose one side is about 50 to 150 μm, good condensing property can be obtained by designing a lens having a stripe pattern with a width of about 20 to 300 μm.

The ratio of the line width or diameter of the fine convex lens to the maximum film thickness (film thickness / line width or diameter) determines the curvature of the fine convex lens, and this ratio is 0.02.
If it is smaller, the state is closer to flat, and the light collecting function is reduced. On the other hand, when the ratio exceeds 1, it is difficult to manufacture by the printing method, and the light of the lens is scattered to reduce the light-collecting property, so-called pixel unevenness occurs, and in some cases, the pixel unevenness occurs depending on the viewing angle. It will be easier.

The gap between each stripe pattern and dot pattern is about 0 to 300 μm, preferably 0 to 300 μm.
It is suitable to be about 100 μm, and if the gap is larger than this range, the display becomes uneven. The liquid crystal color filter of the present invention thus obtained is formed on the surface of the liquid crystal layer 14 in a state in which each color filter layer 2a, 2b, 2c is covered with the overcoat layer 17 as in the normal liquid crystal display device shown in FIG. Alignment film 15 and common electrode (I
It is laminated through a TO film 16 and is suitably used as a high-brightness liquid crystal display in various fields such as personal computers, electronic desk calculators, watches, and televisions.

In the above description, the case where the fine convex lens 3 is exclusively manufactured by the printing method has been described. However, when the color filter is press-molded by the mold, the mold surface is provided with unevenness, and at the same time as the molding. A fine convex lens may be formed. As another method, the fine convex lens can be formed by polishing the surface of the color filter. It goes without saying that liquid crystal color filters obtained by these methods are also included in the scope of the claims of the present invention, but a mold is not required and a high polishing technique is not required, and a printing method and an ink material are used. The most suitable method is a printing method that can easily obtain a fine convex lens having a desired shape by adjusting the ink viscosity and the like.

[0022]

【Example】

Example 1 As the transparent substrate, soda lime glass manufactured by Nippon Sheet Glass Co., Ltd. (surface SiO ₂ immersion treatment product, thickness 1.1 mm) was used, and stripes of 100 μm width were formed on one surface of the substrate at a pitch of 300 μm and red. A green, blue pattern was sequentially printed to form a color filter layer. After printing, it was heated in a clean oven at 220 ° C. for 1 hour.

Then, a thermosetting acrylic resin prepared by mixing 2-hydroxyethyl methacrylate as a monomer and a methylated melamine resin as a co-crosslinking agent was dissolved in n-butyl acetate on the other surface of the transparent substrate. A fine convex lens having a stripe pattern was formed by gravure offset printing using transparent ink to obtain a liquid crystal color filter. The formed fine convex lens had a line width of 10 μm, a thickness of 4 μm and an aspect ratio of 0.40, and the gap between the lenses was 100 μm. The transparent ink used had a viscosity of 500 P and a surface tension of 40 dyn / cm. Examples 2 to 13 Liquid crystal color filters in which fine convex lenses having various lens shapes are provided on the other surface of the transparent substrate having the same color filter layer as that of Example 1 on one surface by the manufacturing methods shown in Tables 1 and 2 are manufactured. did.

In Tables 1 and 2, the ink material described as "acrylic" means the same ink as in Example 1. Moreover, what is described as "epoxy" means that a transparent ink obtained by dissolving an epoxy resin (trade name "Epicoat 1001" manufactured by Yuka Shell Epoxy Co., Ltd.) in butyl cellosolve was used. Further, the term "polyester" means that a transparent ink obtained by dissolving a polyester resin prepared by esterifying trimellitic anhydride and neopentyl glycol in oleyl alcohol was used. Comparative Example A liquid crystal color filter was produced in the same manner as in Example 1 except that fine convex lenses were not formed on the transparent substrate.

Pixel unevenness and screen brightness were measured using each of the obtained liquid crystal color filters. The presence / absence of pixel unevenness was determined by visually observing whether or not there is a shade of color when illuminated with a backlight composed of a three-wavelength fluorescent lamp. The screen brightness is represented by an index when that of the comparative example is 1.00. The screen brightness was measured by incorporating a liquid crystal display panel with a backlight of a three-wavelength fluorescent lamp and measuring the brightness of light passing through a liquid crystal color filter with an illuminometer. The brightness of the comparative example without the lens is set to 2000 cd / m ² , and the brightness of each example is represented by a relative value when the brightness is set to 1.

[0026]

[Table 1]

[0027]

[Table 2]

As is clear from Tables 1 and 2, the liquid crystal color filters of the examples have improved screen brightness as compared with those of the comparative examples, and particularly the size is 10 to 300 μm and the aspect ratio is 0.02 to 0.02. It can be seen that when it is in the range of 1, the screen brightness is significantly high without any pixel unevenness.

[0029]

Since the liquid crystal color filter of the present invention is provided with the fine convex lens on the transparent substrate, it has an effect that high brightness can be achieved without increasing the power consumption of the backlight. Further, according to the present invention, when the fine convex lens is formed of a transparent ink by printing, there is an effect that a liquid crystal color filter can be easily manufactured at low cost.

Further, in the present invention, by defining the size of the fine convex lens, a good light-collecting effect without display unevenness or pixel unevenness can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a liquid crystal color filter of the present invention.

FIG. 2 is an explanatory diagram for explaining the operation of the fine convex lens in the present invention.

FIG. 3 is a cross-sectional view showing a liquid crystal display device based on a normal active matrix driving method.

[Explanation of symbols]

 1 Transparent Substrate 2a Color Filter Layer 2b Color Filter Layer 2c Color Filter Layer 3 Micro Convex Lens 4 Black Matrix

Claims (3)

[Claims] 1. A liquid crystal color filter in which a color filter layer is provided on one surface of a transparent substrate, wherein a fine convex lens is provided on the other surface of the transparent substrate. 2. The liquid crystal color filter according to claim 1, wherein the fine convex lens is made of printed transparent ink. 3. The transparent ink print pattern has a line width of 1.
0 to 3000 μm stripe pattern or diameter 10
The dot pattern is ˜3000 μm, and the ratio of the line width or diameter to the maximum film thickness (film thickness / line width or diameter).
Is in the range of 0.02 to 1, and the liquid crystal color filter according to claim 2.