JPH07253509A - Color filter and liquid crystal display device - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve a color filter used for a liquid crystal display device or the like. An interference layer 12 in which a plurality of thin films having different refractive indexes are laminated is formed on a transparent substrate 11, and the surface of the interference layer 12 for each color region is spherical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color filter, and more particularly, to improvement of an interferometric color filter used for color display of a liquid crystal display device and producing color by utilizing the interference effect of a thin film.

[0002]

2. Description of the Related Art A color filter according to a conventional example will be described below. The interferometric color filter according to the conventional example is
As shown in FIG. 7A, a flat transparent substrate 1 having two kinds of thin films, such as TiO ₂ and SiO _{2, which} have greatly different refractive indexes.
An interference layer 2 is formed by stacking layers on top of each other, and the light incident on the interference layer 2 is multiple-reflected in the interference layer 2 to interfere with each other, thereby creating a color by reflecting / transmitting only light of a specific wavelength. Is.

The color filter using the interference layer 2 described above has almost no absorption at the peak wavelength and reflects light of other wavelengths as compared with the color filter by the conventional pigment dispersion method or the like. It has the advantages of high purity and high brightness, and is currently widely used mainly in projection displays.

[0004]

However, in the above-described conventional interferometric color filter, the wavelength of the specific light reflected or transmitted depends on the film thickness of the interference layer 2. Therefore,
As shown in FIG. 7B, when the angle or the viewing angle of the light incident on the interference layer 2 changes, the distance of the light passing through the interference layer 2, that is, the optical distances ΔL1 and ΔL2 change, and the color that appears appears accordingly. Since it changes, the dependence of the expressed color on the viewing angle is very high, and there is a problem that it is difficult to use it for a direct-view display at this time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an interferometric color filter which has improved viewing angle characteristics and can be applied to a direct-view type liquid crystal display device.

[0006]

The above-mentioned problems are solved by forming an interference layer 12 on a transparent substrate 11 in which a plurality of thin films having different refractive indexes as shown in FIG. The surface of the interference layer 12 is spherical, and the interference layer 12 is provided in each color region in the normal direction of the spherical surface.
This is solved by a color filter characterized by having a uniform film thickness, and by a liquid crystal display device using the color filter according to the present invention.

[0007]

[Operation] According to the present invention, as illustrated in FIG. 1, an interference layer 12 having a plurality of thin films having different refractive indexes laminated is formed on a transparent substrate 11, and the interference layer 12 for each color region is formed. Since the surface is spherical and the film thickness of the interference layer 12 is uniform everywhere in the normal direction of the spherical surface for each color region, even if the viewing angle or the direction of incident light changes, the spherical surface Regarding the light incident in the line direction, the film thickness of the interference layer 2 through which the light optically passes does not change, and the optical distance thereof does not change.

As a result, in the normal direction of the spherical interference layer 12, no color change occurs due to the change in the viewing angle direction, so that only the viewing angle of the surface portion of the spherical interference layer 12 can be secured, A significant improvement in the viewing angle can be expected compared with the interferometric filter of. Therefore, it is possible to obtain a color filter with improved viewing angle characteristics while maintaining good color purity and high brightness.

Incidentally, in the present invention, since the lens layers 13 and 14 for making light incident in the normal direction of the spherical interference layer 12 are formed on the back surface of the interference layer 12, the interference layer 12 is formed.
No matter what direction the back surface of the light enters, the lens layer 1
Since all the light is made incident on the interference layer 12 by the directions 3 and 14, the occurrence of the color change due to the change in the viewing angle direction can be suppressed more reliably.

[0010]

EXAMPLES Color filters according to examples of the present invention will be described below. (1) First Example First, a structure of a color filter according to a first example of the present invention will be described.

The color filter according to this embodiment is shown in FIG.
As shown in (a), a transparent substrate 11 made of glass or the like.
On top of this, thin films of TiO ₂ film and SiO ₂ film are alternately laminated,
Between the two interference layers whose surfaces are spherical in each of the regions corresponding to the three colors of R (red), G (green), and B (blue), the required half of the wavelength of the transmitted light is It has a structure in which a spacer layer having a film thickness that is a multiple is sandwiched, and has a refractive index higher than those of the first lens layer 13 made of resin and the transparent substrate 11 made of glass, which have almost the same refractive index as the glass substrate. This is an interferometric color filter used for color display of a liquid crystal display device, in which a convex lens-shaped second lens layer 14 made of high resin is formed.

According to the above color filter, FIG.
As shown in (a), the surface of the interference layer 12 for each color region is spherical, and the film thickness of the interference layer 12 in the normal direction of the spherical surface is uniform everywhere. For this reason,
Regarding the normal line direction of the spherical interference layer 12, the film thickness of the interference layer 12 through which light optically passes is the same everywhere on the spherical surface and does not change, so that no color change due to a change in the viewing angle direction occurs.

As a result, it is possible to secure a viewing angle of only the angle of the surface portion of the spherical interference layer 12, and it is possible to expect a significant improvement in the viewing angle as compared with the conventional interference method filter. In addition,
In the present invention, since the first and second lens layers 13 and 14 for making light incident in the normal direction of the spherical interference layer 12 are formed on the back surface of the interference layer 12, the back surface of the interference layer 12 is formed. No matter which direction the light enters, the first and second lens layers 13 and 14 cause all the light to enter the interference layer 12 from the normal direction of the interference layer 12, so that the color due to the change in the viewing angle direction It is possible to more surely prevent the occurrence of change.

A method of manufacturing the above-mentioned color filter will be described below with reference to FIGS. First, as shown in FIG. 2A, a light shielding film 15 made of chromium or the like and having a film thickness of 1500 Å is selectively formed at intervals of 110 μm on a transparent substrate 11 made of glass, and as shown in FIG. Dry etching is performed with a gas containing CH ₄ as a main component using the light shielding film 15 as a mask to form a spherical recess 16 having a depth of about 20 μm between the light shielding films 15. In this step, the recess 16 is formed so as to correspond to the pixel region of the liquid crystal display device in which the color filter will be incorporated later.

Next, as shown in FIG. 3 (a), while masking with a resist or the like selectively in the recess 16 so as to form an interference film through which the three colors of R, G, and B are transmitted, respectively. , An interference layer 1 having a spherical surface by alternately sputtering a TiO ₂ film and a SiO ₂ film in the recess 16 with a spacer layer having an optical film thickness half the wavelength to be transmitted sandwiched therebetween.
2 is formed on the concave portion 16. As a result, the thickness of the interference layer 12 is as shown below.

[0016] That is, the region corresponding to R is, the first interference layer TiO ₂ film 534A, a SiO ₂ film is 933A, second interference layer TiO ₂ film 372A, the thickness of the SiO ₂ film is 650Å And the spacer layer between them has a film thickness of 2384Å. In the region corresponding to G, the TiO ₂ film is 6 in the first interference layer.
07Å, 1061Å for the SiO ₂ film, 372Å for the TiO ₂ film and 650Å for the SiO ₂ film in the second interference layer, and the spacer layer between them has a film thickness of 2096Å.

The spacer layer has a refractive index n =
The resin (1.3) is formed by pressing a replica (mold) so as to have the same film thickness in each color region. Furthermore, in the region corresponding to B, the TiO ₂ film is 607Å in the first interference layer,
The SiO ₂ film is 1061Å, and the TiO ₂ film is 534 in the _second interference layer.
The Å, SiO ₂ film has a film thickness of 933Å, and the spacer layer between them has a film thickness of 1461Å.

The formation of the interference layer 12 is described in JP-A-63 / 1988.
-148201, a method of simultaneously forming thin films having different film thicknesses in one step may be used, and the curved surface of the recess 16 does not depend on the anisotropy of sputtering. A metal oxide thin film having a uniform film thickness may be formed on the curved surface by a method as shown in No. 60859. Then, FIG.
As shown in (b), a resin having a refractive index substantially the same as that of the glass substrate (n = about 1.3) is applied by a spinner and cured to form the first lens layer 13.

Thereafter, as shown in FIG. 4A, the refractive index is higher than that of the resin forming the first lens layer 13 (n =
1.5 or more) Resin 14A is applied by a spinner / roll coater or screen printing method, and then a not-illustrated replica (mold) in the shape of a lens is pressed to form convex portions on the surface of resin 14A. Then, the second lens layer 14 for collecting light is formed as shown in FIG.

Further, a top coat 17 made of a resin having a refractive index lower than that of the second lens layer 14 (n = 1.0 to 1.3) is applied and cured. Although the color filter is formed up to the above steps, when incorporating the color filter into the liquid crystal display device, it is preferable to further form the transparent substrate on which the counter electrode of the liquid crystal display device is formed in the following steps.

That is, thereafter, as shown in FIG. 5B, an ITO film is sputtered on the top coat 17 to form a counter electrode 18. The transparent substrate as shown in FIG. 5B, on which the counter electrode 18 is formed in this manner, is made to face a transparent substrate (not shown) on which active elements such as TFT active matrix are formed, and liquid crystal is sealed in the transparent substrate. A liquid crystal display device according to an embodiment of the invention is formed.

At this time, if a liquid crystal display device is constructed so that parallel light is incident on the above-mentioned color filter by using a directional backlight (not shown) or the like, color change due to a change in the viewing angle direction is further generated. It is possible to surely suppress it. (2) Second Example A color filter according to a second example of the present invention will be described below. Note that the description of the items common to the first embodiment will be omitted because they overlap.

The color filter according to this embodiment is shown in FIG.
As shown in (a), a transparent substrate 11 made of glass or the like.
The same interference layer 12 as that of the first embodiment is formed on the upper surface, and the top coat layer 20 made of resin having substantially the same refractive index as that of the transparent substrate 11 made of glass is formed on the interference layer 12. It is an interferometric color filter used for color display.

In the color filter according to this embodiment, the first
Unlike the color filter described in the embodiment of the first embodiment, the first and second lens layers 13 and 14 for collecting the incident light and making the light incident on the interference layer 12 from the normal direction of the interference layer 12 are not formed. In addition, the top coat layer 20 is formed directly on the interference layer 12. Therefore, as in the first embodiment, it is possible to improve the viewing angle characteristics of the color filter, and, like the color filter described in the first embodiment,
When the light incident on the color filter is incident on the interference layer 12, not all the light is incident from the normal direction of the interference layer 12, so there is room for some color change depending on the viewing angle, etc. Compared with other interferometric color filters, a sufficient viewing angle can be secured.

Further, unlike the first embodiment, since the first and second lens layers 13 and 14 are not formed, the steps related to the formation can be omitted and the manufacturing becomes easy. The method for manufacturing the color filter according to this embodiment will be described below. Note that the steps up to the step of forming the interference layer 12 as shown in FIG. 3A are the same as those in the first embodiment, so description thereof will be omitted.

Thereafter, a top coat 17 made of a resin having a refractive index similar to that of the transparent substrate 11 is applied and cured to form a color filter according to this embodiment as shown in FIG. 6 (a). . When incorporating the color filter into the liquid crystal display device, it is preferable to further form the transparent substrate on which the counter electrode of the liquid crystal display device is formed in the following steps.

That is, an ITO film is sputtered on the top coat layer 20 as shown in FIG. 6A to form a counter electrode (not shown), and this transparent substrate is formed with active elements such as a TFT active matrix. By enclosing the liquid crystal so as to face the transparent substrate (not shown), it is possible to form the liquid crystal display device according to the present embodiment in which the viewing angle characteristics are improved as in the first embodiment.

At this time, since it is not necessary to use the directional backlight as in the first embodiment, this embodiment is also effective in this respect.

[0029]

As described above, according to the present invention, an interference layer in which two kinds of thin films having different refractive indexes are alternately laminated is formed on a transparent substrate, and the surface of the interference layer for each color region is formed. Is spherical and the film thickness of the interference layer is uniform everywhere in the normal direction of the spherical surface, so even if the viewing angle or the direction of incident light is changed, the color change does not occur due to the change in the viewing angle direction. The viewing angle can be secured only for the angle of the surface portion of the interference layer, and a significant improvement in the viewing angle can be expected as compared with the conventional interferometry filter.

Therefore, it is possible to obtain a color filter with improved viewing angle characteristics while maintaining good color purity and high brightness, which greatly contributes to improvement in display quality of a color liquid crystal display.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating a color filter according to a first embodiment of the present invention.

FIG. 2 is a sectional view (No. 1) for explaining the manufacturing method of the color filter according to the first embodiment of the present invention.

FIG. 3 is a sectional view (No. 2) for explaining the manufacturing method of the color filter according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view (3) explaining the method of manufacturing the color filter according to the first embodiment of the invention.

FIG. 5 is a cross-sectional view (4) explaining the method of manufacturing the color filter according to the first embodiment of the invention.

FIG. 6 is a sectional view illustrating a color filter according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a color filter according to a conventional example.

[Explanation of symbols]

 11 Transparent Substrate 12 Interference Layer 13 First Lens Layer 14 Second Lens Layer 15 Light-Shielding Film 16 Recesses 17 Top Coat 18 Counter Electrode 20 Top Coat Layer

Claims (5)

[Claims] 1. An interference layer (12) in which a plurality of thin films having different refractive indexes are laminated is formed on a transparent substrate (11), and the surface of the interference layer (12) for each color region is spherical. A color filter characterized by being present. 2. The surface of the interference layer (12) is spherical, and the thickness of the interference layer (12) is uniform in each color region in the normal direction of the spherical surface. The color filter according to claim 1. 3. The back surface of the interference layer (12) is characterized in that a lens layer (13, 14) that allows light to enter in a direction normal to the spherical interference layer (12) is formed. Item 1
Color filter as described. 4. The color filter according to claim 1, wherein the interference layer (12) is formed by alternately laminating thin films of TiO ₂ and SiO ₂ . 5. A liquid crystal display device, comprising the color filter according to claim 1, claim 2, claim 3 or claim 4.