KR19980083634A - Color liquid crystal display device - Google Patents

Abstract

The present invention discloses a transmissive and reflective color liquid crystal display device capable of realizing various colors without a color filter. The liquid crystal display device may include a first substrate on which a thickness control film, a transparent electrode film, and an alignment film are sequentially formed; A second substrate disposed to face the first substrate and having a transparent electrode film and an alignment film sequentially formed thereon; And a liquid crystal layer interposed between the first substrate and the second substrate, wherein one surface of the liquid crystal layer comprises a plurality of first, second, and third regions each having a different transparent electrode layer. Each of the first, second and third regions is composed of auxiliary regions each having two or more film steps, and the auxiliary regions have a predetermined thickness that transmits a maximum wavelength selected from red, green, and blue wavelengths. It is characterized by consisting of each. Since the liquid crystal display device according to the present invention does not use the color filter, the manufacturing cost is low, the alignment defect of the liquid crystal due to the step of the color filter is reduced, and the light efficiency is also increased, thereby improving its performance. The number of colors that can be implemented per LAT of the liquid crystal display also increases.

Description

Color liquid crystal display device

The present invention relates to a color liquid crystal display device, and to a color liquid crystal display device capable of realizing various colors without a color filter.

Currently used image display devices include a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display device (PDP), and the like.

Among the image display devices, the cathode ray tube has better image quality than other devices. However, it has the disadvantage of being too bulky and heavy for large screens.

On the other hand, the liquid crystal display device is widely used in various fields because it has the advantage that the volume and weight is very small compared to the cathode ray tube. In particular, liquid crystals are easy to handle and have inherent characteristics in which crystallinity changes depending on whether or not an external electric field is used. Therefore, liquid crystal display devices have been widely used from small sizes such as display units of electronic calculators to large sizes of notebook computers.

In a conventional color liquid crystal display element, three color filter layers of red (R), green (G), and blue (B) are formed on a substrate. The principle of color implementation in such a liquid crystal display device is based on a combination of the three color filter and the switching function of the liquid crystal. That is, the transmittance of light is determined based on the characteristics of the liquid crystal whose initial arrangement is changed by the application of an electric field, and the transmitted light passes through the red, blue, and green color filters, and only red, blue, and green are transmitted. Color is implemented by adding color.

FIG. 1 is a schematic cross-sectional view showing the structure of a color liquid crystal display device with a color filter. Referring to FIG. 1, a method of manufacturing a general color liquid crystal display device is as follows.

First, a black matrix pattern (not shown) is formed on the substrate 10. Subsequently, the red color filter layer 11a is formed by apply | coating, drying, exposing, and developing a photosensitive resin composition in which the red pigment is disperse | distributed on the whole surface of the board | substrate 10. FIG. The green color filter layer 11b and the blue color filter layer 11c are formed in the same manner as the red color filter layer. Thereafter, the ITO electrode film 12a capable of driving the liquid crystal is formed in a predetermined pattern.

As described above, the alignment layers 13a and 13b are formed on the first substrate 10 provided with the color filter and the second substrate 17 on which the ITO electrode film 12b of the predetermined pattern is formed. Subsequently, the first substrate 10 and the second substrate 17 are bonded to each other with a real material 15 with a spacer 14 between the alignment film 13a and the alignment film 13b, and then the alignment film 13a and the alignment film 13b. The liquid crystal is formed by injecting the liquid crystal into the cell gap formed between the two layers to complete the liquid crystal display device.

As described above, in the conventional color liquid crystal display device, a color filter is used to express colors. However, there is a problem in that it is difficult to realize a high transmissive color liquid crystal display device because the cost of manufacturing the color filter is high and not only raises the manufacturing cost of the liquid crystal display device but also lowers the light transmittance of about 14% by installing the color filter. . In addition, reproducibility of color display is poor due to film thickness nonuniformity generated during color filter manufacture, and defects may occur during liquid crystal alignment due to the film step difference of the color filter.

In order to solve the above problems, as shown in FIG. 2, a liquid crystal display device capable of realizing a color without a color filter has been proposed.

Referring to FIG. 2, thickness control films 21a and 21b are formed on the first substrate 20 so that a liquid crystal layer having a thickness calculated by simulation can be formed in place of the red, green and blue color filters. Transparent electrode films 22a, 22b, and 22c are formed on the upper side, respectively.

Subsequently, alignment films 23a, 23b, 23c and 23d are formed on the entire surface of the first substrate 20 formed as described above and the second substrate 27 on which the transparent electrode film 22d of the predetermined pattern is formed. Each is formed. At this time, in order to manufacture a high-quality liquid crystal display device, an insulating film (not shown) may be further formed between the transparent electrode film and the alignment film.

Two substrates are bonded to each other with a spacer 24 between the alignment layer 23a and the alignment layer 23d, and a liquid crystal layer 26 is formed in a cell gap formed in the space between the two substrates.

The liquid crystal display device having the structure as described above may implement color by forming a liquid crystal layer having a specific thickness instead of the existing red, blue, and green color filters.

However, in such a liquid crystal display device, only one color having one gray level (gray lebel) can be expressed per unit dot, so there is a problem that the number of colors that can be implemented is limited to a maximum of eight colors.

The first technical problem to be achieved by the present invention is to provide a transmissive color liquid crystal display device that can implement a variety of colors without a color filter to solve the above problems.

The second technical problem to be achieved by the present invention is to provide a reflective color liquid crystal display device which can implement various colors without a color filter.

1 and 2 are views showing the structure of a liquid crystal display device according to the prior art,

3 is a view showing the structure of a color liquid crystal display device according to the present invention;

4 is a graph showing changes in transmittance of red (R), green (G), and blue (B) wavelengths according to the thickness of the liquid crystal layer.

Explanation of symbols for the main parts of the drawings

10, 20, 30 ... First substrate 11a ... Red color filter layer

11b ... green color filter layer 11c ... blue color filter layer

12a, (32b-1), (32b-2), (32b-3), 22a, 22b, 22c, 22d ... ITO (transparent) electrode layer

17, 27, 37 ... 2nd board

13a, 13b, 23a, 23b, 23c, 23d, 33a, 33b ... alignment film

14, 24 ... spacer 15, 25 ... seal

16, 26, 36 ... liquid crystal layer

21a, 21b, 38B ₁ , 38G ₁ , 38R ₁ , 38B ₂ , 38G ₂ ... thickness control film

34a, 34b insulation film

In order to achieve the first object, in the present invention, the first substrate is formed sequentially the thickness control film, the transparent electrode film and the alignment film; A second substrate disposed to face the first substrate and having a transparent electrode film and an alignment film sequentially formed thereon; And a liquid crystal layer interposed between the first substrate and the second substrate, wherein one surface of the liquid crystal layer comprises a plurality of first, second, and third regions each having a different transparent electrode layer. Each of the first, second and third regions is composed of auxiliary regions each having two or more film steps, and the auxiliary regions have a predetermined thickness that transmits a maximum wavelength selected from red, green, and blue wavelengths. There is provided a color liquid crystal display device, each of which is configured.

In the present invention, an insulating film may be further formed between the transparent electrode film and the alignment film of the first and second substrates.

The second object of the present invention is a first substrate in which the thickness control film, the reflective film and the alignment film are sequentially formed; A second substrate disposed to face the first substrate and having a transparent electrode film and an alignment film sequentially formed thereon; And a liquid crystal layer interposed between the first substrate and the second substrate, wherein one surface of the liquid crystal layer comprises a plurality of first, second and third regions each having a different reflective film. Each of the first, second, and third regions consists of auxiliary regions each having two or more film steps, and the auxiliary regions have a thickness adjusted to allow maximum transmission of a selected wavelength among red, green, and blue wavelengths. It is made by a reflective color liquid crystal display device, characterized in that each consisting of 1/2 of the thickness.

In the reflective liquid crystal display device, an insulating film may be further formed between the reflective film and the alignment film of the first substrate and between the transparent electrode film and the alignment film of the second substrate. It is more preferable to further form an insulating film because the film resistance between the reflective film and the alignment film is reduced, so that a high quality liquid crystal display device can be obtained.

The liquid crystal layer is preferably made of a ferroelectric liquid crystal. This is because when the ferroelectric liquid crystal layer is used as the liquid crystal layer constituent material, the transmittances of the red, green, and blue wavelengths change periodically according to the thickness of the liquid crystal layer. On the other hand, when a liquid crystal other than ferroelectric is used as the liquid crystal layer constituent material, the change in transmittance according to the thickness of the liquid crystal layer is not preferable.

The liquid crystal display device of the present invention can implement a color without a color filter by filtering a specific wavelength of transmitted light by adjusting the thickness of the liquid crystal layer, and by varying the magnitude of the liquid crystal driving threshold voltage according to the thickness difference of the liquid crystal layer. You can increase the number of colors you can implement.

In general, liquid crystal is an optically anisotropic material, and the phase of the incident light is changed as the light passes through the liquid crystal layer, and the light passing through the liquid crystal layer causes retardation with respect to the incident light. The ratio of the light passing through the incident light is the transmittance. The transmittance not only occurs differently depending on the wavelength of light, but also varies depending on the type of liquid crystal used and the thickness of the liquid crystal layer.

Equation 1 shows the transmittance of light passing through the ferroelectric liquid crystal layer.

[Equation 1]

Here, θ: twist angle of liquid crystal

λ: wavelength of incident light

Δn: refractive index anisotropy of the liquid crystal

d: thickness of liquid crystal layer

As can be seen from Equation 1, the light transmittance (T) varies depending on the thickness (d) of the liquid crystal layer and the wavelength (λ) of the incident light, and the transmittance is changed from blue, green, and red while changing the thickness of the liquid crystal layer. When calculated according to each wavelength of, the transmittances of the red, green, and blue wavelengths are maximized at a specific thickness, respectively, and the results of the simulation are shown in FIG. 4.

4 is a graph showing transmittances of red, green, and blue wavelengths with respect to the thickness of the ferroelectric liquid crystal layer.

Referring to this, when the thickness of the liquid crystal layer is about 3.0 μm, the transmittance of the blue wavelength is maximized, the transmittance of the green wavelength is about 3.8 μm, and the transmittance of the red wavelength is about 4.5 μm. If the thickness of the liquid crystal layer is adjusted by using the winry, color can be realized without applying a color filter.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration of the present invention.

3 is a cross-sectional view showing a transmissive color liquid crystal display device according to an exemplary embodiment of the present invention. The liquid crystal display device having such a structure includes a liquid crystal layer having a specific thickness instead of the existing color filters of red, blue, and green colors. By forming, the color can be realized.

Referring to this, the first region A, the second region B and the first region 30 having different ITO electrode films 32b-1, 32b-2 and 32b-3 on the first substrate 30 are provided. Three zones (C) are formed. Each of these areas, that is, one dot (DOT) is composed of an auxiliary area having three film steps by thickness control films having different thicknesses. That is, the first region A is composed of three auxiliary regions by the thickness control films 38B ₂ and 38R ₁ having different thicknesses, and the second region B has thickness adjustments having different thicknesses. The membranes 38B ₂ , 38R ₁ and 38G ₁ consist of three auxiliary regions. In addition, like the first region A and the second region B, the third region C is also divided into three auxiliary regions by the thickness adjusting films 38R ₁ , 38G ₁ , and 38B ₁ . have. Here, the thickness control film is made of a transparent material. Such a transparent material is not particularly limited, but benzocyclobutene (BCB, Dow Chemical Co., Ltd.) is mainly used.

When a voltage is applied to the ITO electrode film 32b-1 in the first region A, the color of the liquid crystal layer 36 is sequentially switched from the liquid crystal of the auxiliary region having a small thickness according to the voltage applied thereto. Is implemented. For example, when voltage V ₁ is applied, red (R ₁ ) is implemented, and when V ₂ is applied, a mixed color of red and blue (R ₁ + B ₂ ) is implemented, and when V ₃ is applied, red, A mixed color of blue and green (R ₁ + B ₂ + G ₂ ) is realized (V ₁ <V ₂ <V ₃ ). In the same manner, the colors of the second region B and the third region C may be embodied so that a maximum of 27 colors may be represented.

An insulating film 34b and an alignment film 33b are sequentially formed on the ITO electrode film in the first region A, the second region B, and the third region C. FIG.

The ITO electrode film 32a, the insulating film 34a, and the alignment film 33a are sequentially formed on the second substrate 37 provided to face the first substrate 30. The first substrate 30 and the second substrate 37 are joined by a seal material.

In the liquid crystal display device having the structure as described above, the liquid crystal is sequentially switched from a portion having a small thickness of the liquid crystal layer according to the magnitude of the voltage applied to one transparent electrode film to determine the transmittance of light, and thus to the transmitted light. This allows up to 27 colors to be expressed per one row Line At a Time (LAT). That is, in such a liquid crystal display device, up to 27 colors can be expressed in one LAT without using a gray scale by time division or a color display method.

The color implementation method according to the present invention can be applied to not only a transmissive liquid crystal display but also a reflective liquid crystal display. In the reflective color liquid crystal display device, a reflective film is formed instead of the ITO electrode films 32b-1, 32b-2, and 32b-3 on the first substrate, and the liquid crystal is transmitted so that the transmitted light has a phase difference of 1/2. It has the structure as shown in FIG. 3, except that the thickness of the layer is each formed to half of the thickness calculated in the simulation. Here, the reflecting film is preferably made of aluminum.

Since the liquid crystal display device according to the present invention does not use the color filter, the manufacturing cost is low, the alignment defect of the liquid crystal due to the step of the color filter is reduced, and the light efficiency is also increased, thereby improving its performance. The number of colors that can be implemented per LAT of the liquid crystal display also increases.

Claims (6)

A first substrate on which a thickness control film, a transparent electrode film, and an alignment film are sequentially formed; A second substrate disposed to face the first substrate and having a transparent electrode film and an alignment film sequentially formed thereon; And a liquid crystal layer interposed between the first substrate and the second substrate. One surface of the liquid crystal layer is composed of a plurality of first, second and third regions each having a different transparent electrode layer, The first, second and third regions each consist of auxiliary regions having two or more film steps, And the auxiliary regions each have a predetermined thickness that transmits at most one selected from among red, green, and blue wavelengths. The color liquid crystal display device according to claim 1, wherein an insulating film is further formed between the transparent electrode film and the alignment film of the first and second substrates. The color liquid crystal display device according to claim 1 or 2, wherein the liquid crystal layer is made of a ferroelectric liquid crystal. A first substrate on which a thickness control film, a reflection film, and an alignment film are sequentially formed; A second substrate disposed to face the first substrate and having a transparent electrode film and an alignment film sequentially formed thereon; And a liquid crystal layer interposed between the first substrate and the second substrate. One surface of the liquid crystal layer has a plurality of first, second and third regions each having a different reflective film, The first, second and third regions each consist of auxiliary regions having two or more film steps, And the auxiliary regions each have a thickness of 1/2 of a thickness adjusted to transmit a selected wavelength among red, green, and blue wavelengths to the maximum. The reflective color liquid crystal display device according to claim 4, wherein an insulating film is further formed between the reflective film and the alignment film of the first substrate and between the transparent electrode and the alignment film of the second substrate. The reflective color liquid crystal display device according to claim 4 or 5, wherein the liquid crystal layer is made of a ferroelectric liquid crystal.