KR100282332B1 - Cholesteric liquid crystal color filter and method for making the same - Google Patents

Abstract

The cholesteric liquid crystal color filter according to the present invention comprises a cholesteric liquid crystal circular polarizing plate, first and second color filter layers formed on the circular polarizing plate, and a reflecting plate formed to be separated from the circular polarizing plate by a predetermined distance.

Description

Cholesteric liquid crystal color filter and its manufacturing method {CHOLESTERIC LIQUID CRYSTAL COLOR FILTER AND METHOD FOR MAKING THE SAME}

The present invention relates to a color filter, and more particularly, to a cholesteric liquid crystal color filter and a manufacturing method thereof.

A general color filter is a type in which dyes and pigments are used as a dyeing material in a photosensitive resin. When light is incident, only a specific color of light is transmitted and the remaining light is absorbed. Although the color filter has been applied to various fields, a large portion of incident light is absorbed to lower light transmittance, and the absorbed light is converted into thermal energy to increase the temperature of the color filter and to change chromaticity characteristics. In order to solve the above problems, recently, studies on cholesteric liquid crystal color filters in which the above problems due to light absorption have been actively conducted.

1A-1B illustrate the principle of operation of a cholesteric liquid crystal color filter, which has a right (+) linear spiral structure and has a p (pitch) = λ / n (n: average value of abnormal light refractive index and normal light refractive index). When unpolarized light is incident on a cholesteric liquid crystal film made of a mixture of a cholesteric liquid crystal and a photopolymer, the wavelength is λ, and the right polarized light λ (+) is reflected, and the rest and is transmitted. As shown in Fig. 1B, about 50% of the light transmitted in the? Region is left circularly polarized by preserving linear polarization. Such a cholesteric liquid crystal film is formed in several layers to implement a color filter for selectively transmitting a desired color.

2 is a view showing a conventional cholesteric liquid crystal color filter, hereinafter, red, blue, and green are represented by R, B, and G, respectively, and the right polarized light is R (+), B (+ ) And B (+), and left circularly polarized light as R (-), B (-) and G (-). In addition, the color filter layer that selectively reflects light A is designated as A layer. As shown in the figure, when light is incident on the R region of the substrate 1 of the color filter, first, B (-) and G (-) are reflected by B (-) (3), and B (+) and G (+) Is transmitted through the B (-) layer (2) and the G (-) layer (3), but is changed to B (-) and G (-), which are left circularly polarized light by the λ / 2 retardation plate (4), and B (-) Reflected by the layers 5 and G (-) layer 6, only R (+) and R (-) pass through the R region of the color filter. In addition, B (-) / B (+) and G (-) / G (+), which are reflected by the reflector 7 and then re-injected, pass through the B region and the G region, respectively.

Although the above-mentioned reflective cholesteric liquid crystal color filter has the advantage that there is no temperature rise and light efficiency of the color filter due to absorption and absorption, it is composed of several layers, which not only makes the manufacturing process complicated but also gently enters the light simultaneously. Since it is possible to pass over the area, the color characteristics may deteriorate, and as the reflection and scattering increase between the layers, the light efficiency may decrease.

It is a first object of the present invention to provide a cholesteric liquid crystal color filter and a method of manufacturing the same, which eliminates the above-mentioned problems by reducing the number of color filter layers by using a cholesteric liquid crystal circular polarizer.

A second object of the present invention is to provide a liquid crystal display device having excellent light effect by employing the above-described color filter.

The cholesteric liquid crystal color filter according to the present invention for achieving the first object is divided into a first region, a second region, and a third region, each region having a second color (first region), a third color (first A second color) and a first color filter layer reflecting only a second color (third area), and formed on the first color filter layer and divided into the first area, the second area, and the third area. A second color filter layer reflecting only a first region, a third color (second region) and a first color (third region), a cholesteric liquid crystal circular polarizer formed on the second color filter layer, and the cholesteric It is made of a reflecting plate formed in isolation from the liquid crystal circular polarizing plate.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes a first substrate having a polarizing plate, a second substrate having a color filter and a phase difference plate, the first substrate, and the second substrate. It consists of a liquid crystal layer formed in between.

The cholesteric liquid crystal color filter and the liquid crystal display device have the advantage that the number of color filter layers is reduced and the manufacturing process is simple, and the color characteristics and the light efficiency are excellent as compared with the prior art.

1A and 1B are views showing the operation principle of a cholesteric liquid crystal color filter.

2 is a view showing a conventional cholesteric liquid crystal color filter.

3 is a view showing a cholesteric liquid crystal circular polarizing plate.

Figure 4a is a view showing a cholesteric liquid crystal color filter according to the present invention.

4b illustrates another embodiment of the present invention.

5a to 5f are views showing a method of manufacturing a cholesteric liquid crystal color filter according to the present invention.

6 is a view showing a liquid crystal display device according to the present invention.

-Explanation of symbols for the main parts of the drawing-

10a: first color filter layer 10b: second color filter layer

11 color filter layer 12 cholesteric liquid crystal color filter

13: reflector 14: light source

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

First, FIG. 3 is a view showing the structure of the cholesteric liquid crystal circular polarizing plate 8 used in the present invention, in which the cholesteric liquid crystal has a left (-) linear spiral structure and the pitch 9 gradually increases. Since it includes all of the pitch corresponding to the visible light region and the left (-) circular polarization component of the visible light region reflects and plays the role of transmitting the right (+) circular polarization component.

4A is a diagram illustrating a cholesteric liquid crystal color filter according to the present invention, which is divided into a region B, a region G, and an region R, and each region reflects only G (+), B (+), and G (+). The second color filter layer (10a) is divided into the B region, the G region, and the R region, and each region reflects only R (+), R (+) and B (+), and is formed on the first color filter layer 10a. 10b) and a cholesteric liquid crystal circular polarizing plate 12 formed on the second color filter layer 10b and transmitting only the right circularly polarized light component, and a reflecting plate 13 formed separately from the circular polarizing plate 12. As shown in the drawing, when the light from the light source 14 is incident on the region B, the color filter is circularly polarized by the circular polarizing plate 12 and the second color filter layer 10b and the first color filter layer 10a are shown in the drawing. ) In turn, R (+) and G (+) are reflected and eventually only B (+) passes. In the same principle as above, the R region passes only R (+) and the G region passes only G (+). In addition, the left circularly polarized light R (-), G (-) and B (-) reflected by the circular plate 12 are reflected back by the reflecting plate and R (+), G (+) and B (+) After reentry, the light passes through the R, G, and B regions, respectively. The circular polarizing plate may transmit only the left circularly polarized light, and in this case, the cholesteric liquid crystals of the first color filter layer and the second color filter layer should have a spiral structure reflecting the left circularly polarized light. In the case of applying the color filter to various color display elements, the reflector 13 may be removed if the reflector 13 is a barrier. In this case, the light transmittance may be lowered, but the number of the color filter layers may be reduced. There is an advantage. In addition, the color filter layer may be divided into three regions, but a color filter displaying a single color without dividing the region may be possible.

4B is another embodiment of the present invention, in which the color filter 16 in the drawing adds a linear polarization function by attaching a λ / 4 phase difference plate 15 for converting circularly polarized light into linearly polarized light under the first color filter layer 10a. Let's have Conventional polarizers have a light efficiency of less than 50%, but by using the polarization function, the light efficiency can be improved to nearly 100%.

FIG. 5 illustrates a method of manufacturing a cholesteric liquid crystal color filter according to the present invention. As shown in FIG. 5A, a substrate 20 having a B region, a G region, and an R region is prepared, and then, on the substrate 20. The mixture of the preferential spiral cholesteric liquid crystal and the photopolymer, which is adjusted so that the addition amount of the chiral dopant has a pitch corresponding to the G color, is applied, and the mask 22 is omitted (hereinafter, the use of the mask is omitted). ) Expose only the B and R regions, and then irradiate ultraviolet rays to form G (+) layers in the B and R regions. Thereafter, although not shown in the figure, the mixed liquid of the uncured region (the region not exposed to ultraviolet rays) is removed. Subsequently, as shown in FIG. 5B, the mixture of the cholesteric liquid crystal and the photopolymer in the preferential spiral direction adjusted to have a pitch corresponding to the BT color is coated so that the addition amount of the chiral dopant is cured after irradiating only the R region with UV. The unmixed liquid mixture is removed to form the second color filter layer 21a. Subsequently, as shown in FIG. 5C, a mixed solution of the cholesteric liquid crystal and the photopolymer in the preferential spiral direction, in which the amount of the chiral dopant is added on the first color filter layer 21a, has a pitch corresponding to the color R, is applied. After irradiating only the region and the G region with ultraviolet rays, the uncured mixed liquid is removed. Subsequently, as shown in FIG. 5D, the priority spiral direction in which the addition amount of the chiral dopant is adjusted to have a pitch corresponding to the color B is applied to the cholesteric liquid crystal and the photopolymer, and irradiated with only the R region. The mixed solution is removed to form a second color filter layer 21b on the first color filter layer 21a. Subsequently, as shown in FIG. 5E, the cholesteric liquid crystal polarizing plate 25 which transmits only the right circularly polarized light component is formed on the second color filter layer 21b, and then the reflecting plate 26 is the circularly flat plate 25 as shown in FIG. 5F. Formed by isolation from In the above production method, the pitch is controlled by adjusting the amount of chiral dopant added, but a method of controlling the pitch by controlling the temperature is also possible. In the method of manufacturing a color filter by controlling the temperature, the mixture of cholesteric liquid crystal and the photopolymer is coated on a substrate, and then the temperature of the mixture is adjusted to correspond to a desired pitch and then irradiated with ultraviolet rays to cure the desired area. Thereafter, the uncured region is cured by adjusting the temperature to have a different pitch as described above and then irradiating ultraviolet rays to a desired region.

The present invention may optionally use the method of adjusting the amount of the chiral dopant described above and the temperature adjusting method to adjust the pitch.

The color filter manufacturing method according to the present invention described above provides a cholesteric liquid crystal color filter having a reduced number of color filter 23 layers to two layers and a simplified process and excellent light efficiency and color characteristics.

6 illustrates a liquid crystal display device according to the present invention, which includes a first substrate 31 having a polarizing plate 30, a second substrate 32 having a color filter 16 in FIG. And a liquid crystal layer 33 formed between the first substrate 31 and the second substrate 32 and a light source 34 that provides light between the reflecting plate and the cholesteric liquid crystal circular polarizing plate 12. The liquid crystal display device not only has no light loss due to the polarizing plate but also has a reduced number of color filter layers, thereby providing excellent light efficiency and color characteristics.

The color filter according to the present invention has the advantages of reducing the number of color filter layers, simplifying the manufacturing process, and reducing light scattering and reflection between the layers by employing a cholesteric liquid crystal circular polarizing plate, which is excellent in light efficiency.

The liquid crystal display device according to the present invention has superior color efficiency than the conventional one by providing a color filter and a retardation plate having a reduced number of layers.

Claims (15)

Cholesteric liquid crystal circular polarizer, The first and second color filter layers formed on the cholesteric liquid crystal circular polarizer are divided into first, second and third regions, and the first, second and third regions of the first color filter layer are respectively divided into second, third and third regions. Reflecting light of the first and second wavelength regions, and the first, second and third regions of the second color filter layer reflecting only the light of the third, third and first wavelength regions, respectively. Cholesteric liquid color filter. The cholesteric liquid crystal color filter according to claim 1, wherein the circular polarizing plate is separated from the circular polarizing plate by a predetermined distance to further form a reflecting plate. The cholesteric liquid crystal color filter according to claim 1, further comprising a phase difference plate for converting circularly polarized light into linearly polarized light on the first and second color filter layers. The first substrate, A second substrate having a cholesteric liquid crystal color filter according to claim 1, And a liquid crystal layer formed between the first substrate and the second substrate. The liquid crystal display device of claim 4, wherein the first substrate further comprises a polarizing plate. The liquid crystal display device according to claim 4, wherein the second substrate further comprises a phase difference plate for converting circularly polarized light into linearly polarized light. The liquid crystal display device according to claim 4, wherein a reflection plate is further provided to isolate the second substrate from the second substrate. The liquid crystal display device of claim 7, further comprising a light source for supplying light between the reflective plate and the second substrate. Preparing a substrate having first, second and third regions, Forming a first color filter layer made of a cholesteric liquid crystal film having second, first and second pitches in the first, second and third regions, respectively; Forming a second color filter layer made of a cholesteric liquid crystal film having third, third and first pitches in the first, second and third regions, respectively; Forming a cholesteric liquid crystal circular polarizing plate on the first and second color filter layer. The method of claim 9, wherein the forming of the first and third regions of the first color filter layer comprises: Applying a mixed solution of a cholesteric liquid crystal and a photopolymer to which the chiral dopant is added in an amount corresponding to the second pitch on the substrate; Method for producing a cholesteric liquid crystal color filter, characterized in that the step consisting of irradiating ultraviolet rays to the first and third regions of the mixed solution. The method of claim 9, wherein the forming of the second region of the first color filter layer comprises: Applying a mixed solution of a cholesteric liquid crystal and a photopolymer to which the yay chiral dopant corresponding to the first pitch is added on the substrate; Method for producing a cholesteric liquid crystal color filter, characterized in that the step of irradiating ultraviolet light to the second region of the mixed solution. The method of claim 9, wherein the forming of the first and second regions of the second color filter layer comprises: Applying a mixed solution of a cholesteric liquid crystal and a photopolymer to which the chiral topant is added in an amount corresponding to the third pitch on the substrate; And the mixing ag is irradiated with ultraviolet rays to the first and second regions. The method of claim 9, wherein the forming of the third region of the second color filter layer comprises: Applying a mixed solution of a cholesteric liquid crystal and an optical polymer to which the chiral dopant is added in an amount corresponding to the first pitch on the substrate; And irradiating ultraviolet rays to the third region of the mixed solution. The method of claim 9, wherein the forming of the first color filter layer, Applying a mixed solution of a cholesteric liquid crystal and a photopolymer to which the chiral dopant is added in an amount corresponding to the second pitch on the substrate; Irradiating ultraviolet rays to the first and third regions of the mixed solution and then removing the second region of the mixed solution; Applying a mixed solution of a cholesteric liquid crystal and an optical polymer to which the chiral dopant is added in an amount corresponding to the first pitch on the substrate; Irradiating ultraviolet rays to the first and third regions of the mixed solution and then removing the second region of the fraud mixture; Applying a mixture solution of the cholesteric liquid crystal and the photopolymer to which the chiral dopant is added in an amount corresponding to the first pitch on the substrate; Method for producing a cholesteric liquid crystal color filter comprising the step of removing the first and third regions of the mixed solution after irradiating the second region of the mixed solution with ultraviolet light. The method of claim 9, wherein forming the second color filter layer comprises: Applying a mixed solution of a cholesteric liquid crystal and an optical polymer to which the chiral dopant is added in an amount corresponding to the third pitch on the substrate; Removing the third region of the mixed solution after irradiating ultraviolet rays to the first and second regions of the mixed solution; Applying a mixed solution of a cholesteric liquid crystal and an optical polymer to which the chiral dopant is added in an amount corresponding to the first pitch on the substrate; And irradiating ultraviolet rays to the third region of the mixed liquid, and then removing the first and second regions of the mixed liquid.

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