JP4324267B2 - Color filter for reflective LCD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color filter for a reflection type liquid crystal display(LCD) which produces scattered light components and magnifies a viewing angle utilizing a cholesteric liquid crystal or a chiral nematic liquid crystal. SOLUTION: A cell 18 in a color filter 10 for a reflection type LCD comprises two substrates 12, 14 and a cholesteric liquid crystal layer 16 between the both substrates. The inner side face of the substrate 12 on the incident side of external light is left as an untreated face and the inner side face of the other substrate 14 is made to be a homogeneous alignment treated face. Scattered light components are produced in reflected light of the external light owing to disturbance of helical axes of the cholesteric liquid crystal on the side of the untreated face 12A.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color filter for a reflective liquid crystal display (LCD).
[0002]
[Prior art]
For example, as disclosed in Japanese Patent Laid-Open No. 10-282324, a color filter using a cholesteric liquid crystal or a chiral nematic liquid crystal has been proposed as a color filter for a reflective liquid crystal display.
[0003]
This color filter has superior performance in luminance and color purity compared to conventional color filters using pigments and dyes. In particular, there is an advantage that the wavelength of the selectively reflected light changes depending on the temperature, and furthermore, the use of an ultraviolet curable cholesteric liquid crystal capable of maintaining the liquid crystal state by irradiation with ultraviolet rays can be easily manufactured as compared with the conventional case.
[0004]
The cholesteric liquid crystal and chiral nematic liquid crystal as described above have a characteristic that the director spirally changes in space in addition to the long-range alignment order of the liquid crystal molecular axes. That is, in the plane parallel to the liquid crystal molecular axis, the liquid crystal has the same alignment order as the nematic phase, but when moving to the adjacent plane, this local alignment direction is slightly rotated, and this is successively continuous. And has a spiral structure.
[0005]
On the other hand, natural light can be divided into right-handed circularly polarized light and left-handed circularly polarized light, and the cholesteric liquid crystal or chiral nematic liquid crystal has the above-mentioned right-handed and left-handed light components incident in parallel to the spiral axis of the liquid crystal. , Only the circularly polarized light component having the same rotational direction as the twist direction of the liquid crystal is reflected and the other circularly polarized light component is transmitted.
[0006]
At this time, since the phase of the reflected light does not change with respect to the incident light, the polarization direction before and after the incident of the reflected light is not changed, and the wavelength of the reflected light is equal to the twist pitch of the cholesteric liquid crystal or the chiral nematic liquid crystal. Proportional relationship. This pitch varies depending on the addition amount of a chiral agent that generates a twisting force in the liquid crystal and an appropriate external field (for example, temperature, electric field, magnetic field, etc.).
[0007]
This pitch can be adjusted by adding a chiral agent having a different turning ability or a chiral agent having an opposite volume. For example, if a left-handed chiral agent is added to a right-handed spirally structured liquid crystal, the reflection wavelength will be different even if the liquid crystal is cured at the same temperature.
[0008]
Therefore, by controlling the above parameters in the visible range, reflected light of red, green, and blue can be formed, and the reflectance should be set higher than that of the conventional color filter. Can do.
[0009]
[Problems to be solved by the invention]
Here, the cholesteric liquid crystal or the chiral nematic liquid crystal as described above constitutes a cell while being sandwiched between two substrates, and the liquid crystal side surface of the substrate in each cell is planarly aligned. Therefore, the spiral axis of the liquid crystal is perpendicular to the substrate, and the reflected light has a regular reflection relationship in which the incident angle and the reflection angle are equal. Therefore, the reflective LCD having this color filter is viewed from a certain direction. When the image is recognized only at the same time, and the LCD surface reflection occurs at the same time, and even if it is slightly deviated from the viewing direction, the surface reflection disappears, but the image cannot be seen, that is, the viewing angle is very small. was there.
[0010]
The present invention has been made in view of the above-described conventional problems, and uses a cholesteric liquid crystal or a chiral nematic liquid crystal to generate a scattered light component and to expand a viewing angle. An object is to provide a color filter for LCD.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, as described in claim 1, one layer of a photocurable cholesteric liquid crystal or a photocurable chiral nematic liquid crystal is formed on a substrate, and the liquid crystal layer has a light incident side on the outside light incident side. surface is exposed in a vertical oriented, and, by the reflective color filter for liquid crystal display, characterized in that the surface of the substrate side is a parallel orientation treated surface is intended to achieve the above object.
[0012]
In the color filter for a reflective liquid crystal display, a transparent protective layer may be formed on the surface of the liquid crystal layer on the outside light incident side.
[0014]
According to the second aspect of the present invention, as in claim 3 , a cell is formed by sandwiching one of cholesteric liquid crystal or chiral nematic liquid crystal between two substrates. A color filter for a reflective liquid crystal display that achieves the above-described object, wherein the inner surface of the base material on the side is a vertical alignment treatment surface and the inner surface of the other substrate is a parallel alignment treatment surface It is.
[0015]
In this invention, the scattered light component is generated on the observation side by intentionally disturbing the orientation axis of the spiral of the cholesteric liquid crystal or the chiral nematic liquid crystal on the external light incident side, that is, the display light side, thereby improving the viewing angle. I am able to plan.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0017]
As shown in FIG. 1, a reflective LCD color filter 10 according to a first example of an embodiment of the present invention is sandwiched between two substrates 12 and 14 made of glass plates, and between them. It has a cell 18 composed of a cholesteric liquid crystal layer 16.
[0018]
FIG. 1 shows one picture element of the color filter 10 for the reflective liquid crystal LCD.
[0019]
The inner surface of the substrate 12 on the outside light incident side of the two substrates 12 and 14 is an untreated surface 12A, and the inner surface of the other substrate 14 is a parallel alignment treatment surface 14A. ing.
[0020]
Here, “untreated” in the untreated surface 12A means that the surface of the glass substrate 12 is left as it is, for example, as a smooth surface, and the alignment treatment is not performed.
[0021]
The parallel alignment surface 14A of the other base material 14 is formed into an alignment film by, for example, applying polyimide to the substrate 14 and baking it, followed by rubbing with a cloth and parallel alignment.
[0022]
Accordingly, the liquid crystal molecules of the cholesteric liquid crystal layer 16 sandwiched between the untreated surface 12A and the parallel alignment treatment surface 14A are molecules in the alignment direction on the parallel alignment treatment surface 14A side as shown in FIG. The major axis is aligned, and on the other untreated surface 12A side, the molecular major axis is irregularly oriented, and this causes the disordered orientation axis of the cholesteric liquid crystal spiral at the end on the substrate 12 side. It has become.
[0023]
Therefore, when external light is incident on such a cell 18, the reflected light from the cholesteric liquid crystal layer 16, that is, the reflected light from the external light at the position of the untreated surface 12A, has the helical alignment axis of the cholesteric liquid crystal as described above. Since it is disturbed, a scattered light component is generated and the viewing angle of the observer is improved.
[0024]
Next, a reflective LCD color filter 20 according to a second example of the embodiment of the present invention will be described with reference to FIG.
[0025]
The cell 22 in the reflective LCD color filter 20 is formed by sandwiching the cholesteric liquid crystal layer 16 between the base 24 on the outside light incident side and the other base 26, and the inner surface of the base 24. Is the vertical alignment treatment surface 24A, and the inner surface of the other base material 26 is the parallel alignment treatment surface 26A as in the first example of the embodiment.
[0026]
The vertical alignment treatment surface 24A is for aligning the liquid crystal so that the molecular long axis of the cholesteric liquid crystal is perpendicular to this surface. A vertical alignment film such as polyimide is applied and baked to obtain the vertical alignment. It is a thing.
[0027]
In this reflective LCD color filter 20, the molecular long axes of the liquid crystals in the cholesteric liquid crystal layer 16 sandwiched between the base materials 24 and 26 are aligned along the alignment direction on the parallel alignment processing surface 26A side, and the other In the vertical alignment treatment surface 24A, the molecular long axis is perpendicular to this surface.
[0028]
Therefore, the spiral alignment axis of the cholesteric liquid crystal is irregular at the end portion on the vertical alignment treatment surface 24A side, and incident external light is irregularly reflected. Accordingly, a scattered light component is generated on the observation side, and the viewing angle is improved.
[0029]
Although the base materials 12, 14, 24, and 26 in the example of the above embodiment are all glass plates, the present invention is not limited to this, and may be a light transmissive film or the like.
[0030]
Furthermore, such a color filter for a reflective liquid crystal display is disposed in a liquid crystal cell by curing the liquid crystal layer with ultraviolet rays, and then peeling off the substrate on the outside light incident side and forming a transparent protective film if necessary. can do.
[0031]
In the cholesteric liquid crystal according to the present invention, the external liquid crystal near the external light incident side surface is unoriented or vertically aligned, and the liquid crystal near the surface opposite to the external light incident side of the liquid crystal is aligned. Therefore, when the liquid crystal on the external light incident side is unaligned or vertically aligned, an external light reflected light component can be generated to improve the viewing angle.
[0032]
The liquid crystal in the reflective LCD color filters 10 and 20 is cholesteric liquid crystal, but it may be chiral nematic liquid crystal.
[0033]
【Example】
Examples of the present invention will be described in detail below.
[0034]
[Example 1]
This embodiment has the same configuration as that of the reflective LCD color filter 10 shown in FIG. 1, and its manufacturing process will be described first.
[0035]
Appropriate cleaning treatment was performed, and a polyimide was spin-coated on a glass substrate as a cleaned base material and baked at 200 ° C. for 1 hour. Next, the baked polyimide was rubbed with a cloth to obtain an alignment film having a thickness of about 600 mm.
[0036]
The cell is composed of a glass substrate provided with the alignment film, an untreated glass substrate as an external light incident side substrate, that is, a smooth surface, and a cholesteric liquid crystal layer sandwiched therebetween.
[0037]
The cholesteric liquid crystal is an ultraviolet curable type, and the cholesteric liquid crystal is heated to an isotropic phase on a hot plate and injected between the alignment-treated glass substrate and the untreated glass substrate using a capillary phenomenon. did.
[0038]
After the cell is completely filled with liquid crystal, a cholesteric liquid crystal state is developed and gradually cooled to a temperature at which the desired reflection color is obtained, and after confirming that the desired reflection spectrum is obtained, ultraviolet rays are passed through the mask. Was applied to solidify the cholesteric liquid crystal in red, green and blue patterns.
[0039]
Using the Otsuka Electronics spectrometer LCD5100, the reflection characteristics of the cell thus manufactured were fixed at an incident angle α = 25 ° C. of external light 2 with respect to the cell 1, as shown in FIG. Further, when the light reception angle (reflection angle β) of the light receiver 3 was changed to 35 °, 40 °, and 45 ° and the reflected light was measured, the respective reflection intensities of the green reflection wavelength are as shown in FIG. Became.
[0040]
[Example 2]
Appropriate cleaning treatment is performed, and an alignment film SE-1211 made by Nissan Chemical is spin-coated on a cleaned glass substrate as a base material on the incident side of external light, baked at 200 ° C. for 1 hour, and has a thickness of about 600 mm. A reflective liquid crystal display color filter was constructed in the same manner as in Example 1 except that the substrate was provided with an alignment film.
[0041]
Using the Otsuka Electronics spectrometer LCD5100, the reflection characteristic of the cell thus configured is fixed to the cell 1 at an incident angle α = 25 ° C. with respect to the cell 1, as shown in FIG. Further, when the light reception angle (reflection β) of the light receiver 3 was changed to 35 °, 40 °, and 45 ° and the reflection was measured, the reflection intensity of the green reflection wavelength was as shown in FIG.
[0042]
[Comparative example]
On the other hand, a comparative example in which two substrates constituting a cell are rubbed together and subjected to a parallel alignment process is fixed in the same manner as described above, while the incident light angle is fixed at 25 ° and the reflection angle is 35 °, The intensity of reflected green light measured by changing the angle between 45 ° and 45 ° was as shown in FIG. 4 to 6, the reflected light intensity is a numerical value when the reflected light intensity on a standard white plate (magnesium sulfate) is 100.
[0043]
From these figures, it can be seen that in the embodiment of the present invention, although the incident angle of the external light is constant, the reflected light having a constant intensity can be obtained at a plurality of angles.
[0044]
【The invention's effect】
Since the present invention is configured as described above, in a color filter using a cholesteric liquid crystal or a chiral nematic liquid crystal, a scattered light component is generated in reflected light from outside light without using a scattering plate or the like, thereby improving the viewing angle. It has an excellent effect of being able to.
[Brief description of the drawings]
FIG. 1 is an enlarged schematic sectional view showing a first example of an embodiment of a color filter for a reflective liquid crystal display according to the present invention. FIG. 2 is an enlarged schematic sectional view showing a second example of the embodiment. 3 is a schematic cross-sectional view showing a reflected light measurement structure according to an embodiment of the present invention. FIG. 4 is a diagram showing a green reflected light intensity in the first embodiment. FIG. 5 is a green reflected light in the second embodiment. Diagram showing intensity [Fig. 6] Diagram showing green reflected light intensity in comparative example [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10, 20 ... Color filter 12, 14, 24, 26 for reflection type liquid crystal displays (LCD) ... Base material 12A ... Untreated surface 14A, 26A ... Parallel alignment processing surface 16 ... Cholesteric liquid crystal layer 18, 22 ... Cell 24A ... Vertical Oriented surface

Claims (3)

Becomes the light curing of the cholesteric liquid crystal or light-curing one layer of chiral nematic liquid crystal on a substrate is formed, the surface of the external light incident side of the liquid crystal layer is exposed in a vertical Oriented, and the group A color filter for a reflective liquid crystal display, characterized in that the material side surface is a parallel-aligned surface.   2. The color filter for a reflective liquid crystal display according to claim 1, wherein a transparent protective layer is formed on the surface of the liquid crystal layer on the outside light incident side.   A cell is formed by sandwiching one of cholesteric liquid crystal or chiral nematic liquid crystal between two substrates, and the inner surface of the substrate on the outside light incident side of the two substrates is a vertical alignment treatment surface. And a color filter for a reflective liquid crystal display, characterized in that the inner surface of the other substrate is a parallel-aligned surface.

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