JPH11282387A - Reflection type color liquid-crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type color liquid-crystal display element which has good color purity while securing brightness. SOLUTION: A reflection type color liquid-crystal display element has a color filter 13 having a cholesteric layer 17 provided on a transparent substrate 16, the helix axis of the cholesteric layer 17 being perpendicular to the substrate surface of the transparent substrate 16; a polarizing plate 11 provided parallel to time color filter 13; a quarter wavelength plate 12 provided between the color filter 13 and the polarizing plate 11 to convert light h2 transmitted through the polarizing plate 11 into circularly polarized light to allow the light to be transmitted to the color filter 13; a reflector 15 provided parallel to the polarizing plate 11 with the color filter 13 located therebetween; and a liquid-crystal cell 14 provided between the reflector 15 and the color filter 13. Therefore, only light h4 of specific color components having the same wavelength as the helix pitch of the cholesteric layer 17 is Bragg reflected and removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective color liquid crystal display device, and more particularly to a reflective color liquid crystal display device using a complementary color filter.

[0002]

2. Description of the Related Art A reflection type liquid crystal display element is provided with a liquid crystal cell filled with a liquid crystal agent between transparent electrode forming surfaces of two transparent substrates, and a liquid crystal cell sandwiched from the transparent substrate side. It is composed of two polarizing plates and a reflector provided in parallel with the liquid crystal cell with one of the polarizing plates interposed therebetween. In particular, in a reflective type color liquid crystal display device, a color filter is provided between one transparent substrate and a transparent electrode in a liquid crystal cell. This color filter is made of a resin colored with a pigment or dye (hereinafter, referred to as a resin).
(Referred to as a colored resin) are arranged on a transparent substrate.

In the above-mentioned reflection type color liquid crystal display device, since a reflection plate is provided on one polarizing plate, a backlight is not required and power consumption can be suppressed low. In addition, in the reflective color liquid crystal display device, it has been proposed to change the color filter from a primary color system to a complementary color system in order to secure display brightness.

[0004]

However, when a color filter using the above colored resin is made to be a complementary color system, the absorption spectrum does not become an ideal complementary color. There is a problem that the color purity to be ensured decreases. Therefore, an object of the present invention is to provide a reflective color liquid crystal display device having good color purity while ensuring brightness.

[0005]

According to the present invention, there is provided a reflection type color liquid crystal display device comprising: a color filter comprising a transparent substrate provided with a cholesteric layer; and a polarization filter provided in parallel with the color filter. Plate, a quarter-wave plate provided between the color filter and the polarizing plate, a reflector provided in parallel with the polarizing plate with the color filter interposed therebetween, and between the reflector and the color filter. Is provided. The cholesteric layer is provided with a helical axis perpendicular to the substrate surface of the transparent substrate. The quarter-wave plate is provided so that light from the polarizing plate is converted into circularly polarized light and transmitted to the color filter.

In the reflection type color liquid crystal display device having the above structure, the circularly polarized light transmitted through the polarizing plate and the quarter-wave plate is incident on the cholesteric layer of the color filter. The cholesteric layer is provided so that the helical axis is perpendicular to the substrate surface of the transparent substrate, and only light of a specific wavelength that satisfies the Bragg condition of the circularly polarized light, that is, light of a specific color component is reflected. You. The reflected light passes through the quarter-wave plate again, becomes linearly polarized light perpendicular to the polarization plane of the polarizing plate, and is blocked by the polarizing plate. On the other hand, the light of the complementary color component that has passed through the color filter after the light of the specific color component has been removed passes through the liquid crystal cell, the reflector, the liquid crystal cell and the color filter again, and reaches the quarter-wave plate again. At this time, if the liquid crystal cell is set to have no birefringence, the light that has reached the quarter-wave plate again is in the same state as the light reflected by the color filter because the circularly polarized light is maintained. And is blocked by the polarizing plate. As a result, all incident light is blocked by the polarizing plate, and black display is performed. On the other hand, if the liquid crystal cell is set to be a quarter-wave plate, the light that has reached the quarter-wave plate again (that is, the light of the complementary color component) is reversed from that before entering the liquid crystal cell. It becomes circularly polarized light. Therefore, the light that has passed through the quarter-wave plate again becomes
It becomes linearly polarized light parallel to the polarization plane of the polarizing plate and transmits through the polarizing plate. As a result, only the light of the complementary color component is emitted from the polarizing plate, and color display is performed.

Further, in the reflection type color liquid crystal display device having the above-mentioned structure, the cholesteric layer has a helical pitch having a helical pitch corresponding to a predetermined wavelength in a red band and a helical pitch having a helical pitch matching a predetermined wavelength in a green band. A green reflection region and a blue-violet reflection region having a helical pitch corresponding to a predetermined wavelength in the blue-violet band, and on the transparent substrate,
It is assumed that these areas are alternately arranged.

[0008] In the reflective color liquid crystal display device having the above structure, the light of the complementary color component from which the light of the red component is removed, the light of the complementary color component from which the light of the green component is removed, and the light of the blue-violet component are removed. Color display is performed with the light of the complementary color component.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a reflection type color liquid crystal display device to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a main part configuration diagram for explaining one configuration example of the reflection type color liquid crystal display element of the present invention.

As shown in FIG. 1, this reflection type color liquid crystal display element has a quarter-wave plate 12, a color filter 13, a liquid crystal, The cell 14 and the reflection plate 15 are sequentially arranged in parallel.

The polarizing plate 11 and the quarter-wave plate 12 are
The external light h1 incident from the front surface side of the polarizing plate 11 is converted into clockwise or counterclockwise circularly polarized light and emitted from the back surface side of the quarter-wave plate 12, so that the external light h1 is 4
The wave plate 12 is arranged so that the angle formed by the main axes is 45 °. Here, the arrangement state of the polarizing plate 11 and the quarter-wave plate 12 is set so as to obtain clockwise circularly polarized light. Note that the rotation direction of the circularly polarized light is the rotation direction when viewed directly against the traveling direction of light.

The color filter 13 is provided on the transparent substrate 1.
6 on the front surface or the back surface of the cholesteric layer 17 with the helical axis perpendicular to the substrate surface of the transparent substrate 16.
Is provided. In the drawing, the transparent substrate 1
The example in which the cholesteric layer 17 was provided on the surface of No. 6 was shown. The cholesteric layer 17 has the same spiral direction as the rotation direction of the light h3 incident from the polarizing plate 11 and emitted from the quarter-wave plate 12. Also,
The cholesteric layer 17 is divided into a red reflection region, a green reflection region, and a blue-violet reflection region, and a plurality of these regions are alternately arranged on the surface of the transparent substrate 16. This arrangement state may be the same as that of a normal color liquid crystal display element, and the most suitable arrangement is selected depending on the product.

Here, it is assumed that the red reflection region is a cholesteric layer 17 region having a helical pitch corresponding to a predetermined wavelength (for example, 630 nm) in the red band. The green reflection region is a cholesteric layer 17 region having a helical pitch that matches a predetermined wavelength (for example, 510 nm) in the green band. Furthermore, the blue-violet reflection region is a cholesteric layer 17 region having a helical pitch that matches a predetermined wavelength (for example, 450 nm) in the blue-violet band.

Further, the liquid crystal cell 14 is formed by filling a liquid crystal agent between the transparent electrode forming surfaces formed on the surfaces of two transparent substrates.
The one set to be a / 4 wavelength plate is used. Here, for example, ECB (electrically controlled birefrin
(gence) effect is used. Note that one of the transparent substrates constituting the liquid crystal cell 14 may be the transparent substrate 16 constituting the above-mentioned color filter.

The reflecting plate 15 is provided on the back surface of the liquid crystal cell 14 with the surface on the liquid crystal cell 14 side as a reflecting surface.

Next, a display operation by the reflective color liquid crystal display device having the above-mentioned configuration will be described with reference to FIGS. First, black display in the present color liquid crystal display device will be described with reference to FIG. 1, and subsequently, color display in the present color liquid crystal display device will be described with reference to FIG.

As shown in FIG. 1, the external light h ₁ incident on the polarizing plate 11 from its surface side is polarized when passing through the polarizing plate 11. Then, the light h emitted from the polarizing plate 11
2 is linearly polarized light parallel to the polarization plane of the polarizing plate 11, and 1 /
The light enters the four-wavelength plate 12 from the front side. The light h2 incident on the quarter wave plate 12 causes a phase delay of 1/4 wavelength when passing through the quarter wave plate 12. For this reason,
The light h3 emitted from the quarter-wave plate 12 becomes clockwise circularly polarized light.

This light h3 is incident on the color filter 13 from the surface side. Of the light h3 incident on the red reflection area of the cholesteric layer 17 in the color filter 13, the light h4 of the red component having the same wavelength (for example, 630 nm) as the helical pitch of the red reflection area is reflected by the Bragg reflection in the red reflection area. Is done. Similarly, in the green reflection area of the cholesteric layer 17, the light h4 of the green component is Br
The light h4 of the blue-violet component is Bragg-reflected in the blue-violet reflection area of the cholesteric layer 17 after being agg-reflected.

The light h4 of each monochromatic component reflected by the cholesteric layer 17 again enters the quarter-wave plate 12 from the back side. The light h5 transmitted through the quarter-wave plate 12 and emitted from the front side thereof becomes linearly polarized light orthogonal to the polarization plane of the polarizing plate 11. Therefore, the polarizing plate 1
The light h5 incident on the back surface 1 from the back side is blocked by the polarizing plate 11 and is not emitted to the front side.

On the other hand, in the red reflection region of the cholesteric layer 17, a complementary color component from which only the red component light h4 has been removed,
That is, the light h6 of the cyan component is transmitted. Similarly, in the green reflection region, the magenta component light h6 from which only the green component light h4 is removed is transmitted, and in the blue-violet reflection region, the yellow component light h6 from which only the blue-violet component light h4 is removed is transmitted. .

Then, the light 6 transmitted through the color filter 13 passes through the liquid crystal cell 14 and passes through the reflection plate 15.
Reflected by the liquid crystal cell 14 and the color filter 13 again.
From the back side to the front side. On this occasion,
The liquid crystal cell 14 utilizes the P-type ECB effect. When the power of the liquid crystal cell 14 is turned on, the liquid crystal cell 14 has no birefringence. In such a case, the light h6 keeps the state of clockwise circularly polarized light,
The light passes through the liquid crystal cell 14, is reflected by the reflector 15, passes through the liquid crystal cell 14 again, and is emitted from the surface of the color filter 13. Therefore, the light h7 emitted from the surface side of the color filter 13 becomes clockwise circularly polarized light.

The light h7 emitted from the front side of the color filter 13 again enters the quarter-wave plate 12 from the back side. Then, the light h8 transmitted through the quarter-wave plate 12 and emitted from the front side thereof is
When the light is transmitted, a phase delay of 1/4 wavelength is further generated, so that the light becomes linearly polarized light orthogonal to the polarization plane of the polarizing plate 11.
The light h8 is incident on the polarizing plate 11 from the back side, but is not blocked by the polarizing plate 11 and is not emitted to the front side. As described above, when the power of the liquid crystal cell 14 is turned on, the reflective type color liquid crystal display element performs black display.

On the other hand, as shown in FIG. 2, when the power of the liquid crystal cell 14 is turned off, the liquid crystal cell 14 becomes equivalent to a quarter-wave plate having birefringence. For this reason,
The light h6 transmitted through the color filter 13 and emitted from the back side thereof passes through the liquid crystal cell 14, is reflected by the reflection plate 15, and passes through the liquid crystal cell 14 and the color filter 13 again. Light h emitted from
9 is a further 1/2 of the light h6, which is right-handed circularly polarized light.
It becomes a left-handed circularly polarized light having a phase delay of the wavelength.

The light h9 is incident on the quarter-wave plate 12 from the back side, and passes through the quarter-wave plate 12. And 1
The light h10 emitted from the front surface side of the 波長 wavelength plate 12 further has a phase delay of １ ／ wavelength with respect to the counterclockwise circularly polarized light (light h9), and is linearly polarized light parallel to the polarization plane of the polarizing plate 11. become. Therefore, the light h10 applied to the polarizing plate 11 from the rear surface side passes through the polarizing plate 11. Then, from the surface side of the polarizing plate 11, each light h11 composed of a cyan component, a magenta component or a yellow component from which a single color component has been removed is emitted. As described above, when the power supply of the liquid crystal cell 14 is turned on, the reflective type color liquid crystal display element performs a color display of a complementary color system.

[0025]

As described above, according to the present invention, the cholesteric layer for removing light of a specific color component has a 1 /
Providing a combination with a four-wavelength plate enables a complementary color reflective color liquid crystal display. Therefore, the absorption spectrum becomes an ideal complementary color, and it is possible to provide a reflective color liquid crystal display device having good color purity while securing brightness.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a color liquid crystal display device of the present invention and a black display thereof.

FIG. 2 is a diagram illustrating color display in the color liquid crystal display device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Polarizer, 12 ... 1/4 wavelength plate, 13 ... Color filter, 14 ... Liquid crystal cell, 15 ... Reflector, 16 ... Transparent substrate, 17 ... Cholesteric layer

Claims (3)

[Claims] 1. A color filter comprising: a cholesteric layer having a helical axis perpendicular to a substrate surface of the transparent substrate provided on a transparent substrate; a polarizing plate provided in parallel with the color filter; A quarter-wave plate that is provided between the polarizer and the polarizer, and that converts the light that has passed through the polarizer into circularly polarized light and transmits the light toward the color filter; and is provided in parallel with the polarizer with the color filter interposed therebetween. And a liquid crystal cell provided between the reflector and the color filter. 2. The reflective color liquid crystal display device according to claim 1, wherein the cholesteric layer has a red reflection region having a helical pitch corresponding to a predetermined wavelength in a red band, and a helix corresponding to a predetermined wavelength in a green band. The pitch comprises a green reflection region and a blue-violet reflection region having a helical pitch corresponding to a predetermined wavelength in the blue-violet band.On the transparent substrate, the red reflection region, the green reflection region, and the blue-violet reflection region are provided. A reflective color liquid crystal display device, which is arranged alternately. 3. The color liquid crystal display device according to claim 1, wherein the １ ／ wavelength plate is configured such that light incident on the 波長 wavelength plate from the polarizing plate side is the same as the direction of rotation of the helix of the cholesteric layer. A reflective color liquid crystal display device, which is provided between the polarizing plate and the color filter so as to be circularly polarized light rotating in a direction.