JPH10111505A - Reflection type color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type color liquid crystal display device whose display brightness is enhanced. SOLUTION: This reflection type color liquid crystal display device 1 is provided with a an insulative transparent substrate 2 having translucency, a counter substrate 3 arranged by being opposed to the transparent substrate 2, liquid crystal 4 filled in between the transparent substrate 2 and the counter substrate 3, a reflecting film 9 provided at the counter 3 substrate side nearer than the liquid crystal 4 and a color filter 12 provided at the transparent substrate 2 side nearer than the reflecting film 9. The color filter 12 transmits lights of a necessary wavelength region and also absorps lights of the wavelength region other than the region and is made of material emitting lights of the necessary region by being excited while receiving lights of the wavelength region other than the necessary wavelength region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device, and more particularly, to a reflection type color liquid crystal display device having improved display brightness by high light reflection.

[0002]

2. Description of the Related Art In general, in a reflection type liquid crystal display device, a color display is provided by providing a color filter on one of a transparent substrate on a light incident / exit side or a counter substrate on a light reflection side. I'm trying to do it. A color filter transmits light in a specific wavelength range, that is, a required wavelength range, and absorbs light in other wavelength ranges.For example, a color filter for red filters light in a red wavelength range. It transmits light and absorbs light in other wavelength regions.

In general, when performing full-color display,
Three types of color filters, red, green, and blue, are used. These are arranged in a plane in a mosaic, triangle, stripe, etc., pixels are formed for each color, and light transmitted through each pixel is synthesized. I am trying to do it. That is, the light transmitted through the color filter constituting each pixel is reflected by the reflective film provided behind the pixel, is transmitted again through the color filter, and is extracted to the incident side as emission light. An image having a desired color tone is displayed by combining light with the pixels.

[0004]

By the way, in such a reflection type liquid crystal display device of a color display, all the color filters of each color absorb light in a wavelength region other than the color, so that it is natural for incident light. There is a disadvantage that the intensity of the emitted light is reduced. That is, when white light is used as the incident light, light in the wavelength region of green light or blue light as shown in FIG. 4A for the red color filter, and FIG. 4B for the green color filter. As shown in FIG. 4C, light in the wavelength region of blue light or red light is absorbed by the color filter for blue, and light in the wavelength region of red light or green light is absorbed by the color filter for blue as shown in FIG. As shown in FIG. 5, the outgoing light reflected and taken out by the light is at most about 1/3 or less of the incident light.

[0005] In addition to the theoretically maximum output light of about 1/3 of the incident light, the liquid crystal display device further outputs the incident light based on the liquid crystal layer transmittance and the pixel aperture ratio. Since the ratio of the emitted light is reduced, the display itself does not have sufficient brightness with respect to the incident light and becomes very dark. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reflective color liquid crystal display device having improved display brightness.

[0006]

According to the reflection type color liquid crystal display device of the present invention, there is provided an insulating transparent substrate having a light transmitting property;
An insulating opposing substrate disposed opposite to the transparent substrate,
A liquid crystal filled between the transparent substrate and the counter substrate,
A reflection film provided on the opposite substrate side from the liquid crystal, and a color filter provided on the transparent substrate side from the reflection film, the color filter transmits light in a required wavelength region, And while absorbing the light in the other wavelength range, the material is excited by receiving light in the wavelength range other than the required wavelength range, and is made of a material that emits light in the required wavelength range. This was the solution to the problem.

According to this reflection type color liquid crystal display device,
The color filter transmits light in the required wavelength range,
And because it absorbs light in the other wavelength range and is excited by receiving light in the wavelength range other than the required wavelength range, it is made of a material that emits light in the required wavelength range. The light that exits the color filter, reaches the reflective film, and is reflected and extracted as emitted light is combined with the transmitted light in the required wavelength region and the excitation light in the required wavelength region. Minutes,
The light intensity increases. In addition, color filters
If the light in the required wavelength region is composed of a plurality of types of filters in which the light is in a different wavelength region, that is, if the required color is composed of a plurality of types of filters having different colors, a combination of these colors can provide an arbitrary color tone. Color display can be performed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a reflective type color liquid crystal display device of the present invention will be described in detail. FIG. 1 is a diagram showing an embodiment of the reflective color liquid crystal display device according to the present invention.
Reference numeral 1 denotes a reflective color liquid crystal display device (hereinafter abbreviated as a liquid crystal display device). This liquid crystal display device 1
Has a transparent substrate 2 having a light-transmitting property, and an opposing substrate 3 disposed opposite to the transparent substrate 2, and a liquid crystal 4 is filled between the transparent substrate 2 and the opposing substrate 3. It is.
The transparent substrate 2 and the opposing substrate 3 are insulative made of glass, quartz, resin, or the like. The transparent substrate 2 is disposed on the light incident / exit side, and the opposing substrate 3 is disposed on the light reflecting side. Has become. The liquid crystal 4 is, for example, a nematic type, and a dichroic dye 5 is contained in a layer composed of the liquid crystal 4. The dichroic dye 5 is a so-called p-type dye having a transition dipole moment almost parallel to the long axis of the molecule.

On the inner surface of the transparent substrate 2, that is, on the liquid crystal 4 side, a transparent electrode 6 made of ITO (indium tin oxide) or the like is provided in a pixel portion thereof, and a TFT (thin film transistor) 7 serving as a switching element is provided in a driving portion. An alignment film 8 is provided on the transparent electrode 6 and the TFT 7.
Is provided. The opposing substrate 3 is provided with a reflective film 9, a λ / 4 plate 10, and a transparent electrode 11 in this order on the surface on the liquid crystal 4 side. In the pixel portion, a color is provided on the inner surface side (the liquid crystal 4 side) of the transparent electrode 11. A filter 12 is provided.
A color filter 12 is provided on the inner side of the transparent electrode 11.
The alignment film 13 is provided so as to cover the surface.

The color filter 12 corresponds to a wavelength region of each of the three primary colors of light, red, green and blue. For example, a fluorescent substance such as a fluorescent dye or a fluorescent pigment is added to gelatin, a resin, a photoresist solution or the like. It is an addition. Here, a red light filter (not shown) of the color filters 12 is used.
Transmits light in the red wavelength region and absorbs light in the other wavelength regions, and emits light in the wavelength region other than the red light wavelength region (including the invisible light region) by the action of a fluorescent substance. It is excited by receiving the light and emits red light. As the red light filter, for example, rhodamine B, thioflavin T, eosin, or the like is added as a fluorescent dye to gelatin, polyvinyl alcohol, or an acrylic resin, or Zn is used as a fluorescent pigment.
What added CdS / Cu etc. is used.

Similarly, the green light filter transmits light in the green wavelength region and absorbs light in the other wavelength regions, and operates in a wavelength region other than the green light wavelength region by the action of the fluorescent substance. (Including the invisible light region), it is excited by receiving light and emits green light. As the green light filter, for example, uranine or the like is added as a fluorescent dye to gelatin, polyvinyl alcohol, or an acrylic resin, or ZnS /
What added Cu etc. is used. Further, the blue light filter transmits light in the blue wavelength region and absorbs light in the other wavelength regions, and operates in a wavelength region other than the blue light wavelength region (in the invisible light region) due to the action of a fluorescent substance. ) And emit blue light. As a filter for blue light, gelatin, polyvinyl alcohol or acrylic resin,
A fluorescent dye to which diaminostilbene or the like is added, or a fluorescent pigment to which CaS / Bi, CaSrS / Bi, or the like is added is used.

The reflection film 9 provided on the counter substrate 3 is made of aluminum or the like.
It is made of a polymer film such as polystyrene, polypropylene, and polycarbonate. The transparent electrode 11 is made of ITO or the like, like the transparent electrode 6 on the transparent substrate 2 side. The alignment films 8 and 13 are formed of a polyimide resin, and the surfaces thereof are rubbed.

Next, the operation of the liquid crystal display device 1 having such a configuration will be described. In the pixel where no voltage is applied, the molecules of the liquid crystal 4 are aligned along the alignment process of the alignment films 8 and 13.
That is, the dichroic dye 5 is oriented in a direction parallel to the transparent substrate 2 and the counter substrate 3, and the dichroic dye 5 is similarly oriented. Then, when white light enters the pixel from the transparent electrode 3 in this state,
The incident light enters the layer made of the liquid crystal 4, and of the incident light, light having a vibration plane in a direction parallel to the major axis direction of the molecules of the dichroic dye 5 is absorbed by the dichroic dye 5. Also,
Light having a vibrating surface in a direction perpendicular to the major axis direction of the molecules of the dichroic dye 5 passes through the layer made of the liquid crystal 4, and
Is incident on the color filter 12 formed in the color filter. Then
This incident light is applied to the color filter 1 as described later.
According to the two types, transmission and optical excitation are performed for each wavelength region, and the light is emitted to the counter substrate 3 side.

The emitted light is applied to the λ
The light is converted into circularly polarized light by the ４ plate 10 and further reflected by the reflection film 9. When the reflection occurs in this manner, the reflected light passes through the λ / 4 plate 10 again with its polarized light in the opposite direction, and forms a vibrating surface in a direction parallel to the major axis direction of the molecules of the dichroic dye 5. Light. Then, this light is absorbed by the dichroic dye 5 and, therefore, no light is emitted from this pixel, so that the pixel has a black display.

In a pixel in a voltage-applied state, the molecules of the liquid crystal 4 are oriented along the direction of the electric field, that is, in the direction perpendicular to the transparent substrate 2 and the opposing substrate 3, and the dichroic dye 5
Are similarly oriented. Then, when white light enters the pixel from the transparent electrode 3 in this state, the incident light passes through the layer made of the liquid crystal 4 without being absorbed by the dichroic dye 5, and the color formed on the counter substrate 2 is formed. The light enters the filter 12. Then, for example, when the color filter 12 is the above-described red light filter, the incident light transmits and emits light in the red wavelength region, and absorbs light in the other wavelength regions. However, the absorbed light, that is, light outside the red wavelength region, excites the fluorescent substance in the color filter 12, thereby emitting light in the red wavelength region. Therefore, the white light incident on the color filter 12 originally had a substantially uniform distribution for each wavelength in the visible light region, but the light in the required wavelength region, in this case, the red wavelength region The strength is greatly increased.

As a result of passing through the color filter 12, the transmitted light and the excitation light are combined, resulting in a specific wavelength region (required wavelength region).
The light having the increased intensity reaches the reflection film 9 without being polarized by the λ / 4 plate 10 and is reflected there. When reflection occurs in this way, the reflected light passes through the λ / 4 plate 10 again without being polarized, and enters the color filter 12. Then, since the reflected light passes through the color filter 12 first and becomes a light whose distribution is biased in a red wavelength region as shown in FIG. 2, for example, most of the reflected light is transmitted through the color filter 12. The light is incident on the layer composed of the liquid crystal 4.

Light incident on the layer composed of the liquid crystal 4 is absorbed by the layer because the liquid crystal 4 and the dichroic dye 5 are oriented in a direction perpendicular to the transparent substrate 2 and the counter substrate 3. The light is emitted to the transparent substrate 2 side without being emitted, is extracted as light of a color (red light in this example) according to the type of the color filter 12, and is combined with the emitted light of another pixel to obtain a desired light. The color tone is displayed.

As described above, the light that has passed through the color filter 12 and is further reflected and extracted has an increased light intensity in a required wavelength region due to light excitation by the fluorescent substance. As shown in FIG. 3, the light (white light) obtained by synthesizing the outgoing lights of the three colors has substantially the same intensity as the incident light (white light) which originally had a substantially uniform distribution for each wavelength in the visible light region. It will be. Therefore, in the liquid crystal display device 1, by using the color filter 12 to which the fluorescent substance is added, the ratio of the light emitted from the color filter 12 to the incident light can be greatly increased. The display brightness can be improved by high light reflection.

In the above embodiment, the color filter 12 is provided on the counter substrate 3 side, but may be provided on the transparent substrate 2 side. Also, color filter 1
The two types are not limited to the three colors of red, green, and blue, and any color that enables color display and the number thereof can be used.

[0020]

As described above, in the reflection type color liquid crystal display device of the present invention, the color filter transmits light in a required wavelength region and absorbs light in other wavelength regions. At the same time, it is made of a material that is excited by receiving light in a wavelength region other than the required wavelength region and emits light in the required wavelength region. The light reflected and extracted as the outgoing light can be combined with the transmitted light in the required wavelength region and the excitation light in the required wavelength region. , Thereby improving display brightness by high light reflection and realizing paper white display. Further, if the color filter is composed of a plurality of types of filters in which light in a required wavelength region is light in a different wavelength region, that is, if the color filter is composed of a plurality of types of filters having different required colors, a combination of these colors is used. Thus, color display of an arbitrary color tone can be performed.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a principal part showing a schematic configuration of an embodiment of a reflection type color liquid crystal display device of the present invention.

FIG. 2 is a graph showing a comparison between the intensity distribution with respect to the wavelength of reflected light that has passed through a red color filter and the intensity of incident light.

FIG. 3 is a graph showing a comparison between an intensity distribution with respect to a wavelength of reflected light emitted from a color filter and an intensity distribution with respect to a wavelength of incident light in the present invention.

FIG. 4 is a graph showing a comparison between the intensity distribution of reflected light passing through a color filter with respect to the wavelength and the intensity of incident light in a conventional reflective color liquid crystal display device;
(A) shows an example when the color filter is for red, (b) shows an example when the color filter is for green, and (c) shows an example when the color filter is for blue. ing.

FIG. 5 is a graph showing a comparison between an intensity distribution with respect to a wavelength of reflected light emitted from a color filter and an intensity distribution with respect to a wavelength of incident light in a conventional reflective color liquid crystal display device.

[Explanation of symbols]

REFERENCE SIGNS 1 reflective color liquid crystal display device 2 transparent substrate 3
Counter substrate 4 Liquid crystal 9 Reflective film 12 Color filter

Claims (2)

[Claims] 1. An insulative transparent substrate having a light-transmitting property, an insulative counter substrate disposed to face the transparent substrate, and a liquid crystal filled between the transparent substrate and the counter substrate. A reflective film provided on the opposite substrate side from the liquid crystal, and a color filter provided on the transparent substrate side from the reflective film,
In the reflection type color liquid crystal display device provided with, the color filter transmits light in a required wavelength region, and absorbs light in other wavelength regions, and the color filter in a region other than the required wavelength region. A reflective color liquid crystal display device comprising a material that is excited by receiving light in a wavelength region and emits light in a required wavelength region. 2. The reflection type color liquid crystal display device according to claim 1, wherein the color filter comprises a plurality of types of filters in which light in a required wavelength region is light in a different wavelength region.