JPH0153795B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color display device.

Conventionally, color display devices that combine twisted nematic liquid crystals and color polarizing plates have been known. Since this display device uses a polarizing plate, the amount of light decreases and becomes dark, and since there is no fully functional color polarizing plate, parts other than the color display part are colored similarly, resulting in low visual contrast. There were drawbacks such as: Guest-host type liquid crystal display devices are also known, but the contrast is low because the two-color ratio of the pigment is insufficient, and the display and non-display areas become similar in color, resulting in poor visual contrast. Since the number of dyes that can be used is limited, there are drawbacks such as the inability to produce clear colors when mixed dyes are used to produce various colors.

This invention provides a clear color display device using an optically active material.

Next, examples will be described.

An optically active material layer 2 that selectively scatters light of a specific wavelength in the visible range is provided on the front surface of a display panel 1 of a color display device.
will be provided. Cholesteric polymer films are known as such optically active substances.
This is a polymer film made of liquid crystal that exhibits a cholesteric color and can be polymerized and fixed.By changing the polymerization temperature or polymer composition, a film with any selective scattering wavelength can be obtained. Other optically active substances that can be used include cholesteric liquid crystals, chiral nematic liquid crystals, and mixed liquid crystals thereof, as well as optically active substances that do not form a liquid crystal phase by themselves, and mixed liquid crystals with optically inactive substances. The illustration shows an example using a cholesteric polymer film, but if a liquid crystal is used, it will naturally be sandwiched between glass substrates. However, a method has now been developed to microcapsule liquid crystals, so if microencapsulated liquid crystals are dispersed in a transparent binder and applied to a transparent substrate, manufacturing can be facilitated and the device can be made thinner. A display layer 3 using liquid crystal is arranged behind this optically active material layer 2. This display layer 3 must be capable of controlling transparent mode and scattering mode. As a liquid crystal,
A phase-change type that is a P-type nematic liquid crystal mixed with a chiral material, an electro-thermo-optic type that is a P-type smectic liquid crystal that is mixed with a chiral material, a DSM type that is an n-type nematic liquid crystal that is mixed with an ion dopant, etc. However, in short, any device that can control the transparent mode and the scattering mode will suffice. The liquid crystal used for the display layer 3 includes transparent substrates 4 facing each other using glass substrates or the like.
A mirror reflector plate 7 is formed as a mirror electrode on both of these substrates, and is provided facing the transparent electrode 6 to form a display segment. A transparent electrode 8 provided on the lower surface of the mirror electrode is for extraction. In addition, like this, the specular reflector plate 7
It goes without saying that when the mirror electrode 6 is used as a mirror electrode, the mirror electrode may be used as a segment electrode, and the transparent electrode 6 may be used as a common electrode. Further, the front and back of the mirror reflector 7 and the transparent electrode 8, which form the mirror electrode, may be reversed. In short, the specular reflection plate 7 may have a segment shape and be positioned behind the display layer 3. Further behind this display layer 3, a light-colored scattering/reflection plate 9 is arranged. As a material for the scattering/reflection plate 9, white paper or a polyester film whose surface is subjected to glass treatment and whose back surface is vapor-deposited with aluminum is used. Of course, the material is not limited to a plate-like material, and the back surface of the glass substrate 5 may be coated with paint.

Next, the display effect will be explained.

Assume now that the cholesteric polymer film of the optically active material layer 2 selectively scatters green light and transmits other light, that is, reddish-violet light. In the part A where the display layer 3 is in the transparent mode, the middle green light of the incident light L is selectively scattered, and the red-violet light is transmitted, passes through the display layer 3, is reflected by the specular reflector 7, and comes out. In normal use when the display panel 1 is placed vertically and light mainly enters from diagonally above, the specular reflector 7
Most of the reddish-violet light reflected by the light is reflected diagonally downward, and when viewed from the front, the green light is better than the reddish-violet light, and this part A appears bright green. B in which the display layer 3 is in scattering mode
In this section, green light among the incident light is selectively scattered by the cholesteric polymer film. The transmitted reddish-violet light is scattered by the display layer 3, and part of it is transmitted therethrough, reflected by the specular reflection plate 7, and scattered again to come out. In other words, green light and reddish-violet light are both scattered here, so they appear together as a bright scattered white.

Now, in the part C where the display electrode is not provided, the display layer 3 is always in the transparent mode, and the reddish-violet light that has passed through the optically active material layer 2 is transmitted through the display layer 3.
It is reflected by the scattering reflector 9 and comes out. Therefore, this part C appears bright white like part B.
Rather, it is necessary to make part C look the same as part B, so when selecting a material for the light-colored scattering reflector plate 9, compare it with part B and choose one that is not conspicuous. That is important. Due to this display action, numbers, etc. can be displayed by applying voltage to display segments that are not used for display among the display segments, setting them to scattering mode, and turning the display to the same color and brightness as the ground and erasing it. . In the above example, green can be displayed on a bright white background.

The above explanation assumes that the display panel 1 is upright and light enters from above, but the display panel 1
When rotated at various angles, the above-mentioned display can be obtained unless the display is placed at an angle where there is a lot of reddish-purple reflected light from light sources such as the sun or electric lights, which is sufficient for practical use. Ta.

One of the features of this invention is that the specular reflector is arranged in a segment shape rather than over the entire surface. In order to make it easy to see by displaying green on a bright white background, if a specular reflector is provided on the entire surface, all the display layers on the ground must be in scattering mode, and normally scattering mode is voltage is applied, and the current consumption increases. Also, voltage cannot be applied to the so-called gear line parts between segments or around the lead wires, so if a display is made, this gear line will run as a green line on the ground, making it difficult to see.

According to the color display device of the present invention having the above-described configuration, it is possible to display color segments on a bright white background with high contrast and easy to see.
Since voltage only needs to be applied to the segment portions that are not needed for display, current consumption can be reduced. Furthermore, known materials can be used for the optically active material layer, and
Since it is extremely easy to form the specular reflection plate into segment shapes, there is no difficulty in manufacturing it.

[Brief explanation of drawings]

The drawings are cross-sectional explanatory views of embodiments of the present invention. 2... Optically active material layer, 3... Display layer, 4,
5... Transparent substrate, 6, 8... Transparent electrode, 7... Specular reflection plate, 9... Scattering reflection plate.

Claims (1)

[Claims] 1: a pair of transparent substrates facing each other; a display layer made of liquid crystal sealed between the pair of transparent substrates and capable of controlling a transparent mode and a scattering mode; a transparent electrode formed on at least one opposing surface; a specular reflector formed in a segment-like shape on one opposing surface of the pair of transparent substrates; an optically active material layer that is provided on the front side of the transparent substrate on which the reflecting plate is not formed and selectively scatters light of a specific wavelength in the visible range; A color display device consisting of a light-colored scattering and reflecting means provided behind a transparent substrate. 2. The color display device according to claim 1, wherein the optically active substance is a cholesteric polymer film. 3. The color display device according to claim 1, wherein the optically active substance is a cholesteric liquid crystal.