JPH0311449B2 - - 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 visual contrast is poor because the display area and non-display area are of similar color. Since the number of dyes that can be used is limited, there are drawbacks such as the inability to produce clear colors when mixing dyes to produce various colors.

The present invention provides a bright and easy-to-see color display device using an optically active material that has the property of selectively scattering light of a specific wavelength in the visible range.

Next, examples will be described.

A display layer 2 is provided on the front surface of a display panel 1 of a color display device. This display layer 2 is capable of controlling transparent mode and scattering mode. Examples of materials used as the display layer 2 include liquid crystal and ferroelectric transparent ceramic. The liquid crystals are phase-change type, which is P-type nematic liquid crystal mixed with a chiral material, electrothermo-optic type, which is P-type smectic liquid crystal mixed with chiral material, and n-type nematic liquid crystal mixed with ion dopants.
Examples include a DSM type, but in short, any type that can control the transparent mode and scattering mode will suffice. As a ferroelectric transparent ceramic, PLZT ceramic is known, whose optical properties change depending on the applied voltage. Here, this display layer 2
is a liquid crystal and is sandwiched between transparent glass substrates 3 and 4, with transparent electrodes 8 for display segments provided on the front substrate 3 and transparent counter electrodes 6 provided on the counter substrate 4. An optically active material layer 7 is arranged behind this display layer 2. This optically active substance layer 7 selectively scatters light of a specific wavelength in the visible range, and includes cholesteric liquid crystal, chiral nematic liquid crystal, and mixed liquid crystal thereof, as well as optically active substances that do not form a liquid crystal layer by themselves, and optically inactive substances. In addition to liquid crystals such as mixed liquid crystals with active liquid crystals, recently, polymer films of liquid crystals that exhibit cholesteric colors and can be polymerized and fixed are known as cholesteric polymer films. Good too. 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 of microcapsulating liquid crystal has now been developed, so a method such as dispersing microcapsulated liquid crystal in a transparent binder and coating it on a transparent substrate may also be used. Behind this optically active material layer 7, a specular reflection plate 8 is provided at a portion facing the display segment. Furthermore, a light-colored scattering reflection plate 9 is provided behind it. It goes without saying that the specular reflection plate 8 may be attached to the front surface of the scattering reflection plate 9 or provided by vapor deposition.

Next, the display effect will be explained.

Assume now that the cholesteric polymer film that is the optically active material layer 7 selectively scatters green light and transmits reddish-violet light, which is its complementary color. Regarding part A where the display segment is in the transparent mode, the incident light L passes through the display layer 2, the green light is selectively scattered by the optically active material layer 7, and the red-violet light passes through and is specularly reflected. It is reflected by plate 8 and comes out. When the display panel 1 is placed vertically, light enters diagonally from above, so the reddish-purple light is reflected diagonally downward and the portion A appears bright green.

Next, looking at the part B where the display segment of the display layer 2 is in the scattering mode, a part of the incident light is scattered and reflected, but the green light that passes through is selectively scattered by the polymer film, and is transmitted through this part. The reddish-violet light is reflected by the specular reflector 8 and exits again through the film and the scattering mode display layer. Therefore, the green light is slightly superior to the reddish-violet light in this area, so it appears as white scattering with a slight green tinge. In the part C where no display segment is provided, the incident light passes through the display layer 2, the green light is selectively scattered by the optically active material layer 7, and the red-violet light passes through this and is scattered in bright colors. The light is scattered by the reflector 9 and comes out. Since the intensity of the red-violet light is reduced, in the end, this portion C appears as white scattered light with a slight green tinge. Part C needs to look the same as part B, so use a light colored scattering reflector 9.
choose the one that looks the same as part B. Due to this display effect, numbers, etc. can be displayed by applying a voltage to display segments that are not used for display in the display segments, setting them to scattering mode, and erasing the display with the same color and brightness as the background. Can be displayed.

In the above-described embodiment, segments can be displayed in bright green in a white scattered area with a slight green tinge. One of the features of this invention is that the specular reflector is arranged not over the entire surface but in a segment shape. In order to obtain an easy-to-read color display on a white background, if a specular reflector is provided on the entire surface, the entire display layer on the background must be in the scattering mode, and the scattering mode is usually in the state where a voltage is applied. Yes, the current consumption increases. In addition, voltage cannot be applied to the so-called gear line parts between segments or around the lead wires, so when a display is made, the gear line runs in this area, making it difficult to see.

According to the color display device of the present invention having the above-described configuration, a bright color display is performed in a bright white or white-based background, so that a display with good contrast and easy to see can be achieved, and voltage is applied only to segment portions that are not used for display. Since it is only necessary to apply

[Brief explanation of the drawing]

The drawings are cross-sectional explanatory views of embodiments of the present invention. 2... Display layer, 7... Optically active material layer, 8...
...Specular reflector, 9...Scattered reflector.

Claims (1)

[Claims] 1. A display layer with display segments that can control transparent mode and scattering mode is arranged in front, and behind it is an optically active material that selectively scatters light of a specific wavelength in the visible range. A specular reflector is provided behind the layer in a portion facing the display segment, and a light-colored scattering reflector is provided at the rearmost position, and in the scattering reflector, the display layer is in a scattering mode. A color display device characterized in that a portion and a portion where the display segment is not provided appear to have substantially the same color. 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.