JPH0372969B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a liquid crystal display element.

Generally, a liquid crystal display element is constructed as follows. Two electrode substrates are fixed with adhesive so as to maintain a constant distance of about 10 μm, liquid crystal is sealed in the gap between the substrates, and liquid crystal molecules are arranged uniformly on the inner surface of the substrate in contact with the liquid crystal as necessary. A liquid crystal display element is constructed by applying an alignment treatment to make the substrate transparent, and further disposing a linear polarizing plate on the outer surface of the substrate as necessary. Incidentally, since the characteristics of a liquid crystal display element, such as response speed, strongly depend on the thickness of the liquid crystal layer, it is necessary to make the thickness of the liquid crystal layer, that is, the spacing between the substrates, uniform. For this purpose, a method is known in which an adhesive mixed with a spacer is applied around the substrate by screen printing, thereby adhering and fixing two substrates at a constant interval. If further uniformity in thickness is required, a method is known in which spacers are almost uniformly distributed over the entire inner surface of the substrate in contact with the liquid crystal, and the spacers are fixed using the spacer-containing adhesive described above. however,
When the above-described spacers are dispersed to improve the thickness uniformity, a problem arises in that the contrast of the liquid crystal display element decreases.

That is, liquid crystals exhibit optical changes upon application of voltage, whereas the materials used for the spacers, generally solid powders, do not exhibit electro-optical effects. For example, in a liquid crystal display device that utilizes the twisted or nematic effect (abbreviated as TN effect), if two linearly polarizing plates are arranged so that their polarization axes are parallel, the liquid crystal will rotate at a 90° angle with no voltage applied. It has optical rotation, and since the optical rotation is canceled by applying a voltage, it displays white/black when the voltage is turned on/off. At this time, if crushed fiberglass (milled fiber) is sprinkled as a spacer, only the area where the spacer exists always appears white regardless of whether the voltage is on or off. In addition, for example, in a liquid crystal display element that utilizes the guest/host effect (abbreviated as GH effect) of a liquid crystal with positive dielectric anisotropy in which a black dichroic dye is dissolved, it is possible to change the color between white and white by turning on and off the voltage. Although black is displayed, the spacer portion always appears white.

Thus, as the amount of spacers dispersed (density on the substrate surface) increases, the darkness of the black color decreases, leading to a decrease in contrast. In particular, in the case of a transmissive liquid crystal display element that is illuminated from the back, the entire element is black when no voltage is applied, so even the slightest bright spot is relatively noticeable, resulting in a significant drop in display contrast. arise.

The present invention solves the above-mentioned conventional problems and provides a liquid crystal display element in which the contrast does not deteriorate and the thickness of the liquid crystal layer is made uniform.

That is, the present invention provides a liquid crystal display element in which two electrode substrates are arranged so that the electrodes face each other, and liquid crystal is sealed in the gap between the substrates, and black spacers are scattered over the entire surface of the substrate in contact with the liquid crystal in the gap. The present invention is a liquid crystal display element characterized in that the spacers are colored black, so there is no reduction in contrast, and the thickness of the liquid crystal layer is made uniform.

This will be explained in more detail with reference to Examples. FIGS. 1 and 2 are diagrams schematically showing a cross section a and a display form b of a liquid crystal display element according to a conventional example and the present invention, respectively. On the periphery of the first glass substrate 1 having the transparent electrode 1', a 7 μΦ milled fiber-added epoxy adhesive 3 is screen-printed as a spacer in the form of a crack, and on the other hand, the second glass substrate 1 having the transparent electrode 2' is After scattering 7μφ plastic spherical powder almost uniformly over the entire surface of the substrate 2 as a spacer, the first and second glass substrates 1 and 2 are stacked, and the adhesive 3 is cured to form a liquid crystal container with a uniform gap. form. Note that the inner surfaces of the first and second substrates that are in contact with the liquid crystal have been subjected to an alignment treatment in advance by rubbing in one direction with absorbent cotton in order to horizontally align the liquid crystal molecules. In the liquid crystal container mentioned above, there is a black 2
A nematic liquid crystal 5 with a positive dielectric anisotropy in which a colored dye is dissolved is sealed, and a linear polarizing plate 6 is arranged on the outer surface of one of the substrates so that its polarization axis is parallel to the direction of molecular alignment to produce a liquid crystal display. It was named Element. In the conventional example shown in FIG. 1, the transparent 7 μΦ plastic spherical powder 4 is used, and in the liquid crystal display element according to the present invention shown in FIG.
Plastic spherical powder 4' colored black and having a diameter of 7 μι is sprinkled on the substrate surface. The amount of spraying is 1mm ²
Approximately 10 pieces each.

The difference in display contrast between the conventional liquid crystal display device and the liquid crystal display device according to the present invention thus constructed was investigated by illuminating the device from behind. In the conventional example, the entire element is black and dark when no voltage is applied, so a transparent spacer is used, so even though it is a fine powder of 7μφ,
Shining dots were easily noticeable against the black background, and the display did not appear completely black; the overall appearance was grayish, and the display contrast was significantly reduced. On the other hand, since the liquid crystal display element according to the present invention uses spacers colored black, it appears completely black when no voltage is applied, and when a voltage is applied, the entire area becomes brighter, making it difficult to identify the black spacers, making them more visible than conventional products. Contrast was improved. The above is a display using the GH effect, but a display using the TN effect was also effective. In this way, the liquid crystal display element according to the present invention maintains a uniform substrate gap and does not reduce the display contrast. Therefore, especially in large liquid crystal display elements, it is necessary to scatter a large number of spacers. Most effective.

[Brief explanation of drawings]

FIG. 1a is a schematic diagram showing a cross section of a conventional liquid crystal display element, FIG. 1b is a diagram showing its display form, and FIG. 2a is a schematic diagram showing a cross section of a liquid crystal display element of the present invention.
FIG. 2b is a diagram showing the display form. 1'...Glass substrate, 2'...Transparent electrode, 3...
Epoxy adhesive, 4'... Spacer, 5... Liquid crystal,
6...Polarizing plate.

Claims (1)

[Claims] 1. In a liquid crystal display element utilizing twisted or nematic effect, in which two electrode substrates are arranged so that their electrodes face each other and liquid crystal is sealed in the gap between the substrates, the entire surface of the substrate in contact with the liquid crystal in the gap is A liquid crystal display element characterized by interspersing black spacers and performing black and white display.