JPS6326621A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To uniform the darkness of a display part and a background part uniform when no voltage is applied by making a mask layer thick and making the liquid crystal layer of the background part thinner than the liquid crystal layer of the display part, and reducing the rotary polarizing performance of the liquid crystal of the background part. CONSTITUTION:A black mask layer 9 is formed except at the display pattern of at least one substrate 6, and this mask layer 9 is made thick to make the thickness of the liquid crystal layer 2 of the background part thinner than the thickness of the liquid crystal layer of the display part, thereby reducing the rotary polarizing performance of the liquid crystal of the background part. Therefore, when no voltage is applied, the display part becomes dark in a crossed nicols state. Consequently, the darkness of the mask layer of the background part in the crossed nicols state and the darkness of the mask layer of the background part are set nearly equal to each other to prevent the display part from being seen floating over the background part in the no-voltage application state.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention is directed to a transmission type negative display using a color filter.
This invention relates to an N-type liquid crystal display element.

"Prior Art" Conventionally, a TN type liquid crystal display element with a transmissive negative display using a color filter has a backlight, a color filter,
It includes a pair of polarizing plates whose polarization axes are in the same direction, and a TN type liquid crystal cell inserted between the polarizing plates.

In the off state where no voltage is applied, the light from the backlight that has passed through the color filter passes through the first polarizing plate and then rotates in the TN type liquid crystal cell, and cannot pass through the second polarizing plate. , a dark background is formed (hereinafter, this state is referred to as a crossed Nicol state).Also, when a voltage is applied, the optical rotation power of the TN type liquid crystal cell disappears, so the backlighting that passes through the color filter is The light is visually recognized through the first polarizing plate, the liquid crystal cell, and the second polarizing plate, and a negative display consisting of colored light is produced on a dark background.

In such a negative display TN type liquid crystal display element,
It is preferable that the background part be light colored, or roughly black. For this reason, it is known that a mask layer such as a black mask is formed on at least one of the substrates except for the display pattern.

"Problems to be Solved by the Invention" However, in the above liquid crystal display element, when no voltage is applied, the display area exhibits darkness due to a crossed nicol state, and the background area other than the display area is in a crossed nicol state and a mask layer. Since the display area appears brighter than the background area due to the absence of the mask layer, the display area may appear to be raised.

Therefore, an object of the present invention is to make the darkness of the display area and the background area uniform when no voltage is applied in a TN type liquid crystal display element of a transmission type negative display using a color filter.

"Means for Solving the Problems" The present invention provides a transmission type negative display using color filters.
In an N-type liquid crystal display element, a black mask layer is formed on the part of at least one substrate excluding the display pattern, and this mask layer is made thicker so that the thickness of the liquid crystal layer in the background part is equal to the thickness of the liquid crystal layer in the display part. It is characterized by making it thinner than before, thereby reducing the optical rotation of the liquid crystal in the background.

"Function" Therefore, in a state where no voltage is applied, the display section exhibits darkness due to the crossed Nicol state, and the background section exhibits darkness due to the mask layer. That is, by making the liquid crystal layer in the background part thinner, its optical rotation is lowered, so that the darkness caused by the crossed nicol state disappears in the background part. For this reason,
By setting the darkness due to the crossed nicol state in the display area and the darkness due to the mask layer in the background area to be approximately the same,
It is possible to prevent the display portion from appearing to stand out from the background portion when no voltage is applied.

"Preferred Embodiment of the Invention" In a preferred embodiment of the present invention, when the thickness of the liquid crystal layer in the background part is dum and the refractive index anisotropy of the liquid crystal is Δn, Δnd<0.4. Set d. Thereby, it is possible to reliably reduce the optical rotation of the liquid crystal in the background area, thereby increasing the effect of making the display area and the background area the same in darkness when no voltage is applied.

In the present invention, the mask layer does not need to be completely black, but may be a dark color close to black.

In a particularly preferred embodiment of the present invention, 1 fr:, gA of a dichroic dye is added to the liquid crystal. As a result, the brightness when no voltage is applied can be made darker and the contrast can be improved.

Embodiments of the Invention As shown in FIG. 1, a liquid crystal display device embodying the present invention includes a backlight 1 and a TN-type liquid crystal cell 2 disposed in the light traveling direction of the backlight 1. There is. This TN type liquid crystal cell 2 has a display substrate 4 made of a glass plate on which a transparent display electrode 3 is formed on the inner surface, and a counter substrate 6 made of a glass plate on which a transparent counter electrode 5 is formed on the inner surface. , a twisted nematic liquid crystal 8 containing a dichroic dye 7 is interposed therebetween. A mask layer 9 is formed on the surface of the counter substrate 6 on which the counter electrode 5 is formed, excluding the display pattern, and an alignment film 10 is formed roughly inside the mask layer 9.
is formed.

In the case of this embodiment, the mask layer 9 is made of a metal ink (trade name rMc8) made of an alkyd resin mixed with carbon black.
5" (manufactured by Dainippon Ink Co., Ltd.)@offset printing method to form a thickness of about 6 um by printing and coating three times and baking. As a result, the thickness of the liquid crystal layer 2 in the background portion is set to 2 um or less.

Further, an alignment film 11 is formed on the surface of the display substrate 4 on which the display electrodes 3 are formed. The alignment films 10 and 11 are subjected to a rubbing treatment so that their edging directions are perpendicular to each other.

Note that both the display electrode 3 and the counter electrode 5 are I
It consists of TO. In addition, as the twisted nematic type liquid crystal 8, a PCM type liquid crystal (product name: r2LI 1
565J, manufactured by Merck & Co.), and the dichroic dye 7 was a yellow azo dye rG232J (trade name, manufactured by Nippon Kanko Shiki Co., Ltd.), a magenta anthraquinone dye rLsR405 (trade name, manufactured by Mitsubishi Kasei Co., Ltd.). Co., Ltd.), r
LcO208J (trade name, manufactured by Nippon Kayaku Co., Ltd.), r
LM8048J (trade name, made by Mitsubishi Kasei Co., Ltd.), cyan dye rLM8040J (trade name, made by Sanl Kasei Co., Ltd.), and rLsB335J (trade name, made by Mitsubishi Kasei Co., Ltd.) were mixed in appropriate proportions. , a dye prepared to have a pigment content of 1181 to 4% by weight is used.

In the TN type liquid crystal cell 2 thus obtained, the thickness of the liquid crystal layer in the background part was 2 μm or less, and the thickness of the liquid crystal layer in the display part was 8 μm.

A first polarizing plate 12 is attached to the light irradiation side of the TN type liquid crystal cell 2, and a second polarizing plate 13 is attached to the opposite side. Roughly speaking, a color filter 14 is attached to the outside of the first polarizing plate 12.

In this liquid crystal display element, when no voltage is applied, the display part becomes dark due to the formation of a crossed Nicol state due to the optical rotation of the liquid crystal 8, and the light from the back illumination 1 is continuously illuminated by the mask layer 9 in the background part. It's getting dark. In the background area, since the thickness of the liquid crystal layer is 2 um or less, there is almost no continuous light effect due to the crossed Nicol state.
Therefore, the darkness between the display part and the background part when no voltage is applied is balanced, resulting in uniform darkness, and it is possible to prevent problems such as the display part appearing to stand out from the background part.

In this example, since a dichroic dye is added, the contrast between when no voltage is applied and when a voltage is applied is greatly improved, and good display quality can be obtained. In addition, since the liquid crystal layer is thicker in the display area, the effect of the dichroic dye, which is smaller when no voltage is applied, appears more strongly in the display area, which also explains the dark contrast between the background area and the display area. This contributes to equalizing the quality.

"Effects of the Invention" As explained above, according to the present invention, the thickness of the liquid crystal layer in the background area is made thinner than the thickness of the liquid crystal layer in the display area by thickening the mask layer, thereby making the liquid crystal layer in the background area thinner. Since the optical rotation is reduced, when no voltage is applied, the display area exhibits darkness due to the crossed Nicol state, the background area exhibits darkness due to the mask layer, and the darkness due to the crossed Nicol state does not appear as strongly. , both of them are balanced, resulting in uniform darkness, and it is possible to eliminate inconveniences such as the display section appearing raised.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an embodiment of a liquid crystal display element according to the present invention. In the figure, 1 is a backlight, 2 is a TN type liquid crystal cell, 3 is a display electrode, 4 is a display substrate, 5 is a counter electrode, 6 is a counter substrate, 7
8 is a twisted nematic liquid crystal, 9 is a mask layer, 1O111 is an alignment film, 12 is a first polarizing plate,
13 is a second polarizing plate, and 14 is a color filter. Patent applicant: Alps Electric Co., Ltd. ↓ Figure 1

Claims (2)

[Claims] (1) In a transmissive negative display TN type liquid crystal display element using a color filter, a blackish mask layer is formed on the portion of at least one substrate excluding the display pattern, and this mask layer is thickened to cover the background portion. 1. A liquid crystal display element characterized in that the thickness of the liquid crystal layer is made thinner than that of the liquid crystal layer in the display part, thereby reducing the optical rotation of the liquid crystal in the background part. (2) In claim 1, when the thickness of the liquid crystal layer in the background part is dum and the refractive index anisotropy of the liquid crystal is Δn, d is set so that Δnd<0.4. Liquid crystal display element.