JPS5868018A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a bright display of good contrast by applying horizontal orientation treatments which are intersected orthogonally with each other on the surfaces of an electrode substrate sandwiched by two layers of liquid crystal layers of the same hue differing in spiral directions from each other and applying perpendicular orientation on the surfaces of the two electrode substrates on the outer sides. CONSTITUTION:Horizontal orientations which are intersected orthogonally with each other are applied on both surfaces of an intermediate substrate 1 among 3 pieces of electrode substrates1, and vertical orientations are applied on the surfaces of two sheets of the substrates on the outer sides. Liquid crystal compsns. which are varied in spiral directions from each other by adding dyes of roughly the same colors to nematic liquid crystals of positive dielectric anisotropy and adding a material giving right-hand spirality to one of these and a material giving left-hand spirality to the other are sealed in two liquid crystal layers 13. The layers 13 are so constituted that the thickness (d) and pitch (p) thereof attain d/p>=2. Thus the bright guest-hose type liquid crystal display element of good contrast and a short turning-off time is obtained without using any polarizing plate.

Description

[Detailed Description of the Invention] In more detail, five or more sheets of electronic paper. The present invention relates to a display element having two or more liquid crystal layers consisting of polar substrates.

Both electrode substrate surfaces are in the same direction. When performing display by sandwiching a liquid crystal containing a pleochroic dye such as a dichroic dye into a nematic liquid crystal with positive dielectric anisotropy between a pair of horizontally aligned electrode substrates, the liquid crystal layer Because the linear polarization of the light passing through is maintained, the component light polarized in a direction almost parallel to the long axis of the dye molecule is absorbed by the dye in the visible C. Component light polarized in this direction is not absorbed by the dye. Therefore, in the non-machined liquid crystal layer, only about half of the light incident on the liquid crystal layer can contribute to coloring, so the display contrast ratio that can be obtained is about 2 at most. However, if two similar display elements are placed one on top of the other and installed so that the alignment direction of the liquid crystal molecules in each liquid crystal layer is adjusted to form a single display element, the light passing through these two liquid crystal layers will be Since all of the liquid crystals are absorbed by the dye, a sufficiently colored state can be obtained, and when a voltage higher than the threshold value is simultaneously applied to the two liquid crystal layers, the liquid crystal layer becomes in a non-absorbed state, so that the contrast becomes -1.

FIG. 1 is a schematic diagram for explaining the operating principle of a conventional display element. 1 is a transparent electrode substrate, 2 is a patterned transparent electrode, 5 is an alignment state of liquid crystal and dye molecules,
4 is a switch, 5 is an AC power supply, and 6 is a peripheral sealing material. In each liquid crystal layer, the liquid crystal and dye molecules are aligned in a certain direction and perpendicular to each other. Therefore, light passing through the display element when no voltage is applied is effectively absorbed by the dye, resulting in deep coloring.

Next, when voltage is applied to the two liquid crystal layers at the same time, the liquid crystal and dye molecules are aligned perpendicular to the electrode surface, so the light passing through the display element is not absorbed by the dye. Transition to bleached state.

This display element has the advantage that good contrast can be obtained without using a polarizing plate, and a display with a bright appearance can be obtained because the polarizing plate is a lower mold. however,
This display element uses the same cell gap and the same host liquid crystal compared to the twisted nematic element (TNg element), which uses two polarizing plates and is used in conventional telegraphs, watches, clocks, etc. In this case, the turn-off time was about five times longer.

The object of the present invention is to improve such drawbacks, and is to provide a guest-bost type liquid crystal display that has practical advantages such as a bright display with good contrast and a known turn-off time. The purpose is to provide an element.

That is, the present invention provides two spaces formed by an electrode substrate and a sealing material, which are treated so that liquid crystal molecules are vertically aligned on one electrode surface and water-oriented on the other electrode surface. In a liquid crystal display element in which a liquid crystal substance consisting of a nematic liquid crystal with positive dielectric anisotropy, a pleochroic dye, and an optically active substance is injected into the space, each liquid crystal layer has a different spiral direction. A liquid crystal having almost the same hue is sealed in the liquid crystal layer, and the orientation directions of the surfaces of the electrode substrates sandwiched between the two liquid crystal layers are almost perpendicular to each other, and the display pattern on each liquid crystal layer is almost the same. This is a liquid crystal display element characterized by the following.

The liquid crystal display element of the present invention has four electrode substrates, two layers, five electrode substrates, and two layers.
Although any of the layers can be used, five layers and two layers is preferable because the thickness can be reduced.

The horizontal alignment directions of both surfaces of the intermediate substrate sandwiched between the two liquid crystal layers are shifted by approximately 90 degrees.

The transparent electrodes of this electrode substrate are substantially the same in both liquid crystal layers, thereby achieving high contrast and fast response characteristics.

Note that some differences may be provided, such as providing electrodes only on one liquid crystal layer side for intermediate color display, or providing patterns slightly shifted for visibility from a specific oblique direction -1-.

In realizing the display element according to the present invention, the method for treating the surface of the electrode substrate to give horizontal alignment to liquid crystal molecules is a rubbing method in which the electrode, the substrate, or its organic or inorganic overcoat material is rubbed in a fixed direction with a cloth or the like. A method such as oblique vapor deposition of silica or the like may be used.Also, as a method of treating the surface of the electrode substrate to give vertical alignment to liquid crystal molecules, a method for treating the surface of the electrode substrate that gives vertical alignment to the liquid crystal molecules may be a method such as non-irregular sobbing containing long-chain alkyl or fluoro groups, etc. A known treatment method may be used to treat the surface of the electrode substrate with a chemical agent, quaternary ammonium, pyridium salt, lentin, surfactant, etc. , and in order to arrange them substantially in parallel, cells are formed through a peripheral sealing material such as Evokin resin or glass frit. At this time, a spacer, a conductive transfer, etc. may be formed within the cell or the peripheral seal cavity.

After forming the cell in this way, liquid crystal is filled in from the injection port,
A liquid crystal display element is formed by sealing the injection port with an epoxy resin, /, etc. Furthermore, the effect remains the same whether it is a phenylcyclohexane system, a fluorine base system, a cyclohexane phenyl ester system, a pyrimidine system, or a mixed system based on these. Further, as the optically active substance that gives the nematic liquid crystal a helical structure, various known optically active substances, cholesteric liquid crystals, etc. can be used, and these may be added alone or in combination. Furthermore, as a method of adding a substance to a nematic liquid crystal to impart a different helical direction, for example, as a substance imparting a right-handed helix, BDH's C
B-15, Merck's S-1082, Sensuji's commercial
-19, CM-20, etc. Substances that give left helix include C-15 from BDH, CM and CM-1 from Chisomoto Co.
Examples include 0° cholesterol nonanoate and cholesterol chloride.

In the device of the present invention, in order to better achieve the effects of the invention, it is important that the rotation angles of the liquid crystal molecules in the two liquid crystal layers be equal in order to obtain uniform electro-optical characteristics.

Further, it is preferable that d/p≧2, and a liquid crystal display element with high contrast and short turn-on time can be obtained. Note that d/p is generally used in two layers of about 5, but it can also be used even if the d/p is larger;
If p exceeds 10, the driving ratio becomes quite high, and it becomes difficult to accurately align d/p between the two layers, making it difficult to obtain the desired characteristics.
). There are the following methods to achieve this. That is, the relationship pxc = α (constant) can be obtained between the concentration (C) of an additive that gives a nematic liquid crystal with positive dielectric anisotropy a spiral groove structure and the obtained bottle 1,000. Therefore, α can be experimentally determined for both the substance that gives right helix and the substance that gives left helix so that d/p falls within the above range, and the concentration C of the additive can be adjusted.

Furthermore, a pleochroic dye is added to the liquid crystal of the present invention. Various known pleochroic dyes can be used as the pleochroic dye, and may be used alone or in combination within a range that dissolves in the liquid crystal.

According to the present invention, since the two liquid crystal layers are driven in the same way with the same pattern in principle, it is preferable that the liquid crystal is also made of the same material except for the two layers having different rotation directions. The types of liquid crystal substances, optically active substances, and pleochroic dyes may be changed, as long as they rotate equally. Father: When using the same liquid crystal, the thickness of the two liquid crystal layers should be approximately the same. Therefore, the characteristics of the two liquid crystal layers can be made equal, and the response characteristics can be improved.

Further, one purpose of the present invention is to provide a display with good contrast, and essentially, electrode patterns are formed in both liquid crystal layers so that the same display can be obtained at the same location. In order to obtain good contrast, it is necessary to simultaneously drive the seven corresponding display parts of each liquid crystal layer. However, depending on the purpose, for example, when it is desired to obtain an intermediate color tone, it is also possible to drive only one of them.

In the above explanation, only the case of two layers has been explained, but it may be five or more layers, and the fifth and subsequent layers are the first layer and the second layer of the present invention.
A liquid crystal similar to that of the layer may be used, or a liquid crystal of a different type may be used.

Furthermore, although not mentioned here, if necessary, UV cut filters, color filters, polarizing films, reflective films, light guides, light sources, etc. can be laminated, the lead part has a special structure, and the cable can be directly bonded. Various known display patterns can be used, such as figures, bar graphs, analog clocks, and numeric displays using Japanese character segments.

A schematic diagram for explaining the operating principle of the display element according to the present invention is shown in FIG. 2, where the case where the M rotation angles of liquid crystal molecules are both 2 fists is set as f1/ll.

Unlike the conventional example shown above, when no voltage is applied, (10
) As shown on the left side of the figure, the liquid crystal molecules 15 are rotated by 2 degrees in each liquid crystal layer, but the molecular alignment direction differs by 9110 degrees between the two liquid crystal layers, and the direction of the inner part is reversed. As a result, light absorption Lf'l can be carried out efficiently, and a good coloring state can be obtained, as is the case with non-machink. Then the second
As shown in the diagram, when an electric current fE higher than the threshold value is simultaneously applied to both liquid crystal layers, both the liquid crystal and dye molecules align their molecular long axes perpendicular to the electrode surface, resulting in a bleached state. .

Next, examples according to the present invention will be shown. Horizontal alignment of liquid crystal 4
A rubbing method is used in which the surface of the electrode is rubbed in a fixed direction with a cloth, and the rubbing direction differs by 9θ0 on the surface of the central electrode substrate.

In addition, as a method for imparting vertical alignment to liquid crystals, the electrodes of 5 ida [Evoquin type tree] Fingers were heat-pressed as a peripheral sealing material, and the fingers were arranged approximately in parallel, and each (11) and the used immaculate liquid crystal composition (8-1) showed the alkyl group. ) was added with 2 g of anthraquinone dye D-57 produced by BDH to obtain a purple liquid crystal with a clearing point of 92°C.

In this I-Matic composition, CM-20 manufactured by Chisso Corporation was used as a substance imparting right-handed helical properties, and cholesterol nonanoate (CN) was used as a substance imparting left-handed helical properties. α of CM-20 and CN at 20°C is 2o, respectively.
CM-
20 and CN stress 1i were selected by the method described above to construct a device according to the invention with (d/p) of 0111.20.2.9.

For comparison, only composition A-1 was sealed in a cell having the same gap to form a conventional device. Furthermore, as a comparison, a two-layer element with two rotations, both right-handed helical, and a left-handed helical element were formed.

Table 1 shows the display characteristics when 10 V was applied at 20°C. In Table 1, Examples relate to display elements according to the present invention, and Comparative Example 1 relates to conventional display elements.

Furthermore, in Comparative Examples 2 and 5, the cell configuration was the same as that of the present invention, but the liquid crystals filled in the two liquid crystal layers were oriented in the same direction.

Table 1 (15) As is clear from this example, the contrast ratio is d
/p≧2, the display element according to the present invention is equivalent to the conventional element and exhibits good contrast.

The turn-off time is d/p≧2, and the display element according to the present invention is faster than the conventional element.

Since the dependence of the off time on driving voltage is considerably smaller than that of the turn on time, the off time is determined by the cell gap of the i-son used, the mode, the viscosity of the liquid crystal composition used, etc. On the other hand, the turn-on time generally has a strong dependence on the driving voltage, and in order to obtain a faster response, it is better to drive at a higher voltage, and the turn-off time [shortening li is This can greatly contribute to improving the response speed of the element.

From the above, the liquid crystal display element of the present invention is a display element with good contrast and quick response, can provide a display element of high quality in practical use, and can be used alone or in combination with other materials. It is possible to apply
As a transmissive type or a reflective type, it can be applied as a display for a city table, a clock, various measuring instruments, a game machine (14), a torpedo, etc., a display for a camera, an audio device, and other home appliances.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the operating principle of a conventional element, and Fig. 2 is a schematic diagram showing the operating principle of the display element of the present invention.

Claims (3)

[Claims] (1) Two electrode substrates treated so that the liquid crystal molecules are oriented vertically on one electrode surface and horizontally oriented on the other electrode surface, and a hole formed by Nurli. In a liquid crystal display element in which a liquid crystal substance consisting of a nematic liquid crystal with positive dielectric anisotropy, a pleochroic dye, and an optically active substance is injected into the space, each liquid crystal layer has a spiral layer. Liquid crystals with different directions and almost the same hue are sealed, and the surface of the electrode substrate sandwiched between two liquid crystal layers is horizontally aligned.
A liquid crystal display element characterized in that the orientation directions of the respective surfaces are substantially perpendicular to each other, and the display patterns of each liquid crystal layer are substantially the same. (2) In each liquid crystal layer, the liquid crystal layer j stain and liquid crystal pitch are adjusted between each pair of electrodes so that the thickness of the liquid crystal layer (dl and the pinch (p) of the liquid crystal becomes d/p≧2). A liquid crystal display element according to claim 1, characterized in that: (3) A liquid crystal display element according to claims 1 and 2, which comprises five electrode substrates and two liquid crystal layers.