JPS6212898B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrode substrate for a liquid crystal display device that utilizes cholesteric-nematic phase transition, and a method for manufacturing the same. Liquid crystal display devices (LCDs) have advantages such as low power consumption, low voltage drive, small size, and thinness, and have been put to practical use in wristwatches, calculator displays, etc. As the next application field for LCDs, X-Y matrix type displays and color displays for various information processing terminals, measurement displays, etc. are thought to be promising, and various systems for X-Y matrix type LCDs have been reported so far. There is. Among these, liquid crystals having a memory effect (memory liquid crystals) are characterized in that they do not require refreshing and can be driven even with a large number of scanning lines. Furthermore, color display liquid crystals have the characteristic of being able to provide design properties and improve visibility. Cholesteric-nematic phase transition (CNT) type liquid crystals are applied to two types: a type that has the characteristics of memory display and high-speed writing, and a guest-host type type in which a dichroic dye is added. Applicable to A CNT type liquid crystal cell has a structure in which a P-type nematic-cholesteric mixed liquid crystal is sandwiched between vertically aligned transparent electrode substrates, and exhibits a light transmission intensity-applied voltage characteristic as shown in FIG.
Figure 2 is an explanatory diagram of the principle of memory writing using the above characteristics, where figures a and c are applied voltage-time relationships, and figures b and d are light transmission intensities of the liquid crystal corresponding to figures a and c, respectively. It is a figure showing the relationship of one hour. Explaining with reference to FIGS. 1 and 2, the memory display is divided into two stable states obtained after removing the applied voltage shown in FIG. 1: a relatively transparent state S and an opaque state Fo. This is done using the. Figure 3a is an example of a partial cross-sectional view of a CNT liquid crystal display element that performs a conventional X-Y matrix display. 3 and 3' are liquid crystal vertical alignment layers provided on a glass substrate including the electrodes, and 4 is a CNT type liquid crystal. When driving an element with a fine pattern using such an X-Y matrix,
In the vicinity of the intersection of the X and Y electrodes 2 and 2', where a voltage higher than V _H is applied between the X and Y electrodes, an electric force line distribution as shown by arrow 5 in FIG. If such an electric force line distribution is shown as a voltage distribution in the cross section in the direction of the X electrode 2, it will be as shown in Figure 3b.
A region where sufficient voltage is applied to scatter light is created in the non-electrode portion near the intersection of the Y electrodes 2 and 2', as shown in Fig. 3c.
Light scattering occurs around the pixel as shown in
A part 6 in the F′ state appears, and this scattering part expands over time and becomes the Fo state at the time of fixation.
There was a drawback that scattering was memorized. The present inventors utilized the property that the smaller the helical pitch of the liquid crystal in the thickness direction of the liquid crystal cell, the weaker the light scattering intensity and the memory effect.
and b are partial end views cut at a non-electrode portion and an electrode portion of the upper electrode substrate, respectively. ), insulating protrusions 7, 7' are provided on the non-electrode parts of the electrodes 2, 2' side of the substrates 1, 1', each having X and Y electrodes 2, 2' on their respective surfaces. Further, colored coatings 8, 8' are provided thereon, and vertically aligned liquid crystal layers 3,
The two electrode substrates 9 and 9' provided with
The electrodes 2 and 2' are arranged to face each other at right angles, and a CNT type liquid crystal is sandwiched between them to form a liquid crystal cell. The thickness of the liquid crystal between the colored film 8 or 8' on the part 7 or 7' and the electrode part of the other electrode substrate 9 or 9', that is, the Y electrode 2' or the X electrode 2, is The present invention was achieved by discovering that the above-mentioned drawbacks of the prior art can be eliminated by making the thickness of the liquid crystal thinner than the thickness of the liquid crystal between the intersections of . be. In this case, the thickness of the liquid crystal in the non-electrode parts, that is, the colored coatings 8 and 8' on the convex parts 7 and 7', is generally equal to or less than the number of pitches at which the helix of the CNT type liquid crystal has a memory effect. I will make it happen. In normal cases,
It is desirable to keep the distance to about 3 pitches or less. Moreover, it is clear from the principle that the above-mentioned convex part has the above-mentioned effect even if it is formed partially overlapping the electrode part. Furthermore, the height of the convex portion is determined by taking into account the thickness of the liquid crystal cell, the driving voltage, the type of liquid crystal, the manufacturing method of the liquid crystal cell, etc.
The height is usually about 0.1 to 5μ. Furthermore, when dichroic dye is added at a rate of 0.01 to 5% to a system that uses cholesteric phase liquid crystals larger than the pitch described above and does not have a memory function, the liquid crystal and dichroic dye become almost parallel to the electrode surface inside the cell. When voltage is applied, the color disappears as it stands vertically. Originally, in this system, since the background is colored, only negative display can be performed by erasing the color with electrodes, but by using the substrate of the present invention, it is possible to reduce the thickness of the liquid crystal in the non-electrode area to a thickness that does not form a spiral. Therefore, a display with high color contrast can be achieved by changing the coloring of the background. The height of the convex portion is usually about 0.5 to 10 μm, but the height is determined not only by the thickness of the liquid crystal layer but also by taking into consideration the strength of the vertical alignment agent, the helical pitch of the liquid crystal, etc. Usually one-fifth to two-fifth of the cell thickness
It becomes 1/1. The manufacturing process of the electrode substrate for a liquid crystal display element according to the present invention will be explained in detail below with reference to FIG. (1) Formation of a resist layer for substrate electrode patterning As shown in Figure a, a conductive layer corresponding to a predetermined electrode pattern is etched on the conductive layer 22 of the substrate 21, the surface of which is provided with the conductive layer 22 for electrode formation. A resist layer 23 is provided. This resist layer 23 is made of a layer of soluble resin, inorganic material, or a composite thereof, and is formed using techniques such as printing, photosynthesis, or photolysis. (2) Etching the conductive layer As shown in FIG. 2B, the conductive layer 22 is etched using the resist layer 23 as a mask, leaving the patterned conductive layer 22 that will become an electrode only under the resist layer 23. In this case, it goes without saying that the etching solution needs to dissolve the conductive layer 22 but not the resist layer 23 and the substrate 21. (3) Formation of an insulating film As shown in FIG. 2c, an insulating film 24 is provided over the entire surface of the substrate 21 so as to fill the electrode 22 and the resist layer 23 thereon. The material for the insulating film is an organic or inorganic insulating substance that is resistant to the etching solution that dissolves the resist layer 23 and has adhesive properties to the substrate 21. For the constituent material of the layer 23, it is dissolved in a solvent that is insoluble and applied by a method such as flow coating, dipping, roll coating, or spin coating, or a coating is applied by a method such as vacuum deposition, sputtering, or chemical vapor deposition. The insulating film 24 is formed using a forming method. Note that in order to improve the adhesion between the insulating film 24 and the substrate 21, the substrate 2
It is also possible to apply primer, corona, or plasma treatment to the surface of 1 to further strengthen the adhesion. In addition, if the coating material is a hardening type substance,
After the film is formed, a curing treatment using heat or light is performed. (4) Formation of colored coating As shown in Figure d, a colored coating 25 is provided on the insulating coating 24. Materials for the colored film include black pigments, colored pigments, metals, metal oxides,
Metal carbides and the like are used, and these can be used as they are or in the form of being dispersed or dissolved in a resin or the like to form a film by spin coating, dipping, roll coating, sputtering, vapor deposition, CVD, or the like. This coating varies depending on the material used, but generally
The thickness is preferably about 0.01 to 5 μm. (5) Resist layer etching As shown in Figure e, after the step in Figure d, the insulating coating 24 and the colored coating 25 are not immersed, but the resist layer 23 is etched by the etching solution that dissolves it.
At the same time as the resist layer 23 is dissolved and removed, the thin insulating film 24 formed on its upper surface and the colored film 25 thereon are lifted off, and the substrate 2 is removed.
1 to expose the patterned electrode 22 on top. Methods for resist etching and film lift-off at this time include immersion treatment in an etching solution, immersion in an etching solution with ultrasonic treatment, etching solution spray treatment, and scraping treatment in an etching solution. (6) Formation of liquid crystal vertical alignment film After the process shown in FIG. It will be done. Materials for this liquid crystal vertical alignment film include silane coupling agents having alkyl groups, organic chromium complexes, organic silicones, etc., and the film is made by coating one of these materials by spin coating.
It is applied by a coating method such as a dipping method or a roll coating method. Before forming the vertical alignment film, SiO, SiO ₂ ,
An inorganic insulating layer made of MgF ₂ , Al ₂ O ₃ , LiO-SiO, etc. may be provided in advance. An embodiment of the present invention will be described below with reference to FIG. Example 1 A positive resist layer is formed by a spinner coating method on the conductive layers of two glass substrates 21 having transparent conductive layers 22 on their surfaces, and this resist layer is exposed and developed by a conventional method to form a conductive layer. A resist layer 23 corresponding to a predetermined parallel electrode pattern is provided on 22 (FIG. 5a), and the conductive layer 22 is etched using this resist layer 23 as a mask, leaving only the conductive layer 22 under the resist layer 23. The other portions of the conductive layer are removed to expose the surface of the non-electrode portion of the glass substrate 21 (FIG. 5b). After priming the entire surface of the glass substrate 21 on the resist layer 23 side with a 1% ethylcyclohexane solution of alkyl titanium-epoxy primer, thermosetting silicone
A 10% ethylcyclohexane solution is spinner-coated and heat-cured at 100° C. for 20 minutes to form an insulating film 24 thick enough to slightly cover the upper surface of the resist layer 23 (FIG. 5c). After this substrate is subjected to oxygen plasma treatment, chromium is deposited to a thickness of 1000 Å by vacuum evaporation to form a colored film 25 (FIG. 5d). Next, the resist layer 23 is dissolved and removed using methyl ethyl ketone. At this time, the thin insulating film and colored film on the resist layer 23 are also lifted off and removed at the same time, exposing the electrode layer 22 under the resist layer, and forming an insulating film with a height of 1 μm in the non-electrode portion between the electrode layers 22. Convex portion 24 made of film
A colored film 25 with a thickness of 1000 Å is formed thereon to obtain the electrode substrate of the present invention (FIG. 5e). A 10% methyl ethyl ketone solution of a silicone-based vertical alignment agent is spinner coated on the entire surface of the electrode side of these two electrode substrates to form a vertical alignment film, and then both substrates are placed so that the electrodes are perpendicular to each other and facing each other with an electrode spacing of 8μ. A liquid crystal cell was prepared using a conventional method, and biphenyl-based P-type cholesteric liquid crystal with a pitch of 1.5 μm was sealed in this liquid crystal cell to produce a transmissive matrix display memory liquid crystal display element. Its specifications and performance measurement results are shown in Table 1.
This liquid crystal display element had no clouding in the non-electrode portion, and exhibited a colored display with good color contrast.

[Table] Example 2 In the same manner as in Example 1, a convex portion with a height of 4μ and a colored film were formed thereon, and a 10μ cell was manufactured in the same manner as in Example 1, and the liquid crystal was E-7. (BDH
When 5% of CB15 (manufactured by BDH) was added to 5% of CB15 (manufactured by BDH) and 1% of D3 (dichroic dye for guest hosts manufactured by BDH) was held, the coloring of the background of the display area was reduced. , we obtained a guest-host type cell capable of positive display.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the light transmission intensity vs. applied voltage characteristics of a CNT type liquid crystal, Figure 2 is a diagram explaining the principle of memory writing in a CNT type liquid crystal cell, and Figure 3a is an X-Y matrix display memory element. , a diagram showing the distribution of electric lines of force near the intersection of the Y electrodes, Figure 3b is a diagram showing the voltage distribution between the two electrodes around the intersection of the X and Y electrodes, and Figure 3c is a diagram similar to Figure 3b. Figures 4a and 4b show a focal conic region appearing near the intersection of the X and Y electrodes due to the voltage distribution between the X and Y electrodes. FIG. 5 is a partial end view showing the non-electrode portion and the electrode portion of the upper electrode substrate of the device, respectively, and is an explanatory diagram of the manufacturing process of the electrode substrate for a liquid crystal display device according to the present invention. 1, 1'... Glass substrate, 2, 2'... Transparent electrode, 3, 3'... Vertical alignment agent layer, 4... CNT type liquid crystal, 5... Lines of electric force, 6... Focal conic part , 7, 7'... Insulating convex portion, 8, 8'... Colored coating, 9, 9'... Electrode substrate, 21... Substrate, 22
...Transparent conductive layer, 23...Resist layer, 24...
Insulating coating, 25...Colored coating.

Claims (1)

[Scope of Claims] 1. In an electrode substrate for a liquid crystal display element, in which a conductive layer having a predetermined electrode pattern is provided on one surface of an insulating substrate, on a non-electrode portion of the surface of the substrate on the electrode side. A convex portion made of an insulating film is provided on the
An electrode substrate for a liquid crystal display element, further comprising a colored film provided on the insulating film. 2. A resist layer for a conductive layer etching mask having a predetermined thickness corresponding to a predetermined electrode pattern is provided on the conductive layer of an insulating substrate provided with a conductive layer on one surface, and the resist layer is used as a mask. The conductive layer other than the bottom part is removed by etching to expose the non-electrode surface of the substrate, an insulating film is applied to the entire surface of the substrate including the resist layer, and a colored film is further applied on the insulating film. After the formation, the resist layer is dissolved and removed using an etching solution that does not attack the insulating film and the colored film but does attack the resist layer, and at the same time removes the insulating film and the colored film on the surface of the resist layer. A method for manufacturing an electrode substrate for a liquid crystal display device, characterized in that a convex portion made of the insulating film and a colored film are provided on the non-electrode portion of the substrate.