JPS6231328B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a guest-host type liquid crystal display device having a fixed display of numbers, characters, symbols, etc. within a color liquid crystal display.

Color display systems that utilize the pleochroic properties of liquid crystals are known. This type of display device is broadly divided into a polychromatic liquid crystal display device that utilizes the dichroism of liquid crystals and a guest-host type display device that utilizes the dichroism of dyes. Positive nematic liquid crystals and dielectrically negative nematic liquid crystals are used. A nematic liquid crystal with positive dielectric anisotropy has a so-called homogeneous molecular alignment structure in which its molecules are aligned horizontally along the substrate, and a nematic liquid crystal with negative dielectric anisotropy has a so-called homogeneous molecular alignment structure in which its molecules are aligned horizontally along the substrate. It is known to have a homeotropic molecular arrangement structure in which the molecules are oriented in a direction perpendicular to the other, or a tilted molecular arrangement structure having an inclination angle.

A guest-host type liquid crystal display device dissolves a dichroic guest dye into a host liquid crystal with a fixed arrangement.
By controlling the alignment of the liquid crystal with an electric field, the alignment of the dye is also controlled at the same time, and the changes in color density at this time are displayed in color through a single polarizing film. In particular, by using a nematic liquid crystal with positive dielectric anisotropy in a guest-host type display device, negative color display is possible, so it has been widely used in the fields of watches and calculators in recent years.

Until now, it has often been necessary to form fixed displays such as numbers, letters, symbols, etc. within the color display of the guest-host type liquid crystal display device as described above. As a method of forming a fixed display of numbers, letters, symbols, etc., for example, as described in JP-A-49-113651, an adhesive that also serves as a spacer is screen printed in the form of numbers or letters within the liquid crystal display. There are known methods for forming such a structure. However, with this method, it is difficult to accurately print numbers or letters on the spacer adhesive, and furthermore, the spacer adhesive printed in numbers or letters is pressed against the two electrode plates. When the device is held in place, the adhesive layer spreads in the plane direction, making it difficult to clearly distinguish even small numbers or letters.

As another method, a method is known in which a fixed display is created by placing a transparent film on which characters or figures are printed in advance on the outside of the substrate of the display device. However, since this method uses film, the display surface becomes darker, and the fixed display surface and the operating display surface are separated by the thickness of the transparent electrode substrate, so the fixed display appears floating. There are drawbacks to this.

The inventor of the present invention has conducted intensive studies in view of the various drawbacks mentioned above, and has discovered a guest-host type liquid crystal display device that has a fixed display of numbers, letters, symbols, etc. with the same accuracy as the operation display of a liquid crystal. .

Therefore, it is an object of the present invention to provide a guest display having a fixed display within the liquid crystal display with the same accuracy as the operating display.
An object of the present invention is to provide a host type liquid crystal display device.

Another object of the present invention is to provide a guest-host type liquid crystal display device that has a fixed display of clear numbers, letters, symbols, etc. within a color liquid crystal display.

Furthermore, another object of the present invention is to provide a guest-host type liquid crystal display device having a fixed display that eliminates floating appearance.

Such an object of the present invention is to apply a voltage to a portion forming a fixed display in a color liquid crystal display at a level higher than that which will not cause the liquid crystal molecules in that portion to become horizontally aligned as before the voltage was applied again. This is achieved by vertical orientation.

Quite unexpectedly, the present inventor discovered that a liquid crystal with positive dielectric anisotropy that is horizontally aligned along two electrode plates can be applied with a DC or AC voltage higher than the drive voltage of the display device. When you receive for a certain period of time,
It was found that the alignment state is again vertically aligned instead of horizontally aligned. The present invention was made based on this unexpected alignment state of liquid crystals.

A method for forming a fixed display in a liquid crystal display according to the present invention involves preparing at least one electrode plate on which conductive patterns such as numbers, letters, and symbols are formed, and using this and a predetermined member such as a liquid crystal. After forming a negative guest-host type liquid crystal display device by cell assembly, a DC or AC voltage higher than the driving voltage of the display device is applied between the conductive pattern and one electrode for a certain period of time or more. There are several methods. FIG. 1 shows a cross-sectional view of a guest-host type liquid crystal display device having a fixed display according to the present invention.

In FIG. 1, 11 and 16 are substrates, 15
13 and 14 are alignment agents or alignment films, and 17 is a liquid crystal layer having positive dielectric anisotropy in which a dichroic dye is dissolved. 12a is a conductive film on which patterns of numbers, letters, symbols, etc. are formed to form a fixed display. The liquid crystal molecules, which were horizontally aligned before the voltage was applied, are applied with an applied voltage between the conductive films 12a and 15 at a level higher than that which will not cause them to be horizontally aligned again even if the voltage applied between the conductive films 12a and 15 is removed. When the voltage is applied, due to the vertically aligned liquid crystal molecules 18a and dichroic dye 19a,
A cloudy fixed liquid crystal pattern is formed on a colored background. Therefore, 18a indicates liquid crystal molecules that are vertically aligned (hereinafter referred to as "permanently vertically aligned") in such a state that they will not be horizontally aligned again even if the applied voltage is removed.
Reference numeral 12b denotes a conductive film for forming a liquid crystal operation display. When a driving voltage is applied to these conductive films 12b and 15, horizontally aligned liquid crystal molecules 1
8b and dichroic dye molecules 19b are converted into vertical alignment to form a motion display pattern. When this driving voltage is removed, the vertically aligned liquid crystal molecules are returned to the horizontal alignment and the operating display pattern also disappears. Although the driving voltage cannot be specified depending on the type of liquid crystal used, it is generally around 1V to 15V, at or below the saturation voltage. In particular, in order to increase display contrast, it is preferable to drive at a saturation voltage.

FIG. 2 is a plan view of a guest-host type liquid crystal display device having a fixed display according to the present invention within the liquid crystal display. 21a, 21b,...21h are the first
Permanently vertically aligned liquid crystal molecules 18a in the figure.
and dichroic dye molecules 19a are formed, and 22a, 22b, ... 22e are the horizontally aligned liquid crystal molecules 18b and dichroic dye molecules 19b in FIG. This is an operation display section that is vertically oriented by applying . The operational display is driven by an external circuit (not shown) through electrode terminal 23. In the figure, 24 indicates a sealing material formed by a method such as screen printing, and 25 indicates a sealing material. As the sealing material 24 and the sealing material 25, epoxy resin adhesive or the like can be used.

The height of the voltage required to form the permanently vertically aligned liquid crystal molecules 18a shown in FIG. 1 depends on the type of liquid crystal used and the type of alignment agent (film). It cannot be determined unambiguously because the interaction between the liquid crystals changes and the alignment force of the liquid crystal varies depending on the current application time. However, generally 10V or more, preferably 20V or more is suitable. Further, if the applied voltage is high, the energization time can be shortened, but if the applied voltage is low, the energization time needs to be increased. When using "Nematic Phase 1565TNC Crystal" (product name) manufactured by Merck & Co., West Germany as the liquid crystal, an anthraquinone dye as the dichroic dye, and a unidirectionally rubbed silicon dioxide film as the alignment film. The above relationship is shown in FIG. Curve 31 shown in FIG. 3 was created by plotting the DC current time required to form permanently vertically aligned liquid crystal molecules 18a as shown in FIG. 1 depending on the applied voltage. It is. According to FIG. 3, it is clear that the height of the voltage applied at this time and the energization time should be selected according to the conditions suitable for the alignment film and liquid crystal used.

Liquid crystals with positive dielectric anisotropy that can be used in the present invention include Schiff-type liquid crystals, biphenyl-type liquid crystals, azoxy-type liquid crystals, ester-type liquid crystals, and cyclohexane-type nematic liquid crystals, such as those shown below. can.

These mixed crystals can contain small amounts of cholesteric liquid crystals. In addition to these liquid crystals, cholesteric liquid crystals and smectic liquid crystals can also be used.

As the electrode plate used in the guest-host liquid crystal display device of the present invention, at least one side is a transparent conductive film (for example, indium oxide, tin oxide, indium oxide-tin oxide (tin oxide: 0.1 to 40% by weight), etc.) Substrate (glass, plastic, etc.) with
It is preferable to use Further, as the opaque conductive film used in the present invention, aluminum,
Examples include gold, silver, copper, and lead.

Furthermore, an alignment film made of a suitable insulating film can be used in the guest-host type liquid crystal display device of the present invention. The alignment film is a film that has been oriented by a method such as rubbing so that the wall is oriented in one direction. Nylene diamine, m-xylene diamine, P-xylene diamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 4,4'- diaminodiphenylsulfone,
Diamines such as 1.5-diaminonaphthalene, 3.3'-dimethylbenzidine, bis(4-β-amino-t-butylphenyl) ether, pyromellitic anhydride, 2,3,6,7-naphthalenetetracarboxylic anhydride, 3, 3,4',4'-diphenyltetracarboxylic anhydride, 1,2,5,6-naphthalenetetracarboxylic anhydride, thiophene-2,3,
It can be produced by a condensation reaction with dicarboxylic anhydrides such as 4,5-tetracarboxylic anhydride and 2,2'-bis(3,4-biscarboxyphenyl)propane anhydride. ), polybenzoxazole, polybenzimidazole, polybenzothiadiazole, polyparaxylylene, polyolefins (eg, polyethylene, polypropylene, etc.), fluoroethylene, polyesters (eg, polyethylene terephthalate), and the like are available. It is also possible to provide a suitable silane coupling agent (for example, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, etc.) between the conductive film and the alignment film. Furthermore, the alignment film may contain a suitable alignment improver (eg, titanium oxide, zinc oxide, etc.).

The dichroic dye used in the guest-host type liquid crystal display device of the present invention can be selected from a wide variety of dyes. Specific dichroic dyes are listed below.

Among these dichroic dyes, anthraquinone dyes are particularly preferred.

Although not shown in FIG. 1, in the guest-host type liquid crystal display device of the present invention, a spacer material such as glass beads, granular aluminum oxide, glass fiber, etc. can be placed between two electrode plates.

The cell structure is arranged in such a way that the liquid crystal molecules are aligned parallel to each other.
This can be done by arranging two electrode plates facing each other. At this time, the two electrode plates may be arranged in a twisted orientation such that the rubbing directions of the two electrode plates are orthogonal to each other. For example, in the cells assembled in this way,
No. 36998, No. 47-22693, No. 48-30397, No. 49
- No. 79543, No. 53-17751, No. 49-130756, No.
No. 50-50055, No. 52-27653, No. 49-79541,
A guest-host type liquid crystal display device can be produced by injecting liquid crystal according to the method described in each publication, No. 49-79542, and then sealing the injection port with an epoxy adhesive or the like.

Polarizing films that can be used in the guest-host type liquid crystal display device of the present invention include a polyhalogen polarizing film in which iodine molecules are arranged in a certain direction on a polyvinyl alcohol film, and a dye-polarized film in which dichroic dyes are arranged in a certain direction in polyvinyl alcohol film. film,
Examples include a polyvinylene polarizing film with a polyene structure obtained by intramolecularly dehydrochlorinating polyvinyl chloride, and a metal polarizing film. The polarizing film can be arranged in a guest-host type liquid crystal display device by setting the direction of the polarization axis parallel to the alignment direction or at right angles to the orientation direction.

According to the present invention, it is possible to eliminate the floating appearance of fixed displays that appear cloudy on a colored background, and furthermore, it has the advantage that fixed displays such as numbers, letters, symbols, etc. can be distinguished brightly and clearly. . Furthermore, it has the advantage of being able to display fixed images with the same accuracy as the dynamic display of liquid crystals.

Hereinafter, the present invention will be explained according to examples.

Example 1 A display electrode plate was prepared by patterning a transparent conductive film of indium oxide on a glass substrate. The patterning is performed by fixed displays 21a and 21 shown in FIG.
b,...21h and operation display sections 22a, 22b,
...It was carried out so as to form letters or numbers of 22e. Then, on top of this, ``ethyl orthosilicate''
60'' (manufactured by Nippon Colcoat Co., Ltd.) was applied and then heat treated to form a silicon dioxide film. The orientation treatment was carried out by rubbing the silicon dioxide film in one direction with a cotton cloth.

On the other hand, a common electrode plate was created by patterning a transparent conductive film of indium oxide to serve as a common electrode on a glass substrate. Next, a silicon dioxide coating was provided by the same method as the coating on the display electrode plate, and then an alignment treatment was performed.

In order to form the sealing material shown at 24 in Figure 2, glass frit is coated along the frame of the common electrode plate by screen printing, and then the common electrode plate and the display electrode plate are coated with liquid crystal molecules. After arranging the glass frits to face each other so as to be horizontally oriented, a heat treatment was performed to melt the glass frit, and cells were assembled. Thereafter, a liquid crystal of "Nematic Phase 1565TNC Crystal" (manufactured by Merck & Co., West Germany) in which the anthraquinone dye of the dichroic dye (t) mentioned above is dissolved is injected, and the injection port is sealed with a sealing material. It stopped. A guest-host type display device was then created by arranging the polarizing film at a predetermined position.

A DC voltage of 50 V was applied for 5 hours between the conductive film forming the fixed display section of the guest-host type display device thus prepared and the common electrode. As a result, even if the applied voltage is removed, the liquid crystal molecules do not become horizontally aligned again, and are in a permanent vertically aligned state.
Fixed display characters that appeared cloudy were formed at b, . . . 21h.

The opaque numbers on the operation display were formed by applying a driving voltage (DC 5V) between the conductive film forming the operation display sections 22a, 22b, . . . 22e and the common electrode.

As is clear from this example, if a high voltage is applied for a certain period of time or more, even when the applied voltage is O, the first
It can be seen that the alignment state of liquid crystal molecules shown in 18a in the figure can be obtained, and that this alignment state can be effectively used for fixed display.

Example 2 A fixed display was formed in the same manner as in Example 1, except that polyparaxylylene was used instead of the silicon dioxide alignment film used in Example 1, and the same results were obtained. was gotten.

Example 3 The liquid crystal used in the previous Example 1 was replaced with a mixed liquid crystal of the biphenyl liquid crystal 2, ester liquid crystal 4, azoxy type liquid crystal 3, Schiff type liquid crystal 1, and cyclohexane type liquid crystal 5, respectively. Example 1
When a fixed display was formed using the same method as above, similar results were obtained.

Example 4 A fixed display was formed on the guest-host liquid crystal display device used in Example 1 using the same method, except that the applied voltage was 200 V AC and the current supply time was 10 hours. The results were obtained.

Example 5 The same method as in Example 1 was used except that the dichroic dye (i), which is an azo dye, was used instead of the anthraquinone dichroic dye used in Example 1. When a fixed display was formed, similar results were obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a guest-host type liquid crystal display device of the present invention, and FIG. 2 is a plan view thereof. Third
The figure is a diagram showing the relationship between applied voltage and energization time when forming a fixed display according to the present invention. DESCRIPTION OF SYMBOLS 11, 16... Substrate, 12a... Conductive coating of fixed display part, 12b... Conductive coating of operation display part, 1
3, 14... Aligning agent or alignment film, 15... Conductive film serving as a common electrode, 17... Liquid crystal layer with positive dielectric anisotropy in which dichroic dye is dissolved, 18a... Even if the applied voltage is removed Liquid crystal molecules vertically aligned in a state where they will not be horizontally aligned again, 18b... horizontally aligned liquid crystal molecules, 19a... vertically aligned dichroic dye, 19b... horizontally aligned dichroic dye, 21a, 21b,...21h...Fixed display section, 2
2a, 22b,...22e...operation display section, 23...electrode terminal, 24...sealing material, 25...sealing material, 31...
A curve plotting the applied voltage and energization time required to vertically align the material so that it will not become horizontally aligned again even if the applied voltage is removed.

Claims (1)

[Scope of Claims] 1. A guest liquid crystal having a dichroic dye dissolved therein and having a positive dielectric anisotropy sandwiched between two horizontally aligned substrates, at least one of which has a transparent conductive film. A host-type liquid crystal device, characterized in that it has a fixed display pattern formed by vertically aligning the liquid crystal by applying a voltage higher than the driving voltage of the display device to the liquid crystal for a certain period of time. type liquid crystal device. 2. The guest-host liquid crystal device according to claim 1, wherein the dichroic dye is an anthraquinone dye. 3. The guest-host liquid crystal device according to claim 1, wherein the dichroic dye is an azo dye. 4. The guest-host type liquid crystal device according to claim 1, wherein the liquid crystal is a nematic liquid crystal. 5. The guest-host type liquid crystal device according to claim 4, wherein the liquid crystal is an azoxy-type nematic liquid crystal. 6. The guest-host type liquid crystal device according to claim 4, wherein the liquid crystal is a Schiff-type nematic liquid crystal. 7. The guest-host liquid crystal device according to claim 4, wherein the liquid crystal is a biphenyl nematic liquid crystal. 8. The guest-host type liquid crystal device according to claim 4, wherein the liquid crystal is an ester type nematic liquid crystal. 9. The guest-host type liquid crystal device according to claim 4, wherein the liquid crystal is a cyclohexane type nematic liquid crystal. 10. The guest-host liquid crystal device according to claim 1, wherein the alignment state before voltage application is horizontal alignment. 11. The guest-host liquid crystal device according to claim 9, wherein the horizontal alignment is a twisted alignment.