JPS6231327B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a guest-host type liquid crystal display device having a fixed color display of numbers, characters, symbols, etc. within the 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 mainly 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 negative dielectric anisotropy in a guest-host type display device, positive color display is possible, so it has been widely used in the fields of watches and calculators in recent years.

Up to now, it has often been necessary to form fixed displays such as numbers, characters, symbols, etc. within the 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. A method is known in which the formation is made by, for example, 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. The disadvantage is that 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.
Also, fixed displays cannot be colored.

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 plate, so the fixed display appears to be floating. There are drawbacks to this.

The inventor of the present invention, after conducting extensive studies in view of the various drawbacks mentioned above, has discovered a guest-host type liquid crystal display device that has a fixed color display of numbers, characters, symbols, etc. with the same accuracy as the operation display of a liquid crystal. Ta.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a guest-host liquid crystal display having a fixed color display within the liquid crystal display with the same accuracy as the dynamic display.

Another object of the present invention is to provide a guest-host type liquid crystal display device having a fixed display of clearly colored numbers, characters, symbols, etc. within the liquid crystal display.

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

Such an object of the present invention is to apply a voltage to a portion of the liquid crystal display that forms a fixed display at a level higher than that which prevents the liquid crystal display from returning to the vertical alignment or tilted alignment before applying the voltage again. This is achieved by horizontally aligning the molecules.

Although completely unexpected, the present inventor discovered that a liquid crystal with negative dielectric anisotropy that is aligned vertically or tilted with respect to two electrode plates is exposed to a direct current or a voltage higher than the drive voltage of the display device. It has been found that when an alternating current voltage is applied for a certain period of time, the alignment state returns to horizontal alignment without vertical alignment or tilt alignment. The present invention was made based on this unexpected alignment state of liquid crystals.

As a method for forming a fixed color display in a liquid crystal display based on the present invention, at least one electrode plate on which a conductive pattern such as numbers, letters, symbols, etc. is formed is prepared, and a dichroic dye is mixed with this electrode plate. After forming a positive guest-host type liquid crystal display device by assembling cells using predetermined materials such as melted liquid crystal, a voltage higher than the driving voltage of the display device is applied between the conductive pattern and one electrode. Examples include a method of applying a DC or AC voltage for a certain period of time or more. FIG. 1 shows a cross-sectional view of a guest-host type liquid crystal display device having a fixed color 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 negative dielectric anisotropy in which a dichroic dye is dissolved. 12a is a number for forming a fixed display,
It is a conductive film with patterns such as letters and symbols formed on it. The conductive coating 12a is applied to liquid crystal molecules that were vertically aligned or tilted before voltage application.
When an applied voltage higher than the level at which the vertical or tilted orientation does not occur again even if the applied voltage between and 15 is removed, the horizontally oriented double A fixed color liquid crystal pattern is formed by the colored dye molecules 19a and the liquid crystal molecules 18a. Therefore,
18a and 19a are liquid crystal molecules that are horizontally aligned (hereinafter referred to as "permanently horizontally aligned") so that they will not be vertically aligned or tilted again even if the applied voltage is removed. Shows the molecules of a colored dye. Reference numeral 12b denotes a conductive coating for forming a liquid crystal operation display. When a driving voltage is applied to the conductive coatings 12b and 15, liquid crystal molecules 18b that are vertically aligned or tilted are aligned.
and dichroic dye 19b are converted into horizontal orientation to form a working color display pattern. When this driving voltage is removed, the horizontally aligned liquid crystal and dichroic dye molecules are returned to the vertical or tilted alignment, and the operating color display pattern also disappears.
Although the driving voltage cannot be specified depending on the type of liquid crystal used, it is generally at or below the saturation voltage, and is approximately 1V to 15V. 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 liquid crystal display device having a fixed color display according to the invention within the liquid crystal display. 21a, 21b, . . . 21h are fixed display portions in which liquid crystal molecules 18a and dichroic dye 19a are formed, respectively, which are permanently aligned horizontally in FIG. 1, and 22a, 22b, .
The operation display section is formed by horizontally aligning the liquid crystal molecules 18b and the dichroic dye 19b, which are vertically aligned or tilted in FIG. 1, by applying a driving voltage. 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 etc. can be used.

The voltage required to form the permanently horizontally aligned liquid crystal molecules 18a and the dichroic dye 19a shown in FIG. 1 depends on the type of liquid crystal and the type of alignment agent (film) used. However, it cannot be determined uniquely because the interaction on the alignment force of the liquid crystal 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. FIG. 3 shows the above relationship when an electrode plate coated with P-methoxybenzoic acid as an alignment agent and paraazoxyanisole in which an anthraquinone dye is dissolved are used as a liquid crystal. Curve 3 shown in Figure 3
1 was prepared by plotting the DC current time required to form the liquid crystal molecules 18a and the dichroic dye 19a, which were permanently aligned horizontally 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 current application time can be selected according to conditions suitable for the alignment agent and liquid crystal used.

Examples of liquid crystals with negative dielectric anisotropy that can be used in the present invention include nematic liquid crystals shown below.

Azoxy type benzylidenearyne type In addition to these liquid crystals, cholesteric liquid crystals and smectic liquid crystals can also be used. A suitable alignment agent can be added to these liquid crystals. Examples of alignment agents include organic chlorosilane, organic alkoxysilane, organic silanol, fatty acid, fatty acid ester, 4-aminobenzoic acid, 4-butylbenzoic acid, 4-methoxybenzoic acid, p-benzylidene aminobenzoic acid, and p-carboxyphenol. ,
3,5-di-hydroxybenzoic acid, 3,4,5-
Examples include tri-hydroxybenzoic acid, trifluoromethyltrimethoxylan, and fluorine-based surfactants. Moreover, these alignment agents can also be used by forming a film on the electrode plate.

The dichroic dye used in the present invention can be selected from a wide variety of dyes. Specifically, the following can be mentioned.

Among these dichroic dyes, anthraquinone dyes are particularly preferred.

The electrode plate used in the liquid crystal display device of the present invention is a substrate on which at least one side is provided with a transparent conductive film (for example, indium oxide, tin oxide, indium oxide-tin oxide (tin oxide: 0.1 to 40% by weight), etc.) (glass, plastic, etc.) is preferably used. Furthermore, examples of the opaque conductive film used in the present invention include aluminum, gold, silver, copper, and lead.

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

Cell assembly can be performed by arranging two electrode plates to face 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,
49-79542, liquid crystal with dichroic dye dissolved therein is injected, and then the injection port is sealed with epoxy adhesive or the like to create a guest-host type liquid crystal display device. can be created.

Polarizing films that can be used in the guest-host 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 in which dichroic dyes are arranged in a certain direction in polyvinyl alcohol. polarizing film,
Examples include a polyvinylene polarizing film with a polyene structure obtained by intramolecularly dehydrochlorinating polyvinyl chloride, and a metal polarizing film.

According to the present invention, the floating appearance of a fixed color display can be eliminated, and the fixed color display of numbers, characters, 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 was created by patterning a transparent conductive film of indium oxide on a glass substrate. The patterning includes fixed displays 21a, 21b, and
...21h and operation display sections 22a, 22b, ...2
2e letters or numbers were formed.
Next, p-methoxybenzoic acid was applied thereon and dried to form an alignment agent film.

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 film of an alignment agent was formed by the same method as that used to form the film on the display electrode plate.

To form the sealing material shown at 24 in Figure 2, glass frit is applied along the frame of the common electrode plate by screen printing, and then the common electrode plate and the display electrode plate are placed facing each other. After that, a heat treatment was performed to melt the glass frit, and cells were assembled. Thereafter, the liquid crystal of para-azoxyanisole of the exemplified compound No. (2) in which the exemplified dichroic dye (t) is dissolved is injected from the injection port, and the injection port is sealed with a sealing material. did. A guest-host type display device was then created by arranging the polarizing film at a predetermined position. The molecules of this liquid crystal were tilted.

A DC voltage is applied between the conductive film that forms the fixed display part of the display device created in this way and the common electrode.
40V was applied for 5 hours. As a result, even if the applied voltage is removed, the liquid crystal molecules do not assume the tilted orientation again, and are in a permanent horizontal alignment state, and are fixed in the fixed display areas 21a, 21b, ... 21h in Fig. 2. Colored characters were formed.

The numbers on the operation display are the operation display parts 22a, 22.
b, . . . 22e were formed by applying a driving voltage (DC 5 V) between the conductive coating 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 0, 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 utilized for color fixed display.

Example 2 Instead of the p-methoxybenzoic acid alignment agent used in Example 1, C ₈ F ₁₇ SO ₂ NHCH ₂ CH ₂ N
A fixed color display was formed in the same manner as in Example 1, except that (CH ₃ ) ₃ ·I fluorine surfactant was used, and similar results were obtained.

Example 3 Except for using the N-(4-methoxybenzylidene)-4-butylaniline liquid crystal of Compound No. 3 in place of the liquid crystal used in Example 1,
When a fixed color display was formed by the same method as in Example 1, similar results were obtained.

Example 4 A fixed color display was formed on the guest-host type liquid crystal display device used in Example 1 using the same method, except that the applied voltage was 100 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. Similar results were obtained when a fixed color display was formed.

[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... Layer of liquid crystal with negative dielectric anisotropy in which dichroic dye is dissolved, 18a... Even if the applied voltage is removed Liquid crystal molecules horizontally aligned in a state where they are not vertically aligned or tilted again, 18b...Liquid crystal molecules vertically aligned or tilted, 19a...Horizontally aligned dichroic dye molecules, 19b...vertically Oriented or tilt-oriented dichroic dye molecules, 21a, 21b,...2
1h...Fixed display section, 22a, 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 horizontally align the material so that it will not be vertically aligned or tilted 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 negative dielectric anisotropy sandwiched between two vertically 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 horizontally 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 benzylideneaniline type nematic liquid crystal. 7. The guest-host liquid crystal device according to claim 1, wherein the alignment state before voltage application is vertical alignment or tilted alignment.