JPH05313143A - High-molecular polymer and liquid crystal display element formed by using the same - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display element which has high long-term reliability and does not generate unequal colors, etc., by using a high-molecular polymer exhibiting dichromaticity according to the external force impressed thereto. CONSTITUTION:The respective surfaces of the oriented films 7 of two sheets of substrates 5, 6 are disposed to face each other to form a fixed cell and a mixture composed of the high-molecular polymer 1 exhibiting the dichromaticity according to the external force impressed thereto and a low-molecular liquid crystal 2 is sealed into the spacing thereof. Side chain parts 11 exhibiting the dichromaticity orient in nearly the same direction as the orientation direction of the low-molecular liquid crystal 2 to be mixed and dissolved together and, therefore, the display element appears colored. The low-molecular liquid crystal 2 orients in an electric field direction and the side chain parts 11 exhibiting the dichromaticity orient in the electric field direction as well when a voltage is impressed between the electrodes. Consequently, the degree of coloring decreases and the display element appears transparent. The degree of coloring is controlled by the presence or absence of the electric field in such a manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device applied to a liquid crystal display or a projector, and more particularly to a so-called guest-host type liquid crystal display device using a dichroic polymer and a driving method thereof.

[0002]

2. Description of the Related Art Conventionally, many display modes have been proposed for guest-host type liquid crystal display devices using a dichroic dye.
Specifically, there were a white Taylor type, a phase transition type and the like. For detailed operation principles of these, see, for example, “Liquid Crystal Device Handbook, edited by Japan Society for the Promotion of Science, No. 142.
Committee Publishing Office Nikkan Kogyo Shimbun "or" LCD
It is described in detail in the editors such as Mitsuharu Okano and Shunsuke Kobayashi. Basically, the display is performed by using the anisotropy of the absorption coefficient of the low molecular weight dichroic dye which is added and dissolved in the low molecular weight liquid crystal. Since the low molecular weight dichroic dye has a rod-shaped structure, when dissolved in liquid crystal, the dye molecule has the property of being aligned parallel to the liquid crystal molecules. When the orientation direction of liquid crystal molecules is changed by applying an electric field, the orientation of dye molecules also changes accordingly, resulting in a change in the absorption coefficient,
The coloring state changes.

[0003]

However, the conventional guest-host type liquid crystal display device using the low molecular weight dichroic dye is as follows.
Since a low-molecular dichroic dye must be used, the solubility in the liquid crystal is limited to a low concentration and contrast cannot be obtained. The solubility of the dye changes depending on the temperature, and thus the low-molecular dichroic dye dissolved in the liquid crystal at high temperature 2 There are problems such as color dyes that deposit at low temperatures and affect long-term reliability.Ordinary dichroic dyes are a mixture of several low molecular weight dyes, but the dyes separate in the liquid crystal resulting in color unevenness. I had.

[0004]

The present invention shows a nematic or cholesteric liquid crystal state at a specific temperature,
It is characterized by containing a polymer having a double bond site showing dichroism in the side chain between two substrates, and as the double bond site showing the dichroism, an azo dye, an anthraquinone dye,
A naphthoquinone dye, a perylene dye, an azomethine dye or a quinophthalone dye is desirable. The polymer may include a chiral side chain or a liquid crystal side chain. The rotatable side chains of dichroic side chains are arranged substantially parallel to the main chain of the polymer. The liquid crystal and the above polymer are mixed and mixed between the two substrates, and the liquid crystal has a
A color dye and a chiral component may be mixed. The liquid crystal and polymer mixture is driven by static drive, time division drive, or a two-terminal or three-terminal element.

[0005]

【Example】

(Embodiment 1) FIG. 1 shows a vertical sectional view of a display device used in this embodiment. In the figure, 5 and 6 are substrates having a flat surface, and 3 and 4 have electrodes formed on the surface by a vapor deposition method or the like. A 5% solution of polyimide was spin-coated on this electrode as an alignment film 7 at 2000 rpm.
These substrates were fired at 150 ° C., and then the surface of the alignment film was rubbed in one direction by a rotary rubbing method to perform rubbing treatment. In this example, the rubbing directions were set to be substantially parallel when the two substrates were combined.
A cell was made by fixing the orientation films of the two substrates so that their surfaces face each other so as to have a cell thickness of 10 μm.

As a polymer showing dichroism in the gap

[0007]

[Chemical 1]

A mixture of the high molecular weight polymer 1 represented by 1 and the low molecular weight liquid crystal 2 in the ratio of 3:97 (weight ratio) was enclosed. When a voltage is not applied to the electrodes 3 and 4, the side chain portion showing dichroism is aligned in the same direction as the alignment direction of the low-molecular liquid crystal mixed and dissolved together, so that it is colored as a display element. Visible (Fig. 1-a). When a voltage is applied between the electrodes, the low-molecular liquid crystal is aligned in the electric field direction, and the side chain portion showing dichroism is also aligned in the electric field direction. As a result, the display element has a reduced degree of coloring and appears almost transparent (FIG. 1-b). In this way, it becomes possible to control the degree of coloring depending on the presence or absence of an electric field. The contrast at 100 ° C. was 1: 3.

When conventional low-molecular dichroic dyes were used, when stored at low temperature, an amount of the dyes exceeding the solubility of the dyes was deposited and the display quality was remarkably deteriorated. Since it has a liquid crystal structure by itself, it has good compatibility with low-molecular liquid crystals, and because it has a side chain, it does not precipitate even if left at low temperature.

The dichroic double bond site of the dichroic high molecular polymer used herein includes azo dyes, anthraquinone dyes, naphthoquinone dyes, perylene dyes, azomethine dyes or quinophthalone dyes. Those having a structure such as a pigment are desirable.

The alignment film used here is not limited to polyimide, but may be an oblique vapor deposition method, polyvinyl alcohol or the like as long as it has a force to align the liquid crystal. Furthermore, even rubbing the substrate surface is effective. In addition, the alignment treatment is effective even with a single-sided substrate.

In addition to the method shown here, any method can be used for the alignment treatment as long as the liquid crystal is aligned, such as the oblique vapor deposition method and the LB film method.

Further, in order to make the display easier to see, a polarizing plate, a reflecting plate, a light source, etc. may be installed on one side of at least one substrate.

(Example 2) In this example, a case where the dichroic polymer is a polymer having both liquid crystalline side chains and chiral side chains is shown.

In the same manner as in Example 1, the cell thickness is 10 μm.
m cells were created.

As a polymer showing dichroism in the gap

[0017]

[Chemical 2]

A high molecular polymer having a liquid crystalline side chain 12, represented by 12 and a chiral side chain 13, represented by 1 (b) and a low molecular weight liquid crystal, 2 at a ratio of 5:95 (weight ratio). The mixture was sealed. Further, in order to make the display easier to see, a polarizing plate, 8, and a reflecting plate, 9 were installed on one side of one substrate. When no voltage is applied to the electrodes, the side chains that exhibit dichroism are aligned in the same direction as the alignment direction of the low-molecular liquid crystal that is mixed and dissolved together. It is visible (Fig. 2-a). When a voltage is applied between the electrodes, the low-molecular liquid crystal is aligned in the electric field direction, and the side chain portion showing dichroism is also aligned in the electric field direction. As a result, the display element has a reduced degree of coloring and appears almost transparent (FIG. 2-b). In this way, it becomes possible to control the degree of coloring depending on the presence or absence of an electric field. At 120 ° C. the contrast was 1: 4.

The dichroic double bond site of the dichroic high molecular polymer used herein includes azo dyes, anthraquinone dyes, naphthoquinone dyes, perylene dyes, azomethine dyes or quinophthalone dyes. Those having a structure such as a pigment are desirable.

The alignment film used here is not limited to polyimide, and any film having a force to align the liquid crystal, such as an oblique vapor deposition method or polyvinyl alcohol, may be used. Furthermore, even rubbing the substrate surface is effective. In addition, the alignment treatment is effective even with a single-sided substrate. When the surfaces of the substrates on both sides are subjected to the alignment treatment, the mutual orientation treatment directions may be related to the content of the chiral component, so that it is necessary to optimize each direction.

In addition to the method shown here, any method can be used for the alignment treatment, such as the oblique vapor deposition method and the LB film method as long as the liquid crystal is aligned.

(Embodiment 3) This embodiment shows a case where a dichroic dye and a chiral component are added to a low molecular weight liquid crystal.

Low molecular weight liquid crystal, dichroic dye for 2, 1% by weight of congo red as low molecular weight liquid crystal for 11, chiral component as CB-15 for 0.1% of low molecular weight liquid crystal. Wt% was added respectively. The low-molecular liquid crystal mixture thus obtained was mixed with the dichroic high molecular weight polymer 1 used in Example 1 at a ratio of 98: 2 (weight ratio). A display element was assembled in the same manner as in Example 1 except for the above. A slightly colored element was obtained. 10
The contrast at 0 ° C. was 1: 2.5. The characteristics are not so good, but it is expected that the characteristics will be further improved by optimizing the addition amount of the dichroic dye. When the surfaces of the substrates on both sides are subjected to the alignment treatment, the mutual orientation treatment directions may be related to the content of the chiral component, so that it is necessary to optimize each direction.

(Embodiment 4) This embodiment shows a case where the above-mentioned display element is combined with an MIM element as a two-terminal element. The MIM element is an active element basically composed of metal / insulator / metal. FIG. 4 shows a cross-sectional view of the display body showing this embodiment. A typical MIM device stacks metal / insulator / metal layers vertically to form a device.

Next, a method of forming the element portion will be described.
A tantalum film 15 is formed on the substrate by vapor deposition, sputtering, etc., and tantalum is selectively etched by a photoetching method. Next, tantalum was oxidized by an anodic oxidation method to form tantalum oxide (insulator) 16, and chromium 17 was formed thereon to complete the MIM element. Further, a polyimide film was applied as an alignment film 7 on the film, baked, and subjected to an alignment treatment. For this alignment treatment, not only a method of combining an alignment film and rubbing but also oblique vapor deposition or the like can be used. The element substrate thus prepared and the counter substrate were combined, fixed to a cell thickness of 10 μm, and the periphery was molded.

A mixture of a polymer and a liquid crystal was filled in the voids thus obtained in the same manner as in Example 2 to prepare a display device.

When no voltage was applied between the electrodes, the element was colored, but when an alternating electric field of 100 Hz and 10 V was applied at 80 ° C., the element became almost transparent.

(Embodiment 5) This embodiment shows a case where the above-mentioned display element is combined with a lateral MIM element as a two-terminal element. The lateral type MIM element is
Basically, the same metal / metal as the normal MIM element shown above
It is an active element composed of an insulator / metal. Figure 5
A sectional view of a display body showing this embodiment is shown in FIG. The difference from the fourth embodiment is that the normal MIM device shown in the fourth embodiment forms a device by stacking metal / insulator / metal layers in the direction perpendicular to the substrate, whereas in the present embodiment, the substrate is formed on the substrate. It is a point that metal / insulator / metal layers are stacked almost in parallel to form a lateral type element. By adopting the lateral type MIM element, the parasitic capacitance of the element itself can be greatly reduced, so that the direct current component applied to the liquid crystal can be significantly reduced, and the display image quality and reliability are greatly improved. To do. Next, a method of forming the element portion will be described. A tantalum film 15 is formed on the substrate by vapor deposition, sputtering, etc., and tantalum is selectively etched by a photoetching method to form a taper shape. Next, tantalum oxide was converted into tantalum oxide 16 by an anodizing method, and then a chromium layer was formed to complete a lateral MIM element. Further, a polyimide film was applied as an alignment film 7 on the film, baked, and subjected to an alignment treatment. For this alignment treatment, besides the method of combining an alignment film and rubbing, only rubbing without an alignment film or oblique vapor deposition can be used. The counter substrate was subjected to orientation treatment. A cell thickness of 1
It was fixed to 0 μm and the periphery was molded. A mixture of the polymer and the liquid crystal used in Example 1 was filled in this gap.
An element colored slightly blue was obtained. It is colored when no voltage is applied between the electrodes, but 100H at 80 ° C
When an alternating electric field of z and 10v was applied, the device became almost transparent.

(Embodiment 6) In the present invention, the case where the above-mentioned display element is used as a three-terminal element and a TFT element is combined will be described. The TFT element is an active element composed of a drain / gate / source phase. FIG. 6 is a sectional view of a part of the display body showing the present embodiment. The basic structure of the element part is the same as that of the fourth embodiment.

A method of forming the element portion will be described. The difference from the fourth or fifth embodiment is that a TFT element substrate is used. TFT element on the substrate by the usual method, 1
9 was formed. An alignment film 7 was formed on this element substrate and subjected to alignment treatment. For this alignment treatment, an oblique vapor deposition method or the like can be used as well as a method of combining an alignment film and rubbing. Regarding the counter substrate, only electrodes were formed and no special alignment treatment was applied. Next, these two substrates were combined, fixed so that the cell thickness was 12 μm, and the periphery was molded.

An element was prepared in this gap by the same method as that illustrated in Example 2. It is colored when no voltage is applied between the electrodes, but at 80 ° C, 100 Hz, 1
When an AC electric field of 0 V was applied, the device became almost transparent.

In this embodiment, a display body having 20 scanning lines and 60 signal lines was prototyped, but a uniform display could be obtained on the entire screen. As described above, by combining with the TFT element, application to a display element having a high density and large display capacity has become possible.

(Embodiment 7) In this embodiment, a case is shown in which the above-mentioned display element and a FEMT element as a composite two-terminal element are combined. FEMT element is metal / ferroelectric /
It is an active element composed of a metal layer and provided with a ferroelectric layer between the electrodes for driving. FIG. 7 shows a cross-sectional view of the display device showing the present embodiment. In the figure, after forming an aluminum electrode 22 on the surface of a flat substrate 6, a ferroelectric layer 21 is formed, and further ITO is formed as a pixel electrode 20 to form a FEMT.
The device was formed. An alignment film 7 was formed on this substrate and an alignment treatment was performed. Regarding the counter substrate, an electrode was formed and an alignment treatment was performed. Next, these two substrates were combined so that the orientation directions were substantially parallel, fixed so that the cell thickness was 8 μm, and the periphery was molded.

An element was formed in this gap by the same method as that illustrated in Example 2. It is colored when no voltage is applied between the electrodes, but at 80 ° C, 100 Hz, 1
When an AC electric field of 0 V was applied, the device became almost transparent.

In this embodiment, the electrode 22 and the ferroelectric substance 21 are used.
Also, the portion formed by the pixel electrode 20 becomes an active device portion for driving liquid crystal, and a ferroelectric layer is used, and is generally called a FEMT element.

The ferroelectric layer 21 is made of TiBaO ₃ , PbT.
In addition to perovskite type ferroelectrics such as iO ₃ and WO ₃ , Roche salt type ferroelectrics, polyvinylidene fluoride and its copolymers, copolymers with polyvinylidene fluoride tetrafluoroethylene and vinylidene cyanide A polymer ferroelectric such as a copolymer with vinyl acetate or a copolymer of polyvinylidene fluoride and refluoroethylene is used. Further, the connection relationship of the three layers of electrode / ferroelectric material / electrode is not limited to that formed in parallel on the planar substrate as shown in FIG. 7, and the switching function utilizing the remanent polarization of the ferroelectric layer 20 is provided. Any connection relationship that can be exerted will do. For example, the ferroelectric layer may be sandwiched between conductive electrodes in a sandwiched layer structure.

[0037]

INDUSTRIAL APPLICABILITY As described above, the present invention is a basic technique in which a high molecular polymer exhibiting dichroism is applied to a display device to expand the possibility of application. At the same time, the TN type display system,
Alternatively, it can be made easier to see by combining with a GH type display system.

In addition, TFT element, MIM element, FEMT
A display body capable of a large display capacity has also been made possible by combining with an active matrix type display element such as an element.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross section of a display element of the present invention.

FIG. 2 is a schematic view showing a cross-sectional view of a display device using a dichroic polymer having a liquid crystal side chain and a chiral side chain.

FIG. 3 is a schematic diagram showing a cross-sectional view of a display device in which a dichroic dye and a chiral component are mixed in a low molecular liquid crystal.

FIG. 4 is a schematic view showing a cross section of a display element according to the present invention using a MIM element as a driving element.

FIG. 5 is a schematic view showing a cross section of a display device according to the present invention in which a lateral MIM device is used as a driving device.

FIG. 6 is a schematic view showing a cross section of a display element according to the present invention using a TFT element as a driving element.

FIG. 7 is a schematic view showing a cross section of a display element according to the present invention using a FEMT element as a driving element.

[Explanation of symbols]

1 high-molecular polymer exhibiting dichroism 1 (b) high-molecular polymer exhibiting dichroism containing a liquid crystalline side chain and a chiral side chain 2 low-molecular liquid crystal 3, 4 electrode 5, 6 substrate 7 alignment film 11 Side chains exhibiting dichroism 12 Liquid crystal side chains 13 Chiral side chains 14 Low molecular weight dichroic dyes 15 Low molecular weight chiral components 16 Electrodes such as tantalum 17 Tantalum oxide 18 Chromium 19 TFT element 20 ITO 21 Ferroelectric 22 Aluminum electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G02F 1/136 505 9018-2K 1/137 101 7348-2K

Claims (16)

[Claims] 1. A high-molecular polymer which exhibits dichroism in response to an applied external force. 2. The high molecular polymer according to claim 1, which is in a liquid crystal state at a specific temperature. 3. The high-molecular polymer according to claim 1, which has a double bond site showing dichroism in a side chain. 4. The high molecular polymer according to claim 1, 2, or 3, wherein a rotatable axial direction of a side chain exhibiting dichroism is substantially parallel to an axial direction of the main chain. 5. The high-molecular weight dye according to claim 4, wherein the side chain exhibiting dichroism contains an azo dye, an anthraquinone dye, a naphthoquinone dye, a perylene dye, an azomethine dye or a quinophthalone dye. Molecular polymer. 6. The high molecular polymer according to claim 4, wherein the side chain contains a chiral side chain. 7. The high molecular polymer according to claim 4, wherein the side chain contains a liquid crystalline side chain. 8. A liquid crystal and a high-molecular polymer exhibiting dichroism are mixed or compatibilized and held between two substrates, and the high-molecular polymer exhibiting dichroism is a side chain exhibiting dichroism. A liquid crystal display device using a high molecular polymer, wherein the rotatable axial direction of is substantially parallel to the axial direction of the main chain of the high molecular polymer. 9. The polymer according to claim 8, wherein the polymer mixed with the liquid crystal is the polymer showing dichroism as set forth in claim 5. Liquid crystal display device. 10. A liquid crystal display device using the high molecular polymer according to claim 8 or 9, wherein a chiral component is mixed in the liquid crystal. 11. A liquid crystal display device using the high molecular polymer according to claim 8, wherein the dichroic dye is mixed in the liquid crystal. 12. A liquid crystal display using a polymer, comprising a display device in which a liquid crystal and a polymer exhibiting dichroism are mixed, and an electrode for statically driving or time-divisionally driving the display device. element. 13. A liquid crystal display device using a polymer, comprising a display device in which a liquid crystal and a polymer showing dichroism are mixed, and a two-terminal device or a three-terminal device for driving the display device. .. 14. A liquid crystal display device using a polymer according to claim 13, wherein the two-terminal device is composed of a metal / insulator / metal layer. 15. A liquid crystal display device using a polymer according to claim 13, wherein the two-terminal device is composed of a metal / ferroelectric / metal layer. 16. A liquid crystal display device using a polymer according to claim 13, wherein the 3-terminal device is composed of a drain / gate / source layer.