JPH052210B2 - - Google Patents

Description

[Detailed Description of the Invention] "Field of Application of the Invention" This invention relates to a liquid crystal device, and includes:
By providing a liquid crystal display device using a liquid crystal material and a ferroelectric material (hereinafter referred to as FE), it is possible to make the display part of a microcomputer, word processor, television, etc. thinner. The present invention particularly relates to a liquid crystal display device that is capable of displaying gradations in a substantially gray scale (gray lightness) and full color display.

``Prior Art'' For solid-state display panels, a system in which each picture element is controlled independently is effective for large-area displays. Conventionally, such panels use dual-frequency liquid crystals, such as twisted nematic liquid crystals (hereinafter referred to as TN liquid crystals), and have 400 elements in the horizontal direction and 200 elements in the vertical direction.
A display device using a multiplexing drive method in a simple matrix configuration of format size is known.

However, when such a TN liquid crystal is used, its frequency response characteristic is on the order of milliseconds and is extremely slow. For this reason, it has been virtually impossible to create 640×400 segments or more.

Furthermore, in a display device using such a TN,
It was virtually impossible to produce the gray scale (lightness of gray) that is essential for full-color printing because the peripheral circuitry was complicated.

"Problems to be Solved by the Invention" When using such a TN liquid, (1) Since the information on the liquid crystal is volatile, a signal must be given to repeatedly maintain "0" and "1". . For this reason, even if it were to produce the gray scale required for full color, the peripheral circuitry would become extremely complex.

(2) On the other hand, ferroelectric liquid crystals are known. However, conventional liquid crystal devices using FLC improve the contrast ratio of "0" and "1" by making a large area into one domain (region or range with the same characteristics). It was something like that.

For this reason, it was considered theoretically impossible to produce grayscale using this FLC.

However, the present invention aims to obtain a substantially gray scale using such FLC.

"Means for Solving the Problem" In order to solve the problem, the present invention provides a guest-host type or birefringence type liquid crystal using a ferroelectric liquid crystal (referred to as FLC) exhibiting a smectic C phase (SmC ^* ) as a liquid crystal material. It has the following configuration. Furthermore, this ferroelectric liquid crystal is made into a multi-domain (a large number of domains are present in the same region), preferably a micro-multidomain (a plurality of domains of at least 10 or more are present in one region, that is, a region constituting a pair of electrodes). ). Therefore, multiple electrodes are placed on the electrode within one pixel.
FE is interspersed or substantially interspersed. Then, if a sufficiently positive or negative voltage is applied to this FLC, it can display transmission, that is, "1", or non-transmission, that is, "0". However, if an intermediate voltage is applied, a certain domain will display "0" and another domain will display "1" within one pixel, resulting in a mixed state. As a result, a substantially gray (semi-transparent) state can be obtained. Therefore, the brightness can be controlled in proportion to the applied voltage, making it possible to create a gray scale.

That is, the distance between a pair of electrodes of a liquid crystal device is set to 4 μm or less, liquid crystal is mixed in an isotropic liquid crystal state into such a thin cell, the temperature is lowered, SmA is obtained, and bistable SmC ^* is obtained. be able to.
When a sufficiently large positive voltage is applied to such SmC ^* , the molecules align in one direction, and the tilt angle can generally be approximately +22.5 degrees (varies depending on the type of FLC). Conversely, if a sufficiently large negative voltage is applied, a temperature of approximately -22.5 degrees can be obtained.
These two states have non-volatility (bistability), which hardly changes even when the voltage is turned off, and they form an angle of about 45 degrees (cone angle) to each other.
Therefore, it has been found that two polarizing plates can achieve transmission and non-transmission of light, and a birefringent display device can be obtained.

If this voltage is again set to a positive intermediate voltage, the long axes of some of the liquid crystal molecules in the multiple domains in the pixel will be about +22.5 degrees, and the other parts will be about -22.5 degrees.
It will maintain the degree.

When applying this intermediate voltage, ferroelectric material (FE) is used interspersed in a part of the alignment treatment layer.
Alternatively, an organic ferroelectric material is used, which is a mixture of crystalline ferroelectric fine particles and an amorphous material (with a low degree of ferroelectricity) surrounding the ferroelectric particles. Such an organic ferroelectric material has its own Ec (critical voltage) and polarization as a ferroelectric material in areas where microcrystalline particles (approximately 100 to 1000 Å in size) are present. However, the amorphous region between the fine particles does not necessarily have a strong Ec. For this reason, by forming an organic ferroelectric thin film with a low average crystallinity as an alignment layer within one pixel,
The ferroelectric material can be substantially scattered (distributed in clusters) and provided on the electrode.

When a voltage is applied only to the portion where this ferroelectric material exists, FLC inversion occurs quickly. Therefore, a plurality of domains can be formed within one region or pixel according to the applied voltage.

That is, within one region or pixel, each domain has an area of S ₁ ...Si ...Sn, and each domain has a polarization P of P ₁ ...Pi ...Pn. Furthermore, if up to 1...m is inverted by an intermediate voltage Vm, the polarization P in this region is given by P=ΣSiPi/ΣSi. Then, this polarization P becomes a value smaller than when all domains are inverted by Vm, and one pixel can substantially obtain an intermediate polarization, that is, a transparent state, that is, a gray scale. This allows for substantial gradation and is extremely effective when applied to full-color displays.

For this purpose, the present invention consists of a pair of substrates (the light incident side is referred to as a counter substrate, and the reflective side is simply referred to as a substrate) and an electrode existing inside the substrates (the electrode on the light incident side is referred to as a counter electrode, and the inner side is simply referred to as an electrode). ), and further includes FLC and FE as an alignment layer sealed between them. Then, place the polarizing plate 1 on the incident light side.
A total of two sheets were disposed, one on the opposite side of the substrate and one on the opposite side of the substrate.

Particularly, in order to make the liquid crystal device of the present invention a reflective type, a reflective plate is disposed outside the polarizing plate. In the case of a transmission type, transmitted light was irradiated from the back side.

In that case, the path of the incident light goes through the first polarizing plate, the opposing substrate, the opposing electrode, the alignment layer, the FLC, the alignment layer, the electrode, the substrate, the second polarizing plate, the reflective surface, and is further reflected here. Take the opposite route. Furthermore, the present invention can be applied to the lower side of the electrode (substrate side) for large-area devices.
It is also possible to provide active elements connected in series to prevent crosstalk. That is, the present invention has attempted to combine a bidirectional nonlinear element (hereinafter referred to as NE) as an active element with an FLC to form a liquid crystal display device.

The present invention can further be applied to a liquid crystal display device in which a region constituted by a pair of electrodes is formed into a matrix and used as a display device. In this case, the size of the domain formed by the liquid crystal is smaller, preferably several tenths, of the area (hereinafter referred to simply as a pixel when applied to a display device) formed by opposing electrodes.

``Operation'' By using such a multi-domain FLC, (1) it becomes possible to achieve gray scale.

(2) Although it is technically impossible to create a monodomain at the A4 size level, it is possible to create a uniform FLC by using a multidomain and making the domain sufficiently small compared to the pixel size. Orientation becomes easier.

(3) To create a multi-domain structure, crystalline ferroelectric material is scattered in clusters on one or both of the alignment layers. By doing so, SS
(Surface Stabilized) Critical voltage of FLC (Ec)
can be set according to the amount of polarization of each ferroelectric material and according to the applied voltage. Therefore, the degree of gray scale can be freely created by controlling the size and amount of FE clusters for the alignment treatment layer.

Furthermore, by using non-linear elements and FLC, both of them operate synergistically, there is no crosstalk, the process is not very complicated, and since FLC is used, the viewing angle can be improved, making it possible to achieve a configuration that is very close to the ideal type. I found out that it can be achieved.

Therefore, since gray scale can be achieved for the first time with the present invention, R (red), G (green), B (blue)
A filter can be provided corresponding to each pixel. It was also found that by allowing light to pass through this filter, full-color display becomes possible, and that it can be put to practical use as a display for microcomputers and the like.

The present invention will be explained below with reference to Examples.

Example 1 FIG. 1 is an enlarged view of a part of a liquid crystal device using an integrated FE and FLC of the present invention. In the drawings, a transparent substrate such as Corning
A 7059 glass substrate 20 was used. One transparent electrode 23 was formed on this substrate by vacuum evaporation. Further, a light-transmitting conductive film is formed as the other counter electrode 26 on the glass substrate (counter substrate) 20'.
Then, alignment treatment layers 25' and 25 are provided inside the pair of electrodes 23 and the opposing substrate 26, with spacers (not shown) interposed therebetween. This alignment treatment layer 25',
25 are both ferroelectric materials in FIG. 2A. These sandwich the FLC (thickness: 1.5 μm) 3.

On the other hand, 25' is the crystal ferroelectric fine particle 2.
4 and an amorphous dielectric material 24', and the crystallization rate of this alignment layer was set to 20 to 50%. Then, the ferroelectric material 24 is scattered and the dielectric material surrounds the ferroelectric material 24, resulting in a substantially scattered configuration. For the other orientation treatment layer 25, a ferroelectric thin film of which 80% or more was crystallized was used.

A copolymer of VDF (vinylidene fluoride) and TrFE (trifluoroethylene) (component ratio of 50 or less/50 or more, for example 45/55) was used as the alignment treatment layer on the counter electrode 26. Add this to 10% by weight methyl
A solution diluted in ethyl ketone is applied by spin method, dried, and the final film thickness is approx.
It was formed to a thickness of 200 Å. Further, as the other alignment treatment layer 25, a VDF/TrFE copolymer (component ratio such that the crystallization rate is 70 to 100% and substantially all of the components are considered to be ferroelectric, for example, component ratio 52/48) is used,
Similarly, it was formed to a thickness of about 200 Å. The upper surface of one electrode 26 was an alignment film that was not subjected to rubbing treatment, and the alignment treatment layer on the other electrode 23 was formed with an organic compound ferroelectric thin film and subjected to rubbing treatment.
As an example of the rubbing process, a velvet cloth is rotated at 900 PPM using a rubbing machine, and its surface is
The substrate was formed by moving in the same direction at a speed of 2 m/min (peripheral area).

This organic ferroelectric material is polyvinylidene fluoride (PVDF) or vinylidene chloride (CH ₂ Cl ₂ ).
Alternatively, it may be used in combination selectively from polymers of vinylidene fluoride (VDF: CH ₂ CF ₂ ), trifluoroethylene (TrFE: CHF・CF ₂ ), and tetrafluoroethylene (CF ₂ CF ₂ ). good. _CH2C instead of vinylidene fluoride ( _{CH2CF2 )}
(CN ₂ ) may also be used.

Furthermore, a liquid crystal blend of S8 (octyl oxy benzylidene amino methyl butyl benzoate) and B7 or B8 was filled in this space. In addition to this, a liquid crystal material such as DOBAMBC or a blend of a plurality of liquid crystal materials may be filled. As an example,
Ferroelectrics1984 Vol.59 pp126-136J.W.
“Ferroelectrics” shown by Goodby et al.
Switching in the Titled Smectic Phase of R
-C-3-4-n-Hexyloxydenzylidene4'-
Am′no−(2−Chloropropyl)(innamate
(HOBA CPC)'', JP-A-59-98051 or JP-A-Sho
59-118744 may be used.

FIGS. 1B to 1D are examples of modified versions of FIG. 1A. In FIG. 1B, the first alignment layer consists of a ferroelectric thin film 25'-1 and a polyimide resin thin film 25'-2 coated thereon. and
FLC3 and FE25'-1 have a configuration in which they are substantially in contact with each other. A predetermined rubbing treatment was performed on this polyimide resin thin film 25'-2. The other alignment layer 25 was a ferroelectric thin film. In FIG. 1C, only one of the alignment layers 25' is FE. The other layer 25 was a polyimide resin thin film, and its upper surface was subjected to a prescribed rubbing treatment. FIG. 1D shows a non-ferroelectric thin film 25-2' provided on the FE 25'-1. Many embodiments other than these four types can be considered.

First multi-domain type liquid crystal pixel of the present invention
The characteristics obtained in Figure A are shown in Figure 2. As shown in the drawing, when +15V is applied to the electrode from 0V,
Starting from point 31, a curve 29 is obtained, leading to point 32. Furthermore, even if the voltage is set to 0V again, it passes through the curve 30 and reaches the point 31, where "1", that is, transmission is obtained. Also, if -15V is applied in this state, the state at point 32' is obtained via curve 29', and when 0V is applied again, point 31 is obtained.
"0", that is, a non-transparent state is obtained. Further, in the multi-domain orientation of the present invention, if, for example, +6V is applied and the voltage is set to 0V again, a point 31' is obtained from a point 32' via a curve 30', and becomes translucent.
Also, if you add +4V from point 31, point 3
It becomes semi-opaque at point 31" after passing through curve 30" from 2". In other words, by applying a sufficiently negative voltage and then applying a mid-way positive voltage, a semi-transparent and semi-opaque gray scale can be created. .Conversely, a similar tendency can be obtained even if an intermediate negative voltage is applied to a pixel to which a sufficiently positive voltage is applied.The extent of this gray scale depends on the type and characteristics of the FLC used. , also depends on the size of one domain.
In effect, a gray scale can be created such that each domain is much smaller than one pixel.

Embodiment 2 FIG. 3 shows a circuit diagram in which the present invention is applied to an active element type liquid crystal display device.

In the drawing, the pixel is an electrode 21 (the first
(in the figure, a symbol surrounding a number with a rectangle) connects to one electrode 23 (third electrode) of the ferroelectric liquid crystal 3. SCLAD is connected to the Y wirings 4 and 5 by a second electrode 22. On the other hand, the fourth electrode 34 (counter electrode) of FLC3 is
It is connected to wirings 6 and 7. The X wiring is provided in close proximity to another light-transmitting insulating substrate, typically a glass substrate (20' in FIG. 4C) (6 or 34 in FIG. 4C).

FIG. 4 shows an embodiment of a liquid crystal display device with a matrix structure to which the present invention is actively applied. It is shown.

Furthermore, FIGS. 4B, C, and D show longitudinal cross-sectional views taken along lines AA', BB', and CC' in A, respectively.
In addition, FIGS. 5C and 5D show polarizing plates 30, 30', liquid crystal 3, alignment treatment layers 25,'25, and color filter 2.
6, 26', counter electrode 34 and counter substrate 20' are also shown. The other A and B show only the side having the nonlinear element 2 for simplicity.

The present invention has a plurality of FLC domains inside one pixel 23 shown in FIG. 4A, and when an intermediate voltage is applied, some of them are "1" and the other are "0".
This is to display grayscale by configuring the .

A method of manufacturing an element connected to this pixel will be briefly described.

That is, by using two masks, a rectangular first electrode 21, a rectangular third electrode 23, and a semiconductor 2 having the same shape as the first electrode, a second electrode 22, and a lead 4 are formed between them. Further, the shape of the transparent conductive film constituting the third electrode was 420 μm×420 μm.

In the drawing, the FLC 3 includes a pair of substrates 20 and a counter substrate 20', a pair of electrodes 23 and a counter electrode 3.
4. It is filled between the alignment treatment layers 25 and 25'.

Furthermore, the peripheral circuits 8 and 9 shown in FIG. 3 were arranged on a printed circuit board, and the leads of this printed circuit board and the leads of the display element were connected in correspondence with each other. In addition, Figure 5 shows the V− of the NIN structure SCLAD used in Figure 3.
An example of I characteristics is shown. By connecting this SCLAD in series to a liquid crystal that integrates FLC and FE, it is possible to achieve an ON/OFF ratio of 6 digits.
It can be seen that crosstalk can be sufficiently reduced.

In FIG. 4, FE was provided as 25' on the thin film. However, FEs were scattered on the other electrode 23 so that each FE constituted a cluster.
This can be obtained by removing the amorphous portion in FIG. 1A. In this way, each pixel can be displayed in good gray scale.

"Effects" As described above, the present invention uses FLC as a liquid crystal in a transmission type liquid crystal display device.
By interspersing or substantially interspersing FE in one electrode, the multidomains can be made finer, for example, preferably on average 300 to 2500 μm ² (because the shape generally does not have a fixed shape when observed with a microscope,
Area is approximate) One pixel is 420μm×
It can be obtained by reducing one domain to 1/600 to 1/10 of 420 μm.

Furthermore, as shown in Examples 1 and 2, the present invention is a full-color system, and when displaying grayscale, it is effective to use an active element system to prevent crosstalk between adjacent pixels.

The embodiment of the present invention shows a 2x2 matrix. However, the experiment was conducted by creating a 100 x 100 matrix. It was also confirmed that characters, etc. could be displayed sufficiently. Considering the frequency characteristics, 8-bit parallel processing is applied and 1920
It is estimated that it is also possible to create a full color display of (640 x 3) x 400 pixels.

In the liquid crystal device using the FLC of the present invention, a multi-domain area, particularly a region of a predetermined size, for example, sufficiently small compared to a pixel (including at least several domains, preferably several tens or more domains)
This can only be achieved by configuring the structure.
One of its major applications is full-color displays. However, instead of a display device, it is also possible to try combining it with an optical disk memory device, an audio device such as a speaker, a printer, an optical sensor, and the like.

[Brief explanation of the drawing]

FIG. 1 shows a partial longitudinal sectional view of a liquid crystal device of the present invention. FIG. 2 shows the operating characteristics of a display device that integrates a ferroelectric liquid crystal and a ferroelectric material according to the present invention. Third
The figure shows a circuit diagram of a liquid crystal display panel of the present invention. FIG. 4 shows a plan view and a longitudinal sectional view of the display panel of the present invention. FIG. 5 shows an example of the characteristics of a nonlinear element of a space charge limited current composite diode.

Claims (1)

[Claims] 1. A pair of substrates each having electrodes are provided facing each other with the surfaces having the electrodes facing each other, and a ferroelectric material is provided scattered or substantially scattered on the electrodes. . A liquid crystal device, characterized in that a liquid crystal material is provided between the substrates. 2 A pair of substrates each having electrodes are provided facing each other with the surfaces having the electrodes inside, and a ferroelectric material is provided scattered or substantially scattered on the electrodes, and a liquid crystal is provided between the substrates. material, and by applying an intermediate voltage, the liquid crystal close to the ferroelectric material is made to selectively become a transmissive region or a non-transmissive region within a region constituted by a pair of opposing electrodes, thereby substantially graying the liquid crystal. A liquid crystal device characterized by having a scale. 3 In claim 1 or 2,
A liquid crystal device characterized in that regions forming a pair of opposing electrodes form pixels arranged in a matrix, and the pixels are substantially subjected to gradation operation. 4 In claim 1 or 2,
A liquid crystal device characterized in that the liquid crystal material is a liquid crystal exhibiting a smectic C phase or a liquid crystal obtained by adding an additive such as a dye to the liquid crystal. 5 In claims 1 and 2,
A liquid crystal device characterized in that the ferroelectric material is made of polyvinylidene fluoride or a copolymer of vinylidene fluoride or vinylidene chloride and trifluoroethylene or tetrafluoroethylene.