JPH06242409A - Liquid crystal display unit and manufacture of same - Google Patents

Abstract

PURPOSE:To make the liquid crystal display unit rigid by orienting and supporting ferroelectric liquid crystal with resin molecules and to obtain uniform orientation by constituting a resin net while holding the affinity of the resin. CONSTITUTION:A polarizing plate 7 is arranged outside the ferroelectric liquid crystal 6 which is homogeneously oriented on the surface of a substrate which has an electric field applying means while clamped by the substrate 1, and charged in porous macromolecular resin 5. The axis of polarization of the polarizing plate 7 is so arranged to develop black when no electric field is applied. This display unit is constituted by mixing the resin 5 and ferroelectric liquid crystal 6 together and charging the mixture between substrates while holding the liquid crystal in a nematic state by raising its temperature. Then the resin 5 is polymerized in an electric or magnetic field. In another way, a liquid crystal cell is formed of a substrate 1 after orientation processing is performed on its internal surface, and the resin 5 and ferroelectric liquid crystal 6 are held in liquid state, injected into the liquid crystal cell, and lowered in temperature to polymerize the resin 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display using a ferroelectric liquid crystal.

[0002]

2. Description of the Related Art Conventionally, ferroelectric liquid crystals have been disclosed in JP-A-62-1.
It has been proposed in Japanese Patent No. 75712, etc. that it can be used for a display, and in this case, it has advantages such as high contrast and good responsiveness in simple driving.

On the other hand, instead of encapsulating liquid crystal molecules in a cell and then encapsulating the liquid crystal in a porous polymer resin like a three-dimensional network,
JP-A-61-502128, JP-A-62-223
This is disclosed in Japanese Patent Publication No. 1 and the like. This is a new field-effect type display mode that does not require a polarizing plate by utilizing light scattering like the focal conic structure or the Williams domain structure which is an old technology. It came to be noticed as and was studied.

[0004]

However, it is difficult for a ferroelectric liquid crystal to have bistability in alignment characteristics, and even if it is once aligned, the alignment tends to be disturbed, and it is difficult to obtain an extremely thin layer. There was a flaw. In particular, the disorder of the alignment does not occur in the normal chiral nematic liquid crystal when the substrate is lightly impacted to some extent, and the display quality deteriorates while the pressure is applied to the extent that the substrate is sluggish. However, when the applied pressure is removed, the liquid crystal has a restoring force because it is basically a fluid, whereas the ferroelectric liquid crystal has weak alignment force and multiple stable states, and it is weak against shock. Therefore, it is difficult to obtain a uniform orientation, and even after the uniform orientation is obtained, an extremely slight impact causes an abnormal orientation, and a color or pattern appears on the display. Even after the impact or pressure is removed, it will not be restored unless a reorientation treatment is performed.

On the other hand, in a porous polymer resin impregnated with liquid crystal, since light scattering by liquid crystal molecules is used, either white or black becomes an unclear color,
The contrast cannot be obtained, the electric field applied to the nematic liquid crystal is dispersed due to the polymer resin, steepness cannot be obtained, and the response speed is slow.

[0006]

The present invention has been made in view of the above points, and is sandwiched by a substrate having an electric field applying means, homogeneously oriented on the substrate surface, and filled with a porous polymer resin. A polarizing plate is arranged outside the ferroelectric liquid crystal, and more preferably, the polarizing axis of the polarizing plate is arranged to exhibit black color when no electric field is applied.

The present invention also provides a step of mixing a resin and a ferroelectric liquid crystal, a step of heating the mixture to keep the liquid crystal in a nematic state and filling the space between substrates, an electric field or a magnetic field of the mixture. It is a manufacturing method of a liquid crystal display including a step of polymerizing a resin. Furthermore, the present invention forms a liquid crystal cell with a substrate whose inner surface is subjected to an alignment treatment, mixes a resin and a ferroelectric liquid crystal, injects the mixture into a liquid crystal cell while keeping the mixture in a fluid state, and lowers the temperature. A method for manufacturing a liquid crystal display, comprising a step of polymerizing the resin of the mixture.

[0008]

In such a liquid crystal display, since the ferroelectric liquid crystal is oriented and supported by the resin molecular network, the liquid crystal display is extremely robust, and characteristics such as high-speed response characteristic of the ferroelectric liquid crystal are not impaired.
Moreover, since the resin net is basically formed by orienting the ferroelectric liquid crystal while maintaining the affinity of the resin, the manufacturing process is stable and uniform alignment can be obtained.

[0009]

1 is a schematic sectional view of a liquid crystal display according to an embodiment of the present invention. In the figure, 1 is an electrode 11 which is an electric field applying means.
This is a substrate having a striped matrix electrode 11 formed of an ITO film having a resistance value of about 20Ω per unit area by low-temperature sputtering an indium oxide film or the like on a glass substrate. These substrates 1 compose a liquid crystal cell by appropriately dispersing spacers 2 and adhering them with a sealant 3 as needed, and a liquid crystal layer 4 is held by both substrates. The liquid crystal layer 4 is composed of a ferroelectric liquid crystal 6 filled in a porous polymer resin 5 (resin net) formed between the substrates 1. The ferroelectric liquid crystal 6 is homogeneously aligned on the surface of the substrate 1, and a polarizing plate 7 is arranged outside the substrate 1.

In such a liquid crystal display, for example, a substrate having electrodes is prepared, a mixture of acrylic elastomer and acrylic monomer is radically polymerized or crosslinked as a UV-curable polymer resin agent, and then a ferroelectric liquid crystal is added. Dissolve this as a solvent, apply it to the previous substrate and bond it,
It can be obtained by applying ultraviolet rays to this and curing it. The elastomer or the monomer can be used alone, and when the elastomer is used alone or as a mixture, the one having 40,000 to 50,000 molecular units is easily used. Further, it is preferable that the cross-linking be dispersed in the liquid crystal in the intermediate state, rather than being completely cross-linked. In addition, since the coating is in a gel state, a sealing agent is not required in principle, but it can be used.

However, unlike the light scattering mode in which a nematic liquid crystal is impregnated in a conventional polymer resin, what is required in the display mode according to the present invention is that the liquid crystal molecules are aligned in a uniform direction even after the resin is polymerized. Is what you are doing.

For this purpose, a step of mixing the resin and the ferroelectric liquid crystal, a step of raising the temperature of the mixture to keep the liquid crystal in a nematic state, and filling the space between the substrates, rather than the above manufacturing method, Alternatively, a step of polymerizing the resin of the mixture in a magnetic field may be followed. When a ferroelectric liquid crystal and a monomer or oligomer resin are mixed and photopolymerization is performed while applying an electric field or magnetic field in the direction in which the liquid crystal is aligned during photopolymerization, the so-called ferroelectric The initial alignment of the liquid crystal becomes uniform. For example, as shown in FIG. 2, when an applied voltage at the time of photopolymerization and the light transmittance of the liquid crystal layer after completion of the polymerization are examined, a clear causal relationship is recognized. Further, in this photopolymerization, when the thickness of the liquid crystal layer after the photopolymerization is 6 to 10 μm, the temperature of the liquid crystal layer before the photopolymerization is maintained at the transition temperature of the ferroelectric liquid crystal to the nematic liquid crystal or more, preferably the transition temperature or less. It is more preferable to polymerize in the state. At this time, the nematic liquid crystal is N type, but a small amount of N type nematic liquid crystal may be added if necessary, and the electric field is applied by, for example, about 5 V by an electrode applied to the display after photopolymerization. Keep it. Liquid crystal molecule is N
Since it is in a nematic state, it has a homogeneous orientation, but when the directionality is not determined, the inner surface of the substrate may be rubbed in advance. When a magnetic field is used, S and N poles are respectively arranged in the width direction of the substrate, that is, at both edges of the substrate, so that a magnetic field of, for example, 15000 gauss is applied to perform light irradiation and polymerization. If a liquid crystal having a negative magnetic susceptibility is used, the liquid crystal molecules are aligned in a specific direction with respect to the direction of the magnetic field. Therefore, the nematic liquid crystal state is maintained and a magnetic field perpendicular to the substrate surface is applied to perform UV irradiation. By doing so, the liquid crystal can be aligned in a predetermined direction even if the substrate surface is not subjected to alignment treatment such as rubbing.

According to such a manufacturing method, the orientation can be freely controlled by the strength of the electric field or magnetic field applied during the photopolymerization, and the degree of bistability of the ferroelectric liquid crystal can be controlled by the combination with the liquid crystal composition. Can be raised sufficiently,
Since the resin network in the liquid crystal display acts as a buffering agent, the stability of the alignment against shocks is dramatically improved.

In the above-mentioned method, the electric field and the magnetic field were positively utilized for the initial alignment of the liquid crystal molecules, but attention was paid to the improvement of the contrast in achromatic color which is a peculiar condition required for a display device. A more efficient method of uniformly aligning ferroelectric liquid crystals has been found. That is, one color, for example, black is made vivid, and the other color, for example, white is determined in view of the retardation. For example, black is displayed in the entire liquid crystal display when no electric field is applied. Gap (thickness of liquid crystal layer) that can be displayed uniformly and densely over the entire area
Is found, the retardation is the birefringence anisotropy Δ.
Since it is the product of n and the thickness d, it suffices to select a liquid crystal having birefringence anisotropy that exhibits white when an electric field is applied. Focusing on this point, we examined the orientation of liquid crystal molecules in a porous polymer resin, and found that the inner surface of the substrate should be subjected to orientation treatment such as rubbing, even when no electric field or magnetic field is applied during photopolymerization. It was found that uniform alignment can be obtained by controlling the photopolymerization rate, and the darkness of black when no electric field is applied can be controlled by the thickness of the liquid crystal layer. FIG. 3 shows the photopolymerization rate at this time and the light transmission characteristics (trans. =) Of the completed liquid crystal display.
4 shows the vertical axis, and FIG. 4 is based on FIG.
5 shows the thickness of the liquid crystal layer when photopolymerized for 5 seconds) and the light transmission characteristics of the liquid crystal display under the crossed Nicols.

Based on such studies, the most effective method of initial alignment is to form a liquid crystal cell on a substrate whose inner surface is subjected to alignment treatment, mix the resin and the ferroelectric liquid crystal, and a mixture thereof. Injecting into the liquid crystal cell by heating the liquid to keep it in a fluid state,
Was to lower the temperature to polymerize the resin of the mixture.

More specifically, a ferroelectric liquid crystal CS1022 manufactured by Chisso Corporation was mixed with 95% of 1.6 hexadiol diacrylate and kept at 90 ° C. to show a liquid phase. On the other hand, a mixture in which a substrate having an electrode and an alignment film is pasted with a peripheral sealant and a spacer forms a liquid crystal cell having 1.4 to 2.6 μm 0.2 μm unit seven kinds of gaps to form a liquid phase. Was injected into the liquid crystal cell. After the inlet was sealed and the temperature was lowered to 50 ° C., the liquid crystal of the mixture showed a smectic phase. In that state, UV irradiation was carried out to photopolymerize the resin of the mixture. It is considered that the liquid crystal layer after the polymerization has a thickness controlled by Gipp control, and the polarizing plate was arranged after confirming the alignment of the liquid crystal molecules by utilizing interference. However, the polarization axis was selected so that it exhibited black color when no electric field was applied. As a result, a black uniform display surface was confirmed when there was no electric field. In this liquid crystal display, even if a static load was applied to the extent that the glass substrate was sluggish, there was no misalignment such that a color shift or a pattern was observed, and a black uniform display surface was confirmed. Next, when an alternating electric field was applied to the electrodes, when the electric field was applied, white with good color removal was obtained.
High contrast display was possible. In place of the above-mentioned liquid crystal, CS1023 and CS103 of Chisso Corporation are also used.
A liquid crystal display was formed by using 0, but similar results were obtained, and when a substrate in which three primary color stripe color filters of R, G and B were incorporated was used, a liquid crystal display capable of controlling 64 colors was obtained. Was given.

According to the method of manufacturing a liquid crystal display, a liquid crystal cell of a liquid crystal cell in which a ferroelectric liquid crystal is sealed is uniformly oriented, and a resin net is stretched around so that the liquid crystal molecule alignment is not broken in that state. I can say. Explaining this in the state diagram of FIG. 5, the mixture of acrylate and liquid crystal tends to exhibit a liquid phase when the amount of liquid crystal is small and the temperature is high, and tends to exhibit the original phase of the liquid crystal when the amount of liquid crystal is high and the temperature is low. Therefore, when the liquid crystal component of the mixture is increased to some extent and maintained at a high temperature, a liquid phase (marked by A in the figure) is exhibited, and when the temperature is lowered in that state, the liquid crystal layer transitions to a smectic phase (marked by B in the figure). In the process, the liquid crystal molecules are easily aligned with each other in a certain direction, and are easily affected by the alignment treatment on the substrate surface. When the compatibility between the liquid crystal molecules and the resin molecules is good, the resin molecules are aligned along the alignment of the liquid crystal molecules. If photopolymerization is started in this state, the resin molecules crosslink without hindering the alignment of liquid crystal molecules. How the alignment of the liquid crystal molecules is maintained can be determined by observing the display surface by using interference such as crossed Nicols after the photopolymerization is completed or after the polymerization is started. The pattern is observed where cross-linking occurs, so evaluation is easy. Further, from these studies, if the mixture is formed at a lower mixing ratio of the liquid crystal and injected into the liquid crystal cell and partially polymerized, the resin concentration relatively decreases, so that the mixture is transferred to the smectic phase and polymerization is performed. The production can be further facilitated by restarting or by selecting a material such as a resin oligomer having a high affinity with the liquid crystal molecules so that a smectic phase can be easily obtained at a low temperature and a low concentration.

Further, in the liquid crystal display according to the present invention, the liquid crystal layer tends to be thin, so that when the transparent electrode is totally reflected, the display is not observed or the thin film interference color is observed. Therefore, in this case, a wide viewing angle can be maintained as it is by roughening the transparent electrode and its underlying surface by etching. In order to further improve the response of display, it is sufficient that the characteristic characteristic of the liquid crystal appears remarkably regardless of the presence / absence of the color filter. At this time, many parts depend on the curing conditions of the polymer resin,
Care must be taken because the robustness, which is an advantage of the present invention, is easily impaired. Regarding the thickness, the magnitude of the electric field that moves the liquid crystal molecules in each region is substantially constant, but the voltage must be increased depending on the thickness of the liquid crystal layer. Furthermore, if necessary, for each pixel, for example, Japanese Patent Laid-Open No. 58-70555 can be used.
Non-linear elements such as the metal-insulator-metal element of the publication can be used. When a substrate having such a non-linear element for each pixel is used, a plurality of signal electrodes made of tantalum having a width of 5 to 70 μm or a thin film containing tantalum as a main component, and a thickness provided on the surface of the signal electrodes Dozens of Å ~ Thousands of Å
an insulating layer such as a ₂ O _5, a metal made of a thin film of chromium or aluminum laminated with the insulating layer in a certain area, and an indium oxide thin film of, for example, 330 × 280 mm electrically connected to the metal It is composed of pixel electrodes.
However, in the present invention, which basically uses the characteristics of the ferroelectric liquid crystal as it is, it is important to consider that the thickness of the liquid crystal is not changed by providing the non-linear element.

[0019]

As described above, a robust display can be obtained because the orientation is maintained even if a resin net is used, while making the best use of the characteristics of the ferroelectric liquid crystal such as high contrast and good response in simple driving. In particular, the display quality is good, the black background is clear and the contrast is high, and the color display can be performed in vivid colors. In addition, such a robust display could be manufactured with good reproducibility.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining an example of the present invention.

FIG. 3 is a characteristic diagram of a photopolymerization rate and a light transmission characteristic for explaining an example of the present invention.

FIG. 4 is a characteristic diagram of a thickness of a liquid crystal layer and a light transmission characteristic for explaining an example of the present invention.

FIG. 5 is a state diagram for explaining an embodiment of the present invention.

[Explanation of symbols]

 1 Substrate 11 Electrode 2 Spacer 3 Sealant 4 Liquid Crystal Layer 5 Polymer Resin 6 Ferroelectric Liquid Crystal 7 Polarizing Plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Suzuki 3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Santoyo Sanyo Electric Co., Ltd. (72) Inventor Takayuki Koyama 3-201 Minamiyoshikata, Tottori City Tottori Sanyo Denki Within the corporation

Claims (4)

[Claims] 1. A ferroelectric liquid crystal held between a substrate having an electric field applying means, homogeneously aligned on the surface of the substrate and filled in a porous polymer resin, and a polarizing plate arranged outside the ferroelectric liquid crystal. A liquid crystal display characterized by comprising: 2. A step of mixing a resin and a ferroelectric liquid crystal,
A liquid crystal display characterized by comprising the steps of heating the mixture to keep the liquid crystal in a nematic state and filling between the substrates, and polymerizing the resin of the mixture in an electric field or a magnetic field. Production method. 3. A step of forming a liquid crystal cell with a substrate having an inner surface subjected to an alignment treatment, mixing a resin and a ferroelectric liquid crystal, injecting the mixture in a liquid state into the liquid crystal cell, and lowering the temperature. And a step of polymerizing the resin of the mixture. 4. A substrate having an electric field applying means, a ferroelectric liquid crystal filled between molecules of a polymer resin, and a polarization axis which is arranged outside the ferroelectric liquid crystal and exhibits a black color when no electric field is applied. A liquid crystal display, comprising: a polarizing plate in which is disposed.