JPH0843835A - Production of liquid crystal cell - Google Patents

Abstract

PURPOSE:To prevent generation of orientation defects by the defect in control of dispersion of granular adhesives by independently dispersing the spacer particles and granular adhesives dispersed and arranged between substrates to constitute a liquid crystal cell on the substrates different from each other, then assembling both substrates and injecting liquid crystals therebetween. CONSTITUTION:The particulate adhesives 15 are sprayed in the form of stripes on the upper substrate 11a having dielectric electrodes 12a and the spacer particles 14 are distributed uniformly on the lower substrate 11b having the electric electrodes 12b. The granular adhesives 15 and the space particles 14 are electrified to reverse polarities and are fixed by spraying in order to disperse both respectively on the substrates 11a, 11b. Both substrates 11a, 11b are combined to form the empty cell having the specified spacing determined by the spacer particles 14 between the two substrates. The ferroelectric smectic liquid crystals 17 of a non-spiral structure having two stable states are injected into this empty cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal cell, and more particularly to a method for manufacturing a cell suitable for a ferroelectric liquid crystal.

[0002]

2. Description of the Related Art A display device of a type in which transmitted light rays are controlled by combining with a polarizing element by utilizing the refractive index anisotropy of ferroelectric liquid crystal molecules has been proposed by Clark and Lagerwall. (Unexamined-Japanese-Patent No. 56-107216, US Patent No. 436792.
No. 4, etc.). This ferroelectric liquid crystal generally has a chiral smectic C phase (SmC ^* ) in a specific temperature range.
Or having an H phase (SmH ^* ), in which, in response to an applied electric field, either the first optically stable state or the second optically stable state is taken and no electric field is applied. Has the property of maintaining that state, that is, bistability, and has a quick response to changes in the electric field, and is expected to be widely used as a high-speed and memory type display element.

By the way, it has been pointed out that in a liquid crystal cell having a layered structure such as a chiral smectic phase, the layered structure is likely to be disturbed by mechanical strain or impact of the cell, and defective alignment is likely to occur. As a method for solving the above-mentioned drawbacks, for example, it is proposed that an epoxy-based particulate adhesive is dispersed in the gap between the substrates and the two substrates are adhered to each other so that the substrate gap is not easily deformed against external stress. (Japanese Patent Laid-Open No. 174726/1987), and in fact, it has been recognized by the present inventors that the occurrence of alignment defects due to the application of external stress is suppressed.

[0004]

However, when the above-mentioned particulate adhesive is applied to a large-sized liquid crystal cell, particularly a ferroelectric liquid crystal cell, zigzag sawtooth-shaped alignment defects immediately after the production of the cell are rather avoided. A significantly increasing problem was observed.

Therefore, an object of the present invention is to provide a method for producing a liquid crystal cell having improved durability by using a particulate adhesive, which further reduces the occurrence of initial alignment defects, particularly a ferroelectric liquid crystal cell. It is to provide a manufacturing method.

[0006]

According to the present invention, the granular adhesive and the spacer beads that coexist in a dispersed state between the pair of substrates described above are independently controlled without being disturbed by the dispersed state of both. By dispersing in this state, the occurrence of alignment defects caused by the distribution of both in the non-controlled state is prevented as much as possible. That is, the present invention is a method for producing a liquid crystal cell in which spacer particles and a particulate adhesive are dispersedly arranged between a pair of substrates on which electrodes are formed, and a liquid crystal is injected between the substrates. After distributing the particulate adhesive on the other substrate, dispersing the spacer particles on the other substrate, and combining the two substrates to form an empty cell having a certain gap defined by the spacer particles between the two substrates. Liquid crystal is injected into the empty cell.

Further, according to a preferred embodiment of the present invention, if the dispersion density of the granular adhesive is not substantially uniform throughout the cell and has a distribution of density, a cell in which initial alignment defects are further reduced is obtained. be able to. That is, according to the study by the present inventors, the alignment defect immediately after the production in the liquid crystal cell using the above-mentioned granular adhesive mainly occurs as a portion where the liquid crystal is not filled in the cell (an injection defective portion). It was recognized that this is,
It is presumed that this is related to the volume contraction of the liquid crystal material, particularly the ferroelectric liquid crystal material, in the cooling process from the isotropic phase to the liquid crystal phase used.

That is, generally, in the process of manufacturing a ferroelectric liquid crystal cell, for example, a liquid crystal material heated to an isotropic phase by raising the ambient temperature is injected into the cell and sealed,
A method of cooling to a smectic phase temperature (preferably normal temperature), which is an operating liquid crystal phase of the liquid crystal material, is adopted. However, the alignment defect occurs as an injection defect in the cooling process from the isotropic phase to the smectic phase. It turned out that During this cooling process, experimentally, a volume shrinkage of several% occurred.
On the other hand, in the cell using the above-mentioned granular adhesive, the cell interval is maintained regardless of the temperature, therefore the cell volume is kept substantially constant, and the volume contraction of the liquid crystal in the cooling process is not compensated by the cell volume change, It is presumed that minute voids were generated.

On the other hand, in the liquid crystal cell using only the spacer particles without using the granular adhesive, there is flexibility with respect to the change in the cell thickness due to the deflection of the substrate and the like, so that the volume change of the liquid crystal is compensated by the local change in the cell thickness. can do.
At this time, the spacer particles have a function of restricting the decrease of the cell thickness, but (a) there is less constraint as compared with the granular adhesive that basically makes point contact with the substrate and makes area contact. , (B) Since the substrate is allowed to bend in the direction away from the spacer in advance, there is room for absorbing volume contraction in the opposite direction. (C) Some irregularity in grain size allows local deformation of the substrate. It is understood that the above does not prevent the volume shrinkage due to the local change of the cell thickness while controlling the overall thickness of the cell. Therefore, it is considered that no void is generated as in the cell using the above-mentioned granular adhesive.

On the other hand, in the preferred embodiment of the present invention,
While basically maintaining the effect of improving the durability of the cell by restraining the mutual adhesiveness of the granular adhesive, the adverse effect of the excessively homogeneous restraint effect is mitigated by making the distribution uneven, and the local change of the cell thickness By allowing the above, it is possible to compensate for the volume shrinkage in the cooling process of the liquid crystal described above, and reduce the alignment defect at the time of manufacturing the liquid crystal cell, that is, the liquid crystal injection defect.

More specifically, by giving a distribution to the dispersion density of the granular adhesive according to the present invention, it is possible to distribute a region where the distance between the granular adhesives is short and a region where the distance is long. In a region where the distance between the granular adhesives is long, the substrate is likely to be deformed,
It becomes possible to change the cell thickness so as to compensate for the volume change of the liquid crystal. As a result, it is considered that the defective injection due to the volume contraction of the liquid crystal can be prevented.

On the other hand, even if the distribution density is distributed, as long as the total number of the granular adhesives is sufficient, the effect is exerted against an external impact unless a very local external force is applied. be able to.

[0013]

1 (A) and 1 (B) are schematic plan views showing an embodiment of a liquid crystal device manufactured by the present invention and a portion taken along line BB, respectively. It is an expanded sectional view. Referring to FIG. 1 (B), the liquid crystal element includes a pair of upper and lower substrates 11a and 11b arranged in parallel.
And the thickness of the wiring on each substrate is about 400-
It is provided with 2000 Å transparent electrodes 12a and 12b. A ferroelectric liquid crystal, preferably, a non-helical ferroelectric smectic liquid crystal 17 having at least two stable states is arranged between the upper substrate 11a and the lower substrate 11b.

On the transparent electrodes 12a and 12b, for example, a polymer organic film having a thickness of 10 to 1000Å, for example, alignment control films 13a and 13b formed of a polyimide resin are arranged.

In the present invention, at least one of the alignment control films 13a and 13b described above can be provided with a uniaxial alignment axis. This uniaxial orientation axis can be preferably imparted by a rubbing treatment. In addition, the orientation control film 13
An insulating film such as SiO ₂ having a thickness of 100 to 2000 Å may be disposed between the transparent electrode 12a and the transparent electrodes 12a and 12b.

The space between the substrates is held by silica beads 14 having an average particle diameter of about 1.5 μm (generally 0.1 to 3.5 μm) dispersed in the liquid crystal layer 17. Furthermore, in the liquid crystal layer 17, an epoxy-based granular adhesive (trade name “Trepearl” manufactured by Toray Industries, Inc.) 15 for adhering both substrates is arranged. The average particle size of the granular adhesive is about 5 μ, and the liquid crystal layer 17 has a crushed columnar shape by pressing both substrates together as shown in FIG. 1 (B). The outer peripheries of both substrates are sealed with an epoxy adhesive 16.

In the present invention, it is preferable that the granular adhesive 15 is not evenly distributed over the entire cell but is distributed with a density distribution.

FIG. 1 (A) is a schematic view showing an example of spraying, and the granular adhesive 15 can be arranged in a stripe shape with a distribution of spraying density. At this time, the average distribution density of the cells as a whole can be 10 to 100 cells / mm ² . As a specific method of giving a distribution to the distribution density, for example, a hard mask on which a distribution shape to be imparted is patterned is arranged on the dispersion surface, and the granular adhesive can be dispersed through the hard mask.

The preferred degree of non-uniform distribution of the granular adhesive in order to obtain the effect of reducing the initial orientation failure according to the present invention is a particle distribution density (number / mm ²⁾ in a 1 mm square area taken along the cell surface. It is preferable that the distribution coefficient defined as the ratio between the maximum and the minimum of 2) is 2 or more, and particularly 4 or more (here, the minimum dispersion density can be 0). Also,
The condition that the distribution coefficient is 2 or more, especially 4 or more is that the distribution density in the area of 10% from the maximum density side and the area of 10% from the minimum density side is divided when the entire cell surface is divided into 1 mm square areas. It is desirable that the 10% distribution coefficient defined as a ratio is also satisfied.

On the other hand, the granular spacers prevent a short circuit between electrodes due to a local decrease in cell thickness, prevent image unevenness due to a decrease in transmittance, and prevent nonuniform drive characteristics due to nonuniform electric field with respect to applied voltage. For this reason, it is desirable that the particles are evenly distributed over the entire cell surface at a dispersion density of, for example, 50 to 1000 cells / mm ² , and the above 10%
The distribution coefficient (further, a simple distribution coefficient) is preferably less than 2, and particularly preferably 1.5 or less. Even if the granular spacers are uniformly distributed in this manner, the above (a) to
As described in (c), the effect of the preferred embodiment of the present invention is not essentially impaired.

As described above, in order to mix the non-uniform distribution state of the granular adhesive and the uniform distribution state of the granular spacers, for example, the non-uniform distribution of the granular adhesive as described above is weakly heated to After temporarily adhering to the substrate, the other substrate on which the granular spacers are evenly distributed is overlapped, and the granular adhesive and the sealant are heated and cured to assemble the cells. At the time of dispersion, the dispersed particles and the substrate may be charged with opposite polarities to promote uniform dispersion. As described above, according to the present invention, the granular adhesive is non-uniformly distributed on one substrate and the granular spacers are uniformly dispersed on the other substrate, and then both substrates are combined to form the granular adhesive and the spacer. The dispersion state with the beads can be independently controlled without being influenced by each other, and the occurrence of alignment defects due to poor dispersion control can be prevented.

In the present invention, a ferroelectric liquid crystal having a chiral smectic phase state can be used. Specifically, a chiral smectic C phase (SmC ^* ) and an H phase (S
mH ^* ), I-phase (SmI ^* ), K-phase (SmK ^* ), and G-phase (SmG ^* ) liquid crystals can be used.

As a particularly preferable ferroelectric liquid crystal, a liquid crystal exhibiting a cholesteric phase on the higher temperature side can be used. For example, a phenyl ester liquid crystal having a phase transition temperature as described below (“CS” manufactured by Chisso Corporation) is used. -1014 ") can be used.

[0024]

Embedded image

As a concrete example, FIG. 1 (A),
According to the schematic structure of (B), effective area 265 mm x 145
A granular adhesive having an average particle size of about 5 μm is provided on one of a pair of substrates each having a width of 10 mm and a high density distribution stripe region having a width of about 10 mm (a density of about 80 pieces / mm ² ) and a stripe-shaped nonexistent region having a width of about 10 mm (a density of Particles / mm ² ) are alternately formed, and are non-uniformly distributed so as to give a dispersion density of about 40 particles / mm ² on average, and about 300 silica beads having an average particle size of about 1.5 μm are provided on the other substrate. / Mm ² to distribute evenly,
The liquid crystal cell formed by encapsulating the phenyl ester liquid crystal at 85 ° C. in an empty cell formed by combining both substrates and gradually cooling to room temperature at a rate of 10 ° C./hr is a sawtooth-like initial alignment defect. Was only found for 5 cell sumps.

As described above, even if there is a distribution in the distribution density, as long as the total number of granular adhesives is sufficient, unless a very local external force is applied, an external impact is applied. , Can be effective. In this sense, the mode of uneven distribution of the granular adhesive has some degree of arbitraryness. For example, in addition to the examples of FIGS. 1 (A) and 1 (B) described above, for example, FIG. Is distributed at a high density in the vicinity of the center of the cell as shown in Fig. 4) to form a low-density distribution area in the periphery, or in the vicinity of the center as shown in Fig. 4 (the granular spacers are not shown). It is also possible to form a high-density distribution area in the area and reduce the density of the distribution radially toward the periphery. However, from the essential function of ensuring durability against external stress such as impact resistance of the liquid crystal cell, a large adhesive blank area in which the interval between adjacent granular adhesives is 100 mm or more is formed in the central area. It is desirable not to form it.

[0027]

As described above, according to the present invention,
Spacer particles and granular adhesive dispersedly distributed between a pair of substrates constituting a liquid crystal cell are independently dispersed on different substrates, and then liquid crystal is injected into an empty cell formed by combining both substrates. By adopting this method, it is possible to control the dispersion state of the spacer particles and the granular adhesive independently of each other independently, and to manufacture a liquid crystal cell in which the occurrence of alignment defects due to poor dispersion control is prevented. You can

[Brief description of drawings]

FIG. 1A is a schematic plan view of a liquid crystal device having a non-uniform granular adhesive distribution manufactured according to a preferred embodiment of the present invention, and FIG. 1B is taken along line BB of FIG. FIG.

FIG. 2 is a schematic plan view of a liquid crystal element having a uniform granular adhesive distribution.

FIG. 3 is a schematic plan view of a liquid crystal element having an uneven distribution of granular adhesive.

FIG. 4 is a schematic plan view of a liquid crystal element having an uneven distribution of granular adhesive.

[Explanation of symbols]

 11a Upper substrate 11b Lower substrate 12a Upper transparent electrode 12b Lower transparent electrode 13 Alignment control film 14 Beads 15 Granular adhesive 16 Sealant 17 Liquid crystal layer

Claims (7)

[Claims] 1. A method of manufacturing a liquid crystal cell, in which spacer particles and a particulate adhesive are dispersedly arranged between a pair of substrates on which electrodes are formed, and a liquid crystal is injected between the substrates, one of the pair of substrates. After distributing the particulate adhesive on the other substrate, dispersing the spacer particles on the other substrate, and combining the two substrates to form an empty cell having a certain gap defined by the spacer particles between the two substrates. A method for manufacturing a liquid crystal cell, which comprises injecting liquid crystal into an empty cell. 2. The average dispersion density of the granular adhesive is 10
The method for producing a liquid crystal cell according to claim 1, wherein the number is 100 / mm ² . 3. The dispersion density of the granular spacers is 50 to 50.
The method for producing a liquid crystal cell according to claim 1, wherein the number is 1000 cells / mm ² . 4. The method for producing a liquid crystal cell according to claim 1, wherein the granular adhesive and / or the granular spacer is charged in a polarity opposite to that of the substrate and dispersed on the substrate. 5. The method for producing a liquid crystal cell according to claim 1, wherein the liquid crystal is heated to an isotropic phase and injected into an empty cell, and then cooled to an operating liquid crystal phase. 6. The method for producing a liquid crystal cell according to claim 1, wherein a liquid crystal exhibiting a chiral smectic phase is used as the liquid crystal. 7. The method for producing a liquid crystal cell according to claim 1, wherein a ferroelectric liquid crystal is used as the liquid crystal.