JPH0511234A - Manufacture of liquid crystal display element - Google Patents

Abstract

PURPOSE:To easily remove a high polymer dispersed liquid crystal material sticking on a part except the interior of cell when the liquid crystal display element is manufactured by sandwiching a high polymer dispersed liquid crystal layer. CONSTITUTION:A solution prepared by uniformly dissolving resin and liquid crystal is injected into the gap between two upper and lower glass substrates 1 and 10, one of which is transparent. A film 7 is formed at the part of the substrate which has a lead-out electrode, the resin-liquid crystal uniformly mixed liquid is injected and irradiated with ultraviolet rays form the high polymer dispersed liquid crystal layer, and then the film 7 is removed to obtain the liquid crystal display element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal display element used as a display device by electrically or thermally switching the display.

[0002]

2. Description of the Related Art Liquid crystal display elements, such as twisted nematic type using nematic liquid crystal and super nematic type with a twist angle of 90 ° or more, have features such as low power consumption, low voltage drive, light weight and thinness. Utilizing this effectively, it is widely used as a display device for a personal word processor, a handheld computer, a pocket TV, etc. as a flat display. Further, in recent years, colorization has progressed, and an active matrix type liquid crystal display element in which an active element is provided for each pixel electrode can be highly densified, and is becoming the mainstream. However, all of the above require polarizing plates, and alignment treatment is indispensable. A large-scale, inexpensive liquid crystal display element that does not require these and has a good contrast, and thus a method of performing display by switching between a scattering state and a transparent state is drawing attention. Formerly DSM as this kind of mode
A liquid crystal display device using a liquid crystal of (dynamic scattering) type or a PC (phase transition) type has also been proposed, but each has a drawback that the current value flowing in the liquid crystal is high and the current consumption is large, and the liquid crystal layer The thickness control was difficult, and there was a defect that color unevenness was likely to occur, so it was not put to practical use.

Recently, there has been known a method of encapsulating a liquid crystal as a liquid crystal display element which does not have such drawbacks and can be driven at a low voltage, thereby dispersing liquid crystal droplets in the polymer and forming the polymer into a film. ing. Here, gelatin, gum arabic, polyvinyl alcohol, etc. are proposed as the encapsulating material (Japanese Patent Publication No. 58-501631).
U.S. Pat. No. 4,435,047), liquid crystals dispersed in an epoxy resin (Japanese Patent Publication No. 61-502128), and liquid crystals dispersed in an ultraviolet curable polymer (Japanese Patent No. 435047). However, when an electric field is applied, the liquid crystal molecules are aligned in the direction of the electric field, and the refractive index of the liquid crystal is n _o or n _e . It is based on the principle of displaying in two states that the polymers have the same refractive index n _p and have transparency, and the liquid crystal molecules return to a random arrangement when the electric field is removed, and the light passing through this liquid crystal is scattered. Is.

[0004]

If the polymer matrix in the polymer-dispersed liquid crystal layer, which is the liquid crystal layer of such a dispersion type liquid crystal display device, is basically transparent, even a thermoplastic resin may be thermoset. Although it can be used even if it is a resin, an ultraviolet curable resin is generally the easiest and
Often used for good performance. The reason for this is that as a conventional liquid crystal panel manufacturing method, a predetermined electrode pattern is previously formed on the upper and lower substrates, and the two substrates are stacked so that the electrodes face each other. At this time, a spacer having a predetermined size and a uniform grain size is sandwiched between the substrates, and the two substrates are fixed by an epoxy resin sealing material in a state where a gap can be maintained between the two substrates. A manufacturing method in which a liquid crystal is injected into an empty cell thus obtained is often used. In order to manufacture a dispersion type liquid crystal panel by applying this manufacturing method, the polymer matrix may be made of an ultraviolet curable resin. Especially when using acrylic resin as an example,
Prior to injection, it exists as a low-viscosity precursor such as a monomer and / or an oligomer, and a blend with liquid crystal has sufficient fluidity to be injected at room temperature, so that a conventional liquid crystal panel. The manufacturing method of can be applied.

Further, by irradiating the panel with ultraviolet rays after injection, only the resin undergoes a polymerization reaction to become a polymer, and only the liquid crystal is phase-separated. On the other hand, when the amount of the liquid crystal is large, the polymer matrix exists in the liquid crystal material in the form of particles or networks, and the liquid crystal is formed so as to form a continuous phase. At this time, unless the particle diameter of the liquid crystal droplets or the pore diameter of the polymer network is uniform to some extent and the size is in the range of 0.1 μm to several μm, the dispersion performance is poor and the contrast cannot be improved.
For this reason, it must be a material that can be cured in a short time, such as an ultraviolet curable resin.

For the reasons described above, it is best to use an ultraviolet curable resin as the polymer matrix.

As a most general method for producing a liquid crystal display element, two glass substrates having a predetermined electrode pattern and / or active element are made to face each other with their electrode sides facing each other so that a certain gap is maintained. Put them on top of each other and seal around the periphery leaving only the inlet to solidify. After this, liquid crystal is injected from the injection port. As an injection method, it is generally known that the injection port is attached to the liquid crystal reservoir in a vacuum and the liquid crystal is injected into the liquid crystal panel by vacuum suction when the atmosphere is opened. At that time, the liquid crystal material adheres to the gap between the glass substrate and the seal portion due to the capillary phenomenon, but it can be easily removed by washing the liquid crystal panel after the injection port is sealed.

However, when a polymer-dispersed liquid crystal display device is manufactured by the same method, a uniform solution of an uncured ultraviolet curable resin and liquid crystal is injected, and then ultraviolet rays are irradiated from the outside of the substrate to make the resin. In order to cure the polymer to form a polymer matrix and obtain a polymer liquid crystal layer, the uncured resin adhering to the gap between the glass substrate and the seal part or the surface of the extraction electrode also undergoes a polymerization reaction to become a polymer. A film is formed on the surface. The formed polymer film cannot be removed with a solvent or the like, and it is difficult to completely peel off the film even by using a method such as ozone asher or plasma etching, and also the destruction of the element itself is promoted.

As another method, a method of dropping a resin liquid crystal uniform solution at the time of stacking two upper and lower substrates and squeezing out the excess solution to seal the periphery while keeping a predetermined interval is conceivable. Even in this case, the portion to which the squeezed solution adheres should be completely removed before the resin in the liquid crystal panel is cured by irradiation with light, especially after the coating is formed on the extraction electrode portion. The connection with the IC to be driven becomes impossible and the drive signal cannot be applied, and the panel cannot be lighted. However, it is extremely difficult to remove the above-mentioned solution that has been excessively adhered before the resin-liquid crystal uniform solution in the panel is cured without attacking the solution in the panel.

Particularly in recent years, an active matrix system in which an active element is arranged in one pixel is often used. Furthermore, if a chip-on-glass (COG) mounting with a drive IC in the panel is used as a panel module, the space saving
Development is underway because it has the feature that it can be designed into a space. However, as described above, when a polymer film is formed on the glass substrate during the manufacture of the liquid crystal panel, particularly when it is formed on the portion where the drive IC is mounted, the protruding electrode of the drive IC and the signal electrode of the liquid crystal panel are formed. During that time, electrical continuity cannot be established, resulting in a failure.

Similarly, when the polymer matrix of the polymer liquid crystal layer is other than the ultraviolet curable resin, such as a thermosetting resin, heat is not applied when the resin in the liquid crystal panel is cured. For example, the resin that has excessively adhered to the outside of the panel will be hardened and cannot be removed. Further, if it is removed before curing, the uncured resin liquid crystal uniform solution in the panel is soaked, which makes it difficult to manufacture the liquid crystal panel.

[0012]

The present invention has been made to solve the above problems, and a polymer dispersed liquid crystal layer is sandwiched between at least one of upper and lower two transparent electrode substrates. In the liquid crystal display element formed as described above, a coating film is previously provided on the entire surface or a part of the electrode side of the substrate, and the coating film is partially removed after the liquid crystal display element is manufactured.

The substrate is, for example, glass, metal, plastic film or the like, and may be a rigid material or a flexible material, but two substrates are faced to each other with an appropriate interval. is there. At least one of the substrates should be transparent so that the liquid crystal sandwiched between the two substrates can be seen from the outside. Inside the two substrates, appropriate transparent and opaque electrodes are arranged on the whole surface or a part thereof according to the purpose.

A liquid crystal material in which a nematic liquid crystal is dispersed and held in a polymer matrix between the two substrates, or a polymer in which the polymer matrix exists in the liquid crystal material in the form of particles or a network. An intermediary of dispersed liquid crystals.

The liquid crystal material is preferably a nematic liquid crystal, a smectic liquid crystal, or a cholesteric liquid crystal, which is single or two.
It may be a mixture containing one or more kinds of liquid crystal compounds or substances other than the liquid crystal compounds.

The polymer matrix material is preferably a transparent polymer, and may be any of a thermoplastic resin, a thermosetting resin and a photocurable resin. It is preferable to use an ultraviolet curable resin from the standpoint of separation from the phase. As a specific example, an ultraviolet curable acrylic resin is exemplified, and a resin containing an acrylic monomer or an acrylic oligomer which is polymerized and cured by ultraviolet irradiation is particularly preferable.

As such a polymer-forming monomer,
For example, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, neopentyl glycol diacrylate, hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, etc. Is mentioned.

Examples of the oligomer or prepolymer include polyester acrylate, epoxy acrylate and polyurethane acrylate.

A polymerization initiator may be used in order to carry out the polymerization rapidly, and an example thereof is 2-hydroxy-2-
Methyl-1-phenylpropan-1-one (“Darocur 1173” manufactured by Merck), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-
On (Merck's "Darocur 1116"), 1-vidroxycyclohexyl phenyl ketone (Ciba-Gaiki "Irgacure 184"), benzyl methyl ketal (Ciba-Geigy "Irgacure 651"), etc. are mentioned.

In addition, a chain transfer agent, a photosensitizer, a dye, a cross-linking agent and the like can be appropriately used in combination as optional components.

After injecting a liquid or viscous material in which a liquid crystal material is uniformly dissolved into this ultraviolet curable compound between two substrates, ultraviolet irradiation is carried out to cure only the ultraviolet curable compound, At that time, only the liquid crystal material is phase-separated to form a polymer dispersed liquid crystal layer.

The proportion of the liquid crystal material in the polymer dispersed liquid crystal layer is not specified here, but is generally 20% by weight to 90% by weight.
The degree is good, preferably about 50 to 70% by weight. If it is 20% by weight or less, the amount of liquid crystal droplets is small and the scattering effect is poor. On the other hand, when it is 90% by weight or more, the polymer and the liquid crystal tend to be phase-separated into upper and lower layers, the ratio of the interface becomes small, and the light scattering decreases. The structure of the polymer-dispersed liquid crystal layer changes depending on the liquid crystal fraction. At about 50% by weight or less, the liquid crystal droplets exist as independent droplets, and at 50% by weight or more, the polymer and the liquid crystal are in a continuous phase. .

A coating film is provided in advance on the inside of these two substrates, that is, on the entire surface on the electrode side or at least the signal electrode and the extraction electrode of the signal electrode outside the panel. This film is preferably formed after patterning the electrode layer on the glass substrate into a predetermined pattern and, if necessary, after manufacturing active elements and the like, but it may be formed after two upper and lower substrates are superposed and fixed. I don't care. It is necessary to form at least before injecting the resin liquid crystal uniform solution. After injecting the resin liquid crystal uniform solution, the resin portion is cured to form a polymer matrix, and then the coating film is peeled off. Therefore, both organic and inorganic materials can be considered as the material used for the coating film, but a material that can be easily dissolved and removed in a short time with a solvent or the like is preferable. Alternatively, it is most preferable that the coating film is easily peeled mechanically and chemically.

As an easily peelable coating, for example, acrylic resin,
BACKGROUND ART A coating material is known in which an alkyd resin, urethane resin, polyvinyl butyral resin or the like is mixed with a plasticizer, a surfactant, an organic solvent or the like. Dibutyl phthalate as a plasticizer,
Phthalic acid ester-based and fatty acid ester-based plasticizers such as dioctyl phthalate, dioctyl sebacate, dioctyl adipate, epoxidized soybean oil, trifyl phosphate, and triethoxybutyl phosphate are effective. Also, as the surfactant, an alkyl ester,
Polyoxyethylene alkyl ether phosphate,
A phosphate ester-based surfactant such as polyoxyethylene alkylphenyl ether phosphate ester may be used. As the organic solvent, ketone, ester, glycol ether, alcohol, etc. are effective.

However, it is necessary to clean the substrate after removing the coating film.

[0026]

According to the present invention, a polymer dispersed liquid crystal type liquid crystal display device having a bright and high contrast can be easily manufactured without defects.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings based on embodiments. However, the present invention is not limited to these examples. Further, the drawings are model diagrams, and some unnecessary parts are omitted.

FIG. 1A is a schematic sectional view of a part of the liquid crystal display element before liquid crystal injection in the first embodiment of the present invention, and FIG. 1B is a liquid crystal display after liquid crystal injection. A schematic cross-sectional view of a part of the element, (FIG. 1C) shows a driving IC after the film is peeled off.
FIG. 3 is a schematic cross-sectional view of a part of a liquid crystal display element on which is mounted. 1 in the figure is a glass substrate for an active matrix substrate, 2
Is a pixel electrode, 3 is an active element, 4 is a signal electrode, 5 is a silicon nitride insulating film, 6 is a polymer dispersed liquid crystal layer, 7 is a film, 8 is a sealing material, 9 is a counter electrode, 10 is glass for a counter substrate. A substrate, 11 is a driving IC, and 12 is an extraction electrode. The active element 3 was manufactured by the following procedure.

First, 0.1 μm of chromium is applied on the glass substrate 1.
m was evaporated and patterned to form a gate electrode. A silicon nitride film, an amorphous silicon film, and a silicon nitride film were sequentially formed on the film by plasma CVD and then patterned to form an insulating layer and a semiconductor layer. Doped amorphous silicon is formed on these by plasma CVD, patterned to further form the pixel electrode 2 with ITO, and then aluminum is vapor-deposited to a thickness of 0.5 μm to form a source electrode and a drain electrode. Then, the active element 3 was created. Pixel electrode 2
Was about 100 μm square, and the width of the gate electrode and the source electrode was 5 μm. A silicon nitride film is formed on the active matrix substrate 1 so as to cover the pixel electrode 2, the active element 3 and the signal electrode 4 manufactured here. Then, 5 parts of nylon resin, 1 part of organopolysiloxane, 90 parts of ethanol, and 10 parts of water on the surface of the extraction electrode part.
Part, 0.2 part of glycerin is coated to form a film 7.

The active matrix substrate 1 and the glass substrate 9 facing the active matrix substrate 1 are superposed and bonded with the electrode surface inside. The two substrates are fixed by the seal material 8 with a predetermined gap. At this time, spherical glass beads, plastic beads or the like, or glass fibers may be dispersed on the surface of the substrate for use in order to maintain a stable gap, or may be mixed in the sealing material 8 for use.

Thus, an empty cell as shown in FIG. 1 (a) was prepared. From the injection port, 10 parts of trimethylolpropane triacrylate, 10 parts of 2-hydroxyethyl acrylate, 25 parts of an acrylic oligomer (Toa Gosei Chemical Co., Ltd. “M-1200”), and a photocuring initiator “Darocur-1173” manufactured by Merck & Co., Inc. To 0.5
Parts, 50 parts of "E-7" manufactured by BDH as liquid crystal,
The mixed solution which was uniformly dissolved was injected. After that, ultraviolet rays were irradiated from the glass substrate 10 side to prepare a polymer dispersed liquid crystal display device as shown in FIG. 1 (b).

After that, the take-out electrode portion 12 is immersed in water to remove the coating film. At that time, the excess polymer-dispersed liquid crystal layer formed on the film is also completely removed at the same time. Then, the dirt remaining on the surface of the extraction electrode portion 12 is washed with an organic solvent or the like.

After that, the drive IC 11 is turned on (FIG. 1 (c)).
As shown in FIG. 5, the electrodes are loaded at a predetermined position on the extraction electrode section.
As a loading method, a few μm to 1 formed on the IC by using plating technology or nail head bonding technology
A few μm on a protruding electrode made of Au with a height of 00 μm
To several tens of μm are provided as the conductive bonding layer. The conductive bonding layer is a mixture of epoxy, urethane, phenol, etc. as a main agent as an adhesive and flakes of Ag, Au, Ni, C, SnO ₂ etc. mixed on the protruding electrode by a technique such as transfer. To form.

The driving IC 11 as described above is placed at a predetermined position on the glass substrate 1 so that the conductive bonding layer and the signal electrode 4 are opposed to each other, and they are connected by a heat bonding method using an electric oven, a heat column or the like.

FIG. 2 (a) is a schematic sectional view of a part of the liquid crystal display element before the liquid crystal is injected in the second embodiment of the present invention, and FIG. 2 (b) is the liquid crystal after the liquid crystal is injected. A schematic cross-sectional view of a part of the display element, (FIG. 2C) shows the drive IC after the film is peeled off.
It is a schematic sectional drawing of a part of liquid crystal display element connected with. In the figure, 21 and 22 are glass substrates, and 23 and 24 are transparent electrodes such as ITO, which are patterned in stripes. Reference numeral 25 is a polymer dispersed liquid crystal layer, 26 is a film, 27 is a sealing material, 28 is an anisotropic conductive film connector, and 29 is a flexible printed circuit board on which a driving IC is mounted. The coating film 26 is formed by coating a paint composed of 5 parts of polyvinyl butyral, 1 part of dibutyl phthalate, 2 parts of alkyl phosphate and 30 parts of ethanol.

As shown in FIG. 2 (a), the glass substrates 1 and 10 are each patterned into stripes.
The electrode surfaces are overlapped with each other so that the O transparent electrodes 23 and 24 are orthogonal to each other. An empty cell as shown in FIG. 2 (a) was obtained after fixing with a sealing material 8 while maintaining a predetermined gap to form an empty cell and forming a coating film 26 on the glass substrate 1 side. . As in the case of the first embodiment, 5 parts of trimethylolpropane triacrylate and an acrylic oligomer were previously prepared from the injection port (Toa Gosei Kagaku "M-620").
0 ") 50 parts, Darocur 1116 (Merck).
A resin-liquid crystal mixed solution in which 5 parts and 60 parts of "E-8" (BDH Co.) were uniformly dissolved was injected. Thereafter, this is irradiated with ultraviolet rays to form a polymer dispersed liquid crystal layer 25 as shown in FIG. 2 (b). After that, the coating film 26 is peeled and removed to remove an excessive cured product of the polymer dispersed liquid crystal. .

After that, as shown in FIG. 2 (c), it is connected to the flexible printed circuit board 29 on which the driving IC is mounted via the anisotropic conductive film connector 28.

[0038]

As described above in detail, according to the method for manufacturing a liquid crystal display device of the present invention, an uncured resin-liquid crystal uniform mixed solution is injected into an empty cell, and then the resin-liquid crystal uniform mixed solution inside the cell is injected. When the polymer is cured to form the polymer dispersed liquid crystal layer, the resin-liquid crystal uniform mixed liquid adhering to the periphery of the cell is simultaneously cured and polymerized, and the panel is soiled, or the drive IC cannot be mounted. The problem can be solved easily.

Further, by preliminarily providing a film on a necessary portion, the above problems can be solved, and a polymer dispersed liquid crystal display device can be obtained easily and at low cost. The liquid crystal display device using the polymer-dispersed liquid crystal layer of the present invention does not require a polarizing plate because the display is switched by scattering-transmission, and the transmittance of transmitted light can be greatly improved. Therefore, in the conventional case, the polarizing plate causes a light loss of more than 50%, which is changed to heat and causes a problem of temperature rise of the element, which is unreliable. A bright liquid crystal display device with high utilization efficiency can be obtained.

Further, the alignment treatment such as rubbing which is indispensable for the TN type liquid crystal display element is unnecessary, and the problem of destruction of the active element due to the generation of static electricity accompanying it can be avoided, so that the yield of the liquid crystal display element is improved. be able to.
Further, according to the present invention, it is possible to manufacture the liquid crystal display device of the conventional TN mode by only removing the alignment film forming process from the manufacturing process, and the production is facilitated.

[Brief description of drawings]

FIG. 1A is a schematic sectional view of a part of a liquid crystal display device according to a first embodiment of the present invention before liquid crystal injection. (B) is a partial schematic cross-sectional view according to the first embodiment of the liquid crystal display element of the present invention after liquid crystal injection. (C) is a partial schematic cross-sectional view of a liquid crystal display device of the present invention mounted with a drive IC according to a first embodiment.

FIG. 2A is a schematic cross-sectional view of part of a liquid crystal display device according to a second embodiment of the present invention before liquid crystal injection. (B) is a partial schematic cross-sectional view according to the second embodiment of the liquid crystal display element of the present invention after liquid crystal injection. (C) is a partial schematic sectional view of a second embodiment of the liquid crystal display device of the present invention in which a driving IC is mounted.

[Explanation of symbols]

1 Glass substrate for active matrix substrate 2 pixel electrodes 3 active elements 4 signal electrodes 5 insulating film 6 Polymer dispersed liquid crystal layer 7 film 8 Seal material 9 Counter electrode 10 Glass substrate for counter substrate 11 Driving IC 12 Extraction electrode

Claims (5)

[Claims] 1. A liquid crystal display device comprising a polymer-dispersed liquid crystal layer sandwiched between at least one of upper and lower transparent electrode substrates, and a film is previously provided on the entire surface or a part of the electrode side of the substrate. In addition, a method for manufacturing a liquid crystal display element, characterized in that all or part of the coating film is removed after the liquid crystal display element is manufactured. 2. The polymer matrix of the polymer-dispersed liquid crystal layer is an ultraviolet curable resin, and a solution in which the resin and the liquid crystal are uniformly dissolved in advance is irradiated with light to cure the resin. The method for manufacturing a liquid crystal display element according to claim 1. 3. A coating is provided in advance on at least a portion of the substrate on the electrode side to be connected to a drive circuit as an extraction electrode, and after the liquid crystal display element is manufactured, a part of the coating is removed to expose the electrode portion. The method of manufacturing a liquid crystal display device according to claim 1, wherein the electrode portion and the drive circuit are connected to each other. 4. One of the electrode substrates is an active matrix substrate composed of pixel electrodes and active elements, and a film is formed on the electrode lead-out portion and the IC loading portion of the X direction signal lines and the Y direction signal lines in a plurality of independent display areas. Is provided in advance, and after the liquid crystal display element is manufactured, a part of the film is removed to expose the electrode part and the IC loading part, and the driving I
The method for manufacturing a liquid crystal display device according to claim 1, wherein the liquid crystal display device is equipped with C. 5. The method for producing a liquid crystal display element according to claim 1, wherein the coating film provided on the entire surface or a part of the electrode side of the substrate is a resin coating film having easy peeling property.