KR20030022431A - Thermal crosslinking Polyimide Based Materials And Method For Fabricating Liquid Crystal Display Device By Said It - Google Patents

Abstract

PURPOSE: A thermal crosslinking polyimide, and a method for manufacturing a liquid crystal display device using the same are provided to compensate a viewing angle without attaching a compensating film to an outer surface of a substrate, thereby reducing size and weight of the liquid crystal display device. CONSTITUTION: Gate wires and data wires(117) are formed on a first substrate(111), crossing each other to define pixels in matrix shape. A thin film transistor is formed at each crossing point of the gate wires and the data wires, and selectively turns on and off data signals of the data wires. A pixel electrode(119) is formed at each pixel. Black matrix(131) is formed on a second substrate(112) to prevent light loss. R,G,B color filter layers(132) are formed between the black matrixes to present colors. Common electrodes(133) apply regular voltage to a liquid crystal layer(150). A high molecular substance is applied to the first substrate or the second substrate. The high molecular substance includes a discotic liquid crystal derivative having a characteristic of compensating an optical viewing angle.

Description

Thermal crosslinking polyimide material and method for manufacturing liquid crystal display device using the same {Thermal crosslinking Polyimide Based Materials And Method For Fabricating Liquid Crystal Display Device By Said It}

The present invention relates to a liquid crystal display device (LCD), and more particularly, to an alignment layer having a wide viewing angle compensation function and a liquid crystal display device using the same.

In recent years, active matrix liquid crystal display devices have been widely used in flat panel TVs, portable computers, monitors, and the like, as their performance is rapidly developed.

Among the active matrix liquid crystal display devices, twisted nematic (TN) type liquid crystal display devices are mainly used. In the twisted nematic method, electrodes are disposed on two substrates and the liquid crystal directors are arranged to be twisted by 90 °. It is a technique of driving a liquid crystal director by applying a voltage to an electrode.

Twisted nematic liquid crystal display devices are spotlighted for providing excellent contrast and color reproducibility, but suffer from the chronic problem of narrow viewing angles.

In order to solve the viewing angle problem of the TN method, a compensation film using a discotic liquid crystal is used.

Hereinafter, a liquid crystal display device according to the related art will be described with reference to the accompanying drawings.

1 is a cross-sectional view of a liquid crystal display device according to the prior art.

In the conventional liquid crystal display device, as shown in FIG. 1, the first and second substrates 11 and 12 disposed to face each other, the liquid crystal layer 50 formed between the two substrates, and the first and second substrates ( 11 and 12 are attached to the compensation film 42 selectively attached to the outer circumferential surface and the outer circumferential surfaces of the first and second substrates 11 and 12 to which the compensation film 42 is selectively attached to transmit only light having a specific wavelength. In the liquid crystal display device provided with the polarizing plates 51 and 52, a gate wiring (not shown) and a data wiring 17 arranged in a matrix form on the first substrate 11 to define pixels, and the gate wiring A switching element for selectively transferring the data voltage of the data line 17 to each pixel by a scan signal of the pixel; and a pixel electrode 19 connected to the switching element to finally apply a data voltage to the pixel, and the second On the substrate 12, an array of liquid crystals can be controlled to prevent light leakage. A black matrix 31 formed in a region that cannot be formed, a color filter layer 32 of R, G, and B for realizing color on the black matrix 31, and the pixel electrode on the color filter layer 32. A common electrode 33 to which a common voltage is applied is formed opposite to 19).

At this time, the liquid crystal is driven by the data voltage applied to the pixel electrode 19 and the common voltage applied to the common electrode 33. The pixel electrode 19 or First and second alignment layers 13a and 13b are further provided on the upper surface of the common electrode 33.

A polyimide resin is mainly used as the alignment film, but a rubbing process is performed to provide anisotropy to the alignment film. The thickness of such a polyimide membrane is only several hundred micrometers.

The alignment layer is mainly used a polyimide organic polymer material having excellent affinity with liquid crystals, and is generally formed by imidizing a solution of polyimide acid on a substrate and drying it.

Subsequently, an alignment pattern is formed on the alignment film by a rubbing method for rubbing the surface with a cloth of a special shape.

The rubbing method is widely used in the manufacture of liquid crystal display devices because of easy implementation and simple process.

On the other hand, the compensation film 42 is provided to solve the narrow viewing angle problem in the TN-type liquid crystal display device, and compensates for the phase change of the light according to the visual direction to widen the viewing angle.

Compensation films include uni-axial films, bi-axial films, or wide view films, and are mainly disco to compensate for the phase of light caused by nematic liquid crystals. It is produced using a tick liquid crystal.

In other words, nematic liquid crystals are positive uniaxial and have an extraordinary refractive index greater than ordinary refractive index, and discotic liquid crystals are negative uniaxial and have an abnormal refractive index more than normal refractive index. Since it is small, it can reduce the phase difference change of the nematic liquid crystal according to a direction as a discotic liquid crystal.

The compensation film 42 and the polarizing plates 51 and 52 may be integrally formed and attached to the outer surface of the substrate.

However, the conventional liquid crystal display device as described above has the following problems.

First, in order to solve the narrow viewing angle problem of the TN type liquid crystal display device, a compensation film is further attached to the outer surface of the substrate to compensate the viewing angle, but there is a limitation in compensating the tilt birefringence with the compensation film. Film production is also difficult and difficult.

Second, since the compensation film is additionally provided in the device, it is difficult to manufacture a liquid crystal display device having a light weight and thinness.

Third, the conventional polymerization type polyimide alignment film is unstable in solvent resistance and dimensional stability, so that the alignment state is disturbed by the cleaning solvent or heat, which causes defects.

The present invention has been made to solve the above problems, and an object thereof is to provide a cross-linked polyimide material having a wide viewing angle compensation characteristics and a method of manufacturing a liquid crystal display device using the same.

1 is a cross-sectional view of a liquid crystal display device according to the prior art.

2 is a cross-sectional view of a liquid crystal display device according to the present invention.

* Explanation of symbols on the main parts of the drawings

111: first substrate 112: second substrate

113 alignment film 114 gate electrode

115: gate insulating film 116: semiconductor layer

117: data wiring 117a: source electrode

117b: drain electrode 118: protective film

119: pixel electrode 131: black matrix

132: color filter layer 133: common electrode

140: spacer 141: sealant

150: liquid crystal layer

Cross-linked polyimide material of the present invention for achieving the above object is characterized in that it comprises a discotic (discotic) liquid crystal derivative having an epoxy group (epoxy group).

In addition, a method of manufacturing a liquid crystal display device using the crosslinked polyimide material may include a liquid crystal layer provided between a first substrate and a second substrate that are opposed to each other. It is characterized by forming an alignment film containing a discotic liquid crystal derivative having an epoxy group on the inner side.

Hereinafter, a cross-linked polyimide material and a method of manufacturing a liquid crystal display device using the same according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view of a liquid crystal display device according to the present invention.

First, a polyimide-based material of Chemical Formula 1 having diamine on both sides by an equivalent-to-equivalent reaction of diamine and dianhydride is synthesized.

Here, the diamine is 2,5-diaminobenzonitrile, 2- (trifluoromethyl) -1,4-benzenediamine (2- (trifluoromethyl) -1,4-benzenediamine), p-phenylene P-phenyl1enediamine, 2-chloro-1,4-benzenediamine, 2-fluoro-1,4-benzenediamine , m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diamino ratio Phenyl (4,4'-diaminobiphenyl), 3,3'-dimethyl-4,4'-diaminobiphenyl (3,3'-dimethyl-4,4'-diaminobiphenyl), 3,3'-dimethoxy- 4,4'-diamino-4,4'-diaminobiphenyl, diaminodiphenylmethane, diaminodiphenyl ether, 2,2-diamino Diphenylpropane (2,2-diaminodiphenylpropane), bis (3,5-diethyl-4-aminophenyl) methane (bis (3,5-diethyl-4-aminophenyl) methane), diaminodiphenylsulfone one), diaminonaphthalene, 1,4-bis (4-aminophenoxy) benzene (4,4'-diaminobenzophenone (4,4) '-diaminobenzophenone), 3,4'-diaminobenzophenone, 1,4-bis (4-aminophenyl) benzene, 1,4-bis (4-aminophenyl) benzene, 9 , 10-bis (4-aminophenyl) anthracene (9,10-bis (4-aminophenyl) anthracene), 4,4'-bis (4-aminophenoxy) diphenylsulfone (4,4'-bis (4 -aminophenoxy) diphenylsulfone), 2,2-bis [4- (4-aminophenoxy) phenyl] propane (2,2-bis [4- (4-aminophenoxy) phenyl] propane), 2,2-bis (4 -Aminophenyl) hexafluoropropane (2,2-bis (4-aminophenyl) hexafluoropropane), 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane (2,2-bis [4 Alicyclic diamines such as-(4-aminophenoxy) phenyl] hexafluoropropane), bis (4-aminocyclohexyl) methane, tetramethylene diamine, hexamethylene diamine aliphatic diamine such as hexamethylene diamine, diaminosiloxane such as bis (3-aminopropyl) tetramethyldisiloxane, and derivatives of the above materials. Selected from the group.

In addition, the dianhydride is pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride (2,3,6,7-naphthalenetetracarboxylic dianhydride), 1,2 , 5,6-naphthalenetetracarboxylic dianhydride (1,2,5,6-naphthalenetetracarboxylic dianhydride), 1,4,5,8-naphthalenetetracarboxylic dianhydride (1,4,5,8 -naphthalenetetracarboxylic dianhydride), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride), 2,3,2 ', 3'-ratio Phenyltetracarboxylic dianhydride (2,3,2 ', 3'-biphenyltetracarboxylic dianhydride), bis (3,4-dicarboxyphenyl) ether dianhydride (bis (3,4-dicarboxyphenyl) ether dianhydride), Bis (3,4-dicarboxyphenyl) diphenylsulfon dianhydride (bis (3,4-dicarboxyphenyl) diphenylsulfone dianhydride), bis (3,4-dicarboxyphenyl) methane dianhydride Bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 1 , 1,1,3,3,3-hexafluoro-2,2-bis (3,4-dicarboxyphenyl) propane dianhydride (1,1,1,3,3,3-hexafluoro-2,2 -bis (3,4-dicarboxyphenyl) propane dianhydride), bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride (bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride), 2,3,4,5-pyridine Tetracarboxylic dianhydride (2,3,4,5-pyridinetetracarboxylic dianhydride), 1,2,3,4-butanetetracarboxylic dianhydride (1,2,3,4-butanetetracarboxylic dianhydride), 1 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride (1,2,3,4-cyclobutanetetracarboxylic dianhydride) , 2,3,4-cyclopentanetetracarboxylic dianhydride), 1,2,4,5-cyclohexanetetracarboxyl 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,4- Dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic Dianhydride (3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride) and the like and derivatives thereof and Cl-, F- derivatives.

For reference, a derivative having an aliphatic long-chain in the two monomers may be further included to increase tilt control or solubility.

An epoxy group is introduced by synthesizing a functional group of a discotic liquid crystal to a polyimide material, which is an intermediate synthesized in the form as described above.

Here, the discotic liquid crystal has an epoxy series as a functional group is selected from the group of the following formula (2).

Where R has an epoxy group

(n is an integer).

In other words, when a derivative of a polyimide-based material having a diamine and a discotic liquid crystal having an epoxy group is dissolved in a suitable solvent while being heated, the amine of the polyimide binds to the epoxy group of the discotic liquid crystal by repeating this process. A thermal crosslinked polyimide-based material having wide viewing angle compensation characteristics is made.

As the solvent, NMP (N-methylpyrrolidinone), gamma-butyllactone (γ-butyllactone), BC (Butyl Cellosolve) and the like are used, and dissolved in the solvent to prepare a solution phase of 1 to 30wt%.

The solution phase is applied onto a substrate to form an alignment layer, and then cured to evaporate the solvent to form a crosslinked polyimide alignment layer having a wide viewing angle characteristic.

The alignment layer formed as described above compensates for the phase of light according to the direction of light to implement a wide viewing angle.

In the above embodiment, one kind of discotic liquid crystal is synthesized in one kind of intermediate, but two or more kinds of intermediates may be introduced or two or more kinds of discotic liquid crystals may be introduced.

The alignment film material according to the present invention is applied to the method of manufacturing a liquid crystal display device as follows.

First, the gate wiring (not shown) and the data wiring 114 which are insulated from each other on the first substrate 111 are vertically formed to define a pixel in a matrix array form, and the gate voltage of the gate wiring is formed at the intersection of the two wirings. As a result, a thin film transistor for selectively turning on / off a data signal of a data line is formed, and then a pixel electrode 119 connected to the thin film transistor is formed in each pixel.

In this case, the thin film transistor is formed on the gate electrode 114 branched from the gate wiring, the gate insulating film 115 formed on the entire surface including the gate electrode 114, and the gate insulating film on the gate electrode 114. The semiconductor layer 116 is formed and source / drain electrodes 117a and 117b extending from the data line 117. An ohmic contact layer of n ⁺ a-Si may be formed on the semiconductor layer 116.

Next, a black matrix 131 formed to prevent light leakage on the second substrate 112, a color filter layer 132 of R, G, and B formed between the black matrix 131 to express color, and The common electrode 133 that applies a predetermined voltage to the liquid crystal layer 150 is formed to face the pixel electrode 119.

Subsequently, a spin coating method and a coating method are performed on a polymer material including a discotic liquid crystal derivative having a wide viewing angle compensation characteristic on the first substrate 111 or the second substrate 112 on which the various patterns are formed. The coating is carried out using the back.

The polymer material is dissolved in NMP, γ-butyllactone, BC and the like by heating polyimide and discotic liquid crystal partially synthesized with dianhydride and diamine to prepare a solution-like polymer material of 1 to 30 wt%.

At this time, in order to adjust the tilt and increase the solubility, the polyimide may be synthesized including a derivative having an aliphatic long chain.

In this manner, by inducing a thermal crosslinking reaction between the discotic liquid crystal and the polyimide, an alignment film having excellent solvent resistance and dimensional stability as well as viewing angle compensation characteristics can be obtained.

Subsequently, the alignment layer 113 is formed by curing the polymer material applied in a solution state on the substrate to completely remove the solvent remaining therein and densifying the polymer material.

Next, after the alignment layer 113 is rubbed or irradiated with light to form an alignment process, a sealant 141 is formed at an edge of the first substrate 111 and the spacer 140 is formed in an active region of the second substrate 112. ) Is uniformly distributed, and the first and second substrates 111 and 112 are opposed to each other.

Finally, a liquid crystal is injected between two oppositely bonded substrates to form the liquid crystal layer 150 and the sealing process is completed.

The liquid crystal is usually a liquid crystal having a nematic structure, and the liquid crystal may have positive dielectric anisotropy and negative dielectric anisotropy, and chiral dopants may be added.

Since the liquid crystal display device formed as described above compensates the viewing angle in the alignment layer itself, it is not necessary to attach a compensation film for the viewing angle compensation on the outer surface of the substrate, and the device is made thin.

For reference, the alignment layer may be used as a rubbing alignment layer or a photoalignment layer, and may include twisted nematic (TN), super twisted nematic (STN), optically compensated birefrigence (OCB), vertical alignment (VA), and ferroelectric (FLC). Effective for modes that require viewing angle compensation, including liquid crystal display (AFLC), anti-ferroelectric liquid crystal (AFLC), polymer dispersed liquid crystal display (PDLC), a-Si TFT, poly-Si TFT, and metal-insulator-metal (MIM) to be.

The cross-linked polyimide material and the method of manufacturing the liquid crystal display device using the same according to the present invention as described above have the following effects.

First, since the alignment film capable of viewing angle compensation is provided, it is not necessary to further attach a compensation film for viewing angle compensation on the outer surface of the substrate, thereby enabling a lighter and thinner device.

In addition, it is possible to solve the costs and process additions due to the use of compensation film.

Second, the alignment film according to the present invention is a thermally cross-linked polyimide, which has thermal stability, so that the alignment is not disturbed, the solvent resistance is excellent, and the cleaning solvent is easily selected.

Claims (10)

A thermal crosslinked polyimide material comprising a discotic liquid crystal derivative having an epoxy group. "The discotic liquid crystal is It is selected from the group of. Where R is And n is an integer. The method of claim 1, wherein the discotic (discotic) is a thermal crosslinked polyimide material, characterized in that consisting of the imide intermediate represented by the formula (1). [Formula 1] 3. The thermally crosslinked polyimide material according to claim 2, wherein the imide intermediate is a composite of diamine and dianhydride. A liquid crystal display device comprising a liquid crystal layer between a first bonded substrate and a second substrate opposed to each other, An alignment film comprising a discotic liquid crystal derivative having an epoxy group is formed on the inner surface of the first substrate or the second substrate. The method of claim 4, further comprising forming a thin film transistor and a pixel electrode on the first substrate. The method of claim 1, wherein the alignment layer is manufactured by synthesizing an imide intermediate represented by Chemical Formula 1 and a discotic liquid crystal selected from the group of Chemical Formula 2. [Formula 1] [Formula 2] Where R is And n is an integer. The method of claim 6, wherein the imide intermediate is prepared by synthesizing dianhydride and diamine. The method of claim 6, further comprising a derivative having an aliphatic long-chain in the imide intermediate to synthesize the liquid crystal display device. The method of claim 4, wherein the alignment layer comprises two or more discotic liquid crystal derivatives. The method of claim 4, wherein the alignment layer comprises two or more kinds of imide intermediates.