JP2988466B2 - Liquid crystal display device, its manufacturing method and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has no increase in the number of processes but is excellent in a visual angle. SOLUTION: In a liquid crystal display device wherein a liquid crystal layer is held between two sheets of substrates 23, 33, and two or more sorts of minute areas coexist in the liquid crystal layer, in order to provide a liquid crystal display excellent in a visual angle, the liquid crystal display device is to be so arranged that at least one substrate 23 has an electrode 22 having an opening part 24 thereon and a second electrode 25 is provided at the position of the opening part 24 for controlling initial orientation of the liquid crystal 11, and the liquid crystal is aligned vertical to the substrate at the side of one substrate, but aligned horizontal to the substrate at the side of the other substrate. In this case, an optical correction plate can be mounted between the substrate and a polarizing plate. Moreover, on this liquid crystal display device, it is possible to control and drive the initial orientation of the liquid crystal by impressing a voltage across a 2nd electrode and its counter electrode and generating a diagonal electric field. A voltage is impressed across the 2nd electrode and the counter electrode to generate the diagonal electric field for controlling the initial alignment, and a liquid crystal display device storing this alignment by polymerizing a small amount of monomer or oligomer mixed with the liquid crystal is manufactured.

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 device, a method of manufacturing the same, and a method of driving the same, and more particularly, to a device which is easy to manufacture and is used as a liquid crystal display device having excellent viewing angle characteristics, and its manufacture. The present invention relates to a method and a driving method thereof.

[0002]

2. Description of the Related Art In a twisted nematic (hereinafter abbreviated as "TN") type liquid crystal display device widely used in the past, liquid crystal molecules when no voltage is applied are parallel to the substrate surface. From the “white” display state, the liquid crystal molecules change the direction of the orientation vector in the direction of the electric field according to the applied voltage, so that the “white” display state gradually changes to “black” display. However, the TN type liquid crystal display device has a problem that the viewing angle is narrow due to the specific behavior of the liquid crystal molecules when the voltage is applied. The problem that the viewing angle is narrow is particularly remarkable in the rising direction of liquid crystal molecules in halftone display.

As a method for improving the viewing angle characteristics of a liquid crystal display device, a technique as disclosed in Japanese Patent Application Laid-Open No. 9-1005041 has been proposed. In this technology, liquid crystal molecules are aligned so that they are almost perpendicular to the substrate surface on one substrate side, and the liquid crystal molecules are aligned so that they are almost parallel to the substrate surface on the other substrate side. Is the rising of liquid crystal molecules (falling from the vertical alignment part)
It is divided into a plurality of areas in different directions, and the viewing angle characteristics are compensated for in each other, so that the viewing angle can be widened. Japanese Patent Application Laid-Open No. 6-43461 discloses a technique for improving viewing angle characteristics by dividing each pixel into two or more domains by an oblique electric field by cutting one pixel electrode in a TN-oriented cell. Is disclosed.

[0004]

SUMMARY OF THE INVENTION
In the technique disclosed in JP-A-9-105041, a complicated process such as a photoresist process or irradiation of polarized light through a mask is added to divide each pixel into a plurality of regions. FIG. 4 shows a case where the region is divided into two regions.
In rubbing, in order to make the orientation direction of the liquid crystal different by 180 °, rubbing is performed on the substrate in one direction with a half of the pixel area covered with a resist mask or the like, and then the resist mask is peeled off. Then, a step of covering the remaining half of the exposed pixel region with a resist mask and then performing rubbing in the opposite direction to the previous one is added. When using polarized light irradiation, a similar mask is used to irradiate half of the pixel with polarized light in an oblique direction, and then the mask is changed and the other half that is not exposed is polarized in a different direction by 180 °. And the step of irradiating.

On the other hand, in the technology disclosed in Japanese Patent Application Laid-Open No. 6-43461, a "fine processing step such as a photoresist step for the common electrode 32" which is not required in a manufacturing process of a normal TN type liquid crystal display device. Is required, and an advanced bonding technique of the upper and lower substrates 22 and 33 is required. This problem is particularly serious in the case of an active matrix liquid crystal display device using a switching element such as a TFT. That is, in an ordinary active matrix liquid crystal display device, an active element such as a thin film diode is manufactured on one transparent substrate, so that a fine processing step such as a photoresist step is required on one side for manufacturing the active element. Other substrates, which are usually called "common electrodes", do not need to be subjected to fine processing, and only have electrodes formed on the entire surface. However, in the technique disclosed in JP-A-6-43461, a fine processing step such as a photoresist step is required even for a “common electrode” that does not normally require fine processing. With the increase, an advanced bonding technique of the upper and lower substrates 22 and 33 is required. Further, in this technology, an opening is provided in an electrode for each pixel region, and the orientation is controlled by an electric field generated. However, as shown in FIGS. Even when a voltage is applied to the electrode 32, a sufficient electric field is not applied to this portion, and the liquid crystal does not respond sufficiently to the applied voltage.

An object of the present invention is to provide a liquid crystal display device having high contrast, quick response and excellent viewing angle characteristics without increasing the above-mentioned problems of the prior art, ie, complicated steps such as a photoresist process. To provide.

Another object of the present invention is to provide a manufacturing method for easily manufacturing such a liquid crystal display device.

Still another object of the present invention is to provide a driving method capable of sufficiently exhibiting the characteristics of a liquid crystal display device having such a high contrast, a fast response, and an excellent viewing angle characteristic.

[0009]

In the liquid crystal display device according to the present invention, the liquid crystal is oriented vertically to the substrate on one substrate side, and the liquid crystal is oriented horizontally to the substrate on the other substrate side. And an electrode having an opening on at least one of the two substrates, a second electrode for controlling the initial alignment of the liquid crystal is provided at the position of the opening, and the second electrode is opposed to the second electrode. By controlling the initial alignment of the liquid crystal by applying a voltage to the electrodes to be formed, and dividing the liquid crystal layer into two or more types of minute regions, high contrast and response can be achieved without increasing the number of complicated steps such as a photoresist step. And realizes excellent viewing angle characteristics of a wide viewing angle.

At this time, "at the position of the opening" means that when the liquid crystal display device is viewed from the front, the opening and the electrode are substantially at the same position and overlap. However, when the liquid crystal display device according to the present invention is viewed as a cross section, it does not mean that the electrode is located at the same position as the opening. That is, the opening and the electrode may be "the same layer" or "different layers" via an insulating film.

Further, in the liquid crystal display device according to the present invention, the liquid crystal has a vertical alignment with respect to the substrate on one substrate side, and the liquid crystal has a horizontal alignment with the substrate on the other substrate side.
At least one of the two substrates is provided with a second electrode for controlling the initial alignment of the liquid crystal insulated from the electrode, and a voltage is applied to the second electrode and the electrode facing the second electrode. By controlling the initial alignment of the liquid crystal and dividing the liquid crystal layer into two or more types of fine regions, high contrast, fast response, and a wide viewing angle can be achieved without increasing the number of complicated steps such as the photoresist process. Viewing angle characteristics. Here, the initial alignment of the liquid crystal is broadly the liquid crystal alignment at the start of driving, but also means the initial alignment at the time of manufacturing a panel.

The liquid crystal display device according to the present invention further comprises:
In order to improve the viewing angle characteristics, at least one optical compensator is provided between the polarizing plate and the liquid crystal cell. It is preferable to use an optically negative compensator from the viewpoint of canceling a change in retardation when viewed from an oblique direction. Such a compensating plate may be a single film produced by a method such as biaxial stretching, or a uniaxially stretched film may be formed by two-axis stretching.
The same effect can be obtained even when a plurality of sheets are stacked and used as a substantially optically negative uniaxial compensator.

If necessary, an optically positive compensator is used to compensate for the optical anisotropy of the liquid crystal layer in the in-plane direction.
White floating when viewed from an oblique direction during black display can be suppressed more effectively.

According to the method of manufacturing a liquid crystal display device of the present invention, a voltage is applied to a control electrode to control the initial alignment, and then a polymerizable monomer or oligomer mixed in a small amount into the liquid crystal is polymerized. In addition, the initial liquid crystal alignment can be further ensured. When controlling the initial alignment, the temperature may be lowered while applying a voltage to the control electrode after the liquid crystal layer is made isotropic by heating, or only a voltage may be applied to the control electrode at room temperature. Further, the reaction of the monomer may be caused before heating to the isotropic phase, may be caused during heating, or may be caused after cooling. When a voltage is applied to the control electrode at room temperature to control the initial alignment, a reaction may be caused before the voltage is applied, or the reaction may be caused after the voltage is applied.

In the method of manufacturing a liquid crystal display device according to the present invention, the pretilt angle is controlled in accordance with the divided shape by using a method such as rubbing or optical alignment on the substrate in advance, and the initial alignment is controlled by the control electrode. In order to make the control extremely reliable and prevent such an orientation from being disturbed by the drive voltage, a more excellent effect can be obtained by polymerizing a polymerizable monomer or oligomer mixed in a small amount in the liquid crystal. At this time, in the case of rubbing, division orientation using a photoresist is performed. In the case of optical alignment,
For example, the digest of technical papers of AMLC'96 / IDW'96 (AM-LCD'96 / IDW'96 Digest of Technical Pape)
rs) P. Using a polymer in which the photosensitive group is polymerized by irradiation with polarized light as described in 337, polarized light is obliquely applied to each part through a mask so that a pretilt angle is obtained in the direction along the divided shape. Irradiate. Although such a split orientation method is well known, the use of a control electrode as in the present invention is much better with respect to the stability of the split. In addition, by polymerizing a polymerizable monomer or oligomer mixed in a small amount in the liquid crystal, the division can be maintained more reliably even during driving. Further, by making the monomer or oligomer into a polymer in order to memorize the orientation of the liquid crystal, there is also an advantage that the response speed is increased.

As the monomers and oligomers used in the present invention, any of photo-curable monomers, thermo-curable monomers, and oligomers thereof can be used. May be included. The "photocurable monomer or oligomer" used in the present invention includes not only those which react with visible light but also ultraviolet curable monomers which react with ultraviolet light, and the latter is particularly desirable from the viewpoint of easy operation.

The polymer compound used in the present invention is:
It may have a structure similar to liquid crystal molecules including monomers and oligomers exhibiting liquid crystallinity, but is not necessarily used for the purpose of aligning liquid crystal, and therefore has flexibility such as having an alkylene chain. You may. Further, it may be a monofunctional one, a bifunctional one, or a monomer having a trifunctional or higher polyfunctionality.

The light or ultraviolet curable monomers used in the present invention include, for example, 2-ethylhexyl acrylate, butylethyl acrylate, butoxyethyl acrylate, 2-cyanoethyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-hydroxypropyl acrylate, 2-ethoxyethyl acrylate, N, N-ethylaminoethyl acrylate, N,
N-dimethylaminoethyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, isobonyl acrylate, isodecyl acrylate, lauryl acrylate, morpholine acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, 2, 2,2-trifluoroethyl acrylate, 2,2,2,2,3-pentafluoropropyl acrylate, 2,2,2,3-tetrafluoropropyl acrylate, 2,2,2,4
Monofunctional acrylate compounds such as 4,4-hexafluorobutyl acrylate can be used.

Also, 2-ethylhexyl methacrylate, butylethyl methacrylate, butoxyethyl methacrylate, 2-cyanoethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate,
-Hydroxypropyl methacrylate, 2-ethoxyethyl acrylate, N, N-diethylaminoethyl methacrylate, N, N-dimethylaminoethyl methacrylate, dicyclopentanyl methacrylate, dicyclopentenyl methacrylate, glycidyl methacrylate,
Tetrahydrofurfuryl methacrylate, isobonyl methacrylate, isodecyl methacrylate, lauryl methacrylate, morpholine methacrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol methacrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,2,3-tetrafluoropropyl methacrylate And monofunctional methacrylate compounds such as 2,2,2,4,4,4-hexafluorobutyl methacrylate.

Further, 4,4'-biphenyl diacrylate, diethylstilbestrol diacrylate,
1,4-bisacryloyloxybenzene, 4,4′-
Bisacryloyloxydiphenyl ether, 4,4 '
-Bisacryloyloxydiphenylmethane, 2,9-
Bis [1,1-dimethyl-2-acryloyloxyethyl] -2,4,8,10-tetraspiro [5,5] undecane, α, α′-bis [4-acryloyloxyphenyl] -1,4-diisopropyl Benzene, 1,4-bisacryloyloxytetrafluorobenzene, 4,
4'-bisacryloyloxyoctafluorobiphenyl, diethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, dicyclopentanyl diacrylate, glycerol diacrylate, 1,6-hexanediol diacrylate Acrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate,
Trimethylolpropane triacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, 4,4'-diacryloyloxystilbene, 4,4 ' -Diacryloyloxydimethylstilbene, 4,4'-diacryloyloxydiethylstilbene, 4,4'-diacryloyloxydipropylstilbene, 4,4'-diacryloyloxydibutylstilbene, 4,4'-diacryloyloxydipentyl Stilbene, 4,4'-diacryloyloxydihexylstilbene, 4,4'-diacryloyloxydifluorostilbene, 2,2,2,2 , 4-hexafluoro-pentanediol-1,5 diacrylate, 1,1,
Polyfunctional acrylate compounds such as 2,2,2,3-hexafluoropropyl-1,3-diacrylate and urethane acrylate oligomer can be used.

Furthermore, diethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,3-butylene glycol dimethacrylate, dicyclopentanyl dimethacrylate, glycerol dimethacrylate, 1,6-hexanediol dimethacrylate, Pentyl glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, pentaerythritol trimethacrylate, ditrimethylolpropane tetramethacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol monohydroxypentamethacrylate, 2,2 , 2,2,4,4-hexafluoropentanediol-1 5-dimethacrylate, polyfunctional methacrylate compounds such as urethane methacrylate oligomer, other styrene, amino styrene, there are vinyl acetate, but is not limited thereto.

Further, since the driving voltage of the device of the present invention is also affected by the interfacial interaction between the polymer material and the liquid crystal material, a polymer compound containing a fluorine atom may be used. As such a polymer compound, 2,2,2,2,4,4-hexafluoropentanediol-1,5-diacrylate, 1,1,2,2,2,3-hexafluoropropyl- 1,3-diacrylate, 2,2,2-trifluoroethyl acrylate, 2,2,2,2,3-pentafluoropropyl acrylate, 2,2,2,3-tetrafluoropropyl acrylate, 2,2 2,4,4,4
-Hexafluorobutyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,2,3-tetrafluoropropyl methacrylate, 2,2,2
Examples include, but are not limited to, high molecular compounds synthesized from compounds including 4,4,4-hexafluorobutyl methacrylate, urethane acrylate oligomers, and the like.

When a light or ultraviolet curable monomer is used as the polymer compound used in the present invention, an initiator for light or ultraviolet light may be used. Various initiators can be used, for example,
2,2-diethoxyacetophenone, 2-hydroxy-
2-methyl-1-phenyl-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-
Acetophenones such as hydroxy-2-methylpropan-1-one, benzoin methyl ether, benzoin ethyl ether, benzoin such as benzyldimethyl ketal, benzophenone, benzoylbenzoic acid, 4-phenylbenzophenone, 2,3-dimethyl-4- Benzophenones such as methoxybenzophenone and the like, thioxanthones such as thioxanthone, 2-chlorothioxanthone and 2-methylthioxanthone, diazonium salts, sulfonium salts, iodonium salts and selenium salts can be used.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.

(Embodiment 1) In a liquid crystal display device of the present invention, as shown in FIG. 1, a layer composed of liquid crystal molecules 11 is provided between two substrates 22 and 33 having electrodes 22 and 32, respectively. Have been. A vertical alignment film 31 is applied to one of the electrodes, and rubbed as necessary. An alignment film 21 for aligning the liquid crystal substantially parallel to the substrate surface is applied to one of the electrodes, and rubbed as necessary. An opening 24 is provided in the electrode 22 of one substrate 23, and a second electrode 25 for controlling the initial alignment of the liquid crystal is provided at the same position as the opening 24. 25 can be applied with different voltages.

When the opening 24 and the second electrode 25 are not provided, the direction in which the liquid crystal molecules fall (tilt) when a voltage is applied is such that rubbing is performed on the alignment film on the vertical alignment substrate side. If not, it is random, and if rubbed, it matches the rubbing direction. Therefore, in order to divide the direction in which the liquid crystal falls, a photoresist step or a polarized light irradiation step through a mask is required. On the horizontal alignment substrate side, the rubbing direction has a pretilt angle, and the rising direction of the liquid crystal molecules when a voltage is applied coincides with the direction of the pretilt angle. Therefore, the rising direction is limited to either one. Therefore, also in this case, in order to divide the rising direction, a photoresist step or a polarized light irradiation step through a mask is required. On the other hand, in the liquid crystal display device of the present invention, since the second electrode 25 for controlling the initial alignment of the liquid crystal exists in addition to the electrode 22, between the second electrode 25 and the electrode 32. By applying a voltage, an oblique electric field is generated in the liquid crystal layer. Therefore, the liquid crystal molecules 11 fall in the direction along the oblique electric field as shown in FIG. At this time, rubbing is performed on the side of the horizontal alignment substrate to define the alignment direction of the liquid crystal in the plane. Regulations are effectively implemented. At this time, the control electrode may be located on either the vertical alignment substrate side or the horizontal alignment substrate side, but is preferably on the horizontal alignment side from the viewpoint of alignment stability.

Dividing the orientation of the liquid crystal by using an oblique electric field can be realized by using an electrode provided with an opening as in the conventional example shown in FIGS. However, in the prior art, as shown in FIGS. 5 and 6, since there is no electrode in the portion of the opening 34, even when a voltage is applied to the electrode 32, a sufficient electric field is not applied to this portion. However, there is a disadvantage that the liquid crystal does not sufficiently respond to the applied voltage.

Further, it has been found that a desired effect cannot be obtained simply by providing an opening when driving with an active element. That is, in the case of a generally manufactured active element, the photoresist process is not required for the electrode on the color filter side (generally called a common electrode), and the electrode is formed on the entire surface. Also,
On the substrate on the active element side, switching elements are formed for each pixel, and pixel electrodes are isolated. In such an element, in order to divide the liquid crystal by the effect of the oblique electric field due to the difference in size between the upper and lower electrodes,
It is essential that the opening be opened in the common electrode. FIG.
FIG. 6 shows a cross section when an opening is formed in the common electrode, and FIG. 7 shows a cross section when an opening is formed in the electrode on the active element side. As is clear from FIG. 7, when the electrode 22 on the active element side is small, unless an opening is provided on the common electrode side,
Conversely, there is a tilting portion, and a portion in which an oblique electric field is not generated therebetween, and this portion does not produce a desired alignment such that disclination occurs, and a tilt direction of liquid crystal molecules cannot be defined. As a result, a uniform display cannot be obtained. However, in order to form an opening in the common electrode, a photoresist process is required on the common electrode side. For this reason, the number of photoresist steps that are not required in a normal liquid crystal display device increases, leading to a decrease in yield and an increase in price.

When an opening is provided in a pixel electrode on the active element side as in the present invention, the number of photoresist steps does not increase only by changing the mask. Also, with this alone,
Since there is a drawback that an oblique electric field is not generated due to a difference in size between the upper and lower electrodes, a second electrode for controlling liquid crystal alignment is formed in the opening, and a voltage is applied to this second electrode to generate an oblique electric field. This situation is shown by a broken line in FIG. The second electrode for this control can be formed in a separate layer from an electrode layer such as a signal line and a drain line when manufacturing an active element.
It is desirable to manufacture the same layer as any of the electrode layers. Thus, a desired oblique electric field can be formed only by changing the mask without increasing the number of photoresist steps. For example, the use of an electrode layer constituting a gate electrode layer as a second electrode layer can be given. Note that the effect remains the same whether the second electrode is in the opening or at the same position as the opening through the insulating layer.

The shape of the control electrode in the present invention is shown in FIG.
As shown in (a), the "-" type is basic,
It may be a "|" type as shown in FIG. Further, the smaller the division unit is, the more effectively the control electric field works. Therefore, as shown in FIGS. 3C and 3D, a shape in which a plurality of “−” types or “|” types exist is more preferable. desirable. In addition, it may be formed obliquely to the pixel in consideration of the influence of the horizontal electric field. The “−” type or “|” type electrode may be connected to another control electrode portion as a control electrode or may be floating. In the figure, for convenience, the control electrodes of each pixel are depicted as being independent, but they are actually connected so that a voltage can be applied collectively from an extraction terminal at the end of the panel.

In a further preferred embodiment of the present invention, a liquid crystal cell having a structure as shown in FIG.
This is realized by heating the cell above the liquid crystal isotropic phase-liquid crystal layer transition temperature while applying a voltage to the control electrode 25 and the counter electrode 32, and cooling the cell to a temperature below the isotropic phase-liquid crystal layer transition temperature. You. By this operation, the control of the initial alignment of the liquid crystal is performed more uniformly.

In still another embodiment of the present invention, a liquid crystal cell having a structure as shown in FIG. 1 is manufactured, a liquid crystal containing a small amount of monomer or oligomer is injected, and a voltage is applied to the control electrode 25 and the counter electrode 32. While polymerizing the monomer or oligomer with light or heat. As a result, the initial alignment of the liquid crystal becomes stronger, and the liquid crystal also becomes more resistant to physical shock during use.

In this polymerizing step, the cell is heated to a temperature equal to or higher than the isotropic phase-liquid crystal layer transition temperature of the liquid crystal as described above, if necessary, to a temperature equal to or lower than the isotropic phase-liquid crystal layer transition temperature. It may be carried out after cooling to make the orientation of the liquid crystal sufficiently uniform.

Further, a substrate which has been subjected to a normal division alignment treatment such as changing the rubbing direction or irradiating polarized light obliquely according to the structure of the control electrode is prepared.
When a voltage is applied to the counter electrode 5 and the counter electrode 32, the division boundary can be fixed firmly over the entire panel, and the reliability is greatly improved. At this time, the reliability is further improved by using a liquid crystal containing a monomer or an oligomer, forming a divided state, and then polymerizing the divided state. As the vertical alignment film applied to one of the substrates at this time, a normal vertical alignment film can be used in the case of rubbing, and in the case of irradiating polarized light obliquely, for example, AMC '96 / IDW 96 digests of technical papers (AM-LCD'96 / ID
W'96 Digest of Technical Papers) As described in 337, a polymer capable of polymerizing a photosensitive group by irradiation with polarized light can be used.

(Embodiment 2) In still another embodiment of the present invention, the second electrode for controlling the initial alignment of the liquid crystal is insulated on one of the electrodes for driving the liquid crystal. It exists through the membrane. FIG. 2 shows this structure. Also in this case, in the case of a liquid crystal display device that drives liquid crystal using an active element, the second shape for controlling the initial alignment of the liquid crystal on the electrode of the substrate on the side where the active element is located is determined from the shape of the electrode. Desirably, electrodes are present.
Also in this case, if the form of the active element is selected, the number of photolithography steps is not increased, and at the time of driving, there is no portion where no voltage is applied in the pixel as compared with the case where the opening is simply provided. An image excellent in terms of contrast and aperture ratio can be obtained.

Also in this case, after injecting the liquid crystal,
While applying voltage to the second electrode for controlling the initial alignment of the liquid crystal and the electrode of the opposite substrate, the liquid crystal is heated to a temperature higher than the liquid crystal phase-isotropic phase transition point temperature, and the liquid crystal phase-isotropic phase transition is performed. Cooling to a temperature below the point ensures the alignment of the liquid crystal.

Also, exactly as in the first embodiment,
A small amount of monomer or oligomer is mixed with the liquid crystal, and while applying voltage to the second electrode for controlling the initial alignment of the liquid crystal and the electrode of the opposite substrate, the monomer or oligomer is polymerized by light or heat. As a result, the orientation of the liquid crystal becomes stronger, and the occurrence of disclination and the like can be more reliably suppressed even during driving.

Further, by using a substrate that has been subjected to divisional alignment along the shape of the second electrode by rubbing, optical alignment, or the like, the orientation of the liquid crystal during the division and driving of the liquid crystal becomes strong, The occurrence of disclination and the like can be further suppressed. At this time, while applying a voltage to the second electrode for controlling the initial alignment of the liquid crystal and the electrode of the counter substrate, if necessary, heating to a temperature higher than the liquid crystal phase-isotropic phase transition temperature of the liquid crystal, Even when cooled to a temperature below the liquid crystal phase-isotropic phase transition point, a small amount of a monomer or oligomer is mixed in the liquid crystal, and the second electrode for controlling the initial alignment of the liquid crystal and the electrode on the opposite substrate are used. When a monomer or oligomer is polymerized by light or heat while applying a voltage to the substrate, the alignment can be more reliably regulated, and excellent image quality can be obtained.

[0039]

Next, the present invention will be described in detail with reference to examples. (Example 1) Size of one pixel: 100 μm × 300 μ
A substrate having an amorphous silicon thin film transistor array (TFT) with m, the number of pixels: 480 × 640 × 2, and the diagonal size of the display screen: 240 mm was formed on a glass substrate by repeating the film formation process and the lithography process.

The TFT according to the first embodiment has an inverted staggered structure and includes a gate-chromium layer, a silicon nitride-insulating layer, an amorphous silicon-semiconductor layer, a drain-source-chromium layer, and a pixel-ITO layer from the substrate side. Have been.
5 μm width in diagonal direction is applied to ITO of each pixel electrode
An opening having a “−” shape was provided, and an electrode having a “−” shape was made of chromium so as to match the opening. This electrode was designed so that a voltage different from that of the pixel portion could be externally applied. (Because this electrode was made of chromium in the same layer as the gate electrode, there was no new additional step as compared with the conventional manufacturing process.) An RGB color filter substrate was used.

After these substrates were washed, alignment films 21 and 31 made of polyimide vertical alignment agent: SE1211 (trade name, manufactured by Nissan Chemical Industries, Ltd.) were applied to the color filter substrate side, and then 90 ° C., 15 minutes and 200 ° C. The firing was performed for one hour. On the TFT substrate side, polyimide JALS428 (JSR
Co., Ltd.), 90 ° C, 15 minutes and 200
The firing was performed at a temperature of 1 ° C. for one hour. The alignment film on the TFT substrate side was subjected to a rubbing treatment in a direction parallel to the long side of the “−” shaped electrode. In this orientation film, the liquid crystal was oriented perpendicular to the rubbing direction, and the pretilt angle was almost 0 °.

Thereafter, an adhesive is applied to the periphery of the substrate,
Latex spheres having a diameter of 6 μm were sprayed as spacers.
Subsequently, both substrates were aligned and bonded together under pressure. Place the bonded substrates in a vacuum chamber, and after evacuation,
A normal nematic liquid crystal excluding the chiral agent was injected.
Next, two stretched films made of polycarbonate are bonded to the obtained liquid crystal panel so that the stretching axes are orthogonal to each other.
A film having a substantially optically uniaxial negative anisotropy
nd was set so that the sign was opposite to and equal to Δnd of the liquid crystal cell, and the liquid crystal cell was attached to the liquid crystal panel. 2 on this
Two polarizing films were stuck so as to be orthogonal to each other to obtain a liquid crystal display device.

A voltage of 8 V was applied to the "-" shaped electrode of the obtained liquid crystal display device with respect to the counter electrode, and a display was performed in the same manner as usual. The pixel display voltage is about 5.5V. It was found that there was no gradation inversion in any direction, and an excellent image was obtained.

Comparative Example 1 For comparison, the liquid crystal display device used in Example 1 was driven in the same manner as in Example 1 except that the liquid crystal display device was driven without applying a voltage to the “−” shaped electrode. I let it. In Comparative Example 1, many afterimages were observed. Also, when viewed from an oblique direction, a rough feeling was observed. When observed with a microscope, it was observed that disclination was generated in each pixel and changed over time immediately after voltage application.

Example 2 A panel was produced in the same manner as in Example 1 except that a TFT having a staggered structure was produced as a TFT substrate. Size of one pixel: 100 μm × 30
A substrate having an amorphous silicon thin film transistor array (TFT) of 0 μm, the number of pixels: 480 × 640 × 2, and the diagonal size of the display screen: 240 mm was formed on a glass substrate by repeating the film formation process and the lithography process.

The TFT according to the second embodiment has a forward staggered structure, and includes a pixel-ITO layer, a source / drain-chromium layer, an amorphous silicon-semiconductor layer, a silicon nitride-insulating layer, and a gate-chromium layer from the substrate side. It is configured. The width of the ITO of each pixel electrode is 5 mm in the diagonal direction.
An opening having a “-” shape of μm was provided, and an electrode having a “-” shape was made of chromium so as to coincide with the opening. This electrode was designed so that a voltage different from that of the pixel portion could be externally applied. (Because this electrode was made of chromium in the same layer as the gate electrode, there was no additional step compared to the conventional manufacturing process.)

A panel was assembled and liquid crystal was injected in the same manner as in Example 1 to produce a liquid crystal display. A voltage of 8 V was applied to the "-" shaped electrode of the obtained liquid crystal display device with respect to the counter electrode, and display was performed in the same manner as usual. The pixel display voltage is about 5V.

Also in the second embodiment, similar to the first embodiment, it was found that there was no gradation inversion in any direction and an excellent image was obtained.

(Comparative Example 2) For comparison, the same as in Example 2 except that no voltage was applied to the “−” shaped electrode when a voltage was applied.
A device was prepared and driven in the same manner as described above. The divided state of the two regions was irregular, and afterimages and roughness in oblique directions were recognized.

Example 3 A TFT substrate was manufactured in the same manner as in Example 1, and a panel was manufactured in combination with a color filter substrate. The bonded substrate is placed in a vacuum chamber, and after evacuation, the nematic liquid crystal and the ultraviolet curable monomer (Kayarad PE manufactured by Nippon Kayaku Co., Ltd.)
T-30) (1.0 wt% based on liquid crystal), initiator (trade name Irganox 907, 5 wt% based on monomer)
%) Was injected.

The obtained panel was heated to 110 ° C.
UV (0.1 mW / cm ^Two) For 30 minutes
Was. Then, apply a 10 V, 5 Hz sine
5V, 5Hz sine wave voltage applied to pixel
Then, the substrate was cooled at 1 ° C./min. Obtain the obtained cell with a polarizing microscope.
When observed with a microscope, each section follows the “-” shaped electrode,
It was divided into two minute areas. When the cell is tilted
From the change in brightness, the two micro regions are aligned with the orientation shown in FIG.
It was confirmed that it had become.

An optical compensator and a polarizing plate were attached, and the voltage of the "-" shaped electrode of the obtained liquid crystal display was turned off, and the display was performed in a normal state. Even in the halftone, good display was obtained with a wide viewing angle in which no grayscale inversion occurred. When the viewing angle characteristics at the time of gradation display were measured at an azimuth angle of 45 ° using a liquid crystal evaluation device (LCD-5000: trade name), almost the same viewing angle characteristics were obtained in all directions, and gradation inversion was performed. Was not found.

(Example 4) In exactly the same manner as in Example 3,
A liquid crystal display device was prepared, a mixture of liquid crystal, an ultraviolet curable monomer, and an initiator was injected, and at room temperature, a square wave voltage of 40 V and 1 Hz was applied to the “−” shaped electrode, and the pixel electrode and drain of the counter substrate were applied. Line and gate line were kept at 0V.
The voltage was changed to 15 V and 30 Hz, and in this state, ultraviolet rays (0.1 mW / cm ² ) from a high-pressure mercury lamp were irradiated for 1 hour. Observation of the obtained cell with a polarizing microscope revealed that each section was divided into two minute areas according to the “−” shaped electrode. From the change in brightness when the cell was tilted, it was confirmed that the two minute regions had the orientation shown in FIG.

An optical compensator and a polarizing plate were attached, and the voltage of the "-" shaped electrode of the obtained liquid crystal display device was turned off, and the display was performed in a normal state. Even in the halftone, good display was obtained with a wide viewing angle in which no grayscale inversion occurred. When the viewing angle characteristics at the time of gradation display were measured at an azimuth angle of 45 ° using a liquid crystal evaluation device (LCD-5000: trade name), almost the same viewing angle characteristics were obtained in all directions, and gradation inversion was performed. Was not found.

(Example 5) In exactly the same manner as in Example 4,
As shown in FIG. 3B, only the shape of the opening was made rectangular, and a liquid crystal display device installed at the center of the pixel was manufactured. In the same manner as in Example 4, the control electrode having a [-]
A rectangular wave voltage in the Hz state was applied, and the pixel electrode, drain line, and gate line on the opposite substrate were kept at 0V. Voltage 10
V and 30 Hz, and in this state, ultraviolet rays (0.1 mW / cm ² ) from a high-pressure mercury lamp were irradiated for 1 hour. Observation of the obtained cell with a polarizing microscope revealed that each section was divided into two minute areas according to the “−” shaped electrode. From the change in brightness when the cell was tilted, it was confirmed that the two minute regions had a liquid crystal orientation as shown in FIG.

An optical compensator and a polarizing plate were attached, and the voltage of the “−” shaped electrode of the obtained liquid crystal display was turned off, and the display was performed in a normal state. Even in the halftone, good display was obtained with a wide viewing angle in which no grayscale inversion occurred. When the viewing angle characteristics at the time of gradation display were measured at an azimuth angle of 45 ° using a liquid crystal evaluation device (LCD-5000: trade name), almost the same viewing angle characteristics were obtained in all directions, and gradation inversion was performed. Was not found.

(Example 6) Only a liquid crystal display device produced by the same method as in Example 2 was used, and a mixture of liquid crystal, an ultraviolet curable monomer and an initiator was injected in the same manner as in Example 4, and Was cured with ultraviolet light. Observation of the obtained cell with a polarizing microscope revealed that each section was divided into two minute areas according to the “−” shaped electrode. From the change in brightness when the cell was tilted, it was confirmed that the two minute regions had the orientation shown in FIG.

An optical compensator and a polarizing plate were attached, and the voltage of the "-" shaped electrode of the obtained liquid crystal display was turned off, and the display was performed in a normal state. Even in the halftone, good display was obtained with a wide viewing angle in which no grayscale inversion occurred. When the viewing angle characteristics at the time of gradation display were measured at an azimuth angle of 45 ° using a liquid crystal evaluation device (LCD-5000: trade name), almost the same viewing angle characteristics were obtained in all directions, and gradation inversion was performed. Was not found.

Example 7 Using the same substrate as in Example 1, a polyimide vertical alignment agent was applied to the color filter substrate side and baked, and a horizontal alignment film was applied and baked on the TFT substrate. Only the substrate was subjected to a divisional orientation so that the tilting direction of the liquid crystal and the rubbing direction coincided with each other by applying a voltage to the control electrode using a photoresist process. Thereafter, a spacer agent was sprayed in exactly the same manner as in Example 1, the two substrates were bonded together, and after injecting liquid crystal, a compensating plate and a polarizing film were bonded to prepare a liquid crystal display device.

A voltage of 8 V was applied to the "-" shaped electrode of the obtained liquid crystal display device with respect to the counter electrode, and a display was performed in the same manner as usual. The pixel display voltage is about 5.5V. It was found that there was no gradation inversion in any direction, and an excellent image was obtained. No disclination was observed.

[0061]

As described above, according to the present invention, a liquid crystal display device having excellent viewing angle characteristics can be manufactured without increasing the number of photolithography steps.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a sectional view of another embodiment of the liquid crystal display device of the present invention.

FIG. 3 is a plan view of one pixel of an example of the liquid crystal display device of the present invention.

FIG. 4 is a cross-sectional view showing a conventional liquid crystal display device.

FIG. 5 is a sectional view showing a conventional liquid crystal display device.

FIG. 6 is a plan view of one pixel of an example of a conventional liquid crystal display device.

FIG. 7 is a sectional view showing a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Liquid crystal molecule 21, 31 Alignment film 22, 32 Transparent electrode 22, 33 Substrate 24, 34 Opening 25 Electrode 26 Insulating film 41 Rubbing direction

────────────────────────────────────────────────── ─── Continuing on the front page (72) Hideya Murai, Inventor 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Kazumi Kobayashi 5-7-1 Shiba, Minato-ku, Tokyo NEC (72) Inventor Yoshihiko Hirai 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-11-109393 (JP, A) (58) Fields surveyed (Int .Cl. ⁶ , DB name) G02F 1/1337 G02F 1/133

Claims (24)

(57) [Claims] In a liquid crystal display device in which a liquid crystal layer is sandwiched between two substrates and two or more types of minute regions coexist in the liquid crystal layer, there is an electrode having an opening on at least one of the substrates. A second electrode for controlling the initial alignment of the liquid crystal is provided at the position of, and the liquid crystal is oriented perpendicular to the substrate on one substrate side, and the liquid crystal is oriented horizontally with the substrate on the other substrate side. A liquid crystal display device that specializes in: 2. A liquid crystal display device in which a liquid crystal layer is sandwiched between two substrates and two or more types of minute regions coexist in the liquid crystal layer. At least one electrode on one of the substrates has a liquid crystal insulated from the electrode. A second electrode is provided for controlling the initial alignment of the liquid crystal, and the liquid crystal is oriented perpendicular to the substrate on one substrate side and the liquid crystal is oriented horizontally with the substrate on the other substrate side. Liquid crystal display device to be fine. 3. The liquid crystal display device according to claim 1, wherein at least one optical compensator is provided between at least one of the upper and lower substrates and the polarizing plate. 4. The pixel according to claim 1, wherein the second electrode has a portion parallel to the short side of each pixel.
A liquid crystal display device according to the item. 5. The liquid crystal display device according to claim 1, wherein the second electrode is provided on a diagonal line of each pixel. 6. The method according to claim 1, wherein the second electrode has a portion parallel to the long side of each pixel.
A liquid crystal display device according to the item. 7. The method for manufacturing a liquid crystal display device according to claim 1, wherein an electrode having an opening is provided on at least one substrate, and the electrode is provided at a position of the opening. The liquid crystal is injected into an empty panel provided with a second electrode for controlling the initial alignment of the liquid crystal, and then the isotropic phase of the liquid crystal is applied while a voltage is applied between the second electrode and the opposite electrode.
A method for manufacturing a liquid crystal display device, comprising cooling from a temperature equal to or higher than a liquid crystal layer transition temperature to a temperature equal to or lower than an isotropic phase-liquid crystal layer transition temperature. 8. The method of manufacturing a liquid crystal display device according to claim 1, wherein an electrode having an opening is provided on at least one of the substrates, and the electrode is provided at a position of the opening. A second electrode for controlling the initial alignment of the liquid crystal is provided, and the liquid crystal is injected into an empty panel that has been subjected to an operation of dividing the alignment direction of the liquid crystal on at least one substrate, and then faces the second electrode. A method for manufacturing a liquid crystal display device, comprising cooling from a temperature equal to or higher than the isotropic phase-liquid crystal layer transition temperature of a liquid crystal to a temperature equal to or lower than the isotropic phase-liquid crystal layer transition temperature while a voltage is applied between the electrodes. . 9. The method for manufacturing a liquid crystal display device according to claim 2, wherein an initial alignment of a liquid crystal insulated from the electrode on at least one substrate is controlled. The liquid crystal is injected into an empty panel provided with a second electrode, and then a voltage is applied between the electrode facing the second electrode and a liquid crystal at a temperature equal to or higher than the isotropic phase-liquid crystal layer transition temperature. And cooling to a temperature equal to or lower than an isotropic phase-liquid crystal layer transition temperature. 10. The method for manufacturing a liquid crystal display device according to claim 2, wherein an initial alignment of a liquid crystal insulated from the electrode on at least one substrate is controlled. A second electrode was provided, and the liquid crystal was injected into an empty panel that had been subjected to an operation of dividing the alignment direction of the liquid crystal on at least one of the substrates, and then a voltage was applied between the electrode facing the second electrode. A method for manufacturing a liquid crystal display device, comprising cooling the liquid crystal in a state from a temperature equal to or higher than a transition temperature of an isotropic phase to a liquid crystal layer to a temperature equal to or lower than a transition temperature of an isotropic phase to a liquid crystal layer. 11. The method according to claim 7, wherein the liquid crystal contains a high molecular weight organic compound. 12. The liquid crystal contains a monomer or an oligomer, and after the liquid crystal is injected between the substrates, the monomer or the oligomer is polymerized in the liquid crystal.
11. The method for manufacturing a liquid crystal display device according to any one of items 10. 13. The method for manufacturing a liquid crystal display device according to claim 1, wherein an electrode having an opening is provided on at least one substrate, and the electrode is provided at a position of the opening. A liquid crystal containing a monomer or an oligomer is injected into an empty panel provided with a second electrode for controlling the initial alignment of the liquid crystal, and then light is applied while a voltage is applied between the second electrode and the opposite electrode. And producing a monomer or oligomer into a polymer. 14. The method of manufacturing a liquid crystal display device according to claim 1, wherein an electrode having an opening is provided on at least one of the substrates, and the electrode is provided at a position of the opening. A second electrode for controlling the initial alignment of the liquid crystal is provided, and a liquid crystal containing a monomer or an oligomer is injected into an empty panel that has been subjected to an operation of dividing the alignment direction of the liquid crystal on at least one substrate. A method for producing a liquid crystal display device, comprising irradiating light in a state where a voltage is applied between an electrode and an opposite electrode to polymerize a monomer or an oligomer. 15. The method for manufacturing a liquid crystal display device according to claim 1, wherein an electrode having an opening is provided on at least one substrate, and the electrode is provided at a position of the opening. After injecting a liquid crystal containing a monomer or oligomer into an empty panel provided with a second electrode for controlling the initial alignment of the liquid crystal, the liquid crystal is heated to an isotropic phase, and a voltage is applied between the second electrode and the opposite electrode. Is applied, cooling from a temperature above the isotropic phase-liquid crystal layer transition temperature to a temperature below the isotropic phase-liquid crystal layer transition temperature, irradiating light, and polymerizing the monomer or oligomer. A method for manufacturing a liquid crystal display device, comprising: 16. The method for manufacturing a liquid crystal display device according to claim 1, wherein an electrode having an opening is provided on at least one of the substrates. A second electrode for controlling the initial alignment of the liquid crystal is provided at the position, and after injecting the liquid crystal containing the monomer or oligomer into the empty panel that has been subjected to the operation of dividing the alignment direction of the liquid crystal on at least one substrate, Heating to the isotropic phase and applying a voltage between the second electrode and the opposing electrode, from a temperature above the isotropic phase-liquid crystal layer transition temperature of the liquid crystal to a temperature below the isotropic phase-liquid crystal layer transition temperature Cooling, irradiating light, and polymerizing monomers or oligomers. 17. The method for manufacturing a liquid crystal display device according to claim 2, wherein an initial alignment of a liquid crystal insulated from the electrode on at least one of the electrodes is controlled. A liquid crystal containing a monomer or an oligomer is injected into an empty panel provided with a second electrode for the second electrode, and thereafter, light is irradiated while a voltage is applied between the second electrode and the opposing electrode, and the monomer or the oligomer is irradiated. A method for producing a liquid crystal display device, comprising polymerizing a polymer. 18. The method for manufacturing a liquid crystal display device according to claim 2, wherein an initial alignment of a liquid crystal insulated from the electrode on at least one substrate is controlled. A liquid crystal containing a monomer or an oligomer is injected into an empty panel on which at least one substrate has been subjected to an operation of dividing the alignment direction of the liquid crystal, and then a second electrode is provided between the electrodes facing the second electrode. A method of manufacturing a liquid crystal display device, comprising irradiating light with a voltage applied thereto to polymerize a monomer or oligomer. 19. The method for manufacturing a liquid crystal display device according to claim 2, wherein an initial alignment of a liquid crystal insulated from the electrodes on at least one of the substrates is controlled. After injecting a liquid crystal containing a monomer or an oligomer into the empty panel provided with the second electrode, the liquid crystal is heated to an isotropic phase, and light is applied while a voltage is applied between the second electrode and the opposite electrode. A method for producing a liquid crystal display device, comprising irradiating to polymerize a monomer or oligomer. 20. The method for manufacturing a liquid crystal display device according to claim 2, wherein an initial alignment of a liquid crystal insulated from at least one of the electrodes on one of the substrates is controlled. A second electrode is provided, and after injecting a liquid crystal containing a monomer or an oligomer into an empty panel on which at least one substrate has been subjected to an operation of dividing the orientation direction of the liquid crystal, heating to an isotropic phase, A method for manufacturing a liquid crystal display device, comprising irradiating light with a voltage applied between electrodes facing an electrode to polymerize a monomer or oligomer. 21. The method according to claim 8, wherein the operation of dividing the alignment direction of the liquid crystal is rubbing in different directions.
21. The method for manufacturing a liquid crystal display device according to 10, 14, 16, 18 or 20. 22. The method according to claim 8, wherein the operation of dividing the alignment direction of the liquid crystal is light irradiation.
21. The method for manufacturing a liquid crystal display device according to 6, 18, or 20. 23. The liquid crystal display according to claim 1, wherein an electrode having an opening is provided on at least one substrate, and a second electrode is provided at a position of the opening. A method for driving a liquid crystal display device, comprising: applying a voltage equal to or higher than a voltage applied between an electrode having an opening and an opposing electrode to between a second electrode and an opposing electrode. Method. 24. The liquid crystal according to claim 2, wherein a second electrode for controlling the initial alignment of the liquid crystal insulated from the electrode is provided on at least one substrate. A method for driving a display device, wherein a voltage equal to or higher than a voltage applied between an electrode having a second electrode and an opposite electrode,
A method for driving a liquid crystal display device, wherein a voltage is applied between an electrode facing the second electrode.