JP3269771B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a liquid crystal display device and a method of manufacturing the same, and more particularly to a liquid crystal display device having excellent viewing angle characteristics, a high contrast ratio, and excellent display quality without disclination lines. The present invention relates to a structure of a liquid crystal display device and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, twisted nematic (T)
N) type liquid crystal display devices are widely used. Below, TN
Display principle of the liquid crystal display device will be described.

In a TN type liquid crystal display device, an alignment process is performed so that liquid crystals are orthogonal to each other between upper and lower substrates. Therefore, the liquid crystal when no voltage is applied is twisted by 90 ° between the upper and lower substrates. Further, the liquid crystal display device is capable of rotating the liquid crystal by sandwiching the two polarizing plates from the outside of the upper and lower substrates so that their polarization axes and the alignment direction of the alignment process are the same and the polarization axes are orthogonal to each other. Light is transmitted by the property, and a bright display is shown.

On the other hand, when a voltage is applied to the liquid crystal display device, the liquid crystal molecules rise up with respect to the substrate and release the twist, so that the liquid crystal display device cuts off light and displays a dark image. However, since the liquid crystal molecules are oriented in one direction with respect to the substrate, they rise in one direction by applying a voltage. As a result, this liquid crystal display device has a problem that the contrast greatly changes depending on the viewing angle, and black-and-white inversion occurs.

Further, in the above liquid crystal display device, since the polarization axes of the two polarizing plates are orthogonal to each other, the direction forming an angle of 45 ° with the polarizing axis of the polarizing plate apparently has the polarization axes orthogonal to each other. Not. Accordingly, in such a direction, the incident light becomes elliptically polarized light and enters the eyes, so that light leakage of the liquid crystal display device occurs and the contrast is reduced. As described above, the liquid crystal display device has a large viewing angle dependency.

Several methods have been proposed to improve the viewing angle dependence of the contrast of the TN type liquid crystal display device.

Japanese Patent Application Laid-Open No. 6-194655 discloses that a liquid crystal cell is prepared without performing a rubbing treatment on a substrate on which an isotropic film is formed, and a chiral agent is added so that a 90 ° twist can be obtained in the liquid crystal. A liquid crystal display device in which liquid crystal molecules are randomly aligned is disclosed. In this liquid crystal display device, since the liquid crystal molecules are randomly aligned, the viewing angle dependence on the contrast is small.

However, since the liquid crystal domain is an aggregate of minute domains, the obtained liquid crystal display device has low light transmission efficiency and cannot obtain a sufficient bright display. Further, there is a problem that disclination occurs between the domains when a voltage is applied, and the contrast is reduced.

JP-A-6-265902 and JP-A-6-265902
Japanese Patent Application Laid-Open No. 324337 discloses a liquid crystal display device in which a radial or concentric alignment process is performed in pixel units.

However, the pixel unit is usually several hundred μm.
Therefore, it is very difficult to physically or chemically perform radial or concentric alignment processing on a pixel-by-pixel basis. Furthermore, these liquid crystal display devices generate a disclination line at the boundary between pixels when a voltage is applied, and since the disclination line penetrates into the inside of the pixel, it cannot be hidden by a black mask. There is a problem that can not be.

On the other hand, recently, a liquid crystal display device utilizing a dynamic scattering (DS) effect or a phase transition (PC) effect of a liquid crystal has been developed. This liquid crystal display device electrically controls the transparent or opaque state by the birefringence of the liquid crystal without requiring a polarizing plate and an alignment treatment. That is, this liquid crystal display device basically displays the transparent state by aligning the orientation of the liquid crystal when a voltage is applied, by matching the ordinary light refractive index of the liquid crystal molecules with the refractive index of the supporting medium,
When no voltage is applied, the orientation of liquid crystal molecules is disturbed to display a light scattering state.

As a method for producing such a liquid crystal display device, a method of embedding a liquid crystal in a polymer capsule (Japanese Patent Application Publication No. 58-501631), a method of embedding a liquid crystal and a photocurable resin or a thermosetting resin A liquid crystal is precipitated by hardening a mixture containing (a) and (b), and a liquid crystal droplet is formed in the resin (Japanese Unexamined Patent Publication (Kokai) No. 61-502128).

Further, in order to improve the viewing angle, Japanese Patent Application Laid-Open No. 4-338923 and Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open Publication No. H11-157210 discloses a liquid crystal display device in which the above-mentioned polymer-dispersed liquid crystal is sandwiched between orthogonal polarizing plates.

However, while these liquid crystal display elements greatly improve the viewing angle characteristics, they use depolarization due to scattering in principle, so that the brightness is lower than half that of the TN mode. Low utility value.

Japanese Patent Application Laid-Open No. Hei 5-27242 discloses a method in which the alignment state of liquid crystal is disturbed by polymer walls or protrusions to create random domains and improve the viewing angle.

However, in this method, the domains are random, the polymer material penetrates into the picture element portions, and disclination lines are randomly generated between the liquid crystal domains. Do not disappear. Therefore, the liquid crystal display device manufactured by this method has a low light transmittance when no voltage is applied, and a low black level when a voltage is applied, so that a sufficient contrast cannot be obtained.

Japanese Patent Application Laid-Open No. 7-120728 discloses a liquid crystal display device in which liquid crystal molecules surrounded by polymer walls are oriented in an axially symmetric manner with respect to the normal line of the substrate, and a manufacturing method thereof. I have. According to this method, the liquid crystal molecules 6 in the liquid crystal cell are radially aligned with respect to the normal line of the substrate as the axis of symmetry (FIG. 10A), as shown in FIG. 10 (b)), the middle layer (FIG. 10 (c)), and the lower layer (FIG. 10 (d)) twist 90 °. Thus, a liquid crystal display device having a wide viewing angle with little change in contrast even when the viewing angle is changed can be obtained. However, in the liquid crystal display device obtained by this method, as shown in FIG. 11, the liquid crystal molecules 6 are horizontally oriented with respect to the substrates 1a and 1b, and the rising of the liquid crystal molecules near the symmetry axis when a voltage is applied. Then, the rising of the liquid crystal molecules near the inside of the polymer wall becomes a reverse tilt. As a result, in this liquid crystal display device, the disclination line appears as a bright line,
There is a problem that the contrast is reduced or the surface is rough. Therefore, Japanese Patent Application Laid-Open No. 7-120728 further discloses a liquid crystal display element in which display characteristics are improved by appropriately selecting a polymer material and operating exposure conditions.

However, according to this method of manufacturing a liquid crystal display element, it was not possible to sufficiently suppress the desquamation line generated when a voltage was applied at the interface between the polymer wall and the liquid crystal region.

[0019]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and it is an object of the present invention to provide a display screen that is free from roughness due to disclination, has no light leakage due to bright lines, and has high contrast. An object of the present invention is to provide an excellent method for manufacturing a liquid crystal display device.

[0020]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly to a method for manufacturing a liquid crystal display device, comprising a liquid crystal and a photocurable resin between a pair of opposed substrates.
Implanting the non-resin mixture; injected between the substrates
In a predetermined area of the liquid crystal, process and precipitating the nematic phase domains; was deposited to a nematic phase domain the
Aligning the liquid crystal molecules of the liquid crystal with respect to the axis of symmetry about the normal line of the substrate ; and thereafter, applying a voltage between the substrates.
Exposure of the substrate in a state where the liquid crystal molecules are axially symmetrically aligned.
So that the resin mixture is maintained in a predetermined pretilt state.
An exposure step of curing the compound photocurable resin ; and thereafter
Then, the substrate is re-exposed to cure the uncured photo-curable resin.
A re-exposure step.

In the re-exposure step , the substrates are mutually short-circuited outside the substrate.

Immediately before the exposure step, the substrate is
An exposure step of exposing and curing the photocurable resin in advance.
In addition .

In the exposure step immediately before the exposure step, the substrates are mutually short-circuited outside the substrate.

The exposure energy in the exposure step is 0.0001 J / cm ^{2 to 5} J / cm ² , and the magnitude of the voltage is 0.1 Vrms to 5.0 Vrms.

The exposure energy in the exposure step immediately before the exposure step is 0.0001 J / cm ^{2 to} 14 J / cm ^2.
It is.

[0026]

[0027]

[0028]

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device obtained according to the present invention will be described below in detail with reference to FIG.

FIG. 1 is a schematic sectional view showing a preferred example of a liquid crystal display device obtained by the present invention. In the liquid crystal display device 100, a pair of substrates 1a and 1b are disposed so as to face each other.
Are formed. On the transparent electrode 2 of one substrate 1a, projections 3 made of a light shielding layer 3a and a resist 3b are further arranged in a lattice. A spacer (not shown) is provided between the pair of substrates 1a and 1b so as to maintain the cell thickness.
Is pinched. A polymer wall 4 is disposed between the protrusion 3 formed on one substrate 1a and the other substrate 1b, and liquid crystal molecules 6 forming a liquid crystal region 5 are arranged between the substrates 1a and 1b. It is surrounded by the polymer wall 4.

The first manufacturing method of the present invention will be described below.

Substrate 1 made of glass, plastic, etc.
a (Indium oxide and tin oxide)
The transparent electrode 2 is deposited by using a known method. Here, the thicknesses of the substrates 1a and 1b used and the thickness of the formed transparent electrode 2 are not particularly limited, and any commonly used thickness is selected. No alignment film for aligning the liquid crystal is formed on the substrates 1a and 1b, and there is no need to perform a rubbing process.

Next, a light shielding layer 3a made of Mo or the like is deposited on one of the substrates 1a by a known method, and a resist 3b is formed on the light shielding film 3 by a known method. Then, by etching the light-shielding film 3a and the resist 3b, the projections 3 are formed together with the pixel regions 7 preferably having a square of 100 μm to 400 μm and a constant pitch (for example, 125 μm) as shown in FIGS. Is formed. The protrusions 3 are provided in the liquid crystal region 5
Formed to control the position of

Next, as shown in FIG.
The ends of the substrates 1a and 1b are bonded together using a sealing material made of a known material such that the substrate 1b and the other substrate 1b face each other via a spacer 7 made of a known material. At the time of bonding the substrates 1a and 1b, an injection port (not shown) is formed in at least one place around the substrate.

A liquid crystal and a resin mixture are injected into the pair of bonded substrates 1a and 1b through an injection port.

The liquid crystal used in the present invention is an organic mixture which shows a liquid crystal state at around normal temperature, and includes nematic liquid crystal (including two-frequency driving liquid crystal and liquid crystal with Δε <0) and cholesteric liquid crystal (especially visible light). Liquid crystal having selective reflection characteristics with respect to light), smectic liquid crystal, ferroelectric liquid crystal, discotic liquid crystal, and the like. In the present invention, the above liquid crystals can be used alone or as a mixture. In terms of characteristics, a nematic liquid crystal, or a nematic liquid crystal containing a cholesteric liquid crystal (chiral agent) is particularly preferable.
More preferably, the liquid crystal is twisted 90 ° above and below the substrate holding the liquid crystal. Further, it is more preferable that the liquid crystal has excellent chemical reaction resistance to a photopolymerization reaction. Examples of liquid crystals having such properties include:
A liquid crystal having a functional group such as a fluorine atom is given. Typically, ZLI-4801-000, ZLI-480
1-001, ZLI-4792 (manufactured by Merck & Co.) and the like.

Further, the resin mixture used in the present invention contains a photocurable resin, a photopolymerization initiator, and a liquid crystal polymerizable material.

Examples of the photo-curable resin include a long-chain alkyl group having 3 or more carbon atoms or a (meth)
Monomers made of acrylic acid and (meth) acrylic acid ester are exemplified. Typically, isobutyl acrylate, stearyl acrylate, lauryl acrylate, isoamyl acrylate, n-butyl methacrylate, n-
Lauryl methacrylate, tridecyl methacrylate,
2-ethyl exyl acrylate, n-stearyl (meth) acrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-phenoxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, bifunctional or higher functional polymer that improves the physical strength of the polymer Multifunctional monomers (eg, bisphenol A
Dimethacrylate, bisphenol A diacrylate,
1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, neopentyl diacrylate, and R-684
(Nippon Kayaku Co., Ltd.)), and a resin obtained by halogenating the above monomer, particularly fluorinated or chlorinated (for example, 2,2) in order to clarify the phase separation between the liquid crystal and the photocurable resin.
2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,4,4,4-hexachlorobutyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3 3-tetrachloropropyl methacrylate, perfluorooctylethyl methacrylate, perchlorooctylethyl methacrylate, perfluorooctylethyl acrylate, and perchlorooctylethyl acrylate).

Examples of the photopolymerization initiator include Irgacure 65
1, Irgacure 184, Irgacure 907, Darocure 1173, Daro
Conventional photopolymerization initiators such as cure 1116 and Darocure 2956 (manufactured by Ciba-Gaiky) can be used. Further, a sensitizer that can be polymerized by visible light can be used to improve the retention.

The addition amount of the photopolymerization initiator is not particularly limited in the present invention since it varies depending on the individual reactivity of the photocurable resin. However, the liquid crystal and the photocurable resin (including the liquid crystal polymerizable material described later) are used. 5) to 0.about.
It is preferably 01% by weight. When the addition amount of the photopolymerization initiator exceeds 5% by weight, the phase separation speed between the liquid crystal and the photocurable resin is too high to control, the liquid crystal droplet becomes small, the driving voltage becomes high, and The alignment control power of the upper alignment film is weakened, and the liquid crystal region in the picture element is reduced (when a photomask is used, liquid crystal droplets are formed in the light shielding portion), and the contrast may be reduced. 0.01% by weight of photopolymerization initiator
If the amount is less than the above, the photocurable resin may not be sufficiently cured in some cases.

Since the liquid crystalline polymer material has a molecular skeleton similar to liquid crystal molecules, it has an effect of stabilizing the alignment of liquid crystal molecules.

The liquid crystalline polymer material is not particularly limited.
A compound that does not easily disturb the liquid crystal properties of the host liquid crystal molecules.
For example, the formula

[0043]

Embedded image

Is a compound represented by the formula:

Here, in the above formula, A is C
_{H 2 = CH-, CH 2 =} CH-COO-, CH 2 = C (C
H ₃₎ -COO-,

[0046]

Embedded image

[0047] be polymerizable functional group having a heterocyclic structure having an unsaturated bond or distortion, such as; B is a group that links the liquid crystal compound L _c below with the polymerizable functional group A, a representative thereof include an alkyl chain _{(- (CH 2) n -} ), an ester bond (-COO-), ether bond (-O-), a polyethylene glycol chain (-CH ₂ CH ₂ O-), and combinations of these groups , and the preferably exhibit liquid crystallinity when mixed with the liquid crystal material, the polymerizable functional group is a group having a rigid portion to the above six binding of a liquid crystal compound; with L _c is a liquid crystal compound And the following formula

[0048]

Embedded image

Or a cholesterol ring and its derivative.

Here, in the above formula (3), D is a part which binds to B in the above formula (1) and affects the magnitude of the dielectric anisotropy and the refractive index anisotropy of the liquid crystal molecules. G is, for example, a paraphenyl ring, 1,10-diphenyl ring, 1,4-cyclohexane ring, 1,10-phenylcyclohexane ring, and the like; a polar group to express anisotropic, _{typically, -CN, -OCH 3, -F,} -Cl, -OCF 3, -
A benzene ring, a cyclohexane ring, a paradiphenyl ring, a phenylcyclohexane ring, or the like having a functional group such as OCCl ₃ , —H, or —R (where R is an alkyl group); a functional group linking a single _{bond, -CH 2 -, - CH 2} CH 2 -, - O -, -
C≡C—, —CH ＝ CH— and the like. Examples of such a liquid crystalline polymer material include the following compound A

[0051]

Embedded image

And the like. The content of the liquid crystalline polymer material in the resin mixture is preferably 0.5% by weight or more.

The resin mixture used in the present invention contains a photopolymerization inhibitor other than the above-mentioned photocurable resin, photopolymerization initiator and liquid crystal polymerizable material for suppressing the polymerization reaction in order to enlarge the domain shape of the nematic phase. Is preferable. Such a photopolymerization inhibitor is a monomer or compound that stabilizes a radical in a resonance system after radical generation. Typically, styrene, p-chlorostyrene, p-
Methylstyrene, p-phenylstyrene, nitrobenzene and the like can be mentioned.

The mixing weight ratio between the liquid crystal material and the resin mixture is as follows:
Liquid crystal material: Resin mixture is 5 depending on the pixel size
It is preferably in the range of 0:50 to 97: 3, and more preferably 70:30 to 95: 5. If the content of the liquid crystal material is less than 50% by weight, the size of the predetermined region may not be reached even when the domain of the nematic phase is precipitated. When the content of the liquid crystal material exceeds 97% by weight, the physical strength of the polymer wall is reduced, and the performance of the obtained liquid crystal display device may not be stable.

The liquid crystal and the resin mixture are injected, for example, by a vacuum injection method.
It is injected between a and 1b. Next, the injection port can be sealed with a known ultraviolet curable resin using ultraviolet rays, or can be sealed with a known adhesive such as a two-part mixed adhesive or a flash adhesive. Thus, a liquid crystal cell is formed.

The liquid crystal cell is heated at a temperature 2 ° C. to 3 ° C. higher than a temperature at which the entire liquid crystal cell becomes an isotropic phase for 1 minute to 10 minutes in order to precipitate a domain of a nematic phase in a predetermined region. The domain is then allowed to cool to a temperature that fills the predetermined area. Alternatively, a nematic phase domain can be precipitated by performing only heating, or a nematic phase domain can be deposited by combining heating and cooling several times. Here, the “predetermined region” may vary depending on the purpose, but typically refers to a pixel region of the substrates 1a and 1b. The temperature at which the entire liquid crystal cell becomes isotropic is
The temperature at which this liquid crystal cell is heated is also uniquely determined by the type of the liquid crystal material and the resin mixture, and the mixing ratio of the liquid crystal material and the resin mixture. And the size of the predetermined region.

Next, the liquid crystal molecules 6 in the liquid crystal cell are oriented axially symmetric with the normal line of the substrates 1a and 1b as the axis of symmetry. Here, "Axisymmetrically oriented with the normal line of the substrate as the axis of symmetry"
The term typically means that liquid crystal molecules are aligned in a spiral, concentric, or radial manner.

The method of aligning the liquid crystal molecules with respect to the axis of symmetry with the normal line of the substrate as the axis of symmetry as described above is carried out, for example, as follows: First, when the domain of the nematic phase reaches the size of a predetermined region. Then, the liquid crystal cell is heated. Since the domain is reduced by heating, the voltage is applied while maintaining the heating state of the liquid crystal cell at a temperature at which the domain does not disappear. The temperature and the magnitude of the voltage at the time of voltage application are typically 50 ° C. to 90 ° C., and 0.1 Vrms to 1 Vrms.
0 Vrms. In this state, the liquid crystal region and the resin mixture are phase-separated, but the photocurable resin in the resin mixture remains uncured, so that the axis-symmetric alignment of the liquid crystal molecules is not fixed.

Next, the substrate is irradiated with ultraviolet rays using, for example, a high-pressure mercury lamp to cure the photocurable resin in the resin mixture. In this exposure step, the substrate is preferably short-circuited outside the substrate using a known method. If a short circuit outside the substrate is not performed, the liquid crystal molecules may disturb the axisymmetric alignment due to static electricity. In such an exposure step, ultraviolet light is irradiated from both outsides of the substrates 1a and 1b, or is irradiated on the outside of one substrate, and then is irradiated on the outside of the other substrate, or one of the substrates Can be irradiated only to the outside. The exposure energy of the ultraviolet light is preferably 0.0001 J / cm ^{2 to} 14 J / cm ^2.
And more preferably 0.01 J / cm ^{2 to} 2.4.
J / cm ² . Exposure energy is 0.0001J /
If the molecular weight is less than cm ² , the photocurable resin is insufficiently cured, so that the axially symmetric alignment of the liquid crystal molecules is not stored on the substrate, and the initial axially symmetric alignment of the liquid crystal molecules may be unstable. If the exposure energy exceeds 14 J / cm ² , the curing of the photocurable resin is completed, and then the pretilt angle of the liquid crystal molecules cannot be controlled. Nation lines may occur.

Next, a voltage is applied to the substrate at the same time that the substrate is irradiated with further ultraviolet rays.

In this exposure and voltage application step, the direction of irradiation of the substrate with ultraviolet rays is the same as in the above exposure step. The applied voltage is preferably 0.1 Vrms or more.
5.0 Vrms, more preferably 1.0 Vrms
３3.0 Vrms. The applied voltage is 0.1 Vr
If the time is less than ms, the liquid crystal molecules do not rise and may not exhibit pretilt. If it exceeds 5.0 Vrms, the pretilt becomes too high and the display screen of the liquid crystal display device may be dark. The exposure energy at this time is preferably 0.0001 J / cm ^{2 to 5} J / cm ² ,
More preferably, it is 0.01 J / cm ^{2 to} 2.4 J / cm ² . If the exposure energy is less than 0.0001 J / cm ² , the liquid crystal molecules may not be able to sufficiently maintain a pretilt state. If it exceeds 5 J / cm ² , the curing of the photocurable resin will occur rapidly, and the liquid crystal material and the resin mixture will not be sufficiently phase-separated, which may affect the display characteristics of the liquid crystal display device.

Further, in order to ensure the phase separation between the liquid crystal material and the resin mixture, not to leave the uncured photopolymerizable resin, and to prevent the alignment of the liquid crystal molecules from being disturbed with the passage of time, the substrate is made of an ultraviolet ray. Is re-exposed. The irradiation direction of the ultraviolet rays to the substrate is the same as in the above-mentioned exposure step. The exposure energy in this re-exposure step is preferably set at 0.1.
A ^{0001J / cm 2 ~20J / cm 2} , more preferably ^{0.1J / cm 2 ~15J / cm 2} . If the exposure energy is less than 0.0001 J / cm ² , the axially symmetric alignment of the liquid crystal molecules becomes unstable, and this alignment may be disturbed over time. If it exceeds 20 J / cm ² , curing of the photocurable resin will occur rapidly, which may disturb the axially symmetric alignment of the liquid crystal molecules. In such an exposure step, the substrate is preferably short-circuited outside the substrate using a known method.

Thus, a liquid crystal display device is manufactured.

The liquid crystal display device obtained by using the first manufacturing method of the present invention does not generate disclination lines at the interface inside the polymer wall when voltage is applied. this is,
By first exposing, as shown in FIG.
Alignment layers 8a and 8b are formed at the interface between the substrate and the liquid crystal region, and then exposed at the same time as applying a voltage,
High pretilt liquid crystal molecules 6 existing near this alignment layer
Is considered to form the high pretilt layers 9a and 9b. That is, the liquid crystal molecules have a pretilt around the axis of symmetry and in the same direction, and do not reverse tilt near the polymer wall even when a voltage is applied.

In the liquid crystal display device obtained by the first manufacturing method of the present invention, a cross-shaped schlieren pattern is observed in the light portion a with respect to the dark portion b as shown in FIG. The center position of the schlieren pattern is fixed.

When a substrate containing liquid crystal molecules and a resin mixture which is axially symmetrically aligned with the normal line of the substrate as the axis of symmetry is irradiated with ultraviolet light for a short time, the resin mixture cures while maintaining the axially symmetric alignment of the liquid crystal molecules. I do. Therefore, even if a voltage is subsequently applied, the liquid crystal molecules form a high pretilt layer on the substrate while maintaining the initial axially symmetric orientation, and thus no disclination lines are generated.

The second manufacturing method of the present invention will be described below.

First, in the same manner as in the first manufacturing method of the present invention, the liquid crystal molecules 6 are oriented axially symmetric with the normal line of the substrates 1a and 1b as the axis of symmetry. Next, a voltage is applied to the substrate simultaneously with the irradiation of the ultraviolet rays.

In this exposure and voltage application step, the direction of irradiation of the substrate with ultraviolet rays is the same as in the above-mentioned exposure step. The applied voltage is preferably 0.1 Vrms or more.
5.0 Vrms, more preferably 1.0 Vrms
３3.0 Vrms. The applied voltage is 0.1 Vr
If the time is less than ms, the liquid crystal molecules do not rise and may not exhibit pretilt. If it exceeds 5.0 Vrms, the pretilt becomes too high and the display screen of the liquid crystal display device may be dark. The exposure energy at this time is preferably 0.0001 J / cm ^{2 to 5} J / cm ² ,
More preferably, it is 0.01 J / cm ^{2 to} 2.4 J / cm ² . If the exposure energy is less than 0.0001 J / cm ² , the liquid crystal molecules may not be able to sufficiently maintain a pretilt state. If it exceeds 5 J / cm ² , the curing of the photocurable resin will occur rapidly, and the liquid crystal material and the resin mixture will not be sufficiently phase-separated, which may affect the display characteristics of the liquid crystal display device.

Further, in order to ensure the phase separation between the liquid crystal material and the resin mixture, not to leave the uncured photopolymerizable resin, and to prevent the alignment of the liquid crystal molecules from being disturbed with the passage of time, the substrate is made of an ultraviolet ray. Is re-exposed. The irradiation direction of the ultraviolet rays to the substrate is the same as in the above-mentioned exposure step. The exposure energy in this re-exposure step is preferably set at 0.1.
A ^{0001J / cm 2 ~20J / cm 2} , more preferably ^{0.1J / cm 2 ~15J / cm 2} . If the exposure energy is less than 0.0001 J / cm ² , the axially symmetric alignment of the liquid crystal molecules becomes unstable, and this alignment may be disturbed over time. If it exceeds 20 J / cm ² , curing of the photocurable resin will occur rapidly, which may disturb the axially symmetric alignment of the liquid crystal molecules. In such an exposure step, the substrate is preferably short-circuited outside the substrate using a known method.

Thus, a liquid crystal display device is manufactured.

The liquid crystal display device obtained by using the second manufacturing method of the present invention does not generate disclination lines at the interface inside the polymer wall when voltage is applied. this is,
As shown in FIG. 5, it is considered that the high pretilt layers 9a and 9b are formed at the interface between the substrate and the liquid crystal region by applying a voltage simultaneously with the exposure. That is,
Liquid crystal molecules have a pretilt around the center of axial symmetry and in the same direction, and do not reverse tilt near the polymer wall even when a voltage is applied.

In the liquid crystal display device obtained by the second manufacturing method of the present invention, a swirly schlieren pattern is observed in the light part a with respect to the dark part b as shown in FIG. The center position of the schlieren pattern is fixed.

In the swastika schlieren pattern, when a voltage is applied at the same time as exposing the substrate, the interaction between the liquid crystal molecules and the substrate interface is weak, so that the alignment state of the liquid crystal molecules slightly deviates from the state before the voltage application. It represents that. However, the liquid crystal display device obtained by the above method has sufficient viewing angle characteristics without generating disclination lines.

[0075]

The present invention will be described in more detail with reference to the following examples. Note that the present invention is not limited to the following embodiments.

Example 1 Two glass substrates 1a, 1
b (thickness: 1.1 mm), an ITO film (a mixture of indium oxide and tin oxide: 50 nm in thickness) on each surface
Was deposited. Further, Mo is vapor-deposited on the ITO film of one substrate 1a, and a resist (OM) is further formed thereon.
R83: manufactured by Tokyo Ohkasha Co., Ltd.) by a known method.
Next, the Mo and the resist on the substrate 1a were etched to obtain a pixel region 7 having a 100 μm square and a 125 μm pitch and a projection 3 as a light shielding mask as shown in FIG. Further, this substrate 1a,
An injection port is formed around the substrate by using a sealing material so that the other substrate 1b faces through a spacer,
The ends of the substrates 1a and 1b were bonded together. The thickness of the obtained liquid crystal cell was 5 μm.

Next, 0.20 g of R-684 (manufactured by Nippon Kayaku Co., Ltd.), 0.20 g of p-phenylstyrene, and the compound A0.
10 g and ZLI-4792 (0.4% by weight) as a liquid crystal.
4.5 g of Irgacue 651 (manufactured by Merck) and a polymerization initiator Irgacue 651 (manufactured by Ciba-Gaiky) were injected from the inlet by a vacuum injection method. The liquid crystal cell was heated at 90 ° C. for 30 minutes, and then cooled to 50 ° C. to precipitate a nematic phase domain. Then, by raising the temperature to 80 ° C., this domain is reduced to such an extent that it does not disappear.
By applying a voltage of 0 Vrms, the liquid crystal molecules were axisymmetrically oriented with the normal line of the substrate as the axis of symmetry.

Further, the bonded substrates 1a and 1b were short-circuited outside the substrates and irradiated with ultraviolet rays for 120 seconds (exposure energy was 0.48 J / cm ² ). Next, an AC voltage of an effective voltage of 2.5 V (60 Hz) was applied, and at the same time, ultraviolet irradiation was performed for 120 seconds (exposure energy was 0.48 J / cm ² ). Further, ultraviolet light was irradiated for 2400 seconds (exposure energy was 9.6 J / cm ² ) to produce a liquid crystal display device.

In the obtained liquid crystal display device, liquid crystal molecules had a monodomain structure in pixel units.

The liquid crystal display was rotated and observed under a polarizing microscope. The polarizer and analyzer of this polarizing microscope are orthogonal to each other, and a quenching pattern (Schlieren pattern) having a cross-shaped bright portion a is observed in each pixel region as shown in FIG. The center position of the schlieren pattern was fixed even when rotated. As described above, in each pixel of the manufactured cell, the alignment in which the liquid crystal molecules have the symmetry axis of the normal to the substrate surface was achieved.

Further, the upper and lower electrodes of this liquid crystal display device
When an effective voltage of 5.0 V (60 Hz) was applied and observed under a polarizing microscope, no disclination line occurred. Then, the substrates 1a, 1
b. A polarizing plate is attached to the outside of b by a known method at a position where orthogonal Nicols will be formed, and LCD-5100 manufactured by Otsuka Electronics Co., Ltd.
To measure the voltage-transmittance characteristics. FIG. 9 shows viewing angle characteristics of the obtained liquid crystal display device. In FIG.
(A) is an isocontrast curve with a contrast of 10, (b) is an isocontrast curve with a contrast of 20, and (c) is an isocontrast curve with a contrast of 50. The contrast ratio at 0 V to 5 V was 200: 1, and the viewing angle at which the contrast was 10: 1 or more was 60 ° or more in the polarization axis direction.

<Embodiment 2> Bonded substrates 1a and 1b
While applying an AC voltage of an effective voltage of 2.5 V (60 Hz) to one side of the substrate, using a high-pressure mercury lamp (irradiation intensity at 365 nm: 4 mW / cm ² ) to irradiate ultraviolet rays for 120 seconds (exposure energy is 0.48 J / cm ² )
Then, the substrates 1a and 1b are short-circuited outside the substrate, and this ultraviolet light is applied for 2400 seconds (exposure energy is 9.6 J /
cm ² ) except that the irradiation was carried out to produce a liquid crystal display device in the same manner as in Example 1.

In the obtained liquid crystal display device, liquid crystal molecules had a monodomain structure in pixel units.

This liquid crystal display was rotated and observed under a polarizing microscope. The polarizer and analyzer of this polarizing microscope are orthogonal to each other, and an extinction pattern (Schlieren pattern) having a cross-shaped bright portion a is observed in each pixel region as shown in FIG. The center position of the schlieren pattern was fixed even when rotated. As described above, in each pixel of the manufactured cell, the alignment in which the liquid crystal molecules have the symmetry axis of the normal to the substrate surface was achieved.

Further, the upper and lower electrodes of the liquid crystal display element
When an effective voltage of 5.0 V (60 Hz) was applied and observed under a polarizing microscope, no disclination line occurred. Then, the substrates 1a, 1
b. A polarizing plate is attached to the outside of b by a known method at a position where orthogonal Nicols will be formed, and LCD-5100 manufactured by Otsuka Electronics Co., Ltd.
To measure the voltage-transmittance characteristics. The contrast ratio from 0 V to 5 V is 200: 1, and the contrast ratio is 10:
The viewing angle of 1 or more was 60 ° or more in the polarization axis direction.

<Comparative Example 1> Bonded substrates 1a and 1b
A liquid crystal display device was prepared in the same manner as in Example 1, except that UV irradiation was performed for 2400 seconds (exposure energy was 9.6 J / cm ² ) without applying a voltage.

The liquid crystal display was rotated and observed under a polarizing microscope. The polarizer and analyzer of this polarizing microscope are orthogonal to each other, and an extinction pattern (Schlieren pattern) having a cross-shaped bright portion a is observed in each pixel region as shown in FIG. The center position of the schlieren pattern was fixed even when rotated. As described above, in each pixel of the manufactured cell, the alignment in which the liquid crystal molecules have the symmetry axis of the normal to the substrate surface was achieved.

However, as shown in FIG. 8, an effective voltage of 5.0 V (60 Hz) is applied to the upper and lower electrodes of the liquid crystal display device.
Was observed under a polarizing microscope, and a disclination line 10 was generated around the pixel area. A part of the disclination line penetrated into the pixel from the black matrix that shields the outside of the pixel.

[0089]

According to the present invention, there is provided a liquid crystal display device which is free from roughness of a display screen due to generation of a disclination line when a voltage is applied and has excellent contrast without light leakage.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display device manufactured according to a preferred example of the present invention.

FIG. 2 is a schematic plan view showing a preferred example of the production method of the present invention.

FIG. 3 is a schematic sectional view showing a preferred example of the production method of the present invention.

FIG. 4 is a schematic sectional view showing a preferred example of the production method of the present invention.

FIG. 5 is a schematic sectional view of a liquid crystal display device manufactured according to a preferred example of the present invention.

FIG. 6 is a diagram illustrating a schlieren pattern of a liquid crystal display device obtained according to a preferred example of the present invention when the polarization axis is in the vertical and horizontal directions of the pixel.

FIG. 7 is a diagram illustrating a schlieren pattern of a liquid crystal display device obtained according to a preferred example of the present invention when the polarization axis is in the vertical and horizontal directions of the pixel.

FIG. 8 is a diagram illustrating a schlieren pattern of a liquid crystal display device manufactured by irradiating only ultraviolet rays without applying a voltage, when the polarization axis is in the vertical and horizontal directions of the pixel.

FIG. 9 is a graph showing viewing angle characteristics of the liquid crystal display device obtained in the example.

FIG. 10 is a schematic view showing the orientation of liquid crystal molecules in a conventional liquid crystal display device.

FIG. 11 is a schematic sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 1a, 1b substrate 2 transparent electrode 3 protrusion 4 polymer wall 5 liquid crystal region 6 liquid crystal molecule 7 pixel region 8a, 8b alignment layer 9a, 9b high pretilt layer 100 liquid crystal display device

──────────────────────────────────────────────────続 き Continued on the front page (72) Nobuaki Yamada 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A 7-120728 (JP, A) (58) Investigated Field (Int.Cl. ⁷ , DB name) G02F 1/1333 G02F 1/1337

Claims (7)

(57) [Claims] 1. A method of manufacturing a liquid crystal display device, a liquid crystal between a pair of substrates facing each other, process and injecting a tree <br/> fat mixture containing a photocurable resin; injected between substrates Depositing a nematic phase domain in a predetermined region of the liquid crystal ; and liquid crystal molecules of the liquid crystal having a nematic phase domain deposited thereon.
Is oriented axially symmetrically with respect to the normal line of the substrate as an axis of symmetry; and thereafter, the substrate is exposed while a voltage is applied between the substrates.
The liquid crystal molecules that are axisymmetrically aligned by the light
The photo-curable resin of the resin mixture is maintained in a state.
An exposure step of curing ; thereafter, the substrate is re-exposed to form an uncured photo-curable resin.
And a re-exposure step of curing the liquid crystal display device . 2. The method according to claim 1, wherein in the re-exposure step , the substrates are short-circuited to each other outside the substrate. 3. The method according to claim 1 , wherein the substrate is disposed immediately before the exposure step.
Exposure step of exposing to cure the photocurable resin in advance
The method for manufacturing a liquid crystal display device according to claim 1 , further comprising : In the exposure process in the immediately preceding wherein said exposing step, the substrate to each other is short-circuited to each other at the outside of the substrate, The method according to claim 3. 5. The liquid crystal display device according to claim 1, wherein an exposure energy in the exposure step is 0.0001 J / cm ^{2 to 5} J / cm ² , and a voltage magnitude is 0.1 Vrms to 5.0 Vrms. Manufacturing method. 6. An exposure energy in an exposure step immediately before said exposure step is 0.0001 J / cm ^{2 to} 14 J / c.
The method for manufacturing a liquid crystal display device according to claim 3 , wherein m ² is m ² . 7. An exposure energy in the re-exposure step is ^{0.0001J / cm 2 ~20J / cm 2} , wherein
Item 2. The method for manufacturing a liquid crystal display device according to item 1 .