JPH1121554A - Production of liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an element capable of half-tone display by curing a liquid crystal composition containing a liquid crystal (meth)acrylate monomer and a ferroelectric liquid crystal during or after alignment in the state showing a chiral smectic C phase. SOLUTION: Between a pair of transparent substrates, a liquid crystal composition containing a liquid crystal (meth)acrylate monomer in a concentration of 0.1-10 wt.%, a ferroelectric liquid crystal and optionally a photopolymerization initiator is cured by irradiation with ultraviolet rays or electron beams during or after alignment under applied direct current voltage in the state showing a chiral smectic C phase to obtain a liquid crystal display element. The ferroelectric liquid crystal is desirably one which shows a smectic A phase and a nematic phase in a temperature region above that of a chiral smectic C phase. In the formula, X is H or methyl: r is 0 or 1; six-membered rings A, B and C are each a group represented by formula III; Y<1> and Y<2> are each a single bond, -OCH2 -, -CH2 CH2 - or the like; and Y<3> is H, a halogen, cyano or the like.

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, and more particularly to a method for manufacturing a ferroelectric liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device using a ferroelectric liquid crystal proposed by Clark and Lager-Wall (Japanese Patent Laid-Open No.
No. 107216) has bistability and has a fast response to a change in an electric field, and is therefore expected to be applied to a large-screen and high-definition liquid crystal display device. However, since it has bistability, there is a problem that it is difficult to display a halftone.

[0003]

An object of the present invention is to provide a method of manufacturing a liquid crystal display device capable of displaying a halftone using a ferroelectric liquid crystal.

[0004]

Means for Solving the Problems In order to solve the above problems, the present inventors have focused on a liquid crystal composition, which is one of the components of a liquid crystal element, and as a result of studying the ferroelectric liquid crystal, The present invention has been found to be able to solve the problem by incorporating a liquid crystal (meth) acrylate monomer into the composition and polymerizing the liquid crystal (meth) acrylate monomer while applying a voltage to the composition, and has provided the present invention.

[0005] That is, In a method for obtaining a liquid crystal display device by interposing a liquid crystal composition containing a liquid crystal (meth) acrylate monomer and a ferroelectric liquid crystal between a pair of substrates, the liquid crystal composition is oriented in a state showing a chiral smectic C phase. A method for manufacturing a liquid crystal display device, comprising: curing while orienting. 2. 2. The method for producing a liquid crystal display device according to the above 1, wherein the concentration of the liquid crystalline (meth) acrylate monomer in the liquid crystal composition is 0.1 to 10% by weight. 3. The liquid crystalline (meth) acrylate monomer has a general formula (I)

[0006]

Embedded image

(Wherein, X represents a hydrogen atom or a methyl group, r represents an integer of 0 or 1, and the 6-membered rings A, B and C each independently represent

[0008]

Embedded image

Wherein m is an integer of 1 to 4, Y ¹ and Y ² are each independently a single bond, —CH ₂ CH ₂ —,
_{-CH 2 O -, - OCH 2} -, - COO -, - OCO-,
-C≡C-, -CH = CH-, -CF = CF-,-(C
_{H 2) 4 -, - CH} 2 CH 2 CH 2 O -, - OCH 2 CH 2 C
_{H 2 -, - CH = CH} -CH 2 CH 2 -, - CH 2 CH 2 C
H ₂ O-a represents, Y ³ represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an alkenyl group, an alkenyloxy group. 3. The method for producing a liquid crystal display device according to the above item 1 or 2, wherein the compound is a (meth) acrylate compound represented by the following formula: 4. In the general formula (I), X represents a hydrogen atom, r represents 0, and the 6-membered ring A is

[0010]

Embedded image

Wherein the six-membered ring C is

[0012]

Embedded image

Or

[0014]

Embedded image

Wherein Y ¹ represents a single bond or C≡C—, and Y ³ represents an alkyl group having 1 to 10 carbon atoms. )
4. The method for producing a liquid crystal display device according to the above item 1, 2 or 3, wherein 5. (1) A liquid crystal (meth) acrylate monomer and a ferroelectric liquid crystal material are contained between a first transparent substrate having an electrode layer and an alignment control film and a second substrate having an electrode layer and an alignment control film. And (2) irradiating an ultraviolet ray or an electron beam with or after applying a DC voltage in a state in which the interposed liquid crystal composition exhibits a chiral smectic C phase to thereby obtain a liquid crystal composition. (Meta)
5. The method for producing a liquid crystal display device according to the above 1, 2, 3, or 4, further comprising a second step of polymerizing the acrylate monomer. Was found as a means for solving the above-mentioned problem.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described below. The production method of the present invention is intended to make the alignment direction of the liquid crystalline skeleton of the liquid crystalline (meth) acrylate coincide with one of the bistable states of the ferroelectric liquid crystal. And a liquid crystal composition containing a ferroelectric liquid crystal and a liquid crystal composition while maintaining a state showing a chiral smectic C phase, and irradiating an ultraviolet ray or an electron beam to the liquid crystal composition with or after applying a DC voltage to the liquid crystal composition ( It is characterized by photo-curing (meth) acrylate. Thus, in the liquid crystal display device manufactured by the manufacturing method of the present invention, the orientation direction of the ferroelectric liquid crystal when no driving voltage is applied is changed when the ferroelectric liquid crystal is irradiated with ultraviolet light or electron beam during manufacturing. Almost coincides with the orientation direction. This is considered to be due to the effect of stabilizing the alignment of the liquid crystal skeleton of the liquid crystalline (meth) acrylate photo-cured material that has been aligned in accordance with the alignment direction of the ferroelectric liquid crystal during irradiation with ultraviolet light or electron beam during production. The orientation of the ferroelectric liquid crystal when a voltage having the same sign as the DC voltage at the time of production is hardly changed from the orientation of the ferroelectric liquid crystal at the time of irradiation with ultraviolet rays or electron beams during production. The orientation of the ferroelectric liquid crystal when a voltage having a different sign from the voltage is applied is not the orientation of the ferroelectric liquid crystal at the time of irradiation with ultraviolet rays or electron beams during production as the absolute value of the applied voltage increases. , Approaching the orientation direction of the other bistable state. That is, the alignment state of the ferroelectric liquid crystal in the liquid crystal display device manufactured by the manufacturing method of the present invention can be continuously controlled between the two kinds of alignment states of the bistable state of the ferroelectric liquid crystal. Key display has been realized. Hereinafter, the present invention will be described in more detail.

The ferroelectric liquid crystal used in the present invention is:
In general, any liquid crystal that is recognized as a ferroelectric liquid crystal in this technical field can be used without any particular limitation. However, in order to obtain a good orientation state of the chiral smectic C phase, the temperature is higher than the chiral smectic C phase. It is preferable to use one that exhibits a smectic A phase, and more preferably, one that exhibits a smectic A phase and a nematic phase in a temperature range above the smectic C phase in order to obtain a good orientation state. The liquid crystalline (meth) acrylate monomer used in the present invention is one in which a polymer obtained by photocuring exerts an alignment stabilizing effect on a ferroelectric liquid crystal due to a demand as a display element, and a ferroelectric liquid crystal. It is preferable that the driving voltage is not increased. Such a liquid crystalline (meth) acrylate is a monofunctional (meth) acrylate which is an acrylic acid or methacrylic acid ester of a cyclic alcohol, phenol or aromatic hydroxy compound having a liquid crystal skeleton having at least two 6-membered rings as a partial structure. Acrylates are preferred. This is because such a monofunctional (meth) acrylate does not have a flexible connecting group called a spacer in the technical field of liquid crystal such as an alkylene group or an oxyalkylene group between the (meth) acryloyloxy group and the liquid crystal skeleton. . Therefore, a rigid liquid crystal skeleton is directly bonded to the main chain of the polymer obtained by polymerizing such a monofunctional (meth) acrylate without using a spacer, and the thermal motion of the liquid crystal skeleton is limited by the polymer main chain. This is because it is considered that the ferroelectric liquid crystal can have an alignment stabilizing effect. In addition, since the polymer is a monofunctional (meth) acrylate, the polymer does not form a three-dimensional cross-linked structure even when photocured, and the drive voltage increases due to the effect of surrounding the ferroelectric liquid crystal with a polymer cage. It is thought that it can be avoided.

Such a liquid crystalline (meth) acrylate is represented by the general formula (I)

[0019]

Embedded image

(Wherein X represents a hydrogen atom or a methyl group, r represents an integer of 0 or 1, and the 6-membered rings A, B and C each independently represent

[0021]

Embedded image

Wherein m is an integer of 1 to 4, Y ¹ and Y ² are each independently a single bond, —CH ₂ CH ₂ —,
_{-CH 2 O -, - OCH 2} -, - COO -, - OCO-,
-C≡C-, -CH = CH-, -CF = CF-,-(C
_{H 2) 4 -, - CH} 2 CH 2 CH 2 O -, - OCH 2 CH 2 C
_{H 2 -, - CH = CH} -CH 2 CH 2 -, - CH 2 CH 2 C
H ₂ O-a represents, Y ³ represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an alkenyl group, an alkenyloxy group. ) Is particularly preferable.

As specific examples of such a monofunctional (meth) acrylate, the compounds listed in the formulas (1) to (11) are preferable, but the monofunctional (meth) acrylate which can be used in the liquid crystal composition of the present invention is preferred. The (meth) acrylate is not limited to these.

[0024]

Embedded image

[0025]

Embedded image

(In the above, C represents a crystal phase, N represents a nematic phase, S represents a smectic phase, I represents an isotropic liquid phase, and a number represents a phase transition temperature.) In addition, liquid crystal (meth) acrylate and The concentration of the liquid crystalline (meth) acrylate in the liquid crystal composition containing the ferroelectric liquid crystal is preferably adjusted to 0.1 to 10% by weight, more preferably adjusted to 0.5 to 7% by weight. From 1 to 5% by weight are particularly preferred. If the concentration of the liquid crystalline (meth) acrylate is lower than 0.1%, the effect of stabilizing the alignment is hardly obtained, and the contrast is lowered. If the concentration is higher than 10% by weight, the driving voltage of the ferroelectric liquid crystal is increased. Would.

As the alignment control film, a conventionally used polyimide alignment film subjected to a rubbing treatment can be used without any particular limitation. Further, an orientation control film called a photo-alignment control film in this technical field, in which an organic thin film such as a polyvinyl cinnamate thin film is irradiated with polarized ultraviolet light, can also be used.

As the substrate, a glass substrate with a thin film transistor, a glass substrate with an ITO, a plastic substrate with an ITO or the like can be used. Those in which a color filter layer is provided on these substrates can also be suitably used.

According to the production method of the present invention, the polymerizable liquid crystal composition injected between a pair of substrates is irradiated with energy rays such as ultraviolet rays or electron beams to polymerize and cure the polymerizable liquid crystal composition. Therefore, at least the substrate on the irradiation surface side must be given appropriate transparency. That is, (1) a liquid crystal (meth) acrylate monomer and a ferroelectric liquid crystal material are interposed between a first transparent substrate having an electrode layer and an alignment control film and a second substrate having an electrode layer and an alignment control film. And (2) irradiating an ultraviolet ray or an electron beam with or after applying a DC voltage in a state where the interposed liquid crystal composition exhibits a chiral smectic C phase. A method for producing a liquid crystal display device having a second step of polymerizing a liquid crystalline (meth) acrylate monomer is preferable.

The distance between the pair of substrates, that is, the thickness of the liquid crystal layer depends on the anisotropy of the refractive index of the ferroelectric liquid crystal used, but is preferably 1 to 10 μm, and is preferably 1.5 μm.
To 7 microns is even more preferred, and 2 to 6 microns is particularly preferred. If the thickness of the liquid crystal layer is smaller than 1 micron, a sufficient amount of optical switching cannot be obtained, and the contrast tends to decrease. The helical structure of the crystalline liquid crystal is formed, and the essential bistability tends not to be obtained in the production stage.

To the liquid crystal composition containing a liquid crystal acrylate monomer and a ferroelectric liquid crystal, a photopolymerization initiator may be added for the purpose of rapidly photocuring the photocurable composition in the chiral smectic C phase. Good. The photopolymerization initiator that can be used here can be selected from, for example, known benzoin ethers, benzophenones, acetophenones, and benzyl ketals. The addition amount is preferably 10% by weight or less based on the liquid crystal acrylate monomer contained in the liquid crystal composition.

Further, a stabilizer may be added to the liquid crystal composition containing the liquid crystal acrylate monomer and the ferroelectric liquid crystal for the purpose of improving the storage stability. As the stabilizer that can be used here, for example, known hydroquinone, hydroquinone monoalkyl ethers, tertiary butyl catechols, and the like can be selected and used. Further, the amount of addition is preferably 0.05% by weight or less based on the photocurable composition contained in the liquid crystal composition.

The irradiation amount of the ultraviolet ray or the electron beam in the process of polymerizing the photocurable composition depends on the liquid crystal composition used and the concentration of the photopolymerization initiator, but is from 50 to 10,000 mJ / cm ^2. Is preferable. When the irradiation amount of ultraviolet rays or electron beams is 50 mJ / cm ² or less,
The photocurable composition is not sufficiently cured, the change with time after production becomes large, and if it is 10,000 mJ / cm ² or more, the liquid crystal composition itself tends to deteriorate.

The sign and magnitude of the DC voltage applied during or before the step of irradiating ultraviolet rays or electron beams can be freely set depending on the purpose of the device, but the magnitude is ferroelectric. It is preferable that the voltage is set to be equal to or higher than the voltage at which the reactive liquid crystal responds. Also, applying a DC voltage even during irradiation with ultraviolet rays or electron beams is more excellent in the uniformity of orientation of the ferroelectric liquid crystal in the liquid crystal display element than applying a DC voltage only before irradiation. It is preferable to keep applying the DC voltage.

[0035]

The present invention will be described below in more detail with reference to Examples of the present invention. However, the invention is not limited to these examples. (Example 1) A glass substrate having a thickness of 1.1 mm with an ITO transparent electrode was prepared, and a polyimide film was coated on the transparent electrode surface with a thickness of 300 mm.
After forming to a thickness of Å, a rubbing treatment was performed to obtain a glass substrate with a polyimide alignment film. The two substrates with a polyimide alignment film thus obtained were opposed to each other with an interval of 5.4 μm so that the surface on which the alignment film was formed faced inside, to produce a liquid crystal cell (A). At this time, the rubbing directions of the two substrates of the liquid crystal cell are
It was set to be in the parallel direction.

Next, the liquid crystalline acrylate compound (1)

[0037]

Embedded image

49.5 parts by weight of a liquid crystalline acrylate compound (4)

[0039]

Embedded image

A photocurable composition (I) was prepared comprising 49.5 parts by weight of the above and 1 part by weight of a photopolymerization initiator "Irgacure 651" (manufactured by Ciba Geigy). This photocurable composition (I) exhibited nematic liquid crystallinity in the range from room temperature to 46 ° C. A liquid crystal composition (L-1) comprising 2 parts by weight of the photocurable composition (I) and 98 parts by weight of a ferroelectric liquid crystal "TA-C100" (manufactured by Chisso) was prepared.

Next, while maintaining the liquid crystal cell (A) at 80 ° C., the liquid crystal composition (L-1) was injected in an isotropic liquid phase, and the temperature was gradually lowered to room temperature. (L-1) was subjected to a phase transition to a chiral smectic C phase via a nematic phase and a smectic A phase in this order. Observation with a polarizing microscope while applying a voltage of +4 V to the liquid crystal cell (A) confirmed that the liquid crystal cell (A) was substantially uniaxially oriented. The azimuthal angle of the uniaxial orientation was inclined about +10.5 degrees with respect to the rubbing direction. While maintaining the liquid crystal cell (A) at room temperature and showing a chiral smectic C phase, while applying a DC voltage of +4 V,
Ultraviolet light with a central wavelength of 365 nm and an intensity of ² mW / cm ²
By irradiating for 0 second, the photocurable composition (I) contained in the liquid crystal composition was photocured. Observation of the liquid crystal cell (A) with a polarizing microscope confirmed that the ferroelectric liquid crystal had a uniform uniaxial orientation without any defect. In addition, when no voltage was applied, the orientation direction of the ferroelectric liquid crystal was about +7.5 degrees with respect to the rubbing direction, and it was confirmed that the orientation was almost the same as the orientation at the time of ultraviolet irradiation. . Further, under observation with a polarizing microscope, the liquid crystal cell (A)
When a voltage of +4 V was applied, the orientation direction of the ferroelectric liquid crystal was about +10 degrees with respect to the rubbing direction. Next, the voltage applied to the liquid crystal cell (A) is gradually reduced from +4 V to 0
When the voltage was changed to 0 V, the orientation direction of the ferroelectric liquid crystal hardly changed. On the other hand, when the voltage was changed from 0 V to -4 V, the orientation direction of the ferroelectric liquid crystal was approximately +7. A continuous change from 5 degrees to about -10 degrees was observed. This liquid crystal cell (A) was placed between two orthogonal polarizing plates, and the applied voltage-light transmittance characteristics were measured.
At this time, the angle between the rubbing direction of the liquid crystal cell (A) and the transmission axis of the polarizing plate is 22.5 degrees, and the temperature is 3 degrees.
It was set to 0 degrees. FIG. 1 shows the measurement results of the applied voltage-light transmittance characteristics. From FIG. 1, it is understood that the transmittance of the liquid crystal display device of the present invention can be controlled by changing the applied voltage, that is, halftone display is possible. (Example 2) A liquid crystal cell was manufactured in the same manner as in Example 1 except that the applied voltage at the time of ultraviolet irradiation was changed to -4 V DC. This liquid crystal cell was placed between two orthogonal polarizing plates, and the applied voltage-contrast characteristics were measured. At this time, the liquid crystal cells were arranged such that the transmittance was lowest when no voltage was applied. FIG. 2 shows the applied voltage-contrast characteristics measured while changing the temperature from 26 ° C. to 32 ° C. FIG. 2 also shows that the liquid crystal display element of the present invention can control the transmittance by changing the applied voltage, that is, it can display a halftone. Example 3 A liquid crystal cell (B) similar to the liquid crystal cell (A) manufactured in Example 1 was manufactured. This liquid crystal cell (B)
While maintaining the temperature at 0 ° C., the liquid crystal composition (L
-1) is injected in an isotropic liquid phase, and then the temperature is gradually lowered to room temperature, whereby the liquid crystal composition (L-1) passes through the nematic phase and the smectic A phase in order to the chiral smectic C phase. Phase transition was performed. The liquid crystal cell (B) was kept at room temperature, and a DC voltage of +4 V was applied for 5 minutes. Immediately thereafter, the liquid crystal cell (B) was irradiated with ultraviolet light having a central wavelength of 365 nm and an intensity of ² mW / cm ² for 30 seconds at room temperature to light-cur the photocurable composition (I) contained in the liquid crystal composition. . When the applied voltage-light transmittance characteristic of the liquid crystal cell (B) was measured in the same manner as in Example 1, it was observed that the light transmittance continuously changed according to the change of the applied voltage.

[0042]

The method of manufacturing a liquid crystal display device according to the present invention provides a method of manufacturing a liquid crystal display device capable of halftone display in a display device using a ferroelectric liquid crystal. Therefore, the method for manufacturing a liquid crystal display element of the present invention is very useful as a display element capable of performing halftone display with excellent viewing angle characteristics in combination with a TFT element or the like.

[0043]

[Brief description of the drawings]

[0044]

FIG. 1 is a view showing a measurement result of an applied voltage-light transmittance characteristic of a liquid crystal display element obtained by a method of manufacturing a liquid crystal display element of the present invention in Example 1.

[0045]

FIG. 2 is a view showing a measurement result of an applied voltage-contrast characteristic of a liquid crystal display element obtained by a method of manufacturing a liquid crystal display element of the present invention in Example 2.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Haruyoshi Takatsu 3-6-27 Nakahara, Higashiyamato-shi, Tokyo

Claims (5)

[Claims] 1. A method for obtaining a liquid crystal display device by interposing a liquid crystal composition containing a liquid crystal (meth) acrylate monomer and a ferroelectric liquid crystal between a pair of substrates, wherein the liquid crystal composition is converted into a chiral smectic C phase. A method for producing a liquid crystal display element, comprising curing while orienting in the state shown in the figure. 2. The method according to claim 1, wherein a concentration of the liquid crystalline (meth) acrylate monomer in the liquid crystal composition is 0.1 to 10% by weight. 3. A liquid crystalline (meth) acrylate monomer represented by the following general formula (I): (Wherein, X represents a hydrogen atom or a methyl group, r represents an integer of 0 or 1, and the 6-membered rings A, B, and C each independently represent: And m represents an integer of 1 to 4, Y ¹ and Y ² are each independently a single bond, —CH ₂ CH ₂ —, —CH ₂ O—,
—OCH ₂ —, —COO—, —OCO—, —C≡C—,
-CH = CH -, - CF = CF -, - (CH 2) 4 -, -
_{CH 2 CH 2 CH 2 O -} , - OCH 2 CH 2 CH 2 -, - CH
ＣＨCH—CH ₂ CH ₂ —, —CH ₂ CH ₂ CH ₂ O—, Y ³ represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an alkenyl group, an alkenyloxy group. Represents a group. ) (Meta)
The method according to claim 1, wherein the method is an acrylate compound. 4. In the general formula (I), X represents a hydrogen atom, r represents 0, and the 6-membered ring A has the following formula: And the 6-membered ring C is Or Y ¹ represents a single bond or C≡C—, and Y ³ represents an alkyl group having 1 to 10 carbon atoms. 4. The method for producing a liquid crystal display device according to claim 1, wherein the method is represented by the following formula: 5. A first transparent substrate having an electrode layer and an orientation control film, and a second transparent substrate having an electrode layer and an orientation control film.
A first step comprising a liquid crystal (meth) acrylate monomer and a ferroelectric liquid crystal material between the substrates (1) and (2) in a state where the interposed liquid crystal composition exhibits a chiral smectic C phase, Irradiating ultraviolet rays or electron beams with or after the application, the second liquid crystal (meth) acrylate monomer is polymerized.
5. The method according to claim 1, further comprising a step.
The manufacturing method of the liquid crystal display element described in.