JP3401680B2 - Liquid crystal 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 liquid crystal encapsulating thin film which does not use a polarizing plate, and more specifically, it can electrically control the blocking and transmission of a visual field, and particularly, it can be used for building windows and show windows. Is used as a screen to block the field of view,
Further, by displaying characters or figures and electrically switching the display with high-speed response, a decorative display board such as an advertising board, a clock, a display device of a calculator, or a display device requiring a bright screen, for example, The present invention relates to a liquid crystal device used as a display device of a computer terminal or a display device of a projection.

[0002]

2. Description of the Related Art As a method for producing a liquid crystal device having a bright and good contrast without using a polarizing plate or an alignment treatment, a method is known in which liquid crystal droplets are dispersed in a polymer and the polymer is formed into a film.

Further, as a technique for enabling low voltage drivability, which is an important characteristic required for practical use of a liquid crystal display device, higher contrast, and time-division drivability, Japanese Patent Laid-Open Publication No. Sho 63-63 is known.
-240460 discloses a liquid crystal device having a structure in which a transparent solid substance is distributed in a three-dimensional network in a continuous layer of a liquid crystal material.

Such a liquid crystal device is used in a so-called normal mode in which light is clouded due to light scattering when no voltage is applied and light is transmitted when a voltage is applied.

However, in the liquid crystal device having the above-mentioned structure, it is difficult to manufacture a liquid crystal device which transmits light when no voltage is applied and scatters light when voltage is applied, which is driven in a so-called reverse mode.

[0006] As a technology of a liquid crystal display device that enables driving in the reverse mode, Young (Yang) et al. [ALCOM SYMPOSIUM Volume 1 (1991)] describes two transparent films having an alignment film on an electrode layer. Between the substrates, gel-like 4,
A liquid crystal device in which a cholesteric liquid crystal is dispersed in a polymer of 4′-bisacryloylbiphenyl has been reported.

[0007]

However, although the above liquid crystal device achieves the reverse mode drive, it has a high drive voltage and does not have a low drive voltage characteristic which is important in the practical application of the display liquid crystal device. .

Further, the driving voltage in the normal mode of the above liquid crystal device is high, and there is a large hysteresis phenomenon in which the electro-optical characteristics have different transmittances when the voltage rises and when the voltage falls. This causes a margin for time division drive. It was extremely problematic in lowering the gradation display.

An object of the present invention is to provide a liquid crystal device having a low driving voltage in the normal mode and the reverse mode and a small hysteresis width.

[0010]

In order to solve the above problems, the inventors of the present invention have made earnest studies on the liquid crystal material in the light control layer, and as a result, the driving voltage in the normal mode and the reverse mode is low and the hysteresis width is small. We have made a small liquid crystal device.

That is, in order to solve the above problems, the present invention provides a photopolymerizable composition and a general formula (1).

[0012]

[Chemical 2]

(In the formula, R ¹ and R ² each independently represent an alkyl group having 1 to 12 carbon atoms, an alkoxyl group, an alkenyl group having 2 to 12 carbon atoms or an alkenyloxy group, and ring A is It represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group which may be substituted by a fluorine atom or a methyl group, and ring B and ring C are each independently substituted by a fluorine atom or a methyl group. Represents a 1,4-phenylene group which may be
X ¹ and X ² are each independently a single bond, —COO—, —O.
_{CO -, - CH 2 CH 2} -, - C≡C -, - CH 2 O- or -OCH ₂ - represents, n represents 0 or 1, * denotes an optically active center. ) A liquid crystal device material comprising a liquid crystal material containing a compound represented by the formula (2), and further, two substrates having at least one having an electrode layer having transparency, and a substrate supported between the substrates. A light-scattering liquid crystal device having a light layer, wherein the light control layer comprises a transparent solid substance and the above liquid crystal material, wherein the transparent solid substance is obtained by polymerizing the above photopolymerizable composition. A liquid crystal device characterized by the above.

Further, the liquid crystal composition containing the compound represented by the general formula (1) in the present invention has good temperature dependence of the helical pitch and can provide a liquid crystal device having excellent temperature characteristics.

The substrate used in the present invention may be a rigid material such as glass or metal, or a flexible material such as a plastic film. The two substrates are opposed to each other and are separated by an appropriate distance.

At least one of them has transparency, but complete transparency is not essential. If the liquid crystal device is used to act on light passing from one side of the device to the other, both substrates will be provided with appropriate transparency.

On this substrate, appropriate transparent or opaque electrodes may be arranged entirely or partially on the substrate depending on the purpose.

When the liquid crystal device of the present invention is used in a display device of a computer terminal, a display device of a projection or the like, it is preferable to provide an active element on the electrode layer.

An alignment film made of polyimide or the like may be arranged on the entire surface or a part thereof. It should be noted that a spacer for holding a space can be usually interposed between the two substrates, as in a known liquid crystal device.

As the spacer, for example, Mylar,
Alumina, rod-type glass fiber, glass beads, polymer beads, and other various liquid crystal cells can be used.

The liquid crystal material used in the present invention does not need to be a single liquid crystal compound, but may be a liquid crystal compound other than this or a mixture containing a substance other than the liquid crystal compound, and Any material that can be recognized as a liquid crystal material in this technical field may be used, and a material made of a compound having a positive dielectric anisotropy is preferable. In order to optimize its performance, a chiral nematic liquid crystal or a cholesteric liquid crystal is preferable, but a chiral smectic liquid crystal or a chiral compound other than the compound of the general formula (1) may be appropriately contained. As these compounds, those commonly used can be used without particular limitation.

The helical pitch of the chiral nematic liquid crystal material or cholesteric liquid crystal material used in the present invention is
It can be selected according to the purpose of use, but in order to obtain sufficient contrast between opacity and transparency due to light scattering,
The range of 0.5 to 5 μm is particularly preferable.

Examples of the liquid crystal material include 4-substituted benzoic acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted biphenyl ester, 4- (4-substituted cyclohexanecarbonyloxy)
Benzoic acid 4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted cyclohexyl ester, 4-substituted 4'-substituted Biphenyl, 4-substituted phenyl 4'-substituted cyclohexane, 4
-Substituted 4 "-substituted terphenyl, 4-substituted biphenyl 4'-substituted cyclohexane, 2- (4-substituted phenyl)
Examples thereof include -5-substituted pyridine and cholesterol derivatives.

The transparent solid substance in the light control layer has a fibrous or particulate dispersion, a film-like dispersion of a liquid crystal material in the form of droplets, or a three-dimensional network structure. Although it may be one, a gel is preferable.

Further, the liquid crystal material preferably forms a continuous layer, which is essential for forming a disordered state of liquid crystal molecules to form an optical boundary surface and to express light scattering.

The content of the photopolymerizable composition used in the present invention can be adjusted according to the purpose of use, but in order to obtain sufficient contrast between opacity and transparency due to light scattering. , 0.1 to 7% by weight in the light control layer forming material
The content is preferably in the range of 0.1 to 5% by weight, particularly preferably in the range of 0.1 to 5% by weight.

Further, in order to control the structure of the transparent solid substance according to the purpose, a photocurable polymerizable composition containing a polymer-forming monomer or oligomer is preferable.

Examples of the polymer-forming monomer that forms the transparent solid substance include styrene, chlorostyrene,
α-methylstyrene, divinylbenzene: As a substituent, methyl, ethyl, propyl, butyl, amyl, 2-
Ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, allyl, methallyl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, Acrylate, methacrylate or fumarate having a group such as dimethylaminoethyl, diethylaminoethyl, etc .; ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, tri Mono (meth) acrylates such as methylolpropane, glycerin and pentaerythritol, or poly (meth) a Relate; vinyl acetate, vinyl butyrate or vinyl benzoate, acrylonitrile, cetyl vinyl ether, limonene, cyclohexene, diallyl phthalate, diallyl isophthalate, 2-, 3- or 4-
Vinyl pyridine, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-hydroxymethyl acrylamide or N-hydroxyethyl methacrylamide and their alkyl ether compounds; 2 mol or more of ethylene oxide or propylene oxide is added to 1 mol of neopentyl glycol. Di (meth) acrylate of diol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane; di or tri (meth) acrylate of triol; 2 mol or more per 1 mol of bisphenol A Di (meth) acrylate of diol obtained by adding ethylene oxide or propylene oxide of 2;
-A reaction product of 1 mol of hydroxyethyl (meth) acrylate and 1 mol of phenyl isocyanate or n-bruchisocyanate; poly (meth) acrylate of dipentaerythritol and the like.

As the polymer-forming oligomer,
For example, epoxy (meth) acrylate, polyester (meth) acrylate, polyurethane (meth) acrylate, polyether (meth) acrylate and the like can be used.

Examples of the photopolymerization initiator that can be used in the present invention include 2-hydroxy-2-methyl-1.
-Phenylpropan-1-one ("Darocur 1173" manufactured by Merck), 1-hydroxycyclohexyl phenyl ketone ("Irgacure 184" manufactured by Ciba-Geigy), 1
-(4-Isopropylphenyl) -2-hydroxy-2
-Methylpropan-1-one (Merck's "Darocur
1116 "), benzyl dimethyl ketal (" Irgacure 651 "manufactured by Ciba-Geigy), 2-methyl-1- [4-
(Methylthio) phenyl] -2-morpholinopropane-
1-on (Ciba-Geigy "Irgacure 90"
7 ”), a mixture of 2,4-diethylthioxanthone (“ Kayacure DETX ”manufactured by Nippon Kayaku Co., Ltd.) and ethyl p-dimethylaminobenzoate (“ Kayacure EPA ”manufactured by Nippon Kayaku Co., Ltd.), isopropylthioxanthone (Wordprekin) Examples of the liquid include 2-hydroxy-2-methyl-1-phenylpropane-, which is a mixture of "Cantacure ITX" manufactured by Sop Co.) and ethyl p-dimethylaminobenzoate.
1-one is particularly preferable in terms of compatibility with the liquid crystal material and the polymer-forming monomer or oligomer.

The reverse mode drive liquid crystal device of the present invention can be manufactured, for example, as follows.

That is, a liquid crystal material containing a compound of the general formula (1) and a polymer-forming monomer or oligomer, and, if necessary, a light source, are provided between two substrates having at least one electrode layer having transparency. Polymerization initiator, chain transfer agent,
It is composed of a transparent solid substance and a liquid crystal material by interposing a light control layer forming material containing a photosensitizer and a dye cross-linking agent and irradiating ultraviolet rays through the transparent substrate to polymerize the polymerizable composition. A liquid crystal device having a light control layer can be manufactured.

The normal mode drive liquid crystal device of the present invention can be manufactured, for example, as follows.

That is, a liquid crystal material containing a compound of the general formula (1) and a polymer-forming monomer or oligomer, and, if necessary, a light source, are provided between two substrates having at least one electrode layer having transparency. Polymerization initiator, chain transfer agent,
By interposing a light control layer forming material containing a photosensitizer and a dye cross-linking agent and applying a saturation voltage of a liquid crystal material, irradiating ultraviolet rays through the transparent substrate to polymerize the polymerizable composition. It is possible to manufacture a liquid crystal device having a light control layer composed of a transparent solid substance and a liquid crystal material.

In order to interpose the light control layer forming material between the two substrates, the light control layer forming material may be injected between the substrates by a known injection technique, but an appropriate solution is formed on one of the substrates. You may apply | coat uniformly using a coating machine, a spin coater, etc., and then superimpose and press-bond the other substrate.

The layer thickness of the layer having a light-scattering property in the liquid crystal device of the present invention can be adjusted according to the purpose of use, but it is sufficient between opacity and transparency due to light scattering. To obtain contrast, the substrate spacing is 2
The range of -40 μm is preferable, and the range of 6-25 μm is particularly preferable.

[0037]

EXAMPLES The present invention will be described more specifically below by showing examples of the present invention. However, the invention is not limited to these examples. In the following examples and comparative examples, "%" means "% by weight". Further, each of the evaluation characteristics in each example means the following symbols and contents.

(1) T ₀ ^NOR , T ₁₀₀ ^NOR : When the light transmittance of the light source is 100% and the light transmittance is 0% when the light source is on, with the device removed from the light metering state, Light transmittance (%) of liquid crystal device when no voltage is applied in normal mode
Is T ₀ ^NOR , and the transmittance when the light transmittance does not change with an increase in applied voltage is T ₁₀₀ ^NOR .

(2) T ₀ ^REV , T ₁₀₀ ^REV : When the light transmittance of the light source is set to 100% and the light transmittance is set to 0% when the light source is turned on with the device removed from the metering state, Light transmittance (%) of liquid crystal device when no voltage is applied in reverse mode
Is T ₁₀₀ ^REV , and T ₀ ^REV is the transmittance when the light transmittance is minimized as the applied voltage increases.

(3) V ₉₀ ^NOR , V ₁₀ ^NOR : The light transmittance (T ₀ ^NOR ) of the liquid crystal device when no voltage is applied is set to 0%, and the light transmittance does not change as the applied voltage increases. When the transmittance (T ₁₀₀ ^NOR ) at the time is 100%, the applied voltage (V) at which the light transmittance is 90% is V ₉₀ ^NOR , and at the time when the light transmittance is 10% is V ₁₀ ^NOR . .

(4) V ₉₀ ^REV , V ₁₀ ^REV : The light transmittance (T ₁₀₀ ^REV ) of the liquid crystal device when no voltage was applied was set to 100%, and the light transmittance was minimized as the applied voltage was increased. When the transmittance (T ₀ ^REV ) at the time is 0%, the applied voltage (V) at which the light transmittance is 90% is V ₉₀ ^REV , and at the time when the light transmittance is 10% is V ₁₀ ^REV . .

(5) Steepness γ: γ = V ₁₀ ^REV / V ₉₀ ^REV , or γ = V ₉₀ ^NOR / V ₁₀ ^NOR

(6) Hysteresis: When the voltage is raised from 0 V, the voltage at which the light transmittance is 50% (T ₅₀ ^NOR or T ₅₀ ^REV ) is V ₅₀ ^UP, and when the voltage is lowered from a sufficiently high voltage, the light is emitted. When the voltage at which the transmittance is 50% is V ₅₀ ^DOWN , ΔV = V ₅₀ ^UP −V ₅₀ ^DOWN is used as the evaluation value of the hysteresis phenomenon and the hysteresis width.

(Example 1)

[0045]

[Chemical 3]

4.2% of the compound of and a nematic liquid crystal composition "RO-571" manufactured by F. Hoffmann-La Roche 95.
A liquid crystal composition (A) consisting of 8% was prepared. The properties of this liquid crystal composition (A) were as follows.

Transition temperature 65.6 ° C. (N−I) Helical pitch 2.0 μm (In the above, N represents a nematic phase and I represents an isotropic liquid phase. The same applies hereinafter.)

This liquid crystal composition (A) was 97.8%, and the polymerizable composition was of the formula (a)

[0049]

[Chemical 4]

2.0% of the compound of
"Darocur 1173" (Merck 2-hydroxy-2-
Methyl-1-phenylpropan-1-one) 0.2% of a dimming layer forming material was sprayed on the electrode layer with a spacer having an average particle diameter of 9 μm in a small amount to form a 5 × 5 cm ITO electrode layer and a polyimide alignment film. The polymerizable composition was polymerized by sandwiching it between the two glass plates and irradiating it with ultraviolet rays. The polymerization conditions are metal halide lamp (80W /
A glass substrate sandwiching the material for forming a light control layer was passed under cm ² ) at a speed of 3.5 m / min and irradiated with ultraviolet rays having an energy corresponding to 500 mJ / cm ² to obtain a liquid crystal device.

The obtained liquid crystal device was driven in the reverse mode, and the characteristics were as follows. V ₁₀ ^REV : 13.8V V ₉₀ ^REV : 10.1V γ: 1.4 Hysteresis: 0.7V

(Example 2)

[0053]

[Chemical 5]

4.5% of the compound of "RO-571" and 95.5
% Liquid crystal composition (B) was prepared.

The characteristics of this liquid crystal composition (B) were as follows. Transition temperature 60.9 ℃ (NI) Spiral pitch 2.0 μm

A liquid crystal device was obtained in the same manner as in Example 1 except that the liquid crystal composition (B) was used instead of the liquid crystal composition (A).

The obtained liquid crystal device was driven in the reverse mode, and the characteristics were as follows. V ₁₀ ^REV : 12.9V V ₉₀ ^REV : 9.7V γ: 1.3 Hysteresis: 0.8V

Example 3 The above liquid crystal composition (A) 97.
8%, 2.0% of a compound of formula (a) as a polymerizable composition,
2 pieces of ITO electrode layer and polyimide alignment film of 5 × 5 cm in which a light control layer forming material consisting of 0.2% of “Darocur 1173” as a polymerization initiator is dispersed on the electrode layer with a spacer having an average particle diameter of 9 μm. Sandwiched between two glass plates, 2
The polymerizable composition was polymerized by irradiating with ultraviolet rays while applying a voltage of 0V. The polymerization conditions are as follows: a glass substrate sandwiching the light control layer forming material is passed under a metal halide lamp (80 W / cm ² ) at a speed of 3.5 m / min.
A liquid crystal device was obtained by irradiating ultraviolet rays having an energy equivalent to 500 mJ / cm ² .

The liquid crystal device thus obtained was driven in the normal mode and had the following characteristics. V ₁₀ ^NOR : 3.0V V ₉₀ ^NOR : 9.4V Hysteresis: 3.2V

Example 4 A liquid crystal device was obtained in the same manner as in Example 3, except that the liquid crystal composition (B) was used instead of the liquid crystal composition (A).

The liquid crystal device thus obtained was driven in the normal mode and had the following characteristics. V ₁₀ ^NOR : 2.6V V ₉₀ ^NOR : 9.1V Hysteresis: 3.5V

[0062]

The liquid crystal device of the present invention is a light-scattering liquid crystal device which can be driven in the normal mode and the reverse mode, has low voltage drivability, and has a small hysteresis width.

Therefore, the liquid crystal device of the present invention is extremely useful as a display device for computer terminals, a display element for projection, glass for automobiles and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-200927 (JP, A) JP-A-1-279223 (JP, A) JP-A-3-292389 (JP, A) JP-A-64- 42454 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/13 500

Claims (6)

(57) [Claims] 1. A photopolymerizable composition and a compound represented by the general formula (1): (In the formula, each of R ¹ and R ² independently has 1 carbon atom.
~ 12 alkyl group, alkoxyl group, carbon number 2
Represents 12 alkenyl groups or alkenyloxy groups,
Ring A represents trans-1,4-cyclohexylene group, B ring and C ring is in each independently represent a fluorine atom or may be substituted by a methyl group 1,4-phenylene group, X ¹ is Represents a single bond, X ² is a single bond
Represents -COO- or -C≡C-, and n is 0 or 1.
And * represents an optically active center. ) A light comprising a liquid crystal material containing a compound represented by
Materials for scattering type liquid crystal devices. 2. At least one substrate having an electrode layer is transparent, and two dimming layers supported between the substrates,
A light-scattering liquid crystal device, wherein the light control layer comprises a transparent solid substance and the liquid crystal material according to claim 1, wherein the transparent solid substance polymerizes the photopolymerizable composition according to claim 1. A light-scattering type liquid crystal device comprising: 3. The light scattering according to claim 2, wherein the transparent solid substance is contained in a gel state in the liquid crystal material.
Shaped liquid crystal device. 4. The light-scattering type liquid crystal device according to claim 3, wherein at least one of the electrode layers has a transparent alignment film on two transparent substrates. 5. The content of the transparent solid substance in the light control layer is
The light-scattering liquid crystal device according to claim 3, wherein the amount is in the range of 0.1 to 7% by weight. 6. The light-scattering liquid crystal device according to claim 2, wherein the liquid crystal material is a chiral nematic liquid crystal material or a cholesteric liquid crystal material, and the spiral pitch is 0.5 to 5 μm.