JPH0973073A - Liquid crystal optical element, liquid crystal display element and projection type liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high-contrast halftone display at low driving voltage without sticking phenomenon. SOLUTION: A vinyl monomer represented by the formula CXY=CZ-COO-R- OH (where each of X, Y and Z is -H or -CH3 , R is 4-8C divalent hydrocarbon contg. one or more C atoms between a C atom bonding to the ester bond in the formula and a C atom bonding to the hydroxyl group in the formula and the hydrocarbon may contain one or more kinds of bonds selected from among ether, ester and carbonate bonds between C-C bonds) is used as a part of a resin material used for a liq. crystal-resin composite 7. Sticking is hardly caused even in the case of animation display in a low working temp. region of <=20 deg.C and high-contrast display is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal optical element, a liquid crystal display element, and a projection type liquid crystal display device using the same, in which a composite containing a liquid crystal and a resin is sandwiched between a pair of substrates with electrodes.

[0002]

2. Description of the Related Art Liquid crystal displays have been widely used in recent years in personal word processors, handheld computers, pocket TVs, etc. by taking advantage of their low power consumption and low voltage driving. Among them, a liquid crystal display element having an active element that has a good viewing angle and is capable of high-speed and high-density display is attracting attention and is being actively developed.

Initially, a liquid crystal display element (LCD) of dynamic scattering type (DSM) was proposed. However, DSM-LC
In D, the current value flowing through the liquid crystal is high, and therefore, there is a drawback that the current consumption is large. At present, a twisted nematic (TN) LCD using a polarizing plate is in the mainstream and is used in the market as a display element of a pocket TV or a portable information device. The TN-LCD has an extremely small leakage current and consumes less power, and thus is suitable for applications using a battery as a power source.

In the case of a DSM-LCD having an active element, the leakage current of the liquid crystal itself is large. Therefore, a large storage capacitance must be provided in parallel with each pixel. In addition, there is a problem that the power consumption of the liquid crystal display element itself increases.

In the TN-LCD, since the leakage current of the liquid crystal itself is extremely small, it is not necessary to add a large storage capacity, and the power consumption of the liquid crystal display element itself can be reduced. However, since the TN-LCD requires two polarizing plates, there is a problem that the light transmittance becomes small.
In particular, when performing color display using a color filter, only a few percent of the incident light can be used, and a strong light source is required, resulting in an increase in power consumption.

Further, when projecting an image, an extremely strong light source is required, which makes it difficult to obtain high contrast on the projection screen, and heat generated from the light source changes the operating state of the liquid crystal display element. is there.

Therefore, in order to solve these problems, a liquid crystal / resin composite in which a nematic liquid crystal is dispersed and held in a matrix such as a resin or a continuous liquid crystal phase is combined with a resin in a network form is proposed. was suggested. Then, a liquid crystal display device was obtained in which the scattering-transmission property was utilized to directly control the on / off of light without using a polarizing plate. It is called a dispersion type liquid crystal display element, a polymer dispersion type liquid crystal display element, or the like. The basic structure and manufacturing method will be described below.

A nematic liquid crystal having a positive dielectric anisotropy is used for this liquid crystal optical element, and it is usually provided so that the refractive index of the polymer phase is substantially the same as the ordinary refractive index (n _o ) of the liquid crystal. Then, the liquid crystal / resin composite is sandwiched between the pair of substrates with electrodes.

Substrates with electrodes include glass, plastic,
Transparent electrodes such as ITO on a substrate such as ceramic
(In ₂ O ₃ -SnO ₂₎ and in which SnO ₂ or the like is formed. Further, if necessary, a metal electrode such as chromium or aluminum may be used together. When used in a reflective type operation mode, it may be a reflective electrode.

In this liquid crystal / resin composite, the refractive index of the liquid crystal in the liquid crystal / resin composite changes depending on the applied state of the voltage between the electrode substrates. Light is transmitted when the refractive index of the resin phase substantially matches the refractive index of the liquid crystal, and light is scattered when they do not match. Since this liquid crystal optical element does not use a polarizing plate, a bright display is basically obtained.

When a voltage is applied, the liquid crystal molecules are aligned parallel to the direction of the electric field, so that the refractive index can be easily controlled, and this liquid crystal optical element can obtain a high transmittance when transmitting. Next, LCD /
A conventional example of a liquid crystal optical element using a resin composite will be described.

JP-A-63-271233 (conventional example 1) uses a vinyl compound as a polymer material, specifically, an acryloyl compound containing a high molecular weight acrylic urethane compound, to form a liquid crystal and a polymer material. It is disclosed that a high-performance liquid crystal / resin composite can be formed by forming a liquid crystal phase and a resin phase from a mixture by a process of photopolymerization phase separation. Then, it is shown that ON / OFF of light passing through the layer of the liquid crystal / resin composite is controlled by an external electric signal to obtain a high-performance dimmer having good appearance.

In Conventional Example 1, 2-hydroxyethyl acrylate (2-HEA), that is, a compound in which R in the formula (1) described below corresponds to an ethylene group, is used. It has been proposed to use the material in the manufacture of liquid crystal / resin composites. The use of the cured product of the curable material containing the —OH group-containing vinyl-based monomer as the resin phase controls the contact interaction at the interface between the liquid crystal phase and the resin phase in the liquid crystal / resin composite to provide a suitable phase. It was an important technical requirement for obtaining the separated structure.

Further, Japanese Patent Application Laid-Open No. 61-196229 (Prior Art 2) has a general description of a liquid crystal display device in which a liquid crystal / resin composite layer comprising a polymer and liquid crystal and an active matrix substrate are combined. .

The active matrix substrate is a substrate on which electrodes and active elements such as thin film transistors (TFTs), thin film diodes, metal insulator metal nonlinear resistance elements (MIM) are formed. 1 for each pixel electrode
One or more active elements are connected. In addition, a common electrode or a patterned electrode is formed on the counter electrode substrate, and display is performed in combination with the active matrix substrate substrate.

When a three-terminal element such as a TFT is used as an active element, the counter electrode substrate is provided with a solid electrode common to all pixels. When using a two-terminal element such as an MIM element or a PIN diode, the counter electrode substrate is subjected to stripe patterning.

Further, Japanese Patent Laid-Open No. 1-35233 (conventional example 3).
As described in (1), when the liquid crystal / resin composite is formed by photopolymerization, an electric field is externally applied to the liquid crystal in the liquid crystal / resin composite to regulate the orientation of the liquid crystal to a certain extent. It is also practiced to form the semi-transparent portion in advance. When there is something that is desired to be fixedly displayed, such a normal transmission part can be formed.

However, in the initial liquid crystal display device provided with the liquid crystal / resin composite shown in the above-mentioned conventional examples 1 and 2, the voltage-transmittance characteristic (V
-T curve) had hysteresis. Although this is not a problem for windows and shutters that are used in a substantially binary state, high-performance display elements that require halftone have the problem that the light transmittance differs when the drive voltage is stepped up and when it is stepped down. It was Therefore, when the display screen changes, the image sticking phenomenon may occur in which the information on the previous screen remains for several seconds or more.

Therefore, in Japanese Unexamined Patent Publication No. 6-186535 (Prior Art 4), focusing on the physical properties of the liquid crystal used and the spatial dispersion of the liquid crystal domains in the liquid crystal cell, a proposal on the physical properties of the liquid crystal material and the structural control of the resin phase is proposed. It is described that the reduction of hysteresis required for the display element has been achieved. For example, it is described that the refractive index anisotropy Δn of the liquid crystal is preferably 0.18 or more and the dielectric anisotropy Δε is preferably 5 to 13. At the same time, it is described that the shape of the liquid crystal domain has a certain distortion and the random director arrangement of the liquid crystal domains in the liquid crystal cell contributes to the reduction of hysteresis.

Further, in JP-A-5-134238 (conventional example 5), attention is paid to the elastic modulus of the resin phase used, and the elastic modulus is 3 × 10 ⁷ N / m ² or less at 20 ° C. and 1 × 10 ³ at 40 ° C.
It has been shown that a resin material having a N / m ² or more is used. It is described that the control of the elastic modulus of the resin phase greatly contributes to the reduction of hysteresis, and that even in the case of displaying a moving image, an extremely beautiful display without an afterimage or image sticking can be obtained.

[0021]

However, the conventional liquid crystal /
In the resin composite, the voltage-transmittance characteristic still has a large temperature dependency, and particularly when the ambient temperature is 20 ° C.
In the low temperature range below, the scattering ability of the liquid crystal optical element decreases, and the hysteresis shown by the transmittance difference between the voltage-transmittance characteristics at the time of step-up and step-down becomes large, and therefore the contrast of the display screen is lowered. Further, there is a problem that the image sticking phenomenon may occur in which the information on the previous screen remains for several seconds or more when the display screen changes.

[0022]

According to the present invention, even in a low temperature range of 20 ° C. or lower, the scattering characteristics can be maintained, a high contrast ratio can be obtained, and halftone display can be performed neatly, and image sticking due to hysteresis of a liquid crystal / resin composite can be achieved. Provided are a liquid crystal optical element and a liquid crystal display element in which the phenomenon is reduced.

That is, according to the present invention, in a liquid crystal optical element in which a liquid crystal resin composite containing a liquid crystal and a resin is sandwiched between a pair of substrates with electrodes, a resin phase is an addition polymerization represented by the following formula (1). Compound (hereinafter, also referred to as a compound of formula (1))
A liquid crystal optical element, which is a polymerized and cured product of a polymerized and curable material containing.

[0024]

Embedded image CXY = CZ—CO—O—R—OH (1)

(However, X, Y, and Z are --H or --CH ₃
Is shown. R may contain at least one bond selected from an ether bond, an ester bond and a carbonate bond between carbon-carbon bonds, has a total carbon number of 4 to 8, and is an ester of the formula (1). A divalent hydrocarbon group containing at least one carbon atom between a carbon atom bound to a bond and a carbon atom bound to a hydroxyl group is shown. )

In this liquid crystal optical element, for example,
The refractive index (n _p ) of the resin phase when a voltage is applied or not applied is the ordinary refractive index (n _o ) or extraordinary refractive index (n _o ) of the liquid crystal used.
_It is provided so that it can be almost matched with _e ).

Further, in the present invention, the ratio of the compound of the formula (1) to the total addition polymerizable compound in the polymerization-curable material is 1
The liquid crystal optical element is 0 to 70% by weight. Also,
Invention, R is - (CH _{2) n} - (where, n is 4-8
Is an integer) of the above-mentioned liquid crystal optical element.

Further, the present invention is the above liquid crystal optical element, wherein the compound represented by the formula (1) is a hydroxyl group-containing acrylate. Further, the present invention is the above liquid crystal optical element, wherein the polymerization curable material further contains a high molecular weight compound having one or more functional groups that are cured by heat or light.

Further, the present invention comprises an active matrix substrate having an active element provided for each pixel electrode and a counter electrode substrate provided with a counter electrode, wherein the liquid crystal optical substrate is provided between the active matrix substrate and the counter electrode substrate. It is a liquid crystal display device characterized by sandwiching a liquid crystal / resin composite of the device.

Further, the present invention is a projection type liquid crystal display device characterized by combining the above liquid crystal display element, a projection light source and a projection optical system.

According to the present invention, by adopting the above-mentioned structure, the liquid crystal optical element and the liquid crystal display element capable of reducing the image sticking phenomenon due to hysteresis even in a low temperature range, having a high contrast and being driven at a low voltage. Is obtained.

The greatest object of the present invention is to provide a liquid crystal optical element which reduces the image sticking phenomenon due to the hysteresis of the liquid crystal / resin composite and exhibits a high contrast at a low driving voltage. Next, the microstructure of the liquid crystal / resin composite will be described and the relationship with hysteresis will be described.

These three-dimensional phase-separated structures include a continuous liquid crystal phase structure in which 60 to 100% of the liquid crystal phase is continuous or connected through a resin phase, and an independent liquid crystal in which the continuous or continuous liquid crystal phase is 30% or less. They are roughly classified into phase-separated structures that exhibit phases. In the case of a phase-separated structure having few internal continuous liquid crystal phases, such as a liquid crystal phase-separated into a granular or separated capsule, that is, a discrete liquid crystal capsule, the interface exhibiting scattering properties is the interface between the liquid crystal phase and the resin phase. Limited to In such a case, in order to increase the scattering ability of the liquid crystal / resin composite, it is necessary to increase the number of liquid crystal capsules to be separated, but with the density of the capsules kept at a certain optimum average particle size. There is a limit to how high can be considered from the spatial arrangement.

Comparing a discrete liquid crystal capsule structure with a structure in which liquid crystal is present in the form of a continuous phase, a liquid crystal optical element having a high haze value in the scattering state (low transmittance) and a high contrast ratio is obtained. In order to obtain the above, it is preferable to use a continuous liquid crystal phase. The structure of the continuous liquid crystal phase scatters light not only at the interface between the resin and the liquid crystal but also at the interface of the liquid crystal domain. It is known that a liquid crystal that is not under the influence of an electric field and is in contact with a certain surface exists in the form of randomly arranged domains and contributes to light scattering. When the liquid crystal is present as a continuous phase in the liquid crystal / resin composite, it is considered that the liquid crystal does not exist as a discrete capsule form but the liquid crystal of the continuous body is divided into a plurality of liquid crystal domains and the liquid crystal is present. .

In the conventional liquid crystal / resin composite, there is a hysteresis in the voltage-transmittance characteristic, which has been a problem in gradation display. Hysteresis is a phenomenon in which the transmittance is different in the process of increasing the voltage and the process of decreasing the voltage. The presence of hysteresis causes a phenomenon in which information on the previous screen remains when displaying a gradation screen, that is, a phenomenon in which an image is burned, which deteriorates the image quality.

One of the causes of the existence of hysteresis in the liquid crystal / resin composite is that the liquid crystal / resin composite has the liquid crystal dispersed and held in the resin phase, or a plurality of domains are formed in the liquid crystal phase due to the interposition of the resin. It depends on the structure.
That is, it is considered that there is hysteresis due to the interaction between the liquid crystals separated and present in the resin phase or the interaction between the plurality of liquid crystal domains formed in the liquid crystal phase. The nature of the interaction between the resin phase and the liquid crystal phase is different when an electric field is applied and when no electric field is present. When no electric field is applied, the interaction between the liquid crystal and the resin is controlled by the surface tension generated at the boundary. When an electric field is applied, the interaction includes not only the boundary effect but also the energy caused by the rearrangement of the liquid crystal, that is, the elastic energy.

The magnitude of this hysteresis depends on the liquid crystal existing in the resin phase, which is separated from the elastic energy stored in the liquid crystal held in a dispersed state, the elastic energy stored in the adjacent liquid crystal domain, and the electric energy generated by the electric field applied from the outside. It is determined by the interaction energy between them and the interaction energy between a plurality of liquid crystal domains formed in the liquid crystal phase. Therefore, by optimizing this energy balance, hysteresis can be reduced, and excellent display without image sticking can be obtained even in gradation display.

An object of the present invention is to obtain a liquid crystal optical element having high contrast, high brightness, excellent responsiveness and reduced hysteresis. Further, it is to obtain a liquid crystal optical element that can be driven by an active element that operates at a low voltage or a driving circuit.

The role of the resin phase includes stabilization of the liquid crystal alignment, elastic energy storage, and structural stability of the entire liquid crystal / resin composite. Taking these points into consideration, the material of the resin phase is optimized. To be done.

Of these, what is important for the electro-optical characteristics is the accumulation of elastic energy and the interaction between the liquid crystal and the resin phase, that is, the surface tension at the boundary between the liquid crystal and the resin. Closely related to the hysteresis in the voltage-transmittance characteristics of the liquid crystal / resin composite, which is one of the causes of image sticking, which is a particular problem in the display of halftones, and the responsiveness when the voltage changes and the reproducibility of the transmittance characteristics. is connected with.

Above all, elimination of hysteresis of the liquid crystal / resin composite is indispensable for fine halftone display and is mentioned as an important requirement. The resin phase is also related to the stability of individual liquid crystal particles or liquid crystal domains, and the structural stability of the liquid crystal / resin composite as a whole, so the surface tension with the liquid crystal and the elastic modulus of the resin phase should also be considered. Then, it is required to determine the material of the resin phase.

In the compound represented by the formula (1), R represents a hydrocarbon group such as an alkylene group. This hydrocarbon group has an ether bond between carbon-carbon bonds of the alkylene group,
It may have one or more bonds selected from ester bonds and carbonate bonds.

In the present invention, the number of carbon atoms of R in the formula (1) needs to be 4 to 8, and the object of the invention cannot be achieved if the carbon number is less than or more than that. R is preferably a residue obtained by removing two hydroxyl groups from various diols. R may be a cycloalkylene group or a chain hydrocarbon group containing a cycloalkyl group or a cycloalkylene group.

Further, R may be a chain hydrocarbon group containing a phenyl group or a phenylene group. However, preferably R does not contain such a hydrocarbon ring. Further, R may contain an ether bond, an ester bond or a carbonate bond between the carbon-carbon bonds of the chain hydrocarbon group as described above. The carbon atoms of the ester bond and the carbonate bond are included in the carbon atoms counted in the requirement for the carbon number of R.

When it does not have a bond such as an ether bond, R is a residue of a usual dihydric alcohol. As the dihydric alcohol, there are various dihydric alcohols having 4 to 8 carbon atoms. This dihydric alcohol may be linear or branched. The hydroxyl group may be a primary hydroxyl group or a secondary or tertiary hydroxyl group.

As the diol having at least one ether bond, a polyhydric glycol such as dialkylene glycol or trialkylene glycol, a dihydric alcohol monoepoxide addition obtained by adding a monoepoxide such as ethylene oxide or propylene oxide to a dihydric alcohol. There are things.

As the diol having one or more ester bonds, a diester of one dicarboxylic acid molecule and two dihydric alcohol molecules, such as a dihydric alcohol cyclic ester adduct obtained by adding a cyclic ester such as caprolactone to a dihydric alcohol. and so on.

Examples of the diol having a carbonate bond include a dihydric alcohol cyclic carbonate adduct obtained by adding a cyclic carbonate such as ethylene carbonate to a dihydric alcohol.

X and Y in the compound represented by the formula (1)
Is preferably a hydrogen atom because the compound has high polymerizability. When both X and Y are hydrogen atoms, unsaturated carboxylic acid residue (CH ₂
= CH-CO-O-) is an acryloyloxy group,
The unsaturated carboxylic acid residue in which Z is a methyl group is a methacryloyloxy group.

In order to carry out polymerization and curing by light as described later, an acryloyloxy group having high photopolymerizability is preferable. When performing thermal polymerization, methacryloyloxy group or X
Alternatively, a compound in which Y is a methyl group may be used. In the following description, a compound in which the unsaturated carboxylic acid residue is an acryloyloxy group will be described. However, as described above, the compound represented by the formula (1) is not limited to this.

A compound having an acryloyloxy group is shown below as an example of the compound of the formula (1) which is specifically used.

In the formula (1), an example of a vinyl-based monomer in which R is only a hydrocarbon group such as alkylene and the total number of carbon atoms in R is 4 to 8 is shown. The A in the following formula when the acryloyloxy group _{(CH 2 = CH-CO-} O-), if the total number of carbon atoms of R is 4, material of the following Formula 3 is illustrated. Similarly, when the total number of carbons is 5, it is chemical formula 4, when the total number of carbons is 6, chemical formula 5, when the total carbon number is 7, chemical formula 6, and when the total carbon number is 8, chemical formula 7 The substances are exemplified.

[0053]

Embedded image A- (CH ₂ ) ₄ OH (4-hydroxybutyl acrylate) A-CH (CH ₃ ) CH ₂ CH ₂ OH (1-methyl-3-hydroxypropyl acrylate)

[0054]

Embedded image A- (CH ₂ ) ₅ OH (5-hydroxypentyl acrylate) A-CH (CH ₃ ) CH ₂ CH (OH) CH ₃ (1-methyl-3-hydroxybutyl acrylate)

[0055]

Embedded image A- (CH ₂ ) ₆ OH (6-hydroxyhexyl acrylate) A-CH (CH ₃ ) CH ₂ CH ₂ CH (OH) CH ₃ (1-methyl-4-hydroxypentyl acrylate) A-CH ₂ C (CH ₂ CH ₃ ) (CH ₃ ) CH ₂ OH (2-ethyl-2-methyl-3-hydroxypropyl acrylate)

[0056]

Embedded image A- (CH ₂ ) ₇ OH (7-hydroxyheptyl acrylate) AC (CH ₃ ) ₂ CH ₂ C (CH ₃ ) (OH) CH ₃ (1,1,3-trimethyl-3-hydroxybutyl Acrylate) A-CH ₂ C (CH ₂ CH ₂ CH ₃ ) (CH ₃ ) CH ₂ OH (2-methyl-2-hydroxymethylpentyl acrylate)

[0057]

Embedded image A- (CH ₂ ) ₈ OH (8-hydroxyoctyl acrylate) A-CH ₂ CH (CH ₂ CH ₃ ) CH (OH) (CH ₂ ) ₂ CH ₃ (2-ethyl-3-hydroxyhexyl Acrylate)

When R contains an ether bond and has 4 carbon atoms, A- (CH ₂ ) ₂ -O- (CH ₂ ) ₂ OH (diethylene glycol monoacrylate) is exemplified.

Similarly, when the carbon number is 6, A- (CH ₂ ) ₂ -O- (CH ₂ )
₂ -O- (CH ₂ ) ₂ OH (triethylene glycol monoacrylate) and A-CH ₂ CH (CH ₃ ) -O-CH ₂ CH (CH ₃ ) OH (dipropylene glycol monoacrylate), as well as the number of carbon atoms In case of 8,
_{A- (CH 2) 2 -O- (} CH 2) 2 -O- (CH 2) 2 -O- (CH 2) 2 OH ( tetraethylene glycol monoacrylate) and A- (CH _{2) 4} -O- (C
H ₂ ) ₄ OH (ditetramethylene glycol monoacrylate) and the like are exemplified.

Examples of compounds in which R contains an ester bond and has 8 carbon atoms include A- (CH ₂ ) ₂ -O-CO (CH ₂ ) ₅ OH (2-hydroxyethyl acrylate-caprolactone monomolecular adduct) and the like. Is exemplified.

The compound of the formula (1) has R of an appropriate length and --OH group as a polar site, and has a liquid crystal phase and a resin phase when a liquid crystal / resin composite is formed. It is preferable for optimizing the contact interaction of In addition, the glass transition temperature of the resin itself is low, it has a high scattering ability in terms of elastic energy even in a low temperature range, and it is possible to form a liquid crystal / resin composite with reduced hysteresis, and it can be driven by an active element. A liquid crystal panel having a high display contrast and free from a burn-in phenomenon can be obtained.

Until now, as disclosed in Conventional Example 1, a cured product of an addition polymerizable compound containing an —OH group such as 2-HEA has been used in a liquid crystal / resin composite. This is the basis for controlling the contact interaction at the interface between the liquid crystal phase and the resin phase in the liquid crystal / resin composite and obtaining an appropriate phase separation structure.

However, in 2-HEA, the polar group-
With respect to the OH group, the number of carbon atoms of the ester part alkylene which is a non-polar part is only 2, the polarity of the cured product is high, and it is difficult to control the phase separation structure at the interface between the liquid crystal phase and the resin phase. Further, since the glass transition temperature of the resin becomes high, the hysteresis in the low temperature region increases.

Therefore, --OH used for the liquid crystal / resin composite is used.
In the cured product of a group-containing addition-polymerizable compound, the size of the non-polar portion with respect to the —OH group was studied earnestly, and as a result, 2
A compound having a small number of carbon atoms of R, represented by -HEA, has a too high ratio of polar moieties and has a high polarity of the cured product.
It was difficult to form a stable phase-separated structure at the interface between the liquid crystal phase and the resin phase, and in the low temperature range of 20 ° C. or lower, the obtained liquid crystal / resin composite had low contrast and large hysteresis.

Further, as the carbon number of R increases, the ratio of polar sites in the cured product of the addition-polymerizable compound decreases, but if the polarity of the resin is too low, the liquid crystal may partially dissolve in the cured resin. As a result, the driving voltage of the obtained liquid crystal / resin composite was increased and the contrast was low.

That is, in the liquid crystal / resin composite containing the cured product of the compound of formula (1) in the present invention, the ratio of the non-polar part to the polar part of the resin phase controls the contact interaction at the liquid crystal / resin interface. It was found that a suitable phase separation structure can be formed, a high contrast is exhibited at a low driving voltage, and a hysteresis in a low temperature region is small.

The polymerization-curable material in the present invention contains the compound of formula (1). Formula (1) in all polymerization curable materials
It is preferable that the ratio of the compound is 10 to 70% by weight. A particularly desirable ratio is 15 to 50% by weight. If this proportion exceeds 70% by weight, the density of —OH groups in the resin phase becomes too high, and depending on the liquid crystal species used, problems may occur in the stability of the composition in the mixture of the uncured polymerization curable material and the liquid crystal. May occur. If this ratio is too small, the effects of the present invention will not be sufficiently exhibited.

The polymerization-curable material in the present invention contains a "polymerization-curable compound other than the compound of the formula (1)" (hereinafter, also referred to as "curable compound"). The curable compound is preferably a compound that is copolymerizable with the compound of formula (1), but is not necessarily limited thereto. For example, even if it is not copolymerizable with the compound of formula (1), it can be polymerized and cured by itself. Compounds can be used.

These curable compounds have one or more cure sites. The curing site includes an acryloyl group, a methacryloyl group, a vinyl group, an epoxy group, a thiol group and the like. Preferably, a compound having a curing site copolymerizable with the compound of formula (1) such as an acryloyl group or a methacryloyl group is used, and a compound having an acryloyl group having high photocurability as described below is particularly preferable. The compound having an acryloyl group will be described below.

As the curable compound having an acryloyl group, various compounds other than the compound of formula (1) can be used. Particularly, acrylates having no —OH group are preferable. The acrylates may be relatively low molecular weight compounds such as alkyl acrylates, or high molecular weight compounds such as so-called acrylic urethane compounds. In particular, at least a part of the curable compound is preferably this high molecular weight compound.

The number of acryloyl groups in the compound having an acryloyl group is preferably 1 or more, and particularly preferably 1 to 4. Most preferred number of acryloyl groups is 1-2
It is. In the case of a high molecular weight compound, it is preferably 2 to 4.

The curable compound having an acryloyl group is preferably an acrylate of a monohydric alcohol or a polyhydric alcohol. As acrylate of monohydric alcohol,
For example, there is an alkanol acrylate having 1 to 22 carbon atoms. Specifically, there are methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dodecyl acrylate, hexadecyl acrylate, behenyl acrylate and the like.

Further, there are acrylates of various monohydric alcohols such as cycloalkyl alcohols, cycloalkyl-substituted alkanols, aryl group-substituted alcohols and heterocyclic ring-containing alcohols such as tetrahydrofurfuryl alcohol. Furthermore, acrylates of alkanols substituted with halogen such as fluorine and chlorine can also be used.

As the acrylate of polyhydric alcohol,
A polyacrylate in which all the hydroxyl groups of the polyhydric alcohol are esterified is preferable. Specific examples include ethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, butanediol diacrylate, octanediol diacrylate, glycerin triacrylate, pentaerythritol tetraacrylate and the like.

The curable compound having an acryloyl group is
It may be a compound having a relatively high molecular weight. For example, there are monoacrylates and polyacrylates of high molecular weight polyols such as polyether polyols, polyester polyols and polycarbonate polyols. Further, urethane bond-containing acrylates using these polyols are also preferable. Specifically, for example, a reaction product of these polyols, a polyisocyanate compound, and three kinds of compounds consisting of a hydroxyl group-containing acrylate such as 2-HEA is preferable as the urethane bond-containing acrylate.

Examples of the polyisocyanate compound include aliphatic diisocyanates, alicyclic diisocyanates, non-yellowing aromatic diisocyanates, prepolymer-type modified products thereof, and other modified products. The molecular weight of the high molecular weight acrylate is preferably 500 to 50,000 from the viewpoints of uniformity of phase separation due to curing, liquid crystal diffusivity, system stability, and the like.

As the polymerization-curable material in the present invention,
It is preferable to use a mixture of three or more kinds of the compound of the formula (1), a low molecular weight acrylate, and a high molecular weight acrylate as described above (particularly a compound having two or more acryloyl groups). The proportion of the high molecular weight acrylate in the polymerization curable material is preferably 5% by weight or more, and particularly preferably 10% by weight or more. The proportion of low molecular weight acrylate is also preferably 5% by weight or more, and particularly preferably 10% by weight or more. By using these curable compounds in combination, the stability of the mixture of the polymerization-curable material and the liquid crystal is improved, and the phase separation of the liquid crystal due to the curing of the polymerization-curable material is controlled to obtain a good liquid crystal / resin composite. Can be formed.

The polymerization-curable material is cured from a uniform mixture of the polymerization-curable material and the liquid crystal, and the liquid crystal is precipitated from the cured product. Alternatively, a liquid crystal / resin composite is obtained by precipitating a cured product from the liquid crystal to form a phase separation structure of the liquid crystal and the resin (cured polymerization-curable material).

The polymerization-curable material may be cured by thermal polymerization, but it is preferably cured by ultraviolet rays, electron beams or other energy rays in order to reduce the influence of heat on the liquid crystal. In particular, it is preferable to cure the polymerization curable material by photopolymerization using ultraviolet rays. Therefore, it is preferable to use a photopolymerization initiator or a photopolymerization accelerator mixed with the polymerization curable material.

The liquid crystal optical element provided with this liquid crystal / resin composite is mainly used as a display element visually recognized by humans. It can also be used as a light control window or an optical shutter by using a driving method such as a solid electrode on the entire surface or a simple matrix. Further, this liquid crystal optical element can be used as both a direct-view type display element and a projection type display element. When used as a direct-view display device,
A display device is configured by combining a backlight, a lens, a prism, a mirror, a diffusion plate, a light absorber, a color filter, and the like according to the desired display characteristics.

In addition, an infrared cut filter, an ultraviolet cut filter or the like may be laminated, or characters or figures may be printed. Further, it can be configured by using a plurality of liquid crystal optical elements.

Further, when used as a light control body, a protective plate such as a glass plate or a plastic plate is laminated outside the liquid crystal optical element. As a result, even if the surface is pressed, the risk of damage is reduced, and safety is improved.

This liquid crystal display element is particularly suitable for a projection type display device using a strong light source, and is combined with a projection light source, a projection optical system, etc. to form a projection type liquid crystal display device. As the projection light source and the projection optical system, a conventionally known projection optical system such as a projection light source and a lens can be used. Usually, the liquid crystal display device is used by being arranged between the projection light source and the projection lens.

Further, for example, when a projection type liquid crystal display device is constructed using three liquid crystal display elements and light of three colors of RGB is divided and transmitted to each liquid crystal display element, the particle size of the liquid crystal for each color, Alternatively, it is possible to adjust the size of the liquid crystal domain, the substrate gap, the refractive index of the liquid crystal, and the like to make the characteristics uniform for each color.

As the liquid crystal used in the liquid crystal / resin composite, nematic liquid crystal or smectic liquid crystal can be used, and nematic liquid crystal is preferably used. Further, a cholesteric liquid crystal may be added to a part thereof, or a dichroic dye or a simple dye may be added. Further, a viscosity modifier, alumina particles, ceramic particles, plastic particles, spacers such as glass fibers, pigments, dyes, viscosity modifiers, and other additives that do not adversely affect the performance of the present invention may be added.

In the present invention, in the state where voltage is applied,
It is preferable to set n _{p of the} resin phase (after curing) substantially equal to n _{o of the} liquid crystal used. As a result, high transmittance can be obtained when the refractive index of the resin phase and the refractive index of the liquid crystal phase substantially match. When the two do not match, the light will be more scattered (cloudy). A liquid crystal optical element using this liquid crystal / resin composite has a high transmittance in a transmissive state and a haze value of 80% or more in a scattering state.

Further, by making the refractive indexes of the liquid crystal phase and the resin phase match when a voltage is applied, the transmittance at the time of transmission becomes high. Therefore, using a nematic liquid crystal having positive dielectric anisotropy, it is disposed so that the liquid crystal of the n _O substantially coincides with the refractive index n _p of the resin phase. At this time, high transparency is obtained when a voltage is applied. More specifically, n _o -0.03 <n _p <
The relationship of n _o +0.05 is satisfied.

FIG. 1 is a sectional view of an example of the liquid crystal display device of the present invention when an active matrix substrate is used.
In FIG. 1, 1 is a liquid crystal display element, 2 is a substrate such as glass or plastic for an active matrix substrate, and 3 is I
Transparent pixel electrodes such as TO and SnO ₂ , 4 are active elements such as transistors, diodes, and non-linear resistance elements, 5 is a glass or plastic substrate for the counter electrode substrate, and 6 is I
A transparent counter electrode such as TO or SnO ₂ is shown, and 7 is a liquid crystal / resin composite sandwiched between both substrates. When performing full-color display with a single-plate liquid crystal display element, RGB color filters, black masks, and the like are further provided.

FIG. 2 is a schematic view of a projection type liquid crystal display device using the liquid crystal display element of FIG. In FIG. 2, 11 is a light source for projection, 12 is a liquid crystal display element, 13 is a projection optical system including a lens and an aperture, and 14 is a projection screen for projection. In this example, the projection optical system is an aperture or spot 15 which is a plate with holes, and a condenser lens 1.
6, the projection lens 17 is included.

When a three-terminal element such as a TFT is used as an active element, the counter electrode substrate may be provided with a solid electrode common to all pixels. When using a two-terminal element such as an MIM element or a PIN diode, the counter electrode substrate is patterned in a stripe shape.

A device for reducing diffused light in a projection type liquid crystal display device is a device that takes out, from the light that has passed through a liquid crystal optical element, the light that goes straight on with respect to the incident light (the light that passes through the portion where the pixel portion is in the transmitting state). Any light that does not go straight (light that is scattered in the portion where the liquid crystal resin composite is in the scattering state) can be reduced. In particular, it is preferable that the light that goes straight does not decrease, and the light that does not go straight decreases the diffused light.

As a concrete apparatus, as shown in FIG. 2, the liquid crystal display element 1 is composed of a liquid crystal display element and a projection optical system.
2, a condenser lens 16, an aperture or a plate 15 having a hole, and a projection lens 17 are provided.

According to this example, of the light emitted from the projection light source and passing through the liquid crystal display element 12, the light that goes straight on with respect to the incident light is condensed by the condenser lens 16 and is opened to the aperture or spot 15. Projection lens 1
It is projected through 7. On the other hand, the non-straightened light scattered by the liquid crystal display element 12 does not pass through the aperture or the hole formed in the spot 15 even if condensed by the condenser lens 16. Therefore, scattered light is not projected, and the contrast is improved.

As another example, instead of the aperture or the spot 15, a mirror having a small area is obliquely arranged at the same position, reflected and projected through a projection lens arranged on the optical axis. You can also Further, a spot, a mirror or the like may be installed at a position where the light beam is focused by the projection lens without using such a condenser lens.
Further, the focal length and aperture of the projection lens may be selected so that scattered light is removed without using a special aperture or the like.

Also, a microlens system or the like can be used. Specifically, by disposing a microlens array and a spot array in which fine holes are arrayed on the projection optical system side of the liquid crystal display element, unnecessary scattered light can be removed. In this case, there is an advantage that the entire projection type display device can be made compact because the optical path length required for removing scattered light can be made very short. In order to shorten the optical path length, it is also effective to incorporate a scattering elimination system in the projection optical system. In this case, the size of the optical system can be reduced and the size of the optical system can be simplified as compared with the case where the projection optical system and the scattering elimination system are independently installed.

These optical systems can be combined with a mirror, a dichroic mirror, a prism, a dichroic prism, a lens or the like to synthesize an image and colorize it. In addition, an image can be colored by combining it with a color filter.

The ratio of the straight-ahead component and the scattered component reaching the projection screen can be controlled by the diameter of the spot, the mirror, etc. and the focal length of the lens, and may be set so as to obtain a desired display contrast and display brightness. .

When a device for reducing diffused light as shown in FIG. 2 is used, in order to increase the display brightness, it is preferable that the light incident on the liquid crystal display element from the projection light source be more parallel. For that purpose, it is preferable to configure a projection light source by combining a light source with high brightness and as close as possible to a point light source, a concave mirror, a condenser lens, and the like.

Further, in the above description, the transmission type liquid crystal display device was mainly described, but a reflection type projection type liquid crystal display device may be used. For example, a small mirror may be placed instead of the spot so that only necessary light is extracted.
Although FIG. 2 shows an example of a system configuration of a single plate configuration, the present invention is disclosed in JP-A-7-134295 (transmission type) and JP-A-7-134295.
It is also applicable to the system configuration of the RGB 3 plate configuration as shown in 5419 (reflection type). In this case, the white light source is R
Since the color light of GB is separated, a liquid crystal display element is provided for each color, and color synthesis is performed again, the light utilization efficiency is improved. Next, examples will be described.

[0100]

【Example】

Example 1 (Example) Bifunctional acrylic urethane, 2-ethylhexyl acrylate and 4-hydroxybutyl acrylate, which are reaction products of polypropylene glycol having a molecular weight of about 1000, trimethylhexamethylene diisocyanate, and 2-HEA. Were mixed at a weight ratio of 5: 2: 3 to prepare a polymerization curable material. Furthermore, a trace amount of a photopolymerization initiator was added thereto. The physical properties of this material at 25 ° C. were Δn = 0.215, Δε = 12.0, and K ₃₃ = 1.2.
A liquid crystal having a liquid crystal ratio of 6 × 10 ⁻¹¹ and η = 25 cSt was used.
It dissolved uniformly so that it might be 2%.

On the other hand, the active matrix substrate in which the polycrystalline silicon TFT is formed for each pixel and the counter electrode substrate in which the entire surface solid electrode is formed are sealed with the sealing material arranged in the peripheral portion, and the gap between the electrode substrates is 10 μm. Cells were formed.

An uncured mixture of the above-mentioned liquid crystal and polymerization curable material was injected into this cell, and then the polymerization curable material was cured by exposure to ultraviolet rays to form a liquid crystal / resin composite. The n _p of this resin was almost the same as the n _o of the liquid crystal. This liquid crystal display element, a light source for projection, and a projection optical system are combined to form a projection type liquid crystal display device. In a room at room temperature of 28 ° C., a luminous flux of about 800,000 lux is applied to the liquid crystal display element to display an image on the screen. The projection was done.

At this time, the liquid crystal display element was air-cooled by the cooling fan provided in the projection type display device, and the average temperature of the liquid crystal display element was adjusted to about 40.degree. Drive voltage about 8
V, the contrast on the screen obtained at a converging angle of the projection optical system of 5 ° was about 65. When this liquid crystal display device was driven by a video signal, a moving image with almost no image sticking was obtained even when the images were switched.

This projection type liquid crystal display device was irradiated with a light flux of about 800,000 lux to the liquid crystal display element in a room at room temperature of 15 ° C. to project an image on the screen.

At this time, the liquid crystal display element was air-cooled by the cooling fan provided in the projection type liquid crystal display device, and the average temperature of the liquid crystal display element was adjusted to about 20.degree. The contrast on the screen obtained at a drive voltage of about 8 V and a converging angle of 5 ° of the projection optical system was 75. When this liquid crystal display device was driven by a video signal, a moving image with almost no image sticking was obtained even when the images were switched.

Example 2 (Comparative Example) Similarly to the uncured liquid crystal except that 4-hydroxybutyl acrylate in Example 1 was replaced with 2-hydroxypropyl acrylate.
A resin mixture was prepared and a liquid crystal display device was obtained by the same method as in Example 1.

Further, a projection type liquid crystal display device was constructed as in Example 1, and an image was projected on the screen under the same conditions as in Example 1 in a room at room temperature of 28 ° C. The contrast on the screen obtained when the average temperature of this liquid crystal display device was adjusted to about 40 ° C. at a driving voltage of about 8 V and a converging angle of 5 ° of the projection optical system was 80. When this liquid crystal display device was driven by a video signal, a moving image with almost no image sticking was obtained even when the images were switched.

Then, as in Example 1, when the average temperature of the liquid crystal display device was adjusted to about 20 ° C. in a room at room temperature of 15 ° C., the contrast on the screen of this liquid crystal display device decreased to 22, When it was driven by a video signal, when the images were switched, a burn-in phenomenon of the previous screen occurred due to the hysteresis on the voltage-transmittance characteristic.

Example 3 (Example) In the same manner as in Example 1, except that 4-hydroxybutyl acrylate was replaced with 6-hydroxyhexyl acrylate, an uncured liquid crystal /
A resin mixture was prepared and a liquid crystal display device was obtained by the same method as in Example 1.

Example 4 (Example) An uncured liquid crystal / resin was similarly prepared except that 4-hydroxybutyl acrylate in Example 1 was replaced with 2-hydroxyethyl acrylate modified with caprolactone (one molecule of caprolactone ring-opening addition). A mixture was prepared and a liquid crystal display device was obtained in the same manner as in Example 1.

Example 5 (Comparative Example) An uncured liquid crystal / resin mixture was prepared in the same manner as in Example 1 except that 4-hydroxybutyl acrylate was replaced with 2-hydroxyethyl acrylate. A liquid crystal display device was obtained.

Example 6 (Comparative Example) An uncured liquid crystal / resin mixture was prepared in the same manner as in Example 1 except that 4-hydroxybutyl acrylate was replaced with 10-hydroxydecyl acrylate. A liquid crystal display device was obtained.

Example 7 (Comparative Example) 2-hydroxyethyl obtained by modifying the 4-hydroxybutyl acrylate of Example 1 with caprolactone (caprolactone 2 molecule ring-opening addition) corresponding to R in the formula (1) having 14 carbon atoms. An uncured liquid crystal / resin mixture was prepared in the same manner except that it was replaced with acrylate, and a liquid crystal display device was obtained by the same method as in Example 1.

Example 8 (Comparative Example) An uncured liquid crystal / resin mixture was prepared in the same manner as in Example 1 except that 4-hydroxybutyl acrylate was replaced with n-hexyl acrylate. A display device was obtained.

These liquid crystal display elements were combined with the same projection light source and projection optical system as those used in Example 1 to form a projection type liquid crystal display device, and a light flux of about 800,000 lux was produced in a room at room temperature of 15 ° C. The display element was irradiated to project an image on the screen. At this time, the liquid crystal display element was air-cooled by a cooling fan provided in the projection type liquid crystal display device, and the average temperature of the liquid crystal display element was adjusted to about 20 ° C.

Driving voltage of about 8 V, light collecting angle of projection optical system 5 °
Table 1 shows the contrast on the screen of these liquid crystal display elements obtained in the above step and the presence / absence of the burn-in phenomenon at the time of switching the image when driven by a video signal. The hysteresis values in the table are applied at the time of voltage boosting when the transmittance is (transmittance when no voltage is applied + saturated transmittance when voltage is applied) / 2 in the voltage-transmittance characteristic of the liquid crystal display element. The voltage difference between the voltage value and the applied voltage value when the voltage is lowered (V
_RMS ).

[0117]

[Table 1]

[0118]

In the liquid crystal optical element of the present invention, an improved liquid crystal / resin composite capable of electrically controlling the scattering state and the transmitting state is sandwiched between a pair of substrates with electrodes. By selecting the polymerization-curable material that forms the liquid crystal / resin composite, the structure of the liquid crystal / resin composite can be controlled extremely precisely and stably. You can greatly improve the property. Optimal liquid crystal for optical characteristics /
The resin composite, that is, the spatial structure such that the liquid crystal phases separated in the resin phase are three-dimensionally connected, or the resin of the three-dimensional network form deposited in the liquid crystal forms multiple domains in the liquid crystal. You can build a unique spatial structure.

Also, by selecting the resin material, it becomes possible to control the respective states before and after the polymerization phase separation. In particular, when photopolymerization phase separation is used, the compatibility of the mixture of the liquid crystal and the resin material (photocurable cured product) is stable, and the subsequent injection process into the liquid crystal empty cell and the curing process by light irradiation are stable. I can do it now.

Further, the formed liquid crystal / resin composite can have a desired fine structure which is electro-optically preferable. This is because the interaction at the interface between the liquid crystal phase and the resin phase during phase separation is appropriately adjusted by the elastic properties and polarities derived from the molecular structure of the resin material used.

Further, it is possible to reduce hysteresis in the liquid crystal / resin composite during operation in a wide temperature range, in other words, at a low temperature lower than room temperature, which has not been easily obtained in the past, and to prevent image sticking from occurring. A projection type liquid crystal display device with a clear display was obtained. Specifically, in a projection type liquid crystal display device in which a liquid crystal display element is irradiated with a light flux of about 500,000 lux or more, good operating characteristics can be obtained in the ambient temperature range of +15 to 40 ° C.

Further, the liquid crystal optical element of the present invention is the same as the conventional T
Even when driving a low voltage (~ 10 V) using an N-LCD driving IC, display with high contrast and high brightness is possible.

Further, according to the present invention, even when gradation driving is performed, it is possible to perform a clear halftone gradation display and reduce the burn-in phenomenon due to hysteresis.

Therefore, the liquid crystal optical element of the present invention is effective for a projection type display intended to obtain a high-luminance image, and a bright, high-contrast projection type display without image burn-in can be obtained. Also, the light source can be downsized.

Further, since it is not necessary to use a polarizing plate, there is an advantage that the wavelength dependency of optical characteristics is small and color correction of the light source is almost unnecessary. In addition, since problems such as rubbing and other alignment treatments, which are indispensable for TN-LCDs, and destruction of active elements due to the generation of static electricity, can be avoided,
The manufacturing yield of liquid crystal optical elements can be significantly improved.

Furthermore, since this liquid crystal / resin composite is in the form of a film after curing, problems such as short-circuiting between substrates due to pressurization of substrates and breakage of active elements due to movement of spacers are unlikely to occur.

Further, this liquid crystal / resin composite has the same specific resistance as that of the conventional TN-LCD, and the conventional DSM.
-It is not necessary to provide a large storage capacitor for each pixel electrode as in an LCD. Therefore, the active element can be easily designed, the ratio of the effective pixel electrode area can be easily increased, and the power consumption of the liquid crystal optical element can be kept small.

Further, since it can be manufactured only by removing the alignment film forming step from the manufacturing process of the conventional TN-LCD, the production is easy.

A liquid crystal optical element using this liquid crystal / resin composite can be stably manufactured, and products satisfying the required performance can be obtained with a high yield.

In addition to the above, the present invention can be applied in various ways within a range that does not impair the effects of the present invention.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic configuration of a liquid crystal optical element of the present invention.

FIG. 2 is a schematic diagram showing a basic configuration of a projection type liquid crystal display device of the present invention.

[Explanation of symbols]

 1, 12: Liquid crystal optical element 2, 5: Substrate 3: Pixel electrode 4: Active element 6: Counter electrode 7: Liquid crystal / resin composite 11: Projection light source 13: Projection optical system 14: Projection screen 15: Spot 16: Condensing lens 17: Projection lens

Claims (7)

[Claims] 1. In a liquid crystal optical element in which a liquid crystal / resin composite containing a liquid crystal and a resin is sandwiched between a pair of substrates with electrodes, a resin phase comprises an addition polymerizable compound represented by the following formula (1). A liquid crystal optical element, which is a polymerized and cured product of a polymerized and curable material containing. Embedded image CXY═CZ—CO—O—R—OH (1) (where X, Y and Z represent —H or —CH ₃ ; R represents an ether bond, an ester bond and a carbon-carbon bond between carbon bonds). It may contain one or more bonds selected from carbonate bonds, has a total carbon number of 4 to 8, and has the formula (1)
Shows a divalent hydrocarbon group containing at least one carbon atom between the carbon atom bonded to the ester bond and the carbon atom bonded to the hydroxyl group. ) 2. The ratio of the compound represented by the formula (1) to all addition-polymerizable compounds in the polymerization-curable material is 10 to 70.
The liquid crystal optical element according to claim 1, wherein the liquid crystal optical element has a weight percentage. 3. R is — (CH ₂ ) _n — (where n is 4 to
8. The liquid crystal optical element according to claim 1, which is an integer of 8. 4. The liquid crystal optical element according to claim 1, 2 or 3, wherein the compound represented by the formula (1) is a hydroxyl group-containing acrylate. 5. The liquid crystal optical element according to claim 1, 2, 3 or 4, wherein the curable material further contains a high molecular weight compound having one or more functional groups capable of being polymerized by heat or light. 6. An active matrix substrate provided with an active element for each pixel electrode, and a counter electrode substrate provided with a counter electrode, wherein the active matrix substrate and the counter electrode substrate are provided between the active matrix substrate and the counter electrode substrate. A liquid crystal display device comprising a liquid crystal / resin composite of 4 or 5 liquid crystal optical devices sandwiched therebetween. 7. A projection type liquid crystal display device comprising a combination of the liquid crystal display device according to claim 6, a projection light source and a projection optical system.