JP5594662B2 - Display element and method for manufacturing display element - Google Patents

Description

  The present invention relates to a display element useful as a component of a display such as a liquid crystal television and a monitor, and a method for manufacturing the display element.

  In addition to the essential features such as small size, light weight, and low power consumption, the liquid crystal display element has been developed as an active matrix type liquid crystal display device with excellent display quality. Widely applied in the market. There are various types of liquid crystal display devices: dynamic scattering type, TN (twisted nematic method), STN (super twisted nematic method), SSFLC (surface stabilized ferroelectric liquid crystal), OCB (optically compensated). A display method such as a bend method), a VA (vertical alignment method), or an IPS (in-plane orientation method) is widely applied to portable terminals, liquid crystal televisions, projectors, computers, and the like.

On the other hand, liquid crystal display elements are still not sufficient in terms of response speed and viewing angle characteristics compared to CRTs that have been used in the past and plasma display elements that have been widely used alongside liquid crystals. . In particular, in order to meet the demand for 3D video or field sequential display that is being developed, it is strongly required to improve the response speed.
As a technology to improve the response speed, the overdrive method with improved voltage application method in the drive circuit and the apparent response speed of the display element are improved by changing the frame frequency from the conventional 60Hz to 120Hz, 240Hz, etc. Improvements have been made to achieve this. However, there is a limit to exceeding the limit of the response speed inherent to the liquid crystal material only by improving the electronic circuit of these liquid crystal display devices, and drastic improvement of the response speed by improving the entire display device including the liquid crystal material. Is required.

  In addition, high contrast is required to improve image quality, and for that purpose, it is important to reduce light leakage in a dark state. In a mode in which liquid crystal molecules are aligned with an in-plane anisotropy in the dark state, light leakage occurs unless the alignment direction and the polarization direction of the polarizer are precisely matched. Further, although there is a pseudo isotropic mode in the plane like VA, anisotropy appears in the plane when the molecule is tilted to improve the viewing angle characteristic or the response. In any mode, if an alignment defect occurs intentionally or accidentally, it causes light leakage. Therefore, in the dark state, it is not pseudo-isotropic only in the direction along the molecular axis as in VA, but isotropic in all directions, and light leakage is prevented in the crossed Nicol arrangement. There is a strong demand for modes.

  As a method for drastically improving such a problem, a display element using the Kerr effect has been proposed. The Kerr effect is a phenomenon in which, when an electric field is applied to a substance having isotropic phase polarity, birefringence is developed in proportion to the square of the electric field. The induced birefringence is expressed by the following equation.

（式中、Δｎは誘起複屈折を表し、λは光の波長を表し、Ｂはカー定数を表し、Ｅは印加電場を表す。）

(In the formula, Δn represents induced birefringence, λ represents the wavelength of light, B represents the Kerr constant, and E represents the applied electric field.)

Since the expression of birefringence due to the Kerr effect is proportional to the square of the electric field, it can be driven at a low voltage, and the response speed is essentially high, and a microsecond response speed can also be achieved. .
On the other hand, there is an attempt to use the Kerr effect of nematic liquid crystal. A large Kerr effect (called an anomalous Kerr effect) can be obtained in a nematic liquid crystal only in a narrow temperature range immediately above the nematic phase-isotropic liquid phase transition temperature (T _NI ). An anomalous Kerr effect is not observed in the isotropic liquid phase sufficiently high from T _NI, and in the nematic phase below the temperature range of T _NI , realignment of nematic liquid crystal occurs and no anomalous Kerr effect is observed. The realignment of the nematic liquid crystal is because a physical quantity called a correlation length (ξ) of the nematic liquid crystal diverges infinitely and a long-range order is formed.

Here, the correlation length (ξ) is a length representing how far the nematic short-range order is maintained. In the nematic liquid crystal phase, the entire phase (that is, the entire molecular assembly) is in a nematic order, and it can be considered that the nematic short-range order is maintained indefinitely. Therefore, the correlation length is infinite. On the other hand, in a special situation, there may be a state showing a finite value of the correlation length. For example, in the case of a liquid crystal, such as transition from the liquid phase to the nematic phase, a sufficiently high temperature state than T _NI in the liquid phase, similar to the liquid phase of the compound showing no liquid phase, the sequence between the molecules randomly No nematic order is formed even at short distances between molecules, and therefore the correlation length is very small. However, the temperature drops and approaches the T _NI, gradually nematic manner short-range order is formed. The molecular assembly as a whole has no nematic order and is a liquid, but a nematic short-range order is formed. Therefore, the distance that maintains the short-range order is expressed as the correlation length. As T _NI is approached, the distance that nematic short-range order lasts increases, and therefore the correlation length increases. Further temperature but becomes nematic phase at falling T _NI, the correlation length is in that state is infinite. In this way, the correlation length varies with temperature, but if the nematic short-range order does not persist over long distances due to spatial limitations in addition to temperature, a finite factor related to the strength of the spatial limitations. The value of will be taken.

  Therefore, in order to perform display using the Kerr effect of liquid crystal, it is necessary to set the correlation length (ξ) of the liquid crystal to a finite value, and such an attempt has been made (see Non-Patent Document 1). ). The liquid crystal element described in Non-Patent Document 1 divides a liquid crystalline substance into small regions by a polymer network, and as a result, the correlation length (ξ) can be shortened even in a liquid crystal state, and the Kerr effect can be used. It is a thing. However, in the liquid crystal element described in Non-Patent Document 1, it has been shown that by using a chiral nematic liquid crystal (also referred to as cholesteric liquid crystal), a finite correlation length (ξ) is obtained even in the temperature range of the liquid crystal state. In the case of using a normal nematic liquid crystal, even when a polymer network is formed, the same state as that of a normal nematic liquid crystal is observed. For this reason, in the liquid crystal display element described in Non-Patent Document 1, when a normal nematic liquid crystal is used, the correlation length (ξ) does not become a finite value but diverges infinitely. Thus, in the example of Non-Patent Document 1, it is essential to use a chiral nematic phase containing a chiral compound, and there is a small range of selection of materials, and there is also a problem in terms of material costs. It was.

A display element using a similar liquid crystal / polymer composite material and a liquid crystal composition used therefor have been proposed (see Patent Document 1). However, the liquid crystal composition of Patent Document 1 is also required to be chiral, and there is a small range of selection of materials, and there is a problem in terms of material costs.
On the other hand, there is a proposal of a display element in which a non-chiral nematic liquid crystal and a polymer are used and the liquid crystal is divided into small regions by a polymer network (see Patent Document 2). In the liquid crystal display described in Patent Document 2, it is disclosed that the Kerr effect is expressed by setting the average diameter of each small area of the liquid crystal material to 0.1 μm or less using a polymer material. However, it has not been proved at all whether the liquid crystal material divided into sub-regions of 0.1 μm or less shows an aggregate state similar to that of an original nematic liquid crystal characterized by having an alignment fluctuation, There is no specific correlation length (ξ). Therefore, it is not clear whether the display element described in Patent Document 2 has a Kerr effect obtained from a crystalline state, an amorphous state, or a pseudo liquid state, or exhibits a large Kerr effect based on an original nematic liquid crystal state. . Further, in the polymer dispersion type liquid crystal display element, it is not always easy to divide the light control layer into small areas of 0.1 μm or less, and there is a problem that it is difficult to efficiently manufacture the display element. .

  Similarly, to obtain a liquid crystal divided into small areas for the purpose of exhibiting the Kerr effect in a display element using a non-chiral nematic liquid crystal and a polymer and dividing the liquid crystal into small areas by a polymer network. A method of adding fine particles having a particle size of 0.1 μm or less has been proposed. (See Patent Document 3). However, in the liquid crystal display described in Patent Document 3, it has been completely proved whether the liquid crystal divided into small regions shows a collective state similar to the original nematic liquid crystal characterized by having an alignment fluctuation. In addition, there is no description of a specific correlation length (ξ). Therefore, like the display element described in Patent Document 2, there is a possibility that a large Kerr effect based on the original nematic liquid crystal state is not obtained. Furthermore, new problems such as production of fine particles that are well dispersed in liquid crystals and new problems such as material non-uniformity and reduced reliability due to the dispersion of fine particles are caused.

JP 2009-57460 A JP-A-11-183937 JP-A-2005-70076

Adv. Mater. , 2005, 17, 2311, Haseba et al.

  An object of the present invention is to provide a display element that applies a Kerr effect that has high-speed response, isotropic in a dark field, and has no light leakage, and a manufacturing method thereof.

As a result of intensive studies to solve the above problems, the inventors of the present application are in a state in which the nematic liquid crystal originally exhibits alignment fluctuations even when the liquid crystal is divided into small regions by a polymer network, and the liquid crystal It has been found that when the correlation length (ξ) becomes finite, a good display element utilizing the Kerr effect is obtained, and the present invention has been completed.
The present invention comprises a pair of substrates facing each other and a substance layer containing a nematic liquid crystalline substance sandwiched between the pair of substrates and divided into small areas by a polymer material, and applying an electric field to the substance layer Accordingly, the display element performs display utilizing optical isotropy when no electric field is applied and optical anisotropy when an electric field is applied, and the liquid crystalline substance is in a nematic liquid crystal state exhibiting alignment fluctuations. And a correlation element (ξ) of the nematic liquid crystal is 0.100 μm to 1 μm, and a method for manufacturing the display element.

  In the composition of the present invention, the liquid crystal divided into smaller regions in the polymer network is an original nematic liquid crystal state having alignment fluctuations, and the correlation length (ξ) does not diverge and is a finite value. Based on the original nematic liquid crystal, a large Kerr effect is obtained, and since the correlation length (ξ) takes a finite value, unnecessary intermolecular interactions can be eliminated, so that a high-speed response can be achieved. Since it is isotropic when no electric field is applied, a high-quality black level can be obtained and the contrast becomes high. In addition, since an in-plane anisotropic state is obtained by applying a voltage, the viewing angle is wide, and the cost can be reduced by not using a retardation film for correcting the viewing angle.

It is sectional drawing which shows an example of the liquid crystal display element of this invention which has an electrode in the board | substrate of one side. It is sectional drawing which shows an example of the liquid crystal display element of this invention which has an electrode on two board | substrates. It is a setup schematic diagram of static light scattering measurement.

The present invention will be described as follows.
(Material layer)
In the present invention, the substance layer is composed of a liquid crystalline substance sandwiched between a pair of substrates described later and a polymer material that divides the liquid crystalline substance into small areas.
Here, the liquid crystalline material is a nematic liquid crystal state exhibiting alignment fluctuation, and in the present invention, such a liquid crystalline material is referred to as “nematic liquid crystal component” or “nematic liquid crystal”.

(Nematic liquid crystal component)
As the nematic liquid crystal component, the following general formula (I),

(Wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms, and one or more non-adjacent —CH ₂ — groups in the alkyl group are oxygen atoms, —COO— Or one or more —CH ₂ — groups may be replaced by —CH═CH—, and ring A ¹ is a 1,4-phenylene group, 1,4 -Represents a cyclohexylene group, a 1,3-dioxane-2,5-diyl group, a pyridine-2,5-diyl group, or a pyrimidine-2,5-diyl group, and the 1,4-phenylene group is unsubstituted. Or may have one or more fluorine atoms, chlorine atoms, CF ₃ groups, OCF ₃ groups, or methyl groups as substituents, and X ¹ , X ² , X ³ , and X ⁴ are Each independently a hydrogen atom, a fluorine atom, a chlorine atom, a CF ₃ group, Or an OCF ₃ group, ^{Y 1} represents a fluorine atom, a chlorine atom, a cyano group, CF ₃ group, OCF ₃ group, OCHF ₂ group, or NCS group, ^{Z 1,} and ^{Z 2} are each independently, Single bond, —COO—, —OCO—, —CH ₂ —CH ₂ —, —CH═CH—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, or —C Preferably represents at least one compound represented by ≡C-, n represents 0 or 1. In the formula, R ¹ is an alkyl group having 1 to 10 carbon atoms or an alkoxy group. More preferably, the ring A ¹ is a 1,4-phenylene group or a 1,4-cyclohexylene group (the 1,4-phenylene group is unsubstituted or includes one or two or more substituents). More preferably a fluorine atom). X ^{1 to} X ⁴ are each independently more preferably a hydrogen atom or a fluorine atom, and Z ¹ and Z ² are each independently a single bond, —COO—, —OCO— or More preferably, -C≡C-. Specifically, the following general formula:

（式中、Ｒ^１２は炭素原子数２〜８のアルキル基、又はアルコキシ基を表す）

(Wherein R ¹² represents an alkyl group having 2 to 8 carbon atoms or an alkoxy group)

（式中、Ｒ^１２は炭素原子数２〜８のアルキル基、又はアルコキシ基を表す）

（式中、Ｒ^１２は炭素原子数２〜８のアルキル基、又はアルコキシ基を表す）

(Wherein R ¹² represents an alkyl group having 2 to 8 carbon atoms or an alkoxy group)

(Wherein R ¹² represents an alkyl group having 2 to 8 carbon atoms or an alkoxy group)

（式中、Ｒ^１３は炭素原子数２〜８のアルキル基、又はアルコキシ基を表し、Ｘ^１１〜Ｘ^５２は、それぞれ独立して水素原子あるいはフッ素原子を表す。）

(In the formula, R ¹³ represents an alkyl group having 2 to 8 carbon atoms or an alkoxy group, and X ^{11 to} X ⁵² each independently represents a hydrogen atom or a fluorine atom.)

(In the formula, R ¹³ represents an alkyl group having 2 to 8 carbon atoms or an alkoxy group, and X ^{61 to} X ⁹⁴ each independently represents a hydrogen atom or a fluorine atom). In the compounds represented by the general formulas (I3-1) to (I3-16), it is more preferable that R ¹³ is an alkyl group having 2 to 6 carbon atoms or an alkoxy group.
In order to obtain a stable nematic liquid crystal phase, the nematic liquid crystal component is preferably a composition containing at least two compounds represented by formula (I). Among them, at least one compound represented by n = 0 among the compounds represented by general formula (I) and a compound represented by n = 1 among compounds represented by general formula (I) It is more preferable that the composition is a mixture containing at least one kind.

As the nematic liquid crystal component for the display element of the present invention, in order to obtain a large birefringence even if the nematic liquid crystal component content in the element is small, the nematic liquid crystal component has a large Δn and an externally applied electric field. In order to improve the responsiveness, a nematic liquid crystal component having a large Δε is preferable. For this purpose, a liquid crystal composition containing a compound represented by formula (I) wherein Y ¹ is a cyano group is used. Preferably there is. The compound in which Y ¹ is a cyano group is preferably a compound represented by the general formulas (I2-1) to (I2-8) and the general formula (I3-1). Particularly preferred are compounds represented by formula (I2-1) and compounds represented by general formula (I3-1) in which X ^{11 to} X ¹⁶ are all hydrogen atoms.

When the content of the nematic liquid crystal component, which is a liquid crystalline substance in the material layer, is large, birefringence increases when a voltage is applied to generate birefringence, and a bright display is obtained. Since it becomes difficult to show isotropic properties, the content of the compound represented by the general formula (I) in the material layer is preferably 5% to 50%, more preferably 10% to 40%, and more preferably 20% to 40%. % Is particularly preferred.
In the present specification,% represents mass%.

The compound represented by n = 0 contributes to the stabilization of the liquid crystal phase at low temperature, and the compound represented by n = 1 contributes to the stabilization of the liquid crystal phase at high temperature. The content ratio of the compound represented by n = 0 and the compound represented by n = 1 among the compounds represented by the general formula (I) is appropriately selected depending on the temperature range. It is preferably 5:95 to 95: 5, more preferably 30:70 to 95: 5, further preferably 50:50 to 95: 5, and particularly preferably 60:40 to 95: 5.
In terms of being advantageous in high-speed response and being easy to produce a display device, a nematic liquid crystal component having a low viscosity is preferable. In that respect, among the compounds represented by the general formula (I), Z ¹ and Z ² Is a single bond, but the content in the nematic liquid crystal component is preferably 50% to 100%, more preferably 70% to 100%, and particularly preferably 90% to 100%.
The value of Δn of the nematic liquid crystal component is preferably 0.160 or more, more preferably 0.180 or more, further preferably 0.200 or more, and most preferably 0.220 or more. Further, the value of Δε of the nematic liquid crystal component is preferably 8.0 or more, more preferably 10.0 or more, further preferably 12.0 or more, and most preferably 13.0 or more.

(Polymer material)
The polymer material used in the present invention is preferably transparent, and the transparent polymer material is preferably a synthetic resin, and is preferably a thermosetting resin or an ultraviolet curable resin. A synthetic resin soluble in an organic solvent and a synthetic resin soluble in water are also suitable. Polymer-forming compounds that form transparent polymer materials include polymerizable monomers that are precursors of polymers, or oligomers derived from monomers or oligomers in terms of reactivity and viscosity selection. And monomers may be used. An ultraviolet curable resin is preferable from the viewpoint that a micro mixed state with the liquid crystal material can be controlled by controlling the temperature during polymerization. Preferred examples of the polymerizable monomer or oligomer include a monoacryl monomer or oligomer that is polymerized and cured by irradiation with ultraviolet rays, a diacryl monomer or oligomer, and a trifunctional or higher polyfunctional acrylic monomer or oligomer. Note that the hydrogen at the α-position and / or β-position of the vinyl group in these materials may be substituted with a phenyl group, an alkyl group, a halogen group, a cyano group, or the like.

  Examples of the polymer-forming compound that forms a transparent polymer material include styrene, chlorostyrene, α-methylstyrene, divinylbenzene; as substituents, 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, dimethylaminoethyl Acrylate, methacrylate or fumarate having a group such as diethylaminoethyl; ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol Mono (meth) acrylate or poly (meth) acrylate such as tetramethylene glycol, hexamethylene glycol, neopentyl glycol, trimethylolpropane, glycerin and pentaerythritol; vinyl acetate, vinyl butyrate or vinyl benzoate, acrylonitrile, cetyl vinyl ether, Limonene, cyclohexene, diallyl phthalate, diallyl isophthalate, 2-, 3- or 4-vinylpyridine, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-hydroxymethyl acrylamide or N-hydroxyethyl methacrylamide and their alkyl ethers Compound: Diol of diol obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol Meth) acrylate; diol or tri (meth) acrylate of triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane; adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A Di (meth) acrylate of diol obtained as above; reaction product of 1 mol of 2-hydroxyethyl (meth) acrylate and 1 mol of phenyl isocyanate or n-butyl isocyanate; poly (meth) acrylate of dipentaerythritol; trimethylol Propane triacrylate, tricyclodecane dimethylol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, hexanediol diacrylate, ne Neopentyl glycol diacrylate, tris - (acryloxyethyl) isocyanurate, caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate are preferable.

  Moreover, you may use what is marketed and can be obtained easily as a polymer formation compound. For example, Kayrad R-551 and Kayalad R-712 (all manufactured by Nippon Kayaku Co., Ltd.), NOA60, NOA61, NOA63, NOA65, NOA68, NOA71, NOA72, NOA73, NOA81, NOA83H, NOA88 (all manufactured by Norland) Is mentioned. Examples of the oligomer of the polymer-forming compound include caprolactone-modified hydroxypivalate ester neopentyl glycol diacrylate (“HX-620” and “HX-220” manufactured by Nippon Kayaku Co., Ltd.).

  A photopolymerization initiator may be used to rapidly polymerize the above-described polymer-forming compound to obtain a desired polymer. As the photopolymerization initiator, any monomer suitable for the selected monomers and oligomers can be used. For example, 2-hydroxy-2-methyl-1-phenylpropan-1-one ("Darocur 1173" manufactured by Merck & Co., Inc.) can be used. 1) -hydroxycyclohexyl phenyl ketone ("Irgacure 184" manufactured by Ciba-Geigy), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one ("Darocure 1116" manufactured by Merck & Co., Inc.) ), Benzyldimethyl ketal (“Irgacure 651” manufactured by Ciba Geigy), 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (“Irgacure 907” manufactured by Ciba Geigy) 2,4-diethylthioxanthone (“Kayacure DETX” manufactured by Nippon Kayaku Co., Ltd.) and p- Mixture of methyl amino benzoate (manufactured by Nippon Kayaku Co., Ltd., "Kayacure EPA"), a mixture of isopropylthioxanthone (word pre Kin Sop Co. "Kantakyua ITX") and p- dimethylaminobenzoic acid ethyl.

(Correlation length (ξ))
The correlation length (ξ) of the nematic liquid crystal component of the present invention is characterized by 0.100 μm to 1 μm. However, when the correlation length (ξ) is increased, light leakage in a quasi-isotropic phase state is likely to occur. If the correlation length (ξ) becomes small, anchoring becomes strong, resulting in a slow response and difficulty in manufacturing the element. Therefore, the correlation length (ξ) is selected in consideration of these factors. The correlation length is preferably 0.100 μm to 0.500 μm, more preferably 0.100 μm to 0.200 μm.

(Element structure)
The configuration of the display element of the present invention is not particularly limited as long as it is in a quasi-isotropic state when no voltage is applied and birefringence generated when a voltage is applied can be used for display.
FIG. 1 and FIG. 2 show examples of element configurations in which the electric field applied to the material layer is substantially parallel to the substrate surface. An electrode for applying a voltage to one or both of the substrates 1 so that a substance layer 2 containing a nematic liquid crystal phase is sandwiched between two substrates 1 and an electric field substantially parallel to the substrate surface is applied to the substance layers. 3 is provided. The configuration of FIG. 1 is an embodiment in which electrodes are provided on one side of the substrate 1, and the configuration of FIG. 2 is an example of an embodiment in which electrodes are provided on both of the substrates 1. Polarizers 4 are disposed on both sides of the substrate 1 with the material layer 2 sandwiched therebetween, and the polarization axes thereof are orthogonal to each other, and one of the two axes is at a certain angle with the direction of the electric field parallel to the substrate 1 applied to the material layer 2. If it is arranged so as to deviate only, since the material layer is isotropic when no voltage is applied, the light from the light source 6 does not reach the observer 7, but when the voltage is applied, birefringence appears and becomes anisotropic. The light from the light source 6 reaches the observer 7 and can be used as a display element. The angle is preferably 45 degrees in order to increase the amount of light that is transmitted when a voltage is applied and to obtain a bright display element. 1 and 2 exemplify a transmissive display element, but a reflective plate is installed at the rear of the display element as viewed from the observer 7, and the reflection type is similarly used by using the principle based on birefringence. It is also possible to make a device.

  In the display element of the present invention, the electrode 3 for applying a voltage to the material layer 2 is not particularly limited, and examples thereof include a thin film of ITO (indium tin oxide). Various electrodes such as aluminum, nickel, copper, silver, gold, and platinum may be used for electrodes that do not require transparency. Moreover, when forming an electrode on a board | substrate, normal methods, such as vapor deposition, sputtering, and photolithography, are employable.

In the display element of the present invention, the substrate 1 for sandwiching the substance layer 2 is particularly limited as long as it has sufficient strength and insulation and at least the substrate on the observer side has transparency. Is not to be done. Examples thereof include glass, plastic, and ceramic.
In the display element of the present invention, when the distance between the pair of substrates 1 is more accurately controlled, a spacer 5 may be disposed between them. As the spacer 5, spherical spacers can be dispersed on the substrate surface as usual. Alternatively, columnar spacers may be formed on the substrate at regular intervals.
In the display element of the present invention, the polarizer 4 is not particularly limited, and functions to divide incident light into two polarization components orthogonal to each other, pass only one of them, and absorb or disperse the other components. If there is something. For example, a polymer dichroic polarizer such as a multi-halogen polarizer, a dye polarizer, or a metal polarizer can be used.

(Production method)
The display element of the present invention is, for example, a mixture of a liquid crystal material, a polymer-forming compound, and, if necessary, a photopolymerization initiator sandwiched between two substrates, or on one substrate. The substrate may be applied using a coater such as a spin coater, and then the other substrate may be overlaid. This can be produced by irradiating the substrate with ultraviolet light or thermally polymerizing and curing.
In the production method of the present invention, the polymerization of the monomer component for obtaining the polymer material contained in the substance layer is a temperature higher by 4 ° C. or more than the nematic phase-isotropic liquid phase transition temperature (T _NI ), or T _NI It is characterized in that it is carried out in a temperature range from 5 ° C. to T _NI , but in the case of polymerization at a temperature higher than T _NI , the light in the quasi-isotropic phase state of the completed device when the polymerization temperature is higher Although less leaking is preferable, since material deterioration may occur when the material is handled at a very high temperature, it is preferable to polymerize at a temperature below which the material deterioration does not occur. Specifically, when T _NI is 200 ° C. or lower, the polymerization temperature is preferably a temperature range higher than T _NI by 4 ° C. or higher and 200 ° C. or lower, more preferably 4 ° C. or higher and 150 ° C. or lower, more preferably 4 ° C. A temperature range higher than 100 ° C. is more preferable, a temperature range higher than 4 ° C. and lower than 50 ° C. is particularly preferable, and a temperature range higher than 8 ° C. and lower than 50 ° C. is most preferable. When T _NI is higher than 200 ° C., a temperature range that is 4 ° C. or more and 50 ° C. or less is preferable, a temperature range that is 4 ° C. or more and 20 ° C. or less is more preferable, and a temperature range that is 4 ° C. or more and 15 ° C. or less is particularly preferable. When the polymerization is carried out at a temperature lower than T _NI is preferred for carrying out the polymerization at a temperature close to T _NI to reduce light leakage in the Pseudo isotropic phase state of the element, specifically, T _NI it is preferred to carry out the polymerization at a temperature range of T _NI from more 5 ° C. lower temperature, it is further preferable to carry out the polymerization at a temperature range of T _NI 2 ° C. from a temperature lower than T _NI.

Hereinafter, although an example is given and this invention is further explained in full detail, this invention is not limited by these.
In the present invention, the correlation length (ξ) can be obtained by fitting the static light scattering profile to the Orstein-Zernike equation (the following equation 4.1). Light scattering due to correlation length fluctuations in the vicinity of the Iso-N transition of the liquid crystal can be obtained from Landau's free density energy, which discusses symmetry. When the system has infinite long-wavelength fluctuations, that is, in the vicinity of the Iso-N transition point of the liquid crystal, the Hv scattering intensity (I _Hv ) can be obtained as follows by developing the Landau free density energy.

(Where δε _xz represents the xz component in the tensor of dielectric constant fluctuation, the z direction represents the vibration direction of light, the x direction represents the direction perpendicular thereto, and <| δε _xz | ² > represents the dielectric constant fluctuation. This represents the mean square of the xz component in the tensor, ξ is the correlation length, q is the wave number, k is the Boltzmann constant, T is the temperature, α is the temperature dependence of the quadratic term during Landau free energy expansion Coefficient and the following formula

（式中、ａ_０はランダウ理論で自由エネルギー展開時の二次項において現象に合わせるための定数、Ｔは温度、Ｔ^＊は臨界転移温度を表す。）で定義される。）

(Where, a ₀ is a constant for adjusting to a phenomenon in the second order term at the time of free energy expansion in Landau theory, T is a temperature, and T ^* is a critical transition temperature). )

Hv scattering is defined as light scattering when the analyzer has a horizontal axis while the incident light is vertically polarized with respect to the incident surface (that is, the projected light is vertically polarized). It is. Hv scattering was measured by the apparatus shown in FIG.
Since there is a relationship of q = (4π / λ) sin (θ / 2) between the wave number q and the scattering angle, the correlation length (ξ) of the liquid crystal in the isotropic nematic liquid crystal phase is expressed by the equation 4.1. It was determined by fitting from the intensity dependence (spectrum) of the scattering angle in small angle scattering.

Example 1
(Production of polymer-dispersed liquid crystal element)
As the nematic liquid crystal, a composition of the compound represented by the general formula (X) was used. This composition had Δn = 0.224 (589 nm) and Δε = 13.8. Moreover, it was _TNI = 58 _degreeC .

NOA81 (manufactured by Norland Optics) was used as the UV photopolymerizable monomer. After the composition represented by the general formula (X) and NOA81 are mixed well at a ratio of 27.3% of the composition represented by the general formula (X), the gap is 10 μm and the electrode width The inter-electrode distance was 5 μm, and the substrate surface was injected by capillary action into a cell composed of a glass substrate that was not oriented. This cell was controlled on a hot stage at 70 ° C., 12 ° C. higher than T _{NI of the} composition represented by the general formula (X), and irradiated with UV light from a mercury lamp (manufactured by Electro-Lite, 365 nm) ( The UV light intensity was 35 mW · cm ⁻² ) and the polymerization reaction of NOA81 was promoted to induce microphase separation, thereby producing a polymer dispersed display element. Even if this element was changed in temperature from the isotropic phase to the nematic state, the dark field was maintained until room temperature in the polarization microscope (crossed Nicol) observation. There was a possibility that the molecule was in the dark field because it stood up with respect to the substrate (homeotropic orientation), but this possibility could be eliminated by conoscopic observation. Therefore, it was found that this element is optically isotropic when no voltage is applied. It was confirmed that when an electric field was applied to this device in the temperature range from 48 ° C., which is the temperature range of the nematic liquid crystal, to room temperature, birefringence (Δn) was switched by the Kerr effect proportional to the square of the electric field. When the response time was measured by applying an electric field of 10 Vpp / μm at room temperature, the rising response time was 50 μs and the falling response time was 17 μs.

(Measurement of orientation fluctuation of nematic phase)
Regarding the polymer-dispersed liquid crystal element of Example 1, optical isotropy can be confirmed by texture observation with a polarizing microscope, but it cannot be confirmed whether an optically isotropic nematic phase in which the liquid crystal exhibits a nematic state is induced. In order to investigate whether or not the optical isotropy of the polymer dispersed liquid crystal element of Example 1 is derived from the nematic phase, it is determined whether or not alignment fluctuations derived from the nematic phase are observed in the optical isotropic phase. The light scattering was measured by the setup shown in FIG. When a time-division small-angle light scattering image by static light scattering measurement was observed, a four-leaf glover-type Hv time-division light scattering image was observed in the range from room temperature to 45.5 ° C., and orientation fluctuation was confirmed. From this scattering result, it was determined that the optically isotropic phase was a nematic phase exhibiting orientation fluctuations.

(Calculation of correlation length (ξ))
The polymer dispersion type liquid crystal element of Example 1 was fitted to the above-mentioned Orstein-Zernike equation using static light scattering intensity data, and the correlation length (ξ) was calculated for each measured temperature. The correlation length (ξ) did not diverge even in the nematic temperature region, and showed a finite value of 140 nm at room temperature. In the nematic liquid crystal composition represented by the general formula (X), the correlation length (ξ) diverges in the nematic phase, but the nematic liquid crystal composition represented by the general formula (X) was manufactured using the nematic liquid crystal composition of Example 1. As for the polymer dispersion type liquid crystal element, it was found that the correlation length (ξ) did not diverge and showed a value of 130 nm at 30 ° C.

(Evaluation of the order of transfer)
The polymer / liquid crystal composite material used in the polymer dispersion type liquid crystal element of Example 1 was subjected to DSC measurement, and the behavior of the thermal change accompanying the phase transition was examined. The nematic liquid crystal composition represented by the general formula (X) exhibited a sharp DSC peak accompanying a phase transition in the vicinity of TNI, indicating that it was a first order transition. However, the polymer / liquid crystal composite material used in the polymer dispersion type liquid crystal element of Example 1 shows a broad DSC peak having a peak top near 48 ° C. and a shoulder at 10 ° C. or more before and after that. The polymer / liquid crystal composite material was found to exhibit a quasi-secondary transition.

(Example 2)
A polymer dispersed liquid crystal display element of Example 2 was produced in the same manner as in Example 1 except that the composition represented by the general formula (X) was mixed with NOA81 at a ratio of 36.5%. When an electric field is applied to this element in the temperature range from 48 ° C. which is a nematic liquid crystal temperature range to room temperature, no birefringence (Δn) is proportional to the square of the electric field. It turned out that it becomes a polymer dispersion type element which performs switching by an effect. In addition, the liquid crystal in this element is nematic having alignment fluctuation, the correlation length (ξ) is 160 nm at 30 ° C., and DSC measurement shows a quasi-secondary transition that expresses a broad peak associated with the phase transition. all right.

(Example 3)
A polymer-dispersed liquid crystal display element of Example 3 was produced in the same manner as in Example 1 except that the UV light irradiation temperature was 63 ° C., which was 5 ° C. higher than T _NI. It has been found that when an electric field is applied, it becomes a polymer dispersion type element that performs switching by the Kerr effect in which birefringence (Δn) is proportional to the square of the electric field. In addition, the liquid crystal in this element is nematic having alignment fluctuation, the correlation length (ξ) is 170 nm at 30 ° C., and the DSC measurement shows a pseudo-secondary transition that expresses a broad peak associated with the phase transition. all right.

Example 4
A polymer dispersed liquid crystal display element of Example 4 was produced in the same manner as in Example 1 except that the irradiation temperature of UV light was irradiated at 56 ° C. which is a temperature range of a nematic phase 2 ° C. lower than T _NI . It was found that when a voltage was not applied, it was optically isotropic, and when an electric field was applied, it became a polymer dispersion type element that switched by the Kerr effect in which birefringence (Δn) was proportional to the square of the electric field. In addition, the liquid crystal in this element is nematic having an alignment fluctuation, the correlation length (ξ) is 200 nm at 30 ° C., and DSC measurement shows a quasi-secondary transition that exhibits a broad peak associated with the phase transition. all right.

(Comparative Example 1)
A polymer dispersed liquid crystal display device was produced in the same manner as in Example 1 except that the composition represented by the general formula (X) was mixed with NOA81 at a ratio of 68.8%. In the temperature range of the nematic phase, the value of the correlation length became infinite and became a value of 1 μ or more. This element was not isotropic in the state where no voltage was applied, and exhibited birefringence. For this reason, a good dark field based on isotropic properties could not be obtained. When the response time was measured at room temperature by applying an electric field equivalent to that in Example 1, the response time was very slow, with a rise response time of 10 ms and a fall response time of 30 ms.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Material layer 3 Electrode 4 Polarizer 5 Spacer 6 Light source 7 Observer 11 Computer 12 CCD camera 13 Screen 14 Analyzer 15 Sample 16 Hot stage 17 Temperature controller 18 Polarizer 19 Pinhole 20 Helium-neon laser (632.8 nm )

Claims (10)

  A pair of opposing substrates, and a substance layer containing a liquid crystalline substance sandwiched between the pair of substrates and divided into small areas by a polymer material, and applying an electric field to the substance layer, no electric field is applied A display element that performs display using optical isotropy at the time and optical anisotropy at the time of electric field application, wherein the liquid crystalline substance is in a nematic liquid crystal state exhibiting alignment fluctuations, and the liquid crystal A display element, wherein the correlation length (ξ) of the active substance is 0.100 μm to 1 μm. The liquid crystal substance contained in the material layer is a liquid crystal that exhibits a broad peak accompanying a phase transition between the liquid layer and the liquid crystal phase in DSC measurement, and is accompanied by a phase transition between the liquid layer and the liquid crystal phase in DSC measurement. The width of the peak obtained in this way is a liquid crystal that is wider than the width of the peak obtained with the phase transition between the liquid layer and the liquid crystal phase in the DSC measurement of the liquid crystalline substance alone that is not divided into small areas by the polymer material. Item 1. A display element according to Item 1. The liquid crystal substance contained in the substance layer is a liquid crystal that expresses a broad peak having a shoulder at 10 ° C. or more before and after the peak top, accompanying a phase transition between the liquid layer and the liquid crystal phase in DSC measurement. 2. The display element according to 2. Liquid crystal material contained in the material layer, a dielectric anisotropy ([Delta] [epsilon]) is 8.0 or more, and any of claims 1 to 3, the refractive index anisotropy ([Delta] n) is 0.160 or more display element of crab described. Display device according to any one of claims 1 is substantially parallel the fourth to the electric field is the substrate surface to be applied to the material layer. The liquid crystalline substance contained in the substance layer is represented by the following general formula (I)

(Wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms, and one or more non-adjacent —CH ₂ — groups in the alkyl group are oxygen atoms, —COO— Or one or more —CH ₂ — groups may be replaced by —CH═CH—, A ¹ is a 1,4-phenylene group, 1,4- Represents a cyclohexylene group, a 1,3-dioxane-2,5-diyl group, a pyridine-2,5-diyl group, or a pyrimidine-2,5-diyl group, and the 1,4-phenylene group is unsubstituted. Or may have one or more fluorine atoms, chlorine atoms, CF ₃ groups, OCF ₃ groups, or methyl groups as substituents, and X ¹ , X ² , X ³ , and X ⁴ are each Independently, hydrogen atom, fluorine atom, chlorine atom, CF ₃ group, Represents an OCF ₃ group, Y ¹ represents a fluorine atom, a chlorine atom, a cyano group, a CF ₃ group, an OCF ₃ group, an OCHF ₂ group, or an NCS group, and Z ¹ and Z ² each independently represent: Single bond, —COO—, —OCO—, —CH ₂ —CH ₂ —, —CH═CH—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, or —C represents ≡C-, display element according to n claim 1, comprising at least one or more compounds represented by represents.) 0 or 1 in any one of 5. The display element according to claim 6 , wherein the liquid crystalline substance contained in the substance layer contains a mixture of two or more compounds represented by the general formula (I). The liquid crystalline substance contained in the material layer is at least one compound represented by n = 0 among the compounds represented by the general formula (I) and n among the compounds represented by the general formula (I). The display element according to claim 7 , which is a mixture containing at least one compound represented by = 1. The liquid crystal material contained in the material layer, the display device according to claim 6 8, Y ¹ in the general formula (I) comprises a compound which is a cyano group. A monomer for obtaining a polymer material contained in the substance layer, comprising a pair of opposing substrates and a substance layer containing a liquid crystalline substance sandwiched between the pair of substrates and divided into small areas by a polymer material the polymerization of the component, the nematic phase - isotropic liquid phase transition temperature (T _NI) than 4 ° C. or higher high temperature or a nematic phase - isotropic liquid phase transition temperature (T _NI) from 5 ° C. nematic phase from a low temperature - and performing in a temperature range of isotropic liquid phase transition temperature (T _NI), a method of manufacturing a display device according to any one of claims 1 to 9.

Images