JP2007016156A - Liquid crystal composition and liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition exhibiting a cholesteric phase that is capable of effecting the changeover of the state of the crystal liquid by application of a low driving voltage and affords good brightness and good whiteness (background whiteness), and to provide a liquid crystal display element using the liquid crystal composition. <P>SOLUTION: The liquid crystal composition comprises a self-organizing type gelling agent and a liquid crystal exhibiting a cholesteric phase at a room temperature wherein the gelling agent comprises a compound containing a siloxane skeleton in the molecule. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal composition and a liquid crystal display element.

  In the field of liquid crystal display elements, conventionally, liquid crystal display elements using a chiral nematic (cholesteric) liquid crystal composition capable of exhibiting a cholesteric phase at room temperature are known. In such a liquid crystal display element, basically, a chiral nematic (cholesteric) liquid crystal composition is sandwiched between a pair of substrates having transparent electrodes, and a high and low pulse voltage (driving voltage) is applied between the electrodes. Thus, the liquid crystal is switched from the planar (PL) state to the focal conic (FC) state or the homeotropic state to display an image. Among these, the planar (PL) state has a property of selectively reflecting light of a specific wavelength.

  When these liquid crystal materials are used as display elements, for example, a cholesteric liquid crystal composition contains a monomer and a polymerization initiator to produce a display element in order to perform good monochrome display and wide viewing angle display. After that, a polymer is formed by ultraviolet (UV) irradiation or the like to control the alignment characteristics of the liquid crystal composition (see, for example, Non-Patent Document 1).

  However, in the above technique, it is extremely difficult to completely perform polymerization so that unreacted monomer does not remain, and the remaining unreacted monomer reacts gradually with ultraviolet rays, and as a result, the display performance is affected when the device is used. There was a problem. As described above, the technique of suppressing the fluidity of the liquid crystal composition by performing a polymerization reaction in the liquid crystal composition is not preferable because it affects the display performance.

  Therefore, we focused on organic compounds that form a network structure in the liquid crystal composition by expressing intermolecular interactions such as hydrogen bonding, and such self-organizing gelling agents were applied to cholesteric liquid crystal compositions. The liquid crystal display element which makes it contain and performs a monochrome display was examined. However, it has been very difficult to improve the whiteness and brightness of a display image and to enable transition with a low driving voltage. That is, in order to suppress the coloring of the liquid crystal display element, it is necessary to increase the addition amount of the gelling agent. When the addition amount is increased, it is inevitable that the drive voltage increases and the brightness of the image decreases.

On the other hand, gelling agents containing a siloxane skeleton in the molecule are known. Specifically, there is a gelling agent containing a siloxane polymer containing an amino acid derivative segment (for example, see Patent Document 1). It has been known that these gelling agents are excellent in long-term stability near normal temperature as compared with gelling agents that do not contain a siloxane skeleton in the molecule. Also disclosed is a technique for a liquid crystal display element in which a gelling agent containing a siloxane skeleton in the molecule is added to a ferroelectric liquid crystal (see, for example, Patent Document 2).
JP 2002-80599 A JP 2004-133436 A R. Q. Ma, 1 other person, “SID 97 DIGEST”, pp. 101-104

  However, the technique disclosed in Patent Document 2 is to add a gelling agent having a siloxane skeleton to a ferroelectric liquid crystal, and the liquid crystal layer itself is an achromatic liquid crystal element in a transmission mode. Unlike liquid crystal display elements that exhibit a cholesteric phase, transmissive mode liquid crystal elements do not have the property of reflecting light of a specific wavelength at the liquid crystal layer, and thus provide a solution to the above-described problems of brightness and coloring of white images. It was not a thing.

  The present invention relates to a liquid crystal composition exhibiting a cholesteric phase, capable of switching states with a low driving voltage, and capable of obtaining good brightness and whiteness (white background), and the liquid crystal composition An object of the present invention is to provide a liquid crystal display element using the.

  As a result of extensive research, the present inventor was able to solve the above-described problems by the following means.

  The liquid crystal composition according to claim 1, wherein the liquid crystal composition contains a self-organizing gelling agent and a liquid crystal exhibiting a cholesteric phase at room temperature, wherein the gelling agent includes a siloxane skeleton in the molecule. It is characterized by comprising.

  The liquid crystal composition according to claim 2 is the liquid crystal composition according to claim 1, wherein the compound has a structure represented by the following general formula (1).

(Wherein R ₁ and R ₂ independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group optionally substituted with a substituent. At least _one of L ₁ , L ₂ and L _{3 represents} One is a group having a divalent amide bond part capable of forming a hydrogen bond between molecules, and the other is independently substituted with a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms or a substituent. I is an integer of 0 to 30, but when L ₂ or L ₃ is not a group having an amide bond capable of intermolecular hydrogen bonding, it is a natural number of 30 or less, j Is an integer from 0 to 30, but when i is 0, it is a natural number of 30 or less, i and j represent the ratio of the partial structures in the molecule, and the arrangement of these partial structures is irregular May be.)
The liquid crystal composition according to claim 3 is the liquid crystal composition according to claim 2, wherein the group having a divalent amide bond portion capable of forming a hydrogen bond between the molecules is represented by the following general formula (2). ) Or (3).

(In the formula, Re ₁ is an alkylene group having 1 to 20 carbon atoms, A ₁ and A ₂ are each independently —O—, —NH— or a single bond, and R ₃ is 1 to 20 carbon atoms. Alkyl groups, benzyl groups optionally substituted with substituents, monocyclic or bicyclic heterocyclic groups optionally substituted with substituents, — (CH ₂ ) _a —COO—R ₄ , — (CH _{2) a -OCO-R 4,} - (CH 2) a -CONH-R 4, - (CH 2) a -NHCO-R 4, - (CH 2) a -NHCONH-R 4, - (CH 2) _a —NHCOO—R ₄ , — (CH ₂ ) _a —OCONH—R ₄ , or — (CH ₂ ) _a —S—R ₄ (where a is a natural number of 5 or less, and R ₄ is carbon number 1) To 20 alkyl groups), n is a natural number of 5 or less.)
A liquid crystal composition according to a fourth aspect is the liquid crystal composition according to the first aspect, wherein the gelling agent comprises a compound represented by the following general formula (4).

(Wherein Re ₁ and Re ₂ are each independently an alkylene group having 1 to 20 carbon atoms, A ₁ and A ₂ are each independently any of —O—, —NH— and a single bond, G ₁ , G ₂ Is a structure represented by the following general formula (5) or (6).)

(Wherein R ₅ , R ₆ , R ₇ and R ₈ independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a phenyl group which may be substituted with a substituent, and i and j are 0 30) Although i and j are not 0 at the same time, i and j represent the ratio of the partial structures in the molecule, and the arrangement of these partial structures may be irregular.)
The liquid crystal composition according to claim 5 is the liquid crystal composition according to any one of claims 1 to 4, wherein a content of the gelling agent exhibits a cholesteric phase at the room temperature and the gelling agent. It is characterized by being 0.5% by mass or more and 4.0% by mass or less with respect to the total amount.

  The liquid crystal composition according to claim 6 is the liquid crystal composition according to any one of claims 1 to 5, wherein the liquid crystal exhibiting a cholesteric phase at room temperature contains a nematic liquid crystal and a chiral agent. It is characterized by.

  The liquid crystal composition according to claim 7 is the liquid crystal composition according to any one of claims 1 to 6, wherein a peak wavelength of selective reflection of the liquid crystal composition is 500 to 700 nm. It is.

  A liquid crystal display element according to an eighth aspect is characterized by having a liquid crystal layer made of the liquid crystal composition according to any one of the first to seventh aspects on a base material.

  A liquid crystal display element according to a ninth aspect is the liquid crystal display element according to the eighth aspect, wherein an electrode is provided on at least one of the pair of substrates.

  The present invention includes a self-organizing type gelling agent containing a siloxane skeleton in the molecule, so that the brightness and color at the time of white display can be reduced with a smaller amount of addition than when a conventional gelling agent is used. The present inventors have found a liquid crystal composition capable of improving the touch and capable of changing the state with a low driving voltage. Although the detailed mechanism by which such an effect is obtained is not clear, one reason is that a gelling agent containing a siloxane skeleton can form a dense network structure between gelling agent molecules due to the presence of the siloxane skeleton. It is guessed that it became.

  As a result, the helical axis of the cholesteric liquid crystal can be efficiently directed in various directions in the planar state, and the wavelength range capable of selective reflection can be widened to improve the white background. It is speculated that it was possible.

  It is also speculated that the brightness and white background were further improved by increasing the scattering between liquid crystal domains and the scattering caused by the refractive index difference between the gelling agent and the liquid crystal. That is, since the gelling agent containing a siloxane skeleton has a relatively low refractive index, the difference from the refractive index of the liquid crystal becomes large. As a result, it is considered that the scattering due to the refractive index difference is increased and the brightness and white background are improved.

  FIG. 1 is a schematic view showing a cross-sectional structure of a liquid crystal display element according to an embodiment of the present invention. The liquid crystal display element shown in FIG. 1 has a structure in which a liquid crystal layer (liquid crystal composition) 11 is sandwiched between a pair of substrates 1 and 2. In FIG. 1, transparent electrodes 3 and 4 formed in a plurality of parallel strips are provided on the surfaces of substrates 1 and 2, respectively. The transparent electrode 3 and the transparent electrode 4 are arranged to face each other so as to cross each other. An insulating thin film 5 is coated on the transparent electrodes 3 and 4. Further, an alignment film 7 is formed on the insulating thin film 5. 10 is a polymer structure as a space holding member, and 13 is a spacer as a space holding member. Reference numeral 12 denotes a sealing material for sealing the liquid crystal composition 11 inside the cell. A black visible light absorbing layer 9 is provided on the outer surface (back surface) of the substrate 2 on the side opposite to the side on which light is incident, if necessary. Instead of providing the visible light absorbing layer 9, the substrate 2 itself having visible light absorptivity may be used.

Hereinafter, main components of the liquid crystal display element will be described in detail.
(substrate)
In FIG. 1, the substrates 1 and 2 are both translucent, but the pair of substrates that can be used in the above-described liquid crystal display element is at least one substrate (at least the substrate 1 on the light incident side). ) Should have translucency. As the light-transmitting substrate, a glass substrate and a flexible substrate such as polycarbonate, polyethersulfone, polyarylate, and polyethylene terephthalate can be used. From the viewpoint of reducing the weight of the element, it is preferable to use a flexible substrate. When a flexible substrate is used as at least one of the pair of substrates, preferably both substrates, a lightweight and thin element can be manufactured and damage (cracking) can be suppressed.
(electrode)
Examples of the transparent electrodes 3 and 4 include a transparent conductive film such as ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide), a metal electrode such as aluminum and silicon, or an amorphous material. A photoconductive film such as silicon or BSO (Bismuth Silicon Oxide) can be used. In the liquid crystal display element shown in FIG. 1, as described above, a plurality of strip-like transparent electrodes 3 and 4 parallel to each other are formed on the surfaces of the substrates 1 and 2, and these transparent electrodes 3 and 4 intersect each other. Are facing each other. In order to form the electrode in this manner, for example, an ITO film may be deposited on the substrate by a masking method using a sputtering method or the like, or an ITO film may be formed on the entire surface and then patterned by a photolithography method.
(Insulating thin film)
Although not essential in principle, an insulating thin film 5 is formed on at least one of the transparent electrodes 3 and 4 in order to prevent a short circuit between the electrodes and to improve the reliability of the gas barrier property of the liquid crystal display element. It is preferable that Examples of the insulating thin film 5 include inorganic films made of silicon oxide, titanium oxide, zirconium oxide, alkoxides thereof, and the like, and organic films such as polyimide resin, epoxy resin, acrylic resin, and urethane resin. It can form by well-known methods, such as a vapor deposition method, a spin coat method, and a roll coat method, using such materials. Furthermore, the insulating thin film 5 can also be formed using the same material as the polymer resin used for the polymer structure 10.
(Alignment film)
The alignment film 7 is not essential in principle, but it is preferable to provide it for the purpose of stabilizing the element. When the alignment film 7 is formed, when the insulating thin film 5 is formed on the transparent electrodes 3 and 4, the insulating thin film 5 is formed on the transparent electrodes 3 and 4 on the insulating thin film 5. When not present, it is formed on the transparent electrodes 3 and 4. Examples of the alignment film 7 include organic films such as polyimide resin, silicone resin, polyamideimide resin, polyetherimide resin, polyvinyl butyral resin, and acrylic resin, and inorganic films such as silicon oxide and aluminum oxide. The alignment film formed using these materials may be subjected to a rubbing treatment or the like. Furthermore, the alignment film 7 can also be formed using the same material as the polymer resin used for the polymer structure 10.
(spacer)
A spacer 13 is provided between the pair of substrates 1 and 2 to keep the gap between the substrates 1 and 2 uniform. Examples of the spacer 13 include a sphere made of resin or inorganic oxide. For example, ball-shaped glass, ceramic powder, or spherical particles made of an organic material can be used. Further, a fixed spacer having a surface coated with a thermoplastic resin is also preferably used. In order to keep the gap between the substrates 1 and 2 more uniform, it is preferable to provide both the spacer 13 and the polymer structure 10 as shown in FIG. 1, but only one of them is provided. May be. When the polymer structure 10 is formed, the diameter of the spacer 13 is equal to or less than the height, preferably equal to the height. When the polymer structure 10 is not formed, the diameter of the spacer 13 corresponds to the thickness of the cell gap, that is, the thickness of the liquid crystal layer 11 made of the liquid crystal composition.
(Liquid crystal layer)
The liquid crystal layer 11 is made of a liquid crystal composition in which a cholesteric liquid crystal contains a self-organizing gelling agent. In the present embodiment, the liquid crystal composition is prepared by adjusting the components and the content ratio of the liquid crystal composition so that the selective reflection has a peak wavelength of 500 to 700 nm, particularly 550 to 650 nm. It is preferable to be prepared. By setting the peak wavelength to 500 to 700 nm, all visible rays are reliably reflected in the planar state, and a good white background can be realized and a high contrast monochrome image can be displayed.

  The gelling agent used in the present embodiment is a so-called self-organizing gelling agent containing a compound capable of forming a pseudo network structure between molecules by hydrogen bonding or the like. Self-organizing type gelling agent can increase the viscosity of cholesteric liquid crystal by forming a pseudo network structure by adding and mixing the gelling agent without using other means such as UV irradiation. It is. Therefore, in this embodiment, good black-and-white display is possible over a long period of time by using a self-organizing gelling agent. Specifically, the initial display color and contrast are stably maintained.

  Although the detailed mechanism for obtaining such an effect is not clear, it is presumed that the gelling agent molecules are easily dispersed uniformly in the liquid crystal composition. That is, it is considered that the pseudo-network structure formed by hydrogen bonding between molecules uniformly dispersed in the liquid crystal composition has a fine and dense structure, and appropriate flexibility can be obtained. In addition, compared with a method of improving the reflectance over a wide wavelength range, it is not necessary to increase the cell gap, so that it can be driven with a low applied voltage and there are few restrictions on material selection. Further, it has a feature that a wide viewing angle display can be performed as compared with an element to which no gelling agent is added.

  A self-organizing gelling agent is an organic compound that can form a pseudo-network structure between molecules by hydrogen bonding or the like. Specifically, it forms hydrogen bonds between molecules in the structure. And an organic compound having an alkyl group and a functional group that forms a hydrogen bond between molecules. When an organic compound having an alkyl group together with a functional group that forms a hydrogen bond is used as a gelling agent, intermolecular attractive force between alkyl groups in addition to intermolecular hydrogen bonding contributes to the formation of a pseudo-network structure. A stable network structure can be formed even if the amount of gelling agent added is small.

  Examples of the group capable of forming a hydrogen bond between molecules include an amide bond group (—NHCO—). The number of groups that form hydrogen bonds between molecules is 1 or more, preferably 2 or more in one molecule. The alkyl group is a long-chain alkyl group or a long-chain alkylene group, and examples thereof include saturated hydrocarbon groups having 4 or more carbon atoms, preferably 6 to 20 carbon atoms.

  Further, in the embodiment of the present invention, in particular, the compound constituting the above-mentioned gelling agent has a siloxane skeleton in the molecule, so that when white display is performed with a smaller addition amount than a gelling agent not having a siloxane skeleton. Brightness and white background can be improved. As a result, the drive voltage can be kept low.

  Although the detailed mechanism by which such an effect is obtained is not clear, it is presumed that a finer network structure can be formed by the presence of the siloxane skeleton. As a result, the helical axis of the cholesteric liquid crystal can be efficiently directed in various directions in the planar state, and as a result of increasing the wavelength range capable of selective reflection, it is estimated that the white background is improved.

  In addition, scattering between the liquid crystal domains and scattering due to the difference in refractive index between the gelling agent and the liquid crystal are also increased, and it is presumed that they contributed to the improvement of brightness and white background. Further, it is also presumed that the gelling agent containing a siloxane skeleton has a relatively low refractive index and an increased difference from the refractive index of the liquid crystal, thereby improving brightness and white background.

  The gelling agent used in the present embodiment contains at least a siloxane skeleton in the molecule and a group that forms a hydrogen bond between molecules, preferably an organic compound that contains a group that forms a hydrogen bond and an alkyl group If so, the structure is not particularly limited.

  What the gelling agent in this invention is represented by General formula (1) is preferable.

In the general formula (1), R ₁ and R ₂ independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group which may be substituted with a substituent. At least one of L ₁ , L ₂ and L ₃ is a group having a divalent amide bond part capable of forming a hydrogen bond between molecules, and the other is independently a hydrogen atom or a carbon number 1 to 10 alkyl groups or phenyl groups which may be substituted with substituents;

i is an integer of 0 to 30, but is a natural number of 30 or less when L ₂ or L ₃ is not a group having an amide bond part capable of forming a hydrogen bond between molecules. j is an integer from 0 to 30, but when i is 0, it is a natural number of 30 or less, and i and j represent the ratios of the partial structures in the molecule, and the arrangement of these partial structures is improper. It may be a rule.

  Further, in the general formula (1), if the group having a divalent amide bond part capable of forming a hydrogen bond between molecules has the structure of the following general formula (2) or (3), preferable.

In the general formulas (2) and (3), Re ₁ is an alkylene group having 1 to 20 carbon atoms, A ₁ and A ₂ are each independently —O—, —NH—, or a single bond; ₃ represents an alkyl group having 1 to 20 carbon atoms, a benzyl group which may be substituted with a substituent, a monocyclic or bicyclic heterocyclic group which may be substituted with a substituent, — (CH ₂ ) _a —COO— _{R 4, - (CH 2)} a -OCO-R 4, - (CH 2) a -CONH-R 4, - (CH 2) a -NHCO-R 4, - (CH 2) a -NHCONH-R 4 , — (CH ₂ ) _a —NHCOO—R ₄ , — (CH ₂ ) _a —OCONH—R ₄ , or — (CH ₂ ) _a —S—R ₄ (where a is a natural number of 5 or less, R ₄ is an alkyl group having 1 to 20 carbon atoms), and n is a natural number of 5 or less.

In the general formula (2), the carbon to which R ₃ is bonded has chirality, and an optical isomer can be considered. From the viewpoint of availability and cost of synthetic raw materials, those having the same configuration as natural amino acids are more preferable. The structure represented by the general formula (2) includes these stereoisomers and mixtures thereof.

  The stereo of the cyclic dipeptide moiety in general formula (3) is the same as in general formula (2).

About R < ₃ >, Preferably following formula (7-1)-(7-18) is mentioned.

  Another preferred structure of the gelling agent is represented by the following general formula (4).

In General Formula (4), Re ₁ and Re ₂ are each independently an alkylene group having 1 to 20 carbon atoms, A ₁ and A ₂ are each independently any of —O—, —NH—, and a single bond, G ₁ , G ₂ has a structure represented by the following general formula (5) or (6).

  In the general formula (4), carbon with a cyclohexane ring substituent has chirality, and an optical isomer is considered. Trans is preferable for the arrangement of the substituents on the cyclohexane ring in that the effect is high with a smaller amount (the following formula (8)). More preferred examples are trans 1 and 2 substituted products (the following formulas (9) and (10)). However, as long as it has the structure represented by the general formula (4), the present invention includes these stereoisomers, isomers having different substitution positions, and mixtures thereof. In addition to these, some substituents may have stereoisomers, but in any case, all stereoisomers and mixtures thereof are also included.

  Examples of the gelling agent include compounds represented by the following formulas (11) to (28).

  These compounds can be synthesized according to a known synthesis method.

  The content of the gelling agent is not particularly limited as long as the object of the present invention can be achieved. For example, the content is preferably 0.5 to 4.0% by mass with respect to the total amount of the cholesteric liquid crystal and the gelling agent. When set to this range, the Y value during black display can be reduced, and as a result, the contrast can be improved more effectively. Details of the Y value will be described later.

  A cholesteric liquid crystal containing a gelling agent exhibits a cholesteric phase at room temperature, and examples thereof include a chiral nematic liquid crystal composed of a nematic liquid crystal and a chiral agent.

  The nematic liquid crystal is not particularly limited, and a nematic liquid crystal conventionally known in the field of liquid crystal display elements can be used. Examples of such nematic liquid crystal materials include liquid crystal ester compounds, liquid crystal pyrimidine compounds, liquid crystal cyanobiphenyl compounds, liquid crystal tolan compounds, liquid crystal phenyl cyclohexane compounds, liquid crystal terphenyl compounds, fluorine atoms, and fluoroalkyls. Other liquid crystalline compounds having a polar group such as a cyano group and a cyano group, and mixtures thereof.

  As the chiral agent, various materials conventionally known in the field of liquid crystal display elements can be used. For example, a cholesteric compound having a cholesteric ring, a biphenyl compound having a biphenyl skeleton, a terphenyl compound having a terphenyl skeleton, an ester compound having a skeleton in which two benzene rings are connected by an ester bond, and a cyclohexane ring directly on the benzene ring A cyclohexane compound having a skeleton formed by linking a ring, a pyrimidine compound having a skeleton formed by directly linking a pyrimidine ring to a benzene ring, and an azoxy having a skeleton formed by linking two benzene rings by an azoxy bond or an azo bond Or an azo compound etc. are mentioned. The content of the chiral agent is not particularly limited, and is usually 3 to 40% by mass with respect to the total amount of the cholesteric liquid crystal and the gelling agent.

  An additive such as an ultraviolet absorber may be further added to the liquid crystal composition. The ultraviolet absorber is intended to prevent ultraviolet deterioration of the liquid crystal composition, for example, fading or change in responsiveness with time. For example, materials such as a benzophenone compound, a benzotriazole compound, and a salicylate compound can be used. The addition amount is 5% by mass or less, preferably 3% by mass or less, based on the total amount of the cholesteric liquid crystal and the gelling agent.

Such a liquid crystal composition is obtained by mixing each material at a predetermined ratio. If desired, the liquid crystal composition may be purified by bringing it into contact with an ion exchange resin, an adsorbent or the like to remove moisture and impurities, and then used for manufacturing the device.
(Seal material)
The sealing material 12 is for sealing the liquid crystal composition 11 so that it does not leak from between the substrates 1 and 2, and includes a thermosetting resin such as an epoxy resin or an acrylic resin, or a photocurable adhesive. Can be used.
(Polymer structure)
The polymer structure 10 may have any shape such as a columnar body, an elliptical columnar body, a quadrangular columnar body, the arrangement may be random, and has regularity such as a lattice shape. It may be a thing. Providing such a polymer structure 10 makes it easy to keep the gap between the substrates 1 and 2 constant, and can enhance the self-holding property of the liquid crystal display element itself. In particular, when the dot-shaped polymer structures 10 are arranged at regular intervals, the display performance can be easily made uniform. The height of the polymer structure 10 corresponds to the thickness of the cell gap, that is, the thickness of the liquid crystal layer 11 made of the liquid crystal composition. It is particularly effective to provide the polymer structure 10 when a flexible resin substrate is used as the substrates 1 and 2 sandwiching the liquid crystal layer 11.

  The polymer structure 10 is formed by using a photocurable resin material such as a photoresist material made of an ultraviolet curable monomer, with a desired thickness on the outermost surface films (insulating thin film 5, A so-called photolithography method can be used in which an alignment film 7) is applied, and pattern exposure is performed by irradiating the film with ultraviolet rays through a mask to remove uncured portions.

Alternatively, the polymer structure 10 made of a thermoplastic resin may be formed using a resin material obtained by dissolving a thermoplastic resin in an appropriate solvent. In this case, the resin material is applied onto the substrate from the tip of the nozzle, such as a printing method in which printing is performed on the substrate by extruding the thermoplastic resin material with a squeegee using a screen plate or a metal mask, or a dispenser method or an inkjet method. The polymer structure 10 can be disposed by a method of forming by discharging, or a transfer method in which a resin material is supplied onto a flat plate or a roller and then transferred to the surfaces of the substrates 1 and 2.
(Scattering layer)
A scattering layer (not shown) may be provided on the surface (upper surface in the figure) of the substrate 1 and / or between the substrate 2 and the visible light absorbing layer 9. By providing the scattering layer, the degree of scattering during white display increases, and the white background is improved. Examples of the scattering layer include product name FT-014 (manufactured by Polatechno).
(Cell gap)
As the thickness of the cell gap in the liquid crystal display element, that is, the thickness of the liquid crystal layer 11 made of the liquid crystal composition is increased, the reflectance during white display increases, but the reflectance during drive voltage and black display also increases. Therefore, in the present invention, the thickness of the cell gap is preferably 2 to 50 μm, more preferably 3 to 15 μm. By setting it as such a preferable range, it is because the effect of this invention that a high contrast can be achieved even with a comparatively low applied voltage can be acquired more effectively.
(Production method)
A method for producing a liquid crystal display device according to a preferred embodiment of the present invention is a method in which a cholesteric liquid crystal containing a gelling agent is vacuum-injected into a liquid crystal empty cell in a heated state. Also good.

  When enclosing the liquid crystal composition, the following method may be employed.

The heated liquid crystal composition is vacuum-injected into the empty cell of the liquid crystal display element, and then the injection hole is closed. The liquid crystal composition is thermoreversible. An empty cell of a liquid crystal display element heats and / or pressurizes two substrates 1 and 2 on which the predetermined constituent members of the liquid crystal display element are formed so that their member formation surfaces face each other. Can be produced. Since the liquid crystal composition increases fluidity by heating, the injection between the substrates 1 and 2 and the formation of the liquid crystal layer 11 can be easily performed in a short time.
(Display method)
In the liquid crystal display element having the above-described configuration, display is performed by applying a pulse voltage from the drive circuit 20 to the transparent electrodes 3 and 4. For example, a PL-FC driving system that performs display by switching the liquid crystal layer 11 between a planar state and a focal conic state may be employed, or the liquid crystal layer 11 may be switched between a planar state and a homeotropic state. You may employ | adopt the PL-Home drive system which displays by switching.

  For example, in the PL-FC driving method, by applying a pulse voltage of relatively high energy, the liquid crystal becomes a planar state, and selectively reflects light having a wavelength determined based on the helical pitch and refractive index of the liquid crystal molecules. . On the other hand, by applying a pulse voltage with relatively low energy, the liquid crystal is in a focal conic state and is in a transparent state. Several drive waveforms have been proposed, for example, a drive waveform that changes the liquid crystal to the focal conic state by applying a relatively low voltage for a long time and then changes to a planar state only in a desired part, a state in which a high voltage is applied After the liquid crystal is reset to the planar state by suddenly turning off the voltage from the drive waveform, the drive waveform that changes only the desired part to the focal conic state, applying the reset pulse to bring the liquid crystal to the homeotropic state, and finally getting it A driving waveform composed of three stages to which a selection pulse having a magnitude corresponding to the display state to be applied is applied and a pulse for establishing the last selected state can be employed. In these drive systems, the display can be maintained even after the voltage application is stopped by utilizing the memory property of the liquid crystal display element. When the visible light absorption layer 9 is provided, black is displayed in the focal conic state.

  Further, for example, in the PL-Home drive system, a planar state is realized by rapidly turning off the voltage from a state where a high voltage is applied, while the liquid crystal is kept in a homeotropic state by continuing to apply a high voltage. The transparency in the homeotropic state is higher than that in the focal conic state, which is advantageous for improving the contrast (the visible light absorbing layer 9 is also black in the homeotropic state), but the voltage is required to maintain the display. Need to continue to be applied.

Examples of the present invention will be described below, but the present invention is not limited by the following examples.
1. Preparation of Sample As shown below, a nematic liquid crystal, a chiral material, and a gelling agent were mixed to prepare a liquid crystal composition. The ratio of the nematic liquid crystal to the chiral material is such that a selective reflection peak is shown at a wavelength of 600 nm.
(1) Preparation of liquid crystal compositions A and B 79 parts by weight of nematic liquid crystal (BL035; manufactured by Merck & Co., Inc.), 18 parts by weight of a chiral material represented by the following formula (29), and 3 gelling agents shown in Table 1 Mass parts were mixed to prepare chiral nematic liquid crystal compositions A and B.

  The gelling agent added to the liquid crystal composition B for comparison has the following structure.

(2) Preparation of liquid crystal compositions C to K Nematic liquid crystal (BL006; manufactured by Merck & Co., Inc.) 84 parts by mass, a chiral material represented by the following formula (31) and a chiral material represented by the following formula (32): Chiral nematic liquid crystal compositions C to K were prepared using 15 parts by mass of one mixture and the gelling agent shown in Table 1. At this time, the addition amount of the gelling agent was 1 part by mass for liquid crystal compositions C, E, G, H and I, 0.7 part by mass for liquid crystal composition D, and 1.5 parts for liquid crystal composition F. About 1 part by mass, the liquid crystal compositions J and K for comparison and the comparative liquid crystal were used. As the gelling agent for I, m average value = about 7 and n average value = about 6 were used.

  Note that the gelling agents added to the liquid crystal compositions J and K for comparison are shown in the formulas (33) and (34).

(3) Production of liquid crystal display elements (production of Examples 1 to 8 and Comparative Examples 1 to 3)
An empty cell was prepared by the following procedure. First, a soluble polyimide alignment film AL2022 (manufactured by JSR) was formed by printing on a 0.7 mm thick glass substrate on which an ITO electrode was formed. Next, a spacer (Micropearl, manufactured by Sekisui Fine Chemical Co., Ltd.) is sandwiched between the substrates facing each other and adjusted to 5.5 μm, and sealing materials (Sumilite ERS-2400 (main agent) and ERS-2840 (curing agent), Sumitomo) Bakelite Co., Ltd.) was used to seal a portion other than the liquid crystal injection part and the air discharge part to produce an empty cell. This empty cell was prepared for the liquid crystal composition.

Next, the liquid crystal composition was filled in the empty cell by the following procedure to produce a liquid crystal display element. A predetermined amount of the liquid crystal composition brought into an isotropic phase state by heat treatment was injected into the empty cell by utilizing capillary action. After the injection, it was cooled and the opening was sealed using Photorec (manufactured by Sekisui Fine Chemical Co., Ltd.). Further, a black light absorber was provided on the substrate disposed on the side opposite to the incident light side to produce a liquid crystal display element having the structure shown in FIG. As shown in Table 1, the produced liquid crystal display elements were designated as Examples 1 to 8 and Comparative Examples 1 to 3.
2. Evaluation Method (1) Contrast Evaluation A VY curve was obtained by applying the pulse shown in FIG. 2 to the display element (in this drive waveform, the liquid crystal was once reset to the planar state by the preceding pulse).

Specifically, the spectral distribution curve (wavelength-reflectance curve) and Y value (Y) of the element at the described measurement points while changing the voltage (V) of the section (X) in the pulse of FIG. 2 from ± 20 to ± 50 V. ) Was repeatedly measured with a spectrocolorimeter (CM3700d; manufactured by Konica Minolta Sensing) to create a V (absolute value of voltage) -Y (Y value) curve. The measurement was performed at 25 ° C. FIG. 3 shows an example of the VY curve. In the VY curve, the state showing the maximum Y value (Ymax) is the planar state (PL: white display state), and the state showing the minimum Y value (Ymin) is the focal conic state (FC: black display state). Expressed in terms of Y value (PL) and Y value (FC). The contrast is expressed by Y value (PL) / Y value (FC).
(2) Evaluation of white background property Further, the spectral distribution curve of the display element in the planar state (white display state) at 25 ° C. is measured using the above spectrocolorimeter, and the chromaticity of the CIE1931 color system is determined from the spectral distribution curve. The coordinates (x, y) were obtained, and the distance (d) from the standard light D65 (x = 0.3127, y = 0.3290) was calculated from the following equation.

This distance (d) was evaluated as follows. A sample having d of 0.04 or less was regarded as acceptable. The distance (d) is one parameter representing whiteness, and the smaller the distance (d) is, the whiter the color is.
<Evaluation details>
d ≦ 0.04: Can be judged as almost white regardless of the light source 0.04 <d <0.05; Some light sources may not be judged as white d ≧ 0.05; May appear yellow or green In addition, the cell display portion in the white display state was visually observed and evaluated.

  The results are as shown in Table 1.

  As shown in Table 1, Examples 1 to 8, which are liquid crystal display elements, all had good contrast and white background. On the other hand, in Comparative Examples 1 to 3, the contrast and white background were inferior to those of the Examples.

It is a schematic sectional drawing of an example of the liquid crystal display element which is embodiment of this invention. It is a figure which shows the example of the drive waveform used in the Example. It is a figure which shows an example of the VY curve created in the Example. It is a schematic sectional drawing of the liquid crystal display element used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Substrate 3, 4 Transparent electrode 5 Insulating thin film 7 Alignment film 9 Visible light absorption layer 10 Polymer structure 11 Liquid crystal layer (liquid crystal composition)
12 Sealing material 13 Spacer 20 Drive circuit

Claims (9)

In a liquid crystal composition containing a self-organizing type gelling agent and a liquid crystal exhibiting a cholesteric phase at room temperature,
The liquid crystal composition, wherein the gelling agent comprises a compound containing a siloxane skeleton in the molecule. The liquid crystal composition according to claim 1, wherein the compound has a structure represented by the following general formula (1).

(Wherein R ₁ and R ₂ independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group optionally substituted with a substituent. At least _one of L ₁ , L ₂ and L _{3 represents} One is a group having a divalent amide bond part capable of forming a hydrogen bond between molecules, and the other is independently substituted with a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms or a substituent. I is an integer of 0 to 30, but when L ₂ or L ₃ is not a group having an amide bond capable of intermolecular hydrogen bonding, it is a natural number of 30 or less, j Is an integer from 0 to 30, but when i is 0, it is a natural number of 30 or less, i and j represent the ratio of the partial structures in the molecule, and the arrangement of these partial structures is irregular May be.) The group having a divalent amide bond portion capable of forming a hydrogen bond between molecules has a structure represented by the following general formula (2) or (3): The liquid crystal composition described.

(In the formula, Re ₁ is an alkylene group having 1 to 20 carbon atoms, A ₁ and A ₂ are each independently —O—, —NH— or a single bond, and R ₃ is 1 to 20 carbon atoms. Alkyl groups, benzyl groups optionally substituted with substituents, monocyclic or bicyclic heterocyclic groups optionally substituted with substituents, — (CH ₂ ) _a —COO—R ₄ , — (CH _{2) a -OCO-R 4,} - (CH 2) a -CONH-R 4, - (CH 2) a -NHCO-R 4, - (CH 2) a -NHCONH-R 4, - (CH 2) _a —NHCOO—R ₄ , — (CH ₂ ) _a —OCONH—R ₄ , or — (CH ₂ ) _a —S—R ₄ (where a is a natural number of 5 or less, and R ₄ is carbon number 1) To 20 alkyl groups), n is a natural number of 5 or less.) The liquid crystal composition according to claim 1, wherein the gelling agent comprises a compound represented by the following general formula (4).

(Wherein Re ₁ and Re ₂ are each independently an alkylene group having 1 to 20 carbon atoms, A ₁ and A ₂ are each independently any of —O—, —NH— and a single bond, G ₁ , G ₂ Is a structure represented by the following general formula (5) or (6).)

(Wherein R ₅ , R ₆ , R ₇ and R ₈ independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a phenyl group which may be substituted with a substituent, and i and j are 0 30) Although i and j are not 0 at the same time, i and j represent the ratio of the partial structures in the molecule, and the arrangement of these partial structures may be irregular.) The content of the gelling agent is 0.5% by mass or more and 4.0% by mass or less based on a total amount of the liquid crystal exhibiting a cholesteric phase at the room temperature and the gelling agent. 5. The liquid crystal composition according to any one of items 4 to 4. 6. The liquid crystal composition according to claim 1, wherein the liquid crystal exhibiting a cholesteric phase at room temperature contains a nematic liquid crystal and a chiral agent. The liquid crystal composition according to claim 1, wherein a peak wavelength of selective reflection of the liquid crystal composition is 500 to 700 nm. A liquid crystal display element comprising a liquid crystal layer made of the liquid crystal composition according to claim 1 on a substrate. The liquid crystal display element according to claim 8, wherein an electrode is provided on at least one of the pair of substrates.

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