WO2019026775A1 - Liquid crystal composition, liquid crystal display device and method for producing liquid crystal display device - Google Patents

Abstract

The present invention uses a liquid crystal composition which contains a liquid crystal material and a self-cleavable radically polymerizable monomer that is represented by chemical formula (1). (In chemical formula (1), R1 represents a linear, branched or cyclic alkyl group having 1-8 carbon atoms or an alkenyl group; each of Z1 and Z2 independently represents -O-, -S-, -NH-, -CO-, -COO-, -OCO- or a direct bond; each of Sp1 and Sp2 represents a linear, branched or cyclic alkylene group having 1-8 carbon atoms, an alkenylene group or a direct bond; and each of P1 and P2 independently represents a (meth)acryloyloxy group or a (meth)acryloylamino group.)

Description

Liquid crystal composition, liquid crystal display device, and method of manufacturing liquid crystal display device

The technology disclosed by the present specification relates to a liquid crystal composition, a liquid crystal display device, and a method of manufacturing the liquid crystal display device.

The liquid crystal display device includes a liquid crystal panel as a display unit for displaying information such as an image, and the liquid crystal panel is roughly configured such that a liquid crystal layer is sealed between a pair of glass substrates. The substrate is provided with an electrode for applying a voltage to the liquid crystal layer, and by controlling the applied voltage, the orientation of the liquid crystal material in the liquid crystal composition constituting the liquid crystal layer is changed, and light passing through the liquid crystal layer Is adjusted, and an image is displayed on the display unit.

As a liquid crystal material, nematic liquid crystal, which is an elongated organic molecule, is usually used. The nematic liquid crystal is a positive type liquid crystal whose dielectric constant is large in the major axis direction and small in the direction perpendicular to the major axis (having positive dielectric anisotropy) due to dielectric anisotropy, and is small in the major axis direction The liquid crystal is classified into large (negative dielectric anisotropy) negative liquid crystals in the direction perpendicular to.

As a main liquid crystal alignment mode in a liquid crystal panel, twisted nematic (TN: Twisted Nematic) mode, positive liquid crystal in which positive liquid crystal is aligned so as to twist in the thickness direction of the liquid crystal layer without applying voltage. In-plane switching (IPS: In-Plane Switching) mode in which the liquid crystal is horizontally aligned and rotated in the horizontal direction with respect to the substrate surface, vertical alignment (VA: Vertical Alignment in which a negative liquid crystal is vertically aligned with respect to the substrate surface and switched by a vertical electric field ) Mode etc.

With the demand for higher definition and larger display screen, development of IPS mode and VA mode capable of obtaining relatively high contrast and wide viewing angle has been promoted. Above all, in the multi-domain vertical alignment (MVA) mode in which the alignment of the liquid crystal is changed for each section of the screen by providing an alignment control structure on a transparent electrode, etc., a wider viewing angle can be obtained. It is known to be. Then, as a technique for reducing the delay in response speed of the liquid crystal while reducing the structure for alignment control in order to suppress the decrease in aperture ratio and light leakage in the MVA mode, a polymerizable component such as a monomer is mixed in the liquid crystal composition. A PSA technology has been proposed in which a liquid crystal is maintained between a substrate and then polymerized to form a polymer sustained alignment (PSA) layer to provide a pretilt angle (pretilt angle) to a liquid crystal (Patent Document 1 below) .

By the way, conventionally, an alignment film made of polyimide (PI) or the like is applied and formed on the most liquid crystal layer side of each substrate, and in the state where no voltage is applied, a liquid crystal material depends on the memory property of this alignment film. Is generally oriented. However, the formation of the alignment film not only requires many steps but also causes problems such as uneven coating and generation of dust due to rubbing treatment. Therefore, a technology for making an alignment developing functional group derived from the surface of a polymer layer selectively formed at the interface between a liquid crystal layer and a substrate, orienting a liquid crystal material with this polymer layer, and eliminating the need for a conventional alignment film (Hereinafter, referred to as “conventional alignment film-less liquid crystal alignment technology”) has been proposed (Patent Document 2 below).

International Publication No. 2012-121319 JP, 2006-58755, A

(Problems to be solved by the invention)
In the above-described PSA technology or conventional alignment film-less liquid crystal alignment technology, after the liquid crystal composition is enclosed between the substrates, the polymerizing component mixed in the liquid crystal composition is polymerized to form a polymer layer. There is a need.
In Patent Document 2, a self-cleavage type photopolymerization initiator is added to a liquid crystal composition in order to advance a polymerization reaction within a certain processing time (tact time) to form a polymer layer. However, when the photopolymerization initiator is cleaved, a compound which is likely to be charged is generated and remains in the liquid crystal layer, so that the liquid crystal alignment state at the time of voltage application can not be made constant, and the display quality declines and burn-in occurs. Could lead to

In Patent Document 1, a self-cleavage type photopolymerization initiator is used as a polymer layer-forming material, whereby the initiator component is separated from the liquid crystal layer as the polymer layer is formed, and the compound in the liquid crystal layer is formed. The survival is reduced. Here, an acetophenone-based monomer having a structure in which two alkoxy groups are adjacent to a ketyl group is used as a radically polymerizable monomer for forming a self-cleavage type photopolymerization initiator / polymer layer (self-cleavage type radical copolymerizable monomer) ing. However, as shown in FIG. 7, such an acetophenone-based monomer may generate a radical having no polymerizable group by self-cleavage, which may remain in the liquid crystal layer and cause a reduction in display quality. (In FIG. 7, R ⁵ and R ⁶ each independently represent a linear or branched alkyl or alkenyl group having 1 to 4 carbon atoms. “·” Represents an unpaired electron Represents In addition, since the solubility in a negative liquid crystal material is not necessarily good, distribution unevenness of the polymer layer may occur, resulting in a portion where the liquid crystal can not be sufficiently aligned, which may cause deterioration in display quality.

The present technology has been completed based on the above circumstances, and can be used for PSA technology and conventional alignment film-less liquid crystal alignment technology, and provides a liquid crystal composition capable of expressing excellent display quality. The purpose is The present technology also provides a liquid crystal display device using the above liquid crystal composition and a method of manufacturing the same.

(Means to solve the problem)
The liquid crystal composition according to the present technology is a liquid crystal composition including a liquid crystal material and a self-cleavage type radically polymerizable monomer represented by the following chemical formula (1).

In the above chemical formula (1), R ¹ represents a linear, branched or cyclic alkyl group or alkenyl group having 1 to 8 carbon atoms. Z ¹ and Z ² independently of each other represent —O—, —S—, —NH—, —CO—, —COO—, —OCO— or a direct bond. Sp ¹ and Sp ^{2 each} represent a linear, branched or cyclic, alkylene or alkenylene group having 1 to 8 carbon atoms, or a direct bond. P ¹ and P ² independently of one another represent a (meth) acryloyloxy group or a (meth) acryloylamino group.
In the present specification, the (meth) acryloyloxy group represents an acryloyloxy group or a methacryloyloxy group, and the (meth) acryloylamino group represents an acryloylamino group or a methacryloylamino group.

According to the above configuration, when the liquid crystal composition is irradiated with light, the self-cleavage type radically polymerizable monomer represented by the chemical formula (1) is self-cleaved as shown in FIG. , “·” In FIG. 1 represents an unpaired electron (radical)). A polymerization reaction proceeds by these radicals, and an alignment control layer made of a polymer is formed at the interface between the liquid crystal layer and the other member. Thereby, a polymerization process can be performed without adding a polymerization initiator separately. In addition, since the light irradiation time can be shortened, material deterioration due to light irradiation is also suppressed. Here, in the benzoin type self-cleavage type radically polymerizable monomer of the above-mentioned structure, as shown in FIG. 1, since both of the two generated radicals have a polymerizable group, all radicals generated by cleavage are polymerized. It can be incorporated into the orientation control layer. Accordingly, radicals are less likely to remain in the liquid crystal layer, and a reduction in voltage holding ratio and display quality due to impurities in the liquid crystal layer is suppressed. As a result, by applying the liquid crystal composition according to the present technology to PSA technology or conventional alignment filmless liquid crystal alignment technology, it is possible to obtain a liquid crystal display device capable of expressing excellent display quality.

The liquid crystal material contained in the liquid crystal composition according to the present technology may be one having a negative dielectric anisotropy (Δε), that is, a negative liquid crystal, and a functional group represented by the following chemical formula (2) It can be set as the negative type liquid crystal which it has. In Chemical Formula (2), X ¹ and X ² can both be fluorine.

In the above chemical formula (2), X ¹ and X ² independently represent a halogen group. R ² represents a saturated alkyl group having 1 to 6 carbon atoms. "*" Represents a bond.

The liquid crystal composition according to the present technology preferably further includes a radical polymerizable monomer represented by the following chemical formula (3).

In the above chemical formula (3), R ³ represents a —R ⁴ —Sp ³ —P ³ group, a hydrogen atom, a halogen atom, a —CN group, an —NO ₂ group, or a linear or 1 to 18 carbon atoms It is a branched alkyl group. P ³ represents a (meth) acryloyloxy group, or a (meth) acryloyl amino group. Sp ³ represents a linear, branched or cyclic, alkylene or alkyleneoxy group having 1 to 6 carbon atoms, or a direct bond. The hydrogen atom which R ³ has may be substituted by a fluorine atom or a chlorine atom. R ⁴ represents —O— group, —S— group, —NH— group, —CO— group, —COO— group, —OCO— group, or a direct bond. A ¹ and A ² are the same or different and each represents a 1,4-phenylene group, a naphthalene-2,6-diyl group, a phenanthrene-2,7-diyl group, or an anthracene-2,6-diyl group. One or more hydrogen atoms possessed by A ¹ and A ² are a fluorine atom, a chlorine atom, a —CN group, or an alkyl group having 1 to 6 carbon atoms, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group or an alkyl group It may be substituted by a carbonyloxy group. Z ² is, -O- group, an -S- group, -NH- group, -CO- group, -COO- group, -OCO- group, or a direct bond. N in the chemical formula (3) is 0, 1 or 2.

Alternatively, the liquid crystal composition according to the present technology preferably further includes a radically polymerizable monomer represented by any one of the following chemical formulas (4-1) to (4-5).

In the chemical formulas (4-1) to (4-5), n represents an integer of 8 to 20, and m represents an integer of 1 to 6, respectively.

In the liquid crystal display device according to the present technology, a liquid crystal layer sandwiched between a pair of substrates and the pair of substrates, containing a liquid crystal material, and the liquid crystal layer is in contact with the substrate. And an alignment control layer for controlling the alignment at a predetermined angle, the alignment control layer being formed of a polymer formed by polymerizing a polymerizable monomer added to the liquid crystal composition forming the liquid crystal layer. And at least one of the polymerizable monomers is a self-cleavage type radically polymerizable monomer represented by the following chemical formula (1).

The liquid crystal display device as described above comprises an arranging step of arranging a liquid crystal composition containing a liquid crystal material and a polymerizable monomer between a pair of substrates arranged such that the plate surfaces face each other, and after the arranging step. Alignment control of polymerizing the polymerizable monomer in the liquid crystal composition, liquid crystal layer containing the liquid crystal material, and alignment control of the liquid crystal material in contact with the liquid crystal layer at a predetermined angle with respect to the substrate And a polymerization step of forming a layer between the pair of substrates, wherein the alignment control layer is formed of a polymer formed by polymerizing the polymerizable monomer. Thus, at least one of the polymerizable monomers can be manufactured by the method of manufacturing a liquid crystal display device which is a self-cleavage type radically polymerizable monomer represented by the following chemical formula (1).

(Effect of the invention)
According to the present technology, a liquid crystal display device excellent in display quality can be manufactured.

An explanatory view showing a mechanism in which a benzoin type self-cleavage type radically polymerizable monomer represented by the chemical formula (1) is cleaved by ultraviolet irradiation A schematic view showing a cross-sectional configuration before the polymerization step of the liquid crystal cell included in the liquid crystal display device according to Embodiment 1. FIG. 2 is a schematic view showing a cross-sectional configuration of the liquid crystal cell of FIG. 2 after a polymerization step. The schematic diagram which shows the cross-sectional structure before the superposition | polymerization process of the liquid crystal cell contained in the liquid crystal display device which concerns on Embodiment 2. The liquid crystal cell of FIG. 4 is a schematic diagram which shows the cross-sectional structure after the superposition | polymerization process. Top view of vacuum injection cell used for evaluation of liquid crystal solubility Explanatory drawing showing the mechanism by which conventional acetophenone type self-cleavage type monomers are cleaved by ultraviolet irradiation

<Embodiment 1: Liquid Crystal Display Device without Conventional Alignment Film>
Embodiment 1 will be described with reference to FIGS. 2 and 3. In the present embodiment, a conventional alignment film-less liquid crystal display device which does not have a so-called conventional alignment film is illustrated. In the present specification, the conventional alignment film refers to an alignment film formed by applying a resin composition made of polyimide or the like on a substrate.

[Liquid crystal display device]
The liquid crystal display device according to the present embodiment can be used for a television receiver, a personal computer, a tablet terminal, a display or a monitor of a mobile phone, and the like.
The liquid crystal display device includes a panel-like liquid crystal cell (liquid crystal panel) 1. The liquid crystal display device may be of any type such as transmissive type or reflective type. In the case of the transmissive type, the liquid crystal display device is disposed on the back side of the liquid crystal cell 1 (the array substrate side described later) It further comprises a backlight device (not shown) for supplying. In the case of the reflection type, the liquid crystal cell 1 further includes a reflector disposed on the back side of the liquid crystal cell 1 to reflect outward toward the liquid crystal cell 1. Further, in the liquid crystal cell 1, a polarizing plate, a phase plate, and the like (not shown) are stacked.

[Liquid crystal cell]
As the liquid crystal cell 1, one having a known configuration that does not have a conventional alignment film can be used. As shown in FIGS. 2 and 3, the liquid crystal cell 1 is interposed between a pair of substrates 11a and 11b arranged in a state where the plate surfaces face each other, and both substrates 11a and 11b, and along with voltage application. And a liquid crystal layer 30 containing liquid crystal molecules, which is a substance whose optical characteristics change.
Each of the substrates 11a and 11b is provided with a glass substrate excellent in light transmitting property and made of non-alkali glass, quartz glass or the like, and a plurality of films are laminated on each glass substrate by a known photolithography method or the like. Become.

(Pixel electrode substrate)
One substrate 11 b of the pair of substrates 11 a and 11 b is a pixel electrode substrate (array substrate, active matrix substrate, element substrate) 11 b. Although not shown in detail, the pixel electrode substrate 11b is provided with switching elements (for example, TFTs) connected to source wiring and gate wiring which are orthogonal to each other, and pixel electrodes and the like connected to the switching elements. For example, a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) is used as the pixel electrode. In the pixel electrode substrate 11b, asperities (structures for controlling alignment) or the like formed of fine linear protrusions (bank-like structures) or slits (groove-like structures) may be formed.

(Opposite substrate)
The other substrate 11a of the pair of substrates 11a and 11b is an opposing substrate 11a, and in the present embodiment, an opposing electrode (common electrode) is formed on the opposing substrate 11a. Similar to the pixel electrode, a transparent conductive material such as ITO or IZO is used as the counter electrode. Although details are not illustrated, in addition to the counter electrode (common electrode) etc., each colored portion such as R (red), G (green), B (blue), etc. has a predetermined array on the counter substrate 11a according to this embodiment. The color filter disposed in the above is provided to be a color filter substrate (CF substrate). Further, also on the counter substrate 11a, it is possible to form asperities (structures for alignment control) or the like formed of linear protrusions and slits, as necessary. The counter substrate 11a does not necessarily have a color filter, and the liquid crystal display device does not have a color filter even if it has a color filter on array structure in which the color filter is provided on the pixel electrode substrate 11b. It may be a display. Further, the two types of electrodes for applying a voltage to the liquid crystal layer do not necessarily have to be formed on different substrates, and for example, the common electrode may be formed on the pixel electrode substrate 11 b.

(Seal agent)
A sealing agent (not shown) is disposed between the two substrates 11 a and 11 b so as to surround and seal the liquid crystal layer 30 while maintaining the cell gap for the thickness of the liquid crystal layer 30. Both substrates 11a and 11b are bonded together by this sealing agent.
As the sealing agent, known ones can be used, and for example, thermosetting type, ultraviolet ray curing type, and ultraviolet and heat combined use type made of epoxy resin or acrylic resin can be preferably used.

(Liquid crystal layer)
The liquid crystal layer 30 includes a liquid crystal material described later. The liquid crystal molecules in the liquid crystal material have a property of being oriented in a specific direction, and the orientation is controlled by applying a voltage equal to or higher than a threshold. In the liquid crystal layer 30, the liquid crystal alignment mode in the state of no voltage application is appropriately selected from known modes. For example, the TN mode, the IPS mode, the VA mode, etc. described above can be used.

(Alignment control layer)
As shown in FIG. 3, in the present embodiment, alignment control layers 21 a and 21 b are formed on both sides of the pixel electrode substrate 11 b of the liquid crystal layer 30 and the counter substrate 11 a.
In the alignment control layers 21a and 21b, the polymerizable monomer 20 (see FIG. 2) containing a self-cleavage type radically polymerizable monomer and a radically polymerizable monomer contained in a liquid crystal composition described later is polymerized to form the liquid crystal layer 30 and both layers. It is a polymer layer selectively formed at the interface with the substrates 11a and 11b. Here, “the interface between the liquid crystal layer 30 and the both substrates 11a and 11b” means the structure disposed closest to the liquid crystal layer 30 among the structures formed on the two substrates 11a and 11b, the liquid crystal layer 30, and The alignment control layers 21 a and 21 b are formed to be in direct contact with the liquid crystal layer 30.
In the present embodiment, a conventional alignment film made of polyimide or the like is not formed on either of the substrates 11a and 11b, and the liquid crystal alignment mode in the liquid crystal layer 30 in the state of no voltage application is the alignment control layer or It is defined by an alignment control structure or the like.

[Liquid crystal composition]
The liquid crystal composition according to the present technology at least includes a liquid crystal material and a self-cleavage type radically polymerizable monomer.

(Liquid crystal material)
Known liquid crystal materials can be used. For example, nematic liquid crystal, smectic liquid crystal, etc. can be used, but use of nematic liquid crystal is preferable. The liquid crystal material can be selected to have a desired dielectric anisotropy (Δε) in addition to the liquid crystal alignment mode and the like.
Examples of (positive) nematic liquid crystals having positive dielectric anisotropy include biphenyl liquid crystals, phenylcyclohexane liquid crystals, ester liquid crystals, terphenyl liquid crystals, biphenylcyclohexane liquid crystals, pyrimidine liquid crystals, and dioxane liquid crystals. And bicyclooctane liquid crystals, cubane liquid crystals and the like can be used.
Examples of (negative) nematic liquid crystals having negative dielectric anisotropy include (di) fluorinated liquid crystals, dicyanobenzene liquid crystals, pyridazine liquid crystals, Schiff base liquid crystals, azoxy liquid crystals, biphenyl liquid crystals, phenylcyclohexane Liquid crystal and the like can be mentioned.
A chiral agent, a ferroelectric liquid crystal, etc. may be further added to these liquid crystals.

The benzoin type self-cleavage type radical polymerizable monomer described later can be suitably used regardless of whether the liquid crystal material contained in the liquid crystal composition is a positive type liquid crystal or a negative type liquid crystal. It is useful for a liquid crystal composition containing a negative liquid crystal.
In the present technology, examples of the negative liquid crystal that is suitably used as a liquid crystal material include those having a functional group represented by the following chemical formula (2).

In the above chemical formula (2), X ¹ and X ² independently represent a halogen group. R ² represents a saturated alkyl group having 1 to 6 carbon atoms. "*" Represents a bond.

The negative liquid crystal having the functional group represented by the chemical formula (2) has high proton acceptability of the portion. The benzoin type self-cleavage type radically polymerizable monomer described later has a relatively low proton acceptability due to one alkoxy group adjacent to the ketyl group as represented by the chemical formula (1), and is proton acceptable. Repulsion with high negative type liquid crystal is small. Therefore, it is possible to be well dispersed in the liquid crystal composition containing the same, and form homogeneous alignment control layers 21a and 21b by the polymerization reaction.

In the present technology, among the negative liquid crystals having a functional group represented by the chemical formula (2), a difluorinated liquid crystal in which both X ¹ and X ² in the chemical formula (2) are fluorine is particularly suitably used it can. Specifically, it is preferable to use a difluorinated liquid crystal having a structure as shown in the following chemical formulas (2-1) to (2-5).

N and m in the chemical formulas (2-1) to (2-5) each independently represent an integer of 1 to 6.

(Self-cleavage type radically polymerizable monomer)
The self-cleavage type radically polymerizable monomer according to the present technology (hereinafter, the self-cleavage type radically polymerizable monomer may be referred to as a first monomer) is represented by the following chemical formula (1).

In the above chemical formula (1), R ¹ represents a linear, branched or cyclic alkyl group or alkenyl group having 1 to 8 carbon atoms. Z ¹ and Z ² independently of each other represent —O—, —S—, —NH—, —CO—, —COO—, —OCO— or a direct bond. Sp ¹ and Sp ^{2 each} represent a linear, branched or cyclic, alkylene or alkenylene group having 1 to 8 carbon atoms, or a direct bond. P ¹ and P ² independently of one another represent a (meth) acryloyloxy group or a (meth) acryloylamino group.

When the liquid crystal composition is irradiated with light, the self-cleavage type radically polymerizable monomer represented by the chemical formula (1) self-cleaves to generate two radicals as shown in FIG. A polymerization reaction proceeds by these radicals, and an alignment control layer made of a polymer is formed at the interface between the liquid crystal layer and the other member. Thereby, a polymerization process can be performed without adding a polymerization initiator separately. In addition, since the light irradiation time can be shortened, material deterioration due to light irradiation is also suppressed. Here, in the benzoin self-cleavage type radically polymerizable monomer of the above-mentioned structure, as shown in FIG. 1, both of the two generated radicals have a polymerizable group. Therefore, all of the radicals generated by cleavage can be polymerized and taken into the orientation control layer. Therefore, radicals are less likely to remain in the liquid crystal layer, and a decrease in voltage holding ratio and a decrease in display quality due to impurities in the liquid crystal layer are suppressed. As a result, by applying the liquid crystal composition according to the present technology to PSA technology or conventional alignment filmless liquid crystal alignment technology, it is possible to obtain a liquid crystal display device capable of expressing excellent display quality.

In the chemical formula (1), P ¹ and P ² are polymerizable groups, and at least one of them is preferably a (meth) acryloyloxy group. When it is a (meth) acryloyloxy group, the solubility in a negative liquid crystal material can be kept high (0.5% by weight or more).
Alternatively, at least one of the P ¹ and P ² polymerizable groups is preferably a (meth) acryloylamino group. When it is a (meth) acryloylamino group, adsorption of water molecules and the like easily occurs, and the moisture resistance is improved.

In the chemical formula (1), Sp ¹ and Sp ² are spacer groups, and the solubility in the negative liquid crystal material increases (the solubility increases) as the number of carbon atoms constituting the spacer group increases. However, on the other hand, as the number of carbon atoms increases, the amount of change in tilt angle (Δtilt) due to voltage application increases, and there is a concern that burn-in may be noticeable. In view of these balances, Sp ¹ and Sp ² most preferably have 0 carbon atoms, that is, a direct bond.
Also preferably, Z ¹ and Z ² are direct bonds.

In the chemical formula (1), R ¹ is preferably an alkyl group. As the number of carbon atoms constituting R ¹ increases, the solubility in the negative liquid crystal material increases. However, on the other hand, like the spacer group, there is a concern that the amount of change in tilt angle may deteriorate with the increase of the number of carbon atoms, and burn-in may occur. In consideration of these balances, the carbon number is most preferably 1, that is, a methyl group.

From the above, in the chemical formula (1), P ¹ and P ² are each independently an acrylate group or a methacrylate group, Sp ¹ and Sp ² and Z ¹ and Z ² are direct bonds, and R ¹ is a methyl group It is most preferable that In this case, the solubility in the negative liquid crystal material is high, and the molecular rigidity is also high. For example, it is possible to further suppress the tilt angle change amount in energization in the vertical alignment (RTN, RECB) mode.

Specific examples of the self-cleavage type radically polymerizable monomer represented by the chemical formula (1) include those represented by the following chemical formulas (1A) to (1F). From the above, among the following, those represented by the chemical formula (1A) or (1B) are preferable.

(Radical polymerizable monomer)
In the liquid crystal composition according to the present embodiment, a radically polymerizable monomer having a structure different from that of the first monomer (self-cleavage type radically polymerizable monomer) (hereinafter, such a radically polymerizable monomer copolymerized with the first monomer) Is preferably further included as a second monomer).

According to the above configuration, the liquid crystal composition includes at least two types of polymerizable monomers, the first monomer and the second monomer. Thereby, the first monomer and the second monomer can be polymerized using the first monomer as an initiator to form the alignment control layers 21a and 21b made of a copolymer including at least two or more types of monomer units. It is known that when the orientation control layers 21a and 21b are formed of a copolymer containing two or more types of monomer units, both the change in pretilt angle and the generation of the residual DC voltage are suppressed, and the image sticking becomes difficult to occur. ing.

In the present embodiment in which the liquid crystal cell 1 is not provided with a conventional alignment film, the second monomer is copolymerized with the first monomer to form a copolymer having a side chain of an alignment exhibiting group It is preferable to use Here, the alignment property developing group is derived from the main chain of the copolymer forming the alignment control layers 21a and 21b so as to abut on the liquid crystal layer 30, and extends from the interface of both layers to the liquid crystal layer 30 side. It refers to a group having a function of orienting the liquid crystal material at a certain angle. The alignment developing group can be classified into a vertical alignment developing group, a horizontal alignment developing group, etc. according to the angle at which the liquid crystal material is aligned, and the alignment can be expressed by appropriately selecting the structure of the radical polymerizable monomer used as the second monomer. It is possible to change the structure of the polymer group and control the orientation angle of the liquid crystal.

As the second monomer, for example, those represented by any one of the following chemical formulas (4-1) to (4-5) can be used.

In the chemical formulas (4-1) to (4-5), n represents an integer of 8 to 20, and m represents an integer of 1 to 6, respectively.

According to such a configuration, the copolymer of the first monomer and the second monomer has relatively bulky side chains derived from the radical polymerizable monomers of chemical formulas (4-1) to (4-5). It becomes a thing. Although not shown, for example, in FIG. 3, these side chains extend from the interface between the alignment control layers 21a and 21b and the liquid crystal layer 30 toward the liquid crystal layer 30, and function as a vertical alignment exhibiting group. Therefore, even if the conventional alignment film is not provided as in the present embodiment, the liquid crystals in the liquid crystal layer 30 can be vertically aligned.

As described above, the liquid crystal display device according to the present embodiment does not include the conventional alignment film, and in the liquid crystal cell 1, the alignment control layers 21a and 21b having the alignment exhibiting group are in contact with the liquid crystal layer 30. The liquid crystal is oriented at a predetermined angle with respect to the substrates 11a and 11b in the state of no voltage application.

Such a liquid crystal display device has an arrangement step of arranging a liquid crystal composition containing a liquid crystal material and a polymerizable monomer 20 between a pair of substrates 11a and 11b, and polymerizability in the liquid crystal composition after the arrangement step. The two substrates are a liquid crystal layer 30 containing a liquid crystal material by polymerizing the monomer 20, and an alignment control layer 21a, 21b which abuts on the liquid crystal layer 30 to control the alignment of the liquid crystal material to a predetermined angle with respect to the substrates And a polymerization step formed between 11a and 11b. The orientation control layers 21a and 21b are made of a polymer formed by polymerizing the polymerizable monomer 20, and at least one of the polymerizable monomers 20 is a self-cleavage type radical polymerizable property represented by the chemical formula (1). It is a monomer. The polymerizable monomer 20 may contain other polymerizable monomers, and for example, radical polymerization having an orientation developing group as represented by the chemical formulas (4-1) to (4-5). Monomers can be used.

Second Embodiment Liquid Crystal Display Device Having Conventional Alignment Film
The second embodiment will be described with reference to FIGS. 4 and 5. In this embodiment, a liquid crystal display (display) having a panel-like liquid crystal cell 201 provided with a conventional alignment film will be exemplified. The same components as those of the first embodiment described above are denoted by the same reference numerals, and redundant description will be omitted.

(Alignment film)
In the liquid crystal cell 201 according to the second embodiment, as shown in FIG. 4, conventional alignment films 12a and 12b for aligning liquid crystal molecules contained in the liquid crystal layer are formed on the inner surface side of both substrates 11a and 11b. Each is formed. Although a known film can be used for the alignment film, it is preferable to use a polymer containing polyimide, polyamide, or polysiloxane from the viewpoint of thermal stability and film forming property.
Such a conventional alignment film does not necessarily have to be formed on both the substrates 11a and 11b, and may be formed on only one of them.

Depending on the purpose, various alignment films such as vertical alignment film, horizontal alignment film, and photo alignment film are appropriately selected for alignment films 12a and 12b, and alignment processes such as rubbing process and photo alignment process are appropriately performed and used. Be done.

In the case of performing the alignment process, it is preferable to use a photo alignment process. According to the photo-alignment process, generation of dust and breakage of the structure can be reduced as compared with the rubbing alignment process. In order to enable photo alignment processing, the alignment films 12 a and 12 b preferably have a photo alignment functional group. The photoalignable functional group is a functional group that changes in structure by reaction (for example, photoisomerization reaction) when receiving predetermined light (polarized ultraviolet light or the like). By introducing a photoalignable functional group into the side chain, it is possible to impart photoalignment to the alignment film while maintaining the structure of the main chain. The photoalignable functional group is preferably at least one selected from the group consisting of, for example, a cinnamate group, a chalconyl group, a coumarin group, an azobenzene group, etc., from the viewpoint of introduction of the functional group to the side chain and reactivity. .

(Radical polymerizable monomer)
The liquid crystal composition according to Embodiment 2 includes the liquid crystal material described above and the first monomer, which is the benzoin-based self-cleavage type radically polymerizable monomer represented by the chemical formula (1) described above, and the first monomer. It is preferable to further include a second monomer which is a polymerizable monomer having a structure different from.
In Embodiment 2, for example, a radically polymerizable monomer represented by the following chemical formula (3) can be preferably used as the second monomer.

In the above chemical formula (3), R ³ represents a —R ⁴ —Sp ³ —P ³ group, a hydrogen atom, a halogen atom, a —CN group, an —NO ₂ group, or a linear or 1 to 18 carbon atoms It is a branched alkyl group. P ³ is a polymerizable group, a (meth) acryloyloxy group, or a (meth) acryloyl amino group. Sp ³ is a spacer group and represents a linear, branched or cyclic, alkylene group or alkyleneoxy group having 1 to 6 carbon atoms, or a direct bond. The hydrogen atom which R ³ has may be substituted by a fluorine atom or a chlorine atom. R ⁴ represents —O— group, —S— group, —NH— group, —CO— group, —COO— group, —OCO— group, or a direct bond. A ¹ and A ² are the same or different and each represents a 1,4-phenylene group, a naphthalene-2,6-diyl group, a phenanthrene-2,7-diyl group, or an anthracene-2,6-diyl group. One or more hydrogen atoms possessed by A ¹ and A ² are a fluorine atom, a chlorine atom, a —CN group, or an alkyl group having 1 to 6 carbon atoms, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group or an alkyl group It may be substituted by a carbonyloxy group. Z ² is, -O- group, an -S- group, -NH- group, -CO- group, -COO- group, -OCO- group, or a direct bond. N in the chemical formula (3) is 0, 1 or 2.

According to the above configuration, the first monomer and the second monomer are polymerized using the first monomer which is a self-cleavage type radically polymerizable monomer as an initiator, and the orientation control layers 21a and 21b made of these copolymers are It can be formed on the mold alignment film 12a, 12b.

In the above chemical formula (3), R ³ is preferably a —R ⁴ —Sp ³ —P ³ group. P ³ is preferably a (meth) acryloyloxy group. Also, Z ² is preferably a direct bond. In this way, the solubility of the second monomer in the negative type liquid crystal can be kept high, and the alignment control layers 21a and 21b can be easily formed homogeneously. Specifically, those represented by the following chemical formulas (3A) to (3F) can be preferably used as the second monomer.

As shown in FIG. 5, the liquid crystal display device according to the second embodiment includes the alignment films 12a and 12b, and the alignment control layers 21a and 21b in contact with the liquid crystal layer 30 in the liquid crystal cell 201 are formed. The pretilt angle is given to the liquid crystal, and the delay of the response speed of the liquid crystal is suppressed.

In such a liquid crystal display device, a liquid crystal material and a polymerizable material are formed between an alignment film forming step of forming conventional alignment films 12a and 12b on opposing surfaces of a pair of substrates 11a and 11b, and both substrates 11a and 11b. A step of arranging a liquid crystal composition containing the monomer 20, and polymerization of the polymerizable monomer 20 in the liquid crystal composition after the step of arranging the liquid crystal layer 30 containing a liquid crystal material and the liquid crystal layer 30 And a polymerization step of forming, between the substrates 11a and 11b, alignment control layers 21a and 21b for controlling the alignment of the liquid crystal material at a predetermined angle with respect to the substrates 11a and 11b. The orientation control layers 21a and 21b are made of a polymer formed by polymerizing the polymerizable monomer 20, and at least one of the polymerizable monomers 20 is a self-cleavage type radical polymerizable property represented by the chemical formula (1). It is a monomer. The polymerizable monomer 20 may contain another polymerizable monomer, and for example, a radical polymerizable monomer represented by the chemical formula (3) can be used. In addition, the formation method of alignment film is not specifically limited, It can carry out by a known method.

Hereinafter, the present technology will be described in detail based on examples. The present technology is not limited at all by these examples.

Example 1
(Preparation of Liquid Crystal Composition)
In the following chemical formula (2), a difluorinated negative-type liquid crystal material having a functional group having X ¹ and X ² as fluorine has an acryloyloxy group as a first monomer (self-cleavage type radically polymerizable monomer): Polymerization of the following chemical formula (4A) having a vertical alignment developing group as the second monomer (radically polymerizable monomer having a different structure from the first monomer) by 0.2% by weight of the benzoin polymerizable monomer of the chemical formula (1A) Liquid crystal composition (nematic-isotropic phase transition temperature Tni: 75.degree. C., dielectric anisotropy .DELTA..epsilon .: -3.4) was prepared by dissolving 1.5 wt.

In the above chemical formula (2), X ¹ and X ² independently represent a halogen group. R ² represents a saturated alkyl group having 1 to 6 carbon atoms. "*" Represents a bond.

(Preparation of liquid crystal cell)
Using the liquid crystal composition prepared as described above, a liquid crystal cell according to Embodiment 1 without the conventional alignment film was produced as follows.
A pair of substrates on which an ITO electrode was formed was prepared, and a sealant was drawn on one of the substrates. In addition, as a sealing agent, the thing hardened | cured by heat, the thing hardened | cured by irradiation of UV light, or both of them was used. Of the pair of substrates, one having a fishbone type slit was used as one of the substrates, and none of the substrates had a conventional alignment film such as so-called polyimide. Subsequently, the liquid crystal composition prepared above was dropped onto the substrate on which the sealing agent was drawn, and the other substrate was attached (arrangement step).
Subsequently, the liquid crystal cell was irradiated with ² J / cm ^{2 of} non-polarized UV from the normal direction in the state of no voltage application (using a black light FHF-32BLB manufactured by Toshiba as the UV light source and using 313 nm ± 10 nm illuminance system) Estimated). As a result, the polymerizable monomer in the liquid crystal composition was polymerized to form an alignment control layer for vertically aligning the liquid crystal (polymerization step).
Finally, the liquid crystal cell was heated to 120 ° C. and then quenched. Thus, the liquid crystal layer was subjected to realignment treatment to complete the vertically aligned liquid crystal cell of Example 1 having no conventional alignment film.

Example 2
A liquid crystal cell of Example 2 is prepared in the same manner as Example 1, except that the addition amount of the benzoin type polymerizable monomer of the chemical formula (1A) used as the first monomer is 0.4% by weight. Was produced.

Comparative Example 1
As a first monomer, 0.2 wt% of an acetophenone-based polymerizable monomer represented by the following chemical formula (5A) is added instead of 0.2 wt% of the benzoin-based polymerizable monomer of the chemical formula (1A) A liquid crystal cell of Comparative Example 1 was produced in the same manner as in Example 1 except that the product was prepared.

Comparative Example 2
A liquid crystal cell of Comparative Example 2 was prepared in the same manner as Comparative Example 1, except that the addition amount of the acetophenone-based polymerizable monomer of Chemical Formula (5A) used as the first monomer was 0.4% by weight. Was produced.

Comparative Example 3
A liquid crystal cell of Comparative Example 3 was produced in the same manner as in Example 1 except that a liquid crystal composition was prepared without the addition of a self-cleavage type radically polymerizable monomer as a first monomer.

[Evaluation of Liquid Crystal Cell of Example 1 and Example 2 and Comparative Examples 1 to 3]
[Evaluation of contrast]
For each liquid crystal cell to be evaluated, using the SR-1 manufactured by Topcon Corporation, the illuminance at the time of black display and the illuminance at the white display were measured in a dark room at 25 ° C. to obtain the contrast. The results are shown in Table 1.

[Measurement of residual DC (rDC)]
About each liquid crystal cell made into evaluation object, rDC after applying DC offset voltage of 3V for 2 hours in a 25 degreeC environment was measured by the flicker elimination method. The results are shown in Table 1.

[Measurement of Voltage Holding Ratio (VHR)]
About each liquid crystal cell made into evaluation object, VHR was measured on condition of 1V and 70 ° C using 6254 type VHR measurement system made by Toyo Technica. The results are shown in Table 1.

[Evaluation of liquid crystal solubility]
About the liquid crystal composition prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2, the first monomer (benzoin-based polymerizable monomer represented by the above-mentioned chemical formula (1A) or the above which functions as a polymerization initiator) The solubility of the acetophenone-based polymerizable monomer represented by the chemical formula (5A) in the negative liquid crystal material was evaluated as follows.
Two glass substrates were bonded to each other to prepare an evaluation cell as shown in FIG. The liquid crystal compositions prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 are injected by vacuum injection from the injection port provided at one side edge (lower edge in FIG. 6) of this cell. Each evaluation sample was obtained.
The evaluation cell obtained above was disassembled, and each liquid crystal composition was recovered from the 1.0 cm line, 3.0 cm line, and 5.0 cm line shown in FIG. The collected liquid crystal composition was analyzed by gas chromatography (GC), and the relative concentration of the first monomer in each line was calculated from the obtained peak intensity to confirm the concentration distribution of the first monomer in the cell. . In the calculation of the relative concentration, the relative concentration of the 3.0 cm line and the 5.0 cm line was determined, where the concentration of the first monomer in the 1.0 cm line was 1.0. The relative concentrations of the obtained first monomers are shown in Table 1.

As shown in Table 1, in the liquid crystal cells of Example 1 and Example 2, higher contrast was obtained than those of Comparative Examples 1 and 2. As one of the factors described above, the difference in the compatibility (solubility) of the first monomer functioning as a polymerization initiator in the negative liquid crystal material is considered. We will consider below.

In Example 1 and Example 2, a benzoin-based self-cleavage type radically polymerizable monomer represented by the chemical formula (1A) is used as the first monomer. In the case of a benzoin monomer, the presence of a (mono) alkoxy group adjacent to a ketyl group (C 開裂 O) causes the ketyl group and -CHOR ¹ -to be cleaved by ultraviolet light irradiation to generate a radical (see FIG. 1). ). The radicals thus generated initiate polymerization of the polymerizable monomer in the liquid crystal composition.
Here, in the case of the benzoin polymerizable monomer, since it is the (mono) alkoxy group adjacent to the ketyl group, compared with the acetophenone polymerizable monomer used in Comparative Examples 1 and 2 described later, proton acceptance It is possible to keep the quality low. Therefore, the compatibility with a negative type liquid crystal compound having high proton acceptability is relatively good, and the solubility is high. Specifically, the saturation solubility in the negative liquid crystal material is 0.5% by weight or more. Therefore, the first polymer is uniformly distributed in the liquid crystal layer 30, and the polymerization reaction proceeds uniformly. For this reason, it is considered that unevenness in forming the alignment control layer made of a polymer is eliminated, light leakage at the time of black display is less likely to occur, and high contrast is obtained.

On the other hand, in Comparative Examples 1 and 2, the acetophenone-based polymerizable monomer represented by the chemical formula (5A) is used as the first monomer. Also in this case, the ketyl group and the dialkoxy group adjacent thereto are cleaved by ultraviolet irradiation to generate a radical, whereby polymerization of the polymerizable monomer is initiated.
However, the acetophenone-based polymerizable monomer of the chemical formula (5A) has a problem that the solubility in the negative liquid crystal material is low. In the acetophenone type polymerizable monomer, two alkoxy groups (methoxy group) are adjacent to a ketyl group (C = O), but both the ketyl group and the alkoxy group have high proton acceptability, and the above chemical formula of the negative liquid crystal material The representative functional groups represented by (2) also have high proton acceptability, and thus repel each other. That is, when the acetophenone-based polymerizable monomer is used as the first monomer, micro electrostatic repulsion derived from unpaired electrons occurs to reduce the compatibility with the negative liquid crystal material. As a result, it is assumed that the formation of the alignment control layer is not uniformly performed, which causes the display unevenness and the like.

In Comparative Example 3 in which the self-cleavage type radical polymerizable monomer corresponding to the first monomer was not used, the monomer was not polymerized even when irradiated with ultraviolet light, and the orientation control layer was not formed. Therefore, vertical alignment was not obtained.

Further, it is known from Table 1 that good VHR and rDC were obtained in all of Example 1 and Example 2 and Comparative Example 1, and there was no problem in actual use. However, in Comparative Example 2 in which 0.4 wt% of acetophenone-based polymerizable monomer was introduced as the first monomer, VHR showed a decreasing tendency and rDC showed an increasing tendency. This is presumed to be due to the residual radicals generated from the first monomer in the negative liquid crystal material. We will consider below.

In the benzoin polymerizable monomer, as shown in FIG. 1, both of the two radicals generated by self-cleavage have a polymerizable group. Therefore, all of the radicals are polymerized to be able to be incorporated into the alignment control layers 21a and 21b, and the probability that the radicals finally remain in the liquid crystal layer 30 seems to be extremely low.

On the other hand, in the acetophenone-based polymerizable monomer, as shown in FIG. 7, a radical having no polymerizable group such as a (meth) acrylic group may be partially formed by self-cleavage. Radicals having no polymerizable group easily remain in the liquid crystal layer 30 unless they contribute to the initiation of polymerization. In Comparative Example 2 in which a relatively large amount of acetophenone-based polymerizable monomer is introduced, it is considered that a decrease in VHR and an increase in rDC occur because the radical (alkyl radical) generated by self-cleavage remains in the liquid crystal layer 30. Be

In the evaluation cells of Example 1 and Example 2, there is no significant change in the relative concentration of the first monomer up to the 5.0 cm line, and the first monomer comprising the benzoin polymerizable monomer represented by the chemical formula (1A) Were found to be approximately uniformly distributed in the cells.
On the other hand, in Comparative Example 1 and Comparative Example 2, the relative concentration decreased from the 3.0 cm line toward the 5.0 cm line. The first monomer consisting of an acetophenone-based polymerizable monomer represented by the chemical formula (5A) has a relative concentration of about half and 0.4 wt% or 0.6 wt% in the 5.0 cm line, in the cell. It is known that the distribution unevenness in the

This is because the acetophenone-based first monomer represented by the chemical formula (5A) has lower solubility in the negative liquid crystal material than the benzoin-based first monomer represented by the chemical formula (1A). It can be said that the results support the consideration of That is, when the liquid crystal composition containing the acetophenone-based first monomer having low solubility in the liquid crystal material is injected into the cell and moves in the cell, the first monomer is left behind from the liquid crystal material and adsorbed to the substrate It is guessed. When unevenness occurs in the concentration distribution of the first monomer in the cell, unevenness occurs in thickness and the like also in the alignment control layer formed by the progress of polymerization by radicals generated from the first monomer, and a uniform alignment control layer is not formed. . For this reason, it is considered that unevenness occurs in the alignment of the liquid crystal material, black display unevenness occurs, and the contrast decreases. Further, in the portion where the first monomer concentration is low, the polymerization of the monomer hardly progresses, and it is considered that a further decrease in contrast is caused because a domain in which the liquid crystal material is not oriented is generated.
As described above, in the liquid crystal cell manufactured using the acetophenone-based monomer represented by the chemical formula (5A), unevenness occurs in the concentration distribution of the first monomer in the cell, and as a result, Comparative Example 1 and Comparative Example It is inferred that the decrease in contrast as shown in Table 1 was observed for No. 2.

Example 3
(Preparation of Liquid Crystal Composition)
In a negative-type liquid crystal material similar to that used in Example 1, 0.2% by weight of a benzoin-based polymerizable monomer having an acryloylamide group as a first monomer and having an acryloylamide group as a second monomer is used. The polymerizable monomer represented by the following chemical formula (4B) having a vertical alignment developing group was dissolved in 1.0% by weight to prepare a liquid crystal composition.

(Preparation of liquid crystal cell)
The liquid crystal cell according to Embodiment 1 having no conventional alignment film was produced using the liquid crystal composition prepared as described above. The alignment process and the polymerization process were the same as in Example 1, and the realignment process was performed to complete the vertically aligned liquid crystal cell of Example 3 without the conventional alignment film.

Example 4
A liquid crystal cell of Example 4 is prepared in the same manner as Example 3, except that the addition amount of the benzoin type polymerizable monomer of the chemical formula (1F) used as the first monomer is 0.4% by weight. Was produced.

Comparative Example 4
As a first monomer, 0.2 wt% of the acetophenone-based polymerizable monomer represented by the chemical formula (5A) used in Comparative Example 1 is replaced with 0.2 wt% of the benzoin polymerizable monomer of the chemical formula (1F) A liquid crystal cell of Comparative Example 4 was produced in the same manner as in Example 3 except that a liquid crystal composition was prepared by addition.

Comparative Example 5
A liquid crystal cell of Comparative Example 5 was prepared in the same manner as in Comparative Example 4 except that the liquid crystal composition was prepared with 0.4 wt% of the acetophenone-based polymerizable monomer of Chemical Formula (5A) used as the first monomer. Made.

[Evaluation of Liquid Crystal Cell of Examples 3 and 4 and Comparative Examples 4 and 5]
[Evaluation of contrast and measurement of residual DC (rDC)]
The contrast was determined and the residual DC was measured for each liquid crystal cell to be evaluated in the same manner as the liquid crystal cell of Example 1 and the like was evaluated. The results are shown in Table 2.

[Measurement of VHR (moisture resistance test)]
For each liquid crystal cell to be evaluated, VHR was measured as in the case of measuring the liquid crystal cell of Example 1 (initial stage). Thereafter, a humidity resistance test was conducted by leaving it to stand for 500 hours in an environment of humidity 60 ° C. and humidity 90%, and VHR was also measured for each liquid crystal cell after the test under the same measurement conditions as before the humidity resistance test (after 500 hours humidity resistance test) . The results are shown in Table 2.

From Table 2, it was known that in the liquid crystal cells of Examples 3 and 4 using the first monomer having an acrylamide group, a high VHR of 96% or more was maintained even after the moisture resistance test. In particular, in Example 4 in which the first monomer concentration was high, the decrease in VHR by the moisture resistance test was extremely small. It is considered that this is because the alignment control layers 21a and 21b formed of a polymer having a highly hygroscopic acrylamide group adsorb the moisture which has infiltrated into the liquid crystal layer 30, and the polar component derived from the sealing agent.

Example 5
(Preparation of Liquid Crystal Composition)
In a negative-type liquid crystal material similar to that used in Example 1, as a first monomer, 0.03% by weight of a benzoin-based polymerizable monomer having a methacryloyloxy group of the following chemical formula (1B) and as a second monomer: 0.3% by weight of a polymerizable monomer represented by the following chemical formula (3A) having no orientation expression group was dissolved to prepare a liquid crystal composition (Tni: 80 ° C., Δε: −3.0).

(Preparation of liquid crystal cell)
Using the liquid crystal composition prepared as described above, a liquid crystal cell according to Embodiment 2 having a conventional alignment film was produced as follows.
A substrate having a pair of ITO electrodes (solid) is prepared, and after applying a vertical photo alignment film material (polyimide) represented by the following chemical formula (6-1) containing a cinnamate group, it is calcined at 90 ° C. for 1 minute Followed by main firing at 200.degree. C. for 40 minutes. Thereafter, linearly polarized light was irradiated at 20 mJ / cm ² from an oblique 40 ° direction (alignment film forming step).
Next, a sealing agent was drawn on one of the substrates. In addition, as a sealing agent, the thing hardened | cured by heat, the thing hardened | cured by irradiation of UV light, or both of sealing agents were used. The liquid crystal composition prepared above was dropped onto the substrate on which the sealing agent was drawn, and the other substrate was attached (arrangement step).
Subsequently, 1 J / cm ^{2 of} non-polarized UV was irradiated from the normal direction to the liquid crystal cell in a non-voltage applied state (using a black light FHF-32BLB made by Toshiba as the UV light source and using 313 nm ± 10 nm illuminance system) I estimated the illuminance). As a result, the polymerizing monomer in the liquid crystal composition was polymerized to form a polymer layer in which the liquid crystal was aligned substantially perpendicularly (pretilt angle 88.5 °) (polymerization step).
Finally, the liquid crystal cell was heated and quenched at 120 ° C. Thus, the liquid crystal layer was subjected to realignment treatment, and the vertical alignment liquid crystal cell of Example 5 provided with the conventional alignment film was completed.

N in the above chemical formula (6-1) represents a natural number. In the above chemical formula (6-1), “*” represents a bond.

Example 6
A liquid crystal cell of Example 6 is prepared in the same manner as Example 5, except that the addition amount of the benzoin type polymerizable monomer of the chemical formula (1B) used as the first monomer is 0.06% by weight and the liquid crystal composition is prepared. Was produced.

Example 7
A liquid crystal cell of Example 7 was prepared in the same manner as Example 5, except that the addition amount of the benzoin type polymerizable monomer of the chemical formula (1B) used as the first monomer was 0.1% by weight and the liquid crystal composition was prepared. Was produced.

Comparative Example 6
A liquid crystal cell of Comparative Example 4 was produced in the same manner as in Example 5 except that a liquid crystal composition was prepared without the addition of the self-cleavage type radically polymerizable monomer as the first monomer.

[Evaluation of Liquid Crystal Cell of Examples 5 to 7 and Comparative Example 6]
[Evaluation of contrast and measurement of residual DC (rDC)]
The contrast was determined and the residual DC was measured for each liquid crystal cell to be evaluated in the same manner as the liquid crystal cell of Example 1 and the like was evaluated. The results are shown in Table 3.

[Measurement of tilt angle change amount (Δ tilt)]
For each liquid crystal cell to be evaluated, the amount of change in tilt angle from the initial stage when a rectangular wave voltage of 10 V (60 Hz) was applied for 100 hours was measured. The results are shown in Table 3.

[Measurement of VHR (light resistance test)]
For each liquid crystal cell to be evaluated, VHR was measured as in the case of measuring the liquid crystal cell of Example 1 (initial stage). Thereafter, a light resistance test was conducted by leaving it on a backlight at 30 ° C. for 1000 hours, and VHR was measured for each liquid crystal cell after the light resistance test under the same measurement conditions as before the light resistance test (1000 hours light resistance) After the test). The results are shown in Table 3.

From Table 3, from the comparison of Example 5, Example 6, and Example 7, as the addition amount of the benzoin-based polymerizable monomer of the chemical formula (1B) increases, the initial VHR becomes higher, and the Δ tilt becomes smaller. It was known to be. These liquid crystal cells were also excellent in contrast, rDC and light resistance. In Comparative Example 6, since the liquid crystal cell was provided with the conventional alignment film made of polyimide, vertical alignment was obtained regardless of the presence or absence of the polymer layer formation. However, compared with Example 5 grade | etc., VHR (both initial stage and after a light resistance test) was low, and (DELTA) tilt was large.

Example 8
(Preparation of Liquid Crystal Composition)
In a positive type liquid crystal material containing liquid crystal molecules having a structure represented by the following chemical formula (7), 0.02% by weight of a benzoin type polymerizable monomer having a methacryloyloxy group as a first monomer, having a methacryloyloxy group: As a second monomer, 0.25 wt% of a polymerizable monomer represented by the following chemical formula (3B) having no orientation developing group is dissolved to obtain a liquid crystal composition (Tni: 85 ° C., Δε: +7.5) Was prepared.

In the above chemical formula (7), "*" represents a bond.

(Preparation of liquid crystal cell)
The liquid crystal cell according to Embodiment 2 having a conventional alignment film was manufactured using the liquid crystal composition prepared as described above.
A pixel electrode substrate having a common electrode (solid) made of ITO and a pixel electrode made of ITO having a slit formed on the common electrode through a dielectric layer as a pair of substrates, and an electrode Prepared opposite substrate. After applying a horizontal light alignment film material (polyimide) represented by the following chemical formula (6-2) containing a cyclobutane ring to both substrates, temporary baking is performed at 90 ° C. for 1 minute, and then straight lines from the normal direction Polarized light was irradiated at 500 mJ / cm ² , and finally, main baking was performed at 200 ° C. for 40 minutes (alignment film forming step).
Subsequently, through the same arrangement step and polymerization step as in Example 5, the realignment process was performed to complete the horizontally aligned liquid crystal cell of Example 8 provided with the conventional alignment film.

N in the above chemical formula (6-2) represents a natural number. In the above chemical formula (6-2), "*" represents a bond.

Example 9
A liquid crystal cell of Example 9 is prepared in the same manner as Example 8, except that the addition amount of the benzoin type polymerizable monomer of the chemical formula (1B) used as the first monomer is 0.04% by weight. Was produced.

Comparative Example 7
A liquid crystal cell of Comparative Example 7 was produced in the same manner as in Example 8 except that a liquid crystal composition was prepared without the addition of the self-cleavage type radically polymerizable monomer as the first monomer.

[Evaluation of Liquid Crystal Cell of Example 8 and Example 9 and Comparative Example 7]
[Evaluation of contrast and measurement of residual DC (rDC), and measurement of VHR (light resistance test)]
The contrast was determined and the residual DC was measured for each liquid crystal cell to be evaluated in the same manner as the liquid crystal cell of Example 1 and the like was evaluated. Further, for each liquid crystal cell to be evaluated, VHR measurement (light resistance test) was performed in the same manner as the liquid crystal cell in Example 5 and the like was evaluated. The results are shown in Table 4.

From Table 4, it is known from the comparison of Example 8 and Example 9 that the initial VHR becomes higher and the rDC becomes smaller as the addition amount of the benzoin type polymerizable monomer of the chemical formula (1B) increases. The These liquid crystal cells were also excellent in contrast, rDC and light resistance. In Comparative Example 7, since the liquid crystal cell was provided with the conventional alignment film made of polyimide, horizontal alignment was obtained regardless of the presence or absence of the polymer layer formation. However, compared to Examples 8 and 9, VHR (both initial and after the light resistance test) was low and rDC was large.

1, 201: liquid crystal cell (liquid crystal panel), 11a, 11b: substrate, 12a, 12b (conventional type) alignment film, 20: polymerizable monomer, 21a, 21b: alignment control layer, 30: liquid crystal layer

Claims (7)

1. A liquid crystal composition comprising a liquid crystal material and a self-cleavage type radically polymerizable monomer represented by the following chemical formula (1).
   

   

   (In the above chemical formula (1),
   R ¹ represents a linear, branched or cyclic alkyl or alkenyl group having 1 to 8 carbon atoms.
   Z ¹ and Z ² independently of each other represent —O—, —S—, —NH—, —CO—, —COO—, —OCO— or a direct bond.
   Sp ¹ and Sp ^{2 each} represent a linear, branched or cyclic, alkylene or alkenylene group having 1 to 8 carbon atoms, or a direct bond.
   P ¹ and P ² independently of each other represent a (meth) acryloyloxy group or a (meth) acryloylamino group)
2. The liquid crystal composition according to claim 1, wherein the liquid crystal material has a functional group represented by the following chemical formula (2).
   

   

   (In the above chemical formula (2),
   X ¹ and X ² independently of each other represent a halogen group.
   R ² represents a saturated alkyl group having 1 to 6 carbon atoms.
   "*" Represents a bond)
3. The liquid crystal composition according to claim 2, wherein in the chemical formula (2), both of X ¹ and X ^{2 in the} liquid crystal material are fluorine.
4. The liquid crystal composition according to any one of claims 1 to 3, further comprising a radically polymerizable monomer represented by the following formula (3).
   

   

   (In the above chemical formula (3),
   R ³ is a -R ⁴ -Sp ³ -P ³ group, a hydrogen atom, a halogen atom, a -CN group, a -NO ₂ group, or a linear or branched alkyl group having 1 to 18 carbon atoms is there.
   P ³ represents a (meth) acryloyloxy group, or a (meth) acryloyl amino group.
   Sp ³ represents a linear, branched or cyclic, alkylene or alkyleneoxy group having 1 to 6 carbon atoms, or a direct bond.
   The hydrogen atom which R ³ has may be substituted by a fluorine atom or a chlorine atom.
   R ⁴ represents —O— group, —S— group, —NH— group, —CO— group, —COO— group, —OCO— group, or a direct bond.
   A ¹ and A ² are the same or different and each represents a 1,4-phenylene group, a naphthalene-2,6-diyl group, a phenanthrene-2,7-diyl group, or an anthracene-2,6-diyl group.
   One or more hydrogen atoms possessed by A ¹ and A ² are a fluorine atom, a chlorine atom, a —CN group, or an alkyl group having 1 to 6 carbon atoms, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group or an alkyl group It may be substituted by a carbonyloxy group.
   Z ² is, -O- group, an -S- group, -NH- group, -CO- group, -COO- group, -OCO- group, or a direct bond.
   N in the above chemical formula (3) is 0, 1 or 2)
5. The liquid crystal composition according to any one of claims 1 to 4, further comprising a radically polymerizable monomer represented by any one of the following formulas (4-1) to (4-5).
   

   

   (In the above chemical formulas (4-1) to (4-5), n represents an integer of 8 to 20, and m represents an integer of 1 to 6)
6. A pair of substrates,
   A liquid crystal layer sandwiched between the pair of substrates and containing a liquid crystal material;
   And an alignment control layer that contacts the liquid crystal layer and controls the alignment of the liquid crystal material at a predetermined angle with respect to the substrate.
   The alignment control layer is made of a polymer formed by polymerizing a polymerizable monomer added to the liquid crystal composition forming the liquid crystal layer,
   The liquid crystal display device, wherein at least one of the polymerizable monomers is a self-cleavage type radically polymerizable monomer represented by the following chemical formula (1).
   

   

   (In the above chemical formula (1),
   R ¹ represents a linear, branched or cyclic alkyl or alkenyl group having 1 to 8 carbon atoms.
   Z ¹ and Z ² independently of each other represent —O—, —S—, —NH—, —CO—, —COO—, —OCO— or a direct bond.
   Sp ¹ and Sp ^{2 each} represent a linear, branched or cyclic, alkylene or alkenylene group having 1 to 8 carbon atoms, or a direct bond.
   P ¹ and P ² independently of each other represent a (meth) acryloyloxy group or a (meth) acryloylamino group)
7. Arranging a liquid crystal composition containing a liquid crystal material and a polymerizable monomer between a pair of substrates arranged such that the plate surfaces face each other;
   After the disposing step, the polymerizable monomer in the liquid crystal composition is polymerized to be in contact with the liquid crystal layer containing the liquid crystal material and the liquid crystal layer to align the liquid crystal material at a predetermined angle with respect to the substrate And a polymerization step of forming an alignment control layer to be controlled between the pair of substrates, the method comprising the steps of:
   The orientation control layer comprises a polymer formed by polymerizing the polymerizable monomer,
   The manufacturing method of the liquid crystal display device whose at least 1 of the said polymerizable monomer is a self-cleavage type radically polymerizable monomer represented by following Chemical formula (1).
   

   

   (In the above chemical formula (1),
   R ¹ represents a linear, branched or cyclic alkyl or alkenyl group having 1 to 8 carbon atoms.
   Z ¹ and Z ² independently of each other represent —O—, —S—, —NH—, —CO—, —COO—, —OCO— or a direct bond.
   Sp ¹ and Sp ^{2 each} represent a linear, branched or cyclic, alkylene or alkenylene group having 1 to 8 carbon atoms, or a direct bond.
   P ¹ and P ² independently of each other represent a (meth) acryloyloxy group or a (meth) acryloylamino group)

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