WO2012056947A1

WO2012056947A1 - Liquid crystal display panel, liquid crystal display, and polymer for alignment film material

Info

Publication number: WO2012056947A1
Application number: PCT/JP2011/073958
Authority: WO
Inventors: 寺下　慎一; 平井　明; 寺岡　優子; 敢三宅; 伸一平戸
Original assignee: シャープ株式会社
Priority date: 2010-10-26
Filing date: 2011-10-18
Publication date: 2012-05-03

Abstract

In order to improve the basic performance and high image quality of a liquid crystal display panel and a liquid crystal display, the structural composition of a desired polymer as a photo-alignment film, in which the constitutional unit has at least two side chains having a photo functional group, was required to be found in a photo-alignment liquid crystal panel capable of achieving uniform display quality, highly reliable photo orientation, and excellent electrooptic properties (transmittance, contrast, viewing angle, and response). The present invention was completed by containing a compound having photo orientation and optimizing the photo-polymer copolymerization ratio and the degeneration ratio so that the photo-alignment film has photo orientation and by finding the structural composition of the desired polymer as a photo-alignment film. The purpose of the present invention is to produce efficiently and provide a display panel and a liquid crystal display that have excellent electrical properties and optical properties, sufficient liquid crystal display quality, and reliability.

Description

Liquid crystal display panel, liquid crystal display device, and polymer for alignment film material

The present invention relates to a liquid crystal display panel, a liquid crystal display device, and a polymer for alignment film material. More specifically, personal digital assistants used for large numbers of people, personal computers, word processors, amusement equipment, educational equipment, flat displays such as television devices, display boards using the shutter effect of liquid crystals, display windows, display doors, The present invention relates to a liquid crystal display device having a wide viewing angle characteristic suitable for a display wall and the like, and a liquid crystal display panel and a polymer for alignment film material used therefor.

Liquid crystal display devices are used in a wide range of fields, taking advantage of their thinness, light weight, and low power consumption. The liquid crystal display device includes a pair of substrates that sandwich a liquid crystal layer, and appropriately applies a voltage to electrodes provided on the substrate on the liquid crystal layer side to control the alignment direction of liquid crystal molecules contained in the liquid crystal layer. This enables liquid crystal display. The liquid crystal display device usually has an alignment film provided on the surface of the substrate on the liquid crystal layer side in order to control the alignment direction of the liquid crystal molecules.

Conventionally, resins (including derivatives thereof) such as polyamic acid, polyimide, polyamide, polysiloxane, and polyester have been used as the material of the alignment film constituting the liquid crystal display device. Among these, polyimides have been used in many liquid crystal display devices because they exhibit excellent physical properties such as heat resistance, affinity with liquid crystals, and mechanical strength among organic resins.

In addition, the alignment film is usually subjected to an alignment treatment in order to give a certain pretilt angle to the liquid crystal molecules on the surface of the alignment film. Examples of the alignment treatment method include a rubbing method and a photo-alignment method. In the rubbing method, the alignment treatment is performed by rubbing the surface of the alignment film with a cloth wound around a roller. On the other hand, the photo-alignment method uses a photo-alignment film as an alignment film material, and irradiates (exposes) light such as ultraviolet rays to the photo-alignment film, thereby generating an alignment regulating force in the alignment film and / or the alignment film. This is an alignment method for changing the alignment regulating direction of.

However, in a liquid crystal display device provided with a conventional alignment film, image sticking may occur when lighting for a long time, and there is room for improvement in terms of suppressing the occurrence of image sticking even after lighting for a long time. there were.

On the other hand, a liquid crystal alignment film is formed that prevents display defects, has good afterimage characteristics even after long-time driving, does not decrease the ability to align liquid crystal, and has little decrease in voltage holding ratio against light and heat. As a technique for providing a liquid crystal aligning agent that can be used, a tetrafunctional silicon compound such as tetrachalcoxysilane, a trifunctional compound such as trialkoxysilane, and 0.8 to 3.0 moles per mole of functional group such as an alkoxy group. A liquid crystal aligning agent composition containing a reaction product with water and a glycol ether solvent is disclosed (for example, see Patent Document 1).

Also provided is a liquid crystal aligning agent that can exhibit good coating properties and liquid crystal alignment characteristics, and can form a liquid crystal alignment film that has a short period of time until the afterimage is erased after voltage application is canceled in a liquid crystal display element. As a technique, a liquid crystal aligning agent comprising a polyamic acid having a structure derived from a monoamine compound or an imidized polymer thereof is disclosed (for example, see Patent Document 2).

In addition, as a technique for providing a liquid crystal aligning agent that provides a vertical liquid crystal alignment film having excellent image sticking characteristics and reliability even when used with a reflective electrode, a polymer 100 having an amic acid repeating unit and / or an imide repeating unit. A vertical liquid crystal aligning agent comprising at least 5 parts by weight of a compound having at least 5 parts by weight and a compound having at least two epoxy groups in the molecule is disclosed (for example, see Patent Document 3).

Furthermore, in the literature regarding the photo-alignment film, it is reported that the burn-in time is shortened as the electrical resistivity of the photo-alignment film is small (see, for example, Non-Patent Document 1).

In the literature on the material development of the alignment film, it has been reported that the burn-in can be reduced by reducing the residual DC in the liquid crystal cell of the vertical electric field (see, for example, Non-Patent Document 2).

Residual DC is usually generated by offset voltage deviation between electrodes formed on opposing substrates in an AC-driven liquid crystal display device.

On the other hand, for photoreactive polymers that produce stable high-resolution alignment patterns that have a defined tilt angle when irradiated with polarized light and at the same time have a sufficiently high resistance (retention ratio) in the adjacent liquid crystal medium. -Polyimides are further disclosed which further include as side groups that can be structurally derived from arylacrylic acid (see, for example, Patent Document 4).

Also, for photoreactive polymers that produce a stable, high-resolution alignment pattern with a very large tilt angle when irradiated with polarized light, while at the same time producing a sufficiently high retention in the adjacent liquid crystal media. There is disclosed a polyimide containing a cinnamate group derivative such that a cinnamate group is bonded to a polyimide main chain via a carboxyl group by a flexible spacer (see, for example, Patent Document 5). ).

Further, a functionalized photoreactive compound in which a specific electron-withdrawing group is added to a specific molecular structure having unsaturation directly bonded to two unsaturated ring structures, which is used for a liquid crystal alignment material Is disclosed (for example, see Patent Document 6).

And as a photocrosslinkable material, the specific diamine compound and the polymer, copolymer, polyamic acid, polyamic acid ester, or polyimide based on such a compound are proposed (for example, refer patent document 7).

JP 2005-250244 A JP 2006-52317 A JP 2006-10896 A JP-T-2001-517719 Special table 2003-520878 gazette Special table 2009-511431 gazette Special table 2009-520702 gazette

However, in order to improve the basic performance and high image quality of liquid crystal panels and liquid crystal display devices, uniform display quality, highly reliable photo-alignment, and excellent electro-optical properties (transmittance, contrast, viewing angle, response) In the photoalignment liquid crystal panel that can be achieved, the structural composition of a desirable polymer having at least two side chains having photofunctional groups as the photoalignment film as the photoalignment film was unknown. For example, the material described in Patent Document 7 described above is not a photo-alignment film material that can obtain practically desirable reliability and electro-optical characteristics.

In addition, if the resin (polymer), which is the alignment film contained in the liquid crystal panel, and its constituent materials are new chemical substances, the amount of use should be reduced as much as possible in order to reduce the burden on the environment. Consideration to suppress is essential.

In particular, in the alignment film, mixing different types of polymers deteriorates the electrical characteristics such as the problem of precipitation in the ink solvent, the uniformity of liquid crystal alignment, and the voltage holding ratio and residual DC that cause image sticking. The display quality and reliability may be reduced.

In the vertical photo-alignment films of

Patent Documents

5 and 6, not only strong residual DC mode image sticking, but also AC mode image sticking (AC memory (ACM)) due to a change in pretilt angle when an AC voltage is applied occurs simultaneously. There was a need to resolve.
A photo-alignment film (homopolymer) having a photofunctional group capable of giving a pretilt angle to liquid crystal molecules by causing a photochemical reaction (photocrosslinking reaction (including photodimerization reaction), photoisomerization reaction, photolysis reaction). However, even if the molecular structures of the materials having photofunctional groups are similar, the image sticking (ACM) due to the application of AC voltage is different at an inherent level.
Furthermore, a photo-alignment film material that can have photo-alignment by including a compound having photo-alignment is desired.

In the TN (Twisted Nematic) mode, ECB (Electrically Controlled Birefringence) mode, VATN (Vertical Alignment Twisted Nematic) mode, etc., liquid crystal alignment processing in one direction is performed in the substrate plane. Because of the dependency, the direction in which the burn-in phenomenon can be observed depends on the viewing angle characteristics of the liquid crystal alignment mode in addition to the front direction. On the other hand, in liquid crystal TVs and large information displays, liquid crystal alignment is divided for viewing angle compensation during white display. As described above, in the orientation division mode in which the viewing angle is compensated, the image sticking phenomenon can be seen uniformly in all directions, so it is essential to improve the image sticking phenomenon. The VATN mode may be referred to as an RTN (reverse twist TN; vertical alignment TN) mode. The ECB mode may be of a vertical alignment when no voltage is applied, a horizontal alignment type when a voltage is applied (VAECB), a horizontal alignment when no voltage is applied, and a vertical alignment type when a voltage is applied.

The present invention has been made in view of the above situation, and efficiently produces and provides a display panel and a liquid crystal display device having excellent electro-optical characteristics, uniform display quality, and sufficient reliability. It is intended.

As a method for producing an alignment film in a liquid crystal display panel, there is a method of imparting functionality to the alignment film by forming a layer made of a different polymer on the substrate. There is a method called processing, two-layer processing, or hybridization processing. For example, a polymer of a horizontal alignment film and a polymer of a vertical alignment film, or a non-fluorine-introduced polymer and a fluorine-introduced polymer, for example, a non-fluorine-introduced vertical alignment film and a fluorine-introduced polymer without light alignment By blending a vertical alignment film having orientation with a weight ratio of a certain solid content (for example, 77:23 to 5:95), in the baking process immediately after application to the substrate or after application of the alignment film, A horizontal alignment film is formed on the substrate side and a vertical alignment film is formed on the liquid crystal side by utilizing the action of phase separation between the polymers. By this action, the volume of the alignment film exposed on the liquid crystal side (the volume of the vertical alignment film formed on the liquid crystal side) can be reduced, and an alignment film material (for example, an alignment film material that is a new chemical substance, and / or Alternatively, the use of the alignment film material can be reduced because the alignment film exposed to the liquid crystal side only needs to be included in the alignment film exposed to the liquid crystal side. Since it is possible to reduce the residual DC that causes image sticking while maintaining the thickness of the alignment film, the above-described treatment can be performed if necessary. The modification ratio of the present invention refers to the weight ratio (wt% (wt%)) of the solid content of the non-photo-alignment polymer, where the weight of the total solid content of the photo-alignment polymer and the non-photo-alignment polymer is 100%. For example, depending on the variation of the manufacturing condition of the liquid crystal panel when the modification ratio is 70% by weight or less and the reliability test conditions, the seizure and the spot unevenness due to the residual DC may occur remarkably due to high-temperature energization aging. A higher denaturation ratio configuration is desirable. However, if the amount of the photo-alignment film is too high to cover the surface area on the liquid crystal side, the modification treatment material is present on the surface of the liquid crystal side because the photo-alignment film is not sufficiently exposed to the liquid crystal side. , AC image sticking may worsen. Therefore, a denaturation ratio that simultaneously solves residual DC image sticking and AC image sticking is desired.

In addition, it is expected that AC image sticking can be suppressed by introducing a chemical substance capable of preventing liquid crystal adsorption and side chain deformation. Furthermore, improvement in print applicability such as spin coating, flexographic printing, and inkjet can be expected.

So far, homopolymers using only photo-aligned diamine units, and copolymerization of photo-aligned diamine units and non-photo-aligned diamine units, liquid crystal tilt due to high-temperature energization aging, although depending on the manufacturing conditions of the liquid crystal panel. The resulting alignment unevenness sometimes causes display quality and reliability problems. The introduction of a diamine unit that is not photo-aligned tends to reduce the above problem. Furthermore, the copolymerization of a high introduction rate of a photo-aligned diamine unit and a non-photo-aligned diamine unit results in a decrease in photosensitivity due to a decrease in photofunctional group density, a longer light irradiation time, transmittance, response characteristics, etc. There was concern about deterioration of display characteristics. According to the present invention, it is possible to provide a plurality of types of photo-alignment film materials having the same electrical characteristics and optical characteristics.

The inventor of the present invention includes a polymer for alignment film material that can have photoalignment by including a compound having photoalignment and has excellent display quality, reliability, and display characteristics, and a liquid crystal display panel using the same Then, the liquid crystal display device was examined, and various structures included in the alignment film and the polymer for the alignment film material were examined, and attention was paid to the molecular structure and composition of the main chain and the side chain.
The present inventor optimized the photopolymer copolymerization ratio in a compound having at least two side chains having a photofunctional group so that the compound can be incorporated to have photo-alignment properties, and has no problem in electro-optical characteristics. The range of the amount of use in which no occurrence occurred was found. Furthermore, the modification ratio was also optimized, and a range in which the electro-optical characteristics were similarly excellent was found. Then, the present inventors have found a desirable polymer structural composition as a photo-alignment film while having excellent electro-optical characteristics. As a result, the inventors have conceived that the above-mentioned problems can be solved brilliantly in the present invention, and have reached the present invention.

That is, the present invention is a liquid crystal display panel having a configuration in which a liquid crystal layer containing liquid crystal molecules is sandwiched between a pair of substrates, and having a photo-alignment film on the liquid crystal layer side surface of at least one substrate, The alignment film is a polymer having an essential structural unit as a first structural unit having a photofunctional group that exhibits, by light irradiation, the property of controlling the orientation of liquid crystal molecules by photochemical reaction of at least one of photocrosslinking reaction and photoisomerization reaction. A film formed by using an alignment film material that has been subjected to alignment treatment by light irradiation, wherein the first structural unit has at least two side chains having the photofunctional group, and the polymer Is the introduction ratio of the second structural unit that exhibits the property of controlling the orientation of the liquid crystal molecules regardless of light irradiation, and the total of the first structural unit and the second structural unit is 100 mol%, it is 0 mol% or more, The photo-alignment film has the alignment. Consists of a film formed using a film material and a film of a material other than that, and the liquid crystal layer side surface portion of the photo-alignment film is configured to be a film formed using the alignment film material. When the ratio of the solid content of the other material to the solid content of 100% by weight of the alignment film material and the other material is defined as the modification ratio, the modification ratio is the introduction ratio of the second constituent unit. A liquid crystal display panel (also referred to as the first aspect of the present invention) is 0 to 90% by weight when 0 mol% or more and less than 4 mol%, and 0 to 95% by weight when the introduction ratio is 4 mol% or more. . In addition, 0 to 90% by weight means 0% by weight or more and 90% by weight or less. 0 to 95% by weight means 0% by weight or more and 95% by weight or less. Further, assuming that the polymer in the alignment film material has a polysiloxane structure, a first structural unit in which two vertical side chains are attached to the same Si atom can be considered. In the first structural unit having a branched chain structure portion, the number of side chains is counted with each branched chain as a side chain.

The second structural unit is a structural unit (monomer unit) in the polymer that exhibits the property of controlling the alignment of liquid crystal molecules regardless of light irradiation. In the alignment control technology for liquid crystal molecules, the liquid crystal molecules are aligned. What is necessary is just to express the characteristic to control and to evaluate that such a characteristic is expressed by methods other than light irradiation. As the introduction ratio of the second structural unit, when the total of the first structural unit and the second structural unit is 100 mol%, it is 0 mol% or more (with all diamine units being 100 mol%) (or the total unit composition ratio is 100 In the case of%, the unit is only%. In other words, the unit of the monomer component introduction ratio can be expressed in mol%, but may be expressed in% as the composition ratio of the constituent units. The term “0 mol% or more” means that the polymer does not have to have a second structural unit, that is, the second structural unit is an optional component, but the use of a material having a high-cost photo-orientation property. In order to achieve an advantageous effect such as reducing the amount, it is preferable that the second structural unit is present in the polymer. That is, the introduction ratio is preferably more than 0 mol%. More preferably, it is in a form exceeding 4 mol%. The introduction ratio of the second structural unit is preferably 10 mol% or less. More preferably, it is 8 mol% or less, and particularly preferably 6 mol% or less. By adopting such a configuration, a liquid crystal display panel having practically uniform display quality, sufficient reliability, and excellent electro-optical characteristics while keeping the modification ratio and pretilt angle within a more preferable range. Can be obtained.

The modification ratio is a ratio of the solid content of the material other than the alignment film material to the solid content of 100% by weight of the alignment film material and the other material for forming the photo-alignment film. When the introduction ratio is 0 mol% or more and less than 4 mol%, the modification ratio is 0 to 90 wt%, and when the introduction ratio of the second structural unit is 4 mol% or more, the modification ratio is 0 to 95 wt%. This is supported by the result of the reliability test in Examples described later. In addition, the modification ratio is optimized in order to reduce the amount of photo-alignment diamine, photo-alignment material, and the like used.
Here, the upper limit of the modification ratio can be set higher when the introduction ratio of the second structural unit is higher than when it is relatively low as described above.

The photo-alignment film includes a film formed using the alignment film material and a film formed using other materials, and the liquid crystal layer side surface portion of the photo-alignment film uses the alignment film material. When the ratio of the solid content of the other material with respect to 100% by weight of the solid content of the alignment film material and the other material is defined as the modification ratio, The modification ratio is preferably 23 to 95% by weight. Particularly preferred is a form exceeding 70% by weight. In the present specification, the base polymer that is not localized on the liquid crystal layer side surface is called a modification treatment material. In other words, the modification ratio is, in other words, the alignment film material and modification of the solid content of the modification treatment material. This is the ratio of the solid content of the treatment material to the total weight.
Desirable polymer structural composition in which the first structural unit has at least two side chains having a photofunctional group as a photo-alignment film while making the modification ratio within the above range excellent in electro-optical characteristics. Can be revealed. In the present specification, the above-mentioned “film of other materials” means a film (hereinafter referred to as the above-mentioned film) formed in the technical field of the present invention using the alignment film material on the liquid crystal layer side surface portion of the photo-alignment film. It may be different from the film formed on the liquid crystal layer side surface portion of the photo-alignment film. Among them, the above-mentioned “film of other materials” preferably has a higher introduction ratio of the second structural unit than the film formed on the liquid crystal layer side surface portion of the photo-alignment film. Is particularly preferably a film formed using a polymer that does not substantially contain the first structural unit and that is not a novel chemical substance. Thereby, the usage-amount of the said raw material which has the photo-alignment diamine or photo-alignment property can be reduced as mentioned above. In other words, a mode in which the photo-alignment film layer of the photo-alignment film is localized on the surface of the liquid crystal layer side of at least one substrate is preferable. The localization need not be completely localized as long as it is localized to the extent that the effects of the present invention are exhibited. In addition, the form comprised by mixing the polymer which comprises the substrate side layer of a photo-alignment film and the polymer which comprises the liquid crystal side layer of a photo-alignment film is suitable.

The photo-alignment film preferably controls the alignment of liquid crystal molecules so that the average pretilt angle of the liquid crystal layer is 88.6 ° ± 0.3 °. Within such a range, it can be said that it is within an allowable range in the technical field of the present invention, and the amount of gradation shift can be sufficiently reduced. If the amount of gradation deviation is within ± 2 gradations, a more preferable range is 88.6 ° ± 0.15 °. Further, when the gradation shift amount is within ± 1 gradation, an even more preferable range is 88.6 ° ± 0.1 °.

The photo-alignment film is composed of a film formed using the alignment film material and a film formed using other materials, and the liquid crystal layer side surface portion of the photo-alignment film uses the alignment film material. When the ratio of the solid content of the other material to the solid content of 100% by weight of the alignment film material and the other material is defined as a modification ratio, The modification ratio is 23 to 95 wt% when the introduction ratio of the second structural unit is 0 mol% or more and less than 4 mol%, and 70 to 95 wt% when the introduction ratio is 4 mol% or more and 6 mol% or less. When the introduction ratio exceeds 6 mol% and less than 8 mol%, it is preferably 85 to 95% by weight, and when the introduction ratio is 8 mol%, it is preferably 92 to 95% by weight.
Such a configuration is preferable in that a range of a pretilt angle desirable from the viewpoint of optical characteristics can be satisfied.
A preferable embodiment of the present invention includes a combination of a preferable range of the introduction ratio of the second structural unit and a desirable pretilt angle range. For example, when the form in which the introduction ratio of the second structural unit is 6 mol% or less is preferable and the above-described desirable pretilt angle range is combined, the modification ratio is such that the introduction ratio of the second structural unit is 0 mol%. As mentioned above, one of the preferred embodiments of the present invention is a form in which the content is 23 to 95% by weight when it is less than 4 mol%, and 70 to 95% by weight when the introduction ratio is 4 mol% or more and 6 mol% or less. It is done.

In order to exhibit the effect of solving the seizure due to residual DC and the occurrence of spot unevenness, the range in which the modification ratio is set is preferably 23% by weight or more as described above. More preferably, it is in a form exceeding 70% by weight.

As described above, it is desirable from the viewpoint of display quality and reliability of the liquid crystal panel that the diamine unit that is not photo-aligned is introduced in an amount exceeding 0 mol%, more preferably in an amount exceeding 4 mol%. In the present invention, it is preferable to satisfy the relationship between the introduction ratio of the second structural unit and / or the numerical range of the modification ratio and the relationship between the introduction ratio of the second structural unit and the modification ratio. The introduction ratio and the modification ratio may be in the preferred pretilt angle range described above without any problem in reliability.

The photo-alignment film allows the liquid crystal display panel to have a difference in pretilt angle of −0.05 ° or more when the application time of AC voltage to the liquid crystal display panel is 0 hour and an average value of 36 to 40 hours. It is preferable to control the orientation of molecules. In other words, the photo-alignment film in the liquid crystal display panel has a difference in pretilt angle when the application time of the AC voltage to the liquid crystal display panel is 0 hour and a simple average of 36 to 40 hours (in this specification, , Which is also referred to as Δtilt) is preferably one in which the orientation of liquid crystal molecules is controlled so that it is −0.05 ° or more. Note that the simple average means that the average value was calculated by the 5-point average value method recently in consideration of the measurement error, that is, the Δ tilt value was measured every other hour from 36 hours to 40 hours later, It means that those 5 points are averaged.
More preferably, for example, the difference in pretilt angle between the application time of 0 hour and 36 hours is −0.05 ° or more.

As for the said modification | denaturation ratio, it is especially preferable that the introduction ratio of a 2nd structural unit is 10 mol% or less. With such a configuration, it is possible to satisfy a desirable Δ tilt range from the viewpoint of AC image sticking characteristics.

The first structural unit of the polymer in the alignment film material has at least two side chains having the photofunctional group. Having at least two side chains having a photofunctional group means having two side chains, each having a photofunctional group, further having side chains, at least two side chains, or each side. The form which has a photofunctional group in a chain | strand is mentioned. In other words, as long as the first structural unit has at least two side chains each having a photofunctional group, the first structural unit may further have a side chain not having a photofunctional group. Among these, a form in which the first structural unit has two or more side chains and each has a photofunctional group is more preferable. Further, having at least two side chains having a photofunctional group may be a form in which at least two side chains extend from the main chain portion of the polymer, and the side chains are the main chain of the polymer. It may extend from the chain portion as a starting point, and the side chain may have a branched chain structure portion. In the present specification, the branched chain structure portion means a portion of two or more chains extending from the main chain side starting from the branch point of the side chain, and each of these chains is counted as one side chain. A mode in which the first structural unit has a branched chain structure portion having two or more side chains is preferable, and a mode in which each of the side chains has a photofunctional group is particularly preferable. And it is preferable that the 2nd structural unit of the polymer in the said alignment film material has a side chain which has an orientational functional group. For example, as a combination of structural units, the first structural unit has a vertical alignment (VA) side chain having a photofunctional group (first structural unit (1)) and another type of side chain (first structural unit). (2)) having two types, and the first structural unit has a vertical alignment side chain having a photofunctional group, and the second structural unit has a vertical alignment side chain having no photofunctional group, The first structural unit has a vertical alignment side chain having a photofunctional group, and the second structural unit has a vertical alignment side chain (second structural unit (1)) that does not have a photofunctional group. (2nd structural unit (2)) etc. which are mentioned are mentioned as a suitable form. Here, the different types of side chains include those having different bonding groups to the main chain.

The essential constituent unit of the polymer in the alignment film material preferably has the same orientation control direction. The said same direction should just be what can be said that an orientation control direction is the same direction in the technical field of this invention, and should just be substantially the same direction.

The photo-alignment film preferably controls the alignment of liquid crystal molecules uniformly in the plane of the alignment film. The term “uniform” may be anything that can be said to uniformly control the orientation of liquid crystal molecules in the technical field of the present invention, and may be substantially uniform.

The photo-alignment film is preferably a vertical alignment film that controls the vertical alignment of liquid crystal molecules. For example, the vertical alignment film preferably controls the vertical alignment of liquid crystal molecules when no voltage is applied.

The second structural unit of the polymer in the alignment film material preferably has a side chain having a vertical alignment functional group. In other words, the orientation functional group is preferably a vertical orientation functional group. The “vertical alignment” in the above “vertical alignment control” and “vertical alignment” may be anything that can be said to be vertical alignment in the technical field of the present invention. Further, the second structural unit may have one of the vertical alignment functional groups, or may have two or more of the vertical alignment functional groups. For example, the second structural unit may have one or two side chains each having a vertical alignment functional group as one of the preferable embodiments of the present invention.

The first structural unit of the polymer in the alignment film material preferably has a side chain having at least one photofunctional group selected from the group consisting of a coumarin group, a cinnamate group, a chalcone group, an azobenzene group, and a stilbene group. Further, it is more preferable that the first structural unit has at least two side chains having the at least one photofunctional group. In other words, the photofunctional group is preferably at least one selected from the group consisting of a coumarin group, a cinnamate group, a chalcone group, an azobenzene group, and a stilbene group.

The second structural unit of the polymer in the alignment film material preferably has a side chain having a steroid skeleton. In other words, the orientation functional group is preferably a steroid skeleton.

Examples of the second structural unit of the polymer in the alignment film material include 3 to 4 rings selected from 1,4-cyclohexylene and 1,4-phenylene either directly or via 1,2-ethylene. It is preferable to have a side chain having a linearly bonded structure. In other words, the second structural unit may have 3 or 4 1,4-cyclohexylenes, 3 or 4 1,4-phenylenes, 1 , 4-cyclohexylene and 1,4-phenylene, and the total number thereof may be 3 or 4.

The polymer in the alignment film material preferably has at least one main chain structure selected from the group consisting of polyamic acid, polyimide, polyamide, and polysiloxane. In addition, as long as the effect of the present invention is exhibited, the polymer may have the main chain structure in a portion that can be called a side chain portion branched from the main chain in the technical field of the present invention.

The essential constituent unit of the polymer in the alignment film material is preferably formed of diamine. The term “formed by diamine” means that the polymer is composed of monomer units derived from monomer components essentially containing diamine, and the polymer is composed only of monomer units derived from diamine. It is not limited to the form. For example, it is particularly preferable that the polymer in the alignment film material is a copolymer of monomer components containing diamine and at least one of acid dianhydride and dicarboxylic acid.

The polymer in the alignment film material is such that the monomer component of the second structural unit is 0 mol% or more and 10 mol% with respect to 100 mol% of the total amount of the monomer component of the first structural unit and the monomer component of the second structural unit. The following is preferable. More preferred is a form exceeding 4 mol%, and still more preferred is a form being 6 mol% or less.

The liquid crystal display panel has pixels arranged in a matrix including pixel electrodes arranged in a matrix on the liquid crystal layer side of one substrate and a common electrode arranged on the liquid crystal layer side of the other substrate. The pixel preferably has two or more domains arranged adjacent to each other.
The domains preferably have liquid crystal pretilts in different directions. For example, in the case of having two domains, it is preferable that the two domains have liquid crystal pretilts in opposite directions. In the case of having four domains, one of the substrates is divided into two equal pitches, By arranging both substrates so that the dividing directions are perpendicular to each other, it is preferable to form four-divided domains in which the alignment directions of the liquid crystal molecules are four different directions.

The present invention is also a liquid crystal display panel having a configuration in which a liquid crystal layer containing liquid crystal molecules is sandwiched between a pair of substrates, and having a photo-alignment film on the liquid crystal layer side surface of at least one substrate, The film has a third structural unit having a structure derived from a photofunctional group, and a fourth structural unit having an orientation functional group, which does not have a photofunctional group and a structure derived from a photofunctional group, as essential structural units. A liquid crystal display panel (second liquid crystal display panel) in which the introduction ratio of the fourth structural unit is 0 mol% or more and 10 mol% or less when the total of the third structural unit and the fourth structural unit is 100 mol%. (Also referred to as the present invention).
Also according to the said form, it is possible to exhibit the effect of this invention similarly.
The third structural unit having a structure derived from the photofunctional group is, for example, light of the trans isomer (or cis isomer) through the excited state of the photofunctional group of the cis isomer (or trans isomer) by light irradiation. It has a structure changed to a functional group. The photorealignment structure of the photofunctional group is a structure in which the photofunctional group is photoreoriented. The photoreorientation means that only the direction of the photofunctional group is changed by light irradiation without isomerization of the photofunctional group. Therefore, the third structural unit has, for example, a structure in which the photofunctional group of the cis isomer (or trans isomer) undergoes an excited state by light irradiation, and the direction of the photofunctional group is changed as it is. That is, the structure derived from the photofunctional group means that the reversible change of the photoisomerization reaction is the main functional group in the case of low energy light even though it has the property of dimerization reaction. In other words, the structure derived from the photofunctional group may be any structure that causes a reversible change in the photoisomerization reaction.
The preferable form of the second aspect of the present invention is the same as the preferable aspect of the first aspect of the present invention described above. In addition, as a preferable form of the liquid crystal display panel in the second aspect of the present invention, as long as the effects of the present invention are exhibited, the preferable forms of the first structural unit and the second structural unit in the first aspect of the present invention are the second form. The present invention can be appropriately applied after replacing the preferred form of the third structural unit and the fourth structural unit in the present invention. For example, a mode in which the introduction ratio of the fourth structural unit exceeds 4 mol% is suitable.

In the photo-alignment film, the polymer constituting the substrate layer side is preferably a polymer of a horizontal alignment film, and the polymer constituting the liquid crystal layer side is preferably a polymer of a vertical alignment film. In other words, it is preferable that the film formed of the modification treatment material is a horizontal alignment film, and the film formed using the alignment film material is a vertical alignment film.
This reduces the amount of material used to form the polymer of the vertical alignment film, thereby reducing the cost of the photo-alignment film material and providing a vertical alignment type liquid crystal display panel when voltage is applied. It can be suitably obtained.

The present invention is also a liquid crystal display device including the liquid crystal display panel of the present invention.
The preferred form of the liquid crystal display panel provided in the liquid crystal display device of the present invention is the same as the preferred form of the liquid crystal display panel of the present invention described above.

The present invention also provides a polymer for alignment film material including a polymer having a first structural unit as an essential structural unit included in an alignment film material for forming a photo-alignment film provided in the liquid crystal display panel of the present invention. is there. As another embodiment of the present invention, a polymer having the first structural unit and the second structural unit as essential structural units, or a polymer having the third structural unit and the fourth structural unit as essential structural units is used. The polymer for alignment film materials containing a coalescence is also mentioned. The preferred form of the polymer for alignment film material of the present invention is the same as the preferred form of the polymer for alignment film material used for the liquid crystal display panel of the present invention.

As the configuration of the liquid crystal display panel and the liquid crystal display device of the present invention, in addition to the essential constituent elements having the above-mentioned specific photo-alignment film and the preferred constituent elements described above, a liquid crystal display panel and a liquid crystal display apparatus are usually used. It can have other components to configure. The same applies to the configuration of the polymer for alignment film material of the present invention. Such other components are not particularly limited.

Each form mentioned above may be combined suitably in the range which does not deviate from the gist of the present invention.

According to the liquid crystal display panel, the liquid crystal display device and the polymer for alignment film material of the present invention, it is proposed that the polymer has a desirable composition as a photo-alignment film while having excellent display quality, reliability, and electro-optical characteristics. can do.

FIG. 3 is a schematic diagram illustrating a basic structure of a molecule of a photo-alignment film polymer that can be used in Embodiment 1. FIG. 2 is a conceptual cross-sectional view illustrating a configuration after firing of a substrate according to Embodiment 1 and a conceptual diagram illustrating a configuration of a photopolymer. FIG. 3 is a schematic perspective view illustrating a relationship between a UV light alignment treatment direction and a pretilt direction of liquid crystal molecules in the first embodiment. FIG. 3 is a diagram showing a photo-alignment mechanism of Embodiment 1. FIG. 3 is a diagram showing a photo-alignment mechanism of Embodiment 1. A schematic plan view showing the direction of a liquid crystal director in one pixel (one pixel or one subpixel) and the photo-alignment processing direction for a pair of substrates (upper and lower substrates) when the liquid crystal display device of Embodiment 1 has a monodomain. FIG. A schematic plan view showing the direction of a liquid crystal director in one pixel (one pixel or one subpixel) and the photo-alignment processing direction for a pair of substrates (upper and lower substrates) when the liquid crystal display device of Embodiment 1 has a monodomain. FIG. It is a cross-sectional schematic diagram which shows the 1st arrangement | positioning relationship of the board | substrate and photomask in the division | segmentation optical alignment processing process by the mask alignment by a proxy UV exposure method. It is a cross-sectional schematic diagram which shows the 2nd arrangement | positioning relationship of the board | substrate and photomask in the division | segmentation optical alignment processing process by the mask alignment by a proxy UV exposure method. FIG. 6 is a schematic plan view showing a liquid crystal display device, a liquid crystal division pattern of one picture element, a photo-alignment processing direction, and an average liquid crystal director direction when a 7.5 V voltage is applied. 3 is a schematic plan view showing a liquid crystal division pattern of one picture element, a UV light irradiation direction, and a liquid crystal alignment direction in the liquid crystal display device of Embodiment 1. FIG. FIG. 12 is a cross-sectional view taken along the line AB of FIG. 11 when a voltage is applied, and is an alignment cross-sectional view of liquid crystal molecules. Normalized transmittance with respect to voltage / a. u. It is a graph which shows. Gray scale level / a. u. Normalized transmittance for a / a. u. It is a graph which shows. Gray scale level / a. u. Normalized transmittance for a / a. u. It is a graph which shows. Gray scale level of reference evaluation cell / a. u. Gray scale level for a / a. u. It is a graph which shows. Gray scale level of reference evaluation cell / a. u. Gray scale level difference for a / a. u. It is a graph to show. Gray scale level / a. u. Normalized transmittance for a / a. u. It is a graph which shows. Gray scale level / a. u. Gray scale level for a / a. u. It is a graph which shows. Gray scale level / a. u. Gray scale level difference for a / a. u. It is a graph which shows. It is a graph which shows the amount of gradation shifts to a pretilt angle / degree (Pretil angle / degree). 3 is a graph showing a pretilt angle / degree with respect to a modification ratio in the first embodiment. 6 is a graph showing Δtilt / degree with respect to the modification ratio in the first embodiment. 3 is a bar graph showing a voltage holding ratio (VHR) /% with respect to the modification ratio and the introduction ratio of the second constituent in Embodiment 1. 6 is a bar graph showing residual DC / V with respect to the modification ratio and the introduction ratio of the second constituent in Embodiment 1. The graph of pretilt angle / degree with respect to UV irradiation amount / mJ · cm ⁻² to the photo-alignment film is shown. A graph of Δtilt / degree against UV irradiation amount / mJ · cm ⁻² to the photo-alignment film is shown. A graph of VHR /% with respect to UV irradiation amount / mJ · cm ⁻² to the photo-alignment film is shown. It is a bar graph which shows the liquid crystal dependence of the pretilt angle / degree which arises with alignment film. FIG. 10 is a window pattern display video diagram in the second embodiment. 6 is a video diagram for evaluation of burn-in in Embodiment 2. FIG.

In this specification, the introduction ratio of the second structural unit is a value when the total of the first structural unit and the second structural unit is 100 mol%. Similarly, the introduction ratio of the fourth structural unit is a value when the total of the third structural unit and the fourth structural unit is 100 mol%. Further, the range indicated by “˜” regarding the range of the modification ratio, etc. includes the upper limit and the lower limit. For example, “23 to 95% by weight” means 23% by weight or more and 95% by weight or less. In the present specification, the side chain refers to a side chain with respect to the main chain of the polymer composed of at least one of the first structural unit to the fourth structural unit as a structural unit. In the branched chain structure portion, as described above, each branched chain is referred to as a side chain. In addition, the photo-aligned diamine having a side chain in this specification has a chain that is a side chain with respect to the polymer main chain when a polymer is formed using the photo-aligned diamine as a monomer component. Say.

Embodiment 1
(Photo-alignment film material)
The photo-alignment film material in the present embodiment exhibits a vertical alignment that can be used in a VA (Vertical Alignment) mode, and a photochemical reaction (the material of the example of the present invention has a dimerization property, It is thought that the reaction mainly using isomerization is used.) Examples of those that can give a pretilt to the liquid crystal include cinnamate, cinnamoyl, azobenzene, polyimide or polyamide having coumarin, and polysiloxane derivatives. It is done. Examples of those that cause a photodegradation reaction and give a pretilt to the liquid crystal include polyvinyl alcohol, polyamide, polyimide, polysiloxane derivatives, and the like. It should be noted that not only in the present embodiment, but also in horizontally oriented TN, ECB, and IPS (In-Plane-Switching) applications, imides and amides having no photofunctional group and imides and amides having no photofunctional group. Application can also be expected to a horizontal alignment film made into a copolymer (copolymer) with a derivative such as.

FIG. 1A and FIG. 1B are schematic views showing the basic structure of the molecules of the photo-alignment film polymer that can be used in the first embodiment.
FIG. 1A shows a polyimide structure, and FIG. 1B shows a polyamic acid structure. Note that the photopolymer and the base polymer actually used in this embodiment both have a polyamic acid structure, and both are partially thermally imidized after firing.
A vertical photo-alignment film in which a copolymer (copolymer) of a derivative such as imide and amide having the photofunctional group and a derivative such as imide and amide having no photofunctional group was formed. In FIGS. 1 (a) and 1 (b), the portion surrounded by a solid line is a unit derived from an acid dianhydride (acid dianhydride unit), and the portion surrounded by a broken line is a light beam. A unit derived from a diamine having a side chain having a functional group (photo-alignment diamine unit), and a portion surrounded by a one-dot chain line is a unit derived from a diamine having a side chain having a vertical alignment functional group (vertical Oriented diamine unit). Moreover, the introduction composition of the photo-alignment side chain having a photofunctional group and the side chain unit not having a photofunctional group of the present invention can be applied even to a main chain having a polysiloxane structure. 1 (a) and 1 (b), the photo-alignment diamine unit is drawn so as to have two side chains 21 extending from the main chain in the part surrounded by a broken line. The diamine unit has a side chain extending from the main chain, the side chain extending from the main chain has a branched chain structure part, and the branched chain structure part has at least two side chains having a photofunctional group A form may be sufficient and the said form is especially suitable.

(Example of acid dianhydride)
Preferred examples of the acid dianhydride used in Embodiment 1 include those represented by the following formulas (1-1) to (1-8). An acid dianhydride represented by the following formula (1-6) (4,10-dioxatricyclo (6,3,0) dodecane-3,5,9,11-tetraone) is particularly preferred. . In addition, the alphabet written together with a formula number is an abbreviation of each compound. In addition, dicarboxylic acid can be used suitably instead of acid dianhydride or with acid dianhydride.

As an example of the vertical diamine material used in Embodiment 1, a material having a structure represented by the following formulas (2-1) to (2-13) is preferable. Moreover, it is a form which uses 2 or more types of these, Especially, with respect to 100 mol% of diamines, a plurality of different structural units may be introduced at 1 mol% or more. In the following, the second structural unit includes one having a vertical alignment functional group (vertical side chain that is not photo-alignment). In the present embodiment, the second structural unit includes the vertical alignment function. It may have at least two functional groups. For example, the second structural unit may have two of the vertical alignment functional groups. Having two vertical alignment functional groups may be a form in which the second structural unit has two side chains extending from the main chain, and the second structural unit has a side chain extending from the main chain. In addition, the side chain extending from the main chain may have a branched chain structure portion, and the branched chain structure portion may have two side chains each having a vertical alignment functional group. For example, assuming a case where the polymer in the alignment film material has a polysiloxane structure, a second structural unit in which two vertical side chains are attached to the same Si atom can be considered. In the second structural unit having a branched chain structure portion, the number of side chains is counted with each branched chain as a side chain. Further, the second structural unit has a structure in which 3 to 4 rings selected from any of 1,4-cyclohexylene and 1,4-phenylene are linearly bonded directly or via 1,2-ethylene. It may have a side chain.

Further, for example, diamines described in JP-A Nos. 2004-67589 and 2008-299317 can be used as appropriate.

The photo-alignment diamine used in Embodiment 1 may be any one having at least two chains having a photofunctional group (photoreactive group), and is represented by the following formulas (3-1) to (3-5). A substance having a cinnamoyl group, a cinnamate group, a chalcone group, an azo group, a stilbene group, or a coumarin group in the structure diagram is preferable. Assuming that the polymer in the alignment film material has a polysiloxane structure, it may be a photo-alignment diamine in which two vertical side chains are attached to the same Si atom. In the present specification, the photofunctional group is one that causes at least one of photocrosslinking reaction and photoisomerization reaction in the technical field of the present invention, and the liquid crystal display panel has on the liquid crystal layer side surface. Any material that can be said to exhibit characteristics of controlling alignment of liquid crystal molecules in an alignment film formed by light irradiation by being included in the alignment film material forming the photo-alignment film, for example, photocrosslinking (dimerization). , Photoisomerization (cis-trans reaction), both photocrosslinking and photoisomerization can occur.

As the photo-alignment diamine used in Embodiment 1, a diamine compound described in JP-T-2009-520702 can be suitably used. Moreover, it is preferable that it is a compound represented by following Chemical formula (4). Among these, a form having a cinnamate group and / or a form having 1 to 5 fluorine atoms are preferable. In the following chemical formula (4), R ¹ and R ² are the same or different and each represents an alkyl group having 1 to 12 carbon atoms, A represents an aromatic group having 5 to 14 carbon atoms, and the aromatic group The hydrogen atom may have a part or all substituted with fluorine or chlorine atoms, B represents an alkyl group having 1 to 16 carbon atoms, and D represents a diamine having 1 to 40 carbon atoms. E represents an aromatic group, an oxygen atom, a sulfur atom, —NR ³ —, or —CR ⁴ R ⁵ —, and R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. , R ⁴ and R ⁵ are the same or different and are a hydrogen atom or an alkyl group having 1 to 24 carbon atoms, and X and Y are the same or different and are hydrogen, fluorine, chlorine, cyano group, or unsubstituted Or an alkyl group having 1 to 15 carbon atoms substituted with fluorine (preferably Details, represents an alkyl group) having 1 to 12 carbon atoms, m is an integer of 1 ~ 4, n is an integer of 2 to 4. In the formula (4), the fluorine atom (F) is substituted with a dialkylamino group having 2 to 32 carbon atoms, an alkyloxy group having 1 to 6 carbon atoms, a nitro group, and / or chlorine. Also good. Further, n is particularly preferably 2.
The photo-alignment diamine in the present invention has at least two side chains having a photofunctional group. Having at least two side chains having a photofunctional group means having two side chains, each having a photofunctional group, further having side chains, at least two side chains, or each side. The form which has a photofunctional group in a chain | strand is mentioned. In addition, in preparation of the photopolymer of this embodiment, in addition to the photo-alignment diamine in this embodiment, you may use together photo-alignment diamine other than the photo-alignment diamine in this embodiment.

Preferable specific examples of the photo-alignment diamine include, for example, compounds 4, 4 ′-() having a branched chain moiety having two side chains having a photofunctional group, represented by the following formula (5-1): 1E, 1'E) -3,3 '-(2- (2,4-diaminophenyl) propane-1,3-diyl) bis (oxy) bis (3-oxoprop-1-en-3,1-diyl ) Bis (4,1-phenylene) bis (4- (4,4,4-trifluorobutoxy) benzoate), compound 4,4 ′-(1E, 1 ′ shown by the following formula (5-2) E) -3,3 '-(2,2-bis (4-aminobenzyl) propane-1,3-diyl) bis (oxy) bis (3-oxoprop-1-en-3,1-diyl) bis ( 4,1-phenylene) bis (4- (4,4,4-trifluorobutoxy) benzoa G) Compound 4,4 ′-(1E, 1′E) -3,3 ′-(4,4′-diaminobiphenyl-2,2′-diyl) bis represented by the following formula (5-3) (Methylene) bis (oxy) bis (3-oxoprop-1-ene-3,1-diyl) bis (4,1-phenylene) bis (4- (4,4,4-trifluorobutoxy) benzoate) Can be mentioned.

The above-described polymerization of the photo-alignment film material can be synthesized by a conventionally disclosed technique (JP 2007-224273 A, JP 2007-256484 A, etc.).

The introduction ratio of imides, amides and other derivatives that do not have a photofunctional group (vertical diamine substance) is 0 mol%, 4 mol%, 6 mol%, and 10 mol%, and the photoalignment diamine is unified to polymerize the photoalignment film material. Then, the varnish was adjusted with a solvent for inkjet printing. Regarding the pretilt, Δtilt, VHR, and residual DC characteristics, the dependence on the introduction rate of derivatives such as imide and amide having no photofunctional group was examined.

As a varnish solvent for inkjet printing on a substrate, a mixed solvent of γ-butyllactone (BL), N-methylpyrrolidone (NMP), dietine glycol diethyl ether (DEDG), and diisobutyl ketone (DIBK) is suitable. . For rotary printing, a mixed solvent of BL, NMP and BC is suitable.

FIG. 2 is a conceptual cross-sectional view illustrating a configuration of the substrate according to Embodiment 1 after firing and a conceptual diagram illustrating a configuration of a photopolymer. As shown in the structural cross-sectional view after firing the substrate, the photo-alignment film of this embodiment has two layers of the modification treatment material (base polymer) 4 and the photopolymer 2 laminated in this order from the substrate 6. . In such a form, it can be said that the alignment film formed using the base polymer as a substrate is modified by the photopolymer on the surface on the liquid crystal layer side and in the vicinity thereof. The expression “modified material” means a material that becomes a substrate to be modified by a photopolymer. In 100% by weight of the alignment film, if the base polymer is 0% by weight, it is non-modified, and the modification rate increases as the weight% of the photopolymer decreases. The alignment function of the liquid crystal molecules in the alignment film is expressed by the photopolymer. As the entire alignment film, the volume of the alignment film exposed on the liquid crystal side described above is reduced, the use of new chemical substances is reduced, and the film thickness of the alignment film. The function of realizing maintenance and residual DC reduction will be exhibited. In the conceptual cross-sectional view of FIG. 2, the boundary between the base polymer and the photopolymer is clearly shown. However, in the actual embodiment, the boundary may not be clear, and the photopolymer is inclined in a gradient. It may be a form in which the ratio decreases from the liquid crystal side of the alignment film. In other words, a preferred embodiment is one in which a photopolymer and a base polymer are divided into two layers and an alignment film is formed, but the photopolymer is a liquid crystal of the alignment film so that the alignment function of liquid crystal molecules can be achieved. It only has to be unevenly distributed on the side surface. In the modification treatment between the polymers for the vertical alignment film, if the polymer is a fluorine non-introduced side chain polymer and a polymer in which fluorine is introduced into the side chain (side chain end substitution), the substrate side is a non-fluorine polymer, surface side It was confirmed that the fluoropolymer separated into layers. Therefore, a vertical alignment film of a non-fluorine-introduced side chain polymer capable of causing layer separation from the fluorine-containing photoalignment film as described above can also be used as the base polymer of the modified material.
In the conceptual diagram showing the configuration of the photopolymer in FIG. 2, as a preferable form of the photopolymer 2 which is a film formed on the surface portion on the liquid crystal layer side, the form shown in FIG. 2A and the form shown in FIG. The photopolymer 2 (photopolymer 2p or photopolymer 2q) is composed of a monomer unit 2a formed from an acid dianhydride, a monomer unit 2b formed from a photo-aligned diamine, a non-fluorine diamine ( For example, it is the form which has the monomer unit 2c formed from the above-mentioned vertical diamine) as a structural unit. The non-fluorine diamine may be a vertical diamine having a so-called vertical alignment function of liquid crystal molecules, and may have a fluorine atom. Thereby, the usage-amount of photo-alignment diamine can be suppressed and cost can be reduced. In such a form, the distribution mode of the monomer unit may be any of random, block, alternating, etc., but is formed from the monomer unit 2a formed from an acid dianhydride and a photo-aligned diamine. The form in which the monomer units 2b formed and the monomer units 2c formed from non-fluorine diamine are alternately present is preferable. As shown in the photopolymer 2p of FIG. 2, the monomer unit formed from the photo-aligned diamine has a side chain extending from the main chain, and the side chain has a branched chain structure portion. The chain structure portion may have a form having at least two side chains having a photofunctional group. As shown in the photopolymer 2q of FIG. 2, the side chain having a photofunctional group extending from the main chain is used. The form which has at least 2 may be sufficient. Here, it is preferable that the monomer unit 2c formed from the non-fluorine diamine is also distributed in the polymer to some extent without being too biased. In the conceptual diagram of FIG. 2, it is shown that F (fluorine atom) is bonded to the end of the side chain of the monomer unit 2b formed from the photo-aligned diamine. Although the form couple | bonded with the side chain terminal part of this is preferable, as long as the alignment film formed by light irradiation fulfill | performs the function to orientate a liquid crystal molecule in the direction of light irradiation, it will not specifically limit.
The non-fluorine diamine, which is a constituent of the photopolymer copolymer, plays a role of causing the pretilt to stand in the vertical direction, and improves the uniform alignment in the alignment film surface of the liquid crystal molecules when a voltage is applied, It is possible to suppress the ACM of the change with respect to the pretilt voltage.

In the photopolymer in the present embodiment, the vertical alignment diamine unit (vertical diamine unit) may be any component (0 mol% or more), but from the viewpoint of reducing the amount of photoalignment diamine used, the vertical diamine unit is an essential component. It is preferable to do. For example, the introduction ratio of the vertical diamine that is the second structural unit is 4 mol% or more (more preferably, when the total of the photo-aligned diamine that is the first structural unit and the vertical diamine that is the second structural unit is 100 mol% (more preferably, More than 4 mol%) is preferable. The upper limit may be 10 mol% or less, but is preferably 8 mol% or less. More preferably, it is 6 mol% or less. As described later, this makes it possible to have practically uniform display quality, sufficient reliability, and excellent electro-optical characteristics while keeping the pretilt angle and the modification ratio within suitable ranges. As the alignment film, a desirable polymer structural composition can be proposed.

(Method for producing alignment film)
Below, the preparation method of the alignment film of this embodiment is demonstrated.
First, the monomer components of the first structural unit and the second structural unit and acid dianhydride are copolymerized (copolymerized) by a conventionally known method.
Next, a varnish for inkjet coating (printing) the copolymerized polymer on the substrate is prepared. As the varnish solvent, a mixed solvent containing a solvent such as γ-butyllactone (BL), N-methylpyrrolidone (NMP), diethylene glycol diethyl ether (DEDG), diisobutyl ketone (DIBK) (including isomer mixture) is preferable. It is. For example, a form using 30% by weight of γ-butyllactone, 20% by weight of N-methylpyrrolidone, 40% by weight of diethyl ether dibutyl glycol, and 10% by weight of diisobutyl ketone (including isomer mixture) is preferable.

Next, varnish is applied to the substrate. As a method for applying the varnish, spin coating, flexographic printing, inkjet, and the like are preferable.
After printing the varnish, temporary baking is performed on a temporary baking hot plate, and then main baking is performed on the main baking hot plate. In addition, the heating temperature and heating time in temporary baking and main baking can be set suitably. Moreover, the film thickness of the alignment film of this embodiment can also be set suitably.

The alignment film of the present embodiment may be formed by a method called a modification process, a two-layer process, or a hybrid process. Until now, residual DC has been considered as the main cause of image sticking in liquid crystal display devices. The residual DC becomes larger as the thickness (volume) of the alignment film is thicker (larger). Accordingly, the thinner (smaller) the film thickness (volume) of the alignment film, the smaller the residual DC. On the other hand, in order to prevent coating defects in the alignment film printing process of panel manufacture, it is indispensable to maintain the alignment film to a certain thickness, for example, 60 nm or more. Therefore, as means for solving this, there is a method called a denaturing process, a two-layer process or a hybrid process. That is, the polymer of the vertical alignment film and the polymer of the horizontal alignment film, or the fluorine introduction polymer as the vertical alignment film and the non-fluorine introduction polymer as the horizontal alignment film have a certain ratio (for example, 77: 23-5 95, preferably 30:70 to 5:95, more preferably 25:75 to 10:90), by applying a uniformly mixed varnish to the substrate, immediately after coating or after alignment film coating. During the firing process, phase separation occurs between the polymers. By utilizing this action, a horizontal alignment film is formed on the substrate side, and a vertical alignment film is formed on the liquid crystal layer side. Thereby, the volume of the alignment film exposed to the liquid crystal layer side can be reduced, and the image sticking caused by the residual DC and the residual DC can be reduced. Also in this embodiment, the above-described processing can be performed if necessary. Accordingly, it is possible to realize a liquid crystal display device in which both the image sticking caused by the residual DC and the image sticking in the AC mode are reduced. From the viewpoint of reliability, it is preferable that the above-described modification ratio exceeds 70% by weight and is 90% by weight or less. Further, by setting the upper limit to 90% by weight or less, the photo-alignment film on the liquid crystal layer side surface can sufficiently function as the photo-alignment film.

Preferred examples of the diamine for modification treatment used in Embodiment 1 include compounds represented by the following formulas (6-1) to (6-6). In addition, the alphabet written together with a formula number is an abbreviation of each compound.

Examples of the acid dianhydride for modification treatment include the above-mentioned acid dianhydrides.
Furthermore, when a photo-alignment film material is required, a photopolymer having similar material characteristics and electro-optical characteristics can be produced by changing the other diamine of the copolymer composition without changing the photo-alignment diamine. By blending them, it becomes possible to stably supply and use necessary materials.

(Photopolymer of this embodiment)
For example, the photo-aligned diamine may be 4,4 ′-(1E, 1′E) -3,3 ′-(2- (2,4-diaminophenyl) propane-1,3-diyl) bis (oxy) bis ( 3-oxoprop-1-ene-3,1-diyl) bis (4,1-phenylene) bis (4- (4,4,4-trifluorobutoxy) benzoate), and the vertically-aligned diamine is 5α- A copolymer is known as cholestane-3β-ol diamine, acid dihydrate as 4,10-dioxatricyclo (6,3,1,0) dodecane-3,5,9,11-tetraone. (See Japanese Patent Publication No. 2009-520702).

(Base polymer of this embodiment)
For example, a polymer was formed by a known technique using diamine as MBDA, acid dianhydride, and cyclohexanetetracarboxylic dianhydride.

As the compound that can be contained for improving the reliability, for example, an epoxy compound described in JP-A-2008-299317 and an epoxy group-containing compound described in Japanese Patent No. 4434862 are appropriately used. Is possible.

(Liquid crystal cell manufacturing process)
After printing the varnish of the photo-alignment film, 90 ° C. for 1 minute on the pre-baked hot plate (the photo-alignment film thickness is 100 nm at this time), and 200 ° C. for 60 minutes on the main-fired hot plate, Then, P-polarized UV light having an extinction ratio of 10: 1 was irradiated at 20 mJ / cm ² from the direction of 40 ° from the substrate normal. On one substrate, a cell thickness holding material, for example, micropearl (plastic beads) 3.5 μm diameter manufactured by Sekisui Fine Chemical Co., Ltd. may be dry-sprayed in a desired amount (density: about 4 to 5 per 100 μm ² ). The ink containing the cell thickness holding material (fixed beads) may be inkjet-printed at a desired position, or a photo spacer is used at a predetermined position by using a photosensitive resin material before forming the photo-alignment film. May be formed. For other substrates, a method of screen printing or dispensing a sealing agent, for example, Structbond XN-21S manufactured by Mitsui Chemicals, or a photothermal sealing agent manufactured by Kyoritsu Chemical Industry, is suitable. As the liquid crystal injection, a vacuum injection method or a drop injection method is suitable. In the vacuum injection method, a photocurable bond manufactured by Three Bond Co., Ltd. and Sekisui Fine Chemical Co., Ltd. is suitable as the sealant.

(Basic operation-mono domain)
FIG. 3 is a schematic perspective view showing the relationship between the UV light alignment treatment direction and the pretilt direction of the liquid crystal molecules in the first embodiment. 4 and 5 are diagrams showing a photo-alignment mechanism. FIGS. 6 and 7 show the case where the photo-alignment processing in the case where the liquid crystal alignment domain is a monodomain is perpendicular to the upper and lower substrates (FIG. 6) and the case where the upper and lower substrates are antiparallel (FIG. 7). That is, FIG. 6 shows the direction of the liquid crystal director in one pixel (one pixel or one subpixel) and the optical alignment processing for a pair of substrates (upper and lower substrates) when the liquid crystal display device of Embodiment 1 has a monodomain. It is a plane schematic diagram which shows a direction (VATN [RTN]). FIG. 7 shows the direction of the liquid crystal director in one pixel (one pixel or one subpixel) and the optical alignment processing direction for a pair of substrates (upper and lower substrates) when the liquid crystal display device of Embodiment 1 has a monodomain. It is a plane schematic diagram which shows (VAECB). 8 and 9 are schematic cross-sectional views showing the first and second positional relationships between the substrate and the photomask in the split light alignment processing process by mask alignment by the proxy UV exposure method, respectively. FIG. 10 clearly shows a liquid crystal display device, a liquid crystal division pattern of one picture element, a photo-alignment processing direction, and an average liquid crystal director direction when a voltage of 7.5 V is applied. The operation principle of the liquid crystal display device of the present invention will be described with reference to FIGS.

In the liquid crystal display device of the present invention, a liquid crystal layer composed of liquid crystal molecules having negative dielectric anisotropy is sandwiched between a pair of glass substrates. A transparent electrode is formed on each surface of the pair of glass substrates in contact with the liquid crystal layer, and a vertical alignment photo-alignment film layer is formed thereon. As shown in FIG. 3, when UV light polarized parallel to the incident surface is irradiated at an angle of, for example, 40 ° (angle 3) from the substrate normal direction, the UV irradiation direction 5 is shown in FIG. The liquid crystal molecules 7 are tilted in such a direction, and a liquid crystal pretilt angle 1 can be generated. That is, a liquid crystal pretilt is generated on the incident direction side in the incident surface of the UV polarized light. In FIG. 3, the double arrows indicate the UV polarization direction.

As shown in FIG. 6, when the liquid crystal pretilt of the upper and lower substrates is almost the same and the liquid crystal material not including the chiral material is injected by directing the irradiation direction between the upper and lower substrates, the liquid crystal molecules are 90% between the upper and lower substrates when voltage is applied. Although it has a twisted structure, almost all liquid crystal molecules are aligned in the direction shown in FIG. 6 that bisects the irradiation direction (average liquid crystal director direction 18 when an AC voltage is applied). In FIG. 6, the solid line arrow indicates the light irradiation direction (upper substrate 1 direction photo-alignment processing direction) with respect to the upper substrate, and the dotted line arrow indicates the light irradiation direction (lower substrate 1 direction photo-alignment processing direction) with respect to the lower substrate. Show.

(Photo-alignment mechanism)
For example, in the photoreaction in the cinnamate-based photoalignment side chain, as shown in FIG. 4, in the unirradiated alignment film 15, the easy axis extends from the unreacted side chain 11 in a direction substantially perpendicular to the alignment film plane. 13 is formed. However, when light is obliquely irradiated to this, an easy axis 113 is generated. This is thought to be due to the reaction of the photosensitive side chain parallel to the electric vector, the unreacted side chain 111 remains, and the occurrence of a realigned side chain, resulting in the loss of the alignment regulating force in that direction. . As a result, the pretilt for aligning the liquid crystal appears so that the liquid crystal is inclined so as to be parallel to the incident plane of the polarized oblique irradiation and to be opposite to the irradiation direction.

As described above, if the unreacted photo-alignment side chain is distributed in advance with the substrate normal direction as the center, the tilt in the optical axis direction can be explained. FIG. 5 is a schematic diagram in which the photosensitive side chain 10 parallel to the electric vector E reacts, the unreacted side chain 12 remains, and the reoriented side chain is generated, and the orientation direction of the resulting structure (that is, The easy axis 14), the original average side chain distribution 16 and the correlation diagram of the electric vector E are shown. The polarized light (P wave having an electric vector E parallel to the incident surface) is ideally linearly polarized in order to efficiently photoreact the photoalignment side chain for aligning the liquid crystal. Specifically, in order to suppress an increase in light irradiation time due to illuminance loss, elliptical polarization or partial polarization is used. As the pretilt angle generation amount increases, the pretilt absolute value (angle from the normal line) becomes smaller, that is, tilts, as the extinction ratio of polarized light increases. For example, as a P wave, it has been proved by a verification experiment that polarized light having an extinction ratio of 30: 1 is lower by about 0.2 ° than polarized light having an extinction ratio of 10: 1.

As shown in FIG. 7, when the liquid crystal pretilt of the upper and lower substrates is almost the same and the liquid crystal material containing no chiral material is injected with the irradiation direction being antiparallel to the upper and lower substrates, the liquid crystal molecules are placed between the upper and lower substrates when voltage is applied. The vicinity of the interface has a homogeneous structure with a liquid crystal pretilt of about 88 ° and is oriented in the direction shown in FIG. 7 (average liquid crystal director direction 18 ′ when an AC voltage is applied). In FIG. 7, the solid line arrow indicates the light irradiation direction (upper substrate 1 direction photo-alignment processing direction) with respect to the upper substrate, and the dotted line arrow indicates the light irradiation direction (lower substrate 1 direction photo-alignment processing direction) with respect to the lower substrate. Show.

In this basic operation, the VA mode has been described in detail. However, in the horizontal alignment type TN, IPS, and ECB, the present technology can also be applied to a diamine that does not have a vertical alignment functional group or a side chain portion with hydrophilicity. It is expected that ACM can be suppressed by adapting to a copolymer (copolymer) of a diamine having a photo-alignment or horizontal alignment functional group and a diamine having a horizontal alignment type photo-alignment functional group. That is, as described above, application can be expected to a horizontal alignment film of a fluorine-free polymer that can generate layer separation with a horizontal alignment photo-alignment film.

(Divided orientation)
8 and 9 are diagrams for explaining a proxy UV exposure process using an alignment mask (photomask 29). The width of one pixel (one pixel or sub-pixel) of the liquid crystal display device is divided into two, half is exposed in one direction (the light irradiation direction 27 is the back direction from the paper surface), and half is shielded by using the photomask shading unit 23. (FIG. 8). The substrate 22 is, for example, a drive element substrate or a color filter. In the next step, the photomask light-shielding portion 23 is shifted by a half pitch to shield the exposed portion, and the light-shielded portion is exposed in the direction opposite to that in FIG. 8 (the light irradiation direction 31 is the front side from the paper surface). (FIG. 9). Accordingly, one pixel (one pixel or sub-pixel) width of the liquid crystal display device is divided into two, and regions having liquid crystal pretilts in opposite directions are present in a stripe shape. The proxy gap 21 is a gap between the photomask 29 and the photo-alignment film (vertical alignment film) 25. As for the exposure method, the irradiation direction of the substrate fixing and mask shifting alignment method, the driving element substrate, and the color filter substrate are 180 ° different within the same substrate and 90 ° between different types of substrates. A scanning exposure method may be used in which two types of exposure unit groups each having a dedicated mask of 0 ° and 180 ° are prepared.

Each of the substrates is divided into two equal pitches, and the two substrates are arranged so that the dividing directions are perpendicular to each other, whereby the alignment directions of the liquid crystal molecules are four different I, II, III, and IV. Split domains are formed (FIG. 10). In each domain boundary, the liquid crystal alignment direction on one substrate coincides with the polarizing plate absorption axis, and the liquid crystal alignment direction on one substrate is substantially perpendicular to the substrate. When applying voltage, it becomes a dark line.

In FIG. 10, dotted arrows indicate the light irradiation direction (driving element side UV alignment processing direction) with respect to the lower substrate (driving display element (TFT) substrate). A solid line arrow indicates a light irradiation direction (color filter substrate side UV light alignment processing direction) with respect to the upper substrate (color filter substrate). The up / down arrow 415 indicates the drive display element side polarizing plate absorption axis direction, and the left / right arrow 416 indicates the color filter side polarizing plate absorption axis direction.

FIG. 11 is a schematic plan view showing a liquid crystal division pattern of one picture element, a UV light irradiation direction, and a liquid crystal alignment direction in the liquid crystal display device of Embodiment 1. FIG. 12 is a cross-sectional view taken along the line AB of FIG. 11 when a voltage is applied, and is a cross-sectional view of alignment of liquid crystal molecules.

In the liquid crystal display device of the present invention, a liquid crystal layer composed of liquid crystal molecules having negative dielectric anisotropy is sandwiched between a pair of glass substrates. Transparent electrodes are formed on the surfaces of the pair of glass substrates in contact with the liquid crystal layer, respectively, and a vertical alignment layer is formed thereon.

Each substrate is divided into two equal divisions, and both substrates are arranged with a half-pitch shift, so that four different domains i, ii, iii, and iv are divided into four domains. Form (FIG. 11).

When no voltage is applied, the liquid crystal molecules are aligned in a direction perpendicular to the substrate by the alignment regulating force of the vertical alignment layer. When a voltage is applied, as shown in FIG. 12, there are four different alignment states in the four domains in which the liquid crystal molecules are twisted approximately 90 ° between the upper and lower substrates. It is considered that the average liquid crystal director in the liquid crystal cell thickness direction when a voltage is applied is aligned in a direction of approximately 45 ° between the photo-alignment processing directions perpendicular to the upper and lower substrates.

In FIG. 11, a dotted line arrow indicates a light irradiation direction (a driving display element side two-direction photo-alignment processing direction) with respect to the lower substrate (driving display element (TFT) substrate). A solid line arrow indicates a light irradiation direction (color filter side two-direction light alignment processing direction) with respect to the upper substrate (color filter substrate). The up / down arrow 515 indicates the drive display element side polarizing plate absorption axis direction, and the left / right arrow 516 indicates the color filter side polarizing plate absorption axis direction. In FIG. 12, dotted lines indicate domain boundaries.

If necessary, the substrate is heated to a predetermined temperature after drying the ink in order to fix the PB. After the formation of the cell thickness holding material, the UV alignment process of FIG. 3 or FIGS.

(Pretilt tolerance analysis by gradation deviation evaluation)
The liquid crystal panel is corrected so as to have the same characteristics as the CRT in order to provide compatibility with the CRT (compatibility). That is, as is well known, the gamma characteristic of the liquid crystal panel is close to γ = 2.2. The gradation luminance characteristics of the actual liquid crystal module (including the drive circuit) is required to be in the range of γ = 2.2 ± 0.2 in terms of video display.
When developing a new alignment film material, when the range of gradation luminance characteristics allowed for the alignment film material is set to γ = 2.2 ± 0.1, the allowable gradation shift amount is ± 4 gradations. In order to investigate the allowable range of the required pretilt angle, the voltage transmittance characteristics of liquid crystal cells having different pretilts of 88 ° to 89 ° were converted into gradation transmittance characteristics, and the amount of gradation deviation was evaluated. As a result, it was found that the permissible range was 88.6 ° ± 0.3 °. This pretilt is generated using a P-polarized light irradiation device having an extinction ratio of 10: 1. When the extinction ratio is high, the absolute value of the pretilt becomes small, but the ± relative range of the pretilt is considered not to change.

I. Measurement of voltage vs. transmission intensity of liquid crystal cell FIG. 13 shows normalized transmittance / a. u. It is a graph which shows. a. u. Means Arbitrary Unit (arbitrary unit).
(1) A voltage of 0 to 10 V was applied to each cell having a different pretilt, and the transmitted light at each voltage value was measured. The voltage vs. transmitted light intensity was plotted.
(2) Normalization of transmitted light intensity (transmittance)
Normalization was performed with the intensity when the applied voltage was 0.5 V being 0, and the intensity when being 7.5 V being 1 (VT curve).

The experimental conditions are as follows.
Liquid crystal alignment: A liquid crystal display device subjected to the photo-alignment treatment shown in FIG. 6 is manufactured. LC (Liquid crystal material name): Liquid crystal A
PI (alignment film name): photo-alignment film A (introduction ratio 4 mol% of second structural unit of single side chain type diamine and modification ratio 70 wt%)
In addition, the single side chain type diamine is a photo-aligned diamine that does not have at least two side chains having a photofunctional group, that is, 4- (4,4,4-trimethyl) which is a diamine represented by the following chemical formula (7). It means that fluorobutoxy) benzoic acid 4- {2- [2- (2,4-diaminophenyl) ethoxycarbonyl] -2- (E) -vinyl} phenyl ester was used in the preparation of the photopolymer.

-Irradiation conditions In order to change several pretilt angles in the range of 88.0 ° to 89.4 °, the UV irradiation energy was adjusted in the range of 10 mJ / cm ² to 100 mJ / cm ² .
Reference evaluation cell:
・ Pretilt: 88.6 °
-Cell thickness: 3.4 μm

II. FIG. 14 shows the normalized transmittance / a. For each gradation (gray scale level / au). u. It is a graph which shows.
The display characteristic (gradation transmittance characteristic) of the liquid crystal is corrected to γ = 2.2 so that the CRT gradation vs. luminance characteristic is obtained.
The correction of γ = 2.2, not γ = 1, makes it possible for the human eye to visually recognize the gradation transmittance (luminance) characteristic in a directly proportional relationship.
The gradation transmittance curve with γ = 2.2 is expressed by transmittance = (gradation) ^2.2 / 255 ^2.2 .
(3) Setting of gradation voltage of reference evaluation cell A cell selected as a reference (pretilt; 88.6 °, cell thickness) with a transmittance of 0.5V set to 0 gradation and a transmittance of 7.5V set to 255 gradations A gradation voltage (V gradation) corresponding to each gradation is set from the transmittance data of the VT curve (3.4 μm) (calculated by two-point measurement voltage interpolation).

(4) Calculation of cell grayscale transmittance (T _grayscale ) FIG. 15 shows normalized transmittance / a.gamma for each grayscale level (grayscale level / au). u. It is a graph which shows. FIG. 16 is a graph showing each gradation (grayscale level / au) with respect to each gradation (grayscale level / au) of the reference evaluation cell.
For each reference gradation voltage, each gradation transmittance (T _gradation ) was analyzed from the VT curve data of the evaluation target cell (two-point interpolation of measured transmittance).
(5) Calculation of the actual gradation value at the reference gradation (γ = 2.2) From the gradation transmittance curve data of the evaluation target cell, each gradation transmittance of the gradation transmittance curve of γ = 2.2 A real gradation equal to is calculated (two-point interpolation).

(6) Gradation shift evaluation FIG. 17 shows the gray scale level / a. u. Gray scale level difference for a / a. u. It is a graph which shows.
The maximum deviation (difference) between the reference gradation of γ = 2.2 and the actual gradation of the evaluation target cell was calculated for 100 gradations or less.

III. FIG. 18 shows the gray level tolerance / a. u. Normalized transmittance for a / a. u. It is a graph which shows. An actual gradation equal to each gradation transmittance of the gradation transmittance curve with γ = 2.2 was calculated (two-point interpolation). FIG. 19 shows gray scale levels / a. u. Real grayscale level at γ = 2.2 for a / a. u. It is a graph which shows. FIG. 20 shows the gray scale level / a. u. Gray scale level difference for a / a. u. It is a graph which shows.
Due to the effect of cell gap fluctuations and restrictions on the drive circuit, in the pre-tilt design of the new alignment film material, a deviation within 100 gradations or less and a maximum of ± 4 gradations was set as an allowable value with higher visibility. Therefore, the allowable value of pretilt was found to be 88.6 ° ± 0.3 °.

(Preferable range of pretilt angle)
FIG. 21 is a graph showing the amount of gradation shift with respect to the pretilt angle / degree (Pretilt angle / degree). A liquid crystal display device subjected to the photo-alignment treatment shown in FIG. 6 is manufactured, the pretilt angle when no voltage is applied is evaluated, the voltage-luminance characteristic curves of liquid crystal display devices with different pretilt angles are measured, and 7.5 V is applied. Each characteristic curve was normalized by setting the time to 255 gradations and 0.5V to 0 gradations, and the voltage-luminance characteristic at a pretilt of 88.6 ° was set to a γ2.2 curve. The maximum gradation shift amount from the γ2.2 curve was analyzed with 100 gradations or less, and plotted for each pretilt angle. The pretilt angle measuring device used was OPTI-Pro manufactured by Shintech. Assuming that the deviation tolerance value of the gradation luminance characteristic of the liquid crystal display device is ± 4 gradations, the desirable range of the pretilt angle is 88.6 ° ± 0.3 ° as described above (the hatched square area) ). If the gradation shift amount is within ± 2 gradations, a more desirable range is 88.6 ° ± 0.15 °. Further, when the gradation shift amount is within ± 1 gradation, an even more preferable range is 88.6 ° ± 0.1 °. In the experimental conditions I to III, a photo-aligned diamine that does not have at least two side chains having a photofunctional group was used. However, a light having two or more side chains having a photofunctional group according to this embodiment is used. When the oriented diamine is used, the desirable range of the pretilt angle is the same. In the following, unless otherwise specified, evaluation such as reliability evaluation is performed using a liquid crystal display device manufactured using the photo-alignment diamine of the present embodiment.

(Pretilt evaluation)
FIG. 22 is a graph showing the pretilt angle / degree with respect to the modification ratio in the first embodiment. The liquid crystal display device (non-chiral RTN) subjected to the photo-alignment treatment shown in FIG. 6 was manufactured, and the dependency of the modification ratio on the pretilt angle characteristics when no voltage was applied and the introduction of the second component of the copolymer The dependence of the ratio (0% to 10%) was investigated. The pretilt angle measuring device used was OPTI-Pro manufactured by Shintech.

From the viewpoint of optical characteristics, when the desirable pretilt angle range is 88.6 ° ± 0.3 ° (more desirably, 88.6 ° ± 0.15 °), the hatched range is a preferable condition. That is, when the introduction ratio of the second constituent is 0 mol%, the modification ratio is 23 to 90% by weight, when the introduction ratio of the second constituent is 4 mol%, the modification ratio is 70 to 95% by weight, and the introduction ratio of the second constituent is The desired pretilt angle range can be achieved when the modification ratio is 85 to 95% by weight at 6 mol%, and the modification ratio is 92 to 95% by weight when the introduction ratio of the second constituent is 8 mol%. it can.

In the photo-alignment film, the modification ratio is 23 to 95% by weight when the introduction ratio of the second structural unit is 0 mol% or more and less than 4 mol%, and the introduction ratio is 4 mol% or more and 6 mol% or less. In this case, it is 70 to 95% by weight, and when the introduction ratio of the second structural unit exceeds 6 mol% and less than 8 mol%, it is 85 to 95% by weight, and the introduction ratio of the second structural unit is 8 mol%. In this case, a desired pretilt angle range can be achieved by the condition of 92 to 95% by weight.

In a more preferred embodiment, the modification ratio is 23 to 90% by weight when the introduction ratio of the second structural unit is 0 mol%, and 70 to 95 when the introduction ratio is more than 0 mol% and 4 mol% or less. Wt% (more preferably 70 to 90 wt%), and when the introduction ratio exceeds 4 mol% and 6 mol% or less, it is 85 to 95 wt%, and the introduction ratio exceeds 6 mol% and 8 mol%. In the following cases, the form is 92 to 95% by weight. In addition, the introduction ratio of the second structural unit is from the viewpoint of practically uniform display quality, sufficient reliability, and excellent electro-optical properties while keeping the pretilt angle and the modification ratio within the preferred ranges. It is preferable that it is 6 mol% or less, and from this, the embodiment in which the introduction ratio of the second structural unit is 6 mol% or less is preferable in the above-described desirable pretilt angle range. In consideration of the fact that the modification ratio for solving the above-mentioned burn-in is preferably more than 70% by weight, the modification ratio exceeds 70% by weight when the introduction ratio of the second structural unit is 0 mol%. When the introduction ratio is more than 0% by weight and more than 0% by mole and less than 4% by mole, it can be said that one of the preferred forms is more than 70% by weight and less than 95% by weight.

Furthermore, the conditions showing the same value as the pretilt 88.6 ° which is a preferable condition are that the introduction ratio of the second constituent is 4 mol% and the modification ratio is 90 wt%, and the introduction ratio of the second constituent is 6 mol% and the modification ratio is 92 wt%. %.
In this diamine having two photofunctional functional side chains per diamine (branched chain structure), when the introduction ratio of the pretilt angle is high, a single side chain photodiamine type photopolymer (Japanese Patent Application No. 2010-192954). Compared to the above, the tendency curve depending on the denaturation ratio is different and the pretilt decreasing slope is steep.

(ACM evaluation (Δ tilt evaluation))
FIG. 23 is a graph showing Δtilt / degree with respect to the modification ratio in the first embodiment. The liquid crystal display device subjected to the photo-alignment treatment shown in FIG. 6 was manufactured, and the Δ tilt characteristics depended on the modification ratio and the copolymer introduction ratio (0% to 10%). I investigated. ACM applies AC voltage application stress 30Hz, 7.5V, AC voltage application is set to 0V after a certain time, pretilt angle is measured, the AC voltage is applied again, and AC voltage is applied again after a certain time. Was measured, and the pretilt angle was measured repeatedly until the cumulative AC voltage application time was 0 to 40 hours. Furthermore, the average value of the most recent five points of the difference (Δtilt) of the pretilt angle of each hour was evaluated at the initial stage (AC voltage application time was 0 hour) and after 36 to 40 hours. As the Δ tilt measuring device, OPTI-Pro manufactured by Shintech Co., Ltd. was used.

From the viewpoint of image sticking characteristics, if the desirable range of Δ tilt is −0.05 ° or more, when the introduction ratio of the second constituent is 0 mol% or more and less than 4 mol%, the modification ratio is 0 to 90 wt%, When the introduction ratio of the two constituents is 4 mol% or more and 10 mol% or less, the modification ratio can be achieved from 0 to 95% by weight. Compared with a single side chain photodiamine type photopolymer, the Δ tilt characteristic is good.

Furthermore, considering the conditions for achieving the desirable pretilt angle of 88.6 ° ± 0.3 ° (more desirably, 88.6 ° ± 0.15 °), the modification ratio is the second When the introduction ratio of the constituent is 0 mol% or more and 4 mol% or less, it is 70 to 90% by weight. When the introduction ratio of the second constituent is more than 4 mol% and 6 mol% or less, it is 85 to 95% by weight. When the body introduction ratio exceeds 6 mol% and is 8 mol% or less, the respective conditions are 92 to 95 wt%.
When the introduction ratio of the second constituent is 4%, the modification ratio is 90%, the introduction ratio of the second constituent is 6%, and the modification ratio is 92%, the same condition as the pretilt of 88.6 ° is preferable. It was found that the tilt characteristic shows approximately −0.03 °.

(VHR evaluation)
FIG. 24 is a bar graph showing the voltage holding ratio (VHR) /% with respect to the modification ratio and the introduction ratio of the second constituent in Embodiment 1. The liquid crystal display device subjected to the photo-alignment treatment shown in FIG. 6 was prepared, and the dependency of the modification ratio and the introduction ratio of the second constituent of the copolymer were 0 mol% or 4 mol on the voltage holding ratio (VHR) characteristics. %, The dependence of the modification ratio of 70 to 95% by weight was examined. The evaluation device used was a liquid crystal property measuring system manufactured by Toyo Technica. The frame period was 16.7 msec, voltage application was 5 V, measurement temperature was 70 ° C., and area ratio was evaluated. Regarding the voltage holding ratio (VHR) characteristics, the modification ratio and the introduction ratio of the second constituent of the copolymer were compared for the conditions shown in FIG. 24. As a result, the introduction ratio of the second constituent was kept constant at 4%. It was found that VHR tends to increase as the denaturation ratio increases.
When the introduction ratio of the second component is 4% and the modification ratio is 90% under the condition showing the same value as the pretilt of 88.6 °, which is a preferable condition, the VHR characteristics are at a level with almost no problem (about 99.5%). I confirmed that there was.
In the photopolymer in FIG. 24, the use of branched side chain type diamine means that a photo-aligned diamine having a branched chain having a photofunctional group in at least two chains, that is, a diamine represented by the above chemical formula (5-1), It means that it was used for preparation. In addition, the use of a single side chain type diamine means a photo-aligned diamine having no photofunctional group in at least two chains, that is, 4- (4,4,4-trifluoro) which is a diamine represented by the above chemical formula (7). Means that butoxy) benzoic acid 4- {2- [2- (2,4-diaminophenyl) ethoxycarbonyl] -2- (E) -vinyl} phenyl ester was used in the preparation of the photopolymer. The photo-alignment film prepared in the same manner as in this embodiment except that this single side chain type diamine was used was measured in the same manner as in this embodiment as a reference example. The same applies to evaluation results of residual DC described later.

(Residual DC evaluation)
FIG. 25 is a bar graph showing residual DC / V with respect to the modification ratio and the introduction ratio of the second constituent in the first embodiment. A liquid crystal display device subjected to the photo-alignment treatment shown in FIG. 6 was produced, and the voltage holding ratio (VHR) characteristics were dependent on the modification ratio and the introduction ratio of the second component of the copolymer was 4 mol%. The dependence of the denaturation ratio of 70 to 95% by weight was examined. The evaluation procedure was stress conditions: AC 2.9 V (30 Hz) + DC 2.0 V, temperatures were 40 ° C. and 70 ° C., and the flicker erasing voltage after applying stress for 2 hours was measured at each temperature. The offset voltage difference before and after stress was defined as residual DC. It was found that the residual DC tends to decrease by increasing the modification ratio while keeping the introduction ratio 4 mol% of the second constituent of the copolymer having residual DC characteristics constant.
When the introduction ratio of the second component is 4% and the modification ratio is 90% by weight under the same conditions as the pretilt of 88.6 °, the residual DC characteristic is a reference using a single side chain type diamine. It was confirmed that it was below the same level as the example.
Considering all the above evaluation results, the introduction ratio of the second constituent is preferably 4 mol% and the modification ratio is preferably 90% by weight.

(Dose dependency of pretilt angle)
FIG. 26 shows a graph of pretilt angle / degree against UV irradiation amount / mJ · cm ⁻² on the photo-alignment film. The variation of the pretilt angle depending on the UV irradiation amount of the photo-alignment film was investigated.
In the photo-alignment film X, the first structural unit of the present embodiment has a branched side chain structure in which the side chain has a photofunctional group, the introduction ratio of the second structural unit is 0 mol%, and the modification ratio is 70 wt%. Material.
The photo-alignment film A is a material in which the first structural unit of this embodiment has a single side chain structure having a photofunctional group, the introduction ratio of the second structural unit is 4 mol%, and the modification ratio is 70 wt%. .
Under the condition of a UV irradiation amount of 20 mJ / cm ² , the difference in pretilt angle of 0.15 ° between the photo-alignment film X and the photo-alignment film A is within a preferable range. The amount of irradiation within the pretilt tolerance (88.6 ° ± 0.3 °) in the photo-alignment film X is 18 mJ / cm ² to 41 mJ / cm ² .

(Dose dependency of Δtilt)
FIG. 27 shows a graph of Δtilt / degree against UV irradiation amount / mJ · cm ⁻² to the photo-alignment film. The value of Δtilt is almost constant in the range of irradiation amounts 11 to 66 mJ / cm ² of the photo-alignment film X and photo-alignment film A, and the absolute value of the photo-alignment film X is larger than that of the photo-alignment film A. It is good.

(VHR dose dependency)
FIG. 28 shows a graph of VHR /% with respect to UV irradiation amount / mJ · cm ⁻² to the photo-alignment film. The value of VHR is almost constant in the range of irradiation doses 11 to 66 mJ / cm ² of the photo-alignment film X and photo-alignment film A. The absolute value of the photo-alignment film X is slightly lower than that of the photo-alignment film A.

(Tilt liquid crystal dependency)
FIG. 29 is a bar graph showing the liquid crystal dependence of the pretilt angle / degree generated by the alignment film.
The difference in physical properties (relative values of response characteristics) of the liquid crystals A to C used is shown in Table 1 below. From the results shown in FIG. 29, it is clear that the pretilt angle of the liquid crystal hardly depends on the type of the alignment film. Moreover, the pretilt value can be made constant by adjusting the photo-alignment film composition. That is, it can be said that the above-described desirable pretilt angle range, Δtilt range, and the like are hardly affected by the types of the alignment film and the liquid crystal.
However, this pretilt evaluation is performed in a state in which no voltage is applied to the liquid crystal cell twisted by 90 ° between the upper and lower substrates, and as described above, using a P-polarized light irradiation device with an extinction ratio of 10: 1. Pretilt is generated. When the extinction ratio is high, the absolute value of the pretilt becomes small, but the ± relative range of the pretilt is considered not to change.

Embodiment 2
(Evaluation test for seizure under 60 ° C environment)
In a liquid crystal display device in which, for example, a four-domain domain in FIG. 10 is formed in one pixel or sub-pixel formed of TFT (driving element substrate) and CF (color filter substrate), the reliability of the liquid crystal driving circuit and the liquid crystal module with backlight is reliable. As a property evaluation, a high-temperature image sticking evaluation test was performed in a 60 ° C environment. The configuration of the liquid crystal display device is the same as that of the first embodiment, except for what is explicitly described in the second embodiment.

The background black display is 0 gradation (V0) display, and the white display of the window pattern display portion is 255 gradation (V255) display. FIG. 30 is a window pattern display image at this time. As an example of the case where the reliability is not good, as shown in the image in FIG. 31, edge burn-in occurs at the edge of the white display portion. FIG. 31 is a video diagram for evaluating burn-in in the halftone (V16) display.

When the display product was confirmed after 5,000 hours in an environment of 60 ° C., the result was as shown in Table 2 below, in which the first constituent unit was a branched side chain type (two side chain type) copolymer and the second constituent. In the case where a photo-alignment film having an introduction ratio of 0 mol% and a modification ratio of 70 wt% is formed on both CF and TFT substrates, the introduction of the second constituent in a copolymer having a single side chain type first constituent unit It was found that the photo-alignment film having a ratio of 4 mol% and a modification ratio of 70% by weight had superior reliability characteristics than those formed on both the CF and TFT substrates. Further, it was found that the one in which the different-type photo-alignment film was formed between the CF substrate and the TFT substrate had insufficient reliability. The branched side chain type (double side chain type) means that the branched side chain type diamine described above was used for the preparation of the photo-alignment film. The single side chain type copolymer means that the single side chain type diamine described above was used for the preparation of the photo-alignment film.

From the reliability test shown in the second embodiment, for example, the following can be said from the viewpoint of reliability. That is, in the case where an alignment film is formed using an alignment film material in which the first constituent unit includes a branched side chain type copolymer, the introduction ratio of the second constituent is 0 mol% and the modification ratio is 70 wt%. Sometimes, it is very good as a liquid crystal display device. Moreover, it can be said that the liquid crystal display panel or the liquid crystal display device preferably has a photo-alignment film having the same introduction ratio and modification ratio on the liquid crystal layer side surfaces of the pair of substrates. A photo-alignment film having the same introduction ratio and modification ratio may be any film that can be said to be substantially the same in the technical field of the present invention. In addition, it is particularly preferable that the amount of raw material used, the amount used with respect to the substrate area, the film forming process, and the like are the same. A photo-alignment film having the same introduction ratio and modification ratio may be any film that can be said to be substantially the same in the technical field of the present invention. In addition, it is particularly preferable that the amount of raw material used, the amount used with respect to the substrate area, the film forming process, and the like are the same. In Table 2 below, ◯ indicates that the liquid crystal display device is very good, and Δ indicates that the liquid crystal display device has reached a sufficient standard. Δ to ○ are intermediate evaluations between ○ and Δ. The item “determination” indicates the result of comprehensive evaluation of image sticking, spots, unevenness, and flicker.

Each form in embodiment mentioned above may be combined suitably in the range which does not deviate from the summary of this invention.

The present application claims priority based on the Paris Convention or the laws and regulations in the country to which the transition is based on Japanese Patent Application No. 2010-240118 filed on October 26, 2010. The contents of the application are hereby incorporated by reference in their entirety.

Claims

A liquid crystal display panel having a configuration in which a liquid crystal layer containing liquid crystal molecules is sandwiched between a pair of substrates, and having a photo-alignment film on the liquid crystal layer side surface of at least one substrate,
The photo-alignment film includes a first structural unit having a photofunctional group that exhibits the property of controlling the alignment of liquid crystal molecules by light irradiation by at least one photochemical reaction of a photocrosslinking reaction and a photoisomerization reaction as an essential structural unit. A film formed by using an alignment film material containing coalescence is subjected to alignment treatment by light irradiation,
The first structural unit has at least two side chains having the photofunctional group,
In the polymer, the introduction ratio of the second structural unit that exhibits the property of controlling the alignment of liquid crystal molecules regardless of light irradiation is 0 mol% or more, assuming that the total of the first structural unit and the second structural unit is 100 mol%. And
The photo-alignment film is composed of a film formed using the alignment film material and a film made of other materials, and a liquid crystal layer side surface portion of the photo-alignment film is formed using the alignment film material. And the ratio of the solid content of the other material to the solid content of 100% by weight of the alignment film material and the other material is defined as the modification ratio. When the introduction ratio of the second structural unit is 0 mol% or more and less than 4 mol%, it is 0 to 90 wt%, and when the introduction ratio is 4 mol% or more, the liquid crystal display is 0 to 95 wt% panel.
The liquid crystal display panel according to claim 1, wherein the introduction ratio of the second structural unit is 10 mol% or less.
3. The liquid crystal display panel according to claim 1, wherein the modification ratio is 23 to 95% by weight.
4. The photo-alignment film controls the alignment of liquid crystal molecules so that an average pretilt angle of the liquid crystal layer is 88.6 ° ± 0.3 °. LCD panel.
The photo-alignment film includes a film formed using the alignment film material and a film formed using other materials, and the liquid crystal layer side surface portion of the photo-alignment film uses the alignment film material. When the ratio of the solid content of the other material with respect to 100% by weight of the solid content of the alignment film material and the other material is defined as the modification ratio, The modification ratio is 23 to 95 wt% when the introduction ratio of the second structural unit is 0 mol% or more and less than 4 mol%, and 70 to 95 wt% when the introduction ratio is 4 mol% or more and 6 mol% or less. When the introduction ratio of the second structural unit is more than 6 mol% and less than 8 mol%, it is 85 to 95% by weight. When the introduction ratio of the second structural unit is 8 mol%, it is 92 to 95% by weight. Claim characterized by% The liquid crystal display panel according to any one of 1 to 4.
The photo-alignment film is a liquid crystal such that the difference in pretilt angle between an application time of AC voltage to the liquid crystal display panel is 0 hour and an average value of 36 to 40 hours is −0.05 ° or more. 6. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel controls the orientation of molecules.
7. The liquid crystal display panel according to claim 1, wherein the introduction ratio of the second structural unit exceeds 0 mol%.
The liquid crystal display panel according to claim 1, wherein the second structural unit of the polymer in the alignment film material has a side chain having an alignment functional group.
9. The liquid crystal display panel according to claim 1, wherein the essential structural unit of the polymer in the alignment film material has an alignment control direction in the same direction.
10. The liquid crystal display panel according to claim 1, wherein the photo-alignment film uniformly controls liquid crystal molecules within the alignment film plane.
The liquid crystal display panel according to claim 1, wherein the photo-alignment film is a vertical alignment film for controlling vertical alignment of liquid crystal molecules.
12. The liquid crystal display panel according to claim 11, wherein the second structural unit of the polymer in the alignment film material has a side chain having a vertical alignment functional group.
13. The liquid crystal display panel according to claim 12, wherein the second structural unit of the polymer in the alignment film material has one or two side chains each having a vertical alignment functional group.
The first structural unit of the polymer in the alignment film material has a side chain having at least one photofunctional group selected from the group consisting of a coumarin group, a cinnamate group, a chalcone group, an azobenzene group, and a stilbene group. The liquid crystal display panel according to claim 11.
12. The liquid crystal display panel according to claim 11, wherein the second structural unit of the polymer in the alignment film material has a side chain having a steroid skeleton.
The second structural unit of the polymer in the alignment film material is a linear structure of 3 to 4 rings selected from any of 1,4-cyclohexylene and 1,4-phenylene directly or via 1,2-ethylene. The liquid crystal display panel according to claim 11, wherein the liquid crystal display panel has a side chain having a structure bonded in a shape.
The liquid crystal display panel according to claim 11, wherein the polymer in the alignment film material has at least one main chain structure selected from the group consisting of polyamic acid, polyimide, polyamide, and polysiloxane.
The liquid crystal display panel according to claim 11, wherein the essential constituent unit of the polymer in the alignment film material is formed of diamine.
12. The liquid crystal display panel according to claim 11, wherein the polymer in the alignment film material is a copolymer of monomer components including diamine and at least one of acid dianhydride and dicarboxylic acid.
20. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel has photo-alignment films having the same introduction ratio and modification ratio on the liquid crystal layer side surfaces of a pair of substrates.
A liquid crystal display device comprising the liquid crystal display panel according to any one of claims 1 to 20.
21. A polymer comprising an essential constituent unit as a first constituent unit contained in an alignment film material for forming a photo-alignment film provided in the liquid crystal display panel according to claim 1. Polymer for alignment film material.