JP2021032982A - Liquid crystal panel - Google Patents

Abstract

To provide a liquid crystal panel including a liquid crystal layer that can prevent phase transition of a nematic liquid crystal composition.SOLUTION: According to an embodiment, there is provided a liquid crystal panel including a first substrate, a second substrate arranged separated from and opposite to the first substrate, and a liquid crystal layer arranged between the first substrate and second substrate. The liquid crystal layer includes a phase transition inhibitor composed of a nitroxyl radical type hindered amine compound that includes at least one liquid crystal material and prevent phase transition of the liquid crystal composition, and is composed of a nematic liquid crystal composition exhibiting positive dielectric anisotropy as a whole.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid crystal panel.

The liquid crystal panel includes a first substrate and a second substrate on which a color filter or the like arranged so as to be separated from the first substrate is formed. A liquid crystal layer made of a liquid crystal composition containing one or more kinds of liquid crystal materials is arranged between the first substrate and the second substrate. The liquid crystal material is oriented by the alignment films provided on the first substrate and the second substrate, respectively. The liquid crystal composition is selected and blended according to the display method and drive method of the liquid crystal panel, or the application thereof.

In such a liquid crystal panel, in order to prevent display defects from occurring even when used in a high temperature or low temperature environment, the temperature range that guarantees the effective operation of the liquid crystal panel, that is, the guaranteed operating temperature range is expanded. Is required. In order to expand the guaranteed operating temperature range, it is important to expand the temperature range in which the nematic liquid crystal composition maintains the nematic phase without phase transition (hereinafter referred to as the nematic phase temperature range). In particular, in a low temperature environment, the nematic liquid crystal composition may undergo a phase transition to the smectic phase. When the nematic liquid crystal composition undergoes a phase transition to the smectic phase, the alignment film may be damaged due to the volume expansion of the liquid crystal layer. Damage to the alignment film causes misalignment of the liquid crystal material, and causes display defects such as bright spots and optical patterns on the liquid crystal panel.

Japanese Unexamined Patent Publication No. 2016-153468

An object of the present embodiment is to provide a liquid crystal panel including a liquid crystal layer capable of suppressing a phase transition of a nematic liquid crystal composition.

The liquid crystal panel according to one embodiment includes a first substrate, a second substrate arranged so as to be separated from the first substrate, and a liquid crystal layer arranged between the first substrate and the second substrate. The liquid crystal layer contains at least one liquid crystal material, contains a phase transition inhibitor composed of a nitroxyl radical type hindered amine compound that suppresses the phase transition of the liquid crystal composition, and has positive dielectric anisotropy as a whole. Consists of a nematic liquid crystal composition showing the above.

FIG. 1 is a perspective view of a liquid crystal panel according to an embodiment. FIG. 2 is an enlarged view showing a partially fractured schematic cross section along the ii-ii line of FIG.

Hereinafter, some embodiments will be described with reference to the drawings. In addition, in order to clarify the description, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the actual embodiment, but this is merely an example, and the present invention is provided. It does not limit the interpretation. Further, in this specification and each figure, components exhibiting the same or similar functions as those described with respect to the preceding figures may be designated by the same reference numerals, and duplicate detailed description may be omitted as appropriate. ..

<LCD panel>
Hereinafter, the liquid crystal panel PNL according to the embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of the liquid crystal panel PNL according to the embodiment, and FIG. 2 is an enlarged view showing a partially broken schematic cross section along the ii-ii line of FIG. The liquid crystal panel of the present invention may include members other than those specifically described in the embodiments.

In the present embodiment, the direction parallel to the short side of the liquid crystal panel PNL is the first direction X, the direction parallel to the long side of the liquid crystal panel PNL is the second direction Y, and the first direction X and the second direction Y are The vertical direction is the third direction Z. The first direction X and the second direction Y are orthogonal to each other, but may intersect at an angle other than 90 degrees. Further, in the present embodiment, the positive direction of the third direction Z is defined as up or up, and the negative direction of the third direction Z is defined as down or down.

The liquid crystal panel PNL has a first substrate SUB1 and a second substrate SUB2 arranged to face each other. The first substrate SUB1 has a terminal portion TR. The second substrate SUB2 faces the first substrate SUB1 except for the terminal portion TR of the first substrate SUB1.

A pixel electrode PE, a common electrode CE, and the like are provided in a region of the first substrate SUB1 facing the second substrate SUB2. A drive IC chip IC and a flexible circuit board (not shown) are mounted on the terminal portion TR of the first board SUB1. The second substrate SUB2 is provided with a color filter CF, a light-shielding film BM, and the like.

The first substrate SUB1 and the second substrate SUB2 define a certain cell gap between them, and the peripheral portion of the first substrate SUB1 and the peripheral portion of the second substrate SUB2 excluding the terminal portion TR are frames. It is adhered by a sealing material SP formed in a shape. A liquid crystal is sealed inside the sealing material SP to form a liquid crystal layer LC. The frame-shaped sealing material SP and the light-shielding film BM define a non-display area NDA. The non-display area NDA defines the display area DA inside the non-display area NDA. The display area DA is, for example, rectangular, and is composed of a plurality of pixels PX arranged in a matrix of m × n (where m and n are positive integers).

In the present embodiment, the liquid crystal panel PNL selectively transmits light incident on the first substrate SUB1, the liquid crystal layer LC, and the second substrate SUB2 from the lighting device (not shown) at each pixel PX to obtain an image. It corresponds to a so-called transmissive liquid crystal panel having a transmissive display function for displaying.

As shown in FIG. 2, the first substrate SUB1 has a first insulating substrate S1. The first insulating substrate S1 is a light-transmitting insulating substrate, for example, a glass substrate. An optical element OD1 including a first polarizing plate PL1 is attached to the lower surface of the first insulating substrate S1.

The first insulating film IL1 is provided on the surface of the first insulating substrate S1 on the liquid crystal layer LC side. The first insulating film IL1 can be formed of an organic material such as an acrylic resin.

A common electrode CE is provided on the surface of the first insulating film IL1 on the liquid crystal layer LC side. The common electrode CE is formed of, for example, a light-transmitting conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), a light-reflecting conductive material containing Ag, Al, Al alloy, or the like. can do.

A second insulating film IL2 is provided on the surface of the common electrode CE on the liquid crystal layer LC side. The second insulating film IL2 can be formed of, for example, an inorganic material such as silicon oxide or silicon nitride.

A pixel electrode PE is provided on the surface of the second insulating film IL2 on the liquid crystal layer LC side. The pixel electrode PE faces the common electrode CE via the second insulating film IL2. A slit is formed in the pixel electrode PE, and the slit penetrates the pixel electrode PE to expose a part of the surface of the second insulating film IL2. The pixel electrode PE can be formed of, for example, a light-transmitting conductive material such as ITO or IZO.

The first alignment film AL1 is arranged on the surface of the first substrate SUB1 on the LC side of the liquid crystal layer. The first alignment film AL1 covers the second insulating film IL2 and the pixel electrode PE. The first alignment film AL1 is, for example, a photodecomposable polyimide that has been photoaligned.

The second substrate SUB2 has a second insulating substrate S2. The second insulating substrate S2 is a light-transmitting insulating substrate, for example, a glass substrate. An optical element OD2 including a second polarizing plate PL2 is attached to the upper surface of the second insulating substrate S2.

A color filter CF is arranged on the surface of the second insulating substrate S2 on the liquid crystal layer LC side. In the color filter CF, red (R), green (G), and blue (B) color filters CFR, CFG, and CFB (subpixels) are periodically arranged. A set of these three color sub-pixels constitutes one pixel.

A light-shielding film BM is arranged between the red, green, and blue color filters CFR, CFG, and CFB, and in the non-display region NDA. The light-shielding film BM in the display region DA is formed in a grid pattern in a plan view, and divides the red, green, and blue color filters CFR, CFG, and CFB to prevent color mixing between adjacent color filters. The light-shielding film BM is, for example, a black resin, a low-reflection metal, or the like.

The overcoat layer OC is arranged so as to cover the color filters CFR, CFG, CFB and the light-shielding film BM, and covers the surface irregularities of the color filters CFR, CFG, CFB and the light-shielding film BM to form a flat surface. (Flattening film).

A second alignment film AL2 is arranged on the surface of the second substrate SUB2 on the liquid crystal layer LC side. The second alignment film AL2 is, for example, a photodegradable polyimide similar to the first alignment film AL1.

The sealing material SP adheres the peripheral edge portion of the first substrate SUB1 excluding the terminal portion TR and the peripheral edge portion of the second substrate SUB2 in a frame shape. Such a sealing material SP is formed of, for example, a sealing material such as an ultraviolet curable resin or a thermosetting resin, and can be formed by a method of continuously drawing from a start point to an end point using a dispenser or the like.

The liquid crystal layer LC is provided between the first substrate SUB1 and the second substrate SUB2 excluding the terminal portion TR. More specifically, the liquid crystal layer LC is located between the first alignment film AL1 and the second alignment film AL2. In the present embodiment, the liquid crystal layer LC is composed of a nematic liquid crystal composition having a positive dielectric anisotropy as a whole. The nematic liquid crystal composition constituting the liquid crystal layer LC will be described in detail later.

The liquid crystal panel PNL in which the common electrode CE and the pixel electrode PE are formed on the first substrate SUB1 has a component in which the electric field applied to the liquid crystal when driven has a component substantially parallel to the first substrate SUB1, so-called transverse electric field. This is an IPS mode liquid crystal panel that utilizes.

In such a liquid crystal panel PNL, in an off state in which a voltage is not applied between the pixel electrode PE and the common electrode CE, the liquid crystal material is predetermined between the first alignment film AL1 and the second alignment film AL2. Initially oriented in the direction. In such an off state, the light emitted from the lighting device (not shown) toward the lower surface of the liquid crystal panel PNL is absorbed by the optical element OD1 and the optical element OD2, resulting in a dark display. On the other hand, in the on state where an electric field is formed between the pixel electrode PE and the common electrode CE, the liquid crystal material is oriented in a direction different from the initial orientation direction due to the electric field, and the orientation direction is controlled by the electric field. In such an on state, a part of the light from the lighting device (not shown) passes through the optical element OD1 and the optical element OD2 and is displayed brightly.

Although the liquid crystal panel PNL has been described in the IPS mode in FIGS. 1 and 2, the liquid crystal panel including a liquid crystal layer made of a nematic liquid crystal composition having a positive dielectric anisotropy as a whole is particularly suitable. Not limited. That is, a liquid crystal panel such as an IPS (In-Plane Switching) mode using a horizontal electric field or an FFS (Fringe Field Switching) mode may be used, or a TN (Twisted Nematic) mode using a vertical electric field or a positive VA ( A liquid crystal panel such as a vertical element) mode may be used.

<Liquid crystal composition>
The liquid crystal layer LC comprises a nematic liquid crystal composition containing at least one liquid crystal material. The liquid crystal layer LC exhibits positive dielectric anisotropy as a whole. The liquid crystal composition constituting the liquid crystal layer LC contains, in addition to the above liquid crystal material, a nitroxyl radical type hindered amine compound as a phase transition inhibitor that suppresses the phase transition of the nematic liquid crystal composition.

In order to suppress the phase transition of the nematic liquid crystal composition, the present inventor has diligently studied a phase transition inhibitor as an additive to be added to the liquid crystal composition, and as a result, the nitroxyl radical type hindered amine compound is particularly useful. I found.

<Phase transition inhibitor>
As described above, the liquid crystal composition constituting the liquid crystal layer LC contains a nitroxyl radical type hindered amine compound as a phase transition inhibitor that suppresses the phase transition of the nematic liquid crystal composition. The nitroxyl radical type hindered amine compound is a compound in which a monovalent oxygen atom having an unpaired electron is bonded to nitrogen of a nitrogen-containing heterocycle (piperidin or the like). In some embodiments, the nitroxyl radical type hindered amine compound can be represented by the following formula (1).

In formula (1), D is a monovalent oxygen atom having an unpaired electron. n is an integer of 1 to 4. Each R ¹ is an alkyl group having 1 to 4 carbon atoms independently. Each R ¹ is preferably an ethyl group or a methyl group, more preferably a methyl group.
Y is, -O -, - CO-O -, - O-CO -, - NR 2 -, or ^{-NR 2} -CO- ^(R 2 in the Y are independently a 1 to 10 carbon atoms alkyl It is a group or an acyl group, or an aromatic group or a carbonyl group having 6 to 12 carbon atoms). Y is preferably —O— or −CO—O−.
E is an organic group having an n-valent binding site. E is, for example, a linear or branched alkylene group having 1 to 12 carbon atoms (one or two or more non-adjacent −CH ₂ − present in E is −O− and / or −. CO− may be substituted), or a cycloalkylene group, an aromatic group or a complex aromatic group (one or two or more H atoms present in E is a linear chain having 1 to 12 carbon atoms. Jo or branched alkyl ^group, -OR 2, is -N ^(R ₂₎ can be substituted by ₂ (same as ^{R 2} in the ^{R 2} is Y)).

In some embodiments, the compound of formula (1) is, for example, n = 2, Y is -CO-O-, E is a linear or branched alkylene group having 1 to 12 carbon atoms, each R. ^{Formula (1-1) in which 1} is a methyl group, n = 2, Y is −O−, E is a linear or branched alkylene group having 1 to 12 carbon atoms, and each R ¹ is a methyl group. It can be represented by any of the following formulas (1-2), n = 1, Y is -CO-O-, and each R ^{1 is a methyl group.} T in the following equation (1-1) is an integer of 1-12. T in the following equation (1-2) is an integer from 0 to 10.

Specific examples of the above formula (1-1) are represented by the following formulas (1-1-1) to (1-1-5), and specific examples of the above formula (1-2) are represented by the following formulas (1-2-2). It is represented by 1) to (1-2-2), and specific examples of the above formula (1-3) are represented by the following formulas (1-3-1) to (1-3-6).

In some embodiments, the compound of the above formula (1) is, for example, the following formulas (1-4), (1-5), and formulas, apart from the above formulas (1-1) to (1-3). It can be expressed by (1-6) and the formula (1-7).

From the viewpoint of having high solubility in the liquid crystal material, the compound of the above formula (1) is (1-1-1), (1-1-4), (1-1-5), or (1-2). The compound represented by -2) is preferable.

The nitroxyl radical type hindered amine compound is a phase transition inhibitor capable of effectively suppressing the phase transition from the nematic phase to the smectic phase. In a low temperature environment, the kinetic energy of the molecules of the liquid crystal material decreases, the intermolecular distance becomes closer, and the intermolecular interaction increases. As a result, the molecules of the liquid crystal material undergo a phase transition from the nemastic phase to the highly ordered smectic phase. Since the nitroxyl radical type hindered amine compound has a large steric hindrance, it can effectively inhibit the intermolecular interaction of the liquid crystal material and effectively suppress the phase transition of the liquid crystal material to the smectic phase.

In the liquid crystal panel according to the present embodiment, since the liquid crystal layer LC contains the above-mentioned phase transition inhibitor, the phase transition of the liquid crystal material can be effectively suppressed, and the nematic phase temperature range can be expanded. As a result, it is possible to extend the guaranteed operating temperature range while suppressing the occurrence of display defects of the liquid crystal panel, and it is possible to provide a liquid crystal panel having high reliability.

In some embodiments, the nitroxyl radical type hindered amine compound is contained in the liquid crystal composition constituting the liquid crystal layer LC at 1 ppm or more and 1000 ppm or less, and preferably 100 ppm or more and 1000 ppm or less in the liquid crystal composition. If the concentration of the nitroxyl radical type hindered amine compound in the liquid crystal layer LC is less than 1 ppm, there is a possibility that the phase transition of the liquid crystal layer LC cannot be sufficiently suppressed. If the concentration of the nitroxyl radical type hindered amine compound in the liquid crystal layer LC exceeds 1000 ppm, it becomes difficult to dissolve in the liquid crystal layer LC of the hindered amine compound, and there is a possibility that the nitroxyl radical type hindered amine compound is precipitated in the liquid crystal layer LC.

In the liquid crystal panel PNL, the nitroxyl radical type hindered amine compound acts as a phase transition inhibitor and can also function as a light stabilizer for the liquid crystal material constituting the liquid crystal layer. Generally, the liquid crystal layer is in an environment in which a voltage is applied and light is incident over the period of use of the liquid crystal panel. Therefore, if the liquid crystal panel is used for a long period of time, radicals may be generated in the liquid crystal layer to decompose a part of the liquid crystal material and deteriorate the physical characteristics of the liquid crystal layer. The nitroxyl radical type hindered amine compound can deactivate radicals generated in the liquid crystal layer as a light stabilizer and suppress the decomposition of the liquid crystal material in an environment where high voltage and light are incident. Deterioration of physical properties of the layer can be suppressed.

<Liquid crystal material>
As described above, the liquid crystal layer LC is composed of a nematic liquid crystal composition having positive dielectric anisotropy as a whole. Nematic liquid crystal compositions are generally used by selecting and blending one or more liquid crystal materials in order to obtain optical properties, electrical properties, and physical properties suitable for each application such as drive mode. Will be done.
Permittivity anisotropy (Δε _r ) is calculated by _{Δε r} = ε _// −ε _{⊥ , ε //} represents the relative permittivity parallel to the molecular length axis, and ε _⊥ is the relative permittivity perpendicular to it. Represents the rate. Molecules of liquid crystal materials generally contain a rod-shaped rigid central skeleton portion, and its relative permittivity (ε _// , ε _⊥ ) depends on the type, number, and arrangement of polar groups attached to the central skeleton portion. , Permittivity anisotropy (Δε _r ) is determined. Examples of the polar group include a cyano group and a group containing a fluorine atom.

In the present specification, having "positive permittivity anisotropy" means having 1.5 or more permittivity anisotropy, and having "neutral permittivity anisotropy". Means having a permittivity anisotropy of more than -1.5 and less than 1.5, and having "negative permittivity anisotropy" means having a permittivity anisotropy of -1.5 or less. Means that. Further, in the present specification, the nematic liquid crystal composition means a liquid crystal composition showing a nematic phase under conditions of at least normal temperature (20 ° C.) and atmospheric pressure (1 atm). The liquid crystal composition according to this embodiment has a nematic phase temperature range of, for example, −30 ° C., preferably −40 ° C., and more preferably −50 ° C. in a low temperature environment.

In the present embodiment, the nematic liquid crystal composition is configured to have positive dielectric anisotropy as a whole. By using a nematic liquid crystal composition having a positive dielectric anisotropy, the operating voltage of the liquid crystal panel can be lowered and the response speed can be improved as compared with the case where a negative dielectric anisotropy is used. The preferred dielectric anisotropy of the nematic liquid crystal composition differs depending on the drive mode of the liquid crystal panel and the like. For example, in the case of a liquid crystal panel in IPS mode or FFS mode, the dielectric anisotropy of the nematic liquid crystal composition as a whole is preferably 3.0 or more and 15.0 or less, and more preferably 5.0 or more and 10. It is 0 or less.

In some embodiments, the nematic liquid crystal composition comprises a first liquid crystal material having a positive dielectric anisotropy of 3.0 or greater. It is preferable to use a liquid crystal material having a large absolute value of dielectric anisotropy because the operating voltage of the liquid crystal panel can be lowered and the response speed can be improved. In general, when a liquid crystal material having a large absolute value of dielectric anisotropy is used, the intermolecular interaction of the liquid crystal material increases, and the liquid crystal material may undergo a phase transition to the smectic phase in a low temperature environment. .. In the present embodiment, since the nematic liquid crystal composition contains the above-mentioned phase transition inhibitor, both suppression of the above-mentioned phase transition and improvement of the response speed can be achieved at the same time. An example of the first liquid crystal material will be described in detail later.

In some embodiments, the nematic liquid crystal composition has a permittivity anisotropy greater than 0.5 and has a relative permittivity (ε _⊥ ) perpendicular to the major axis of the molecule of 2 or greater. 2 Includes liquid crystal material. When the nematic liquid crystal composition containing the second liquid crystal material is used as a liquid crystal layer of a liquid crystal panel in an IPS mode or an FFS mode that utilizes a transverse electric field, the transparency of the liquid crystal panel can be improved and the response speed can be improved. An example of the second liquid crystal material will be described in detail later.

In some embodiments, the nematic liquid crystal composition comprises a third liquid crystal material having a neutral dielectric anisotropy. In the nematic liquid crystal composition containing the third liquid crystal material, the viscosity can be reduced, the operating voltage of the liquid crystal panel can be lowered, and the response speed can be improved. In some embodiments, the viscosity under an environment of 20 ° C. of the liquid crystal composition or less 350 mPa · ^{S -1,} more preferably not more than 250 mPa · ^{S -1.} An example of the third liquid crystal material will be described in detail later.

<First liquid crystal material>
The first liquid crystal material is a liquid crystal material having a positive dielectric anisotropy of 3.0 or more as described above. The first liquid crystal material is a liquid crystal material having a positive dielectric anisotropy of 3.0 or more, excluding the second liquid crystal material. An example of the first liquid crystal material is a compound represented by the following formula (2).

In the above formula (2), R ⁴ is a halogenated or unsubstituted alkyl group or alkoxy group having 1 to 5 carbon atoms. A ¹ , A ² , and A ³ are any cyclic groups represented by the following formulas (3-1) to (3-16) independently of each other.

X ¹ is -F, -Cl, -CN, -NCS, -OCN, or -SF ₅ , or an alkyl fluoride group having 1 to 5 carbon atoms, an alkoxy fluoride group, an alkenyl fluoride group, or fluorine. It is an alkenyloxy group. L ¹ and L ² are −H or −F independently of each other. Z ¹ , Z ² and Z ³ are independent of each other, -CO-O-, -O- _{CO-, -CF 2} O-, -OCF _{2- , -CH 2} O-, -OCH ₂ -,-, respectively. _{, - - CH 2 CH 2 (} CH 2) 4 -, - C 2 F 4 -, - CH 2 CF 2 -, - CF 2 CH 2 -, - CF = CF -, - CH = CH -, - C≡ C- or single bond. a, b and c are integers 1 to 3 independently of each other (here, a + b + c = 1 to 4).

Another example of the first liquid crystal material is a compound represented by the following formula (4).

In the above formula (4), R ⁵ is a halogenated or unsubstituted alkyl group or alkoxy group having 1 to 5 carbon atoms. X ² is -F, -Cl, -OCF ₃ , -OCHF ₂ , -OCH = CF ₂ , -OCF = CF ₂ , -OCHFCF ₃ , -OCF ₂ CFHCF ₃ , -CH ₃ , -C ₂ H ₅ , Or n-C ₃ H ₇ . L ³ and L ⁴ are −H or −F independently of each other.

Specific examples of the liquid crystal material of the above formula (2) are represented by the following formulas (2-1) to (2-3), and specific examples of the liquid crystal material of the above formula (4) are represented by the following formulas (4-1) to (4-1). It is represented by (4-2).

In some embodiments, the liquid crystal composition includes both one or more liquid crystal materials of the above formula (2) and one or more liquid crystal materials of the above formula (4) as the first liquid crystal material.
In some embodiments, the liquid crystal material of the above formula (2) is 5% by weight or more and 95% by weight or more, preferably 5% by weight or more and 60% by weight or less, more preferably 15% by weight or more, based on the total weight of the liquid crystal material. Includes% by weight or more and 40% by weight or less. In some embodiments, the liquid crystal material of the above formula (4) is 1% by weight or more and 25% by weight or less, preferably 3% by weight or more and 20% by weight or less, more preferably 3 with respect to the total weight of the liquid crystal material. Includes% by weight or more and 15% by weight or less.

In some embodiments, the first liquid crystal material is 6% by weight or more and 98% by weight or less, preferably 8% by weight or more and 80% by weight or less, more preferably 18% by weight or more and 55% by weight, based on the total weight of the liquid crystal material. Includes less than% by weight.

<Second liquid crystal material>
As described above, the second liquid crystal material has a permittivity anisotropy (0.5 <Δε _r ) of more than 0.5, and has a relative permittivity of 2 or more (2 ≦) perpendicular to the major axis direction of the molecule. ε _⊥ ). That is, the second liquid crystal material has a relative permittivity (ε _// ) parallel to the molecular length axis and a relative permittivity (ε _⊥ ) perpendicular to the relatively large molecular length axis.

An example of the second liquid crystal material is a compound represented by the following formula (5).

In the above formula (5), R ⁶ and R ⁷ are each independently an alkyl group having 7 or less carbon atoms, an alkoxy group, a fluorinated alkyl group, or a fluorinated alkoxy group.
A ⁴ represents a 1 or 2 phenyl group, and two or more fluorine atoms bound organic radicals so as to be located on one side with respect to the molecular long axis. n represents 0 or 1. A ⁴ has a structure represented by any of the following formulas (6-1) to (6-3), for example.

A ⁵ represents a cyclic group having one or less fluorine atoms. A ⁵ has a structure represented by any of the following formulas (7-1) to (7-4).

Another example of the second liquid crystal material is a compound represented by the following formula (8).

In the above formula (8), R ⁸ is an alkyl group having 7 carbon atoms or less, an alkenyl group, an alkoxy group, an alkenyloxy group, an alkoxyalkyl group, a fluorinated alkyl group, a fluorinated alkenyl group, or a fluorinated alkoxy group. Represents. A ⁴ and A ⁵ are the same as those in the above formula (5), and n represents 0 or 1. X ³ represents -F, -Cl, or a fluorinated alkyl group having 4 or less carbon atoms, a fluorinated alkenyl group, a fluorinated alkoxy group, or a fluorinated alkenyloxy group.

Specific examples of the liquid crystal material of the above formula (5) are represented by the following formulas (5-1) to (5-2), and specific examples of the liquid crystal material of the above formula (8) are represented by the following formulas (8-1) to (5-2). It is represented by 8-2).

In the above equations (5-1), (5-2), (8-1), and (8-2), n and m are integers of 9 or less independently of each other.

As described above, when the nematic liquid crystal composition containing the second liquid crystal material is used as a liquid crystal layer of a liquid crystal panel such as an IPS mode or an FFS mode that utilizes a transverse electric field, the transparency of the liquid crystal panel can be improved and the response speed can be increased. Can be improved. Specifically, when a nematic liquid crystal composition containing a second liquid crystal material is used by mixing with a first liquid crystal material having a positive dielectric anisotropy of 3.0 or more, the first liquid crystal composition is oriented according to a transverse electric field. 1 The transmittance of the liquid crystal layer LC of the liquid crystal panel can be improved by directing the liquid crystal material in the direction perpendicular to the electric field.

In some embodiments, the liquid crystal composition comprises one or more second liquid crystal materials. In some embodiments, the second liquid crystal material is, for example, 1% by weight or more and 60% by weight or less, preferably 5% by weight or more and 60% by weight or less, more preferably 8% by weight or more, based on the total weight of the liquid crystal material. Contains 30% by weight or less.

_{The second liquid crystal material preferably has a dielectric anisotropy (Δε r} ) of 1.5 or more and 20.0 or less, more preferably 3.0 or more and 8.0 or less, and further preferably 4.0 or more and 7.0 or less. Has. The second liquid crystal material has a relative permittivity (ε _⊥ ) of preferably 5.0 or more, more preferably 7.0 or more, more preferably 8.0 or more, still more preferably 10.0 or more.

<Third liquid crystal material>
The third liquid crystal material is a liquid crystal material having a neutral dielectric anisotropy as described above. As described above, having a neutral dielectric anisotropy means that the permittivity anisotropy (Δε _r ) is −1.5 or more and 1.5 or less. The third liquid crystal material is a liquid crystal material having a neutral dielectric anisotropy excluding the second liquid crystal material. The third liquid crystal material is, for example, a liquid crystal material in which the molecules of the liquid crystal material do not have a polar group.

Specific examples of the third liquid crystal material are compounds represented by the following formulas (9-1) to (9-4).

In the above equations (9-1) to (9-4), n and m are integers of 9 or less independently of each other.

In some embodiments, the liquid crystal composition comprises one or more third liquid crystal materials. In some embodiments, the third liquid crystal material preferably comprises 20% by weight or more and 60% by weight or less, more preferably 40% by weight or more and 60% by weight or less, based on the total weight of the liquid crystal material. When the liquid crystal composition contains 20% by weight or more of the third liquid crystal material, the viscosity of the liquid crystal composition can be lowered, the operating voltage of the liquid crystal panel can be further lowered, and the response speed can be improved, which is preferable.

In one preferred embodiment, the liquid crystal composition constituting the liquid crystal layer LC includes the first liquid crystal material, the second liquid crystal material, and the third liquid crystal material as the liquid crystal material. In that case, the first liquid crystal material is contained in a proportion of 6% by weight to 98% by weight, preferably 8% by weight to 80% by weight, more preferably 18% by weight to 55% by weight, and the second liquid crystal material is 1% by weight. It is contained in a proportion of% to 60% by weight, preferably 5% to 60% by weight, more preferably 8% to 30% by weight, and the third liquid crystal material is preferably 20% by weight to 60% by weight, further. It is preferably contained in an amount of 40% by weight to 60% by weight. Here, the total weight of the liquid crystal material is 100% by weight. In some embodiments, the liquid crystal material contained in the nematic liquid crystal composition constituting the liquid crystal layer LC may consist of the above-mentioned first liquid crystal material, the above-mentioned second liquid crystal material, and the above-mentioned third liquid crystal material, respectively.

In some embodiments, the liquid crystal composition may comprise a liquid crystal material having a known negative dielectric anisotropy. Even if a liquid crystal material having a negative dielectric anisotropy is contained, the liquid crystal composition as a whole is contained within a range showing a positive dielectric anisotropy. Further, the nematic liquid crystal composition may have a nematic phase as a whole, and may contain a small amount of cholesteric liquid crystal, smectic liquid crystal and the like.

In some embodiments, the liquid crystal composition constituting the liquid crystal layer LC contains the first liquid crystal material and the third liquid crystal material as the liquid crystal material, and has the second liquid crystal material and negative dielectric anisotropy. The liquid crystal material to have is selectively included. In one preferred embodiment, the liquid crystal material contained in the liquid crystal composition constituting the liquid crystal layer LC is a combination of the first liquid crystal material and the third liquid crystal material, the first liquid crystal material, the second liquid crystal material, and the above. It may consist of a combination of a third liquid crystal material, or a combination of the first liquid crystal material, the second liquid crystal material, the third liquid crystal material, and a liquid crystal material having a negative dielectric constant anisotropy. Even if a liquid crystal material having a negative dielectric anisotropy is contained, the liquid crystal composition as a whole is contained within a range showing a positive dielectric anisotropy.

<Example>
Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. The low temperature stability of the liquid crystal layer was evaluated under the measurement conditions shown below for the test cells according to Examples and Comparative Examples.

In the test cells according to Examples and Comparative Examples, the configurations of the liquid crystal compositions constituting the liquid crystal layer are different from each other. As the liquid crystal composition of the test cells according to the examples and the comparative examples, a liquid crystal composition having a positive dielectric anisotropy (Δε _r = 4.1) as a whole was used. The liquid crystal composition of the test cell of the example further contains 200 ppm of the nitroxy radical type hindered amine compound of the above formula (1-1-4) as a phase transition inhibitor. On the other hand, the liquid crystal composition of the test cell of the comparative example contained only the same liquid crystal material as that of the example and did not contain the above hindered amine compound.

(Creation of test cell)
The test cell was prepared as follows. First, two glass substrates having an ITO thin film, each having a liquid crystal injection port, were prepared. Subsequently, an alignment film was formed on a glass substrate having two ITO thin films. This alignment film is a two-layer structure alignment film in which the upper layer is an imide of a photodegradable polyamic acid ester and the lower layer is an imide of a polyamic acid, and the light is subjected to photoalignment treatment by irradiating with polarized ultraviolet rays. It was an alignment film. Subsequently, the two substrates were bonded together via a spacer so that the photoalignment film had a homogeneous orientation to prepare an empty cell. Next, after injecting each liquid crystal composition into an empty cell, the test cell was prepared by sealing with an ultraviolet curable resin.

(Evaluation of low temperature stability)
The low temperature stability of the liquid crystal layer of the liquid crystal layer of the test cell was evaluated as follows. First, the test cells according to Examples and Comparative Examples were allowed to stand in a constant temperature bath maintained at an extremely low temperature of −40 ° C. Next, the presence or absence of display defects in each test cell was visually confirmed after standing for 168 hours, 336 hours, 504 hours and 1020 hours, respectively. When a display defect of a bright spot or an optical pattern was confirmed in the test cell, it was determined that a phase transition of the liquid crystal material to the smectic phase had occurred. The results are shown in Table 1 below.

As shown in Table 1, in the test cells of the examples, the phase transition to the smectic phase did not occur even after standing for 1000 hours or more in an extremely low temperature environment, and the phase transition was suppressed. On the other hand, in the test cell of the comparative example, a phase transition to the smectic phase occurred after standing for 500 hours or more in an extremely low temperature environment. From this result, it was proved that the nitroxyl radical type hindered amine compound can effectively suppress the phase transition to the smectic phase of the liquid crystal material. That is, the nematic liquid crystal composition containing the nitroxy radical type hindered amine compound has an expanded nematic phase temperature range, and the liquid crystal panel provided with the liquid crystal layer made of the liquid crystal composition can expand the guaranteed operating temperature range.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

PNL ... Liquid crystal panel SUB1 ... 1st substrate SUB2 ... 2nd substrate TR ... Terminal part PE ... Pixel electrode CE ... Common electrode CF ... Color filter BM ... Light-shielding film SP ... Sealing material LC ... Liquid crystal layer NDA ... Non-display area DA ... Display Region PX ... Pixel S1 ... First insulating substrate OD1 (PL1) ... Optical element (first polarizing plate) IL1 ... First insulating film IL2 ... Second insulating film AL1 ... First alignment film S2 ... Second insulating substrate OD2 (PL2) ) ... Optical element (second polarizing plate) CFR ... Color filter (red) CFG ... Color filter (green) CFB ... Color filter (blue) AL2 ... Second alignment film

Claims (7)

1st board and
The second substrate, which is arranged so as to be separated from the first substrate and opposed to the first substrate,
A liquid crystal layer arranged between the first substrate and the second substrate,
With
The liquid crystal layer contains at least one liquid crystal material, contains a phase transition inhibitor composed of a nitroxyl radical type hindered amine compound that suppresses the phase transition of the liquid crystal composition, and has a positive dielectric anisotropy as a whole. Consisting of anisotropy liquid crystal composition
Liquid crystal panel. The liquid crystal panel according to claim 1, wherein the phase transition is a transition from a nematic phase to a smectic phase. The liquid crystal panel according to claim 1 or 2, wherein the nematic liquid crystal composition contains 1 ppm or more and 1000 ppm or less of the phase transition inhibitor. The nitroxyl radical type hindered amine compound has the following formula (1):

(In the formula (1), D is a monovalent oxygen atom having an unpaired electron, n is an integer of 1 to 4, and each R ¹ is an alkyl group having 1 to 4 carbon atoms independently. in it, Y is, -O -, - CO-O -, - O-CO -, - NR 2 -, or ^{-NR 2} -CO- ^(R 2 in Y is alkyl of 1 to 10 carbon atoms A group or an acyl group, or an aromatic group or a carbonyl group having 6 to 12 carbon atoms), and E is an organic group having an n-valent bond site), according to claims 1 to 3. The liquid crystal panel according to any one item. The liquid crystal panel according to any one of claims 1 to 4, wherein the nematic liquid crystal composition contains a first liquid crystal material having a positive dielectric anisotropy of 3.0 or more. The nematic liquid crystal composition further contains a second liquid crystal material having a dielectric anisotropy of more than 0.5, and the second liquid crystal material has a relative permittivity of 2 or more perpendicular to the major axis direction of the molecule. The liquid crystal panel according to any one of claims 1 to 5. The liquid crystal panel according to any one of claims 1 to 6, wherein the nematic liquid crystal composition contains a third liquid crystal material having a neutral dielectric anisotropy.

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