JP7183697B2 - Vertically aligned liquid crystal display element - Google Patents

Description

The present invention relates to a vertically aligned liquid crystal display device.

Liquid crystal displays (LCDs) are required to have high light transmittance, and studies are being conducted to improve the light transmittance of liquid crystal display elements.

Here, in the liquid crystal display element, the alignment state of the liquid crystal molecules changes depending on whether or not a voltage is applied, and the transmission of light is controlled according to the alignment state of the liquid crystal molecules. As a method of improving the light transmittance of a liquid crystal display element, for example, a method of lowering the threshold voltage is known.

JP-A-2002-116463 JP-A-11-24032

LCDs and liquid crystal display elements are required to further improve their light transmittance. It has been found that adjustment alone does not sufficiently improve light transmission. In addition, the method of lowering the threshold voltage is to lower the threshold voltage and shift the VT curve showing the applied voltage-transmittance characteristics to the low voltage side, thereby increasing the transmittance under low voltage conditions. It becomes possible. However, with this method, the slope of the VT curve of the VA type liquid crystal display element does not become steep, and the maximum transmittance does not increase, so it is difficult to achieve high light transmittance at a low driving voltage.

Incidentally, Patent Documents 1 and 2 disclose methods for improving the optical characteristics of liquid crystal display elements, such as improving wide-field display performance. However, there is no disclosure of the problem to be solved and a method for improving the light transmittance of the VA type liquid crystal display device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a VA type liquid crystal display element capable of exhibiting high light transmittance even at a low driving voltage.

As a result of intensive studies by the present inventors on the above problems, the VA type liquid crystal composition can be obtained by adjusting the ratio between the spray elastic constant (K11) and the bend elastic constant (K33) of the liquid crystal composition constituting the liquid crystal layer. It has been found that the VT curve of the liquid crystal display device becomes steeper and the light transmittance can be improved even at a low driving voltage. In the specification of the present application, the spray elastic constant (K11) at 20° C. and the bend elastic constant (K33) at 20° C. may be simply expressed as K11 and K33, respectively.

That is, the present invention comprises a first substrate and a second substrate facing each other, a liquid crystal layer provided between the first substrate and the second substrate, and a liquid crystal layer comprising the first substrate and the second substrate. and an electrode layer disposed on at least one of the substrates, wherein the liquid crystal layer is composed of a liquid crystal composition in which K11 at 20° C. and K33 at 20° C. satisfy the following formula (1): A VA type liquid crystal display element is provided.
K11/K33 ≤ 1.0 (1)

The VA-type liquid crystal display device of the present invention exhibits high light transmittance even at a low driving voltage because the liquid crystal layer is composed of a liquid crystal composition having a predetermined relationship between the elastic constants K11 and K33. can.

It is a figure which shows typically one Embodiment of a VA-type liquid crystal display element. FIG. 2 is an enlarged plan view of a region surrounded by line I in FIG. 1; 4 is a graph showing VT curves of VA liquid crystal display elements of Examples 1 and 2 and Comparative Examples 1 and 2 obtained by simulation. 5 is a graph showing VT curves of VA-type liquid crystal display elements of Examples 3 to 6 and Comparative Example 3 obtained by simulation.

The VA type liquid crystal display device of the present invention will be described below. A VA liquid crystal display element of the present invention comprises: a first substrate and a second substrate facing each other; a liquid crystal layer provided between the first substrate and the second substrate; and an electrode layer disposed on at least one of the second substrates, wherein the liquid crystal layer is composed of a liquid crystal composition in which K11 and K33 at 20° C. satisfy the following formula (1): It is
K11/K33 ≤ 1.0 (1)

FIG. 1 is an exploded perspective view schematically showing an embodiment of the VA liquid crystal display element of the present invention, and FIG. 2 is an enlarged plan view of the area surrounded by line I in FIG. In FIGS. 1 and 2, the dimensions of each part and their ratios are exaggerated for the sake of convenience, and may differ from the actual dimensions. Also, the materials, dimensions, and the like shown below are examples, and the present invention is not limited to them, and can be changed as appropriate without changing the gist of the invention.

As shown in FIG. 1, a VA liquid crystal display element 1 of the present invention includes a first substrate 2 and a second substrate 3 facing each other, and a substrate provided between the first substrate 2 and the second substrate 3. It has a liquid crystal layer 4, an electrode layer (pixel electrode layer 5) arranged on the first substrate 2, and an electrode layer (common electrode layer 6) arranged on the second substrate 3, and the liquid crystal layer 4 , K11 and K33 at 20° C. satisfy the following formula (1).
K11/K33 ≤ 1.0 (1)

In the VA type liquid crystal display element 1 shown in FIG. 1, the pixel electrode layer 5 is provided on the surface of the first substrate 2 facing the liquid crystal layer 4 , and the pixel electrode layer 5 is provided on the surface of the first substrate 2 opposite to the liquid crystal layer 4 . A first polarizing plate 7 is provided on the surface. A common electrode layer 6 and a color filter 9 are provided on the surface of the second substrate 3 facing the liquid crystal layer 4 from the liquid crystal layer 4 side. is provided with a second polarizing plate 8 . 1 includes a first polarizing plate 7, a first substrate 2, a pixel electrode layer 5, a liquid crystal layer 4, a common electrode layer 6, and a color filter 9. , the second substrate 3, and the second polarizing plate 8 are laminated in this order.

In addition, as shown in FIG. 1, a laminate positioned on one main surface side of the liquid crystal layer 4 and including at least the first substrate 2 can be used as an active matrix substrate AM. The active matrix substrate AM in FIG. 1 includes a first polarizing plate 7, a first substrate 2, and a pixel electrode layer 5. FIG. Also, a laminate positioned on the other main surface side of the liquid crystal layer 4 and including at least the second substrate 3 can be used as the color filter substrate CF. The color filter substrate CF in FIG. 1 includes a common electrode layer 6 , color filters 9 , a second substrate 3 and a second polarizing plate 8 .

According to the VA-type liquid crystal display element of the present invention, the liquid crystal composition constituting the liquid crystal layer has a spray elastic constant (K11) at 20° C. and a bend elastic constant (K33) at 20° C. that are expressed by the formula ( By showing the predetermined relationship shown in 1), the VT curve showing the applied voltage-transmittance characteristics of the liquid crystal becomes steep, and high light transmittance can be exhibited even at a low driving voltage.

Here, the VA type liquid crystal display element refers to a liquid crystal display element in which the initial alignment state of liquid crystal molecules in the liquid crystal composition is substantially perpendicular to the substrate. Specific examples of such liquid crystal display devices include a PSA (Polymer Sustained Alignment) type, a PSVA type, a VA type, an ECB type, and the like. Further, the VA-type liquid crystal display element of the present invention is a PI-less type having no polyimide alignment film on at least one of the substrates, preferably on two opposing substrates, depending on the composition of the liquid crystal composition. is also possible.

The details of the configuration of the VA type liquid crystal display device of the present invention will be described below.

1. Liquid Crystal Layer The liquid crystal layer in the present invention is composed of a liquid crystal composition that satisfies the relationship of the following formula (1) between the elastic constant of spray (K11) at 20° C. and the elastic constant of bend (K33) at 20° C. .
K11/K33 ≤ 1.0 (1)

Among them, the value of K11/K33 is preferably 0.95 or less, more preferably 0.90 or less. This is because, by setting the value of K11/K33 to be equal to or less than the above value, the VT curve becomes steep and high transmittance can be exhibited even when driven at a low voltage. Further, the value of K11/K33 is greater than 0, preferably 0.70 or more, more preferably 0.71 or more, 0.75 or more, 0.80 or more, and 0 0.85 or higher. If the value of K11/K33 is too small, the value of K33 becomes too large and the threshold voltage increases. Therefore, it is preferable to set the value of K11/K33 to the above value or more from the viewpoint of suppressing the rise of the threshold voltage.

In the present invention, the lower limit of K11 of the liquid crystal composition is preferably 10 pN, 11 pN, 12 pN, and 13 pN. Moreover, the upper limit of K11 is preferably 20 pN, 18 pN, 16 pN, and 14 pN. When the K11 value of the liquid crystal composition is within the above range, a steep VT curve can be obtained, and high transmittance can be exhibited even when driven at a low voltage.

In the present invention, the lower limit of K33 of the liquid crystal composition is preferably 10 pN, 11 pN, 12 pN, and 13 pN. Moreover, the upper limit of K33 is preferably 20 pN, 18 pN, 16 pN, and 14 pN. If the K33 value of the liquid crystal composition is too large, the threshold voltage becomes high, and if it is too small, problems such as slow Toff response occur, so this range is preferable.

K11 and K33 of the liquid crystal composition can be measured, for example, with an elastic constant measurement system EC-1 type (liquid crystal physical property evaluation) manufactured by Toyo Technica.

In the VA type liquid crystal display element of the present invention, the liquid crystal molecules in the liquid crystal composition constituting the liquid crystal layer are substantially vertically aligned with respect to the main surfaces of the first and second substrates in a saturated voltage state (initial alignment state), It is preferable to align substantially horizontally with respect to the major surfaces of the first and second substrates by applying a voltage equal to or higher than the threshold. Here, the liquid crystal molecules are "substantially vertically aligned with respect to the main surface of the substrate", not only the state in which the liquid crystal molecules are aligned vertically with respect to the main surface of the substrate, but also the state in which the liquid crystal molecules are vertically aligned with respect to the main surface of the substrate. It also includes a state in which the directors of the liquid crystal molecules are tilted slightly from the vertical direction to give a pretilt angle. When the liquid crystal molecules are homeotropically aligned (perfectly perpendicular to the main surface of the substrate), the angle between the direction completely parallel to the main surface of the substrate and the direction of the director of the liquid crystal molecules. is 90°. On the other hand, when the liquid crystal molecules are completely homogeneously aligned (aligned horizontally with respect to the main surface of the substrate), the above angle is 0°.

When the liquid crystal molecules are aligned substantially perpendicular to the main surface of the substrate, the pretilt angle of the liquid crystal molecules in the liquid crystal composition is preferably in the range of 89.9° to 85°, preferably 89.5° to 85°. More preferably within the range of 87°.

(1) Compound Contained in Liquid Crystal Composition The liquid crystal composition constituting the liquid crystal layer contains at least liquid crystal molecules. Among them, it is preferable to contain one or two or more kinds of liquid crystal molecules and one or two or more kinds of at least one of a polymerizable compound and an alignment aid, and one or two or more kinds of liquid crystal molecules, More preferably, one or two or more polymerizable compounds and one or two or more alignment aids are included. Since the polymerizable compound and the alignment aid have a polymerizable group as described later, they can be generally referred to as compounds having a polymerizable group. When the liquid crystal layer is composed of a composition containing a compound having such a polymerizable group, the liquid crystal molecules can spontaneously align without an alignment film, and the alignment film is more advantageous than the alignment film. This is because the effect of defining K11/K33 in the VA type liquid crystal display element can be exhibited more remarkably.

When the vertical alignment property of the liquid crystal compound is imparted by an alignment film using polyimide, although the alignment control force for the liquid crystal molecules is increased, the TFT may be damaged by the contamination of foreign matter and the generated static electricity due to rubbing, and the alignment film may be difficult to form. There is a problem such as multi-step process for As a method for solving such problems, there is a vertical alignment treatment using an alignment aid. By satisfying the conditions, the effect of improving the light transmittance of the VA-type liquid crystal display device when driven at a low voltage becomes more pronounced, which is preferable.

Various compounds contained in the liquid crystal composition are described below.

<Liquid crystal molecule>
The liquid crystal composition forming the liquid crystal layer contains one or more liquid crystal molecules. As liquid crystal molecules, for example, compounds having negative dielectric anisotropy are preferably used. In the compound, the sign of Δε is negative and the absolute value thereof is preferably greater than 2.

Examples of compounds having negative dielectric anisotropy include compounds selected from the group of compounds represented by general formulas (N-01) to (N-05). These compounds have a negative sign of Δε and an absolute value of more than 2. The Δε of the compound is a value extrapolated from the measured value of the dielectric anisotropy of a composition obtained by adding the compound to a composition that is dielectrically neutral at 20°C.

In formulas (N-01) to (N-05), R ²¹ and R ²² are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or 2 carbon atoms. represents an alkenyl group having from 8 to 8 and an alkenyloxy group having from 2 to 8 carbon atoms, wherein one or two or more non-adjacent -CH ₂ - in the group are each independently -CH=CH-, - optionally substituted by C≡C-, -O-, -CO-, -COO- or -OCO-, and Z ¹ is each independently a single bond, -CH ₂ CH ₂ -, -OCH ₂ -, -CH ₂ O-, -COO-, -OCO-, -OCF ₂ -, -CF ₂ O-, -CH=CH-, -CF=CF- or -C≡C-, and m is Each independently represents 1 or 2.

R ²¹ is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, and still more preferably an alkyl group having 1 to 4 carbon atoms. However, when Z ¹ represents other than a single bond, R ²¹ is preferably an alkyl group having 1 to 3 carbon atoms.

R ²² is preferably an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. Preferred are alkoxy groups having 1 to 4 carbon atoms.

R ²¹ and R ²² may also be an alkenyl group, and a group represented by any one of formulas (R1) to (R5) (the black dots in each formula represent a carbon atom in the ring structure) to Formula (R1) or Formula (R2) is preferable, but the content of the compound in which R ²¹ and R ²² are alkenyl groups should be as small as possible, and when used together with a polymerizable compound, It is often preferable not to contain it.

Z ¹ is each independently a single bond, -CH ₂ CH ₂ -, -OCH ₂ -, -CH ₂ O-, -COO-, -OCO-, -OCF ₂ -, -CF ₂ O-, - represents CH=CH-, -CF=CF- or -C≡C-, preferably a single bond, -CH ₂ CH ₂ -, -OCH ₂ - or -CH ₂ O-, and a single bond or -CH ₂ O - is more preferred.

When m is 1, ^Z1 is preferably a single bond.

When m is 2, Z ¹ is preferably -CH ₂ CH ₂ -, -CH ₂ O-.

The compounds represented by the general formulas (N-01), (N-02), (N-03), (N-04) and (N-05) have a negative Δε and an absolute value of 3 Large compounds are preferred. Specifically, R ²² preferably represents an alkoxy group having 1 to 8 carbon atoms or an alkenyloxy group having 2 to 8 carbon atoms.

With respect to the total amount of the liquid crystal composition, the preferred lower limit of the content of the compound represented by the general formula (N-01) is 0%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%. The upper limit of the preferred content is 95%, 85%, 75%, 65%, 55%, 45%, 35%, 25%, 20% , 15%, and 10%.

With respect to the total amount of the liquid crystal composition, the preferred lower limit of the content of the compound represented by the general formula (N-02) is 0%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%. The upper limit of the preferred content is 95%, 85%, 75%, 65%, 55%, 45%, 35%, 25%, 20% , 15%, and 10%.

With respect to the total amount of the liquid crystal composition, the preferred lower limit of the content of the compound represented by the general formula (N-03) is 0%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%. The upper limit of the preferred content is 95%, 85%, 75%, 65%, 55%, 45%, 35%, 25%, 20% , 15%, and 10%.

With respect to the total amount of the liquid crystal composition, the preferable lower limit of the content of the compound represented by the general formula (N-04) is 0%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%. The upper limit of the preferred content is 95%, 85%, 75%, 65%, 55%, 45%, 35%, 25%, 20% , 15%, and 10%.
With respect to the total amount of the liquid crystal composition, the lower limit of the preferable content of the compound represented by formula (N-05) is 0%, 2%, 5%, 8%, 10%. %, 13%, 15%, 17%, and 20%. Preferred upper limits of the content are 30%, 28%, 25%, 23%, 20%, 18%, 15% and 13%.

<Polymerizable compound>
The liquid crystal composition forming the liquid crystal layer may contain one or more polymerizable compounds. The polymerizable compound may be any compound having a polymerizable group that can be polymerized by irradiation with active energy rays, and for example, a compound represented by the general formula (RM) can be used.

In formula (RM), R ¹⁰¹ , R ¹⁰² , R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ are independently substituted with P ¹³ —S ¹³ —, a fluorine atom, an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms which may be substituted with a fluorine atom, a fluorine atom or a hydrogen atom, and P ¹¹ , P ¹² and P ¹³ are Each independently, formula (Re-1) to formula (Re-9)

(In formulas (Re-1) to (Re-9), R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are each independently an alkyl group having 1 to 5 carbon atoms, a fluorine atom or represents any hydrogen atom, m ^r5 , m ^r7 , n ^r5 and n ^r7 each independently represents 0, 1 or 2, and m ^r5 , m ^r7 , n ^r5 and/or n ^r7 When representing 0, it represents a single bond.)

represents a polymerizable group represented by S ¹¹ , S ¹² and S ¹³ each independently represents a single bond or an alkylene group having 1 to 15 carbon atoms, and one —CH in the alkylene group ₂ - or two or more non-adjacent -CH ₂ - may be replaced with -O-, -OCO- or -COO-, and when a plurality of P ¹³ and S ¹³ are present, each may be different.

A liquid crystal composition containing a polymerizable compound represented by the general formula (RM) is suitable for producing a PSA-type or PSVA-type liquid crystal display element among VA-type liquid crystal display elements. can control the pretilt angle. It is also suitable for producing an NPS type liquid crystal display element. It is also suitable for producing a PI-less type liquid crystal display device that does not have a PI alignment film.

P ¹¹ , P ¹² and P ¹³ may all be the same polymerizable group (formulas (Re-1) to (Re-9)) or different polymerizable groups.

<Orientation aid>
The liquid crystal composition forming the liquid crystal layer may contain one or more alignment aids. The alignment aid is a compound having a function of spontaneously aligning liquid crystal molecules.

Here, the alignment aid having a function of spontaneously aligning liquid crystal molecules means that the alignment aid (spontaneous alignment compound) is a member (electrode (for example, ITO), substrates (e.g., glass substrates, acrylic substrates, transparent substrates, flexible substrates, etc.), resin layers (e.g., color filters, alignment films, overcoat layers, etc.), insulating films (e.g., inorganic material films, SiNx, etc.) ) to induce homeotropic alignment of liquid crystal molecules contained in the liquid crystal layer.

The alignment aid contains a polymerizable group for polymerization, a mesogenic group similar to liquid crystal molecules, an adsorbing group (polar group) capable of interacting with a member that directly contacts the liquid crystal layer, and induces the alignment of the liquid crystal molecules. and an orientation-inducing group.

Adsorbing groups and orientation-inducing groups are preferably bound to mesogenic groups. Moreover, the polymerizable group preferably substitutes the mesogenic group, the adsorptive group, and the orientation-inducing group directly or, if necessary, via a spacer group.

The alignment-inducing group in the alignment aid has a function of inducing the alignment of liquid crystal molecules. Examples of orientation-inducing groups include groups represented by the following general formula (AK).

(In formula (AK), R ^AK1 represents a linear or branched alkyl group having 1 to 20 carbon atoms, provided that one or more —CH ₂ — in the alkyl group is oxygen. Each atom may be independently substituted with -CH=CH-, -C≡C-, -O-, -CO-, -COO- or -OCO- without direct bonding, and One or two or more hydrogen atoms in may be independently substituted with a halogeno group (* in the formula represents a bond).

The polymerizable group in the alignment aid is preferably represented by P ^AP1 -Sp ^AP1 -. ^PAP1 is preferably a group selected from the group represented by the following general formulas (AP-1) to (AP-9).

In formulas (AP-1) to (AP-9), R ^AP1 and R ^AP2 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 10 carbon atoms. represents a group. However, one or more —CH ₂ — in the alkyl group may be substituted with —O— or —CO—, and one or more hydrogen atoms in the alkyl group are each independently may be substituted with a halogen atom or a hydroxyl group.
W ^AP1 represents a single bond, -O-, -COO- or -CH ₂ -.
^tAP1 represents 0, 1 or 2;
Sp ^AP1 preferably represents a single bond or a linear or branched alkylene group having 1 to 20 carbon atoms, more preferably a single bond or a linear alkylene group having 1 to 20 carbon atoms. It preferably represents a single bond or a linear alkylene group having 2 to 10 carbon atoms.
In Sp ^AP1 , one or two or more non-adjacent —CH ₂ — in the alkylene group are each independently —CH═CH—, —C≡C—, —O—, —CO—, -COO- or -OCO- may be substituted.
* in the formula represents a bond.

In the alignment aid, the number of polymerizable groups (P ^AP1 -Sp ^AP1 -) is preferably 1 or more and 5 or less, more preferably 1 or more and 4 or less, and further preferably 2 or more and 4 or less. Preferably, 2 or 3 is particularly preferred, and 2 is most preferred.

A hydrogen atom in P ^AP1 -Sp ^AP1 - may be substituted with a polymerizable group, an adsorptive group and/or an orientation-inducing group. The polymerizable group (P ^AP1 -Sp ^AP1 -) may be attached to the polymerizable group, the mesogenic group, the adsorbing group and/or the orientation inducing group. Also, the polymerizable group (P ^AP1 -Sp ^AP1 -) preferably binds to a mesogenic group, an adsorptive group or an orientation-inducing group, and more preferably binds to a mesogenic group or an adsorptive group. When a plurality of P ^AP1 and/or Sp ^AP1 - are present in the molecule, they may be the same or different.

The mesogenic group in the alignment aid refers to a group having a rigid portion, such as a group having one or more cyclic groups, preferably a group having 2 to 4 cyclic groups, and a cyclic group. Groups with 3 to 4 are more preferred. In addition, the cyclic group may be connected by a connecting group as necessary. The mesogenic group preferably has a skeleton similar to that of liquid crystal molecules (liquid crystal compounds) used in the liquid crystal layer.
As used herein, the term "cyclic group" refers to an atomic group in which constituent atoms are cyclically bonded, and includes a carbocyclic ring, a heterocyclic ring, a saturated or unsaturated cyclic structure, a monocyclic structure, a bicyclic structure, Including polycyclic structures, aromatics, non-aromatics, and the like.

The cyclic group may also contain at least one heteroatom and may be further substituted with at least one substituent (halogeno group, polymerizable group, organic group (alkyl, alkoxy, aryl, etc.). Ring If the formula group is monocyclic, the mesogenic group preferably contains two or more monocyclic rings.

The mesogenic group is preferably represented by general formula (AL), for example.

In formula (AL), Z ^AL1 is a single bond, -CH=CH-, -CF=CF-, -C≡C-, -COO-, -OCO-, -OCOO-, -CF ₂ O-, - OCF ₂ -, -CH=CHCOO-, -OCOCH=CH-, -CH ₂ -CH ₂ COO-, -OCOCH ₂ -CH ₂ -, -CH=C(CH ₃ )COO-, -OCOC(CH ₃ ) ═CH—, —CH ₂ —CH(CH ₃ )COO—, —OCOCH(CH ₃ )—CH ₂ —, —OCH ₂ CH ₂ O— or an alkylene group having 1 to 20 carbon atoms. However, one or two or more non-adjacent -CH ₂ - in the alkylene group may be replaced with -O-, -COO- or -OCO-.
A ^AL1 and A ^AL2 each independently represent a divalent cyclic group.
One or more hydrogen atoms in Z ^AL1 , A ^AL1 and A ^AL2 may each independently be substituted with a halogeno group, an adsorptive group, P ^AP1 —Sp ^AP1 — or a monovalent organic group. , when there are a plurality of Z ^AL1 and A ^AL1 in the molecule, they may be the same or different.
m ^AL1 represents an integer of 1-5. * in the formula represents a bond.

The adsorptive group in the alignment aid is a group having a role of adsorbing an adsorbent, which is a layer in contact with the liquid crystal composition, such as a substrate, film, or electrode. The adsorption may be chemisorption in which a chemical bond (covalent bond, ionic bond or metallic bond) is formed between the adsorbent and the adsorbate, or may be physical adsorption other than chemisorption. Good, but preferably physisorption. Examples of adsorptive groups include groups represented by the following general formula (AT).

In formula (AT), Sp ^AT1 represents a single bond or a linear or branched alkylene group having 1 to 25 carbon atoms. However, a hydrogen atom in the alkylene group may be substituted with —OH, —CN, —W ^AT1 —Z ^AT1 or P ^AP1 —Sp ^AP1 —, and —CH ₂ — in the alkylene group is directly It may be substituted with a cyclic group, -O-, -COO-, -C(=O)-, -OCO-, -CH=CH- or -OCO-COO- so as not to bond.
^WAT1 represents a single bond or the following general formula (WAT1) or (WAT2).
Z ^AT1 represents a monovalent group containing a polar element. However, a hydrogen atom in Z ^AT1 may be replaced with —OH, —CN, —Sp ^AT1 —W ^AT1 —Z ^AT1 or P ^AP1 —Sp ^AP1 —. * in the formula represents a bond.

(In the formulas (WAT1) and (WAT2), Sp ^WAT1 and Sp ^WAT2 each independently represent a single bond, a linear or branched alkylene group having 1 to 25 carbon atoms, and hydrogen in the alkylene group Atoms may be substituted with -OH, -CN, -Sp ^AT1 -W ^AT1 -Z ^AT1 or P ^AP1 -Sp ^AP1 -, and -CH ₂ - in the alkylene group is may be substituted with a cyclic group, -O-, -COO-, -C(=O)-, -OCO- or -CH=CH-, where * represents a bond.)

<Other compounds>
The liquid crystal composition of the present invention may contain one or two or more dielectrically substantially neutral compounds (with a Δε value of −2 to 2 at 20° C.) as liquid crystal molecules. Examples of dielectrically substantially neutral compounds include compounds represented by general formula (L).

(In formula (L), R ^L1 and R ^L2 each independently represent an alkyl group having 1 to 8 carbon atoms, and one or two or more non-adjacent —CH ₂ — in the alkyl group are each independently optionally substituted by -CH=CH-, -C≡C-, -O-, -CO-, -COO- or -OCO-;
n ^L1 represents 0, 1, 2 or 3,
A ^L1 , A ^L2 and A ^L3 are each independently (a) a 1,4-cyclohexylene group (one —CH ₂ — present in this group or two or more non-adjacent —CH ₂ — may be replaced with —O—.) and (b) 1,4-phenylene groups (one —CH= or two or more non-adjacent —CH= present in this group may be —N = may be replaced.)
(c) naphthalene-2,6-diyl group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group or decahydronaphthalene-2,6-diyl group (naphthalene-2,6-diyl group or One —CH= or two or more non-adjacent —CH= present in the 1,2,3,4-tetrahydronaphthalene-2,6-diyl group may be replaced with —N=. )
represents a group selected from the group consisting of, the above group (a), group (b) and group (c) may each independently be substituted with a cyano group, a fluorine atom or a chlorine atom,
Z ^L1 and Z ^L2 are each independently a single bond, -CH ₂ CH ₂ -, -(CH ₂ ) ₄ -, -OCH ₂ -, -CH ₂ O-, -COO-, -OCO-, -OCF ₂ -, -CF ₂ O-, -CH=N-N=CH-, -CH=CH-, -CF=CF- or -C≡C-,
When n ^L1 is 2 or 3 and there are a plurality of A ^L2 , they may be the same or different, and when n ^L1 is 2 or 3 and there are a plurality of Z ^L3 , they may be the same or different, excluding compounds represented by general formulas (N-01) to (N-05). )

Moreover, the liquid crystal composition in the present invention can contain an antioxidant. Above all, the liquid crystal composition preferably contains a hindered phenol-based antioxidant.

Moreover, the liquid crystal composition in the present invention can contain a light stabilizer. As the light stabilizer, hindered amine light stabilizers (HALS) such as Tinuvin 770 and LA-57 can be preferably used.

(2) Physical properties The liquid crystal composition in the invention preferably has a nematic phase-isotropic liquid phase transition temperature (T _ni ) within the range of 60°C to 120°C. Specifically, the lower limit is preferably 65°C, preferably 70°C, preferably 71°C, preferably 72°C, preferably 73°C, preferably 74°C, preferably 75°C, and the upper limit is preferably 110°C. C., preferably 100.degree. C., preferably 95.degree. C., preferably 90.degree. C., preferably 88.degree. C., preferably 86.degree.

The liquid crystal composition in the present invention preferably has a rotational viscosity (γ ₁ ) at 20° C. within the range of 50 mPa·s to 200 mPa·s. Specifically, the lower limit is preferably 55 mPa s, preferably 60 mPa s, preferably 62 mPa s, preferably 64 mPa s, preferably 66 mPa s, preferably 68 mPa s, preferably 70 mPa s, and the upper limit is preferably 190 mPa·s, preferably 180 mPa·s, preferably 170 mPa·s, preferably 160 mPa·s, and preferably 150 mPa·s.

The liquid crystal composition of the present invention preferably has a negative dielectric anisotropy (Δε) value at 20° C. and an absolute value of 2.0 or more. Specifically, the liquid crystal composition of the present invention preferably has a dielectric anisotropy (Δε) at 20° C. within the range of −2.0 to −8.0. Specifically, the lower limit is preferably -7.0, preferably -6.5, preferably -6.0, preferably -5.5, preferably -5.0, preferably -4.5, -4 .0 is preferred, -3.9 is preferred, -3.8 is preferred, -3.7 is preferred, the upper limit thereof is preferably -2.5, -2.6 is preferred, -2.7 is preferred, -2.8 is preferred, -2.9 is preferred, -3.0 is preferred.

The liquid crystal composition in the present invention preferably has a refractive index anisotropy (Δn) at 20° C. within the range of 0.08 to 0.20. Specifically, the lower limit is preferably 0.09, preferably 0.10, preferably 0.11, preferably 0.12, preferably 0.13, and the upper limit is preferably 0.19, preferably 0.18. , preferably 0.17, preferably 0.16, preferably 0.15. More specifically, it should be in the range of 0.10 to 0.20 for thin cell gaps and 0.08 to 0.12 for thick cell gaps. is preferred.

2. First Substrate and Second Substrate In the present invention, the first substrate and the second substrate are arranged to face each other with the liquid crystal layer interposed therebetween. The first substrate and the second substrate are each made of a flexible material such as a glass material or a plastic material. Both the first substrate and the second substrate may be translucent, or only one of them may be translucent. A non-light-transmitting substrate can be made of an opaque material such as a metal material or a silicon material.

3. Electrode Layer In the present invention, the electrode layer is arranged on at least one of the first substrate and the second substrate. Normally, a pixel electrode layer is arranged on the surface of the first substrate facing the liquid crystal layer, and a common electrode layer is arranged on the surface of the second substrate facing the liquid crystal layer.

As shown in FIG. 2, the pixel electrode layer 5 includes a plurality of gate bus lines 11 for supplying scanning signals, a plurality of data bus lines 12 for supplying display signals, and a plurality of pixel electrodes 13 . have. A pair of gate bus lines 11, 11 and a pair of data bus lines 12, 12 are shown in FIG. A plurality of gate bus lines 11 and a plurality of data bus lines 12 intersect each other and are arranged in a matrix, and the area surrounded by these lines forms a unit pixel of the VA type liquid crystal display element 1 . One pixel electrode 13 is formed in each unit pixel.

The pixel electrode 13 has a structure (a so-called fishbone structure) including two cross-shaped trunks perpendicular to each other and a plurality of branch portions branching from each trunk and extending outward. there is A Cs electrode 14 is provided between the pair of gate bus lines 11 , 11 substantially parallel to the gate bus line 11 . A thin film transistor including a source electrode 15 and a drain electrode 16 is provided in the vicinity of an intersection where the gate bus line 11 and the data bus line 12 intersect each other. A contact hole 17 is provided in the drain electrode 16 .

The gate bus lines 11 and the data bus lines 12 are preferably made of, for example, Al, Cu, Au, Ag, Cr, Ta, Ti, Mo, W, Ni, or alloys containing these. It is more preferable to form with an alloy containing these.

The pixel electrode 13 is preferably made of a transparent electrode, for example, in order to improve light transmittance. The transparent electrode can be formed by sputtering an oxide semiconductor such as ZnO, InGaZnO, SiGe, GaAs, IZO (Indium Zinc Oxide), ITO (Indium Tin Oxide), SnO, TiO, AZTO (AlZnSnO). . The average thickness of the transparent electrode is preferably about 10 nm to 200 nm. Also, in order to reduce electrical resistance, the transparent electrode can be formed as a polycrystalline ITO film by firing an amorphous ITO film.

On the other hand, the common electrode layer 6 has, for example, a plurality of parallel striped common electrodes (transparent electrodes). This common electrode can also be formed in the same manner as the pixel electrode 13 .

4. Color Filter The VA type liquid crystal display element of the present invention can usually have a color filter between the second substrate and the common electrode layer. A color filter can be produced by, for example, a pigment dispersion method, a printing method, an electrodeposition method, a dyeing method, or the like. In the pigment dispersion method, a curable coloring composition for color filters is applied to a second substrate in a predetermined pattern, and then cured by heating or light irradiation. A color filter can be obtained by performing this operation for the three colors of red, green, and blue. Note that the color filters may be arranged on the first substrate side.

5. First Polarizing Plate and Second Polarizing Plate In the VA liquid crystal display element of the present invention, the first polarizing plate can be provided on the surface of the first substrate opposite to the liquid crystal layer, and the second substrate can be provided with the first polarizing plate. A second polarizing plate can be provided on the surface opposite to the liquid crystal layer.

The first polarizing plate and the second polarizing plate can be designed to improve the viewing angle and contrast by adjusting the positional relationship of their transmission axes. Specifically, the first polarizer and the second polarizer are preferably arranged orthogonal to each other so that their transmission axes operate in the normally black mode. In particular, one of the first polarizing plate and the second polarizing plate is preferably arranged such that its transmission axis is parallel to the alignment direction of the liquid crystal molecules when no voltage is applied.

When using the first polarizing plate and the second polarizing plate, the product of the refractive index anisotropy (Δn) of the liquid crystal layer and the average thickness of the liquid crystal layer should be adjusted so as to maximize the contrast. is preferred. Furthermore, the VA-type liquid crystal display element may be provided with a retardation film for widening the viewing angle.

6. Black Matrix The VA liquid crystal display element of the present invention may have a black matrix (not shown) from the viewpoint of preventing light leakage. The black matrix is preferably formed in a portion corresponding to the thin film transistor. The black matrix may be arranged with the color filter on the second substrate side with respect to the liquid crystal layer, or may be arranged with the color filter on the first substrate side with respect to the liquid crystal layer. Also, the black matrix and the color filters may be arranged separately. That is, the black matrix may be arranged on the first substrate side with respect to the liquid crystal layer, and the color filters may be arranged on the second substrate side with respect to the liquid crystal layer. Furthermore, the black matrix can also be configured by overlapping the colors of the color filters to reduce the transmittance.

7. Other Configurations The first substrate and the second substrate are arranged to face each other such that the surface on which the pixel electrode layer is arranged and the surface on which the common electrode layer is arranged face the liquid crystal layer. In addition, the first substrate and the second substrate are arranged apart from each other, and are bonded to each other at their peripheral regions with a sealing material (sealing material) made of an epoxy-based thermosetting composition or the like. . The average distance between the first substrate and the second substrate (that is, the average thickness of the liquid crystal layer) is preferably about 1 μm to 100 μm.

A spacer for maintaining a separation distance may be arranged between the first substrate and the second substrate. Examples of spacers include glass particles, plastic particles, granular spacers such as alumina particles, resin spacer columns formed by photolithography, and the like.

An insulating film or a planarization film covering part or all of the pixel electrode layer may be disposed on the pixel electrode layer. Further, an insulating film or a planarization film covering part or all of the common electrode layer may be disposed on the common electrode layer.

In the VA liquid crystal display element of the present invention, it is preferable that the anchoring energy in the polar angle direction of the surface of the member with which the liquid crystal layer is in direct contact is as small as possible. This is because the effect of defining K11/K33 in the VA-type liquid crystal display element is exhibited more remarkably. Specifically, the anchoring energy in the polar angle direction of the surface of the member with which the liquid crystal layer is in direct contact is preferably in the range of 1E-0J/m ² to 1E-5J/m ² , especially 1E-2J. /m ² to 1E-5 J/m ² , more preferably 1E-3 J/m ² to 1E-5 J/m ² . The polar anchoring energy can be measured, for example, by the method described in Japanese Journal of the Applied Physics, Vol47, No12, 2008, p8892-8897 (written by Takahiro Ishinabe, Tohoku University).

The VA liquid crystal display element of the present invention may have an alignment film on at least one of the first substrate and the second substrate, and at least one of the first substrate and the second substrate may have an alignment film. In addition, the alignment film may not be provided. The alignment film has the function of aligning the liquid crystal molecules, and is usually placed in direct contact with the liquid crystal layer. Organic polymer films such as polyimide films, nylon films and polyvinyl alcohol films are preferably used as the alignment film.

Above all, it is preferable that at least one of the first substrate and the second substrate does not have an alignment film, and neither the first substrate nor the second substrate has an alignment film. is more preferred. In other words, at least one main surface of the liquid crystal layer is preferably not in contact with the alignment film. This is because the alignment film usually has a large anchoring energy in the polar angle direction of the surface in order to exert the function of controlling the alignment of the liquid crystal molecules. The alignment film in the present invention does not include a polymer film composed of a polymer of at least one of the above-mentioned polymerizable compound and alignment aid.

In the VA type liquid crystal display element of the present invention, the surface of the member with which the liquid crystal layer is in direct contact may or may not be subjected to alignment treatment. Above all, it is preferable that the surface of the member with which the liquid crystal layer is in direct contact is not subjected to alignment treatment. This is because a member whose surface has been subjected to an orientation treatment has a large surface anchoring energy. Orientation treatment includes stretching treatment, rubbing treatment, polarized UV-visible light irradiation treatment, ion beam treatment, oblique vapor deposition treatment of SiO ₂ on the base material, and the like.

When the liquid crystal composition constituting the liquid crystal layer contains an alignment aid and/or a polymerizable compound, the VA liquid crystal display element of the present invention has the alignment aid interposed between the first substrate and the second substrate. A polymer obtained by polymerizing an agent and/or a polymerizable compound may be provided. In other words, a polymer of a compound having a polymerizable group may be provided between the first substrate and the second substrate. This is because the alignment aid and/or the polymer of the polymerizable compound can align the liquid crystal molecules without an alignment film. The polymer of the compound having a polymerizable group (orientation aid and/or the polymer of the polymerizable compound) may be present on at least one of the first substrate and the second substrate, and may be present on both. or may be present in the liquid crystal composition. Among them, it is preferable that the compound having the polymerizable group constituting the polymer further has a mesogenic group.

Note that when a polymer of a compound having a polymerizable group is present between the first substrate and the second substrate, the first substrate and the second substrate may not have an alignment film. However, at least one of the first substrate and the second substrate may have an alignment film.

8. Manufacturing Method The VA-type liquid crystal display element of the present invention can be manufactured by a known method. Alternatively, the ODF method may be used to drop the liquid crystal composition onto at least one of the opposing first and second substrates. When the liquid crystal composition contains at least one compound of a polymerizable compound and an alignment aid, the method for producing a VA-type liquid crystal display element of the present invention polymerizes the polymerizable compound and the alignment aid by irradiating an active energy ray. including the step of allowing

It should be noted that the present invention is not limited to the above embodiments. The above embodiment is an example, and any device that has substantially the same configuration as the technical idea described in the claims of the present invention and produces similar effects is the present invention. It is included in the technical scope of the invention.

The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. In addition, "%" in the compositions of the following examples and comparative examples means "% by mass".

[Examples 1 and 2, Comparative Examples 1 and 2]
A VT curve of the VA type liquid crystal display element was obtained by simulation. For the simulation, Shintech's LCD Master 1D was used. The structure of the liquid crystal display element was such that the liquid crystal layer was placed between the upper and lower glass substrates on which solid ITO electrode layers were respectively placed, and the liquid crystal layer was placed outside each substrate (liquid crystal layer side). On the opposite side), the polarizing plate was set to cross Nicols. Both main surfaces of the liquid crystal layer were designed on the assumption that they were in contact with polyimide alignment films (anchoring energy: 1E+20 [J/m ² ]). The liquid crystal cell thickness was 3.2 μm. The polarizing plate placed on the upper glass substrate was arranged so that the transmission axis was at 90 degrees, and the polarizing plate placed on the lower glass substrate was arranged so that the transmission axis was at 0 degree. In addition, the liquid crystal molecules were set at a pretilt angle of 45 degrees (polar angle of 89 degrees).

The liquid crystal composition constituting the liquid crystal layer was assumed to contain the liquid crystal molecules described above and not contain the polymerizable compound and alignment aid described above. K11 and K33 of the liquid crystal composition constituting the liquid crystal layer were set as shown in Table 1 below. Further, the physical property values of the liquid crystal composition other than K11 and K33 were set as follows.
・K22=(K11+K33)/4
・Δε=−3.3
・Δn (589 nm) = 0.11

The threshold voltage (Vth) was a value (2.14 V) calculated by substituting the K33 value for K in the following theoretical formula. ε ₀ in the formula indicates the permittivity of vacuum.

A potential difference was provided between the upper and lower electrode layers from 0 V to 10 V in increments of 0.1 V, and the orientation of the liquid crystal molecules and the light transmittance were calculated for each potential difference. FIG. 3 shows the VT curve of the VA type liquid crystal display element in each simulation. From the results of FIG. 3, it was confirmed that the smaller the value of K11/K33, the steeper the VT curve and the higher the light transmittance even when driven at a low voltage.

[Examples 3 to 6, Comparative Example 3]
As the liquid crystal composition constituting the liquid crystal layer, a composition (PI-less composition) containing the above-described liquid crystal molecules, the above-described polymerizable compound, and the above-described alignment aid is assumed, and the liquid crystal composition In the same manner as in Example 1, except that K11 and K33 and the anchoring energy of the surface in contact with the liquid crystal layer were set to the values shown in Table 2, the V- A T-curve was obtained. In Examples 4 to 6, a PI-less liquid crystal display element was designed in which both main surfaces of the liquid crystal layer were not in contact with the polyimide alignment film. The physical properties of the liquid crystal compositions of Examples 3 to 6 and Comparative Example 3, other than K11 and K33, were the same as those of Example 1 and the like. FIG. 4 shows the VT curve of the VA type liquid crystal display element under each condition.

From the results of FIG. 4 (especially the results of conditions 2 to 5), when the values of K11/K33 are the same, the smaller the anchoring energy of the surface in contact with the liquid crystal layer, the higher the VT curve (high transmittance side). It was suggested that it shifts and shows higher transmittance even under the same voltage condition.

1 VA type liquid crystal display element AM active matrix substrate CF color filter substrate 2 first substrate 3 second substrate 4 liquid crystal layer 5 pixel electrode layer 6 common electrode layer 7 first polarizing plate 8 second polarizing plate 9 color filter

Claims (6)

a first substrate and a second substrate facing each other;
a liquid crystal layer provided between the first substrate and the second substrate;
an electrode layer disposed on at least one of the first substrate and the second substrate;
Neither the first substrate nor the second substrate has an alignment film,
The liquid crystal layer is composed of a liquid crystal composition that satisfies the following formula (1) between the elastic constant of spray (K11) at 20° C. and the elastic constant of bend (K33) at 20° C. type liquid crystal display element,
The vertically aligned liquid crystal display device, wherein the bending elastic constant (K33) at 20° C. is 14 pN or less.
K11/K33 ≤ 1.0 (1) 2. The vertically aligned liquid crystal display element according to claim 1, wherein a polymer of a compound having a polymerizable group is provided between said first substrate and said second substrate. 3. The vertical alignment liquid crystal display device according to claim 2, wherein the compound having a polymerizable group further has a mesogenic group. 4. The perpendicular according to any one of claims 1 to 3 , wherein the liquid crystal composition has a negative dielectric anisotropy (Δε) value at 20° C. and an absolute value of 2.0 or more. Alignment type liquid crystal display element. 5. The vertical alignment liquid crystal display element according to claim 1 , wherein the liquid crystal composition contains a hindered phenol antioxidant. 6. The vertically aligned liquid crystal display element according to claim 1, wherein the liquid crystal molecules in the liquid crystal composition have a pretilt angle of 85° to 89.9 °.

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