JPH0262513A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To reduce a change in display color with a visual angle and to improve visual angle characteristics by setting the maximum refractive index direction in a birefringent surface and the orienting direction of liquid crystal molecules close to the birefringent layer within specific ranges. CONSTITUTION:A liquid crystal layer 31 is sandwiched between a substrate 11 which has a transparent electrode 13 and an orienting film 15 and a substrate 21 which has a transparent electrode 23 and an orienting film 25, polarizing plates 41 and 43 are arranged outside them, and a birefringent layer 50 is formed between the polarizing plate 41 and substrate 11. The maximum refractive index direction in the birefringent layer surface is set to <=5 deg. to the transmission axis or absorption axis of the polarizing plate 41 close to the birefringent layer 50, so a display image is prevented from decreasing in contrast. In the direction where the optical axis of the birefringent layer 50 is projected on the surface of the birefringent layer, the direction which is at a small angle to the orienting direction of liquid crystal close to the birefringent layer 50 is set to 0-45 deg. from the direction of the liquid crystal close to the birefringent layer 50 and then the color change with the visual angle is reducible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a liquid crystal display element, specifically an STN type liquid crystal display element, and can be widely used in various displays.

[Prior art] S T N (SUPERTWISTED NEMAT)
IC) type liquid crystal display elements have a structure in which liquid crystal molecules are twisted between substrates.

This is a liquid crystal display element in which the alignment direction of liquid crystal molecules on a substrate and the transmission axis or absorption axis of each polarizer are shifted by a predetermined angle to provide a birefringence effect.

In this STN type liquid crystal display element, the alignment direction of liquid crystal molecules changes near the threshold voltage, and the display color changes depending on the drive voltage due to the above-mentioned birefringence effect, so the brightness changes due to voltage are steep and has excellent time division characteristics. ing.

[Problems to be Solved by the Invention] However, on the other hand, since STN type liquid crystal display elements utilize the birefringence effect of liquid crystal, the product Δn−d of the thickness d of the liquid crystal layer and the refractive index anisotropy Δi of the liquid crystal The color tone of the display changes accordingly.

The apparent value of Δn−d changes depending on the viewing angle direction, that is, the direction in which the liquid crystal display element is viewed. Therefore, there is a problem in that the displayed colors appear different depending on the viewing direction.

The present invention has been made for the purpose of reducing the change in display color depending on the viewing angle and improving the viewing angle characteristics.

[Means to solve the problem] The present invention will be explained below.

In the liquid crystal display element of the present invention, in both claims 1 and 2, a liquid crystal layer made of liquid crystal molecules having positive dielectric anisotropy is sandwiched between a pair of substrates provided with electrodes, and the liquid crystal molecules are An STN type liquid crystal display element having a liquid crystal cell configured to be oriented substantially parallel to the substrate during application, and a pair of polarizers provided to sandwich the liquid crystal cell, wherein the liquid crystal layer on at least one side of

A birefringent layer is provided between the liquid crystal layer and the polarizer.

The invention according to claim 1 is characterized in that the angle formed by the maximum refractive index direction in the plane of the birefringent layer with respect to the direction of the transmission axis or absorption axis of the polarizer adjacent to the birefringent layer is 5 degrees or less, and the liquid crystal layer has a structure in which the liquid crystal molecules are twisted by 180 degrees or more in the layer thickness direction of the liquid crystal layer between the pair of substrates, and the liquid crystal molecules are twisted toward the front side in the birefringent layer. The invention according to claim 2 is characterized in that the maximum refractive index direction in the plane of the birefringent layer is in the range of 0 to 90 degrees with respect to the direction of the transmission axis or absorption axis of the polarizer close to the birefringent layer. The angle formed by the liquid crystal molecules is within 5 degrees, and the liquid crystal molecules in the liquid crystal layer have a structure twisted by 180 degrees or less in the thickness direction of the liquid crystal layer between the pair of substrates, and the liquid crystal molecules in the birefringent layer are twisted in opposite directions. It is characterized by being in the range of 0 to 90 degrees.

The birefringent layer mentioned here has refractive index anisotropy and needs to have light transmittance.

Specifically, aromatic polymers such as polyester, polycarbonate, polyarylate, polyetheretherketone, polysulfone, polyethersulfone, polyolefin polymers such as polyethylene and polypropylene, vinylidene chloride, polyvinyl alcohol, polystyrene,
Exemplary examples include stretched or extruded films of vinyl polymers such as acrylic resins, cellulose and its conductors, such as regenerated cellulose (cellophane), diacetyl cellulose, and triacetyl cellulose. Alternatively, a thin piece of crystal such as mica, calcite, or quartz cut out along a plane parallel to the optical axis can also be used.

Polymer-based materials can be particularly advantageously used because they can easily be obtained with a large area.

The birefringent layer is provided between the liquid crystal layer and the polarizer on one or both sides of the liquid crystal layer, but it may also be provided between the substrate of the liquid crystal cell and the polarizer and separate from the liquid crystal cell. It may also serve as a substrate in a liquid crystal cell, or may be configured as a part of the liquid crystal cell. Furthermore, a birefringent layer may be formed on the substrate by vapor deposition or the like. Alternatively, a film having a birefringent layer may be used as a protective film for the polarizer.

[Production use] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows two examples of the structure of the liquid crystal display element of the present invention. The configuration example shown in Figure 1 (1) is an example in which the birefringent layer is configured separately from the liquid crystal cell, and the configuration example shown in Figure 1 (m) is an example in which the birefringence layer is configured as one substrate of the liquid crystal cell. It is. In order to avoid complexity, the same reference numerals are used in FIGS. 1 (■) and (II) for items that are not likely to be confused.

In FIG. 1(I), reference numeral 10 indicates a liquid crystal cell. This liquid crystal cell 10 includes a substrate 11 on which a transparent electrode 13 and an alignment film 15 are formed, and a substrate 21 on which a transparent electrode 23 and an alignment film 25 are formed, which are arranged so as to face each other substantially parallel to each other. A liquid crystal layer 31 is formed by sealing a liquid crystal between them. Substrates 11 and 21 sandwiching liquid crystal layer 31
Electrode 13. Is is formed to constitute, for example, a dot matrix. Further, reference numeral 33 indicates a gap material, and reference numeral 35 indicates a sealing material. Polarizing plates 41 and 43 forming a pair of polarizers are arranged substantially parallel to each other and in parallel to the liquid crystal cell 1.
It is arranged to sandwich 0.

Between the polarizing plate 41 and the substrate 11, a birefringent layer 50 is arranged substantially parallel to the substrate 11.

Contrary to this example, a birefringent layer may be provided between the substrate 21 and the polarizing plate 43, and between the substrate 11 and the polarizing plate 41.

Also, one birefringent layer may be provided between the substrate 21 and the polarizing plate 43, respectively.

In the configuration example shown in FIG. 1 (II), the structure of the liquid crystal cell 10^ is different from the liquid crystal cell 10 shown in FIG. 1 (1), and in the liquid crystal cell IOA, the substrate 11A also serves as a birefringent layer.

Instead of the configuration shown in FIG. 1 (II), the substrate 21 may be configured with a birefringent layer, or both substrates may be configured with a birefringent layer. Furthermore, when birefringent layers are provided on both sides of a liquid crystal cell, one may be made separate from the liquid crystal cell and the other may be used as a substrate of the liquid crystal cell.

As the substrate 11.21, a translucent substrate such as glass or plastic film is used. The alignment films 15 and 25 are typically made of a polymer film made of polyamide, polyimide, or the like that has been subjected to a rubbing treatment.

The liquid crystal forming the liquid crystal layer 31 is one having positive dielectric anisotropy, and a typical example is a mixed liquid crystal in which chiral nematic liquid crystal or cholesteric liquid crystal is mixed into p-type nematic liquid crystal.

The liquid crystal molecules are oriented substantially parallel to the substrate surface, that is, the molecular structure is oriented substantially parallel to the substrate surface, and has a twisted structure.

Referring now to FIG. 2, this figure shows the angular relationship regarding the liquid crystal display element as seen from the polarizing plate 41 side, with a clockwise spiral moving upward from the bottom side, that is, the substrate 21 side. This shows the case where a structure is adopted.

In FIG. 2, the direction indicated by the reference numeral indicates the direction of liquid crystal molecules in the central portion of the liquid crystal layer 31 in the thickness direction. Also,
The transmission axis 43a of the polarizing plate 43 and the alignment direction of liquid crystal molecules in contact with the substrate 23, that is, the rubbing direction 21r of the alignment film z5)
βL is the angle formed by the transmission axis 41a of the polarizing plate 41 and the substrate 1.
1 (i.e., the rubbing direction 11r of the alignment film 15) is defined as βU. The angle α is the twist angle of the liquid crystal molecules.

Further, the direction of the maximum refractive index within the plate plane of the birefringent layer 50 (or the substrate 11A having the birefringent layer) is defined as the X direction, and the angle between this X direction and the rubbing direction 11r is defined as γ. Note that Figure 2 shows the side with the birefringent layer, that is, Figure 1 (
In r) and (H), the direction of the twist of the liquid crystal from the bottom to the top when the liquid crystal display element is predicted from the top is defined as positive. When the birefringent layer is provided below the liquid crystal [31] in FIGS. 1(T) and (II), the direction of twist from top to bottom when viewed from the bottom may be positive.

Furthermore, as shown in FIG. 3, a birefringent layer 50 (IIA)
The direction orthogonal to the X direction within the plate plane is defined as the X direction, and the direction orthogonal to both of these X+M directions, that is, the thickness direction of the birefringent layer, is defined as two directions, and the refractive index in these directions is respectively nmtny+n□.

Furthermore, the viewing angle direction is defined as shown in FIG. That is, the direction perpendicular to the substrate plane is N, the angle between this direction N and the direction of the incident light is θ, and the angle between the projection of the incident light onto the substrate plane and the direction MP is φ. Therefore, the viewing angle direction is determined by θ and φ.

As mentioned above, the X direction is the maximum refractive index direction in the plane of the birefringent layer, and if this direction and the transmission axis or absorption axis of the polarizing plate close to the birefringent layer are misaligned, the contrast of the displayed image will decrease. Therefore, in the present invention, the angle that the X direction makes with the transmission axis or the absorption axis is set to 5 degrees or less to prevent the contrast in the displayed image from decreasing.

Figure 5 shows an example of color change at five viewing angles for a conventionally known general STN type liquid crystal display element (tZV
) The cell parameters that characterize a liquid crystal display element are shown using a chromaticity diagram.

a = 220 degrees, βL = 45 degrees, βu = 45 degrees, Δn-
d ; O, Ij6 ttm. In this case, it becomes a yellow mode in which it is colored yellow when no voltage is applied.

As shown in FIG. 5, in the direction of φ: 0 degrees (indicated by 0), the color of the liquid crystal cell becomes reddish as θ increases.

φ: In the direction of 90 degrees (indicated by Δ), the color of the liquid crystal cell becomes bluish as θ increases. As is clear from this figure, the color change due to viewing angle is significant in the (u, v) chromaticity diagram, where the change in the value of U is significant.

Therefore, the color change due to viewing angle is expressed as ΔU(θ)=U(θ)−u(0) (1)
Evaluation is performed using ΔU(θ) defined by .

U(θ) is the value of U when the viewing angle is θ, u (0) is θ=0
The larger the value of ΔU(θ), the greater the color change depending on the viewing angle, that is, the worse the viewing angle characteristics are.

The results of evaluation using the above ΔU(θ) for the liquid crystal display elements having the configurations shown in FIGS. 1(I) and (II) will be explained. Each element has the same cell parameters, except for the location of the birefringent layer (which is separate from the liquid crystal cell or which also serves as a substrate), and the cell parameter values are as shown in Figure 5 above. Same as the example.

Δu(4o)(0240
FIG. 7 shows the change in ΔU(θ)) when the temperature increases. nX=
1.69. As nyn□ increases, the value of Δu(40) (curve 71) in the direction of φ:0 degrees increases, and φ=90
It becomes smaller in the direction of degrees (72 degrees). Furthermore, in the above example, when n2 is equal to the average value of n8 and n, Δu (
40) has the same value regardless of the presence or absence of a birefringent layer. Therefore, as shown in FIG. 1 (IL(II)), when a birefringent layer is used between the liquid crystal N31 and the polarizing plate 41, 124
For 5 degrees, change nl to n.

The viewing angle characteristics can be improved by making n smaller than the average value of n.

Also, when the X direction of the birefringent layer is y = -45 degrees, the seventh
As is clear from the figure, the larger n is, the smaller the value of Δu(40) (song @ 73) in the direction of φ = 0 degrees, and φ:
(74) becomes larger in the 90 degree direction. Therefore, γ
When the knee is 45 degrees, the viewing angle characteristics can be improved by making n larger than the average value of n8 and n.

In the above explanation, the case where the X direction of the plate member and the transmission axis of the polarizing plate coincide with each other at an angle of 45 degrees from the originating direction of the liquid crystal molecules has been explained. Even if the absorption axis of the polarizing plate is made to coincide with the X direction, the above explanation holds true as is.

Here, consider the optical axis of the birefringent layer when ntlnll is fixed and n is changed. nR+ nW 9 n
When the relationship of H is n, > n, > n □, there are two optical axes of the birefringent layer in the xz plane symmetrically to the
When projected onto the y plane), the direction becomes the X direction, which is the direction of the maximum refractive index in the plane of the birefringent layer. When nR:nW, the optical axis of the birefringent layer becomes the X axis. Also, n, >n, >n,
In this case, there are two optical axes of the birefringent layer in the xy plane symmetrically with respect to the X axis. In particular, when n□=(n8÷n)/2, the optical axis is in the direction of ±45 degrees from the Parallel or perpendicular to the direction.

When n,=n, the optical axis of the birefringent layer is the y-axis.

Furthermore, if n, > n, )n, the optical axis of the birefringent layer is x
There are two in the z-plane symmetrically about two axes, and when projected onto the birefringent layer plane, the direction becomes the X direction, which is a direction perpendicular to the maximum refractive index direction in the birefringent layer plane.

In the STN type liquid crystal display element of the above example, the case of 7245 degrees will be explained. When n≦n, the direction in which the optical axis of the birefringent layer is projected onto the plane of the birefringent layer coincides with the direction of the maximum refractive index of the birefringent layer, and is in the positive direction from the orientation direction of liquid crystal molecules close to the birefringent layer. It will be 45 degrees. ny〈nx＜(n
j”ny)/2, as shown in FIG. 6, among the optical axis directions of the birefringent layer, the direction (referred to as A direction) that makes a smaller angle with the liquid crystal molecule alignment direction is the liquid crystal molecule alignment direction. 0 to 45 degrees in the positive direction from nz = (n, +n,)
/2, the six directions and the liquid crystal molecule alignment direction match e nx>
When nz〉(nx”ny)/2, the six directions are at 0 to 45 degrees in the negative direction from the liquid crystal molecule orientation direction.n, ≦n
In the case of , the direction in which the optical axis of the birefringent layer is projected onto the birefringent layer plane is perpendicular to the maximum refractive index direction within the birefringent layer plane, and is 45 degrees in the negative direction from the liquid crystal molecule alignment direction.

Next, the case of γ=-45 degrees will be explained.

In the case of n, ≦n, the direction in which the optical axis of the birefringent layer is projected into the plane of the birefringent layer coincides with the maximum refractive index direction of the birefringent layer, and is 45 degrees in the negative direction from the liquid crystal molecule orientation direction. . ny
When 〈nR〈(nx”ny)/2, the six directions are at 0 to 45 degrees in the negative direction from the liquid crystal molecule alignment direction, and n□
= (n8÷n,)/2, when the six directions and the liquid crystal molecule alignment direction match - nm〉nz〉(r+R+nw)/2,
The A direction is 0 to 45 in the positive direction from the liquid crystal molecule orientation direction.
When mnz≦08, the direction in which the optical axis of the birefringent layer is projected onto the birefringent layer plane is perpendicular to the maximum refractive index direction in the birefringent layer plane, and is in the positive direction from the liquid crystal molecule orientation direction. It will be 45 degrees.

As can be seen from the above explanation, in order to reduce the color change depending on the viewing angle in the STN type liquid crystal display element of the above example, it is necessary to The direction that makes the smallest angle with the orientation direction of liquid crystal molecules close to the birefringent layer.

It is necessary to set the angle in the positive direction from 0 to 45 degrees from the alignment direction of liquid crystal molecules close to the birefringent layer.

The yellow mode has been explained above, and now the blue mode will be explained.

The cell parameters are α=220 degrees, βL=45 degrees, β
When U=-45 degrees and Δn-d=0.86 μm, the color becomes blue when no voltage is applied and yellow when a voltage is applied. This blue mode STN type liquid crystal display element is shown in Figures 1 (1) and (I
FIG. 8 shows the change in Δu(40) when refractive in the birefringent layer 50 (IIA).

As is clear from this figure, at 1245 degrees, n,
As becomes larger, the value of Δu(40) in the direction of φ=θ degrees becomes smaller (curve 81), and increases in the direction of φ:90 degrees (curve 82).

Also, when n is equal to the average value of nX and n, Δu
(40) has the same value regardless of the presence or absence of a birefringent layer.

Therefore, in the case of 1245 degrees, n! By making n8 smaller than the average value of n, the viewing angle characteristics can be improved.

When γ=-45 degrees, as is clear from song 1IIc83.84 in Figure 8, the larger nIl is, the larger the value of Δu (40) in the direction of φ=0 degrees, and the value of Δu (40) in the direction of φ: 90 degrees becomes It becomes smaller in the direction. Therefore, in the case of γ knee 45 degrees, n is n8
The viewing angle characteristics can be improved by increasing the average value of and n.

Similar to the yellow mode, the polarizing plates 41 and 43 are each 90
Even if the polarizing plate is rotated by a degree so that the absorption axis of the polarizing plate coincides with the X direction, the above explanation still holds true.

Therefore, the conditions for reducing the color change depending on the viewing angle of the STN type liquid crystal display element in the blue mode are the same as in the yellow mode.

Furthermore, this relationship holds true even when the value of γ is at angles other than ±45 degrees, and color changes due to viewing angle can be reduced.

Among the directions in which the optical axis of the birefringent layer is projected onto the birefringent layer surface, the direction that has a smaller angle with the orientation direction of liquid crystal molecules close to the birefringence layer is 0 to 90 degrees in the positive direction from the orientation direction of the liquid crystal molecules. It needs to be within the range.

Next, changes in viewing angle characteristics when the twist angle α is changed will be explained.

In Figure 7, Δu(40) in the direction of φ=0 degrees and φ=
02 when Δu(40) in the 90 degree direction is the same as n
c, and the difference between the average value of n8 and n and nc is Δn2.

That is, Δn2min-((n, +n,)/2) (2
).

In Figure 7, when 7245 degrees, Δnz is negative and γ=-
When the angle is 45 degrees, Δn2 is positive.

FIG. 9 shows the change in Δnz when the twist angle α is changed. All polarizing plate angles for each twist angle are βL:β
U: 45°, the value of Δn−d is as shown in Table 1.

Table 1 Twist angle (degrees) 160 180 200 22
0 240Δn-d (μm) 0.98 0.
95 0.91 0.86 0.81 As shown in Figure 9, at 7245 degrees, when α is 180 degrees or more, Δn2 is negative, when α is 180 degrees or less, Δn2 is positive, and when γ = -45 degrees, α is When α is 180 degrees or more, Δnz is positive, and when α is 180 degrees or less, Δnz is negative. Therefore, the condition for reducing color change due to viewing angle is that the twist angle is 18. The relationship between the molecular orientation directions is opposite when the twist angle is 180 degrees or more and 180 degrees or less.

From the above, in the STN type liquid crystal display element, a birefringent layer is provided between the liquid crystal layer 31 and the polarizing plate 41 as shown in FIGS. 1(I) and (II) to reduce color change depending on the viewing angle. In order to do so, it is necessary to satisfy the following conditions.

(1) When the twist angle is 180 degrees or more, among the directions in which the optical axis of the birefringent layer is projected onto the plane of the birefringent layer, the direction that has the smallest angle with the orientation direction of liquid crystal molecules close to the birefringent layer is the direction of the liquid crystal. It is in the range of 0 degrees to 90 degrees in the positive direction from the molecular orientation direction.

(2) When the twist angle is 180 degrees or less, among the directions in which the optical axis of the birefringent layer is projected onto the birefringent layer surface, the direction that has the smallest angle with the orientation direction of liquid crystal molecules close to the birefringent layer is the direction of the liquid crystal. It is in the range of 0 degrees to 90 degrees in the negative direction from the molecular orientation direction.

The case where the birefringent layer is provided between the liquid crystal layer 31 and the polarized light Fi 41 has been described above.
1 and the polarizing plate 43, the X direction and the substrate 2
If the angle formed with the rubbing direction of the alignment film 25 in No. 1 is γ, the conditions for reducing color change due to viewing angle are as follows.
The conditions are the same as above, and the liquid crystal layer 31 and polarizing plate 41.
In the case where a birefringent layer is provided between each of the layers 43, it is sufficient that the above conditions are satisfied for at least one of the birefringent layers.

[Example] Hereinafter, specific examples will be explained.

Example 1 A striped ITO transparent electrode was formed on a glass plate, an alignment film was formed from polyamide on the transparent electrode, and a rubbing treatment was applied to this to form a substrate 11.21, and a nematic film was placed between these substrates. A liquid crystal cell 10 was prepared by filling a liquid crystal obtained by mixing a chiral nematic liquid crystal with a liquid crystal. Polarizing plates 4] and 43 were provided on both sides of this liquid crystal cell IO. The cell parameters are (t = 200 degrees, βL = β
U = 45 degrees, Δnd = 0.86 p m.

For this liquid crystal display element, spectra were measured in various viewing angle directions φ and θ, and chromaticity coordinates (u, v) were calculated. A curve 101 in FIG. 10 shows a change in ΔU(θ) in the direction of φ=0 degrees, and a curve 102 shows a change in the direction of φ=90 degrees in the case where there is no birefringent layer.

Next, the liquid crystal cell 1 is made of -m stretched PET as the birefringent layer 50.
0 and the polarizing plate 41, a liquid crystal display element having the configuration as shown in FIG. 1(1) was constructed as an example, and similar measurements were performed. In FIG. 10, for 7245 degrees, curve 103 is the change in ΔU (θ) in the direction of φ: 0 degrees, curve 104 is the change in ΔU (θ) in the direction of φ: 90 degrees, and curve 105 is for γ = -45 degrees.
106 indicates a change in the direction of φ=θ degrees, and 106 indicates a change in the direction of φ:90 degrees. In addition, the refractive index and Δn of −-axis oriented PET
The values of -d are as shown in Table 2.

Table 2 n4 ny nx Δ
rrd1.6922 1.5903 1.52
07 10.0 As you can see from Figure 10, 7245
At the same time, the use of the birefringent layer 50 reduces color change depending on the viewing angle and improves viewing angle characteristics. But γ knee 45
degree, the viewing angle characteristics actually deteriorate. In uniaxially stretched PET that constitutes a birefringent layer, the refractive index n z Hn M + n
Since the relationship of l is n, > n, > n, the projection direction of the optical axis of -axis stretched PET onto the plane is the X direction, so when γ is 45 degrees, condition (1) is satisfied. is satisfied, but γ
Condition (1) is not satisfied when = -45 degrees.

Example 2 Uniaxially stretched PE with striped ITO transparent electrodes formed
A polyamide film was coated as an alignment film on the T film, and this was subjected to a rubbing treatment to form a substrate. A liquid crystal cell made of a mixture of nematic liquid crystal and chiral nematic liquid crystal was sealed between these substrates. This cell is an example in which the substrate 21 is also made of a uniaxially oriented PET film in the structure shown in FIG. 1 (II). This liquid crystal cell was sandwiched between two polarizing plates to form a liquid crystal display cell.

Cell parameters are α=210 degrees, βL:βU=45
Every time.

Δnd=0.89 prn, yu=45 degrees,
Yd=-45 degrees. Here, γU is the angle from the rubbing direction of the upper substrate to the X direction of the upper substrate, and the twisting direction of the liquid crystal molecules from bottom to top when viewed from the top (
(clockwise when viewed from above) is positive. γd is the angle from the rubbing direction of the lower substrate to the X direction of the same substrate,
The direction in which the liquid crystal molecules twist from top to bottom when viewed from the bottom (counterclockwise when viewed from the bottom) is positive. Further, the refractive index of the uniaxially stretched PET constituting the substrate is the same as that given in the table.

Example 3 Same configuration as Example 2, cell parameter α=2
10 degrees, βL=βU=45 degrees, Δn-d =0.89μ
n, yu = 45 degrees, and γd = 45 degrees.

Comparative Example 1 Same configuration as Example 2, cell parameter α: 210
degree, βL: βU = 45 degrees, Δn-d = 0.89 μm,
yu=-45 degrees and γd=-45 degrees.

Comparative Example 2 A polyamide film was coated as an alignment film on the electrode of a glass plate on which a striped ITO transparent electrode was formed, and this was subjected to a rubbing treatment to obtain a substrate.

A liquid crystal cell made of a mixture of nematic liquid crystal and chiral nematic liquid crystal was sealed between these substrates. This liquid crystal cell was sandwiched between two polarizing plates to form a liquid crystal display element. This element has a structure shown in FIG. 1(I) with a birefringent layer 5
This is the configuration excluding 0.

Cell parameters are α: 210 degrees, βL: βU = 45
Every time.

Δn−d=0.89 μn.

Regarding these Examples 2 and 3 and Comparative Examples 1 and 2, the O dependence of ΔU(θ) was investigated using the same measurements as in Example 1. Figure 11 shows the results.

Songs fi111 and 112 are similar to Example 2, and are similar to Example 11.
3.114 relates to Example 3, 115,116
117 and 118 are related to Comparative Example 2.

Example 2 is a case where the upper substrate satisfies the above condition (1) but the lower substrate does not satisfy the condition (1). In this example, since condition (1) is satisfied by the upper substrate, the viewing angle characteristics are good as shown in FIG. Also, Example 3
Since both the upper and lower substrates satisfy condition (1), the color change due to viewing angle is small. In Comparative Example 1, both the upper and lower substrates do not satisfy condition (1), so the color changes depending on the viewing angle are large. Furthermore, in Comparative Example 2, since no birefringent layer was used, the color change was large depending on the viewing angle.

Example 4 A polyamide film was coated as an alignment film on the electrode of a glass plate on which a striped ITO transparent electrode was formed, and this was subjected to a rubbing treatment to obtain a substrate. A liquid crystal obtained by mixing nematic liquid crystal and chiral nematic liquid crystal was sealed between these substrates to form a liquid crystal cell, and polarizing plates were provided on both sides of the liquid crystal cell.

The cell parameters are a''160 degrees, β, = βl, = 4
5 degrees, Δn-d=0.98 μm.

Regarding this liquid crystal display element, the θ dependence of Δn(θ) was investigated using the same measurements as in Example 1. The result is the 12th
This is shown in songs g121 and g122 in the figure.

Next, -axis-stretched PET was placed between a liquid crystal cell and a polarizing plate with a birefringence of /1t50 to form a liquid crystal display element having the configuration as shown in FIG. 1(I), and similar measurements were performed. 1st
In Figure 2, for γ = 45 degrees, the curve 123,1
24 corresponds, and for γ=-45 degrees the curve 125.1
26 corresponds. - The refractive index of axially stretched PET is the same as given in Table 1.

As can be seen from Figure 12, when γ = 45 degrees, the condition (2
), the color change depending on the viewing angle becomes large, and γ
When = -45 degrees, condition (2) is satisfied, so the color change depending on the viewing angle is small.

[Effects of the Invention] According to the present invention, a novel STN type liquid crystal display element can be provided. Since this liquid crystal display element has the above-mentioned configuration, it is possible to reduce color change depending on the viewing angle and to provide a high-contrast display with good viewing angle characteristics. Therefore 1
Display characteristics have been improved and images of high quality can be displayed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing two configuration examples of a liquid crystal display element according to the present invention, FIGS. 2 to 9 are diagrams for explaining the present invention,
FIG. 10, FIG. 11, and FIG. 12 are diagrams for explaining the embodiment. 11A, birefringent layer that also serves as a substrate, 501. Birefringent layer, shape d mouth N shape b ■chi7 difficultμgwel ? 9 δ Horizontal shape 6 Illusion φ = θ. p=%. △ll(θ9 max.

Claims (1)

[Claims] 1. A liquid crystal layer made of a liquid crystal composition having positive dielectric anisotropy is sandwiched between a pair of substrates provided with electrodes, and liquid crystal molecules are substantially parallel to the substrates when no voltage is applied. The liquid crystal molecules are aligned in the thickness direction of the liquid crystal layer between the pair of substrates.
It has a liquid crystal cell configured to have a twisted structure of 80 degrees or more, and a pair of polarizers provided to sandwich this liquid crystal cell, and the alignment direction of liquid crystal molecules close to the polarizer and the polarizer A liquid crystal display element configured by shifting the transmission axis or absorption axis direction of the liquid crystal layer, wherein a birefringent layer is provided between the liquid crystal layer and a polarizer on at least one side of the liquid crystal layer, and the birefringent layer The angle formed by the direction of the maximum refractive index in the plane of the birefringent layer with respect to the direction of the transmission axis or absorption axis of the polarizer in the vicinity of Among the directions, the direction that has a smaller angle with the orientation direction of liquid crystal molecules close to the birefringent layer is from the orientation direction of liquid crystal molecules adjacent to the birefringence layer toward the front side when viewed from the side of the birefringence layer. A liquid crystal display element characterized in that the direction in which liquid crystal molecules are twisted is within a range of 0 to 90 degrees. 2. A liquid crystal layer made of a liquid crystal composition having positive dielectric anisotropy is sandwiched between a pair of substrates provided with electrodes, and the liquid crystal molecules are oriented approximately parallel to the substrates when no voltage is applied. 1 molecule in the thickness direction of the liquid crystal layer between the pair of substrates.
It has a liquid crystal cell configured to have a twisted structure of 80 degrees or less, and a pair of polarizers provided to sandwich this liquid crystal cell, and the alignment direction of liquid crystal molecules close to the polarizer and the polarizer A liquid crystal display element configured by shifting the transmission axis or absorption axis direction of the liquid crystal layer, wherein a birefringent layer is provided between the liquid crystal layer and a polarizer on at least one side of the liquid crystal layer, and the birefringent layer The angle formed by the direction of the maximum refractive index in the plane of the birefringent layer with respect to the direction of the transmission axis or absorption axis of the polarizer in the vicinity of Among the directions, the direction that has a smaller angle with the orientation direction of liquid crystal molecules close to the birefringent layer is from the orientation direction of liquid crystal molecules adjacent to the birefringence layer toward the front side when viewed from the side of the birefringence layer. 0 to 9 in the opposite direction to the direction in which the liquid crystal molecules twist.
A liquid crystal display element characterized by being in the 0 degree range. 3. The liquid crystal display element according to claim 1 or 2, wherein a birefringent layer is provided between the substrate and the polarizer. 4. The liquid crystal display element according to claim 1 or 2, wherein at least one of the substrates has birefringence.