JP2003279992A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element capable of widening a viewing angle, almost eliminating the band color of display and obtaining excellent contrast. <P>SOLUTION: Between polarizing plates 2 and 3 in front and at the rear of a liquid crystal cell 1, optical films 4 and 5 for viewing angle compensation having a retardation cancelling the residual retardation of a liquid crystal layer at the time of applying an electric field to vertically orient a liquid crystal polymer in the middle of the thickness direction of the liquid crystal layer of the liquid crystal cell are arranged. Between the optical film 4 on the front side and the front side polarizing plate 2, an optical retardation layer 6 composed of the first optical retardation film 7 of the low wavelength dependency of the retardation, whose main agent is norbornene, and the second optical retardation film 8 of the high wavelength dependency of the retardation, whose main agent is polycarbonate, and provided with the retardations for respective wavelengths corresponding to the difference of synthetic retardations for respective wavelength lights in the wavelength dependency of the synthetic retardation for which the liquid crystal layer and the optical films 4 and 5 are synthesized is arranged in optical axis arrangement in which the synthesis of the synthetic retardations for the respective wavelength lights becomes the retardation difference. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art As a liquid crystal display device, in order to widen the viewing angle, a liquid crystal cell provided with a liquid crystal layer in which an alignment state of liquid crystal molecules is changed between a pair of substrates according to an applied electric field,
There is a liquid crystal cell in which an optical film for compensating for a viewing angle is arranged between the liquid crystal cell and a polarizing plate arranged so as to face at least one surface of the liquid crystal cell.

[0003]

However, in the conventional liquid crystal display device provided with the optical film for viewing angle compensation, the wavelength dependence of the retardation of the liquid crystal layer of the liquid crystal cell,
Since the wavelength dependence of the retardation of the optical film is different, the transmitted light is colored due to the difference in the wavelength dependence of these retardations, which causes a banding in the display and lowers the contrast.

It is an object of the present invention to provide a liquid crystal display device having a wide viewing angle, almost no display color band, and good contrast.

[0005]

A liquid crystal display device according to the present invention includes a liquid crystal cell having a liquid crystal layer in which an alignment state of liquid crystal molecules is changed between a pair of substrates according to an applied electric field, and at least the liquid crystal cell. A polarizing plate disposed so as to face one surface, and a retardation that cancels the residual retardation of the liquid crystal layer when an electric field is applied to align the liquid crystal molecules of the liquid crystal layer substantially perpendicular to the substrate surface. Then, an optical film for viewing angle compensation disposed between the liquid crystal cell and the polarizing plate, of the synthetic retardation for each wavelength light in the wavelength dependence of the synthetic retardation synthesized the liquid crystal layer and the optical film. Having a retardation for each wavelength corresponding to the difference, with the liquid crystal cell in the optical axis arrangement such that the composition with the composite retardation for each wavelength light is the retardation difference. Characterized in that a retardation layer disposed to overlap with the optical film between the light plate.

This liquid crystal display device has a viewing angle compensation having a retardation that cancels the residual retardation of the liquid crystal layer when an electric field is applied to the liquid crystal layer of the liquid crystal cell so as to align the liquid crystal molecules substantially perpendicularly to the substrate surface. Since it is provided with an optical film for, it is possible to widen the viewing angle, each corresponding to the difference in retardation for each wavelength light in the wavelength dependence of the retardation synthesized the liquid crystal layer and the optical film A retardation layer having a retardation for each wavelength is provided in an optical axis arrangement in which the composition with the synthetic retardation for each wavelength light is a retardation difference, so that the liquid crystal layer and the optical film, and further a retardation layer. The wavelength dependence of the synthesized retardation is virtually eliminated, the coloring of transmitted light is reduced, and the banding of the display is almost eliminated. Together, it is possible to obtain a good contrast.

As described above, the liquid crystal display element of the present invention is
For viewing angle compensation having retardation that cancels residual retardation of the liquid crystal layer when an electric field is applied to align liquid crystal molecules positioned in the middle of the liquid crystal layer of the liquid crystal cell in a direction substantially perpendicular to the substrate surface. With the optical film, the liquid crystal layer and the optical film has a retardation for each wavelength corresponding to the difference in the synthetic retardation for each wavelength light in the wavelength dependence of the synthetic retardation synthesized, the each wavelength Providing a retardation layer provided with an optical axis arrangement that results in a retardation difference when combined with the combined retardation for each light, widens the viewing angle, and almost eliminates the color band of the display, and provides good contrast. It was done like this.

In the liquid crystal display device of the present invention, it is preferable that the retardation layer is formed of a plurality of substances having different wavelength dependences of retardation.

Further, the retardation layer comprises a first retardation plate containing norbornene or polysulfone as a main component and having a small wavelength dependence of retardation, and a second retardation plate containing polycarbonate as a main component and having a large wavelength dependence of retardation. More preferably, it is formed by a plate.

[0010]

1 is an exploded perspective view of a liquid crystal display element showing an embodiment of the present invention.

The liquid crystal display element of this embodiment is of a transmissive type, and is composed of a liquid crystal cell 1 and a pair of polarizing plates which are arranged so as to face each other on the front side and the rear side of the liquid crystal cell 1 which are the viewing side of the display. 2 and 3, two optical films 4 and 5 for compensating the viewing angle, which are respectively arranged between the liquid crystal cell 1 and the front and rear polarizing plates 2 and 3, and the liquid crystal cell 1 and the front and rear polarizing plates 2. , 3 and the optical film 4 or 5 and the retardation layer 6 disposed so as to overlap.

In this embodiment, the retardation layer 6 is used.
Are disposed between the front optical film 4 disposed on the front side of the liquid crystal cell 1 and the front polarizing plate 2.

The liquid crystal cell 1 is, for example, an active matrix liquid crystal cell, and the structure thereof is not shown, but of the pair of front and rear transparent substrates bonded via a frame-shaped sealing material, the inner surface of one substrate is A plurality of pixel electrodes arranged in the row direction and the column direction, TFTs (thin film transistors) connected to these pixel electrodes, and TFTs in each row
A plurality of gate wirings that respectively supply a gate signal to
A plurality of data lines for supplying a data signal are provided to the TFTs in each column, a counter electrode is provided on the inner surface of the other substrate, and an alignment film is formed on the innermost surface of both substrates. A liquid crystal layer is provided in a region surrounded by the sealing material.

This liquid crystal cell 1 is of a homogeneous alignment type, and in the liquid crystal layer, liquid crystal molecules are substantially horizontal with a predetermined pretilt angle with respect to the substrate surface in an electric field-free state in which no electric field is applied. It is made of nematic liquid crystal that is homogeneously aligned in one direction and changes its alignment state in the direction in which liquid crystal molecules stand up with respect to the substrate surface when an electric field is applied.

In FIG. 1, reference numeral 1a indicates the alignment direction of the liquid crystal molecules of the liquid crystal cell 1, and the liquid crystal molecules intersect at an angle of substantially 90 ° with respect to the horizontal axis x of the screen of the liquid crystal display element. It is homogeneously oriented along the direction.

Then, of the pair of polarizing plates 2 and 3,
The polarizing plate 2 on the front side has its absorption axis 2a substantially 45 ° counterclockwise when viewed from the front side with respect to the horizontal axis x of the screen, that is, with respect to the liquid crystal molecule alignment 1a of the liquid crystal cell 1. The polarizing plate 3 on the rear side is arranged so that the absorption axis 3a thereof is counterclockwise with respect to the horizontal axis x of the screen in the direction of 135 °. That is,
The front polarizing plate 2 is arranged in a direction substantially orthogonal to the absorption axis 2a.

The two viewing angle compensating optical films 4 and 5 are, for example, disk-shaped discotic liquid crystal molecules which are laid down with a slight tilt angle in one direction with respect to one surface. A retardation film comprising a discotic liquid crystal film which is oriented and gradually rises in a direction in which the tilt angle is increased from the one surface to the other surface, and is a disc-shaped discotic liquid crystal molecule. It has slow axes 4a and 5a in a direction parallel to the surface and parallel to the film surface.

Optical films 4 for compensating for these viewing angles
Reference numeral 5 indicates that the planes in which the discotic liquid crystal molecules have the same alignment state (opposite alignment planes or rising alignment planes) face each other, and their slow axes 4a and 5a are set to the horizontal axis x of the screen. They are arranged in a parallel direction, that is, in a direction substantially orthogonal to the liquid crystal molecule alignment 1a of the liquid crystal cell 1.

The two viewing angle compensating optical films 4 and 5 are arranged such that liquid crystal molecules located in the middle of the liquid crystal layer of the liquid crystal cell 1 are vertically oriented substantially perpendicular to the substrate surface. It is intended to cancel the residual retardation of the liquid crystal layer when an electric field is applied to compensate for the narrowing of the viewing angle due to the residual retardation of the liquid crystal layer. These optical films 4 and 5 have a total retardation of both of them. When the electric field is applied to the liquid crystal layer of the liquid crystal cell 1 so that the liquid crystal molecules in the middle in the layer thickness direction rise and align substantially perpendicularly to the substrate surface, the liquid crystal molecules near the substrate sufficiently rise. It has a retardation that is a value that cancels the residual retardation of the liquid crystal layer due to not cutting.

On the other hand, the retardation layer 6 is formed in the liquid crystal cell 1.
Which has a retardation for each wavelength corresponding to a difference in synthetic retardation for each wavelength light in the wavelength dependence of the synthetic retardation obtained by synthesizing the liquid crystal layer and the optical films 4 and 5 for viewing angle compensation, The optical axes are arranged such that the combination with the combined retardation for each wavelength light gives a retardation difference. The retardation layer 6 is made of a plurality of substances having different wavelength dependences of retardation.

The retardation layer 6 used in this example is the first and second retardation plates 7 and 8 made of a uniaxially stretched film.
The first retardation plate 7 among these retardation plates 7 and 8 is a retardation plate having norbornene as a main component and having a small wavelength dependence of retardation, and a second retardation plate 8 Is a retardation plate containing polycarbonate as a main component and having a large wavelength dependence of retardation.

Both norbornene, which is the main ingredient of the first retardation plate 7, and polycarbonate, which is the main ingredient of the second retardation plate 8, have positive photoelastic constants, and The retardation plates 7 and 8 have slow axes 7a and 8a in the extending direction.

The first and second retardation plates 7 and 8 are laminated such that their slow axes 7a and 8a are substantially orthogonal to each other, and are composed of these two retardation plates 7 and 8. In the retardation layer 6, the first retardation plate 7 having a small retardation wavelength dependency is opposed to the front polarizing plate 2, and the second retardation plate 8 having a large retardation wavelength dependency is compensated for the front viewing angle. Facing the optical film 4 for use, and the slow axis 7a of the first retardation plate 7 is in a direction parallel to the horizontal axis x of the screen, that is, substantially orthogonal to the liquid crystal molecule alignment 1a of the liquid crystal cell 1. In the direction perpendicular to the horizontal axis x of the screen, that is, in the direction substantially parallel to the liquid crystal molecule alignment 1a of the liquid crystal cell 1. It is arranged toward.

The liquid crystal layer of the liquid crystal cell 1, the two viewing angle compensating optical films 4 and 5, and the retardation layer 6 are provided.
The respective retardations of the first and second retardation plates 7 and 8 are set to the following values.

That is, Δn of the liquid crystal layer of the liquid crystal cell 1
d (product of refractive index anisotropy Δn of liquid crystal and liquid crystal layer thickness d) is
The residual retardation when an electric field is applied (hereinafter referred to as ON) when a liquid crystal molecule positioned in the middle of the thickness direction of the liquid crystal layer is vertically oriented and oriented substantially perpendicular to the substrate surface (hereinafter referred to as ON) is in the middle of the visible light band. 60 between the ordinary light and the extraordinary light with respect to the transmitted light (green wavelength light) having a wavelength of 550 nm.
It is set to a value that gives a phase difference of nm.

The retardation of this liquid crystal layer has wavelength dependence, and the residual retardation for light of wavelength 450 nm (light of blue wavelength) is 64 nm, and the residual retardation for light of wavelength 650 nm (light of red wavelength) is 58 nm.
Is.

The two viewing angle compensating optical films 4 and 5 have a retardation that gives a retardation in the opposite direction to the retardation due to the retardation of the liquid crystal layer between the ordinary light of the transmitted light and the extraordinary light. However, assuming that the retardation value is a negative value, the retardation of each of the optical films 4 and 5 is set to −30 nm with respect to light having a wavelength of 550 nm.

That is, the two optical films 4, 5
The total value of the retardation of both is -60 nm with respect to the light having a wavelength of 550 nm. Therefore, these optical films 4 and 5 have residual retardation when the liquid crystal layer is ON (60 nm with respect to the light having a wavelength of 550 nm). Acts to cancel.

450 nm of these optical films 4 and 5
Of -41 nm, 650
The retardation with respect to light having a wavelength of nm is -25 nm, and the wavelength dependence of the retardation is different from the wavelength dependence of the retardation of the liquid crystal layer.

On the other hand, of the first and second retardation plates 7 and 8 of the retardation layer 6, the first retardation plate 7 whose main component is norbornene is the one between the ordinary and extraordinary rays of transmitted light. Has a retardation that gives a retardation in a direction opposite to the retardation due to the retardation of the liquid crystal layer, that is, a retardation of a negative value, and the retardation of the first retardation plate 7 is -270 nm with respect to light having a wavelength of 550 nm. Is set to.

The retardation of the first retardation plate 7 containing norbornene as the main component with respect to the light of wavelength 450 nm is -274 nm and the retardation with respect to the light of wavelength 650 nm is -268 nm, and the wavelength dependence of the retardation is extremely small.

A second resin containing polycarbonate as a main component
The retardation plate 8 has a retardation retardation in the same direction as the retardation due to the retardation of the liquid crystal layer between the ordinary light of the transmitted light and the extraordinary light, that is, a retardation of a positive value. 8 retardation is 5
The absolute value of the retardation (-270 nm) of 270 nm with respect to the light of wavelength of 50 nm, that is, the retardation (-270 nm) of the first retardation plate 7 with respect to the light of wavelength of 550 nm is set.

The retardation of the second retardation plate 8 containing this polycarbonate as the main component with respect to the light having a wavelength of 450 nm is 290 nm and the retardation with respect to the light having a wavelength of 650 nm is 258 nm. It is considerably larger than that of the first retardation plate 7.

This liquid crystal display device transmits light when turned on when an electric field is applied to align the liquid crystal molecules located in the middle of the liquid crystal layer of the liquid crystal cell 1 in a direction substantially vertical to the substrate surface. The display is black due to the minimum ratio, and the applied electric field is controlled between the ON electric field and the OFF electric field value in which the liquid crystal molecules are aligned in the alignment state in which the light transmittance is maximum. The display is driven by.

Since this liquid crystal display device is provided with the viewing angle compensating optical films 4 and 5 having a retardation for canceling the residual retardation when the liquid crystal layer of the liquid crystal cell 1 is turned on, the viewing angle can be widened.

That is, the retardation of the liquid crystal layer of the liquid crystal cell 1 becomes smaller as the liquid crystal molecules rise and align with respect to the substrate surface, but the liquid crystal molecules located substantially in the middle of the thickness direction of the liquid crystal layer are substantially retarded. Even when an ON electric field is applied to the substrate, the liquid crystal molecules in the vicinity of the substrate, which are strongly affected by the alignment regulating force of the alignment film, do not rise sufficiently, and thus retardation remains in the liquid crystal layer.

Therefore, when a liquid crystal display element is composed of the liquid crystal cell 1 and a pair of polarizing plates 2 and 3 arranged before and after the liquid crystal cell 1, the residual retardation when the liquid crystal layer of the liquid crystal cell 1 is turned on is displayed. The viewing angle is affected, and a sufficient viewing angle cannot be obtained.

On the other hand, since the liquid crystal display device is provided with the viewing angle compensating optical films 4 and 5, the residual retardation when the liquid crystal layer of the liquid crystal cell 1 is turned on is canceled by the optical films 4 and 5. The viewing angle can be widened.

In addition, this liquid crystal display device corresponds to the difference in the synthetic retardation for each wavelength light in the wavelength dependence of the synthetic retardation obtained by synthesizing the liquid crystal layer of the liquid crystal cell 1 and the viewing angle compensating optical films 4, 5. The retardation layer 6 having retardation for each wavelength is an optical axis arrangement in which the retardation layer 6 has a retardation difference when combined with the combined retardation for each wavelength light, that is, the liquid crystal layer and the optical films 4 and 5 are combined. The liquid crystal layer and the optical films 4 and 5 are synthesized because the retardation of the retardation layer 6 is provided with an optical axis arrangement that causes a difference (subtraction) in the synthesis when the retardation of the retardation layer 6 is further synthesized. The wavelength dependence existing in the synthetic retardation, and the wavelength dependence obtained by synthesizing the retardation of the retardation layer 6 as a whole By making the value substantially zero, the coloring of transmitted light due to the difference in the wavelength dependence of the retardation of each of the liquid crystal layer and the optical films 4 and 5 is reduced, the band color of the display is almost eliminated, and a good contrast is obtained. Can be obtained.

That is, in this embodiment, the residual retardation when the liquid crystal layer of the liquid crystal cell 1 is ON is 2
Since the retardation values of the viewing angle compensation optical films 4 and 5 are set as described above, the residual retardation value (60 nm) of the liquid crystal layer and two The total value with the total retardation value (−60 nm) of both the optical films 4 and 5 is 0.

However, since there is the above-mentioned difference in the wavelength dependence of the retardation of the liquid crystal layer and the wavelength dependence of the retardation of the two optical films 4 and 5,
For light having a wavelength of 50 nm, the total value of the residual retardation of the liquid crystal layer (64 nm) and the retardation of both of the two optical films 4 and −41 nm × 2 = −
82nm) becomes -18nm, and 650nm
With respect to the light having the wavelength of, the total retardation of the liquid crystal layer (58 nm) and the retardation of both of the two optical films 4 and 5 are −25 nm × 2 = −50 n.
The total value with m) is 8 nm.

Therefore, in the case where the retardation layer 6 is not provided, the transmittance of light having a wavelength of 550 nm, which is the intermediate wavelength of the visible light band, is minimal when it is ON, but the transmittance of light of other wavelengths when it is ON. Does not become extremely small. Therefore, the transmitted light is colored and the black display becomes colored, and the darkness of the black display rises, so that sufficient contrast cannot be obtained.

On the other hand, in this liquid crystal display element, the retardation layer 6 having a retardation corresponding to the difference between the respective wavelengths of the synthetic retardation of the liquid crystal layer and the optical films 4 and 5 is provided for each wavelength. The optical axis arrangement is such that when the retardation of the retardation layer 6 is further combined with the retardation obtained by combining the liquid crystal layer and the viewing angle compensation optical films 4 and 5, the combination becomes a difference (subtraction). Since it is provided, coloring of the transmitted light due to the difference in the wavelength dependence of the retardation of each of the liquid crystal layer and the optical films 4 and 5 is reduced, the black color band at the time of ON is almost eliminated, and good contrast is obtained. Obtainable.

In this embodiment, the retardation layer 6 is composed of a first retardation plate 7 containing norbornene as a main component and having a small wavelength dependence of retardation, and a second retardation plate containing polycarbonate as a main component and having a large wavelength dependence of retardation. And the retardation values of the phase difference plates 7 and 8 are set as described above, the transmittance at the time of ON is minimized over the entire visible light band. You can

The following [Table 1] shows 450 nm and 550 n.
m, the residual retardation when the liquid crystal layer of the liquid crystal cell 1 is turned on for each wavelength of 650 nm, the retardation of the two viewing angle compensating optical films 4 and 5, and the first and second positions of the retardation layer 6. The retardation of the phase difference plates 7 and 8 and the total value of all these retardations are shown.

[0046]

[Table 1]

As shown in [Table 1], the liquid crystal display device of this example has a residual retardation when the liquid crystal layer of the liquid crystal cell 1 is turned on and two viewing angle compensating optical films 4, 4.
5 and the retardation of the first and second retardation layers 7 and 8 of the retardation layer 6 are 450
nm wavelength light is -2 nm, 550 nm wavelength light is 0, and 650 nm wavelength light is -2 nm. Therefore, the transmittance when ON is minimized over the entire visible light band, and It is possible to obtain a good contrast while almost eliminating the above.

As described above, the liquid crystal display element has the viewing angle compensating optical film 4 having a retardation for canceling the residual retardation when the liquid crystal layer of the liquid crystal cell 1 is turned on.
5, which has the property of reducing the difference between the wavelength dependence of the retardation of the liquid crystal layer and the wavelength dependence of the retardation of the optical films 4 and 5.
Therefore, it is possible to widen the viewing angle, almost eliminate the color band of the display, and obtain good contrast.

Moreover, in the above embodiment, the retardation layer 6 is formed.
Are two phase difference plates, a first retardation plate 7 containing norbornene as a main component and having a small wavelength dependence of retardation, and a second phase difference plate 8 containing polycarbonate as a main component and having a large wavelength dependence of retardation. Since it is formed by a combination of the retardation of these retardation plates 7 and 8 and the wavelength dependence thereof, the wavelength dependence of the retardation of the liquid crystal layer and the wavelength dependence of the retardation of the optical films 4 and 5 are obtained. It is possible to easily obtain the retardation layer 6 having the characteristic of reducing the difference between the two.

In the above examples, the retardation of the viewing angle compensating optical films 4 and 5 is set to the residual retardation when the liquid crystal layer of the liquid crystal cell 1 is turned on with respect to light having a wavelength of 550 nm which is an intermediate wavelength in the visible light band. However, the retardation of the viewing angle compensating optical films 4 and 5 is a value that cancels the residual retardation when the liquid crystal layer is turned on with respect to other wavelength light in the visible light band. You may set so that it becomes.

The following [Table 2] is set so that the retardation of the viewing angle compensating optical films 4 and 5 is a value that cancels the residual retardation when the liquid crystal layer is turned on with respect to the light having a wavelength of 650 nm. When, 450nm, 5
Residual retardation when the liquid crystal layer is turned on for light of each wavelength of 50 nm and 650 nm, retardation of the two viewing angle compensating optical films 4 and 5, and first and second retardation plates 7 of the retardation layer 6. , 8 and the total value of all these retardations.

[0052]

[Table 2]

[Table 2] shows that O of the liquid crystal layer of the liquid crystal cell 1
The value of the residual retardation at the time of N is 52 nm, 450 with respect to the wavelength light of 550 nm which is the intermediate wavelength of the visible light band.
It is an example in the case of 55 nm for wavelength light of 50 nm and 50 nm for wavelength light of 650 nm, in which case the retardation of the viewing angle compensation optical films 4 and 5 and the retardation layer 6 By setting 1 and the retardation of the second retardation films 7 and 8 to values as shown in the table,
It is possible to widen the viewing angle, almost eliminate the display color band, and obtain good contrast.

In the above embodiment, the retardation layer 6 is used.
Is formed by a first retardation plate 7 containing norbornene as a main component and having a small wavelength dependence of retardation, and a second retardation plate 7 containing polycarbonate as a main component and having a large wavelength dependence of retardation. Of these retardation plates 7 and 8, the first retardation plate 7 in which the retardation has a small wavelength dependency is not limited to those containing norbornene as the main component, and may be those containing polysulfone as the main component.

The two retardation plates forming the retardation layer 6 used in the above-mentioned examples are composed of a stretched film containing a substance having a positive photoelastic constant as a main component, and the stretched film extends in the stretching direction. Although it has slow axes 7a and 8a, one of the two retardation plates is a stretched film mainly composed of a substance having a negative photoelastic constant such as polymethylmethacrylate. It may have a slow axis in a direction orthogonal to the direction.

Further, the retardation layer 6 is not limited to the two retardation plates 7 and 8, and for example, a mixture or copolymer of two kinds of polymers having different wavelength dependences of retardation is stretched. As described above, the liquid crystal cell 1 can be obtained by forming the retardation layer from a plurality of substances having different retardation wavelength dependences.
By synthesizing the wavelength dependence depending on the synthetic retardation obtained by synthesizing the liquid crystal layer and the viewing angle compensating optical films 4 and 5, and further synthesizing the retardation of the retardation layer,
It is possible to make the wavelength dependence of the entire combination substantially zero.

In the above embodiment, the two viewing angle compensating optical films 4 and 5 are arranged between the liquid crystal cell 1 and the front and rear polarizing plates 2 and 3, respectively. The optical films 4 and 5 may be overlapped and arranged between the liquid crystal cell 1 and either of the front and rear polarizing plates 2 and 3, and the retardation of both of the two optical films 4 and 5 may be further provided. It is also possible to use a single viewing angle compensating optical film having a retardation equivalent to the total value of, and to dispose the optical film between the liquid crystal cell 1 and either of the front and rear polarizing plates 2 and 3.

Further, although the liquid crystal display element of the above embodiment is of a transmission type, the present invention is a reflection type liquid crystal display element,
It can also be applied to a reflective / transmissive liquid crystal display device that performs both reflective display and transmissive display.

In the reflection type or reflection / transmission type liquid crystal display element, polarizing plates are respectively arranged on the front side and the rear side of the liquid crystal cell, and a reflection film or a semi-transmissive reflection film is provided on the rear side of the rear side polarizing plate. Of the external reflection type in which is arranged, and one polarizing plate is arranged only on the front side of the liquid crystal cell, and the internal reflection type in which a reflective film or a semi-transmissive reflective film is provided on the inner or outer surface of the rear substrate of the liquid crystal cell. However, when the present invention is applied to an internal reflection type reflection type or reflection / transmission type liquid crystal display element, a viewing angle compensator is provided between a liquid crystal cell and a polarizing plate arranged in front of the liquid crystal cell. The optical film, a retardation layer having a retardation for each wavelength corresponding to the difference in synthetic retardation for each wavelength light in the wavelength dependence of the synthetic retardation synthesized the liquid crystal layer of the liquid crystal cell and the optical film. , Each wavelength light Synthesis of synthetic retardation may be disposed in an optical axis arranged to be retardation difference.

Further, the liquid crystal display element of the above-mentioned embodiment includes the homogeneous alignment type liquid crystal cell 1,
The present invention can be applied not only to the homogeneous alignment type, but also to a TN type or STN type liquid crystal cell, a liquid crystal display device including a ferroelectric or antiferroelectric liquid crystal cell, and the like.

[0061]

According to the liquid crystal display element of the present invention, the liquid crystal is applied when an electric field is applied to align liquid crystal molecules positioned in the middle of the liquid crystal layer of the liquid crystal cell in a direction substantially perpendicular to the substrate surface. With an optical film for viewing angle compensation having a retardation that cancels the residual retardation of the layer, the wavelength dependence of the synthetic retardation of the liquid crystal layer and the optical film and each wavelength in the wavelength dependence of the retardation of the optical film. Having a retardation for each of the wavelengths corresponding to the difference in the synthetic retardation for each light, with a retardation layer provided in the optical axis arrangement that the combined retardation for each wavelength light becomes a retardation difference Therefore, it is necessary to widen the viewing angle, almost eliminate the display color band, and obtain good contrast. It can be.

In the liquid crystal display element of the present invention, it is desirable that the retardation layer is formed of a plurality of substances having different wavelength dependences of retardation. By doing so, the wavelength dependence of the retardation of the liquid crystal layer is increased. It is possible to obtain a retardation layer having a property of reducing the difference between the property and the wavelength dependence of the retardation of the optical film.

The retardation layer further comprises a first retardation plate containing norbornene or polysulfone as a main component and having a small wavelength dependence of retardation, and a second retardation plate containing polycarbonate as a main component and having a large wavelength dependence of retardation. It is more preferable to form a plate, and by doing so, it is easy to form a retardation layer having the property of reducing the difference between the wavelength dependence of the retardation of the liquid crystal layer and the wavelength dependence of the retardation of the optical film. Can be obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display element showing an embodiment of the present invention.

[Explanation of symbols]

1 ... Liquid crystal cell 2, 3 ... Polarizing plate 2a, 3a ... Absorption axis 4, 5 ... Optical film for viewing angle compensation 4a, 5a ... Slow axis 6 ... Retardation layer 7 ... Norbornene-based retarder 8 ... Retardation plate mainly composed of polycarbonate 7a, 8a ... Slow axis

Claims (3)

[Claims] 1. A liquid crystal cell in which a liquid crystal layer in which the alignment state of liquid crystal molecules is changed according to an applied electric field is provided between a pair of substrates, and a polarizing plate disposed so as to face at least one surface of the liquid crystal cell. And a retardation that cancels the residual retardation of the liquid crystal layer when an electric field is applied to align liquid crystal molecules positioned in the middle of the thickness direction of the liquid crystal layer substantially perpendicularly to the substrate surface, and the liquid crystal An optical film for viewing angle compensation arranged between the cell and the polarizing plate, which corresponds to the difference in the synthetic retardation for each wavelength light in the wavelength dependence of the synthetic retardation obtained by synthesizing the liquid crystal layer and the optical film. It has a retardation for each of the wavelengths, and is arranged between the liquid crystal cell and the polarizing plate in an optical axis arrangement in which the synthesis with the synthetic retardation for each of the wavelengths is a retardation difference. The liquid crystal display element characterized by comprising a retardation layer disposed to overlap with the optical film. 2. The liquid crystal display element according to claim 1, wherein the retardation layer is made of a plurality of substances having different wavelength dependences of retardation. 3. A retardation layer comprising a first retardation plate containing norbornene or polysulfone as a main component and having a small wavelength dependence of retardation, and a second retardation plate containing polycarbonate as a main component and having a large wavelength dependence of retardation. The liquid crystal display element according to claim 2, wherein the liquid crystal display element comprises: