JP2000221506A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent voids of light due to deformation of a phase difference plate. SOLUTION: The liquid crystal display device is equipped with a polarizing plate outside a liquid crystal cell and is equipped with a phase difference plate 2 to improve the viewing angle characteristics in the liquid crystal cell. Since the phase difference plate 2 is separated from the polarizing plate and disposed in the liquid crystal cell, the distance between the liquid crystal layer 9 and the phase difference plate 2 is reduced, which decreases deviation of rays by the thickness of the glass substrate 1 and significantly improves the viewing angle characteristics. Further, lamination of the phase difference plate 2 and the polarizing plate is unnecessary, which significantly reduces voids accompanied with changes in the phase difference of the phase difference plate 2 caused by deformation of the phase difference or thermal shrinkage of the plate 2 caused by lamination of the phase difference plate 2 and polarizing plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device which requires a wide viewing angle characteristic and is suitable for large-screen display.

[0002]

2. Description of the Related Art A wide viewing angle display (ASM mode) in which liquid crystal molecules are axially symmetrically aligned for each picture element is disclosed in, for example, Japanese Patent Application Laid-Open No.
It is disclosed in JP-A-301015. As a method of realizing the ASM mode, a method in which a lattice-like wall structure is formed on a substrate and an axially symmetric alignment is formed by the interaction between the wall and liquid crystal molecules is disclosed in, for example, Japanese Patent Application Laid-Open No. H7-120728. I have. Furthermore, according to this method, it is possible to use a liquid crystal material having a negative dielectric anisotropy to perform axially symmetric alignment.
SM orientation is possible (for example, see JP-A-10-1332).
No. 06). These axially symmetric modes use a retardation plate having a negative refractive index anisotropy between the liquid crystal cell and the polarizing plate in order to further improve the viewing angle characteristics in the direction of 45 ° from the polarizing axis of the polarizing plate. .

A plasma substrate having an anode electrode and a cathode electrode in a plasma channel separated by a rib, and switching by a plasma state of a rare gas existing in a plasma chamber formed by the substrate and a thin dielectric layer; A plasma-addressed liquid crystal display that performs display by applying a voltage to the liquid crystal layer between the switching plasma substrate and the counter electrode present on the liquid crystal substrate, with the substrate and the liquid crystal layer separated by a thin dielectric layer. An apparatus (PALC) is disclosed in JP-A-1-217396. This PALC technology is expected to be applied to a large display due to its simple structure.
However, this technique has a problem in viewing angle characteristics because the liquid crystal is used as an optical switch for display. As a method for solving this problem, Japanese Patent Application Laid-Open No. H9-19738 discloses that the ASM mode is adapted to PALC technology.

[0004] Among the methods for manufacturing a retardation plate, the methods for producing a retardation plate using a discotic liquid crystal material include:
It is disclosed in JP-A-9-222511. In this invention, a reactive functional group is bonded to the discotic liquid crystal material to orient the discotic liquid crystal material to form a retardation plate having negative refractive index anisotropy. These retardation plates are provided outside the liquid crystal cell.

[0005]

However, the above-mentioned prior art has the following problems.

That is, when a phase difference plate is attached to the outside of a liquid crystal cell, when a stress is applied to the attachment destination (polarization plate), the phase difference of the phase difference plate is deformed, and depolarization is caused. As a result, light leakage (white loss) in a black state occurs in the region subjected to the stress deformation.

Further, when a polarizing plate and a retardation plate are attached to each other and attached to a liquid crystal cell, when the polarizing plate and the retardation plate are attached to each other, similarly, light leakage occurs due to stress deformation.

During the operation of the liquid crystal panel, when heat is applied by the heat radiation of the backlight, the polarizing plate causes thermal deformation, and the phase difference plate is deformed accordingly. In this case, as in the case of the deformation due to the stress, light leakage occurs in a black state at a portion deformed by heat.

In the ASM mode, the upper and lower sides of the liquid crystal panel,
In order to secure the right and left viewing angle characteristics, two polarizing plates are attached to the liquid crystal panel so that the polarization axes are directed up and down and left and right as shown in FIG. Occurs, light leakage occurs at four corners of the display surface as shown by reference numeral 15 in FIG. 14B (white voids occur at four corners in a black state). Such a phenomenon occurs more remarkably as the size of the liquid crystal panel increases. That is, as the size of the liquid crystal panel increases, the polarizing plate also increases in size and the amount of heat shrinkage increases. Therefore, the amount of deformation of the retardation plate also increases, and a noticeable white spot occurs.

In the conventional ASM mode, a retardation plate is disposed outside the liquid crystal cell, the polarizing plate and the retardation plate are bonded together with an adhesive, and viewing angle compensation is performed by the retardation plate configured as described above. I was

As described above, in the above-mentioned prior art, light leakage occurs due to deformation due to stress acting on the retardation plate, bonding of the retardation plate and the polarizing plate, contraction due to heat, and deformation due to a difference in expansion. Had been invited. The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display device capable of avoiding deformation of a phase difference plate and preventing light leakage caused by the deformation.

[0012]

According to a first aspect of the present invention, there is provided a liquid crystal display device in which a polarizing plate is provided outside a liquid crystal cell to improve viewing angle characteristics. The phase difference plate is provided in the liquid crystal cell.

According to the above invention, the viewing angle characteristic is improved because the retardation plate is provided separately from the polarizing plate.

When a phase difference plate is attached to a polarizing plate and a stress acts on the polarizing plate, the phase difference may be deformed,
The phase difference plate may be deformed due to the thermal deformation of the polarizing plate by the backlight, and light leakage may occur.

Therefore, according to the liquid crystal display device of the first aspect, the retardation plate is provided in the liquid crystal cell.
Separated from the polarizer. In addition, since the retardation plate is provided in the liquid crystal cell, the distance between the liquid crystal layer and the retardation plate is reduced, and the shift of light rays due to the thickness of the substrate is reduced, so that the viewing angle characteristics are significantly improved. Moreover, it is not necessary to attach the retardation plate and the polarizing plate, and the phase difference of the retardation plate caused by the attachment of the retardation plate and the polarizing plate and the position of the retardation plate caused by the heat shrinkage as described above. Light leakage accompanying a change in phase difference is significantly reduced.

According to a second aspect of the present invention, there is provided a liquid crystal display device according to the first aspect, wherein the liquid crystal cell has a negative dielectric anisotropy between opposing substrates. A liquid crystal layer comprising a liquid crystal material having the following. The retardation plate is provided between the opposing substrate and the liquid crystal layer, has a negative refractive index anisotropy, and It is characterized in that a vertical alignment film is formed on the surface.

According to the above invention, in addition to the operation of the liquid crystal display device according to the first aspect, the liquid crystal material having the negative dielectric anisotropy causes the liquid crystal molecules to be oriented axially symmetrically. In addition, ASM orientation can be achieved by using the vertical orientation film formed on the substrate surface in combination. Therefore, in the ASM mode, it is possible to eliminate the stress applied to the phase difference plate when the polarizing plate is bonded and when the liquid crystal display device is operated, and when the polarizing plate undergoes thermal contraction due to a temperature rise, thereby preventing display whiteout. .

According to a third aspect of the present invention, there is provided a liquid crystal display device, wherein at least one of the opposing substrates has at least two orientation control grooves formed on at least one of the opposing substrates, and a vertical alignment groove is formed on the surface of the substrate. A film is formed, a liquid crystal material having a negative dielectric anisotropy is used, and the alignment control groove is formed by a retardation plate having a negative refractive index anisotropy.

According to the invention, the retardation plate has both the function of the original retardation plate and the function of the alignment control groove. Further, the retardation plate is present in almost all areas where light is transmitted, and the effect of improving the viewing angle characteristics becomes remarkable.

The following functions are performed as the alignment control grooves. That is, an axially symmetric alignment is formed by the interaction between the alignment control groove and the liquid crystal molecules. The liquid crystal material having a negative dielectric anisotropy causes the liquid crystal molecules to be aligned in an axially symmetrical manner, and further enables ASM alignment when used in combination with a vertical alignment film. In these axially symmetric modes, the viewing angle characteristics in the direction of 45 ° from the polarization axis of the polarizing plate are further improved by the retardation plate having negative refractive index anisotropy.

Further, the following functions are performed as a phase difference plate.
That is, since the retardation plate is provided in the liquid crystal cell, it is separated from the polarizing plate. In addition, since the retardation plate is provided in the liquid crystal cell, the distance between the liquid crystal layer and the retardation plate is reduced, and the shift of light rays due to the thickness of the substrate is reduced, so that the viewing angle characteristics are significantly improved. Moreover, it is not necessary to attach the retardation plate and the polarizing plate, and the phase difference of the retardation plate caused by the attachment of the retardation plate and the polarizing plate and the position of the retardation plate caused by the heat shrinkage as described above. Light leakage accompanying a change in phase difference is significantly reduced.

According to a fourth aspect of the present invention, there is provided a liquid crystal display device according to the third aspect, wherein a transparent electrode is provided on a surface of the structure forming the alignment control groove. Is formed.

If the transparent electrode is formed under the groove structure, a voltage is applied across the structure forming the groove and the liquid crystal layer, and the driving voltage increases. However, according to the above invention, since the transparent electrode is formed on the surface of the structure forming the groove, it is not necessary to apply a voltage through the structure forming the groove. Can be lowered.

According to a fifth aspect of the present invention, there is provided a liquid crystal display device according to the third aspect, wherein a polymer for fixing an alignment state is attached on the vertical alignment film. It is characterized by doing.

According to the above invention, in addition to the operation of the liquid crystal display device according to the third aspect, the alignment is stabilized, so that the dynamic change of the liquid crystal molecule arrangement due to the application of a voltage is improved, and especially in the halftone. Response speed is improved.

According to a sixth aspect of the present invention, there is provided a liquid crystal display device according to the third, fourth, or fifth aspect, wherein the side surface forming the alignment control groove has a predetermined angle. It is characterized by being inclined.

According to the above invention, the third, fourth, or fifth aspect is provided.
In addition to the operation of the liquid crystal display device according to the above, if the side surface forming the alignment control groove is inclined at a predetermined angle, it effectively acts on the alignment control of the liquid crystal molecules.

On the other hand, when the side surfaces forming the alignment control groove are vertically steep, the liquid crystal molecules are already vertically aligned with the inner wall of the alignment control groove, and the liquid crystal molecules are applied even when a voltage is further applied. It is difficult to tilt molecules with respect to the substrate.

When the orientation of the liquid crystal molecules in the alignment control groove is inclined with respect to the substrate, the liquid crystal molecules above the alignment control groove are similarly aligned in the liquid crystal layer following this alignment. The alignment region of the liquid crystal molecules formed in this manner affects the liquid crystal molecules outside the alignment control groove, and a predetermined alignment is performed as a whole.

According to a seventh aspect of the present invention, there is provided a liquid crystal display device according to the third, fourth, fifth, or sixth aspect, wherein the alignment control groove is provided in a picture element. It is characterized by being formed.

According to the present invention, in addition to the operation of the liquid crystal display device according to the third, fourth, fifth, or sixth aspect, the alignment control grooves can be arranged in accordance with the pitch and size of the picture elements. In other words, even if the control structure of the orientation is formed in the picture element, the structure does not greatly reduce the transmittance, so that a large picture element can be dealt with by dividing the picture element. . In this case, in order to prevent moiré, it is preferable to make the divided structure rectangular and to match the pixel pitch.

According to an eighth aspect of the present invention, there is provided a liquid crystal display device according to the third, fourth, fifth, sixth, or seventh aspect, wherein the alignment control grooves are formed in a lattice shape. It is characterized by being formed in.

According to the above invention, claims 3, 4, 5,
In addition to the operation of the liquid crystal display device according to 6 or 7, by arranging the alignment control grooves in a lattice shape, an alignment regulating force acts on the liquid crystal molecules from four sides of the retardation plate. The orientation can be surely performed in an axially symmetric manner.

According to a ninth aspect of the present invention, there is provided a liquid crystal display according to the second, third, fourth, fifth, or sixth aspect, wherein the liquid crystal display is a plasma type. It is a liquid crystal display device.

According to the above invention, claims 2, 3, 4,
In addition to the functions of the liquid crystal display device according to 5 or 6, the structure of the plasma type liquid crystal display device is simple, so that it can be applied to a large display.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

According to the liquid crystal display device of this embodiment, as shown in FIG. 1, the retardation plate 2 is provided between the liquid crystal layer 9 and the glass substrate 1 in the liquid crystal cell. .

The liquid crystal cell of the above-mentioned liquid crystal display device has liquid crystal (corresponding to the liquid crystal layer 9 in FIG. 1) sealed in two glass substrates, and one glass substrate (corresponding to the glass substrate 1 in FIG. 1). A phase difference plate 2 is formed thereon, and a color filter 4 is formed thereon with an overcoat film 3 interposed therebetween. The transparent electrode 6 and the ASM wall (of ASM) are formed on the color filter 4 with an overcoat film 5 interposed therebetween. Orientation control factor member)
7 and spacers 8 are formed. On the other glass substrate, the above-mentioned ASM wall (ASM orientation control factor member)
The same members as those in FIG. 1 are laminated except for the spacer 7 and the spacer 8 (both are not shown). The phase difference plate 2
May be provided on at least one of the glass substrates.

The retardation plate 2 is not limited to the case where it is provided between the liquid crystal layer 9 and the glass substrate 1 as shown in FIG. 1. For example, as shown in FIG. And may be provided on the color filter 4. Note that, for convenience of description, the same reference numerals as those in FIG. 1 are used for the members having the same functions as those in FIG.

As shown in FIG. 2, a color filter 4 is formed on a glass substrate 1, and a retardation plate 2 is formed thereon. On this retardation plate 2, a transparent electrode 6, an ASM wall 7, and a spacer 8 are formed via an overcoat film 5.

The phase difference plate 2 is not limited to the above-described configuration. When the phase difference plate 2 is made of a material that can be patterned, as shown in FIG. By forming the groove 12 as a groove, it is possible to combine the function of the phase difference plate 2 and the function of the ASM wall 7 (groove structure). Note that, for convenience of description, the same reference numerals as those in FIG. 1 are used for the members having the same functions as those in FIG.

For example, as shown in FIG. 3, in a liquid crystal cell, a color filter 4 is formed on a glass substrate 1, and a transparent electrode 6 is patterned on the glass substrate 1 via an overcoat film 5. Phase difference plate 1 having the above function
2 and a spacer 8 are formed. The above retardation plate 1
2 may be provided on two glass substrates facing each other.

When the retardation plate 12 is configured as shown in FIG. 3, the retardation plate is present in almost all areas where light is transmitted, and the effect of improving the viewing angle characteristics becomes remarkable.

When the retardation plate is configured as shown in FIGS. 1 to 3, the distance between the liquid crystal layer and the retardation plate becomes shorter as compared with the conventional configuration in which the retardation plate is provided outside the liquid crystal cell. Since the shift of the light beam due to the thickness of the glass substrate is reduced, the viewing angle characteristics are remarkably improved. Moreover, it is not necessary to bond the phase difference plate and the polarizing plate (not shown), and the phase difference between the phase difference plate caused by the bonding of the phase difference plate and the polarizing plate and the position caused by the heat shrinkage as described above. Light leakage due to a change in the phase difference of the phase difference plate is significantly reduced.

The case where the phase difference plate 12 has a groove-like structure will be described below with reference to FIGS. When the retardation plate 12 has a groove-like structure, an alignment control technique using the groove-like structure can be combined, and the liquid crystal display device according to the present embodiment can be realized at lower cost. That is, by forming the groove-like structure using the phase difference plate itself made of a patternable material, it is possible to simultaneously achieve the function as the alignment control factor and the function as the phase difference plate.

In the ASM mode, a method has generally been adopted in which a convex portion is provided on a substrate to regulate the direction in which liquid crystal molecules fall (the direction in which the liquid crystal molecules tilt). However, in this method, in addition to the decrease in transmittance due to the convex portion, a sufficient voltage is not applied to the liquid crystal molecules in the convex portion.
This resulted in a decrease in transmittance (in the case of the p-type, a decrease in contrast). In particular, in the case of PALC, this effect was remarkable because a voltage was applied across the thin glass and the liquid crystal layer.

In order to avoid such a problem, the present applicant has made intensive studies to control the liquid crystal molecules without lowering the transmittance or the contrast, that is, without using the convex portions. As a result, the groove structure shown in FIG. 4 (the phase difference plate 12 having the two functions described above is provided on the glass substrate 1 and the groove structure is formed by the adjacent phase difference plates 12). It has been found that the liquid crystal cell can be axially symmetrically aligned by using it and a liquid crystal cell can be realized without lowering transmittance or contrast. Less than,
The structure and characteristics of the present invention will be described in detail.

First, the fact that the axially symmetric liquid orientation can be controlled by the groove structure will be described below with reference to FIGS.

When the groove structure as shown in FIG. 5 is formed on the glass substrate 1, before applying a voltage to the liquid crystal cell (corresponding to the state shown in FIG. 5A), the liquid crystal molecules are aligned vertically. I have. Then, when a voltage is applied to the liquid crystal cell, first, the liquid crystal molecules in the groove start to incline toward the inside of the groove (corresponding to the state of FIG. 5B. Does not show the orientation of the liquid crystal molecules in the groove for convenience, but the liquid crystal molecules are oriented with the same inclination as that above the groove.) In this case, the inclined surface 2a (side surface forming the groove) in the groove effectively acts on the orientation control, and the inclined surface 2a has a vertically steep groove (the angle of the inclined surface 2a with respect to the glass substrate 1 is 9 degrees).
The groove inclined at 5 ° or more and 45 ° or less is more preferable than the groove of 0 °.

This is based on the following reason. That is, when the inclination angle of the slope in the groove is larger than 45 ° and equal to or less than 70 °, light leakage near the slope at the time of black display occurs due to liquid crystal molecules which are aligned perpendicularly to the slope of the groove, and the contrast is reduced. Also, when the inclination angle of the slope in the groove is 5 ° or less, the inclination is too gentle to sufficiently control the alignment of the liquid crystal molecules.

Next, following the orientation of the liquid crystal molecules in the groove,
The upper part of the groove is oriented in the liquid crystal layer 9 (corresponding to the state in FIG. 5B). The alignment region of the liquid crystal molecules formed in this way also affects the liquid crystal molecules outside the groove, and a predetermined alignment is performed as a whole (corresponding to the state of FIG. 6).

The advantage of such orientation control is that PAL
This is noticeable in the C system. That is, as shown in FIG. 7, in the PALC system, on one substrate 31,
A plasma electrode 33, a rib 34, and a thin glass 35 are provided, a transparent electrode 36 is provided on the other substrate 32, and a liquid crystal layer 37 is provided between the two substrates. Since a voltage is applied across the liquid crystal layer 37, the voltage applied to the liquid crystal layer 37 is expressed by the following formula. The thicker the liquid crystal layer 37, the easier the voltage is applied to the liquid crystal layer 37. The diagram on the right side of FIG. 7 shows an equivalent circuit.

V _LC = V / (1 + d _G · ε _LC / d _LC · ε _G ) In the above equation, V _LC is a voltage applied to the liquid crystal layer 37, and V is a voltage applied to the thin glass 35 and the liquid crystal layer 37. The external voltage, d _G is the thickness of the thin glass 35, ε _LC is the dielectric constant of the liquid crystal, d _LC is the thickness of the liquid crystal layer 37, and ε _G is the dielectric constant of the thin glass 35.

Therefore, in the case of the PALC system, as shown in FIG. 8, the liquid crystal layer 37 causes the liquid crystal molecules to react at a low voltage in the groove portion where the thickness of the liquid crystal cell is increased.
On the other hand, the liquid crystal molecules react at a high voltage in portions other than the groove where the thickness of the liquid crystal cell is reduced, and the liquid crystal cells start to move.

Further, this also has an advantageous effect on the response speed of the intermediate tone. That is, in a liquid crystal display element using a normal nematic liquid crystal material, a response speed in a medium tone is slow, and this is a problem for a fast moving image. However, in the combination of the liquid crystal cell and the PALC system of the present embodiment, since the liquid crystal molecules in the groove structure move first at the halftone voltage, the response speed in the halftone apparently increases. When the groove is further deepened, as shown in FIG. 8, the applied voltage-transmittance curve of the liquid crystal molecules in the groove portion and the liquid crystal molecules other than the groove greatly differ, and the groove is affected by the deep portion of the groove which moves at a low voltage. Since the liquid crystal regions in other portions are also driven, the driving voltage is reduced.

Here, the structure of the groove will be described below with reference to FIG.

As the planar arrangement of the grooves, as shown in FIG. 9A, by arranging the grooves in a grid pattern,
Since the alignment regulating force acts on the liquid crystal molecules from the four sides of 2, the liquid crystal molecules can be surely aligned in an axially symmetric manner. Note that the hatched portion in FIG. 9A indicates a groove region, and FIG.
(B) shows an alignment state in a voltage applied state after injecting liquid crystal in the structure of FIG. 9 (a).

The shape of the phase difference plate 12 does not need to be a square, but can be arranged according to the pitch and size of picture elements. In other words, even if the control structure of the orientation is formed in the picture element, the structure does not greatly reduce the transmittance, so that a large picture element can be dealt with by dividing the picture element. . In this case, in order to prevent moiré, it is preferable to make the divided structure rectangular and to match the pixel pitch. Further, the grooves may be formed so as to have different sizes. In addition, although the alignment is not axially symmetric, the stripe direction, zigzag structure (these are effective to be formed on the upper and lower substrates, respectively, becomes a quadrant alignment) and the like are also controlled by the grooves to be in the wide viewing angle display mode.

As described above, the structure of the above-described groove is the slope 2
It is preferable that a is gently inclined at an angle of not less than 5 ° and not more than 45 ° from a vertically steep groove. This is based on the following reasons. That is, the inclination angle of the slope 2a is 5 °
In the following, the inclination is too gentle and the orientation of the liquid crystal molecules cannot be sufficiently controlled.When the inclination angle of the slope is more than 45 ° and 70 ° or less, the inclination is perpendicular to the slope of the groove. This is because the liquid crystal molecules to be aligned cause light leakage near the slope during black display, causing a decrease in contrast.

The transparent electrode is preferably formed on the surface of the structure forming the groove, and when formed under the groove structure, a voltage is applied across the structure forming the groove and the liquid crystal layer. The drive voltage is increased due to the application. Therefore, it is preferable that the vertical alignment film is formed on the transparent electrode so as to cover the structure forming the groove.

Here, a method of forming the above-mentioned inclined groove will be described below.

As a method of manufacturing the inclined groove, a photolithography technique based on photoreactivity is used for the discotic material, or a resist is formed on the discotic material except for a region to be a groove with a resist material, and an etchant is used. A method of partially dissolving or the like is preferable. Further, a groove structure can be formed by irradiating ultraviolet rays through a photomask to partially decompose the discotic liquid crystal portion. In particular, when forming a groove having a slope (having a slope), it can be formed by increasing the distance (proxy gap) between the mask and the substrate or by setting the developing time excessively.

Next, the fixing of the orientation will be described. The orientation state formed by applying a voltage has different stability depending on the size of the region surrounded by the groove. In particular, even if the liquid crystal molecules once determine the alignment state, the flow alignment may be formed due to external pressure or the like. In such a case, a so-called polymer stabilizing technique using a monomer can be applied to stabilize the alignment state of the liquid crystal molecules. That is, a mixture of liquid crystal and a photocurable monomer is added to a liquid crystal cell obtained using the substrate having the above-mentioned groove structure, and a voltage is applied to form an alignment state. The photocurable monomer reacts to fix the alignment state of the liquid crystal. By reducing the amount of the photocurable monomer, the vertical alignment when no voltage is applied can be maintained.

The above is described as the structure of the groove, for example, in FIG.
As shown in (a), the case where the planar arrangement is a lattice shape (a state in which grooves are continuous in a lattice shape) has been described, but the present invention is not limited to this, and FIGS. )
As shown in (1), the grooves may not be formed continuously in a lattice shape, but may be formed so that the grooves are isolated from each other and discontinuous. Also in this case, similarly to the case of the lattice-shaped groove structure, a sufficiently desired alignment control ability can be obtained.

The optical characteristics of a liquid crystal display device having a groove for controlling alignment include the optical characteristics of a liquid crystal layer in a region where a groove is formed and the optical characteristics of a liquid crystal layer on a phase difference plate where a groove is not formed. And the sum of In the case of the structure shown in FIGS. 15A and 15B, when the area of the region where the groove is formed decreases, the area of the liquid crystal layer on the phase difference plate where the groove is not formed increases. It is possible to expand a region where the gradation is not inverted and to improve the color tone viewing angle characteristics in the halftone.

Here, an embodiment of the liquid crystal display device according to the present invention will be described below with reference to FIGS. Note that members having the same functions as those described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

Example 1 The groove structure shown in Example 1 has a planar structure as shown in FIG.
As shown in (1), an alignment film for orienting a discotic material A having a photofunctional group on one of the color-patterned substrates (the glass substrate 1, the retardation plate 2, and the color filter 4 are laminated). Was formed, a discotic material A was applied thereon, and light irradiation was performed. The characteristics of the retardation layer thus obtained were measured and analyzed using an ellipsometer, and as a result, the apparent retardation value in the thickness direction was 190 nm. An overcoat layer was formed thereon, and a groove-like structure shown in FIGS. 10A and 10B was formed thereon by photolithography. This shape has a groove width of 25 μm and a groove inclination angle of 20 °.
Met. Note that FIG. 10B is a cross-sectional view of FIG.
It is X 'line arrow sectional drawing.

On the one substrate formed as described above, ITO (not shown) as a transparent electrode was further sputtered, and the electrode was etched to the width of a picture element. Further BM
A columnar structure (6 μm) was formed on this substrate on (black matrix) to form a spacer 8. Therefore,
The thickness of the liquid crystal layer in the groove portion is 8 μm, and the thickness of the liquid crystal layer in a region other than the large-area groove is 6 μm. Further, a vertical alignment film not shown (JALS-945:
(Manufactured by JSR), and the processing on the color filter 4 side was completed. On the other hand, a vertical alignment film was applied on thin glass on a plasma substrate (the other substrate) having an anode electrode and a cathode electrode, thereby completing the substrate.

The two substrates thus obtained were bonded to each other to realize a liquid crystal cell. A liquid crystal material (△ ε =
One 4.0, Δn = 0.08, chiral pitch 24 μm)
And monomer A were mixed and injected. After applying a voltage to the liquid crystal cell and confirming the formation of the axially symmetric alignment, the liquid crystal cell was irradiated with ultraviolet rays. The viewing angle characteristics of the liquid crystal cell showed a wide viewing angle characteristic in all directions.

(Example 2) As shown in FIG. 11, the groove structure was further subdivided (a plurality of types of groove width and depth were set), and a liquid crystal cell was obtained in the same manner as in Example 1. Further, a liquid crystal material was put into the liquid crystal cell to complete the liquid crystal cell. Also in this liquid crystal cell, an axially symmetric alignment was obtained when a voltage was applied, and wide viewing angle characteristics were obtained as in Example 1. In order to stabilize the alignment without using a monomer as described above, the pitch between the grooves is 60 μm, preferably 30 μm.
It is as follows. In such a structure in which the groove structure is subdivided, the alignment regulating force from the groove is strong and spreads over the entire liquid crystal layer, so that the axially symmetric alignment can be fixed without using a monomer.

Example 3 As shown in FIG. 12, a colored layer was formed on a glass substrate 1 in the same manner as the color filter 4 of Example 1, and the discotic material used in Example 1 was formed thereon. It was applied and solidified by ultraviolet rays in the same manner as in Example 1. A groove was formed by applying a photomask on this film to disassemble the groove structure by ultraviolet light having a wavelength of 254 nm. An overcoat layer 5 was applied on the substrate thus obtained, and an ITO transparent electrode 6 was formed thereon.

As shown in FIG. 12, the structure of the groove is not etched with respect to the entire thickness of the retardation layer 12,
Only a partial area of the surface is etched. Even in such a structure, no problem occurred in the formation of the axially symmetric orientation and the viewing angle characteristics. A vertical alignment film (not shown) is applied and formed on the retardation layer 12.

(Embodiment 4) Color filter 4 of Embodiment 1
A lattice-shaped wall 13 shown in FIG. The height of the formed wall 13 was 2 μm. Using the substrate, a liquid crystal cell was prepared in the same manner as in Example 1. This liquid crystal cell had an axially symmetric alignment, and was excellent in viewing angle characteristics, which was comparable to the cell of the comparative example. FIG. 13B is a cross-sectional view taken along line XX ′ of FIG.

(Comparative Example) A substrate was prepared without forming a retardation plate on the same color filter as in Example 1, and a 3 μm-height lattice-like wall structure was formed on the substrate instead of the groove structure. After forming and further processing the transparent electrode thereon, 3 μm
m columnar structures were formed as spacers. A mixture of a liquid crystal and a monomer was injected into the prepared liquid crystal cell in the same manner as in Example 1 to complete the liquid crystal cell in the same manner as in Example 1. Further, a retardation plate (zx direction: 190 n) is provided outside the liquid crystal cell.
(m, y directions: 190 nm, xy directions: 45 nm) and a polarizing plate were combined and attached to a liquid crystal cell. Table 1 summarizes the viewing angle characteristics and white spots due to thermal deformation of the liquid crystal cell thus obtained.

[0075]

[Table 1]

(Note) Transmittance ratio = (Transmittance of blank area at four corners of screen) / (Transmittance of normal part) As shown in Table 1, in the comparative example, white spots were severely missing at the four corners. regardless of,
Example 1 and Example 2 in which a retardation plate is formed in a liquid crystal cell
As for, there was almost no change in the black state. Also,
With respect to the viewing angle characteristics, it was demonstrated that characteristics comparable to those of the examples and comparative examples can be obtained.

As described above, in the ASM mode, the retardation plate necessary for improving the viewing angle characteristics can be separated from the polarizing plate by forming the retardation plate in the cell. The stress applied to the phase difference plate during the heat release of the polarizing plate due to the temperature rise can be eliminated, and white spots on the display can be prevented.

Further, by forming a groove structure serving as an orientation control factor for forming an axially symmetric alignment by using a retardation plate formed in a cell, the retardation plate and the groove structure forming member can be used as well. In addition, the cost reduction effect due to the reduction in the number of members becomes significant. Further, in a structure in which this groove structure is formed by a retardation plate, picture elements can be divided without reducing the transmittance but rather improving the transmittance.

The discotic material A described above is
It has the following chemical formula:

[0080]

Embedded image

The above-mentioned monomer A has the following chemical formula.

[0082]

Embedded image

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

[0084]

According to the first aspect of the present invention, there is provided a liquid crystal display device.
As described above, the retardation plate for improving the viewing angle characteristics is provided in the liquid crystal cell.

Therefore, since the retardation plate is provided in the liquid crystal cell, the distance between the liquid crystal layer and the retardation plate is reduced, and the displacement of light rays due to the thickness of the substrate is reduced, so that the viewing angle characteristic is significantly improved. be able to.

Further, it is not necessary to bond the phase difference plate and the polarizing plate, and the phase difference of the phase difference plate caused by the bonding of the phase difference plate and the polarizing plate and the phase difference caused by the heat shrinkage as described above. In addition, there is an effect that light leakage accompanying a change in the phase difference of the plate can be significantly reduced.

As described above, the liquid crystal display device according to the second aspect of the present invention is the liquid crystal display device according to the first aspect,
In the liquid crystal cell, a liquid crystal layer using a liquid crystal material having negative dielectric anisotropy is sandwiched between opposed substrates, and the retardation plate is provided between the opposed substrate and the liquid crystal layer. A vertical alignment film is formed on the surface of the substrate.

Therefore, in addition to the effect of the liquid crystal display device according to the first aspect, the liquid crystal material having a negative dielectric anisotropy causes the liquid crystal molecules to be oriented axially symmetrically, and the vertical alignment formed on the substrate surface. When used in combination with the film, ASM orientation becomes possible.
Therefore, in the ASM mode, it is possible to eliminate the stress applied to the phase difference plate when the polarizing plate is bonded and when the liquid crystal display device is operated, and when the polarizing plate undergoes thermal contraction due to a temperature rise, thereby preventing display whiteout. The effect is also achieved.

In the liquid crystal display device according to the third aspect of the present invention, as described above, at least two orientation control grooves are formed on at least one of the opposing substrates, and a vertical alignment film is formed on the surface of the substrate. In addition, a liquid crystal material having negative dielectric anisotropy is used, and the alignment control groove is formed by a retardation plate having negative refractive index anisotropy.

Therefore, the retardation plate has both the function of the original retardation plate and the function as the alignment control groove.
Further, the retardation plate is present in almost all areas where light is transmitted, and the effect of improving the viewing angle characteristics becomes remarkable.

The following effects are obtained as the orientation control grooves. That is, an axially symmetric alignment is formed by the interaction between the alignment control grooves and the liquid crystal molecules, and the liquid crystal molecules are axially symmetrically aligned by the liquid crystal material having a negative dielectric anisotropy, and further used together with the vertical alignment film. This enables ASM orientation. In these axially symmetric modes, the viewing angle characteristic in the direction of 45 ° from the polarization axis of the polarizing plate can be further improved by the retardation plate having negative refractive index anisotropy.

The following effects can be obtained as a phase difference plate. That is, since the retardation plate is provided in the liquid crystal cell, the liquid crystal cell is separated from the polarizing plate. Since the retardation plate is provided in the liquid crystal cell, the distance between the liquid crystal layer and the retardation plate is reduced. In addition, the shift of the light beam due to the thickness of the substrate is reduced, and the viewing angle characteristic is remarkably improved. Moreover, it is not necessary to attach the retardation plate and the polarizing plate, and the phase difference of the retardation plate caused by the attachment of the retardation plate and the polarizing plate and the position of the retardation plate caused by the heat shrinkage as described above. Light leakage due to a change in phase difference can be significantly reduced.

According to a fourth aspect of the present invention, there is provided a liquid crystal display according to the third aspect, wherein:
A transparent electrode is formed on the surface of the structure constituting the alignment control groove.

Therefore, in addition to the effect of the liquid crystal display device according to the third aspect, since the transparent electrode is formed on the surface of the structure forming the groove, the voltage is applied through the structure forming the groove. Does not need to be applied, and the driving voltage can be reduced.

According to a fifth aspect of the present invention, there is provided a liquid crystal display device according to the third aspect,
A polymer for fixing the alignment state is attached on the vertical alignment film.

Therefore, in addition to the effect of the liquid crystal display device according to the third aspect, since the alignment is stabilized, the dynamic change of the liquid crystal molecule arrangement due to the application of the voltage is improved, and particularly, the response speed in the half tone is improved. improves.

According to a sixth aspect of the present invention, as described above, in the liquid crystal display device according to the third, fourth or fifth aspect, the side surface forming the alignment control groove is inclined at a predetermined angle. I have.

Therefore, in addition to the effects of the liquid crystal display device according to the third, fourth, or fifth aspect, since the side surface forming the alignment control groove is inclined at a predetermined angle, it is effective in controlling the alignment of liquid crystal molecules. It has the effect of acting.

According to a seventh aspect of the present invention, as described above, in the liquid crystal display device according to the third, fourth, fifth, or sixth aspect, the alignment control groove is formed in a picture element. I have.

Therefore, in addition to the effects of the liquid crystal display device according to the third, fourth, fifth, or sixth aspect, the alignment control grooves can be arranged in accordance with the pitch and size of the picture elements. In other words, even if the control structure of the orientation is formed in the picture element, the structure does not greatly reduce the transmittance, so that a large picture element can be dealt with by dividing the picture element. . In this case, by making the divided structure rectangular and matching it with the picture element pitch, an effect that moire can be prevented can be achieved.

As described above, in the liquid crystal display device according to the eighth aspect of the present invention, in the liquid crystal display device according to the third, fourth, fifth, sixth, or seventh aspect, the alignment control grooves are formed in a lattice shape. ing.

Therefore, claims 3, 4, 5, 6, or 7
In addition to the effects of the liquid crystal display device according to the above, the alignment control force acts on the liquid crystal molecules from the four sides of the retardation plate by arranging the alignment control grooves in a lattice shape, so that the liquid crystal molecules are reliably axially symmetric. This has the effect that the liquid crystal molecules can be oriented in the same shape.

The liquid crystal display device according to the ninth aspect of the present invention is the liquid crystal display device according to the second, third, fourth, fifth or sixth aspect, wherein the liquid crystal display device is a plasma type liquid crystal. A display device.

Therefore, claim 2, 3, 4, 5, or 6
In addition to the effects of the liquid crystal display device according to the above, since the structure of the plasma type liquid crystal display device is simple, there is an effect that adaptation to a large display is possible.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of an arrangement of a retardation plate in a liquid crystal cell of a liquid crystal display device according to the present invention.

FIG. 2 is an explanatory view showing another example of the arrangement of the phase difference plate in the liquid crystal cell of the liquid crystal display device according to the present invention.

FIG. 3 is an explanatory view showing still another example of the arrangement of the phase difference plate in the liquid crystal cell of the liquid crystal display device according to the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a groove structure and an axially symmetric orientation.

5A and 5B are explanatory diagrams showing a change in alignment of liquid crystal molecules due to a voltage in a groove structure, where FIG. 5A shows a state before a voltage is applied to a liquid crystal cell, and FIG. The state which started to incline toward the inside of a groove is shown.

FIG. 6 is an explanatory view showing a process of forming an orientation by a groove structure.

FIG. 7 is an explanatory diagram for explaining voltage application to a liquid crystal layer in a PALC system.

FIG. 8 is an applied voltage-transmittance characteristic diagram for explaining characteristics of a groove structure in a PALC system.

FIG. 9A is a plan view illustrating an example of a groove structure,
(B) is a plan view showing an alignment state of the structure of (a) in a voltage applied state after injecting liquid crystal.

10A is a plan view related to the arrangement of the groove structure used in Example 1, and FIG. 10B is a cross-sectional view taken along line XX ′ of FIG. 10A.

FIG. 11 shows a groove structure used in Example 2 (picture element subdivision type).
It is a top view which concerns on arrangement | positioning.

FIG. 12 is an explanatory diagram illustrating a cross section of a groove structure formed on a retardation plate according to a third embodiment.

13A is a plan view of a wall structure for realizing an axially symmetric orientation used in Example 4, and FIG. 13B is a cross-sectional view taken along line XX ′ of FIG. 13A.

14A is an explanatory diagram showing a direction of setting a polarization axis of a polarizing plate, and FIG. 14B is an explanatory diagram showing light leakage occurring at four corners of a liquid crystal panel during storage at a high temperature.

15A is a plan view showing another example of the groove structure, and FIG. 15B is a cross-sectional view taken along line AA ′ of FIG. 15A.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 glass substrate 2 phase difference plate 3 overcoat film 4 color filter 6 transparent electrode 7 ASM wall 8 spacer 9 liquid crystal layer 12 phase difference plate

 ──────────────────────────────────────────────────続 き Continued on front page F-term (reference) 2H089 LA04 LA09 QA15 QA16 RA04 SA01 TA04 TA14 TA15 TA18 UA05 2H090 HA04 HB13X HC05 HD06 KA04 LA01 LA02 LA06 MA01 MA17 2H091 FA02Y FA08X FA08Z FA11Y FA50Z FB02 FC10 FC08 FD03 GA03 HA06 KA10 LA04 LA19 MA07 5C094 AA01 AA12 AA33 AA36 BA43 EA05 ED14 GA10

Claims (9)

[Claims] 1. A liquid crystal display device in which a polarizing plate is provided outside a liquid crystal cell, wherein a retardation plate for improving viewing angle characteristics is provided in the liquid crystal cell. 2. The liquid crystal cell according to claim 1, wherein a liquid crystal layer made of a liquid crystal material having negative dielectric anisotropy is sandwiched between opposing substrates, and the retardation plate is provided between the opposing substrate and the liquid crystal. 2. A vertical alignment film provided between the substrate and the substrate, having a negative refractive index anisotropy, and having a vertical alignment film formed on the substrate surface.
3. The liquid crystal display device according to 1. 3. A liquid crystal material having a negative dielectric anisotropy, wherein an alignment control groove in at least two directions is formed on at least one of the opposing substrates, and a vertical alignment film is formed on the substrate surface. The liquid crystal display device, wherein the alignment control groove is formed by a retardation plate having negative refractive index anisotropy. 4. The liquid crystal display device according to claim 3, wherein a transparent electrode is formed on a surface of the structure forming the alignment control groove. 5. The liquid crystal display device according to claim 3, wherein a polymer for fixing an alignment state is attached on the vertical alignment film. 6. The liquid crystal display device according to claim 3, wherein a side surface constituting the alignment control groove is inclined at a predetermined angle. 7. The liquid crystal display device according to claim 3, wherein said alignment control groove is formed in a picture element. 8. The liquid crystal display device according to claim 3, wherein the alignment control grooves are formed in a lattice shape. 9. The liquid crystal display device according to claim 2, wherein said liquid crystal display device is a plasma type liquid crystal display device.