JP2011033967A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an in-plane switching liquid crystal display device with which widening of a viewing angle with the same level as that of the conventional in-plane switching liquid crystal display device or superior thereto and improvement of the picture quality are achieved. <P>SOLUTION: The in-plane switching liquid crystal display device 10 has a liquid crystal layer 32 interposed between a pair of substrates 11, 26, and a pair of polarizing plates 39, 40 formed on the sides opposite to the liquid crystal layer 32 of the pair of substrates 11, 26, wherein the polarizing plate 39 formed on either one of the pair of substrates 11, 26 is formed of a protective film 39a, a polarizer 39b and two sheets of negative biaxial films 42, the two sheets of negative biaxial films 42 are configured of a first negative biaxial film 43 and a second negative biaxial film 44, and the first negative biaxial film 43 and the second negative biaxial film 44 are stacked together and arranged on the one substrate 11 side or the other substrate 26 side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a horizontal electric field type liquid crystal display device. More specifically, the present invention relates to a lateral electric field type liquid crystal display device in which a wide viewing angle is achieved by using two negative biaxial films as retardation plates.

A liquid crystal display device has characteristics of light weight, thinness, and low power consumption as compared with a CRT (cathode ray tube), and thus is used in many electronic devices for display. The liquid crystal display device displays an image by changing the direction of liquid crystal molecules aligned in a predetermined direction by an electric field and changing the amount of light transmitted through the liquid crystal layer. As a method for applying an electric field to a liquid crystal layer of a liquid crystal display device, there are a vertical electric field method and a horizontal electric field method. A vertical electric field type liquid crystal display device applies a substantially vertical electric field to liquid crystal molecules by a pair of electrodes arranged with a liquid crystal layer interposed therebetween. This vertical electric field type liquid crystal display device includes a TN (Twisted Nematic) mode, VA (Vertical Alignmen).
t) mode, MVA (Multi-domain Vertical Alignment) mode, etc. are known.

A horizontal electric field type liquid crystal display device has a pair of electrodes insulated from each other on one inner surface side of a pair of substrates arranged with a liquid crystal layer interposed therebetween, and an electric field in a substantially horizontal direction is used as liquid crystal molecules. In contrast, it is applied. This horizontal electric field type liquid crystal display device includes an IPS (In-Plane Switching) mode in which a pair of electrodes do not overlap in a plan view, and an overlapping FFS (Fringe Field).
Switching) mode is known. A horizontal electric field type liquid crystal display device has an effect that a wide viewing angle can be obtained.

This horizontal electric field type liquid crystal display device uses liquid crystal that is homogeneously aligned and a pair of polarizing plates that are disposed on both sides of the liquid crystal layer so that the transmission axes are perpendicular to each other vertically and horizontally with respect to the front of the screen. In the horizontal electric field type liquid crystal display device having such a configuration, when the screen is viewed obliquely from the top, bottom, left, and right directions, the two transmission axes are in a positional relationship that they appear to be orthogonal, so that sufficient contrast can be obtained. However, when the screen is viewed obliquely from a direction with an azimuth angle of 45 °, the angle formed by the transmission axes of the pair of polarizing plates is deviated from 90 °. Therefore, birefringence occurs in the transmitted light and light leakage occurs. However, there are problems such as a decrease in contrast and a decrease in viewing angle.

Therefore, in order to solve the problem of such a horizontal electric field type liquid crystal display device, there has been conventionally known a liquid crystal display device using various retardation plates for the purpose of widening the viewing angle and improving the image quality. . For example, Patent Document 1 below discloses an invention of a liquid crystal display device including an optical compensation sheet having optically negative uniaxiality. Patent Document 2 below discloses an invention of a liquid crystal display device having two layers having positive uniaxial optical anisotropy as a compensation layer for compensating the birefringence of a liquid crystal layer. .

Patent Document 3 below discloses an invention of a liquid crystal display device using a negative biaxial retardation film and a + C-plate as a viewing angle compensation film. Further, in Patent Document 4 below, a negative substantially uniaxial optical film having an optical axis in the plane and a second optical film (negative) having a refractive index in the thickness direction smaller than any direction in the plane. An invention of a liquid crystal display device using a biaxial optical film) is disclosed.

Further, Patent Document 5 below discloses an invention of a liquid crystal display using a C-type or P-type wide viewing angle polarizing plate. Here, the C type means that the in-plane retardation of the polarizer = 250 nm to 300 nm.
It is a wide viewing angle polarizing plate in which biaxial retardation films having birefringence characteristics of nm and Nz = 0.1 to 0.4 are stacked in an orthogonal type, and the P type is in-plane with a polarizer. Phase difference = 250 nm to 300
This is a wide viewing angle polarizing plate in which biaxial retardation films having birefringence characteristics of nm and Nz = 0.6 to 1.1 are stacked in parallel.

Japanese Patent No. 3118208 Japanese Patent No. 3204182 JP-T 2006-520008 JP 2006-293108 A Japanese Patent No. 4276392

As disclosed in Patent Documents 1 to 5, various retardation plates and the like have been conventionally used to achieve a wide viewing angle of a liquid crystal display device. However, the progress of the technology related to the liquid crystal display device is remarkable, and a new technology is demanded for wider viewing angle and improved image quality.

Therefore, the present inventors have a structure that is different from the above-described conventional technology, and can achieve a wide viewing angle and improved image quality at least as good as or better than the conventional horizontal electric field type liquid crystal display device. As a result of repeated studies, the inventors have found that it can be achieved by using two negative biaxial films as retardation plates, and have completed the present invention.

That is, an object of the present invention is to provide a horizontal electric field type liquid crystal display device that can achieve a wide viewing angle and an improvement in image quality that are comparable to or better than conventional horizontal electric field type liquid crystal display devices. To do.

In order to achieve the above object, the liquid crystal display device of the present invention has a liquid crystal layer sandwiched between a pair of substrates,
On the opposite side of the pair of substrates from the liquid crystal layer, a pair of polarizing plates are provided so that their light transmission axes are orthogonal to each other,
A first electrode and a second electrode are formed on one of the pair of substrates,
A horizontal electric field type liquid crystal display device in which the liquid crystal is driven by an electric field generated between the first electrode and the second electrode,
The polarizing plate formed on one of the pair of substrates is formed of a protective film, a polarizer, and two negative biaxial films,
The two negative biaxial films are composed of a first negative biaxial film and a second negative biaxial film,
The first negative biaxial film and the second negative biaxial film are overlapped and arranged on the one substrate side or the other substrate side.

According to the liquid layer display device of the present invention, since two negative biaxial films are provided as retardation plates, the viewing angle compensation function can be greatly improved. A wide viewing angle similar to or greater than that in the case of an electric field type liquid crystal display device can be obtained. Further, since the negative biaxial film can also serve as one protective film of the polarizing plate, the protective film can be omitted, and the polarizing plate is obtained by using two negative biaxial films. The increase in thickness can be reduced.

In the liquid crystal display device of the present invention, the first negative biaxial film is disposed on the polarizer side of the polarizing plate, and the optical axis of the second negative biaxial film is the liquid crystal. Preferably, the optical axis of the first negative biaxial film is parallel or perpendicular to the initial alignment direction of the liquid crystal.

In a horizontal electric field type liquid crystal display device, a pair of polarizing plates are arranged in a crossed Nicol arrangement,
One light transmission axis of the pair of polarizing plates is arranged in a direction parallel or orthogonal to the initial alignment direction of the liquid crystal. Note that the initial alignment direction of the liquid crystal is determined by the rubbing direction of the alignment film formed on the liquid crystal layer side of the pair of substrates. Therefore, in the liquid crystal display device of the present invention, in order for the viewing angle compensation film to perform the viewing angle compensation function, the two negative biaxial films are disposed between the liquid crystal display element and the polarizer of the polarizing plate. The two negative biaxial films are arranged so that their optical axes are orthogonal or parallel to each other, and are also required to be orthogonal or parallel to the light transmission axis of the polarizer.

In the liquid crystal display device of the present invention, the first negative biaxial film is disposed on the polarizer side of the polarizing plate, and the optical axis of the second negative biaxial film is relative to the initial alignment direction of the liquid crystal. Since the optical axis of the first negative biaxial film is parallel or orthogonal to the initial alignment direction of the liquid crystal, the viewing angle compensation function can be effectively performed.

In the liquid crystal display device of the present invention, the second negative biaxial film is disposed on the polarizer side of the polarizing plate, and the optical axis of the second negative biaxial film is It is also possible to make the optical axis of the first negative biaxial film perpendicular to the initial alignment direction of the liquid crystal and parallel or orthogonal to the initial alignment direction of the liquid crystal layer.

According to the liquid crystal display device of the present invention, even if such a configuration is adopted, the same effects as those described above can be obtained.

In the liquid crystal display device of the present invention, the first negative biaxial film is nx> ny.
> Nz (where nx, ny and nz represent the refractive indexes in the respective axial directions, and d represents the thickness of the retardation plate), and in-plane retardation Ro: 0 nm <(nx−ny) * d ≦ 20 nm, thickness direction retardation Rth: 50 nm ≦ {(nx + ny) / 2−nz} * d ≦ 100 nm,
The second negative biaxial film satisfies nx>nz> ny, and has an in-plane retardation Ro: 100.
nm ≦ (nx−ny) * d ≦ 200 nm, birefringence coefficient Nz: (nx−nz) / (nx−ny)
Is preferably −0.3 to 0.3.

According to the liquid crystal display device of the present invention, a favorable viewing angle compensation function can be achieved in the visible light range by adopting the above numerical range.

In the liquid crystal display device of the present invention, both the first negative biaxial film and the second negative biaxial film are preferably made of stretched films such as triacetyl cellulose, polycarbonate, polynorbornene and the like. .

These stretched films are generally used as viewing angle compensation films, and are not special materials, and can be easily obtained. Therefore, a liquid crystal display layer having the above effects can be obtained at a low cost. It can be made.

It is a top view of the liquid crystal display device common to Embodiments 1-4. FIG. 2 is an enlarged plan view for one pixel in the display area of FIG. 1. It is an expanded sectional view along the III-III line of FIG. 1 is an exploded perspective view showing a liquid crystal display device of Embodiment 1. FIG. FIG. 5A is a schematic diagram illustrating the first film, and FIG. 5B is a schematic diagram illustrating the second film. 3 is a schematic diagram illustrating an example of the phase of each layer in Embodiment 1. FIG. 6 is an exploded perspective view showing a liquid crystal display device of Embodiment 2. FIG. 6 is a schematic diagram illustrating an example of the phase of each layer according to Embodiment 2. FIG. 6 is an exploded perspective view showing a liquid crystal display device according to Embodiment 3. FIG. 10 is a schematic diagram illustrating an example of the phase of each layer according to Embodiment 3. FIG. 6 is an exploded perspective view showing a liquid crystal display device of Embodiment 4. FIG. FIG. 6 is a schematic diagram illustrating an example of the phase of each layer in the fourth embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, each embodiment described below is described by taking an FFS mode liquid crystal display device as an example in order to embody the technical idea of the present invention. The present invention is not limited to the FFS mode described in this embodiment. It is not intended to be specific to a liquid crystal display device and the invention is equally applicable to other embodiments within the scope of the claims. In each drawing used for the description in this specification, each layer and each member are displayed in different scales so that each layer and each member can be recognized on the drawing. However, it is not necessarily displayed in proportion to the actual dimensions.

The “surface” of the array substrate and the color filter substrate described below refers to the surface on which various wirings are formed or the surface facing the liquid crystal, and the “back surface” refers to the display surface side (of the color filter substrate). Case) or the surface on the backlight side (in the case of an array substrate). In addition, the horizontal electric field type liquid crystal display device according to the present invention can be applied to one manufactured by using a liquid crystal injection method.
An example manufactured by using the “F” method will be described. Further, although the liquid crystal display device is manufactured using a mother substrate, in the following, for convenience of explanation, one FFS mode liquid crystal display device will be described as a representative.

[Embodiment 1]
First, the configuration of the FFS mode liquid crystal display device 10 according to the first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the liquid crystal display device 10 according to the first embodiment includes an array substrate 11 and a color filter substrate 26, and a sealing material 33 that bonds the substrates 11 and 26 together. 26 is a so-called COG (Chip On Glass) type liquid crystal display device in which liquid crystal (see FIG. 3) is sealed in a region surrounded by the sealant 26 and the sealing material 33. In this liquid crystal display device 10, a display region 34 is formed in an inner region surrounded by the sealing material 33, and a region provided around the display region 34 where an image is not recognized is not displayed on the liquid crystal display device 10. Region 35 is formed. Further, since the liquid crystal display device 10 according to the first embodiment is manufactured by the ODF method, a liquid crystal injection port is not formed. And the 1st polarizing plate 39 and the 2nd polarizing plate 40 are each installed in the back surface of the color filter board | substrate 26, and the back surface of the array board | substrate 11 (refer FIG. 3).

The array substrate 11 is obtained by forming various wirings for driving liquid crystal on the surface of a rectangular first transparent substrate 12 made of glass or the like. The array substrate 11 is longer in the longitudinal direction than the color filter substrate 26, and an extended portion 12a extending to the outside when the substrates 11 and 26 are bonded together is formed. The extending portion 12a is provided with a driver 36 made of an IC chip or LSI for outputting a drive signal. Further, the common wiring 14 further extends from the driver 36.

In the display area 34 of the array substrate 11, as shown in FIGS.
3 and the signal line 17, a plurality of common wires 14 a parallel to the scanning line 13 are provided between the plurality of scanning lines 13. Further, a gate insulating film 15 made of an inorganic insulating material such as silicon oxide or silicon nitride is provided so as to cover the scanning lines 13, the common wirings 14 a, and the exposed transparent substrate 12. A thin film transistor TFT as a switching element including the source electrode S, the gate electrode G, the drain electrode D, and the semiconductor layer 16
(TFT: Thin Film Transistor) is formed near the intersection of the scanning line 13 and the signal line 17.

Further, a passivation film 18 made of an inorganic insulating material such as silicon oxide or silicon nitride for stabilizing the surface is formed so as to cover these, and an organic insulating material for flattening the surface of the array substrate 11 An interlayer film 19 made of is formed.

Next, the first contact hole 20 is formed so as to penetrate the gate insulating film 15 and the passivation film 18 on the common wiring 14a by photolithography and etching.
Is formed. For the formation of the first contact hole 20, a plasma etching method which is a kind of dry etching method or a wet etching method using buffered hydrofluoric acid can be employed. Thereby, the common wiring 14a is exposed.

Next, over the entire surface of the transparent substrate 12 on which the interlayer film 19 is formed, for example, ITO or IZ
A transparent conductive layer made of O is coated, and a lower electrode 21 is formed on the surface of the interlayer film 19 for each pixel by photolithography and etching. At this time, the lower electrode 21 for each pixel is electrically connected to the common wiring 14 a through the first contact hole 20. Therefore, the lower electrode 21 operates as a common electrode.

Further, an insulating film 22 made of a silicon nitride layer or a silicon oxide layer is formed over the entire surface of the first transparent substrate 12 on which the lower electrode 21 is formed. At this time, the surface of the interlayer film 19 where the contact hole is to be formed on the drain electrode D is also covered with the insulating film 22. Next, a second contact hole 23 is formed in the interlayer film 19 and the insulating film 22 in a portion where a contact hole is to be formed on the drain electrode D by photolithography and etching.

Further, a transparent conductive layer made of, for example, ITO or IZO is coated over the entire surface of the first transparent substrate 12 on which the insulating film 22 is formed, and the insulating film is formed for each pixel by photolithography and etching. Upper electrode 2 having a plurality of slits 24 formed on the surface of 22
5 is formed. The upper electrode 25 is electrically connected to the drain electrode D of the thin film transistor TFT in the second contact hole 23 and operates as a pixel electrode. Thereafter, the first alignment film 37 made of, for example, polyimide is provided on the entire surface including the upper electrode 25 of the display region 34, whereby the array substrate 11 of the liquid crystal display device 10 of the first embodiment is obtained.
The first alignment film 37 is subjected to a liquid crystal direction alignment process (rubbing process) in a direction crossing the extending direction of the slit 24. In addition, a region surrounded by the plurality of scanning lines 13 and signal lines 17 becomes one sub-pixel region PA.

The color filter substrate 26 is formed on the surface of the second transparent substrate 27 made of glass or the like.
A light shielding film 28 made of a metal material is formed so as to cover the positions corresponding to the scanning lines 13, the signal lines 17 and the thin film transistor TFTs of the array substrate 11 and the non-display area 35.

Further, a color filter layer 29 of a predetermined color, for example, red (R), green (G), blue (B), or the like is formed on the surface of the second transparent substrate 27 surrounded by the light shielding film 28 in the display region 34. And the overcoat layer 3 so that the surfaces of the light shielding film 28 and the color filter layer 29 are covered.
0 is formed.

Then, a second alignment film 38 made of, for example, polyimide is formed so as to cover the overcoat layer 30, and the color filter substrate 26 of the first embodiment is obtained. The second alignment film 38 is subjected to a liquid crystal direction alignment process in a direction opposite to that of the first alignment film 37 formed on the array substrate 11.

The array substrate 11 and the color filter substrate 26 described above are formed of, for example, a resin or the like in which liquid crystal is dropped on the display region 34 of the array substrate 11 and the non-display region 35 of the color filter substrate 26 can be cured by ultraviolet light. A sealing material 33 is applied and both the substrates 11 and 26 are applied.
Are pasted together. Thereafter, the sealing material 33 is irradiated with ultraviolet light to cure the sealing material 33, and the driver 36 is installed in the extending portion 12 a of the array substrate 11. A columnar spacer (not shown) is formed between the color filter substrate 26 and the array substrate 11 to keep the cell gap between the two substrates constant.

Thereafter, the first polarizing plate 39 and the second polarizing plate 40 are respectively installed on the back side of the bonded substrates, and a backlight device (not shown) is arranged outside the first polarizing plate 39 on the array substrate 11 side. Thus, the FFS mode liquid crystal display device 10 according to the first embodiment is completed. In addition,
The first polarizing plate 39 and the second polarizing plate 40 are arranged in crossed Nicols, and one light transmission axis of the first polarizing plate 39 and the second polarizing plate 40 is the rubbing direction of the first alignment film 37 or the second alignment film 38. That is, they are arranged in a direction parallel or orthogonal to the initial alignment direction of the liquid crystal.

Here, with reference to FIG. 4, the specific structure of the 1st polarizing plate 39 and the 2nd polarizing plate 40 is demonstrated. For convenience of explanation, the array substrate 11 and the color filter substrate 26 sandwiching the liquid crystal layer 32 are collectively referred to as a liquid crystal display substrate 41. A commonly used polarizing plate has a configuration in which protective films are arranged on both sides of a polarizer obtained by uniaxially stretching a polyvinyl alcohol (PVA) film adsorbed with an iodine complex or a dichroic dye. Yes. As this protective film, transparent triacetyl cellulose (TAC) is often used. In the liquid crystal display device 10 of Embodiment 1, the second polarizing plate 40 disposed on one outer surface of the liquid crystal display substrate 41.
As in the case of a conventional polarizing plate, a polarizer having a protective film 40a and 40c made of TAC attached on both sides of a polarizer 40b is used.

However, as the first polarizing plate 39 disposed on the other outer surface of the liquid crystal display substrate 41,
Although the protective film 39a made of TAC is used on the outer surface of the polarizer 39b, the liquid crystal display substrate 41 is used.
The side uses what consists of two negative biaxial films 42 as a protective film. here,
Of the two negative biaxial films 42, one is a first negative biaxial film 43 and the other is a second negative biaxial film 44.

In the liquid crystal display device of the present invention, in order to perform a predetermined viewing angle compensation function, the two negative biaxial films are disposed between the liquid crystal display element and the polarizer of the polarizing plate, and The two negative biaxial films need to have optical axes orthogonal or parallel to each other and orthogonal or parallel to the light transmission axis of the polarizer.

Therefore, in the liquid crystal display device 10 of Embodiment 1, the second negative biaxial film 44 and the first negative electrode 44 are arranged on the array substrate 11 side in order from the array substrate 11 side with the liquid crystal display substrate 41 as the center.
Negative biaxial film 43, negative biaxial film 42, polarizer 39b, TA
A first polarizing plate 39 made of a protective film 39a made of C is disposed. Further, on the color filter substrate 26 side, the protective film 40 made of TAC is sequentially formed from the color filter substrate 26 side.
a, a polarizer 40b, and a second polarizing plate 40 made of a protective film 40c made of TAC are disposed.

In addition, the biaxial film indicates a case where the refractive indexes in the three axial directions of x, y, and z are all different. The first negative biaxial film 43 has triaxial refractive indexes of nx, ny, and nz, respectively.
nx>ny> nz
Is a negative biaxial film satisfying the relationship (see FIG. 5A). On the other hand, the second negative biaxial film 44 has triaxial refractive indexes of nx, ny, and nz, respectively.
nx>nz> ny
Is a negative biaxial film satisfying the relationship (see FIG. 5B).

As such a negative biaxial film, for example, a uniaxially stretched TAC, polycarbonate, polynorbornene, or other uniaxially or biaxially stretched film can be used.
This negative biaxial film can be used as a protective film for the polarizer as in the case of the polarizing plate of the conventional example. The polarizer 39b of the first polarizing plate 39 and the polarizer 40b of the second polarizing plate 40 have light transmission axes 39 ₁ and 40 ₁ that are orthogonal to each other.
First negative biaxial film 43 is disposed on the polarizer 39b side, the optical axis 44 ₁ in the plane of the second negative biaxial film 44 of the liquid crystal layer 32 in the liquid crystal display substrate 41 It is parallel to the initial alignment direction, and the optical axis 43 ₁ of the plane of the first negative biaxial film 43 are parallel or perpendicular to the initial alignment direction of the liquid crystal layer 32 (FIG. 6 reference).

By adopting such a configuration, it becomes possible to greatly improve the viewing angle characteristics in the diagonal direction in the lateral electric field type liquid crystal display device by summing up the in-plane retardation in all directions. A wide viewing angle similar to or greater than the case of the horizontal electric field type liquid crystal display device of the example can be obtained. In addition, since the negative biaxial film can also serve as one protective film of the polarizing plate, the protective film can be omitted separately, and by using two negative biaxial films. The increase in the thickness of the polarizing plate is reduced.

[Embodiment 2]
As the liquid crystal display device 10A according to the second embodiment, the two negative 2 plates provided on the second polarizing plate 40A.
An axial film 42A is provided on the color filter substrate 26 side, the second negative biaxial film 44A on the liquid crystal display substrate 41 side, and the first negative biaxial on the polarizer 40Ab side of the second polarizing plate 40A. A case where the conductive film 43A is arranged will be described. The liquid crystal display substrate 41 in the FFS mode liquid crystal display device 10A of the second embodiment is the same as the liquid crystal display device 10 of the first embodiment.
This is the same as described in. In addition, the liquid crystal display device 10A of the second embodiment is different from the liquid crystal display device 10 of the first embodiment in that the arrangement positions of the first negative biaxial film and the second negative biaxial film are as follows. Are the same as those described in the first embodiment, and the same reference numerals are given, and detailed description thereof is omitted.

As shown in FIG. 7, the liquid crystal display device 10A according to the second embodiment is centered on the liquid crystal display substrate 41, and on the array substrate 11 side, in order from the array substrate 11 side, is a protective film 39Ac and a polarizer 39Ab.
The first polarizing plate 39A made of the protective film 39Aa is disposed, and the second negative biaxial film 44A and the first negative biaxial film are arranged on the color filter substrate 26 side in this order from the color filter substrate 26 side. A second polarizing plate 40A composed of a film 43A, a polarizer 40Ab, and a protective film 40Aa is disposed.

In the liquid crystal display device 10A of embodiment 2, the first negative biaxial film 43A is disposed on the polarizer 40Ab side, the optical axis 44A ₁ of the second negative biaxial film 44A is The optical axis 43A1 of the _first negative biaxial film 43A is parallel to the initial alignment direction of the liquid crystal layer 32 or parallel to the initial alignment direction of the liquid crystal layer 32 in the liquid crystal display substrate 41. They are orthogonal (see FIG. 8). With such a configuration, the liquid crystal display device 10 of Embodiment 2 is used.
Also in A, the wide viewing angle similar to that of the liquid crystal display device 10 of Embodiment 1 can be achieved.

[Embodiment 3]
As the liquid crystal display device 10B according to the third embodiment, two negative 2 provided on the first polarizing plate 39B are provided.
An axial film 42B is provided on the array substrate 11 side, the first negative biaxial film 43B on the liquid crystal display substrate 41 side, and the second negative biaxial property on the polarizer 39Bb side of the first polarizing plate 39B. A case where the film 44B is disposed will be described. The liquid crystal display substrate 41 in the FFS mode liquid crystal display device 10B of the third embodiment is the same as that described in the liquid crystal display device 10 of the first embodiment. In addition, the liquid crystal display device 10B of the third embodiment is different from the liquid crystal display device 10 of the first embodiment in the arrangement position of the first negative biaxial film and the second negative biaxial film. Are the same as those described in the first embodiment, and the same reference numerals are given, and detailed description thereof is omitted.

As shown in FIG. 9, the liquid crystal display device 10B of Embodiment 3 is centered on the liquid crystal display substrate 41, and the first negative biaxial film 43B is arranged on the array substrate 11 side sequentially from the array substrate 11 side.
, A first polarizing plate 39B including a second negative biaxial film 44B, a polarizer 39Bb, and a protective film 39Ba is disposed, and the protective film 40Bc, in order from the color filter substrate 26 side, is disposed on the color filter substrate 26 side. A second polarizing plate 40B including a polarizer 40Bb and a protective film 40Ba is disposed.

In the liquid crystal display device 10B of the third embodiment, the second negative biaxial film 44B is disposed on the polarizer 39Bb side. The optical axis 44B of the second negative biaxial film 44B in this case
₁ is orthogonal to the initial alignment direction of the liquid crystal layer 32 in the liquid crystal display substrate 41, and the optical axis 43B1 of the _first negative biaxial film 43B is relative to the initial alignment direction of the liquid crystal layer 32. Are parallel or orthogonal (see FIG. 10). By adopting such a configuration, the wide viewing angle similar to that of the liquid crystal display device 10 of the first embodiment can be achieved also in the liquid crystal display device 10B of the third embodiment.

[Embodiment 4]
As the liquid crystal display device 10C according to the fourth embodiment, a negative biaxial film 42C provided on the second polarizing plate 40C is provided on the color filter substrate 26 side, and the first negative 2 is provided on the liquid crystal display substrate 41 side. The case where the second negative biaxial film 44C is arranged on the polarizer 40Cb side of the axial film 43C and the second polarizing plate 40C will be described. The liquid crystal display substrate 41 in the FFS mode liquid crystal display device 10C of the fourth embodiment is the same as that described in the liquid crystal display device 10 of the first embodiment. In the liquid crystal display device 10C of the fourth embodiment, the first embodiment is used.
The difference from the liquid crystal display device 10 is that the first negative biaxial film and the second negative 2
Since only the arrangement position of the axial film is different, the same structure as that described in Embodiment 1 is denoted by the same reference numeral, and detailed description thereof is omitted.

As shown in FIG. 11, the liquid crystal display device 10C according to the fourth embodiment is centered on the liquid crystal display substrate 41, and the first negative 2 in order from the color filter substrate 26 side to the color filter substrate 26 side.
The axial film 43C is a second negative biaxial film 44C, a polarizer 40Cb, and a protective film 40.
A second polarizing plate 40C made of Ca is arranged, and on the array substrate 11 side, a first polarizing plate 39C made of a protective film 39Cc, a polarizer 39Cb, and a protective film 39Ca is arranged in this order from the array substrate 11 side. .

In the liquid crystal display device 10C of the fourth embodiment, the second negative biaxial film 44C is disposed on the polarizer 40Cb side. The optical axis 44C of the second negative biaxial film 44C in this case
₁ is orthogonal to the initial alignment direction of the liquid crystal layer 32 in the liquid crystal display substrate 41, and the optical axis 43C1 of the _first negative biaxial film 43C is relative to the initial alignment direction of the liquid crystal layer 32. Are parallel or orthogonal (see FIG. 12). With this configuration, also in the liquid crystal display device 10C of the fourth embodiment, the same wide viewing angle as that of the liquid crystal display device 10 of the first embodiment can be achieved.

10, 10A to 10C: Liquid crystal display device 11: Array substrate 12: Transparent substrate 12a: Extension portion 13: Scanning line 14: Common wiring 14a: Common wiring 15: Gate insulating film 16
: Semiconductor layer 17: Signal line 18: Passivation film 19: Interlayer film 20: Contact hole 21: Lower electrode 22: Insulating film 23: Contact hole 24: Slit 2
5: Upper electrode 26: Color filter substrate 27: Transparent substrate 28: Light shielding film 29: Color filter layer 30: Overcoat layer 32: Liquid crystal 33: Sealing material 34: Display area 35: Non-display area 36: Driver 37: First Alignment film 38: second alignment film 39
: First polarizing plate 40: second polarizing plate 41: liquid crystal display substrate 42: two negative biaxial films 43, 43A to 43C: first negative biaxial films 44, 44A to 44C: second Negative biaxial film D: Drain electrode G: Gate electrode S: Source electrode PA: Sub-pixel region TFT: Thin film transistor

Claims (5)

A liquid crystal layer is sandwiched between a pair of substrates,
On the opposite side of the pair of substrates from the liquid crystal layer, a pair of polarizing plates are provided so that their light transmission axes are orthogonal to each other,
A first electrode and a second electrode are formed on one of the pair of substrates,
A horizontal electric field type liquid crystal display device in which the liquid crystal is driven by an electric field generated between the first electrode and the second electrode,
The polarizing plate formed on one of the pair of substrates is formed of a protective film, a polarizer, and two negative biaxial films,
The two negative biaxial films are composed of a first negative biaxial film and a second negative biaxial film,
The first negative biaxial film and the second negative biaxial film are overlapped and arranged on the one substrate side or the other substrate side. Liquid crystal display device. The first negative biaxial film is disposed on the polarizer side of the polarizing plate, and the optical axis of the second negative biaxial film is parallel to the initial alignment direction of the liquid crystal, 2. The liquid crystal display device according to claim 1, wherein an optical axis of the first negative biaxial film is parallel or orthogonal to an initial alignment direction of the liquid crystal. The second negative biaxial film is disposed on the polarizer side of the polarizing plate, and the optical axis of the second negative biaxial film is orthogonal to the initial alignment direction of the liquid crystal. 2. The liquid crystal display device according to claim 1, wherein an optical axis of the first negative biaxial film is parallel or orthogonal to an initial alignment direction of the liquid crystal layer. The first negative biaxial film is nx>ny> nz (where nx, ny, and nz represent the refractive index in each axial direction, and d represents the thickness of the retardation plate), and the surface. Inner phase difference Ro: 0 nm <
(nx−ny) * d ≦ 20 nm, large thickness direction retardation Rth: 50 nm ≦ {(nx + ny)
/ 2-nz} * d ≦ 100 nm,
The second negative biaxial film satisfies nx>nz> ny, and has an in-plane retardation Ro: 100.
nm ≦ (nx−ny) * d ≦ 200 nm, birefringence coefficient Nz: (nx−nz) / (nx−ny)
Is -0.3 to 0.3,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. The first negative biaxial film and the second negative biaxial film are both made of stretched films such as triacetyl cellulose, polycarbonate, polynorbornene, and the like. A liquid crystal display device according to claim 1.

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