KR101157963B1 - Liquid Crystal Display Device - Google Patents

Abstract

The present invention provides a liquid crystal display device suitable for compensating for a viewing angle problem in a transflective ECB mode. The liquid crystal display device for achieving the above object includes an upper and lower substrates facing each other; An ECB liquid crystal layer filled between the upper and lower substrates; Λ / 2 phase difference plate (HWP (Half wave plate)) and λ / 4 phase difference plate (QWP (Quarter wave plate) of (+) A plate and (-) A plate on the outer side of the upper substrate and the outer side of the lower substrate The first and second anti-reflection film parts having a combination of the two and the at least one (-) C plate at an adjacent outer side of the upper and lower substrates; A first polarizing plate provided outside the first anti-reflection film portion; Characterized in that the second polarizing plate on the outside of the second anti-reflection film portion.

ECB, viewing angle, retardation, (+) A plate, (-) A plate, (-) C plate

Description

[0001] The present invention relates to a liquid crystal display device,

1 is a film configuration of a liquid crystal display device according to the prior art

2 is a view showing a contour having the same contrast ratio of a conventional liquid crystal display device;

3 to 6 are exemplary film configurations of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 7 shows contours having the same contrast ratio when the retardation of (-) C palte is 250 nm. FIG.

8 to 10 is an exemplary view showing a combination of (-) C plate

11 to 13 show contours having the same contrast ratio when having the configuration shown in FIGS. 8 to 10.

14 shows nx, ny, and nz.

Explanation of symbols on the main parts of the drawings

31: upper substrate 32: lower substrate

33: ECB liquid crystal layer 34: first retardation plate

35: second phase difference plate 36: third phase difference plate

37: fourth retardation plate 38: fifth retardation plate

39: sixth retardation plate 40: first TAC layer

41: first polarizing plate 42: second TAC layer

43: second polarizing plate 50: first antireflection film portion

51: second antireflection film portion

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device configured in a transflective ECB mode suitable for improving a viewing angle.

In recent years, there has been a demand for a display device in accordance with the development of an information society, and in recent years, a display device such as a liquid crystal display (LCD), a plasma display panel (PDP), an electro luminescent display (ELD), a vacuum fluorescent display ) Have been studied, and some of them have already been used as display devices in various devices.

Among them, LCDs are currently being used most frequently, replacing CRTs (Cathode Ray Tubes) for mobile image display devices due to the advantages of excellent image quality, light weight, thinness, and low power consumption.

The liquid crystal display (LCD) as described above is characterized by light weight, thin, low power consumption, and small and medium-sized mobile display fields including mobile phones, personal digital assistants (PDAs) as well as large displays such as notebook PCs, monitors, and televisions. It is widely used to.

The liquid crystal display has a structure in which a color filter substrate as an upper substrate and a thin film transistor (TFT) substrate as a lower substrate are disposed to face each other, and a liquid crystal having dielectric anisotropy is formed therebetween. The TFTs are driven by switching a TFT added to hundreds of thousands of pixels through a pixel selection address wiring to apply a voltage to the corresponding pixels.

On the other hand, the liquid crystal display device has the disadvantages of a transmission type using a backlight unit as a light source, a reflection type using external natural light without using the backlight unit as a light source, and a transmission type having high power consumption due to the use of the backlight unit and dark external natural light. It can be divided into semi-transmissive type to overcome the disadvantage of the reflective type that can not be used.

Since the transflective liquid crystal display has a reflective part and a transmissive part at the same time inside the unit pixel, both the transmissive type and the transmissive type can be used as necessary.

Accordingly, according to the liquid crystal display, the pixel electrode is formed of a transmissive electrode or a reflective electrode. A transmissive electrode is formed in the transmissive portion of the transmissive liquid crystal display and the transflective liquid crystal display and the reflection of the reflective liquid crystal display and the transflective liquid crystal display. The reflection electrode is formed in the portion.

Here, the transmissive electrodes of the transmissive and transflective liquid crystal display devices emit light from the backlight unit incident through the lower substrate into the liquid crystal layer to brighten the brightness, and the reflecting electrodes of the reflective and transflective liquid crystal display elements are external natural light. When it is bright, it reflects the external light incident through the upper substrate to brighten the brightness.

The transmissive liquid crystal display device is mainly used in large LCDs, and the reflection type and transflective liquid crystal display devices are used in small and medium sized LCDs.

Hereinafter, a liquid crystal display according to the related art will be described with reference to the accompanying drawings.

1 is a view illustrating a film configuration of a liquid crystal display device according to the prior art, and FIG. 2 is a view illustrating a contour having the same contrast ratio of a conventional liquid crystal display device.

Conventional liquid crystal display device is a transflective electrically controlled Birefringence (ECB) mode liquid crystal display device, as shown in Figure 1, the upper and lower substrates (1, 2) facing each other, and the upper and lower substrates (1.2) An ECB liquid crystal layer 3 filled therebetween, and a first (+) A plate QWP (Quarter wave plate) 4 and a first (+) A plate HWP (Half wave) formed on the outer surface of the upper substrate 1. a first anti-reflection film part 6 composed of a plate (5), and a second (+) A plate QWP (Quarter wave plate) 7 and a second (+) A on an outer surface of the lower substrate (2). A second anti-reflection film portion 9 composed of a plate half wave plate (HWP) 8, and a first tri-acetyl-cellulose (TAC) 10 sequentially provided outside the first anti-reflection film portion 6. ) And a first polarizing plate 11, and a second TAC 12 and a second polarizing plate 13 which are sequentially provided outside the second antireflection film part 9.

As described above, in the conventional ECB mode liquid crystal display device, the reflection mode, that is, the anti-reflective film portion is provided with two sheets of HWP and QWP on the upper and lower substrates, respectively.

In general, HWP and QWP are made of (+) A plate and must be used for transflective on-off.

The (+) A plate represents a case where nz = ny and nx> nz when the refractive index is represented by the axis of nx, ny, nz.

As shown in FIG. 2, the conventional transflective ECB mode liquid crystal display having the above configuration has a narrow viewing angle characteristic because the viewing angle is 80/45/40/45 when CR> 10 or more in the transmissive portion. have.

Such narrow viewing angle characteristics are attributable to the HWP, QWP, and ECB liquid crystal layers constituting the first and second antireflection film parts, and thus, a structure capable of compensating for such viewing angle problems in an inclined direction is required.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device suitable for compensating for the viewing angle problem in the transflective ECB mode.

Liquid crystal display device according to the present invention for achieving the above object is the upper and lower substrates opposed to each other; An ECB liquid crystal layer filled between the upper and lower substrates; Λ / 2 phase difference plate (HWP (Half wave plate)) and λ / 4 phase difference plate (QWP (Quarter wave plate) of (+) A plate and (-) A plate on the outer side of the upper substrate and the outer side of the lower substrate The first and second anti-reflection film parts having a combination of the two and the at least one (-) C plate at an adjacent outer side of the upper and lower substrates; A first polarizing plate provided outside the first anti-reflection film portion; Characterized in that the second polarizing plate on the outside of the second anti-reflection film portion.

The first anti-reflection film portion is composed of a first retardation plate composed of (+) A plate 30nm, a second retardation plate composed of (+) A plate QWP, and a third retardation plate composed of (+) A plate HWP, The second anti-reflection film part includes a fourth retardation plate made of (-) C plate, a fifth retardation plate made of (-) A plate QWP, and a sixth retardation plate made of (-) A plate HWP. It is characterized by the presence.

The first anti-reflection film portion is composed of a first retardation plate composed of (+) A plate 30nm, a second retardation plate composed of (-) A plate QWP, and a third retardation plate composed of (+) A plate HWP, The second anti-reflection film portion includes a fourth retardation plate composed of (-) C plate, a fifth retardation plate composed of (+) A plate QWP, and a sixth retardation plate composed of (-) A plate HWP. It is characterized in that it further comprises.

The first anti-reflection film portion is composed of a first retardation plate consisting of (+) A plate 30nm, a second retardation plate consisting of (+) A plate QWP, and a third retardation plate consisting of (-) A plate HWP The second anti-reflection film part includes a fourth retardation plate made of (-) C plate, a fifth retardation plate made of (-) A plate QWP, and a sixth retardation plate made of (+) A plate HWP. It is characterized by the presence.

The first anti-reflection film portion is composed of a first retardation plate composed of (+) A plate 30nm, a second retardation plate composed of (-) A plate QWP, and a third retardation plate composed of (-) A plate HWP The second antireflection film part includes a fourth retardation plate composed of (-) C plate, a fifth retardation plate composed of (+) A plate QWP, and a sixth retardation plate composed of (+) A plate HWP. It is characterized by the presence.

The (-) C plate is characterized by using a retardation of 150 ~ 350nm.

The (-) C plate further includes disposing between the first retardation plate and the second retardation plate, or between the first retardation plate and the second retardation plate and at a position adjacent to the lower substrate. It is characterized by.

A first Tri-Acetyl-Cellulose (TAC) layer between the first anti-reflection film portion and the first polarizing plate, and a second TAC (Tri-Acetyl) between the second anti-reflection film portion and the second polarizing plate -Cellulose) is characterized in that it further comprises being provided.

As the information contents to be displayed are greatly developed quantitatively and qualitatively, improvement of the viewing angle has become a more important task in LCD.

The reason why the viewing angle characteristic of the LCD is degraded is that the birefringence of the liquid crystal itself affects the light passing through the LCD cell. When the linearly polarized light produced by the polarizer passes through the LCD cell, its polarization performance is not maintained and some light leaks and passes, which is undesirable in contrast reduction or color change.

How to correct the change of birefringence due to the liquid crystal viewing angle is a key technology in the optical compensation film.

The present invention improves the viewing angle by including an optical compensation film, and relates to applying the optical compensation film to a semi-transmissive electrically controlled birefringence (ECB) mode that achieves a homogeneous orientation without twisting the liquid crystal. will be.

The ECB mode refers to an electrically controlled birefringence mode using interference between the normal light beam and the abnormal light beam of the incident light. The operation principle of the uniform ECB mode is as follows.

The light beam incident on the liquid crystal cell through the polarizing plate has a specific polarization direction. When the polarized light beam passes through the liquid crystal cell, retardation is generated between the normal light beam and the abnormal light beam of the polarized light beam. Thus, the polarization direction of the polarized light beam is changed by passing through the liquid crystal cell. The analyzer passes a light beam with a specific polarization direction. Therefore, the transmittance of the incident light beam depends on the retardation of the liquid crystal layer and the arrangement state of the polarizer and the analyzer. If the thickness of the liquid crystal layer is d and the difference between the normal refractive index n0 and the abnormal refractive index ne generated by the refractive index anisotropy of the liquid crystal layer is Δn, the retardation of the liquid crystal layer is given by d × Δn. The optical response is obtained by electrically changing the retardation (optical path difference) for the liquid crystal layer.

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

3 to 6 are exemplary diagrams of a film configuration of a liquid crystal display according to a first embodiment of the present invention.

7 is a view showing contours having the same contrast ratio when the retardation of (-) C palte is 250nm, and FIGS. 8 to 10 are exemplary views showing a combination of (-) C plates, and FIG. 11. 13 to 13 illustrate contours having the same contrast ratio when the retardation of (−) C palte is 250 nm with the configuration shown in FIGS. 8 to 10.

The present invention relates to a semi-transmissive electrically controlled birefringence (ECB) mode liquid crystal display device, wherein upper and lower substrates include λ / 2 (HWP: Half wave plate) and λ / 4 (QWP: Quarter wave plate). Retardation of light passing in the oblique direction of HWP (Half wave plate) and QWP (Quarter wave plate) by applying combination of (+) A plate and (-) A plate instead of only (+) A plate ), And the light in the oblique direction passing through the liquid crystal layer is compensated by applying at least one negative (-) C plate to the adjacent outer portions of the upper and lower substrates.

In more detail, as shown in FIG. 3, the liquid crystal display according to the first exemplary embodiment of the present invention includes upper and lower substrates 31 and 32 facing each other, and upper and lower substrates 31 and 32. A first anti-reflection film part composed of an ECB liquid crystal layer 33 filled between the first and second retardation plates 34, 35, and 36 formed on an outer surface of the upper substrate 31. 50, a second anti-reflection film portion 51 composed of fourth, fifth, and sixth retardation plates 37, 38, and 39 on the outer surface of the lower substrate 32, and the first anti-reflection film portion (50) A first TAC (Tri-Acetyl-Cellulose) layer 40 and a first polarizing plate 41, which are sequentially provided on the outside, and a second TAC layer, which are sequentially provided on the outside of the second anti-reflection film part 51. (42) and the second polarizing plate (43).

In the above, the first retardation plate 34 is composed of (+) A palte having a retardation of 30 nm, the second retardation plate 35 is composed of (+) A plate QWP, and the third retardation plate 36 is It consists of (+) A plate HWP.

The fourth retardation plate 37 is composed of (-) C palte, the fifth retardation plate 38 is composed of (-) A plate QWP, and the sixth retardation plate 39 is (-) A plate HWP. It consists of.

As described above, the HWP and QWP are applied to the upper and lower substrates 31 and 32 as a combination of (+) A plate and (-) A plate instead of a combination of only (+) A plate. Compensate each other for the retardation that light feels.

In addition, the light in the oblique direction passing through the ECB liquid crystal layer 33 is compensated by using a (-) C plate.

The (+) A plate represents a case where nz = ny and nx> nz when the refractive index is represented by the axis of nx, ny, nz.

The (-) A plate represents a case where nz = ny and nx <nz when the refractive index is represented by the axis of nx, ny, nz.

The (-) C plate represents a case where nx = ny and nz <nx when the refractive index is represented by the axis of nx, ny, nz.

At this time, the directions of nx and ny lie on the film surface as shown in FIG.

In the above, the second and third retardation plates (35,36) and the fifth and sixth phase differences consisting of (+) A plate QWP, (+) A plate HWP, (-) A plate QWP and (-) A plate HWP As shown in Figs. 3 to 6, the plates 38 and 39 can be arranged in four cases in combination with the upper and lower substrates 31 and 32, respectively. This is shown in Table 1 below.

Table 1

Second retarder Third retardation plate Fifth retarder 6th phase difference plate First configuration example (+) A plate QWP (+) A plate HWP (-) A plate QWP (-) A plate HWP Second configuration example (-) A plate QWP (+) A plate HWP (+) A plate QWP (-) A plate HWP Third configuration example (+) A plate QWP (-) A plate HWP (-) A plate QWP (+) A plate HWP Fourth Configuration Example (-) A plate QWP (-) A plate HWP (+) A plate QWP (+) A plate HWP

 When the retardation plates are configured as described above, in the case of the first configuration example, as shown in FIG. 3, the first antireflection film portion 50 includes a first retardation plate 34 composed of (+) A plate 30 nm. And a second retardation plate 35 composed of (+) A plate QWP, and a third retardation plate 36 composed of (+) A plate HWP, wherein the second antireflection film portion 51 is ( A fourth retardation plate 37 composed of -C plates, a fifth retardation plate 38 composed of (-) A plate QWPs, and a sixth retardation plate 39 composed of (-) A plate HWPs. .

In the second configuration example, as shown in FIG. 4, the first antireflection film part 50 includes a first retardation plate 34 composed of (+) A plate 30nm, and a (-) A plate QWP. And a second retardation plate 35 composed of a third retardation plate 36 composed of (+) A plate HWP, and the second anti-reflection film portion 51 comprises a fourth composed of (-) C plate. It consists of a phase difference plate 37, the 5th phase difference plate 38 which consists of (+) A plate QWP, and the 6th phase difference plate 39 which consists of (-) A plate HWP.

In the third configuration example, as shown in FIG. 5, the first antireflection film portion 50 includes a first retardation plate 34 composed of (+) A plate 30nm, and a (+) A plate QWP. And a second retardation plate 35 composed of a third retardation plate 36 composed of (-) A plate HWP, and the second anti-reflection film portion 51 comprises a fourth composed of (-) C plate. It consists of a phase difference plate 37, the 5th phase difference plate 38 comprised from (-) A plate QWP, and the 6th phase difference plate 39 comprised from (+) A plate HWP.

In the fourth configuration example, as shown in FIG. 6, the first antireflection film part 50 is formed of a first retardation plate 34 composed of (+) A plate 30nm and a (−) A plate QWP. The second retardation plate 35 is configured, and the third retardation plate 36 is constituted by (-) A plate HWP, and the second anti-reflection film portion 51 is the fourth retardation composed of (-) C plate. A plate 37, a fifth retardation plate 38 composed of (+) A plate QWP, and a sixth retardation plate 39 composed of (+) A plate HWP.

In the above configurations, since the ECB liquid crystal layer 33 has the same shape as the (+) C plate in black, the ECB liquid crystal layer 33 is provided with a (-) C plate to compensate.

Therefore, the retardation of the (-) C plate is generally similar to that of the ECB liquid crystal layer 33. If the retardation of the ECB liquid crystal layer 33 is set to about 300 nm, the retardation of the (-) C plate is It should be approximately 150 ~ 350nm.

For example, FIG. 7 is a diagram showing contours having the same contrast ratio when the retardation of (−) C palte is 250 nm, and it can be seen that the viewing angle is improved than that shown in FIG. 2.

As described above, the (-) C plate not only makes the retardation approximately 150-350 nm as described above to compensate for the light in the oblique direction passing through the ECB liquid crystal layer 33, but also the upper substrate 31 or the lower substrate. It can also arrange | position to at least one of (32), and make viewing angle characteristic symmetrical.

That is, as shown in FIG. 8, it may be disposed at a position adjacent to the lower substrate 32, and as shown in FIG. 9, between the first retardation plate 34 and the second retardation plate 35. As shown in FIG. 10, between the first retardation plate 34 and the second retardation plate 35 adjacent to the upper substrate 31 in combination with FIGS. 8 and 9, and between the lower substrate 32. Can be placed in adjacent positions. At this time, in FIG. 10, a portion formed between the first retardation plate 34 and the second retardation plate 35 is represented by a first (-) C palte 37a, and is disposed at a position adjacent to the lower substrate 32. Represented by the second (-) C palte (37b).

The structure in which the (-) C plate is disposed at a position adjacent to the lower substrate 32 is shown in FIGS. 3 to 6.

In addition, the arrangement structure of the (-) C plate as shown in FIGS. 9 and 10 is applied to the structures having the first and second antireflection film parts 50 and 51 illustrated in FIGS. 3 to 6, respectively. You can.

11 to 12 show contours having the same contrast ratio when the (-) C plate is arranged as shown in FIGS. 8 and 9 as described above, when the retardation of the (-) C palte is 250 nm. As a diagram showing the contour, it can be seen that the viewing angle characteristic is improved than that shown in FIG. 2.

13, the first (-) C plate 37a and the second (-) C plate 37b are arranged as shown in FIG. 10, and the first and second (-) C palte (37a) are disposed. , 37b) is a diagram showing contours having the same contrast ratio when the retardation is 125 nm, respectively, and it can be seen that the viewing angle characteristic is improved than that shown in FIG. 2.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention.

Accordingly, the technical scope of the present invention should not be limited to the contents described in the above embodiments, but should be determined by the claims.

The liquid crystal display according to the present invention as described above has the following effects.

By arranging (+) A plate and (-) A plate outside the upper and lower substrates, the retardation of the light passing in the oblique direction of HWP (Half Wave Plate) and QWP (Quarter Wave Plate) is felt. You can compensate. In addition, at least one (-) C plate may be provided on the upper and lower substrates to compensate the light in the inclination direction passing through the liquid crystal layer.

Accordingly, there is an effect that the narrow viewing angle problem of the transflective ECB mode liquid crystal display device can be solved.

Claims (9)

Upper and lower substrates opposed to each other; An electrically controlled Birefringence (ECB) liquid crystal layer filled between the upper and lower substrates; A first anti-reflection film part having first to third retardation plates sequentially stacked on the outer surface of the upper substrate; A second anti-reflection film part having fourth to sixth retardation plates sequentially stacked on the outer surface of the lower substrate; A first polarizing plate provided outside the first anti-reflection film part; And A second polarizing plate provided outside the second anti-reflection film portion; The first retardation plate is composed of (+) A plate; The fourth retardation plate is composed of a (-) C plate; The second and fifth retardation plates consist of (+) A plate λ / 4 retardation plates (Quarter wave plate) or (-) A plate QWP; And the third and sixth retardation plates are configured of (+) A plate λ / 2 retardation plates (HWP (Half Wave plate)) or (-) A plate HWP. The method of claim 1, The first anti-reflection film portion is composed of a first retardation plate composed of (+) A plate 30nm, a second retardation plate composed of (+) A plate QWP, and a third retardation plate composed of (+) A plate HWP, , The second anti-reflection film portion is composed of a fourth retardation plate made of (-) C plate, a fifth retardation plate made of (-) A plate QWP, and a sixth retardation plate made of (-) A plate HWP. Liquid crystal display device characterized in that. The method of claim 1, The first anti-reflection film portion is composed of a first retardation plate composed of (+) A plate 30nm, a second retardation plate composed of (-) A plate QWP, and a third retardation plate composed of (+) A plate HWP, , The second anti-reflection film portion includes a fourth retardation plate composed of (-) C plate, a fifth retardation plate composed of (+) A plate QWP, and a sixth retardation plate composed of (-) A plate HWP Liquid crystal display device characterized in that. The method of claim 1, The first anti-reflection film portion is composed of a first retardation plate consisting of (+) A plate 30nm, a second retardation plate consisting of (+) A plate QWP, and a third retardation plate consisting of (-) A plate HWP , The second anti-reflection film part is composed of a fourth retardation plate made of (-) C plate, a fifth retardation plate made of (-) A plate QWP, and a sixth retardation plate made of (+) A plate HWP. Liquid crystal display device characterized in that. The method of claim 1, The first anti-reflection film portion includes a first retardation plate composed of (+) A plate 30nm, a second retardation plate composed of (-) A plate QWP, and a third retardation plate composed of (-) A plate HWP , The second anti-reflection film part is composed of a fourth retardation plate made of (-) C plate, a fifth retardation plate made of (+) A plate QWP, and a sixth retardation plate made of (+) A plate HWP Liquid crystal display device characterized in that. The method of claim 1, The (-) C plate is a liquid crystal display characterized in that the retardation is used 150 ~ 350nm. The method of claim 1, The first antireflection film portion And a negative (-) C plate between the first retardation plate and the second retardation plate. The method of claim 1, A first Tri-Acetyl-Cellulose (TAC) layer between the first anti-reflection film portion and the first polarizing plate, And a second Tri-Acetyl-Cellulose (TAC) layer between the second anti-reflection film portion and the second polarizing plate. Upper and lower substrates opposed to each other; An electrically controlled Birefringence (ECB) liquid crystal layer filled between the upper and lower substrates; A first anti-reflection film part having first to fourth retardation plates sequentially stacked on the outer surface of the upper substrate; A second anti-reflection film part having fifth and sixth retardation plates sequentially stacked on the outer surface of the lower substrate; A first polarizing plate provided outside the first anti-reflection film part; And A second polarizing plate provided outside the second anti-reflection film portion; The first retardation plate is composed of (+) A plate 30 nm; The second retardation plate is composed of a (-) C plate; The third and fifth retardation plates consist of a (+) A plate λ / 4 retardation plate (Quarter wave plate) or (-) A plate QWP; And the fourth and sixth retardation plates are configured as (+) A plate λ / 2 retardation plates (HWP) or (-) A plate HWP.

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