JP2001290149A - Method of manufacturing liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform excellent black display and to attain high contrast in a dual refraction mode liquid crystal display device provided with a phase compensating plate. SOLUTION: In a method of manufacturing the dual refraction mode liquid crystal display device consisting of a liquid crystal panel 1 provided with RGB color filters 3R, 3G and 3B and the phase compensating plate 9, wavelength dispersibility of retardation of a liquid crystal layer is obtained by measuring the retardation in the wavelength of the color filter of the liquid crystal layer corresponding to each color region of the RGB color filters 3R, 3G and 3B. Phase compensating performance of the phase compensating plate 9 is set so as to conform to the obtained wavelength dispersibility of the retardation of the liquid crystal layer in a stage for setting the phase compensating performance of the phase compensating plate 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to birefringence (Electric
The present invention relates to a technique for obtaining a good black display by optimizing a phase compensator in an ally controlled birefringence (ECB) mode color liquid crystal display device, thereby achieving high contrast.

[0002]

2. Description of the Related Art In a color TFT liquid crystal display device put into practical use today, a liquid crystal display mode generally used is a TN (Twisted Nematic) mode. However, in the TN mode, the viewing angle is narrow, and when the screen is viewed from an oblique direction, gradation inversion occurs and the display quality is significantly reduced. The response speed is also particularly slow in the halftone area, and the outline of an image becomes unclear when a moving image is displayed. Such a problem of the TN mode cannot be sufficiently solved even by performing the phase compensation.

In recent years, various liquid crystal display modes replacing the TN mode have been actively developed. For example, as a wide viewing angle technology, MVA (Multi Vertical Alignme
nt) mode and IPS (In-Plane Switching) mode.

In the MVA mode, black display is generally performed in an electric field-free state (a state in which the liquid crystal is vertically aligned). Black display is performed in a state where the liquid crystal is slightly tilted by applying a voltage, and the switching response is improved. It has also been made to improve. In this case, even in the black display state, birefringence occurs because the liquid crystal is tilted, so that it is necessary to perform phase compensation during black display.

As a liquid crystal display mode having both a wide viewing angle and high-speed response, an OCB (Optical Compensated Bire
fringence) mode. Even in the OCB mode, phase compensation is required at the time of black display.

[0006]

Incidentally, in a color liquid crystal display device, RGB color filters are used, but the transmittance of the liquid crystal differs depending on the RGB wavelength.
Further, the refractive index of the liquid crystal also differs depending on the RGB wavelength. For this reason, birefringence (Electrically controlled birefringence) utilizing the birefringence effect of liquid crystal such as MVA mode and OCB mode.
In the color liquid crystal display device of the fringence (ECB) mode, there is a problem that, during black display, the transmittance of light passing through the liquid crystal is different for each color region of the RGB color filter, and good black display cannot be performed. .

To solve this problem, the thickness of the liquid crystal layer, that is, the cell gap, is changed for each color region of the RGB color filter to optimize the light transmittance of the liquid crystal layer corresponding to each color region of RGB. There is a gap technology (Japanese Patent Laid-Open No. 9-
No. 230332). However, in the publication showing this multi-gap technique, the phase compensating ability of the phase compensating plate is determined by using the retardation of each color of RGB of the liquid crystal layer (retardat).
There is no mention of adjusting according to ion).

In general, in a liquid crystal display mode requiring phase compensation such as an MVA mode or an OCB mode, the phase compensating ability of the phase compensating plate is set on the basis of G color. Therefore, at the time of displaying black, there is a problem that the retardation of the R color or the B color becomes large and the black level floats, and the contrast cannot be increased.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a birefringence mode color liquid crystal display device having a phase compensating plate to perform good black display and achieve high contrast.

[0010]

According to the present invention, there is provided a method of manufacturing a birefringence mode liquid crystal display device comprising a liquid crystal panel having a plurality of color filters and a phase compensator. In the step of setting the phase compensation capability of the phase compensator, the retardation of the liquid crystal layer corresponding to each color region of the plurality of color filters is measured at the wavelength of the color filter, thereby obtaining the wavelength dispersion of the retardation of the liquid crystal layer. A method of manufacturing a liquid crystal display device, characterized in that the phase compensating plate has a phase compensating ability set so as to be adapted to the wavelength dispersion of retardation of the liquid crystal layer.

According to the method of manufacturing a liquid crystal display device of the present invention, the phase compensation capability of the phase compensator is set so as to match the wavelength dispersion of the retardation of the liquid crystal layer. Therefore,
When an RGB color filter is provided on a liquid crystal panel,
At the time of black display, it is possible to prevent the floating of the black level from occurring due to a large difference in the retardation of any one of RGB wavelengths. Therefore, it is possible to obtain good black display and achieve high contrast.

In particular, an OC having a wide viewing angle and excellent high-speed response
In a B-mode liquid crystal display device, even when the liquid crystal layer is multi-gap and the light transmittance of the liquid crystal layer is optimized for each of the RGB colors, good black display and high contrast can be achieved. It becomes possible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of an example of a color liquid crystal display device having an OCB mode liquid crystal panel. In this liquid crystal display device, an RGB color filter 3 is provided on a liquid crystal panel 1.
Comprising a _R, 3 _G, 3 _B, introduced multi-gap technology, and are those subjected to phase compensation in consideration of the multi-gap reduction, are prepared as follows.

That is, the liquid crystal panel 1 has a TFT substrate 2 in which TFT elements are formed on a glass substrate, and an RG
CR formed with B color filter (Color Filter) 3
A substrate 4 is composed of a nematic liquid crystal 5 held between these substrates. On the TFT substrate 2, an ITO electrode 6a and an alignment film 7a are sequentially formed, and on the CR substrate 4, an ITO electrode 6b and an alignment film 7b are sequentially formed.

In manufacturing the liquid crystal panel 1, the layer thickness of the liquid crystal 5, that is, the cell gap is made multi-gap,
In order to optimize the transmittance of light transmitted through the liquid crystal layer for each color of the RGB color filters 3, first, at each wavelength λ of RGB, the maximum retardation change width ΔR caused by a change in the drive voltage of the liquid crystal layer is: The RGB color filters 3 _R , 3 _G , 3
The thickness of _B is set (see JP-A-9-230332).

When the liquid crystal panel 1 is made multi-gap as described above, the transmittance of light for each color of RGB is optimized, so that unnecessary coloring can be prevented, and the retardation of each color during white display is also optimized. And the transmittance of the white level is improved. Therefore, a liquid crystal display device having excellent white balance can be obtained.

Alignment films 7a and 7b are formed on the TFT substrate 2 and the CR substrate 4, respectively, and rubbing is performed.
The rubbing direction is set to the direction indicated by the arrow in FIG. 1 so that the rubbing direction is parallel when the TFT substrate 2 and the CR substrate 4 are overlapped. This is for causing the liquid crystal 5 to take a bent orientation when an electric field is applied.

After rubbing the alignment films 7a and 7b, a spacer material is sprayed on one of the panel surfaces of the TFT substrate 2 or the CR substrate 4, a seal material is printed on a peripheral portion of the substrate, and both substrates 2 and 4 are overlapped. Then, the liquid crystal panel 1 is assembled. Thus, a multi-gap liquid crystal panel 1 can be obtained.

Next, the nematic liquid crystal 5 is injected into the liquid crystal panel 1, the injection port is sealed, and an isotropic process is performed to complete the liquid crystal panel 1. Then, a polarizing plate 8a is disposed on the TFT substrate 2 side of the liquid crystal panel 1, and
On the CR substrate 4 side, a phase compensating plate 9 and a polarizing plate 8b are sequentially disposed to obtain a liquid crystal display device.

In the present invention, in the step of setting the phase compensating ability of the phase compensating plate 9, the retardation at the wavelength of the color filter 3 is measured for each liquid crystal layer corresponding to each color region of the RGB color filter 3, and the liquid crystal is measured. It is characterized in that the wavelength dispersion of the retardation of the layer is determined, and the phase compensating ability of the phase compensator 9 is set so as to match the wavelength dispersion of the retardation of the obtained liquid crystal layer.

When the phase compensating plate 9 is composed of a plurality of films, the phase compensating capability of the phase compensating plate 9 refers to the total phase compensating capability of all the films. For example, in the normal OCB mode, one biaxial anisotropic film and two cholesteric liquid crystal tilt films are used as the phase compensating plate 9, but in the present invention, the total phase compensating ability is set. .

In the step of setting the phase compensating ability of the phase compensating plate 9, as a specific method for obtaining the wavelength dispersion of the retardation of the liquid crystal layer, for example, first, a predetermined voltage is applied to the liquid crystal panel 1, by transferring from a splay alignment to a bent orientation, for each liquid crystal layer corresponding to the region of the color filter 3 _R, 3 _G, 3 _B of RGB in this state, the transmission peak wavelength of the color filters 3 _R, 3 _G, 3 _B Is measured.

Next, a phase compensating plate 9 having a phase compensating ability that matches the wavelength dispersion of retardation of the liquid crystal layer thus measured is selected. By selecting the phase compensator 9 in this manner, even when a liquid crystal material having a refractive index anisotropy and a large wavelength dispersion is used as the liquid crystal 5, a good black display can be performed and a high-contrast image can be obtained. Can be obtained. Therefore, according to this liquid crystal display device, the quality of the liquid crystal image can be remarkably improved in combination with the effect of the multi-gap described above.

Further, the phase compensating ability of the phase compensating plate 9 determined as described above has smaller wavelength dispersion than the phase compensating ability set based on the conventional G color (ie, retardation). Is small due to the wavelength, and the relationship between the wavelength and the retardation is flattened as shown in the examples described later). Therefore, even when a liquid crystal material having a large refractive index anisotropy is used as the liquid crystal 5, the phase compensator 9 can be easily manufactured from a general polymer material. That is, generally, a liquid crystal material having a large refractive index anisotropy has a large wavelength dispersion. If the wavelength dispersion is large, it is difficult to obtain a polymer film having the same wavelength dispersion as a phase compensator suitable for the wavelength dispersion. On the other hand, according to the present invention, since the wavelength dispersion of the phase compensation ability required for the phase compensator 9 is reduced, the phase compensator 9 can be easily manufactured from a general polymer material.

When the phase compensating ability of the phase compensating plate 9 is determined so as to conform to the wavelength dispersion of the retardation of the liquid crystal layer, the following equation (1) is used in order to improve black display.
(2), (3),

[0027]

Equation 3] _{│R (Lc, Black, λ R} ) -R (film, λ R) │ <30nm (1) │R (Lc, Black, λ G) -R (film, λ G) │ <30nm ( 2) │R (Lc, Black, λ _B ) −R (film, λ _B ) │ <30 nm (3) (where R (Lc, Black, λ _R ) is a liquid crystal corresponding to an R color filter In-plane retardation at the transmission peak wavelength of the R color filter during black display of the layer, R (Lc, B
lack, λ _G ) is the in-plane retardation at the transmission peak wavelength of the G color filter during black display of the liquid crystal layer corresponding to the G color filter, and R (Lc, Black, λ _B ) is B
The in-plane retardation, R (film, λ _R ), at the transmission peak wavelength of the B color filter during black display of the liquid crystal layer corresponding to the color filter is the transmission peak wavelength of the R color filter of the phase compensator. plane retardation in, R (film, λ _G) is plane retardation at the G color transmission peak wavelength of the color filter of the phase compensator, R
(Film, λ _B ) represents in-plane retardation at the transmission peak wavelength of the B color filter of the phase compensator. ) Is preferably satisfied.

Further, the maximum retardation change width ΔR due to the change in the drive voltage of the liquid crystal layer is expressed by the following equation at each wavelength λ of RGB.

[0029]

It is preferable to satisfy ΔR / λ ≧ 0.4. Thereby, the black level can be lowered and the white level can be raised at the same time.

Although the present invention has been described with reference to the method of manufacturing the liquid crystal display device having the OCB mode liquid crystal panel 1 having a multi-gap liquid crystal layer as shown in FIG. 1, the present invention is not limited to this. . The present invention can be applied regardless of whether or not the liquid crystal layer has a multi-gap. Further, the present invention can be applied to a liquid crystal display device of any birefringence mode such as a VA mode, an in-plane switching mode, and a homogeneous alignment mode. Further, the present invention can be applied regardless of a reflection type or a transmission type.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

Comparative Example 1 FIG. 1 shows that the liquid crystal panel 1 having a multi-gap
The liquid crystal display device was the same as the liquid crystal display device described above, except that the phase compensating ability of the phase compensating plate 9 was adapted to the G color without optimizing it according to the wavelength dispersion of the retardation of the liquid crystal layer.

In this case, when producing the CR substrate 4,
The thickness of the _G color filter 3 _G is set to be 0.8 μm thicker than the thickness of the _B color filter 3 _B , and the thickness of the R color filter 3 _{R is changed to} the thickness of the B color filter 3 _B. 1.0 μm thicker than

The alignment film 7a of the TFT substrate 2 and the CR substrate 4
As the upper alignment film 7b, SE7792 manufactured by Nissan Chemical Industries, Ltd. was formed and rubbed in the direction of the arrow in FIG. Then, TF
Micropearl having a particle size of 5 μm is wet-sprayed as a spacer material in the panel surface on the T substrate 2 or the CR substrate 4, and a sealing material is printed on the periphery of the TFT substrate 2 or the CR substrate 4. And the liquid crystal panel 1 was assembled. The cell thickness of the region B of the liquid crystal panel 1 is 5.0 μm,
The cell thickness in the G region is 5.8 μm, and the cell thickness in the R region is 6.0.
It was multi-gap to μm.

Next, a fluorine-based liquid crystal was vacuum-injected into the liquid crystal panel 1 as a nematic liquid crystal 5 having a positive dielectric anisotropy. Was determined the wavelength dispersion of the refractive index anisotropy of the liquid crystal 5 (graph showing the relationship between wavelength and birefringence), becomes as shown in FIG. 2, the refractive index at 589nm is d _n = 0.1
35. After vacuum injection of the liquid crystal 5, the injection port was sealed and an isotropic treatment was performed to complete the liquid crystal panel 1.

Next, in order to set the phase compensating ability of the phase compensating plate 9 disposed on the liquid crystal panel 1 on the basis of the G color, a 6 V rectangular wave is applied to the liquid crystal panel 1, and the liquid crystal 5 is shifted from the splay alignment. After transition to the bent orientation, the retardation of the _3G region of the _G color filter was measured in this state. As a result, the retardation value at 546 nm was 80 nm.

Accordingly, the phase compensation plate 9 for compensating the black level has a retardation of 546 nm of 80 nm.
A polycarbonate film having the same wavelength dispersion as the refractive index anisotropy of the liquid crystal 5 shown in FIG. 2 was selected. FIG. 3 shows the wavelength dispersion (the relationship between the wavelength and the retardation) of the phase compensator 9.

On the other hand, plastic polarizing plates are prepared as the polarizing plates 8a and 8b, and the polarizing plates 8a and 8b and the phase compensating plate 9 made of the above-mentioned polycarbonate film are combined with the liquid crystal panel 1 to obtain the liquid crystal display of Comparative Example 1. Produced.

The contrast ratio of the obtained liquid crystal display device was defined as the ratio between the luminance of black display (when 6 V was applied) and the luminance of white display (when 2 V was applied), and the contrast ratio was measured. As a result, the contrast ratio of this liquid crystal display was about 70. Since the contrast ratio is required to be 100 or more in practical use, it is understood that the contrast ratio of the liquid crystal display device of Comparative Example 1 is insufficient. It is considered that the cause of the low contrast ratio is the floating of the black display, and the phase compensation has not been optimized.

Example 1 A liquid crystal panel 1 was produced in the same manner as in Comparative Example 1. Next, in order to optimize the phase compensating ability of the phase compensating plate 9 in accordance with the wavelength dispersion of the retardation of the liquid crystal layer, a voltage of 6 V is applied to the liquid crystal panel 1.
And the liquid crystal 5 is changed from the splay alignment to the bent alignment. In this state, each of the RGB color filters 3 is applied.
_R, 3 _G, 3 for each liquid crystal layer in the region of _B, the color filter 3 _R, 3 _G, 3 _B of the transmission peak wavelength (610 nm, 55
(0 nm, 450 nm). The result is shown in FIG. It can be seen that the wavelength dispersion of the retardation in FIG. 4 is significantly different from the wavelength dispersion of the refractive index anisotropy of the liquid crystal 5 shown in FIG. 2 (a diagram showing the relationship between the wavelength and the birefringence). This is because the value of the retardation also changed according to the thickness of the liquid crystal layer because the liquid crystal panel 1 was multi-gap.

Therefore, as the phase compensator 9, a polyvinyl alcohol film having a substantially flat retardation wavelength dispersion in the panel surface, like the retardation wavelength dispersion of the liquid crystal layer shown in FIG. 4, was used. FIG. 5 shows the wavelength dispersion of the retardation of the phase compensator 9 made of the polyvinyl alcohol film.

The liquid crystal display of Example 1 was manufactured by combining the phase compensator 9 and the same polarizers 8a and 8b as those used in Comparative Example 1 with the liquid crystal panel 1.

When the contrast ratio of the obtained liquid crystal display device was measured, it was about 200. This contrast ratio is a practically sufficient value. It is considered that the reason why a good contrast ratio was obtained in the present embodiment is that the black level could be sufficiently reduced by optimizing the phase compensation.

[0044]

According to the present invention, in a color liquid crystal display device provided with a phase compensator, black display can be performed well and high contrast can be achieved. In particular, by applying the present invention to a liquid crystal display device having a multi-gap OCB mode liquid crystal panel, a liquid crystal display device having a wide viewing angle, high-speed response, and high image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a panel structure of an OCB mode liquid crystal display device in which a liquid crystal layer has a multi-gap.

FIG. 2 is a graph showing the relationship between the wavelength and the birefringence of a liquid crystal.

FIG. 3 is a diagram showing the relationship between wavelength and retardation of the phase compensator used in Comparative Example 1.

FIG. 4 is a diagram showing the relationship between the transmission peak wavelengths of the color filters 3 _R , 3 _G , and 3 _B and the retardation of the liquid crystal layer at that wavelength.

FIG. 5 is a diagram showing the relationship between wavelength and retardation of the phase compensator used in Example 1.

[Explanation of symbols]

1. OCB mode liquid crystal panel, 2. TFT substrate,
3 ... color filter, 3 _R ... R color filter,
3 _G : color filter of G color; 3 _B : color filter of B color; 4: CR substrate; 5: liquid crystal; 6a, 6b: I
TO electrode, 7a, 7b: alignment film, 8a, 8b: polarizing plate, 9: phase compensation plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G09F 9/30 349 G09F 9/30 349E G02F 1/137 505 (72) Inventor Yasushi Amano Kita, Shinagawa-ku, Tokyo Shinagawa 6-chome 7-35 Sony Corporation F-term (reference) 2H088 HA12 HA15 JA09 KA02 MA05 MA07 2H089 HA07 QA16 RA07 SA01 SA04 TA12 TA14 2H090 LA06 LA15 MA01 MA02 MA03 MB01 2H091 FA02Y FA11X FA11Z FD01 FD24 GA06 HA09 HA04 LA16 LA19 5C094 AA02 AA06 AA08 BA03 BA43 DA07 EA05 EB02 ED02 ED14 ED20 HA08

Claims (7)

[Claims] 1. A method of manufacturing a birefringence mode liquid crystal display device comprising a liquid crystal panel having a plurality of color filters and a phase compensator, wherein the step of setting the phase compensating capability of the phase compensator comprises a plurality of color filters. By measuring the retardation of the liquid crystal layer corresponding to each color region at the wavelength of the color filter, the wavelength dispersion of the retardation of the liquid crystal layer is obtained, and the phase is adjusted to match the wavelength dispersion of the retardation of the obtained liquid crystal layer. A method for manufacturing a liquid crystal display device, wherein a phase compensating ability of a compensating plate is set. Wherein the following equation (1), (2), (3), Equation 1] _{│R (Lc, Black, λ R} ) -R (film, λ R) │ <30nm (1) │R ( Lc, Black, λ _G ) −R (film, λ _G ) | <30 nm (2) | R (Lc, Black, λ _B ) −R (film, λ _B ) | <30 nm (3) (Lc, Black, λ _R ) is the in-plane retardation at the transmission peak wavelength of the R color filter at the time of black display of the liquid crystal layer corresponding to the R color filter, and R (Lc, Black, λ _G ) is The in-plane retardation at the transmission peak wavelength of the G color filter at the time of black display of the liquid crystal layer corresponding to the G color filter, R (Lc, Black, λ _B ) is the liquid crystal layer corresponding to the B color filter plane retardation in the transmission peak wavelength of the B color color filter of the black display, R (film, lambda _R), the transmission peak of the color filter of R color phase compensator Plane retardation in peak wavelength, R (film, λ _G) is plane retardation at the G color transmission peak wavelength of the color filter of the phase compensator, R (film, λ _B) is a phase compensator B color 2. The method according to claim 1, wherein the phase compensator satisfies an in-plane retardation at a transmission peak wavelength of the color filter. 3. The method according to claim 1, wherein the thickness of the liquid crystal layer is different for each of the RGB color filters. 4. The liquid crystal panel is an OCB (Optical Compensa).
The production method according to any one of claims 1 to 3, wherein the production mode is a ted birefringence mode. 5. The liquid crystal panel is VA (Vertical Alignment).
The method according to claim 1, wherein the method is a t) mode. 6. The method according to claim 1, wherein the maximum retardation change width ΔR due to a change in the drive voltage of the liquid crystal layer satisfies the following expression at each wavelength λ of RGB: ΔR / λ ≧ 0.4. The production method according to any one of the above. 7. A liquid crystal display device manufactured by the method according to claim 1.