KR20120071855A - Vertically aligned liquid crystal display - Google Patents

Abstract

PURPOSE: A vertically aligned liquid crystal display device is provided to variously laminate two phase difference films, thereby suppressing light leakage and drastically increasing a contrast ratio. CONSTITUTION: A phase difference film is placed on at least one gap between a lower polarization plate(10) and a vertical alignment panel(20) or an upper polarization plate(30) and the vertical alignment panel. A first phase difference film(40) is a positive uniaxial film. A second phase difference film(50) is a negative biaxial film. The phase difference film is a pair of films which are selected from the first or second phase difference film.

Description

Vertically oriented liquid crystal display {VERTICALLY ALIGNED LIQUID CRYSTAL DISPLAY}

The present invention relates to a compensation film for improving display characteristics at a viewing angle of a vertically aligned liquid crystal display (hereinafter referred to as VA-LCD).

More specifically, the VA-LCD can obtain high contrast characteristics at the front and inclination angles of the VA-LCD filled with liquid crystals having positive or negative dielectric anisotropy, and minimize light leakage and color change in the dark state at the inclination angle. It relates to a compensation film.

There are two major causes of deteriorating the viewing angle characteristic of VA-LCD. The first is the viewing angle dependence of the orthogonal polarizer and the second is the viewing angle dependence of the birefringence characteristic of the VA-LCD panel.

The liquid crystal display used for various purposes has a narrow viewing angle, and when viewed from an oblique angle from the front with respect to the front of the liquid crystal display, the image quality of the display information is not clear, and thus the recognition rate is lowered, especially dark. In the state, there is a problem that true black is not realized due to light leakage. In particular, in the VA (Vertical Alignment) mode LCD, since the liquid crystal (Liquid Crystal) inside the liquid crystal cell has a different phase difference depending on the viewing angle, the image quality distortion according to the viewing angle is large.

Therefore, when the optical compensation structure to which the retardation film is applied is not introduced, due to light leakage at the viewing angle, the contrast ratio is lowered, and it is difficult to obtain a clear image image. In addition, the color characteristics are also affected, resulting in an overall blurry and low quality image. Today, the importance of picture quality in viewing angles is becoming more important, especially with the application of LCD video displays to home TVs and home theaters.

The existing optical compensation technology of some VA LCDs has a problem of low light efficiency, volume increase, and high production cost due to the introduction of a complicated laminated structure and three to four retardation films.

An object of the present invention is to provide a vertically aligned liquid crystal display (VA-LCD) having high contrast characteristics in front and inclination angles by minimizing light leakage in a black state at an inclination angle.

The present invention relates to a retardation film for a liquid crystal display device and a liquid crystal display device using the same.

Specifically, the present invention selects between the lower polarizing plate and the vertical alignment panel, or between the upper polarizing plate and the vertical alignment panel of the vertical alignment liquid crystal display device including a vertical alignment panel between the lower polarizing plate and the upper polarizing plate where the absorption axes are perpendicular to each other. As a retardation film located in any one or more of

The retardation film satisfies the following formulas (1) to (2) and is a positive uniaxial film; And a second retardation film satisfying the following formulas (3) to (5) and being a negative biaxial film; It relates to a retardation film consisting of a pair of films selected from.

Nx> Nz = Ny equation (1)

50 nm ≤ R _th (550) ≤ 300 nm Equation (2)

Nx> Ny> Nz equation (3)

200 nm ≤ R _th (550) ≤ 400 nm Equation (4)

5 ≤ NAZ ≤ 30 Formula (5)

Where Nx is the refractive index in the direction of highest refractive index in the plane, Ny is the refractive index in the direction perpendicular to Nx in the plane, Nz is the refractive index in the direction perpendicular to the plane, and d is the thickness of the film (in the Nz direction Length), and R _th (λ) is a retardation value in the film thickness direction at a wavelength λ nm, wherein R _th and NAZ are defined by the following equations (1) and (2).

[Equation 1]

R _th = (((Nx + Ny) / 2) -Nz) × d

[Equation 2]

NAZ = (Nx-Nz) / (Nx-Ny)

In addition, the present invention is a vertical alignment liquid crystal display device comprising a vertical alignment panel between the lower polarizing plate and the upper polarizing plate of the absorption axis is perpendicular to each other, between the lower polarizing plate and the vertical alignment panel, or between the upper polarizing plate and the vertical alignment panel. On any one or more selected,

A first retardation film that satisfies the following formulas (1) to (2) and is a positive uniaxial film; And a second retardation film satisfying the following formulas (3) to (5) and being a negative biaxial film; It relates to a vertically aligned liquid crystal display device comprising one or more retardation film selected from.

Nx> Nz = Ny equation (1)

50 nm ≤ R _th (550) ≤ 300 nm Equation (2)

Nx> Ny> Nz equation (3)

200 nm ≤ R _th (550) ≤ 400 nm Equation (4)

5 ≤ NAZ ≤ 30 Formula (5)

Where Nx is the refractive index in the direction of highest refractive index in the plane, Ny is the refractive index in the direction perpendicular to Nx in the plane, Nz is the refractive index in the direction perpendicular to the plane, and d is the thickness of the film (in the Nz direction Length), and R _th (λ) is a retardation value in the film thickness direction at a wavelength λ nm, wherein R _th and NAZ are defined by the following equations (1) and (2).

[Equation 1]

R _th = (((Nx + Ny) / 2) -Nz) × d

[Equation 2]

NAZ = (Nx-Nz) / (Nx-Ny)

More specifically, the first aspect of the present invention provides a vertically aligned liquid crystal display device comprising a vertical alignment panel between a lower polarizing plate and an upper polarizing plate whose absorption axes are perpendicular to each other.

Between the lower polarizing plate and the vertical alignment panel, the slow axis is perpendicular to the absorption axis of the lower polarizing plate, has the characteristics of Nx> Nz = Ny, the Rth value is 50 to 300 nm, and the phase difference according to the wavelength has reverse dispersion. 1st retardation film which is a positive uniaxial film,

Between the upper polarizing plate and the vertical alignment panel, the slow axis is parallel to the absorption axis of the upper polarizing plate, has a characteristic of Nx> Ny> Nz, Rth value is 200-400 nm, NAZ value is 5-30, according to the wavelength It is a vertically-aligned liquid crystal display device containing the 2nd phase difference film which is a negative biaxial film whose phase difference is reverse dispersion.

According to a second aspect of the present invention, there is provided a vertical alignment liquid crystal display device comprising a vertical alignment panel between a lower polarizing plate and an upper polarizing plate whose absorption axes are perpendicular to each other.

Between the lower polarizing plate and the vertical alignment panel, the slow axis is parallel to the absorption axis of the lower polarizing plate, has a characteristic of Nx> Ny> Nz, Rth value is 200-400 nm, NAZ value is 5-30, The retardation includes a second retardation film which is a negative biaxial film having reverse dispersion,

Between the upper polarizing plate and the vertical alignment panel, the slow axis is perpendicular to the absorption axis of the upper polarizing plate, has the characteristics of Nx> Nz = Ny, Rth value is 50-300 nm, and the phase difference according to the wavelength has reverse dispersion It is a vertical alignment liquid crystal display device containing the 1st retardation film which is a positive uniaxial film.

According to a third aspect of the present invention, there is provided a vertical alignment liquid crystal display device comprising a vertical alignment panel between a lower polarizing plate and an upper polarizing plate whose absorption axes are perpendicular to each other.

Between the upper polarizing plate and the vertical alignment panel, the slow axis is perpendicular to the absorption axis of the upper polarizing plate, has the characteristics of Nx> Nz = Ny, Rth value is 50-300 nm, and the phase difference according to the wavelength has reverse dispersion The first retardation film, which is a positive uniaxial film, has a slow axis parallel to the absorption axis of the upper polarizer, and has a characteristic of Nx> Ny> Nz, a Rth value of 200 to 400 nm, a NAZ value of 5 to 30, and a phase difference according to a wavelength. It is a vertically-aligned liquid crystal display device containing the 2nd retardation film which is a negative biaxial film which has a reverse dispersion property. Specifically, the vertically aligned liquid crystal display device is a vertically aligned liquid crystal display device that is stacked in the order from the upper polarizing plate, the first retardation film, the second retardation film, the vertical alignment panel, the lower polarizing plate in order.

A fourth aspect of the present invention is a vertical alignment liquid crystal display device comprising a vertical alignment panel between a lower polarizing plate and an upper polarizing plate whose absorption axes are perpendicular to each other,

Between the lower polarizing plate and the vertical alignment panel, the slow axis is perpendicular to the absorption axis of the lower polarizing plate, has the characteristics of Nx> Nz = Ny, the Rth value is 50 to 300 nm, and the phase difference according to the wavelength has reverse dispersion. The first retardation film, which is a negative uniaxial film, and the second retardation, which is a negative biaxial film having the characteristics of Nx>Ny> Nz, and having a Rth value of 200 to 400 nm, a NAZ value of 5 to 30, and a phase difference depending on the wavelength. It is a vertical alignment liquid crystal display device containing a film. Specifically, the vertically aligned liquid crystal display device is a vertically aligned liquid crystal display device that is stacked in the order from the upper polarizing plate, the vertical alignment panel, the second retardation film, the first retardation film, the lower polarizing plate.

Hereinafter, the present invention will be described in more detail.

The retardation film according to the present invention has a retardation value capable of improving the diagonal black luminance characteristic of a liquid crystal display device, particularly a VA mode liquid crystal display device.

The retardation film according to the present invention is a pair of retardation films composed of a first retardation film and a second retardation film, wherein the first retardation film satisfies the following formulas (1) to (2) and is a positive uniaxial film. The biphasic retardation film satisfies the following formulas (3) to (5) and is a negative biaxial film.

Nx> Nz = Ny equation (1)

50 nm ≤ R _th (550) ≤ 300 nm Equation (2)

Nx> Ny> Nz equation (3)

200 nm ≤ R _th (550) ≤ 400 nm Equation (4)

5 ≤ NAZ ≤ 30 Formula (5)

Where Nx is the refractive index in the direction of highest refractive index in the plane, Ny is the refractive index in the direction perpendicular to Nx in the plane, Nz is the refractive index in the direction perpendicular to the plane, and d is the thickness of the film (in the Nz direction Length), and R _th (λ) is a retardation value in the film thickness direction at a wavelength λ nm, wherein R _th and NAZ are defined by the following equations (1) and (2).

[Equation 1]

R _th = (((Nx + Ny) / 2) -Nz) × d

[Equation 2]

NAZ = (Nx-Nz) / (Nx-Ny)

The first retardation film and the second retardation film according to the present invention are respectively disposed between the lower polarizing plate and the vertical alignment panel, which are polarizing plates in the backlight (light source) direction, or between the upper polarizing plate and the vertical alignment panel, which are polarizing plates in the image display direction (observer side). Can be located.

Specifically, in the retardation film, a first retardation film may be positioned between the lower polarizer and the vertical alignment panel, and a second retardation film may be positioned between the upper polarizer and the vertical alignment panel. Alternatively, the second retardation film may be positioned between the lower polarizer and the vertical alignment panel, and the first retardation film may be positioned between the upper polarizer and the vertical alignment panel.

The retardation film of the present invention may have a form in which a first retardation film and a second retardation film are stacked between the upper polarizing plate and the vertical alignment panel. Specifically, the retardation film may have a form in which the first retardation film and the second retardation film are sequentially stacked between the upper polarizing plate and the vertical alignment panel.

In addition, the retardation film of the present invention may have a form in which the first retardation film and the second retardation film are stacked between the vertical alignment panel and the lower polarizing plate. Specifically, the retardation film may have a form in which the second retardation film and the first retardation film are sequentially stacked between the vertical alignment panel and the lower polarizing plate.

Next, the structure of the liquid crystal display device using the retardation film of the present invention will be described with reference to FIGS. 2 to 5.

The liquid crystal display device of the present invention is an alignment liquid crystal display device (VA-LCD) in which the optical axis of the liquid crystal in the liquid crystal cell is perpendicular to the polarizing plate. The liquid crystal having negative dielectric anisotropy is filled between the lower polarizing plate 10 and the two glass substrates. The liquid crystal cell 20 and the upper polarizing plate 30 are vertically aligned, and the absorption axis 11 of the lower polarizing plate 10 and the absorption axis 31 of the upper polarizing plate 30 are perpendicular to each other.

The vertically aligned liquid crystal display includes a multidomain vertical aligned (MVA) mode or a kairang additive, in which a ridge including an electrode pair is formed on a surface adjacent to the liquid crystal layer on the first substrate and the second substrate, and forms a multi-domain. VA (vertical aligned) mode can be used.

It is preferable that the cell gap of the said liquid crystal cell is 3-8 micrometers.

In VA-LCD, the white state is 0 ° linearly polarized light from the backlight in the state of orthogonal polarizer, and 0 ° linearly polarized light is transmitted through 90 ° rotated linearly polarized light after passing through the liquid crystal layer. Use In order for a 0 ° linearly polarized light to be 90 ° linearly polarized light, the retardation value must be 1/2 of the incident light wavelength.

The present invention is any one or more selected between the lower polarizing plate and the vertical alignment panel, or between the upper polarizing plate and the vertical alignment panel as a retardation film for the viewing angle compensation of VA-LCD,

A first retardation film having a characteristic of Nx> Nz = Ny, and having a Rth value of 50 nm to 300 nm at a wavelength of 550 nm and a positive uniaxial film having a retardation of retardation according to the wavelength; And a second retardation film having a characteristic of Nx> Ny> Nz, a negative biaxial film having a Rth value of 200 to 400 nm, a NAZ value of 5 to 30, and a phase difference according to a wavelength at a wavelength of 550 nm; By using one or more retardation film selected from the to enable a wide viewing angle characteristics.

Referring to Figure 1, look at the refractive index of the retardation film used for the viewing angle compensation of the VA-LCD as follows.

When the refractive index in the x-axis direction is nx (100), the y-direction refractive index is ny (200), and the thickness (d) refractive index is nz (300), the characteristics of the retardation film are different according to the magnitude of the refractive index. Is determined.

The case where the refractive indexes in the two axial directions are different among the refractive indices in the three axial directions is called a uniaxial retardation film, and when the refractive indices in the three axial directions are all different, it is called a biaxial retardation film.

The uniaxial retardation film can be defined as follows.

When Nx> Nz = Ny, the thickness direction retardation value (Rth) is defined by the following equation (1).

[Equation 1]

Rth = (((Nx + Ny) / 2) -Nz) x d

Where Nx is the refractive index in the direction of highest refractive index in the plane, Ny is the refractive index in the direction perpendicular to Nx in the plane, and Nz is the refractive index in the direction perpendicular to the plane. D is the thickness of the film (the length in the Nz direction). )

The first retardation film (positive uniaxial retardation film, positive A plate) of the present invention is a film in which the retardation value in the thickness direction is a positive value, and the planar retardation value is 100 to 600 nm at a wavelength of (Re) 550 nm, and NAZ = 1. Is preferably.

The retardation value Rth in the thickness direction of the first retardation film used for VA-LCD compensation is preferably in the range of 50 nm to 300 nm at a wavelength of 550 nm. As the first retardation film, a polymer film or a UV curable liquid crystal film may be used.

A biaxial retardation film can be defined as follows.

When Nx> Ny> Nz, the thickness direction retardation value (Rth) is defined by following formula (1).

[Equation 1]

Rth = (((Nx + Ny) / 2) -Nz) x d

In addition, the NAZ value is defined by Equation 2 below.

[Equation 2]

NAZ = (Nx-Nz) / (Nx-Ny)

Where Nx is the refractive index in the direction of highest refractive index in the plane, Ny is the refractive index in the direction perpendicular to Nx in the plane, and Nz is the refractive index in the direction perpendicular to the plane. D is the thickness of the film (the length in the Nz direction). )

The second retardation film (negative biaxial retardation film) of the present invention is a film in which the retardation value in the thickness direction is a positive value, and the in-plane retardation is preferably not 0. More specifically, the in-plane retardation (Re) value is 550 nm. It is preferred that the wavelength is 7 nm to 89 nm.

The retardation value in the thickness direction of the second retardation film used for VA-LCD compensation is preferably a value in the range of 200 to 400 nm at a wavelength of 550 nm, and preferably a NAZ value of 5 to 30.

As a viewing angle compensation film, a structure including one uniaxial film (first retardation film) and biaxial negative film (second retardation film) between the lower polarizer and the vertical alignment panel and between the upper polarizer and the vertical alignment panel is shown in FIG. 2. And illustrated in FIG. 3.

In addition, a structure including one uniaxial film (first retardation film) and biaxial negative film (second retardation film) between the upper polarizing plate and the vertical alignment panel as the viewing angle compensation film is illustrated in FIG. 4.

In addition, a structure including one uniaxial film (first retardation film) and biaxial negative film (second retardation film) between the lower polarizing plate and the vertical alignment panel as the viewing angle compensation film is illustrated in FIG. 5.

The vertical alignment liquid crystal display according to the present invention introduces two retardation films and stacks them in various ways to suppress light leakage at the viewing angle and to greatly increase the contrast ratio. It also exhibits excellent viewing angle color characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the refractive index of retardation film.
FIG. 2 is a view schematically showing a first embodiment VA-LCD structure including a compensation film. FIG.
3 is a view schematically showing a second embodiment VA-LCD structure including a compensation film.
4 is a view schematically showing a third embodiment VA-LCD structure including a compensation film.
FIG. 5 is a view schematically showing a fourth embodiment VA-LCD structure including a compensation film. FIG.
FIG. 6 is a diagram showing the results of simulation of the contrast ratio for the VA-LCD structure of Example 1 when white light was used for tilt angles in the range of 0 ° to 80 ° at all Tokyo angles.
Fig. 7 is a diagram showing the results of simulation of the contrast ratio with respect to the VA-LCD structure of Example 2 when white light was used for inclination angles in the range of 0 ° to 80 ° at all Tokyo angles.
Fig. 8 is a diagram showing the results of simulation of the contrast ratio for the Example 3 VA-LCD structure when white light was used for the inclination angles in the range of 0 ° to 80 ° at all the Tokyo angles.
Fig. 9 is a diagram showing the results of simulation of the contrast ratio for the Example 4 VA-LCD structure when white light was used for the inclination angles in the range of 0 ° to 80 ° at all the Tokyo angles.
FIG. 10 is a diagram showing a result of simulating contrast ratio when white light is used for all tilt angles in the range of 0 ° to 80 ° at all east angles according to Comparative Example 1. FIG.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the examples.

Example 1

As shown in FIG. 2, the upper polarizing plate 30, the negative biaxial second retardation film 50, the vertical alignment panel 20, the positive uniaxial first retardation film 40, and the lower polarizing plate 10 are disposed from the top. A laminated VA-LCD panel was manufactured.

At this time, the slow axis 41 of the first retardation film 40 is perpendicular to the absorption axis 11 of the lower polarizing plate 10. The slow axis 51 of the second retardation film 50 was made horizontal with the absorption axis 31 of the upper polarizing plate 30.

The vertical alignment panel 20 is composed of VA liquid crystal cells filled with a liquid crystal having a cell gap of 3 μm, a pre-tilt angle of 90 °, a dielectric anisotropy (Δε) of -5.0, and a birefringence (Δn) of 0.10859. .

The lower polarizing plate 10 and the upper polarizing plate 30 are iodine-coated PVA films, which are triacetate cellulose (TAC) films having a thickness retardation value of about 40 nm as inner protective films on the vertical alignment panel. Polarized plate was used.

The first retardation film 40 A positive uniaxial film having a characteristic of Nx> Nz = Ny, having a surface retardation value (Re) of 260 nm, a thickness retardation value (Rth) of 130 nm at a wavelength of 550 nm, and a retardation of the phase difference according to the wavelength was used. .

The second retardation film 50 has a characteristic of Nx>Ny> Nz, a negative biaxial film having a thickness retardation value (Rth) of 290 nm, a NAZ value of 20, and a retardation of the retardation according to the wavelength at a wavelength of 550 nm. Was used.

When white light is used, contrast characteristics are shown in FIG. 6 at tilt angles in the range of 0 ° to 80 ° with respect to all the mirror angles.

In FIG. 6, the center of the circle is a case where the angle of inclination is 0 °, indicating that the angle of inclination increases as the radius of the circle increases. In FIG. 6, 20, 40, 60, and 80, which are displayed in proportion to the radius of the circle, indicate an inclination angle.

Numerical values 0 ° to 330 ° indicated along the circumference represent an azimuth angle. When the upper polarizer is disposed in the 90 ° direction and the lower polarizer is disposed in the 0 ° direction, it shows contrast characteristics in all viewing directions (incline angle 0 ° to 80 °, east angle 0 ° to 360 °). The result is. VA-LCD using only a polarizing plate exhibited a contrast characteristic of less than 2: 1 at an inclination angle of 60 °, while in FIG. 6, a contrast characteristic of 71: 1 or more was excellent even at an inclination angle of 45 °.

In addition, the color characteristics in the viewing angle exhibit symmetrically excellent color quality without red deflection or blue deflection.

[Example 2]

As shown in FIG. 3, the upper polarizing plate 30, the positive uniaxial first retardation film 40, the vertical alignment panel 20, the negative biaxial second retardation film 50, and the lower polarizing plate 10 are stacked from the top. Prepared VA-LCD panel.

At this time, the slow axis 41 of the first retardation film 40 was perpendicular to the absorption axis 31 of the upper polarizing plate 30. The slow axis 51 of the second retardation film 50 is horizontal to the absorption axis 11 of the lower polarizing plate 10.

The vertical alignment panel 20 is composed of VA liquid crystal cells filled with a liquid crystal having a cell gap of 3 μm, a pre-tilt angle of 90 °, a dielectric anisotropy (Δε) of -5.0, and a birefringence (Δn) of 0.10859. .

The lower polarizing plate 10 and the upper polarizing plate 30 are iodine-coated PVA films, which are triacetate cellulose (TAC) films having a thickness retardation value of about 40 nm as inner protective films on the vertical alignment panel. Polarized plate was used.

The first retardation film 40 A positive uniaxial film having a characteristic of Nx> Nz = Ny, having a surface retardation value (Re) of 260 nm, a thickness retardation value (Rth) of 130 nm at a wavelength of 550 nm, and a retardation of the phase difference according to the wavelength was used. .

The second retardation film 50 has a characteristic of Nx> Ny> Nz, a negative biaxial film having a thickness retardation value (Rth) of 290 nm, a NAZ value of 20, and a retardation of the retardation according to the wavelength at a wavelength of 550 nm. Was used.

When white light is used, contrast characteristics are shown in FIG. 7 at an inclination angle in a range of 0 ° to 80 ° with respect to all east angles. In FIG. 7, the center of the circle is a case where the inclination angle is 0 °, indicating that the inclination angle increases as the radius of the circle increases. In FIG. 8, 20, 40, 60, and 80, which are displayed in proportion to the radius of the circle, indicate an inclination angle.

Numerical values 0 ° to 330 ° indicated along the circumference represent an azimuth angle. When the upper polarizer is disposed in the 90 ° direction and the lower polarizer is disposed in the 0 ° direction, it exhibits contrast characteristics in all viewing directions (incline angle 0 ° to 80 °, east angle 0 ° to 360 °). The result is. The VA-LCD using only a polarizing plate exhibited contrast characteristics of less than 2: 1 at an inclination angle of 60 °, while contrast characteristics of 71: 1 or more were shown in FIG. 7 even at an inclination angle of 45 °.

In addition, the color characteristics in the viewing angle exhibit symmetrically excellent color quality without red deflection or blue deflection.

[Example 3]

As shown in FIG. 4, the upper polarizing plate 30, the positive uniaxial first retardation film 40, the negative biaxial second retardation film 50, the vertical alignment panel 20, and the lower polarizing plate 10 are stacked from the top. Prepared VA-LCD panel.

At this time, the slow axis 41 of the first retardation film 40 was perpendicular to the absorption axis 31 of the upper polarizing plate 30. The slow axis 51 of the second retardation film 50 was made horizontal with the absorption axis 31 of the upper polarizing plate 30.

The vertical alignment panel 20 is composed of VA liquid crystal cells filled with a liquid crystal having a cell gap of 3 μm, a pre-tilt angle of 90 °, a dielectric anisotropy (Δε) of -5.0, and a birefringence (Δn) of 0.10859. .

The lower polarizing plate 10 and the upper polarizing plate 30 are iodine-coated PVA films, which are triacetate cellulose (TAC) films having a thickness retardation value of about 40 nm as inner protective films on the vertical alignment panel. Polarized plate was used.

The first retardation film 40 A positive uniaxial film having a characteristic of Nx> Nz = Ny, having a surface retardation value (Re) of 260 nm, a thickness retardation value (Rth) of 130 nm at a wavelength of 550 nm, and a retardation of the phase difference according to the wavelength was used. .

The second retardation film 50 has a characteristic of Nx> Ny> Nz, a negative biaxial film having a thickness retardation value (Rth) of 290 nm, a NAZ value of 20, and a retardation of the retardation according to the wavelength at a wavelength of 550 nm. Was used.

When the white light is used, contrast characteristics are shown in FIG. 10 at an inclination angle in the range of 0 ° to 80 ° for all east angles.

In FIG. 8, the center of the circle is a case where the angle of inclination is 0 °, indicating that the angle of inclination increases as the radius of the circle increases. In FIG. 8, 20, 40, 60, and 80, which are displayed in proportion to the radius of the circle, indicate an inclination angle.

Numerical values 0 ° to 330 ° indicated along the circumference represent an azimuth angle. When the upper polarizer is disposed in the 90 ° direction and the lower polarizer is disposed in the 0 ° direction, it exhibits contrast characteristics in all viewing directions (incline angle 0 ° to 80 °, east angle 0 ° to 360 °). The result is. The VA-LCD using only a polarizing plate exhibited a contrast characteristic of less than 2: 1 at an inclination angle of 60 °, whereas the contrast characteristic of 63: 1 or more was shown in FIG. 8 even at an inclination angle of 45 °.

In addition, the color characteristics in the viewing angle exhibit symmetrically excellent color quality without red deflection or blue deflection.

Example 4

As shown in FIG. 5, the upper polarizing plate 30, the vertical alignment panel 20, the negative biaxial second retardation film 50, the positive uniaxial first retardation film 40, and the lower polarizing plate 10 are stacked from the top. Prepared VA-LCD panel.

At this time, the slow axis 41 of the first retardation film 40 is perpendicular to the absorption axis 11 of the lower polarizing plate 10. The slow axis 51 of the second retardation film 50 is horizontal to the absorption axis 11 of the lower polarizing plate 10.

The vertical alignment panel 20 is composed of VA liquid crystal cells filled with a liquid crystal having a cell gap of 3 μm, a pre-tilt angle of 90 °, a dielectric anisotropy (Δε) of -5.0, and a birefringence (Δn) of 0.10859. .

The lower polarizing plate 10 and the upper polarizing plate 30 are iodine-coated PVA films, which are triacetate cellulose (TAC) films having a thickness retardation value of about 40 nm as inner protective films on the vertical alignment panel. Polarized plate was used.

The first retardation film 40 A positive uniaxial film having a characteristic of Nx> Nz = Ny, having a surface retardation value (Re) of 260 nm, a thickness retardation value (Rth) of 130 nm at a wavelength of 550 nm, and a retardation of the phase difference according to the wavelength was used. .

The second retardation film 50 has a characteristic of Nx> Ny> Nz, a negative biaxial film having a thickness retardation value (Rth) of 290 nm, a NAZ value of 20, and a retardation of the retardation according to the wavelength at a wavelength of 550 nm. Was used.

When the white light is used, contrast characteristics are shown in FIG. 12 at an inclination angle in the range of 0 ° to 80 ° for all east angles.

In FIG. 9, the center of the circle is a case where the inclination angle is 0 °, indicating that the inclination angle increases as the radius of the circle increases. In FIG. 9, 20, 40, 60, and 80, which are displayed in proportion to the radius of the circle, increase inclination angle.

Numerical values 0 ° to 330 ° indicated along the circumference represent an azimuth angle. When the upper polarizer is disposed in the 90 ° direction and the lower polarizer is disposed in the 0 ° direction, it exhibits contrast characteristics in all viewing directions (incline angle 0 ° to 80 °, east angle 0 ° to 360 °). The result is. VA-LCD using only a polarizing plate exhibited a contrast characteristic of less than 2: 1 at an inclination angle of 60 °, while in FIG. 9, a contrast characteristic of 63: 1 or more was shown even at an inclination angle of 45 °, showing excellent contrast characteristics.

In addition, the color characteristics in the viewing angle exhibit symmetrically excellent color quality without red deflection or blue deflection.

Comparative Example 1

In Example 1, the first phase difference film and the second phase difference film were not used, and a VA-LCD panel in which the upper polarizing plate 30, the vertical alignment panel 20, and the lower polarizing plate 10 were stacked from the top was manufactured.

The vertical alignment panel 20 is composed of VA liquid crystal cells filled with a liquid crystal having a cell gap of 3 μm, a pre-tilt angle of 90 °, a dielectric anisotropy (Δε) of -5.0, and a birefringence (Δn) of 0.10859. .

The lower polarizing plate 10 and the upper polarizing plate 30 are iodine-coated PVA films, which are triacetate cellulose (TAC) films having a thickness retardation value of about 40 nm as inner protective films on the vertical alignment panel. Polarized plate was used.

When the white light is used, contrast characteristics are shown in FIG. 10 at an inclination angle in the range of 0 ° to 80 ° for all east angles.

As shown in FIG. 10, the VA-LCD without retardation film has a contrast characteristic of 8: 1 or less at an inclination angle of 45 °, and a viewing angle light leakage occurs in a dark state.

10 lower polarizing plate 11: absorption axis of lower polarizing plate
20: vertical alignment panel
30: upper polarizing plate 31: absorption axis of the upper polarizing plate
40: first retardation film 41: slow axis of the first retardation film
50: second retardation film 51: slow axis of the second retardation film
100: refractive index in the x-axis direction 200: refractive index in the y-axis direction
300: refractive index in the thickness (d) direction

Claims (16)

At least one selected between the lower polarizing plate and the vertical alignment panel of the vertically aligned liquid crystal display device including a vertical alignment panel between the lower polarizing plate and the upper polarizing plate whose absorption axes are perpendicular to each other, or between the upper polarizing plate and the vertical alignment panel. As a retardation film to be located,
The retardation film satisfies the following formulas (1) to (2) and is a positive uniaxial film; And a second retardation film satisfying the following formulas (3) to (5) and being a negative biaxial film; Retardation film consisting of a pair of films selected from.
Nx> Nz = Ny equation (1)
50 nm ≤ R _th (550) ≤ 300 nm Equation (2)
Nx>Ny> Nz equation (3)
200 nm ≤ R _th (550) ≤ 400 nm Equation (4)
5 ≤ NAZ ≤ 30 Formula (5)
Where Nx is the refractive index in the direction of highest refractive index in the plane, Ny is the refractive index in the direction perpendicular to Nx in the plane, Nz is the refractive index in the direction perpendicular to the plane, and d is the thickness of the film (in the Nz direction Length), and R _th (λ) is a retardation value in the film thickness direction at a wavelength λ nm, wherein R _th and NAZ are defined by the following equations (1) and (2).
[Equation 1]
R _th = (((Nx + Ny) / 2) -Nz) × d
&Quot; (2) "
NAZ = (Nx-Nz) / (Nx-Ny) The method of claim 1,
The retardation film is a retardation film is a first retardation film is positioned between the lower polarizing plate and the vertical alignment panel, the second retardation film is located between the upper polarizing plate and the vertical alignment panel. The method of claim 1,
The retardation film is a retardation film is a second retardation film is positioned between the lower polarizing plate and the vertical alignment panel, the first retardation film is located between the upper polarizing plate and the vertical alignment panel. The method of claim 1,
The retardation film is a retardation film is laminated between the first retardation film and the second retardation film between the upper polarizing plate and the vertical alignment panel. The method of claim 4, wherein
The retardation film is a retardation film of the first retardation film, the second retardation film is sequentially stacked between the upper polarizing plate and the vertical alignment panel. The method of claim 1,
The retardation film is a retardation film is laminated between the first retardation film and the second retardation film between the vertical alignment panel and the lower polarizing plate. The method according to claim 6,
The retardation film is a retardation film is laminated between the second retardation film, the first retardation film sequentially between the vertical alignment panel and the lower polarizing plate. The method according to any one of claims 1 to 7, wherein
The slow axis of the first retardation film is perpendicular to the absorption axis of the adjacent polarizing plate, the slow axis of the second retardation film is parallel to the absorption axis of the adjacent polarizing plate. A vertically oriented liquid crystal display device comprising a vertical alignment panel between a lower polarizer and an upper polarizer having absorption axes perpendicular to each other.
At least one selected between the lower polarizer and the vertical alignment panel, or between the upper polarizer and the vertical alignment panel,
A first retardation film that satisfies the following formulas (1) to (2) and is a positive uniaxial film; And a second retardation film satisfying the following formulas (3) to (5) and being a negative biaxial film; Vertically aligned liquid crystal display device comprising one or more retardation film selected from.
Nx> Nz = Ny equation (1)
50 nm ≤ R _th (550) ≤ 300 nm Equation (2)
Nx>Ny> Nz equation (3)
200 nm ≤ R _th (550) ≤ 400 nm Equation (4)
5 ≤ NAZ ≤ 30 Formula (5)
Where Nx is the refractive index in the direction of highest refractive index in the plane, Ny is the refractive index in the direction perpendicular to Nx in the plane, Nz is the refractive index in the direction perpendicular to the plane, and d is the thickness of the film (in the Nz direction Length), and R _th (λ) is a retardation value in the film thickness direction at a wavelength λ nm, wherein R _th and NAZ are defined by the following equations (1) and (2).
[Equation 1]
R _th = (((Nx + Ny) / 2) -Nz) × d
&Quot; (2) "
NAZ = (Nx-Nz) / (Nx-Ny) The method of claim 9,
The vertically aligned liquid crystal display device
Between the lower polarizing plate and the vertical alignment panel, including a first retardation film,
Between the upper polarizing plate and the vertical alignment panel, comprising a second retardation film
Vertically aligned liquid crystal display device. The method of claim 9,
The vertically aligned liquid crystal display device
Between the lower polarizing plate and the vertical alignment panel, a second phase difference film,
Between the upper polarizing plate and the vertical alignment panel, comprising a first retardation film
Vertically aligned liquid crystal display device. The method of claim 9,
The vertically aligned liquid crystal display device
And a first retardation film and a second retardation film between the upper polarizer and the vertical alignment panel. 13. The method of claim 12,
The vertically aligned liquid crystal display device
The vertically aligned liquid crystal display device of which the upper polarizing plate, the first retardation film, the second retardation film, the vertical alignment panel, and the lower polarizing plate are stacked in order from the top. The method of claim 9,
The vertically aligned liquid crystal display device
And a first retardation film and a second retardation film between the lower polarizer and the vertical alignment panel. The method of claim 14,
The vertically aligned liquid crystal display device
The vertically aligned liquid crystal display device of which the upper polarizing plate, the vertical alignment panel, the second retardation film, the first retardation film, and the lower polarizing plate are stacked in order from the top. The method according to any one of claims 9 to 15,
The slow axis of the first retardation film is perpendicular to the absorption axis of the adjacent polarizing plate, the slow axis of the second retardation film is parallel to the absorption axis of the adjacent polarizing plate.

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