KR100627651B1 - Liquid crystal display device and the method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including a nematic liquid crystal having a low twist angle of 90 ^° or less. The gap between the first substrate and the second substrate is designed to be 2 μm. The angle between the first polarizing plate and the second polarizing plate positioned in proximity to the first substrate and the second substrate with respect to the rubbing axes of the first alignment layer and the second alignment layer respectively formed on opposite surfaces of the first substrate and the second substrate is determined. By forming (90 ^° -Φ) / 2 for each twist angle Φ of the liquid crystal, it is possible to obtain a high-quality liquid crystal display device having high-speed response characteristics and no afterimage.

Description

Liquid crystal display device and method for manufacturing same             

1 is a cross-sectional view showing a liquid crystal display device according to the present invention;

2 is a schematic view of a liquid crystal display according to the present invention.

<Description of the symbols for the main parts of the drawings>

107a: rubbing axis direction of the first alignment layer 109a: rubbing axis direction of the second alignment layer

115a: Transmission axis direction of first polarizing plate 117a: Transmission axis direction of second polarizing plate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including a nematic liquid crystal having a low twist angle.

In general, an LCD includes an upper substrate and a lower substrate bonded to each other, and injects liquid crystal between the upper substrate and the lower substrate to form a display panel.

A polarizer, a retardation film, and the like are attached to outer surfaces of the upper and lower substrates of the display panel. By selectively configuring such a configuration cell, a liquid crystal display device having high brightness and contrast characteristics by changing the light propagation state or the refractive index is constructed.

The plurality of cells are designed in consideration of the characteristics of the liquid crystal filled in the liquid crystal display. In general, the liquid crystal layer used in the liquid crystal display device must be capable of fast response to an applied electric field and low voltage, and should have no afterimage due to gray scale and have a wide viewing angle characteristic. Good to have.

Of course, it is very rare to meet all of these requirements, and liquid crystal displays have been manufactured with attempts to approach these requirements.

For example, a conventional liquid crystal display including a 90 ^o twisted nematic liquid crystal, or a liquid crystal display using the IPS (In-Plane Switching) operation mode has a wide viewing angle but afterimages appear when a video is displayed. There is a problem in displaying high quality video such as falling.

In order to solve these problems, currently developed methods such as AFLC (anti ferroelectric liquid crystal) or optical compensated birefringence (OCB) have fast response time and wide viewing angle, but they do not improve problems such as cell gap adjustment and contrast. It is a state.

Accordingly, an object of the present invention is to propose a method of manufacturing a liquid crystal display device which can obtain a wide viewing angle characteristic along with high speed response characteristics and reduce afterimages according to gray scale.

According to an aspect of the present invention, a liquid crystal display device includes: a first substrate on which a first alignment layer is formed; A second substrate on which a second alignment film is formed; A compensation film positioned on the first substrate; A first polarizing plate positioned on the compensation film and having a rubbing axis of the first alignment layer and a polarization direction formed at an angle of (90 ^o −Φ) / 2; A second polarizing plate disposed under the second substrate and having a rubbing axis of the second alignment layer and a polarization direction formed at an angle of (90 ^o −Φ) / 2; A spacer patterned between the first substrate and the second substrate; And a nematic liquid crystal disposed between the first substrate and the second substrate and having a twist angle of Φ.

The polarization direction of the first polarizing plate and the second polarizing plate is characterized in that the perpendicular.

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The height of the spacer is characterized in that 2㎛.

The phase difference of the compensation film is characterized in that the range of 10-60nm.

The first alignment layer and the second alignment layer are characterized in that the polyimide.

According to an aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, comprising: providing a first substrate and a second substrate; Forming a first alignment layer on the first substrate and a second alignment layer on the second substrate to perform a rubbing treatment; Patterning a spacer on said first substrate; Bonding the first substrate and the second substrate to each other; Injecting a twisted nematic liquid crystal having a twist angle of φ between the first substrate and the second substrate; Attaching a compensation film on the second substrate; Attaching a second polarizing plate on the compensating film such that a rubbing axis of the second alignment layer and a polarization direction form an angle of (90 ^o −Φ) / 2; And attaching a first polarizing plate to a lower portion of the first substrate such that a rubbing axis of the first alignment layer and a polarization direction form an angle of (90 ^o −Φ) / 2.

Hereinafter will be described a preferred embodiment according to the present invention.

The liquid crystal display according to the present invention is designed using a low twisted nematic liquid crystal (LTN LCD) (hereinafter referred to as "LTN liquid crystal") having a low twist angle. The LTN liquid crystal is a liquid crystal having a low twist angle of 90 ^° or less and is a liquid crystal having high speed response characteristics.

In general, in order to exhibit high-speed response characteristics, the gap of the liquid crystal cell between the first and second substrates filled with the liquid crystal should be made as small as possible with the inherent response characteristics of the liquid crystal.

Therefore, in the present invention, the gap of the liquid crystal cell is designed to 2 μm in consideration of the high speed response characteristics and the pitch of the liquid crystal having the low twist angle.

In general, a spacer is used to maintain a gap between the first substrate and the second substrate, and the spacer is arranged by using a plastic ball or silica sphere having a desired aperture. Use a method to spread.

The general size of the spacer is 4 to 5㎛ in size and the smaller the size of the spacer, it is difficult to uniformly maintain a low cell gap through the entire panel by a general spacer scattering method, in the present invention to obtain a constant cell gap To form a patterned spacer that can replace the spacer function.

1 is a cross-sectional view showing a cross section of a liquid crystal display according to the present invention.

As shown in the drawing, in order to maintain a gap between the first substrate 101 and the second substrate 103, the spacer is patterned on the first substrate 101 at predetermined intervals, and then the first substrate 101 is patterned. The substrate 101 and the second substrate 103 are bonded to each other, and the nematic liquid crystal 113 having a low twist angle is filled between the first substrate 101 and the second substrate 103.

At this time, the method of patterning the spacer can be considered in various ways.

For example, one method may be to spread the polymer material to a predetermined thickness and then harden and pattern the polymer material into a desired shape.

The first polarizing plate 107 is formed on the outer surface of the first substrate 101, and the second polarizing plate 109 is formed on the outer surface of the second substrate 103. In this case, the second substrate 103 and the second polarizing plate 109 are interposed between the compensation film 111.

The compensation film 111 is a uniaxial film, and is formed between the second substrate 109 and the second polarizing plate 109 to increase the contrast of the liquid crystal display device.

In this case, the first surface of the first substrate 101 and the second substrate 103 is coated with an alignment material such as polyimide and then rubbed to have a predetermined orientation considering the alignment characteristics of the liquid crystal. The alignment layer 115 and the second alignment layer 117 are formed.

In addition, a photo alignment layer may be used by using light instead of the rubbing.

In the above-described configuration, factors influencing the transmission characteristics of light include the transmission axis directions of the first polarizing plate 107 and the second polarizing plate 109, and the first alignment layer 115 and the second alignment layer 117. Is the angle formed by the rubbing axis, the twist angle φ of the nematic liquid crystal, the thickness d of the liquid crystal cell, the refractive index Δn of the liquid crystal cell, and the like.

In this case, the first polarizing plate 107 and the second polarizing plate 109 are positioned to form a vertical 90 ^o .

In the present invention, the first polarizing plate 107 and the second polarizing plate 109 and the polarization direction perpendicular to each other in order to find the optimal d △ n for any twist angle of the low-angle nematic liquid crystal By varying the angle between the rubbing axis of the first alignment layer and the rubbing axis of the second alignment layer, optimized dΔn (phase value: Δn having a high transmittance for liquid crystals having any twist angle of 90 ^° or less) Refractive index, d is the thickness of the liquid crystal).

This algorithm was applied to the program used to design the operation mode of the LTN liquid crystal display, and the results are shown in Table 1 below.

Table 1 is a result table that changes the factor of each component cell in the LTN liquid crystal according to the present invention, showing the optimum dΔn value for each twist angle of the LTN liquid crystal.

Table 1 shows values obtained by a Jones matrix method for finding an optimal transmittance by changing dΔn of the liquid crystal with respect to the thickness of the liquid crystal layer.

As shown, it is possible to find an optimal dΔn value that can have a high transmittance for each twist angle.

For example, when the twist angle of the twisted nematic liquid crystal is 60 ^° , the optimized phase value of the nematic liquid crystal is Δnd = 0.349, which shows that a high transmittance can be obtained.

In order to obtain such a result, the first polarizing plate (107 of FIG. 1) and the second polarizing plate (of FIG. 1) are applied to each of the rubbing axes of the first alignment layer (115 of FIG. 1) and the second alignment layer (117 of FIG. 1). 109) must make a predetermined angle with respect to the twist angle of the twisted nematic liquid crystal (113 in FIG. 1).

Hereinafter, a detailed description will be made with reference to FIG. 2.

2 is a design of the LTN liquid crystal panel according to the present invention.

As shown, the polarization direction 107a of the first polarizing plate and the polarization direction 109a of the second polarization perpendicular to each other according to the twist angle Φ of the twisted nematic liquid crystal are the rubbing axis 115a of the first alignment layer. The rubbing axes 117a of the second alignment layer are disposed so as to form an angle of (90 ^°- ?) / 2 respectively.

In addition, the phase difference of the uniaxial compensation film is designed in the range of 10-60nm according to the twist angle of the low twisted nematic liquid crystal.

In this case, the liquid crystal has a low viscosity and should use a liquid crystal having an optimum refractive index (Δn) according to the twist angle of the liquid crystal.

As described above, the LTN liquid crystal display according to the present invention can be driven within 10ms, has a fast response speed, and can significantly reduce afterimages, thereby displaying a higher quality video.

Claims (7)

A first substrate on which a first alignment layer is formed; A second substrate on which a second alignment film is formed; A compensation film positioned on the first substrate; A first polarizing plate positioned on the compensation film and having a rubbing axis of the first alignment layer and a polarization direction formed at an angle of (90 ^o −Φ) / 2; A second polarizing plate disposed under the second substrate and having a rubbing axis of the second alignment layer and a polarization direction formed at an angle of (90 ^o −Φ) / 2; A spacer patterned between the first substrate and the second substrate; A nematic liquid crystal positioned between the first substrate and the second substrate and having a twist angle of Φ; Liquid crystal display comprising a. delete The method of claim 2, The height of the spacer is 2㎛ liquid crystal display device. According to claim 1, The retardation of the compensation film is a liquid crystal display, characterized in that in the range of 10-60nm. Providing a first substrate and a second substrate; Forming a first alignment layer on the first substrate and a second alignment layer on the second substrate to perform a rubbing treatment; Patterning a spacer on said first substrate; Bonding the first substrate and the second substrate to each other; Injecting a twisted nematic liquid crystal having a twist angle of φ between the first substrate and the second substrate; Attaching a compensation film on the second substrate; Attaching a second polarizing plate on the compensating film such that a rubbing axis of the second alignment layer and a polarization direction form an angle of (90 ^o −Φ) / 2; And attaching a first polarizing plate to a lower portion of the first substrate such that a rubbing axis of the first alignment layer and a polarization direction form an angle of (90 ^o −Φ) / 2. The method of claim 5, The polarization direction of the first polarizing plate and the second polarizing plate is perpendicular to the manufacturing method of the liquid crystal display device.  The method of claim 5,   And the height of the patterned spacer is 2 [mu] m.

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