JPH0895031A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To provide a high quality liquid crystal display element having a good appearance for a display screen and excellent visibility by extremely lowering surface reflection. CONSTITUTION: Reflected light to be emitted to the outside of a liquid crystal display element through an optical anisotropic element 2 is shifted by 1/4 wavelength when it passes through the optical anisotropic element 2 once, and is shifted by 1/4 wavelength when it is reflected on BM (a light shielding film 3) and passes through the optical anisotropic element 2 again, and as a result, rotatory polarization by 90 degrees equivalent to 1/2 wavelength in total is carried out, so that straight polarized light is directed in the direction orthogonal to that of the straight polarized light which passed through the polarizing plate 12a at first. Therefore, this reflected light cannot pass through the polarizing plate 12a. In this way, reflected light reflected on BM (light shielding film 3), which is made of metallic material, for example, and has a high light reflecting property, in a non-picture element part is not emitted theoretically to an observation side, and in fact, the reflected light is scarcely emitted to the observation side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display element, and more particularly to a liquid crystal display element which prevents surface reflection and has a display screen that is easy to see and has good apparent contrast characteristics.

[0002]

2. Description of the Related Art In recent years, liquid crystal display elements having the great advantages of thinness, lightness and low power consumption are display devices for personal OA equipment such as Japanese word processors and desktop personal computers which are particularly required to be thin and lightweight. It is often used as

Most of the liquid crystal display elements (hereinafter abbreviated as LCD) use twisted nematic liquid crystal, and the display system can be roughly classified into two systems, an optical rotation mode and a birefringence mode.

The LCD of the optical rotation mode uses, for example, a twisted nematic (TN) type liquid crystal with a molecular arrangement twisted by 90 °. Due to its operation principle, black and white display is basically used, and a high contrast ratio and a good gradation display property are provided. Also, since the response speed is fast (several tens of milliseconds), segment drive for clocks and calculators, simple matrix drive in which pixels are arranged in a matrix, or active matrix drive with switching elements for each pixel Is displayed. Also, in combination with a color filter, a full-color display LCD TV etc. (TFT-LCD or MIM
-Application to LCD) (TN method).

On the other hand, a birefringence mode display type LCD
Is a super twisted nematic (STN; Super Twisted) with a molecular arrangement that is generally twisted by 90 ° or more.
An LCD using d Nematic) type liquid crystal shows a steep electro-optical characteristic. Therefore, even if switching elements such as thin film transistors and diodes arranged for each pixel are not used, electrodes arranged in rows and columns A large capacity (large screen) display can be easily realized by time-division driving in a simple matrix type LCD which has a simple structure in which a pixel is formed at each intersection of and has a low manufacturing cost.

When any liquid crystal display element is viewed in a place other than a dark place, the face, scenery, and ambient light sources are reflected on the screen due to reflection of natural light on the surface of the display element, indoor illumination light, and the like, which is unattractive. However, there is a problem such as reduced visibility. In particular, in a liquid crystal display element using a color filter, in many cases, a light-shielding film made of a metal material (hereinafter, abbreviated as BM (Black Matrix)) is used for light shielding in a non-pixel portion, and this problem is more remarkable. is there.

In order to reduce the surface reflection, a measure to dispose an antireflection glass or an antireflection film on the surface, or a measure to perform antireflection (or reflection reduction) treatment on the polarizing plate on the observation side (front side) Also, measures such as using a material with low reflection, or in the case of a TN type LCD, a BM is arranged on the light source side (rear side) are taken.

[0008]

However, in the method of disposing the antireflection glass or the antireflection film, using the antireflection polarizing plate, or using the low reflection BM, the reduction of the surface reflection on the display side is effective. Is not performed, and there is still a problem of unsightly screen due to surface reflection. Also BM
There is a problem that the method of arranging the rear side on the rear side is technically and processally difficult and is not excellent in cost.

The present invention has been made in order to solve such a problem, and an object thereof is to provide a high-quality liquid crystal display in which the surface reflection is extremely low so that the display screen looks good and the visibility is excellent. It is to provide an element.

[0010]

In order to solve the above problems, in a liquid crystal display element of the present invention, at least one substrate is provided with two substrates having electrodes and facing each other with a gap, A liquid crystal composition is sandwiched in the gap to form a liquid crystal layer, and light is applied to an area other than the optical modulation area on the surface of the two substrates facing the liquid crystal layer on the viewing side. In a liquid crystal display element in which a light blocking layer for blocking is provided and a polarizing plate is arranged on the outer surface side of the substrate provided with the light blocking layer, between the light blocking layer and the substrate on which the light blocking layer is formed. And the retardation value is (550N +
137) An optical anisotropic element of ± 9 nm (N is 0 and a positive integer) is arranged such that its optical axis forms an angle of 45 ± 3 ° with the polarization axis of the polarizing plate. There is.

[0011]

In the liquid crystal display element of the present invention, the retardation value (5
An optically anisotropic element having a polarization of 50 N + 137) ± 9 [nm] and no optical rotatory power is arranged so that its optical axis forms an angle of about 45 ° ± 3 ° with the polarization axis of the polarizing plate.

The light that has passed through the polarizing plate disposed on the observation side is visible light, and the light of λ = 550 nm, which is the central wavelength and has the strongest light intensity, becomes linearly polarized light and enters the optically anisotropic element. To do.

Then, due to the optical delay effect of the optically anisotropic element, it is emitted as circularly polarized light and reflected by, for example, the metal BM in the non-pixel portion. The reflected light enters the optical anisotropic element as circularly polarized light. At this time, the reflected light emitted from the optically anisotropic element becomes linearly polarized light in a direction orthogonal to the linearly polarized light that first passed through the polarizing plate and cannot pass through the polarizing plate. Thus, the reflected light from the BM, which is made of, for example, a metal material in the non-pixel portion and has high light reflectivity, is theoretically emitted to the observation side, and practically disappears. as a result,
Surface reflection can be made extremely low, and a high-quality liquid crystal display device with good appearance and excellent visibility can be realized.

The above retardation value is 550N.
By setting +137 [nm] (N = 0, 1, 2, 3, ...) As its center within the allowable range of ± 9 nm, it is possible to effectively suppress the reflected light as described above.

Further, the angle formed by the optical axis and the polarizing axis of the polarizing plate is set within the permissible range of ± 3 ° around 45 °, so that the reflected light is effectively suppressed as described above. be able to.

Further, since the above-mentioned optical anisotropic element is formed to prevent light reflection on the light-shielding film, it is formed in a pattern overlapping the pattern of the light-shielding film, that is, the light-shielding film in the non-pixel portion is covered. It is desirable to form the pattern.

[0017]

Embodiments of the liquid crystal display device of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a TN according to a first embodiment of the present invention.
FIG. 3 is a cross-sectional view schematically showing a structure of a color filter substrate side used as a substrate on an observation side in a liquid crystal display element of the system. An outline of the structure of the first embodiment will be described with reference to FIG. 1 while following the manufacturing process thereof.

A glass substrate 1 is prepared. On this glass substrate 1, as a material layer for forming the optically anisotropic element 2, a homogeneously oriented polymer dispersed liquid crystal layer having a birefringence with a retardation value of 137 nm is formed. It goes without saying that this polymer-dispersed liquid crystal layer is a liquid crystal layer different from the liquid crystal layer as a liquid crystal cell for display. The retardation value of this polymer-dispersed liquid crystal layer of 137 nm is equal to the retardation value of the liquid crystal display element according to the present invention (550 N + 137) ±
This corresponds to the case where N = 0 of 9 [nm] (N = 0, 1, 2 ...). Other applicable values for the retardation of the optically anisotropic element 2 are 687 nm (when N = 1) and 1237 nm.
It is possible to take values such as (when N = 1). Here, it goes without saying that the numerical value 137 of the above (550N + 137) is 1/4 cycle of the wavelength of 550 nm.

On the optical anisotropic element 2, a chromium layer for forming the light shielding film 3 is formed by sputtering to a thickness of 0.15 μm. A resist film (not shown) made of positive photosensitive polyimide is formed on the chromium layer, and the resist film is patterned. Then, the chromium layer and the polymer-dispersed liquid crystal layer in the portion exposed from the resist film are
Etching is performed by the EP process to pattern the light-shielding film 3 and the optical anisotropic element 2 into a grid pattern of a non-pixel portion as shown in FIG.

On the double layer of the optically anisotropic layer 2 and the light shielding film 3 thus patterned on the glass substrate 1, R, G,
B (Red, Green, Blue) color resists are applied step by step to a thickness of 1.5 μm, and patterning is repeated to form R, G, and B color cells (coloring layers) 4, 5 and 6 as color filters. Form.

Then, an overcoat layer 7 having a thickness of 1 μm is formed so as to cover almost the entire surface including the above, and a counter electrode 8 made of ITO is further formed thereon to form the overcoat layer 7 of the first embodiment of the present invention. The counter substrate 9 on which the color filter of the TN liquid crystal display element is formed is obtained.

On the other hand, a TFT substrate 10 arranged facing the glass substrate 1 is prepared. An alignment film 11 is formed on each of the surfaces of the counter substrate 9 and the TFT substrate 10 that face each other.
AL-1051 (made by Japan Synthetic Rubber Co., Ltd.) as a and 11b
Then, the surfaces of the alignment films 10 and 11 are rubbed so that liquid crystal molecules (not shown) are twisted by 90 °.

Then, the alignment films 10 and 1 are arranged via the spacers.
The counter substrate 9 and the TFT substrate 10 so that the ones face each other.
And were opposed to each other, and were adhered and sealed with a sealant while maintaining a cell gap around them, to prepare a liquid crystal cell in an empty cell state. Then, in this empty cell, as a liquid crystal composition, ZL
A liquid crystal display device was completed by injecting I-1132 (manufactured by E. Merck).

As for the liquid crystal display device manufactured in such a structure, when the screen was confirmed, the surface reflection could be suppressed to be extremely low even in a bright place, and the display screen had good appearance and high visibility. Was confirmed to be observable.

As described above, in the liquid crystal display element of the present invention, the retardation value is (550 N +) on the surface of the non-pixel portion inside the substrate (counter substrate 9 in the above embodiment) arranged on the observation side.
137) An optically anisotropic element with no optical activity at ± 9 [nm]
It is arranged so that its optical axis forms an angle of about 45 ° ± 3 ° with the polarizing axis of the polarizing plate 12a. The light that enters the substrate 1 further through the polarizing plate 12a disposed on the observation side of the polarizing plates 12a and 12b is visible light, that is, the central wavelength of the visible light and the light intensity is The most intense light of λ = 550 nm becomes linearly polarized light and enters the optically anisotropic element 2.

Then, the light is emitted as circularly polarized light due to the optical delay effect of the optical anisotropic element 2, and is reflected by the BM (the light shielding film 3 in the above embodiment) made of a metal material having a high light blocking property in the non-pixel portion. The reflected light again enters the optical anisotropic element 2 as circularly polarized light. At this time, the reflected light which is going to be emitted to the outside of the liquid crystal display element through the optical anisotropic element 2 once passes through the optical anisotropic element 2 and is shifted by 1/4 wavelength, and further, BM
Since the light is reflected by the (light-shielding film 3), passes through the optical anisotropic element 2 again, and is shifted by 1/4 wavelength, a 90-degree optical rotation equivalent to a shift of 1/2 wavelength is made. It becomes linearly polarized light in a direction orthogonal to the linearly polarized light that has passed through 12a. Therefore, this reflected light cannot pass through the polarizing plate 12a. As a result, the non-pixel portion is made of, for example, a metal material and has high light reflectivity.
The reflected light from M (light-shielding film 3) is not emitted to the observation side theoretically, and practically disappears. As a result, the surface reflection can be made extremely low, and a high-quality liquid crystal display element having a good appearance and excellent visibility can be realized.

The above retardation value is 550N.
By keeping +137 [nm] in the allowable range ± 9 nm, the reflected light can be effectively suppressed as described above. Further, the angle formed between the optical axis and the polarization axis of the polarizing plate is set within the permissible range of ± 3 ° centering around 45 °, whereby the reflected light can be effectively suppressed as described above. . At this time, needless to say, the optical rotatory power of the optical anisotropic element 2 does not adversely affect the display light for displaying. What happens is that the display light is emitted from the liquid crystal layer 13
This is because the optical anisotropic element 2 is formed in the non-pixel portion so as to overlap the pattern of the light-shielding film 3 in the non-pixel portion.

The present invention also includes the materials described in the above embodiments,
It is not limited to the conditions and the liquid crystal mode, and similar effects can be obtained with other materials and other conditions. For example, the liquid crystal display mode is not limited to the TN type liquid crystal shown in the above-mentioned embodiment, but is the same as that of STN, ECB, GH, PC, and PDLC type liquid crystal using LCD having optical rotatory liquid crystal layer. It goes without saying that the same effect as the example can be obtained. Needless to say, the driving method can be applied not only to the TFT active matrix system but also to the MIM active matrix system LCD and the simple matrix system LCD.

Further, the present invention is not limited to only the LCD which is equipped with the color filter as in the above embodiment and performs color display. In addition to this, it goes without saying that the present invention can also be applied to an LCD that performs monochrome display.

[0031]

As described above in detail, according to the present invention, a high-quality liquid crystal display device having a very low surface reflection and a good display screen and excellent visibility is provided. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a color filter substrate of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a light-shielding film 3 and an optical anisotropic element 2 which are patterned in a grid pattern of a non-pixel portion.

[Explanation of symbols]

 1 ... Glass substrate 2 ... Optical anisotropic element 3 ... Light-shielding film 4 ... Color filter color cell (Red) 5 ... Color filter color cell (Green) 6 ... Color filter color cell (Blue) 7 ... Overcoat layer 8 ... Counter electrode 9 ... Counter substrate 10 ... TFT substrate 11a ... Alignment film 11b ... Alignment film 12a ... Polarizing plate 12b ... Polarizing plate 13 ... Liquid crystal layer

Claims (1)

[Claims] 1. An electrode having an electrode on at least one substrate 2
A pair of substrates are installed facing each other with a gap, a liquid crystal composition is sandwiched in the gap to form a liquid crystal layer, and faces the liquid crystal layer of the substrate disposed on the observation side of the two substrates. In a liquid crystal display element in which a light-shielding layer that shields light is provided in an area other than the optical modulation area on the side surface, and a polarizing plate is arranged on the outer surface side of the substrate on which the light-shielding layer is provided, An optical anisotropic element having a retardation value of (550N + 137) ± 9 nm (N is 0 and a positive integer) between the layer and the substrate on which the light shielding layer is formed, the optical axis of which is the polarization of the polarizing plate. A liquid crystal display device characterized by being arranged so as to form an angle of 45 ± 3 ° with the axis.