KR20000073286A - Vertical Aligned LCD with Wide Viewing Angle - Google Patents

Abstract

PURPOSE: A vertical aligned LCD is provided to simplify the manufacturing process by forming a pixel electrode while forming a source electrode and a drain electrode without an ITO having the difficulty in etching. CONSTITUTION: In a vertical aligned LCD, a vertical alignment film is deposited on the upper and underlying glass substrates. A liquid crystal in which a dielectric anisotropy is negative is injected between the vertical alignment films. The vertical alignment film of at least one of both the glass substrates is aligned so that a line inclination angle of a liquid crystal element in the alignment film is less than 90 degrees. A pixel electrode(5) of a glass substrate having an active device is a metal film. The pixel electrode has a slit pattern(7) or floating electrode(30) by etching. By adjusting the direction of an electric field induced into the slit pattern or floating electrode, the alignment direction of the vertical alignment film, the liquid crystal element between the adjacent slit patterns when the voltage value of the liquid crystal layer is more than the threshold voltage value has a structure twisted into the direction of the left hand and a structure twisted into the direction of the right hand.

Description

Wide viewing vertical alignment liquid crystal display device {Vertical Aligned LCD with Wide Viewing Angle}

According to the present invention, at least one of the vertical alignment films 3 and 3 'of the upper and lower glass substrates is oriented in a specific direction, the pixel electrode is made of an opaque metal film, and the metal film of the pixel electrode is partially etched to form a slit pattern. (7) Alternatively, a vertical alignment is realized by using a floating electrode 30 to realize a multi-domain by using the lateral field induced around the slit pattern and the floating electrode and the alignment processing direction of the vertical alignment layer. The present invention relates to a liquid crystal display device. The present invention not only widens the viewing angle by continuously displaying the liquid crystal alignment structure and the parallel alignment structure and the liquid crystal alignment structure twisted with the left hand between the slit pattern and the slit pattern, but also simultaneously expands the pixel electrode with the scan line or the signal line. As a result, the number of processes is reduced and productivity is increased.

The liquid crystal display is divided into active matrix driving method and passive matrix addressing method according to the driving method. Among the active matrix driving method, the TFT liquid crystal display device and the MIM liquid crystal display device are used for moving picture and Since 256 gray levels can be realized, the most widely commercialized product is currently in progress. A cross-sectional view of a liquid crystal cell of one example of a conventional vertically aligned TFT liquid crystal display element is shown in FIG. The operation principle of the TFT liquid crystal display device is as follows. The gate electrode 11 of the TFT in each pixel is connected to the scanning line, the source electrode to the signal line, and the drain electrode to the pixel electrode 5, respectively. There is a liquid crystal layer 4 between the common electrode 6 and the pixel electrode. In the selection period, a voltage higher than that of the signal line is applied to the gate electrode connected to the scan line, so that the connection resistance of the channel between the drain electrode and the source electrode is reduced, so that the voltage applied to the signal line is applied to the liquid crystal layer across the pixel electrode. In the non-selection period, a voltage lower than that of the signal line is applied to the gate electrode connected to the scan line, and the drain electrode and the source electrode are electrically disconnected to maintain the charge accumulated in the liquid crystal layer during the selection period. While scanning the scan lines sequentially, each pixel electrode is charged through the signal lines to apply voltage to the liquid crystal layer. When the rms (root means square) voltage applied to the liquid crystal layer between the pixel electrode and the common electrode is adjusted, the polarized state changes as the linearly polarized light passes through the liquid crystal layer and passes through the liquid crystal layer. Display information.

In the TFT liquid crystal display device, a vertical alignment liquid crystal display device using a negative liquid crystal in order to widen the mainstream or the viewing angle of the 90 ° TN mode has been studied. In the vertically aligned LCD, when no voltage is applied to the liquid crystal layer, the long axis of the liquid crystal molecules is vertically aligned with the plane of the alignment layer, and when the voltage exceeds the threshold, the long axis of the liquid crystal molecules lies on the plane of the alignment layer. In the vertical alignment liquid crystal display, the viewing angle can be increased by attaching a negative retardation plate having a refractive index of light oscillating in the vertical direction to a plane of the alignment layer smaller than the refractive index oscillating in the horizontal direction. Single domain vertical aligned LCDs generally perform rubbing to determine the lying direction of liquid crystals having negative dielectric anisotropy in the rubbing direction. In the single-zone vertical alignment liquid crystal display device, the vertical alignment layers 3, 3 'are usually parallel-aligned by rubbing in the opposite direction or aligning them with the optical alignment.

The single-zone vertical alignment liquid crystal display device has a large gray level inversion at an azimuth angle of 45 ° with the transmission axis of the polarizer. Therefore, in order to realize a wide viewing angle, the liquid crystal cell must be made of a structure having a multi-domain. Multi-domain realization includes rubbing, UV alignment, projection, rounding electrode (SE), patterned vertical alignment (PVA), etc. The inventors proposed LFIMD (Lateral Field Induced Multi Domain; 1998 patent application 11918, 29992, 1999 4531), which is the most excellent considering the transmittance, viewing angle, and mass production. In patent application 11918, the mode exists when the bonding energy between the vertical alignment film and the negative liquid crystal is close to zero, and the method of 29992 exists when the surface anchroing energy of the vertical alignment film and the negative liquid crystal is above a certain value. Mode. The main contents of the three patents are to prevent the disinclination line of negative liquid crystals (liquid crystals having negative dielectric anisotropy) at the interface between the domains, thereby greatly improving the transmittance and operating stability according to the voltage of the negative liquid crystals. It is. The operation principle is as follows. At least one of the upper and lower vertical alignment films is oriented, and a slit pattern 7 or a floating electrode 30 having a width of 5 to 20 µm is disposed on a pixel electrode of another substrate or a glass substrate having active elements which are not oriented. . The boundary condition of the orientation of the liquid crystal molecules in the rubbing substrate becomes the rubbing direction, and the boundary condition of the orientation of the liquid crystal molecules of the substrate with the slit pattern or floating electrode becomes the side electric field induced in the slit pattern. 3 is a cross-sectional view of a conventional LFIMD vertical alignment liquid crystal display device using a slit pattern. 4 is a plan view of the electrode of FIG. 3 is a cross-sectional view of the vertically aligned liquid crystal cell in the short axis direction of the slit pattern of FIG. Induction of the lateral electric field by the slit pattern in the vertical orientation was proposed by Lien in 1992 in SID. The slit pattern is a portion obtained by etching the pixel electrode. Conventionally, the pixel electrode is made of a transparent conductive film. Since the remaining portion of the transparent conductive film becomes an equipotential, an equipotential line is formed parallel to the long axis direction of the slit pattern. Since the vertical direction of the equipotential curve becomes the electric field direction, the side electric field is induced in the short direction of the slit pattern. Since the equipotential curve also occurs in the vertical direction (liquid crystal cell thickness direction) of the pixel electrode, electric field components in the vertical direction also occur in the slit pattern portion. The electric field in the vertical direction is mirror symmetry around the center of the slit pattern. If the substrate facing the slit pattern is not oriented by rubbing, etc., when the liquid crystal layer is subjected to a voltage higher than the threshold, the direction of the liquid crystal molecules is not determined so that a disinclination line is formed around the center of the slit pattern. . However, if the substrate facing the slit pattern is oriented in the long axis direction of the slit pattern by rubbing or other method, when the voltage above the threshold is applied to the liquid crystal layer, the orientation direction in the common electrode glass substrate becomes the azimuth angle of the liquid crystal molecules, and the slit The liquid crystal molecules in the center of the pattern lie in the alignment direction and there is no disincretion line. In Fig. 3, the vertical alignment film of the critical plate (common electrode glass substrate) is rubbed in the y direction. In the parts A and C of FIG. 3, since there is no side electric field, when a voltage above the threshold is applied to the liquid crystal layer, the negative liquid crystal lies in the rubbing direction of the critical plate vertical alignment layer. In B of the lower substrate (TFT glass substrate), the negative liquid crystal molecules lie on the x axis, D in the -x axis, and the liquid crystal molecules lie in the rubbing direction in the alignment layer of the upper substrate, so that the left hand is twisted in the liquid crystal cell B. The twist becomes right twisted in the liquid crystal cell D. 5 is a plan view of an electrode of a conventional LFIMD vertically aligned liquid crystal display device using a floating electrode. The floating electrode is an electrode that is not connected to the peripheral electrode and is separated by a hole. The voltage induced on the floating electrode depends on the storage capacitance and voltage distribution of the peripheral electrode. Therefore, the voltage applied to the floating electrode can be known from the coupling capacitance with the peripheral electrode and the voltage distribution. The voltage induced to the floating electrode becomes a value between the voltage applied to the common electrode 6 and the pixel electrode 5, which are opposite substrates. The value is determined in accordance with the ratio of the storage capacitance between the opposite common electrode and the ratio of the storage capacitance between the pixel electrode and the floating electrode. A side electric field is formed between the floating electrode 30 and the pixel electrode due to a voltage difference, and a vertical electric field is formed between the floating electrode and the common electrode. If the liquid crystals lie in a direction other than the alignment process direction of the vertical alignment liquid crystal display element in the absence of the side electric field, the liquid crystal becomes a twisted structure, and since the twisted structure has a higher free energy than the parallel aligned structure, there is little possibility of existence. If the angle formed between the alignment direction of the vertical alignment film and the major axis of the slit pattern is q, the right hand twist is 90-q and the left hand twist angle is 90 + q. Therefore, the most stable structure is when q is 0, which is homogeneous in left and right. The larger q, the greater the twist angle in one direction, thus increasing the dynamic instability. There are many differences depending on the alignment stability of the alignment layer and the elastic modulus of the liquid crystal. The stability was experimentally confirmed within the major axis of the slit pattern and the range of 45 °. In LFIVA mode, a wide viewing angle is realized because parallel alignment, right-hand twisted structure, parallel-aligned, and left-hand twisted structure appear in succession.

A cross-sectional structure of a metal insulator metal (MIM) liquid crystal display device in LFIMD mode is shown in FIG. Currently, the most widely used MIM device is a stacked structure of Ta, Ta ₂ O ₃ and Cr. Ta ₂ O ₃ film is made by anodizing Ta film. The upper glass substrate 2 has a signal line made of ITO, and the lower glass substrate 1 has a scanning line made of two layers of Ta and Ta ₂ O ₃ , a MIM element, and a pixel electrode 5 made of IT0. The part where the signal line and the pixel electrode overlap with each other is a transparent part of the pixel. The upper glass substrate of the MIM liquid crystal display element has the same structure as the simple active element liquid crystal display element. Apply a Ta film about 2000A ° on the lower glass substrate, perform a photo and etching process to make a T-shape, and anodize the Ta film to make a Ta ₂ O ₃ film, and then apply Cr film on it to make a pattern by photo and etching process. A pixel electrode is made of an ITO film, which is a transparent conductive film. The IT0 film and the Cr film are in contact with each other. A vertical alignment liquid crystal display device can be realized as shown in FIG. 3 by using a slit pattern or a floating electrode as shown in FIG. 9 or using a side electric field and a vertical electric field between the signal line and the pixel electrode.

The process of making the most representative TFT among the active liquid crystal display devices is as follows.

1) Gate electrode formation

The larger the resolution, the shorter the selection period. Therefore, the signal delay is reduced by using a metal with low specific resistance such as Al. However, pure Al is weak in chemical resistance and has a hillock in which a specific part grows up to several μm at 20 ° C or higher. Thus, Al ₂ O ₃ is coated on the surface by anodizing at room temperature or a metal structure such as MoW is doubled. Laminate. Although the resistivity is lower than that of pure Al, Al alloys such as Al-Nd, which have excellent chemical resistance and thermal stability, are used.

2) gate insulating film formation, amorphous silicon, etching stopper (etching stopper) formation

As the gate insulating film, many double layers of SiOx grown by APCVD and SiN _x grown by PECVD are used. The gate insulating film has a double film structure such as SiO _x / SiN _x , TaO _x / SiN _x , AlO _x / SiN _x . A-Si: H and E / S films are successively deposited on the gate insulating film. When depositing amorphous Si: H, a mixed gas of SiH ₄ and H ₂ is used, and SiNX of an E / S film uses a mixed gas of SiH ₂ , NH ₃ , and N ₂ .

3) Etch stop film formation

The exposure process can be used by combining the front exposure of the E / S dedicated mask and the back exposure using the gate pattern as the exposure mask. If both front and back exposures are used, semi self-aligning TFTs can be made, and only back exposure can produce fully self-aligning TFTs.

4) n ⁺ layer forming

The ohmic contact layer is made of a mixed gas of SiH ₄ , PH ₃ , H ₃ .

5) Amorphous Silicon Layer Formation

N ⁺ and amorphous silicon are etched to form a pattern.

6) pixel electrode formation

Transparency electrode ITO (Indium Tin Oxide) is deposited by sputtering, exposed and wet etched with aqua regia.

7) Source and drain electrode formation

Source drain and signal line electrodes are made.

8) Protective film formation

A protective film is made of SiN _x or the like in order to prevent the TFTs from being damaged or degraded due to scratches and moisture infiltration during rubbing or conveyance of the liquid crystal cell process.

9) Etching Shield

Peel off the protective film on the electrode pad portion of the scan line and the signal line to be connected to the external driving circuit.

The least productive part of the above process and yield is the formation of the pixel electrode. Conventional pixel electrodes are mostly ITO, which is a transparent conductive film, which is not dry etched but wet etched with aqua regia. It takes a long time to etch the ITO, and because the aqua regia dissolves most of the minerals, if there is a defect such as a small crack (cracks) in the TFT structure, the acu repel penetrates and etches the other wiring, so that the yield decreases. Currently, TFT equipment companies are discussing various methods of dry etching of ITO, but in this case, the unit process takes a long time, so the productivity is low and it has not been applied yet.

In the present invention, without using ITO, which is difficult to etch, the present invention has been invented for various conditions of the LFIVA mode in which a pixel electrode is formed at the same time when the source electrode and the drain electrode are made, thereby reducing the number of processes to increase productivity and yield.

1 is a cross-sectional view of a liquid crystal cell of a conventional vertically aligned TFT liquid crystal display device.

2 is a cross-sectional view of a liquid crystal cell of a vertically aligned TFT liquid crystal display device of the present invention.

Fig. 3 An example of the orientation of liquid crystal molecules in LFIVA mode

4 shows the shape of the pixel electrode, the alignment of the alignment layer, and the transmission axis direction of the polarizing plate.

5 The shape of the pixel electrode, the alignment direction of the vertical alignment film, and the transmission axis direction of the polarizing plate when the floating electrode is used.

6 is a plan view of a pixel electrode and a slit pattern

7 Shapes of the various electrodes of the present invention

8 is a cross-sectional view of a liquid crystal cell of a conventional vertically aligned MIM liquid crystal display device.

9 is a cross-sectional view of a vertically aligned MIM liquid crystal display device of the present invention.

10 is an example of an electro-optic transmission curve of a vertical alignment liquid crystal display device of the present invention.

※ Explanation of codes for main parts of drawing

1 Active element glass substrate 2 Common electrode glass substrate 3, 3 'vertical alignment layer

4 negative liquid crystal 5 pixel electrode 6 common electrode

7 Slit Pattern 8 Source Electrode 9 Drain Electrode

11 Gate electrode 14 Orientation direction 15 Transmissive axis of photosensitive plate

16 Transmission axis of analyzer plate 30 Floating electrode 20 Insulation film

2 is a cross-sectional view of a TFT liquid crystal display device of the present invention. In FIG. 2, the pixel electrode is formed in the same manner as the source electrode 8 and the drain electrode 9. In the case of the structure as shown in Fig. 2, the ITO portion is omitted in the above TFT process and the rest is the same as before. When the present invention is applied to a MIM liquid crystal display device, a scan line is applied, an anodization of the scan line is performed, and a thin film of Cr, a pixel electrode, is immediately formed to form a pixel electrode having a slit pattern. When the pixel electrode is made of a metal film, light transmission is limited to the slit pattern portion etched, so the width of the slit pattern and the width of the pixel electrode pattern should be well controlled to increase the light transmittance. If the width of the slit pattern is small, the light transmittance is low. If the width of the slit pattern is large, the driving voltage is high and the side electric field is generated only at the edge of the pixel electrode. In order to find the optimal condition, computer simulation using finite element method should be used to optimize the transmittance, driving voltage, viewing angle, and response characteristics of the liquid crystal cell. The computer simulation results are as follows. When both the width of the slit pattern and the line width of the pixel electrode were small (<5 μm), the liquid crystal molecules of liquid sound did not lie down in the center of the slit pattern because of the elastic force of the liquid crystal molecules, resulting in low transmittance. On the other hand, when the width of the slit pattern is large and the width of the pixel electrode is also large (> 10㎛), the azimuth angle of the negative liquid crystal molecules is concentrated around 45 ° by the side electric field, so that the azimuth angle of the negative liquid crystal molecules is about 45 °, and the center of the slit pattern is 0 °. Therefore, if the transmission axis of the polarizer is 45 °, the transmittance is low at the corners of the pixel electrode. On the contrary, if the transmission axis of the polarizer is 0 °, the transmittance is lowered at the center of the slit pattern. The orientation direction at this time was the major axis direction of the slit pattern. In the case where the width of the slit pattern is large (> 10 μm) and the line width of the pixel electrode is small (<5 μm), the change in the side electric field is uniformly changed in the entire pixel and is larger than the elastic force of the liquid crystal molecules. When the negative liquid crystals of the liquid crystals were 180 ° and 0 °, and the transmission axis of the polarizing plate was placed at 45 °, the light transmittance was almost 90% or more. Fig. 11 is an electro-optical transmission curve when the polar angle is 50 ° when the line width of the pixel electrode is 4 m and the width of the slit pattern is 10 m. It can be seen that there is little change in transmittance depending on the azimuth angle. When there is a floating electrode as shown in Fig. 5, the side electric field between the pixel electrode and the floating electrode becomes stronger, and the vertical electric field becomes weak on average. In this case, although the transmittance is very low, the side electric field component becomes stronger, so that a wider viewing angle can be realized because negative liquid crystal molecules are arranged in the left and right directions based on the long axis of the slit pattern. The driving voltage varies depending on the width of the slit pattern (d1 in FIG. 7) and the width of the pixel electrode (d2 in FIG. 7). The larger the width of the slit pattern is, the higher the driving voltage is. On the contrary, the smaller the width of the slit pattern is, the lower the driving voltage is. In particular, when the LFIMD is realized by using the floating electrode, the viewing angle and the driving voltage must be well balanced. Since the value of the elastic modulus (K22) of the currently used liquid crystal is approximately 10pN, the threshold voltage should be 4V or less to drive about 10V, and the width of the floating electrode and the width of the slit pattern should be within about 20 μm. If the slit pattern width is 3 μm or less, the liquid crystal cannot overcome the elasticity, and the viewing angle improvement effect is very small.

When all the alignment layers of the lower glass substrate are aligned, the lying direction of the negative liquid crystal is determined before the voltage is applied, thereby improving the reaction characteristics. If only the vertical alignment film of one substrate is subjected to a rubbing treatment, the response is slow because the direction in which negative liquid crystals lie after the voltage is applied to the opposite substrate is determined. However, when the glass substrate with the active element is oriented, the yield decreases due to static electricity or dust generated during the alignment process, so that the vertical alignment layer of the glass substrate with the active element is not oriented. The vertical alignment film is oriented by rubbing, photo-alignment or vapor deposition such as SiO, but at present, the rubbing method is generally assumed. The orientation direction in the rubbing method becomes the rubbing direction, and in the optical orientation, it is the electric field direction of incident light, and in the vapor deposition method, the incident angle of the material to be deposited. In the LFIMD mode, when the vertical inclination film is aligned vertically, the response characteristic decreases when the vertical inclination is close to the vertical. On the contrary, when the deviation is 90 °, the liquid crystal is oriented in a constant direction without voltage applied. It acts as a light leakage and reduces the contrast ratio. Therefore, the pretilt angle of the vertical alignment film should be properly adjusted. The pretilt angle of the oriented vertical alignment film depends on the product standard, but the product from JSR, NISSAN, etc. can realize 80 ~ 89 ° range. Orientation is performed to have a pretilt angle of 84 to 89 degrees. Liquid crystal display devices used in simulators, such as aircrafts, in which response characteristics are very important, have a pretilt angle of 83 to 85 degrees for the aligned vertical alignment film.

Vertical alignment liquid crystal cells using negative liquid crystals have poor image quality due to gray level inversion in the direction of 45 ° to the transmission axis of the polarizing plate. Like other vertically aligned liquid crystal cells, LFIMD mode has a degree of difference, but there is a color phenomena due to the change of transmittance of R (red), G (green), and B (blue) color according to the gray level inversion and direction. Color shading can be reduced by adjusting the shape and direction of the slit pattern of one pixel. As shown in FIG. 7, if the width d1 of the slit pattern and the distance d2 between the adjacent slit patterns are different in each pixel, the magnitude of the horizontal and vertical electric fields in each region is different, and thus the average effect according to the voltage (halttone gray scale). Also, since the light passing obliquely through the liquid crystal layer passes through various alignment structures, the effect of color shift and gray level inversion can be reduced. In addition, the slit patterns of the pixels, the shapes of the floating electrodes, and the shapes of the floating electrodes are changed, respectively, so that the transmittance and color phenomena can be minimized even though each pixel is subjected to the same voltage.

8 illustrates an example of a slit pattern in a pixel electrode and a common electrode in consideration of color light phenomenon, transmittance, and interference with surrounding wiring (scanning line, signal line). In the figure on the right, the long axis direction of the slit pattern is different from 90 ° in one pixel. The figure on the right is a characteristic in consideration of the transmittance and the viewing angle at the same time to reverse the bending direction (φ) of the slit pattern with respect to the center. As φ increases, the transmittance decreases because the arrangement of liquid crystal molecules is different from each other. The transmission is the lowest when φ is 45 degrees.

It should be between 0.8 and 1.2 times the product of the refractive index anisotropy (Δn) of the liquid crystal and the thickness of the liquid crystal layer (d). Assuming that the transmittance of light incident at 60 ° is about 60% of the front when the brightest voltage is applied to the liquid crystal layer, the transmittance of light at a voltage below the threshold is 6% or less. The ratio is ten. In the state where the transmission axis directions of the polarizing plate and the analyzer plate are orthogonal to each other, the specification of the phase plate can be derived from the condition that the phase difference δ should be less than about 30 ° so that the contrast ratio is 10 or more. The widest viewing angle is when Δnd of the liquid crystal cell and the phase plate are the same. Transmittance is greatest when Δnd is half wavelength. Since the liquid crystal molecules do not lie in the vicinity of the alignment film, Δnd is usually larger than half wavelength. The product of the refractive index anisotropy (Δn) and the liquid crystal layer thickness (d) of the liquid crystal at a wavelength of 550 nm is set in a range larger than 0.25 µm and smaller than 0.35 µm.

The TFT liquid crystal display device of the present invention has a lower light transmittance than when using a conventional transparent conductive material, but shortens the number of processes, and also improves the yield since it does not use ITO, which is the most problematic problem in the TFT process. In particular, when the area of the substrate is large, when the present invention is applied to make a TFT liquid crystal display device, the viewing angle is wide, the reaction time is fast, and the yield is improved. In addition, when applied to the MIM liquid crystal display device according to the present invention, since the device can be made in two steps of the exposure process, the productivity is very high. In addition, the viewing angle characteristic is maximized by changing the line width of the slit pattern and the direction of the major axis of the slit pattern for each pixel. The multi-zone vertical alignment liquid crystal display device of the present invention has a fast response time and a wide viewing angle, and thus is suitable as a display device of a large monitor for multimedia.

Claims (11)

A vertical alignment film is coated on the upper and lower glass substrate substrates; Liquid crystals having negative dielectric anisotropy (Δε) are injected between the vertical alignment films; At least one of the two glass substrates has the vertical alignment film oriented so that the pretilt angle of the liquid crystal molecules in the alignment film is smaller than 90 °; The pixel electrode 5 of the glass substrate with active elements is a metal film, and the pixel electrode is formed with a slit pattern 7 or a floating electrode 30 from which the metal film is etched, and the direction of the electric field induced by the slit pattern or the floating electrode. A vertical alignment liquid crystal display device having a structure in which liquid crystal molecules between adjacent slit patterns when the liquid crystal layer is subjected to a voltage greater than or equal to the threshold by adjusting the alignment direction of the vertical alignment layer are twisted in the left hand direction and twisted in the right hand direction. The liquid crystal display of claim 1, wherein the active element is a thin film transistor (TFT) and the material of the pixel electrode is a signal line. The liquid crystal display of claim 1, wherein the active element is a metal insulator metal (MIM) and the pixel electrode is made of a scanning line. The liquid crystal display of claim 1, wherein an angle formed between the long axis of the slit pattern and the alignment direction of the vertical alignment layer is smaller than 30 degrees. The liquid crystal display device of claim 1, wherein a product of the refractive index anisotropy (Δn) of the liquid crystal and the liquid crystal layer thickness (d) at a wavelength of 550 nm is larger than 0.25 µm and smaller than 0.35 µm. The liquid crystal display device according to claim 1, wherein the width in the short axis direction of the slit pattern is 4 to 20 µm or the width of the floating electrode is 4 to 20 µm. The liquid crystal display device according to claim 1, wherein an angle formed between the transmission axis of the polarizing plate and the major axis direction of the slit pattern is 0 to 45 degrees. The method of claim 1, wherein the shape of the slit pattern (or the floating electrode) is "[" or "]" shaped; The bending angle of the slit pattern (or floating electrode) to the center and top or to the center and bottom is 10 to 20 °; The angle between the alignment direction of the vertical alignment film and the major axis direction of the center slit pattern (or floating electrode) is less than 45 °; A liquid crystal display device having an angle of 30 to 60 degrees between the transmission axis of the polarizing plate and the long axis direction of the longest slit pattern. The liquid crystal display device according to claim 1, wherein the width of the slit pattern or the width of the floating electrode or the distance between the floating electrode and the pixel electrode is two or more types in one pixel. The liquid crystal display device of claim 1, wherein the width of the slit pattern, the width of the floating electrode, or the distance between the floating electrode and the pixel electrode, the shape of the slit pattern, or the direction of the major axis of the slit pattern is different for each pixel. The product of the refractive index anisotropy of the liquid crystal according to claim 1, wherein the product of the refractive index difference (n _Z- (n _x + n _y ) / 2) of the light vibrating in the horizontal direction and the thickness of the retardation plate is the product of the refractive index anisotropy ( Liquid crystal display element which is between 0.8 and 1.2 times the product of Δn) and the liquid crystal layer thickness d.