JPH08179296A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display element which has a wide field angle by arranging a normal pixel and a voltage drop pixel for each pixel. CONSTITUTION: On the insulating film of a color filter 33, etc., formed on a counter electrode 31, a stripe electrode 35 which is set in a potential the same as that of the counter electrode is formed in approximately 30 to 50% area of pixels. The insulating film of the color filter 33, etc., has 1 to 2μm thickness. A part of each pixel where the stripe electrode 35 is not formed is applied with a voltage which is stepped down by the insulating film and a part of each pixel where the stripe electrode 35 is formed is applied with a voltage which is not stepped down to form areas is different orientation states in one pixel, thereby widening the angle of visibility.

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 device having a wide viewing angle.

[0002]

2. Description of the Related Art Liquid crystal display devices can be made thin and lightweight and are used as display devices for various electronic devices. However, the liquid crystal display element has a drawback that the viewing angle is narrower than that of a CRT or the like, and that the viewing angle dependency during halftone display is remarkable. For example,
In a TN liquid crystal display element constituted by sandwiching a TN (twisted nematic) liquid crystal cell between a pair of polarizing plates, it has a practically sufficient viewing angle characteristic when displaying black and white binary.
When displaying halftones with 8 or more gradations, there is a drawback that the viewing angle dependency is large.

This point will be specifically described with reference to the drawings. First, the definition of angles (definition of vertical and horizontal directions) used in the description and the arrangement of the TN liquid crystal display element viewed from the viewing direction are
As shown in FIG.

Alignment treatment such as rubbing is applied to the opposing surfaces of a pair of substrates constituting the TN liquid crystal display element in a direction orthogonal to each other. Corresponding to this alignment treatment, the TN liquid crystal is twisted clockwise by 90 ° from the lower substrate to the upper substrate. One of the pair of polarizing plates arranged to sandwich the TN liquid crystal cell is arranged so that its optical axis (transmission axis or absorption axis) is parallel or orthogonal to one of the alignment treatment directions, and the other polarizing plate is The optical axis is arranged so as to be orthogonal or parallel to the optical axis of one polarizing plate.

A typical log Y-V curve (Y: luminance, V:
21 and 22 show the viewing angle dependence of the voltage applied to the liquid crystal).
FIG. 23 shows a log Y-θ (viewing angle) curve. That is,
21 (A) to 22 (B) are defined in FIG.
23 shows typical log Y-V curves for each viewing angle when the TN liquid crystal display device is observed from the bottom, right, and left directions, respectively.
(A) and (B) show typical log Y-θ curves for each applied voltage when the TN liquid crystal display device is observed from the upper, lower, left and right directions. Note that these characteristics are such that the liquid crystal display element is a positive type (normally white), and the transmission axis of the incident side polarizing plate and the direction of the orientation processing of the incident side substrate are approximately 90 °.
And the cell gap is 5 μm, Δn
It was obtained when d was 380 nm (λ = 580 nm).

As shown in FIG. 21A, in the upward direction,
Although the luminance Y increases as the viewing angle θ increases and the black level becomes white, the gradation inversion phenomenon is not conspicuous (lo
As long as the gY-V curve is a monotonically decreasing function, the gradation inversion phenomenon does not occur). However, as shown in FIG.
In the downward direction, for example, when the viewing angle is θ = 50 °, when the applied voltage is about 2V, the luminance Y is the smallest, and when the applied voltage is about 3V, the brightness Y is maximized and the gradation inversion phenomenon occurs. Figure 2
As shown in FIGS. 2 (A) and 2 (B), the left and right characteristics are symmetrical, and when the viewing angle θ = 50 °, the luminance Y is the smallest at about 3V, and becomes the maximum at about 6V. The gradation reversal phenomenon occurs.

Next, the display voltage of each gradation of 8 gradations is defined as follows. (1) The bright state voltage is fixed to 1.5V, and (2) the dark state voltage is fixed to 6.0V. (3) 6
It is assumed that one halftone voltage is a voltage having a value obtained by dividing the luminance Y at 1.5V into seven equal parts. Then, set the eight voltages from V to V
₁ , ..., Let's call it V ₈ .

In FIGS. 23A and 23B, the voltage is V ₁ , ...
..., luminance Y ₁ when fixed to V _8, ......, show the changes to the viewing angle θ of Y _8. It can be understood from FIGS. 23 (A) and 23 (B) that even if the order of the 8 gradations is correctly taken on the front side, the order of the gradations is disturbed when the viewing angle θ is changed in the up, down, left, and right directions. The range of the viewing angle θ in which the luminance order of 8 gradations can be correctly taken is −23 ° to + 23 ° (−: downward, +:
-34 to + 34 ° (-: leftward, up)
+: To the right). As described above, in the conventional TN liquid crystal display element, the range of the viewing angle θ at which halftone can be normally displayed is narrow, that is, the viewing angle is narrow.

As a method of widening the viewing angle, a method has been proposed in which each pixel is divided into a plurality of pixels and one of the divided pixels is connected with a control capacitor in series with a liquid crystal capacitor. In this method, the voltage applied to the liquid crystal layer drops in the divided pixels to which the control capacitors are connected, so that regions having different alignment states are formed in each pixel, and the viewing angle is widened.

However, in this method, the control capacitance is set to the TFT.
Since it is formed on the substrate on which the TFT is formed, the yield of the TFT substrate is reduced. Further, since the control capacitor is made of metal inside the pixel, the aperture ratio is reduced and the displayed image is dark.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device having a high yield rate, a high aperture ratio, and a wide viewing angle.

[0012]

In order to achieve the above object, a liquid crystal display element according to a first aspect of the present invention comprises a first substrate and a second substrate which is arranged so as to face the first substrate.
A substrate, a first electrode formed on a surface of the first substrate facing the second substrate, and a region disposed on the second substrate and facing the first electrode in the pixel region. And a liquid crystal sealed between the first and second substrates, and a polarizing plate disposed on at least one of the first and second substrates. The first electrode is arranged in a lower layer of an insulating film arranged in each pixel region, and is arranged in a lower layer electrode forming the first region, and is arranged in an upper layer of the insulating film so as to be connected to the lower layer electrode. And a different voltage is applied to the liquid crystal in the first region and the second region in the same pixel.

The insulating film may be composed of a color filter arranged in each pixel, an insulating overcoat layer formed on the color filter, and the like. The dielectric constant of the insulating film is 3.0 to 4.0, and the thickness is 1.0 to 2.0 μ.
m, the ratio of the area of one pixel to the area of the first region in each pixel is 30 to 50%, and the retardation value Δn of the liquid crystal is
-By setting d to be 300 to 600 nm, the characteristics of the liquid crystal display element can be optimized.

[0014]

According to the above configuration, the first region and the second region of each pixel are
Different voltages are applied in the region. Therefore, the first
The area and the second area show different voltage-luminance characteristics. Therefore, for example, if the maximum of the applied voltage-luminance curve in the first region and the minimum of the applied voltage-luminance curve in the second region are generated at the same voltage, the average voltage-luminance characteristic monotonously increases. By drawing a curve or a monotonous descending curve, it is possible to suppress grayscale inversion between adjacent grayscales and widen the viewing angle.

[0015]

Embodiments of the present invention will be described below with reference to the drawings by taking a TFT liquid crystal display device as an example. FIG. 1 shows a sectional structure of a TN liquid crystal display device according to an embodiment of the present invention.
2 shows a planar structure of the TFT substrate, and FIG. 3 shows a planar structure of the counter substrate.

As shown in FIG. 1, this liquid crystal display device is
A pair of transparent substrates 11 and 1 joined by a sealing material SC
2 and a TN sealed between the pair of transparent substrates 11 and 12
A liquid crystal cell 16 including a (twisted nematic) liquid crystal 13 and polarizing plates 14 and 15 arranged with the liquid crystal cell 16 interposed therebetween.

The transparent substrates 11 and 12 are made of glass or the like. On the lower transparent substrate (hereinafter, TFT substrate) 11,
As shown in FIGS. 1 and 2, T as an active element
FTs (thin film transistors) 21 and pixel electrodes 22 are arranged in a matrix, and an alignment film 23 is arranged thereon. The TFT 21 is connected to a gate electrode formed on the TFT substrate 11, a gate insulating film formed to cover the gate electrode, a semiconductor layer formed on the gate insulating film facing the gate electrode, and connected to the semiconductor layer. And a source electrode and a drain electrode.

The source electrode of each TFT 21 is connected to the corresponding pixel electrode 22, the gate electrode of the TFT 21 in each row is connected to the corresponding gate line GL, and the TFT 2 in each column is connected.
The drain electrode of No. 1 is connected to the corresponding data line DL. The pixel electrode 22 is formed of a transparent conductive film made of ITO (oxide of indium and tin) or the like.

A counter electrode (lower layer electrode) 31 is formed on the other transparent substrate (hereinafter, counter substrate) 12. The counter electrode 31 is made of ITO having a thickness of about 0.08 ± 0.02 μm and is applied with a predetermined voltage, for example, a ground voltage. A light-shielding black mask 32 is arranged at a portion of the counter electrode 31 that faces the TFT 21 and a portion that faces the portion between the pixel electrodes 22. The black mask 32 is composed of a metal film or the like having a thickness of about 0.15 μm. In each pixel area of the counter electrode 31, color filters 33 (33R, 33G, 33B) of RGB colors are arranged. The color filter 33 is made of an acrylic resin or the like with a pigment added to have a thickness of about 1.0 μm, and is colored R, G, or B with the pigment. The color filter 33 may be arranged by any method such as stripe, diagonal mosaic, or triangular mosaic.

Color filters 33 (33R, 33G, 3)
3B), an overcoat layer (protective layer) 34 is arranged on the entire surface of the substrate. The overcoat layer 34 is
It is made of acrylic resin or the like having a thickness of about 1 μm. As shown in FIG. 3 or 4, on the overcoat layer 34, stripe-shaped electrodes (upper layer electrodes) 35 arranged so as to be located in the respective pixel regions are arranged. The stripe electrode 35 is made of ITO having a thickness of about 0.08 ± 0.02 μm, is connected to the counter electrode 31 at its end or the like, and is maintained at the same potential as the counter electrode 31. An alignment film 36 made of polyimide or the like is formed on the stripe electrode 35 and the overcoat layer 34.

The orientation film 23 on the lower side in FIG. 1 is subjected to orientation treatment such as rubbing in the direction shown by the broken line in FIG. 5 (direction of 0 °), and the orientation film 36 on the upper side is indicated by the solid line in FIG. The orientation treatment is applied in the direction (direction of 90 °) indicated by.

The liquid crystal 13 is composed of a nematic liquid crystal to which a chiral agent is added, and the lower substrate 11 is subjected to an alignment treatment.
From the top to the upper substrate 12 in the clockwise direction by 90 ° (0 ° ~
-90 °) Twisted and oriented.

The lower (light incident side) polarizing plate 14 is set so that its transmission axis is perpendicular (90 °) to the direction of the alignment treatment applied to the lower alignment film 23, and the upper (light incident side) polarizing plate 14 is set. Output side)
The polarizing plate 15 is set so that its transmission axis is perpendicular to the transmission axis of the lower polarizing plate 14.

In the liquid crystal display device having such a structure,
By applying a voltage between the pixel electrode 22 and the counter electrode 31 and the stripe electrode 35, the alignment state of the liquid crystal 13 continuously changes, and the amount of light passing between the polarizing plates 14 and 15 changes. The display gradually darkens. Moreover, the transmitted light is colored by each color filter 33. Therefore, by controlling the gate pulse applied to the gate line GL, the on / off of the TFT 21 is controlled, and a desired gradation voltage is written in the pixel electrode 22 via the data line DL, thereby enabling color gradation display. Become.

In the region where the stripe electrode 35 is arranged, the voltage between the pixel electrode 22 and the stripe electrode 35 is applied to the liquid crystal 13. On the other hand, the stripe electrode 3
In the area where 5 is not arranged, the voltage stepped down by the color filter 33 and the overcoat layer 34 is applied to the liquid crystal 13.
Is applied to For this reason, regions of different alignment states are formed in each pixel and their optical characteristics are averaged, so that the viewing angle becomes wide. Further, unlike the configuration in which the control capacitor is arranged on the TFT substrate, the aperture ratio does not decrease, the manufacturing process on the TFT substrate 11 side, which is difficult to manufacture, does not increase, and the manufacturing process on the counter substrate 12 side also slightly increases. And
The device is easy to manufacture.

Next, the viewing angle characteristics of the liquid crystal display device of this embodiment will be described in more detail. FIG. 6 shows an enlarged cross section of each pixel. In such a configuration, each pixel has an area (divided pixel) A1 having an area of S1 and an area (divided pixel) A1 having an area of S2.
In one region A1, the stripe electrode 35 applies a voltage to the liquid crystal 13 via the alignment film 36. Such a structure is called a top ITO structure. In the other area A2, the counter electrode 31 applies a voltage to the liquid crystal 13 via the color filter 33, the overcoat layer 34, and the alignment film 36. Such a structure is called a bottom ITO structure.

In the area A1 of the top ITO structure, the voltage V applied between the pixel electrode 22 and the stripe electrode 35 is applied.
1 is applied to the liquid crystal 13 almost as it is (here, the voltage drop in the alignment films 23 and 36 is ignored.
Since the voltage drops due to 3, 36 are substantially the same in the areas A1 and A2, practically no problem occurs even if ignored. In the area A2 of the bottom ITO structure, the voltage V2 (V1 = Vi + V2), which is a voltage drop caused by Vi in the insulating film of the color filter 33 and the overcoat layer 34, is applied to the liquid crystal 13.

The cell gap, that is, the thickness of the layer of the liquid crystal 13 is d1 common to both divided pixels, and the insulating film (the color filter 33 and the overcoat layer 34) for dropping the voltage.
Is the thickness of di. Liquid crystal 1 that changes with applied voltage
The relative permittivity of 3 is ε LC, and the relative permittivity of the liquid crystal 13 in the parallel direction is ε LC.
‖, The vertical relative permittivity of the liquid crystal 13 is represented by ε⊥, and the spatial relative permittivity defined by Equation 1 is represented by εAV.

## EQU00001 ## .epsilon.AV.ident. (. Epsilon..parallel. + 2.epsilon..perp.) / 3 Hereinafter, the divided pixel A1 is called a normal pixel and the divided pixel A2 is called a voltage drop pixel.

From the viewpoint of an equivalent circuit, the voltage drop pixel A2 has a structure in which the liquid crystal capacitor CLC and the insulating film capacitor Ci are connected in series. Therefore, the voltage drop pixel A2 is
It can be characterized by the following two parameters.

(2) Voltage drop rate: α≡Vi / V1 = 1 / (R + 1) Voltage stretch rate: β≡V1 / V2-1 = 1 / R where R≡Ci / CLC Ci ≡εi ・ S2 / di CLC = ΕLC ・ S2 / di

The voltage drop rate α indicates the rate of voltage drop caused by the color filter 33 and the overcoat layer 34 when the voltage V1 is applied between the pixel electrode 22 and the counter electrode 31. In order for the voltage drop pixel A2 to have the same brightness as the normal pixel A1, it is necessary to apply a higher voltage to the voltage drop pixel A2. Voltage stretch ratio β is insulation film 3
3, 34 shows the proportion of voltage that must be applied higher. The liquid crystal capacitance CLC is a monotonically increasing function with respect to the applied voltage, where C‖ and C⊥ are given as the upper and lower limits of the liquid crystal capacitance, respectively.

[Equation 3] C‖≡ε‖ ・ S2 / d1 C⊥≡ε⊥ ・ S2 / d1

The voltage drop rate α and the voltage stretch rate β increase as the applied voltage increases. Therefore, the average voltage drop rate αAV and the average voltage stretch rate βAV are defined as in Equation 4.

[Formula 4] αAV≡1 / (RAV + 1) βAV≡1 / RAV RVA≡Ci / CAV CAV≡εAV ・ S2 / d1

Regarding the voltage stretch ratio β, when the applied voltage of the normal pixel A1 when 50% luminance (50% of maximum luminance) Y50 is obtained and the stretch voltage is defined as V50, ΔV50 is defined as It is given by the number 5.

[Formula 5] ΔV50≡ {CLC (V50) / Ci} · V50 ΔV50 is caused by the voltage drop in the insulating films 33 and 34, and Y−
The shift amount of the V curve in the voltage axis direction is shown. Fig. 7 shows V50 and Δ
A definition diagram of Y50 is shown.

The display characteristics of the entire pixel are determined by the area average of the display characteristics of the normal pixel A1 and the voltage drop pixel A2. If the ratio of the area S2 of the voltage drop pixel A2 to the total area S1 + S2 of one pixel is S, the area ratio S is given by the equation 6.

[Equation 6] S≡S2 / (S1 + S2)

Color filter 33 and overcoat layer 3
The relative permittivity εi of the insulating film made of 4 was set to 3.5, and the thickness di of the insulating film and the area ratio S were changed as shown by ◯ in Table 1, and the tendency of the 8-gradation viewing angle was analyzed.

[0035]

[Table 1]

The relative permittivity of the color filter 33 differs for each color of RGB, and for example, ε for a frequency of 100 HZ.
It has values of R = 3.4, εG = 3.8, εB = 3.2. Here, 3.5 which is the average value of these is adopted as the relative dielectric constant. The relative dielectric constant of the overcoat layer 34 is also 3.5.

The liquid crystal 13 has T having the following physical properties.
N (nematic) liquid crystal was used.

Refractive index wavelength dependence

[Table 2] Pretilt angle θ0 = 3 ° Twist angle φ0 = −90 ° Cell gap d = 5 μm Δn · d = 380 nm (λ = 589 nm) Anchoring strength de / d = 0 (strong anchoring)

A 1% chiral agent having the following physical properties is added to the nematic liquid crystal having the above physical properties.

As the polarizing plates 14 and 15, those having the following characteristics were used. Refractive index wavelength dependence

[Table 3] Thickness of polarizer dpol = 35 μm Parallel transmittance T‖ = 34.12 Cross transmittance T⊥ = 0.019

First, the area ratio S was fixed at 50%, and the thickness di of the insulating film composed of the color filter 33 and the overcoat layer 34 was changed to 0.0, 0.4, 1.0, 1.4, 2.0 and 2.4. The average voltage drop rate αAV, the average voltage stretch rate βAV, and ΔV50 at this time are as shown in Table 4.

[0042]

[Table 4]

FIG. 8 shows the relationship between the display contrast and .DELTA.V50. In FIGS. 9A to 9C, when an image with different gradations is displayed in 8 steps, the phenomenon that adjacent gradations are inverted occurs. The relationship between the angle and ΔV50 is defined in FIG. 5, which is shown in the lower, upper and right directions. The left direction has the same characteristics as the right direction.

The brightness of the nth gradation is Yn, and the voltage at that time is Vn
(N = 1, 2, ..., 8) is defined as follows. V1 = 1.5V, V8 = 6.0V, contrast = Y1 /
Y8 Brightness Y between adjacent gradations when observed from the bottom, top and right
The minimum angle (viewing angle) at which the reversal occurs is θdow
Let n, θup, and θright. It should be noted that θ is an angle formed by the line of sight and the normal line of the display surface of the liquid crystal display element.

As shown in FIG. 8, the contrast sharply decreases as ΔV50 increases. This is the voltage drop pixel A
This is because the Y-V curve of 2 is stretched so that the black level is lowered and becomes whitish, and the white level is almost the same as that of a normal pixel. As shown in FIG. 9A, when ΔV50 = 0.820V, the downward viewing angle θdown is twice or more that of a normal pixel (ΔV50 = 0) (23 ° spreads to 50 °). The thickness of the insulating film when ΔV50 = 0.820V is 1.4 μm. As shown in FIG. 9B, the viewing angle θup in the upward direction hardly changes. As shown in FIG. 9C, the viewing angle θright in the right direction monotonically widens as ΔV50 increases.

Next, with ΔV50 fixed at 0.820 V,
The contrast and the viewing angle were measured when the area ratio S was changed to 30, 40, 50, 60, 70%. FIG. 10 shows the relationship between the contrast and the area ratio S. FIG. 11 (A)-
(C) shows the relationship between the angle (viewing angle) at which a phenomenon occurs in which adjacent grayscales are inverted and S in the downward, upward, and rightward directions. The left direction has the same characteristics as the right direction.

As shown in FIG. 10, the contrast decreases as the area ratio S increases. This is because as the area ratio S increases, the ratio of the voltage drop pixel A2 to each pixel increases. As shown in FIG. 11 (A), the downward viewing angle θdown becomes maximum when S = 40%, and the viewing angle θdo
wn widens to 54 °. As shown in FIGS. 11B and 11C, the viewing angles θup and θright in the upper direction and the right direction hardly change even if the area ratio S changes. S = 0, 10
The viewing angle in the case of 0% usually matches the viewing angle of the pixel A1.

From the above trend analysis, the downward viewing angle θdo
It can be concluded that the optimum values of the insulating film thickness di and the area ratio S for obtaining the optimum value (maximum value) of wn are 1.4 μm and 40%, respectively. The contrast at this time is 1 for normal pixels.
/ 4 (1190 is reduced to 302).

The characteristics of the brightness Y and the applied voltage of the liquid crystal display device optimized as described above are shown in FIGS. It is shown in B) for each viewing angle. Similarly, FIG. 14 (A), (B), FIG.
(A) and (B) show the logY-applied voltage characteristics,
The viewing angles are shown in the bottom, right, and left directions.

Further, the optimized characteristics of the luminance Y and the viewing angle of the liquid crystal display element are shown in FIG.
Each of the applied voltages is shown in (A) and (B). Similarly, FIG.
(A) and (B) show the logY-viewing angle characteristics in the vertical direction,
The left and right directions are shown for each applied voltage.

As shown in FIG. 14A, in the upward direction, the luminance Y increases with the increase of the viewing angle, and the black level becomes white, as in the conventional characteristic shown in FIG. 21A. However, the reversal phenomenon of gradation is inconspicuous (the reversal phenomenon of gradation does not occur as long as the YV curve is a monotonically decreasing function). As shown in FIG. 14B, in the downward direction, the luminance Y decreases as the viewing angle increases. However, unlike the conventional characteristic shown in FIG. 21B, the YV curve with a viewing angle of 50 ° does not have a gradation inversion phenomenon because it is a halftone and has no bumps.

As shown in FIGS. 15 (A) and 15 (B), the luminance Y also decreases in the left-right direction as the viewing angle increases. However, unlike the conventional characteristics shown in FIGS.
The Y-V curve at 0 ° has a shallow valley at the halftone voltage,
Bumps at moderate voltages are alleviated (Fig. 17
(See log Y-voltage curves shown in (A) and (B)).

In FIG. 12 and FIG. 13, voltages of 8 gradations are defined as follows. The light state voltage is fixed at 1.5V and the dark state voltage is fixed at 6.0V. The six halftone voltages are 1.5
It is assumed that the voltage has a value obtained by dividing the luminance Y at V into seven equal parts. The eight voltages will be referred to as V1, V2, ..., V8 from the lowest. Therefore, the six intermediate voltages V2 to V7 are shown in FIG.
This is different from the cases of (A) and (B).

16 and 17, the voltage applied between the pixel electrode 22 and the counter electrode 31 and the stripe electrode 35 is V
The viewing angle characteristics of luminances Y1, ..., Y8 and their logarithmic values when fixed to 1 to V8 are shown. From FIG. 16 and FIG. 17, it can be understood that the viewing angle region in which the luminance order of 8 gradations can be correctly taken, that is, the viewing angle has spread to the following regions. Vertical direction: −54 ° to + 23 ° (−downward direction, + upward direction) Horizontal direction: −39 ° to + 39 ° (−leftward direction, + rightward direction)

The reason why the downward viewing angle is particularly improved will be described with reference to FIG. Consider the YV curve of the normal pixel A1 and the voltage drop pixel A2 when S = 50% and the downward viewing angle θ = 50 °. As described above, the Y-V curve of the normal pixel A1 has a maximum value at a certain halftone voltage VMAX. Here, the film thicknesses of the color filter 33 and the overcoat layer 34 are selected so that the voltage VMIN that gives the minimum value to the YV curve of the voltage drop pixel A2 matches VMAX, and the YV of both divided pixels are selected. When the curves are averaged, the maximum and minimum interfere and the bump disappears. In this way, the Y-V curve of each pixel in this embodiment becomes a monotonically decreasing function, and the gradation inversion phenomenon is eliminated.

Next, a method of manufacturing the liquid crystal display device having the above structure will be described. First, the TFT 21, the pixel electrode 22, and the alignment film 23 are formed on the TFT substrate 11, and alignment treatment such as rubbing treatment is performed in a predetermined direction. On the other hand, IT on the counter substrate 12
A transparent conductive material such as O is formed by sputtering or the like to form the counter electrode 31. Next, a black mask (black matrix) 32 is formed by sputtering and patterning a light shielding metal or the like.

Next, the color filter 33 (33R, 33G, 33B) is formed by using a printing method, a dyeing method or the like. Further, on the color filter 33, SiO of about 1 μm thick is formed.
2. An insulating film such as SiN is deposited to form the overcoat layer 34. The peripheral portion of the overcoat layer 34 is patterned to expose the peripheral portion of the counter electrode 31 (connection portion with the stripe electrode 35). Then, the overcoat layer 34
A transparent conductive material such as ITO is deposited on the top by sputtering or the like. Pattern this transparent conductive material,
The stripe electrode 35 is formed. At this time, the patterning mask is formed so that the area ratio S is 30 to 50%.

Next, an alignment film 36 made of polyimide or the like is formed on the stripe electrode 35 and the overcoat layer 34, and an alignment treatment is performed in a predetermined direction.

Next, the TFT substrate 11 and the counter substrate 12 are
The liquid crystal cell 16 is formed by bonding via a spacer and a sealing material SC so that the cell gap becomes 5 to 6 μm. The liquid crystal cell 16 is filled with the liquid crystal 13 using a vacuum injection method or the like. Then, the polarizing plates 14 and 15 are arranged to complete the liquid crystal display element.

The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, in the above embodiment, the counter electrode 31 is formed on the entire surface of the pixel. Therefore, the ITO is formed on the counter substrate 12 as the counter electrode (lower layer electrode) 3
1 and stripe electrode 35 exist in two layers. 2 ITO
There is a concern that the transmittance may decrease in the layer portion. Therefore, as shown in FIG. 19, the counter electrode 31 in the area of the normal pixel A1 is used.
May be removed. According to this configuration, as shown in FIG. 19, the normal pixel A1 and the voltage drop pixel A2 are respectively subjected to IT.
Only one layer of O is arranged. Therefore, the transmittance of each pixel is higher than that of the pixel having the configuration shown in FIG. 1, and the display becomes bright. Moreover, with respect to the viewing angle, the same effect as that of the embodiment can be obtained.

In the above embodiment, the color filter 33 is arranged on the side of the counter substrate 12, but, for example, as shown in FIG. 20, the color filter 33 and the overcoat layer 34 are arranged on the pixel electrode 22, and the color filter 33 is formed. ITO may be arranged on the filter 33 so as to cover 30 to 50% of the pixels. Overcoat layer 3 on color filter 33
It is not always necessary to dispose 4 and the overcoat layer 34 may be removed. In this case, the color filter 33
To 1.0 to 2.0 μm, and the stripe electrode 35 is formed thereon. The thickness of the color filter 33 differs by about 0.3 μm depending on the color of the color filter 33, but this does not have a particularly bad influence.

Further, although the present invention is applied to the color liquid crystal display device using the color filter in the above-mentioned embodiment, it is also applicable to the liquid crystal display device for monochrome gradation display. In this case, instead of the color filter, an insulating film having a relative dielectric constant of 3.0 to 4.0 is formed to 1.0 to 2.0 μm, and the stripe electrode 35 is formed thereon. With such a structure, it is possible to obtain a monochrome TN liquid crystal display element having a wide viewing angle.

The direction of the alignment treatment applied to the upper and lower alignment films 23 and 36 and the arrangement of the transmission axes of the polarizing plates 14 and 15 are not limited to those in the above embodiment, and can be arbitrarily changed. For example, the transmission axis of the polarizing plate 14 on the light incident side may be parallel to the alignment treatment of the lower alignment film 23. Further, the transmission axis of the polarizing plate 15 on the light emitting side may be parallel to the transmission axis of the lower polarizing plate 36.

In the above embodiments, the present invention has been described by taking the TFT liquid crystal display element as an example, but the present invention can also be applied to a liquid crystal display element using an MIM as an active element. Further, it is also applicable to a passive matrix type liquid crystal display element which does not use an active element.

The present invention is not limited to TN (twisted nematic) liquid crystal display elements, but can be similarly applied to STN liquid crystal displays and the like. Further, the present invention is not limited to the transmissive liquid crystal display element, but can be applied to a reflective liquid crystal display element having a reflective film. In this case, the polarizing plate on the reflective film side may be omitted.

According to the present invention, the pixel is divided into a plurality of partial pixels, and the voltage drop is applied to one of the divided pixels. Therefore, regions of different alignment states are formed in one pixel, and the field of view is reduced. The corners get wider. Further, since it is only necessary to adjust the thickness of the color filter and the overcoat layer that are conventionally present in a normal color liquid crystal display element, and to form the stripe electrode on it, unlike the conventional method of forming the control capacitor, It is easy to manufacture and the aperture ratio does not decrease. Further, since the counter substrate side is processed, it is possible to prevent a situation in which the TFT is destroyed and the yield is reduced.

[0067]

As described above, according to the present invention, since the normal pixel and the voltage drop pixel are arranged in each pixel, it is possible to provide a liquid crystal display element having a wide viewing angle.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a color TN type liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a diagram showing a planar configuration of a TFT substrate.

FIG. 3 is a diagram showing a planar configuration of a counter substrate.

FIG. 4 is a diagram showing another example of a planar configuration of a counter substrate.

FIG. 5 is a diagram showing definitions of an alignment treatment direction, a liquid crystal alignment direction, and vertical and horizontal directions of a liquid crystal display element.

FIG. 6 is a cross-sectional view showing a configuration of one pixel of a liquid crystal display element.

FIG. 7 is a diagram showing a relationship between applied voltage and luminance Y of a normal pixel and a voltage drop pixel, and definitions of V50 and ΔV50.

FIG. 8 is a diagram showing a change in contrast when the area ratio S is fixed at 50% and ΔV50 is changed.

FIG. 9 is a diagram showing changes in the viewing angle θ when the area ratio S is fixed at 50% and ΔV50 is changed, and FIGS.
(C) shows downward, upward, and rightward viewing angles θdo, respectively.
It is a figure which shows wn, (theta) up, and (theta) right.

FIG. 10 is a diagram showing a change in contrast when ΔV50 is fixed at 0.82 V and an area ratio S is changed.

FIG. 11 is a diagram showing changes in the viewing angle θ when ΔV50 is fixed at 0.82 V and the area ratio S is changed.
(C) is a diagram showing downward, upward, and rightward viewing angles θdown, θup, and θright, respectively.

FIG. 12 is a graph showing the relationship between the applied voltage V and the luminance Y when ΔV50 is fixed to 0.82 V and the area ratio S is fixed to 40%. (A) is the upward direction and (B) is the downward direction. The characteristics of

FIG. 13 is a graph showing the relationship between the applied voltage V and the brightness Y when ΔV50 is fixed to 0.82 V and the area ratio S is fixed to 40%, (A) in the right direction and (B) in the left direction. The characteristics of

FIG. 14 is a graph showing the relationship between the applied voltage V and the logarithm of the luminance Y when ΔV50 is fixed to 0.82 V and the area ratio S is fixed to 40%. (A) is an upward direction and (B) is a downward direction. The characteristics in each direction are shown.

FIG. 15 is a graph showing the relationship between the applied voltage V and the logarithm of the luminance Y when ΔV50 is fixed at 0.82 V and the area ratio S is fixed at 40%, (A) to the right and (B) to the left. The characteristics in each direction are shown.

FIG. 16 is a graph showing the relationship between the viewing angle and the luminance Y when ΔV50 is fixed to 0.82 V and the area ratio S is fixed to 40%,
(A) is a figure which shows the up-down direction, (B) is a figure which shows the characteristic of a horizontal direction, respectively.

FIG. 17 is a graph showing the relationship between the viewing angle and the logarithm of the luminance Y when ΔV50 is fixed to 0.82 V and the area ratio S is fixed to 40%. (A) is the vertical direction and (B) is the horizontal direction. It is a figure which shows each characteristic.

FIG. 18 is a graph for explaining the reason why the present invention widens the viewing angle.

19 is a cross-sectional view of a modified example of the color TN type liquid crystal display element shown in FIG.

FIG. 20 is a cross-sectional view of another modification of the color TN type liquid crystal display element shown in FIG.

FIG. 21 is a graph showing a relationship between a voltage V applied to a conventional liquid crystal display element and a logarithm of luminance Y, (A) is an upward direction,
(B) shows the characteristics in the downward direction.

FIG. 22 is a graph showing a relationship between a voltage V applied to a conventional liquid crystal display element and a logarithm of luminance Y, (A) showing a rightward direction,
(B) shows the characteristics in the left direction.

FIG. 23 is a graph showing the relationship between the viewing angle and the logarithm of the luminance Y of a conventional liquid crystal display device, (A) in the vertical direction and (B).
[Fig. 4] is a diagram showing respective characteristics in the left-right direction.

[Explanation of symbols]

11 ... TFT substrate, 12 ... counter substrate, 13 ... liquid crystal,
14 ... Polarizing plate, 15 ... Polarizing plate, 16 ... Liquid crystal cell, 2
1 ... TFT, 22 ... Pixel electrode, 23 ... Alignment film, 31 ...
..Counter electrodes (lower layer electrodes), 32 ... Black mask, 3
3 ... Color filter, 34 ... Overcoat layer, 35
... Stripe electrode (upper layer electrode), 36 ... Alignment film, SC
... Seal material, GL ... Gate line, DL ... Data line, A1 ... Divided pixel (normal pixel), A2 ... Divided pixel (voltage drop pixel)

Claims (11)

[Claims] 1. A first substrate, a second substrate arranged to face the first substrate, and a first substrate formed on a surface of the first substrate facing the second substrate. An electrode, a second electrode disposed on the second substrate and forming a pixel region in a region facing the first electrode, and a liquid crystal sealed between the first and second substrates. A polarizing plate disposed on at least one of the first and second substrates, the first electrode disposed on a lower layer of an insulating film disposed in each pixel region, and the first region. And a lower layer electrode forming a second layer electrode connected to the lower layer electrode on the upper layer of the insulating film.
And an upper layer electrode forming a region, wherein different voltages are applied to the liquid crystal in the first region and the second region in the same pixel. 2. The liquid crystal display device according to claim 1, wherein the insulating film includes a color filter arranged in each pixel. 3. The liquid crystal display element according to claim 1, wherein the insulating film includes a color filter arranged in each pixel and an insulating overcoat layer formed on the color filter. . 4. The relative dielectric constant of the insulating film is 3.0 to 4.0,
4. The thickness according to claim 1, 2 or 3, wherein the thickness is 1.0 to 2.0 μm, and the ratio of the area of each pixel to the area of the first region in each pixel is 30 to 50%. Liquid crystal display element. 5. The retardation value Δn · d of the liquid crystal is
The liquid crystal display element according to claim 1, 2, 3 or 4, which has a thickness of 300 to 600 nm. 6. The polarizing plates are arranged on both sides of the first and second substrates, and the inner surface of the first substrate is subjected to an alignment treatment in a first direction, The inner surface of the second substrate is subjected to an alignment treatment in a second direction substantially orthogonal to the first direction, and the transmission axis of the polarizing plate on the first substrate side is the same as the first direction. It arrange | positions so that it may be parallel or orthogonal, and the transmission axis of the polarizing plate by the side of the said 2nd substrate is arrange | positioned so that it may be parallel or orthogonal to the said 2nd direction, It is characterized by the above-mentioned. 5. The liquid crystal display element according to any one of 5. 7. The liquid crystal display element according to claim 1, wherein the lower layer electrode also extends to the second region. 8. The liquid crystal display element according to claim 1, wherein the upper layer electrode is composed of a striped electrode extending over a plurality of pixels. 9. A liquid crystal composed of a pair of substrates, on which electrodes forming pixel regions are arranged in areas facing each other on the facing surface, and a pair of substrates facing each other, and a liquid crystal disposed between the pair of substrates. In a liquid crystal display element composed of a cell and a polarizing plate arranged in at least one of the liquid crystal cells, each pixel region is divided into a plurality of partial pixels including first and second partial pixels, A first voltage corresponding to a display gradation is applied to the liquid crystal of the first partial pixel, and a second voltage obtained by reducing the first voltage is applied to the liquid crystal of the second partial pixel. The first and second voltages are set so that the maximum of the characteristic curve of the applied voltage and luminance of the first partial pixel and the minimum of the characteristic curve of the applied voltage and luminance of the second partial pixel occur at substantially the same voltage. Further comprising a voltage setting means for setting . 10. A liquid crystal cell composed of a pair of substrates having electrodes formed on the surfaces facing each other and facing each other, and a liquid crystal cell disposed between the pair of substrates, and at least the liquid crystal cell. In a liquid crystal display element including a polarizing plate disposed on one side, each pixel region formed in a region where the electrodes face each other is divided into a plurality of partial pixels including a first partial pixel and a second partial pixel. An insulating film is arranged in each pixel region of one of the pair of substrates, a lower electrode is arranged under the insulating film in the first partial pixel region, and a lower electrode is formed in the second partial pixel region. An upper layer electrode connected to the lower layer electrode is disposed on the insulating film, and the first partial pixel region and the second partial pixel are provided in each pixel region of the other substrate of the pair of substrates. Liquid crystal characterized by arranging a common electrode in the area示素Ko. 11. The insulating film includes a color filter arranged in each pixel region and an insulating overcoat layer formed on the color filter, and the relative dielectric constant of the insulating film is 3.0 to 4. 0, thickness is 1.0
To 2.0 μm, the ratio of the area of each pixel to the area of the first pixel region in each pixel is 30 to 50%, and the retardation value Δn · d of the liquid crystal is 300 to 6
It is 00 nm, The liquid crystal display element of Claim 10 characterized by the above-mentioned.