JP2000089230A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device with which a high display characteristic and uniformity may be obtained in a wide temp. range by setting the angle formed by the synthesized optical axis of plural phase difference plates and the perpendicular axis of a display and the angles formed by the optical axes of the phase difference plates which exist on the side outermost from a display cell and are adjacent to the polarizing plates and the absorption axes of the polarizing plates at respectively specific ranges. SOLUTION: A pair of the polarizing plates 1A, 1B are arranged on both sides of a liquid crystal cell. The uniaxially stretched liquid crystal-containing high-polymer phase difference plate 2 and the uniaxially stretched polycarbonate phase difference plate 3A are arranged between the liquid crystal cell and the polarizing plate 1A and the uniaxially stretched polycarbonate phase difference plate 3b between the liquid crystal cell and the polarizing plate 1B. Two or more sheets of the phase difference plates 2, 3A, 3B are used in such a manner and the angle formed by the synthesized optical axis thereof and the perpendicular axis of the display is set at 30 to 60 deg.. In addition, the angles formed by the optical axes of the phase difference plates 2, 3B which exist on the outermost side from the display cell and are adjacent to the polarizing plates 1A, 1B and the absorption axes of the polarizing plates 1A, 1B are set at 25 to 65 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multiplex driven simple matrix type liquid crystal display device.

[0002]

2. Description of the Related Art Twisted nematic elements and super twisted nematic (STN) elements are widely used as simple matrix type liquid crystal display elements which respond to an effective voltage value. Above all, the STN element can perform multiplex driving at a high duty ratio,
It is widely used for high-density information display such as word processors and portable information devices such as mobile phones and PDAs.

Although the STN element was originally a display mode in which the display was colored, a compensation type STN element in which phase compensation was introduced to achieve monochrome display is mainly used mainly for high-density display. These black and white elements are used as black and white display elements.
Further, it is widely used as a color element using a color filter or the like in combination. This method is roughly classified into three types: (1) a self-compensation type STN that achieves black and white by setting the phase difference of the display panel itself, and (2) a two-layer panel type STN that uses a compensation panel over the display panel. , (3) a film-compensated STN in which a film for compensation is superimposed on a display panel.

[0004] As a feature of each, the method of (1) is as follows.
The retardation of the display panel is set lower than that of a normal STN element (Δnd: 700 nm or less) to avoid coloring, and black and white can be achieved at low cost, but high luminance and high contrast can be achieved due to restrictions on the element. Have difficulty.

The method (2) uses a liquid crystal panel having the same refractive index characteristics (wavelength, temperature characteristics, etc.) as the liquid crystal of the display panel for phase compensation. Since a two-layer liquid crystal panel is used, not only the cost is high but also the thickness and weight are difficult.

The method (3) is the most widely used method for high-density display at present, and uses a film having optical anisotropy for phase compensation of a liquid crystal display panel, and is inexpensive and simple. A black and white display can be obtained. These methods are properly used depending on the application depending on cost and display characteristics.

[0007]

In recent years, with the development of information infrastructure and the like, the state of information equipment has changed drastically. In particular, in what is called mobile computing, it has become commonplace for users to communicate using information devices whenever they need, regardless of location or time. In addition, such a flow of computerization extends to the field of automobiles, and the importance of information display is increasing in automobiles as well.

In a conventional portable information device or in-vehicle information device, the amount of information by communication is not so large and only the text level needs to be displayed, and the resolution and display performance are not so high. The STN of black and white display has been mainly used from the viewpoint of cost. However, in recent information flows, the demand for display bodies has become extremely sophisticated, and display devices capable of responding to such demands are strongly expected. The required changes in characteristics are summarized as follows.

(1) Expansion of operating temperature range: Compared to conventional consumer products mainly for indoor use, portable and in-vehicle use require operation in a wide temperature range. Conventionally, the temperature range was about 0 to 40 ° C., but −20 to + 70 ° C., in some cases,
In the temperature range of −30 to + 90 ° C., which is in the range of about 40 ° C., operation in the temperature range of 90 to 120 ° C. (two to three times the conventional range) is required.

(2) Demand for high performance in high-density display: In portable and in-vehicle display devices, low-density displays that can be driven statically or multiplexed at low duty are used for personal computers and the like. There is a demand for high-density display, and there is an increasing demand for colorization.

As described above, the technical requirements for expanding the high-density information display, which has conventionally been centered on consumer products, to the application area where a wide temperature range operation is required have been advanced, and the wide temperature range has been advanced. There is a strong demand for the development of a new display device that can simultaneously achieve high-density information display.

As a display device that can cope with these, TF
There is an active matrix liquid crystal display device using an active element such as T (thin film transistor).
It is unsuitable for the needs that require a variety of designs and customization, such as the complicated and expensive manufacturing process and the need for multiple masks to make one type of display device. It is expected that a simple matrix drive liquid crystal display device having an advantage in this point will achieve the above characteristics.

[0013] From the viewpoints described above, a film-compensated STN that can operate in a wide temperature range is considered as an optimal candidate for a simple matrix liquid crystal display device. Although the refractive index varies with temperature, the temperature dependence of the refractive index of the film used for phase compensation is smaller than that of liquid crystal, making it difficult to establish a compensation relationship at a temperature other than a specific temperature. , It was difficult to secure the characteristics. In addition, it is difficult to achieve high characteristics (contrast and brightness) with the self-compensation type.
The layer panel type has a problem that the structure is complicated and it is difficult to reduce the thickness and weight at a high cost, and it is not suitable for such an application.

Therefore, a temperature-compensated film STN using a film having characteristics close to the temperature dependence of the refractive index of the liquid crystal for phase compensation has been proposed (Japanese Patent Laid-Open No. 9-1997).
101517). This film is a liquid crystalline polymer film (or a liquid crystal-containing polymer film) that has liquid crystallinity in the entire or part of the operating temperature range, and has a refractive index close to the temperature dependence of the refractive index of liquid crystal. , And a phase compensation close to the compensation relationship of the two-layer type STN can be obtained by the film.

In this configuration, it is possible in principle to achieve high characteristics in a wide temperature range, but it has become clear from our detailed examination that there is a large problem in practical use. This is because when the film has at least uniaxial anisotropy (different refractive index in the plane of the film), it can exhibit high characteristics without any problem in a certain temperature range, but has a display area in another specific temperature range. This causes a problem of unevenness in the inside, which has been a major obstacle to achieving operation in a wide temperature range.

This unevenness is caused by a loss of in-plane uniformity of the refractive index of the film and a special distribution. Avoiding this unevenness is an essential requirement for achieving both high characteristics and wide temperature operation. . The cause of unevenness will be described in detail later.

Of course, at a low duty ratio (a low-to-medium density display of less than 1/30 duty ratio) with no noticeable unevenness,
In addition, in the case of the positive display (normally white), the demand for uniformity in the plane is relatively small, so this is not a significant problem, but in the case of the high-density display (high-density display with a 1/50 duty ratio or more). This problem is very remarkable. In the case of negative display (normally black, no voltage applied, black display when off voltage is applied), the refractive index of this film is reduced because black is produced using phase compensation. The influence of the in-plane distribution was the strongest and it was impossible to use it without solving this problem.

An object of the present invention is to provide a film-compensated STN.
Therefore, it is an object of the present invention to provide a configuration which achieves a wide temperature range operation, uniformity, and high characteristics at the same time, and is summarized in the following two points. The first is to obtain a film compensation STN that suppresses the occurrence of unevenness in a wide temperature range, finds an optical configuration that is resistant to fluctuations in the refractive index of the film, and aims at securing high uniformity, and at the same time, aims at securing high uniformity in a wide temperature range. The purpose is to achieve the operation. The second is to obtain an STN having excellent characteristics in negative display (normally black), and achieve excellent display performance such as contrast, brightness, and viewing angle characteristics in an optical configuration satisfying the first condition. The purpose is to obtain a configuration for performing

The present invention achieves the above-mentioned object, thereby enabling a high-performance STN, which can be used only in a narrow temperature range, to be applied to a wide range of applications requiring a wide temperature operation. It has a significant industrial impact.

[0020]

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned problems and enables a film-compensated STN that can operate in a wide temperature range. Liquid crystal comprising a liquid crystal layer containing a rotatory substance, having a positive dielectric anisotropy, and having a twist angle of 180 to 300 °, between a pair of substrates with a transparent electrode having an alignment control film disposed at A cell, a pair of polarizing plates disposed on both sides of the cell, a retardation plate having a total number of two or more disposed between the liquid crystal cell and at least one polarizing plate, and a drive for applying a voltage between the transparent electrodes. A liquid crystal display device having
The product Δn _L d _L of the refractive index anisotropy Δn _L of the liquid crystal layer of the liquid crystal cell and the thickness d _{L of the} liquid crystal layer is 600 to 1700 nm, and the difference between the upper and lower limits of the operation temperature of the liquid crystal display device is 5
0 ° C. or higher, at least one of the retardation plates changes in retardation value with temperature, and the retardation of the i-th retardation plate at room temperature is (Δnd) _i , When the angle with respect to the vertical axis of the display device is represented by θ _i , Σ ((Δnd) _i · θ _i ) / Σ (Δn
d) the absolute value of _i is 30-60 ° or 120-15
It is characterized by being 0 °. By adopting such a configuration, the phase difference unevenness of the phase difference plate as the compensation film and the display unevenness due to the unevenness are suppressed over a wide temperature range.

A feature of the liquid crystal display device according to the present invention is that the angle of the optical axis of the j-th polarizing plate with respect to the vertical axis of the liquid crystal display device is φ _j , and the phase difference adjacent to the j-th polarizing plate is also When the angle of the plate is represented by θ _k , the absolute value of the difference between θ _k and φ _j is 25 to 65 ° or 115 to 155 °
Where By adopting such a configuration, display quality such as contrast and color tone is improved.

The liquid crystal display device of the present invention according to claim 3 is characterized in that an optically rotatory substance is contained between a pair of substrates with a transparent electrode having an alignment control film arranged substantially in parallel and dielectric anisotropy is obtained. A liquid crystal cell comprising a liquid crystal layer having a positive twist angle of 180 to 300 °, a pair of polarizing plates disposed on both sides thereof, and a total number of liquid crystal cells disposed between the liquid crystal cell and at least one polarizing plate. Is a liquid crystal display device having two or more retardation plates and a driving means for applying a voltage between the transparent electrodes, the refractive index anisotropy Δn _L of the liquid crystal layer of the liquid crystal cell and the thickness d _{L of the} liquid crystal layer. The product of Δn _L d _L is 600 to 1700 nm
That is, the number of retardation plates is three, one on one side of the liquid crystal cell and two on the opposite side, and the retardation values of the three retardation plates are not the same but are maximum and minimum Are different by 10% or more. By adopting such a configuration, a degree of freedom in optical design is ensured.

The liquid crystal display device of the present invention according to claim 4 is characterized in that the retardation of the i-th retardation plate at room temperature is (Δnd) _i , and the angle of its optical axis with respect to the vertical axis of the liquid crystal display device is θ _i.表 ((Δnd) _i · θ
_i ) / Σ (Δnd) The absolute value of _i is 30 to 60 ° or 120 to 150 °. By adopting such a configuration, the phase difference unevenness of the phase difference plate as the compensation film and the display unevenness due to the unevenness are suppressed over a wide temperature range.

According to a fifth aspect of the present invention, the difference between the upper limit and the lower limit of the operating temperature is 50 ° C. or more, and at least one of the phase difference plates changes the phase difference value depending on the temperature. The point is that it is. By employing such a configuration, the effect of suppressing display unevenness over a wide temperature range becomes more remarkable.

The liquid crystal display device according to the present invention is characterized in that the angle of the optical axis of the j-th polarizing plate with respect to the vertical axis of the liquid crystal display device is φ _j , and the phase difference adjacent to the j-th polarizing plate is also When the angle of the plate is represented by θ _k , the absolute value of the difference between θ _k and φ _j is 25 to 65 ° or 115 to 155 °
It is in the point that is. By adopting such a configuration, display quality such as contrast and color tone is improved.

The characteristics of the liquid crystal display device of the present invention according to claim 7, comprising at least one retardation plate is anisotropic in the vertical direction of the film plane, the refractive index in the plane direction n _x, n _y , however, n _x> n _y, the relationship of the refractive index of the refractive index in the vertical direction when expressed in n _{z is, 0.2 ≦ | n x -n z} | / | n x
−n _y | <1. By adopting such a configuration, the viewing angle with high contrast is enlarged.

A feature of the liquid crystal display device according to the present invention is that the number of lines to be scanned is 50 or more. By employing such a configuration, the effect of suppressing display unevenness over a wide temperature range becomes more remarkable. Claim 9
The feature of the liquid crystal display device according to the present invention is that when the number of lines to be simultaneously selected at the time of driving is represented by L and the frame frequency is represented by F, L is 1 to 8, and FL is 120 to 800 Hz.
It is in the point that is. By employing such a configuration, the effect of suppressing display unevenness over a wide temperature range is more remarkably exhibited.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail, including the operation of the present invention, based on the circumstances leading to the completion of the present invention. First, the reason why the conventional film-compensated STN cannot be used in a wide temperature range will be described.

[Refractive index distribution of film and film compensation S
TN display unevenness] A compensation film (retardation plate) widely used in the conventional film-compensated STN is obtained by stretching a film such as polycarbonate and has optical anisotropy (anisotropic refractive index). It was made. Therefore, the retardation plate has a different refractive index depending on the in-plane direction, and the retardation plate as a whole exhibits birefringence (phase difference: Δnd).

Such a phase difference plate is formed in a rectangular shape, and S
A film-compensated STN compensates for chromatic dispersion generated in a TN display panel to achieve black and white display. As a well-known high-performance compensation relationship, STN
There is a type in which a phase difference plate having substantially the same phase difference is attached to both sides of the panel to compensate.

FIG. 5 shows a typical configuration example. In this example, the stretching axis (the axis having a large refractive index) of the upper and lower retardation plates and the absorption axis of the polarizing plate are arranged at an angle as shown in FIG. Is arranged. The display panel of this configuration is used at room temperature (2
(5 ° C.) and then set to 80 ° C., luminance unevenness occurs as shown in FIG. This is the point described in the above-mentioned problem to be solved by the present invention.

When the film (retardation plate) used in this configuration is independently adhered to glass and observed at a high temperature in the same manner, the retardation unevenness as shown in FIG. 7 is observed, and the display unevenness generated on the panel described above. It can be seen that this is due to uneven phase difference of the phase difference plate. In order to elucidate the mechanism of occurrence of this unevenness, the present inventors examined the correlation between parameters that might be involved and unevenness.

First, as a parameter, a shape (circular,
The study focused on the shape and aspect ratio of a rectangle or the like) and size, the axis angle of the retardation plate, the type of film (polycarbonate, liquid crystal film, polyarylate), the bonding strength, and the like. In relation to the unevenness, the one having a strong correlation was the axis angle of the retardation plate, the one having a weak correlation was the shape factor, and the other parameters were hardly correlated with the unevenness. That is, it has been found that the basic pattern of the unevenness is determined by the (optically anisotropic) axis angle of the retardation plate, and the unevenness is modulated by the effect of the shape.

From these studies, the mechanism is presumed as follows. The main factor that the retarder itself is the dominant factor is the properties (elasticity and optical properties) of the retarder itself, rather than the sticking irregularity caused by the shape factor often seen in ordinary retarders. It means that it becomes. That is, in a retardation plate having optical anisotropy by stretching or the like, elastic deformation (or accompanying change in optical properties) due to temperature change also has anisotropy, so that high temperature It is considered that unevenness in time has occurred.

The molecular chain of the polymer is continuous in the stretching axis direction, and the elasticity and optical characteristics are greatly different from those in the vertical direction. Therefore, an internal deformation having anisotropy occurs due to an internal stress induced by a temperature change from room temperature to a high temperature, and this is a main factor of the unevenness. This point is apparent from the fact that the same unevenness is observed with respect to the optical axis even in the case of the phase difference plate cut in a circular shape.

The irregularities in the present problem include, in addition to the main factor, an external factor (a secondary factor) of being attached in a certain shape. In other words, it can be said that the cause of the unevenness itself is caused by the internal elastic properties of the phase difference plate itself, and the pattern is modulated by the modulation of the stress distribution by the shape factor. This indicates that a certain degree of phase difference unevenness cannot be avoided as long as it is used in a wide temperature range. Conventionally, the subject itself was not recognized because it was used only in a narrow temperature range.

[Thought to reduce / avoid unevenness]
In order to make the film-compensated STN usable in a wide temperature range, a study was made from two viewpoints. One of them is an idea of trying to avoid unevenness by balancing the above main factors and sub factors. From this point of view, when the relationship between the axial angle and the unevenness in the shape having the aspect ratio of 3: 4 is examined in detail,
It was found that unevenness was hardly observed when the angle between the horizontal axis and the stretching axis was in the range of 30 to 60 °. However, fixing the axis angle of the retardation plate used in that range is a strong constraint condition for achieving high display characteristics, and it is difficult to achieve compatibility with high characteristics.

Another idea is to avoid unevenness by using a plurality of phase difference plates and arranging the actual optical axes appropriately. In this case, the phase difference value that effectively contributes is also related to the angle with respect to the absorption axis of the polarizing plate, so that the relationship with the polarizing plate is also important.

From this viewpoint, the following conditions have been found. (1) Two or more retardation plates are used, and the combined optical axis forms an angle of 30 to 60 ° with the vertical axis of the display. (2) The optical axis of the retardation plate which is the outermost from the display panel and is adjacent to the polarizing plate and the absorption axis of the polarizing plate are 25 to 65.
Making an angle of °.

In a configuration satisfying these two conditions,
It became clear that there was almost no unevenness even in a very wide temperature range of -30 to + 90 ° C. This condition is expressed by the following equation in relation to the phase difference value Δnd of the phase difference plate and its optical axis. (1) i th retardation at room temperature retarder ([Delta] nd) _i, the angle relative to the vertical axis of the liquid crystal display device of the optical axis when expressed in _{θ i, Σ ((Δnd)} i · θ
_i ) / Σ (Δnd) The absolute value of _i is 30 to 60 ° or 120 to 150 °. (2) when representing the angle of the phase difference plate adjacent to the j-th angle phi _j of the optical axes of the polarizing plate, also j-th polarizing plate with respect to the vertical axis of the liquid crystal display device in theta _k, and theta _k The absolute value of the difference from φ _j is 25 to 65 ° or 115 to 155 °
That.

In the present invention, the liquid crystal cell has a twist angle of 180 to 360 °, preferably 180 to 270.
°, the product Δn _L d _L of the refractive index anisotropy Δn _L of the liquid crystal layer and the thickness d _{L of the} liquid crystal layer is 600 to 1700 nm, preferably 700 to 1400 nm. However, the present invention can be similarly applied to a retardation / color mode in which a color is developed using retardation.

[Practical Configuration and Scope of Application of the Present Invention] A more specific configuration will be described below. In the present invention, what is important in terms of characteristics is to establish an appropriate compensation relationship to achieve a black level, that is, to achieve high contrast. For this reason, the relationship between the optical anisotropy of the liquid crystal portion of the liquid crystal panel and the optical axis of the retardation plate becomes important, and it is necessary to satisfy both the above-mentioned conditions without unevenness. For this reason,
The concept in terms of the configuration is organized by the total number of retardation plates used and the number of plates on each side of the display panel.

In the case of one retardation plate, only one plate is used on one side. The optical axis is set as described above, and the liquid crystal state of the display panel is optimized so that the display characteristics are optimized. That is, it is necessary to set the rubbing angle and the twist angle.

When two retardation plates are used, and when one is used on one side of the display panel, half of the display cells are compensated by the retardation plate on one side. Two phase difference plates are arranged at positions symmetrical with respect to the optical axis of the portion. Therefore, the combined optical axis of the two retardation plates almost coincides with or has a very strong relationship with the optical axis of the liquid crystal portion of the display panel, and the rubbing angle is the same as in the case of one retardation plate. It is necessary to set the twist angle.

Here, the optical axis of the liquid crystal portion of the display panel indicates an axis angle indicating a half of the twist angle. In the case where two retardation plates are used one by one on each side, the optical axis itself needs to be at an angle of 30 to 60 ° with the horizontal axis of the display panel.

When two or more retardation plates are used on one side, the degree of freedom becomes very large due to the relationship between the respective retardation plates. For this reason, the constraint that the optical axis of the liquid crystal panel must have a specific relationship is reduced. This is a desirable point in view of the fact that the optical axis of the liquid crystal panel is related to the viewing angle characteristics and the production process. However, in terms of characteristics, higher contrast characteristics can be achieved by disposing retarders on both sides.

One of the specific solutions provided by the present invention is a new configuration developed in consideration of these points, and uses three or more retardation plates, and always includes a retardation plate on both sides of the display panel. A plate is arranged, and one side has two or more sheets. In this case, it is possible to satisfy both the advantage of the contrast characteristic that the compensation films are arranged on both sides and the advantage of the flexibility of the configuration that two or more retardation plates are used on one side. This is one of the most desirable configurations.

In particular, when three retardation plates are used, the combination of the types of retardation plates can be improved by taking advantage of the fact that the three retardation plates contribute differently. , Phase difference value, and the like, and the front characteristics and the viewing angle characteristics can be obtained in a well-balanced manner. This effectively takes advantage of the asymmetry that one and two retardation plates are disposed on both sides, respectively, and the fact that the two retardation plates disposed on one side have different phase differences. Configuration.

For example, there is a degree of freedom in that three phase difference values can be set independently. In addition, there is a degree of freedom regarding how many temperature compensation type retardation plates whose phase difference values change with temperature are used. As a result, 2
When one retardation plate is used one by one on each side, both of them must be constituted by a temperature compensation type retardation plate,
When three retardation plates are used, one is a temperature compensation type,
This can be used as a normal retardation plate. The temperature compensation type retardation plate is expensive because a special material such as a polymer material having liquid crystallinity is used in the production thereof, but according to the above configuration, this number is minimized, The advantage that the total cost can be reduced is also exhibited. Also, it is not necessary to make the three phase difference values the same, but rather,
From the viewpoint of the effective phase difference, it is desirable that the maximum and minimum of the three phase difference values have a difference of 10% or more.

The above description is basically based on a retardation plate having uniaxial anisotropy (ie, having in-plane refractive index anisotropy). As a part of the retardation plate used, a retardation film having a refractive index in a direction perpendicular to the film different from that in the plane (that is, having three main values of the refractive index) can be used. In this case, the refractive index in the plane direction n _x, n _y, however, n _x>
n _y, the relationship of the refractive index of the refractive index in the vertical direction when expressed in n _{z is, 0.2 ≦ | n x -n z} | / | n x -n y | <
By setting so as to satisfy 1, the widening of the viewing angle is achieved. When this condition is combined with the above-described embodiment in which the total number of retardation plates is three, the viewing angle improving effect becomes more remarkable.

[Drive System and Display Device] As a basic drive system (multiplex drive) of a simple matrix type liquid crystal display element, a one-line sequential selection method (for example, APT)
The method and the improved IAPT method have been well known. This method is very effective as a multiplex driving method because the on / off level can be easily driven. However, the simple matrix type liquid crystal display element is TF
Since an active element such as T is not used, when a liquid crystal display element having a high response speed is driven, there is a problem that a contrast is reduced due to a frame response.

The method proposed to solve this is as follows:
This is a multiple line simultaneous selection (MLA) method, which enables high-speed and high-contrast display. In addition, an attempt using a type of simultaneously selecting all lines (active addressing) for the same purpose has been reported. As described above, new addressing techniques have been developed, and display quality has been improved.

In the liquid crystal display device of the present invention, the MLA driving method is suitable as a driving method. This is because in the operation in a wide temperature range, the temperature change of the response time due to the temperature change of the viscosity of the liquid crystal is large, so that the driving method for suppressing the frame response is effective for achieving high display characteristics.
In the MLA driving method, the circuit scale and the suppression rate of the frame response differ depending on the number of selected lines (L) selected at the same time. From these two viewpoints, a suitable number of simultaneous selections is set to 2 lines or more and 16 lines or less, and more preferably 8 lines or less.

It is also possible to use a method of increasing the driving frequency (high-frequency driving). In the case of high-frequency driving, the width of the applied voltage pulse is narrow, which is not suitable for large-area, high-resolution display. However, when the display size is 10 inches or less and the display density is about 1/240 duty ratio or less, Can increase the suppression rate of the frame response by increasing the frame frequency.

In this case, the frame frequency (F) for driving the liquid crystal is preferably about 120 to 800 Hz, and particularly, 240 to 500 Hz is suitable. In the MLA driving method, since the frame frequency is considered to be approximately L times as effective, the above numerical range is preferably adopted as the value of the product of F and L.

[0056]

EXAMPLES Examples will now be described in more detail with reference to examples including details of the optical configuration of the retardation plate. In addition,
In each of the following examples, the angle is expressed as 0 ° with respect to the 12 o'clock direction of the clock with respect to the vertical axis of the liquid crystal display device, and the clockwise direction as the positive direction. The angle of the retardation plate indicates the direction of the stretching axis, and the angle of the polarizing plate indicates the direction of the absorption axis of the polarizing plate. Further, the retardation of each retardation plate is obtained by spectroscopy.

Example 1 A liquid crystal cell of 64 × 256 dots and 1 DIN size was used. Liquid crystal cell has a twist angle of 240 °
And the main viewing angle direction was set at 6 o'clock. The retardation of the liquid crystal layer at 25 ° C. was 832 nm,
The clearing temperature (T _C ) of the liquid crystal was 105 ° C. Using this liquid crystal cell, a display device whose schematic sectional view is shown in FIG. 1 was assembled.

A pair of polarizing plates 1A (polarizing plate 1) and 1B (polarizing plate 2) are arranged on both sides of the liquid crystal cell, and a uniaxially stretched liquid crystal-containing polymer retardation plate 2 ( A retardation plate 1) and a uniaxially stretched polycarbonate retardation plate 3A (a retardation plate 2), and a uniaxially stretched polycarbonate retardation plate 3B (a retardation plate 3) between a liquid crystal cell and a polarizing plate 1B.
Was placed. Then, a backlight 8 was disposed on the back surface of the polarizing plate 1B. In this example, the phase difference plate 1 is adjacent to the polarizing plate 1, and the phase difference plate 3 is adjacent to the polarizing plate 2.

The installation angle (θ _i ) of each retardation plate and 25 ° C.
And the retardation ((Δnd) _{i, 25} and (Δnd) _{i, 80} ) at 80 ° C. and the installation angle (φ _j ) of each polarizing plate
In addition to the above, they are summarized below.

Θ ₁ = −75 °, θ ₂ = −25 °, θ ₃ = −15 ° (Δnd) _1,25 = 440 nm, (Δnd) _1,80 = 363 nm, (Δnd) _2,25 = 319 nm, _{(Δnd) 2,80 = 319nm, (} Δnd) 3,25 = 440nm, (Δnd) 3,80 = 440nm, φ 1 = 60 °, φ 2 = 15 °. Σ ((Δnd) _i · θ _i ) / Σ (Δnd) _{i in} this case
Is 39.7 °, and the absolute value of the difference between the installation angles of the polarizing plate and the adjacent retardation plate is 135 ° and 30 °.
°.

This liquid crystal display device is operated at 64 duty, 1 /
When driven with 9 bias and 140 Hz multiplex, the contrast at -30 ° C was 80: 1, 2
The contrast at 5 ° C. was 105: 1 and the contrast at 80 ° C. was 30: 1. In addition, although retardation unevenness was generated at a temperature of 60 to 90 ° C. in the used retardation plate alone, a liquid crystal display device having a high display quality without unevenness over the entire display unit can be obtained.
In a wide temperature range of + 90 ° C. A uniform display with high contrast was obtained. Further, when the angles of the upper and lower polarizing plates were simultaneously rotated by 90 °, the same display characteristics as described above could be obtained.

(Examples 2 to 4) All were the same as Example 1 except that the configuration of the installation angle of the polarizing plate and the phase difference plate was changed as follows.

In each of these examples, it was possible to obtain a liquid crystal display device having a high display quality without unevenness over the entire display section at a high temperature of 60 to 90 ° C. Further, in each example, even if the angles of the upper and lower polarizing plates are simultaneously rotated by 90 °, no unevenness occurs even at a high temperature of 60 to 90 ° C.
At a temperature of from + 90 ° C. to + 90 ° C., display quality of high contrast without unevenness over the entire display portion was obtained.

Example 5 The same liquid crystal cell as in Example 1 was used.
However, the retardation of the liquid crystal layer at 25 ° C. is 900 n.
m, the main viewing angle direction was 6 o'clock. T of liquid crystal used
_C was 108.4 ° C. A polarizing plate 1A and two uniaxially stretched liquid crystal-containing polymer retardation plates 2A and 2B were attached to one side of the liquid crystal cell, and a polarizing plate 1B was attached to the other surface. FIG. 2 is a schematic cross-sectional view. The liquid crystal display was assembled.

The installation angles of the retardation plates and the retardations at 25 ° C. and 80 ° C. are shown below together with the installation angles of the respective polarizing plates. θ ₁ = 50 °, θ ₂ = 15 °, (Δnd) _1,25 = 470 nm, (Δnd) _1,80 = 420 nm, (Δnd) _2,25 = 470 nm, (Δnd) _2,80 = 420 nm, φ ₁ = 85 °, φ ₂ = 5 °.

This liquid crystal display device is provided with a 64 duty ratio, 1
Driven at 140 Hz with a / 9 bias. The contrast of this liquid crystal display device is 1:37 at 25 ° C. and 8
It was 10 at 0 ° C. Even at a high temperature of 60 ° C. to 90 ° C., the liquid crystal display maintained high display quality without unevenness over the entire display section. Further, even if the angles of the upper and lower polarizing plates were simultaneously rotated by 90 °, the same characteristics as above could be obtained.

(Example 6) 240 × 320 × １ ／ of RGB
A VGA size liquid crystal cell was prepared. The twist angle of the liquid crystal layer was 240 ° STN, and the main viewing angle direction was 1:30.
This liquid crystal cell was colored in combination with an inner surface color filter, and a fluorescent lamp backlight was arranged on the back surface. The liquid crystal had a T _C of 105 ° C. and a retardation of 850 nm.

A polarizing plate 1A and a uniaxially-stretched liquid crystal-containing polymer retardation plate 2A are attached to one surface of the liquid crystal cell, and a polarizing plate 1B and a uniaxially-stretched liquid crystal-containing polymer retardation plate 2B are attached to the other surface. In addition, a liquid crystal display device whose schematic cross-sectional view is shown in FIG. 3 was assembled.

The installation angles of the retardation plates and the retardations at 25 ° C. and 80 ° C. are shown below together with the installation angles of the polarizing plates. θ ₁ = 65 °, θ ₂ = 25 °, (Δnd) _1,25 = 435 nm, (Δnd) _1,80 = 365 nm, (Δnd) _2,25 = 435 nm, (Δnd) _2,80 = 365 nm, φ ₁ = −55 °, φ ₂ = 55 °.

This liquid crystal display device has four simultaneously selected lines.
Was driven by the MLA driving method described above. Here, the 240 selection lines are divided into 60 subgroups, and one virtual subgroup is further added, and the number of subgroups is set to 61. A selection pulse sequence is defined by a 4 × 4 orthogonal matrix so that the effective voltage value is determined when each subgroup is selected four times. Here, one virtual line is provided for each subgroup, and four lines are virtually selected and driven.

The contrast of this liquid crystal display device is 25 ° C.
Was 1:55 and at 80 ° C. was 18. Even at a high temperature of 60 to 90 [deg.] C., the liquid crystal display maintained high display quality without unevenness over the entire display section. Further, even if the angles of the upper and lower polarizing plates were simultaneously rotated by 90 °, the same characteristics as above could be obtained.

(Example 7) 240 × 320 × １ ／ of RGB
A VGA size liquid crystal cell was prepared. The twist angle of the liquid crystal layer was STN of 240 °, and the main viewing angle direction was 12:00. The liquid crystal from T _C is 105 ° C., the thickness of the liquid crystal layer 6 [mu] m, 2
The retardation at 5 ° C. was 850 nm. The liquid crystal cell was colored in combination with an inner surface color filter, and a fluorescent lamp backlight was arranged on the back surface.

A polarizing plate 1A, a uniaxially-stretched liquid crystal-containing polymer retardation plate 2A and a uniaxially-stretched polycarbonate retardation plate 3A are adhered to one surface of the liquid crystal cell, and a polarizing plate 1B and a uniaxially-stretched polycarbonate film are adhered to the other surface. The liquid crystal display having the cross-sectional configuration of FIG. 4 was assembled by attaching the retardation plate 2B.

The installation angle of each phase difference plate, 25 ° C. and 8
The retardation at 0 ° C. is shown below together with the installation angle of each polarizing plate. θ ₁ = −75 °, θ ₂ = −25 °, θ ₃ = −15 °, (Δnd) _1,25 = 430 nm, (Δnd) _1,80 = 340 nm, (Δnd) _2,25 = 310 nm, (Δnd _{) 2,80 = 310nm, (Δnd)} 3,25 = 430nm, (Δnd) 3,80 = 430nm, φ 1 = 60 °, φ 2 = 15 °.

When this liquid crystal display device has three simultaneously selected lines.
Was driven by the MLA driving method described above. Here, the 240 selection lines are divided into 80 subgroups, and three virtual subgroups are further added, so that the number of subgroups is 83. A selection pulse sequence is defined by a “4 × 4” orthogonal matrix so that the effective voltage value is determined when each subgroup is selected four times. Here, one virtual line is provided for each subgroup, and four lines are virtually selected and driven.

The contrast of this liquid crystal display device is 25 ° C.
At 1:50 and at 80 ° C. at 20,
Good contrast was obtained over a wide temperature range. Also, 6
Even at a high temperature of 0 to 90 [deg.] C., a liquid crystal display device having a high display quality without unevenness over the entire display portion as a liquid crystal display device could be obtained. In addition, the angles of the upper and lower polarizing plates are simultaneously set to 9
Even when rotated by 0 °, the same characteristics as above could be obtained.

(Example 8) As a comparative example, the main viewing angle direction is 1
A liquid crystal display device similar to that of Example 6 was assembled, except that the axis angles of the liquid crystal, the phase difference plate, and the polarizing plate were all rotated 45 degrees counterclockwise so that the direction was at 2 o'clock. In this case, a good display quality with a contrast of 50: 1 was achieved at room temperature, but when the temperature exceeded 60 ° C., unevenness as shown in FIG. 6 occurred, and at 80 ° C. or more, the unevenness level was completely unacceptable.

[0078]

According to the present invention, a film-compensated STN in which unevenness is suppressed in a wide temperature range can be obtained, and high uniformity and operation in a wide temperature range can be achieved.
Further, in a preferred embodiment, an STN having excellent characteristics in negative display (normally black) can be obtained, and in addition to the above, excellent display performance such as contrast, luminance, and viewing angle characteristics can also be achieved. As a result, a high-performance STN that can be used only in a narrow temperature range conventionally
Has been developed for a wide range of applications requiring wide temperature operation.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a liquid crystal display according to another embodiment of the present invention.

FIG. 3 is a schematic sectional view of a liquid crystal display device according to another embodiment of the present invention.

FIG. 4 is a schematic sectional view of a liquid crystal display device according to another embodiment of the present invention.

FIG. 5 is a schematic sectional view of a conventional liquid crystal display device.

FIG. 6 is a schematic plan view showing a state of display unevenness.

FIG. 7 is a schematic plan view showing a state of uneven retardation.

[Explanation of symbols]

 1A, 1B: polarizing plate 2A, 2B, 3A, 3B: retardation plate 4A, 4B: glass substrate 5A, 5B: transparent electrode 6A, 6B: alignment film 7: liquid crystal layer 8: backlight 9: color filter

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hikaru Nakagawa 1-2-1, Kamisakabe, Amagasaki City, Hyogo Prefecture Optrex Amagasaki Plant (72) Inventor Yoshinori Hirai 1150 Hazawacho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Asahi Glass Co., Ltd. (72) Inventor Shinichi Unanyama 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. 2H089 QA06 RA05 RA10 SA04 SA13 SA14 SA15 TA12 TA14 TA17 TA18 2H091 FA02Y FA08X FA08Z FA11Z FA42Z FB02 FD09 GA06 HA10 KA02 LA04 LA16 LA18 LA19 LA20

Claims (9)

[Claims] 1. A liquid crystal containing a rotatory substance, having a positive dielectric anisotropy and having a twist angle of 180 to 300 °, between a pair of substrates having a transparent electrode having an alignment control film arranged substantially in parallel. A liquid crystal cell sandwiching a layer, a pair of polarizing plates disposed on both sides thereof, a total of two or more retardation plates disposed between the liquid crystal cell and at least one polarizing plate, and the transparent electrode In a liquid crystal display device having a driving means for applying a voltage therebetween, a product Δn _L d _L of the refractive index anisotropy Δn _L of the liquid crystal layer of the liquid crystal cell and the thickness d _{L of the} liquid crystal layer is 600 to 170.
0 nm, the difference between the upper and lower limits of the operating temperature of the liquid crystal display device is 50 ° C. or more, and at least 1
The retardation value of the i-th retardation plate at room temperature must be (Δ
nd) _i , when the angle of the optical axis with respect to the vertical axis of the liquid crystal display device is represented by θ _i , Σ ((Δnd) _i · θ _i )
/ Σ (Δnd) _i is 30 to 60 ° or 1
A liquid crystal display device characterized in that the angle is 20 to 150 °. 2. The angle of the optical axis of the j-th polarizing plate with respect to the vertical axis of the liquid crystal display device is represented by φ _j , and the angle of the phase difference plate adjacent to the j-th polarizing plate is represented by θ _{k. k} and φ
The absolute value of the difference from _j is 25 to 65 ° or 115 to 1
2. The liquid crystal display device according to claim 1, wherein the angle is 55 [deg.]. 3. A liquid crystal containing a rotatory substance, having a positive dielectric anisotropy and having a twist angle of 180 to 300.degree. Between a pair of substrates with a transparent electrode having an alignment control film arranged substantially in parallel. A liquid crystal cell sandwiching a layer, a pair of polarizing plates disposed on both sides thereof, a total of two or more retardation plates disposed between the liquid crystal cell and at least one polarizing plate, and the transparent electrode In a liquid crystal display device having a driving means for applying a voltage therebetween, a product Δn _L d _L of the refractive index anisotropy Δn _L of the liquid crystal layer of the liquid crystal cell and the thickness d _{L of the} liquid crystal layer is 600 to 170.
0 nm, the number of retardation plates is three, one is disposed on one side of the liquid crystal cell, and two are disposed on the opposite side, and the retardation values of the three retardation plates are not the same but are maximum and minimum. And 10
% Or more. 4. When the retardation of the i-th retardation plate at room temperature is represented by (Δnd) _i , and the angle of its optical axis with respect to the vertical axis of the liquid crystal display device is represented by θ _i , Σ ((Δnd) _i
The liquid crystal display device according to claim 3, wherein the absolute value of? _I ) /? (? Nd) _i is 30 to 60 degrees or 120 to 150 degrees. 5. The liquid crystal display device according to claim 3, wherein the difference between the upper limit and the lower limit of the operating temperature of the liquid crystal display device is 50 ° C. or more, and at least one of the phase difference plates changes the phase difference value depending on the temperature. Liquid crystal display device. 6. The angle of the optical axis of the j-th polarizing plate with respect to the vertical axis of the liquid crystal display device is represented by φ _j , and the angle of the phase difference plate adjacent to the j-th polarizing plate is represented by θ _{k. k} and φ
The absolute value of the difference from _j is 25 to 65 ° or 115 to 1
2. The liquid crystal display device according to claim 1, wherein the angle is 55 [deg.]. 7. A comprising at least one retardation plate is anisotropic in the vertical direction of the film plane, the refractive index in the plane direction n _x, n
_y, however, n _x> n _y, the relationship between the refractive index of the refractive index in the vertical direction when expressed in _{n z, 0.2 ≦ | n x} -n z |
/ | N _x -n _y | <liquid crystal display device of any one of claims 1 to 6, characterized in that satisfies 1. 8. The liquid crystal display device according to claim 1, wherein the number of lines to be scanned is 50 lines or more. 9. When the number of lines to be simultaneously selected during driving is represented by L and the frame frequency is represented by F, L is 1 to 8,
9. The liquid crystal display device according to claim 8, wherein FL is 120 to 800 Hz.