JPS62208024A - Driving method for sbe type liquid crystal display element - Google Patents

Abstract

PURPOSE:To eliminate an irregularity in the color tone of the display part of a liquid crystal cell by applying an unselected waveform of a positive type display to the display part and changing the display color into light brown, and applying a selected waveform to a non-display part and changing the background color into yellow. CONSTITUTION:The liquid crystal cell consists of electrode substrates 1 and 2 which are arranged opposite each other and nematic liquid crystal 3 injected into between the substrates 1 and 2, and polarizing plates 5 and 7 are arranged on both sides of the cell. Then, the liquid crystal 3 is adjusted so that the product of its refractive index anisotropy and thickness is 0.90-1.10, the polarizing plates 5 and 7 are arranged making a negative type display, and a yellow color polarizing plate is used as at least either of them. The display part of the cell is applied with the unselected waveform of the positive display to change the display color into light brown and the non-display part is applied with the selected waveform of the positive display to change the background color into yellow. This method eliminates the irregularity in the color toner of the display part and improves the display quality.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for driving an SBE type liquid crystal display element having a 180 degree twisted orientation.

<Summary of the Invention> The present invention provides 18
In an SBE type liquid crystal display element comprising a liquid crystal cell sandwiching a nematic liquid crystal with a 0 degree twist orientation, and a pair of polarizing plates disposed on both sides of the liquid crystal cell, the refractive index difference of the nematic liquid crystal is A structure in which the product Δn-d of the orientation Δn and the thickness d of the liquid crystal layer is set in the range of 0.90 to 1.10 μyn, and a yellow color polarizing plate is used as at least one of the pair of polarizing plates. A non-selection waveform in positive display is applied to the display part of the liquid crystal cell to make the display color brown, and a non-selection waveform in positive display is applied to the non-display part of the liquid crystal cell. By applying a waveform to make the background color yellow, color tone unevenness peculiar to SBE type liquid crystal display elements can be prevented and a driving method with excellent display quality can be provided.

<Prior art> In this technique, an electrode substrate on which an alignment film such as a metal oxide film or an organic polymer film for aligning liquid crystal is formed is sealed by sliding it. Polarizing plates are disposed above and below the liquid crystal cell constructed in this manner to impart electro-optical characteristics. Twisted alignment of the liquid crystal is carried out by, for example, a method of rubbing the surface of an alignment film made of a metal oxide film or an organic polymer film in one direction with a cloth or the like, that is, a so-called rubbing method. Twisted orientation of the M crystal is created by a rubbing method in which two electrode substrates that have been subjected to orientation treatment are made to face each other so that their respective rubbing directions, that is, the orientation directions intersect at 90 degrees. At this time, the liquid crystal molecules assume a molecular arrangement in a helical structure rotated by 90 degrees between the opposing electrode substrates. The liquid crystal layer and hydrogen atoms with such a configuration are T N (Twi
This type of liquid crystal display element is called a sted nemd'atic) type liquid crystal display element. However, in a TN type liquid crystal display element, for example, the steepness of the liquid crystal is poor, and as a result, the time division characteristics are extremely poor. In order to solve this problem, a liquid crystal display element that utilizes the birefringence effect of liquid crystal has been proposed. That is, by twisting the twisted orientation of the liquid crystal by 160 degrees or more, the birefringence effect of the liquid crystal is enhanced. As shown in FIG.
．． 2 in each rubbing direction, the helical pitch is shortened so that the molecular arrangement of the rotated helical structure is further rotated. Note that 1 and 2 are electrode substrates, and 4.
5 is a polarizing plate, and 6 is a backlight for illumination. This is called 5BE (Supertwisted Birefring).
It is called a gence effect) type liquid crystal display element.
Since the liquid crystal has superior sharpness compared to a TN type liquid crystal display element, time division characteristics are significantly improved. However, in an SBE type liquid crystal display element with a twisted orientation of 160 degrees or more, the color tone becomes noticeable due to a slight difference in the product Δn-d of the refractive index anisotropy Δn of the liquid crystal and the thickness d of the liquid crystal layer due to its birefringence effect. different. This color tone appears, for example, in the order of red → orange → yellow → green → blue → indigo → violet, and this is due to the absorption axis of the pair of polarizing plates that sandwich the liquid crystal cell, as well as the Δn・d value. It varies depending on the angle of intersection of the polarization axes or the angle with respect to the alignment direction. Normally, from the viewpoint of visibility as a liquid crystal display element, the setting of Δn-d and the polarizing plate 4.5 are set so that a color tone in the yellow to green region is obtained. The settings have been made.

<Problem to be solved by the invention> However, even if the Δn of the liquid crystal is adjusted to change the color tone from yellow to green, there will be slight variations in the thickness d of the liquid crystal layer, that is, the gap between the two opposing electrode substrates. This results in uneven color tone. This non-uniformity is caused by the two opposing electrode substrates 1.2.
In addition to being used for variations in the particle size of spacers and variations in spacer distribution in order to uniformly control the gap between them, it is also caused by the waviness of the surface of the glass material itself, which becomes the electrode substrate 1.2. be. For this reason, for example, the color tone differs between areas where the spacers are relatively concentrated and areas where the spacers are scattered, resulting in spotty unevenness in tone, resulting in a significant deterioration of the quality of the appearance.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a method for driving an SBE type liquid crystal display element with excellent display quality, which can eliminate the above-mentioned drawbacks.

Means for Solving the Problems〉 The present invention provides 18
An SBE type liquid crystal display element comprising a liquid crystal cell sandwiching a nematic liquid crystal with a 0 degree twist orientation, and a pair of polarizing plates disposed on both sides of the liquid crystal cell.

The product Δn−d of the refractive index anisotropy Δn of the nematic liquid crystal and the thickness d of the liquid crystal layer is set in a range of 0.90 to 1.10 μm, and the pair of polarizing plates can provide a negative type display. A yellow colored polarizing plate was used as at least one of the pair of polarizing plates.

A non-selection waveform in positive display is applied to the display part of the liquid crystal cell to make the display color brown, and a non-selection waveform in positive display is applied to the non-display part of the liquid crystal cell. It is characterized by applying a waveform and making the background color yellow.

<Function> By driving the SBE type liquid crystal display element having the above structure by the above method, color tone unevenness peculiar to the SBE type liquid crystal display element can be prevented.

<Example> Hereinafter, an example of the present invention will be described in detail using the drawings.

In FIG. 1, an electrode pattern made of tin oxide and indium oxide is formed on a glass substrate, and an alignment film such as a polyimide-based organic polymer film for aligning liquid crystal is formed thereon. Two electronic sign substrates 1.2 on which the surface of the alignment film has been subjected to an alignment treatment by a rubbing method are placed facing each other, and a spacer is interposed between them so that the distance between them is constant between 7 and 8μ.
The electrode substrates 1 and 2 are pasted together.

Next, the liquid crystal 3 is adjusted so that the product Δn-d of the refractive index anisotropy Δn of the liquid crystal 3 and the thickness d of the liquid crystal layer is in the range of 0.90 to 1.10 μrn, and the electrode substrate is The mixture was injected between 1° and 2° to produce a liquid crystal cell. Here, the orientation direction of the liquid crystal 3 is a twist angle of 180 degrees.

Polarizing plates 5 and 7 are arranged to sandwich this liquid crystal cell so that a negative display can be obtained. At this time, as the upper polarizing plate 7, a yellow color polarizing plate (for example, LLY manufactured by Royal Electric Co., Ltd.,
-81-4O8), as the lower polarizing plate 5, a neutral gray polarizing plate (for example, LL-81-18 manufactured by Royal Electric Machinery Co., Ltd.)
5'I was used. Note that the lower polarizing plate 5 can also be made of the same yellow color polarizing plate as the upper polarizing plate 7, and in this case, the color of the non-display area becomes more yellowish.

When driving the SBE type liquid crystal display element having the above structure under the backlight 8, a non-selection waveform for positive type display (hereinafter referred to as the first driving waveform) is applied to the display section of the liquid crystal cell, A selection waveform (hereinafter referred to as a second drive waveform) for positive type display is applied to the wide display portion of the liquid crystal cell. The first drive waveform example is shown in Fig. 2 (axis), and the example of the first drive waveform is shown in Fig.
) shows an example of the second drive waveform. Note that the value of a is a>2. As shown in the dot matrix display example in Figure M3 where such a drive waveform is applied, the display area 9 is brown, the non-display area 10 is yellow, and the non-ignition area 11 to which no drive waveform is applied is yellow. , brown or green in color.

Further, FIG. 4 shows the relationship between the drive waveform and the display color for one picture element; when the first drive waveform is applied, the display is brown, and when the second drive waveform is applied, the display is yellow.

The following table shows the values of Δn-d as 0.90 ttm, 0.
94μm, 0.98μyrz, 1.04μyn, 1.1
Display color and display quality when 0 μTrL and 1.18 μm are shown.

The color contrast between the color and the color of the non-display area 10 is poor, and the display quality is poor. Due to this, when a good display is obtained, Δ
It can be said that the n-d value is about 0.90 μrn to 1.10 μm.

In addition, the value of Δn-d is 0.90μyrL to 1.10μ
Among m, when the value of Δn-d is small, the color contrast is better and the display is clearer. By the way, reflective type S
The uneven color tone seen in BE type liquid crystal display elements or ordinary transmission type SBE type liquid crystal display elements is caused by the undulations and unevenness of the glass surface that occur when manufacturing the glass substrate material. As the thickness d becomes slightly thinner, the product Δn−d of the refractive index anisotropy Δn of the liquid crystal
However, this color tone unevenness in the display area is not observed in the SBE type liquid crystal display element of the present invention, and the liquid crystal display has very good display quality. We were able to obtain the element.

<Effects of the Invention> According to the present invention as described above, it is possible to provide an SBE type liquid crystal display element that prevents color tone unevenness in the display portion and has excellent display quality.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2(a)
, (b) is a diagram of the same drive waveform, Figure 3 is a front view showing an example of display in the same matrix, Figure 4 is a waveform diagram showing the relationship between the drive waveform and display color, and Figure 5 is a conventional example. FIG. 1.2... Electrode substrate, 3... Nematic liquid crystal,
5.7...Polarizing plate. Agent: Patent attorney Takeshi Sugiyama (and 1 other person) Figure 2

Claims (1)

[Claims] 1. A liquid crystal cell in which a nematic liquid crystal with a 180 degree twist orientation is sandwiched between two electrode substrates placed opposite each other, and a pair of electrode substrates placed on both sides of the liquid crystal cell. and a polarizing plate, the product Δn·d of the refractive index anisotropy Δn of the nematic liquid crystal and the thickness d of the liquid crystal layer is set in the range of 0.90 to 1.10 μm. and the pair of polarizing plates are arranged so as to obtain a negative type display, and at least one of the pair of polarizing plates is a yellowish color polarizing plate, and the display part of the liquid crystal cell is provided with a color in a positive type display. An SBE type liquid crystal display element characterized in that a non-selective waveform is applied to make the display color brown, and a positive type display selection waveform is applied to the non-display part of the liquid crystal cell to make the background color yellow. Driving method.