JPS58168034A - Liquid crystal display of twisted nematic type - Google Patents

Abstract

PURPOSE:To increase easily an operation margin, by changing the orienting direction of the liquid crystal molecule near the substrates of a liquid crystal cell and the adhering direction of polarizing plates. CONSTITUTION:The orienting direction of the liquid crystal molecule to be determined from the direction of bright view is deviated by 5-60 deg. and two sheets of polarizing plates 6a, 6b are disposed with at least one sheet thereof deviated by 1-30 deg. in a liquid crystal device of a twisted nematic type using the plates 6a, 6b. The plates 6a, 6b are so provided that the axes of polarization thereof are asymmetrical with respect to the linear symmetrical axis 18 in the orienting direction of the liquid crystal molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a twisted nematic (TN) w-height display device suitable for matrix driving.

In recent years, liquid display devices have become well-established as small-sized displays for watches, calculators, etc., but with the development of microcomputers, they are also expected to be used as large-sized, high-capacity displays. In order to perform this large-capacity display, matrix driving is necessary, and it is an important issue to increase the operating margin when using in-situ @liquid crystals at high duty.

Possible ways to increase this operating margin include improving the liquid crystal itself and improving cell parameters outside of the liquid crystal. The present invention makes it possible to easily increase the operating margin by changing the alignment direction of the crystal molecules near the liquid crystal cell substrate and the method of attaching the polarizing plate, without making any changes to the image height itself. It is possible.

By the way, in general, the refractive index anisotropy △n and the gap d of liquid crystal
The product △n-d with (μm) affects the characteristics of the liquid crystal cell, but when driving a TN liquid crystal cell in a matrix, △
Visibility varies greatly depending on the size of nd. That is, Δ
When n-d is large, contrast streaks tend to occur in front of the liquid crystal cell, but the viewing angle is narrow.
On the other hand, when Δn−d is relatively small, the viewing angle is wide, but there is a drawback that it is difficult to obtain contrast when viewed from the front. The present invention relates to a liquid crystal cell with a large Δn-d, and is intended for a liquid crystal cell with Δn-d≧09 from the viewpoint of background layer color, and relates to a twisted nematic liquid crystal display using two polarizing plates. In the device, the alignment direction determined from the clear viewing direction is shifted by 5 to 60 degrees, and at least one of the inner polarizing plates is shifted by 1 to 30 degrees, and the polarization of the two sheets is adjusted with respect to the line symmetry axis of the alignment direction. The polarization axis of the plate was made to be asymmetric! This is a twisted nematic type liquid crystal display device.

This will be explained below according to the diagram. FIG. 1 is a sectional view of a twisted nematic liquid crystal cell of the present invention.

The basic structure of the cell is exactly the same as Jubei's reflective TN liquid crystal cell. That is, a transparent electrode (2a).

The substrates (la) and (11)) provided with (2b) are facing each other and sealed with a sealing material (8), and liquid crystal (4) is injected to form a liquid crystal cell (5). Image light plate (6a).

(6b), and a reflecting plate (7) is further installed on one side thereof.

The alignment direction of the liquid crystal molecules in the vicinity of (la) and (lb) is made to differ by approximately 90 degrees, so the liquid crystal molecules form a helical structure of approximately 90 degrees in the vicinity of the substrate (1).However, , in the twisting direction of this helical structure, there is a second
As shown in the figure, two types can be considered.
) is set toward the front, the case where the liquid crystal molecules are twisted counterclockwise as in (a) is defined as levorotatory, and the case where the liquid crystal molecules are twisted clockwise as in (b) is defined as dextrorotatory.

This direction of clear vision is the ψ5 position when the eye is placed in that direction, that is, the direction that is easiest to see when that direction is used as the observation direction.When using levorotatory Ha, the orientation direction is As shown in Figure 2 (A), the orientation direction θA on the front side is 45° clockwise, and the orientation direction θB on the back side is 145° clockwise.
In addition, when a dextrorotatory liquid crystal is used, the orientation direction is 45 degrees clockwise for the orientation direction θA on the front side and 45° clockwise for the orientation direction θB on the back side, as shown in Figure 2 (B). 45
°.

In addition, polarizing plates (6a) and (6b) installed in the liquid crystal cell
The sound path is to set the polarization axis almost parallel (parallel lamination) or almost perpendicular (vertical lamination) to the alignment direction of liquid crystal molecules at the adjacent base edge, but vertical lamination has a lower degree of coloring due to retardation. Since this is more advantageous, only the case of vertical attachment will be described below, but parallel attachment is also possible.

Also, the intersection angle of the polarization axes of the polarizing plate. Taking a levorotatory cell as an example, 1 is the included angle in the direction in which the incident polarized light plane propagates as shown in FIG. The signs of the rotation directions of the front polarizing plate 021 and the back polarizing plate 021 are DA, as shown in the figure for the polarizing axes of the front and back polarizing plates. The direction of increasing , is positive, and Daa. The direction in which , is made smaller is negative, and the rotation state of the polarizing plate is (OA).

sB). Here, mA indicates the deviation from the normal polarization axis of the polarizing plate on the front side. Clockwise rotation is negative. JZIB indicates the deviation of the polarization axis of the polarizing plate on the back side, and in FIG. 3, clockwise rotation is negative, and counterclockwise rotation is positive.

GuA=-5°, χB=-5°, daa. , = 80°, dam -09, ρB = 069 door a. ,=90
It is known that the margin is improved compared to the liquid crystal display device 1 of ', but in this case it is expressed as (-5°, -5°). In these two cases, Mori symmetry axis in the orientation direction 03)
In contrast, the polarization axes of the two polarizing plates are symmetrical.

As is well known, the clear viewing direction of a TN liquid crystal display device is an intermediate direction between the alignment directions of liquid crystal molecules in the vicinity of the front and back substrates, and in FIGS. It shows.

In the present invention, as shown in FIG. In the following description, the case where the direction is in the rotational direction is taken as positive, and the case where the clear viewing direction (14b) is in the counterclockwise direction with respect to the observation direction a9 is taken as negative.

In the present invention, the refractive index anisotropy Δn of the liquid crystal and the gap d of the liquid crystal layer are
It is preferable to use a liquid crystal cell in which the product Δn-d of (μm) is Δn-d≧09 μm.This means that a liquid crystal cell with a large Δn-a has poor visibility and sharpness when viewed from a specific direction. In order for the background coloring to be good and not to have a reddish tinge when the aerial light plate is slightly rotated, Δn-d≧0.9μ
It is assumed that m.

Using such a liquid crystal cell, the alignment direction is shifted by 5 to 60 degrees from the original alignment direction determined by the clear viewing direction, and at least one of the inner polarizing plates is shifted by 1 to 30 degrees. The polarization axes of the two polarizing plates are asymmetrical with respect to the line symmetry axis of the alignment direction, that is, pA to g.
B.

This is because the margin is improved by moving the polarization axis symmetrically, for example, (-5°, -5°), where aA=OB in a liquid crystal cell with a normal alignment direction as shown in Figure 2. However, when the alignment direction is deviated from the original alignment direction determined by the clear viewing direction as in the present invention, it is not necessarily easy to see, and there is hardly any improvement in the margin. may even decrease.

Therefore, in the present invention, when a levorotatory liquid crystal is used as the liquid crystal, the alignment direction and polarizing plate are determined as shown in FIG. In the figure, the clear viewing direction Q6) is the observation direction Q6).
7) An example is shown in which the orientation direction is determined from the clear viewing direction, and the orientation direction on the front side is θ clockwise.
A=7561 The orientation direction of the back side is θB=-15 clockwise.
°.

In this example, ψ=300, but in the present invention, it is 5 to 60.
When ψ is less than 5 degrees, there is almost no margin improvement effect, and when ψ is greater than 60', the driving voltage becomes extremely high and there is a slight deviation in the observation direction, i.e.
This is not preferable because a phenomenon in which visibility is extremely reduced due to a shift in which ψ becomes large is observed.

In this case, when a levorotatory liquid crystal is used, the orientation direction on the red side is clockwise from θA=105 to
50', and the orientation direction on the food side may be set so that θB=15° to -40° clockwise.

In addition, in this example, only the polarization axis of the front polarizing plate is shifted, and since it is attached vertically, the deviation from the orientation direction is lp, = -1o°, and yJB = o°. .

In this case, the polarizing plate on the front side is 3
The polarizing plate on the back side is shifted by 45 degrees, and the polarizer on the back side is shifted by 45 degrees.
The two polarizing plates are said to be asymmetrical. Furthermore, these two polarizing plates are arranged so that the polarizing axis of the front polarizing plate is set in a direction in which, among the intersection angles of the two polarizing plates, the intersection angle g5POL in the direction in which the polarization plane propagates is smaller than the rotation angle of the liquid crystal molecules. This means that it is shifted by 10 degrees.

In the present invention, by asymmetrically shifting the two polarizing plates from the line symmetry axis U of the alignment direction in combination with shifting the alignment direction, a specific direction different from the clear viewing direction defined by the alignment direction A thin margin can be generated in the viewing direction, and even better multiplex drive performance can be obtained using the same liquid crystal as the conventional one.

In the present invention, the angle at which the polarizing plate is shifted is 1 to 30 degrees.

Further, in this example, the front polarizing plate was moved in the direction of FBA≦−1°, but shifting in the direction of 121A≧1° is not very effective, and the polarizing plate is shifted in the direction in which the polarization plane propagates. 1
is smaller than the rotation angle of liquid crystal molecules, that is, 60°
≦ It is preferable that 1≦89° from the viewpoint of improving the margin.

Conversely, when a dextrorotatory liquid crystal is used, H'', as shown in Figure 6, the clear vision direction Q9i is said to be the viewing power direction (A). 11 Viewed from the observation direction, the front side is placed in the same direction as θA = -50・5 clockwise.
The orientation direction of the back side may be set to θB=40° to −15° clockwise.

Also, in this example, only the polarization axis of the Hayabusa plate on the front side is shifted, and it is set to ρA--100, and ρB = 0°, so the two polarizing plates are is considered to be asymmetric. The direction in which this polarization axis is shifted is door a. , is smaller than the rotation angle of the liquid crystal molecules by at least 30' toward the polarizing plate 1 on the front side.

If the angle at which this polarizing plate is slid is less than 1 degree, the effect will be poor, and if it exceeds 30 degrees, the snoring coloring will become inappropriate for display and the stain will be difficult to attach. It is assumed to be 30°.

Next, test examples will be explained.

A few liquid crystals with refractive index anisotropy Δn=0.132 were injected into a cell fW+ha-7 μm to obtain Δn-d=0.9.
2, the direction of clear vision was shifted by ψ-30' from the direction of observation. That is, a levorotatory cell with the orientation shown in FIG. 5 was prepared.

Using this bath crystal cell, attach the polarizing plates (o', o'), that is, without shifting them at all, and adjust the rapid aging M8 and viewing angle dependence Mq, which are parameters that serve as a guideline for multiplex drive. was measured. This conclusion, 11. .

The result is shown in Figure 7.

Nao, Me, and Mq are represented by the following formula, ■. ,■,.

are the voltages at which the relative brightness is 90% and 50%, respectively, and θ
is the angle from the normal direction of the liquid crystal cell toward the viewing direction.

MS=v90 (θ=10°)/V50(θ-10°)
Mq,=V,O(θ=40°)/V*o(θ=10°)
As is clear from FIG. 7, the operating margins of Me and Mq, which have a horizontal relationship, are lower in the viewing direction than in the clear viewing direction, and are not useful for improving the margin at all. Further, in this case, Me/MqU is about 0.76% degree in the clear vision direction, and although not shown in the figure, it is almost symmetrical about the clear vision direction.

As described above, in the conventional system, it is most suitable to perform orientation processing so that the clear viewing direction becomes the viewing direction.

Figure 8 shows the same liquid crystal cell with polarizing plates (-5°, -
5 degrees), that is, 5 paL = s o', and the polarization axes of the two polarizing plates are symmetrical with respect to the line symmetry axis of the orientation direction. In this case, since the polarizing plate is shifted, both Me-Mq in the clear viewing direction and Me・Mq in the observation direction are improved, but Me・Mq in the clear viewing direction is still higher, and when the clear viewing direction is changed from the viewing direction. It is more preferable that Me.Mq in the clear vision direction is a little less than 0.78.

On the other hand, Fig. 9 shows an example of the present invention, which was measured with the configuration shown in Fig. 5 with the polarizing plate on the front side bent by 10 degrees and set as "POL-80", and near the observation direction. Me-
The one with improved Mq is 30 degrees, which is the clear vision direction.
Ms-Mq is approximately 0.78 or more from the position to the opposite direction (/-=-30° tii), and a high margin can be obtained.

By arranging the polarizing plate asymmetrically with respect to the line symmetry axis in the orientation direction, Me/Mq also becomes asymmetrical with respect to the clear viewing direction, and Me/Mq increases in a specific direction, making it symmetrical. It was higher than if it were.

As is clear from this figure, the observation direction is 9 degrees to the right from 25 degrees.
i1j has excellent angle dependence Mq and Me-Mq,
It can be seen that ψ≧5° is excellent. Furthermore, if the distance from the viewing direction exceeds 130', the increase in VSO is more significant than the improvement in Ms-Mq, and the display becomes difficult to see, so ψ≦60
It can also be seen that ° is preferable. That is, yso(θ=10°
) increases, a slight deviation in the viewing direction will cause the display on one side to be blurred due to insufficient voltage, and on the other side to be extremely difficult to see as the display may indicate excessive blood pressure and crosstalk. From this, the difference between the clear vision direction and the observation direction is
It can be seen that ψ=5 to 60° is appropriate. Note that in the opposite direction, that is, when ψ≦θ°, 1:M days·Mq decreases.

As described above, in the present invention, by appropriately setting the alignment direction and the optical axis, a TN liquid crystal display device with good multiplex characteristics can be produced.

In addition, in the above embodiment, since a levorotatory cell was used, ψ
Although it was set to -5 to 60 degrees, equivalent performance can be obtained if ψ is set to -5@ to -60' completely symmetrically in the W1 case of a dextrorotatory cell.

In addition, in the above embodiment, the polarizing plate of 111 was moved, but it is also possible to move only the polarizing plate of % (@), or both of the polarizing plates, or move at least one polarizing plate. , and the orientation direction of the two polarizing plates with respect to the 0-leg symmetry axis =
*The axes may be set asymmetrically, and the angle may be determined as appropriate within the range specified by Motoaki by experiment.

The present invention is not limited to this, and for example, a polarizing plate may be formed as an undercoat on the inner surface of the G plate, or a side light plate substrate with electrodes formed on the polarizing plate may be used, and various resins,
Providing an overcoat of inorganic material, performing alignment treatments such as oblique vapor deposition and rubbing, mixing pleochroic dyes into liquid crystal,
It is possible to use it in a variety of ways, such as using polarizing films, color filters, and creating multilayer cells.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a TN liquid crystal display device. 2 to 6 show the songs of the TN liquid crystal display device of the present invention,
Ming diagram. FIG. 7 to FIG. 9 are graphs showing measurement results of Examples and Comparative Examples. la, lb... board 2a, 2b... battery case 6a,
6b...Polarizing plate calyx 2 ffi. Kaya 5 Illustrated Kayotokawa f, Kyoto Town Kauri-reba shoulder 1-year-old 1-ku heart J-reba" Cod ρI preside over 3 Yasu Kazuei procedure 5 UzLE fortune telling: (Method) 1988 411 Nol ['' Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, 1987'1 Patent Application No. 50165! 9) Name of the invention) Stonematic type liquid crystal display device, 3. Relationship with shells and attrition matters to be amended Patent applicant address: Marunouchi-2, Chiyoda-ku, Tokyo] ll & 2 name
(004) Asahi Glass Co., Ltd. 10 agents 105 J2. 11 (-1 Akira [LL + 8 years 3JI 29 days (shipment date)) (・, Number of inventions increased by amendment None 7 or more 2 (A)

Claims (1)

[Claims] (1) In a twisted nematic liquid crystal display device using two polarizing plates, the alignment direction from the clear viewing direction is
In addition to shifting the polarizer by 60 degrees, the inner angle of the two polarizing plates should be at least 1
Align the sheets by 1 to 30 degrees, 2 to the axis of symmetry in the orientation direction.
Twisted nematic purification liquid characterized by the fact that the polarization axes of the polarizing plates are asymmetrical? 9 display device. (2) Refractive index anisotropy Δn of liquid crystal,! 2. The twisted nematic liquid crystal display device according to claim 1, wherein the gain Δn-d of the gap d (μm) between the :'p product and the product is 0.9 μm or more. (8) The polarization axis of the polarizing plate on the front side is shifted by 1 to 30 degrees in a direction such that among the intersection angles of the opposing polarizing plates, the intersection angle in the direction in which the polarization plane propagates is smaller than the rotation angle of the liquid crystal molecules. A twisted nematic liquid crystal display device according to claim 1 or claim 2, characterized in that: (4) A levorotatory liquid crystal is used as the liquid crystal, and the orientation direction on the front side is 105° to 506° clockwise when viewed from the viewing direction, and the orientation direction on the back side is 15° to -40' clockwise. A twisted nematic liquid crystal display device according to claim 3. (5) A dextrorotatory liquid crystal is used as the liquid crystal, and the orientation direction of the front side is -50° to -105° clockwise when viewed from the viewing direction.
°, and the orientation direction of the back side is 40° to -15° clockwise.
A twisted nematic liquid crystal display device according to claim 3, characterized in that: