JPH05203922A - Ferroelectric liquid crystal device - Google Patents

Abstract

(57) [Abstract] [Purpose] To suppress the movement of liquid crystal molecules in the non-display area and improve the display quality. [Structure] A liquid crystal display element 101 having a display area 103 of a matrix-type electrode structure in which a ferroelectric smectic liquid crystal layer 12 having a spiral structure is disposed between two upper and lower transparent electrode substrates. A liquid crystal display device having non-display regions 105 and 107 made of a ferroelectric smectic liquid crystal layer sandwiched between the upper and lower electrodes also on the outer side is provided in the smectic liquid crystal layer in which the average molecular arrangement of liquid crystals in the non-display region is the same. Drive so that they are not aligned in a specific direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric liquid crystal device using a ferroelectric liquid crystal, and more particularly to a ferroelectric liquid crystal device used for displaying.

[0002]

2. Description of the Related Art Conventionally, in a display device using liquid crystal, a liquid crystal panel unit is usually constructed by mounting a liquid crystal panel in a cosmetic case. However, when the liquid crystal panel is mounted using a cosmetic case, the height of the cosmetic case is higher than the surface of the liquid crystal panel, and the display unit cannot be visually recognized when viewed from an angle. Therefore, a non-display portion having a width of about 5 to 10 mm is provided in the adjacent portion on the outer side of the display portion to improve the visibility of the display. This non-display portion is often near the sealing member of the cell that constitutes the liquid crystal panel.

By the way, when a liquid crystal having bistability is used in such a liquid crystal panel, an electric signal is applied to the non-display portion to control the non-display portion to have a uniform display state. is doing. As a method for controlling the non-display portion to be uniform, the same writing as in the display portion is performed in the non-display portion, and the average molecular directions in the non-display portion are aligned in the same direction (see FIG. 7). ) Or a ferroelectric liquid crystal present in a non-display area as shown in Japanese Patent Application No. 3-45627 (hereinafter,
(Referred to as FLC) is the first and second with different average molecular directions.
In this method, an electric field having a value sufficient to bring the electric field to a stable state is alternately applied in a predetermined cycle.

[0004]

[Problems to be solved by the invention] However,
Clark Ragaval (P213-P234, MCL
C, 1983, Vol. In the so-called SSFLC type liquid crystal element proposed by J. 94), there are two stable states (first and second stable states) in which the average molecular directions of the liquid crystal are different. It is known that, when such an element is refresh-displayed by matrix driving, FLC molecules also move to some extent by a non-selection signal at the matrix driving device. This is also clear from the fact that when the optical response of the pixel to which the non-selection signal is applied is taken, the light amount varies in synchronization with the applied pulse. In so-called splay orientation, in which the angle of the major axis of the molecule is greatly twisted between the upper and lower substrates, such fluctuations in the molecule can hold the displayed content unless the stable position of the molecule changes (switching). There was no problem other than a slight decrease in contrast. However, in a so-called uniform orientation cell (display panel) in which the change in the angle of the molecular long axis direction between the upper and lower substrates is relatively small,
There is a phenomenon in which liquid crystal molecules move in the layer by applying a voltage (for example, a non-selection signal). This phenomenon will be described in detail with reference to FIG.

FIG. 6A shows a cell state before voltage application,
(B) is a cell state after voltage application. The FLC 36 is enclosed in the seal member 35. A polyimide thin film is used as the alignment layer, and the rubbing direction is parallel to the upper and lower substrates from bottom to top in both (a) and (b). When such processing is performed, the smectic liquid crystal layer 37 is generated in a direction orthogonal to the rubbing direction as shown in FIG. 6 (c).

When the cell thickness is made thin enough to release the helical pitch, the FLC molecule 38 can be in two stable states, but one of the states 38 is aligned with the orientation of all molecules in the cell. deep. Assuming that this state is + θ (FIG. 6D), −θ is almost symmetrical with respect to the layer normal h.
There is another stable state at the position.

When an electric field (for example, a square wave of 10 Hz and ± 8 V) is applied to the entire surface of the cell under this state (+ θ), the liquid crystal molecules are kept in the inclination with respect to the layer normal line of + θ.
Start moving in the layer from point A to point B in (a).
As a result, when the voltage application is continued for a long time, a portion E having no liquid crystal is generated at the A end as shown in FIG. 6B, and the cell thickness of the B portion becomes thicker than that of the A portion. In such a phenomenon, when the liquid crystal molecule is in the state of −θ, the liquid crystal moves in the layer from the B end to the A end, and a void portion without liquid crystal such as the E portion occurs at the B end.

Then, the above-mentioned phenomenon is likely to occur particularly in the non-display area near the sealing member as described in the conventional example, and as shown in FIG. 7, no movement of the liquid crystal occurs in the display section 103. Even in the case where it does not occur, the liquid crystal moves in the non-display portions 105 and 107 in the direction parallel to the smectic liquid crystal layer 37 (FIG. 6). In FIG. 7, 71 is a void portion generated by the movement of liquid crystal molecules,
72 is a deposition portion of liquid crystal molecules. The cause is still unknown,
In particular, the liquid crystal tends to move in the non-display area. This is considered to be one of the reasons that the cell thickness is slightly thicker in the vicinity of the sealing material 35 (FIG. 6).

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a FLC element in which movement of liquid crystal molecules in a non-display area is suppressed and display quality is improved.

[0010]

In order to achieve the above object, the ferroelectric liquid crystal device of the present invention comprises a ferroelectric smectic liquid crystal layer having a spiral structure formed between two upper and lower transparent electrode substrates. A liquid crystal display element having a display area of a matrix type electrode structure, which has a non-display area formed of a ferroelectric smectic liquid crystal layer sandwiched between the upper and lower electrodes outside the display area. And driving means for driving so that the average molecular arrangement of the liquid crystal in the non-display portion is not aligned in a specific direction within the same smectic liquid crystal layer.

In a preferred embodiment of the present invention, the driving means sets two types of average molecular directions in the same smectic liquid crystal layer in the non-display area and equalizes areas having the respective molecular directions. Therefore, the liquid crystal element is driven. For that purpose, for example, driving is performed so that the average molecular direction in the same smectic liquid crystal layer in the non-display area is different for each adjacent electrode. Further, the drive means writes the pixels in the non-display area at least once within the display time of one frame.

[0012]

In the present invention, the liquid crystal molecule state in the non-display area is avoided to be the same state in the same smectic liquid crystal layer, and the molecular arrangement position in the same smectic liquid crystal layer is directed along the smectic liquid crystal layer. Thus, the regions of different alignment states are set alternately in a cycle as short as possible.
Thereby, the movement of liquid crystal molecules in the layer can be suppressed. Further, at this time, by making the regions occupied by the respective states substantially the same in the same smectic liquid crystal layer, it is possible to more effectively suppress the intra-layer movement of the liquid crystal molecules.

[0013]

Embodiment 1 FIG. 2 is a block diagram of a liquid crystal display device according to an embodiment of the present invention. This device is 640 (information line) x 480
The FLC panel 101 having the number of (scan line) pixels is provided, and the non-display area adjacent to the display section 103 is formed by the scanning electrodes and the signal electrodes existing in the common non-display section 105 and the segment non-display section 107. There is. Further, the FLC panel controller 109 is provided, and the driving voltage power supply 111, the non-display portion display pattern control portion 113, the logic control portion 115, and the logic control power supply 117, which are included in the FLC panel controller 109, set driving conditions such as a driving waveform and a driving voltage. All the controls of the FLC panel 101 such as control of the segment and common drive drivers 119 and 121, communication between the data generator 123 and the driver groups 119 and 121, and display pattern control of the non-display portion are performed.

FIG. 3 is a waveform diagram showing drive waveforms for describing a desired pattern. As shown in the figure, when the information signal m is applied to the scanning signals n to n + 2, (n,
The (m) pixel is in the dark state, and the (n + 1, m) and (n + 2, m) pixels are in the bright state. Driving conditions for good drawing are V1 = 15V, V2 = −15V, V at room temperature.
3 = 6V, V4 = -6V and one horizontal scanning period = 80 μ
sec. However, each voltage value is a potential difference from the common potential Vc.

FIG. 1 shows the layout of the display section 103 and the non-display sections 105 and 107 of the FLC panel 101 shown in FIG. When the inner surfaces of the upper and lower substrates are oriented in the rubbing direction 11 shown in FIG.
A smectic liquid crystal layer 12 is formed. 12 can be considered as a projection view of the smectic liquid crystal layer on the electrode substrate. When the smectic liquid crystal layer indicated by 12 has an average molecular axis as shown in the figure, the movement of the liquid crystal molecules occurs from right to left in the figure. In order to prevent the movement of the liquid crystal molecules in the non-display portion, a layer of the liquid crystal molecules in the non-display portion is provided by periodically and uniformly providing two alignment state portions in a direction parallel to the smectic liquid crystal layer as shown by 13. I was able to prevent inward movement. 1 of FIG.
In 3, white stripes and black stripes are FLC
Each of the two possible states of D is shown.

Panel size 260 mm (information edge) × 20
When writing was performed in a cell of 0 mm (scanning end) under the above-mentioned driving conditions, when the non-display portion was aligned in the single molecule direction, the cell thickness portion of 1.1 μm was 2.10 after driving for about 170 hours.
Although it has increased to 0 μm, the non-display part is shown in FIG.
In the case of the uniform stripe pattern orthogonal to the direction of the smectic liquid crystal layer as shown in, the cell thickness of 1.1 μm was maintained.

The cell used in Example 1 is a combination of electrode substrates as shown in FIG. 4 so that their stripe electrode directions are orthogonal to each other. In FIG. 4, 1 is a glass substrate, 2 is a striped transparent electrode made of ITO, 3
Is an insulating film made of SiO ₂ , 4 is a polyimide alignment film, 6
Is a liquid crystal (FLCD), and 35 is a sealing member.

The molecular arrangement (13 in FIG. 1) in the direction parallel to the direction of the smectic liquid crystal layer formed in the non-display portion of FIG. 1 has a shorter alternating cycle, and the display quality as a liquid crystal panel tends to be excellent. It is in. In FIG. 1, therefore, the minimum pitch is realized by changing the molecular arrangement for each stripe electrode in FIG. 4 (white and black stripes 13 in FIG. 1). The characteristics of the FLC material used in the present invention are shown below. Shown in the table.

【table 1】 As the alignment film, LQ-1802 manufactured by Hitachi Chemical Co., Ltd. was used.
As the alignment treatment, the upper and lower substrates were rubbed in the same direction (polyimide alignment film 4 in FIG. 4).

Embodiment 2 FIG. 5 shows a layout of a display portion and a non-display portion of an FLC cell according to another embodiment of the present invention. The difference from the first embodiment is only that the data of the non-display portion display pattern built in the non-display portion display pattern control unit 113 of FIG. 2 is converted from the stripe pattern for each line into a checker pattern in 1-dot units. is there. White dots and black dots indicated by 51 in FIG. 5 represent two states that the FLCD can take.

By making the non-display portion a checker pattern in units of one dot, the effect of suppressing liquid crystal movement of the non-display portion similar to that of the first embodiment and the effect of making the non-display portion inconspicuous are relatively obtained. This has the effect of enhancing the display quality by emphasizing the display section. In addition, the liquid crystal movement of the non-display portion is suppressed regardless of the rubbing direction.

[0021]

As described above, according to the present invention, the matrix type FL having the non-display portion other than the display portion is provided.
In the C cell, the molecular alignment state of the non-display area was periodically and evenly distributed in the direction parallel to the smectic liquid crystal layer, so that the liquid crystal migration phenomenon, which was particularly remarkable in the non-display area, could be suppressed.

[Brief description of drawings]

FIG. 1 is a plan view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 2 is a block diagram of a drive circuit for driving the liquid crystal panel of FIG.

FIG. 3 is a drive waveform diagram used to drive the liquid crystal panel of FIG.

4A and 4B are a cross-sectional view and a plan view for wetting a stripe electrode pattern and a cell structure of the liquid crystal panel of FIG.

FIG. 5 is a plan view of a liquid crystal panel according to another embodiment of the present invention.

6 and 7 are diagrams illustrating problems in a conventional liquid crystal element.

[Explanation of symbols]

1: Glass substrate, 2: Striped transparent electrode, 3: Insulating film, 4: Polyimide alignment film, 6: Ferroelectric liquid crystal (FLC)
D), 11: rubbing direction, 12: smectic liquid crystal layer, 13: uniform stripe pattern for each stripe electrode, 35: sealing member, checker pattern in 51: 1 dot unit, 101: FLC panel 101, 10.
3: display unit (display region), 105: common non-display unit (non-display region), 107: segment non-display unit (non-display region), 109: FLC panel controller, 113: non-display unit display pattern control unit, 115 : Logic control unit.

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[Procedure amendment]

[Submission date] November 27, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a plan view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 2 is a block diagram of a drive circuit for driving the liquid crystal panel of FIG.

FIG. 3 is a drive waveform diagram used to drive the liquid crystal panel of FIG.

4A and 4B are a cross-sectional view and a plan view for wetting a stripe electrode pattern and a cell structure of the liquid crystal panel of FIG.

FIG. 5 is a plan view of a liquid crystal panel according to another embodiment of the present invention.

FIG. 6 is a diagram illustrating a problem in a conventional liquid crystal element.

FIG. 7 is a diagram illustrating a problem in a conventional liquid crystal element.

[Explanation of symbols] 1: glass substrate, 2: transparent electrode in stripe form, 3: insulating film, 4: polyimide alignment film, 6: ferroelectric liquid crystal (FLC)
D), 11: rubbing direction, 12: smectic liquid crystal layer, 13: uniform stripe pattern for each stripe electrode, 35: sealing member, checker pattern in 51: 1 dot unit, 101: FLC panel 101, 10.
3: display unit (display region), 105: common non-display unit (non-display region), 107: segment non-display unit (non-display region), 109: FLC panel controller, 113: non-display unit display pattern control unit, 115 : Logic control unit.

Claims (4)

[Claims] 1. A liquid crystal display device having a display area of a matrix-type electrode structure, in which a ferroelectric smectic liquid crystal layer having a spiral structure is arranged between two upper and lower transparent electrode substrates, and the display area is outside the display area. A liquid crystal display element having a non-display region composed of a ferroelectric smectic liquid crystal layer sandwiched between the upper and lower electrodes also in a portion, and the average molecular arrangement of liquid crystals in the non-display portion is the same in a specific direction in the same smectic liquid crystal layer. 2. A ferroelectric liquid crystal device, comprising: a driving unit that drives the liquid crystal so that the ferroelectric liquid crystal is not aligned. 2. The driving means sets the average molecular direction in the same smectic liquid crystal layer in the non-display area to 2
2. The ferroelectric liquid crystal device according to claim 1, wherein the liquid crystal display element is driven so as to equalize the types and the areas of the respective molecular directions. 3. The driving device according to claim 1, wherein the driving unit drives the adjacent smectic liquid crystal layer in the non-display region so that the average molecular direction of the adjacent smectic liquid crystal layer is different between adjacent electrodes. Ferroelectric liquid crystal device. 4. The ferroelectric substance according to claim 1, wherein the driving unit writes the pixels in the non-display area at least once within a display time of one frame. Liquid crystal device.