JP2001281681A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve workability, when shilding an electrode leading about part of a liquid crystal display element using liquid crystal having a memory function by an image frame part. SOLUTION: A dummy display part A2 to display fixed data and which that is, can restore a display state by voltage impression is provided in the peripheral part of a display area A to which the voltage is applied in a transparent electrode, and a positioning margin with respect to the image frame part 6 is provided between an effective display part A1, which actually displays display data and the electrode leading about part B in the dummy display part A2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a liquid crystal layer having a memory property.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) is lightweight.
Because of its low power consumption, it is widely used especially for reflective portable information display devices. In recent years, the spread of portable information display devices has been remarkable, and it is expected that this field will continue to expand. However, how to attain high definition and high brightness is a current problem.

[0003] Among the liquid crystal display elements, a low-priced reflective STN element has been mainly used. However, due to higher definition in the future, an increase in power consumption accompanying an increase in drive voltage and an increase in the number of drive lines are required. Since the contrast is expected to decrease due to the increase, it is probably difficult to satisfy the required display performance with the STN element.

[0004] According to the TFT liquid crystal display element, the required display performance will be satisfied, but its use is limited in terms of price and power consumption. In addition, regarding the brightness, the liquid crystal display element that has been put to practical use requires one or two polarizing plates, so that the reflectance with respect to external light is limited, and unless a backlight is used. However, there is a problem that only display with insufficient brightness can be obtained.

In order to solve the problems such as an increase in power consumption due to high definition and the problem of insufficient display quality, LC
A cholesteric LCD having a memory property of a type that does not use a polarizing plate for limiting the brightness of D has been proposed (George H. Heilmeier, Joel).
E. FIG. Goldmacher et al. Appl. P
hys. Lett. , 13 (1968), 132).

The cholesteric LCD will be briefly described. A cholesteric liquid crystal having a cholesteric phase is obtained by adding a chiral agent as an optically active substance to a nematic liquid crystal. Nematic liquid crystals include biphenyl, tolan, pyrimidine, cyclohexane,
Difluorostilbenzene or the like is used alone or in combination.

[0007] The cholesteric phase has a layer structure, and the direction normal to the layer is called a helical axis. The long axis of the molecule is distributed perpendicular to the helical axis and forms a helical structure that is slightly shifted for each adjacent layer. The distance until the molecular long axis rotates 360 degrees along the helical axis is called a helical pitch.

[0008] A cholesteric LCD is manufactured by injecting the cholesteric liquid crystal into a cell formed by bonding a pair of substrates with transparent electrodes through an epoxy-based peripheral sealing material. At this time, an electric insulating film or a resin thin film may be provided on the transparent electrode as needed.

In a cholesteric LCD, a desired display can be realized by applying a predetermined voltage through the transparent electrode. At that time, by providing a light absorbing layer such as black on the substrate surface opposite to the display side,
The display contrast can be improved.

The cholesteric LCD is unique in that a desired display is obtained not after the voltage is applied but after the voltage is applied, that is, after the writing is completed.
Furthermore, the effective value of a series of applied voltage waveforms does not directly determine the state after voltage erasure, but the display state after voltage erasure depends on the application time of the voltage pulse applied immediately before and the display state. The point that depends on the amplitude value is unique.

Therefore, the cholesteric LCD does not need to constantly apply a voltage to maintain the display unlike the STN element conventionally used in practical use, and furthermore, the number of scanning electrodes associated with higher definition is reduced. It is characterized in that the drive voltage does not increase regardless of the increase. The relationship between the applied voltage and the optical characteristics can be elucidated by repeating an experiment in which a predetermined voltage pulse is applied to the cholesteric LCD, and that is erased to confirm the display state.

According to the experimental results, when the voltage pulse application time is fixed and the voltage amplitude is increased, while the voltage amplitude is small, the orientation state does not change in the initial stage after the voltage is erased. The reflectivity does not change, but when the voltage amplitude is increased, it becomes a fine scattering state after voltage erasure, and if a light absorbing layer is provided on the substrate on the opposite side of the display surface, the light absorption layer According to the display, when the light absorbing layer is a black light shielding layer, a dark display is obtained. The orientation state at this time is called a focal conic state.

Further, when the voltage is increased, a planar state is obtained in which the state after voltage erasure reflects light of a specific wavelength with respect to external light. The specific orientation of each state is shown in FIG.
It is assumed that That is, FIG.
In the planar state shown in (a), many domains are generated, and the helical axis direction is slightly different for each domain, and the average helical axis direction is almost perpendicular to the substrate.

At this time, it is known that a specific wavelength is reflected with respect to external light, and this wavelength is called a selected wavelength. In an ideal planar state, the selected wavelength is determined by the product of the helical pitch and the average refractive index of the liquid crystal. In practice, however, the selected wavelength tends to shift to a shorter wavelength side than this wavelength. In addition,
Depending on the type of resin thin film formed between the transparent electrodes and the rubbing applied, the helical axis can be oriented almost completely perpendicular to the substrate.

On the other hand, in the focal conic state shown in FIG. 4B, the helical axis direction of each domain is randomly distributed, and a scattering phenomenon occurs. At this time, if there is a light absorbing layer on the back side, a display corresponding to the color of the light absorbing layer can be obtained.

When the light-absorbing layer is a black light-shielding layer, it can take two states, a planar state as a bright state and a focal conic state as a dark state. A stable intermediate state has been confirmed by the ratio of both domains, and a halftone display is also possible depending on the voltage application condition.

Next, a case where the display pattern is a dot matrix arrangement will be described. Note that the voltage written in the focal conic state is VF, the voltage written in the planar state is VP, and the upper limit voltage at which the display state does not change even when the voltage is applied is VS. By the line-sequential driving, a voltage pulse having a voltage amplitude Vr is input to the row electrode, and a voltage pulse having the voltage amplitude Vc is input to the column electrode in synchronization with the input. The display sequence is completed by applying a voltage to each electrode once.

At this time, if ON display is selected,
When the voltage amplitude of Vr + Vc is input only once to the display pixel, and then the non-selection voltage Vc is applied, and when the off display is selected, the voltage amplitude of Vr−Vc is 1 in the display pixel.
And then the non-selection voltage Vc is applied.

Here, assuming that the planar state is selected at the time of on display and the focal conic state is selected at the time of off display, Vr + Vc> VP, Vr-Vc =
In VF, Vc is set so that the written state does not change.
It is required that Vc <VS. If this condition is satisfied, matrix display becomes possible.

[0020]

As described above, in a cholesteric LCD having a memory property, display data is held without applying a voltage. There is a problem that the state changes.

The display is restored by the voltage processing at the time of rewriting, but there is an electrode routing portion which does not contribute to the display around the actual display. This electrode routing portion is a portion to which no voltage is applied, and when the display state is changed by an external force, the display state is not restored semipermanently and is visually recognized as display unevenness.

In order to make the display unevenness invisible, there is a method of forming a thin film of chromium or the like on the inner surface of the substrate as an inner surface black mask method. However, the inner black mask method is not preferable because it requires a considerable cost.

On the outer surface of the substrate, a light-shielding layer such as a light-shielding film may be stuck around the display section in a frame shape, or the frame itself may be attached. In this case, the inner edge of the frame is removed. It is necessary to accurately align the position between the display unit and the non-display unit (electrode routing part), and the productivity is greatly reduced.

[0024]

According to the present invention, it is possible to obviate the need for accurate positioning of the frame when the display unevenness of the electrode routing portion is blinded by the frame.

For this reason, the present invention provides a liquid crystal display device having a liquid crystal layer having a memory property sandwiched between a pair of substrates each having a transparent electrode formed on the opposing surface side. A dummy display section for displaying fixed data is provided in a peripheral portion in the display area to which the voltage is applied, and an effective display section for actually displaying display data is surrounded by the dummy display section.

That is, when the light-shielding layer is attached to the outer surface of the substrate in a frame shape or when the frame itself is attached, the presence of the dummy display portion causes a gap between the effective display portion and the non-display portion (electrode routing portion). A predetermined bonding (positioning) margin can be secured, the workability is improved, and the productivity is enhanced. Since a voltage can be applied to the dummy display portion by the transparent electrode, even if the display is changed by an external force, the display can be easily restored.

When the display pattern of the transparent electrodes has a dot matrix arrangement, the width of the dummy display section (bonding margin) is preferably 1 to 10 dots or 0.1 to 10 mm.

The liquid crystal layer is preferably a cholesteric liquid crystal, but a surface stabilized ferroelectric liquid crystal (SSFL)
C). When cholesteric liquid crystal is used, the liquid crystal array of the dummy display section may be in a planar state or a focal conic state depending on the color of the frame and the color of the light-shielding layer provided on the rear substrate. When the color of the light shielding layer and the frame of the back side substrate are both black,
It is preferable for the display quality that the dummy display section be in the focal conic state.

[0029]

Next, embodiments of the present invention will be described. First, the overall configuration will be described with reference to the cross-sectional view of FIG. 1. The liquid crystal display device 1 includes a first substrate 2 and a second substrate 3. The material of the substrate may be glass or plastic.

In this embodiment, the display mode is a full dot display, and a plurality of row electrodes (X electrodes) 21 are arranged on the first substrate 2 side at a predetermined interval (line width) in a stripe pattern. They are formed in parallel.

Similarly, on the second substrate 3 side, a plurality of column electrodes (Y electrodes) 31 are formed in a stripe pattern in parallel with each other at a predetermined interval. The row electrode 2
1. Both column electrode 31 is ITO (indium tin oxide)
Consisting of In this embodiment, the number of pixels is 160 × 24
At 0, the size of one pixel is 0.3 mm square.

Although not shown, an electric insulating film and a resin film made of polyimide are formed on the electrode forming surfaces of the substrates 2 and 3, respectively. A color filter may be provided on the inner surface side of one of the substrates for the purpose of adjusting visibility. Each of the substrates 2 and 3 is pressure-bonded via a peripheral sealing material 4 made of an epoxy resin, and a liquid crystal layer 5 is sealed between the substrates 2 and 3.

In this case, the liquid crystal layer 5 contains a nematic liquid crystal (Tc = 97 ° C., Δn = 0.242, Δε = 13.8).
A cholesteric liquid crystal having a composition of 66.5 parts, 16.75 parts of an optically active substance of the following formula 1, and 16.75 parts of an optically active substance of the following formula 2 is used.

[0034]

Embedded image

[0035]

Embedded image

In this embodiment, a terminal portion 3a is continuously provided on the second substrate 3 side, and a lead electrode group 32 is formed on the terminal portion 3a. The column electrode 31 on the second substrate 3 side is
Although the row electrodes 21 on the first substrate 2 side are directly connected to predetermined electrodes in the extraction electrode group 32, the extraction electrode group 32 is connected via a transfer material such as a conductive bead included in the peripheral sealing material 4. Conduction is established with a predetermined electrode in the inside. Note that the lead electrode group may be provided on each of the first substrate and the second substrate without conducting the conductive connection between the substrates.

In this liquid crystal display element 1, the row electrodes 21
The entire area to which a voltage is applied by the column electrodes 31 is a dot matrix display area, which is provided in the plan view of FIG. 2 as a part of the display area A, between the display area A and the terminal portion 3a. 3 shows a configuration of an electrode routing portion B and a lead electrode group 32 formed in a terminal portion.

Although the liquid crystal layer 5 extends into the electrode routing section B, there is no effective counter electrode in the electrode routing section B. Therefore, even when a voltage is applied to the display area A, the electrode routing section B does not move. No voltage is applied. Therefore, even if the display state of the liquid crystal layer 5 in the electrode routing section B is changed from the off-contrast focal conic state to the planar state by the external pressure, the restoration cannot be performed, and the display is visually recognized as display unevenness.

Therefore, as shown exaggeratedly in FIG. 3, the electrode routing portion B is shielded so as not to be seen. In the inner surface black mask method for forming a thin film of chromium or the like on the inner surface side of the substrate, a fine processing technique is used. In other words, the cost is greatly increased due to the equipment burden, and therefore, in the present invention, the frame portion 6 is provided on the outer surface of the substrate (panel). The frame portion 6 may be any of a coating film made of a light-shielding resin, a light-shielding film, a frame formed on an external housing, and the like.

However, there is considerable difficulty in accurately aligning the inner edge of the frame portion 6 along the boundary between the display area A and the electrode routing section B, resulting in poor productivity. Therefore, in the present invention, the periphery of the display area A is a dummy display section A2 for displaying fixed data, and the internal area surrounded by the dummy display section A2 is an effective display section A1 for actually displaying display data.

In this embodiment, the fixed data displayed on the dummy display section A2 is either the OFF display in the focal conic state or the ON display in the planar state, and has no meaning as display data. Since the dummy display section A2 has the row electrodes 21 and the column electrodes 31, even if the display is disturbed by an external pressure, the display can be restored by writing fixed data.

The effective display section A1 is provided by the dummy display section A2.
A positioning margin (margin width) with respect to the frame portion 6 is provided between the frame and the electrode routing portion B. In this sense, the dummy display portion A2 plays a role as a part of the frame portion 6.

The width of the mounting margin may be appropriately selected within the range of 1 to 10 dots. In this example, since one dot is 0.3 mm square, the preferable width is 0.3 to 3 mm.
It is. In addition, regardless of the number of dots, 0.1 to 10
A range of mm may be applied.

In any case, the presence of the dummy display portion A2 between the effective display portion A1 and the electrode routing portion B enables the frame portion 6 to be formed without much precision.
Can be mounted on panels, increasing productivity.

[0045]

As described above, according to the present invention,
When shielding the electrode routing portion of a liquid crystal display element using a liquid crystal having a memory property with a frame portion, fixed data is displayed in a peripheral portion in a display area to which a voltage is applied by a transparent electrode, that is, voltage application. By providing a dummy display part whose display state can be restored, the frame part can be easily aligned, and the overall productivity can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an overall configuration of one embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a partially enlarged plan view showing the electrode configuration of the embodiment.

FIG. 3 is a plan view schematically showing a display unit of the embodiment.

FIG. 4 is a schematic diagram showing an alignment state of a cholesteric liquid crystal in a planar state (a) and a focal conic state (b).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2, 3 Substrate 21, 31 Transparent electrode 3a Terminal part 4 Peripheral sealing material 5 Liquid crystal layer 6 Frame A Display area A1 Effective display part A2 Dummy display part B Electrode routing part

Continuing from the front page (72) Inventor Satoshi Niiyama 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 2H091 FA34Y FD04 GA02 HA12 LA12 2H092 GA20 GA26 GA33 GA44 NA25 PA07 QA12 QA13 5C094 AA43 BA49 CA19 CA24 DB02 EA04 EA05 EB02 ED03 ED15 FB12 FB15

Claims (6)

[Claims] 1. A liquid crystal display device comprising a pair of substrates, each having a transparent electrode formed on an opposing surface thereof, having a liquid crystal layer having a memory property sandwiched therebetween. A dummy display section for displaying fixed data is provided in a peripheral portion inside the
A liquid crystal display element, wherein an effective display section for actually displaying display data is surrounded by the dummy display section. 2. The liquid crystal display according to claim 1, wherein a light-shielding layer is provided on the outer surface of one of the substrates from the dummy display portion to an end of the substrate over the entire periphery thereof. element. 3. The liquid crystal display device according to claim 1, wherein the width of the dummy display portion is 1 to 10 dots or 0.1 to 10 mm when the display pattern of the transparent electrodes is in a dot matrix arrangement. . 4. The liquid crystal display device according to claim 1, wherein said liquid crystal layer is made of cholesteric liquid crystal. 5. The liquid crystal display device according to claim 4, wherein the liquid crystal array of the dummy display section is in a focal conic state. 6. The liquid crystal display device according to claim 4, wherein the liquid crystal array of the dummy display section is in a planar state.