JP5087089B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element, and more particularly, to a liquid crystal display element using a plastic substrate that is characterized by a distribution density of spacers and that can reduce cell gap unevenness.

  In liquid crystal display devices, particularly portable small-sized information terminal devices and mobile phone devices, it is required to reduce the weight of the liquid crystal panel and to reduce the thickness thereof. For this purpose, a substrate constituting the liquid crystal display element As a plastic substrate has been adopted.

  Japanese Patent Laid-Open No. 9-258233 discloses that a spacer is fixed with a UV curable resin in order to prevent deterioration in display quality such as color unevenness in a liquid crystal display element using a flexible substrate such as a plastic film. Thus, a technique of a liquid crystal display device is disclosed in which the gap between the upper and lower substrates is prevented from becoming larger than a predetermined value, and the gap between the upper and lower substrates is not changed by an external stress. In this technique, as shown in FIG. 10, the frame seal portion 7 of the liquid crystal display device is formed with a higher density than the spacer 6 provided on the inner side of the frame seal portion.

  Since plastic is essentially gas permeable, in liquid crystal display elements using plastic substrates, oxygen and nitrogen enter the liquid crystal display element with the passage of time and bubbles are generated, which impairs display quality. was there. In order to cope with this problem, a gas barrier layer for preventing gas permeation is conventionally laminated on a plastic substrate.

  In addition, attempts have been made to divide the surface of the liquid crystal display element into a plurality of regions and assign different functions to each region. For example, in Japanese Patent Laid-Open No. 6-160818, a plurality of functions / characteristics such as a display function, a fixed display function, a signal electricity generation function, and a sound generation function are arbitrarily combined in the plane of one substrate. A technique for realizing a liquid crystal display device by an exposure process of changing a light irradiation pattern is disclosed.

  In a liquid crystal cell using a plastic substrate, a plurality of liquid crystal cell portions are formed on a plastic sheet having a large area, and then individual liquid crystal display elements are manufactured through a cutting process. Since the gas barrier layer for preventing gas permeation is not provided on the cut surface of the liquid crystal cell (see FIG. 11A), gas components such as oxygen and nitrogen are passed through the cut surface with the passage of time inside the liquid crystal cell. There is a problem that the accumulated gas component becomes bubbles 10 to deteriorate the display quality and shorten the life of the liquid crystal display element as a display device (see FIG. 11B).

  A liquid crystal display element has a region where functions such as display are concentrated, and a region where nothing functions like a peripheral portion of the device. If bubbles are generated in a region where the functions are concentrated, there is a big problem, but even if bubbles are generated in a region where nothing functions, there are few problems.

  Further, when a partial area of the liquid crystal display element is a switch area, the liquid crystal display screen is often deformed by repeatedly pressing the switch area for an input operation. The pressure in the liquid crystal display cell also varies due to the deformation of the liquid crystal display screen. This pressing causes the oxygen and nitrogen gas in the outside air outside the liquid crystal cell to pass through the liquid crystal cell through the cut section of the liquid crystal cell, and the gas component that has gradually dissolved in the liquid crystal layer in the liquid crystal cell is bubbled. Cause.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display element that eliminates the cause of bubble generation, collects bubbles in an area where there is little problem even if bubbles are generated, and has a long lifetime with little deterioration in display quality. That is.

  A liquid crystal display device according to the present invention comprises a pair of opposed plastic substrates, a spacer for defining a gap disposed between the opposed plastic substrates, and a liquid crystal material sandwiched between the opposed plastic substrates. It has a display area and a switch area. In the liquid crystal display device, in order to achieve the above object, the arrangement density of the spacers in the switch area is set higher than the arrangement density of the spacers in the display area.

  In addition to the display area and the switch area, the liquid crystal display element may have a peripheral area surrounding the display area and the switch area. In that case, the arrangement density of the spacers in the peripheral area is set lower than the arrangement density of the spacers in the display area.

  The liquid crystal display element may further include a boundary region between the display region and the switch region. In this case, the arrangement density of the spacers in the boundary region is gradually increased from the display region side toward the switch region side.

  The spacer may be a photo spacer.

  The pitch at which the spacers are arranged may be approximately 200 μm in the display area and 100 μm to 150 μm in the switch area.

  Since the present invention has the above-described configuration, the liquid crystal display element can be reduced in deformation due to stress, can eliminate the cause of bubble generation, and can provide a liquid crystal display element with a long display life with little deterioration in display quality. Further, in the present invention, it is possible to take a good countermeasure against bubbles by selecting spacer arrangements suitable for the display area and the switch area. In addition, a good aperture ratio can be ensured for the display area. In addition, by arranging the spacers in the switch area densely as compared with the spacers in the display area, it is possible to prevent a local gap change that is one of the causes of bubble generation.

It is a top view of a plastic substrate liquid crystal element. 1A schematically shows the arrangement density of spacers in the plastic substrate liquid crystal element of FIG. 1A. It is a figure explaining the arrangement | positioning density of the spacer in the peripheral part of the plastic substrate liquid crystal element of FIG. 1A. It is a figure explaining the arrangement | positioning density of the spacer in the center part of the plastic substrate liquid crystal element of FIG. 1A. It is a top view which shows arrangement | positioning of each function area | region in the plastic substrate liquid crystal element which is one Embodiment of this invention. It is a front view of the liquid crystal device using the plastic substrate liquid crystal element in one embodiment of the present invention. FIG. 4B is a side view of the liquid crystal device of FIG. 4A. It is a figure which shows roughly the arrangement | positioning density of the spacer in each function area | region of the plastic substrate liquid crystal element in one Embodiment of this invention. It is a figure which shows roughly the arrangement | positioning density of the spacer in each function area | region of the plastic substrate liquid crystal element in other embodiment of this invention. It is a schematic diagram of the aa cross section of the liquid crystal display element shown in FIG. It is a schematic diagram of the bb cross section of the liquid crystal display element shown in FIG. It is a schematic diagram of the cc cross section of the liquid crystal display element shown in FIG. It is a figure for demonstrating the arrangement density of the spacer of the boundary region part in a plastic substrate liquid crystal element. It is the figure which expanded the display part, boundary area | region part, and switch part in the area | region enclosed with the broken line of FIG. 9A is a graph showing a distribution of arrangement density of spacers shown in FIG. 9A. It is an example of the liquid crystal display element which distributed the spacer which is a prior art uniformly. 1 shows a cross-sectional view of a liquid crystal cell using a plastic substrate according to the prior art. FIG. 6 is a diagram showing an example of a display device according to the prior art having a liquid crystal display element in which gas components such as oxygen and nitrogen enter and accumulate inside the liquid crystal cell through a cut surface of the liquid crystal display element to generate bubbles 10. is there.

  FIG. 1A is a plan view of a plastic substrate liquid crystal element. In FIG. 1A, reference numeral 1 denotes a plastic substrate liquid crystal element, reference numeral 20 denotes a peripheral portion, and reference numeral 30 denotes a central portion. The arrangement density of the spacers 6 in the central portion 30 is higher than the arrangement density of the peripheral portions 20. Cross sections of the plastic substrate liquid crystal element 1 at the positions of the broken lines c1-c1 and c2-c2 in FIG. 1A are shown in FIGS. 2A and 2B, respectively.

  FIG. 1B schematically shows the arrangement density of the spacers of the plastic substrate liquid crystal element of FIG. 1A.

  As shown in FIG. 1B, since the peripheral portion 20 of the plastic substrate liquid crystal element has spacers arranged sparsely as in the prior art, the plastic substrate has a shape in which the central portion sinks as shown in FIG. 2A. ing. On the other hand, since the spacers are densely arranged in the central portion 30 of the plastic substrate liquid crystal element, as shown in FIG. 2B, the plastic substrate sinks due to deformation in which the central portion becomes the inside of the plastic substrate. , And the arrangement density of the spacers 6 is relatively higher than that of the peripheral part 20. Here, the sinking shape and the expanded shape are based on the average value of the height between the two substrates at the peripheral portion 20 and the central portion 30.

  Since the plastic substrate is small in rigidity, it tends to have a shape that is inside the liquid crystal element due to the surface tension of the liquid crystal. For this reason, the sinking amount in the central portion 30 where the spacer arrangement density is large is smaller on average than the peripheral portion 20 where the spacer 6 arrangement density is small. In other words, it can be said that the liquid crystal layer of the central portion 30 of the plastic substrate liquid crystal element 1 is in an expanded state.

  FIG. 3 is a plan view showing the arrangement of the functional areas in the plastic substrate liquid crystal element 1 according to one embodiment of the present invention. The plastic substrate liquid crystal device 1 shown in FIG. 3 corresponds to a display portion 3 and a switch portion 4 arranged in the central portion 30 of the plastic substrate liquid crystal device of FIG. 1A.

  In FIG. 3, reference numeral 1 indicates a plastic substrate liquid crystal element, and reference numeral 2 indicates a peripheral region. The peripheral region portion 2 is a region where the arrangement density of the spacers 6 provided in the peripheral portion of the plastic substrate constituting the plastic substrate liquid crystal element 1 is low. Reference numeral 3 denotes a display portion, and the arrangement density of the spacers 6 is higher than that of the peripheral region portion 2. Reference numeral 4 denotes a switch unit, and the arrangement density of the spacers 6 is higher than that of the peripheral region unit 2 and the display unit 3. Reference numeral 5 denotes a boundary region that is continuous with the peripheral region 2 and is provided at a portion between the display unit 3 and the switch unit 4.

  4A and 4B respectively show a front view and a side view of a liquid crystal device using the plastic substrate liquid crystal element 1 in one embodiment of the present invention. With reference to FIG. 4A and FIG. 4B, the function of the member attached to the back surface of the plastic substrate liquid crystal element 1, the display part 3, and the switch part 4 is demonstrated.

  A TFT liquid crystal panel 11 and a backlight 12 are attached to the back surface of the display unit 3 of the plastic substrate liquid crystal element 1 as shown in FIG. 4B. When an image is displayed on the TFT liquid crystal panel 11, the display unit 3 is in a transmissive state so that the image on the TFT liquid crystal panel 11 can be recognized (at this time, the backlight is lit). When no image is displayed on the TFT liquid crystal panel 11, the display unit 3 is in a non-transmissive state, and the TFT liquid crystal panel 11 cannot be visually recognized (at this time, the backlight is turned off).

  In this manner, the display unit 3 functions as a shutter that shows or hides the TFT liquid crystal panel 11. A switch sheet 13 is attached to the back surface of the switch portion 4 of the plastic substrate liquid crystal element 1. When a switch button (not shown) displayed on the switch unit 4 is pressed, the plastic substrate liquid crystal element 1 is locally deformed, and the pressed switch element (not shown) provided at a corresponding position on the switch sheet 13. (The cell gap does not change even when locally deformed).

  The switch element senses the pressure and transmits the information to a control block (not shown). As described above, the switch unit 4 has a function of transmitting a pressure applied from the outside to the switch sheet in addition to the display of the switch button and the like.

  FIG. 5 schematically shows the arrangement density of the spacers in each functional region of the plastic substrate liquid crystal element in one embodiment of the present invention. FIG. 5 shows that the arrangement density of the spacers 6 is increased in the order of the peripheral region portion 2, the display portion 3, and the switch portion 4 as described with reference to FIG. 3. Moreover, as shown in FIG. 6, you may arrange | position the spacer of the display part 3 to each vertex of an equilateral triangle. The arrangement of the spacers at the vertices of the regular triangle is not limited to the display unit 3, and may be applied to the peripheral region unit 2 and the switch unit 4.

  7A, FIG. 7B, and FIG. 7C are schematic views of the aa cross section, the bb cross section, and the cc cross section of the liquid crystal display element shown in FIG. According to these figures, as described with reference to FIGS. 3, 5, and 6, the peripheral area 2 (FIG. 7A), the display 3 (FIG. 7B), and the switch 4 (FIG. 7C) in this order. It can be seen that the arrangement density of the spacers 6 is high.

  The liquid crystal display element according to the present invention is composed of an ultrathin plastic substrate of 0.1 mm or less and has flexibility. Examples of the material of the plastic sheet that is a raw material of the plastic substrate include polyethersulfone, polyacrylate, polyethylene terephthalate, polycarbonate, and epoxy acrylate from the viewpoint of transparency and moldability. These plastic sheets are formed with members necessary for the liquid crystal display element, such as electrode wiring, marks, and photo spacers, using an exposure technique.

  As described with reference to FIGS. 3 to 7C, the arrangement density of the spacers 6 in the display unit 3 and the switch unit 4 formed in the central portion of the liquid crystal display element is the same as the arrangement density of the spacers 6 in the peripheral region unit 2. Since it is set higher, the amount of subsidence due to deformation that becomes internal due to the surface tension of the liquid crystal of the plastic substrate in this region is reduced, and relative to the peripheral region portion 2 where the arrangement density of the spacers 6 is small. To be high. For this reason, the liquid crystal layer inside is swollen and it becomes possible to suppress the entry of new bubbles.

  Further, the deformation of the plastic substrate caused by pressing the switch unit 4 can be absorbed by the continuous portion 5 and not transmitted to the display unit 3. For this reason, it is possible to prevent the display quality of the display unit 3 from being lowered. Further, when the temperature of the liquid crystal display element changes, the peripheral region 2 can absorb the deformation of the liquid crystal display substrate due to the expansion and contraction of the liquid crystal material, and the deformation of the display 3 and the switch 4 is suppressed. And display quality can be prevented from deteriorating.

  Hereinafter, an evaluation example of the display quality of the liquid crystal display element using the plastic substrate and the generation of bubbles when the pitch and diameter of the photo spacer are changed will be described.

Table 1 shows the arrangement pitch of spacers, which is the arrangement density, the display quality, and the degree of bubble generation. When the pitch is 50 μm, the display quality is not good and is not acceptable, but there is no problem in terms of the generation of bubbles. When the pitch is 100 μm, the display quality is in an acceptable range, and there is no problem in terms of the generation of bubbles. When the pitch is 150 μm, there is no problem in display quality, and there is no problem in the generation of bubbles. When the pitch is 200 μm, there is no problem in display quality, but the generation of bubbles is unacceptable. When the pitch is 250 μm, there is no problem in display quality, but the generation of bubbles is not acceptable.
The display unit 3 requires high-quality display, but almost no pressure is applied, so that the spacer pitch can be 200 μm.

×：許容できない △：許容範囲内 ○：良好

×: Not acceptable △: Within acceptable range ○: Good

  Table 2 is a table in which the aperture ratio with respect to the pitch and diameter of the photo spacer is calculated. The pitch and diameter of the photo spacer are selected so that an aperture ratio of 90% or more can be secured.

  In the present embodiment, when the diameter of the photo spacer is set to 9 μm as a design value, the finished dimension is 16 to 22 μm.

  According to Table 1 and Table 2, since the pitch of the photo spacer is defined based on the display quality and the generation of bubbles, referring to Table 1, the pitch is set in the range of 100 μm to 150 μm, and Table 2 The diameter of the photo spacer can be set so that the aperture ratio is 90% or more.

  In other words, changing the arrangement density of the spacers described above is equivalent to changing the contact area per unit area of the spacers. The contact area of the spacer may be such that the switch portion is the largest. In this case, the pitch of the spacers may be equally spaced as shown in FIG.

  As described above, the present invention is characterized in that the arrangement density of the spacers is different between the display unit 3 and the switch unit 4 in the liquid crystal display element (see FIG. 5). In the boundary region 5 between the display unit 3 and the switch unit 4, a boundary line discontinuous in the arrangement density of the spacers is present between the display unit 3 and the boundary region unit 5 and between the switch unit 4 and the boundary region unit 5. Occurs between. Such a discontinuous boundary line in the arrangement density of the spacers may cause the boundary line to appear on the display screen, thereby degrading the display quality.

  Therefore, the arrangement density distribution of the spacers in the boundary region portion 5 is gradually increased from the display portion 3 toward the switch portion 4. Thus, the arrangement of the spacers at the boundary portion 5 will be described with reference to FIGS. 8, 9A, and 9B. Here, FIG. 8 is a diagram for explaining the arrangement density of the spacers in the boundary region. FIG. 9A is an enlarged view of the display unit 3, the boundary region unit 5, and the switch unit 4 in the region surrounded by the broken line in FIG. FIG. 9B is a graph showing the distribution of the arrangement density of the spacers in FIG. 9A.

  9A and 9B, the distribution of the spacer arrangement density in the boundary region 5 is equal to the spacer arrangement density of the display unit 3 on the side in contact with the display unit 3, and the side in contact with the switch unit 4 Then, it is equal to the arrangement | positioning density of the spacer of the switch part 4, and the arrangement | positioning density of the spacer in the meantime becomes high gradually. By changing the spacer arrangement density in this way, the discontinuity of the spacer arrangement density on the boundary line between the display unit 3 and the boundary region unit 5 and the boundary line between the switch unit 4 and the boundary region unit 5 is obtained. Thus, it is possible to prevent a line that deteriorates display quality from appearing on the display screen.

Claims (4)

A liquid crystal display element comprising a pair of opposed plastic substrates, a spacer for defining a gap disposed between the opposed plastic substrates, and a liquid crystal material sandwiched between the opposed plastic substrates. And
The liquid crystal display device has a display area and a switch area,
The arrangement density of spacers in the switch region is higher than the arrangement density of spacers in the display region ;
Further, there is a boundary region between the display region and the switch region, and the disposition is eliminated by gradually increasing the arrangement density of the spacers in the boundary region from the display region side toward the switch region side. the liquid crystal display device, characterized in that the the like.   The liquid crystal display element further includes a peripheral region surrounding the display region and the switch region, and a spacer arrangement density in the peripheral region is lower than a spacer arrangement density in the display region. The liquid crystal display element according to claim 1. The liquid crystal display element according to claim 1 , wherein the spacer is a photospacer . 4. The liquid crystal display element according to claim 1, wherein a pitch for arranging the spacers is approximately 200 μm in the display region and 100 μm to 150 μm in the switch region . 5.

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