JP2005114821A - Display panel for reflective display and reflective display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display panel for a reflective display which brings about little eye fatigue, has paper like texture and has excellent visibility, and a reflective display. <P>SOLUTION: In the display panel for the reflective display equipped with a substrate, an electrode layer, a picture display layer, a transparent electrode layer and a surface layer, the display panel for the reflective display is characterized by having 35% or higher reflectance of a white picture and 5:1 or higher contrast ratio of white to black observed in a direction normal to the display panel with respect to incident light from the surface layer side with 20-80° incident angle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reflective display panel and a reflective display having excellent visibility such as paper.

  As a flat panel display device, a liquid crystal display (LCD) is now widely used in various applications because it is thin and can be miniaturized. However, a light-emitting display such as a transmissive LCD has a problem that the eyes are easily fatigued and the optical characteristics greatly vary depending on the viewing angle.

  As another display method aiming at further thinner and lower power consumption than such an LCD, a display device using an electrophoretic phenomenon has been developed.

  As one of display devices using the electrophoresis phenomenon, a microcapsule electrophoresis system has been put into practical use. In this type of display device, positive and negatively charged white and black particles are placed in a microcapsule filled with a transparent solvent, and an image is formed by pulling up each particle to the display surface by applying an external voltage. It is. Since the size of the microcapsule is as small as several tens μm to several hundred μm, when the microcapsule is dispersed in a transparent binder, it can be coated like ink. This ink is called electronic ink because an image can be drawn by applying a voltage from the outside.

  When this electronic ink is coated on a transparent resin film on which a transparent electrode is formed and bonded to a substrate on which an electrode circuit for driving an active matrix is formed, an active matrix display panel as shown in Patent Document 1, for example, can be obtained. it can.

The microcapsule-type electrophoretic display device as described above is said to have a paper-like texture and less eye fatigue than an LCD, but its visibility has not yet been fully elucidated.
JP 2000-221546 A

  The present invention has been made under the circumstances as described above, and an object thereof is to provide a reflective display panel and a reflective display having excellent visibility with less eye fatigue and a paper-like texture. To do.

  In order to solve the above problems, the present invention provides a display panel for a reflective display comprising a substrate, an electrode layer, an image display layer, a transparent electrode layer, and a surface layer, and an angle of 20 to 80 ° from the surface layer side. Reflective display characterized in that the reflectance of a white image is 35% or more with respect to the incident light and the contrast ratio of white: black observed in the normal direction of the display panel is 5: 1 or more A display panel is provided.

  Further, the present invention provides a display panel for a reflective display comprising a substrate, an electrode layer, an image display layer, a transparent electrode layer, and a surface layer, and applying the voltage to the electrode layer and the transparent electrode layer to apply the image display layer A reflective display having a driving means for driving a white image with a reflectance of 35% or more with respect to incident light at an angle of 20 to 80 ° from the surface layer side, and a normal line of the display panel Provided is a reflective display characterized in that the white: black contrast ratio observed in the direction is 5: 1 or more.

  According to the reflective display panel and the reflective display of the present invention configured as described above, the reflectance of a white image is 35 even if incident light from the surface layer side is incident at any angle of 20 to 80 °. % And a white: black contrast ratio of 5: 1 or more can provide excellent visibility.

  Since the display according to the present invention is a reflective display that is not a light emitting type, it has less eye fatigue, uses the same pigment as a printed matter such as titanium oxide or carbon black, and has a surface layer having an antiglare function, so that paper You can get a texture like this. Furthermore, while the white reflectance of an existing black and white reflective display such as a liquid crystal is about 4% and the contrast is about 4, the display of the present invention is excellent in terms of reflectance, contrast, and viewing angle. Visibility closer to that of paper can be obtained.

  In this case, the reflectance of the white image and the white: black contrast, which are the parameters that characterize the present invention, in the case of a microcapsule type display panel, the arrangement of the microcapsules, the particle size of the microcapsules, the display layer 4 and the adhesion The above condition can be realized by adjusting the thickness of the layer 3 and the like. The reflectance of the white image can be measured with a spectrophotometer using a standard white plate.

  More preferably, if the reflectance of a white image is 50% or more and the contrast ratio of white: black is 5: 1 or more, it is equivalent to newspaper.

  In the display panel for a reflective display according to the present invention, the haze value of the surface layer is preferably 2 to 11%, more preferably 7 to 11%. With such a haze value, it is possible to obtain a texture and matte feeling close to paper with reduced glare, and to obtain better visibility.

  In addition, the present invention is preferably applied to a microcapsule type display panel, that is, the image display layer is a microcapsule type display layer including black particles, white particles and a microcapsule containing a dispersion medium in which these particles are dispersed. I can do it. In this case, the white image is displayed by moving white particles to the transparent electrode layer side by electrophoresis and moving black particles to the electrode layer side according to the voltage applied to the transparent electrode layer.

  The image display layer is desirably rewritable. In this case, the response speed at the time of image rewriting is preferably 500 ms or less. Since the image display layer can be rewritten in this manner, it can be applied to a wider range of uses.

  Further, the resolution of the image display layer is desirably 63 pixels / cm or more. The resolution of a general display is about 35 to 47 pixels / cm, and it is said that even 8-point (2.8 mm square) kanji is difficult to read. On the other hand, at a resolution of 63 pixels / cm or more, which is a feature of a preferred embodiment of the present invention, 6-7 point kanji characters can be displayed smoothly. The resolution of the printed material is about 230 pixels / cm.

  The above resolution can be realized by adjusting the particle size of the microcapsules, the material and thickness of the adhesive layer 3, and the like.

  The surface layer may have a configuration having at least one functional layer selected from the group consisting of an antiglare hard coat layer, an ultraviolet absorption layer, and a gas barrier layer. Such various functional layers exhibit their respective functions, thereby improving visibility.

  According to the present invention, since the reflectance of a white image is 35% or more and the white: black contrast ratio is 5: 1 or more, a reflective display panel and a reflective display exhibiting excellent visibility are provided. Provided.

  The best mode for carrying out the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a microcapsule type electrophoretic display panel according to an embodiment of the present invention. That is, the electrode layer 2, the first adhesive layer 3, the microcapsule display layer 4, the transparent electrode layer 5, the transparent resin layer 6, the second adhesive layer 7, and the surface layer 8 are sequentially laminated on the substrate 1. Thus, a microcapsule electrophoretic display panel is configured.

  In the microcapsule type electrophoretic display panel shown in FIG. 1, the microcapsule display layer 4 has a transparent electrode (ITO) of a transparent resin layer 6 made of polyethylene terephthalate or the like having a transparent electrode layer (ITO film) 5 formed on the surface. ) It is formed by printing electronic ink on the surface of the layer 5. Next, the transparent resin layer 6 having the transparent electrode layer (ITO film) 5 and the microcapsule display layer 4 is attached to the substrate 1 having the electrode layer 2 on the surface via the first adhesive layer 3. The transparent electrode layer 5 can be a common electrode having the same potential on the entire surface.

  As the first pressure-sensitive adhesive layer 3, a known pressure-sensitive adhesive or heat-sensitive adhesive can be used. These can be used in the form of a single-sided adhesive tape or a double-sided adhesive tape having release paper on the adhesive surface. That is, the first pressure-sensitive adhesive layer 3 is affixed to the microcapsule display layer 3 with a non-adhesive surface of a single-sided pressure-sensitive adhesive tape by an adhesive, or is peeled off and peeled off from one side of the double-sided pressure-sensitive adhesive tape. Can be formed.

  Affixing can be performed, for example, by removing the release paper, adhering the adhesive surface of the first adhesive layer 3 to the substrate 1, pressing or heating. The substrate 1 is a glass substrate or a resin film provided with an electrode layer (not shown) on the surface, and the electrode layer 2 on the surface is patterned independently for each pixel as a pixel electrode, and a thin film transistor, a signal electrode, and a scanning (not shown) An electrode with an electrode can be used.

  Next, the surface layer 8 is deposited on the transparent resin layer 6 of the laminate obtained as described above via the second adhesive layer 7. It is preferable that the second adhesive layer 7 has high self-holding property and high elasticity such as silicon rubber. The second pressure-sensitive adhesive layer 7 having high elasticity can serve not only as a mere adhesive action but also as a cushion to reduce impact.

  The surface layer 8 may include at least one functional layer selected from the group consisting of an antiglare hard coat layer, an ultraviolet absorption layer, and a gas barrier layer. These functional layers can be formed by a known method using a known material.

  In the microcapsule-type electrophoretic display panel described above, the microcapsules included in the microcapsule display layer 3 include, for example, a methacrylic acid resin, urea resin, gum arabic or the like as a capsule shell 111 as shown in FIG. Inside, white particles 113 made of titanium oxide and black particles 114 made of carbon black are enclosed in a state of being dispersed in a highly viscous dispersion medium 112 such as silicone oil. Titanium oxide, which is a white particle 113, has a negative charge, while carbon black, which is a black particle 114, has a positive charge.

  A display body using such a microcapsule type electrophoresis system including the microcapsules 110 operates as follows.

  That is, as shown in the schematic diagram of FIG. 3, an electric field is applied to the transparent electrode layer 5 on the transparent resin layer 6 side and the electrode layer 2 on the base material layer 1 side, the transparent electrode layer 5 is the negative electrode, and the electrode layer 2 is In the case of a positive electrode, positively charged white particles 113 are attracted to the electrode layer 5 side, and negatively charged black particles 114 are attracted to the electrode layer 2 side. Therefore, when observed from above the transparent electrode layer 5 side, That part looks white.

  Conversely, when the transparent electrode layer 5 is a positive electrode and the electrode layer 2 is a negative electrode, the negatively charged black particles 114 are drawn to the transparent electrode layer 5 side, and the positively charged white particles 113 are Since it is drawn to the electrode layer 2 side, when observed from above the transparent electrode layer 5 side, the portion looks black.

  As shown in the schematic side sectional view of FIG. 4, the microcapsule display layer 4 includes a large number of microcapsules 110, the transparent electrode layer 5 is a common electrode having the same potential, and the electric field of each address electrode of the electrode layer 2 is By controlling, it is possible to display desired characters and figures as white and black pixels by moving particles in the microcapsule based on the above-described principle.

  Similarly, by using the electrode layer 2 as a common electrode (with a potential of zero) and controlling the electric field of each address electrode on the transparent electrode 5 side (giving positive or negative potential), You may make it display a desired image by moving particle | grains.

  Various diameters of the microcapsules can be adopted. However, when a diameter of about 40 μm to about 100 μm is adopted, sufficient resolution and responsiveness can be obtained. The resolution of the display image mainly depends on the material of the microcapsule display layer 4 and the adhesive layer 3, but if the diameter of the microcapsule is small, the distance between the electrodes becomes short, and the electric field generated between the electrodes is difficult to leak to adjacent pixels. Therefore, sufficient resolution can be obtained. Further, there is an advantage that the moving speed of the microcapsules in the dispersion medium is increased, and as a result, the responsiveness at the time of display is excellent.

  A paper-like electronic display can be realized by producing a flexible material and patterning electrodes and the like on a plastic film by a printing method or a vapor deposition method. The display screen size can be created in any size according to the application and demand.

  In the microcapsule display layer 4, there is no problem in display even if the position of the microcapsules 110 varies slightly. Therefore, it is possible to bend and use it by attaching it to a curved surface.

  In the microcapsule-type electrophoretic display panel, each particle is dispersed in a highly viscous dispersion medium. Therefore, once the electric field is applied, the position of the particle does not change even when the power is turned off. In this way, the display image does not disappear even when the display is turned off. It has non-volatility (memory property), so it is only necessary to apply an electric field at the time of initial display or rewriting, and it is necessary for display compared to a normal display device. It requires less power and can save a lot of power.

  Further, in the display panel, there is no problem in display even if the position of the microcapsules 110 is slightly changed. Therefore, by using a material that makes the entire display including the transparent electrode layer 5 and the electrode layer 2 thin and portable, flexibility such as paper can be provided.

  In the microcapsule type electrophoretic display described above, a voltage was applied between the electrode layer 2 and the transparent electrode layer 5 to drive the microcapsule display layer 4. The haze value of the surface layer is 2 to 11%, the incident angle of the light source is 45 °, and when viewed from the normal direction (α = 0 °) of the display as shown in FIG. Was over 35%. Further, the white: black contrast ratio was 5: 1 or more even when the incident angle α of the light source was any angle of 20 to 80 ° and the azimuth θ was any angle of 0 to 360 °.

  According to the microcapsule type electrophoretic display having such optical characteristics, excellent visibility with a paper-like texture with little eye fatigue was obtained.

  Next, the incident angle was variously changed, and the white state reflectance, the black state reflectance, and the white: black contrast ratio were obtained. The results are shown in FIGS. The measurement conditions are as follows.

Light source: A light source Drive voltage: 15V
Voltage application time: 1s or more

  As shown in Table 1 and FIGS. 6 to 8, when the incident angle is less than 20 °, the reflectivity in the black state increases, so the white: black contrast ratio does not exceed 5: 1. This is considered to be due to the influence of regular reflection.

  In contrast, a white state reflectance of 35% or more and a white: black contrast ratio of 5: 1 or more were obtained in a wide range of incident angles of 20 to 80 °. Thereby, it is possible to obtain excellent visibility with a paper-like texture with less eye fatigue.

  The display panel for a reflective display according to the present invention has excellent visibility such as paper-like texture with less eye fatigue, and thus can be widely used as a display panel in various applications.

1 is a cross-sectional view illustrating a microcapsule type electrophoretic display panel according to one embodiment of the present invention. FIG. 3 is a diagram schematically illustrating a microcapsule included in a microcapsule display layer of a microcapsule type electrophoretic display panel according to one embodiment of the present invention. The perspective view which represents typically an example of the display form of the microcapsule display layer of the microcapsule type | mold electrophoretic display panel which concerns on one form of this invention. FIG. 6 is a side cross-sectional view schematically illustrating an example of a display form of a microcapsule display layer of a microcapsule type electrophoretic display panel according to an embodiment of the present invention. 4A and 4B illustrate an incident angle and an orientation when measuring optical characteristics of a microcapsule electrophoretic display panel according to one embodiment of the present invention. The characteristic view which shows the relationship between an incident angle and the reflectance of a white state. The characteristic view which shows the relationship between an incident angle and the reflectance of a black state. The characteristic view which shows the relationship between an incident angle and the contrast ratio of white: black.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base material layer, 2 ... Electrode layer, 3 ... 1st adhesion layer, 4 ... Microcapsule display layer, 5 ... Transparent electrode layer, 6 ... Transparent resin layer, 7 ... second adhesive layer, 8 ... surface layer, 110 ... microcapsule, 111 ... capsule shell, 112 ... dispersion medium, 113 ... white particles, 114 ... Black particles.

Claims (7)

  In a reflective display panel comprising a substrate, an electrode layer, an image display layer, a transparent electrode layer, and a surface layer, a white image is reflected with respect to incident light at an angle of 20 to 80 ° from the surface layer side. A reflective display panel, wherein the ratio is 35% or more, and the white: black contrast ratio observed in the normal direction of the display panel is 5: 1 or more.   2. The display panel for a reflective display according to claim 1, wherein the haze value of the surface layer is 2 to 11%.   The image display layer is a microcapsule type display layer including black particles, white particles and a microcapsule containing a dispersion medium in which these particles are dispersed, and the white image corresponds to a voltage applied to the transparent electrode layer. 3. The display panel for a reflective display according to claim 1, wherein the white particles are displayed by moving to the transparent electrode layer side by electrophoresis and the black particles are moved to the electrode layer side.   The reflective display panel according to claim 1, wherein the image display layer is rewritable, and a response speed at the time of image rewriting is 500 ms or less.   5. The display panel for a reflective display according to claim 1, wherein the resolution of the image display layer is 63 pixels / cm or more.   6. The reflection according to claim 1, wherein the surface layer has at least one functional layer selected from the group consisting of an antiglare hard coat layer, an ultraviolet absorption layer, and a gas barrier layer. Type display panel.   A reflective display panel comprising a substrate, an electrode layer, an image display layer, a transparent electrode layer, and a surface layer; and a driving means for driving the image display layer by applying a voltage to the electrode layer and the transparent electrode layer. In a reflective display comprising: the reflectance of a white image reflecting incident light from the surface layer side is 35% or more, and for incident light at an angle of 20 to 80 ° from the surface layer side, A reflective display characterized in that the contrast ratio of white: black observed in the normal direction of the display panel is 5: 1 or more.

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