JP2007034037A - Particle movement type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particle migration type display device with which a bright color display without color mixing is materialized. <P>SOLUTION: The particle transfer type display device includes: a display substrate and a rear substrate which includes a diffuse reflection layer or a light scattering layer, arranged so as to hold a predetermined gap in between; partition walls which are formed of a light transmitting material and arranged in the gap between the substrates; an insulating liquid and a plurality of charged particles which are arranged in the gap between the substrates; a first electrode which is arranged in the vicinity of the insulating liquid; and a second electrode which is arranged so as to be in contact with the partition walls. The diffuse reflection layer or the light scattering layer is included in the partition wall section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a particle movement type display device that performs display by moving charged particles in an insulating liquid.

  With the development of information equipment, the need for low power consumption and thin display devices is increasing, and research and development of display devices that meet these needs are actively conducted. In particular, liquid crystal display devices have been actively developed and commercialized as display devices that can meet such needs. However, the current liquid crystal display devices have problems that it is difficult to see the characters on the screen due to the angle at which the screen is viewed and reflected light, and that the burden on the vision caused by flickering, low brightness, etc. of the light source is heavy. Is still not fully resolved. For this reason, a reflective display device is expected from the viewpoint of low power consumption and reduction of visual burden.

  As the reflective display device, there is an electrophoretic display device that performs display by moving charged particles in an insulating liquid.

  This electrophoretic display device is configured by arranging a pair of substrates with a predetermined gap therebetween, and an insulating liquid and charged particles are arranged in the gap between the substrates. A pair of electrodes are arranged so as to be close to the insulating liquid, and the charged particles are moved by applying a voltage to these electrodes (see, for example, Patent Document 1). .

In such an electrophoretic display device, in view of display quality, it is necessary to prevent the charged particles from freely moving to other pixels, and a partition is arranged at the pixel boundary to prevent the movement of the charged particles. What has been proposed is proposed.
JP 9-2111499 A

  By the way, when the electrophoretic display device as described above is used as a color reflection type display device by arranging a color filter layer on the rear substrate side, it may be mixed colors or dark display depending on the viewing angle. There was a problem.

  The reason for this is that the partition walls are optically transparent, so that light transmitted through the color filter layer and diffuse reflection layer on the rear substrate side penetrates into the partition walls, and light from different color filters is mixed in each adjacent pixel. By doing. Further, when the partition wall is formed of a light-shielding member such as a black matrix, a part of the reflected light is absorbed, so that the reflectance is lowered depending on the viewing angle direction.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a particle movement type display device that can realize bright color display while preventing color mixing and maintaining a wide viewing angle characteristic.

  The present invention has been made in consideration of the above circumstances, and is disposed in a display substrate disposed in a state where a predetermined gap is provided, a rear substrate including a diffuse reflection layer or a light scattering layer, and a gap between these substrates. Partition walls, an insulating liquid and a plurality of charged particles disposed in the gap between the substrates, a first electrode disposed so as to be close to the insulating liquid, and a first electrode disposed in contact with the partition walls. Particles that perform display based on applying a voltage to these electrodes to move the charged particles and reflecting light incident from the display substrate side on the rear substrate side. In the mobile display device, the partition wall portion includes a diffuse reflection layer or a light scattering layer.

  As described above, according to the present invention, it is possible to obtain a particle movement display device with bright color display without color mixture.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the electrophoretic display device according to the present invention includes a display substrate 1 and a rear substrate 2 that are arranged with a predetermined gap therebetween. 3 is arranged. In addition, an insulating liquid 4 and a plurality of charged particles 5 are disposed in the gap between the substrates 1 and 2, and a first electrode 6 is disposed so as to be close to the insulating liquid 4. The 2nd electrode 7 is arrange | positioned so that it may contact | connect.

  This electrophoretic display device is of a so-called reflection type, and is configured such that light is incident with the display substrate 1 being transparent, and the rear substrate 2 is configured to reflect the incident light. ing. That is, in this specification, the display substrate 1 means a substrate disposed on the viewer side, and the other substrate is referred to as a “rear substrate”. That is, in the electrophoretic display device according to the present embodiment, a voltage is applied to the electrodes 6 and 7 to move the charged particles 5 and display based on incident and reflected light as described above. It is configured.

By the way, as a method of reflecting light by the rear substrate 2,
A method of providing a light scattering layer or a diffuse reflection layer (see reference numeral 10 in FIG. 1) on the rear substrate 2 side;
A method in which the first electrode 6 disposed on the rear substrate 2 side is also used as a diffuse reflection layer;
Can be mentioned.

  The partition 3 described above is made of a material that can transmit light, and is configured to shield light at a portion where the second electrode 7 is disposed. Such shielding is necessary for the purpose of improving display contrast, preventing color mixing during color display, and shielding light from switching elements.

Here, as a method for shielding light at the portion where the second electrode 7 is disposed,
A method of providing the light shielding layer 9 so as to cover the second electrode 7,
A method in which the second electrode 7 is also used as a light shielding layer;
Can be mentioned.

In the electrophoretic display device shown in FIG. 1, the first electrode 6 is supported on the rear substrate 2 in the same manner as the second electrode 7 (that is, the charged particles 5 are the first electrode 6 and the second electrode 7. However, the present invention is not limited to this, and the charged particles 5 are supported by the display substrate 1 along the normal direction of the substrate. It may be a “vertical movement type” that moves. In the case of the horizontal movement type, when the area where the first electrode 6 is arranged is white and the charged particles 5 are black,
When the charged particles 5 are attracted to the second electrode 7, a white display is made,
When the charged particles 5 are attracted to the first electrode 6, a black display is made.
It will be.

  Next, the effect of the present invention will be described with reference to FIG. 3A, a light scattering layer or a diffuse reflection layer 13 is provided on the surface of the partition wall 3 in the present invention. On the other hand, FIGS. 3B and 3C are conventional examples. In FIG. 3B, the partition wall is formed of a transparent member, and in FIG. 3C, a light shielding material is used on the surface of the partition wall.

  In FIG. 3A of the present invention, light incident from the outside is reflected by the diffuse reflection layer 10, passes through the color filter layer 2, and then is scattered by the reflection layer 4 on the surface of the partition wall 3. Head for. Further, a part of the light is again directed to the color filter layer 12, the reflective layer 10, and so on.

  The same phenomenon occurs in adjacent pixels, and as shown in FIG. 3A, for example, reflected light directed upward from the R pixel and the G pixel rarely cross each other. It has the effect of preventing color mixing.

  On the other hand, in FIG. 3B, since the partition member is transparent, it can be seen that the reflected light directed upward from the R pixel and the G pixel of adjacent pixels is mixed and color mixing occurs. Further, in FIG. 3C, since the partition member is light-shielding, color mixing is unlikely to occur, but a part of the reflected light is absorbed by light absorption at the partition surface, so that reflection may occur depending on the viewing angle direction. The rate will drop.

  By imparting light scattering properties to the partition wall as in the present invention, color mixing can be prevented and a bright color display can be realized.

  Hereinafter, each component of the electrophoretic display device will be supplemented with reference to FIG.

The partition 3 is
・ Even if it is arranged to partition the pixels one by one,
-It may be arranged so as to partition a plurality of pixels. The partition wall 3 is preferably made of a material having a refractive index as small as possible and using a photosensitive resin such as epoxy, polyimide, or acrylic.

  For the display substrate 1 and the rear substrate 2, glass, quartz, or the like can be used in addition to plastic films such as polyethylene terephthalate (PET), polycarbonate (PC), and polyethersulfone (PES). Although it is necessary to use a transparent material for the display substrate 1 as described above, a colored substrate such as polyimide (PI) may be used for the rear substrate 2.

  Any conductive material that can be patterned may be used for the first electrode 6. For example, a metal such as chromium (Cr), aluminum (Al), copper (Cu), carbon or silver paste, or an organic conductive film can be used. When the first electrode is also used as the light reflecting layer, a material having a high light reflectance such as silver (Ag) or Al can be preferably used.

  In FIG. 1, the second electrode 7 is disposed between the partition wall 3 and the rear substrate 2. It may be arranged. As the second electrode 7, a conductive film formed by a vacuum deposition method or the like can be used, but it is preferable to use an electrode formed by a plating method.

  The insulating liquid 4 is preferably a non-polar solvent such as isoparaffin, silicone oil, xylene, toluene, and the like, which is transparent, and particularly preferably mixed with a liquid having a large refractive index to adjust the refractive index. .

  As the charged particles 5, it is preferable to use a material that is colored and exhibits a positive or negative charge characteristic in an insulating liquid. For example, various inorganic pigments, organic pigments, carbon black, or a resin containing them may be used. A particle having a particle size of about 0.01 μm to 50 μm can be used, but preferably about 0.1 to 10 μm.

  Note that a charge control agent for controlling and stabilizing the charging of the charged particles may be added to the above-described insulating liquid or charged particles. Examples of such charge control agents include metal complex salts of monoazo dyes, salicylic acid, organic quaternary ammonium salts, and nigrosine compounds.

  In addition, a dispersing agent for preventing aggregation of charged particles and maintaining a dispersed state may be added to the insulating liquid. As such a dispersing agent, polyvalent metal phosphates such as calcium phosphate and magnesium phosphate, carbonates such as calcium carbonate, other inorganic salts, inorganic oxides, or organic polymer materials can be used.

  For the light scattering layer or the diffuse reflection layer 10, for example, a pigment such as titanium oxide or aluminum oxide dispersed in a resin such as urethane, phenol, epoxy, or fluorine can be applied and used. The thickness of the light scattering layer is not particularly limited as long as the driving voltage applied to the insulating liquid does not increase, but is preferably 0.4 to 20 μm in order to obtain sufficient light scattering characteristics.

  Moreover, as a diffuse reflection layer, what has an uneven | corrugated pattern can be used in order to scatter light. The surface of the photosensitive resin film coated on the substrate or the partition wall can be processed into a concavo-convex pattern by photolithography, and a metal film such as aluminum is vapor deposited so as to cover it. The first electrode 6 may also be used.

Furthermore, it can also be set as the structure of a front scattering layer / specular reflection layer.
The forward scattering layer has a configuration in which transparent particles made of SiO2 or polystyrene beads having different refractive indexes are dispersed in a base substrate such as acrylic, polyimide, or epoxy resin.

  As the light shielding layer 11, a material in which carbon black, an inorganic pigment, an organic pigment or the like is dispersed in a resin can be used. The light shielding layer can be formed by a usual method such as vapor deposition, printing, and coating. The film thickness is preferably about 1 μm in order to provide sufficient light absorption performance.

  Furthermore, a switching element 9 may be disposed in each pixel, and the switching element 9 and the first electrode 6 described above may be electrically connected. The switching element 9 may be connected to the bottom of the first electrode 6, and the second electrode 7 of each pixel is preferably connected to each other so that the same signal is supplied.

  Next, the effect of this embodiment will be described.

  According to the present embodiment, it is possible to realize a particle movement display device that prevents color mixing. Specifically, a bright color display particle movement display device can be realized by imparting light scattering properties to the partition wall.

  In the above description, electrophoretic display has been described as an example. However, particles such as a dry display device called a toner display described in Japanese Patent Application Laid-Open No. 2000-347483 and a fine particle dispersion display device are moved. Any display device having such a configuration can be used widely.

An automatic goniophotometer (manufactured by Murakami Color Research Laboratory Co., Ltd.) GP-200 was used to measure the reflectance and the viewing angle characteristics of the reflectance used in the present invention. As shown in FIG. 2, parallel rays are incident from the direction of 30 ° with respect to the display surface normal line of the measurement sample, the reflectance in the range of the viewing angle of −90 ° to 90 ° is measured, and the viewing angle is 0 °. The value at was obtained as a representative value. The reflectance value was calculated with a barium sulfate plate as a standard white plate and a value of 100%.
The viewing angle range is indicated by an angle range where the reflectance value is larger than 0 in this apparatus.
Hereinafter, the present invention will be described in more detail with reference to examples.

  In this example, an electrophoretic display device having the structure shown in FIG. 1 was produced. The size of the electrophoretic display device was 52 mm × 52 mm, the number of pixels was 130 × 43, and the size of one pixel was 73 μm × 73 μm. Further, the partition wall 3 is arranged at the pixel boundary portion so as to partition each pixel, the width is 5 μm, and the height is 17 μm. Further, the switching element 9, the insulating layer 8, the first electrode 6, and the light scattering layer 10 are disposed on the rear substrate 2, and the light shielding layer 11 is disposed between the second electrode 7 and the partition 3. The length of one side of the first electrode 6 was 68 μm, and the thickness of the second electrode 7 was 50 nm. As the rear substrate 2, a plastic substrate having a thickness of 0.2 mm was used.

  Next, a method for manufacturing the electrophoretic display device according to this embodiment will be described.

  First, the switching element 9 was formed on the rear substrate 2, and the insulating layer 8 was formed so as to cover the switching element 9. A contact hole was formed in the insulating layer 8, and the first electrode 6 was formed so as to be electrically connected to the switching element 9 through the contact hole.

  The first electrode 6 also serving as the diffuse reflection layer was made of aluminum. First, a photosensitive resin (trade name: OMR83-20Cp, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to the rear substrate 2 so as to have a thickness of 1.2 μm, and one region of the first electrode is formed by photolithography and wet development. After patterning so that the ratio of the photosensitive resin to the pixels was 50%, heat treatment was further performed at 120 ° C. for 30 minutes. Next, aluminum was formed to a thickness of 150 nm in the first electrode region, and patterning was performed by photolithography and wet etching to form the first electrode 6 that also served as the diffuse reflection layer.

  Furthermore, a color filter layer 12 having a size of 6.5 mm × 6.5 mm and having a different color for each pixel area (trade name: FUJIFILM (registered trademark) ARCH Co., Ltd. Red: CR- 8960L, green: CG-8960L, blue: CB-8960L). The color filter layer had a thickness of 1 μm and was formed by spin coating.

  Further, a second electrode 7 made of titanium was formed on the surface of the color filter layer 12 at a portion corresponding to the pixel boundary portion, and a light shielding layer 11 was formed on the surface of the second electrode 7. For the light shielding layer 11, a resin containing carbon black (trade name: CFPR (registered trademark) BK series, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used, and the film thickness was 1 μm.

  In addition, a partition wall 3 was formed on the light shielding layer 11 by patterning. An epoxy resin, which is a transparent photosensitive resin, was used for the partition 3.

  A light scattering layer 10 was formed by spin coating so as to cover the periphery of the partition wall 3. As the light scattering layer 10, a urethane resin layer containing titanium oxide fine particles was used, and the film thickness was 0.5 μm. The scattering layer other than the periphery of the partition walls was removed by etching.

  Next, the insulating liquid 4 and the charged particles 5 were filled in the recesses defined by the partition walls 3. In the dispersion medium as the insulating liquid, 100 parts by weight of isoparaffin (trade name: Isopar (registered trademark) H, manufactured by Exxon), which is an aliphatic hydrocarbon solvent, and styrene-butadiene copolymer, which is a butadiene copolymer, are used. 0.8 parts by weight of coalescence (Asapur Kasei Co., Ltd., Asaprene (registered trademark) 1205), 2.5 parts by weight of rosin ester (Harima Kasei Co., Ltd., Neotol (registered trademark) 125H), zirconium octenoate ( Nippon Chemical Industry Co., Ltd., Nikka (registered trademark) Octix Zirconium) 0.012 parts by weight and polyethylene wax (Tomen Plastics Co., Ltd., AC6) were mixed and stirred for 24 hours.

  The charged particles 5 were polymethyl methacrylate particles containing 10% by weight of carbon having an average particle diameter of 2 μm. A dispersion for electrophoretic display was obtained by mixing and dispersing the above-mentioned liquid and charged particles.

  Thereafter, the display substrate 1 and the partition walls were sufficiently brought into contact with each other, and the periphery of both substrates was sealed with the bubbles removed.

  Next, a driving method will be described. The voltage applied to the first electrode 6 is Vd1, and the voltage applied to the second electrode 7 is Vd2. When driving was performed under the conditions of Vd1 = + 50 V, Vd2 = 0 V, or Vd1 = −50 V, Vd2 = 0 V and a voltage application time of 100 msec, the charged electrophoretic particles 5 moved without remaining. In addition, it was possible to perform color display with good contrast and no color mixture without being affected by the driving voltage of adjacent pixels. In addition, even when the substrate is bent, the partition walls can be prevented from being broken or the charged particles can be prevented from moving to adjacent pixels.

  Next, when the reflectance of the display device (value at a viewing angle of 0 °) was measured at a temperature of 22 ° C., the value was as high as 86%, and the viewing angle range was also wide from −70 ° to 88 °. It was a characteristic.

  On the other hand, Comparative Example 1 was obtained by forming a display device in which the light scattering layer 10 was not formed around the partition walls 3 and other configurations and manufacturing methods were the same as those in Example 1. When the reflectance of the display device (value at a viewing angle of 0 °) was measured at a temperature of 22 ° C., it was as low as 60%, and the viewing angle range was −80 to 87 degrees. When this display device was driven, display blur occurred in the character pattern display. Color mixing occurred in the color display.

  Further, the other configuration and manufacturing method are the same as those of the first embodiment except that the first electrode 6 also serving as the diffuse reflection layer is formed by vapor deposition of aluminum to form the first reflective electrode having a thickness of 150 nm. The display device produced was designated as Comparative Example 2. When the reflectance of the display device (value at a viewing angle of 0 °) was measured at a temperature of 22 ° C., it was 50%, and the viewing angle range was narrow at 16 to 34 degrees. It was not possible to obtain sufficient reflectivity and viewing angle characteristics only by using the first electrode as a mirror reflection.

  In the present embodiment, the periphery of the partition wall 3 is configured as a forward scattering layer / specular reflection layer, and other configurations and manufacturing methods are the same as those in the first embodiment.

First, aluminum was formed to a thickness of 150 nm by vapor deposition so as to cover the periphery of the partition wall 3. Further, a photosensitive resin is applied thereon, and exposure, development, and wet etching are performed, and patterning is performed so that only the aluminum on the surface of the partition wall 3 is protected and the other aluminum is exposed. The exposed aluminum was removed by wet etching, and an aluminum mirror reflection layer was formed around the partition wall. Next, the forward scattering layer 10 was formed on the specular reflection layer by spin coating. As the forward scattering layer 10, an acrylic resin layer containing SiO ₂ fine particles was used, and its film thickness was 1.0 μm. The scattering layer other than the periphery of the partition walls was removed by etching.

The scattering characteristic of the forward scattering layer is a Harvey function that is one of the scattering distribution functions F used for the diffuse reflection characteristic of the surface.
F (θ) = b (ABS (sin (θ) −sin (θin)) ^ S [Formula 1]
(Θ: scattering angle θin: incident angle)
The two scattering parameters were adjusted so that b = 30 and S = −0.9.

  When the display device thus created was driven, bright color display without color mixture could be performed.

  Next, when the reflectance (value at a viewing angle of 0 °) of the display device was measured at a temperature of 22 ° C., the value was as high as 112%, and the viewing angle range was also wide from −70 ° to 70 °. It was a characteristic.

  Examples 1 and 2 described above are summarized in the table below together with Comparative Examples 1 and 2.

これらの結果より、実施例のように隔壁に光散乱性または拡散反射性を付与することによって、混色のない明るいカラー表示の粒子移動型表示装置を実現できることがわかった。

From these results, it was found that a bright particle display particle movement type display device with no color mixture can be realized by giving light scattering or diffuse reflection to the partition walls as in the example.

Sectional drawing which shows an example of the structure of the particle movement display apparatus which concerns on this invention. The schematic diagram for demonstrating the mode of measurement, such as a reflection angle. The schematic diagram for demonstrating the effect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display substrate 2 Back substrate 3 Partition 4 Insulating liquid 5 Charged particle 6 1st electrode 7 2nd electrode 8 Insulating layer 9 Switching element 10 Light scattering layer or diffuse reflection layer 11 Light-shielding layer 12 Color filter layer 13 Partition surface

Claims (3)

Display substrate arranged in a state where a predetermined gap is opened, a rear substrate including a diffuse reflection layer or a light scattering layer, a partition wall arranged in the gap between the substrates, and an insulating property arranged in the gap between the substrates. A liquid and a plurality of charged particles, a first electrode disposed so as to be close to the insulating liquid, and a second electrode disposed so as to be in contact with the partition wall, and applying a voltage to these electrodes In the particle movement type display device for performing display based on moving the charged particles and reflecting light incident from the display substrate side on the rear substrate side,
A particle movement type display device, wherein the partition wall portion includes a diffuse reflection layer or a light scattering layer.   The particle movement display device according to claim 1, wherein the particle movement display device is an electrophoretic display device.   2. The particle movement type display device according to claim 1, wherein display is performed by moving the charged electrophoretic particles horizontally.

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