JP5664412B2 - Front plate of microcapsule type electrophoretic display device and microcapsule type electrophoretic display device - Google Patents

Description

  The present invention relates to a microcapsule electrophoretic display device that realizes colorization using a color filter.

A microcapsule type electrophoretic display device is a dispersion system in which fine particles of positively charged first color (for example, white) and fine particles of negative color (for example, black) are dispersed in a liquid dispersion medium. And an electrophoretic display layer in which microcapsules having an average particle diameter of about several tens of μm are fixed with a binder resin. The microcapsule type electrophoretic display device is a display device that becomes a display panel of an active matrix driving method or the like by combining the electrophoretic display layer with a pixel electrode by an active matrix driving method or the like and a driving circuit thereof.
In the production of this display device, for example, a microcapsule ink is prepared by dispersing microcapsules and a binder resin in a liquid and the like, and this is applied onto a continuously running film support. It is possible to form an electrophoretic display layer on a film support.

  Moreover, in such a manufacturing method, the film support which apply | coated this microcapsule with the electrophoretic display layer which consists of the formed microcapsule also becomes a part of a display panel. In the above microcapsule type electrophoretic display device, both sides of the microcapsule layer need to be sandwiched between electrodes. In the above example, one of them is an electrode combined with a driving circuit such as an active matrix system, That is, the electrode on the display surface side that is the film support side only needs to have conductivity uniformly distributed in the surface. Therefore, the film support which becomes a part of the display device has a configuration in which the transparent electrodes are uniformly distributed on the surface thereof.

JP 2007-41169 A

  As one of the methods for colorizing such an electrophoretic display device, there is a method of realizing colorization by adding two types of colored fine particles to white and black and applying a color filter thereto to add color. However, when a color filter is applied to the electrophoretic display device manufactured by the above method, the color filter cannot be formed in contact with the microcapsule layer and must be formed through a film support. . In this case, a gap corresponding to the thickness of the film support is generated between the color filter and the microcapsule layer by interposing the film support, and thereby, when viewed from an oblique direction, the gap from the microcapsule layer is generated. The reflected light causes a parallax due to the color adjacent to the intended color in the color filter, and the viewing angle of the electrophoretic display device is narrowed.

  Therefore, a front plate that can be colored by applying a color filter to a front plate having a part of a structure formed by, for example, applying a single layer of microcapsules to a continuously running film support. In order to increase the viewing angle, it is necessary to make the thickness of the film support as thin as possible.

  The parallax caused by the gap between the microcapsule layer and the color filter layer has been discussed as a problem to be solved. For example, in Patent Document 1, it is necessary for alignment when bonding the back electrode and the color filter. Assuming that the buffer layer produces parallax, this is avoided by forming a color filter on the TFT substrate. At the same time, it is also intended to solve the difficulty in aligning the back electrode and the color filter.

  However, when a color filter layer is provided between the microcapsule layer and the back electrode layer, light passes through the microcapsule layer twice, so that the range of chromaticity that can be expressed becomes extremely narrow. That is, vivid color reproducibility cannot be expected. On the other hand, the ease of alignment by directly forming the color filter on the back electrode is due to the direct formation on the back electrode, and the same is true for any layer.

  Based on this, when forming the color filter on the display surface side of the film support as described above, in order to avoid the narrowing of the viewing angle, the thin film support, more specifically, the microcapsule particle size and In forming an electrophoretic display layer composed of microcapsules on a film support having a thickness equal to or less than that, as will be described below, irregularities are generated in the film support, which causes various problems.

  That is, when an electrophoretic display layer is formed by applying a microcapsule layer prepared as a microcapsule ink, a step of drying the microcapsule layer after application is performed. The film support cannot withstand the shrinkage, and irregularities corresponding to the shrinkage of the microcapsule layer are generated on the film support.

In addition, when an adhesive layer with the back electrode is formed on the formed microcapsule layer in order to combine the film support on which the microcapsule layer is formed with the back electrode such as an active matrix, this is laminated. If realized by the above, irregularities are generated on the film support so as to follow the irregularities of the microcapsule layer according to its diameter.
As described above, when unevenness having the same roughness as the microcapsule diameter is generated on the surface of the film support, various troubles are caused in the subsequent processing performed on the surface of the film support.

  For example, when a protective layer or the like is formed on the surface side of the film support, when this is realized by a laminating method, an adhesive layer that adheres the film support and the protective layer is formed on the surface of the film support. Bubbles are generated without following the recess, and the visibility of the display device is significantly reduced. The same applies to the case where a color filter is formed on the surface of the film support by the laminating method.

In addition, even when a color filter is formed by coating on a film support, it is impossible or very difficult to form a color filter stably due to the roughness having the roughness described above. This causes a phenomenon of reducing the visibility of the display device.
Therefore, the present invention avoids the problem caused by the unevenness on the surface of the film support, which is caused by forming a microcapsule layer on a relatively thin film support in order to suppress the narrowing of the viewing angle of the electrophoretic display device. It is an object of the present invention to provide a front plate of a microcapsule type electrophoretic display device that can be used, and a microcapsule type electrophoretic display device having the front plate.

The present invention has been made in view of the above problems, and according to one aspect of the present invention, a microcapsule layer in which microcapsules in which electrophoretic particles are enclosed in a dispersion medium are fixed with a binder resin, and the microcapsules are provided. has a thickness of under size or less of the the film support layered formed on the surface of the microcapsule layer is formed on the surface of the film support irregularity has occurred, an overcoat layer that planarize the surface A front plate of a microcapsule type electrophoretic display device is provided.

According to another aspect of the present invention, the film support is made of a PET film having a thickness of 10 μm or more and 75 μm or less as a base material, and has a conductive layer on the surface. A front plate of a capsule electrophoretic display device is provided.
According to another aspect of the present invention, the overcoat layer has a difference between the refractive index of the material and an average refractive index in a direction perpendicular to the surface of the film support within 5%. A front plate of the microcapsule-type electrophoretic display device is provided.

According to another aspect of the present invention, there is provided a front plate of a microcapsule type electrophoretic display device, wherein the overcoat layer is made of a resin containing a metal oxide as a refractive index adjusting agent.
According to another aspect of the present invention, there is provided the front plate of the microcapsule type electrophoretic display device, wherein the overcoat layer has a thickness of 5 μm or less at the thinnest portion.
According to another aspect of the present invention, there is provided a microcapsule type electrophoretic display device comprising the above-described front plate, wherein a color filter is formed on a surface of an overcoat layer of the front plate. Is done.

  According to the present invention, when the microcapsule type electrophoretic display device is colored with a color filter, the surface irregularities generated on the film support having a thickness equal to or smaller than the microcapsule diameter formed on the microcapsule layer are The surface is flattened by relaxing by forming an overcoat layer. Thereby, it is possible to eliminate the problem of visibility of the microcapsule type electrophoretic display device that may be caused by the unevenness of the support surface.

It is a typical sectional view showing an example of composition of a front board of a microcapsule type electrophoretic display device concerning one embodiment of the present invention. It is a figure showing typically the microcapsule which constitutes the front board of the microcapsule type electrophoretic display device concerning one embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a configuration example of a front plate of a microcapsule type electrophoretic display device according to this embodiment. Note that, as described above, the microcapsule type electrophoretic display device according to this embodiment is a microcapsule type electrophoretic display device that realizes colorization by interposing a film support between the color filter and the microcapsule layer. It is.

Further, FIG. 1 shows that the microcapsule layer 1a formed by the microcapsules 1 has irregularities due to the reasons described above, that is, the binder 6 mainly connecting the microcapsules 1 contracts in the drying process. The film support 2 is also shown with unevenness corresponding thereto. Further, the front plate shown in FIG. 1 is characterized in that the unevenness is reduced by forming the overcoat layer 3 on the display surface side of the uneven film support 2. On the overcoat layer 3, a color filter layer (not shown) for colorization is formed.
The adhesive layer 4 is an adhesive layer formed for combining with a back electrode such as an active matrix, and the release layer 5 is a release layer that covers the adhesive layer 4. That is, the adhesive layer 4 and the release layer 5 are not essential for carrying out the present invention.

  In addition, the material for forming the overcoat layer 3 is not necessarily limited to a specific resin, and can be applied including an epoxy resin, an acrylic resin, a polyester resin, and a urethane resin. Can be adopted. Further, in order to reduce the difference between the refractive index of the film support 2 and the refractive index of the overcoat layer 3, an adjusting agent for adjusting the refractive index may be added to the material forming the overcoat layer 3. it can. As the additive, for example, zirconium oxide and titanium oxide are suitable.

When the overcoat layer 3 is formed by coating, die coating, comma coating, bar coating, roll coating, screen printing, or the like can be employed. In either case, the overcoating layer 3 is formed on the film support 2 in the coating process. It is necessary to perform flattening to alleviate the unevenness.
FIG. 2 is a diagram schematically showing a microcapsule which is one of main elements constituting the front plate of the microcapsule type electrophoretic display device according to the present embodiment. The microcapsule 1 includes a transparent dispersion medium 10 in which white particles 8 and colored particles 9 are dispersed in a shell (microcapsule shell) 7. The average particle size of the microcapsules 1 is preferably 20 to 60 μm, and can be purified by any method such as sieving and specific gravity separation.

As the colored particles 9, in addition to inorganic pigments such as inorganic carbon, fine powders such as glass or resin, and composites thereof can be used. As the white particles 8, known white inorganic pigments such as titanium oxide, silica, alumina and zinc oxide, organic compounds such as vinyl acetate emulsion, and composites thereof can be used.
The colored particles 9 and the white particles 8 are provided with a desired surface electrification by treating the surface of the particles with various surfactants, dispersants, organic and inorganic compounds, metals, and the like as necessary. In addition, it is possible to prevent aggregation due to electrostatic force or the like between different kinds of particles in the transparent dispersion medium 10, thereby improving dispersion stability.

  The transparent dispersion medium 10 is a solvent in which aliphatic hydrocarbons, aromatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, various esters, alcohol solvents, or other resins are used alone or appropriately mixed. This can be used, and is encapsulated in a microcapsule 1 manufactured using a known method such as a phase separation method such as a mixed coacervation method, an interfacial polymerization method, an in-situ method, or a solution dispersion cooling method. The microcapsule shell 7 is, for example, methacrylic acid resin, urea resin, gum arabic or the like.

  The microcapsule 1 is dispersed in a dispersion containing water as a main component, and a binder 6 made of a dielectric resin such as polylactic acid, phenol resin, polypropylene resin, acrylic resin, or urethane resin is added to the microcapsule 1. A suitable range of the weight ratio of the solid content to the total weight in the microcapsule coating liquid is the coating liquid of the microcapsule coating liquid. Since it depends on the method, the width is wide, approximately 25% to 50%.

As a coating method for coating the microcapsule coating liquid on the film support 2, various methods such as micro gravure coating, kiss coating, comma coating, die coating, bar coating, roll coating, and screen printing can be adopted. Since the film support 2 can be continuously processed with bending in the coating process of the microcapsule coating solution, a film support 2 having flexibility enough to withstand bending is preferable.
Specific examples of the material of the film support 2 satisfying such requirements include polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), polyethersulfone (PES), PEN, and triacetyl cellulose (TAC). Various resins such as, but not limited to, can be mentioned.

  In the front plate of this embodiment, an electrode layer (not shown) is provided between the film support 2 and the microcapsule layer 1a. The front plate of this embodiment can be driven by providing electrodes facing both surfaces of the microcapsule 1 and applying a voltage between the electrodes. As the electrode layer forming material, indium oxide-based oxide such as indium tin oxide (ITO), tin oxide-based, conductive oxide having transparency such as zinc oxide-based, carbon nanotube, thiophene-based compound, or the like is used. it can. For forming the transparent electrode layer, conventional techniques such as a dry film forming method such as an evaporation method, a sputtering method, and a CVD method, and a wet film forming method using a coating liquid can be used.

  In the present embodiment, the thickness of the film support 2 is preferably 10 μm or more and 75 μm or less. Again, in the electrophoretic display device of this embodiment, the microcapsule layer 1a and the color filter layer are provided with the film support 2 interposed therebetween. At this time, the distance between the microcapsule layer and the color filter is preferably as short as possible from the viewpoint of the viewing angle of the electrophoretic display device to be manufactured. Therefore, the film support 2 is preferably as thin as possible. When the distance between the microcapsule layer and the color filter is increased, the viewing angle is narrowed due to a problem that the color becomes faint when the electrophoretic display device is observed from an oblique direction. An electrode layer also exists between the microcapsule layer and the film support, but the thickness of the electrode layer is on the submicron order and can be ignored.

  In the front plate of the present embodiment, when the microcapsule layer and the color filter layer are provided with the film support 2 sandwiched therebetween, the film support is made thin in response to a request to make the thickness of the film support as thin as possible. It is made in order to eliminate the trouble caused by the unevenness of the film support that occurs at the time. When the thickness of the film support exceeds 75 μm, the viewing angle of the electrophoretic display device becomes narrow, and the effect of this embodiment cannot be obtained sufficiently. In addition, when the thickness of the film support exceeds 75 μm, the unevenness on the surface of the film support becomes small, so the effect of providing an overcoat layer becomes small in the first place. On the other hand, when the thickness of the film support is less than 10 μm, the handleability is deteriorated and it is difficult to form a microcapsule layer on the film support.

  Moreover, in the front plate of the present embodiment, the thickness of the overcoat layer is preferably 5 μm or less at the thinnest portion. Since the distance between the microcapsule layer and the color filter is preferably as short as possible from the viewpoint of the viewing angle of the manufactured electrophoretic display device, the thickness of the overcoat layer is preferably as thin as possible. When the thickness of the thinnest part of the overcoat layer exceeds 5 μm, the viewing angle of the electrophoretic display device becomes narrow, and the effect of the present embodiment cannot be sufficiently obtained. In the front plate of the present embodiment, the thickness of the overcoat layer may be 0 μm at the thinnest portion.

Here, as described above, both FIG. 1 and FIG. 2 are schematic diagrams. Therefore, the shape of the microcapsule 1, the unevenness of the film support 2, the degree of planarization by the overcoat layer 3, and the microcapsule 1 The ratio of the size of the encapsulated white particles 8 and the colored particles 9 to the microcapsules 1 and the ratio of the thickness of the microcapsule shell 7 to the thickness of the microcapsules 1 are the same as those in the actual microcapsules. May be different.
Examples of the present invention will be described below.

  First, the microcapsule 1 was produced as follows. Titanium oxide powder (white particles 8) having an average particle diameter of 3 μm coated with a polyethylene resin in a tetrachloroethylene solvent, and carbon black powder (black particles (colored particles) 9) having an average particle diameter of 4 μm surface-treated with alkyltrimethylammonium chloride. And a dispersion liquid (transparent dispersion medium) 10 was prepared.

Next, the dispersion 10 was mixed with an aqueous solution in which gelatin and sodium polystyrene sulfonate were mixed in water, the liquid temperature was adjusted to 40 ° C., and the mixture was stirred with a homogenizer while maintaining the liquid temperature to obtain an O / W emulsion. Got.
Next, the obtained O / W emulsion and an aqueous solution prepared by mixing gum arabic with water prepared at 40 ° C. are mixed using a dispenser, and acetic acid is added while maintaining the solution temperature at 40 ° C. Using this, the pH of the solution was adjusted to 4, and a microcapsule wall (microcapsule shell) 7 was formed by coacervation.

  Further, after the liquid temperature is lowered to 5 ° C., a 37 wt% formalin solution is added to cure the microcapsule wall 7, and dispersion in which white particles (titanium oxide particles) 8 and black particles 9 (carbon black particles) are dispersed. A microcapsule 1 enclosing the liquid 10 was obtained. Thereafter, by sieving, a microcapsule group having an average particle diameter by volume of 45 μm and a ratio of microcapsules 1 included in the range of 30 μm to 65 μm was 75% or more was obtained.

  Next, a group of microcapsules dispersed in pure water having a solid content of 40% by weight was mixed with a urethane binder 6 having a solid content of 40% by weight, a surfactant, and a thickener to prepare a microcapsule coating solution. . Next, this microcapsule coating solution was applied to an ITO / PET film support 2 having a thickness of 25 μm and dried at 60 ° C. for 10 minutes to form a microcapsule layer 1a on the film support 2.

Further, after protecting the formed microcapsule layer 1a with a protective film, the surface of the ITO / PET film support 2 laminated on the opposite side is oxidized as an equipment with an acrylic resin as a refractive index adjusting agent. The overcoat layer 3 was formed by applying an overcoat material coating liquid in which zirconium was dispersed with a bar coater.
Here, regarding the refractive index of the overcoat layer 3 described above, when an overcoat layer having a layer thickness of 10 μm was separately formed on the support and the refractive index was measured, the average refractive index was 1.62. Since the average refractive index of the PET layer of the ITO / PET film support 2 formed in this example was 1.65, the refractive index difference between the two was 0.03, which was 5 compared to the average refractive index of the PET layer. The difference was within%.

  Further, the unevenness before and after forming the overcoat layer 3, that is, the unevenness of the display surface in the ITO / PET film support 2 after forming the microcapsule layer 1a, and the overcoat layer after forming the overcoat layer 3 Evaluation of the unevenness of 3 was performed as follows. That is, the profile of unevenness on each surface is measured over 25 mm, the maximum value is 5 points, the minimum value is 5 points, and a total of 10 points are calculated from the points where the absolute values are large, and the average value is calculated. It evaluated by calculating | requiring ten-point average roughness.

As a result, the ten-point average roughness of the display surface of the ITO / PET film support 2 was 6.7 μm, whereas that of the overcoat layer 3 was 1.4 μm, and the unevenness of the display surface was alleviated. It was shown that
The back electrode of the active matrix is bonded to the front plate of the microcapsule type electrophoretic display device produced by forming the adhesive layer 4 on the microcapsule layer 1a on which the overcoat layer 3 is formed as described above. When the display device was driven, the desired operation was obtained without problems.

On the other hand, the front plate is formed by forming an adhesive layer even for the case where the overcoat layer 3 is not formed. Each of the front plate and the front plate having the overcoat layer 3 manufactured as described above, A 190 μm film having a 10 μm adhesive layer on the surface was laminated by a laminating method.
As a result, no bubbles were observed in the case where the overcoat layer 3 was formed as described above, whereas many bubbles having a diameter of about 50 μm were observed in the case where the overcoat layer 3 was not formed. The visibility as the display device was lowered.

  Here, the lamination conditions are the same as those used when the ITO / PET film having a thickness of 125 μm is used as the support 2. Therefore, by forming the overcoat layer 3, even when the ITO / PET film support 2 having a thickness of 50 μm is used, this is the same as using the ITO / PET film of 125 μm as the support 2 in the subsequent step. It was shown that it is possible to handle.

The microcapsule coating solution produced in the same manner as in Example 1 was applied to an ITO / PET film support 2 having a thickness of 25 μm and dried in the same manner as in Example 1 to dry the microcapsule layer 1a on the film support 2. Formed.
Next, the back electrode of the active matrix was bonded to the front plate of the microcapsule type electrophoretic display device produced by forming the adhesive layer 4 on the formed microcapsule layer 1a to obtain a display device. At this time, the ten-point average roughness of the surface of the display surface of the ITO / PET film support 2 was 5.4 μm.
The overcoat layer 3 was formed on the surface of the display surface by applying an overcoat material coating solution made of the same material as in Example 1 using a bar coater. From the measurement results of this surface, the ten-point average roughness was 1.5 μm, indicating that the unevenness of the display surface was also alleviated.

  In addition, as a result of laminating a 190 μm film having a 10 μm adhesive layer, which is a film as a protective layer as in Example 1, to the display device on which the overcoat layer 3 is formed, the main lamination conditions are as follows. It was possible to perform lamination without observing bubbles without changing from the case of using an ITO / PET film having a thickness of 125 μm as the support 2.

DESCRIPTION OF SYMBOLS 1 ... Microcapsule 1a ... Microcapsule layer 2 ... Film support 3 ... Overcoat layer 4 ... Adhesive layer 5 ... Release material 6 with respect to adhesive layer ... Binder 7 in microcapsule layer ... Microcapsule shell 8 ... First color coloring Electrophoretic particles 9 ... 2nd colored electrophoretic particles 10 ... Transparent dispersion medium in microcapsules

Claims (6)

A microcapsule layer in which microcapsules encapsulating electrophoretic particles in a dispersion medium are fixed with a binder resin;
A layered film support having a thickness equal to or less than the diameter of the microcapsule and formed on the surface of the microcapsule layer;
Irregularities are formed on the surface of the film support has occurred, and an overcoat layer that planarize the surface,
A front plate of a microcapsule-type electrophoretic display device.   2. The microcapsule electrophoretic display device according to claim 1, wherein the film support has a PET film having a thickness of 10 μm or more and 75 μm or less as a base material and has a conductive layer on a surface thereof. Front plate.   The difference between the refractive index of the material of the overcoat layer and the average refractive index in a direction perpendicular to the surface of the film support is within 5%. Front plate of the microcapsule type electrophoretic display device.   The front plate of the microcapsule type electrophoretic display device according to any one of claims 1 to 3, wherein the overcoat layer is made of a resin containing a metal oxide as a refractive index adjusting agent.   5. The front plate of the microcapsule electrophoretic display device according to claim 1, wherein the thickness of the overcoat layer is 5 μm or less at the thinnest portion. The front plate according to any one of claims 1 to 5,
A microcapsule type electrophoretic display device comprising a color filter formed on a surface of an overcoat layer of the front plate.

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