JP4682761B2 - Electrophoretic display medium and method for producing electrophoretic display medium - Google Patents

Description

  The present invention relates to an electrophoretic display medium and a method for producing an electrophoretic display medium.

  Conventionally, an electrophoretic display medium that displays an image using positively or negatively charged charged particles is known. Such an electrophoretic display medium includes a display liquid in which charged particles are dispersed, and a pair of substrates including a display substrate having electrodes for applying an electric field to the display liquid and a back substrate. By applying an electric field to each pixel with an electrode disposed on the substrate, charged particles in the display liquid can be migrated to each pixel. According to the electrophoretic display medium, at least the substrate constituting the display surface of the pair of substrates is composed of a transparent member, specifically, a transparent glass and a transparent electrode such as ITO (indium tin oxide). Therefore, by moving charged particles on the display substrate side to display the color of the charged particles, or by moving charged particles on the back substrate side to not display the color of the charged particles, a desired image can be displayed. Can be displayed.

  In such an electrophoretic display medium, when the display surface continues to be inclined with respect to the horizontal direction, the charged particles gradually settle in one direction of the display surface due to their own weight. If the concentration of the charged particles becomes non-uniform due to sedimentation, it becomes difficult to move the charged particles in a portion where the concentration of the charged particles is high, or a desired contrast cannot be obtained in a portion where the concentration of the charged particles is low. As a result, there is a problem that display quality deteriorates with time.

Therefore, for example, Japanese Patent No. 3189958 (Patent Document 1) proposes an electrophoretic display medium in which a partition wall is provided between a pair of substrates and a small space is formed between the substrates. By subdividing the space between the substrates, even if the display surface is inclined with respect to the horizontal direction, the movement of the charged particles to the adjacent area is limited, so that sedimentation and aggregation in one direction of the charged particles can be suppressed. Can do. Therefore, stable display quality can be obtained for a long time. Furthermore, according to the electrophoretic display medium described in Patent Document 1, a passage that connects each small section is formed in the partition wall. Accordingly, when manufacturing an electrophoretic display medium, first, a partition is provided between a pair of substrates, and then a display liquid is injected between the pair of substrates from one direction, whereby each small liquid is passed through a passage formed in the partition. The display liquid can be filled in the compartment.
Japanese Patent No. 3189958

  However, in the electrophoretic display medium described in Patent Document 1, since the partition is provided before the display liquid is injected, the flow of the display liquid is inhibited by the partition. As a result, bubbles tend to stay when the display liquid is injected, and charged particles cannot migrate freely in the area where bubbles are present, that is, the image cannot be formed with charged particles, resulting in a deterioration in display quality. was there. In addition, the electrophoretic display medium described in Patent Document 1 has a problem that bubbles are likely to stay in particular because the structure of the partition walls is complicated.

  Further, according to the conventional electrophoretic display medium, it is necessary to form partition walls having a fine lattice structure for partitioning a pair of substrates, which makes it difficult to manufacture. For example, according to the electrophoretic display medium described in Patent Document 1, since the partition walls are formed on the pair of upper and lower substrates, high accuracy is required for alignment of the partition walls formed on the pair of upper and lower substrates. There was a problem that it was difficult to manufacture.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an electrophoretic display medium that is easy to manufacture and has good display quality, and a method for manufacturing the electrophoretic display medium. .

  To achieve this object, an electrophoretic display medium according to claim 1 is a substrate surface of a pair of first substrate and second substrate having the substrate surfaces facing each other, and the first substrate and the second substrate. A frame member that maintains a predetermined distance therebetween, and a display liquid that is sealed between the first substrate and the second substrate and in which charged particles that move according to the direction of the electric field are dispersed. A character or an image is displayed by migration of the charged particles on a display surface constituted by at least one of the substrate and the second substrate, and the first substrate or the second substrate under a predetermined first condition. A plurality of concave portions and convex portions are formed on at least one of the substrate surfaces, and the organic polymer is dissolved in the display liquid under a second condition different from the predetermined first condition. It has a partition part.

  The electrophoretic display medium according to claim 2 is the electrophoretic display medium according to claim 1, wherein the convex portion formed by the partition wall is a substrate of the first substrate or the second substrate facing the partition wall. When the electrophoretic display medium is viewed from a direction perpendicular to the substrate surface and the distance between the surfaces is smaller than the diameter of the charged particles, the convex portions of the adjacent partition walls are not parallel. These are arranged arbitrarily (non-uniformly).

  An electrophoretic display medium according to a third aspect is the electrophoretic display medium according to the first aspect, wherein the partition wall portion has a non-constant difference in height between the adjacent convex portion and the concave portion.

  An electrophoretic display medium according to a fourth aspect is the electrophoretic display medium according to the first aspect, wherein in the partition portion, the interval between the adjacent convex portions is non-constant.

  An electrophoretic display medium according to a fifth aspect is the electrophoretic display medium according to the first aspect, wherein in the partition portion, the height of the convex portion is non-constant.

  The electrophoretic display medium according to claim 6 is the electrophoretic display medium according to claim 1, wherein the partition wall portion has a difference in height between the adjacent convex portion and the concave portion that is larger than a diameter of the charged particle. It is more than twice as large.

  An electrophoretic display medium according to a seventh aspect is the electrophoretic display medium according to the first aspect, wherein a plurality of convex portions of the partition wall are arranged in one pixel.

  An electrophoretic display medium according to an eighth aspect is the electrophoretic display medium according to the first aspect, wherein the organic polymer is a wax.

  The method of manufacturing an electrophoretic display medium according to claim 9, wherein a pair of first substrate and second substrate having substrate surfaces facing each other and a predetermined distance between each substrate surface of the first substrate and the second substrate are provided. A holding frame member, a display liquid that is sealed between the first substrate and the second substrate and in which charged particles that move according to the direction of the electric field are dispersed, and the first substrate or the second substrate. The charged particles migrate to the display surface that includes at least one of the first substrate and the second substrate, and includes a partition wall having a plurality of recesses and protrusions on at least one of the substrate surfaces. A method for manufacturing an electrophoretic display medium that displays characters and images by a substrate preparing step of preparing the first substrate and the second substrate bonded to each other with the frame member interposed therebetween, The substrate preparation process An injection step of injecting a display liquid in which the charged particles are dispersed and an organic polymer is dissolved between the first substrate and the second substrate, and injected by the injection step The organic polymer is precipitated from the display liquid, and the partition wall formed of the organic polymer crystal and the crystal laminate formed is at least one of the first substrate and the second substrate. And a crystallization process formed on the substrate surface.

  The method for producing an electrophoretic display medium according to claim 10 is the method for producing an electrophoretic display medium according to claim 9, wherein the organic polymer dissolved in the display liquid injected in the injection step is Dissolving in the display liquid at a predetermined temperature higher than a use environment temperature of the electrophoretic display medium and depositing at the use environment temperature of the electrophoretic display medium, and the crystallization step includes the first substrate. And the second substrate are cooled at the use environment temperature to crystallize the organic polymer.

  The method for producing an electrophoretic display medium according to claim 11 is the method for producing an electrophoretic display medium according to claim 10, wherein the organic polymer dissolved in the display liquid injected in the injection step is a wax. is there.

  The method for producing an electrophoretic display medium according to claim 12 is the method for producing an electrophoretic display medium according to claim 11, wherein the display liquid injected in the injection step is a paraffinic hydrocarbon solvent.

  The method for producing an electrophoretic display medium according to claim 13 is the method for producing an electrophoretic display medium according to any one of claims 9 to 12, wherein the crystallization step is performed on the first substrate or the second substrate. Either one is arranged on the upper side in the vertical direction, and the one substrate side arranged on the upper side is at a lower temperature than the other substrate side, in the substrate surface of the one substrate arranged on the upper side, The organic polymer is formed into a crystal and a crystal laminate.

  The method for manufacturing an electrophoretic display medium according to claim 14 is the method for manufacturing an electrophoretic display medium according to any one of claims 9 to 13, wherein at least one of the first substrate and the second substrate. The surface has a plurality of protrusions having a height lower than the predetermined distance between the substrate surfaces, and the substrate preparation step includes the step of causing the substrate surface provided with the protrusions to face the substrate surface of the other substrate. One substrate and the second substrate are prepared.

  According to the electrophoretic display medium according to any one of claims 1 to 8, the partition wall includes a plurality of recesses and protrusions on at least one of the first substrate and the second substrate under a predetermined first condition. Since it is formed of an organic polymer that is formed and dissolves in the display liquid under a second condition different from the predetermined first condition, the material for forming the partition wall in the display liquid under the second condition during manufacture The display liquid can be injected between the first substrate and the second substrate in a state where the organic polymer is dissolved. Accordingly, since the display liquid can be injected between a pair of substrates that do not have a complicated partition wall that prevents the flow of the display liquid, bubbles stay due to the partition wall blocking the flow of the display liquid. Therefore, the display quality is improved. On the other hand, after injecting the display liquid, by placing the electrophoretic display medium in the first condition, a plurality of concave portions and convex portions are formed on the partition wall portion on at least one of the first substrate and the second substrate. Can be formed. Therefore, the movement of the charged particles in the direction parallel to the substrate surface is suppressed by the concave portions and the convex portions formed by the partition walls. Therefore, there is an effect that unevenness of the charged particle concentration due to a large deviation in the direction parallel to the substrate surface of the charged particles is suppressed, and deterioration of display quality with time is suppressed. Furthermore, by placing the electrophoretic display medium under a predetermined first condition, it is possible to form a plurality of concave portions and convex portions in the partition wall portion, so that there is an effect that manufacture is facilitated. Conventionally, since a partition member having a fine lattice structure is provided between the first substrate and the second substrate in order to suppress a large deviation in the direction parallel to the substrate surface of the charged particles, it has been difficult to manufacture. It is.

  According to the method for manufacturing an electrophoretic display medium according to claim 9, the display liquid in which the charged particles are dispersed and the organic polymer is dissolved is injected between the first substrate and the second substrate by the injection step. In the crystallization process, the organic polymer is precipitated from the injected display liquid, and the partition wall formed by the generated organic polymer crystal and the crystal laminate is formed on the first substrate or the first substrate. It is formed on at least one of the two substrates. That is, the organic polymer for constituting the partition wall is dissolved in the display liquid in the injection process. Accordingly, since the display liquid can be injected between a pair of substrates that do not have a complicated partition wall that prevents the flow of the display liquid, bubbles stay due to the partition wall blocking the flow of the display liquid. Therefore, there is an effect that an electrophoretic display medium with good display quality can be manufactured. On the other hand, after injection of the display liquid, a partition having a plurality of concave portions and convex portions is formed by generating an organic polymer crystal and a crystal laminate. Therefore, the movement of the charged particles in the direction parallel to the substrate surface is suppressed by the concave and convex portions of the partition wall. Therefore, it is possible to produce an electrophoretic display medium in which the unevenness of the charged particle concentration due to the large deviation in the direction parallel to the substrate surface of the charged particles is suppressed and the deterioration of display quality over time is suppressed. is there. Furthermore, since the partition part which has several recessed part and convex part is formed by a crystallization process, there exists an effect that an electrophoretic display medium can be manufactured easily. Conventionally, since a partition member having a fine lattice structure for suppressing the settling and aggregation of charged particles is provided between the first substrate and the second substrate, it is difficult to manufacture.

  According to the method for manufacturing an electrophoretic display medium according to claim 10 or 11, in addition to the effect exhibited by the method for manufacturing an electrophoretic display medium according to claim 9, the first substrate and the second substrate are formed by a crystallization step. Since the organic polymer is crystallized by cooling the display liquid injected between the two at the use environment temperature, a partition wall having a plurality of recesses and projections can be easily formed. As a result, there is an effect that an electrophoretic display medium that can suppress non-uniformity of the charged particle concentration due to a large deviation in the direction parallel to the substrate surface of the charged particles can be easily manufactured.

  According to the method for producing an electrophoretic display medium according to claim 12, in addition to the effect exhibited by the method for producing an electrophoretic display medium according to claim 11, the display liquid is a paraffinic hydrocarbon solvent, so An organic polymer is easily dissolved under a predetermined second condition. Therefore, it is possible to easily adjust the display liquid to be injected between the first substrate and the second substrate in the injection step. Therefore, there is an effect that the electrophoretic display medium can be easily manufactured.

  According to the method for manufacturing an electrophoretic display medium according to claim 13, in addition to the effect exhibited by the method for manufacturing an electrophoretic display medium according to any of claims 9 to 12, in the crystallization step, the first substrate or Since any one of the second substrates is arranged above the vertical direction, the charged particles settle to the substrate side below the vertical direction due to gravity. Accordingly, since the charged particles are prevented from being mixed into the partition wall formed on the substrate surface of the one substrate disposed on the upper side, sufficiently charged charged particles can be secured. Therefore, the produced electrophoretic display medium has an effect of suppressing deterioration in display quality due to a lack of charged particles capable of migrating in the display liquid.

  According to the method for manufacturing an electrophoretic display medium according to claim 14, in addition to the effect exhibited by the method for manufacturing an electrophoretic display medium according to any one of claims 9 to 13, the protrusion is provided by the substrate preparation step. Since the first substrate and the second substrate having the substrate surface opposed to the substrate surface of the other substrate are prepared, as a result, in the produced electrophoretic display medium, the charged particles in the direction parallel to the substrate surface There is an effect that the unevenness of the charged particle concentration due to the large deviation is further suppressed, and the display quality is improved.

  That is, in the crystallization step, when the partition wall is formed on the substrate surface provided with the protrusion, the organic polymer is precipitated on the surface of the protrusion provided on the substrate surface. In addition, it is possible to make the arrangement of the partition walls regular by increasing the difference in height between the recesses and projections of the partition walls made of a laminated body of crystals and by providing protrusions with regularity. It becomes. Therefore, the effect of suppressing the large deviation of the charged particles in the direction parallel to the substrate surface by the concave and convex portions of the partition wall portion is further increased, and an electrophoretic display medium having a good display quality can be manufactured. is there.

  On the other hand, in the crystallization step, when the partition wall portion is formed on the substrate surface opposite to the substrate surface on which the protrusion is provided, the height of the protrusion of the partition wall portion to be generated is lowered by the height of the protrusion. Therefore, it is possible to reduce the amount of organic high molecular weight used. By increasing the volume of the partition wall and the volume of the display liquid, the amount of charged particles can be increased and the contrast can be improved. Therefore, there is an effect that an electrophoretic display medium with good display quality can be manufactured.

  Furthermore, since the protrusions are lower than a predetermined distance between the substrate surfaces, the protrusions are inhibited from inhibiting display liquid flow when the display liquid is injected in the injection process. Can be suppressed. Therefore, there is an effect that an electrophoretic display medium with good display quality can be manufactured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 is a diagram for explaining an electrophoretic display medium 10 according to an embodiment of the present invention. FIG. 1A is a top view of the electrophoretic display medium 10, and FIG. It is sectional drawing which showed typically the cross section of the Ib-Ib line | wire direction in (a). First, the overall configuration of the electrophoretic display medium 10 will be described with reference to FIG.

  As shown in FIG. 1A, the electrophoretic display medium 10 is a rectangular electrophoretic display panel, and an electric signal (applied to the X electrode 12b and the Y electrode 13b (see FIG. 1B)). It is connected to a drive control unit (not shown) that controls current and voltage, and displays an image corresponding to a user operation on the display area D of the first substrate 12 that is a display surface.

  As shown in FIG. 1B, the electrophoretic display medium 10 includes a first substrate 12, a second substrate 13, and a frame member 17 interposed between the second substrate 13 and the first substrate 12. The liquid chamber R, the injection port 21, the discharge port 22, the display liquid 33 sealed in the liquid chamber R, and the partition wall 34 are mainly provided.

  The first substrate 12 includes a substrate body 12a, an X electrode 12b, a protective layer 12c, and a substrate surface 12d. The second substrate 13 includes a substrate body 13a, a Y electrode 13b, a protective layer 13c, and a substrate surface 13d. In the electrophoretic display medium 10, the substrate surface 12 d of the first substrate 12 and the substrate surface 13 d of the second substrate 13 face each other.

  Each of the substrate bodies 12a and 13a is a plate-like body having a thickness of about 100 μm, and is made of a synthetic resin such as glass or polyethylene terephthalate, a natural resin, or paper. In the portions corresponding to the display area D in the substrate bodies 12a and 13a, an X electrode 12b and a Y electrode 13b are provided on the surfaces facing each other.

  The X electrode 12b and the Y electrode 13b bear a polarity for applying an electric field to the display liquid 33 sealed in the liquid chamber R. Both the X electrode 12b and the Y electrode 13b are formed in a plurality of substantially parallel lines, and are arranged so as to be substantially orthogonal to each other. In other words, the electrophoretic display medium 10 is a simple matrix drive type electrophoretic display medium that performs display control by switching these electrodes 12b and 13b on or off, and is an intersection of the X electrode 12b and the Y electrode 13b. Constitutes a pixel P (see FIG. 1A).

  As long as both the X electrode 12b and the Y electrode 13b have conductivity, a metal, a metal oxide, a conductive polymer, or the like can be used. However, the X electrode 12b and the Y electrode 13b are formed on a substrate serving as a display surface. The electrode 12b is preferably formed of ITO (indium tin oxide), polythiophene or the like having high light transmittance. The X electrode 12b and the Y electrode 13b are formed on the substrate bodies 12a and 13a, respectively, using the above-described materials by a known electroless plating method, sputtering method, ink jet method, printing method, etching method, or the like. can do.

  Liquid-resistant protective films 12c and 13c are provided on the surface of the substrate body 12a where the X electrode 12b is formed and the surface of the substrate body 13a where the Y electrode 13a is formed. The protective films 12c and 13c prevent direct contact between the display liquid 33 and the electrodes (X electrode 12b and Y electrode 13b), so that the electrodes (X electrode 12b and Y electrode 13b) in the electrophoretic display medium 10 are deteriorated. Can be prevented. The protective films 12c and 13c are excellent in chemical resistance and the like. For example, polycarbonate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polytetrafluoroethylene (polychlorotrifluoroethylene, tetra It is composed of a film containing a fluorine-containing compound such as a fluoroethylene / perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer.

  The frame member 17 is a plate-like member having a thickness of about 20 μm, for example, and is provided along the edges of the first substrate 12 and the second substrate 13. The frame member 17 is made of an insulating material such as a synthetic resin such as an epoxy resin or polyethylene terephthalate, a natural resin, ceramics, or glass. The frame member 17 maintains the distance between the substrate surfaces 12 d and 13 d at a distance corresponding to the thickness of the frame member 17.

  The liquid chamber R is a space having a shape corresponding to the thickness of the frame member 17, which is formed between the first substrate 12 and the second substrate 13 that are separated by the interposition of the frame member 17. The liquid chamber R is sealed with a display liquid 33 that is a liquid in which charged particles 31 a and charged particles 31 b are dispersed in the electrophoretic medium 30. The electrophoretic medium 30 that is a dispersion medium of the display liquid 33 sealed in the liquid chamber R is preferably a solvent having high insulation (high electric resistance), and a preferable solvent is a hydrocarbon solvent (for example, Hexane, cyclohexane, kerosene, xylene, linear paraffinic hydrocarbon solvent, isoparaffinic hydrocarbon solvent, cyclic paraffinic hydrocarbon solvent, etc.), and oily polysiloxanes such as silicone oil. In addition, each of the above solvents may be used alone, as a mixture of two or more, or may be used after being modified according to the purpose.

  On the other hand, the charged particles 31 that are the dispersoid of the display liquid 33 are composed of white charged particles 31a that are positively charged and black charged particles 31b that are negatively charged. As the white charged particles 31a, for example, those obtained by forming a polyethylene resin layer and a positively charged portion on the surface of titanium dioxide, and as the black charged particles 31b, for example, those obtained by forming a polyethylene resin layer and a negatively charged portion on the carbon black display surface. Although it is used, for example, a material obtained by forming a fluorine-based monomolecular film on the surface of an organic pigment such as a phthalocyanine pigment, or a material obtained by treating the surface of the organic pigment with a silane coupling agent may be used. In the electrophoretic display medium 10 of the present embodiment, particles having an average particle diameter of 1 μm are used as the charged particles 31a and 31b.

  The white charged particles 31a and the black charged particles 31b are respectively migrated to the first substrate 12 side or the second substrate 13 side according to the direction of the electric field generated between the X electrode 12b and the Y electrode 13b. The

  More specifically, in the region (pixel P) where the electric field is formed such that the X electrode 12b is positive with respect to the Y electrode 13b, the black charged particles 31b that are negatively charged are the first substrate 12. On the other hand, the positively charged white charged particles 31a migrate to the second substrate 13 side (Y electrode 13b side).

  On the other hand, in the region (pixel P) where the electric field is formed such that the X electrode 12b is negative with respect to the Y electrode 13b, the positively charged white charged particles 31a are on the first substrate 12 side (X On the other hand, the negatively charged black charged particles 31b migrate to the second substrate 13 side (Y electrode 13a side). Therefore, by applying an electric field according to the image data between the X electrode 12b and the Y electrode 13a by a control unit (not shown), the image data is applied to the display area D on the first substrate 12 which is the display surface. Accordingly, a black image caused by the black charged particles 31b migrated to the first substrate 12 side can be displayed.

  In addition to the electrophoretic medium 30 and the charged particles 31a and 31b that are the dispersion medium, the display liquid 33 includes, for example, organic solvents such as alcohols, ketones, and esters for adjusting viscosity and insulating properties, Alternatively, nonionic, anionic, cationic or amphoteric surfactants for increasing the dispersibility of the charged particles 31a and 31b, resins such as polyvinyl alcohols, electrolytes, charge control agents, corrosion inhibitors, friction A regulator, an ultraviolet absorber, or the like may be appropriately added as an additive.

  On the first substrate 12 of the electrophoretic display medium 10, the inlet 21, which is a passage for injecting the display liquid 33 into the liquid chamber R, and the display liquid 33 from the inlet 21 to the liquid chamber R. When the gas is injected, a discharge port 22 that is a passage for discharging the gas existing in the liquid chamber R to the outside is provided. After injecting and filling the display liquid 33 into the liquid chamber R, the display liquid 33 is sealed in the liquid chamber R by sealing the openings of the inlet 21 and the outlet 22 with the sealing materials 21a and 22a, respectively. The

  The partition wall 34 is a layer formed on the substrate surface 13 d of the second substrate 13. The partition wall portion 34 has a plurality of concave portions 34a and convex portions 34b on the substrate surface 13d. Here, the recess 34a refers to a portion having a thickness smaller than the average thickness of the partition wall 34 in the direction perpendicular to the substrate surface 13d. Moreover, the convex part 34b means a part whose thickness is thinner than the average thickness of the partition part 34 in the direction perpendicular to the substrate surface 13d. The movement of the charged particles 31a and 31b in the direction parallel to the substrate surfaces 12d and 13d is suppressed by the concave portions 34a and the convex portions 34b. Therefore, even if the electrophoretic display medium 10 is placed for a long time with the substrate surfaces 12d and 13d inclined with respect to the horizontal direction, a large displacement in the direction parallel to the substrate surface of the charged particles 31a and 31b is suppressed. The As a result, the deterioration of display quality over time due to the non-uniform density of the charged particles 31a and 31b is suppressed, and good display quality is ensured over a long period of time.

  Next, an example of a method for producing the electrophoretic display medium 10 of the present invention will be described with reference to FIGS. In the electrophoretic display medium 10 of the above-described embodiment, the first substrate 12 and the second substrate 13 are prepared (substrate preparation process, see FIG. 2A), and the first substrate 12 and the second substrate 13 are connected. In the meantime, a display liquid 33 in which wax (corresponding to the claimed organic polymer and wax) is dissolved is injected and sealed (injection process, see FIGS. 2B and 2C), and the display liquid 33 is sealed. It is manufactured by precipitating the wax dissolved in the solution and crystallizing the wax (crystallization step, see FIG. 3). Each step will be described in detail with reference to FIGS.

  FIG. 2A is a diagram illustrating an example of the substrate preparation process. As shown in FIG. 2A, in the substrate preparation step, the first substrate 12 and the second substrate 13 bonded to each other with an adhesive such as an epoxy resin are prepared with the frame member 17 interposed.

  Next, the implantation process will be described with reference to FIGS. 2 (b) and 2 (c). 2B and 2C are diagrams for explaining an example of the implantation process. In the injection step, first, as shown in FIG. 2B, the injection device 36 is attached to the injection port 21, and the discharge device 38 is attached to the discharge port 22. Then, the display liquid 33 is injected from the injection port 21 while discharging the air in the liquid chamber R from the discharge port 22. At this time, the charged particles 31a and 31b are dispersed and the wax is dissolved in the display liquid 33 injected between the first substrate 12 and the second substrate.

  Here, the wax dissolved in the display liquid 33 is a substance that becomes a liquid having a relatively low viscosity when heated in a solid state at room temperature, and in particular, a predetermined temperature higher than the use environment temperature of the electrophoretic display medium 10 (claimed). (Equivalent to the second condition of the term), for example, a liquid that becomes liquid at 65 ° C. or higher, and that becomes a solid at the use environment temperature (equivalent to the first condition of the claim) is preferably used. Specifically, for example, natural wax (paraffin wax, microcrystalline wax, carnauba wax, candelilla wax, etc.), synthetic wax (polyethylene wax, Fischer-Tropsch wax, fatty acid ester wax that is solid at room temperature, fatty acid amide, ketone Amines, hydrogenated oils, etc.) are preferably used. The use environment temperature is a temperature in a range that is assumed in advance as an environment temperature in which the electrophoretic display medium 10 is used, and is, for example, −20 ° C. to 50 ° C.

  In order to adjust the display liquid 33 in which the wax is dissolved, first, the display liquid 33 in which the wax is easily dissolved is obtained by adding the wax into the display liquid 33 heated to the melting point of the wax or more and stirring sufficiently. Can be adjusted.

  In the electrophoretic display medium 10 of this embodiment, isoparaffin as the electrophoretic medium 30, specifically 70% by weight of Pearl Ream 4 (manufactured by NOF Corporation), paraffin as wax, specifically paraffin 150 A raw material composed of 10% by weight (manufactured by Nippon Seiki Co., Ltd.), 10% by weight of white charged particles 31a, and 10% by weight of black charged particles 31b was heated to 75 ° C. in a disperse mat ( The display liquid 33 is adjusted by mixing at 5000 rpm for 30 minutes using Eihiro Seiki Co., Ltd., and it will be described as being manufactured using the adjusted display liquid 33.

  In the injection process, the display liquid 33 adjusted as described above is maintained at a temperature equal to or higher than the melting point of the wax by a heater (not shown) and is also equal to or higher than the melting point of the wax by a heater (not shown). It is injected by the injection device 36 between the first substrate 12 and the second substrate 13 which are kept at a temperature.

  Then, as shown in FIG. 2C, after the display liquid 33 is injected between the first substrate 12 and the second substrate 13, the injection port 21 and the discharge port 22 are sealed with the sealing materials 21a and 21b. To do. Thereby, the display liquid 33 in which the wax is dissolved can be sealed between the first substrate 12 and the second substrate 13.

  Next, the crystallization process will be described with reference to FIG. 3A and 3B are diagrams for explaining an example of the crystallization process. According to the liquid crystallizing step, the partition wall made of the crystallized wax is formed by depositing wax from the display liquid 33 injected between the first substrate 12 and the second substrate 13 and crystallizing the wax. The portion 34 can be formed on the substrate surface 13 a of the second substrate 13.

  As shown in FIG. 3A, in order to deposit wax from the display liquid 33 and crystallize the wax in the crystallization step, the second substrate 13 is arranged on the upper side in the vertical direction, and the first substrate 12 is Arranged vertically below. Then, by placing the first substrate 12 side on the heater 40 such as a hot plate, the first substrate 12 side is set to a temperature higher than the use environment of the electrophoresis medium and higher than the melting point of the wax, for example, 70 ° C. While keeping or heating, the second substrate 13 side is kept at a temperature below the melting point of the wax, for example, 60 ° C. Then, as shown in FIG. 3B, the wax is deposited on the substrate surface 13d from the second substrate 13 side, and the partition wall portion 34 formed of a layered body of wax crystals is formed on the substrate surface 13d of the second substrate 13. It is formed.

  As described above, in the liquid crystallizing step, the substrate surface 13d on which the partition wall portion 34 is to be formed is disposed vertically upward, so that the charged particles 31a and 31b are caused by gravity during the crystallization step, due to gravity. Settle to the side. Therefore, mixing of the charged particles 31a and 31b into the partition wall portion 34 is suppressed as much as possible. As a result, display quality deterioration due to a shortage of charged particles 31a and 31b capable of migrating in the display liquid is suppressed.

  FIG. 4 is a diagram schematically showing an enlarged region corresponding to the region F shown in FIG. As shown in FIG. 4, the wax that is precipitated and crystallized from the display liquid 33 constitutes a layered crystal. Accordingly, the partition wall portion 34 having a plurality of concave portions 34 a and convex portions 34 b due to the layered crystal structure is formed on the substrate surface 13 d of the second substrate 13.

  According to the manufacturing method of the present embodiment, the wax for forming the partition wall 34 is dissolved in the display liquid 33 in the injection step (see FIGS. 2B and 2C). Therefore, the retention of bubbles due to the partition wall 34 hindering the flow of the display liquid 33 is suppressed, so that the electrophoretic display medium 10 with good display quality can be manufactured. Furthermore, since the partition wall 34 having a plurality of concave portions 34a and convex portions 34b is formed by crystallizing the wax in the crystallization step (see FIG. 3), the electrophoretic display medium 10 is easily manufactured. be able to.

  In general, in electrophoretic display media, if the viscosity of the display liquid changes, the response of charged particles when an electric field is applied changes, causing variations in display quality. It is desirable to suppress as much as possible. In the electrophoretic display medium 10 manufactured according to the above manufacturing method, the wax dissolved in the display liquid 33 in the injection process (see FIGS. 2B and 2C) is converted into the liquid crystal forming process (see FIG. 3). Not all is deposited, and some remains in the display liquid 33 after the liquid crystal formation step. As a result, the viscosity variation of the display liquid 33 due to the temperature change due to the wax remaining in the dissolved state is suppressed, so that the electrophoretic display medium 10 can be manufactured with little variation in display quality due to the environmental change. That is, the display liquid 33 in which the wax is dissolved has a smaller variation in viscosity due to a temperature change than the display liquid 33 in which the wax is not dissolved. In other words, the display liquid 33 in which the wax is dissolved has a smaller increase in viscosity of the display liquid 33 due to the precipitation of wax as a high viscosity component when the temperature is lower than the display liquid 33 in which the wax is not dissolved. On the other hand, when the temperature rises, the viscosity of the display liquid 33 is small because the high-viscosity component wax is dissolved. Since the amount of the wax to be re-dissolved is small, there is no problem in the performance of the partition wall portion 34, and it is preferentially deposited on the partition wall portion at the time of deposition, so there is no influence on the display.

  In addition, according to the electrophoretic display medium 10 manufactured according to the above manufacturing method, the partition wall portion 34 is formed of a crystal and a laminated body of crystals, and therefore the shape and arrangement of the concave portion 34a and the convex portion 34b are not uniform. It will be a thing. Therefore, the height difference L between the adjacent concave portion 34a and the convex portion 34b of the partition wall 34, the interval W between the adjacent convex portions 34b, and the height T of the convex portion 34b are not constant. Here, the height of the concave portion 34a is a value corresponding to the shortest distance between the surface of each concave portion 34a and the substrate surface 13d, and the height T of the convex portion 34b is the first of the convex portions 34b. This is a value corresponding to the distance between the point close to the substrate 12 side and the substrate surface 13d.

  Further, as shown in FIG. 4, according to the electrophoretic display medium 10 manufactured according to the above manufacturing method, the convex portion 34b formed by the partition wall portion 34 and the substrate surface of the first substrate 12 facing the partition wall portion. The distance t between the particles 12b was smaller than the diameter w of the charged particles 31a and 31b. Therefore, the partition wall 34 can surely suppress the movement of the charged particles 31a and 31b in the direction parallel to the substrate surfaces 12b and 13b, and the display quality can be further prevented from deteriorating. In addition, the description in the claims and the specification “The convex portion formed by the partition wall portion is such that the distance between the substrate surface of the first substrate or the second substrate facing the partition wall portion is larger than the diameter of the charged particles. The term “small” means that the distance between the convex portions 34b formed by the partition walls 34 and the substrate surfaces 12d and 13d of the first substrate 12 or the second substrate 13 facing the partition walls 34 is the charged particles 31a, The first substrate 12 or the second substrate 13 is not limited to the meaning that it is smaller than the average particle diameter of 31 b, and a large number (for example, 50% or more) of the convex portions 34 b formed by the partition walls 34 are opposed to the partition walls 34. This also includes the meaning that the distance between the substrate surfaces 12d and 13d is smaller than the average particle diameter of the charged particles 31a and 31b.

  Further, as shown in FIG. 4, according to the electrophoretic display medium 10 manufactured according to the above manufacturing method, the height difference L between the adjacent convex portion 34b and the concave portion 34a is the diameter of the charged particles 31a and 31b. What was twice or more larger than w was obtained. Therefore, when the two colors of the white charged particles 31a and the black charged particles 31b are dispersed, the charged particles 31a and 31b are arranged in layers for each color by applying a voltage to the electrodes 12b and 13b. be able to. Therefore, since the display using the charged particles 31a and 31b of two colors can be performed, an image with high contrast can be displayed. In addition, the description in the claims and the specification “the partition wall portion has a height difference of two or more times larger than the diameter of the charged particle between the adjacent convex portion and the concave portion” means that the adjacent convex portion in the partition wall portion. The difference in height is not limited to two or more times larger than the diameter w of the charged particles in all of the portions and the recesses, but in the majority (for example, 70% or more) of the adjacent protrusions and recesses in the partition wall portion. In addition, it means that the difference in height is more than twice as large as the diameter w of the charged particles.

  FIG. 5 is a cross-sectional view of the electrophoretic display medium 10 taken along line VV in FIG. In FIG. 5, the pixel P (corresponding to a region where the X electrode 12 b and the Y electrode 13 b intersect) is indicated by a broken line for easy understanding of the drawing. As described above, since the partition wall portion 34 is composed of the precipitated wax, as shown in FIG. 5, when viewed from a direction perpendicular to the substrate surface 13d (perpendicular to the paper surface in FIG. 5), adjacent convex portions. 34b is not parallel but is arranged arbitrarily (non-uniformly).

  In addition, according to the electrophoretic display medium 10 manufactured according to the above manufacturing method, a plurality of protrusions 34b of the partition wall 34 arranged in one pixel P was obtained. In the claims and the specification, “a plurality of protrusions are arranged in one pixel” means that the number of protrusions included in the partition wall 34 is the number of pixels in the entire electrophoretic display medium 10. This means that the value divided by is 2 or more.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be easily made without departing from the spirit of the present invention. Can be inferred.

  An example of a modification of the present invention will be described with reference to FIG. FIG. 6 is a sectional view showing an electrophoretic display medium 10 according to a modification, and corresponds to FIG. In addition, in the electrophoretic display medium 10 of the modification shown in FIG. 6, the same code | symbol is attached | subjected about the part same as the electrophoretic display medium 10 of an Example, and description is abbreviate | omitted.

  As shown in FIG. 6, according to the electrophoretic display medium 10 of the modified example, the first substrate side protrusion 34 c having a height lower than the distance between the substrate surfaces 12 d and 13 d is formed on the substrate surface 12 d of the first substrate 12. Is provided. The first substrate side 34c is provided in advance on the substrate surface 12d of the substrate 12 prepared in the substrate preparation step (see FIG. 2A).

  In this way, the region filled with the display liquid 34 is formed by the first substrate-side protrusion 34c provided on the substrate surface 12d and the concave portion 34a and the convex portion 34b formed by the partition wall portion 34 on the substrate surface 13d. Since it is partitioned, the effect of suppressing the sedimentation and aggregation of the charged particles 31a and 31b by the concave portion 34a and the convex portion 34b is further enhanced, and the electrophoretic display medium 10 with good display quality can be obtained. Even if the difference between the concave portion 34a and the convex portion 34b formed in the partition wall portion 34 cannot be sufficiently ensured depending on the type of wax or the like, the charged particles 31a can be combined with the first substrate side one protrusion 34c. , 31b can be sufficiently suppressed from being greatly displaced in a direction parallel to the substrate surface. In this case, the convex portion 34b is a portion having a thickness larger than ½ of the distance of the surface where the first substrate side protrusion 34c and the second substrate 13 face each other, and the concave portion 34a has the same distance. This is a portion having a thickness smaller than 1/2.

  Further, since the height of the first substrate-side protrusion 34c is configured to be smaller than the distance between the substrate surfaces 12d and 13d, the display liquid 33 is applied between the first substrate 12 and the second substrate 13. When injecting, it is possible to suppress the first substrate side protrusion 34 c from inhibiting the inflow of the display liquid 33. Accordingly, it is possible to manufacture the electrophoretic display medium 10 that suppresses the retention of bubbles during the injection of the display liquid 33 and has good display quality.

  Next, another modification of the present invention will be described with reference to FIG. FIG. 7A is a diagram showing another example of the substrate preparation process, which corresponds to FIG. 2A, and FIG. 7B is the substrate preparation process shown in FIG. It is sectional drawing which shows the electrophoretic display medium 10 manufactured using the board | substrate prepared by 1 and is a figure corresponded to Fig.1 (a). In FIG. 7, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 7A, in the substrate preparation process of the modified example, the height of the substrate 12 and 13 on the substrate surface 13d on the second substrate 13 side is lower than the distance between the substrate surfaces 12d and 13d. The substrates 12 and 13 provided with the second substrate side protrusion 34d in advance are prepared.

  Then, the display liquid 33 is injected between the substrates 12 and 13 prepared in the substrate preparation step shown in FIG. 7A, and wax is precipitated from the injected display liquid 33 to form the partition wall 34. The electrophoretic display medium 10 is manufactured.

  As shown in FIG. 7B, according to the electrophoretic display medium 10 manufactured as described above, the wax is deposited on the surface of the second substrate side protrusion 34d provided on the substrate surface 13d. As a result, the height difference between the concave portion 34a and the convex portion 34b of the partition wall 34 is increased. Accordingly, the electrophoretic display medium 10 having a sufficient effect of suppressing the sedimentation and aggregation of the charged particles 31a and 31b by the concave portions 34a and the convex portions 34b can be obtained. In addition, when the display liquid 33 is injected between the first substrate 12 and the second substrate 13 by configuring the height of the second substrate side protrusion 34d to be low, the second substrate side protrusion 34d is displayed on the display liquid 33. Inhibiting the inflow of can be suppressed. Accordingly, it is possible to manufacture the electrophoretic display medium 10 that suppresses the retention of bubbles during the injection of the display liquid 33 and has good display quality.

  In the above embodiment, the X electrode 12a and the Y electrode 13a are provided on the opposing surfaces of the first substrate 12 and the second substrate 13, but the X electrode 12a and the Y electrode 13a are provided on the electrophoretic display medium 10. You may comprise so that the Y electrode 13a may not be provided. In this case, a device provided with a pair of electrodes corresponding to the X electrode 12a and the Y electrode 13a is prepared, and an electrophoretic display in which the X electrode 12a and the Y electrode 13A are not provided by the pair of electrodes provided in the device. What is necessary is just to comprise so that an image may be displayed by inserting | pinching the medium 10. FIG.

  Moreover, in the said Example, although only the spacer 17 was interposed between the 1st board | substrate 12 and the 2nd board | substrate 13, the 1st board | substrate 12 and the 2nd board | substrate prepared in a board | substrate preparation process. 13 to which a particulate spacer is added. By adding the particulate spacer, the bending of the substrates 12 and 13 is suppressed, and the distance between the substrates 12 and 13 can be maintained in the entire display region D.

  Therefore, even when a force is applied to the surface of the first substrate 12 or the second substrate 13, it is possible to reliably prevent the surface from being bent excessively, so that the first substrate 12 or the second substrate 13 is It can be surely prevented from being damaged. In particular, when the first substrate 12 and the second substrate 13 are flexible, it is possible to reliably prevent the first substrate 12 and the second substrate 13 from contacting each other due to the bending of the substrate. Display quality deterioration and electrophoretic display medium damage can be reliably prevented.

  Moreover, in the said Example, although the partition part 34 was comprised so that it might provide in the 2nd board | substrate 13 side, you may comprise so that it may provide in the 1st board | substrate 12 side. In such a configuration, the second substrate 13 forms a display surface. This is because a substrate without the partition wall 34 has higher light transmittance than a substrate with the partition wall 34, and can display a high-quality image.

  Moreover, in the said Example, although the injection port 21 and the discharge port 22 were provided so that the 1st board | substrate 12 might be penetrated, the injection port 21 and the discharge port 22 connect the liquid chamber R and the exterior. For example, it may be provided so as to penetrate the spacer 17 or the second substrate 13.

  Moreover, when the use environment temperature of the display apparatus 10 exceeds 60 degreeC, for example, what is necessary is just to use the wax whose melting | fusing point is higher than the use environment temperature.

(A) is a top view of the electrophoretic display medium, and (b) is a cross-sectional view schematically showing a cross section in the Ib-Ib line direction in (a). (A) is a figure explaining an example of a board | substrate preparation process, (b), (c) is a figure explaining an example of an injection | pouring process. (A), (b) is a figure explaining an example of a crystallization process. It is a figure which expands and shows typically the area | region corresponded to the area | region F shown in FIG.3 (b). It is sectional drawing of the electrophoretic display medium in the VV line | wire of FIG. It is sectional drawing which shows the electrophoretic display medium of a modification. (A) is a figure which shows another example of a board | substrate preparation process, (b) is sectional drawing which shows the electrophoretic display medium manufactured using the board | substrate prepared by the board | substrate preparation process shown to (a). It is.

Explanation of symbols

10 Electrophoretic display medium 12 First substrate 12d Substrate surface 13 Second substrate 13d Substrate surface 17 Frame member 31a White charged particles (charged particles)
31b Black charged particles (charged particles)
33 Display liquid 34 Partition part 34a Concave part 34b Convex part 34c First substrate side protrusion (protrusion)
34d First substrate side protrusion (protrusion)
D Display area (display surface)
t Distance between the substrate surface of the first substrate or the second substrate facing the partition wall portion w Diameter of the charged particle T Height of the convex portion P Pixel L Difference in height between adjacent convex portions and concave portions W Adjacent Spacing between protrusions

Claims (14)

A pair of first and second substrates having opposite substrate surfaces, a frame member that maintains a predetermined distance between the substrate surfaces of the first substrate and the second substrate, the first substrate, and the second substrate And a display liquid in which charged particles that move according to the direction of the electric field are dispersed, and a display surface configured by at least one of the first substrate and the second substrate, In an electrophoretic display medium that displays characters and images by migration of the charged particles,
In a second condition different from the predetermined first condition, a plurality of concave portions and convex portions are formed on at least one of the first substrate and the second substrate in the predetermined first condition. An electrophoretic display medium, comprising a partition wall composed of an organic polymer dissolved in the display liquid.   The convex portion formed by the partition wall has a distance between the substrate surface of the first substrate or the second substrate facing the partition wall smaller than the diameter of the charged particles, and the substrate surface 2. The electrophoretic display medium according to claim 1, wherein when the electrophoretic display medium is viewed from a direction perpendicular to the vertical direction, the convex portions of the adjacent partition walls are not parallel but arbitrarily arranged. .   The electrophoretic display medium according to claim 1, wherein the partition wall has a non-constant difference in height between the adjacent protrusions and the recesses.   The electrophoretic display medium according to claim 1, wherein the partition wall has a non-constant interval between the adjacent protrusions.   The electrophoretic display medium according to claim 1, wherein the partition wall has a non-constant height of the protrusion.   2. The electrophoretic display medium according to claim 1, wherein the partition wall has a height difference of at least twice as large as a diameter of the charged particles between the adjacent convex portion and the concave portion.   The electrophoretic display medium according to claim 1, wherein a plurality of protrusions of the partition wall are arranged in one pixel.   The electrophoretic display medium according to claim 1, wherein the organic polymer is a wax. A pair of first and second substrates having opposite substrate surfaces, a frame member that maintains a predetermined distance between the substrate surfaces of the first substrate and the second substrate, the first substrate, and the second substrate And a display liquid in which charged particles that move according to the direction of the electric field are dispersed, and a plurality of concave portions and convex portions on at least one of the first substrate and the second substrate. A method of manufacturing an electrophoretic display medium that displays characters and images on the display surface configured by at least one of the first substrate and the second substrate by migration of the charged particles In
A substrate preparing step of preparing the first substrate and the second substrate bonded to each other with the frame member interposed therebetween;
An injection step of injecting a display liquid in which the charged particles are dispersed and the organic polymer is dissolved between the first substrate and the second substrate prepared by the substrate preparation step;
The organic polymer is precipitated from the display liquid injected in the injection step, and the partition portion composed of the generated organic polymer crystal and crystal laminate is used as the first substrate or the second substrate. And a crystallization step of forming on at least one of the substrate surfaces. A method for manufacturing an electrophoretic display medium.   The organic polymer dissolved in the display liquid injected in the injection step is dissolved in the display liquid at a predetermined temperature higher than a use environment temperature of the electrophoretic display medium, and the electrophoretic display medium The crystallization step is performed by cooling the display liquid injected between the first substrate and the second substrate at the use environment temperature, thereby increasing the organic high temperature. 10. The method for producing an electrophoretic display medium according to claim 9, wherein the molecules are crystallized.   11. The method for manufacturing an electrophoretic display medium according to claim 10, wherein the organic polymer dissolved in the display liquid injected in the injection step is a wax.   12. The method for manufacturing an electrophoretic display medium according to claim 11, wherein the display liquid injected in the injection step is a paraffinic hydrocarbon solvent.   In the crystallization step, either the first substrate or the second substrate is arranged on the upper side in the vertical direction, and one substrate side arranged on the upper side is set to a lower temperature than the other substrate side. The method of manufacturing an electrophoretic display medium according to claim 9, wherein the organic polymer is crystallized on a substrate surface of the one substrate disposed on the upper side in a state. At least one of the first substrate and the second substrate has a plurality of protrusions having a height lower than the predetermined distance between the substrate surfaces,
The said board | substrate preparation process prepares the said 1st board | substrate and the said 2nd board | substrate which made the board | substrate surface in which the said protrusion was provided facing the board | substrate surface of the other board | substrate, The any one of Claim 9-13 characterized by the above-mentioned. A method for producing an electrophoretic display medium according to claim 1.

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