JP2007248932A - Electrophoretic display medium and manufacturing method thereof - Google Patents

Abstract

An electrophoretic display medium in which adverse effects of partition walls on display are reduced and a method for manufacturing the same are provided.
In a resist film forming step, a negative resist film including a base resin, a crosslinking initiator, and a light absorber is formed on the opposing surface of a first substrate. In the exposure step, the crosslinking initiator is subjected to a crosslinking reaction. The film is irradiated with light having a wavelength for starting the process. Since the light absorber absorbs the light as needed, a light transmission amount gradient is formed in the negative resist film 26, and the activity of initiating the crosslinking reaction of the crosslinking initiator existing on the first substrate 18 side away from the light source is active. Since it becomes smaller, the base resin is cured so that the width becomes narrower toward the first substrate 18 side. Accordingly, the partition obtained after the development process has a larger area on the surface facing the second substrate of the partition than the area of the contact surface where the facing surface of the first substrate 18 and the partition contact each other, which affects the display. The adverse effect of the partition can be reduced.
[Selection] Figure 12

Description

  The present invention relates to an electrophoretic display medium and a method for manufacturing the same, and more particularly to an electrophoretic display medium in which a dispersion medium containing charged particles is enclosed in a plurality of cells partitioned by partition walls, and a method for manufacturing the same. is there.

  Conventionally, an electrophoretic display medium is known as a medium for displaying an image. This electrophoretic display medium has a configuration in which a dispersion medium containing charged particles is filled between a pair of substrates including a first substrate that is a transparent or translucent display surface and a second substrate that is paired with the first substrate. Have. When this charged particle has a color different from that of the dispersion medium, the color of the charged particle is observed when the charged particle moves to the display substrate side due to voltage application, and the charged particle moves to the second substrate side. Sometimes the color of the dispersion medium is observed.

  When the charged particles are migrated using the entire electrophoretic display medium as one cell, the charged particles cannot be uniformly moved due to aggregation or lateral movement of the charged particles, resulting in display unevenness. Therefore, in general, partition walls are formed on a substrate to divide the space between the substrates into a plurality of cells, and charged particles are enclosed in these cells to limit particle aggregation and lateral movement.

Since this partition wall is provided so as to reduce display unevenness, it is preferable that the partition wall has a narrow shape so as not to affect display performance. If the height of the partition wall is lowered, the width of the partition wall can be easily narrowed. However, when the partition wall is lowered, the charged particles that have moved to the second substrate through the dispersion medium are visually recognized, and the display contrast is lowered. A new problem occurs. For this reason, it is considered preferable that the partition walls have a sufficient height to ensure display contrast and have a narrow width that does not affect display performance. In view of this, for example, there has been proposed a structure in which a partition wall having a width narrowing toward the display substrate is provided on the surface of the second substrate (see Patent Document 1).
JP 2004-20640 A

  However, in the electrophoretic display medium described in Patent Document 1, in the electrophoretic display medium in which a driving electrode such as a thin film transistor (TFT, Thin Film Transistor) is provided in each cell partitioned by the partition walls, the driving electrode is provided in the first. Since the surfaces of the two substrates are not flat, it is difficult to accurately provide fine partition walls on the surface of the second substrate. In addition, driving electrodes such as thin film transistors are vulnerable to heat treatment, and the manufacturing method for forming the partition wall is limited by the heat resistance of the driving electrodes.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrophoretic display medium in which the adverse effects of partition walls on the display are reduced, and a method for manufacturing the same.

  In order to solve the above problems, an electrophoretic display medium according to a first aspect of the present invention includes a first substrate having a display surface for displaying an image formed in units of pixels, and a drive electrode having at least a portion corresponding to the pixels. A plurality of second substrates provided opposite to the first substrate; and a first substrate and the second substrate, wherein the first substrate and the second substrate are erected on a facing surface that is a surface facing the second substrate of the first substrate. In an electrophoretic display medium comprising a partition wall that divides a space between a plurality of cells and a charged particle that is contained in the cell and moves by the action of an electric field, the partition wall is a base that cures by a crosslinking reaction. A resin, a crosslinking initiator that initiates crosslinking of the base resin when irradiated with light, and a light absorber that absorbs light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator. It is made of a resist material of a mold, and the area of the surface of the partition facing the second substrate is larger than the area of the contact surface where the facing surface of the first substrate contacts the partition Features. In addition, the 1st board | substrate which concerns on this invention is not only the board | substrate which comprises a 1st board | substrate, but when the said board | substrate is provided with various films | membranes, such as a protective film for protecting a common electrode and a common electrode, these In addition, various films such as a common electrode and a protective film are included. The light in the present invention is intended to include not only electromagnetic waves having a wavelength in the range of about 1 nm to 1 mm but also electron beams.

  According to a second aspect of the present invention, in addition to the structure of the first aspect of the invention, the cross-linking initiator starts the cross-linking of the base resin by being irradiated with ultraviolet rays, and the light The absorber is characterized by comprising an ultraviolet absorber.

  Further, in the electrophoretic display medium of the invention according to claim 3, in addition to the configuration of the invention of claim 2, the light absorber is an azomethyl compound, diphenyl sulfoxide compound, diphenyl sulfone compound, benzotriazole It consists of a compound and at least 1 sort (s) of compound chosen from the benzophenone series compound, It is characterized by the above-mentioned.

  According to a fourth aspect of the present invention, in addition to the structure of the second aspect, the base resin is an epoxy resin, and the light absorber is 4-benzyloxy-2-hydroxy. It is at least one compound selected from benzophenone and 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole.

  An electrophoretic display medium according to a fifth aspect of the invention is the electrophoretic display medium according to any one of the first to fourth aspects, wherein the opposed surface of the first substrate is the opposed surface of the first substrate. An adhesion improver film that improves the hydrophobicity of the first substrate and improves the adhesion between the first substrate and the partition.

  According to a sixth aspect of the present invention, there is provided a method of manufacturing an electrophoretic display medium, comprising: a first substrate having a display surface for displaying an image formed in units of pixels; and a plurality of drive electrodes having at least portions corresponding to the pixels. A second substrate provided to face the first substrate, and an opposing surface that is a surface facing the second substrate of the first substrate, and the first substrate and the second substrate In a method for manufacturing an electrophoretic display medium comprising a partition wall that partitions a sandwiched space into a plurality of cells, and charged particles that are contained in the cells and move by the action of an electric field, a base resin that cures by a crosslinking reaction; A negative resist comprising at least a crosslinking initiator that initiates crosslinking of the base resin upon irradiation with light, and a light absorber that absorbs light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator. A resist film forming step for forming the film on the opposite surface of the first substrate, an exposure step for irradiating light to a position where the partition wall is to be formed on the resist formed in the resist film forming step, and the exposure And a developing step of developing the resist irradiated with light in the irradiation step.

  According to a seventh aspect of the present invention, there is provided a method for producing an electrophoretic display medium, wherein, in addition to the configuration of the sixth aspect of the invention, in the resist film forming step, the base resin is crosslinked by being irradiated with ultraviolet rays. A negative resist film containing a crosslinking initiator to be started and the light absorber made of an ultraviolet absorber is formed on the opposing surface of the first substrate.

  The method for producing an electrophoretic display medium according to an eighth aspect of the invention includes the azomethyl compound, the diphenyl sulfoxide compound, and the diphenyl sulfone compound in the resist film forming step in addition to the structure of the invention according to the seventh aspect. A negative resist film containing the light absorber composed of at least one compound selected from benzotriazole compounds and benzophenone compounds is formed on the facing surface of the first substrate.

  According to a ninth aspect of the present invention, there is provided a method for producing an electrophoretic display medium, wherein, in addition to the configuration of the seventh aspect of the invention, in the resist film forming step, the base resin made of an epoxy resin and 4-benzyl A negative resist film containing the light absorber comprising at least one compound selected from oxy-2-hydroxybenzophenone and 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole It forms on the said opposing surface of a 1st board | substrate, It is characterized by the above-mentioned.

  According to a tenth aspect of the present invention, there is provided a method for manufacturing an electrophoretic display medium, in addition to the structure according to any one of the sixth to ninth aspects, the first substrate may include the first substrate before the resist film forming step. An adhesion improver film forming step of forming an adhesion improver film on the opposing surface of the first substrate for improving the hydrophobicity of the opposing surface and improving the adhesion between the first substrate and the partition; Features.

  An electrophoretic display medium manufacturing method according to an eleventh aspect of the invention includes the exposure irradiation between the exposure step and the development step, in addition to the configuration of the invention according to any one of the sixth to tenth aspects. It has the post-exposure heating process of heat-treating the resist irradiated with light in the process.

  According to the electrophoretic display medium of the first aspect of the present invention, the area of the surface of the partition facing the second substrate is larger than the area of the contact surface where the facing surface of the first substrate contacts the partition. Since it is configured to be large, display is performed while securing the partition wall width necessary for stably forming the partition wall having a sufficient height to ensure display contrast in the second substrate side portion. It is possible to reduce the adverse effect of the partition walls on the surface.

  According to the electrophoretic display medium of the invention according to claim 2, in addition to the effect of the invention of claim 1, the second partition wall is larger than the area of the contact surface where the opposing surface of the first substrate contacts the partition wall. Since the area of the surface facing the substrate is configured to be larger, the width of the partition required to stably form a partition having a sufficient height to ensure display contrast is set. It is possible to reduce the adverse effect of the partition wall on the display while securing the portion on the second substrate side.

  According to the electrophoretic display medium of the invention of claim 3, in addition to the effect of the invention of claim 2, an azomethyl compound or diphenyl sulfoxide compound having relatively little color such as white, slightly yellowish white, and yellow Since the light absorber consisting of at least one selected from a compound, a diphenylsulfone compound, a benzotriazole compound and a benzophenone compound is used, the influence of the addition of the light absorber on the display performance is suppressed. .

  According to the electrophoretic display medium of the invention of claim 4, in addition to the effect of the invention of claim 2, 4-benzyloxy-2-hydroxybenzophenone and 2- (2), which are less colored, are used as a light absorber. Since at least one compound selected from 2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole is used, the influence of the addition of the light absorber on the display performance is suppressed.

  According to the electrophoretic display medium of the invention according to claim 5, in addition to the effect of the invention according to any of claims 1 to 4, the opposing surface of the first substrate is provided with a first substrate and a partition wall. Since the adhesion improver film for improving the adhesion is formed, the partition wall is difficult to peel from the first substrate. For this reason, it is possible to prevent a decrease in display performance due to the separation of the partition walls from the first substrate.

  According to the method for producing an electrophoretic display medium of the invention according to claim 6, as a negative resist constituting the partition, the base resin cured by a crosslinking reaction and the crosslinking of the base resin by irradiation with light are performed. A negative resist containing at least a crosslinking initiator to be initiated and a light absorber that absorbs light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator is used. Among these, the light absorber that absorbs light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator absorbs light from the light source and controls the amount of light transmitted through the negative resist film. That is, in the exposure process, the light emitted from the light source is absorbed by the light absorber as needed. Therefore, in the negative resist film, the closer to the light source, the larger the amount of light transmission, and the first substrate of the negative resist film. On the side, a light transmission amount gradient is formed such that the light transmission amount decreases. For this reason, the crosslinking initiator present on the first substrate side reduces the amount of light irradiated and the activity for initiating the crosslinking reaction compared to the crosslinking initiator present on the light source side. The portion on one substrate side is harder to cure than the portion on the light source side of the negative resist film. Therefore, if the method for producing an electrophoretic display medium of the present invention is used, the partition using the negative resist film is formed so that the width becomes narrower toward the first substrate side. Can be reduced. Further, when adjusting the width of the partition wall, a light absorbent having a desired light absorption amount may be selected or the addition amount may be adjusted, and the width of the partition wall can be easily controlled.

  According to the method for producing an electrophoretic display medium of the invention of claim 7, in addition to the effect of the invention of claim 6, there is provided a crosslinking initiator for initiating crosslinking of the base resin by irradiation with ultraviolet rays. The activity can be efficiently controlled by the ultraviolet absorber.

  According to the method for producing an electrophoretic display medium of the invention of claim 8, in addition to the effect of the invention of claim 7, an azomethyl compound, diphenyl sulfoxide compound, diphenyl having a relatively large amount of ultraviolet absorption. A light absorber composed of at least one compound selected from sulfone compounds, benzotriazole compounds, and benzophenone compounds is used. Therefore, the amount of addition of the light absorbent necessary for controlling the width of the partition wall can be suppressed as compared with the case where a light absorbent having a small amount of ultraviolet absorption is used.

  According to the method for producing an electrophoretic display medium of the invention according to claim 9, in addition to the effect of the invention of claim 7, when an epoxy resin is used as the base resin, 4-benzyloxy-2- Hydroxybenzophenone is easy to mix well with epoxy resins. For this reason, 4-benzyloxy-2-hydroxybenzophenone tends to be uniformly distributed in the negative resist film, and a light transmission amount gradient can be uniformly formed in the negative resist film. Therefore, it is possible to stably manufacture the partition wall whose width decreases from the second substrate side toward the first substrate side. Further, 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole has a large amount of absorption of ultraviolet rays having a wavelength of about 365 nm. For this reason, when the wavelength of the light source in the exposure process is about 365 nm, the width of the partition wall is reduced by using 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole as a light absorber. It is possible to suppress the amount of light absorber added necessary for control.

  According to the method for manufacturing an electrophoretic display medium of the invention according to claim 10, in addition to the effect of the invention according to any one of claims 6 to 9, the opposing surface of the first substrate has a first substrate and Since the adhesion improver film for improving the adhesion to the partition walls is formed, an electrophoretic display medium in which the partition walls are difficult to peel from the first substrate can be manufactured.

  According to the method for producing an electrophoretic display medium of the invention according to claim 11, in addition to the effect of the invention according to claim 6, the post-exposure heating step allows the first substrate and the partition wall to be separated. Adhesion is further improved. Moreover, since the side surface of the negative resist film cured by exposure in the post-exposure heating step is smoothed, an electrophoretic display medium having partition walls with smooth side surfaces can be manufactured.

  Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, a first embodiment of an electrophoretic display medium 1 embodying an electrophoretic display medium according to the present invention will be described with reference to the drawings. The electrophoretic display medium 1 exemplified as the present embodiment is a small display panel that can be provided in a portable electronic device.

  First, the configuration of the electrophoretic display medium 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view showing the appearance of the electrophoretic display medium 1. FIG. 2 is an exploded perspective view showing the main part of the electrophoretic display medium 1, and FIG. 3 is an explanatory diagram for explaining the internal configuration of the main part of the electrophoretic display medium 1.

  As shown in FIGS. 1 to 3, the electrophoretic display medium 1 is held such that the first substrate 18 and the second substrate 12 face each other with a spacer 14 therebetween. On the facing surface that is the surface facing the substrate 12, a partition wall 13 is provided that partitions a space sandwiched between the first substrate 18 and the second substrate 12 into a plurality of cells. A dispersion liquid composed of the dispersion medium 16 and the plurality of charged particles 15 is sealed between the first substrate 18 and the second substrate 12.

  The first substrate 18 having a display surface is provided on the surface of the substrate 11, the common electrode 20 provided on the surface of the substrate 11 facing the second substrate 12, and the surface of the common electrode 20 facing the second substrate 12. It is comprised from the improver film | membrane 25 (refer FIG. 10).

  The board | substrate 11 is a board | substrate which has a display surface which displays the image formed in a pixel unit, for example, is formed with materials, such as transparent glass, a polyimide resin, a polypropylene resin, a polyethylene resin. On the other hand, since the second substrate 12 is not a substrate on the display surface side, it does not necessarily have to be transparent. In addition to a transparent material for forming the substrate 11, for example, a transparent material such as stainless steel or aluminum provided with an insulating layer on the surface. It may be formed using a non-material. In the explanatory view for explaining the internal configuration of the electrophoretic display medium 1 shown in FIG. 3, the case where the substrate 11 and the second substrate 12 are formed of a resin material such as a polyimide resin, a polypropylene resin, or a polyethylene resin is shown. However, it is not limited to this.

  The spacer 14 is formed in a rectangular shape so as to surround the lattice-shaped partition wall 13, holds the first substrate 18 and the second substrate 12 at a predetermined interval, and a dispersion medium 16 and charged particles 15 described later leak to the outside. It plays the role of sealing so that it does not come out. For example, an epoxy resin, an acrylic resin, or the like is used for the spacer 14. In FIG. 3, the spacer 14 is formed of a resin material, but the present invention is not limited to this, and various materials can be used.

  The common electrode 20 and the drive electrode 21 bear a polarity for applying an electric field to the electrophoretic display medium 1, and are preferably covered with a protective film (not shown) using a coating agent or the like having a fluorine compound. ing. The common electrode 20 provided on the first substrate 18 is composed of a light-transmitting conductive thin film such as indium tin oxide (ITO). On the other hand, the drive electrodes 21 arranged in a matrix on the surface of the second substrate facing the first substrate are not light transmissive in addition to a light transmissive conductive thin film such as indium tin oxide (ITO). You may be comprised with the thin film of the electrically-conductive material. A thin film transistor 22 (see FIG. 2) functioning as a switching element is provided at the periphery of the drive electrode 21 and a selection signal is applied to each row of the matrix from a drive circuit (not shown) that controls each drive electrode 21. Further, a control signal and an output from the thin film transistor 22 are applied to each column of the matrix, so that a desired electric field can be applied to the charged particles 15 and the dispersion medium 16 in each cell. The number of drive electrodes 21 corresponding to one pixel is not particularly limited. Moreover, there is no limitation in particular in the planar shape of the drive electrode 21, Arbitrary shapes, such as a square, a rectangle, and a circle, are applicable.

  The dispersion medium 16 is a solvent for dispersing the charged particles 15, and a liquid having high electrical resistance and high transparency is used. For example, aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as hexane and cyclohexane, insulating organic solvents such as polysiloxane and high-purity petroleum are used. In the electrophoretic display medium 1, each of the above dispersion media may be used alone or as a mixture of two or more. Furthermore, the dispersion medium 16 can contain other components as necessary. As other components, for example, a dispersant such as a surfactant used to assist dispersion of charged particles, a charge control agent such as alcohol used to adjust the electrophoretic properties of charged particles in the dispersion medium And viscosity modifiers such as polymer resins used for preventing sedimentation of charged particles in the dispersion medium.

  The charged particles 15 are particles that migrate to the first substrate or the second substrate side according to an electric field applied to each pixel and form a display image on the display surface. The charged particles 15 are, for example, known inorganic pigments such as titanium oxide and zinc oxide, organic pigments such as carbon black, azo pigments, and phthalocyanine pigments, suspension polymerization methods, dispersion polymerization methods, seed polymerization methods, and the like. Polymer particles made of a polymer material obtained by the method, or composite particles obtained by combining an inorganic material and a polymer material are used. Of course, polymer particles, composite particles, and the like may be colored in an arbitrary color with pigments or dyes. The charged particles 15 may be used alone or as a mixture of two or more kinds as described above.

  Here, the structure of the partition wall 13 which is an important component of the present invention will be described with reference to FIGS. As shown in FIG. 2, the partition wall 13 has a lattice shape in plan view, and divides a space between the first substrate 18 and the second substrate 12 into a plurality of cells. As shown in FIG. 3, the partition wall 13 has a trapezoidal shape when viewed from the front, and the side of the partition wall 13 facing the second substrate 12 rather than the area of the surface of the partition wall 13 facing the first substrate 18. The area of the surface of is larger. With such a configuration, it is possible to reduce the influence of the partition wall 13 on the display performance of the display surface while ensuring a sufficient height to ensure display contrast. Note that the partition wall 13 of the electrophoretic display medium 1 shown in FIG. 3 is erected on the first substrate 18 and is in contact with the second substrate 12. May not be in contact.

  The partition wall 13 is formed of a negative resist containing at least a base resin, a crosslinking initiator, and a light absorber.

  The base resin that constitutes the partition wall 13 is a material that is cured by a crosslinking reaction to form the partition wall. For example, an epoxy resin, an acrylic resin, or a polyvinyl phenol resin is used.

  The crosslinking initiator constituting the partition wall 13 is to start crosslinking of the base resin when irradiated with light. As the crosslinking initiator, various commercially available crosslinking initiators can be used. For example, melamine-based, urea-based, guanamine-based, onium salt-based, and alkylsulfonyl-based crosslinking initiators are used.

  The light absorber constituting the partition wall 13 is one that absorbs light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator, and preferably has a color that does not affect display performance. For example, when the light having a wavelength for initiating crosslinking of the base resin by the crosslinking initiator is ultraviolet light, an azomethyl compound, a diphenyl sulfoxide compound, a diphenyl sulfone compound, a benzotriazole compound, and Benzophenone compounds are used. These compounds may be used alone or in combination of two or more as the light absorber.

  As the azomethyl compound, for example, 3-hydroxy-N- (4-diethylaminobenzylidene) aniline, 2-hydroxy-N- (4-diethylaminobenzylidene) aniline and the like are used.

  Examples of the diphenyl sulfoxide compound include bis (2,3-dihydroxyphenyl) sulfoxide, bis (5-chloro-2,3-dihydroxyphenyl) sulfoxide, and the like.

  Examples of the diphenylsulfone compound include bis (2,4-dihydroxyphenyl) sulfone and bis (3,4-dihydroxyphenyl) sulfone.

  Examples of the benzotriazole compounds include 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3,4,5,6-tetrahydrophthalimidylmethyl) phenol, 2- ( 2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole and the like are used, and the wavelength is preferably 365 nm. 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3,4,5,6-tetrahydrophthalimidylmethyl) phenol, 2- (2 2-Hydroxy-5-tert-octylphenyl) -2H-benzotriazole is used, more preferably 2- (2-hydride with little color) Roxy-5-tert-octylphenyl) -2H-benzotriazole is used.

  Examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid trihydrate, 4-benzyloxy-2-hydroxybenzophenone, 2,2 ′, 4. , 4'-tetrahydroxybenzophenone, 2-hydroxy-4'-dimethylaminobenzophenone, 2,4-dihydroxy-4'-dimethylaminobenzophenone, 2,4-dihydroxy-4'-diethylaminobenzophenone, 4,4'-bis (Diethylamino) benzophenone, 4,4′-bis (dimethylamino) benzophenone, etc. are used, and 4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfone, preferably having a large amount of ultraviolet absorption at around 365 nm. acid· Hydrate, 4-benzyloxy-2-hydroxybenzophenone is used, or more preferably easy mix with epoxy resins, 4-benzyloxy-2-hydroxybenzophenone is used.

  Other examples of the ultraviolet absorber include perylene, phenothiazine, 2-amino-5-azotoluene, dimethylaminoazobenzene, methyl violet 2B, crystal violet, malachite green, Victoria Bull-B, phenyl salicylate, 4-tert. -Butylphenyl salicylate, ethyl-2-cyano-3,3-diphenyl acrylate, etc. are also used. These light absorbers may be used alone or in combination of two or more.

  The light absorber is selected in consideration of ease of mixing with the base resin, absorption of light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator, and the presence or absence of coloring. For example, when using a base resin and an epoxy resin and using a crosslinking initiator that initiates a reaction by irradiating ultraviolet rays, 4-benzyloxy-2-hydroxybenzophenone among the above compounds as a light absorber, 2- (2-Hydroxy-5-tert-octylphenyl) -2H-benzotriazole can be selected.

  On the facing surface of the partition wall 13 and the first substrate 18, an adhesion improver film 25 that improves the adhesion of the negative resist constituting the partition wall 13 by improving the hydrophobicity of the facing surface of the first substrate 18. (See FIG. 10) is preferably formed. This adhesion improver film 25 (see FIG. 10) plays a role of preventing separation of the partition wall 13 from the first substrate 18. For example, hexamethyldisilazane (HMDS) is used as the adhesion improver. In the first embodiment, the substrate 11, the common electrode 20, and the adhesion improver film 25 (see FIG. 10) constitute the first substrate 18 of the present invention, and the partition wall 13 is the first substrate of the present invention. 18 is provided upright on an adhesion improver film 25 (see FIG. 10) provided on the opposing surface.

  Next, the display switching operation in the electrophoretic display medium 1 will be described with reference to FIGS. FIG. 4 is an explanatory diagram for explaining a state in which black is displayed over the entire display area of the display surface of the first substrate 18, and FIG. 5 illustrates that white is displayed over the entire display area of the display surface of the first substrate 18. It is explanatory drawing explaining the state. In order to simplify the description, negatively charged black particles are used as the charged particles 15, and the dispersion medium 16 is colored white, and the second substrate 12 has a drive electrode 21 for each pixel. The case where it is arranged will be described.

  In FIG. 4, a voltage of 0 V is applied to the common electrode 20 included in the first substrate 18, 50 V is applied to all the drive electrodes 21 provided on the second substrate 12, and the charged particles 15 having a negative charge are It moves to one substrate 18 side. The black charged particles 15 are attached to the first substrate 18. Thus, black is displayed on the display surface of the first substrate 18.

  In addition, although the voltage was applied to the common electrode 20 and the drive electrode 21 in order to move the charged particles 15, even if this voltage is dropped and both voltages become 0 V, the charged particles 15 are applied to the second substrate 12. The attached state is maintained.

  In FIG. 5, a voltage of 0 V is applied to the common electrode 20, a voltage of −50 V is applied to the drive electrode 21, and the charged particles 15 having negative charges are moved to the second substrate 12 side. Then, black charged particles 15 are attached to the second substrate 12. Thus, since only the white dispersion medium 16 remains on the first substrate 18 side, white is displayed on the entire display surface of the first substrate 18. The voltage applied to each electrode can be variously changed according to the distance between the electrodes, the chargeability of charged particles, and the like.

  In the electrophoretic display medium 1 of the present invention described above, since the first substrate and the second substrate are partitioned into a plurality of cells by the partition walls, the region where the charged particles can migrate is limited within the cells. . Therefore, it is possible to prevent uneven dispersion of particles in the dispersion system and to prevent display unevenness. In the partition of the electrophoretic display medium of the present invention, the area of the surface of the partition facing the second substrate is larger than the area of the contact surface where the facing surface of the first substrate contacts the partition. ing. With such a configuration, it is possible to reduce the influence of the partition walls on the display performance of the display surface while ensuring a sufficient height.

  The light absorber is at least one selected from azomethyl compounds, diphenyl sulfoxide compounds, diphenyl sulfone compounds, benzotriazole compounds, and benzophenone compounds, such as white, slightly yellowish white, and yellow, which are relatively less colored. When a seed compound is used, it is possible to suppress the influence of the addition of the light absorber on the display performance. Similarly, at least one compound selected from 4-benzyloxy-2-hydroxybenzophenone and 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole, which are less colored, is used as a light absorber. When used, the influence of the addition of the light absorber on the display performance can be further suppressed.

  Further, when an adhesion improver film is provided between the partition walls and the first substrate, the partition walls are difficult to peel from the first substrate. For this reason, it is possible to prevent a decrease in display performance due to the separation of the partition walls from the first substrate.

  In addition, this invention is not limited to 1st embodiment explained in full detail above, A various change is possible. Although the first embodiment has been described as a small panel that can be provided in a portable electronic device, the size, application, and the like of the electrophoretic display medium can be variously selected and are not limited thereto.

  In the first embodiment, the common electrode 20 is provided on the opposing surface of the first substrate 18. However, the common electrode 20 may be provided on the display surface side of the substrate 11 or may be an electrode from the outside. Is supplied, the common electrode 20 may not be provided on the first substrate 18. Also in these cases, the partition wall 13 is erected on the surface of the substrate 11 facing the second substrate 12.

  In the first embodiment, the partition wall 13 has a lattice shape. However, the partition wall 13 is not limited thereto, and has various shapes for partitioning a space sandwiched between the first substrate and the second substrate. It can be adopted. For example, the shape of the partition wall may be partitioned into a rectangular shape, a circular shape, or an elliptical shape in plan view. In the first embodiment, the partition wall 13 is provided so as to form a cell corresponding to each drive electrode 21. However, the partition wall is provided so as to form a cell corresponding to a plurality of drive electrodes 21. Also good.

  Next, as a first embodiment, an outline of a method for manufacturing the electrophoretic display medium 1 according to the present invention will be described with reference to FIGS. FIG. 6 is an explanatory diagram showing an outline of the partition wall forming step for forming the partition wall 13 made of lattice-shaped convex portions on the first substrate 18, and FIG. 7 shows the formation of the spacer 14 on the peripheral edge portion of the first substrate 18. FIG. 8 is an explanatory view showing an outline of a spacer forming process, and FIG. 8 is an explanatory view showing an outline of a dispersion injecting process for injecting a dispersion into a cell composed of a plurality of recesses formed by grid-like partition walls 13. FIG. 9 is an explanatory diagram showing an outline of a second substrate bonding step in which the second substrate 12 having the drive electrode 21 is bonded to the first substrate 18.

  First, in the partition formation step shown in FIG. 6, the partition 13 made up of lattice-shaped convex portions is formed on the first substrate 18. Details of the partition wall forming process, which is an important manufacturing process of the present invention, will be described later. In the first embodiment shown in FIG. 6, a common electrode 20 made of a thin film of a conductive material such as ITO is provided on the facing surface of the first substrate 18. The thin film is formed using a known technique such as an inkjet method, a spray method, or a coating method. When the common electrode 20 is provided on the facing surface of the first substrate 18, the partition wall 13 is provided on the surface of the common electrode 20 facing the second substrate. The common electrode 20 may not be provided on the facing surface of the first substrate 18, and in this case, the partition wall 13 is provided on the facing surface of the substrate 11. FIG. 6 shows the case where a resin material such as the substrate 11 is used, but as described above, a transparent material such as glass can be used in addition to the resin material.

  Next, in the spacer forming step shown in FIG. 7, the spacer 14 is formed on the peripheral edge portion of the first substrate 18. The spacer 14 is formed using a known method such as a photolithography method. Although FIG. 7 shows the case where the spacer 14 having the same height as the partition wall 13 is formed, the height of the spacer 14 may be made higher than the height of the partition wall 13 without being limited to this. In this case, the partition wall 13 and the second substrate 12 do not come into contact with each other in the second substrate bonding step described later. Although FIG. 7 shows the case where a resin material such as the spacer 14 is used, as described above, a material other than the resin material may be used.

  Next, in the dispersion injecting step shown in FIG. 8, a dispersion composed of charged particles 15 and a dispersion medium 16 for dispersing the charged particles 15 is injected into a cell composed of a plurality of recesses formed by lattice-shaped partition walls. .

  Thereafter, in the second substrate bonding step shown in FIG. 9, the second substrate 12 is bonded to the first substrate 18. On the surface of the second substrate 12 facing the first substrate 18, a drive electrode 21, a thin film transistor 22 (see FIG. 2), and a drive circuit (not shown) for controlling each drive electrode 21 are provided in advance. It has been. These drive electrode 21, thin film transistor 22 (see FIG. 2), and drive circuit (not shown) for controlling each drive electrode 21 are formed by a known technique such as a photolithography method, for example. FIG. 9 shows a case where a resin material is used as the material of the second substrate 12. As described above, in addition to the resin material, for example, a transparent material such as glass, an opaque material is used. A material may be used, and for example, it may be formed using a non-transparent material such as stainless steel or aluminum having an insulating layer on the surface.

  Next, a partition formation process for forming the partition 13 on the first substrate 18 which is a characteristic part of the present invention shown in FIG. 6 will be described with reference to FIGS. FIG. 10 is an enlarged explanatory view of the first substrate 18 showing the outline of the adhesion improver film forming step of the present invention, and FIG. 11 is an explanatory view showing the outline of the resist film forming step of the present invention. FIG. 13 is an explanatory view showing the outline of the exposure process of the present invention, FIG. 13 is an explanatory view showing the outline of the post-exposure heating process of the present invention, and FIG. 14 is an explanatory view showing the outline of the developing process of the present invention. .

  In the first embodiment, as a negative resist material constituting the partition wall 13, by irradiating light with a wavelength of about 365 nm, SU-8 (made by Kayaku Microchem Co., Ltd.) which is an epoxy resin as a base resin. The case where 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole is used as the crosslinking initiator for initiating the crosslinking reaction of the base resin and cyclopentanone as the solvent will be described. In addition, the material used for 1st embodiment is not limited to these, The constituent material of the various electrophoretic display media 1 mentioned above is employable.

  First, in the adhesion improving agent film forming step shown in FIG. 10, the adhesion improving agent film 25 is formed on the opposing surface of the first substrate 18. This adhesion improver improves the adhesion between the first substrate 18 and the partition wall 13 by improving the hydrophobicity of the surface of the first substrate 18, and is, for example, a colorless and transparent liquid at room temperature. Hexamethyldisilazane (HMDS) is used. Since the first substrate 18 is a substrate on which the display surface of the electrophoretic display medium 1 is formed, the adhesion improver is preferably a colorless and transparent material that does not affect the display performance. As a method for forming the adhesion improver film, for example, in addition to a method of directly applying to the facing surface of the first substrate 18, the adhesion improving agent is gasified and sprayed on the facing surface of the first substrate 18. For example, a vapor deposition method for forming the adhesion improver film 25 is used. The adhesion improving agent film forming step is preferably performed before the resist film forming step in order to improve the adhesion between the first substrate 18 and the partition wall 13, but may be omitted.

  Subsequently, in the resist film forming step shown in FIG. 11, a negative resist film 26, which is a negative resist film made of a base resin, a crosslinking initiator, a light absorber, and a solvent for dissolving them, is first formed. It is applied on one substrate 18. As described above, in the first embodiment, the negative resist film 26 is formed by irradiating light having a wavelength of about 365 nm with SU-8 (made by Kayaku Microchem Co., Ltd.), which is an epoxy resin, as a base resin. A crosslinking initiator for initiating a crosslinking reaction of the base resin, 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole as a light absorber, and cyclopentanone as a solvent were used. The addition amount of the light absorber is determined in consideration of the desired partition wall width, the light absorption amount of the light absorber, the performance of the resist, and the like, and preferably 1 to 10% by weight.

  In the first embodiment, the negative resist film 26 made of the above material is applied onto the first substrate 18 by spin coating so that the thickness becomes 20 μm. The thickness of the negative resist film 26 is basically applied to a desired partition wall height. Depending on the type of resist, the film may be reduced in any one of the exposure process, the development process, the heat treatment after the development process, or in each process. In such a case, measure the film thickness of the negative resist film formed in the resist film forming step in advance and the film thickness after completion of the final process, and form a thick negative resist film in advance in consideration of the difference. To do. Since SU-8 (manufactured by Kayaku Microchem Co., Ltd.) used in the first embodiment has almost no film reduction, such adjustment is unnecessary. Preferably, after the resist film forming step, a soft baking process for heating the negative resist film 26 is performed to adjust the residual solvent amount. In the first embodiment, a soft baking process at 95 ° C. for 10 minutes was performed.

  Next, in the exposure step shown in FIG. 12, light is irradiated to the portion of the negative resist film 26 where the partition walls are to be formed. First, a mask 27 having a light shielding material printed on a transparent glass substrate was placed on the first substrate 18 in a state where the mask 27 was separated from the negative resist film 26 by a predetermined distance. The mask 27 is made of glass so that light is transmitted through a portion of the negative resist film 26 where the partition wall 13 is formed, and light is blocked at a portion of the negative resist film 26 where the partition wall 13 is not formed. A light shielding material is printed on the substrate. In the drawing, a mask 27 indicated by a line indicates a portion where a light shielding material is printed on a glass substrate. The negative resist film 26 was exposed through such a mask 27. In the first embodiment, a mercury lamp was used as a light source used for exposure, and two types of filters of UV-D35 and V42 manufactured by Asahi Techno Glass Co., Ltd. were used to extract light having a wavelength of 365 nm.

In the first embodiment, 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole used as a light absorber is a wavelength extracted from the light source by the two types of filters described above in the exposure step. A 365 nm light is absorbed, and a light transmission amount gradient is formed in the negative resist film 26 such that the closer to the light source, the larger the light transmission amount and the smaller the light transmission amount on the first substrate side of the negative resist film. . For this reason, the crosslinking initiator present on the first substrate side is less active than the crosslinking initiator present on the light source side, which reduces the amount of light with a wavelength of 365 nm to be irradiated and initiates the crosslinking reaction. The portion on the first substrate side of the resist film 26 is harder to cure than the portion on the light source side of the negative resist film. Therefore, as shown in FIG. 12, the latent image 17 formed by curing the base resin in the negative resist film 26 by crosslinking is formed so that the width becomes narrower toward the first substrate 18. The exposure amount at this time was 1000 mJ / cm ² . However, the exposure amount changes according to the fluctuation of the lamp illuminance. Note that the exposure amount in the exposure step is preferably determined by considering in advance the exposure amount with which a desired pattern size / shape can be obtained.

  Next, in the post-exposure heating step shown in FIG. 13, post-exposure heat treatment PEB (Post Exposure Bake) is performed on the negative resist film 26 in order to smooth the side surface of the portion hardened by the exposure. By this step, the solvent is evaporated, the latent image 17 becomes smooth, and the side surfaces of the partition walls obtained after development have the effect of being flat. In 1st embodiment, the process heated at 95 degreeC for 4 minute (s) was performed.

  Next, in the development step shown in FIG. 14, the negative resist film excluding the exposed portion in the exposure step is dissolved with a developer. In the first embodiment, dip development was performed for 6 minutes using propylene glycol monomethyl ether acetate (PGMEA) as a developer, and washing was performed with isopropyl alcohol (IPA) for 5 minutes. Finally, hard baking is performed to cure the partition wall 13 and further improve the adhesion to the first substrate 18. In 1st embodiment, the process heated at 150 degreeC for 30 minute (s) was performed.

  The above is the formation process of the partition wall 13 in the first embodiment. Through the above partition formation step, the partition wall width is 10 μm at the contact surface where the facing surface of the first substrate 18 and the partition wall contact, the partition wall 13 width at the surface facing the second substrate 12 is 20 μm, and the height of the partition wall 13. A partition wall of 20 μm was formed. The width of the partition wall at the contact surface where the facing surface of the first substrate and the partition wall contact, the width of the partition wall facing the second substrate, and the height of the partition wall are the negative resist formed in the resist film forming step. The thickness can be adjusted depending on the thickness of the film, the material used for the negative resist film, the mask used for the exposure process, the exposure amount in the exposure process, and the like.

  According to the first embodiment described above, when a partition is formed using a negative resist film to be applied, due to the light transmittance gradient in the negative resist film formed by the light absorber. Since the width is narrowed toward the first substrate side, an electrophoretic display medium in which the adverse effect of the partition walls on the display can be reduced can be manufactured. Further, when adjusting the width of the partition wall, a light absorbent having a desired light absorption amount may be selected or the addition amount may be adjusted, and the width of the partition wall can be easily controlled.

  Further, since azomethyl compounds, diphenyl sulfoxide compounds, diphenyl sulfone compounds, benzotriazole compounds, and benzophenone compounds have a large amount of ultraviolet absorption, at least one compound selected from these compounds is used as a light absorber. As described above, when used together with a crosslinking initiator that initiates crosslinking of the base resin by irradiating with ultraviolet rays, it is possible to suppress the addition amount of the light absorbent necessary for controlling the width of the partition wall. In addition, since these compounds have colors that have a relatively small influence on display performance such as white, light yellow, and yellow, when these are used as light absorbers, the addition of light absorbers is not possible. It is possible to manufacture an electrophoretic display medium in which the width of the partition wall is narrowed while suppressing the influence on the display performance.

  When an epoxy resin is used as the base resin, 4-benzyloxy-2-hydroxybenzophenone is easily mixed with the epoxy resin. For this reason, when 4-benzyloxy-2-hydroxybenzophenone is used as a light absorber, the light absorber is likely to be uniformly distributed in the negative resist film, so that uniform light transmission in the negative resist film is achieved. A quantity gradient can be formed. Therefore, it is possible to stably manufacture the partition wall having a shape whose width becomes narrower from the second substrate side toward the first substrate side.

  In addition, 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole has a large amount of absorption of ultraviolet rays in the vicinity of a wavelength of 365 nm. For this reason, in the exposure step, when ultraviolet light having a wavelength of around 365 nm is used, if 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole is used as a light absorber, absorption of ultraviolet light at a wavelength of around 365 nm is achieved. Compared with the case where the same amount of the compound having a small amount is used, the gradient of the light transmission amount in the negative resist film can be increased. Therefore, in the case of using a crosslinking initiator that initiates crosslinking of the base resin by irradiating with ultraviolet rays having a wavelength of around 365 nm, 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole absorbs light. By using it as an agent, the amount of light absorber added can be reduced. In the case of using at least one compound selected from 4-benzyloxy-2-hydroxybenzophenone and 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole, a light absorber It is possible to manufacture an electrophoretic display medium in which the width of the partition wall is narrowed while suppressing the influence of the addition of the above on display performance as much as possible.

  When a post-exposure heating step is performed between the exposure step and before the development step, the adhesion between the first substrate and the partition is further improved. In addition, since the side surface of the negative resist film cured by exposure in the post-exposure heating step is smoothed, an electrophoretic display medium having partition walls having flat side surfaces can be manufactured.

  Further, when an adhesion improver film is provided between the partition walls and the first substrate, the partition walls are difficult to peel from the first substrate. Therefore, it is possible to manufacture an electrophoretic display medium that prevents display performance from being deteriorated due to separation of the partition walls from the first substrate.

  In addition, the manufacturing method of the electrophoretic display medium in which the partition wall of the present invention is formed on the first substrate is not limited to the above-described first embodiment, and various modifications can be made without departing from the gist of the present invention. May be added.

  In the first embodiment, the height of the partition wall 13 is 20 μm. However, the height is not particularly limited to this, and various heights can be selected according to the size, application, display performance, etc. of the electrophoretic display medium. It can be adopted.

  In the first embodiment, the wavelength of the light source in the exposure step is 365 nm. However, the present invention is not limited to this, and light having a wavelength that causes the crosslinking initiator to initiate the crosslinking reaction of the base resin may be irradiated. Moreover, what is necessary is just to select what absorbs the wavelength of the light with which a crosslinking initiator starts the crosslinking reaction of a base resin as a light absorber.

  In the first embodiment, an epoxy resin is used as a base resin for the material of the negative resist film, and a crosslinking initiator that initiates a crosslinking reaction of the base resin by irradiating light with a wavelength of about 365 nm as a crosslinking initiator. However, the present invention is not limited to these, and the constituent materials of the various electrophoretic display media 1 described above can be used. For example, when an electron beam is used as the light for the exposure process, a polyvinylphenol-based or acrylic-based resin can be used as the base resin, and an onium salt-based or alkylsulfonyl-based crosslinking initiator can be used as the crosslinking initiator. Etc. can be used.

  In the first embodiment described above, the first substrate 18 and the second substrate 12 of the electrophoretic display medium 1 are electrodes for applying an electric field to the charged particles 15, and the first substrate 18 includes the common electrode 20. In the above description, the second substrate 12 is provided with the drive electrode 21. However, when the electrode is supplied from the outside, the first substrate 18 may not include the common electrode 20. The step of forming the common electrode 20 on the first substrate 18 can be omitted.

  In the first embodiment, the spacers 14 are formed only on the outer periphery of the first substrate 18 and the second substrate 12. However, the partition wall 13 is formed so that a part of the partition wall 13 is in contact with the second substrate 12. The spacer may also be used as a spacer for determining the distance between the first substrate 18 and the second substrate 12. In that case, since the spacer is formed in the partition forming step, the spacer forming step can be omitted.

  In the first embodiment, the post-exposure heating step is performed between the exposure step and the development step, but the post-exposure heating step can be omitted.

  Next, a second embodiment in which a film type negative resist is used will be described. The method of forming the partition using the film type negative resist is different between the manufacturing method of the first embodiment, the adhesion improving agent film forming step shown in FIG. 10, and the resist film forming step shown in FIG. Description of common steps is omitted, and steps different from the manufacturing method of the first embodiment will be described below with reference to FIGS. 10 and 11.

  First, in the adhesion improver film forming step shown in FIG. 10, a film type negative resist is obtained by processing a liquid negative resist into a film, and a commercially available negative resist usually has an adhesive. It is attached to the pasting surface. Therefore, when the adhesive is attached to the pasting surface, the first substrate 18 and the negative resist film 26 are made of the adhesive without performing the adhesion improving agent film forming step shown in FIG. It comes to adhere closely.

  Next, in the resist film forming step shown in FIG. 11, the film type negative resist is attached to the facing surface of the first substrate 18 using a laminator, and the negative resist film 26 is formed. At this time, a desired negative resist film can be obtained by adjusting the affixing pressure, roller temperature, and roller rotation speed. In the case of a film-like negative resist film, soft baking is not particularly necessary. Since other manufacturing processes are the same as those of the manufacturing method of the first embodiment, description thereof is omitted.

  According to the second embodiment described above, even when a film-type negative resist is used, the same effect as that of the first embodiment can be obtained.

1 is a perspective view showing an appearance of an electrophoretic display medium 1. FIG. 2 is an exploded perspective view showing the main part of the electrophoretic display medium 1. FIG. 2 is an explanatory diagram illustrating an internal configuration of a main part of the electrophoretic display medium 1. FIG. It is explanatory drawing explaining the state by which black was displayed on the whole display area of the display surface of the 1st board | substrate 18. FIG. 10 is an explanatory diagram illustrating a state in which white is displayed over the entire display area of the display surface of the first substrate 18. It is explanatory drawing showing the outline of the partition formation process which forms the partition 13 which consists of a grid | lattice-like convex part on the 1st board | substrate 18. FIG. FIG. 5 is an explanatory diagram illustrating an outline of a spacer forming process for forming a spacer 14 on the peripheral edge of the first substrate 18. It is explanatory drawing showing the outline of the dispersion liquid injection | pouring process which inject | pours the dispersion medium 16 in the cell which consists of several recessed part formed of the grid | lattice-like partition 13. FIG. 6 is an explanatory diagram illustrating an outline of a second substrate bonding step in which a second substrate 12 having a drive electrode 21 is bonded to the first substrate 18. It is explanatory drawing which expanded the 1st board | substrate 18 showing the outline of the adhesive improvement agent film formation process of this invention. It is explanatory drawing showing the outline of the resist film-forming process of this invention. It is explanatory drawing showing the outline of the exposure process of this invention. It is explanatory drawing showing the outline of the post-exposure heating process of this invention. It is explanatory drawing showing the outline of the image development process of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrophoretic display medium 11 Substrate 12 Second substrate 13 Partition 18 First substrate 20 Common electrode 21 Drive electrode 25 Adhesion improver film 26 Negative resist film

Claims (11)

A first substrate having a display surface for displaying an image formed in units of pixels; a plurality of drive electrodes having at least portions corresponding to the pixels; and a second substrate provided facing the first substrate; A partition that stands on a facing surface that is a surface facing the second substrate of the first substrate, partitions a space sandwiched between the first substrate and the second substrate into a plurality of cells, and is included in the cell. In an electrophoretic display medium comprising charged particles that move by the action of an electric field,
The partition wall includes a base resin that is cured by a crosslinking reaction, a crosslinking initiator that initiates crosslinking of the base resin when irradiated with light, and light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator. It consists of a negative resist material containing at least a light absorbing agent,
An electrophoretic display medium, wherein an area of a surface of the partition facing the second substrate is larger than an area of a contact surface where the facing surface of the first substrate contacts the partition. .   The electrophoretic display medium according to claim 1, wherein the cross-linking initiator starts cross-linking of the base resin when irradiated with ultraviolet light, and the light absorber is made of an ultraviolet light absorber.   The said light absorber consists of an at least 1 sort (s) of compound chosen from the azomethyl type compound, the diphenyl sulfoxide type compound, the diphenyl sulfone type compound, the benzotriazole type compound, and the benzophenone type compound. Electrophoretic display medium.   The base resin is an epoxy resin, and the light absorber is at least one selected from 4-benzyloxy-2-hydroxybenzophenone and 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole. The electrophoretic display medium according to claim 2, wherein the electrophoretic display medium is a seed compound.   The facing surface of the first substrate includes an adhesion improver film that improves the hydrophobicity of the facing surface of the first substrate and improves the adhesion between the first substrate and the partition wall. The electrophoretic display medium according to claim 1. A first substrate having a display surface for displaying an image formed in units of pixels; a plurality of drive electrodes having at least portions corresponding to the pixels; and a second substrate provided facing the first substrate; A partition that stands on a facing surface that is a surface facing the second substrate of the first substrate, partitions a space sandwiched between the first substrate and the second substrate into a plurality of cells, and is included in the cell. In the method of manufacturing an electrophoretic display medium comprising charged particles that move by the action of an electric field,
A base resin that cures by a crosslinking reaction; a crosslinking initiator that initiates crosslinking of the base resin when irradiated with light; and a light absorption that absorbs light having a wavelength that initiates crosslinking of the base resin by the crosslinking initiator. A resist film forming step of forming a negative resist film containing at least an agent on the facing surface of the first substrate;
An exposure step of irradiating the resist formed in the resist film-forming step with light at a position where the partition is to be formed;
And a developing step of developing the resist irradiated with light in the exposure irradiation step.   In the resist film forming step, a negative resist film including a crosslinking initiator that initiates crosslinking of the base resin by being irradiated with ultraviolet rays and the light absorber made of an ultraviolet absorber is formed on the first substrate. The method of manufacturing an electrophoretic display medium according to claim 6, wherein the electrophoretic display medium is formed on the facing surface.   In the resist film-forming step, a negative resist containing the light absorber comprising at least one compound selected from azomethyl compounds, diphenyl sulfoxide compounds, diphenyl sulfone compounds, benzotriazole compounds, and benzophenone compounds The method of manufacturing an electrophoretic display medium according to claim 7, wherein the film is formed on the facing surface of the first substrate.   In the resist film forming step, the base resin made of an epoxy resin, 4-benzyloxy-2-hydroxybenzophenone and 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole were selected. The method of manufacturing an electrophoretic display medium according to claim 7, wherein a negative resist film including the light absorber made of at least one compound is formed on the facing surface of the first substrate.   Prior to the resist film forming step, an adhesion improver film that improves the hydrophobicity of the facing surface of the first substrate and improves the adhesion between the first substrate and the partition wall is formed on the first substrate. The method for producing an electrophoretic display medium according to claim 6, further comprising a step of forming an adhesion improver film formed on the opposing surface.   The electrophoresis according to any one of claims 6 to 10, further comprising a post-exposure heating step of heat-treating the resist irradiated with light in the exposure irradiation step between the exposure step and the development step. A method for manufacturing a display medium.

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