JP2004264613A - Manufacturing method of display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a display device capable of enhancing economic efficiency by simplifying a manufacturing process while sufficient visibility is secured. <P>SOLUTION: A lower electrode layer 2 consisting of ITO is deposited on a substrate 1 and a dispersion system solution wherein migration particles 10a and 10b are dispersed in a fluorine solvent is applied in a liquid drop state onto the lower electrode layer to deposit a dispersion system solution phase 3. A binder liquid containing a UV curing monomer is applied thereon in a liquid drop state and the binder liquid is cured by irradiating the substrate 1 with an ultra-violet ray V to form a partition wall 4. A flattening layer 5 is provided thereon as needed and an upper electrode layer 6 and an upper protective layer 7 are film-deposited thereon to obtain the display device 100. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００９０】
これらの結果より、各実施例で得られた表示装置は、平均的なコントラストが２以上であり、特に実施例１〜４の表示装置は、概ね１０以上のコントラストを達成しており、実施例５〜８に対して優位であることが確認された。なお、実施例１で得た表示装置は、輝度の測定点の９０％以上で１０以上の値を示した。また、表示面を垂直にたてた状態で、１万回の白黒反転表示を行ったところ、画面全体の表示は均一であり、表示ムラは認められなかった。
【００９１】
【発明の効果】
以上説明したように、本発明の表示装置の製造方法によれば、十分な視認性を確保しつつ製造工程を簡略化して経済性を向上できる表示装置を得ることができる。
【図面の簡単な説明】
【図１】本発明による表示装置の製造方法で得られる表示装置の好適な一実施形態を示す模式断面図である。
【図２】図１におけるＩＩ−ＩＩ線に沿った模式断面図である。
【図３】（Ａ）〜（Ｄ）は、本発明の製造方法により表示装置１００を製造している状態を示す工程図である。
【図４】（Ａ）〜（Ｄ）は、本発明の製造方法により表示装置１００を製造している状態を示す工程図である。
【符号の説明】
１…基板、２…下部電極層、３…分散系溶液相、４ａ…バインダー液滴、４ｂ，４ｃ…固化バインダー、４…隔壁、５…平坦化層、６…上部電極層、７…上部保護層、１０ａ，１０ｂ…泳動粒子（粒子体）、１００…表示装置、Ｖ…紫外線。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a display device, and in particular, a display device in which display is performed by a change in the spatial distribution state of a plurality of particles in a dispersion solution in which a plurality of particles are dispersed in a solvent, for example, And a method for manufacturing a display device usable as electronic paper.
[0002]
[Prior art]
Electronic paper is positioned between a conventional paper display (so-called "hard copy") and an electronic display (so-called "soft copy") typified by a CRT, a liquid crystal display, and the like. Is expected. Unlike an electronic display device, electronic paper is required to be able to maintain a once displayed screen (images, characters, and the like) without power thereafter (self-holding property). In particular, even if a viewer looks at the display screen for a long time, a feeling of fatigue is small, and high visibility (contrast) equivalent to that of a printed matter is desired.
[0003]
Conventionally, as a method for displaying images and characters on such electronic paper, techniques such as rotation of colored particles, electrophoresis, thermal rewritable, liquid crystal, and electrochromy are known. Among them, an electrophoretic display device using an electrophoretic phenomenon is excellent in various points such as contrast, self-holding property, and drive current. In an electrophoretic display device, basically, two substrates, at least one of which is transparent, are arranged to face each other, and a dispersion solution in which electrophoretic particles are dispersed in an organic solvent (dispersion solvent) is held between these substrates. It has a structure. Further, electrodes are provided on the opposing surfaces of the respective substrates.
[0004]
In such an electrophoretic display device, when a voltage is applied between the electrodes, an electric field is generated between the substrates. The electrophoretic particles in the dispersion solution are attracted to or separated from the display surface by the action of the electric field, and the spatial distribution of the electrophoretic particles changes. As a result, the reflectance of the display surface changes. Therefore, by controlling the applied voltage and thus the electric field, it is possible to display required figures and characters. Note that there is also known an apparatus that forms an electric field using an external device without providing an electrode on a substrate.
[0005]
Also, for example, Patent Document 1 discloses an electrophoretic display device having an upper substrate formed so that an upper electrode has a curved surface structure. In this device, the upper substrate naturally plays the role of a concave lens, and when observed from the upper substrate side, the lower electrode can appear small, thereby improving the contrast. Therefore, even when a transparent solution containing no dye material is used as the dispersion solution in which the electrophoretic particles are dispersed, the contrasting color of the electrophoretic particles (for example, opposing colors in the hue circle of the Ostwald system, or By forming a colored layer that expresses the vertexes of the same hue triangle of the same system), a sufficient contrast and a sufficiently fast response speed can be obtained.
[0006]
Further, Patent Document 2 discloses an electro-magnetic optical device using a guiding medium in which microcapsules containing fine particles are dispersed, and a light control film that changes the transmittance of light by applying an electric field to the fine particles. I have. In this device, a large number of minute microcapsules are arranged at random in an induction medium.
[0007]
[Patent Document 1]
JP 2001-148553 A
[Patent Document 2]
JP-A-63-303325
[0008]
[Problems to be solved by the invention]
However, although these display devices are expected to be widely applied as electronic paper such as electronic newspapers and electronic magazines, their manufacturing methods are complicated, the number of steps is increased, and the throughput is sufficiently increased. It tends to be impossible. Specifically, of course, the process of encapsulating in a microcapsule to prevent the uneven distribution of the dispersion solution, as well as the complicated and time-consuming fine processing to create 'cells' and 'dents' to enclose the dispersion solution Required. Therefore, it is still expensive from a commercial point of view, and its use in the sense of conventional "paper" was not realistic at present. Therefore, realization of a cheaper display device is desired.
[0009]
Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of manufacturing a display device that can simplify the manufacturing process and improve economical efficiency while securing sufficient visibility.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in a method of manufacturing a display device according to the present invention, display is performed by changing a spatial distribution state of a plurality of particles in a dispersion solution in which a plurality of particles are dispersed in a solvent. A method for manufacturing a display device, comprising: a first step of supplying a dispersion solution in the form of droplets onto a substrate; and a step of dispersing the dispersion solution on a substrate containing a binder component and insoluble in a solvent. It is characterized by comprising a second step of supplying a certain binder liquid in a droplet state, and a third step of solidifying a binder component in the binder liquid applied on the substrate or the binder liquid itself.
[0011]
Note that “insoluble” in the second step indicates that the dispersion solution and the binder liquid are not substantially compatible with each other, but in reality, it is difficult to consider a combination of liquid phases that are strictly completely incompatible with each other ( That is, the solubility in one of the two cannot be completely 0), and the present invention indicates that the solubility of the binder liquid in the dispersion solution or the solvent constituting the binder solution is 1% by volume or less at room temperature. . If the solubility is 1% by volume or less, no substantial adverse effect is observed, while if it exceeds 1% by volume, the viscosity of the dispersion solution increases to an inconvenient degree, and the movement of the particles as the migrating particles moves. The speed tends to decrease, and the particles may move to the binder liquid phase. Further, the `` binder component '' is capable of immobilizing the dispersion solution on the substrate when it is solidified, and in the present invention, includes the case where the `` binder component '' itself is a `` binder liquid '' .
[0012]
In such a method, the dispersion solution supplied in the first step is applied on a substrate, and the droplets are projected on the substrate in a convex shape according to the difference in the interfacial tension between the substrate and the dispersion solution. Be worn. Next, in a second step to be performed, the binder liquid is supplied in a droplet state on the large number of droplets having such a convex shape, and is applied to the substrate. The binder liquid is insoluble in the dispersion solution and both are phase separated into two layers. At this time, since both are in a liquid phase (liquid-liquid system), they can be adhered so that the droplets of the binder solution cover the droplets of the dispersion solution. In this way, the droplets of the individual dispersion solution are fractionated and held and fixed on the substrate by the binder liquid.
[0013]
Next, in the third step, when the binder liquid or the binder component contained therein is solidified, the binder liquid that has been applied so as to cover the droplets of the dispersion solution is fixed to the site, and the partition walls are formed. Once formed, the dispersion solution is sealed between the partition and the substrate while maintaining the shape of the convex droplet. Due to the binding action of such a binder component, the droplets of the individual dispersion solutions are reliably isolated from each other and sufficiently stabilized without using conventional microcapsules or the like. In order to solidify the binder liquid itself, it is preferable to cure the entire liquid, and to solidify the binder component in the liquid, another component (for example, a solvent or the like) holding the binder component in a liquid state is used. The removal process is preferable, and both processes may be combined.
[0014]
Further, in the first step, it is preferable to supply the dispersion solution onto the substrate such that the average particle diameter of the droplets of the dispersion solution is 10 to 100 μm.
[0015]
In this case, the height of the droplets of the dispersion solution deposited on the substrate can be sufficiently increased, and as a result, a good contrast can be obtained and the deterioration of the display quality (resolution) can be sufficiently suppressed. Is done.
[0016]
Further, in the second step, it is more preferable to use a binder liquid having a specific gravity lower than that of the dispersion solution.
[0017]
In this case, a difference in specific gravity between the dispersion solution and the binder liquid occurs, and when the droplets of the dispersion solution and the binder liquid are phase-separated in the second step, the binder liquid phase is separated from the dispersion solution phase. It becomes easy to be maintained in a state. At this time, since the binder liquid has a lower specific gravity than the dispersion solution, the binder liquid phase is easily held on the dispersion solution phase of the convex droplets. Therefore, the sealing property of the dispersion solution when the solidification treatment is performed in the third step is surely enhanced. Here, the specific gravity difference between the binder solution and the dispersion solution is more preferably an absolute value of 0.1 or more, and particularly preferably 0.2 or more.
[0018]
Furthermore, in the second step, it is preferable that the binder liquid is supplied onto the substrate such that the average particle diameter of the droplet of the binder liquid is 1/5 or less of the average particle diameter of the droplet of the dispersion solution. Although it is not particularly necessary to limit the lower limit of this ratio, it can be said that about 1/100 is realistic. By setting the value of the ratio to 1/5 or less, it is possible to prevent the partition walls formed by solidifying the binder liquid in the third step from becoming excessively thick compared to the dispersion solution phase.
[0019]
Furthermore, it is more preferable to repeat the second step and the third step a plurality of times in that order.
[0020]
In this case, the amount of the binder liquid applied once is reduced, and the binder liquid is unevenly distributed due to the surface tension in each of the second steps as compared with the case where the second and third steps are performed only once. Is suppressed. As a result, the thickness of the partition wall for sealing the finally formed dispersion solution is reduced as compared with the case where the second and third steps are performed only once.
[0021]
Specifically, in the first step, it is more preferable to use a fluorinated solvent as the solvent contained in the dispersion solution.
[0022]
Fluorinated solvents are chemically stable and tend to be poorly compatible with many other organic solvents. Therefore, when an organic substance is used for the binder liquid, the choice of the binder liquid can be expanded, in other words, the versatility of the material used can be enhanced. Many of the fluorine-based solvents have a specific gravity as high as about 1.6 to 1.9, and the difference in specific gravity from the binder liquid is larger than other organic solvents. And the phase separation speed at that time increases.
[0023]
More specifically, in the second step, a monomer or oligomer (a so-called low-molecular binder) that generates a polymer by polymerization curing is used, or a polymer (plastic polymer) that is cured or solidified by external energy is used, and It is useful to polymerize and cure the monomer or oligomer or to cure or solidify the polymer.
[0024]
Further, as the monomer or oligomer, a polymerization curing reaction is caused by heat, moisture (humidity), and active energy rays (ultraviolet rays, visible rays, electron beams, other charged particle beams, ionizing radiation such as X-rays and γ-rays). Among them, more preferred are monomers or oligomers constituting a photo-curable resin or radiation-curable resin, and particularly preferred are monomers or oligomers constituting an ultraviolet-curable resin. Further, as the polymer that is cured or solidified by external energy, a curable polymer that is cured by light or radiation sensitive modification or thermal denaturation is preferable, and a plastic polymer having ultraviolet curability is more preferable. In these cases, in the third step, the substrate to which the binder liquid has been applied is preferably irradiated with light or radiation, more preferably ultraviolet light.
[0025]
In this case, the binder liquid itself applied on the substrate in the second step or the monomer or oligomer as a binder component contained therein is polymerized and cured in the third step to form a partition. Alternatively, the curable polymer is cured or solidified to form a partition. Therefore, the liquid and easily applied binder liquid is easily solidified to form a strong partition wall. It is more preferable to use a photo-curable or ultraviolet-curable one because non-contact and rapid solidification can be performed.
[0026]
Alternatively, a polymer obtained by dissolving or mixing a polymer (a so-called resin binder or polymer binder) as a binder component in a solvent is used as the binder liquid in the second step, and the solvent contained in the binder liquid is removed in the third step. May be. In this case, in the third step, only the solvent is volatilized and removed, so that the binder liquid is solidified very easily and the partition wall made of polymer is formed.
[0027]
Further, the present invention is extremely suitable as a method for manufacturing an electrophoretic display device provided as a display device so that particles move by electrophoresis.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted. The positional relationship such as up, down, left, and right is based on the positional relationship in the drawing.
[0029]
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a display device obtained by a method of manufacturing a display device according to the present invention, and FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. . The display device 100 is an electrophoretic display device that can be used as electronic paper, and includes a dispersion solution phase 3 between a lower electrode layer 2 and an upper electrode layer 6 made of a transparent conductive material formed on a substrate 1. Are provided so as to be covered by the partition walls 4.
[0030]
The dispersion solution phase 3 contains migrating particles 10 a and 10 b (particles), is arranged as a plurality of convex droplets on the lower electrode layer 2, and is formed by the partition 4, the substrate 1, and the lower electrode layer 2. They are isolated and sealed from each other. The partition 4 is made of a polymer in a solid state, and a space between the partition 4 and the upper electrode layer 6 is filled with a flattening layer. Further, an upper protective layer 7 is formed on the entire upper surface of the upper electrode layer 6.
[0031]
A procedure for manufacturing the display device 100 having such a configuration and an example of members to be used will be described below. 3 (A) to 3 (D) and FIGS. 4 (A) to 4 (D) are process diagrams showing a state where the display device 100 is manufactured by the manufacturing method of the present invention.
[0032]
<A. Formation of lower electrode layer>
First, the lower electrode layer 2 is formed on the substrate 1 by a known method such as an RF magnetron sputtering method using a target made of a transparent conductive material (see FIG. 3A).
[0033]
(substrate)
Although the material of the substrate 1 is not particularly limited, a flexible transparent resin film having a thickness of 500 μm or less is preferable. Accordingly, flexibility can be given to the display device 100, and wide application as electronic paper is possible.
[0034]
(Transparent conductive material)
The transparent conductive material used for the lower electrode layer 2 is In ₂ O ₃ , SnO ₂ An oxide conductive material such as ITO (Indium Tin Oxide) or ZnO-Al, a conductive polymer film, or the like can be used. The thickness of the lower electrode layer 2 is generally set to about 0.05 to 5 μm. The pattern shape, arrangement, and the like of the lower electrode layer 2 can use various conventionally known methods. That is, at least one of the lower electrode layer 2 and the upper electrode layer 6 may be patterned according to the display pattern, or a TFT circuit for driving may be formed. Further, by providing the lower electrode layer 2 only at the center of the pattern, the migrating particles 10a and 10b can be gathered at one position at the center.
[0035]
<B. Formation of Dispersion Solution Phase 3; First Step>
Next, fine particles constituting the migrating particles 10a and 10b are dispersed in an appropriate solvent to prepare a dispersion solution. This dispersion solution is applied by supplying it in the form of droplets (mist) having a constant average particle size on the substrate 1 on which the lower electrode layer 2 is formed, thereby forming a plurality of dispersion solution phases 3 ( FIG. 4 (B)).
[0036]
(Dispersion solvent)
Here, the solvent used in the dispersion solution (hereinafter, referred to as “dispersion solvent”) is selected from solvents having sufficiently low compatibility with a binder liquid (described later) for forming the partition walls 4. When a water-soluble polymer (resin) is used as a contained binder, many organic solvents which are hydrophobic solvents can be preferably used. On the other hand, when a binder having lipophilicity, that is, a binder which is dissolved in an organic solvent in many cases, is used, a hydrophilic solvent is preferred as a solvent usable as a dispersion solution, and the options are narrowed.
[0037]
Further, the dispersion solvent preferably has a higher specific gravity than the binder liquid. In this case, a significant difference in specific gravity between the dispersion solution and the binder solution occurs, and the binder liquid phase and the dispersion solution phase 3 formed when obtaining the partition walls 4 are easily separated from each other. And the binder liquid phase is easily retained on the dispersion solution phase 3. That is, the absolute value of the specific gravity of the dispersion solution solvent is not so important, and the difference in specific gravity between the two affects the phase separation ability. Further, the absolute value of the specific gravity difference between the two is more preferably 0.1 or more, and particularly preferably 0.2 or more. When the difference in specific gravity is less than 0.1, the phase separation speed of the binder liquid phase and the dispersion solution phase 3 may be undesirably reduced, and both tend to be difficult to sufficiently separate. In this case, it is difficult to sufficiently seal the dispersion solution phase 3 with the partition walls 4 when performing the subsequent solidification treatment of the binder liquid phase.
[0038]
Specifically, it is preferable to appropriately select a dispersion solvent that satisfies the above-mentioned preferable requirements from various known solvents. For example, a silicone oil (particularly, a modified silicone oil is preferable, and a modified form thereof is, for example, alcohol Denaturation, polyether modification, carboxyl modification, or amino modification.), Aromatic hydrocarbons such as benzene, toluene, xylene, and naphthenic hydrocarbons, and aliphatics such as hexane, cyclohexane, kerosene, and paraffinic hydrocarbons. Solvents with relatively high resistivity, such as hydrocarbons, halogenated carbons (hydrogen) such as trichloroethylene, tetrachloroethylene, trichlorofluoroethylene, and ethyl bromide, fluorine-containing ether compounds, fluorine-containing ester compounds, and other various types Oil etc. alone or as a mixture of two or more The can be used.
[0039]
Among these, it is more preferable to use a fluorinated solvent as the dispersion solvent. Examples of such a fluorine-based solvent include perfluorodecane, perfluoro-2,7-dimethyloctane, perfluoro-15-crown-5-ether, perfluorodecalin, perfluoro- (1,2-dimethylcyclohexane ), Perfluoro (methyldecalin), perfluoroperhydrophenathrene, perfluoro-1,3,5-trimethylcyclohexane, perfluorotripropylamine, perfluorotributylamine, perfluorotripentylamine, 2-trifluoromethyl -3-ethoxydodecafluorohexane, ethoxynonafluorobutane and the like. However, the fluorine-based solvent is not limited to these.
[0040]
Commercially available fluorinated solvents include Fluorinert FC-40, Fluorinert FC-75, Fluorinert FC-3283, Fluorinert FC-43, etc., manufactured by Sumitomo 3M, containing perfluoroalkylamine as a main component. Trifluoromethyl-3-ethoxide decafluorohexane (HFE7500 manufactured by 3M, USA) can be exemplified. These can be appropriately mixed and used for the purpose of viscosity adjustment, volatility control and the like. Further, these fluorine-based solvents have very low viscosity and low volatility, so that they are very easy to handle.
[0041]
Such fluorinated solvents are generally chemically stable and tend to have poor compatibility with many other organic solvents. Therefore, even when an organic substance is used as the binder liquid, the choice of the binder liquid can be expanded. In addition, many of the above-mentioned fluorine-based solvents have a specific gravity as high as about 1.6 to 1.9, and the difference in specific gravity from the binder liquid is larger than that of other organic solvents. The mutual separation property with the system solution phase 3 is improved, and the phase separation speed at that time is increased.
[0042]
(Electrophoretic particles)
As the particles used as the migrating particles 10a and 10b, particles generally used for an electrophoretic display device can be used without limitation. For example, titanium oxide, aluminum oxide, carbon black, navy blue, phthalocyanine green, and well-known particles can be used. In addition to the above colloidal particles, various organic and inorganic pigments, dyes, metal powders, fine powders such as glass or resin can be used. It is also preferable to use carbon fullerene and carbon nanotube, and carbon fullerene soot and carbon nanotube soot obtained in the production process thereof.
[0043]
Further, among these particle bodies, titanium dioxide, carbon black, carbon fullerene, carbon nanotube, carbon fullerene soot, carbon nanotube soot, and spherical acrylic particles and spherical styrene particles obtained by combining them are more preferable. . Titanium dioxide, and carbon black, carbon black, carbon fullerene, carbon nanotube, carbon fullerene soot, and carbon nanotube soot are optimal particle materials for obtaining white and black, respectively, and have durability and light resistance. Is also excellent. Therefore, the display device 100 that can achieve a stable contrast ratio without fading or discoloring over a long period of time is realized.
[0044]
Here, when using a substance having a relatively high specific gravity, such as an inorganic pigment or a metal powder, as a particle body, it is preferable to combine with a substance having a relatively low specific gravity such as a resin for adjusting the specific gravity. As a method of compounding, for example, a method of attaching a high specific gravity substance to a resin surface, a method of including a high specific gravity substance in a resin, and the like are generally used.
[0045]
The particle size (average particle size) of the particles is not particularly limited, but is preferably about 0.1 to 10 μm. When the average particle size is less than 0.1 μm, the particles tend to aggregate, and the dispersion stability of the migrating particles 10 a and 10 b in the dispersion solution phase 3 may be undesirably reduced. is there. On the other hand, if the average particle size exceeds 10 μm, the flow resistance to the dispersing solvent is excessively increased, which causes a decrease in the responsiveness of the migrating particles 10a and 10b. It tends to settle under its own weight.
[0046]
(Dropping of dispersion solution and coating method)
There is no particular limitation on a specific method of forming the dispersion solution into droplets and applying the dispersion solution on the substrate 1, and a known method such as a spray nozzle method, an ultrasonic spray method, or an ink jet method can be used. Here, it is preferable to spray such that the average particle diameter of the droplets of the dispersion solution is 10 to 100 μm. If the average particle size is less than 10 μm, the height (bump) of the droplets deposited on the substrate 1 tends to be insufficient, and in such a case, good contrast of a display image may not be obtained. There is. On the other hand, if the average particle size exceeds 100 μm, the display quality (resolution) of the display device 100 may be reduced.
[0047]
It is known that the shape of the droplet of the dispersion solution formed in a state of being adhered on the substrate 1 varies (changes) according to the respective interfacial tensions of the substrate 1 and the droplet. That is, the larger the difference between the surface tensions of the liquid droplet application surface and the dispersion solution on the substrate 1, the more the liquid droplets tend to have a convex shape. Therefore, in order to obtain a desired shape of the droplet, it is preferable to perform a surface treatment on the substrate 1 on which the lower electrode layer 2 is formed in advance and change the surface tension thereof before the application of the dispersion solution.
[0048]
Specifically, the difference in surface tension between the surface of the lower electrode layer 2 and the dispersion solution is preferably large, more preferably the surface tension difference is 3 mN / m or more, and particularly preferably 5 mN / m or more. If the difference in surface tension is less than 3 mN / m, the applied dispersion solution tends to be less likely to be bent. The upper limit of the difference in surface tension is not particularly limited, and the larger the difference, the better.
[0049]
Some examples of the surface tension of the dispersion solvent described above are as follows (all units are mN / m).
・ Fluorinert FC-75: 15
・ Fluorinert FC-70: 18
・ Fluorinert FC-40: 16
・ Water: 73
・ Toluene: 28
・ Ethanol, acetone: 23
・ Silicone oil: 16-21
[0050]
For example, when toluene (surface tension: 28 mN / m) is used as the dispersion solvent, when forming a liquid-repellent region on the surface of the substrate 1 on which the lower electrode layer 2 is formed, the surface tension is 25 mN / m. m or less, and conversely, when forming a lyophilic region, the surface tension is preferably 31 mN / m or more.
[0051]
Further, as a surface treatment method for changing the surface tension of the surface to be coated of the substrate 1, in order to reduce the surface tension to form a water-repellent surface, the surface of the substrate 1 is formed using silazane fluoride or the like. -CF near ₃ It is effective to introduce a fluorine-containing group such as a group, and in some cases, a surface tension of 7 mN / m or less is achieved. Conversely, to form a hydrophilic surface by increasing the surface tension, it is effective to introduce a hydroxyl group or the like, and a surface tension of, for example, 70 mN / m or more is achieved. In addition, the surface tension of the substrate 1 changes depending on the surface state other than the material or the morphology more microscopically, and a surface having moderately fine irregularities is usually a surface having no such irregularities. It is known that the surface tension increases in comparison.
[0052]
<C. Coating of binder liquid; second step>
Next, a binder solution is prepared and applied by supplying the binder solution in the form of droplets (mist) having a constant average particle size onto the substrate 1 on which the dispersion solution phase 3 is formed. The applied binder liquid is deposited on the dispersion solution phase 3 as binder droplets 4a having a convex shape (see FIG. 4C).
[0053]
There is no particular limitation on the specific method of applying the binder liquid into droplets and applying the liquid onto the substrate 1, and the spray nozzle method, the ultrasonic spray method, the ink jet method, and the like are the same as those applied to the dispersion solution described above. Can be used. Here, it is preferable that the binder liquid is supplied onto the substrate such that the average particle diameter of the droplets of the binder liquid is 1/5 or less of the average particle diameter of the droplets of the dispersion solution. Although it is not particularly necessary to limit the lower limit of this ratio, it can be said that about 1/100 is realistic. If the value of the ratio exceeds 1/5, the partition walls 4 formed by solidifying the binder liquid in the third step described later become excessively thick as compared with the dispersion solution phase 3, and if this occurs, the display device There is a possibility that the applied voltage for driving to 100 may increase excessively.
[0054]
Further, the binder liquid is preferably lower in specific gravity than the dispersion solution, and as described above, the absolute value of the specific gravity difference between the two is more preferably 0.1 or more, and particularly preferably 0.2 or more. . However, even when the specific gravity difference is less than 0.1, or when the binder liquid has a higher specific gravity than the dispersion solution, the interfacial tension with the lyophobic or lyophilic region formed on the surface of the substrate 1 By action, it is not impossible to deflect to the desired position after phase separation. In such a case, a desired skew can be realized by performing a long-time careful vibration treatment or the like during the phase separation.
[0055]
(Binder component)
The binder liquid is one containing a binder component or the binder component itself. The binder component is an organic substance that constitutes the partition wall 4, and includes a monomer (monomer) and an oligomer that are low-molecular compounds that form such a polymer by polymerization and curing. Specifically, those which cause a polymerization curing reaction preferably by heat, water or the above-mentioned active energy rays are mentioned, and particularly preferred are monomers or oligomers constituting an ultraviolet curable resin.
[0056]
Examples of the monomer or oligomer constituting the active energy ray-curable resin include acrylic acid, methacrylic acid, and an ester compound thereof having an unsaturated double bond exhibiting radical polymerizability in response to ionization energy of radiation ( A group which is crosslinked or polymerized by irradiation such as a meth) acrylic double bond, an allylic double bond such as diallyl phthalate, or an unsaturated double bond such as maleic acid or a maleic acid derivative is contained or introduced into a molecule. And the like. These are preferably polyfunctional, especially trifunctional or more, and may be used alone or in combination of two or more.
[0057]
The radiation-curable monomer preferably has a molecular weight of less than 2,000, and the radiation-curable oligomer has a molecular weight of 2,000 to 10,000. More specifically, styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,6-hexane glycol diacrylate, 1,6-hexane glycol dimethacrylate, and the like, Particularly preferred examples include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), and acrylic modified products of urethane elastomer.
[0058]
In addition, examples of the radiation-curable oligomer include oligoester acrylates and acrylic modified products of urethane elastomers, and those in which functional groups such as -COOH groups are introduced.
[0059]
Further, as the binder component, in addition to or instead of these monomers or oligomers, a thermoplastic polymer which is preferably cured or solidified by light or radiation sensitive modification, more preferably radiation functional modification, may be used. Specific examples of such radiation-curable polymers include acrylic double bonds such as acrylic acid having an unsaturated double bond exhibiting radical polymerizability, methacrylic acid, or an ester compound thereof, such as diallyl phthalate. Thermoplastic polymers having a group that crosslinks or polymerizes upon irradiation, such as an unsaturated bond such as an allylic double bond, maleic acid, or a maleic acid derivative.
[0060]
Further, as a thermoplastic polymer that can be modified into a radiation-curable polymer, a vinyl chloride copolymer, a saturated polyester resin, a polyvinyl alcohol resin, and a polyamide resin are also effective.
[0061]
Since these photo- or radiation-curable monomers or oligomers, or photo- or radiation-curable polymers are cured by irradiation with radiation, particularly ultraviolet irradiation, additives such as a photopolymerization initiator or a sensitizer are contained in the binder liquid. Preferably, it is contained. Such additives are not particularly limited, and may be appropriately selected and used from, for example, commonly used ones such as acetophenone-based, benzoin-based, benzophenone-based, and thioxanthone-based additives. Various additives may be used alone or in combination of two or more. It can be mixed and used. The content of these additives is usually about 0.5 to 5% by weight in the binder liquid. The binder liquid as a polymerization composition containing such an additive can be synthesized according to a conventional method, or may be prepared using an available commercially available compound.
[0062]
Furthermore, the binder liquid may contain an epoxy resin and a photocationic polymerization catalyst. As the epoxy resin, an alicyclic epoxy resin is preferable, and a resin having two or more epoxy groups in a molecule is more preferable. Examples of such alicyclic epoxy resins include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis- (3,4-epoxycyclohexylmethyl) adipate, and bis- (3,4-epoxycyclohexyl). And adipate and the like, and it is preferable to use one or more of these. The epoxy equivalent of the alicyclic epoxy resin is not particularly limited, but is preferably from 60 to 300, and more preferably from 100 to 200, from the viewpoint of obtaining good curability.
[0063]
In addition, a known cationic photopolymerization catalyst can be used, and there is no particular limitation. For example, one or more metal fluoroborates and complexes of boron trifluoride, bis (perfluoroalkylsulfonyl) methane metal salts, aryldiazonium compounds, aromatic onium salts of 6A (16) group elements, 5A (15) group elements It is preferable to use at least one of an aromatic onium salt, a dicarbonyl chelate of a 3A (13) to 5A (15) group element, and a thiopyrylium salt.
[0064]
Further, an organic polymer other than the above radiation-curable polymer may be used as the binder component. In this case, a liquid composition obtained by dissolving such a polymer in an appropriate solvent having solubility for the polymer can be used as the polymer liquid. Such polymers are not particularly limited, and include polymers of the above-described monomers or oligomers.
[0065]
Further, a diluting solvent such as toluene (specific gravity 0.87) and ethylene glycol monoethyl ether acetate (specific gravity 0.975) for adjusting the viscosity and / or specific gravity may be added to the binder liquid. This is effective regardless of whether the binder component is a monomer, an oligomer, or a polymer.
[0066]
Further, a commercially available product such as a binder liquid or a polymerization initiator containing such a radiation-curable or radiation-curable binder component may be used. Such commercially available products include, for example, NK esters and NK oligos, which are acrylic monomers and oligomers manufactured by Shin-Nakamura Chemical Co., Ltd., and these are introduced into the structure and molecular weight of the main chain constituting the molecule and introduced into the molecule. Various products are available depending on the type and concentration of the functional group to be performed.
[0067]
Further, in the case of a structure in which the display is visually recognized through the partition wall 4 which is a binder cured layer, since the particle color is observed as it is, it is desirable that the binder droplet 4a be colorless and transparent after the curing treatment (solidification treatment). , At least colored and transparent. However, it is also possible to enhance the impression of the viewer by performing desired coloring. For example, when each of the electrophoretic particles 10a and 10b has a two-color configuration of white and black, a black-and-white display is normally obtained. However, if a red dye is added to a colorless and transparent binder solution to be colored, a white-red display is obtained. It becomes possible. When the display is visible from the substrate 1 side, it is not necessary to use a binder liquid having transparency after curing.
[0068]
<D. Solidification treatment of binder liquid; third step>
Next, a solidifying process of the binder droplet 4a is performed. When the binder liquid contains a light- or radiation-curable monomer or the like as a binder component, or a light- or radiation-curable polymer, the substrate 1 is irradiated with ultraviolet rays V or the like from the side where the binder droplets 4a are applied. Then, the binder droplets 4a are polymerized and cured to obtain a solidified binder 4b (see FIG. 3D). When the binder solution contains a diluting solvent, after the phase separation, the diluting solvent is volatilized and removed by heat treatment or the like, and then irradiation with ultraviolet rays V or the like is performed to perform polymerization and curing.
[0069]
When the binder solution is a solution in which a polymer other than the radiation-curable polymer is dissolved in a solvent as a binder component, after the phase separation, the solvent is volatilized and removed by heat treatment or the like to form the binder droplet 4a. Solidify. In this case, even if the binder liquid contains a diluting solvent, it can be volatilized and removed at the same time.
[0070]
<E. Binder liquid re-coating and re-solidification treatment; second step and third step, respectively> The partition liquid 4 may be formed by performing the above-mentioned binder liquid coating and solidification treatment only once, From the viewpoint of reducing the drive voltage of the display device 100 as much as possible by thinning, it is advantageous to carry out a series of binder liquid application and solidification processes in a plurality of times. That is, it is possible to prevent the binder droplets 4a from being unevenly distributed due to the surface tension by performing the application in a plurality of times. FIGS. 4A and 4B show a state in which such a re-coating and re-solidification process is being performed, and the partition walls 4 are formed by further laminating the solidified binders 4b and 4c. Although the number of times of such repetitive processing varies depending on the thickness required for the partition walls 4 and the droplet size of the binder liquid, it is preferable that the number of times of the repetitive processing is, for example, several times to about 10 times.
[0071]
The hardness of the partition wall 4 made of the polymer formed by curing or solidifying the binder component varies depending on the molecular structure of the polymer, particularly the main chain structure. For example, those having a urethane skeleton have flexibility. There are many. Furthermore, in the case of manufacturing a flexible (flexible) display device 100, it is preferable to use a binder component in which the hardness of the partition walls 4 is a pencil hardness value that is softer than HB.
[0072]
Among them, as a binder component, those containing an acrylic group or an acrylic skeleton among the above-mentioned radiation-curable monomers or oligomers or ultraviolet-curable polymers, and radiation of a binder liquid containing a photopolymerization sensitizer or an initiator, particularly Those obtained by ultraviolet curing are preferred.
[0073]
<F. Flattening treatment>
Further, when the thickness of the partition walls 4 is as small as shown in FIG. 1, minute unevenness which is inevitable on the surface of the partition walls 4 may be caused due to the thin coating thickness of the binder droplet. In this case, when the upper electrode layer 6 is formed directly thereon, an unnecessary electric field distribution may be generated, and the migration of the migrating particles 10a and 10b may not be performed quickly. Therefore, in such a case, it is preferable to provide the planarization layer 5 on the partition wall 4 in order to eliminate such inconvenience (see FIG. 4C). The flattening layer 5 may be formed of the same polymer as the partition 4, or may be formed of a different polymer, and it is also possible to use a thermoplastic polymer or the like.
[0074]
As a specific method of forming the flattening layer 5, for example, the partition wall 4 may be formed in a liquid or droplet form from a monomer composition containing an ultraviolet curable monomer or the like or a resin composition obtained by dissolving a polymer. After coating on the formed substrate 1, a method of polymerizing and curing or solidifying may be mentioned. At this time, since the purpose of the flattening is to apply, after the application of the composition, an appropriate time is allowed, and after waiting for the entire layer to be leveled using the leveling effect of the liquid, the polymerization hardening or solidification treatment is performed. It is desirable to do.
[0075]
<G. Formation of upper electrode layer etc.>
Then, a known conductive material (for example, copper, aluminum, carbon fine particles or the like when the upper electrode layer 6 is a non-light-transmitting layer, and the same as the lower electrode layer 2 when the upper electrode layer 6 is a light-transmitting layer) The upper electrode layer 6 is formed on the planarization layer 5 by using the material) and the method. Specifically, a film made of a conductive material may be formed on the planarization layer 5, or a substrate on which a conductive film is formed in advance is used as an upper substrate (corresponding to the upper protective layer 7). It may be tightly fixed on the flattening layer 5. In this case, the curing treatment of the monomer composition constituting the flattening layer 5 may be performed in a state where the upper substrate is placed on the uncured flattening layer 5. Thereafter, if necessary, an upper protective layer 7 is formed, electrodes are further attached to the lower electrode layer 2 and the upper electrode layer 6, and further a drive circuit and a power supply are connected to obtain the display device 100.
[0076]
According to such a manufacturing method of the display device of the present invention, after the droplets of the dispersion solution containing the migrating particles 10a and 10b are applied to the substrate 1 and the plurality of dispersion solution phases 3 are applied, A binder liquid is also applied thereon in the form of droplets to cover the dispersion solution phase 3, and in this state, the binder droplets 4a to 4c are solidified. Since the partition walls 4 formed in this manner individually seal the dispersion solution phases 3 while securely isolating them, mixing and dissipation of the dispersion solution and the migrating particles 10a and 10b are prevented, and sufficient contrast is obtained. Display device 100 can be configured.
[0077]
By such a manufacturing procedure, complicated and difficult and troublesome steps such as encapsulation of the dispersion solution in the microcapsules and formation of cells and recesses for enclosing the dispersion solution, which have been conventionally performed, are omitted. can do. Therefore, the throughput in manufacturing the display device 100 can be improved, and thereby the manufacturing cost can be reduced and the economic efficiency can be significantly improved.
[0078]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the upper protective layer 7 and / or the planarizing layer 5 may not be provided. The display device 100 is not only an electrophoretic display device but also an external device (an electric field applying head, an electrostatic ion flow device, or the like) that applies an electric field to the migrating particles 10a and 10b to charge the migrating particles 10a and 10b. It is also possible to provide a display device that performs display by controlling the distribution state of 10a and 10b. Further, the display device 100 may be a magnetophoretic display device that performs display by controlling the distribution state of the migrating particles by applying a magnetic field from the outside.
[0079]
Further, as a solvent (dispersion solvent) of the dispersion solution, a mixture of a plurality of types of solvents having no compatibility with each other can be used. As the binder liquid used at this time, a binder liquid insoluble in these plural kinds of solvents is selected and used. For example, when a mixed solvent of a fluorine-based solvent and an organic solvent is used as the dispersion solvent, an aqueous binder liquid is used. Furthermore, when two types of migrating particles 10a and 10b having different colors are used, one of them is subjected to a fluorinated solvent surface treatment to be dispersed in a fluorinated solvent, and the other is subjected to a fluorinated organic solvent surface treatment to form an organic solvent. It is preferable to disperse them.
[0080]
In addition, it is also preferable to perform a defoaming process under reduced pressure before performing a solidifying process (curing process) of the binder droplets 4a to 4c. In addition, when performing the fluorinating treatment of the substrate 1, it is preferable to perform a hydrophilizing treatment by introducing a hydroxyl group or the like over the entire surface of the substrate 1 before that. In this case, a stronger fluorinated surface is formed by bonding the fluoride group to the hydrophilic functional group. For this purpose, it is possible to apply a known method such as heating in an oxygen atmosphere, ultraviolet irradiation, plasma CVD, or surface modification by corona discharge treatment. In addition, when the hydrophilization treatment is performed, the region that has not been subjected to the fluorinated treatment expresses strong hydrophilicity, so that the liquid repellency of the dispersion solution using an organic solvent as the dispersion solvent is enhanced, and the dispersion solvent is unevenly distributed. Can be further promoted.
[0081]
Hereinafter, the content of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
[0082]
<Examples 1 to 8>
A 100 μm thick polyethylene terephthalate film was prepared as the substrate 1. First, an ITO transparent conductive film was formed on the substrate 1 by a sputtering method, and then heat treatment was performed at 80 ° C. in the air for 1 hour to form a lower electrode layer 2. Further, a fluorine-based silazane oligomer (KP-801M manufactured by Shin-Etsu Chemical Co., Ltd.) was applied on the surface of the lower electrode layer 2 by spray coating, and then left at 80 ° C. for 1 hour.
[0083]
On the other hand, as the electrophoretic particles 10a and 10b, spherical acrylic particles (black colored particles) having a carboxy group on the surface and having an average particle diameter of 1 μm, and spherical acrylic particles having an average particle diameter of 3.5 μm and having titanium oxide fixed on the surface, respectively ( The white particles were subjected to a surface treatment using a fluorine-based silazane oligomer (KP-801M manufactured by Shin-Etsu Chemical Co., Ltd.) as a fluorine-based surface treatment agent. 8 parts of the black particles, 3 parts of the white particles, 3 parts of a fluoropolyether as a solvent additive (manufactured by Daikin Industries, Ltd .: Demnum S-20), 95 parts of a fluorinated solvent, Fluorinert FC-40 (manufactured by Sumitomo 3M) and 15 parts of HFE7500 (manufactured by 3M) was mixed by ultrasonic dispersion to prepare a dispersion solution.
[0084]
Next, the dispersion solution was formed into droplets having various average particle diameters by an inkjet nozzle, and was applied to the surface of the lower electrode layer 2 on the substrate 1. When the surface state was observed with a microscope, when the droplet diameter was 50 μm, a pattern in which a large number of droplets of the dispersion solution having a substantially circular cross section having a diameter of about 70 to 100 μm were randomly present in an isolated state. The formation was confirmed. In some cases, adjacent droplets contacted each other to form one large pattern.
[0085]
Further, a polymerizable composition having the following composition was prepared as a binder liquid.
-Oligoester acrylate (molecular weight 5,000): 50 parts by weight
-Trimethylolpropane triacrylate: 50 parts by weight
・ Acetophenone-based photopolymerization initiator: 3 parts by weight
[0086]
The binder liquid was formed into droplets having various average particle diameters by a spray nozzle, and was applied onto the substrate 1 on which the dispersion solution was applied. Then, ultraviolet light V was irradiated using a high-pressure mercury lamp to cure the binder liquid. Thereafter, the application of a dispersion solution of droplets having the same average particle size as described above and the UV curing treatment were repeated three times to form the partition walls 4. Further, a binder liquid having an average particle diameter of 50 μm was spray-coated thereon and cured to form a flattening layer 5.
[0087]
Next, a carbon paste-containing conductive polymer was applied to the surface to form an upper electrode layer 6, and an upper protective layer 7 made of a 100 μm polyethylene terephthalate film was further adhered. Finally, conductive lines were attached to the lower electrode layer 2 and the upper electrode layer 6 and connected to an external voltage application device to complete various display devices. The specific gravity of the dispersion solution was 1.85, the specific gravity of the binder solution was 1.25, and the specific gravity difference was 0.6.
[0088]
<Characteristic evaluation>
A voltage of ± 10 V was applied to each of the display devices obtained in Examples 1 to 8 to change the display device to black and white, and the brightness of a range of 0.2 mmφ was measured at 100 points with a microscope, and the maximum value and the minimum value of the contrast were measured. Were calculated and their average was calculated. Note that the area of 0.2 mmφ, which is the luminance measurement range, is a size where roughness is generally felt when the display surface is visually observed when the display surface has a variation in contrast. The obtained results are shown in Table 1 together with the average droplet diameter of the dispersion solution, the average particle diameter of the binder droplet, and the particle diameter ratio thereof.
[0089]
[Table 1]

[0090]
From these results, the display devices obtained in each example had an average contrast of 2 or more, and particularly the display devices of Examples 1 to 4 achieved a contrast of approximately 10 or more. It was confirmed to be superior to 5 to 8. The display device obtained in Example 1 exhibited a value of 10 or more at 90% or more of the luminance measurement points. Further, when black-and-white inverted display was performed 10,000 times with the display surface set up vertically, the display on the entire screen was uniform and no display unevenness was observed.
[0091]
【The invention's effect】
As described above, according to the method for manufacturing a display device of the present invention, it is possible to obtain a display device capable of simplifying a manufacturing process and improving economic efficiency while securing sufficient visibility.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a preferred embodiment of a display device obtained by a method of manufacturing a display device according to the present invention.
FIG. 2 is a schematic sectional view taken along line II-II in FIG.
FIGS. 3A to 3D are process diagrams showing a state in which the display device 100 is manufactured by the manufacturing method of the present invention.
FIGS. 4A to 4D are process diagrams showing a state in which the display device 100 is manufactured by the manufacturing method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Lower electrode layer, 3 ... Dispersion solution phase, 4a ... Binder droplet, 4b, 4c ... Solidified binder, 4 ... Partition wall, 5 ... Flattening layer, 6 ... Upper electrode layer, 7 ... Upper protection Layers 10a, 10b: migrating particles (particles), 100: display device, V: ultraviolet light.

Claims (9)

A method for manufacturing a display device in which display is performed by a change in a spatial distribution state of the plurality of particles in a dispersion solution including a plurality of particles dispersed in a solvent,
A first step of supplying the dispersion solution in the form of droplets onto a substrate,
A second step of supplying a binder liquid containing a binder component and being insoluble in the solvent in a droplet state on the substrate on which the dispersion solution is applied,
A third step of solidifying the binder component in the binder liquid applied on the substrate, or the binder liquid itself,
A method for manufacturing a display device, comprising: In the first step, the dispersion solution is supplied onto the substrate such that the average particle diameter of the droplets of the dispersion solution is 10 to 100 μm.
The method for manufacturing a display device according to claim 1, wherein: In the second step, using a binder liquid having a lower specific gravity than the dispersion solution,
The method for manufacturing a display device according to claim 1, wherein: In the second step, the binder liquid is supplied onto the base such that the average particle diameter of the droplet of the binder liquid is 1/5 or less of the average particle diameter of the droplet of the dispersion solution.
The method for manufacturing a display device according to claim 1, wherein: Repeating the second step and the third step a plurality of times in that order;
The method of manufacturing a display device according to claim 1, wherein: In the first step, a fluorine-based solvent is used as the solvent contained in the dispersion solution,
The method for manufacturing a display device according to claim 1, wherein: In the second step, an ultraviolet-curable monomer or an ultraviolet-curable oligomer or an ultraviolet-curable polymer is used as the binder component or the binder liquid,
In the third step, irradiating light or radiation on the substrate coated with the binder liquid,
The method of manufacturing a display device according to claim 1, wherein: In the second step, as the binder liquid, a polymer obtained by dissolving or mixing a polymer as the binder component in a solvent is used,
The method according to any one of claims 1 to 6, wherein, in the third step, the solvent contained in the binder liquid is removed. As the display device, to manufacture an electrophoretic display device provided so that the particles move by electrophoresis,
The method of manufacturing a display device according to claim 1, wherein:

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