A method for manufacturing color electronic paper

Abstract

This invention discloses a method for manufacturing color electronic paper. Using a lower flexible substrate with a release layer as the base material, a lower adhesive layer is coated on the lower flexible substrate, an electronic ink layer is fabricated on the lower adhesive layer, and an upper adhesive layer is fabricated on the electronic ink layer. Using an upper flexible substrate as the base material, a transparent moisture barrier layer is fabricated on the upper flexible substrate. A transparent conductive layer is fabricated on the moisture barrier layer. A color filter layer is fabricated on the conductive layer, where the color pixels formed by the color photoresist are red, green, and blue primary colors. A bonding process is used to bond the upper adhesive layer to the color filter layer, completing the bonding of the upper and lower roll substrates. This invention features a roll-to-roll process that allows for mass production, high speed, and high yield. Besides eliminating the need for a transparent flexible substrate for the color filter and electronic ink layer, it improves brightness and viewing angle. Furthermore, the moisture barrier layer reduces the number of steps in manufacturing module products using this color electronic paper, thereby improving efficiency and yield, and reducing production costs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic paper manufacturing, in particular to a manufacturing method of color electronic paper. BACKGROUND

[0002] Electronic paper technology is a kind of paper-like reflective display, and its material characteristics are light, thin, non-eye-damaging, low power consumption, flexible, etc., which is suitable for reading and education-related applications. At present, the more mature way of colorizing electronic paper is to use color resist to achieve the colorization effect of electronic paper. The existing technology using color resist for colorization is briefly described as follows:

[0003] a. Using yellow light lithography process to manufacture color resist

[0004] The so-called RGB project is to form R, G, and B three-color patterns in the opening part. First, the color resist colored with R is coated by rotation, and then exposed to ultraviolet light through an R-pattern mask. Then, the unexposed part is removed using a developer to form an R pattern. Then, post-baking is performed at a temperature of 200 degrees Celsius or higher to make the pattern resistant to chemical changes. Then, the same process is repeated to form G and B patterns. Each pattern is separated by a black matrix to increase the contrast ratio during display to avoid mixed color light. The simple production process is shown in Figure 1 .

[0005] The current implementation method of this technology is to manufacture on a glass substrate. After completing the RGB lithography pattern, the glass is cut and assembled with the electronic paper module. The disadvantages of this method are thick, heavy, high price, and not suitable for portable devices. The light and thin characteristics of electronic paper cannot be highlighted in this technical solution.

[0006] b. Using inkjet printing to manufacture color resist

[0007] Currently, the inkjet method is used to manufacture color filters for electronic paper, which is the most commonly used method. The inkjet technology disclosed in patent US6162510 by Canon sprays 3 primary color pigments of the color filter into 3 groups of holes defined by the yellow process to form a pixel. The process is as follows Figure 2As shown, inkjet printing technology mainly involves coating tiny droplets onto a substrate according to a predetermined pattern. Because it allows for digital output, it overcomes the size limitations of the substrate. However, while inkjet printing has solved the problems of material loss and large-area fabrication for color filters, the ink-storing barriers on the substrate still rely on photolithography. Therefore, it still faces the challenges of wasting photoresist material in the photolithography process and limitations in large-area fabrication. Furthermore, the width of the ink-storing barriers is generally required to be within 30μm, especially for color filter assemblies in liquid crystal displays. Therefore, with the increasing requirement for aperture ratio, the barrier width needs to be as thin as possible. However, if inkjet printing technology is used to simultaneously fabricate barriers to achieve a fully inkjet-printed color filter, the current limitations of inkjet printing droplet size prevent the production of micro-patterns smaller than 30μm, and the manufacturing process is more complex with lower production speed and yield.

[0008] The existing color filter technology used to produce color electronic paper has the following problems:

[0009] 1) Using the current panel process, color filters are made on glass substrates and then module processes are carried out to achieve electronic paper colorization. This will make the module thicker, heavier, and more expensive to produce. It will also cause the electronic paper structure to lose the characteristics of flexible materials. It is only suitable for rigid module processes and not for flexible module processes.

[0010] 2) Inkjet printing processes have problems such as low production speed, difficulty in controlling yield, and high equipment and production costs, which may cause problems in mass production.

[0011] 3) The electronic ink and adhesive used in electronic paper may also cause reliability issues in the baking process of color filters made by inkjet printing.

[0012] 4) Applying color filter technology to electronic paper will result in a loss of brightness and color viewing angle due to the thickness of the transparent flexible substrate of the electrodes on the electronic paper.

[0013] 5) With the current modular manufacturing technology, a waterproof layer encapsulation process is still required on top of the color filter, which makes the module manufacturing process inefficient and involves many steps. Summary of the Invention

[0014] To address the aforementioned problems, the present invention aims to provide a method for manufacturing color electronic paper, featuring a roll-to-roll process that enables mass production, high output speed, and high yield. This method eliminates the need for a transparent flexible substrate for the color filter and electronic ink layer, resulting in improved brightness and viewing angles. Furthermore, the inclusion of a moisture barrier layer reduces the number of steps required for manufacturing module products using this color electronic paper, thereby improving efficiency and yield, and lowering production costs. The technical solution is as follows:

[0015] A method for manufacturing color electronic paper includes the following steps:

[0016] Step 1: Fabricate the lower roll substrate

[0017] Using a flexible substrate with a release layer as the base material, a lower adhesive layer is coated on the flexible substrate, an electronic ink layer is fabricated on the lower adhesive layer, and an upper adhesive layer is fabricated on the electronic ink layer.

[0018] Step 2: Fabricate the upper roll substrate

[0019] Step 2.1: Fabrication of a moisture barrier layer: Using the above flexible substrate as the base material, a transparent moisture barrier layer is fabricated on the flexible substrate.

[0020] Step 2.2: Fabrication of a conductive layer: Fabricate a transparent conductive layer on the moisture barrier layer;

[0021] Step 2.3: Fabrication of a color filter layer: A color filter layer is fabricated on the conductive layer, wherein the color pixels formed by the color photoresist are the three primary colors of red, green, and blue;

[0022] Step 3: The upper and lower roll substrates are bonded together by using a bonding process to create the adhesive layer and bond the color filter layer.

[0023] Furthermore, the adhesive layer is a transparent organic material, such as OCA, PU, ​​PI, PMMA, Epoxy, or Acrylic.

[0024] Furthermore, the upper flexible substrate is a transparent material with a light transmittance of ≥85%, such as CPI, TAC, PEN, PET, or Hybrid glass.

[0025] Furthermore, the water vapor barrier layer is a transparent layer with a light transmittance of ≥85%, and is made of inorganic materials, organic materials, or inorganic-organic composite materials, and is completed through a coating or plating process.

[0026] Furthermore, the color filter layer is a negative photoresist that can be patterned through a photoluminescence development process, with a maximum process temperature of 150°C, and the photoresist material is PMMA, Epoxy, or Acrylic.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. This invention proposes a method for producing flexible color electronic paper using a roll-to-roll process. The colorization of the electronic paper is completed using a flexible process, which can combine rigid and flexible color module products.

[0029] 2. This invention is achieved through a roll-to-roll production process, which improves production speed, output and efficiency.

[0030] 3. The colored electronic paper of the present invention has waterproof and gas-permeable properties, which can prevent the electronic ink or adhesive layer from undergoing qualitative changes.

[0031] 4. This invention uses photolithography to fabricate a color filter layer, which can meet the product requirements for high resolution.

[0032] 5. The color filter layer of this invention is close to the electronic ink layer, which can improve the color effect and viewing angle. Attached Figure Description

[0033] Figure 1 The process for fabricating colored photoresist using photolithography is shown in (a) and (b) is a structural diagram.

[0034] Figure 2 This describes the manufacturing process for producing color photoresist using inkjet printing.

[0035] Figure 3 This is a flowchart illustrating the overall process of manufacturing the color electronic paper of this invention.

[0036] Figure 4 A schematic diagram of the fabrication of the lower roll substrate for the electronic ink layer.

[0037] Figure 5 A schematic diagram of the water vapor barrier layer.

[0038] Figure 6 A schematic diagram of the conductive layer is shown.

[0039] Figure 7 A schematic diagram of the color filter layer.

[0040] In the diagram: 101 - lower flexible substrate; 102 - lower adhesive layer; 103 - electronic ink layer; 104 - upper adhesive layer; 201 - upper flexible substrate; 202 - moisture barrier layer; 301 - conductive layer; 401, 402, 403 - color pixels. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0042] This invention is based on a flexible roll-to-roll process, maintaining the high production speed and flexibility of flexible electronic paper, allowing its end products to be compatible with both rigid and flexible materials. It references the glass photolithography process used in panel manufacturing to achieve colorization, ensuring that the color filter fabrication process does not affect the electronic ink and adhesive layer, and is implemented using a roll-to-roll manufacturing process. Furthermore, to ensure closer adhesion between the color filter layer and the electronic ink layer, a moisture barrier layer is fabricated using a roll-to-roll process, reducing subsequent module product processes and offering advantages in mass production and cost. This invention not only overcomes the shortcomings of existing technologies but also combines different processes, making this technology feasible for mass production. A schematic diagram of the overall process is shown below. Figure 3As shown, the specific production process is as follows:

[0043] 1. Fabrication of the lower roll substrate:

[0044] Electronic ink layer fabrication:

[0045] 1) The lower flexible substrate 101 with a release layer is used as the base material. The purpose of the release layer is to facilitate the subsequent separation of the color electronic paper module process without affecting the lower adhesive layer 102. The release layer can be an organic or inorganic material, and its purpose is to facilitate peeling without affecting the adhesive layer.

[0046] 2) Apply a lower adhesive layer 102 to the lower flexible substrate 101. The lower adhesive layer 102 may be a transparent or non-transparent organic material, such as PU, PI, PMMA, Epoxy, Acrylic, etc., including but not limited to this.

[0047] 3) An electronic ink layer 103 is fabricated on the lower adhesive layer 102. This electronic ink layer 103 is a suspension mixture of black and white nanoparticles or capsules.

[0048] 4) Apply an adhesive layer 104 to the electronic ink layer. This adhesive layer is a transparent organic material, such as OCA, PU, ​​PI, PMMA, Epoxy, Acrylic, etc., including but not limited to these.

[0049] like Figure 4 As shown, the fabrication of the lower roll substrate with an electronic ink layer is completed.

[0050] 2. Fabrication of the upper roll substrate:

[0051] (1) Fabrication of the water vapor barrier layer: such as Figure 5 As shown.

[0052] 1) The above flexible substrate 201 is a base material. This base material is a transparent material with high transparency, such as CPI, TAC, PEN, PET, Hybrid glass, etc., including but not limited to this.

[0053] 2) A moisture barrier layer 202 is fabricated on the substrate. The moisture barrier layer 202 is a highly transparent layer that can be made of inorganic or organic materials or inorganic / organic composite materials. It can be completed by a coating or plating process. Its purpose is to prevent water and oxygen from penetrating and affecting the electronic ink or adhesive layer.

[0054] (2) Fabrication of conductive layer: such as Figure 6 As shown.

[0055] A conductive layer 301 is fabricated on the moisture barrier layer 202. This conductive layer 301 is a highly transparent layer and can be made of organic materials (such as nano-silver, C60, PEDOT, etc.) or inorganic materials (such as ITO, IGZO, etc.), including but not limited to these. The function of this conductive layer is to provide the base electrode layer for the electronic ink layer 103, enabling the electronic ink to form a display effect through voltage driving in subsequent module products. The conductive layer 301 can be completed by a coating process, reducing production costs.

[0056] (3) Fabrication of color filter layer: such as Figure 7 As shown.

[0057] 1) A color filter layer is fabricated on the conductive layer 301. This color filter layer is used to enable the electronic ink to have a color display effect. This color photoresist is a negative photoresist that can be patterned by photoluminescence development process. The maximum process temperature is 150°C. This photoresist material can be PMMA, Epoxy, Acrylic, etc., including but not limited to these.

[0058] Using photolithography can improve the yield and resolution of colorization. The color filter layer and electronic ink layer are only the thickness of an adhesive layer, enhancing color effects and viewing angles.

[0059] 2) The color pixels 401, 402, and 403 formed by the color photoresist are the three primary colors of red, green, and blue. Their arrangement is a regular arrangement, such as green, red, blue, green, red, blue, etc. The arrangement includes but is not limited to this.

[0060] This completes the fabrication of the substrate with transparent conductive electrodes, which includes a color filter layer and a moisture barrier layer. The color filter layer of this invention is fabricated on the moisture barrier layer 202 and the conductive layer 301. This method reduces the reduction in color brightness caused by film thickness or multilayer structures, and minimizes the impact of reflection and scattering characteristics on the viewing angle and color saturation of the final product.

[0061] To reduce the effects of total internal reflection and scattering, the distance between the color filter layer and the electronic ink layer needs to be reduced. The method of this invention not only eliminates this physical phenomenon (reduced distance, requiring only a micrometer-thick adhesive layer), but also incorporates a moisture barrier layer for colorization, preventing color and brightness loss caused by the stacking of different functional films. It also realizes a roll-to-roll color electronic paper manufacturing process, enabling mass production, high yield, and a price advantage. In contrast, traditional inkjet printing, for example, requires 4 million pixel electrodes for a 10-inch display screen. Its yield and production speed are significantly different from roll-to-roll, making mass production, high yield, and price competitiveness difficult.

[0062] 3. Through a bonding process, the upper and lower roll substrates are bonded together to complete the production of a roll-to-roll colored electronic paper.

[0063] The color electronic paper assembly process is completed by bonding (hot pressing or room temperature), which reduces production costs and improves production efficiency.

[0064] In summary, this invention takes into account the susceptibility of organic materials such as electronic paper to moisture and the reflective and scattering characteristics of reflective display media, as well as the feasibility of the material properties in terms of process implementation. The proposed method for manufacturing colored electronic paper with a waterproof and vapor-barrier layer is produced using a roll-to-roll process, which features high production speed, high output, high efficiency, low mass production cost, and easy large-scale production.

[0065] The manufacturing processes, methods, and accompanying drawings described above are merely illustrative of common embodiments of the present invention. Various additions, modifications, and substitutions may be made without departing from the spirit and scope of the invention as defined in the claims. In practical applications, the present invention may vary in form, structure, layout, components, and other aspects according to specific environments and working requirements, without departing from the inventive principles. Therefore, the embodiments disclosed herein are for illustrative purposes only and not for limitation, and are not limited to the preceding description.

Claims

1. A method for manufacturing a color electronic paper, characterized by, The method comprises the following steps: Step 1: making a lower roll substrate A lower flexible substrate (101) with a release layer is used as a base material, a lower glue layer (102) is coated on the lower flexible substrate (101), an electronic ink layer (103) is made on the lower glue layer (102), and an upper glue layer (104) is made on the electronic ink layer (103); the electronic ink layer (103) is a suspension mixed liquid containing black and white nanoparticles or capsules; Step 2: making an upper roll substrate Step 2.1: making a water vapor barrier layer: using the upper flexible substrate (201) as a base material, a transparent water vapor barrier layer (202) is made on the upper flexible substrate (201); Step 2.2: making a conductive layer: a transparent conductive layer (301) is made on the water vapor barrier layer (202); Step 2.3: making a color filter layer: a color filter layer is made on the conductive layer (301), and the color pixels (401, 402, 403) formed by the color filter layer are red, green, and blue primary colors; Step 3: making the upper glue layer (104) by a lamination process to complete the lamination of the upper roll substrate and the lower roll substrate.

2. The method of manufacturing color electronic paper according to claim 1, wherein The upper glue layer (104) is a transparent organic material, which is OCA, PU, PI, PMMA, Epoxy or Acrylic.

3. The method of claim 1, wherein The upper flexible substrate (201) is a transparent material with a light transmittance of ≧85%, which is CPI, TAC, PEN, PET or Hybrid glass.

4. The method of claim 1, wherein The water vapor barrier layer (202) is a transparent layer with a light transmittance of ≧85%, which is an inorganic material, an organic material or an inorganic-organic composite material, and is completed by a plating or coating process.

5. The method of claim 1, wherein The color filter layer is a negative photoresist that can be patterned by yellow light development process, and the process temperature is at most 150℃, and the photoresist material is PMMA, Epoxy or Acrylic.

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