KR20080090781A - Electronic display paper made with cellulose - Google Patents

Abstract

An electronic paper display is provided to produce an environment-friendly electronic paper display device such as flexible paper, by forming a cell structure of cellulose, sealing the cell structure with cellulose, and forming transparent electrodes on upper and lower surfaces of the cell structure. A cell structure of micro unit is formed in flexible cellulose plate type materials. Transparent electrodes(3,4) are formed above and below the cell structure. Organic luminous bodies(2-1,2-2,2-3) or an electro-phoretic dispersion liquid is injected between the transparent electrodes. The lower transparent electrode is formed on a lower surface of the cell structure before the organic luminous bodies are injected into the cell structure. The injected organic luminous bodies are sealed by an upper portion of the cellulose materials and a sealing layer(5), and then the upper transparent electrode is formed on an upper surface of the cell structure. The upper and lower transparent electrodes are coated with cellulose surface layers(6,7), respectively.

Description

Electronic Display Paper Made with Cellulose}

1 is an exemplary view showing an embodiment of a general configuration of a unit portion of an electronic display paper according to the present invention;

2 is an exemplary view showing another embodiment of the present invention;

3 is an exemplary view showing another embodiment of the present invention, and

Figure 4 is a process diagram showing an embodiment in which the cell structure according to the present invention is made.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic paper (E-Paper) of low cost, which is a flexible, lightweight display device made of cellulose.

Electronic paper is a digital paper having the best visual characteristics among display media. E-paper, which can be easily rolled up like ordinary paper, is considered the next generation of flat panel displays such as PDPs and LCDs. Electronic paper is the foundation technology required by the ubiquitous computing era where information can be accessed anytime and anywhere, and general paper can replace printed materials and conventional display devices, and it will soon be as portable as paper. Electronic paper has a high resolution, a wide viewing angle, a bright background like conventional paper printing, and does not need a backlight like LCD, so the battery life is long, cost reduction and light weight.

BACKGROUND ART [0002] Conventional electronic papers generally use various principles such as flexible LCDs, organic light emitting diodes (OLEDs), and electrophoresis. OLED has the advantages of wide viewing angle, ultra-fast response, and self-luminous, so it is suitable for any moving picture display medium from small to large, and it does not need a backlight, and thus has a small consumption strategy and a light weight. In addition, the manufacturing process is simple, which can lower the manufacturing cost. Currently, according to the development trend of electronic paper, IBM, Sarnoff, UDC, E-ink, Bell Lab, Palo Alto Research Center, etc. in the US are conducting the overall research of electronic paper using flexible LCD, OLED, and microcapsules. have. In Japan, Hitachi, Sony, AIST, and Seiko-Epson are conducting research on OTFTs, polysilicon TFTs, and OLEDs. In addition, Gyricon's Gyricon display using twisted ball, Neolux and Kent's cholesterol liquid crystal display using electrophoresis, electrowetting display of Philips, electronic paper using Iridigm's MEMS technology, LPD's LPD in Korea, Samsung Electronics, Samsung SDI, LG Electronics, SoftPixel, i-Components, ETRI, KETI, and various universities are studying electronic paper and LPD using flexible LCD, OLED, and electrophoresis. Xerox's rudimentary implementation of electronic paper in 1975 and Immedia ^{TM in} 1999 by E-ink Although many prototypes have been introduced since the launch of the product, most of the electronic papers developed so far use glass for cell structures, substrates, etc., and thus are inflexible, which necessitates the use of plastic substrates. However, for this purpose, the problem of forming a transparent electrode on the plastic substrate and gas barrier property of the substrate should be solved. On the other hand, Sony and Seiko-Epson have developed displays with polycrystalline silicon TFTs having very excellent properties on polymer substrates based on excellent polycrystalline silicon fabrication and transfer techniques. However, such plastic substrates are more flexible than glass substrates, but cause environmental pollution because they do not rot when discarded. As an electronic paper that does not cause environmental pollution, the University of Texas at Austin attempted to change the color by coating a dye on cellulose, but this has the disadvantage of slow response time and complicated manufacturing process.

The present invention relates to the production of electronic paper using cell structures or substrates from biodegradable cellulose without using glass having low flexibility or plastic with environmental pollution. The substrate of the electronic paper is a structural material for supporting the electronic paper, which has a great influence on flexibility, but it is preferable not to cause environmental pollution during disposal. Plastic films are not biodegradable and thus become environmental waste, and there is a difficulty in printing for forming transparent electrodes. In contrast, cellulose is a main component of paper, which is flexible, structurally tough, easy to form a thin film, and inexpensive. In particular, it is biodegradable and does not cause environmental problems since it decays upon disposal.

If the electronic paper is to be made of cellulose, it is necessary to be able to make a display cell structure in micro units, which is a basic element of the electronic paper. Accordingly, the present invention discloses the concept and manufacturing method of an electronic paper made of cellulose.

A general structural embodiment of the present invention for an electronic display paper made of cellulose is shown in FIG. 1. The microstructure cell structure 1 is made of a flexible cellulose plate-like material, and the transparent electrodes 3 and 4 are mounted on the upper and lower portions of the cell structure 1, respectively, and then the organic material is formed between the two electrodes 3 and 4. Inject light emitter or electrophoretic dispersions (2-1, 2-2, 2-3). Before injecting the organic light emitting bodies 2-1, 2-2, 2-3, the lower transparent electrode 4 is installed on the lower surface of the cellulose cell structure 1 having the partition walls, and the organic light emitting body is injected into the cell. The organic light emitting body is encapsulated again with the upper sealing layer 5 of cellulose, and then the upper transparent electrode 3 is installed. On the upper and lower electrodes 3, 4 again, by coating the skin layers 6, 7 of cellulose, a transparent display element can be made of cellulose paper.

On the upper and lower portions of the organic light emitters 2-1, 2-2, and 2-3, an electron transport layer (ETL), a hole transport layer (HTL), and a hole injection layer (ETL) are formed as in general OLED technology. When a voltage is applied by stacking a hole injection layer (HIL) or the like, electrons and holes are injected into the organic light emitting body from the cathode and the anode, respectively, and light is generated through the electron-hole recombination process in the light emitting body. The OLED may be made of a single layer structure in which one organic material layer is sandwiched between two electrodes, and an electron transport layer, a hole transport layer, and a hole injection layer may be stacked on the upper and lower portions of the light emitter to further activate charge injection. . As the organic layer of the OLED, low molecular weight and high molecular materials may be used, and both fluorescent and phosphorescent methods may be used. In addition, a passive matrix and an active matrix may be used as the driving method of the OLED. The passive type has a simple structure in which an organic material layer is inserted between the anode wiring and the cathode wiring. The power consumption is relatively high, but the manufacturing cost is low. On the other hand, in the active type, TFTs are attached to each pixel, so that power consumption is small and image quality such as resolution is excellent, but manufacturing cost is high.

On the other hand, when the microcapsule of the electrophoresis method is filled in the cellulose cell structure 1, it is possible to produce a reflective electronic paper in which the reflection of light varies according to the electric signal. Such a reflective electronic paper is capable of both black and white and color depending on the type of ink whose color changes with electrophoresis.

The cellulose cell structure 1 is tens or hundreds of microns in size, making it difficult to produce the same cell structure on a large area of cellulose paper or film. In particular, when cellulose is dissolved in a solution and then made into a paper or film form, the shrinkage and expansion is large. Accordingly, the present invention discloses a method for producing a cell structure on a cellulose paper by using micro-molding. In this case, the cellulose may use a mixed solution in which cellulose fibers are dissolved using a DMAc (N, N-dimethylacetamide) solvent, or cellulose acetate may be used. Figure 4 shows an example of the micro-molding method, showing a process of making a cell structure using a solution of cellulose fibers dissolved in DMAc solvent. The cellulose solution is coated onto the silicon wafer 12 on which the cell structure has already been formed. The coated cellulose film 11 is heated with a silicon wafer 12 in an oven for a predetermined temperature and time, and then washed and dried to form a cellulose paper having a cell structure.

The dried cellulose film has a micro cell structure, and indium tin oxide (ITO) is coated on the lower surface where the cell is not formed and micro patterned to form a lower transparent electrode. The method of forming the OLED layer in the cell structure is widely used in low molecular materials such as thermal vacuum deposition, organic vapor phase deposition, and laser-induced thermal imaging , Wet Process, Ink Jet, Spin Coating, LITI, etc. are widely used in polymer materials. Recently, an inkjet method is used to form a light emitting layer of a large area, and an organic polymer dissolved in an aqueous solution is printed by inkjet only in a selected region of a cellulose cell structure in which partition walls are periodically formed. This method can form a light emitting layer in a selected area irrespective of the area, and is advantageous in terms of productivity because there is no damage to the material. In the color OLED, as shown in FIGS. 1 to 3, three light emitters, red (2-1), green (2-2), and blue (2-3), are sequentially filled with the cell structure, and the electrode 4 Form and then seal. The cell structure 1 may have various shapes such as square, rectangular, circular, hexagonal, and the like, and the depth of the cell is sufficiently buried in the light emitting body.

After formation of the emitter layer, the conductor layer is coated and micropatterned to make the upper electrode 3. Then, the outer layer is coated with a cellulose solution and sealed again. At this time, if the opaque coating with a conductor layer such as gold, aluminum, platinum, etc., the light emitted from the light emitting layer goes out only to the lower layer, which becomes an electronic paper which can see light only in one direction. On the other hand, when the upper electrode is made of a transparent electrode such as ITO, it becomes a transmissive OLED electronic paper that can be seen in both directions. Since cellulose has the best light transmittance in the visible range, it is possible to make a transmissive electronic paper. In addition, microlens arrays 8-1 and 8-2 may be provided as shown in Figs. In this embodiment, FIG. 2 shows a state in which the micro lens arrays 8-1 are provided only in the lower portion, and FIG. 3 shows a state in which the micro lens arrays 8-1 and 8-2 are provided in both the upper and lower portions. .

As described above, a cell structure is made of cellulose, and an OLED light emitting layer or an electrophoretic ink layer is installed on the cell structure thus formed, sealed with cellulose, and transparent electrodes are installed on upper and lower surfaces to make an eco-friendly electronic paper such as a flexible paper. Can be. Due to the biodegradability of cellulose, it is harmless to human body without causing environmental pollution problem at the time of disposal. In addition, there is an effect that the manufacturing cost for this.

Claims (7)

In an electronic display paper consisting of a cell structure (1), a luminous body or electrophoretic dispersion (2), an upper transparent electrode (3), a lower transparent electrode (4), an upper sealing layer (5) and a skin layer (6, 7), Electronic display paper in which at least one of the cell structure 1, the sealing layer 5 and the skin layers 6, 7 is made of cellulose. The electronic display paper according to claim 1, wherein the light emitting body (2) is injected into the cellulose cell structure (1), sealed with a natural transparent material of cellulose, and the transparent electrodes (3, 4) are installed on the upper and lower surfaces to display in both directions. . The electronic display according to claim 1, wherein the light emitting body (2) is injected into the cellulose cell structure (1) and sealed with a natural transparent material of cellulose, and then the transparent electrode (3) is installed on only one side to display the display in only one direction. paper. The electronic display paper according to claim 1, injected with ink that selectively reflects light when an electric field is applied instead of the light emitter (2). The electronic display paper according to claim 1, wherein black and white or color emitters or inks are injected so that black and white and color colors are selectively expressed. The electronic display paper as set forth in claim 1, wherein operation of the pixel corresponding to the cell is performed in a passive or active manner. The electronic display paper according to any one of the preceding claims, wherein a microlens array (8) is provided on the surface of the display to improve color mixing and sharpness of light.

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