WO2004068203A1

WO2004068203A1 - Display screen using optical fiber sheet and method thereof

Info

Publication number: WO2004068203A1
Application number: PCT/KR2004/000152
Authority: WO
Inventors: Suckman Bae; Seongho Cho; Hosuk Song
Original assignee: Samyang Corp
Current assignee: Samyang Corp
Priority date: 2003-01-29
Filing date: 2004-01-29
Publication date: 2004-08-12
Anticipated expiration: 2005-07-29
Also published as: KR20040070033A; KR100548195B1

Abstract

Provided are a method of manufacturing a display screen having medium or large size capable of improving an image quality with fine pixels, implementing a low cost display screen with simplified processes, and implementing an easily movable and installable flexible screen, and a display screen manufactured by the same method. The display screen manufacturing method using an optical fiber sheet comprises: a first step of weaving an optical fiber sheet in a plain structure using warp and weft optical fibers; a second step of applying a coating agent on the optical fiber sheet; a third step of curing the coated optical fiber sheet and cutting the cured optical fiber sheet; and a fourth step of grinding the optical fiber sheet to expose a portion of protrusions of the optical fibers at intersections of the warp and weft optical fibers. In addition, the fifth step may be a step of attaching a protective film on a surface of ground optical fiber sheet can be applied.

Description

DISPLAY SCREEN USING OPTICAL FIBER SHEET AND METHOD THEREOF

TECHNICAL FIELD

The present invention relates to a display screen using an optical fiber sheet and a method of manufacturing the same, and more particularly, to a display screen using an optical fiber sheet and a method of manufacturing the same capable of improving image quality

BACKGROUND ART Display apparatuses are mainly classified into a CRT (cathode ray tube) display apparatus, a FPD (flat panel display) type apparatus, and a projection type display apparatus.

The CRT display apparatus has been used for a long time due to its high image quality and low price. However, the CRT display apparatus has a disadvantage in that it requires a large space for installation and has difficulty in being implemented with a large screen. Therefore, the CRT display apparatuses have been gradually replaced with the FPD type apparatuses. The FPD type apparatuses include LCD, PDP, OLED, FED, and so on. Each of the LCD, PDP, OLED, and FED has its own advantages and competitiveness in a specific field, and intensively competes with others.

The OLED has advantages of an excellent image quality and flexibility. However, since there are problems in luminescent materials and manufacturing processes, it is difficult for the OLED to be placed on the market. The LCD has advantages of an excellent image quality, a small space for installation, and low power consumption. However, the LCD has problems in viewing angle, response time, image quality for a large screen, and price. The PDP has advantages of an excellent image quality. However, the PDP has problems in power consumption and price. Although its large screen can be relatively easily made, it is difficult to adapt the PDP to an outdoor large screen. The projection type display apparatus has different durability and image quality depending on the material of the screen. A screen made of a semitransparent synthetic resin has been used for the conventional billboards have utilized. A white screen cloth has been used for a conventional theater screen. The synthetic resin screen has a problem in that it is difficult to move and install the screen due to its large volume. The screen containing plasticizers has a problem in that the screen may be easily damaged. In addition, since the screen cloth simply reflects or scatters rays of light projected from projector, the image quality of the screen cloth adapted for a large screen may be lowered.

Because of these problems, a display apparatus having a high image quality, a large screen size, a low power consumption, and various applications, and a method of simply manufacturing the display apparatus has not been developed.

SUMMARY OF THE INVENTION

In order to solve problems of a conventional rear projection type screen, an object of the present invention is to provide a method of manufacturing a display screen having medium or large size capable of improving an image quality with fine pixels, implementing a low cost display screen with simplified processes, and implementing an easily movable and installable flexible screen, and a display screen manufactured by the same method. According to an aspect of the present invention, there is provided a display screen manufacturing method using an optical fiber sheet, the method comprising: a first step of weaving an optical fiber sheet in a plain structure using warp and weft optical fibers; a second step of applying a coating agent on the optical fiber sheet; a third step of curing the coated optical fiber sheet and cutting the cured optical fiber sheet; and a fourth step of grinding the optical fiber sheet to expose a portion of protrusions of the optical fibers at intersections of the warp and weft optical fibers.

. Another aspect of the present invention, there is provided a display screen manufactured by using an optical sheet, wherein the optical sheet is manufactured by a method comprising steps of: weaving an optical fiber sheet in a plain structure using warp and weft optical fibers; applying a coating agent on the optical fiber sheet; curing the coated optical fiber sheet and cutting the cured optical fiber sheet; and grinding the optical fiber sheet to expose a portion of protrusions of the optical fibers at intersections of the warp and weft optical fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a flowchart illustrating a method of manufacturing a display screen using an optical fiber sheet according to the present invention;

FIG. 2a is a perspective view illustrating an embodiment of an optical fiber sheet according to the present invention;

FIG. 2b is a cross sectional view of the optical fiber sheet of FIG. 2a; FIG. 2c is a plan view of another embodiment of an optical fiber sheet according to present invention; FIG. 3 is a view illustrating processes of the method of FIG. 1 ;

FIG. 4 is a cross sectional view of the optical fiber sheet subjected to coating and cutting processes of FIG. 3;

FIG. 5 is a perspective view illustrating a grinding process performed on the optical fiber sheet of FIG. 4;

FIG. 6 is a perspective view of the optical fiber sheet subjected to the processes of FIG. 5;

FIG. 7 is a cross sectional view of the optical fiber sheet of FIG. 6

FIG. 8a is a perspective view illustrating a process for attaching a protective film on the optical fiber sheet of FIG. 7;

FIG. 8b is a cross sectional view of a display screen with the protected film attached to;

FIG. 9 is a view for explaining the operation of the display screen according to the present invention; and FIG. 10 is an exploded view of the display screen of FIG. 9.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the preferred embodiments according to the present invention will be described in details with reference to the accompanying drawings. FIG. 1 is a flowchart illustrating a method of manufacturing a display screen using an optical fiber sheet according to the present invention. Optical fibers used in the method have excellent transmittance and workability. The method may comprise: a first step of weaving an optical fiber sheet in a plain structure using warp and weft optical fibers; a second step of applying a coating agent on the optical fiber sheet extended to be flat; a third step of curing the coated optical fiber sheet by a UV curing method or a thermal curing process, and cutting the cured optical fiber sheet; and a fourth step of grinding the optical fiber sheet to expose a portion of protrusions of the optical fibers at intersections of the weft and warp optical fibers. In addition, the method may further comprise a fifth step of attaching a protective film on a surface of the ground optical fiber sheet. The steps are consecutively performed in an automatic manner.

As shown in FIGS. 2a and 2b, in the first step, an optical fiber 110 having a core 110a and a clad 110b coating the 110a is prepared. An optical fiber sheet is woven in a plain structure having the optical fibers 110 as the warp and weft yarns with a loom. For the purpose of mass production of the optical fiber sheet, the diameter of the optical fiber 110 is in a range of 0.01 to 3.00 mm, and more preferably, 0.10 to 2.00 mm. If the diameter of the optical fiber is below 0.10 mm, it is difficult to manufacture the optical fiber with plastic and to moving the weft yarns 130a with a gripper of the loom. If the diameter of the optical fiber is above 3.00 mm, it is difficult to perform a weaving operation using the thick warp and weft yarns 130b and 130a. On the other hand, a preferred weaving density of the warp and weft yarns is in a range of 10 to 50 line/inch. If the weaving density is below 10 line/inch, the optical fiber sheet cannot exhibit sufficient brightness and image quality due to its coarseness. If the weaving density is above 50 line/inch, it is difficult to perform a weaving operation due to its denseness.

On the other hand, as shown in FIG. 2c, the optical fiber sheet 130 may be woven in a modified plain structure using 2 to 5 lines of the warp/weft yarns 130b and 130a of the optical fibers 110 having a diameter of 0.01 to 3.00 mm, so that sizes of pixels can be adjusted. As a result, light loss of the optical fiber sheet 130 is prevented, and the optical fiber sheet can be used for a medium or large sized display screen.

In the second step, a coating agent 160 is applied on the optical fiber sheet 130 extended to be flat. As shown in FIG. 3, the optical fiber sheet 130 woven in the loom 280 proceeds to a coating chamber 290. In the coating chamber 290, the optical fiber sheet extended to be flat with tension beams 270 is immersed into the coating agent 160. The coating agent is transparent. Examples of the coating agent include acryl, epoxy, and EVA (ethylene vinyl acetate) resins. The coating agent is a resin cured at a temperature of 23 to 75 °C, which is lower than a glass transition temperature of an optical fiber, and more preferably at a temperature of 35 to 70 °C. The epoxy resin out of the coating agent 160 is made by mixing polyamine containing a curing material and a curing promoter and tertiary amine. The curing time is inversely proportional to the curing temperature. If the curing temperature of the coating agent 160 were below 23 °C, the curing time would be longer than 5 hours, so that it is difficult to perform consecutive processes. If the curing temperature of the coating agent 160 were above 75 °C, PMMA as a transformer of light would deform minutely due to the heat with tension, so that optical property such as index of reflection may change. Therefore, displayed image is distorted. The coating agent 160 is preferably selected from a product having a curing time of 1.5 to 3 hours in order to reduce process time. Examples of the product include the aforementioned epoxy resin.

In addition, coal tar or carbon black may be added to the coating agent 160 in order to induce so-called "black mark effect." In the second step, since the coating is performed in a state where the optical fiber sheet is extend to be flat with the tension beams 270, the interval between the warp and weft yarns 130b and 130a and the height of protrusions thereof (140 of FIG. 7) can be maintained constant. The thickness of the coated layer is three to six times the diameter of the optical fiber. For example, the coating layer having a thickness of 3 to 6 mm is formed on the optical fiber sheet woven with an optical fiber having a diameter of 1 mm. If the thickness of the coated layer is lower than three times the diameter of the optical fiber, the optical fiber 110 may be not completely immersed with the coating agent, so that a predetermined flatness cannot be maintained during the later-described grinding step. If the thickness of the coated layer is larger than six times the diameter of the optical fiber, heat and dust may occur and process time may increase during the later-described grinding step. In addition, the thickness of the coated layer is dependent on the installation space of the optical fiber sheet. For example, in case of a larger screen, the thickness of the coated layer has to increase in order to ensure dimensional stability of the overall screen. On the other hand, in case of a small sized screen, the thickness of the coated layer may be smaller than that in the large screen since it can ensure dimensional stability of the overall screen. In addition, the thickness of the coated layer is closely associated with the arrangement of the pixels and uniformity of the area generated in the later-described grinding step. [Examples of Coating agents]

The coating agent used in the present invention will be compared with conventional epoxy coating agents A, B, and C in terms of curing conditions. Table 1 shows the results of the comparison. The coating agent used in the present invention is an epoxy resin made by mixing polyamine containing a curing material and a curing promoter and tertiary amine. The coating agent A, B, and C are epoxy products obtained from a foreign company S, a foreign company B, and a domestic company O, respectively. The coating agents A, B, and C are not suitable for the present invention since their curing temperatures are above 110 °C, that is, a glass transition temperature of poly methyl methacrylate used as a material for the core of the optical fiber. In addition, since it has too long curing time, the curing agent C is not suitable for a coating process in consecutive processes. The coating agent of the present invention is most suitable for a coating process in consecutive processes in terms of the curing temperature and time. [Table 1]

* Weight Scale of Coating Agents: 100 g

In the third step, the coated optical fiber sheet 300 is subjected to a curing process and a cutting process. The curing process after the coating process may be a combination of the UV and thermal curing processes or only a thermal curing process. In FIG. 3, the UV and thermal curing process are performed by a UV illuminator 210 and a heater 220, respectively. In case of using the combination of the UV and thermal curing processes, the UV curing time is in a range of 3 to 5 minutes, and the thermal curing time is in a range of 3 to 5 minutes. In case of using only the thermal curing process, the curing time is in a range of 5 to 8 minutes in order to maintain suitable curing properties and optimal process speed. The curing temperature obtained the heater is set to 50 to 70 °C. During the curing time, the roller continues to rotate and the whole system does not stop. The curing process is performed during the optical fiber sheet passes though the chamber. In case of the UV curing process, the suitable curing time is in a range of 3 to 5 minutes. If the curing time is shorter than 3 minutes, an appropriate dimension of the optical fiber sheet cannot be stably obtained. If the curing time is longer than 5 minutes, the curing degree of the optical fiber sheet does not substantially increase, so that the curing time shorter than 5 minutes is appropriate. In case of the thermal curing process with the UV curing process being previously performed, if the curing time is shorter than 3 minutes, a complete curing of the optical fiber sheet cannot be obtained. If the curing time is longer than 5 minutes, the curing degree of the optical fiber sheet does not substantially increase, so that the curing time shorter than 5 minutes is appropriate. Even in case of using only the thermal curing process, the optimal curing time is in a range of 5 to 8 minutes for the same reason. As shown in FIG. 3, the cured optical fiber sheet 300 is cut in a predetermined size with a cutter 340. The cutting process is performed with a diamond cutter in a wet cutting manner.

As shown in the cross sectional view of the optical fiber sheet 310 of FIG. 4, the weft optical fibers 130a intersect the warp optical fibers 130b, and the weft and warp optical fibers 130a and 130b are supported and protected by the cured coating agent 160. As described above, each of the weft and warp optical fibers 130a and 130b comprises the core 110a and the clad 110b.

In the fourth step, the grinding process is performed on the optical fiber sheet in order to expose top portions of protrusions of the optical fibers at the intersections of the weft and warp optical fibers. As shown in FIG. 5, after the cut optical fiber sheet is mounted on an upper surface of a lower base plate 360, the grinding process is performed on the upper surface of the optical fiber sheet 310. The optical fiber sheet 310 is flatted and attached on the base 360 by vacuum, so that it can be supported and expended uniformly. The grinding process is a wet grinding process using a diamond grinder. The grinding degree of the cladding layer is controlled by adjusting rotational speed, translational speed, height, etc., of a grinder 250 with a computer 260.

The grinding process is performed in order to expose the top portions of the protrusions (140 of FIG. 7) of the optical fiber. More specifically, the grinding process is performed up to such a depth that only a cladding layer 110b or the cladding layer and a portion of core 110a can be ground and removed. As a result, light passing through the core 110a can emit from the ground portions of the optical fiber. On the other hand, the grinding process is performed on the back surface of the optical fiber sheet. As a result, the ground optical fiber sheet has a structure shown in FIG. 6. The ground portions of the cladding layer or the ground portions of the cladding layer and a portion of the core becomes a pixel 150 capable of emitting light. FIG. 7 illustrates the cross section of the optical fiber sheet of which front and back surfaces are subjected to the grinding process. In FIG. 7, light can enter and emit from the ground protrusions 140, that is, the pixels 150. More specifically, light entering a pixel 150 on the one surface emits from an adjacent pixel 150 of the other surface.

The fifth step is a step of attaching a protective film on a surface of the ground optical fiber. The fifth step is optional. As shown in FIGS. 8a and 8b, in order to improve viewing angle, a protective film 170a containing diffusion elements 230 is attached on the front surface of the optical fiber sheet 370 having the ground portions, that is, the pixels 150. In order to uniformly emit light, the diffusion elements 230 are uniformly distributed in the protective film 170a. The diffusion elements have a function of increasing the viewing angle, so that image can be seen at wide angles. The detailed description will be made in the following section Comparative Examples of Diffusion Elements. The protective film 170a has a function of protecting the optical fiber sheet 370 from external environment. The rays of light from the pixels 150 are scattered by the diffusion elements 230 in the protective film 170a, so that the viewing angle can increase. Transmittance of the protective film 170a is above about 85% in order to prevent unnecessary light loss. If the transmittance of the protective film 170a is below about 85%, the brightness of the display screen is lowered.

Another protective film 170b is attached on the back surface of the optical fiber sheet 370. The protective film 170b does not contain the diffusion elements 230. The material of the protective film 170b is the same as that of the protective film 170a. Rays of light entering the back surface of the optical fiber sheet 370 emit from the front surface of the optical fiber sheet 370. [Comparative Examples of Protective Film] The protective film used in the present invention will be compared with other protective films in terms of transmittance. Table 2 shows the results of measurement and comparison.

As shown in Table 2, the other protective films rather than the protective film of the present invention have so much loss at the wavelengths of blue light due to their absorption of materials and diffusion elements, so that the transmittance cannot be above 85%. The transmittance is measured with a hase/turbidity measuring system of Nippon Denshoku industries Model NDH-300A. [Table 2]

The commercial grade PMMA (Case A) has low transmittance of visible light due to non-reactive monomers and CO-O groups. The non-reactive monomers cause yellowing phenomena, and the CO-O groups cause the transmittance of blue light to be lowered. The optical grade PMMA (Case B) and the PMMA used in the present invention solve the problem of the general grade PMMA (Case A). Although the PC (Case C) has an acceptable transmittance, the PC shows yellowing phenomena and absorption of visible light due to aromatic ring. Therefore, it is difficult to fabricate a film having a high transmittance with the PC (Polycarbonate). [Comparative Examples of Diffusion Elements]

Changes of viewing angle in accordance with presence and absence of the diffusion elements are measured.

Table 3 show viewing angles are measured with Minolta CS-100A. A viewing angle is defined to be an angle between the center of the optical fiber sheet and a position at which brightness is half of that of the center. [Table 3]

The wider viewing angle of the display screen is, the more persons can see an image on the display screen. According to the present invention, since a wide viewing angle of the display screen is obtained by using the diffusion elements in the protective film, the display screen can be advantageously used for an outdoor screen through which a large number of persons can simultaneously see an image.

Now, the operation of the display screen using the optical fiber sheet manufactured by the above-described method will be described. As shown in FIG. 9, rays of light 180 projected from a projector 330 are incident on ground portions 450a of the optical fiber at a back surface of a display screen 400. The rays of light incident on the display screen 400 have an internal total reflection due to difference between reflective indices of the core and the clad so that the rays of light can propagate the optical fibers. As shown in FIG. 10, if the rays of light 190 propagating the optical fibers reach the ground portions 200 (the pixels 150 of FIG. 8b) where the core or the core and clad are exposed, the rays of light can not propagate the optical fiber but emit from the ground portions. Therefore, light 240 can emit from the front surface of the display screen 400. The rays of light 240 from the ground portions 200, that is, pixels, forms an image on the display screen.

In addition, according to the present invention, a pixel size and a pixel density can be adjusted depending on the number of the optical fibers and the weaving density of the optical fiber sheet. In addition, according to the present invention, since the optical fiber sheet is woven in a plain structure, it is possible to obtain uniform density of pixels over the display screen. In FIG. 10, since the rays of light 240 from the ground portions are scattered with the diffusion elements in the protective film, the emitting angle is wider than the incident angle, so that the viewing angle can increase. The diffusion elements 230 may or may not be added to the protective film in accordance with the usage of the display screen.

In addition, according to the present invention, the brightness of the display screen having large size can be improved by simply increasing the number of the projectors. Therefore, it is possible to implement various sizes of display screens with a simple process. [Experimental Example]

An experimental example of the optical fiber display screen manufactured according to the method of the present invention will be described.

In a first step of the experimental example, optical fiber sheets are woven by using plastic optical fibers having diameters of 0.25, 0.5, 0.75, and 1.0 mm as warp and weft yarns with a test loom. The warp and weft density are in a range of 20 x 20 to 50 x 50 line/inch. The weaving speed is 100 rpm. Each of the obtained optical fiber sheets has a length of 300 m and a width of 1 m with reference to the warp direction.

In a second step, the woven optical fiber sheet extended to be flat with tension beam is immersed red into a coating material. The thickness of the coated layer is three to six times the diameter of the optical fiber. A transparent resin such as acryl, epoxy, and EVA (ethylene vinyl acetate) resins is used for the coating agent. In a third step, the coated optical fiber sheet is cured in an UV chamber for three to five minutes. Consecutively, the optical fiber sheet is further cured by using heater at a temperature of 70 °C for three to five minutes. On the other hand, in another experimental example, only the heater is used. In this example that only the heating is used for curing, it is preferable to cure the optical fiber sheet for five to eight minutes.

In a fourth step, the cured optical fiber sheet is cut. The cut optical fiber sheet is mounted on a lower base plate in a vacuum suction method. The optical fiber sheet is ground with a grinder controlled by a computer in accordance with the programmed grinding depth, area, and time. As a result, the ground optical fiber sheet has ground portions of the clad or the clad and a portion of core.

In a fifth step, protective films are attached on both surfaces of the ground optical fiber sheet. The protective film containing diffusion elements is attached on the front surface of the optical fiber sheet. The protective film containing no diffusion elements is attached on the back surface of the optical fiber sheet. In some cases, the protective films containing no diffusion elements may be attached on both of the surfaces of the optical fiber sheet. PMMA or PC having a high transmittance is used for the protective film.

The differences of manufacturing for display between the experimental examples and the conventional method are as follows. [Comparison of Process]

The process for manufacturing the display apparatus using the optical fiber sheet is simpler than those of PDP, LCD, OLED display apparatuses. The comparison of the processes of manufacturing theses display apparatuses is shown in the following Table 4. As shown in Table 4, according to the present invention, since processes requiring high cost facilities such as an inorganic deposition process, a lithography process, a assembly process, and a packaging process are not used, production cost can be lowered. In addition, since complicated and high cost processes are not used, production cost can be further lowered. [Table 4]

Now, comparison of brightness between the optical fiber display screen manufactured according to the present invention and the conventional display screen will be described.

[Comparison of Brightness]

The following Table 5 show the comparison of brightness between the optical fiber display screen and other conventional display apparatus such as a conventional rear-projection type screen made of polycarbonate (hereinafter, referred to as a PC projection screen), a screen used for the PDP display apparatus, a screen used for the LCD display apparatus. The optical fiber display screen has a size of 49 inch (1 m x 0.75 m). The rear-projection type projector, a combination of two projectors of Sharp Model XG-P25X, is used. The PC projection screen is a commercial one, and the same rear-projection type projector is also used in the same condition. The brightness is measured with a luminance meter of Minolta model CS-100A. As shown in Table 5, the optical fiber display screen according to the present invention has much higher brightness than those of the screens used for the LCD and PDP display apparatus and the PC projection screen.

[Table 5]

[Comparison of Power Consumption with LED Display Board] The following Table 6 shows the comparison of power consumption between the optical fiber display screen and an LED display board. The optical fiber display screen and the used projector are the same as those of the aforementioned Comparative Example, so that the conditions and results of Comparative Example are used. The data of the LED display board is the information of a commercial RGB type product. Since the power consumption of the optical fiber display screen is involved in the only operation of the projector, the power consumption of the optical fiber display screen is calculated based on that of the projector. As shown in Table 5, the optical fiber display screen has lower power consumption by a factor of 3.85 than that of the LED display board. [Table 6]

The optical fiber display screen manufactured by the method according to the present invention has the following advantages. Since weaving, coating, cutting, grinding, protective-film attaching processes are simple, it is possible to reduce the production cost of the optical fiber display screen. Therefore, it is possible to manufacture a low cost medium or large size display apparatus. Since uniformly aligned fine pixels can be obtained by adjusting the weaving density and size, it is possible to effectively display an image projected from a projector (a light source).

In addition, it is possible to display an image having a high brightness without loss of light due to the excellent transparency of optical fiber. Since the optical fiber screen has no power consumption, it is possible to display various images with low power consumption. Therefore, the optical fiber display screen can be widely adapted for medium or large size display applications such as interior design applications, outdoor AD boards, various formative billboards, video AD vehicles, wide TV screens, etc.

Claims

WHAT IS CLAIMED IS:

1. A display screen manufacturing method using an optical fiber sheet, the method comprising: a first step of weaving an optical fiber sheet in a plain structure using warp and weft optical fibers; a second step of applying a coating agent on the optical fiber sheet; a third step of curing the coated optical fiber sheet and cutting the cured optical fiber sheet; and a fourth step of grinding the optical fiber sheet to expose a portion of protrusions of the optical fibers at intersections of the warp and weft optical fibers.

2. The method according to claim 1 , wherein the method further comprises a fifth step of attaching a protective film on a surface of the ground optical fiber sheet.

3. The method according to claim 2, wherein, in the fifth step, the protective film is attached on a front surface or front and rear surfaces of the ground optical fiber sheet.

4. The method according to claim 3, wherein the protective film attached on the front surface of the optical fiber sheet contains diffusion elements.

5. The method according to any one of claim 2 to 4, wherein the light transmittance of the protective film is 85% or more.

6. The method according to claim 1 , wherein the diameter of the optical fiber is in a range of 0.10 to 2.00 mm.

7. The method according to claim 1 , wherein the weaving density of the warp and weft optical fibers is in a range of 10 to 50 line/inch.

8. The method according to claim 1, wherein, in the first step, the optical fiber sheet is woven in a modified plain structure using 2 to 5 lines of the warp/weft optical fibers.

9. The method according to claim 1 , wherein the coating agent comprising coal tar or carbon black.

10. The method according to claim 1 , wherein, in the third step, the coated optical sheet is subjected to a UV curing process, and then, a thermal curing process.

11. The method according to claim 1 , wherein, in the third step, the coated optical sheet is subjected to a thermal curing process.

12. A display screen manufactured by using an optical sheet, wherein the optical sheet is manufactured by a method comprising steps of: weaving an optical fiber sheet in a plain structure using warp and weft optical fibers; applying a coating agent on the optical fiber sheet; curing the coated optical fiber sheet and cutting the cured optical fiber sheet; and grinding the optical fiber sheet to expose a portion of protrusions of the optical fibers at intersections of the warp and weft optical fibers.

13. The display screen according to claim 12, wherein a protective film attached on a surface of the ground optical fiber sheet.

14. The display screen according to claim 13, wherein the protective film is attached on a front surface or front and rear surfaces of the ground optical fiber sheet.

15. The display screen according to claim 14, wherein the protective film attached on the front surface of the optical fiber sheet contains diffusion elements.

16. The display screen according to claim 12, wherein the optical fiber sheet is woven in a modified plain structure using 2 to 5 lines of the warp/weft optical fibers

17. The display screen according to claim 12, wherein the coating agent comprising coal tar or carbon black.

18. The display screen according to claim 12, wherein the diameter of the optical fiber is in a range of 0.10 to 2.00 mm.

19. The display screen according to claim 12, wherein the weaving density of the warp and weft optical fibers is in a range of 10 to 50 line/inch.