JP2013020923A - Light guide plate with light scattering element of intaglio-in-intaglio structure, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate that can greatly improve optical output efficiency, luminance uniformity, viewing angle, and softness of output light, and its manufacturing method.SOLUTION: One side face of an acrylic plate material is primarily processed by blasting sand particles of a larger size (for example, 30-80 mesh) by a first blasting device, then, it is secondarily processed by blasting sand particles of a smaller size (for example, 120-250 mesh) than the size of the sand particles used in the primary processing, on the processing surface of the acrylic plate material primarily processed by a second blasting device. A part of the formed secondary intaglio is positioned inside the intaglio formed by the primary processing and forms a multiple intaglio structure of an intaglio-in-intaglio, and the remainder is formed on the smooth surface at the outside of the intaglio. The primary and the secondary processings are carried out so that distribution density of pixels (intaglios) may be relatively higher as they are away from the side face where the light source is arranged, and the primary processing and the secondary processing are carried out so that they may form the pixels (intaglios) bearing about 20-40% and 60-80%, respectively, of the total brightness of the light guide plate output light. As the case may be, one more sand blasting processing may be carried out with the sand particles of a further smaller size (for example, 300-400 mesh). The light guide plate processed by this multiple processing method has a wider spread angle of light of around 130-170° output on the upper side of the light guide plate, is improved by about 20% in optical output efficiency, and has a luminance uniformity on the surface of the light guide plate of 93% or more, as compared with a conventional one processed by one-time processing using a single size.

Description

  The present invention relates to a light guide plate and a method of manufacturing the same, and more particularly, a light scattering characteristic is obtained by multiplexing a fine indentation structure formed as a light scattering element of a light guide plate used in a backlight of a large monitor, an advertising billboard or the like. The present invention relates to an improved light guide plate and a manufacturing method for processing such a light guide plate.

  Backlight units are used for LCD monitors or large advertising signs. The backlight unit includes a light guide plate, which guides incident light from the light source to the upper surface to be emitted. A light scattering element for guiding incident light to the upper surface is provided on the lower surface of the light guide plate. For example, in an edge-type backlight device, light from a light source that has flowed into and moved into which side of the light guide plate (all of the light guide plate upper surface and external boundary surface or the lower surface and external boundary surface in the forward process) If the light enters the light scattering element on the lower surface, the light is scattered irregularly in many directions at an angle different from the incident angle. A part of the scattered light is incident on the upper boundary surface at an angle smaller than the critical angle, and comes out of the upper surface, but the light is just output light from the light guide plate.

  Typical types of light scattering elements known so far include dot ink printed on the lower surface of the light guide plate, V-shaped grooves dug out by a cutter on the bottom surface, and sand blasting or mold process on the bottom surface. And fine indentations (grooves). The present inventor forms an unlimited number of fine indentations as light scattering elements on the lower surface of the light guide plate using a sandblasting method through Korean Patent Publication Nos. 10-2003-0079659 and 10-2003-0079749. Have disclosed technology.

  In these conventional techniques, sand particles are strongly jetted onto one side surface of the light guide plate by an jetting device so that the surface is crushed by the colliding sand particles. The method of forming is presented. FIG. 1 is a gradation pattern in which sand particles 12 are sprayed onto a transparent acrylic plate material 40, which is a material of a light guide plate, using the typical jetting device 10 proposed by the above-described prior art, and an unlimited number of fine indentations are formed on the acrylic plate material 40. FIG. 2 is a photograph of the acrylic plate material 40 processed in such a manner. The injection pipe 20 is located on the surface of the acrylic plate 40 placed on the conveyor belt 30, and the second blower 18 and the first blower 16 are sequentially connected to the inlet of the injection pipe 20. Sand particles in the sand container 14 are transmitted to the second blower 18 by the first blower 16 while freely falling, and are strongly ejected by the wind of the second blower 18 and to the outlet side of the injection pipe 20. In the process, the sand particles spread in the form of the internal space of the injection tube 20 and collide with the acrylic plate 40. The distribution density of the colliding sand particles gradually decreases from the inside of the injection tube 20 toward both ends. Due to the collision, the surface of the acrylic plate member 40 is crushed and an extremely large number of fine indentations are formed to constitute a light scattering element.

  In order to improve the luminance uniformity of the output light, as shown in FIG. 3, it is necessary to gradually increase the distribution density of fine inscriptions (displayed as dots in the drawing) according to the distance from the light source ( 3 (a) shows a case where a light source is arranged on the left side, and FIG. 3 (b) shows a case where a light source is arranged on both the left and right sides. The particles are also preferably jetted so as to have a density distribution in the form of a fine indentation. This injection device 10 satisfies such a requirement by adopting a configuration in which the injection tube 20 is a fan-shaped flat tube, and the shape of the outlet of the tube is wide and narrows toward both ends.

  However, in the above prior art, the size of the sand particles used is one. FIG. 4 conceptually shows two-dimensional (2D) and three-dimensional (3D) shapes of the fine indentation 50 formed when single-size sand particles are jetted onto the surface of the light guide plate 40. Individual fine indentations 50 are formed by surface crushing due to the impact of one or several sand particles. However, when sprayed with a single size of sand particles, the indentation 50 formed as shown in the figure is generally simple in shape, and the inner surface is smoother and rough with many grooves and bends. It is difficult to obtain a surface. The inclination angle of the fine indentation 50 is also somewhat steep (compared to the present invention described later).

  The form of light scattering depends on the surface state of the fine indentation that is the light scattering element. FIG. 5 is a graph showing the result of measuring the spread angle of the output light of the light guide plate in which fine indentations are formed with single-size sand particles according to the conventional technique. According to this, the measured divergence angle did not exceed approximately 120 degrees. When the light guide plate is used as a surface light source, its irradiation area is limited to its spread angle. As a result, the amount of light output from the light guide plate is also so limited. Moreover, when using a light-guide plate for the backlight of an advertising film, the viewing angle of an advertising signboard is also limited to the spread angle. When considering such aspects, the larger the spread angle of the output light, the better. However, in this respect, the light guide plate according to the prior art has room for improvement.

  The size of the light scattering angle by the light scattering element and the moving distance of the light within the light guide plate (that is, the actual traveling distance of light from the side surface on which the light source is disposed to the opposite side surface) are inversely proportional. As described above, the light incident through one side surface of the light guide plate 40 is totally reflected by the upper boundary surface and the lower boundary surface of the light guide plate and travels to the opposite side surface. Scattered. Light components having a light scattering angle that is not large are not allowed to escape to the upper surface of the light guide plate 40, and are continuously advanced in a zigzag shape on the opposite side of the light source while repeating total reflection at the upper and lower boundary surfaces. The mileage becomes longer. As a result, the intensity of the light becomes so weak that the luminance in a region far from the light source is remarkably lowered. Recently, a light guide plate used for a backlight of an outdoor advertising billboard has started to be used in a large size with a horizontal and vertical length of 1 to several meters. In the case of such a large light guide plate, the actual travel distance of light becomes longer until it is meshed with the light scattering characteristics of fine intaglio and output to the upper surface of the light guide plate 40, so that the distance from the light source to the farthest distance region is increased. The intensity of the light that arrives is greatly reduced, and the luminance of the area is relatively lowered. This not only lowers the light output efficiency, but also reduces the overall luminance uniformity of the light guide plate.

  There are other problems. The output light of the light guide plate is a part of the light scattered from the fine indentation. At such a point, each fine indentation can be viewed as one pixel. According to the conventional processing method, in order to contribute to the light output that the indentation functions as a pixel, and to obtain the desired light output efficiency in the entire light guide plate, the size of the sand particles is more than a certain size. As a result, the size of the intaglio (pixel) was relatively large. If the light from the light source is incident on the light guide plate, the intaglio (pixel) portion looks very bright, while the area where no indentation is formed (non-pixel portion) looks relatively dark. However, the size of the intaglio (pixel) is so large that the output light appears to be hardened and is not soft, and a rough light atmosphere can be felt. FIG. 6 is an enlarged photograph of the surface of the light guide plate processed by the conventional processing method. This point can also be confirmed in this photograph. There is a need to improve the quality of the output light.

  As described above, if a single-size sand particle is injected to form a finely inscribed light scattering element on the surface of the light guide plate, the shape of the pixel (ie, individual finely inscribed) is generally simple, and A three-dimensional structure with gentle corners and a relatively low internal surface roughness. Such a form of pixel cannot scatter incident light over a relatively wide angular range. Therefore, the light divergence angle of the output light coming out through the upper surface of the light guide plate does not exceed 120 degrees. In addition, such a pixel structure makes the traveling distance of light longer inside the light guide plate. For a light guide plate of a certain size or more, where light must reach far, the light output efficiency is low, and the brightness uniformity of the entire light guide plate drops sharply. When arranged on one side of the light plate, the region near the opposite side, and when arranged on the two opposite sides, the central region of the light guide plate corresponds to this relatively darker.

  The present invention aims to improve the disadvantages of the prior art as described above. Specifically, a light-scattering element having a groove-in-groove structure is formed on the surface of the light guide plate, which can scatter incident light far more effectively than before and can scatter at various angles. Can improve the light output efficiency, luminance uniformity, viewing angle (irradiation angle), and softness of the output light of the light guide plate, and a light guide plate manufacturing method for processing the same The purpose is to provide.

  According to one aspect of the present invention for achieving the above object, there are many light guide plates processed with a transparent acrylic plate material that are difficult to identify with the naked eye on one side surface of the plate material. Are formed as a light scattering element, and at least a part of the second incline is an inner surface of at least a part of the first incline. Accordingly, at least a part of the first intaglio is a multiple intaglio structure of intaglio-inner-indentation, and the light guide plate is provided.

  The first intaglio and the second intaglio are formed by a sandblasting process using first size sand particles and second size second sand particles smaller than the first size.

  The surface roughness of one side of the acrylic plate material, the distribution density (number) of the second inscriptions located on the inner surface of the first inscription, which is a multiple inscription structure of the inscription-inner-inscription form, the first inscription (above And the one side surface of the acrylic plate material of the second inscription formed on the outside of the first inscription. Occupying area per unit area, and the average diameter and the maximum depth of the first indentation and the second inscription existing within the unit area are as follows: (a) From any one side of the acrylic plate The more it goes to the opposite side, or (b) the more it goes from the two opposite sides into the two sides.

  The maximum light spread angle of the output light output to the upper surface of the light guide plate is about 130-170 degrees due to the first indentation having a multiple indentation structure of the inscription-inner-inscription form in which the second inscription is formed on the inner surface. Become.

  The first indentation and the second inscription act as a light scattering element that scatters light flowing through any one side surface or both opposite side surfaces of the plate material and outputs the scattered light to the upper surface of the plate material. It is preferable that the contribution ratio of the first negative scattering and the second negative scattering is 20-40% versus 60-80% with respect to the output light output on the upper surface of the light guide plate.

  On the other hand, according to another aspect of the present invention for achieving the above object, the first injection device for injecting large size (first size) sand particles and the small size (second size) sand particles are injected. The second injection device is provided, and one side surface of the acrylic plate material is first processed by first injecting sand particles having a large size (preferably 30-80 mesh) onto the first injection device. As the injected sand particles collide with the surface of the acrylic plate material, an infinitely large number of first indentations are formed while the surface is crushed.

  The primary processing is such that the farther away from the side surface on which the light source is disposed (if the light source is disposed on one side surface of the light guide plate, the closer to the side surface on the opposite side of the side surface, the more the light source faces the light guide plate). If it is arranged on the two side surfaces, it is an injection condition for relatively increasing the intaglio (pixel) distribution density as it goes to the region in the two side surfaces, and it is 20% of the overall brightness of the light output from the light guide plate. Processing is performed so that an indentation of about −40% is formed.

  Next, sand particles having a second size (preferably 120-250 mesh) smaller than the size of the sand particles used during the primary processing are jetted onto the processed surface of the acrylic plate material that has been primary processed by the secondary injection device. Then, secondary processing is performed. As a result, a large number of second indentations having a size smaller than the first inscription are formed on at least a part of the inner surface of the first inscription and the outer surface of the first inscription.

  When the density ratio between the nearest distance area and the farthest distance area is set to 1: N from the light source of the first indent processed by the first processing, the second indent of the second indent processed by the second processing is performed. It is preferable to perform the first and second processing so that the density ratio between the nearest distance area and the farthest distance area is 1: N / 3 to 1: N / 1.5.

  Further, the second processing is performed so that indentations (pixels) that bear about 60 to 80% of the overall brightness of the light output from the light guide plate are formed.

  Thus, in order to improve the disadvantages of the prior art, the present invention sequentially jets the plate material of the light guide plate using the large size sand particles and the small size sand particles. Then, a small size indentation is formed by secondary processing on the inner surface of the large size inscription formed by the primary processing (a so-called multiple inscription structure in the form of 'indentation-inner-inscription'). Of course, there may be a small size inscription alone or a large size inscription alone. Such a multiple intaglio structure allows light scattering at a wide angle. Accordingly, the incident light is output from the light guide plate through a relatively shorter run than in the past. As a result, the light output efficiency and luminance uniformity are improved. In addition, the maximum light divergence angle of the output light output on the upper surface of the light guide plate is widened to about 130-170 degrees due to the multiple indentation structure of intaglio-inner-intaglio form, and soft light dispersion is made wide. The side visibility according to the viewing angle is improved, and the photo blind spot area can be minimized.

  In such a light guide plate processing method, (a) the acrylic plate material as it goes from one side surface of the acrylic plate material to the opposite side surface, or (b) the two side surfaces facing each other into the two side surfaces. At least one of the number of sand particles of the first size and the number of sand particles of the second size that collide per unit area is gradually increased, while the number of sand particles that collide per unit area of the plate material is increased. It is preferable to inject the first and second size sand particles so that the incident angles of the first and second size sand particles gradually decrease.

  In some cases, the processing surface of the acrylic plate material can be sandblasted (third processing) once again by the third injection device. In this case, processing is performed by adjusting the wind strength and the sand particle density so that the desired maximum efficiency light guide plate condition is achieved with sand particles having a size smaller than the second size (preferably 300 to 400 mesh).

  Meanwhile, according to another aspect of the present invention, a method of manufacturing a light guide plate by processing the surface of a transparent acrylic plate material, wherein two or three different size sand particles are mixed in a container of an injection device The step of supplying to the container of the injection device, and (a) from one side of the acrylic plate to the side of the opposite side, or (b) from two opposite sides to the side of the two In order to gradually increase the number of sand particles that collide per unit area of the plate material, the mixed sand particles are sprayed onto one side surface of the plate material (sand-blasting) to form an unlimited number of indentations by surface crushing A plurality of indentations formed on the one side surface, wherein at least a part of the indentation-inner-indentation shape has a small size indentation formed on the inner surface of the large size inscription. A light guide plate manufacturing method is provided.

  The method of processing acrylic plate materials sequentially using sand particles of different sizes allows the use of various sand particles for each injection device (injection nozzle) and the amount of injection air flow and wind pressure conditions can be adjusted. The size, depth, and density of the intaglio (pixel) can be freely controlled for each light guide plate region.

  Since the light guide plate processed according to the present invention has a large size and a small size indentation superimposed on the lower surface (multiple inscription structure of inscription-inner-inscription form) or a non-overlapped form, the pixel size is mixed. The effect of downsizing can be obtained. Also, the size of the intaglio varies from large to small, and the large intaglio has a largely intaglio-inner-intaglio structure, which has the effect of gathering small pixels. Therefore, the present situation where the output light is hardened is greatly weakened, and a soft light atmosphere is produced.

  The intaglio-inner-intaglio structure scatters incident light over a wide range of angles, thus reducing the average travel distance of the output light. As a result, the improvement of the light output efficiency of the output light coming out through the light guide plate according to the present invention is about 20% as compared with the conventional technique (the technique of processing into single size sand particles).

  In addition, the average brightness of the light guide plate as a whole can be significantly improved compared to the conventional one by shortening the average travel distance of light and appropriately adjusting the distribution of fine indentations of small size. According to the present invention, luminance uniformity was obtained up to about 93%. Since the luminance uniformity of the light guide plate processed by the prior art is about 80-88%, the luminance uniformity can be improved by about 5-13%.

  By extension, the light divergence angle of the output light of the light guide plate according to the present invention is measured to a maximum of about 170 degrees, and the viewing angle is much wider than the light guide plate according to the prior art having a light spread angle of about 120-130 degrees. Provide the irradiation angle.

It is a figure for demonstrating the method of processing a fine inscription on the surface of an acrylic board | plate material by the sandblasting process which concerns on a prior art. It is the photograph which image | photographed the acrylic board material by which the fine inscription was processed by the prior art. The fine indentation of the processed acrylic plate material is distributed so as to gradually increase with the distance from the light source. (A) is a case where the light source is arranged on the left side, and (b) is the left and right side. This is a case where light sources are arranged on both sides. FIG. 2 conceptually shows a two-dimensional (2D) and a three-dimensional (3D) shape of a fine indentation formed when single-size sand particles are jetted onto an acrylic plate according to a conventional technique. It is a graph which shows the spreading angle of the output light which comes out from the upper surface of the light-guide plate processed by the prior art. It is the photograph which expanded and photographed the surface of the light-guide plate processed by the conventional processing method. FIG. 5 is a view for explaining a method of processing an acrylic plate material in two steps by sequentially injecting sand particles of different sizes from each other by two injection devices according to a preferred embodiment of the present invention. It is a figure which shows the light-guide plate processing method in case a light source is arrange | positioned only at one side of a light-guide plate. The figure which shows notionally the two-dimensional (2D) and three-dimensional (3D) shape of the multiple inscription structure of the inscription-inner-inscription form formed in the surface of the acrylic board | plate material by the 2-step sandblasting processing method which concerns on this invention It is. (A) is the figure which image | photographed a part of processed surface of the acrylic board processed by the 2-step sandblasting processing method which concerns on this invention with the electron microscope. FIG. 11B is an enlarged view of one of the multiple indentation structures in the inscription-inner-inscription form shown in FIG. It is the figure which image | photographed the light emission surface of the light-guide plate processed by the 2-step sandblasting processing method which concerns on this invention. (A) and (b) are a light guide plate made of an acrylic plate material (left side) processed into single-size sand particles according to the prior art and an acrylic plate material (right side) sequentially processed into two size sand particles according to the present invention. It is the photograph which image | photographed the state which mounted the same advertising film on each employ | adopted backlight unit. It is the graph which measured the light divergence angle of the light-guide plate processed by this invention.

(1) Light guide plate processing method by sandblasting process A transparent PMMA acrylic plate material (the critical angle is 42.19 degrees and the refractive index is 1.49 is mainly used) which is the material of the light guide plate. For example, a processing material is prepared by cutting into a square or other desired shape. If a cut acrylic plate material is prepared, sandblasting is performed on it. This processing proceeds by a two-step sequential processing process using two types of sand particles having different sizes. Although it is possible to perform processing while changing the type of sand in one sand spraying device, it is more preferable in terms of productivity to prepare and process a separate spraying device for each sand size.

  FIG. 7 shows a case where the acrylic plate material 140 is processed in two steps by using sand particles having different sizes by the two jetting apparatuses 10-1 and 10-2. A first jet device 10-1 and a second jet device 10-2 that jet large sand particles and small sand particles, respectively, are arranged side by side on the upper side of the conveyor belt 30. The acrylic plate material 140 to be processed is placed on the conveyor belt 30, and the outlets of the injection pipes (injection nozzles) 20 of the injection devices 10-1 and 10-2 are arranged close to the plate material 140. Is done.

  First, one-step machining is performed by the first injection device 10-1. The one-step processing uses sand particles having a size larger than that of the two-step processing, for example, about 30-80 mesh sand particles. In one step processing, if the sand particles are larger than 30 mesh, the size of the indentation is too large and the output light looks very rough. If it is less than 80 mesh, the degree of formation of the indentation-inner-indentation structure by the two-step processing May be low. However, it is preferable to relatively determine the size of the sand particles used in the one-step processing and the two-step processing.

  In the first injection device 10-1, the large-sized sand particles 12-1 are free-falled and are blown to the injection pipe 20 at a high speed by the first blower 16 and the second blower 18. It collides with the acrylic plate material 140 while being diffused. Separately from this, the conveyor belt 30 moves in a predetermined direction (lateral direction) at a predetermined speed. In the primary processing, the farther away from the side surface on which the light source is arranged (if the light source is arranged on one side surface of the light guide plate, the closer to the side surface on the opposite side of the side surface, the more the light source faces the light guide plate 2) If it is arranged on the side surface, the injecting (pixel) distribution density is relatively increased as it goes to the region in the two side surfaces. The outlet portion form of the injection tube 20 has such a wide width that it is narrower toward both ends to satisfy such injection requirements. That is, the sand particles 12-1 coming out from the outlet portion of the injection pipe 20 spread according to the shape of the injection pipe 20. Therefore, the number of the sand particles 12-1 that collide with the acrylic plate 140 (that is, the distribution of the indentation formed on the acrylic plate 140 after the completion of the one-step processing) is the injection pipe as shown in FIG. It is the most in the part in 20 exit parts, and it decreases gradually, so that it goes to both ends. In this way, a relatively large indentation (however, this indentation is an irregular shape) is formed on the surface of the acrylic plate member 140 that has completed the one-step processing.

  Subsequently, two-step processing is performed while the primary processed acrylic sheet 140 is passed under the second injection device 10-2. The main purpose of this two-step processing is to form a small indentation (indentation-inner-indentation multiple structure inscription) on the inner surface of the inscription formed by one-step processing. Considering this, the size of the sand particles used in the two-step processing is preferably smaller than about 1/2 to １ ／ of the size of the sand particles used in the one-step processing. For example, when sand particles of about 30-80 mesh are used in one step processing, it is preferable to use sand particles of about 120-250 mesh in two step processing.

  The indentation formed by the two-step processing is much smaller than the intaglio formed by the one-step processing. Therefore, it is also formed on a smooth surface that is not engraved, but also on the inner surface of the intaglio formed by one-step processing. It is preferable that the distribution density of the intaglio by secondary processing decreases as it goes from the middle portion in the longitudinal direction of the acrylic plate member 140 to both ends, similar to the one-step processing. In this case, light sources (not shown) must be disposed on the upper side surface 142a and the lower side surface 142b of the acrylic plate member 140.

  If the light source is arranged on only one of the upper side surface 142a and the lower side surface 142b of the acrylic plate member 140, the distribution density of the primary processed intaglio and the secondary processed intaglio is the one side (light source It is necessary to increase gradually from the side of the arrangement to the side of the opposite side. For this purpose, as shown in FIG. 8, it is only necessary to process the acrylic plate member 140 using only half of the injection pipes 20 of the injection apparatuses 10-3 and 10-4. In other words, the acrylic plate material 140 may be sprayed in a form that only covers half of the outlet portion of the spray tube 20.

  In the two-step sandblasting process as described above, (a) as one goes from any one side of the acrylic sheet 140 to the opposite side, or (b) from two opposite sides into the two sides. The incident angles of the first and second size sand particles 12-1 and 12-2 that collide per unit area of the acrylic plate member 140 gradually decrease.

  On one side surface of the acrylic plate member 140 that has been subjected to the two-step sandblasting process as described above, there are a large number of first indentations that are difficult to identify with the naked eye, and a large number of first indentations that are smaller than the first indentation. Two indentations are formed as light scattering elements. At least a part of the second inscription is formed on the inner surface of at least a part of the first inscription, and the first inscription has a multi-inscription structure of inscription-inner-inscription. FIG. 9 conceptually illustrates the two-dimensional (2D) and three-dimensional (3D) shapes of the multiple indentation structure of the inscription-inner-inscription type among the inscriptions formed on the surface of the acrylic plate member 140 through the two-step processing described above. Show. As shown in the drawing, among the large indentations 150 and 152 formed by the primary processing, at least a part of the inner surface of 150 is further formed with a smaller indentation 155 due to the collision of the secondary processing sand particles 12-2. -It becomes a multiple indentation structure of the inner-indentation form. Since the secondary processed sand particles 12-2 do not collide with the inner surface of the remaining part 152 of the first processed first indent, the second indent is not formed, and the surface in the primary processed state is maintained as it is. You can also. The remainder of the second indentation formed by the secondary processing is formed on a clean surface where the first indentation is not formed.

  FIG. 10A shows a part of the processed surface of the acrylic plate material 140 processed by the two-step processing method as described above, taken with an electron microscope. Also through this photograph, the processed surface of the acrylic plate material 140 includes the indentation 152 in the primary processing state, the multiple intaglio 150 in the indentation-inner-indentation form by the primary and secondary processing, and the secondary processing inscription 157. I can confirm that. FIG. 10B is an enlarged form of any one of the multiple intaglios 150 in the inscription-inner-inscription form shown in FIG. It can be confirmed that a number of second indentations 155 are formed in the intaglio 150 by secondary processing. In addition, it can be confirmed that the degree of roughness of the inner surface of the intaglio 150 is far greater when the inclination angle becomes gentler than that of the inscription according to the prior art (see 50 in FIG. 4).

  In performing such a two-step injection process, the density distribution of the second intaglio is made different from the density distribution of the first intaglio by the one-step injection process. That is, when the density ratio of the first indentation in the nearest distance region and the farthest distance region is 1: N from the first intaglio light source processed by the first processing, the second processing is performed by the second processing. It is preferable to perform the primary and secondary processing so that the density ratio between the nearest distance area and the farthest distance area is 1: N / 3 to 1: N / 1.5.

  In addition, the primary processing is performed so that pixels (indentation) of about 20 to 40% of the overall brightness of the light guide plate output light are formed, and the secondary processing is the remainder, that is, the light guide plate output light. It is preferable to process so that a pixel (an intaglio) that bears about 60 to 80% of the overall brightness is formed. If the indentation specific gravity by the primary processing exceeds 40%, the light guide plate output light looks relatively rough. On the other hand, if it is less than 20%, the light output efficiency becomes low.

  FIG. 11 is a photograph of the light-emitting surface of the light guide plate that is processed so that a large indentation by the primary processing and a small indentation by the secondary processing are mixed in such a ratio. It can be seen that the roughness of the output light is significantly reduced compared to the light guide plate of FIG.

  Further, FIG. 12 shows a backlight in which an acrylic plate material (left side) processed into sand particles of a single size according to the prior art and an acrylic plate material (right side) processed into sand particles of two sizes according to the present invention are respectively adopted as light guide plates. It is the photograph which image | photographed the state which mounted the same advertisement film on the unit. The acrylic plate material has a large size of about 4 m wide and 1.5 m long. It can be confirmed that the right film looks much brighter than the left film (difference in light output efficiency). In particular, in the case of the left film, it can be seen that the inner region looks much darker than the edge region, and the luminance difference is large (difference in luminance uniformity). That is, the present invention considerably improves the brightness of the output light and the luminance uniformity over the entire surface of the light guide plate. When the light efficiency and the luminance uniformity for the two light guide plates were compared and measured, the light output efficiency of the light guide plate according to the present invention was improved by about 20% compared to the light guide plate according to the prior art. The luminance uniformity of the light guide plate processed according to the present invention was 93% or more. Considering that the luminance uniformity of the light guide plate processed by the above-described prior art is about 80-88%, it can be said that the numerical value is considerably improved.

  The surface characteristics of the processed surface of the acrylic plate material 140 processed through the two-step processing are as follows: (a) surface roughness of the processed surface of the processed acrylic plate material 140, (b) inscription-inner-inscription The distribution density (number) of the second inscriptions located on the inner surface of the first inscription of the multiple inscription structure of the form, (c) included in the first inscription of the multiple inscription structure of the inscription-inner-inscription form Including the second indentation), the occupied area per unit area on the processed surface of the acrylic plate 140 of the second indentation formed outside the first indentation, and (d) the above-mentioned second existing within the unit area As shown in FIG. 7, the average of the diameter and the maximum depth of one indentation and the second indentation increase in the two side surfaces 142a and 142b facing each other as shown in FIG. In the case of spraying as in FIG. To increase as it goes from one side 142b of the throat to the side 142a of the opposite side.

  As a result, the surface of the light guide plate 140 processed according to the present invention is formed with a fine indentation in the form of indentation-inner-indentation. Because of its large size, it scatters and reflects incident light at a wide variety of angles. Therefore, the spread angle of the output light of the light guide plate 140 is further increased, and soft light dispersion is performed. The more such multiple indentations are formed, the more the light spread angle of the light guide plate is expanded. FIG. 13 is a graph obtained by measuring the light spread angle of the light guide plate 140 processed according to the present invention. Since the maximum light divergence angle is about 130 to 170 degrees, it can be seen that it is much wider than before.

  In the above description, the two-step processing has been described. However, if necessary, the acrylic plate material 140 that has been subjected to secondary processing by a tertiary spraying device (not shown) has a size smaller than that of sand particles used for the secondary processing ( For example, it can be processed once again using sand particles of about 300 to 400 mesh. In this case, if the sand particles are processed by adjusting the wind strength and the density of the sand particles so as to satisfy the desired maximum efficiency light guide plate conditions, higher quality output light can be obtained.

  On the other hand, the above-described processing method is a method in which large-sized sand particles and small-sized sand particles are distinguished and sequentially injected, and two or three types of sand particles having different sizes are modified by changing this. It can be mixed at one place and sprayed at a time. It is preferable to select sand particles to be mixed at least twice as much as the size difference between them is small. In addition, for example, when two sizes of sand particles are mixed, it is preferable to mix large size particles and small size sand particles in a ratio of 1: 1 to 1: 4. When mixing three sizes of sand particles, the mixing ratio of large size (example: 100 mesh): intermediate size (example: 150 mesh): small size (example: 200 mesh) is 1: 1: 1.5. It is preferable to mix differently depending on the processing size of the light guide plate within a range of 1: 1.5: 2.5.

  Even if the acrylic plate material 140 is processed by such a method, compared to the conventional technique of processing into a single size sand particle, various light scattering characteristics of the processed acrylic plate material (light output efficiency, luminance uniformity, (Softness of output light, spread angle of output light, etc.) can be obtained better. However, the method in which sand particles of different sizes are mixed and sprayed at one time has a disadvantage that it is difficult to control the indentation density for each light guide plate position if the mixed sand has a large size deviation. In addition, the indentation previously formed by the small size sand particles may be lost due to the indentation formed by the large size sand particles that collided later, and the small size indentation formed on the inner surface of the large size inscription. As compared with a method of processing in so many stages, the light scattering characteristics of the processed acrylic plate material may be lowered.

  The above-described method of sequentially processing separately for each size can control the processing conditions according to the size separately, so that the flatness is improved. The mixed sand particles can also be used in the method of dividing into 2-3 steps. When the size of the light guide plate is large (the width is 1000 mm or more), control of light efficiency and flatness is better if the particles are mixed and used. At this time, the mixing ratio and particle size of the sand particles must be adjusted according to the surface strength of the material. However, if the width is less than 1000 mm, an effective result can be obtained by only primary and secondary sand injection without mixing sand particles.

  The above-described injection device is merely an example, and other injection devices presented in the above-mentioned Korean Patent Publication Nos. 10-2003-0079659 and 10-2003-0079749 may be used.

  The present invention can be applied to manufacture of a light guide plate used as one part of a backlight unit of a display device such as an advertising signboard, a monitor and a television.

Claims (18)

A method of manufacturing a light guide plate by processing the surface of a transparent acrylic plate material,
A primary processing step of forming a plurality of first indentations by surface-crushing by sand-blasting a first-size sand particle on one side surface of the plate;
A sand particle having a second size smaller than the first size is sprayed on one side surface of the acrylic plate member on which the first indentations are formed, and at least a part of the inner surface of the first incline and the first surface are crushed by surface crushing. A second processing step of forming a number of second indents having a size smaller than the first indent on the outer surface of the one indent;
A method of manufacturing a light guide plate, comprising:   (A) the more that the acrylic plate material collides per unit area as it goes from any one side surface of the acrylic plate material to the opposite side surface, or (b) from the two opposite side surfaces into the two side surfaces. The first and second size sand particles are jetted so that at least one of the number of one size sand particles and the number of second size sand particles gradually increases. The light guide plate manufacturing method according to claim 1.   (A) the more that the acrylic plate material collides per unit area as it goes from any one side surface of the acrylic plate material to the opposite side surface, or (b) from the two opposite side surfaces into the two side surfaces. 2. The light guide plate manufacturing method according to claim 1, wherein the first and second size sand particles are jetted so that the incident angles of the first and second size sand particles gradually decrease.   The light guide plate manufacturing method according to any one of claims 1 to 3, wherein the first size is 30-80 mesh and the second size is 120-250 mesh. .   2. The method according to claim 1, further comprising a third processing step of forming a fine indentation by injecting sand particles having a size smaller than the second size on one side surface of the acrylic plate material that has been subjected to the secondary processing. The light-guide plate manufacturing method of description.   The light guide plate manufacturing method according to claim 5, wherein the size of the sand particles used in the third processing step is 300 to 400 mesh.   When the density ratio between the nearest distance area and the farthest distance area is 1: N from the light source of the first intaglio processed by the first machining, the latest of the second intaglio machined by the second machining. The primary processing and the secondary processing are performed so that a density ratio between the distance region and the farthest distance region is 1: N / 3 to 1: N / 1.5. The light-guide plate manufacturing method of description.   The contribution ratio of the first intaglio scattering formed in the first processing step and the second intaglio scattering formed in the second processing step with respect to the output light output on the upper surface of the light guide plate The light guide plate manufacturing method according to claim 1, wherein is 20-40% vs. 60-80%.   Due to the first indentation having a multi-indentation structure in which the second inscription is formed on the inner surface, the maximum light spread angle of the output light output on the upper surface of the light guide plate is 130 degrees or more and 170 degrees. The light guide plate manufacturing method according to claim 1, wherein: A method of manufacturing a light guide plate by processing the surface of a transparent acrylic plate material,
Mixing two or three different sizes of sand particles in the container of the injector and supplying the mixture to the container of the injector;
(A) The sand particles that collide per unit area of the plate as it goes from any one side of the acrylic plate to the opposite side, or (b) from the two opposite sides into the two sides A step of forming an infinite number of indentations by surface-crushing by sand-blasting the mixed sand particles so as to gradually increase the number of
The light guide plate has an indentation-inner-indentation shape in which at least a part of a plurality of indentations formed on the one side surface has a small size indentation formed on an inner surface of a large size inscription. Production method. A light guide plate processed with a transparent acrylic plate material,
A large number of first indents having a size that is difficult to identify with the naked eye and a plurality of second indents having a size smaller than the first indent are mixed and formed on one side surface of the acrylic plate material as light scattering elements. And
Since at least a part of the second incline is formed on an inner surface of at least a part of the first incline, at least a part of the first incline has a multiple incline structure of incline-inner-incline form. A light guide plate.   The first indentation and the second inscription are formed by a sand blasting process using a first size sand particle and a second size second sand particle smaller than the first size, respectively. The light guide plate according to claim 11.   The surface roughness of one surface of the acrylic plate material is (a) going from one side surface of the acrylic plate material to the opposite side surface, or (b) going from the two opposite side surfaces into the two side surfaces. The light guide plate according to claim 11, wherein the light guide plate increases as the number increases.   The distribution density (number) of the second inscriptions located on the inner surface of the first inscription, which is a multi-inscription structure of the inscription-inner-inscription form, is (a) from one side surface of the acrylic plate material to the opposite side. The light guide plate according to claim 11, wherein the light guide plate increases as it goes to a side surface or (b) from two opposing side surfaces into the two side surfaces.   The first inscription (including the second inscription included in the first inscription, which is a multi-inscription structure of the inscription-inner-inscription form), and the second inscription formed outside the first inscription. Occupied area per unit area on the one side surface of the acrylic plate material is (a) from one side surface of the acrylic plate material to the side surface on the opposite side, or (b) from the two opposite side surfaces to the two side surfaces. The light guide plate according to claim 11, wherein the light guide plate increases as going inward.   The average of the diameter and the maximum depth of the first indentation and the second inscription existing in a unit area is: (a) as the distance from one side surface of the acrylic plate material to the side surface on the opposite side, or The light guide plate according to claim 11, wherein the light guide plate increases from the two side surfaces facing each other into the two side surfaces.   The maximum light spread angle of the output light output to the upper surface of the light guide plate by the first indentation, which is a multi-indentation structure of the inscription-inner-inscription form in which the second inscription is formed on the inner surface, is 130 degrees or more and 170 or less. The light guide plate according to claim 11, wherein:   The first indentation and the second indentation act as a light scattering element that scatters light flowing in through one side surface of the plate material, or both side surfaces facing each other, and outputs the scattered light to the upper surface of the plate material, 12. The contribution ratio of the first and second inflections to the output light output on the top surface of the light guide plate is 20-40% vs. 60-80%. The light guide plate described.