JP4402803B2 - Directional light guide plate and method for manufacturing mold for light guide plate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel texture pattern of a directional light guide plate and a method of manufacturing the light guide plate mold.
[0002]
[Prior art]
Printing light guide plates and directional light guide plates are known as light guide plates for sidelight type surface light source devices, but printing light guide plates that are easy to manufacture have been mainstream so far. However, as the display screen has been increased in size and saved in energy, the printing light guide plate cannot satisfy the above requirement in terms of luminance, regardless of the uniformity.
[0003]
Thus, although the directional light guide plate has begun to attract attention, the light guide action of the directional light guide plate is greatly different from that of the printing type light guide plate, and research on a texture pattern unique to the directional light guide plate has become necessary. In addition, the formation of the texture is naturally required to be as simple and highly reproducible as possible in terms of cost.
[0004]
[Problems to be solved by the invention]
The first problem of the present invention is the development of a texture pattern unique to the directional light guide plate. Second, the development of a manufacturing method that can form the pattern in the cavity of the light guide plate forming mold easily and with high reproducibility. It is in.
[0005]
[Means for Solving the Problems]
The directional light guide plate (1) according to the first aspect is “at least one of the light exit surface (1d) of the wedge-shaped light guide plate body (11) or the non-light exit surface (1b) facing the light exit surface (1d)”. In the directional light guide plate (1) in which a large number of wrinkles (9) whose surface (9a) is formed of a smooth curved surface is formed on the surface , the wrinkle shape is a part of a spherical surface, and the unit of wrinkles (9) The density per area is highest in the range of 1/5 to 1/4 of the total length from the light incident side end surface (1a) to the reflection side end surface (1c) as measured from the light incident side end surface (1a). It is configured to gradually increase in density from the light incident side end face (1a) side toward the reflection side end face (1c) and gradually decrease the density from the position (M) where the maximum density is reached. '' To do.
[0006]
Due to its characteristics, the directional light guide plate (1) has a significant part of the light entering from the incident side end surface (1a) side reaching the reflecting side end surface (1c) side, and the amount of light reflected from the reflecting side end surface (1c). There is a problem in that the reflection side end face (1c) side becomes too bright, but the roughening pattern is made rough, dense, and rough so that the amount of light emitted on the reflection side end face (1c) side is suppressed. The amount of light emitted from the portion close to the reflection side end face (1c) beyond the central portion where the amount of emitted light increases can be reduced, and a light emitting surface (1d) with high uniformity can be obtained as a whole. Moreover, since the surface (9a) of the wrinkle (9) is a smooth curved surface, the light reflected by the surface (9a) is not scattered but reflected in a predetermined direction, and is emitted with high directivity. This leads to improved brightness.
[0008]
As a characteristic of the directional light guide plate (1), as described above, the amount of light emitted from the portion adjacent to the reflection side end surface (1c) increases and becomes brighter, but the light incident side end surface is measured from the light incident side end surface (1a). Incident light end face that tends to reduce the amount of emitted light by setting the maximum wrinkle density in the range of 1/5 to 1/4 of the total length from the (1a) side to the reflective end face (1c) (1a) It is possible to increase the amount of light emitted in the vicinity and simultaneously reduce the amount of light emitted from the excessive amount of emitted light, so that a light emitting surface (1d) having high uniformity and high luminance as a whole can be obtained.
[0009]
In addition , by constructing so that the “texture shape is a part of the spherical surface” , the light reflected by the surface (9a) of the texture (9) is not scattered and the direction of the light is changed slightly, and the incident angle is changed. Reflected with equal reflection angle. Part of the reflected light is emitted as it is from the light exit surface (1d), and the rest is reflected and eventually emitted, but unlike the scattering type light guide plate, there is regularity in the reflected direction. In the case of the light source (3) having the same output, the principal axis light intensity is increased and the luminance is improved as compared with the scattering type light guide plate. The embossed shape may be convex or concave, but in this embodiment, it is convex because it is manufactured by an injection molding method using a mold (21).
[0010]
“Claim 2” relates to a first example of the manufacturing method of the mold (21) for manufacturing the directional light guide plate (1). The fine spherical shot is moved to the cavity surface (21d) while moving from the light incident side end face forming side end (21a) of the mold (21) to the reflecting side end face forming side end (21c) or in the opposite direction. ) to be emitted toward the patterned with me by the fact that innumerable forms a textured forming indentation marks on the cavity surface (21d), the light exit surface of the wedge-shaped light guide plate main body (11) (1d) or Idemitsu In order to form a directional light guide plate (1) on which at least one of the non-light-emitting surface (1b) facing the surface (1d) is formed with a large number of wrinkles (9) having a smooth curved surface. A method for manufacturing a directional light guide plate mold (21) used in the invention, wherein the embossed concave marks are part of a spherical surface formed of a smooth curved surface, The density per unit area of the trace is the highest density in the range of 1/5 to 1/4 of the total length from the light incident side end surface (21a) to the reflection side end surface (21c) as measured from the light incident side end surface (21a). From the incident side end face forming side end (21a) to the reflecting side end face forming side end (21c), the density gradually increases, and the density gradually decreases from the position (M) where the maximum density is reached. Next, the exit port (23a) is gradually approached from the light incident side end face forming side end (21a) to the highest density position (M), and beyond the highest density position (M), the reflection side end face forming side end (21c) It is characterized by the fact that it is moved gradually away from each other.
[0011]
“Claim 3” relates to the second example of the method of manufacturing the mold (21) for manufacturing the directional light guide plate (1). Move the fine spherical shot toward the cavity surface (21d) while moving from the incident side end surface formation side end (21a) of the mold cavity (21b) to the reflection side end surface formation side end (21c) or the opposite direction. The light exit surface (1d) or the light exit surface (1d) of the wedge-shaped light guide plate body (1), which is patterned by emitting and forming innumerable depression forming marks on the cavity surface (21d). Directional light guide plate gold used to form a directional light guide plate in which a large number of embossments (9) having a smooth curved surface are formed on at least one surface of the non-light-emitting surface (1b) a method of manufacturing a mold (21), grain shape of grain forming indentation marks is part of a spherical surface that is composed of smooth curved surface, a single of grain formation indentation marks The density per area is highest in the range of 1/5 to 1/4 of the total length from the light incident side end surface (21a) to the reflection side end surface (21c) as measured from the light incident side end surface (21a). In order to gradually increase the density from the light incident side end face forming side end (21a) toward the reflection side end face forming side end (21c), and gradually decreasing the density from the position (M) where the maximum density is reached. The pressure is gradually increased from the light incident side end face forming side end (21a) to the highest density position (M) and beyond the maximum density position (M) to gradually decrease to the reflecting end face forming side end (21c). '' It is characterized by.
[0012]
In this way, the mold (21) having the embossed pattern of the present invention can be easily and reproducibly produced, and by using this mold (21), the embossed pattern of the mold (21) can be produced. The correctly transferred wedge-shaped light guide plate (1) can be obtained by injection molding. The shot used is a fine spherical glass ball or steel ball.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. The sidelight type surface light source device (A) of this example includes a wedge-shaped light guide plate (1), a reflection sheet (2) disposed on the non-light-emitting surface (1b) side of the wedge-type light guide plate (1), a wedge Cold cathode discharge tube (3) [or fluorescent lamp or halogen lamp] arranged along the light incident side end face (1a) of the mold light guide plate (1), arranged on the back side of the cold cathode discharge tube (3) A reflector (4) for reflecting the light of the cold cathode discharge tube (3) and entering the light incident side end surface (1a), and a light emitting surface (1d) side of the wedge-shaped light guide plate (1). A prism sheet (5) and a light diffusion sheet (6), and a liquid crystal display panel (7) is further provided thereon.
[0014]
The wedge-shaped light guide plate (1) is a plate-like member in which a light-transmitting resin such as acrylic (PMMA resin) is formed in a wedge shape by an injection molding method. The wide end surface is the light incident side end surface (1a), the opposite narrow side end is the reflection side end surface (1c), one surface is the non-light emitting surface (1b), and the opposite surface is the light emitting surface ( 1d).
[0015]
The wrinkles (9) are formed on the non-light-emitting surface (1b), the light-emitting surface (1d), or both sides (1b) (1d). In this embodiment, a texture (9) is formed on the light exit surface (1d) side. As shown in FIG. 2, the wrinkles (9) are spherical projections, and the surface (9a) is formed into a smooth curved surface so that the reflected light does not scatter and faces a predetermined direction regularly.
[0016]
The gradation pattern of the wrinkles (9) is formed so as to be rough, dense, and rough from the light incident side end face (1a) to the reflection side end face (1c). The place where the wrinkles (9) are formed most densely is 1/5 to 1/1 in total width from the light incident side end surface (1a) in the entire width from the light incident side end surface (1a) to the reflection side end surface (1c). 4. The wrinkle density per unit area gradually becomes larger toward the light incident side end face (1a) and the reflection side end face (1c) around the place where the wrinkles (9) are most densely formed. It is formed to go.
[0017]
The prism sheet (5) is formed of a light-transmitting resin sheet such as an acrylic resin, and a plurality of parallel protrusions (5a) having a triangular cross-section are formed on one side, and in the extending direction of the protrusions (5a). Directional light emitted from the light exit surface (1d) in the orthogonal direction is turned in the normal direction. As shown in FIG. 3, parallel ridges (5a) are arranged in a direction orthogonal to the vertical axis from the light incident side end face (1a) to the reflection side end face (1c).
[0018]
The light diffusion sheet (6) has a function of relaxing the directivity corrected by the prism sheet (5) by scattering the transmitted light from the prism sheet (5), and improves the appearance and quality.
[0019]
The reflection sheet (2) and the reflection tape (8) are formed of a scattering type white sheet or a specular reflection sheet, and cover the entire surface of the non-light-emitting surface (1b) and the reflection side end surface (1c) of the light guide plate (1). It is arranged like this. In addition, you may adjoin a white chassis.
[0020]
The reflector (4) has a semi-cylindrical shape, and a cold cathode discharge tube (3) is disposed at the center or focal position thereof, and is disposed along the light incident side end surface (1a) of the light guide plate (1). Of the light emitted from the discharge tube (3), light that does not directly enter the incident side end face (1a) is efficiently reflected and incident on the incident side end face (1a), such as a metal foil. It is formed with the regular reflection member formed in (1) or the sheet-like irregular reflection member formed with a white PET film.
[0021]
Next, in order to describe the characteristics of the directional light guide plate, the directional light guide plate formed in FIG. This is the case where the wrinkles (9) are uniformly formed on the entire surface. When the cold cathode discharge tube (3) is turned on, the light emitted from the cold cathode discharge tube (3) is reflected either directly on the light incident side end face (1a) of the light guide plate (1) or by the reflector (4) and reflected by the light guide plate. Light enters (1). Part of the incident light exits from the exit surface (1d), and the remaining part reflects between the exit surface (1d) and the non-exit surface (1b), which becomes gradually narrower toward the reflection-side end surface (1c). While proceeding.
[0022]
Since the surface (9a) of the texture (9) of the light guide plate (1) has a smooth spherical shape, the light reflected by the surface (9a) of the texture (9) is not scattered, and the direction of the light is very slight. Multi-reflection is repeated while changing the light. Therefore, as shown in FIG. 5 (a), the directional light guide plate (1) has a characteristic in which the luminance gradually increases from the light incident side end surface (1a), and shows the maximum luminance at about 1/4 of the total length. The brightness gradually decreases. Then, the lowest luminance is shown at about 3/4 of the total length, and thereafter the luminance rapidly increases toward the reflection side end face (1c). This is because, in the directional light guide plate (1), a considerable part of the light incident from the light incident side end surface (1a) does not come out, and the light is reflected in the light guide plate (1) and reflected on the reflection side end surface (1c). The light travels toward the reflection side end surface (1c), is reflected by the action of the reflection sheet (8), and is reflected back toward the light incident side end surface (1a). This is because the light is emitted in the vicinity of the side end face (1c). As a result, the luminance in the vicinity of the reflection side end face (1c) increases rapidly.
[0023]
From such a point, the embossed pattern of the directional light guide plate (1) used in the side light type surface light source device (A) is required to be a special pattern different from the conventional printing type. Hereinafter, a method of manufacturing the directional light guide plate (1) used in the sidelight type surface light source device (A) and its operation will be described together with Comparative Examples 1 and 2.
[0024]
FIG. 4 shows a method for manufacturing a directional light guide plate mold. (A) relates to a method for manufacturing the directional light guide plate mold (20) of Comparative Example 1 described above. The shot gun (23) is moved back and forth, left and right in parallel with the mold (20), and the spherical shut is shot at the specified pressure evenly onto the cavity surface (20d) of the directional light guide plate mold (20) for blast etching. Went. A uniform recess is formed on the entire cavity surface (20d). On the textured surface of the aforementioned light guide plate formed using this mold (20), a spherically convex textured surface in which the uniform recesses of the cavity surface (20d) are transferred is uniform over the entire surface. Formed.
[0025]
FIG. 4B shows a light guide plate mold (21) manufacturing method according to the present embodiment. The light incident side end face (1a) of the directional light guide plate mold (21) is placed on the support base (24). The shot gun (23) is moved back and forth, left and right, and the spherical shut is uniformly shot at a predetermined pressure onto the cavity surface (21d) of the directional light guide plate mold (20) and blasted. Etching was performed. In this case, the position gradually approaches the cavity surface (21d) up to a position on the way from the light incident side end surface (1a) side to the reflection side end surface (1c) (from the light incident side end surface (1a) to 1/5 to 1/4). The shot gun (23) is moved as described above, and when the closest position is passed, the shot gun (23) is gradually moved away from the cavity surface (21d). As a result, a gradation pattern of coarse, dense, and coarse is obtained from the light incident side end face (1a) toward the reflection side end face (1c). The light guide plate (1) of this example can be obtained by injection molding using this mold (21).
[0026]
FIG. 4C shows a light guide plate manufacturing method according to Comparative Example 2, in which a texture pattern similar to that of a conventional print type light guide plate is formed. That is, the reflective side end face (1c) of the directional light guide plate mold (21) is placed on the support base (24) and arranged obliquely, the shotgun (23) is moved back and forth, and left and right, and a spherical shut is placed. Blast etching was performed by shots on the cavity surface (21d) of the directional light guide plate mold (20) uniformly at a predetermined pressure. In this case, the shotgun (23) was moved so as to gradually move away from the cavity surface (21d) consistently from the reflection side end surface (1c) side to the light incident side end surface (1a). Thereby, a gradation pattern of dense and coarse is obtained from the reflection side end face (1c) toward the light incident side end face (1a).
[0027]
The uniformity and luminance of the light exit surface (1d) of the light guide plates (1) of Comparative Examples 1 and 2 and this example are as shown in FIGS. 5 (a), (b) and (c). In the figure, the horizontal axis represents the distance from the light source (3), and the vertical axis represents the luminance. Assuming that “0” is the light incident side end face (1a) and 180 is the reflection side end face (1c), in the present embodiment, the central portion 90 has the highest luminance, and slightly increases toward the periphery. Overall, it shows 80% uniformity. About 2000 cd / m ² brightness at the maximum value, showed 1600 cd / m ² at least.
[0028]
On the other hand, in Comparative Example 1, as described above, the entire surface is a uniform textured type with a directional light guide plate. Therefore, a considerable amount of incident light reaches the reflection side end surface (1c) and is reflected, and is reflected. The amount of reflected light on the 1c) side is large, the luminance on the reflecting side end face (1c) side increases rapidly, and the uniformity is very bad at 48%. The brightness of the portion excluding the vicinity of the reflection side end face (1c) is as low as 1600 cd / m ² to 1300 cd / m ^2, and most of the light exit surface (1d) is dark.
[0029]
Comparative Example 2 is also a directional light guide plate, but is formed by forming a texture (9) with a conventional printing pattern, and the texture density gradually increases toward the reflection side end face (1c) side. In this case, the light incident side end face (1a) side is remarkably dark, the brightness rapidly increases toward the reflection side end face (1c) side, and the uniformity is very poor at 25%. From the above, it can be seen that the directional light guide plate (1) requires a texture pattern different from the printed light guide plate, and the texture pattern of the embodiment is most preferable.
[0030]
In other words, by reducing the texture density per unit area on the reflection side end face (1c) side, the light emission amount in the vicinity of the reflection side end face (1c) is suppressed, and the light output quantity in the central part from the vicinity in the reflection side end face (1c) is reduced. The amount of light emitted from the relatively lowered portion is compensated by the emitted light of the reflected light, thereby forming a screen with high overall uniformity.
[0031]
In addition, the formation method of the embossed pattern is such that the exit port (23a) of the blast gun (23) is gradually approached from the light incident side end surface formation side end (21a) to the maximum density position (M) as described above, and the highest density is obtained. In addition to the method of moving gradually away from the position (M) to the reflection side end face formation side end (21c), the outgoing pressure is changed from the incident side end face formation side end (21a) to the highest density position (M ), And gradually weaken the reflection side end face formation side end (21c) beyond the maximum density position (M). In any case, the shot used for blasting is a fine spherical glass ball or steel ball.
[0032]
【The invention's effect】
The directional light guide plate of the present invention is configured such that the density per unit area of the texture gradually increases from the light incident side end surface side toward the reflection side end surface, and gradually decreases from the position where the maximum density is reached. Therefore, the amount of light emitted from the part of the screen from the center of the screen where the amount of light emitted is relatively increased to the vicinity of the reflection side end surface is reflected and reflected from the end surface of the reflection side. It was possible to make a screen with high uniformity as a whole.
[0033]
In addition, by making the surface of the wrinkle a smooth curved surface, scattering of the light reflected by the surface is suppressed, it is emitted in a predetermined direction with high directivity, and the principal axis light is turned in the normal direction by the prism sheet. As a result, a high-luminance surface light source was obtained.
[0034]
Furthermore, for the manufacture of molds for directional light guide plates, the blast gun exit port is gradually approached from the light-incident side end surface forming side end to the maximum density position, and beyond the maximum density position, the reflection side end surface forming side end Or the output pressure is gradually increased from the incident side end surface forming side end to the maximum density position, and beyond the maximum density position to the reflecting side end surface forming side end, it is gradually weakened. It is now possible to easily and reproducibly manufacture a mold having a grain pattern.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a sidelight type surface light source device of the present invention. FIG. 2 is a detailed enlarged cross-sectional view of an embossed shape of a light guide plate of the present invention. FIG. 4 is an explanatory diagram at the time of blasting of an example of the present invention and comparative examples 1 and 2; FIG. 5 is a comparison graph of uniformity and luminance of screens of the example of the present invention and comparative examples 1 and 2 ]
(1) Directional light guide plate
(1a) Light incident side end face
(1b) Non-light emitting surface
(1c) Reflective end face
(1d) Light emitting surface
(9) Wrinkles
(9a) Surface
(11) Wedge-type light guide plate body
(M) Position where maximum density is reached

Claims (3)

In a directional light guide plate in which a lot of wrinkles whose surface is formed of a smooth curved surface is formed on at least one of the light exit surface or the non-light exit surface facing the light exit surface of the wedge-shaped light guide plate body,
The embossed shape is a part of a spherical surface,
On the light incident side end surface side, the density per unit area is the highest density in the range of 1/5 to 1/4 of the total length from the light incident side end surface to the reflection side end surface as measured from the light incident side end surface. A directional light guide plate configured to gradually increase in density from the position toward the reflection side end face and gradually decrease in density from a position where the maximum density is reached. The fine spherical shot is moved to the cavity surface while moving the exit port of the fine spherical shot from the light incident side end face forming side end of the cavity of the directional light guide plate molding die to the reflecting side end face forming side end or in the opposite direction. The light exit surface of the wedge-shaped light guide plate body or the non-light exit surface opposite to the light exit surface, which is patterned by forming an infinite number of recess-forming recesses on the cavity surface. In addition, a method of manufacturing a directional light guide plate mold used to form a directional light guide plate in which a large number of textures having a smooth curved surface are formed ,
The wrinkle shape of the wrinkle forming indentation is a part of a spherical surface composed of a smooth curved surface ,
The density per unit area of the wrinkle forming indentations is measured so that it is the highest density in the range of 1/5 to 1/4 of the total length from the light incident side end surface to the reflection side end surface as measured from the light incident side end surface. From the light side end face forming side end to the reflecting side end face forming side end gradually becomes dense,
In order to gradually reduce the density from the position where the maximum density is reached, the exit port is gradually approached from the light incident side end face formation side end to the maximum density position, and gradually exceeds the reflection density end face formation side end beyond the maximum density position. The manufacturing method of the metal mold | die for directional light-guide plates characterized by moving like this. The fine spherical shot is moved to the cavity surface while moving the exit port of the fine spherical shot from the light incident side end face forming side end of the directional light guide plate molding die to the reflecting side end face forming side end or the opposite direction. On the light exit surface of the wedge-shaped light guide plate body or the non-light exit surface opposite to the light exit surface, which is patterned by being emitted toward the cavity surface and forming innumerable depressions on the cavity surface. , A method of manufacturing a directional light guide plate mold used to form a directional light guide plate in which a large number of textures having a smooth curved surface are formed ,
The wrinkle shape of the wrinkle forming indentation is a part of a spherical surface composed of a smooth curved surface ,
The density per unit area of the wrinkle forming indentations is measured so that it is the highest density in the range of 1/5 to 1/4 of the total length from the light incident side end surface to the reflection side end surface as measured from the light incident side end surface. From the light side end face forming side end to the reflecting side end face forming side end gradually becomes dense,
In order to gradually reduce the density from the position where the maximum density is reached, the emission pressure is gradually increased from the incident side end face formation side end to the maximum density position, and beyond the maximum density position, the reflection side end face formation side end is gradually weakened. A method for producing a mold for a directional light guide plate, characterized in that:

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