JP4736287B2 - Gradient pattern formation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
According to the present invention, the surface roughness of the surface of a mirror-finished flat workpiece is reduced by performing a sandblast scanning process of injecting an injection material from a nozzle with a high-pressure gas to disperse a large number of minute recesses. The present invention relates to a gradation pattern forming method that can be changed to form a light diffusion surface that does not cause uneven brightness.
[0002]
[Prior art]
Edge light type surface light source devices are widely used for liquid crystal display devices such as personal computers and mobile phones, or for advertisement illumination, guidance display panels, clock dials and other illumination backlights. The light guide plate used in such a surface light source device is subjected to a satin finish for providing light diffusion unevenness on the reflection surface or the emission surface in order to efficiently emit the introduced illumination light from the light emission surface. ing. This satin finish may be applied directly to the light guide plate material, or the light guide plate can be produced by using the mold after applying the satin finish to the mold surface of the light guide plate mold. As one of the means for performing such a satin processing, a sand blasting process that can be easily performed with high accuracy by a dry process is used.
[0003]
In order to form an uneven surface for light diffusion by sandblasting, the processed surface of a flat plate work, which is a light guide plate material or a light guide plate molding material, is made into a mirror-like smooth state, and an injection material is applied to the processed surface. As shown in FIG. 4, the nozzle can be scanned left and right along the scanning line 11 while spraying. For example, as shown in FIG. 5, first, sandblasting with a constant surface roughness is performed in the No. 1 zone, and then the surface roughness is slightly increased as the No. 2, No. 3, and No. 4 zones are shifted. While increasing or decreasing, a gradation pattern can be formed by sandblasting. However, in the prior art, at the boundary between adjacent bands having different surface roughness, that is, at the stepped portion, a long and narrow muscular cloud-like unevenness 12 that rises depending on the viewing angle as shown in FIG. 6 and adversely affects the light guide of the light guide plate. Frequently occurred. Such bright unevenness 12 is likely to occur at the boundary between bands having a small surface roughness, but the bright unevenness 12 naturally affects the light guide of the light guide plate and causes unevenness in light emission. Therefore, the occurrence of this phenomenon must be prevented.
[0004]
As a method for forming a gradation pattern by sandblasting, for example, Japanese Patent Laid-Open No. 8-160229 discloses a light guide plate, a method for manufacturing a light guide plate, and the like. It is only disclosed that no coarse sand is used, and no disclosure is made on the nozzle size, the nozzle or workpiece scanning pitch, the scanning speed, the injection pressure of the injection material, or the injection distance between the nozzle and the workpiece. This is merely a conceptual disclosure of a gradation pattern forming method. Normally, a nozzle having a diameter of about φ6 to φ12 mm is used in sandblasting, but when such a nozzle is used, the change in surface roughness in the gradation pattern cannot be changed smoothly and smoothly. It is difficult to suppress the occurrence of the elongated mysterious cloud-like glitter unevenness 12 at the boundary between adjacent bands having different surface roughnesses. In addition, the average depth of the surface roughness formed on the surface of the workpiece is extremely deep, 3 to 9 μm, and when the surface roughness of the workpiece is so deep, distinct luminescent spots are generated in which individual recesses shine. Thus, the luminance uniformity as the light guide plate is impaired.
[0005]
Japanese Patent Application Laid-Open No. 11-281976 discloses a light guide plate and a method for manufacturing the light guide plate. In this disclosure as well, a No. 100 (average particle size of about 110 μm) or No. 100 injection material is used. It is described that the surface roughness is formed to a depth of 3 to 7 μm. Therefore, it is clear that there is a problem with light guiding properties, and the point that no other sandblasting conditions are disclosed is the same as the above-mentioned publication. Further, in forming a good gradation pattern in which the bright unevenness 12 and the bright spots do not occur, if the flow rate of the ejected sand varies, the surface roughness varies and a problem arises in light guide properties. Therefore, in order to form a gradation pattern with excellent light guiding properties, it is necessary to first control the flow rate of the injection material to always inject a constant injection material from the nozzle, and strictly control the processing conditions of various sandblasting. However, in the past, since such strict control was not performed, a high-definition gradation pattern excellent in light guiding properties could not be formed.
[0006]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-described conventional problems and to provide a gradation pattern forming method capable of forming a light diffusing surface free from uneven brightness or bright spots on a light guide plate or a light guide plate mold.
[0007]
[Means for Solving the Problems]
The present invention, which has been made to solve the above-mentioned problems, performs a surface roughening process by performing a sandblast scanning process for injecting an injection material from a nozzle with a high-pressure gas to disperse a large number of minute recesses. In the gradation pattern forming method that changes the thickness, the injection amount of the injection material set to 10 g / min or less is controlled to a variation of ± 3 to 10%, the scanning pitch of the nozzle or workpiece is 10 mm or less, and the adjustment amount is 0.1 to 5 mm. The scanning speed is 300 mm / sec or less, the injection pressure is 1.50 MPa or less, the adjustment amount is 0.001 to 0.05 MPa, the injection distance between the nozzle and the workpiece is 100 to 300 mm, and scanning processing is performed while changing at least one of these. The surface roughness Ra (JIS B061; 1994) at one end of the workpiece is 0.02 μm or more, the surface roughness Ra at the other end is 0.5 μm or less, and the surface roughness at one end of the workpiece is smaller than the central portion and Degree of change As small have a gradation pattern forming method characterized by increasing the surface roughness curvilinear from one end of the workpiece toward the other end.
[0008]
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
Figure 1 is a diagram showing a main configuration of a grayed La retardation patterning device, the tank 1 is that the injection material is stored, 2 but is compressor as a high-pressure gas supply apparatus for supplying compressed air, stored in a tank 1 The flow rate of the injected material is always adjusted to a predetermined amount by the fixed amount supply device 3 and is pumped to the nozzle 4 by compressed air and is injected from the tip. Reference numeral 5 denotes a work table, and a work 6 is placed on the work table 5. Reference numeral 7 denotes a nozzle 4 scanning mechanism for moving the nozzle 4 horizontally and vertically. The nozzle 4 is moved in the horizontal direction or the vertical direction while spraying the spray material from the nozzle 4 toward the workpiece 6. 6 can form a gradation pattern. Further, the control device 8 can control the scanning pitch of the nozzle 4, the scanning speed, the injection distance between the nozzle 4 and the work 6, the pressure of the high-pressure gas, and the supply amount of the injection material. In this embodiment, the nozzle 4 is assumed to move. However, there is no problem even if the nozzle 4 is fixed and the work table 5 moves in the horizontal direction and the vertical direction. In addition to compressed air, nitrogen gas or the like can be used as the high-pressure gas. The workpiece 6 is usually a flat plate such as a stainless steel plate. However, the workpiece 6 may be a concave surface, a convex surface, or a material having appropriate relatively large irregularities.
[0010]
By using the gradation pattern forming apparatus described above, for example, a gradation pattern that does not cause uneven brightness 12 is generated on a flat work 6 that is a light guide plate material such as an acrylic resin or a light guide plate forming mold material such as stainless steel. The gradation pattern forming method of the present invention will be described in detail below.
In the gradation pattern forming method of the present invention, a high-pressure gas supplied from the compressor 2 or the like is used to inject and spray an injection material to the nozzle 4 via the quantitative supply device 3, and the surface is mirror-finished with a large number of workpieces 6. Dispersion of minute recesses increases or decreases the surface roughness from one end to the other end of the work 6 in a linear or arcuate manner. Since it tends to appear in a portion having a small roughness, the occurrence of bright unevenness 12 can be prevented more accurately, particularly when the degree of change in surface roughness at one end portion having a small surface roughness is made small and gentle. be able to. Further, the illumination light introduced without generating uneven brightness 12 can be efficiently obtained by reducing the change in surface roughness near the both ends of the work 6 and greatly changing it near the center as shown in FIG. It is possible to manufacture a light guide plate that can be well emitted from the light exit surface and its mold.
[0011]
As an example in the gradation pattern forming method of the present invention, the surface roughness of the workpiece 6 is Ra, 0.02 μm or more at one end of the workpiece and 0.50 μm or less at the other end, and continuously from one end to the other end. Some are rough. That is, when the surface roughness Ra is less than 0.02 μm, the diffusion of light due to irregular reflection is insufficient. On the other hand, when the surface roughness Ra exceeds 0.50 μm, bright spots are generated and light irregular reflection increases. This is because the light guide property is hindered.
[0012]
In forming the gradation pattern, it is first necessary to control the injection amount of the injection material to a predetermined flow rate by the quantitative supply device 3. If the flow rate is not controlled within a variation of, for example, ± 3 to 10%, unevenness in the depth of the surface roughness occurs, and hence unevenness in the brightness of the light guide plate. The degree of surface roughness can be changed by adjusting at least one of the scanning pitch of the nozzles 4, the scanning speed of the nozzles 4, the spraying pressure, and the spraying distance between the nozzles 4 and the workpiece 6. In the gradation pattern forming method of the present invention, it is desirable to change the sandblast scanning pitch of 10 mm or less by an adjustment amount of 0.1 to 5 mm. This is because when the scanning pitch is larger than 10 mm, the surface roughness cannot be changed small, and the change becomes a stepped step, resulting in bright unevenness 12. Further, if the adjustment amount is less than 0.1 mm, the machining efficiency is lowered and it takes a long time for processing. On the other hand, if the adjustment amount exceeds 5 mm, the degree of change in the surface roughness becomes too large. Because. Further, it is desirable to adjust the pressure of the high-pressure gas to 1.50 MPa or less and the amount of change from 0.001 to 0.05 MPa. This is because if the pressure exceeds 1.50 MPa, the workpiece tends to be distorted. On the other hand, if the amount of change is less than 0.001 MPa, it is difficult to change the surface roughness, and it becomes difficult to form a gradation pattern. On the other hand, if it exceeds 0.05 MPa, the surface roughness changes abruptly and brightness unevenness 12 This is because the occurrence of If the sandblast scanning speed is higher than 300 mm / sec, mechanically stable processing cannot be performed, and the scanning speed is preferably 300 mm / sec or less.
[0013]
Also, as the spray material, one with an average particle diameter of 5 to 500 μm is used, and this is injected from a round hole nozzle with a jet port of φ0.3 to φ3.0 mm or a rectangular hole nozzle with a 0.5 × 3.0 to 1.5 × 3.0 mm. It is desirable to perform sandblasting by injecting with a high-pressure gas of 1.50 MPa or less at an injection material flow rate of 10 g / min or less. In other words, if the average particle size of the propellant is less than 5 μm, it is not possible to obtain a sufficient polishing ability. On the other hand, if the propellant has a large particle size exceeding 500 μm, sufficiently fine and highly accurate processing can be performed. It is not possible. In addition, it is especially preferable that the average particle diameter of the injection material is 40 μm or less in that fine processing is performed. Here, the material of the propellant is not particularly limited, but glass beads and alumina are mainly used, and SiC, silica sand and the like can also be used. Further, when the nozzle 4 to be used has a round hole injection port, a round hole nozzle having a diameter of φ0.3 to φ3.0 mm is used, and when the injection port is rectangular, 0.5 × 3.0 to A 1.5 x 3.0 mm rectangular hole nozzle should be used. That is, when the size of the injection port is within the above-described range, the gradation pattern can be formed with high processing efficiency and processing accuracy. Furthermore, if the flow rate of the propellant is set to 10 g / min or less, it is difficult to form a concave portion having a surface roughness Ra of about 0.05 μm on the surface of the mirror-finished workpiece 6 when the flow rate exceeds 10 g / min. Because it becomes.
[0014]
It is appropriate that the distance between the nozzle 4 and the workpiece 6 is 100 to 300 mm. This is because if the injection distance between the nozzle 4 and the workpiece 6 is less than 100 mm, the rebound of the injection material hitting the workpiece 6 is large, while if it exceeds 300 mm, the collision speed of the injection material decreases and the machining efficiency decreases. By applying the sandblasting process as described above to the surface of the mirror-finished work 6, a light guide plate or a light guide plate molding die with good light guide property that does not generate uneven brightness 12 can be manufactured.
[0015]
【Example】
Hereinafter, the present invention will be described in detail according to examples.
The gradation pattern forming conditions were as follows.
Nozzle: Rectangular nozzle of 1.0 × 3.0mm, Injection material: Glass beads with an average particle diameter of 30μm, Injection material flow rate: 10g / min, Nozzle scanning speed: 50mm / sec, Injection distance between nozzle and workpiece: 200mm.
Then, while gradually reducing the scanning pitch from 10 mm to 2 mm, the injection pressure of 0.35 MPa at the initial stage of machining was gradually increased to 1.1 MPa with an increase of 0.01 to 0.02 MPa, and the width 100 mm and length 190 mm The light guide plate molding material made of stainless steel plate was subjected to sandblasting. The nozzle 4 was scanned by fixing the nozzle 4 side and moving the work table 5 on which the work 6 was placed in the X direction and the Y direction.
As a result of the gradation pattern formation under the above conditions, the surface roughness as shown in FIG. 3 gradually increases at the start, increases greatly at the middle, and gradually increases again at the end. It was possible to form a surface roughness that changed to As shown in the figure, the surface roughness Ra is about 0.15 μm at one end and about 0.37 μm at the other end. It was possible to form a gradation pattern that did not.
[0016]
【The invention's effect】
As described above, the gradation pattern forming method of the present invention controls the injection amount of the injection material to a predetermined flow rate, and also includes the scanning pitch, the scanning speed, the injection pressure, and the injection distance between the nozzle and the workpiece. By performing sandblast scanning while changing at least one of the above, the surface roughness can be changed linearly or curvedly from one end of the workpiece to the other, and the change in surface roughness is stepped in steps. Therefore, the brightness unevenness appearing at the boundary between the bands having different surface roughness as in the conventional case does not occur. In particular, by making the surface roughness at one end of the workpiece smaller than that of the central part and with a small degree of change, it is possible to produce a light guide plate and its mold that have no light unevenness and have excellent light guide properties. can do. In addition, the pressure of the high-pressure gas is adjusted while changing the scanning pitch by an adjustment amount of 0.1 to 5 mm so that the surface roughness is 0.02 μm or more at one end of the workpiece and 0.50 μm or less at the other end. By performing the change with an adjustment amount of 0.001 to 0.05 MPa, it is possible to form a gradation pattern on the workpiece, which does not generate uneven brightness or bright spots . What follow, the present invention is a gradation pattern forming method capable of producing the light guide plate or light guide plate mold having an excellent light diffusing surface light guide is very large ones industrial value.
[Brief description of the drawings]
1 is a block diagram illustrating the principal components of a grayed La retardation patterning device.
FIG. 2 is a conceptual diagram of surface roughness distribution in a gradation pattern formed by the method of the present invention.
FIG. 3 is a distribution diagram of surface roughness in a gradation pattern formed by the method of the present invention.
FIG. 4 is an explanatory diagram of a sandblast scanning process.
FIG. 5 is a distribution diagram of surface roughness in a conventional gradation pattern.
FIG. 6 is a plan view of a work in which bright unevenness occurs.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tank 2 Compressor 3 Fixed_quantity | feed_rate supply apparatus 4 Nozzle 5 Worktable 6 Work 7 Scanning mechanism 8 Control apparatus

Claims (1)

In the gradation pattern forming method in which the surface roughness is changed by dispersing a large number of minute recesses by performing a sandblast scanning process in which an injection material is injected from a nozzle with a high-pressure gas to the surface of the workpiece.
Controlling the injection amount of the injection material set to 10 g / min or less to ± 3 to 10% variation, nozzle or workpiece scanning pitch is 10 mm or less, adjustment amount 0.1 to 5 mm, scanning speed is 300 mm / sec or less, injection By setting the pressure to 1.50 MPa or less, the adjustment amount from 0.001 to 0.05 MPa, and the injection distance between the nozzle and the workpiece from 100 to 300 mm, the scanning process is performed while changing at least one of these, thereby the surface of one end of the workpiece. The roughness Ra (JIS B061; 1994) is 0.02μm or more, the surface roughness Ra of the other end is 0.5μm or less, and the surface roughness at one end of the work is smaller than the center and the degree of change is small. A method for forming a gradation pattern, wherein the surface roughness is increased in a curved manner from one end to the other end of the workpiece.

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