JP2003066613A - Method for producing stamper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a stamper for manufacturing a light guide for eliminating unevenness in luminance on the whole surface of the light guide. SOLUTION: A region 52 with a formed rugged pattern and a dummy electroforming area 53 are exposed as electrically conductive parts on an electrically conductive substrate 51 passed through a developing step. A photoresist layer 54 is left on the other region. The dummy electroforming area is not disposed on the counter incident light side 56 of a light guide to be manufactured. The electrically conductive substrate is placed as a cathode in such a way that it confronts an anode to carryout plating. Plating thickness depends on current density distribution. Current density to the individual portion of the rugged part can be made uniform by disposing the dummy electroforming area, the rugged pattern is made uniform in height and a light guide manufactured with this stamper is free of unevenness in luminance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a stamper used for manufacturing a light guide plate for a back surface used in a liquid crystal display device or the like.

[0002]

2. Description of the Related Art Light diffusion provided with a light guide plate of a so-called edge light system in which light is incident from a side end surface of a transparent plate and is emitted from one surface (light emitting surface) of the transparent plate to illuminate. The device is used as a back lighting device used in a liquid crystal display device provided in a word processor, a personal computer, a flat-screen television, or the like. In such a light diffusion device, a tubular light source is arranged on one side end surface of the light guide plate or on the side end surfaces facing each other, and the remaining surface of the light guide plate excluding the side end surface on which light is incident and the light emission surface on which light is emitted. Is an element that changes the angle of light transmitted through the light guide plate or the angle of light reflected by the light guide plate (hereinafter referred to as "deflection element").
Say. ) Is provided and configured.

Light incident from the side end surface of the light guide plate is redirected at the light exit surface and the surface facing the light exit surface and exits from the light exit surface. It is reflected and propagates in the light guide plate. Generally, the density distribution of the deflection elements and the angle at which the light is deflected by the deflection elements are determined so that the brightness of the light diffusing device is uniform over the entire light exit surface.

As the above-mentioned deflecting element, a white ink or paint that scatters or reflects light is applied to the surface of the light guide plate, and an uneven portion for scattering or reflecting light is provided on the surface of the light guide plate. , A light guide plate containing a light diffusing agent.

The above-mentioned type of light guide plate is manufactured by screen printing or the like. However, when the composition of the white ink or paint changes, the light reflectivity changes and the brightness is not uniform. If dust is mixed in white ink or paint or adheres to the printing surface or the coating surface, unexpected scattering of light is caused by the dust, and the planned brightness cannot be made uniform. Further, in the above-mentioned type of light guide plate, it is difficult to disperse the light diffusing agent in the substrate with high reproducibility even if the deflecting element is provided so as to have a predetermined density distribution.

For the above reasons, the light guide plate of the above-mentioned type, that is, the light guide plate provided with the uneven portion for scattering or reflecting the light on the surface of the light guide plate, is used for the back lighting device of many liquid crystal display devices. Is used for.

In the uneven portion of the type of light guide plate, the density of the uneven portion of the light guide plate on the light incident side (light incident side) is higher than that of the uneven portion on the opposite side of the light incident side (anti-light incident side). It is formed to be rough. That is, the unevenness on the light incident side of the light guide plate is rough, and the unevenness on the non-light incident side of the light guide plate is dense. The reason for this is that the amount of light that enters the light guide plate and passes through the light guide plate decreases from the light incident side to the non-light incident side. To lower the diffusion rate, and on the side opposite to the light incident side far from the light incident side,
This is because the density of the uneven portion is increased and the diffusion ratio is increased so that the entire surface of the light guide plate has uniform brightness.

FIG. 8 is a schematic view showing a general manufacturing process of a light guide plate having an uneven portion as a deflecting element on the surface.
In the figure, 81 is a glass master, 82 is a photoresist layer, 8
Reference numeral 2a is an exposed portion, 82b is an unexposed portion, 83 is a photomask, 83a is a transmissive portion, 83b is a light shielding portion, 84 is a conductive film, 85 is an electroformed body, 87 is a stamper, and 88 is a light guide plate.

FIG. 8A shows a disk-shaped glass master disk 81. One side of the glass master 81 is mirror-polished and washed.

FIG. 8B shows a photoresist layer forming step. A disk-shaped glass master disk 81 whose surface has been polished is placed on a turntable of a spin coater (not shown), and a positive photoresist is applied to the polished surface of the glass master disk 81 to form a photoresist layer 82. .

FIG. 8C shows an exposure process. A photomask 83 having a plurality of patterns (hereinafter referred to as “deflection patterns”) corresponding to the deflection elements is adhered to the surface of the photoresist layer 82. In the photomask 83, the deflection pattern portion is formed as a light transmitting portion 83a that transmits light, and the area other than the deflection pattern portion is formed as a light shielding portion 83b that does not transmit light. The upper surface of the photomask 83 is exposed to light having a wavelength with which the photoresist layer 82 is exposed. At this time, a region of the photoresist layer 82 corresponding to the transmissive part 83a is exposed and becomes an exposed part 82a, and a region not exposed by the light shielding part 83b becomes an unexposed part 82b.

FIG. 8D shows a developing process. The glass master 81 on which the exposed photoresist layer 82 is formed is attached to a developing device, the photoresist layer 82 is developed with a developing solution, and the developing solution is washed with pure water. At this time,
The exposed area 82a, which is the exposed area of the photoresist layer 82 corresponding to the deflection pattern of the photomask 83 exposed in the exposure step, is removed, and the unexposed area 82b remains on the glass master 81.

FIG. 8E shows a conductor film forming step.
The glass master 81, which has been developed in the developing step and has the unexposed portion 82b left, is attached to a sputtering device or an evaporation device, and the unexposed portion 82b of the photoresist layer of the glass master 81 is formed by a sputtering method or an evaporation method. Chrome (Cr), nickel (N
A conductor film 84 such as i) is formed.

FIG. 8F shows an electroforming process. The glass master 81 having the conductor film 84 formed thereon is attached to the cathode of an electroforming apparatus, and nickel electroforming is performed to form an electroformed body 85 to which the deflection pattern is transferred. The thickness of the electroformed body 85 is about 0.
It is 1 mm to 0.5 mm.

FIG. 8G shows a stamper working process.
After the electroforming step, the electroformed body 85 is peeled off from the glass master 81,
To wash. Then, the back surface of the electroformed body 85 is polished, and the outer periphery is cut into a desired shape to obtain a stamper 87.

FIG. 8H shows a molding process. The stamper 87 is mounted in the mold of the injection molding machine. The injection molding machine injects a molten resin such as an acrylic resin into a mold to which a stamper 87 is attached to mold the light guide plate 88.
The formed light guide plate 88 is cooled in the mold and taken out.

Further, Japanese Patent Laid-Open No. 4-259938 discloses a method of manufacturing a stamper for manufacturing an information recording body. This manufacturing method uses a silicon wafer or a metal plate instead of the glass master, forms a photoresist layer on the silicon wafer or the metal plate, exposes the pattern,
After development, by dry etching using the developed photoresist layer as a mask member, a concave portion corresponding to the pattern is formed on the silicon wafer or the metal plate to obtain a mother board, and the mother board is electroformed. It is a way to get a stamper.

In the conventional method of manufacturing a stamper for a light guide plate shown in FIG. 8 and the method of manufacturing a stamper for manufacturing an information recording body disclosed in Japanese Patent Laid-Open No. 4-259938, the time required for the electroforming step is shown. Is long and the manufacturing cost is high. A stamper for a light guide plate needs to have a thickness of about 0.1 to 0.5 mm. For example, in order to obtain an electroformed body having a diameter of 200 mm and a thickness of 0.3 mm, electroforming for 1 hour or more is required. It takes time. In order to manufacture a stamper of a light guide plate for a large liquid crystal display device having a diagonal of 15 inches, it is necessary to use a glass master having a diameter of 500 mm.
In this case, there is a problem that it takes 4 hours or more to form an electroformed body having a thickness of 0.3 mm.

Further, in the method of manufacturing a stamper for manufacturing an information recording body disclosed in Japanese Patent Laid-Open No. 4-259938, it is necessary to sufficiently dry the developed photoresist layer in order to carry out dry etching. It is necessary to bake the photoresist layer at 120 ° C. for 1 hour. Furthermore, when a large area silicon wafer or metal plate is used, a large dry etching apparatus is required, and there is a problem that equipment cost increases.

A method for manufacturing a stamper has been proposed which can solve the problems of electroforming time and dry etching described above. This method is disclosed in Japanese Patent Laid-Open No. 2001-336.
No. 34 publication.

FIG. 9 shows the above-mentioned Japanese Patent Laid-Open No. 2001-33634.
It is a schematic diagram which shows the manufacturing process of the stamper for manufacturing the light guide plate described in the publication. In the figure, 91 is a conductive substrate, 92 is a photoresist layer, 92a is an exposed portion, and 92b.
Is an unexposed portion, 93 is a photomask, 93a is a transmissive portion, 9
3b is a light shielding part, 94 is light, 95 is an electroformed part, and 96 is a stamper.

FIG. 9A shows a conductive substrate 91. FIG. 9B shows a photoresist forming process. A positive photoresist is applied on the conductive substrate 91 by a spin coat method, a spray coat method, a roll coat method, a dip method or the like to form a photoresist layer 92. At this time, the photoresist layer 92 is formed to be thicker than the depth (height) of the deflection pattern of the light guide plate to be obtained. As will be described later, the height of the deflection pattern of the stamper corresponding to the deflection pattern of the light guide plate is determined by the height at which the electroformed body is stacked on the stamper. Photoresist layer 92
Is the depth (height) of the deflection pattern of the light guide plate to be obtained
The thickness of the photoresist layer 92 need only be made thicker, and it is not necessary to control the thickness of the photoresist layer 92 with high accuracy.

FIG. 9C shows an exposure process. A photomask 93 in which a plurality of deflection patterns are drawn as the transmissive portions 93a is brought into close contact with the surface of the photoresist layer 92, and light having a wavelength with which the photoresist layer 92 is exposed from the upper surface of the photomask 93 (ultraviolet (UV) light). It exposes at 94. At this time, the portion of the photoresist layer 92 corresponding to the transmissive portion 93a is exposed to light to become an exposed portion 92a, and the other portion corresponding to the light shielding portion 93b becomes an unexposed portion 92b. Next, baking processing is performed as needed.

FIG. 9D shows the developing process. The conductive substrate 91 on which the exposed photoresist layer 92 is formed is attached to a developing device, the photoresist layer 92 is developed with a developing solution, and the developing solution is washed with pure water. At this time,
The exposed portion 92a of the photoresist layer 92 corresponding to the deflection pattern of the photomask exposed in the exposure step is removed, and the unexposed portion 92b remains on the conductive substrate 91.

FIG. 9E shows an electroforming process. The electroconductive substrate 91 that has undergone the developing process and the surface treatment process is attached to the cathode of the electroforming apparatus, nickel electroforming is performed, and the electroformed portion 95 is formed in a portion where the exposed portion 92a is removed, that is, a region corresponding to the deflection pattern. Form.

In a general stamper manufacturing method,
The thickness of the electroformed body is the thickness of the stamper (generally 0.1 to
It was necessary to perform electroforming until the thickness became 0.5 mm). However, according to this stamper manufacturing method, electroforming may be performed until the thickness of the electroformed portion 95 reaches the height of the deflection pattern of the light guide plate. The time spent for electroforming may be, for example, about tens of minutes.

FIG. 9F shows the stamper cleaning process.
The photoresist on the surface of the stamper is removed from the conductive substrate 91 that has undergone the electroforming process by using a photoresist remover, acetone, alcohol or the like. Next, the stamper 96 can be obtained by processing into a desired shape.

In the stamper manufacturing process shown in FIG. 9, it is possible to shorten the time required for manufacturing the stamper without requiring special equipment such as dry etching, but in the case of forming the uneven portion by electroforming. However, there is a problem that the height of the deflection pattern varies due to the nonuniformity of the electroformed thickness.
This is a variation in the current density distribution depending on the physical positions of the anode and the cathode. In other words, it is due to the difference in the resistance value of the bath from the anode to the electroformed portion on the conductive substrate. This difference in resistance value is determined by the composition of the plating bath (including impurities), bath temperature, pH, and current density.

The cross-sectional shape of the dot includes a concave dot as shown in FIG. 2 (B) and a convex dot as shown in FIG. 2 (C). When such dots are used, the density of the irregularities on the light-incident side of the light guide plate is rough, and the density of the irregularities on the light-incident side of the light guide plate is high. If the height is not constant, the luminance distribution will not be uniform. Therefore, due to the non-uniformity of electroforming thickness,
If the heights of the uneven portions vary, the luminance distribution becomes uneven.

FIG. 3 shows conditions of a general nickel sulfamate bath (nickel ion concentration 400 g / liter, bath temperature 50 ° C., pH) on a nickel substrate having a diameter of 500 mm.
FIG. 4 is a diagram showing an electroformed thickness distribution when electroformed for 2 hours at a current density of 2.5 A / dm ² ). The vertical axis is the electroformed thickness (μ
m), the horizontal axis has a center of 0 and the cross-sectional position along the diameter is ± 2
It is represented by 50 mm. It can be seen that the center is electroformed with a uniform thickness, but the ends are thicker.

FIG. 4 is a schematic sectional view for explaining a current distribution when electroforming. In the figure, 41 is a plating solution, 42
Is a plating tank, 43 is a cathode, 44 is an anode, 45 is a DC power supply, and 46 is a current distribution. In a plating tank 42 filled with the plating solution 41, the electroformed surface is used as a cathode 43, soluble nickel is used as an anode 44, and a DC power supply 45 is applied to perform plating. The current density is high at the end of the cathode 43, as shown in the figure. As a result, the electroformed thickness varies.

When the stamper is manufactured by the method shown in FIG. 9, the current distribution is biased due to the difference in the density of the concavo-convex pattern and the physical position. Where the uneven pattern is dense, the electroformed area is large, the current density per uneven part of the uneven pattern is low, the electroforming amount is small, and the height of the uneven part is small. Where the uneven pattern is sparse, the electroformed area becomes small, the current density per uneven part of the uneven pattern becomes high, the electroforming amount becomes large, and the height of the uneven part becomes large. At some ends of the uneven pattern, current flows in, so the current distribution density is high. Therefore, the height of the uneven portion becomes higher than that of the central portion of the uneven pattern, and there is a problem in that the height varies.

[0033]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in a stamper for manufacturing a light guide plate, there is no unevenness in the height of the uneven portion of the light guide plate to be manufactured, and the unevenness of brightness is obtained. It is an object of the present invention to provide a method of manufacturing a stamper for manufacturing a light guide plate that does not cause a decrease in brightness.

[0034]

According to a first aspect of the invention, in a method of manufacturing a stamper for manufacturing a light guide plate, a photoresist forming step of forming a photoresist layer on one surface of a substrate having conductivity. An exposure step of exposing using a photomask having a pattern such that the light-incident side and the non-light-incident side of the light guide plate on which the photoresist layer is formed are uneven patterns having different unevenness densities; A development process for developing a layer and a dummy electrode are provided on a portion of the conductive substrate other than the area where the concave-convex pattern is formed, except for the side corresponding to the non-light incident side of the light guide plate to be manufactured. A dummy electroformed portion forming step of forming a cast portion; and an electroformed step of forming an electroformed portion according to the uneven pattern of the photoresist layer on the conductive substrate, The height of the electroformed part formed in extent are those heights of the concavo-convex portion of the light guide plate to be manufactured is characterized in that it is a kind of height the same.

According to a second aspect of the present invention, in the stamper manufacturing method according to the first aspect, a pattern corresponding to the dummy electroformed portion is formed in advance on the photomask. is there.

[0036]

1 is a schematic diagram for explaining an example of an embodiment of a manufacturing process of a stamper of the present invention for manufacturing a light guide plate. In the figure, 11 is a conductive substrate, 1
2 is a photoresist layer, 12a is an exposed part, 12b is an unexposed part, 13 is a photomask, 13a is a light shielding part, 13b is a transmissive part, 14 is UV light, 15 is an electroformed part, and 16 is a stamper.

FIG. 1A shows the conductive substrate 11. In this embodiment, a nickel plate is used as the conductive substrate 11. As the conductive substrate, a metal substrate other than nickel may be used, or an insulating substrate such as a glass master having a conductive metal film formed on one surface may be used. In this embodiment, the conductive substrate is
Although a conductive substrate having a circular shape with a diameter of 500 mm and a plate thickness of 0.3 mm and having an arithmetic average roughness of 0.01 μm or less was used, the size is not limited to this.

FIG. 1B shows a photoresist forming process. The conductive substrate 11 using a nickel plate is attached to a spin coater, a negative type photo resist (ZPN1100 manufactured by Zeon Corporation) is applied at 280 rpm, and the entire surface of the nickel plate is coated with the resist. At this point, the resist is in a liquid state and has ripples on the surface, so that the resist surface is left flat for 5 minutes so that the resist surface is flat and the film thickness is constant. This is baked at 80 ° C. for 30 minutes to be completely dried. Thus, the photoresist layer 1 having a thickness of 10 μm
Form 2. At this time, the thickness of the photoresist layer 12 is made slightly higher than the height of the deflection pattern of the light guide plate to be obtained.

The formation of the photoresist layer 12 is not limited to the spin coating method, but the spray coating method,
A roll coat method, a dip method or the like may be used. Also,
The photoresist is a negative type, but may be a positive type.
However, the negative type is preferred. Also in the present invention, the photoresist layer 12 may be formed thicker than the depth (height) of the deflection pattern of the light guide plate to be obtained, and it is not necessary to precisely control the thickness of the photoresist layer 12. There is an advantage.

FIG. 1C shows an exposure process. The pattern of the photomask used for the exposure was formed so that the density of the irregularities on the light-incident side of the light guide plate to be manufactured was rougher than the density of the irregularities on the side opposite to the light-incident side (anti-light-incident side). It is a pattern. That is, the pattern is formed such that the unevenness of the light-incident side of the light guide plate is rough and the density of the unevenness becomes denser toward the non-light-incident side of the light guide plate.
The photomask 13 on which this pattern is drawn is brought into close contact with the surface of the photoresist layer 12. Photo mask 13
In the above, the deflection pattern is composed of a light-shielding portion 13a which does not transmit the UV light 14 which will be described later and a transmission portion 13b which transmits the UV light 14 in the other portions. In this embodiment, a 10-inch photomask 13 is used. Then, UV light (ultraviolet light) 1 which is light having a wavelength that the photoresist layer 12 sensitizes from the upper surface of the photomask 13
Exposure at 4. At this time, the region corresponding to the transmissive portion 13b other than the region corresponding to the light shielding portion 13a of the photoresist layer 12 is exposed to light and becomes the exposure portion 12a.
The area shielded by becomes the unexposed portion 12b. Next, put it in the oven and put PEB (POST EXPOS
URE BAKE) at 90 ° C. for 5 minutes. At this time, in the exposed portion 12a, a crosslinking reaction occurs due to the catalyst generated by the exposure, and the exposed portion 12a becomes insoluble in the developing solution.

FIG. 1D shows the developing process. Photoresist layer 1 which was not exposed by the developing solution by attaching the nickel plate 11 that has undergone the exposure process and PEB to the developing device.
2 is developed and the developer is washed with pure water. At this time,
The unexposed portion 12b of the photoresist layer 12 that was not exposed to the UV light 14 in the exposure step is removed, and the exposed portion 12a remains on the nickel plate 11.

FIG. 1E shows an electroforming process. In order to remove excess water from the conductive substrate 11 having the patterned photoresist layer 12, baking is performed at 80 ° C. for 30 minutes.
After that, an electrocasting is performed to form an uneven pattern. The electrocasting process will be described with reference to FIGS. 5 to 7.

FIG. 5 is an explanatory view of a conductive substrate applied to the electroforming process. In the figure, 51 is a conductive substrate, 52 is a concavo-convex pattern forming region, 53 is a dummy electroformed part, 54 is a photoresist layer, 55 is an incident light side, 56 is an anti-incident light side, 57.
Is a stamper cutting line.

On the conductive substrate 51 that has undergone the development process, a concave / convex pattern, in this example, a portion corresponding to a dot forming a convex portion is formed as a concave / convex pattern forming region 52 from which the photoresist layer is removed, The dummy electroformed portion 53, which is a temporary electroformed surface, is exposed as a conductive portion. In the other regions, the exposed portion is developed and the photoresist layer 54 remains. The dummy electroformed portion 53 is provided so as to surround the incident light side 55 and both side portions of the light guide plate manufactured corresponding to the uneven pattern formation region 52, and is not provided on the counter incident light side 56. The stamper cutting line 57 is a line formed by exposing and developing the cutting line pattern printed on the photomask together with the concavo-convex pattern on the photoresist layer 54.

The dummy electroformed portion 53 is formed on the conductive substrate 51 by printing the dummy electroformed pattern together with the concavo-convex pattern on the photomask. The photoresist layer in the region where the dummy electroformed portion of the conductive substrate is formed. It is only necessary to form the region electrically connected to the conductive substrate 51 by a method such as a method in which a conductive jig provided separately is used as a dummy electroformed portion.

In the method, the dummy electroformed pattern is printed in advance on the portion corresponding to the dummy electroformed portion of the photomask, the photomask is brought into close contact with the conductive substrate and exposed, and the conductive substrate and the concavo-convex pattern are formed together. This is a method of forming a dummy electroformed part.

In the method (1), the exposed photoresist layer is removed by removing the photoresist layer on the dummy electroformed portion on the conductive substrate with a solvent such as photoresist remover, acetone, alcohol, etc. In this method, the substrate surface is used as a dummy electroformed part.

In the method of (1), a conductive jig having a shape of a part of the stamper cutting line 57, which is the end surface of the stamper shape, or the outside one surface at the time of the electroforming step is prepared in advance, and an uneven pattern is formed. Overlap with the conductive substrate 51,
This is a method in which a metal fitting is attached to the end surface to energize, and the jig surface is used as a dummy electroformed part.

FIG. 6 is a schematic configuration diagram for explaining the electroforming apparatus. In the figure, 61 is an adjusting tank, 62 is a pump, 63
Is a filter, 64 is an electroforming tank, 65 is an electroforming liquid discharge pipe, 66
Is a cathode tip jig, 67 is an anode case, 68 is a conductive substrate, and 69 is an energizing shaft.

The electroforming liquid pumped up by the pump 62 from the adjusting tank 61 is filtered by the filter 63 and sent to the electroforming tank 64. The sent electroforming liquid overflows in the electroforming liquid 64 and returns to the adjusting tank 61 through the electroforming liquid discharge pipe 65. The adjusting tank 61 is provided with a heater and a cooler,
After the temperature is adjusted here, it is sent to the electroforming tank 64 again.

Inside the electroforming tank 64, a cathode tip jig 66 at the cathode tip and an anode case 67 are installed opposite to each other. On the cathode tip jig 66, a conductive substrate 68, which is an electroformed object to be electroformed, is attached. The anode case 67 is filled with granular nickel. The electric current reaches the surface of the conductive substrate 68 from the power source through the anode case 67 and the electroforming liquid, and deposits nickel. Further, it returns to the power source via the energizing shaft 69. The energizing shaft 69 and the cathode tip jig 66 are connected to the conductive substrate 6
It is rotated in the electroforming tank 64 so that the exposed conductive surface of 8 is uniformly electroformed.

FIG. 7A is an explanatory view of the operation in the electroforming apparatus of FIG. In the figure, 71 is an uneven pattern forming region, 72 is a dummy electroformed part, 73 is a conductive substrate, 74 is a resist mask, and 75 is a current density distribution.

The conductive substrate 73 is set as a cathode so as to face the anode. Electroforming is, for example, with a nickel sulfamate bath, nickel sulfamate 450 g
/ L, boric acid 30g / l, pH 4.0, bath temperature 50 ° C, current value 0.5A, electroforming is carried out for 40 minutes, and the height of electroformed part is 8
formed to a thickness of μm. Electroforming is performed by plating nickel on the removed portion of the resist mask (exposed portion of the photoresist layer), and the plating thickness depends on the current density distribution. Regarding the current density distribution, on the side where the dummy electroformed portion 72 of the uneven pattern forming region 71 is provided, the current is drawn to the dummy electroformed portion 72 side due to the electroforming area ratio including the dummy electroformed portion 72, The density distribution 75 becomes almost uniform. Dummy electroformed part 72 of the uneven pattern forming region 71
On the side where no pattern is provided, that is, on the side where the concavo-convex pattern is incident on the opposite side of the light, the dummy electroformed part 72 that causes a current diversion is formed.
Therefore, the current density distribution 75 becomes dense. On the side opposite to the incident light side, the density of the uneven portions is high, so the current density for each uneven portion is small, but the current density for each uneven portion is increased by the absence of the dummy electroformed portion 72. Can be the same as a whole.

Normally, a large current of about 50 A is used during electroforming, but here the height of the electroformed part can be easily controlled and the surface roughness of the electroformed part is reduced. Use low current. Other than nickel, for example, a metal such as chromium or copper can be used as the electroformed product. In this embodiment, the electroformed portion corresponds to the uneven pattern of the light guide. Generally, the height of the uneven pattern of the light guide is 2 to 50 μm.
The degree is appropriate. Therefore, the thickness of the electroformed body is 2 to 5
Nickel electroforming is carried out to a desired height in the range of 0 μm.

The density distribution of the uneven pattern is shown in FIG. On the incident light side, the density of the concave-convex pattern is low, so that current is likely to concentrate. Therefore, in order to let the current escape to the outside, the dummy electroformed portion 72 is provided on the incident light side of the concavo-convex pattern. On the side of the non-incident light, the current density is low because the uneven pattern has a high density. Therefore, without providing a dummy electroformed part,
By making use of the fact that the current is easily concentrated at the end portions, the current density in each uneven portion can be made the same as a whole. By electroforming with such a current density distribution, the height of the uneven pattern in the uneven pattern forming region 71 can be made constant. In this specification, the height of the concavo-convex pattern means the height of the convex portion in the case of the convex portion,
In the case of a recess, it is the depth of the recess. Therefore, as for the concave portion, the high height of the concave-convex portion means that the depth of the concave portion is large.

The above is the electroforming step of FIG. 1 (E).

In the stamper cleaning step of FIG. 1 (F), after removing the photoresist layer 12 to some extent by a photoresist remover, acetone, alcohol, or the like on the conductive substrate that has undergone the electroforming step, oxygen ashing is performed as a finish. Oxygen gas pressure 0.5Pa, ashing power 500W
Then, for 3 minutes, the photoresist layer 12 on the surface of the stamper 16 is completely removed. Next, a stamper having a constant height of the concavo-convex pattern can be obtained by processing the stamper into a desired shape. When injection molding is performed using this stamper, an uneven pattern having a constant height (depth in this example) of the uneven pattern can be produced, and a light guide plate having no uneven brightness is obtained.

In the stamper manufacturing method described with reference to FIG. 1, a surface treatment step may be provided between the developing step and the electroforming step. In the surface treatment step, first, a nickel plate is attached to an ashing device, oxygen ashing and UV ozone ashing are performed, and the resist residue left on the surface of the nickel plate exposed by removing the photoresist layer by development is removed. . Subsequently, the nickel plate is dipped in a dilute sulfuric acid solution, and the photoresist film is removed by development to remove the oxide film formed on the surface of the nickel plate. By performing such processing,
In the electroforming step, the adhesion between the electroformed part formed on the nickel plate and the nickel plate is enhanced, and the electroformed part can be prevented from falling off from the nickel plate.

FIG. 2 is a perspective view of a part of a light guide plate manufactured by the stamper of the present invention. The cross-sectional shape of the concave-convex portion 22 of the light guide plate 21 is formed as a concave portion as shown in FIG. 2 (B) in the case of the stamper obtained in FIG. 1 (F).

It is also possible to form a peeling film such as an oxide film on the surface of the light guide plate stamper obtained by the manufacturing method of FIG. 1 and perform electroforming to transfer and manufacture the light guide plate stamper in which the unevenness of the uneven pattern is reversed. it can. When injection molding is performed using this stamper,
The unevenness of the uneven pattern is opposite to that of FIG.
The light guide plate having the convex and concave portions shown in (C) is produced.

[0061]

As is apparent from the above description, according to the present invention, a stamper manufacturing method for shortening the electroforming time,
There is an effect that the height of the concavo-convex pattern is made uniform, uneven brightness is eliminated in the light guide plate, and a light guide plate capable of obtaining good brightness is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an example of an embodiment of a manufacturing process of a stamper of the present invention for manufacturing a light guide plate.

FIG. 2 (A) is a perspective view of a part of a light guide plate manufactured by the stamper of the present invention, FIG. 2 (B) is a sectional view of a concave portion, and FIG. 2 (C) is a sectional view of a convex portion. It is a figure.

FIG. 3 is a diagram showing a distribution state of electroformed thickness.

FIG. 4 is a schematic cross-sectional view for explaining a current distribution when electroforming.

5 is an explanatory view of a conductive substrate applied to the electroforming process of FIG.

6 is a schematic configuration diagram for explaining an electroforming apparatus used in the electroforming step of FIG.

7 (A) is an explanatory diagram of the operation in the electroforming apparatus of FIG. 6, and FIG. 7 (B) is an explanatory diagram of the density distribution of the concavo-convex pattern.

FIG. 8 is a schematic view showing a manufacturing process of a conventional example of a light guide plate having an uneven portion.

FIG. 9 is a schematic view showing another conventional manufacturing process of a light guide plate having an uneven portion.

[Explanation of symbols]

11 ... Conductive substrate, 12 ... Photoresist layer, 12a ...
Exposed part, 12b ... Unexposed part, 13 ... Photomask, 13
a ... light-shielding part, 13b ... transmissive part, 14 ... UV light, 15 ... electroformed part, 16 ... stamper, 21 ... light guide plate, 22 ... concave part or ... convex part, 41 ... plating solution, 42 ... plating tank, 43 ... Cathode, 44 ... Anode, 45 ... DC power supply, 46 ... Current distribution, 5
1 ... Conductive substrate, 52 ... Concavo-convex pattern forming region, 53 ...
Dummy electroformed part, 54 ... Photoresist layer, 55 ... Incident light side, 56 ... Anti-incident light side, 57 ... Stamper cutting line, 61 ...
Adjusting tank, 62 ... Pump, 63 ... Filter, 64 ... Electroforming tank, 65 ... Electroforming liquid discharge pipe, 66 ... Cathode tip jig, 67 ...
Anode case, 68 ... Conductive substrate, 69 ... Energizing shaft, 71 ... Concavo-convex pattern forming region, 72 ... Dummy electroformed part, 73 ... Conductive substrate, 74 ... Resist mask, 75 ...
Current density distribution.

Continued front page    F-term (reference) 2H038 AA55 BA06                 2H091 FA23Z FA41Z FC19 FC29                       LA18                 2H095 BA12 BB02 BB36 BC09                 2H097 CA12 LA17                 4F202 AF01 AG05 AH79 CA11 CB01                       CD07 CD12 CD22 CD30 CK43

Claims (2)

[Claims] 1. A method of manufacturing a stamper for manufacturing a light guide plate, comprising: a photoresist forming step of forming a photoresist layer on one surface of a conductive substrate; and a light guide plate light on which the photoresist layer is manufactured. An exposure step of exposing using a photomask having a pattern such that the unevenness density is different between the incident side and the counter-light incident side, a developing step of developing the photoresist layer, and the uneven pattern is formed. A dummy electroformed portion forming step of forming a dummy electroformed portion on a portion other than the side corresponding to the side opposite to the light incident side of the light guide plate to be produced, which is on the conductive substrate other than the range, There is an electroforming step of forming an electroformed portion according to the uneven pattern of the photoresist layer on the conductive substrate, and the height of the electroformed portion formed in the electroforming step is A method for manufacturing a stamper, characterized in that the heights of the uneven portions of the manufactured light guide plate are the same. 2. The stamper manufacturing method according to claim 1, wherein a pattern corresponding to the dummy electroformed portion is previously formed on the photomask.