JP2007033998A - Manufacturing method for microlens sheet, the microlens sheet, manufacturing method for projection screen and the projection screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a microlens, and the like, whereby when recesses for forming microlenses are formed, improved discharge properties of foreign matter from etching holes is ensured, while holding a satisfactory shape. <P>SOLUTION: The manufacturing method for a microlens sheet 3 having the plurality of microlenses 3a includes a step of disposing an etching mask film 12 having the etching holes 13 onto a substrate 11; a first etching step of etching the substrate 11 via the etching holes 13; a processing step of increasing the area of the opening of each etching hole 13; a second etching step of etching the substrate 11 via the processed etching holes 13; a step of removing the etching mask film 12 from the substrate 11; and a step of transferring recesses 14, formed in the substrate 11, to a resin sheet 17. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a microlens sheet having microlenses.

In a liquid crystal rear projection television, a CRT rear projection television, or the like, a microlens sheet having a microlens (also referred to as a microlens array) is used for a projection screen that projects an image from the rear surface of the screen.
Such a projection screen includes a Fresnel lens (Fresnel sheet) that converts incident light from a projection lens into parallel light, and a microlens (microlens layer) that diffuses parallel light from the Fresnel lens.
As a microlens manufacturing method, it is formed by punching a thermoplastic resin or the like with a microlens mold. When forming this microlens mold, an etching hole for forming each recess must be provided in the etching mask film disposed on the surface of the substrate for the hemispherical recess corresponding to each microlens. There is. In particular, the etching hole formed in the etching mask film is preferably formed by, for example, a laser because it has a fine hole diameter in order to obtain a recess having a good shape.
However, since the etching hole is fine, the etching hole is blocked by foreign matter (etched base material) when etching the base material, and the concave portion is not formed or the shape of the concave portion varies. There was a problem that it occurred.
For this reason, as shown in Patent Document 1 or the like, a technique has been proposed in which the etching mask film is provided with etching holes made up of a plurality of holes, thereby improving the discharge of foreign matters from the etching holes.
JP 2004-286906 A

  However, in the above-described technique, the formation of a well-shaped recess is sacrificed in order to ensure the discharge of foreign matters from the etching hole. In other words, since the diameter of the etching holes is increased or the number thereof is increased, the substrate is etched more than necessary, particularly in the initial stage of etching, and the concave portion having a good shape (hemispherical shape) is formed. There is a problem that it is difficult to obtain.

  The present invention has been made in view of the above-described circumstances, and when forming a recess for forming a microlens, the discharge of foreign matters from an etching hole is improved while maintaining a good shape. An object of the present invention is to propose a method for manufacturing a microlens that can be used.

In the method for manufacturing a microlens sheet, the method for manufacturing a microlens sheet, the method for manufacturing a projection screen, and the projection screen according to the present invention, the following means are employed in order to solve the above problems.
1st invention is the manufacturing method of the microlens sheet | seat which has a several microlens, the process of arrange | positioning the etching mask film | membrane which has an etching hole with respect to a base material, The said base material through the said etching hole A first etching step for etching, a processing step for increasing the opening area of the etching hole, a second etching step for etching the base material through the etching hole after processing, and the etching from the base material A step of removing the mask film and a step of transferring the recess formed in the base material to the resin sheet are provided.
According to this invention, when etching the base material to be a mold for the microlens sheet, the hole diameter, the number of holes, etc. of the etching holes formed in the etching mask film are increased during the etching process. In one etching process, it is possible to form a recess having an ideal shape on the substrate using fine etching holes, and in the second etching process, foreign matter (dissolved substrate) is increased by increasing the hole diameter of the etching holes. Material) is easy to discharge.
As a result, a concave portion having an ideal shape is formed in the base material (molding die for microlens sheet), and a microlens sheet having a large number of microlenses having ideal optical characteristics is manufactured by using this molding die. It becomes possible.

In addition, when the processing time in the first etching step and the processing time in the second etching step are substantially the same, the first step and the second step of the etching process can be easily managed. .
Prior to the processing step, a step of measuring the diameter of the recess formed in the base material in the first etching step, and a step of obtaining a processing amount of the etching hole in the processing step based on the measurement result Therefore, even if the shape of the plurality of recesses formed on the substrate in the first etching step varies, the etching hole can be processed based on the shape of the recesses. By passing through the second etching step, a plurality of concave portions having a substantially uniform shape can be formed on the substrate.
Further, in the processing step, if the laser processing method is used, the etching hole can be processed easily and accurately.

  In the second invention, the microlens sheet is manufactured by the method of the first invention. According to the present invention, a microlens sheet including a plurality of microlenses having an ideal shape is manufactured, and desired optical characteristics can be obtained.

A third invention is a method of manufacturing a projection screen having a microlens sheet and a Fresnel lens sheet, and the method of the first invention is used as a method of manufacturing a microlens sheet.
According to this invention, since the microlens sheet on which high-quality microlenses are formed is provided, a projection screen with high yield and high reliability can be manufactured.

A fourth invention is a projection screen having a microlens sheet and a Fresnel lens sheet, and the microlens sheet of the second invention is used as the microlens sheet.
According to the present invention, since the microlens sheet on which high quality microlenses are formed is provided, a projection screen with excellent display performance can be obtained.

Embodiments of a microlens sheet manufacturing method, a microlens sheet, a projection screen manufacturing method, and a projection screen according to the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a microlens sheet according to an embodiment of the present invention.
The microlens sheet 3 is obtained by forming a plurality of substantially uniform microlenses 3a on one surface side of a sheet material made of PET, for example. For example, the microlens 3a is formed in a hemispherical shape having a maximum diameter of about 70 μm.
The microlens sheet 3 diffuses parallel light with a lens, and is used together with a Fresnel sheet having a Fresnel lens, for example, in a projection screen of a video projection apparatus such as a rear projection television.

Next, a method for manufacturing the microlens sheet 3 will be described.
FIG. 2 is a diagram showing manufacturing steps of the microlens sheet 3 in the order of steps.
(Etching mask film placement process)
First, as shown in FIG. 2A, for example, a CrO-Cr film (CrO is formed and then Cr is formed on one of the outer surfaces of a substrate 11 made of quartz, for example, which becomes a microlens sheet molding die. An etching mask film 12 such as the above is disposed.
The thickness of the etching mask film 12 is, for example, about 400 mm (CrO: 100 mm, Cr: 300 mm). In addition, the etching mask film 12 is not limited to be disposed on the entire surface of the substrate 11, and the etching mask film 12 may be disposed only on one surface (upper surface).

(Etching hole forming process)
Next, as shown in FIG. 2B, an etching hole 13 is formed at a predetermined position of the etching mask film 12 on one surface (upper surface) of the substrate 11 by laser processing using a laser processing device 21. To do. By etching the base material 11 through the etching holes 13, a plurality of recesses are formed in the base material 11 to obtain a microlens sheet molding die. That is, the microlens 3a is molded at a position where the etching hole 13 is to be formed.

Here, the configuration and operation of the laser processing apparatus 21 will be described.
FIG. 3 is a schematic diagram showing a schematic configuration of the laser processing apparatus.
The laser processing apparatus 21 includes, for example, a laser oscillator 22 that oscillates a YAG laser, a total reflection mirror 23, a condenser lens 25, a table 26 on which the base material 11 is placed, and the like.
The total reflection mirror 23 is disposed on the traveling path of the laser beam 24 from the laser oscillator 22 and reflects the laser beam 24 toward the substrate 11 that is a workpiece.
The condenser lens 25 is disposed between the total reflection mirror 23 and the base material 11, condenses the laser beam 24 reflected by the total reflection mirror 23, and etches the etching hole 13 in the etching mask film 12 of the base material 11. Irradiate the processing point 11a to form
The table 26 mounts the base material 11 and is movable in the X-axis or Y-axis direction by a control means (not shown). Alternatively, the laser oscillator 22, the total reflection mirror 23, and the condenser lens 25 may be configured to be movable in the X-axis or Y-axis direction without moving the table 26.
Further, the table 26 on which the base material 11 is placed may be surrounded by a glass chamber or the like to prevent foreign matters from adhering to the base material 11.

Then, an etching hole 13 is formed in the etching mask film 12 of the base material 11 using such a laser processing device 21.
Specifically, first, the base material 11 having the etching mask film 12 disposed on the outer surface is placed on the table 26, and the table is so irradiated with the laser beam 24 that the etching hole 13 is to be formed. 26 is moved.
Next, the laser oscillator 22 is driven, and the laser beam 24 irradiated from the laser oscillator 22 is condensed at the processing point 11 a to form the etching hole 13.
Then, the base material 11 on the table 26 is moved to the next etching hole forming position, and a plurality of etching holes 13 are sequentially formed.
In the present embodiment, since one concave portion 14 is formed for one etching hole 13, each etching hole 13 has a substantially uniform hole diameter (for example, a diameter of about 2 μm) and is disposed substantially uniformly. The
As long as the base material 11 can be etched, the size, shape, number and arrangement of the etching holes 13 are not limited thereto.

(First etching process)
Returning to FIG. 2C, the substrate 11 is wet-etched through the etching mask film 12 in which the etching holes 13 are formed. The substrate 11 is etched through the etching hole 13 made of a fine pinhole, and a substantially ideal hemispherical recess 14 centering on the etching hole 13 is gradually formed in the substrate 11.
However, as the etching process proceeds and the concave portion 14 approaches the final shape, the amount of foreign matter (etched base material) discharged from the etching hole 13 gradually increases. For this reason, the etching holes 13 are gradually clogged, and the foreign matter discharge efficiency is lowered.
Since the method of clogging foreign matter and the change in foreign matter discharge efficiency differ for each etching hole 13, the formation progress of the plurality of recesses 14 formed in the substrate 11 is different. Thereby, dispersion | variation generate | occur | produces in the shape of each recessed part 14, and manufacture of the microlens sheet | seat 3 of uniform quality becomes difficult.

(Etching hole expansion process)
Therefore, during the formation of the recess 14, the opening area (hole diameter, etc.) of the etching hole 13 formed in the etching mask film 12 is increased. That is, during the etching process of the base material 11, when the amount of foreign matter (base material) discharged from the etching hole 13 increases, the hole diameter of the etching hole 13 is enlarged to smoothly discharge the foreign matter. This prevents clogging of foreign matters.
Specifically, first, the base material 11 is taken out from the etching solution, washed with pure water, and the progress of the etching process is stopped. Next, as shown in FIG. It is placed on the table 26 of the laser processing apparatus 21, and the opening area (hole diameter, etc.) of the etching hole 13 is enlarged by the laser beam 24.

The timing for interrupting the etching process is controlled by the etching time. For example, when etching is performed for a total of 10 minutes, the processing is temporarily interrupted after about 5 minutes of etching. That is, the base material 11 is etched by the etching hole 13 with a fine hole diameter for about 5 minutes in the first half, and the base material 11 is etched by the etching hole 13 with an enlarged hole diameter for about 5 minutes in the second half.
In this way, the etching reproducibility can be easily ensured by managing the etching process in time.
It should be noted that the timing of interrupting the etching process can be appropriately changed depending on conditions such as the size of the microlens 3a to be formed, the initial hole diameter of the etching hole 13, the material of the base material 11, the type of the etchant, and the like.

When the hemispherical concave portion 14 having a maximum diameter of about 70 μm is formed, the etching process is interrupted when the maximum diameter is about 35 μm. Therefore, the hole diameter of the etching hole 13 is changed from about 2 μm (initial hole diameter), For example, it can be enlarged to about 20 μm. In this way, when the hole diameter is 10 times, the discharge capability of the foreign matter (base material) from the etching hole 13 is about 100 times.
In addition, the hole diameter after processing of the etching hole 13 may be substantially the same for all of the plurality of etching holes 13 or may be different from each other.

For example, when the etching hole 13 is processed into a different hole diameter, the following method can be used.
First, after the etching process on the base material 11 is stopped, the size of the recess 14 in the middle of formation existing in the base material 11, specifically, the maximum diameter of the recess 14 is measured. Since the base material 11 consists of a very thin film | membrane, it is possible to measure the maximum diameter of the recessed part 14 in the middle of formation from the outside. By measuring the maximum diameter of the recess 14 in the middle of formation, the progress of etching, in other words, the progress of formation of each recess 14 can be grasped. In this way, variations in the shape of the plurality of recesses 14 present in the base material 11 can be confirmed.
Next, when the hole diameter of the etching hole 13 is enlarged, the opening area (processing amount) of each etching hole 13 is determined according to the progress of the formation of each recess 14. For example, when the diameter of the recess 14a is smaller than the average diameter of all the recesses 14, it is necessary to increase the etching amount of the recess 14a, so that the diameter of the etching hole 13a is set to a predetermined diameter (for example, 20 μm). (For example, 22 μm). On the other hand, when the diameter of the concave portion 14b is larger than the average diameter of all the concave portions 14, it is necessary to suppress the etching amount of the concave portion 14b. Therefore, the diameter of the etching hole 13b is made smaller than the planned diameter. (For example, 18 μm).
In this way, when variation occurs in the shape of the recess 14, a difference is provided in the processing amount of the hole diameter of each etching hole 13 according to the variation.

(Second etching process)
Thereafter, as shown in FIG. 2E, the substrate 11 is wet-etched again. That is, the base material 11 is etched through the etching hole 13 having an enlarged diameter, thereby completing the formation of the recess 14.
At this time, since each of the plurality of etching holes 13 formed in the etching mask film 12 has an enlarged opening area, that is, a hole diameter, the foreign substances are discharged well without being clogged with foreign substances (base material). It is possible to do. Therefore, the etching solution penetrates into the base material 11 and is etched to form the recesses 14 having a substantially ideal shape.

  In particular, when a difference is provided in the opening area (processing amount) of each etching hole 13, this variation is improved even when variations occur in the shape of the recess 14 in the initial stage of the etching process. The shapes of all the recesses 14 can be made substantially uniform.

  Thus, in the formation of the recess 14, in the first half of the etching process, the hole diameter of the etching hole 13 is made fine in order to form the recess 14 having a substantially ideal shape, and in the second half of the etching process, By increasing the hole diameter of the etching hole 13 in order to cope with an increase in the amount of foreign matter (base material) discharged from the etching hole 13, the concave portion 14 having a substantially uniform and substantially ideal shape is formed on the base material 11. A plurality are formed.

(Etching mask film removal process)
When the formation of the recesses 14 is completed, the etching mask film 12 is removed from the base material 11 by wet etching, as shown in FIG.
In addition, it cannot be overemphasized that the etching liquid in this case differs from the etching liquid in the etching process of the base material 11. FIG.
Thereby, formation of the mold 16 for microlenses is completed.

(Transfer process)
Finally, as shown in FIG. 2 (G), a resin sheet 17 having a predetermined thickness, such as PMMA (polymethyl methacrylate), is formed on the upper surface of the microlens mold 16 (the surface on which the recesses 14 are formed). Press the thermoplastic resin while heating. Then, as shown in FIG. 2 (H), the resin sheet 17 is separated from the microlens mold 16 to correspond to the shape of the recess 14 of the microlens mold 16 on one surface of the resin sheet 17. The microlens 3a is transferred.
Thus, the microlens sheet 3 made of resin is completed.

As described above, in the manufacturing process of the microlens sheet 3, when the concave portion 14 of the base material 11 serving as the mold of the microlens 3 a is formed by wet etching, the opening area of the etching hole 13 of the etching mask film 12 is set to be small. Since it expands during the etching process, even if the amount of foreign matter (base material) generated by the etching process gradually increases, it can be discharged well from the etching hole 13.
Thereby, the formation defect of the recessed part 14 by the etching hole 13 being plugged up with a foreign material is prevented, and the recessed part 14 can be formed reliably.
In particular, even when variations in the shape of the recesses 14 occur during the formation of the recesses 14, the recesses 14 having a substantially uniform shape can be obtained by adjusting the opening area of the etching holes 13 according to the variations. A plurality of can be formed on the substrate 11.
Therefore, the microlens sheet 3 having the high-quality microlens 3a can be manufactured.

(Projection screen manufacturing process)
When a projection screen is manufactured using this microlens sheet 3, as shown in FIG. 4, the microlens sheet 3 is placed on the Fresnel sheet 2 so that the microlens 3a side faces the Fresnel sheet 2 side. Arrange in parallel.
According to the projection screen 1, when light is irradiated from the projection lens, the Fresnel sheet 2 converts incident light into parallel light, and the microlens sheet 3 diffuses parallel light in the horizontal and vertical directions by the microlens 3a. Thus, light (video) can be delivered to the user.
That is, by using the microlens sheet 3 described above, the projection screen 1 with high reliability can be manufactured.

Although the embodiments of the present invention have been described above, the shapes, combinations, or processes of the respective constituent members shown in the above-described embodiments are examples, and the design requirements and the like can be met without departing from the gist of the present invention. Various changes can be made based on this.
For example, the present invention includes the following modifications.

In the above-described embodiment, the case where the opening area of the etching hole 13 is increased by enlarging the hole diameter of the etching hole 13 formed in the etching mask film 12 is not limited to this.
The opening area may be increased by increasing the number of holes in the etching hole 13. For example, the number of etching holes 13 (FIG. 5A) may be increased to 5 (FIG. 5B).
Further, the hole diameter may be increased while increasing the number of holes. For example, one etching hole 13 having a diameter of 2 μm may be replaced with four etching holes 13 having a diameter of 5 μm.
Moreover, when increasing the number of holes, the diameters of all the etching holes 13 may not be the same. For example, the hole diameter of the etching hole 13 arranged in the center may be 5 μm in diameter, and the hole diameter of the peripheral etching hole 13 may be 3 μm in diameter.
Further, the etching hole 13 may be composed of a plurality of holes from the beginning, and the number of holes may be further increased. Then, by adjusting the formation position (distribution) of the etching holes 13, the recesses 14 having an ideal shape may be formed.

  The shape of the etching hole 13 is not limited to a round hole, but may be a triangle, a quadrangle, a polygon, a star, a cross, or the like. In any case, in the second half of the etching process, the opening area of the etching hole 13 may be enlarged, and the foreign matter (base material discretion) may be discharged well.

  In addition, although the case where the process is temporarily stopped at the approximately intermediate point of the etching process has been described, the timing (timing) for stopping the process can be changed as appropriate. Further, the number of times to stop is not limited to once, and may be multiple times.

  Further, although the case where the etching mask film is processed by the laser beam has been described, other processing methods such as a photolithography method may be used.

It is a lineblock diagram of the micro lens sheet concerning this embodiment. It is the figure which showed the manufacturing process of the micro lens sheet in order of the process. It is a schematic diagram which shows schematic structure of a laser processing apparatus. It is a schematic diagram which shows schematic structure of a projection screen. It is a figure which shows the modification of the hole for an etching formed in an etching mask film | membrane.

Explanation of symbols

1 ... projection screen, 2 ... Fresnel sheet, 3a ... micro lens,
3 ... Microlens sheet, 11 ... Base material, 12 ... Etching mask film,
13 ... Etching hole, 14 ... Recess, 16 ... Microlens mold,
17 ... Resin sheet, 21 ... Laser processing device, 24 ... Laser beam

Claims (7)

A method of manufacturing a microlens sheet having a plurality of microlenses,
Arranging an etching mask film having an etching hole with respect to the substrate;
A first etching step of etching the substrate through the etching hole;
A processing step for increasing the opening area of the etching hole;
A second etching step of etching the substrate through the etching hole after processing;
Removing the etching mask film from the substrate;
Transferring the recess formed in the base material to a resin sheet;
A method for producing a microlens sheet, comprising:   2. The method of manufacturing a microlens sheet according to claim 1, wherein the processing time in the first etching step and the processing time in the second etching step are substantially the same. Prior to the processing step,
Measuring the diameter of the recess formed in the substrate in the first etching step;
Obtaining a processing amount of the etching hole in the processing step based on the measurement result; and
The method for producing a microlens sheet according to claim 1, wherein the method comprises: In the processing step,
The method for manufacturing a microlens sheet according to any one of claims 1 to 3, wherein a laser processing method is used.   A microlens sheet manufactured by the method according to any one of claims 1 to 4. A method for producing a projection screen having a microlens sheet and a Fresnel lens sheet,
A method for manufacturing a projection screen, wherein the method according to any one of claims 1 to 4 is used as a method for manufacturing a microlens sheet. A projection screen having a microlens sheet and a Fresnel lens sheet,
A projection screen using the microlens sheet according to claim 5 as the microlens sheet.

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