JP3555626B2 - Manufacturing method of micro lens - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for manufacturing a microlens, and more particularly, to a method for manufacturing a microlens array by a stamper method.
[0002]
[Prior art]
A conventional method of manufacturing a microlens used for optical communication, a solid-state imaging device light collector, a light diffuser, and the like will be described with reference to FIGS. Although FIG. 1 shows only a single microlens, a plurality of microlens arrays are formed by the same manufacturing method.
[0003]
First, the manufacturing process will be described. FIG. 9A shows a substrate 4 for producing a lens such as glass, the surface of which is polished. A photoresist 38 is applied on the substrate 4 to expose a microlens pattern 39 (FIG. 9B). Next, the resist other than the microlens forming portion is removed by development [FIG. 9 (c)], and the portion of the substrate 4 that is not masked by the resist is removed by etching to a depth corresponding to the thickness of the lens. As a result, a columnar lens mold 40 can be formed on the substrate 4 at the portion where the microlenses 17 are to be formed (FIG. 9D).
[0004]
After removing the resist on the lens prototype 40 in the last step, the substrate 4 is subjected to a heat treatment to melt the lens prototype 40, form a hemispherical water droplet by surface tension, and then cool and solidify to form the microlenses 17. It is formed (FIG. 9E). In the heat treatment step, the main body of the substrate 4 having a large heat capacity does not melt.
[0005]
When the microlens array is created by the above-described method, when the adjacent lens molds 40 are melted by the heat treatment and deformed into a hemispherical water droplet shape, there is a possibility that the lens molds 40 come into contact with each other to form a large lump. A frame is formed from a material having poor wettability with the lens base material in the gap portion between the lenses of the substrate 4 or a small hemispherical shape is formed first, and the hemispherical surface is covered with a transparent film to narrow the lens gap. Ingenuity has been made.
[0006]
Also, in addition to using the microlens array created by the above method as it is as a lens, a metal stamper is created by electroless plating or electroforming using the microlens array as a master, and a microlens array is created by injection molding or the like. Was.
[0007]
In the conventional method for manufacturing a microlens as described above, steps such as resist coating, exposure, development, etching, and heating are required, and the number of steps is large. In addition, in the wet process in the above-described process, it is necessary to maintain strict quality control such as temperature control in the heating process and temperature control in the heating process.
[0008]
When a microlens array is formed, when adjacent lens molds 40 are melted by heat treatment and deformed into a hemispherical water droplet shape, there is a possibility that the lens molds 40 come into contact with each other to form a single large lump, and a high density is obtained. It is difficult to dispose the microlenses 17, and the countermeasures further complicate the manufacturing process, which also causes the lens performance to deteriorate.
[0009]
[Problems to be solved by the invention]
As described above, the conventional method of manufacturing microlenses and microlens arrays requires a long manufacturing time, requires many types of manufacturing apparatuses, and further maintains the quality of a chemical solution in a wet process. There were problems such as strict process control. In addition, when a microlens array is formed, it is difficult to arrange the microlenses with high density, and it is difficult to improve the performance of the lens array.
[0010]
[Means for Solving the Problems]
The present invention has been devised to solve these problems, and forms a hemispherical projection by irradiating a laser in the ultraviolet wavelength range on the surface of a substrate such as glass that absorbs ultraviolet light. Is used as a matrix to form a stamper, and a transparent material is molded by the stamper to form a microlens.
[0011]
Further, the position of the laser in the ultraviolet wavelength range and the substrate to be irradiated on the substrate surface is relatively displaced, a plurality of protrusions are sequentially formed on the substrate surface, and a stamper is created using this as a matrix, and the stamper is transparent. The material is molded to form a microlens array.
[0012]
Further, a laser in the ultraviolet wavelength range for irradiating the substrate surface is formed into a plurality of beams, a plurality of protrusions are formed at one time on the substrate surface, and a stamper is formed using this as a matrix, and a transparent material is formed by the stamper. Mold to create a microlens array.
[0013]
Furthermore, a mask having a plurality of holes substantially the same size as the microlenses corresponding to the positions where the microlenses are formed is formed of a material that does not transmit laser light in the ultraviolet wavelength range, and the mask is formed on the upper surface of the substrate. A plurality of protrusions are formed on the substrate surface by sequentially and simultaneously irradiating laser light on the entire surface of the substrate, a stamper is formed using the protrusions as a matrix, and a transparent material is molded by the stamper to form a microlens array. It is intended to solve the above problems.
[0014]
[Action]
According to the method of manufacturing a microlens according to the present invention, various projections in photolithography, and the step of heating and melting can be omitted, and only the ultraviolet irradiation step can be used to form a projection with high light-collection efficiency, that is, the shape of the microlens. it can.
[0015]
In addition, the protrusion formed on the substrate surface by the method of the present invention does not act as an optical lens as it is because there are fine bubbles in the inside, but this is used as a master mold by electroless plating or electroforming. A stamper is formed, and a transparent material is molded by injection molding or the like to manufacture a microlens array.
[0016]
【Example】
A method of manufacturing a microlens according to the present invention will be described with reference to FIGS.
[0017]
As shown in FIG. 1, the outline of the method of manufacturing the microlens is, as shown in FIG. 1, an ultraviolet light source 1 as a heating source, an optical system 3 for condensing and modulating ultraviolet light 2 emitted from the ultraviolet light source 1, and an ultraviolet light 2. And a substrate 4 that absorbs light and forms a projection corresponding to the lens. The ultraviolet light source 1 is a light source that emits light continuously or in a pulsed manner at a wavelength of 360 nm or less, and is irradiated onto the substrate 4 by being narrowed down to an extremely small spot by the optical system 3.
[0018]
FIG. 2 shows the heat distribution of the substrate surface layer irradiated with the ultraviolet light 2. The ultraviolet light 2 is slightly condensed from the surface of the substrate 4 at the center 8 of the surface layer inside, and at the same time as the temperature of the center 8 of the surface layer rises, a heat flow 7 is generated from the center 8 of the surface layer to the outside. A temperature distribution is formed in which the temperature gradually decreases toward.
[0019]
In FIG. 2, when the temperature of the central portion 8 of the surface layer becomes sufficiently high, a protruding portion 9 is formed on the substrate surface 6 as shown in FIG. This process will be described with reference to FIG.
[0020]
The spot irradiation of the ultraviolet rays 2 causes the temperature of the surface layer central portion 8 to rise, and the substrate surface 6 is softened and melted, and the substrate 4 is easily volatilized around the surface layer central portion 8, that is, gasification of a component having a low boiling point occurs. Beginning, foaming 10 begins.
In this process, the internal pressure 11 rises, and the softened substrate surface 6 is pushed up and deformed into a hemispherical water droplet shape by surface tension. When the irradiation of the ultraviolet light 2 is stopped at this point, the heat diffuses to the surroundings and cools rapidly, so that the substrate surface 6 is solidified in a hemispherical shape, thereby forming a projection 9 having a lens shape.
[0021]
Since the projection 9 formed as described above contains air bubbles therein, it does not function as a lens as it is, but as shown in FIGS. 4A to 4E, the substrate 4 having the projection 9 is used as a base. A stamper is created as a mold and duplicated to create a microlens.
[0022]
With reference to FIG. 4, a description will be given of a replication method using a stamper of a microlens array in which a plurality of microlenses are arranged.
First, FIG. 4A shows a substrate 4 having a plurality of projections 9 in the shape of a plurality of lenses to be used as a master of a stamper, on which an electroless plating, an electroforming, a method using an ultraviolet curing resin, or the like is used. [FIG. 4 (b)], and then the stamper 15 is peeled off from the substrate 4 [FIG. 4 (c)], and the stamper 15 is used as a master mold by a method using an ultraviolet curable resin, injection molding or the like. A microlens array 16 is formed by the method (FIG. 4D), and finally, the microlens array 16 is formed by peeling off the stamper 15 (FIG. 4E).
[0023]
Next, a method for irradiating the substrate 4 with the ultraviolet light 2 to form a microlens array will be described with reference to FIGS.
[0024]
Example 1
As shown in FIG. 5, the light source is a semiconductor-pumped YAG laser 20 having an oscillation wavelength of approximately 1 μm, which is used as an ultraviolet light source by continuously generating a fourth harmonic by passing twice through an SHG element 21. The laser beam from the laser light source enters the objective lens 23 through the modulation optical system 22 that changes the light intensity of the laser light, and is focused on the substrate 4. The substrate 4 is mounted on, for example, an XY moving stage 24, and the substrate 4 is moved by a generally known driving method according to the arrangement of the microlenses 17 to be formed. Although not shown, a configuration in which the optical system is moved may be used.
[0025]
The modulation optical system 22 includes a lens, a mirror, an acousto-optic modulator, and the like (not shown) that can be used at an ultraviolet wavelength, and performs irradiation intensity adjustment, ON / OFF of irradiation light, and the like. The optical modulation element may be configured using an electro-optic effect, a magneto-optic effect, or an optical effect of a liquid crystal in addition to the one using the acousto-optic effect.
[0026]
The actual laser beam irradiation conditions are, for example, soda glass as the substrate 4 with a laser spot diameter of 1 μm, light intensity density of 120 mW / μm ² , irradiation pulse width of ² msec, irradiation interval of 500 μsec, irradiation frequency of 100 times, and obtain a good lens. I was able to. It should be noted that the determination of the irradiation conditions is not limited to the above conditions and may be determined depending on the substrate material, the diameter, the curvature, and the height of the lens.
[0027]
Example 2
As shown in FIG. 6A, a beam splitting optical system 30 is installed between the modulation optical system 22 and the substrate 4 in place of the objective lens 23 of the first embodiment, and a laser beam modulated by the modulation optical system 22 is provided. A plurality of laser beams 31 corresponding to the arrangement of the microlenses 17 are created and irradiated on the substrate 4.
[0028]
FIG. 6B shows a configuration example of the light beam splitting optical system 30. In the figure, the main laser beam L is split by the beam splitter 32 into n laser beams L1 to Ln. In order to make the intensities of the laser beams split by the beam splitters 32 the same, the split ratio of each beam splitter 32 must be appropriately determined. The light beam splitting optical system 30 is not limited to this example, and may be configured using other optical components. Although FIG. 6B shows a linear arrangement, the arrangement is not limited to this, and an arrangement in an area is also possible.
[0029]
Example 3
FIG. 7 shows that the light beam diameter conversion optical system 34 is installed between the modulation optical system 22 and the substrate 4 in place of the objective lens 23 of the first embodiment, and the laser beam modulated by the modulation optical system 22 is transmitted to the micro lens array 16. In this case, the diameter of the laser beam 31 is increased to a size that covers the area of FIG. At this time, the substrate 4 is covered with an ultraviolet light reflection mask 35 having a hole corresponding to the arrangement of the microlenses 17 and having a diameter substantially equal to the diameter of the microlenses 17. The ultraviolet light reflection mask 35 may be disposed at any position between the light beam diameter conversion optical system 34 and the substrate 4.
[0030]
Example 4
FIG. 8 shows a case where a microlens array 33 is used in place of the ultraviolet light reflection mask 35 of the third embodiment. The arrangement of the microlens array 33 is the same as the arrangement of the microlenses 17 formed on the substrate 4, and is optically arranged so that a plurality of laser beams 31 generated through the microlens array 33 are condensed on the substrate 4. Determine the system. This embodiment has an advantage that the laser beam can be used more effectively than the third embodiment.
[0031]
As described above, the manufacturing method using soda glass as a substrate material and ultraviolet light as a light source for creating a lens shape by foaming this substrate has been described. It goes without saying that microlenses or microlens arrays can be formed using light and a material that absorbs and emits light in these wavelength bands for the substrate. In this case, it is necessary to use reflection, light shielding masks and optical components corresponding to the light in the wavelength band to be used.
[0032]
It should be noted that the method for manufacturing a microlens and a microlens array according to the present invention is not limited to these manufacturing methods, but can be applied to the manufacturing of an optical disk, an optical card, and the like that record and reproduce signals using similar fine projections. .
[0033]
【The invention's effect】
As described above, a metal stamper is formed by electroless plating or electroforming using a substrate having a microlens-shaped projection formed by the microlens manufacturing method of the present invention as a matrix, and the microlens is formed by injection molding or the like. Can be created quickly and in large quantities. Also, a microlens array in which a plurality of microlenses are arranged can be created in a similar manner.
[0034]
In addition, the only part that is melted and subjected to the effect of surface tension is the place where the temperature is raised by irradiating ultraviolet light, and by irradiating sequentially, a microlens array shape is formed at high density without leaving a gap. be able to.
[0035]
Also, in the method of simultaneously irradiating a plurality of spots using a mask or the like, only the surface layer to be irradiated is heated and the entire substrate is not heated. A lens array shape can be formed.
[0036]
Further, a microlens array shape having high light-collecting efficiency can be formed only by the ultraviolet irradiation step, omitting various steps before and after the photolithography and the heating and melting step, which are necessary in the prior art.
[0037]
Furthermore, a pattern that reflects ultraviolet light is formed on a portion of the substrate where the microlenses are not formed, and the substrate portion having the pattern to be reflected by sequentially or simultaneously irradiating the ultraviolet light from above is heated. However, a foaming phenomenon occurs in other portions, and a heating and melting step can be omitted to form a high-density microlens array shape.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a microlens manufacturing method of the present invention.
FIG. 2 is a schematic sectional view showing an interaction between a substrate and ultraviolet light.
FIG. 3 is a schematic cross-sectional view showing formation of a lens portion shape following FIG. 2;
FIG. 4 is a schematic sectional view showing a microlens manufacturing process.
FIG. 5 is a block diagram showing a first embodiment of the present invention.
FIG. 6 is a block diagram showing a second embodiment of the present invention.
FIG. 7 is a block diagram showing a third embodiment of the present invention.
FIG. 8 is a block diagram showing a fourth embodiment of the present invention.
FIG. 9 is a schematic perspective view showing a conventional microlens manufacturing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ultraviolet light source 2 Ultraviolet light 3 Optical system 4 Substrate 5 Lens formation part 6 Substrate surface 7 Heat flow 8 Surface layer central part 9 Protrusion part 10 Foaming 11 Pressure 15 Stamper 16, 33 Micro lens array 17 Micro lens 20 YAG laser 21 SHG element 22 Modulation optical system 23 Objective lens 24 XY moving stage 30 Beam splitting optical system 31 Laser beam 32 Beam splitter 34 Beam diameter conversion optical system 35 Ultraviolet light reflection mask 38 Photoresist 39 Microlens pattern 40 Lens prototype

Claims (7)

In a manufacturing method of making a micro lens by a stamper method,
The surface of a substrate made of a material that absorbs ultraviolet light is selectively irradiated with laser light in an ultraviolet wavelength band to foam the substrate to form a hemispherical protrusion, and the substrate having the protrusion is used as a matrix. Forming a microlens by forming a transparent material with the stamper. The laser light in the ultraviolet wavelength band and the position of the substrate to be irradiated on the surface of the substrate are relatively displaced, a plurality of protrusions are sequentially formed on the surface of the substrate, and the substrate having the plurality of protrusions is used as a matrix. The method for manufacturing a microlens according to claim 1, wherein a stamper for the microlens array is formed. The laser beam in the ultraviolet wavelength band to be irradiated on the surface of the substrate is formed into a plurality of beams, a plurality of protrusions are formed on the surface of the substrate at one time, and the substrate having the plurality of protrusions is used as a matrix to form a microlens. The method for manufacturing a microlens according to claim 1, wherein a stamper for the array is formed. A mask is created by drilling a hole having a size substantially equal to the diameter of the microlens in a flat plate material that reflects laser light in the ultraviolet wavelength band in accordance with the arrangement of the microlens, and making the mask adhere to the surface of the substrate, or The method is characterized in that a projection is formed on the surface of the substrate by irradiating the laser beam sequentially or simultaneously on the entire surface of the substrate and the substrate having the plurality of projections is used as a master to form a microlens array stamper. The method for manufacturing a microlens according to claim 1, wherein The method for manufacturing a microlens according to claim 1, wherein a plurality of laser beams for irradiating the substrate according to claim 3 are formed from one laser beam. 5. The method of manufacturing a microlens according to claim 1, wherein the laser beam for simultaneously irradiating the entire surface of the substrate according to claim 4 is created by a light beam diameter conversion optical system. A method for manufacturing a microlens according to claim 1, wherein a plurality of laser beams for irradiating the substrate according to claim 3 are formed from a single laser beam using a light beam diameter conversion optical system and a microlens array. Method.

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