JPH04147101A - Microlens array and its production - Google Patents

Abstract

PURPOSE:To easily carry out production and to obtain a constitution at a low cost by forming a mother in such a way that protrusion corresponding to a large number of lenses are accurately and easily aligned by means of photolithographic technical skill, making a mold through the use of the mother, and obtaining a microlens array. CONSTITUTION:Protruding parts 26 by a photoresist 22 formed by the photolithographic technical skill is made to a half melted state in such a manner that the whole is heated for a fixed time, the surfaces of the protruding parts 26 are smoothened by the surface tension of a material, and their shapes are changed to almost semi-spheres. The semi-spherical protruding parts 26 are cooled to form the mother 30, the mold is formed through the use of the mother 30, and the microlens array made of a translucent material is obtained by using the mold. Therefore, the pillar-protruding parts 26 can accurately and easily be positioned, and it is unnecessary that each of the lenses is accurately aligned. Thus, the production can easily be carried out at the low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microlens array used as an integrated optical device such as an optical reading device or an optical writing device, and a method for manufacturing the same.

[Prior art] Conventionally, microlens arrays used as integrated optical devices include arrays of extremely small spherical lenses or convex lenses arranged in a straight line, and refractive index lenses such as Selfoc lenses. There was one in which distributed lenses were arranged in a staggered manner to form an array.

[Problems to be Solved by the Invention] However, since the microlenses described above need to be arranged in parallel while being accurately aligned, the manufacturing thereof is complicated, and the unit cost of the components is also high. .

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a microlens array that is easy to manufacture and can be manufactured at low cost, and a method for manufacturing the same.

[Means for Solving the Problems] In order to achieve this object, the method for manufacturing a microlens array according to the present invention includes forming columnar shapes made of a photoresist that is easily melted by heat on a flat plate using a photolithography technique. The mother of the microlens array is formed by forming a large number of protrusions, heating the entire surface to smooth the surface of the protrusions, and at the same time changing the shape to a substantially hemispherical shape, and then cooling and hardening. a step of forming;
The method includes a step of forming a mold using the mother, and a step of obtaining a microlens array made of a transparent material using the mold.

[Function] In the present invention having the above configuration, the protrusions made of photoresist formed by photolithography become semi-molten by heating the whole for a certain period of time, and the surface of the protrusions melts due to the surface tension of the material. The surface roughness is smoothed to within 0.01 μm, and the shape changes to a substantially hemispherical shape. A mother is formed by cooling this hemispherical protrusion. A mold is formed using this mother, and a microlens array made of a translucent material is obtained using the mold. The position of the pillar-shaped protrusion can be determined easily and accurately using photolithography, and there is no need to accurately align each lens as in the past.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

FIG. 1 shows steps (1) to (5) in the figure up to forming a mother by photolithography in the method for manufacturing a microlens array according to the present invention.

(1) In the photoresist coating step, first, a photoresist 22 is applied to a thickness of 3 by spin code on one surface of a flat plate 21 made of a silicon wafer or glass.
Apply to 0 μm. A thick film positive type photoresist is used as the photoresist material.

FIG. 1(2): As a mask exposure step, a mask 23 is placed on the photoresist 22 layer, and ultraviolet light is irradiated. The shape of the mask 23 in this example is 50 μm in diameter.
An example is one in which the circular light-shielding parts are linearly arranged in parallel at a pitch of 85 μm.

FIG. 1(3): Next, in a developing step, when the photoresist 22 is immersed in a developer, the photoresist 22 irradiated with light is selectively dissolved and a flat plate is exposed.

FIG. 1 (4): The photoresist 2 is used as a rinsing process.
Rinse 2 with pure water. As a result, a substantially cylindrical protrusion 26 made of the layer of photoresist 22 is formed on the flat plate 21. The surface roughness of the protrusion 26 is 1μ
It is within m. Therefore, if left as is, the surface will be extremely rough for an optical element.

FIG. 1 (5): As a boss baking process, the flat plate 21
The upper protrusion 26 is heated at a high temperature for a certain period of time. For example, 1
It is heated at 35°C for 30 minutes. As a result, as the protrusions melt due to heat, their surface area decreases due to their surface tension, so their shape changes over time, and eventually the surface roughness is within 0.01 μm and its surface area is reduced. The shape becomes approximately hemispherical.The protrusion 26 and the flat plate 2 which have undergone this process are collectively referred to as a mother 30.

FIG. 2 shows steps (1) to (3) in order of the method for manufacturing a microlens array according to the present invention, from forming a mother 30 to forming a stamper 40 as a mold.

FIG. 2 (1): As the conductive film forming process, the mother 30
A nickel conductive film 31 is deposited on the surface of the film to a thickness of 0 by sputtering.
．． It is formed with a thickness of about 1 μm.

Figure 2 (2): As the electroforming process, the nickel conductive film 3
For the mother 30 on which 1 was formed, 30 was formed by electroforming.
A nickel layer 32 of about 0 μm is formed.

FIG. 2(3) In the Nistamper forming step, the flat plate 21 is peeled off from the nickel layer 32. Then nickel layer 3
The remaining material of the protrusion 26 is completely removed by ultrasonic cleaning with acetone. As a result, the mother 30 is completely invertedly transferred onto the nickel layer 32, and this is fixed to the mold 33, which is called a stamper 40 and is used as a mold. Therefore, the stamper 40 has a large number of hemispherical depressions, and the surface roughness of these parts is equal to that of the mother 30 and is 0.01 μm or less.

FIG. 3 shows the process from the stamper 40, which is a mold, to finally manufacturing the microlens array 50 by a casting method, in the method for manufacturing a microlens array according to the present invention.
), (2).

First, a transparent plate 4 with a thickness of about 0.3 mm is placed on the surface of the stamper 40 with a small gap of about 200 μm.
1 is placed parallel to the plane. Next, this void is filled with ultraviolet light curing resin 42. Next, ultraviolet light (UV) is irradiated through the transparent plate 41 to completely cure the ultraviolet light curing resin 42. Next, the stamper 40 is attached to the transparent plate 41.
By peeling the microlens array 50 from the ultraviolet curing resin 42, a microlens array 50 having a large number of spherical convex portions 43 can be obtained.

As the ultraviolet light curing resin 42, a colorless and transparent acrylic resin was used. Further, as the transparent plate 41, a resin plate made of borosilicate glass, polycarbonate, etc., which has been subjected to UV-OS ashes treatment to improve adhesion, may be used. Also,
The casting process described above also needs to be performed under a nitrogen atmosphere in consideration of the anaerobic nature of the ultraviolet light curing resin 42.

In the microlens array manufactured through the above process, the surface roughness of each spherical convex portion 43 is 0.
．． 0111 m or less, the light is ideally refracted without being scattered, and because it has a hemispherical shape, it also works as a convex lens.In addition, the individual convex parts Since the position of 43 is uniquely determined by the shape of the mask, accurate positioning of the microlens,
That is, there is no problem that the microlenses on each side must be arranged while accurately aligning them as in the conventional case. Furthermore, by adjusting the thickness of the transparent material 41, the gap from a certain light output end to the microlens array can be determined accurately. Further, the curvature of the substantially hemispherical convex portion 43 can be controlled by the diameter of the circular light-shielding portion of the mask 23, the coating thickness of the photoresist 22, and the heating temperature and time in the post-baking step. For example, when manufacturing a microlens array under the above conditions, the radius of curvature of the surface of each convex portion 43 is 25μ.
It should be noted that the present invention is not limited to the above-mentioned embodiments (it is possible to make changes as appropriate. For example, the ultraviolet light curing resin 42 is not limited to the above-mentioned materials, but also acrylic). You can freely choose urethane resin, fluorine resin, etc.

Furthermore, it is also possible to form the microlens array described above by injection molding using the stamper 40 as the mold described above. Further, the protrusion formed by photolithography is not necessarily limited to a substantially cylindrical shape, but may be columnar, such as a substantially square prism. Even in this case, it is possible to form a substantially hemispherical protrusion by increasing the heating temperature or heating time.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, a mother can be formed by accurately and easily aligning protrusions corresponding to a large number of lenses using a photolithography method. Since a mold can be made using this mold and a microlens array can be obtained using this mold, it is possible to obtain a microlens array that is easy to manufacture and can be constructed at low cost.

[Brief explanation of the drawing]

FIGS. 1 to 3 show specific examples, and FIGS. 1 (1) to (5) are explanatory diagrams showing the mother forming process, and FIGS. 2 (1), (2), ( 3) is an explanatory view showing the step of forming a stamper mold, and FIGS. 3(1) and 3(2) are explanatory views showing the step of forming a microlens array from the stamper mold by a casting method. 21... Flat plate, 22... Photoresist, 26...
-Protrusion, 30...Mother, 42...Translucent material, 50...Microlens array.

Claims (3)

[Claims] (1) In the manufacturing method of a microlens array formed using a homogeneous light-transmitting material, a large number of pillar-shaped protrusions made of photoresist that easily melts in heat are formed on a flat plate using a photolithography method. a step of smoothing the surface of the protrusion by heating the whole, and at the same time changing the shape into a substantially hemispherical shape, and then cooling and hardening to form the mother of the microlens array; A method for manufacturing a microlens array, comprising: forming a mold using a mother; and using the mold to obtain a microlens array made of a transparent material. (2) The method for manufacturing a microlens array according to claim 1, wherein a casting method or an injection molding method is used as a method for obtaining the microlens array using the mold. (3) A microlens array manufactured by the manufacturing method according to claim 1 or 2.