JP2002243910A - Optical element array and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-length optical element array where occurrence of an interference, what is called cross-talk between adjacent optical elements, is reduced by narrowing the space between the optical elements of a lens array, and a manufacturing method of the optical element array by which the optical element array is molded with high accuracy. SOLUTION: Optical surface 11 being a plurality of optical elements are adjacently formed on the optical element array 10, and recessed parts 12 concave to the surface 11 and having low surface roughness are formed between the optical elements, then the light transmittance of the recessed part 12 is made lower than that of the surface 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element array and a method for manufacturing the same.

[0002]

2. Description of the Related Art In an image forming apparatus or an image recording apparatus such as a printer, a facsimile, a copying machine, a plotter, etc., as a reading and / or writing optical system, a thermoplastic resin in a molten state between molds having a desired lens shape. An optical element array (lens array) formed by an injection molding method of filling and molding is mainly used.

Conventionally, for example, as described in Japanese Patent Application Laid-Open No. 10-58550, when a composite lens having an aspherical molding surface is formed on a glass lens using an ultraviolet curable resin, irradiation is performed according to the resin thickness. A method in which the occurrence of sink marks is prevented by changing the amount of light,
As disclosed in Japanese Patent No. 03125, there is an arrangement in which a light-shielding plate is arranged between lens arrays to prevent light from entering and to improve image quality.

[0004]

By the way, the demand for higher resolution has been increasing in recent years, and accordingly, the dimensions and spacing of lens elements have to be made smaller and higher precision has been required. Therefore, the lens array also needs to have a small thickness and width and a relatively long length.

However, when the lens array is formed by the injection molding method, there is a problem that the resin is not spread to the end portion due to the small thickness and long length of the molded product, and transfer failure due to insufficient filling is likely to occur. Also, as a product, the narrowing of the interval between optical elements causes a problem of occurrence of so-called crosstalk between adjacent optical elements.

The present invention has been made in view of the above problems, and provides a long optical element array with reduced occurrence of crosstalk and a method of manufacturing an optical element array capable of molding the optical element array with high precision. The purpose is to do.

[0007]

In order to solve the above-mentioned problems, an optical element array according to the present invention has a plurality of optical surfaces formed adjacent to each other, and at least the surfaces are formed of an ultraviolet curable resin. In the composite optical element array, a concave portion having a low surface roughness is formed between each optical element and has a low surface roughness, and the light transmittance of the concave portion is low with respect to the optical surface.

Here, it is preferable to form a substance having a low transmittance in the concave portion. Further, when the thickness of the ultraviolet curable resin is 15
Preferably it does not exceed 0 μm.

In the method of manufacturing an optical element array according to the present invention, an ultraviolet curable resin is dropped on a plurality of adjacent optical elements having a spherical surface or an aspherical surface, and a mold having an inverted optical surface is mounted. A method for manufacturing the optical element array according to the present invention by releasing the resin after irradiating the resin with ultraviolet rays and then releasing the resin, wherein the irradiation intensity of the ultraviolet rays in a portion corresponding to the concave portion is reduced. It is.

Here, the mold is formed of an ultraviolet transmitting material,
It is preferable to perform a surface roughening treatment on a portion corresponding to the concave portion around the optical element. Further, it is preferable that the mold is formed of an ultraviolet transmitting material and a metal thin film is formed in a portion corresponding to a concave portion around the optical element. Further, the transmittance at a wavelength of 365 nm at a portion corresponding to the concave portion around the optical element of the mold is preferably within a range of 10 to 90% with respect to the optical element forming portion.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram for explaining an optical element array according to the present invention together with a method for manufacturing the same.
As shown in FIG. 1A, a blank material 1 having a substantially finished product shape is formed in advance by a known means such as injection molding or embossing. The blank 1 does not need to be formed with an accuracy that satisfies the required optical characteristics.

Then, as shown in FIG. 1B, an ultraviolet curable resin layer 2 is applied on the lens forming surface of the blank material 1.
It is formed to have a predetermined volume by means such as transfer or dropping. In this case, in order to improve the adhesiveness between the material of the blank material 1 and the ultraviolet curable resin layer 2, it is preferable that the blank material 1 is previously subjected to an adhesion enhancing treatment such as a silane coupling treatment as necessary. .

Subsequently, as shown in FIG. 1C, a mold 3 made of a material that transmits ultraviolet light and processed into an inverted shape of a target lens array is formed so that the ultraviolet-curable resin layer 2 has a predetermined thickness. As shown. The mold 3 is provided with a transmittance attenuating portion 4 for attenuating the transmittance of ultraviolet light with respect to other portions at each lens element boundary (a portion corresponding to a concave portion between the optical elements of the optical element array). The transmittance attenuating portion 4 is formed by forming a thin film of metal or the like or roughening the mold surface. The transmittance of the transmittance attenuating portion 4 at a wavelength of 365 nm is preferably in the range of 10 to 90%, more preferably 70% or less, with respect to the optical element forming portion. Further, it is preferable to form a fluorine-based coating film on the surface of the mold 3 which comes into contact with the ultraviolet-curable resin layer 2 in order to improve the releasability from the cured resin.

Next, as shown in FIG. 1D, with the mold 3 placed on the blank material 1 via the ultraviolet curable resin layer 2, ultraviolet rays are irradiated from the mold 3 side. At this time, since the illuminance of the portion other than the transmittance attenuating portion 4 of the mold 3 is higher than that of the transmittance attenuating portion 4, the portion of the ultraviolet curable resin layer 2 corresponding to the portion other than the transmittance attenuating portion 4 has priority. Hardens to

[0015] Since the ultraviolet curable resin undergoes volume shrinkage during curing, the uncured resin in the illuminance attenuation portion moves to the high illuminance portion. As a result, the amount of resin in the portion corresponding to the transmittance attenuating portion 4 of the mold 3 is reduced to be equal to or less than the thickness formed by the blank 1 and the mold 3. Then, since the surface of the mold 3 has been subjected to the release treatment, the resin is cured while receiving the ultraviolet rays on the surface opened apart from the mold 3 while further contracting. As a result, the surface of this portion becomes a depression as a so-called sink to the high illuminance portion, and the surface condition becomes rough.

According to the experiment, the ultraviolet curable resin layer 2
When the film thickness was 150 μm or less, a good shape was obtained from the relationship between supply from the periphery and shrinkage.
When it exceeds 50 μm, the supply is not sufficiently performed, and transfer failure occurs. Therefore, it is preferable that the thickness of the ultraviolet curable resin layer 2 does not exceed 150 μm.

Thereafter, as shown in FIG. 1E, the mold 3 is peeled off to obtain the optical element array 10. In the optical element array 10, an optical surface 11 serving as a plurality of optical elements is formed adjacent to the ultraviolet curable resin layer 2 provided on the blank material 1, and a concave shape with respect to the optical surface 11 is provided between each optical element. A concave portion 12 having a low surface roughness is formed, and the light transmittance of the concave portion 12 is lower than that of the optical surface 11.

The surface shape of the optical element array 10 and the transmittance corresponding thereto were measured, and the results are as shown in FIG. The surface state of the ultraviolet-curing resin layer 2 obtained when the illuminance attenuation processing section (the transmittance attenuation section 4 of the mold 3) is provided and cured, the thickness of the portion where the transmittance is attenuated is thin, and the flatness is reduced. You can see that it is also getting worse.

The optical element array 1 thus obtained
In the case of 0, since the boundary of each lens element (optical surface 11) is roughened, light incident from this part is scattered and attenuated, so that so-called crosstalk affecting adjacent optical elements is reduced.

Since this boundary is a concave portion 12, as shown in FIG. 3, a material 13 having excellent light-shielding properties (substance having a low transmittance) 13 is applied to the concave portion 12 more reliably. Crosstalk can be reduced.

In the above embodiment, the mold 3 is overlapped after the formation of the UV-curable resin layer 2. However, a predetermined gap is provided in advance between the blank material 1 and the mold 3, and the UV-curable resin is injected therebetween. It is also possible.

Although the transmittance attenuating process (formation of metal film or surface roughening process) of the mold 3 is performed on the contact surface with the ultraviolet curable resin layer 2, the same effect can be expected by performing the process on the opposite surface. it can. However, in this case, the difference in illuminance when light passes through the thickness of the mold 3 becomes small, so that a large difference does not occur in the curing speed at the boundary portion, and it becomes difficult to generate extreme sink marks as in the above embodiment. Therefore, it is preferable to perform the transmittance attenuation treatment on the contact surface with the ultraviolet curable resin layer 2.

[0023]

As described above, according to the optical element array according to the present invention, a region having a low light transmittance and a low surface roughness is provided between each optical element, so that light from sources other than the intended light source is provided. Scattering and attenuation can be achieved, and crosstalk can be reduced.

Here, by forming a material having a low transmittance in the concave portion, crosstalk can be reduced more reliably. Further, when the thickness of the ultraviolet curable resin does not exceed 150 μm, it is possible to prevent a shape defect due to shrinkage during curing of the resin.

According to the method of manufacturing an optical element array according to the present invention, an ultraviolet curable resin is dropped on a plurality of adjacent optical elements having a spherical surface or an aspherical surface to form a mold having an inverted optical surface. When the optical element array according to the present invention is manufactured by mounting, releasing after curing the resin by irradiating ultraviolet rays, the irradiation intensity of the ultraviolet rays in the portion corresponding to the concave portion is reduced, Since the curing of the portion corresponding to the concave portion is delayed, it becomes a resin supply source when the optical element region cures and contracts, and prevents a change in the shape of the optical element region. Therefore, the light transmittance can be reduced.

Here, the mold is formed of an ultraviolet transmitting material,
By performing the surface roughening treatment on the portion corresponding to the concave portion around the optical element, it is possible to surely roughen only the region to be the concave portion. Also, by forming the mold with an ultraviolet transmitting material and forming a metal thin film on a portion corresponding to the concave portion around the optical element, it is possible to surely roughen only the region to be the concave portion.

Further, since the transmittance at a wavelength of 365 nm of the portion corresponding to the concave portion around the optical element of the mold is within the range of 10 to 90% with respect to the optical element forming portion, the portion corresponding to the concave portion can be cured. Can be delayed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an optical element array according to the present invention together with a method for manufacturing the optical element array.

FIG. 2 is an explanatory diagram illustrating the surface shape and transmittance of the optical element array.

FIG. 3 is an explanatory view illustrating another embodiment of the optical element array according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Blank material, 2 ... UV curable resin layer, 3 ... Type, 4 ...
Transmittance attenuating section, 10: optical element array, 11: optical surface,
12 ... recess.

Claims (7)

[Claims] 1. A composite optical element array in which a plurality of optical surfaces are formed adjacent to each other and at least the surfaces of which are formed of an ultraviolet curable resin, a concave surface between the optical elements and a concave surface between the optical elements. An optical element array, wherein a concave portion having low roughness is formed, and a light transmittance of the concave portion is lower than that of the optical surface. 2. The optical element array according to claim 1, wherein a material having a low transmittance is formed in said concave portion. 3. The optical element array according to claim 1, wherein the thickness of the ultraviolet curable resin does not exceed 150 μm. 4. An ultraviolet curable resin is dropped on an optical element having a plurality of adjacent spherical or aspherical surfaces, a mold having an inverted shape of an optical surface is placed, and the resin is cured by irradiating ultraviolet light. 4. A method of manufacturing the optical element array according to claim 1, wherein the mold is released and then the irradiation intensity of ultraviolet rays in a portion corresponding to the concave portion is reduced. A method for manufacturing an optical element array. 5. The method of manufacturing an optical element array according to claim 4, wherein the mold is formed of an ultraviolet transmitting material, and a portion corresponding to a concave portion around the optical element is subjected to a surface roughening treatment. Of manufacturing an optical element array. 6. The method for manufacturing an optical element array according to claim 4, wherein the mold is formed of an ultraviolet transmitting material, and a metal thin film is formed in a portion corresponding to a concave portion around the optical element. A method for manufacturing an optical element array. 7. The method for manufacturing an optical element array according to claim 5, wherein a transmittance at a wavelength of 365 nm at a portion corresponding to a concave portion around the optical element of the mold has a transmittance of 10 to 90 with respect to an optical element forming portion. % Of the optical element array.