JPH09329721A - Polymer optical waveguide and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive and compact product having high mechanical intensity and an excellent light guiding characteristic and capable of suppressing crosstalk without depending upon combination between a substrate material and core material by forming a groove part charged with the same material as a core material on a part where the core parts of a polymer optical waveguide are not formed. SOLUTION: An optical waveguide type reduced image sensor is constituted of a light source for irradiating an original with light, a micro-lens array 3 for converting reflected light from the original, a polymer waveguide 4 having plural core parts 6 upon which light converged by the array 3 is made incident, and a CCD array 5 to be a photoelectric conversion element arranged on the output ends of the core parts 6 to which light reduced and propagated through the core parts 6 is outputted and capable of converting the output light into an electric signal. In addition, groove parts (dummy grooves) 7 charged with the same material as the core parts 6 is formed on a part where the core parts 6 are not formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer optical waveguide used in an optical waveguide type reduction image sensor used in a one-dimensional reading optical system of a hard copy image such as a facsimile, a copying machine, an image scanner and a method for manufacturing the same. It is about.

[0002]

2. Description of the Related Art In recent years, as the demand for image reading of facsimile machines, image scanners, digital copiers and the like has increased, there has been a demand for higher performance and smaller size of one-dimensional image sensors for converting image information into electric signals. Conventionally, as a one-dimensional image sensor, there are a reduction optical type image sensor that reads an image formation screen using a reduction optical system and a contact type image sensor that reads an image formation screen of equal size using a one-to-one optical system. is there.

The reduction optical type image sensor is low in price and capable of high-speed reading, but on the other hand, since reduction image formation by a lens is required, the size of the device is large and it is difficult to miniaturize it. In addition, the adjustment of the optical system is complicated, so that there is a drawback that adjustment is required for each unit.

On the other hand, the contact image sensor has the advantage that the distance from the original to the photoelectric conversion element array is small and no adjustment is required, but since the reduction optical system is not provided, the size of the photoelectric conversion element array is large. In addition, it is difficult to reduce the cost because a complicated electronic circuit for driving such a large photoelectric conversion element array is required.

Therefore, a reduced image sensor using a plurality of optical waveguide arrays has recently been proposed. As shown in the plan view of the main part of FIG. 5, the schematic structure of the light detecting portion of this optical waveguide type reduced image sensor is such that the microlens array 13 formed in the document surface width and the light is condensed by the microlens array 13. The polymer optical waveguide 14 is formed with a plurality of core portions 16 for guiding light, and a CCD array 15 which is a photoelectric conversion element for receiving light and converting it into an electric signal. According to this, not only can the cost be reduced and the device can be downsized, but also the adjustment of the optical system becomes unnecessary.

In such an optical waveguide type reduced image sensor, an optical waveguide type reduced image sensor using a polymer as a material used for the optical waveguide has been proposed. The following methods have been proposed as main methods for producing this polymer optical waveguide.

First, a patterned substrate made of a polymer material such as PMMA in which a groove serving as a core portion through which light propagates is formed is manufactured by using an injection molding technique. Next, the groove of this pattern substrate was filled with a polymer precursor material (monomer solution) for the core of the optical waveguide, and a flat plate substrate made of a polymer such as PMMA was brought into close contact with the groove side of the pattern substrate. After that, there is a method in which a core portion is formed by photopolymerizing a polymer precursor material for a core by irradiating with an ultraviolet ray to manufacture an optical waveguide made of a polymer material.

As another method, the pattern surface of the pattern substrate on which the groove pattern to be the capillary is formed is brought into close contact with the flat plate substrate to form the capillary, and then the polymer precursor (raw material for the core of the optical waveguide Monomer solution)
After filling the capillary with the capillary phenomenon,
There is one that polymerizes a polymer precursor.

According to these manufacturing methods, since no gap is formed at the boundary between the pattern substrate and the flat plate substrate, there is no crosstalk due to light leaked from between the cores, and the polymer optical waveguide having excellent optical waveguide characteristics. Can be realized.

[0010]

However, in the above-mentioned method for producing a polymer optical waveguide, firstly, there is a problem that peeling occurs between the pattern substrate and the core or between the core and the flat substrate. . This is because the substrate has a grooved portion and a grooveless portion, which causes distortion and deteriorates flatness, and poor adhesion between the monomer solution, which is the raw material of the core, and the substrate. The combination with the core material is bad), and the core portion that is the adhesive portion is small (the area is small).

Secondly, the groove serving as the core portion of the polymer optical waveguide is formed by the injection molding technique, but since the distance between the grooves is small, the resin is sufficiently filled in the groove of the mold. Not injected, the height of the walls A2, B2, C2, D2 between the grooves of the pattern substrate 14a becomes low as shown in the partially enlarged plan view of FIG. Therefore, the grooved portion 1 of the patterned substrate 14a
The height of A2, B2, C2, D2 of 6 and the height of E2 of the flat portion 17 having no groove are not the same, and the patterned substrate 14a as shown in FIG. 6 is manufactured. For this reason,
Various problems such as crosstalk occur, and for example, in the manufacturing method using the above-mentioned capillary phenomenon, as shown in FIG. 6, a gap is formed at the boundary between the pattern substrate 14a and the flat substrate 14b, and the role of the capillary is obtained. In some cases, the core raw material could not be sufficiently filled because it did not fulfill.

The present invention has been made to solve the above problems, and does not depend on the combination of the substrate material and the core material of the polymer optical waveguide forming the optical waveguide type reduced image sensor. The present invention provides a polymer optical waveguide, which has excellent mechanical strength, suppresses crosstalk, has excellent optical waveguide characteristics, can be manufactured at a low price and can be downsized, and can be manufactured by a simple manufacturing process, and a manufacturing method thereof. is there.

[0013]

In order to solve the above problems, according to the present invention, in a polymer optical waveguide in which incident light propagates through the core portion and is reduced and emitted, the core portion of the polymer optical waveguide is formed. A groove portion filled with the same material as that of the core portion is provided in the non-open portion.

Further, in the present invention, in the above-mentioned polymer optical waveguide, the core portion and the groove portion are provided on the entire surface of the polymer optical waveguide.

Further, in the present invention, in the above-mentioned polymer optical waveguide, the groove portion is provided symmetrically with the core portion.

Further, according to the present invention, in the polymer optical waveguide in which the incident light propagates through the core portion and is reduced and emitted, a plurality of grooves serving as the core portion are formed in the substrate made of transparent resin, and the core portion is A step of forming a plurality of unformed grooves to form a patterned substrate, and a step of filling the grooves of the patterned substrate with a transparent polymer precursor material having a higher refractive index than the substrate,
The step of bringing the flat substrate into close contact with the grooved side of the patterned substrate and then polymerizing the transparent polymer precursor material filled in the groove is included.

Further, in the present invention, in the above-mentioned method for producing a polymer optical waveguide, in the groove forming step of the pattern substrate,
It is supposed that a plurality of grooves that will be the core portion and a plurality of grooves that will not be the core portion will be formed on the entire surface of the substrate.

Further, according to the present invention, in the above-mentioned method for manufacturing a polymer optical waveguide, in the groove forming step of the pattern substrate, the plurality of grooves which are core portions and the plurality of grooves which are not core portions are symmetrical. The groove is formed as described above.

According to the present invention, as described above, the groove portion, which should be called a dummy groove, is provided in the plane portion where the core portion is not provided in the conventional one. Therefore, between the pattern substrate and the core, Alternatively, the bonding area between the core and the flat substrate, that is, the bonding area through the groove can be significantly increased. As a result, even if the adhesion of the monomer solution, which is the core material, to the substrate is somewhat poor, since there are many adhered parts, there is a gap between the pattern substrate and the core or between the core and the flat substrate in the pattern substrate. Peeling is less likely to occur, and the mechanical strength of the polymer optical waveguide can be greatly improved.

Further, by providing the groove portion (dummy groove) and the core portion on the entire surface of the polymer optical waveguide or by making the groove portion (dummy groove) symmetrical with the core portion, distortion is less likely to occur, and the polymer optical waveguide The flatness can be improved.

Further, when the pattern substrate is manufactured by the injection molding method, the problem that the wall between the grooves of the pattern substrate becomes low due to the resin not being completely injected into the groove of the mold can be solved. it can. That is, by providing the core portion and the groove portion (dummy groove) on the entire surface of the polymer optical waveguide, the height of the wall between the grooves and the height of the plane portion are made uniform, and crosstalk is suppressed. The optical waveguide characteristics of the polymer optical waveguide can be greatly improved.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below is an example in which the present invention is applied to a one-dimensional image sensor for G3 facsimile having a resolution of 200 dpi (scan width: 256 mm: compatible with B4 paper). As a photoelectric conversion element,
A 14 μm pitch, 2048 pixel CCD, μPD3743D manufactured by NEC Corporation was used.

FIG. 1 is a perspective view showing a schematic structure of an optical waveguide type reduction image sensor using a polymer optical waveguide according to an embodiment of the present invention, and FIG. 2 is an overall plan view of its photodetecting section.
FIG. 3 is a partially enlarged plan view of the detector. As shown in FIGS. 1, 2 and 3, this optical waveguide reduction image sensor includes a light source 2 for illuminating a document 1, a microlens array 3 for collecting reflected light from the document 1, and a microlens. A polymer optical waveguide 4 having a plurality of core portions 6 into which the light collected by the array 3 is incident, and a core portion 6 to which the light reduced and propagated by each core portion 6 of the polymer optical waveguide 4 is output. And a CCD array 5 which is a photoelectric conversion element which is disposed at the output end of and which converts the output light into an electric signal,
Further, a groove portion (dummy groove) 7 filled with the same material as the core portion 6 is provided in a portion of the polymer optical waveguide 4 where the core portion 6 is not formed.

Next, a method of manufacturing the polymer optical waveguide of this embodiment will be described. First, a groove that becomes a core part and a groove that does not become a core part (dummy groove) on the substrate surface by injection molding
In order to manufacture a pattern substrate made of a transparent resin having a and, a mold is prepared as follows.

A photoresist film having a film thickness of 9 μm is formed on a glass substrate, and by using a photolithography technique, a groove pattern is transferred between a groove to be a core portion of a pattern substrate and a groove not to be a core portion (dummy groove). I do. That is, the groove pattern of the mask is transferred to the photoresist film by adhering the mask to the photoresist film and exposing it to ultraviolet rays, and then performing development processing. Here, since the transfer rate at the time of injection molding from the mold is about 90%, the film thickness of the photoresist film was made larger than the groove depth of 8 μm.

Next, the surface of the patterned photoresist film is electroplated using an aqueous nickel chloride solution. A nickel thin metal plate having a thickness of 10 μm is formed. The support plate is bonded to the flat surface of the thin metal plate thus formed, which is opposite to the pattern surface. Finally, the thin metal plate was separated from the glass substrate by dissolving the photoresist film using a resist stripping agent, and a rectangular convex portion corresponding to a groove pattern with a depth of 8 μm of a pattern substrate usable for an injection molding machine was obtained. It is possible to produce a mold having

Using the mold produced as described above,
A patterned substrate is manufactured. In the present embodiment, PMMA (refractive index 1.49) is used as the substrate material, and the shape thereof is as shown as the polymer optical waveguide 4 in FIGS. 2 and 3, and is 260 mm × 25 mm × 2 mm. By size, each of 2048 core grooves is a pattern of a reduced-type waveguide having a bent portion. In addition, in the present embodiment, a dummy groove is formed in addition to the core groove, which is symmetrical about a diagonal line of the pattern substrate, and the groove is formed on the entire surface of the pattern substrate. In addition,
The pitch of the core grooves is 127 μm at the light incident end and 4 μm at the light emitting end. The groove size and width were set to 8 μm so that the shape of the core of the waveguide was square.

Here, the depth of the groove of the patterned substrate manufactured as described above was measured using a surface roughness meter. The measurement is shown in FIG. 4 used in the later description (partial cross-sectional view when the flat substrate 4b is closely attached to the pattern substrate 4a).
At the height of the inter-groove wall of the core groove portion (A1, B1, C
1, D1, E1) and the height of the inter-groove wall of the dummy groove portion (F
1, G1, H1, I1, J1) and the results are shown in Table 1.

[0029]

[Table 1]

For comparison, a patterned substrate having no dummy groove described in the above-mentioned prior art was also manufactured in the same manner as this embodiment, and the height (A2, B2, A2, B2) of the inter-groove wall of the core groove portion of FIG.
Table 2 shows the measurement results of C2, D2) and the height of the plane portion (E1) in the same manner as in the present embodiment.

[0031]

[Table 2]

From these results, the error O.S. While the error range is about 1 μm and the accuracy is high, the conventional one without the dummy groove has an error of 1.0 μm, and the present embodiment has almost no variation and a substantially uniform groove wall height. It can be seen that is obtained.

Next, as shown in the partial sectional view of FIG.
A transparent polymer precursor material is filled in the core groove and the dummy groove of the patterned substrate 4a, and the flat substrate 4b (thickness: 0.
(5 mm) is closely attached and fixed using a jig such as a clamp, and then the polymer precursor material with which the groove is filled is polymerized to form the core portion 6 and the dummy groove portion 7, thereby producing a polymer optical waveguide. Complete. In the present embodiment, the same PMMA as that of the patterned substrate is used as the material of the flat substrate, and the UV curable resin TB3042 (manufactured by ThreeBond, refractive index 1.53) is used as the core material. The dummy groove portion is also filled with the same material as the core portion. Further, since an ultraviolet curable resin was used as the core material, its polymerization was performed by irradiation with ultraviolet rays.

Thereafter, the surface of the polymer optical waveguide thus manufactured is polished by a standard polishing machine using a suspension containing diamond having a size of 0.5 μm or less.

Then, a PMMA microlens array is attached to the incident end face and the outgoing end face of the polymer optical waveguide by using an ultraviolet curable resin. In addition, in the present embodiment, the size of the microlens array is 1
The thickness was 25 μm.

Further, in order to eliminate crosstalk between adjacent optical waveguide cores, it is necessary to provide a light limiting member on the end face of the optical waveguide. Therefore, for example, a metal reflection film is formed on the end surface of the optical waveguide substrate by an evaporation method or a sputter deposition method, or an organic film containing a dye that absorbs the light of the LED, which is a light source, is applied to the end surface of the optical waveguide substrate. Just do it.

For the polymer optical waveguide of the present embodiment produced as described above and the comparative example produced in the same manner as the present embodiment without providing a dummy groove for comparison, the laser light at the incident end of the core Table 3 below shows the result of measuring the emitted light when the light was made incident and determining the propagation loss of the light in the waveguide.

[0038]

[Table 3]

As shown in Table 3, the propagation loss was 2 dB / cm in the conventional type polymer optical waveguide having no dummy groove, but it was 0 in the polymer optical waveguide having the dummy groove of the present embodiment. It can be seen that the propagation loss of 0.5 dB / cm and the propagation loss could be greatly reduced to ¼.

In the above embodiment, the method called the sandwich method is used as the method for manufacturing the polymer optical waveguide, but a method called the squeegee method may be used instead. The squeegee method is to fill the grooves of the patterned substrate with the polymer precursor material for the core, sweep away the excess core material with a spatula such as polyurethane rubber, and then cure the core material by UV irradiation (polymerization). )
Then, the flat substrate is attached. Although not described in detail, even when this squeegee method is used, if the present invention is adopted, the height of the inter-groove wall is substantially uniform, so that the polymer precursor material is almost evenly filled and good characteristics are exhibited. It has been confirmed that a polymer optical waveguide can be produced.

[0041]

As described above, according to the present invention, no matter what combination of materials the substrate and the core are made of, as long as they have adhesiveness, they have sufficient mechanical strength, An excellent polymer optical waveguide with a small propagation loss can be realized. Furthermore, when the polymer optical waveguide of the present invention is used for a reduction optical type image sensor, since an organic polymer material is used for the optical waveguide, the document width is relatively large as compared with the conventional one which does not use a polymer material. It is possible to easily manufacture even an image sensor compatible with, and it is possible to simplify the manufacturing process and reduce the cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic structure of an optical waveguide type reduction image sensor using a polymer optical waveguide according to the present invention.

FIG. 2 is an overall plan view of a photodetector of the optical waveguide reduced image sensor of FIG.

FIG. 3 is a partially enlarged view of the photodetector section in FIG.

4 is a partially enlarged cross-sectional view of the polymer optical waveguide of FIG.

FIG. 5 is a plan view of a light detection unit of a conventional optical waveguide type reduction image sensor.

6 is a partially enlarged cross-sectional view of a polymer optical waveguide used in the optical waveguide reduced image sensor of FIG.

[Explanation of symbols]

 1 Original 2 Light Source 3 Microphone Lens Array 4 Polymer Optical Waveguide 5 CCD Array 6 Core 7 Groove (Dummy Groove)

Claims (6)

[Claims] 1. In a polymer optical waveguide in which incident light propagates through a core portion and is reduced and emitted, a groove portion in which the same material as the core portion is filled in a portion of the polymer optical waveguide where the core portion is not formed. A polymer optical waveguide comprising: 2. The polymer optical waveguide according to claim 1, wherein the core portion and the groove portion are provided on the entire surface of the polymer optical waveguide. 3. The polymer optical waveguide according to claim 1, wherein the groove portion is provided symmetrically with the core portion. 4. In a polymer optical waveguide in which incident light propagates through a core portion and is reduced and emitted, a plurality of grooves which are core portions are formed on a substrate made of a transparent resin and a plurality of grooves which are not core portions are formed. A step of forming a groove to form a patterned substrate, a step of filling the groove of the patterned substrate with a transparent polymer precursor material having a higher refractive index than the substrate, and a flat substrate on the grooved side of the patterned substrate And then polymerizing the transparent polymer precursor material filled in the groove. 5. The step of forming a groove in the patterned substrate, wherein a plurality of grooves that are the core portion and a plurality of grooves that are not the core portion are formed on the entire surface of the substrate. Method for producing polymer optical waveguide of. 6. The groove formation step of the pattern substrate, wherein the grooves are formed such that a plurality of grooves that form the core portion and a plurality of grooves that do not form the core portion are symmetrical. Item 6. A method for producing a polymer optical waveguide according to Item 4 or 5.