JPS6142241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a light guide array, so-called fiber plate or self-focusing lens array, in which a large number of rod-shaped portions having a high refractive index are arranged using a high molecular weight polymer.

Conventionally, to manufacture this type of fiber plate, a single core of glass optical fiber was manufactured, then several hundred of these were bundled to form a multi-fiber with a diameter of 1 to 5 mm, and then this multi-fiber was placed in a mold. They were assembled and welded together at high temperature and pressure, then cooled, taken out of the mold, cut, and polished to become products. In the fiber plate obtained in this way, the fibers must be sufficiently welded to each other to maintain a sufficient airtightness, so controlling the welding conditions is troublesome, and as can be seen from the above steps, the process is difficult. The drawback was that the process was complicated, such as the large number of fibers required, the arrangement of fibers, and the need for high temperature and pressure. Also,
Conventional self-focusing lens arrays consist of glass rods (typically 1 to 5 mm in diameter) with a square-curve refractive index distribution.
It was manufactured by arranging and assembling a large number of materials, gluing them together, and then cutting and polishing them. However, this method has the disadvantage that the process is complicated by the work of arranging a large number of rods. Furthermore, it has been difficult to produce patterns such as rod arrays using conventional photolithography techniques.

In order to solve these drawbacks, the present invention places a substrate in a monomer solution that undergoes photopolymerization, and gradually lowers the substrate while performing mask exposure with ultraviolet rays to polymerize and grow a rod-shaped array on the substrate. rear,
A light guide array was manufactured by removing unexposed monomers, replacing them with monomers having a low refractive index, and polymerizing them, which will be explained below based on the drawings.

FIG. 1 shows the manufacturing process of an embodiment of the invention. A container 14 is filled with a liquid 11 containing a monomer as a raw material for a transparent polymer having a high refractive index, a photosensitizer, and, if necessary, a crosslinking agent and a solvent. Further, the substrate 15 is in the liquid 11 in a state where it is moved up and down by a support rod 16 connected to a feed mechanism that is linked to a motor (not shown). The photomask 13 is located directly above the liquid, and is configured to be irradiated with parallel ultraviolet light 17 from above.

In the initial state, the substrate 15 is set on the same level as the liquid 11, and then the substrate 15 starts to be lowered at a constant speed at the same time as the ultraviolet light 17 starts to be irradiated. Then, as shown in FIG. 1, the portions exposed through the mask are photopolymerized by the ultraviolet rays and begin to harden onto the substrate 15. At this time, since the substrate gradually descends, polymerization always occurs near the surface of the liquid, and rod-like bodies 12 grow on the substrate. The descending speed v of the substrate at this time satisfies the condition v<i ₀ /αw ₁ , where w ₁ is the saturation exposure amount required for monomer polymerization, and i ₀ is the intensity of ultraviolet light at the liquid surface. If you lower it slowly like this, the rod-shaped body 12 will always grow. Here, α is the ultraviolet absorption coefficient of the liquid.

When the transparent rod-shaped body 12 is thus exposed in the process shown in FIG. 1 until it reaches the required length, and the substrate is taken out from the liquid, it becomes as shown in FIG. 2.
Next, a wall 19 is attached around this as shown in FIG.
As shown in the figure, the monomer 18 is polymerized, and the rod-shaped body 12
A transparent polymeric plate 29 is formed with the inside thereof lined with. Finally, by peeling off the substrate 15 and polishing the surface if necessary, the light guide array 20 is completed as shown in FIG. 4. Here, since the rod-shaped body 12 has a higher refractive index than the surrounding polymer plate 29, it becomes a light guide in which light propagates in the length direction, and a light guide array 20 having the same function as a fiber plate is obtained.

In the above steps, as shown in FIG. 5, an image 23 of the pattern of the photomask 13 is formed on the upper surface of the liquid through the lens 22 using ultraviolet light from the ultraviolet light source 21, and the lens and the photomask are linked. You can also move it up and down. At this time, if the pattern image is initially large and gradually made smaller by the zoom effect,
A tapered rod-shaped body 24 as shown in FIG. 6 is obtained,
Accordingly, a tapered fiber plate 25 as shown in FIG. 7 is obtained through the above-described steps. This device has a tapered light guiding portion, so it has the function of enlarging or reducing the image.

Further, in the process shown in FIG. 3, if the low refractive index monomer 18 is left for a long time after flowing, the monomer will diffuse into the rod-shaped body 12. At this time, if the monomer is diffused at a high temperature for a certain period of time, the distribution of the amount of monomer in the rod-shaped body becomes as shown in FIG. The monomer amount M at this time can be set as M∝r ² with respect to the distance r from the center of the rod-shaped body. Therefore, when the monomer is polymerized by raising the temperature to a higher temperature in such a distributed state, the monomer inside the rod-shaped body is also polymerized at the same time, and is fixed in this distribution. Therefore, the refractive index distribution within the rod-shaped body takes the form shown in FIG. 9, and the refractive index decreases as the square of the distance from the center of the rod-shaped body to the periphery. It is well known that rod-shaped bodies with such a refractive index distribution have a lens effect, and therefore all the rod-shaped bodies 12 in the plate shown in FIG. 4 have such a squared refractive index distribution. In addition, a lens array having a lens function can be manufactured.

Example (1) A liquid mixture of 100 g of methyl methacrylate monomer, 10 g of NN' methylene bisacrylamide as a crosslinking agent, and 0.5 g of benzoin ethyl ether as a photosensitizer was placed in a container, and a 50 x 50 mm glass substrate was placed on the liquid surface. It was set on the same side. Photo mask is number 10
Using an array of circles with a diameter of 0.4 mm as shown in the figure, and using a 500W ultra-high pressure mercury lamp as the ultraviolet light source, we assembled the manufacturing equipment shown in Figure 1. Next, at the same time as the exposure started, the substrate was lowered at a speed of 1 mm/min, and after 7 minutes of exposure, the substrate was taken out and the final
A rod-shaped array with a length of mm was obtained as shown in FIG. Next, a fluorinated alkyl methacrylate monomer containing 0.5% of azobisisobutylnitrile was poured at 70°C.
C. for 2 hours in a nitrogen atmosphere to polymerize. Finally, this plate-like polymer was removed from the substrate, the surface was polished, and the core diameter was 0.4 mm, the array pitch was 0.5 mm, 40×40×
A 6.5 mm fiber plate was obtained. The refractive index difference between the core and the cladding was 0.08.

Example (2) 100g of styrene monomer, 10g of divinylbenzene
Examples were carried out using a photomask having a circular pattern with a diameter of 2.5 mm as shown in FIG.
Exposure was carried out using the same equipment as in (1). At this time, the substrate was moved at a speed of 0.5 mm/min and exposed for about 10 minutes. Through this process, a cylindrical array as shown in Figure 2 is created, and then methyl acrylate monomer containing 0.5% azobisisobutyronenitrile is poured around this.
It was left at 40°C for about 2 hours. Next, it was left in a nitrogen atmosphere at 70°C for 2 hours to polymerize the methyl acrylate monomer, producing a microlens array. The refractive index distribution of this lens array is n=1.57 (1-0.06/2r ²
). The lens diameter was 2.5mm, thickness was 4.0mm, array pitch was 2.7mm, and focal length was 3.1mm.

As explained above, according to the present invention, a fiber plate or a tapered fiber plate with an arbitrary cross section such as a circle or a rectangle, and with an arbitrary diameter and pitch can be produced by simply changing the pattern of the photomask.
Compared to conventional techniques, it can be manufactured through a simpler process and is economically advantageous. Further, there is an advantage that a microlens array having a self-focusing lens function can be manufactured in a similar manner at a low cost through a simple process. The fiber plate manufactured in this way can be applied to a window material for an image pickup tube or a line scanning type recording tube, and the microlens array can be applied to an optical system of a copying machine.

[Brief explanation of the drawing]

1 to 3 are process diagrams of an embodiment of the present invention,
FIG. 4 is a perspective view of the light guide array of the present invention obtained by the above process, FIGS. 5 to 7 are process diagrams of other embodiments of the present invention, and FIGS. 8 and 9 are respectively Diagrams of monomer amount distribution and refractive index distribution, Figure 10 is the pattern of the photomask used in Example (1), Figure 11 is
The figure shows the pattern used in Example (2). 11... Photosensitive liquid, 12... Rod-shaped polymer, 1
3...Photomask, 14...Container, 15...Substrate, 16...Support rod, 17...Ultraviolet light, 18...
Low refractive index monomer, 29...Low refractive index polymer.

Claims (1)

[Scope of Claims] 1. A vertically movable substrate is placed in a photosensitive liquid containing a monomer and a photosensitizer, and a photomask is placed on the top of the liquid, and ultraviolet rays are irradiated from the top of the mask. forming a polymer array on the substrate by curing the monomers in the irradiated areas by continuously and gradually submerging the substrate into the liquid while irradiating; removing the remaining uncured liquid and replacing it with a monomer having a lower refractive index than the monomer;
A method for manufacturing a light guide array, comprising the steps of polymerizing the low refractive index monomer; and peeling the substrate from a bonded product consisting of the substrate, the polymer array, and the low refractive index polymer. 2. A photomask having a pattern of circular or rectangular windows arranged between the upper surface of the photosensitive liquid and the ultraviolet light source and a lens system are arranged to image the pattern of the photomask at a position on the upper surface of the liquid, and While the substrate is continuously submerged in the liquid, the positions of the photomask and the lens system are sequentially changed to gradually reduce the pattern of the photomask on the upper surface of the liquid by zooming. 2. The method of manufacturing a light guide array according to claim 1, wherein the step of forming a tapered polymer array having a high refractive index is adopted in place of the step of forming the polymer array.