JP3291583B2 - Indexable plastic optical transmitter, optical transmitter array, and image scanner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic light transmitting body, a light transmitting array, and a light transmitting body which can be effectively used as various light transmission paths such as a light converging optical fiber, a light converging rod lens, and a light sensor. And an image scanner using the same.

[0002]

2. Description of the Related Art In a cross section of an optical transmission body, an optical transmission body having a continuous refractive index distribution from the center to the outer periphery is disclosed in Japanese Patent Publication Nos. 47-816 and 47-28059, published in Europe. This is disclosed in Japanese Patent Publication No. 0208159. The refractive index distribution type optical transmission body disclosed in Japanese Patent Publication No. 47-816 is made of glass and is made by an ion exchange method, so that its productivity is low and the same shape (especially the same length) and the same performance. It is difficult to manufacture the optical transmission media having different characteristics in different lots, and the refractive index distribution type optical transmission media having the same performance is not uniform in length.

A graded-index plastic optical transmitter disclosed in Japanese Patent Publication No. 47-28059 is a mixture of two or more transparent polymers having different refractive indices and different solubilities in a specific solvent. After shaping into a rod shape or a fiber shape, the polymer is immersed in the solvent and a part of the polymer is extracted from the surface of the molded product, whereby the weight from the surface of the polymer molded product to the center thereof is increased. It is made by assuming that the mixing ratio of coalescence has changed. By this method, it is possible to make a graded-index optical transmitter made of plastic, but a mixture of two or more polymers with different refractive indexes has a large fluctuation of the refractive index, and its transparency is reduced. Light scattering is likely to occur, and there is a problem that characteristics as a refractive index distribution type optical transmission body are not sufficient.

[0004] EP 0208159 discloses that at least one thermoplastic polymer (A) is compatible with the polymer (A) when polymerized and is different from the polymer (A). The monomer (B) is volatilized from the surface of the molded article obtained by molding a homogeneous mixture of the monomer (B) to be a polymer having a refractive index into a rod shape, so that the monomer (B) is volatilized from the surface to the inside of the molded article. There is disclosed a method for producing a graded-index plastic optical transmission body by giving a continuous concentration distribution of the monomer (B) and then polymerizing the unpolymerized monomer in the molded product.

[0005] The refractive index distribution curve of the graded index optical transmission body is ideally represented by the following equation: N = N ₀ (1−ar ² ), and is said to be the curve shown in FIG. I have. However, according to the study of the present inventor, the refractive index distribution curve of the refractive index distribution type optical transmission body produced by the above method measured under the conditions described later with an interfaco interference microscope is shown in FIG. Radial direction from center 0.
The range from 5r _{0 to} 0.75r ₀ (the range from c to d in the figure, e indicates the outermost peripheral portion) has a refractive index distribution curve relatively close to the ideal curve shown by the above equation. The outer and inner refractive index distributions have a large deviation from the ideal curve.

When observing a lattice pattern in such an optical transmission body, if the refractive index distribution has a refractive index distribution almost exactly following the quadratic curve defined by the equation (1), it is shown in FIG. 3
As shown in FIG. 2A, a normal lattice image can be observed. However, as shown in FIG. 2B, the lattice image is observed with an optical transmitter whose refractive index distribution is farther from the ideal refractive index distribution. Then, a greatly distorted lattice image as shown in FIG. 3B or 3C is observed, and accurate image transmission cannot be performed. Further, only a very low modulation transfer function (MTF) showing the resolution of 30% or less was obtained, and it could not be used as a facsimile optical transmitter at all.

Therefore, in a refractive index distribution type optical transmission body having a refractive index distribution as shown in FIG. 2 (b), which is formed by a conventional method, a portion in the outer peripheral direction is cut by cutting as compared with FIG. 2 (d). Or leaching and embedding the relevant part with a solvent,
Since the optical path of the optical transmission body has a relatively ideal refractive index distribution, it is difficult to obtain a high-resolution optical transmission body, and its productivity is extremely low, so that a uniform product can always be manufactured. There was a drawback that it was extremely difficult.

[0008]

SUMMARY OF THE INVENTION The present invention uses a monochromatic light source such as an LED, and has a high resolution and a low refractive index distribution type plastic optical transmitter and optical transmitter array which can be used as a facsimile or an image sensor. It is an object of the present invention to provide an image scanner using a transmitter array.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a monomer
And a plurality of uncured substances consisting of a polymer and
Obtained by the method of polymerizing and curing by interdiffusion
A first polymer and a second polymer provided concentrically
Consisting of multiple layers consisting of a mixture of
The content of the first polymer in the
Qualitatively the same and an interface between at least two of the plurality of layers
In the area that includes the surface, the second polymer
Forming a copolymer whose copolymer composition ratio changes by diffusion
A refractive index distribution type plastic optical transmission body having a circular cross section with a radius ro, wherein a refractive index distribution in a range of at least 0.25 ro to 0.70 ro from the central axis of the optical transmission body toward the outer peripheral surface is represented by the formula ( 1) n (r) = no [1- (g 2/2)] r 2 ... (1) ( wherein, no is the refractive index of the central axis of the optical transmission body, n (r) is the light
Refraction at a position at a distance in the radial direction r from the central axis of the transmission body
Index, g is the refractive index distribution constant of the optical transmitter, and r is in the optical transmitter.
Bei a refractive index profile of substantially approximate to the refractive index distribution curve defined by the distance) in the outer circumferential direction from the mandrel
Eteori comprises 1.4 ≦ no ≦ 1.6 0.4 ≦ ro ≦ 0.6 (mm) 0.7 ≧ g ≧ 0.3 (mm -1) becomes a characteristic value, and 4-line pairs / mm grid
An image is formed on the CCD line sensor through the light transmitter.
The maximum value of the measured light amount imax and the minimum value of the measured light amount im
to measure the in, the following equation (2) MTF (%) = [(imax-imin) / (imax + imin)] modulation transfer function calculated in × 100 ... (2)
That the characteristic (MTF) is 40% or more.
Graded index plastic optical transmitter,
is there.

[0010]

[0011]

[0012]

[0013]

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 (b), the refractive index distribution of the optical transmission body of the present invention is at least 0.
25r ₀ ~0.70r _0, preferably 0.20r ₀ ~0.
The range of 75r ₀ has a distribution curve approximately similar to the ideal refractive index distribution curve (FIG. 1A) shown in the equation (1).
The optical transmission body of the present invention in which the range specified above from the central axis of the graded index optical transmission body has the ideal refractive index distribution shown in equation (1) is in a range of 0.25r ₀ from the central axis. And even if the refractive index distributions in the region outside of 0.70r ₀ are considerably different from the refractive index distribution curve shown in the equation (1), the image obtained by observing the lattice image is almost accurate. A lattice image can be obtained.

The plastic optical transmission body of the present invention has a _value of n ₀ in the range of 1.5 ± 0.1, and it is difficult to manufacture a refractive index distribution type plastic optical transmission body in which n ₀ exceeds 1.6. On the other hand, an optical transmitter having n ₀ less than 1.4 is a plastic optical transmitter having a good resolution characteristic because it is difficult to obtain a large difference between the refractive index of the central axis portion and the refractive index of the outer peripheral portion. Can not do. Further, the g value is calculated by the equation (3).

G = √ [2 (No−Nr) / No × r ² ] (3)

This is a value that defines the lens length of the optical transmission body and its image forming distance. An optical transmitter having a g value exceeding 0.7 mm ^-1 has an extremely short imaging distance, and it is difficult to always obtain an optical transmitter having uniform characteristics. An optical transmitter having a g value of less than 0.3 mm ^-1 has a low resolution, and the performance is insufficient as a gradient index optical transmitter for a facsimile or an image scanner.

The graded-index plastic optical transmission member of the present invention is 1 when used as an optical transmission member such as a facsimile.
Rather than being used in books, the books are often used as an array used as a single or multi-row bale array, where the image obtained is a partial of the image from each light transmitter. This is a superimposed image. In order to improve the clarity of the overlapped image, the degree of overlap of these overlapped images greatly contributes. A factor that governs the degree of overlap is the diameter of the optical transmission body, and the radius r ₀ is 0.5 ± 0.5. Preferably, it is in the range of 0.1 mm. If the thickness is smaller, the brightness is insufficient, it is difficult to efficiently manufacture an optical transmission body having a uniform refractive index distribution, and if the thickness is larger than the above range, The degree of overlap of images obtained when an array is manufactured by arranging a large number of optical transmission bodies is not uniform, and it is not preferable since an array capable of transmitting clear images cannot be obtained.

The MTF indicating the resolution of the graded index plastic optical transmitter according to the present invention is a grating having a spatial frequency of 4 (line pairs / mm), and a graded index optical transmitter as shown in FIG. FIG. 4 shows a plurality of arrays and light sources.
The grid image is read by a CCD line sensor installed on the image plane (FIG. 5), and the maximum value (i _max ) and the minimum value (i _min ) of the measured light amount are measured as shown in FIG. It was determined by the following equation (2) .

MTF (%) = [(imax−imin) / (imax + imin)] × 100 (2)

Here, as shown in the grid of FIG. 4, the spatial frequency is a combination of a white line and a black line as one line pair (hereinafter referred to as "lp" as appropriate), which is 1 mm.
The number of lines provided in the width is expressed in units of line pairs / mm.

The MTF of the graded index type plastic optical transmission body of the present invention is 40% or more. An optical transmitter having an MTF of less than 40% has a low resolution, and when used as an optical transmitter for a copying machine such as a facsimile, a clear image cannot be formed. The MTF is preferably set to 45% or more.

The graded index optical transmission body made of plastic of the present invention is preferably manufactured as follows. Prepare N uncured substances whose viscosity in the uncured state is 10 ³ to 10 ⁸ poise and the refractive index n when cured is n ₁ > n ₂ > n ₃ ‥‥ n _{N, where} N ≧ 3. A multi-layered rod-shaped or fiber-shaped shaped article is formed so that the refractive index of each of the layers becomes lower in order concentrically from the center, and is diffused so that the refractive index distribution between each layer becomes a continuous refractive index distribution. It is preferable to manufacture by performing a curing treatment during the treatment or after the diffusion treatment. N
Is 2, when the difference n ₁ −n ₂ between the center layer and the outermost layer of the graded index optical transmitter is increased, the difference between the center and the center is 0.1 mm.
The refractive index distribution in the range of 25r _{0 to} 0.70r ₀ is calculated by the equation (1).
It is difficult to make the curve approximate to the curve (1), and it is impossible to obtain the optical transmission object targeted by the present invention. Therefore, N is in the range of 3 or more, and preferably in the range of 3 to 5.

The uncured substance used in practicing the present invention must have a viscosity of 10 ³ to 10 ⁸ poise and be curable. If the viscosity is less than 10 ³ poise, thread breakage occurs during shaping, and it is difficult to form a thread. On the other hand, if the viscosity is more than 10 ⁸ poise, the shaping operability is poor, and concentricity of each layer is impaired, or a shaping material having large unevenness in thickness is apt to occur, which is not preferable.

The uncured that can be used in practicing the present invention
Examples of the substance include compositions become more soluble in the polymer radical polymerizable vinyl monomer and the monomer.

Specific examples of usable radically polymerizable vinyl monomers include methyl methacrylate (n = 1.49),
Styrene (n = 1.59), chlorostyrene (n = 1.
61), vinyl acetate (n = 1.47), 2,2,3,3
-Tetrafluoropropyl (meth) acrylate, 2,
2,3,3,4,4,5,5-octafluoropropyl (meth) acrylate, 2,2,3,4,4,4-hexafluoropropyl (meth) acrylate, 2,2,2
Fluorinated alkyl (meth) acrylates such as trifluoroethyl (meth) acrylate (n = 1.37 to 1.4)
4), (meth) acrylates having a refractive index of 1.43 to 1.62, for example, ethyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, hydroxyalkyl (meth) acrylate, and alkylene glycol di (meth) acrylate. A) acrylate, trimethylolpropane di or tri (meth) acrylate, pentaerythritol di, tri or tetra (meth) acrylate, diglycerin tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and also diethylene glycol bisallyl carbonate; And fluorinated alkylene glycol poly (meth) acrylate.

In order to adjust the viscosity of the uncured material used for shaping the uncured material into a thread and to impart a refractive index distribution from the center to the outside in the obtained filament, the uncured material is a vinyl monomer. It is preferably composed of a body and a soluble polymer.

The polymer which can be used here preferably has good compatibility with the polymer formed from the above-mentioned radically polymerizable vinyl monomer. For example, polymethyl methacrylate (n = 1.49), polymethyl methacrylate Styrene copolymer (n = 1.47 to 1.50), poly-4 methylpentene-1 (n = 1.46), ethylene / vinyl acetate copolymer (n = 1.46 to 1.50), polycarbonate (n = 1.50 to 1.57), polyvinylidene fluoride (n = 1.42), vinylidene fluoride / tetrafluoroethylene copolymer (n = 1.42 to 1.46), vinylidene fluoride / tetrafluoroethylene / Hexafluoropropene copolymer (n = 1.40-1.46), polyfluorinated alkyl (meth) acrylate polymer and the like.

When a polymer having the same refractive index is used for each layer in order to adjust the viscosity, a plastic optical transmission body having a continuous refractive index distribution from the center to the surface is preferably obtained. In particular, polymethyl methacrylate has excellent transparency and a high refractive index of itself, so that it is suitable as a polymer used in producing the gradient index optical transmission body of the present invention.

In order to cure the thread formed from the uncured material, it is preferable to add a thermosetting catalyst or a photocuring catalyst to the uncured material. As the thermosetting catalyst, a peroxide catalyst is usually used. Used. Benzophenone, benzoin alkyl ether, 4'-
Isopropyl-2-hydroxy-2-methyl-propiophenone, 1-hydroxycyclohexylphenyl ketone, benzyl methyl ketal, 2,2-diethoxyacetophenone, chlorothioxanthone, thioxanthone compounds, benzophenone compounds, 4-dimethylaminobenzoic acid Examples include ethyl, isoamyl 4-dimethylaminobenzoate, N-methyldiethanolamine, and triethylamine.

Next, in order to cure the uncured thread, the thread containing the thermosetting catalyst and / or the photocuring catalyst is subjected to a heat treatment or a light irradiation treatment, preferably by applying ultraviolet rays from the surroundings in the curing section.

The optical transmission body of the present invention can be manufactured using, for example, the yarn forming apparatus shown in FIG. FIG.
Is a process diagram schematically showing a yarn forming apparatus, and an interdiffusion section.
And is intended to be vertical sectional view only curing unit, FIG. 6
Symbol 61 in the center is a concentric composite nozzle, 62 is an extruded uncured thread, 63 is an interdiffusion unit for diffusing monomers of each layer of the thread to give a refractive index distribution,
64 is a curing processing section for curing the uncured material, 65 is a take-up roller, 66 is a manufactured refractive index distribution type plastic optical transmission body, 67 is a winding section, 68 is an inert gas inlet, and 69 is an inactive gas introducing port. Active gas outlet. Filament 62
In order to remove volatile substances liberated from the interdiffusion section 63 and the curing processing section 64, an inert gas such as nitrogen gas is introduced from the inert gas inlet 68.

The light source used for photopolymerization is 150 to 60
A carbon arc lamp, a high-pressure mercury lamp that emits light having a wavelength of 0 nm,
Examples include an ultra-high pressure mercury lamp, a low pressure mercury lamp, a chemical lamp, a xenon lamp, and a laser beam.

The plastic graded-index optical transmission body of the present invention has the above-described features. A plurality of such optical transmission bodies are arranged in one or more rows as shown in FIG. By using an integrated optical transmitter array,
It can be usefully used as an image transmitter for a copier or a facsimile. When used as an optical transmitter array, its lens length (Zn) is 5 to 15 mm, preferably 6 to 1 mm.
2 mm and an imaging distance (Tc) of 10 to 40 mm, preferably 13 to 25 mm, an optical transmitter array having uniform performance and uniform array length can be obtained.
And MT measured using a grid of 4 line pairs / mm
A high-resolution optical transmitter array with F of 40% or more can be obtained.

[0035]

The present invention will be described in more detail with reference to the following examples. The lens performance and the refractive index distribution in the examples were measured by the following methods.

A. Measurement of Lens Performance Evaluation Apparatus The measurement of lens performance was performed using an evaluation apparatus shown in FIG. Preparation of Sample He-Ne passing through the optical transmitter obtained in the example
The laser beam is cut so as to have a length (λ / 4) of approximately １ ／ of the period (λ) of the light beam determined from the undulation of the laser beam, and a parallel plane in which both end surfaces of the sample are perpendicular to the long axis using a polishing machine. And polished so as to obtain an evaluation sample.

Measuring Method A trial evaluation sample (78) was set on a sample stage (76) placed on an optical bench (71) in FIG. 7, and an aperture (74) was adjusted to adjust a light source ( The light from 72) is collected by a condenser lens (73), an aperture (74), and a glass plate (75).
, And incident on the entire end face of the sample, the positions of the sample (78) and the polaroid camera (77) are adjusted so as to be in focus on a Polaroid (Polaroid) film, and a square grid image is taken. , The lattice distortion was observed. The glass plate (75) used was a chrome coating of chrome-plated glass for a photomask which was precisely processed into a 0.1 mm square lattice pattern.

B. Measurement of refractive index distribution It was measured by a known method using an Interfaco interference microscope manufactured by Carl Zeiss.

Example 1 Polymethyl methacrylate ([η] = 0.56, methyl ethyl ketone (MEK))
Medium, measured at 25 ° C.) 46 parts by weight, benzyl methacrylate 44 parts by weight, methyl methacrylate 10 parts by weight, 1
-Hydroxycyclohexyl phenyl ketone (0.2 parts by weight) and hydroquinone (0.1 parts by weight) were heated and kneaded at 70 ° C to prepare a first layer forming (center) stock solution. Also, polymethyl methacrylate ([η] = 0.41, 25% in MEK)
50 parts by weight, 50 parts by weight of methyl methacrylate, 0.2 parts by weight of 1-hydroxycyclohexyl phenyl ketone and 0.1 parts by weight of hydroquinone at 70 ° C.
Into a stock solution for forming a second layer, and further, polymethyl methacrylate ([η] = 0.34, 25 ° C. in MEK)
45 parts by weight, 2, 2, 3, 3, 4, 4, 5,
35 parts by weight of 5-octafluoropentyl methacrylate, 20 parts by weight of methyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by weight of hydroquinone were heated and kneaded at 70 ° C. for forming a third layer. The stock solution was used.

The three types of stock solutions were attached to the molding apparatus shown in FIG. 6 with a concentric three-layer composite spinning nozzle, arranged in order from the center so that the refractive index of the uncured material became lower, and simultaneously extruded into strand fibers. . The viscosity at the time of extrusion was 4.5 × 10 ⁴ poise for the stock solution of the first layer, 2.0 × 10 ⁴ poise for the stock solution of the second layer, and 2.2 × 1 for the stock solution of the third layer.
0 was ⁴ poise. The temperature of the composite spinning nozzle is 55 ° C.
Met. Next, the light was passed through a 90 cm-long inter-diffusion treatment section, and then a 120 cm-long 40 W fluorescent lamp 12 was used.
The book was passed through a strand fiber through the center of light irradiating portions arranged at equal intervals in a circular shape, and was taken out by a nip roller at a speed of 50 cm / min.

The discharge ratio is (first layer) :( second layer) :( third layer).
The optical transmitter obtained with (layer) = 1: 1: 1 has a radius (r ₀ ) of 0.50 mm, a refractive index distribution of 1.512 at the center (n ₀ ), and 1.470 at the periphery. The refractive index distribution constant (g) is 0.52, and as shown in FIG. 1, the range of 0.25r ₀ to 0.75r ₀ from the center to the outer surface is approximately equal to the above-mentioned formula (1). Had a distribution. The MTF measured by using a grating having a lens length of 7.2 mm and a length of 4 lP / mm was 57%, and the conjugate length at this time was 15.4 m.
m. The image of the obtained lattice was a clear image with little distortion.

Further, an optical transmitter array having a structure as shown at 41 in FIG.
MTF measured using a grating of / mm has a conjugate length of 1
It became 49% at 5.4 mm. An image using an LED as a light source and a CCD as a light receiving element using this optical transmitter array.
Assembled the scanner. This image scanner was able to transmit clear images with high resolution.

Example 2 The undiluted solution of the first layer used in Example 1 was applied to the first layer as polymethyl methacrylate ([η] = 0.40 in MEK at 25 ° C.).
50 parts by weight, 20 parts by weight of methyl methacrylate, 30 parts by weight of benzyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by weight of hydroquinone are heated and kneaded at 65 ° C. to form a second layer. The stock solution was used. Using the stock solution for forming the second layer used in Example 1 as the stock solution for the third layer, polymethyl methacrylate ([η] = 0.40, measured in MEK at 25 ° C.) 5
0 parts by weight, methyl methacrylate 30 parts by weight, 2,2,2
20 parts by weight of 3,3-tetrafluoropropyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by weight of hydroquinone were placed at 65 ° C.
And heated and kneaded to obtain a stock solution for forming a fourth layer.

The above four kinds of stock solutions were simultaneously extruded using a concentric four-layer composite nozzle in the same manner as in Example 1 to obtain strand fibers. The viscosity at the time of extrusion was 4.5 × 10 ⁴ poise for the stock solution of the first layer, and 4.0 × 10 ^{4 for} the stock solution of the second layer.
Poise, the stock solution of the third layer was 2.0 × 10 ⁴ poise, and the stock solution of the fourth layer was 2.2 × 10 ⁴ poise. The temperature of the composite nozzle was 60 ° C. Then, curing was performed in the same manner as in Example 1 to obtain an optical transmitter having a radius (r ₀ ) of 0.48 mm. The discharge ratio is (first layer) :( second layer) :( third layer) :( fourth layer)
= 2: 1: 1: 1, the refractive index distribution of the optical transmission medium measured by an interfaco interference microscope was at the center (n ₀ ).
Is 1.513, the peripheral part is 1.479, and the refractive index distribution constant (g) is 0.53.
In the range of 2r _{0 to} 0.8r ₀ , the refractive index distribution was approximately the same as the above formula (1). MTF measured using a 4 lP / 1 m grating was 60% at a lens length of 7.1 mm and a conjugate length of 14.9 mm.

Further, a plurality of such optical transmission bodies are combined.
As a result of producing an optical transmitter array in the same manner as
Was 53%, and the image scanner using this array was able to transmit high-resolution images similarly to the image scanner of Example 1.

Example 3 The undiluted solution for forming the first to fourth layers used in Example 2 and the undiluted solution for forming the third layer in Example 1 were used as the undiluted solution for forming the fifth layer. The stock solutions from the first layer to the fifth layer were simultaneously extruded using a concentric composite nozzle in the same manner as in Example 1 to obtain strand fibers. Thereafter, a radius (r ₀ ) of 0.
An optical transmitter of 48 mm was obtained. The discharge ratio is (first layer) :( second layer) :( third layer) :( fourth layer) :( fifth layer) = 3:
The refractive index distribution of the optical transmitter obtained at 1: 1: 1: 2 measured by an interfaco interference microscope was 1.514 at the center (n ₀ ) and 1.469 at the periphery, and the refractive index distribution constant. (G) is 0.57 and 0.15 from the center toward the outer surface.
r ₀ ～0.85R refractive index distribution in the range of ₀ coincides pot and approximately the formula (1), the MTF is the lens length 8.
It was 65% at 0 mm and conjugate length of 15.9 mm.

Further, the MTF of the optical transmitter array prepared in the same manner as in Example 1 is 60% (measured with a grid of 41 P / mm), and an image scanner using this array transmits a high-resolution image. I was able to.

Comparative Example 1 60 parts by weight of a 2,2,3,3-tetrafluoropropyl methacrylate polymer ([η] = 2.268, measured in MEK at 25 ° C.), 40 parts by weight of methyl methacrylate,
A mixture of 0.1 part by weight of 1-hydroxyhexyl phenyl ketone and 0.1 part by weight of hydroquinone was heated to 80 ° C. and extruded through a kneading section through a nozzle having a diameter of 2.0 mm. At this time, the viscosity of the kneaded composition at the time of extrusion was 1 × 1
0 was ⁴ poise. Subsequently, the strand fiber obtained by extrusion was heated to 80 ° C.
After passing through a volatilizing part flowing at a speed of / mm over 13 minutes to partially evaporate methyl methacrylate from the surface thereof, the center of six 500 W ultra-high pressure mercury lamps arranged in a circle at equal intervals is placed on the center. It was passed through a strand fiber, irradiated with light for about 0.5 minutes, and picked up with a nip roller at a speed of 20 cm / mm.

The radius (r ₀ ) of the obtained untransmitted body is 0.3
The refractive index measured by an interfaco interference microscope was 1.441 at the center (n ₀ ) and 1.441 at the periphery.
427, the refractive index distribution constant (g) is 0.48, and 0.35 r _{0 to} 0.5 from the center toward the outer surface.
The refractive index distribution in the range of r ₀ approximately coincided with the equation (1). The MTF measured using a 4 lP / mm grating was 6.6 mm in lens length and 13.8 m in conjugate length.
m was 23%, and the combined image of the obtained lattice had large distortion. Further, an optical transmitter array was prepared using the plurality of optical transmitters in the same manner as in Example 1, and as a result, the MTF (4
(IP / mm) was 13%. The image scanner using this array had a remarkably low resolution and was unsuitable for image transmission.

Example 4 Polymethyl methacrylate ([η] = 0.45, measured in MEK at 25 ° C.) 50
Parts by weight, methyl methacrylate 40 parts by weight, phenyl methacrylate 10 parts by weight, 1-hydroxycyclohexyl phenyl ketone 0.2 parts by weight, hydroquinone 0.1
An uncured substance obtained by heating and kneading parts by weight at 60 ° C. was used as a stock solution for forming a first layer, and polymethyl methacrylate ([η] = 0.
48 parts by weight, 40 parts by weight of methyl methacrylate, 12 parts by weight of 2,2,3,3-tetrafluoropropyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone, 0.1 part by weight of hydroquinone Part of the uncured material heated and kneaded at 60 ° C.
As a stock solution for forming a layer, polymethyl methacrylate ([η]
= 0.34, MEK, 25 ° C) 40 parts by weight, 2, 2,
40 parts by weight of 3,3,4,4,5,5-octafluoropentyl methacrylate, 20 parts by weight of methyl methacrylate, 1-hydroxycyclohexyl phenyl ketone 0.1 part by weight.
An uncured product obtained by heating and kneading 2 parts by weight and 0.1 part by weight of hydroquinone at 60 ° C. was used as a stock solution for forming a third layer.

These stock solutions were simultaneously extruded using a concentric composite nozzle. The viscosity at the time of extrusion at this time was 5.0 × 10 ⁴ poise for the stock solution of the first layer, and 3.5 for the stock solution of the second layer.
× 10 ⁴ poise, and the stock solution of the third layer was 2.4 × 10 ⁴ poise. The temperature of the composite nozzle was 60 ° C. The discharge ratio is (first layer) :( second layer) :( third layer) = 2: 1: 1
The fiber strands subjected to the diffusion treatment in the same manner as in Example 1 were cured to obtain an optical transmitter having r ₀ = 0.52.
The refractive index distribution of this optical transmission medium measured by an interfaco interference microscope was 1.495 at the center (n ₀ ), 1.461 at the periphery, and the refractive index distribution constant (g) was 0.41 m.
toward the outer peripheral surface from the center in m ^-1, 0.18r ₀ ~0.
The refractive index distribution in the range of 75r ₀ approximately matches the equation (1), and its MTF is 9.1 mm in lens length,
The conjugate length was 60% at 19.8 mm.

Further, the MTF of the optical transmitter array produced in the same manner as in Example 1 is 56% (measured with a grid of 4 line pairs / mm). When this array is incorporated in an image scanner, high resolution is obtained. Images could be transmitted.

(Embodiment 5) Using the three kinds of stock solutions used in Embodiment 4, the discharge ratio was set to (1st
(Layer): (Second layer): (Third layer) = 2.2: 1: 0.8, a fiber strand was made in the same manner as in Example 4, and then cured to obtain a fiber having a radius (r ₀ ) of 0.60 mm. An optical transmitter was obtained.
The refractive index distribution of this optical transmission medium measured by an interfaco interference microscope was 1.494 at the center and 1.463 at the periphery.
And the refractive index distribution constant (g) is 0.34 mm ⁻¹ , and 0.19 r ₀ to 0.76 from the center toward the outer peripheral surface.
The refractive index distribution in the range of r ₀ approximately agreed with the equation (1), and its MTF was 57% at a lens length of 11.3 mm and a conjugate length of 22.1 mm. Further, the MTF of the optical transmitter array prepared in the same manner as in Example 1 is 50% (measured with a grid of 4 line pairs / mm). When this array is incorporated in an image scanner, an image with high resolution is transmitted. We were able to.

(Comparative Example 2) Using the three kinds of stock solutions prepared in Example 4, the discharge ratio was set to (first layer) :( second layer) :( third layer).
The composition was cured in the same manner as in Example 4 except that the layer was 4.0: 1.0: 3.0 to obtain an optical transmitter having a radius (r ₀ ) of 0.50 mm. The refractive index distribution of this optical transmission medium measured by an interfaco interference microscope was 1.498 at the center and 1.459 at the periphery, and the refractive index distribution constant (g) was 0.46 m.
a m ^-1, 0.30r ₀ ~ toward the outer peripheral surface from the center
The refractive index distribution in the range of 0.65r ₀ approximately coincided with the equation (1). At this time, the MT of the optical transmitter is
F is 35% at 8.4mm lens length and 16.0mm conjugate length
Met. Further, the MTF of the optical transmitter array prepared in the same manner as in Example 1 was 30%. When this array was incorporated in an image scanner, the resolution was low and the image was distorted or the edges were blurred.

[0055]

Graded index plastic optical transmission medium of the present invention exhibits, in comparison to an optical transmission medium of the same type that have been previously developed, the refractive index distribution in the range of at least 0.25r ₀ ~0.70r ₀ from the center Has a distribution very similar to the distribution curve in the above equation (1), so that the lens has extremely good lens characteristics without cutting the outer peripheral portion thereof. It is extremely useful as an optical transmitter for a facsimile or image sensor requiring a high resolution.

[Brief description of the drawings]

FIG. 1 is a diagram showing a measurement result of a refractive index distribution of an example of an optical transmission body of the present invention.

FIG. 2 is a diagram showing a measurement result of a refractive index distribution of an optical transmission body made by a conventional method.

FIG. 3 is a diagram illustrating an example of a grid image formation of an optical transmission body.

FIG. 4 is a diagram schematically showing a resolution measuring device for an optical transmitter.

FIG. 5 is a graph showing resolution measured by a CCD sensor.

FIG. 6 is a schematic view of a manufacturing apparatus that can be preferably used for manufacturing the optical transmission body of the present invention.

FIG. 7 is a schematic diagram of a lens performance measuring device.

[Description of Signs] 61 Concentric composite nozzle 62 Uncured thread 63 Mutual diffusion part 64 Curing part 65 Take-up roller 66 Optical transmission body 67 Winding part 68 Inert gas inlet 69 Inert gas outlet 71 Optical Bench 72 Light source 73 Condensing lens 74 Aperture 75 Glass plate 76 Sample table 77 Polaroid camera 78 Evaluation sample

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H04N 1/028 H04N 1/028 Z (72) Inventor Ryuji Murata 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Inside the research institute (72) Yoshihiro Uozu 20-1, Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. (72) Inventor Masaaki Oda 20-1, Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Inside the laboratory (72) Inventor Keita Ishimaru 20-1 Miyukicho, Otake City, Hiroshima Prefecture Inside the Central Research Laboratory, Mitsubishi Rayon Co., Ltd. (56) References JP-A-57-120901 (JP, A) JP-A-62-209402 (JP, A) JP-A-62-25705 (JP, A) JP-A-51-45538 (JP, A) JP-A-1-68702 (JP, A) JP-A-1-172804 (JP, A) Ko55-18881 JP, B2)

Claims (6)

(57) [Claims] 1. An uncured substance comprising a monomer and a polymer.
Laminate multiple layers, polymerize and cure by interdiffusion of monomers
The first weight obtained in a concentric manner
Consists of multiple layers consisting of a mixture of coalesced and second polymers
The content of the first polymer in each of the plurality of layers is
Are substantially the same before and after interdiffusion, and
At least in the region including the interface between the two layers,
In the coalesced copolymer composition ratio changes due to mutual diffusion of monomers.
A graded-index plastic optical transmitter having a circular cross section with a radius ro forming a copolymer , wherein at least 0.25 ro from the central axis of the optical transmitter toward the outer peripheral surface.
Refractive index distribution in the range of 0.70ro has the formula (1) n (r) = no [1- (g 2/2)] r 2 ... (1) ( wherein, no is the central axis of the optical transmission medium Refractive index, n (r) is the refractive index at a position at a distance in the radial direction r from the central axis of the optical transmitter, g is the refractive index distribution constant of the optical transmitter, and r is the outer peripheral direction from the central axis of the optical transmitter. The distance has a refractive index distribution approximately similar to the refractive index distribution curve defined by: 1.4 ≦ no ≦ 1.6 0.4 ≦ ro ≦ 0.6 (mm) 0.7 ≧ g ≧ 0 .3 (mm ^-1 ), and a grid image of 4 line pairs / mm is formed on the CCD line sensor through the light transmitting body, and the maximum value imax of the measured light amount and the minimum value of the measured light amount Value im
is measured, and MTF (%) = [(imax−imin) / (imax + imin)] × 100 (100 ) The characteristic that the modulation transfer function (MTF) calculated by (2 ) is 40% or more is obtained. A graded-index-type plastic optical transmission body, comprising: 2. A refractive index distribution in the range of 0.20ro~0.75ro toward the outer periphery from the center axis of the optical transmission body, wherein (1) n (r) = no [1- (g 2/2) R ² (1) (where no, n (r), g, and r are the same as described above), and the refractive index distribution substantially satisfies the refractive index distribution curve. 2. The graded-index plastic light transmitting body according to 1. 3. An optical transmitter array, wherein a plurality of the gradient index plastic optical transmitters according to claim 1 are arranged in a line or a plurality of lines. 4. The optical transmitter array according to claim 3, wherein the CC is provided on one side.
An image scanner comprising a D-line sensor. 5. The lens according to claim 3, wherein the lens length (Zo) of the lenses constituting the array is in the range of 5 to 15 mm, and the imaging distance (Tc) is in the range of 10 to 40 mm. Optical transmitter array. 6. The method according to claim 3, wherein the MTF measured using a grid of 4 line pairs / mm is 40%.
An optical transmitter array as described above.