JP3370658B2 - Graded-index plastic optical transmitter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is useful as various optical transmission lines such as a light converging optical fiber, a light converging rod lens, and an optical sensor, and is also useful as an image transmitting array of a copying machine using a white light source. The present invention relates to an optical transmission body that can be used for.

[0002]

2. Description of the Related Art An optical transmission medium having a continuous refractive index distribution from a central portion to an outer peripheral portion in a cross section of the optical transmission medium is disclosed in Japanese Examined Patent Publication Nos. 47-816 and 47-28059, published in Europe. It is disclosed in the publication 0208159.

[0003]

The graded index optical transmission body disclosed in Japanese Patent Publication No. 47-816 is made of glass and is manufactured by the ion exchange method, so that the productivity is low and the same. It was difficult to make the shape (especially the same length) to have the same performance, and the gradient index optical transmission bodies having the same performance were likely to have uneven lengths, and there was a problem that the handling property was insufficient. .

The gradient index plastic optical transmission body disclosed in Japanese Patent Publication No. 47-28059 is a mixture of two or more transparent polymers having different refractive indexes and different solubilities in a specific solvent. After shaping into a rod shape or a fiber shape, it is immersed in the solvent and a part of the polymer is subjected to an extraction treatment from the surface of the molded product, so that the weight from the surface of the polymer molded product to its central portion is increased. It is made by assuming that the mixing ratio of coalescence has changed. Although it is possible to make a plastic rod lens by this method, a mixture of two or more kinds of polymers having different refractive indices has a large fluctuation of refraction, its transparency is lowered, and light scattering easily occurs. However, there is a problem that the characteristics as a graded index optical transmission body are not sufficient, and the application development thereof has not progressed.

EP-A-0208159 discloses that at least one thermoplastic polymer (A) is compatible with the polymer (A) when polymerized and the polymer (A) is
And a monomer (B) which becomes a polymer having a different refractive index from the surface of the molded article formed into a rod shape by volatilizing the monomer (B) from the surface of the molded article. A method for producing a gradient index plastic light transmission body by giving a continuous concentration distribution of the monomer (B) from the surface to the inside and then polymerizing the unpolymerized monomer in the molded article is shown. ing.

The refractive index distribution curve of the gradient index optical transmission body is ideally expressed by the following equation, and is said to be the curve shown by a in FIG. N = N ₀ (1-ar ² )

However, according to the study by the present inventor, a refractive index distribution curve measured by an interphaco interference microscope of the refractive index distribution type optical transmission body produced by the above method under the conditions described later is shown by b in FIG. As described above, the range from the center to the radial direction of 0.5r _{0 to} 0.75r ₀ (the range of c to d in the figure, e is the outermost peripheral portion) is relatively the ideal curve shown by the equation (1). Although the refractive index distribution curves are close to each other, the refractive index distributions inside and outside the distribution curve deviate greatly from the ideal curve.

Observing the lattice pattern on the optical transmitter,
If a refractive index distribution that almost exactly follows the quadratic curve is obtained, a normal grating image can be transmitted as shown in FIG. 3A. However, as shown in FIG. When a lattice image is observed with an optical transmission body that is away from the ideal refractive index distribution, a greatly distorted lattice image is observed as shown in FIG. 3 (b) or (c), and accurate image transmission cannot be performed. Has become. Further, the moderation transfer function (MTF) showing the resolution was only as low as about 30% or less, and it could not be used as an optical transmitter for a copying machine.

Therefore, in the refractive index distribution type optical transmission body having the refractive index distribution as shown in FIG. 2B, which is produced by the conventional method, a portion in the outer peripheral direction as compared with FIG. Alternatively, since the relevant portion is subjected to dissolution treatment with a solvent so that the optical path of the optical transmission medium has a relatively ideal refractive index distribution, it is not possible to obtain an optical transmission medium with high resolution, and its production It has a very poor property, and it is extremely difficult to always manufacture a uniform product.

[0010]

Therefore, the inventors of the present invention are a gradient index plastic optical transmitter which can be used in a copying machine using a white light source, and which has a higher resolution and brighter optical transmission than those conventionally developed. The present invention has been completed as a result of studies to obtain an optical transmission body which is a body and whose productivity is remarkably improved.

The gist of the present invention is as follows. That is, the first invention is a plastic optical transmission body composed of a plurality of layers formed of a mixture of the same polymer and another polymer, which are concentrically provided, and in each layer of the plurality of layers. The content of the same polymer is substantially the same, and the content of the same polymer in at least two layers constituting the plurality of layers is different, and further, in each layer of the plurality of layers, of the copolymer composition of the polymer, by varying toward the outer periphery from the center of the optical transmission body has a radius r ₀ becomes circular cross-section, at least 0.25 r ₀ ~ toward from the central axis to the outer peripheral surface The refractive index distribution in the range of 0.70r ₀ is expressed by the formula (1)

[Equation 3] The refractive index distribution curve defined by 1. is provided, and a grating image of 4 line pairs / mm is imaged on the CCD line sensor through the optical transmitter, and the maximum value imax and the minimum value of the measured light amount are obtained. A gradient index plastic optical transmission medium characterized by having a characteristic that the modulation transfer function (MTF) calculated by the following equation (2) by measuring the value imin is 40% or more.

[Equation 4] A second invention is the gradient index plastic light according to the first invention, which has a characteristic value of 1.4 ≦ n ₀ ≦ 1.6 0.15 ≦ g <0.3 mm ^−1. It is a transmitter. A third aspect of the invention is the first or second aspect, wherein the r ₀ is 0.6 mm or less.
It is a gradient index plastic optical transmission article according to the invention. A fourth aspect of the present invention is an optical transmission element array in which a plurality of the gradient index plastic optical transmission elements according to any one of the first to third aspects are arranged and assembled in one line or a plurality of lines.

[0012] refractive index distribution of the refractive index distribution type plastic optical transmission article of the present invention, 0.25r ₀ ~0.70r ₀ from the central axis as shown in b of FIG. 1, preferably 0.20R ₀
The range from to 0.75r ₀ has a distribution curve that is almost approximate to the ideal refractive index distribution curve [a in FIG. 1] shown in equation (1).

From the central axis of the optical transmission body, 0.25r ₀ ~
A refractive index distribution type plastic optical transmission body which does not have a refractive index distribution similar to the refractive index distribution curve of the formula (1) shown in FIG. 1A in the range of 0.70r ₀ can perform accurate image transmission. It cannot be used for these purposes because it cannot satisfy the required characteristics as an optical transmission body for a copying machine.

The n ₀ value of the gradient index plastic optical transmitter of the present invention is in the range of 1.4 ≦ n ₀ ≦ 1.6, and this value exceeds 1.6 and the plastic optical transmission is large. The body is difficult to make. On the other hand, an optical transmission medium in which n ₀ is less than 1.4 cannot have a large difference between the refractive index of the central axis portion and the refractive index of the outer peripheral portion thereof, and has excellent resolution and excellent image transmission characteristics. Difficult to do.

Further, the g value is calculated by the equation (3).

[Equation 5] Is a value that defines the lens length and its imaging distance. The optical transmission body of the present invention has 0.15 ≦ g <0.3 mm.
^-1 is met. When the g value is 0.3 or more, the optical transmission body having chromatic aberration is likely to be obtained, and the optical transmission body using white light as a light source becomes unsuitable. On the other hand, when the g value is less than 0.15, the image forming distance becomes long and the handling property becomes insufficient.

When the graded index plastic optical transmission medium of the present invention is used as an optical transmission medium for a copying machine or the like, it is used as a single line or a multiple line bales arrangement rather than a single line. It is often used as an array, and the image obtained by this array is a partial overlapping image of the images from the respective optical transmission bodies. In order to improve the sharpness of this overlapping image, the overlapping degree of these overlapping images greatly contributes. The factor that governs this overlapping degree is the diameter of the optical transmission medium, and its radius r ₀ is 0.4 m.
It is preferably m or more and 0.6 mm or less. If the thickness is thinner, the brightness is insufficient and it is difficult to efficiently manufacture an optical transmission body with a uniform refractive index distribution. Also, if the thickness exceeds the above range, the optical transmission body is It is not preferable because the overlapping degree of the images obtained when a large number of the above are arranged to form an array becomes non-uniform and it may be impossible to obtain an array capable of performing clear image transmission.

The MTF showing the resolution of the plastic gradient index optical transmission medium of the present invention is a grating having a spatial frequency of 4 (line pair / mm), an array in which a plurality of gradient index optical transmission elements are arranged, and a light source. 4 are arranged as shown in FIG. 4, and the grating image is read by the CCD line sensor installed on the image plane (FIG. 5). The maximum value (imax) and the minimum value (imin) of the light quantity level are measured and calculated by the following equation.

[0018]

[Equation 6]

Here, the spatial frequency is as shown in FIG.
One set of a combination of a white line and a black line is defined as one line pair, and how many of these lines are provided within a width of 1 mm is expressed in a unit of line pair / mm.

The plastic gradient index optical transmission body of the present invention has an MTF of 40% or more. An optical transmission medium having an MTF of less than 40% has a low resolution, and when used as an optical transmission medium for a copying machine such as a facsimile, it becomes impossible to form a clear copy image. The MTF is preferably 45% or more.

The plastic gradient index optical transmission body of the present invention is preferably manufactured as follows. The viscosity in the uncured state is 10 3 to 10 8 poise and the refractive index n when cured is n.
N ₁ > n ₂ > n ₃ ... n _N (N ≧ 3) N uncured substances are prepared, and a plurality of layers are laminated concentrically from the center so that the refractive index of each layer is gradually decreased. It is preferable that a body or a fibrous shaped object is formed and is subjected to a diffusing treatment so that the refractive index distribution between the respective layers becomes a continuous refractive index distribution, or by carrying out a hardening treatment after the diffusing treatment.

When g value is 0.3> g ≧ 0.15, N ≧ 3
Then, n between the central layer and the outermost layer of the gradient index optical transmission medium
The difference of ₁₋ n _N can be set in an appropriate range, and the refractive index distribution within the range of 0.25r ₀ to 0.70r ₀ from the center thereof is approximated to the curve of the formula (1). Easy,
It can be an optical transmission body which is the object of the present invention. Therefore, N is preferably in the range of 3-5.

The uncured material used in the practice of the present invention must be curable with a viscosity of 10 ³ -10 ⁸ poise. If the viscosity is less than 10 ³ poise, yarn breakage occurs during shaping, and it is difficult to form filaments. On the other hand, if the viscosity is higher than 10 ⁸ poise, the shaping operability becomes poor, the concentricity of each layer is impaired, and a shaped article with large thickness unevenness is likely to be formed, which is not preferable.

As the curable substance that can be used in the practice of the present invention, a radically polymerizable vinyl monomer or a composition comprising the monomer and a polymer soluble in the monomer can be used. .

Specific examples of radically polymerizable vinyl monomers that can be used 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 = 1.37-1.4
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, alkylene glycol di (meth). Acrylate, trimethylolpropane di- or tri (meth) acrylate, pentaerythritol di, tri- or tetra (meth) acrylate, diglycerin tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc., as well as diethylene glycol bisallyl carbonate, fluorine Alkylene glycol poly (meth) acrylate and the like.

In order to adjust the viscosity of the uncured material used to shape these materials into a thread and to impart a refractive index distribution from the center to the outside in the obtained thread, the uncured material is a vinyl-based monomer. And a soluble polymer. The polymer that can be used here preferably has good compatibility with the polymer formed from the radically polymerizable vinyl monomer, and examples thereof include polymethyl methacrylate (n = 1.49) and polymethyl methacrylate 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 / hexafluoro Examples include propene copolymer (n = 1.40 to 1.46), polyfluorinated alkyl (meth) acrylate polymer, and the like.

When the same polymer having the same refractive index is used for each layer to adjust the viscosity, a plastic optical transmission medium having a continuous refractive index distribution from the center to the surface is obtained, which is preferable. . In particular, polymethylmethacrylate is excellent in transparency and has a high refractive index by itself, and therefore it is suitable as a polymer to be used for producing the gradient index optical transmission body of the present invention.

To cure the filamentous material 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, usually a peroxide catalyst is used. Used. As a photopolymerization catalyst, benzophenone, benzoin alkyl ether, 4'-
Isopropyl-2-hydroxy-2-methyl-propiophenone, 1-hydroxycyclohexyl phenyl ketone, benzylmethyl ketal, 2,2-diethoxyacetophenone, chlorothioxanthone, thioxanthone compound, benzophenone compound, 4-dimethylaminobenzoic acid Examples thereof include ethyl, isoamyl 4-dimethylaminobenzoate, N-methyldiethanolamine, triethylamine and the like.

Next, in order to cure the uncured filamentous material, ultraviolet rays preferably act from the surroundings in the curing part, and the filamentous material containing the thermosetting catalyst and / or the photocuring catalyst is subjected to heat treatment or light irradiation treatment.

The optical transmission article of the present invention can be produced by using, for example, the yarn forming apparatus shown in FIG. FIG. 6 is a process diagram schematically showing the filamentous material forming apparatus, in which only the mutual diffusion portion and the curing treatment portion are vertical cross-sectional views, and symbol 61 in the drawing is a concentric compound nozzle and 62 is extruded. An uncured filamentous material, 63 is a mutual diffusion portion for mutually diffusing the monomers of each layer of the filamentous material to give a refractive index distribution, 64 is a curing processing portion for curing the uncured material, and 65 is A take-up roller, 66 is a manufactured gradient index plastic optical transmission body, 67 is a winding section, 68 is an inert gas inlet, and 69 is an inert gas outlet. The volatile substance released from the filamentous material 62 is added to the mutual diffusion section 63 and the curing processing section 64.
In order to remove it from the inside, an inert gas such as nitrogen gas is introduced from the inert gas inlet 68.

The gradient index optical transmission body obtained by the above method may be further provided with a coating layer having a low refractive index. To form the coating layer, trifluoroalkyl acrylate, pentafluoroalkyl acrylate, hexafluoroalkyl acrylate, fluoroalkylene diacrylate, 1,1,2,2-tetrahydroheptadecafluorodecyl acrylate, hexanediol diacrylate, neo Pentyl glycol diacrylate, dipentaerythritol hexaacrylate, etc. are appropriately mixed, and if necessary, the above-mentioned fluorinated acrylate or methacrylate polymer is added in order to adjust the coating property and the refractive index, and further the above photopolymerization initiator is added. It is preferable to use the one to which is added.

The light source used for photopolymerization is 150 to 60
Carbon arc lamp, high pressure mercury lamp, which emits light of 0 nm wavelength,
Examples include ultra-high pressure mercury lamps, low pressure mercury lamps, chemical lamps, xenon lamps, and laser light.

[0033]

EFFECT OF THE INVENTION The gradient index plastic optical transmission body of the present invention has a refractive index distribution in the range of 0.25r ₀ to 0.70r ₀ from the center of the same type of optical transmission body that has been conventionally developed. Since the distribution is extremely close to the distribution curve of the expression (1), the lens characteristics are extremely good without cutting the outer peripheral portion.

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. I. Measurement of lens performance (evaluation apparatus) The lens performance was measured using the evaluation apparatus shown in FIG. (Preparation of Sample) The length of the light transmission body obtained in the example was approximately ¼ of the period (λ) of the light beam determined from the swell of the He—Ne laser beam (λ / 4). The sample was cut and polished using a polishing machine so that both end faces of the sample would be parallel planes perpendicular to the long axis to obtain an evaluation sample. (Measurement method) A trial evaluation sample 78 is set on a sample table 76 arranged on the optical bench 71 in FIG.
The light from the light source 72 is adjusted by adjusting the diaphragm 74 and the condensing lens 7
3. After passing through the diaphragm 74, the glass plate 75 and the entire end surface of the sample, the positions of the sample 78 and the Polaroid camera 77 are adjusted so that they are focused on the Polaroid (trademark of Polaroid Co.) film, and a square grid is formed. Images were taken and the distortion of the lattice was observed. As the glass plate 75, a chrome coating of chrome-plated glass for a photomask, which was precisely processed into a 0.1 mm square lattice pattern, was used. II. Measurement of refractive index distribution The refractive index distribution was measured by a known method using an Interphaco interference microscope manufactured by Carl Zeiss.

Example 1 Polymethylmethacrylate ([η] = 0.34, MEK
52 parts by weight, benzyl methacrylate 35 parts by weight, methyl methacrylate 13 parts by weight, 1
-Hydroxycyclohexyl phenyl ketone (0.2 parts by weight) and hydroquinone (0.1 parts by weight) were kneaded by heating at 60 ° C., and an uncured product was used as a first layer forming stock solution, and polymethyl methacrylate ([η] = 0.34, MEK 50 parts by weight, benzyl methacrylate 15 parts by weight, methyl methacrylate 35 parts by weight, 1-hydroxycyclohexyl phenyl ketone 0.2 parts by weight, and hydroquinone 0.1 parts by weight were heated and kneaded at 60 ° C. The uncured product is used as the second layer forming stock solution, and polymethylmethacrylate ([η] = 0.34, measured in MEK at 25 ° C.) 50
An uncured product obtained by heating and kneading parts by weight, methyl methacrylate 50 parts by weight, 1-hydroxycyclohexyl phenyl ketone 0.2 part by weight, and hydroquinone 0.1 part by weight is used as a third layer forming stock solution, and these three stock solutions are prepared. A composite nozzle was used to simultaneously extrude as concentric fiber strands. The viscosity of the component of the first layer at the time of extrusion at this time is 4.
7 × 10 4 poise, viscosity of the second layer component is 3.7 × 10
The viscosity of the component of the third layer was 4 poise and 2.9 × 10 4 poise. The temperature of the composite nozzle was 60 ° C.

The fiber strand 62 discharged from the spinning nozzle is then subjected to a mutual diffusion part having a length of 45 cm [6 in FIG. 6].
3] to cause interdiffusion of the monomers between the layers of the strand fiber, and then the 12 fluorescent lamps (120 cm in length, 40 W) are placed at the center of the light irradiation section arranged in a circle at equal intervals. Strand speed 40 cm
/ Min to polymerize the monomer in the fiber strand to obtain a gradient index plastic light transmission material, which was taken up by a nip roller.

The discharge ratio of each layer when forming the fiber strands is (first layer) :( second layer) :( third layer) = 7:
The radius (r
₀ ) 0.59 mm, the refractive index distribution measured by an interphaco interference microscope is 1.508 at the central portion and 1.498 at the peripheral portion, and the refractive index distribution constant (g) value is 0.
As shown in FIG. 8, the refractive index distribution in the range of 0.15r _{0 to} 0.75r ₀ from the center to the outer surface at 20 mm ⁻¹ approximately agrees with the formula (1). The MTF measured by polishing both end faces of the lens with a lens length of 18.4 mm and a grating of 4 lp / mm is 60%, and when the conjugate length at that time is 42.4 mm, the image of the grating obtained is clear with little distortion. It was a statue.

Further, an optical transmission medium array having a lens length of 18.4 mm having a structure as shown at 41 in FIG. 4 is prepared by using a plurality of this optical transmission medium, and the M is formed by using a grating of 4 lP / mm.
As a result of measuring TF, it was 52%. The conjugation length of the rod-shaped lens forming this optical transmission element array was 42.4 mm. Using this light transmitting element array as an LED light source, C
When an image scanner using a CD as a light receiving element was assembled, its resolution was high and a clear image could be transmitted.

Example 2 The three kinds of stock solutions used in Example 1 and polymethylmethacrylate ([η] = 0.34, as a stock solution for forming the fourth layer)
47 parts by weight, 40 parts by weight of methyl methacrylate 2,2,3,3,4,4,5,5-
Octafluoropentyl methacrylate 13 parts by weight, 1
-Hydroxycyclohexyl phenyl ketone (0.2 parts by weight) and hydroquinone (0.1 parts by weight) are kneaded by heating at 60 ° C, and an uncured substance is used. Using a concentric four-layer composite spinning nozzle, the above four stock solutions are concentrically formed. Was simultaneously extruded as a fiber strand placed in the. The viscosities of the first to third layers at the time of extrusion were almost the same as in Example 1, and the viscosity of the fourth layer forming component was 2.5.times.10@4 poise. or,
The temperature of the composite nozzle at this time was 60 ° C. Then, the same operation as in Example 1 was performed to obtain a gradient index plastic optical transmission body.

When forming fiber strands (first layer):
The discharge ratio of (second layer) :( third layer) :( fourth layer) is 7:
The optical transmission body obtained as 4: 1: 0.5 has a radius (r ₀ ).
Is 0.60 mm, and the refractive index profile measured by an interferco interference microscope is 1.507 at the center and 1.4 at the periphery.
96, and the refractive index distribution constant (g) value is 0.20 m.
m ⁻¹ , 0.15r _{0 to} 0.
The refractive index distribution approximately agrees with the formula (1) in the range of 80r ₀ , and both end faces of this optical transmission medium are polished to have a lens length of 18.4 mm and MTF measured using a 4 lP / mm grating. Was 65%. Conjugate length at that time is 42.4m
It was m. A plurality of this optical transmission medium was combined to form an optical transmission medium array having a lens length of 18.4 mm in the same manner as in Example 1, and the MTF was measured using a grating of 4 lP / mm. As a result, the conjugate length was 58%. Was 42.4 mm. An image scanner using an LED as a light source and a CCD as a light receiving element was assembled using this optical transmission element array. This image scanner was able to transmit clear images with high resolution.

Example 3 The four types of stock solutions used in Example 2 were used as stock solutions for forming the first to fourth layers, and polymethylmethacrylate ([η]
= 0.34, measured at 25 ° C. in MEK) 40 parts by weight,
18 parts by weight of methyl methacrylate, 2, 2, 3, 3,
42 parts by weight of 4,4,6,6-octafluoropentyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.1 part by weight of hydroquinone were heated and kneaded at 60 ° C. to obtain a stock solution for forming a fifth layer. The five stock solutions were simultaneously extruded as concentric fiber strands using a composite nozzle. 1st to 4th layers when extruded
The viscosity of the undiluted solution up to the layer is almost the same as in Example 2,
The viscosity of the layer forming component was 2.2.times.10@4 poise.
The temperature of the composite spinning nozzle at this time was 60 ° C.

Then, the same operation as in Example 1 was carried out to carry out the light transmission.
I got a sender. When forming fiber strands (first layer):
(Second layer): (Third layer): (Fourth layer): (Fifth layer)
It was obtained with an output ratio of 7: 4: 1.1: 0.6: 0.4.
The optical transmitter has a radius (r₀ ) 0.60 mm, interfero
The refractive index distribution measured by an interference microscope is 1.
507, the peripheral portion is 1.494, and the refractive index distribution constant is
(G) value is 0.22mm ^-1And from its center to the outside
Towards 0.15r₀ ~ 0.85r₀ Refractive index distribution in the range
Was approximately coincident with the equation (1). This optical transmitter
Both ends of the lens are polished to a lens length of 17.8 mm, 4 lP
The MTF measured using a / mm grid was 72%.
It was The conjugate length at that time was 32.6 mm. This light
A combination of a plurality of feeders and a lens length of 1 as in the first embodiment
Create a 7.8 mm optical transmitter array and obtain 4 lP / mm
As a result of measuring MTF using a lattice, the conjugate length is 32.6 m.
It was 65% in m. LE using this optical transmitter array
Image scan with D as light source and CCD as light receiving element
I assembled the na. This image scanner has high resolution
It was possible to transmit clear images.

Example 4 Polymethylmethacrylate ([η] = 0.34, MEK
51 parts by weight, benzyl methacrylate 20 parts by weight, methyl methacrylate 29 parts by weight, 1
The uncured material obtained by kneading 0.2 parts by weight of hydroxycyclohexyl phenyl ketone and 0.1 parts by weight of hydroquinone at 60 ° C. was used as the first layer forming stock solution, and the third layer forming stock solution used in Example 1 was used. Used as the second layer forming stock solution, the fourth layer forming stock solution used in Example 2 was used as the third layer forming stock solution, and the same operation as in Example 1 was performed by using these three kinds of stock solutions. A type optical transmitter was obtained. At this time, the viscosity of the component of the first layer was 4.5 × 10 4 poise.

The discharge ratio at the time of forming the fiber strand is (first layer) :( second layer) :( third layer) = 7: 3: 1,
The (r ₀ ) of the obtained optical transmission medium was 0.46 mm, the refractive index distribution measured by an interferco interference microscope was 1.500 in the central portion and 1.490 in the peripheral portion, and the refractive index distribution constant (g ) Value is 0.25 mm ^-1 , and the refractive index distribution approximately agrees with the formula (1) in the range of 0.15r _{0 to} 0.81r ₀ from the center to the outer surface. Both ends of the light transmission body are polished to make the lens length 15.6 mm, and 4
MTF measured using a 1 P / mm grating has a conjugate length of 2
It was 62% at 9.0 mm. A plurality of the optical transmission bodies were combined to form an optical transmission body array having a lens length of 15.6 mm in the same manner as in Example 1, and the MTF was measured using a grating of 4 lP / mm. As a result, the conjugate length was 29.0 mm and 55. It became%. Using this light transmitter array as an LED light source,
An image scanner using a CCD as a light receiving element was assembled. This image scanner was able to transmit clear images with high resolution.

Example 5 Polymer [A] (n ₀ = 1.456, [η] = 1.0) consisting of 50 parts by weight of methyl methacrylate and 50 parts by weight of 2,2,3,3-tetrafluoropropyl methacrylate.
0) 50 parts by weight, 50 parts by weight of methyl methacrylate, 1
An uncured product obtained by kneading 0.2 parts by weight of hydroxycyclohexyl phenyl ketone and 0.1 parts by weight of hydroquinone at 60 ° C. was used as a first layer forming stock solution. Further, 48 parts by weight of the polymer [A], 22 parts by weight of 2,2,3,3-tetrafluoropropyl methacrylate, 30 parts by weight of methyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone, 0.1 part by weight of hydroquinone. 6 parts
The uncured material kneaded by heating at 0 ° C. is used as the second layer forming stock solution,
46 parts by weight of polymer [A], 44 parts by weight of 2,2,3,3-tetrafluoropropyl methacrylate, 10 parts by weight of methyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.1 part by weight of hydroquinone. The uncured product obtained by heating and kneading at 60 ° C. was used as a third layer forming stock solution. When these three stock solutions were extruded, the viscosity of the first layer forming component was 4.0 × 10 4 poise, the viscosity of the second layer forming component was 3.3 × 10 4 poise, and the viscosity of the third layer forming component was The composition was 3.1.times.10@4 poise, and composite spinning was carried out in the same manner as in Example 1, followed by curing treatment to obtain a gradient index optical transmission member.

The discharge ratio of each layer at the time of forming the fiber strand was (first layer) :( second layer) :( third layer) = 7: 4: 1. The radius (r ₀ ) of the obtained optical transmission medium is 0.50 mm
The refractive index distribution measured by the interphaco interference microscope is 1.472 in the central portion and 1.459 in the peripheral portion, and the refractive index distribution constant (g) value is 0.27 mm ⁻¹ , the outer surface from the center. In the range of 0.15r _{0 to} 0.78r ₀ , the refractive index distribution approximately agrees with the formula (1), and both end faces of this optical transmission medium are polished to obtain a lens length of 14.0.
mm and MTF measured using a 4 lP / mm grating
Was 64% with a conjugation length of 29.0 mm. A plurality of this optical transmitters are combined and the lens length is 14.
As a result of making an optical transmission medium array of 0 mm and measuring the MTF using a grating of 4 lP / mm, the conjugate length was 29.0 mm.
Was 57%. LED using this optical transmitter array
An image scanner having a CCD as a light source and a CCD as a light receiving element was assembled. This image scanner was able to transmit clear images with high resolution.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a measurement result of a refractive index distribution of a gradient index plastic optical transmission body produced by a conventional method.

FIG. 3 is a diagram showing an example of a lattice image combined image of these optical transmission bodies.

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

FIG. 5 is a graph in which a light amount level is measured by a CCD sensor.

FIG. 6 is a schematic view of a manufacturing apparatus that can be preferably used to manufacture the gradient index plastic optical transmission body of the present invention.

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

FIG. 8 is a refractive index distribution measurement diagram of an example of a gradient index plastic optical transmission body of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Uozu 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Inventor Masaaki Oda 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Inventor Teruta Ishimaru 20-1 Miyuki-cho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Central Research Laboratory (56) References JP2000-155224 (JP, A) ) 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) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 6/00-6/02 G02B 6/10 G02B 6/16- 6/22 G02B 6/44

Claims (4)

(57) [Claims] 1. A plastic optical transmission body comprising a plurality of layers formed of a mixture of the same polymer and another polymer, which are concentrically provided, wherein the same layer in each layer of the plurality of layers. The polymer content is substantially the same, and at least 2 constituting the plurality of layers.
The contents of the same polymer in the layers are different, and the copolymerization composition of the other polymer in each layer of the plurality of layers changes from the center of the optical transmission member toward the outer periphery, thereby It has a circular cross section r _{0, and} the refractive index distribution in the range of at least 0.25r _{0 to} 0.70r ₀ from the central axis toward the outer peripheral surface is given by the formula (1) , Which has a refractive index distribution approximately similar to the refractive index distribution curve defined by, and a lattice image of 4 line pairs / mm is C through the optical transmission medium.
An image is formed on the CD line sensor, the maximum value imax and the minimum value imin of the measured light amount are measured, and the modulation transfer function (MTF) calculated by the following equation (2) has a characteristic of 40% or more. A graded index plastic optical transmitter characterized by being characterized in that: [Equation 2] 2. The gradient index plastic optical transmission medium according to claim 1, having a characteristic value of 1.4 ≦ n ₀ ≦ 1.6 0.15 ≦ g <0.3 mm ^−1. . 3. The gradient index plastic optical transmission medium according to claim 1, wherein r ₀ is 0.6 mm or less. 4. An optical transmission medium array comprising a plurality of the gradient index plastic optical transmission mediums according to claim 1 arranged in a line or in a plurality of lines.