JPH03213806A - Manufacturing method of refractive index gradient plastic optical transmitter - Google Patents

Abstract

PURPOSE:To obtain the light transmission body having a high resolution by setting the refractive index distribution in a 0.25 to 0.70 r0 range from the center at the distri bution extremely approximate to a prescribed distribution curve. CONSTITUTION:The refractive index distribution in the 0.25 to 0.70 r0 range from the center of the light transmission body having the circular section of a radius r0 is expressed by equation I. This refractive index distribution is imparted with distribu tion extremely approximate to a refractive index distribution constant curve. This transmission body has the characteristic values n0=1.5+ or -0.1, r0=0.5+ or -0.1mm, 0.3>g>=0.15mm<-1> and the characteristics that the modulation transfer function measured by using a grating of 4 line pair/mm is >=40%. In the equation I, n0 denotes the refrac tive index at the central axis of the light transmission body; n(r) denotes the refractive index in the position of the outer peripheral direction (r) from the central axis of this light transmission body; (g) denotes a refractive index distribution constant; (r) denotes the distance in the outer peripheral direction from the central axis of this light transmission body. The light transmission body having the high resolution is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention relates to a light-focusing optical fiber, a light-focusing rod-shaped lens,
The present invention relates to an optical transmission body that is useful as an optical transmission path for a number of optical sensors, etc., and can be usefully used as an image transmission array for a copying machine using a white light source, and a method for manufacturing the same.

U Prior Art] An optical transmission body having a continuous refractive index distribution from the center to the outer periphery in the cross section of the optical transmission body was disclosed in Japanese Patent Publication No. 47-
This method is disclosed in Japanese Patent No. 816, Japanese Patent No. 47-28059, and European Publication No. 0208159.

[Problems to be Solved by the Present Invention] The refractive index distribution type optical transmission body disclosed in Japanese Patent Publication No. 47-816 is made of glass and manufactured by an ion exchange method, so its productivity is low. It is difficult to have the same shape (especially the same length) and the same performance, and the lengths of graded index optical transmission bodies with the same performance tend to be uneven.
There was a problem in that it was not easy to handle.

The refractive index gradient plastic optical transmitter disclosed in Japanese Patent Publication No. 47-28059 is a rod-shaped mixture of two transparent polymers with different refractive indexes and different solubility in specific solvents. Alternatively, after shaping into a fiber, a part of the polymer is extracted from the surface of the molded product by immersing it in the solvent, so that the polymer is formed from the surface to the center of the molded polymer. It is made by changing the mixing ratio of

Although it is possible to make some plastic rod-shaped lenses using this method, when two or more polymers with different refractive indexes are mixed, the refractive index fluctuates more, reducing its transparency and causing light scattering. However, there is a problem in that the characteristics of the refractive index distribution type optical transmitter are not sufficient, and the development of its applications has not progressed.

European Patent Publication No. 0208159 discloses that at least one thermoplastic polymer (A) is compatible with the polymer (A) when polymerized and has a refractive index different from that of the polymer (A). By volatilizing the monomer (B) from the surface of a loft-shaped molded product obtained by molding a homogeneous mixture with the monomer (B) to form a polymer, the monomer is formed from the surface to the inside of the molded product. A method for producing a graded refractive index plastic optical transmitter is disclosed by providing a continuous concentration distribution of (B) and then polymerizing unpolymerized monomers in the molded product.

The refractive index distribution curve of a refractive index distribution type optical transmission body is ideally expressed by the following equation, and is said to be the curve shown in a in FIG. 2.

N=No (1-ar2) However, according to the inventor's study, the refractive index distribution curve of the refractive index distribution type optical transmission body made by the above method measured with an interfaco interference microscope under the conditions described later is as shown in the figure. As shown in b, the radius direction from the center is 0.5r, ~0
．． The range up to 75ro (the range c = d in the same figure, e indicates the outermost periphery) has a refractive index distribution curve relatively close to the ideal curve shown in equation (1), but the inner and outer regions The outer refractive index profile deviates significantly from its ideal curve.

When observing the lattice pattern in such an optical transmission body, the refractive index distribution will be as shown in Figure 3 (a) if the quadratic curve has a refractive index distribution that exactly follows X°. However, if the grating image is observed in an optical transmission medium whose refractive index distribution is far from the ideal refractive index distribution as shown in Fig. 2, the third (Ex) or (C)
As shown in Figure 2, a highly distorted lattice image is observed, making accurate image transmission impossible. In addition, the moderation transfer function (MTP), which indicates the resolution, was only about 30% or less, which was extremely low, and it could not be used as an optical transmission medium for copying machines.

Therefore, the refractive index distribution type optical transmission body made by the conventional method with the refractive index distribution as shown in FIG.
Either remove the area in the outer circumferential direction from the figure (d), or
Alternatively, since the part is dissolved with a solvent so that the optical path of the optical transmission body has a relatively ideal refractive index distribution, it is not possible to obtain an optical transmission body with high resolution, and its production is difficult. There was a problem in that it was extremely difficult to consistently produce uniform products with extremely low temperatures.

[Means for Solving the Problems] Therefore, the present inventors have developed a gradient index plastic optical transmitter that can be used in copying machines that use a white light source, and which has higher resolution and brighter light than those previously developed. It is a transmitting body,
The present invention was completed as a result of studies aimed at obtaining an optical transmission body with significantly improved productivity.

The gist of the present invention is that the radius r0 to 0.75r0
A refractive index distribution type optical transmission body having a range of 0.25r0 to 0,7Or=preferably 0.20ro to 0.75ro from the center of the optical transmission body toward the outer periphery,
The refractive index distribution constant curve expressed by the following formula (1) has a null approximation distribution, no=1.5±0.1 ro=0.5±0.1 0.3>g≧0. It has a characteristic value of 15 mm and a modulation transfer function measured using a grid of 4 line pairs/'.
The present invention relates to a plastic gradient index optical transmission body characterized by having a characteristic that the r function (hereinafter referred to as MTP) is 40% or more.

The refractive index distribution of the plastic gradient index optical transmission body of the present invention is 0.0 mm from its central axis, as shown in FIG.
25r=~0.70r0, especially 0.2 leaves, ~0.75
It is necessary that the ideal refractive index distribution curve [FIG. 1(a)] in which the range of ro is expressed by equation (1) has a distribution curve approximating -'.

A gradient index plastic that does not have a refractive index distribution that approximates the refractive index distribution curve of formula (1) shown in FIG. 1(a) in the range of 0.25ro to 0.75r0 from the central axis of the optical transmission body The manufactured light transmitting body cannot perform accurate image transmission and does not satisfy the required characteristics as a light transmitting body for a copying machine, and cannot be used for these purposes.

Further, n of the gradient index plastic optical transmission body of the present invention. The value must be in the range of 1.5±0.1; if this value exceeds 1.6, it becomes difficult to manufacture a large plastic optical transmission body.

On the other hand, an optical transmission body with a no less than 1.4 cannot have a large difference between the refractive index of its central axis and its outer circumference, and is therefore not an optical transmission body with excellent resolution and image transmission characteristics. difficult to do.

Furthermore, the g value is defined by equation (3) and is a value that defines the lens length and its imaging distance. If g4tL becomes larger than 0.3, the light transmission body tends to have chromatic aberration, and becomes unsuitable for use as a light transmission body using white light as a light source. On the other hand, when the g value is smaller than 0.15, the imaging distance becomes longer,
Its handling is insufficient.

When the plastic gradient index optical transmitter of the present invention is used as an optical transmitter in a copying machine, etc., it is not used as a single piece, but as an array in which many pieces are used in a single row or multi-row stacked arrangement. Often used, the image obtained with this array is a partially overlapping image of images from each optical transmission body. In order to improve the clarity of these overlapping images, the degree of overlapping of these overlapping images greatly contributes, and the factor that governs this degree of overlapping is the diameter of the optical transmission body, whose radius r0 is 0.5±0 .1++u
It is preferably within the range of *. If this thickness is even thinner, the brightness will be insufficient and it will be difficult to efficiently produce an optical transmission body with a uniform refractive index distribution.If this thickness exceeds the above range, the optical transmission body When an array is made by arranging a large number of these, the degree of overlapping of the images obtained becomes non-uniform, making it impossible to create an array capable of transmitting clear images, which is not preferable.

In addition, the MTF indicating the resolution of the plastic gradient index optical transmitter of the present invention has a spatial frequency of 4 (linebare/ll1
ffl), an array of multiple refractive index distribution type optical transmitters as shown in Fig. 4, and a light source arranged as shown in Fig. 4, and a CCD line sensor installed on the imaging plane generates a grating image. (Fig. 5) and measured the maximum value (1, , ) and minimum value (1, i,) of the light intensity level, and calculated it using the following formula: i□JilI;n Here, the lattice constant is the fourth As shown in the grid in the figure, a combination of a white line and a black line is considered to be one line, and line pairs/■ indicate how many lines are provided in the white area in one battle.

MTF of the plastic gradient index optical transmission body of the present invention
must be 40% or more.

An optical transmission medium with an MTF of less than 40% has a low resolution, and when used as an optical transmission medium for a copier such as a facsimile machine, it will not be possible to form a clear copy image, so it is preferable that the MTF is 45% or more. Good.

The plastic gradient index optical transmission body of the present invention is preferably manufactured as follows.

Prepare N uncured substances, N22, with a viscosity of 103 to 10'voise in an uncured state and a refractive index n when cured, >nz>n,...n7, and form concentric circles from the center. A rod-shaped body or a fiber-shaped object is formed by stacking multiple layers such that the refractive index of each layer decreases sequentially, and while performing a diffusion treatment so that the refractive index distribution between each layer becomes a continuous refractive index distribution, Alternatively, it is preferable to perform a hardening treatment after a diffusion treatment.

When the g value is 0.3>g≧0.15, and N≧2, the overlap between the center layer and the outermost layer of the gradient index optical transmission body.

The difference in n8 can be set within an appropriate range, and the refractive index distribution within the range of 0.25ro-0.75r0 from the center can be easily approximated to the curve 2(1). It can be used as a desired optical transmission body. Therefore, it is preferable that N be in the range of 2 or more and 7, preferably in the range of 3 to 5.

The uncured material used in carrying out the present invention must have a viscosity of 10 3 to 10 6 poise and be curable. If the viscosity is less than 103 voids, thread breakage occurs during shaping, making it difficult to form a thread-like material. Further, if the viscosity is greater than 10b voids, the shaping operability will be poor, the concentricity of each layer will be impaired, and the shaped product will tend to have large unevenness in thickness, which is not preferable.

As the curable substance that can be used in carrying out 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), chlorstyrene (n = 1.61), vinyl acetate (n = 147), 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-trifluoroethyl (meth)acrylate ) Acrylates and other fluorinated alkyl (meth)azilylates (n=1.37-1.44), (meth)acrylates with a refractive index of 1.43-1.62, such as 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, diglycerine tetra(meth)acrylate ) acrylate, dipentaerythritol hexa(meth)acrylate, diethylene glycol bisallyl carbonate, fluorinated alkylene glycol poly(meth)acrylate, and the like.

In order to adjust the viscosity of the uncured material used to shape these substances into threads and to provide a refractive index distribution from the center to the outside in the obtained threads, the above substances are made of vinyl monomers and soluble polymers. It is preferable that it be configured. The polymer that can be used here needs to have good compatibility with the polymer produced from the above-mentioned radically polymerizable vinyl monomer; for example, polymethyl methacrylate (n=
1.49), polymethyl methacrylate copolymer (n=1.47~1.50), poly-4-methylpentene-1 (n=1.46), ethylene/vinyl acetate copolymer (n=1.46~ 1.50), polycarbonate (n=1.50-1.57), polyvinylidene fluoride (n=1.42), vinylidene fluoride/tetrafluoroethylene copolymer (n=1.42-1.46), vinylidene fluoride/tetrafluoroethylene/hexafluoropropene copolymer (n=1.40-1.46),
Examples include polyfluorinated alkyl (meth)acrylate polymers.

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

In order 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, and a peroxide catalyst is usually used as the thermosetting catalyst. .

As a photopolymerization catalyst, benzophenone, benzoin alkyl ether, 4'-isopropyl-2hydroxy-2-
Methyl-propiophenone, l-hydroxycyclohexylphenyl ketone, benzyl methyl ketal, 2.2
-jethoxyacetophenone, chlorothioxanthone,
Thioxanthone compounds, benzophenone compounds, 4
-Ethyl dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, N-methyljetanolamine,
Examples include triethylamine.

Next, in order to cure the uncured filament, the filament containing the thermosetting catalyst and/or photocuring catalyst is subjected to heat treatment or 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 produced using, for example, the thread forming apparatus shown in FIG. 6. Fig. 6 is a process diagram schematically showing the yarn forming device, in which only the interdiffusion section and the hardening section are shown in longitudinal section. 63 is an interdiffusion section for mutually diffusing monomers in each layer of the thread to provide a refractive index distribution; 64 is a curing section for curing the uncured material; 65 is a take-up roller, 66 is a manufactured refractive index distribution type plastic optical transmission body, 7 is a winding part, 68 is an inert gas inlet, and 69 is an inert gas outlet.

In order to remove volatile substances liberated from the filament 62 from the interdiffusion section 63 and the curing section 64, an inert gas such as nitrogen gas is introduced from the inert gas inlet 68.

The gradient index optical transmission body obtained by the method described above can 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-tetrahydrohebbutadecafluorodecyl acrylate, hexanediol diacrylate, neopentyl glycol diacrylate,
Dipentaerythritol mixed with hexaacrylate, etc. as appropriate, added with the above-mentioned fluorinated acrylate or methacrylate polymer to adjust coating properties and refractive index as necessary, and further added with the above-mentioned photopolymerization initiator. It is preferable to use

Examples of the light source used for photopolymerization include carbon arc lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, low-pressure mercury lamps, chemical lamps, xenon lamps, and laser lights that emit light with a wavelength of 150 to 600 nm.

[Effects of the present invention] The plastic gradient index optical transmitter of the present invention has a 0.0
．． The refractive index distribution in the range of 25r- to 0.75ro is expressed by the formula (1
), the lens has extremely good lens characteristics even without cutting the outer periphery.

Furthermore, this is the first time that we have successfully manufactured the light transmitting body of the present invention in an extremely efficient manner by using a concentric multilayer extrusion molding method of three or more layers using an uncured material.

The present invention will be explained in more detail with reference to Examples below.

Lens performance and refractive index distribution in Examples were measured by the following method.

(2) Measurement and Evaluation Apparatus for Lens Performance Lens performance was measured using an evaluation apparatus shown in FIG.

He-N passing through the optical transmission body obtained in Sample Preparation Example
e Period of the light beam (λ) determined from the undulation of the laser beam
The sample was cut to a length of approximately 2 (λ/4), and polished using a polishing machine so that both end surfaces of the sample became parallel planes perpendicular to the long axis to obtain an evaluation sample.

Measurement method: Set the prototype evaluation sample (7B) on the sample stand (76) placed on the optical bench (71) in Fig. 7, adjust the aperture (74), and turn on the light source (72). After the light passes through the condensing lens (73), the aperture (74), and the glass plate (75) and enters the entire end surface of the sample, the positions of the sample (18) and the Polaroid camera (77) are adjusted. The focus was adjusted to be on the Polaroid (Polaroid Company trademark) film, a square grid image was photographed, and the distortion of the grid was observed. The glass plate (75) used was a chrome-plated photomask glass coated with precision processed into a 0.1 mm square grid pattern.

(2) Measurement of refractive index distribution Measurement was carried out by a known method using an Interfaco interference microscope manufactured by Carl Zeiss.

Example 1 Polymethyl methacrylate ([η) = 0.34. M.E.
52 parts by weight (measured in K at 25°C), 35 parts by weight of benzyl methacrylate, 13 parts by weight of methyl methacrylate, 0.2 parts by weight of 1-hydroxycyclohexylphenyl ketone.
Part by weight of polymethyl methacrylate ([η] = 0.34.
50 parts by weight (measured at 5°C), 15 parts by weight of benzyl methacrylate, 35 parts by weight of methyl methacrylate, 0.2 parts by weight of 1-hydroxycyclohexylphenyl ketone,
An uncured product obtained by heating and kneading 0.1 part by weight of hydroquinone at 60°C was used as the stock solution for forming the second layer, and polymethyl methacrylate ([η) = 0.34. In MEK, 25°C
) 50 parts by weight, 50 parts by weight of methyl methacrylate, 0.2 parts of 1-hydroxycyclohexylphenyl ketone
part by weight and 0.1 part by weight of hydroquinone were heated and kneaded as a third layer forming stock solution, and these three stock solutions were simultaneously extruded as concentric fiber strands using a composite nozzle. At this time, the viscosity of the first layer component during extrusion is 4.7XIO'poise, the viscosity of the second layer component is 3.7X10'poise, and the viscosity of the third layer component is 2.9X
It was 10' Boise. The temperature of the composite nozzle was 60°C.

Fiber strand (62) discharged from the spinning nozzle
Then there is a 45 cm long interdiffusion section [(63) in Figure 6].
) to cause interdiffusion of monomer between each layer of the strand fiber, followed by 12 fluorescent lamps (
The fiber strand speed is 40 cm at the center of the light irradiation part arranged at equal intervals in a circle with a length of 120 c + a, 40 -
The monomer in the fiber strand was polymerized by passing through the fiber at a speed of 1/2 min to form a graded index plastic optical transmitter, which was then taken off with a nip roller.

The radius (ro )0.59m
m, and the refractive index distribution measured using an interfaco interference microscope is 1.508 at the center and 1.4 at the periphery.
98, and the refractive index distribution constant (the odor value is 0.20 mm-', as shown in Fig. 8 from the center to the outer surface) is < 0.15.
The refractive index distribution in the range of ro to 0.75ro is approximately (1
) formula, the MTF measured by polishing both end faces of this optical transmitter and using a grating of 41P/run with a lens length of 18.41W11 is 60%, and the conjugate length at that time is 42.4m++. The image of the obtained grating was clear with little distortion.

Furthermore, using a plurality of these optical transmitters, an optical transmitter array with a lens length of 18.4 mm was created as shown in 41 in FIG. 4, and its MTF was measured using a grating of 41P/rrm. %. The conjugate length of the rod-shaped lenses constituting this optical transmitter array was 42.4 mm. When an image scanner was assembled using this optical transmitter array, with an LED as a light source and a CCD as a light receiving element, the resolution was high and clear images could be transmitted.

Example 2 In addition to the three stock solutions used in Example 1, polymethyl methacrylate ([η) -0,34 was used as the stock solution for forming the fourth layer.
, 47 parts by weight (measured in MEK at 25°C), 40 parts by weight of methyl methacrylate 2.2.3,3°4.4,5.
13 parts by weight of 5-octafluoropentyl methacrylate, 0.2 parts of 1-hydroxycyclohexylphenyl ketone
Part by weight and 0.1 part by weight of hydroquinone were heated and kneaded at 60°C to form an uncured material, and a concentric four-layer composite spinning nozzle was used to simultaneously form fiber strands in which the above four stock solutions were arranged in concentric circles. I pushed it out. The viscosity of the first to third layers during extrusion was the same as in Example 1, and the viscosity of the component forming the fourth layer was 2.5 x 10' poise. Further, the temperature of the composite nozzle at this time was 60°C.

Next, the same operation as in Example 1 was performed to obtain a gradient index plastic optical transmission body.

(2nd layer) during fiber strand formation: (2nd layer) =
(Third layer) = (Fourth layer) discharge ratio of 7:4:1
: The radius (ro) of the optical transmission body obtained as 0.5 is 0.
．． 60mm, the refractive index distribution measured using an interfaco interference microscope is 1.507 at the center and 1.496 at the periphery.
and the refractive index distribution constant (g) value is 0.20 om-',
0.15r0~0.80r from the center to the outer surface
The refractive index distribution approximately matches the formula (1) in the range of o, and both end surfaces of this optical transmission body are polished and the lens length is 18.
MTF measured using a grid of 4mm and 41P/mm
was 65%. The conjugate length at that time was 42.4 am. A plurality of these optical transmission bodies were combined in the same manner as in Example 1 to create an optical transmission body array with a lens length of 18.4nan.
The MTF was measured using a lattice of 41P/ltm and found to be 58%, and the conjugate length at this time was 42.4 mm. Using this optical transmitter array, an image scanner was assembled using an LED as a light source and a CCD as a light receiving element. This image scanner was able to transmit clear images with high resolution.

Example 3 The four kinds of stock solutions used in Example 2 were used as stock solutions for forming the fourth layer to polymethylmethac')
(77) =0.34. 40 parts by weight (measured in MEK at 25°C), 1-18 parts by weight of methyl methacrylate, 2
．． 42 parts by weight of 2,3,3,4,4,6.6-octafluoropentyl methacrylate, 0.2 parts by weight of ■-hydroxycyclohexylphenyl ketone, 0 parts by weight of hydroquinone
．． 1 part by weight was heated and kneaded at 60°C to obtain a stock solution for forming the fifth layer, and these five stock solutions were simultaneously extruded as concentric fiber strands using a composite nozzle. The viscosity of the stock solution from the first layer to the fourth layer during extrusion was the same as in Example 2, and the viscosity of the component forming the fifth layer was 2.2×10′.
It was Poise. Further, the temperature of the composite spinning nozzle at this time was 60°C.

Next, the same operation as in Example 1 was performed to obtain an optical transmission body.

During fiber strand formation (first layer): (second layer):
The discharge ratio of (third layer) = (fourth layer): (fifth layer) is 7:
The radius (re) of the optical transmission body obtained as 4:1.1:0.6:0.4 is 0.60aia, and the refractive index distribution measured with an interfaco interference g microscope is 1.50 at the center.
7. The peripheral part is 1.494, and the refractive index distribution constant (6)
The value was 0.22 mm-', and the refractive index distribution approximately coincided with equation (1) in the range of 0.15ro to 0.85ro from the center to the outer surface.

Both end faces of this optical transmission body were polished, the lens length was set to 17.8-, and the MTF measured using a 41P/am grating was 72.
%Met. The conjugate length at that time was 32.6 mm.

A plurality of these optical transmitters were combined to create an optical transmitter array with a lens length of 17.8 mm in the same manner as in Example 1.
As a result of measuring the MTF using a lattice called IIn, it was 65% at a conjugate length of 32.6 mm. Using this optical transmitter array, an image scanner was assembled using an LED as a light source and a CCD as a light receiving element.

This image scanner had high resolution and was able to transmit clear images.

Comparative Example 1 Using the same four stock solutions as those used in Example 2, the discharge ratio (-layer): (second layer): (third layer) = (fourth layer>1
A fiber strand was prepared in the same manner as in Example 2 except that the ratio was 1:1:1, and the monomer was diffused and hardened to obtain an optical transmission body. The radius (ro) of the obtained optical transmission body is 0.
55, and the refractive index distribution measured using an interfaco interference microscope is 1, 506 at the center and 1.48 at the periphery.
6, and the refractive index distribution constant (g) value is 0.29m++-
' However, the refractive index distribution matched Equation (1) only within about 10% of the range in the radial direction. Both end faces of this optical transmission body were polished to a lens length of 13.5, and 4! The MTF measured using the P/Peng lattice has a conjugate length of 24.7-22
%Met. A plurality of these optical transmitters were combined to create an optical transmitter array with lens lengths of 13 and 5 mm in the same manner as in Example 1, and 4i! , P/mm grating, the MTF was measured to be 19% at a conjugate length of 24.7 mm. Using this optical transmitter array, an image scanner was assembled using an LED as a light source and a CCD as a light receiving element, but its resolution was very poor.

Example 4 Polymethyl methacrylate ((η) = 0.34°ME
(Measured at 25°C in K) 51 parts by weight, 20 parts by weight of Hensyl methacrylate, 29 parts by weight of methyl methacrylate
Parts, ■-Hydroxycyclohexylphenyl ketone 0.
The uncured material obtained by heating and kneading 2 parts by weight and 0.1 part by weight of hydroquinone at 60°C was used as the stock solution for forming the first layer, and the stock solution for forming the third layer used in Example 1 was used as the stock solution for forming the second layer. The stock solution for forming the fourth layer used in Example 2 was used as the stock solution for forming the third layer, and these three stock solutions were used in the same manner as in Example 1 to obtain a gradient index optical transmission body. The viscosity of the component of the first layer at this time was 4.5XIO'voices.

The ejection ratio during fiber strand formation was (first layer): (second layer) = (third layer) -7: 3: 1, and the (ro) of the obtained optical transmission body was 0.46 aun, and the interface The refractive index distribution measured with an Aco interference microscope is 1 at the center.
, 500, the peripheral part is 1.490, the refractive index distribution constant (local value is 0.2511DI-', and the refractive index distribution is in the range of 0.15ro to 0.8b0 from the center to the outer surface. Approximately, it almost agrees with equation (1), and both end faces of this optical transmission body are polished and the lens length is 15.6 cm, and 4
! ! Was it measured using a P/1m grid? The conjugation length of fTF was 29.0nio, which was 62%. A plurality of these optical transmission bodies were combined, and the lens length was 15.6 m in the same manner as in Example 1.
An optical transmitter array of m was created, and the MTF was measured using a 41P/mm grating.
It became 5%. Using this optical transmitter array, an image scanner was assembled using an LED as a light source and a CCD as a light receiving element. This image scanner was able to transmit clear images with high resolution.

Example 5 50 parts by weight of methyl methacrylate, 50 parts by weight of 2.2.3.3-tetrafluoropropyl methacrylate. Polymer consisting of t1 part [^] (n6=1.456, [η]=1
．． 00) 50 parts by weight, 50 parts by weight of methyl methacrylate, 0.0 parts by weight of 1-hydroxycyclohexylphenyl ketone.
An uncured product obtained by heating and kneading 2 parts by weight of hydroquinone and 0.1 part by weight at 6°C was used as a stock solution for forming the first layer. Further, 48 parts by weight of the above polymer [A], 22 parts by weight of 2,2,3.3 tetrafluoropropyl methacrylate, 30 parts by weight of methyl methacrylate, 0.2 parts by weight of -hydroxycyclohexylphenyl ketone, An uncured product obtained by heating and kneading 0.1 part by weight of hydroquinone at 60°C was used as the stock solution for forming the second layer, and 46 parts by weight of polymer (A), 2, 2, 3.3
- 44 parts by weight of tetrafluoropropyl methacrylate,
An uncured product obtained by heating and kneading 10 parts by weight of methyl methacrylate, 0.2 parts by weight of 1-hydroxycyclohexylphenyl ketone, and 0.1 parts by weight of hydroquinone at 60°C was used as a stock solution for forming the third layer. When extruding these three stock solutions, the viscosity of the components for forming the first layer was 4.0 x 104 poise,
The viscosity of the second layer forming component is 3.3×104 poise, and the viscosity of the third layer forming component is 3.3×104 poise. After composite spinning was carried out in the same manner as in Example 1 at 1×10' poise, a refractive index distribution type optical transmission body was obtained by curing treatment.

The discharge ratio of each layer during fiber strand formation is (layer -th)
:(second layer)=(third layer)=7:4:1.

The radius (ro) of the obtained optical transmission body is 0.50 cylinders,
The refractive index distribution measured by an interfaco interference microscope is 1.472 at the center and 1.459 at the periphery, and the refractive index distribution constant (barrel value is 0.27 am-'0.15 ro from the center to the outer surface). The refractive index distribution approximately matches the formula (1) in the range of ~0.78r0, and both end surfaces of this optical transmission body are polished to have a lens length of 14.0 mm.
The MTF measured using a 41P/mm grating has a conjugate length of 2
9. It was 64% in Oan. A plurality of these optical transmitters were combined to create an optical transmitter array with a lens length of 14.0 mm in the same manner as in Example 1, and the MTF was measured using a grating of 4 fP/mm. %. Using this optical transmitter array and using LED as a light source, CC
An image scanner was assembled using D as a light receiving element. This image scanner was able to transmit clear images with high resolution.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the measurement results of the refractive index distribution of an example of the refractive index distribution type optical transmission body of the present invention, and Fig. 2 is a diagram showing the refractive index distribution of the refractive index distribution type plastic optical transmission body made by the conventional method. Figure 3 is a diagram showing an example of a combined lattice image of these optical transmission bodies, Figure 4 is a diagram showing an outline of a resolution measuring device for optical transmission bodies, and Figure 5 is a diagram showing a CCO sensor. It is a graph obtained by measuring the light amount level. FIG. 6 is a schematic diagram of a manufacturing apparatus that can be preferably used for manufacturing the gradient index plastic optical transmission body of the present invention, and FIG. 7 is a schematic diagram of a lens performance measuring device. FIG. 8 is a measurement diagram of the refractive index distribution of an example of the refractive index distribution type plastic optical transmission body of the present invention.

Claims (1)

Scope of Claims: (1) A graded index plastic optical transmission body having a circular cross section with a radius r_0, and at least 0.25r_0 to 0.70r_ from the central axis of the optical transmission body toward the outer peripheral surface.
The refractive index distribution in the range of 0 is expressed by the formula (1) n(r)=n_0{
1-(g^2/2)r^2}...(1) (n_
0 is the refractive index at the central axis of the optical transmission body n(r) is the refractive index g at a position at a radius r from the central axis of the optical transmission body is the refractive index distribution constant r of the optical transmission body It has a refractive index distribution that approximates the refractive index distribution curve defined by (distance from the central axis of the body to the outer peripheral surface) A grating image having a characteristic value of g<0.3mm^-^1 and 4 line pairs/mm is formed on a CCD line sensor through the optical transmission body, and the maximum value of the measured light amount i_m_a_x is minimum value i
Modulation transfer MTF = [(i_m_a_x-i_m_i_n)/(i
_m_a_x+i_m_i_n)]×100...(2
) A graded refractive index plastic optical transmission material having a characteristic of having a function (MTF) of 40% or more. (2) The viscosity in the uncured state is 10^3 to 10^8 poise, and the refractive index n of the cured product obtained by curing the substance is n_1>
n_2>n_3...n_N (N≧2), an uncured state in which N uncured liquid substances are stacked concentrically in multiple layers in such a way that the refractive index decreases from the center to the outer circumferential surface. The uncured strand is shaped into a fiber strand, and the uncured strand is subjected to mutual diffusion treatment with adjacent interlayer materials so that the refractive index distribution between each layer of the strand fiber becomes a continuous refractive index distribution, or after mutual diffusion treatment. A refractive index gradient plastic optical transmission body made by hardening the fiber and having a circular cross section with a radius r_0, and at least 0.20r_0 to 0.75r from the central axis of the optical transmission body to the outer peripheral surface.
The refractive index distribution in the range of _0 is expressed by the formula (1) n(r)=n_0{1-(g^2/2)r^2}...
・In the formula (1), n_0 is the refractive index n of the central axis of the optical transmission body
(r) is the refractive index g at a position at a radius r from the central axis of the optical transmission body, and the refractive index distribution constant r of the optical transmission body is the refraction defined by the distance from the central axis of the optical transmission body to the outer peripheral surface. It has a refractive index distribution that approximates the index distribution curve, and has the following characteristic values: n_0=1.5±0.1 r_0=0.5±0.1 mm 0.15≦g<0.3 mm^-^1 , and a grating image of 4 line pairs/mm is formed on the CCD line sensor through the optical transmission body, and the maximum value i_m_a_x and minimum value i of the measured light amount are determined.
MTF measured by _m_i_n and calculated using the following formula (2)
A method for producing a graded refractive index plastic optical transmitter having a characteristic of 40% or more. (3) A graded index plastic optical transmission body having a circular cross section with a radius r_0, and at least 0.25r_0 to 0.70r_ from the central axis of the optical transmission body toward the outer peripheral surface.
The refractive index distribution in the range of 0 is expressed by the formula (1) n(r)=n_0{
1-(g^2/2)r^2}...(1) (n_
0 is the refractive index at the central axis of the optical transmission body n(r) is the refractive index g at a position at a radius r from the central axis of the optical transmission body is the refractive index distribution constant r of the optical transmission body It has a refractive index distribution that approximates the refractive index distribution curve defined by (distance from the central axis of the body to the outer peripheral surface) A grating image having a characteristic value of g<0.3mm^-^1 and 4 line pairs/mm is formed on a CCD line sensor through the optical transmission body, and the maximum value of the measured light amount i_m_a_x is minimum value i
MTF measured by _m_i_n and calculated using the following formula (2)
is 40% or more MTF = [(i_m_a_x-i_m_i_n)/(i
_m_a_x+i_m_i_n)]×100...(2
1.) An optical transmitter array characterized in that a plurality of refractive index distribution type plastic optical transmitters having the above characteristics are arranged and aggregated in one line or in a plurality of lines.