JP2002202417A - Refractive index distribution type plastic optical transmission body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bright optical transmission body which has high solution and productivity of which is remarkably improved. SOLUTION: In the plastic optical transmission body which is composed of a plurality of layers consisting of a mixture of the same polymers and the other polymers which are provided in a concentric circular shape, the same polymer content within respective layers of the plurality of layers is substantially same, moreover the same polymer contents of at least two layers composing the plurality of layers are different, and further the composition of the other polymer within respective layers of the plurality of layers changes from the center toward the outer periphery of the transmission body. Thus, the refractive index distribution type plastic optical transmission body having the ideal refractive index distribution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is useful as various light transmission paths such as a light focusing optical fiber, a light focusing rod lens, and an optical sensor, and is useful as an image transmission 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 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.

[0003]

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 that the productivity is low and the same. It is difficult to have the same performance with a shape (especially the same length), and the length of the graded-index optical transmission body having the same performance tends to be irregular, and there is a drawback that the handleability is insufficient. .

[0004] 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. Although plastic rod lenses can be produced by this method, a mixture of two or more polymers having different refractive indexes has a large fluctuation of refraction, and its transparency is reduced and light scattering is likely to occur. Therefore, there is a problem that the characteristics as a refractive index distribution type optical transmission body are not sufficient, and the use development thereof has not been advanced.

EP-A 0208159 discloses that at least one thermoplastic polymer (A) is compatible with the polymer (A) when polymerized, and the polymer (A)
By subjecting the monomer (B) to volatilization from the surface of a rod-shaped molded article obtained by molding a homogeneous mixture with the monomer (B) to be a polymer having a different refractive index from the molded article, After giving a continuous concentration distribution of the monomer (B) from the surface to the inside, a method of producing a graded index plastic light transmitting body by polymerizing the unpolymerized monomer in the molded article is shown. ing.

[0006] The refractive index distribution curve of the graded index type optical transmission body is ideally represented by the following equation, and is said to be the curve shown in FIG. N = N ₀ (1-ar ² )

However, according to the study of the present inventor, a refractive index distribution curve of the refractive index distribution type optical transmission body produced by the above method measured by an interfaco interference microscope under the conditions described later is shown by b in FIG. as, ranging from the center to a radius direction 0.5r ₀ ~0.75r ₀ (the range of the figure c to d, e denotes the outermost portion) of the ideal curve shown by relatively formula (1) Although it has a close refractive index distribution curve, the refractive index distributions inside and outside it have a large deviation from the ideal curve.

When observing a lattice pattern in an optical transmission body,
If a refractive index distribution almost exactly follows a quadratic curve, a normal lattice image can be transmitted as shown in FIG. 3A, but a refractive index distribution as shown in FIG. However, when a lattice image is observed with an optical transmission member separated from the ideal refractive index distribution, a large distorted lattice image is observed as shown in FIG. 3B or 3C, and accurate image transmission cannot be performed. Has become. In addition, a moderation transfer function (MTF) indicating the resolution was as low as about 30% or less, and could not be used as an optical transmitter for a copying machine.

Therefore, in a refractive index distribution type optical transmission body having a refractive index distribution as shown in FIG. 2B, which is formed by a conventional method, a portion in the outer peripheral direction is cut off more by cutting than in FIG. Alternatively, the portion is dissolved with a solvent, and the optical path of the optical transmission member has a relatively ideal refractive index distribution. There is a drawback that the properties are extremely low and it is extremely difficult to always produce a uniform product.

[0010]

Accordingly, the present inventors have developed a graded-index plastic optical transmission body which can be used in a copying machine using a white light source, and have higher resolution and brighter optical transmission than those conventionally developed. As a result of studying to obtain an optical transmission body which is a body and whose productivity is remarkably improved, the present invention has been completed.

The gist of the present invention is as follows. That is, the first invention is a plastic optical transmission body comprising a plurality of layers formed of a mixture of the same polymer and another polymer provided concentrically, wherein each of the plurality of layers has 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. The copolymer composition of the polymer changes from the center of the optical transmission body to the outer periphery, so that the optical transmission body has a circular cross section having a radius of r ₀ , and at least 0.25 r _0- The refractive index distribution in the range of 0.70r ₀ is given by the formula (1)

(Equation 3) A refractive index distribution approximately similar to the refractive index distribution curve defined by the formula (1), a grid image of 4 line pairs / mm is formed on the CCD line sensor through the optical transmission body, and the maximum value imax and the minimum value of the measured light amount are formed. A refractive index distribution type plastic optical transmitter characterized in that a value imin is measured and a modulation transfer function (MTF) calculated by the following equation (2) has a characteristic of 40% or more.

(Equation 4) According to a second aspect, in the first aspect, the gradient index plastic light has a characteristic value of 1.4 ≦ n ₀ ≦ 1.6 0.15 ≦ g <0.3 mm ^−1. Transmitter. A third invention is characterized in that the r ₀ is 0.6 mm or less,
And a refractive index distribution type plastic optical transmission body according to the invention. A fourth invention is an optical transmitter array, wherein a plurality of the refractive index distribution type plastic optical transmitters according to any one of the first to third inventions are arranged in one line or a plurality of lines and are assembled.

[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 substantially similar to the ideal refractive index distribution curve (a in FIG. 1) shown in the equation (1).

From the central axis of the optical transmission member, 0.25 r ₀ to
A range of 0.70r ₀ does not have a refractive index distribution approximate to the refractive index distribution curve of the equation (1) shown in FIG. 1A. It cannot be used for these applications because it cannot satisfy the required characteristics as an optical transmitter for a copying machine.

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

The g value is given by equation (3)

(Equation 5) Is a value that defines the lens length and its image forming distance. The optical transmission body of the present invention has a thickness of 0.15 ≦ g <0.3 mm.
^{Satisfies -1} . When the g value is 0.3 or more, the optical transmission body having chromatic aberration tends to be formed, and the optical transmission body using white light as a light source is not suitable. On the other hand, when the g value is less than 0.15, the imaging distance becomes long, and the handling property is insufficient.

In the case of using the graded-index plastic optical transmission member of the present invention as an optical transmission member of a copying machine or the like, a large number of single-line or multiple-row bales are used rather than a single line. Often used as an array, the image obtained with this array is a partially overlapping image of the image from each light transmitter. In order to improve the clarity of the overlapped image, the degree of overlap of these overlapped images greatly contributes. A factor governing the degree of overlap is the diameter of the optical transmitter, and the radius r ₀ is 0.4 m.
m or more, and preferably 0.6 mm or less. If the thickness is smaller, the brightness is insufficient and it is difficult to efficiently produce an optical transmission body having a uniform refractive index distribution. However, the degree of overlapping of the images obtained when an array is formed by arranging a large number of these images is not uniform, and there is a possibility that an array capable of performing clear image transmission may not be obtained.

The MTF indicating the resolution of the plastic graded index optical transmitter of the present invention is a grating having a spatial frequency of 4 (line pairs / mm), an array in which a plurality of graded index optical transmitters are arranged, and a light source. Are arranged as shown in FIG. 4 and a grid image is read by a CCD line sensor provided on the image forming surface (FIG. 5). The maximum value (imax) and the minimum value (imin) of the light amount level are measured and calculated by the following equation.

[0018]

(Equation 6)

Here, the spatial frequency is, as shown in FIG.
One combination of a white line and a black line is defined as one line pair, and the number of lines provided in a 1 mm width is expressed in units of line pairs / mm.

The MTF of the plastic graded-index optical transmission body of the present invention is at least 40%. 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 copied image cannot be formed. Preferably, the MTF is set to 45% or more.

The graded index optical transmission member made of plastic of the present invention is preferably produced as follows. The viscosity in the uncured state is 103 to 108 poise, and the refractive index n when cured.
Is a rod-like structure in which N uncured substances of n ₁ > n ₂ > n ₃ ... _{N N} (N ≧ 3) are prepared, and a plurality of layers are laminated concentrically from the center so that the refractive index of each of the layers becomes lower in order. It is preferable to form a body or a fibrous shaped article and perform a curing treatment while performing a diffusion treatment so that the refractive index distribution between the respective layers becomes a continuous refractive index distribution, or a curing treatment after the diffusion treatment.

N ≧ 3 when g value is 0.3> g ≧ 0.15
Then, n between the central layer and the outermost layer of the gradient index optical transmission body
The difference of ₁ -n _N can be any suitable range, the refractive index distribution in the range from the center of 0.25r ₀ ~0.70r ₀ that shall approximate the curve of the equation (1) Easier,
The optical transmission object of the present invention can be obtained. Therefore, N is preferably in the range of 3 to 5.

The uncured material 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, formation of filamentous materials is as yarn breakage occurs is difficult upon shaping. 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, and a shaped article having a large unevenness in thickness is apt to be produced.

As the curable substance that can be used in carrying out the present invention, a radical polymerizable vinyl monomer or a composition comprising the monomer and a polymer soluble in the monomer can be used. .

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, 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, diethylene glycol bisallyl carbonate, fluorine Alkylene glycol poly (meth) acrylate and the like.

In order to adjust the viscosity of the uncured material used for shaping these materials into a thread and to provide a refractive index distribution from the center to the outside in the obtained filament, the uncured material is a vinyl monomer. And a soluble polymer. The polymer which can be used here preferably has good compatibility with the polymer formed from the above-mentioned radical 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 to 1.57), polyvinylidene fluoride (n = 1.42), vinylidene fluoride / tetrafluoroethylene copolymer (n = 1.42 to 1.46), vinylidene fluoride / tetrafluoroethylene / hexafluoro Propene copolymer (n = 1.40-1.46), polyfluorinated alkyl (meth) acrylate polymer and the like.

When the same 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 toward the surface is obtained, which is preferable. . In particular, polymethyl methacrylate has excellent transparency and a high refractive index of itself, so that it is suitable as a polymer to be used for producing the gradient index optical transmitter 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. 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, benzylmethyl 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 light from the periphery in the curing section.

The optical transmission body of the present invention can be manufactured by using, for example, the yarn forming apparatus shown in FIG. FIG. 6 is a process diagram schematically showing the thread forming apparatus, in which only the mutual diffusion portion and the hardening portion are formed in a longitudinal sectional view, in which 61 is a concentric composite nozzle, and 62 is extruded. Uncured thread-like material, 63 is a mutual diffusion part for diffusing monomers of each layer of the thread-like material to give a refractive index distribution, 64 is a curing treatment part 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 inert gas outlet. Volatile substances released from the filamentous material 62 are interdiffused by the interdiffusion unit 63 and cured by the curing unit 64.
An inert gas, for example, a nitrogen gas, is introduced from the inert gas inlet 68 in order to remove the gas.

The coating layer having a low refractive index can be further provided on the refractive index distribution optical transmission body obtained by the above method. To form the coating layer, trifluoroalkyl acrylate, pentafluoroalkyl acrylate, hexafluoroalkyl acrylate, fluoroalkylene diacrylate, 1,1,2,2-tetrahydroheptadecafluorodecyl acrylate, hexanediol diacrylate, Pentyl glycol diacrylate, dipentaerythritol hexaacrylate and the like are appropriately mixed, and if necessary, the fluorinated acrylate or methacrylate polymer is added in order to adjust coatability and refractive index. Is preferably used.

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.

[0033]

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 from the center of 0.25r ₀ ~0.70r ₀ Since the distribution is very similar to the distribution curve of the equation (1), the lens has extremely good lens characteristics without cutting the outer peripheral portion.

Hereinafter, the present invention will be described in more detail with reference to 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) Measurement of lens performance was performed using an evaluation apparatus shown in FIG. (Preparation of sample) The optical transmission medium obtained in the example was set to have a length (λ / 4) of approximately の of the period (λ) of the light beam determined from the undulation of the passing He-Ne laser beam. The sample was cut and polished using a polishing machine such that both end surfaces of the sample became parallel planes perpendicular to the long axis, thereby obtaining an evaluation sample. (Measurement method) A trial evaluation sample 78 was set on a sample stage 76 placed on an optical bench 71 in FIG.
By adjusting the aperture 74, the light from the light source 72 is
3. After passing through the stop 74 and the 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 Corporation) film, and a square grid is formed. Images were taken and the lattice distortion was observed. As the glass plate 75, a chrome coating film of chromium-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 It was measured by a known method using an Interfaco interference microscope manufactured by Carl Zeiss.

Example 1 Polymethyl methacrylate ([η] = 0.34, MEK)
Medium, measured at 25 ° C) 52 parts by weight, benzyl methacrylate 35 parts by weight, methyl methacrylate 13 parts by weight, 1
An uncured material obtained by heating and kneading 0.2 part by weight of hydroxycyclohexyl phenyl ketone and 0.1 part by weight of hydroquinone at 60 ° C. was used as a stock solution for forming a first layer, and polymethyl methacrylate ([η] = 0.34, MEK) Medium, measured at 25 ° C.) 50 parts by weight, 15 parts by weight of benzyl methacrylate, 35 parts by weight of methyl methacrylate, 0.2 parts by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.1 part by weight of hydroquinone were heated and kneaded at 60 ° C. The uncured material is used as a stock solution for forming a second layer, and polymethyl methacrylate ([η] = 0.34, measured in MEK at 25 ° C.) 50
An uncured material obtained by heating and kneading 50 parts by weight of methyl methacrylate, 0.2 part by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.1 part by weight of hydroquinone was used as a stock solution for forming a third layer. Using a composite nozzle, they were extruded simultaneously as concentric fiber strands. At this time, the viscosity of the components of the first layer during extrusion is 4.
7 × 10 4 poise, viscosity of the second layer component is 3.7 × 10
The viscosity of the components of the 4th poise and the third layer was 2.9 × 10 4 poises. The temperature of the composite nozzle was 60 ° C.

The fiber strand 62 discharged from the spinning nozzle is then subjected to a 45 cm long interdiffusion section [6 in FIG.
3] to cause mutual diffusion of the monomers between the layers of the strand fiber. Then, 12 fluorescent lamps (length: 120 cm, 40 W) are placed at the center of the light irradiating sections arranged at equal intervals in a circle. Strand speed 40cm
The monomer in the fiber strand was polymerized by passing at a rate of / min to obtain a graded-index plastic optical transmitter, which was taken up by a nip roller.

The discharge ratio of each layer when forming the fiber strand is (first layer) :( second layer) :( third layer) = 7:
The radius (r) of the graded index optical transmitter obtained as 4: 1
₀ ) 0.59 mm, the refractive index distribution measured by an interfaco interference microscope was 1.508 at the center and 1.498 at the periphery, and the refractive index distribution constant (g) was 0.48.
At 20 mm ^-1 , the refractive index distribution in the range of 0.15r _{0 to} 0.75r ₀ from the center to the outer surface of the optical transmission body approximately matches Equation (1) as shown in FIG. The MTF measured by using a grating having a lens length of 18.4 mm and a lens length of 4 lP / mm was 60%, and the image formed on the grating obtained with a conjugate length of 42.4 mm was sharp with little distortion. It was a statue.

Further, an optical transmitter array having a lens length of 18.4 mm and having a structure as shown at 41 in FIG.
The TF was measured to be 52%. The conjugate length of the rod-shaped lens constituting this optical transmitter array was 42.4 mm. Using this optical transmitter array as an LED as a light source, C
When an image scanner using a CD as a light receiving element was assembled, the resolution was high and a clear image could be transmitted.

Example 2 The three kinds of stock solutions used in Example 1 were further used as polymethyl methacrylate ([η] = 0.34,
47 parts by weight, measured at 25 ° C. in MEK) 40 parts by weight of methyl methacrylate 2,2,3,3,4,4,5,5-
13 parts by weight of octafluoropentyl methacrylate, 1
Using an uncured material obtained by heating and kneading 0.2 parts by weight of hydroxycyclohexyl phenyl ketone and 0.1 parts by weight of hydroquinone at 60 ° C., and using a concentric four-layer composite spinning nozzle, the above four kinds of stock solutions are concentrically formed. At the same time. The viscosities of the first to third layers during 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,
At this time, the temperature of the composite nozzle was 60 ° C. Next, the same operation as in Example 1 was performed to obtain a graded-index-type plastic optical transmission body.

At the time of forming the fiber strand (first layer):
The discharge ratio of (second layer) :( third layer) :( fourth layer) is 7:
The optical transmitter obtained as 4: 1: 0.5 has a radius (r ₀ )
Is 0.60 mm, and the refractive index distribution measured by an interfaco 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 , 0.15 r _{0 to} 0.
Refractive index distribution in the range of 80 r ₀ are substantially coincides with approximately the formula (1), MTF measured using a grid of 4LP / mm and the lens length 18.4mm polished end faces of the optical transmission body Was 65%. The conjugate length at that time is 42.4m
m. An optical transmitter array having a lens length of 18.4 mm was prepared in the same manner as in Example 1 by combining a plurality of the optical transmitters, and the MTF was measured using a 4 lp / mm grating. As a result, the conjugate length was 58%. Was 42.4 mm. Using this light transmitter array, an image scanner using an LED 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.

Example 3 The four kinds of stock solutions used in Example 2 were used as stock solutions for forming the first to fourth layers, and polymethyl methacrylate ([η]) was used.
= 0.34, measured in MEK at 25 ° C) 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 parts by weight of 1-hydroxycyclohexylphenyl ketone, and 0.1 parts 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 layer to 4th layer during extrusion
The viscosity of the stock solution up to the layer was almost the same as in Example 2,
The viscosity of the layer forming component was 2.2.times.10@4 poise.
At this time, the temperature of the composite spinning nozzle was 60 ° C.

Next, the same operation as in the first embodiment is performed, and light transmission is performed.
You got the sender. At the time of fiber strand formation (first layer):
(Second layer): (third layer): (fourth layer): (fifth layer)
The output ratio was obtained as 7: 4: 1.1: 0.6: 0.4.
The optical transmitter has a radius (r₀ ) 0.60mm, Interfaco
The distribution of the refractive index measured by an interference microscope was 1.
507, the peripheral portion is 1.494, and the refractive index distribution constant is
(G) The value is 0.22 mm ^-1From the center to the outside
0.15r towards₀ ~ 0.85r₀ Refractive index distribution in the range
Was approximately equal to the equation (1). This optical transmitter
Are polished at both ends to make the lens length 17.8 mm and 4 lP
MTF was 72% measured using a / mm grid.
Was. The conjugate length at that time was 32.6 mm. This light transmission
A plurality of feeders are combined, and a lens length of 1 is set in the same manner as in Example 1.
Create a 7.8mm optical transmitter array and obtain 4lP / mm
As a result of measuring the MTF using the grating, the conjugate length was 32.6 m.
m was 65%. LE using this optical transmitter array
Image scan using D as light source and CCD as light receiving element
Assembled na. This image scanner has high resolution
And clear images could be transmitted.

Example 4 Polymethyl methacrylate ([η] = 0.34, MEK
Medium, measured at 25 ° C.) 51 parts by weight, benzyl methacrylate 20 parts by weight, methyl methacrylate 29 parts by weight, 1 part by weight
An uncured substance obtained by heating and kneading 0.2 part by weight of hydroxycyclohexylphenyl ketone 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. The stock solution for forming the fourth layer used in Example 2 was used as the stock solution for forming the second layer, and the stock solution for forming the third layer was used as the stock solution for forming the third layer. Type optical transmission body was obtained. At this time, the viscosity of the component of the first layer was 4.5.times.10@4 poise.

The discharge ratio at the time of forming the fiber strand is (first layer) :( second layer) :( third layer) = 7: 3: 1,
(R ₀ ) of the obtained optical transmission body was 0.46 mm, the refractive index distribution measured by an interfaco interference microscope was 1.500 at the center, 1.490 at the periphery, and the refractive index distribution constant (g) ) Value is 0.25 mm ⁻¹ , and from the center to the outer surface, the refractive index distribution approximately matches the equation (1) in the range of 0.15 r _{0 to} 0.81 r _0. Both ends of the optical transmission body are polished to a lens length of 15.6 mm.
The MTF measured using a 1 P / mm grating has a conjugate length of 2
It was 62% at 9.0 mm. A plurality of these optical transmitters were combined, an optical transmitter array having a lens length of 15.6 mm was prepared in the same manner as in Example 1, and the MTF was measured using a grid of 4 lP / mm. As a result, 55 was obtained at a conjugate length of 29.0 mm. %. LED is used as a light source using this optical transmitter array,
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] comprising 50 parts by weight of methyl methacrylate and 50 parts by weight of 2,2,3,3-tetrafluoropropyl methacrylate (n ₀ = 1.456, [η] = 1.0
0) 50 parts by weight, 50 parts by weight of methyl methacrylate, 1
An uncured product obtained by kneading 0.2 part by weight of hydroxycyclohexyl phenyl ketone and 0.1 part by weight of hydroquinone at 60 ° C. was used as a first layer forming stock solution. 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 Part 6
An uncured material heated and kneaded at 0 ° C. is used as a stock solution for forming a second layer,
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, 0.1 part by weight of hydroquinone Was heated and kneaded at 60 ° C. to obtain an uncured product as a third layer forming stock solution. When the three kinds of stock solutions are extruded, the viscosity of the first layer forming component is 4.0 × 10 4 poise, the viscosity of the second layer forming component is 3.3 × 10 4 poise, and the viscosity of the third layer forming component is 3.1 × 10 4 poises, composite spinning was performed in the same manner as in Example 1, and curing treatment was performed to obtain a refractive index distribution type optical transmission body.

The discharge ratio of each layer when forming the fiber strand was (first layer) :( second layer) :( third layer) = 7: 4: 1. The radius (r ₀ ) of the obtained optical transmission body is 0.50 mm
The refractive index distribution measured by an interfaco interference microscope is 1.472 at the center and 1.459 at the periphery, the refractive index distribution constant (g) value is 0.27 mm ⁻¹ , and the outer surface from the center. In the range of 0.15 r ₀ to 0.78 r ₀ , the refractive index distribution approximately matches the equation (1), and both end faces of the optical transmission body are polished to obtain a lens length of 14.0.
mm and MTF measured using a 4 lP / mm grid
Was 64% at a conjugate length of 29.0 mm. 13. A plurality of the optical transmission bodies are combined, and the lens length is set in the same manner as in the first embodiment.
A 0 mm optical transmitter array was prepared, and the MTF was measured using a 4 lp / mm grating. As a result, the conjugate length was 29.0 mm.
It was 57%. LED using this optical transmitter array
Was used as a light source, and 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.

[Brief description of the 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 refractive index distribution type plastic optical transmission body made 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 illustrating a resolution measuring device for an optical transmission body.

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

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

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

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

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuji Murata 20-1, Miyukicho, Otake City, Hiroshima Prefecture Inside Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Inventor Yoshihiro Uozu 20-1, Miyukicho, Otake City, Hiroshima Prefecture (72) Inventor Masaaki Oda 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. (72) Inventor Keita Ishimaru 20 Miyukicho, Otake City, Hiroshima Prefecture No. 1 Mitsubishi Rayon Co., Ltd. Central Research Laboratory F-term (reference) 2H050 AA15 AB43 AC26 AC28

Claims (4)

[Claims] 1. A plastic optical transmission body comprising a plurality of layers made of a mixture of the same polymer and another polymer, the plastic optical transmission bodies being provided concentrically, the plastic optical transmission body being included in each of the plurality of layers. And the content of the polymer is substantially the same, and at least 2
The content of the same polymer in the layers is different, and the copolymer composition of the other polymer in each layer of the plurality of layers changes from the center to the outer periphery of the optical transmission body, so that the radius is increased. It has a circular cross section of r _{0, and} the refractive index distribution in the range of at least 0.25r _{0 to} 0.70r ₀ from the central axis to the outer peripheral surface is represented by the following equation (1). Is provided with a refractive index distribution approximately similar to the refractive index distribution curve defined by, and a grid image of 4 line pairs / mm is passed through the optical transmission body through C.
An image is formed on a CD line sensor, the maximum value imax and the minimum value imin of the measured light amount are measured, and a characteristic that the modulation transfer function (MTF) calculated by the following equation (2) is 40% or more is provided. A graded-index plastic optical transmitter. (Equation 2) 2. The graded-index plastic optical transmission body according to claim 1, having a characteristic value of 1.4 ≦ n ₀ ≦ 1.6 0.15 ≦ g <0.3 mm ^−1. . 3. The refractive index distribution type plastic optical transmission body according to claim 1, wherein r ₀ is 0.6 mm or less. 4. An optical transmitter array, wherein a plurality of the gradient index plastic optical transmitters according to any one of claims 1 to 3 are arranged in a line or a plurality of lines and are assembled.