JP3850941B2 - Optical transmitter array - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plastic optical transmission body that can be used as various optical transmission lines, a manufacturing method thereof, and an optical transmission body array.
[0002]
[Prior art]
In general, the gradient index optical transmission body is mirror-polished to a parallel plane perpendicular to the central axis at both end faces, and is used alone as a microlens. Many of them are closely arranged and bonded and integrated to form a lens array, which is widely used as a line sensor component for copying machines, facsimiles, scanners, etc., and for a writing device of an LED printer. In a specific application, one or both end surfaces are used as spherical surfaces having a slight curvature.
[0003]
In a gradient index lens and lens array used for image transmission, unevenness in the amount of light on the image plane becomes a problem. As shown in FIG. 1, the lens element is E (X) = E ₀ (1− (X / X ₀ ) ² ) ^1/2 (1) on the imaging plane.
When the lens element has a light amount distribution as shown in FIG. On the other hand, the light amount distribution on the imaging surface of the lens array in which a large number of lens elements are arranged is the sum of the light amounts of the individual lens elements. For this reason, even in the lens array, periodic light amount unevenness occurs depending on the arrangement pitch of the lenses. The unevenness in the amount of light that occurs in this way causes a problem when an image is transmitted using a lens or a lens array. For example, when a lens array is used for a line sensor component such as a copying machine, a facsimile machine, a scanner, etc., uneven reading occurs, and there is a problem that an electric signal must be corrected to reduce the unevenness.
[0004]
Japanese Patent Laid-Open No. 4-251805 discloses an attempt to solve such a problem. This is to reduce the unevenness in the amount of light by allowing a light-absorbing substance to exist in the optical transmission body so that the concentration distribution changes continuously.
[0005]
[Problems to be solved by the invention]
However, this optical transmission member has a problem that the amount of light of the lens is reduced because the dye is put in the center of the lens.
[0006]
As described above, a lens and a lens array having a small light amount unevenness and a sufficient light amount value are not conventionally provided. Also, a method for easily manufacturing such a lens is not provided.
[0007]
[Means for Solving the Problems]
The gist of the present invention is a circular cross section having a radius r ₀ , and the refractive index is approximately in the range of ₀ to 0.85 r _{0 in the} radial direction from the central axis.
N (r) = N ₀ (1-Ar ² )
(Where N ₀ is the refractive index on the central axis, A is the refractive index distribution constant, N (r) is the refractive index at the position where the radial distance from the central axis is r)
In the optical transmission element array in which a plurality of refractive index distribution type optical transmission elements having a refractive index distribution represented by the following are arranged in parallel, the refractive index of the optical transmission element is 0 to 0 in the radial direction from the center. _{R ((1-30 / 315) r} 0 ≦ R ≦ (1-35 / 465) r 0) decreases from the center in a range of continuously radially outward, the distance in the range of R～r ₀ An optical transmitter array characterized by continuously rising from the center toward the outside in the radial direction.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an optical transmission body (hereinafter referred to as a lens as appropriate) and a manufacturing method thereof according to the present invention will be described in detail.
In a gradient index lens, a light beam incident from one end face travels in a sine curve in the lens body and exits from the other end face to form an image. In general, the refractive index distribution in the lens body is not always ideal. It is not consistent with the distribution. In particular, it is deviated from the ideal distribution in the vicinity of the outer periphery, and blurred light called flare light is generated around the lens due to the distortion of the refractive index distribution in the vicinity of the outer periphery and the external light entering the lens through the outer periphery of the lens. To do. In the optical transmission body of the present invention, since the refractive index is increased near the outer periphery of the optical transmission body, the amount of flare light is increased, and as a result, the light amount unevenness is reduced.
[0011]
FIG. 2 is an example of the refractive index distribution of the optical transmission body of the present invention. When the refractive index on the central axis 4 is N ₀ and the refractive index distribution constant is A, the lens material 1 has a refractive index N (r) of approximately ₀ to 0.85 r _{0 in} the radial direction from the central axis. It is a transparent cylinder having a refractive index distribution represented by the relationship of the following formula.
[0012]
N (r) = N ₀ (1-Ar ² ) (2)
The present invention is characterized in that the refractive index of the portion whose radius direction distance from the center of the lens material 1 is in the range of R to r ₀ continuously increases from the center toward the outside in the radial direction. For this reason, the amount of flare light generated in the vicinity thereof is large, and the light amount unevenness of the lens element is reduced. Further, when a lens array is formed by arranging a plurality of lens elements, since the flare light is reflected, scattered, and transmitted at the interface with the adjacent lens, the periodic light amount unevenness caused by the lens arrangement pitch is reduced.
[0013]
The refractive index of the outer peripheral portion is preferably greater than the refractive index at the position where the distance from the center is R by 0.003 or more, and more preferably greater than 0.005.
[0014]
The thickness of the portion where the refractive index is rising radially outward is preferably 5 to 50 μm. If the thickness is too thin, the effect of increasing flare light is small, and if the thickness is too thick, the lens performance is degraded.
[0015]
The optical transmission element array in the present invention can be manufactured by a conventionally known method using the optical transmission element. The shape and material of the array are not limited as long as the optical transmission bodies are arranged in parallel in one or more rows.
[0016]
The optical transmission body of the present invention can be manufactured as follows. Arrangement in which the refractive index n after curing is such that N uncured materials having a refractive index n of n ₁ > n ₂ >...> _{N N} (N ≧ 3) sequentially decrease from the center toward the outer peripheral surface. In addition, it is shaped into an uncured laminated body (hereinafter referred to as “filamentous body” where appropriate) that is formed by concentrically laminating multiple layers, and adjacent so that the refractive index distribution between each layer of the filamentous body becomes a continuous distribution. In the method of manufacturing the gradient index fiber by curing the laminate while performing the interdiffusion treatment of the inter-layer material and / or the volatilization treatment of the components of the outermost circumference layer, and performing these treatments, the outermost circumference It is manufactured by preparing an uncured material of the outermost peripheral layer so as to volatilize a relatively large amount of the low refractive index component from the layer and performing a volatilization treatment.
[0017]
In order to make the refractive index distribution of the obtained optical transmission body close to an ideal distribution, N is preferably in the range of 4-6.
[0018]
The thickness of each layer of the uncured laminate at the time of production of the optical transmission body in the present invention is set to a condition that allows the lens performance to be expressed.
[0019]
The uncured material used in the present invention preferably has a viscosity of 10 ³ to 10 ⁸ poise and is curable. If the viscosity is too small, thread breakage occurs during shaping, and it is difficult to form a filament. On the other hand, if the viscosity is too large, the operability is poor at the time of shaping, and the concentricity of each layer is impaired, or a filamentous body having a large thickness is liable to be formed.
[0020]
As a substance constituting the uncured material, a radical polymerizable vinyl monomer or a composition comprising the monomer and a polymer soluble in the monomer can be used.
Specific examples of the radical polymerizable vinyl monomer 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-octafluoropentyl (meth) acrylate, 2,2,3,4,4 , Fluorinated alkyl (meth) acrylates such as 2,4-hexafluorobutyl (meth) acrylate and 2,2,2-trifluoroethyl (meth) acrylate (n = 1.37 to 1.44), refractive index 1.43 ~ 1.62 (meth) acrylates such as ethyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, hydroxyalkyl (meth) acrylate, alkylene glycol (meth) acrylate, trimethylo Rupropanedi or tri (meth) acrylate, pentaerythritol di, tri or tetra (meth) acrylate, diglycerin tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, diethylene glycol bisallyl carbonate, fluorinated alkylene glycol (meth) acrylate Etc.
[0021]
In order to easily adjust the viscosity of the uncured material when forming the filament from these uncured materials, and to have a continuous refractive index distribution from the center to the outer periphery of the filament, The material is preferably composed of a vinyl monomer and a soluble polymer.
[0022]
The polymer that can be used here needs to have good compatibility with the polymer produced from the 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 / hexa Examples thereof include a fluoropropene copolymer (n = 1.40 to 1.46) and a polyfluorinated alkyl (meth) acrylate polymer.
[0023]
In order to adjust the viscosity, it is preferable to use a polymer having the same refractive index in each layer because a plastic optical transmission body having a continuous refractive index distribution from the center toward the outer periphery can be obtained. In particular, since polymethyl methacrylate is excellent in transparency and has a high refractive index, it is suitable as a polymer for use in preparing the gradient index optical transmission material of the present invention.
[0024]
The uncured material of the outermost peripheral layer is prepared so that the low refractive index component is easily volatilized in the volatilization treatment. For example, when the uncured material of the outermost peripheral layer is composed of a vinyl monomer and a soluble polymer, it is desirable to use a monomer having a relatively low refractive index. In this case, when two or more kinds of volatile components are used, it is preferable to use a low refractive index component in a larger amount than a high refractive index component, and it is preferable to use a high volatile component as the low refractive index component.
[0025]
A part of the component of the outermost peripheral layer is volatilized while performing the mutual diffusion treatment on the filament formed from the uncured material or after performing the mutual diffusion treatment. The volatilization process is performed so that the amount of the low refractive index component is relatively large and a sufficient amount is volatilized to increase the refractive index of the outer peripheral portion. The more the low refractive index component is volatilized, the higher the refractive index of the outer periphery of the obtained optical transmission body. In this case, the volatilization treatment is preferably performed so that the high refractive index component is not volatilized as much as possible, and more preferably not volatilized at all. The volatilization amount of the component to be volatilized may be controlled in any way, and can be controlled by, for example, the flow rate of the inert gas introduced into the volatilization processing unit.
[0026]
In order to cure the filaments subjected to the interdiffusion treatment and the volatilization treatment from the outer peripheral surface, it is preferable to add a thermosetting catalyst or a photocuring catalyst to the uncured product. Oxide-based or azo-based catalysts are used. Photocuring catalysts include benzophenone, benzoin alkyl ether, 4'-isopropyl-2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, benzyl methyl ketal, 2,2-diethoxyacetophenone, chlorothioxanthone, thioxanthone compounds, benzophenone Examples thereof include ethyl compounds, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, N-methyldiethanolamine, and triethylamine.
[0027]
Next, in order to cure the uncured product, ultraviolet rays are preferably applied from the surroundings in the cured part, and the filament containing the thermosetting catalyst and / or the photocuring catalyst is subjected to heat treatment or photocuring treatment.
[0028]
The optical transmission body of the present invention can be manufactured, for example, using the filamentous body forming apparatus shown in FIG. FIG. 3 is a process diagram schematically showing the filamentous body forming apparatus, in which only the portions of the interdiffusion processing unit 2 and the curing processing unit 3 are shown in a longitudinal sectional view. In the figure, symbol 9 is a concentric composite nozzle, 1 is an uncured extruded filament, 2 is a mutual diffusion processing unit for diffusing monomers of each layer of the filament to give a refractive index distribution, 3 is a curing processing unit for curing an uncured material, 4 is a take-up roller, 5 is a manufactured optical transmission body, 6 is a winding unit, 7 is an inert gas inlet, and 8 is an inert gas outlet. It is. In order to remove volatile substances released from the filament 1 in the interdiffusion treatment unit 2 and the curing treatment unit 3, an inert gas such as nitrogen gas is introduced from the inert gas inlet 7.
[0029]
Examples of the light source used for photopolymerization include a carbon arc lamp that generates light having a wavelength of 150 to 600 nm, a high-pressure mercury lamp, a medium-pressure mercury lamp, a low-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a chemical lamp, a xenon lamp, and a laser beam.
[0030]
【Example】
The present invention will be specifically described below with reference to examples.
In Examples and Comparative Examples, the refractive index distribution and the light amount distribution were measured by the following methods.
I. Measurement of refractive index distribution The refractive index distribution was measured by a known method using an Interfaco interference microscope manufactured by Carl Zeiss.
II. Measurement of unevenness of light amount of lens array The unevenness of light amount of the lens array was measured using a CCD with a white light source combined with a 570 nm interference filter. The uneven light intensity value is
ΔI = (Imax.−Imin.) / Imin. × 100 (%)
Calculated with
[0031]
Comparative Example 1
52 parts by weight of polymethyl methacrylate ([η] = 0.40, measured in MEK at 25 ° C., the same is used in the following examples and comparative examples) 52 parts by weight, 35 parts by weight of benzyl methacrylate, 13 parts by weight of methyl methacrylate Part, 1-hydroxycyclohexyl phenyl ketone 0.25 part by weight and hydroquinone 0.1 part by weight were kneaded at 70 ° C. to obtain a stock solution for forming the first layer. 48 parts by weight of polymethyl methacrylate, 10 parts by weight of benzyl methacrylate, 35 parts by weight of methyl methacrylate, 7 parts by weight of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 1-hydroxycyclohexyl phenyl ketone 0 25 parts by weight and 0.1 part by weight of hydroquinone were heated and kneaded at 70 ° C. to obtain a stock solution for forming the second layer. 47 parts by weight of polymethyl methacrylate, 30 parts by weight of methyl methacrylate, 23 parts by weight of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 part by weight of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by weight was heated and kneaded at 70 ° C. to obtain a third layer forming stock solution. 40 parts by weight of polymethyl methacrylate, 18 parts by weight of methyl methacrylate, 42 parts by weight of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 part by weight of 1-hydroxycyclohexyl phenyl ketone Hydroquinone 0 .1 part by weight was heated and kneaded at 70 ° C. to obtain a fourth layer forming stock solution. 37 parts by weight of polymethyl methacrylate, 4 parts by weight of methyl methacrylate, 59 parts by weight of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 part by weight of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by weight was heated and kneaded at 70 ° C. to obtain a fifth layer forming stock solution. These five types of undiluted solutions were sequentially arranged from the center using a concentric five-layer composite nozzle so that the refractive index of the uncured product was lowered and extruded simultaneously.
The temperature of the composite spinning nozzle was 48 ° C. The ejection ratio of each layer was 34.7 / 38.7 / 19.5 / 6.3 / 0.8 in order from the first layer in terms of radius ratio.
[0032]
Then, the strand fiber was passed through the center of the curing processing section arranged at equal intervals in a circular manner at a rate of 120 cm / min through 12 chemical lamps of 120 cm length and 40 W after passing through the 30 cm long interdiffusion processing section. It was taken up with a nip roller. The nitrogen flow rate in the interdiffusion treatment part was 50 L / min.
[0033]
The obtained optical transmission body had a radius r ₀ of 0.465 mm, and the refractive index distribution was 1.512 at the center and 1.469 at the outer periphery. There was no increase in refractive index at the outer periphery. Using two or more of these optical transmission bodies, two phenolic resins (thickness 1.2 mm) are used for the side plates, and an epiform (manufactured by Somar Co.) added with 2% by weight of carbon black is used between the side plates. The optical transmission bodies were arranged in a row and filled with an adhesive, the adhesive was cured, and then both end surfaces were cut and polished to produce a lens array with a lens length of 6.6 mm. When the light amount of the lens array was measured, periodic light amount unevenness corresponding to the lens arrangement pitch as seen in a normal lens array was noticeable, and the light amount unevenness was 19%.
[0034]
Example 1
The stock solution of the first layer to the fifth layer was the same as that of Comparative Example 1, except that the nitrogen flow rate in the interdiffusion treatment unit was 80 L / min, and the volatilization of the monomer of the filaments from the composite spinning nozzle was actively performed. Manufactured an optical transmission member in the same manner as in Comparative Example 1. The volatilized monomer was mainly 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate with low refractive index after curing.
[0035]
The radius of this optical transmission member was 0.465 mm, and the refractive index distribution was 1.512 at the center and 1.473 at the outer periphery. The refractive index continuously increased by about 0.004 from the center of the lens toward the outer periphery at a portion of about 35 μm from the outer periphery of the optical transmission body.
[0036]
As a result of manufacturing a lens array and measuring the amount of light in the same manner as in Comparative Example 1, although the periodic light amount unevenness corresponding to the lens arrangement pitch was seen, the value of the light amount unevenness was 10%, and the lens array of Comparative Example 1 It was small compared to the case.
[0037]
Example 2
The composite spinning nozzle temperature was 40 ° C., the discharge ratio of each layer was 34.3 / 38.5 / 20.1 / 6.1 / 1.0 in order from the first layer in the radius ratio, the spinning speed was 150 cm / min, An optical transmission body was obtained in the same manner as in Example 1 except that the nitrogen flow rate was set to 72 L / min. The radius of the obtained optical transmission body was 0.315 mm.
[0038]
The refractive index distribution of this optical transmission member was 1.512 at the center and 1.477 at the outer periphery. The refractive index increased by about 0.006 from the center of the lens toward the outer periphery at a portion approximately 30 μm from the outer periphery of the optical transmission body.
[0039]
As a result of manufacturing the lens array and measuring the amount of light in the same manner as in Comparative Example 1, although the periodic light amount unevenness corresponding to the lens arrangement pitch was seen, the value of the light amount unevenness was 12%. It was small compared to the case.
[0040]
【The invention's effect】
The light transmission body and the light transmission body array of the present invention have a small light amount unevenness and a sufficient light amount value. Moreover, according to the manufacturing method of the optical transmission body of this invention, such an optical transmission body can be manufactured easily.
[Brief description of the drawings]
FIG. 1 is a diagram showing a light amount distribution of a conventional optical transmission body.
FIG. 2 is a diagram showing a refractive index distribution of an optical transmission body of the present invention.
FIG. 3 is a schematic view of a manufacturing apparatus for manufacturing the optical transmission body of the present invention.
[Brief description of symbols]
DESCRIPTION OF SYMBOLS 1 Uncured thread body 2 Interdiffusion processing part 3 Curing process part 4 Take-off roller 5 Optical transmission body 6 Winding part 7 Inert gas introduction port 8 Inert gas discharge port 9 Concentric composite nozzle

Claims (1)

It has a circular cross-section with a radius r ₀ , and the refractive index in the range from ₀ to 0.85 r _{0 in the} radial direction from the central axis is approximately
N (r) = N ₀ (1-Ar ² )
(Where N ₀ is the refractive index on the central axis, A is the refractive index distribution constant, N (r) is the refractive index at the position where the radial distance from the central axis is r)
In the optical transmission element array in which a plurality of refractive index distribution type optical transmission elements having a refractive index distribution represented by the following are arranged in parallel, the refractive index of the optical transmission element is 0 to 0 in the radial direction from the center. _{R ((1-30 / 315) r} 0 ≦ R ≦ (1-35 / 465) r 0) decreases from the center in a range of continuously radially outward, the distance in the range of R～r ₀ An optical transmitter array characterized by continuously rising from the center toward the outside in the radial direction.

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