JP2010060611A - Plastic rod lens and plastic rod lens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens array which has heat resistance and excellent resolution, and to provide a rod lens used for the lens array. <P>SOLUTION: The plastic rod lens is produced by polymerizing a mixture of at least one transparent resin polymer (A) selected from polymethylmethacrylate (PMMA), polystyrene (PSt) and a methylmethacrylate-styrene resin (MS resin), and a monomer (B) essentially comprising isobornylmethacrylate, in which the proportion of isobornylmethacrylate in the whole polymer within a range from 0 to 0.8r of the rod lens, from the center to the periphery, is set 10 to 60 parts by mass. The obtained rod lens shows a change rate in a conjugate length of within 6% under the conditions of at 80°C for 1,000 hours. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plastic rod lens array used as an optical transmission body of a scanner, an image sensor, a printer or the like, and a plastic rod lens used therefor.

  A plastic rod lens (hereinafter simply referred to as “rod lens”) is composed mainly of polymethyl methacrylate and a monomer having a radical polymerizable group, and the refractive index continuously decreases from the center toward the outer periphery. It is a cylindrical lens having a refractive index distribution. The rod lenses are arranged in one row or two or more rows and bonded and fixed between two substrates so that the central axes of the rod lenses are substantially parallel to each other. It is simply used as a “lens array”) for various scanners such as hand scanners, parts for image sensors in copying machines and facsimiles, writing devices such as LED printers, and the like.

In order to facilitate handling of the rod lens at the time of manufacturing the lens array, it is required to increase the mechanical strength of the rod lens. In order to improve this, Patent Document 1 discloses a method for manufacturing a plastic rod lens in which heat treatment is performed at a temperature higher than the heat shrinkage starting temperature when the temperature is increased at a rate of temperature increase of 4 ° C./min. Has been.

However, the thermal contraction is large only by controlling the heat treatment conditions of the plastic rod lens, and when used in a high temperature environment, the rod lens contracts due to heat and the conjugate length changes, so the resolution (MTF: moderation transfer, Function) decreases.
JP2007-34259

In particular, when such a rod lens is used as a lens array in an image sensor or LED printer having a high resolution of 600 dpi or more, this problem becomes serious.

An object of the present invention is to provide a heat-resistant lens array having a conjugate length change rate within 6% at 80 ° C. under 1000 hours and a rod lens used therefor.

The inventors of the present invention polymerize a transparent resin polymer (A) and a mixture composed of a monomer (B) containing an isobornyl methacrylate unit as a constituent unit to constitute a rod lens. The present invention has been found.

That is, the rod lens array of the present invention is obtained by polymerizing a transparent resin polymer (A) and a polymer (B) containing an isobornyl methacrylate unit as a structural unit, and when the condition is at 80 ° C. for 1000 hours. Even so, the resolution of the rod lens can be kept high because the contraction of the rod lens and the change in conjugate length due to heat are small.

Furthermore, the present invention can provide a lens array excellent in heat resistance characteristics with little deterioration in optical characteristics such as resolution even when used in a high temperature environment in an image sensor or LED printer having a high resolution of 600 dpi or more. .

The rod lens array of the present invention is excellent in heat resistance because the deterioration and dispersion of optical characteristics are suppressed even under the condition of 1000 hours at 80 ° C.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The plastic rod lens of the present invention is a cylindrical lens having a refractive index distribution in which the refractive index continuously decreases from the center toward the outer periphery. As the refractive index distribution, when the radius of the rod lens is r in a cross section perpendicular to the central axis of the rod lens, the refractive index distribution in the range of 0.3r to 0.7r at least from the central axis toward the outer periphery is as follows. It is preferable to approximate a quadratic curve distribution defined by the following formula (1).
^{n (L) = n0 {1-} (g 2/2) L 2} (1)
(Where n0 is the refractive index (central refractive index) at the central axis of the rod lens, L is the distance from the central axis of the rod lens (0 ≦ L ≦ r), and g is the refractive index distribution of the rod lens. (It is a constant, and n (L) is a refractive index at a position of a distance L from the central axis of the rod lens.)

The radius r of the rod lens is not particularly limited, but the radius r is preferably small from the viewpoint of compacting the optical system, and the radius r is preferably large from the viewpoint of handling at the time of processing the rod lens. For this reason, the radius r of the rod lens is preferably in the range of 0.05 to 1 mm, more preferably in the range of 0.1 to 0.5 mm.

In addition, the refractive index n0 of the central axis of the rod lens is 1.4 to 1.6, so that material options for the rod lens are widened, and a favorable refractive index distribution is easily formed. It is preferable from the viewpoint.
Further, the refractive index distribution constant g of the rod lens is not particularly limited. However, from the viewpoint of compacting the optical system, securing the working distance of the optical system, and handling properties, the range is from 0.2 to 3 mm-1. More preferably, it is the range of 0.5-2 mm <-1>.

Moreover, it is preferable that the rod lens is provided with a light absorption layer containing a light absorber that absorbs at least a part of light transmitted through the rod lens on an outer peripheral portion of 0.6r or more from the central axis. In general, with a rod lens, an irregular portion in which the refractive index distribution deviates from the ideal distribution tends to be formed as the distance from the central axis increases, and the optical characteristics due to this are absorbed by the outer periphery of the rod lens. This is because it is suppressed by providing a layer. The thickness of the light absorption layer is preferably 50 μm or more and 100 μm or less. By setting the thickness of the light absorption layer within this range, flare light and crosstalk light can be sufficiently removed and a sufficient amount of transmitted light can be secured.

As a light absorber to be used, in an image sensor, an LED printer, or the like, a light source that emits light having a wavelength of 400 to 900 nm is generally used as a light source. It is preferable to use one that absorbs light. As such a light absorber, for example, Kayasorb CY-10 manufactured by Nippon Kayaku which absorbs in the 600 nm to near infrared region, Diaresin Blue 4G manufactured by Mitsubishi Chemical which absorbs at 600 to 700 nm, and the like are absorbed at 550 to 650 nm. Examples include Kayset Blue ACR made by Nippon Kayaku, etc., Mitsui Toatsu dye MS Magenta HM-1450, which absorbs at 500 to 600 nm, Mitsui Toatsu dye MS Yellow HD-180, which absorbs at 400 to 500 nm, etc. Can do. Moreover, a black dye etc. can be mentioned as a light absorber which absorbs the light of all the wavelength ranges among 400-900 nm. These light absorbers may be used alone or in combination of two or more.

Next, a method for manufacturing the above rod lens will be described.
There is no limitation on the method of forming the refractive index distribution of the rod lens, and any method such as an addition reaction method, a copolymerization method, a gel polymerization method, a monomer volatilization method, and an interdiffusion method may be used. In this respect, the interdiffusion method is preferable. The mutual diffusion method will be described.
First, N uncured materials having a refractive index n after curing satisfying n1>n2>...> NN (N ≧ 3) gradually decrease in refractive index from the center toward the outer periphery. The material between adjacent layers is shaped into an uncured laminate (hereinafter referred to as “thread-like body”) that is concentrically stacked and arranged so that the refractive index distribution between each layer of the filamentous body is continuous. While performing the mutual diffusion treatment or after performing the mutual diffusion treatment, the filamentous body is cured to obtain a rod lens raw yarn (spinning step). The interdiffusion treatment refers to giving the filament a thermal history of several seconds to several minutes at 10 to 60 ° C., more preferably 20 to 50 ° C., under a nitrogen atmosphere.

As a substance constituting the uncured product, a transparent resin polymer (A) and a monomer (B) mainly composed of isobornyl methacrylate are used.

Examples of the transparent resin polymer (A) constituting the plastic rod lens of the present invention include polydiethylene glycol bisallyl carbonate (PADC), polymethyl methacrylate (PMMA), polystyrene (PSt), and a heavy polymer comprising methyl methacrylate units and styrene units. Examples include coalescence (MS resin), polycarbonate resin, cycloolefin resin, fluorene resin, and the like. Among these, PMMA, PSt, and MS resin are preferable from the viewpoint of solubility in the monomer (B) having an isobornyl methacrylate unit as a main component.

Moreover, it is preferable that the ratio contained in the rod lens of a transparent resin polymer (A) is 30-70 mass parts from a viewpoint of the viscosity for obtaining a rod lens raw yarn.

Other monomers used in combination with isobornyl methacrylate as monomer (B) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) Acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, tricyclo [ ^5.2.1.0.2,6 ] decanyl (meth) acrylate, adamantyl (meth) acrylate, phenyl (meth) acrylate, benzyl (Meth) acrylate, 2,2,3,3,4,4,5,5-octafluoropentyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate and the like.

The proportion of isobornyl methacrylate in the polymer is preferably 10 to 60 parts by mass, more preferably 15 in the resin material constituting the range of 0 to 0.8r of the rod lens from the viewpoint of heat resistance and spinnability. -30 mass parts. When the proportion of isobornyl methacrylate is less than 10 parts by mass, the heat resistance becomes insufficient in a high temperature environment, and when it exceeds 60 parts by mass, the viscosity is increased and the spinnability is lowered. Moreover, it is preferable that it is 0-10 mass parts in the resin material which comprises the range of 0.8r-r which goes to an outer peripheral part from a center, More preferably, it is 0-5 mass parts. If the proportion of isobornyl methacrylate exceeds 10 parts by mass, the refractive index will not be sufficiently reduced from the center to the outer peripheral part, making it difficult to form a refractive index distribution.

In order to cure the filament formed from the uncured product, a thermosetting catalyst or a photocuring catalyst is added to the uncured product, and a thermosetting process and / or a photocuring process is performed. As the thermosetting catalyst, a peroxide-based or azo-based catalyst or the like is 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 compounds, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, N-methyldiethanolamine, triethylamine and the like.

The lens array of the present invention is configured by arranging a plurality of rod lenses in one or more rows between two substrates so that the optical axis directions of the rod lenses are parallel to each other. An adhesive is used for fixing the rod lens and the substrate. Adjacent rod lenses may be in close contact with each other, or may be arranged with a certain gap. Further, in the case of a lens array in which the same kind of rod lenses are stacked and arranged in two or more stages, it is preferable that they are arranged in a stacked manner so that the gap between the rod lenses is minimized.

The substrate constituting the lens array of the present invention may have a flat plate shape, or may have a U-shaped or V-shaped groove for arranging and storing rod lenses at a constant interval. Although the material of a board | substrate is not specifically limited, It is preferable that it is a material easy to process in the process of producing a lens array. As the material for the substrate, various thermoplastic resins, various thermosetting resins, and the like are preferable, and acrylic resins, ABS resins, polyimide resins, liquid crystal polymers, epoxy resins, and the like are particularly preferable. Further, fibers or paper may be used as the base material and reinforcing material of the substrate, and a release agent, a dye, a pigment, and the like may be added to the substrate.

The adhesive is not particularly limited as long as it has an adhesive strength enough to attach the lens array and the substrate or between the lens arrays. A melt-type pressure-sensitive adhesive or the like can be used. In addition, as a method of applying the adhesive to the substrate or the lens array, a known coating method such as a screen printing method or a spray coating method can be used depending on the type of the adhesive.

Hereinafter, the present invention will be described specifically by way of examples.
<Refractive index distribution>
The measurement was performed using an Interfaco interference microscope manufactured by Carl Zeiss.
<Heat shrinkage start temperature>
A TMA / SS6100 manufactured by Seiko Instruments Inc. was used. The sample length was 5 mm, and the heat shrinkage start temperature was measured when the temperature was increased at a temperature increase rate of 4 ° C./min under no load condition.
<Conjugate length and resolution (average MTF, MTF standard deviation)>
Using a grating pattern having a spatial frequency of 12 (line pair / mm, Lp / mm), light from a light source is incident on a rod lens array whose both end surfaces perpendicular to the optical axis are polished through the grating pattern and placed on the imaging surface. The lattice image was read by the CCD line sensor, the maximum value (imax) and the minimum value (imin) of the measured light quantity were measured, and MTF (Moderation Transfer Function) was obtained by the following equation.
MTF (%) = {(imax−imin) / (imax + imin)} × 100
At that time, the distance between the grating pattern and the entrance end of the rod lens array and the distance between the exit end of the rod lens array and the CCD line sensor were made equal. Then, the MTF was measured by moving the grating pattern and the CCD line sensor symmetrically with respect to the rod lens array, and the distance between the grating pattern and the CCD line sensor when the MTF was the best was defined as the conjugate length.
The distance between the lattice pattern and the CCD line sensor was fixed at a conjugate length, and the entire width of the rod lens array was scanned to measure 50 MTFs, and the average value and standard deviation were obtained to obtain resolution and its variation index.
Here, the spatial frequency indicates a combination of white lines and black lines as one line, and indicates how many combinations of these lines are provided within a width of 1 mm.
<Heat resistance test>
The rod lens array was placed in a dryer set at 80 ° C. (relative humidity 30% or less) and heat treatment was performed for 1000 hours. Thereafter, the conjugate length, MTF average value, and standard deviation of the rod lens array before heat treatment and the rod lens array after heat treatment were determined. The case where the conjugate length [mm] of the rod lens array after the heat treatment was 9.6 mm or more was evaluated as ◎, the case of 9.4 to 9.5 mm was evaluated as ○, and the case of 9.3 mm or less was evaluated as ×. Further, the case where the average MTF [%] of the rod lens array after the heat treatment was 60% or more was evaluated as ◎, the case of 50 to 60% was evaluated as ○, and the case of 50% or less was evaluated as ×. Further, the case where the MTF standard deviation [%] of the rod lens array after heat treatment was 4% or less was evaluated as ◎, the case where it was 5 to 6% was evaluated as ○, and the case where it was 7% or more was evaluated as ×.

<Example 1>
45 parts by mass of PMMA, 25 parts by mass of methyl methacrylate (MMA), 30 parts by mass of isobornyl methacrylate (IBXMA), 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of hydroquinone (HQ) The part was heated and kneaded at 70 ° C. to obtain a stock solution for forming the first layer.
45 parts by mass of PMMA, 25 parts by mass of MMA, 25 parts by mass of IBXMA, 5 parts by mass of BzMA, 5 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate (8FM), 1-hydroxycyclohexyl phenyl ketone 25 parts by mass and 0.1 part by mass of HQ were heated and kneaded at 70 ° C. to obtain a second layer forming stock solution.
45 parts by mass of PMMA, 28.2 parts by mass of MMA, 10 parts by mass of IBXMA, 6.8 parts by mass of BzMA, 10 parts by mass of 8FM, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of HQ were heated and kneaded at 70 ° C. A three-layer forming stock solution was obtained.
45 parts by mass of PMMA, 7.7 parts by mass of MMA, 5 parts by mass of IBXMA, 13.1 parts by mass of BzMA, 29.2 parts by mass of 8FM, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 parts by mass of HQ were heated and kneaded at 70 ° C. Thus, a fourth layer forming stock solution was obtained.
45 parts by mass of PMMA, 2.7 parts by mass of IBXMA, 16.9 parts by mass of BzMA, 35.4 parts by mass of 8FM, 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of HQ are heated and kneaded at 70 ° C. to form a fifth layer. A stock solution for formation was obtained.

In addition, in order to suppress crosstalk light and flare light, dye Blue ACR (manufactured by Nippon Kayaku Co., Ltd.) 0. 57% by mass, dye MS Yellow HD-180 (manufactured by Mitsui Toatsu Dye Co., Ltd.) and MS Ma
genta HM-1450 (manufactured by Mitsui Toatsu Dye Co., Ltd.) 0.14 parts by mass, dyes Diaresin Blue 4G (manufactured by Mitsubishi Chemical Co., Ltd.) and Kayasorb CY
0.02 parts by mass of -10 (manufactured by Nippon Kayaku Co., Ltd.) was added.

These five types of stock solutions were sequentially extruded from the concentric five-layer composite spinning nozzle in order from the center so that the refractive index after curing was lowered. The temperature of the composite spinning nozzle was 54 ° C.
The ejection ratio of each layer is converted into the ratio of the thickness of each layer in the diameter direction of the lens (the radius in the first layer). First layer / 2nd layer / 3rd layer / 4th layer / 5th layer = 18/50/29/2/1. The first layer is a portion corresponding to the central portion of the rod lens, and the fifth layer is a portion corresponding to the outermost peripheral portion.

Next, the filaments extruded from the composite spinning nozzle are taken up with a nip roller (20
0 cm / min), a 30 cm long interdiffusion treatment unit, followed by a first curing treatment unit (light irradiation unit) in which 18 chemical lamps of 120 cm length and 40 W are arranged at equal intervals around the central axis ) And three 2 KW high-pressure mercury lamps were passed through the center of the second curing treatment part (light irradiation part) disposed at equal intervals around the central axis and cured. The nitrogen flow rate in the interdiffusion treatment part was 72 L / min. The radius of the obtained lens yarn was 0.30 mm, and Tg was 120 ° C.
This lens yarn is continuously stretched 3.8 times in a 140 ° C. atmosphere from the spinning step (stretching roller speed 750 cm / min), and the relaxation rate becomes 12/15 in a 115 ° C. atmosphere. In this way, relaxation treatment (relaxation roller speed 600 cm / min) was performed, and in the cutting step, the material was cut into a length of 166 mm to obtain many rod lenses having a length of 166 mm.

The ratio of IBXMA in the whole polymer in the range of 0 to 0.8r from the center to the outer peripheral part in the obtained rod lens is 22 parts by mass, and in the whole polymer in the range of 0.8r to r The ratio of IBXMA was 5 parts by mass.

The obtained rod lens has a radius of 0.17 mm, a center refractive index of 1.514, and a refractive index distribution approximated by the formula (1) in the range of 0.2r to 0.8r from the central axis toward the outer periphery, and is 525 nm. The refractive index distribution constant g was 0.83 mm @ -1 at the wavelength of. In addition, a layer having a thickness of about 5 μm from the outer peripheral surface of the rod lens toward the center and a substantially uniform mixture of dyes was formed. The heat shrink start temperature was 70 ° C.
The obtained rod lens was heat-treated for 24 hours under no tension in a drier set at 70 ° C. (relative humidity of 30% or less). The rod lens obtained after the treatment had a thermal shrinkage start temperature of 95 ° C., and a large number of rod lenses were used to form a single-row rod lens array with an array pitch of 0.36 mm (gap 20 μm between adjacent lenses). It was produced (lens length 4.4 mm). The conjugate length, MTF average value, and standard deviation at 525 nm of the prepared rod lens array were measured before and after the heat resistance test, and are summarized in Table 1.

<Example 2>
45 parts by mass of PMMA, 25 parts by mass of MMA, 30 parts by mass of IBXMA, phenyl methacrylate (PhMA), 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of hydroquinone (HQ) are heated and kneaded at 70 ° C. to form a first layer. A stock solution for formation was obtained.
45 parts by mass of PMMA, 25 parts by mass of MMA, 25 parts by mass of IBXMA, 5 parts by mass of PhMA, 5 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate (8FM), 1-hydroxycyclohexyl phenyl ketone 25 parts by mass and 0.1 part by mass of HQ were heated and kneaded at 70 ° C. to obtain a second layer forming stock solution.
45 mass parts of PMMA, 28.2 mass parts of MMA, 10 mass parts of IBXMA, 6.8 mass parts of PhMA, 10 mass parts of 8FM, 0.25 mass part of 1-hydroxycyclohexyl phenyl ketone and 0.1 mass part of HQ are heated and kneaded at 70 ° C. A three-layer forming stock solution was obtained.
45 parts by mass of PMMA, 7.7 parts by mass of MMA, 5 parts by mass of IBXMA, 13.1 parts by mass of PhMA, 29.2 parts by mass of 8FM, 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of HQ were heated and kneaded at 70 ° C. Thus, a fourth layer forming stock solution was obtained.
PMMA 45 parts by mass, IBXMA 2.7 parts by mass, PhMA 16.9 parts by mass, 8FM 35.4 parts by mass, 1-hydroxycyclohexyl phenyl ketone 0.25 parts by mass and HQ 0.1 part by mass at 70 ° C. and kneaded to the fifth layer A stock solution for formation was obtained.

In addition, in order to suppress crosstalk light and flare light, dye Blue ACR (manufactured by Nippon Kayaku Co., Ltd.) 0. 57% by mass, dye MS Yellow HD-180 (manufactured by Mitsui Toatsu Dye Co., Ltd.) and MS Ma
genta HM-1450 (manufactured by Mitsui Toatsu Dye Co., Ltd.) 0.14 parts by mass, dyes Diaresin Blue 4G (manufactured by Mitsubishi Chemical Co., Ltd.) and Kayasorb CY
0.02 parts by mass of -10 (manufactured by Nippon Kayaku Co., Ltd.) was added.

These five types of stock solutions were sequentially arranged from the center so that the refractive index after curing was lowered and simultaneously extruded from a concentric five-layer composite spinning nozzle. The temperature of the composite spinning nozzle was 54 ° C.
The ejection ratio of each layer is converted into the ratio of the thickness of each layer in the diameter direction of the lens (the radius in the first layer). First layer / 2nd layer / 3rd layer / 4th layer / 5th layer = 18/50/29/2/1.

Next, the filaments extruded from the composite spinning nozzle are taken up with a nip roller (20
0 cm / min), a 30 cm long interdiffusion treatment unit, followed by a first curing treatment unit (light irradiation unit) in which 18 chemical lamps of 120 cm length and 40 W are arranged at equal intervals around the central axis ) And three 2 KW high-pressure mercury lamps were passed through the center of the second curing treatment part (light irradiation part) disposed at equal intervals around the central axis and cured. The nitrogen flow rate in the interdiffusion treatment part was 72 L / min. The obtained lens raw yarn had a radius of 0.30 mm and Tg of 122 ° C.
This lens yarn is continuously stretched 3.8 times in a 140 ° C. atmosphere from the spinning step (stretching roller speed 750 cm / min), and the relaxation rate becomes 12/15 in a 115 ° C. atmosphere. In this way, relaxation treatment (relaxation roller speed 600 cm / min) was performed, and in the cutting step, the material was cut into a length of 166 mm to obtain many rod lenses having a length of 166 mm.

The ratio of IBXMA in the whole polymer in the range of 0 to 0.8r from the center to the outer peripheral part in the obtained rod lens is 22 parts by mass, and in the whole polymer in the range of 0.8r to r The ratio of IBXMA was 5 parts by mass.

The obtained rod lens has a radius of 0.17 mm, a center refractive index of 1.512, and a refractive index distribution approximated by the formula (1) in the range of 0.2r to 0.8r from the central axis toward the outer periphery, and is 525 nm. The refractive index distribution constant g was 0.82 mm @ -1 at the wavelength of. In addition, a layer having a thickness of about 5 μm from the outer peripheral surface of the rod lens toward the center and a substantially uniform mixture of dyes was formed. The heat shrink start temperature was 72 ° C.
The obtained rod lens was heat-treated for 24 hours under no tension in a drier set at 70 ° C. (relative humidity of 30% or less). The rod lens obtained after the treatment had a thermal shrinkage start temperature of 97 ° C., and a large number of rod lenses were used to form a single row of rod lens array with an array pitch of 0.36 mm (gap 20 μm between adjacent lenses). It was produced (lens length 4.4 mm). The conjugate length, MTF average value, and standard deviation at 525 nm of the prepared rod lens array were measured before and after the heat resistance test, and are summarized in Table 1.

<Comparative Example 1>
PMMA47 parts by mass, tricyclo [5 · 2 · 1 ^{· 0 2,6]} decanyl methacrylate (TCDMA) 30 parts by weight, MMA23 parts by mass, 0.25 parts by weight of 1-hydroxycyclohexyl phenyl ketone and HQ0.1 parts by 70 The mixture was heated and kneaded at a temperature of 1 ° C. to obtain a first layer forming stock solution.
50 parts by mass of PMMA, 10 parts by mass of TCDMA, 40 parts by mass of MMA, 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of HQ were heated and kneaded at 70 ° C. to obtain a stock solution for forming the second layer.
PMMA 50 parts by mass 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate (8FM) 10 parts by mass, MMA 40 parts by mass, 1-hydroxycyclohexyl phenyl ketone 0.25 part by mass, HQ 0.1 A mass part was heated and kneaded at 70 ° C. to obtain a third layer forming stock solution.
50 parts by mass of PMMA, 10 parts by mass of 8FM, 40 parts by mass of MMA, 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone, and 0.1 part by mass of HQ were heated and kneaded at 70 ° C. to obtain a fourth layer forming stock solution.
42 parts by mass of PMMA, 18 parts by mass of MMA, 40 parts by mass of 8FM, 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of HQ were heated and kneaded at 70 ° C. to obtain a stock solution for forming the fifth layer.

In addition, in order to suppress crosstalk light and flare light, dye Blue ACR (manufactured by Nippon Kayaku Co., Ltd.) 0. 57% by mass, dye MS Yellow HD-180 (manufactured by Mitsui Toatsu Dye Co., Ltd.) and MS Ma
genta HM-1450 (manufactured by Mitsui Toatsu Dye Co., Ltd.) 0.14 parts by mass, dyes Diaresin Blue 4G (manufactured by Mitsubishi Chemical Co., Ltd.) and Kayasorb CY
0.02 parts by mass of -10 (manufactured by Nippon Kayaku Co., Ltd.) was added.

These five types of stock solutions were sequentially arranged from the center so that the refractive index after curing was lowered and simultaneously extruded from a concentric five-layer composite spinning nozzle. The temperature of the composite spinning nozzle was 54 ° C.
The ejection ratio of each layer is converted into the ratio of the thickness of each layer in the diameter direction of the lens (the radius in the first layer). First layer / 2nd layer / 3rd layer / 4th layer / 5th layer = 18/50/29/2/1.

Next, the filaments extruded from the composite spinning nozzle are taken up with a nip roller (20
0 cm / min), a 30 cm long interdiffusion treatment unit, followed by a first curing treatment unit (light irradiation unit) in which 18 chemical lamps of 120 cm length and 40 W are arranged at equal intervals around the central axis ) And three 2 KW high-pressure mercury lamps were passed through the center of the second curing treatment part (light irradiation part) disposed at equal intervals around the central axis and cured. The nitrogen flow rate in the interdiffusion treatment part was 72 L / min. The radius of the obtained lens yarn was 0.30 mm, and Tg was 112 ° C.
This lens yarn is continuously stretched 3.8 times in a 140 ° C. atmosphere from the spinning step (stretching roller speed 750 cm / min), and the relaxation rate becomes 12/15 in a 115 ° C. atmosphere. In this way, relaxation treatment (relaxation roller speed 600 cm / min) was performed, and in the cutting step, the material was cut into a length of 166 mm to obtain many rod lenses having a length of 166 mm.

The obtained rod lens has a radius of 0.17 mm, a central refractive index of 1.497, and a refractive index distribution approximated by the formula (1) in the range of 0.2r to 0.8r from the central axis toward the outer periphery, and is 525 nm. The refractive index distribution constant g was 0.84 mm @ -1 at the wavelength of. In addition, a layer having a thickness of about 5 μm from the outer peripheral surface of the rod lens toward the center and a substantially uniform mixture of dyes was formed. The heat shrink start temperature was as low as 61 ° C.
The obtained rod lens was heat-treated for 24 hours under no tension in a drier set at 70 ° C. (relative humidity of 30% or less). The heat shrinkage starting temperature of the rod lens obtained after the treatment was 85 ° C.
A large number of rod lenses were used to produce a single-row rod lens array (lens length 4.4 mm) with an arrangement pitch of 0.36 mm (gap between adjacent lenses 20 μm). The conjugate length, MTF average value, and standard deviation at 525 nm of the prepared rod lens array were measured before and after the heat resistance test, and are summarized in Table 1.

Claims (4)

A transparent resin polymer (A) and a polymer (B) containing an isobornyl methacrylate unit as a constituent unit are polymerized, and the conjugate length change rate under 1000 hours at 80 ° C. is within 6%. Plastic rod lens. The transparent resin polymer (A) is at least one polymer selected from polymethyl methacrylate (PMMA), polystyrene (PSt), and a resin (MS resin) composed of a methyl methacrylate unit and a styrene unit. The plastic rod lens according to claim 1. The proportion of isobornyl methacrylate units in the total polymer in the resin material having a circular cross section with a radius of r and constituting a range of 0 to 0.8r from the center toward the outer periphery is 10 to 60 mass. The plastic rod lens according to claim 1, wherein the plastic rod lens is a portion. A rod lens array in which a plurality of the plastic rod lenses according to any one of claims 1 to 3 are arranged and fixed between two substrates so that the central axes of the rod lenses are substantially parallel to each other. A plastic rod lens array comprising at least one row.