JP2007034259A - Plastic rod lens, its manufacturing method, and plastic rod lens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens array having heat resistance which suppresses change in a conjugate length even if the lens array is used under a high temperature environment, and also to provide a rod lens used for the array. <P>SOLUTION: The plastic rod lens has a columnar shape, having a refractive index that continuously decreases from the center to the outer circumference, and having a heat contraction starting temperature of ≥80°C when the temperature is elevated at the temperature rising rate of 4°C/min. The invention includes a manufacturing method of a second plastic rod lens for which the first plastic rod lens manufactured through a fiber forming step, a drawing step and a relaxing step is heat treated for one hour or longer, at a temperature ≤100°C but not lower than the heat contraction starting temperature when heated at the temperature rising rate of 4°C/min. <P>COPYRIGHT: (C)2007,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 a “rod lens”) is a cylindrical lens having a refractive index distribution in which the refractive index continuously decreases from the center toward the outer peripheral portion. A rod lens array (hereinafter, simply referred to as “lens array”) made of plastic rods is arranged and bonded and fixed in one or more rows so that the central axes of the rod lenses are substantially parallel to each other between the two substrates. Are widely used in various scanners such as hand scanners, parts for image sensors in copiers 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 of heating and stretching a rod lens.
However, the heat-stretched rod lens has a large thermal shrinkage, 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. .

  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.

Therefore, as a method for providing a rod lens array having heat resistance that is unlikely to change in conjugate length even when used in a high temperature environment and having excellent resolution, a method for relaxing after heating and stretching a rod lens in Patent Document 2. Is disclosed. However, even with this method, the heat resistance of the obtained rod lens was not sufficient.
JP-A-8-211122 JP 2001-337244 A

  An object of the present invention is to provide a lens array having heat resistance that hardly causes a change in conjugate length even when used in a high temperature environment, and excellent in resolution, and a rod lens used therefor.

  The present inventors have found that the above problem can be solved by using a rod lens having a heat shrinkage starting temperature of 80 ° C. or higher when the temperature is increased at a temperature rising rate of 4 ° C./min.

That is, the first gist of the present invention is a plastic rod lens having a cylindrical shape and having a refractive index that continuously decreases from the center toward the outer peripheral portion, at a heating rate of 4 ° C./min. This is a plastic rod lens having a thermal shrinkage starting temperature of 80 ° C. or higher when the temperature is raised.
Therefore, even when used in a high-temperature environment, the resolution can be kept high because the rod lens shrinkage and the conjugate length change due to heat are small.

The thermal shrinkage start temperature can be measured as follows using a commercially available thermomechanical measurement (TMA) apparatus.
First, the sample is chucked with no load, the temperature is increased at a temperature increase rate of 4 ° C./min, and the length of the rod lens at each temperature is measured.
Next, when the temperature is plotted on the horizontal axis and the length of the rod lens is plotted on the vertical axis, the measurement results are plotted on a graph. The length shows a constant value from the start of temperature rise to a certain level, but begins to decrease when a certain temperature is exceeded. . The temperature at which this length begins to decrease is taken as the heat shrinkage start temperature. In some cases, the graph once increases before the length decreases, and the graph shows a maximum value. In this case, the temperature indicating the maximum value is set as the shrinkage start temperature.

The second gist of the present invention is that the first plastic rod lens manufactured through the spinning step, the drawing step and the relaxation step is heated at a temperature increase rate of 4 ° C./min at a heat shrinkage start temperature ( Hereinafter, this is a second plastic rod lens manufacturing method in which heat treatment is performed for 1 hour or more at a temperature of 100 ° C. or less (hereinafter simply referred to as a heat shrink start temperature).
By this method, a plastic rod lens having a cylindrical shape and having a refractive index continuously decreasing from the center toward the outer peripheral portion, the heat when the temperature is increased at a temperature increase rate of 4 ° C./min. A plastic rod lens having a shrinkage start temperature of 80 ° C. or higher can be obtained.
In the present invention, the rod lens before the heat treatment is referred to as a first (plastic) rod lens, and the rod lens after the heat treatment is referred to as a second (plastic rod lens).

  The third gist of the present invention is a rod lens array in which the plastic rod lenses are arranged and fixed between two substrates so that the central axes of the rod lenses are substantially parallel to each other.

  The rod lens array according to the present invention is excellent in heat resistance because deterioration and variation in optical characteristics such as resolution are suppressed even when used in a high temperature environment.

  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) = n 0 {}} 1- (g 2/2) L 2} (1)

(Where n ₀ 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 of the rod lens. (It is a distribution 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 during processing of 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 n ₀ 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. From the viewpoint of
Further, the refractive index distribution constant g of the rod lens is not particularly limited, but is in the range of 0.2 to 3 mm ⁻¹ from the viewpoint of compacting the optical system, ensuring the working distance of the optical system, and handling. 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 Co., Ltd., Mitsui Toatsu dye MS Magenta HM-1450 having absorption at 500 to 600 nm, Mitsui Toatsu dye MS Yellow HD-180 having absorption 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 n ₁ > n ₂ >...> _{N N} (N ≧ 3) are gradually decreased from the center toward the outer periphery. In such an arrangement, it is shaped into an uncured laminated body (hereinafter referred to as “filamentous body”) that is concentrically laminated, and adjacent so that the refractive index distribution between each layer of the filamentous body is continuous. While performing the interdiffusion treatment of the substances between the layers or after 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 the material constituting the uncured material, a radical polymerizable vinyl monomer, or a composition comprising a radical polymerizable vinyl 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 Other diethylene glycol bisallyl carbonates such as rupropanedi or tri (meth) acrylate, pentaerythritol di, tri or tetra (meth) acrylate, diglycerin tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, fluorinated alkylene glycol poly (Meth) acrylate etc. are mentioned.

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 product is preferably composed of a vinyl monomer and the polymer.
The polymer must 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 / A hexafluoropropene copolymer (n = 1.40-1.46), a polyfluorinated alkyl (meth) acrylate polymer, etc. are mentioned. In particular, polymethylmethacrylate is excellent in transparency and has a high refractive index, so that it is suitable as a polymer for use in preparing the gradient index optical transmission material of the present invention.

  In order to adjust the viscosity, it is preferable to use a polymer having the same refractive index in each layer as the polymer because a plastic optical transmission body having a continuous refractive index distribution from the center toward the outer periphery can be obtained.

  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 photocuring treatment can be performed by irradiating an uncured material containing a photocuring catalyst with ultraviolet rays from the surroundings. Examples of the light source used for the photocuring treatment 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. Further, these light sources may be used in appropriate combination in order to increase the polymerization rate.

The thermosetting treatment is preferably performed by heating an uncured product containing a thermosetting catalyst for a predetermined time in a curing processing section such as a heating furnace controlled at a constant temperature.
The rod lens yarn thus obtained becomes a first plastic rod lens through a stretching process and a relaxation process, and then the heat shrinkage start temperature of the rod lens is 100 ° C. or less, more preferably heat shrinkage start. By performing the heat treatment at a temperature of 80 ° C. or higher, the heat shrinkage start temperature can be increased.
Stretching can be performed by a known method. For example, the rod lens raw yarn obtained by curing is supplied to a heating furnace with a first nip roller, and the rod lens that has passed through the heating furnace is drawn with a second nip roller at a higher speed than the first nip roller and drawn. Methods and the like.
The atmospheric temperature (stretching temperature) in the stretching process is set according to the material of the rod lens and the like, but the glass transition temperature (Tg) of the rod lens yarn is preferably + 20 ° C. or more, and preferably Tg + 60 ° C. In addition, when a rod lens is comprised with multiple types of material, let the maximum value of those Tg be Tg of a rod lens.
Moreover, although a draw ratio is determined by a desired rod lens diameter and can be adjusted by a speed ratio of the first and second nip rollers, 1.1 to 10 times is preferable, and 2 to 6 times is more preferable.
The relaxation can be performed by a known method. For example, there is a method in which the drawn rod lens yarn is supplied to a heating furnace with a third nip roller, and the rod lens that has passed through the heating furnace is pulled off with a fourth nip roller at a slower speed than the third nip roller, etc. can give.
The ambient temperature (relaxation temperature) in the relaxation process is set according to the material of the rod lens and the like, but considering the optical characteristics of the rod lens array using the obtained rod lens, it is preferably Tg or more and Tg + 60 ° C. or less. Tg or more and a stretching temperature of −5 ° C. or less are more preferable.
Further, the relaxation magnification is determined by the desired rod lens diameter and can be adjusted by the speed ratio of the third and fourth nip rollers, but is preferably 0.5 or more and less than 1 time, 0.6 to 0.9 Double is more preferred.
The stretching step may be performed in a batch manner or continuously. Further, the stretching step and the relaxation step may be performed continuously, or may be performed separately for each step. From the viewpoint of productivity, it is preferable to carry out continuously.

The first rod lens having a desired diameter through the stretching and relaxation processes may be continuously cut to a desired length, or may be cut after being wound around a bobbin or the like. The thermal contraction start temperature of the first rod lens obtained through the steps so far is about 45 to 75 ° C., and sufficient heat resistance cannot be obtained yet.
In the manufacturing method of the rod lens (second rod lens) of the present invention, the first rod lens obtained as described above is further subjected to heat treatment at a temperature higher than the heat shrinkage start temperature and not higher than 100 ° C. , Improve heat resistance.
The heat treatment temperature needs to be equal to or higher than the heat shrinkage start temperature in order to achieve the effect of increasing heat resistance, and needs to be 100 ° C. or lower in order to avoid deformation of the rod lens.

By performing the heat treatment at such a temperature, the thermal contraction start temperature of the (first) rod lens can be increased, and the deformation of the (second) rod lens is suppressed even in a high temperature environment, and the heat resistance of the lens array is increased. Can be improved.
Although there is no restriction | limiting in particular in the time which heat-processes, when the point which improves heat resistance and the balance of productivity is considered, it is preferable to carry out for 0.5 to 48 hours, 5 to 30 hours are more preferable, and 18 to 30 hours Is particularly preferred.
It is particularly preferable that the heat treatment is performed in a state in which no tension is applied to the (first) rod lens. For example, if it is in a state cut to a predetermined length, it may be flattened so that rod lenses do not overlap each other on the top plate, or a U-shaped container or U-shaped container The rod lenses may be put in a container and aligned so that the rod lenses are parallel by applying vibration. In addition, if it is wound around a drum or the like, there is a method of winding the rod lens in parallel by traversing at a constant pitch.
The humidity during the heat treatment is not particularly limited as long as the conditions do not damage the rod lens, and the relative humidity is preferably about 0 to 90%. If the relative humidity exceeds 90%, dew condensation may occur (due to cooling) when the rod lens is taken out from a constant temperature and humidity machine or the like.
The heat treatment method is not particularly limited as long as the rod lens can be uniformly heat treated, and may be performed in a heating oven, a hot air dryer or the like, and is controlled at a constant humidity and a constant humidity. You can go on board. Moreover, you may carry out in liquids, such as a liquid paraffin which does not damage a rod lens. Further, it may be immersed in warm water or may be treated with supercritical carbon dioxide.

  In the lens array of the present invention, the plurality of (second) rod lenses obtained as described above have one or more rows between two substrates so that the optical axis directions of the rod lenses are parallel to each other. Arranged. 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 regular intervals. 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, as the base material and reinforcing material of the substrate, fibers or paper may be used, or a release agent, a dye, a pigment, or 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 for 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 drier set at 60 ° C. (relative humidity 30% or less) and held for 1000 hours. The conjugate length, MTF average value, and standard deviation before and after the test were determined.
The case where the conjugate length [mm] after the test 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 ×.
The case where the average MTF [%] after the test 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 ×.
The case where the MTF standard deviation [%] after the test 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 ×.

メチルメタクリレート（ＭＭＡ）２３質量部、１−ヒドロキシシクロヘキシルフェニルケトン０．２５質量部及びハイドロキノン（ＨＱ）０．１質量部を７０℃に加熱混練して第１層形成用原液とした。
ＰＭＭＡ５０質量部、ＴＣＤＭＡ１０質量部、ＭＭＡ４０質量部、１−ヒドロキシシクロヘキシルフェニルケトン０．２５質量部及びＨＱ０．１質量部を７０℃に加熱混練して第２層形成用原液とした。
ＰＭＭＡ５０質量部、2,2,3,3,4,4,5,5-オクタフルオロペンチルメタクリレート（８ＦＭ）１０質量部、ＭＭＡ４０質量部、１−ヒドロキシシクロヘキシルフェニルケトン０．２５質量部、ＨＱ０．１質量部を７０℃に加熱混練して第３層形成用原液とした。
ＰＭＭＡ５０質量部、８ＦＭ１０質量部、ＭＭＡ４０質量部、１−ヒドロキシシクロヘキシルフェニルケトン０．２５質量部、ＨＱ０．１質量部を７０℃に加熱混練して第４層形成用原液とした。
ＰＭＭＡ４２質量部、ＭＭＡ１８質量部、８ＦＭ４０質量部、１−ヒドロキシシクロヘキシルフェニルケトン０．２５質量部、ＨＱ０．１質量部を７０℃に加熱混練して第５層形成用原液とした。 <Example 1>
47 parts by mass of polymethyl methacrylate (PMMA, [η] = 0.40, measured in MEK at 25 ° C., and the same polymethyl methacrylate was used in the following Examples and Comparative Examples). 30 parts by mass of tricyclo [5.2.1.0 ^2,6 ] decanyl-8-methacrylate (TCDMA) represented by the formula:

23 parts by mass of methyl methacrylate (MMA), 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of hydroquinone (HQ) were heated and kneaded at 70 ° 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, dyes MS Yellow HD-180 (Mitsui Toatsu Dye Co., Ltd.) and MS Magenta HM-1450 (Mitsui Toatsu Dye Co., Ltd.) 0.14% by mass, dye Diaresin Blue 4G (Mitsubishi) Chemical Co., Ltd.) and Kayasorb CY-10 (Nippon Kayaku Co., Ltd.) were added in an amount of 0.02% by mass.

  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 by a nip roller (200 cm / min), passed through an interdiffusion treatment section having a length of 30 cm, and subsequently, 18 chemical lamps having a length of 120 cm and 40 W have a central axis. A first curing processing unit (light irradiation unit) disposed at equal intervals around the periphery and a second curing processing unit (light irradiation unit) in which three 2 KW high-pressure mercury lamps are disposed at equal intervals around the central axis. The filament was passed through the center 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 110 ° 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 manner, relaxation treatment (relaxation roller speed 600 cm / min) was performed, and the cutting process was performed to cut a length of 166 mm to obtain a large number of rod lenses (first rod lenses) having a length of 166 mm.

The obtained first rod lens has a radius of 0.17 mm, a central refractive index of 1.497, and a refractive index distribution that approximates Equation (1) in the range of 0.2r to 0.8r from the central axis toward the outer periphery. The refractive index distribution constant g was 0.84 mm ⁻¹ at a wavelength of 525 nm. In addition, a layer having a thickness of about 5 μm from the outer peripheral surface of the first 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 first rod lens was heat-treated in a drier set at 70 ° C. (relative humidity of 30% or less) under no tension for 24 hours. The thermal contraction start temperature of the second rod lens obtained after the treatment was 85 ° C.
A large number of the second rod lenses were used to produce a single-row rod lens array with a pitch of 0.36 mm (gap 20 μm between adjacent lenses) (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>
A lens array was prepared in the same manner as in Example 1 except that a rod lens (first rod lens) that was not heat-treated was used. 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>
A lens array similar to that in Example 1 was prepared using a rod lens obtained by the same method as in Example 1 except that the relaxation treatment was performed in an atmosphere at 140 ° C. The heat shrinkage start temperature of the rod lens before the heat treatment was 48 ° C., and the heat shrinkage start temperature after the heat treatment was 84 ° C. 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 2>
A lens array was prepared in the same manner as in Example 2 except that the first rod lens that was not heat-treated was used. 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 3>
A lens array similar to that in Example 1 was prepared using a second rod lens obtained by the same method as in Example 1 except that the relaxation treatment was performed in an atmosphere at 160 ° C. The thermal contraction start temperature of the first rod lens before the heat treatment was 65 ° C., and the thermal contraction start temperature after the heat treatment was 87 ° C. 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 3>
A lens array similar to that of Example 3 was prepared except that the first rod lens that was not heat-treated was used. 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 4>
47 parts by mass of PMMA, 30 parts by mass of TCDMA, 23 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 first layer.
46 parts by mass of PMMA, 15 parts by mass of TCDMA, 29 parts by mass of MMA, 5 parts by mass of benzyl methacrylate (BzMA), 5 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate (8FM), 1- 0.25 parts by mass of hydroxycyclohexyl phenyl ketone and 0.1 parts by mass of HQ were heated and kneaded at 70 ° C. to obtain a second layer forming stock solution.
49 parts by mass of PMMA, 6 parts by mass of BzMA, 8 parts by mass of 8FM, 37 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 third layer forming stock solution.
46 parts by mass of PMMA, 10 parts by mass of BzMA, 20 parts by mass of 8FM, 24 parts by mass of MMA, 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. to obtain a fourth layer forming stock solution.
PMMA 39 parts by mass, BzMA 17 parts by mass, 8FM41 parts by mass, MMA 3 parts by mass, 1-hydroxycyclohexyl phenyl ketone 0.25 parts by mass, and HQ 0.1 parts by mass were heated and kneaded at 70 ° C. to obtain a fifth layer forming stock solution.

Dye Blue ACR, MS Magenta HM-1450, Diaresin Blue 4G, and Kayasorb CY-10 are each 0.003 mass% and dye MS Yellow HD-180 in each stock solution of the fourth layer before heating and kneading. 0.006% by mass was added.
In each stock solution for the fifth layer, Blue ACR 0.57% by mass, MS Yellow HD-180 and MS Magenta HM-1450 are 0.14% by mass, Diaresin Blue 4G and Kayasorb CY- Each 10 was added in an amount of 0.01% by mass.

  These five types of stock solutions were kneaded at 70 ° C., arranged in order from the center so that the refractive index after curing was lowered, and extruded simultaneously from a concentric five-layer composite spinning nozzle. The temperature of the composite spinning nozzle was 50 ° C. The ejection ratio of each layer is converted into the ratio of the thickness of each layer in the radial direction of the plastic rod lens (the radius in the first layer). The first layer / 2nd layer / 3rd layer / 4th layer / 5th layer Eye = 21/25/33/19/2.

Next, the filaments extruded from the composite spinning nozzle are taken up by a nip roller (200 cm / min), passed through a 30 cm-long interdiffusion treatment section, and subsequently 18 chemical lamps with a length of 60 cm and 20 W have a central axis. A first curing processing unit (light irradiation unit) disposed at equal intervals around the periphery and a second curing processing unit (light irradiation unit) in which three 2 KW high-pressure mercury lamps are disposed at equal intervals around the central axis. The filament was passed through the center and cured. The nitrogen flow rate in the interdiffusion treatment part was 80 L / min. The obtained lens yarn had a radius of 0.295 mm and Tg of 105 ° C.
This lens raw yarn is continuously stretched 3.50 times in an atmosphere of 135 ° C. from the spinning step (stretching roller speed 700 cm / min), and the relaxation rate becomes 500/700 in an atmosphere of 115 ° C. In this manner, relaxation treatment (relaxation roller speed of 500 cm / min) was performed, and in the cutting step, a length of 166 mm was cut to obtain a number of rod lenses (first rod lenses) having a length of 166 mm.

The obtained first rod lens has a radius of 0.187 mm, a central refractive index of 1.497, and a refractive index distribution that approximates the formula (1) in the range of 0.2r to 0.8r from the central axis toward the outer periphery. The refractive index distribution constant g was 0.84 mm ⁻¹ at a wavelength of 525 nm. In addition, a layer having a thickness of about 40 μm from the outer peripheral surface of the first rod lens toward the center and a substantially uniform mixture of dyes was formed. The heat shrink start temperature was as low as 65 ° C.
The obtained first rod lens was heat-treated in a drier set at 70 ° C. (relative humidity of 30% or less) under no tension for 24 hours. The thermal contraction start temperature of the second rod lens obtained after the treatment was 81 ° C.
A number of the second rod lenses were used to produce a single-row rod lens array (lens length of 4.4 mm) with an arrangement pitch of 0.39 mm (a gap of 20 μm between adjacent lenses). 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.

実施例１〜４のロッドレンズアレイはいずれも耐熱試験後においても共役長、平均ＭＴＦ値、ＭＴＦ標準偏差が良好であった。
これに対し、比較例１〜４のロッドレンズアレイは耐熱試験後における上記の性質がよくなかった。 <Comparative example 4>
A lens array similar to that of Example 4 was prepared except that the first rod lens that was not heat-treated was used. 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.

The rod lens arrays of Examples 1 to 4 all had good conjugate length, average MTF value, and MTF standard deviation even after the heat test.
On the other hand, the rod lens arrays of Comparative Examples 1 to 4 did not have the above properties after the heat resistance test.

Claims (3)

  A plastic rod lens having a cylindrical shape and having a refractive index that continuously decreases from the center toward the outer periphery, and the heat shrinkage starting temperature when the temperature is increased at a rate of temperature increase of 4 ° C./min. Plastic rod lens that is 80 ℃ or higher   The first plastic rod lens manufactured through the spinning process, stretching process and relaxation process is heat-treated at a temperature higher than the heat shrinkage starting temperature at 100 ° C. for 1 hour or more when the temperature is increased at a temperature rising rate of 4 ° C./min. The manufacturing method of the 2nd plastic rod lens performed.   A rod lens array in which the plastic rod lenses according to claim 1 are arranged and fixed between two substrates so that the central axes of the rod lenses are substantially parallel to each other.