JP2003114306A - Rod lens, lens array and led printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rod lens capable of obtaining a lens array of high resolution. SOLUTION: The rod lens is constituted so that the cross section may be formed to a circular shape, and also, the refractive index may be continuously reduced from the center axis to the outer peripheral surface, and the radius (r) of the cross section is 0.2 to 0.4 mm, and the rod lens is provided with a light absorbing layer having a thickness of >=50 μm, including light absorbing agent for absorbing at least a part of light transmitted through the rod lens in an area outside >=0.6 r from the center axis, the refractive index distributed constant (g) satisfies 0.7 mm<-1> <=g<=2.0 mm<-1> as for a wavelength of 740 nm, and (g)×(r) satisfies 0.2<=g×r<=0.3. Besides, it is preferable that the thickness of the light absorbing layer is <=100 μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high resolution LED.
The present invention relates to a rod lens for a lens array, which is preferably used in a printer or the like, a lens array in which a plurality of rod lenses are arranged, and an LED printer including the lens array.

[0002]

2. Description of the Related Art As one of minute lenses, a cylindrical plastic rod lens whose both end faces are mirror-polished is known. Such a plastic rod lens is used alone, and is also used in the form of a lens array in which a plurality of lenses are arranged and integrated, and a component for an image sensor such as a copying machine, a facsimile, a scanner, a hand scanner, or the like,
It is widely used as a writing device of an LED printer using an LED (light emitting diode) as a light source. Further, the plastic rod lens is expected to be used more and more in the future because of its low manufacturing cost.

By the way, the LED printer is used as a business printer or the like since it has advantages such as a high printing speed particularly in the case of performing color printing and the miniaturization of the apparatus as compared with a laser printer or the like. But
For LED printers, 600 dpi or 1200 d
The high resolution of pi is being advanced, and along with this, development of a high resolution lens array is required.

[0004]

In order to increase the resolution of the lens array, it is important to remove flare light and crosstalk light from the lens array and to arrange the rod lenses accurately. For example, Japanese Patent Application Laid-Open No. 11-352307 discloses a technique for removing flare light and crosstalk light by uniformly mixing a light absorber in a range including a portion having an irregular refractive index distribution. . However,
When the rod lens disclosed in JP-A-11-352307 is applied to an LED printer, there is a problem that sufficient resolution cannot be obtained.

Therefore, an object of the present invention is to provide a rod lens capable of obtaining a high resolution lens array, a lens array formed by using the rod lens, and an LED printer provided with the lens array. .

[0006]

As a result of studies to solve the above problems, the present inventor has invented the following rod lens, lens array and LED printer. The rod lens of the present invention is circular in cross section, and in the rod lens in which the refractive index continuously decreases from the central axis toward the outer peripheral surface, the radius r of the cross section is 0.2 to 0.4 mm, The refractive index distribution in the range of at least 0.3r to 0.7r from the central axis is approximated by a quadratic curve defined by the following formula (1), and the rod is provided outside the central axis by 0.6r or more. A light absorbing layer having a thickness of 50 μm or more containing a light absorbing agent that absorbs at least a part of light transmitted by the lens is provided, and a refractive index distribution constant g at a wavelength of 740 nm is 0.7 mm ^−1. ≦ g ≦ 2.0 mm ⁻¹ , and g · r satisfies 0.2 ≦ g · r ≦ 0.3. _{n (L) = n 0 {} 1- (g 2/2) L 2} ··· (1) ( In the formula (1), n ₀ is the refractive index of the central axis of the rod lens, L is the rod lens From the center axis of (0 ≤ L ≤
r) and g represent the refractive index distribution constant of the rod lens, and n (L) represents the refractive index at the position of the distance L from the central axis of the rod lens. )

Further, in the rod lens of the present invention, it is more preferable that the thickness of the light absorbing layer is 100 μm or less. Further, in general, in an LED printer or the like,
Since a light source that emits light having a wavelength of 500 to 900 nm is used as the light source, the light absorber is
It is preferable to use one that absorbs light in at least a part of the wavelength range of 900 nm. In addition, when the rod lens of the present invention transmits light with a wavelength of 740 nm,
The effective diameter R for light with a wavelength of 40 nm is 0.6r
It is preferably 0.8r.

By using the rod lens of the present invention as described above, flare light and crosstalk light can be largely removed, and a high resolution lens array can be provided.

A lens array of the present invention comprises a plurality of rod lenses of the present invention, which are arranged in a direction perpendicular to the central axis direction of the rod lenses such that the central axis directions of the rod lenses are substantially parallel to each other. At least one row of rod lenses arranged toward each other is provided, and the standard deviation of the optical axis unevenness per unit rod lens length (Z ₀ ) of the rod lens is 0.
It is characterized by being less than 7 (μm / Z ₀ ). In addition,
The definition and the measuring method of the "standard deviation of the optical axis unevenness per unit rod lens length (Z ₀ ) of the rod lens" in the present specification will be described in detail in the section "Embodiment of the Invention". Further, it is preferable that the lens array of the present invention includes two or four rod lens rows.

Since the above lens array of the present invention is constructed by using the rod lens of the present invention, flare light and crosstalk light can be largely removed.
It becomes a high resolution lens array.

Further, by providing the lens array of the present invention, it is possible to provide an LED printer excellent in printing characteristics even with high resolution.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail. [Structure of Rod Lens] Hereinafter, the structure of the rod lens of the present invention will be described with reference to a plastic rod lens that is a preferred embodiment of the present invention, and the plastic rod lens will be simply referred to as “rod lens” as appropriate. The present invention is not limited to plastic rod lenses.

The plastic rod lens of the present invention is circular in cross section, has a refractive index continuously decreasing from the central axis toward the outer peripheral surface, and at least 0.3r to 0.7r (however, from the central axis). , R is characterized in that the refractive index distribution in the range of the radius of the cross section is approximated by a quadratic curve defined by the following equation (1). _{n (L) = n 0 {} 1- (g 2/2) r 2} ··· (1) ( In the formula (1), n ₀ is the refractive index at the center axis of the rod lens, L is the rod lens Center axis distance (0 ≤ L
≦ r), g is the refractive index distribution constant of the rod lens, n (L)
Represents the refractive index at a position at a distance L from the central axis of the rod lens. ) In this specification, the “cross section” of the rod lens is
It means the cross section when cut in the direction perpendicular to the central axis.

Refractive index n of the central axis of the rod lens of the present invention
₀ is preferably 1.4 to 1.6. If the refractive index n ₀ of the central axis is in this range, the choice of materials that can be used for the rod lens of the present invention is wide, so that a rod lens having a good refractive index distribution and excellent transparency can be easily manufactured. It can be obtained and is suitable. In the rod lens of the present invention, the radius r of the cross section is 0.2 to 0.4 m.
It is preferably m. When the radius r of the cross section exceeds 0.4 mm, the conjugate length Tc of the rod lens becomes long. Therefore, when the rod lens of the present invention is used to form an optical system such as an LED printer, the optical system is small in size. It will be difficult to achieve this. If the radius r of the cross section is less than 0.2 mm, the working distance of the rod lens becomes too short, and L
This is not preferable because the restrictions on the arrangement of the components that make up the ED printer and the like are increased. For example, the radius r of the cross section is 0.
If it is less than 2 mm, when the LED printer is constructed using the rod lens of the present invention, the lens array and LE are
The distance between the D chips and the distance between the lens array and the photosensitive drum become too short, and the restrictions on the arrangement of these parts become large.

Further, in the rod lens of the present invention, at least a part of the transmitted light of the rod lens is in the range of 0.6r or more outside from the central axis, and more preferably in the range of 0.8r to r from the central axis. It is characterized by comprising a light absorbing layer having a thickness of 50 μm or more, which contains a light absorbing agent for absorbing the above light.

Generally, when manufacturing a plastic rod lens, as the distance from the central axis increases, a portion with a large deviation from the ideal distribution and an irregular refractive index distribution is likely to be formed. It has been found that such a portion is likely to be formed in a range outside the central axis by 0.6 r or more. Further, the present inventor has found that a portion having an irregular refractive index distribution is particularly likely to be formed in the range of 0.8r to r from the central axis. That is, in the rod lens of the present invention, the light absorption layer having a thickness of 50 μm or more is provided so as to include a range in which an irregular refractive index distribution is likely to be formed.

Then, the present inventor can absorb at least a part of the light incident on the portion where the refractive index distribution is irregular by forming the lens array by using the rod lens of the present invention having such a constitution. In addition to suppressing flare light itself, even if flare light is generated in a portion where the refractive index distribution is irregular, at least a part of the generated flare light can be absorbed by the light absorption layer. It has been found that it can be significantly removed.

Further, since the thickness of the light absorption layer is set to be as thick as 50 μm or more, the crosstalk light that crosstalks between the adjacent rod lenses when the lens array is formed by using the rod lenses of the present invention. Also, the light can be absorbed by the light absorption layer, and the crosstalk light can be largely removed. This is because, when the thickness of the light absorption layer is X times, the transmittance of light from the lens outer periphery (amount of crosstalk light transmitted) decreases with the Xth power.

If the thickness of the light absorption layer is less than 50 μm, flare light and crosstalk light are not sufficiently removed when a lens array is formed using the rod lens of the present invention, which is not preferable. . Further, the thicker the light absorption layer is, the more light incident on the portion where the refractive index distribution is irregular can be absorbed in a wider range, which is preferable. However, as the thickness of the light absorption layer is increased, the amount of light transmitted through the rod lens decreases. Therefore, it is preferable to design the thickness of the light absorption layer in consideration of these points. As a result of the study by the present inventor, the thickness of the light absorption layer was set to 5
It was found that the flare light and the crosstalk light can be sufficiently removed and a sufficient transmitted light amount can be secured by setting the thickness to 0 to 100 μm. Further, by forming a lens array using the rod lens of the present invention as described above, both flare light and crosstalk light can be significantly removed, and as a result, the resolution of the lens array can be significantly improved. I found it.

Generally, in an LED printer or the like, since a light source that emits light having a wavelength of 500 to 900 nm is used as a light source, the light absorbing agent contained in the light absorbing layer is at least one of 500 to 900 nm. It is preferable to use a material that absorbs light in the partial wavelength range.
As a light absorbing agent that absorbs only light in a specific wavelength range of 500 to 900 nm, there are 6 types such as Kayasorb CY-10 manufactured by Nippon Kayaku, which absorbs light in the range of 600 nm to near infrared.
Mitsubishi Chemical Diares with absorption at 00-700 nm
in Blue 4G, etc., such as Kayase Blue ACR manufactured by Nippon Kayaku, which has absorption at 550 to 650 nm, 5
Nippon Kayaku's Kayaso with absorption in the range of 00-600 nm
rbRed G, Red 130, Red B, etc., 50
Mitsui Toatsu Dye MS Mag which absorbs at 0-600nm
enta HM-1450 etc. can be illustrated.
Moreover, a black dye etc. can be illustrated as a light absorber which absorbs the light of the whole wavelength range of 500-900 nm.

The light absorber may be used alone,
It is also possible to use a combination of a plurality of types. Also, 50
When using a light absorbing agent that absorbs only light in a specific wavelength range of 0 to 900 nm, by using a plurality of types of light absorbing agents that absorb light in different wavelength ranges,
Since the light absorption layer can absorb light in a wider wavelength range, it is suitable for various light sources, which is preferable.

Further, since the rod lens of the present invention further adopts the following constitution, it is particularly suitably used for a lens array mounted on an LED printer. L
In ED printers, LEDs of various wavelengths are used as a light source, but LEDs that emit light of 740 nm wavelength are used.
Is commonly used. In the rod lens of the present invention, the refractive index distribution constant g for light having a wavelength of 740 nm satisfies 0.7 mm ⁻¹ ≦ g ≦ 2.0 mm ⁻¹ , and g
Since r is configured to satisfy 0.2 ≦ g · r ≦ 0.3, particularly when used for a lens array mounted in an LED printer, it has good optical characteristics as described later.

When the refractive index distribution constant g for light having a wavelength of 740 nm exceeds 2 mm ^-1 , the working distance of the rod lens becomes too short, and an LED printer is constructed using the rod lens of the present invention. In addition, the restrictions on the arrangement of the components that make up the LED printer are increased. Also, 74
The refractive index distribution constant g for light with a wavelength of 0 nm is 0.7
When it is less than mm ⁻¹ , the conjugate length Tc of the rod lens becomes too long, and L obtained by using the rod lens of the present invention.
It becomes difficult to reduce the size of the optical system of the ED printer. On the other hand, the refractive index distribution constant g is 0.7 to 2.0.
In the case of mm ^-1 , it is possible to reduce the size of the optical system of the LED printer using the rod lens of the present invention while ensuring a sufficient working distance of the rod lens.

Further, when the product g · r of the refractive index distribution constant and the radius for light having a wavelength of 740 nm is less than 0.2, the depth of focus becomes deep, which is preferable, but the amount of light that can be taken in decreases. As a bright rod lens cannot be obtained,
Not preferable. Further, when the product g · r of the refractive index distribution constant and the radius for light with a wavelength of 740 nm exceeds 0.3, the amount of light that can be taken in becomes large and a bright rod lens can be obtained, but the depth of focus is It is not preferable because it becomes shallow. On the other hand, the product g · r of the refractive index distribution constant and the radius for light having a wavelength of 740 nm is 0.2 to
By configuring so as to be 0.3, it is possible to provide a bright rod lens while ensuring good depth of focus characteristics.

When the plastic rod lens of the present invention is for a lens array mounted in an LED printer, the effective diameter R for light having a wavelength of 740 nm is R.
Is preferably 0.6r to 0.8r. With such a configuration, flare light generated in a portion where the refractive index distribution is irregular and light that crosstalks between adjacent lenses can be completely removed. Therefore, when the light emission of the LED is imaged on the photosensitive drum, Since the emission peak on the image plane becomes sharp and the baseline becomes almost zero, the gradation characteristics are excellent. Therefore, by using the rod lens of the present invention, it is possible to provide a high-resolution lens array in which deterioration of lens performance due to flare light or crosstalk light is extremely small. If the effective diameter R of light having a wavelength of 740 nm exceeds 0.8r, it becomes difficult to completely remove flare light and crosstalk light.

In the present specification, "effective diameter of rod lens for light with wavelength of 740 nm" is 740
It is the radius of the transparent portion for light of nm, and is defined by the distance from the central axis of the lens to the inner end of the portion containing the light absorber that absorbs light of 740 nm.

As described above, according to the present invention, a light absorbing agent that absorbs at least a part of the transmitted light of the rod lens is contained in a range outside the central axis by 0.6 r or more, and the light absorbing agent is 50 μm or more. A feature is that a thick light absorption layer is provided. By forming a lens array using the rod lens of the present invention having such a configuration, both flare light and crosstalk light are significantly removed. It is possible to provide a high resolution lens array.

Further, since the radius r of the cross section and the refractive index distribution constant g for light having a wavelength of 740 nm are regulated within a predetermined range, the conjugate length Tc of the rod lens can be shortened, and the present invention can be realized. The optical system such as an LED printer obtained by using the rod lens can be miniaturized.

[Method for Manufacturing Rod Lens] Next, an example of the method for manufacturing the plastic rod lens of the present invention will be described. _First, the refractive index n after curing is n ₁ > n ₂
····> _{N N} (where N ≧ 3) N layer forming solutions (first layer forming solution to Nth layer forming solution) are prepared and these N layer forming solutions are prepared. An uncured thread shape in which the first layer to the Nth layer are concentrically laminated and formed by concentrically extruding in a solution using a solution in which the refractive index gradually decreases from the central axis toward the outer peripheral surface after curing. Spin the body. In addition,
After spinning, at least one layer out of the central axis of 0.6r or more, more preferably 0.8 from the central axis.
The layer-forming solution that constitutes at least one layer out of the layers r to r contains a light absorber in advance when the solution is prepared.

Next, the filaments after spinning are subjected to an interdiffusion treatment in which substances in adjacent layers are mutually diffused so that the refractive index distribution of the filaments continuously changes from the central axis toward the outer peripheral surface. After the application, a curing treatment is applied. Note that the mutual diffusion treatment can be performed by holding the uncured filamentous material at a predetermined temperature for a predetermined time in an atmosphere of an inert gas such as nitrogen, and diffusing the substances in the adjacent layers due to the difference in concentration. . It is also possible to perform the mutual diffusion treatment and the curing treatment at the same time.

The filament obtained after the curing treatment may be used as it is as a lens, or if necessary, it may be heated and stretched.
You may perform relaxation treatment. The rod lens of the present invention can be manufactured by obtaining a filamentous body having a diameter of 0.2 to 0.4 mm and then cutting the filamentous body into pieces each having a predetermined length. Incidentally, mutual diffusion treatment, curing treatment, heat stretching treatment,
The relaxation treatment may be performed continuously or batchwise.

The outline of the rod lens manufacturing method of the present invention has been described above. Further, the above manufacturing method will be described in detail. Number of layers to be laminated when spinning a filament N
Is preferably 4 to 6. When the number N of layers is less than 4, it is difficult to make the refractive index distribution of the obtained rod lens close to an ideal distribution, and when the number N of layers exceeds 6, it becomes difficult to spin the filamentous material. , Not preferable.

The viscosity of each layer forming solution prepared when spinning the filament is preferably 10 ³ to 10 ⁸ poise. When the viscosity of the layer forming solution is less than 10 ³ poise, yarn breakage is likely to occur during spinning, and spinning may be difficult. When the viscosity of the layer-forming solution exceeds 10 ⁸ poises, the operability during spinning is deteriorated, the concentricity of each layer is impaired, and it becomes difficult to obtain filaments having a uniform diameter. There is a risk of becoming.

Here, as the curable material which is the main component of each layer forming solution, a radical polymerizable vinyl monomer or the like can be exemplified. Radical-polymerizable vinyl monomers include methyl methacrylate (n = 1.49), styrene (n = 1.59), chlorostyrene (n = 1.6).
1), vinyl acetate (n = 1.47), 2,2,3,3-
Tetrafluoropropyl (meth) acrylate, 2,
2,3,3,4,4,5,5-octafluoropentyl (meth) acrylate, 2,2,3,4,4,4-hexafluorobutyl (meth) acrylate, 2,2,2-
Fluorinated alkyl (meth) acrylates such as trifluoroethyl (meth) acrylate (n = 1.37 to 1.4
4), n = 1.43 to 1.62 (meth) acrylates, for example, ethyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, alicyclic (meth) acrylate, hydroxyalkyl ( (Meth) acrylate, alkylene glycol (meth)
Acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate,
Examples thereof include pentaerythritol tetra (meth) acrylate, diglycerin tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate and the like. Further, diethylene glycol bisallyl carbonate, fluorinated alkylene glycol poly (meth) acrylate and the like can also be used.

For the purpose of adjusting the viscosity of the layer forming solution and continuously changing the refractive index from the central axis toward the outer peripheral surface, the layer forming solution contains a curable material and It is preferable to include a polymer soluble in the curable material. Here, as the polymer to be blended for the purpose of continuously changing the refractive index from the central axis toward the outer peripheral surface, there is compatibility with the polymer produced from the above-mentioned radically polymerizable vinyl monomer. It is preferable to use good ones such as polymethylmethacrylate (n = 1.49) and polymethylmethacrylate copolymer (n = 1.47 to
1.50), poly-4-methylpentene-1 (n = 1.4
6), ethylene / vinyl acetate copolymer (n = 1.46 to
1.50), polycarbonate (n = 1.50 to 1.5)
7), polyvinylidene fluoride (n = 1.42), vinylidene fluoride / tetrafluoroethylene copolymer (n =
1.42 to 1.46), vinylidene fluoride / tetrafluoroethylene / hexafluoropropene copolymer (n =
1.40 to 1.46), fluorinated alkyl (meth) acrylate polymers and the like are preferable. Among these,
Polymethylmethacrylate is preferable because it has excellent transparency and has a high refractive index itself. Further, it is preferable that each layer constituting the filamentous material contains a polymer having substantially the same refractive index. In such a structure, the refractive index continuously changes from the central axis toward the outer peripheral surface. This is preferable because a rod lens can be easily obtained.

Further, in order to cure the filamentous material, it is preferable to add a thermosetting catalyst or a photocuring catalyst to each layer forming solution. Here, examples of the thermosetting catalyst include peroxide-based and azo-based catalysts. Further, as the photo-curing catalyst, benzophenone, benzoin alkyl ether, 4'-isopropyl-2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexylphenyl ketone, benzylmethyl ketal, 2,2-diethoxyacetophenone, chloro. Examples thereof include thioxanthone, thioxanthone compounds, benzophenone compounds, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, N-methyldiethanolamine and triethylamine.

The relationship between the molecular weights of the light absorbing agent and the curable material (monomer) is not particularly limited, but those exemplified as the curable material (monomer) are used. In the case of using the one exemplified as, since the light absorber has a much larger molecular weight than the curable material (monomer), the diffusion speed in the filament is much slower. Therefore, in the filamentous material, only the curable material can be diffused without substantially diffusing the light absorber, so that a rod lens having a substantially uniform radial concentration distribution of the light absorber can be obtained. It is possible and preferable.

Further, when the filamentous material is cured by thermal polymerization, it takes a long time for the polymerization and curing, so that the light absorbing agent may diffuse and the concentration of the light absorbing agent in the light absorbing layer may become uneven. In addition to that, there is a possibility that the light absorbing agent diffuses to a portion where the refractive index distribution is normal, the amount of transmitted light of the obtained rod lens decreases, and the light transmitting function is impaired. Therefore, when there is such a possibility, it is preferable to employ photopolymerization that can be polymerized and cured in a short time.

When the filamentous material is cured by photopolymerization, it can be cured by irradiating the uncured filamentous material with light such as ultraviolet rays.
A carbon arc lamp, a high-pressure mercury lamp, a medium-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a xenon lamp, a laser beam and the like, which generate light with a wavelength of 600 nm, are suitable. Further, in order to cure the filamentous material by photopolymerization as described above, it is necessary to transmit light for photopolymerization to each uncured layer. Therefore, when the filamentous material is cured by photopolymerization, it is preferable to use a light absorbing agent having a property of absorbing the transmitted light of the rod lens but not transmitting the polymerization light.

The heating and stretching treatment of the filamentous material after the curing treatment can be carried out by a known method. For example, the filamentous material after the curing treatment is fed into the heating furnace by the first nip roller at a predetermined speed, and the filamentous material that has passed through the heating furnace is fed by the second nip roller at a speed faster than that of the first nip roller. By heat-trapping, the heat-stretching treatment can be performed. In this step, the heating temperature of the filament is set according to the material of the rod lens and the like, but it is preferably Tg−20 ° C. or higher (where Tg is the glass transition temperature of the rod lens). The draw ratio is determined by the diameter of the uncured filamentous material and the desired rod lens diameter.
And the speed ratio of the second nip roller.

The relaxation treatment of the filamentous material after the heat drawing treatment can be carried out by a known method. For example, the filamentous material after the stretching treatment is fed into the heating furnace at a predetermined speed by the third nip roller, and the filamentous material that has passed through the heating furnace is fed by the fourth nip roller at a speed lower than that of the third nip roller. It is possible to carry out a relaxation treatment by picking up. In this step, the heating temperature of the filament is set according to the material of the rod lens and the like, but it is preferably Tg or higher. The relaxation ratio is determined by the diameter of the filamentous material after the stretching treatment and the desired diameter of the rod lens.
And the speed ratio of the fourth nip roller can be adjusted, but the relaxation treatment is performed so that the length of the filamentous material after the relaxation treatment is about 99 to 80% of the length of the filamentous material before the relaxation treatment. Is preferably applied. If the relaxation treatment is insufficient, the rod lens after manufacturing tends to shrink due to heat, which is not preferable. Further, if the relaxation treatment is excessive, the diameter of the rod lens may become uneven, which is not preferable.

According to the manufacturing method described above, the rod lens of the present invention can be easily manufactured, which is preferable.

[Structure of Lens Array] The lens array of the present invention comprises a plurality of plastic rod lenses of the present invention, which are arranged so that the central axis directions of the plastic rod lenses are substantially parallel to each other. At least one row of plastic rod lenses arranged in a direction perpendicular to the central axis direction is provided.

An embodiment of the lens array of the present invention will be described with reference to FIG. FIG. 1 is a partial schematic perspective view of an embodiment of the lens array of the present invention. As shown in FIG. 1, the lens array 10 according to the present embodiment has the above-described lens array 10 between a first substrate (lower substrate) 11 and a second substrate (upper substrate) 12 which are arranged to face each other. Rod lens 20
At least one row of rod lens rows 2 in which a plurality of rod lens rows 20 are arranged in a direction perpendicular to the central axis direction of the rod lenses 20 is arranged so that the central axis directions of the rod lenses 20 are substantially parallel to each other. It is roughly configured. Note that FIG. 1 illustrates a case where two rod lens rows 2 are provided. Further, in each rod lens 20, the light incident surface and the light emitting surface are indicated by reference numerals 21 and 22, respectively.

In the lens array 10 of this embodiment,
Adjacent rod lenses 20 may be arranged separately, but they are preferably arranged closely. Further, when the rod lens array 2 is provided in two or more stages, it is preferable that the rod lenses 20 are arranged in a bale stack. By adopting such a configuration, a larger number of rod lenses 20 can be arranged, so that the amount of light transmitted through the rod lenses 20 can be increased, which is preferable. When the adjacent rod lenses 20 are arranged apart from each other, it is preferable to arrange the rod lenses 20 so that the distances between the central axes of the adjacent rod lenses 20 are equal.

Further, the adjacent rod lenses 20 or the rod lenses 20 adjacent to the substrates 11 and 12 and the substrates 11 and 12 are adhered to each other via an adhesive agent containing a light shielding agent such as carbon black or dye. Preferably. With such a configuration, the rod lenses 20 adjacent to each other, or the substrates 11, 12 and the substrate 11,
The rod lens 20 adjacent to 12 can be fixed via an adhesive. Furthermore, among the light that has entered the lens array 10, it is between the adjacent rod lenses 20 and the substrate 1
Rod lenses 20 adjacent to 1 and 12 and substrates 11 and 12
Between the light incident between and and the incident surface 21 of the rod lens 20.
Before being emitted from the emission surface 22 and emitted from the side surface of the rod lens 20 and adjacent to the adjacent rod lens 20.
The light emitted between the substrates 11 and 12 and the rod lens 20 adjacent to the substrates 11 and 12 can be blocked. Therefore, between the adjacent rod lenses 20 or between the substrates 11 and 12 and the rod lenses 2 adjacent to the substrates 11 and 12.
Since it is possible to prevent light from being scattered between 0 and 0, it is possible to prevent flare light from being generated, and it is possible to provide the lens array 10 with high resolution.

In addition, between both sides of the lens array 10, between the first substrate 11 and the second substrate 12, rod lenses 20 fall from the substrate when the lens array 10 is manufactured. A stop plate 13 is attached to prevent this. In addition, the lens array 1 of the present embodiment
It is preferable that 0 has two or four rod lens rows 2. With such a configuration, it is possible to reduce unevenness in the amount of light and unevenness in the resolution of the lens array 10 and increase the amount of transmitted light (improve the brightness), which is preferable.

Further, the lens array 10 of this embodiment is L
When the rod lens 20 is mounted on an ED printer, it is preferable that the conjugate length of each rod lens 20 at 740 nm is about 12 mm or less. With such a configuration, the lens array 10 of the present embodiment is configured. The optical system of the LED printer equipped with can be miniaturized.

Further, in the lens array 10 of this embodiment, the standard deviation of the optical axis unevenness per lens length (Z ₀ ) of the rod lens 20 constituting the lens array 10 is 0.7.
It is preferable to arrange the rod lenses 20 so as to be less than (μm / Z ₀ ). With such a configuration, the lens array 10 according to the present embodiment can be preferably used for devices that require highly accurate optical characteristics. Further, when used for equipment requiring higher precision optical characteristics, the standard deviation of optical axis unevenness per lens length (Z ₀ ) of the rod lens 20 constituting the lens array 10 is 0.5 (μm). / Z ₀ ), the rod lenses 20 are more preferably arranged, and the lens length (Z ₀ ) of the rod lenses 20 forming the lens array 10 is preferably set.
It is further preferable to arrange the rod lenses 20 so that the standard deviation of the optical axis unevenness is 0.4 (μm / Z ₀ ) or less. That is, the higher the resolution of the mounted device is, the smaller the standard deviation of the optical axis unevenness of the rod lens 20 forming the lens array 10 becomes.
Are preferably arranged. The average value of the optical axis unevenness per lens length (Z ₀ ) of the rod lens 20 forming the lens array 10 is not particularly limited, but is generally about 1/10 or less of the rod lens length.

In the lens array 10 of the present embodiment, the variation of the optical axis per lens length between the adjacent rod lenses 20 is preferably 0.5% or less of the rod lens diameter, and 0.4%. It is more preferably at most 0.3%, particularly preferably at most 0.3%. With such a configuration, it is possible to prevent the performance such as resolution from locally deteriorating. In the present specification, the “variation of the optical axis per lens length between adjacent rod lenses” is defined by the difference in optical axis unevenness between the adjacent rod lenses 20.

Here, based on FIG. 2, measurement of optical axis unevenness per lens length of each rod lens forming the lens array and standard deviation of optical axis unevenness per lens length of the rod lens forming the lens array. The method will be described by taking the lens array 10 shown in FIG. FIG. 2 is a schematic perspective view showing a state in which the lens array 10 is installed in the optical axis unevenness measuring device 30 capable of measuring the optical axis unevenness of each rod lens forming the lens array 10.

As shown in FIG. 2, a device 30 for measuring optical axis spots
Is a movable stage 40 capable of installing the lens array 10 and adjusting the position of the lens array 10 in the X-axis direction (arrangement direction of rod lenses) and the Y-axis direction (normal direction of the substrate surface). And a He-Ne laser 31 installed on the light incident side of the lens array 10 and capable of emitting laser light toward the lens array 10,
A condenser lens 32 that condenses the light emitted from the Ne laser 31 and a condensing point that is installed on the light emission side of the lens array 10 and condenses the light emitted from the rod lens 20. It is roughly composed of an objective lens 37 and a two-dimensional sensor 38.

In the lens array 10, when the rod lenses 20 are ideally arranged, He-N
The optical axis of the light emitted from the e-laser 31 and the lens array 1
The He-Ne laser 31 and the lens array 10 are installed so that the optical axis (center axis) of the rod lens 20 forming 0 is parallel to each other.

By using the optical axis unevenness measuring device 30 having such a configuration, the optical axis unevenness of each rod lens 20 constituting the lens array 10 can be measured as follows. That is, the laser light emitted from the He-Ne laser 31 is once condensed by the condenser lens 32 at the object point (array focus on the laser side) 34 on the image plane (object plane) 33, and the lens array 10 is formed. The aperture is narrowed down so that the light is incident only on one rod lens 20 that constitutes it, and the light is incident on one rod lens 20.

The light incident on the light incident surface 21 of the rod lens 20 repeats total reflection in the rod lens 20, and then is emitted from the light emitting surface 22 and collected at the image forming point 36 on the image forming surface 35. Glow. Then, this condensing point is converted into an image forming point 39 on the two-dimensional sensor 38 by using the objective lens 37.
The image is formed on, and the image forming position is recorded. Then, from the obtained image-forming position, it is possible to calculate the optical axis unevenness per lens length of the rod lens 20 on which light is incident.

Here, FIG. 3 shows an example of the image forming position at the image forming point 36. FIG. 3 shows the image forming position in XY coordinates, and the image forming position (intersection point of the optical axis of the rod lens 20 and the image forming surface) when the rod lens 20 is ideally arranged is shown in FIG. Corresponds to the origin. In FIG. 3, the image forming position when the rod lens 20 is ideally arranged is a black circle, and the array position of the rod lens 20 is generated, and an example of the image forming position when the optical axis is deviated from the ideal position 6 Points and white circles are shown.

The deviation of the actual image forming position (white circle) from the ideal image forming position (black circle) is due to the deviation in the X-axis direction (arrangement direction of rod lenses) and the Y-axis direction (normal direction of the substrate surface). When divided into shifts and considered, it is the shift in the X-axis direction that has an influence when mounted on a printer or the like. Therefore, in this specification, "optical axis unevenness per lens length" is defined by "a value obtained by dividing the deviation between the actual image forming position and the ideal image forming position in the X axis direction by the lens length (mm)". Shall be done.
Then, based on this definition, from the obtained imaging position,
It is possible to calculate the optical axis unevenness per lens length of the rod lens 20 on which light is incident.

As described above, one rod lens 2
After measuring the optical axis unevenness per lens length of 0, the lens array 10 is moved by the moving stage 40, the same operation is performed for the other rod lenses 20, and these operations are repeated, whereby all the rod lenses are obtained. The measurement of the optical axis unevenness per lens length of 20 is completed. Here, in the present specification, “standard deviation of optical axis spots of rod lenses forming a lens array” is defined by “standard deviation of optical axis spots of all rod lenses forming a lens array”. To do. Therefore, all rod lenses 20
From the optical axis unevenness per lens length, the standard deviation of the optical axis unevenness of the rod lens 20 forming the lens array 10 can be calculated.

The lens array 10 of this embodiment is configured as described above, and since the lens array 10 of this embodiment is configured by using the rod lens 20 of the present invention, flare light and crosstalk light are used. It becomes a high resolution lens array that can largely remove both of the above. Also,
The optical system such as an LED printer obtained by using the lens array of the present invention can be downsized.

[Manufacturing Method of Lens Array] Next, a manufacturing method of the lens array 10 of the above-described embodiment will be described by taking the case where the rod lenses 20 are closely arranged as an example. The method of manufacturing the lens array 10 of the above embodiment is not limited to the one described below.

First, a plurality of rod lenses 20 are arranged in parallel so as to be in close contact with each other on an arrangement jig having a suction mechanism to form the first stage rod lens array 2. As an array jig having a suction mechanism, an array jig having a vacuum suction mechanism is suitable. As an array jig having a vacuum suction mechanism, a hole portion or a groove portion connected to a vacuum suction means such as a vacuum pump is used. A flat plate having such a structure that the rod lenses 20 can be arranged in parallel on the flat plate so as to be in close contact with each other by utilizing the suction force from the hole or groove connected to the vacuum suction means. It can be illustrated.

Next, a first substrate having one surface coated with an adhesive is prepared, and the first substrate 11 and the rod lens array 2 on the arrangement jig are adhered to the first substrate 11. The rod lens array 2 is transferred to the first substrate 11 by sticking it through an agent and peeling off the rod lens array 2 from the array jig. The adhesive used in this step is not particularly limited as long as it has an adhesive force capable of transferring the rod lens array 2 on the arrangement jig to the first substrate 11, and can be applied in a thin film form. An adhesive, a spray adhesive, a hot melt adhesive, etc. can be used. Further, as a method of applying the adhesive on the first substrate 11,
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.

Next, the stop plates 13 are attached to both sides of the first substrate 11 where the rod lens array 2 is not formed. Next, the rod lenses 20 are arranged on the rod lens array 2 on the first substrate 11 in a bale stack so that the rod lenses 20 are most closely packed to form the second stage rod lens array 2. By repeating the same operation, the rod lens array 2 having a desired number of steps is formed. Next, a second substrate 12 having an adhesive applied on one side is prepared, and the second substrate 12 and the rod lens array 2 on the uppermost stage are provided with the adhesive applied to the second substrate 12 therebetween. Stick it.

Next, the light incident side of the rod lens 20 sandwiched between the first substrate 11 and the second substrate 12 is treated with an uncured liquid adhesive containing a light shielding agent such as carbon black or dye. After the contact, by reducing the pressure on the light emitting side, the adhesive is filled between the adjacent rod lenses 20, or between the substrates 11, 12 and the rod lenses 20 adjacent to the substrates 11, 12. Then, the adhesive is cured. In addition, an adhesive is brought into contact with the light emitting side of the rod lens 20,
Also by reducing the pressure on the light incident side, similarly, between the adjacent rod lenses 20, or between the substrates 11, 12 and the substrate 11,
The gap between the rod lens 20 adjacent to 12 can be filled with an adhesive.

In this step, when a thermosetting adhesive is used as the adhesive, the adhesive can be hardened by heating. However, when the adhesive is hardened, the temperature is not more than Tg of the rod lens 20. , And the difference from Tg is 50
It is preferable to heat at a temperature within the range of ℃. Also,
As the adhesive, an ultraviolet curable adhesive or a reactive adhesive (epoxy or silicone adhesive) may be used. Further, since it is necessary to fill the adhesive in the minute gaps, it is preferable to use an adhesive having a low viscosity. Specifically, at the injection temperature of the adhesive, an adhesive having a viscosity of 1000 poise or less is used. It is preferable to use.

After the adhesive is hardened, the first substrate 11, the second substrate 12, and the rod lens 20 are cut into desired lengths, and both end faces (the light incident surface 21 and the light emitting surface) of each rod lens 20 are cut. 22) can be used as an imaging system by finishing it into a mirror surface using a diamond blade or the like.
The lens array 10 of the above embodiment can be manufactured.

According to the above manufacturing method, the lens array 10 of the above embodiment can be easily manufactured. In the above manufacturing method, the case where the rod lens array 2 of the first stage is formed on the array jig and then transferred onto the first substrate 11 has been described, but without using the array jig,
It is also possible to directly form the rod lens array 2 of the first stage on the first substrate 11. In this case, the rod lenses 20 may be arranged on the first substrate 11 after attaching the stopper plates 13 to both sides of the first substrate 11 in advance.

Further, although the case where the stopper plate 13 is attached to form the rod lens array 2 of the second and subsequent stages has been described, the rod lens 20 positioned at the side end of the rod lens array 2 of the second and subsequent stages is first described. The rod lenses 20 other than the above may be arranged in advance after being fixed to the substrate 11 of No. 1 in this case. In this case, the rod lenses 20 located at the side end portions of the rod lens row 2 of the second and subsequent stages are stopped. Since it can be made to function as, a stop plate is not necessary and the number of parts can be reduced, which is preferable.

Further, the rod lens 2 is formed on the first substrate 11.
Although the case where the second substrate 12 is attached after arranging 0s has been described, even if the first substrate 11 is attached after arranging the rod lenses 20 on the second substrate 12, It is possible to manufacture the lens array 10 of the above-described embodiment in the same manner by only reversing the substrate 11 and the second substrate 12.

[LED Printer] The LED printer of the present invention is constructed by using the lens array of the present invention. For example, an LED chip in which LEDs as light sources are arranged in an array, the lens array of the present invention, and The LED head is composed of a photosensitive drum, and a printing unit that transfers toner to paper based on optical information detected on the photosensitive drum. In the printer of the present invention, the printing method is not particularly limited, but the tandem method is preferable because high-speed color printing is possible.

Since the printer of the present invention is equipped with the lens array of the present invention, it is possible to suppress the print unevenness even with a high resolution of, for example, 600 dpi or more, and to have excellent printing characteristics. Further, the optical system is downsized, and the entire printer is downsized.

[0072]

EXAMPLES Next, examples and comparative examples according to the present invention will be described. In addition, in each of the examples and comparative examples, the refractive index distribution was measured by an interfero interference microscope manufactured by Carl Zeiss Co., Ltd. based on a known method. In addition, in the material of the rod lens, [η] represents the relative viscosity measured at 25 ° C. in methyl ethyl ketone (MEK).

(Example 1) <Preparation of plastic rod lens> 52 parts by mass of polymethylmethacrylate ([η] = 0.40), 35 parts by mass of benzyl methacrylate, 13 parts by mass of methylmethacrylate, 1-hydroxycyclohexylphenylketone 0 0.25 part by mass, hydroquinone 0.1 part by mass, 70
The mixture was heated and kneaded at 0 ° C. to obtain a first layer forming solution. 48 parts by mass of polymethyl methacrylate ([η] = 0.40), 10 parts by mass of benzyl methacrylate, 35 parts by mass of methyl methacrylate, 2,2,3,3,4,4,5,5
-Octafluoropentyl methacrylate 7 parts by mass, 1
0.25 parts by mass of hydroxycyclohexyl phenyl ketone and 0.1 parts by mass of hydroquinone were heated and kneaded at 70 ° C. to obtain a second layer forming solution.

Polymethylmethacrylate ([η] = 0.
40) 47 parts by mass, 30 parts by mass of methyl methacrylate,
2,2,3,3,4,4,5,5-octafluoropentyl methacrylate 23 parts by mass, 1-hydroxycyclohexyl phenyl ketone 0.25 parts by mass, hydroquinone 0.1 parts by mass, manufactured by Nippon Kayaku Co., Ltd. Dye CY-100.
014 parts by mass were heated and kneaded at 70 ° C. to obtain a third layer forming solution. Polymethylmethacrylate ([η] = 0.4
0) 40 parts by mass, 18 parts by mass of methyl methacrylate,
2,2,3,3,4,4,5,5-octafluoropentyl methacrylate 42 parts by mass, 1-hydroxycyclohexyl phenyl ketone 0.25 parts by mass, hydroquinone 0.1 parts by mass, manufactured by Nippon Kayaku Co., Ltd. Dye CY-100.
014 parts by mass were heated and kneaded at 70 ° C. to obtain a fourth layer forming solution. Polymethylmethacrylate ([η] = 0.4
0) 37 parts by mass, 4 parts by mass of methyl methacrylate, 2,
59 parts by weight of 2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 parts by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.1 parts by weight of hydroquinone were heated and kneaded at 70 ° C. A 5-layer forming solution was obtained.

That is, in Example 1, the third layer forming solution and the fourth layer forming solution were made to contain a dye having an absorption in the region of 600 nm to near infrared, and the other layer forming solutions were made of a dye. Each layer forming solution was prepared without containing. Further, the solutions for forming the first layer to the fifth layer were prepared so that the refractive index was gradually decreased after shaping.

Next, the obtained five kinds of layer forming solutions were used so that the central axis side was the first layer forming solution and the outer peripheral surface side was the fifth layer forming solution, using a concentric five layer composite nozzle. It was extruded and spun into a filament having a structure in which the first to fifth layers were laminated. The heating temperature of the composite spinning nozzle was 42 ° C., and the radius ratio of the first layer to the fifth layer was 36/37/20/6 /.
The fiber was spun so that the number became 1.

Next, after passing through an interdiffusion treatment section having a length of 30 cm and subjecting the obtained filamentous material to interdiffusion treatment,
Each layer was cured by irradiating the filamentous material with light by passing 18 chemical lamps of 120 cm in length and 40 W through a center of a light irradiation portion arranged in a circle at equal intervals. In addition,
The nitrogen flow rate in the mutual diffusion treatment section was 72 L / min. Next, with a nip roller, 220 cm / min
The plastic rod lens of the present invention was obtained by picking up at a speed of, and finally cutting to a length of 200 mm.

In the obtained rod lens, the radius r of the cross section is 0.30 mm, the refractive index of the central axis is 1.506,
The refractive index distribution in the range of 0.22r to 0.78r from the central axis can be approximated by the above formula (1), and the refractive index distribution constant g for light having a wavelength of 740nm was 0.87mm- ¹ . Also, 0.73r to 0.9 from the center of the rod lens
In the range of 9r, the light absorption layer containing the dye substantially uniformly,
It was formed with a thickness of about 78 μm.

<Production of Lens Array> A plurality of obtained rod lenses were used to obtain a lens array of the present invention as described in the above embodiment. In addition, the adjacent rod lenses were arranged in two layers in a bale stack so as to be in close contact with each other to obtain a lens array of the present invention having two rows of rod lens rows. The rod lens length was 4.2 mm.
Further, as the first substrate and the second substrate, substrates made of phenol resin and having a thickness of 1.0 mm were used, and as an adhesive, Epiform (manufactured by Somar) containing 2% by mass of carbon black was used and stopped. As a plate, made of black resin plate,
The width was 4 mm, and the end portion on the side in contact with the rod lens was cut at an angle of 60 degrees.

The conjugate length of the rod lens constituting the obtained lens array for light having a wavelength of 740 nm is 9.
9 mm, MT of the obtained lens array is 12 Lp / mm
The average value of F (moduration transfer function) is 70%
Met. The standard deviation of the optical axis unevenness of the rod lenses forming the obtained lens array is 0.37 μm / mm on the upper side (second substrate side) and 0.38 μm on the lower side (first substrate side). / Mm. Also, the maximum value of the variation of the optical axis per lens length between adjacent rod lenses is
The diameter was 0.29% of the rod lens diameter.

<Production of Printer> Using the lens array thus obtained, an LED printer of the present invention (LED emission wavelength 740 nm) having a resolution of 600 dpi was produced. When a 600 dpi test chart was printed with this printer, good printing was obtained with no printing spots and excellent gradation characteristics.

(Example 2) <Production of plastic rod lens> The same procedure as in Example 1 was carried out except that 0.014 parts by mass of dye CY-10 manufactured by Nippon Kayaku Co., Ltd. was added to the solution for forming the fifth layer. The rod lens of the present invention was obtained. That is, in the second embodiment, the third
The layer-forming solution, the fourth layer-forming solution, the fifth layer-forming solution contains a dye having absorption in the region of 600 nm to near-infrared, and the other layer-forming solutions do not contain a dye,
A solution for forming each layer was prepared to obtain a plastic rod lens. In the obtained rod lens, the radius r of the cross section
Is 0.30 mm, the central axis has a refractive index of 1.506, and the refractive index distribution in the range of 0.22 r to 0.78 r from the central axis can be approximated by the above formula (1), and the refractive index for light having a wavelength of 740 nm is The distribution constant g was 0.87 mm ⁻¹ . Further, the light absorption layer containing the dye substantially uniformly was formed in a thickness of about 81 μm in the range of 0.73 r to r from the center axis of the rod lens.

<Production of Lens Array> Using the obtained rod lens, a lens array of the present invention having two stages of rod lens rows was produced in the same manner as in Example 1. 740 nm of the rod lens constituting the obtained lens array
The conjugate length for light of wavelength is 9.9 mm, the average value of MTF of 12 Lp / mm of the obtained lens array is 71%.
Met. The standard deviation of the optical axis unevenness of the rod lenses constituting the obtained lens array is 0.37 μm on the upper side.
/ Mm, and the lower side was 0.37 μm / mm. Also,
The maximum value of the variation of the optical axis per rod lens length between adjacent rod lenses was 0.29% of the rod lens diameter.

<Production of Printer> Using the lens array thus obtained, an LED printer of the present invention having a resolution of 600 dpi was produced in the same manner as in Example 1. 6 with this printer
When a test chart of 00 dpi was printed, no printing spots were found, excellent gradation characteristics were obtained, and good printing was obtained.

Comparative Example <Production of Plastic Rod Lens> A plastic rod lens was obtained in the same manner as in Example 1 except that the dye for forming the third layer was not added. That is, in the comparative example, only the fourth layer forming solution contains a dye having an absorption in the 600 nm to near infrared region, the other layer forming solutions do not contain a dye, and each layer forming solution is It prepared and obtained the plastic rod lens. In the obtained rod lens, the radius r of the cross section was 0.30 mm, the refractive index of the central axis was 1.506, and the radius r from the central axis was 0.22 r.
The refractive index distribution in the range of 0.78r can be approximated by the above formula (1), and the refractive index distribution constant g for light having a wavelength of 740 nm was 0.87 mm ^-1 . Further, a light absorbing layer containing the dye substantially uniformly was formed in a thickness of about 18 μm in the range of 0.93r to 0.99r from the central axis of the rod lens.

<Production of Lens Array> Using the obtained rod lens, a lens array having two stages of rod lens rows was obtained in the same manner as in Example 1. The conjugate length of the rod lens constituting the obtained lens array for light having a wavelength of 740 nm is 9.9 mm, and 1 of the obtained lens array.
The average value of MTF of 2 Lp / mm was 40%. The standard deviation of the optical axis unevenness of the obtained lens array is 0.38 μm / mm on the upper side and 0.37 μm / mm on the lower side.
Met. Further, the maximum value of the variation of the optical axis per rod lens length between adjacent rod lenses was 0.30% of the rod lens diameter.

<Production of Printer> Using the lens array thus obtained, an LED printer (LED emission wavelength 740 nm) having a resolution of 600 dpi was produced in the same manner as in Example 1. When a 600 dpi test chart was printed with this printer, uneven printing was observed and the gradation characteristics of printing were not good.

From the results of Examples 1 and 2 and the Comparative Example, a plastic rod lens having a light absorbing layer having a thickness of 50 μm or more, which absorbs light having a wavelength of 740 nm, is located outside the central axis by 0.6 r or more. It has been found that a high resolution lens array can be provided by using the LED array, and an LED printer having excellent printing characteristics can be provided by using the obtained lens array.

[0089]

As described above in detail, the plast of the present invention is used.
In the rod rod lens, 0.6r or more from the center axis
Range, at least some of the transmitted light of the rod lens
A thickness of 50 μm or more containing a light absorber that absorbs light
With a light absorption layer of about 740 nm
The refractive index distribution constant g of is 0.7 mm^-1≤ g ≤ 2.0 mm
^-1And g · r satisfies 0.2 ≦ g · r ≦ 0.3
Since the configuration is adopted, the rod lens of the present invention can be used.
This greatly removes both flare light and crosstalk light.
Can be removed, especially applied to LED printer applications
Can provide high resolution lens array if
It Further, the lens array of the present invention is a plastic array of the present invention.
Since it is constructed using a Kukrod lens,
It is possible to significantly remove flare light and crosstalk light.
High resolution especially when applied to LED printer applications
Lens array. In addition, the lens array of the present invention
By providing it, it has excellent printing characteristics even with high resolution.
An LED printer can be provided.

[Brief description of drawings]

FIG. 1 is a partial schematic perspective view of an embodiment of a lens array of the present invention.

FIG. 2 is a diagram for explaining a method of measuring optical axis unevenness of each rod lens forming a lens array.

FIG. 3 is a diagram for explaining a method of measuring the optical axis unevenness of each rod lens forming the lens array.

[Explanation of symbols] 10 lens array 20 plastic rod lens (rod lens) 2 rod lens row 11 First substrate 12 Second substrate 13 Stop plate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 27/18 G02B 27/18 A // B41J 2/44 B41J 3/21 L 2/45 2/455 ( 72) Inventor Yoshihiko Hoshide 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Inventor Teruta Ishimaru 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. F-term in Technical Research Laboratory (reference) 2C162 AE28 AE47 FA17 FA45 FA50 2H046 AA06 AD05 AZ02 2H048 CA04 CA12 CA14 CA17 CA24 2H050 AC26 AC72 AC74

Claims (7)

[Claims] 1. A rod lens, which is circular in cross section and whose refractive index continuously decreases from the central axis toward the outer peripheral surface, has a cross section radius r of 0.2 to 0.4 mm, and at least the center. The refractive index distribution in the range of 0.3r to 0.7r from the axis is approximated by a quadratic curve defined by the following formula (1), and the refractive index distribution of the rod lens is in the range of 0.6r or more outside from the central axis. A light absorbing layer having a thickness of 50 μm or more containing a light absorbing agent that absorbs at least a part of the transmitted light, and a refractive index distribution constant g for a wavelength of 740 nm is 0.
7 mm ^-1 ≤ g ≤ 2.0 mm ^-1 and g · r is 0.2
A rod lens satisfying ≦ g · r ≦ 0.3. _{n (L) = n 0 {} 1- (g 2/2) L 2} ··· (1) ( In the formula (1), n ₀ is the refractive index of the central axis of the rod lens, L is the rod lens From the center axis of (0 ≤ L ≤
r) and g represent the refractive index distribution constant of the rod lens, and n (L) represents the refractive index at the position of the distance L from the central axis of the rod lens. ) 2. The rod lens according to claim 1, wherein the thickness of the light absorption layer is 100 μm or less. 3. The rod lens according to claim 1, wherein the light absorber absorbs light in at least a part of a wavelength range of 500 to 900 nm. 4. The effective diameter R of the rod lens for light having a wavelength of 740 nm is from 0.6r to 0.8r.
The rod lens according to item. 5. Any one of claims 1 to 4
The rod lens array in which a plurality of rod lenses according to the item is arranged in a direction perpendicular to the central axis direction of the rod lenses such that the central axis directions of the rod lenses are substantially parallel to each other is at least 1 A lens array comprising a plurality of steps, wherein the standard deviation of the optical axis unevenness per unit rod lens length (Z ₀ ) of the rod lens is less than 0.7 (μm / Z ₀ ). 6. The lens array according to claim 5, wherein the rod lens array comprises two or four stages. 7. An LED printer comprising the lens array according to claim 5 or 6.