WO2014098085A1

WO2014098085A1 - Rod lens array, and manufacturing method therefor

Info

Publication number: WO2014098085A1
Application number: PCT/JP2013/083772
Authority: WO
Inventors: 成史北村; 菊枝入江; 川原田　泰
Original assignee: 三菱レイヨン株式会社
Priority date: 2012-12-17
Filing date: 2013-12-17
Publication date: 2014-06-26
Also published as: TW201432320A; JPWO2014098085A1

Abstract

Provided are a rod lens array and a manufacturing method therefor, which enable deformation of rod lenses and/or variation in the refractive index of the rod lenses to be suppressed, even if an adhesive agent has contracted during curing. This rod lens array (1), in which a plurality of rod lenses (9) are fixed between two substrates (3, 5) using an adhesive agent (7), is provided with intersubstrate-rod lens buffer layers (11) between the rod lenses (9) and the two substrates (3, 5) severally.

Description

Rod lens array and manufacturing method thereof

The present invention relates to a rod lens array and a manufacturing method thereof, and more particularly to a rod lens array in which a plurality of rod lenses are arranged between substrates and a manufacturing method thereof.

Conventionally, a cylindrical rod lens whose both end surfaces are mirror-polished is known as one of microlenses. In addition to being used alone, such a rod lens is in the form of a rod lens array in which a large number of rod lenses are arranged and integrated, and is used in a copying machine, facsimile, scanner, hand scanner, etc. As a writing device in an apparatus such as an LED printer using an LED (light emitting diode) as a light source, a liquid crystal printer using a liquid crystal element, or an EL printer using an EL element.

In such a rod lens array, two substrates are prepared, an adhesive is applied on one substrate, a rod lens is arranged thereon, and then the other substrate having an adhesive applied on the surface is arranged. It is manufactured by a method of overlapping (Patent Document 1).

Japanese Patent No. 4778220

In general, the rod lens array as described above is configured such that the rod lens is sandwiched between the two substrates so that the rod lens is in contact with the two substrates in order to eliminate the uneven arrangement of the rod lenses. .

However, if the rod lens is sandwiched so that the rod lens comes into contact with the two substrates in this way, the substrate is pulled in the direction of compressing the rod lens due to the shrinkage of the adhesive when the adhesive is cured, and the lens Unnecessary force will be applied. As a result, the lens is deformed or the refractive index of the lens is changed. As a result, anisotropy occurs in the optical performance of the rod lens, and the optical performance as the array deteriorates. It was. Furthermore, when the durability test of the rod lens is performed in a high temperature and high humidity environment, there is a problem that the shrinkage of the adhesive proceeds and the optical performance is further deteriorated. In recent years, LED printers and copiers have become more precise, faster printing speeds, and smaller devices, and the required performance required for rod lens arrays has also become higher. However, the rod lens array whose optical performance is lowered due to shrinkage of the adhesive cannot satisfy the required performance.

Accordingly, the present invention has been made to solve the above-described problems, and a rod lens array capable of satisfying the required advanced performance even when the adhesive shrinks upon curing, and a method for manufacturing the same. The purpose is to provide.

In order to solve the above-described problems, according to the present invention, there is provided a rod lens array in which a plurality of rod lenses are arranged between two substrates so that the central axes of the rod lenses are substantially parallel to each other. And
(1) TC difference ΔTC ≦ 1.0 mm between the main scanning direction and the sub-scanning direction before performing the durability test,
(2) ΔTC ≦ 1.0 mm after performing a durability test for 500 hours at a temperature of 60 ° C. and a humidity of 90%,
(3) MTFave ≧ 70% @ 6Lp / mm at BestTC,
A rod lens array is provided.
(Here, BestTC is the average TC of the TC in the main scanning direction and the TC in the sub-scanning direction.)

According to another aspect of the present invention, in addition to the above, there is provided a rod lens array characterized by the depth of focus DOF ≧ 0.9 mm at BestTC.

According to another aspect of the present invention, a rod lens array that satisfies the following four requirements is provided.
(1) ΔTC ≦ 0.1 mm before endurance test
(2) ΔTC ≦ 0.1 mm after a 500 hour durability test at a temperature of 60 ° C. and a humidity of 90%
(3) MTFave ≧ 80% @ 12Lp / mm at BestTC
(4) MTCvv ≦ 3% at BestTC @ 12 Lp / mm

According to another aspect of the present invention, there is provided a rod lens array in which a plurality of rod lenses are arranged between two substrates so that the central axes of the rod lenses are substantially parallel to each other. A rod lens array is provided, wherein a buffer layer having a thickness of more than 5 μm is provided between the lens and the two substrates, respectively, between the substrate and the rod lens.

According to another aspect of the invention,
Providing a buffer layer on each of the two substrates;
An application step of applying an adhesive on the buffer layer formed on the two substrates;
An arrangement step of arranging rod lenses on an adhesive applied to any one of the two substrates;
An arrangement step of disposing the other substrate on the rod lens so that the adhesive applied to the other substrate of the two substrates is adhered to the rod lens;
There is provided a method of manufacturing a rod lens array, comprising: a curing step of curing the adhesive applied to the two substrates to form a rod lens array.

As a means for solving the above problems, the present invention includes the following aspects.

The rod lens array wherein the thickness of the buffer layer between the substrate and the rod lens is 10 μm or more.

The thickness of the buffer layer between the substrate and the rod lens is a rod lens array having a thickness of 15 μm or more.

Rod lens array in which a buffer layer between rod lenses is provided between adjacent rod lenses.

The rod lens array has a buffer layer thickness between 5 μm and 30 μm.

A rod lens array in which the buffer layer between the rod lenses has a thickness of 10 μm or more and 20 μm or less.

The buffer layer between the substrate and the rod lens is a rod lens array satisfying hardness (JIS 6253): A50 to A95 and tensile strength (JIS 6251): 1 MPa to 100 MPa.

The rod lens buffer layer has a hardness (JIS 6253): A50 to A95 and a tensile strength (JIS 6251): 1 MPa to 100 MPa.

The buffer layer between the substrate and the rod lens is a rod lens array formed by interposing the adhesive between the substrate and the rod lens.

The rod lens array is formed by interposing the adhesive between the rod lenses adjacent to each other.

A rod lens array in which the rod lens is a plastic rod lens.

Rod lens array satisfying the following four requirements (1) 0.06 ≦ numerical aperture NA ≦ 0.4
(2) 0.3 mm ⁻¹ ≦ refractive index distribution constant g ≦ 1.0 mm ⁻¹
(3) 0.1 mm ≦ lens effective radius re ≦ 0.4 mm
(4) 0.70 ≦ 2re / P (effective lens radius / arrangement pitch)

A first application step of applying an adhesive on each of the two substrates;
A first curing step of curing the adhesive applied on the two substrates;
A second application step of further applying an adhesive on the adhesive cured on the two substrates;
An arrangement step of arranging rod lenses on an adhesive applied to any one of the two substrates;
An arrangement step of disposing the other substrate on the rod lens so that the adhesive applied to the other substrate of the two substrates is adhered to the rod lens;
A second curing step of curing the adhesive applied to the two substrates to form a rod lens array;
A method for manufacturing a rod lens array, comprising:

In the first application step, the adhesive is applied so that the thickness of the adhesive after the first curing step exceeds 5 μm.

In the arranging step, the rod lenses are arranged so that an interval between the rod lenses is 5 μm or more and 30 μm or less, and in the second application step, an interval between the rod lenses of the rod lens array is an adhesive. The method for manufacturing a rod lens array according to claim 1, wherein the adhesive is filled with an amount of the adhesive.

As described above, according to the present invention, even when the adhesive shrinks during curing, the required advanced performance can be satisfied.

It is a perspective view showing a rod lens array according to an embodiment of the present invention. It is a perspective view which shows the process for manufacturing the rod lens array by embodiment of this invention. It is a graph which shows the conjugate length (TC) of the rod lens array by a comparative example, and its time-dependent change. It is a graph which shows the conjugate length (TC) of the rod lens array by a comparative example, and its time-dependent change. It is a graph which shows the conjugate length (TC) of the rod lens array by a comparative example, and its time-dependent change. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. 4 is a graph illustrating a conjugate length (TC) of a rod lens array according to an embodiment of the present invention and its change with time. It is a graph which shows the relationship between the difference (DELTA) TC of conjugate length TC in the main scanning direction of the rod lens array by the Example of this invention and a comparative example, and a subscanning direction, and a buffer layer thickness. The difference ΔTC between the conjugate length TC in the main scanning direction and the sub-scanning direction after the rod lens array according to the example of the present invention and the comparative example was treated for 500 h under high temperature and high humidity conditions of 60 ° C. and 90% RH, and the buffer layer It is a graph which shows the relationship with thickness. It is a cross-sectional photograph of the rod lens array by a comparative example, and the change of the lattice image before and after an endurance test. 6 is a cross-sectional photograph of a rod lens array according to an embodiment of the present invention and a change in a lattice image before and after a durability test. 6 is a cross-sectional photograph of a rod lens array according to an embodiment of the present invention and a change in a lattice image before and after a durability test.

Hereinafter, a rod lens array 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a rod lens array.

(Rod lens)
The rod lens according to the present invention will be described with reference to FIG. First, as shown in FIG. 1, the rod lens array 1 includes two substrates 3, 5, a substrate-rod lens buffer layer 11, a rod lens buffer layer 13, and an adhesive 7. A plurality of rod lenses 9 fixed between the substrates 3 and 5 through a buffer layer between the substrate and rod lenses. In the rod lens array 1 according to the present embodiment, a plurality of the rod lenses 9 are arranged in a line between the two substrates 3 and 5 so that the central axes of the rod lenses 9 are substantially parallel to each other. Has been placed.

As the substrates 3 and 5, plates such as bakelite (phenol resin), ABS resin, epoxy resin, and acrylic resin containing a light shielding agent such as carbon black and dye are used.

Moreover, as shown in FIG. 1, the board | substrates 3 and 5 may use a plate-shaped thing, and the U-shape or V-shape used as the standard for arrange | positioning a rod lens on the surface at fixed intervals. A groove having a shape or the like may be provided.

The material of the substrates 3 and 5 is not particularly limited, but is preferably a material that can be easily processed in the process of manufacturing the rod lens array 1. As the material for the substrate, various thermoplastic resins, various thermosetting resins, and the like are preferably used, and acrylic resins, ABS resins, polyimide resins, liquid crystal polymers, epoxy resins, and the like are more preferable. Further, fibers and paper may be used as the base material and the reinforcing material of the substrate, and a release agent, a dye, a pigment, and the like may be added to the substrate.

The rod lens array in the rod lens array may be one in which rod lenses are arranged between two substrates as illustrated in FIG. 1, or two or more rows of rod lenses are stacked between two substrates. May be arranged. In a configuration in which two or more rod lenses are stacked, it is preferable that the rod lenses are arranged so as to be shifted in the arrangement direction by a distance corresponding to the radius of the rod lens so that a gap between adjacent rod lens rows is minimized. A surface protective layer may be provided on the end surface of the rod lens 9 for the purpose of preventing dust adhesion and damage. Examples of the surface protective layer include a protective layer made of an existing UV curable hard coating agent, a cover glass installed on the lens end face, and the like. In the following, an example in which a plurality of rod lenses 9 are arranged in a row between two substrates 3 and 5 will be described.

The rod lenses 9 have a cylindrical shape and are arranged in parallel at equal intervals. The rod lens 9 is preferably a plastic or glass rod lens of a refractive index distribution (GI) type in which the refractive index continuously decreases from the center of the circular cross section toward the outer periphery. More specifically, the rod lens used in the present embodiment has a refractive index n distribution in the range of 0.2r to 0.9r (where r is the radius of the cross section) from the central axis. It is a lens approximated by a quadratic curve defined by
_{n (L) = n 0 {} 1- (g 2/2) L 2} ... (1)
(N (L) is the refractive index n _{0 at} the position of the radial distance L from the central axis of the rod lens, the refractive index at the radial central axis of the rod lens, and L is the radial distance from the radial center of the rod lens. (0 ≦ L ≦ r), g represents the refractive index distribution constant of the rod lens.

The refractive index distribution constant g is a second-order coefficient related to the position L of the refractive index distribution curve approximated by the above formula, and is a constant that defines the slope of the refractive index distribution curve. That is, the larger the refractive index distribution constant g, the steeper shape of the refractive index distribution curve, which means that the refractive index decreases more rapidly from the central axis toward the outer peripheral surface in the rod lens. In the rod lens used in the present invention, the value of the refractive index n _{0 at} the radial center is not particularly limited, but preferably satisfies the following formula (2).
1.45 ≦ n ₀ ≦ 1.65 (2)

If the refractive index n ₀ is in this range, the choices of materials that can be used for the rod lens are widened, so that a rod lens having a favorable refractive index distribution and excellent transparency can be obtained.

The rod lens and rod lens array used in this embodiment preferably satisfy the following requirements.
0.06 ≦ Numerical aperture NA ≦ 0.4
0.3 mm <-1 ≦ refractive index distribution constant g ≦ 1.0 mm −1
0.1 mm ≤ effective lens radius re ≤ 0.4 mm
0.70 ≦ 2re / P (effective lens radius / arrangement pitch)

By setting the numerical aperture NA ≦ 0.4, the depth of focus DOF having an inversely proportional relationship with the numerical aperture NA can be increased. From the viewpoint of increasing the depth of focus DOF, the upper limit value of the numerical aperture NA is preferably 0.15 or less. Further, since the light quantity has a proportional relationship with the square of the numerical aperture NA, from the viewpoint of increasing the light quantity, the lower limit value of the numerical aperture NA is preferably 0.06 or more, and more preferably 0.1 or more. preferable.

By setting the refractive index distribution constant g to 1.0 mm ⁻¹ or less, the numerical aperture NA represented by the product of n ₀ × g × re can be designed to be small, thereby increasing the depth of focus. . Furthermore, by setting the refractive index distribution constant g to 0.3 mm ⁻¹ or more, the working distance L ₀ does not become too long and the entire apparatus can be miniaturized, and the product of the formula n ₀ × g × re The numerical aperture NA expressed can be designed to be large, thereby increasing the amount of light. The lower limit value of the refractive index distribution constant g is more preferably 0.35 mm ⁻¹ or more, and the upper limit value of the refractive index distribution constant g is more preferably 0.95 mm ⁻¹ or less.

The radius r of the rod lens used in the present invention preferably satisfies the following formula (3).
0.1 mm ≦ r ≦ 0.4 mm (3)

When the radius r is 0.4 mm or less, the numerical aperture NA can be designed to be small, and the depth of focus can be increased accordingly. By setting the radius r to 0.1 mm or more, workability and handleability when manufacturing the rod lens array of the present invention are improved. The lower limit value of the radius r is preferably 0.15 mm or more.

In addition, by setting the effective radius re, which is the radius of the effective portion that performs the lens action, to 0.4 mm or less, the numerical aperture NA expressed by the product of the formula n ₀ × g × re can be designed to be small. This can increase the depth of focus. By configuring the effective radius re to be 0.1 mm or more, when configuring the rod lens array of the present invention and an optical system such as an image sensor incorporating the rod lens array, the optical axis of the rod lens and the light source or It is difficult for the optical axis to be shifted from the light receiving sensor, and it is possible to suppress a decrease in optical characteristics associated therewith. In addition, by setting the effective radius re to be 0.1 mm or more, the numerical aperture NA expressed by the product of the formula n ₀ × g × re can be designed to be large, thereby increasing the amount of light. A preferable range of the effective radius re is 0.15 mm or more and 0.35 mm or less, and more preferably 0.16 or more and 0.30 or less. The radius r and the effective radius re may be the same value, but preferably satisfy the relationship of the equation re ≦ r, and more preferably satisfy the relationship of the equation 0.70r ≦ re ≦ r.

The arrangement pitch P is the distance between the centers of adjacent rod lenses in the rod lens array, and the value 2re is the diameter of the effective portion that performs the lens action of the rod lens used. A preferable range of the value 2re / P is 0.7 or more and 1 or less, and a more preferable range is 0.85 or more and 1 or less.

When manufacturing the rod lens array 1 by arranging the rod lenses 9, the clearance between the rod lenses 9 is improved for the purpose of improving the alignment accuracy, removing crosstalk light, and providing the inter-rod lens buffer layer 13. Are arranged. The arrangement pitch P is larger than the diameter 2r of the rod lens 9 and the diameter 2re of the effective portion.

As a result, in the lens array, the effective portion that performs the lens action exists in “jumping”. When an image is formed by a plurality of rod lenses, on the image plane of the rod lens array, due to lens aberration, the position between the optical axes of adjacent lenses is more than the position on the optical axis of each lens. However, the depth of focus tends to be narrow. For this reason, if there is an “excessive” effective portion that performs the lens action in the lens array, the depth of focus tends to increase. In addition, if there is an effective portion that performs the lens action in “jumping”, the ratio of the effective portion that performs the lens action is reduced, so that the amount of light is likely to be small and the unevenness in the amount of light is likely to be large. On the other hand, in the rod lens array 1, the ratio 2re / P between the diameter 2re of the effective portion of the rod lens 9 and the center-to-center distance P of the adjacent rod lenses 9 in the rod lens array is 0.70 ≦ 2re / By setting P ≦ 1, the depth of focus spot can be reduced, the light amount can be increased, and the light amount spot can be further reduced.

The rod lens array 1 includes a substrate-rod lens buffer layer 11 between the rod lens 9 and the substrates 3, 5 so that the substrates 3, 5 and the rod lens 9 do not come into contact with each other. By providing the buffer layer 11 between the substrate and the rod lens, even when the adhesive 7 is solidified and contracts and the substrates 3 and 5 are deformed, the deformation of the substrates 3 and 5 is not transmitted to the rod lens 9. be able to. The buffer layer 11 between the substrate and rod lens is provided between all the rod lenses 9 and the substrates 3 and 5, so that the rod lens 9 is not in contact with the substrates 3 and 5. .

The material of the buffer layer 11 between the substrate and the rod lens is not particularly limited as long as the hardness defined by JIS6253 is A50 to A95 and the tensile strength defined by JIS6251 satisfies 1 MPa to 100 MPa. As a material for forming the buffer layer 11 between the substrate and the rod lens, a urethane polymer, an epoxy polymer, a silicon polymer, an EVA polymer, a rubber polymer, or the like can be used. Maintaining the workability of machining such as cutting, cutting and polishing in the process of manufacturing the rod lens array 1 by setting the hardness of the buffer layer 11 between the substrate and the rod lens to A50 or more and the tensile strength to 1 MPa or more. Can do. Further, by setting the hardness to A95 or less and the tensile strength of 100 MPa or less, even when the adhesive 7 is solidified and contracts, the force acting on the rod lens 9 can be suppressed, and the deformation of the rod lens 9 can be suppressed. Or a change in refractive index can be suppressed. The inter-rod lens buffer layer 11 preferably has a hardness of A55 or more and A90 or less, a tensile strength of 2 MPa or more and 50 MPa or less, a hardness of A60 or more and A85 or less, and a tensile strength of 3 MPa or more and 20 MPa or less. Is more preferable. The buffer layer 11 between the substrate and rod lens may be formed by interposing a layer of adhesive 7 (adhesive layer) between the substrates 3 and 5 and the rod lens 9. Since the buffer layer 11 between the substrate and the rod lens is formed of an adhesive layer, the periphery of the rod lens 9 can be made of a single material. Therefore, when the adhesive 7 contracts, it acts on the rod lens 9. Anisotropic force can be reduced.

As the adhesive 7, the rod lens 9 and the substrates 3 and 5, the rod lens 9 and the substrate-rod lens buffer layer 11, the rod lens 9 and the rod lens buffer layer 13, and the

rod lenses

9 and 9 can be fixed to each other. There is no particular limitation as long as it has an adhesive strength of. As the adhesive 7, a cyanoacrylic adhesive, a urethane adhesive, an epoxy adhesive, a silicone adhesive, an EVA adhesive, a rubber adhesive, or the like can be used. As the adhesive 7, an adhesive that can be applied in a thin film, a spray-type adhesive, a hot-melt-type adhesive, or the like can be used. Among these, urethane adhesives, epoxy adhesives, silicone adhesives, EVA adhesives, and the like are preferable. As a method for applying the adhesive 7 to the substrates 3 and 5 and the rod lens 9, 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.

Further, the buffer layer 11 between the substrate and the rod lens may be composed only of the adhesive 7 layer, or may have a cushioning layer other than the adhesive layer. When the substrate-rod lens buffer layer 11 has a cushion layer in addition to the adhesive 7 layer, the cushion layer may be a urethane polymer, an epoxy polymer, a silicon polymer, an EVA polymer. In addition, a cushion layer made of a rubber polymer or the like can be used.

The ratio of the thickness of the adhesive layer and the cushion layer is not particularly limited, and can be appropriately selected according to the type of the rod lens array, the thickness of the buffer layer, and the like. Further, the arrangement of the adhesive layer and the cushion layer is not particularly limited. For example, a layer that adheres to the substrate and a layer that adheres to the rod lens is used as an adhesive layer, and a cushion layer is provided between these adhesive layers. be able to.

Further, as described above, the inter-rod lens buffer layer 13 is provided between the adjacent rod lenses 9 so that the adjacent rod lenses 9 do not come into contact with each other. The inter-rod lens buffer layer 13 can prevent the rod lens 9 from deforming due to the adhesive 7 solidifying and contracting, and the adjacent rod lenses 9 interfering with each other. When there is no buffer layer between rod lenses as in the past, the adhesive 7 is solidified and contracts, and adjacent rod lenses interfere with each other. Therefore, unnecessary force acts in the direction of compressing the rod lens, and the lens is deformed. Alternatively, the refractive index of the lens changes, and as a result, anisotropy occurs in the optical performance of the rod lens, and the resolution decreases. On the other hand, by providing the inter-rod lens buffer layer 13 between the adjacent rod lenses 9, it is possible to prevent unnecessary force from acting on the rod lens 9 when the adhesive 7 is solidified and contracts. it can.

The thickness of the inter-rod lens buffer layer 13 is preferably 5 to 30 μm, and more preferably 10 to 20 μm. By setting the thickness of the inter-rod lens buffer layer 13 to 5 μm or more, deformation of the rod lens can be sufficiently suppressed. The reason why the thickness of the inter-rod lens buffer layer 13 is set to 30 μm or less is that a dramatic improvement in the effect is not recognized even if the thickness is increased beyond that.

The material composing the inter-rod lens buffer layer 13 is not particularly limited as long as the material has a hardness defined by JIS6253 of A50 to A95 and a tensile strength defined by JIS6251 of 1 MPa to 100 MPa. As a material constituting the inter-rod lens buffer layer 13, urethane polymer, epoxy polymer, silicon polymer, EVA polymer, rubber polymer, or the like can be used. By setting the hardness of the inter-rod lens buffer layer 13 to A50 or more and the tensile strength to 1 MPa or more, it is possible to maintain the workability of machining such as cutting, cutting and polishing in the process of manufacturing the rod lens array 1. . Further, by setting the hardness of the inter-rod lens buffer layer 13 to A95 or less and a tensile strength of 100 MPa or less, the force acting on the rod lens 9 when the adhesive 7 is solidified and contracted can be reduced. The deformation of the lens 9 or the change in the refractive index of the rod lens 9 can be suppressed. The inter-rod lens buffer layer 13 preferably has a hardness of A55 or more and A90 or less, a tensile strength of 2 MPa or more and 50 MPa or less, a hardness of A60 or more and A85 or less, and a tensile strength of 3 MPa or more and 20 PMa or less. .

The inter-rod lens buffer layer 13 may be formed by interposing an adhesive 7 layer (adhesive layer) between the adjacent first rod lenses. By forming the inter-rod lens buffer layer 13 with the adhesive 7, the periphery of the rod lens 9 can be made of a single material, so that the anisotropic action acting on the rod lens 9 when the adhesive 7 contracts. Force can be reduced.

FIG. 2 is a perspective view showing a process for manufacturing the rod lens array described above. In order to simplify the description, a case where an adhesive layer is used for the buffer layer will be described.

First, as shown in FIG. 2A, an adhesive 7a is applied on the substrate 3 to a thickness of more than 5 μm. The adhesive 7a is applied on the surface of the substrate 3 so as to form a large number of strips extending linearly. Then, the adhesive 7a is cured for a certain period of time to form the substrate-rod lens buffer layer 11 having a thickness of more than 5 μm. After that, as shown in FIG. 2B, the adhesive 7b is applied again on the strip of the cured adhesive 7a (substrate-rod lens buffer layer 11). And as shown in FIG.2 (c), the some rod lens 9 is arrange | positioned on the adhesive agent 7 of two layers. The rod lens 9 is disposed on the adhesive 7 so as to extend perpendicular to the direction in which the layer of the adhesive 7 extends. At this time, in order to form the inter-rod lens buffer layer 13, the rod lens 9 is disposed with a gap of about 5 to 30 μm provided between the rod lenses 9. Thereafter, another substrate 5 on which a layer of the adhesive 7 is formed as shown in FIG. 2B is prepared. The prepared substrate 5 is placed on the rod lens 9 and the rod lens 9 is sandwiched between the two substrates 3 and 5. Thus, a sheet in which the rod lens 9 is sandwiched between the two substrates 3 and 5 is formed. At this time, by adjusting the force for pressing the substrates 3 and 5, the uncured adhesive 7b is deformed and filled between the rod lenses 9, so that a predetermined thickness is established between the rod lenses 9. The inter-rod lens buffer layer 13 is formed. Further, by bringing the rod lens 9 and the cured adhesive layer 7a (substrate-rod lens buffer layer 11) into contact, a substrate-rod having a predetermined thickness is provided between the rod lens 9 and the substrates 3, 5. The inter-lens buffer layer 11 is formed. Thereafter, the rod lens array 1 can be obtained by cutting the sheet in a direction orthogonal to the extending direction of the rod lens 9.

Since the layer of the adhesive 7b becomes an adhesive to be filled between the lenses in a later step, the adhesive 7b is applied with a thickness corresponding to the diameter of the rod lens 9 so as not to cause overfilling or underfilling of the adhesive. It is preferable. For example, when the rod lens array 1 is manufactured using a lens having a diameter of 1000 μm, the layer of the adhesive 7b is preferably applied with a thickness of 110 μm to 140 μm, and the rod lens array 1 using a lens having a diameter of 600 μm. When manufacturing the rod lens array 1 using a lens having a diameter of 300 μm, it is preferable that the layer of the adhesive 7b is applied with a thickness of 70 μm to 100 μm. It is preferably applied with a thickness of ˜70 μm.

Next, the operation of the rod lens array having the above-described configuration will be described in detail.

When there is no substrate-rod lens buffer layer as in the past, the adhesive solidifies and shrinks, and unnecessary force acts in the direction of compressing the rod lens, so the lens is deformed or the refractive index of the lens is It will change. As a result, anisotropy occurs in the optical performance of the rod lens, and the resolution decreases.

More specifically, when the adhesive contracts when the adhesive is solidified, the conjugate length TC in the arrangement direction of the rod lenses (main scanning direction) and the conjugate in the sub-scanning direction orthogonal to the main scanning direction in the circular cross section of the lens. A difference (sub scanning direction TC−main scanning direction TC = ΔTC) occurs with respect to the length TC. At a position that is out of the conjugate length TC, the resolution is lowered when the optical performance is evaluated or when the image is read. Therefore, the rod is in a state where a difference ΔTC is generated between the sub-scanning direction TC and the main scanning direction TC. When the optical performance of the lens array is evaluated or when an image is read, the resolution decreases in the main scanning direction or the sub-scanning direction.

Here, the conjugate length TC is obtained as follows. In order to obtain the conjugate length TC, as shown in FIG. 19, a chart 20 having a spatial frequency of 6 line pairs / mm (Lp / mm) is used, and a light source is applied to the rod lens array 1 whose both end faces perpendicular to the optical axis are polished. 21 is incident through the chart 20 (only the light having a wavelength of 525 nm is used by the color filter 23 and the diffusion plate 24 is placed between the color filter and the chart so that the chart is uniformly irradiated with light). Then, the image is read by the CCD line sensor 22 installed on the imaging surface, the maximum value (i _max ) and the minimum value (i _min ) of the measured light quantity are measured, and MTF (modulation transfer function) is obtained by the following equation.
MTF (%) = {(i _max −i _min ) / (i _max + i _min )} × 100

With the distance between the chart and the incident end of the rod lens array equal to the distance between the exit end of the rod lens array 1 and the CCD line sensor 22, the chart and the CCD line sensor 22 are symmetrical with respect to the rod lens array 1. The MTF is measured by moving, and the distance between the chart and the CCD line sensor when the MTF is the best is the conjugate length TC. Here, the spatial frequency indicates a combination of the white line 20 and the black line 20 as one line, and indicates how many combinations of the lines are provided within a width of 1 mm.

The conjugate length TC in the main scanning direction and the sub-scanning direction can be measured by adjusting the orientation of the chart 20 and the CCD line sensor 22 as shown in FIGS. 19a and 19b. For example, when measuring the TC in the main scanning direction (FIG. 19a), the chart is installed in such a direction that the extending direction of the white and black lines provided in the chart is perpendicular to the main scanning direction. Measurement can be performed by installing a CCD line sensor in such a direction that the direction in which the pixels are arranged is parallel to the main scanning direction. When measuring the TC in the sub-scanning direction (FIG. 19b), the chart and the CCD line sensor can be measured by rotating them 90 ° C. from the direction in the main scanning direction. Thereafter, unless otherwise specified, when measuring in the main scanning direction, install the chart in a direction in which the extending direction of the white and black lines provided in the chart is perpendicular to the main scanning direction, The CCD line sensor is installed in a direction in which the pixels of the CCD line sensor are arranged in parallel with the main scanning direction. When measuring in the sub-scanning direction, the white and black lines provided in the chart are displayed. It is assumed that the chart is installed in a direction in which the extending direction is parallel to the main scanning direction, and the CCD line sensor is installed in a direction in which the direction in which the pixels of the CCD line sensor are arranged is perpendicular to the main scanning direction.

In the rod lens array 1 according to the embodiment of the present invention, the periphery of the rod lens 9 is made of the same material by interposing the substrate-rod lens buffer layer 11 for the purpose of reducing the above-described ΔTC. Therefore, even when the adhesive 7 contracts, the anisotropic force acting on the rod lens 9 can be reduced. Then, by reducing the force acting on the rod lens 9 to suppress the difference ΔTC, it is possible to reduce the decrease in resolution. Further, even when the rod lens array 1 is placed under a high temperature and high humidity condition and the adhesive further contracts, the anisotropic force acting on the rod lens 9 can be reduced. As a result, even when the rod lens array 1 is placed under a high temperature and high humidity condition, the difference ΔTC can be kept small, and a reduction in resolution can be reduced.

In particular, by setting the value BestTC indicating the average TC between the TC in the main scanning direction and the TC in the sub-scanning direction as the average value of the main scanning direction TC and the sub-scanning direction TC, the difference ΔTC is set in the main scanning direction and the sub-scanning direction. The influence on the optical performance can be reduced to the minimum. However, even in this case, the resolution in the main scanning direction and the sub-scanning direction is lowered when the difference ΔTC is large. Further, when reading is performed using such a rod lens array 1, the read image is blurred in the main scanning direction and the sub-scanning direction. Therefore, a decrease in resolution can be suppressed by setting the difference ΔTC to 1 mm or less. Further, the difference ΔTC is preferably 0.6 mm or less, and more preferably 0.1 mm or less. Particularly in a lens for an LED printer, a high resolution requirement can be satisfied by setting the difference ΔTC to 0.1 mm or less, and it is more preferable to set the difference ΔTC to 0.08 mm or less.

In order to reduce the difference ΔTC, the thickness of the buffer layer 11 between the substrate and the rod lens should be more than 5 μm, preferably 10 μm or more, more preferably 15 μm or more. By setting the thickness of the buffer layer 11 between the substrate and the rod lens to be more than 5 μm, the deformation of the substrates 3 and 5 can be prevented from being transmitted to the rod lens 9, and thus the difference ΔTC can be suppressed small. The thickness of the substrate-rod lens buffer layer 11 is preferably 2000 μm or less. This is because even if the buffer layer 11 between the substrate and the rod lens is made thicker, the dramatic improvement in the effect is hardly recognized, and the arrangement of the rod lenses 9 is likely to occur.

Thus, by providing the buffer layers 11 and 13, the difference ΔTC can be suppressed to a small value, thereby reducing the resolution. Further, even when the adhesive further shrinks in the high-temperature and high-humidity conditions of the rod lens array 1, the anisotropic force acting on the rod lens 9 can be reduced, so that the difference ΔTC is kept small. Reduction in resolution can be reduced.

Further, in the rod lens array 1 according to the present embodiment, the difference ΔTC at room temperature before being placed in a high temperature and high humidity environment is 1.0 mm or less, and more preferably 0.6 mm or less. Further, the difference ΔTC when the rod lens array 1 is treated for 500 hours in a high-temperature and high-humidity environment at a temperature of 60 ° C. and a humidity of 90% is preferably 1.0 mm or less, more preferably 0.6 mm or less. Preferably, it is 0.1 mm or less. The average resolution MTFave at the value BestTC over the entire length of the rod lens 9 is 70% @ 6 Lp / mm or more. By setting the difference ΔTC between the TC in the main scanning direction and the sub-scanning direction to 1.0 mm or less, the anisotropy of the optical performance of the rod lens array 1 can be reduced, and an image can be obtained using the rod lens array 1. It is possible to maintain a high resolution when the image is formed.

In addition, the average resolution MTFave measured at the value BestTC over the entire length of the rod lens array 1 is set to 70% @ 6 Lp / mm or more, so that the resolution when an image is formed using the rod lens array is kept high. can do. A more preferable range of the average resolution MTFave is 73% @ 6Lp / mm or more, and further preferably 75% @ 6Lp / mm. Here, the average resolution MTFave (%) is a chart having a value of 6 Lp / mm, in which the distance between the chart and the CCD line sensor is fixed at a value BestTC set as an average value in the main scanning direction TC and the sub-scanning direction TC. The main scanning of the rod lens and the light receiving sensor is performed by scanning the entire width of the rod lens array with the distance between the chart and the incident end of the rod lens array equal to the distance between the exit end of the rod lens array and the CCD line sensor. It is an average value (MTFave) when the MTF in the direction is measured at 50 points. The average resolution MTFave is an index of resolution. The larger the average resolution MTFave value, the better the resolution. The rod lens array 1 according to the present embodiment has the above-described average resolution MTFave, and can be used in applications such as a copying machine and an LED printer that require high resolution.

(Rod lens for copier)
In addition to the above-described conditions, it is preferable that the rod lens and the rod lens array used for the copying machine satisfy the following requirements.
0.06 ≦ Numerical aperture NA ≦ 0.175
0.3 mm ⁻¹ ≦ refractive index distribution constant g ≦ 0.6 mm ⁻¹

In copying machine applications, it is particularly required to increase the depth of focus. By setting the numerical aperture NA ≦ 0.175, the depth of focus DOF having an inversely proportional relationship with the numerical aperture NA can be sufficiently deepened. From the viewpoint of increasing the depth of focus, the upper limit value of NA is preferably 0.15 or less. From the viewpoint of increasing the amount of light, the lower limit value of NA is preferably 0.06 or more, and more preferably 0.1 or more.

Also, due to the recent demand for miniaturization of copying machines, the thickness of the platen glass of the image scanner in which the rod lens array is incorporated is about 3 mm or less.

In consideration of the floating of the focus caused by the platen glass having a refractive index of 1.52, the thickness of 3 mm (about −1 mm), and the clearance between the platen glass and the lens end surface (preferably 1 mm or more), the working distance L _{0 of the} rod lens. Needs to be at least 3 mm or more, and the working distance of the rod lens can be 3 mm or more by setting the refractive index distribution constant g to 0.6 mm ⁻¹ or less.

Further, by setting the refractive index distribution constant g to 0.6 mm ⁻¹ or less, the numerical aperture NA represented by the product of n ₀ × g × re can be designed to be small as will be described later, and the depth of focus can be reduced. Can be deep.

Furthermore, by setting the refractive index distribution constant g to 0.3 mm ⁻¹ or more, the working distance L ₀ does not become too long and the entire apparatus can be miniaturized, and the product of the formula n ₀ × g × re The numerical aperture NA expressed can be designed to be large, and the amount of light can be increased.

The lower limit value of the refractive index distribution constant g is more preferably 0.35 mm ⁻¹ or more, and the upper limit value of the refractive index distribution constant g is more preferably 0.5 mm ⁻¹ or less.

In addition to the above requirements, the depth of focus DOF can be 0.9 mm or more. By taking the depth of focus in this way, the image can be read clearly even when the original is lifted from the reading table when the original is read by combining the rod lens array and the image sensor. The focal depth DOF is more preferably 1.0 mm or more, and further preferably 1.1 mm or more. Here, the depth of focus DOF refers to a chart having a value of 6 Lp / mm, a rod lens, and a light receiving sensor, a distance between the chart and the entrance end of the rod lens array, and a distance between the exit end of the rod lens array and the CCD line sensor. When the distance between the chart and the CCD line sensor is set to the value BestTC determined as described above in the state where the values are equal, the MTF in the main scanning direction is 40% when only the chart is moved back and forth. This is the width (mm) of the moving range of the chart. The larger the depth of focus value, the easier it is to maintain a high resolution even when the document is displaced from the focal position.

Since the rod lens array 1 of the present embodiment has a value in the above range, the optical performance is low and the optical performance is low even when used in a high-temperature and high-humidity environment. Since there is no focus and the depth of focus is deep, the image can be read clearly and unevenly even when the read original is lifted, and is suitable for copying machines.

(Rod lens for LED printer)
Moreover, in the rod lens and rod lens array used for LED printer application, it is preferable to satisfy the following requirements.
0.15 ≦ Numerical aperture NA ≦ 0.4
0.7 mm ⁻¹ ≦ refractive index distribution constant g ≦ 1.0 mm ⁻¹

In LED printer applications, it is required to increase the amount of light especially in response to demands for higher printing speed. Since the amount of light is proportional to the square of the numerical aperture NA, the lower limit of NA is required from the viewpoint of increasing the amount of light. The value is preferably 0.15 or more, and more preferably 0.175 or more. By setting the numerical aperture NA to 0.4 or less, the depth of focus DOF having an inversely proportional relationship with the numerical aperture NA can be increased. From the viewpoint of increasing the depth of focus, the upper limit of the numerical aperture NA is preferably 0.35 or less, and more preferably 0.30 or less.

Further, due to recent demands for downsizing LED printers, the working distance L ₀ of the rod lens needs to be 3.5 mm or less. In response to this requirement, the working distance of the rod lens can be 3.5 mm or less by setting the refractive index distribution constant g to 0.6 mm ⁻¹ or more. Further, by setting the refractive index distribution constant g to 0.6 mm ⁻¹ or more, the numerical aperture NA represented by the product of the formula n ₀ × g × re can be designed large, and the amount of light can be increased. .

In addition, by setting the refractive index distribution constant g to 1.0 mm ⁻¹ or less, it is possible to prevent the working distance L ₀ from becoming too short and causing interference with peripheral members. growing. In addition, by setting the refractive index distribution constant g to 1.0 mm ⁻¹ or less, the numerical aperture NA represented by the product of n ₀ × g × re can be designed to be small, and the depth of focus can be increased. it can. The lower limit value of the refractive index distribution constant g is more preferably 0.7 mm ⁻¹ or more, and the upper limit value of the refractive index distribution constant g is more preferably 0.95 mm ⁻¹ or less.

The plastic material constituting the rod lens 9 preferably has a glass transition temperature Tg of 60 ° C. or higher. If the glass transition temperature is too low, the heat resistance of the rod lens array may be insufficient, and it becomes difficult to select an adhesive to be filled inside. Specifically, as the plastic material constituting the rod lens 9, polymethyl methacrylate, a copolymer of methyl methacrylate and another monomer, or the like is used. Other monomers include 2,2,3,3-tetrafluoropropyl (meth) acrylate, 2,2,3,3,4,4,5,5-octafluoropentyl (meth) acrylate, 2, Fluorinated alkyl (meth) acrylates such as 2,3,4,4,4-hexafluorobutyl (meth) acrylate and 2,2,2-trifluoroethyl (meth) acrylate (refractive index n = 1.37 to 1) .44), (meth) acrylates having a refractive index of 1.43 to 1.62, such as ethyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, hydroxyalkyl (meth) acrylate, alkylene glycol (meth) Acrylate, trimethylolpropane-di or tri- (meth) acrylate, pentaerythritol-di, tri or teto - (meth) acrylate, diglycerol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, other, diethylene glycol bis allyl carbonate, a fluorinated alkylene glycol poly (meth) acrylate.

In the rod lens array of the present invention, the difference ΔTC between the main scanning direction TC and the sub-scanning direction TC is 0.1 mm or less, and the difference ΔTC when treated in a high temperature and high humidity environment of 60 ° C. and 90% humidity is 500 ° C. The average resolution MTFave over the entire length of the rod lens 9 may be 80% @ 12 Lp / mm or more, and the resolution spot MTFcv over the entire length of the rod lens 9 may be 3% @ 12 Lp / mm or less. By setting the difference ΔTC between the main scanning direction TC and the sub-scanning direction TC to be 0.1 mm or less, the anisotropy of the optical performance of the rod lens array 1 can be reduced, and an image can be obtained using the rod lens array 1. It is possible to maintain a high resolution when the image is formed. A more preferable range of the difference ΔTC between the main scanning direction TC and the sub-scanning direction TC is ΔTC 0.08 mm or less, and more preferably 0.06 mm or less. Further, when the difference ΔTC when treated for 500 hours in a high temperature and high humidity environment of 60 ° C. and 90% humidity is 0.1 mm or less, the rod lens array 1 is used in a high temperature and high humidity environment for a long time. However, the anisotropy of the optical performance can be reduced, and the resolution when the image is formed using the rod lens array 1 can be kept high. A more preferable range of the difference ΔTC when treated for 500 hours in a high-temperature and high-humidity environment with a temperature of 60 ° C. and a humidity of 90% is 0.08 mm or less, and more preferably 0.06 mm or less.

Further, by setting the average resolution MTFave measured over the entire length of the array to 80% @ 12 Lp / mm or more, it is possible to maintain a high resolution when the rod lens array 1 is used to form an image. A more preferable range of the average resolution MTFave is 83% @ 12 Lp / mm or more, and more preferably 85% @ 12 Lp / mm or more. Further, by setting the resolution unevenness MTFcv measured over the entire length of the array to 3% @ 12 Lp / mm or less, when the image is formed using the rod lens array 1, the unevenness in resolution can be suppressed to be small. Thereby, when writing the image by combining the rod lens array 1 and the LED array according to the present embodiment, it is possible to provide a uniform and spotless image. A more preferable range of the average resolution MTFave is 83% @ 12 Lp / mm or more, and more preferably 85% @ 12 Lp / mm or more.

Here, the resolution spot MTFcv (%) is a value obtained by dividing the standard deviation of the resolution MTF by the average resolution MTFave when the MTF in the main scanning direction is measured at 50 points by scanning the entire width of the rod lens array by the above method. Is a value obtained by multiplying 100 by 100, and is an index of resolution spots. The smaller the value of MTFcv, the smaller the resolution spot and the more uniform the image.

Since the rod lens array 1 of the present embodiment has a value in the above range, the optical performance is low and the optical performance is low even when used in a high-temperature and high-humidity environment. In addition, since there are few optical performance spots, it is possible to provide a rod lens array suitable for LED printer applications, which can provide a uniform and spotless image.

In this embodiment, the plastic rod lens is used for detailed description. However, according to the present invention, a glass rod lens may be used. When the glass rod lens 9 is used, it is not necessary to consider the deformation of the rod lens 9 due to the shrinkage of the adhesive 7 when it is cured, so that the substrate-rod lens is interposed between the rod lens 9 and the substrates 3 and 5. There is no need to provide the intermediate buffer layer 11. Even if the inter-substrate rod lens buffer layer 11 is provided, it can be made thinner than the thickness of the inter-substrate rod lens buffer layer 11 described above.

Hereinafter, examples and comparative examples of the present invention will be described in detail. 3 and 4 are graphs showing the conjugate length (TC) of the rod lens array according to the comparative example and its change with time, and FIGS. 5 to 7 are the conjugate length (TC) of the rod lens array according to the embodiment of the present invention. It is a graph which shows the time-dependent change.

First, in Examples 1 to 6 and Comparative Examples 1 to 3 of the present invention, polymethyl methacrylate, methyl methacrylate, phenyl methacrylate, t-butyl methacrylate, tricyclo [5.2.1.0 ^2,6 ] decanyl methacrylate, Using 2,2,3,3-tetrafluoropropyl methacrylate as a raw material, radius r is 0.232 mm, center refractive index n ₀ is 1.503 at a wavelength of 525 nm, and 0.2 r to 0.9 r from the center toward the outer periphery. The refractive index distribution is approximated by the formula (1) in the range of λ, the refractive index distribution constant g is 0.43 mm ⁻¹ at the wavelength of 525 nm, the effective diameter re is 0.220 mm, the numerical aperture NA is 0.142, and the length is long. A plastic rod lens having a length of 166 mm was used.

Further, in Examples 7 to 9 of the present invention, the radius r is made from polymethyl methacrylate, methyl methacrylate, benzyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate as a raw material. The center refractive index n ₀ is 1.513 at a wavelength of 525 nm, the refractive index distribution constant g is 0.88 mm ⁻¹ at a wavelength of 525 nm, the effective diameter re is 0.222 mm, and the numerical aperture NA is 0.1. A plastic rod lens with a length of 166 mm was used.

[Comparative Example 1]
For the production of the rod lens array, a Bakelite substrate having a length of 330 mm, a width of 170 mm, and a thickness of 0.42 mm, a moisture curable urethane hot melt (Esdyne 9607R: manufactured by Sekisui Fuller; JIS 6253 hardness A71; JIS 6251 tensile strength 3 .1 MPa), and the device described in Patent Document 1 was used for the production.

First, the adhesive was applied onto the substrate in multiple strips so that the coating width was 8.8 mm, the coating pitch was 10.3 mm, and the coating thickness was 60 μm. Approximately 700 rod lenses were arranged in close contact with each other so that there was no gap between adjacent rod lenses, and were arranged on the adhesive so that the direction in which the adhesive extends and the lenses were orthogonal. Further, two substrates are prepared by preparing another substrate coated with an adhesive in the same manner as described above, and placing the rod lens on the rod lens so that the substrate on which the rod lens has already been disposed faces the adhesive coated surface. The rod lens was inserted. Thereafter, when the specimen was heated to 60 ° C. and pressed at a pressure of 0.4 MPa / cm ² for 30 seconds, the uncured adhesive was deformed and filled between the lenses. It became the state which adhered completely. Thereafter, the specimen was cooled to 20 ° C. to obtain a rod lens array original plate in which rod lenses were sandwiched between two substrates and filled with an adhesive. The rod lens array original plate thus obtained is cut at intervals of 10 mm parallel to the direction in which the adhesive extends, and then treated in an environment of temperature 60 ° C. and humidity 90% RH for 24 hours. Cured. After the adhesive was cured, the cut surface of the rod lens array was mirror-cut to obtain a finished rod lens array having a width of 8.5 mm. When both ends of this rod lens array were observed with a microscope (Leica stereomicroscope M205C magnification 100 ×), the buffer layer between the rod lenses and the buffer layer between the substrate and the rod lens were not formed. The rod lens was completely adhered, and the ratio between the effective diameter and the arrangement pitch of the rod lens represented by the formula 2re / P was 0.95.

When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 19.77 mm, the sub-scanning direction TC was 20.84 mm, and the difference ΔTC in the conjugate length between the main scanning direction and the sub-scanning direction was 1. 07 mm and BestTC were 20.31 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 59%, and the depth of focus DOF @ 6Lp / mm was 0.75 mm. The main scanning direction TC after the endurance test of exposing the rod lens array thus fabricated to a high temperature and high humidity condition of 60 ° C. and 90% RH for 500 hours is 18.19 mm, and the sub-scanning direction The TC was 19.55 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 1.36 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was unclear, and when the original floated, the image was extremely unclear.

[Comparative Example 2]
A rod lens array was produced in the same manner as in Comparative Example 1 except that approximately 670 rod lenses were arrayed using a plate having array grooves formed at intervals of 480 μm. When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.95. Further, no buffer layer was formed between the substrate and the rod lens, and it was completely in contact. When the conjugate length TC of the rod lens array was measured, the main scanning direction TC was 18.99 mm, the sub-scanning direction TC was 20.57 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 1. 58 mm, BestTC was 19.78 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 55%, and the depth of focus DOF @ 6Lp / mm was 0.72 mm. The main scanning direction TC after the endurance test of exposing the rod lens array thus fabricated to a high temperature and high humidity condition of 60 ° C. and 90% RH for 500 hours is 17.78 mm, and the sub-scanning direction The TC was 19.41 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 1.63 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was unclear, and when the original floated, the image was extremely unclear.

[Comparative Example 3]
For the production of the rod lens array, a Bakelite substrate having a length of 330 mm, a width of 170 mm, and a thickness of 0.42 mm, a moisture curable urethane hot melt (Esdyne 9607R: manufactured by Sekisui Fuller; JIS 6253 hardness A71; JIS 6251 tensile strength 3 .1 MPa), and the device described in Patent Document 1 was used for the production.

First, an adhesive is applied on the substrate in multiple strips so that the application width is 8.8 mm, the application pitch is 10.3 mm, and the application thickness is 5 μm, and the treatment is performed in an environment of a temperature of 60 ° C. and a humidity of 90% RH for 24 hours. Then, the adhesive was cured to provide a buffer layer between the substrate and the rod lens. After the adhesive was cured, the adhesive was applied in multiple strips so that the coating width was 8.8 mm, the coating pitch was 10.3 mm, and the coating thickness was 60 μm so as to overlap the cured adhesive. Approximately 670 rod lenses were arranged using a plate in which an array groove having an interval of 480 μm was formed, and arranged on the adhesive so that the direction in which the adhesive extends and the lens were orthogonal. Furthermore, a substrate-rod lens buffer layer is provided in the same manner as described above, and another substrate on which an adhesive is applied is prepared, and the substrate on which the rod lens is already arranged faces the adhesive application surface. As described above, the rod lens was sandwiched between the two substrates by being arranged on the rod lens. After that, when the specimen was heated to 60 ° C. and pressed at a pressure of 0.4 MPa / cm ² for 30 seconds, the uncured adhesive was deformed and filled between the lenses, and the lens and the cured The adhesive (substrate-rod lens buffer layer) was in complete contact. Thereafter, the specimen was cooled to 20 ° C. to obtain a rod lens array original plate in which rod lenses were sandwiched between two substrates and filled with an adhesive. The rod lens array original plate thus obtained is cut at intervals of 10 mm parallel to the direction in which the adhesive extends, and then cured in an environment of temperature 60 ° C. and humidity 90% RH for 24 hours to cure the adhesive. I let you. After the adhesive was cured, the cut surface of the rod lens array original plate was mirror-cut and finished to a width of 9.0 mm to obtain a rod lens array.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.92. A buffer layer of 5 μm was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 18.14 mm, the sub-scanning direction TC was 19.25 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub-scanning direction was 1. 11 mm and BestTC were 18.70 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 65%, and the focal depth DOF @ 6Lp / mm was 0.89 mm. The main scanning direction TC after the endurance test of exposing the rod lens array thus manufactured to a high temperature and high humidity condition of a temperature of 60 ° C. and a humidity of 90% RH for 500 hours is 17.36 mm and the sub scanning direction. The TC was 18.17 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 0.81 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was unclear, and when the original floated, the image was extremely unclear.

Then, the rod lens array according to the comparative example manufactured as described above was subjected to a durability test of being exposed to a high temperature and high humidity condition of a temperature of 60 ° C. and a humidity of 90% RH for 500 hours after the main scanning direction (array arrangement). 3) and FIG. 5 show the conjugate length TC (mm) in the direction) and the sub-scanning direction (substrate surface direction), and the difference ΔTC (mm) between the conjugate lengths in the main scanning direction and the sub-scanning direction.

[Example 1]
Adhesive is applied onto the substrate in multiple strips so that the coating width is 8.8 mm, the coating pitch is 10.3 mm, and the coating thickness is 10 μm, and the bonding is performed by treating for 24 hours in an environment of 60 ° C. and 90% humidity. A rod lens array was prepared in the same manner as in Comparative Example 3 except that the agent was cured and a buffer layer between the substrate and the rod lens was provided.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.92. A 10 μm buffer layer was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 18.32 mm, the sub-scanning direction TC was 19.14 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 0. 83 mm and BestTC were 18.73 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 87%, and the focal depth DOF @ 6Lp / mm was 1.15 mm. The main scanning direction TC is 17.49 mm and the sub-scanning direction TC after the endurance test in which the rod lens array thus produced is subjected to a high temperature and high humidity condition of 60 ° C. and 90% RH for 500 hours. Was 17.99 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub-scanning direction was 0.50 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was clear, and a clear image was obtained even when the original floated.

[Example 2]
For the production of the rod lens array, a Bakelite substrate having a length of 330 mm, a width of 170 mm, and a thickness of 0.42 mm, a moisture curable urethane hot melt (Esdyne 9607R: manufactured by Sekisui Fuller; JIS 6253 hardness A71; JIS 6251 tensile strength 3 .1 MPa), and the device described in Patent Document 1 was used for the production. First, an adhesive is applied on the substrate in multiple strips so that the application width is 8.8 mm, the application pitch is 10.3 mm, and the application thickness is 20 μm, and the treatment is performed for 24 hours in an environment of temperature 60 ° C. and humidity 90% RH. Then, the adhesive was cured to provide a buffer layer between the substrate and the rod lens. After the adhesive was cured, the adhesive was applied in multiple strips so that the coating width was 8.8 mm, the coating pitch was 10.3 mm, and the coating thickness was 60 μm so as to overlap the cured adhesive. Approximately 670 rod lenses were arranged using a plate in which an array groove having an interval of 480 μm was formed, and arranged on the adhesive so that the direction in which the adhesive extends and the lens were orthogonal. Furthermore, a substrate-rod lens buffer layer is provided in the same manner as described above, and another substrate on which an adhesive is applied is prepared, and the substrate on which the rod lens is already arranged faces the adhesive application surface. As described above, the rod lens was sandwiched between the two substrates by being arranged on the rod lens. Then, when the specimen was heated to 60 ° C. and pressed at a pressure of 0.4 MPa / cm 2 for 30 seconds, the uncured adhesive was deformed and filled between the lenses, and the lens and the cured Since the adhesive (buffer layer between the substrate and the rod lens) is completely in contact with each other, the rod lens is sandwiched between the two substrates by cooling the specimen to 20 ° C. and filled with the adhesive. I got the original plate. The rod lens array original plate thus obtained is cut at intervals of 10 mm parallel to the direction in which the adhesive extends, and then treated in an environment of temperature 60 ° C. and humidity 90% RH for 24 hours. Cured. After the adhesive was cured, the cut surface of the rod lens array was mirror-cut to a width of 8.5 mm.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.92. A buffer layer of 24 μm was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 19.69 mm, the sub-scanning direction TC was 20.12 mm, and the difference ΔTC in the conjugate length between the main scanning direction and the sub-scanning direction was 0. 44 mm, BestTC was 19.91 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 91%, and the focal depth DOF @ 6Lp / mm was 1.19 mm. The main scanning direction TC is 18.59 mm and the sub-scanning direction TC after a durability test of exposing the rod lens array thus manufactured to a high temperature and high humidity condition of an air temperature of 60 ° C. and a humidity of 90% RH for 500 hours. Was 19.11 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub-scanning direction was 0.52 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was clear, and a clear image was obtained even when the original floated.

Example 3
Adhesive is applied onto the substrate in multiple strips so that the coating width is 8.8 mm, the coating pitch is 10.3 mm, and the coating thickness is 30 μm, and it is bonded by treating for 24 hours in an environment of temperature 60 ° C. and humidity 90% RH. A rod lens array was prepared in the same manner as in Example 2 except that the agent was cured and a buffer layer between the substrate and the rod lens was provided. When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.92. In addition, a 34 μm buffer layer was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 19.70 mm, the sub scanning direction TC was 20.04 mm, and the difference ΔTC in the conjugate length between the main scanning direction and the sub scanning direction was 0. 33 mm and BestTC were 19.87 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 89.0%, and the depth of focus DOF @ 6Lp / mm was 1.2 mm. In the rod lens array thus manufactured, the main scanning direction TC is 18.63 mm after the endurance test in which the rod lens array is exposed to a high temperature and high humidity condition of a temperature of 60 ° C. and a humidity of 90% RH is 18.63 mm. The scanning direction TC was 19.10 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 0.47 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was clear, and a clear image was obtained even when the original floated.

Example 4
Adhesive is coated on the substrate in multiple strips so that the coating width is 8.8 mm, the coating pitch is 10.3 mm, and the coating thickness is 40 μm, and the adhesive is bonded for 24 hours in an environment of temperature 60 ° C. and humidity 90% RH. A rod lens array was prepared in the same manner as in Example 2 except that the agent was cured and a buffer layer between the substrate and the rod lens was provided.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.92. In addition, a buffer layer of 41 μm was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 19.69 mm, the sub scanning direction TC was 20.08 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub scanning direction was 0. 38 mm and BestTC were 19.89 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 90%, and the focal depth DOF @ 6Lp / mm was 1.18 mm. The main scanning direction TC after the endurance test in which the rod lens array thus manufactured is subjected to a high temperature and high humidity condition of an air temperature of 60 ° C. and a humidity of 90% RH for 500 hours is 18.57 mm. The sub-scanning direction TC was 19.06 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 0.49 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was clear, and a clear image was obtained even when the original floated.

Example 5
Adhesive is coated on the substrate in multiple strips so that the coating width is 8.8 mm, the coating pitch is 10.3 mm, and the coating thickness is 100 μm, and the adhesive is bonded by treating for 24 hours in an environment of 60 ° C. and 90% humidity. A rod lens array was produced in the same manner as in Example 1 except that the agent was cured and a buffer layer between the substrate and the rod lens was provided. When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.92. A buffer layer of 100 μm was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 18.58 mm, the sub-scanning direction TC was 18.67 mm, and the difference ΔTC in the conjugate length between the main scanning direction and the sub-scanning direction was 0.8. 09 mm and BestTC were 18.62 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 87%, and the focal depth DOF @ 6Lp / mm was 1.17 mm. The main scanning direction TC is 17.75 mm and the sub-scanning direction TC after a durability test in which the rod lens array thus produced is subjected to a high temperature and high humidity condition of 60 ° C. and 90% RH for 500 hours. Was 17.88 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub-scanning direction was 0.14 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was clear, and a clear image was obtained even when the original floated.

Example 6
The rod lens array was manufactured by laminating a 1.0 mm thick ethylene propylene rubber on the surface of a phenolic substrate having a length of 330 mm, a width of 170 mm, and a thickness of 2.0 mm (recycled rubber-laminated laminate RS -1769X: manufactured by Risho Kogyo Co., Ltd .; JIS 6253 hardness A71 of rubber part; JIS 6251 tensile strength 24.2 MPa), moisture curable urethane hot melt (Esdyne 9607R: manufactured by Sekisui Fuller Co., Ltd .; JIS 6253 hardness A71; JIS 6251 tensile strength 3. 1 MPa), and the device described in Patent Document 1 was used for production. First, an adhesive was applied in multiple stripes on the rubber surface of the substrate so that the application width was 8.8 mm, the application pitch was 10.3 mm, and the application thickness was 60 μm. Approximately 670 rod lenses were arrayed using a plate on which array grooves having an interval of 480 μm were formed, and arranged on the adhesive so that the direction in which the adhesive extends and the lens were orthogonal. Further, as described above, another substrate coated with an adhesive is prepared, and the two substrates are arranged on the rod lens so that the substrate on which the rod lens has already been disposed and the adhesive coated surface face each other. A rod lens was sandwiched between the substrates. After that, when the specimen was heated to 60 ° C. and pressed at a pressure of 0.4 MPa / cm ² for 30 seconds, the uncured adhesive was deformed and filled between the lenses, and the lens and the substrate rubber The surface (buffer layer between the substrate and the rod lens) was in close contact. Thereafter, the specimen was cooled to 20 ° C. to obtain a rod lens array original plate in which rod lenses were sandwiched between two substrates and filled with an adhesive. The rod lens array original plate thus obtained is cut at intervals of 10 mm parallel to the direction in which the adhesive extends, and then treated in an environment of temperature 60 ° C. and humidity 90% RH for 24 hours. Cured. After the adhesive was cured, the cut surface of the rod lens array was mirror-cut to a width of 9.0 mm.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.92. In addition, a 1068 μm buffer layer was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 18.43 mm, the sub-scanning direction TC was 18.53 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 0.8. 10 mm, BestTC was 18.48 mm. The main scanning MTFave @ 6Lp / mm at BestTC of this rod lens array was 83%, and the focal depth DOF @ 6Lp / mm was 1.13 mm. The main scanning direction TC is 17.84 mm and the sub-scanning direction TC after the endurance test in which the rod lens array thus produced is subjected to a high temperature and high humidity condition of 60 ° C. and 90% RH for 500 hours. Was 17.95 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub-scanning direction was 0.11 mm. When reading was performed by combining this rod lens array and an image sensor, the read image was clear, and a clear image was obtained even when the original floated.

Example 7
For the production of the rod lens array, a Bakelite substrate having a length of 330 mm, a width of 170 mm, and a thickness of 0.42 mm, a moisture curable urethane hot melt (Esdyne 9607R: manufactured by Sekisui Fuller; JIS 6253 hardness A71; JIS 6251 tensile strength 3 .1 MPa), and the device described in Patent Document 1 was used for the production. First, an adhesive is applied onto a substrate in multiple strips so that the coating width is 4.0 mm, the coating pitch is 5.3 mm, and the coating thickness is 20 μm, and the substrate is treated in an environment of a temperature of 60 ° C. and a humidity of 90% RH for 24 hours. Then, the adhesive was cured to provide a buffer layer between the substrate and the rod lens. After the adhesive was cured, the adhesive was applied in multiple strips so as to have a coating width of 8.8 mm, a coating pitch of 10.3 mm, and a coating thickness of 90 μm so as to overlap the cured adhesive. Approximately 520 rod lenses were arranged using a plate in which arrangement grooves with a spacing of 615 μm were formed, and arranged on the adhesive so that the direction in which the adhesive extends and the lens were orthogonal. Furthermore, a substrate-rod lens buffer layer is provided in the same manner as described above, and another substrate on which an adhesive is applied is prepared, and the substrate on which the rod lens is already arranged faces the adhesive application surface. As described above, the rod lens was sandwiched between the two substrates by being arranged on the rod lens. After that, when the specimen was heated to 60 ° C. and pressed at a pressure of 0.4 MPa / cm ² for 30 seconds, the uncured adhesive was deformed and filled between the lenses, and the lens and the cured The adhesive (substrate-rod lens buffer layer) was in complete contact. Thereafter, the specimen was cooled to 20 ° C. to obtain a rod lens array original plate in which rod lenses were sandwiched between two substrates and filled with an adhesive. The rod lens array original plate thus obtained is cut at 5.0 mm intervals parallel to the direction in which the adhesive extends, and then treated in an environment of a temperature of 60 ° C. and a humidity of 90% RH for 24 hours. The agent was cured. After the adhesive was cured, the cut surface of the rod lens array was mirror-cut to a 4.4 mm width.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.72. In addition, a 20 μm buffer layer was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 9.90 mm, the sub scanning direction TC was 9.97 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub scanning direction was 0.8. 07 mm and BestTC were 9.94 mm. The main scanning MTFave @ 12Lp / mm at BestTC of this rod lens array was 85%, and the main scanning MTFcv @ 12Lp / mm at BestTC was 2.0%. The main scanning direction TC is 9.80 mm and the sub-scanning direction TC after a durability test of exposing the rod lens array thus manufactured to a high temperature and high humidity condition of 60 ° C. and 90% RH for 500 hours. Was 9.88 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub-scanning direction was 0.08 mm. When this rod lens array and LED array were combined and printed on a photosensitive drum, followed by printing with black toner, the printed image was clear and there were few image spots.

Example 8
Adhesive is applied on the substrate in multiple strips so that the coating width is 4.0 mm, the coating pitch is 5.3 mm, and the coating thickness is 30 μm. A rod lens array was prepared in the same manner as in Example 7 except that the agent was cured and a buffer layer between the substrate and the rod lens was provided.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.72. A buffer layer of 30 μm was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 9.89 mm, the sub scanning direction TC was 9.94 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub scanning direction was 0.8. 05 mm and BestTC were 9.92 mm. This rod lens array had a main scan MTFave @ 12Lp / mm at BestTC of 88% and a main scan MTFcv @ 12Lp / mm at BestTC of 2.3%. The main scanning direction TC is 9.84 mm and the sub-scanning direction TC after a durability test of exposing the rod lens array thus manufactured to a high temperature and high humidity condition of 60 ° C. and humidity 90% RH for 500 hours. Was 9.90 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub-scanning direction was 0.06 mm. When this rod lens array and LED array were combined and printed on a photosensitive drum, followed by printing with black toner, the printed image was clear and there were few image spots.

Example 9
Adhesive is applied onto the substrate in multiple strips so that the coating width is 4.0 mm, the coating pitch is 5.3 mm, and the coating thickness is 40 μm, and the adhesive is bonded by treating for 24 hours in an environment of temperature 60 ° C. and humidity 90% RH. A rod lens array was prepared in the same manner as in Example 7 except that the agent was cured and a buffer layer between the substrate and the rod lens was provided.

When both end surfaces of this rod lens array were observed with a microscope (Leica stereomicroscope M205C, magnification 100 ×), a buffer layer of 15 μm was formed between the rod lenses, and the effective diameter of the rod lens represented by the formula 2re / P And the array pitch was 0.72. A buffer layer of 40 μm was formed between the substrate and the rod lens. When the conjugate length TC of this rod lens array was measured, the main scanning direction TC was 9.93 mm, the sub scanning direction TC was 9.96 mm, and the conjugate length difference ΔTC between the main scanning direction and the sub scanning direction was 0.8. 03 mm and BestTC were 9.95 mm. This rod lens array had a main scan MTFave @ 12Lp / mm at BestTC of 84% and a main scan MTFcv @ 12Lp / mm at BestTC of 1.9%. The main scanning direction TC is 9.88 mm and the sub-scanning direction TC after a durability test of exposing the rod lens array thus fabricated to a high temperature and high humidity condition of 60 ° C. and 90% RH for 500 hours. Was 9.93 mm, and the difference ΔTC in conjugate length between the main scanning direction and the sub-scanning direction was 0.05 mm. When this rod lens array and LED array were combined and printed on a photosensitive drum, followed by printing with black toner, the printed image was clear and there were few image spots. The main scanning direction (array arrangement direction) and sub-scanning direction after the endurance test in which the rod lens array thus manufactured is subjected to a high temperature and high humidity condition of 60 ° C. and humidity 90% RH for 500 hours. 6 to 14 show the conjugate length TC (mm) in the (plane direction of the substrate) and the difference ΔTC (mm) between the conjugate lengths in the main scanning direction and the sub-scanning direction. FIG. 15 shows the relationship between the conjugate length difference ΔTC (mm) and the buffer layer thickness. In addition, the relationship between the thickness of the buffer layer and the value of the difference ΔTC (mm) in the conjugate length that occurs after 500 hours of endurance test of exposure to high temperature and high humidity conditions of 60 ° C and 90% RH is shown. 16 shows.

Also, the test results of the comparative examples and examples are summarized in Table 1.

As can be seen from FIGS. 3 to 5 and Table 1, in Comparative Example 2 in which the substrate-rod lens buffer layer is not provided, and in Comparative Example 1 in which the substrate-rod lens buffer layer and the rod lens buffer layer are not provided. The difference in conjugate length between the main scanning direction and the sub-operation direction is large, and the difference tends to increase due to the durability test. On the other hand, in the example in which the buffer layer between the substrate and the rod lens shown in FIGS. 6 to 14 is provided, the difference in the conjugate length between the main scanning direction and the sub-operation direction is small, and the difference in the conjugate length in the durability test. It was found that there was almost no change, and the rate decreased at almost the same rate. Therefore, according to the embodiment of the present invention, by providing a substrate-rod lens buffer layer of more than 5 μm between the substrate and the rod lens, the deformation of the lens due to the shrinkage of the adhesive can be suppressed. It has been found that the optical characteristics of the rod lens array can be maintained while suppressing a significant difference in conjugate length between the main scanning direction and the sub-scanning direction of the lens.

FIG. 17 shows a rod lens array (Comparative Example 1) that does not have a buffer layer between a rod lens and a buffer layer between a substrate and a rod lens, and has a buffer layer between a rod lens of 15 μm, but has a buffer layer between a substrate and a rod lens. A cross-sectional photograph of a rod lens array (Comparative Example 2) that is not provided and a rod lens array (Comparative Example 3) that has a buffer layer between rod lenses of 15 μm and a buffer layer between the substrate and rod lenses of 5 μm is shown. . In addition to this, FIG. 18 shows an image (grating image) obtained by forming an image of a lattice having a spacing of 100 μm using these rod lens arrays, and these rod lens arrays are subjected to a high temperature and high humidity condition of 60 ° C. and 90% RH. The lattice image after performing the durability test of exposing to 500 hours is shown.

FIG. 18 shows a rod lens array (Example 1) having a buffer layer between the rod lenses of 15 μm and a buffer layer between the substrate and rod lenses of 10 μm, a buffer layer between the rod lenses of 15 μm, and a buffer layer between the substrate and rod lenses of 20 μm. Rod lens array (Example 2), 15 μm buffer lens between rod lenses and 24 μm substrate-lens buffer layer (Example 3), buffer layer between 15 μm rod lenses and 34 μm substrate -Rod lens array having a buffer layer between rod lenses (Example 4), 15 [mu] m rod lens buffer layer and 41 [mu] m rod lens array having a substrate-rod lens buffer layer (Example 4), between 15 [mu] m rod lenses Rod lens array having a buffer layer and a buffer layer between a substrate and a rod lens of 100 μm (Example 5) , And 15μm of the rod lens between the substrates of the buffer layer and 1068Myuemu - shows a cross-sectional photograph of the rod lens array having a buffer layer between the rod lens (Example 6). In addition to this, FIG. 18 shows an image (grating image) obtained by forming an image of a grid having an interval of 100 μm using these rod lens arrays, and these rod lens arrays under a high temperature and high humidity condition of 60 ° C. and 90% RH. The lattice image after performing the durability test of exposing to 500 hours is shown. In FIGS. 17 and 18, the left and right are the main scanning direction, and the upper and lower are the sub scanning direction.

As can be seen from the figure, a lattice image of a rod lens array that does not have a buffer layer between rod lenses and a buffer layer between substrate and rod lens, and a rod lens array that does not have a buffer layer between substrate and rod lens, or The lattice image of the rod lens array having a substrate-rod lens buffer layer of 5 μm or less is disturbed before and after the durability test. On the other hand, it was found that the lattice image of the rod lens array having the substrate-rod lens buffer layer was hardly disturbed even after the durability test. This also shows that according to the embodiment of the present invention, it is possible to prevent the lattice image from being disturbed by providing the substrate-rod lens buffer layer.

DESCRIPTION OF SYMBOLS 1 Rod lens array 3, 5 Substrate 7 Adhesive 9 Rod lens 11 Buffer layer between substrate and rod lens 13 Buffer layer between rod lenses 20 Chart 21 Light source 22 CCD line sensor 23 Color filter 24 Diffusion plate

Claims

A rod lens array in which a plurality of rod lenses are arranged between two substrates so that the central axes of the rod lenses are substantially parallel to each other, and satisfy the following three requirements.
(1) TC difference ΔTC ≦ 1.0 mm between the main scanning direction and the sub-scanning direction
(2) ΔTC ≦ 1.0 mm after 60 ° C. and 90% 500 h durability test
(3) MTFave ≧ 70% @ 6Lp / mm at BestTC
(Here, BestTC is an average TC in the main scanning direction TC and the sub-scanning direction TC)
The rod lens array according to claim 1, wherein the focal depth DOF ≧ 0.9 mm.
The rod lens array according to claim 1, which satisfies the following four requirements.
(1) ΔTC ≦ 0.1mm
(2) ΔTC ≦ 0.1mm after durability test
(3) MTFave ≧ 80% @ 12Lp / mm at BestTC
(4) MTCvv ≦ 3% at BestTC @ 12 Lp / mm
(Here, BestTC is an average TC in the main scanning direction TC and the sub-scanning direction TC)
4. The rod lens array according to claim 1, wherein a buffer layer having a thickness of more than 5 μm is provided between the rod lens and the two substrates, respectively, between the substrate and the rod lens.
The rod lens array according to claim 4, wherein the thickness of the buffer layer between the substrate and the rod lens is 10 μm or more.
The rod lens array according to claim 5, wherein a thickness of the buffer layer between the substrate and the rod lens is 15 µm or more.
The rod lens array according to any one of claims 4 to 6, wherein a buffer layer between rod lenses is provided between adjacent rod lenses.
The rod lens array according to claim 7, wherein the buffer layer between the rod lenses has a thickness of 5 µm to 30 µm.
The rod lens array according to claim 8, wherein the buffer layer between the rod lenses has a thickness of 10 µm or more and 20 µm or less.
The rod lens array according to claim 4, wherein the buffer layer between the substrate and the rod lens has a hardness (JIS 6253): A50 to A95 and a tensile strength (JIS 6251): 1 MPa to 100 MPa.
The rod lens array according to claim 7, wherein the buffer layer between the rod lenses has a hardness (JIS 6253): A50 to A95 and a tensile strength (JIS 6251): 1 MPa to 100 MPa.
The rod lens array according to claim 4, wherein the buffer layer between the substrate and the rod lens is formed by interposing the adhesive between the substrate and the rod lens.
The rod lens array according to claim 7, wherein the buffer layer between rod lenses is formed by interposing the adhesive between the adjacent rod lenses.
The rod lens array according to claim 4, wherein the rod lens is a plastic rod lens.
The rod lens array according to any one of claims 1 to 14, which satisfies the following four requirements: (1) 0.06 ≤ numerical aperture NA ≤ 0.4
(2) 0.3 mm −1 ≦ refractive index distribution constant g ≦ 1.0 mm −1
(3) 0.1 mm ≦ lens effective radius re ≦ 0.4 mm
(4) 0.70 ≦ 2re / P (effective lens radius / arrangement pitch)
Providing a buffer layer on each of the two substrates;
An application step of applying an adhesive on the buffer layer formed on the two substrates;
An arrangement step of arranging rod lenses on an adhesive applied to any one of the two substrates;
An arrangement step of disposing the other substrate on the rod lens so that the adhesive applied to the other substrate of the two substrates is adhered to the rod lens;
Curing the adhesive applied to the two substrates to form a rod lens array; and
A method for manufacturing a rod lens array, comprising:
A first application step of applying an adhesive on each of the two substrates;
A first curing step of curing the adhesive applied on the two substrates;
A second application step of further applying an adhesive on the adhesive cured on the two substrates;
An arrangement step of arranging rod lenses on an adhesive applied to any one of the two substrates;
An arrangement step of disposing the other substrate on the rod lens so that the adhesive applied to the other substrate of the two substrates is adhered to the rod lens;
A second curing step of curing the adhesive applied to the two substrates to form a rod lens array;
The manufacturing method of the rod lens array of Claim 16 provided with these.
18. The method of manufacturing a rod lens array according to claim 17, wherein, in the first application step, the adhesive is applied so that the thickness of the adhesive after the first curing step is more than 5 [mu] m. .
In the arranging step, the rod lenses are arranged so that an interval between the rod lenses is 5 μm or more and 30 μm or less, and in the second application step, an interval between the rod lenses of the rod lens array is an adhesive. The method for manufacturing a rod lens array according to claim 17, wherein an amount of adhesive filled in is applied.