Lens array

Abstract

A lens array 1a is provided with a plurality of lenses 11, an adhesive part 12, a housing 15, and an antireflection film 20. The lens array 1a is used in a device for inspecting for the presence of defects through use of reflected light from a conveyed object under inspection. The plurality of lenses 11 are arranged in a first direction (y-axis direction) that is the conveyance direction of the object under inspection, and a second direction (x-axis direction) that is perpendicular to the conveyance direction. The plurality of lenses 11 condense the reflected light from the conveyed object under inspection. The adhesive part 12 secures the lenses 11. The housing 15 accommodates the plurality of lenses 11 and the adhesive part 12. The antireflection film 20 includes fine particles 21 and a binder 22. The antireflection film 20 is disposed in contact with at least one selected from the group consisting of first surfaces 11a of the lenses 11 on which reflected light is incident, and second surfaces 11b of the lenses 11 from which light that is incident on the first surface 11a is emitted.

Description

Lens array

[0001] The present invention relates to a lens array.

[0002] Conventionally, a lens array is used for image reading.

[0003] For example, Patent Document 1 describes a laminated lens array unit for a compound eye optical system. This laminated lens array unit includes a first lens array, a second lens array, and a positioning unit. Each of the first lens array and the second lens array has a rectangular outline when viewed from the optical axis direction and includes a plurality of lens elements arranged two-dimensionally. The first lens array and the second lens array are stacked in the optical axis direction. The positioning unit is provided in a surrounding region surrounding the plurality of lens elements along the edges of the first lens array and the second lens array. The positioning unit has a first abutment portion disposed on the first lens array side and a second abutment portion disposed on the second lens array side and facing the first abutment portion, and has a predetermined tapered surface. This allows for the lens array to be regulated in the planar direction and the rotational direction around an axis perpendicular to the planar direction, as required, without applying stress to the lens array. This allows for high-precision assembly while maintaining high optical performance. Furthermore, since the structure between adjacent lens elements of the lens array can be simplified, molding can be performed with high precision, and it becomes easier to ensure a wide effective area for the lens elements.

[0004] International Publication No. 2014 / 192933

[0005] It is not anticipated that the lens array unit described in Patent Document 1 will be used in an apparatus that inspects for defects using light reflected from a transported object to be inspected. When using a lens array in such an apparatus, it is considered advantageous for the lens array to be able to accommodate various measurement wavelengths, depending on the object to be inspected.

[0006] Therefore, the present invention provides a lens array that is advantageous in terms of the range of measurement wavelengths that can be accommodated by an instrument that inspects for defects using light reflected from an object being transported.

[0007] The present invention provides a lens array used in an apparatus that inspects for defects using reflected light from a transported object to be inspected, the lens array comprising: a plurality of lenses that are arranged in a first direction that is the transport direction of the object to be inspected and a second direction perpendicular to the transport direction and that focus the reflected light; an adhesive portion that fixes the lenses together; a housing that houses the plurality of lenses and the adhesive portion; and an anti-reflection film, wherein the anti-reflection film contains fine particles having a refractive index lower than that of the lenses and a binder, and is arranged in contact with at least one selected from the group consisting of a first surface of the lens on which the reflected light is incident and a second surface of the lens from which light that has entered the first surface is emitted, and the binder adheres the fine particles to the first surface or the second surface.

[0008] The above-mentioned lens array is advantageous in terms of the range of measurement wavelengths that can be accommodated by an instrument that inspects for defects by using light reflected from an object being transported.

[0009] FIG. 1 is a schematic perspective view showing an example of a lens array according to the present invention. FIG. 2 is a graph showing the refractive index distribution of a lens. FIG. 3 is a side view showing an example of a lens shown in FIG. 1. FIG. 4 is a cross-sectional view showing an example of an inspection device equipped with the lens array shown in FIG. 1. FIG. 5A is an FE-SEM photograph showing a cross section of an antireflection coating of a lens array according to Example 1. FIG. 5B is an FE-SEM photograph showing a cross section of an antireflection coating of a lens array according to Example 6. FIG. 5C is an FE-SEM photograph showing a cross section of an antireflection coating of a lens array according to Example 7. FIG. 6 is a cross-sectional view schematically showing a cross section of an antireflection coating of a lens array according to Example 8.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following description relates to an example of the present invention, and the present invention is not limited to the following embodiments.

[0011] As shown in FIG. 1, the lens array 1a includes a plurality of lenses 11, an adhesive portion 12, and a housing 15. The lens array 1a is used in equipment that inspects for defects using light reflected from an object being transported. The plurality of lenses 11 are arranged in a first direction (y-axis direction) that is the transport direction of the object being transported, and a second direction (x-axis direction) that is perpendicular to the transport direction. The plurality of lenses 11 focus the light reflected from the object being transported. The adhesive portion 12 fixes the lenses 11 to each other. The housing 15 houses the plurality of lenses 11 and the adhesive portion 12. The lenses 11 have a working distance L1 of, for example, 5 mm or more.

[0012] Lens arrays are often used for applications such as image reading. In this case, considering the miniaturization of devices equipped with lens arrays, a small working distance of the lens array is advantageous because it allows for a small distance between the object to be read and the lens array. On the other hand, when a lens array is used in an instrument that inspects for defects using reflected light from a transported object, foreign matter from the transported object is likely to adhere to the surface of the lens array. For this reason, such an instrument may require periodic or irregular maintenance. In this case, if the distance between the lens array and the object is small, it is difficult to secure sufficient space for equipment maintenance. With the lens array 1a, the lens 11 has a working distance of 5 mm or more. Therefore, when the lens array 1a is used in an instrument that inspects for defects using reflected light from a transported object, the distance between the lens array 1a and the object is likely to be large, making it easy to secure sufficient space for equipment maintenance.

[0013] The working distance L1 of the lens 11 is preferably 8 mm or more, more preferably 10 mm or more, even more preferably 15 mm or more, particularly preferably 20 mm or more, and especially preferably 25 mm or more. The working distance L1 is, for example, 60 mm or less, or may be 55 mm or less, or may be 50 mm or less.

[0014] The lens 11 is, for example, a gradient index lens. In FIG. 1, OP is the object plane, IP is the image plane, TC is the conjugate length, Z is the lens length, X is the field radius, and θ C is the aperture angle.

[0015] In Fig. 1, L0 is the distance between the image plane IP and the lens 11 when the modulation transfer function (MTF) value is maximized. In Fig. 1, the lens array 1a constitutes, for example, a substantially erect, equal-magnification imaging system, and the working distance L1 is substantially equal to the distance L0.

[0016] In the lens 11, the conjugate length TC is, for example, 35 mm to 160 mm, preferably 40 mm to 150 mm, and more preferably 48 mm to 100 mm. In the lens 11, the relationship TC=L1+Z+L0 holds.

[0017] In the lens 11, the aperture angle θ C is, for example, 3° to 22°, and preferably 4° to 12°.

[0018] The lens 11 is, for example, a rod lens, and the central axis of the lens 11 extends in the optical axis direction of the lens 11. As shown in Fig. 2, the lens 11 has a refractive index distribution in its radial direction. In Fig. 2, n0 is the refractive index at the central axis of the lens 11, and r is the distance [mm] from the central axis of the lens 11 in the radial direction of the lens 11. The refractive index n(r) of the lens 11 at a distance r is expressed by the following formula (1). In formula (1), g is the refractive index distribution constant [mm -1 ]. n(r) ２ = n0 ２ {1-(g r) ２} Formula (1)

[0019] The refractive index distribution constant of the lens 11 is, for example, 0.06 mm. －１ ~0.48mm －１ and preferably 0.08 mm －１ ~0.26mm －１ is.

[0020] The lens 11 may be made of resin or glass. When the lens 11 is made of resin, examples of the resin that forms the lens 11 include translucent acrylic resin, polycarbonate resin, polyolefin resin, and silicone resin. On the other hand, when the lens 11 is made of glass, the center of the lens 11 has, for example, the following composition. When the center of the lens 11 has such a composition, the working distance L1 tends to be large, and the working distance L1 tends to be a desired value. The center of the lens 11 is, for example, the portion that forms the optical axis of the lens 11. A composition including, in mole percent, 40%≦SiO2≦65%, 0%≦TiO2≦10%, 0.1%≦MgO≦22%, 0.15%≦ZnO≦15%, 0.5%≦Li2O≦15%, 2%≦Na2O≦20%, 0%≦B2O3≦20%, 0%≦Al2O3≦10%, 0%≦K2O≦3%, 0%≦Cs2O≦3%, 0%≦Y2O3≦5%, 0%≦ZrO2≦2%, 0%≦Nb2O5≦5%, 0%≦In2O3≦5%, 0%≦La2O3≦5%, and 0%≦Ta2O5≦5%.

[0021] When the lens 11 is made of glass, the lens 11 can be manufactured by, for example, a method including the following steps (I) and (II): (I) preparing a glass wire having the above-described composition; (II) immersing the glass wire in a molten salt containing a second alkali metal element R different from the first alkali metal element Q contained in the above-described composition to perform an ion exchange treatment between the first alkali metal element Q in the glass wire and the second alkali metal element R in the molten salt, thereby forming a refractive index profile in the glass wire.

[0022] In step (II), for example, a glass wire is placed in molten salt in a container and immersed in the molten salt for a predetermined period of time. The molten salt contains, for example, at least one of potassium nitrate and sodium nitrate. When the glass wire is immersed in the molten salt, cations of a first alkali metal element Q, such as Li (lithium), contained in the glass wire dissolve into the molten salt. Meanwhile, cations of a second alkali metal element R, such as Na (sodium), in the molten salt penetrate into the glass wire. By adjusting the temperature of the molten salt and the immersion time of the glass wire in the molten salt, the ion exchange between the cations of the first alkali metal element Q and the cations of the second alkali metal element R can be appropriately controlled. A concentration distribution of specific monovalent cations occurs within the glass wire, and a lens 11 having a refractive index distribution as shown in FIG. 2 is obtained according to this concentration distribution. Since almost no ion exchange occurs in the center of the glass wire, the center of the lens 11 retains the initial composition of the glass wire. Therefore, the center of the lens 11 has the above-described composition.

[0023] As shown in FIG. 1 , the plurality of lenses 11 are arranged in, for example, a plurality of rows in the second direction (x-axis direction). With this configuration, even if the field of view radius X0 is small, reflected light from the object to be inspected is likely to be focused over the entire second direction of the arrangement of the plurality of lenses 11. As a result, the accuracy of inspecting the presence or absence of defects in the object to be inspected is likely to be high. The number of rows of the plurality of lenses 11 formed in the second direction may be two, or may be three or more. In the row of the plurality of lenses 11 formed in the second direction, rows of lenses 11 adjacent to each other in the first direction are formed so that, for example, the central axes of the plurality of lenses 11 are offset in the second direction.

[0024] The adhesive portion 12 fills the gaps between the lenses 11, thereby integrating the plurality of lenses 11. The adhesive portion 12 contains, for example, a resin and is colored black.

[0025] The housing 15 is not limited to a specific configuration as long as it can accommodate the plurality of lenses 11 and adhesive portions 12. The housing 15 includes, for example, a pair of plate materials aligned in a first direction and a pair of plate materials aligned in a second direction, and is formed as a frame made of these plate materials. These plate materials include, for example, fiber-reinforced plastic (FRP).

[0026] 3, the lens array 1a further includes, for example, an anti-reflection film 20. The anti-reflection film 20 is disposed in contact with, for example, at least one surface selected from the group consisting of the first surface 11a and the second surface 11b. The first surface 11a is the surface of the lens 11 onto which reflected light from an object being transported is incident. The second surface 11b is the surface of the lens 11 from which the light incident on the first surface 11a is emitted.

[0027] As described above, the working distance L1 of the lens 11 is 5 mm or greater, which means that the image obtained by the lens 11 is unlikely to be bright, and the amount of light incident on an imaging element such as a charge-coupled device (CCD) used to inspect the presence or absence of defects in the object being inspected in the above-mentioned instrument is likely to be low. Depending on the lens working distance L1 or aperture angle, for example, using a lens with a working distance L1 1.5 times longer may result in a reduction in brightness by approximately 30%. Therefore, for example, increasing the brightness of the light source used to generate reflected light from the object being inspected is considered. However, a high light source brightness can increase the running costs of the instrument and raise concerns about the impact on the object being inspected due to increased heat generation from the light source. On the other hand, if the lens array 1a is provided with an anti-reflection coating 20, re-reflection of reflected light from the object being inspected at the first surface 11a and the second surface 11b of the lens 11 is suppressed. As a result, even without increasing the brightness of the light source, the lens 11 is likely to produce a bright image, and the amount of light incident on the imaging element is unlikely to be reduced.

[0028] The anti-reflection film 20 may be disposed in contact with only the first surface 11a, may be disposed in contact with only the second surface 11b, or may be disposed in contact with both the first surface 11a and the second surface 11b.

[0029] The anti-reflection film 20 is not limited to a specific form as long as it can increase the amount of light emitted from the second surface 11b compared to when the anti-reflection film 20 is not formed.

[0030] As shown in FIG. 3 , the anti-reflection coating 20 includes, for example, fine particles 21 and a binder 22. The fine particles 21 have a refractive index equal to or lower than that of the lens 11. In this case, the refractive index of the lens 11 is the maximum value of the refractive index of the lens 11, e.g., the refractive index at the center of the lens 11. The binder 22 adheres the fine particles 21 to the first surface 11a or the second surface 11b. With this configuration, the anti-reflection coating 20 easily exhibits the desired anti-reflection properties over a wide wavelength range. This makes it easy for the lens array 1a to accommodate various measurement wavelengths. For example, the desired anti-reflection properties are easily exhibited not only when the measurement wavelength is in the visible light range but also when the measurement wavelength is in the near-infrared range, thereby increasing the amount of light emitted from the second surface 11b. The anti-reflection coating 20 easily exhibits the desired anti-reflection properties even when formed to have a relatively simple structure, such as a single layer structure. In addition, vacuum processes or high-temperature treatments are not required, which prevents the effects of such processes or treatments on the lens 11 and reduces the manufacturing cost of the lens array 1a.

[0031] One possible method for forming an anti-reflection coating on a lens is to form an optical interference film, which is a dielectric multilayer film, by methods such as vacuum deposition, sputtering, and chemical vapor deposition (CVD). However, in this case, the reflectance increases rapidly outside the design wavelength range, and there is a limit to the anti-reflection effect over a wide wavelength range. In addition, this method requires a vacuum process or high-temperature heating, and there is a possibility that the resin contained in the lens array 1a may foam during the vacuum process. For this reason, it is difficult to say that it is practical to form a dielectric optical interference film as an anti-reflection coating on the lens 11.

[0032] For example, the surface layer of the anti-reflection coating 20 is unevenly formed by the fine particles 21. This forms low-refractive-index portions 25a having a refractive index lower than that of the lens 11. With this configuration, the anti-reflection coating 20 is more likely to exhibit the desired anti-reflection characteristics over a wide wavelength range.

[0033] As shown in FIG. 3 , the anti-reflection coating 20 includes a base portion 25b between the low-refractive-index portion 25a and the lens 11 in the thickness direction of the anti-reflection coating 20. The binder 22 forms layers between the fine particles 21 in the base portion 25b. The low-refractive-index portion 25a is a portion of the anti-reflection coating 20 other than the base portion 25b. The binder 22 content in the base portion 25b is higher than the binder 22 content in the low-refractive-index portion 25a, based on mass. This makes it easier for the anti-reflection coating 20 to exhibit the desired anti-reflection performance and makes the anti-reflection coating 20 less likely to peel off from the lens 11. There is a possibility that the anti-reflection coating 20 may come into contact with other objects during maintenance of the above-mentioned equipment. However, because the binder 22 content in the base portion 25b is higher than the binder 22 content in the low-refractive-index portion 25a, the bonding strength of the anti-reflection coating 20 to the lens 11 is likely to be high.

[0034] The anti-reflection coating 20 contains, for example, silicon atoms, and a bond involving silicon atoms, such as an Si—O—Si bond, is formed between the anti-reflection coating 20 and the lens 11. This configuration tends to increase the bonding strength of the anti-reflection coating 20 to the lens 11. If the lens 11 is made of glass, silanol groups may be present on the surface of the lens 11. Therefore, a bond involving silicon atoms, such as an Si—O—Si bond, may be formed by a condensation reaction between the silanol groups on the surface of the lens 11 and the silanol groups contained in the anti-reflection coating 20. If the lens 11 is made of resin, the surface of the lens 11 may be treated with a primer. This may form a bond involving silicon atoms, such as an Si—O—Si bond, between the lens 11 and the anti-reflection coating 20.

[0035] The components contained in the microparticles 21 are not limited to a specific component. The microparticles 21 are mainly composed of, for example, silica. In this specification, a main component is a component that is contained in the largest amount by mass. A bond involving silicon atoms, such as an Si-O-Si bond, is formed between the microparticles 21 and the binder 22. With this configuration, the bonding strength of the antireflection coating 20 to the lens 11 is likely to be higher. The bonding strength between the microparticles 21 and the binder 22 is high, and the microparticles 21 are less likely to come off the antireflection coating 20. As a result, the bonding strength of the antireflection coating 20 to the lens 11 is likely to be high.

[0036] The average particle size of the particles 21 is not limited to a specific value. The average particle size of the particles 21 is, for example, 80 to 600 nm. This makes it easier to adjust the size of the irregularities formed in the low refractive index portion 25a of the anti-reflection coating 20 to a desired range, thereby improving the anti-reflection performance of the anti-reflection coating 20. The average particle size of the particles 21 is determined, for example, by observing the cross section of the anti-reflection coating 20 using a scanning electron microscope (SEM). Specifically, the maximum and minimum diameters of any 50 particles that can be observed in their entirety are measured, and the average value is taken as the particle size of each particle. The average value of the diameters of the 50 particles is taken as the "average particle size." The average particle size of the particles 21 is preferably 100 nm to 500 nm, more preferably 100 nm to 300 nm, even more preferably 100 nm to 200 nm, and particularly preferably greater than 100 nm and 150 nm or less.

[0037] The shape of the fine particles 21 is, for example, a spherical particle. This makes it easier for the unevenness in the low refractive index portion 25a of the antireflection coating 20 to be uniformly formed along the first surface 11a or the second surface 11b, and makes it easier to improve the antireflection performance of the antireflection coating 20. In this specification, "spherical" means a shape in which, when the fine particles 21 are observed with an SEM, the ratio (Dl / Ds) of the minimum diameter (Ds) of the fine particles 21 to the maximum diameter (Dl) of the fine particles 21 is 1.5 or less.

[0038] In a plan view of the antireflection coating 20, the particles 21 are arranged, for example, to cover the entire first surface 11a or the second surface 11b. In the antireflection coating 20, the particles 21 are arranged to form a single layer. For example, in a pair of adjacent particles 21, if the center of one particle is located closer to the first surface 11a or the second surface 11b than the outermost portion of the other particle 21 in the thickness direction of the antireflection coating 20, the particles 21 can be considered to form a single layer. The particles 21 may also be arranged to form multiple layers. In a pair of adjacent particles 21, if the center of one particle is located closer to the outermost portion of the antireflection coating 20 than the outermost portion of the other particle 21 in the thickness direction of the antireflection coating 20, the particles 21 can be considered to form multiple layers.

[0039] The fine particles 21 are, for example, solid particles. In this case, the antireflection coating 20 is likely to have the desired mechanical strength. Since the antireflection coating 20 may come into contact with other objects during the maintenance of the above-mentioned equipment, it is advantageous for the antireflection coating 20 to have high mechanical strength in terms of suppressing deterioration in the antireflection performance of the antireflection coating 20 despite the equipment maintenance.

[0040] The content of the fine particles 21 in the anti-reflection coating 20 is not limited to a specific value. The content is, for example, 35% to 90% by mass. In this case, the fine particles 21 are likely to be arranged in a desired state in the anti-reflection coating 20, and the anti-reflection performance of the anti-reflection coating 20 is likely to be improved. The content of the fine particles 21 in the anti-reflection coating 20 is preferably 40% to 90%, and more preferably 45% to 85%.

[0041] The thickness of the anti-reflection coating 20 is not limited to a specific value. The thickness of the anti-reflection coating 20 is, for example, 80 nm to 800 nm. In this case, the anti-reflection performance of the anti-reflection coating 20 is likely to be enhanced. The thickness of the anti-reflection coating 20 is preferably 100 nm to 500 nm, and more preferably greater than 100 nm but not greater than 150 nm. The thickness of the anti-reflection coating 20 can be determined, for example, as the product of the average distance from the first surface 11a or the second surface 11b in the thickness direction of the anti-reflection coating 20 to the outermost convex portions of the uneven surface layer of the anti-reflection coating 20 and the packing rate of the fine particles 21 per unit distance. The unit distance is, for example, a distance equivalent to an integer multiple (e.g., 10 times) of the average particle diameter of the fine particles 21. The packing rate is the value obtained by dividing the number of convex portions included in a unit distance by an integer multiple of the average particle diameter of the fine particles 21 corresponding to that unit distance. The thickness of the anti-reflection coating 20 can be determined by observing a cross section of the anti-reflection coating 20 with an SEM.

[0042] The ratio of the average particle size of the particles 21 to the thickness of the anti-reflection film 20 is not limited to a specific value. The ratio is, for example, 0.3 to 1, preferably 0.5 to 1, and more preferably 0.8 to 1.

[0043] The thickness of the base 25b of the antireflection coating 20 is not limited to a specific value. The thickness of the base 25b is, for example, the arithmetic mean of the thicknesses of the base 25b at the locations where the thickness of the antireflection coating 20 is determined. The thickness of the base 25b is, for example, 10 nm to 300 nm, preferably 10 nm to 200 nm, and more preferably 10 nm to 70 nm.

[0044] The thickness of the low refractive index portion 25a in the antireflection coating 20 is not limited to a specific value. The thickness of the low refractive index portion 25a is determined, for example, by subtracting the thickness of the base portion 25b from the thickness of the antireflection coating 20 determined as described above. The thickness of the low refractive index portion 25a is, for example, 30 nm to 600 nm, preferably 35 nm to 500 nm, more preferably 40 nm to 300 nm, even more preferably 40 nm to 200 nm, and particularly preferably 40 nm to 130 nm.

[0045] The ratio of the thickness of the low refractive index portion 25a to the thickness of the base portion 25b is not limited to a specific value. This ratio is, for example, 1 to 8. With this configuration, the bonding strength of the anti-reflection coating 20 to the lens 11 tends to be higher. This ratio is preferably 1 to 7, and more preferably 1 to 6.

[0046] The components contained in the binder 22 are not limited to specific components. The binder 22 contains, for example, silica as a main component. The binder 22 may contain only silica, may contain a hydrophobic group, or may contain an aluminum compound.

[0047] The binder content in the anti-reflection coating 20 is not limited to a specific value. The content is, for example, 5% to 64% by mass. In this case, the surface irregularities of the anti-reflection coating 20 are likely to be formed in a desired state, and the anti-reflection performance of the anti-reflection coating 20 is likely to be improved. In addition, the base 25b is likely to be formed over the entire anti-reflection coating 20, and the bonding strength of the anti-reflection coating 20 to the lens 11 is likely to be higher. The binder content in the anti-reflection coating 20 is preferably 10% to 60%, and more preferably 15% to 55%.

[0048] For example, when the binder content in the antireflection film 20 is 5% to 35%, the antireflection performance of the antireflection film 20 is likely to be higher. From the viewpoint of antireflection performance, this content is preferably 10% to 35%, and more preferably 15% to 35%.

[0049] When the binder content in the anti-reflection coating 20 is 35% to 64%, the bonding strength of the anti-reflection coating 20 to the lens 11 is likely to be higher, and the anti-reflection coating 20 is likely to have high durability. For example, the anti-reflection coating 20 is likely to have high scratch resistance. From the viewpoint of scratch resistance, this content is preferably 35% to 60%, more preferably 35% to 50%, and even more preferably 35% to 40%. For example, the anti-reflection coating 20 has a pencil hardness of HB or higher, at which the anti-reflection coating 20 remains when scratched with a pencil under specified conditions. This pencil hardness is preferably H or higher, and more preferably 2H or higher.

[0050] When the bonding strength of the anti-reflection coating 20 to the lens 11 is high, the anti-reflection coating 20 is likely to have excellent peel resistance. As described above, the lens array 1a can be used in equipment that inspects for defects using reflected light from transported inspection objects. Such equipment may require space for maintenance. Even if the lens working distance L1 is equal to or greater than a predetermined value, as in the lens array 1a, sufficient space for equipment maintenance may not always be secured. For this reason, the anti-reflection coating 20 imparting high scratch resistance or peel resistance to the lens 11 is particularly advantageous when considering contact between the lens array and other objects during equipment maintenance, etc.

[0051] The silica contained in the binder 22 is derived from, for example, a hydrolyzable silicon compound or a hydrolyzate of a hydrolyzable silicon compound added to the coating liquid for forming the anti-reflection film 20. This hydrolyzable silicon compound includes, for example, a compound shown in the following formula (Ia). In the following formula (Ia), X is at least one selected from the group consisting of an alkoxyl group, an acetoxy group, an alkenyloxy group, an amino group, and a halogen atom. In this specification, the hydrolyzable silicon compound includes an oligomer of a hydrolyzable silicon compound. This oligomer is formed by condensing, for example, about 2 to 200 molecules of the same type. SiX4 (Ia)

[0052] A hydrolyzable silicon compound, such as silicon alkoxide, can be used as a supply source of silica contained in the binder 22. Examples of silicon alkoxide include tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane. These hydrolyzable silicon compounds are hydrolyzed and polycondensed by a so-called sol-gel method to form the binder 22.

[0053] The hydrolysis of the hydrolyzable silicon compound can be carried out as needed, but is preferably carried out in a solution containing the microparticles 21. This is because the condensation polymerization reaction between the silanol groups present on the surface of the microparticles 21 and the silanol groups generated by hydrolysis of the hydrolyzable silicon compound, such as silicon alkoxide, is promoted, thereby increasing the proportion of binder 22 that contributes to improving the bonding strength of the microparticles 21. The coating liquid is preferably prepared by sequentially adding a hydrolysis catalyst and silicon alkoxide to a solution containing the microparticles 21 while stirring. The silicon alkoxide may be a monomer or an oligomer. While either an acid or a base can be used as the hydrolysis catalyst, it is preferable to use an acid, particularly an acid with a high degree of ionization in aqueous solution. Specifically, it is preferable to use an acid with an acid dissociation constant pKa (meaning the first acid dissociation constant when the acid is a polybasic acid) of 2.5 or less. Examples of suitable acids include volatile inorganic acids such as hydrochloric acid and nitric acid, organic acids such as trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid, and polybasic acids such as maleic acid, phosphoric acid, and oxalic acid. Acidic solutions are more effective than basic solutions in dispersing silica particles and providing a coating solution with excellent stability. Furthermore, chloride ions derived from hydrochloric acid increase the chloride ion concentration in the coating solution, which can further enhance the effects of aluminum chloride when added to the coating solution.

[0054] When the binder 22 contains a hydrophobic group, the content of the hydrophobic group in the antireflection film 20 is not limited to a specific value. The content of the hydrophobic group is, for example, 0 to 10% by mass. With this configuration, dirt adhering to the antireflection film 20 is easily removed. The content of the hydrophobic group contained in the binder 22 in the antireflection film 20 is preferably 0.2 to 10%, and more preferably 0.2 to 8%.

[0055] The hydrophobic group contained in the binder 22 is preferably derived from a hydrolyzable silicon compound or a hydrolyzate of a hydrolyzable silicon compound having a hydrophobic group directly bonded to silicon, which is added to the coating liquid for forming the anti-reflection film 20. This hydrolyzable silicon compound includes, for example, a compound shown in the following formula (IIa). In the following formula (IIa), the hydrolyzable group Y is preferably at least one selected from the group consisting of an alkoxyl group, an acetoxy group, an alkenyloxy group, an amino group, and a halogen atom. In the following formula (IIa), the hydrophobic group R is preferably a linear or cyclic alkyl group having 1 to 30 carbon atoms, at least a portion of whose hydrogen atoms may be substituted with fluorine atoms, more preferably a linear alkyl group, even more preferably a linear alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. RSiY3 (IIa)

[0056] When the binder 22 contains an aluminum compound, the content of the aluminum compound in the anti-reflection coating 20 is not limited to a specific value. The content is, for example, 0 to 7% by mass, calculated as Al2O3. This configuration tends to increase the chemical durability of the anti-reflection coating 20. Therefore, the anti-reflection coating 20 tends to have the desired chemical resistance, particularly the desired alkali resistance. As a result, the range of objects that can be inspected using the lens array 1a tends to be wider. The content of the aluminum compound in the anti-reflection coating 20 is preferably 2 to 7%, and more preferably 4 to 7%.

[0057] As shown in FIG. 4 , an apparatus 2a including a lens array 1a can be provided. The apparatus 2a is an apparatus that inspects the presence or absence of defects using light reflected from an inspection object T being transported. The apparatus 2a includes a reading device 71, an illumination device 72, a controller 73, an output device 74, a conveying device 75, and a transport control device 76. The lens array 1a is disposed inside the reading device 71. The conveying device 75 is, for example, a belt conveyor. The conveying device 75 may also be a conveying device compatible with a roll-to-roll system. The conveying device 75 transports the inspection object T, such as a printed circuit board, textile, film, or paper. The transport control device 76 is a digital computer for controlling the conveying device 75 and outputs a control signal to the conveying device 75 to adjust the transport speed of the conveying device 75. The reading device 71 and the illumination device 72 are disposed, for example, above the conveying device 75, and the inspection object T passes directly below the reading device 71 by the conveying device 75. The reading device 71 and the illumination device 72 are arranged so that light emitted from the illumination device 72 is reflected by the object to be inspected T and the reflected light is focused on the lens array 1a. This allows the reading device 71 to obtain image data of the object to be inspected T. The controller 73 is a digital computer for forming image data of the object to be inspected T. When the object to be inspected T passes directly below the reading device 71, the controller 73 continuously acquires image information from the reading device 71. In addition, the controller 73 acquires transport position information of the object to be inspected T from the reading device 71. The controller 73 performs calculations based on the image information acquired from the reading device 71 and the transport position information acquired from the transport control device 76 to form two-dimensional image information. The formed two-dimensional image information is compared with information characterizing defects such as foreign objects, cracks, and pinholes that is pre-stored in the controller 73. This allows the controller 73 to identify the presence or absence of defects in the object to be inspected T, the number of defects, and their locations. Based on the comparison result, the controller 73 may determine whether the inspection object T is good or bad. The output device 74 is, for example, a monitor, and displays the two-dimensional image information formed by the controller 73.

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0059] Reference Example 1 Glass raw materials were mixed to obtain the composition shown in Table 1, and the mixture was melted to obtain a glass melt (glass composition) according to Reference Example 1. The values ​​in Table 1 indicate mol %. The glass melt according to Reference Example 1 was spun into fibers, and the obtained glass fibers were cut to a predetermined length and the cut surfaces were polished. This resulted in a glass strand according to Reference Example 1. The diameter (filament diameter) of the glass strand was 1000 μm. Next, each glass strand was immersed in molten sodium nitrate heated to near the glass transition temperature of the glass composition constituting each glass strand, and an ion exchange treatment was performed. This resulted in a refractive index distribution in each glass strand. The glass strand after the ion exchange treatment was then cut to a predetermined length to obtain a lens according to Reference Example 1. Table 2 shows the working distance L1, lens length Z, conjugate length TC, field of view radius X0, and aperture angle θ of this lens. C , refractive index distribution constant g [mm －１ ] denotes the refractive index n0 at the central axis of the lens.

[0060] Between a pair of parallel rectangular FRP flat plates, a plurality of lenses according to Reference Example 1 were arranged in two rows along the longitudinal direction of the plates, spaced 1 mm apart so that they were parallel to each other. A black-colored adhesive resin was then filled between the plates and cured to fix the lenses. Both ends of each lens were then cut and polished. Another pair of FRP substrates was placed at both longitudinal ends of the flat plates, and the frames formed by these FRP flat plates housed the lenses and the adhesive joints obtained by curing the adhesive resin. In this manner, the lens array according to Reference Example 1 was obtained.

[0061] Example 1 28.3 parts by mass of silica fine particle dispersion (Quartrone PL-7, approximately spherical primary particles with an average particle size of 125 nm, solids concentration 23% by weight, manufactured by Fuso Chemical Co., Ltd.), 58.6 parts by mass of 1-methoxy-2-propanol (solvent), and 1 part by mass of 1N hydrochloric acid (hydrolysis catalyst) were mixed by stirring, and 12.1 parts by mass of tetraethoxysilane (ethyl orthosilicate, manufactured by Tama Chemicals Co., Ltd.) was added with further stirring, and the mixture was subsequently stirred for 8 hours while maintaining the temperature at 40°C to hydrolyze the tetraethoxysilane, thereby obtaining a stock solution A. In stock solution A, the ratio of the mass of the silica fine particles to the mass of the hydrolysis condensation product of the hydrolyzable silicon compound contained in the binder was 65:35.

[0062] 16.0 g of the above-mentioned stock solution A, 5.0 g of propylene glycol (solvent), 78.5 g of 1-methoxy-2-propanol (solvent), 0.4 g of an aqueous aluminum chloride solution (47.6% by mass as AlCl3, prepared by dissolving reagent-grade aluminum chloride hexahydrate (manufactured by Sigma-Aldrich) in deionized water), and 0.1 g of KP-112 (Shin-Etsu Chemical Co., Ltd., polyether-type surface modifier, 50% by mass concentration, 1-methoxy-2-propanol solution) were stirred and mixed to obtain a coating liquid according to Example 1. In this coating liquid, the solids concentration of silica (derived from silica fine particles and alkoxysilane) converted to SiO2 was 1.6% by mass, and the aluminum compound converted to Al2O3 was 5.0 parts by mass when the silicon oxide converted to SiO2 was 100 parts by mass.

[0063] The coating liquid according to Example 1 was applied by dip coating to both end surfaces in the lens length direction of a lens array produced in the same manner as in Reference Example 1 to form a coating film. In the dip coating, the lens array was fixed to a support fixture of a dip coater with a clip, immersed in the coating liquid according to Example 1 that filled a container, and pulled up at a speed of 2.6 mm / sec to form a coating film. This coating film was heated at 200°C for 1800 seconds to form an anti-reflection film on both end surfaces in the lens length direction of the lens array. In this way, the lens array according to Example 1 was obtained.

[0064] Example 2 A coating liquid according to Example 2 was obtained in the same manner as Example 1, except that the aluminum chloride aqueous solution was not added. A lens array according to Example 2 was obtained in the same manner as Example 1, except that the coating liquid according to Example 2 was used instead of the coating liquid according to Example 1.

[0065] Example 3 A coating liquid according to Example 3 was prepared in the same manner as in Example 2, except that the amount of each raw material added was adjusted so that the content of each component was as shown in Table 3. The solid content of the coating liquid according to Example 3 was 1.3 mass %. A lens array according to Example 3 was obtained in the same manner as in Example 1, except that the coating liquid according to Example 3 was used instead of the coating liquid according to Example 1, and the pull-up speed in dip coating was adjusted to 2.0 mm / sec.

[0066] Example 4 A coating liquid according to Example 4 was prepared in the same manner as Example 1, except that methyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was further added in addition to tetraethoxysilane, and the amount of each raw material added was adjusted so that the content of each component was as shown in Table 3. Aluminum nitrate was used as the aluminum compound instead of aluminum chloride. The solid content of the coating liquid according to Example 4 was 1.6 mass%. The content of methyl groups, which are hydrophobic groups, in the solid content of the coating liquid was 2.8 mass%. A lens array according to Example 4 was obtained in the same manner as Example 1, except that the coating liquid according to Example 4 was used instead of the coating liquid according to Example 1.

[0067] Example 5 A coating liquid according to Example 5 was prepared in the same manner as in Example 4, except that methyltriethoxysilane was not added and the amount of each raw material added was adjusted so that the content of each component was as shown in Table 3. A lens array according to Example 5 was obtained in the same manner as in Example 1, except that the coating liquid according to Example 5 was used instead of the coating liquid according to Example 1.

[0068] Example 6 A lens array according to Example 6 was obtained in the same manner as in Example 1, except for the following points. A coating liquid according to Example 6 was prepared by adjusting the amount of each component so that the solid content concentration was 2.5% by mass. In the dip coating, the coating liquid according to Example 6 was used instead of the coating liquid according to Example 1, and the pull-up speed in the dip coating was adjusted to 1.0 mm / sec.

[0069] Example 7 A lens array according to Example 7 was obtained in the same manner as in Example 1, except for the following points. The amount of each component was adjusted to prepare a coating liquid according to Example 7 so that the solid content concentration was 3.5% by mass. In the dip coating, the coating liquid according to Example 7 was used instead of the coating liquid according to Example 1, and the pull-up speed in the dip coating was adjusted to 1.0 mm / sec.

[0070] Example 8 0.6 g of tetraethoxysilane (TEOS) (Tokyo Chemical Industry Co., Ltd.), 1.18 g of methyltriethoxysilane (MTES) (Tokyo Chemical Industry Co., Ltd.), 0.82 g of 0.3% by mass formic acid (Kishida Chemical Co., Ltd.), 3 g of hollow silica particle-containing sol (JGC Catalysts and Chemicals, product name: Sururia 4110), and 22.4 g of ethanol (Kishida Chemical Co., Ltd.) were mixed and reacted at 35°C for 3 hours. The hollow silica particle-containing sol used contained a solvent and 25% by mass of hollow silica as a solid content, and the average particle diameter of the hollow silica particles in the number-based particle size distribution was approximately 50 nm. The thickness of the silica shell of the hollow silica particles was 10 to 20 nm. The maximum dimension of the internal space of the hollow silica particles was approximately 10 to 30 nm. The refractive index of the hollow particles was 1.25. In this way, a coating liquid according to Example 8 was obtained. In the coating liquid of Example 8, the content of solids derived from TEOS was 0.6 mass% in terms of silica, the content of methylsilsesquioxane (MeSq), which is a solid content derived from MTES, was 1.6 mass%, and the content of hollow silica particles was 2.6 mass%. The solids of the coating liquid of Example 8 contained, by mass, 13% silica derived from TEOS, 33% MeSq derived from MTES, and 54% hollow silica particles. The content of hollow silica particles was calculated assuming that the solid content of the hollow silica particle-containing sol was 25 mass%, and that the solid content was hollow silica particles. The ratio of the mass of MTES to the mass of TEOS added in the preparation of the coating liquid of Example 8 was 7 / 3. A lens array of Example 8 was obtained in the same manner as Example 2, except that the coating liquid of Example 8 was used instead of the coating liquid of Example 2. Fig. 6 is a cross-sectional view schematically showing an antireflection film in a lens array according to Example 8. As shown in Fig. 6, the antireflection film 20 is disposed in contact with the end face of the lens 11 in the longitudinal direction. The antireflection film 20 contains hollow silica particles 53 and a binder 54, and voids 55 exist inside the antireflection film 20 and at the boundary between the antireflection film 20 and the end face of the lens 11.

[0071] (Light Intensity Measurement) A flat reflector was placed on the object plane corresponding to the working distance of the lenses of the lens array of each example. The reflected light generated by reflecting light from the light source was incident on the lens array, and the light intensity [lx] at a position corresponding to the image plane of the lens array was measured. The relative values ​​of the light intensity at a wavelength of 530 nm when using the lens array of Examples 1 to 7 were calculated, assuming the light intensity when using the lens array of Reference Example 1 at a wavelength of 530 nm to be 100. The results are shown in Table 4. For the lens arrays of Examples 1, 3, 4, 6, and 7, the end faces of the lens arrays were rubbed 40 times with Toraysee (registered trademark), a cloth manufactured by Toray Industries, Inc., and then the light intensity was evaluated in the same manner. The cloth was dried. For the lens arrays of Examples 1, 3, 4, 6, and 7, the end faces of the lens arrays were rubbed 40 times with a cloth soaked in ethanol and then the light intensity was evaluated in the same manner. The results are shown in Table 4.

[0072] (Pencil Hardness) A pencil hardness test was performed on the anti-reflection films formed on the lens arrays according to Examples 1 to 8 in accordance with Japanese Industrial Standards (JIS) K 5600-5-4 using a pencil hardness tester (Pencil Scratch Hardness Tester Model: 720N, Brand: Sheen Instruments - UK) and a pencil (UNI, Mitsubishi Pencil, hardness 2B to 9H). In this test, the angle of the pencil to the anti-reflection film was 45°, and the pencil was pressed with a load of 750 g. The pencil hardness was measured by pressing and moving pencil leads with several levels of hardness against the anti-reflection film while gradually increasing the hardness. In this measurement, the pencil was moved at a speed of 1 mm / sec, and the pencil movement distance was adjusted to 20 mm or more. After the test, the pencil lead powder adhering to the anti-reflection film was wiped off with ethanol-soaked Bemcot, and scratches on the anti-reflection film resulting from the test were observed under an optical microscope. The pencil hardness of the anti-reflective film was evaluated as the hardness that was one level softer than the hardness at which scratches that removed the anti-reflective film occurred or peeling of the anti-reflective film occurred to expose the substrate surface, in other words, the maximum hardness at which no scratches were generated on the anti-reflective film or no peeling that exposed the substrate surface occurred. The results are shown in Table 4.

[0073] (SEM Observation) A field emission scanning electron microscope (FE-SEM) (Hitachi, Ltd., Model: S-4500) was used to observe the cross section of the antireflection coating formed on the lens array according to Examples 1 to 7. In an FE-SEM photograph of a cross section of the antireflection coating taken from a 10° oblique angle above, the distance in the thickness direction of the antireflection coating between the outermost convex portion of the unevenness of the surface layer of the antireflection coating that appears at a distance (1250 nm) equivalent to 10 times the average particle size of the silica microparticles and the end face of the lens array that contacts the antireflection coating was measured, and the arithmetic mean D1 of this distance was calculated. Furthermore, the number of convex portions appearing at that location was determined. This number was divided by 10 to determine the filling rate f of the silica microparticles per unit distance. The thickness T1 of the antireflection coating was determined as the product of the arithmetic mean D1 and the filling rate f. The results are shown in Table 4. In addition, the arithmetic mean T2 of the thickness of the base at the antireflection coating location used to calculate the arithmetic mean D1 was calculated. The thickness T3 of the low refractive index portion was determined by subtracting the arithmetic mean T2 of the thickness of the base portion from the thickness T1 of the antireflection film. The results are shown in Table 4. FE-SEM photographs of the cross sections of the antireflection films formed on the lens arrays according to Examples 1, 6, and 7 are shown in Figures 5A, 5B, and 5C, respectively.

[0074] (Reflectance Measurement A) Using an Olympus USPM-RU-W near-infrared microspectrometer, the reflectance of one end face in the lens length direction of the lens arrays according to Reference Example 1 and Examples 1 to 7 was measured. In this measurement, the wavelength range was set to 380 to 1050 nm, and the diameter of the measurement range was adjusted to 70 μm using an objective lens with a 10x magnification. In addition, the reflectance measurement position was adjusted to the center position of the lens in the lens array. The results are shown in Table 4.

[0075] (Reflectance Measurement B) An antireflection film was formed on the surface of a glass plate in the same manner as in Examples 1 and 3, except that a float glass substrate was used instead of a lens array. In addition, an optical interference film, a dielectric multilayer film, was formed on the surface of the float glass substrate by physical vapor deposition (PVD), to obtain an antireflection film according to Comparative Example 1. The reflectance of these antireflection films formed on the surface of the glass plate was measured using an Olympus USPM-RU-W near-infrared microspectrophotometer. In addition, the reflectance of the surface of a glass plate without an antireflection film was also measured. In this measurement, the wavelength range was set to 380 to 1050 nm, and the diameter of the measurement range was adjusted to 70 μm using an objective lens with a 10x magnification. The results are shown in Table 5.

[0076] (Salt Spray Test) A salt spray test was conducted with reference to JIS C8917:2005, in which salt water was sprayed onto the end faces of the lenses in the lens length direction of the lens arrays according to Examples 1 to 5. In this salt spray test, the environmental temperature of the lens array was adjusted to 35°C, and a 5% by mass aqueous solution of sodium chloride was used as the salt water. In addition, the salt spray test was carried out for 96 hours. The amount of change in transmittance of the lens array before and after the salt spray test was measured. For this measurement, light with a wavelength in the range of 380 to 850 nm was used, and the amount of change in the average transmittance in this range was determined. The results are shown in Table 5.

[0077] The working distance L1 of the lenses in the lens array according to each embodiment is 5 mm or more, so even when used in equipment that inspects for defects using reflected light from an object being transported, sufficient space can be secured for equipment maintenance.

[0078] As shown in Table 4, a comparison of the lens array of Reference Example 1 with the lens arrays of Examples 1 to 8 reveals that forming an anti-reflection coating on the end faces of the lenses of the lens array increases the amount of light passing through the lens array. Therefore, forming an anti-reflection coating is considered advantageous from the perspective of suppressing a decrease in the amount of light due to a long working distance L1. Additionally, it can be seen that a large amount of light passes through the lens array even when the anti-reflection coating of the lens arrays of Examples 1, 3, 4, 6, and 7 is rubbed with a specified cloth. The results of reflectance measurement A reveal that the anti-reflection coating of the lens arrays of Examples 1 to 7 reduces the reflectance of the end faces in the lens length direction compared to the lens array of Reference Example 1.

[0079] In particular, it is understood that according to Example 3, the antireflection film can exhibit high antireflection performance, and the amount of light passing through the lens array can be increased.

[0080] According to Example 4, it is suggested that the antireflection film exhibits a predetermined antireflection performance, has a high pencil hardness, and has high scratch resistance.

[0081] As shown in Table 5, the antireflection films formed using the coating liquids according to Examples 1 and 3 can reduce the reflectance at wavelengths of 530 nm, 700 nm, 900 nm, and 1000 nm compared to a glass plate on which no antireflection film is formed. In addition, it is understood that these antireflection films can prevent the reflectance from increasing sharply with increasing wavelength, as seen in Comparative Example 1, and can exhibit antireflection properties even at wavelengths in the near-infrared region.

[0082] As shown in Table 4, a comparison between Example 1 and Example 2 shows that the change in transmittance before and after the salt spray test is small in Example 1, and it is understood that the antireflection film of the lens array according to Example 1 has higher chemical resistance, particularly higher alkali resistance, than the antireflection film of the lens array according to Example 2. It is understood that the inclusion of an aluminum compound in the binder of the antireflection film is advantageous from the perspective of improving chemical resistance, particularly alkali resistance. A comparison between Example 4 and Example 5 shows that the change in transmittance before and after the salt spray test is small in Example 4, and it is understood that the antireflection film of the lens array according to Example 4 has higher chemical resistance, particularly higher alkali resistance, than the antireflection film of the lens array according to Example 5. It is understood that the inclusion of a hydrophobic group such as a methyl group in the binder of the antireflection film is advantageous from the perspective of improving chemical resistance, particularly alkali resistance.

[0083] As shown in Figures 5A to 5C, the surface layer of the anti-reflection coating formed on the lens arrays according to Examples 1, 6, and 7 had a low refractive index portion with irregularities formed by arranging silica fine particles in a single layer or multiple layers. Considering the refractive index of silica, it can be understood that the refractive index of the low refractive index portion is lower than the refractive index n0 at the central axis of the lenses in the lens array. Additionally, a base was formed between the irregularities of this surface layer and the lens array, and the binder formed a phase in the base. The base of the anti-reflection coating contained a large amount of binder, and it is believed that the binder content in the base was higher, by mass, than the binder content in the low refractive index portion.

[0084]

[0085]

[0086]

[0087]

[0088]

Claims

1. A lens array used in an apparatus for inspecting the presence or absence of defects by reflected light from a conveyed inspection object, a plurality of lenses arranged in a first direction which is the conveyance direction of the inspection object and a second direction perpendicular to the conveyance direction, and condensing the reflected light, an adhesive portion for fixing the lenses to each other, a housing that houses the plurality of lenses and the adhesive portion, and an antireflection film, wherein the antireflection film includes fine particles having a refractive index equal to or lower than the refractive index of the lens and a binder, and is disposed in contact with at least one selected from the group consisting of a first surface of the lens on which the reflected light is incident and a second surface of the lens from which the light incident on the first surface exits, and the binder adheres the fine particles to the first surface or the second surface, a lens array.

2. The lens is a refractive index distribution type lens, The lens array according to claim 1.

3. The antireflection film has a surface layer including irregularities formed by the fine particles, The lens array according to claim 1.

4. The antireflection film includes a base portion between the irregularities and the lens in the thickness direction of the antireflection film, and the binder forms a layer between the fine particles at the base portion, The lens array according to claim 3.

5. A bond involving silicon atoms is formed between the antireflection film and the lens, The lens array according to claim 1.

6. The fine particles mainly contain silica, The lens array according to claim 1.

7. A bond involving silicon atoms is formed between the fine particles and the binder, The lens array according to claim 6.

8. The fine particles have an average particle size of 80 to 600 nm, The lens array according to claim 1.

9. The antireflection film has a film thickness of 80 to 800 nm, The lens array according to claim 1.

10. The content of the binder in the antireflection film is 5 to 64% by mass, and the content of the fine particles in the antireflection film is 35 to 90% by mass, The lens array according to claim 1.

11. The binder contains a hydrophobic group, The lens array according to claim 1.

12. The content of the hydrophobic group in the binder is 10% by mass or less. The lens array according to claim 11.

13. The binder contains an aluminum compound. The lens array according to claim 1.

14. The content rate of the aluminum compound in the antireflection film is 7% by mass or less in terms of converting the aluminum compound into Al 2 O 3 ​ The lens array according to claim 13.

15. The lens has an operating distance of 15 mm or more. The lens array according to claim 1.

16. The lens is expressed in mol%. 40% ≤ SiO 2 ≤ 65% 0% ≤ TiO 2 ≤ 10% 0.1% ≤ MgO ≤ 22% 0.15% ≤ ZnO ≤ 15% 0.5% ≤ Li 2 O ≤ 15% 2% ≤ Na 2 O ≤ 20% 0% ≤ B 2 O 3 ≤ 20% 0% ≤ Al 2 O 3 ≤ 10% 0% ≤ K 2 O ≤ 3% 0% ≤ Cs 2 O ≤ 3% 0% ≤ Y 2 O 3 ≤ 5% 0% ≤ ZrO 2 ≤ 2% 0% ≤ Nb 2 O 5 ≤ 5% 0% ≤ In 2 O 3 ≤ 5% 0% ≤ La 2 O 3 ≤ 5% 0% ≤ Ta 2 O 5 ≤ 5%, having a central portion containing The lens array according to claim 1.

17. The plurality of lenses form a plurality of columns in the second direction. The lens array according to claim 1.