JP2014031288A - Molding die for microlens array and method and apparatus for manufacturing microlens array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding die for a microlens array capable of forming a smooth optical surface shape without reflecting surface roughness of the molding die, and a method and apparatus for manufacturing the microlens array.SOLUTION: An apparatus for manufacturing a microlens array 21 includes: a molding die 1 for a microlens array having a laminate plate in which a plurality of thin metal plates, in which etching holes are arranged to form penetration etching holes, are laminated to provide through holes, and a separation film formed on at least one side of the laminate plate; a holding vessel 22 which holds the molding die 1 for the microlens array and is divided into a first space 24 formed in a side of a contact surface between the molding die 1 for the microlens array and a glass material 80 and a second space 25 formed in a side of an opposite surface of the contact surface of the molding die 1 for the microlens array; and a pressure control part 23 which generates a differential pressure so that a pressure in the second space 25 becomes lower than that in the first space 24.

Description

  The present invention relates to a mold for microlens array and a method and apparatus for manufacturing a microlens array, and in particular, a microlens array capable of forming a convex microlens with a smooth surface and a uniform shape without variation. The present invention relates to a molding die and a microlens array manufacturing method and manufacturing apparatus using the same.

  A microlens used in an image sensor of a digital camera, a liquid crystal projector, a laser projector for optical communication, or the like is usually used in a form called a microlens array in which a plurality of microlenses are arranged in a grid pattern.

  In this microlens array, a glass material for molding is sandwiched and pressed between an upper mold formed by aligning a plurality of concave surfaces corresponding to microlenses on a molding surface and a lower mold having a molding surface in a flat plate shape. A plurality of aligned microlens shapes can be transferred to a glass material by a single molding operation.

  The molding surface of the upper mold used here is formed as a concave surface corresponding to the microlens array by pressing the surface of a plate-shaped material serving as a molding die with a punch tool having a spherical tip. A method of manufacturing a microlens array having an optical surface having the above-described molding surface shape by pressing a heated and softened glass material against a molding die having a concave molding surface is known (see Patent Document 1). ).

  In addition, when manufacturing a glass article having a recess, although not a microlens array, a through hole that leads to the molding surface is formed in the molding die with the aim of uniform thickness and appropriate surface properties. There is also known a method in which molding is performed by generating a force that draws softened glass into the molding surface side by making the pressure in the molding surface negative (see Patent Documents 2 and 3).

  However, in the microlens array described in Patent Document 1, the surface roughness of the optical surface is affected by the surface roughness of the concave molding surface forming the optical surface, and particularly when the lens diameter is small, the molding surface It was also difficult to polish the surface, and a sufficiently smooth optical surface could not be obtained. In addition, in the glass article of Patent Document 2 and the glass molded article of Patent Document 3, molding is assisted by forming a negative pressure in the molding surface, but eventually the shape of the molding surface is transferred to the glass article or the glass molded product. As in Patent Document 1, the surface of a glass article or glass molded product is affected by the surface roughness of the molding surface. In addition, since patent document 2 is a glass article and patent document 3 is a glass molded product and is not an optical product such as a microlens array, the surface roughness of the product is not particularly mentioned.

  On the other hand, instead of molding the microlens by transfer, a method is known in which a concave portion is formed so that the molded portion surface of the mold does not contact the optical surface, and the optical surface is molded as a free surface. (For example, see Patent Documents 4 and 5).

  However, the method of molding without contacting these optical surfaces uses a pressing pressure of the molding die by sandwiching the glass material with the molding die, and therefore generates a uniform pressure on the entire surface of the microlens. However, when the pressure becomes non-uniform, there is a problem that the individual lens shapes vary. In addition, since the pressure escapes to the side of the glass during molding by pressing, the shape is not symmetrical with respect to the top of the surface, and there is a limit to pushing the glass material into the molding surface, and the height of the optical surface There are problems such as making adjustment difficult.

  In order to solve such problems, the inventors of the present invention can form a smooth lens shape without reflecting the surface roughness of the mold and adjust the height of the lens when manufacturing the microlens array. In addition, in the manufacture of microlens arrays, an application has already been filed for an optical element manufacturing method and apparatus capable of forming individual lens shapes into a uniform shape (Japanese Patent Application No. 2011-183976). .

  By the way, the size of the micro lens is determined by the diameter of the through hole formed in the mold. As such a hole processing method, for example, a machining method by laser processing, drill processing, or the like is known for a plate that is a base material of a mold.

  Also, although not related to the production of the microlens array, a metal plate having fine holes smaller in diameter than the plate thickness is formed by forming a plurality of pores in the metal thin plate by etching, aligning the pores, and laminating them. It is known (see, for example, Patent Document 6).

JP-A-11-277543 JP 2007-131499 A JP 2011-153051 A JP 2007-182372 A JP 2006-111491 A Japanese Patent No. 3409153

  However, although drilling is easy to produce a hole with a relatively large diameter, it has a small diameter of 100 μm or less and a depth of about 0.8 mm to 5 mm according to the thickness that can ensure strength as a microlens array mold. When producing holes, drilling as well as laser processing was difficult. In addition, since the microlens array can have thousands of holes, when creating a mold with a large number of holes, drilling or laser processing is performed one by one. This method takes time and effort. In addition, when a large number of holes are processed by laser processing, the entire plate is warped due to thermal strain, and there is a problem that flatness necessary for a mold cannot be ensured. In addition, if a large number of holes are drilled, there is a risk that the hole diameter may change due to tool wear or the pitch may be shifted due to drill replacement, and it is necessary to remove burrs on the drill penetration side. Become. Furthermore, in both drilling and laser processing, there is a problem that the manufacturing cost increases.

  In addition, the metal plate having micropores produced by the method of Patent Document 6 has no description regarding handling as a mold for glass, and there is no description regarding a glass microlens array. In particular, since the microlens array is required to have a highly accurate surface shape with little variation for each microlens, high precision is similarly required for a mold used for molding a glass microlens array. Even if it is assumed that the metal plate produced by the method of Patent Document 6 is used as a mold for molding in contact with glass softened by heating, the surface of the microlens array after molding is smoothed. There was a problem that it was not possible.

  Therefore, the present invention reduces the labor of manufacturing and realizes processing of a large number of minute holes with high accuracy, with respect to a glass mold for micro-les array having a hole diameter that has been difficult to manufacture. An object of the present invention is to provide a manufacturing method and a manufacturing apparatus of a microlens array using a mold.

  The mold for forming a microlens array of the present invention has a plurality of metal thin plates formed by aligning through-etching holes, which are etching holes, and laminated so that the positions of the through-etching holes coincide with each other. It has the laminated board provided with the through-hole, and the release film formed in the at least one surface of the said laminated board, It is characterized by the above-mentioned. The release film is preferably made of a noble metal-based or carbon-based material.

  The method for producing a microlens array of the present invention includes a heating step of bringing a glass material into contact with the mold for microlens array of the present invention and softening the glass material by heating, and after the heating step, the microlens array. Between the first space on the contact surface side with the glass material of the mold for molding and the second space on the opposite surface side to the contact surface with the glass material of the mold for microlens array, A differential pressure is generated so that the second space has a lower pressure than the first space, the glass material is brought into close contact with the mold for microlens array and sucked into a through hole, and the microlens A molding process for forming a convex microlens without contact with a mold for an array; and a cooling process for cooling a glass material having a desired shape by the molding process. That.

  An apparatus for manufacturing a microlens array according to the present invention includes a mold for a microlens array according to the present invention, a peripheral portion of the mold for a microlens array, and the glass material of the mold for the microlens array. A holding container capable of dividing the first space formed on the contact surface side and the second space formed on the opposite surface side of the contact surface with the glass material of the mold for microlens array; And a pressure control unit that generates a differential pressure so that the second space has a lower pressure than the first space.

  According to the mold for microlens array of the present invention, it is possible to realize a mold for microlens array in which the labor of manufacturing is reduced and minute holes are processed with high accuracy. Furthermore, according to the microlens array manufacturing method and manufacturing apparatus of the present invention, a microlens array having a smooth lens shape can be obtained. Furthermore, if the microlens is formed by suction, the lens height can be easily adjusted and the variation in the lens shape can be suppressed, so that a microlens array having a desired shape and performance can be manufactured stably and with a high yield. .

  In particular, even a microlens array mold having a lens diameter of about 50 to 100 μm, which takes time to manufacture the molding surface of the microlens array mold, can be manufactured with high accuracy by a simple operation. . Therefore, a highly accurate microlens array can be manufactured by using the microlens array mold of the present invention.

It is a schematic sectional drawing of the shaping | molding die for microlens arrays which is one Embodiment of this invention. 1B is a schematic plan view of the microlens array mold of FIG. 1A. FIG. It is a schematic sectional drawing of the shaping | molding die for microlens arrays which is other embodiment of this invention. It is a schematic block diagram of the manufacturing apparatus of the micro lens array which is one Embodiment of this invention. It is the figure which showed the modification of the manufacturing apparatus of the micro lens array shown in FIG. It is the figure which showed the modification of the manufacturing apparatus of the micro lens array shown in FIG. It is a figure explaining the manufacturing method (heating process) of the micro lens array using the manufacturing apparatus of the micro lens array of FIG. It is a figure explaining the manufacturing method (molding process) of the micro lens array using the manufacturing apparatus of the micro lens array of FIG. It is a figure explaining the manufacturing method (cooling process) of the micro lens array using the manufacturing apparatus of the micro lens array of FIG. It is a schematic block diagram of the manufacturing apparatus of the micro lens array which is other embodiment of this invention. 6 is a graph showing the relationship between [cell height / diameter of through-etching hole] and [curvature radius of microlens / radius of through-etching hole] of the microlens arrays obtained in Examples 1 to 5.

  The present invention will be described below with reference to the drawings.

(First embodiment of mold for microlens array)
1A and 1B are a schematic cross-sectional view and a schematic plan view, respectively, of a microlens array mold that is an embodiment of the present invention. As shown in the schematic plan view of FIG. 1B, the microlens array mold 1 shown here includes a laminated plate 2 formed by laminating a plurality of thin metal plates 2a having through-etching holes formed in alignment. The through-hole 3 provided in the laminated plate 2 by the through-etching hole and the release film 4 formed on the surface of the laminated plate 2 are configured.

  As described above, the laminated plate 2 is formed by laminating a plurality of thin metal plates 2a having aligned through-etching holes. When the thin metal plates 2a are laminated, the positions of the through-etching holes of the thin metal plate 2a are matched. Thus, the through holes 3 are provided in the laminated plate 2. The planar shape of the through-etching hole is not particularly limited, such as a circle, an ellipse, a polygon including a square or a triangle, but is preferably a circle in order to form a microlens close to a perfect circle. As used herein, a circle is defined as a shape having an ellipticity of 0.9 or more. More specifically, when a circular through-etching hole having a diameter of about 50 to 100 μm is formed, a shape in which the deviation from the approximate circle of the formed through-etching hole is within ± 2 μm is preferable.

  The thin metal plates 2a are prepared so as to be stacked. At this time, the through-etching holes formed in the metal thin plate 2a are formed by the etching process as described above, and the minimum diameter of the through-etching holes formed at this time is substantially determined by the thickness of the metal thin plate 2a to be used. That is, in order to make the minimum diameter of the through-etching hole as small as possible, it is necessary to reduce the thickness of the metal thin plate 2a. In general, the minimum thickness of the through-etching hole to be formed is about the same as the plate thickness. Limited. When the diameter of the through-etching hole is made larger than the plate thickness, the etching process condition may be adjusted, and the size can be arbitrarily set.

  The material of the metal thin plate 2a is preferably a material having heat resistance capable of withstanding the molding temperature in an air atmosphere or an inert gas atmosphere as a mold of the microlens array. For example, stainless steel (SUS304, 316, etc.) And iron-nickel alloy (42 alloy, etc.). Further, the thickness of the metal thin plate 2a is appropriately selected according to the diameter of the through-etching hole to be formed (diameter of the through-hole 3), and is usually about the same as the diameter of the through-etching hole as described above. That's fine. For example, when a through-etching hole having a diameter of 100 μm is formed by etching, the thickness of the metal thin plate 2a may be 60 to 100 μm.

  The etching process is a process such as bringing an etching solution into contact with the position where the through-etching holes of the metal thin plate 2a are provided, and a plurality of through-etching holes can be formed by a single process. In addition, what is necessary is just to select the etching liquid used at this time suitably according to the raw material of the metal thin plate 2a. For example, when the metal thin plate 2a is stainless steel or an iron-nickel alloy, an etching solution mainly containing ferric chloride can be used.

  The plurality of through-etching holes formed in the metal thin plate 2a by such an etching process are aligned as viewed from the plane of the metal thin plate 2a. The through-etching holes formed at this time may be formed at positions corresponding to the positions of the respective microlenses of the desired microlens array. For example, the through-etching holes may be formed in a zigzag arrangement or a grid pattern. Hereinafter, the shape of the through-etching hole will be described as being circular unless otherwise specified.

  A plurality of thin metal plates 2a provided with a plurality of through-etching holes arranged in this manner are prepared, and laminated so that the positions of the through-etching holes of the respective thin metal plates 2a coincide with each other. obtain. In laminating, for example, the metal thin plates 2a may be integrated by diffusion bonding in which a pressure is applied and thermocompression bonded while heating to about 900 ° C. in a vacuum state. In addition, as long as it can be integrated as the laminated plate 2, a method other than diffusion bonding may be used.

  In FIG. 1A, for the sake of convenience, the configuration of the laminated plate 2 in which four metal thin plates 2a are laminated is shown. However, the number of laminated metal thin plates is not limited to this, and may be a desired thickness. It is sufficient to stack as many as necessary.

  However, when the hole diameter of the through-etching hole is made smaller, it can be dealt with by reducing the thickness of the metal thin plate 2a as described above, but if the metal thin plate 2a is too thin, its strength is low. In addition, the production of the laminate 2 may be complicated due to difficulty in handling. Therefore, the thickness of the thin metal plate 2a is preferably 20 to 50 μm. And the thickness of the laminated plate 2 finally obtained by laminating such metal thin plates 2a ensures the strength of the laminated plate 2, avoids the complexity of production, and reduces the cost of mold production. What is necessary is just to determine suitably the point which can be suppressed.

  For example, when a microlens array mold is used by generating a pressure difference (differential pressure) between the front and back of the mold, the laminated plate 2 is a thin metal plate in order to maintain a certain strength that can withstand the differential pressure. Adjustment is possible by increasing the number of layers 2a. In this case, when the thickness of the laminated plate 2 is determined by the differential pressure by the molding method described later, the deflection amount of the laminated plate 2 at the time of forming the microlens array is defined as 10% or less of the cell height of the microlens array. Good. At this time, as the differential pressure for forming the microlens array, the thickness of the laminated plate 2 capable of maintaining the strength against the differential pressure of 0.09 MPa or more is preferably 0.8 mm or more, and more preferably 0.85 mm or more. .

  When the mold is released by applying pressure from the mold after molding the microlens array, the thickness of the laminated plate 2 is sufficient to withstand 0.15 MPa, which is assumed as the required pressure release force at that time. Is preferably 0.9 mm or more.

  However, as the thickness of the laminated plate 2 increases, the number of laminated layers increases, which not only simply increases the amount of labor, but also makes it difficult to align the through-etching holes when forming the laminated plate. Is preferably 5 mm or less, more preferably 3 mm or less, and even more preferably 1.2 mm or less.

  Considering the above points comprehensively, the thickness of the laminate 2 is preferably 0.8 mm to 5 mm, more preferably 0.85 to 3 mm, and particularly preferably 0.85 to 1.2 mm.

  The laminated plate 2 obtained in this way has the through holes 3 at the positions of the through etching holes because the through etching holes of the metal thin plate 2a are formed continuously in the depth direction of the holes. The diameter of the through-hole 3 is a size that enhances the light extraction efficiency of the microlens array, and is preferably 50 to 100 μm, more preferably 70 to 80 μm in consideration of the pitch of the microlens array. . Moreover, although this through-hole 3 is arranged and provided as above-mentioned, 50-200 micrometers is preferable, for example, and, as for the pitch, 80-120 micrometers is more preferable. Moreover, 0.1-0.9 are preferable and, as for the ratio represented by (diameter / pitch) of the through-hole 3, 0.2-0.9 are more preferable. The pitch of the through holes corresponds to the distance between the centers of the openings of the adjacent through holes 3. If this (diameter / pitch) ratio is greater than 0.9, adjacent through holes 3 may come into contact with each other. On the other hand, if the (diameter / pitch) ratio is smaller than 0.1, the adjacent through-holes 3 may be too discrete to satisfy the optical characteristics required for the microlens array.

  The release film 4 is provided on at least one surface of the laminated plate 2, and this one surface corresponds to a surface that comes into contact with the glass material when used as a mold for a microlens array. Thus, by providing the release film 4, it is possible to prevent the glass material and the mold from sticking after the molding operation, and to facilitate the separation.

  In addition, although not shown, the release film 4 may be formed not only on the surface contacting the glass material but also on the opposite surface. If the release films 4 are thus provided on both surfaces of the laminated plate 2, it is possible to prevent the laminated plate 2 from coming into direct contact with air or the like during molding of the microlens array, and the laminated plate 2 made of metal is oxidized. It is possible to prevent problems such as

  Examples of the release film 4 include release films used for molds such as microlenses and optical elements. For example, platinum (Pt), palladium (Pd), gold (Au), rhodium (Rh), osmium. Preferred are noble metal materials such as (Os), ruthenium (Ru), iridium (Ir), rhenium (Re) and alloys thereof, and carbon materials such as diamond-like carbon. These release films 4 may be formed on the laminate 2 by a known film formation method, such as PVD (physical vapor deposition) such as vapor deposition and sputtering, CVD (such as thermal CVD, MOCVD, plasma CVD). Examples thereof include a chemical vapor deposition method). Moreover, the release film 4 to be formed may have a thickness that does not adversely affect the formation of the through hole 3 and can sufficiently secure the release performance. Specifically, the thickness of the release film 4 is preferably 0.05 μm or more and 1 μm or less, and typically about 250 nm. If the film thickness is less than 0.05 μm, the function and durability of the release film may be reduced, and if it exceeds 1 μm, poor adhesion may occur when the release film is laminated.

(Second Embodiment of Micro Lens Array Mold)
Further, the microlens array mold may be in the form shown in FIG. The mold 11 for microlens array shown in FIG. 2 is formed by laminating a plurality of thin metal plates 2a having through-etching holes formed in alignment so that the positions of the through-etching holes coincide with each other. On the contact surface between the laminated plate 12 provided with the through holes 13 for forming the microlens by laminating the thin metal plates 2b having through-etching holes formed in alignment with the laminated surfaces, and the glass material of the laminated plate 12 And a release film 14 formed.

  The microlens array molding die 11 has basically the same configuration as the microlens array molding die 1 shown in FIGS. 1A and 1B, except that the metal thin plate constituting the laminated plate 12 is different. The two thin metal plates 2a and 2b having different through-etching hole diameters are used.

  At this time, the diameter of the through-etching hole of the metal thin plate 2b is smaller than the diameter of the through-etching hole of the metal thin plate 2a, and the through-etching hole of the metal thin plate 2b is on the side closer to the glass material contact, Used as a hole for forming a microlens array. The diameter of each microlens constituting the microlens array depends on the size of the hole with which the glass material directly contacts. In this case, since it is determined by the diameter of the through-etching hole of the metal thin plate 2b on which the release film is formed, a microlens having a smaller diameter can be formed with the laminated plate configuration as shown in FIG. Note that the glass material is actually in contact with the release film 14. However, in this specification, for convenience, the metal thin plate closest to the release film 14 is referred to as “the metal thin plate on the side in contact with the glass material”. "

  That is, as described above, the diameter of the through-etching hole formed by the etching hole is limited to some extent by the thickness of the metal thin plate to be used. Therefore, when trying to make a microlens array mold having a small diameter, What is necessary is just to make thickness thin. However, as shown in FIGS. 1A and 1B, when the through-etching holes of all the thin metal plates are made to have the same diameter, the thin metal plate 2b to be used is formed when trying to form a small diameter like the through-hole 13 of FIG. Since it is too thin, it must be handled with care due to its low strength and difficulty in handling, and it may take time to align the holes even during diffusion bonding.

  Therefore, in order to produce a microlens array molding die that can realize a microlens array having a smaller diameter, only a thin metal plate on the side in contact with the glass material of the laminated plate 12 has through-etching holes with a smaller diameter. It is good also as the metal thin plate 2b which has. For example, the etching hole of the metal thin plate on the side in contact with the glass material among all the metal thin plates may be minimized. Other than that, it is easier to handle and the metal thin plate 2a having through-etching holes that can appropriately form the through-holes 13 for forming the microlens array makes it possible to manufacture the mold more. Simple and efficient.

  As described above, the diameter of each microlens constituting the microlens array is determined by the diameter of the through-etching hole formed in the outermost metal thin plate on the side in contact with the glass material. The through-etching hole of the thin plate is not particularly limited as long as the through-hole can be appropriately formed when a laminated plate is used. For example, the laminated plate 12 may be configured by laminating a first group of metal thin plates in which a plurality of metal thin plates 2b are laminated and a second group of metal thin plates in which a plurality of metal thin plates 2a are laminated. In addition, there is no problem even if the laminated plate has a configuration in which the diameters of the through-etching holes of the metal thin plate forming the laminated plate are laminated differently.

  Further, if the diameter of the through-etching hole of the metal thin plate on the side opposite to the contact surface side with the glass material is made small, the open diameter of the hole serving as the opening can be made small, and contamination with foreign matters can be suppressed. That is, in FIG. 2, the diameter of the through-etching hole of the metal thin plate 2b on the side in contact with the glass material is smaller than the diameter of the through-etching hole of the thin metal plate 2a. Only the diameter of the through-etching hole of the thin metal plate 2a that is the farthest may be made as small as the diameter of the through-etching hole of the metal thin plate 2b.

(First Embodiment of Microlens Array Manufacturing Apparatus)
Next, the manufacturing apparatus and manufacturing method of the microlens array of this invention are demonstrated.

  Here, FIG. 3 is a diagram showing a schematic configuration of a microlens array manufacturing apparatus according to an embodiment of the present invention. The inside of the molded container is shown as a cross-sectional view.

  The microlens array manufacturing apparatus 21 shown in FIG. 3 holds the microlens array molding die 1 and the peripheral edge of the molding die 1, and the molding die 1 makes the microlens array molding die 1. A holding container 22 capable of forming an airtight space divided into the contact surface side with the glass material 80 and the opposite surface side thereof, a pressure control unit 23 for generating a differential pressure in the airtight space divided by the holding container 22, Consists of

  Here, when the microlens array molding die 1 is molded, the glass material 80 used for molding is brought into contact with one surface, that is, the surface having the release film, and then the pressure difference is used. Close. Then, the glass material 80 located in the portion corresponding to the through hole 3 in the microlens array mold 1 is sucked (extruded) into the through hole 3, and the convex microlens is formed without contacting the mold 1. It was possible to form.

  The present invention has a particularly favorable effect when the diameter of the microlens is small like this microlens array and it is difficult to mirror-polish the molding surface with the conventional mold. Although details will be described later, according to the present invention, since the optical surface is not formed by transferring the molding surface, there is no need to perform operations such as mirror polishing of the molding surface, and a smooth optical surface can be obtained. .

  The holding container 22 holds the peripheral portion of the microlens array mold 1 and the first space 24 formed on the contact surface side with the glass material 80 of the microlens array mold 1 and the contact surface. The second space 25 formed on the opposite side of the second space 25 is divided. FIG. 3 shows an example in which a glass material is molded in close contact with the upper surface of the microlens array mold 1.

  The holding container 22 may be any container that can hold the microlens array molding die 1 horizontally and can spatially divide the upper and lower sides of the microlens array molding die 1 during molding. Further, in order to generate differential pressure in the divided spaces as will be described later, FIG. 3 shows an example in which both the first space 24 and the second space 25 are sealed. Yes.

  The pressure control unit 23 controls the pressure in the first space 24 and the pressure in the second space 25 as described above, and is connected to the first space 24 and the second space 25. The air pressure in each space can be controlled. At this time, the space (second space 25) on the opposite side of the space (first space 24) on the contact surface side with the glass material 80 of the microlens array mold 1 is pressed by the pressure control unit 23. A differential pressure is generated so as to be a low pressure.

  Specifically, a pressure pump or the like is used to increase the pressure in the first space 24, and a vacuum pump or the like is used to decrease the pressure in the second space 25. The differential pressure between these two spaces is used. Is adjusted to a predetermined value.

  In addition, although the manufacturing apparatus 21 of the microlens array of FIG. 3 showed the case where the 1st space 24 and the 2nd space 25 will be in the sealed state, since a differential pressure should just arise in both space, Either one may be a sealed space and the other may be open. In this case, since the open space is at atmospheric pressure, whether the pressure in the sealed space is negative or positive is determined depending on which one is sealed.

  That is, when the first space 24 in FIG. 3 is sealed and the second space 25 is opened, the apparatus configuration shown in FIG. 4A is obtained. The microlens array manufacturing apparatus 31 shown in FIG. 4A holds the peripheral portion of the mold 1 for the microlens array, the contact surface side with the glass material 80 of the mold 1, and its The holding container 32 divides the space formed on each of the opposite surfaces, and the pressure control unit 33 that generates a differential pressure in the space divided by the holding container 32.

  Here, the holding container 32 seals the first space 34 and opens the second space 35. Since the second space 35 is at atmospheric pressure, the first space 34 has a large pressure. The pressure needs to be higher than atmospheric pressure. Therefore, the pressure control unit 33 used here is a pressurizing pump that can pressurize the inside of the first space 34.

  Moreover, when the 2nd space 25 of FIG. 3 is sealed and the 1st space 24 is open | released, it becomes an apparatus structure shown to FIG. 4B. The microlens array manufacturing apparatus 41 shown in FIG. 4B holds the peripheral portion of the microlens array molding die 1 and the microlens array molding die 1, and the glass material 80 of the microlens array molding die 1. The holding container 42 that divides the space formed on each of the contact surface side and the opposite surface side thereof, and a pressure control unit 43 that generates a differential pressure in the space divided by the holding container 42.

  Here, the holding container 42 opens the first space 44 and seals the second space 45. Since the first space 44 is at atmospheric pressure, the second space 45 is large. The pressure needs to be lower than atmospheric pressure. Therefore, the pressure control unit 43 used here is a vacuum pump that can depressurize the inside of the second space 45.

  In addition, the raw material of the holding container 42 should just have the tolerance at the temperature at the time of shaping | molding of a microlens array, and a pressure, For example, stainless steel, a cemented carbide, etc. are mentioned.

  Next, the manufacturing method of the microlens array of this invention is demonstrated, referring FIG. FIG. 5A shows an example in which the microlens array manufacturing apparatus 21 of FIG. 3 is used, and the pressure controller 23 is not shown. 5B and 5C are enlarged views of the glass material 80 and a part of the microlens array mold 1 so that the change of the glass material 80 can be seen when the environment is changed to the molding condition in FIG. 5A. However, the laminated body of the thin metal plate constituting the mold 1 for the microlens array is omitted in the drawing. Hereinafter, the case where the microlens array molding die 1 shown in FIGS. 1A and 1B is used will be described with reference to FIGS. 5B and 5C. However, the microlens array molding die 11 shown in FIG. The same applies when used.

  First, the glass material 80 is placed on the microlens array mold 1. Next, the microlens array mold 1 is heated to the molding temperature, and the glass material 80 is also heated to the same temperature and softened (FIG. 5A; heating step). The heating temperature at this time may be a temperature at which the glass material 80 is softened, and is generally about 500 to 1100 ° C. although it varies depending on the glass material to be used. At this time, the viscosity of the glass may be η [dpa · s], and log η may be in the range of 4.8 to 12.37, preferably 5 to 9, and more preferably 5 to 7.

  After the glass material 80 is sufficiently heated and softened, the relationship between the pressure (P1) in the first space 24 and the pressure (P2) in the second space 25 is determined from the first space 24. Also, the differential pressure is generated so that the second space 25 has a lower pressure (P1> P2).

  When the differential pressure is generated in this way, the softened glass material 80 is sucked (extruded) through the through hole 3 toward the low pressure second space 25 side, and the first space 24 and the second space 25 are Are securely divided and sealed. As this state continues, the glass material 80 is sucked into the through holes 3 to form convex microlenses (FIG. 5B; molding step). FIG. 5B shows a state in which the glass material 80 is being formed.

  At this time, the top height of the optical surface of the microlens array is determined by the relationship between the viscosity of the glass material 80, the differential pressure (P1-P2) between the first space 24 and the second space 25, and the molding time. These are set to conditions for obtaining a desired lens shape. For example, when the viscosity and the differential pressure are fixed, the height of the microlens can be easily adjusted by adjusting the suction time.

  More specifically, the pressure difference (P1-P2) between the first space 24 and the second space 25 during molding is 10 to achieve sufficient deformation of the glass material 80 in a practical time. -1000 kPa is preferable, and 50-800 kPa is more preferable. In addition, the time for deforming the glass material due to the differential pressure is preferably in the range of 1 to 1000 seconds, more preferably 1 to 150 seconds so as not to impair the function as a microlens array and considering the manufacturing efficiency. preferable.

  Then, when the microlens has a desired shape, the differential pressure between the first space 24 and the second space 25 is eliminated, and the first space 24 and the second space so that the glass material 80 is not further deformed. The pressure in the space 25 is the same.

  Next, the deformed glass material 80 is cooled to a strain point or less to solidify the glass material 80 (FIG. 5C; cooling step). Further, the cooled glass material 80 is released from the mold, and finally cooled to room temperature to obtain a microlens array. In this way, a microlens array in which spherical microlenses are arranged in a grid pattern at equal intervals is obtained. When the thermal expansion coefficient of the material of the microlens array molding die 1 and the thermal expansion coefficient of the glass material 80 are substantially equal, the microlens array molding die 1 is integrally cooled and solidified, and then the microlens The microlens array may be obtained by releasing from the array mold 1.

  The microlens array thus obtained has a convex spherical shape, and each microlens has a radius of curvature R in the range of 0.005 to 100 mm and can be obtained in a desired shape by adjusting the molding conditions. . Moreover, although the above showed the absolute range of the curvature radius, it is preferable that the ratio of the curvature radius of the molded microlens to the radius of the microlens can be adjusted. In particular, a small ratio is preferable in that the high light utilization efficiency required for a microlens array can be obtained and the space in which the microlens array is disposed can be reduced. In addition, since the diameter (radius) of the microlens is substantially determined by the diameter (radius) of the through-etching hole, the suction time is calculated using [the radius of curvature of the lens / the radius of the through-etching hole] as an index for the above ratio. The value obtained by adjusting the production conditions such as is preferably 1.8 or less, more preferably 1.5 or less, and further preferably 1.3 or less.

In addition, this molding is performed in a state heated to a high temperature, and in order to prevent deterioration due to oxidation of the mold, for example, both the first space 24 and the second space 25 are in an inert gas atmosphere such as nitrogen or argon. It is preferable that the second space 25 side (low pressure side) is under vacuum conditions of 1 × 10 ⁻² Pa or less.

  Furthermore, a chamber capable of accommodating the microlens array molding die 1 and the holding container 22 (the pressure control unit 23 may be disposed outside the chamber) may be provided. In this case, the atmosphere of the molding die described above may be provided. Substitution is easy and the internal temperature can be stabilized, which is preferable.

  The glass material 80 is not particularly limited as long as a microlens array can be manufactured, and conventionally known glass materials can be used. Although the shape of the glass raw material 80 before a heating is not specifically limited, The planar shape has a rectangular or circular flat shape, and the thickness before a press is 0.1 mm-20 mm at that time. Further, the glass material can be used in various shapes such as a flat shape in which the spherical shape is crushed, as well as the flat plate shape described above.

(Second Embodiment of Microlens Array Manufacturing Apparatus)
FIG. 6 is a diagram showing a schematic configuration of a microlens array manufacturing apparatus according to another embodiment of the present invention.

  The microlens array manufacturing apparatus 51 shown in FIG. 6 holds the mold 1 for the microlens array and the peripheral edge of the mold 1, and the contact surface side with the glass material of the mold 1 and vice versa. The holding containers 52 and 53 that can form a space divided on the surface side, and a pressure control unit 54 that generates a differential pressure in the space divided by the holding containers 52 and 53 are configured. Furthermore, a gasket 56 is also provided in order to make the space formed by the holding containers 52 and 53 airtight.

  Here, since the microlens array molding die 1 is the microlens array molding die 1 in the first embodiment, the description thereof is omitted. In addition, this embodiment is an example in which the glass material 80 is brought into contact with and intimate contact with the microlens array molding die 1. In this embodiment, the holding container is divided into two parts, a lower holding container 52 and an upper holding container 53, and a glass material is formed in a space formed in the center when the holding containers 52 and 53 are overlapped. 80 and the microlens array mold 1 are accommodated.

  In the example shown in FIG. 6, the lower holding container 52 is provided with a step so that the glass material 80 and the microlens array mold 1 can be placed at predetermined positions, and further the glass material 80 is mounted. The surface to be placed is provided with a hole 52a connected to the external space, and the first space is opened to be at atmospheric pressure. On the other hand, in the upper holding container 53, the second space 55 on the side opposite to the contact surface with the glass material 80 of the mold 1 for microlens array is a sealed space, and the second space 55 is a vacuum. It is connected to a pump 54 so that the internal pressure can be reduced and adjusted to a negative pressure.

  The microlens array manufacturing apparatus 51 described here is basically operated in the same manner as in the first embodiment except that the glass material 80 is molded in close contact with the lower side of the microlens array mold 1. A lens array can be manufactured. As the apparatus configuration, the microlens array manufacturing apparatus 41 shown in FIG. 4B is turned upside down, and a member that supports the glass material 80 and the microlens array molding die 1 so as not to drop downward is provided. Is.

Hereinafter, the present invention will be described in more detail with reference to Examples (Examples 1 to 6).
(Example 1)
The microlens array was manufactured as follows using the microlens array manufacturing apparatus of FIG. 4B.

The microlens array mold used in this example is a disk-shaped iron-nickel alloy (42 alloy; thermal expansion coefficient α is 50 × 10 ⁻⁷ / K (at ~ 200 ° C.)) was laminated by diffusion bonding to obtain a laminate having a thickness of about 1 mm. The metal thin plate is formed by etching in a region of 8 mm × 8 mm in the center thereof by arranging 81 × 81 circular through-etching holes of φ78.1 μm in a grid pattern at a pitch of 100 μm, Since these through-etching holes are laminated at the same position, through-holes are formed in the laminated plate in the same arrangement as the through-etching holes.

  In addition, the metal thin plate which has a through-etching hole was produced in the following procedure. First, a photoresist is applied to both surfaces of a thin metal plate with no holes, and the shape drawn on the pattern film original plate is exposed and baked on the surface of the photoresist. The mask of the etching pattern which exposed the metal surface of was formed. Next, an etching solution was brought into contact with the metal plate material with masking to perform an etching process, and the metal plate was processed into a position and shape according to the pattern (original plate) to form a through-etching hole. Finally, the masking by the photoresist remaining on the surface of the metal thin plate was removed, washed and dried to obtain a metal thin plate having a through-etching hole.

  An iridium-rhenium alloy (Ir-Re alloy) film having a thickness of 250 nm was further formed as a release film on one surface of the laminated plate obtained as described above to obtain a mold for microlens array.

  In the microlens array manufacturing apparatus, as shown in FIG. 4B, the holding container has an open space (first space) above the microlens array mold, and a lower space (first space). (Space 2) is an apparatus in which a holding container, a mold for microlens array, and a space sealed with a glass material are formed. Further, the lower space (second space) is connected to a decompression / pressurization pump.

  First, a microlens array mold is placed and fixed on the holding container, and a glass material is placed on the mold so that the space above and below the microlens array mold can be divided. did. The glass material used here is a barium borosilicate low melting glass (glass transition point: 495 ° C., yield point: 542 ° C., softening point: 591 ° C., manufactured by Asahi Glass Co., Ltd., trade name: A-BAR12). It has a disk shape of φ15.95 mm and a thickness of 4.4 mm.

  Next, the holding container was heated, and the glass material was heated to 587 ° C. and softened. When the viscosity of the glass material at this time is η [dpa · s], log η is 9.04. After sufficiently heating and softening the glass material, operate the vacuum / pressurization pump to make the lower space (second space) negative pressure and hold it for 100 seconds to deform the glass material and remove the micro lens. Molded. The differential pressure at this time was 88 kPa.

  Thereafter, the pressure in the lower space was immediately released to return to atmospheric pressure, and the glass material was cooled. When the glass material became 500 ° C. or lower, the lower space was set to a positive pressure (0.15 MPa) by a decompression / pressurization pump, the glass material and the mold were released, and immediately returned to atmospheric pressure. Further, when the glass material was cooled to room temperature, the molded glass material was taken out, and a microlens array having microlenses having a diameter of 76.4 μm and a height of 18.0 μm aligned was obtained.

(Examples 2 to 5)
Next, a microlens was obtained by the same operation as in Example 1 except that the predetermined holding times in the molding operation were 120 seconds, 240 seconds, 270 seconds, and 310 seconds (in order, Example 2 to 5). An array was manufactured. The sizes of the microlenses of the microlens array obtained here were (Example 2) diameter 77.8 μm, height 25.0 μm, (Example 3) diameter 76.5 μm, height 30.3 μm, (Example 4). ) Diameter 76.2 μm, height 35.3 μm, (Example 5) Diameter 77.5 μm, height 36.5 μm.

(Lens shape check)
For the microlens arrays obtained in Examples 1 to 5, the shape of the molding surface of the lens was measured with a non-contact three-dimensional measuring machine (trade name: VK9700, manufactured by Keyence Corporation). The obtained microlens array was able to form a lens having a smooth surface shape without being affected by the surface roughness of the molding surface. Further, the variation in shape between the central portion and the outer peripheral portion of the mold was extremely small, and a uniform optical surface shape could be formed.

  At this time, the relationship of [the radius of curvature of the lens / the radius of the through-etching hole] was examined. As the molding time became longer, the relationship became smaller (the radius of curvature became smaller), and the lens shape was controlled by the suction time. I knew it was possible. The results are shown in FIG. Here, the radius of the pore is the radius of the through-etching hole in the outermost metal sheet that contributes to the formation of the microlens.

  Typically, with respect to the microlens array obtained in Example 3, the lens diameter, height, and curvature of one central microlens and four outer microlenses were examined. The results are as follows. Central microlens: diameter / height / curvature radius = 73 μm / 29.1 μm / 41 μm, outer microlens-1: diameter / height / curvature radius = 78 μm / 29.0 μm / 46 μm, outer microlens-2 : Diameter / height / curvature radius = 77 μm / 31.5 μm / 47 μm, outer microlens-3: diameter / height / curvature radius = 79 μm / 31.2 μm / 47 μm, outer microlens-4: diameter / high It was confirmed that the thickness / curvature radius = 76 μm / 30.2 μm / 45 μm and the variation was small.

  In addition, when the molding time was 270 seconds (Example 4) and 310 seconds (Example 5), some peeling occurred, but this is because the glass material is sucked too much into the inside of the through hole and is difficult to release. It is thought that it originates in becoming. That is, in order to safely perform the mold release and improve the product yield, it is preferable that the value of [the radius of curvature of the lens / the radius of the through-etching hole] is 1.18 or more.

(Example 6)
The microlens array mold used in this example is a disk-shaped iron-nickel alloy (42 alloy; thermal expansion coefficient α is 50 × 10 ⁻⁷ / K (at ~ 19) was laminated by diffusion bonding, and one layer of a disk-shaped iron-nickel alloy (same as above) of φ20 mm and thickness of 30 μm was added thereto to obtain a laminate having a total thickness of about 1 mm. The added one-layer metal thin plate is provided on the outermost layer on the side in contact with the glass. By etching, 8 × 8 mm circular through-holes with a diameter of 68.0 μm are formed in an 8 mm × 8 mm region at the center thereof, and 100 μm. Are arranged in a grid pattern with a pitch of. The remaining 19 layers each have a hole diameter of 81.times.81 circular through-etching holes having a diameter of 78.1 .mu.m and are arranged in a grid pattern at a pitch of 100 .mu.m.
And since all the metal thin plates to be used are laminated by aligning the positions of these through-etching holes, through-holes are formed in the laminated plate in the same arrangement as the through-etching holes.

  Furthermore, an iridium-rhenium alloy (Ir—Re alloy) film having a thickness of 250 nm was formed on one side of the additional layer of the obtained laminated plate, thereby obtaining a mold for a microlens array.

  In the microlens array manufacturing apparatus, as shown in FIG. 4B, the holding container has an open space (first space) above the microlens array mold, and a lower space (first space). (Space 2) is an apparatus in which a holding container, a mold for microlens array, and a space sealed with a glass material are formed. Further, the lower space (second space) is connected to a decompression / pressurization pump.

  First, a microlens array molding die that differs only in the diameter of the outermost through-hole prepared above is placed and fixed on the upper part of the holding container, and a glass material is placed on the molding die, and the microlens is placed. The space above and below the array mold can be divided. The glass material used here is a barium borosilicate low melting glass (glass transition point: 495 ° C., yield point: 542 ° C., softening point: 591 ° C., manufactured by Asahi Glass Co., Ltd., trade name: A-BAR12). It has a disk shape of φ15.95 mm and a thickness of 4.4 mm.

  Next, the holding container was heated, and the glass material was heated to 587 ° C. and softened. When the viscosity of the glass material at this time is η [dPa · s], log η is 9.04. After sufficiently heating and softening the glass material, operate the vacuum / pressurization pump to make the lower space (second space) negative pressure and hold it for 150 seconds to deform the glass material and remove the micro lens. Molded. The differential pressure at this time was 88 kPa.

  Thereafter, the pressure in the lower space was immediately released to return to atmospheric pressure, and the glass material was cooled. When the glass material became 500 ° C. or lower, the lower space was set to a positive pressure (0.15 MPa) by a decompression / pressurization pump, the glass material and the mold were released, and immediately returned to atmospheric pressure. Further, when the glass material was cooled to room temperature, the molded glass material was taken out to obtain a microlens array having microlenses having a diameter of 66 μm and a height of 18.4 μm aligned.

  As shown here, by reducing the hole diameter of the mold, it can be confirmed that the size of the obtained microlens is formed according to the hole diameter, and the size of the hole diameter of the mold is controlled. Thus, it was confirmed that the shape of the obtained microlens array could be a desired shape.

  As described above, the microlens array mold, the microlens array manufacturing method, and the manufacturing apparatus of the present invention can obtain a microlens array having a smooth optical surface by a simple operation. This microlens array mold can be manufactured with a simple operation even if the through-etching hole has a small diameter or a large number of through-etching holes. realizable.

  Furthermore, according to the microlens array manufacturing apparatus and manufacturing method of the present invention, it has been found that the microlens array having uniform characteristics can be manufactured by eliminating the shape variation of the individual microlenses.

  The mold for microlens array, the method for manufacturing a microlens array, and the manufacturing apparatus of the present invention are useful for forming a microlens array having a large number of convex microlenses.

DESCRIPTION OF SYMBOLS 1 ... Microlens array shaping | molding die, 2 ... Laminated board, 3 ... Through-hole, 4 ... Release film, 21 ... Microlens array manufacturing apparatus, 22 ... Holding container, 23 ... Pressure control part, 24 ... 1st Space, 25 ... second space, 80 ... glass material

Claims (18)

A plurality of metal thin plates formed by aligning through-etching holes as etching holes, a laminated plate provided with through-holes for forming microlenses by being laminated so that the positions of the through-etching holes coincide with each other;
A release film formed on at least one surface of the laminate,
A mold for forming a microlens array, comprising:   The mold for a microlens array according to claim 1, wherein the through-etching hole has a hole diameter of 50 to 80 μm.   The mold for a microlens array according to claim 1 or 2, wherein a pitch of the through-etching holes is 50 to 200 µm.   The mold for microlens array according to any one of claims 1 to 3, wherein the through-etching holes are arranged in 30 to 1000 columns × 30 to 1000 rows.   The mold for a microlens array according to any one of claims 1 to 4, wherein the thickness of the laminated plate is 0.8 mm to 5 mm.   The mold for microlens array according to any one of claims 1 to 5, wherein all the through-etching holes of the metal thin plate have the same diameter in the stacking direction.   The through etching hole of the metal thin plate used for the outermost surface by the side of the release film among the said metal thin plates is made into the smallest diameter among the through etching holes of the said metal thin plate. Mold for micro lens array.   8. The mold for microlens array according to claim 7, wherein the diameter of the through-etching hole in the outermost metal sheet is 50 to 75 [mu] m, and the diameter of the through-etching hole in the other metal sheet is 50 to 80 [mu] m.   The mold for microlens array according to claim 1, wherein the release film is made of a noble metal-based or carbon-based material.   A glass material is brought into contact with the mold for microlens array according to any one of claims 1 to 9, and the glass material is sucked by a pressure difference between the front and back surfaces of the mold for microlens array. A microlens array is produced by forming a microlens on the surface of the microlens array. A heating step of bringing a glass material into contact with the mold for microlens array according to any one of claims 1 to 9 and softening the glass material by heating,
After the heating step, the first space on the contact surface side of the microlens array mold with the glass material and the first surface on the opposite surface side of the contact surface with the glass material of the microlens array mold. A differential pressure is generated between the second space and the second space so that the pressure in the second space is lower than that in the first space, and the glass material is in close contact with the mold for forming the microlens array. A molding step of sucking into the hole and forming a convex microlens without making contact with the microlens array mold, and
A cooling step for cooling the glass material in a desired shape by the molding step;
A method for manufacturing a microlens array, comprising:   The method of manufacturing a microlens array according to claim 11, wherein the first space is set to atmospheric pressure, and the second space is set to negative pressure.   The method of manufacturing a microlens array according to claim 11, wherein the first space is set to a positive pressure and the second space is set to an atmospheric pressure.   The method for manufacturing a microlens array according to any one of claims 11 to 13, wherein the differential pressure is 10 to 1000 kPa.   The method of manufacturing a microlens array according to any one of claims 11 to 14, wherein log η is 4.86 to 12.37 when the viscosity of the glass material is η [dpa · s] in the heating step. A microlens array molding die according to any one of claims 1 to 9,
A first space that holds a peripheral portion of the microlens array mold and is formed on the contact surface side of the microlens array mold with the glass material, and the glass material of the microlens array mold A holding container capable of dividing the second space formed on the opposite side of the contact surface with
A pressure control unit that generates a differential pressure so that the second space has a lower pressure than the first space;
An apparatus for manufacturing a microlens array, comprising:   The microlens array manufacturing apparatus according to claim 16, wherein the pressure control unit is a vacuum pump connected to the second space.   The microlens array manufacturing apparatus according to claim 16, wherein the pressure control unit is a pressurizing pump connected to the first space.

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