JP2014156378A - Manufacturing method and manufacturing apparatus for microlens array, and microlens array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method and a manufacturing apparatus for a microlens array that can manufacture, in a good yield, a microlens array such that microlenses have a smooth and uniform shape and also have a large effective area.SOLUTION: A manufacturing apparatus 1 for a microlens array includes: a molding tool 2 for a microlens array which has a plurality of through holes 2a for microlens formation on a surface of a glass raw material 50; a retaining container 3 which retains a peripheral edge of the molding tool 2 for a microlens array, and partitions off a first space 7 formed on the side of a contact surface of the molding tool 2 for a microlens array and the glass raw material 50 and a second space 8 formed on the opposite side from the contact surface; a pressure control part 4 which generates differential pressure so that the second space is lower in pressure than the first space; heating means 5 of heating the glass raw material 50; and a temperature difference generation part 6 which cools the molding tool 2 for a microlens array when microlenses are molded.

Description

  The present invention relates to a microlens array manufacturing method and manufacturing apparatus, and a microlens array, and in particular, a microlens array manufacturing method and a microlens array manufacturing method capable of forming a microlens having a smooth optical surface shape with less variation. The present invention relates to a manufacturing apparatus and a microlens array having a predetermined shape.

  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 arranging a plurality of concave surfaces corresponding to microlenses on the molding surface and a lower mold having a molding surface that is flat. A plurality of 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, there is a method in which a concave portion is formed so that the molding surface of the molding die does not contact the optical surface of the microlens, and the optical surface is molded as a free surface. Known (for example, see Patent Documents 4 to 6). In these methods, since the optical surface is molded as a free surface, the surface roughness of the glass material before molding becomes the surface roughness of the optical surface of the microlens as it is. That is, if a sufficiently smooth optical surface is formed in advance on a glass material before molding, a microlens having a smooth surface can be obtained without being affected by the surface roughness of the mold.

JP-A-11-277543 JP 2007-131499 A JP 2011-153051 A JP 2007-182372 A JP 2006-111491 A JP 2012-148907 A

  However, as a method of forming without contacting the optical surface, these methods of sandwiching a glass material with a mold and using the press pressure of the mold generate a uniform pressure on the entire surface of the microlens array. Is difficult. Therefore, when the pressure becomes non-uniform, there is a variation in individual microlens shapes, and there is a problem that an effective area where microlenses having a desired shape exist as a microlens array cannot be manufactured over a wide range. . Also, in the case of molding using press pressure, the pressure escapes to the glass side surface, so the shape of the micro lens is not symmetrical with respect to the top of the surface, there is a limit to push the glass material into the molding surface, There has been a problem that it is difficult to adjust the height of the optical surface.

  Therefore, the present invention provides a microlens array manufacturing method and manufacturing apparatus, and a microlens having a predetermined shape, which can manufacture a microlens array having a wide effective area with a high yield while making the shape of the microlens smooth and uniform. The purpose is to provide an array.

  In the method for producing a microlens array of the present invention, a glass material is brought into contact with a microlens array mold having a plurality of through holes for forming a microlens, and suction is performed by pressure difference between the front and back of the microlens array mold. A microlens array manufacturing method for forming a microlens on a surface of the glass material by an action, wherein the microlens array molding is cooled by cooling the microlens array molding die at the time of molding the microlens. It has the temperature difference production | generation process which produces a temperature difference in the thickness direction of the said glass raw material which contacts a type | mold.

  The microlens array manufacturing apparatus of the present invention includes a microlens array mold having a plurality of microlens forming through holes for molding microlenses on the surface of a glass material, and the microlens array mold. A first space formed on the contact surface side of the microlens array mold with the glass material, holding the peripheral edge, and the opposite surface side of the contact surface between the glass material of the microlens array mold A holding container that can divide the second space formed in the first space, a pressure control unit that generates a differential pressure so that the second space has a lower pressure than the first space, and the glass material. A heating unit for heating the glass lens, and a method of cooling the glass lens mold when the micro lens is molded, and a thickness of the glass material in contact with the micro lens array mold And having a temperature difference generator for generating a temperature difference, to.

The microlens array of the present invention is a microlens array in which a plurality of microlenses are arrayed, and the lens diameter of the microlens is 10 to 100 μm, the radius of curvature of the lens / the radius of the lens in plan view. The curvature radius ratio is 1.35 or less, the arithmetic average surface roughness Ra of the optical surface is 100 nm or less, and the effective area of the microlens array is 50 mm ² or more.

  According to the method and apparatus for manufacturing a microlens array of the present invention, a microlens array having microlenses having a smooth optical surface (molded surface) is obtained. In particular, even when forming a small-diameter microlens that makes it difficult to mirror-finish the molding surface of the mold, the microlens surface can be made smooth and the height of the lens can be adjusted. A microlens array having the following shape and performance is obtained. Furthermore, according to this manufacturing method and manufacturing apparatus, it is possible to suppress variations in the microlens shape in the microlens array, and even when the effective area where the arranged microlenses are large is large, such as peeling of the microlens. The occurrence of defects can be suppressed. Therefore, the product can be manufactured stably and with a high yield. In this specification, the optical surface and the molding surface of the microlens (array) may be simply referred to as the surface of the microlens (array).

  Further, according to the microlens array of the present invention, a microlens having a predetermined shape (particularly, the surface of the microlens is smooth and the effective area of the microlens array is large) can be provided. As an array, the characteristics are improved as compared with the conventional array, and the array is stable, so that the product reliability can be improved.

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 (temperature difference production | generation process) of the microlens array using the manufacturing apparatus of the microlens 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 (solidification process) of the microlens array using the manufacturing apparatus of the microlens array of FIG. It is the graph which showed the relationship with [the lens height / the diameter of the lens in planar view] about the curvature radius ratio of the microlens array obtained in Examples 1-3. It is the graph which showed the relationship with [the lens height / the diameter of the lens in planar view] about the curvature radius ratio of the microlens array obtained in Examples 1-5.

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

(Embodiment of Microlens Array Manufacturing Apparatus and Manufacturing Method)
First, the manufacturing apparatus and manufacturing method of the microlens array of this invention are demonstrated. Here, FIG. 1 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.

  A microlens array manufacturing apparatus 1 shown in FIG. 1 holds a microlens array molding die 2 and a peripheral portion of the molding die 2, and the molding die 2 makes the glass of the microlens array molding die 2 glass. A holding container 3 capable of dividing a space formed on the contact surface side with the material 50 and a space formed on the opposite surface side thereof, and a pressure control unit 4 for generating a differential pressure in the space divided by the holding container 3 And a heating unit 5 that heats the glass material 50 and a temperature difference generation unit 6 that lowers the temperature of the microlens array mold 2 during molding and generates a temperature difference from the glass material 50.

  Here, the mold 2 for microlens array is capable of forming a plurality of microlenses, and a through hole 2a is provided as a microlens forming portion at a position corresponding to the microlens.

  When the microlens array mold 2 is formed, the glass lens 50 used for molding is brought into contact with one surface and then brought into close contact using a pressure difference. Then, the glass material 50 located in the portion corresponding to the through hole 2a in the microlens array mold 2 is sucked (extruded) into the through hole 2a, and the portion that becomes the optical surface of the microlens array is formed into the mold 2. It is possible to form a convex microlens array without contacting the surface. Therefore, the shape of the opening part of the contact surface with the glass raw material 50 of the through-hole 2a should just be formed so that the microlens to form may become a predetermined | prescribed diameter. On the other hand, the shape of the opening on the surface opposite to the contact surface in the microlens array mold 2 is not particularly limited as long as it is formed as a through hole.

  Further, the internal shape of the through hole 2a is not particularly limited as long as it does not come into contact with the portion that becomes the optical surface of the microlens array during molding. For example, in addition to the case of providing a typical cylindrical through hole, the through hole 2a is tapered or widened from the contact surface with the glass material 50 toward the opposite surface side. It is also possible to provide a stepping gradient, or to form multi-stage cylinders with different diameters in the inner cylindrical shape of the through-hole 2a. At this time, when providing a draft gradient, the inclination angle is preferably 1 to 10 degrees with respect to the vertical direction, and more preferably 4 to 6 degrees. As described above, if the through hole has an inclination of 10 degrees or less with respect to the vertical direction or can be approximated by an inclination of 10 degrees or less, the shape of the through hole is defined as a substantially cylindrical shape. Includes a shape whose inclination angle changes midway.

  If a draft angle is provided, the microlens array molding die 2 and the glass material 50 are prevented from coming into close contact with each other after the microlens array is formed, thereby facilitating release. In addition, when the taper shape or the multistage shape is gradually narrowed from the contact surface side to the opposite surface side, the open diameter can be reduced, and contamination with foreign matters can be suppressed.

  The through-holes 2a are provided with such openings arranged in a grid pattern or a staggered arrangement, so that a microlens can be formed at a position corresponding to each through-hole, and a microlens array can be manufactured. At this time, the opening diameter is preferably 10 to 5000 μm, the pitch of the openings is 10 to 20000 μm, and the ratio represented by [diameter / pitch] of the through hole 2a is 0.1 to 1, preferably 0.2-0.9. Note that the pitch of the openings corresponds to the distance between the centers of the openings of the adjacent through holes 2a.

Here, the effective area of the microlens array will be described. As described above, a microlens array is formed corresponding to the arranged through-holes, and an area obtained by continuously arranging the microlenses in plan view is an effective area. Note that the effective area here is not limited to a square in plan view as in the above example, but may be a rectangle or a circle, or a microlens array in which a region is formed by an arbitrary outer edge. Furthermore, in the case of a donut shape in which the microlenses are arranged in an annular shape in plan view, the effective area includes the inside (cavity portion) of the annular shape. The effective area is preferably 50 mm ² or more, more preferably 60 mm ² or more, and even more preferably 75 mm ² or more. In addition, although the upper limit of an effective area is not particularly provided, it may be, for example, 1500 mm ² or less. If it is larger than this, when the microlens array is molded, the microlens array mold may bend and the flatness may deteriorate. As an example of the form in which the microlenses are continuously arranged, typically, the form in which the microlenses are arranged at the same pitch in two dimensions (for example, the X direction and the Y direction in the XY plane) The form etc. which are arrange | positioned radially by the same pitch are mentioned.

  The planar shape of the through hole is not particularly limited, such as a circle, an ellipse, a polygon including a quadrangle and a triangle, but is preferably a circle in order to form a microlens close to a perfect circle in plan view. As used herein, a circle is defined as a shape having an ellipticity of 0.9 or more. For example, when a circular through 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 hole is within ± 2 μm is preferable.

  The present invention is a microlens array in which the diameter of the microlens is small (the opening diameter of the through hole 2a is small), and it is difficult to perform mirror polishing of the molding surface that can be performed using a conventional mold for transfer. Particularly advantageous effects are exhibited. According to the present invention, since the microlens array is not formed by transferring the molding surface, it is not necessary to perform operations such as mirror polishing of the molding surface, and a microlens array having a smooth surface shape can be formed.

  The microlens array molding die 2 may be a molding die by forming a plurality of microlens forming through holes at predetermined locations on a flat metal plate, or a metal having a plurality of through etching holes previously formed. A plurality of thin plates may be laminated so that the positions of the through-etching holes coincide with each other to form a mold having the through-holes. In addition, a release film may be formed on the surface of the mold as necessary for these molds for a microlens array.

  The material of the metal plate and the metal thin plate is preferably a material having heat resistance capable of withstanding a molding temperature in an air atmosphere or an inert gas atmosphere as a mold for a microlens array. For example, stainless steel (SUS304, 316), iron-nickel alloys (42 alloys, etc.), super steel alloys, and the like.

  Moreover, it is preferable that the microlens array mold has a strength that can withstand a pressure difference during molding and a pressure applied during mold release from the glass material. If the microlens array mold is greatly bent due to such a pressure difference, it becomes impossible to form a microlens with a uniform shape, or shape defects such as peeling of the microlens are likely to occur at the time of mold release. End up.

  When the release film is provided, it is provided on at least one surface of the microlens array mold 2, and this one surface corresponds to a surface in contact with the glass material 50. Thus, by providing the release film, it is possible to suppress the glass material 50 and the microlens array mold 2 from sticking after the molding operation.

  Moreover, you may form a release film not only on the surface side which contacts the glass raw material 50 but on the surface on the opposite side. By providing release films on both surfaces of the microlens array molding die 2 in this way, it is possible to prevent the microlens array molding die 2 from coming into direct contact with air or the like when molding the microlens array. Problems such as oxidation of a certain mold 2 for a microlens array can be suppressed.

  Examples of the release film include known release films used for molds such as microlens arrays and optical elements. For example, platinum (Pt), palladium (Pd), gold (Au), rhodium (Rh) Preferred are noble metal materials such as osmium (Os), ruthenium (Ru), iridium (Ir), rhenium (Re), and alloys thereof, and carbon materials such as diamond-like carbon. These release films may be formed on the microlens array mold 2 by a known film formation method, such as PVD (physical vapor deposition) such as vapor deposition and sputtering, thermal CVD, MOCVD, plasma CVD, and the like. And a film forming method such as CVD (chemical vapor deposition).

  Moreover, the release film to be formed may have a thickness that does not adversely affect the formation of the through hole 2a and can sufficiently ensure the release performance. Specifically, the thickness of the release film 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.

  The holding container 3 used in the present invention holds the peripheral portion of the microlens array mold 2 and is formed on the contact surface side with the glass material 50 of the microlens array mold 2. And the second space 8 formed on the opposite surface side of the contact surface. Here, an example in which the glass material is molded in close contact with the upper surface of the microlens array mold 2 is shown, but it is also possible to mold in close contact with the lower surface.

  The holding container 3 may be any container that can hold the microlens array mold 2 horizontally and can be spatially divided above and below the microlens array mold 2 at the time of molding. Further, in order to generate differential pressure in the divided spaces as will be described later, FIG. 1 shows an example in which both the first space 7 and the second space 8 are sealed. The holding container 3 is composed of an upper member 3a and a lower member 3b. Here, the upper member 3a and the lower member 3b can constitute a sealed space by overlapping them, and the microlens array molding die 2 can be fixed and held between these members. . That is, the microlens array mold 2 divides the internal space of the holding container 3 (the glass material 50 also contributes to the space division during molding).

  The lower member 3b supports the microlens array mold 2 from below, and a cooling medium flow path is provided therein. When the cooling medium is caused to flow through the flow path of the cooling medium, the lower member 3b is cooled, and the microlens array mold 2 in contact therewith can be indirectly cooled. Therefore, at this time, it is preferable to design the contact area between the microlens array mold 2 and the lower member 3b as large as possible. This is because the cooling efficiency of the microlens array mold 2 varies depending on the contact area.

  The pressure control unit 4 used in the present invention controls the pressure in the first space 7 and the pressure in the second space 8 as described above, and in the first space 7 and the second space 8. Are connected to each other so that the air pressure in each space can be controlled. At this time, the space (second space 8) on the side opposite to the space (first space 7) on the contact surface side with the glass material 50 of the mold 2 for microlens array is pressed by the pressure control unit 4. A differential pressure is generated so as to be a low pressure. That is, the pressure control unit 4 has a mechanism for generating a pressure difference between the front and back of the microlens array mold 2.

  Specifically, a pressure pump or the like is used to increase the pressure in the first space 7, and a vacuum pump or the like is used to decrease the pressure in the second space 8. Is adjusted to a predetermined value.

  The heating unit 5 heats and softens the glass material 50. In general, examples of the heating means used for glass forming include infrared heating, resistance heating, and high-frequency heating. This heating part 5 is arrange | positioned so that the glass raw material 50 may be heated from the 1st space side. At the time of this heating, a heater may be provided inside the microlens array mold 2 as an auxiliary, and the glass material 50 may be efficiently softened by heating simultaneously.

  The temperature difference generator 6 reduces the temperature of the microlens array mold 2 during molding, and includes a cooling medium flow path provided inside the lower member 3b and a flow path (not shown). And a pump capable of delivering a cooling medium.

  The cooling medium used here cools the lower member 3b by circulating inside the lower member 3b, and indirectly cools the microlens array mold 2 in contact with the lower member 3b. In addition, although it cools indirectly in FIG. 1, it is good also as a structure which is made to contact directly the shaping | molding die 2 for micro lens arrays, and is not restricted to this form. In that case, care should be taken so that the cooling medium does not leak outside or inside the holding container 3. Examples of the cooling medium to be used include air, inert gas, water, and a mist-like combination of these, and if the optimum one is selected in consideration of the heat transfer coefficient required for cooling, Good. Moreover, the well-known thing which can send out the above cooling media is mentioned for a pump.

  In addition, although the manufacturing apparatus 1 of the microlens array of FIG. 1 showed the case where the 1st space 7 and the 2nd space 8 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 7 in FIG. 1 is sealed and the second space 8 is opened, the apparatus configuration shown in FIG. 2A is obtained. The microlens array manufacturing apparatus 11 shown in FIG. 2A holds the mold 2 for the microlens array, the peripheral edge of the mold 2, the contact surface side of the mold 2 with the glass material 50, and its A holding container 12 that divides a space formed on each of the opposite surfaces, a pressure control unit 13 that generates a differential pressure in the space divided by the holding container 12, a heating unit 5, and a temperature difference generation unit 6, Have

  Here, the holding container 12 seals the first space 14 and opens the second space 15. Since the second space 15 is at atmospheric pressure, the first space 14 is large. The pressure needs to be higher than atmospheric pressure. Therefore, the pressure control unit 13 used here is a pressurizing pump that can pressurize the inside of the first space 14. The holding container 12 is different only in that the lower member 3b of the holding container 3 in FIG. 1 is a lower member 12b configured to be released to the atmosphere without forming a sealed space. Other than that, the configuration is the same as that of the holding container 3 (that is, the upper member 12a is the same as the upper member 3a).

  Moreover, when the 1st space 7 of FIG. 1 is open | released and the 2nd space 8 is sealed, it becomes an apparatus structure shown to FIG. 2B. The microlens array manufacturing apparatus 21 shown in FIG. 2B holds the peripheral portion of the microlens array molding die 2 and the microlens array molding die 2, and the glass material 50 of the microlens array molding die 2 The holding container 22 that divides the space formed on each of the contact surface side and the opposite surface side thereof, the pressure control unit 23 that generates a differential pressure in the space divided by the holding container 22, the heating unit 5, and the temperature A difference generation unit 6.

  Here, the holding container 22 opens the first space 24 and seals the second space 25. Since the first space 24 is at atmospheric pressure, the second space 25 is large. The pressure needs to be lower than atmospheric pressure. Therefore, the pressure control unit 23 used here is a vacuum pump that can depressurize the second space 25. The holding container 22 is composed of only the lower member 3b without the upper member 3a of the holding container 3 of FIG.

  Here, the material of the holding containers 3, 12, and 22 may be any material having resistance to temperature and pressure at the time of forming the microlens array, and examples thereof include cast iron, stainless steel, copper alloy, and carbide. .

  Next, the manufacturing method of the microlens array of this invention is demonstrated, referring FIG. FIG. 3A shows an example in which the microlens array manufacturing apparatus 1 of FIG. 1 is used, and the pressure control unit 4 is not shown. 3B to 3D are diagrams showing changes in the glass material 50 when the environment is changed to each processing condition in order to perform the forming operation in FIG. 3A. In these drawings, the pressure in the first space 7 is P1, and the pressure in the second space 8 is P2.

  First, the glass material 50 is placed on the microlens array mold 2 and accommodated in the holding container 3. Next, the glass material 50 is heated to the molding temperature by the heating unit 5 and is softened (FIG. 3A; heating process). The heating temperature at this time may be a temperature at which the glass material 50 is softened, and is generally about 500 to 1100 ° C. although it varies depending on the glass material to be used. At this time, if the viscosity of the glass is η [dPa · s], the range of log η may be 4.8 to 12.37, preferably 5 to 10, and preferably 5 to 8. More preferred is 5.5 to 7.5. If lоg η exceeds 12.37, the viscosity is too high to be deformed by suction and cannot be molded. On the other hand, if l η is less than 4.8, the viscosity is too low and deforms by its own weight. In either case, shape control becomes difficult. In this step, the pressures P1 and P2 are the same.

  Further, as described in the description of the apparatus, when a heater is provided inside the microlens array mold 2 or the lower member 3b, the microlens array mold 2 of the microlens array mold 2 is activated by operating the heater. The temperature can be raised, and the heating process can be quickly achieved by heating the glass material 50 not only from the first space side but also from the second space side. Such a heater is used in the heating process, but is not used in the temperature difference generation process, the molding process, and the solidification process described below in order to lower the temperature of the microlens array mold 2.

  Next, the microlens array mold 2 is cooled when the microlens array is molded. In cooling the mold 2, the cooling medium is circulated through the flow path provided in the lower member 3 b to cool the lower member 3 b, and the microlens array mold 2 in contact with the lower member 3 b is removed. Can also be cooled. In this way, a temperature difference is generated in the thickness direction of the glass material 50 by cooling the mold 2 for microlens array. At this time, since the glass material 50 is heated on the opposite surface to be cooled by the heating unit 5, the glass material 50 has a larger temperature distribution than when the glass material 50 is not cooled (FIG. 3B). Temperature difference generation step). Moreover, since the glass material 50 is heated by the heating unit 5 on the opposite side to be cooled, the temperature of the microlens array mold 2 rises after starting cooling due to the balance between heating and cooling. In some cases. However, even in this case, the temperature increase rate is different between the heating part 5 side of the glass material 50 and the microlens array mold 2 side, and thus the glass material 50 has a temperature distribution in the thickness direction. In this process, “when forming a microlens array” means that it is before the molding process described below or at the same time as the molding process, and a sufficient temperature difference was actually caused when the glass material was deformed. It is only necessary to obtain a softened glass material.

  In this step, since the glass material 50 must be kept deformable in the molding step described later, the microlens array molding die 2 is cooled to such an extent that the softened state is maintained. That is, if the microlens array mold 2 is cooled too much, the viscosity of the surface of the glass material 50 in contact with the mold may become too high, making it impossible to form the desired shape.

  In order to obtain the glass material 50 in the softened state in which the temperature difference is generated, for example, the glass material 50 is softened by a heating process and then the temperature difference generating process is performed to maintain the softened state of the glass raw material 50. The temperature difference may be generated as it is, or the temperature difference generation step is started immediately before the glass material 50 becomes softened in the heating process, and the glass material 50 is further heated while generating the temperature difference to be softened. May be reached. As in the latter case, in order to further raise the temperature of the glass material 50 while generating a temperature difference to make it softer, the temperature is increased under the condition that the temperature of the mold 2 for microlens array rises due to the balance between heating and cooling described above. What is necessary is just to perform a difference production | generation process.

  In this step, the temperature difference between the glass material 50 and the microlens array mold 2 is preferably 10 ° C. or higher, and more preferably 20 ° C. or higher. In determining this temperature difference, the temperature of the glass material 50 is 1 mm from the glass material surface on the microlens array mold side toward the inside of the glass material, and the temperature of the microlens array mold 2 is microscopic. The temperature at the contact surface with the glass material of the lens array mold may be taken and the temperature difference between them may be taken. Each temperature can be measured, for example, by arranging a thermocouple at each position or using an infrared camera. In this process, the pressures P1 and P2 are the same.

  Next, as described above, a predetermined temperature difference between the glass material 50 and the microlens array mold 2 is generated at the same time or after the predetermined temperature difference is generated. The relationship is changed so that the second space 8 has a lower pressure (P1> P2) than the first space 7 to generate a differential pressure.

  When the differential pressure is generated as described above, the glass material 50 in the softened state is sucked to the low pressure second space 8 side through the through-hole 2 a and is brought into close contact with the microlens array molding die 2. And the second space 8 are surely divided and become airtight. That is, if the state where the pressure difference between the front and back sides of the microlens array mold is continued is continued, the glass material 50 is sucked (extruded) into the through-hole 2a to form a convex microlens. (FIG. 3C; molding process).

  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 50, the differential pressure (P1-P2) between the first space 7 and the second space 8, 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 differential pressure (P1-P2) between the first space 7 and the second space 8 at the time of molding is 5 in order to achieve sufficient deformation of the glass material 50 in a practical time. -1000 kPa is preferable, and 10-800 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 3600 seconds, more preferably 1 to 300 seconds so as not to impair the function as a microlens array and also consider the manufacturing efficiency. preferable.

  The “viscosity of the glass material” in the present specification refers to the viscosity of the glass material at the time of molding. Specifically, the temperature of the microlens array mold 2, that is, the microlens array mold 2. It is the viscosity at the temperature on the surface of the contact surface with the glass material 50.

  Then, when the microlens array has a desired shape, the pressure difference between the first space 7 and the second space 8 is eliminated, and the first space 7 and the first space 7 are prevented from further deformation. The pressures in the two spaces 8 are the same.

  Next, the deformed glass material 50 is cooled to near the glass transition point, and the glass material 50 is solidified (FIG. 3D; solidification step). The cooled glass material 50 is released from the microlens array mold 2 with P1 <P2, and finally cooled to room temperature to obtain a microlens array. In this way, a microlens array in which microlenses with spherical optical surfaces are arranged is obtained. The cooling in this solidification process should just reduce the output of the heating part 5 to 0 or to reduce. At this time, the temperature difference generator 6 may be operated to promote the cooling of the glass material 50. The thermal expansion coefficient of the material for the microlens array mold 2 and the thermal expansion coefficient of the glass material 50 are substantially equal, and the thermal expansion coefficient of the material for the microlens array mold 2 is the thermal expansion coefficient of the glass material 50. The glass material 50 is cooled to room temperature integrally with the microlens array mold 2 and solidified, and then released from the microlens array mold 2 to obtain a microlens array. Good.

  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 1 mm and can be obtained in a desired shape by adjusting the molding conditions. . The above shows the absolute range of the radius of curvature, but the ratio of the radius of curvature of the formed microlens to the radius of the microlens in plan view ([curvature radius of lens / lens radius in plan view]; , Also referred to as “curvature radius ratio”). In particular, a small radius-of-curvature ratio is preferable in that the high light utilization efficiency required for a microlens array can be obtained and the space where the microlens array is arranged can be reduced. The curvature radius ratio is not particularly limited, but is preferably 1.35 or less, more preferably 1.3 or less, still more preferably 1.2 or less, and particularly preferably 1.1 or less. On the other hand, there is a possibility that lens peeling will occur even if this radius ratio is too small. Therefore, the lower limit of the radius-of-curvature ratio can be reduced within a range in which peeling does not occur. For example, 0.7 or more is preferable, 0.8 or more is more preferable, and 0.9 or more is more preferable.

  When the radius-of-curvature ratio is 1.2 or less, the relationship between the viscosity lｌgη and the differential pressure of the glass material at the time of molding is as follows: (1) lögη7 to 8, differential pressure 10 to 88 kPa, (2) lögη6 to 7, It is preferable to set so that it may become the range of the combination of differential pressure 20-1000 kPa, (3) lota [eta] 5-6, differential pressure 40-1000 kPa. With such a combination, the occurrence of lens separation can be sufficiently suppressed even with a micro lens closer to a hemisphere, and a micro lens array can be manufactured with a high yield.

Further, such molding is performed in a state heated to a high temperature, and in order to prevent deterioration due to oxidation of the microlens array mold, for example, both the first space 7 and the second space 8 are made of nitrogen or argon. It is preferable that the atmosphere is an inert gas atmosphere or the like, or the second space 8 side (low pressure side) is set to a vacuum condition of 1 × 10 ⁻² Pa or less.

  In the present invention, a chamber capable of accommodating the microlens array mold 2 and the holding container 3 inside (the pressure control unit 4 may be disposed outside the chamber) may be provided. It is preferable because the atmosphere of the mold can be easily replaced and the internal temperature can be stabilized.

  The glass material 50 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 50 before a heating is not specifically limited, The planar shape has a rectangular or circular flat shape, and the thickness at that time is 0.1 mm-20 mm. 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.

  In the microlens array obtained from the manufacturing apparatus and the manufacturing method described above, the surface of the microlens array has a surface roughness Ra of 100 nm or less because the lens surface of the microlens is not in contact with the microlens array mold or the like in molding. A very smooth shape can be obtained. In addition, since the glass material is deformed by the differential pressure, the variation in the lens shape is small between the central portion and the outer peripheral portion of the microlens array, and the uniformity is excellent. In the present specification, the surface roughness (arithmetic average surface roughness) of the surface of the microlens array can be measured with an atomic force microscope, and for example, JIS R 1683 can be applied.

  The most characteristic feature of the present invention is that the glass material is heated and softened during molding, and before or simultaneously with the molding of the microlens array, the thickness direction of the glass material in contact with the microlens array molding die. The point is to generate a temperature difference. By generating the temperature difference in this way, the fluidity of the glass material on the contact surface side with the mold for microlens array can be adjusted. It is also possible to manufacture a microlens array having a large effective area with a high yield. This is presumably because the glass material is less likely to enter the through-hole 2a, so that the contact area with the molding die wall surface is reduced and lens peeling is less likely to occur at the time of release. And according to this manufacturing method, as a microlens array manufactured by differential pressure, a microlens array having a small curvature radius ratio can be improved in yield and efficiently manufactured.

(Embodiment of microlens array)
The microlens array in the present invention can be manufactured by the manufacturing apparatus and the manufacturing method described above. The microlens array obtained at this time has a plurality of convex spherical microlenses, the viscosity of the glass material 50, the differential pressure (P1-P2) between the first space 7 and the second space 8, and molding. It can be obtained by adjusting the curvature radius ratio of the microlens to a desired one by time or the like. Therefore, microlens arrays having various curvature radius ratios can be manufactured by appropriately setting manufacturing conditions.

  In this microlens array, for example, the microlens diameter is 10 to 5000 μm, the microlens array pitch is 10 to 20000 μm, and the ratio represented by [lens diameter / pitch] is 0.1 to 1. Preferably, the microlens array has a wide shape such as 0.2 to 0.9. Note that the pitch of the microlens array corresponds to the distance between the centers of adjacent microlenses.

By the way, although the microlens obtained by the manufacturing apparatus and the manufacturing method described above can manufacture microlens arrays having various shapes as described above, it is also possible to manufacture a microlens having an unprecedented characteristic. That is, while the lens diameter of the microlens is as small as 10 to 100 μm, the curvature radius ratio is 1.35 or less, close to a hemispherical shape, and has a smooth surface shape with a surface roughness Ra of 100 nm or less, and A microlens array having a wide effective area with an effective area of 50 mm ² or more can be manufactured. The lens diameter of the microlens is preferably 20 to 90 μm, and more preferably 40 to 80 μm.

  Here, in a microlens having a lens diameter of 10 to 100 μm, depending on the transfer molding, the surface roughness of the lens depends on the surface roughness of the molding surface. It is difficult to perform mirror polishing, and it is not possible to obtain a microlens having a surface roughness Ra of 100 nm or less. However, according to the microlens array manufacturing method and manufacturing apparatus described above, a microlens having a surface roughness Ra of 100 nm or less can be obtained. Further, the surface roughness Ra is preferably 70 nm or less, more preferably 10 nm or less, and further preferably 1 nm or less.

And by the manufacturing method of the microlens array of this invention mentioned above, it has a microlens with a curvature radius ratio of 1.35 or less, and the microlens array has a wide effective area such that the effective area of the microlens array is 50 mm ² or more. Can be produced, and it is possible to suppress the peeling of the microlens and the like in a wide range, and thus the product yield can be improved. Further, as described above, the curvature radius ratio is more preferably 1.3 or less, further preferably 1.2 or less, and particularly preferably 1.1 or less. On the other hand, as described above, the radius-of-curvature ratio can be set, for example, as a preferable range of 0.7 or more, a more preferable range of 0.8 or more, and a more preferable range of 0.9 or more.

In such a microlens array, the number of microlenses contained in the microlens array is not particularly limited. However, it is preferable that 5 to 400 microlenses are formed per 1 mm ² , and the total number of microlenses is 4000 or more. Those having a very large number of microlenses are preferred. At this time, the microlenses are preferably arranged in a matrix of columns (60 to 1000) × rows (60 to 1000). In this microlens array, the pitch between the microlenses is preferably 20 to 500 μm, more preferably 40 to 300 μm, and further preferably 80 to 150 μm.

For example, in a plan view, in a microlens array in which 65 columns and 65 rows are arranged at regular intervals at a pitch of 150 μm in a vertical direction, the lens diameter of each microlens is 10 to 100 μm and the curvature radius ratio is 1.35. Hereinafter, when the surface roughness satisfies the specification of 100 nm or less, the effective area is about 92 mm ² . Even with such a microlens array having a wide effective area, according to the microlens array manufacturing apparatus and manufacturing method of the present invention described above, it is possible to effectively suppress the occurrence of peeling and the like and manufacture with good yield. it can. As micro-lens array of the above specifications, the effective area may if 50 mm ² or more, preferably if 60 mm ² or more, and more preferably equal to 75 mm ² or more. In addition, although the upper limit of an effective area is not particularly provided, it may be, for example, 1500 mm ² or less as described above.

  Hereinafter, the present invention will be described in more detail with reference to Examples (Examples 1, 4 and 5) and Comparative Examples (Examples 2 and 3).

(Example 1)
Using the microlens array manufacturing apparatus of FIG. 2B, a microlens array was manufactured as follows.
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) as a thin metal plate and a diameter of 20 mm and a thickness of 50 μm. 20) is laminated by diffusion bonding to obtain a laminated plate having a thickness of about 1 mm. The metal thin plate has an 8 mm × 8 mm region at the center thereof, and by etching, circular through-etching holes with an average diameter of 67.9 μm are arranged in 81 rows × 81 rows in a grid pattern at a pitch of 100 μm. Since these through-etching holes are formed and laminated, the 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 both surfaces of the laminate obtained as described above, to obtain a mold for a microlens array.

  In the microlens array manufacturing apparatus, as shown in FIG. 2B, 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. The lower space (second space) is connected to a pressurizing / depressurizing 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 glass material was heated and softened by the heating unit. After sufficiently heating and softening the glass material, the temperature difference generating unit was operated, and the holding container was cooled by circulating nitrogen gas at room temperature inside the holding container. By cooling the holding container, the microlens array mold that is in contact with the holding container is also indirectly cooled to lower the temperature, creating a temperature difference between the glass material and the microlens array mold. Is done. In this example, a lamp heater was used as the heating unit.

  Here, the temperature of the glass material is determined by a thermocouple provided at a position of 1 mm from the surface of the glass material on the mold side for the micro lens array, and the temperature of the mold for the micro lens array is determined by the mold for the micro lens array. It measured with the thermocouple provided in the contact surface surface with the glass raw material.

  Simultaneously with the supply of the nitrogen gas, the pressure reducing / pressurizing pump is also operated, the lower space (second space) is set to a negative pressure, held for a predetermined molding time, and the glass material is deformed to form a micro lens. . The molding time was appropriately adjusted so as to obtain a desired shape in the range of 1 second to 60 minutes while observing the lens height of the microlens.

  Then, immediately after releasing the pressure in the lower space to return to atmospheric pressure, the glass material was cooled. When the glass material becomes 500 ° C. or less, the lower space is set to a positive pressure (0.15 MPa) by a decompression / pressurization pump, the glass material and the mold for the microlens array are released, and immediately the atmospheric pressure is reached. Returned. Furthermore, when the glass material was cooled to room temperature, the molded glass material was taken out to obtain a microlens array having a plurality of microlenses arranged.

  The manufacturing conditions and the shape of the obtained microlens array are summarized in Table 1. Also, a graph was created for the relationship between the curvature radius ratio and [lens height / lens diameter in plan view] and is shown in FIG. In addition, although the result regarding the lens of Table 1 is based on the result of measuring the dimension of a typical microlens among the obtained microlens arrays, in the condition where peeling was not confirmed, in the microlens array Variations in the curvature radius ratio of each microlens and [lens height / lens diameter in plan view] were small and were generally the values shown in Table 1. In Tables 2, 4 and 5, which will be described later as conditions under which peeling was not confirmed, similarly, the curvature radius ratio of each microlens in the microlens array and [lens height / plan view]. The variation in the diameter of the lens] was small and was generally the value shown in each table.

(Example 2)
In Example 1, a microlens array was manufactured by the same operation except that the temperature difference generation step using nitrogen gas was not performed. In Example 2, the temperature difference between the glass material and the microlens array mold was 0 ° C.
The manufacturing conditions and the shape of the obtained microlens array are summarized in Table 2. Also, a graph was created for the relationship between the curvature radius ratio and [lens height / lens diameter in plan view] and is shown in FIG. In addition, although peeling of the microlens was confirmed under the conditions of Example 2-2, Table 2 shows a result of measuring typical dimensions of some of the microlenses that did not peel.

(Example 3)
In Example 2, a microlens array was manufactured by the same operation except that the temperature of the glass material during molding was changed. In Example 3, the temperature difference between the glass material and the microlens array mold was 0 ° C.
The manufacturing conditions and the shape of the obtained microlens array are summarized in Table 3. Also, a graph was created for the relationship between the curvature radius ratio and [lens height / lens diameter in plan view] and is shown in FIG. In addition, although peeling of the microlens was confirmed under the conditions of Example 3, Table 3 shows a result of measuring typical dimensions of some microlenses that did not peel.

(Example 4)
In Example 1, a microlens array was manufactured by the same operation except that the differential pressure during molding was 10 kPa.
The manufacturing conditions and the shape of the obtained microlens array are shown in Table 4. In addition, a graph was created for the relationship between the curvature radius ratio and [lens height / lens diameter in plan view] and shown in FIG. In addition, in FIG. 5, the thing whose curvature radius ratio becomes 1.40 or less among Examples 1-3 is also shown collectively.

(Example 5)
A microlens array was manufactured by the same operation except that the temperature and differential pressure of the glass material during molding were changed.
The manufacturing conditions and the shape of the obtained microlens array are summarized in Table 5. In addition, a graph was created for the relationship between the curvature radius ratio and [lens height / lens diameter in plan view] and shown in FIG.

Incidentally, in FIG. 4 and FIG. 5, the example obtained as a non-defective product with no microlens peeling is painted out, and the example obtained as a defective product with peeling is shown as a white mark. Further, in Examples 2-2 and 3, the microlens was peeled over the entire surface, and a microlens array having a wide effective area could not be obtained without lens peeling.
From the above, it has been found that according to the manufacturing method of the present invention, a product having a wide effective area can be manufactured, and particularly effective when the curvature radius ratio of the microlens becomes small.

(Surface roughness)
As a representative, when the surface roughness of the microlens array obtained in Example 5-1 was measured before and after molding, the surface roughness Ra was 0.5 nm both before molding and after molding.

(Lens shape check)
Regarding 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 surface roughness is an atomic force microscope (manufactured by Park Systems, trade name: XE-HDM), and the cantilever is manufactured by Park Systems, trade name: Non-Contact Cantilever, PPP-NCHR 10M. And measured. The obtained microlens array was a lens having a smooth surface shape without being affected by the surface roughness of the mold as in the transfer method. In addition, the variation in shape between the central portion and the outer peripheral portion of the obtained microlens array was extremely small, and a uniform optical surface shape could be formed.

  From the above, it was confirmed that the microlens array manufacturing method and manufacturing apparatus of the present invention have a smooth optical surface and a large yield of a microlens array having a large effective area with a simple operation. Further, it is easy to form a microlens having a small radius of curvature ratio, and a highly accurate microlens array can be realized. The microlens array thus obtained is a microlens array having uniform characteristics with little variation in the shape of individual microlenses.

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

  The microlens array of the present invention is a microlens array having the characteristics that the surface of the microlens is smooth, the shape is uniform, the effective area is large, and has unprecedented characteristics. Can be provided.

DESCRIPTION OF SYMBOLS 1 ... Micro lens array manufacturing apparatus, 2 ... Mold for micro lens array, 3 ... Holding container, 4 ... Pressure control part, 5 ... Heating part, 6 ... Temperature difference production | generation part, 7 ... 1st space, 8 ... Second space, 50 ... glass material

Claims (16)

The glass material is brought into contact with a microlens array mold having a plurality of through holes for forming microlenses, and the microlens is formed on the surface of the glass material by a suction action due to a pressure difference between the front and back surfaces of the mold for microlens array. A method of manufacturing a microlens array for molding
A temperature difference generating step of causing a temperature difference in the thickness direction of the glass material in contact with the microlens array mold by cooling the microlens array mold during molding of the microlens; A manufacturing method of a microlens array characterized by the above. A heating step of bringing a glass material into contact with a mold for forming a microlens array having a plurality of through holes for forming a microlens, and softening the glass material by heating;
A temperature difference generating step of obtaining a softened glass material in which a temperature difference is generated in a thickness direction of the glass material in contact with the microlens array mold by cooling the microlens array mold; and
Simultaneously with or after the temperature difference generating step, the first space on the contact surface side with the glass material of the microlens array mold and the contact surface with the glass material of the microlens array mold A differential pressure is generated between the second space on the opposite surface side so that the second space has a lower pressure than the first space, and the glass material is used as the mold for the microlens array. Forming a convex microlens so as not to come into contact with the mold for microlens array;
A solidification step of cooling and solidifying the glass material in a desired shape by the molding step;
A method for manufacturing a microlens array, comprising:   The method for manufacturing a microlens array according to claim 1 or 2, wherein, in the temperature difference generating step, a temperature difference between the glass material and the microlens array mold is 10 ° C or more.   The method of manufacturing a microlens array according to claim 2 or 3, wherein the first space is set to atmospheric pressure and the second space is set to negative pressure.   The method for manufacturing a microlens array according to claim 2 or 3, 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 2 to 5, wherein the differential pressure is 5 to 1000 kPa.   The manufacturing method of the microlens array of any one of Claims 2 thru | or 6 which sets log (eta) to 4.86-12.37 when the viscosity of a glass raw material is set to (eta) [dPa * s] in the said heating process. A microlens array molding die having a plurality of through holes for forming microlenses for molding microlenses on the surface of the glass material;
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;
A heating unit for heating the glass material;
A temperature difference generating section that cools the microlens array mold during the molding of the microlens and generates a temperature difference in the thickness direction of the glass material in contact with the microlens array mold;
An apparatus for manufacturing a microlens array, comprising:   The microlens array manufacturing apparatus according to claim 8, wherein the temperature difference generation unit includes a flow path provided in the holding container and a pump for circulating a cooling medium through the flow path.   The microlens array manufacturing apparatus according to claim 9, wherein the cooling medium is composed of any one of air, an inert gas, water, and a combination thereof to form a mist.   The microlens array manufacturing apparatus according to claim 8, wherein the pressure control unit includes a vacuum pump connected to the second space.   The microlens array manufacturing apparatus according to claim 8, wherein the pressure control unit includes a pressurizing pump connected to the first space. A microlens array in which a plurality of microlenses are arranged,
The microlens has a lens diameter of 10 to 100 μm, a radius of curvature of the lens / a radius of the lens in plan view, a curvature radius ratio of 1.35 or less, an arithmetic average surface roughness of the optical surface of 100 nm or less, and An effective area of the microlens array is 50 mm ² or more.   The microlens array according to claim 13, wherein the number of the microlenses is 4000 or more.   The microlens array according to claim 13 or 14, wherein the microlenses are arranged in 60 to 1000 columns × 60 to 1000 rows.   The microlens array according to any one of claims 13 to 15, wherein a pitch of the microlens is 20 to 500 µm.

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