JP2009113311A - Manufacturing process of micro-lens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process which inexpensively manufactures a micro-lens array and enables designing the size and the pitch of the micro-lens array. <P>SOLUTION: The process includes a step to form a particle film composed of lens shape-determining particles 2 by utilizing the self-organizing phenomenon of the lens shape-determining particles 2 on a substrate 1, a step to form a resin layer 4 on a substrate 4, a step to oppose the substrate 1 with the particle film formed on it to the substrate 3 with the resin layer 4 formed on it and press the substrate 1 against the substrate 3 with a predetermined pressure, a step to separate the substrate 1 and the substrate 3 after the pressing step and a step to manufacture a micro-lens array 7 by using the substrate 3 having holes formed by the lens shape-determining particles 2 pressed on it as a mold. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a microlens array.

  The microlens array is an optical element that is used as a means for supplementing the light collecting power of a solid-state imaging device such as a CCD mounted on a liquid crystal panel or a digital camera inside the liquid crystal projector.

  In recent years, organic electroluminescence (EL) elements have been actively studied as candidates for large-area illumination utilizing the characteristics of self-luminous displays and flat light emission. Also in that element, Non-Patent Document 1 and Non-Patent Document 2 show the microlens array as an optical element that can improve the light extraction efficiency. According to this, the light extraction efficiency of about 20% is the theoretical maximum value in the configuration of a general organic EL element, but 30% which is about 1.5 times by application of the microlens array. Simulations show that the degree of improvement is possible.

  Several methods for producing such useful microlenses have been shown so far. For example, there is a mechanical method in which a metal mold or the like is engraved and manufactured by precisely cutting a metal plate or the like with a cutting tool, and then a resin or glass is poured into the mold. In addition, there is a registry flow method in which a resist patterned at a predetermined position is heated and melted into a hemispherical structure by a microfabrication technique such as photolithography to form a microlens.

  However, according to the former mechanical method, in addition to a long processing time, the size that can be cut is limited to about 10 μm. Further, the smaller the machining size, the longer the machining time, and the higher the machine precision of the required tool, resulting in higher costs. This problem becomes particularly noticeable when a large-area mold is manufactured.

  In the registry flow method, the size of a lens that can be produced can be several microns or less. However, a large-sized exposure apparatus is required for producing a large-area mold, and it is difficult to manufacture at a low cost. Furthermore, since the registry flow method is based on the melting and flow phenomenon caused by heating of the patterned resist, it is difficult to reduce the distance between the lenses, and it is not easy to manufacture a microlens array having a high fill factor. Currently.

  However, even with an organic EL element as an example, there is a tendency to increase in area as a display or illumination application, and a corresponding microlens array and its mold are important. Therefore, a new method for manufacturing a microlens array having a large area and a high fill factor at low cost has begun to be sought.

  For example, there is a breath figure template method disclosed in Non-Patent Document 3. This is because when a polymer such as polycarbonate and a surfactant dissolved in a volatile solvent such as dichloromethane are applied to a substrate and placed in a high-humidity chamber and the solvent is evaporated, a porous polymer thin film is formed. That's it. The produced porous polymer thin film is used as a mold, and after the resin is poured and cured, the resin is peeled off and used as a microlens array. This method is based on a structure in which water droplets produced by condensation of water molecules in the atmosphere when dichloromethane volatilizes are closely packed via a surfactant. Although it can be developed over a large area at a low cost, the uniformity of the water droplet size is somewhat inferior, and when applied to a display or illumination, the luminance distribution may be uneven. Furthermore, it is difficult to change design parameters such as pitch adjustment between concave centers corresponding to the lens portions.

  Patent Document 1 discloses a method using particles having a diameter of about 100 microns as a template. In this method, particles having a predetermined diameter are first arranged on a particle fixing substrate at a predetermined pitch, and the particle fixing substrate is immersed at a predetermined depth in a substrate coated with an uncured UV curable resin. After curing by irradiation, the particles are removed to form a mold for a microlens array. In the examples in the patent document, it is described that a mold for a microlens array was manufactured using particles made of nickel, glass and wax having a diameter of about 100 microns. According to this, if the monodispersity of the particles is ensured, a mold having a more uniform lens size than the above-described breath figure template method can be produced in a large area at a low cost. However, although it is necessary in the process to arrange the particles at a predetermined pitch in advance, a detailed description of the arrangement method is not made.

  That is, it is not easy to arrange particles having a size of 100 microns or less at a predetermined position with an accuracy of several microns. In particular, this problem becomes more prominent as the particle diameter decreases. If a mechanical method such as a micromanipulator is used for the arrangement of the particles, eventually, a long time is required to arrange a large number of particles in a large area with high accuracy, which is not practical. In addition, if photolithography is used in the process for disposing the particles at a predetermined position as disclosed in Non-Patent Document 4, the maximum advantage of a low-cost mold manufacturing method using the particles is reduced. .

JP 2004-351838 A Journal of Applied Physics 91 vol.5 (2002) p3324 Journal of Applied Physics 100 vol.7 (2006) p073106 SID Symposium DIJEST (2007) p857 Advanced Materials 13 (2001) p34

  Therefore, an object of the present invention is to provide a method for manufacturing a microlens array at a low cost and a manufacturing method that enables designing the diameter and pitch of the microlens array.

  As means for solving the above-described problems, the present invention includes a method for manufacturing a microlens array including the following steps.

  First, the first invention relates to the one in which the pitch between the final lens centers becomes equal to the diameter of the lens shape determining particles.

That is, forming a particle film composed of the lens shape determining particles on the substrate (1) using the self-organization phenomenon of the lens shape determining particles;
Forming a resin layer on the substrate (3);
A step of pressing the substrate (1) on which the particle film is formed and the substrate (3) on which the resin layer is formed to face each other with a predetermined pressure;
A step of peeling the substrate (1) and the substrate (3) after pressing;
A step of manufacturing a microlens array using a substrate (3) having a hole generated by pressing the lens shape determining particles as a mold;
It is characterized by including.

  Next, the second invention relates to a configuration in which the pitch between the final lens centers is different from the diameter of the lens for determining the lens shape.

That is, forming a particle film composed of the pitch determining particles on the substrate (101) using a self-organization phenomenon of the pitch determining particles;
Forming a resin layer on the substrate (104);
A step of pressing the substrate (101) on which the particle film is formed and the substrate (104) on which the resin layer is formed to face each other with a predetermined pressure;
Separating the substrate (101) and the substrate (104) after pressing;
A step of creating a template with particles having particles by using the substrate (104) having holes generated by pressing the particles for pitch determination as a template and dispersing the particles for determining the lens shape on the template;
Forming a resin layer on the substrate (108);
Pressing the template with particles and the substrate (108) against each other with a predetermined pressure;
Peeling the template with particles and the substrate (108) after pressing;
Producing a microlens array using a substrate (108) having holes generated by pressing a template with particles as a mold;
It is characterized by including.

  According to the present invention, it is possible to provide a method for manufacturing a microlens array at a low cost and a manufacturing method that enables designing the diameter and pitch of the microlens array.

  The best mode for carrying out the present invention will be described below for each process with reference to the drawings.

<Embodiment 1>
First, the first invention relating to an arrangement in which the pitch between the lens centers is equal to the diameter of the particles will be described.

  FIG. 1 shows the process of the first invention.

The first step is a step of forming a lens shape determining particle film on the substrate 1. The lens shape determination particles 2 having a predetermined diameter D _L is dispersed in a solvent, and the particle dispersion. At this time, it is desirable that the CV value of the particles to be used (the ratio of the standard deviation to the average diameter of the particles) is less than 10%, preferably less than 5%. This is because the larger the CV value exceeds the above range, the more defects in the structure of the finally formed particle film. The particle concentration of the particle dispersion may be appropriately adjusted in consideration of the coating area, but it is desirable that the generated particle film be a single layer particle film. If there is a part that has a multilayer structure in the particle film, the pressure is concentrated on the lens shape determination particles in the multilayer part in the subsequent pressing process, and the substrate is destroyed or sufficient pressure is applied to the periphery. This is because a mold having a hole with a desired depth cannot be obtained.

  As shown in FIG. 1A, the particle dispersion is applied to the substrate 1 and dried. During the drying process, a self-organization phenomenon caused by capillary force occurs between the particles, and a particle film in which the lens shape determining particles 2 are densely packed is formed (FIG. 1B).

  Here, the self-organization phenomenon refers to a phenomenon in which particles are densely packed using a capillary force generated between the fine particles when the solvent is dried after the particle dispersion is applied to the substrate.

  In addition, the board | substrate 1 should just be a raw material which does not deform | transform at the heating temperature in a later press process, and glass and a silicon wafer are desirable.

  The second step is a step of forming the resin layer 4 on the substrate 3. The resin layer 4 may be formed by a commonly used forming method such as a coating method such as a spin coating method or a dip method, or a vapor deposition method. The resin may be selected from either a thermosetting resin or a thermoplastic resin, but the glass transition point or melting point of the resin should not exceed the glass transition point or melting point of the particles used. The film thickness of the resin layer 4 is desirably set in advance to be equal to the desired desired hole depth. Thereby, it is only necessary to abut the substrate 1 on the surface of the substrate 3 at the time of subsequent pressing, and precise control of the press becomes unnecessary.

  The third step is a pressing step. The substrate 1 on which the particle film is formed is opposed to the substrate 3 on which the resin layer 4 is formed (FIG. 1C). Then, it presses with a predetermined pressure (FIG.1 (d)). The pressing is performed by heating to a temperature equal to or higher than the glass transition point of the resin to soften and flow the resin. After pressing, it is cooled to solidify the resin. Here, the predetermined pressure refers to a pressure range not less than a minimum pressure sufficient for the particle film on the substrate 1 to contact the surface of the substrate 3 and not more than an upper limit pressure at which the substrate 1 or the substrate 3 is destroyed. .

  The fourth step is a peeling step. The substrate 1 and the substrate 3 are peeled as shown in FIG. After peeling, the particles remaining on the substrate 3 may be detached by ultrasonic cleaning in an appropriate solvent or etched with a solvent that dissolves the particles.

  The fifth step is a step of manufacturing a microlens array using the substrate as a mold. This uses the substrate 3 having the formed holes as a mold 5 after pressing. After performing the peeling process on the mold 5, the resin 6 is injected and cured (FIG. 1 (f)). Thereafter, the resin is peeled to obtain the microlens array 7 reflecting the hole shape (FIG. 1 (g)). Or you may take the method of making it harden | cure after pressing a mold separately on the board | substrate which coated resin.

  By utilizing the self-organization phenomenon, the lens shape determining particles 2 can be regularly arranged on the substrate 1 in a dense state, and the mold can be manufactured simply by pressing the substrate 1 against the substrate 3 on which the resin is formed. can do. Therefore, a microlens array can be manufactured at low cost using this mold.

<Embodiment 2>
Next, a second invention relating to an arrangement in which the pitch between the lens centers is different from the diameter of the lens for determining the lens shape will be described.

  The second invention is characterized by having a step of creating a template for guiding the lens shape determining particles to a predetermined position by the self-organization phenomenon of the pitch determining particles as a previous step of the first invention. . That is, in the first invention, in the first step, since the substrate 1 to be used is flat, the structure of the particle film formed through the self-organization phenomenon is a structure in which the lens shape determining particles are in contact with each other. For this reason, the pitch between the centers of the holes generated in the substrate 3 is equal to the diameter of the lens for determining lens formation, and the lens diameter and the pitch between the lenses cannot be selected independently. Therefore, the following process is added to the previous stage of the first invention.

  FIG. 2 shows the process of the second invention.

Step A is a step in which pitch determining particles 102 are densely packed and arranged on the substrate 101 using a self-organization phenomenon. The pitch determination particles 102 having a diameter D _p is applied to the substrate 101 in the same manner as in Step 1 of the method of the first invention (FIG. 2 (a)), and particle film (Figure 2 (b)).

Step B is a step of forming the resin layer 103 on the substrate 104. The resin layer 103 may be formed on the substrate 104 by the same method as in the first step of the first invention. However, it is desirable that the glass transition point (T _B ) of the resin 103 used in the step B is higher than the glass transition point (T ₂ ) of the resin 107 used in the subsequent step. This is because, in the case of T _B <T _2, the resin trapping the lens for determining the lens shape is melted in the subsequent pressing process, which causes a positional deviation of the particles.

  Step C is a step of creating a template for guiding the lens shape determining particles 106 to a predetermined position. Performed in the same manner as in the third step of the first invention, the substrate 101 on which the particle film made of the pitch determining particles 102 is formed and the substrate 104 on which the resin layer 103 is formed are opposed to each other (FIG. 2C). ) And pressing at a predetermined pressure (FIG. 2D). By separating in the same manner as in the fourth step of the first invention (FIG. 2E), a particle-attached template (hereinafter simply referred to as a template) 105 for guiding the lens shape determining particles 106 to a predetermined position. Is completed.

  Here, the self-organization phenomenon has the same meaning as described above. The pitch determining particles 102 are particles having a diameter corresponding to the pitch of the holes on the template, and the lens shape determining particles 106 are particles having a shape corresponding to the final lens spherical surface.

  The template 105 completed through the process A to the process C is used as an alternative to the substrate 1 in the first invention, and the first process of the first invention is performed. That is, the dispersion liquid of the lens shape determining particles 106 is sprayed on the template 105 and dried. Thereby, the lens shape determining particles 106 are trapped in the holes of the template 105 in the drying process, and distributed in a pattern as shown in FIG. .

FIG. 3 shows a top view and a side view of the template. In this distribution process, the larger the hole depth of the template, that is, the corresponding resin layer thickness (T), is more effective for trapping particles. However, when the diameter of the lens for determining the lens shape is D _L and the particle diameter for determining the pitch is D _p , it is desirable that the film thickness (T) satisfies the following formula 1. This is defined by the geometric condition in which the diameter of the hole in the template exceeds twice the diameter of the lens for determining the lens shape. When T exceeds this range, when the lens shape determining particles are guided into the hole of the template, it becomes easy to trap a plurality of particles instead of a single particle, and a one-to-one correspondence of one particle per hole can be taken. Disappear.

<Formula _{1> T <(D p -} (D p 2 -4D L 2) 0.5) / 2

  Hereinafter, the microlens array 111 having an arrangement in which the pitch between the lenses is different from the diameter of the particles can be created by similarly performing the second to fifth steps of the first invention. That is, a step of forming the resin layer 107 on the substrate 108 is performed. After that, the template 105 in which the lens shape determining particles 106 are trapped is pressed against the substrate 108 coated with the resin layer 107 with a predetermined pressure and peeled off, thereby reflecting the shape of the lens shape determining particles 106. The completed mold 109 is completed. After performing a peeling process on the mold 109, the resin 110 is injected and cured. Thereafter, the resin 110 is peeled to obtain the microlens array 111 reflecting the hole shape. Or you may take the method of making it harden | cure after pressing a mold separately on the board | substrate which coated resin.

  Using the self-organization phenomenon, the pitch determining particles 102 are regularly arranged in a dense state on the substrate 101, and the template 105 is manufactured simply by pressing the substrate 101 against the substrate 104 on which the resin 103 is formed. Can do. Then, the mold 109 is completed simply by disposing the lens shape determining particles 106 in the holes of the template 105. Therefore, a microlens array can be manufactured at low cost using this mold.

  By properly using the first and second embodiments, the diameter and pitch of the microlens array can be designed.

<Example 1>
Silica fine particles (D _L = 11 μm) were dispersed in ethanol as the lens shape determining particles 2 to obtain a 0.5 wt% silica fine particle ethanol dispersion. As the substrate 1, a slide glass having been subjected to UV ozone cleaning was selected. After the particle dispersion was drop cast on this slide glass and dried at room temperature for about 3 minutes, a particle film accompanying a self-organization phenomenon was obtained. An optical micrograph of the obtained particle film is shown in FIG.

  The particle film has a structure based on hexagonal close-packing, and has a characteristic pattern generated by self-organization phenomenon in which point defects and line defects in which particles are missing in some regions. .

Next, silicon wafer with SiO ₂ film is selected as substrate 3, polymethyl methacrylate (PMMA) resin is selected as resin 4, and polymethyl methacrylate resin with a film thickness of 2.8 μm is coated on the silicon wafer with SiO ₂ film by spin coating. did.

  The obtained substrate 1 with particle film and the substrate 3 coated with polymethylmethacrylate resin are opposed to each other and set in a mold holder and a holder for a substrate to be transferred, respectively, in a nanoimprint press apparatus (manufactured by Myeongchang Kiko Co., Ltd.). did. The pressing condition was that the PMMA resin was softened and fluidized in a heated state of 110 ° C. and pressed with a pressing force of 3 kN for 5 minutes. After cooling to room temperature in the pressed state, the substrate 1 and the substrate 3 were separated to obtain a substrate in which regular holes were arranged, that is, a microlens array mold 5. An optical micrograph of the obtained mold 5 for microlens array is shown in FIG. As can be seen from FIG. 5, it can be seen that the hole has an array structure reflecting the structure of the original particle film.

  The microlens array mold 5 was subjected to a surface treatment with OPTOOL DSX (produced by Daikin Industries, Ltd.), which is a fluorine-based release material. Next, polydimethylsiloxane in which SILPOT184 (manufactured by Toray Dow Corning Co., Ltd.) and CATALYST SILPOT184 (manufactured by Toray Dow Corning Co., Ltd.) were mixed at a weight ratio of 10: 1 was poured and heated at 130 ° C. for 6 hours. After curing, the polydimethylsiloxane film was peeled from the mold to obtain a microlens array 7. A scanning electron micrograph of the obtained microlens array 7 is shown in FIG. As can be seen from FIG. 6, a lens shape obtained by inverting the hole structure of the microlens array mold 5 is obtained.

  In addition, a projection experiment was performed to confirm that the obtained microlens array had a function as a lens. In the projection experiment, the microlens array 202 is placed on the mask 201 engraved with the letter “3”, irradiated with white light from the lower part of the mask, and the objective lens 203 is set from the upper part of the lens. This was performed by a method of confirming a reduced image with an optical microscope. The obtained projection image is shown in FIG. As can be seen from FIG. 8, the reduced image was clearly confirmed. From this, it was confirmed that the obtained microlens array has a function as a lens.

<Example 2>
Silica fine particles (D _L = 11μm) is dispersed in ethanol as the pitch determination particles 102, to obtain a 0.5 wt% silica fine particle ethanol dispersion. As the substrate 101, a slide glass that had been subjected to UV ozone cleaning was selected. After the particle dispersion was drop cast on this slide glass and dried at room temperature for about 3 minutes, a particle film accompanying a self-organization phenomenon was obtained.

Next, a silicon wafer with a SiO ₂ film was selected as the substrate 104, and a polyimide resin was selected as the resin 103. A polyimide precursor having a film thickness of 3.2 μm was coated on a silicon wafer with a SiO ₂ film by spin coating, and then dried at room temperature.

  The obtained substrate 104 with particle film and the substrate 103 coated with the polyimide precursor thin film were made to face each other, and set and pressed respectively in a mold holder and a transferred substrate holder of a nanoimprint apparatus (manufactured by Meisho Kiko Co., Ltd.). . The pressing condition was heating at 300 ° C. for 1 hour while being pressed with a pressing force of 3 kN. After cooling to room temperature in the pressed state, the substrate 104 and the substrate 101 were separated to obtain a substrate in which regular holes were arranged, that is, the template 105.

Silica fine particles (D _P = 6.0 μm) were dispersed in ethanol as the lens shape determining particles 106 to obtain a 0.1 wt% silica fine particle ethanol dispersion. The particle dispersion was drop cast on the template 105 obtained earlier and dried at room temperature for about 3 minutes, and a particle film was obtained. When the number of particles trapped in the template 105 was small, drop casting was repeated. As shown in FIG. 9, the obtained particle film had a structure in which the lens shape determining particles 106 were trapped in holes formed in the template 105 in advance as depressions of the pitch determining particles.

Hereinafter, the template 105 on which the lens shape determining particles 106 are arranged was used as a mold. Then, using the silicon wafer with SiO ₂ film coated with 2.0 μm-thick polymethyl methacrylate resin as the substrate 108, the microlens array 111 could be obtained through the same steps as in Example 1.

<Comparative Example 1>
A template was prepared in the same manner as in Example 2 except that silica fine particles having different diameters (D _P = 4.3 μm) were used as the lens shape determining particles 106. In this case, the film thickness T of the resin layer exceeds the range of Equation 1. FIG. 10 shows an optical micrograph image in which silica fine particles are distributed on the template actually obtained. As can be seen from FIG. 10, a plurality of lens-shaped particles were trapped in one hole, making it difficult to place one particle in one hole.

It is a schematic diagram which shows the manufacturing process of the micro lens array which uses the particle | grains for lens shape determination. It is a schematic diagram which shows the manufacturing process of the microlens array which uses the particle | grains for pitch determination. It is a template upper surface schematic diagram and a side surface schematic diagram. It is an optical micrograph of a particle film. It is an optical microscope photograph of a mold. It is a scanning electron micrograph of a microlens array. It is a block diagram of a projection experiment. It is a projected image. It is a single particle image on a template. It is a multiple particle image on a template.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Lens shape determining particle 3 Substrate 4 Resin layer 5 Mold 6 Resin 7 Micro lens array 101 Substrate 102 Pitch determining particle 103 Resin layer 104 Substrate 105 Template 106 Lens shape determining particle 107 Resin layer 108 Substrate 109 Mold 110 Resin 111 Micro lens array 201 Mask 202 Micro lens array 203 Objective lens

Claims (3)

Forming a particle film composed of the lens shape determining particles on the substrate (1) using a self-organization phenomenon of the lens shape determining particles;
Forming a resin layer on the substrate (3);
A step of pressing the substrate (1) on which the particle film is formed and the substrate (3) on which the resin layer is formed to face each other with a predetermined pressure;
A step of peeling the substrate (1) and the substrate (3) after pressing;
A step of manufacturing a microlens array using a substrate (3) having a hole generated by pressing the lens shape determining particles as a mold;
The manufacturing method of the micro lens array characterized by the above-mentioned. Forming a particle film composed of the pitch determining particles on the substrate (101) using a self-organization phenomenon of the pitch determining particles;
Forming a resin layer on the substrate (104);
A step of pressing the substrate (101) on which the particle film is formed and the substrate (104) on which the resin layer is formed to face each other with a predetermined pressure;
Separating the substrate (101) and the substrate (104) after pressing;
A step of creating a template with particles having particles by using the substrate (104) having holes generated by pressing the particles for pitch determination as a template and dispersing the particles for determining the lens shape on the template;
Forming a resin layer on the substrate (108);
Pressing the template with particles and the substrate (108) against each other with a predetermined pressure;
Peeling the template with particles and the substrate (108) after pressing;
Producing a microlens array using a substrate (108) having holes generated by pressing a template with particles as a mold;
The manufacturing method of the micro lens array characterized by the above-mentioned. When the diameter of the pitch determining particles is D _p , the diameter of the lens shape determining particles is D _L , and the film thickness of the resin layer formed on the substrate (104) is T, the following formula 1 is satisfied. The manufacturing method of the micro lens array of Claim 2 characterized by the above-mentioned.
<Formula _{1> T <(D p -} (D p 2 -4D L 2) 0.5) / 2

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