JP2006058720A - Microlens and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microlens that can be easily manufactured and that has high manufacturing accuracy and positional accuracy, and a manufacturing method thereof.
A photosensitive resin 2 is exposed using a gray scale mask 3 having a low gradation to form a photosensitive resin layer 2a having a flat portion at the top. Thereafter, the thermosetting resin 5 is spray coated and heated. Due to the effect of surface tension, at the top, the thermosetting resin 5 rises at the center and hardens into a spherical shape, and a spherical microlens 10 is formed. Since the microlens 10 can be formed using a gray scale mask with a low gradation, the manufacturing cost of the microlens can be reduced.
[Selection] Figure 1

Description

  The present invention relates to a microlens and a manufacturing method thereof.

  The microlens is a lens in which a minute semi-spherical lens is arranged, and has been used for various applications such as a liquid crystal display device, a light receiving device, and an inter-fiber connection in an optical communication system. As for the microlens manufacturing method, a manufacturing method using a photolithography technique using a gray scale mask, a manufacturing method using a thermal reflow technique after resist patterning, a manufacturing method using a 2P method, and the like are known. Yes.

  An example of a manufacturing method using a photolithography technique using a gray scale mask is disclosed in Patent Document 1 below. The gray scale mask is a mask that can have multi-value transmittance continuously or discretely for each minute region. When the photosensitive material is exposed through the gray scale mask, the exposure amount of a minute region can be changed. Since the photosensitive depth of the photosensitive material changes according to the exposure amount, an arbitrary three-dimensional shape can be formed with the photosensitive material by modulating the exposure amount. Since the microlens is composed of a curved surface, this transmittance control also requires multiple gradations.

On the other hand, there is an example disclosed in Patent Document 2 below regarding a manufacturing method using a thermal reflow technique after resist patterning. The photosensitive material applied on the transparent substrate is patterned into a disk shape by photolithography. The disc-shaped photosensitive material is rounded into a spherical shape by heat treatment, and the shape is transferred to the substrate by dry etching. In the manufacturing method using the thermal reflow technology, it is necessary to pattern the disc-shaped photosensitive material at intervals, so that a dense microlens array cannot be formed and the fill factor cannot be increased. . As a countermeasure for this problem, a method of improving the fill factor by performing dip coating or spin coating after thermal reflow has been proposed. In the manufacturing method using the 2P method, a photocurable resin is applied on a transparent substrate, a lens mold is pressed, light is irradiated from the substrate side, and the photocurable resin is photocured to form a microlens. It is.
JP 2002-287325 A JP 2002-122707 A

  In a manufacturing method using a photolithography technique using a gray scale mask, a mask including many gradations is required for forming a curved surface. However, the cost of the gray scale mask is extremely high, and the cost for manufacturing the mask increases as the number of gradations increases. Therefore, a lens manufacturing method using a gray scale mask with a lower gradation is desired. In addition, in the manufacturing method using the thermal reflow technique after resist patterning, it is difficult to produce a microlens array having a high fill factor, and a high temperature process is required, so that the work to be used is limited. Since these two manufacturing methods apply photolithography technology, it is possible to form a microlens by positioning the pattern previously engraved on the substrate. However, in the manufacturing method using the 2P method, it is difficult to align the lens mold and the substrate, and it is difficult to apply to a use in which a microlens is manufactured by positioning on the substrate. Therefore, the present invention has been made in view of the problems of the background art described above, and its main object is to provide a microlens that is inexpensive and has good shape accuracy and position accuracy, and a method for manufacturing the same. is there.

  In the microlens based on the present invention, a substantially convex microlens composed of a substantially convex translucent photosensitive material and a translucent thin film laminated on the photosensitive material. In the top of the microlens, the translucent thin film is thicker than the surrounding film surrounding the top.

  In the microlens manufacturing method according to the present invention, the substantially convex light-transmitting photosensitive material and the light-transmitting thin film laminated on the photosensitive material are substantially convex. A method of manufacturing a mold-like microlens, the step of forming a photosensitive material layer, the step of exposing the photosensitive material layer to form a convex three-dimensional shaped exposure region, and the photosensitive material layer And a step of forming a translucent thin film by spray coating on the photosensitive material layer from which the uncured portion has been removed.

  According to the microlens of the present invention, it is composed of a convex photosensitive material layer and a thin film provided on the photosensitive material layer. If the thin film is a hard coating film, the hardness and resistance of the microlens are improved. Solvent property is improved. In particular, at the top of the lens where there are many opportunities for contact with the outside, the hard coating film is thick, so the effect of improving the hardness is enhanced. Further, when an organic material or an inorganic-organic hybrid material is used as the thin film material, it can be easily applied by spray coating. Further, when a flat portion is formed on the top of the convex photosensitive material layer, the thickness of the thin film on the top can be easily increased. In particular, when spray coating is performed, a spherical shape can be easily formed due to the effect of surface tension.

  Further, according to the method for manufacturing a microlens of the present invention, the photosensitive material layer is exposed by a photolithography technique, and a thin film is laminated thereon by spray coating. Since it is formed by photolithography, it is easy to position and form the microlens on a pre-patterned substrate, and a spherical shape can be easily obtained by spray coating of a thin film on the top of the lens. For photolithography, a low gray scale mask or a normal photomask may be used. When an ordinary photomask is used, a microlens can be formed by changing the incident angle of light on the photomask and performing exposure.

  Hereinafter, a microlens and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings. The microlens and the manufacturing method thereof described below are examples, and the present invention is not limited to these contents.

  With reference to FIG. 1, the microlens and the manufacturing method thereof in the present embodiment will be described. First, as shown in FIG. 1A, a photosensitive resin layer 2 is formed on a substrate 1. The photosensitive resin layer 2 can be made of a material having both negative characteristics (light-irradiated portions remain) and positive characteristics (light-irradiated portions remain). Although a case where a photosensitive resin material exhibiting negative characteristics is used will be described here, the same concept can be applied to a photosensitive resin material having positive characteristics.

  Next, as shown in FIG. 1B, a gray scale mask 3 is placed over the photosensitive resin layer 2. Exposure light 4 is irradiated from above the grayscale mask 3, and the photosensitive resin layer 2 is exposed using light that passes through the grayscale mask 3. The gray scale mask 3 is a mask in which the optical density is changed for each minute region. The exposure light 4 is intensity-modulated by this mask, and the photosensitive resin layer 2 is exposed by the light subjected to the intensity modulation. Thereafter, when the development process is performed, the remaining film thickness of the photosensitive resin layer 2 follows the sensitivity curve shown in FIG. 2A. Therefore, as shown in FIG. 1C, a three-dimensional convex photosensitive resin is used. Layer 2a is formed.

The sensitivity curve shown in FIG. 2A represents the characteristics of the exposure amount (exposure light illuminance × irradiation time) and the remaining film thickness. When the remaining film thickness is H, the exposure amount is E, and the critical exposure amount (threshold value at which the photosensitive resin is exposed) is E _th , the relationship is expressed by the following formula (1). A is a constant representing the slope of the sensitivity curve. An exposure amount E for obtaining a desired film thickness H is expressed by the following formula (2).

H = A × log _e (E / E _th ) (1)
E = E _th × exp (H / A) (2)
A graph of the necessary exposure amount E for obtaining a desired film thickness H is shown in FIG. From FIG. 2B, it can be seen that the change in the required exposure E is small where the film thickness H is thin, but the change in the required exposure E increases as the film thickness H increases. When forming a shape having a curved surface such as a microlens, it is necessary to continuously change the exposure amount. Since a change in exposure amount can only be given discretely in a gray scale mask, a step may be formed on the curved surface. However, a smooth curved surface can be obtained by setting the minimum unit area of the gray scale mask pattern to about half or less of the resist resolution. For example, when the resolution of the resist is 20 μm, the optical density of the gray scale mask pattern is changed every 10 μm.

  When the convex photosensitive resin layer 2a as shown in FIG. 3B is formed, the exposure amount distribution at each position is given as shown in FIG. As can be seen from FIG. 3A, the increment value of the required exposure amount differs between the central portion (top) and the peripheral portion of the photosensitive resin layer 2a. Therefore, in the gray scale mask, the optical density must be finely set at the central portion (top) of the photosensitive resin layer 2a, and the optical density must be set roughly at the peripheral portion, so that the number of gradations is high and the optical accuracy is high. A gray scale mask capable of adjusting the density is required. However, since the multi-tone grayscale mask is expensive to manufacture, it is desirable to reduce the number of required tones. Here, exposure is performed using a gray scale mask of low gradation having an exposure amount distribution as shown in FIG. At this time, the shape obtained after development has a cross-sectional shape as shown in FIG. Since the optical density of the central portion (top) of the photosensitive resin layer 2a is not set appropriately, the shape has a flat portion 2t on the top, but the mask pattern is simplified, so that a gray scale mask is manufactured. Cost can be reduced.

  Next, as shown in FIG. 1D, the coating agent 5 is spray-coated. As the coating agent 5, a thermosetting or photocurable material is used. After spray coating, the coating agent 5 is cured by heat curing and light irradiation. Examples of the coating agent 5 used here include a mixture of an acrylic monomer or an epoxy monomer with a photoinitiator, a silicone, an epoxy-silica hybrid material, or a mixture of inorganic fine particles in an organic material. . Organic materials and inorganic-organic hybrid materials can easily maintain high adhesion to the substrate 1 and can easily be added with functions such as thermal curing and photo-curing. A hybrid material may be used. The spray coating parameters include coating agent viscosity, coating agent flow rate, spray pressure, spray nozzle-workpiece distance, work temperature, etc., and these are controlled to perform coating with a desired thickness.

At this time, in the spray coating, the flow rate of the coating agent is adjusted to be small, and the workpiece is heated in order to suppress the fluidity of the coating agent after adhering to the microlens. The coating agent to be formed can be thickly coated, and a microlens having a flat portion can be formed into a spherical shape. Since the fluidity of the coating agent 5 is lower in the flat portion than in the curved surface portion, the film thickness of the coating agent 5 is increased in the flat portion. Due to the effect of the surface tension of the coating agent 5, the coating agent 5 is The central portion rises and hardens into a spherical shape, and a spherical microlens 10 is formed. At this time, the accumulation of the coating agent 5 in the lens valleys can also be suppressed. When an epoxy-silica hybrid coating agent was used as the coating agent 5 and applied under the conditions of a spray pressure of 5 kg / cm ² , a coating agent flow rate of 0.5 cc / min, a spray nozzle-work distance of 70 mm, and a work temperature of 50 ° C. A lens having a cross-sectional shape shown in FIG. 5 was obtained. In FIG. 5, the thin line is the cross-sectional shape of the outer surface of the coating agent 5 before coating and the thick line is after coating.

According to the microlens manufacturing method in the embodiment based on the present invention, it may be applied to a type of lens having a small lens curvature. When the lens curvature is small, the difference in the increment value of the curved surface becomes large between the lens central portion and the lens peripheral portion, so that photolithography with a gray scale mask becomes more difficult. The ratio W _{L /} R _L of the lens width W _L and lens radius of curvature R _L is effective when applied to manufacturing a microlens in the present embodiment in the case of more than 1/3.

  Further, according to the microlens manufacturing method of the present embodiment, a photosensitive resin layer having a convex pattern formed using a gray scale mask of low gradation, and a spray coating film applied thereon By combination, a microlens can be formed with high accuracy at low cost. Further, when a coating agent that functions as a hard coating material after curing is used, the solvent resistance and hardness of the photosensitive material can be improved. In particular, since the hard coating agent is formed thick on the top of the lens that is easily in contact with the outside, the effect of improving the hardness is high. When the photolithographic technique is used, a microlens array can be manufactured with high density and high positional accuracy and reproducibility, but the mask cost is high even with a low gray scale mask, and the mask manufacturing takes time. If a microlens array can be manufactured using a normal photomask, the lens manufacturing cost can be greatly reduced.

  Here, an exposure method for producing a microlens array using a normal photomask will be described with reference to FIG. Here, a method for manufacturing a lenticular lens array will be described. FIG. 6A is a cross-sectional view for explaining the exposure process, and FIG. 6B is a graph showing the exposure amount at each position of the photosensitive material. A photosensitive material layer 2 is formed on a transparent substrate 1 and a photomask 6 having a plurality of slits is disposed. The photomask 6 is disposed on the opposite side of the transparent substrate 1 from the photosensitive material layer 2, and the photosensitive material layer 2 is irradiated with the exposure light 4 through the photomask 6 and the transparent substrate 1. When the incident angle of the exposure light 4 is changed, the position of the exposed region of the photosensitive material layer 2 changes. Exposure is performed while changing the incident angle continuously or stepwise.

When parallel light is used as the exposure light and the incident angle of the illumination light is changed at a constant angular velocity, the distribution of the exposure amount at each point on the photosensitive material layer 2 irradiated with the illumination light is shown in FIG. It becomes a thing. When the sensitivity curve of the photosensitive material layer 2 is superimposed on this, the photosensitive material layer 2 having a shape indicated by a broken line in FIG. 6A is obtained. In this exposure step, a region where the exposure amount is constant is generated in the central portion, so that a flat surface is formed in the central portion of the photosensitive material layer 2. For example, when the width W _A of the slit aperture of the photomask 6 is 40% of the width W _L of the photosensitive material layer 2, the width W _P of the flat portion becomes a value of about 20% of the lens width W _L. At this time, when the incident angles θ1 and θ2 of the irradiation light are set so that the convex photosensitive material layer 2 is formed without a gap, a dense microlens array can be obtained.

  Next, an irradiation light scanning method will be described. In the present application, “scan” includes two-dimensional scanning of a region irradiated with exposure irradiation light and changing the incident angle of the irradiation light. In addition, since “scan” only requires that the positional relationship and angle between the exposure light 4 and the photocurable resin layer 2 change relatively, the substrate 1 coated with the photocurable resin 2 may be moved. The light source of the exposure light 4 may be moved. If a “scan” is performed in two orthogonal directions using a photomask 6 in which a circular opening or a rectangular opening is formed, a microlens having a lens effect in two directions can also be formed. This method is used, for example, as a method of manufacturing a microlens in a transmissive liquid crystal panel having an opening. That is, by using the pixel opening as a mask opening, a microlens is manufactured on the light source side of the transmissive liquid crystal panel, and the light use efficiency from the light source to the liquid crystal panel can be increased. The formed convex lens has a flat portion at the top of the photocurable resin 2, but can be formed into a spherical shape by spray coating thereafter.

  When a microlens is provided on a transmissive liquid crystal panel, moire may occur with the periodic structure of the prism sheet provided on the backlight side. This can be suppressed by making the microlens spherical. Is possible. In this embodiment, a spherical lens can be formed by combining an exposure method using an aperture and spray coating, whereby a structure effective in suppressing moire can be obtained.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It does not become the basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

  The microlens and the manufacturing method thereof according to the present invention can be applied to a liquid crystal display device, a light receiving device, an interfiber connection in an optical communication system, and the like.

(A)-(D) are 1st-4th process sectional drawing explaining the manufacturing method of the microlens in embodiment based on this invention. (A) is a figure which shows the sensitivity curve of the photosensitive material when taking a "exposure amount" on a horizontal axis and taking a "remaining film thickness" on a vertical axis | shaft, (B) is a "residual film thickness on a horizontal axis. ] Is a diagram showing a sensitivity curve of a photosensitive material when “exposure amount” is taken on the vertical axis. It is a figure which shows the shape of the photosensitive resin layer at the time of using a multi-tone grayscale mask, (A) is a figure which shows the relationship between "position" and "required exposure amount", (B) These are figures which show the shape of the photosensitive resin layer corresponding to (A). It is a figure which shows the shape of the photosensitive resin layer at the time of using a gray scale mask of a low gradation, (A) is a figure which shows the relationship between "position" and "required exposure amount", (B) These are figures which show the shape of the photosensitive resin layer corresponding to (A). It is a figure which shows the cross-sectional shape of the micro lens (outer surface of a coating agent) produced with the manufacturing method of the micro lens in embodiment based on this invention. It is a figure explaining the manufacturing method from which the photolithography for producing the microlens in embodiment based on this invention differs, (A) is sectional drawing for demonstrating an exposure process, (B) is a photosensitive material. It is a figure which shows the exposure amount in each position.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 board | substrate, 2 photosensitive resin layer, 2a photosensitive resin layer (three-dimensional convex type), 2t flat part, 3 gray scale mask, 5 coating agent, 6 photomask, 10 micro lens.

Claims (9)

A substantially convex microlens composed of a substantially convex light-transmitting photosensitive material and a light-transmitting thin film laminated on the photosensitive material,
A microlens characterized in that, at the top of the microlens, the thickness of the translucent thin film is larger than the thickness of the surrounding film surrounding the top.   The microlens according to claim 1, wherein the translucent thin film is made of an organic material or an inorganic-organic hybrid material.   The top part of the convex part formed of the photosensitive material has a flat part, and the outer surface of the translucent thin film is formed into a spherical shape by laminating the translucent thin film on the top part. The microlens according to claim 1, wherein the microlens is characterized.   The micro lens according to claim 1, wherein a radius of curvature of the micro lens is three times or less of a lens width. A method for producing a substantially convex microlens composed of a substantially convex translucent photosensitive material and a translucent thin film laminated on the photosensitive material,
Forming a photosensitive material layer;
Exposing the photosensitive material layer to form a convex three-dimensional exposure region;
Removing the uncured portion of the photosensitive material layer;
Forming a light-transmitting thin film by spray coating on the photosensitive material layer from which the uncured portion has been removed;
A method for producing a microlens, comprising:   6. The method of manufacturing a microlens according to claim 5, wherein a photosensitive process is performed on the photosensitive material layer using transmitted light that has passed through a gray scale mask.   The microlens manufacturing method according to claim 5, wherein a photosensitive process is performed while changing an incident angle to the transparent opening using a mask provided with a plurality of transparent openings on the photosensitive material layer. Method.   The method for manufacturing a microlens according to claim 5, wherein heat treatment is also performed at the same time in the spray coating process.   The micro surface according to claim 5, wherein an outer surface of the light transmissive thin film is formed into a spherical shape by forming a light transmissive thin film by spray coating on the photosensitive material layer having a three-dimensional shape. Lens manufacturing method.

Images