JP4133652B2 - Pattern forming method and two-layer structure microlens using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pattern forming method using a microlens array.
[0002]
[Prior art]
In fields such as a liquid crystal display element and a liquid crystal projector, or optical communication, a transparent substrate having a spherical portion or a prism formed on at least one surface portion, such as a microlens and a microlens array, is being used.
[0003]
For example, in a projection-type liquid crystal display device that displays a color image using a liquid crystal display element, a single-plate liquid crystal element using a microlens array as disclosed in Patent Document 1 has been proposed.
[0004]
Conventional projection color image display systems using liquid crystal display elements include a three-plate type using three liquid crystal display elements according to the three primary colors and a single-plate type using only one sheet. The former three-plate type is equipped with an optical system that divides white light into three primary colors of red, green, and blue, and three liquid crystal display elements that control each color light to form an image independently. The full color display is performed by optically superimposing the images of the respective colors. This three-plate configuration has the advantage that light emitted from a white light source can be used effectively and has high color purity. However, as described above, a color separation system and a color synthesis system are required. However, the number of parts is increased and the number of parts is increased, which is generally disadvantageous as compared with a single plate type described later in terms of cost reduction and size reduction.
[0005]
On the other hand, the latter single-plate type uses only one liquid crystal display element, and there is one in which a liquid crystal display element having a three-primary color filter pattern such as a mosaic shape or a stripe shape is projected by a projection optical system. . The single-plate type requires only one liquid crystal display element and the optical system is simpler than the three-plate type, making it suitable for low-cost, small projection systems.
[0006]
Such a single-plate type liquid crystal display element uses a microlens having a two-layer structure as described in Patent Document 1 described above, thereby eliminating the need for an absorption color filter and improving the light utilization efficiency. The chief rays of each color after passing through the microlens array are substantially parallel, so the spread of the chief rays of each color until reaching the projection lens is small, and there is no decrease in the amount of light due to vignetting in the projection lens. Can be provided.
[0007]
As a method of manufacturing the microlens having the two-layer structure, there is a method in which the first-layer microlens and the second-layer microlens are arranged on the same optical axis, and are bonded and fixed.
[0008]
In addition, as a general pattern forming method, there is a method of forming a desired pattern shape by exposing a photosensitive resin according to a pattern. In this case, it is also known that by exposing the photosensitive material layer using a microlens provided on the substrate, the focal position of the microlens is irradiated with a fine exposure distribution to form a fine pattern. It has been.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-181487 (published July 21, 1995)
[0010]
[Problems to be solved by the invention]
However, in the conventional method for manufacturing a microlens having a two-layer structure, in order to reduce the aberration of the combined lens, the first-layer microlens is bonded in the bonding process of the first-layer microlens and the second-layer microlens. It is necessary to minimize the positional deviation of the optical axis between the lens and the second-layer microlens. To this end, the optical axis must be adjusted using a complicated adjustment mechanism, which has a problem in productivity. .
[0011]
As a method of forming a pattern by exposing a photosensitive resin, a method of obtaining a desired three-dimensional pattern, particularly a pattern having a substantially vertical wall surface with respect to a substrate coated with the photosensitive resin is known. Not.
[0012]
The present invention has been made in view of the above-described problems, and an object thereof is to provide a pattern forming method capable of obtaining a desired three-dimensional pattern.
[0013]
Another object of the present invention is to provide a two-layer microlens that can simplify the optical axis adjustment and can simplify the manufacturing process.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the pattern forming method of the present invention includes a microlens forming step for forming a microlens on a transparent substrate, and a photosensitive resin layer forming for forming a photosensitive resin layer at a focal position of the microlens. An exposure step of curing the photosensitive resin layer into an uneven shape having a wall surface substantially perpendicular to the transparent substrate by exposing the photosensitive resin layer through the microlens to the photosensitive resin layer; In the exposure step, a difference between an exposure amount in a portion of the photosensitive resin layer that becomes an edge of the concavo-convex convex portion and an exposure amount in a portion that becomes a concave portion adjacent to the convex portion is determined as desired. It is characterized in that it is larger than the difference in exposure amount necessary to form the height of the unevenness.
[0015]
The above-mentioned “concave and convex shape having a substantially vertical wall surface” may be a shape having at least a substantially vertical wall surface, and the concave portion here is a surface that follows the wall surface and is closer to the transparent substrate than the wall surface, The convex portion is a surface that continues from the wall surface and is farther from the transparent substrate than the wall surface.
[0016]
The photosensitive resin layer has a thickness that cures in proportion to the logarithm of the exposure amount. Here, the “difference in the exposure amount necessary to form a desired uneven height” Is a theoretical value derived from this proportional relationship.
[0017]
According to said structure, since pattern formation is performed using the light which permeate | transmitted the micro lens, the photosensitive resin can be exposed by fine exposure distribution, and a fine pattern can be formed. Moreover, if another microlens is formed using this pattern, the microlens arrange | positioned on the same optical axis of two layers can be formed. According to this, the optical axis of the two-layer microlens can be adjusted with high accuracy without requiring a complicated adjustment mechanism.
[0018]
Further, when forming the uneven pattern, the difference in the exposure amount inside and outside the boundary between the concave and convex portions is made larger than the difference in the exposure amount necessary for forming the desired uneven height. Thus, the rising of the exposure amount distribution, that is, the change in the exposure amount becomes steeper, so that the patterned uneven wall surface can be made substantially vertical.
[0019]
Further, in the pattern forming method of the present invention, the photosensitive resin layer is made of a positive photosensitive resin, and in the exposure step, from the portion that becomes the concave and convex portion of the photosensitive resin layer to the portion that becomes the concave portion. The exposure amount is discontinuously increased, and the exposure amount in a portion that becomes a concave portion adjacent to the convex portion is increased more than the exposure amount in other portions that become concave portions.
[0020]
When a positive photosensitive resin is used as the photosensitive resin, the thickness of the photosensitive resin layer decreases as the exposure amount increases. Therefore, when a positive photosensitive resin is used as the photosensitive resin layer, the amount of exposure is increased discontinuously from the convex portion of the concave-convex shape to the concave portion of the photosensitive resin layer. Thus, an uneven shape can be formed. Furthermore, if the exposure amount at the concave portion adjacent to the convex portion is made larger than the exposure amount at the other portions that become the concave portions, the rise of the exposure amount distribution becomes steep, so that the patterned uneven wall surface is substantially vertical. It becomes possible.
[0021]
Further, in the pattern forming method of the present invention, the photosensitive resin layer is made of a negative photosensitive resin, and in the exposure step, from the concave portion of the photosensitive resin layer to the convex portion of the photosensitive resin layer. The exposure amount is increased discontinuously, and the exposure amount at the portion that becomes the edge of the convex portion is characterized by being larger than the exposure amount at the center portion of the convex portion.
[0022]
When a negative photosensitive resin is used as the photosensitive resin, the photosensitive resin layer becomes thicker as the exposure amount increases. Therefore, when a negative photosensitive resin is used as the photosensitive resin, the exposure dose is increased discontinuously from the concave portion to the convex portion of the photosensitive resin layer. Uneven shape can be formed. Furthermore, if the exposure amount at the edge of the convex part is made larger than the exposure amount at the central part of the convex part, the rise of the exposure amount distribution becomes steep, so that a vertical shape can be patterned. Become.
[0023]
Further, in the pattern forming method of the present invention, in the exposure step, the difference between the average exposure amount of the portion to be the convex portion and the average exposure amount of the portion to be the concave portion is formed to form a desired projection height. It is characterized by being equal to the difference in required exposure amount.
[0024]
As described above, when the amount of exposure in the portion that becomes the concave portion adjacent to the convex portion or the portion that becomes the edge of the convex portion is increased, the shape of the concave and convex wall surface is improved substantially vertically, compared to the case where it is not increased As a result, the thickness slightly changes by the increase in the exposure amount. For example, when the exposure amount in the portion that becomes the edge of the convex portion is increased, the convex portion becomes slightly thick.
[0025]
However, according to the above configuration, the amount of increase in the exposure amount is reduced in another portion, and the difference between the average exposure amount of the portion that becomes the convex portion and the average exposure amount of the portion that becomes the concave portion is determined as desired. Since the difference in exposure amount necessary to form the height of the unevenness is made equal, the unevenness has a desired thickness. For this purpose, when the exposure amount at the edge of the convex portion is increased, the exposure amount at the portion near the center of the convex portion is decreased, and the exposure amount at the concave portion adjacent to the convex portion is increased. In such a case, it is only necessary to reduce the exposure amount of the other portions that become the concave portions. As a result, the increase in the exposure amount is canceled out, and a concavo-convex shape having a desired height can be obtained.
[0026]
The pattern forming method of the present invention is characterized in that, in the photosensitive resin layer forming step, the thickness of the photosensitive resin layer is equal to the thickness of the thickest portion of the uneven shape.
[0027]
By using the photosensitive resin layer having the above-described configuration, it is only necessary to maintain the thickness of the photosensitive resin layer as it is in the portion to be a convex portion, and the thickness can be easily controlled. For example, when increasing the exposure amount at the edge of the convex portion, the uneven shape obtained will not be thicker than the photosensitive resin layer no matter how much the exposure amount is increased. It will be larger than the thickness and will not rise.
[0028]
Moreover, the pattern formation method of this invention WHEREIN: In the said exposure process, the exposure amount in the part used as the edge of the said convex part shall be 1.5 times or more and 4 times or less of the exposure amount of the part used as the center of a convex part. It is a feature.
[0029]
With the above configuration, by increasing the exposure amount at the portion that becomes the edge of the convex portion, the wall surface of the concave and convex shape is substantially vertical, and the thickness of the convex portion becomes uniform. If the amount of increase in exposure is smaller than the above range, the effect of the present invention that makes the uneven wall surface substantially vertical is not sufficient, and the wall surface is inclined. Moreover, when the increase amount of exposure amount is larger than the said range, the part irradiated with the light of the increased exposure amount will rise more than desired thickness.
[0030]
The pattern forming method of the present invention further includes a substrate forming step of forming an intermediate substrate between the microlens and the photosensitive resin layer, and dry etching the pattern formed by the exposure step, thereby And a transfer step of transferring to a substrate.
[0031]
Thereby, the pattern formed on the photosensitive resin layer can be transferred to the intermediate substrate, and the pattern can be formed on the substrate made of a desired material formed on the surface of the microlens.
[0032]
Moreover, the two-layer structure microlens of the present invention is obtained by the pattern forming method.
[0033]
As a result, a two-layer microlens having a wall surface substantially perpendicular to the transparent substrate and disposed on the same optical axis can be easily formed.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment relating to the pattern forming method of the present invention will be described below with reference to FIGS. In the present embodiment, a method for forming a two-layer microlens array 40 used in a projection type liquid crystal display device will be described as an example.
[0035]
First, a projection type liquid crystal display device 70 using the liquid crystal display element will be described with reference to FIG.
[0036]
The projection-type liquid crystal display device 70 includes a white light source 16, a spherical reflecting mirror 17, a collimating lens 19, dichroic mirrors 15G, 15R, and 15B, a two-layer microlens array (two-layer structure microlens) 40, a liquid crystal display element 18, and a condenser. The lens 25, the projection lens 20, and the projection screen 21 are included.
[0037]
The white light source 16 emits white light as a light source when projecting an image. The spherical reflecting mirror 17 reflects a part of the white light and guides it to the collimating lens 19. The collimating lens 19 passes the white light from the white light source 16 and the white light via the spherical reflecting mirror 17, makes it parallel light, and guides it to the dichroic mirror 15. Three dichroic mirrors 15G, 15R, and 15B arranged in a fan shape divide white light into each color of G (Green), R (Red), and B (Blue), and reflect them at different angles. Guide to the microlens array 40. The two-layer microlens array 40 guides light beams incident at different angles for each color in different directions for each color. The liquid crystal display element (TFT substrate) 18 is disposed on the opposite side of the light source of the two-layer microlens array 40 and controls light transmitted through the two-layer microlens array 40. The condenser lens 25 collects the light from the liquid crystal display element 18 on the projection lens 20, and the projection lens 20 projects an image on the projection screen 21.
[0038]
Here, the liquid crystal display element 18 and the two-layer microlens array 40 will be described in more detail with reference to FIG. FIG. 3 is a cross-sectional view of the liquid crystal display element 18 and the two-layer microlens array 40.
[0039]
The two-layer microlens array 40 includes a first microlens array (microlens) 1 formed on a transparent substrate 7, an intermediate substrate 2 stacked thereon, and a second microlens array 5 on the intermediate substrate 2.
[0040]
The liquid crystal display element 18 has a liquid crystal layer 30 and a substrate 32 from the side in contact with the second microlens array 5. There is a black matrix 14 on the second microlens array 5 side of the liquid crystal layer 30. A pixel 31 is present on the substrate 32 side of the liquid crystal layer 30.
[0041]
As described above, the first microlens array 1 directs incident light beams (R component, G component, and B component) of the three primary colors that are separated from each other with a predetermined angle difference in advance to each corresponding set of three pixels. And concentrate. On the other hand, the second microlens array 5 is interposed between the first microlens array 1 and the set of three pixels corresponding to each other, and the incident light beam inclined with respect to the optical axis of the second microlens array 5 is transmitted to the light beam. It is converted into an incident light beam substantially parallel to the axis.
[0042]
Such an apparatus using the two-layer microlens array 40 does not use an absorption type color filter, so that not only the light use efficiency is improved, but also the main color of each color after passing through the two-layer microlens array 40. The light rays are substantially parallel, the principal rays of the respective colors until reaching the projection lens are small, and there is no decrease in the amount of light due to vignetting in the projection lens, thereby providing an extremely bright image.
[0043]
Next, a method for manufacturing the two-layer microlens array 40 will be described with reference to FIGS. 4A and 4B.
[0044]
In this method, the first microlens array 1 is used to pattern the lens shape of the second microlens array 5. That is, the resist layer 3 formed near the focal position of the first microlens array 1 is exposed to light through the first microlens array 1 to form a pattern, thereby producing the second microlens array 5. To do. As a result, the optical axes of the lenses constituting the first microlens array 1 and the optical axes of the lenses constituting the second microlens array 5 can be made to coincide with each other. The process is simplified.
[0045]
FIG. 4 is a cross-sectional view schematically showing the steps of forming the two-layer microlens array 40 step by step.
[0046]
First, as shown in FIG. 4A, the first microlens array 1 is formed on the transparent substrate 7 by a well-known method (microlens forming step), and the first microlens array 1 of the transparent substrate 7 is formed. Quartz is attached as an intermediate substrate 2 to the surface. At this time, each microlens of the first microlens array 1 is designed so that its focal position is substantially located on the surface of the intermediate substrate 2. Then, a negative photoresist is applied as a photosensitive material to the surface of the intermediate substrate 2 to form a resist layer (photosensitive resin layer) 3 (photosensitive resin layer forming step). Since the resist layer 3 becomes a mold of a second microlens array 5 described later, the thickness of the resist layer 3 needs to be set to be equal to or greater than the thickness of the second microlens array 5.
[0047]
Next, as shown in FIG. 4B, the resist layer 3 is irradiated with ultraviolet parallel light 4 through the first microlens array 1 (exposure process). Here, as described above, since the microlens focal point of the first microlens array 1 is located on the surface of the intermediate substrate 2 (that is, the boundary surface between the intermediate substrate 2 and the resist layer 3), the ultraviolet parallel light 4 is condensed at one point by the resist layer 3 by the first microlens array 1. Then, the resist layer 3 is exposed by this condensed spot.
[0048]
At this time, by controlling the exposure time or exposure light intensity, a desired exposure amount can be given to the resist layer 3 at the focused spot position. Further, this condensing spot moves by changing the incident angle of the parallel ultraviolet light 4 to the first microlens array 1. Therefore, a desired exposure amount distribution can be given inside the resist layer 3 by controlling the exposure amount at each point while changing the incident angle of the parallel ultraviolet light incident on the first microlens array 1. Thereby, the resist layer 3 is hardened in a desired shape according to the exposure amount.
[0049]
Then, by performing development processing after this exposure step, a shape corresponding to the exposure amount distribution is formed on the resist layer 3, and a microlens mold 5 ′ can be formed (FIG. 4C).
[0050]
Further, by performing dry etching on the microlens mold 5 ′ thus obtained, the microlens mold 5 ′ can be transferred to the intermediate substrate 2 as a base, whereby the second microlens array 5 is formed. It is formed (FIG. 4D).
[0051]
Here, examples of the dry etching method include reactive ion etching and ion milling. At this time, the thickness of the microlens mold 5 ′ can be increased by selecting the etching conditions.
[0052]
For example, if an etching condition is selected such that the etching selectivity between the microlens mold 5 ′ and the intermediate substrate 2 is 1: 2, the thickness of the microlens mold 5 ′ is doubled after being transferred to the intermediate substrate 2. . For example, when the etching conditions are selected such that the intermediate substrate 2 is made of quartz and the etching selectivity ratio between the resist layer 3 and quartz is 1: 2, the microlens mold 5 ′ having a thickness of 50 μm in the resist layer 3 is Is enlarged to a second microlens array 5 having a thickness of 100 μm.
[0053]
Through the above process, the second microlens array 5 is formed on the upper surface of the first microlens array 1.
[0054]
Thus, in the present embodiment, the lens shape of the second microlens array 5 is patterned using the first microlens array 1. That is, the first microlens array 1 is formed by exposing the resist layer 3 formed near the focal position of the first microlens array 1 through the first microlens array 1 to form the microlens mold 5 ′. It is possible to make the optical axis of each lens constituting the optical axis of the microlens mold 5 ′ coincide with each other.
[0055]
Further, following these steps, the second microlens array 5 is formed by etching the microlens mold 5 '(transfer step). Thereby, the optical axes of the first microlens array 1 and the second microlens array 5 can be easily matched. Therefore, the optical axis alignment of the two-layer microlens array 40 can be simplified and the manufacturing process can be simplified.
[0056]
Next, the exposure conditions in the exposure process will be described below. Here, an exposure method for forming the two-layer microlens array 40 for a projection type liquid crystal display device shown in FIG. 5 will be described. The convex part of the second microlens array 5 of the two-layer microlens array 40 in FIG. 5 has a trapezoidal cross section in the X direction and a rectangular cross section in the Y direction in the X and Y directions orthogonal to each other. The convex portion has a wall surface 47 that is substantially vertical.
[0057]
In the pattern formation method by exposure using the first microlens array 1 described above, the resist layer 3 that hardens in proportion to the logarithm of the exposure dose becomes thicker, so that an exposure dose distribution according to the film thickness distribution is given. The thickness can be changed. In this method, the pattern whose thickness changes continuously, such as a trapezoidal shape such as a cross-sectional shape in the X direction in FIG. It can be formed by changing the thickness.
[0058]
However, as shown in the Y-direction cross section of FIG. 5, it is difficult to form a pattern shape having a wall surface 47 substantially perpendicular to the transparent substrate 7, that is, a pattern shape whose height changes abruptly. That is, in the above method, even if the exposure amount is changed abruptly, it is not always possible to form a pattern whose height changes abruptly according to the exposure amount distribution.
[0059]
This is because the resist layer 3 needs to have a thickness corresponding to the shape of the second microlens array 5. In such a thick resist layer 3, the light spot collected by the first microlens array 1. This is because it is impossible to focus on the entire thickness direction of the resist layer 3. Thereby, when it is going to form the shape which has the wall surface which stood in the perpendicular | vertical direction, exposure in the wall surface part which thickness increases rapidly cannot fully be performed, but the problem that a wall inclines arises. In addition, since the wall is inclined, the patterned structure becomes narrower toward the tip, resulting in a problem that a desired shape cannot be obtained.
[0060]
More specifically, FIG. 6 shows the exposure amount distribution (FIG. 6A) when the pattern is formed with the exposure amount distribution in which the exposure amount is rapidly changed in the above pattern forming method, and this exposure. The pattern shape (FIG. 6B) obtained by the quantity distribution is shown. Here, the resist layer 3 is made of a negative resist (negative photosensitive resin). In addition, the X axis in the graphs of FIGS. 1 and 6 to 8 indicates the position in the resist layer 3, and corresponds to the position in the Y direction of the two-layer microlens array 40 in FIG. The exposure amount on the Y axis indicates the exposure amount corresponding to the position, and the pattern height on the Y axis indicates the thickness of the unevenness after exposure and development at the position.
[0061]
When an attempt is made to form a rectangular projection pattern perpendicular to the transparent substrate 7, as shown in FIG. 6 (a), a constant exposure amount Ix is exposed at a portion 45 which is a recess at the position indicated by the X axis, and a projection It is conceivable to expose a constant exposure amount Is larger than Ix in the portion 46 that becomes. That is, using two kinds of exposure amounts, the exposure amount is increased discontinuously at the boundary between the concave portion and the convex portion. Here, the difference between the exposure amounts Ix and Is forms the desired uneven height derived from the relationship between the exposure amount and the cured thickness of the photosensitive resin in the photosensitive resin used and the exposure light. This is the difference in the amount of exposure necessary to achieve this.
[0062]
However, the convex pattern actually obtained by such an exposure amount distribution is not a pattern having a wall surface substantially perpendicular to the transparent substrate 7, but the wall surface is inclined as shown in FIG. 6B. The cross section is a trapezoidal pattern. This is because at the portion where the exposure amount switches from Ix to Is, the change in the exposure amount is not accurately reflected in the pattern shape, and the edge portion of the convex portion becomes lower than the others. For this reason, the width of the upper surface of the rectangular pattern becomes smaller than the original design value.
[0063]
Therefore, in the present embodiment, as shown in FIG. 1A, the exposure amount at the portion 41a that becomes the edge portion of the convex portion (the edge of the convex portion) at the position indicated by the X axis is increased by 10 from the above Is. Let Iy be increased only by. As a result, as shown in FIG. 1B, the difference in the exposure amount becomes larger and the rise of the exposure amount distribution becomes steep at the inside and outside of the boundary between the concave portion and the convex portion. The angle with respect to 7 is approximately 90 degrees.
[0064]
Note that the exposure amount Iz at the portion that becomes the center 41b of the convex portion is set lower than the exposure amount Iy. Furthermore, it is preferable that the change from the exposure amount Iy to Iz in the portion that becomes the edge portion 41a of the convex portion is continuous. Thereby, it becomes difficult to produce a difference in thickness between the edge portion 41a of the convex portion and the center 41b of the convex portion.
[0065]
The amount of increase 10 varies depending on the condensing characteristics of the lens, the focal position, or the exposure sensitivity and resolution of the resist. Therefore, it may be set to an appropriate value, but the exposure amount Iy is 1.5 to 4 times the exposure amount Iz. The following is preferable. By setting the exposure amount in this manner, as shown in FIG. 1B, the convex wall surface 47 perpendicular to the transparent substrate 7 can be obtained without lowering the convex edge.
[0066]
If the exposure amount Iy at the edge is smaller than 1.5 times Iz, the wall surface 47 is inclined. If the exposure amount Iy at the edge is larger than four times Iz, the residual resist film thickness becomes larger than a desired value, and the edge is raised.
[0067]
Such correction of the exposure amount is not limited to a rectangular cross section, and can be commonly applied when forming a pattern having a substantially vertical wall surface.
[0068]
Further, when the exposure amount Iy of the edge portion is increased, the shape of the rectangular edge portion is improved and the film thickness of the entire upper surface of the convex portion is slightly increased. Therefore, the exposure amount other than the edge portion of the convex portion (in the center of the convex portion) is set to an exposure amount Iz smaller than the exposure amount Is, and the exposure amount of the entire portion 41 that becomes the convex portion (inside the portion 41 that becomes the convex portion in FIG. 1) It is preferable to adjust so that the average of the exposure amount indicated by the solid line in FIG. 1 becomes equal to the exposure amount Is (the portion indicated by the broken line in FIG. 1). By setting the exposure amount distribution in this way, the increase amount 10 of the exposure amount is canceled out, and a convex portion having a desired height can be formed.
[0069]
Further, a positive resist (positive photosensitive resin) may be used as the photosensitive material. In this case, since the thickness of the resist film 3 that hardens as the exposure amount of the positive resist increases, the exposure amount of the portion 43 that becomes the convex portion is Ix as shown in FIG. The exposure amount of the portion 44 is increased. At this time, the exposure amount Iy of the portion 44a that becomes a concave portion adjacent to the convex portion is made larger than the exposure amount Iz of the portion 44b that becomes another concave portion. As a result, the difference in the exposure amount becomes larger inside and outside the portion that becomes the uneven wall surface, and the rising of the exposure amount distribution becomes steep, so that the angle of the protruding wall portion with respect to the transparent substrate 7 becomes approximately 90 degrees.
[0070]
When a positive resist is used, the exposure amount Iz of the portion 44b serving as the other concave portion is set to an exposure amount Iz smaller than the exposure amount Is, and the exposure amount of the entire portion 44 serving as the concave portion (the portion serving as the concave portion in FIG. 1). It is preferable to adjust so that the average of the exposure amount indicated by a solid line in 44 is equal to the exposure amount Is (the portion indicated by the broken line in FIG. 1). By setting the exposure amount distribution in this way, the amount of increase in the exposure amount is canceled out, and a convex portion having a desired height can be formed.
[0071]
Here, when there is no portion thicker than the edge of the convex portion in the desired pattern, such as a rectangular pattern, the thickness of the resist layer 3 formed first can be made equal to the height of the convex portion. preferable. Thereby, it becomes easy to control the thickness of the convex portion. In particular, when the resist layer 3 is made of a negative resist, even if the exposure amount of the edge portion is increased, the edge does not rise because it does not become thicker than the thickness of the resist layer 3. In this case, since the desired convex pattern can be formed even if the exposure amount is excessively increased, the above-described restriction of the exposure amount is not necessary.
[0072]
By correcting the exposure amount in this way, it is possible to avoid the phenomenon that the edge of the resist pattern convex portion is lowered. Thereby, the inclination of the wall part 47 is also improved, and it becomes possible to produce a pattern shape whose thickness changes abruptly.
[0073]
In the present embodiment, quartz is used as the intermediate substrate 7. However, the intermediate substrate 7 only needs to transmit light, and a layer of resin or other inorganic dielectric (for example, glass) is further formed on the intermediate substrate. You may use what formed.
[0074]
In addition, by using an ultraviolet curable resin as the photosensitive material of the resist layer 3, the pattern formed on the resist layer 3 can be used as a microlens or the like as it is without transferring the pattern by dry etching in the transfer process. Is possible.
[0075]
As described above, the pattern forming method of the present embodiment has been described by taking as an example the case of producing a two-layer microlens array for a liquid crystal projector. However, the present invention is not limited to this, and via a microlens provided on a substrate. It can be used for all processing methods for forming a three-dimensional structure at the focal position of a microlens by exposing a layer of a photosensitive material with light. Specifically, it can also be used for the production of an optical waveguide in optical communication, a combination lens in an optical recording apparatus, or a prism sheet.
[0076]
In addition, the pattern forming method of the present invention is not used only in the case of producing an uneven surface such as a microlens array. The present invention can also be applied when forming a groove or a stepped pattern.
[0077]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.
[0078]
The present invention also includes a step of sequentially forming a microlens array, an intermediate substrate, and a photosensitive resin layer on a transparent substrate, a step of exposing the photosensitive resin layer through the microlens array, and a photosensitivity by the exposure step. A method for forming a three-dimensional structure in which a resin layer includes a wall structure substantially perpendicular to a substrate, wherein the exposure step includes an exposure amount at an upper end of the wall structure and an exposure amount at a lower end of the wall structure at the boundary of the wall structure. The first three-dimensional structure forming method is characterized in that the difference between the exposure amount at the upper end of the wall structure and the exposure amount at the lower end of the wall structure corresponding to the height of the wall structure is increased. In other words.
[0079]
In the present invention, in addition to the above features, when a positive photosensitive resin is used for the photosensitive resin, the exposure step is configured to set the exposure amount of the valley portion adjacent to the wall structure and the depth of the valley. In other words, it is a method for forming a three-dimensional structure characterized by increasing the exposure amount necessary for obtaining.
[0080]
In the present invention, in addition to the feature of the first three-dimensional structure forming method, when a negative photosensitive resin is used as the photosensitive resin, the exposure step includes an exposure amount of an edge portion of the wall structure. In other words, it is a method for forming a three-dimensional structure characterized by increasing the exposure amount necessary to obtain the wall height.
[0081]
In addition to the above features, the present invention reduces the sum of the exposure amount other than the boundary portion by the amount of increase in the exposure amount at the boundary portion of the wall structure, thereby reducing the total exposure amount in the entire three-dimensional structure formation region. In other words, it can be said to be a three-dimensional structure forming method characterized in that it is kept constant.
[0082]
In addition to the above features, the present invention is a three-dimensional structure forming method characterized in that the thickness of the photosensitive material layer formed on the intermediate substrate is equal to the thickness of the desired three-dimensional structure. In other words.
[0083]
In addition to the above features, the present invention provides a three-dimensional structure forming method for producing a three-dimensional structure having a rectangular cross section using a negative resist as the photosensitive resin layer. In other words, it is a three-dimensional structure forming method characterized in that the exposure amount of the central portion of the upper surface is 1.5 times or more and 4 times or less.
[0084]
In addition to the above features, the present invention provides a negative resist layer shape by patterning the resist layer through a microlens array and performing dry etching from the negative resist side in addition to the photosensitive resin layer being a negative resist. In other words, it can be said to be a three-dimensional structure forming method characterized in that is transferred to the intermediate substrate.
[0085]
【Example】
Here, the formation of a concavo-convex pattern in which the wall surface of the two-layer microlens 40 shown in FIG. 5 having a cross-sectional shape in the Y direction as shown in FIG. Here, an attempt was made to form a pattern with a convex portion thickness of 30 μm, a convex portion width 50 of 21 μm, and a concave portion thickness 51 of 5 μm.
[0086]
First, the intermediate substrate 2 was disposed on the transparent substrate 7 having the first microlens array 1. Then, a commercially available negative photoresist material (THB-120N manufactured by JSR) was applied as a photosensitive material on the surface of the intermediate substrate 2, and a resist layer 3 having a thickness of 30 μm was formed by a spin coater. The focal length of the first microlens array 1 is about 30 μm, and the focal point is located between the surface of the intermediate substrate 2 and the inside 5 to 10 μm of the resist layer 3.
[0087]
Under this condition, the amount of exposure Is to obtain a desired resist thickness of 30 μm is uniformly exposed to the portion where the convex portion is to be formed, and the amount of exposure Ix to obtain the resist thickness of 5 μm is the portion where the concave portion is to be formed. When the exposure was uniformly performed, the inclination of the wall surface of the obtained pattern with respect to the intermediate substrate 2 was about 10 °.
[0088]
On the other hand, when the exposure amount Is is uniformly exposed to the portion where the convex portion is to be formed and the sum of the exposure amount in the convex portion is not changed, and the center of the convex portion is at the portion which becomes the edge portion of the convex portion. When it was set to be three times as large as the portion, the inclination of the wall surface of the pattern with respect to the intermediate substrate was nearly 4 °, which was almost vertical, which was improved.
[0089]
Further, when the exposure amount of the edge portion is further increased to be four times or more of the central portion of the convex portion, the width of the lower portion of the projection wall surface becomes larger than the desired width, and the inclination of the pattern wall surface with respect to the intermediate substrate Has increased to about 8 °. Therefore, under these conditions, it is most effective to set the exposure amount at the edge portion to three times the exposure amount at the central portion.
[0090]
【The invention's effect】
As described above, in the pattern forming method of the present invention, in the exposure step, in the photosensitive resin layer, the exposure amount in the part that becomes the edge of the convex part of the concave and convex shape, and the part that becomes the concave part adjacent to the convex part. In this method, the difference from the exposure amount is made larger than the difference in exposure amount necessary to form the desired uneven height.
[0091]
Further, in the pattern forming method of the present invention, the photosensitive resin layer is made of a positive photosensitive resin, and in the exposure step, from the portion that becomes the concave and convex portion of the photosensitive resin layer to the portion that becomes the concave portion. The amount of exposure is increased discontinuously, and the amount of exposure in a portion that becomes a concave portion adjacent to the convex portion is increased from the amount of exposure in other portions that become concave portions.
[0092]
Further, in the pattern forming method of the present invention, the photosensitive resin layer is made of a negative photosensitive resin, and in the exposure step, from the concave portion of the photosensitive resin layer to the convex portion of the photosensitive resin layer. In this method, the exposure amount is increased discontinuously, and the exposure amount at the portion that becomes the edge of the convex portion is increased from the exposure amount at the portion that becomes the center of the convex portion.
[0093]
According to this, the productivity of the two-layer microlens is improved, and the change in the exposure amount at the point where the exposure amount is switched becomes steeper, so that the patterned uneven wall surface can be made substantially vertical. It becomes.
[0094]
Further, in the method for forming a three-dimensional structure according to the present invention, in the exposure step, the difference between the average exposure amount of the portion that becomes the convex portion and the average exposure amount of the portion that becomes the concave portion is determined by calculating a desired projection height. This is a method in which the difference in exposure amount necessary for forming is made equal.
[0095]
Thereby, the uneven | corrugated shape of desired thickness can be obtained by setting exposure amount distribution.
[0096]
The two-layer structure microlens of the present invention is a method obtained by the pattern forming method.
[0097]
As a result, a two-layer microlens having a wall surface substantially perpendicular to the transparent substrate and disposed on the same optical axis can be easily formed.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a drawing showing a method for producing a two-layer microlens using a negative resist by a method according to an embodiment of the present invention, where (a) shows an exposure dose distribution and (b) shows this exposure dose. The pattern obtained by distribution is shown.
FIG. 2 is a schematic diagram showing a schematic configuration of a projection liquid crystal display device including a two-layer microlens according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a two-layer microlens and a liquid crystal display element according to an embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a manufacturing process of the two-layer microlens according to the embodiment of the present invention.
FIG. 5 is a perspective view showing a two-layer microlens according to an embodiment of the present invention.
FIG. 6 is a drawing showing a comparative example of a method of manufacturing a two-layer microlens using a negative resist, where (a) shows an exposure amount distribution and (b) shows a pattern obtained by this exposure amount distribution. ing.
FIGS. 7A and 7B are diagrams showing a method of manufacturing a two-layer microlens using a positive resist by the method according to the embodiment of the present invention, in which FIG. 7A shows the exposure dose distribution and FIG. 7B shows the exposure dose. The pattern obtained by distribution is shown.
FIG. 8 is a drawing showing a pattern of a two-layer microlens according to the present example.
[Explanation of symbols]
1 First microlens array (microlens)
2 Intermediate substrate
3 Photosensitive resin layer (resist layer)
4 Ultraviolet parallel light
5 Second micro lens
5 '2nd microlens type (uneven shape)
7 Transparent substrate
14 Black Matrix
15G, 15R, 15B Dichroic mirror
16 White light source
17 Spherical reflector
18 Liquid crystal display elements
19 Collimating lens
20 Projection lens
21 Projection screen
25 condenser lens
30 Liquid crystal layer
31 pixels
32 substrates
40 Two-layer microlens array
41, 43 Projections
41a The part which becomes the edge of a convex part
41b Center part of the convex part
42, 44 Recessed parts
44a The part which becomes a recessed part adjacent to a convex part
44b Other parts to be recessed
47 Wall

Claims (9)

A microlens formation step of forming a microlens on a transparent substrate;
A photosensitive resin layer forming step of forming a photosensitive resin layer at a focal position of the microlens;
Exposing the photosensitive resin layer through the microlens to cure the photosensitive resin layer into a concavo-convex shape having a wall surface substantially perpendicular to the transparent substrate, and
In the exposure step, a difference between an exposure amount in a portion of the photosensitive resin layer that becomes an edge of the concavo-convex convex portion and an exposure amount in a portion that becomes a concave portion adjacent to the convex portion is determined as a desired concavo-convex height. Larger than the difference in exposure required to form
The photosensitive resin layer is made of a positive photosensitive resin,
In the exposure step, in the photosensitive resin layer, the amount of exposure is increased discontinuously from the concave-convex-shaped convex portion to the concave portion, and further in the concave portion adjacent to the convex portion. A pattern forming method, wherein the exposure amount is increased from the exposure amount of other portions that become concave portions. In the exposure step, the difference between the average exposure amount of the portion that becomes the convex portion and the average exposure amount of the portion that becomes the concave portion is made equal to the difference in exposure amount necessary to form a desired projection height. The pattern forming method according to claim 1 . 3. The pattern forming method according to claim 1, wherein in the photosensitive resin layer forming step, the thickness of the photosensitive resin layer is made equal to the thickness of the thickest portion of the uneven shape . A microlens formation step of forming a microlens on a transparent substrate;
A photosensitive resin layer forming step of forming a photosensitive resin layer at a focal position of the microlens;
Exposing the photosensitive resin layer through the microlens to cure the photosensitive resin layer into a concavo-convex shape having a wall surface substantially perpendicular to the transparent substrate, and
In the exposure step, a difference between an exposure amount in a portion of the photosensitive resin layer that becomes an edge of the concavo-convex convex portion and an exposure amount in a portion that becomes a concave portion adjacent to the convex portion is determined as a desired concavo-convex height. Larger than the difference in exposure required to form
The photosensitive resin layer is made of a negative photosensitive resin,
In the exposure step, in the photosensitive resin layer, the exposure amount is discontinuously increased from the concave-convex concave portion to the convex portion, and the exposure amount at the edge of the convex portion is increased. And a pattern forming method characterized by increasing the exposure amount at the center of the convex portion . In the exposure step, the difference between the average exposure amount of the portion that becomes the convex portion and the average exposure amount of the portion that becomes the concave portion is made equal to the difference in exposure amount necessary to form a desired projection height. The pattern forming method according to claim 4 . 6. The pattern forming method according to claim 4 or 5, wherein, in the photosensitive resin layer forming step, the thickness of the photosensitive resin layer is made equal to the thickness of the thickest portion of the concavo-convex shape . 7. The exposure process according to claim 4, wherein, in the exposure step, an exposure amount at a portion serving as an edge of the convex portion is set to be 1.5 times or more and 4 times or less as large as an exposure amount at a center portion of the convex portion. The pattern formation method of any one of Claims 1 . Furthermore, a substrate forming step of forming an intermediate substrate between the microlens and the photosensitive resin layer,
The pattern forming method according to claim 1, further comprising: a transfer step of transferring the pattern formed by the exposure step to the intermediate substrate by dry etching. A two-layer structure microlens obtained by the pattern forming method according to claim 1.

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