JPH05288904A - Manufacture of optical component - Google Patents

Abstract

PURPOSE:To form a lens pattern (optical component) for improving the numerical aperture of a liquid crystal panel, a CCD area sensor, etc., with good reproducibility and productivity by precisely controlling a lens sectional shape at the time of exposure. CONSTITUTION:When a pattern consisting of many small lens groups is formed on a photosensitive resin film, exposure is carried out twice by using two kind of photomasks 15A and 15B which differ in the area of parts corresponding to the small lenses. A 1st exposure is performed with good resolution by using the 1st photomask 15A which is large in the area of the parts corresponding to the small lenses and a 2nd exposure is performed with low resolution by using the 2nd photomask 15B which is small in the area of the parts corresponding to the small lenses. The photomasks are replaced between the 1st exposure and 2nd exposure. Consequently, the specific lens pattern can be formed without making the lens shape uneven nor forming a flat part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens such as a microlens array used for improving the aperture ratio of a liquid crystal panel or a solid-state image pickup device, or an optical device including a light emitting device array or a light receiving device array provided with this lens. The present invention relates to a method of manufacturing parts.

[0002]

2. Description of the Related Art In recent years, in a light-receiving element array for image input such as a CCD area sensor or a CCD line sensor, high definition has been promoted, and the pixel size has been reduced accordingly. The area is small, which causes a decrease in sensitivity. In order to improve this sensitivity, a method is adopted in which an optical component such as a microlens that selectively collects incident light is installed on each pixel in a light receiving area in the pixel.

Further, in the liquid crystal panel, as a result of the higher definition, the area ratio (aperture ratio) of the light transmitting portion is decreased in contrast to the increase in the area occupied by the wiring which is the light non-transmitting portion. In order to solve this problem, it is possible to install an optical component such as a microlens on each pixel to focus the illumination light on the light receiving area in the pixel. Proposed.

Incidentally, conventionally known types of optical components such as microlenses include those having a convex lens shape having a relief pattern on the surface and those having a Fresnel lens shape. These are made of resin or inorganic material. It is known that it can be formed using a material. Also known are those having a flat surface with a refractive index distribution formed in a resin or an inorganic material, and those having both a surface shape and a refractive index distribution.

Among various conventional optical components such as the above-mentioned microlenses, those having a convex lens shape made of resin are formed by forming a columnar pattern on the surface by photolithography and then heating and flowing. Then, a method of forming a pattern of a spherical optical component by surface tension is adopted, and a method of forming a convex lens shape with an inorganic material is a spherical optical component by applying a technique such as etching and polishing. The method of forming the pattern is adopted.

For forming a Fresnel lens shape with a resin or an inorganic material, a method of forming a pattern of an optical component by using a photoresist and drawing with an electron beam or a laser beam is adopted. ..

Further, those having a flat surface and forming a refractive index distribution include a method in which a glass substrate is provided with an appropriate mask and then ion exchange or ion implantation is performed, or a monomer having a different refractive index in a resin is used. The method of polymerizing after distributing is adopted.

[0008]

However, among the above-mentioned conventional methods for manufacturing an optical component, the method of forming a convex lens pattern with photoresist or the like and then heating and flowing it is difficult to control the pattern shape. However, there is a problem that the reproducibility is poor, and a flat portion is likely to remain at the boundary between the lenses, and the condensing characteristic is deteriorated accordingly. Furthermore, if an attempt is made to form a lens having a large radius of curvature and a long focal length by this method, only a small step can be formed compared to the pattern area, so even if an attempt is made to obtain a spherical pattern by using surface tension. Since a wide flat area is formed in the apex area of the lens, there is also a problem that sufficient condensing characteristics cannot be obtained.

Further, in the method of forming the convex lens pattern with the inorganic material, it is difficult to control the pattern shape and the productivity is poor as in the above case. Further, the method of drawing the Fresnel lens shape also lacks in productivity because the drawing time is long. Furthermore, the method of forming a refractive index distribution by applying a mask on an inorganic material such as glass requires a long time for ion exchange or ion implantation, and thus has poor productivity and forms a refractive index distribution in the resin. The method also had a problem that the condition control was difficult and the reproducibility was poor.

The present invention has been made in view of the above circumstances, and manufactures an optical component capable of accurately controlling the lens shape to form a lens pattern having excellent light-collecting characteristics with high productivity and reproducibility. It is intended to provide the law.

[0011]

In order to achieve the above object, an optical component manufacturing method according to the present invention is a method for manufacturing an optical component comprising a lens group in which a large number of small lenses are arranged at a predetermined pitch. , When exposing the pattern of the optical component on the photosensitive resin film through the photomask, use two types of photomasks in which the arrangement pitches of the portions corresponding to the small lenses are the same and the areas of the portions are different. When performing the first exposure using the first photomask having the larger area corresponding to the lens, the second photomask having the smaller area corresponding to the small lens is used for the first exposure. When the second exposure is performed, the exposure is performed with poor resolution, and the exposure is performed twice in the first, second order or the second, first order.

Here, exposure with good resolution means that the light intensity at the position corresponding to the light shielding portion of the photomask is sufficient with respect to the light intensity at the position corresponding to the opening of the photomask on the photosensitive resin film. It means decreasing, for example,
The intensity ratio is preferably less than 0.1. Also, exposure with poor resolution means that the light intensity at the position corresponding to the light shielding portion of the photomask is relatively high with respect to the light intensity at the position corresponding to the opening, and for example, the ratio of the light intensity. Is preferably 0.1 or more.

In the above method, as the second exposure method with poor resolution, the distance between the photomask and the photosensitive resin film is made larger than that in the first exposure, and the distance between the photomask and the light source is increased. Installing a light diffuser, or
Any of using a projection type exposure apparatus to shift the focus position from the photosensitive resin film for exposure may be adopted.

[0014]

According to the method of manufacturing an optical component according to the present invention, when the lens pattern of the optical component is exposed on the photosensitive resin film through the photomask, two kinds of areas corresponding to the small lenses have different areas. By using the photomask of No. 2 and performing the exposure twice with different resolutions, it is possible to form a lens pattern with good light-collecting efficiency with high productivity by controlling precisely without making the pattern shape distorted. ..

When the distance between the photomask and the photosensitive resin film is made larger than that at the time of the first exposure, due to the diffraction phenomenon of light, a portion corresponding to the opening portion and the light shielding portion of the photomask on the photosensitive resin film. The ratio of the above-mentioned ray intensities becomes small, that is, the pattern image is blurred, and the resolution is lowered. Further, if a light diffusing plate is installed between the photomask and the light source, the parallelism of light is lowered and the resolution is also lowered.
Further, by using a projection type exposure apparatus, by shifting the focus position from the photosensitive resin film and exposing,
The resolution is reduced.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. Example 1 FIG. 1 is a sectional view showing a method for manufacturing a liquid crystal panel having a microlens array (optical part) as an example of an optical part according to the present invention, and FIG. 2 (a) is used when manufacturing it. 2B is a plan view of the first photomask shown in FIG.
Plan views of the photomasks, and FIGS. 3 and 4 are views showing the manner of exposure using the photomasks.

The first photomask 15 used in this embodiment.
The specifications of A and the second photomask 15B are shown in FIG.
This is as shown in (a) and (b). These two types of photomasks 15A and 15B are small lenses 4a (FIG. 1).
Corresponding to the pixel pitch of the liquid crystal panel, the vertical pitch pv is 200 μm, and the horizontal pitch ph is 150 μm. Pitch pv,
A portion corresponding to the small lens 4a is formed as a light-shielding portion in a planar lattice shape with ph. Two types of photomask 15
A and 15B have different areas corresponding to the small lenses, and in the first photomask 15A, a rectangular light-shielding portion 13a having a long side (L1) 180 μm and a short side (S1) 135 μm is formed. An opening portion (transparent portion) 14a is formed between each light shielding portion 13a. In the second photomask 15B, the long side (L2) is 80 μm and the short side (S
2) A 60 μm rectangular light-shielding portion 13b is formed, and an opening 14b is formed between these light-shielding portions 13b.

Then, as shown in FIG. 3, the glass substrate 1
A commercially available positive photoresist 19 having a thickness of 15 μm is formed as a photosensitive resin film on the photoresist 8.
The first photomask 15A described above is placed on the substrate 9 through the mask aligner, and the first (first) exposure is performed. The first photomask 1 at the time of this first exposure
The distance (print gap) g between 5A and the surface of the photoresist 19 is 10 μm, and the exposure amount is 50 mJ / cm 2.
Set to ² to expose with good resolution. By this first exposure, as shown in FIG. 5A, in the cross-sectional shape in the short side direction, the portion 16a corresponding to the opening 14a of the first photomask 15A is exposed, and the portion corresponding to the light shielding portion 13a. Remains as a flat unexposed portion 17a.

Then, as shown in FIG. 4, a second photomask 15B is placed via a mask aligner on the photoresist 19 which has been subjected to the first exposure, and the second photomask 15B is formed.
The second (second) exposure is performed. The distance (print gap) g between the second photomask 15B and the surface of the photoresist 19 at the time of the second exposure is expanded to 1000 μm, and the exposure amount is set to 25 mJ / cm ² to perform exposure with poor resolution. By this second exposure, as shown in FIG.
As shown in (b), in the cross-sectional shape in the short side direction, a portion 16b wider than the first exposure corresponding to the opening 14b of the second photomask 15B is exposed, and the light shielding portion 13b is exposed.
In the vicinity of the top of the first unexposed portion 17a corresponding to, the unexposed portion 17b remains. Here, FIG. 5A shows the state after exposure, and FIG. 5B shows the state after exposure and development.

After the first and second exposures as described above, by developing with an alkaline aqueous solution, a step (t) is 13 μm and a large number of spherical small lenses 4a are arranged at the same pitch. A microlens array pattern 4 including lens groups is formed.

By irradiating the entire surface of the glass substrate 18 of FIG. 4 having the microlens array pattern 4 formed as described above with ultraviolet rays, coloring of the photoresist 19 is eliminated. Then, on the lower side of the glass substrate 18 with the microlens array pattern 4, as shown in FIG. 1, the upper transparent insulating substrate 5, the common electrode 6, the black matrix 7, the liquid crystal 8, the TFT 9 and the transparent pixel electrode 10,
The lower transparent insulating substrate 11 and the lower polarizing plate 12 are laminated to produce a liquid crystal panel body 20, and the glass substrate 18
A predetermined liquid crystal panel 21 is assembled and manufactured by stacking and arranging the upper polarizing plate 2 and the illumination light source 1 on the upper side. In the liquid crystal panel 21 manufactured as described above, the brightness of the transparent light when the illumination light is emitted from the back surface of the microlens array pattern 4 is
Compared to the one without microlens array pattern,
It was improved by 1.50 times.

Next, the liquid crystal panel 2 according to the first embodiment described above.
The result of comparing the brightness of the liquid crystal panel of Example 1 with the liquid crystal panels of Comparative Examples 1 to 3 will be described below. From the explanation, it will be understood that the display brightness of the liquid crystal panel 21 shown in the first embodiment is improved.

Comparative Example 1 Using only the first photomask 15A of FIG. 2 shown in Example 1, with a print gap of 10 μm and 50 mJ /
The exposure amount is set to cm ² , exposure is performed only once, and development is performed in the same manner as in Example 1. The microlens array pattern thus formed has a step (t) of 14 μm.
As shown in FIG. 6, the cross-sectional shape in the short side direction was a shape in which a flat portion was formed on the top of the small lens 4a, and a desired spherical shape could not be obtained. This was assembled into a liquid crystal panel in the same manner as in Example 1, and the brightness of the transmitted light when the illumination light was irradiated from the back surface thereof was measured. As a result, it was 1.15 times higher than that without the microlens array pattern. Met.

Comparative Example 2 Second photomask 15B shown in FIG. 2 (b) shown in Example 1
Using only the above, the print gap is set to 1000 μm, the exposure amount is set to 75 mJ / cm ² , the exposure is performed only once, and the development is performed in the same manner as in Example 1. The microlens array pattern formed by this has a step (t) of 12 μm, and the cross-sectional shape in the short side direction is such that the valley portion of the boundary between the adjacent small lenses 4a is wide, as shown in FIG. As shown in Example 1, when the same was assembled into a liquid crystal panel and the brightness of the transmitted light when the illumination light was irradiated from the back surface was measured, it was found to be 1 compared with that without the microlens array pattern. It was 20 times.

Comparative Example 3 First photomask 15A shown in FIG. 2A shown in Example 1
Print gap of 100 μm and 40 m
Set the exposure amount to J / cm ² and perform the first exposure,
Then, the second photomask 15 shown in FIG.
Using B, the print gap 1
The second exposure is performed by setting the exposure amount to 00 μm and 40 mJ / cm ² , that is, the exposure is performed at the same resolution as the first exposure, and the development is performed in the same manner as in Example 1. The microlens array pattern formed by this has a step (t) of 13 μm, and the cross-sectional shape in the short side direction is a shape in which the small lens 4a portion is slightly distorted as shown in FIG. Was assembled into a liquid crystal panel in the same manner as in Example 1 and the brightness of the transmitted light when the illumination light was emitted from the back surface thereof was measured. As a result, it was 1.10 times higher than that without the microlens array pattern. there were.

Example 2 In this example, a microlens array pattern for improving the aperture ratio of a liquid crystal panel was prepared in the same manner as in Example 1 above. The first photomask 25A and the second photomask 25B used in this embodiment are respectively shown in FIG.
It shows in (b). These photomasks 25A and 25B are
The size specifications are the same as those of the two types of photomasks 15A and 15B used in the first embodiment, and the black and white inverted ones, that is, the portions corresponding to the small lenses are the openings 14a and 1a.
4b is used for the photomask.

On the glass substrate 18, a copolymer of methyl methacrylate and 2-butenyl methacrylate and m
A special photosensitive resin film made of a mixture of benzoylbenzophenone (see JP-A-3-15070) with a thickness of 5
It is formed to 0 μm. The first photomask 25A is placed on the resin film via a mask aligner, and the first exposure is performed. The distance (print gap) g between the first photomask 25A and the surface of the resin film during this first exposure is 10 μm, and the exposure amount is 10,000 mJ.
/ Cm ² and expose with good resolution.

Subsequently, the second photomask 25B is placed on the resin film after the first exposure is completed via a mask aligner, and the second exposure is performed. The distance (print gap) g between the second photomask 25B and the surface of the resin film at the time of the second exposure is 100 μm.
And setting a quartz frosted glass (not shown) between the second photomask 25B and the light source.
Exposure is performed with poor resolution at an exposure dose of 000 mJ / cm ² . After the second exposure, vacuum heating is performed to remove unreacted m-benzoylbenzophenone. As a result, as shown in FIG. 10, in the cross-sectional shape in the short side direction, a microlens array pattern 4 is formed which is a lens group in which a step (t) is 12 μm and a large number of small lenses 4a are arranged at the same pitch. Was done.

The microlens array pattern 4 formed as described above is arranged on the light incident surface side of the liquid crystal panel in the same manner as in the first embodiment, and the liquid crystal panel 21 as shown in FIG. 1 is assembled and manufactured. .. The brightness of the transparent light when the liquid crystal panel 21 is illuminated with the illumination light from the back surface is 1.55 as compared with that without the microlens array pattern.
It was doubled.

Embodiment 3 FIG. 11 is a sectional view of a CCD area sensor with a microlens array obtained by a manufacturing method according to another embodiment of the present invention, and FIGS. 12 and 13 are first and second views for manufacturing the same. It is a figure which shows the mode of exposure by a 2nd photomask.

First photomask 15 used in this embodiment
A and the second photomask 15B are those shown in FIG. 2, and their specifications are as follows. These photomasks 15A and 15B include the small lens 4a (see FIG.
The arrangement pitch of the small lens patterns corresponding to 1) is the same and corresponds to the pixel pitch of the CCD, the vertical pitch pv is 15 μm, and the horizontal pitch ph is 12 μm.
The small lenses 4a are arranged in a plane lattice with the arrangement pitches pv and ph.
Is formed as a light-shielding portion. The two types of photomasks 15A and 15B are different in the area of the portion corresponding to the small lens 4a. In the first photomask 15A, a rectangular light-shielding portion 13a having a long side of 13 μm and a short side of 10 μm is formed. An opening 14a is formed between each of the light shielding portions 13a, and a rectangular light shielding portion 13b having a long side of 6 μm and a short side of 4 μm is formed in the second photomask 15B, and between the respective light shielding portions 13b. An opening 14b is formed in the.

Then, a commercially available positive photoresist 19 having a thickness of 5 μm is formed as a photosensitive resin film on the glass substrate 18 of FIG. 12, and the first photomask 15A is arranged so as to face the photoresist 19. As shown in FIG. 12, the trapezoidal mirror 23, the concave mirror 24, and the convex mirror 25
The first exposure is performed using the mirror projection exposure apparatus 26 (projection type exposure apparatus) including the above. The focus f at this time is adjusted to the photoresist surface,
By setting the exposure amount to 0 mJ / cm ² , exposure with good resolution was performed.

Subsequently, as shown in FIG. 13, the second photomask 15B is arranged, and the focus f of the mirror projection exposure device 26 is shifted by 10 μm from the photoresist surface, and the exposure amount of 10 mJ / cm ² is set to 2. The second exposure was performed with poor resolution.

After the first and second exposures as described above, by developing with an alkaline aqueous solution, as shown in FIG. 14, a large number of spherical small lenses 4a having a step (t) of 4 μm are formed. The microlens array pattern 4 including the lens groups arranged at the same pitch was formed.

By irradiating the surface of the microlens array pattern 4 thus formed with ultraviolet rays, coloring of the photoresist 19 is eliminated. Then, as shown in FIG. 11, the microlens array pattern 4 is formed on the substrate 27 such as a silicon wafer by using the small lenses 4a and C.
By aligning and assembling each pixel light receiving portion 29 and non-light receiving portion 30 of the CD area sensor 28,
The CCD area sensor 28 with the microlens array pattern 4 is manufactured. Due to the presence of the microlens array pattern 4, the CCD area sensor 28 thus obtained was 1.50 times more sensitive than a sensor without it.

As a method of exposing with low resolution in the second exposure, as shown in FIG. 15, a light diffusion plate 32 may be installed between the photomasks 15A and 15B and the light source 31.

In each of the above embodiments, a commercially available positive photoresist or a special negative photoresist was used, but the material used is not particularly limited as long as it can form an optical pattern. Further, although the first photomask and the second photomask have been described with the pattern in which the rectangular opening portions or the light shielding portions are combined, the shape of the patterns is not limited to the rectangular shape, and may be, for example, an elliptical shape, a hexagonal shape, or a hexagonal shape.
The shape of the pattern may be different between the first photomask and the second photomask, as long as the shape is set in consideration of the use such as a prism and the pixel arrangement.

In the third embodiment, the mirror projection exposure apparatus is used as the projection type exposure apparatus, but another projection type exposure apparatus such as a stepper may be used. Further, although the method of manufacturing the CCD area sensor has been described in the third embodiment, it may be applied to the manufacturing of the line sensor.

Further, in the above-mentioned Examples 1 and 2,
Although the glass substrate on which the microlens array pattern is formed is pressed onto the liquid crystal panel, the microlens array pattern may be directly formed on the liquid crystal panel.
After forming a microlens array pattern on a glass substrate on which only transparent electrodes and black matrix are formed,
The liquid crystal panel may be assembled. Further, the microlens array pattern may be formed on the polarizing plate provided on the incident side of the liquid crystal panel.

Further, in each of the above embodiments, the microlens array pattern formed by the development process may be subjected to heat treatment to make the lens shape smoother. In each of the above embodiments, an optical pattern is formed. Although the microlens array was used as it is for improving the aperture ratio, it is also possible to make a duplicate of the microlens array and then use this duplicate.

Furthermore, in the above-mentioned embodiment, the description has been made on the case of being applied to the manufacturing method of the liquid crystal panel and the CCD area sensor, but the present invention is a light emitting element array for optical communication,
It can be applied to the formation of a microlens array pattern for various optical elements such as an optical fiber array and a light receiving element array.

[0042]

As described above, according to the present invention, by using two types of photomasks having different areas of the portions corresponding to the lenses, the exposure is performed twice with different resolutions, so that the lens shape is changed. It is possible to precisely control the cross-sectional shape without causing distorting or leaving a flat portion. Therefore, it is possible to manufacture an optical component having a lens pattern with good light collection efficiency with good reproducibility and high productivity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method of manufacturing a liquid crystal panel with a microlens array, which is an example of a method of manufacturing an optical component according to the present invention.

FIG. 2A is a plan view showing a first photomask used in the same manufacturing method, and FIG. 2B is a plan view showing a second photomask.

FIG. 3 is a diagram showing a state during a first exposure.

FIG. 4 is a diagram showing a state during a second exposure.

5A is a diagram showing a state of a main part after the first exposure, and FIG. 5B is a diagram showing a state of a main part after the second exposure / development.

FIG. 6 is a diagram showing a state of a main part after exposure and development in Comparative Example 1.

FIG. 7 is a diagram showing a state of a main part after exposure and development in Comparative Example 2.

FIG. 8 is a diagram showing a state of a main part after exposure and development in Comparative Example 3.

FIG. 9 is a plan view showing another example of the first and second photomasks.

FIG. 10 is a diagram showing a state of a main part after the second exposure and development in the manufacturing process of the liquid crystal panel with the microlens array according to another embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a method of manufacturing a CCD area sensor with a microlens array, which is another example of the method of manufacturing an optical component according to the present invention.

FIG. 12 is a diagram showing a state at the time of the first exposure in the same manufacturing method.

FIG. 13 is a diagram showing a state at the time of second exposure in the same manufacturing method.

FIG. 14 is a diagram showing a state of a main part after the second exposure and development.

FIG. 15 is a diagram showing a second exposure state according to still another embodiment of the present invention.

[Explanation of symbols]

4a ... small lens, 4 ... microlens array pattern (optical component), 15A, 25A ... first photomask, 1
5B, 25B ... Second photomask, 19 ... Photoresist (photosensitive resin film), 26 ... Mirror projection exposure apparatus (projection type exposure apparatus), 31 ... Light source, 32 ... Light diffusion plate.

Claims (4)

[Claims] 1. A method of manufacturing an optical component comprising a lens group in which a large number of small lenses are arranged at a predetermined pitch,
When exposing a pattern of an optical component on a photosensitive resin film through a photomask, two types of photomasks having the same arrangement pitch of parts corresponding to the small lenses and different areas of the parts are used. When the first exposure is performed using the first photomask having the larger area corresponding to the area, the second photomask having the smaller area corresponding to the small lens is used. A method of manufacturing an optical component, characterized in that when the second exposure is carried out, the exposure is performed with poor resolution, and either one of the first and second exposures is carried out first and both are carried out. 2. The method according to claim 1, wherein during the second exposure,
A method of manufacturing an optical component, which comprises exposing the photomask to a photosensitive resin film at a larger distance than that in the first exposure as a method of exposing with a poor resolution. 3. The method according to claim 1, wherein during the second exposure,
A method of manufacturing an optical component, which comprises placing a light diffusion plate between a photomask and a light source as a method of exposing with poor resolution. 4. The method according to claim 1, wherein during the second exposure,
As a method of exposing with poor resolution, a projection type exposure apparatus is used as the exposure apparatus, and the exposure is performed by shifting the focus position from the photosensitive resin film.