JP3237631B2 - Manufacturing method of micro lens array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a microlens array which is used in combination with a liquid crystal display element and contributes to an improvement in an effective aperture ratio.

[0002]

2. Description of the Related Art At present, a liquid crystal display device is a TFT which can obtain a high contrast and is excellent in high image quality and high definition.
(Thin Film Transistor: Thin Film Transistor) drive system is the mainstream. The liquid crystal display element has a structure in which TFTs for controlling a voltage applied to a pixel are arranged in a matrix corresponding to each pixel, and the TFT and the signal wiring are covered with a metal light shielding film called a black matrix. Since the above-mentioned black matrix is opaque, light incident on this portion is absorbed or reflected and is lost. In particular, when the number of pixels is increased to achieve high definition, it is difficult to reduce the size of the TFT and the signal wiring to a certain limit or less, so that the effective portion through which light passes is relatively small, and the aperture ratio is significantly reduced. In order to solve this problem, a technique is known in which a microlens array is used to converge illumination light to the opening of each pixel of a liquid crystal display element to improve the effective aperture ratio.

FIG. 4 is a view showing a schematic structure of the first embodiment.
The glass substrate 101 has a polarizing plate 102 on the outer surface and TF on the inner surface.
T, signal wiring 103 and transparent electrode 104 are formed. Further, the liquid crystal 10 is placed on the first glass substrate 101.
The second glass substrate 106, which is opposed to the first glass substrate 5, has a color filter 107 on the inner surface and the above-described black matrix 108 made of a light-shielding film for masking the TFT and the signal wiring, and a polarizing plate 109 on the outer surface. Is formed. The second glass plate 106 is provided between the transparent electrodes 10 opened between the black matrices 108.
A spherical concave portion is formed corresponding to the pixel constituted by 4, and a transparent material having a refractive index higher than that of the glass substrate 106 is filled in the concave portion to form the microlens 110 described above.

With respect to the method of manufacturing the microlens array, the following method has been conventionally proposed. FIG. 5 is a sectional view of the manufacturing process. First, FIG.
As shown in (a), an acid-resistant metal such as aluminum or chromium is formed as a protective film 13 on the surface of a transparent substrate 11 such as glass by vapor deposition or sputtering. Next, FIG.
As shown in FIG. 2B, a small circular opening 12 is patterned in the protective film 13 by using a photolithography technique so as to correspond to the pixel arrangement of the liquid crystal display element. Since then
The protective film 13 provided with the openings 12 is called an opening mask. Next, as shown in FIG. 5C, the transparent substrate 11 is wet-etched using a glass etching solution mainly composed of hydrofluoric acid and using the opening mask 13. Since the wet etching proceeds isotropically, the hemispherical concave portion 14 is formed at a position corresponding to the opening 12 by etching for a predetermined time.
Is obtained. Finally, as shown in FIG. 5D, the opening mask 13 is removed, and the concave portions 14 arranged in a matrix for forming the microlenses are completed. Thereafter, a transparent material 15 having a larger refractive index than the transparent substrate 11 is used.
Is filled in the concave portion 14, whereby the portion filled with the transparent material becomes a micro lens functioning as a convex lens.

However, in this conventional manufacturing method,
As shown in a plan view in FIG. 7A, the etching progresses isotropically in the wet etching process in FIG. 5C, and the etching is stopped when the adjacent recesses 14 are in contact with each other. . For this reason, the finally formed microlens array is composed of adjacent microlenses 15.
In between, there is a portion that does not function as a lens indicated by oblique lines. The area ratio of the non-lens portion 16 to the whole is 21.5%, which is a considerably large value. For this reason, when the microlens array having the arrangement structure as shown in FIG. 7A is applied to the liquid crystal display device as shown in FIG. And the so-called aperture ratio is reduced.

In order to solve this problem, FIG.
Japanese Patent Application Laid-Open No. 3-214101 describes a method in which the etching is temporarily stopped before reaching the state (d), the opening mask is completely removed, and the etching is performed again. FIG. 6 is a sectional view showing the steps of this method in order. First, as shown in FIG. 6A, an acid-resistant metal such as chromium is formed on the surface of the glass substrate 11 to form a protective film 13.
Next, the circular openings 12 are patterned in a predetermined microlens array arrangement on the protective film by a known lithography method to form an opening mask 13. Next, FIG.
This is immersed in a glass etching solution which is a mixture of hydrofluoric acid, sulfuric acid and hydrochloric acid as shown in FIG. The opening 1 provided in the opening mask 13 by this process
The glass substrate 11 is isotropically etched starting from the point 2 to obtain a concave portion 14 having a substantially hemispherical shape. This first
Is stopped while leaving a flat boundary portion 17 between the adjacent concave portions 14. Next, as shown in FIG. 6C, the glass substrate 11 is once taken out of the glass etching solution, washed, and then the opening mask 13 is removed by using a metal stripping liquid used as a protective film constituting the opening mask 13. Is completely removed. Then, the second wet etching is performed again using the glass etching solution. By this second wet etching, the etching of the flat boundary portion 17 between the concave portions 14 proceeds isotropically. As a result, as shown in FIG. 6D, the adjacent concave portions 14 are enlarged and come into contact with each other, and the boundary between them is a ridge 1 having a sharp upper end.
It becomes 8. Thereby, as shown in FIG. 7B, the ridges 18 form a polygon (quadrangle) in plan view, the concave portions are densely arranged, and the area ratio of the non-lens portion is 0%.
Is formed. Therefore, when applied to a liquid crystal display element, illumination light can be used without waste.

[0007]

However, in the method of manufacturing a microlens array described in the above-mentioned publication, the process of wet etching of the transparent substrate must be performed at least twice with the step of removing the opening mask interposed therebetween. There is a problem that the process becomes complicated. In particular, it is difficult to increase etching accuracy and reproducibility in wet etching, but by repeating this wet etching twice,
It becomes even more difficult to increase accuracy and reproducibility.
Further, glass is generally used as the transparent substrate. However, in wet etching of glass, a very dangerous chemical including hydrofluoric acid is handled, and therefore, it is desired that this step be reduced and simplified. Further, in order to remove the opening mast, in addition to the etching solution for the transparent substrate, a stripping solution for the metal used as the protective film forming the opening mask must be prepared.

An object of the present invention is to provide a method of manufacturing a microlens array which simplifies a manufacturing process and has excellent reproducibility and productivity.

[0009]

According to a method of manufacturing a microlens array of the present invention, an opening mask made of a protective film having a plurality of openings is formed on a transparent substrate, and the transparent substrate is wet-processed through the opening mask. When etching is performed to form a concave portion having a curved bottom surface, the opening mask
The etching rate of the material of the protective coating is
The wet etching is continued until a protective film of the opening mask existing between two adjacent openings is removed using a material having a speed lower than the etching rate of the bright substrate . For example, said openings are arranged in a matrix, you continue the wet etch to the protective film that exists between the openings along the diagonal direction of the two adjacent openings in a diagonal direction is etched away . Also,
The openings of the opening mask are preferably circular. Thus, in the present invention, a concave portion can be formed in a transparent substrate by one wet etching, and a concave portion can be formed without leaving an opening mask. Therefore, a non-lens portion in a finally formed microlens array Micro lens array with high aperture ratio
It can be formed with a simple manufacturing process and with high precision.

Further, a means for monitoring the peeling of the opening mask is provided, whereby the wet etching is performed while grasping the progress of the etching. further,
The means for monitoring the peeling of the opening mask is an imaging display device,
Alternatively, it is desirable that the apparatus be a device that irradiates the opening mask with light and detects the presence or absence or intensity of reflected light. With these devices, the progress of etching can be accurately monitored,
It is possible to reliably grasp the timing at which the etching is stopped. As a result, improvement in reproducibility and productivity of wet etching can be expected.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the progress of wet etching in one embodiment of the method for manufacturing a microlens array of the present invention. In the figure,
(A1) to (a3) are plan views of respective steps, and (b1) to (b)
3) is a sectional view taken along line AA of each step. First, (a1),
In (b1), a protective coating is formed on the surface of the glass substrate 1 on which the microlens array is formed, and a circular opening 2 having a small diameter is patterned at each center position of the microlens array to be formed. Opening mask 3
And Although not shown, the back and side surfaces of the glass substrate 1 are subjected to a surface treatment such as laminating an etching resistant film. Here, the opening mask 3 is etched by wet etching, which will be described later, and a mask whose etching rate is lower than that of the glass substrate 1 is selected. Here, chromium is used.

Next, the glass substrate 1 is immersed in an etching bath containing a mixed solution mainly composed of hydrofluoric acid to perform wet etching. When the glass substrate 1 is etched through the opening 2 of the opening mask 3, the etching proceeds. You. Since this etching is isotropic, the glass substrate 1 is etched into a spherical shape centering on the opening 2 of the opening mask 3, and the etching gradually forms the concave portion 4. Also, the diameter of the opening 2 is increased with this etching. Then, after a predetermined time, the outer peripheries of the adjacent concave portions 4 come into contact with each other as shown by (a2) and (b2). At this point, as indicated by MP in the drawing, the opening mask 3 remains at a position substantially corresponding to the middle point between the two openings 2 which are positioned diagonally in plan view.

In this state, the etching is continued without stopping the etching. For this reason, the etching proceeds, and the adjacent concave portions 4 are enlarged and come into contact with each other. Then, as shown in (a3) and (b3), the protective film at the MP point of the opening mask 3 is almost completely peeled off at the stage where the concave portions 4 at the diagonal positions come into contact with each other. It is formed. Here, the etching is completed. Whether or not the protective film at the MP point of the opening mask 3 has been almost completely removed can be estimated to some extent by experimentally examining the etching rate of the glass substrate 1 in advance. If the etching is further performed, the bottom surface of the concave portion 4 gradually becomes a gentle curved surface, and at the same time, the peripheral portion of the ridge 5 is also shaved and the concave portion 4 becomes gradually shallow. Therefore, the etching is continued as necessary. Is also good. In addition,
After the etching is completed, the etching resistant film is peeled off, and this peeling step can be easily performed manually.

FIG. 2 is a perspective view showing the shape of the glass substrate at the stage when the above-described wet etching is completed. The boundary of the formed concave portion 4 is a sharp edge 5 at the upper end. Also,
A microlens array in which the ridges 5 are square in plan view and the concave portions are densely arranged is obtained. Therefore, although not shown, the microlens array is completed by filling each formed recess with a transparent material having a higher refractive index than the glass substrate. Therefore, by applying this microlens array to the second glass substrate 106 of the liquid crystal display element shown in FIG. 4, a liquid crystal display element having a high aperture ratio can be formed.

As described above, according to the present invention, it is possible to form a concave portion of a microlens array on a glass substrate by one wet etching. For this reason, the first wet etching, the removal of the opening mask, the second
In the step of wet etching, at least two wet etchings are required, but the number of wet etching steps can be reduced. Further, in the present invention, since the opening mask on the glass substrate can be completely removed simultaneously with the wet etching, there is no need to perform a step of removing the opening mask.
Therefore, a stripper for removing the opening mask is not required.

Here, an example of the wet etching method for the glass substrate will be described with reference to FIG. A glass substrate 1 having an opening mask 3 and an etching mask formed on a glass substrate is immersed in a glass etching solution 21 in an etching bath 20 to perform wet etching. Using a stirrer 22 so that the glass etching solution 21 is uniformly stirred, the side of the opening mask 3 of the glass substrate 1 with the opening mask is turned downward. Then, the camera 23 is arranged above the glass substrate 1 with the opening mask to photograph the progress of the etching, and this image is displayed on the monitor 24. That is, the state of peeling of the protective film forming the opening mask 3 is particularly monitored by the imaging display device including the camera 23 and the monitor 24. In the above-described wet etching method of the present invention, it is necessary to continue wet etching until the protective film at the MP point of the opening mask 3 shown in FIG. 1 is completely peeled off. Thus, the state of peeling of the protective film can be grasped reliably. Note that FIG.
, The camera 23 is disposed above the etching solution 21, but the camera 23 is provided with the glass etching solution 21.
By taking measures such as mounting a cover having resistance to the glass etching solution 21, the glass etching solution 21 can be disposed inside.

Further, instead of the image display device, it is also possible to use a device for irradiating the protective film forming the opening mask 3 with light and detecting the presence or absence or intensity of reflected light. If light is applied to the MP point of the opening mask 3, it is possible to detect the moment when the protective coating at this portion is completely removed. Usually, since the aperture mask is made of metal, it can be determined that reflected light remains if there is reflected light, and that peeling is completed if there is no reflected light. Further, a similar determination can be made based on the difference in intensity.

Although the embodiment has been described using glass as an example of the transparent substrate, it is not particularly limited to glass. Various materials such as general soda glass, non-alkali glass, and quartz glass can be used for the glass. However, the optimum composition of the etching solution differs depending on each case. Further, the shape of the opening mask is not limited to the above-described circular shape, but may be a polygonal opening.

[0019]

As described above, according to the present invention, the opening mass
The etching rate is transparent as the material of the protective coating
Since the material is slower than the etching rate of the substrate, the wet etching of the transparent substrate is continued until all the protective coatings existing between two adjacent openings provided in the opening mask are removed. By performing only one wet etching, it is possible to densely form a plurality of concave portions serving as microlenses. As a result, the number of wet etching steps can be reduced, manufacturing can be simplified, and dangerous processing agents can be reduced. In addition, since the formed microlens array has no non-lens portion, a microlens array having a high aperture ratio can be obtained. Further, by providing means for monitoring the peeling of the opening mask, it is possible to reliably grasp the timing of stopping the etching, and it is possible to improve the reproducibility and productivity of wet etching.

[Brief description of the drawings]

1A and 1B are a plan view and a cross-sectional view illustrating a method of manufacturing a microlens array according to the present invention in the order of steps.

FIG. 2 is a perspective view showing a transparent substrate formed by the method for manufacturing a microlens array according to the present invention.

FIG. 3 is a conceptual configuration diagram of a wet etching apparatus for performing the method of manufacturing a microlens array according to the present invention.

FIG. 4 is a schematic sectional view of a liquid crystal display device to which the microlens array of the present invention is applied.

FIG. 5 is a cross-sectional view illustrating an example of a conventional method for manufacturing a microlens array.

FIG. 6 is a cross-sectional view showing another example of a conventional method for manufacturing a microlens array.

FIG. 7 is a plan view of a microlens array manufactured by the conventional techniques.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Opening 3 Opening mask (protective coating) 4 Concave part 5 Edge 11 Transparent substrate (glass substrate) 12 Opening 13 Opening mask 14 Concave part 15 Micro lens 16 Non-lens part 17 Flat boundary part 20 Etching tank 21 Etching solution 22 Stirrer 23 Camera 24 Monitor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 3/00 C03C 15/00

Claims (6)

(57) [Claims] 1. A step of forming an opening mask made of a protective film having a plurality of openings on a transparent substrate, and a step of performing wet etching of the transparent substrate through the opening mask to form a concave portion having a curved bottom surface. When, in the method of manufacturing a microlens array comprising a step of filling materials having different refractive indices and the transparent substrate in the recess, the opening mass
The etching rate of the material of the
Manufacturing a microlens array using a material slower than an etching rate of a transparent substrate and continuing the wet etching until a protective film of the opening mask existing between two adjacent openings is removed. Method. 2. The openings are arranged in a matrix, and the wet etching is continued until the protective film existing between two diagonally adjacent openings along the diagonal direction is removed by etching. A method for manufacturing the microlens array according to claim 1. 3. The method for producing a microlens array according to claim 1 or 2 opening is circular of the aperture mask. Wherein a means for monitoring the release of the aperture mask, thereby producing a microlens array according to any one of claims 1 to 3 perform the wet etching while grasping the progress of etching. 5. The method of manufacturing a microlens array according to claim 4 , wherein the means for monitoring the separation of the opening mask is an image display device. 6. The method of manufacturing a microlens array according to claim 4 , wherein the means for monitoring the separation of the opening mask is an apparatus for irradiating the opening mask with light and detecting the presence or absence or intensity of the reflected light.