JP2001194507A - Optical substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the stack thickness of a microlens array substrate (the optical distance from the surface of the microlens array substrate to the lens edges). SOLUTION: A microlens array pattern 56 is formed on the surface of a lens resin layer 52 formed on base glass 51, a sealing resin layer 58 is laminated on the lens resin layer 52, the surface of the layer 58 is made flat and cover glass 59 is put on the flat surface to form a microlens array substrate 61. In this method, a mark 57 for measurement is formed on the surface of the lens resin layer 52 in the region except the region of the microlens array pattern 56 at the same height as a plane of the pattern 56 including lens edges.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical substrate including an optical element array such as a microlens array and a microprism array, and more particularly to an optical substrate on which a mark for recognition is formed by a stamper method.

[0002]

2. Description of the Related Art A microlens array substrate in which a microlens array pattern is built in advance has conventionally been used as one substrate for forming a liquid crystal display element with a liquid crystal interposed therebetween.

Various methods for manufacturing such a microlens array substrate have been proposed, such as a method using etching and a method using a stamper. Among these methods, a method using a stamper involves forming a microlens array pattern on a lens resin layer by embossing an ultraviolet-curable resin with the stamper, and overlaying a sealing resin layer having a different refractive index from that of the lens resin layer thereon. This method is advantageous in that it is excellent in mass productivity and can manufacture an aspherical lens.

FIG. 1A is a cross-sectional view showing a conventional microlens array substrate, in which a transparent lens resin layer 2 made of an ultraviolet curable resin is laminated on a transparent base glass 1, and a lens resin layer is formed. The microlens array pattern 3 is formed on the surface of 2 by stamping with a stamper. Further, a transparent sealing resin layer 4 is laminated on the lens resin layer 2 by an ultraviolet ray effect type resin having a different refractive index from the lens resin layer 2, and a cover glass 5 is formed on the sealing resin layer 4.
Are laminated and integrated, and the microlens array substrate 8 is manufactured.

The microlens array substrate 8 is used as a substrate of a liquid crystal display element, and requires flatness of the surface.
As shown in (1), both the front and back surfaces are smoothed by the polishing device 6. In particular, the cover glass 5 is polished so that the stack thickness of the microlens array substrate 8 becomes a predetermined value. Next, a transparent electrode (ITO) 7 is formed on the upper surface of the cover glass 5 as shown in FIG.

Here, as shown in FIG. 2, the main lens surface of the microlens array substrate 8 (normally, the lens resin layer 2
The optical distance from the edge of the cover glass 5 to the surface of the cover glass 5 (including the transparent electrode 7) is called a stack thickness Ts, and is one of the quantities that characterize the optical characteristics of the microlens array substrate 8. When the stack thickness Ts is determined by measuring the thickness of the cross section of the microlens array substrate 8, the refractive index of the cover glass 5 and the sealing resin layer 4 must be taken into consideration. In this case, since the refractive index has already been affected, an actually measured value can be used.

Now, consider a case where the microlens array substrate 8 is used as a substrate of a liquid crystal display element, and liquid crystal is sealed between the microlens array substrate 8 and an opposing glass substrate provided with pixel openings. As shown in FIG. 2, when parallel light enters the microlens array substrate 8, the light passing through each microlens converges at each focal point and passes through the pixel opening of the opposite glass substrate. The distance from the main surface to the focal point (focal length fo) is, in principle, the microlens array substrate 8
Is substantially constant irrespective of the stack thickness Ts. But,
Stack thickness Ts of microlens array substrate 8 during polishing
When the stack thickness Ts is equal to the optimum value as shown in FIG. 3, the lens efficiency of the liquid crystal display element (ie, the lens efficiency (fo-Ts) from the surface of the microlens array substrate 8 to the focal point varies. (Brightness when the microlens array substrate 8 is present / brightness when the microlens array substrate 8 is not present) is maximized, but when the stack thickness Ts deviates from the optimum value, the lens efficiency is greatly reduced.

Therefore, in the polishing step of FIG. 1B, the microlens array substrate 8 is polished by setting conditions such as a polishing rate and a polishing time so as to obtain a desired stack thickness Ts. Further, after the polishing is completed, the stack thickness Ts of the microlens array substrate 8 is measured, and if the target stack thickness Ts is not achieved, the polishing is performed again to finally obtain the target stack thickness Ts. Make sure you have Therefore, accurate measurement of the stack thickness Ts is indispensable to accurately obtain the desired stack thickness Ts.

FIG. 4 is a view for explaining a conventional method for measuring the stack thickness Ts. In this method, first, the focal point of the length measuring microscope 9 is focused on the cover glass 5 by irradiating, for example, coaxial incident light from the upper surface of the microlens array substrate 8.
Reset the length measurement counter according to the surface of. Next, the illumination is switched to, for example, transmitted light, and the focal point of the length measuring microscope 9 is shifted to the edge of the microlens array pattern 3 (hereinafter, referred to as the edge).
(Referred to as a lens edge), the movement amount of the focal position at that time is read from a length measurement counter to obtain the stack thickness Ts. Strictly speaking, the stack thickness Ts is the distance from the surface of the cover glass 5 to the principal point of the lens.
Since the distance from the lens edge to the principal point is unique to the microlens array substrate 8 and it is difficult to detect the principal point, the stack thickness measurement is performed by substituting the lens edge located near the principal point position. Is going. Also,
The thickness of the transparent electrode 7 to be applied after polishing is as thin as about 0.2 mm and its thickness is stable. Therefore, the thickness of the transparent electrode 7 may be ignored, and the thickness of the transparent electrode 7 may be treated as a constant. Is also good.

[0010]

However, the lens edge 10 of the microlens array pattern 3 formed on the surface of the lens resin layer 2 has a substantially quadrangular pyramid-like point (point) as shown in FIG. Therefore, in the conventional stack thickness measurement method, for the reasons described below in detail,
It has been difficult to accurately detect the lens edge 10.

FIG. 6A shows the relationship between the lens edge 10 and the focal position of the length-measuring microscope, and FIG. 6B shows a microscope image at an LA position 1-2 μm above the lens edge 10. FIG. 6C shows L passing through the lens edge 10.
FIG. 6D shows a microscope image at the LC position below the lens edge 10 by 1 to 2 μm. When the focal point is located below the lens edge 10, as shown in FIG.
The microscopic image of 0 glows white like a girder (the other part looks dark), but as the focal point approaches the lens edge 10, the end of the girder becomes gradually less clear, and whether the end of this girder exists or not A delicate focal position is the lens edge 10. Therefore, as shown in FIGS. 6C and 6D, it is difficult to determine whether the focal point of the length-measuring microscope coincides with the lens edge 10 or slightly deviates. Actually, the distance is shifted by 1 to 2 μm. Further, even when the focus is shifted above the lens edge as shown in FIG. 6B, the image of the lens edge slightly remains, and is seen as a white point.

As described above, in the conventional measuring method, even when the focal position of the length measuring microscope changes in the thickness direction of the microlens array substrate due to the sharpness of the lens edge, the microscope image does not easily change (the focal position is 1). The change in the microscope image of the lens edge is slight when the change is 2 μm), and the measurement accuracy was poor.

[0013] Furthermore, the precision of the stack thickness can be reduced due to the fact that the appearance of the lens edge changes due to the difference in brightness of the length measuring microscope, and that the image of the lens edge shines due to the wraparound of transmitted light and the outline becomes blurred. The measurement was difficult.

FIGS. 8A and 8C show cross sections of microlens array patterns 3 having different lens shapes (namely, lens size, curvature, depth, etc.) from each other.
FIG. 8B shows the microlens array pattern 3 shown in FIG.
8 shows a microscope image when focusing on the LD surface of FIG.
FIG. 8D shows the microlens array pattern 3 shown in FIG.
3 shows a microscope image when focusing on the LE surface of FIG. Although the microscope images of FIGS. 8B and 8D look almost the same, as shown in FIGS. 8A and 8C, the distances of the focal positions from the lens edges 10 are different from each other by δ. I have. This indicates that if the type (lens shape) of the microlens array substrate 8 is different, the appearance of the microscope image of the lens edge 10 is greatly different. It is necessary to memorize the difference in the appearance of the lens edge for each type, and it takes a long time for the skill of stack thickness measurement.

[0015]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide an optical substrate without being affected by differences in the appearance of a microscope image between varieties and differences in image brightness due to differences in microscopes. The purpose of the present invention is to make it possible to accurately measure the stack thickness.

In the optical substrate according to the present invention, an optical element array layer having an optical pattern is formed above the first base material,
In an optical substrate, a sealing resin layer for flattening at least an upper region of the optical pattern is laminated above the optical element array layer, and a second base material is laminated above the sealing resin layer. A planar mark recognizable from the surface of the second base material is provided in a plane including an edge of the second base material and outside the optical pattern formation region. Here, the optical pattern may be a lens array or a prism array.

In the optical substrate of the present invention, the edge of the optical pattern can be also focused by focusing an optical device such as a length measuring microscope on the mark. In addition, since this mark is formed on the surface, it is easier to detect whether or not the optical pattern is in focus as compared with a case where the edge of the optical pattern is focused, and the detection accuracy of the optical pattern can be increased. it can.
Therefore, according to the present invention, the stack thickness of the optical substrate can be accurately detected.

According to the optical substrate of the present invention, a mark at the same height as the edge is detected instead of directly measuring the edge of the optical pattern. The same appearance can be obtained, so that skill is not required for the measurement, and the dispersion of the measurement is reduced.

In the optical substrate according to one embodiment of the present invention, the mark may be formed by a convex or concave plane provided on the surface of the optical element array layer.

In the optical substrate according to another embodiment of the present invention, the mark is constituted by a convex or concave plane provided on the surface of the optical element array layer, and a corner is formed at an edge of the mark. It may be done. Here, that the corner is formed means that the edge of the mark is not rounded. When the edge of the mark formed by the convex or concave plane is rounded, the boundary of the mark becomes unclear, but as in this embodiment, the corner of the mark is formed by forming a corner at the edge of the mark. Can be clearly distinguished, and the recognizability of the mark can be further improved.

According to still another embodiment of the present invention, the mark is constituted by a convex or concave flat surface provided on the surface of the optical element array layer, and is provided adjacent to the mark. The concave portion or the convex portion is formed by a curved surface. As in this embodiment, if the concave portion or convex portion adjacent to the mark is formed by a curved surface,
The mark can be clarified, and the recognizability of the mark can be further improved.

According to still another embodiment of the present invention, since the marks are formed in a grid or a stripe, the marks can be easily found and the measurement of the stack thickness of the optical substrate can be facilitated. be able to.

In another optical substrate of the present invention, an optical element array layer having an optical pattern is formed above a first base material, and at least an area above the optical pattern is formed above the optical element array layer. Laminate a sealing resin layer to flatten the
In the optical substrate in which the second base material is laminated above the sealing resin layer, in the plane including the main point of the optical pattern, and outside the optical pattern formation region, from the surface of the second base material A recognizable mark is provided.

According to another optical substrate of the present invention, the main point of the optical pattern can be easily focused by focusing an optical device such as a length measuring microscope on the mark. The detection accuracy of the principal point can be increased. Therefore, according to the present invention, the stack thickness of the optical substrate can be accurately detected.

Further, according to the optical substrate of the present invention, the mark at the same height as the principal point is detected instead of directly measuring the principal point of the optical pattern. The images can be made to have the same appearance, the skill does not need to be measured, and the dispersion of the measurements is reduced.

Although the components of the present invention have been described individually here, the components described above of the present invention can be combined as arbitrarily as possible.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a manufacturing process of a microlens array substrate according to an embodiment of the present invention will be described with reference to FIGS.
(D), FIGS. 10 (e) to (g), FIGS. 11, 12 and 13. In manufacturing the microlens array substrate, as shown in FIG. 9A, an uncured ultraviolet curable resin 52 is dropped on a transparent base glass 51 having a size corresponding to a plurality of microlens array substrates. Then, the stamper (mold) 53 is lowered from above the base glass 51 to sandwich an ultraviolet curable resin (hereinafter, referred to as a lens resin layer) 52 between the stamper 53 and the base glass 51, and presses the stamper 53 against the base glass 51. Then, the lens resin layer 52 is spread between the stamper 53 and the base glass 51. On the lower surface of the stamper 53, an inversion mold 54 of a microlens array pattern and an inversion mold 55 of a stack thickness measurement mark are formed. Next, as shown in FIG. 9B, the lens resin layer 52 is irradiated with ultraviolet rays through the base glass 1 to cure the lens resin layer 52. When the stamper 53 is peeled off, a micro lens array pattern 56 is formed on the upper surface of the cured lens resin layer 53 as shown in FIG.
The measurement mark 57 is formed on the surface of No. 2.

Further, as shown in FIG. 9D, an uncured UV-curable resin 58 having a different refractive index from that of the lens resin layer 52 is dropped onto the lens resin layer 52, The cover glass 59 is lowered from above, and an uncured ultraviolet-curable resin (hereinafter, referred to as a sealing resin layer) 58 is provided between the lower lens resin layer 52 and the cover glass 59.
The cover glass 59 is pressed against the sealing resin layer 58 to spread the sealing resin layer 58 between the lower lens resin layer 52 and the cover glass 59. Next, FIG.
As shown in the figure, the base glass 51 and the lens resin layer 52
The sealing resin layer 58 is irradiated with ultraviolet rays through the through-hole to cure the sealing resin layer 58. As a result, a microlens array wafer (hereinafter, referred to as an MLA wafer) 60 including a plurality of microlens array substrates 61 as shown in FIG.
Is manufactured, and a microlens array pattern 56 is formed at the interface between the lens resin layer 52 and the sealing resin layer 58 having different refractive indexes.

The stack thickness measuring mark 57 is shown in FIG.
As shown in FIG. 13 and outside the region of the microlens array pattern 56, it is formed on the upper surface of the convex portion 65 and is in the same plane (same height) as the plane 64 including the lens edge 63 of the microlens array pattern 56. It is located in. The measurement mark 57 is formed of a flat or rough plane so that it can be clearly seen with a length measuring microscope.
Reference numeral 7 denotes a structure in which a plurality of stripes are arranged. Further, the edge of the convex portion 65 on which the measurement mark 57 is provided has an angle of approximately 90 degrees in cross section without being rounded, and the concave portion 66 between the convex portions 65 is formed by a curved groove having an arc-shaped cross section. In addition, the boundary of the measurement mark 57 is clearly seen by the length measuring microscope. Note that the measurement mark 57 may be formed by a grid-like plane provided on the upper surface of the projection 65 as shown in FIG.

When the MLA wafer 60 is manufactured, the stack thickness is measured using a length-measuring microscope, while FIG.
As described above, the lower surface of the base glass 51 and the upper surface of the cover glass 59 are polished by the polishing device 67 to make the surface smooth and adjust the stack thickness of the microlens array substrate 61 to a desired optimum value.

When measuring the stack thickness, instead of directly measuring the lens edge, for example, the surface of the MLA wafer is focused on the surface of the MLA wafer by coaxial incident light, and the focus of the length measuring microscope is focused on the measurement mark by transmitted light. Then, the stack thickness is measured from the distance between the focal positions. At this time, since the measurement mark has a stripe-shaped plane (or a lattice-shaped plane), the focus of the length-measuring microscope can be easily adjusted, and the edge has an angle of approximately 90 degrees, and the concave portion has a curved surface. In this case, the measurement mark can be clearly recognized, and the focus can be accurately focused on the measurement mark, and the stack thickness can be accurately measured. Further, since the focus is not directly focused on the lens edge but on the measurement mark 57 provided at the same height as the lens edge, even if the shape of the microlens array pattern is different, skill is not required. Thus, the stack thickness can be easily measured.

Thereafter, as shown in FIG. 10 (g), a transparent electrode (ITO) was formed on the upper surface of the cover glass 58 by vapor deposition.
A film 68 is formed. Next, as shown in FIG. 11, after positioning the MLA wafer 60 by the alignment mark, the MLA wafer 60 is cut to obtain individual microlens array substrates 61.

Next, a method of manufacturing the stamper 53 will be described with reference to FIG.
4 will be described. First, a flat glass plate 71 as shown in FIG. 14A is prepared, and the surface of the glass plate 71 is irradiated with laser light focused by the imaging lens 72 as shown in FIG. The glass plate 71 is evaporated and removed by processing (laser lithography) into a shape shown by a two-dot chain line, and a desired uneven pattern 7 is formed on the surface of the glass plate 71.
3, 74 are formed [FIG. 14 (b)]. Here, the concavo-convex pattern 73 has the same shape as the microlens array pattern 56, and the concavo-convex pattern 74 corresponds to the convex portion 65 and the concave portion 66 for forming a measurement mark. When forming these concavo-convex patterns 73 and 74, first, a concavo-convex pattern 73 corresponding to the microlens array pattern 56 is formed on the surface of the glass substrate 71.
At this time, in a region other than the concave / convex pattern 73, a reference plane (plane) is formed so as to have the same height as the edge of the concave / convex pattern 73. Then, a convex portion 65 for forming a measurement mark by processing a concave portion on this reference surface.
When the concave / convex pattern 74 corresponding to the concave / convex portion 66 is formed, the upper surface of the convex portion of the concave / convex pattern 74 (the plane corresponding to the measurement mark) is formed at the same height as the edge of the concave / convex pattern 73. Note that the laser processing is performed using a laser processing apparatus controlled by a computer, and even if it is a precise and complicated shape, it can be easily processed by inputting its shape data. .

As described above, after forming the concave / convex patterns 73 and 74 on the surface of the glass substrate 71 to produce a master made of the glass substrate 71, nickel is deposited thereon, and the inverted master is formed by nickel electroforming. A first nickel master 75 is manufactured as shown in FIG.
5 is peeled from the glass plate 71 (FIG. 14D). When preparing the nickel master 75 by the nickel electroforming method, the glass plate 71 serving as the master is made conductive by, for example, a vapor deposition method or an electroless plating method, and the surface of the glass plate 71 that has been made conductive is prepared as a cathode. For example, electroplating in a nickel sulfamate bath to form a nickel master 75
Is prepared. The nickel master 75 has a glass plate 7
The uneven pattern 7 corresponding to the uneven patterns 73 and 74 of FIG.
6, 77 are formed.

The first nickel master 75 is further duplicated by nickel electroforming to form a second nickel master 78 (FIG. 14E). This second nickel master 7
8 shows the uneven pattern 7 of the first nickel master 75.
Concavo-convex patterns 79, 80 are formed corresponding to 6, 77, respectively.

The second nickel master 78 is further duplicated by a nickel electroforming method to form a stamper 53. When duplicating the second nickel master 78,
After an oxide film is formed on the surface of the nickel master 78 using, for example, a potassium dichromate solution, the stamper 53 is again manufactured by nickel electroforming [FIG. 14 (f)]. Thus, the micro lens array pattern 5 corresponding to the concave and convex patterns 79 and 80 of the second nickel master 78 is provided on the stamper 53.
6 and an inversion mold 55 of a stack thickness measurement mark 57 are formed. Therefore, also in the stamper 53 thus manufactured, the edge (valley edge) of the inversion mold 54 and the concave plane of the inversion mold 55 are formed at the same height.

As another method of manufacturing the stamper 53, as shown in FIGS. 16A to 16F, a master 81 is manufactured by laser processing a resist 81 applied to the surface of a glass substrate 71. May be. Resist 81
When is used, as a bonding agent between the glass substrate 71 and the resist 81, for example, a silane coupling agent is applied to the surface of the glass substrate 71, and after laser processing, through exposure, development and cleaning steps, Desired concave and convex patterns 73 and 74 are formed on the surface of the glass substrate 71 by the resist 81 [FIGS. 16A and 16B]. Laser processing is
This is performed in the same manner as in FIG.
Is formed. Subsequent processing is performed in the same manner as in FIG. 14C and thereafter [FIGS. 16C to 16F].

[0038]

According to the optical substrate of the present invention, the stack thickness can be accurately measured. Further, the stack thickness can be measured at the same interval irrespective of the type of the optical substrate, and the stack thickness can be stably measured without skill.

[Brief description of the drawings]

1A is a cross-sectional view showing a microlens array substrate before polishing, FIG. 1B is a cross-sectional view showing a polishing process of the microlens array substrate, and FIG. 1C is a microlens array substrate on which a transparent electrode is formed. FIG.

FIG. 2 is a diagram for explaining a focal length and a stack thickness of a microlens array substrate.

FIG. 3 is a diagram showing a relationship between stack thickness of a microlens array substrate and lens efficiency.

FIG. 4 is a diagram for explaining a method of measuring a stack thickness of a microlens array substrate.

FIG. 5 is a perspective view showing the shape of a microlens array pattern.

6A is a diagram showing a relationship between a lens edge and a focal position, FIG. 6B is a diagram showing an image of the lens edge when focusing on the LA position in FIG. 6A, and FIG. FIG. 7A is a diagram showing an image of a lens edge when focusing on the LB position of FIG.
(D) is a diagram showing an image of a lens edge when focusing on the LC position of (a).

FIG. 7 is a diagram illustrating a change in an image of a lens edge.

8A is a diagram showing a relatively shallow microlens array pattern, FIG. 8B is a diagram showing an image of a lens edge when focusing on an LD position in FIG. 8A, and FIG. FIG. 4D is a diagram showing a deep microlens array pattern, and FIG. 4D is a diagram showing an image of a lens edge when focusing on the LE position in FIG.

FIGS. 9A to 9D are cross-sectional views illustrating steps of manufacturing a microlens array substrate (MLA wafer) according to an embodiment of the present invention.

10 (e) to (g) are continuation diagrams of FIG. 9;

FIG. 11 is a plan view of an MLA wafer manufactured in the above manufacturing process.

FIG. 12 is a diagram showing a relationship between a microlens array pattern and a measurement mark.

FIG. 13 is a partially broken perspective view of a measurement mark.

FIGS. 14A to 14F are cross-sectional views showing steps of manufacturing a stamper.

FIG. 15 is a diagram illustrating a laser processing step of a glass plate.

16 (a) to (f) are cross-sectional views showing another stamper manufacturing process.

FIG. 17 is a partially broken perspective view of a different measurement mark.

[Explanation of symbols]

Reference Signs List 51 base glass 52 lens resin layer 56 macro lens array pattern 57 measurement mark 58 sealing resin layer 59 cover glass 63 lens edge of micro lens array pattern

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomohiko Matsushita Omron Co., Ltd. 10 Hanazono Todocho, Ukyo-ku, Kyoto-shi, Kyoto

Claims (6)

[Claims] An optical element array layer having an optical pattern is formed above a first base material, and a sealing resin layer for flattening at least a region above the optical pattern is formed above the optical element array layer. In the optical substrate in which the second base material is laminated and the second base material is laminated above the sealing resin layer, in the plane including the edge of the optical pattern, and outside the optical pattern formation region, the second base material An optical substrate having a planar mark recognizable from a surface. 2. The mark according to claim 1, wherein the mark is formed by a convex or concave plane provided on a surface of the optical element array layer, and a corner is formed at an edge of the mark. An optical substrate according to item 1. 3. The mark is constituted by a convex or concave flat surface provided on the surface of the optical element array layer, and the concave or convex portion provided adjacent to the mark is constituted by a curved surface. The optical substrate according to claim 1, wherein: 4. The optical substrate according to claim 1, wherein the marks are formed in a lattice. 5. The optical substrate according to claim 1, wherein the mark is formed in a stripe shape. 6. An optical element array layer having an optical pattern is formed above a first base material, and a sealing resin layer for flattening at least an area above the optical pattern is formed above the optical element array layer. In the optical substrate in which the second base material is laminated and the second base material is laminated above the sealing resin layer, the second base material is provided in a plane including a main point of the optical pattern and outside the optical pattern formation region. An optical substrate provided with a mark recognizable from the surface of the optical substrate.