JP2005215417A - Microlens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microlens array, which can obtain proper contrast for images, which has a high light beam transmittance, and which can obtain high gain value and a high visual field angle. <P>SOLUTION: In the microlens array 10, in which a large number of convex, protruding microlenses 12 brought into close contact with one side are arranged two-dimensionally, in which the other side opposite to the side is made planar, in which light-transmitting parts 13a are formed on the other side, with the center on the optical axes K of respective microlenses 12, and in which light shield parts 14 are each formed between the neighboring light transmission parts 13a, the ratio of the total aperture areas of a large number of light-transmitting parts 13a to the total area of the microlens array 10 is set at ≥15% and ≤30%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a microlens array in which a large number of microlenses protruding in a convex shape are closely arranged on a two-dimensional surface.

  A microlens array in which a large number of microlenses projecting in a convex shape are closely arranged on a two-dimensional surface is applied to a liquid crystal display, an optical coupling optical element, an image input device, and the like.

  For example, a liquid crystal display uses a liquid crystal cell in which optical shutters are arranged to change light transmittance and reflectance by applying an electric field to a display unit by utilizing the optical anisotropy, orientation, fluidity, etc. of liquid crystal molecules. This liquid crystal display includes a direct-view display that directly observes the image displayed on the liquid crystal cell and a projection display that projects the display image on the screen from the front or the back. .

  The direct-view display described above has a problem that the display quality changes depending on the viewing direction, and the brightness is the brightest when viewed from the normal direction of the display surface, but the angle (viewing angle) between the normal direction and the viewing direction is the same. There is a problem that the brightness decreases as the value increases, and observation is not possible beyond a certain angle. That is, there is a problem that the viewing angle that allows good observation is narrow.

  Therefore, as a method of expanding the viewing angle by combining a liquid crystal display and a microlens array, there is a method using a microlens array in which a large number of microlenses are closely arranged on a two-dimensional surface on the observation surface of a liquid crystal cell. Proposed.

  Further, among the above-described projection displays, a rear projection display (rear pro display) for projecting from the back to the screen has also been proposed in which a viewing angle is enlarged using a microlens array on the screen.

As this type of microlens array, there is an array in which a large number of microlenses are arranged in a close-packed state (for example, see Patent Document 1).
JP 2001-305315 A (page 4-7, FIG. 6).

  9A to 9C are a front view, a perspective view, and a bottom view showing a conventional microlens array.

  The conventional microlens array 100 shown in FIGS. 9A to 9C is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2001-305315) described above. Briefly described.

  That is, as shown in FIGS. 9A to 9C, a conventional microlens array 100 includes a light-transmitting lens substrate 101 using a transparent resin substrate, a transparent resin sheet, or a transparent glass substrate. On the flat upper surface 101a, a plurality of microlenses 102 projecting in a substantially hemispherical shape are closely arranged two-dimensionally, and a lower surface 101b opposite to the upper surface 101a is formed flat, and this lower surface 101b is formed on the lower surface 101b. Each light incident portion (or each light emitting portion) 103 is opened so as to coincide with the optical axis K of each microlens 102, and other than each light incident portion (or each light emitting portion) 103 is covered with each light shielding portion 104. At the same time, a diffuse reflection film (or antireflection film) 105 is formed on each light shielding portion 104.

  At this time, in order to arrange a large number of microlenses 102 at the highest density on the upper surface 101a of the lens substrate 101, when viewed from the lower surface 101b side of the lens substrate 101, the large number of microlenses 102 are shown in FIG. As shown in FIG.

  9C is a gap between the microlenses 102 when the bottom surfaces of the microlenses 102 are completely circular and arranged in a close-packed state, and the bottom area of the microlenses 102 is shown. And the area of the lens substrate 101, that is, the ratio of the incident area of the light beam to the lens substrate 101 is 90.7%.

  FIG. 9C shows a case where the bottom surface of the microlens 102 is a perfect circle and is arranged in a close-packed state. Instead, the microlens 102 is omitted from the illustration. When the bottom surface of the lens is hexagonal and arranged in a hexagonal close-packed shape (honeycomb shape), it is possible to make the incident area ratio of light to the lens substrate 101 close to 100% at maximum.

  And when the conventional microlens array 100 by the said structure is applied to a liquid crystal display device, a rear projector apparatus, etc., it is disclosed that an image with high contrast can be displayed over a wide viewing angle.

  By the way, when the conventional microlens array 100 shown in FIGS. 9A to 9C is applied to a liquid crystal display device, a rear projector device, etc., the viewing angle to the image can be enlarged, but the image The contrast is important to make it easier to see even in bright places. By providing the light shielding portion 104 between the adjacent microlenses 102 on the lower surface 101b of the lens substrate 101, the external light reflectance is reduced and the black screen is tightened. However, a good contrast may not be obtained depending on the ratio of the total aperture area of many light incident portions (or light emitting portions) 103 to the entire area of the microlens array 100. In other words, the area of the light incident portion (or the light emitting portion) 103 and the area of the light shielding portion 104 are in a trade-off relationship with each other, and the light transmittance is influenced by the relationship between the two. Is not disclosed or even suggested in the above cited reference 1.

  Therefore, there is a demand for a microlens array capable of obtaining a good contrast with respect to an image, having a high light transmittance, a high gain value, and a high viewing angle.

The present invention has been made in view of the above problems, and the first invention is that a plurality of microlenses projecting in a convex shape are closely arranged on one surface in a two-dimensional manner, The other surface opposite to the surface is formed flat, each light transmitting portion is formed on the other surface with the optical axis of each microlens as the center, and each light shielding portion is between the adjacent light transmitting portions. In the microlens array in which the part is formed,
The microlens array is characterized in that the ratio of the total aperture area of a number of the light transmitting portions to the total area of the microlens array is set to 15% or more and 30% or less.

The second invention is a microlens array in which a plurality of microlenses protruding in a convex shape are arranged two-dimensionally.
The optical axis is aligned with the bottom surface side of the first microlens two-dimensionally arranged on the first lens substrate and the bottom surface side of the second microlens two-dimensionally arrayed on the second lens substrate. And each light transmitting portion is formed between the first lens substrate and the second lens substrate with the optical axis of each microlens as the center, and between each adjacent light transmitting portion. A microlens array having a light shielding portion formed thereon.

The third invention is the microlens array of the second invention described above,
In the microlens array, focal lengths of the plurality of first microlenses are set to be positioned in the plurality of second microlenses.

  According to the microlens array of the first aspect, in particular, a plurality of microlenses protruding in a convex shape are closely arranged two-dimensionally on one surface, and the other one on the opposite side of the one surface is arranged. In a microlens array in which each light transmitting portion is formed on the surface with the optical axis of each microlens as the center and each light shielding portion is formed between adjacent light transmitting portions, a large number of the entire area of the microlens array Since the ratio of the total aperture area of the light transmitting portion is set to 15% or more and 30% or less, a good contrast can be obtained for the image, the light transmittance is high, and a high gain value and a high viewing angle are obtained. .

  According to the microlens array of claims 2 and 3, in particular, two on the bottom surface side of the first microlens arranged two-dimensionally on the first lens substrate and on the second lens substrate. The bottom surfaces of the second microlenses arranged in a number of dimensions are opposed to each other with the optical axis aligned, and each of the microlenses is centered on the optical axis of each microlens between the first lens substrate and the second lens substrate. Since the light transmission part is formed and each light shielding part is formed between the adjacent light transmission parts, when the microlens array is used for a screen of a rear projection display (rear pro display), for example, the first microlens The light rays incident on the first lens substrate, the light transmission portion formed between the first lens substrate and the second lens substrate, and the second lens substrate in order are imaged in the second microlens, In addition, since the light is scattered and emitted from the surface of the second microlens 25, the viewing angle is wide in both the X-axis direction (horizontal direction) and the Y-axis direction (vertical direction), and the light transmittance is high while having a high contrast ratio. A high gain value is obtained.

  Hereinafter, an embodiment of a microlens array according to the present invention will be described in detail in the order of Embodiment 1 and Embodiment 2 with reference to FIGS.

1A to 1C are a front view, a perspective view, and a bottom view for explaining a microlens array according to a first embodiment of the present invention.
FIGS. 2A to 2D are process diagrams schematically shown for explaining the manufacturing process of the microlens array of Example 1 according to the present invention.
FIGS. 3A to 3C show the optical characteristics for the aperture diameter φd (μm) of the light transmission part in the three types of microlens arrays having a large number of microlenses having diameters φD = 80 μm, 100 μm, and 150 μm in the first embodiment. Figure showing the characteristics in a list,
FIG. 4 is a graph showing the aperture diameter and optical characteristics of the light transmitting portion in the three types of microlens arrays having a large number of microlenses having diameters φD = 80 μm, 100 μm, and 150 μm in Example 1.
FIG. 5 is a diagram showing a list of aperture ratios and black ratios when the aperture diameter of the light transmission part is φd (μm) with respect to the diameter φD (μm) of the microlens in Example 1.
FIG. 6 is a graph showing the aperture diameter φd (μm) of the light transmission part and the black ratio with respect to the diameter φD (μm) of the microlens in Example 1.

  As shown in FIGS. 1A to 1C, the microlens array 10 according to the first embodiment of the present invention has light transmittance using a transparent resin substrate, a transparent resin sheet, or a transparent glass substrate. A plurality of microlenses 12 protruding in a convex shape using a transparent resin material, glass material, or the like having optical transparency are closely arranged in a two-dimensional manner on a flat upper surface 11a of the lens substrate 11 having the same. The lower surface 11b opposite to the upper surface 11a of the lens substrate 11 is formed flat, and each light transmitting portion 13a is centered on the optical axis K of each microlens 12 using the light transmitting resin material 13 on the lower surface 11b. Each light shielding part (each light absorbing part) 14 is formed by a black light shielding material (light absorbing material) between the adjacent light transmitting parts 13a.

  The many microlenses 12 projecting in a convex shape are formed in a shape such as a substantially hemispherical spherical surface, a substantially hemispherical aspherical surface, or an elliptical convex surface.

  At this time, when the shape of the large number of microlenses 12 is formed in a substantially hemispherical shape with a radius R, for example, in order to arrange the large number of microlenses 12 on the upper surface 11a of the lens substrate 11 with the highest density, the lens substrate When viewed from the side of the lower surface 11b of FIG. 11, a large number of microlenses 12 are arranged in a close-packed state as shown in FIG.

  1C is a gap between the microlenses 12 when the bottom surface of the microlens 12 is a perfect circle and is arranged in a close-packed state. Is in the same state as the light shielding portion (light absorbing portion) 14 made of the black light shielding material (light absorbing material) described above. In this state, the ratio of the bottom area of the microlens 12 and the area of the lens substrate 11, that is, the ratio of the incident area of light rays to the lens substrate 11 is 90.7%.

  FIG. 1C shows a case where the bottom surface of the microlens 12 is a perfect circle and is arranged in a close-packed state. Instead, the microlens 12 is omitted from the illustration. When the bottom surface of the lens is hexagonal and arranged in a hexagonal close-packed shape (honeycomb shape), it is possible to make the incident area ratio of light rays to the lens substrate 11 close to 100% at maximum.

  Here, for example, when a large number of microlenses 12 formed in a substantially hemispherical shape with a radius R are arranged in a close-packed state on a two-dimensional plane composed of the X axis and the Y axis, the pitch Px in the X axis direction is 2R. Further, the pitch Py in the Y-axis direction is 2Rsin 60 ° because the microlenses 12 are arranged along the X-axis direction between the adjacent microlenses 12 in the X-axis direction.

  The light transmitting portion 13a formed on the lower surface 11b of the lens substrate 11 is formed by using a light transmitting resin material 13 having light transmitting properties as described in the manufacturing process described later, or alternatively, the lens substrate 11 By exposing the lower surface 11 b (or the lower surface of the microlens 12) itself, the light incident on the microlens 12 passes through the lens substrate 11 and is emitted from the light transmitting portion 13 a formed on the lower surface 11 b of the lens substrate 11. Can do.

  On the other hand, the light shielding portion (light absorbing portion) 14 made of a black light shielding material (light absorbing material) formed on the lower surface 11b of the lens substrate 11 is required to have at least a light shielding property with respect to visible light, and is incident on the microlens 12. Can block light.

  In Example 1, when a large number of microlenses 12 are formed in a substantially hemispherical shape with a radius R, for example, the diameter φD of the bottom surface of each microlens 12 is 2R. When the opening diameter φd of each light transmission portion 13a facing each other and formed around the optical axis K of each microlens 12 is set as φD> φd, the parallel light L incident from above each microlens 12 is converted into each light. When exiting from the transmission part 13a, the opening diameter φd of each light transmission part 13a is set in the direction in which the angle θ at which the light beam changes its path is increased by the microlens 12 with respect to the traveling direction of one parallel light L. Thus, the viewing angle can be enlarged.

  Therefore, the first embodiment is characterized in that the ratio of the total opening area of the large number of light transmission portions 13a to the entire area of the microlens array 10 is set to 15% or more and 30% or less. Will be discussed later.

Further, for example, the focal length f of the microlens 12 formed in a substantially hemispherical shape with a radius R is the distance from the apex of the microlens 12 to the intersection where one parallel light L intersects on the optical axis K of the microlens 12. . Here, when the microlens 12 is used in the atmosphere, the refractive index n of air is 1. On the other hand, the refractive index n ′ of the microlens 12 is approximately 1 when a transparent resin material or a glass material is used. Therefore, the focal length f of the microlens 12 is approximately 3R from the following equation.
f = n′R / (n′−n) = 1.5R / (1.5−1) = 3R
Accordingly, by appropriately setting the thicknesses of the lens substrate 11 and the light transmissive resin material 13 and setting the distance from the apex of the microlens 12 to the light transmissive portion 13a of the light transmissive resin material 13 to approximately 3R, The light beam input to the microlens 12 can be imaged on a portion of the light transmitting portion 13a of the light transmitting resin material 13 and emitted from the light transmitting portion 13a.

  Here, the manufacturing method of the microlens array 10 of Example 1 is demonstrated in order of a process using Fig.2 (a)-(d).

  First, as shown in FIG. 2A, for example, φD = 80 μm (R) as a molding die (not shown) in which a large number of concave portions formed in a substantially hemispherical shape with a diameter φD (radius R) are formed so as to be closely packed. = 40 μm), φD = 100 μm (R = 50 μm) molding die, and φD = 150 μm (R = 75 μm) molding die are prepared in advance, and the viscosity in each molding die Filled with a UV curable resin having a good light transmittance of 180 mPa · s, and thereafter, the flat upper surface 11a of the lens substrate 11 made of a PC (polycarbonate) film having a thickness of 50 μm is superimposed on each molding die, A large number of substantially hemispherical microlenses 12 having a diameter φD (radius R) were formed on the upper surface 11a of the lens substrate 11 in a close-packed state, and a large number of microlenses 12 were cured by irradiation with ultraviolet rays. Thereafter, each lens substrate 11 was peeled off from each molding die, and a large number of three types of microlenses 12 (diameter φ80 μm, φ100 μm, φ150 μmμ) were two-dimensionally manufactured on the upper surface 11 a of each lens substrate 11. At this time, the lower surface 11b opposite to the upper surface 11a of the lens substrate 11 is also formed flat.

  Next, as shown in FIG. 2B, an ultraviolet curable resin material 13 having a viscosity of 160 mPa · s and a good light transmittance is applied to the lower surface of each lens substrate 11, and parallel ultraviolet rays are applied from the microlens 12 side. , Only the part of the ultraviolet curable resin material 13 where the parallel light L of the ultraviolet rays forms an image with the microlens 12 is cured to become a cured part 13a, and the area between adjacent cured parts 13a is not cured. Part 13b.

  Next, as shown in FIG. 2C, the uncured portion 13b is cleaned by washing out of the cured portion 13a and the uncured portion 13b formed of the ultraviolet curable resin material 13 on the lower surface 11b of each lens substrate 11. Only the portion is removed, and the hardened portion 13a that is not removed remains as the light transmitting portion.

  Next, as shown in FIG. 2D, a black light shielding material (light absorbing material) is applied between the adjacent light transmitting portions 13a in a state where the light transmitting portions 13a are formed on the lower surface 11b of each lens substrate 11. Then, a light shielding portion (light absorbing portion) 14 is formed between the adjacent light transmitting portions 13a, and three types of microlens arrays 10 having a large number of each of three types of microlenses 12 (diameter φ80 μm, φ100 μm, φ150 μmμ). Was completed.

  Thereafter, the surface side of the light transmitting portion 13a and the light shielding portion (light absorbing portion) 14 formed on the lower surface 11b of each lens substrate 11 with respect to the micro lens array 10 of three types (diameter φ80 μm, φ100 μm, φ150 μmμ). For example, the opening diameter φd of the bottom surface of the light transmitting portion 13a is varied by polishing with an abrasive such as # 3000 white alumina.

  Then, the opening diameter φd of the light transmitting portion 13a is measured with an optical microscope, the ratio of the total opening area of the many light transmitting portions 13a to the total area of the microlens array 10 is calculated, and the relationship with the optical characteristics is calculated. Examined.

That is, the aperture ratio (%) of the light transmitting portion 13a is
Opening ratio (%) of light transmitting portion = total opening area of many light transmitting portions 13a / microlens
The total area of the array 10 is shown. Further, the black ratio (%) is indicated by a value obtained by subtracting the aperture ratio (%) of the light transmission portion 13a from 100 (%).

  The optical characteristics were measured by measuring a peak gain value G0 and a viewing angle α ° (an angle at which the peak gain becomes a half value) using a goniophotometer GP-200 manufactured by Murakami Color Research Laboratory. However, the gain value is a relative value when the complete diffusion plate is 1.0, and the peak gain value is a gain value when the viewing angle is 0 °.

  The above results are collectively shown in FIGS. 3 (a) to 3 (c) and FIG. Since the viewing angle α ° is a substantially hemispherical microlens 12, the X-axis direction (horizontal direction) and the Y-axis direction (vertical direction) were substantially the same, although not explicitly described.

  As apparent from FIG. 4, the aperture ratio (%) of the light transmitting portion 13a formed on the lower surface 11b of the lens substrate 11 is 15% or more, and the optical characteristics (peak gain value G0, viewing angle α °) are almost saturated. It turns out that it becomes a favorable value. This means that the aperture ratio (%) of the light transmitting portion 13a needs to be 15% or more in order to transmit light almost completely. The reason for such a result is considered to be that a deviation of the optical axis K of each microlens 12 slightly occurs between the microlens 12 side and the light transmitting portion 13a side because the lens substrate 11 is in a sheet shape. Another reason may be that the shape of the light transmission portion 13a as in theory is not formed due to variations in the resin curing speed, resin sag, and the like.

  Furthermore, the peak gain value G0 and the viewing angle α °, which are the most important optical characteristics, are good when the aperture ratio (%) of the light transmission portion 13a is 15% or more. By increasing the shading occupation area ratio (black ratio) as much as possible, a tight screen can be obtained. Therefore, as shown in FIGS. 5 and 6, judging from the aperture ratio and black ratio when the aperture diameter of the light transmitting portion 13a is φd (μm) with respect to the diameter φD (μm) of the microlens 12, Usually, it is considered good if the black ratio is 70% or more, and up to 30% of the remaining area is an allowable range of the aperture ratio (%) of the light transmitting portion 13a.

  Therefore, by setting the ratio of the total aperture area of the large number of light transmitting portions 13a to the total area of the microlens array 10 from 15% to 30%, good contrast can be obtained for the image, and It is possible to provide the microlens array 10 having a high light transmittance and a high gain value and a high viewing angle.

7A to 7C are a front view, a perspective view, and a bottom view for explaining the microlens array of the second embodiment according to the present invention.
FIGS. 8A to 8D are process diagrams schematically shown for explaining the manufacturing process of the microlens array according to the second embodiment of the present invention.

  As shown in FIGS. 7A to 7C, the microlens array 20 according to the second embodiment of the present invention has light transmittance using a transparent resin substrate, a transparent resin sheet, or a transparent glass substrate. A plurality of first microlenses 22 projecting in a convex shape using a transparent resin material, glass material, or the like having optical transparency are closely arranged on a flat upper surface 21a of the first lens substrate 21 having a two-dimensional array. In addition, a lower surface 21b opposite to the upper surface 21a of the second lens substrate 21 is formed flat, and each light transmitting portion 23a is centered on the optical axis K of each first microlens 22 on the lower surface 21b. The black light-shielding dry film 23 in which each light-shielding part (each light-absorbing part) 23b is formed is bonded between the adjacent light-transmitting parts 23a. In Example 2, the black light-shielding dry film 23 was used to form the light transmission part 23a by the through hole and the light light-shielding part (each light absorption part) 23b by the black film. Each light transmitting portion 23a is formed by using a light transmitting resin material in the same manner as in the first embodiment, and a black light shielding material (light absorbing material) is applied between the adjacent light transmitting portions 23a and adjacent to each other. It is also possible to form a light shielding part (light absorbing part) 23b between the light transmitting parts 23a.

  Further, on the back surface of the black light-shielding dry film 23, a number of second microlenses 25 formed on the second lens substrate 24 are aligned with the optical axes of the number of first microlenses 22 formed on the first lens substrate 21. The plurality of second microlenses 25 are formed to be smaller than the plurality of first microlenses 22.

  The plurality of first microlenses 22 and the plurality of second microlenses 25 that protrude in the above-described convex shape have the same kind of shape such as a substantially hemispherical spherical surface, a substantially hemispherical aspherical surface, or an elliptical convex surface. It is formed in the shape of.

  At this time, the shape of the large number of first microlenses 22 is formed in a substantially hemispherical shape with a diameter φD (radius R), for example, and the shape of the large number of second microlenses 25 is the diameter φD ( In order to arrange a large number of first microlenses 22 on the upper surface 21a of the first lens substrate 21 at the highest density when each of them is formed in a substantially hemispherical shape with a diameter φd (radius r) smaller than the radius R), When viewed from the lower surface 21b side of the lens substrate 21, a large number of first microlenses 22 are arranged in a close-packed state as shown in FIG. 7C.

  7C is a gap between the first microlenses 22 when the bottom surfaces of the first microlenses 22 are completely circular and arranged in a close-packed state. The painted portion is in the same state as the light shielding portion (light absorbing portion) 23b described above. In this state, the ratio between the bottom area of the first microlens 22 and the area of the first lens substrate 21, that is, the incident area ratio of the light beam to the first lens substrate 21 is 90.7%.

  FIG. 7C shows a case where the bottom surface of the first microlens 22 is completely circular and is arranged in a close-packed state, but instead of this, the illustration is omitted. When the bottom surface of one microlens 22 is hexagonal and arranged in a hexagonal close-packed shape (honeycomb shape), it is possible to make the incident area ratio of light rays to the first lens substrate 21 close to 100% at maximum.

  Here, for example, when a large number of first microlenses 22 formed in a substantially hemispherical shape with a radius R are arranged in a close-packed state on a two-dimensional plane by the X axis and the Y axis, the pitch Px in the X axis direction Is 2R, and the pitch Py in the Y-axis direction is 2Rsin 60 ° because the first microlenses 22 are arranged along the X-axis direction between the adjacent first microlenses 22 in the X-axis direction.

  Further, for example, when the parallel light L is incident from the first microlens 22 formed in a substantially hemispherical shape with a diameter φD (radius R), the parallel light L is incident on the first lens substrate 21 and the light transmitting portion of the black light shielding dry film 23. For example, an image is formed in the second microlens 25 formed in a substantially hemispherical shape with a diameter φd (radius r) through the second lens substrate 24. At this time, as described in the first embodiment, for example, the focal length f of the first microlens 22 formed in a substantially hemispherical shape with a diameter φD (radius R) is approximately 3R. When setting the focal length f to be positioned in the second microlens 25, the thicknesses of the first lens substrate 21, the black light-shielding dry film 23, and the second lens substrate 24 are set as appropriate, and the first microlens is set. By setting the distance from the apex of 22 to the inside of the second microlens 25 to be approximately 3R, the light beam input to the first microlens 22 can be imaged in the second microlens 25, thereby Scattered light can be efficiently emitted from the two microlenses 25.

  When the microlens array 20 configured as described above is used for a screen of a rear projection display (rear pro display), for example, the light L incident on the first microlens 22 is the first lens substrate 21 and the first lens substrate 21. And the second lens substrate 24 are sequentially passed through the light transmitting portion 23a and the second lens substrate 24 to form an image in the second microlens 25, and further scattered from the surface of the second microlens 25. As described later, the viewing angle is wide in both the X-axis direction (horizontal direction) and the Y-axis direction (vertical direction), and the light transmittance is high and a high gain value is obtained while maintaining a high contrast ratio.

  Here, the manufacturing method of the microlens array 20 of Example 2 is demonstrated in order of a process using Fig.8 (a)-(d).

  First, as shown in FIG. 8A, for example, φD = 150 μm (R) as a molding die (not shown) in which a large number of concave portions formed in a substantially hemispherical shape with a diameter φD (radius R) are formed so as to be closely packed. = 75 μm) is prepared in advance, and the mold is filled with an ultraviolet curable resin having a viscosity of 180 mPa · s and good light transmittance, and then a PC (polycarbonate) film having a thickness of 75 μm, etc. The first upper surface 21a of the first lens substrate 21 is superimposed on a molding die, and the first microlens 22 having a diameter φD = 150 μm (R = 75 μm) and a substantially hemispherical shape is formed on the upper surface 21a of the first lens substrate 21. For example, the pitch Px in the X-axis direction is set to 150 μm, a large number are formed in a close-packed state, and a large number of first microlenses 22 are cured by irradiation with ultraviolet rays.

  Next, as shown in FIG. 8 (b), using a black light-shielding dry film 23 having a thickness of 20 μm and having a light-shielding property (light absorption property), the carbon dioxide laser processing machine {manufactured by Takeuchi Corp.} The direction pitch Px is set to 150 μm and a through hole having a diameter of 50 μm is formed to form each light transmitting portion 23a, and each light shielding portion (each light absorbing portion) 23b is formed between the adjacent light transmitting portions 23a. .

  Next, as shown in FIG. 8C, as a molding die (not shown) in which a large number of concave portions formed in a substantially hemispherical shape with a diameter φd (radius r), for example, are formed so as to be closely packed, φd = 50 μm ( r = 25 μm) is prepared in advance, and the mold is filled with an ultraviolet curable resin having a viscosity of 160 mPa · s and good light transmittance, and then a PC (polycarbonate) film having a thickness of 25 μm. The second lens substrate 24 is superposed on a molding die, and a second microlens 25 having a diameter φd = 50 μm (R = 25 μm) and a substantially hemispherical shape is placed on the second lens substrate 24 with a pitch Px in the X-axis direction. A large number of films were formed with a thickness of 150 μm, and a large number of second microlenses 25 were cured by irradiation with ultraviolet rays.

  Next, as shown in FIG. 8D, between the first lens substrate 21 on which a large number of first microlenses 22 are formed and the second lens substrate 24 on which a large number of second microlenses 25 are formed, A black shading dry film 23 was interposed and adhered. At this time, the bottom surface side of the first microlens 22 and the bottom surface side of the second microlens 25 are opposed to each other via the first lens substrate 21, the light transmitting portion 23 a of the black light-shielding dry film 23, and the second lens substrate 24. In addition, by aligning the optical axes K of the first and second microlenses 22 and 25, the microlens array 20 of Example 2 was completed.

  At this time, the optical characteristics of the microlens array 20 of Example 2 were measured using a goniophotometer GP-200 type manufactured by Murakami Color Research Laboratory, with a peak gain value G0 and a viewing angle α ° (the peak gain is half value). The visible light transmittance (%) was measured using a haze / transmittance meter HM-150 manufactured by Murakami Color Research Laboratory. However, the gain value is a relative value when the complete diffusion plate is 1.0, and the peak gain value is a gain value when the viewing angle is 0 °.

  As a result, the peak gain value G0 is 3.1 and the viewing angle α ° is substantially hemispherical for both the first and second microlenses 22 and 25. Direction) and the Y-axis direction (vertical direction) were substantially the same value of ± 31 ° (horizontal / vertical), and the visible light transmittance (%) was 90%.

  When the microlens array 20 of Example 2 is used for a screen of a rear projection display (rear pro display), for example, the viewing angle is wide in both the X-axis direction (horizontal direction) and the Y-axis direction (vertical direction). Although the light transmittance was high and a high gain value was obtained even though the contrast ratio was high, a very high-contrast tightened image was obtained on the screen.

(A)-(c) is the front view, perspective view, and bottom view for demonstrating the microlens array of Example 1 which concerns on this invention. (A)-(d) is process drawing typically shown in order to demonstrate the manufacturing process of the micro lens array of Example 1 which concerns on this invention. (A) to (c) show optical characteristics with respect to the aperture diameter φd (μm) of the light transmitting portion in the three types of microlens arrays having a large number of microlenses having diameters φD = 80 μm, 100 μm, and 150 μm in the first embodiment. It is the figure shown by the list. In Example 1, it is the figure which showed by graph the opening diameter and optical characteristic of the light transmissive part in three types of microlens arrays which have many each microlens of diameter (phi) D = 80micrometer, 100micrometer, and 150micrometer. In Example 1, it is the figure which showed the aperture ratio and black ratio when the aperture diameter of the light transmission part is φd (μm) with respect to the diameter φD (μm) of the microlens. In Example 1, it is the figure which graphed and showed opening diameter (phi) d (micrometer) of the light transmissive part with respect to diameter (phi) D (micrometer) of a micro lens, and a black rate. (A)-(c) is the front view, perspective view, and bottom view for demonstrating the microlens array of Example 2 which concerns on this invention. (A)-(d) is process drawing typically shown in order to demonstrate the manufacturing process of the micro lens array of Example 2 which concerns on this invention. (A)-(c) is the front view, perspective view, and bottom view which showed the conventional micro lens array.

Explanation of symbols

10 ... The microlens array of Example 1,
11 ... Lens substrate, 11a ... Upper surface, 11b ... Lower surface,
12 ... Microlens,
13 ... Light transmissive resin material, 13a ... Light transmissive part,
14: Light shielding part (light absorbing part),
20 ... The microlens array of Example 2,
21 ... 1st lens substrate, 21a ... Upper surface, 21b ... Lower surface,
22 ... 1st micro lens,
23 ... Black shading dry film,
23a ... light transmission part, 23b ... light shielding part (light absorption part),
24. Second lens substrate,
25. Second microlens,
f: focal length, K: optical axis.

Claims (3)

A plurality of microlenses projecting in a convex shape are closely arranged two-dimensionally on one surface, and the other surface opposite to the one surface is formed flat so that each of the other surfaces In the microlens array in which each light transmission part is formed around the optical axis of the microlens and each light shielding part is formed between the adjacent light transmission parts,
The ratio of the total opening area of a large number of the light transmission parts to the total area of the microlens array is set to 15% or more and 30% or less. In a microlens array in which a number of microlenses protruding in a convex shape are arranged two-dimensionally,
The optical axis is aligned with the bottom surface side of the first microlens two-dimensionally arranged on the first lens substrate and the bottom surface side of the second microlens two-dimensionally arrayed on the second lens substrate. And each light transmitting portion is formed between the first lens substrate and the second lens substrate with the optical axis of each microlens as the center, and between each adjacent light transmitting portion. A microlens array having a light shielding portion formed thereon. The microlens array according to claim 2, wherein
A microlens array, wherein the focal lengths of the plurality of first microlenses are set to be positioned in the plurality of second microlenses.