JPH08248207A - Optical element and production of optical emenent as well as image display device - Google Patents

Abstract

PURPOSE: To provide a large-area optical element which prevents lens parts from peeling, is strong against thermal deformation and has high mechanical strength. CONSTITUTION: A microlens array 21 formed with the lens parts 24 on the front surface of a resin part 23 is produced by inserting a glass substrate 22 into the cavity 31 of metal molds 29 and molding the resin part 23 so as to enclose the circumference of the glass substrate 22. At this time, a resin material 25 for lenses which is equal in the refractive index n1 of the glass substrate 22 and the refractive index n2 of the lens parts 24 (more preferably n1 =n2 ) is used. Since the circumference of the glass substrate 22 is coated with the resin part 23, the resin part 23 is not easily peeled from the glass substrate 22 and the mechanical strength of the microlens array 21 is enhanced. Since the resin part 23 is formable thin, the distortion by orientation at the time of molding is lessened and double refraction is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element, a method for manufacturing the optical element, and an image display device. Specifically, the present invention relates to an optical element such as a lens array and a diffraction grating used in an image display device such as a liquid crystal projector, a viewfinder, a liquid crystal display, and a head mounted display, and a manufacturing method thereof.

[0002]

BACKGROUND OF THE INVENTION FIG. 1 is a partially broken schematic view of an image display device A using a liquid crystal display panel. 1
Is a microlens array, 2 is a liquid crystal display panel, and light emitted from a backlight light source (not shown) is incident on the aperture area 3 of each pixel of the liquid crystal display panel 2 to display an image on the liquid crystal display panel 2. Is displayed as. At this time, a transparent electrode 4 for controlling the polarization characteristics of the liquid crystal and displaying as an image is formed in the opening region 3 of each pixel, and a thin film transistor (TFT) for switching is formed in the vicinity of the transparent electrode 4. A wiring region (black matrix) 5 is provided. In the image display device A, the wiring area 5 causes the screen to be rough and the image to be distorted. Therefore, as shown in FIG. 2, the microlens array 1 is arranged on the emission side of the liquid crystal display panel 2 so that the light α can be seen as if it is emitted from the direction of the wiring region 5 as well, and the image roughness can be reduced. I am less. Further, as shown in FIG. 3, the light α emitted from the backlight light source cannot pass through the wiring region 5, and if the number of pixels is increased to increase the resolution, the ratio of the wiring region 5 becomes high, and the screen becomes extremely dark. It was getting dark. Therefore, as shown in FIG. 4, the microlens array 1 is arranged on the incident side of the liquid crystal display panel 2, and the light α emitted from the backlight light source is condensed in the opening region 3 of each pixel to improve the light utilization efficiency. The screen is made brighter.

An optical element such as the microlens array 1 is manufactured by the method shown in FIG. 5 or 6. The one shown in FIG. 5 is the so-called 2P method (Photopolymerization-M
In the 2P method, which is a method of manufacturing a microlens array 1 by ethod, first, a mold (stamper) 6 having an inverted pattern 7 of the lens portion 1a on the surface of the microlens array 1 is prepared (see FIG. a)), an optically transparent ultraviolet curable resin 8 is placed on the stamper 6 (FIG. 5).
(B)). The glass substrate 1b is placed thereon and pressed (FIG. 5C), and the light source 9 arranged above the glass substrate 1b.
Is irradiated with ultraviolet rays to cure the ultraviolet curable resin 8 to form the lens portion 1a (FIG. 5 (d)). After that, the lens portion 1a is peeled from the stamper 6 to manufacture the microlens array 1 (FIG. 5E).

However, in the microlens array 1 manufactured by the 2P method, since the lens portion 1a is only attached to the surface of the glass substrate 1b,
There is a problem that the lens portion 1a and the glass substrate 1b are easily peeled off. In particular, in recent years, there has been a demand for the liquid crystal display panel 2 to be large in size for easy viewing, and accordingly, when the microlens array 1 has a large area, it becomes easier to peel off. Further, the 2P method had a poor mass productivity.

FIG. 6 shows a method of manufacturing the microlens array 1 by the injection molding method. In this injection molding method, a mold 13 composed of an upper mold 11 and a lower mold 12 on which the inverted pattern 7 of the lens portion 1a is formed is prepared (FIG. 6 (a)), and the inside of the cavity 14 formed in the mold 13 is prepared. The molten lens resin material 16 is injected from the gate port 15 (FIG. 6).
(B)). Then, the lens resin material 16 is cooled and solidified, and then taken out from the mold 13 to manufacture the microlens array 1 in which the plurality of lens portions 1a are integrated (FIGS. 6C and 6D).

However, the microlens array 1 produced by this injection molding method has a resin material 16 for lenses.
Since it is manufactured from only one, it has a drawback that it is easily deformed by heat and its mechanical strength is weak. In addition, a gate 15a is provided in the microlens array 1 completed as shown in FIG.
Orientation strain (molding strain) 17 of the resin was generated in the vicinity, and birefringence was generated. For this reason, when a viewfinder such as a video camera is viewed through a polarizing filter such as polarizing glasses (sunglasses), optical distortion due to birefringence is observed, and there is a problem that image quality is significantly deteriorated.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the drawbacks of the above-mentioned conventional examples, and its object is to prevent thermal deformation or mechanical deformation without peeling off of a lens portion or the like. An object of the present invention is to provide an optical element having high strength and capable of increasing the area.

[0008]

DISCLOSURE OF THE INVENTION The optical element of the present invention has a resin portion in which at least a part of the glass substrate is sandwiched, and a lens array or a diffraction grating is formed on the surface of at least one surface of the glass substrate. It is characterized by forming an optically functional surface.

Therefore, the resin portion having the optically functional surface is not easily peeled off from the glass substrate and is not peeled off even by a thermal shock. Further, since the glass substrate is sandwiched between the resin parts, mechanical strength against a drop impact and the like is increased, and thermal deformation and warpage are reduced. Therefore, an optical element having a large area can be reliably manufactured.

An optical element according to a second aspect of the present invention is characterized in that an optically functional surface is formed on the resin portion on both surfaces of the glass substrate. Therefore, one optical element can have two optical functions, and by using this optical element, the number of parts can be reduced and the cost of the product incorporating the optical element can be reduced.

The method of manufacturing an optical element of the present invention is characterized in that a glass substrate is placed in a cavity of an injection mold, and a molding resin is injected into the cavity for molding. If insert molding is performed in this manner, a plurality of optical elements can be taken, and the optical elements of the present invention can be easily mass-produced. Further, since the resin portion can be made thin, the orientation strain generated during molding is small and birefringence is unlikely to occur.

The image display device of the present invention comprises a liquid crystal display panel for generating an image, and the optical element according to claim 1 is mounted on the light emitting side or the light incident side of the liquid crystal display panel. I am trying.

As described above, by using the optical element of the present invention, a liquid crystal display panel having a large area can be dealt with and a reliable image display device for a large image can be provided.

[0014]

EXAMPLE FIG. 8 shows a microlens array 21 which is an example of the present invention. 8A is a perspective view of the microlens array 21, FIG. 8B is a longitudinal sectional view thereof, and FIG.
(C) is the plane sectional view. Micro lens array 2
In No. 1, a resin portion 23 is molded so as to surround the entire circumference of the glass substrate 22, and a lens portion 24 having a large number of lens bodies arranged in an array is formed on the surface of the resin portion 23.
The resin portion 23 is made of an optically transparent lens resin material 25 having a refractive index n ₂ substantially equal to the refractive index n ₁ of the glass substrate 22, and preferably a lens such that n ₁ = n _2. It is preferable to use the resin material 25 for use. Further, it is preferable that the difference in thermal expansion coefficient is also small.

FIG. 10 shows a method of manufacturing the microlens array 21. The microlens array 21 is
It can be manufactured by an injection molding method using a mold 29 as shown in FIG. The mold 29 is composed of an upper mold 27 and a lower mold 28, and the inverted pattern 26 of the lens portion 24 of the microlens array 21 is formed on the cavity surface of the upper mold 27.
Are formed at a plurality of locations. Further, the lower die 28 has recesses 33 that form the cavities 31 formed at a plurality of locations, and the upper die 27 is movable along the guide pins 34. Therefore, using this mold 29, a plurality of microlens arrays 21 can be manufactured by molding once. To manufacture the microlens array 21 using the mold 29, first, the upper mold 27 is moved to open the mold 29 (FIG. 10A), and then the pin driving section 35 is driven. Then, both sides of the glass substrate 22 are supported by the thin pins 32, and the glass substrate 22 is placed in the cavity 31 in a floating state (FIG. 10B). Then, the melted lens resin material 25 fed from the sprue 37 is ejected into the respective cavities 31 from the gate ports 30 provided facing the respective cavities 31 through the radially extending runners 36 (FIG. 10 (c)). After cooling and solidification, it is taken out from the cavity 31 and a plurality of microlens arrays 21 can be manufactured by a series of steps (FIG. 10D). Incidentally, 30a is a gate formed corresponding to the gate opening 30.

In the microlens array 21 manufactured in this way, the inserted glass substrate 2 is used.
Since the resin portion 23 is molded around 2, the resin portion 2
3 (lens portion 24) is not easily peeled off from the glass substrate 22, and is not peeled off, for example, by thermal shock due to heating. Moreover, since the resin portion 23 can be made thin by inserting the glass substrate 22, the orientation distortion at the time of molding is reduced, and the birefringence becomes inconspicuous even when viewed through a polarizing filter or the like. Furthermore, since the periphery of the inserted glass substrate 22 is covered with the resin portion 23, the mechanical strength against a drop impact or the like increases to make it difficult to break, and the warp of the microlens array 21 also decreases. Therefore, a large-area microlens array 21 can be manufactured, and the liquid crystal display panel 2 can be made larger.

Further, as shown in FIG.
Alternatively, the glass substrate 22 may be disposed in the cavity 31 so as to be directly supported by the lower mold 28 without using the above, and a part of the glass substrate 22, for example, the outer peripheral portion of the glass substrate 22 may be sandwiched between the resin portions 23. A similar effect can be obtained with the microlens array 21 (FIG. 11B) manufactured as described above. Further, the glass substrate 22 to be inserted can also be manufactured using a glass substrate 22 having a warp as shown in FIG. Design of the microlens array 21 in this case, it is desirable to match the refractive index n ₂ of the refractive index n ₁ and the resin portion 23 of the glass substrate 22, used even if the glass substrate 22 is slightly warped Therefore, the cost can be reduced as a result.

Further, FIG. 13 shows a sectional view of a microlens array 21 which is still another embodiment of the present invention.
Thus, the resin portion 23 is formed so as to cover the entire circumference of the glass substrate 22, and the resin portion 23 on the back surface of the glass substrate 22 is formed.
Another lens unit 24 can be configured as well. To this end, the lens portion 24 is also provided on the cavity surface of the lower mold 28.
It is preferable to form the reverse pattern 26 on the surface.

In the above embodiments, the microlens array has been described as an example, but needless to say, the invention can be applied to various optical elements such as a diffraction grating as well as the microlens array. Further, as shown in FIG. 14, a diffraction grating portion 39 having a triangular cross section, for example, is formed in the resin portion 23 on the back side of the glass substrate 22, so that a microlens array having a plurality of lens bodies and a diffraction grating are formed as one The optical element 40 is sufficient, and by using this optical element 40, the number of parts can be reduced, and the cost of the image display device or the like can be reduced.

FIG. 15 is a schematic configuration diagram of a liquid crystal projector B which is an embodiment of the image display device of the present invention using the microlens array 21 thus manufactured. The liquid crystal projector B includes a light source 43 which is a white lamp 42 with a reflecting mirror 41, a condenser lens 44 which is an optical means for collecting the light from the light source 43 and causing the light to enter the liquid crystal display panel 2, and two polarizing plates. 45
It is composed of the liquid crystal display panel 2 and the projection lens 47 sandwiched between the two. A microlens array 21 according to the present invention is mounted on the incident side of the liquid crystal display panel 2.

Therefore, as shown in FIG.
To turn on the light α from the light source 43 to the condenser lens 44.
By illuminating the liquid crystal display panel 2 that is condensed by the two polarizing plates 45 and is incident on the liquid crystal display panel 2 by the lens portion 24 formed on the microlens array 21. Correspondingly collected. Thus, the light utilization efficiency of the light α is increased by the microlens array 21, and a bright moving image is displayed on the liquid crystal display panel 2.
Then, the moving image displayed on the liquid crystal display panel 2 is enlarged by the projection lens 47 and projected on the screen 48.

FIG. 16 is a schematic structural diagram showing a viewfinder C of a video camera or the like which is another example of the image display device of the present invention using the diffraction grating 51 manufactured as described above. In the viewfinder C, a backlight source 53 and a liquid crystal display panel 2 sandwiched between two polarizing plates 54 are housed in a housing 52 having a lens barrel shape. The diffraction grating 51 is arranged in the housing 52 by the cushion material 56 via the spacer 55, and the diffraction grating 51 is used as an optical low-pass filter. Then, the backlight light source 53
The light emitted from is incident on the liquid crystal display panel 2, and a moving image is displayed on the liquid crystal display panel 2. The moving image thus displayed can be observed through the eyepiece lens 57. With this viewfinder C, the moving image displayed on the liquid crystal display panel 2 can be observed without the image being rough. In particular, since the diffraction grating 41 having a small birefringence is used, the moving image can be enjoyed without deterioration of the image quality even when observed through a polarizing lens or a polarizing filter. Furthermore, a diffraction grating 5 is provided on the color liquid crystal display panel.
If 1 is used as a diffuser, the lights of the three primary colors (red, blue, and green) emitted from the respective pixels of the color liquid crystal display panel are superposed well, and the roughness due to the black matrix is suppressed, so that a high-quality color video image can be obtained. It can be observed as an image.

The image display device of the present invention is not limited to the above embodiment, but can be applied to a liquid crystal display, a liquid crystal television, a head mounted display and the like. Further, it goes without saying that the optical element of the present invention can be applied to various applications other than an image display device using a liquid crystal display panel.

[0024]

According to the optical element of the present invention, the glass substrate and the lens portion are not easily separated from each other, and the mechanical strength against a drop impact can be increased. Further, it becomes an optical element which is less likely to be thermally deformed or warped, and an optical element having high reliability can be provided. In particular, a large area optical element can be provided.

Further, according to the method of manufacturing an optical element of the present invention, the optical element of the present invention can be easily mass-produced, and an optical element having high reliability can be supplied at a low cost. In addition, it is possible to provide an optical element with little orientation distortion during molding and little birefringence.

Therefore, according to the image display device of the present invention, it is possible to provide a reliable large image display device.

[Brief description of drawings]

FIG. 1 is a partially cutaway schematic configuration diagram of a conventional image display device.

FIG. 2 is an explanatory diagram showing a method of using an optical element in the image display device of the above.

FIG. 3 is an explanatory diagram showing how light is transmitted in the image display device of the above.

FIG. 4 is an explanatory diagram showing another usage of the optical element in the image display device of the above.

5A to 5E are explanatory views showing a conventional method of manufacturing an optical element.

6A to 6C are explanatory views showing another conventional method for manufacturing an optical element, and FIG. 6D is a plan view of the optical element.

FIG. 7 is an explanatory diagram showing a problem of an optical element manufactured by the above manufacturing method.

8A is a perspective view of an optical element of the present invention, FIG. 8B is a longitudinal sectional view thereof, and FIG. 8C is a plan sectional view thereof.

FIG. 9 is a sectional structural view showing a mold for manufacturing the optical element of the present invention.

10 (a) to 10 (d) are explanatory views showing a method for manufacturing an optical element using the same mold.

11A is an explanatory view showing a method of manufacturing an optical element according to another embodiment of the present invention, and FIG. 11B is a sectional view of the optical element.

FIG. 12A is an explanatory view showing a method of manufacturing an optical element according to still another embodiment of the present invention, and FIG. 12B is a sectional view of the optical element.

FIG. 13 is a cross-sectional view of an optical element that is still another embodiment of the present invention.

FIG. 14 is a cross-sectional view of an optical element that is still another embodiment of the present invention.

FIG. 15 is a schematic configuration diagram showing a liquid crystal projector which is an image display device according to the present invention.

FIG. 16 is a schematic configuration diagram showing a viewfinder that is an image display device according to the present invention.

[Explanation of symbols]

 21 Micro Lens Array 22 Glass Substrate 24 Lens Part 27 Upper Model 28 Lower Model 39 Diffraction Grating Part 51 Diffraction Grating

Claims (4)

[Claims] 1. A surface of at least one of the glass substrates,
An optical element characterized by molding a resin part sandwiching at least a part of the glass substrate, and forming an optical functional surface having a lens array or a diffraction grating on the surface of the resin part. 2. The optical element according to claim 1, wherein an optically functional surface is formed on the resin portion on both surfaces of the glass substrate. 3. A method of manufacturing an optical element, comprising placing a glass substrate in a cavity of an injection molding die and injecting a molding resin into the cavity for molding. 4. An image display device comprising a liquid crystal display panel for generating an image, wherein the optical element according to claim 1 is mounted on a light emitting side or a light incident side of the liquid crystal display panel.