Optical filter and method for manufacturing optical filter

Abstract

The invention provides an optical filter capable of improving weather resistance compared with a conventional optical filter and a manufacturing method of the optical filter. An optical filter (10) is provided with an infrared-absorbing glass (11), an adhesion layer (13) formed on the main surface of the infrared-absorbing glass, and a resin layer (15) that is formed on the adhesion layer and is capable of absorbing light of a specific wavelength. In addition, a protective member (17) is provided on the surface of the resin layer opposite to the adhesion layer. The protective glass is made of white glass, and the sealing layer is made of an ultraviolet hardening type acrylic acid series adhesive. An anti-reflection film (21) is provided on the surface of the cover glass opposite to the resin layer.

Description

Technical Field

[0001] The present invention relates to an optical filter used on the incident side of an imaging element or the like. Background Art

[0002] In an imaging device such as a digital camera, it is desirable to use an optical filter to obtain an image that conforms to the wavelength range of human visual sensitivity.

[0003] As an example of such an optical filter, for example, Patent Document 1 discloses a near-infrared cut filter. This filter includes a transparent substrate and a resin layer. The transparent substrate is a transparent substrate having a transmittance of 3% or less in the wavelength range of 800 to 950 nm. The resin layer is formed on at least one main surface of the transparent substrate and can absorb light of a specific wavelength (for example, Claim 1 of Patent Document 1). By using the resin layer, light in the desired visible light region can be extracted in cooperation with the transparent substrate (for example, Paragraph 54 of Patent Document 1).

[0004] In addition, Patent Document 1 also discloses a structure in which a bonding layer is provided between the transparent substrate and the resin layer to improve the adhesion between the two (for example, Claim 10, FIG. 16, etc. of Patent Document 1). By providing the bonding layer, the reliability of the filter can be improved (for example, Paragraph 105 of Patent Document 1). As the material of the bonding layer, one or more atoms selected from a silicon atom (Si atom), a titanium atom (Ti atom), a zirconium atom (Zr atom), and an aluminum atom (Al atom) are preferable (for example, Paragraph 106 and Paragraph 111 of Patent Document 1).

[0005] [Prior Art Documents]

[0006] [Patent Documents]

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-15269 Summary of the Invention

[0008] [Problems to be Solved by the Invention]

[0009] Although the optical filter disclosed in Patent Document 1 helps to obtain an imaging device that conforms to the wavelength range of human visual sensitivity, since the resin layer is exposed, there are concerns in terms of weather resistance and the like.

[0010] The present application is proposed in view of the above problems. Therefore, an object of the present application is to provide an optical filter that can improve weather resistance compared to the conventional technology, and a manufacturing method for easily manufacturing the optical filter.

[0011] [Technical means for solving the problem]

[0012] In order to achieve the above object, the optical filter invention according to the present application is characterized in that: in an optical filter including an infrared absorbing glass, an adhesion layer formed on the main surface of the infrared absorbing glass, and a resin layer formed on the adhesion layer and absorbing light of a specific wavelength, a protective member is provided on the opposite surface of the resin layer and the adhesion layer.

[0013] When implementing the optical filter invention, the protective member can be composed of any material that can meet the optical characteristics and weather resistance specifications of the optical filter, but is preferably a material selected from white plate glass, ultraviolet absorbing glass, and quartz glass.

[0014] In addition, when implementing the optical filter invention, the adhesion layer is preferably an acrylic-based adhesive. In particular, it is preferably an acrylic-based adhesive that does not contain silicon atoms, titanium atoms, zirconium atoms, and aluminum atoms. However, not containing means except for the case where silicon atoms, titanium atoms, zirconium atoms, and aluminum atoms are inevitably contained. Since the acrylic-based adhesive is provided as an ultraviolet curable adhesive, it is more convenient in manufacturing. In addition, if it is an acrylic-based adhesive that does not contain silicon atoms, titanium atoms, zirconium atoms, and aluminum atoms, compared with the case where these atoms are contained, for example, it is easier to obtain the softness of the adhesion layer.

[0015] When implementing the optical filter invention, the protective member is preferably a material selected from white plate glass, ultraviolet absorbing glass, and quartz glass.

[0016] When implementing the optical filter invention, the resin layer is preferably a resin layer having infrared absorption properties.

[0017] In addition, the optical filter manufacturing method invention according to the present application is characterized in that, when manufacturing an optical filter including an infrared absorbing glass, an adhesion layer formed on the main surface of the infrared absorbing glass, a resin layer formed on the adhesion layer and absorbing light of a specific wavelength, and a protective member provided on the opposite surface of the resin layer and the adhesion layer, the following steps are included:

[0018] Preparing a glass selected from white plate glass, ultraviolet absorbing glass, and quartz glass as the protective member, and forming the resin layer on the main surface of the glass;

[0019] Preparing the infrared absorbing glass, and forming an adhesive for the adhesion layer on its main surface; and

[0020] Aligning and bonding the infrared absorbing glass on which the adhesive is formed and the protective glass on which the resin layer is formed, with the adhesive and the resin layer facing each other.

[0021] In addition, when implementing the invention of the optical filter manufacturing method, the adhesive is preferably an acrylic adhesive.

[0022] [Advantages of the Invention]

[0023] According to the optical filter invention of the present application, since the protective member is provided, the resin layer is not directly exposed to the environment in which the optical filter is used, so the weather resistance of the optical filter is improved.

[0024] According to the optical filter manufacturing method invention of the present application, a resin layer is formed on the protective member. Here, the protective member can be composed of, for example, white glass or quartz glass. White glass or quartz glass is generally harder than infrared absorbing glass, has a higher surface flatness, and a finer surface roughness, so the adhesion and surface accuracy of the resin layer formed on the protective glass can be improved. In other words, compared with forming the resin layer on the infrared absorbing glass side, the present invention can more effectively improve the adhesion and surface accuracy of the resin layer, etc., thereby improving the characteristics of the optical filter. Therefore, according to the optical filter manufacturing method invention of the present application, an optical filter with excellent weather resistance and more excellent characteristics can be easily manufactured. Description of the Drawings

[0025] Figure 1 It is a cross-sectional view illustrating the optical filter 10 of the first embodiment.

[0026] Figure 2 (A) to (E) thereof are main process diagrams illustrating the embodiments of the manufacturing method invention.

[0027] Figure 3 It is a cross-sectional view illustrating the optical filter 20 of the second embodiment.

[0028] Figure 4 (A) thereof is a cross-sectional view illustrating the optical filter 30 of the third embodiment, Figure 4 (B) thereof is a cross-sectional view illustrating the optical filter 40 of the fourth embodiment.

[0029] Figure 5 It is a diagram illustrating an example of the transmittance characteristic of the optical filter of the present invention.

[0030] Figure 6 It is a diagram illustrating the results of the moisture resistance test of the optical filter 50 of the comparative example.

[0031] [Explanation of Reference Numerals]

[0032] 10: Optical filter (optical filter of the first embodiment)

[0033] 11: Infrared absorbing glass

[0034] 13: Close contact layer

[0035] 13a: Adhesive

[0036] 15: Resin layer

[0037] 15a: Material for forming resin layer

[0038] 17: Protection member

[0039] 17: Protection glass

[0040] 20: Optical filter (optical filter of the second embodiment)

[0041] 21: Anti-reflection film

[0042] 30: Optical filter (optical filter of the third embodiment)

[0043] 31: Close contact layer (second close contact layer)

[0044] 33: Second protection member (second protection glass)

[0045] 40: Optical filter (optical filter of the fourth embodiment)

[0046] 41a: Anti-reflection film (first anti-reflection film)

[0047] 41b: Anti-reflection film (second anti-reflection film)

[0048] 50: Optical filter (optical filter of the comparative example)

[0049] 51: Crack Detailed implementation manners

[0050] Hereinafter, embodiments of each invention of the present application will be described with reference to the accompanying drawings. In addition, each drawing for explanation only shows schematically to the extent that these inventions can be understood. In addition, in each drawing for explanation, the same components are denoted by the same reference numerals, and their explanations may sometimes be omitted. In addition, the shapes, materials, etc. described in the following embodiments are only preferred examples within the scope of the present invention. Therefore, the present invention is not limited to the following embodiments.

[0051] 1. Optical filter of the first embodiment

[0052] Figure 1This is a cross-sectional view of the optical filter 10 of the first embodiment. The optical filter 10 includes an infrared-absorbing glass 11, an adhesion layer 13 formed on the main surface of the infrared-absorbing glass 11, a resin layer 15 formed on the adhesion layer 13 and absorbing light of a specific wavelength, and a protective glass 17 provided on the opposite surface of the adhesion layer 13 to the resin layer 15 as a protective member. Therefore, the optical filter 10 can be used as an infrared cut-off filter.

[0053] The infrared-absorbing glass 11 is made of a material having light absorption and transmittance characteristics in a specific wavelength range, such as the infrared region or the near-infrared region, according to the design of the optical filter 10.

[0054] The planar shape of the infrared-absorbing glass 11 can be any shape according to the design of the imaging device using the optical filter 10, typically a rectangular shape such as a rectangle. The planar size of the infrared-absorbing glass 11 is any size according to the design of the imaging device.

[0055] The thickness of the infrared-absorbing glass 11 can be any thickness according to the design of the imaging device using the optical filter 10.

[0056] The infrared-absorbing glass 11 can be arbitrarily selected and used from commercially available products or individual specification products according to the design of the optical filter 10. As commercially available products, for example, BG38 and BG39 (trade names) manufactured by SCHOTT can be used.

[0057] The adhesion layer 13 is provided to improve the adhesion between the infrared-absorbing glass 11 and the resin layer 15. The adhesion layer 13 is preferably made of a material that can ensure adhesion and can minimize the optical losses at the interfaces between the infrared-absorbing glass 11 and the adhesion layer 13 and between the resin layer 15 and the adhesion layer 13, respectively. Therefore, for the infrared-absorbing glass 11 and the resin layer 15, the adhesion layer 13 is preferably a material having a refractive index close to that of the infrared-absorbing glass 11 and the resin layer 15.

[0058] The thickness of the adhesion layer 13 can be any thickness according to the design of the optical filter 10. For example, it is 3 to 20 μm, preferably 3 to 10 μm, but not limited thereto.

[0059] The material for forming the adhesion layer 13 can be arbitrarily selected and used from commercially available products or individual specification products according to the design of the optical filter 10. As commercially available products, for example, an acrylic-based adhesive can be cited. Specifically, the optical adhesive #300K (Photobond #300K (product name)) manufactured by Sunrise MSI can be used. Since Photobond #300K is an ultraviolet-curable adhesive, it is very convenient in the manufacture of optical filters.

[0060] The resin layer 15 is a layer that absorbs light of a specific wavelength. Here, the specific wavelength refers to a wavelength selected from the infrared region, the near-infrared region, or the ultraviolet region on the short-wavelength side in order to supplement the optical characteristics of the infrared-absorbing glass 11. This can be achieved by containing a pigment or the like that absorbs a specific wavelength region in the resin layer 15. Thereby, in cooperation with the infrared-absorbing glass 11, the transmittance characteristics and incident angle dependence of the optical filter 10 can be controlled.

[0061] The thickness of the resin layer 15 can be any thickness according to the design of the optical filter 10. For example, it is 1 to 20 μm, preferably 1 to 5 μm, but is not limited thereto.

[0062] The forming material of the resin layer 15 can be arbitrarily selected and used appropriately from commercially available products or individually specified products according to the design of the optical filter 10. As a commercially available product, for example, IX-2-KT-B (trade name) manufactured by Nippon Shokubai Co., Ltd. can be used.

[0063] The protective glass 17 is provided to protect the resin layer 15 from the influence of the usage environment of the optical filter 10. Therefore, the protective glass 17 is provided on the opposite side of the resin layer 15 from the adhesive layer 13. The planar shape and size of the protective glass are usually the same as those of the infrared-absorbing glass 11, but may also be different within the range that does not affect the purpose of protecting the resin layer 15.

[0064] The thickness of the protective glass 17 can be any thickness according to the design of the optical filter 10. For example, it can be 0.3 to 1 mm, but is not limited thereto.

[0065] The material of the protective glass 17 is preferably a material that has as little adverse effect as possible on the human visual sensitivity. In addition, considering the manufacturing method described later, a material with a high softening point and high hardness is preferably used. Therefore, the material of the protective glass 17 is preferably selected from white glass, quartz glass, and ultraviolet-absorbing glass.

[0066] The forming material of the protective glass 17 can be arbitrarily selected and used appropriately from commercially available products or individually specified products according to the design of the optical filter 10. As a commercially available product, for example, white plate glass B270i (trade name) manufactured by SCHOTT can be used.

[0067] In the optical filter 10 of the first embodiment, since the protective glass 17 is provided as a protective member, the resin layer 15 is not exposed to the usage environment of the optical filter 10, and thus the resin layer 15, which can improve the degree of freedom of optical characteristics, can be protected from the influence of the usage environment of the optical filter 10.

[0068] Specifically, the hardness of the resin layer 15 is only about 10B in terms of pencil hardness, so it is easily scratched, and since it is resin, its moisture resistance is not high either. The protective glass 17 can compensate for the above-mentioned shortcomings of the resin layer 15.

[0069] 2. Embodiments of the manufacturing method

[0070] Next, embodiments of the invention of the manufacturing method of the optical filter will be described. Figure 2 of (A) to Figure 2 of (E) are its main process diagrams, which are process diagrams of the specimen during the manufacturing process of the optical filter 10 shown in cross-section. The manufacturing method of the embodiment performs the following processes.

[0071] As the protective glass 17, a glass selected from white plate glass, ultraviolet-absorbing glass, and quartz glass is prepared, and a resin layer is formed on the main surface of the glass ( Figure 2 of (A), Figure 2 of (B)). Specifically, a glass for protective glass is prepared, such as white glass (for example, white plate glass B270i (trade name) manufactured by SCHOTT), and on the main surface, a material 15a for forming a resin layer (for example, IX-2-KT-B (trade name) manufactured by Nippon Shokubai Co., Ltd.) is coated using, for example, a spin coater ( Figure 2 of (A)); thereafter, it is heat-cured in a temperature bath at a specific temperature to obtain the protective glass 17 having the resin layer 15 ( Figure 2 of (B)).

[0072] On the other hand, an infrared-absorbing glass 11 (for example, BG38 (trade name) manufactured by SCHOTT) is prepared, and an adhesive 13a for forming the adhesion layer 13 (for example, Photobond #300 (product name) manufactured by Sunrise MSI Co., Ltd.) is coated on its main surface ( Figure 2 of (C), Figure 2 of (D)). After that, the infrared-absorbing glass on which the formation of the adhesive has been completed and the protective glass on which the formation of the resin layer has been completed are made to face each other with the adhesive and the resin layer and bonded ( Figure 2 of (E)). The specimens placed opposite each other can be in a self-weight state or a pressurized state, and are placed for a specific time so that the adhesive is evenly interposed between the resin layer 15 and the infrared-absorbing glass 11. Next, since the above-mentioned Photobond #300K is an ultraviolet-curing type adhesive, the specimen is irradiated with ultraviolet rays under specific conditions to complete the bonding, and the Figure 1 shown optical filter 10 is obtained.

[0073] According to the invention of the manufacturing method, compared with the infrared-absorbing glass 11, when forming the resin layer 15 using a protective glass 17 such as a white glass that is hard, has excellent flatness, and is easy to refine the surface roughness, and then performing the bonding process, a resin layer with good adhesion and flatness can be easily formed on the protective glass, thereby enabling the required optical filter 10 to be manufactured simply and with good characteristics.

[0074] In addition, the order of the process of forming the resin layer on the protective glass and the process of forming the adhesive on the infrared-absorbing glass can, of course, also be the reverse order of the above processes. However, if the adhesive is likely to harden or gel in a short time, the process of forming the resin layer on the protective glass can be performed first.

[0075] 3. Other Embodiments of the Optical Filter

[0076] 3-1. Second Embodiment of the Optical Filter

[0077] Figure 3 FIG. is a cross-sectional view for explaining the optical filter 20 of the second embodiment. The difference between the optical filter 20 of the second embodiment and the optical filter 10 of the first embodiment is that an antireflection film 21 is provided on the opposite surface of the protective glass 17 from the resin layer 15.

[0078] The antireflection film 21 can be composed of an appropriate material and a single-layer or multi-layer structure according to the design of the optical filter 20. The antireflection film 21 is generally designed to allow light within the wavelength range corresponding to the human visual sensitivity to enter the optical filter 20 side as much as possible, while reflecting light in other wavelength ranges as much as possible; typically, the antireflection film 21 can be composed of a dielectric multi-layer film.

[0079] The optical filter 20 of the second embodiment can, in addition to having the effect of the protective resin layer 15 of the optical filter of the first embodiment, also obtain the effect of making light within the wavelength range corresponding to the human visual sensitivity easily enter the optical filter 20.

[0080] 3-2. Third Embodiment of the Optical Filter

[0081] Figure 4 FIG. (A) is a cross-sectional view for explaining the optical filter 30 of the third embodiment. The difference between the optical filter 30 of the third embodiment and the optical filter 10 of the first embodiment is that on the surface on the back side of the infrared-absorbing glass 11, a close contact layer 31, namely a second close contact layer 31, and a second protective glass 33 as a second protective member are sequentially provided starting from the infrared-absorbing glass 11 side.

[0082] In the case of the optical filter 30 of the third embodiment, the back side of the infrared absorptive glass 11 is protected by the second protective glass 33. Compared with the white glass or quartz glass that constitutes the protective glass, the infrared absorptive glass is generally inferior in scratch resistance and weather resistance. In the case of the optical filter of the third embodiment, in addition to the effects of the optical filter 10 of the first embodiment, by using the second protective glass 33 to protect the back side of the infrared absorptive glass 11, the scratch resistance and weather resistance of the optical filter 30 can be further improved. Specifically, the hardness of the infrared absorptive glass 11 is only about 3H in pencil hardness and is easily scratched. The protective glass 33 on the back side can make up for the above-mentioned disadvantages of the infrared absorptive glass 11.

[0083] 3-3. Fourth Embodiment of the Optical Filter

[0084] Figure 4 (B) of FIG. is a cross-sectional view for explaining the optical filter 40 of the fourth embodiment. The optical filter 40 of the fourth embodiment is an improved version of the optical filter 30 of the third embodiment. A first antireflection film 41a is provided on one main surface of the optical filter 30 of the third embodiment, and a second antireflection film 41b is provided on the other main surface.

[0085] The optical characteristics of the first antireflection film 41a and the second antireflection film 41b can be changed according to the specifications of the optical filter 40. For example, the first antireflection film 41a and the second antireflection film 41b can be set to have substantially the same optical characteristics, or the first antireflection film 41a on the light incident side and the second antireflection film 41b on the imaging element side can be set to have different optical characteristics.

[0086] Through the optical filter 40 of this fourth embodiment, an optical filter with a high degree of design freedom in antireflection can be provided.

[0087] In addition, for the sake of convenience of explanation, although the first antireflection film 41a is described as the incident side and the second antireflection film 41b is described as the imaging element side, the incident direction can also be the opposite case.

[0088] 4. Examples and Comparative Examples

[0089] The optical filter of the present invention is an infrared absorption filter having a resin layer, and the weather resistance of the resin layer is improved. For a better understanding, examples of the optical characteristics of the optical filter of the examples and examples of the weather resistance test results are shown below.

[0090] 4-1. Optical Characteristics of the Examples

[0091] Using the above-mentioned BG39 as the infrared-absorbing glass, the above-mentioned Photobond #300K as the adhesive layer, the above-mentioned IX-2-KT-B as the resin layer, the above-mentioned B270i as the protective glass, and a specific dielectric film as the antireflection film, the optical filter 40 of the fourth embodiment was trial-produced. Subsequently, its transmittance characteristics were measured. Figure 5 It is a graph showing its transmittance characteristics with the horizontal axis being the wavelength (nm) and the vertical axis being the transmittance (%).

[0092] From Figure 5 it can be seen that even for the optical filter of the present invention having a protective glass and an adhesive layer, it is possible to realize a required infrared-absorbing filter, that is, an infrared-absorbing filter that transmits light in a wavelength band conforming to the human visual sensitivity and attenuates light of other wavelengths.

[0093] 4-2. Weather resistance experiment

[0094] As a comparative example of the optical filter, a sample in which a resin layer was directly formed on the main surface of the infrared-absorbing glass 11 was prepared. In addition, as an example of the optical filter, the optical filter 10 of the first embodiment as shown in Figure 1 was also prepared. In addition, in both samples, the above-mentioned BG39 was used as the infrared-absorbing glass, and the above-mentioned IX-2-KT-B was used as the resin layer. In the sample of the example, the above-mentioned Photobond #300K was used as the adhesive layer, and the above-mentioned B270i was used as the protective glass.

[0095] The two samples were put into a high-temperature and high-humidity environment at a temperature of 60 °C and a humidity of 95% to evaluate their weather resistance.

[0096] The results are as shown in Figure 6 In the case of the optical filter 50 of the comparative example, after observation after 120 hours, cracks 51 were found in many places in the resin layer 15. These cracks 51 were observed and photographed under the condition of 50 times magnification of an optical microscope. It is speculated that the resin layer 15 absorbed moisture, causing partial swelling and resulting in cracks 51.

[0097] On the other hand, after 120 hours of high-temperature and high-humidity test, the optical filter of the example maintained a good state without observing cracks or phenomena such as fogging even after a considerably long time.

Claims

1. An optical filter, characterized in that: include: Infrared absorbing glass, an adhesive layer formed on a main surface of the infrared absorbing glass, and a resin layer formed on the adhesive layer and absorbing light of a specific wavelength, wherein: A protective member is provided on the surface of the resin layer opposite to the adhesion layer.

2. The optical filter according to claim 1, characterized in that The protective member is selected from white plate glass, ultraviolet absorbing glass and quartz glass.

3. The optical filter according to claim 1, characterized in that The protective member is white plate glass.

4. The optical filter according to claim 1, characterized in that The adhesive layer is an acrylic adhesive.

5. The optical filter according to claim 1, characterized in that The adhesive layer is an acrylic adhesive that does not contain silicon atoms, titanium atoms, zirconium atoms, and aluminum atoms.

6. The optical filter according to claim 1, characterized in that The protective member has an antireflection film on a surface opposite to the resin layer.

7. The optical filter according to claim 1, characterized in that A second adhesion layer and a second protective member are provided in this order on a surface of the infrared absorbing glass opposite to the adhesion layer.

8. The optical filter according to claim 7, characterized in that A first anti-reflection film is provided on the protective member, and a second anti-reflection film is provided on the second protective member.

9. The optical filter according to claim 7, characterized in that: The second protective member is selected from white plate glass, ultraviolet absorbing glass and quartz glass.

10. The optical filter according to claim 7, characterized in that The second protective member is white plate glass.

11. A method for manufacturing an optical filter, characterized in that: When manufacturing an optical filter including infrared absorbing glass, a bonding layer formed on a main surface of the infrared absorbing glass, a resin layer formed on the bonding layer and absorbing light of a specific wavelength, and a protective member provided on a surface of the resin layer opposite to the bonding layer, the following steps are included: A step of preparing a glass selected from white plate glass, ultraviolet absorbing glass and quartz glass as the protective member, and forming the resin layer on a main surface of the glass; A step of preparing the infrared absorbing glass and forming an adhesive as the adhesion layer on the main surface thereof; The infrared absorbing glass on which the adhesive has been formed and the cover glass on which the resin layer has been formed are subjected to a step of making the adhesive and the resin layer face each other and bonding them together.

12. The method for manufacturing an optical filter according to claim 11, characterized in that: As the adhesive, an ultraviolet curing acrylic adhesive was used.

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