JP2014208573A - Optical element and method of manufacturing optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element which is used as a near-infrared cut filter, is formed of fluorophosphate glass, has high strength, and is resistant to cracking, chipping, and the like.SOLUTION: The optical element has a fluorophosphate glass substrate 10 and a transparent film 20 formed on the entire surface of the fluorophosphate glass substrate 10. The fluorophosphate glass substrate 10 is made of fluorophosphate glass containing CuO. The transparent film 20 has one or more transparent material films containing one of oxide, nitride, oxynitride, and carbide as a main component.

Description

  The present invention relates to an optical element and a method for manufacturing the optical element.

  In an electronic device such as a digital camera, a solid-state image sensor such as a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) for capturing an image is used. Since these solid-state image sensors have spectral sensitivity in the near-infrared region having a wavelength of near 1200 nm from the near-ultraviolet region, an image with good color reproducibility cannot be obtained when the image is taken as it is. For this reason, when using a solid-state image sensor, an optical element called a near infrared cut filter containing a specific substance that absorbs infrared light is used at the same time. As a result, correction is performed to selectively absorb light having a wavelength in the near-infrared region out of light incident on the solid-state image sensor and approximate the incident light on the solid-state image sensor to human visibility.

  As such a near-infrared cut filter, for example, a filter formed of a fluorophosphate glass substrate containing CuO or the like is known. The method for producing such a near-infrared cut filter is, for example, mixing raw materials so as to have a desired glass composition, storing in a platinum crucible, capping, melting at a temperature of 800 ° C. to 1300 ° C., and stirring. -After clarification, a method of forming into a flat plate by slowly cooling, cutting and polishing may be mentioned.

Japanese Patent Laid-Open No. 6-16451 Japanese Patent Laid-Open No. 4-139035 JP 2011-8076 A

  By the way, fluorophosphate glass is excellent in optical properties but low in strength and the like. For this reason, optical elements formed of fluorophosphate glass generally tend to be brittle and easily chipped. Specifically, the cutting process performed when the optical element is manufactured is performed by a dicing saw or the like. At this time, microcracks or the like are generated in the cross section and in the vicinity of the cross section. When such micro cracks are generated in the optical element, when an external force is applied to the optical element during the subsequent manufacturing process or use, the optical element is cracked or chipped due to the crack. It tends to occur.

  For this reason, in an optical element formed of a fluorophosphate glass, an optical element that has high strength and is resistant to cracking and chipping is required.

  According to one aspect of the present embodiment, an optical element having a fluorophosphate glass substrate and a transparent film formed on the entire surface of the fluorophosphate glass substrate, wherein the transparent film is an oxide, nitride It has one or more transparent material films which contain any one of a thing, oxynitride, or carbide as a main component.

  Further, according to another aspect of the present embodiment, a step of forming a fluorophosphate glass substrate by cutting the fluorophosphate glass, and transparent on the entire surface of the fluorophosphate glass substrate by atomic layer deposition A step of forming a film, wherein the transparent film has at least one transparent material film containing any one of oxide, nitride, oxynitride, and carbide as a main component. To do.

  According to the present invention, in an optical element having a fluorophosphate glass substrate, the strength can be increased and it can be made strong against cracks and chips.

Structure diagram of optical element in this embodiment Structural diagram of an optical element with a film deposited by a vacuum deposition method Explanatory drawing of the optical element in this Embodiment Explanatory drawing of the manufacturing method of the optical element in this Embodiment Correlation diagram between film thickness of transparent material film and relative value of 4 point intensity in optical element

  Modes for carrying out the invention will be described below. In addition, about the same member etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

(Optical element)
The optical element in the present embodiment has a fluorophosphate glass substrate and a transparent film on the entire surface of the fluorophosphate glass substrate. Further, the transparent film is a film containing, as a main component, any one of oxide, nitride, oxynitride, and carbide formed by atomic layer deposition (hereinafter abbreviated as ALD). Is preferred.

(Atomic layer deposition)
First, ALD will be described. ALD is a film forming method in which a film is formed for each atomic layer by supplying a source gas of a material to be formed. Thereby, in ALD, as described later, it is possible to form a film on the entire periphery of the fluorophosphate glass substrate, that is, on the front surface, side surface, and back surface. Further, the step coverage is high, and micro cracks and the like on the entire surface of the fluorophosphate glass substrate can be filled. Thereby, the strength of the fluorophosphate glass substrate can be improved, that is, the strength of the optical element can be improved.

  FIG. 1 is a cross-sectional view showing the structure of an optical element according to the present embodiment, in which a transparent film is formed on a fluorophosphate glass substrate by ALD. FIG. 2 is a cross-sectional view showing the structure of an optical element in which a transparent film is formed on a fluorophosphate glass substrate by vacuum deposition or the like.

  As shown in FIG. 1, in the optical element in the present embodiment, a transparent film 20 is formed on the entire surface of the fluorophosphate glass substrate 10, that is, on the front surface, side surface, and back surface. In ALD, since the source gas supplied from the supply source 30 goes around the side surface and the back surface of the fluorophosphate glass substrate 10, the transparent film 20 is formed on the entire surface of the fluorophosphate glass substrate 10 with a substantially uniform film thickness. can do.

  On the other hand, as shown in FIG. 2, in the optical element in which the transparent film 920 is formed on the fluorophosphate glass substrate 910 by vacuum vapor deposition or the like, the vapor deposition particles supplied from the supply source 930 are the fluorophosphate glass substrate. The transparent film 920 is hardly formed on the back surface and side surface of the fluorophosphate glass substrate 910 because it slightly wraps around the side surface of the 910, but hardly wraps around the back surface. A film is formed on the surface of the substrate 910.

  Next, the micro crack which arises when a fluorophosphate glass is cut | disconnected is demonstrated. The fluorophosphate glass substrate 10 is formed by cutting a fluorophosphate glass substrate by dicing or the like. At this time, since the fluorophosphate glass substrate is fragile, minute cracks 11 are generated in the vicinity of the cross section of the fluorophosphate glass substrate 10 as shown in FIG. As described above, when such a micro crack 11 is generated, when a force is applied to the fluorophosphate glass substrate 10, the fluorophosphate glass substrate 10 is cracked or chipped due to the micro crack 11. Arise.

In the present embodiment, as shown in FIG. 3B, a minute film generated on the fluorophosphate glass substrate 10 by forming a transparent film 20, for example, a transparent material film made of Al ₂ O ₃ by ALD. The crack 11 can be embedded. Thereby, when a force is applied to the fluorophosphate glass substrate 10, it is possible to suppress cracks and chips caused by the minute cracks 11 and to increase the strength. In ALD, since the source gas wraps around and reaches the depth of the minute crack 11, the dense transparent film 20 can be formed in the depth of the minute crack 11, and the minute crack that causes the crack is buried. Can do.

  Furthermore, when the fluorophosphate glass is cut by dicing or the like, minute cracks 11 are generated on the front surface, side surface, and back surface in the vicinity of the cut surface of the fluorophosphate glass substrate 10. However, in the present embodiment, the transparent film 20 is formed by ALD. In ALD, these minute cracks 11 can be embedded by the transparent film 20 in a single film formation. In addition, by covering the microcracks generated by contact with the surface during the process such as dicing with ALD, it is possible to prevent latent scratches generated by the cleaning process or the like.

  On the other hand, in a film forming method such as vacuum evaporation, since the wraparound of the raw material of the material to be formed is extremely small, minute cracks cannot be embedded densely, and the side surface of the fluorophosphate glass substrate 910 And minute cracks on the back surface can hardly be embedded. Therefore, the strength cannot be sufficiently improved. In addition, since the film is formed on only one side, it is impossible to suppress latent scratches on both sides.

(Transparent film 20)
In the present specification, the transparent film refers to a film having a transmittance of 80% or more in the visible light region of only the film. The above-described transmittance can be calculated from, for example, the difference between the transmittance of glass that has not been formed and the transmittance of glass that has been formed.

  In the present embodiment, the transparent film 20 has one or more transparent material films and exhibits the optical characteristics described above. The transparent material film contains any one of oxide, nitride, oxynitride, and carbide as a main component. In the present specification, the main component refers to a component contained at 80% by mass or more. That is, in this embodiment, the total amount of any of oxide, nitride, oxynitride, and carbide is 80% or more with respect to 100% of the mass of the transparent film 20.

  The transparent material film is preferably made of any one of oxide, nitride, oxynitride, and carbide. In the specification of the present application, “consisting of” does not avoid the inevitable contamination.

Examples of the oxide include Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Y ₂ O ₃ , SiO _{2, and} HfO ₂ . Examples of the nitride include AlN and Si ₃ N ₄ . Examples of the oxynitride include SiON, AlON, and TiON. Examples of the carbide include SiC.

From the viewpoint of ease of film formation by ALD, the transparent material film preferably contains any one of oxide, nitride, and oxynitride as a main component. More preferably, the transparent material film contains Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SiO ₂ , AlN, Si ₃ N ₄ , TiON or AlON as a main component. Furthermore, the transparent material film is particularly preferably made of any one of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SiO ₂ , AlN, Si ₃ N ₄ , TiON, or AlON.

  In the present embodiment, the transparent film 20 is preferably made of one transparent material film.

  The thickness of the transparent film 20 is preferably 5 to 500 nm. If the thickness of the transparent film is less than 5 nm, minute cracks cannot be sufficiently embedded in the transparent film 20, and a desired strength cannot be obtained. On the other hand, when the thickness of the transparent film 20 exceeds 500 nm, it approaches the wavelength range of visible light, affecting the optical characteristics, which is not preferable from the viewpoint of the optical element.

  The lower limit of the thickness of the transparent film 20 is more preferably 10 nm, and further preferably 20 nm. The upper limit of the thickness of the transparent film 20 is more preferably 300 nm and even more preferably 200 nm.

(Fluorophosphate glass)
Next, the fluorophosphate glass substrate 10 will be described. The fluorophosphate glass substrate is a substrate made of fluorophosphate glass containing phosphoric acid as a main component and further containing fluorine. The fluorophosphate glass substrate preferably has a thickness of 0.1 to 4 mm. In addition, the optical element is required to have a high visible light transmittance, and the fluorophosphate glass substrate preferably has an average transmittance of 60% or more at 400 to 600 nm.

  In the optical element in the present embodiment, it is preferable to use a fluorophosphate glass substrate made of fluorophosphate glass containing CuO. Thus, by containing CuO, the fluorophosphate glass substrate 10 can exhibit the function of a near infrared cut filter. In the fluorophosphate glass, the content of CuO is more preferably 1 to 15% by weight on the oxide basis.

Fluorophosphate glass substrate, an oxide _basis, P ₂ O 5 20 to 60 wt%, CuO 1 to 15 _{wt%, Al} 2 O 3 _{0~15 wt%,} Na 2 O 0 wt%, Li ₂ O 0-10% by mass, MgO 0-20% by mass, CaO 0-20% by mass, BaO 0-20% by mass, SrO 0-20% by mass, ZnO 0-20% by mass, Sb ₂ O ₃ 0-3% by mass. %, CeO ₂ 0 to 2% by mass, AlF ₃ 0 to 30% by mass, NaF 0 to 20% by mass, LiF 0 to 20%, MgF ₂ 0 to 30% by mass, CaF ₂ 0 to 30% by mass, SrF _A substrate made of glass containing 20-30% by mass, BaF ₂ 0-40% by mass, and containing any of AlF ₃ , NaF, LiF, MgF ₂ , CaF ₂ , SrF ₂ or BaF ₂ is more preferred.

(Optical element manufacturing method)
Next, the manufacturing method of the optical element in this Embodiment is demonstrated based on FIG. In the optical element in the present embodiment, first, as shown in step 102 (S102), a fluorophosphate glass substrate 10 is formed by cutting a fluorophosphate glass containing CuO or the like by dicing or the like. Next, as shown in step 104 (S104), the transparent film 20 is formed by ALD on the front surface, side surface, and back surface of the formed fluorophosphate glass substrate 10.

(Method for forming transparent film 20)
Next, a method for forming the transparent film 20 will be described. In the present embodiment, as an example, a case where a transparent material layer made of Al ₂ O _{3 is} formed by atomic layer deposition as the transparent film 20 will be described.

In forming a transparent material film made of Al ₂ O ₃ , the fluorophosphate glass substrate 10 is placed in a chamber of an ALD apparatus, evacuated, and after reaching a predetermined degree of vacuum, a source gas is supplied. Is done. At this time, the fluorophosphate glass substrate 10 is heated to a predetermined temperature, for example, 200 ° C. In addition, since the fluorophosphate glass has a low glass transition point, it is preferable that the temperature when forming the transparent material film is as low as possible. For example, the substrate temperature when forming the transparent material film on the fluorophosphate glass substrate 10 is preferably 250 ° C. or less.

When Al ₂ O ₃ is formed as the transparent material film, it can be formed by alternately supplying TMA (trimethylaluminum, Al (CH ₃ ) ₃ ) and H ₂ O.

When forming TiO ₂ as a transparent material film, for example, the fluorophosphate glass substrate 10 is heated to about 200 ° C., and TEMAT (tetrakisethylmethylamido titanium (IV), Ti [N (C ₂ H ₅ ) A film can be formed by alternately supplying (CH ₃ )] ₄ ) and H ₂ O.

(Evaluation)
In the present embodiment, the strength of the optical element can be evaluated by a four-point bending test. The four-point bending test can be measured using, for example, a Shimadzu precision universal testing machine (manufactured by Shimadzu Corporation, trade name: Autograph AGC-10kN).

  Next, examples in the present embodiment will be described. Examples 1 and 2 are examples of the present invention, and Example 3 is a comparative example.

  The strength of the optical element produced as described below was evaluated by a four-point bending test using a Shimadzu precision universal testing machine (manufactured by Shimadzu Corporation, trade name: Autograph). A four-point bending test was performed for each 30 sheets, and the average value was defined as the strength of the optical element in each example. The relative values of the intensity of Example 1 and Example 2 with respect to the intensity of Example 3 are shown in FIG.

(Example 1)
As the fluorophosphate glass substrate, a substrate containing P ₂ O ₅ : 20 mass%, CuO: 4 mass%, and Al ₂ O ₃ : 4 mass% was used. A fluorophosphate glass substrate having a thickness of 0.3 mm was used.

As the optical element in Example 1, a fluorophosphate glass substrate was used, and an optical element having a transparent material film containing Al ₂ O ₃ as a main component was prepared by the ALD method according to the following procedure.

In the procedure, a fluorophosphate glass substrate was placed in the chamber of the ALD apparatus. The inside of the chamber was evacuated to a predetermined degree of vacuum. Thereafter, TMA (trimethylaluminum, Al (CH ₃ ) ₃ ) and H ₂ O are alternately supplied to form a transparent material film containing Al ₂ O ₃ as a main component on the entire surface of the fluorophosphate glass substrate. Filmed. At this time, the fluorophosphate glass substrate was heated to 200 ° C. The film thickness of the formed transparent material film was 25 nm.

(Example 2)
The optical element in Example 2 is the same as in Example 1 except that the film formation time is increased, and a transparent material film containing Al ₂ O ₃ as a main component is formed on the entire surface of the fluorophosphate glass substrate. An element was produced. The film thickness of the formed transparent material film was 196 nm.

(Example 3)
The optical element in Example 3 was made of fluorophosphate glass itself without forming Al ₂ O ₃ by the ALD method in Example 1.

The results are shown in FIG. In FIG. 5, the horizontal axis represents the Al ₂ O ₃ film thickness, and the vertical axis represents the four-point bending strength of the optical element of each example, and shows a relative value with respect to the strength of Example 3. FIG. 5 shows that the strength of the optical element is improved by forming a transparent material film on the entire surface of the fluorophosphate glass. As shown in FIG. 5, in Example 1, the 4-point bending strength is 106%, which is 6% higher than Example 3, and in Example 2, the 4-point bending strength is 126%, which is 26% higher than Example 3. did.

  Although the embodiment has been described in detail above, it is not limited to the specific embodiment, and various modifications and changes can be made within the scope described in the claims.

10 Fluorophosphate glass substrate 11 Minute crack 20 Transparent film 30 Supply source

Claims (8)

An optical element having a fluorophosphate glass substrate and a transparent film formed on the entire surface of the fluorophosphate glass substrate,
The optical element, wherein the transparent film has one or more transparent material films containing any one of oxide, nitride, oxynitride or carbide as a main component.   The optical element according to claim 1, wherein the transparent film is a transparent material film containing, as a main component, any one of oxide, nitride, oxynitride, and carbide formed by atomic layer deposition. The optical element according to claim 1, wherein the transparent material film contains any one of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SiO ₂ , AlN, Si ₃ N ₄ , TiON, and AlON as a main component. .   The optical element according to claim 1, wherein the fluorophosphate glass substrate is a substrate made of a fluorophosphate glass containing CuO. The fluorophosphate glass substrate, _component, P ₂ O 5 20 to 60 wt%, CuO 1 to 15 _{wt%, Al} 2 O 3 _{0~15 wt%,} Na 2 O 0 wt%, _Li 2 O 0-10% by mass, MgO 0-20% by mass, CaO 0-20% by mass, BaO 0-20% by mass, SrO 0-20% by mass, ZnO 0-20% by mass, Sb ₂ O ₃ 0-3% by mass. , CeO ₂ 0 to 2% by mass, AlF ₃ 0 to 30% by mass, NaF 0 to 20% by mass, LiF 0 to 20%, MgF ₂ 0 to 30% by mass, CaF ₂ 0 to 30% by mass, SrF _{2 to} 30% by mass, BaF _{2 to} 40% by mass, and a substrate made of glass containing any one of AlF ₃ , NaF, LiF, MgF ₂ , CaF ₂ , SrF ₂ or BaF ₂ . The optical element according to any one of 4 Child. Forming a fluorophosphate glass substrate by cutting the fluorophosphate glass;
Forming a transparent film on the entire surface of the fluorophosphate glass substrate by atomic layer deposition;
Have
The method for manufacturing an optical element, wherein the transparent film has at least one transparent material film containing any one of oxide, nitride, oxynitride, and carbide as a main component.   The method for producing an optical element according to claim 6, wherein the fluorophosphate glass substrate is a substrate made of fluorophosphate glass containing CuO. The step of forming the transparent film is to form the transparent film by setting the temperature of the fluorophosphate glass substrate to 250 ° C. or less and alternately supplying TMA (trimethylaluminum) and H ₂ O. A method for producing an optical element according to claim 6 or 7.

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