JP2023166765A - Optical element, light source device, image projection device, and method for manufacturing optical element - Google Patents

Abstract

To provide an optical element that prevents a reduction in performance when irradiated with high intensity light for a long time.SOLUTION: An optical element has a substrate, and an optical element part formed of a material including organopolysiloxane as a main component on the substrate. For the optical element, when (C/Si)a is the average value of the atomic concentration ratios of carbon atoms to silicon atoms within a range from 0.5 μm to 3 μm toward the substrate from a surface on the opposite side of a surface of the optical element part in contact with the substrate, and (C/Si)b is the average value of the atomic concentration ratios of carbon atoms to silicon atoms within a range from 0.5 μm to 3 μm toward the inside of an optical element layer from the surface of the optical element part in contact with the substrate, (C/Si)a is larger than (C/Si)b.SELECTED DRAWING: Figure 3

Description

The present invention relates to an optical element, a light source device, an image projection device, and a method for manufacturing an optical element.

In recent years, diffractive optical elements have been combined with laser light sources and used in some electronic devices such as projectors as described in Patent Document 1. The diffractive optical element described in Patent Document 1 includes a diffractive optical section having a diffractive structure formed on a transparent base material made of an inorganic material such as glass. It is desirable that the material constituting the diffractive optical part has heat resistance and light resistance, and Patent Document 1 discloses a siloxane-based resin material having a skeleton of siloxane bonds as the material.

Japanese Patent Application Publication No. 2014-228674

Patent Document 1 discloses an example in which the intensity of light irradiated to the diffractive optical element is, for example, 60 W/cm ² . However, when irradiated with light of higher intensity, for example, about 300 W/cm ² for a long time, even when a siloxane resin material is used as the material constituting the diffractive optical part as in Patent Document 1, the diffractive optical element becomes There were cases where the diffraction efficiency decreased.

The present invention has been made in view of the above problems. That is, an object of the present invention is to provide an optical element that suppresses deterioration in performance when irradiated with high-intensity light for a long time.

An optical element according to one aspect of the present invention is an optical member having a base material, and an optical element portion made of a material containing organopolysiloxane as a main component on the base material, wherein the optical element portion is , the average value of the atomic concentration ratio of carbon atoms to silicon atoms in the range of 0.5 μm to 3 μm toward the base material from the surface of the optical element portion opposite to the surface in contact with the base material ( C/Si)a, the average atomic concentration ratio of carbon atoms to silicon atoms in the range of 0.5 μm to 3 μm from the surface where the optical element portion and the base material are in contact toward the inside of the optical element portion. When the value is (C/Si)b, it is characterized in that (C/Si)a is larger than (C/Si)b.

Further, a method for manufacturing an optical element according to another aspect of the present invention is a method for manufacturing an optical element including a step of forming an optical element portion on a base material, wherein the step of forming the optical element portion is , a step of performing post-processing, and the optical element portion formed through the post-processing is 0.0. The atomic concentration ratio of carbon atoms to silicon atoms in the range of 5 μm to 3 μm is (C/Si)a, and the ratio is 0.000 mm from the surface where the optical element portion and the base material are in contact into the optical element portion. It is characterized in that (C/Si)a is larger than (C/Si)b, where (C/Si)b is the atomic concentration ratio of carbon atoms to silicon atoms in the range of 5 μm to 3 μm.

According to the present invention, it is possible to provide an optical element that suppresses deterioration in performance when irradiated with high-intensity light for a long period of time.

FIG. 1 is an explanatory diagram showing a projector as an image projection device, which is an example of an electronic device including an optical element according to a first embodiment. FIG. 2 is an explanatory diagram of a light source device having an optical element according to a first embodiment. (a) is a top view showing the optical element according to the first embodiment, and (b) is a sectional view showing the optical element according to the first embodiment. (a) to (h) are explanatory diagrams of the method for manufacturing the diffractive optical element according to the first embodiment. FIG. 3 is a diagram showing the results of a surface analysis performed by EDS on a cross section of a diffractive optical element portion of the optical element according to Example 1. FIG. 7 is a diagram showing the results of a surface analysis performed by EDS on a cross section of a diffractive optical element portion of an optical element according to Comparative Example 1.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is an explanatory diagram showing a projector as an image projection device, which is an example of an electronic device including an optical element according to a first embodiment.

The projector 500 includes a projector optical system 550 and a control device 530 that controls the optical system 550. The optical system 550 includes a light source device 501 and a plurality of optical elements (polarization conversion element 502 to projection lens 511).

The light source device 501 emits white light 602. White light 602 consists of red light 602r, green light 602g, and blue light 602b shown by dotted lines. The red light 602r, the green light 602g, and the blue light 602b are incident on the polarization conversion element 502, where they are converted into linearly polarized light having a uniform polarization direction and converted into red illumination light 604r and green illumination light 604g, which are shown by solid lines. , and converted into blue illumination light 604b. These red illumination light 604r, green illumination light 604g, and blue illumination light 604b are separated by dichroic mirror 503 into red illumination light 604r, blue illumination light 604b, and green illumination light 604g.

The green illumination light 604g passes through a polarization beam splitter (hereinafter referred to as PBS) 504, which is a polarization separation element, and a phase compensation plate 505g, and reaches a light modulation element 506g. The red illumination light 604r and the blue illumination light 604b pass through the polarizing plate 507 and enter the color selective phase plate 508. The color selective phase plate 508 rotates the polarization direction of the blue illumination light 604b by 90 degrees while maintaining the polarization direction of the red illumination light 604r.

Red illumination light 604r emitted from color-selective phase plate 508 passes through PBS 509 and phase compensation plate 505r, and reaches light modulation element 506r. The blue illumination light 604b emitted from the color selective phase plate 508 is reflected by the PBS 509, passes through the phase compensation plate 505b, and reaches the light modulation element 506b. Each light modulation element 506r, 506g, 506b is configured by a reflective liquid crystal panel or a digital micromirror device. Note that it is also possible to use transmissive liquid crystal panels as the light modulation elements 506r, 506g, and 506b.

Control device 530 controls light modulation elements 506r, 506g, and 506b according to input image data. As a result, the light modulation elements 506r, 506g, and 506b image-modulate the incident red illumination light 604r, green illumination light 604g, and blue illumination light 604b to generate red image light 615r, green image light 615g, and blue image light. 615b.

These red image light 615r, green image light 615g, and blue image light 615b are combined via the PBSs 504 and 509 and a combining prism 510, and projected onto a projection surface such as a screen by a projection lens 511. As a result, a color image is displayed as a projected image.

FIG. 2 is an explanatory diagram of a light source device having an optical element according to the first embodiment. The light source device 501 includes a plurality of laser light sources 41, a diffractive optical element 10 as an optical element according to the first embodiment, and a phosphor 43. The diffractive optical element 10 is arranged on the light emitting side with respect to the plurality of laser light sources 41, and the phosphor 43 is arranged on the light emitting side with respect to the diffractive optical element 10.

The laser light source 41 includes, for example, a semiconductor laser. The plurality of laser light sources 41 may include a laser light source that emits laser light 44 of at least one color among red, green, and blue. It is preferable to include a laser light source that emits at least blue laser light 44 (having a wavelength within the range of 400 nm to 460 nm, for example). Each laser light source 41 emits laser light 44 with an irradiation intensity of approximately 300 W/cm ² . Each laser light source 41 is driven and controlled by a control device 530 shown in FIG. When the plurality of laser light sources 41 include laser light sources that emit red, green, and blue colors, the phosphor 43 can be omitted. Red light and green light have lower energy than blue light even at the same irradiation intensity, so the diffractive optical element 10 that is irradiated with red light or green light may not suffer from a decrease in diffraction efficiency. In that case, a conventional diffractive optical element may be used as the diffractive optical element 10 that is irradiated with red light or green light.

The plurality of laser light sources 41 are arranged in an array and irradiate the diffractive optical element 10 with laser light 44. The laser beam 44 that has passed through the diffractive optical element 10 is irradiated onto the phosphor 43 . The diffractive optical element 10 includes a base material 12 and a diffractive optical element section 13 as an optical element section on the base material 12.

FIG. 3(a) is a top view showing the diffractive optical element 10 according to the first embodiment, and FIG. 3(b) is a top view of the diffractive optical element 10 according to the first embodiment. FIG. 3 is an enlarged view of a part of the cross section taken along the line AA'.

As described above, the diffractive optical element 10 includes the base material 12 and the diffractive optical element section 13 provided on the base material 12. The diffractive optical element section 13 has a diffractive structure 14 having an uneven shape for diffracting light on the surface opposite to the surface in contact with the base material 12 .

The diffractive optical element 10 further includes a flat part 15 having a flat surface, which is formed integrally with the diffractive optical element part 13 on the base material 12. In the diffractive optical element 10, a plurality of diffractive optical element parts 13 are arranged in an array on the base material 12.

Each diffractive optical element section 13 is irradiated with a circular or elliptical laser beam 44 by a corresponding laser light source 41 . The circular or elliptical laser beam 44 irradiated onto each diffractive optical element section 13 is focused onto the phosphor 43 in a predetermined shape by the corresponding diffractive optical element section 13 . The predetermined shape is, for example, a rectangle. By focusing the laser beam 44 into a rectangular shape according to the shape of the light modulation elements 506r, 506g, and 506b such as reflective liquid crystal panels, the light can be used uniformly and without waste.

As the material used for the phosphor 43, for example, cerium-doped yttrium aluminum oxide (YAG:Ce) or the like is used. A part of the blue laser light 44 irradiated onto the phosphor 43 excites the phosphor 43 and is converted into yellow light. White light 602 is generated by combining this yellow light and the remainder of blue laser light 44. White light 602 emitted as diffused light from the phosphor 43 is converted into parallel light by a collimator lens (not shown), and uniformly distributed light is emitted from the light source device 501.

The base material 12 is an inorganic light-transmitting base material, and is made of a material that transmits at least blue light, for example, a material that transmits visible light having a wavelength of 380 nm or more and 780 nm or less. The base material 12 is preferably made of a material having a sufficient transmittance, specifically, a transmittance of 90% or more so that the irradiated light can pass therethrough, and glass is used, for example.

Glasses include zirconium oxide, titanium oxide, tantalum oxide, niobium oxide, hafnium oxide, lanthanum oxide, lithium oxide, gadolinium oxide, silicon oxide, calcium oxide, barium oxide, sodium oxide, potassium oxide, boron oxide, and aluminum oxide. An inorganic glass containing at least one component selected from the group consisting of:

As the base material 12, a glass base material formed by grinding, polishing, molding, float molding, etc. can be used. In order to improve the adhesion between the base material 12 and the diffractive optical element part 13 and the flat part 15, the strength of the base material 12, the flatness of the base material 12, etc., the surface of the base material 12 may be cleaned or polished. You may also do so. Further, an adhesive layer, a hard coat layer, a refractive index adjusting layer, etc. may be provided between the base material 12, the diffractive optical element section 13, and the flat section 15.

The diffractive optical element portion 13 and the flat portion 15 are made of a material containing organopolysiloxane as a main component. Organopolysiloxane contains siloxane bonds with high bond energy in its main skeleton and has high light resistance. Therefore, since the diffractive optical element section 13 is made of a material containing organopolysiloxane as a main component, deterioration of the diffractive optical element section 13 due to irradiation of the diffractive optical element section 13 with light is suppressed. In particular, when the intensity of the light passing through the diffractive optical element section 13 exceeds 100 W/cm ² or when the light passing through the diffractive optical element section 13 has high photon energy, such as blue light, the diffractive optical element It is effective to use a material containing siloxane as a main component for the portion 13. The organopolysiloxane may be, for example, silicone (silicone rubber, silicone resin).

Organopolysiloxanes are usually obtained by curing curable silicones. Curable silicones are classified into addition reaction silicones and condensation reaction silicones depending on their curing mechanism, and either of them can be used. The type of organopolysiloxane can be appropriately selected based on ease of transferring the shape of the diffraction structure 14 and ease of controlling the fluidity of the material. Curing methods include heat curing, ultraviolet curing, and moisture curing, but ultraviolet curing is preferred because it can uniformly cure the inside of the cured product and there is less stress remaining in the cured product. With ultraviolet curing, for example, when transferring the shape of the diffraction structure 14 with high precision, there is no need to heat the resin before and after the transfer, and the diffraction structure 14 can be formed with high precision.

Raw materials for forming organopolysiloxanes include organopolysiloxanes having single or multiple alkenyl groups in the molecule and organohydrogenpolysiloxanes having single or multiple silicon-bonded hydrogen atoms in the molecule. Other crosslinkable reactive groups include radically polymerizable functional groups with ethylenic double bonds such as vinyl groups, allyl groups, and alkenyl groups such as isopropenyl groups, epoxy groups, oxetane groups, and alicyclic groups. It may have a cationically polymerizable functional group such as an epoxy group and a vinyl ether group. The organopolysiloxane formed from such raw materials may be linear, may include a branched structure as part of its molecular structure, or may be cyclic. Further, they may be three-dimensionally cross-linked in a network shape.

The diffractive optical element portion 13 has a distribution in the ratio of silicon atomic concentration to carbon atomic concentration in the thickness direction. Here, the thickness direction is a direction perpendicular to the surface where the base material 12 and the diffractive optical element portion 13 are in contact, that is, a direction along the traveling direction of the laser beam 44 incident on the diffractive optical element 10. In the thickness direction of the diffractive optical element part 13, from the surface of the diffractive optical element part 13 opposite to the surface in contact with the base material 12 toward the base material 12, the silicon atoms are The average value of the atomic concentration ratio of carbon atoms is defined as the surface side ratio (C/Si)a. On the other hand, in the thickness direction of the diffractive optical element part 13, from the surface where the diffractive optical element part 13 and the base material 12 are in contact with each other, in the range of 0.5 μm to 3 μm toward the inside of the diffractive optical element part 13, The average value of the atomic concentration ratio of carbon atoms is defined as the base material side ratio (C/Si)b. At this time, the diffractive optical element 10 according to the present embodiment is characterized in that the surface side ratio (C/Si) a is larger than the base material side ratio (C/Si) b. As a result, even when the laser light 44 having a high intensity of about 300 W/cm ² is irradiated from the laser light source 41 for a long period of time, the performance of the diffractive optical element 10 deteriorates. Decrease in diffraction efficiency can be suppressed. The surface side ratio (C/Si) a is preferably 1.5 times or more the base material side ratio (C/Si) b.

The reason why the diffractive optical element 10 according to the present embodiment, having the above-mentioned characteristics, can suppress performance deterioration even when irradiated with high-intensity light for a long period of time is as follows. It will be done.

Organopolysiloxane, which is the main component of the material of the diffractive optical element part 13, is produced through polymerization reaction parts in which molecular chains containing siloxane bonds that constitute the main skeleton of organopolysiloxane are bonded by polymerization of acrylic groups, epoxy groups, etc. They are connected three-dimensionally. In addition, a small amount of low-molecular-weight siloxane, such as cyclic siloxane such as hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane, remains in the material constituting the optical element portion, which is not incorporated into the three-dimensional bonds described above. ing. The main component here refers to a component that accounts for 80% by volume or more of the material.

Low-molecular siloxane has high volatility and is present non-uniformly in the diffractive optical element section 13 compared to the three-dimensionally bonded siloxane bond chains and polymerization reaction parts. Regarding the atomic concentration ratio of carbon atoms to silicon atoms, the fact that the surface side ratio (C/Si) a is larger than the base material side ratio (C/Si) b means that the side of the diffractive optical element section 13 from which light is emitted This corresponds to the fact that the content of low-molecular-weight siloxane near the surface is small. That is, since the polymerization reaction parts formed by polymerization of the organic groups of the organopolysiloxane are uniformly distributed in the diffractive optical element part 13, the carbon atoms in the diffractive optical element part 13 are also uniformly distributed. It is distributed. On the other hand, the content of low-molecular-weight siloxane that does not have carbon atoms is small near the light-emitting surface of the diffractive optical element section 13, and as a result, the surface side ratio (C/Si) a is , is a larger value than the base material side ratio (C/Si) b.

In the diffractive optical element 10 according to the present embodiment, the amount of highly volatile low-molecular-weight siloxane remaining near the surface of the diffractive optical element section 13 on the light output side is small, so that the high-intensity laser beam 44 can be emitted for a long time. Even when irradiated for a long time, deformation due to volatilization and increase in refractive index can be suppressed. Thereby, a decrease in diffraction efficiency can be prevented.

In addition, a relatively large amount of low-molecular-weight siloxane with high fluidity remains in the three-dimensional structure of the organopolysiloxane molecular chain near the surface of the diffractive optical element portion 13 that is in contact with the base material 12. are doing. As a result, when the diffractive optical element portion 13 is irradiated with the high-intensity laser beam 44 for a long time in the vicinity of the surface in contact with the base material 12, cracks occur due to the release of residual stress and expansion due to heat generation. This can be suppressed. As a result, a decrease in the diffraction efficiency of the diffractive optical element 10 can be suppressed. If the surface side ratio (C/Si) a is 1.5 times or more the base material side ratio (C/Si) b, the above-mentioned effects can be obtained to a higher degree.

In addition, in the diffractive optical element 10 according to the present embodiment, silicon atoms in a range of 0.5 μm to 3 μm from the surface of the flat portion 15 opposite to the surface in contact with the base material 12 toward the base material 12. The atomic concentration ratio of carbon atoms to (C/Si)c is defined as (C/Si)c. At this time, (C/Si)a is preferably 0.9 times or more and 1.1 times or less of (C/Si)c.

The flat part 15 located around the diffractive optical element part 13 to which the high-intensity laser beam 44 is irradiated for a long time has the same composition as the diffractive optical element part 13, so that the high-intensity laser beam 44 can be irradiated for a long time. Changes in surface shape due to thermal expansion during irradiation can be alleviated. When (C/Si)a is 0.9 times or more as large as (C/Si)c, it is possible to suppress changes in the surface shape due to thermal expansion of the diffractive optical element portion 13 greater than that of the flat portion 15. Furthermore, by setting (C/Si)a to 1.1 times or less of (C/Si)c, changes in the surface shape due to thermal expansion of the flat portion 15 greater than that of the diffractive optical element portion 13 can be suppressed. Can be done.

The thickness of the flat portion 15 may be determined by taking into consideration the ease of molding and the ease with which cracks occur in the material, but it is preferably 20 μm or more. By setting the thickness of the flat portion 15 to 20 μm or more, it is possible to suppress the generation of cracks even when the low molecular weight siloxane volatilizes on the light-emitting side surface of the diffractive optical element portion 13.

The atomic concentration ratio of carbon atoms to silicon atoms in the diffractive optical element portion 13 and the flat portion 15 can be measured by the following method.
First, cross sections of the diffractive optical element portion 13 and the flat portion 15 are cut out at five locations and enlarged using an electron microscope. Next, five locations are subjected to area analysis using energy dispersive X-ray spectroscopy (EDS). The surface analysis is performed so that information about the entire film can be obtained at each of the five locations. Based on the intensity values of silicon atoms and carbon atoms in the film thickness direction (direction perpendicular to the base material 12) detected by surface analysis, the carbon atoms relative to the silicon atoms are calculated for a predetermined range in the film thickness direction. Calculate the average value of the concentration ratio. The average values obtained for the five locations are further averaged to determine the atomic concentration ratio of carbon atoms to silicon atoms.

It is preferable that the diffractive optical element 10 according to the present embodiment further includes a coating layer on the surface of the diffractive optical element section 13 on the side from which light is emitted. Since the diffractive optical element 10 further includes a coating layer, it is possible to suppress deformation and increase in refractive index due to rapid volatilization of low-molecular-weight siloxane when irradiated with high-intensity laser light 44 for a long time. In addition, when the diffractive optical element 10 further has a coating layer, it is preferable that the coating layer is formed so as to cover not only the diffractive optical element part 13 but also the flat part 15 at the same time.

The coating layer preferably contains an inorganic oxide or an inorganic fluoride as a main component. Examples of the inorganic oxide include silicon oxide, titanium oxide, tantalum oxide, and zirconium oxide. Examples of the inorganic fluoride include magnesium fluoride. In particular, since the diffractive optical element part 13 is made of a material containing organopolysiloxane as a main component, the covering layer has good compatibility with organopolysiloxane from the viewpoint of adhesion between the diffractive optical element part 13 and the covering layer. It is preferable to contain silicon oxide as a main component.

The covering layer may consist of one layer or may consist of a plurality of layers. Further, the thickness of the coating layer is preferably 40 nm or more and 500 nm or less. If the thickness of the coating layer is 40 nm or more, it is possible to effectively suppress rapid volatilization of low-molecular-weight siloxane when irradiated with high-intensity laser light 44 for a long time. In addition, if the thickness of the coating layer is 500 nm or less, the stress in the coating layer will not become too large, and the deformation of the diffractive optical element portion 13 will be suppressed when the high-intensity laser beam 44 is irradiated for a long time. can do.

Next, an example of a method for manufacturing the diffractive optical element 10 according to the first embodiment will be described.
The method for manufacturing the diffractive optical element 10 according to the first embodiment includes a step of forming a diffractive optical element section 13 as an optical element section on a base material 12, and the step of forming the diffractive optical element section 13 is performed later. It includes the step of performing processing. Then, regarding the diffractive optical element portion 13 formed through post-processing, a thickness of 0.5 μm to 3 μm from the surface of the diffractive optical element portion 13 opposite to the surface in contact with the base material 12 in the direction of the base material 12 is applied. The atomic concentration ratio of carbon atoms to silicon atoms in the range is defined as (C/Si)a. In addition, the atomic concentration ratio of carbon atoms to silicon atoms (C/Si ) b. At this time, (C/Si)a is larger than (C/Si)b.

The step of forming the diffractive optical element section 13 on the base material 12 preferably includes the following steps.
(1) A step of placing a raw material containing organopolysiloxane as a main component on the base material 12.
(2) A step of sandwiching and pressing the raw material between the base material 12 and the mold member.
(3) A step of curing the raw material to form the diffractive optical element portion 13 made of a material whose main component is organopolysiloxane.
(4) A step of releasing the mold member from the diffractive optical element section 13.
(5) A step of post-processing the diffractive optical element section 13.

Further, the step of forming the diffractive optical element section 13 on the base material 12 includes (4) a step of releasing the mold member from the diffractive optical element section 13, and (5) post-processing the diffractive optical element section 13. It is more preferable to include a step of forming a coating layer on the diffractive optical element portion 13 between the step and the step.

FIGS. 4(a) to 4(h) are explanatory diagrams of a method for manufacturing the diffractive optical element 10 according to the first embodiment.

First, as shown in FIG. 4A, a transfer mold 81 as a mold member including a surface having a shape corresponding to the diffraction structure 14 is prepared. As the transfer mold 81, for example, quartz or the like can be used. A mold release agent 82 is applied to the transfer surface of the transcription mold 81 so that subsequent mold release can be performed smoothly. As the mold release agent 82, for example, a fluorine-based coating agent or the like can be used.

Next, as shown in FIG. 4(b), a certain amount of a raw material 83 whose main component is a raw material for organopolysiloxane is placed on one surface of the base material 12. When placing the raw material 83, it is preferable to take measures so that no air pockets such as bubbles remain in the raw material 83 or between the raw material 83 and the base material 12.

Next, as shown in FIG. 4(c), the raw material 83 placed on the base material 12 and the transfer surface of the transfer mold 81 are made to face each other, and the raw material 83 is transferred to the base material 12 as shown in FIG. 4(d). It is sandwiched between the mold 81 and a pressing force F is applied. At this time as well, it is preferable to carry out evacuation, for example, so that no air pockets remain in the raw material 83.

Next, as shown in FIG. 4(e), the pressurized raw material 83 is irradiated with ultraviolet rays (UV) to harden the raw material 83. UV may be irradiated from the base material 12 side or from the transfer mold 81 side. As a result, a hardened member 84 is formed. After the curing of the curing member 84 has sufficiently progressed, the transfer mold 81 is released from the curing member 84 as shown in FIG. 4(f), thereby producing a diffractive optical element having the diffractive structure 14 shown in FIG. 4(g). A section 13 is formed. Thereafter, as shown in FIG. 4(h), a coating layer 16 is formed on the surface of the diffractive optical element section 13, and then the diffractive optical element section 13 is subjected to post-treatment. In this embodiment, it is preferable that the flat portion 15 is also formed integrally with the diffractive optical element portion 13 at the same time. At this time, it is preferable that the coating layer is formed so as to cover not only the diffractive optical element section 13 but also the flat section 15 at the same time, and post-treatment is also performed on the flat section at the same time as the diffractive optical element section 13. It is preferable that

The post-processing process may be performed using any process that makes (C/Si)a larger than (C/Si)b without impairing the performance of the diffractive optical element portion 13 that has undergone post-processing. It may also be a process. Examples of post-treatment steps include heating and drying under reduced pressure. By performing these post-treatments on the diffractive optical element section 13, the low-molecular-weight siloxane can be volatilized from the surface of the diffractive optical element section 13 opposite to the surface in contact with the base material 12.

The post-treatment is preferably a heat treatment because it can effectively volatilize low molecular weight components. For example, heat treatment can be performed at a temperature within the range of 100-200°C. In particular, the heat treatment as a post-treatment is preferably performed at a temperature of 120° C. or higher and a heating time of 2 hours or longer. By applying heat treatment to the diffractive optical element section 13 as a post-treatment, low molecular weight siloxane is uniformly removed within the surface of the diffractive optical element section 13 from the surface opposite to the surface in contact with the base material 12. be able to. By uniformly removing the low-molecular-weight siloxane from the surface of the diffractive optical element section 13 opposite to the surface in contact with the base material 12, the stress between the irradiated part and the non-irradiated part of the laser beam 44 can be reduced. It is possible to reduce the difference in deformation due to heating and heat generation, and it is possible to effectively suppress the occurrence of cracks.

Further, the post-treatment may be drying under reduced pressure, and specifically, it is preferable to dry under reduced pressure of 50 Pa or less for 2 hours or more. Moreover, heating and decompression treatment may be performed as a post-treatment in combination with the above-mentioned heat treatment.

In the above example, the step of forming the coating layer 16 is performed before the step of performing post-treatment, but it may be performed after the step of performing post-treatment. By performing the post-treatment while the diffractive optical element portion 13 has the coating layer 16, it is possible to suppress the rapid volatilization of the low molecular weight siloxane, and as a result, the diffractive optical element due to the rapid volatilization of the low molecular weight siloxane can be suppressed. The occurrence of cracks in the element portion 13 can be suppressed. Therefore, the step of forming the coating layer 16 is preferably performed before the step of performing post-treatment.

In the step of forming the covering layer 16, a dry film forming method such as a vapor deposition method or a sputtering method, or a wet film forming method using a coating liquid such as a spin coating method, a spray coating method, or a dip coating method can be used. can. From the viewpoint of the ability of the layer to follow the complex shape of the diffraction structure 14, a dry film forming method is preferable, and a wet film forming method is preferably a spin coating method or a spray coating method.

[Example]
Next, the optical element according to the first embodiment will be further explained using Examples and Comparative Examples, but the embodiments of the present invention are not limited to the specific examples shown in the Examples below. do not have.

(Example 1)
A glass base material 12 is prepared, and a diffractive optical element portion 13 having a diffractive structure 14 is formed on the surface of the base material 12 using a siloxane-based UV curing resin (product name: KER-4000-UV, manufactured by Shin-Etsu Chemical Co., Ltd.). Formed. The process for forming the diffractive optical element section 13 having the diffractive structure 14 is as described using FIGS. 4(a) to 4(g). Further, a flat portion 15 is formed around the diffractive optical element portion 13 . Thereafter, a coating layer 16 was formed on the diffractive optical element portion 13, and then post-processing was performed.

A sputtering method was used to form the covering layer 16. A silicon oxide film was formed on the surface of the diffractive optical element part 13 by sputtering so that the layer thickness was 80 nm. Subsequently, as a post-treatment step, heating was performed for 96 hours in a hot air circulation oven heated to 180°C.

Regarding the diffractive optical element 10 according to Example 1 manufactured as described above, the initial diffraction efficiency when transmitting and diffracting the laser beam 44 with a wavelength of 455 nm (300 W/cm ² ) and the irradiation with the laser beam 44 for 1000 hours. The subsequent diffraction efficiency was measured. As a result, the initial diffraction efficiency was 97.5%, and the diffraction efficiency after irradiation with the laser beam 44 for 1000 hours was also 97.5%.

FIG. 5 shows the results of cutting out a cross section of the diffractive optical element portion 13 of the diffractive optical element 10 according to Example 1 produced above and performing surface analysis by EDS using an electron microscope. In addition, in FIG. 5, the distance from the surface of the diffractive optical element section 13 opposite to the surface in contact with the base material 12 toward the direction of the base material 12 is shown as the position in the thickness direction.

As shown in FIG. 5, in the diffractive optical element 10 according to Example 1, the atomic concentration of carbon atoms relative to silicon atoms is The ratio (vertical axis C/Si in FIG. 5) showed a high value. When the surface side ratio (C/Si) a and the base material side ratio (C/Si) b were calculated from the results of the surface analysis with EDS, the surface side ratio (C/Si) a was 2.42, and the base material side ratio (C/Si) a was 2.42. The material side ratio (C/Si) b was 1.08. Further, the flat portion 15 having no diffraction structure 14 was similarly subjected to EDS surface analysis, and (C/Si)c was calculated to be 2.40.

(Example 2)
In Example 2, an optical element was produced in the same manner as in Example 1, except that the coating layer 16 was not formed on the diffractive optical element portion 13.
Regarding the diffractive optical element 10 according to Example 2, as in Example 1, the initial diffraction efficiency when transmitting and diffracting the laser beam 44 with a wavelength of 455 nm (300 W/cm ² ) and the irradiation with the laser beam 44 for 1000 hours. After that, the diffraction efficiency was measured. As a result, the initial diffraction efficiency was 97.1%, and the diffraction efficiency after irradiation with the laser beam 44 for 1000 hours was also 97.1%.
Further, regarding the diffractive optical element 10 according to Example 2, a cross section was cut out and a surface analysis was performed in the same manner as in Example 1. As a result, the surface side ratio (C/Si)a was 2.72, the base material side ratio (C/Si)b was 1.20, and (C/Si)c was 2.67.

(Example 3)
In Example 3, an optical element was produced in the same manner as in Example 1, except that the heating conditions in the post-treatment were heating in a hot air circulation oven at 150° C. for 96 hours.
Regarding the diffractive optical element 10 according to Example 3, as in Example 1, the initial diffraction efficiency when transmitting and diffracting the laser beam 44 with a wavelength of 455 nm (300 W/cm ² ) and the laser beam irradiation for 1000 hours. The subsequent diffraction efficiency was measured. As a result, the initial diffraction efficiency was 97.4%, and the diffraction efficiency after irradiation with the laser beam 44 for 1000 hours was 96.7%.
Further, regarding the diffractive optical element 10 according to Example 3, a cross section was cut out and a surface analysis was performed in the same manner as in Example 1. As a result, the surface side ratio (C/Si) a was 1.62, the base material side ratio (C/Si) b was 1.08, and (C/Si) c was 1.59.

(Example 4)
In Example 4, an optical element was produced in the same manner as in Example 1, except that the heating conditions in the post-treatment were heating in a hot air circulation oven at 150° C. for 24 hours.
Regarding the diffractive optical element 10 according to Example 4, as in Example 1, the initial diffraction efficiency when transmitting and diffracting the laser beam 44 with a wavelength of 455 nm (300 W/cm ² ) and the laser beam irradiation for 1000 hours. The subsequent diffraction efficiency was measured. As a result, the initial diffraction efficiency was 96.9%, and the diffraction efficiency after irradiation with the laser beam 44 for 1000 hours was 88.4%.
Further, regarding the diffractive optical element 10 according to Example 4, a cross section was cut out and a surface analysis was performed in the same manner as in Example 1. As a result, the surface side ratio (C/Si)a was 1.31, the base material side ratio (C/Si)b was 1.08, and the (C/Si)c was 1.33.

(Comparative example 1)
In Comparative Example 1, an optical element was produced in the same manner as in Example 1, except that the formation of the coating layer 16 and the post-treatment were not performed.
Regarding the diffractive optical element 10 according to Comparative Example 1, as in Example 1, the initial diffraction efficiency when transmitting and diffracting laser light with a wavelength of 455 nm (300 W/cm ² ) and after irradiation with laser light for 1000 hours The diffraction efficiency of each was measured. As a result, the initial diffraction efficiency was 97.1%, and the diffraction efficiency after irradiation with the laser beam 44 for 1000 hours was 76.4%.

Further, regarding the diffractive optical element 10 according to Comparative Example 1, a cross section of the diffractive optical element portion 13 was cut out and surface analysis was performed in the same manner as in Example 1. The results are shown in FIG. In addition, in FIG. 6, the distance from the surface of the diffractive optical element section 13 opposite to the surface in contact with the base material 12 toward the direction of the base material 12 is shown as the thickness direction position.
As shown in FIG. 6, in the diffractive optical element 10 according to Comparative Example 1, no distribution was observed in the thickness direction in the atomic concentration ratio of carbon atoms to silicon atoms (vertical axis C/Si in FIG. 6). From the results of the surface analysis by EDS, the surface side ratio (C/Si) a, the base material side ratio (C/Si) b, and (C/Si) c were calculated. As a result, the surface side ratio (C/Si) a was 1.08, the base material side ratio (C/Si) b was 1.09, and (C/Si) c was 1.08.

(Comparative example 2)
In Comparative Example 2, an optical element was produced in the same manner as in Example 1, except that no post-treatment was performed.
Regarding the diffractive optical element 10 according to Comparative Example 2, as in Example 1, the initial diffraction efficiency when transmitting and diffracting the laser beam 44 with a wavelength of 455 nm (300 W/cm ² ) and the laser beam irradiation for 1000 hours. The subsequent diffraction efficiency was measured. As a result, the initial diffraction efficiency was 97.3%, and the diffraction efficiency after irradiation with the laser beam 44 for 1000 hours was 81.2%.
Further, regarding the diffractive optical element 10 according to Comparative Example 2, a cross section was cut out and surface analysis was performed in the same manner as in Example 1. As a result, the surface side ratio (C/Si) a was 1.08, the base material side ratio (C/Si) b was 1.09, and (C/Si) c was 1.08.

(Comparative example 3)
In Comparative Example 3, an optical element was produced in the same manner as in Example 2, except that the diffractive optical element portion 13 was irradiated with a laser beam 44 having a wavelength of 455 nm (1200 W/cm ² ) for 200 hours instead of the post-treatment.
Regarding the diffractive optical element 10 according to Comparative Example 3, as in Example 1, the initial diffraction efficiency when transmitting and diffracting the laser beam 44 with a wavelength of 455 nm (300 W/cm ² ) and the laser beam irradiation for 1000 hours. The subsequent diffraction efficiency was measured. As a result, the initial diffraction efficiency was 85.2%, and the diffraction efficiency after irradiation with the laser beam 44 for 1000 hours was 74.3%.
Further, regarding the diffractive optical element 10 according to Comparative Example 3, a cross section was cut out and a surface analysis was performed in the same manner as in Example 1. As a result, the surface side ratio (C/Si) a was 1.83, the base material side ratio (C/Si) b was 1.10, and (C/Si) c was 1.08.

Table 1 summarizes the results obtained for the diffractive optical elements 10 according to Examples 1 to 4 and Comparative Examples 1 to 3.
Regarding diffraction efficiency, A indicates that the amount of change before and after irradiating the laser beam 44 for 1000 hours is 1.0% or less, and A indicates that the amount of change is greater than 1.0% and 10.0% or less. B. Cases where the amount of change was greater than 10.0% were evaluated as C.

As shown in Table 1, by performing the post-processing, the surface side ratio (C/Si) a of the diffractive optical element 10 became a larger value than the base material side ratio (C/Si) b. As a result, it was confirmed that high diffraction efficiency could be maintained even after irradiation with high-intensity laser light 44 for 1000 hours.

Furthermore, if the surface side ratio (C/Si) a is 1.5 times or more the base material side ratio (C/Si) b, the diffraction efficiency before and after irradiation with the high-intensity laser beam 44 for 1000 hours is The amount of change was 1.0% or less, and a high effect of suppressing the decrease in diffraction efficiency could be obtained.

On the other hand, in Comparative Example 1 in which the formation of the coating layer 16 and the post-treatment were not performed, the amount of change in diffraction efficiency before and after irradiation with the high-intensity laser beam 44 for 1000 hours was greater than 10%. Similarly, in Comparative Example 2 in which no post-treatment was performed, the amount of change in diffraction efficiency before and after irradiation with laser light 44 for 1000 hours was greater than 10%. In both Comparative Examples 1 and 2, the base material side ratio (C/Si) b was larger than the surface side ratio (C/Si) a.

Furthermore, in Comparative Example 3 as well, the amount of change in diffraction efficiency before and after irradiation with laser light 44 for 1000 hours was greater than 10%. In Comparative Example 3, the values of (C/Si)a1 and (C/Si)c are significantly different, and (C/Si)a1 has a value larger than 1.1 times that of (C/Si)c. Ta.

In addition to the projector 500, the optical element according to the present invention can be used in digital cameras, digital video cameras, electronic view finders (EVFs), in-vehicle equipment, head-up displays, and the like.

Disclosures related to embodiments of the present invention include the following configurations and methods.
(Configuration 1)
base material and
an optical element portion made of a material containing organopolysiloxane as a main component on the base material;
An optical element having
Regarding the optical element portion, the atomic concentration ratio of carbon atoms to silicon atoms in a range of 0.5 μm to 3 μm toward the base material from the surface of the optical element portion opposite to the surface in contact with the base material. The average value of (C/Si)a is defined as the ratio of carbon atoms to silicon atoms in the range of 0.5 μm to 3 μm from the surface where the optical element portion and the base material are in contact toward the inside of the optical element portion. When the average value of the atomic concentration ratio is (C/Si)b,
An optical element characterized in that (C/Si)a is larger than (C/Si)b.
(Configuration 2)
The optical element according to configuration 1, wherein the (C/Si)a is 1.5 times or more the (C/Si)b.
(Configuration 3)
The optical element according to configuration 1 or 2, further comprising a coating layer containing an inorganic oxide or an inorganic fluoride as a main component on the optical element part.
(Configuration 4)
The optical element is a diffractive optical element,
The optical element part is a diffractive optical element part having a diffractive structure,
The diffractive optical element further includes a flat part formed integrally with the diffractive optical element part on the base material and having a flat surface,
The average value of the atomic concentration ratio of carbon atoms to silicon atoms in the range of 0.5 μm to 3 μm toward the base material from the surface opposite to the surface in contact with the base material of the flat portion is (C/Si ) The optical element according to any one of configurations 1 to 3, wherein (C/Si)a is 0.9 times or more and 1.1 times or less of (C/Si)c, when c is.
(Configuration 5)
Equipped with multiple laser light sources and diffractive optical elements,
the diffractive optical element is arranged on the light output side with respect to the plurality of laser light sources,
A light source device characterized in that the diffractive optical element is the diffractive optical element according to configuration 4.
(Configuration 6)
The light source device according to configuration 5, wherein the plurality of laser light sources include semiconductor lasers.
(Configuration 7)
7. The light source device according to configuration 5 or 6, wherein the light emitted from the plurality of laser light sources includes blue light.
(Configuration 8)
further comprising a phosphor disposed on the light output side with respect to the diffractive optical element,
8. The light source device according to any one of configurations 5 to 7, wherein the phosphor includes yttrium aluminum oxide doped with cerium.
(Configuration 9)
An image projection device comprising an optical system and a control device for controlling the optical system,
The optical system includes a light source device and a plurality of optical elements,
An image projection device characterized in that the light source device is the light source device according to any one of configurations 5 to 8.
(Configuration 10)
The image projection device according to configuration 9, wherein the plurality of laser light sources include semiconductor lasers.
(Configuration 11)
The image projection device according to configuration 9 or 10, wherein the light emitted from the plurality of laser light sources includes blue light.
(Configuration 12)
The light source device further includes a phosphor disposed on a light output side with respect to the diffractive optical element,
The image projection device according to any one of configurations 9 to 11, wherein the phosphor includes yttrium aluminum oxide doped with cerium.
(Configuration 13)
The optical system separates the light emitted from the light source device through the phosphor into red light, green light, and blue light,
13. An image projection device according to claim 12, wherein the control device generates a color image.
(Method 1)
A method for manufacturing an optical element, the method comprising the step of forming an optical element portion containing organopolysiloxane on a base material,
The step of forming the optical element portion includes a step of performing post-processing,
Regarding the optical element portion formed through the post-processing, silicon atoms in a range of 0.5 μm to 3 μm toward the base material from the surface of the optical element portion opposite to the surface in contact with the base material. The atomic concentration ratio of carbon atoms to the base material is (C/Si)a, and silicon atoms in a range of 0.5 μm to 3 μm from the surface where the optical element portion and the base material are in contact toward the inside of the optical element portion. When the atomic concentration ratio of carbon atoms to (C/Si)b is,
A method for manufacturing an optical element, characterized in that (C/Si)a is larger than (C/Si)b.
(Method 2)
The post-treatment is a heat treatment,
The method for manufacturing an optical element according to method 1, wherein the heat treatment is performed at a temperature of 120° C. or higher and a heating time of 2 hours or longer.
(Method 3)
The step of forming the optical element section includes:
placing a raw material containing organopolysiloxane as a main component on the base material;
sandwiching and pressurizing the raw material between the base material and the mold member;
releasing the raw material from the mold member after curing the raw material;
The method for manufacturing an optical element according to method 1 or 2, comprising:
(Method 4)
The step of forming the optical element portion includes a step of forming a coating layer covering the optical element portion between the step of releasing the mold member from the mold member after curing the raw material and the step of performing the post-treatment. The method for manufacturing an optical element according to method 3, comprising:
(Method 5)
The method for manufacturing an optical element according to method 4, wherein the coating layer is made of silicon oxide.

10 Diffractive optical element 12 Base material 13 Diffractive optical element part 14 Diffractive structure 15 Flat part 16 Covering layer 41 Laser light source 44 Laser light 81 Transfer mold 500 Projector 501 Light source device

Claims (18)

base material and
an optical element portion made of a material containing organopolysiloxane as a main component on the base material;
An optical element having
Regarding the optical element portion, the atomic concentration ratio of carbon atoms to silicon atoms in a range of 0.5 μm to 3 μm toward the base material from the surface of the optical element portion opposite to the surface in contact with the base material. The average value of (C/Si)a is defined as the ratio of carbon atoms to silicon atoms in the range of 0.5 μm to 3 μm from the surface where the optical element portion and the base material are in contact toward the inside of the optical element portion. When the average value of the atomic concentration ratio is (C/Si)b,
An optical element characterized in that (C/Si)a is larger than (C/Si)b. The optical element according to claim 1, wherein the (C/Si)a is 1.5 times or more the (C/Si)b. The optical element according to claim 1, further comprising a coating layer containing an inorganic oxide or an inorganic fluoride as a main component on the optical element portion. The optical element is a diffractive optical element,
The optical element part is a diffractive optical element part having a diffractive structure,
The diffractive optical element further includes a flat part formed integrally with the diffractive optical element part on the base material and having a flat surface,
The average value of the atomic concentration ratio of carbon atoms to silicon atoms in the range of 0.5 μm to 3 μm toward the base material from the surface opposite to the surface in contact with the base material of the flat portion is (C/Si ) The optical element according to claim 1, wherein (C/Si)a is 0.9 times or more and 1.1 times or less of (C/Si)c. Equipped with multiple laser light sources and diffractive optical elements,
the diffractive optical element is arranged on the light output side with respect to the plurality of laser light sources,
A light source device, wherein the diffractive optical element is the diffractive optical element according to claim 4. The light source device according to claim 5, wherein the plurality of laser light sources include semiconductor lasers. The light source device according to claim 5, wherein the light emitted from the plurality of laser light sources includes blue light. further comprising a phosphor disposed on the light output side with respect to the diffractive optical element,
8. The light source device according to claim 7, wherein the phosphor includes yttrium aluminum oxide doped with cerium. An image projection device comprising an optical system and a control device for controlling the optical system,
The optical system includes a light source device and a plurality of optical elements,
An image projection device characterized in that the light source device is the light source device according to claim 6. The image projection device according to claim 9, wherein the plurality of laser light sources include semiconductor lasers. The image projection device according to claim 9, wherein the light emitted from the plurality of laser light sources includes blue light. The light source device further includes a phosphor disposed on a light output side with respect to the diffractive optical element,
12. The image projection device of claim 11, wherein the phosphor comprises cerium-doped yttrium aluminum oxide. The optical system separates the light emitted from the light source device through the phosphor into red light, green light, and blue light,
13. An image projection device according to claim 12, wherein the control device generates a color image. A method for manufacturing an optical element, the method comprising the step of forming an optical element portion containing organopolysiloxane on a base material,
The step of forming the optical element portion includes a step of performing post-processing,
Regarding the optical element portion formed through the post-processing, silicon atoms in a range of 0.5 μm to 3 μm toward the base material from the surface of the optical element portion opposite to the surface in contact with the base material. The atomic concentration ratio of carbon atoms to the base material is (C/Si)a, and silicon atoms in a range of 0.5 μm to 3 μm from the surface where the optical element portion and the base material are in contact toward the inside of the optical element portion. When the atomic concentration ratio of carbon atoms to (C/Si)b is,
A method for manufacturing an optical element, characterized in that (C/Si)a is larger than (C/Si)b. The post-treatment is a heat treatment,
15. The method for manufacturing an optical element according to claim 14, wherein the heat treatment is performed at a temperature of 120° C. or higher and a heating time of 2 hours or longer. The step of forming the optical element section includes:
placing a raw material containing organopolysiloxane as a main component on the base material;
sandwiching and pressurizing the raw material between the base material and the mold member;
releasing the raw material from the mold member after curing the raw material;
The method for manufacturing an optical element according to claim 14, comprising: The step of forming the optical element portion includes a step of forming a coating layer covering the optical element portion between the step of releasing the raw material from the mold member after curing the raw material and the step of performing the post-treatment. The method for manufacturing an optical element according to claim 16, comprising: The method for manufacturing an optical element according to claim 17, wherein the coating layer is made of silicon oxide.

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