Diffractive optical element and method for manufacturing diffractive optical element

Abstract

Provided are: a diffractive optical element that is thin, realizes high mass productivity, has a high light-condensing performance which makes it possible to cope with a minute pixel pitch, and is capable of condensing light of a plurality of wavelengths; and a method for manufacturing the diffractive optical element.　The diffractive optical element comprises: a base board which allows entering light to pass therethrough; and a resin layer which is formed from a curable resin composition, forms recesses and projections on a main surface of the base board, and also forms a diffraction pattern that is substantially concentrical when viewed in a direction orthogonal to the main surface of the base board. The diffraction pattern is divided into a plurality of pattern regions in the circumferential direction. The plurality of pattern regions at least include: a first pattern region which has a shape of a Fresnel zone plate, and which corresponds to light that is included in the entering light and that belongs to a first wavelength range; and a second pattern region which has a shape of a Fresnel zone plate, and which corresponds to light that is included in the entering light and that belongs to a second wavelength range different from the first wavelength range.

Description

Diffractive optical element and method for manufacturing the same

[0001] The present invention relates to a diffractive optical element, and more particularly to a diffractive optical element applicable to imaging, optical sensors, displays, and optical communications. The present invention also relates to a method for manufacturing a diffractive optical element.

[0002] Optical components are used to appropriately control light in image sensors, optical sensors, displays, and optical communications.

[0003] In recent years, there has been a growing demand for thinner optical components. For example, in the case of camera modules in smartphones and mobile phones, the lens is the factor that determines the height of the camera module, and the increase in camera module size due to the increase in sensor area has become a problem, leading to a strong demand for thinner optical elements.

[0004] Optical sensors, such as fingerprint authentication sensors, face authentication sensors, proximity sensors, ambient light sensors, and pulse oximeters, are used in smartphones and smartwatches to detect light of multiple wavelengths, but optical sensors are often built into the back of the display, and there is a strong demand for thinner and more compact optical components. These optical sensors also increase the thickness of the device, so there is a strong demand for thinner devices.

[0005] Furthermore, among display devices, wearable display elements such as glasses and head-mounted displays in devices for AR (Augmented Reality), VR (Virtual Reality), and MR (Mixed Reality) use holographic optical elements that utilize a grating structure and total reflection, or pancake lenses. However, optical elements corresponding to the three colors of red, green, and blue are required, and if ordinary optical lenses are used, the thickness and weight become an issue.

[0006] In order to cope with the trend toward thinner optical components, various types of diffractive optical elements have been reported in recent years.

[0007] For example, Patent Document 1 reports a metalens, an optical element that focuses light with high precision despite having a thickness of 1 μm or less, by optimizing the arrangement of fine pillars made of a high refractive index material. However, metalens requires nanometer-level structural control, and electron beam lithography and atomic layer deposition (ALD) must be used to create the high refractive index pillar structure, which is a time-consuming method, resulting in a very complicated manufacturing process with low productivity.

[0008] Another example of a planar optical element is the Fresnel zone plate. Patent Document 2 proposes the use of a Fresnel zone plate for optical fiber optical coupling, while Patent Document 3 proposes the use of a Fresnel zone plate directly above a CMOS image sensor as a replacement for a color filter. In addition to the Fresnel zone plate, Patent Document 4 discloses light-collecting elements such as a fractal zone plate and a photon sieve. Patent Document 5 discloses a Fresnel lens and a Fresnel phase difference lens using an optical multilayer film with wavelength-specific reflection characteristics. Patent Document 6 discloses a Fresnel lens with improved chromatic aberration using multiple color filters.

[0009] However, the Fresnel zone plates, fractal zone plates, and photon sieves represented by Patent Documents 2 to 4 require the formation of a mask on a metal vapor deposition layer by lithography, followed by metal etching and mask development, resulting in low productivity methods similar to Patent Document 1. Furthermore, the optical multilayer film used in Patent Document 5 requires high film thickness accuracy, necessitating high-precision production with reduced formation speed. Furthermore, the Fresnel zone plate must be formed by subsequent etching, resulting in similarly low productivity methods. Furthermore, Patent Documents 2 to 6 do not achieve the high light-focusing performance required for imaging applications compatible with fine pixels, and design guidelines for achieving this light-focusing performance are unknown. Light-focusing performance can be determined by the full width at half maximum (FWHM), which is the width at which the electromagnetic field intensity at the most focused point is ½. For imaging applications applicable to fine sensors, a light-focusing performance of FWHM 2.51 μm or less is required. However, there are no guidelines for obtaining high light-collecting performance suitable for imaging applications in diffractive imaging elements made of Fresnel zone plates, fractal zone plates, or photon sieves, and the diffractive optical elements of Patent Documents 2 to 6 are not suitable for use as fine imaging elements or sensor elements.Furthermore, they are not diffractive optical elements that can be used as diffractive optical elements in fine display devices such as wearable display elements such as AR or MR glasses or head-mounted displays, or hologram optical elements designed for the three colors of red, green, and blue using a grating structure and total reflection, or for near-infrared light.

[0010] Other known planar optical elements with high productivity include Fresnel lenses and diffractive optical element lenses such as those described in Non-Patent Document 1, which have a light-condensing performance achieved by designing a fine structure.

[0011] However, the Fresnel lens that focuses light using this fine structure and the diffractive optical element of Non-Patent Document 1 are diffractive optical elements that do not have absorption properties and use a positive resist in which the exposed portion dissolves, and due to the influence of light scattering at the interface formed by the fine structure, the light focusing performance is greater than 2.51 μm, which is insufficient for application to fine sensor elements or pixel elements. Note that the diffractive optical element described in Non-Patent Document 1 is intended for infrared light with a wavelength of 8 μm or more, and no consideration has been given to the wavelength range of visible light or the wavelength range of short infrared light with a wavelength of 2 μm or less.

[0012] Furthermore, Patent Document 6 proposes a focusing element that focuses incident light of different wavelengths using a common diffraction pattern. However, the structure of Patent Document 6 involves stacking patterns corresponding to each wavelength in relation to the direction of incidence of the incident light, which requires each pattern to be formed separately, resulting in productivity issues. Furthermore, Patent Document 6 also proposes stacking separately formed patterns, which inevitably results in areas where the patterns overlap in relation to the direction of incidence of the incident light, resulting in issues with light focusing performance. In response to this, Patent Document 6 proposes forming color filters in the areas where the patterns overlap to adjust the degree of focusing of light of different wavelengths, but forming color filters for each pattern is cumbersome, low productivity, and impractical.

[0013] International Publication No. 2017 / 176921 Japanese Patent Application Laid-Open No. 2009-187010 Japanese Patent Application Laid-Open No. 2007-109801 Japanese Patent Application Laid-Open No. 2016-518616 U.S. Patent No. 5,257,132 International Publication No. 2022 / 264488

[0014] PNAS Vol. 116 Jno. 43 21375-21378 (2019)

[0015] Conventional diffractive optical elements have only been fabricated using methods that require complicated manufacturing procedures and are not suitable for mass production, or that have low light-collecting performance. An object of the present invention is to provide a thin diffractive optical element that is suitable for mass production, has high light-collecting performance that can accommodate fine pixel pitches, and is capable of focusing light of multiple wavelengths, and a method for manufacturing the diffractive optical element.

[0016] The present inventors have conducted extensive research to solve the above problems, and as a result, examples of the embodiments of the present invention are shown below.

[0017] [1] A diffractive optical element that diffracts incident light having a wavelength in the range of 380 nm to 1,700 nm, comprising: a substrate that transmits the incident light; and a resin layer formed of a curable resin composition that forms unevenness on a main surface of the substrate and that forms a diffraction pattern that is substantially concentric when viewed in a direction perpendicular to the main surface of the substrate, wherein the diffraction pattern is divided into a plurality of pattern regions in a circumferential direction with respect to a center of the diffraction pattern when viewed in the direction perpendicular to the main surface of the substrate, and the plurality of pattern regions include at least: a first pattern region that exhibits a Fresnel zone plate shape corresponding to light that is included in the incident light and that belongs to a first wavelength range; and a second pattern region that exhibits a Fresnel zone plate shape corresponding to light that is included in the incident light and that belongs to a second wavelength range that is different from the first wavelength range.

[0018] Here, the term "substantially concentric" is used to include not only a shape consisting of multiple annular rings centered on a certain point, but also a shape that is rotationally symmetrical in that a predetermined shape is arranged in the circumferential direction around a certain point. Rotational symmetry refers to a shape that is substantially the same when rotated (360 / n) degrees around the center. Here, n is an integer of 1 or greater. For example, in a diffraction pattern in which resin layers are arranged at equal intervals in the circumferential direction, the number of resin layers, the number of gaps between the resin layers, or the sum of these is determined.

[0019] Specific examples will be described later, but in this specification, "the diffraction pattern is divided into a plurality of pattern areas in the circumferential direction" means that the diffraction pattern has pattern areas in the circumferential direction that correspond to different wavelengths of light.

[0020] [2] The diffractive optical element according to [1], wherein the diffraction pattern has an area in which the number of divisions in the circumferential direction of the diffraction pattern increases in a radial direction from the center of the diffraction pattern to an outer edge.

[0021] [3] The diffractive optical element according to [2] above, wherein the length in the circumferential direction of the resin layer belonging to the first pattern region is substantially equal to the length in the circumferential direction of the resin layer belonging to the first pattern region that is closest to the center of the diffraction pattern.

[0022] [4] The diffractive optical element according to any one of [1] to [3], wherein the plurality of pattern regions include a third pattern region having a Fresnel zone plate shape corresponding to light that belongs to a third wavelength range different from the first wavelength range and the second wavelength range.

[0023] [5] The diffractive optical element according to the above [4], wherein the plurality of pattern regions are composed only of the first pattern region, the second pattern region, and the third pattern region, the first pattern region, the second pattern region, and the third pattern region all have a focal length of 1 mm and present a Fresnel zone plate shape corresponding to light belonging to the visible light range, the lengths in the circumferential direction of the resin layer closest to the center of the diffraction pattern are substantially equal to each other, and the total number of the first pattern region, the second pattern region, and the third pattern region located closest to the center of the diffraction pattern is 132 to 204.

[0024] [6] The diffractive optical element according to the above [4] or [5], wherein the first wavelength range is 600 nm or more and 780 nm or less, the second wavelength range is 500 nm or more and less than 600 nm, and the third wavelength range is 380 nm or more and less than 500 nm.

[0025] [7] The diffractive optical element according to any one of [1] to [6] above, wherein the diffraction pattern exhibits a rotationally symmetric shape with an integral multiple of one or more times when viewed in a direction perpendicular to the main surface of the substrate.

[0026] More preferably, the diffraction pattern exhibits a four-fold rotationally symmetric shape when viewed in a direction perpendicular to the main surface of the substrate.

[0027] [8] The diffractive optical element according to any one of [1] to [7] above, characterized in that the sum of the lengths in the circumferential direction of the resin layer closest to the center of the diffraction pattern in the first pattern region and the sum of the lengths in the circumferential direction of the resin layer closest to the center of the diffraction pattern in the second pattern region are different from each other.

[0028] [9] A method for manufacturing a diffractive optical element applicable to incident light having a wavelength in the range of 380 nm to 1,700 nm, comprising: a step (A) of preparing a substrate that transmits the incident light; a step (B) of applying a material containing a curable resin composition onto a main surface of the substrate to form a coating film; a step (C) of curing a part of the coating film to form a resin layer that blocks the incident light or delays the phase of the incident light on a part of the main surface of the substrate; and a step (D) of removing, after the step (C), the coating film in a part different from the resin layer from the main surface of the substrate, wherein the step (C) comprises a step of forming the resin layer so that a diffraction pattern formed by the resin layer is divided into a plurality of pattern regions in the circumferential direction when viewed in a direction perpendicular to the main surface of the substrate, the plurality of pattern regions include at least a first pattern region having a Fresnel zone plate shape corresponding to light that belongs to a first wavelength range included in the incident light, and a second pattern region having a Fresnel zone plate shape corresponding to light that belongs to a second wavelength range that is different from the first wavelength range and is included in the incident light.

[0029] According to the present invention, it is possible to provide a thin diffractive optical element that is suitable for mass production, has high light-collecting performance that can accommodate a fine pixel pitch, and can collect light of multiple wavelengths, and a method for manufacturing the diffractive optical element.Furthermore, it is possible to provide a thin optical sensor and a thin display device that have excellent characteristics for adjusting the light-collecting position and performance according to the wavelength.

[0030] 5A is a diagram showing an example of a Fresnel zone plate shape. FIG. 5B is a diagram showing an example of a diffraction pattern formed on a main surface of a substrate of a diffractive optical element. FIG. 5C is an enlarged view of a portion of FIG. 2. FIG. 5D is a cross-sectional view taken along the line B-B of FIG. 2. FIG. 5E is a diagram showing a state in which parallel light is incident on a diffractive optical element. FIG. 5F is a diagram showing another example of a diffraction pattern. FIG. 5G is a diagram showing a state in which parallel light is incident on a diffractive optical element. FIG. 5G is a diagram showing a state in which parallel light is incident on a diffractive optical element. FIG. 5H is a diagram showing a state in which parallel light is incident on a diffractive optical element. FIG. 5I is a diagram showing a state in which parallel light is incident on a diffractive optical element. FIG. 5I is a diagram showing a state in which parallel light is incident on a diffractive optical element. FIG. 5I is a diagram showing a state in which parallel light is incident on a diffractive optical element. FIG. 5I is a diagram showing a state in which parallel light is incident on a diffractive optical element. 15B is a graph showing the light intensity distribution in the X direction of FIG. 15C. 15C is a graph showing the light intensity distribution in the X direction of FIG. 15A. 15D is a graph showing the light intensity distribution in the X direction of FIG. 15C. 15E is a graph showing the light intensity distribution in the X direction of FIG. 15C. 15F is a graph showing the light intensity distribution in the X direction of FIG. 15A. 15G is a graph showing the light intensity distribution in the X direction of FIG. 15C. 15G is a graph showing the light intensity distribution in the X direction of FIG. 15C. 15H is a graph showing the light intensity distribution in the X direction of FIG. 15A. 15H is a graph showing the light intensity distribution in the X direction of FIG. 15C. 15H is a graph showing the light intensity distribution in the X direction of FIG. 15C. 15H is a graph showing the light intensity distribution in the X direction of FIG. 15A. 1 is an image captured by a camera equipped with a sample of Example 2. 2 is an image captured by a camera equipped with a sample of Example 3. 3 is a diagram showing the detected intensity of red light at the focusing position obtained from the evaluation of Example 4 in two dimensions of xy coordinates.20B is a diagram showing the light intensity distribution in the X direction of FIG. 20C. FIG. 20C is a diagram showing the light intensity distribution in the X direction of FIG. 20A. FIG. 20B is a diagram showing the light intensity distribution in the X direction of FIG. 20C. FIG. 20C is an image captured by a camera equipped with a sample of Example 4. FIG. 20C is an image captured by a camera equipped with a sample of Example 4. FIG. 20C is an image showing the electric field intensity distribution of red light at the focal length obtained by the simulation of Example 5. FIG. 20C is an image showing the electric field intensity distribution of green light at the focal length obtained by the simulation of Example 5. FIG. 20C is an image showing the electric field intensity distribution of blue light at the focal length obtained by the simulation of Example 5. FIG. 23A is an image showing the electric field intensity distribution in the X direction of FIG. 23B. FIG. 23C is an image showing the electric field intensity distribution of red light at the focal length obtained by the simulation of Example 6. 25A is an electric field intensity distribution of green light at a focal length obtained by the simulation of Example 6. FIG. 25B is an electric field intensity distribution of blue light at a focal length obtained by the simulation of Example 6. FIG. 25C is a diagram showing the electric field intensity distribution in the X direction of FIG. 25A. FIG. 25B is an electric field intensity distribution of X direction of FIG. 25C. FIG. 25A is an electric field intensity distribution of red light at a focal length obtained by the simulation of Example 7. FIG. 25C is an electric field intensity distribution of green light at a focal length obtained by the simulation of Example 7. FIG. 25C is an electric field intensity distribution of blue light at a focal length obtained by the simulation of Example 7. FIG. 27A is an electric field intensity distribution in the X direction of FIG. 27B. FIG. 27C is an electric field intensity distribution of red light at a focal length obtained by the simulation of Example 8. FIG. 27C is an electric field intensity distribution of green light at a focal length obtained by the simulation of Example 8. FIG. 27C is an electric field intensity distribution of blue light at a focal length obtained by the simulation of Example 8. 29A, 29B, and 29C are diagrams showing the electric field intensity distribution in the X direction of FIG. 29A, 29B, and 29C, respectively.33A is a diagram showing a logarithmic plot of the electric field intensity distribution of red light at the focal length of Example 5. FIG. 33B is a diagram showing a logarithmic plot of the electric field intensity distribution of green light at the focal length of Example 5. FIG. 33C is a diagram showing a logarithmic plot of the electric field intensity distribution of blue light at the focal length of Example 5. FIG. 33D is a diagram showing a logarithmic plot of the electric field intensity distribution of red light at the focal length of Example 8. FIG. 33E is a diagram showing a logarithmic plot of the electric field intensity distribution of green light at the focal length of Example 8. FIG. 33F is a diagram showing the electric field intensity distribution of blue light at the focal length of Example 8. FIG. 33G is a diagram showing the electric field intensity distribution of red light at the focal length obtained by simulation of Example 9. FIG. 33H is a diagram showing the electric field intensity distribution of green light at the focal length obtained by simulation of Example 9. FIG. 33H is a diagram showing the electric field intensity distribution in the X direction of FIG. 33A. FIG. 33B is a diagram showing the electric field intensity distribution in the X direction of FIG. 33C. 10 is a diagram showing a logarithmic plot of the electric field intensity distribution of red light at the focal length of Example 9. FIG. 11 is a diagram showing a logarithmic plot of the electric field intensity distribution of green light at the focal length of Example 9. FIG. 12 is a diagram showing a logarithmic plot of the electric field intensity distribution of blue light at the focal length of Example 9. FIG. 13 is an image captured by a camera equipped with the sample of Example 10. FIG. 14 is an image captured by a camera equipped with the sample of Example 11.

[0031] Hereinafter, embodiments of the diffractive optical element of the present invention and a manufacturing method for a diffractive optical element of the present invention will be described with reference to the drawings as appropriate. However, the diffractive optical element of the present invention and the manufacturing method for a diffractive optical element of the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. To clarify the explanation, the drawings may schematically depict the width, thickness, shape, etc. of each part compared to the actual form, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same or similar symbols (symbols simply having a suffix such as "'" after the number), and detailed descriptions may be omitted as appropriate.

[0032] In this specification, "up" refers to a relative position based on the main surface of the support substrate (for example, the surface on which the solid-state imaging element is disposed), and the direction away from the main surface of the support substrate is "up". In this drawing, "up" refers to the upward direction as viewed from the paper. "Up" also includes the case where the substrate is in contact with the top of an object (i.e., "on") and the case where the substrate is positioned above an object (i.e., "over"). Conversely, "down" refers to a relative position based on the main surface of the support substrate, and the direction approaching the main surface of the support substrate is "down". In this drawing, "down" refers to the downward direction as viewed from the paper.

[0033] <Substrate> A substrate having a transmittance of 50% or more at any wavelength between 380 nm and 1,700 nm is used. Examples of such transparent substrates include silicate glass substrates, borosilicate glass substrates, phosphate glass substrates, fluorophosphate glass substrates, plastic substrates, and resin film substrates. Materials having a glass transition temperature of 140°C or higher and a surface roughness Ra of less than 200 nm are preferred. The substrate may contain a near-infrared absorber, and may contain at least one selected from inorganic near-infrared absorbers such as cesium tungsten oxide and copper (II) oxide, near-infrared absorbers utilizing surface plasmons such as gold nanorods, and organic near-infrared absorbers.

[0034] The substrate is preferably made of multiple layers from the viewpoints of crack resistance, ease of addition of a light absorber, and imparting functions and effects. Functions imparted to the substrate include electrical conductivity, antistatic effect, anti-adhesion effect, scratch prevention effect, anti-fogging property, heat resistance improvement effect, gas barrier property, high elasticity, scratch removal effect, flatness, rough surface, moisture absorption, anti-aging effect, near-infrared cutoff property, etc. The substrate may have a dielectric multilayer film for the purpose of imparting control of the transmission wavelength.

[0035] Preferably, the transmittance of the substrate at any wavelength in the wavelength range of 410 nm to 1,100 nm is 60% or more.

[0036] <Curable Resin Composition> The curable resin composition according to the present invention includes a curable resin composition containing a colorant (hereinafter sometimes referred to as a "colored curable resin composition") and a curable resin composition not containing a colorant (hereinafter sometimes referred to as a "transparent curable resin composition"). The curable resin composition according to the present invention has an absorption characteristic with a maximum absorption wavelength in the wavelength range of 380 nm to 1,700 nm. The colored curable resin composition more preferably has a maximum absorption wavelength in the wavelength range of 410 to 1,100 nm, and even more preferably has a maximum absorption wavelength in the wavelength range of 420 to 1,000 nm. By having an absorption characteristic in this wavelength range, the curable resin composition according to the present invention can achieve a refractive index of greater than 1.6 at any wavelength in the wavelength range of 380 nm to 1,700 nm, thereby improving the light-focusing performance of the resulting diffractive optical element.

[0037] As will be described in detail later, the curable resin composition forms a diffraction pattern that focuses incident light. By varying the composition of the curable resin composition, an amplitude zone plate or a phase zone plate can be realized. Specifically, in the case of an amplitude zone plate, the curable resin composition contains a colorant and a polymerizable compound (colored curable resin composition). This enhances the light-blocking ability of the curable resin composition for a predetermined wavelength. Even when a colorant is contained, if the curable resin composition is transparent to a predetermined wavelength, the diffraction effect of a phase zone plate can be expected for light of that wavelength. Furthermore, in the case of a phase zone plate, the curable resin composition is preferably a transparent curable resin composition that does not contain a colorant. This facilitates enhancing the transmittance of the curable resin composition for a predetermined wavelength.

[0038] The curable resin composition of the present invention can be cured by thermal curing or photocuring. Photocuring is preferred, and the curable resin composition is preferably a radiation-sensitive curable resin composition. Examples of the radiation used include ultraviolet light, far ultraviolet light, X-rays, and charged particle beams. Examples of ultraviolet light include g-rays (wavelength 436 nm) and i-rays (wavelength 365 nm). Examples of far ultraviolet light include KrF excimer lasers. Examples of X-rays include synchrotron radiation. Examples of charged particle beams include electron beams. Of these types of radiation, ultraviolet light is preferred, and among ultraviolet light, radiation including g-rays and / or i-rays is particularly preferred.

[0039] The colored curable resin composition according to the present invention includes, for example, a colorant, a polymerizable compound, a photopolymerization initiator, and a binder resin. The transparent curable resin composition includes, for example, a polymerizable compound, a photopolymerization initiator or a photogenerator, and, if necessary, a binder resin and a crosslinking agent. These are described in detail below.

[0040] The colorant has a maximum absorption wavelength in the range of 380 nm to 1,700 nm, and more preferably in the range of 410 nm to 1,100 nm. There are no particular limitations on the colorant as long as it has the above maximum absorption wavelength, but at least one selected from pigments and dyes is preferred.

[0041] The pigment may be either an organic pigment or an inorganic pigment, and preferred specific examples of organic pigments include, in terms of Color Index (C.I.) names, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I. Pigment Red 224, C.I. Pigment Red 242, C.I. Pigment Red 254, C.I. Pigment Red 264, C.I. Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Green 58, C.I. Pigment Blue 15:6, C.I. Pigment Blue 80, C.I. Pigment Yellow 83, C.I. Pigment Yellow 129, C.I. Pigment Yellow 138, C.I. Pigment Yellow 139, C.I. Examples of inorganic pigments include C.I. Pigment Yellow 150, C.I. Pigment Yellow 180, C.I. Pigment Yellow 185, C.I. Pigment Yellow 211, C.I. Pigment Orange 38, C.I. Pigment Violet 23, carbon nanotubes, and fullerenes. Furthermore, the colorant may contain a pigment that does not have a maximum absorption wavelength in the wavelength range of 410 to 1100 nm. Examples of colorants that do not have a maximum absorption wavelength in the wavelength range of 410 to 1100 nm include carbon black, titanium black, and graphene. Specific examples of preferred inorganic pigments include titanium oxide, strontium titanate, barium titanate, zinc oxide, magnesium oxide, zirconium oxide, aluminum oxide, barium sulfate, silica, talc, mica, aluminum hydroxide, calcium silicate, aluminum silicate, and zinc sulfide.

[0042] Examples of the dyes include pyrazole azo compounds, anilino azo compounds, triarylmethane compounds, anthraquinone compounds, anthrapyridone compounds, benzylidene compounds, oxonol compounds, pyrazolotriazole azo compounds, pyridone azo compounds, cyanine compounds, phenothiazine compounds, pyrrolopyrazole azomethine compounds, xanthene compounds, phthalocyanine compounds, benzopyran compounds, indigo compounds, pyrromethene compounds, triarylmethane compounds, cyanine compounds, and azo compounds. Quinophthalone compounds and the like can also be used as yellow dyes. Examples of near-infrared absorbing dyes include pyrrolopyrrole compounds, rylene compounds, oxonol compounds, squarylium compounds, cyanine compounds, croconium compounds, phthalocyanine compounds, naphthalocyanine compounds, pyrylium compounds, azulenium compounds, indigo compounds, and pyrromethene compounds. In addition, squarylium compounds, pyrrole ring-containing compounds, squarylium compounds having an aromatic ring at the amide α-position, compounds having a croconium skeleton, dihydrocarbazole bis-type squarylium compounds, etc. can also be used.

[0043] In the present invention, the pigments and dyes may be used either alone or in combination of two or more.

[0044] When a pigment is used as a colorant in the present invention, the pigment may be purified, if desired, by recrystallization, reprecipitation, solvent washing, sublimation, vacuum heating, or a combination thereof before use. Furthermore, the pigment may be used after modifying its particle surface with a resin, if desired. Examples of resins that modify the pigment particle surface include vehicle resins and various commercially available resins for dispersing pigments. Furthermore, the pigment may be used after micronizing primary particles by so-called salt milling.

[0045] When a pigment is used as a colorant in the present invention, it may be used together with a dispersant or a dispersing aid, if desired. Examples of the dispersant include cationic, anionic, and nonionic dispersants, but polymer dispersants are preferred. Specific examples include urethane dispersants, polyethyleneimine dispersants, polyoxyethylene alkyl ether dispersants, polyoxyethylene alkylphenyl ether dispersants, polyethylene glycol diester dispersants, sorbitan fatty acid ester dispersants, polyester dispersants, and acrylic dispersants.

[0046] <Polymerizable Compound> The polymerizable compound of the present invention has a polymerizable functional group, but is not particularly limited thereto. Examples of the polymerizable functional group include an ethylenically unsaturated group, an oxiranyl group, an oxetanyl group, an N-alkoxymethylamino group, a hydrosiloxane group, and a vinylsilyl group. Examples of the ethylenically unsaturated group include a vinyl group, a styryl group, an allyl group, a (meth)acryloyl group, a (meth)acrylamide group, and a maleimide group, with a (meth)acryloyl group being preferred. From the viewpoint of dimensional stability, a hydrosiloxane group and a vinylsilyl group are preferred. The polymerizable compound used in the present invention is preferably selected from the group consisting of compounds having two or more polymerizable functional groups in the molecule.

[0047] Examples of the compound having two or more (meth)acryloyl groups in the molecule include polyfunctional (meth)acrylates obtained by reacting an aliphatic polyhydroxy compound with (meth)acrylic acid, caprolactone-modified polyfunctional (meth)acrylates, alkylene oxide-modified polyfunctional (meth)acrylates, polyfunctional urethane (meth)acrylates obtained by reacting a (meth)acrylate having a hydroxyl group with a polyfunctional isocyanate, and polyfunctional (meth)acrylates having a carboxyl group obtained by reacting a (meth)acrylate having a hydroxyl group with an acid anhydride. Examples of the aliphatic polyhydroxy compounds include divalent aliphatic polyhydroxy compounds such as ethylene glycol, propylene glycol, polyethylene glycol, and polypropylene glycol; and trivalent or higher aliphatic polyhydroxy compounds such as glycerin, trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0048] Examples of the (meth)acrylate having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and glycerol dimethacrylate; and examples of the polyfunctional isocyanate include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethylene diisocyanate, and isophorone diisocyanate. Examples of the acid anhydrides include dibasic acid anhydrides and tetrabasic acid dianhydrides. Specific examples of these include the dibasic acid anhydrides such as succinic anhydride, maleic anhydride, glutaric anhydride, itaconic anhydride, phthalic anhydride, and hexahydrophthalic anhydride; and the tetrabasic acid dianhydrides such as pyromellitic anhydride, biphenyltetracarboxylic dianhydride, and benzophenonetetracarboxylic dianhydride.

[0049] Examples of the caprolactone-modified polyfunctional (meth)acrylate include, for example, bisphenol A di(meth)acrylate modified with at least one selected from ethylene oxide and propylene oxide, isocyanuric acid tri(meth)acrylate modified with at least one selected from ethylene oxide and propylene oxide, trimethylolpropane tri(meth)acrylate modified with at least one selected from ethylene oxide and propylene oxide, and ethylene oxide. Examples of the modified acrylate include pentaerythritol tri(meth)acrylate modified with at least one selected from ethylene oxide and propylene oxide, pentaerythritol tetra(meth)acrylate modified with at least one selected from ethylene oxide and propylene oxide, dipentaerythritol penta(meth)acrylate modified with at least one selected from ethylene oxide and propylene oxide, and dipentaerythritol hexa(meth)acrylate modified with at least one selected from ethylene oxide and propylene oxide.

[0050] Examples of compounds having two or more N-alkoxymethylamino groups in the molecule include compounds having a melamine structure, a benzoguanamine structure, or a urea structure. Here, the term "melamine structure" refers to a chemical structure having one or more triazine rings as a basic skeleton, and the term "benzoguanamine structure" refers to a chemical structure having one or more phenyl-substituted triazine rings as a basic skeleton, and these concepts encompass melamine, benzoguanamine, and condensates thereof. Specific examples of compounds having two or more N-alkoxymethylamino groups in the molecule include N,N,N',N',N",N"-hexa(alkoxymethyl)melamine, N,N,N',N'-tetra(alkoxymethyl)benzoguanamine, and N,N,N',N'-tetra(alkoxymethyl)glycoluril.

[0051] Examples of compounds having two or more oxiranyl groups in the molecule include bisphenol A epoxy resins such as Epicoat 1001, 1002, 1003, 1004, 1007, 1009, 1010, and 828 (manufactured by Japan Epoxy Resins Co., Ltd.); bisphenol F epoxy resins such as Epicoat 807 (manufactured by Japan Epoxy Resins Co., Ltd.); phenol novolac epoxy resins such as Epicoat 152, 154, and 157S65 (manufactured by Japan Epoxy Resins Co., Ltd.), EPPN201, and 202 (manufactured by Nippon Kayaku Co., Ltd.); cresol novolac epoxy resins such as EOCN102, 103S, 104S, 1020, 1025, and 1027 (manufactured by Nippon Kayaku Co., Ltd.), and Epicoat 180S75 (manufactured by Japan Epoxy Resins Co., Ltd.); Examples of polyphenol-type epoxy resins include Epicoat 1032H60 and XY-4000 (manufactured by Japan Epoxy Resins); examples of cyclic aliphatic epoxy resins include CY-175, CY-177, CY-179, Araldite CY-182, CY-192, and CY-184 (manufactured by Chiba Specialty Chemicals), ERL-4234, 4299, 4221, and 4206 (manufactured by U.C.C.), Shodyne 509 (manufactured by Showa Denko KK), Epiclon 200 and 400 (manufactured by Dainippon Ink Co., Ltd.), Epicoat 871 and 872 (manufactured by Japan Epoxy Resins), and ED-5661 and 5662 (manufactured by Celanese Coatings); Examples of aliphatic polyglycidyl ethers include Epolite 100MF (manufactured by Kyoeisha Chemical Co., Ltd.) and Epiol TMP (manufactured by NOF Corporation).

[0052] Of the above, preferred polymerizable compounds in the present invention include polyfunctional (meth)acrylates obtained by reacting a trivalent or higher aliphatic polyhydroxy compound with (meth)acrylic acid, caprolactone-modified polyfunctional (meth)acrylates, polyfunctional urethane (meth)acrylates, polyfunctional (meth)acrylates having a carboxyl group, N,N,N',N',N",N"-hexa(alkoxymethyl)melamine, and N,N,N',N'-tetra(alkoxymethyl)benzoguanamine. Among the polyfunctional (meth)acrylates obtained by reacting a trivalent or higher aliphatic polyhydroxy compound with a (meth)acrylic and an acid, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate are particularly preferred; and among the polyfunctional (meth)acrylates having a carboxyl group, a compound obtained by reacting pentaerythritol triacrylate with succinic anhydride, a compound obtained by reacting dipentaerythritol pentaacrylate with succinic anhydride, and a compound having two or more oxiranyl groups in the molecule are particularly preferred, since the resulting curable resin composition has high strength and excellent surface smoothness and is less likely to produce background smears, residual film, etc. on the substrate and resin layer in unexposed areas.

[0053] <Binder Resin> The curable resin composition of the present invention may contain a binder resin. The presence of a binder resin can improve the alkali developability and storage stability of the curable resin composition. The binder resin is not particularly limited, but is preferably a resin having an acidic functional group such as a carboxyl group or a phenolic hydroxyl group. Among these, a polymer having a carboxyl group (hereinafter referred to as a "carboxyl group-containing polymer") is preferred, and examples thereof include copolymers of an ethylenically unsaturated monomer having one or more carboxyl groups (hereinafter referred to as an "unsaturated monomer (b1)") and another copolymerizable ethylenically unsaturated monomer (hereinafter referred to as an "unsaturated monomer (b2)").

[0054] Examples of the unsaturated monomer (b1) include (meth)acrylic acid, maleic acid, maleic anhydride, mono[2-(meth)acryloyloxyethyl] succinate, ω-carboxypolycaprolactone mono(meth)acrylate, and p-vinylbenzoic acid.

[0055] These unsaturated monomers (b1) can be used alone or in combination of two or more.

[0056] Examples of the unsaturated monomer (b2) include N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide; aromatic vinyl compounds such as styrene, α-methylstyrene, p-hydroxystyrene, p-hydroxy-α-methylstyrene, p-vinylbenzyl glycidyl ether, and acenaphthylene;

[0057] Methyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, allyl (meth)acrylate, benzyl (meth)acrylate, polyethylene glycol (degree of polymerization 2-10) methyl ether (meth)acrylate, polypropylene glycol (degree of polymerization 2-10) methyl ether (meth)acrylate, polyethylene glycol (degree of polymerization 2-10) mono(meth)acrylate, polypropylene glycol (degree of polymerization 2-10) mono(meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclo[5.2.1.0] 2,6 (meth)acrylic acid esters such as ]decan-8-yl (meth)acrylate, dicyclopentenyl (meth)acrylate, glycerol mono(meth)acrylate, 4-hydroxyphenyl (meth)acrylate, ethylene oxide-modified (meth)acrylate of para-cumylphenol, glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3-[(meth)acryloyloxymethyl]oxetane, and 3-[(meth)acryloyloxymethyl]-3-ethyloxetane;

[0058] Cyclohexyl vinyl ether, isobornyl vinyl ether, tricyclo[5.2.1.0 2,6 ] vinyl ethers such as decan-8-yl vinyl ether, pentacyclopentadecanyl vinyl ether, and 3-(vinyloxymethyl)-3-ethyloxetane; and macromonomers having a mono(meth)acryloyl group at the end of the polymer molecular chain, such as polystyrene, polymethyl(meth)acrylate, poly-n-butyl(meth)acrylate, and polysiloxane.

[0059] These unsaturated monomers (b2) can be used alone or in combination of two or more.

[0060] In the copolymer of the unsaturated monomer (b1) and the unsaturated monomer (b2), the copolymerization ratio of the unsaturated monomer (b1) in the copolymer is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 40% by mass. By copolymerizing the unsaturated monomer (b1) in such a range, a colored composition excellent in alkali developability and storage stability can be obtained.

[0061] In the present invention, for example, a carboxyl group-containing polymer having a polymerizable unsaturated bond such as a (meth)acryloyl group in the side chain can also be used as the binder resin.

[0062] Furthermore, in the present invention, a copolymer of an unsaturated monomer containing a (meth)acrylic acid ester having an oxiranyl group, such as glycidyl (meth)acrylate, may be used, and the hydroxyl groups generated by the reaction of the copolymer with the unsaturated monomer (b1) may be further reacted with a polybasic acid anhydride to form a copolymer, which may be used as the binder resin.

[0063] Examples of such polybasic acid anhydrides include anhydrides of dibasic acids such as maleic anhydride, fumaric anhydride, citraconic anhydride, mesaconic anhydride, itaconic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, himic anhydride, phthalic anhydride, and naphthalene-2,3-dicarboxylic anhydride; monoanhydrides of tribasic or higher polybasic acids such as cyclohexane-1,2,4-tricarboxylic anhydride and trimellitic anhydride; and monoanhydrides of cyclohexane-1,2,4-tricarboxylic anhydride and trimellitic anhydride. Examples of suitable dianhydrides include dianhydrides of polybasic acids having tetrabasic or higher acids, such as hexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, norbornanetetracarboxylic dianhydride, pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, diphenylethertetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, and perylene-3,4,9,10-tetracarboxylic dianhydride.

[0064] The binder resin of the present invention can be a resin having a repeating unit formed by cleavage of a polymerizable unsaturated bond of a polymerizable unsaturated compound having a phenolic hydroxyl group (hereinafter referred to as a "phenolic unsaturated compound"). The structure of the phenolic unsaturated compound is not particularly limited, as long as it contains a phenolic hydroxyl group and an unsaturated bond-containing group. Specific examples of the phenolic unsaturated compound include o-vinylphenol, m-vinylphenol, p-vinylphenol, o-isopropenylphenol, m-isopropenylphenol, and p-isopropenylphenol. The phenolic unsaturated compounds may be used alone or in combination. The molecular weight of the resin is not particularly limited, and can be adjusted to various molecular weight ranges as needed. The weight average molecular weight (Mw) measured by GPC in terms of polystyrene standards is typically 2,000 to 20,000, preferably 3,000 to 15,000, and more preferably 3,000 to 10,000.

[0065] The binder resin in the present invention has a weight average molecular weight (Mw) of typically 1,000 to 100,000, and preferably 3,000 to 50,000, in terms of polystyrene, as measured by GPC (elution solvent: tetrahydrofuran). By adopting such an embodiment, it becomes easier to form a coating film that is excellent in film retention, pattern shape, heat resistance, electrical properties, and resolution, and it is also possible to suppress the generation of dried foreign matter during application by a slit nozzle method.

[0066] The ratio (Mw / Mn) of the weight average molecular weight of the binder resin in the present invention to the polystyrene-equivalent number average molecular weight (Mn) measured by GPC (elution solvent: tetrahydrofuran) is preferably 1.0 to 5.0, and more preferably 1.0 to 3.0.

[0067] In the present invention, the binder resins may be used alone or in combination of two or more.

[0068] In the present invention, the content of the binder resin is preferably 10 parts by mass to 1,000 parts by mass, and particularly preferably 20 parts by mass to 500 parts by mass, relative to 100 parts by mass of the colorant (A). By adopting such an embodiment, the alkali developability, the storage stability, and the chromaticity characteristics of the colored composition can be improved.

[0069] The curable resin composition according to the present invention is preferably a radiation-sensitive curable resin composition for forming a diffractive optical element.

[0070] <Photopolymerization initiator> The curable resin composition of the present invention may contain a photopolymerization initiator or a photoacid generator. This makes it possible to impart radiation sensitivity to the curable resin composition, thereby obtaining a radiation-sensitive curable resin composition. The photopolymerization initiator applicable to the present invention is a compound that generates an active species capable of initiating polymerization of a polymerizable compound upon exposure to radiation such as visible light, ultraviolet light, far ultraviolet light, electron beams, or X-rays.

[0071] Examples of such photopolymerization initiators include thioxanthone-based compounds, acetophenone-based compounds, biimidazole-based compounds, triazine-based compounds, O-acyloxime-based compounds, onium salt-based compounds, benzoin-based compounds, benzophenone-based compounds, α-diketone-based compounds, polynuclear quinone-based compounds, diazo-based compounds, imidosulfonate-based compounds, and onium salt-based compounds.

[0072] In the present invention, the photopolymerization initiator may be used alone or in combination of two or more. The photopolymerization initiator is preferably at least one selected from the group consisting of thioxanthone compounds, acetophenone compounds, biimidazole compounds, triazine compounds, and O-acyloxime compounds.

[0073] Among the preferable photopolymerization initiators in the present invention, specific examples of the thioxanthone-based compounds include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone.

[0074] Specific examples of the acetophenone-based compound include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, and 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one.

[0075] Specific examples of the biimidazole-based compound include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, and 2,2'-bis(2,4,6-trichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole.

[0076] When a biimidazole compound is used as a photopolymerization initiator, it is preferable to use a hydrogen donor in combination, as this can improve sensitivity. The term "hydrogen donor" as used herein refers to a compound capable of donating a hydrogen atom to a radical generated from the biimidazole compound upon exposure. Examples of hydrogen donors include mercaptan hydrogen donors such as 2-mercaptobenzothiazole and 2-mercaptobenzoxazole, and amine hydrogen donors such as 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone. In the present invention, the hydrogen donors can be used alone or in combination of two or more. However, it is preferable to use a combination of one or more mercaptan hydrogen donors and one or more amine hydrogen donors, as this can further improve sensitivity.

[0077] Specific examples of the triazine compounds include 2,4,6-tris(trichloromethyl)-s-triazine, 2-methyl-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(5-methylfuran-2-yl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(furan-2-yl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, 2-[2-(furan-2-yl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, and 2-[2-(4-diethylamino-2-methylphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine.

[0033] Examples of triazine compounds having a halomethyl group include 2-[2-(3,4-dimethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-ethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, and 2-(4-n-butoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine.

[0078] Specific examples of the O-acyloxime compound include 1,2-octanedione, 1-[4-(phenylthio)phenyl]-, 2-(O-benzoyloxime), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), ethanone, 1-[9-ethyl-6-(2-methyl-4-tetrahydrofuranylmethoxybenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), ethanone, 1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxolanyl)methoxybenzoyl}-9H-carbazol-3-yl]-, 1-(O-acetyloxime), and the like.

[0079] In the present invention, when a photopolymerization initiator other than a biimidazole compound, such as an acetophenone compound, is used, a sensitizer can also be used in combination. Examples of such sensitizers include 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4-diethylaminoacetophenone, 4-dimethylaminopropiophenone, ethyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,5-bis(4-diethylaminobenzal)cyclohexanone, 7-diethylamino-3-(4-diethylaminobenzoyl)coumarin, and 4-(diethylamino)chalcone.

[0080] In the present invention, the photoacid generator is not particularly limited as long as it is a compound that generates an acid (e.g., p-toluenesulfonic acid, camphorsulfonic acid, etc.) upon irradiation with radiation. Examples of such photoacid generators include 1-(4-hydroxy-1-naphthalenyl)tetrahydrothiophenium trifluoromethanesulfonate, 1-(4-n-butoxy-1-naphthalenyl)tetrahydrothiophenium trifluoromethanesulfonate, 1-(4,7-diethoxy-1-naphthalenyl)tetrahydrothiophenium trifluoromethanesulfonate, 1-(4,7-dibutoxy-1-naphthalenyl)tetrahydrothiophenium trifluoromethanesulfonate, and the like. thiophenium trifluoromethanesulfonate, 1-(4,7-dipropylhydroxy-1-naphthalenyl)tetrahydrothiophenium trifluoromethanesulfonate, 1-(4,7-dihydroxy-1-naphthalenyl)tetrahydrothiophenium hexafluorophosphate, 1-(4,7-dihydroxy-1-naphthalenyl)tetrahydrothiophenium hexafluorophosphate, etc. Of these, 1-(4,7-dibutoxy-1-naphthalenyl)tetrahydrothiophenium trifluoromethanesulfonate and 1-(4,7-dihydroxy-1-naphthalenyl)tetrahydrothiophenium trifluoromethanesulfonate are preferred. Other examples include diphenyl(4-(phenylthio)phenyl)sulfonium trifluoromethanesulfonate, diphenyl(4-(phenylthio)phenyl)sulfonium hexafluorophosphate, diphenyl(4-(phenylthio)phenyl)sulfonium hexafluoroantimonate, diphenyl(4-(phenylthio)phenyl)sulfonium trifluorotrispentafluoroethylphosphate, diphenyl(4-(phenyl)phenyl)sulfonium trifluorotrispentafluoroethylphosphate, diphenyl(4-(naphthyl)phenyl)sulfonium trifluorotrispentafluoroethylphosphate, diphenyl(4-(anthranyl)phenyl)sulfonium trifluorotrispentafluoroethylphosphate, and the like.Of these, diphenyl(4-(phenylthio)phenyl)sulfonium trifluorotrispentafluoroethyl phosphate and diphenyl(4-(phenyl)phenyl)sulfonium trifluorotrispentafluoroethyl phosphate are preferred. Further examples include bis(t-butylsulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(benzenesulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(4-t-butylbenzenesulfonyl)diazomethane, bis(naphthalenesulfonyl)diazomethane, and bis(anthracenesulfonyl)diazomethane. Of these, bis(cyclohexylsulfonyl)diazomethane and bis(p-toluenesulfonyl)diazomethane are preferred. Furthermore, compounds that are generated within carboxylic acid molecules upon irradiation with light, such as naphthoquinone diazide, can also be used.

[0081] The crosslinking agent in the present invention is not particularly limited, and examples of the crosslinking agent include N-(alkoxymethyl)amino compounds such as N-(alkoxymethyl)glycoluril compounds, N-(alkoxymethyl)urea compounds, N-(alkoxymethyl)melamine compounds, and N-(alkoxymethyl)ethyleneurea compounds.

[0082] Specific examples of the N-(alkoxymethyl)glycoluril compound include N,N,N,N-tetra(methoxymethyl)glycoluril, N,N,N,N-tetra(ethoxymethyl)glycoluril, N,N,N,N-tetra(n-propoxymethyl)glycoluril, N,N,N,N-tetra(i-propoxymethyl)glycoluril, N,N,N,N-tetra(n-butoxymethyl)glycoluril, and N,N,N,N-tetra(t-butoxymethyl)glycoluril. Specific examples of the N-(alkoxymethyl)urea compound include N,N'-di(methoxymethyl)urea, N,N'-di(ethoxymethyl)urea, N,N'-di(n-propoxymethyl)urea, N,N'-di(i-propoxymethyl)urea, N,N'-di(n-butoxymethyl)urea, and N,N'-di(t-butoxymethyl)urea. Specific examples of the N-(alkoxymethyl)melamine compound include N,N,N,N,N,N,N-hexa(methoxymethyl)melamine, N,N,N,N,N,N-hexa(ethoxymethyl)melamine, N,N,N,N,N,N-hexa(n-propoxymethyl)melamine, N,N,N,N,N,N-hexa(i-propoxymethyl)melamine, N,N,N,N,N,N-hexa(n-butoxymethyl)melamine, and N,N,N,N,N,N,N-hexa(t-butoxymethyl)melamine. Specific examples of the N-(alkoxymethyl)ethyleneurea compound include N,N-di(methoxymethyl)-4,5-di(methoxymethyl)ethyleneurea, N,N-di(ethoxymethyl)-4,5-di(ethoxymethyl)ethyleneurea, N,N-di(n-propoxymethyl)-4,5-di(n-propoxymethyl)ethyleneurea, N,N-di(i-propoxymethyl)-4,5-di(i-propoxymethyl)ethyleneurea, N,N-di(n-butoxymethyl)-4,5-di(n-butoxymethyl)ethyleneurea, and N,N-di(t-butoxymethyl)-4,5-di(t-butoxymethyl)ethyleneurea.

[0083] Among these other crosslinking agents, N-(alkoxymethyl)glycoluril compounds are preferred, and N,N,N,N-tetra(methoxymethyl)glycoluril is particularly preferred. The other crosslinking agents can be used alone or in combination of two or more.

[0084] In the present invention, the colored curable resin composition preferably contains the photopolymerization initiator in an amount of 0.01 to 120 parts by mass, and particularly preferably 1 to 100 parts by mass, relative to 100 parts by mass of the polymerizable compound (C). By adopting such an embodiment, the curability and film properties become good.

[0085] In the present invention, the transparent curable resin composition preferably contains the photoacid generator in an amount of 0.01 to 20 parts by mass, and more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the polymerizable compound. By adopting such an embodiment, the curability and film properties become good.

[0086] The curable resin composition has a minimum transmittance of 50% or less for normally incident light having a wavelength of 380 nm to 1,700 nm when applied uniformly to a thickness of 1 μm. When the minimum transmittance for light having a wavelength of 380 nm to 1,700 nm is 50% or less, it becomes possible to form a curable resin region having a wavelength of 380 nm to 1,700 nm, and the resulting diffractive optical element is optimally usable for diffractive optical lenses for imaging, optical lenses for optical sensors, optical lenses for displays, and optical lenses for optical communication.

[0087] The minimum transmittance for light with a wavelength of 380 nm to 1,700 nm is preferably 30% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less.

[0088] The curable resin composition has a maximum extinction coefficient of 0.0001 or more and 1.1 or less for light with a wavelength of 380 nm to 1,700 nm when applied uniformly to a thickness of 1 μm. When the maximum extinction coefficient for light with a wavelength of 380 nm to 1,700 nm is 0.001 or more and 1.1 or less, it is possible to form a curable resin region with a wavelength of 380 nm to 1,700 nm, and the resulting diffractive optical element is optimally usable for imaging diffractive optical lenses, optical lenses for optical sensors, optical lenses for displays, and optical lenses for optical communications. Furthermore, when the colorant concentration satisfies the above maximum extinction coefficient, it becomes easy to achieve a refractive index of 1.6 or more at any wavelength in the wavelength range of 380 nm to 1,700 nm, which is preferable for improving the performance of the diffractive optical element.

[0089] The maximum extinction coefficient for light with a wavelength of 380 nm to 1,700 nm is preferably in the range of 0.005 to 1.1, more preferably in the range of 0.01 to 1.0, and even more preferably in the range of 0.05 to 0.9. When forming a light-shielding resin layer using a curable resin composition, the maximum extinction coefficient is preferably set within the above-mentioned range in order to form a diffractive optical element with sufficient light-shielding ability and to suppress interfacial reflection due to differences in extinction coefficients, i.e., to suppress stray light. Furthermore, in order to make it possible to appropriately adjust the absorber concentration and to suppress the occurrence of agglomerated foreign matter and form a fine diffractive optical element, the maximum extinction coefficient is preferably set below the upper limit of the above-mentioned range. Note that the expression "within the range of A to B" in this specification is synonymous with "A or more and B or less."

[0090] The curable resin composition has a maximum transmittance of 50% or more for light having a wavelength of 380 nm to 1,700 nm that is perpendicularly incident when applied uniformly to a thickness of 1 μm. When the maximum transmittance for light having a wavelength of 380 nm to 1,700 nm is 50% or more, it becomes possible to form transparent regions at different wavelengths in the wavelength range of 380 nm to 1,700 nm while forming a curable resin layer, and the resulting diffractive optical element enables wavelength-selective control of optical properties in diffractive optical lenses for imaging, optical lenses for optical sensors, optical lenses for displays, and optical lenses for optical communication.

[0091] The maximum transmittance for light with a wavelength of 380 nm to 1,700 nm is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 85% or more.

[0092] The dielectric multilayer film according to the present invention is composed of, for example, a multilayer structure in which high-refractive index layers and low-refractive index layers are alternately stacked. The dielectric multilayer film may have a medium-refractive index layer between the high-refractive index layers and the low-refractive index layers.

[0093] The high refractive index layer has a refractive index of n H Then, the refractive index n H is preferably 2.0 or more. As the high refractive index layer, for example, a film containing titanium oxide (TiO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), or a composite oxide thereof may be used. Furthermore, as long as the refractive index is 2.0 or more, an additive may be contained. H A higher refractive index is advantageous for suppressing the amount of wavelength shift at the time of oblique incidence, widening the light transmission blocking band on the ultraviolet side, etc. Therefore, among the above, titanium oxide and niobium oxide, which have higher refractive index, are more suitable for the high refractive index layer.

[0094] The low refractive index layer has a refractive index of n L Then, the refractive index n L is preferably less than 1.6, and more preferably lower than the refractive index of the outermost layer of the transparent substrate. The low refractive index layer may be, for example, a film containing silicon oxide (SiO2), magnesium fluoride (MgF2), barium fluoride (BaF2), lithium fluoride (LiF), or a composite oxide thereof. The low refractive index layer may also be, for example, a film containing silicon oxide (SiO2), magnesium fluoride (MgF2), barium fluoride (BaF2), lithium fluoride (LiF), or a composite oxide thereof. L The film may contain an additive as long as the refractive index is 1.7 or less or lower than the refractive index of the outermost layer of the transparent substrate.

[0095] The medium refractive index layer has a refractive index of n M Then, the refractive index n MThe refractive index of the intermediate refractive index layer is preferably 1.6 or more and less than 2.0, and more preferably lower than the refractive index of the outermost layer of the transparent substrate. For example, a film containing aluminum oxide (Al2O3), cesium fluoride (CeF3), yttrium oxide (YO3), ytterbium oxide (Yb2O3), or a composite oxide thereof can be used as the intermediate refractive index layer. M If the value is 1.6 or more and less than 2.0, additives may be contained.

[0096] Dielectric layers such as high-, medium-, and low-refractive-index layers are formed using, for example, sputtering, vacuum deposition, ion-assisted vacuum deposition, and CVD. Sputtering, vacuum deposition, and ion-assisted vacuum deposition are particularly preferred. The light transmission band is the wavelength band used for receiving light in solid-state imaging devices such as CCD image sensors and CMOS image sensors, making the thickness accuracy of the dielectric layer important. Sputtering, vacuum deposition, and ion-assisted vacuum deposition are excellent at controlling the thickness when forming the dielectric layer. This allows for increased thickness accuracy for each layer constituting the dielectric multilayer film, which is composed of a stack of dielectric layers, resulting in a dielectric multilayer film with desired optical properties. Among these, ion-assisted vacuum deposition is more preferred for achieving both improved film formation speed and control of film thickness.

[0097] The dielectric multilayer film may be preferably provided on both sides of a transparent substrate, which is expected to improve the visible light transmittance by reducing the reflection in the visible light region on both sides of the substrate, and is also suitable for reducing warpage.

[0098] <Fresnel Zone Plate> Fresnel zone plates (FZP) include "amplitude type zone plates" and "phase type zone plates."

[0099] <Amplitude Zone Plate> An amplitude zone plate is a type of diffractive optical element having a diffractive optical structure formed by a concentric pattern in which opaque zones formed by a light-shielding resin layer made of a curable resin composition and transparent zones where, for example, the main surface of a substrate is exposed are alternately combined. The amplitude zone plate increases the intensity of light at the focal position by blocking (attenuating) incident light that destructively interferes with incident light that has passed through the transparent zones.

[0100] The concentric pattern of the amplitude zone plate has a shape as shown in FIG. 1, and the radius r of the nth zone is n is expressed by the following formula (1).

[0101]

[0102] In this specification, a pattern shape that satisfies the above formula (1) is called a "Fresnel zone plate shape." In the above formula (1), λ is the wavelength of light, and f is the focal length of first-order diffraction. A design in which the center starts from light blocking and a design in which the center starts from transmission are possible. For example, in the case of a design in which the center starts from light blocking, r n 2 The zone between n=0 and n=1 is opaque, the zone between n=1 and n=2 is transparent, the zone between n=2 and n=3 is opaque, and so on, alternating between transparent and opaque depending on whether n is odd or even.

[0103] <Light-shielding resin layer> The light-shielding resin layer is a resin layer formed from a material containing a colored curable resin composition, and exhibits light-shielding properties against light having a wavelength in the range of 380 nm to 1,700 nm. That is, the light-shielding resin layer shields at least part of the incident light having a wavelength in the above wavelength range. Preferably, the light-shielding resin layer exhibits light-shielding properties against light having a wavelength in the range of 410 nm to 1,100 nm.

[0104] The diffractive optical element of the present invention preferably has a light-shielding resin layer that forms a diffraction pattern, and the maximum width of the thinnest light-shielding resin layer is preferably 2.0 μm or less. The thinnest light-shielding resin layer of the present invention refers to the light-shielding resin layer with the smallest width, defined as the distance from a transparent region that does not have a light-shielding resin layer to another transparent region diagonally opposite the light-shielding resin layer when the optical element is observed from directly above. The maximum width of the thinnest light-shielding resin layer is more preferably 1.8 μm or less, even more preferably 1.5 μm or less, and particularly preferably 1.2 μm or less. In order to achieve diffractive properties, the lower limit of the width of the thinnest structure is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.25 μm or more. While the width of the thinnest structure in the light-shielding resin layer can be outside the above-mentioned range, it is preferable to set it within the above-mentioned range from the viewpoint of further improving diffraction efficiency.

[0105] From the viewpoint of further increasing the efficiency of the amount of light collected, the light-shielding resin layer has an average thickness of preferably 2 μm or less, more preferably 1.8 μm or less, even more preferably 1.5 μm or less, particularly preferably 1.0 μm or less, and even more preferably 0.8 μm or less.

[0106] <Phase Zone Plate> Like amplitude zone plates, phase zone plates are formed from a transparent curable resin composition. Phase zone plates are a type of diffractive optical element with a diffractive optical structure formed by a concentric pattern of alternating zones formed by a resin layer that transmits incident light and transparent zones where, for example, the main surface of a substrate is exposed. Phase zone plates increase the intensity of light at the focal position by delaying the phase of incident light passing through the zones formed by the resin layer so that the incident light passes through the zones corresponding to the exposed regions constructively. Specifically, the phase difference between incident light passing through the region where the resin layer is formed and incident light passing through the exposed region is π. This design can be achieved, for example, by changing the thickness of the resin layer.

[0107] That is, in the amplitude zone plate, the resin layer blocks light of wavelength λ, whereas in the phase zone plate, the resin layer transmits light of wavelength λ and delays the phase of the light. The concentric circular pattern of the phase zone plate has a shape as shown in FIG. 1, for example, and the radius r of the nth zone is n The same applies to phase-type zone plates in that the above expression (1) is used. Here, "blocking light of wavelength λ" may mean that the transmittance for light of wavelength λ is 30% or less. Also, "transmitting light of wavelength λ" may mean that the transmittance for light of wavelength λ is 60% or more.

[0108] Just to be clear, in the above formula (1), λ is the wavelength of light, and f is the focal length of the first-order diffraction. A design in which the center starts from the resin layer or from the exposed area of ​​the substrate is possible. For example, in the case of a design in which the center starts from the resin layer, r n 2 The zone between n=0 and n=1 is the resin layer, the zone between n=1 and n=2 is the exposed region, and the zone between n=2 and n=3 is the resin layer, and the exposed region and the resin layer appear alternately depending on whether n is an odd or even number.

[0109] Unlike amplitude zone plates, phase zone plates do not block light incident on the region where the resin layer is formed. Therefore, phase zone plates are advantageous in that they can easily increase the light intensity at the focal position. Typically, the light intensity at the focal position of a phase zone plate is about four times that of an amplitude zone plate.

[0110] As described above, the transparent curable resin composition forming the phase-type zone plate does not contain a colorant. The absence of a colorant in the transparent curable resin composition prevents the light irradiated during pattern formation from being attenuated by the colorant. An example of a colorant is a pigment. The absence of a colorant in the transparent curable resin composition prevents the influence of the particle size of the pigment during pattern formation, making it easier to improve the resolution of the pattern formation.

[0111] <Diffraction Pattern> Next, examples of the configuration of the diffraction pattern of the diffractive optical element will be described. Any of the diffraction patterns includes an amplitude zone plate configuration and a phase zone plate configuration.

[0112] Fig. 2 is a diagram schematically illustrating an example of a diffraction pattern formed on the main surface of a substrate of a diffractive optical element. Fig. 2 corresponds to a diagram of the diffraction pattern P1 viewed in a direction perpendicular to the main surface of the substrate. As shown in Fig. 2, the diffraction pattern P1 is divided into a plurality of pattern regions in the circumferential direction with a center C0 as the reference. The center C0 corresponds to the intersection of diagonals (K1, K2) of the substrate 10, which will be described later.

[0113] In the example shown in FIG. 2, the diffraction pattern P1 is divided into a pattern area A1, a pattern area A2, and a pattern area A3.

[0114] As shown in Fig. 2, the pattern region A1 has a plurality of resin layers 20 arranged in a radial direction from the center C0 toward the outer edge. For convenience of illustration, the number of resin layers 20 in the radial direction is omitted in Fig. 2. This also applies to the following drawings.

[0115] As an example, the pattern region A1 is assumed to have a Fresnel zone plate shape corresponding to red light. The red light may refer to light having a peak wavelength in the range of 600 nm to 780 nm. In this case, "exhibiting a Fresnel zone plate shape corresponding to red light" means that the wavelength λ in the above formula (1) is in the range of 600 nm to 780 nm, and the radius r of the nth zone is n This means that the wavelength λ satisfies the formula (1). For example, the wavelength λ is set to 650 nm.

[0116] Similar to pattern region A1, pattern region A2 and pattern region A3 each have a plurality of resin layers 20 arranged in a radial direction from the center C0 toward the outer edge. As an example, pattern region A2 is configured to have a Fresnel zone plate shape corresponding to green light, i.e., light having a peak wavelength in the range of 500 nm or more and less than 600 nm. For example, the wavelength λ is set to 550 nm.

[0117] The pattern region A3 has a Fresnel zone plate shape corresponding to blue light, that is, light having a peak wavelength in the range of 380 nm or more and less than 500 nm. For example, the wavelength λ is 450 nm.

[0118] In this specification, "the diffraction pattern P1 is divided into a plurality of pattern regions in the circumferential direction" means that the diffraction pattern P1 has pattern regions in the circumferential direction that correspond to different light wavelengths λ. Note that the resin layer 20 in the pattern region A1 and the resin layer 20 in the pattern region A2 may be continuous in the circumferential direction or may be spaced apart. The same applies to the pattern region A1 and the pattern region A3, and the pattern region A2 and the pattern region A3.

[0119] 2, the wavelength range to which red light belongs, i.e., the range from 600 nm to 780 nm, corresponds to the "first wavelength range." The wavelength range to which green light belongs, i.e., the range from 500 nm to less than 600 nm, corresponds to the "second wavelength range." The wavelength range to which blue light belongs, i.e., the range from 380 nm to less than 500 nm, corresponds to the "first wavelength range."

[0120] In the Fresnel zone plate shapes of the pattern areas A1, A2, and A3, the focal lengths f of first-order diffraction in the above formula (1) are equal to each other. Here, "the focal lengths f of first-order diffraction in different pattern areas are equal" means that the difference between the focal lengths f of first-order diffraction in each pattern area is within 1% of the focal length f.

[0121] In Fig. 2, the diffraction pattern P1 is divided into three equal parts into the above-mentioned pattern regions (A1, A2, A3), that is, divided at 120° intervals in the circumferential direction with the center C0 of the diffraction pattern P1 as the reference, but the number of divisions of the diffraction pattern P1 is not limited to the example in Fig. 2. Specific examples will be described later.

[0122] When light having a wavelength λ in the range of 380 nm to 1,700 nm is incident as a parallel beam from a direction perpendicular to the main surface of the substrate, and the focal length f is the distance between the substrate and the focusing position D of the light of wavelength λ, the focal length f is preferably 2 μm or more and 70 cm or less. From the viewpoint of focusing more light from the outer periphery of the optical element and increasing the focusing efficiency at the focusing position D, the lower limit of the focal length f of first-order diffraction is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. From the viewpoint of suppressing a decrease in light utilization efficiency due to light diffusion, the upper limit of the focal length f of first-order diffraction is preferably 80 cm or less, and more preferably 50 cm or less.

[0123] Taking an amplitude zone plate as an example, the diffractive optical element preferably has more than 20 boundaries in one direction where the light-shielding regions transition to the light-transmitting regions. Fig. 3A is an enlarged view of a portion of Fig. 2. Fig. 3B is a cross-sectional view taken along the line B-B in Fig. 2. Here, the number of light-shielding regions is the number of boundaries (d1, d2, ..., d) where the light-shielding regions transition to the light-transmitting regions when the diffractive optical element 1 is viewed in a direction perpendicular to the main surface of the substrate 10 and the light-shielding regions are counted in either direction from the center C0 toward the periphery, as shown in Figs. 3A and 3B. n ) is the maximum number of

[0124] In FIG. 3A , the pattern region A1 of the diffraction pattern P1 has four boundaries (d1, d2, d3, d4). That is, the pattern region A1 includes arc-shaped resin layers 20 formed on four concentric circles. However, as described above, the number of resin layers 20 in the radial direction is omitted from the illustration. The number of resin layers 20 in the pattern region A1 is preferably more than 59, more preferably more than 150, even more preferably more than 300, and particularly preferably more than 800. Although not shown, the same discussion as above can be applied to the pattern regions A2 and A3.

[0125] If the number of light-shielding regions is within the above range, a higher light-collecting performance is exhibited, and therefore a diffractive optical element 1 suitable for a fine imaging element is realized.

[0126] 3C is a diagram schematically illustrating a state in which parallel light is incident on a diffractive optical element. In FIG. 3C, cross sections of pattern region A1 and pattern region A2 are shown in consideration of FIG. 3B. Here, the F-number is a value obtained by irradiating parallel light T from a direction perpendicular to the main surface 10a of the substrate 10 (a direction parallel to the optical axis Ax) with light having a wavelength in the range of 380 nm to 1,700 nm and including at least red light and green light. L When the focal length f is the distance between the focal position D of light of wavelength λ incident on the substrate 10 and the substrate 10, the focal length f is calculated by dividing the focal length f by the diameter of the circumscribed circle of the diffraction pattern P1 when viewed in a direction perpendicular to the major surface 10a of the substrate 10 (see FIG. 2 ), and is preferably within the range of 0.2 to 4.0. The range of the F-number is not particularly limited, but if it is 0.2 or greater, it is easy to form and maintain a microstructure that exhibits a diffractive effect. The lower limit of the F-number is preferably 0.3 or greater, and more preferably 0.4 or greater. Furthermore, if the F-number is equal to or less than the above-mentioned upper limit, it is easier to ensure a sufficient amount of light for imaging. Considering the limitations on applications based on the shape and size of the entire optical module and the significant influence of aberration that makes it difficult to focus light on the entire sensor surface, the upper limit of the F-number is preferably 3.5 or less, more preferably 3.2 or less, and even more preferably 3.0 or less.

[0127] 4 is a diagram schematically illustrating another example of the configuration of the diffraction pattern P1. As shown in FIG. 4, the diffraction pattern P1 may be divided into 12 pattern regions in the circumferential direction. More specifically, as shown in FIG. 4, the diffraction pattern P1 includes four pattern regions A1, four pattern regions A2, and four pattern regions A3. The pattern regions are arranged in the order of pattern region A1, pattern region A2, and pattern region A3 in the circumferential direction, and the diffraction pattern P1 exhibits a four-fold rotationally symmetric shape.

[0128] Parallel light T L Ideally, the parallel light beam T (see FIG. 3C) is incident perpendicularly to the main surface 10a of the substrate 10. However, in reality, the parallel light beam T LIt is assumed that the parallel light beam T is incident on the main surface 10a of the substrate 10 with its optical axis slightly tilted relative to the main surface 10a. Here, for example, as shown in FIG. 2, in the diffraction pattern P1, if the pattern region A1, the pattern region A2, and the pattern region A3 are unevenly distributed in the circumferential direction, the parallel light beam T L Depending on the angle of incidence, the light incident on each pattern area may be biased, which may result in variations in the light diffracted and focused in each pattern area.

[0129] In contrast, the diffraction pattern P1 has a four-fold rotational symmetry shape, so that if the parallel light beam T L The optical axis Ax is inclined with respect to the main surface 10a, and the parallel light beam T L is incident on each pattern region (A1, A2, A3), the polarization of the light incident on each pattern region is suppressed when the diffraction pattern P1 is viewed as a whole. In other words, from the viewpoint of suppressing the variation in the light diffracted and focused in each pattern region, it is preferable that the diffraction pattern P1 have a four-fold rotational symmetry shape, as shown in FIG.

[0130] Although the diffraction pattern P1 has been described above as having a four-fold rotational symmetry shape, it is preferable that the diffraction pattern P1 has at least an integral multiple of one rotational symmetry shape.

[0131] Fig. 5A is a diagram showing yet another example configuration of the diffraction pattern P1. Fig. 5B is a diagram schematically showing the diffraction pattern P1 shown in Fig. 5A. As shown in Fig. 5B, the diffraction pattern P1 has an inner region 31 and an outer region 32 located outside the inner region 31. As shown in Fig. 5A, the inner region 31 is shown to include four pattern regions A11, four pattern regions A21, and four pattern regions A31 in the circumferential direction. Furthermore, the outer region 32 is shown to include nine pattern regions A12, nine pattern regions A22, and nine pattern regions A32.

[0132] That is, in the inner region 31, the diffraction pattern P1 is divided into 12 parts in the circumferential direction, and in the outer region 32, the diffraction pattern P1 is divided into 36 parts in the circumferential direction. In this way, the number of divisions of the diffraction pattern P1 in the circumferential direction may increase in the radial direction from the center C0 toward the outer edge of the diffraction pattern P1.

[0133] 6 is a diagram showing yet another example of the configuration of the diffraction pattern P1, in which the diffraction pattern P1 includes an inner region 31 divided into 24 regions in the circumferential direction and an outer region 32 divided into 36 regions in the circumferential direction.

[0134] Here, the diffractive optical element 1 causes the parallel light beam T L In consideration of efficiently collecting the red light, it is preferable that in one pattern region, the difference in the circumferential length between the resin layer 20 closest to the center C0 and the resin layer 20 farthest from the center C0 is small. For example, in the pattern region A11 located in the inner region 31, if the difference in length between the resin layers 20 arranged in the radial direction becomes large, the components of the red light diffracted by the resin layer 20 located on the outer side that do not interfere with the red light diffracted by the resin layer 20 located on the inner side increase, and as a result, the efficiency of collecting the red light in the pattern region A11 decreases.

[0135] Therefore, in the pattern region A11, it is preferable to have as many divisions as possible in the circumferential direction of the diffraction pattern P1 from the viewpoint of minimizing the difference in length between the respective resin layers 20. For example, when the inner region 31 of the diffraction pattern P1 in Fig. 5 is compared with the inner region 31 of the diffraction pattern P1 in Fig. 6, it is clear that, in the example of Fig. 6, the difference in length between the respective resin layers 20 in the pattern region A11 is reduced by increasing the number of divisions in the circumferential direction.

[0136] For convenience, illustration is omitted, but as an example, in the case of a diffraction pattern P1 that focuses light belonging to the visible light range (typically, 380 nm to 780 nm) at a focal length of 1 mm, the number of divisions of the inner region 31 is set to 132 to 204. This number of divisions is preferably an integer multiple of the number of wavelengths that the diffraction pattern P1 corresponds to. Furthermore, although specific examples will be described later, more preferably, the number of divisions is set to an integer multiple of a number determined according to the ratio between the number of wavelengths and the length of each pattern region in the circumferential direction.

[0137] The number of divisions in the outer region 32 is an integer multiple of that in the inner region 31, for example, three times, and is preferably set to 396 to 612. In FIG. 5B , the diffraction pattern P1 has been described as having one outer region 32 for the inner region 31. However, the diffraction pattern P1 may have a region on the outer edge of the outer region 32 that has a different number of divisions in the circumferential direction. An example of this will be described later with reference to FIG. 7 .

[0138] Furthermore, in order to minimize the difference in length between the resin layers 20 in the pattern region A11, it may be possible to reduce the number of resin layers 20 in the radial direction of the pattern region A11 (see also FIG. 3A).

[0139] 4, since the diffraction pattern P1 has a circular shape, the length of each resin layer 20 in one pattern region A11 increases from the center C0 of the diffraction pattern P1 toward the outer edge. Therefore, by reducing the number of resin layers 20 in the radial direction of the pattern region A1, it is possible to suppress an increase in the components of the red light diffracted by the resin layers 20 located on the outer side that do not interfere with the red light diffracted by the resin layers 20 located on the inner side. However, if the parallel light T L If a pattern that diffracts the parallel light beam T is not formed, when the diffraction pattern P1 is viewed as a whole, L On the contrary, the light collection efficiency is reduced.

[0140] 5A , if the number of divisions in the circumferential direction is increased in the region outside pattern region A11, i.e., outer region 32, it is possible to form a plurality of pattern regions (A12, A22, A32) in outer region 32 while reducing the number of resin layers 20 in the radial direction of pattern region A11 belonging to inner region 31. In particular, in this case, the length of the resin layer 20 is shortened in each pattern region located in outer region 32, and therefore, even in the pattern region located in outer region 32, a difference in length between the resin layer 20 close to the center C0 and the resin layer 20 far from the center C0 is unlikely to occur.

[0141] That is, by configuring the diffraction pattern P1 so that the number of divisions in the circumferential direction increases in the radial direction from the center C0 toward the outer edge, it is possible to suppress an increase in the difference between the length of the resin layer 20 close to the center C0 and the length of the resin layer 20 far from the center C0 in both the pattern regions (A11, A21, A31) located in the inner region 31 and the pattern regions (A12, A22, A32) located in the outer region 32. As a result, the overall parallel light beam T L This can increase the light collection efficiency.

[0142] More specifically, in both pattern region A11 and pattern region A12, the circumferential length of each resin layer 20 is preferably substantially equal to the circumferential length of the resin layer 20 closest to the center C0 of pattern region A11. Here, "substantially equal circumferential lengths" may mean that one length is in the range of 0.8 to 1.2 times the other length.

[0143] Although the above description has been given taking the pattern area (A11, A12) as an example, the same discussion can be applied to the pattern area (A21, A22) and the pattern area (A31, A32).

[0144] 5A and 6, the diffraction pattern P1 has a four-fold rotational symmetry shape, as described with reference to FIG.

[0145] Fig. 7 is a diagram schematically illustrating another example of the configuration of the diffraction pattern P1, following Fig. 5B . As shown in Fig. 7 , the diffraction pattern P1 may include an inner region 31, an outer region 32a, an outer region 32b, and an outer region 32c in the radial direction from the center C0 toward the outer edge of the diffraction pattern P1.

[0146] As an example, the number of divisions in the circumferential direction in the inner region 31 and the outer regions (32a, 32b, 32c) in the radial direction from the center C0 toward the outer edge of the diffraction pattern P1 is 336 divisions, 1008 divisions, 3024 divisions, and 9072 divisions. FIG. 8A is a diagram showing the vicinity of the inner region 31 of the diffraction pattern P1 according to FIG. 7. FIG. 8B is an enlarged schematic diagram of a section 33 of the diffraction pattern P1 according to FIG. 7, and FIG. 8C is an enlarged schematic diagram of a section 34 of the diffraction pattern P1 according to FIG. 7. Furthermore, FIG. 8D is an enlarged schematic diagram of a section 35 of the diffraction pattern P1 according to FIG. 7. More specifically, section 33 corresponds to the boundary portion between the inner region 31 and the outer region 32a, section 34 corresponds to the boundary portion between the outer region 32a and the outer region 32b, and section 35 corresponds to the boundary portion between the outer region 32b and the outer region 32c.

[0147] For convenience, illustration is omitted, but in Figures 8A to 8D, each of the inner region 31 and the outer region (32a, 32b, 32c) is divided into pattern region A1, pattern region A2, and pattern region A3, as described with reference to Figures 5A to 5B.

[0148] 8A to 8D, the radius of the nth zone is r n In this example, the inner region 31 corresponds to the region where n = 1 to 8, the outer region 32a corresponds to the region where n = 9 to 80, the outer region 32b corresponds to the region where n = 81 to 278, and the outer region 32c corresponds to the region where n = 279 to 729. Note that the number of divisions in the circumferential direction and the position where the number of divisions is increased from the center C0 toward the outer edge are not limited to this example. Typically, as the focal length increases, the number of annular zones (n) in the radial direction increases, but the number of divisions in the circumferential direction and the position where the number of divisions is increased can be designed appropriately depending on the design of the focal length, etc.

[0149] As an example, in Figures 8A to 8D, the focal length is set to 5 mm.

[0150] In the above description, the circumferential lengths of the resin layers closest to the center C0 of the pattern regions A1, A2, and A3 in the diffraction pattern P1 are substantially equal to each other. However, as shown in FIG. 9A , for example, in the diffraction pattern P1, the multiple pattern regions may be arranged in the order of pattern region A1, pattern region A2, pattern region A3, and pattern region A2. In this case, the ratio of the circumferential lengths of the pattern regions A1, A2, and A3 is 1:2:1. Thus, the sum of the circumferential lengths of the pattern region A1 and the sum of the circumferential lengths of the pattern region A2 may differ from each other. The ratio of the circumferential lengths of the respective pattern regions can be adjusted as appropriate depending on the sensitivity of the sensor that receives the light incident on the diffractive optical element 1 and the light diffracted by the diffractive optical element 1.

[0151] The phrase "the lengths in the circumferential direction are substantially equal to each other" may also mean that one length is in the range of 0.8 to 1.2 times the length of the other.

[0152] Furthermore, as shown in FIG. 9B, the length of the pattern region A2 in the circumferential direction may be made longer than the other pattern regions, and may be made larger than the length of the other pattern regions in the circumferential direction.

[0153] 9A and 9B, the circumferential length of pattern region A2 is greater than the circumferential lengths of the other pattern regions, but this is not limiting. For example, the circumferential length of pattern region A1 or pattern region A3 may be greater than the circumferential length of the other pattern regions.

[0154] The same discussion as that described with reference to Figures 9A and 9B can also be applied to the pattern areas (A11, A21, A31) located in the inner region 31 and the pattern areas (A12, A22, A32) located in the outer region 32.

[0155] Next, the number of divisions of the inner region 31 and the number of divisions of the outer region 32 in the diffraction pattern P1 have been considered and will be described below.

[0156] The maximum wavelength of the light corresponding to each pattern region of the diffraction pattern P1 is λ max , the minimum wavelength is λ min To give a specific example, in the example of FIG. max corresponds to 650 nm, and λ min In this case, in the inner region 31, λ min r corresponding to 1min A circle having a radius of 100 mm (hereinafter referred to as a "first ring") is divided in the circumferential direction.

[0157] Here, in consideration of the fact that each pattern area diffracts light of a corresponding wavelength, the first ring is divided and the circumferential length assigned to each pattern area is at least λ max That is, when the number of divisions in the circumferential direction of the first ring is M1, the following formula (2) is established.

[0158] In the outer region 32, λ min r corresponding to n min Assuming that a circle having a radius of ∇ ...

[0159] By the way, the following equations (4) and (5) are derived from equation (1): max Considering that the value is several orders of magnitude larger than that of the equation (6), the following equation is derived.

[0160] Then, the relationship of the following equation (7) is derived from equations (2), (3), and (6).

[0161] That is, the number of divisions Mn of the outer region 32 in the circumferential direction and the number of divisions M1 of the inner region 31 in the circumferential direction satisfy the relationship of formula (7).

[0162] In addition, the number of divisions in the circumferential direction of the first ring has been examined with specific examples, which will be explained below.

[0163] As described above, it is preferable that the number of divisions M1 in the circumferential direction of the first ring satisfies the following formula (2).

[0164] In practice, the resolution Δ of the resin layer 20 is taken into consideration when determining the length of the resin layer 20 in the circumferential direction. max If it is greater than 1, the minimum value M1 can take is M1 min On the other hand, when the resolution Δ is λ max If it is smaller, the maximum value M1 can take is M1 max is expressed by the following equation (9).

[0165] As an example, when the diffraction pattern P1 is equally divided into a pattern region A11 corresponding to 650 nm, a pattern region A21 corresponding to 550 nm, and a pattern region A31 corresponding to 450 nm in the circumferential direction, and the ratio of the lengths of the resin layer closest to the center C0 of each pattern region in the circumferential direction is 1:1:1, min and M1 max The calculation results of the value of are shown in Table 1 below. In this case, the resolution Δ was set to 1 μm, and f was calculated in the range of 1 mm to 50 mm. min and M1 max Here, for example, when the diffraction pattern P1 has four-fold rotational symmetry, M1 min and M1 max When the ratio of the lengths of the patterns in the circumferential direction is 1:1:1, M1 is derived as the largest integer among multiples of 12 (4 x 3) that is smaller than each calculation result. min and M1 max is shown.

[0166] According to Table 1, when f is 1 mm, M1 min is 132, M1 maxIt can be seen that it is preferable that the number of divisions in the circumferential direction of the first ring, that is, the total number of pattern regions A11, A21, and A31 located closest to the center C0 of the diffraction pattern P1, is 132 to 204.

[0167] As described with reference to FIG. 9A, when the ratio of the lengths of the resin layers closest to the center C0 of the pattern region A11, pattern region A21, and pattern region A31 of the first ring in the circumferential direction is 1:2:1, min and M1 max The calculated values ​​are shown in Table 2 below.

[0168] According to Table 2, in the above case, for example, when f is 1 mm, M1 min is 128, M1 max It can be seen that it is preferable that the value of the .lambda.

[0169] As shown in Table 2, M1 min and M1 max is derived as the largest integer among multiples of 16 (4 × 4) that is smaller than each calculation result, based on the fact that the diffraction pattern P1 has four-fold rotational symmetry and that the ratio of the lengths of each pattern in the circumferential direction is 1:2:1.

[0170] That is, the number of divisions of the first ring is determined according to the ratio of the number of wavelengths corresponding to the diffraction pattern P1 to the length of each pattern region in the circumferential direction.

[0171] The above consideration is merely an example. As will be clear from the simulation results described later, for example, min The number of divisions is about half of the above M1 max Even if a division number of about twice as many as that of the diffraction pattern P1 is adopted, light of a plurality of wavelengths can be sharply focused at a focal point, and a diffraction pattern P1 having light-focusing characteristics sufficient for imaging can be realized.

[0172] In the above description, the diffraction pattern P1 has been described as having the pattern regions A1, A2, and A3, but the diffraction pattern P1 may also be composed of only two pattern regions, for example, the pattern regions A1 and A2. Furthermore, in addition to the pattern regions A1, A2, and A3, the diffraction pattern P1 may also have other pattern regions exhibiting Fresnel zone plate shapes corresponding to different wavelengths λ.

[0173] In the above description, the pattern region A1 has a Fresnel zone plate shape corresponding to red light, the pattern region A2 has a Fresnel zone plate shape corresponding to green light, and the pattern region A3 has a Fresnel zone plate shape corresponding to blue light. However, this is merely an example. The wavelength λ of light corresponding to each pattern region (A1, A2, A3) is not limited to the above and can be appropriately designed within a wavelength range of 380 nm to 1,700 nm.

[0174] <Refractive Index and Extinction Coefficient> The refractive index n and extinction coefficient k of the curable resin were measured by applying a sample to a thickness of 1 μm to a silicon wafer (111 orientation, undoped, diameter 10 mm, thickness 280 μm, manufactured by Universalwafer Inc.) using a spinner, and measuring the refractive index n and extinction coefficient k using a spectroscopic ellipsometry (M-2000D manufactured by J.A. Woollam).

[0175] The evaluation of the maximum absorption wavelength, the evaluation of the maximum transmittance, and the evaluation of the minimum transmittance were calculated by measuring the transmittance in each wavelength range using a 1 μm-thick sample for which the wavelength-specific refractive index and extinction coefficient were measured. The transmittance at each wavelength was measured using a spectrophotometer (U-4100) manufactured by Hitachi High-Technologies Corporation, after leaving the sample to stand for one week in a dark environment at room temperature of 25° C. and humidity of 60%, using unpolarized light incident from a direction perpendicular to the substrate of the diffractive optical element, under an environment at room temperature of 25° C. and humidity of 50%.

[0176] [Colored curable resin composition 1: JSSG-9135 manufactured by JSR Corporation] The refractive index and extinction coefficient for each wavelength of curable resin composition 1 are shown in Figure 10. Within the wavelength range of 410 nm to 1,100 nm, curable resin composition 1 had maximum absorptance for light with wavelengths of 483 nm, 659 nm, and 738 nm, with a maximum transmittance of 86% and a minimum transmittance of 0.5%.

[0177] [Colored curable resin composition 2: BLUE-105 manufactured by JSR Corporation] The refractive index and extinction coefficient for each wavelength of curable resin composition 2 are shown in Figure 11. Within the wavelength range of 410 nm to 1,100 nm, curable resin composition 2 had maximum absorptance for light with wavelengths of 620 nm and 756 nm, with a maximum transmittance of 65% and a minimum transmittance of 1.5%.

[0178] [Colored curable resin composition 3: RED-101 manufactured by JSR Corporation] The refractive index and extinction coefficient of curable resin composition 3 by wavelength are shown in Fig. 12. Within the wavelength range of 410 nm to 1,100 nm, curable resin composition 3 had maximum absorptance for light with wavelengths of 530 nm and 578 nm, with a maximum transmittance of 88% and a minimum transmittance of 5%.

[0179] [Transparent Curable Resin Composition 4: Positive Interlayer Insulating Film Forming Material, Manufactured by JSR] For the curable resin composition 4, a simulation was carried out with a refractive index of 1.5 and an extinction coefficient of 0.

[0180] [Colored Curable Resin Composition 5] Curable resin composition 5 was prepared by mixing 0.083 g of FDB-004 (manufactured by Yamada Chemical Industry Co., Ltd.), 0.017 g of pentaerythritol tetraacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.6 mg of IRGACURE 184 (manufactured by Ciba Japan Co., Ltd.), 0.6 mg of octamethylcyclotetrasiloxane (manufactured by Tokyo Chemical Industry Co., Ltd.), 1 g of cyclopentanone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.05 g of propylene glycol 1-monomethyl ether 2-acetate (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0181] The extinction coefficient of curable resin composition 5 was as shown in Figure 13. The coating film of curable resin composition 5 contained a large amount of aggregates due to the high concentration of dye, making it difficult to stably calculate the refractive index. Furthermore, the amount of aggregates contained in the coating film of curable resin composition 5 was so large that it was not suitable for microfabrication even after ultraviolet irradiation. Note that curable resin composition 5 had a maximum absorption wavelength of 449 nm and an extinction coefficient of 1.1. Furthermore, the maximum transmittance was 89% and the minimum transmittance was 0.0%.

[0182] [Transparent curable resin composition 6: ZP-S206N manufactured by JSR Corporation] The refractive index and extinction coefficient of curable resin composition 6 by wavelength are shown in Figure 14. In particular, it can be seen that curable resin composition 6 has a refractive index of about 1.6 and exhibits transparency to light in the wavelength range of 410 nm to 1,100 nm.

[0183] Example 1 An adhesion promoter (AP3000 manufactured by The Dow Chemical Company) was applied to a glass substrate (Eagle XG manufactured by Corning Incorporated, diameter 8 inches, thickness 0.7 mm) using a spinner, and then heated on a hot plate at 190°C for 300 seconds to form an adhesion promoter layer. Colored curable resin composition 1 (JSSG-9135 manufactured by JSR Corporation) was applied to the quartz glass substrate having this adhesion promoter layer using a spinner, and then prebaked on a hot plate at 100°C for 180 seconds to form a substrate having a coating film. The substrate having this coating film was exposed using an i-line stepper (FPA-3030i5+ manufactured by Canon Inc.) via the following reticle: The conditions for the pattern formed on the reticle were a focal length f = 5 mm in the above formula (1), and the numbers of divisions in the circumferential direction of the inner region 31, outer region 32a, outer region 32b, and outer region 32c described with reference to Figure 7 were 336, 336, 672, and 1680, respectively. The pattern also had periodic Fresnel zone plate shapes corresponding to red light with a wavelength of 650 nm, green light with a wavelength of 550 nm, and blue light with a wavelength of 450 nm, respectively. When n in the above formula (1) was set to a focusing resolution of approximately 1 μm, the radius was 1.72 mm. The focusing resolution of the diffraction pattern was approximately the same as the width of the outermost annular zone. Hereinafter, red light, green light, and blue light may be abbreviated as "RGB."

[0184] After the exposure, the unexposed portions were dissolved by immersing the plate in a resist developer (S-170809 manufactured by Kanto Chemical Co., Ltd.). After rinsing the resist developer with pure water, the plate was air-dried with an air gun and post-baked on a hot plate at 200°C for 300 seconds to obtain a Fresnel zone plate having approximately 200 curable resin layers with a thickness of 0.414 µm.

[0185] To evaluate the optical properties of the obtained Fresnel zone plate, the light-collecting properties at wavelengths of 650 nm, 550 nm, and 450 nm were evaluated using the following optical elements.

[0186] Laser light source: PHAROS (PH1-SP-1mJ) manufactured by LightConversion Wavelength converter: ORPHEUS manufactured by LightConversion Objective lens: PLN40X manufactured by Olympus Corporation Beam profiler: DCC1545M manufactured by Thorlabs

[0187] The light intensity distributions at the focusing position obtained by the beam profiler are shown in Figures 15A to 15C. Figure 15A shows the light intensity distribution at a wavelength of 650 nm, Figure 15B shows the light intensity distribution at a wavelength of 550 nm, and Figure 15C shows the light intensity distribution at a wavelength of 450 nm. Figures 16A to 16C show the light intensity distributions in the x direction for each of Figures 15A to 15C. It can be seen that light of all wavelengths is sharply focused at the designed focal length of 5 mm. Furthermore, the FWHM was approximately 1.1 μm, providing focusing characteristics sufficient for imaging (see Figures 16A to 16C).

[0188] Furthermore, when USAF1951 was imaged using the obtained Fresnel zone plate, the image shown in Fig. 17 was obtained. Incident light of continuous wavelengths in the visible light range was used to acquire this image. Since light of wavelengths 650 nm, 550 nm, and 450 nm contained in the incident light was simultaneously focused at the focal point, the image shown in Fig. 17 exhibited a composite color of the wavelengths, i.e., white.

[0189] As shown in Figure 17, the obtained Fresnel zone plate was found to be a lens suitable for imaging with a resolving power of about Group 8. It should be noted that the entire image in Figure 17 appears hazy, but this is thought to be due to the influence of some of the visible light used to acquire the image, with wavelengths other than the RGB wavelengths that were the design wavelengths in this example. In other words, the fact that the Fresnel zone plate of this example focuses light of each RGB wavelength at a focal point is unrelated to the overall haze in Figure 17. The haze seen in Figure 17 can be removed, for example, by image processing or an optical filter.

[0190] The colored curable resin composition 1 is a material that is transparent to green light (particularly in the range of 500 nm or more and less than 600 nm) (see FIG. 10). That is, it is presumed that in Example 1, the diffraction effect of a phase-type zone plate was obtained for green light, and the diffraction effect of a light-shielding zone plate was obtained for red and blue light. This material can achieve both the diffraction effect of an amplitude-type zone plate and the diffraction effect of a phase-type zone plate, thereby forming a lens with high light-collection efficiency and capable of acquiring brighter images. It is also preferable to increase the transmittance of red and blue light by appropriately setting the thickness of the resin layer in consideration of the refractive index. This also applies to Examples 2 and 3 described below.

[0191] Example 2 An adhesion promoter (AP3000 manufactured by The Dow Chemical Company) was applied to a glass substrate (Corning Incorporated, Eagle XG, 8-inch diameter, 0.7 mm thickness) using a spinner, and then heated on a hot plate at 190°C for 300 seconds to form an adhesion promoter layer. A colored curable resin composition 1 (JSSG-9135 manufactured by JSR Corporation) was applied to the quartz glass substrate with this adhesion promoter layer using a spinner, and then pre-baked on a hot plate at 100°C for 180 seconds to form a substrate with a coating film. The substrate with this coating film was exposed using an i-line stepper (Canon Inc., FPA-3030i5+) through the following reticle. The conditions for the pattern formed on the reticle were the same as those in Example 1, except that, as described with reference to FIG. 9B , the ratio of the lengths of the pattern regions corresponding to red light, green light, and blue light in the circumferential direction was 1:2:1.

[0192] When the resulting Fresnel zone plate was used to capture an image of USAF1951, the image shown in Figure 18 was obtained. In this case, since the RGB ratio was 1:2:1, it can be seen that the image formed had a strong green (G) tint compared to the incident visible light. Furthermore, these results show that each wavelength of RGB can be simultaneously focused at the design focus, and that increasing the RGB ratio increases the light intensity of that wavelength proportionally. In other words, these results demonstrate the effectiveness and usefulness of adjusting the RGB ratio according to the sensor sensitivity, etc.

[0193] Example 3 An adhesion promoter (AP3000 manufactured by The Dow Chemical Company) was applied to a glass substrate (Corning Incorporated, Eagle XG, 8-inch diameter, 0.7 mm thickness) using a spinner, and then heated on a hot plate at 190°C for 300 seconds to form an adhesion promoter layer. A colored curable resin composition 1 (JSSG-9135 manufactured by JSR Corporation) was applied to the quartz glass substrate with this adhesion promoter layer using a spinner, and then pre-baked on a hot plate at 100°C for 180 seconds to form a substrate with a coating film. The substrate with this coating film was exposed using an i-line stepper (Canon Inc., FPA-3030i5+) through the following reticle. The conditions for the pattern formed on the reticle were a focal length f = 10 mm in the above formula (1), and the number of divisions in the circumferential direction of the inner region 31 and the outer region 32 described with reference to FIG. 5B were 480 and 2400, respectively. The pattern had periodic Fresnel zone plate shapes corresponding to red light with a wavelength of 650 nm, green light with a wavelength of 550 nm, and blue light with a wavelength of 450 nm. When n in the above formula (1) was set so that the focusing resolution was about 1 μm, the radius was 3.44 mm.

[0194] After the exposure, the unexposed portions were dissolved by immersing the plate in a resist developer (S-170809 manufactured by Kanto Chemical Co., Ltd.). After rinsing the resist developer with pure water, the plate was air-dried with an air gun and then post-baked on a hot plate at 200°C for 300 seconds to obtain a Fresnel zone plate having approximately 50 curable resin layers with a thickness of 0.414 µm.

[0195] Furthermore, when the obtained Fresnel zone plate was used to image USAF1951 in the same manner as in Example 2, the image shown in Figure 19 was obtained. It was found that the obtained Fresnel zone plate was a lens with sufficient performance for imaging. Figure 19 shows that appropriately calculating and designing the number of divisions in the circumferential direction of the inner region 31 in Figure 5B in accordance with the focal length, and increasing the number of divisions in the circumferential direction of the outer region 32, can bring about good results in imaging with a Fresnel zone plate that focuses light of multiple wavelengths.

[0196] Example 4 Transparent curable resin composition 6 (ZP-S206N, manufactured by JSR Corporation) was applied onto a glass substrate (Eagle XG, manufactured by Corning Incorporated, diameter 8 inches, thickness 0.7 mm) using a spinner, and then pre-baked on a hot plate at 110°C for 300 seconds to form a substrate with a coating film. The substrate with this coating film was exposed using an i-line stepper (FPA-3030i5+, manufactured by Canon Inc.) through the following reticle. The conditions for forming the pattern on the reticle were the same as those in Example 1.

[0197] After the exposure, the plate was post-baked on a hot plate at 100°C for 180 seconds, and then immersed in a resist developer (PD523 manufactured by Tama Chemical Co., Ltd.) to dissolve the unexposed areas. The resist developer was washed away with pure water, and the plate was air-dried to obtain a Fresnel zone plate having approximately 200 curable resin layers with a thickness of 0.44 µm.

[0198] The optical properties of the obtained Fresnel zone plate were evaluated by evaluating the light-collecting characteristics at wavelengths of 650 nm, 550 nm, and 450 nm using the following optical elements: Laser light source: PHAROS (PH1-SP-1mJ) manufactured by LightConversion, Inc. Wavelength converter: ORPHEUS manufactured by LightConversion, Inc. Objective lens: PLN40X manufactured by Olympus Corporation Beam profiler: DCC1545M manufactured by Thorlabs.

[0199] The light intensity distribution at the focusing position obtained by the beam profiler is shown in Figures 20A to 20C, following Figures 15A to 15C. Figures 21A to 21C also show the light intensity distribution in the x direction for each of Figures 20A to 20C. It can be seen that light of all wavelengths is sharply focused at the designed focal length of 10 mm. Furthermore, the FWHM was approximately 1.2 μm, providing focusing characteristics sufficient for imaging (see Figures 21A to 21C).

[0200] Furthermore, when USAF1951 was imaged using the obtained Fresnel zone plate, the image shown in Fig. 22 was obtained. Incident light of continuous wavelengths in the visible light range was used to acquire this image. Since light of wavelengths 650 nm, 550 nm, and 450 nm contained in the incident light was simultaneously focused at the focal point, the image shown in Fig. 22 exhibited a composite color of the wavelengths, i.e., white.

[0201] As shown in Fig. 22, the obtained Fresnel zone plate was found to be a lens suitable for imaging with a resolving power of about Group 8. As for the fact that the whole image appears hazy in Fig. 22, the same argument as that made with reference to Fig. 17 can be made.

[0202] The transparent curable resin composition 6 is a material that is transparent to visible light, and lenses fabricated from this material are colorless and transparent. With this material, by appropriately setting the thickness of the resin layer in consideration of the refractive index, it is possible to achieve both the diffraction effect of an amplitude zone plate and the diffraction effect of a phase zone plate. In other words, this material is characterized by its ability to form lenses that have a higher light-collection efficiency than amplitude zone plates and can acquire brighter images. This point can be understood from this example and Example 9 described below.

[0203] [Example 5] In Example 5, simulation software was used to verify the light-collecting performance of a diffraction pattern having periodic Fresnel zone plate shapes corresponding to red light with a wavelength of 650 nm, green light with a wavelength of 550 nm, and blue light with a wavelength of 450 nm, respectively, where the focal length f in the above formula (1) is 1 mm (see also FIG. 4). In Example 5, the number of divisions in the circumferential direction of the diffraction pattern was set to 204. This number of divisions was set to M1 when the focal length was 1 mm as described above. max (See Table 1.) In this simulation, an amplitude type zone plate was assumed, and the material constituting the diffraction pattern was set to Cu, which blocks visible light.

[0204] As a result of the simulation, as shown in Figures 23A to 23C, it can be seen that red light (650 nm), green light (550 nm), and blue light (450 nm) with design wavelengths are focused at a focal length of 1 mm as designed.

[0205] A Cu layer exhibiting a pattern according to the following conditions was input into electromagnetic field calculation simulation software (Ansys Lumerical, manufactured by Ansys). The conditions for the Cu layer were a focal length f = 1 mm in the above formula (1), and the number of divisions in the circumferential direction of the inner region 31 and the outer region 32 described with reference to FIG. 5B was 204 and 612, respectively. The pattern also had periodic Fresnel zone plate shapes corresponding to red light with a wavelength of 650 nm, green light with a wavelength of 550 nm, and blue light with a wavelength of 450 nm, respectively. The thickness direction of the Cu layer (the optical axis direction of the diffractive optical element) was the z direction, and the Cu layer had a radius of 0.260 mm and a thickness of 0.413 μm on the xy plane perpendicular to the z direction. The number of Cu layers ranged from 102 to 147 for each RGB wavelength, and the finest line width was 1.0 μm (F-number: 0.52). A Cu layer with a radius of 0.260 mm and a thickness of 0.413 μm was uniformly provided on the z-side. For this model, the electric field intensity (Field) in the xy plane at a position −0.5 μm from the upper surface of the Fresnel zone plate was calculated using the FDTD method under the following conditions.

[0206] (Calculation conditions) Fresnel zone plate installation position: x direction: -0.026 mm to 0.026 mm y direction: -0.026 mm to 0.026 mm z direction: 0 μm to 0.5 μm FDTD calculation area: x direction: -0.0375 mm to 0.0375 mm y direction: -0.0375 mm to 0.0375 mm z direction: -1.0 μm to 1.0 μm Mesh size: 0.1 μm in x, y, and z Light source settings: In order to measure the focusing characteristics of the three RGB wavelengths, the wavelength of the incident light was set to a continuous wavelength in the visible light range, and the wavelengths to be observed were 650 nm, 550 nm, and 450 nm. Light source incident position: The position -1 μm in the z direction was set as the light source surface, and it was set to emit in the positive z direction. Light source distribution: Plane wave

[0207] Electric field strength |E| in the x direction at y = 0 obtained for each wavelength of RGB 2 (V 2 / m 2 24A to 24C. In all of the results obtained, the FWHM, which indicates the light-collecting performance, was approximately 1.0 μm, and light of each of the RGB wavelengths could be collected simultaneously at the designed focal point, demonstrating high light-collecting performance suitable for imaging applications.

[0208] From Example 5, it can be seen that by configuring a Fresnel zone plate shape corresponding to each wavelength of RGB and dividing and arranging the pattern areas corresponding to each wavelength in the circumferential direction, the diffraction effect of the amplitude zone plate can be used to simultaneously focus light of each wavelength of RGB at the designed focus. This result is consistent with the results of Examples 1 to 4, in which the Fresnel zone plate shape was formed using a resin layer.

[0209] Example 6 The experiment was carried out under the same conditions as in Example 5, except that the number of divisions of the Cu layer in the circumferential direction was set to 408.

[0210] The results obtained in Example 6 are shown in Figures 25A to 25C and Figures 26A to 26C. Figures 25A to 25C show the electric field intensity distributions for each wavelength of RGB, and Figures 26A to 26C show the electric field intensity |E| in the x direction at y=0 obtained for each wavelength of RGB. 2 (V 2 / m 2) In all of the results obtained, the FWHM, which indicates the light-collecting performance, was about 1.0 μm, and the light-collecting performance was high enough to be applicable to simultaneous imaging at three wavelengths. In Example 6, unlike Example 5, the number of divisions of the inner region 31 in FIG. 5B is M1 when the focal length is 1 mm as described above. max (See Table 1.) According to the sixth embodiment, the number of divisions is M1 max It can be seen that even if the radii are set to about twice the designed focal point, the RGB wavelengths can be simultaneously focused at the designed focal point.

[0211] Example 7 This example was carried out under the same conditions as in Example 5, except that the number of divisions of the Cu layer in the circumferential direction was set to 132.

[0212] The results obtained in Example 7 are shown in Figures 27A to 27C and Figures 28A to 28C. Figures 27A to 27C show the electric field intensity distributions for each wavelength of RGB, and Figures 28A to 28C show the electric field intensity |E| in the x direction at y=0 obtained for each wavelength of RGB. 2 (V 2 / m 2 ) In all of the results obtained, the FWHM, which indicates the light-collecting performance, was about 1.0 μm, and the light-collecting performance was high enough to be applicable to simultaneous imaging at three wavelengths. In Example 7, unlike Example 5, the number of divisions of the inner region 31 in FIG. 5B is M1 when the focal length is 1 mm as described above. min (See Table 1.) According to Example 7, the number of divisions is M1 min Even if the above condition is satisfied, it is understood that the light of each wavelength of RGB can be simultaneously collected at the designed focal point.

[0213] Example 8 This example was carried out under the same conditions as in Example 5, except that the number of divisions of the Cu layer in the circumferential direction was set to 12.

[0214] The results obtained in Example 8 are shown in Figures 29A to 29C and Figures 30A to 30C. Figures 29A to 29C show the electric field strength distributions for each wavelength of RGB, and Figures 30A to 30C show the electric field strength |E| in the x direction at y=0 obtained for each wavelength of RGB. 2 (V 2 / m 2) In Example 8, the light of each wavelength of RGB is focused at the focal position, similarly to, for example, Example 5. However, it can be seen that the light focusing performance of Example 8 is inferior compared to Example 5. In view of this, the number of divisions of the diffraction pattern is at least M1 min It is preferable that the ratio is at least half of M1. min It is more preferable that the above be set.

[0215] From the viewpoint of comparing the results of Example 5 and Example 8 in more detail, logarithmic plots of the electric field intensity distribution at the focal length of Example 5 are shown in FIGS. 31A to 31C. Also, logarithmic plots of the electric field intensity distribution at the focal length of Example 8 are shown in FIGS. 32A to 32C. The logarithmic plots emphasize and display the intensity distribution strength and symmetry of the light collection. As shown in FIGS. 31A to 31C, when the number of divisions is 204 (Example 5), symmetry is observed in the electric field intensity distribution of each wavelength of RGB, resulting in a uniform in-plane distribution. In contrast, as shown in FIGS. 32A to 32C, when the number of divisions is 12 (Example 8), the symmetry of the electric field intensity distribution is poorer than that of Example 5. In other words, a larger number of divisions of the diffraction pattern is preferable, and as mentioned above, it is preferable to have at least M1 min It is preferable that the ratio is at least half of M1. min More preferably, it is set to be equal to or greater than this.

[0216] In Examples 5 to 8, the diffraction pattern is made of a Cu layer, but it is presumed that the same discussion regarding the number of divisions of the diffraction pattern can be made when the diffraction pattern is made of a resin layer.

[0217] [Example 9] This example was carried out under the same conditions as Example 5, except that the material constituting the diffraction pattern was transparent curable resin composition 6. In this case, the thickness of the resin layer formed of transparent curable resin composition 6 was set to 440 nm. In this example, the resin layer transmits light of each wavelength of RGB, and therefore, the diffraction pattern is considered to exhibit the light-collecting performance of a "phase type zone plate."

[0218] The results obtained in Example 9 are shown in Figures 33A to 33C and Figures 34A to 34C. Figures 33A to 33C show the electric field intensity distributions for each wavelength of RGB, and Figures 34A to 34C show the electric field intensity |E| in the x direction at y=0 obtained for each wavelength of RGB. 2 (V 2 / m 2 The FWHM, which indicates the light-gathering performance, was about 1.0 μm in all of the obtained results, and the light-gathering performance was high enough to be applicable to simultaneous imaging at three wavelengths.

[0219] Figures 35A to 35C show logarithmic plots of the electric field intensity distribution at the focal length of Example 9. It can be seen that the RGB electric field intensities are all symmetrically focused simultaneously. Comparing the electric field intensity with that of Example 5 (see Figures 31A to 31C), it can be seen that Example 9 achieved the "improved focusing intensity" expected from a phase-type zone plate for all wavelengths. Furthermore, the refractive index of transparent curable resin composition 6 does not fluctuate significantly in the visible light range, with the fluctuation being approximately ±0.2, based on the average refractive index in the visible light range (see Figure 14). Example 9 demonstrates that a curable resin composition that transmits the wavelengths to be focused while exhibiting minimal change in refractive index for each wavelength is suitable for forming a phase-type zone plate.

[0220] Example 10 An adhesion promoter (AP3000 manufactured by The Dow Chemical Company) was applied to a glass substrate (Corning Incorporated, Eagle XG, 8-inch diameter, 0.7 mm thickness) using a spinner, and then heated on a hot plate at 190°C for 300 seconds to form an adhesion promoter layer. A colored curable resin composition 1 (JSSG-9135 manufactured by JSR Corporation) was applied to the quartz glass substrate with this adhesion promoter layer using a spinner, and then prebaked on a hot plate at 100°C for 180 seconds to form a substrate with a coating film. The substrate with this coating film was exposed using an i-line stepper (Canon Inc., FPA-3030i5+) through the following reticle. The conditions for the pattern formed on the reticle were a focal length f = 5 mm in the above formula (1), and a periodic Fresnel zone plate shape corresponding to each of the RGB wavelengths, as described with reference to FIG. 4 . The number of divisions in the circumferential direction of the pattern was set to 336. When n in the above formula (1) was set so that the focusing resolution was about 1 μm, the radius was 1.72 mm. The focusing resolution of the diffraction pattern is approximately the same as the width of the outermost annular zone.

[0221] After the exposure, the unexposed portions were dissolved by immersing the plate in a resist developer (S-170809 manufactured by Kanto Chemical Co., Ltd.). After rinsing the resist developer with pure water, the plate was air-dried with an air gun and post-baked on a hot plate at 200°C for 300 seconds to obtain a Fresnel zone plate having approximately 200 curable resin layers with a thickness of 0.414 µm.

[0222] When USAF1951 was imaged using the obtained Fresnel zone plate, the image shown in Figure 36 was obtained. It can be seen from Figure 36 that the light of each wavelength of RGB was simultaneously collected at the focal point by the obtained Fresnel zone plate. The image acquisition conditions were the same as those described in Example 1.

[0223] 5B, the pattern formed on the reticle had an inner region 31 and an outer region 32, and the number of divisions in the circumferential direction in the outer region 32 was set to 1680. Just to be clear, the diameter of the area where the pattern was formed was the same as in Example 10.

[0224] When USAF1951 was imaged using the obtained Fresnel zone plate, the image shown in Figure 37 was obtained. From Figure 37, it can be seen that the light of each wavelength of RGB was simultaneously collected at the focal point by the obtained Fresnel zone plate.

[0225] The difference between Example 11 and Example 10 is whether the diffraction pattern has a region where the number of divisions in the circumferential direction increases in the radial direction from the center to the outer edge. From Figures 36 and 37, it can be seen that having a region where the number of divisions in the radial direction increases increases the efficiency of collecting incident light, making it possible to obtain a clearer image.

[0226] In the above Examples 1 to 11, the fact that the resin layer is formed mainly from the colored curable resin composition 1 or the transparent curable resin composition 6 was investigated. However, in view of the above verification results, it can be understood that even when the curable resin compositions 2 to 5 are used, a Fresnel zone plate that can simultaneously collect light of multiple wavelengths, for example, light of each wavelength of RGB, can be realized.

[0227] More specifically, the colored curable resin composition 2, which transmits blue light in particular (see FIG. 11), is expected to exhibit the diffraction effect of a phase zone plate for blue light and the diffraction effect of an amplitude zone plate for red and green light. The colored curable resin composition 3 is expected to exhibit the diffraction effect of a phase zone plate for red light and the diffraction effect of an amplitude zone plate for green and blue light (see FIG. 12). Similarly, the colored curable resin composition 5 is expected to exhibit the diffraction effect of a phase zone plate for red and green light and the diffraction effect of an amplitude zone plate for blue light (see FIG. 13). Furthermore, the transparent curable resin composition 4, like the transparent curable resin composition 6, is expected to exhibit the diffraction effect of a phase zone plate for light of each wavelength of RGB.

[0228] The diffractive optical element and method for manufacturing a diffractive optical element of the present invention are thin, have high light-collecting performance, and are highly suitable for mass production as they can be manufactured without an etching step, and are capable of simultaneously collecting light of multiple wavelengths, and the method for manufacturing such a diffractive optical element can be suitably used for manufacturing diffractive optical lenses for imaging, optical lenses for optical sensors, optical lenses for displays, and optical lenses for optical communication.

[0229] 1: Diffractive optical element 10: Substrate 10a: Main surface 20: Resin layer 31: Inner region 32, 32a, 32b, 32c: Outer region A1, A2, A3: Pattern region A11, A12, A21, A22, A31, A32: Pattern region P1: Diffraction pattern

Claims

1. A diffractive optical element that diffracts incident light having a wavelength in the range of 380 nm to 1,700 nm, comprising: a substrate that transmits the incident light; and a resin layer formed from a curable resin composition that forms irregularities on a main surface of the substrate and that forms a diffraction pattern that is substantially concentric when viewed in a direction perpendicular to the main surface of the substrate, wherein the diffraction pattern is divided into a plurality of pattern regions in the circumferential direction with respect to the center of the diffraction pattern when viewed in the direction perpendicular to the main surface of the substrate, and the plurality of pattern regions include at least: a first pattern region that exhibits a Fresnel zone plate shape corresponding to light that is included in the incident light and that belongs to a first wavelength range; and a second pattern region that exhibits a Fresnel zone plate shape corresponding to light that is included in the incident light and that belongs to a second wavelength range different from the first wavelength range.

2. The diffractive optical element according to claim 1, wherein the diffraction pattern has an area in which the number of divisions in the circumferential direction of the diffraction pattern increases in the radial direction from the center of the diffraction pattern to the outer edge.

3. A diffractive optical element as described in claim 2, wherein the circumferential length of the resin layer belonging to the first pattern region is substantially equal to the circumferential length of the resin layer belonging to the first pattern region that is closest to the center of the diffraction pattern.

4. A diffractive optical element according to any one of claims 1 to 3, wherein the plurality of pattern regions includes a third pattern region having a Fresnel zone plate shape that corresponds to light that falls within a third wavelength range that is different from the first wavelength range and the second wavelength range.

5. A diffractive optical element according to claim 4, wherein the plurality of pattern regions are composed only of the first pattern region, the second pattern region, and the third pattern region, the first pattern region, the second pattern region, and the third pattern region all have a focal length of 1 mm and present a Fresnel zone plate shape corresponding to light belonging to the visible light range, the lengths in the circumferential direction of the resin layer closest to the center of the diffraction pattern are substantially equal to each other, and the total number of the first pattern region, the second pattern region, and the third pattern region located closest to the center of the diffraction pattern is 132 to 204.

6. The diffractive optical element according to claim 4, wherein the first wavelength range is equal to or greater than 600 nm and equal to or less than 780 nm, the second wavelength range is equal to or greater than 500 nm and less than 600 nm, and the third wavelength range is equal to or greater than 380 nm and less than 500 nm.

7. A diffractive optical element according to any one of claims 1 to 3, wherein the diffraction pattern exhibits a shape of rotational symmetry with an integral multiple of one or more times when viewed in a direction perpendicular to the main surface of the substrate.

8. A diffractive optical element described in any one of claims 1 to 3, characterized in that the sum of the lengths in the circumferential direction of the resin layer closest to the center of the diffraction pattern in the first pattern region and the sum of the lengths in the circumferential direction of the resin layer closest to the center of the diffraction pattern in the second pattern region are different from each other.

9. A method for manufacturing a diffractive optical element applicable to incident light having a wavelength in the range of 380 nm or more and 1,700 nm or less, comprising: a step (A) of preparing a substrate that transmits the incident light; a step (B) of applying a material containing a curable resin composition to a main surface of the substrate to form a coating film; a step (C) of curing a part of the coating film to form a resin layer on a part of the main surface of the substrate that blocks the incident light or delays the phase of the incident light; and a step (D) of removing, after step (C), a part of the coating film different from the resin layer from the main surface of the substrate, wherein step (C) comprises a step of forming the resin layer so that a diffraction pattern formed by the resin layer is divided into a plurality of pattern regions in the circumferential direction when viewed in a direction perpendicular to the main surface of the substrate, the plurality of pattern regions include at least a first pattern region having a Fresnel zone plate shape corresponding to light that belongs to a first wavelength range included in the incident light, and a second pattern region having a Fresnel zone plate shape corresponding to light that belongs to a second wavelength range that is different from the first wavelength range and is included in the incident light.

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