Diffractive optical element

Abstract

Provided is a diffractive optical element which can separate incident light for each wavelength, focus the light of each wavelength to different positions, and be manufactured relatively easily.　The present invention includes: a substrate which transmits light; and a plurality of diffraction patterns including a first diffraction pattern and a second diffraction pattern which are formed so as to have different center positions on the same main surface of the substrate. Each of the first diffraction pattern and the second diffraction pattern exhibits a pattern shape selected from the group consisting of a Fresnel zone plate pattern, a fractal zone plate pattern, and a photon sieve plate pattern.

Description

diffractive optical element

[0001] The present invention relates to a diffractive optical element, and more particularly to a diffractive optical element that can be used as an imaging diffractive optical element, an optical element for a light sensor, an optical element for a display, or an optical element for optical communication.

[0002] Optical components are used to appropriately control light in imaging devices, optical sensors, displays, and optical communications. For example, optical sensors such as fingerprint authentication sensors, face authentication sensors, proximity sensors, ambient light sensors, and pulse oximeters are used in smartphones and smartwatches, and perform detection using light of multiple wavelengths from visible light to near-infrared light. Diffractive optical elements that split light have been reported for optical components that use multiple wavelengths. For example, CCD cameras for imaging and projectors for display are equipped with wavelength-specific beam splitters corresponding to red, blue, and green, which perform separation control according to the wavelength of light (Patent Document 1).

[0003] In recent years, optical sensors have often been incorporated into the back of displays, creating a strong demand for thinner and more compact optical components. These optical sensors also contribute to the device's thickness, creating a strong demand for thinner devices. Furthermore, in displays, holographic optical elements utilizing grating structures and total internal reflection, as well as pancake lenses, are used in wearable display elements such as glasses and head-mounted displays for AR (Augmented Reality), VR (Virtual Reality), and MR (Mixed Reality) devices. However, optical elements corresponding to the three colors red, green, and blue are required. In recent years, there has been a growing demand for thinner optical components.

[0004] As an example of an optical element that can accommodate such thinning, Non-Patent Document 1 reports that by forming GaN into a specific shape, three colors of light (red, blue, and green) can be collected at different positions at angles differing by 8 degrees, and the element can be used as a replacement for the color filter of a CMOS image sensor.

[0005] In another report, Non-Patent Document 2 reports that by forming SiN pillars into a specific shape, light of three colors (red, blue, and green) can be focused at positions approximately 2 μm apart, and that this can be used as a substitute for microlenses in CMOS image sensors.

[0006] However, while the methods described in Non-Patent Documents 1 and 2 are suitable for separation at distances equivalent to the pixels of a CMOS image sensor, they have a problem in that the separation angle is small, making it difficult to divide wavelengths among multiple image sensors. Also, because the separation angle is insufficient, in order to focus light at separate positions for each wavelength, it is necessary to provide a large distance between the optical element and the optical sensor, making it difficult to make the device thin.

[0007] Japanese Patent Application Laid-Open No. 2004-045809

[0008] Nano Lett. 2017, 17, 6345-6352 Optica, 2021, 8, 12, 1596

[0009] In the optical elements having the configurations described in the above Non-Patent Documents 1 and 2, the angle of light separated by wavelength is small, and when light is concentrated at different positions, a height is required, making it difficult to make them thin. In other words, the configuration is very complicated, and manufacturing is extremely difficult, which poses the problem of difficulty in mass production.

[0010] An object of the present invention is to provide a diffractive optical element that can separate incident light into wavelengths and collect the light into different positions according to wavelength, and that can be manufactured relatively easily.

[0011] The present inventors have conducted extensive research to solve the above problems. In the process of examining various optical element configurations, the present inventors have succeeded in finding a configuration that is suitable for separating light by wavelength and that can be more easily fabricated than the optical elements described in Non-Patent Documents 1 and 2. Therefore, examples of aspects of the present invention relating to the optical elements discovered by the present inventors are described below.

[0012] [1] A diffractive optical element comprising: a substrate that is transparent to light; and a plurality of diffraction patterns including a first diffraction pattern and a second diffraction pattern that are formed on the same main surface of the substrate so that their central positions are different, wherein each of the first diffraction pattern and the second diffraction pattern has a pattern shape selected from the group consisting of a Fresnel zone plate pattern, a fractal zone plate pattern, and a photon sieve plate pattern.

[0013] In this specification, the term "Fresnel zone plate pattern" is intended to collectively refer to "amplitude type Fresnel zone plate pattern" and "phase type Fresnel zone plate pattern." The configurations of "amplitude type Fresnel zone plate pattern" and "phase type Fresnel zone plate pattern" will be described in detail in the section "Mode for Carrying Out the Invention." Furthermore, the term "fractal zone plate pattern" and "photon sieve plate pattern" is also intended to collectively refer to "amplitude type" and "phase type," as with "Fresnel zone plate pattern."

[0014] [2] The diffractive optical element according to the above [1], wherein the first diffraction pattern and the second diffraction pattern at least partially overlap each other.

[0015] In this specification, the phrase "at least partially overlap" refers to the pattern regions being partially overlapped, and specifically, the distance D between the centers of the first diffraction pattern and the second diffraction pattern is c is smaller than the sum of the radius R of the first diffraction pattern and the radius R of the second diffraction pattern, i.e., D c<R1 + R2. Note that the "radius of each diffraction pattern" refers to the length from the center of the target diffraction pattern to the edge of the diffraction pattern, the "center of the diffraction pattern" refers to the mathematical geometric center or center of gravity, and the "edge of the diffraction pattern" refers to the position of the diffraction pattern at which the radius of the circumference of a circle whose center is the center of the diffraction pattern and at least a portion of which intersects with the diffraction pattern is the maximum. Furthermore, when there are three or more diffraction patterns, this refers to a relationship in which at least a portion of any two of the diffraction patterns overlap with each other, similar to the first and second diffraction patterns described above.

[0016] Furthermore, the terms "first diffraction pattern" and "second diffraction pattern" are names used to distinguish between any two diffraction patterns that are arranged so as to overlap each other, and do not refer to any two specific patterns contained in the diffractive optical element.

[0017] [3] The diffractive optical element according to [2], wherein at least one of the first diffraction pattern and the second diffraction pattern is formed by circumferentially arranging at least two or more patterns having mutually different shapes.

[0018] [4] The diffractive optical element according to the above [3], wherein the first diffraction pattern and the second diffraction pattern have different pattern shapes.

[0019] [5] The diffractive optical element according to any one of [1] to [4], wherein the first diffraction pattern and the second diffraction pattern have a thickness of 200 nm or more and less than 3.4 μm.

[0020] [6] The diffractive optical element according to any one of [1] to [5] above, wherein the first diffraction pattern and the second diffraction pattern are spaced apart from each other by 8 μm or more.

[0021] [7] The diffractive optical element according to any one of [1] to [6], wherein the focal length of any one of the orders of diffraction of the first diffraction pattern and the second diffraction pattern is 3 μm or more and 100 cm or less.

[0022] The focal length of the first diffraction order represents the distance to the point where light is focused at the farthest position from the diffraction pattern. The focal length of the second diffraction order represents the distance to the point where light is focused at the next farthest position after the focal length of the first diffraction order. The third and higher diffraction orders are identified in this order.

[0023] [8] The diffractive optical element according to any one of the above [1] to [7], wherein the first diffraction pattern and the second diffraction pattern are formed from a cured product of a radiation-sensitive resin composition.

[0024] According to the present invention, it is possible to provide a diffractive optical element that can separate incident light into wavelengths and collect the light into different positions according to wavelength.

[0025] 1 is a structural example of an amplitude-type Fresnel zone plate pattern; FIG. 2 is an example of a procedure for calculating the number of blocking regions in a diffractive optical element; FIG. 3 is an example of a procedure for dividing an amplitude-type fractal zone plate pattern; FIG. 4 is a structural example of an amplitude-type fractal zone plate pattern; FIG. 5 is a structural example of an amplitude-type photon sieve plate pattern; FIG. 6 is a structural example of a diffractive optical element having a first diffraction pattern and a second diffraction pattern that overlap each other; FIG. 7 is a structural example of a diffractive optical element having a first diffraction pattern and a second diffraction pattern that are divided in the circumferential direction and overlap each other; FIG. 8 is a schematic cross-sectional view of an example of a configuration of a diffraction pattern; FIG. 9 is a schematic cross-sectional view of an example of a configuration of a diffraction pattern; FIG. 10 is a schematic overall view showing a diffraction pattern of the diffractive optical element of Example 1; FIG. 11 is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 1; FIG. 12 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 450 nm at a focal length of 500 μm in Example 1. 1 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 650 nm at a focal length of 500 μm in Example 1. FIG. 2 is an overall view of the diffraction pattern of the diffractive optical element of Example 2. FIG. 3 is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 2. FIG. 4 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 450 nm at a focal length of 100 μm in Example 2. FIG. 5 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 550 nm at a focal length of 100 μm in Example 2. FIG. 6 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 650 nm at a focal length of 100 μm in Example 2. FIG. 7 is an overall view of the diffraction pattern of the diffractive optical element of Example 3. FIG. 8 is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 3. FIG. 9 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 550 nm at a focal length of 250 μm in Example 3. FIG. 10 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 650 nm at a focal length of 250 μm in Example 3. Fig. 1 is an overall view schematically showing a diffraction pattern of a diffractive optical element of Example 4. Fig. 2 is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 4. Fig. 3 is a distribution diagram of the squared intensity of the electric field strength at a wavelength of 530 nm at a focal length of 200 μm in Example 4. Fig. 4 is a distribution diagram of the squared intensity of the electric field strength at a wavelength of 530 nm at a focal length of 350 μm in Example 4. Fig. 5 is an overall view of the diffraction pattern of a diffractive optical element of Example 5.FIG. 10 is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 5. FIG. 11 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 450 nm at a focal length of 100 μm in Example 5. FIG. 12 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 550 nm at a focal length of 100 μm in Example 5. FIG. 13 is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 650 nm at a focal length of 100 μm in Example 5. FIG. 14 is an overall view of the diffraction pattern of the diffractive optical element of Example 6. FIG. 15 is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 6. FIG. 16 is a diagram showing the focusing behavior when irradiated with light emitted from a halogen light source arranged in a direction perpendicular to the main surface of the substrate of the diffractive optical element in Example 6.

[0026] Hereinafter, embodiments of the 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 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 show the width, thickness, shape, etc. of each part schematically 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 reference symbols (reference symbols simply having a suffix such as "'" after the number), and detailed descriptions may be omitted as appropriate.

[0027] 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.

[0028] <Substrate> The substrate is made of a material that is transparent to light. Specifically, a substrate having a transmittance of 50% or more at any wavelength between 380 nm and 1700 nm is used. Examples of such 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.

[0029] 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.

[0030] <Diffraction Pattern> A diffraction pattern is a pattern that diffracts an incident electromagnetic wave using a fine structure that is equal to or smaller than the wavelength of the electromagnetic wave. For example, in the present invention, if an electromagnetic wave having a wavelength in the range of 380 nm to 1700 nm is incident, the pattern will include a structure of 50 nm to 5 μm. Among the diffraction patterns, the present invention employs a Fresnel zone plate pattern, a fractal zone plate pattern, or a photon sieve plate pattern, which have the property of strongly focusing light at a specific focal position. Furthermore, the diffractive optical element of the present invention has multiple diffraction patterns, including a first diffraction pattern and a second diffraction pattern, that are centered at different positions.

[0031] It is preferable that the first diffraction pattern and the second diffraction pattern at least partially overlap each other. This overlapping allows the overall size of the diffractive optical element to be smaller than when the first diffraction pattern and the second diffraction pattern are provided separately. In a structure in which multiple diffraction patterns overlap, as described below, there are regions in which the presence or absence of the first diffraction pattern does not necessarily coincide with the presence or absence of the second diffraction pattern. For example, by providing the necessary microstructures as they are in positions where both diffraction patterns are present, providing a microstructure for one of the diffraction patterns in positions where one of the diffraction patterns is present, and not providing a microstructure in positions where neither diffraction pattern is present, it is possible to achieve diffractive optical properties even when multiple diffraction patterns overlap.

[0032] The first diffraction pattern and the second diffraction pattern are preferably formed by circumferentially arranging at least two or more patterns having mutually different shapes (e.g., a Fresnel zone plate pattern and a fractal zone plate pattern). By using mutually different patterns, a diffractive optical element can be obtained in which the wavelengths to be focused at specific positions are individually set, or which has multiple focal points that focus light of the same wavelength at different positions. This results in a diffractive optical element that focuses light at different sensor positions depending on the wavelength, or a diffractive optical element that can simultaneously focus light at multiple sensor distances and positions, and can have the function of branching light.

[0033] <Amplitude-Type Fresnel Zone Plate Pattern> Fig. 1 shows an example of the structure of an amplitude-type Fresnel zone plate pattern. As shown in Fig. 1, the amplitude-type Fresnel zone plate is a diffractive optical element having a pattern that is circular as a whole, in which transparent and opaque rings (blocking regions) are alternately combined. The radius r n is generally designed to satisfy the relationship between each parameter as shown in the following formula (1). Here, 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 occlusion 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 occlusion, r n 2The zone between n=0 and n=1 is occluded, the zone between n=1 and n=2 is transparent, the zone between n=2 and n=3 radii is occluded, and so on, alternating between occluded and transparent depending on whether n is odd or even.

[0034]

[0035] The focal length of the first-order diffraction of the diffractive structure is preferably 3 μm or more and 100 cm or less. From the viewpoint of efficiently collecting light from the outer periphery of the optical element, improving light collecting performance and light collecting efficiency, the lower limit of the focal length of the first-order diffraction is more preferably 10 μm, even more preferably 20 μm, and still more preferably 30 μm. From the viewpoint of reducing light utilization efficiency due to light diffusion, the upper limit of the focal length of the first-order diffraction is more preferably 80 cm, even more preferably 50 cm, even more preferably 45 cm, and most preferably 30 cm.

[0036] The number of shielding regions 12 possessed by the diffractive optical element 1 according to this embodiment is greater than 20. FIG. 2 shows an example of a procedure for calculating the number of shielding regions 12 in the diffractive optical element 1. The number of shielding regions 12 possessed by the diffractive optical element 1 according to the present invention is the maximum number of transitions from the shielding regions 12 to the transparent regions 11 when observed from a direction perpendicular to the main surface of the substrate, as shown in FIG. 2 , on diagonal lines parallel to the main surface of the substrate, with the intersection of two or more diagonal lines as the center and the regions of the structure counted in a radial direction from the center. The number of structures possessed by the diffractive optical element 1 according to the present invention is preferably greater than 59, more preferably greater than 150, even more preferably greater than 300, and most preferably greater than 800. Diffraction from the shielding regions within a preferred range can provide high light-gathering performance usable as an imaging element.

[0037] <Phase-Type Fresnel Zone Plate Pattern> The diffractive optical element according to the present invention may have a phase-type Fresnel zone plate pattern made of a transparent structure of a specific thickness, instead of the shielding region in the amplitude-type Fresnel zone plate pattern. The phase-type Fresnel zone plate pattern is a pattern in which diffraction occurs due to interference caused by the phase difference of light between a thin film region and a region where no thin film is provided. The thickness of the transparent thin film is preferably 1 / 2×π or more, and more preferably between 0.9×π and 2×π, in terms of phase with respect to the design wavelength.

[0038] The F-number, which is the ratio of the focal length f to the diameter D of the structure in the diffractive optical element 1, is preferably 0.2 or more and 4 or less. If the F-number is 0.2 or more, it becomes easy to maintain the line width at which the microstructure has a diffraction effect. It is preferably 0.3 or more, and more preferably 0.4 or more. Furthermore, if the F-number is equal to or less than the upper limit, it becomes easy to ensure the amount of light required for imaging. However, if the F-number is too high, the optical module size will be enlarged, limiting its applications, and the influence of aberration will be so great that it will be difficult to focus light on the entire sensor surface. From these viewpoints, the F-number is preferably 3.5 or less, more preferably 3.2 or less, and even more preferably 3.0 or less.

[0039] <Fractal Zone Plate Pattern> Figure 3 shows an example of the division procedure for an amplitude-type fractal zone plate pattern, and Figure 4 shows an example of the structure of an amplitude-type fractal zone plate pattern. Similar to an amplitude-type Fresnel zone plate pattern, an amplitude-type fractal zone plate has a diffractive optical structure in which transparent and opaque rings (zones) are alternately combined. Similar to an amplitude-type Fresnel zone plate pattern, an amplitude-type fractal zone plate pattern is formed by dividing transparent and opaque regions according to the above formula (1) and then connecting the opaque regions using a Cantor set. As shown in Figure 3, a Cantor set is expressed by the division number Nc and the division number S. When the central region of the element is number 1 and the outermost opaque region is number N, these opaque regions are equally divided into (2Nc + 1). Then, both ends are designated as transparent regions and the center is designated as an opaque region. That is, the 1st to ((N / 3)-1)th pixels are transparent regions, ((Nc) / 3) to ((2Nc / 3)-1)th pixels are occluded regions, and (2Nc / 3) to Nth pixels are occluded regions. When S is 2 or more, the transparent region is divided into (2Nc+1) equal parts again, and then the process of making both ends transparent regions and the center occluded regions is repeated (S-1) times. When Nc is 0 to 3, the S １ ~S ４ An example of this is shown in Figure 3. That is, an amplitude-type fractal zone plate pattern is a diffractive optical element in which the alternating divisions of shielding and transparent regions in a Fresnel zone plate pattern are converted into shielding and transparent regions that form a Cantor set. When a fractal zone plate pattern created under these conditions is observed from the perpendicular direction on the main surface of the substrate, a pattern with a shape as shown in Figure 4 is formed.

[0040] Compared with Fresnel zone plates, fractal zone plates tend to have lower light-collecting efficiency at the focal position, but they have less stray light at positions around the focal position, making them preferable when sensors are provided around the periphery.

[0041] The fractal zone plate pattern may be a phase type fractal zone plate pattern in which the shielding region is made of a transparent structure of a specific thickness, similar to a phase type Fresnel zone plate pattern.

[0042] <Photon sieve plate pattern> Figure 5 shows an example of the structure of an amplitude type photon sieve plate pattern. An amplitude type photon sieve plate pattern has a structure in which pinholes are arranged in the circumferential direction instead of the transparent zones in an amplitude type Fresnel zone plate pattern. Since the shielding area is continuous, it is expected that it can be extracted as a free-standing film, which is preferable when using a thin film substrate. The position R from the center of the pinhole n is calculated by the following formula (2).

[0043]

[0044] nth pinhole radius r pn is r pn = fλ / (4 × R n ) and the number of n-th pinholes, N hole can be calculated by the following formula (3): where X is the packing ratio, and is preferably 0.1 to 0.9. ring is the number of rings in the photon sieve plate pattern. hole The decimal points were truncated and used as integers.

[0045]

[0046] The photon sieve plate pattern does not have a repeated circular structure like the Fresnel zone plate or Fresnel fractal zone plate, and is therefore preferable for applications where design is important because it is less likely to cause moire.

[0047] The diffractive optical element according to the present invention comprises at least two or more diffractive optical elements arranged with their centers at different positions on a plane. This makes it possible to focus light at different positions and separate the light. The structure will be explained below using as an example a diffractive optical element configured by overlapping multiple amplitude-type Fresnel zone plate patterns.

[0048] 6 shows an example of the structure of a diffractive optical element having a first diffraction pattern and a second diffraction pattern that overlap each other. In FIG. 6, the white areas indicate diffraction pattern regions, and the black areas indicate regions without diffraction patterns. As a mere example, in this embodiment, the first diffraction pattern is adjusted to a design wavelength λ of 650 nm and a focal length f of 500 μm, and the pattern radius R is designed to be 459 μm. The second diffraction pattern is adjusted to a design wavelength of 550 nm and a focal length f of 500 μm, and the pattern radius R is designed to be 499 μm. Furthermore, the center-to-center distance D between the first and second diffraction patterns is C is set to 424 μm, and D c The relationship of R1 + R2 is satisfied.

[0049] As described above, the radius (R1, R2) of each diffraction pattern is the length from the center (C1, C2) of the target diffraction pattern to the end of the diffraction pattern, and the end of the diffraction pattern is the radial end of the outermost pattern among the patterns that have a shape along an arc of a circle whose center is the center (C1, C2) of each diffraction pattern. Along an arc means that, as shown by the dashed-dot and dashed-dot lines in Figure 6, the circumference of the circle whose center is the center (C1, C2) of each diffraction pattern matches within a range of 1% of the radial width of the outermost pattern, regardless of whether the circumference is continuous or discontinuous, within a total range of 10% or more with respect to the entire circumference.

[0050] Furthermore, when multiple diffraction patterns collect light and deliver it to different sensors, it is preferable that the centers (C1, C2) of the diffraction patterns are spaced apart by 8 μm or more. For example, in a near-infrared sensor, the sensor size is approximately 5 μm or more. In other words, if the distance between the centers (C1, C2) of the diffraction patterns is less than 8 μm, interference occurs with adjacent sensors. It is more preferable that the distance be 20 μm or more.

[0051] 7A shows an example of the structure of a diffractive optical element having a first diffraction pattern and a second diffraction pattern that are circumferentially divided and overlap each other, where at least one of the first diffraction pattern and the second diffraction pattern is formed by circumferentially arranging at least two or more patterns with different shapes. In FIG. 7A, the white areas represent diffraction pattern regions, and the black areas represent regions without a diffraction pattern. By forming a divided diffraction pattern, it is possible to suppress the loss of transparent regions due to overlapping of shielding regions, i.e., the reduction in the amount of transmitted light, when at least two or more diffractive optical elements are arranged around different positions on a planar surface. The number of divisions is arbitrary, but is preferably 9 or more, more preferably 18 or more, even more preferably 36 or more, even more preferably 72 or more, even more preferably 180 or more, and particularly preferably 360 or more.

[0052] In addition, one of the first diffraction pattern and the second diffraction pattern may be divided and the other may not be divided, or both the first diffraction pattern and the second diffraction pattern may be divided.

[0053] As a specific example, the first diffraction pattern has a design wavelength λ = 650 nm and a focal length f = 500 μm, and is divided 360 times by a rotation angle of 1° from the center position in the radial direction, and then the structure is arranged in 0.2° increments. Furthermore, the second diffraction pattern has a design wavelength of 550 nm and a focal length f = 500 μm, and is centered at a position 10 μm shifted in the x direction and 10 μm shifted in the y direction from the center position of the first diffractive optical element. The second diffraction pattern has a design wavelength of 550 nm and a focal length f = 500 μm, and is divided 360 times by a rotation angle of 1° from the radial direction, and then the structure is arranged in 0.2° increments. Even if these diffraction patterns are arranged overlapping as shown in FIG. 7A, a diffractive optical element capable of focusing light of multiple wavelengths at their respective focal positions is constructed.

[0054] <Formation Ratio> The formation ratio according to the present invention represents the ratio of the area of ​​the shielding region of the diffractive optical element after division to the area of ​​the shielding region of the diffractive optical element before division in a diffraction pattern divided in the circumferential direction. For example, in FIG. 7A, the pattern is divided 360 times in 1° increments in the rotational direction, forming shielding regions at 0.2° intervals, resulting in a formation ratio of 0.2. From the viewpoint of maintaining the intensity of transmitted light, the formation ratio is preferably 0.8 or less, more preferably 0.67 or less, and even more preferably 0.5 or less. Furthermore, an excessive decrease in the formation ratio reduces the area of ​​the diffractive optical element that focuses light, and from the viewpoint of reducing the light-focusing efficiency, the formation ratio is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.25 or more.

[0055] The first diffraction pattern and the second diffraction pattern are preferably divided so as to be line-symmetric with respect to a line passing through the center (C1, C2) of the diffraction pattern, or so as to be point-symmetric with respect to the center (C1, C2). Dividing the diffraction pattern so as to be line-symmetric or point-symmetric allows diffraction to occur by light incident at symmetric positions on the optical element, making it possible to obtain higher light-collecting ability.

[0056] The first and second diffraction patterns of the diffractive optical element according to the present invention are selected from the group consisting of an amplitude Fresnel zone plate pattern, a phase Fresnel zone plate pattern, an amplitude linear zone plate pattern, a phase linear zone plate pattern, an amplitude fractal zone plate pattern, a phase fractal zone plate pattern, an amplitude photon sieve plate pattern, and a phase photon sieve plate pattern. As described above, a diffractive optical element having a diffraction pattern selected from this group has high light-collecting performance and is able to collect light of a desired wavelength at a predetermined focal position according to each pattern.

[0057] Each diffraction pattern of the diffractive optical element of the present invention may be, for example, a diffraction pattern divided 360 times in the circumferential direction. A diffractive optical element having such a configuration is formed so that two diffraction patterns overlap, as shown in Fig. 7A. The two diffraction patterns are not configured as continuous patterns in the circumferential direction, but each diffraction pattern has the function of focusing light at a different position depending on the wavelength.

[0058] <Shielding Region> When the diffractive optical element according to the present invention has an amplitude Fresnel zone plate pattern, an amplitude linear zone plate pattern, an amplitude fractal zone plate pattern, or an amplitude photon sieve plate pattern, the diffraction pattern has a portion where shielding regions and light-transmitting regions alternate in the radial direction. In this portion, the narrowest structure width in the radial direction is 2.0 μm or less. The narrowest structure width of the shielding region according to the present invention is the minimum distance from a transparent region without a shielding region to another transparent region diagonally opposite the shielding region when the optical element is observed from directly above. When the diffractive optical element is a phase type, the shielding region may instead be a transparent structure with a phase difference. The narrowest structure width is preferably 1.8 μm or less, more preferably 1.5 μm or less, and most preferably 1.2 μm or less. In order to achieve diffractive effect, the lower limit is preferably 0.1 μm, more preferably 0.2 μm, and even more preferably 0.25 μm. If the thickness is less than the lower limit, the thickness is too small relative to the wavelength of visible light, and the transparent and shielding regions have averaged transmission characteristics, which tends to reduce the diffraction efficiency.

[0059] The shielding region preferably has an average thickness of 2 μm or less. If the shielding region has a thickness exceeding 2 μm, the light that has passed through the transparent region and propagates in a wave-like manner is blocked based on Huygens' principle, resulting in a deterioration in light collection efficiency. The shielding region is more preferably 1.5 μm or less, and even more preferably 1.0 μm or less.

[0060] As for the shielding region, it appears in any of the amplitude Fresnel zone plate pattern, amplitude linear zone plate pattern, amplitude fractal zone plate pattern, and amplitude photon sieve plate pattern as described above, but the phase Fresnel zone plate pattern, phase linear zone plate pattern, phase fractal zone plate pattern, and phase photon sieve plate pattern are patterns that generate diffraction by generating interference due to a phase difference between light passing through the diffraction pattern and light passing through a portion that is not a diffraction pattern, thereby forming a transmittance difference. In other words, the region that forms this phase difference can be considered to correspond to the shielding region. Let d be the height of the formed diffraction pattern, and n be the refractive index of the diffraction pattern. A The refractive index of the area that is not a diffraction pattern is n B Then, the refractive index difference is Δn = |n A -n B |, and the phase difference caused by the analysis pattern is expressed as Δn×d (nm). The thickness of the diffraction pattern, (Δn×d)×2×π / λ, which is the phase difference converted into radian units for light with a wavelength λ, is preferably in the range of 0.5π to 2π, where π is the ratio of the circumference of a circle to its diameter. This corresponds to a preferred range of 200 nm to 3.4 μm when the wavelength of the incident light is 400 nm to 1700 nm.

[0061] 7B to 7E are schematic cross-sectional views of an example of a diffraction pattern. The diffraction pattern of the present invention may be a rectangular uneven surface with two tones, one with a microstructure and one without, as shown in FIG. 7B. The diffraction pattern of the present invention may also be a structure in which the uneven surface is divided into three or more tones. For example, as shown in FIGS. 7C and 7D, a structure divided into four or more tones is preferable because it has higher light collection efficiency. It may also be a curved surface with a substantially infinite number of specific tones. The microstructure of the diffraction pattern of the present invention may have any shape, including a structure in which the thickness gradually decreases in one direction, with the thickest microstructure formed next to the region without a microstructure, as shown in FIGS. 7C and 7D, or a structure in which the thickness repeatedly increases and decreases, as shown in FIG. 7E. In either configuration, the width of each microstructure may vary depending on the position on the substrate 10.

[0062] As shown in Figures 7C to 7E, by increasing the thickness of the microstructure in multiple stages, the phase of light can be more precisely controlled, which is expected to result in effects such as higher resolution, a broader bandwidth for the target light, and reduced chromatic aberration. Furthermore, in the configurations shown in Figures 7C and 7D, it is preferable that the maximum thickness of the microstructure approximately matches the wavelength of the light to be incident. This configuration optimizes the interference of diffracted light and achieves high light collection efficiency. In contrast, in the configuration shown in Figure 7E, abrupt thickness changes are not formed, thereby suppressing stray light.

[0063] Next, the creation of a diffraction pattern will be described.

[0064] The diffraction pattern is formed from an inorganic material, a thermoplastic resin, or a curable resin composition. Among these, a diffraction pattern formed from a thermoplastic resin or a curable resin composition, which does not require an etching step, is preferred. Furthermore, a diffraction pattern formed from a curable resin composition, which makes it easier to form a finer diffraction pattern, is preferred.

[0065] Examples of methods for producing a diffraction pattern include a method in which a radiation-sensitive resin composition is applied to a substrate, and then the portions where a structure is to be formed are irradiated with radiation, followed by the use of a negative curable resin composition to dissolve the unirradiated portions; and a method in which a positive curable resin composition is used, in which the portions where a structure is not to be formed are irradiated with radiation, followed by the use of a positive curable resin composition to dissolve the unirradiated portions, followed by the use of a thermal curing to solidify the remaining portions.

[0066] As the radiation, electron beams and electromagnetic waves are preferred. From the viewpoint of exposure speed, electromagnetic waves are preferred. Furthermore, from the viewpoint of forming a fine structure, the electromagnetic waves are preferably ultraviolet rays. When the radiation is ultraviolet rays, the shorter the wavelength, the easier it is to form a fine structure, but on the other hand, it tends to be more difficult to ensure the height of the structure that can be formed. In consideration of these circumstances, the wavelength of the electromagnetic waves used as the radiation is preferably in the range of 170 nm to 380 nm, and more preferably in the range of 200 nm to 350 nm. Examples of exposure devices capable of irradiating such electromagnetic waves include an i-line exposure device, an ArF exposure device, and a KrF exposure device.

[0067] According to the above-described method, a diffraction pattern including a fine structure can be produced more easily than in the past. In particular, according to the production method using a radiation-sensitive resin composition, it is possible to process the pattern on the order of nanometers by adjusting the radiation irradiation area, which makes it easier to produce a diffraction pattern.

[0068] <Curable Resin Composition> The shielding structure according to the present invention may be made of any material capable of blocking light of a desired wavelength, but is preferably formed of a cured product of a curable resin composition. The transparent structure may be made of any material capable of transmitting light of a desired wavelength, but is preferably formed of a cured product of a curable resin composition. The curable resin composition contains a polymerizable compound.

[0069] <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.

[0070] 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.

[0071] 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.

[0072] Examples of the alkylene oxide-modified polyfunctional (meth)acrylate include 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, 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.

[0073] 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.

[0074] 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 and a compound obtained by reacting dipentaerythritol pentaacrylate with succinic anhydride are particularly preferred, since the resulting curable resin compositions have high strength and excellent surface smoothness and are less likely to produce background smears, film residues, etc. on the substrate and the shielding layer in unexposed areas.

[0075] <Resin> The curable resin composition of the present invention may contain a resin. By containing a resin, the alkali developability and storage stability of the curable resin composition can be improved. The resin is not particularly limited, but a resin having an acidic functional group such as a carboxyl group or a phenolic hydroxyl group is preferred. Among them, a polymer having a carboxyl group (hereinafter referred to as a "carboxyl group-containing polymer") is preferred, and an example thereof can be a copolymer 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)").

[0076] 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.

[0077] These unsaturated monomers (b1) can be used alone or in combination of two or more.

[0078] 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;

[0079] 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 1-(2-methyl-1,2-dimethyl-2,3-dimethyl-2,4 ...

[0080] 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.

[0081] These unsaturated monomers (b2) can be used alone or in combination of two or more.

[0082] 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 to 50% by mass, more preferably 10 to 40% by mass. By copolymerizing the unsaturated monomer (b1) in such a range, a composition excellent in alkali developability and storage stability can be obtained.

[0083] 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 resin.

[0084] 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 this copolymer with the unsaturated monomer (b1) may be further reacted with a polybasic acid anhydride to produce a copolymer, which may be used as the resin.

[0085] 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.

[0086] The resin in the present invention has a weight average molecular weight (Mw) of typically 1,000 to 100,000, 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 that has good 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.

[0087] The ratio (Mw / Mn) of the weight average molecular weight of the 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, more preferably 1.0 to 3.0.

[0088] The resin in the present invention can be produced by a known method, and for example, its structure, Mw, and Mw / Mn can also be controlled.

[0089] In the present invention, the resins may be used alone or in combination of two or more.

[0090] In the present invention, the content of the resin is preferably 10 to 1,000 parts by mass, and particularly preferably 20 to 500 parts by mass, relative to 100 parts by mass of the polymerizable compound. By adopting such an embodiment, the alkali developability, storage stability, and chromaticity properties of the composition can be improved.

[0091] The curable resin composition according to the present invention is preferably a radiation-sensitive resin composition in order to form a diffractive optical element.

[0092] <Photopolymerization initiator> The curable resin composition of the present invention can contain a photopolymerization initiator. This can impart radiation sensitivity to the curable resin composition, thereby obtaining a radiation-sensitive resin composition. The photopolymerization initiator used in the present invention is a compound that generates an active species that can initiate polymerization of a polymerizable compound when exposed to radiation such as visible light, ultraviolet light, far ultraviolet light, electron beams, or X-rays.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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), as well as oxime ester compounds.

[0101] 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.

[0102] In the present invention, the content of the photopolymerization initiator is preferably 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. By adopting such an embodiment, it is possible to improve the curability and film properties.

[0103] As such a curable resin composition, commercially available products may be used, such as so-called negative resists, for example, NFR107 and NFR105G manufactured by JSR, and TSMR-iN080 manufactured by Tokyo Ohka Kogyo Co., Ltd.

[0104] The shielding region or transparent structure region according to the present invention may be formed by etching the surface of a substrate such as glass using a resist.

[0105] The shielding structure according to the present invention may include an inorganic film and a colorant.

[0106] The inorganic film according to the present invention is not particularly limited as long as it has a shielding function at a specific wavelength or has a preferable refractive index at a specific wavelength, but examples thereof include chromium, gold, silver, copper, aluminum, titanium, silicon, germanium, zinc, zirconium, tantalum, hafnium, gallium, and gallium nitride.

[0107] The transparent structure according to the present invention may be a transparent structure made of an oxide of the inorganic film, such as aluminum oxide, titanium oxide, silicon oxide, germanium oxide, zinc oxide, zirconium oxide, tantalum oxide, hafnium oxide, or gallium oxide.

[0108] The colorant according to the present invention is preferably at least one selected from pigments and dyes.The pigment may be either an organic pigment or an inorganic pigment, and preferred examples of the organic pigment 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. Examples of inorganic pigments include C.I. Pigment Yellow 139, 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. A colorant that does not have a maximum absorption wavelength in the wavelength range of 410 to 1100 nm may be contained. 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. Examples of 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.

[0109] Preferred examples of the dye 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. Organic dyes, thiazole compounds, azo compounds, and azo compounds can also be used. Furthermore, quinophthalone compounds and quinophthalone compounds 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. Also usable are squarylium compounds, pyrrole ring-containing compounds, squarylium compounds having an aromatic ring at the amide α-position, amide-linked squarylium compounds, compounds having a pyrrole bis-type squarylium skeleton or a croconium skeleton, dihydrocarbazole bis-type squarylium compounds, pyrrole ring-containing compounds (carbazole type), phthalocyanine compounds, etc. In the present invention, the pigments and dyes can be used either alone or in combination of two or more.

[0110] 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 various commercially available resins for dispersing pigments. Furthermore, the pigment may be used after its primary particles are refined by so-called salt milling.

[0111] 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.

[0112] The substrate according to the present invention preferably has a dielectric multilayer film. By providing the dielectric multilayer film, it is possible to impart antireflection properties, antistatic properties, cut resistance, and wavelength selectivity. This allows the diffractive optical element to suppress stray light of wavelengths other than the specific wavelengths. The dielectric multilayer film is composed of, for example, multiple layers 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 layer and the low refractive index layer.

[0113] The high refractive index layer has a refractive index of n H Assuming that the refractive index is 2.0 or more, it is preferable that the high refractive index layer has a refractive index of 2.0 or more. For example, a film containing titanium oxide (TiO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), or a composite oxide thereof may be used as the high refractive index layer. Furthermore, if 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, of the above three types of materials, titanium oxide and niobium oxide, which have higher refractive indexes, are more suitable for the high refractive index layer.

[0114] The low refractive index layer reduces the refractive index of light having a wavelength of 500 nm to n LIn this case, it is preferable that the refractive index of the low refractive index layer is less than 1.6 for light having a wavelength of 500 nm, and it is more preferable that the refractive index is lower than that of the outermost layer of the transparent substrate. As the low refractive index layer, for example, a film containing silicon oxide (SiO2), magnesium fluoride (MgF2), barium fluoride (BaF2), lithium fluoride (LiF), or a composite oxide thereof may be used. L If the refractive index of the film is 1.7 or less or lower than that of the outermost layer of the transparent substrate, the film may contain an additive.

[0115] The medium refractive index layer has a refractive index of n M In this case, the refractive index of the intermediate refractive index layer is preferably 1.6 or more and less than 2.0 for light having a wavelength of 500 nm, and more preferably lower than the refractive index of the outermost layer of the transparent substrate. As the intermediate refractive index layer, 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. M If the value is 1.6 or more and less than 2.0, additives may be contained.

[0116] 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.

[0117] 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.

[0118] The following materials were used for the shielding structure and the transparent structure. Material 1: NFR107 resist developer manufactured by JSR Corporation (TMAH 2.38% manufactured by Tama Chemical Industries Co., Ltd.) Material 2: JSSG-9135 resist developer manufactured by JSR Corporation (S-170809 manufactured by Kanto Chemical Co., Ltd.) Material 3: RED-101 resist developer manufactured by JSR Corporation (S-170809 manufactured by Kanto Chemical Co., Ltd.) Material 4: BLUE-105 resist developer manufactured by JSR Corporation (S-170809 manufactured by Kanto Chemical Co., Ltd.)

[0119] <Light separation angle> The light separation angle according to the present invention refers to the angle formed by a line parallel to the substrate at the center position of one diffractive optical element and a line segment connecting the lowest part of the center position of one diffractive optical element to the focal position of another diffractive optical element. When there are three or more diffractive optical elements, the light separation angle of each diffractive optical element is calculated from the center of each diffractive optical element, and the largest light separation angle is used.

[0120] Example 1 A first diffractive optical element was designed such that the focal length f in the above formula (1) was 500 μm, the wavelength λ was 450 nm, n=920 (number of structures: 461), the central positions x=0 and y=0, the number of divisions was 72, and the formation ratio was 0.33, and a second diffractive optical element was designed such that the focal length f in the above formula (1) was 500 μm, the wavelength λ was 650 nm, n=550 (number of structures: 226), the central positions x=300 μm and y=300 μm, the number of divisions was 72, and the formation ratio was 0.33. The light-collecting performance of the diffractive optical element was calculated under the following conditions using Lumerical manufactured by Ansys. Luminous calculation conditions: Arrangement of optical elements: xy plane; Refractive index and extinction coefficient of structure: Material 1; Refractive index other than structure: 1; Light source: Emitted from the xy plane at z = -1 μm in the positive z-axis direction; Planewave; FDTD calculation area: z = -1 μm to 1.5 μm; FDTD mesh setting: xyz both 0.1 μm; Far Field calculation: Using the electric field strength in the xy plane at z = 1.5 μm, calculate the squared intensity of the electric field strength E at the focal position z = 500 μm

[0121] FIG. 8A is an overall view schematically illustrating the diffraction pattern of the diffractive optical element of Example 1, and FIG. 8B is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 1. Note that, although multiple circular patterns are visible within the diffraction pattern in the image shown in FIG. 8B , these circular patterns are merely patterns that appear during display and are not patterns that actually appear on the diffractive optical element. Below, drawings in which similar patterns are visible are shown, but in all cases, the circular patterns present inside the diffraction pattern are patterns that appear during display. Furthermore, in cases where, due to image output reasons, the shape of the diffraction pattern is deformed to a degree that could be misleading, or patterns that do not actually exist appear, a schematic diagram will be used to show the overall configuration, as in the drawing shown in FIG. 8A .

[0122] Next, the preparation of the sample will be described. An adhesion promoter (AP3000 manufactured by Dow Chemical Co.) 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. Material 1 (NFR107 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. This substrate with the coating film was then subjected to an i-line stepper (Canon Inc., FPA-3030i5+) to form a diffractive optical element. A diagram of the optical element is shown in Figure 8B. After exposure to light, the unexposed portions were immersed in a resist developer (TMAH 2.38% manufactured by Tama Chemicals Co., Ltd.) to dissolve the light. After rinsing the resist developer with pure water, the substrate was air-dried with an air gun and then post-baked on a hot plate at 200°C for 300 seconds to obtain a diffractive optical element in which two diffraction patterns with different centers on a plane were superimposed.

[0123] The obtained diffractive optical element was confirmed to focus light according to the design wavelengths of the first diffractive optical element and the second diffractive optical element, and to focus light at different positions depending on the wavelength, and had the function of separating wavelengths of 450 nm and 650 nm at a light separation angle of 40.3°.

[0124] 8C is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 450 nm and a focal length of 100 μm in Example 1, and FIG. 8D is a distribution diagram of the squared intensity of the electric field intensity at a wavelength of 650 nm and a focal length of 100 μm in Example 1. FIGS. 8C and 8D show the results of measuring the electric field intensity in Example 1 obtained under the conditions described above, and are distribution diagrams in which the squared intensity values ​​in the X direction, including the peak intensity, are plotted to make the results easier to confirm. The distribution diagrams of the squared intensity of the electric field intensity shown in the following drawings are expressed in the same manner as FIGS. 8C and 8D.

[0125] Examples 2 to 5 In Examples 2 to 5, diffractive optical elements were formed using the same method as in Example 1, except that the materials, developer, thickness, design wavelength, focal length, type of diffractive optical element, formation ratio, shielding structure or number of transparent structures, presence or absence of rotation, and presence or absence of region extraction were changed as described in Tables 1 and 2 below. Furthermore, in Examples in which the design of the dielectric multilayer film is described in Table 1, a near-infrared cut filter made of a dielectric multilayer film was provided on the back surface of the substrate opposite the surface having the diffraction pattern using an ion-assisted device (Sapio 1300, manufactured by Showa Vacuum Co., Ltd.). Furthermore, the light-collecting performance was evaluated using a Lumerical manufactured by Ansys using the same method.

[0126]

[0127]

[0128] Fig. 9A is an overall view of the diffraction pattern of the diffractive optical element of Example 2, and Fig. 9B is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 2. Fig. 9C is a distribution map of the squared intensity of the electric field strength at a wavelength of 450 nm and a focal length of 100 μm in Example 2, Fig. 9D is a distribution map of the squared intensity of the electric field strength at a wavelength of 550 nm and a focal length of 100 μm in Example 2, and Fig. 9E is a distribution map of the squared intensity of the electric field strength at a wavelength of 650 nm and a focal length of 100 μm in Example 2.

[0129] Fig. 10A is an overall view of the diffraction pattern of the diffractive optical element of Example 3, and Fig. 10B is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 3. Fig. 10C is a distribution map of the squared intensity of the electric field strength at a wavelength of 550 nm and a focal length of 250 μm in Example 3, and Fig. 10D is a distribution map of the squared intensity of the electric field strength at a wavelength of 650 nm and a focal length of 250 μm in Example 3.

[0130] Fig. 11A is an overall view schematically showing the diffraction pattern of the diffractive optical element of Example 4, and Fig. 11B is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 4. Fig. 11C is a distribution map of the squared intensity of the electric field strength at a wavelength of 530 nm and a focal length of 200 μm in Example 4, and Fig. 11D is a distribution map of the squared intensity of the electric field strength at a wavelength of 530 nm and a focal length of 350 μm in Example 4.

[0131] Fig. 12A is an overall view of the diffraction pattern of the diffractive optical element of Example 5, and Fig. 12B is a partially enlarged view of the diffraction pattern of the diffractive optical element of Example 5. Fig. 12C is a distribution map of the squared intensity of the electric field strength at a wavelength of 450 nm and a focal length of 100 μm in Example 5, Fig. 12D is a distribution map of the squared intensity of the electric field strength at a wavelength of 550 nm and a focal length of 100 μm in Example 5, and Fig. 12E is a distribution map of the squared intensity of the electric field strength at a wavelength of 650 nm and a focal length of 100 μm in Example 5.

[0132] The obtained diffractive optical element focused light of at least two wavelengths at the respective designed positions, and had a performance in which the light separation angle was 10° or more for both wavelengths.

[0133] Example 6 The first diffractive optical element was set to have a focal length f of 30,000 μm, a wavelength λ of 450 nm, n of 5685 (number of structures: 2,842), central positions x of 22,000 μm and y of 0, a division number of 1,080, and a formation ratio of 0.33 in the above formula (1). The second diffractive optical element was set to have a focal length f of 30,000 μm, a wavelength λ of 550 nm, n of 4,651 (number of structures: 2,325), central positions x of 0 μm and y of 22,000 μm, a division number of 1,080, and a formation ratio of 0.33 in the above formula (1). The first diffractive optical element was designed with a shape in which the focal length in the above formula (1) was f = 30,000 μm, the wavelength λ was 650 nm, n = 3,925 (number of structures: 1,967), the central positions x = 22,000 μm, y = 22,000 μm, the number of divisions was 1,080, and the formation ratio was 0.33, and the fourth diffractive optical element was designed with a shape in which the focal length in the above formula (1) was f = 30,000 μm, the wavelength λ was 940 nm, n = 2,721 (number of structures: 1,360), the central positions x = 0 μm, y = 0 μm, the number of divisions was 1,080, and the formation ratio was 0.33.

[0134] 13A is an overall view of the diffraction pattern of the diffractive optical element of Example 6, and FIG. 13B is an enlarged view of a part of the diffraction pattern of the diffractive optical element of Example 6. FIG.

[0135] Next, the preparation of another sample will be described. An adhesion promoter (AP3000 manufactured by Dow Chemical Co.) 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 a layer of adhesion promoter. Material 2: 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 then subjected to an i-line stepper (Canon Inc., FPA-3030i5+) to form a diffractive optical element. The optical element diagrams are shown in Figures 13A and 13B. After exposure to light, the substrate was immersed in a resist developer (S-170809 manufactured by Kanto Chemical Co., Ltd.) to dissolve the unexposed portions. After rinsing the resist developer with pure water, the substrate was air-dried with an air gun and then post-baked on a hot plate at 200°C for 300 seconds to obtain a diffractive optical element with two overlapping diffraction patterns with different centers on a plane.

[0136] 13C is a diagram showing the focusing behavior when light emitted from a halogen light source arranged in a direction perpendicular to the main surface of the substrate of the diffractive optical element 1 in Example 6 is irradiated. The halogen light source used here was an FHL-102 manufactured by Asahi Spectroscopy Co., Ltd. Also shown in FIG. 13C are a focusing point 4 for a wavelength of 550 nm (green), a focusing point 5 for a wavelength of 650 nm (red), a focusing point 6 for a wavelength of 450 nm (blue), and a focusing point 7 for a wavelength of 940 nm (colorless).

[0137] As shown in FIG. 13C, it was confirmed that light of wavelengths according to the design of the four diffractive optical elements was branched into the respective designed positions and collected at a light separation angle of 46°.

[0138] (Other Configuration Examples) In addition, even if the diffractive optical element described above is designed with the materials, developer, thickness, design wavelength, focal length, type of diffractive optical element, formation ratio, shielding structure or number of transparent structures, rotation, and area extraction shown in Table 3 below, it is expected that a design with a light separation angle of 10° or more will be obtained.

[0139]

[0140] The diffractive optical element of the present invention may have a first diffraction pattern and a second diffraction pattern each having a pattern shape selected from the group consisting of a Fresnel zone plate pattern, a fractal zone plate pattern, and a photon sieve plate pattern, and may additionally have diffraction patterns having shapes different from the above-mentioned patterns as a third diffraction pattern, a fourth diffraction pattern, .... Examples of the additional diffraction pattern shapes include: n Instead of the line length L from the center to the periphery n The diffraction pattern may be a linear zone plate pattern, which is a rectangular diffraction structure, and may be either an amplitude type or a phase type.

[0141] The diffractive optical element of the present invention is a thin diffractive optical element that combines high light-collecting and separation performance with high mass productivity, as it can be produced without the need for an etching process. It enables separation according to wavelength and separation according to focal length, and can be suitably used as a diffractive optical lens for imaging, an optical lens for an optical sensor, an optical lens for a display, or an optical lens for optical communication.

[0142] 1: Diffractive optical element 4: Focusing point 5: Focusing point 6: Focusing point 7: Focusing point 10: Substrate 11: Light-transmitting area 12: Shielding area

Claims

1. A diffractive optical element comprising: a substrate that is transparent to light; and a plurality of diffraction patterns including a first diffraction pattern and a second diffraction pattern that are formed on the same main surface of the substrate so that their central positions are different, wherein each of the first diffraction pattern and the second diffraction pattern exhibits a pattern shape selected from the group consisting of a Fresnel zone plate pattern, a fractal zone plate pattern, and a photon sieve plate pattern.

2. The diffractive optical element according to claim 1, wherein the first diffraction pattern and the second diffraction pattern at least partially overlap each other.

3. A diffractive optical element according to claim 2, wherein at least one of the first diffraction pattern and the second diffraction pattern is formed by arranging at least two or more patterns having mutually different shapes in the circumferential direction.

4. The diffractive optical element according to claim 3, wherein the first diffraction pattern and the second diffraction pattern have different pattern shapes.

5. The diffractive optical element according to claim 1, wherein the first diffraction pattern and the second diffraction pattern have a thickness of 200 nm or more and less than 3.4 μm.

6. The diffractive optical element according to claim 1, wherein the first diffraction pattern and the second diffraction pattern have centers spaced apart by 8 μm or more.

7. The diffractive optical element according to claim 1, wherein the focal length of any one of the orders of diffraction of the first diffraction pattern and the second diffraction pattern is 3 μm or more and 100 cm or less.

8. A diffractive optical element according to any one of claims 1 to 7, wherein the first diffraction pattern and the second diffraction pattern are formed from a cured product of a radiation-sensitive resin composition.

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