JP7186524B2 - Diffractive optical element, manufacturing method thereof, and illumination device - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a diffractive optical element having sticking resistance under wet heat conditions and less pattern loss, a method for manufacturing the same, an acrylic resin composition for forming the diffractive optical element, and an illumination device.

In recent years, the need for sensor systems has increased, such as the need for personal authentication to avoid security risks due to the spread of networks, the trend toward autonomous driving, and the spread of the so-called "Internet of Things." there is There are various types of sensors, and the information they detect varies, but one of them is to irradiate the object with light from the light source and obtain information from the reflected light. . Examples include pattern recognition sensors and infrared radar.

The light source of these sensors has a wavelength distribution, brightness, and spread depending on the application. As the wavelength of light, from visible light wavelength to infrared wavelength is often used. Widely used. As for the types of light sources, LED light sources, laser light sources, and the like are often used. For example, a laser light source with a small spread of light is preferably used for detecting a distant place, and an LED light source is preferably used for detecting a relatively close place or irradiating an area with a certain degree of spread. be done.

The size and shape of the illuminated area on the object does not necessarily match the spread (profile) of the light from the light source. be. Recently, a diffusion plate called a Light Shaping Diffuser (LSD) has been developed that can shape the shape of light to some extent.
Another means for shaping light is a diffractive optical element (DOE). This applies the diffraction phenomenon when light passes through a place where materials with different refractive indices are arranged periodically. Although DOEs are basically designed for light of a single wavelength, they can theoretically shape light into almost any shape. Further, in the LSD described above, the light intensity in the irradiation area has a Gaussian distribution, whereas in the DOE it is possible to control the uniformity of the light distribution in the irradiation area. Such characteristics of the DOE are advantageous in terms of high efficiency by suppressing irradiation to unnecessary areas and miniaturization of the apparatus by reducing the number of light sources.
A DOE can be used with both parallel light sources such as lasers and diffuse light sources such as LEDs, and can be applied to a wide range of wavelengths from ultraviolet light to visible light and infrared light.

DOE requires fine processing on the order of nanometers, and in particular, in order to diffract long-wavelength light, it is necessary to form a fine shape with a high aspect ratio. For this reason, electron beam lithography techniques using electron beams have been conventionally used to manufacture DOEs. For example, after depositing a hard mask or resist on a quartz plate that is transparent in the ultraviolet to near-infrared region, electron beams are used to draw a predetermined shape on the resist, followed by resist development, dry etching of the hard mask, and drying of quartz. A desired DOE can be obtained by sequentially performing etching to form a pattern on the surface of the quartz plate and then removing the hard mask.

As a form of the diffractive optical element, a form called a grating cell array is conventionally used. In a grating cell array type diffractive optical element, for example, fine square unit areas (cells) are arranged in a matrix. In one unit region of the grating cell array type diffractive optical element, diffraction gratings are arranged with a constant pitch and with a constant in-plane rotation direction. In addition, in the grating cell array type diffractive optical element, the pitch and rotation direction of the arranged diffraction gratings are different for each unit area, and an aggregate of them constitutes one diffractive optical element.
Generally, a diffractive optical element mainly composed of this grating cell array is manufactured by patterning glass. Patterning of glass generally includes a direct writing method such as a laser or an electron beam. Since this direct writing method draws one point at a time, it takes a long time to fabricate a diffractive optical element having a fine pattern of several μm or less.

As a technique for producing a diffractive optical element, there is a nanoimprint method that is an alternative to the direct writing method (see Patent Document 1).
The nanoimprint method is a method of contact-transferring a pattern of a master plate to a replica plate, and can produce products of the same type as the master plate at high speed. However, the side to be transferred is not glass but a resin material. In other words, the product replica plate is not patterned with glass, but patterned with resin.
In general, as a resin material used for forming a fine structure pattern having an aspect ratio of 2 or more, an acrylic UV curable resin is known (see Patent Documents 2 and 3).

WO2017/119400 JP 2014-98864 A Japanese Patent Application Laid-Open No. 2004-4515

However, when a diffractive optical element is produced using a resin material by the nanoimprint method, sticking and peeling of the pattern during release tend to occur. Therefore, commercial production of diffractive optical elements by nanoimprinting has been difficult with the prior art.
It is known that the acrylic UV curable resin described above has low heat resistance and deteriorates under high-temperature and high-humidity conditions. In particular, under wet and high-temperature conditions (such conditions are hereinafter referred to as wet-heat conditions), a phenomenon in which adjacent patterns stick together or separate from each other due to the meniscus force generated when moisture escapes from between fine patterns. (sticking) may be confirmed. If only heat resistance is a problem, measures such as improving the cross-linking density of the resin or making the resin polyfunctional can be considered, but sticking cannot be eliminated even by these measures.
On the other hand, if the crosslink density of the resin is improved or the resin is polyfunctionalized, the hardness of the film after curing is improved, and as a result, pattern peeling may occur at the time of mold release.

The present disclosure has been accomplished in view of the above-mentioned actual situation regarding the production of a diffractive optical element by a method other than the direct drawing method, and has a diffractive optical element that has sticking resistance under moist heat conditions and has less pattern loss, and a diffractive optical element thereof. An object of the present invention is to provide a manufacturing method, an acrylic resin composition for forming a diffractive optical element, and an illumination device.

The diffractive optical element of the present disclosure is a diffractive optical element that shapes light from a light source, and includes one or more high refractive index convex portions protruding from the surface of the transparent substrate on at least one surface side of the transparent substrate; One or more low refractive index portions are arranged, and the high refractive index convex portion is formed of a cured product of an acrylic resin composition, and the cured product is heated at 60 ° C. A storage elastic modulus (E') at a humidity of 95% is 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less.

The manufacturing method of the present disclosure includes a diffraction grating section in which one or more high refractive index convex portions protruding from the surface of the transparent substrate and one or more low refractive index portions are arranged on at least one side of the transparent substrate. A method of manufacturing a diffractive optical element for shaping light from a light source, comprising:
preparing a mold having a cavity shape for forming the high refractive index convex portion and the low refractive index portion;
A sample of a cured product obtained by irradiating and curing an acrylic resin composition in the cavity of the mold with ultraviolet rays so that the cumulative light amount of the acrylic resin composition is 1,000 mJ/cm ² . A step of filling an acrylic resin composition having a storage modulus (E′) of 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less at 60° C. and 95% relative humidity;
a step of curing the acrylic resin composition by bringing the transparent base material and the acrylic resin composition into contact with each other on the cavity opening side of the mold, and irradiating the acrylic resin composition with an active energy ray; and forming a diffraction grating portion having high refractive index convex portions formed of a cured product of an acrylic resin composition on a transparent substrate by separating the mold from the substrate;
characterized by having

In the acrylic resin composition of the present disclosure, one or more high refractive index protrusions protruding from the surface of the transparent substrate and one or more low refractive index portions are arranged on at least one side of the transparent substrate. An acrylic resin composition for forming high refractive index convex portions of a diffractive optical element having a diffraction grating portion and shaping light from a light source, wherein the integrated amount of light for the acrylic resin composition is 1,000 mJ. The storage elastic modulus (E ^′ ) at 60° C. and 95% relative humidity of the cured product sample obtained by irradiating and curing with ultraviolet rays so as to be 0.90×10 ⁹ Pa or more and 2.6×10 It is characterized by being ⁹ Pa or less.

In the present disclosure, the cured product of the acrylic resin composition may have a storage modulus (E′) of 1×10 ⁸ Pa or more and 5×10 ⁹ Pa or less at 30° C. and 30% relative humidity.
In the present disclosure, the ratio of the loss elastic modulus (E″) to the storage elastic modulus (E′) at 60° C. and 95% relative humidity of the cured product of the acrylic resin composition (tan δ (=E″/E′)) may be 0.12 or less.
In the present disclosure, the acrylic resin composition preferably contains a urethane bond from the viewpoint of excellent sticking resistance under moist heat conditions and less pattern peeling.
In the present disclosure, the acrylic resin composition is an active energy ray-curable resin composition containing a tetrafunctional or higher (meth)acrylate and a difunctional (meth)acrylate. It is preferable from the viewpoint of excellent properties and less pattern peeling.

In the present disclosure, the active energy ray-curable resin composition contains 40% by mass or more and 80% by mass or less of the tetrafunctional or higher (meth)acrylate with respect to all curable components, and the bifunctional (meth) Containing 10% by mass or more and 60% by mass or less of acrylate is preferable from the viewpoint of excellent sticking resistance under moist heat conditions and less pattern peeling.

In the present disclosure, the tetra- or more functional (meth)acrylate preferably contains a tetra- or more functional urethane (meth)acrylate from the viewpoint of excellent sticking resistance under moist heat conditions and less pattern peeling.
In this case, the urethane (meth)acrylate having a functionality of 4 or more is composed of an isocyanate group of a polyvalent isocyanate compound and a hydroxyl group of a compound having one hydroxyl group and two or more (meth)acrylic groups in the molecule. A urethane-bonded compound is preferable from the viewpoint of excellent sticking resistance under moist heat conditions and less pattern peeling.

In the present disclosure, the bifunctional (meth)acrylate preferably has a molecular weight (Mw) of 100 or more and 5,000 or less from the viewpoint of excellent sticking resistance under wet heat conditions and less pattern peeling. .

In the present disclosure, the cured product of the acrylic resin composition is measured by a Vickers hardness test performed in accordance with JIS Z2244 (2003) under measurement conditions of a maximum load of 0.2 mN and a holding time of 10 seconds. is preferably 60% or more from the standpoint of further excellent sticking resistance under moist heat conditions.

In the present disclosure, the high refractive index convex portion preferably has a portion with a height of 400 nm or more from the viewpoint of being able to diffract light with a relatively long wavelength.
In the present disclosure, the top of the high refractive index convex portion is defined as the upper end, and the position of the bottom of the valley between the high refractive index convex portion and another adjacent high refractive index convex portion, or the high refractive index convex portion of the positions of the flat portions closest to the top of the high refractive index convex portion, when the lower end is defined as the one closer to the top of the high refractive index convex portion, the height difference between the upper end and the lower end of the high refractive index convex portion When the ratio of the height of the high refractive index convex portion to the width of the high refractive index convex portion at the half height position is defined as the aspect ratio of the high refractive index convex portion, the ratio of the high refractive index convex portion An aspect ratio of 2 or more is preferable from the point of being able to diffract light of relatively long wavelengths.

An illumination device according to the present disclosure includes a frame having a conductive portion to which power can be supplied from the outside and an opening serving as a light output surface, a light source, and the diffractive optical element, and the light source is fixed in an internal space of the frame. and the conductive portion, and the diffractive optical element is arranged in the opening.
At this time, the light source may be a light source that emits infrared rays having a wavelength of 780 nm or more.

According to the present disclosure, since the storage elastic modulus (E′) under moist heat conditions of the cured product of the acrylic resin composition forming the high refractive index protrusions is within a specific range, sticking under wet heat conditions is prevented. It is possible to prevent and reduce pattern peeling.

1 is a plan view schematically showing an embodiment of a diffractive optical element; FIG. 1 is a schematic perspective view of one embodiment of a diffractive optical element; FIG. FIG. 3 is a diagram showing an embodiment of a diffractive optical element, and is a cross-sectional view schematically showing an example of the A-A' cross-section of FIG. 2. FIG. FIG. 3 is a cross-sectional view schematically showing another embodiment of a diffractive optical element, in which a base portion 3 is present between a transparent substrate 1 and a diffraction grating portion 2. FIG. FIG. 10 is a cross-sectional view schematically showing another embodiment of a diffractive optical element, in which a coating layer 5 is provided on the opposite side of the transparent substrate 1 with the diffraction grating section 2 interposed therebetween. FIG. 10 is a cross-sectional view schematically showing another embodiment of a diffractive optical element, in which a coating layer 5 is provided on the opposite side of the transparent substrate 1 with the diffraction grating section 2 interposed therebetween. FIG. 10 is a cross-sectional view schematically showing another embodiment of the diffractive optical element, in which a low refractive index portion 3 is filled with a low refractive index resin 7; FIG. 10 is a cross-sectional view schematically showing another embodiment of the diffractive optical element, in which a low refractive index portion 3 is filled with a low refractive index resin 7; FIG. 10 is a cross-sectional view schematically showing another embodiment of the diffractive optical element, which is provided with an antireflection layer 9. FIG. FIG. 10 is a cross-sectional view schematically showing another embodiment of the diffractive optical element, which is provided with an antireflection layer 9. FIG. FIG. 4 is a diagram for explaining an aspect ratio, and is a schematic partial cross-sectional view of a diffraction grating section including binary-shaped high-refractive-index protrusions. FIG. 4 is a diagram for explaining an aspect ratio, and is a schematic partial cross-sectional view of a diffraction grating section including multi-step (4-level) high refractive index convex portions. FIG. 10 is a cross-sectional view schematically showing another embodiment of the cross-sectional shape of the diffraction grating portion, in which the thickness of the high refractive index protrusions 2a intermittently increases from the tip to the root thereof. FIG. 10 is a cross-sectional view schematically showing another embodiment of the cross-sectional shape of the diffraction grating portion, in which the thickness of the high refractive index convex portion 2a continuously increases from its tip to its root; FIG. 10 is a cross-sectional view schematically showing another embodiment of the cross-sectional shape of the diffraction grating portion, in which the high refractive index convex portions 2a have a multi-step shape (4-level). FIG. 10 is a cross-sectional view schematically showing another embodiment of the cross-sectional shape of the diffraction grating portion, in which the high refractive index convex portions 2a have a multi-step shape (8-level). FIG. 2 is a schematic perspective view showing how irradiation light 21 is diffracted by a diffractive optical element 10 to form a square image 24 in the center of a screen 22. FIG. FIG. 2 is a schematic perspective view showing how irradiation light 21 is diffracted by a diffractive optical element 10 and a square image 24 is formed on a screen 22 . 10B is a front view of the screen 22 shown in FIG. 10A; FIG. 10B is a front view of the screen 22 shown in FIG. 10B; FIG. 1 is a schematic diagram of an example of a mold used in the manufacturing method of the present disclosure; FIG. FIG. 3 is a schematic cross-sectional view showing an example of an acrylic resin composition filling step in the manufacturing method of the present disclosure, showing how an acrylic resin composition 32 is placed on the surface of a mold 31. FIG. FIG. 3 is a schematic cross-sectional view showing an example of an acrylic resin composition filling step in the manufacturing method of the present disclosure, showing how an acrylic resin composition 32 is applied to the surface of a mold 31. FIG. FIG. 2 is a schematic diagram of an example of an acrylic resin composition curing step in the production method of the present disclosure; 1 is a schematic diagram of an example of a mold release step in a manufacturing method of the present disclosure; FIG. It is a sectional view showing one embodiment of an illuminating device typically. FIG. 3 is a schematic perspective view showing a case where light is directly projected onto a planar screen 22 so that the irradiation area 23 is circular. FIG. 4 is a schematic perspective view of the diffractive optical element 50 with sticking. FIG. 3 is a schematic cross-sectional view of a diffractive optical element in which water has penetrated between fine patterns. It is a cross-sectional schematic diagram of a diffractive optical element in which sticking has occurred. FIG. 10 is a schematic cross-sectional view showing a state in which the pattern is removed during the manufacture of the diffractive optical element;

Hereinafter, the diffractive optical element of the present disclosure, the method for manufacturing the same, the acrylic resin composition for forming the diffractive optical element, and the illumination device will be described in order, but the present disclosure is not limited to the following embodiments. Instead, various modifications can be made within the scope of the gist of the invention.
It should be noted that terms such as "parallel" and length and angle values used in the present disclosure to specify shapes and geometric conditions and their degrees are not bound by a strict meaning, and are similar to each other. It is interpreted to include the range of the extent that the function can be expected. In addition, "planar view" in this specification means viewing from a direction perpendicular to the upper surface of the diffractive optical element. Normally, "planar view" corresponds to viewing from a direction perpendicular to the surface of the diffractive optical element having the diffraction grating portion (corresponding to the direction of the plan view as shown in FIG. 1).
In the present disclosure, the active energy ray is a general term for not only visible light and electromagnetic waves with wavelengths in the invisible region such as ultraviolet rays and X-rays, but also particle beams such as electron beams and α-rays. It contains radiation with enough quanta of energy to cause Ultraviolet rays are preferable as active energy rays.
In the present disclosure, (meth)acryl represents acrylic or methacrylic, respectively, (meth)acrylate represents acrylate or methacrylate, respectively, and (meth)acryloyl represents acryloyl or methacryloyl, respectively.
In the present disclosure, "to shape the light" means that the shape of the light projected onto the target object or target region (irradiation region) becomes an arbitrary shape by controlling the traveling direction of the light. . For example, by transmitting the light ( FIG. 14 ) that makes the irradiation area 23 circular when projected directly onto the planar screen 22 , the irradiation area becomes square ( 24 in FIG. 10A ) by transmitting the diffractive optical element 10 of the present disclosure. , a rectangular shape, a circular shape (not shown), or the like.
In the present disclosure, the light from the light source that passes through the diffractive optical element and is emitted as it is without being diffracted is referred to as 0th-order light (25 in FIG. 10A), and the diffracted light generated by the diffractive optical element is referred to as 1st-order light. (26a-26d in FIG. 10A).
In the present disclosure, the cross-sectional shape of the diffraction grating section is defined as the diffractive optical element placed on a horizontal plane. In the example of FIG. 2, the X-axis is taken in the repeating direction of the periodic structure, the Y-axis is taken perpendicular to the X-axis so that the XY form a horizontal plane, and the Z-axis is taken in a direction perpendicular to the XY horizontal plane. In the present disclosure, the bottom of the valley between the protrusions (minimum point of Z) is taken as the reference for the height 0, and the portion with the height 0 is taken as the recess. Also, in the present disclosure, a portion having a height H (H>0) is defined as a convex portion. On the other hand, in the present disclosure, the maximum height of the protrusions is used as a reference, and the depth to the bottom of the valley between the protrusions may be defined as the depth. When focusing on the , the height is used, and when focusing on the concave portion, the depth is used, and they are substantially the same.
In the present disclosure, the cross-sectional shape of the diffraction grating portion is a repeating structure of concave portions with a height of 0 and convex portions with a height of H, as shown in the example of FIG. That's what it means. Further, in the present disclosure, in the cross-sectional shape of the diffraction grating portion, a convex portion having two or more flat portions (substantially horizontal portions) may be referred to as a multi-step shape. A shape with flat portions is sometimes called an n-level shape.
In addition, in the present disclosure, “transparent” refers to a material that transmits at least light of a target wavelength. For example, even if a material does not transmit visible light, if it transmits infrared light, it is treated as transparent when used for infrared applications.

1. Diffractive Optical Element The diffractive optical element of the present disclosure is a diffractive optical element that shapes light from a light source, and includes one or more high-refractive-index convexities protruding from the surface of the transparent substrate on at least one side of the transparent substrate. and one or more low refractive index portions, and the high refractive index convex portion is formed of a cured product of an acrylic resin composition, and the cured product 60 It is characterized by having a storage modulus (E′) of 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less at ° C. and a relative humidity of 95%.
Hereinafter, the physical properties of the cured product forming the high refractive index protrusions, which are the main features of the present disclosure, will be described, and then the structure of the diffractive optical element will be described.

(1) Cured product of acrylic resin composition The high refractive index convex portion in the diffractive optical element of the present disclosure is an acrylic resin having a specific storage elastic modulus (E′) under conditions of 60° C. and 95% relative humidity. It is formed by a cured product of the composition. Thus, by having an appropriate storage elastic modulus (E′) under moist heat conditions, the diffraction grating portion in the diffractive optical element can prevent sticking and reduce pattern peeling. The mechanism will be explained below.

FIG. 2 is a schematic perspective view of one embodiment of a diffractive optical element. In this embodiment, on one side of the transparent substrate 1, elongated high-refractive-index convex portions 2a are arranged at regular intervals. DOEs and GCAs usually have such a so-called line-and-space structure.
On the other hand, FIG. 15 is a schematic perspective view of a diffractive optical element with sticking. In FIG. 15, the portions where sticking occurs are indicated by oblique lines. Unlike FIG. 2, in the diffractive optical element of FIG. 15, all or part of the adjacent high refractive index convex portions 2a are in contact with each other due to sticking. In this way, in the DOE and GCA, long and narrow convex portions are arranged in fine sizes, so sticking that occurs once tends to propagate to the whole as compared with a dot-shaped moth-eye structure or the like. In particular, the GCA is more susceptible to sticking due to its typically smaller size compared to the DOE.

As described above, sticking is a phenomenon derived from the meniscus force generated when moisture escapes from between the fine patterns of the diffractive optical element.
FIG. 16A is a schematic cross-sectional view showing a state in which water has penetrated between the fine patterns of the diffractive optical element. FIG. 16B is a schematic cross-sectional view of the diffractive optical element in which sticking has occurred, and corresponds to a part of the BB' section in FIG.
FIG. 16A depicts a diffractive optical element 10 having a diffraction grating portion 2 on a transparent substrate 1. FIG. The diffraction grating portion 2 includes high refractive index convex portions 2a and low refractive index portions 2b, and in the example of FIG. 16A, the low refractive index portions 2b are air. However, as shown in FIG. 16A, water 51 has entered one of the low refractive index portions 2b. In this case, the stress σ acting on the high refractive index convex portion 2a in contact with the moisture 51 is represented by the following formula (1).
Formula (1) σ=(6γ cos θ/D)×(H/W) ²
(In the above formula (1), σ is the stress, γ is the surface tension, θ is the contact angle, D is the line pattern interval, H is the height of the high refractive index convex portion, W is the high refractive index The width of the convex part is indicated respectively.)
When the stress σ exceeds a certain value, the high refractive index protrusions 2a collapse in the stress direction, causing the adjacent high refractive index protrusions 2a to come into contact with each other, resulting in sticking (FIG. 16B). Since the stress σ disappears when the moisture 51 evaporates, the sticking is eliminated and the high refractive index convex portions 2a that were in contact may separate, but especially under moist heat conditions, the high refractive index convex portions 2a are fused together. As a result, sticking may not be resolved.
In order to prevent sticking, the material forming the high-refractive-index convex portion is required to be hard enough to withstand the stress σ.

As shown in FIGS. 15 to 16B, the high refractive index convex portion has a ridge-like extending portion (a portion elongated and linearly extending in the surface direction), and extends along the ridge line of the high refractive index convex portion. Sticking is particularly likely to occur when at least some of the portions are separated by low refractive index portions having a width narrower than the height of the high refractive index convex portions and are adjacent to each other in parallel or substantially parallel.
In the manufacturing process of a diffractive optical element or a product including the same, assembly may be performed under moist heat conditions. In addition, if the completed diffractive optical element is placed under moist heat conditions, the sticking that occurs in a part of the diffraction grating part will chain and spread to the whole, and as a result, there is a possibility that the fine pattern cannot be maintained ( See Figure 15). Thus, avoidance of sticking is particularly important for forming and maintaining desired fine patterns.

However, if the high-refractive-index protrusions are simply hard, the pattern will be peeled off at the time of mold release. The term "pattern removal" as used herein means that all or part of the high refractive index projections that form the fine pattern in the diffraction grating are partly broken off, or all of them come off from the base. means.
FIG. 17 is a schematic cross-sectional view showing how the pattern is removed when the diffractive optical element is released from the mold. Such pattern loss occurs, for example, when replicating a diffractive optical element by imprinting with a resin using a mold made by electron beam lithography.
When the convex cured resin material 102 on the substrate 101 is separated from the mold 103, the cured resin material 102 may break in the mold 103 if the cured resin material 102 is too hard. This is because the cured resin 102 needs to be deformed to some extent at the time of mold release, but if the cured resin 102 is too hard, it cannot be freely deformed, and the load required for mold release increases, resulting in an excessive load. This is thought to be due to the fracture occurring at the portion where the heavy load is particularly concentrated. If the cured resin 102 breaks, high refractive index projections having a desired height cannot be obtained as shown in the figure.
The problem of such pattern peeling is not limited to the cured resin on the molded diffractive optical element. For example, when a resin mold is used to mold a diffractive optical element, the protrusions on the resin mold also have the problem of pattern peeling.
On the other hand, when the cured resin material 102 is easily deformed, it is easy to release from the mold.

Thus, a desired fine pattern cannot be obtained if the high refractive index convex portion is too hard or too soft. As a result of studies by the present inventors, the high refractive index convex portion is formed of a cured product of an acrylic resin composition, and the storage elastic modulus (E') of the cured product at 60 ° C. and 95% relative humidity is 0. It has been clarified that sticking under moist heat conditions can be prevented and pattern peeling during mold release can be suppressed when the pressure is 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less.
When the storage elastic modulus (E′) of the cured product at 60° C. and 95% relative humidity is less than 0.90×10 ⁹ Pa, sticking under wet heat conditions cannot be avoided, and the fine pattern of the diffraction grating portion cannot be avoided. cannot be maintained. If the storage elastic modulus (E′) under moist heat conditions is too low, sticking occurs as a result of excessive deformation of the cured product upon release from the mold.
On the other hand, when the storage elastic modulus (E′) exceeds 2.6×10 ⁹ Pa, the cured product lacks flexibility and is broken at the time of releasing from the mold, resulting in pattern peeling.

It is possible to prevent sticking under moist heat conditions, suppress bending and breaking of the cured product, have excellent mold release properties, and suppress deformation at the time of mold release. % storage modulus (E′) is preferably 1.0×10 ⁹ Pa or more and 2.5×10 ⁹ Pa or less, more preferably 1.1×10 ⁹ Pa or more and 2.3×10 ⁹ Pa or less, more preferably 1.2×10 ⁹ Pa or more and 2.0×10 ⁹ Pa or less.

Patent Literature 1 describes the use of a cured product having a predetermined storage elastic modulus (E') at 25°C. The storage modulus (E') under wet heat conditions in the present disclosure is a completely different physical property from the storage modulus (E') at 25°C. Further, the problem of Patent Document 1 is simply to obtain a diffractive optical element with excellent durability, whereas the problem of the present disclosure is to have sticking resistance under moist heat conditions and less pattern loss. It is to obtain an optical element, and the subject is also different.

The storage modulus (E') is a physical property that does not depend on the shape or size of the object to be measured. In the present disclosure, it is measured with a test piece cut out from the diffractive optical element, or with a test piece obtained by separately polymerizing the acrylic resin composition.
In the present disclosure, the storage modulus (E') is measured according to JISK7244 by the following method. First, a test piece for measurement is prepared. A test piece is obtained by cutting an appropriate size from the diffraction grating portion of the diffractive optical element. Alternatively, the acrylic resin composition is sufficiently cured by irradiating it with ultraviolet rays so that the integrated light amount becomes 1,000 mJ/cm ² , thereby obtaining a single film of appropriate dimensions, which is used as a test piece. can also be
Next, by measuring the dynamic viscoelasticity under the conditions of a measurement temperature of 60 ° C. and a relative humidity of 95% and the measurement conditions shown in Table A in the examples, the storage elastic modulus at 60 ° C. and a relative humidity of 95% (E') is obtained. Alternatively, by measuring the dynamic viscoelasticity under the conditions of a measurement temperature of 30 ° C. and a relative humidity of 30% and the measurement conditions shown in Table A in Examples, the storage elastic modulus at 30 ° C. and a relative humidity of 30% ( E') is obtained. As a measuring device, for example, Rheogel E4000 manufactured by UBM can be used.
Alternatively, the storage modulus (E') of the surface of the test piece can be determined by pressing an indenter into the surface of the test piece. As a measuring device, for example, an AFM (Atomic Force Microscope) nanoindenter such as TI950 TRIBOINDENTER manufactured by Hysitron can be used.
Measurement with an AFM nanoindenter has the advantage of being able to directly measure the surface mechanical strength of the surface of the diffractive optical element. However, in this measurement, it is preferable to press the indenter into the vicinity of the center of the high-refractive-index convex portion in order to prevent variations in the measured values. If a recess on the surface of the diffractive optical element is selected as a measurement location, the width of the Berkovich indenter normally used in the AFM nanoindenter often cannot reach the bottom of the recess. The surface mechanical strength of is difficult to measure. In addition, it is expected that the high refractive index convex portion will be bent at the peripheral portion of the high refractive index convex portion due to the pressing of the indenter, and it is difficult to obtain an accurate measurement value of the surface mechanical strength. As described above, it is difficult to stably obtain an accurate value except in the vicinity of the center of the high refractive index convex portion due to influences other than the material properties.
A summary of the measurements when using the AFM nanoindenter is as follows. First, the measurement sample is set on the stage, and the measurement position is confirmed by the CCD camera. Next, after appropriately calibrating, the sample is moved under the Berkovich indenter, and an AFM image of the surface of the diffractive optical element is acquired by the dynamic force mode (DFM mode). A high refractive index convex portion is specified from the obtained AFM image, and several locations near the center of the high refractive index convex portion are selected as measurement locations. At this measurement location, measurements are made with the contact mode of the AFM. Examples of measurement conditions are shown below. The indentation hardness _HIT can be determined based on the relationship between the displacement and the load obtained during the loading and unloading time. A desired storage elastic modulus (E') is obtained from this indentation hardness _HIT .
<Measurement conditions>
・Control method Displacement control ・Measurement depth 50nm
・Load application time: 10 seconds ・Holding time: 5 seconds ・Load unloading time: 10 seconds ・Indenter Berkovich indenter ・Measurement temperature: 30°C
・Relative temperature 30%

However, in practice, it is difficult to obtain a test piece having a relatively large area as described above from the diffraction grating portion of the diffractive optical element. Therefore, a method of obtaining the storage elastic modulus (E') using a test piece of a single film of the acrylic resin composition is practical.
Since the storage elastic modulus of the base portion adjacent to the high refractive index convex portion on the diffractive optical element is approximately the same value as the storage elastic modulus of the test piece obtained by curing the acrylic resin composition, the acrylic resin The storage elastic modulus (E') of the test piece obtained by curing the composition is the same as the storage elastic modulus (E') of the high refractive index convex portion on the diffractive optical element.

The storage elastic modulus (E′) at 30° C. and 30% relative humidity of the cured product of the acrylic resin composition may be 1×10 ⁸ Pa or more and 5×10 ⁹ Pa or less.
By using a cured product having the storage elastic modulus (1×10 ⁸ Pa or more and 5×10 ⁹ Pa or less) under normal temperature and normal humidity conditions, the physical properties required for the diffractive optical element can be satisfied under the conditions. From such a cured product, by selecting a product that meets the storage elastic modulus condition under the above-described moist heat condition (0.90 × 10 ⁹ Pa or more and 2.6 × 10 ⁹ Pa or less), It is possible to obtain a diffractive optical element that has anti-sticking property and less pattern loss.

It is also important that the present disclosure specifies the storage modulus (E') under high humidity conditions of 95% relative humidity. High humidity conditions are thought to cause sticking because they bring excessive moisture to the diffraction grating portion of the diffractive optical element (FIGS. 16A and 16B above). Furthermore, the high temperature condition of 60° C. promotes the supply of moisture to the diffraction grating section, which is considered to be a factor that promotes sticking. Therefore, the storage modulus (E′) under wet heat conditions of 60° C. and 95% relative humidity is important in examining sticking resistance.
In other technical fields, for example, in the semiconductor technical field, it is known that moisture causes sticking in the grooves of the semiconductor surface. However, since the material cannot be changed in the case of semiconductors, a countermeasure is taken to prevent sticking by previously removing moisture from grooves on the surface of the semiconductor. Here, as a method for removing moisture, a method is known in which a volatile organic solvent such as isopropanol is applied to the semiconductor surface to change the surface tension of the moisture in the grooves, thereby facilitating the removal of moisture. .
On the other hand, in the case of the diffractive optical element of the present disclosure, it is possible to adjust the material (hardened acrylic resin composition) forming the diffraction grating portion. Therefore, the composition of the acrylic resin composition is adjusted so that the storage elastic modulus (E′) at 60° C. and 95% relative humidity is 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less. Thereby, an optimum diffractive optical element having sticking resistance can be obtained.

The contact angle of water on the surface of the diffraction grating portion is preferably 90 degrees or more, more preferably 100 degrees or more, and even more preferably 110 degrees or more. This is because when the surface of the cured acrylic resin composition has water repellency as described above, water is less likely to adhere to the surface of the diffraction grating portion, and sticking is less likely to occur.
The method for measuring the contact angle of water is as follows. A water droplet of 2.0 μL is dropped on the surface of the diffraction grating portion of the diffractive optical element, and the contact angle is measured 0.5 seconds after the droplet has landed. For example, a contact angle meter DM500 manufactured by Kyowa Interface Science Co., Ltd. can be used as a measuring device.
When the composition of the acrylic resin composition used as the raw material for the cured product forming the diffraction grating portion is known, the contact angle of water is measured using the cured product of the acrylic resin composition having that composition. may be measured.
First, the acrylic resin composition is applied onto a transparent substrate, and cured by irradiating the acrylic resin composition with ultraviolet rays so that the integrated light quantity becomes 1,000 mJ/cm ² , and then coated. form a film. With the coating film side up, it is horizontally attached to a black acrylic plate with an adhesive layer. Next, a water droplet of 2.0 μL is dropped on the coating film, and the contact angle is measured 0.5 seconds after the droplet has landed. The measurement equipment is the same as above.

As the physical property corresponding to the sticking resistance, the glass transition temperature (Tg) of the acrylic resin composition used for forming the diffraction grating portion is measured in "5. Glass transition temperature (Tg) measurement of the acrylic resin composition" in Examples described later. A temperature Tg (°C) can be mentioned.
From the viewpoint of having sticking resistance, the glass transition temperature Tg may be 45° C. or higher and 80° C. or lower, or 48° C. or higher and 79° C. or lower.
However, in the present disclosure, the glass transition temperature Tg is a secondary index. In the present disclosure, the storage elastic modulus (E′) at 60° C. and 95% relative humidity is the most important parameter for achieving the effect of anti-sticking and the effect of preventing pattern peeling. If it is difficult to determine whether or not these two effects are present based on the storage elastic modulus (E′), these two effects can be determined using the glass transition temperature Tg or the recovery rate of the cured product of the acrylic resin composition described later as an index. Determine the presence or absence of the effect.

The acrylic resin composition preferably contains a urethane bond because it has sticking resistance under moist heat conditions and is easy to obtain a diffractive optical element with little pattern peeling. For the same reason, the acrylic resin composition is preferably an active energy ray-curable resin composition containing a tetrafunctional or higher (meth)acrylate and a difunctional (meth)acrylate.
Among them, tetrafunctional or higher urethane (meth) acrylate tends to increase the storage elastic modulus (E') under moist heat conditions of the resulting cured product, and bifunctional urethane (meth) acrylate is the resulting cured product. storage modulus (E') under wet heat conditions. Therefore, since the storage elastic modulus (E') of the obtained cured product under wet heat conditions can be adjusted to a desired value, a diffractive optical element having sticking resistance under wet heat conditions and less pattern loss can be obtained. It is more preferable that the acrylic resin composition is an active energy ray-curable resin composition containing a tetrafunctional or more functional urethane (meth)acrylate and a difunctional urethane (meth)acrylate in that it is easy to cure.

It is preferable that the active energy ray-curable resin composition does not contain, as much as possible, materials that are vulnerable to moisture or materials that easily swell due to absorption of water. This is because if a large amount of such a material is included, the sticking resistance of the resulting diffractive optical element may deteriorate.
Materials sensitive to moisture include, for example, known materials that decompose by reacting with water. Materials that easily swell by absorbing water include, for example, highly hydrophilic materials, more specifically vinylpyrrolidone, ammonium acrylate, carboxyethyl acrylate, and the like.
When the active energy ray-curable resin composition as a whole is 100% by mass, the total content of materials vulnerable to moisture and materials that easily swell by absorbing water is preferably 10% by mass or less, more preferably. is 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0% by mass.

Each component contained in the active energy ray-curable resin composition will be described below.
A tetra- or higher functional (meth)acrylate means a polyfunctional acrylate having 4 or more (meth)acryloyl groups in one molecule. Tetra- or higher-functional (meth)acrylates include both monomers and polymers.
Tetra- or higher-functional (meth)acrylates include, for example, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, urethane hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra (meth)acrylate, oligoester tetra(meth)acrylate, and dipentaerythritol polyacrylate; and ethylene oxide-modified compounds, propylene oxide-modified compounds, and ε-caprolactone-modified compounds thereof. In particular, it is preferable that the modification number n≦6 for ethylene oxide-modified compounds, propylene oxide-modified compounds, and ε-caprolactone-modified compounds. This is because when the modification number n>6, the cured product of the active energy ray-curable resin composition tends to be too soft, and sticking may easily occur. These tetrafunctional or higher (meth)acrylates may be used alone or in combination of two or more.
The content of the tetrafunctional or higher (meth)acrylate is preferably 40% by mass or more and 80% by mass or less, and 55% by mass or more and 65% by mass, based on the total curable components of the active energy ray-curable resin composition. % or less.

Tetra- or higher-functional (meth)acrylates are used as tetra- or higher-functional urethanes ( It preferably contains a meth)acrylate. In this case, there are no particular restrictions on the position and number of urethane bonds, whether or not the (meth)acryloyl group is present at the terminal of the molecule, and the like. A compound having 6 or more (meth)acryloyl groups in the molecule is particularly preferred, and a compound having 10 or more (meth)acryloyl groups is more preferred. The upper limit of the number of (meth)acryloyl groups in the molecule is not particularly limited, but 15 or less is particularly preferable. If the number of (meth)acryloyl groups in the urethane (meth)acrylate molecule is too small, the resulting cured product may have poor curability and a low storage modulus. On the other hand, if the number of (meth)acryloyl groups in the urethane (meth)acrylate molecule is too large, the rate of consumption of the carbon-carbon double bonds of the (meth)acryloyl groups by polymerization, that is, the reaction rate may not be sufficiently increased.

The structure of the tetrafunctional or higher urethane (meth)acrylate is not particularly limited, but from the viewpoint of excellent sticking resistance under moist heat conditions and less pattern peeling, the isocyanate group of the polyvalent isocyanate compound (a), It is preferably a compound in which the hydroxyl group of the compound (b) having one hydroxyl group and two or more (meth)acrylic groups in the molecule is urethane-bonded.
Here, it is preferable that almost all of the isocyanate groups in the polyvalent isocyanate compound (a) form urethane bonds with the hydroxyl groups in the compound (b).

The polyvalent isocyanate compound (a) in this case is not particularly limited, and examples thereof include compounds having two or more isocyanate groups in the molecule. Examples of compounds having two isocyanate groups in the molecule include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate. , tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate , isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate and the like. Examples of compounds having three isocyanate groups in the molecule include, for example, isophorone diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, etc. modified trimethylolpropane addition adducts, burettes, and isocyanates. A nurate body and the like can be mentioned. Among these, isophorone diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and the like are particularly preferred for the present disclosure.

The compound (b) having one hydroxyl group and two or more (meth)acrylic groups in the molecule is not particularly limited, but compounds having three or more (p number) hydroxyl groups in the molecule ( Compounds obtained by reaction of (p-1) pieces of (meth)acrylic acid with the hydroxyl group of b-1); compounds obtained by ring-opening reaction of glycidyl (meth)acrylate and (meth)acrylic acid;

Here, the "compound (b) having one hydroxyl group and two or more (meth)acrylic groups in the molecule", when the compound is produced by partially reacting two or more compounds This includes cases where a compound having two or more hydroxyl groups in the molecule or a compound having one (meth)acrylic group is mixed in.

Among the compounds (b), in "a compound (b-1) having p hydroxyl groups in the molecule (p is an integer of 3 or more) reacted with (p-1) (meth)acrylic acid" , "Compound (b-1) having 3 or more hydroxyl groups in the molecule" is not particularly limited, but examples include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, tetramethylolethane, diglycerin, ditri Methylolethane, ditrimethylolpropane, dipentaerythritol, ditetramethylolethane; ethylene oxide-modified compounds thereof; propylene oxide-modified compounds thereof; ethylene oxide-modified compounds of isocyanuric acid, propylene oxide-modified compounds, ε-caprolactone-modified compounds; and esters.

The number of hydroxyl groups in the compound (b-1) is particularly preferably 4 or more, more preferably 6 or more, in that the number of functional groups in the resulting urethane (meth)acrylate can be increased. Specifically, for example, diglycerin, ditrimethylolethane, ditrimethylolpropane, dipentaerythritol, ditetramethylolethane and the like are particularly preferred.

Taking diglycerin as an example, by reacting (meth)acrylic acid with three of the four hydroxyl groups of diglycerin, one hydroxyl group and two or more (in this case, A compound (b) with 3) (meth)acrylic groups is synthesized. Furthermore, taking the case where the polyvalent isocyanate compound (a) is isophorone diisocyanate as an example, the two isocyanate groups of isophorone diisocyanate have one hydroxyl group and two or more (meth)acrylic groups. Two of (b) react to synthesize a "tetrafunctional or higher urethane (meth)acrylate". At this time, if the compound (b) having one hydroxyl group and three (meth)acrylic groups in the molecule reacts with isophorone diisocyanate, as a result, "4 Functional or higher urethane (meth)acrylates” are synthesized.

A bifunctional (meth)acrylate means a polyfunctional acrylate having two (meth)acryloyl groups in one molecule.
Specific examples of bifunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate. linear alkanediol di(meth)acrylates such as;
Ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate (polyethylene glycol #200 di(meth)acrylate , polyethylene glycol #300 di(meth)acrylate, polyethylene glycol #400 di(meth)acrylate, polyethylene glycol #600 di(meth)acrylate, etc.), dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate Alkylene glycol di(meth)acrylates such as , tetrapropylene glycol di(meth)acrylate, polypropylene glycol #400 di(meth)acrylate, polypropylene glycol #700 di(meth)acrylate;
Partial (meth)acrylic acid esters of trihydric or higher alcohols such as pentaerythritol di(meth)acrylate, pentaerythritol di(meth)acrylate monostearate, pentaerythritol di(meth)acrylate monobenzoate;
Bisphenol A di(meth)acrylate, tetrabromobisphenol A di(meth)acrylate, bisphenol S di(meth)acrylate, EO-modified bisphenol A di(meth)acrylate, PO-modified bisphenol A di(meth)acrylate, hydrogenated bisphenol A Di(meth)acrylate, EO-modified hydrogenated bisphenol A di(meth)acrylate, PO-modified hydrogenated bisphenol A di(meth)acrylate, bisphenol F di(meth)acrylate, EO-modified bisphenol F di(meth)acrylate, PO-modified Bisphenol-based di(meth)acrylates such as bisphenol F di(meth)acrylate and EO-modified tetrabromobisphenol A di(meth)acrylate;
Neopentyl glycol di(meth)acrylate, neopentyl glycol PO-modified di(meth)acrylate; hydroxypivalic acid neopentyl glycol ester di(meth)acrylate, caprolactone adduct di(meth)acrylate of hydroxypivalic acid neopentyl glycol ester; 1,6-hexanediol bis(2-hydroxy-3-acryloyloxypropyl) ether; tricyclodecanedimethylol di(meth)acrylate, isocyanuric acid EO-modified di(meth)acrylate; propylene di(meth)acrylate; phthalic acid di(meth)acrylates; di(meth)acrylates such as tricyclodecanemethanol di(meth)acrylate; These bifunctional (meth)acrylates may be used alone or in combination of two or more.
The content of the bifunctional (meth)acrylate is preferably 10% by mass or more and 60% by mass or less, and 30% by mass or more and 45% by mass or less, based on the total curable components of the active energy ray-curable resin composition. is more preferable.

The molecular weight (Mw) of the bifunctional (meth)acrylate is preferably 100 or more and 5,000 or less, more preferably, because the cured product of the active energy ray-curable resin composition has appropriate hardness. is 100 or more and 4,000 or less, more preferably 100 or more and 2,000 or less. When the molecular weight (Mw) of the bifunctional (meth)acrylate is 100 or more, the cured product has appropriate flexibility, and as a result, the obtained diffractive optical element has better sticking resistance. Further, when the molecular weight (Mw) of the bifunctional (meth)acrylate is 5,000 or less, the cured product can maintain appropriate hardness, and as a result, the resulting diffractive optical element is less prone to pattern loss.

The bifunctional (meth)acrylate may contain a bifunctional urethane (meth)acrylate. The content of the bifunctional urethane (meth)acrylate is preferably 30% by mass or less, more preferably 20% by mass or less, relative to the total curable components of the active energy ray-curable resin composition. , more preferably 10% by mass or less, and particularly preferably 0% by mass.
The bifunctional (meth)acrylate may contain a bifunctional (meth)acrylate other than the bifunctional urethane (meth)acrylate. The content of the bifunctional (meth)acrylate other than the bifunctional urethane (meth)acrylate is 10% by mass or more and 50% by mass or less with respect to the total curable components of the active energy ray-curable resin composition. is preferred, and more preferably 20% by mass or more and 45% by mass or less.

The bifunctional urethane (meth)acrylate is preferably bifunctional urethane (meth)acrylate having one (meth)acrylic group at each end of the molecule.
The chemical structure of such bifunctional urethane (meth)acrylate is not particularly limited, and the weight average molecular weight is preferably 1,000 or more and 30,000 or less, and 2,000 or more and 5,000 or less. is particularly preferred. If the molecular weight is too small, the flexibility may decrease, and if the molecular weight is too large, the storage modulus may decrease.

The bifunctional urethane (meth)acrylate is not particularly limited, but the following are particularly preferred. That is, both ends of a polymer or oligomer (c) having hydroxyl groups, amino groups or the like are reacted with a diisocyanate compound (d) to obtain a "polymer or oligomer having isocyanate groups at both ends", A compound (e) having a hydroxyl group and a (meth)acrylic group in the molecule is particularly preferably reacted with both ends thereof.

The polymer or oligomer (c) having hydroxyl groups at both ends is not particularly limited, and examples thereof include ester oligomers, ester polymers, urethane oligomers, urethane polymers, polyethylene glycol and polypropylene glycol. Among these, particularly preferred are ester oligomers and ester polymers. The molecular weight of such oligomers and polymers is not particularly limited, but the weight-average molecular weight is preferably in the range of 1,000 to 5,000, particularly preferably in the range of 2,000 to 3,000, in terms of curability.

The diol component of the above ester is not particularly limited, but is ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, 2,2'-thiodiethanol. etc. Particularly preferred are 1,4-butanediol, 1,6-hexanediol and the like.

The dicarboxylic acid component of the above ester is not particularly limited, but includes alkylene dicarboxylic acids such as oxalic acid, succinic acid, maleic acid and adipic acid; and aromatic dicarboxylic acids such as terephthalic acid and phthalic acid. Particularly preferred are adipic acid, terephthalic acid and the like.

The diisocyanate compound (d) to be reacted with both ends of such a polymer or oligomer is not particularly limited, and the same diisocyanate compounds as those described in the item of the above polyvalent isocyanate compound (a) can be used. Especially preferred are isophorone diisocyanate and the like.

Further, the "compound (e) having a hydroxyl group and a (meth)acrylic group in the molecule" to be reacted with both ends of the polymer or oligomer having isocyanate groups at both ends obtained above is not particularly limited, Examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate and the like.

The active energy ray-curable resin composition contains monofunctional (meth)acrylates and/or trifunctional (meth)acrylates in addition to tetrafunctional (meth)acrylates and difunctional (meth)acrylates. You can stay. A monofunctional (meth)acrylate means an acrylate having one (meth)acryloyl group in one molecule. A trifunctional (meth)acrylate means a polyfunctional acrylate having three (meth)acryloyl groups in one molecule.
However, the smaller the content of monofunctional (meth)acrylate and trifunctional (meth)acrylate, the better. Specifically, the total content of monofunctional (meth)acrylates and trifunctional (meth)acrylates is 10% by mass or less with respect to all curable components of the active energy ray-curable resin composition. is preferred, 5% by mass or less is more preferred, and 0% by mass is even more preferred.
Monofunctional (meth)acrylates include, for example, phenoxyethyl acrylate, trimethylcyclohexanol acrylate, isobornyl acrylate, phenylphenol acrylate, nonylphenol acrylate, and the like.
Examples of trifunctional (meth)acrylates include glycerin PO-modified tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO-modified tri(meth)acrylate, and trimethylolpropane PO-modified tri(meth)acrylate. Acrylates, isocyanuric acid EO-modified tri(meth)acrylate, isocyanuric acid EO-modified ε-caprolactone-modified tri(meth)acrylate, 1,3,5-triacryloylhexahydro-s-triazine, pentaerythritol tri(meth)acrylate, di pentaerythritol tri(meth)acrylate tripropionate and the like.

The curable component in the active energy ray-curable resin composition may have a crosslink density that depends on its molecular weight, which may be a factor in determining the storage elastic modulus under wet heat conditions.

The acrylic resin composition may contain one or more photopolymerization initiators as necessary. The content of the photopolymerization initiator is usually 0.2 to 15% by mass, preferably 0.3 to 13% by mass, based on the total solid content of the acrylic resin composition, and 0.5 More preferably, it is up to 10% by mass.
The photopolymerization initiator is not particularly limited, but conventionally known ones conventionally used for radical polymerization, such as acetophenones, benzophenones, alkylaminobenzophenones, benzyls, benzoins, benzoin ethers, benzyl Aryl ketone photopolymerization initiators such as dimethyl acetals, benzoyl benzoates, and α-acyloxime esters; sulfur-containing photopolymerization initiators such as sulfides and thioxanthones; acylphosphine oxides such as acyldiarylphosphine oxide; and anthraquinones. Moreover, a photosensitizer can also be used together.

The acrylic resin composition preferably contains a releasing agent (a material having releasability). The release agent improves the releasability of the cured product of the acrylic resin composition, thereby suppressing pattern peeling of the cured product. In addition, by appropriately selecting the type of release agent, the storage elastic modulus (E′) of the cured product at 60° C. and 95% relative humidity is 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ It can be adjusted to a range of Pa or less, and the cured product can be imparted with sticking resistance. That is, the release agent brings about better effects in terms of both suppression of pattern peeling and sticking prevention in the cured product.
In addition, in the step of forming a cured product of the acrylic resin composition, the addition of a mold release agent can prevent a reduction in mold life due to resin clogging during mold release.
The release agent is not particularly limited as long as it is commonly used in the production of diffractive optical elements. The mold release agent can be appropriately selected from known mold release agents such as silicone-based, fluorine-based, and phosphoric acid-based as needed. These release agents can be selected according to the application from those that are fixed to the crosslinked structure of the acrylic resin composition or those that exist in a free state.
Among them, it is preferable to use non-reactive silicone, reactive silicone, and phosphoric acid-based releasing agent as the releasing agent, and among these, non-reactive silicone is more preferable.
Non-reactive silicones include KF-352A, KF-354L, KF-4003, KF-412, KF-413, KF-414, KF-415, KF-4701, KF-4917, KF-53, KF-54 , KF-6004, KF-643, KF-7235B, X-22-1877, X-22-2516, X-22-7322, PC-88A (manufactured by Shin-Etsu Silicone Co., Ltd.), TEGO Glide 100, TEGO Glide 410, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Glide ZG400 (these are trade names, manufactured by Evonik Japan) and the like.
Examples of reactive silicones include KF-2012, KF-393, KF-684, KF-8002, KF-8004, KF-8005, KF-8021, KF-860, KF-861, KF-865, KF-867, KF-868, KF-869, KF-869, KF-877, KF-880, KF-889, KF-99, KF-9901, X-22-170, X-22-173, X-22-174, X-22-176, X-22-2404, X-22-2426, X-22-3939A (trade names, manufactured by Shin-Etsu Silicone Co., Ltd.), TEGO Rad 2010, TEGO Rad 2011, TEGO Rad 2100, TEGO Rad 2200N, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2500, TEGO Rad 2650, TEGO Rad 2700, TEGO Rad 2800 (these are trade names, manufactured by Evonik Japan) and the like.

The acrylic resin composition should just contain at least the said active-energy-ray-curable component, and may contain other components further as needed.
As other components, a plurality of antistatic agents, ultraviolet absorbers, infrared absorbers, light stabilizers, antioxidants, and the like can be added. Antistatic agents are effective in preventing dust adhesion during processing and use, and ultraviolet absorbers, infrared absorbers, light stabilizers, and antioxidants are effective in improving durability. When adding a material that absorbs light, care must be taken not to affect the target wavelength of the diffractive optical element. Compositing with an inorganic material such as silsesquioxane is also effective for the purpose of improving heat resistance.
In addition, it is preferable that the acrylic resin composition does not substantially contain a solvent in consideration of the environment. good too. When a solvent is contained, the base material or the mold is coated with the resin, the solvent is dried, and then the mold is formed.
Furthermore, the acrylic resin composition may contain resins other than acrylic resins. The acrylic resin composition is, for example, a compound having an ethylenically unsaturated double bond other than an acrylic resin, specifically triethylene glycol divinyl ether, vinyl such as 2-(2-vinyloxyethoxy)ethyl acrylate. It may contain a system compound or the like.

The diffractive optical element of the present disclosure preferably has excellent reflow resistance. Here, “excellent reflow resistance” means that the mass change rate before and after heating (for example, 260° C. for 1.5 minutes) is 2% or less and the transmittance change before and after the heating is 1% or less. means.
As described later in "(5) Other steps" of "2. Method for manufacturing a diffractive optical element", when manufacturing an illumination device using a diffractive optical element, a temporary assembly including the diffractive optical element is prepared. A process (reflow process) of placing in a reflow furnace and heating under high temperature conditions may be carried out. By this reflow process, the light source and the frame surrounding it can be electrically connected to the mounting substrate by soldering, for example, and the lighting device can be manufactured efficiently.
However, in the reflow process, a high temperature of 200° C. or higher is momentarily applied to the material constituting the lighting device, and the material may melt or sublimate. In particular, since the high refractive index convex portions in the diffraction grating part form a fine structure, the cured product of the acrylic resin composition constituting the high refractive index convex portions is likely to dissolve or sublime. However, as a result of deformation of the shape of the high-refractive-index convex portion, there is a possibility that transmittance fluctuation occurs in the diffractive optical element. Further, even if the shape of the high refractive index protrusions is maintained, the mass of the high refractive index protrusions may decrease when the cured product of the acrylic resin composition decomposes.
Therefore, the diffractive optical element of the present disclosure preferably has excellent reflow resistance. It can be said that a diffractive optical element having excellent reflow resistance is excellent in formability because the shape of the high-refractive-index convex portions is less likely to be damaged in the reflow process.
As a diffractive optical element having excellent reflow resistance, for example, there is a diffractive optical element in which a cured product of an acrylic resin composition containing a tetrafunctional or higher (meth)acrylate is used to form high refractive index convex portions. mentioned.

The calculation method of the mass change rate and transmittance fluctuation is as follows.
(Method for calculating mass change rate of diffractive optical element)
The mass of the diffractive optical element before and after reflow is measured, and the mass change rate a is calculated from Equation I below.
Formula I a = {(M ₀ −M ₁ )/M ₀ }×100
(In Formula I above, a is the mass change rate (%), _M0 is the mass of the diffractive optical element before reflow (mg), and _M1 is the mass of the diffractive optical element after reflow (mg).)
(Method for Calculating Transmittance Variation of Diffractive Optical Element)
The transmittance (%) of the diffractive optical element before and after reflow is measured. The transmittance is measured using an ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrophotometer (eg UV-3150 manufactured by Shimadzu Corporation) or the like. Using this apparatus, the transmittance of the transparent substrate and the diffraction grating portion of the diffractive optical element with a wavelength of 850 nm is measured.
The absolute value of the difference between the transmittance of the diffractive optical element before reflow and the transmittance of the diffractive optical element after reflow is defined as the transmittance variation (%) of the diffractive optical element.

The refractive index of the cured product of the acrylic resin composition that constitutes the high refractive index protrusions is not particularly limited, but is preferably 1.4 to 2.0, more preferably 1.45 to 1.8. more preferred. According to the present disclosure, a shape with an aspect ratio of 2 or more can be stably formed, and a good diffractive optical element can be obtained even with a resin having a lower refractive index than silicon oxide or the like.
In addition, in the present disclosure, the transmittance of the cured product of the resin composition constituting the high refractive index convex portion is not particularly limited, but the infrared transmittance (wavelength 850 nm) is preferably 90% or more, and 92% or more. is more preferable.

From the viewpoint of suppressing sticking, the ratio (tan δ (=E"/E' )) is preferably 0.12 or less, more preferably 0.11 or less, and even more preferably 0.10 or less. When the ratio (tan δ (=E″/E′)) under wet heat conditions is 0.12 or less, the contribution of elasticity is higher than the contribution of viscosity in the cured product of the acrylic resin composition, Since the cured product more strongly exhibits properties as an elastic body, the diffractive optical element has excellent sticking resistance under moist heat conditions.
The loss elastic modulus (E″) of the cured product of the acrylic resin composition at 60° C. and 95% relative humidity can be measured by the same method as for the storage elastic modulus (E′).

It is preferable that the recovery rate of the cured product of the acrylic resin composition is 60% or more. This is because a cured product having such a recovery rate has superior sticking resistance.
The acrylic resin in the acrylic resin composition preferably contains a urethane bond, and more preferably contains a tetrafunctional or higher urethane (meth)acrylate because the recovery rate is 60% or more.

The recovery rate measurement conditions are as follows.
As the cured product of the acrylic resin composition used for measuring the recovery rate, a test piece cut out from the diffractive optical element may be used, or a test piece obtained by separately polymerizing the acrylic resin composition may be used. good too. The method for preparing these test pieces is as described above.
A Vickers hardness test is carried out under the following measurement conditions in accordance with JIS Z2244 (2003). Specifically, an indenter is pushed into the surface of the test piece under the following measurement conditions, and the recovery rate (%) of the surface of the test piece is measured. For example, PICODETER HM-500 manufactured by Fisher Instruments can be used as the measuring device.
<Measurement conditions>
・Maximum load 0.2mN
・Loading speed: 0.2 mN/10 seconds ・Holding time: 5 seconds ・Load unloading speed: 0.2 mN/10 seconds ・Indenter: Vickers indenter ・Measurement temperature: 25°C

(2) Structure of Diffractive Optical Element FIG. 1 is a plan view schematically showing an embodiment of the diffractive optical element of the present disclosure. 2 is a perspective view schematically showing an embodiment of the diffractive optical element of FIG. 1. FIG. FIG. 3 is a cross-sectional view schematically showing an example of the AA' cross-section of FIG.
As shown in FIG. 3 , the diffractive optical element 10 of the present disclosure includes a diffraction grating section 2 on one side of a transparent substrate 1 . The diffraction grating portion 2 is formed by arranging one or more high refractive index convex portions 2a projecting from the surface of the transparent substrate 1 and one or more low refractive index portions 2b. As shown in FIG. 3, when two or more high-refractive-index convex portions 2a and two or more low-refractive-index portions 2b are used, they are arranged so as to appear periodically and alternately.
The diffraction grating portion 2 may be provided on one surface side of the transparent base material 1 or may be provided on both surface sides of the transparent base material 1 .
A diffractive optical element of the present disclosure typically has multiple regions (eg, regions 2A-2D in FIG. 1) with different periodic structures. In the example of FIG. 1, the partial periodic structure 2A to 2D regions are 2-level irregularities (for example, the diffraction grating portion 2 in FIG. 3), but in order to shape the light as desired, the shape of the region and depth should be designed appropriately.

4 to 7B are cross-sectional views schematically showing other embodiments of the diffractive optical element of the present disclosure.
FIG. 4 shows an embodiment in which a base portion 3 is present between the transparent substrate 1 and the diffraction grating portion 2 . When two or more high refractive index convex portions 2a are used, the high refractive index convex portions 2a may be isolated from each other (FIG. 3), or the high refractive index convex portions 2a may They may be linked (Fig. 4). As will be described later, when forming the high refractive index protrusions 2a using a mold, as shown in FIG. , the diffractive optical element 10 may comprise such a base 3 .
5A and 5B show an embodiment comprising a coating layer 5 on the opposite side of the transparent substrate 1 with the diffraction grating portion 2 interposed therebetween. The coating layer 5 may be in direct contact with the diffraction grating portion 2 or may be provided on the diffraction grating portion 2 via an adhesive layer (adhesive layer). Note that the embodiment shown in FIG. 3 with the coating layer 5 added corresponds to the embodiment shown in FIG. 5A, and the embodiment shown in FIG. 4 with the coating layer 5 added corresponds to the embodiment shown in FIG. 5B. do.
6A and 6B show an embodiment in which the low refractive index portion 3 is filled with a low refractive index resin 7. FIG. From the viewpoint of increasing the refractive index difference, the low refractive index portion is preferably air. On the other hand, from the viewpoint of obtaining a diffractive optical element having excellent mechanical strength, it is preferable that the low refractive index portion 3 is made of the low refractive index resin 7 . 3 corresponds to the embodiment shown in FIG. 6A, and the embodiment shown in FIG. 4 to which the low refractive index resin 7 is added is shown in FIG. 6B. It corresponds to the embodiment.

7A and 7B show an embodiment in which an antireflection layer 9 is provided on the opposite side of the diffraction grating section 2 with the transparent substrate 1 interposed therebetween. By providing the antireflection layer 9 in this way, it is possible to suppress reflected light and improve the light utilization efficiency. The antireflection layer 9 may be provided in direct contact with the transparent substrate 1, or another member (such as a glass layer or an adhesive layer) may be interposed between the antireflection layer 9 and the transparent substrate 1. may The embodiment shown in FIG. 3 with an antireflection layer 9 added thereto corresponds to the embodiment shown in FIG. 7A, and the embodiment shown in FIG. 4 with an antireflection layer 9 added thereto is shown in FIG. 7B. It corresponds to the embodiment.

Preferably, the high refractive index convex portion has a portion having an aspect ratio of 2 or more, which is conceptualized as "ratio of height to width" or "elongation of projection".
A diffractive optical element including high refractive index convex portions having an aspect ratio of 2 or more can obtain diffracted light of a desired shape even with infrared rays having a longer wavelength (for example, infrared rays of 780 nm or more) than conventional ones, and Zero-order light can be suppressed in diffracted light. Moreover, as will be described later, the diffractive optical element having a relatively large aspect ratio is preferably a transmissive diffractive optical element.

However, in the present disclosure, the high refractive index convex portion may have a binary shape or a multi-step shape. For example, FIG. 8A is a schematic cross-sectional view of a binary-shaped high-refractive-index convex portion, and FIG. 8B is a cross-sectional schematic view of a multi-level (4-level) high-refractive-index convex portion. The root 41 of the high refractive index convex portion 2a may be a transparent substrate or may be a base portion.
Therefore, the aspect ratio of the high refractive index protrusions in the present disclosure is defined as follows.
First, as shown in FIG. 8A, the aspect ratio in the case where the high refractive index convex portion has a binary shape is (height H of the high refractive index convex portion)/(half the height of the high refractive index convex portion). It is defined as the width W) of the high refractive index protrusion at the position of height (H/2). Here, the height H of the high refractive index convex portion means the height difference from the top of the high refractive index convex portion to the concave portion (the position of the bottom of the valley between another adjacent high refractive index convex portion). .
Further, when the high refractive index convex portion has a multi-step shape, the aspect ratio is (height H of the high refractive index convex portion)/(minimum processing width W _min of the high refractive index convex portion) is defined as Here, as shown in FIG. 8B, the minimum processing width W _min of the high refractive index convex portion in the present disclosure is the portion corresponding to the height h in the drawing, that is, the mid-level of the multi-stepped high refractive index convex portion. Focusing on the portion from the flat portion at the highest position among the flat portions at , to the top of the multi-step-shaped high refractive index convex portion, at the half height position (h / 2) of this portion Defined as width. In other words, as shown in FIG. 8B, the uppermost flat portion (height: H) of the high refractive index convex portion is the upper end, and the second flat portion from the top of the high refractive index convex portion ( With height: Hh) as the lower end, the width at half the height (h/2) from the lower end is the minimum processing width W _min of the high refractive index convex portion.
Therefore, in the present disclosure, the broadly defined "aspect ratio of high refractive index convex portions" that includes both binary high refractive index convex portions and multi-step high refractive index convex portions is The top of the high refractive index convex portion is defined as the upper end, and the position of the bottom of the valley between the high refractive index convex portion and another adjacent high refractive index convex portion, or the closest from the top of the high refractive index convex portion When the lower end is defined as the position of the flat portion closer to the top of the high refractive index convex portion, from the lower end to the upper end of the high refractive index convex portion, at the position corresponding to half the height difference between the upper end and the lower end It is defined as the ratio of the height of the high refractive index protrusion to the width of the high refractive index protrusion.
By defining the aspect ratio in this way, the diffraction grating section can be optically designed precisely, and the correlation between the ease of removal of the high-refractive-index convexities from the mold and the aspect ratio of the high-refractive-index convexities can be determined. can be raised.
The height H, width W, and minimum processing width W _min of the high refractive index convex portion can be calculated from, for example, an SEM image of the cross-sectional shape of the diffraction grating portion.

In general, the shape of a diffraction grating is determined by the wavelength of light, the refractive index (difference) of the material through which light passes, and the required diffraction angle. For example, when a material having a refractive index of 1.5 in air is used and a laser beam is vertically incident on the diffraction grating portion side surface of the diffractive optical element, the longer the wavelength of the light, the more optimal the groove depth of the diffraction grating. A depth of 850 nm is required for infrared rays with a wavelength of 850 nm. That is, in the diffractive optical element of the present disclosure, in the cross-sectional shape of the diffraction grating portion, the high refractive index convex portion preferably includes a portion having a height of 850 nm or more, and cure shrinkage due to active energy rays (for example, 10%) Considering the above, the height is more preferably 944 nm or more, and considering the manufacturing error (for example, 5%), the height is preferably about 994 nm.
Further, in order to diffract the light in the direction of the diffraction angle of 30°, the aspect ratio of the high refractive index convex portion should be about 1.1, and in order to diffract the light in the direction of 70°, the aspect ratio should be about 2.1. .
However, this is a case where light is diffracted in only one direction, and when actually used as a light source for a sensor, it is necessary to spread the diffracted light uniformly over a certain predetermined area. For that purpose, it is necessary to intricately combine regions having various diffraction angles and diffraction directions, but as a result, regions with pitches as narrow as λ/4 are included. Here, since the optimum depth of the diffraction grating is determined by the wavelength of light, the refractive index, and the number of levels, the narrower the pitch, the more the aspect ratio becomes 2.1 or more, and sometimes exceeds 4. For example, for a laser beam of 850 nm, if the material is quartz and a rectangular diffusion shape that spreads over ±50° on the long side and ±3.3° on the short side is designed with 2-levels, the original plate of the diffraction grating is optimal. The maximum aspect ratio exceeds 4 when the depth is 994 nm and the pitch of the finest features is 212 nm.
These designs are performed using various simulation tools such as GratingMOD (manufactured by Rsoft) using a rigorous coupled wave analysis (RCWA) algorithm and Virtuallab (manufactured by LightTrans) using an iterative Fourier transform algorithm (IFTA). be able to. If the light source is an LED instead of a laser, it may be designed in consideration of oblique incident light.

It is preferable that the high-refractive-index convex portion has a portion with an aspect ratio of 2 or more, because infrared rays with a wavelength of 780 nm or more can be shaped into a desired shape.

The cross-sectional shape of the diffraction grating portion may be rectangular as shown in FIGS. 3 to 7B, or may be other shapes. 9A to 9D are cross-sectional schematic diagrams showing other embodiments of the cross-sectional shape of the diffraction grating portion. The root 41 of the high refractive index convex portion 2a may be a transparent substrate or may be a base portion.
In each of the examples shown in FIGS. 9A to 9D, the cross-sectional shape of the high-refractive-index convex portion is tapered, so that it is excellent in releasability from the mold during manufacturing.
The thickness of the high refractive index protrusions 2a may increase intermittently from the tip to the root (FIG. 9A), or may increase continuously from the tip to the root (FIG. 9B).
Further, in order to increase the diffraction efficiency of the diffractive optical element, the cross-sectional shape of the diffraction grating portion is changed from the normal binary (2-level: FIGS. 3 to 7B) to the multi-step shape (4-level (FIG. 9C), 8-level). level (FIG. 9D)). However, if the number of steps in the cross-sectional shape of the diffraction grating portion is increased too much, the mold manufacturing process becomes complicated, leading to an increase in cost.
The groove depth increases as the number of steps in the cross-sectional shape of the diffraction grating increases. For example, when the refractive index of the cured product of the acrylic resin composition is 1.5, the groove depth at 4-level is 1.5 times the target wavelength, and the groove depth at 8-level The depth is 1.75 times the wavelength of interest. The longer the target wavelength, the deeper the required groove depth, and the greater the difficulty of processing.
The minimum processing groove width set at the time of design is usually about 1/4 of the target wavelength. In order to increase efficiency, the minimum machining groove width may be made finer. However, if the minimum processing groove width is too narrow, processing becomes difficult and takes a long time, so the minimum processing groove width is preferably about 80 to 100 nm.
By forming the high refractive index convex portions using the acrylic resin composition, the diffractive optical element of the present disclosure has an aspect ratio of 2 or more, and even when it includes an aspect ratio of 4 or more, reliability is improved. Excellent.

In the diffractive optical element of the present disclosure, the line & space ratio (L/S) is not particularly limited when the high refractive index convex portion is the line (L) and the low refractive index portion is the space (S). The line & space ratio (L/S) is obtained from the following formula (A).
Formula (A) (L/S)=l/(l+s)
(In the above formula (A), (L/S) represents the line & space ratio, l represents the line width (nm), and s represents the space width (nm).)
The line & space ratio (L/S) may be appropriately set so as to obtain the desired diffracted light. A range of 0.4 to 0.6 is preferable from the viewpoint of efficiency.

Moreover, in the diffractive optical element of the present disclosure, it is preferable that the diffractive optical element has a multi-stage shape having two or more flat portions in order to easily increase the diffraction angle.
The diffractive optical element of the present disclosure can attenuate the 0th-order light when the aspect ratio is 2 or more. A desired shape of diffracted light can be obtained by removing the . This will be described with reference to the drawings. 10A and 10B are drawings for explaining the diffractive optical element. 11A is a front view of the screen 22 shown in FIG. 10A, and FIG. 11B is a front view of the screen 22 shown in FIG. 10B.
FIG. 10A is a schematic perspective view showing how the irradiation light 21 is diffracted by the diffractive optical element 10 to form a square image 24 in the center of the screen 22. FIG. As shown in FIG. 11A, the square image 24 contains the 0th order light irradiation position 27, so the image 24 contains the 0th order light. When the aspect ratio is 2 or more, the 0th order light is suppressed, so even if the image 24 contains the 0th order light, good diffracted light can be obtained.
FIG. 10B is a schematic perspective view showing how the irradiation light 21 is diffracted by the diffractive optical element 10 and a square image 24 is formed on the screen 22 . In the example shown in FIG. 10B, the diffraction angles of the first-order lights 26a to 26d are set larger than in the example shown in FIG. 10A. Therefore, as shown in FIG. 11B, square image 24 does not include 0th order light irradiation position 27 .
As shown in FIG. 10B, by setting the maximum diffraction angle large, it is possible to obtain a diffractive optical element that can obtain diffracted light that does not include 0th order light. From the above points, in the diffractive optical element of the present disclosure, the diffraction grating section preferably has a multi-stage shape having two or more flat portions, and further preferably has an aspect ratio of 3.5 or more.

The transparent substrate used in the present disclosure can be appropriately selected from known transparent substrates according to the application and used. Specific examples of the material used for the transparent substrate include, for example, acetylcellulose resins such as triacetylcellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, olefin resins such as polyethylene and polymethylpentene, and acrylic resins. Resin, polyurethane resin, transparent resin such as polyether sulfone, polycarbonate, polysulfone, polyimide, polyether, polyether ketone, acrylonitrile, methacrylonitrile, cycloolefin polymer, cycloolefin copolymer, soda glass, potash glass, Glass such as lead glass, ceramics such as PLZT, transparent inorganic materials such as quartz and fluorite, and the like can be used. The birefringence of the transparent base material does not affect the effect of the diffractive optical element itself, but when the phase difference between the light incident on the diffractive optical element and the light diffusing is considered, the transparent base material has an appropriate birefringence. A base material may be selected.
The term “transparency” here refers to a state in which the other side can be seen through with the naked eye. no. Further, when the acrylic resin composition is cured by irradiating the active energy ray from the transparent substrate side, it is preferable that the transparent substrate does not block the irradiated active energy ray as much as possible.
The thickness of the transparent substrate can be appropriately set according to the application of the present disclosure, and is not particularly limited, but is usually 5 to 5,000 μm, and the transparent substrate is supplied in the form of a roll. , it may be one that does not bend enough to be wound up but bends when a load is applied, or one that does not bend completely.
The structure of the transparent base material used in the present disclosure is not limited to a structure consisting of a single layer, and may have a structure in which a plurality of layers are laminated. When it has a configuration in which a plurality of layers are laminated, layers having the same composition may be laminated, or a plurality of layers having different compositions may be laminated.
In addition, the transparent base material may be subjected to a surface treatment for improving adhesion to the acrylic resin composition, or a primer layer may be formed. As the surface treatment, general adhesion improvement treatments such as corona treatment and atmospheric pressure plasma treatment can be applied. The primer layer preferably has adhesion to both the transparent base material and the resin composition, and preferably transmits light of the target wavelength. However, depending on the application, it is also possible to intentionally keep the adhesion between the transparent base material and the resin composition low so that the diffraction grating portion after molding can be peeled off from the transparent base material. Such usage is particularly effective when it is desired to reduce the thickness of the diffractive optical element.

(3) Other configurations of the diffractive optical element In addition, since the diffractive optical element of the present disclosure can prevent the diffraction grating from being damaged and has excellent mechanical strength, the diffractive optical element of the present disclosure includes the diffraction grating on a transparent base material, and a coating layer in this order (FIGS. 5A and 5B). Although the coating layer is not particularly limited, it is preferable to use the same material as the transparent substrate. Moreover, when providing a coating layer on the diffraction grating section, an adhesive (adhesive) layer may be provided between the diffraction grating section and the coating layer. The pressure-sensitive adhesive or adhesive for the pressure-sensitive adhesive layer (adhesive layer) may be appropriately selected from conventionally known ones, including pressure-sensitive adhesives (adhesives), two-component curing adhesives, ultraviolet curing adhesives, Any form of adhesion such as a thermosetting adhesive or a hot-melt adhesive can be suitably used, but when the low refractive index portion is air, a pressure-sensitive adhesive or adhesive with low fluidity should be used. is preferred. If a portion of the low refractive index portion is filled with an adhesive or adhesive, the diffraction grating portion may be designed in consideration of that portion. By providing such a coating layer, it is possible to expect a secondary effect that it is possible to prevent reverse engineering using the irregularities of the diffraction grating portion as a mold.
Furthermore, by forming the coating layer, it is possible to prevent foreign matter from entering the diffraction grating section, and improve the long-term reliability of the diffractive optical element and the illumination device.

Furthermore, an antireflection layer may be further provided on the surface of the transparent substrate or the coating layer opposite to the diffraction grating section (FIGS. 7A and 7B). The antireflection layer may be appropriately selected from conventionally known ones. For example, it may be a refractive index layer comprising a single layer of a low refractive index layer or a high refractive index layer. It may be a multilayer film in which a dielectric layer is sequentially laminated, or it may be an antireflection layer in which fine unevenness is formed. By providing the antireflection layer, it is possible to improve the diffraction efficiency of the diffractive optical element.

Further, the transparent substrate, the coating layer, and the adhesive layer (adhesive layer) may contain conventionally known additives within a range that does not impair the effects of the present disclosure. Examples of such additives include ultraviolet absorbers, infrared absorbers, light stabilizers, antioxidants, and the like.
The diffractive optical element of the present disclosure may be a transmissive diffractive optical element or a reflective diffractive optical element. Among these, the diffractive optical element of the present disclosure is preferably a transmissive diffractive optical element. Compared to a reflective diffractive optical element, a transmissive diffractive optical element needs to have a large aspect ratio of the high refractive index convex portions in the diffraction grating section, and as a result, sticking tends to occur easily. Therefore, a transmissive diffractive optical element having high refractive index convex portions that satisfies the condition of the storage elastic modulus (E′) under the above-described moist heat condition is more efficient than a reflective diffractive optical element having similar high refractive index convex portions. Highly effective in preventing sticking.

2. Manufacturing method of diffractive optical element The manufacturing method of the present disclosure includes one or more high refractive index convex portions protruding from the surface of the transparent substrate and one or more low refractive index portions on at least one surface side of the transparent substrate. A method of manufacturing a diffractive optical element for shaping light from a light source, comprising:
a step of preparing a mold having a cavity shape for forming the high refractive index convex portion and the low refractive index portion (hereinafter referred to as mold preparation step);
A sample of a cured product obtained by irradiating and curing an acrylic resin composition in the cavity of the mold with ultraviolet rays so that the cumulative light amount of the acrylic resin composition is 1,000 mJ/cm ² . A step of filling an acrylic resin composition having a storage elastic modulus (E′) at 60° C. and 95% relative humidity of 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less (hereinafter referred to as acrylic resin referred to as composition filling step),
A step of curing the acrylic resin composition by contacting the transparent substrate and the acrylic resin composition on the cavity opening side of the mold and irradiating the acrylic resin composition with an active energy ray (hereinafter referred to as acrylic a diffraction grating portion having a high refractive index convex portion formed of a cured product of an acrylic resin composition on a transparent base material by separating the mold from the transparent base material. The step of forming (hereinafter referred to as the mold release step),
characterized by having

12A to 12E are process diagrams schematically showing an example of a method of manufacturing a diffractive optical element.
First, as shown in FIG. 12A, a mold 31 having a cavity shape corresponding to the desired surface structure of the diffraction grating is prepared (mold preparation step).
Next, as shown in FIGS. 12B and 12C, the mold cavity 31a is filled with an acrylic resin composition 32 (acrylic resin composition filling step). Here, the acrylic resin composition 32 is the same composition as the acrylic resin composition described in the above "1. Diffractive optical element". The filling method is not particularly limited, and a conventionally known method may be appropriately selected. For example, as shown in FIGS. 12B and 12C, the cavity 31a may be filled with the acrylic resin composition 32 by coating the surface of the mold 31 with the acrylic resin composition 32. FIG. As a more specific example, first, the acrylic resin composition 32 is placed on the surface of the mold 31 (FIG. 12B), and the transparent substrate 33 is placed thereon. Next, the acrylic resin composition 32 is spread evenly over the surface of the mold 31 over the transparent substrate 33 by the pressure roller 34 (FIG. 12C), and the acrylic resin composition 32 is applied in the cavity 31a. to fill. As shown in FIGS. 12C and 12D, part of the acrylic resin composition 32 may protrude from the mold cavity 31a. The protruding portion of the acrylic resin composition 32 becomes the base after curing. Alternatively, all of the acrylic resin composition 32 may be filled into the cavity 31a of the mold.
Subsequently, as shown in FIG. 12D, the coating film of the acrylic resin composition 32 is irradiated with an active energy ray from the cavity opening side of the mold (35) to cure the acrylic resin composition 32. (acrylic resin composition curing step). The contact between the transparent base material and the acrylic resin composition may be performed at the same time as the filling of the acrylic resin composition, or may be performed after the filling of the acrylic resin composition.
After that, as shown in FIG. 12E, the obtained cured product 36 is released from the mold 31 to obtain a diffractive optical element (mold release step).
Details of each step of the manufacturing method will be described below. Note that the same description as that of the diffractive optical element of the present disclosure will be omitted.

(1) Mold preparation step A mold for manufacturing a diffractive optical element can be processed by techniques such as laser lithography, electron beam lithography, FIB (Focused Ion Beam), etc. Electron beam lithography is usually preferably used. .
Any material can be used as long as it can be processed with a high aspect ratio, but quartz and Si are usually used. It is also possible to use a copy mold (soft mold) that is duplicated from these molds with resin, or a copy mold that is duplicated by Ni electroforming.
If necessary, the surface of the mold can be subjected to mold release treatment. A release agent such as a fluorine-based or silicon-based release agent, diamond-like carbon, Ni plating, or the like can be applied. The processing method can be appropriately selected from vapor phase processing such as vapor deposition, sputtering, ALD (Atomic Layer Deposition), liquid phase processing such as coating, dipping, and plating.
Since the shape required for a diffractive optical element is usually as small as several millimeters square to several centimeters square, the efficiency of duplication can be increased by arranging and processing a plurality of diffraction grating portions in one mold. When the throughput is emphasized, the above molds or copy molds may be arranged side by side and duplicated to form a multifaceted mold for molding.

If the volume change during curing of the acrylic resin composition poses a problem, the mold can be designed by correcting it. Also, in consideration of ease of mold release, the structure may be such that the frontage on the opening side is wider than the depth of the fine structure of the mold (FIGS. 9A to 9D). In this case, the diffraction grating portion of the obtained diffractive optical element becomes narrower on the surface side.
In addition, since the diffractive optical element of the present disclosure usually has a plurality of regions with different periodic structures, one diffractive optical element includes a plurality of grooves with different pitches (frontages). When making a mold, the depth of dry etching tends to vary depending on the pitch (frontage). However, since such variations lead to a decrease in efficiency, it is important to optimize the processing process and suppress the desired depth to ±10% or less.
When forming high refractive index convex portions with an aspect ratio of 2 or more, there is a tendency that the height of the high refractive index convex portions tends to vary. In that case, by making the depth of the mold slightly deeper than the design value, it becomes easier to obtain a diffractive optical element having desired optical characteristics while having variations in height.

(2) Acrylic resin composition filling process “A cured product sample obtained by irradiating and curing the acrylic resin composition with ultraviolet rays so that the integrated light amount is 1,000 mJ / cm ² ” means the obtained diffraction This simulates a cured product of an acrylic resin composition that would actually be contained in the diffraction grating portion of an optical element. Thus, an acrylic resin composition having a storage elastic modulus (E′) at 60° C. and 95% relative humidity in a cured product sample of 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less is used. As a result, a diffractive optical element can be obtained that can prevent sticking under moist heat conditions and can reduce pattern peeling at the time of mold release. The reason is as explained in the above "1. Diffractive optical element".
In the above example, the coating film of the acrylic resin composition is formed on the mold side, but the coating film may be formed on the transparent substrate side. As the method of forming the coating film, in addition to the above examples, a suitable method can be selected from conventionally known coating methods such as die coating, bar coating, gravure coating, and spin coating.
As for the transparent substrate, those described in the above "1. Diffractive optical element" can be used. The transparent base material may be a sheet-fed one, or a long one may be used and the application step, the acrylic resin composition curing step, and the mold release step may be sequentially performed by a roll-to-roll method. If the mold is made of a hard material that is difficult to bend, the transparent substrate is preferably flexible because it is less likely to cause bubbles. Conversely, when a hard material is used as the transparent substrate, it is preferable to use a soft mold.

(3) Acrylic resin composition curing step A step of contacting the transparent substrate with the acrylic resin composition (hereinafter referred to as a contacting step) and a step of irradiating the acrylic resin composition with an active energy ray (hereinafter referred to as (referred to as an irradiation step) may be performed at the same time, or the contact step may be performed prior to the irradiation step.
Irradiation of ultraviolet rays or electron beams may be performed once or in multiple times, and in the case of multiple times, additional irradiation may be performed after curing to some extent and releasing from the mold.

(4) Mold release step As described above, the production method of the present disclosure uses a specific acrylic resin composition, so pattern removal can be suppressed when the mold is separated from the transparent substrate. In particular, in the obtained diffractive optical element, when the aspect ratio of the high-refractive-index convex portions is 2 or more, the pattern tends to be removed during mold release in the past, but according to the manufacturing method of the present disclosure, such a pattern You can keep baldness to a minimum.

(5) Other Steps When using the obtained diffractive optical element to further manufacture an illumination device, for example, the following steps may be carried out. However, the manufacturing method of the lighting device is not limited to the method described below.
Hereinafter, description will be made with reference to the reference numerals shown in FIG. 13 . First, the frame body 11 including the conductive portion 11a and the internal space 11c is prepared. The frame 11 may be a combination of two or more members (for example, a combination of a flat substrate and a hollow cylinder). Next, the light source 12 is placed in the internal space 11c of the frame 11, and the conducting wire 13 or the like is used to electrically connect the light source 12 and the conducting portion 11a. Subsequently, the diffractive optical element 10 is placed on the frame 11 . A temporary assembly is obtained by mounting the structure thus obtained on the mounting board 14 . At this time, alignment is performed so that the positions of the solder balls placed on the mounting board 14 overlap the positions of the conducting portions 11 a of the frame 11 .
This temporary assembly is placed in a reflow oven and heated at a temperature of 260 to 280° C. for 0.5 to 1.5 minutes to solder the mounting board 14 and the frame 11 together, thereby obtaining the lighting device 20. be done.

3. Acrylic resin composition The acrylic resin composition of the present disclosure includes, on at least one side of a transparent substrate, one or more high refractive index protrusions protruding from the surface of the transparent substrate, and one or more low refractive index protrusions. An acrylic resin composition for forming a high refractive index convex portion of a diffractive optical element for shaping light from a light source, wherein the acrylic resin composition is integrated with The storage elastic modulus (E′) at 60° C. and 95% relative humidity of the cured product sample obtained by irradiating and curing with ultraviolet rays so that the light amount is 1,000 mJ/cm ² is 0.90×10 ⁹ Pa or more. It is characterized by being 2.6×10 ⁹ Pa or less.

The acrylic resin composition preferably contains an active energy ray-curable component and provides the physical properties described above after curing. Further, if the light of the designed target wavelength can be transmitted, there is no practical problem even if the material is visually colored after curing.
The details of the acrylic resin composition of the present disclosure are as described in “(1) Cured product of acrylic resin composition” in “1. Diffractive optical element” above.
Also, the method for forming the high refractive index convex portions using the acrylic resin composition of the present disclosure is as described in the above-mentioned “2. Method for manufacturing a diffractive optical element”.

When the acrylic resin composition for forming high refractive index convex portions is filled into a mold, if the fluidity is too low, it will be difficult for it to enter fine grooves. Thickness may not be guaranteed. In the case of roll forming, too high fluidity causes ink dripping. In the present disclosure, an acrylic resin having a viscosity at 25° C. of the acrylic resin composition of about several tens [mPas] to several thousand [mPas] is preferred. Since the viscosity also changes with temperature, it is preferable to appropriately adjust the temperature when forming the high refractive index protrusions using the acrylic resin composition of the present disclosure.

4. Illuminating Device (1) Configuration of Illuminating Device An illuminating device according to the present disclosure includes a frame body having a conductive portion to which power can be supplied from the outside and an opening serving as a light output surface, a light source, and the above-described diffractive optical element. The light source is fixed in the internal space of the body and connected to the conductive portion, and the diffraction optical element is arranged in the opening.
According to the illumination device of the present disclosure, it is possible to irradiate light shaped into a desired shape.

A lighting device of the present disclosure will be described with reference to the drawings. FIG. 13 is a cross-sectional view schematically showing one embodiment of the light irradiation device according to the present disclosure. A lighting device 20 shown in the example of FIG. 13 includes a frame 11, a light source 12, and the diffractive optical element 10 described above. The frame 11 has a conducting portion 11a capable of supplying power from the outside and an opening portion 11b serving as a light exit surface. As shown in FIG. 13, the frame 11 further has an internal space 11c, and the light source 12 is fixed in the internal space 11c. Furthermore, the light source 12 is connected to the conducting portion 11a. The light source 12 may be directly connected to the conductive portion 11a, or may be connected to the conductive portion 11a via a conductive wire 13 as shown in FIG. A diffractive optical element 10 is arranged in the aperture 11b.
The frame 11 may be a combination of two or more members. For example, the frame 11 may be a combination of a plane substrate (base portion) for light source control and a hollow cylinder placed thereon.
By placing the frame 11 on a mounting board 14 (mother board) and connecting the light source 12 to the electrical circuit of the mounting board 14, other equipment on the mounting board 14 and the light source 12 can be interlocked.

In the illumination device of the present disclosure, the light source is not particularly limited, and known light sources can be used. Since the diffractive optical element according to the present disclosure is designed for the purpose of diffracting a specific wavelength, it is preferable to use a laser light source or an LED (light emitting diode) light source with high intensity of a specific wavelength as the light source. In the present disclosure, any light source, such as a directional laser light source or a diffusive LED (light emitting diode) light source, can be suitably used. In the present disclosure, it is preferable that the light source be appropriately selected from those capable of reproducing the light source used in the simulation when designing the diffractive optical element according to the present disclosure. Above all, when using a diffractive optical element that diffracts infrared rays with a wavelength of 780 nm or longer, it is preferable to select a light source capable of emitting infrared rays with a wavelength of 780 nm or longer.

The illumination device of the present disclosure may include at least one diffraction grating according to the present disclosure, and may further include other optical elements as necessary. Other optical elements include, for example, polarizing plates, lenses, prisms, and pass filters that transmit specific wavelengths, especially target wavelengths of diffractive optical elements. When a plurality of optical elements are used in combination, it is preferable to bond the optical elements together from the viewpoint of suppressing interfacial reflection.

(2) Use of lighting device The lighting device according to the present disclosure can irradiate light shaped into a desired shape, and can use infrared rays, so it can be suitably used as a lighting device for sensors. can be done. For example, infrared lighting at night, lighting for crime prevention sensors, lighting for human detection sensors, lighting for anti-collision sensors such as unmanned aircraft and automobiles, lighting for personal authentication devices, and lighting for inspection devices because of the ability to effectively shape light. , etc., and simplification, miniaturization, and power saving of the light source are possible.

Hereinafter, the present disclosure will be specifically described with reference to Examples. These descriptions are not intended to limit the present disclosure.

1. Production of Optical Diffraction Grating [Examples 1 to 9, Comparative Examples 1 to 4]
(Diffraction grating design)
Using a simulation tool, shape design was performed under the following conditions.
Target light source: Laser light with a wavelength of 980 nm Material refractive index: 1.456
Diffusion shape: Rectangular with long side ±50° × short side ±3.3° Area size: 5 mm square Diffraction grating level: 2-level (binary)
The optimum depth of the obtained diffraction grating shape was 1087 nm, the pitch of the finest shape was 250 nm, and the maximum aspect ratio was 4.35.

(mold making)
Using a 6-inch square synthetic quartz plate, a quartz DOE having a designed shape was produced by an electron beam lithography process using an electron beam lithography system and a dry etching system.
By SEM observation, it was confirmed that the finished product had a predetermined size. When a laser of 980 nm was incident and the diffracted light was projected onto a screen and observed with an infrared camera, it was confirmed that it had spread to a predetermined rectangular shape. .

(Preparation of acrylic resin composition)
The (meth)acrylate compounds shown in Table 1 below (tetrafunctional or higher (meth)acrylate, difunctional (meth)acrylate) and a photopolymerization initiator are blended in the amounts shown in Table 1, and acrylic resin compositions 1 to 13 are prepared. was prepared. In addition, the numerical value regarding these compounds in Table 1 shows a mass part, and the total amount of a (meth)acrylate compound becomes 100 mass parts.

(Resin molding method)
Resin molding of the diffraction grating portion was performed as follows.
First, using the quartz DOE as a mold, any one of the acrylic resin compositions 1 to 11 and 13 was dropped onto the diffractive surface. Next, a PET film (Toyobo Cosmoshine A4300, 100 μm thick) was laminated as a transparent substrate with a roller, and the acrylic resin composition was spread uniformly. Further, in this state, ultraviolet light is irradiated from the transparent substrate side so that the integrated light amount becomes 1,000 mJ/cm ² , and after curing the acrylic resin composition, the transparent substrate and the mold transfer layer are put into a mold. The diffractive optical element was obtained (Examples 1 to 9, Comparative Examples 1, 2 and 4). Since the acrylic resin composition 12 had a high viscosity and the composition 12 could not be filled into the cavity of the mold, the cured product could not be shaped and the diffractive optical element could not be obtained (Comparative Example 3).
The diffraction grating portion of the obtained diffractive optical element has the following periodic structure 1. This periodic structure 1 has about 20 high-refractive-index protrusions. Each high-refractive-index convex portion has a linear shape in plan view, a rectangular cross-sectional shape, and a constant height (H). However, the width (W) of each high refractive index convex portion is formed to be different from each other within the following range.
[Periodic structure 1]
Height (H) of high refractive index convexity: 500 nm
Width (W) of high refractive index convex portion: constant width in the range of 50 nm to 500 nm

2. Manufacture of Lighting Device and Evaluation of Reflow Resistance Using the diffractive optical elements of Example 6 and Comparative Example 2, a lighting device was manufactured.
Hereinafter, description will be made with reference to the reference numerals shown in FIG. 13 . First, the light source 12 was placed in the internal space 11c of the frame 11, and the conducting wire 13 was used to electrically connect the light source 12 and the conducting portion 11a. Next, the diffractive optical element of Example 6 or Comparative Example 2 was placed on the frame 11 . A temporary assembly was obtained by mounting the structure thus obtained on the mounting board 14 . At this time, alignment was performed so that the positions of the solder balls placed on the mounting board 14 overlapped with the positions of the conducting portions 11 a of the frame 11 .
This temporary assembly was placed in a reflow furnace and heated at 260° C. for 1.5 minutes to solder the mounting board 14 and frame 11 to manufacture the lighting device of Example 6 or Comparative Example 2. .

Regarding the diffractive optical elements included in the illumination devices of Example 6 and Comparative Example 2, the mass change rate and transmittance variation before and after reflow were examined by the following methods.
(Method for calculating mass change rate of diffractive optical element)
The mass of the diffractive optical element was measured before and after the reflow, and the mass change rate a was calculated from Formula I below.
Formula I a = {(M ₀ −M ₁ )/M ₀ }×100
(In Formula I above, a is the mass change rate (%), _M0 is the mass of the diffractive optical element before reflow (mg), and _M1 is the mass of the diffractive optical element after reflow (mg).)
The allowable range of mass change rate is 2.0% or less.
(Method for Calculating Transmittance Variation of Diffractive Optical Element)
The transmittance (%) of the diffractive optical element before and after reflow was measured. The transmittance was measured using an ultraviolet-visible-near-infrared (UV-Vis-NIR) spectrophotometer (UV-3150, manufactured by Shimadzu Corporation) or the like. Using this apparatus, the transmittance of the transparent substrate and the diffraction grating portion of the diffractive optical element with a wavelength of 850 nm was measured.
The absolute value of the difference between the transmittance of the diffractive optical element before reflow and the transmittance of the diffractive optical element after reflow was defined as the transmittance variation (%) of the diffractive optical element.
The permissible range of transmittance fluctuation is 1.0% or less.

Regarding the diffractive optical element included in the illumination device of Comparative Example 2, the mass change rate before and after the reflow was 3.8%, and the transmittance change before and after the reflow was 0.0% for reflow at 260°C for 1.5 minutes. is. Therefore, this result exceeds the allowable range of the mass change rate. The reason for this is that the compound used in the diffractive optical element of Comparative Example 2 is a bifunctional acrylic resin. As a result of sublimation, it is conceivable that the fine structure of the diffraction grating portion changes.
On the other hand, for the diffractive optical element included in the illumination device of Example 6, the mass change rate before and after reflow was 1.5% for reflow at 260° C. for 1.5 minutes, and the transmittance change before and after reflow was 0.1%. Both of these results are within acceptable limits. The reason for this is that the acrylic resin composition used in the diffractive optical element of Example 6 contains a large amount of highly heat-resistant tetrafunctional or higher urethane acrylate, so that it is instantaneously exposed to a high temperature environment of 260°C. Even in the case of , mass fluctuation is unlikely to occur, and as a result, it is conceivable that changes in the fine structure of the diffraction grating portion can be minimized.

3. Measurement of viscoelasticity of cured product of acrylic resin composition Acrylic resin compositions 1 to 13 were irradiated with ultraviolet rays so that the integrated light amount was 1,000 mJ / cm ² and cured, and the substrate and uneven shape were measured. A test monolayer having a thickness of 0.1 mm, a width of 5 mm, and a length of 15 mm was obtained.
Then, according to JIS K7244, the dynamic viscoelasticity was measured under the conditions of a measurement temperature of 60 ° C. and a relative humidity of 95%, and the measurement conditions shown in Table A below. Storage at 60 ° C. and a relative humidity of 95% An elastic modulus E′ and a loss elastic modulus E″ were determined. From the results of E′ and E″, tan δ was calculated. Rheogel E4000 manufactured by UBM was used as a measuring device. Table 1 shows the values of storage modulus E' (60°C, 95%) and tan δ (60°C, 95%).
Furthermore, using a similar test single film, dynamic viscoelasticity was measured according to JIS K7244 under the conditions of a measurement temperature of 30 ° C. and a relative humidity of 30%, and the measurement conditions shown in Table A below. The storage elastic modulus E' was determined at 30°C and 30% relative humidity. Table 1 shows each value of the storage modulus E' (30°C, 30%).

４．アクリル系樹脂組成物の硬化物の復元率測定
上記「３．アクリル系樹脂組成物の硬化物の粘弾性測定」と同様に、アクリル系樹脂組成物１～１３について、それぞれ試験用単膜を作製した。
ＪＩＳ Ｚ２２４４（２００３）に準拠し、下記測定条件下にてビッカース硬さ試験を実施した。具体的には、各試験用単膜表面に、下記測定条件で圧子を押し込んで、試験用単膜表面の復元率（％）を測定した。測定装置は、フィッシャーインストルメンツ社製ＰＩＣＯＤＥＮＴＥＲ ＨＭ－５００を用いた。結果を表１に示す。
＜測定条件＞
・最大荷重 ０．２ｍＮ
・荷重速度 ０．２ｍＮ／１０秒
・保持時間 ５秒間
・荷重除荷速度 ０．２ｍＮ／１０秒
・圧子 ビッカース圧子
・測定温度 ２５℃

4. Measurement of recovery rate of cured product of acrylic resin composition In the same manner as in “3. did.
A Vickers hardness test was carried out under the following measurement conditions in accordance with JIS Z2244 (2003). Specifically, an indenter was pressed into each test single film surface under the following measurement conditions, and the recovery rate (%) of the test single film surface was measured. As a measurement device, PICODETER HM-500 manufactured by Fisher Instruments was used. Table 1 shows the results.
<Measurement conditions>
・Maximum load 0.2mN
・Loading speed: 0.2 mN/10 seconds ・Holding time: 5 seconds ・Load unloading speed: 0.2 mN/10 seconds ・Indenter: Vickers indenter ・Measurement temperature: 25°C

5. Measurement of the glass transition temperature (Tg) of the acrylic resin composition The acrylic resin compositions 1 to 13 were irradiated with ultraviolet rays so that the integrated light amount was 1,000 mJ / cm ² and cured, and the base material and the unevenness A test monolayer having no shape and having a thickness of 0.1 mm, a width of 5 mm and a length of 20 mm was obtained.
Using a dynamic viscoelasticity tester (manufactured by Seiko Instruments Inc., DMS6100), a periodic external force is applied in the length direction of each test piece at a frequency of 10 Hz, and measured in the range of -20 ° C. to 200 ° C., The storage elastic modulus E′ and loss elastic modulus E″ were determined for each. From the results of E′ and E″, tan δ=E″/E′ was calculated. It was taken as the glass transition temperature Tg (°C) of the resin composition.

6. Evaluation of sticking and evaluation of pattern peeling The diffractive optical elements of Examples 1 to 9 and Comparative Examples 1, 2 and 4 were observed by SEM. As described above, no diffractive optical element was obtained in Comparative Example 3 (using acrylic resin composition 12), so the following evaluation was not performed.
Sticking evaluation was performed as follows. First, regarding the periodic structure 1 (height H=500 nm), among the high refractive index convex portions where sticking did not occur, the narrowest high refractive index convex portion was specified. Then, the width of the high refractive index convex portion is the minimum width W ¹ _min (nm) in the sticking evaluation, and the value obtained by dividing the height H (500 nm) by the minimum width W ¹ _min is the value in the sticking evaluation. Maximum aspect ratio. As the minimum width W ¹ _min is smaller and the maximum aspect ratio is larger, the cured product forming the high-refractive-index protrusions has appropriate hardness, and sticking is less likely to occur.
Pattern peeling evaluation was performed as follows. First, regarding the periodic structure 1, among the high refractive index convex portions in which pattern stripping did not occur, the narrowest high refractive index convex portion was specified. Then, the width of the high refractive index convex portion was taken as the minimum width W ² _min (nm) in evaluation of pattern peeling. After that, the maximum aspect ratio was calculated in the same manner as in the above sticking evaluation. As the minimum width W ² _min is smaller and the maximum aspect ratio is larger, the cured product forming the high-refractive-index protrusions has appropriate flexibility, so it can be said that pattern removal is less likely to occur.

7. Discussion Table 1 below summarizes the compositions, physical properties and evaluation results of the acrylic resin compositions used in Examples 1 to 9 and Comparative Examples 1 to 4.
In Table 1 below, ">500" for the maximum width of sticking evaluation means that sticking occurred for all high refractive index convex portions having a width (W) within the range of 50 nm to 500 nm. do. Therefore, the aspect ratio is not calculated in this case.
As for Comparative Example 3, since no diffractive optical element was obtained as described above, there is no description of the sticking evaluation results and the pattern peeling evaluation results.

In Table 1, compound (1) is a hexafunctional urethane acrylate (Mw: 1,400) represented by PETA-IPDI-PETA. In addition, "PETA" indicates pentaerythritol triacrylate, "IPDI" indicates isophorone diisocyanate, and "-" indicates a urethane bond.

In Table 1, compound (2) is a 9-functional urethane acrylate (Mw: 11,000) represented by the following formula (i).

（上記式（ｉ）中、「ＰＥＴＡ」はペンタエリスリトールトリアクリレートを、「ＨＤＩ」はヘキサメチレンジイソシアネートを、「―」はウレタン結合を、それぞれ示す。）

(In formula (i) above, "PETA" represents pentaerythritol triacrylate, "HDI" represents hexamethylene diisocyanate, and "-" represents a urethane bond.)

In Table 1, compound (3) is a decafunctional urethane acrylate (Mw: 2,000) represented by DPPA-IPDI-DPPA. "DPPA" indicates dipentaerythritol pentaacrylate, "IPDI" indicates isophorone diisocyanate, and "-" indicates a urethane bond.

In Table 1, compound (4) is a 15-functional urethane acrylate (Mw: 2,300) represented by the following formula (ii).

（上記式（ｉｉ）中、「ＤＰＰＡ」はジペンタエリスリトールペンタアクリレートを、「ＨＤＩ」はヘキサメチレンジイソシアネートを、「―」はウレタン結合を、それぞれ示す。）

(In formula (ii) above, "DPPA" represents dipentaerythritol pentaacrylate, "HDI" represents hexamethylene diisocyanate, and "-" represents a urethane bond.)

In Table 1, compound (5) is a bifunctional urethane acrylate (Mw: 2,000) represented by caprolactone-modified HEA-hydrogenated MDI-caprolactone-modified HEA. "HEA" indicates hydroxyethyl acrylate, "MDI" indicates diphenylmethane diisocyanate, and "-" indicates a urethane bond.

In Table 1, compound (6) is 1,9-nonanediol diacrylate (CAS No. 107481-28-7, Mw: 268).

In Table 1, compound (7) is polyethylene glycol #600 diacrylate (Mw: 700).

First, Comparative Example 1 will be examined. In Comparative Example 1, the acrylic resin composition 10 having a storage elastic modulus (E′) of 0.42×10 ⁹ Pa at 60° C. and 95% relative humidity is used.
In Comparative Example 1, the minimum width W ² _min of the high-refractive-index protrusions free from pattern loss was 90 nm, and the maximum aspect ratio was 5.6. Therefore, there is no problem with the flexibility of the high refractive index convex portion.
However, in Comparative Example 1, sticking occurs even when the width W of the high refractive index convex portion is 500 nm. This is probably because the storage elastic modulus (E′) under wet heat conditions is smaller than 0.90×10 ⁹ Pa, and the high refractive index protrusions are too soft.

Next, Comparative Example 2 will be considered. In Comparative Example 2, the acrylic resin composition 11 having a storage elastic modulus (E′) of 0.06×10 ⁹ Pa at 60° C. and 95% relative humidity is used.
In Comparative Example 2, the minimum width W ² _min of the high-refractive-index protrusions free from pattern loss was 85 nm, and the maximum aspect ratio was 5.9. Therefore, there is no problem with the flexibility of the high refractive index convex portion.
However, in Comparative Example 2, the minimum width W ¹ _min of the high-refractive-index protrusions where sticking does not occur is as large as 250 nm, and the maximum aspect ratio is as small as 2.0. Therefore, it can be said that the diffractive optical element of Comparative Example 2 tends to cause sticking. This is formed because the storage modulus (E′) under wet heat conditions is less than 0.90×10 ⁹ Pa and the acrylic resin composition 11 does not contain a tetrafunctional or higher (meth)acrylate. This is probably because the high refractive index convex portion is too soft.

Next, Comparative Example 3 will be examined. In Comparative Example 3, an acrylic resin composition 12 having a storage elastic modulus (E′) of 3.10×10 ⁹ Pa at 60° C. and 95% relative humidity is used.
As described above, the viscosity of the acrylic resin composition 12 was high and the composition 12 could not be filled into the cavity of the mold. This is probably because the acrylic resin composition 12 lacks flexibility as a result of the storage elastic modulus (E′) under wet heat conditions being too large than 2.6×10 ⁹ Pa.

Next, Comparative Example 4 will be examined. In Comparative Example 4, acrylic resin composition 13 having a storage elastic modulus (E′) of 0.18×10 ⁹ Pa at 60° C. and 95% relative humidity is used.
In Comparative Example 4, the minimum width W ² _min of the high-refractive-index protrusions free from pattern loss was 90 nm, and the maximum aspect ratio was 5.6. Therefore, there is no problem with the flexibility of the high refractive index convex portion.
However, in Comparative Example 4, sticking occurs even when the width W of the high refractive index convex portion is 500 nm. This is probably because the storage elastic modulus (E′) under wet heat conditions is smaller than 0.90×10 ⁹ Pa, and the high refractive index protrusions are too soft.

As shown in the results of Examples 1 to 9, the storage elastic modulus (E′) at 60° C. and 95% relative humidity after curing is 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less. It was clarified that the use of an acrylic resin composition can prevent sticking under moist heat conditions and reduce pattern peeling.

From Table 1, among Examples 1 to 9, the storage elastic modulus (E′) at 60° C. and 95% relative humidity after curing is 1.0×10 ⁹ Pa or more and 2.0×10 ⁹ Pa or less. Furthermore, in Examples 1 to 2 and 4 to 6 using an acrylic resin composition having a recovery rate of 60% or more, the maximum number of high refractive index convex portions in which sticking does not occur compared to other Examples It can be seen that the minor width W ¹ _min is as small as 120 nm or less and the maximum aspect ratio is as large as 4.2 or more. It can be said that this is because sticking is less likely to occur due to having an appropriate storage elastic modulus (E′) under wet heat conditions and a high recovery rate.

1 transparent substrate 2 diffraction grating portion 2a high refractive index convex portion 2b low refractive index portions 2A, 2B, 2C, 2D partial periodic structure (region)
3 Base 5 Coating layer 7 Low refractive index resin 9 Antireflection layer 10 Diffractive optical element 11 Frame 11a Conducting part 11b Opening 11c Internal space 12 Light source 13 Lead wire 14 Mounting substrate 20 Illumination device 21 Irradiation light 22 Screen 23 Irradiation of irradiation light Area 24 Irradiation area 25 0th order light 26a, 26b, 26c, 26d 1st order light (diffracted light)
27 0-order light irradiation position 31 mold 31a mold cavity 32 acrylic resin composition 33 transparent substrate 34 pressure roller 35 active energy ray irradiation 36 cured film 41 transparent substrate or base 50 diffractive optical element with sticking 51 Moisture content 101 Base material 102 Fractured cured product 103 Mold

Claims (22)

A diffractive optical element that shapes light from a light source,
At least one side of the transparent base material is provided with a diffraction grating part having one or more high refractive index convex parts protruding from the surface of the transparent base material and one or more low refractive index parts arranged thereon,
The high refractive index convex portion is
It is formed of a cured product of an acrylic resin composition that is an active energy ray-curable resin composition containing a urethane bond and containing a tetrafunctional (meth)acrylate and a difunctional (meth)acrylate,
A diffractive optical element, wherein the cured product has a storage elastic modulus (E′) of 0.90×10 ⁹ Pa or more and 2.6×10 ⁹ Pa or less at 60° C. and 95% relative humidity. The diffractive optics according to claim 1, wherein a cured product of the acrylic resin composition has a storage elastic modulus (E') at 30°C and 30% relative humidity of 1 × 10 ⁸ Pa or more and 5 × 10 ⁹ Pa or less. element. The ratio (tan δ (=E″/E′)) of the loss elastic modulus (E″) to the storage elastic modulus (E′) at 60° C. and 95% relative humidity of the cured product of the acrylic resin composition is 0.5%. 3. The diffractive optical element according to claim 1, which is 12 or less. The active energy ray-curable resin composition contains 40% by mass or more and 80% by mass or less of the tetrafunctional or higher (meth)acrylate and 10% by mass of the bifunctional (meth)acrylate based on the total curable components. % or more and 60% by mass or less, the diffractive optical element according to claim 1 . 5. The diffractive optical element according to claim 1 , wherein said tetra- or more functional (meth)acrylate includes tetra- or more functional urethane (meth)acrylate. The tetrafunctional or higher urethane (meth)acrylate is a compound in which an isocyanate group of a polyvalent isocyanate compound and a hydroxyl group of a compound having one hydroxyl group and two or more (meth)acrylic groups in the molecule are urethane-bonded. 6. The diffractive optical element according to claim 5 , wherein 5. The diffractive optical element according to claim 1 , wherein the bifunctional (meth)acrylate has a molecular weight (Mw) of 100 or more and 5,000 or less. The recovery rate of the cured product of the acrylic resin composition is measured by a Vickers hardness test performed in accordance with JIS Z2244 (2003) under the measurement conditions of a maximum load of 0.2 mN and a holding time of 10 seconds. , 60% or more . The diffractive optical element according to any one of claims 1 to 8 , wherein the high refractive index convex portion has a portion with a height of 400 nm or more. The top of the high refractive index convex portion is defined as the upper end, and the position of the bottom of the valley between the high refractive index convex portion and another adjacent high refractive index convex portion, or the position closest to the top of the high refractive index convex portion When the lower end is defined as the one closer to the top of the high refractive index convex portion among the positions of the flat portions close to each other, the height from the lower end to the upper end of the high refractive index convex portion corresponds to half the height difference between the upper end and the lower end When defining the ratio of the height of the high refractive index convex portion to the width of the high refractive index convex portion at the position of as the aspect ratio of the high refractive index convex portion,
The diffractive optical element according to any one of claims 1 to 9 , wherein the high refractive index convex portion has an aspect ratio of 2 or more. At least one side of the transparent base material is provided with a diffraction grating section having one or more high refractive index convex parts protruding from the surface of the transparent base material and one or more low refractive index parts arranged thereon. A method of manufacturing a diffractive optical element for shaping the
preparing a mold having a cavity shape for forming the high refractive index convex portion and the low refractive index portion;
An acrylic resin composition that is an active energy ray-curable resin composition containing a urethane bond in the mold cavity and containing a tetrafunctional or higher (meth)acrylate and a difunctional (meth)acrylate, , The storage elastic modulus (E') at 60 ° C. and 95% relative humidity of a cured product sample obtained by irradiating and curing the acrylic resin composition with ultraviolet rays so that the integrated light amount becomes 1,000 mJ / cm ² is 0.90 × 10 ⁹ Pa or more and 2.6 × 10 ⁹ Pa or less, filling an acrylic resin composition,
a step of curing the acrylic resin composition by bringing the transparent base material and the acrylic resin composition into contact with each other on the cavity opening side of the mold, and irradiating the acrylic resin composition with an active energy ray; and forming a diffraction grating portion having high refractive index convex portions formed of a cured product of an acrylic resin composition on a transparent substrate by separating the mold from the substrate;
A method for manufacturing a diffractive optical element. The production method according to claim 11 , wherein the cured product of the acrylic resin composition has a storage elastic modulus (E') at 30°C and 30% relative humidity of 1 × 10 ⁸ Pa or more and 5 × 10 ⁹ Pa or less. . The ratio (tan δ (=E″/E′)) of the loss elastic modulus (E″) to the storage elastic modulus (E′) at 60° C. and 95% relative humidity of the cured product of the acrylic resin composition is 0.5%. 13. The production method according to claim 11 or 12 , which is 12 or less. The active energy ray-curable resin composition contains 40% by mass or more and 80% by mass or less of the tetrafunctional or higher (meth)acrylate and 10% by mass of the bifunctional (meth)acrylate based on the total curable components. % or more and 60% by mass or less, the production method according to claim 11 . The production method according to claim 11 or 14 , wherein the tetrafunctional or higher (meth)acrylate includes a tetrafunctional or higher urethane (meth)acrylate. The tetrafunctional or higher urethane (meth)acrylate is a compound in which an isocyanate group of a polyisocyanate compound and a hydroxyl group of a compound having one hydroxyl group and two or more (meth)acrylic groups in the molecule are urethane-bonded. 16. The manufacturing method according to claim 15 , wherein The production method according to claim 11 or 14 , wherein the bifunctional (meth)acrylate has a molecular weight (Mw) of 100 or more and 5,000 or less. The recovery rate of the cured product of the acrylic resin composition is measured by a Vickers hardness test performed in accordance with JIS Z2244 (2003) under the measurement conditions of a maximum load of 0.2 mN and a holding time of 10 seconds. , 60 % or more . 19. The manufacturing method according to any one of claims 11 to 18 , wherein said high refractive index convex portion has a portion with a height of 400 nm or more. The top of the high refractive index convex portion is defined as the upper end, and the position of the bottom of the valley between the high refractive index convex portion and another adjacent high refractive index convex portion, or the position closest to the top of the high refractive index convex portion When the lower end is defined as the one closer to the top of the high refractive index convex portion among the positions of the flat portions close to each other, the height from the lower end to the upper end of the high refractive index convex portion corresponds to half the height difference between the upper end and the lower end When defining the ratio of the height of the high refractive index convex portion to the width of the high refractive index convex portion at the position of as the aspect ratio of the high refractive index convex portion,
20. The manufacturing method according to any one of claims 11 to 19 , wherein the high refractive index convex portion has an aspect ratio of 2 or more. A frame having a conductive portion capable of supplying power from the outside and an opening serving as a light output surface, a light source, and the diffractive optical element according to any one of claims 1 to 10 . An illumination device, wherein the light source is fixed and connected to the conductive portion, and the diffractive optical element is arranged in the opening. 22. The illumination device according to claim 21 , wherein said light source is a light source that emits infrared rays having a wavelength of 780 nm or longer.

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