JP7077524B2 - Diffractive optical element and light irradiation device - Google Patents

Description

The present disclosure relates to a diffractive optical element and a light irradiation 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 automated driving of automobiles, and the spread of the so-called "Internet of Things". There is. There are various types of sensors, and the information to be detected is also various. One of the means is to irradiate an object with light from a light source and obtain information from the reflected light. .. For example, pattern recognition sensors and infrared radars are examples.

The light source of these sensors has a wavelength distribution, brightness, and spread according to the application. Visible light to infrared rays are often used as the wavelength of light, and infrared rays are widely used because they are not easily affected by external light, are invisible, and can observe the inside of an object. There is. Further, as a type of light source, an LED light source, a laser light source, or the like is often used. For example, a laser light source with a small spread of light is preferably used to detect a distant place, and an LED light source is preferably used to detect a relatively close place or to irradiate a region having a certain spread. Will be.

By the way, the size and shape of the target irradiation area do not always match the spread (profile) of the light from the light source, and in that case, the light is shaped by a diffuser plate, a lens, a shielding plate, or the like. There is a need. Recently, a diffuser called Light Shipping Diffuser (LSD), which can shape the shape of light to some extent, has been developed.
Further, as another means for shaping light, a diffractive optical element (DOE) can be mentioned. This is an application of the diffraction phenomenon when light passes through a place where materials with different refractive indexes are arranged with periodicity. DOE is basically designed for light of a single wavelength, but theoretically it is possible to shape the light into almost any shape. Further, in the above-mentioned LSD, the light intensity in the irradiation region has a Gaussian distribution, whereas in DOE, it is possible to control the uniformity of the light distribution in the irradiation region. Such characteristics of DOE are advantageous in terms of high efficiency by suppressing irradiation to unnecessary regions and miniaturization of the device by reducing the number of light sources (for example, Patent Document 1 and the like).
Further, DOE can be applied to both a parallel light source such as a laser and a diffused light source such as an LED, and can be applied to a wide range of wavelengths from ultraviolet light to visible light and infrared light.

DOE requires microfabrication on the order of nm, and in particular, in order to diffract light having a long wavelength, it is necessary to form a fine shape having a high aspect ratio. Therefore, in the production of DOE, an electron beam lithography technique using an electron beam has been conventionally used. For example, after forming a hard mask or resist on a quartz plate that is transparent in the ultraviolet to near-infrared region, a predetermined shape is drawn on the resist using an electron beam, and resist development, hard mask dry etching, and quartz dry are performed. The 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.

Japanese Unexamined Patent Publication No. 2015-170320

As described above, infrared rays are widely used as the wavelength of light used for sensing because they are not easily affected by external light, are invisible, and can observe a little inside of an object. Sunlight is a typical example of external light that interferes with sensing. Visible light is very strong, but infrared light is relatively weak. Especially, sunlight near the surface of the earth has a wavelength of around 940 nm (wavelength 900 nm or more and 1000 nm or less) and a wavelength of 1100 nm or more due to the influence of water vapor in the atmosphere. The strength is reduced below 1200 nm. Therefore, in applications such as outdoor sensors, the use of infrared rays is advantageous in terms of sensitivity, and the use of light in the above wavelength region is particularly advantageous. In order to diffract the light in the infrared wavelength region, it is necessary to deepen the convex portion in the diffraction layer of the DOE (= increase the aspect ratio).
In addition, the conventional electron beam lithography technology in DOE manufacturing requires complicated and multi-step processes as described above, so the throughput (productivity per unit time) is small and mass production is not possible due to this. Therefore, there is a problem that the manufacturing cost becomes high.
As a method for solving such a problem, a method of replicating by imprinting a resin composition using a DOE produced by electron beam lithography as a mold can be considered. Examples of the shaping means include injection molding, thermosetting, two-component curable resin, duplication with a soluble resin, imprint with an ionizing radiation curable resin such as an ultraviolet curable resin and an electron beam curable resin, and the like. .. The present inventors focused on the shaping with an ionizing radiation curable resin because it can be cured in a short time and the throughput can be greatly improved. However, in the case of shaping a fine shape having a high aspect ratio on the order of nm, it is difficult to release the cured resin, and the resin forming the pattern of the diffraction grating may break or break. There was something. On the other hand, if flexibility is given to the resin in order to avoid this, there is a problem that the resin is deformed at the time of mold release, the deformed resins are stuck to each other (sticking), and the obtained DOE is easily damaged. there were.
If the resin forming the pattern of the diffraction grating is broken, broken (Fig. 19), sticking (Fig. 20), etc., uniform light irradiation in the irradiation area may not be possible, or light may not be shaped into a desired shape. there were.
In general, a cured product of artificial quartz or a resin composition tends to have a lower refractive index than a silicon (Si) material that has been widely used as a diffraction grating material for infrared rays. Therefore, when a diffractive optical element capable of obtaining diffracted light similar to that of a silicon material is manufactured by using a resin composition, it is necessary to form a convex portion having a large aspect ratio as compared with the silicon material.
Therefore, the above-mentioned fracture and sticking are particularly problematic in the manufacture of diffractive optical elements.

It is an object of the present disclosure to provide a diffractive optical element capable of obtaining a desired diffracted light and having excellent durability, and a light irradiation device capable of obtaining a desired irradiation region using the diffractive optical element. ..

One embodiment of the present disclosure is an optical element that shapes the light from a light source.
A diffraction layer having a periodic structure of a low refractive index portion and a high refractive index portion is provided.
Provided is a diffractive optical element including one having an aspect ratio of a high refractive index portion of 2 or more in the periodic structure.

One embodiment of the present disclosure provides a diffractive optical element in which the high refractive index portion is made of a cured product of an ionizing radiation curable resin composition.

In one embodiment of the present disclosure, the storage elastic modulus (E') of the cured product of the ionized radiation curable resin composition at 25 ° C. is 1 × 10 ⁸ Pa or more and 5 × 10 ⁹ Pa or less, and the ionization is performed. Diffraction in which the ratio (tan δ (= E "/ E')) of the loss modulus (E") to the storage modulus (E') of the cured product of the radiation curable resin composition at 25 ° C. is 0.3 or less. Provides an optical element.

One embodiment of the present disclosure provides a diffractive optical element including a convex portion forming the high refractive index portion having a height of 1000 nm or more in the cross-sectional shape of the diffractive layer.

One embodiment of the present disclosure provides a diffractive optical element having a multi-stage shape in which the convex portion forming the high refractive index portion has two or more flat portions in the cross-sectional shape of the diffractive layer.

One embodiment of the present disclosure provides a diffractive optical element having an aspect ratio of 3.5 or more in the convex portion of the multistage shape.

One embodiment of the present disclosure provides a diffractive optical element in which the low refractive index portion is air.

One embodiment of the present disclosure provides a diffractive optical element having the diffractive layer and the covering layer in this order on a transparent substrate.

One embodiment of the present disclosure provides a diffractive optical element having an antireflection layer on the outermost surface.

One embodiment of the present disclosure provides a diffractive optical element that diffracts infrared rays having a wavelength of 780 nm or more.

One embodiment of the present disclosure provides a light irradiator comprising a light source and one or more diffractive optical elements of the present disclosure.

One embodiment of the present disclosure provides a light irradiation device in which the light source is a light source capable of emitting infrared rays having a wavelength of 780 nm or more.

According to the present disclosure, a diffractive optical element capable of obtaining a desired diffracted light and having excellent durability, and a light irradiating device capable of obtaining a desired irradiation region using the diffracted optical element can be obtained.

It is a top view which shows one Embodiment of a diffractive optical element schematically. It is a perspective view schematically showing an example of the partial periodic structure in one Embodiment of a diffractive optical element. It is sectional drawing which shows typically an example of the EE'cut surface of FIG. It is sectional drawing which shows 1 Embodiment of a diffractive optical element schematically. It is sectional drawing which shows typically another embodiment of a diffractive optical element. It is sectional drawing which shows typically another embodiment of a diffractive optical element. It is sectional drawing which shows typically another embodiment of a diffractive optical element. It is sectional drawing which shows typically another embodiment of a diffractive optical element. It is sectional drawing which shows typically another embodiment of a diffractive optical element. It is a top view which shows an example of the periodic structure of the diffraction layer (4-level) which spreads incident light circularly. It is sectional drawing which shows one Embodiment of a light irradiation apparatus schematically. It is a drawing provided for the explanation of a diffractive optical element. It is a drawing provided for the explanation of a diffractive optical element. (A) is a front view of the screen 22 in the example of (a) of FIG. Further, (c) is a front view of the screen 22 in the example of (c) of FIG. It is a drawing provided for the explanation of an aspect ratio. It is sectional drawing which shows the modification of the periodic structure schematically. It is a process drawing which shows typically an example of the manufacturing method of a diffractive optical element. It is a screen projection drawing of the diffracted light transmitted through the diffractive optical element obtained in Example 5-2. It is sectional drawing which shows typically an example of the breakage of a resin at the time of manufacturing a conventional diffractive optical element. It is sectional drawing which shows typically an example of sticking of the conventional diffractive optical element.

Hereinafter, the diffractive optical element and the light irradiation device of the present disclosure will be described in detail in order.
It should be noted that the terms used in the present disclosure, such as "parallel", "orthogonal", and "identical", and the values of length and angle, which specify the shape and geometric conditions and their degrees, have strict meanings. It is interpreted including the range where the same function can be expected without being bound by. Further, the term "planar view" as used herein means that the object is visually recognized from a direction perpendicular to the upper surface of the diffractive optical element. Usually, it corresponds to visually recognizing from the direction perpendicular to the surface of the diffractive optical element having the diffraction layer (corresponding to the direction of the plan view as shown in FIG. 1).
In the present disclosure, the ionizing radiation includes electromagnetic waves having wavelengths in the visible and invisible regions, and further includes radiation, and the radiation includes, for example, microwaves and electron beams. Specifically, it refers to an electromagnetic wave having a wavelength of 5 μm or less and an electron beam.
In the present disclosure, (meth) acrylic represents each of acrylic or methacrylic, (meth) acrylate represents each of acrylate or methacrylate, and (meth) acryloyl represents each of acryloyl or methacryloyl.
In the present disclosure, "shaping light" means controlling the traveling direction of light so that the shape (irradiation area) of the light projected on the object or the target area becomes an arbitrary shape. .. For example, as shown in the example of FIG. 12, light (FIG. 12 (b)) whose irradiation region 23 becomes circular when directly projected onto a flat screen 22 is transmitted through the diffractive optical element 10 of the present disclosure. This means that the irradiation area has a desired shape such as a square (24 in FIG. 12A), a rectangle, or a circle (not shown).
In the present disclosure, the light transmitted from the light source through the diffractive optical element and emitted as it is without being diffracted is referred to as 0th-order light (25 in FIG. 12), and the diffracted light generated by the diffractive optical element is referred to as primary light. There is a case (26 in FIG. 12).
In the present disclosure, the cross-sectional shape of the diffractive layer is defined as the diffractive optical element resting 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 so as to be orthogonal to the X-axis and XY forms a horizontal plane, and the Z-axis is taken in the direction perpendicular to the XY horizontal plane. In the present disclosure, the valley bottom between the convex portions (the minimum point of Z) is used as the reference for the height 0, and the portion having the height 0 is used as the concave portion. Further, in the present disclosure, the portion having the height H (H> 0) is referred to as a convex portion. On the other hand, in the present disclosure, the depth may be taken up to the valley bottom between the convex portions based on the maximum height of the convex portion. However, in the present disclosure, the height and the depth are in a front-to-back relationship, and the convex portion. When focusing on, the height is defined, and when focusing on the concave portion, the depth is defined, which are substantially the same.
In the present disclosure, the fact that the cross-sectional shape of the diffraction layer is a repeating structure of a concave portion having a height of 0 and a convex portion having a height H as shown in the example of FIG. 3 is referred to as a binary (2-level) shape. Sometimes. Further, in the present disclosure, a diffraction layer having a convex portion having two or more flat portions (substantially horizontal portions) in the cross-sectional shape may be referred to as a multi-stage shape, and the convex portion and the concave portion of the multi-stage shape may be combined into n pieces. When it has a flat portion of, it may be called an n-value (n-level) shape.
Further, in the present disclosure, the term "transparent" means a substance that transmits light of at least a target wavelength. For example, even if it does not transmit visible light, if it transmits infrared rays, it shall be treated as transparent when used for infrared applications.

[Diffractive optical element]
The diffractive optical element according to the embodiment of the present disclosure is an optical element that shapes light from a light source.
A diffraction layer having a periodic structure of a low refractive index portion and a high refractive index portion is provided.
It is characterized in that the aspect ratio of the high refractive index portion in the periodic structure includes those having an aspect ratio of 2 or more.

The diffractive optical element of one embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a plan view schematically showing one embodiment of the diffractive optical element of the present disclosure, and FIG. 2 is a perspective view schematically showing an example of a partial periodic structure in the example of the diffractive optical element of FIG. Yes, FIG. 3 is a cross-sectional view schematically showing an example of the EE'cut surface of FIG. 2.
The diffractive optical element 10 of the present disclosure includes a diffraction layer 1 having a periodic structure of a low refractive index unit 3 and a high refractive index unit 2, and has an aspect ratio (height H) of the high refractive index unit 2 in the periodic structure. / Width W) is characterized by including two or more. The diffractive optical element of the present disclosure usually has a plurality of regions having different periodic structures (for example, regions A to D in FIG. 1). In the example of FIG. 1, the partial periodic structure A to D regions are binary (2-level) of unevenness (for example, the diffraction layer 1 of FIG. 3), but the shape of the regions and the shape of the regions are used to shape the light as desired. The depth needs to be appropriately designed (for example, in the 4-level diffractive element shown in FIG. 10, 8A, 8B, 8C, and 8D have different depths (see, for example, FIG. 16C)).
4 to 7 are cross-sectional views schematically showing an example of another embodiment of the diffractive optical element of the present disclosure. As shown in the example of FIG. 4, the diffractive optical element of the present disclosure may include the diffractive layer 1 on the transparent substrate 4, and as shown in the example of FIG. 5, on the diffractive layer 1. In addition, the coating layer 5 may be provided, and as shown in the example of FIG. 6, the coating layer 5 may be provided on the diffraction layer 1 via the adhesive layer (adhesive layer) 6. Further, the diffractive optical element of the present disclosure is not limited to the case where the low refractive index portion 3 is air, and may be a low refractive index resin 7 as shown in the example of FIG. 7. From the viewpoint of excellent mechanical strength, it is preferable that the low refractive index portion is made of a low refractive index resin. On the other hand, from the viewpoint of increasing the difference in refractive index, it is preferable that the low refractive index portion is air.

8 to 9 are cross-sectional views schematically showing an example of another embodiment of the diffractive optical element of the present disclosure. As shown in the examples of FIGS. 8 and 9, it is preferable that the diffractive optical element of the present disclosure is provided with the antireflection layer 9 on the outermost surface from the viewpoint of suppressing reflected light and increasing the efficiency of light utilization.
As shown in the example of FIG. 8, the antireflection layer 9 may be provided directly on the diffractive optical element 10 to form the outermost surface, and as shown in the example of FIG. 9, the diffractive optical element 10 may be formed. It may be provided between the antireflection layer 9 and the antireflection layer 9 via another layer or another member. In the example of FIG. 9, the diffractive optical element 10 is bonded to the glass plate 14 via the adhesive layer (adhesive layer) 15, and the antireflection layer is on the surface of the glass plate 14 opposite to the diffractive optical element 10. 9 is provided. The antireflection layer 9 is preferably provided on the outermost surface on the side where light is incident. Specific embodiments of the antireflection layer will be described later.

According to the embodiment of the present disclosure, since the aspect ratio of the convex portion, which is the high refractive index portion, is 2 or more, for example, even an infrared ray having a longer wavelength than the conventional one (for example, an infrared ray having a wavelength of 900 nm or more) has a desired shape. It can be a diffractive optical element capable of obtaining diffracted light formed in the above and with suppressed 0th order light.

In the present disclosure, when the convex portion has a binary shape, the aspect ratio is defined by (height H of the convex portion) / (width W of the convex portion). Further, in the present disclosure, when the convex portion has a multi-stage shape, the aspect ratio is defined by (height H of the convex portion) / (minimum processing width W of the convex portion).
In the present disclosure, the width of the convex portion is defined as the width at half the height (H / 2) of the height H of the convex portion (see FIG. 15 (A)). Further, in the present disclosure, the minimum processing width of the convex portion means the width of the portion corresponding to the range in which the height h is formed in the convex portion of the multi-stage shape, and specifically, as shown in FIG. 15 (B). The height (H-h) having the flat portion of the second step is defined as the lower end, the flat portion of the height H is defined as the upper end, and the width at half the height (h / 2) from the lower end is defined as the minimum processing width W. ..
By defining the aspect ratio in this way, the optical design of the diffraction grating and the correlation between the ease of removal from the mold and the aspect ratio are enhanced.
Specifically, the height H and the width W can be measured from an image obtained by taking a cross section of the diffraction layer with a scanning electron microscope (SEM).

<Shape of diffraction layer>
Generally, the shape of a diffraction grating is determined by the wavelength of light, the refractive index (difference) of the material through which light is transmitted, and the required diffraction angle. For example, when a material having a refractive index of 1.5 is used in the air and laser light is vertically incident on the surface of the diffractive layer of the diffractive optical element, the longer the wavelength of the light, the deeper the optimum groove depth of the diffractive lattice. A depth of about 1000 nm is required for infrared light having a wavelength of 980 nm. That is, in the diffractive optical element of the present disclosure, it is preferable that the convex portion forming the high refractive index portion includes a diffractive optical element having a height of 1000 nm or more in the cross-sectional shape of the diffractive layer.
Further, the aspect ratio of the diffraction grating may be about 1 to diffract the light in the direction of the diffraction angle of 30 °, and the aspect ratio may be about 1.87 to diffract the light in the direction of 70 °.
However, this is a case where the light is diffracted in only one direction, and when it is actually used as a light source of a sensor, it is necessary to uniformly distribute the diffracted light over a predetermined region. For that purpose, it is necessary to combine regions having various diffraction angles and diffraction directions in a complicated manner, but as a result, a region having a very narrow pitch is included (for example, FIGS. 1 and 10). 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 aspect ratio becomes 2 or more due to the narrowing of the pitch, and sometimes exceeds 4. For example, when designing a rectangular diffusion shape that spreads over a long side of ± 50 ° x a short side of ± 3.3 ° with 2-level for a laser beam of 980 nm, the optimum depth of the diffraction grating is used. Is 1087 nm, and the maximum aspect ratio exceeds 4 when the pitch of the finest shape is 250 nm.
These designs are performed using various simulation tools such as GratingMOD (manufactured by Rsoft) using a strict coupled wave analysis (RCWA) algorithm and Virtuallab (manufactured by LightTrans) using an iterative Fourier transform algorithm (IFTA). be able to.
When the light source is not a laser but an LED, the design may be made in consideration of the oblique incident light.

Since the diffractive optical element according to the present disclosure includes an element having an aspect ratio of a high refractive index portion of 2 or more in the periodic structure of the diffractive layer, infrared rays having a wavelength of 780 nm or more can be shaped into a desired shape.

The cross-sectional shape of the periodic structure may be a rectangle as shown in FIGS. 3 to 7, and the cross-sectional shape may be a shape as shown in FIGS. 16A to 16D. Since the cross-sectional shape of the high refractive index portion has a tapered shape as shown in FIGS. 16A to 16D, it is excellent in releasability from the mold at the time of manufacturing.
Further, in order to increase the diffraction efficiency of the diffractive optical element, the diffraction grating is changed from a normal binary value (2-level: FIGS. 3 to 7) to a multi-stage shape (4-level ((C) in FIG. 16), 8-level (FIG. 16)). It is effective to increase the number as shown in (D) of FIG. 16, but if the number is increased too much, the mold making process becomes complicated and the cost increases. Therefore, in the present disclosure, an appropriate selection is made from 2 to 8 values. Is preferable.
The groove depth that affects the aspect ratio increases as the number of levels increases, but when a resin with a refractive index of 1.5 is used as an example, the depth approaches twice the target wavelength. As the target wavelength becomes longer, the required groove depth becomes deeper, so that the difficulty of processing increases. The minimum groove width used in the design is usually set to about 1/4 of the target wavelength, but it may be made finer in order to improve efficiency. However, if it is made too fine, processing is difficult and it takes time, so it is preferable to keep it to about 80 to 100 nm.
The maximum aspect ratio can usually reach up to about 8, and can be as high as about 25 when efficiency is important for infrared rays.
The diffractive optical element of the present disclosure includes a diffractive optical element having an aspect ratio of 2 or more, further 4 or more, by forming a high refractive index portion having a periodic structure using an ionizing radiation curable resin composition described later. Even so, it is possible to obtain a diffractive optical element which is excellent in reliability and includes an aspect ratio of 8 or less and even 25 or less as described above.

In the diffractive optical element of the present disclosure, the line-and-space ratio (L / S) when the convex portion is a line (L) and the concave portion is a space (S) is not particularly limited, and a desired diffracted light can be obtained. It may be set appropriately, but for example, it can be set appropriately in the range of 0.6 to 1.2, and is preferably in the range of 0.8 to 1.0 from the viewpoint of diffraction efficiency.

Further, the diffractive optical element of the present disclosure preferably has a multi-stage shape having two or more flat portions from the viewpoint that the diffraction angle can be easily increased.
Since the diffractive optical element of the present disclosure has an aspect ratio of 2 or more, the 0th-order light can be weakened. However, when the diffraction angle is increased, the diffractive light having a desired shape is removed while the 0th-order light is removed. You can also get. This will be described with reference to the figure. 12 and 13 are drawings provided for explanation of the diffractive optical element. 14 (a) is a front view of the screen 22 in the example of FIG. 12 (a), and FIG. 14 (c) is a front view of the screen 22 in the example of FIG. 13 (c). be.
In the example of FIG. 12A, the irradiation light 21 is diffracted by the diffractive optical element 10, and a square image like 24 is formed on the screen 22. As shown in FIG. 14A, since the square image includes the 0th-order light irradiation position 27, the 0th-order light is included in the image. Since the 0th-order light is suppressed in the embodiment of the present disclosure, good diffracted light is obtained even in such a case.
On the other hand, in the example of FIG. 13 (c), by setting the diffraction angles of the primary lights 26a and 26b to be larger than those of the example of FIG. 12 (a), as shown in FIG. 14 (c), the square shape is formed. The image does not include the 0th-order light irradiation position 27. By designing the maximum diffraction angle to be large in this way, it is possible to obtain diffracted light that does not include the 0th-order light. For this reason, the diffractive optical element of the present disclosure preferably has a multi-stage shape having two or more flat portions, and further preferably has an aspect ratio of 3.5 or more.

<Cured product of ionizing radiation curable resin composition>
In the diffractive optical element of the present disclosure, it is preferable that the high refractive index portion is a cured product of an ionizing radiation curable resin composition from the viewpoint of improving throughput. The cured product of the ionizing radiation curable resin composition is obtained by curing the ionizing radiation curable resin composition described later by the action of light. By the manufacturing method described later, the cured product becomes a high refractive index portion to which a predetermined periodic structure is imparted.

The present inventor has investigated a method of replicating by using a diffractive optical element created by electron beam lithography as a mold and imprinting it with a resin. If the storage elastic modulus (E') of the cured ionizing radiation curable resin is larger than ⁵ × 109 [Pa], the load required for mold removal becomes large, and the resin in the high aspect ratio part may break. rice field. It is presumed that this is due to the fact that the resin cured in the mold needs to be deformed to some extent when it comes out of the mold. On the other hand, if the storage elastic modulus (E') is smaller than 1 × ¹⁰⁸ [Pa], it is easy to peel off, but it is easily deformed. It has been found that the durability of the diffractive layer may be reduced. Furthermore, when the tan δ of the cured resin exceeds 0.3, the deformation at the time of mold release cannot be restored, or the adjacent high refractive index parts stick to each other (sticking) when an external force is applied. I got the finding that there is something.
Based on the results of the study, the ionized radiation curable resin composition in the present disclosure has a storage elastic modulus (E') of 1 × 10 ⁸ Pa or more and 5 × 10 at 25 ° C. of the cured product of the ionized radiation curable resin composition. The ratio of the loss elastic modulus (E ") to the storage elastic modulus (E') at 25 ° C. of the cured product of the ionized radiation curable resin composition which is ⁹ Pa or less (tan δ (= E" / E'). Hereinafter, it may be referred to as loss tangent), and it is preferable to select and use one having a loss of 0.3 or less. This is because by selecting and using such a resin composition, it is possible to suppress breakage and breakage of the resin, excellent releasability, and suppression of deformation at the time of remolding.

In the present disclosure, the storage elastic modulus (E') and the loss elastic modulus (E ") are measured by the following methods in accordance with JIS K7244.
First, the ionizing radiation curable resin composition is sufficiently cured by irradiating it with ultraviolet rays having an energy of 2000 mJ / cm ² for 1 minute or more, and has no substrate and uneven shape, has a thickness of 1 mm, a width of 5 mm, and a length. A single film having a size of 30 mm is used.
Next, E', E "at 25 ° C. is obtained by applying a periodic external force of 25 g at 10 Hz in the length direction of the cured product of the resin composition at 25 ° C. and measuring the dynamic viscoelasticity. As the measuring device, for example, a UBM Rheogel E400 can be used.
Alternatively, an indenter can be pushed into the surface on the DOE side to obtain the storage elastic modulus (E'), loss elastic modulus (E ") and tan δ of the DOE surface. The measuring device is, for example, TI950 TRIBOINDENTER + nanoDMAIII manufactured by Hysiron. Nano indentation method can be used.

In the present disclosure, the storage elastic modulus (E') of the cured product of the ionized radiation curable resin composition at 25 ° C. is 1 × 10 ⁸ Pa or more and 5 × 10 ⁹ Pa or less, and the resin is suppressed from breaking or breaking. Moreover, it is preferable that it is 2 × 10 ⁸ Pa or more and 4 × 10 ⁹ Pa or less from the viewpoint of excellent mold releasability and suppression of deformation at the time of remolding.
Further, in the present disclosure, tan δ is 0.3 or less, which suppresses breakage and breakage of the resin, is excellent in mold release property, and suppresses deformation at the time of mold release. It is preferably 25.

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

(Ionizing radiation curable resin composition)
The ionizing radiation curable resin composition preferably contains an ionizing radiation curable component and can obtain the above physical properties after curing. Further, as long as the light of the designed target wavelength can be transmitted, there is no practical problem even if the color is visually colored after curing.
If the material forming the diffraction layer of the diffractive optical element has birefringence, it is necessary to design the shape in consideration of the birefringence. However, when the ionizing radiation curable resin composition is used for molding, the birefringence is required. There is also the merit that the effect of refraction can be almost ignored in practice.

The ionizing radiation curable component is preferably a composition containing a compound having an ethylenically unsaturated bond, and more preferably a composition containing a (meth) acrylate.
The ionizing radiation curable resin composition may contain at least the above ionizing radiation curable component, and may further contain other components, if necessary.
Further, the resin composition preferably contains a compound having a long-chain alkyl group having 12 or more carbon atoms, because the high refractive index portion of the diffraction layer has excellent flexibility and breakage and breakage are suppressed.
Hereinafter, each component in the composition containing (meth) acrylate, which is preferably used as an ionizing radiation curable component as an example, will be described in order.

The (meth) acrylate is a monofunctional (meth) acrylate having one (meth) acryloyl group in one molecule, or a polyfunctional acrylate having two or more (meth) acryloyl groups in one molecule. Also, a monofunctional (meth) acrylate and a polyfunctional (meth) acrylate may be used in combination.
Above all, it is preferable to use a monofunctional (meth) acrylate and a polyfunctional (meth) acrylate in combination from the viewpoint that the cured product satisfies the above physical properties and the high refractive index portion has both flexibility and elastic resilience.

Specific examples of the monofunctional (meth) acrylate include, for example, methyl (meth) acrylate, hexyl (meth) acrylate, allyl (meth) acrylate, benzyl (meth) acrylate, butoxyethyl (meth) acrylate, and butoxyethylene glycol (meth). ) Acrylate, cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycerol (meth) acrylate, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxy Propyl (meth) acrylate, isobonyl (meth) acrylate, isodexyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, 2-methoxyethyl (meth) acrylate, methoxyethylene glycol (meth) acrylate, phenoxyethyl ( Meta) acrylate, stearyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, biphenyloxyethyl acrylate, bisphenol A diglycidyl (meth) acrylate, biphenylyloxyethyl (meth) acrylate, ethylene oxide-modified biphenylyloxy Examples thereof include ethyl (meth) acrylate and bisphenol A epoxy (meth) acrylate. These monofunctional (meth) acrylic acid esters can be used alone or in combination of two or more.
The content of the monofunctional (meth) acrylate is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, based on the total solid content of the ionizing radiation curable resin composition.
Specific examples of the polyfunctional acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene di (meth) acrylate, hexanediol di (meth) acrylate, and polyethylene glycol di (meth) acrylate. , Bisphenol A di (meth) acrylate, tetrabromobisphenol A di (meth) acrylate, bisphenol S di (meth) acrylate, butanediol di (meth) acrylate, phthalic acid di (meth) acrylate, ethylene oxide-modified bisphenol A di ( Meta) Acrylate, Trimethylol Propanetri (Meta) Acrylate, Pentaerythritol Tri (Meta) Acrylate, Pentaerythritol Tetra (Meta) Acrylate, Tris (Acryloxyethyl) Isocyanurate, Pentaerythritol Tetra (Meta) Acrylate, Dipentaerythritol Hexa Examples thereof include (meth) acrylate, urethane tri (meth) acrylate, ester tri (meth) acrylate, urethane hexa (meth) acrylate, ethylene oxide-modified trimethylol propantri (meth) acrylate and the like. Among them, from the viewpoint of excellent flexibility and restorability, it is preferable to use a polyfunctional (meth) acrylate containing alkylene oxide, more preferably an ethylene oxide-modified polyfunctional (meth) acrylate, and an ethylene oxide-modified bisphenol A di. It is even more preferable to contain at least one of (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, and polyethylene glycol di (meth) acrylate.
The content of the polyfunctional (meth) acrylate is preferably 10 to 70% by mass, more preferably 15 to 65% by mass, based on the total solid content of the ionizing radiation curable resin composition.

The ionizing radiation curable resin composition may contain a photopolymerization initiator, if necessary. The content of the photopolymerization initiator is usually 1 to 20% by mass and preferably 2 to 10% by mass with respect to the total solid content of the ionizing radiation curable resin composition.
Further, it is preferable to add a mold release agent (a material having a mold release property) to the resin composition. In particular, if the peeling stress from the mold is large, the life of the mold will be shortened due to resin clogging. can do. Further, as these release agents, those fixed to the crosslinked structure of the resin composition and those existing in a free state can be selected according to the application.
As other additives, 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 processes 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. Composite with an inorganic material such as silsesquioxane is also effective for the purpose of improving heat resistance.
Further, the ionizing radiation curable resin composition preferably contains substantially no solvent in consideration of the environment, but contains a solvent in consideration of adhesion to the substrate, viscosity adjustment, surface quality improvement, and the like. There may be. When a solvent is contained, the resin is applied to the base material or the mold, the solvent is dried, and then the mold is formed.

<Transparent substrate>
The diffractive optical element of the present disclosure may be configured to have a transparent substrate, if necessary.
The transparent substrate used in the present disclosure can be appropriately selected from known transparent substrates according to the intended use. Specific examples of the material used for the transparent substrate include acetyl cellulose-based resin such as triacetyl cellulose, polyester-based resin such as polyethylene terephthalate and polyethylene naphthalate, olefin-based resin such as polyethylene and polymethylpentene, and acrylic-based resin. Transparent resins such as resins, polyurethane resins, polyether sulfone and polycarbonate, polysulfones, polyethers, polyether ketones, acronitrile, methacrylonitrile, cycloolefin polymers, cycloolefin copolymers, soda glass, potash glass, lead glass Examples thereof include glass such as glass, ceramics such as PLZT, transparent inorganic materials such as quartz and fluorite, and the like. The birefringence of the transparent substrate does not affect the effect of the diffractive optical element itself, but it has a suitable birefringence when the phase difference between the light incident on the diffractive optical element and the diffused light is a problem. The base material may be selected.
Note that transparency here means a state in which the other side can be seen through visually, but if light of the target wavelength designed by the diffractive optical element can be transmitted, it is a practical problem even if it is visually colored. There is no. Further, when the ionizing radiation is irradiated from the transparent substrate side to cure the ionizing radiation curable resin composition, it is preferable that the transparent substrate does not cut the ionizing radiation to be irradiated as much as possible.
The thickness of the transparent substrate can be appropriately set according to the intended use of the present disclosure, and is not particularly limited, but is usually 20 to 5000 μm, and the transparent substrate is supplied in the form of a roll or rolled. It may be either one that does not bend enough to be taken 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 the structure consisting of a single layer, and may have a structure in which a plurality of layers are laminated. When 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.
Further, the transparent substrate may be subjected to surface treatment for improving the adhesion to the above-mentioned resin composition or formation of a primer layer. As the surface treatment, general adhesion improvement treatment such as corona treatment and atmospheric pressure plasma treatment can be applied. Further, the primer layer preferably has adhesion to both the transparent substrate and the resin composition and transmits light of a target wavelength. However, depending on the application, by intentionally keeping the adhesion between the transparent base material and the resin composition low, it is possible to use the diffraction layer after molding by peeling it off from the transparent base material. Such usage is particularly effective when it is desired to reduce the thickness of the diffractive optical element.

Further, from the viewpoint of preventing damage to the diffractive layer and having excellent mechanical strength, the diffractive optical element of the present disclosure may have a structure in which the diffractive layer and the coating layer are provided in this order on a transparent substrate. good. The coating layer is not particularly limited, but it is preferable to use the same layer as the transparent substrate. Further, when the coating layer is provided on the diffraction layer, an adhesive (adhesive) layer may be provided between the diffraction layer and the coating layer. As the pressure-sensitive adhesive or adhesive for the pressure-sensitive adhesive layer (adhesive layer), a pressure-sensitive adhesive (adhesive), a two-component curable adhesive, an ultraviolet curable adhesive, etc. may be appropriately selected from conventionally known ones. Any adhesive form such as a heat-curable adhesive or a heat-melt type adhesive can be preferably used, but when the low refractive index portion is air, a pressure-sensitive adhesive or an adhesive having low fluidity should be used. Is preferable. When a part of the low refractive index portion is filled with an adhesive or an adhesive, the diffraction layer may be designed in consideration of the portion.
It should be noted that by providing such a coating layer, a secondary effect that it is possible to prevent re-replication using the unevenness of the diffraction grating as a mold can be expected.
Further, by forming the coating layer, it is possible to prevent foreign matter from entering the diffraction layer, and it is possible to improve the long-term reliability of the diffraction optical element and the light irradiation device.

Further, an antireflection layer may be further provided on the surface of the transparent substrate or the coating layer on the opposite side of the diffraction layer. The antireflection layer may be appropriately selected from conventionally known ones, and may be, for example, a refractive index layer composed of a single layer having a low refractive index layer or a high refractive index layer, and has a low refractive index layer and a high refractive index layer. It may be a multilayer film in which a rate layer is sequentially laminated, or it may be an antireflection layer having a fine uneven shape. By providing the antireflection layer, it is possible to improve the diffraction efficiency of the diffraction optical element.

Further, the transparent base material, the coating layer, and the adhesive layer (adhesive layer) may contain conventionally known additives as long as the effects of the present disclosure are not impaired. Examples of such additives include ultraviolet absorbers, infrared absorbers, light stabilizers, antioxidants and the like.

<Manufacturing method of diffractive optical element>
Since the diffractive optical element of the present disclosure includes an element having an aspect ratio of a high refractive index portion in the periodic structure of the diffractive layer of 2 or more, breakage and sticking are likely to occur at the time of mold removal.
Therefore, in the present disclosure, it is preferable to manufacture the diffractive optical element by the following manufacturing method.
That is, it is a method of manufacturing an optical element that shapes the light from a light source.
The process of preparing a mold for manufacturing a diffractive optical element having a predetermined periodic structure, and
A step of applying an ionizing radiation curable resin composition to the mold to form a coating film, and
A step of irradiating the coating film with ionizing radiation to form a cured film of the ionizing radiation curable resin composition,
It has a step of releasing the cured film from the mold.
The storage elastic modulus (E') of the cured product of the ionized radiation curable resin composition at 25 ° C. is 1 × 10 ⁸ Pa or more and 5 × 10 ⁹ Pa or less, and the cured product of the ionized radiation curable resin composition is cured. A method for manufacturing a diffractive optical element, wherein the ratio (tan δ (= E ”/ E ′) of the loss elastic modulus (E ″) to the storage elastic modulus (E ′) at 25 ° C. of the object is 0.3 or less. Is preferable.

A preferred method for manufacturing the diffractive optical element will be described with reference to the drawings. FIG. 17 is a process diagram schematically showing an example of a method for manufacturing a diffractive optical element. As shown in the example of FIG. 17, first, a mold 31 having a desired periodic structure formed is prepared (FIG. 17 (A)). Next, the above-mentioned ionizing radiation curable resin composition 32 is applied to the surface of the mold to form a coating film (FIGS. 17B to 17C). The coating means is not particularly limited, and a conventionally known method may be appropriately selected. In the example of FIG. 17, a transparent base material 33 is arranged on the ionizing radiation curable resin composition 32, and a pressure roller 34 is used. , The ionizing radiation curable resin composition 32 is uniformly applied. Next, the obtained coating film is irradiated with ionizing radiation (35), and the ionizing radiation curable resin composition is cured to form a cured film 36 (FIG. 17 (D)). By releasing the obtained cured film 36 from the mold 31, a diffractive optical element can be obtained (FIG. 17 (E)). Then, if necessary, the transparent base material 33 may be peeled off (not shown).
Hereinafter, each step of the manufacturing method will be described, but the description of the same as the diffractive optical element of the present disclosure will be omitted here.

The mold for manufacturing a diffractive optical element can be processed by a technique such as laser lithography, electron beam lithography, or FIB (Focused Ion Beam), but electron beam lithography is usually preferably used.
The material can be used as long as it can be processed with a high aspect ratio, but usually quartz or Si is used. It is also possible to use a copy mold (soft mold) duplicated from these molds with resin or a copy mold duplicated by Ni electroforming.
Further, if necessary, the mold surface can be subjected to a mold release treatment. Fluorine-based and silicon-based mold release agents, diamond-like carbon, Ni plating, etc. can be applied. The treatment method can be appropriately selected from vapor deposition, spatter, vapor phase treatment such as ALD (Atomic Layer Deposition), liquid phase treatment such as coating, dipping, and plating.
Since the shape required for the diffractive optical element is usually as small as several mm square to several cm square, the efficiency of duplication can be improved by processing the shapes of a plurality of diffraction layers side by side in one mold. When emphasis is placed on throughput, the above-mentioned molds or copy molds may be duplicated side by side and used for molding as a multi-sided mold.

If the volume change during curing of the ionizing radiation curable resin composition becomes a problem, it can be corrected and the mold design can be performed. Further, in consideration of ease of mold release, a structure in which the frontage on the opening side is wider than the depth of the fine structure of the mold may be used (FIGS. 16A to 16D). In this case, the diffraction layer of the obtained diffractive optical element has a shape in which the surface side becomes thin.
Further, since the diffractive optical element of the present disclosure usually has a plurality of regions having different periodic structures, a plurality of grooves having different pitches (frontages) are included in one diffractive optical element. When making a mold, the depth of dry etching tends to vary depending on the pitch (frontage). However, since such variation leads to a decrease in efficiency, it is important to optimize the processing process and suppress it to ± 10% or less of the desired depth.
When a convex portion having an aspect ratio of 2 or more is formed, the height variation of the convex portion tends to occur. In that case, by manufacturing the mold slightly deeper than the design value, it becomes easy to obtain a diffractive optical element having desired optical characteristics while having height variations.

Next, a coating film of the ionizing radiation curable resin composition is formed. In the above-mentioned example, the coating film of the ionizing radiation curable resin composition is formed on the mold side, but the coating film may be formed on the transparent substrate side. As a method for forming the coating film, in addition to the above-mentioned examples, a suitable coating method can be selected from conventionally known coating methods such as die coat, bar coat, gravure coat, and spin coat.
Further, the transparent base material may be a single-wafered material, or a long material may be used in which a coating step, an ionizing radiation irradiation step, and a mold removal step are sequentially performed by a roll-to-roll method. When the mold is a hard material that is hard to bend, a transparent base material that is flexible is preferable because it does not easily bite bubbles. On the contrary, when a hard transparent substrate is used, it is preferable to use a soft mold for the mold.
Irradiation of ultraviolet rays or electron beams may be performed once or divided into a plurality of times, and in the case of dividing into a plurality of times, a form of curing to some extent, releasing the mold, and then performing additional irradiation is also applicable.

If the fluidity of the ionizing radiation curable resin at the time of coating is too high, it is difficult for the resin to enter the fine grooves, and if it is too low, the ink may spread thinly and a predetermined thickness may not be secured. In the case of roll type, if the fluidity is too high, it causes ink dripping. In the present disclosure, it is preferable to use a resin having a viscosity of the ionizing radiation curable resin composition at 25 ° C. of about several tens [mPas] to several thousand [mPas]. Since the viscosity also changes with temperature, it is preferable to take an appropriate temperature control as appropriate.

[Light irradiation device]
The light irradiation device according to the present disclosure is characterized by including a light source and one or more diffractive optical elements according to the present disclosure.
According to the light irradiation device of the present disclosure, it is possible to irradiate light shaped into a desired shape.

The light irradiation apparatus of the present disclosure will be described with reference to the drawings. FIG. 11 is a cross-sectional view schematically showing an embodiment of the light irradiation device according to the present disclosure. The light irradiation device 20 shown in the example of FIG. 11 includes the diffractive optical element 10 according to the present disclosure on the light emitting surface side of the light source 13 provided with the substrate 11 and the light emitting body 12. In the example of FIG. 11, the transparent base material 4 is arranged on the light source 13 side, but the covering layer 5 may be arranged on the light source 13 side. For example, when the transparent base material 4, the coating layer 5, or the adhesive layer 6 contains an ultraviolet absorber, the layer containing the ultraviolet absorber is used as a light source from the viewpoint of improving the light resistance of the diffractive optical element. Is preferably placed on the opposite surface (that is, the surface on which sunlight or the like can be incident).
Hereinafter, such a light irradiation device of the present disclosure will be described, but since the diffractive optical element is the same as that of the diffractive optical element according to the present disclosure, the description thereof is omitted here.

In the light irradiation device of the present disclosure, the light source is not particularly limited, and a known light source can be used. Since the diffractive optical element according to the present disclosure is designed for diffraction of a specific wavelength, it is preferable to use a laser light source or an LED (light emitting diode) light source having a high intensity of the specific wavelength as the light source. In the present disclosure, any light source such as a directional laser light source and a diffusible LED (light emitting diode) light source can be suitably used.
In the present disclosure, it is preferable that the light source is appropriately selected from those that can reproduce the light source targeted for simulation in the design of the diffractive optical element according to the present disclosure. Above all, when a diffractive optical element that diffracts infrared rays having a wavelength of 780 nm or more is used, it is preferable to select a light source capable of emitting infrared rays having a wavelength of 780 nm or more.

The light irradiation device of the present disclosure may be provided with at least one diffraction grating according to the present disclosure, and may be further provided with another optical element, if necessary. Examples of other optical elements include polarizing plates, lenses, prisms, pass filters that transmit specific wavelengths, especially the 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.

<Use of light irradiation device>
The light irradiating device according to the present disclosure can irradiate light shaped into a desired shape, and can be suitably used as a light irradiating device for a sensor because infrared rays can be used. From the point of being able to effectively shape the light, for example, infrared lighting at night, lighting for security sensors, lighting for human detection sensors, lighting for collision prevention sensors for unmanned aircraft and automobiles, lighting for personal authentication devices, lighting for inspection devices, etc. , Etc., which makes it possible to simplify the light source, reduce the size, and save power.

Hereinafter, the present disclosure will be specifically described with reference to examples. These statements do not limit this disclosure.
Hereinafter, Examples 3 and 4 will be referred to as Reference Examples A and B.

(Diffraction grating design)
The shape was designed under the following conditions using a simulation tool.
Target light source: Laser light with a wavelength of 980 nm Material refractive index: 1.456
Diffusion shape: Rectangle extending from long side ± 50 ° x short side ± 3.3 ° Area size: 5 mm square Diffraction grating level: 2-level (binary value)
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.

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

(Resin molding method)
The resin shaping of the diffraction layer was performed as follows.
First, the quartz DOE was used as a mold, and the ionizing radiation curable resin compositions of Examples and Comparative Examples described later were dropped onto the diffraction surface. Next, a PET film (Toyobo Cosmo Shine A4300, 100 μm thick) was laminated with a roller from above as a transparent substrate, and the ionizing radiation curable resin composition was uniformly spread. Further, in that state, ultraviolet rays of 2000 mJ / cm ² are irradiated from the transparent base material side to cure the ionizing radiation curable resin, and then the transparent base material and the shaping layer are peeled off from the mold to form a diffractive optical element. Obtained.

(Measurement of physical properties of UV curable resin composition after curing)
The ultraviolet curable resin compositions 1 to 7 shown in Table 1 below are prepared and sufficiently cured by irradiating each of them with ultraviolet rays having an energy of 2000 mJ / cm ² for 1 minute or more, and have no substrate and no uneven shape. , A test single film having a thickness of 1 mm, a width of 5 mm, and a length of 30 mm was obtained, respectively.
Then, in accordance with JIS K7244, a periodic external force of 25 g was applied at 10 Hz in the length direction of the cured product of the resin composition at 25 ° C., and the dynamic viscoelasticity was measured to store elastic modulus at 25 ° C. The rate E'and the loss elastic modulus E'were determined. Further, tan δ was calculated from the results of the E'and E'. A UBM Rheogel E400 was used as the measuring device. The results are shown in Table 1.

(Example 1)
Using the ultraviolet curable resin composition 1, a diffractive optical element 1 was obtained according to the resin shaping method. The appearance of the obtained diffractive optical element 1 was good, and when the diffraction shape of the 980 nm laser was observed with an infrared camera, it was confirmed that the diffraction optical element 1 had a predetermined rectangular shape. In addition, high shape reproducibility was confirmed by SEM (scanning electron microscope) observation, and it was not damaged by rubbing with a soft cloth (manufactured by Zavina Minimax Fuji Chemical).

(Example 2)
A diffractive optical element 2 was obtained in the same manner as in Example 1 except that the ultraviolet curable resin composition 2 was used instead of the ultraviolet curable resin composition 1. The appearance of the obtained diffractive optical element 2 was good, and when the diffraction shape of the 980 nm laser was observed with an infrared camera, it was confirmed that the diffraction optical element 2 had a predetermined rectangular shape. In addition, high shape reproducibility was confirmed by SEM, and it was not damaged by rubbing with a soft cloth (manufactured by Zavina Minimax Fuji Chemical).

(Example 3)
In Example 1, a diffractive optical element 3 was obtained in the same manner as in Example 1 except that the ultraviolet curable resin composition 3 was used instead of the ultraviolet curable resin composition 1. The appearance of the obtained diffractive optical element 3 was good, and when the diffraction shape of the 980 nm laser was observed with an infrared camera, it was confirmed that the diffraction optical element 3 had a predetermined rectangular shape. In addition, high shape reproducibility was confirmed by SEM, and although it was not scratched by rubbing it with a soft cloth (manufactured by Zavina Minimax Fuji Chemical), it was sometimes scratched by rubbing it strongly.

(Example 4)
A diffractive optical element 4 was obtained in the same manner as in Example 1 except that the ultraviolet curable resin composition 4 was used instead of the ultraviolet curable resin composition 1. The appearance of the obtained diffractive optical element 4 was good, and when the diffraction shape of the 980 nm laser was observed with an infrared camera, it was confirmed that the diffraction optical element 4 had a predetermined rectangular shape. In addition, high shape reproducibility could be confirmed by SEM. It wasn't damaged by rubbing it with a soft cloth (made by Zavina Minimax Fuji Chemical), but when it was rubbed hard, it left a mark and was restored over time.

(Reference example 1)
In Example 1, the diffractive optical element was manufactured in the same manner as in Example 1 except that the ultraviolet curable resin composition 5 was used instead of the ultraviolet curable resin composition 1. The resin was cracked, and the SEM observed fine shape damage.

(Reference example 2)
In Example 1, the diffractive optical element was manufactured in the same manner as in Example 1 except that the ultraviolet curable resin composition 6 was used instead of the ultraviolet curable resin composition 1. The obtained diffractive optical element was rubbed with a soft cloth (manufactured by Zavina Minimax Fuji Chemical) to leave a mark, and it was not restored even after that.

(Reference example 3)
In Example 1, the diffractive optical element was manufactured in the same manner as in Example 1 except that the ultraviolet curable resin composition 7 was used instead of the ultraviolet curable resin composition 1. In the obtained diffractive optical element, the diffractive layer was cloudy white, and deformation of a finely shaped wall was observed by SEM observation.

[Example 5]
Various diffractive optical elements were manufactured using the ultraviolet curable resin composition 1.
(Example 5-1)
・ Two-level mold fabrication Using an electron beam lithography process using a 6-inch square size synthetic quartz plate and an electron beam lithography system and a dry etching device, the line / space width is 147 nm / 151 nm and the groove height (depth) is A mold B containing a two-level diffraction pattern of 952 μm was prepared.
Next, a diffractive optical element was obtained by the same procedure as the resin shaping method except that the mold B was used.

(Measurement of shape of UV curable resin composition after curing)
When the cross section of the diffractive optical element obtained in Example 5-1 was confirmed by SEM, the pattern portion (aspect ratio 6.15) having a resin width of 151 nm and a resin height (depth) of 928 nm was found to have a fallen protrusion. I was able to type without any problems. In addition, light diffusion was performed using a predetermined optical system, and the light diffusion shape as designed could be confirmed.

(Example 5-2)
・ Fabrication of multi-stage (4-level) molds 4 levels with a pitch of 400 nm and a depth of 767 nm by an electron beam lithography process using a 6-inch square size synthetic quartz plate and an electron beam drawing device and a dry etching device. A mold C including a diffraction pattern was produced.
Next, a diffractive optical element was obtained by the same procedure as the resin shaping method except that the mold C was used.

(Measurement of shape of UV curable resin composition after curing)
When the cross section of the diffractive optical element obtained in Example 5-2 was confirmed by SEM, the pattern portion (aspect ratio 8.0) of the thinnest step having a resin width of 93 nm and a resin height of 747 nm was found to have a fallen protrusion. I was able to type without any problems. In addition, light diffusion was performed using a predetermined optical system. FIG. 18 shows an image projected on the screen of the diffracted light transmitted through the diffractive optical element obtained in Example 5-2. The image projected on the square was the primary light, and the light diffusion shape as designed could be confirmed. The point on the lower side of the square is the 0th-order light.

As shown in the results of Examples 1 to 5, the storage elastic modulus (E') at 25 ° C. after curing is 1 × 10 ⁸ Pa or more and 5 × 10 ⁹ Pa or less, and the storage at 25 ° C. after curing is performed. By using an ionized radiation resin composition having a ratio (tan δ (= E ”/ E ′) of the loss elastic modulus (E ″) to the elastic modulus (E ′) of 0.3 or less, breakage and sticking are suppressed. It has been clarified that a desired convex portion having an aspect ratio of 2 or more can be formed.

(Example 6)
Next, a simulation of the diffraction image of the binary diffraction optical element was performed according to the following.
The refractive index of the resin material forming the convex portion is set to 1.5, the line and space (L / S convex portion width: concave width) is fixed at 1: 1 and then the width and height of the convex portion are changed. By doing so, the aspect ratio was changed.
The light source was a laser beam having a wavelength of 800 nm or 980 nm, and the incident angles were three points of 15 °, 30 °, and 60 °. The angle of incidence is 0 ° in the direction perpendicular to the surface of the diffractive optical element.
The results are shown in Tables 2-5 below. The numerical values of the 0th-order light intensity and the 1st-order light intensity in the table are relative intensities when the intensity of the incident light is 1.

[Summary of results]
From the results of Example 6, it was clarified that a diffractive optical element having a primary light intensity of 0.3 or more can be designed by setting the aspect ratio of the convex portion to 2 or more. As described above, according to the present disclosure, by shaping the ionizing radiation curable resin composition, desired diffracted light can be obtained, and a diffractive optical element having excellent durability can be manufactured. Further, according to the diffractive optical element of the present disclosure, infrared light having a wavelength of 900 nm or more can be used.

1 Diffractive layer 1A, 1B, 1C, 1D Partial periodic structure (region)
2 High refractive index part 3 Low refractive index part 4 Transparent base material 5 Coating layer 6 Adhesive layer (adhesive layer)
7 Low refractive index resin layers 8A, 8B, 8C, 8D 4-level structure (region) with different depths
9 Antireflection layer 10 Diffractive optical element 11 Substrate 12 Light emitter 13 Light source 14 Glass plate 15 Adhesive layer (adhesive layer)
20 Light irradiation device 21 Irradiation light 22 Screen 23 Irradiation area of irradiation light 24 Irradiation area of light that has passed through the diffractive optical element 25th order light 26a, 26b, 26c, 26d Primary light (diffracted light)
27 0th-order light irradiation position 31 Mold 32 Ionizing radiation curable resin composition 33 Transparent base material 34 Pressurized roller 35 Ionizing radiation irradiation 36 Curing film 101 Base material 102, 103 Broken resin 104 Mold 105 Sticking resin

Claims (7)

An optical element that shapes the light from a light source by transmitting it through the optical element.
A diffraction layer having a periodic structure of a low refractive index portion and a high refractive index portion is provided.
Including those having an aspect ratio of a high refractive index portion of 2 or more in the periodic structure,
In the cross-sectional shape of the diffraction layer, the convex portion forming the high refractive index portion is a multi-stage shape having two or more flat portions.
The aspect ratio of the convex portion of the multi-stage shape is 3.5 or more, and the aspect ratio is 3.5 or more.
The high refractive index portion is made of a cured product of an ionizing radiation curable resin composition.
The storage elastic modulus (E') of the cured product of the ionized radiation curable resin composition at 25 ° C. is 1.4 × 10 ⁹ Pa or more and 5 × 10 ⁹ Pa or less, and the ionized radiation curable resin composition The ratio (tan δ (= E ”/ E ′) of the loss elastic modulus (E ″) to the storage elastic modulus (E ′) at 25 ° C. of the cured product is 0.091 or less, and the infrared rays having a wavelength of 780 nm or more are diffracted. Diffractive optical element . The diffractive optical element according to claim 1, wherein the convex portion forming the high refractive index portion in the cross-sectional shape of the diffractive layer includes an element having a height of 1000 nm or more. The diffractive optical element according to claim 1 or 2, wherein the low refractive index portion is air. The diffractive optical element according to any one of claims 1 to 3, wherein the diffractive layer and the covering layer are provided in this order on a transparent substrate. The diffractive optical element according to any one of claims 1 to 4, further comprising an antireflection layer on the outermost surface. A light irradiation device including a light source and one or more diffractive optical elements according to any one of claims 1 to 5 . The light irradiation device according to claim 6 , wherein the light source is a light source capable of emitting infrared rays having a wavelength of 780 nm or more.

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