JP2013037747A - Wavelength selection diffraction element and optical head device using the same - Google Patents

Abstract

A wavelength selective diffraction element having a diffraction efficiency superior to that of a conventional one and an optical head device using the same are provided.
An incident light having wavelengths λ ₁ , λ _2, and λ ₃ in at least a 405 nm wavelength band, a 660 nm wavelength band, and a 785 nm wavelength band is incident. The second optical material B constituting the concavo-convex member 12 or the filling member 13 is an oxidation having an average particle diameter of 3 nm or more and 15 nm or less coated with a surface modifier having a polymerizable group. A wavelength selective diffraction element 10 obtained by curing a photopolymerizable composition containing zirconium particles, one polymerizable group, and a monofunctional compound having an alicyclic structure having 10 to 14 carbon atoms.
[Selection] Figure 1

Description

  The present invention relates to a wavelength selective diffractive element that selectively transmits or diffracts light of different wavelengths and an optical head device using the same, and more specifically, as an optical system that handles optical storage, CD, DVD, optical Information recording and / or reproduction (hereinafter referred to as “recording / recording”) on an optical recording medium such as a magnetic disk and a high-density optical recording medium (hereinafter referred to as “optical disk”) such as “Blu-ray” (registered trademark: BD). The present invention relates to a wavelength selective diffraction element used in an optical head device that performs “reproduction”) and an optical head device using the same.

  Optical discs such as DVDs and CDs are widely used as optical recording media, high-density information recording optical discs BD are commercialized, and optical head devices are used for recording information on optical discs and reproducing information recorded on optical discs.

  In an optical head device, light having a wavelength corresponding to the standard of each optical disk is emitted from a light source such as a semiconductor laser, and the emitted light from the light source is recorded on the optical disk by an objective lens having a numerical aperture NA corresponding to each wavelength. Information is recorded / reproduced by focusing on the surface, branching the reflected light by a beam splitter, receiving it by a photodetector, and converting it into an electrical signal.

BD, DVD, and CD have different wavelengths of laser light used for recording / reproduction, BD has a wavelength of 395 nm to 425 nm, DVD has a wavelength in the range of 640 nm to 680 nm, and CD has a wavelength of 765 nm to 805 nm. Each laser beam in the wavelength range is used.
For this reason, in an optical head device corresponding to a plurality of optical discs such as BD, DVD, and CD, a light source that emits light in a wavelength band corresponding to each used wavelength region and an objective lens having a numerical aperture NA corresponding to the light source are provided. Used. Specifically, a semiconductor laser that emits light in a 405 nm wavelength band for BD, a 660 nm wavelength band for DVD, and a 785 nm wavelength band for CD is used.

In recording / reproduction of the optical head device, the tracking servo signal detection function controls the operation of the laser light emitted from the light source and then traces on the information recording surface of the optical disk.
As the tracking servo signal, for example, a three-beam method is used in which the emitted light from the semiconductor laser is branched into straight transmitted light (0th order diffracted light) and ± 1st order diffracted light by a diffractive element arranged in the optical path going to the optical disk. It is done.
In addition, a diffraction element (hereinafter, referred to as a hologram diffraction element) in which a different grating pattern is formed for each incident light beam in a plurality of divided regions is disposed in the return optical path from the optical disk to the photodetector. Also, a hologram method that divides the signal light into a plurality of diffracted lights to generate a tracking servo signal, or the like is used.

In recent years, along with the downsizing and thinning of devices such as notebook personal computers, the BD, DVD, and CD optical head devices mounted thereon are also required to be smaller and lighter.
However, in the optical head device corresponding to a plurality of optical discs as described above, if each member is separately provided for each wavelength used for each optical disc, the entire device becomes large and the number of constituent members increases. There is a problem that the mass increases.

  For this reason, from the viewpoint of miniaturization and weight reduction of the optical head device, the optical path of light in each wavelength band for BD, DVD, and CD is made common, and desired optical characteristics for the light in these multiple wavelength bands Attempts have been made to use optical components that exhibit the following.

In recent years, a two-wavelength semiconductor laser in which a semiconductor laser that emits light in the wavelength band for DVD and a semiconductor laser that emits light for CD has been integrated has been used as a light source. A three-wavelength semiconductor laser in which a BD semiconductor laser is integrated with a two-wavelength semiconductor laser including a CD has also been developed.
In addition, a photodetector that can receive signal light reflected by a DVD and signal light reflected by a CD in a common single package is also used.

For example, Patent Document 1 discloses a wavelength selective diffractive element formed by combining outgoing lights having a plurality of wavelengths and arranging them in a common optical path.
The wavelength selective diffractive element of Patent Document 1 is composed of an uneven portion and a filling portion made of a polymer material such as polyester, polyether, acrylic, epoxy, etc. having transparency in a used wavelength region such as BD. By adjusting the grating pitch and grating shape of the diffractive element, only light of a specific wavelength is selectively diffracted.

Similarly, in the hologram system, an attempt is made to dispose a hologram diffraction element in the return path of an optical path that uses light of three wavelengths in common.
In this case, for example, by adjusting the pattern of the hologram diffraction grating, it is possible to allow diffracted light of multiple wavelengths to be incident on the light receiving surface of a single packaged photodetector, and to determine the number of light receiving surfaces and light reception of the photodetector. The area of the surface can be reduced.

However, the wavelength selective diffraction element disclosed in Patent Document 1 has a problem in that the refractive index obtained at the concavo-convex portion and the filling portion is not necessarily high, and a difference in refractive index between the two cannot be sufficiently ensured.
For this reason, for example, when the refractive index of the concavo-convex part and the refractive index of the filling part coincide in the wavelength range of 660 nm, the difference in refractive index between them in the wavelength range of 405 nm was about 0.008. For this reason, for example, when a binary grating shape is employed, it is difficult to obtain a desired first-order diffraction efficiency.

WO2007 / 069660 Publication

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wavelength selective diffraction element having a diffraction efficiency superior to that of the prior art and an optical head device using the same.

That is, the wavelength selective diffraction element of the present invention includes a transparent substrate having translucency, and an uneven member having an uneven shape formed on the transparent substrate and periodically formed so as to extend in one direction, An incident member having at least a wavelength of 405 nm wavelength band (λ ₁ ), a wavelength of 660 nm wavelength band (λ ₂ ), and a wavelength of 785 nm wavelength band (λ ₃ ). A wavelength-selective diffractive element on which light is incident, wherein the concavo-convex member and the filling member are each a first optical material A having high wavelength dispersion or a second optical material B having low wavelength dispersion. On the other hand, the refractive index nA of the first optical material A and the refractive index nB of the second optical material B are | nA−nB | ≦ 0.006 with respect to the light with the wavelength λ _1. And said wavelength ₂ and to the wavelength lambda ₃ of the light | nA-nB |> 0.006 or where the wavelength lambda ₂ and to the wavelength lambda ₃ of the light | nA-nB | be ≦ 0.006 And the second optical material B having the low wavelength dispersibility satisfies the relationship of | n (A) −n (B) |> 0.006 with respect to the light having the wavelength λ ₁ . A zirconium oxide particle having an average particle diameter of 3 nm or more and 15 nm or less and surface-coated with a surface modifying agent having a group, a monofunctional compound having one polymerizable group and an alicyclic structure having 10 to 14 carbon atoms, It is characterized by curing a photopolymerizable composition comprising

（式（１）中、Ａは水素原子又はメチル基を表し、Ｘはそれぞれ独立に水素原子、メチル基又はエチル基を表し、Ｒは水素原子、メチル基又はエチル基を表し、ｎは１〜６の整数を表し、ｍは１〜３の整数を表す。）
また、光重合性組成物における前記酸化ジルコニウム粒子の含有量は４５質量％以上７０質量％以下が好ましい。また、前記高波長分散性を有する第１の光学材料Ａは、芳香族化合物を含有することが好ましい。また、前記高波長分散性を有する第１の光学材料Ａの屈折率ｎ_ｄとアッベ数ν_ｄが１０＜ν_ｄ＜３５、１．５５＜ｎ_ｄ＜１．７０の範囲内にあり、かつ、前記低波長分散性を有する第２の光学材料Ｂの屈折率ｎ_ｄとアッベ数ν_ｄが３８＜ν_ｄ＜５８、１．５３＜ｎ_ｄ＜１．７８、かつ、ｎ_ｄ＞１．８０４−０．００５ν_ｄの範囲内にあることが好ましい。 The first refractive index nB of the refractive index nA and the second optical material B of the optical material A, the wavelength lambda _1, lambda _2, lambda ₃ of the wavelength lambda ₁ with respect to light | nA-nB | ≦ 0 .006, and the relationship of | nA−nB | ≧ 0.013 with respect to light of wavelength λ ₂ and wavelength λ ₃ , and the 0th-order diffraction efficiency for light of wavelength λ ₁ is 90% or more, or the wavelength Among λ ₁ , λ ₂ , and λ ₃ , there is a relationship of | nA−nB | ≦ 0.006 for light of wavelength λ ₂ and wavelength λ ₃ and | nA−nB | ≧ 0.015 for light of wavelength λ ₁ The 0th-order diffraction efficiency for light of wavelengths λ ₂ and λ ₃ is preferably 90% or more.
The alicyclic skeleton of the monofunctional compound is preferably adamantane, diamantane, or tricyclodecane, and the polymerizable group is preferably an acryl group or a methacryl group. The surface modifier is preferably a compound represented by the following general formula (1).

(In Formula (1), A represents a hydrogen atom or a methyl group, X represents a hydrogen atom, a methyl group, or an ethyl group each independently, R represents a hydrogen atom, a methyl group, or an ethyl group, and n is 1- 1). 6 represents an integer, and m represents an integer of 1 to 3.)
Further, the content of the zirconium oxide particles in the photopolymerizable composition is preferably 45% by mass or more and 70% by mass or less. The first optical material A having high wavelength dispersibility preferably contains an aromatic compound. Further, in the range of the high refractive index _{n d} and the Abbe number [nu _d of the first optical material A 10 having a wavelength dispersion _{<ν d <35,1.55 <n d} <1.70, and the refractive index _{n d} and the Abbe number [nu _d of the second optical material B having a low wavelength dispersion is _{38 <ν d <58,1.53 <n} d <1.78 _and,, n d> 1. it is preferably in the range of 804-0.005ν _d.

The optical head device of the present invention includes a light source that emits incident light having a wavelength of at least 405 nm (λ ₁ ), a wavelength of 660 nm (λ ₂ ), and a wavelength of 785 nm (λ ₃ ), An optical head device comprising an objective lens for condensing the light onto a recording layer of an optical disc and a photodetector for detecting reflected light from the optical recording medium, wherein the light between the light source and the objective lens The wavelength selective diffraction element of the present invention described above is installed on the road or on the optical path between the objective lens and the photodetector.

  According to the present invention, a cured product of a polymerizable composition comprising zirconium oxide particles together with a polymerizable monomer component (monofunctional compound) having an alicyclic structure as an optical material having low wavelength dispersion. By using it, the refractive index of the optical material having the low wavelength dispersion can be improved, and a wavelength selective diffraction element having better diffraction efficiency than the conventional one can be obtained.

1 is a schematic cross-sectional view showing an aspect of a wavelength selective diffraction element according to a first embodiment of the present invention. The wavelength selective diffraction element which concerns on the 1st Embodiment of this invention WHEREIN: The figure which shows the relationship between the wavelength of the incident light which injects into an uneven | corrugated member and a filling member, and the transmittance | permeability. The typical cross-sectional view which shows the aspect of the wavelength selective diffraction element which concerns on the 2nd Embodiment of this invention. The figure which shows the relationship between the wavelength of the incident light which injects into an uneven | corrugated member and a filling member, and the transmittance | permeability in the wavelength selective diffraction element which concerns on the 2nd Embodiment of this invention. Sectional drawing which shows the manufacturing process of the wavelength selection diffraction element of this invention. The typical cross-sectional view which shows the aspect of the wavelength selective diffraction element which concerns on the 3rd Embodiment of this invention. 1 is a diagram schematically illustrating a configuration of an optical head device that is an embodiment of the present invention. FIG.

Hereinafter, embodiments of the present invention will be described in detail.
The “average particle diameter” used in the following description is a value evaluated with a transmission scanning microscope (TEM).
The “photopolymerizable composition” refers to a composition containing a radical polymerizable compound that undergoes a polymerization reaction upon irradiation with ultraviolet rays.
“(Meth) acrylic group” means “acrylic group” or “methacrylic group”.
In this specification, among the optical materials constituting the concavo-convex member and the filling member, an optical material having high wavelength dispersion is referred to as a first optical material A, and an optical material having low wavelength dispersion is referred to as a second optical material. Let it be material B.

The wavelength selective diffraction element of the present invention includes a transparent substrate having translucency, a concavo-convex member having a concavo-convex shape formed on the transparent substrate and periodically formed so as to extend in one direction, An incident light having a wavelength (λ ₁ ) of a wavelength band of 405 nm, a wavelength of a wavelength band of 660 nm (λ ₂ ), and a wavelength of a wavelength band of 785 nm (λ ₃ ). An incident wavelength selective diffraction element, wherein the concavo-convex member and the filling member are each one of the first optical material A having high wavelength dispersion and the second optical material B having low wavelength dispersion. The refractive index nA of the first optical material A and the refractive index nB of the second optical material B are | nA−nB | ≦ 0.006 with respect to the light with the wavelength λ ₁ . and the wavelength lambda ₂ and the front Wavelength lambda ₃ with respect to the light | nA-nB |> 0.006 or where the wavelength lambda ₂ and the wavelength lambda ₃ with respect to the light | nA-nB | a ≦ 0.006, and the The second optical material B satisfying the relationship of | n (A) −n (B) |> 0.006 with respect to light of wavelength λ ₁ and having the low wavelength dispersion has a polymerizable group. Zirconium oxide particles having an average particle diameter of 3 nm or more and 15 nm or less and surface-coated with a surface modifier, one polymerizable group, and a monofunctional compound having an alicyclic structure having 10 to 14 carbon atoms The photopolymerizable composition is cured.

The wavelength selective diffraction element of the present invention is a light containing zirconium oxide particles together with a polymerizable monomer component (monofunctional compound) having an alicyclic structure as the second optical material B constituting the concavo-convex member or the filling member. By using the cured product of the polymerizable composition, the refractive index of the second optical material B can be improved, and in the at least one wavelength region of the wavelengths λ ₁ , λ ₂ , λ ₃ , the first optical material A high refractive index difference can be secured between A and the second optical material B. For this reason, it can be set as the wavelength selection diffraction element with improved diffraction efficiency.

Further, the wavelength selective diffraction element of the present invention has the above-described relationship between the refractive index nA of the optical material A having high wavelength dispersion and the refractive index nB of the second optical material B having low wavelength dispersion. , Λ ₁ , λ ₂ , λ ₃ diffracts at least one light and transmits the other light. Therefore, when the light of these three wavelength ranges is combined and arranged in a common optical path, it is desired Can be selectively diffracted, and light loss of incident light having other wavelengths and generation of stray light can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, the configuration of the wavelength selective diffraction element 10 according to the first embodiment of the present invention will be described with reference to FIG. The wavelength selective diffraction element according to the present embodiment will be described with reference to an example in which the BD, DVD and CD standards are supported. The wavelengths of light used for recording / reproducing BD, DVD, and CD are represented by λ ₁ , λ _2, and λ ₃ , respectively. Here, light of wavelengths λ ₁ , λ _2, and λ ₃ is light of wavelengths 405 nm, 660 nm, and 785 nm, respectively. The wavelengths 405 nm, 660 nm, and 785 nm refer to wavelength ranges of 405 ± 20 nm, 660 ± 20 nm, and 785 ± 20 nm, respectively.

Here, FIG. 1A is a schematic cross-sectional view showing an operation when light having a wavelength λ ₁ is incident on the wavelength selective diffraction element 10, and FIG. 1B is a wavelength selective diffraction. 3 is a schematic cross-sectional view showing an operation when light having a wavelength λ ₂ is incident on the element 10. FIG.

  As shown in FIG. 1, the wavelength selective diffraction element 10 according to the present embodiment has a transparent substrate 11 and an uneven shape that is formed on the transparent substrate 11 and periodically formed so as to extend in one direction. The concavo-convex member 12, a filling member 13 filled so as to fill at least the concave portion of the concavo-convex member 12, and a transparent substrate 14 provided on the upper surface of the filling member 13 and protecting the filling member 13 are provided.

  The directions in which the concavo-convex members 12 extend in the substrate plane may be parallel to each other or may be concentric. As the cross-sectional shape of the concavo-convex member 12, that is, a lattice, a rectangular shape, a sawtooth shape, or a shape approximating a desired sawtooth shape to a step shape can be used. Also, the same grating may be formed on the entire surface of the effective area where incident light is incident on the substrate surface. The inside of the substrate surface is divided, and the extension direction and cross-sectional shape of the grating are changed depending on the divided portion. It is also possible to form a lattice only in a part of the region.

  The transparent substrates 11 and 14 are not particularly limited as long as they have translucency. For example, a plastic substrate such as acrylic or a substrate made of an inorganic material such as glass can be used. From the viewpoint of ensuring reliability, the glass substrate is preferably used. In consideration of mass productivity, the transparent substrates 11 and 14 are preferably flat surfaces as shown in the drawing, but the present invention is not limited to this, and for example, a substrate having a curved surface such as a plastic lens may be used.

Further, on the transparent substrates 11 and 14, an antireflection film for light in the 405 nm wavelength band (λ ₁ ), 660 nm wavelength band (λ ₂ ), and 785 nm wavelength band (λ ₃ ) is provided to reduce reflection loss. It is preferable. As the antireflection film, a film having a property of blocking ultraviolet light having a wavelength of 330 nm or less can also be used.

Examples of the grating shape of the wavelength selective diffraction element 10 include a binary shape, a blazed shape, a pseudo-blazed shape (stepped grating shape having a multilevel structure), a Fresnel shape, and the like.
These lattice shapes can be formed, for example, by repeating photolithography and etching. In addition to the above, the lattice shape including a blaze shape and other arbitrary uneven shapes can also be formed by cutting, grinding, pressing using a mold, imprint using a mold, or the like. .

In the present embodiment, as shown in FIG. 2, the concavo-convex member 12 and the filling member 13 have different refractive indexes with respect to incident light in a wavelength of 405 nm band (λ ₁ ), and have a wavelength of 660 nm band (λ ₂ ) and 785 nm. The incident light in the band (λ ₃ ) is composed of an optical material having substantially the same refractive index. The “substantially the same refractive index” described above is not limited to a refractive index that completely matches, but may be a value that can be regarded as substantially the same in use.

In this embodiment, the concavo-convex member 12 is composed of the first optical material A having high wavelength dispersion, and the filling member 13 is composed of the second optical material B having low wavelength dispersion.
The first optical material A having high wavelength dispersion and the second optical material B having low wavelength dispersion will be described in detail later.

In other words, in the present embodiment, the refractive index nA _{12 of} the first optical material A constituting the concavo-convex member 12 and the refractive index nB ₁₃ of the second optical material B constituting the filling member 13 are light having a wavelength λ ₁ . In contrast, | nA ₁₂ −nB ₁₃ |> 0.006, and the relationship of | nA ₁₂ −nB ₁₃ | ≦ 0.006 is satisfied with respect to light having wavelengths λ ₂ and λ ₃ .

The refractive index nA of the optical material A, the refractive index nB of the optical material B, and the difference between these refractive indexes at the wavelengths λ ₁ , λ ₂ , and λ ₃ are the photopolymerizable composition that forms the optical material A. The constituent material of the photopolymerizable composition (β) that forms the product (α) and the optical material B, the blending ratio thereof, and the like can be appropriately adjusted and controlled.

In the present embodiment, the refractive index of the optical material A constituting the concavo-convex member 12 with respect to light having the wavelength λ ₁ is nA ₁₂ (λ ₁ ), and the optical material B constituting the filling member 13 is refracted with respect to light having the wavelength λ _1. rates and _{nB 13 (λ 1), nA} 12 (λ 2) the refractive index for the wavelength lambda ₂ of light of the optical material a constituting the uneven member 12, the wavelength lambda ₂ of the optical material B constituting the filling member 13 When the refractive index with respect to light is nB ₁₃ (λ ₂ ), nA ₁₂ (λ ₁ )> nB ₁₃ (λ ₁ )> 0, | nA ₁₂ (λ ₂ ) −nB ₁₃ (λ ₂ ) | ≦ 0.006 And nA ₁₂ (λ ₁ )> nA ₁₂ (λ ₂ ), nB ₁₃ (λ ₁ )> nB ₁₃ (λ ₂ ), that is, normal dispersion is shown.
In this case, nA ₁₂ (λ ₁ )> nB ₁₃ (λ ₁ )> nA ₁₂ (λ ₂ ), nA ₁₂ (λ ₁ )> nB ₁₃ (λ ₁ )> nB ₁₃ (λ ₂ ), | nA ₁₂ (λ ₂ ) −nB ₁₃ (λ ₂ ) | ≦ 0.006 is satisfied.

Therefore, when the light of wavelength λ ₁ irradiated to the wavelength selective diffraction element 10 according to the present embodiment enters the concavo-convex member 12, it is diffracted and diffracted by the wavelength selective diffraction element 10 as shown in FIG. You can get light. On the other hand, the light having the wavelength λ ₂ that has entered the concavo-convex member 12 passes straight without being diffracted by the wavelength selective diffraction element 10.

If the difference | nA ₁₂ −nB ₁₃ | between the refractive index nA _{12 of} the first optical material A and the refractive index nB _{13 of} the second optical material B for light of wavelength λ ₁ exceeds 0.006, wavelength selection The diffraction element 10 can provide sufficient diffraction efficiency.
The difference | nA ₁₂ −nB ₁₃ | between the refractive index nA ₁₂ of the first optical material A and the refractive index nB _{13 of} the second optical material B with respect to light having the wavelength λ ₁ is 0.015 or more. More preferred.

Further, in the present embodiment, the difference between the refractive index nA _{12 of} the first optical material A and the refractive index nB _{13 of} the second optical material B with respect to light having the wavelengths λ ₂ and λ ₃ | nA ₁₂ −nB _13. If | is 0.006 or less, it is difficult for light of wavelengths λ ₂ and λ ₃ to be diffracted, and light loss and stray light generation are suppressed. The difference | nA ₁₂ −nB ₁₃ | between the refractive index nA _{12 of} the first optical material A and the refractive index nB _{13 of} the second optical material B with respect to light having the wavelengths λ ₂ and λ ₃ is more preferably 0. 0.005 or less.

At this time, for example, the diffraction angle can be controlled by adjusting the grating pitch of the concavo-convex member 12. Further, by changing the grating pattern of the grating height d ₁ or irregularities member 12 can be adjusted and the diffraction efficiency of the transmission efficiency and the diffracted light of the rectilinear light.
In this way, the wavelength-selective diffraction element 10 that exhibits a diffraction function with respect to light with the wavelength λ ₁ and does not function with respect to light with the wavelengths λ ₂ and λ ₃ is obtained.

The grating height d ₁ of the wavelength selective diffraction element 10 is preferably 5 μm to 100 μm, more preferably 5 μm to 45 μm, and even more preferably 5 μm to 30 μm. When the grating height d ₁ is 5 μm or more, a desired diffraction efficiency can be obtained. On the other hand, when the grating height d ₁ is 100 μm or less, the constituent members of the wavelength selective diffraction element 10 are hardly damaged due to external pressure or the like.

The grating pitch of the wavelength selective diffraction element 10 is preferably 1 μm to 1 mm, more preferably 1 μm to 100 μm, and even more preferably 1 μm to 50 μm.
When the grating pitch is 1 μm or more, the wavelength selective diffraction element 10 can be efficiently manufactured. On the other hand, when the grating pitch is 1 mm or less, a desired diffraction efficiency can be obtained.

In the wavelength selective diffraction element 10, the zero-order diffraction efficiency (transmittance) with respect to light of wavelengths λ ₂ and λ _{3 when} the total thickness of the diffraction element 10 is 1 μm or more and 30 μm or less is preferably 90% or more.

(Second Embodiment)
Hereinafter, a wavelength selective diffraction element 20 according to a second embodiment of the present invention will be described with reference to the drawings. Similar to the wavelength selective diffraction element 10 according to the first embodiment of the present invention, the wavelength selective diffraction element 20 according to the present embodiment will be described with reference to an example in which the wavelength selective diffraction element 20 corresponds to the standards of BD, DVD, and CD. Description is omitted.

Here, FIG. 3A is a schematic cross-sectional view showing an operation when light having a wavelength λ ₁ is incident on the wavelength selective diffraction element 20, and FIG. 3B is a wavelength selective diffraction. 3 is a schematic cross-sectional view showing an operation when light having a wavelength λ ₂ is incident on the element 20. FIG.

  As shown in FIG. 3, the wavelength selective diffraction element 20 according to the present embodiment has a transparent substrate 21 and a concavo-convex shape formed on the transparent substrate 21 and periodically formed so as to extend in one direction. The concavo-convex member 22, the filling member 23 filled so as to fill at least the concave portion of the concavo-convex member 22, and a transparent substrate 24 provided on the upper surface of the filling member 23 and protecting the filling member 23.

In the present embodiment, as shown in FIG. 4, the concavo-convex member 22 and the filling member 23 have substantially the same refractive index with respect to incident light in the wavelength 405 nm band (λ ₁ ), and the wavelength 660 nm band (λ ₂ ) and The incident light in the 785 nm band (λ ₃ ) is made of an optical material having a different refractive index.

  In this embodiment, the concavo-convex member 22 is composed of the second optical material B having low wavelength dispersion, and the filling member 23 is composed of the first optical material A having high wavelength dispersion. The first optical material A having high wavelength dispersion and the second optical material B having low wavelength dispersion will be described in detail later.

That is, in the present embodiment, the refractive index nB _{22 of} the second optical material B constituting the concavo-convex member 22 and the refractive index nA ₂₃ of the first optical material A constituting the filling member 23 are light having a wavelength λ ₁ . In contrast, | nA ₂₃ −nB ₂₂ | ≦ 0.006, and the relationship of | nA ₂₃ −nB ₂₂ |> 0.006 is satisfied with respect to light having the wavelength λ ₂ and the wavelength λ ₃ .

The refractive index nA of the optical material A, the refractive index nB of the optical material B, and the difference between these refractive indexes at the wavelengths λ ₁ , λ ₂ , and λ ₃ are the photopolymerizable composition that forms the optical material A. The constituent material of the photopolymerizable composition (β) that forms the product (α) and the optical material B, the blending ratio thereof, and the like can be appropriately adjusted and controlled.

In the present embodiment, the refractive index of the optical material A constituting the filling member 23 with respect to light of wavelength λ ₁ is nA ₂₃ (λ ₁ ), and the refractive index of the optical material B constituting the concavo-convex member 22 with respect to light of wavelength λ ₁ is used. The refractive index for the light of wavelength λ ₂ of the optical material A constituting the filling member 23 is nA ₂₃ (λ ₂ ), and the wavelength λ ₂ of the optical material B constituting the concavo-convex member 22 is assumed to be nB ₂₂ (λ ₁ ). When the refractive index for light is nB ₂₂ (λ ₂ ), | nA ₂₃ (λ ₁ ) −nB ₂₂ (λ ₁ ) | ≦ 0.006, nB ₂₂ (λ ₂ )> nA ₂₃ (λ ₂ )> 0 And nA ₂₃ (λ ₁ )> nA ₂₃ (λ ₂ ), nB ₂₂ (λ ₁ )> nB ₂₂ (λ ₂ ), that is, normal dispersion is shown.
In this case, nB ₂₂ (λ ₁ )> nB ₂₂ (λ ₂ )> nA ₂₃ (λ ₂ ), nA ₂₃ (λ ₁ )> nB ₂₂ (λ ₂ )> nA ₂₃ (λ ₂ ), | nA ₂₃ (λ ₁ ) −nB ₂₂ (λ ₁ ) | ≦ 0.006 is satisfied.

Therefore, the light with the wavelength λ ₁ irradiated to the wavelength selective diffraction element 20 according to the present embodiment has substantially the same refractive index at the concave-convex member 22 and the filling member 23, and as shown in FIG. The concavo-convex member 22 passes straight through without being diffracted by the wavelength selective diffraction element 20.
On the other hand, the light of wavelength λ ₂ is diffracted by the difference in refractive index when entering the concavo-convex member 22 because the refractive index of the concavo-convex member 22 and the refractive index of the filling member 23 are different, as shown in FIG. Diffracted light is obtained.

In the present embodiment, the difference | nA ₂₃ −nB ₂₂ | between the refractive index nA _{23 of} the first optical material A and the refractive index nB _{22 of} the second optical material B with respect to light having the wavelengths λ ₂ and λ ₃ is If it exceeds 0.006, sufficient diffraction efficiency is obtained by the wavelength selective diffraction element 20.
The difference | nA ₂₃ −nB ₂₂ | between the refractive index nA _{23 of} the first optical material A and the refractive index nB _{22 of} the second optical material B with respect to light having the wavelengths λ ₂ and λ ₃ is 0.013 or more. Is more preferable.

In this embodiment, the difference | nA ₂₃ −nB ₂₂ | between the refractive index nA _{23 of} the first optical material A and the refractive index nB _{22 of} the second optical material B with respect to light having the wavelength λ ₁ is 0. If it is 006 or less, it is difficult for light of wavelength λ ₁ to be diffracted, and light quantity loss and stray light are suppressed.
The difference | nA ₂₃ −nB ₂₂ | between the refractive index nA ₂₃ of the first optical material A and the refractive index nB _{22 of} the second optical material B with respect to light having the wavelength λ ₁ is more preferably 0.005 or less. is there.

At this time, for example, the diffraction efficiency can be adjusted by adjusting the grating height d ₂ and the grating shape of the concavo-convex member 22. Further, the diffraction angle can be controlled by adjusting the grating pitch of the concavo-convex member 22. In this manner, the wavelength selective diffraction element 20 that does not function with respect to the light with the wavelength λ ₁ but exhibits the diffraction function with respect to the light with the wavelengths λ ₂ and λ ₃ is obtained.

The preferable range of the grating height d ₂ and the grating pitch of the wavelength selective diffraction element 20 is the same as the preferable range of the grating height d ₁ and the grating pitch of the wavelength selective diffraction element 10 described in the first embodiment. It is.

In the wavelength selective diffraction element 20, the first-order diffraction efficiency with respect to light of wavelengths λ ₂ and λ _{3 when} the total thickness of the diffraction element 20 is 1 μm or more and 30 μm or less is preferably 20% or more.
However, when the thickness of the entire diffraction element 20 is 1 μm or more and 5 μm, even if the first-order diffraction efficiency for light of wavelengths λ ₂ and λ ₃ is 20% or less, it is 90% or more of 0 for light of wavelength λ _1. When the next diffraction efficiency (transmittance) can be obtained, it may have an advantage of being used as a wavelength selective diffraction element. Therefore, in this case, the first-order diffraction efficiency is not necessarily 20% or more.

Further, in the wavelength selective diffraction element 20, the zero-order diffraction efficiency for the wavelength lambda ₁ of the light in the following diffraction element 20 overall thickness 1μm or 30 [mu] m (transmittance) is preferably 90% or more.

[Photopolymerizable composition (β)]
The second optical material B having low wavelength dispersion is composed of zirconium oxide particles having an average particle diameter of 3 nm or more and 15 nm or less coated with a surface modifier having a polymerizable binding group, one polymerizable group, and the number of carbon atoms. It is comprised with the hardening body formed by photopolymerizing the photopolymerizable composition ((beta)) containing the monofunctional compound which has 10 or more and 14 or less alicyclic structure.

(Zirconium oxide)
Zirconium oxide particles are added and dispersed in the polymerizable monomer in order to control optical properties such as the refractive index and wavelength dispersion of the photopolymerizable composition.
Zirconium oxide has a higher refractive index and smaller wavelength dispersion of the refractive index than other inorganic fine particles such as aluminum oxide. Therefore, by dispersing this in a polymerizable monomer, zirconium oxide has a high refractive index, and A photopolymerizable composition (β) having low wavelength dispersion is obtained.
In addition, since zirconium oxide does not have an absorption band in the visible range of 400 to 800 nm, it is a composition (β) in which modification of the resin material due to light irradiation is suppressed.

Zirconium oxide can take a crystal form such as monoclinic system, tetragonal crystal, cubic crystal, etc., but any crystal form may be used as long as it meets the purpose of the present invention (high refractive index, low wavelength dispersion).
Zirconium oxide may be crystalline or amorphous, and is preferably crystalline from the viewpoint of obtaining a high refractive index.

The average particle diameter of the zirconium oxide particles is 3 nm or more and 15 nm or less.
When the average particle diameter of the zirconium oxide particles is 3 nm or more, an increase in the particle surface area is suppressed, and an increase in the amount of the surface modifier per volume of the zirconium oxide particles in the composition is suppressed. For this reason, the relative fall of the content rate of the zirconium oxide in a composition by the increase in the amount of surface modifiers is suppressed, and the effect which raises a refractive index is fully acquired.
Further, when the average particle diameter of the zirconium oxide particles is 3 nm or more, a sufficient refractive index can be obtained with an appropriate addition amount, and an increase in the viscosity of the composition is suppressed. Therefore, when this is applied on the substrate, the application amount and the in-plane distribution can be easily controlled, and excellent moldability can be obtained.
On the other hand, when the average particle diameter of the zirconium oxide particles is 15 nm or less, the average particle diameter of the secondary particles by the aggregated particles is 30 nm or less, and in the optical material B after photocuring, transmission loss due to scattering does not occur and excellent transmission is achieved. You can get a rate.
The average particle diameter of the zirconium oxide particles is more preferably 6 nm or more and 14 nm or less from the viewpoint of suppressing a decrease in moldability due to an increase in viscosity and obtaining a high refractive index and a high transmittance.
Further, the proportion of particles of 30 nm or more in the average particle size distribution of zirconium oxide particles is preferably less than 1%.

(Surface modifier)
The surface coating agent is provided so as to cover the surface of the particles in order to enhance the compatibility between the zirconium oxide particles and the polymerizable monomer component, and can be used without particular limitation as long as it has a polymerizable group.

  Examples of the surface modifier include silane coupling agents, titanate coupling agents, aluminate coupling agents, organic acids (carboxylic acids, sulfonic acids, phosphoric acids, phosphonic acids, etc.) or dispersants having organic acid groups. Used. Among these, a silane coupling agent is preferable because it can form a metalloxane bond (Si-OM) on the particle surface by reaction with zirconium oxide to obtain high stability and has low hygroscopicity.

  In addition, conventionally known conditions can be applied to the reaction between the silane coupling agent and zirconium oxide. For example, a catalyst such as an acid or an alkali may be used, or heating may be performed.

The polymerizable group of the surface modifier is not particularly limited, but the group containing a double bond forms a dense cured product (optical material) by reaction with the (meth) acrylic group of the photopolymerizable compound described later. Since it can be used, it is preferably used. Specifically, for example, an acryl group, a methacryl group, an allyl group, and a vinyl group are preferable.
Among these, an acryl group and a methacryl group are preferable as the polymerizable group in the photopolymerizable composition because a change in refractive index accompanying a temperature change can be suppressed.

  As the silane coupling agent, for example, compounds represented by the following general formulas (1) to (5) can be used.

（式（１）中、Ａは水素原子又はメチル基を表し、Ｘはそれぞれ独立に水素原子、メチル基又はエチル基を表し、Ｒは水素原子、メチル基又はエチル基を表し、ｎは１〜６の整数を表し、ｍは１〜３の整数を表す。）

(In Formula (1), A represents a hydrogen atom or a methyl group, X represents a hydrogen atom, a methyl group, or an ethyl group each independently, R represents a hydrogen atom, a methyl group, or an ethyl group, and n is 1- 1). 6 represents an integer, and m represents an integer of 1 to 3.)

Examples of the compound represented by the formula (1) (compound (1)) include 3-methacryloxypropyldimethylmethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxy. Examples include propyldimethylethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.
More preferably, the compound (1) is 3-methacryloxypropyltrimethoxysilane or 3-acryloxypropyltrimethoxysilane.

（式（２）中、Ｘはそれぞれ独立に水素原子、メチル基又はエチル基を表し、Ｒは水素原子、メチル基又はエチル基を表し、ｎは１〜６の整数を表し、ｍは１〜３の整数を表す。）

(In formula (2), X represents a hydrogen atom, a methyl group, or an ethyl group each independently, R represents a hydrogen atom, a methyl group, or an ethyl group, n represents the integer of 1-6, m is 1-. Represents an integer of 3.)

  Examples of the compound represented by formula (2) (compound (2)) include 3-allyloxyethyltrimethoxysilane, 3-allyloxyethyltriethoxysilane, 2-allyloxypropyltrimethoxysilane, and the like. 3-Allyloxypropyltrimethoxysilane is preferred.

（式（３）中、Ｘはそれぞれ独立に水素原子、メチル基又はエチル基を表し、Ｒは水素原子、メチル基又はエチル基を表し、ｎは０〜６の整数を表し、ｍは１〜３の整数を表す。）

(In Formula (3), X represents a hydrogen atom, a methyl group, or an ethyl group each independently, R represents a hydrogen atom, a methyl group, or an ethyl group, n represents the integer of 0-6, m is 1-. Represents an integer of 3.)

  Specific examples of the compound represented by the formula (3) (compound (3)) include vinyloxytrimethoxysilane and vinyloxytriethoxysilane, with vinyloxytrimethoxysilane being preferred.

（式（４）中、Ｘはそれぞれ独立に水素原子、メチル基又はエチル基を表し、Ｒは水素原子、メチル基又はエチル基を表し、ｎは０〜６の整数を表し、ｍは１〜３の整数を表す。）

(In Formula (4), X represents a hydrogen atom, a methyl group, or an ethyl group each independently, R represents a hydrogen atom, a methyl group, or an ethyl group, n represents the integer of 0-6, m is 1-. Represents an integer of 3.)

  Examples of the compound represented by formula (4) (compound (4)) include vinyltrimethoxysilane, vinyltriethoxysilane, and allyltrimethoxysilane, and vinyltrimethoxysilane is preferable.

（式（５）中、Ｘはそれぞれ独立に水素原子、メチル基又はエチル基を表し、Ｒは水素原子、メチル基又はエチル基を表し、ｎは０〜６の整数を表し、ｍは１〜３の整数を表す。）

(In Formula (5), X represents a hydrogen atom, a methyl group, or an ethyl group each independently, R represents a hydrogen atom, a methyl group, or an ethyl group, n represents the integer of 0-6, m is 1-. Represents an integer of 3.)

  Examples of the compound represented by formula (5) (compound (5)) include 5- (bicycloheptenyl) triethoxysilane and (bicycloheptenyl) ethyltrimethoxysilane, and preferably (bicycloheptenyl). Ethyltrimethoxysilane.

  Among the above compounds (1) to (5), the compound (1) represented by the general formula (1) has a (meth) acrylic group, and its refractive index variation due to temperature change is suppressed, and it is polymerizable. Since it reacts with the monomer component to obtain a dense molded body, it is preferably used.

The addition amount of the surface modifier is preferably 15 to 40% by mass with respect to the zirconium oxide particles.
When the addition amount of the surface modifier is 15% by mass or more with respect to the zirconium oxide particles, the compatibility between the zirconium oxide and the resin is sufficiently enhanced.
On the other hand, when the addition amount of the surface modifier is 40% by mass or less with respect to the zirconium oxide particles, the relative decrease in the content of zirconium oxide in the photopolymerizable composition (β) is suppressed, and a sufficient refractive index is obtained. Is obtained.

The content of zirconium oxide in the photopolymerizable composition (β) is preferably 45 to 70% by mass, and preferably 45 to 60% by mass.
When the content of zirconium oxide is 45% by mass or more, a sufficient refractive index is obtained in the photopolymerizable composition (β), and for example, a refractive index of 1.6 or more is obtained at a wavelength of 589 nm.
On the other hand, when the content of zirconium oxide is 70% by mass or less, an increase in the viscosity of the photopolymerizable composition (β) is suppressed, and when this is coated on a substrate, the coating amount and in-plane distribution can be easily controlled. Excellent moldability and easy to apply and mold on the substrate.

(Monofunctional compound (I))
The monofunctional compound (I) is a monomer that undergoes a photopolymerization reaction by irradiation with ultraviolet rays or the like, has an alicyclic structure having 10 to 14 carbon atoms as a main skeleton, and one polymerizable in one molecule. It has a group. In particular, those having an alicyclic structure having a three-dimensional cross-linked structure are preferable because the molecules have a high density and a high refractive index can be obtained.
When the carbon number of the alicyclic structure is 10 or more, the effect of increasing the refractive index can be sufficiently obtained. In addition, a stable bond angle between carbon and carbon is sufficiently secured, and the molecular skeleton of the entire monofunctional compound (I) is stable with little distortion.
On the other hand, when the alicyclic structure has 14 or less carbon atoms, it is in a liquid state at room temperature and is easy to handle. The number of carbon atoms in the alicyclic structure is more preferably 10-12.

  Examples of the alicyclic structure of the monofunctional compound (I) include adamantane (formula (6), carbon number 10) represented by the following formulas (6) to (9), tricyclodecane (formula (7), Carbon number 10), tetracyclododecane (formula (8), carbon number 12), diamantane (formula (9), carbon number 14), or the like is preferably used because a high refractive index can be obtained.

  Although it does not specifically limit as a polymeric group of monofunctional compound (I), Since an acryl group and a methacryl group have high photoreactivity, they are used suitably.

  Examples of the monofunctional compound (I) include 1-adamantyl acrylate, 1-adamantyl methanol acrylate, 1-adamantyl ethanol acrylate, 2-methyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl acrylate, 2-propyl- 2-adamantyl acrylate, 2-butyl-2-adamantyl acrylate, tricyclodecane acrylate, tricyclodecane methanol acrylate, tricyclodecane-ethanol acrylate, tetracyclododecanyl acrylate, diamantyl acrylate, 2-methyl-2- Examples include diamantyl acrylate, 2-ethyl-2-diamantyl acrylate, and methacrylates thereof. Preferably, adamantyl acrylate, 2-methyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl acrylate, tricyclodecane acrylate, and diamantyl acrylate are preferably exemplified.

(Polyfunctional compound (II))
Moreover, it is preferable that the photopolymerizable composition ((beta)) which comprises the optical material B contains polyfunctional compound (II) with the monofunctional compound (I) mentioned above.
The polyfunctional compound (II) is a monomer that undergoes a photopolymerization reaction upon irradiation with ultraviolet rays or the like, has an alicyclic structure having 10 to 14 carbon atoms as a main skeleton, and two or more polymerizations in one molecule. It has a sex group.

In the photopolymerizable composition (β), the monofunctional compound (I) as a polymerizable monomer component has a low-flexibility alicyclic structure, and further contains zirconium oxide particles that are inferior in flexibility. The molded body after photocuring tends to be brittle, and when the polymerizable monomer component is only the monofunctional compound (I), breakage or the like is likely to occur when the mold of the photoimprint is released. Such a tendency becomes more conspicuous as the particle diameter of the zirconium oxide particles increases and the content thereof increases.
In the photopolymerizable composition (β), in addition to the monofunctional compound (I), the polyfunctional compound (II) is further contained, so that the molded body obtained by curing the photopolymerizable composition (β) has brittleness. An optical material B that is improved and excellent in releasability is obtained.

  As in the case of the monofunctional compound (I), the alicyclic structure of the polyfunctional compound (II) has a three-dimensional cross-linked structure, which has a high molecular structure and a high refractive index. Therefore, it is preferable.

When the alicyclic skeleton has 10 or more carbon atoms, the effect of increasing the refractive index is sufficiently obtained. In addition, a stable bond angle between carbon and carbon is sufficiently secured, and the molecular skeleton of the entire polyfunctional compound (II) becomes stable with little distortion.
On the other hand, when the alicyclic skeleton has 14 or less carbon atoms, it is in a liquid state at room temperature and is easy to handle. The number of carbon atoms in the alicyclic structure is more preferably 10-12.

  As the alicyclic structure of the polyfunctional compound (II), from the viewpoint of obtaining a high refractive index, the adamantane represented by the above formulas (6) to (9) is the same as that of the monofunctional compound (I) described above. , Tricyclodecane, tetracyclododecane, diamantane and the like are preferable.

Although it does not specifically limit as a polymeric group of polyfunctional compound (II), Since an acrylic group and a methacryl group have high photoreactivity, they are used suitably.
The number of polymerizable groups contained in the polyfunctional compound (II) is preferably 2 or more, more preferably 2 to 4.

  Examples of the polyfunctional compound (II) include tricyclodecane diacrylate, tricyclodecane dimethanol diacrylate, adamantane diacrylate, adamantane dimethanol diacrylate, diamantane diacrylate, diamantane dimethanol diacrylate, and adamantane tri An acrylate etc. are mentioned, Preferably a bifunctional tricyclodecane dimethanol diacrylate and an adamantane diacrylate are mentioned as a suitable thing.

The content of the monofunctional compound (I) in the photopolymerizable composition (β) is preferably 15% by mass or more and 45% by mass or less, and more preferably 20% by mass or more and 45% by mass or less.
When the content of the monofunctional compound (I) is 15% by mass or more, it is easy to obtain an appropriate viscosity in the photopolymerizable composition (β), and the film forming property is excellent.
On the other hand, when the content of the monofunctional compound (I) is 45% by mass or less, the content of zirconium oxide particles can be relatively increased in the photopolymerization composition (β), and a high refractive index can be obtained. Cheap.

The content of the polyfunctional compound (II) in the photopolymerizable composition (β) is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.
When the content of the polyfunctional compound (II) is 1% by mass or more, damage due to the external pressure of the optical material B, which is a cured product of the photopolymerizable composition (β), is suppressed, and peeling or the like hardly occurs during release. , Improve product yield.
On the other hand, when the content of the polyfunctional compound (II) is 30% by mass or less, an excessive increase in the strength of the optical material B, which is a cured product of the photopolymerizable composition (β), is suppressed. Excellent adhesion can be obtained. For this reason, peeling of the optical material B from the substrate surface hardly occurs, and the yield of products is improved.

The content ratio (mass ratio) of the monofunctional compound (I) and the polyfunctional compound (II) in the photopolymerizable composition (β) is monofunctional compound (I) / polyfunctional compound (II). 1-40 are preferable.
When the monofunctional compound (I) / polyfunctional compound (II) is 1 or more, an excessive increase in the strength of the optical material B, which is a cured product of the photopolymerizable composition (β), is suppressed, and quartz glass, etc. Excellent adhesion to the substrate.
On the other hand, when the monofunctional compound (I) / polyfunctional compound (II) is 40 or less, sufficient strength can be obtained in the optical material B, which is a cured product of the photopolymerizable composition (β), and it is destroyed when released. It is hard to produce etc.

[Photopolymerizable composition (α)]
As the first optical material A having high wavelength dispersibility, a material obtained by photopolymerizing a photopolymerizable composition (α) containing an aromatic compound is preferable because it is excellent in high wavelength dispersibility.

  As the aromatic compound in the photopolymerizable composition (α), one having a phenyl skeleton, a biphenyl skeleton, or a fluorene skeleton is preferable because higher wavelength dispersibility can be obtained. Aromatic compounds having one or more polymerizable groups are preferred because of excellent photoreactivity.

  As an aromatic compound contained in a photopolymerizable composition ((alpha)), what is shown, for example by following formula (10)-(12) is preferable.

However, the symbols in the above formulas (10) to (12) have the following meanings.
A: A hydrogen atom or a group selected from the following formulas (13) to (16).
V _w H _(3-W) C- (13)
Ph _x Y _(3-x) Si- (14)
_{J- (CH 2) m1 -CH l} (CH 3) (2-l) - ··· (15)
_{J- (CH 2) n1 -SiPh p1} (CH 3) (2-p1) - ··· (16)
B: Group selected from the following formulas (17) to (18).
_{J- (CH 2) m2 -CH k} (CH 3) (2-k) - ··· (17)
_{J- (CH 2) n2 -SiPh p2} (CH 3) (2-p2) - ··· (18)
w: integer of 0-3.
V: A methyl group or an ethyl group. However, when w is 2 to 3, V may be different groups.
x: An integer from 0 to 3.
Y: a group selected from a methyl group, a cyclohexyl group, a tert-butyl group, a sec-butyl group, and an iso-propyl group. However, when x is 0 or 1, Y may be a different group.
J: A group selected from CH ₂ ═CR—COO—, an epoxy group, a vinyl group and a vinyl ether group.
R: a hydrogen atom or a methyl group.
l: An integer from 0 to 1.
k: an integer of 0-2. However, k excludes 2 when A is a hydrogen atom.
_{m 1,} m _2: 0~12 independently of each other.
_{n 1,} n _2: each independently 1-12. _{p 1,} p _2: 0~2 independently of each other.

  However, a part or all of the hydrogen atoms of the substituent V in the formula (13), the phenyl group and the substituent Y in the formula (14), and the alkylene group in the formulas (15) to (18) are a methyl group, a methoxy group, It may be substituted with a fluorine atom, and a part or all of the hydrogen atoms of the biphenyl group or biphenylene group may be substituted with a methyl group, a methoxy group, or a fluorine atom.

  As the polymerizable group of the aromatic compound, an acryl group or a methacryl group is preferably used because of high photoreactivity.

The photopolymerizable composition (α) constituting the first optical material A having high wavelength dispersibility may contain one aromatic compound, or a mixture of two or more aromatic compounds. There may be. It is preferable to contain at least one of the aromatic compounds represented by the above formulas (10) to (12) (hereinafter referred to as aromatic compounds (10) to (12)).
In addition, a photopolymerizable composition ((alpha)) may be comprised only with one compound, for example, may be comprised only with any one compound of aromatic compounds (10)-(12).

The content of the aromatic compounds (10) to (12) in the photopolymerizable composition (α) is preferably 50% by mass or more.
When the content of the aromatic compounds (10) to (12) is 50% by mass or more, sufficiently high wavelength dispersibility is obtained in the optical material A obtained after photopolymerization of the photopolymerizable composition (α). .

  To the photopolymerizable composition (α) and the photopolymerizable composition (β), other components such as a photopolymerization initiator and a stabilizer such as an ultraviolet absorber, an antioxidant, and a light stabilizer are added. it can.

(Photopolymerization initiator)
Examples of the photopolymerization initiator include acetophenones, benzophenones, acylphosphine oxides, benzoins, benzyls, Michler ketones, benzoin alkyl ethers, benzyl dimethyl ketals, etc. Two or more kinds can be appropriately selected and used.
As acetophenones, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)- Butanone-12- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2-hydroxy-1- {4- [4- (2-Hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, and the like.
Examples of the acylphosphine oxides include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -diphenyl-phosphine oxide, and the like.

The addition amount of the photopolymerization initiator is 0.01% by mass to 5% by mass with respect to the total amount of each photopolymerizable composition in each of the photopolymerizable composition (α) and the photopolymerizable composition (β). Is preferable, and 0.1% by mass to 2% by mass is more preferable.
When the addition amount of the photopolymerization initiator is 5% by mass or less, the photopolymerizable composition is hardly colored.
On the other hand, when the addition amount of the photopolymerization initiator is 0.01% by mass or more, the photopolymerization reaction proceeds sufficiently.

  Examples of the ultraviolet absorber include TINUBIN P (manufactured by Ciba Specialty Chemical), TINUBIN 234 (manufactured by Ciba Specialty Chemical), TINUBIN 326 (manufactured by Ciba Specialty Chemical), TINUBIN 328 (manufactured by Ciba Specialty Chemical), and TINUBIN 329 (Ciba Specialty Chemical). TINUBIN 213 (manufactured by Ciba Specialty Chemical), TINUBIN 571 (manufactured by Ciba Specialty Chemical), TINUBIN 1577FF (manufactured by Ciba Specialty Chemical).

  Examples of the antioxidant include 2-normal dodecylphenol, para-methoxyphenol, pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (IRGANOX 1010, Ciba Specialty Chemical), 2,2-thio-diethylenebis [2- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (IRGANOX 1035, manufactured by Ciba Specialty Chemicals), octadecyl-3- (3 5-di-t-butyl-4-hydroxyphenyl) propionate (IRGANOX1076, manufactured by Ciba Specialty Chemicals), N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnama) Mid) (IRGANOX 1098, Ciba ), Isooctyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (IRGANOX 1135, manufactured by Ciba Specialty Chemicals), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (IRGANOX 1330, manufactured by Ciba Specialty Chemicals), 2,4-bis [(octylthio) methyl] -o-cresol (IRGANOX 1520L, manufactured by Ciba Specialty Chemicals) ), Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (IRGANOX245, manufactured by Ciba Specialty Chemicals), 1,6-hexanediol-bis [3- ( 3,5-di-tert-butyl-4-hydride Xylphenyl) propionate] (IRGANOX259, manufactured by Ciba Specialty Chemicals), 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5- Triazine (IRGANOX565, manufactured by Ciba Specialty Chemicals), octadecyl 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate (AO-50, manufactured by ADEKA), tetra-3- (3 ′ , 5′-di-t-butyl-4′-hydroxyphenyl) propoxybutane (AO-60, manufactured by ADEKA), 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionic acid Methyl (AO-50Me, manufactured by ADEKA), 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenylpropionic acid) Sooctyl (AO-50iso-Octyl, manufactured by ADEKA), hydroquinone and the like can be mentioned.

  Examples of the light stabilizer include TINUBIN 144 (manufactured by Ciba Specialty Chemicals), TINUBINTINUBIN 765 (manufactured by Ciba Specialty Chemicals), TINUBIN 770DF (manufactured by Ciba Specialty Chemicals), CHIMASSORB 2020FDL (manufactured by Ciba Specialty Chemicals), and CHIMASSORB TINUBIN 622LD (manufactured by Ciba Specialty Chemical), TINUBIN 123 (manufactured by Ciba Specialty Chemical), LA62 (manufactured by ADEKA), LA67 (manufactured by ADEKA) and the like.

The content of stabilizers such as ultraviolet absorbers, antioxidants, and light stabilizers is the total amount of each photopolymerization in the photopolymerizable composition (α) and the photopolymerizable composition (β). 5 mass% or less is preferable with respect to the whole quantity (100 mass%) of an adhesive composition, and 2 mass% or less is more preferable.
When the stabilizer is 5% by mass or less, the durability against blue laser is excellent and the weather resistance is excellent.

[Method for Producing Photopolymerizable Composition (β)]
The photopolymerizable composition (β) comprises surface-coated zirconium oxide particles, monofunctional compound (I), polyfunctional compound (II) and other components such as the polymerization initiator and stabilizer described above. Can be manufactured by mixing.

In the production of the photopolymerizable composition (β), a solvent may be used for the convenience of the production process.
The solvent is a compound that dissolves at least one of the monofunctional compound (I), the polyfunctional compound (II), the photopolymerization initiator, and the stabilizer, and has a boiling point of 200 ° C. or less at normal pressure. Are preferred, and compounds of 150 ° C. or lower are more preferred. A compound having a boiling point of 200 ° C. or lower does not require heating at a high temperature to remove the compound. Therefore, when removing the compound, the monofunctional compound (I), polyfunctional compound (II), light Deterioration or volatilization of polymerization initiators and stabilizers hardly occurs.

  Solvents include dichloromethane, chloroform, carbon tetrachloride, dichloroethane, cyclohexane, methylcyclohexane, ethylcyclohexane, toluene, xylene, diethyl ether, tetrahydrofuran, dioxane, isobutyl acetate, nbutyl acetate, isopentyl acetate, ethyl butyrate, PGMEA, butanol, Examples thereof include tert-butanol, 2-butanone, 4-methyl-2-pentanone, γ-butyrolactone, cyclohexanone, N-methyl-2-pyrrolidinone and the like.

  Specifically, the photopolymerizable composition (β) can be produced by removing the solvent from, for example, (i) a dispersion in which zirconium oxide particles are dispersed in a solvent (hereinafter also simply referred to as a dispersion of zirconium oxide particles). Then, the monofunctional compound (I), the polyfunctional compound (II), a polymerization initiator, a method of adding a stabilizer and mixing, (ii) the monofunctional compound (I ), Adding a polyfunctional compound (II), a polymerization initiator and a stabilizer, then removing the solvent and mixing, (iii) adding the monofunctional compound (I) to the dispersion of zirconium oxide particles And a method of adding a polyfunctional compound (II), a polymerization initiator and a stabilizer and mixing them after removing the solvent.

The residual solvent amount of the photopolymerizable composition (β) is preferably 1% by mass or less, and more preferably 0.5% by mass or less, with respect to the entire photopolymerizable composition (β) (100% by mass). When the residual solvent amount of the photopolymerizable composition (β) is 1% by mass or less, bubbles are hardly generated in the molded body of the photopolymerizable composition (β), and a uniform optical material B can be obtained. Further, the substrate surface is hardly damaged by the solvent in the photopolymerizable composition (β).
Furthermore, since the alicyclic compound such as the monofunctional compound (I) described above is easily sublimated, if the residual solvent amount of the photopolymerizable composition (β) is large, the composition is removed when the solvent is removed by heat treatment. The ratio is likely to vary, and it is difficult to precisely adjust the composition of each component, and the refractive index of the optical material B obtained after photocuring is likely to vary.
When the residual solvent amount of the photopolymerizable composition (β) is 1% by mass or less with respect to the entire photopolymerizable composition (β), the above-mentioned phenomenon due to solvent removal hardly occurs, and the refractive index variation is suppressed. The

  The photopolymerizable composition (α) can be produced by mixing the aromatic compounds represented by the above formulas (10) to (12) with other components such as the polymerization initiator and the stabilizer described above.

  Mixing of each component of the photopolymerizable composition (α) and the photopolymerizable composition (β) is carried out by stirring with a stirrer chip, rotating and rotating rotary mixer, three roll mill, bead mill disperser, ultrasonic disperser, etc. The method by stirring used is mentioned.

The viscosity of the photopolymerizable composition (α) and the photopolymerizable composition (β) is preferably from 100 mPa · s to 10000 mPa · s, more preferably from 500 mPa · s to 8500 mPa · s, at 25 ° C.
When the viscosity at 25 ° C. of the photopolymerizable composition is 10000 mPa · s or less, the amount of outside air is small and bubbles are not easily mixed into the molded body, and a uniform optical material is obtained. In this case, good fluidity is obtained in the photopolymerizable composition, and a film having a uniform thickness can be formed on the substrate.
On the other hand, when the viscosity at 25 ° C. of the photopolymerizable composition is 100 mPa · s or more, a sufficient film thickness can be secured, for example, during film formation by spin coating or the like.

[Method of manufacturing wavelength selective diffraction element]
The wavelength selective diffraction element of the present invention can be formed by applying the above-described photopolymerizable composition (α) and photopolymerizable composition (β) onto a substrate and then photocuring them.

  A known method can be used for manufacturing the wavelength selective diffraction element. When a grating-shaped optical material is formed, a processing method using optical imprinting is preferable.

  Hereinafter, the wavelength selective diffraction element 10 of the first embodiment will be described as an example with reference to FIG.

The optical imprint method can be performed by, for example, the following steps (a) to (g).
(A) The process of apply | coating a photopolymerizable composition ((alpha)) on a transparent base material, and forming the coating layer of a photopolymerizable composition ((alpha)).
(B) A step of pressing a mold having a reversal pattern of a lattice pattern to be formed on the coating layer of the photopolymerizable composition (α) formed on the substrate.
(C) A step of forming a cured layer by irradiating the coating layer with a light beam such as ultraviolet rays and curing the photopolymerizable composition (α) while being pressurized through a mold.
(D) A step of separating the mold from the cured layer of the photopolymerizable composition (α) to obtain a molded body having a lattice pattern formed on the surface.
(E) The process of apply | coating a photopolymerizable composition ((beta)) on the cured layer of a photopolymerizable composition ((alpha)), and forming the application layer of a photopolymerizable composition ((beta)).
(F) A step of pressing a transparent substrate onto the coating layer of the photopolymerizable composition (β).
(G) In a state of being pressurized through a transparent substrate, the photopolymerizable composition (β) is irradiated with light such as ultraviolet rays to form a cured layer by curing the photopolymerizable composition (β). Process.

<Process (a)>
As shown in FIG. 5A, an uncured photopolymerizable composition (α) is applied onto the adhesive layer 15 formed on the surface of the flat substrate 11 by a spin coat method or the like, and photopolymerizable. The coating layer 12a of the composition (α) is formed.

  Examples of the coating method of the photopolymerizable composition (α) include spin coating, roll coating, casting, dip coating, die coating, and bar coating, and the coating of the photopolymerizable composition (α). The spin coating method is preferable from the viewpoint of the uniformity of the thickness of the layer 12a and the ease of application. The application of the photopolymerizable composition (α) may be performed under normal pressure or under reduced pressure of 3000 Pa or more. It is preferable to carry out in an environment (yellow room or the like) where the photopolymerizable composition (α) is not exposed to light. Moreover, it is preferable to carry out in air, and you may carry out in inert gas atmospheres, such as nitrogen atmosphere and a carbon dioxide atmosphere.

The coating treatment may be performed while heating with a heating device such as a hot plate. In this case, the viscosity of the composition may decrease and work efficiency may improve. The heating temperature during the coating treatment is preferably 100 ° C. or lower.
When the heating temperature is 100 ° C. or less, unintended thermal polymerization reaction and volatilization of the polymerizable monomer component hardly occur, and the obtained molded article has good reproducibility of the refractive index.

<Step (b)>
As shown in FIG.5 (b), it has the reverse pattern of the lattice pattern which should be formed in the pressure reduction atmosphere on the coating layer 12a of the photopolymerizable composition ((alpha)) formed in the process (a) on the surface. The mold 16 is pressed. At this time, in a reduced pressure atmosphere such as a vacuum environment, air is not involved, and defects due to entrainment of bubbles when the lattice pattern is transferred to the molded body can be reduced. Here, the vacuum environment refers to a reduced pressure atmosphere of 3000 Pa or more. If it is a pressure-reduced atmosphere of 3000 Pa or more, the composition will not change significantly due to volatilization of the photopolymerizable composition (α).

<Step (c)>
As shown in FIG. 5C, while pressing the coating layer 12a of the photopolymerizable composition (α) through the mold 16 or the substrate 11, either the substrate 11 or the mold 16 from the side that transmits ultraviolet rays, Ultraviolet rays are irradiated to completely cure the photopolymerizable composition (α) of the coating layer 12a.

  The pressing is preferably performed from the mold 16 side, the substrate 11 side, or both sides. Examples of the pressing method include a mechanical pressing method, a gas or liquid pressing method, and the like. The press pressure (gauge pressure) is preferably more than 0 to 10 MPa, more preferably 0.1 to 5 MPa. 0-100 degreeC is preferable and the temperature at the time of pressurizing has more preferable 10-80 degreeC.

  The photocuring reaction of the photopolymerizable composition (α) is performed using light such as ultraviolet light or visible light. The light beam used for the photocuring reaction is selected according to the purpose, and the wavelength is not particularly limited, and high reactivity is obtained, and therefore ultraviolet light is preferable.

Examples of ultraviolet light sources include ultraviolet LEDs, germicidal lamps, ultraviolet fluorescent lamps, carbon arcs, xenon lamps, high pressure mercury lamps for copying, medium or high pressure mercury lamps, ultrahigh pressure mercury lamps, electrodeless lamps, metal halide lamps, natural light, etc. A high-pressure mercury lamp is preferable from the viewpoint of simplicity of curing control. The ultraviolet light source is preferably a light source that generates ultraviolet light in a wavelength region of 450 to 200 nm, and may be a light source that emits ultraviolet light having a single wavelength or a light source that emits ultraviolet light including a plurality of wavelengths. Illuminance of light having a wavelength of 365nm in the ultraviolet is at 1 mW / cm ² or more, 5 mW / cm ² or more. When the illuminance at a wavelength of 365 nm is 1 mW / cm ² or more, the time until the photopolymerizable composition (α) is cured is reasonably short, and the productivity is good.

  The mold 16 is preferably a mold made of a non-translucent material or a translucent material. Examples of the non-translucent material include silicon, nickel, copper, stainless steel, titanium, SiC, and mica. Examples of the light transmissive material include quartz, glass, polydimethylsiloxane, cyclic polyolefin, polycarbonate, polyethylene terephthalate, and transparent fluororesin. Among these, quartz glass is preferable as a material for the molding material because it has a high ultraviolet transmittance and has few restrictions on the irradiation direction.

  The mold 16 has a reverse pattern on the surface. The inverted pattern is a pattern obtained by inverting the lattice pattern to be formed on the surface of the molded body. The reverse pattern has fine convex portions and / or concave portions. As a convex part, the elongate ridge etc. which extend on the surface of a mold are mentioned. Examples of the recess include a long groove extending on the surface of the mold.

  Examples of the shape of the center line along the longitudinal direction of the ridge or groove include a straight line, a curved line, a bent straight line, and the like. A plurality of ridges or grooves may exist in parallel and have a stripe shape. Examples of the cross-sectional shape of the ridge or groove in the direction perpendicular to the longitudinal direction include a rectangle, a trapezoid, a triangle, and a semicircle.

  The average width of the ridges or grooves is preferably 1 nm to 50 mm, more preferably 1 nm to 500 μm, and even more preferably 10 nm to 100 μm. The width of the ridge means the length of the base in the cross section in the direction orthogonal to the longitudinal direction. The width of the groove means the length of the upper side in the cross section in the direction orthogonal to the longitudinal direction.

  The average height of the protrusions is preferably 1 nm to 50 mm, more preferably 1 nm to 500 μm, and even more preferably 10 nm to 50 μm. The average depth of the recesses is preferably 1 nm to 50 mm, more preferably 1 nm to 500 μm, and even more preferably 10 nm to 50 μm.

The surface of the mold 16 is preferably subjected to a surface treatment with a release agent in order to improve the peelability between the photopolymerizable composition (α) and the mold surface.
Although it does not restrict | limit especially as a mold release agent used for the surface treatment of the mold 16, It can hydrolyze to a silicon atom from the point of the mold release property with respect to the optical material which hardens a photopolymerization composition, and the adhesiveness to a mold. A fluorine-containing organosilane compound having a group bonded thereto is preferred. In particular, a fluorine-containing organic silane compound having an alkoxysilyl group and a silanol group is preferable because it can react with quartz glass to obtain high adhesion.
Specifically, for example, OPTOOL DSX (trade name, manufactured by Daikin Industries, Ltd.), Novec EGC-1720 (trade name, manufactured by Sumitomo 3M Limited), trimethoxy (1H, 1H, 2H, 2H-perfluorodecyl) silane, Commercial release agents such as trimethoxy (1H, 1H, 2H, 2H-perfluorooctyl) silane are preferred.
Only one type of fluorine-based organic material used for the surface treatment of the mold 16 may be used, or two or more types may be used.

<Step (d)>
As shown in FIG.5 (d), the mold 16 is isolate | separated from the hardening layer 12 of the photopolymerizable composition ((alpha)) formed at the process (c), and the molding 17 which has a lattice pattern on the surface is obtained. Examples of a method for separating the molded body 17 and the mold 16 include a method in which both are fixed by vacuum suction and moved in a direction in which one is released, a method in which both are mechanically fixed and moved in a direction in which one is released. It is done.

<Process (e)>
As shown in FIG. 5 (e), an uncured photopolymerizable composition (β) is applied onto the cured layer 12 formed in the step (c) by a spin coat method or the like, and the photopolymerizable composition is formed. A coating layer 13a of (β) is formed.

Examples of the coating method of the photopolymerizable composition (β) include spin coating, roll coating, casting, dip coating, die coating, and bar coating, and the coating of the photopolymerizable composition (β). From the viewpoint of the uniformity of the thickness of the layer 2 and the ease of application, the spin coating method is preferred.
Suitable conditions regarding the pressure, ambient atmosphere, temperature and the like at the time of application of the photopolymerizable composition (β) are the same as the conditions at the time of application of the photopolymerizable composition (α) (step (a)).

<Step (f)>
As shown in FIG.5 (f), the transparent substrate 14 is pressed on the application layer 13a of the photopolymerizable composition ((beta)) formed in the process (e) in a pressure-reduced atmosphere. At this time, if it is a reduced pressure atmosphere such as a vacuum environment, there is no air involved, and generation of defects due to entrainment of bubbles during pressing can be reduced. Here, the vacuum environment refers to a reduced pressure atmosphere of 3000 Pa or more.
If it is a reduced pressure atmosphere of 3000 Pa or more, a significant change in composition due to volatilization of the photopolymerizable composition (β) is unlikely to occur.

<Process (g)>
As shown in FIG. 5 (g), either the transparent substrate 11 or the transparent substrate 14 transmits ultraviolet rays while pressurizing the coating layer 13a of the photopolymerizable composition (β) through the transparent substrate 11 or the transparent substrate 14. From the side to be applied, ultraviolet rays are irradiated to completely cure the photopolymerizable composition (β) of the coating layer 13a. Thereby, the wavelength selective diffraction element 10 in which the cured layer 13 of the photopolymerizable composition (β) is formed together with the cured layer 12 of the photopolymerizable composition (α) between the transparent substrate 11 and the transparent substrate 14 is obtained. (See FIG. 5 (h)).

  The pressurization is preferably performed from the transparent substrate 11 side, the transparent substrate 14 side, or both sides. Examples of the pressurizing method include a mechanical pressing method, a gas or liquid pressing method, and the like, as in the case of the photopolymerizable composition (α) coating layer 12a. The press pressure (gauge pressure) is preferably more than 0 to 10 MPa, more preferably 0.1 to 5 MPa. 0-100 degreeC is preferable and the temperature at the time of pressurizing has more preferable 10-80 degreeC.

  The light and light source used for the photocuring reaction of the photopolymerizable composition (β), the wavelength region and the illuminance thereof are preferably the same as in the case of the coating layer 12a of the photopolymerizable composition (α) described above. Used.

(substrate)
As the transparent substrates 11 and 14, substrates made of an inorganic material or an organic material having translucency are used. Examples of the inorganic material include silicon, glass, quartz glass, metal oxide (such as alumina (including sapphire)), silicon nitride, aluminum nitride, lithium niobate, and compound semiconductors (such as gallium nitride and gallium arsenide). Examples of the organic material include fluorine resin, silicone resin, acrylic resin, polycarbonate, polyester (polyethylene terephthalate, etc.), polyimide, polypropylene, polyethylene, nylon resin, polyphenylene sulfide, and cyclic polyolefin.

  From the viewpoint of excellent adhesion to the photopolymerizable composition, a surface-treated substrate may be used as the substrate. Examples of the surface treatment include primer coating treatment, ozone treatment, plasma etching treatment, and the like. Examples of the primer include polymethyl methacrylate, silane coupling agent, silazane and the like.

As the surface treatment agent for the transparent substrates 11 and 14, a silane coupling agent is preferable because high adhesion to both the glass substrate and the photopolymerizable composition can be obtained.
Examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycol. Sidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldi Ethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) ) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl- N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxy Silane etc. I can get lost.
As the silane coupling agent used for the surface treatment of the transparent substrates 11 and 14, only one type may be used, or two or more types may be used.

Refractive index _{n d} and the Abbe number [nu _d of the second optical material B formed by curing the photopolymerizable composition (beta) _{is, 38 <ν d <58,1.53 <} n d <1.78 and, it is preferably in the range of n _d> 1.804-0.005ν _d.

For example, the refractive index n _d of 2-ethyl-2-adamantyl acrylate as the monofunctional compound (I) is n _d = 1.53, the Abbe number ν _d is ν _d = 58, and 3-methacryloxypropyl tri refractive index _{n d} is _n d = 1.78 for the surface treated particle size 9nm of ZrO ₂ particles with silane, a [nu _d = 38, these contents, etc., appropriately adjusted within the scope of the present invention By photocuring the photopolymerizable composition (β), an optical material having a refractive index n _d and an Abbe number ν _d within the above ranges can be obtained.

As sulfur compounds conventionally used as optical materials, for example, 1,2-bis (acryloyloxyethylthio) ethane (JP-A-1-128966), bis (acryloyloxyethylthioethyl) sulfide (JP-A-2000) -95731) and 2,2'-thiodiethanethiol diacrylate (Japanese Patent Laid-Open No. 63-188660).
When the refractive index _nd and Abbe number ν _d of the cured products of these compounds were measured, 1,2-bis (acryloyloxyethylthio) ethane was ν _d = 45 and n _d = 1.58, respectively. Acryloyloxyethylthioethyl) sulfide is ν _d = 42, n _d = 1.59, and 2,2′-thiodiethanethiol diacrylate is ν _d = 34, n _d = 1.63. The n _d and ν _d of the compound satisfied the relational expression n _d = 1.804−0.005ν _d , respectively.
In contrast, the second optical material B obtained by curing the photopolymerizable composition (β) has a refractive index n _d in a range exceeding (1.804−0.005ν _d ), and the above sulfur compound compared to higher refractive index than against Abbe number [nu _d is obtained.

Photopolymerizable compositions refractive index _{n d} and the Abbe number [nu _d of (alpha) curing the first optical material A comprising the, 10 _{<ν d} <35,1.55 <range of n d <1.70 And more preferably 15 <νd <35 and 1.55 <nd <1.70.

(Third embodiment)
Next, a wavelength selective diffraction element according to a third embodiment of the present invention will be described with reference to FIG. FIG. 6A is a schematic cross-sectional view showing an operation when light having a wavelength λ ₁ is incident on the wavelength selective diffraction element 30, and FIG. It is a typical cross-sectional view which shows an effect | action when the light of wavelength (lambda) ₂ injects.

In FIG. 6, the wavelength selective diffraction element 30 is configured by combining the wavelength selective diffraction element 10 according to the first embodiment and the wavelength selective diffraction element 20 according to the second embodiment, It has the 1st member 320 provided with the transparent substrate 31, the uneven | corrugated member 32 formed in the surface of the transparent substrate 31, and the filling member 33 with which it filled between the uneven | corrugated | grooved parts of the uneven | corrugated member 32. FIG. Above the first member 320, there is provided a transparent substrate 36, an uneven member 35 formed on the surface of the transparent substrate 36, and a filling member 34 filled between the uneven portions of the uneven member 35. Two members 310 are provided, and the first member 320 and the second member 310 are laminated in a state where the transparent substrate 37 is sandwiched between the filling member 33 and the filling member 34.
In the wavelength selective diffractive element 30, the transparent substrate 31, the concavo-convex member 32, the filling member 33, and the transparent substrate 37 constituting the first member 320 are respectively the wavelength selective diffractive element 20 (see FIG. 3). ) Corresponds to the transparent substrate 21, the diffraction grating 22, the filling member 23, and the transparent substrate 24.
In the wavelength-selective diffraction element 30, the transparent substrate 36, the concavo-convex member 35, the filling member 34, and the transparent substrate 37 constituting the second member 310 are each the wavelength-selective diffraction element 10 described above (see FIG. 1). ) Corresponds to the transparent substrate 11, the concavo-convex member 12, the filling member 13, and the transparent substrate 14.

Selective diffraction element 30 is equal the refractive index of the filling member 33 of the concave-convex member 32 with respect to the wavelength lambda ₁ of the light, the refractive index of the refractive index and the filling member 33 of the concave-convex member 32 with respect to the wavelength lambda ₂ of light Are formed differently. The wavelength-selective diffraction element 30 has different refractive index and the filling member 34 of the concave-convex member 35 with respect to the wavelength lambda ₁ of light, refraction of the filling member 34 and the refractive index of the concave-convex member 35 with respect to the wavelength lambda ₂ of light It is formed so that the rates are equal.

For this reason, in FIG. 6A, when the light of wavelength λ ₁ enters the second member 310 of the wavelength-selective diffraction element 30, it is diffracted by the uneven member 35, and then enters the first member 320, the uneven member. 32 does not diffract and transmits. That is, for the wavelength lambda ₁ of the light, only uneven member 35 functions as a diffraction grating. On the other hand, in FIG. 3 (b), when the light of wavelength λ ₂ enters the second member 310 of the wavelength selective diffraction element 30, it passes through the uneven member 35 and then enters the first member 320, the uneven member 32. Diffracted at That is, for the wavelength lambda ₂ of light, only the concave-convex portion 32 functions as a diffraction grating.
Therefore, the wavelength-selective diffraction element 30 can function as a diffraction element independently for two kinds of wavelengths by one element formed by combining different elements.

For example, the wavelength λ ₁ and the wavelength λ ₂ described above are set to a 405 nm wavelength band used for BD and a 660 nm wavelength band used for DVD, respectively.
At this time, when the concavo-convex member 12 and the filling member 13 of the wavelength selective diffraction element 10 shown in FIG. 1 have the relationship of the first embodiment, the light in the 405 nm wavelength band is diffracted and the light in the 660 nm wavelength band is diffracted. Can be produced. Since the refractive index of the 785 nm wavelength band is close to that of the 660 nm wavelength band, a wavelength selective diffraction element that transmits light in the 785 nm wavelength band can be manufactured.
Further, when the concavo-convex member 22 and the filling member 23 of the wavelength selective diffraction element 20 shown in FIG. 3 have the relationship of the second embodiment, the light of the 405 nm wavelength band is transmitted and the light of the 660 nm wavelength band is diffracted. it can. Note that since the 785 nm wavelength band used in CD has a refractive index close to that of the 660 nm wavelength band, a wavelength selective diffraction element capable of diffracting light in the 785 nm wavelength band can also be produced.

In the wavelength selective diffraction elements 10, 20, and 30 described above, the diffraction efficiency can be improved by adjusting the grating heights d ₁ and d ₂ of the concavo-convex members 12, 22, 32, and 35 and changing the grating shape. Can be adjusted. Therefore, a grating height that can obtain suitable efficiency may be used as the three-beam generating element or the hologram beam splitter. In addition, the concavo-convex member of the wavelength selective diffraction element may be used with a blazed grating shape or a stepped grating shape having a multi-level structure to increase the diffraction efficiency in a specific order. Furthermore, the diffraction angle can be adjusted by adjusting the pitch of the diffraction grating, and a desired diffraction angle can be obtained. For these elements, the techniques used in conventional three-beam generating elements and hologram beam splitters can be directly applied to wavelength selective diffraction elements.

  When the optical materials A and B described above are applied to the wavelength selective diffraction element of the present invention, the method is not limited to the above-described embodiment, and a conventionally known method can be applied. In addition, a photopolymerizable composition ((alpha)) and a photopolymerizable composition ((beta)) can also be used as an adhesive agent when laminating | stacking optical elements or fixing an optical component.

  Moreover, the wavelength selective diffraction element of the present invention using the optical materials A and B described above is excellent in light resistance against a blue laser. Therefore, it can be preferably used in the application of the optical pickup device, and can be used for manufacturing an optical head device suitable for increasing the capacity. That is, the wavelength selective diffraction element of the present invention using the optical materials A and B described above is suitable for an optical head device that records information on an optical recording medium and / or reproduces information recorded on the optical recording medium. In particular, it is suitable for an optical head device for an optical information recording / reproducing apparatus using a blue laser such as BD. Specifically, it is preferably arranged in the optical path of the laser beam of the optical head device. Further, it can be suitably used in other applications where a high refractive index resin has been conventionally required.

[Optical head device]
FIG. 7 is a diagram schematically showing a configuration of an optical head device according to an embodiment of the present invention.
As shown in FIG. 7, the optical head device 111 includes a light source 112 that emits laser light, a wavelength-selective diffraction grating 113, a beam splitter 114 that transmits laser light, and a collimator lens 115 that collimates the laser light. And an objective lens 118 that condenses on the recording layer 117 of the optical disc 116 and a photodetector 119 that detects reflected light from the optical disc 116. The wavelength selective diffraction grating 113 is a three-beam generating diffraction grating, and in the present embodiment, the above-described wavelength selective diffraction grating 10 (see FIG. 1) is applied. The three beams obtained by the wavelength selective diffraction grating 113 are used in tracking control when reading information recorded on a BD or the like in the optical head device 111.

  In FIG. 7, the wavelength selective diffraction grating 113 is provided between the light source 112 and the beam splitter 114, but the wavelength selective diffraction grating 113 is provided in the optical path between the light source 112 and the objective lens 118. For example, the wavelength selective diffraction grating 113 may be provided between the beam splitter 114 and the objective lens 118. However, as shown in FIG. 7, if the wavelength selective diffraction grating 113 is disposed between the light source 112 and the beam splitter 114, the reflected light from the optical disk is not diffracted by the wavelength selective diffraction grating 113, and most of them. Is preferable because it reaches the photodetector 119 and the light utilization efficiency is improved.

The light source 112 is composed of, for example, a semiconductor laser diode, generates laser light having a wavelength suitable for the type of the optical disk 116, and emits the laser light to the wavelength selective diffraction grating 113. As the light source 112, a general laser light source used in a normal optical head device is used. Specifically, a semiconductor laser is preferably used, and a laser light source other than the semiconductor laser may be used. Since the optical material applied to the present invention has excellent light resistance with respect to a blue laser, it is suitably used for an optical head device using a blue laser as a light source. In the present embodiment, laser light having a wavelength of 405 nm (wavelength λ ₁ ) and 660 nm (wavelength λ ₂ ) is used. Note that a plurality of light sources that emit laser beams having different wavelengths may be provided, and laser light may be emitted from each light source to the wavelength selective diffraction grating 113.

The wavelength-selective diffraction grating 113 includes three beams including light that is transmitted without diffracting the laser beam having the wavelength λ ₁ (0th order diffracted light) and light that is diffracted from the laser beam having the wavelength λ ₁ (± 1st order diffracted light). The beam (see FIG. 1A) is output to the beam splitter 114. Further, the wavelength selective diffraction grating 113 transmits the laser beam having the wavelength λ ₂ and outputs it to the beam splitter 114. The beam splitter 114 is made of a transmissive material, such as glass or plastic, and includes a reflective surface that reflects the reflected light from the optical disk 116. The collimator lens 115 is also made of a transmissive material, such as glass or plastic, and is configured to collimate incident laser light.
The objective lens 118 has a predetermined numerical aperture NA, and is configured to collect incident light from the collimator lens 115 on the recording layer 117 of the optical disk 116 and to capture reflected light from the recording layer 117. Has been. The photodetector 119 includes a lens, a photodiode, and the like, and converts the reflected light from the optical disk 116 reflected by the reflecting surface of the beam splitter 114 into an electric signal. The photodetector 119 receives three beams of reflected light having a wavelength λ ₁ and receives a main beam generated by the 0th-order diffracted light and two sub beams generated by the ± 1st-order diffracted light. A tracking error is detected based on the light amount difference between the two sub beams and is output to a tracking control unit (not shown).

When the optical disk 116 is a BD, the optical head device 111 operates as follows. First, as shown in FIG. 7, a part of the emitted light of the light having the wavelength λ ₁ emitted from the light source 112 is diffracted by the wavelength selective diffraction grating 113. As a result, light including 0th-order diffracted light and ± 1st-order diffracted light is emitted from the wavelength selective diffraction grating 113, passes through the beam splitter 114, and is collimated by the collimator lens 115. The parallel light emitted from the collimator lens 115 is condensed on the information recording track of the optical disk 116 by the objective lens 118 into three beams of 0th order diffracted light and ± 1st order diffracted light. Next, the light reflected by the optical disk 116 passes through the collimator lens 115 again from the objective lens 118, is reflected by the beam splitter 114, and is generated by the main beam generated by the 0th order diffracted light and the ± 1st order diffracted light. The two sub beams are condensed on the light receiving surface of the photodetector 119. Then, the photodetector 119 detects a tracking error signal based on the light amount difference between the two sub beams and outputs it to a tracking control unit (not shown).

When the optical disk 116 is a DVD, the optical head device 111 operates as follows. First, as shown in FIG. 7, the light of wavelength λ ₂ emitted from the light source 112 is transmitted without being diffracted by the wavelength selective diffraction grating 113, then further transmitted through the beam splitter 114, and collimator lens 115. In parallel light. Thereafter, the parallel light is condensed on the information recording track of the optical disk 116 by the objective lens 118. Then, the light reflected by the optical disk 116 passes through the objective lens 118 and the collimator lens 115 again, is reflected by the beam splitter 114, and is collected on the light receiving surface of the photodetector 119.
As described above, by using the wavelength selective diffraction element of the present invention, an optical head device suitable for increasing the capacity and having high reliability can be configured.

  In this embodiment, the wavelength-selective diffraction grating 113 is provided on the optical path between the light source 112 and the objective lens 118. However, the optical head device 111 of the present invention is not limited to such an embodiment. The wavelength selective diffraction grating of the present invention may be provided as a hologram diffraction element on the optical path between the objective lens 118 and the photodetector 119. As a result, the number of light receiving surfaces and the area of the light receiving surfaces of the photodetector 119 can be reduced, and the overall size of the apparatus can be reduced.

  Further, the optical head device of the present invention may be capable of selectively using the three-beam method and the hologram method according to the type of the optical disk to be recorded / reproduced, and the tracking servo signal is detected by the three-beam method. The focus servo signal may be detected by a hologram method. For example, a 3-beam method may be used when recording / reproducing DVDs and CDs, and a hologram method may be used when recording / reproducing BDs.

  It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the spirit of the present invention.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Measurement of average primary particle diameter of zirconium oxide particles)
The average particle diameter of the zirconia particles was determined by measuring the diameter of about 200 particles using a transmission electron microscope and using the average value.

(Measurement of viscosity of photopolymerizable composition)
The viscosity of the photopolymerizable composition was measured with a viscometer (manufactured by Brookfield, trade name “HBDV-III Ultra CP”) at 25 ° C. and a shear rate of 10 s ⁻¹ .

(Measurement of refractive index of cured product obtained by curing photopolymerizable composition)
The refractive index of the cured product obtained by curing the photopolymerizable composition was measured at room temperature using a prism coupler (manufactured by Metricon, trade name “Model2010”). Refractive indices of three wavelengths measured at 404, 633, and 791 nm are fitted to parameters A, B, and C of Cauchy's formula (n (λ) = A + B / λ ² + C / λ ⁴ ) by the least square method. The refractive index n _d and Abbe number ν _d at a wavelength of 589 nm were obtained.

<Surface modification of zirconium oxide particles>
(Preparation Example 1)
In a 100 mL glass container equipped with a stirrer, 2 g of zirconium oxide particles having an average primary particle diameter of 7 nm and 20 g of toluene were placed and stirred vigorously, and 0.6 g of 3-methacryloxypropyltrimethoxysilane was added as a surface treatment agent. . Then, after stirring for 24 hours, the liquid was removed with an evaporator to obtain white powder.
A part of the obtained white powder was collected, analyzed by ¹ H-NMR after adding CDCl _3, and a spectrum specific to the methoxy group disappeared. Further, when toluene was added to the remaining white powder collected, a transparent liquid was obtained.
Thereby, the production | generation of the surface treatment zirconium oxide particle (Z-1) which the surface of the zirconium oxide particle reacted with 3-methacryloxypropyltrimethoxysilane was confirmed.

(Preparation Example 2)
Instead of 2 g of zirconium oxide particles having an average primary particle diameter of 7 nm, 2 g of zirconium oxide particles having an average primary particle diameter of 9 nm was used, and the amount of 3-methacryloxypropyltrimethoxysilane added was changed from 0.6 g to 0.4 g. Except for the change, preparation of white powder and confirmation of the surface state of the zirconium oxide particles were performed in the same manner as in Preparation Example 1 to obtain surface-treated zirconium oxide particles (Z-2).

<Preparation of Photopolymerizable Composition β>
[Example 1]
A 100 mL glass container was charged with 1.30 g of the surface-treated zirconium oxide particles (Z-1) obtained in Preparation Example 1 and 10 g of toluene to prepare a toluene dispersion.
To this, 0.70 g of 2-ethyl-2-adamantyl acrylate (manufactured by Idemitsu Kosan Co., Ltd.) was added and stirred for 1 hour, and then the solvent was distilled off with a rotary evaporator. A part of the composition obtained after the distillation was collected, added with CDCl ₃ and analyzed by ¹ H-NMR.
From the spectral intensity obtained by NMR analysis, it was confirmed that the toluene concentration in the composition was less than 1%.
1.00 g of this composition, 0.03 g of tricyclodecane dimethanol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd.) and 0.005 g of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator are mixed, and an ultrasonic disperser is used. The dispersion process was performed and the photopolymerizable composition (A) was obtained.
The content of zirconium oxide particles in the photopolymerizable composition (A) was 48.9% by mass, and the content of tricyclodecane dimethanol diacrylate was 2.7% by mass.
Further, the residual concentration of toluene in the photopolymerizable composition (A) (residual solvent amount) was 0.1% by mass with respect to the photopolymerizable composition (100% by mass), and the viscosity was 2900 mPa · s. It was.

[Example 2]
Instead of 1.30 g of the surface-treated zirconium oxide particles (Z-1) obtained in Preparation Example 1, 1.37 g of the surface-treated zirconium oxide particles (Z-2) obtained in Preparation Example 2 were used, and 2-ethyl The amount of addition of -2-adamantyl acrylate was changed from 0.70 g to 0.63 g, and the amount of addition of tricyclodecane dimethanol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd.) was changed from 0.03 g to 0.20 g. In the same manner as in [Example 1], a photopolymerizable composition (B) was obtained.
The content of zirconium oxide particles in the photopolymerizable composition (B) was 47.2% by mass, and the content of tricyclodecane dimethanol diacrylate was 16.9% by mass. Further, the residual concentration (the amount of residual solvent) of toluene in the photopolymerizable composition (B) was 0.1% by mass with respect to the photopolymerizable composition (100% by mass), and the viscosity was 2600 mPa · s. It was.

[Example 3]
Instead of 1.30 g of the surface-treated zirconium oxide particles (Z-1) obtained in Preparation Example 1, 1.37 g of the zirconium oxide particles (Z-2) obtained in Preparation Example 2 were used, and 2-ethyl-2 -In place of 0.73 g of adamantyl acrylate, 0.63 g of diadamantyl acrylate was used, and the addition amount of tricyclodecane dimethanol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd.) was changed from 0.03 g to 0.20 g. In the same manner as in Example 1, a photopolymerizable composition (C) was obtained.
The concentration of zirconium oxide particles in the photopolymerizable composition (C) was 47.2% by mass, and the concentration of tricyclodecane dimethanol diacrylate was 16.9% by mass.
Further, the residual concentration (the amount of residual solvent) of toluene in the photopolymerizable composition (C) is 0.1% by mass with respect to the photopolymerizable composition (100% by mass), and the viscosity is 7000 mPa · s. there were.

[Example 4]
The addition amount of the surface-treated zirconium oxide particles (Z-1) obtained in Preparation Example 1 was changed from 1.30 g to 1.39 g, and the addition amount of 2-ethyl-2-adamantyl acrylate was changed from 0.70 g to 0. The photopolymerizable composition in the same manner as in [Example 1] except that 0.03 g of tricyclodecane dimethanol diacrylate was changed to 0.05 g of adamantyl diacrylate (Mitsubishi Gas Chemical Co., Ltd.). (D) was obtained.
The concentration of the zirconium oxide particles in the photopolymerizable composition (D) was 51.7% by mass, and the concentration of adamantyl diacrylate was 5.0% by mass.
Further, the residual concentration of toluene in the photopolymerizable composition (D) (residual solvent amount) was 0.1% by mass with respect to the photopolymerizable composition (100% by mass), and the viscosity was 8400 mPa · s. It was.

[Example 5]
The amount of the surface-treated zirconium oxide particles (Z-1) obtained in Preparation Example 1 was changed from 1.30 g to 1.55 g, and 2-ethyl-2-adamantyl acrylate (manufactured by Idemitsu Kosan Co., Ltd.) was added. The photopolymerizable composition (E) was obtained in the same manner as in [Example 1] except that the amount was changed from 0.70 g to 0.45 g and tricyclodecane dimethanol diacrylate was not added.
The concentration of the zirconium oxide particles in the photopolymerizable composition (E) was 60.5% by mass.
Further, the residual concentration (residual solvent amount) of toluene in the photopolymerizable composition (E) is 0.4% by mass with respect to the photopolymerizable composition (100% by mass), and the viscosity exceeds 10,000 mPa · s. The value is shown.

[Example 6]
Instead of 1.30 g of the surface-treated zirconium oxide particles (Z-1) obtained in Preparation Example 1, 1.59 g of the zirconium oxide particles (Z-2) obtained in Preparation Example 2 were used, and 2-ethyl-2 -The photopolymerizable composition (F) was prepared in the same manner as in [Example 1] except that the addition amount of adamantyl acrylate was changed from 0.70 g to 0.41 g and tricyclodecane dimethanol diacrylate was not added. Obtained.
The concentration of zirconium oxide particles in the photopolymerizable composition (F) was 65.7% by mass. Moreover, the residual concentration of toluene in the photopolymerizable composition (F) was 0.5% by mass with respect to the photopolymerizable composition (100% by mass), and the viscosity showed a value exceeding 10,000 mPa · s.

  In addition to the average primary particle diameter of zirconium oxide particles and the content thereof in each of the photopolymerization compositions (A) to (F) of Examples 1 to 6, the inclusion of the monofunctional compound (I) and the polyfunctional compound (II) The amounts are shown in Table 1.

<Preparation of photopolymerizable composition (α)>
[Example 7]
Add 1.00 g of Oxol EA-F5003 (manufactured by Osaka Gas Chemical Co., Ltd.) having a bisarylfluorene skeleton and 0.005 g of 1-hydroxycyclohexyl phenyl ketone, which is a photopolymerization initiator, to a 100 mL glass container and stir well. A photopolymerizable composition (G) was obtained.
The ratio of Ogsol EA-F5003 (manufactured by Osaka Gas Chemical Co., Ltd.) in the photopolymerizable composition (G) was 99.5% by mass.

[Example 8]
1.00 g of the aromatic compound (19) represented by the following formula (19) and 0.005 g of 1-hydroxycyclohexyl phenyl ketone, which is a photopolymerization initiator, are placed in a 100 mL glass container, sufficiently stirred, and photopolymerized. Sex composition (H) was obtained.
The ratio of the aromatic compound (19) in the photopolymerizable composition (H) was 99.5% by mass.

[Example 9]
In a 100 mL glass container, 1.0 g of a mixture of Ogsol EA-F5003 (manufactured by Osaka Gas Chemical Co., Ltd.) and an aromatic compound (20) represented by the following formula (20), and a photopolymerization initiator 1- 0.005 g of hydroxycyclohexyl phenyl ketone was placed in a 100 mL glass container and sufficiently stirred to obtain a photopolymerizable composition (I).
The proportion of Ogsol EA-F5003 (manufactured by Osaka Gas Chemical Co., Ltd.) in the photopolymerizable composition (I) was 58.9% by mass, and the proportion of the aromatic compound (20) was 40.6% by mass. It was.

<Refractive index of optical material>
[Example 10]
Four corners of the two glass plates were bonded together using an adhesive containing glass beads having a diameter of 10 μm to produce a glass cell having a 10 μm gap between the glasses. After injecting the photopolymerizable composition (A) in a liquid state into the glass cell, the glass plate is irradiated with ultraviolet rays for 2 minutes from the vertical direction to cure the photopolymerizable composition (A). Cured product A was obtained.
The illuminance of the high-pressure mercury lamp used for photocuring was 100 mW / cm ² at a wavelength of 365 nm. Measurement of the refractive index of the cured product A, the refractive index n _d 1.603, Abbe number [nu _d is 47, it was confirmed wavelength dependence of the high refractive index and the refractive index is small.

[Example 11] to [Example 18]
Photopolymerizable compositions (B) to (I) in the same manner as in [Example 10] except that photopolymerizable compositions (B) to (I) were used instead of the photopolymerizable composition (A). And cured products B to I were obtained.

Table 2 shows the refractive index n _d and Abbe number ν _d of the cured products (A) to (I) obtained in Examples 10 to 18.

<Wavelength selective diffraction element>
[Example 19]
A quartz glass substrate having a concavo-convex shape in which a photopolymerizable composition (A) is dropped onto a quartz glass substrate (hereinafter also referred to as a supporting glass substrate), and then the surface is treated with OPTOOL DSX (manufactured by Daikin Industries, Ltd.) Hereinafter, the pressure was slowly applied using a releasable uneven glass substrate) while paying attention to the entrainment of bubbles.
The uneven shape was a binary shape with a duty of 0.55, the lattice height was 9.4 μm, and the lattice pitch was 10 μm.
The quartz glass substrate and the releasable uneven glass substrate were irradiated with ultraviolet rays from the vertical direction for 2 minutes to obtain a laminate in which a cured body of the photopolymerizable composition (A) was formed inside both glass substrates.
The illuminance of the high-pressure mercury lamp used for photocuring was 100 mW / cm ² at a wavelength of 365 nm.
Then, when the releaseable concavo-convex glass substrate was carefully peeled from the cured body, an optical material having the concavo-convex shape transferred onto the support glass substrate was obtained. Next, after dropping the photopolymerizable composition (G) onto an optical material composed of a cured product of the photopolymerizable composition (A), a quartz glass substrate (hereinafter also referred to as a protective glass substrate) is formed on the composition (G). The protective glass substrate was slowly pressurized while paying attention to entrainment of bubbles.
The supporting glass substrate and the protective glass substrate are irradiated with ultraviolet rays from the vertical direction for 2 minutes, and from the cured body of the photopolymerizable composition (A) and the cured body of the photopolymerizable composition (G) inside the glass substrate. A wavelength selective diffraction element in which an optical material was formed was obtained.

[Example 20]
The photopolymerizable composition (E) is used instead of the photopolymerizable composition (A), and the photopolymerizable composition (H) is used instead of the photopolymerizable composition (G). A wavelength selective diffraction element was obtained in the same manner as in Example 16 except that the thickness was 3 μm.

[Example 21]
Example 16 except that the photopolymerizable composition (I) was used instead of the photopolymerizable composition (G), the uneven shape was a binary shape of duty 0.45, and the lattice height was 21.5 μm. In the same manner, a wavelength selective diffraction element was obtained.

[Example 22]
The photopolymerizable composition (F) is used instead of the photopolymerizable composition (A), the photopolymerizable composition (H) is used instead of the photopolymerizable composition (G), and the concavo-convex shape is duty 0.45. A wavelength selective diffraction element was obtained in the same manner as in Example 16 except that the binary shape was used and the grating height was 11.0 μm.

[Example 23]
A wavelength selective diffraction element was obtained in the same manner as in Example 16 except that the uneven shape was an 8-step blaze shape and the grating height was 16.5 μm.

[Example 24]
A wavelength selective diffraction element was obtained in the same manner as in Example 17 except that the uneven shape was an 8-step blaze shape and the grating height was 10.9 μm.

[Example 25]
A wavelength selective diffraction element was obtained in the same manner as in Example 18 except that the uneven shape was an 8-step blaze shape and the grating height was 42.0 μm.

[Example 26]
A wavelength selective diffraction element was obtained in the same manner as in Example 19 except that the uneven shape was an 8-step blaze shape and the grating height was 21.0 μm.

Zero-order diffraction is performed by vertically injecting laser beams of three wavelengths of 405, 660, and 785 nm into the wavelength selective diffraction elements obtained in Examples 19 to 26 having a binary or 8-step blaze type grating shape. Efficiency and + 1st order diffraction efficiency were measured. The evaluation results are shown in Tables 3 and 4 together with the grating height, grating pitch and grating shape of each uneven part, and the refractive index n _d , Abbe number v _d and refractive index difference Δn of each cured product (optical material). Shown in

  As is clear from Table 3, Examples 19 to 22 using cured products of photopolymerizable compositions (A), (E), and (F) containing zirconium oxide particles as an optical material having low wavelength dispersion. In the wavelength selective diffraction element, a refractive index difference of 0.019 or more is obtained in the wavelength 405 nm band or the wavelength 785 nm band, and even in the binary-shaped diffraction grating, it is as high as 30% or more, 40.3 to 42.2%. First order diffraction efficiency was obtained.

As is clear from Table 4, the wavelength selective diffractive elements of Examples 23 to 26 having an 8-step blazed grating shape are similarly photopolymerizable containing zirconium oxide particles as an optical material having low wavelength dispersion. A cured product of the compositions (A), (E), and (F) is used, and a refractive index difference of 0.019 or more is obtained in the wavelength 405 nm band or the wavelength 785 nm band, and 67.3 to 85.1%. A first-order diffraction efficiency as high as 50% or more was obtained.
Further, in the wavelength selective diffraction elements of Examples 19 to 26, stray light and light loss were suppressed, and a high zero-order diffraction efficiency of 97.5% or higher was obtained in the wavelength 405 nm band or the wavelength 785 nm band.

  By using the wavelength selective diffraction element of the present invention, a highly reliable optical head device corresponding to each wavelength band of BD, DVD, and CD can be configured.

10, 20, 30 ... wavelength selective diffraction element, 11, 14, 21, 24, 31, 36, 37 ... transparent substrate, 12, 22, 32, 35 ... uneven member, 13, 23, 33, 34 ... filling member, DESCRIPTION OF SYMBOLS 15 ... Adhesion layer, 16 ... Mold, 17 ... Molded object, 310 ... 2nd member, 320 ... 1st member,
DESCRIPTION OF SYMBOLS 111 ... Optical head apparatus, 112 ... Light source, 113 ... Wavelength selective diffraction grating, 114 ... Beam splitter, 115 ... Collimator lens, 116 ... Optical disk, 117 ... Recording layer, 118 ... Objective lens, 119 ... Photodetector

Claims (8)

A transparent substrate having translucency, a concavo-convex member formed on the transparent substrate and having a concavo-convex shape periodically formed so as to extend in one direction, and filled so as to fill at least the concavo-convex member A wavelength-selective diffractive element including incident light having a wavelength of at least 405 nm (λ ₁ ), a wavelength of 660 nm (λ ₂ ), and a wavelength of 785 nm (λ ₃ ). The concavo-convex member and the filling member are each formed of either the first optical material A having high wavelength dispersion or the second optical material B having low wavelength dispersion. The refractive index nA of the optical material A and the refractive index nB of the second optical material B are | nA−nB | ≦ 0.006 with respect to the light with the wavelength λ ₁ , and the wavelength λ ₂ and the wavelength λ ₃ with respect to the light | nA nB |> 0.006 or where to the wavelength lambda ₂ and the wavelength lambda ₃ of the light | nA-nB | a ≦ 0.006, and the wavelength lambda ₁ with respect to light | n ( A) -n (B) |> 0.006 and the second optical material B having low wavelength dispersion has an average particle diameter whose surface is coated with a surface modifying agent having a polymerizable group. It is obtained by curing a photopolymerizable composition containing zirconium oxide particles of 3 nm or more and 15 nm or less, one polymerizable group, and a monofunctional compound having an alicyclic structure having 10 to 14 carbon atoms. A wavelength selective diffraction element characterized by the above. The first refractive index nB of the refractive index nA and the second optical material B of the optical material A, the wavelength lambda _1, lambda _2, lambda ₃ of the wavelength lambda ₁ with respect to light | nA-nB | ≦ 0 .006, and the relationship of | nA−nB | ≧ 0.013 with respect to light of wavelength λ ₂ and wavelength λ ₃ , and the 0th-order diffraction efficiency for light of wavelength λ ₁ is 90% or more, or the wavelength Among λ ₁ , λ ₂ , and λ ₃ , there is a relationship of | nA−nB | ≦ 0.006 for light of wavelength λ ₂ and wavelength λ ₃ and | nA−nB | ≧ 0.015 for light of wavelength λ ₁ The wavelength selective diffraction element according to claim 1, wherein the zero-order diffraction efficiency for light of wavelengths λ ₂ and λ ₃ is 90% or more.   3. The wavelength selective diffraction element according to claim 1, wherein the alicyclic skeleton of the monofunctional compound is adamantane, diamantane, or tricyclodecane, and the polymerizable group is an acrylic group or a methacryl group. The wavelength selective diffraction element according to claim 1, wherein the surface modifier is a compound represented by the following general formula (1).

(In Formula (1), A represents a hydrogen atom or a methyl group, X represents a hydrogen atom, a methyl group, or an ethyl group each independently, R represents a hydrogen atom, a methyl group, or an ethyl group, and n is 1- 1). 6 represents an integer, and m represents an integer of 1 to 3.)   5. The wavelength selective diffraction element according to claim 1, wherein a content of the zirconium oxide particles is 45% by mass or more and 70% by mass or less.   The wavelength selective diffraction element according to any one of claims 1 to 5, wherein the first optical material A having high wavelength dispersion contains an aromatic compound. Refractive index _{n d} and the Abbe number [nu _d of the first optical material A having the high wavelength dispersion is in the range 10 <ν _d <a 35,1.55 _<n d _<1.70, and wherein refractive index _{n d} and the Abbe number [nu _d of the second optical material B having a low wavelength dispersion is _{38 <ν d <58,1.53 <n} d <1.78 _and,, n d> 1.804- wavelength selective diffraction element according to any one of claims 1 to 6 in the range of 0.005ν _d. A light source that emits incident light having at least a wavelength of 405 nm wavelength band (λ ₁ ), a wavelength of 660 nm wavelength band (λ ₂ ), and a wavelength of 785 nm wavelength band (λ ₃ ), and condensing the light on the recording layer of the optical disc An optical head device comprising an objective lens that detects light reflected from the optical recording medium, and an optical head device that is on an optical path between the light source and the objective lens, or the objective lens and the light detection device. An optical head device comprising the wavelength selective diffraction element according to any one of claims 1 to 7 on an optical path between the optical device and the optical device.

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