JP2007291291A - Composite material and optical component using the same - Google Patents

Abstract

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【選択図】図１A composite material having an excellent balance between high refractive index and low wavelength dispersion and excellent workability, and an optical component formed using the composite material are provided.
By dispersing inorganic particles 11 containing yttrium oxide and one or more other inorganic substances in a resin 12, the refractive index n _COM is 1.60 or more, the Abbe number ν _COM is 20 or more, and

A composite material 10 satisfying the following relationship is obtained.
[Selection] Figure 1

Description

  The present invention relates to a composite material and an optical component using the same. More specifically, the present invention relates to a composite material having a high refractive index and low wavelength dispersion, and an optical component using the composite material, such as a lens, a diffractive optical element, a solid-state imaging element, and the like.

  In recent years, optoelectronics have attracted attention as a key technology for realizing high-speed information communication and reducing the size and weight of various electronic devices, and the development of optical materials for realizing this is urgently needed.

  Conventionally, inorganic materials such as optical glass are generally used as the optical material. However, the inorganic optical material has a problem that it is difficult to process, and it is difficult to produce optical components that are becoming finer and more complicated in large quantities and at low cost.

  On the other hand, organic optical materials centering on resin are expected to be materials that will support future optoelectronics technology because they are excellent in processability and can reduce production costs and are lightweight. In recent years, development tends to accelerate.

A problem with organic optical materials is that when an optical component is formed alone, the refractive index is not sufficiently high, or there are few materials that balance the refractive index and wavelength dispersion. As for the resin material most used as an organic optical material, it is known that the refractive index _nm and the Abbe number ν _m indicating wavelength dispersion are generally in the range shown in (Equation 1) (non-patent document). Reference 1).

  The fact that the refractive index of the resin is not sufficiently high, or that there are few materials that have a good balance between the refractive index and the wavelength dispersibility, for example, when considering a lens as an optical component, sufficient characteristics due to chromatic aberration and curvature of field. Will lead to problems such as Further, when considering a solid-state imaging device having an optical waveguide as an optical component, a sufficient refractive index difference cannot be obtained between the optical waveguide and its peripheral material, resulting in a reduction in light collection efficiency.

In order to solve these problems, it has been studied to disperse inorganic fine particles in the base resin, prepare an organic optical material having a high refractive index, and to construct an optical component using this material. ing. As a method for obtaining an optical component made of an organic optical material exhibiting a high refractive index and low wavelength dispersion, an optical component is composed of a resin composition in which fine particles such as alumina are dispersed in a transparent base polymer such as methacrylic resin. Is disclosed (Patent Document 1). In addition, a method is disclosed in which an optical component is formed from a thermoplastic resin composition in which fine particles of titanium oxide or zinc oxide are dispersed in a thermoplastic resin having a certain level of optical characteristics (Patent Documents 2 to 4).
JP 2001-183501 A JP 2003-073559 A JP 2003-0753563 A JP 2003-073564 A Quarterly Chemical Review No. 39 Controlling the refractive index of transparent polymers

  However, in the method disclosed in Patent Document 1, alumina having a refractive index of 1.76 at a wavelength of 587 nm is dispersed in the base resin, so that it was in principle difficult to obtain a resin composition having a high refractive index. . Patent Document 1 also discloses a method of dispersing inorganic fine particles other than alumina in a base resin. In this case, in order to obtain a sufficiently high Abbe number, that is, low wavelength dispersibility, an infrared absorbing dye Anomalous dispersion material such as is further dispersed. In addition, in the method disclosed in Patent Document 2, titanium oxide (Abbe number 12) or zinc oxide (Abbe number 12) having high wavelength dispersion is used as the inorganic fine particles to be dispersed in the base resin. When the dispersion ratio of the inorganic fine particles is increased in order to obtain a resin composition having a refractive index, the wavelength dispersibility is remarkably increased, and it has been difficult to obtain a composition having an excellent balance between high refractive index and low wavelength dispersibility.

  Under such circumstances, an object of the present invention is to provide a composite material having an excellent balance between high refractive index and low wavelength dispersion and excellent workability, and an optical component using the composite material.

In order to achieve the above object, the composite material of the present invention comprises a resin and inorganic particles dispersed in the resin and containing at least yttrium oxide and one or more other inorganic substances, and the refractive index n _COM is 1.60 or more, Abbe number ν _COM is 20 or more, and

  The relationship is established.

  In this specification, “refractive index of composite material” means an effective refractive index when the composite material is regarded as a medium having one refractive index.

  In the above structure, the inorganic particles are preferably a complex oxide of yttrium oxide. The inorganic particles are preferably yttrium aluminum garnet.

In the above structure, it is preferable to further include second inorganic particles dispersed in the resin and having an Abbe number ν _p of 50 or more. The second inorganic particles are preferably silica or alumina.

  Furthermore, the volume ratio of the inorganic particles to the entire composite material is preferably 50% by volume or less. Moreover, it is preferable that the sum total of the volume ratio with respect to the whole composite material of the said 1st inorganic particle and the said 2nd inorganic particle is 50 volume% or less.

  Furthermore, it is preferable that the effective particle diameter of the inorganic particles is in the range of 1 nm to 100 nm. Moreover, it is preferable that the effective particle diameter of the said 1st inorganic particle and the said 2nd inorganic particle exists in the range of 1 nm or more and 100 nm or less.

  The above-described composite material is used for the optical component of the present invention.

  The lens of the present invention is made of the composite material described above.

  The diffractive optical element according to the present invention includes a base material made of a first material and having a diffraction grating shape formed on a surface thereof, and a diffraction film made of a second material and formed to cover the diffraction grating shape. An optical element, the first material and the second material are both composed of a resin, and at least one of the first material and the second material is made of the composite material described above. .

  The solid-state imaging device of the present invention is a solid-state imaging device having a photoelectric conversion unit and an optical waveguide disposed on the photoelectric conversion unit, and the optical waveguide is made of the composite material described above.

  In the composite material of the present invention, a composition having an excellent balance between high refractive index and low wavelength dispersion and excellent workability can be obtained. In addition, the optical component of the present invention is formed by using a composite material having an excellent balance between high refractive index and low wavelength dispersion as described above, so that the wavelength characteristics are good and the size can be reduced. Become.

  Embodiments of the present invention will be described below. In addition, although an example is given and demonstrated below, this invention is not limited to the following examples.

(Embodiment 1)
An embodiment of the composite material of the present invention will be described with reference to FIG.

  The composite material 10 of the present invention is configured by uniformly dispersing inorganic particles 11 containing at least yttrium oxide and one or more other inorganic substances in a resin 12 as a base material. Among these, the inorganic particles 11 are generally configured to include primary particles 11a and secondary particles 11b formed by aggregating a plurality of primary particles 11a. Therefore, that the inorganic particles 11 are uniformly dispersed in the resin 12 means that the primary particles 11 a and the secondary particles 11 b of the inorganic particles 11 are substantially not unevenly distributed at specific positions in the composite material 10. It means that it is uniformly dispersed. In the present invention, in order that the composite material 10 has good particle dispersibility, the inorganic particles 11 are more preferably composed of only the primary particles 11a.

  In order to ensure the translucency of the composite material 10 in which the inorganic particles 11 containing yttrium oxide and one or more other inorganic materials are dispersed, the particle size of the inorganic particles 11 is important. When the particle size of the inorganic particles 11 is sufficiently smaller than the wavelength of light, the composite material in which the inorganic particles are dispersed can be regarded as a homogeneous medium having no refractive index variation. Further, when the particle size of the inorganic particles 11 is ¼ or less of the wavelength of light, the scattering in the composite material 10 is only Rayleigh scattering and the translucency becomes high. Therefore, in order to realize high translucency, the particle diameter of the inorganic particles 11 is preferably 100 nm or less. On the other hand, if the particle size of the inorganic particles 11 is less than 1 nm, the material having the quantum effect may cause fluorescence, and thus the characteristics when the optical component is formed may be affected. From the above viewpoint, the effective particle diameter of the inorganic particles 11 is preferably in the range of 1 nm to 100 nm, particularly in the range of 1 nm to 50 nm. Among these, if it is in the range of 1 nm or more and 15 nm or less, the influence of Rayleigh scattering becomes very small, and the translucency of the composite material 10 becomes particularly high, which is further preferable.

  Here, the effective particle diameter will be described with reference to FIG. In FIG. 2, the horizontal axis represents the particle size of the inorganic particles, the left vertical axis represents the frequency of the inorganic particles relative to the horizontal axis particle size, and the right vertical axis represents the cumulative frequency of the particle size. As the effective particle diameter, the center particle diameter (median diameter: d50) having a cumulative frequency of 50% in the particle diameter frequency distribution of the entire inorganic particles can be taken. Furthermore, it is more preferable to use the inorganic particles 11 having a particle size B having a cumulative frequency of 75% within the above range because more particles can contribute to the improvement of the refractive index without inducing light loss due to Rayleigh scattering. . In order to accurately determine the effective particle size, for example, 200 or more inorganic particles may be targeted.

  The particle size and effective particle size of the inorganic particles 11 in the composite material 10 can be confirmed by an electron microscope, X-ray small angle scattering, or the like. The particle size and effective particle size of the primary particles 11a can be obtained by measurement with a particle size distribution meter such as a light scattering method in a solution, measurement with a gas adsorption method in a powder state, observation with an electron microscope, or the like.

  The inorganic particles 11 dispersed in the resin 12 in the composite material 10 of the present invention will be described.

  The inorganic particles 11 include yttrium oxide and one or more other inorganic materials. Examples of other oxides include titanium oxide, zinc oxide, tantalum oxide, niobium oxide, tungsten oxide, indium oxide, tin oxide, zirconium oxide, hafnium oxide, cerium oxide, lanthanum oxide, barium titanate, silica, and alumina. More selected oxides can be used. Examples of the inorganic material include composite oxides of these oxides and yttrium oxide. In particular, yttrium aluminum garnet (hereinafter referred to as YAG), which is a kind of composite oxide of yttrium oxide and alumina, is preferable because of its excellent transparency. Alternatively, an oxide obtained by doping a metal element with a complex oxide containing yttrium oxide and yttrium oxide may be used. In addition to yttrium oxide, metal nitrides such as silicon nitride (refractive index 1.9 to 2.0), metal carbides such as silicon carbide (refractive index 2.6), diamond (refractive index 3.0), diamond A translucent carbon compound such as like carbon (refractive index of 3.0) may be used. Further, sulfides such as copper sulfide and tin sulfide, and metal materials such as gold, platinum, palladium, silver, copper and nickel may be used in combination.

  As described above, the composite material 10 of the present invention is configured by dispersing inorganic particles 11 containing at least yttrium oxide and one or more other inorganic materials. Based on the following examination, the inventor in the composite material 10 in which the inorganic particles 11 are dispersed in the resin, the inorganic material containing yttrium oxide is used to improve the refractive index while suppressing the decrease in the Abbe number as an optical material. It has been found that it is effective to use.

3, various inorganic substances, the refractive index n _d at the d-line (wavelength 587 nm), by measuring the Abbe number ν of a wavelength dispersion, shows the relationship between them. The Abbe number ν is a numerical value defined by (Equation 3). In (Equation 3), n _F and n _C are the refractive indexes of the F line (wavelength 486 nm) and the C line (wavelength 656 nm), respectively.

Since the Abbe number of inorganic substances has not been sufficiently known in the past, FIG. 3 shows that an inorganic thin film is formed on a silicon substrate by sputtering or CVD, and the wavelength dependence of the refractive index is measured by spectroscopic ellipsometry. The Abbe number obtained is shown. As shown in FIG. 3, yttrium oxide has a refractive index n _d of 1.88, an Abbe number of 35, YAG has a refractive index of 1.83 and an Abbe number of 52, both of which have a relatively high refractive index. The Abbe number was also large. These values were close to the zinc oxide is known as a high refractive index material for the refractive index n _d. Further, the Abbe number was higher than that of titanium oxide or the like, and it was found that the Abbe number is a material having a low wavelength dispersion property and an excellent balance between high refractive index and low wavelength dispersion property.

The relationship between the refractive index n _d of the band gap and the d-line (wavelength 587 nm) of various inorganic oxides in FIG. 4, the relationship between the Abbe number ν showing a band gap and a wavelength dispersibility of various inorganic oxides in Fig Each is shown. From these results, it was inferred that the refractive index in a semiconductor such as a metal oxide is related to the band gap, which is the energy difference between the valence band and the conduction band.

  Since a semiconductor absorbs electromagnetic waves having a wavelength corresponding to its band gap energy, it has an absorption edge from the visible light region to the ultraviolet region. For this reason, in order to ensure optical transparency in the visible light region (wavelength 400 to 800 nm), a band gap of about 3 eV or more corresponding to energy of wavelength 400 nm is required. The wavelength dispersion of the refractive index is the change in the refractive index at the bottom of the absorption edge. Thus, the material has a small refractive index change and a low wavelength dispersion. However, when the band gap is further increased, the material exhibits insulating properties, and the dielectric constant and the refractive index, which is the square root thereof, decrease.

  As shown in FIG. 4, yttrium oxide has a band gap of 6.0 eV, which has a high refractive index but high wavelength dispersion, such as titanium oxide and zinc oxide, and an insulator that has a relatively low refractive index such as silica and alumina. Located in the middle. That is, from the viewpoint of the band gap, it was suggested that yttrium oxide is a material having an excellent balance between refractive index and wavelength dispersion. By allowing other inorganic substances to coexist with this yttrium oxide, it becomes possible to prepare various inorganic particles having a wide range of refractive index and wavelength dispersion. For example, YAG, which is a composite oxide of yttrium oxide and alumina, has an intermediate refractive index and wavelength dispersion between yttrium oxide and alumina.

  As described above, yttrium oxide has an excellent balance between refractive index and wavelength dispersibility, and can obtain inorganic particles having a wide range of refractive index and wavelength dispersibility by coexistence with other inorganic substances. By composing the composite material 10 by appropriately combining the inorganic particles 11 containing other inorganic materials with the resin 12 having various refractive indexes, a high refractive index and low wavelength dispersion which has been difficult to realize with conventional resin materials. It is possible to prepare a wide range of materials having optical characteristics in the optical region, and as a result, the degree of freedom in optical component design can be dramatically expanded.

  The resin 12 serving as a base material of the composite material 10 of the present invention is translucent and has a refractive index of 1 in order to ensure a high translucency and obtain a composite material exhibiting a high refractive index and low wavelength dispersion. It is preferable that it exists in the range of 4-1.7. It is particularly preferable to use an ultraviolet curable acrylic resin or epoxy resin because various properties can be easily controlled by introducing functional groups and the process of forming optical components described later is facilitated.

  As the resin 12, a resin having high translucency can be used among resins such as a thermoplastic resin, a thermosetting resin, a photocurable resin, and an electron beam curable resin. For example, acrylic resins such as polymethyl methacrylate; epoxy resins; polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polycaprolactone; polystyrene resins such as polystyrene; olefin resins such as polypropylene; polyamide resins such as nylon; polyimides and polyethers Polyimide resin such as imide; polyvinyl alcohol; butyral resin; vinyl acetate resin; alicyclic polyolefin resin may be used. Further, engineering plastics such as polycarbonate, liquid crystal polymer, polyphenylene ether, polysulfone, polyethersulfone, polyarylate, and amorphous polyolefin may be used. Also, a mixture or copolymer of these resins (polymers) may be used. Moreover, you may use what modified | denatured these resin.

  Among these, acrylic resin, epoxy resin, polyimide resin, butyral resin, polyolefin, and polycarbonate resin have high transparency and good moldability. These resins can have a refractive index in the range of 1.4 to 1.7 (preferably 1.5 or more) by selecting a predetermined molecular skeleton.

The Abbe number ν _m of the resin 12 is not particularly limited, but the Abbe number ν _COM of the composite material 10 obtained by dispersing the inorganic particles 11 is improved as the Abbe number ν _{m of the} resin 12 serving as the base material is higher. Needless to say. In particular, by using a resin 12 having an Abbe number ν _m of 50 or more, a composite material 10 having an Abbe number ν _COM of 40 or more and sufficient optical characteristics for application to an optical component such as a lens is obtained. This is more preferable. Examples of the resin having an Abbe number ν _m of 50 or more include alicyclic olefin resins, polysiloxane resins, resins containing a fluorine atom in the basic skeleton, and the like, but are not limited thereto.

  The resin 12 is selected in consideration of characteristics such as moldability, film formability, substrate adhesion, and environment resistance corresponding to the optical component in which the composite material 10 is used in addition to the above optical characteristics. The resin 12 is selected in consideration of the dispersibility of the inorganic particles 11.

  The refractive index of the composite material 10 can be estimated by, for example, Maxwell-Garnet theory expressed by (Equation 4). It is also possible to estimate the Abbe number of the composite material 10 by estimating the refractive indexes of the d-line, the F-line, and the C-line by (Equation 4). From the estimation based on this theory, the blending ratio of the resin 12 and the inorganic particles 11 may be determined.

In (Equation 4), n _COM is the average refractive index of the composite material, and n _p and _nm are the refractive indexes of the inorganic particles 11 and the resin 12, respectively. P is a volume ratio of the inorganic particles 11 to the entire composite material 10. When the inorganic particles 11 absorb light or when the inorganic particles 11 contain a metal, the refractive index of (Equation 4) is calculated as a complex refractive index. Incidentally, the estimation of the refractive index using equation (4) is an expression that holds when the _{n p ≧ n m, n p} < For _{n m} following equation (5).

  The evaluation of the actual refractive index of the composite material 10 is performed by forming or molding the prepared composite material 10 and performing spectroscopic measurement methods such as ellipsometry, Abeles method, optical waveguide method, spectral reflectance method, prism coupler method, etc. It can be obtained by actually measuring with.

  For example, when a resin having a refractive index of 1.5 is used, a composite material having a refractive index of 1.6 or more can be obtained by mixing YAG having a refractive index of 1.83 so that the volume ratio is 30% or more. It is expected to be. Since (Equation 4) or (Equation 5) is similarly used for the d-line, F-line, and C-line, the refractive index at each wavelength is calculated. Therefore, by substituting the obtained refractive index into (Equation 3), Abbe The number can be estimated.

  As an example, two types of resins (resin having a refractive index of 1.5 and an Abbe number of 50, or a resin having a refractive index of 1.6 and an Abbe number of 25) are used as inorganic particles. 83, the Abbe number 52) is obtained by mixing so that the volume ratio of the entire composite material is 0%, 10%, 20%, and 30%. Calculated from Equation 4). The results are shown in FIG. For comparison, FIG. 6 also shows the refractive index of a composite material obtained by similarly mixing titanium oxide (refractive index 2.61, Abbe number 12) or alumina (refractive index 1.76, Abbe number 76). The Abbe number relationship is displayed.

The alternate long and short dash line in FIG. 6 indicates a refractive index n _COM = 1.60, an Abbe number ν _COM = 20, and

  Indicates. In FIG. 6, the material having the refractive index and the Abbe number in the region above the one-dot chain line is superior in balance between the high refractive index and the low wavelength dispersion as compared with the general resin material represented by (Equation 1). By using such a material, it is possible to form a small and high-performance optical component.

  As shown in FIG. 6, the composite material excellent in the balance between high refractive index and low wavelength dispersibility by coexisting in the resin 12 the first inorganic particles 11 containing yttrium oxide and one or more other inorganic materials. 10 can be obtained.

(Embodiment 2)
Another embodiment of the composite material of the present invention will be described with reference to FIG.

The composite material 70 of the present invention includes first inorganic particles 11 containing at least yttrium oxide, and second inorganic particles 13 having a composition different from that of the first inorganic particles 11 and an Abbe number ν _p of 50 or more. , And is uniformly dispersed in the resin 12 as the base material. Similarly to the first inorganic particles 11, the second inorganic particles 13 include primary particles 13 a and secondary particles 13 b formed by aggregating a plurality of primary particles 13 a. Therefore, the fact that the first inorganic particles 11 and the second inorganic particles 13 are uniformly dispersed in the resin 12 means that the primary particles 11a and the secondary particles 11b of the first inorganic particles 11 and the second inorganic particles. It means that the primary particles 13 a and the secondary particles 13 b of the particles 13 are substantially uniformly dispersed without being unevenly distributed at specific positions in the composite material 70. The second inorganic particles 13 also preferably have an effective particle diameter in the range of 1 nm to 100 nm, particularly in the range of 1 nm to 50 nm, for the same reason as the first inorganic particles 11.

  For the resin 12 serving as the base material, the same materials as those described in Embodiment 1 can be used. This also applies to the following embodiments.

  The Maxwell-Garnet theory shown in (Equation 4) is originally valid for a binary system, but regarding the refractive index of a ternary composite material in which two types of inorganic particles are dispersed in a resin. , (Equation 4) can be estimated to some extent by expanding (Equation 7) and (Equation 8).

In (Expression 7), n _CB is the refractive index of the composite material in which the second inorganic particles 13 are dispersed alone in the resin 12, and n _pB is the refractive index of the second inorganic particles 13. P _m and P _B are volume ratios of the resin 12 and the second inorganic particles 13 in the entire composite material 10, respectively. (Equation 7) is an equation that holds when n _pB ≧ n _pm , and when n _pB <n _pm , (Equation 5) is corrected in the same way as (Equation 5) to estimate the refractive index.

In ( _Equation 8), n _pA is the refractive index of the first inorganic particles 11. P _A is configured, the volume ratio of the first inorganic particles 11 in the entire composite material 10, the composite material 10 is a resin 12, only the three components of the first inorganic particles 11 and the second inorganic particles 13 In this case, P _A + P _B + P _m = 1. (Equation 8) is an expression that is established when n _pA ≧ n _CB . When n _pA <n _CB , (Equation 5) is corrected in the same manner as in (Equation 5), and the refractive index of the composite material 10 is estimated.

  As an example, two kinds of resins having a refractive index of 1.5 and an Abbe number of 50, or a resin having a refractive index of 1.6 and an Abbe number of 25, and yttrium oxide (refractive index of 1.88) as inorganic particles. , Abbe number 35) and alumina (refractive index 1.76, Abbe number 76) or silica (refractive index 1.46, Abbe number 68), the volume ratio of inorganic particles in the total composite material is 0% in total, 10 The relationship between the refractive index and the Abbe number was calculated from (Equation 7) and (Equation 8) for the composite material obtained by mixing so as to be%, 30%, or 50%. The volume ratio of yttrium oxide to alumina or silica was changed to 10: 0, 8: 2, 6: 4, 5: 5, 4: 6, 2: 8, and 1: 9. The results are shown in FIG.

The dashed-dotted line in FIG. 7 is similar to FIG. 5 in refractive index n _COM = 1.60, Abbe number ν _COM = 20, and

  Indicates. In FIG. 7, the material having the refractive index and the Abbe number in the region above the alternate long and short dash line has an excellent balance between the high refractive index and the low wavelength dispersion as compared with the general resin material represented by (Equation 1). By using such a material, it is possible to form a small and high-performance optical component.

As shown in FIG. 8, together with the first inorganic particles 11 containing yttrium oxide, as the second inorganic particles 13, particles having a wavelength dispersibility lower than that of yttrium oxide, for example, an Abbe number ν _p of 50 or more are resin 12. By making it coexist, the decrease in the Abbe number of the composite material 70 can be further suppressed. From FIG. 5, it is considered that the Abbe number ν _p is 50 or more in the case of a substance having a band gap of approximately 6 to 7 eV or more. Examples of inorganic particles corresponding to this include silica (band gap 9.7 eV), alumina (7.4 to 9 eV, depending on the crystal system), magnesium oxide (7.8 eV), calcium oxide (7.1 eV), and the like. Examples thereof include metal oxides, metal nitrides such as aluminum nitride (6.2 eV), and metal halides such as calcium fluoride (11.5 eV) and potassium chloride (10.9 eV).

  In addition, coexistence in the resin with the first inorganic particles 11 containing yttrium oxide and the second inorganic particles 13 containing at least either silica or alumina in the resin decreases the Abbe number of the composite material 70 as described above. In addition to being able to control, the influence on the durability of the resin 12 serving as a base material is relatively small, the inorganic particles can be easily obtained or prepared, and the production cost of the composite material 70 is further reduced.

  As described above, yttrium oxide having an excellent balance between refractive index and wavelength dispersion and inorganic fine particles having low wavelength dispersion coexist in the resin, so that the refractive index and Abbe number can be increased without increasing wavelength dispersion. Adjustment can be easily performed, and the degree of freedom in optical component design is further expanded.

In the composite material 70 of the present invention, the first inorganic particles 11 dispersed in the resin 12 may include inorganic components other than yttrium oxide as long as the effects of the present invention are obtained. For example, as in the case of the composite material 10 of Embodiment 1, a composite oxide of yttrium oxide, an oxide obtained by doping a composite oxide containing yttrium oxide with a metal element, or yttrium oxide, a metal nitride, a metal Carbides, translucent carbon compounds, metal sulfides, metals, and the like may be used in combination. The second inorganic particles 13 may also contain inorganic components other than the metal oxides, metal nitrides, and metal halides as long as the Abbe number ν _p is 50 or more. Further, inorganic components other than silica or alumina may be included.

  Next, composite materials 10 and 70 according to the first and second embodiments of the present invention will be described. A preferable ratio (volume ratio) of the inorganic particles in the entire composite material 10 or 70 varies depending on the combination of the resin 12 and the inorganic particles 11 and 13 and the applied optical component. When the proportion of the inorganic particles 11 and 13 becomes too large, the translucency is lowered. Therefore, the upper limit of the proportion of the inorganic particles 11 and 13 in the composite material is usually about 50% by volume to 80% by volume. In order to achieve a high refractive index and high translucency, the proportion of the inorganic particles 11 and 13 in the composite material is in the range of 5% by volume to 50% by volume in total for all types of inorganic particles. It is preferable.

  The ratio of the resin and inorganic particles in the composite material is selected according to the characteristics required for the applied optical component, the types of the resin and inorganic particles, and the like. In one example, the proportion of the resin in the composite material is preferably in the range of 50 volume% to 95 volume% (particularly 60 volume% to 80 volume%). The proportion of the inorganic particles in the composite material is preferably in the range of 5% to 50% by volume (for example, 20% to 40% by volume).

  In the composite materials 10 and 70 of the present invention, the first inorganic particles 11 containing yttrium oxide excellent in the balance between the refractive index and the wavelength dispersion and the second inorganic particles 13 having a low wavelength dispersion are dispersed in the resin 12. By adopting such a configuration, it is possible to obtain an optical component material that satisfies (Equation 10), which has been difficult to achieve with a resin alone.

  The refractive indexes of the composite materials 10 and 70 of the present invention are not particularly limited as long as they can satisfy (Equation 10), but satisfy the characteristics required for optical components, and realize a reduction in thickness and size. From the viewpoint, it is preferably 1.60 or more. The upper limit of the refractive index of the composite material is 1.88, which is theoretically the refractive index of yttrium oxide, from (Equation 4), (Equation 7), and (Equation 8). However, as described above, the ratio of the first inorganic particles 11 and the second inorganic particles 13 to the inorganic particles C in the composite materials 10 and 70 is preferably 50% by volume or less in total, Since the refractive index of the resin 12 as the material is generally 1.7 or less, it is considered that the upper limit of the refractive index of the composite materials 10 and 70 is practically about 1.8.

  The Abbe number of the composite materials 10 and 70 of the present invention is not particularly limited as long as it can satisfy (Equation 10), but from the viewpoint of improving characteristics required as an optical component, particularly chromatic aberration of a lens, and the like. It is preferable that it is 20 or more. The upper limit of the Abbe number of the composite material is theoretically the Abbe number of the second inorganic particles 13 having low wavelength dispersion, that is, 76 of alumina at maximum, from (Equation 7) and (Equation 8). However, as described above, the proportion of the inorganic particles in the composite materials 10 to 70 is preferably 50% by volume or less, and the Abbe number of the resin 12 serving as the base material is generally 65 or less. In practice, the upper limit of the Abbe number of the composite materials 10 and 70 is considered to be about 70.

  Furthermore, since the composite materials 10 and 70 of the present invention are based on the resin 12, the inorganic particles 11 include yttrium oxide having excellent workability and a smaller thermal expansion coefficient than the resin, and one or more other inorganic materials. In addition, it has a feature that there is little deterioration due to the influence of temperature change.

(Preparation method of composite material)
There is no limitation on the method for preparing the composite materials 10 and 70 obtained by dispersing the inorganic particles 11 and 13 shown above in the resin 12 as the base material, and the material may be prepared by a physical method or a chemical method. May be prepared. For example, the composite material 10 can be prepared by any of the following methods.

  (1) A method of mechanically and physically mixing a resin or a resin-dissolved solution and inorganic particles.

  (2) A method of polymerizing a resin raw material after mechanically and physically mixing the resin raw material (monomer, oligomer, etc.) and inorganic particles to obtain a mixture.

  (3) A method of forming inorganic particles in the resin by mixing the resin or a solution in which the resin is dissolved and the raw materials of the inorganic particles, and then reacting the raw materials of the inorganic particles.

  (4) After mixing the raw material of the resin (monomer, oligomer, etc.) and the raw material of the inorganic particles, reacting the raw material of the inorganic particles to synthesize the inorganic particles, polymerizing the raw material of the resin, And a process of synthesizing.

  In the composite material of the present invention, the raw material of the inorganic particles is yttrium alkoxide (yttrium triethoxide, yttrium trimethoxide, yttrium tri-i-propoxide, yttrium tri-n-propoxide, Yttrium tri-n-butoxide, yttrium tri-sec-butoxide, yttrium tri-tert-butoxide, etc.), yttrium coordination compounds (such as yttrium acetylacetonate), yttrium halides (such as yttrium chloride), and the like. In addition, a composite oxide of yttrium oxide can be prepared from an alkoxide (such as yttrium aluminum-i-propoxide). In addition to these, raw materials for other inorganic particles, for example, organometallic compounds including alkoxides and coordination compounds, metal halides, and the like may be used in combination. For silica, alkoxysilane (tetraethoxysilane, tetra-i-propoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, methyltriethoxysilane, methyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxy Silane, dimethyldiethoxysilane, etc.), silicon halides (tetrachlorosilane, methyltrichlorosilane, ethyltrichlorosilane, etc.) and the like. In the case of alumina, aluminum alkoxide (aluminum triethoxide, aluminum tri-i-propoxide, aluminum tributoxide, etc.), chelate compound (aluminum acetylacetonate, etc.) and the like can be used.

  In the methods (1) and (2), various inorganic particles formed in advance can be used, and there is an advantage that a composite material can be prepared by a general-purpose dispersion apparatus. In the methods (3) and (4), it is necessary to perform a chemical reaction, and thus there are limitations on materials. However, these methods have the advantage that the raw materials can be mixed at the molecular level to increase the dispersibility of the inorganic particles.

  In addition, when the 1st inorganic particle 11 containing yttrium oxide and the 2nd inorganic particle 13 of low wavelength dispersibility coexist in the resin 12, both particle | grains are carried out by the same method of said (1) to (4). They may be prepared or prepared by different methods. For example, one particle may be mixed as preformed inorganic particles, and the other particle may be formed from a raw material.

  In the above method, the order of mixing the inorganic particles or the raw material of the inorganic particles and the resin or the raw material of the resin is not particularly limited, and a preferable order may be appropriately selected. For example, a resin, a raw material of resin, or a solution in which they are dissolved may be added to a solution in which inorganic particles having a primary particle size substantially in the range of 1 nm to 100 nm are dispersed and mixed mechanically and physically. Good. Further, when the first inorganic particles 11 containing yttrium oxide and the second inorganic particles 13 having low wavelength dispersibility coexist in the resin, the effect of the present invention can be obtained with respect to the order of preparing the respective particles. There is no particular limitation. For example, in the methods (3) and (4), when an alkoxide is used as a raw material for inorganic particles, a relatively low reactivity alkoxysilane or aluminum alkoxide is first reacted for a certain period of time, and then this system is reactive. A method of further mixing and reacting high yttrium alkoxide can be employed.

  In addition, in the composite materials 10 and 70 of this invention, as long as the effect of this invention is acquired, components other than the inorganic particle 11 and 13 and resin 12 used as a base material may be included. For example, although not shown, even if a dispersant or surfactant that improves the dispersibility of the inorganic particles in the resin, a dye or pigment that absorbs electromagnetic waves of a specific range of wavelengths coexists in the composite material. There is no problem.

  The processing method of the composite materials 10 and 70 for forming the optical component of the present invention varies depending on the type of the resin 12 as the base material, the shape and required characteristics of the optical component to be formed, and the like. For example, when a molded body such as a lens substrate, a disk substrate, or a fiber is obtained, if the resin is a thermoplastic resin, the composite material can be softened or melted by heating to a certain temperature range, and various molding processes can be performed. it can. Examples of the molding method include extrusion molding, injection molding, vacuum molding, blow molding, compression molding, calender molding, laminate molding, and heat press, and it is possible to obtain molded bodies having various shapes. If the resin is a thermosetting resin and a photocurable or electron beam curable resin, the resin raw material is cast in a state where inorganic particles or inorganic particle raw materials are mixed with monomers or oligomers, and heated or heated. A molded body of the composite material of the present invention can be obtained by a method of polymerizing a resin raw material by light or electron beam irradiation (cast polymerization). Moreover, you may implement processing by cutting and grinding | polishing with respect to these molded objects as needed, or surface treatment processing, such as a hard coat and an antireflection film.

  On the other hand, when forming a coating on the surface of the molded body or an optical waveguide into the hole, a mixture containing a substance for constituting the composite material, for example, a coating solution can be used. This mixture (coating liquid) contains a resin or a raw material of the resin, inorganic particles, and a solvent (dispersion medium). Moreover, you may use the mixture which does not contain a solvent. In this case, a thermoplastic resin is used and a mixture whose viscosity is lowered by heating is used, or a film-like mixture is used. The coating liquid can be prepared, for example, by the following method.

  (1) A method of preparing a coating liquid by diluting a composite material with a solvent. When this coating liquid is used, the solvent is removed after the coating liquid is applied.

  (2) A method of preparing a coating liquid by mixing resin monomers, oligomers, low molecular weight substances and the like with inorganic particles. When this coating solution is used, it is necessary to synthesize a resin by reacting raw materials such as monomers, oligomers, and low molecular weight substances. The timing for performing the synthesis is determined according to the subsequent process.

  (3) A method of preparing a coating liquid by mixing a raw material of inorganic particles, a resin, and a solvent. In the case of using this coating liquid, after coating the coating liquid, the inorganic particles are reacted by a sol-gel method or the like to synthesize the inorganic particles in the coating film.

  (4) A method of preparing a coating liquid by dispersing inorganic particles in a heated resin having a reduced viscosity. In this method, when the temperature of the coating film is lowered, the coating film is solidified to form a coating film or an optical waveguide.

  These methods may be appropriately selected according to the types of the resin 12 and the inorganic particles 11 and 13, the coating method, and the like. The coating liquid may contain a crosslinking agent, a polymerization initiator, a dispersing agent, etc. as necessary.

  There is no limitation on the method of disposing the mixture on the surface of the molded body or in the holes, and for example, a known method can be applied. Specifically, application using an injection nozzle such as a dispenser, spray application such as spray coating or inkjet method, application by rotation such as spin coating, application by squeezing such as roll coating or die coating, screen printing, pad printing, Application by transfer such as imprint may be applied. Such a method can be performed using existing equipment.

  After applying the coating liquid, the film or the optical waveguide can be formed by removing the solvent. In addition, when a coating liquid contains the raw material of resin material (monomer, oligomer, etc.) and inorganic particle | grains, you may make them react after application | coating as needed and synthesize | combine resin and inorganic particle | grains. Further, a film formed by applying a coating liquid may be cured to form a coating film or an optical waveguide. The curing treatment can be performed by photocuring, electron beam curing, heat curing, drying treatment or the like.

(Embodiment 3)
One embodiment of an optical component using the composite material of the present invention will be described with reference to FIG.

  In the present invention, an optical component formed using a composite material formed by dispersing inorganic particles containing at least yttrium oxide and one or more other inorganic substances in a resin includes a lens, a diffractive optical element (diffraction A lens having a grating, a spatial low-pass filter, a polarization hologram, and the like), a solid-state imaging device having an optical waveguide, an optical fiber, an optical disk substrate, an optical filter, an optical adhesive, and the like. In FIG. 9, a sectional view of an example of a lens having a diffraction grating shape formed on the surface thereof will be described. The lens shown in FIG. 9 is an example, and the present invention can be applied to various other forms.

  An annular diffractive grating shape 92a is formed on the surface of the lens substrate 91, and an annular diffractive grating 92b is also formed on the opposite surface. Protective films 93a and 93b are formed so as to cover these diffraction grating shapes 92a and 92b, respectively. The diffraction grating shape 92 formed on the surface of the lens substrate 91 may be formed on one side or both sides of the lens. When formed on both sides, the diffraction grating shapes 92a and 92b on both sides do not necessarily have the same depth and shape. Also, the annular zone pitch in the diffraction grating need not be the same. Further, it does not have to be an annular zone, and a linear or curved diffraction grating or a holographic diffraction grating may be used. Further, the materials and the thicknesses of the protective films 93a and 93b on both sides need not be the same. Both surfaces of the lens shape need not be convex, and may be concave and convex, double-sided concave, double-sided flat, flat and convex, flat and concave.

  In the lens of the present invention, the composite material can be used as the lens substrate 91. Since the composite material of the present invention exhibits a high refractive index and low wavelength dispersion, the use of the composite material as the lens substrate 91 enables a reduction in thickness as compared with a conventional plastic lens, and also provides an image surface. The influence of curvature and chromatic aberration is also reduced. In particular, by forming the diffraction grating shape 92 on at least one of the lens surfaces, it is possible to obtain a lens that is thinner and has excellent optical characteristics.

  The processing method as the lens base material 91 differs depending on the resin used as the base material of the composite material. For example, a composite material is supplied in a softened or melted state to a mold that forms a lens shape and molding is performed, or a monomer or oligomer that is a resin raw material is mixed with inorganic particles or inorganic particle raw materials It is conceivable to mold in a desired lens shape by a method such as casting in a state and polymerizing a resin raw material by heating or light or electron beam irradiation. At this time, a diffraction grating shape 92 is formed on the surface of the obtained lens by forming a diffraction grating shape in the mold. In addition, the processing method of a lens is not limited to these.

  When the composite material of the present invention is used as the lens base material 91, the resin used as the base material of the composite material should be a translucent resin generally used for plastic lenses and the like as long as the effects of the present invention can be obtained. Can do. For example, methacrylic resin, polycarbonate resin, polystyrene, alicyclic polyolefin resin, and the like can be used, but are not necessarily limited thereto. Among them, it is particularly preferable to use a thermoplastic resin as a base material because it is easy to mold and has higher productivity.

  In addition, the protection which has the effect | action which adjusts mechanical characteristics, such as optical characteristics, such as refractive index and a reflectance, friction resistance, and thermal expansibility, on the lens base material 91 formed using the composite material of this invention. A film may be formed.

  The lens base 91 using the composite material of the present invention is easy to manufacture because the composite material is based on resin. The processing method of the lens base material 91 on which the diffraction grating shape 92 is formed differs depending on the resin used as the base material of the composite material, but can be easily mass-produced by molding with a mold, for example. As an example of processing of the mold, a plating film is formed on the surface of the mold, and a lens forming piece having a diffraction grating shape is processed on the plating film using a turning process with a diamond tool. Since the above materials are blended with polycarbonate and cycloolefin resin, which are thermoplastic resins, a lens having a diffraction grating shape 92 formed by injection molding can be easily manufactured. Alternatively, the resin raw material monomer or oligomer is cast in a state where inorganic particles or inorganic particle raw materials are mixed, and the resin raw material is polymerized by heating or irradiation with light or electron beam, etc. It is also conceivable to form the lens shape.

  Further, a stepped diffraction grating (inverted shape) may be formed by dry etching or the like on a material that transmits ultraviolet light or visible light such as quartz as a mold material. By using such a mold material, a method of applying a mixture of a composite material containing a photo-curable resin to the mold material and curing and releasing an ultraviolet curable resin or a visible light curable resin, so-called photopolymer molding is used. The lens substrate 91 made of a composite material and having the diffraction grating shape 92 formed can be easily manufactured. In addition, the processing method of a lens is not limited to these.

  In order to secure the ease of mold processing, the contribution of the diffraction grating shape 92 in terms of lens performance, and stability with respect to the ambient temperature, it is desirable that the depth of the diffraction grating shape 92 be 20 μm or less. For a diffraction grating shape 92 having a depth exceeding several tens of μm, it is difficult to perform mold processing with high processing accuracy. This is because die machining is generally performed using a cutting tool, but if the diffraction grating shape 92 is deep, the processing amount increases and the tip of the cutting tool wears, so that the processing accuracy deteriorates. At the same time, if the diffraction grating shape 92 becomes deep, the pitch of the diffraction grating shape 92 cannot be reduced. When the diffraction grating shape 92 becomes deeper, it is necessary to process the die with a tool having a large curvature radius at the tip, and as a result, the diffraction grating shape 92 cannot be processed unless the pitch of the diffraction grating shape 92 is increased to some extent. Accordingly, as the diffraction grating shape 92 is deeper, the degree of freedom in shape design of the diffraction grating shape 92 is lost, and the aberration reduction effect by the diffraction grating shape 92 is almost lost.

  In the lens of the present invention, a composite material may be used as the protective film 93 formed on the lens substrate 91. Even when the composite material is formed as the protective film 93 on the lens base material 91, it is possible to reduce the influence of field curvature and chromatic aberration as in the case of using the lens base material 91.

When the protective film 93 is formed from the composite material of the present invention on the lens base material 91 having the diffraction grating shape 92 formed on at least one of the surfaces, the first-order diffraction efficiency of the lens is 100% at a certain wavelength λ. The lattice depth d ′ is given by (Equation 11). In (Equation 11), n _COM is the refractive index of the composite material, and n _L is the refractive index of the lens substrate 91 at the wavelength λ.

  If the right side of (Equation 11) becomes a constant value in a certain wavelength region, the wavelength dependence of the diffraction efficiency in that wavelength region is lost. That is, the lens base material 91 and the protective film 93 may be configured by a combination of a high refractive index / low wavelength dispersion material and a low refractive index / high wavelength dispersion material. Here, the composite material of the present invention is prepared by selecting an appropriate resin, inorganic particle type and volume ratio, and used as the protective film 93, so that the diffraction efficiency can be improved without increasing the diffraction grating depth d '. A lens with less wavelength dependency can be formed. With this configuration, the pitch of the diffraction grating shape 92 can be reduced, and a lens having no chromatic aberration and excellent MTF characteristics in a wide wavelength region can be formed without combining a plurality of lenses. As a result, the optical device can be reduced in thickness and size.

  The protective film 93 using the composite material can be formed on the lens substrate 91 using the coating liquid described above. In this case, as the lens base material 91, a material that can keep translucency without being affected by a solvent (dispersion medium) used for a coating liquid from among translucent materials generally used as a lens base material. Must be selected. That is, a solvent used for coating liquid from among various translucent resins used for optical glass, translucent ceramics, plastic lenses, etc., such as methacrylic resin, polycarbonate resin, polystyrene, alicyclic polyolefin resin, etc. It may be selected according to durability. When resins are used as the lens substrate 91, inorganic particles for adjusting optical properties such as refractive index and mechanical properties such as thermal expansibility and dyes that absorb electromagnetic waves in a specific wavelength region are used for these resins. Or pigments may coexist if necessary. Further, as the lens base material 91, the composite material of the present invention may be used as described above.

  The resin used as the base material of the composite material used for the protective film 93 is that the refractive index distribution of the protective film 93 obtained by dispersing inorganic particles can satisfy (Equation 11) in the wavelength region where the lens is used. Are selected in consideration of film forming properties, adhesion to a lens substrate, dispersibility of inorganic particles, and the like. Furthermore, when the lens of the present invention is used in an optical device that does not use a cover glass or the like, a certain degree of strength (friction resistance) is required for the resin itself that is the base material of the protective film 93.

  The kind and volume ratio of the inorganic particles in the protective film 93 are determined so that the refractive index distribution of the protective film 93 satisfies (Equation 11) in the wavelength region where the lens is used. When the refractive index distribution of the lens substrate 91 is determined, the refractive index of the protective film 93 that can satisfy (Equation 11) and its wavelength dispersion (Abbe number) are calculated, so the calculated refractive index and Abbe number. The composition of the resin base material and the inorganic particles showing the above may be estimated using the Maxwell-Garnet theory shown in (Equation 4) to (Equation 7) and (Equation 8).

  Note that an antireflection film may be further formed on the surface of the protective film 93. As a material of the antireflection film, any material having a refractive index lower than that of the composite material used as the protective film 93 may be used. For example, either a resin or a composite material of resin and inorganic particles, an inorganic thin film formed by vacuum deposition, or the like can be given. Examples of the inorganic particles used in the composite material as the antireflection film include silica, alumina, and magnesium oxide having a low refractive index. By using a composite material for the antireflection film, manufacturing becomes easy, and at least one of the lens and the protective film is a composite material. The characteristic stability with respect to temperature is improved, and cracks and film peeling are less likely to occur. Moreover, you may form the antireflection shape of nanostructure on the surface of a protective film. For example, it can be easily formed by a transfer method (nanoimprint or the like) using a mold.

(Embodiment 4)
Another embodiment of the optical component using the composite material of the present invention will be described with reference to FIG. In FIG. 10, an example of a CCD type solid-state imaging device in which an optical waveguide is formed using the composite material of the present invention is shown and described. In the present embodiment, the CCD type is described as the solid-state imaging device, but other types of devices such as a MOS type can also be applied.

  FIG. 10 shows only one pixel portion of the CCD. A CCD solid-state imaging device 1010 shown in FIG. 10 includes a substrate 103 (hatching is omitted) on which a photoelectric conversion unit (light receiving sensor) 101 and a charge transfer unit 102 are formed, and an insulating layer formed on the substrate 103. 104, a charge transfer electrode 105, an antireflection film 106, a light shielding film 107, an interlayer insulating film 108, and an optical waveguide 109.

  The substrate 103 is a semiconductor substrate such as silicon. A plurality of photoelectric conversion portions 101 that perform photoelectric conversion are formed on the surface. The two charge transfer units 102 are arranged so as to sandwich the photoelectric conversion unit 101 therebetween. The photoelectric conversion unit 101 and the charge transfer unit 102 can be formed, for example, by doping impurities into a specific conductivity type semiconductor substrate.

  The insulating layer 104 is made of, for example, silicon oxide (SiO 2) and can be formed by a thermal oxidation method, a CVD method, or the like. The charge transfer electrode 105 is disposed so as to face the charge transfer portion 102 with the insulating layer 104 interposed therebetween. The charge transfer electrode 105 is made of, for example, polysilicon. Signal charges obtained by photoelectric conversion in the photoelectric conversion unit 101 are read out to the charge transfer unit 102 and transferred by the charge transfer electrode 105.

  The antireflection film 106 is a film for preventing light incident from the optical waveguide 109 from being reflected, and is disposed above the photoelectric conversion unit 101. The antireflection film 106 also serves as an etching stopper layer. The antireflection film 106 can be formed of, for example, aluminum oxide or silicon nitride.

  A light shielding film 107 is formed on the surface of the insulating layer 104 except for the portion above the photoelectric conversion portion 101. The light shielding film 107 is formed so as to cover the charge transfer electrode 105. The light shielding film is made of a metal such as aluminum (Al) or tungsten (W).

  An interlayer insulating film 108 is formed above the substrate 103, specifically, above the light shielding film 107. The interlayer insulating film 108 plays a role as a planarizing film. The interlayer insulating film 108 is made of, for example, SiO2. In the interlayer insulating film 108, a hole 108 h penetrating the interlayer insulating film 108 is formed above the photoelectric conversion unit 101.

  An optical waveguide 109 made of the composite material of the present invention is formed in the hole 108h. The refractive index of the composite material (optical waveguide 109) is larger than that of the interlayer insulating film. The hole 108h may be subjected to pretreatment for improving the adhesion between the hole 108h and the composite material. As the pretreatment, for example, surface treatment using a coupling agent or the like, plasma treatment, or the like can be used.

  The cross-sectional shape of the optical waveguide 109 (the shape when the optical waveguide is viewed from the upper surface) is circular or rectangular. The size of the optical waveguide 109 (cross-sectional diameter or side length) is, for example, about 0.5 μm to 3 μm. The aspect ratio of the optical waveguide 109, that is, the ratio between the length (length in the direction perpendicular to the surface of the substrate 103) and the size of the bottom surface of the optical waveguide (surface on the substrate 103 side) [length] / [size ] Is about 1 to 5. Note that the shape of the optical waveguide 109 varies depending on the design of the solid-state imaging device, and is not limited to the above-described shape.

  Note that the solid-state imaging device shown in FIG. 10 is an example, and the present invention can be applied to various other forms. For example, an on-chip lens may be formed above the optical waveguide 109. Further, as the shape of the optical waveguide 109, FIG. 1 shows a tapered shape in which the cross-sectional area decreases from the front surface side to the bottom surface side, but a columnar shape with a constant cross-sectional area size, The shape of the interface may be stepped. A plurality of electrodes may be formed inside the interlayer insulating film.

  Further, the optical waveguide 109 of the present invention may function as a wavelength filter. For example, a dye or pigment that absorbs light in a specific range of wavelengths may be further mixed into the composite material of the present invention to function as a color filter. In addition, a material that absorbs infrared rays, for example, a complex salt of metal ions such as copper ions, a dye having absorption in the near infrared wavelength, or inorganic particles such as indium tin oxide (ITO) and tin antimony oxide (ATO) are mixed, It may function as an infrared shielding filter. Similarly, a material that absorbs ultraviolet rays such as zinc oxide or cerium oxide may be mixed to function as an ultraviolet shielding filter.

  As described above, the optical waveguide 109 of the present invention can be formed, for example, by applying a coating liquid and then removing or curing the solvent. When forming an optical waveguide in a hole having a complicated shape such as a hole with a high aspect ratio or a stepped shape, the pressure is increased after a mixture containing a substance for forming a composite material is placed in the hole under reduced pressure. You may use the method of making it fill with a hole. Further, depending on the application application of the optical waveguide 109, a step of flattening the film formed of the composite material may be performed. Examples of the flattening method include a method of increasing the number of rotations of spin coating, grinding such as CMP (Chemical Mechanical Polishing), etching using plasma or an etching solution, and removal of excess composite material by squeezing.

  By using the composite material of the present invention, an optical waveguide used for an optical communication device, a solid-state imaging device or the like can be formed. With the progress of device miniaturization, the aspect ratio of the hole forming the optical waveguide is increased, and as a result, the coverage of the material embedded in the hole is deteriorated, resulting in a phenomenon in which a void is generated inside the optical waveguide. Such a problem is particularly remarkable in an optical waveguide formed by a vacuum film forming method such as a silicon nitride film or a DLC film. On the other hand, an optical waveguide formed by application of polyimide resin or the like has good coverage, but there is a problem that the difference in refractive index from the surrounding material is not sufficient and the light collection efficiency is low.

  Since the composite material of the present invention improves the refractive index by dispersing inorganic particles containing yttrium oxide and one or more other inorganic substances, it is possible to form an optical waveguide with high light collection efficiency. As a result, as shown in the present embodiment, by applying the optical waveguide 109 of the present invention to a solid-state imaging device, it is possible to suppress a decrease in sensitivity when pixels are miniaturized. On the other hand, when the optical waveguide 109 of the present invention is applied to an optical communication device, the bending radius of the optical circuit can be reduced, and a complicated circuit can be formed with a smaller area. In addition, since the resin is a base material, the coverage is good and the resin can be formed by a coating method. Therefore, the optical waveguide can be formed in a shorter time and with lower energy than an optical waveguide formed by a vacuum film forming method. Furthermore, since the composite material of the present invention has a smaller thermal expansion coefficient than that of resin alone, it can suppress delamination due to temperature changes of the optical waveguide.

  Below, the composite material of this invention and the specific example of the optical component formed using this are demonstrated.

Example 1
A composite material in which YAG particles were dispersed as yttrium oxide and one or more other inorganic particles was prepared by the following method. First, YAG (primary particle size 50 nm) powder and a dispersant (G-820, manufactured by Kyoeisha Chemical Co., Ltd.) are charged into propylene glycol monomethyl ether, and zirconia beads are used to carry out bead mill treatment, thereby propagating YAG propylene glycol monomethyl ether. A liquid was obtained. A propylene glycol monomethyl ether dispersion of the above YAG is added to a propylene glycol monomethyl ether solution of an epoxy oligomer (Optomer KRX manufactured by Asahi Denka Co., Ltd., refractive index 1.62, Abbe number 24), and the volume ratio of YAG in the solid content is It added so that it might become 30 volume%, and it stirred and obtained the uniform coating liquid. This coating solution is applied by spin coating to a thickness of 500 nm on a silicon substrate, and an oligomer is converted into an epoxy resin (indicated in Table 1 as resin A) by UV irradiation, whereby a composite material is formed on the substrate. A coating consisting of

(Example 2)
A composite material in which yttrium oxide particles and silica particles were dispersed was prepared by the following method. First, yttrium oxide (primary particle size: 15 nm) powder and a dispersant (G-820, manufactured by Kyoeisha Chemical Co., Ltd.) are added to propylene glycol monomethyl ether, and bead mill treatment is performed using zirconia beads, thereby propylene glycol monomethyl of yttrium oxide. An ether dispersion was obtained. To the propylene glycol monomethyl ether solution of the epoxy oligomer shown in Example 1, the propylene glycol monomethyl ether dispersion of yttrium oxide and the propylene glycol monomethyl ether dispersion of silica (primary particle size 16 nm) were oxidized in a solid content. The mixture was added so that the volume ratio of yttrium was 22.5% by volume and the volume ratio of silica was 7.5% by volume, and stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate by the same method as in Example 1.

(Example 3)
A composite material in which yttrium oxide particles and alumina particles were dispersed was prepared by the following method. First, to the propylene glycol monomethyl ether solution of the epoxy oligomer shown in Example 1, the propylene glycol monomethyl ether dispersion of yttrium oxide and the methyl isobutyl ketone dispersion of alumina (primary particle size 30 nm) shown in Example 2, The mixture was added so that the volume ratio of yttrium oxide in the solid content was 20% by volume and the volume ratio of alumina was 10% by volume, and stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate by the same method as in Example 1.

(Comparative Example 1)
A composite material in which alumina particles were dispersed was prepared by the following method. First, the methyl isobutyl ketone dispersion of alumina (primary particle size 30 nm) shown in Example 3 is added to the methyl isobutyl ketone solution of the epoxy oligomer shown in Example 1 and the volume ratio of alumina in the solid content is 30% by volume. And stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate by the same method as in Example 1.

(Comparative Example 2)
A composite material in which titanium oxide particles were dispersed was prepared by the following method. First, the propylene glycol monomethyl ether dispersion of titanium oxide (primary particle size 15 nm) is added to the propylene glycol monomethyl ether solution of the epoxy oligomer shown in Example 1 so that the volume ratio of titanium oxide in the solid content is 30% by volume. And stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate by the same method as in Example 1.

  The refractive indexes of the coatings obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were measured with an ellipsometer (spectral ellipsometer manufactured by JA Woollam). The results are shown in (Table 1).

  In the composite material in which the alumina of Comparative Example 1 is dispersed, the refractive index is 1.63, and the refractive index improvement effect by alumina is not so great, and (Equation 2) cannot be satisfied. Moreover, in the composite material in which the titanium oxide of Comparative Example 2 is dispersed, the refractive index is improved to 1.81, but the Abbe number is 16 which is significantly lower than the resin value.

  On the other hand, in the composite material containing the yttrium oxide of Examples 1 to 3 and one or more other inorganic substances, the refractive index is 1.68 to 1.69, and the Abbe number is 27 to 30, both of which (Equation 2) It can be said that this is a material having a high refractive index and low wavelength dispersion that satisfies the above.

Example 4
A composite material in which YAG particles were dispersed as yttrium oxide and one or more other inorganic particles was prepared by the following method. First, a propylene glycol monomethyl ether dispersion of YAG shown in Example 1 was added to a propylene glycol monomethyl ether solution of an acrylic oligomer (UV-7000B, refractive index 1.51, Abbe number 51, manufactured by Nippon Synthetic Chemical). It added so that the volume ratio of the yttrium oxide in a part might be 30 volume%, and it stirred and obtained the uniform coating liquid. This coating solution is applied on a silicon substrate to a thickness of 500 nm by spin coating, and an oligomer is converted into an acrylic resin (indicated in Table 1 as resin B) by UV irradiation, whereby a composite material is formed on the substrate. A coating consisting of

(Example 5)
A composite material in which yttrium oxide particles and silica particles were dispersed was prepared by the following method. First, in the propylene glycol monomethyl ether solution of the acrylic oligomer shown in Example 4, the propylene glycol monomethyl ether dispersion of yttrium oxide shown in Example 1 and the propylene of silica (primary particle size 16 nm) shown in Example 2 The glycol monomethyl ether dispersion was added so that the volume ratio of yttrium oxide in the solid content was 27% by volume and the volume ratio of silica was 3% by volume, and stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate in the same manner as in Example 4.

(Example 6)
A composite material in which yttrium oxide particles and alumina particles were dispersed was prepared by the following method. First, the propylene glycol monomethyl ether solution of the acrylic oligomer shown in Example 4 was added to the propylene glycol monomethyl ether dispersion of yttrium oxide shown in Example 1 and the methyl of alumina (primary particle size 30 nm) shown in Example 3. The isobutyl ketone dispersion was added so that the volume ratio of yttrium oxide in the solid content was 20% by volume and the volume ratio of alumina was 10% by volume, and stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate in the same manner as in Example 4.

(Comparative Example 3)
A composite material in which alumina particles were dispersed was prepared by the following method. First, the methyl isobutyl ketone dispersion of alumina (primary particle size 30 nm) shown in Example 3 was added to the methyl isobutyl ketone solution of the acrylic oligomer shown in Example 4 and the volume ratio of alumina in the solid content was 30% by volume. And stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate in the same manner as in Example 4.

(Comparative Example 4)
A composite material in which titanium oxide particles were dispersed was prepared by the following method. First, the propylene glycol monomethyl ether dispersion of titanium oxide (primary particle size 15 nm) shown in Comparative Example 2 was added to the propylene glycol monomethyl ether solution of the acrylic oligomer shown in Example 4 and the volume ratio of titanium oxide in the solid content. Was added so as to be 30% by volume and stirred to obtain a uniform coating solution. Using this coating solution, a film made of a composite material was formed on a silicon substrate in the same manner as in Example 4.

  The refractive indexes of the coatings obtained in Examples 4 to 6 and Comparative Examples 3 to 4 were measured with an ellipsometer (spectral ellipsometer manufactured by JA Woollam). The results are shown in (Table 2).

  In the composite material in which alumina of Comparative Example 3 is dispersed, (Equation 2) is satisfied, but the refractive index is as low as 1.56, and the refractive index improvement effect by alumina is not sufficient. Moreover, in the composite material in which the titanium oxide of Comparative Example 4 is dispersed, the refractive index is improved to 1.72, but the Abbe number is 19 which is significantly lower than the resin value.

  On the other hand, in the composite material containing yttrium oxide of Examples 4 to 6, the refractive index is 1.60 to 1.61, the Abbe number is 44 to 51, and both satisfy (Equation 2) and have a high refractive index and low It can be said that it is a wavelength-dispersing material.

(Example 7)
A lens using the composite material of the present invention was produced by the following method. As the lens substrate 91, a material (d-line refractive index 1.65, Abbe number 21) in which 20% by volume of zinc oxide particles (primary particle size 20 nm) are mixed with polycarbonate resin is used, and a ring having a depth of 11.3 μm is used therefor. Band-shaped diffraction grating shapes 92a and 92b were added to both surfaces, respectively. Spin a composite material in which 40% by volume of yttrium oxide and 10% by volume of alumina are dispersed and mixed in an epoxy resin (d-line refractive index 1.62, Abbe number 24) so as to cover the diffraction grating shapes 92a and 92b. After coating by coating, it was cured by ultraviolet irradiation to form protective films 93a and 93b on both sides. This composite material had a d-line refractive index of 1.70 and an Abbe number of 30.

  The wavelength dependence of the first-order diffraction efficiency of this lens is shown in FIG. This is a single-sided characteristic. A diffraction efficiency of 90% or more is obtained over the entire wavelength range of 400 to 700 nm, which is the visible light region. In addition, the lens base material and the protective film material are replaced, and a composite material in which 50% by volume of yttrium oxide is dispersed and mixed in epoxy resin is used as the lens base material 91, and a diffraction grating having a depth of 11.3 μm is added to the composite material. Even if a material in which 20% by volume of zinc oxide is mixed with polycarbonate resin is used as the material of the film 93, the same characteristics as in FIG. 11 can be obtained.

(Example 8)
A lens using the composite material of the present invention was produced by the following method. As the lens substrate 91, optical glass N-SF5 (d-line refractive index 1.67, Abbe number 32) was used, and ring-shaped diffraction grating shapes 92a and 92b having a depth of 21.0 μm were added to both surfaces, respectively. A composite material, in which 45% by volume of yttrium oxide and 5% by volume of alumina are dispersed and mixed in a cycloolefin-based resin so as to cover the diffraction grating shapes 92a and 92b, is applied by spin coating, and then naturally cured, and the protective film 93a , 93b. This composite material had a d-line refractive index of 1.70 and an Abbe number of 43.

  When the first-order diffraction efficiency of the lens of Example 8 was evaluated, a diffraction efficiency of 90% or more was obtained over the entire wavelength range of 400 to 700 nm, which is the visible light region.

Example 9
A CCD type solid-state imaging device 1010 having an optical waveguide formed using the composite material of the present invention was produced by the following method.

  First, a photodiode (photoelectric conversion unit) 101 was formed by ion-implanting phosphorus (n-type impurity) into the p-type silicon substrate 103. Then, a 20 nm-thickness silicon oxide film (insulating layer) 104 was grown on the substrate by thermal oxidation. An aluminum oxide film (having a thickness of 60 nm) was formed on the insulating layer 104 by a thermal CVD method. The aluminum oxide film was formed at 450 ° C. in an Ar / O 2 mixed atmosphere using aluminum acetylacetonate as a starting material. Thereafter, an antireflection film 106 made of aluminum oxide was formed on the photoelectric conversion portion 101 by forming a resist pattern and etching the aluminum oxide film.

  Next, a 300 nm-thickness polysilicon film was grown by low pressure CVD. The charge transfer electrode 105 was formed by selectively etching a part of this polysilicon film by dry etching. Further, a silicon oxide film was formed on the charge transfer electrode 105 by thermal oxidation, and the periphery of the charge transfer electrode 105 was covered with an insulating layer 104.

  Next, a tungsten film serving as a light shielding film was formed on the entire surface. A light shielding film 107 covering the periphery of the charge transfer electrode was formed by performing resist pattern formation and anisotropic dry etching on the tungsten film.

  Next, an interlayer insulating film 108 that also serves as a planarizing film was formed by a CVD method. The interlayer insulating film 108 was formed of silicon oxide having a refractive index of 1.45. Then, a resist pattern was formed on the interlayer insulating film 108, and anisotropic dry etching with CF4 was performed to form a hole 108h (width 1 μm × depth 2 μm) above the photoelectric conversion portion. At this time, the aluminum oxide layer 106 which is an antireflection film functions as an etching stopper layer.

  Thus, the substrate before forming the optical waveguide was produced. Hereinafter, this substrate may be referred to as “substrate (A)”.

  Next, an optical waveguide 109 made of a composite material was formed in the hole in the interlayer insulating film of the substrate (A). An epoxy resin having a refractive index of 1.61 was used as a resin constituting the composite material, and yttrium oxide (primary particle size: 15 nm) and alumina (primary particle size: 30 nm) were used as inorganic particles. The composite material had a proportion of yttrium oxide particles of 35% by volume, a proportion of alumina of 15% by volume, and a refractive index of 1.73.

  Below, the formation method of an optical waveguide is demonstrated. First, the substrate (A) was fixed at a pressure of 10 Pa to a fixed stage in the decompression vessel, and the pressure inside the vessel was set to 100 Pa. And the coating liquid was apply | coated on the board | substrate (A) with the vacuum injection nozzle, and spin coating was performed by rotating a board | substrate (A) for 10 second at 100 rpm. The coating solution was prepared by dispersing a predetermined amount of yttrium oxide particles and alumina particles in an epoxy oligomer solution (Optomer KRX manufactured by Asahi Denka).

  After applying the coating liquid, the reduced pressure in the container was released, and the coating liquid was sufficiently embedded in the hole 108h. Thereafter, the substrate (A) was flattened by rotating at 2000 rpm for 20 seconds. Finally, ultraviolet irradiation was performed to make an epoxy oligomer as an epoxy resin. Thus, an optical waveguide 109 made of a composite material was formed, and a CCD solid-state imaging device 1010 of Example 9 was obtained.

  On the other hand, as a comparative example, a solid-state imaging device was formed without forming the hole 108h and the optical waveguide 109 in the interlayer insulating film. The sensitivity characteristics of the image sensors of Example 9 and the comparative example thus obtained were evaluated. As a result, the image pickup device of Example 9 had a sensitivity of about 1.7 times the image brightness of the entire device as compared with the device of the comparative example, and the sensitivity was high. This is because the light collection efficiency of the device of Example 9 is high.

  Further, the relationship between the angle of the incident light and the efficiency with which the incident light enters the photoelectric conversion unit was measured for the image sensor of Example 9 and the image sensor of the comparative example. In the case of the imaging device of Example 9, assuming that the efficiency of vertically incident light is 100, it was about 65 for oblique 20 ° incident light and about 45 for oblique 30 ° incident light. On the other hand, in the case of the imaging device of the comparative example, when the efficiency of vertically incident light is 100, it is about 40 for oblique 20 ° incident light and about 20 for oblique 30 ° incident light. In the device of the comparative example, the light collection efficiency greatly decreased as the incident angle increased. Thus, it was confirmed that the formation of the optical waveguide 109 greatly improves the detection efficiency of obliquely incident light.

  Since the composite material of the present invention is excellent in the balance between high refractive index and low wavelength dispersion, it can be used for small optical components having good wavelength characteristics. For example, for lenses, diffractive optical elements (lenses with diffraction gratings, spatial low-pass filters, polarization holograms, etc.), optical waveguides, optical fibers, optical disk substrates, optical filters, optical adhesives, etc., and optical devices and systems using these It can be deployed.

Sectional drawing which shows typically the composite material which concerns on Embodiment 1 of this invention Graph explaining the effective particle size of inorganic particles added to the composite material according to Embodiment 1 of the present invention Inorganic material used for the composite material of the present invention, and graphs showing the other inorganic, refractive index and n _d of the d-line (wavelength 587 nm), the relationship between the Abbe number ν of a wavelength dispersion Inorganic material used for the composite material of the present invention, as well as in other inorganics graph showing the relationship between the refractive index n _d of the band gap and the d-line (wavelength 587 nm) The graph which shows the relationship between the band gap and Abbe number (nu) in the inorganic substance used for the composite material of this invention, and another inorganic substance The graph which shows an example of the relationship between the refractive index estimated in the composite material which concerns on Embodiment 1 of this invention, and Abbe number Sectional drawing which shows typically the composite material which concerns on Embodiment 2 of this invention The graph which shows an example of the relationship between the refractive index estimated in the composite material which concerns on Embodiment 2 of this invention, and Abbe number Sectional drawing which shows typically an example of the lens which concerns on Embodiment 3 of this invention. Sectional drawing which shows typically an example of the solid-state image sensor in which the optical waveguide which concerns on Embodiment 4 of this invention was formed. The graph which shows the wavelength dependence of the 1st diffraction efficiency of the lens which concerns on Example 7 of this invention.

Explanation of symbols

10, 70 Composite material 11 First inorganic particle 11a Primary particle of first inorganic particle 11b Secondary particle of first inorganic particle 12 Resin 13 Second inorganic particle 13a Primary particle of second inorganic particle 13b Second Secondary particles of inorganic particles 91 Lens 92a, 92b Diffraction grating shape 93a, 93b Protective film 101 Photoelectric conversion unit 102 Charge transfer unit 103 Substrate 104 Insulating layer 105 Charge transfer electrode 106 Antireflection film 107 Light shielding film 108 Interlayer insulating film 108h Hole 109 Optical waveguide 1010 CCD type solid-state imaging device

Claims (13)

And the resin is dispersed in the resin, yttrium oxide and one or more other inorganic and at least including inorganic particles, the refractive index n _COM 1.60 or more, an Abbe number [nu _COM 20 or more, And

A composite material that satisfies this relationship. The composite material according to claim 1, wherein the inorganic particles are a composite oxide of yttrium oxide. The composite material according to claim 2, wherein the inorganic particles are yttrium aluminum garnet. The inorganic particles, a first inorganic particles containing at least yttrium oxide, composite material according to any one of claims 1 to 3, the Abbe number [nu _p is the second inorganic particles is 50 or more. The composite material according to claim 4, wherein the second inorganic particles are silica or alumina. The composite material according to any one of claims 1 to 3, wherein a volume ratio of the inorganic particles to the entire composite material is 50% by volume or less. The composite material according to claim 4 or 5, wherein the total volume ratio of the first inorganic particles and the second inorganic particles to the entire composite material is 50% by volume or less. The composite material according to any one of claims 1 to 3, wherein an effective particle diameter of the inorganic particles is in a range of 1 nm to 100 nm. The composite material according to claim 4 or 5, wherein an effective particle diameter of the first inorganic particles and the second inorganic particles is in a range of 1 nm to 100 nm. An optical component using the composite material according to claim 1. A lens made of the composite material according to claim 1. A diffractive optical element comprising: a base material made of a first material and having a diffraction grating shape formed on a surface thereof; and a protective film made of a second material and formed to cover the diffraction grating shape. The first material and the second material are both composed of a resin, and at least one of the first material and the second material is made of the composite material according to any one of claims 1 to 9. A diffractive optical element. A solid-state imaging device comprising a photoelectric conversion unit and an optical waveguide disposed on the photoelectric conversion unit, wherein the optical waveguide is made of a composite material according to any one of claims 1 to 9.

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