JP2018018108A - Sol for infrared absorption layer, infrared absorption layer, manufacturing method of infrared absorption layer, and manufacturing method of infrared cut filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared cut filter which has good infrared shielding property with small incident angle dependence and exhibits high scratch resistance and environmental resistance.SOLUTION: An infrared cut filter 10 comprises: a transparent dielectric substrate 12; an infrared reflective layer 14 formed on one surface of the transparent dielectric substrate 12 to reflect infrared rays; and an infrared absorptive layer 16 formed on the other surface of the transparent dielectric substrate 12 to absorb infrared rays. The infrared absorptive layer 16 includes a matrix formed of a sol-gel method and having silica as a main ingredient with an infrared absorbing pigment contained therein.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an infrared cut filter and an imaging apparatus using the infrared cut filter.

  An imaging apparatus such as a digital camera is equipped with a semiconductor solid-state imaging device such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). The sensitivity of these solid-state imaging devices ranges from the visible region to the infrared region. Therefore, in the imaging device, an infrared cut filter for blocking infrared rays is provided between the imaging lens and the solid-state imaging device. With this infrared cut filter, the sensitivity of the solid-state imaging device can be corrected so as to approach human visibility.

  Conventionally, as such an infrared cut filter, a resin substrate having an infrared reflection layer formed of a dielectric multilayer film is known (for example, see Patent Document 1).

JP 2005-338395 A

  However, since the infrared reflective layer made of a dielectric multilayer film has an incident angle dependency in which the infrared blocking characteristic changes depending on the incident angle, when the light transmitted through the infrared reflective layer is imaged, the central portion and the periphery of the image There may be a difference in color between parts.

  In addition, since the infrared cut filter is provided in front of the solid-state image sensor, high scratch resistance and environmental resistance are required.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an infrared cut filter having good infrared ray shielding characteristics with small incident angle dependency, high scratch resistance and environmental resistance, and the infrared ray cut filter. An object of the present invention is to provide an imaging apparatus using a filter.

  In order to solve the above problems, an infrared cut filter according to an aspect of the present invention includes a transparent dielectric substrate, an infrared reflective layer that reflects infrared rays formed on one surface of the transparent dielectric substrate, and a transparent dielectric. An infrared absorption layer for absorbing infrared rays formed on the other surface of the substrate, comprising an infrared absorption layer comprising an infrared absorption dye encapsulated in a matrix mainly composed of silica formed by a sol-gel method.

  The infrared reflective layer may be formed from a dielectric multilayer film.

Transmittance of the infrared reflective layer and the wavelength at which the 50% λ _RT50% nm, the transmittance of the infrared absorbing layer when the wavelength to be 50% λ _AT50% nm, satisfying the λ _AT50% <λ _RT50% As described above, an infrared reflection layer and an infrared absorption layer may be formed.

Infrared reflective layer and the infrared-absorbing layer may be formed so as to satisfy the more _{λ AT50% -λ RT50% ≦ -10nm} .

The infrared reflective layer and the infrared-absorbing layer may be formed so as to satisfy the more _{λ AT50% -λ RT50% ≦ -20nm} .

The infrared reflective layer and the infrared-absorbing layer may be formed so as to satisfy the more _{λ AT50% -λ RT50% ≦ -30nm} .

Infrared reflective layer and the infrared-absorbing layer may be formed so as to further satisfy _{-50nm ≦ λ AT50% -λ RT50%} .

  The infrared absorption layer may contain, as a raw material, a mixture of phenyltriethoxysilane and tetraethoxysilane having a compounding ratio of 50:50 to 80:20.

  The transparent dielectric substrate may be formed from glass. The infrared reflecting layer may be formed to reflect ultraviolet rays.

  This infrared cut filter may further include an antireflection layer for preventing reflection of visible light on the infrared absorption layer. The antireflection layer may have a function of preventing transmission of ultraviolet rays.

  The infrared reflective layer may be warped so that the surface facing the surface on the transparent dielectric substrate side becomes a convex surface.

  Another aspect of the present invention is an imaging apparatus. The apparatus includes the infrared cut filter and an image sensor on which light transmitted through the infrared cut filter enters.

  It should be noted that any combination of the above-described constituent elements and a representation obtained by converting the expression of the present invention between a method, an apparatus, a system, and the like are also effective as an aspect of the present invention.

  According to the present invention, it is possible to provide an infrared cut filter having good infrared blocking characteristics with small incident angle dependency and high scratch resistance and environmental resistance, and an imaging device using the infrared cut filter.

It is sectional drawing for demonstrating the structure of the infrared cut filter which concerns on embodiment of this invention. It is a figure which shows the solubility of a sol-gel raw material and a pigment | dye. An example of the spectral transmittance curve of the infrared reflective layer which consists of a dielectric multilayer film concerning the 1st comparative example is shown. An example of the spectral transmittance curve which consists of an infrared rays absorption layer concerning the 2nd comparative example is shown. It is a figure which shows an example of the spectral transmittance curve of the infrared cut filter which concerns on this embodiment. It is a figure which shows the examination result of the compounding ratio of phenyltriethoxysilane and tetraethoxysilane, and the addition amount of water essential for hydrolysis. It is a figure which shows the composition of the infrared rays absorption layer used for the 1st-3rd Example. It is a figure which shows the spectral transmittance curve of the infrared cut filter which formed only the infrared rays absorption layer which concerns on the 1st-3rd Example. It is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 60nm _λ in the first embodiment. It is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 50nm _λ in the first embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 40nm _λ in the first embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 30nm _λ in the first embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 20nm _λ in the first embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 10nm _λ in the first embodiment. Λ _AT50% -λ _RT50% in the first embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the 0 nm. Λ _AT50% -λ _RT50% in the first embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -10 nm. Λ _AT50% -λ _RT50% in the first embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -20 nm. Λ _AT50% -λ _RT50% in the first embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -30 nm. Λ _AT50% -λ _RT50% in the first embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -40 nm. Λ _AT50% -λ _RT50% in the first embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -50 nm. Λ _AT50% -λ _RT50% in the first embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -60 nm. It is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 60nm _λ in the second embodiment. It is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 50nm _λ in the second embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 40nm _λ in the second embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 30nm _λ in the second embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 20nm _λ in the second embodiment. Is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 10nm _λ in the second embodiment. Λ _AT50% -λ _RT50% in the second embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the 0 nm. Λ _AT50% -λ _RT50% in the second embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -10 nm. Λ _AT50% -λ _RT50% in the second embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -20 nm. Λ _AT50% -λ _RT50% in the second embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -30 nm. Λ _AT50% -λ _RT50% in the second embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -40 nm. Λ _AT50% -λ _RT50% in the second embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -50 nm. Λ _AT50% -λ _RT50% in the second embodiment = a diagram showing a spectral transmittance curve of the infrared cut filter when the -60 nm. It is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 60nm _λ in the third embodiment. It is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 50nm _λ in the third embodiment. 3 is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 40nm _λ in Example. 3 is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 30nm _λ in Example. 3 is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 20nm _λ in Example. 3 is a diagram showing a spectral transmittance curve of the infrared cut filter when the _{AT50% -λ RT50%} = 10nm _λ in Example. The 3 lambda in Example _{AT50% -λ RT50%} = a diagram showing a spectral transmittance curve of the infrared cut filter when the 0 nm. The 3 lambda in Example _{AT50% -λ RT50%} = a diagram showing a spectral transmittance curve of the infrared cut filter when the -10 nm. The 3 lambda in Example _{AT50% -λ RT50%} = a diagram showing a spectral transmittance curve of the infrared cut filter when the -20 nm. The 3 lambda in Example _{AT50% -λ RT50%} = a diagram showing a spectral transmittance curve of the infrared cut filter when the -30 nm. The 3 lambda in Example _{AT50% -λ RT50%} = a diagram showing a spectral transmittance curve of the infrared cut filter when the -40 nm. The 3 lambda in Example _{AT50% -λ RT50%} = a diagram showing a spectral transmittance curve of the infrared cut filter when the -50 nm. The 3 lambda in Example _{AT50% -λ RT50%} = a diagram showing a spectral transmittance curve of the infrared cut filter when the -60 nm. It is a figure which shows the table | surface which put together the main parameters of the spectral transmittance curve shown to Fig.9 (a)-(m). It is a figure which shows the table | surface which put together the main parameters of the spectral transmittance curve shown to Fig.10 (a)-(m). It is a figure which shows the table | surface which put together the main parameters of the spectral transmittance curve shown to Fig.11 (a)-(m). It is a figure which shows the relationship between the difference of the cutoff wavelength of the infrared rays absorption layer in 1st Example, and the cutoff wavelength of an infrared reflective layer, and the steepness of the transient area | region of a spectral transmittance curve. It is a figure which shows the relationship between the difference of the cutoff wavelength of the infrared absorption layer in 1st Example, and the cutoff wavelength of an infrared reflective layer, and the amount of shifts of the cutoff wavelength when an incident angle changes from 0 degree to 35 degrees. is there. It is a figure which shows the relationship between the difference of the cutoff wavelength of the infrared rays absorption layer in 2nd Example, and the cutoff wavelength of an infrared rays reflection layer, and the steepness of the transient area | region of a spectral transmittance curve. It is a figure which shows the relationship between the difference of the cutoff wavelength of the infrared rays absorption layer in 2nd Example, and the cutoff wavelength of an infrared reflective layer, and the shift amount of cutoff wavelength when an incident angle changes from 0 degree to 35 degrees. is there. It is a figure which shows the relationship between the difference of the cutoff wavelength of the infrared rays absorption layer in 3rd Example, and the cutoff wavelength of an infrared reflective layer, and the steepness of the transient area | region of a spectral transmittance curve. It is a figure which shows the relationship between the difference of the cutoff wavelength of the infrared rays absorption layer in 3rd Example, and the cutoff wavelength of an infrared reflective layer, and the shift amount of cutoff wavelength when an incident angle changes from 0 degree to 35 degrees. is there. It is a figure which shows the infrared cut filter which concerns on another embodiment of this invention. It is a figure which shows the infrared cut filter which concerns on another embodiment of this invention. It is a figure for demonstrating the imaging device using the infrared cut filter which concerns on embodiment of this invention.

  FIG. 1 is a cross-sectional view for explaining the configuration of an infrared cut filter 10 according to an embodiment of the present invention. As shown in FIG. 1, the infrared cut filter 10 includes a transparent dielectric substrate 12, an infrared reflection layer 14, and an infrared absorption layer 16. The infrared reflecting layer 14 is formed on one surface of the transparent dielectric substrate 12. The infrared absorption layer 16 is formed on the other surface of the transparent dielectric substrate 12.

  The infrared cut filter 10 shown in FIG. 1 is provided between an imaging lens and an imaging element, for example, in a digital camera. The infrared cut filter 10 is mounted so that light is incident from the infrared reflection layer 14 and light is emitted from the infrared absorption layer 16. That is, in the mounted state, the infrared reflection layer 14 faces the imaging lens, and the infrared absorption layer 16 faces the imaging element.

  The transparent dielectric substrate 12 may be a plate-like body having a thickness of about 0.1 mm to 0.3 mm, for example. The material constituting the transparent dielectric substrate 12 is not particularly limited as long as it transmits visible light, and may be glass, for example. A glass substrate formed of glass is preferable from the viewpoint of cost because it is inexpensive. Alternatively, as the transparent dielectric substrate 12, a synthetic resin film or a synthetic resin substrate such as PMMA (Polymethylmethacrylate), PET (Polyethylene terephthalate), PC (Polycarbonate), PI (Polyimide) can be used.

As described above, the infrared reflection layer 14 is formed on one surface of the transparent dielectric substrate 12 and functions as a light incident surface. The infrared reflection layer 14 is configured to transmit visible light and reflect infrared light. The infrared reflective layer 14 may be formed of a dielectric multilayer film in which dielectrics having different refractive indexes are stacked in a multilayer. The dielectric multilayer film can freely design optical characteristics such as spectral transmittance characteristics by controlling the refractive index and layer thickness of each layer. The infrared reflective layer 14 may be formed by alternately depositing a titanium oxide (TiO ₂ ) layer and a silicon oxide (SiO ₂ ) layer having different refractive indexes on the transparent dielectric substrate 12, for example. In addition to TiO ₂ and SiO ₂ , dielectric materials such as MgF ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ can also be used as the material for the dielectric multilayer film.

  As described above, the infrared absorption layer 16 is formed on the other surface of the transparent dielectric substrate 12 and functions as a light emission surface. The infrared absorbing layer 16 is configured to transmit visible light and absorb infrared light. The light that has entered the infrared cut filter 10 passes through the infrared reflection layer 14 and the transparent dielectric substrate 12 and then enters the infrared absorption layer 16, so that the infrared absorption layer 16 includes the infrared reflection layer 14 and the transparent dielectric substrate 12. It absorbs the infrared rays that were not blocked by.

  In the infrared cut filter 10 according to the present embodiment, the infrared absorption layer 16 includes a matrix mainly composed of silica formed by a sol-gel method and an infrared absorption dye. Infrared absorbing films that have been widely used in the past are resin matrixes that are transparent dielectrics such as polyester, polyacryl, polyolefin, polyvinyl butyral, polycarbonate, and other infrared absorbing dyes made of organic compounds such as phthalocyanine, cyanine, and diimmonium. It is included. However, the organic resin matrix has a low hardness and has a problem with respect to scratch resistance due to its physical properties. In actual use, it is necessary to laminate a protective layer such as a hard coat on the upper surface.

  The infrared cut filter 10 according to the present embodiment pays attention to such problems, and employs an infrared absorption layer 16 in which silica formed by a sol-gel method is used as a main component of the matrix. The effect of employing the infrared absorption layer 16 having silica formed by the sol-gel method as the main component of the matrix will be described below.

  First, it is mentioned that the infrared absorption layer 16 is obtained with high hardness. Conventionally, an infrared absorbing dye made of an organic compound such as phthalocyanine, cyanine or diimmonium is usually contained in a binder made of an organic matrix. However, the organic matrix has low physical properties and has a problem with respect to scratch resistance. In actual use, it is necessary to laminate a protective layer such as a hard coat on the upper surface.

  The infrared absorption layer 16 according to the present embodiment is formed of a layer made of a matrix containing silica as a main component, which is called an organic-inorganic hybrid, and therefore there is no problem in the technical field applied for hardness. In addition to the physical properties, there is no need for a hard coating or the like for protecting the physical properties, so that the manufacturing cost can be reduced.

  Secondly, an improvement in environmental resistance is obtained. Since the infrared absorbing layer 16 is obtained from a matrix containing silica as its main component, the barrier property against moisture is improved as compared with the infrared absorbing film made of a conventional organic binder, and the surrounding environment is improved. The effect which suppresses the bad influence to the infrared rays absorption pigment | dye which consists of the organic compound to include can be anticipated more.

  Thirdly, a strong adhesion to a substrate such as glass can be obtained. Considering the application of an infrared absorbing film made of a resin binder that is often used in the past to an inorganic glass substrate, a primer treatment such as applying a silane coupling agent on the glass substrate prior to installation is actually necessary. Met. Otherwise, there was a problem that the infrared absorption film peeled off from the glass substrate under a certain severe environment. Since the infrared absorption layer 16 according to this embodiment uses a matrix containing silica as its main component, it can be expected that adhesion to a similar glass substrate will be improved.

  Next, materials necessary for forming a silica-based film formed by the sol-gel method and effects thereof will be described.

First, the raw material for silica will be described. In the infrared cut filter 10 according to the present embodiment, tetraethoxysilane (TEOS / chemical formula = Si (OC ₂ H ₅ ) ₄ )) is used as a main component as a material of the infrared absorption layer 16, and the infrared absorption layer is formed by a sol-gel method. Sixteen matrices are formed. Tetraethoxysilane is a kind of alkoxysilane (SiR _4-m (OC _n H _{2n + 1} ) _m ) described later (R is a functional group, m is an integer from 0 to 4).

  General glass is manufactured by a melting method in which a raw material is melted at a high temperature exceeding 1500 ° C. and cooled. On the other hand, the sol-gel method is a relatively new method for producing glass and ceramics at a low temperature. In the sol-gel method, a solution of a metal organic or inorganic compound is used as a starting material, and the solution is made into a sol in which fine particles of metal oxide or hydroxide are dissolved by hydrolysis / polycondensation reaction of the compound in the solution. In this method, the reaction is allowed to progress to gelation and solidification, and the gel is heated to obtain an oxide solid. In the sol-gel method, it is possible to produce a thin film on various substrates in order to produce glass from a solution, and it is possible to produce glass at a lower temperature than the glass production temperature by the melting method. Has characteristics.

  The sol-gel process will be described. As an example, formation of a silica-based film formed by a sol-gel method will be described. For example, in a sol-gel method using alkoxysilane as a starting material, a sol composed of an oligomer composed of siloxane bonds is formed in alkoxysilane by a hydrolysis reaction and a dehydration condensation reaction with water and a catalyst. When this sol solution is applied to a substrate or the like, water and solvent are volatilized, and the oligomer is concentrated to increase the molecular weight and lose fluidity to be in a gel state. Immediately after gelation, the gap between the networks is filled with a solvent or water. When the gel is dried and water and solvent are volatilized, the siloxane polymer further shrinks and solidifies.

In general, the hydrolysis reaction between alkoxysilane and water is expressed as follows. Taking tetraethoxysilane as an example;
n · Si (OC ₂ H ₅ ) ₄ + 4n · H ₂ O → n · Si (OH) ₄ + 4n · C ₂ H ₅ OH
nSi (OH) ₄ → n · SiO ₂ + 2n · H ₂ O
That is, in terms of stoichiometry, when 4 moles or more of water is present per mole of alkoxysilane, all alkoxy groups (—O—CnH _{2n + 1} ) are hydrolyzed. Generally, an alkali or an acid is added as a reaction catalyst.

As a starting material for the silica-based film formed by the sol-gel method, tetraalkoxysilanes typified by the above tetraethoxysilane are often used. When forming a sol-gel film starting from these, a strong network is formed by four reactive groups, and a dense and glassy preferable film is easily obtained. As other tetraalkoxysilanes, tetramethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and the like can be used. The silanes can be selected depending on the characteristics of the resulting product and the convenience of the process because the hydrolysis rate decreases as the alkoxy group coordinated to Si (—O—CnH _{2n + 1} ) increases.

  In the present embodiment, a trialkoxysilane composed of a trifunctional group such as phenyltriethoxysilane is mixed in addition to the tetraethoxysilane as a raw material for the sol-gel film. The tetraethoxysilane employed above is suitably used as a raw material for silica constituting the sol-gel film. This is because it is easy to obtain a preferable appearance and properties of glass by firing at a relatively low temperature.

  However, in a sol-gel film using only tetraethoxysilane as a raw material, there is a tendency to reduce a spatial margin in the crosslinked structure at the time of gelation in the film formation process, so that cracks are likely to occur in the film. This is noticeable when trying to increase the film thickness.

  Furthermore, in this embodiment, it is necessary to enclose one or more infrared absorbing dyes made of an organic compound in the film, and it is impossible to enclose a predetermined amount in a sol-gel film using only tetraethoxysilane as a raw material. There was a problem.

  If the sol-gel film is given a certain degree of flexibility, the cracks are hardly generated. Therefore, means for adding trialkoxysilane having three reactive functional groups to tetraethoxysilane is known. Trialkoxysilane has three alkoxy groups around Si, and the remaining one is a general term for silanes having a relatively low reactive activity modifying group consisting of a methyl group, an ethyl group, and a phenyl group. Since the silica film formed from trialkoxysilane having three reactive functional groups has a spatial margin, the generated stress at the time of gelation is relatively small and cracks are unlikely to occur. Further, since there are three reactive functional groups, one silicon compound forms three strong siloxane bonds, so that a crosslinked network can be formed. A dialkoxysilane having two alkoxy groups actually exists, but it tends to be linear in the condensation polymerization by hydrolysis, and only a chain network is formed, so that the wear resistance of the film is reduced, etc. Cause a malfunction.

  The trialkoxysilane includes methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, isopropyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyltriethoxy Silane, phenyltriisopropoxysilane, ethyltriethoxysilane, propyltriethoxysilane and the like can be used.

Among them, trialkoxysilane having a phenyl group (—C ₆ H ₅ ) as a functional group is preferable. It is considered that the phenyl group remains in the film even after the sol-gel reaction and produces flexibility under baking conditions of about 100 to 200 ° C.

Further, it has been found that trialkoxysilane having a phenyl group also works advantageously for inclusion of an infrared absorbing dye made of an organic compound. As will be described later, when the inclusion property of a dye of methyltriethoxysilane and phenyltriethoxysilane (PhTEOS / chemical formula = Si (C ₆ H ₅ ) (C ₂ H ₅ O) ₃ ), which is a kind of trialkoxysilane, was examined, the former In, the dye aggregated after the sol-gel reaction, and a uniform transparent silica main component film could not be formed. The latter was able to sufficiently encapsulate the predetermined infrared absorbing dye. This is considered that a large amount of an infrared-absorbing dye of an organic compound can be introduced into pores generated in a silica main component film formed from an alkoxysilane containing a phenyl group. Examples of trialkoxysilane having a phenyl group as a functional group include phenyltrimethoxysilane, phenyltriisopropoxysilane, and phenyltrinormalpropoxysilane in addition to the phenyltriethoxysilane.
A trialkoxysilane having a phenyl group having these advantages (hereinafter referred to as phenyltrialkoxysilane) is mixed with a tetraalkoxysilane such as tetraethoxysilane described above to be a raw material for a silica film formed by a sol-gel method. This is because when an excessive amount of phenyltrialkoxysilane is administered or only phenyltriethoxysilane is used as a raw material, it does not cure or is cured when trying to form a silica film formed by the sol-gel method because of its flexibility. However, there are cases where a very high baking temperature is required or the mechanical strength of the film is not satisfactory. Therefore, trifunctional phenyltrialkoxysilane needs to be appropriately blended with tetrafunctional tetraalkoxysilane.

  FIG. 2 shows an experimental result when tetratrioxysilane is mixed with methyltriethoxysilane and phenyltriethoxysilane to try to encapsulate a phthalocyanine infrared absorbing dye and a cyanine infrared absorbing dye.

  From the results of this experiment, when a mixture of tetraethoxysilane and methyltriethoxysilane is used as the raw material for the sol-gel film, there is a limit that the amount of inclusion and inclusion is unacceptable when any dye is added. I understand. On the other hand, when a mixture of tetraethoxysilane and phenyltriethoxysilane is used as the raw material for the sol-gel film, sufficient inclusion capacity and film thickness selectivity can be obtained for any dye, which is advantageous for inclusion of infrared absorbing dyes. It turns out that it brings about an effect.

  Next, water will be described. Water is an essential component for hydrolysis of alkoxysilane. As described above, stoichiometrically, 4 mol of water is required for 1 mol of alkoxysilane. However, since water continues to evaporate during the formation of the silica film formed by the sol-gel method, in general, an amount of water exceeding the stoichiometry is often left.

  However, the presence of a large amount of water may hinder the encapsulation of the infrared absorbing film. Infrared absorbing dyes composed of organic compounds are generally low in polarity and hydrophobic. On the other hand, since water is highly polar, excess water hinders dissolution of the hydrophobic infrared absorbing dye in a solvent and inclusion in alkoxysilane.

  Next, the solvent will be described. The solvent is added for the purpose of increasing the compatibility of alkoxysilane, water, and the acid that is the catalyst. In the present invention, it is necessary to have high solubility with respect to infrared absorbing dyes composed of organic compounds. Therefore, a solvent having an appropriate polarity is preferable.

  Furthermore, the solvent must be evaporated at least at the firing temperature or lower when forming the silica film formed by the sol-gel method. Conversely, if the boiling point is too low, the silica network is being formed immediately after application to the substrate. Volatilizes rapidly, causing problems in the pigment encapsulation. Further, when the boiling point of the solvent is lower than that of water, water having a high surface tension is finally left in the silica film at the time of firing, and there is a risk that defects such as cracks may occur due to rapid film shrinkage.

  Infrared absorbing dyes composed of organic compounds deteriorate under high temperature environments, and their absorption characteristics are very different from the original ones, making it impossible to obtain the intended infrared absorbing film. Therefore, it is necessary to perform the baking temperature within a temperature range in which the infrared absorbing dye does not thermally deteriorate. In general, the heat-resistant temperature of the infrared absorbing dye is 200 ° C. (phthalocyanine type) and 140 to 160 ° C. (cyanine type), although it depends on the characteristics, and it is necessary to complete firing at least below this temperature.

  From the above consideration, the boiling point required for the solvent is 100 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 160 ° C. or lower.

  Commonly used solvents are, for example, methanol, ethanol, propyl alcohol, isopropyl alcohol, acetone, acetonitrile, dimethyl sulfoxide, dimethylformamide, dimethylimidazolidinone, ethylene glycol, tetraethylene glycol, dimethylacetamide, N-methyl-2- Examples include pyrrolidone, tetrahydrofuran, dioxane, methyl ethyl ketone, cyclohexanone, cyclopentanone, 2-methoxyethanol (methyl cellosolve), 2-ethoxyethanol (ethyl cellosolve), and ethyl acetate.

  In the present invention, cyclohexanone (boiling point 131 ° C.) and cyclopentanone (boiling point 156 ° C.) are preferably used from the viewpoint of solubility with infrared absorbing dyes and boiling point.

  Next, the acid will be described. The acid serves as a catalyst during hydrolysis of the alkoxysilane. A strong acid is desirable, and the following can be mentioned. Examples include hydrochloric acid, nitric acid, trichloroacetic acid, trifluoroacetic acid, sulfuric acid, phosphoric acid, methanesulfonic acid, paratoluenesulfonic acid, and oxalic acid.

  The operation of the infrared cut filter 10 configured as described above will be described. Before describing the operation of the infrared cut filter 10 according to the present embodiment, first, the operation of the infrared cut filter according to the comparative example will be described.

  FIG. 3 shows an example of a spectral transmittance curve of an infrared cut filter in which only an infrared reflective layer made of a dielectric multilayer film is formed on a glass substrate as a first comparative example. FIG. 4 shows the spectral transmittance of an infrared cut filter in which only an infrared absorption layer composed of a matrix mainly composed of silica formed by a sol-gel method and an infrared absorption dye is formed on a glass substrate as a second comparative example. An example of a curve is shown.

In the infrared cut filter according to the first comparative example, as shown in FIG. 3, the incident angle dependence of the blocking characteristic, which is a feature of the dielectric multilayer film, is observed. In FIG. 3, the solid line indicates the spectral transmittance curve when the incident angle is 0 °, the broken line indicates the spectral transmittance curve when the incident angle is 25 °, and the alternate long and short dash line indicates the spectral transmittance when the incident angle is 35 °. The transmittance curve is shown. When transmittance and the wavelength at which _50% λ _RT50%, but when the incident angle is 0 ° is lambda _RT50% = about 655 nm, the incident angle is 25 ° λ _RT50% = about 637 nm, incident When the angle is 35 °, λ RT50 _% = about 625 nm. Thus, in the infrared cut filter according to the first comparative example, when the incident angle changes from 0 ° to 35 °, _λRT50% is shifted to the short wavelength side by about 30 nm.

  When an infrared cut filter is applied to an image sensor, light having a small incident angle (for example, an incident angle of 0 °) is normally incident on the center of the image sensor. Light having a large incident angle (for example, an incident angle of 25 ° or 35 °) is incident on the peripheral portion. Therefore, when an infrared cut filter having an infrared blocking characteristic as shown in FIG. 3 is applied to an image pickup device, the spectral transmittance curve characteristic of light incident on the image pickup element (particularly around a wavelength of 650 nm, depending on the position of the light receiving surface of the image pickup element Spectral characteristics) are different. This causes a phenomenon in which the color is different between the central portion and the peripheral portion of the image, which may adversely affect the color reproducibility.

  In addition, in the infrared cut filter according to the second comparative example, unlike the infrared cut filter according to the first comparative example, there is no incident angle dependency of the cutoff characteristic. However, as shown in FIG. 4, in the infrared cut filter according to the second comparative example, the spectral transmittance curve in the transition region where the transmittance changes from a relatively high region to a low region gradually decreases. In general, an infrared cut filter has the transition region in the vicinity of a wavelength of 600 nm to 700 nm so as not to affect the color reproducibility, and the transmittance in this region changes sharply (“sharp cut characteristic”). Called). Therefore, in the infrared cut filter according to the second comparative example, it is difficult to satisfactorily realize control of color reproducibility.

  In consideration of the drawbacks in these comparative examples, the present inventor formed an infrared reflecting layer 14 on one surface of the transparent dielectric substrate 12 and formed an infrared absorbing layer 16 on the other surface, thereby blocking the blocking. It was found that the incident angle dependency of the characteristic is small and that a good sharp cut characteristic can be realized.

  FIG. 5 shows an example of the spectral transmittance curve of the infrared cut filter 10 according to the present embodiment. Also in FIG. 5, the solid line shows the spectral transmittance curve when the incident angle is 0 °, the broken line shows the spectral transmittance curve when the incident angle is 25 °, and the one-dot chain line shows the spectral transmittance when the incident angle is 35 °. The transmittance curve is shown.

The characteristics of the infrared cut filter 10 according to this embodiment are determined by a combination of the optical characteristics of the infrared reflection layer 14 and the optical characteristics of the infrared absorption layer 16. In this case the infrared reflective layer alone, the wavelength at which transmittance is 50% at an incident angle of 0 ° λ _RT50% (nm) and to the wavelength lambda _AT50% transmittance in the infrared-absorbing layer alone is 50% (nm) And Figure 4 shows a _{λ AT50% = λ RT50% -30nm} , i.e. the spectral transmittance curve of the infrared cut filter 10 when lambda _AT50% is 30nm shorter than lambda _RT50%.

If the wavelength at which the transmittance is 50% at the incident angle of 0 ° of the infrared cut filter 10 according to the present embodiment is λ _T50% (nm), as shown in FIG. the angle of incidence is _T50% = about 650 nm lambda when the 0 °, the incident angle is when the 25 ° λ _T50% = about 650 nm, incident angle when the 35 ° λ _T50% = about 642nm It is. As described above, in the infrared cut filter 10 according to the present embodiment, even when the incident angle changes from 0 ° to 35 °, λ _T50% is shifted only to the short wavelength side by about 8 nm, and the incident angle of _λT50% . The dependency is smaller than the incident angle dependency of λ _{RT 50% in} the first comparative example. Further, as shown in FIG. 5, in the region where the transmittance is higher than 50%, there is almost no difference in the spectral transmittance curve even if the incident angle is changed. On the other hand, in the region where the transmittance is lower than 50%, a difference appears in the spectral transmittance curve when the incident angle changes. However, the difference in the spectral transmittance curve in the region where the transmittance is lower than 50% is not particularly problematic because the influence on the color reproducibility is small.

  Further, as shown in FIG. 5, the infrared cut filter 10 according to the present embodiment has a transient region in the vicinity of a wavelength of 600 nm to 700 nm, and the transmittance changes sharply in this region, and has good sharp cut characteristics. Can be realized.

  The optical characteristics of the infrared cut filter 10 according to this embodiment are determined by the combination of the infrared reflection layer 14 and the infrared absorption layer 16. Hereinafter, preferable optical characteristics of the infrared reflecting layer 14 and the infrared absorbing layer 16 will be described.

First, suitable optical characteristics of the infrared reflecting layer 14 will be described. The infrared reflecting layer 14 is designed to transmit visible light in a band of at least 400 nm to 600 nm and reflect infrared light having a wavelength of at least 750 nm in view of required performance. In the transition region between the transmission region and the reflection region, a wavelength at which the spectral transmittance is 50 _% is defined as a cutoff wavelength λ _RT50% . Although also on the spectral sensitivity region of an imaging element, lambda _RT50% of the infrared reflective layer 14 is a region of the cutoff wavelength lambda _AT50% of the infrared absorbing layer 16, preferably λ _AT50% <λ _RT50% It is preferable to set as follows. The cutoff wavelength λ RT50 _% of the infrared reflecting layer 14 is preferably in the range of 630 nm to 690 nm.

  The infrared reflective layer 14 is designed so that the transmittance in the visible region is as high as possible. This is because light in the visible region necessary for constructing an image is made to reach the light receiving surface of the image sensor as much as possible. On the other hand, the infrared reflective layer 14 is designed so that the transmittance in the infrared region is as low as possible. This is to block as much as possible light rays that do not contribute to the image construction or are harmful. The infrared reflective layer 14 has, for example, an average spectral transmittance of 90% or more in a visible region of at least a wavelength range of 400 nm to 600 nm and a spectral transmittance of less than 2% in an infrared region of at least a wavelength of 750 nm. preferable.

Furthermore, the infrared reflective layer 14 preferably has a sharp change in spectral transmittance in a transient region (referred to as “sharp cut characteristic”). This is because if the sharp cut characteristics are lost and the transition region becomes too large, it becomes difficult to control the color reproducibility. When the steepness of the transmittance in the transient region is defined as λ _RSLOPE = | λ _{RT50 %} −λ _RT2% | (λ _RT2% is a wavelength at which the spectral transmittance is 2%), λ _RSLOPE of the infrared reflecting layer 14 is as much as possible. For example, λ _RSLOPE is preferably less than 70 nm.

In the spectral transmittance curve shown in FIG. 3, the average spectral transmittance in the visible region is 90% or more and the average spectral transmittance in the infrared region is 2 for any of the incident angles of 0 °, 25 °, and 35 °. %. Furthermore, in the spectral transmittance curve shown in FIG. 3, λ _RSLOPE is less than 70 nm at any of incident angles of 0 °, 25 °, and 35 °. Therefore, the infrared reflective layer 14 having the spectral transmittance curve shown in FIG. 3 can be suitably applied to the infrared cut filter 10 according to the present embodiment.

  Next, suitable optical characteristics of the infrared absorption layer 16 will be described. In the present embodiment, the optical characteristics required for the infrared absorption layer 16 vary depending on the optical characteristics of the infrared reflection layer 14 to be combined.

In the present embodiment, it cut-off wavelength lambda _AT50% of the infrared absorbing layer 16 is less than the cutoff wavelength lambda _RT50% of the infrared reflective layer 14, i.e., is preferably λ _AT50% <λ _RT50% . When the infrared absorption layer 16 satisfies this condition, the incident angle dependency of the infrared cut-off characteristic of the infrared cut filter 10, in other words, the cutoff wavelength of the infrared cut filter 10 when the incident angle changes from 0 ° to 35 °. The shift amount of _λT50% can be reduced. The cutoff wavelength λ _AT50% of the infrared absorption layer 16 is preferably in the range of 630 nm to ₆₉₀ nm.

  Furthermore, in this embodiment, it is preferable that the average transmittance of the infrared absorption layer 16 in the visible region is as high as possible. This is because when the average transmittance of the infrared absorption layer 16 is low, the amount of light reaching the imaging device is reduced. For example, the average transmittance of the infrared absorption layer 16 at a wavelength of 400 nm to 600 nm is preferably 75% or more.

In the present embodiment, the spectral transmittance of the infrared absorption layer 16 is not limited in the region of a wavelength longer than _λRT2% . This is because, in this region, the spectral transmittance of the infrared reflecting layer 14 is very small, so that the transmittance of the infrared cut filter 10 as a whole can be lowered.

In the present embodiment, it is preferable that the spectral transmittance curve of the infrared absorption layer 16 monotonously decreases in a transient region (for example, 600 nm to λ _RT2% ). It is easy to obtain a standard of the cutoff wavelength λ _T50% of the infrared cut filter 10 by synthesis with the infrared reflective layer 14, the advantage that it can be set easily and freely, and the advantage that the color reproducibility can be easily controlled. Because it is.

Examples of infrared cut filters using an infrared reflection layer and an infrared absorption layer that satisfy all of the above preferred conditions are shown as first to third examples, and the cutoff wavelength λ _{RT 50% of the} infrared reflection layer 14 is shown below. And a detailed study on the relationship between the cutoff wavelength λ _{AT of 50%} of the infrared absorbing layer 16.

  First, an appropriate blending ratio of phenyltriethoxysilane and tetraethoxysilane will be described. FIG. 6 shows the examination results of the blending ratio of phenyltriethoxysilane and tetraethoxysilane and the amount of water necessary for hydrolysis (water / Si ratio).

  In the table | surface shown in FIG. 6, (circle) mark shows the thing which can include the pigment | dye shown in below-mentioned Examples 1-3, and passed about mechanical strength. X mark is other than that. Regarding the indicators related to mechanical strength, (a) there is no film dropout such as peeling even after wiping with a soft paper wiper containing ethanol after film formation; (b) a notch is made in advance in the grid. After a predetermined tape was stuck on the film, it was peeled off to stipulate that the film did not fall off.

  From the table shown in FIG. 6, the blending ratio of phenyltriethoxysilane and tetraethoxysilane is preferably in the range of 50:50 to 80:20, and the amount of water to be added is 4 mol or more with respect to 1 mol of Si. It is understood that 6 to 8 moles may be preferable.

  From the table shown in FIG. 6, it can be seen that when the blending ratio of phenyltriethoxysilane and tetraethoxysilane is 40:60 or less, aggregation does not occur even if a predetermined amount of a predetermined dye is added.

  FIG. 7 shows the composition of the infrared absorption layer 16 used in the first to third examples. In FIG. 7, CY-10 and IRG-022 are manufactured by Nippon Kayaku Co., Ltd., NIA-7200H is manufactured by Hakko Chemical Co., Ltd., SEPc-6 is manufactured by Yamada Chemical Co., Ltd., and CIR-RL is manufactured by Nippon Carlit Co., Ltd. is there. Based on the examination results shown in FIG. 6, a material for which the blending ratio of phenyltriethoxysilane and tetraethoxysilane was set to 50:50 was used as a raw material for the sol-gel film. Cyclopentanone was used as the solvent. As the acidic catalyst, 1 mol / liter hydrochloric acid was used. 6 mol of water was administered to 1 mol of Si. In order to obtain a predetermined spectral characteristic of the infrared absorption film, the group of dyes shown in FIG. 7 was administered to obtain first to third examples.

  The infrared absorption layer 16 according to each example was formed by the following procedure. First, a sol-gel raw material, water, and hydrochloric acid as an acid catalyst (about 1/10 wt% with respect to water) are placed in a suitable container and stirred at room temperature for about 4 hours to obtain a sol. Thereafter, a predetermined amount of a predetermined dye was weighed and administered to cyclopentanone as a solvent, and a solution stirred for 20 minutes at room temperature was mixed with the sol.

On the other hand, the infrared reflective layer 14 according to each example was formed by the following procedure. For example, a dielectric multilayer film having a spectral transmittance curve shown in FIG. 3 is formed on one side of a washed D263 glass (□ 76 to 90 mm ² × t0.1 to about 0.2 mm), which is the transparent dielectric substrate 12. The infrared reflection layer 14 to be formed is formed by an ion plating method, a sputtering method, a vapor deposition method or the like. The dielectric material used may be one or more materials selected from SiO ₂ , TiO ₂ , Ta ₂ O ₃ , MgF _{2 and the} like.

  In the case where the infrared reflecting layer 14 made of a dielectric multilayer film is formed by any of the above-described methods, it is necessary to carry out it before forming the infrared absorbing layer 16 described later. In these multilayer film forming methods, the transparent dielectric substrate 12 is exposed to vacuum and high temperature (about 100 ° C. to about 200 ° C.) in the process, and therefore, it is performed after the infrared absorption layer 16 is formed. Infrared absorbing dye may be deteriorated.

  The surface on which the infrared reflective layer 14 of the transparent dielectric substrate 12 is not formed is subjected to predetermined cleaning, and then a sol containing an infrared absorbing dye is applied. The coating is performed by spin coating at a rotation speed of about 500 rpm in a room temperature environment.

  The transparent dielectric substrate 12 coated with the sol is heated in an oven at 140 ° C. for 20 minutes, for example. This is to promote the sol-gel reaction by hydrolysis and to evaporate excess water and solvent. The infrared absorption layer 16 thus obtained is suitable because the surface thereof is glassy and has high hardness.

FIG. 8 shows a spectral transmittance curve of an infrared cut filter in which only the infrared absorption layer according to the first to third embodiments is formed. The spectral transmittance curve of any of the examples has an average transmittance of 75% or more in the visible range of 400 to 600 nm and a cut-off wavelength λ _AT50 between ₆₃₀ to ₆₉₀ nm, and the required characteristics as the infrared absorption layer 16. You can see that you are satisfied.

A more preferable condition of the cutoff wavelength λ _{RT 50% of the} infrared reflecting layer 14 and the cutoff wavelength λ _{AT 50%} of the infrared absorbing layer 16 will be described. Figure 9 (a) ~ FIG 9 (m) shows the spectral transmittance curve of the infrared cut filter when the difference between the lambda _AT50% and lambda _RT50% in the first embodiment is changed by 10 nm. Figure 10 (a) ~ FIG 10 (m) shows the spectral transmittance curve of the infrared cut filter when the difference between the lambda _AT50% and lambda _RT50% in the second embodiment is changed by 10 nm. Figure 11 (a) ~ FIG 11 (m) shows the spectral transmittance curve of the infrared cut filter when the difference between the lambda _AT50% and lambda _RT50% in the third embodiment is changed by 10 nm. 9 (a) to (m), FIGS. 10 (a) to (m), and FIGS. 11 (a) to (m), a solid line indicates a spectral transmittance curve when the incident angle is 0 °, and a broken line indicates The spectral transmittance curve when the incident angle is 25 ° is shown, and the alternate long and short dash line shows the spectral transmittance curve when the incident angle is 35 °. Note also in the case of either embodiment, the fix lambda _AT50% of the infrared absorbing layer 16, by varying the _RT50% cut-off wavelength lambda of the infrared reflective layer 14, the difference between the lambda _AT50% and lambda _RT50% Set. Since the infrared reflective layer 14 is formed of a dielectric multilayer film, the transition region can be easily changed by adjusting the film thickness and the number of layers.

FIG. 9 (a), the FIG. 10 (a), the FIG. 11 (a), 60 nm longer than the first to third exemplary lambda _AT50% in Example -λ _RT50% = 60nm, i.e. lambda _AT50% is lambda _RT50% respectively The spectral transmittance curve of the infrared cut filter in the case is shown. 9B, FIG. 10B, and FIG. _11B are λ _AT50% −λ _{RT50 %} = 50 nm in the first to third embodiments, that is, _λAT50% is ₅₀ nm longer than _λRT50%. The spectral transmittance curve of the infrared cut filter in the case is shown. FIG. 9 (c), the FIG. 10 (c), the FIG. 11 (c), 40 nm longer than the first to third exemplary lambda _AT50% in Example -λ _RT50% = 40nm, i.e. lambda _AT50% is lambda _RT50% respectively The spectral transmittance curve of the infrared cut filter in the case is shown. FIG. 9 (d), the FIG. 10 (d), the FIG. 11 (d) is, 30 nm longer than the first to third exemplary lambda _AT50% in Example -λ _RT50% = 30nm, i.e. lambda _AT50% is lambda _RT50% respectively The spectral transmittance curve of the infrared cut filter in the case is shown. FIG. 9 (e), the FIG. 10 (e), the FIG. 11 (e) is, 20 nm longer than the first to third exemplary lambda _AT50% in Example -λ _RT50% = 20nm, i.e. lambda _AT50% is lambda _RT50% respectively The spectral transmittance curve of the infrared cut filter in the case is shown. FIG. 9 (f), the FIG. 10 (f), FIG. 11 (f) is, 10 nm longer than the first to third exemplary lambda _AT50% in Example -λ _RT50% = 10nm, i.e. lambda _AT50% is lambda _RT50% respectively The spectral transmittance curve of the infrared cut filter in the case is shown. 9 (g), FIG. 10 (g), and FIG. 11 (g) are the cases where λ _AT50% −λ _{RT50 %} = 0 nm in the first to third embodiments, that is, _λAT50% and _{λRT50 %} are equal. The spectral transmittance curve of an infrared cut filter is shown. Figure 9 (h), FIG. 10 (h), FIG. 11 (h) is, lambda in the first to third embodiments, respectively _{AT50% -λ RT50%} = _-10nm, i.e. 10nm than lambda _AT50% is lambda _RT50% The spectral transmittance curve of the infrared cut filter in the case of being short is shown. Figure 9 (i), FIG. 10 (i), FIG. 11 (i) is, lambda in the first to third embodiments, respectively _{AT50% -λ RT50%} = _-20nm, i.e. 20nm than lambda _AT50% is lambda _RT50% The spectral transmittance curve of the infrared cut filter in the case of being short is shown. Figure 9 (j), FIG. 10 (j), FIG. 11 (j) is, lambda in the first to third embodiments, respectively _{AT50% -λ RT50%} = _-30nm, i.e. 30nm than lambda _AT50% is lambda _RT50% The spectral transmittance curve of the infrared cut filter in the case of being short is shown. Figure 9 (k), FIG. 10 (k), FIG. 11 (k) is, lambda in the first to third embodiments, respectively _{AT50% -λ RT50%} = _-40nm, i.e. 40nm than lambda _AT50% is lambda _RT50% The spectral transmittance curve of the infrared cut filter in the case of being short is shown. 9 (l), FIG. 10 (l), and FIG. 11 (l) show _λAT50% −λRT50 _% = − _{50 nm} in the first to third embodiments, that is, _λAT50% is ₅₀ nm than _λRT50%. The spectral transmittance curve of the infrared cut filter in the case of being short is shown. Figure 9 (m), FIG. 10 (m), FIG. 11 (m) is, lambda _AT50% in the first to third embodiments, respectively -λ _RT50% = -60nm, i.e. 60nm than lambda _AT50% is lambda _RT50% The spectral transmittance curve of the infrared cut filter in the case of being short is shown.

  FIG. 12 shows the main parameters of the spectral transmittance curves (first embodiment) of FIGS. FIG. 13 shows the main parameters of the spectral transmittance curves (second embodiment) of FIGS. FIG. 14 shows the main parameters of the spectral transmittance curves (third embodiment) of FIGS.

In evaluating the spectral transmittance curves shown in FIGS. 9 (a) to (m), FIGS. 10 (a) to (m), and FIGS. 11 (a) to (m), the present inventor The following (1) and (2) were set as the fundamentally required characteristics (hereinafter referred to as “required characteristics”).
(1) Average transmittance T _ave > 70% at wavelengths of 400 nm to 600 nm
(2) λ _SLOPE = | λ _T50% -λ _T2% | <70 nm (sharp cut characteristics)

Regarding the required characteristic of the average transmittance T _ave shown in (1) above, the spectral transmittance curve in the case of λ _AT50% −λ _{RT50 %} = 60 nm shown in FIG. 10A does not satisfy this condition. The spectral transmittance curves shown in FIGS. 9 (a) to (m), FIGS. 10 (b) to (m), and FIGS. 11 (a) to (m) satisfy this required characteristic.

FIG. 15 (a), the FIG. 16 (a), the FIG. 17 (a), cut-off wavelength of the cut-off wavelength lambda _AT50% and the infrared reflective layer 14 of the infrared absorbing layer 16 in the first to third embodiments, respectively lambda _{RT50 %} difference and λ _AT50% -λ _RT50%, steepness lambda _SLOPE = the transition region of the spectral transmittance curve of | showing a relationship between | lambda _T50% 1-? _T2%. As described above, in the infrared cut filter, the steepness (sharp cut characteristic) in the transient region of the spectral transmittance curve is preferably as small as possible, and is preferably less than 70 nm from the above condition (2). Thus FIG. 15 (a), the FIG. 16 (a), the more FIG. 17 (a), the it is desirable that _{-50 ≦ λ AT50% -λ RT50%} .

Furthermore, based on the viewpoint that the spectral transmittance curve characteristic changes depending on the incident angle, which is a problem of the infrared cut filter composed only of the above-described infrared reflecting film, it is the transmittance of 50 that a person feels a difference in color. It is known that it is based on the difference in spectral transmittance in the region of% or more. Therefore, the present inventors set the following (3-1) to (3-3) as required characteristics for improving the incident angle dependency of the infrared ray blocking characteristics. Assuming that the shift amount of the cutoff wavelength λ _T50% when the incident angle is changed from 0 ° to 35 ° is Δλ _T50% ,
(3-1) Δλ _T50% <25 nm, more preferably (3-2) Δλ _T50% <20 nm, and even more preferably (3-3) Δλ _T50% <12.5 nm.

Although it is easy to satisfy the above required characteristics (1) and (2) for an infrared cut filter composed only of a general infrared reflection film, Δλ _T50% as an index of incident angle dependency is Usually, the wavelength is 30 to 40 nm or more, and the magnitude of the shift of the cut-off wavelength λ _T50% appears as a difference in color in the plane of the image.

FIG. 15 (b), the FIG. 16 (b), the FIG. 17 (b), the cut-off wavelength of the cut-off wavelength lambda _AT50% and the infrared reflective layer 14 of the infrared absorbing layer 16 in the first to third embodiments, respectively lambda _{RT50 %} indicating the difference and λ _AT50% -λ _RT50%, the relationship between the _T50% cut-off wavelength lambda _T50% shift amount Δλ of when the incident angle is changed to 35 ° from 0 ° to. From the above required characteristics (3-1) to (3-3), it is desirable that Δλ _T50% is less than 25 nm, more preferably less than 20 nm, and even more preferably less than 12.5 nm. Therefore, from FIG. 15B, FIG. 16B, and FIG. 17B, it is desirable that λ _AT50% −λ RT50 _% ≦ −10 nm, and more preferably λ _AT50% −λ _{RT50 %} ≦ −. The thickness is desirably 20 nm, and more preferably _λAT50% −λRT50 _% ≦ −30 nm.

From the above consideration, it is desirable that the difference between the cutoff wavelength λ _{AT 50%} of the infrared absorbing layer 16 and the cutoff wavelength λ _{RT 50%} of the infrared reflecting layer 14 satisfies the following condition (4).
(4) −50 nm ≦ λ _{AT 50%} −λ _{RT 50%} ≦ −10 nm

Furthermore, it is desirable that the cutoff wavelength λ _{RT 50%} of the infrared reflecting layer 14 and the cutoff wavelength λ _{AT 50%} of the infrared absorbing layer 16 satisfy the following condition (5).
_{(5) 630nm ≦ λ RT50%} , λ AT50% ≦ 690nm

  By forming the infrared reflecting layer 14 and the infrared absorbing layer 16 so as to satisfy the above conditions (4) and (5), a good image with balanced image quality factors such as transmittance and color quality can be obtained. You can get it. It is known that a person feels a difference in color based on a difference in spectral transmittance in a region where the transmittance is 50% or more. Looking at the spectral transmittance curves of the infrared cut filters 10 according to the first to third embodiments, those satisfying the above conditions (4) and (5) have a transmittance of 50% or more even if the incident angle changes. It can be seen that there is almost no change in the spectral transmittance curve in this region. Note that the above-described required characteristics are examples, and the required specifications can be changed to match the characteristics of the image sensor, for example.

  The infrared cut filter 10 according to this embodiment has been described above. According to the infrared cut filter 10 according to the present embodiment, the infrared reflection layer 14 is formed on one surface of the transparent dielectric substrate 12, and the infrared absorption layer 16 is formed on the other surface. It is possible to provide an infrared cut filter having a small number of good infrared blocking characteristics.

  Further, in the infrared cut filter 10 according to the present embodiment, a general glass substrate can be used as the transparent dielectric substrate 12. Since it is not necessary to use a glass that is brittle and difficult to process such as polishing, such as fluorophosphate glass, it is possible to perform general processing such as polishing and cutting, and as a result, it is easy to change the thickness such as thinning.

  In the infrared cut filter 10 according to this embodiment, the characteristics of the infrared cut filter 10 as a whole are determined by the combination of the optical characteristics of the infrared reflection layer 14 and the optical characteristics of the infrared absorption layer 16. The optical characteristics of the infrared reflecting layer 14 can be easily changed by adjusting the layer structure of the dielectric multilayer film. The optical properties of the infrared absorption layer 16 are easier than adjusting the type and concentration of the infrared absorbing dye contained in the matrix mainly composed of silica formed by the sol-gel method, and adjusting the thickness of the infrared absorbing layer. Can be changed. On the other hand, for example, when fluorophosphate glass is used to provide an infrared absorption function, the infrared absorption characteristics are changed by melting the fluorophosphate glass using a furnace, cutting the fluorophosphate glass, and adjusting the thickness of the fluorophosphate glass for thickness adjustment. Since polishing is required, it is not easy. Thus, the infrared cut filter 10 according to the present embodiment is also excellent in that the optical characteristics of the infrared cut filter 10 can be easily changed.

  Furthermore, in the infrared cut filter 10 according to the present embodiment, the infrared absorption layer 16 is composed of silica formed by a sol-gel method as a main component of the matrix. Thereby, since the hardness of the infrared absorption layer 16 can be increased, high scratch resistance can be realized without laminating a protective layer such as a hard coat. Moreover, by forming the infrared absorption layer 16 from a matrix containing silica as its main component, the barrier property against moisture is improved, and high environmental resistance can be realized.

  Furthermore, in the infrared cut filter 10 according to the present embodiment, since a matrix containing silica as its main component is used as the infrared absorption layer 16, adhesion to a similar glass substrate can be improved. As a result, a primer process for forming the infrared absorption layer 16 on the transparent dielectric substrate 12 is not required, so that the cost can be reduced.

  In the infrared cut filter 10 shown in FIG. 1, the infrared reflection layer 14 may be formed to reflect ultraviolet rays. When the infrared cut filter 10 is formed of a dielectric multilayer film, the ultraviolet reflection function can be easily incorporated into the infrared cut filter 10 by adjusting the layer configuration. The color filter provided in the image sensor may have an adverse effect such as a decrease in life due to ultraviolet rays. Therefore, it is possible to avoid such an adverse effect by removing the ultraviolet rays in the infrared reflecting layer 14 located in front of the imaging device. Further, when the ultraviolet reflecting function is incorporated in the infrared reflecting layer 14, the ultraviolet absorbing light can be removed before reaching the infrared absorbing layer 16 formed of a resin matrix, so that the infrared absorbing layer 16 can be prevented from being deteriorated.

  FIG. 18 shows an infrared cut filter 10 according to another embodiment of the present invention. In the infrared cut filter 10 shown in FIG. 18, the same or corresponding components as those of the infrared cut filter shown in FIG.

  The infrared cut filter 10 according to this embodiment is different from the infrared cut filter illustrated in FIG. 1 in that an antireflection layer 18 that prevents reflection of visible light is formed on the infrared absorption layer 16. As shown in FIG. 18, the antireflection layer 18 is formed on the surface of the infrared absorption layer 16 that faces the surface on the transparent dielectric substrate 12 side. In the infrared cut filter 10 according to the present embodiment, light is emitted from the antireflection layer 18.

  When the antireflection layer 18 is formed on the infrared absorption layer 16 as in the infrared cut filter 10 according to this embodiment, the visible light transmittance of the infrared cut filter 10 as a whole can be improved.

  In the infrared cut filter 10 shown in FIG. 18, the antireflection layer 18 may be formed so as to prevent the transmission of ultraviolet rays. In this case, since it is possible to prevent the ultraviolet rays incident from the light exit surface side from reaching the image sensor, it is possible to prevent deterioration of the color filter provided in the image sensor.

  FIG. 19 shows an infrared cut filter 10 according to still another embodiment of the present invention. In the infrared cut filter 10 shown in FIG. 19, the same or corresponding components as those in the infrared cut filter shown in FIG.

  The infrared cut filter 10 according to the present embodiment is different from the infrared cut filter shown in FIG. 1 in that the infrared reflective layer 14 is warped. The infrared reflective layer 14 is warped so that the surface facing the surface on the transparent dielectric substrate 12 side is a convex surface. In the present embodiment, the transparent dielectric substrate 12 and the infrared absorption layer 16 are also warped with the warp of the infrared reflecting layer 14.

  As described above, when the infrared cut filter 10 is used in an imaging apparatus, the infrared reflection layer 14 is mounted so as to face the imaging lens, and the infrared absorption layer 16 faces the imaging element. However, since the infrared cut filter 10 is very thin and small, it is not easy to distinguish between the infrared reflection layer 14 and the infrared absorption layer 16. Therefore, as in the present embodiment, by warping the infrared reflection layer 14, it is possible to visually determine which surface is the infrared reflection layer 14. By controlling the stress on the film surface when the dielectric multilayer film is deposited on the transparent dielectric substrate 12, the degree of warping of the infrared reflecting layer 14 can be adjusted within a range that does not affect the optical characteristics.

  FIG. 20 is a diagram for explaining an imaging apparatus 100 using the infrared cut filter 10 according to the embodiment of the present invention. As illustrated in FIG. 20, the imaging apparatus 100 includes an imaging lens 102, an infrared cut filter 10, and an imaging element 104. The image sensor 104 may be a semiconductor solid-state image sensor such as a CCD or a CMOS. As shown in FIG. 20, the infrared cut filter 10 is provided between the imaging lens 102 and the imaging element 104 so that the infrared reflection layer 14 faces the imaging lens 102 and the infrared absorption layer 16 faces the imaging element 104. It is done.

  As shown in FIG. 20, the light from the subject is collected by the imaging lens 102, and after the infrared rays are removed by the infrared cut filter 10, the light enters the imaging element 104. As shown in FIG. 20, light is incident on the infrared cut filter 10 from the imaging lens 102 at various incident angles. However, by using the infrared cut filter 10 according to the present embodiment, infrared rays are preferably used regardless of the incident angle. Since it can block | interrupt, a favorable image with high color reproducibility can be imaged.

  In the above description, the embodiment in which the infrared cut filter 10 is applied to the imaging apparatus has been described. However, the infrared cut filter 10 according to the above-described embodiment can be applied to other applications. For example, the infrared cut filter 10 can be used as a heat ray blocking film such as a windshield glass, a side window, and architectural glass of an automobile. The infrared cut filter 10 can also be used as a near infrared cut filter for a PDP (Plasma Display Panel).

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  DESCRIPTION OF SYMBOLS 10 Infrared cut filter, 12 Transparent dielectric substrate, 14 Infrared reflective layer, 16 Infrared absorption layer, 18 Antireflection layer, 100 Imaging device, 102 Imaging lens, 104 Imaging element.

Claims (10)

  A mixture of a trialkoxysilane having a phenyl group with a compounding ratio of 50:50 to 80:20 and an alkoxysilane containing tetraalkoxysilane and / or a hydrolyzate thereof, and an infrared absorbing dye, Sol for infrared absorption layer. When cured to form an infrared absorbing layer, the spectral transmittance curve is 600 ≦ λ _AT50% ≦ 700 (λ _AT50% nm is a wavelength at which the transmittance of the infrared absorbing layer is 50%). The sol for an infrared absorption layer according to claim 1.   3. The infrared absorbing layer sol according to claim 1, wherein when cured to form an infrared absorbing layer, the transmittance at a wavelength of 450 nm to 600 nm is 70% or more in a spectral transmittance curve.   4. The infrared absorbing dye includes at least one compound selected from the group consisting of a cyanine compound, an azo compound, a diimmonium compound, a phthalocyanine compound, and a conjugated heterocyclic compound. The infrared absorbing layer sol according to any one of the above.   An infrared absorption layer formed using the sol for infrared absorption layers according to claim 1. Applying the sol for infrared absorption layer according to any one of claims 1 to 4 on a transparent substrate;
Heating and curing the infrared absorbing layer sol;
The manufacturing method of the infrared rays absorption layer characterized by comprising. Forming an infrared reflective layer composed of a dielectric multilayer film on one surface of the transparent substrate;
Applying the infrared absorbing layer sol according to claim 1 on the other surface of the transparent substrate;
Forming an infrared absorbing layer by heating and curing the infrared absorbing layer sol;
An infrared cut filter manufacturing method comprising: The transmittance of the infrared reflective layer and the wavelength at which the 50% λ _RT50% nm, when the transmittance of the infrared-absorbing layer has a wavelength to be _{50% λ AT50% nm, λ} AT50% <λ RT50% The method for producing an infrared cut filter according to claim 7, wherein the infrared reflection layer and the infrared absorption layer are formed so as to satisfy the above. Method for manufacturing an infrared cutoff filter according to claim 8, characterized in that said -50nm ≦ λ _AT50% -λ _RT50% to meet ≦ -10 nm infrared reflective layer and the infrared-absorbing layer is formed.   The method for producing an infrared cut filter according to claim 7, further comprising a step of forming an antireflection layer on the infrared absorption layer.