JP6952823B2 - Infrared cut filter - Google Patents

Description

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

An image pickup device such as a digital camera is equipped with a semiconductor solid-state image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). The sensitivities of these solid-state image sensors range from the visible region to the infrared region. Therefore, in the image pickup apparatus, an infrared cut filter for blocking infrared rays is provided between the image pickup lens and the solid-state image sensor. With this infrared cut filter, the sensitivity of the solid-state image sensor can be corrected so as to approach the human visual sensitivity.

Conventionally, as such an infrared cut filter, one in which an infrared reflective layer made of a dielectric multilayer film is formed on a resin substrate is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-338395

However, since the infrared reflective layer made of a dielectric multilayer film has an incident angle dependence that 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 are imaged. There may be a difference in color between the parts.

Further, 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 these circumstances, and an object of the present invention is an infrared cut filter having good infrared blocking characteristics with little dependence on the angle of incidence, and high scratch resistance and environmental resistance, and the infrared cut. An object of the present invention is to provide an imaging device using a filter.

In order to solve the above problems, the infrared cut filter according to an embodiment 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 material. It is an infrared absorbing layer formed on the other surface of the substrate and absorbing infrared rays, and includes an infrared absorbing layer formed by encapsulating an infrared absorbing dye in a silica-based matrix formed by the Zolgel method.

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

When the wavelength at which the transmittance of the infrared reflecting layer becomes 50% is λ _{RT 50%} nm and the wavelength at which the transmittance of the infrared absorbing layer becomes 50% is λ _AT 50% nm, λ _AT 50% <λ _{RT 50%} is satisfied. The infrared reflecting layer and the infrared absorbing layer may be formed as described above.

Further, the infrared reflecting layer and the infrared absorbing layer may be formed so as to satisfy _{λ AT} 50% −λ _{RT 50% ≦ −10 nm.}

Further, the infrared reflecting layer and the infrared absorbing layer may be formed so as to satisfy _{λ AT} 50% −λ _{RT 50% ≦ −20 nm.}

Further, the infrared reflecting layer and the infrared absorbing layer may be formed so as to satisfy _{λ AT} 50% −λ _{RT 50% ≦ −30 nm.}

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

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

The transparent dielectric substrate may be made of glass. The infrared reflective layer may be formed to reflect ultraviolet rays.

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

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

Another aspect of the present invention is an imaging device. This device includes the infrared cut filter and an image sensor in which light transmitted through the infrared cut filter is incident.

It should be noted that any combination of the above components and the conversion of the expression of the present invention between methods, devices, systems, etc. are also effective as aspects of the present invention.

According to the present invention, it is possible to provide an infrared cut filter having good infrared blocking characteristics with little dependence on the incident angle and having high scratch resistance and environmental resistance, and an image pickup apparatus using the infrared cut filter.

It is sectional drawing for demonstrating the structure of the infrared ray 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 dye. An example of the spectral transmittance curve of the infrared reflective layer made of the dielectric multilayer film according to the first comparative example is shown. An example of the spectral transmittance curve composed of the infrared absorbing layer according to the second comparative example is shown. It is a figure which shows an example of the spectral transmittance curve of the infrared ray 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 absorption layer used in 1st to 3rd Examples. It is a figure which shows the spectral transmittance curve of the infrared ray cut filter which formed only the infrared ray absorption layer which concerns on 1st to 3rd Examples. Is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 60nm _λ in the first embodiment. 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. Is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 60nm _λ in the second embodiment. 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. Is a diagram showing a spectral transmittance of the infrared cut filter when the _{AT50% -λ RT50%} = 60nm _λ in the third embodiment. 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. 9 is a diagram showing a table summarizing the main parameters of the spectral transmittance curves shown in FIGS. 9A to 9M. It is a figure which shows the table which summarized the main parameters of the spectral transmittance curve shown in FIGS. 10 (a) to 10 (m). 11 is a diagram showing a table summarizing the main parameters of the spectral transmittance curves shown in FIGS. 11A to 11M. It is a figure which shows the relationship between the difference between the cutoff wavelength of an infrared absorption layer and the cutoff wavelength of an infrared reflection layer in 1st Example, and the steepness of a transient region of a spectral transmittance curve. It is a figure which shows the relationship between the difference between the cutoff wavelength of an infrared absorption layer and the cutoff wavelength of an infrared reflection layer in 1st Example, and the shift amount of the cutoff wavelength when an incident angle changes from 0 ° to 35 °. be. It is a figure which shows the relationship between the difference between the cutoff wavelength of an infrared absorption layer and the cutoff wavelength of an infrared reflection layer in 2nd Example, and the steepness of a transient region of a spectral transmittance curve. It is a figure which shows the relationship between the difference between the cutoff wavelength of an infrared absorption layer and the cutoff wavelength of an infrared reflection layer in the 2nd Example, and the shift amount of the cutoff wavelength when an incident angle changes from 0 ° to 35 °. be. It is a figure which shows the relationship between the difference between the cutoff wavelength of an infrared absorption layer and the cutoff wavelength of an infrared reflection layer in 3rd Example, and the steepness of a transient region of a spectral transmittance curve. It is a figure which shows the relationship between the difference between the cutoff wavelength of an infrared absorption layer and the cutoff wavelength of an infrared reflection layer in 3rd Example, and the shift amount of the cutoff wavelength when an incident angle changes from 0 ° to 35 °. be. It is a figure which shows the infrared ray cut filter which concerns on another embodiment of this invention. It is a figure which shows the infrared ray cut filter which concerns on still another Embodiment of this invention. It is a figure for demonstrating the image pickup apparatus which used the infrared ray cut filter which concerns on embodiment of this invention.

FIG. 1 is a cross-sectional view for explaining the configuration of the infrared cut filter 10 according to the embodiment of the present invention. As shown in FIG. 1, the infrared cut filter 10 includes a transparent dielectric substrate 12, an infrared reflecting layer 14, and an infrared absorbing layer 16. The infrared reflective layer 14 is formed on one surface of the transparent dielectric substrate 12. The infrared absorbing 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 image pickup lens and an image pickup element in, for example, a digital camera. The infrared cut filter 10 is mounted so as to enter light from the infrared reflecting layer 14 and emit light from the infrared absorbing layer 16. That is, in the mounted state, the infrared reflecting layer 14 faces the image pickup lens, and the infrared absorbing layer 16 faces the image sensor.

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

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

The infrared absorbing layer 16 is formed on the other surface of the transparent dielectric substrate 12 as described above, and functions as a light emitting surface. The infrared absorbing layer 16 is configured to transmit visible light and absorb infrared light. Since the light incident on the infrared cut filter 10 passes through the infrared reflecting layer 14 and the transparent dielectric substrate 12 and then enters the infrared absorbing layer 16, the infrared absorbing layer 16 is the infrared reflecting layer 14 and the transparent dielectric substrate 12. It will absorb infrared rays that were not blocked by.

In the infrared cut filter 10 according to the present embodiment, the infrared absorbing layer 16 is composed of a matrix containing silica as a main component formed by the sol-gel method and an infrared absorbing dye. The infrared absorbing film that is often seen in the past is a resin matrix in which an infrared absorbing dye composed of organic compounds such as phthalocyanine, cyanine, and diimmonium is a transparent dielectric such as polyester, polyacrylic, polyolefin, polyvinyl butyral, and polycarbonate. It is made to be included in. However, due to the physical characteristics of the organic resin matrix, the hardness is low and there is a problem in scratch resistance, and in actual use, it is necessary to laminate a protective layer such as a hard coat on the upper surface thereof.

In the infrared cut filter 10 according to the present embodiment, paying attention to such a problem, a silica formed by the sol-gel method as a main component of the matrix was adopted as the infrared absorbing layer 16. The effect of adopting the infrared absorbing layer 16 containing silica formed by the sol-gel method as a main component of the matrix will be described below.

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

Since the infrared absorbing layer 16 according to the present embodiment is formed of a layer composed of a matrix containing silica as a main component, which is called an organic-inorganic hybrid, there is no problem in the technical field to which hardness is applied. Not only in terms of physical properties, but also because there is virtually no need for a hard coating or the like to protect it, there is an advantage that the manufacturing cost can be kept low.

Secondly, it is possible to obtain an improvement in environmental resistance. 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 conventional infrared absorbing film made of an organic binder, and from the surrounding environment. The effect of suppressing the adverse effect on the infrared absorbing dye composed of the contained organic compound can be expected more.

Thirdly, strong adhesion to a substrate such as glass can be obtained. Considering that an infrared absorbing film made of a resin-based binder, which is often used in the past, is applied to a glass substrate which is an inorganic substance, it is practically necessary to apply a silane coupling agent on the glass substrate before the application. Met. Otherwise, there is a problem that the infrared absorbing film is peeled off from the glass substrate under a certain harsh environment. Since the infrared absorbing layer 16 according to the present embodiment uses a matrix containing silica as a main component, it can be expected that the adhesion to a glass substrate of the same type will be improved.

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

First, the raw material of 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 the main component of the infrared absorbing layer 16 and the infrared absorbing layer is subjected to the sol-gel method. 16 matrices are formed. Tetraethoxysilane is a type 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 the raw material is cooled. On the other hand, the sol-gel method is a relatively new method for producing glass and ceramics at low temperatures. The sol-gel method uses a solution of an organic or inorganic compound of a metal as a starting material, and the solution is made into a sol in which fine particles of metal oxides or hydroxides are dissolved by a hydrolysis / polycondensation reaction of the compound in the solution, and further. This is a method in which the reaction proceeds to gel and solidify, and this gel is heated to obtain an oxide solid. In the sol-gel method, thin films can be formed on various substrates in order to produce glass from a solution, and glass can be produced at a lower temperature than the glass production temperature by the melting method. It has characteristics.

The sol-gel process will be described. As an example, the formation of a silica-based film formed by the sol-gel method will be described. For example, in the sol-gel method using alkoxysilane as a starting material, in a solution of alkoxysilane, a sol composed of an oligomer composed of a siloxane bond is formed 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 or a solvent volatilizes, and the oligomer is concentrated to increase its molecular weight, lose its fluidity, and become a gel state. Immediately after gelation, the gaps in the network are filled with solvent and water. When the gel dries and the water or solvent volatilizes, the siloxane polymer further shrinks and solidifies.

Generally, the hydrolysis reaction between alkoxysilane and water is expressed as follows. Taking tetraethoxysilane as an example;
n ・ Si (OC ₂ H ₅ ) ₄ + 4 n ・ H ₂ O → n ・ Si (OH) ₄ + 4 n ・ C ₂ H ₅ OH
nSi (OH) ₄ → n · SiO ₂ + 2n · H ₂ O
That is, stoichiometrically, if there are 4 mol or more of water with respect to 1 mol of alkoxysilane, all the alkoxy groups (-O-CnH _{2n + 1} ) are hydrolyzed. In general, alkalis and acids are added as catalysts for the reaction.

Tetraalkoxysilane typified by the above tetraethoxysilane is often used as a starting material for the silica-based film formed by the sol-gel method. When forming a sol-gel film using these as a starting point, a strong network is formed by the four reactive groups, and it is easy to obtain a dense and glassy preferable film. As other tetraalkoxysilanes, tetramethoxysilane, tetrapropoxysilane, tetraisopropoxysilane and the like can be used. The larger the alkoxy group (-O-CnH _{2n + 1} ) coordinated with Si, the lower the rate of hydrolysis of the silanes, so that the silanes can be selected according to the characteristics of the product and the convenience of the process.

In the present embodiment, in addition to the tetraethoxysilane, a trialkoxysilane composed of a trifunctional group such as phenyltriethoxysilane is mixed and used as a raw material for a sol-gel film. The tetraethoxysilane adopted above is preferably used as a raw material for silica constituting a sol-gel film. This is because it is easy to obtain a preferable appearance and characteristics 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 the spatial margin in the crosslinked structure during gelation in the film forming process, so that cracks are likely to occur in the film. This is noticeable when trying to increase the film thickness.

Further, in the present embodiment, it is necessary to enclose one or more kinds of infrared absorbing dyes composed of organic compounds in the film, and it is not possible to enclose a predetermined amount in the sol-gel film made only of tetraethoxysilane. There was a problem.

If the sol-gel film is given a certain degree of flexibility, the cracks are unlikely to occur. Therefore, a means for adding trialkoxysilane having three reaction functional groups to tetraethoxysilane is known. Trialkoxysilane is a general term for silanes having three alkoxy groups around Si, and the remaining one having a modifying group consisting of a methyl group, an ethyl group, and a phenyl group and having a relatively low reactive activity. Since the silica film formed of trialkoxysilane having three reaction functional groups has a spatial margin, the stress generated during gelation is relatively small and cracks are unlikely to occur. Further, since there are three reaction functional groups, one silicon compound forms three strong siloxane bonds, so that a crosslinked network can be formed. Dialkoxysilanes having two alkoxy groups also exist in practice, but they tend to become linear during polycondensation by hydrolysis, and only a chain network is formed, so that the wear resistance of the film is reduced. Causes problems.

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

Of these, a trialkoxysilane having a phenyl group (-C ₆ H _{5) as a functional group is preferable.} It is considered that the phenyl group remains on the film even after the sol-gel reaction under firing conditions of about 100 to 200 ° C., and produces flexibility.

It was also found that the trialkoxysilane having a phenyl group also works advantageously for the inclusion of an infrared absorbing dye composed of an organic compound. As will be described later, the inclusion properties of the dyes of methyltriethoxysilane and phenyltriethoxysilane (PhTEOS / chemical formula = Si (C ₆ H ₅ ) (C ₂ H ₅ O) _{3), which are trialkoxysilanes, were examined.} After the sol-gel reaction, the dye aggregated and a uniform transparent silica main component film was not formed. The latter was able to sufficiently contain a predetermined infrared absorbing dye. It is considered that this can introduce a large amount of infrared absorbing dye of an organic compound into the pores formed in the silica main component film formed of the alkoxysilane containing a phenyl group. Examples of the trialkoxysilane having a phenyl group as a functional group include phenyltrimethoxysilane, phenyltriisopropoxysilane, phenyltrinormal propoxysilane, and the like, in addition to the above-mentioned phenyltriethoxysilane.
A trialkoxysilane having a phenyl group having these advantages (hereinafter referred to as phenyltrialkoxysilane) is mixed with a tetraalkoxysilane such as the above-mentioned tetraethoxysilane to be used as 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 when only phenyltriethoxysilane is used as a raw material, the silica film formed by the sol-gel method is not cured or is cured due to its flexibility. However, there are cases where a very high firing temperature is required or the mechanical strength of the film is not satisfactory. Therefore, the trifunctional phenyltrialkoxysilane needs to be appropriately blended with the tetrafunctional tetraalkoxysilane.

FIG. 2 shows the experimental results when methyltriethoxysilane and phenyltriethoxysilane were mixed with tetraethoxysilane to enclose a phthalocyanine-based infrared absorbing dye and a cyanine-based 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, it becomes aggregated regardless of the addition of any dye, and the amount of inclusion is unacceptably limited. I understand. On the other hand, when a mixture of tetraethoxysilane and phenyltriethoxysilane is used as a raw material for the sol-gel film, sufficient inclusion capacity and film thickness selectivity can be obtained for any of the dyes, which is advantageous for inclusion of an infrared absorbing dye. It can be seen that it has a positive effect.

Next, water will be described. Water is an essential component for the hydrolysis of alkoxysilane. As mentioned above, stoichiometrically, 4 mol of water is required for 1 mol of alkoxysilane. However, since water continues to evaporate even when the silica film formed by the sol-gel method is formed, in general, there are many cases where the amount of water exceeds the stoichiometry.

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

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

Furthermore, the solvent must be evaporated at least below the firing temperature when forming the silica film formed by the sol-gel method, and conversely, if the boiling point is too low, the silica network is being formed immediately after application to the substrate. , It volatilizes rapidly and causes a problem in the inclusion of the dye. Furthermore, if the boiling point of the solvent is lower than that of water, water having a high surface tension will remain in the silica film at the end during firing, and there is a risk that problems such as cracks may occur due to rapid film shrinkage.

Further, the infrared absorbing dye made of an organic compound deteriorates in a high temperature environment, and the absorption characteristics are significantly different from the initial ones, so that the desired infrared absorbing film cannot be obtained. Therefore, the firing temperature needs to be set in a temperature range in which the infrared absorbing dye does not thermally deteriorate. Generally, 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 its characteristics, and it is necessary to complete the firing at least at this temperature or lower.

From the above consideration, it is desirable that 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 thereof include pyrrolidone, tetrahydrofuran, dioxane, methyl ethyl ketone, cyclohexanone, cyclopentanone, 2-methoxyethanol (methyl cellsolve), 2-ethoxyethanol (ethyl cell solve), ethyl acetate and the like.

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

Next, the acid will be described. The acid acts as a catalyst for the hydrolysis of alkoxysilane. It is desirable that it is a strong acid, and the following can be mentioned. Hydroxic acid, nitrate, trichloroacetic acid, trifluoroacetic acid, sulfuric acid, phosphoric acid, methanesulfonic acid, paratoluenesulfonic acid, oxalic acid, etc.

The operation of the infrared cut filter 10 configured as described above will be described. Before explaining 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 the 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. Further, FIG. 4 shows the spectral transmittance of an infrared cut filter in which only an infrared absorbing layer composed of a matrix mainly composed of silica formed by a sol-gel method and an infrared absorbing 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, can be seen. In FIG. 3, 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 alternate long and short dash line shows the spectroscopy 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 _{RT 50%} = about 625 nm. As described above, in the infrared cut filter according to the first comparative example, when the incident angle changes from 0 ° to 35 °, λ _{RT 50%} shifts 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 to the infrared cut filter (for example, an incident angle of 0 °) is normally incident on the central portion of the image sensor, but on the other hand, the image sensor Light having a large incident angle (for example, an incident angle of 25 ° or 35 °) incident on the infrared cut filter is incident on the peripheral portion. Therefore, when an infrared cut filter having infrared blocking characteristics as shown in FIG. 3 is applied to the image pickup device, the spectral transmittance curve characteristics of the light incident on the image pickup element (particularly around 650 nm wavelength) depending on the position of the light receiving surface of the image pickup element. (Spectroscopic characteristics) will be different. This causes a phenomenon in which the color tone differs between the central portion and the peripheral portion of the image, which may adversely affect the color reproducibility.

Further, in the infrared cut filter according to the second comparative example, unlike the infrared cut filter according to the first comparative example, the incident angle dependence of the blocking characteristic does not exist. However, as shown in FIG. 4, in the infrared cut filter according to the second comparative example, the spectral transmittance curve in the transient region changing from the region where the transmittance is relatively high to the region where the transmittance is low gradually decreases. Generally, an infrared cut filter has the transient region in the wavelength range 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”). Is called) is required. Therefore, it is difficult to satisfactorily control the color reproducibility with the infrared cut filter according to the second comparative example.

In consideration of the drawbacks in these comparative examples, the present invention blocks the infrared rays by forming the infrared reflecting layer 14 on one surface of the transparent dielectric substrate 12 and forming the infrared absorbing layer 16 on the other surface. It has been found that the characteristics have little dependence on the incident angle and that good sharp cut characteristics 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 alternate long and short dash line shows the spectroscopy when the incident angle is 35 °. The transmittance curve is shown.

The characteristics of the infrared cut filter 10 according to the present embodiment are determined by the combination of the optical characteristics of the infrared reflecting layer 14 and the optical characteristics of the infrared absorbing layer 16. Here, the wavelength at which the transmittance is 50% at an incident angle of 0 ° in the infrared reflecting layer alone is λ _{RT 50%} (nm), and the wavelength at which the transmittance is 50% in the infrared absorbing layer alone is λ _AT 50% (nm). And. FIG. 4 shows the spectral transmittance curve of the infrared cut filter 10 when _{λ AT 50%} = λ _{RT 50%} -30 nm, that is, λ AT 50% is 30 nm shorter than λ _{RT 50%.}

Assuming that the wavelength at which the transmittance is 50% at an incident angle of 0 ° of the infrared cut filter 10 according to the present embodiment is λ _T50% (nm), as shown in FIG. 5, the infrared cut filter 10 according to the present embodiment 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 Is. As described above, in the infrared cut filter 10 according to the present embodiment, even if the incident angle changes from 0 ° to 35 °, λ _T50% is shifted to the short wavelength side by only about 8 nm, and the incident angle of _{λ T50%.} The dependence is smaller than the incident angle dependence of _{λ RT 50% in} the first comparative example described above. Further, looking at 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 changes. 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 curves in the region where the transmittance is lower than 50% has a small effect on the color reproducibility, and thus does not cause any particular problem.

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. It turns out that can be realized.

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

First, suitable optical characteristics of the infrared reflective layer 14 will be described. The infrared reflecting layer 14 is designed to transmit visible light having a wavelength of at least 400 nm to 600 nm and to reflect infrared rays having a wavelength of at least 750 nm in terms of required performance. In the transient region between the transmission region and the reflection region, the wavelength at which the spectral transmittance is 50% is defined _{as the cutoff wavelength λ RT 50%.} Although it depends on the spectral sensitivity region of the image pickup element or the like, the λ _{RT 50% of the infrared reflecting layer 14 is near the cutoff wavelength λ AT} 50% of the infrared absorbing layer 16, and is preferably λ _AT 50% <λ _{RT 50%} . It is preferable to set as such. The cutoff wavelength λ _RT50% of the infrared reflecting layer 14 is preferably in the range of 630 nm to 690 nm.

Further, the infrared reflecting layer 14 is designed so that the transmittance in the visible region is as high as possible. This is to allow light in the visible region, which is necessary for composing an image, 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 light rays in bands that do not contribute to image composition or are harmful to the image composition as much as possible. The infrared reflective layer 14 may have, for example, an average spectral transmittance of 90% or more in the visible region in the band of at least 400 nm to 600 nm, and a spectral transmittance of less than 2% in the infrared region having a wavelength of at least 750 nm or more. preferable.

Further, it is preferable that the spectral transmittance of the infrared reflecting layer 14 changes sharply in the transient region (referred to as "sharp cut characteristic"). This is because if the sharp cut characteristic is lost and the transient 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 the wavelength at which the spectral transmittance is 2%), the λ _RSLOPE of the infrared reflecting layer 14 is as much as possible. It is preferably small, 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 at any of the incident angles of 0 °, 25 °, and 35 °. It is less than%. _{Further, in the spectral transmittance curve shown in FIG. 3, λ RSLOPE} is less than 70 nm at any of the 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 absorbing layer 16 will be described. In the present embodiment, the optical characteristics required for the infrared absorbing layer 16 vary depending on the optical characteristics of the combined infrared reflecting layer 14.

In the present embodiment, 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 absorbing layer 16 satisfies this condition, the infrared cutoff characteristic of the infrared cut filter 10 depends on the incident angle, 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 λ _{T50% can be reduced.} The cutoff wavelength λ _AT50% of the infrared absorbing layer 16 is preferably in the range of 630 nm to 690 nm.

Further, in the present embodiment, it is preferable that the average transmittance of the infrared absorbing layer 16 in the visible region is as high as possible. This is because when the average transmittance of the infrared absorbing layer 16 is low, the amount of light reaching the image sensor is small. For example, the average transmittance of the infrared absorbing 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 absorbing layer 16 does not matter in the region having a wavelength longer than _{λ RT 2%.} This is because the spectral transmittance of the infrared reflecting layer 14 is very small in this region, so that the transmittance of the infrared cut filter 10 as a whole can be lowered.

Further, in the present embodiment, the spectral transmittance curve of the infrared absorbing layer 16 preferably decreases monotonically in the _{transient region (for example, 600 nm to λ RT 2%). It has the advantages that it is easy to obtain a guideline for the cutoff wavelength λ T50%} of the infrared cut filter 10 by combining with the infrared reflecting layer 14, that it can be set easily and freely, and that the color reproducibility can be easily controlled. Because it is possible.

Hereinafter, examples of an infrared cut filter using an infrared reflecting layer and an infrared absorbing layer that satisfy all of the above suitable conditions are shown as first to third examples, and the cutoff wavelength λ _{RT of the infrared reflecting layer 14 is 50%.} The relationship between the infrared ray absorbing layer 16 and the cutoff wavelength λ _AT50% of the infrared absorbing layer 16 was examined in detail.

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 added (water / Si ratio) essential for hydrolysis.

In the table shown in FIG. 6, ◯ indicates that the dyes shown in Examples 1 to 3 described later can be encapsulated and have passed the mechanical strength. The x mark is other than that. Regarding the index related to mechanical strength, (a) the film does not come off such as peeling even by wiping with a soft paper wiper soaked in ethanol after film formation, and (b) cuts are made in advance on the grid. It is stipulated that after a predetermined tape is attached to the film, it is peeled off so that the film does not come off.

From the table shown in FIG. 6, the compounding 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 can be seen that it may be preferably 6 to 8 mol.

Further, 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, even if a predetermined amount of a predetermined dye is added, it aggregates and cannot be encapsulated.

FIG. 7 shows the composition of the infrared absorbing 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. be. From the examination results shown in FIG. 6, a sol-gel film having a blending ratio of phenyltriethoxysilane and tetraethoxysilane set to 50:50 was used as a raw material for the sol-gel film. Cyclopentanone was used as the solvent. 1 mol / liter of hydrochloric acid was used as the acidic catalyst. 6 mol of water was administered to 1 mol of Si. In order to obtain the spectral characteristics of the predetermined infrared absorbing film, the group of dyes shown in FIG. 7 was administered and used as the first to third examples.

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

On the other hand, the infrared reflective layer 14 according to each embodiment was formed by the following procedure. From a dielectric multilayer film having a spectral transmittance curve shown in FIG. 3, for example, on one cleaned side of ^{D263 glass (□ 76 to 90 mm 2} × t 0.1 to 0.2 mm) manufactured by Shot Co., Ltd., which is the transparent dielectric substrate 12. The infrared reflective layer 14 is formed by an ion plating method, a sputtering method, a vapor deposition method, or the like. The dielectric material may be one or more materials selected from _{SiO 2} , TiO ₂ , Ta ₂ O ₃ , MgF _{2, and the like.}

When the infrared reflecting layer 14 made of a dielectric multilayer film is formed by any of the above methods, it is necessary to perform the infrared reflecting layer 14 before forming the infrared absorbing layer 16 described later. In these multilayer film forming methods, the transparent dielectric substrate 12 is exposed to a vacuum and a high temperature (around 100 ° C. to about 200 ° C.) in the process. Therefore, it is assumed that the infrared absorbing layer 16 is formed after the formation. , Infrared absorbing dye may deteriorate.

After performing a predetermined cleaning on the surface of the transparent dielectric substrate 12 on which the infrared reflecting layer 14 is not formed, a sol containing an infrared absorbing dye is applied. Spin coating is performed 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, for example, 140 ° C. for 20 minutes. This is to promote the sol-gel reaction by hydrolysis and to evaporate excess water, solvent and the like. The surface of the infrared absorbing layer 16 thus obtained is glassy and has high hardness, which is suitable.

FIG. 8 shows the spectral transmittance curve of the infrared cut filter having only the infrared absorbing layer according to the first to third embodiments. The spectral transmittance curves of all the examples have an average transmittance of 75% or more in the visible region of 400 to 600 nm, a cutoff wavelength λ _AT50 between 630 and 690 nm, and required characteristics as the infrared absorption layer 16. It turns out that you are satisfied.

More preferable conditions 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. 9 (a) to 9 (m) show the spectral transmittance curves of the infrared cut filter when the difference between _{λ AT} 50% and λ _{RT 50% in the first embodiment is changed by 10 nm.} 10 (a) to 10 (m) show the spectral transmittance curves of the infrared cut filter when the difference between _{λ AT} 50% and λ _{RT 50% in the second embodiment is changed by 10 nm.} 11 (a) to 11 (m) show the spectral transmittance curves of the infrared cut filter when the difference between _{λ AT} 50% and λ _{RT 50% in the third embodiment is changed by 10 nm.} In FIGS. 9 (a) to 9 (m), FIGS. 10 (a) to (m), and 11 (a) to (m), the solid line shows the spectral transmittance curve when the incident angle is 0 °, and the broken line indicates the spectral transmittance curve. 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% I set it. Since the infrared reflective layer 14 is formed of a dielectric multilayer film, it is possible to easily realize a change in the transient region 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. 9 (b), 10 (b), and 11 (b) show λ _AT50% −λ _RT50% = 50 nm in the first to third embodiments, respectively, that is, λ AT50% is ₅₀ nm longer than _{λ RT50%.} 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), 10 (g), and 11 (g) show λ _AT50% −λ _RT50% = 0 nm in the first to third embodiments, respectively, that is, when λ _AT50% and λ _RT50% are equal. The spectral transmittance curve of the 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 when it is 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 when it is 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 when it is 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 when it is short is shown. 9 (l), 10 (l), and 11 (l) show λ _AT50% −λ _RT50% = −50 nm in the first to third embodiments, respectively, that is, λ AT50% is _{50 nm more than λ RT50%.} The spectral transmittance curve of the infrared cut filter when it is 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 when it is short is shown.

FIG. 12 shows the main parameters of the spectral transmittance curves (first embodiment) of FIGS. 9 (a) to 9 (m). FIG. 13 shows the main parameters of the spectral transmittance curves (second embodiment) of FIGS. 10 (a) to 10 (m). FIG. 14 shows the main parameters of the spectral transmittance curves (third embodiment) of FIGS. 11 (a) to 11 (m).

In evaluating the spectral transmittance curves shown in FIGS. 9 (a) to 9 (m), FIGS. 10 (a) to (m), and FIGS. 11 (a) to 11 (m), the present inventor used the infrared cut filter. The following (1) and (2) are set as the basically required characteristics (hereinafter referred to as "required characteristics").
(1) Average transmittance at a wavelength 400nm~600nm _T ave> 70%
(2) λ _SLOPE = | λ _T50% -λ _T2% | <70 nm (sharp cut characteristics)

Regarding the characteristics required of the average transmittance _{T ave} shown above (1), to indicate lambda _AT50% Figure _{10 (a) -λ RT50% =} 60nm spectral transmittance curve for but does not meet this condition, FIG. The spectral transmittance curves shown in 9 (a) to (m), FIGS. 10 (b) to (m), and FIGS. 11 (a) to 11 (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) of 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 characteristics change depending on the incident angle, which is a problem of the infrared cut filter consisting only of the infrared reflective film, it is the transmittance of 50 that a person perceives 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 inventor has set the following (3-1) to (3-3) as required characteristics for improving the incident angle dependence of the infrared blocking characteristic. Let the shift amount of _{the cutoff wavelength λ T50%} when the incident angle changes from 0 ° to 35 ° be _{Δλ T50%} .
(3-1) Δλ _T50% <25 nm, more preferably (3-2) Δλ _T50% <20 nm, more preferably (3-3) Δλ _T50% <12.5 nm

It is easy to satisfy the above required characteristics (1) and (2) for an infrared cut filter consisting only of a general infrared reflective film, but for Δλ _T50%, which is an index of incident angle dependence, It is usually 30 to 40 nm or more, and _{the magnitude of the shift of the cutoff wavelength λ T50%} appears as a difference in in-plane tint 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 FIGS. 15 (b), 16 (b), and 17 (b), _{it is desirable that λ AT50%} −λ _RT50% ≦ −10 nm, and more preferably λ _AT50% −λ _RT50% ≦ −. It is preferably 20 nm, and more preferably λ _AT 50% −λ _{RT 50%} ≦ −30 nm.

From the above consideration, the difference in the cutoff wavelength lambda _RT50% cutoff wavelength lambda _AT50% and the infrared reflective layer 14 of the infrared absorbing layer 16, it is desirable to satisfy the following condition (4).
(4) -50 nm ≤ λ _AT 50% -λ _{RT 50%} ≤ -10 nm

Further, the cutoff wavelength lambda _RT50% of the infrared reflective layer 14 and the cut-off wavelength lambda _AT50% of the infrared absorbing layer 16, it is desirable to satisfy the following condition (5).
(5) 630 nm ≤ λ _{RT 50%} , λ _AT 50% ≤ 690 nm

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 in which image quality factors such as transmittance and color quality are balanced can be obtained. You can get it. It is known that the difference in color tones is due to the difference in spectral transmittance in the 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. The above required characteristics are an example, and the required specifications can be changed so as to match the characteristics of the image sensor, for example.

The infrared cut filter 10 according to the present embodiment has been described above. According to the infrared cut filter 10 according to the present embodiment, the infrared reflecting layer 14 is formed on one surface of the transparent dielectric substrate 12, and the infrared absorbing layer 16 is formed on the other surface, so that the incident angle dependence is increased. It is possible to provide an infrared cut filter having few 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 glass that is brittle and difficult to process such as polishing, such as borosilicate glass, general processing such as polishing and cutting is possible, and as a result, it is easy to change the thickness such as thinning.

In the infrared cut filter 10 according to the present embodiment, the characteristics of the infrared cut filter 10 as a whole are determined by the combination of the optical characteristics of the infrared reflecting layer 14 and the optical characteristics of the infrared absorbing layer 16. The optical characteristics of the infrared reflective layer 14 can be easily changed by adjusting the layer structure of the dielectric multilayer film. Further, the optical characteristics of the infrared absorbing layer 16 are easier than adjusting the type and concentration of the infrared absorbing dye contained in the matrix containing silica as a main component formed by the sol-gel method and adjusting the thickness of the infrared absorbing layer. Can be changed to. On the other hand, for example, when borosilicate glass is used to have an infrared absorption function, the change in the infrared absorption characteristics can be made by melting the borosilicate glass using a furnace, cutting the borosilicate glass, and adjusting the thickness of the borosilicate glass. It is not easy because it requires polishing. As described above, 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.

Further, in the infrared cut filter 10 according to the present embodiment, as the infrared absorbing layer 16, silica formed by the sol-gel method is used as a main component of the matrix. As a result, the hardness of the infrared absorbing layer 16 can be increased, so that high scratch resistance can be realized without laminating a protective layer such as a hard coat. Further, by forming the infrared absorbing layer 16 from the matrix containing silica as its main component, the barrier property against moisture and the like are improved, and high environmental resistance can be realized.

Further, in the infrared cut filter 10 according to the present embodiment, since a matrix containing silica as a main component is used as the infrared absorbing layer 16, the adhesion to a glass substrate of the same type can be improved. As a result, the priming process when forming the infrared absorbing layer 16 on the transparent dielectric substrate 12 becomes unnecessary, so that the cost can be reduced.

In the infrared cut filter 10 shown in FIG. 1, the infrared reflecting layer 14 may be formed so as 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 structure. The color filter provided in the image sensor may have an adverse effect such as a shortened life due to ultraviolet rays. Therefore, by removing the ultraviolet rays in the infrared reflecting layer 14 located in front of the image sensor, it is possible to avoid a situation in which such an adverse effect occurs. Further, when the infrared reflecting function is incorporated in the infrared reflecting layer 14, the ultraviolet rays can be removed before reaching the infrared absorbing layer 16 formed of the resin matrix, so that the deterioration of the infrared absorbing layer 16 can be prevented.

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 the infrared cut filter shown in FIG. 1 are designated by the same reference numerals, and overlapping description will be omitted as appropriate.

The infrared cut filter 10 according to the present embodiment is different from the infrared cut filter shown in FIG. 1 in that an antireflection layer 18 for preventing 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 absorbing layer 16 facing 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 absorbing layer 16 like the infrared cut filter 10 according to the present embodiment, the transmittance of visible light as a whole of the infrared cut filter 10 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 emitting 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 the infrared cut filter shown in FIG. 1 are designated by the same reference numerals, and overlapping description will be omitted as appropriate.

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 reflecting layer 14 is warped. The infrared reflective layer 14 is warped so that the surface facing the surface of the transparent dielectric substrate 12 is a convex surface. Further, in the present embodiment, the transparent dielectric substrate 12 and the infrared absorbing layer 16 are also warped as the infrared reflecting layer 14 is warped.

As described above, when the infrared cut filter 10 is used in the image pickup apparatus, the infrared reflection layer 14 is mounted so as to face the image pickup lens, and the infrared absorption layer 16 faces the image pickup element. However, since the infrared cut filter 10 is very thin and small, it is not easy to distinguish between the infrared reflecting layer 14 and the infrared absorbing layer 16. Therefore, by warping the infrared reflecting layer 14 as in the present embodiment, it is possible to visually determine which surface is the infrared reflecting 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 warpage 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 image pickup apparatus 100 using the infrared cut filter 10 according to the embodiment of the present invention. As shown in FIG. 20, the image pickup device 100 includes an image pickup lens 102, an infrared cut filter 10, and an image pickup element 104. The image pickup device 104 may be a semiconductor solid-state image pickup device such as a CCD or CMOS. As shown in FIG. 20, the infrared cut filter 10 is provided between the image pickup lens 102 and the image pickup element 104 so that the infrared reflection layer 14 faces the image pickup lens 102 and the infrared absorption layer 16 faces the image pickup element 104. Be done.

As shown in FIG. 20, the light from the subject is focused by the image pickup lens 102, the infrared rays are removed by the infrared ray cut filter 10, and then the light is incident on the image pickup device 104. As shown in FIG. 20, light is incident on the infrared cut filter 10 from the image pickup lens 102 at various incident angles. However, by using the infrared cut filter 10 according to the present embodiment, infrared rays are preferably emitted regardless of the incident angle. Since it can be blocked, a good image with high color reproducibility can be captured.

In the above description, the embodiment in which the infrared cut filter 10 is applied to the image pickup apparatus has been described, but the infrared cut filter 10 according to the above-described embodiment can also be applied to other uses. For example, the infrared cut filter 10 can be used as a heat ray blocking film for, for example, windshield glass for automobiles, side windows, and architectural glass. 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 above based on the embodiments. This embodiment is an example, and it is understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. be.

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

Claims (12)

A transparent dielectric substrate, an infrared reflecting layer that reflects infrared rays formed on one surface of the transparent dielectric substrate, and an infrared absorbing layer that absorbs infrared rays formed on the other surface of the transparent dielectric substrate. It is an infrared cut filter equipped with
The infrared reflective layer is formed of a dielectric multilayer film and is formed of a dielectric multilayer film.
The infrared absorbing layer contains an infrared absorbing dye that absorbs a part of infrared rays and silica.
In the spectral transmittance curve of the infrared cut filter when the incident angles are 0 °, 25 ° and 35 °, the average spectral transmittance at a wavelength of 400 nm to 600 nm is 75% or more.
In the spectral transmittance curves of the infrared reflecting layer and the infrared absorbing layer when the incident angle is 0 °, the wavelength at which the transmittance of the infrared reflecting layer becomes 50% is set to λ _{RT 50%} nm, and the transmission of the infrared absorbing layer is set. When the wavelength at which the rate becomes 50% is λ _AT 50% nm, the infrared reflective layer and the above are satisfied so as to satisfy 630 nm ≤ λ _{RT 50%} ≤ 690 nm, 630 nm ≤ λ _AT 50% ≤ 690 nm and λ _AT 50% <λ _{RT 50%.} An infrared absorbing layer is formed,
The wavelength at which the transmittance is 50% in the spectral transmittance curve of the infrared cut filter when the incident angle is 0 °, and the transmittance is 50 in the spectral transmittance curve of the infrared cut filter when the incident angle is 35 °. When the absolute value of the difference from the wavelength that becomes% is Δλ _T50% , Δλ _T50% <25 nm.
An antireflection layer for preventing the reflection of visible light is further provided on the infrared absorbing layer.
The antireflection layer is an infrared cut filter having a function of preventing the transmission of ultraviolet rays. In the spectral transmittance curve of the infrared cut filter when the incident angles are 0 °, 25 ° and 35 °, the wavelength at which the transmittance is 50% is λ _T50% nm, and the wavelength at which the transmittance is 2% is λ. The infrared cut filter according to claim 1, wherein _{when T2%} nm and the sharp cut characteristic is λ _SLOPE = | λ _T50% −λ _T2% |, λ _{SLOPE <70 nm.} Claim 1 or 2 is characterized in that the average spectral transmittance at a wavelength of 400 nm to 600 nm is 90% or more in the spectral transmittance curve of the infrared reflecting layer when the incident angles are 0 °, 25 ° and 35 °. Infrared cut filter described in. Spectral transmittance curve of the infrared absorption layer when the incident angle is 0 °, the (wavelength at which the transmittance is 2% in the spectral transmittance curve of lambda _RT2% the infrared reflective layer) Wavelength 600nm~λ _RT2% nm The infrared cut filter according to any one of claims 1 to 3, wherein the infrared cut filter is monotonically reduced within the range of. Infrared cut filter according to any one of claims 1 to 4, characterized in that said infrared reflective layer and the infrared-absorbing layer is formed so as to satisfy the _{-50nm ≦ λ AT50% -λ RT50%} ≦ -10nm. The infrared cut filter according to any one of claims 1 to 5, wherein the infrared reflecting layer is warped so that a surface facing the transparent dielectric substrate side surface becomes a convex surface. The infrared cut filter is used in an imaging device and is used.
The image pickup device includes a lens and an image pickup device.
The infrared cut filter according to any one of claims 1 to 6, wherein the infrared reflecting layer faces the lens in the imaging device. The infrared absorbing layer is formed of a sol for an infrared absorbing layer.
The sol for an infrared absorbing layer comprises a mixture of a trialkoxysilane having a phenyl group having a molar ratio of 50:50 to 80:20 and an alkoxysilane containing a tetraalkoxysilane and / or a hydrolyzate thereof. The infrared cut filter according to any one of claims 1 to 7, further comprising the infrared absorbing dye. The infrared cut filter according to claim 8, wherein the sol for an infrared absorbing layer contains an acid as a catalyst and an organic solvent having a boiling point of 100 ° C. to 160 ° C. The infrared cut filter according to claim 8 or 9, wherein the infrared absorbing layer sol contains 6 mol to 8 mol of water with respect to 1 mol of Si. The infrared absorbing dye according to claims 8 to 10, wherein the infrared absorbing dye contains one or more compounds selected from the group consisting of a cyanine-based compound, an azo-based compound, a diimmonium-based compound, a phthalocyanine-based compound, and a conjugated heterocyclic compound. The infrared cut filter described in either. A transparent dielectric substrate, an infrared reflecting layer that reflects infrared rays formed on one surface of the transparent dielectric substrate, and an infrared absorbing layer that absorbs infrared rays formed on the other surface of the transparent dielectric substrate. It is an infrared cut filter equipped with
The infrared reflective layer is formed of a dielectric multilayer film and is formed of a dielectric multilayer film.
The infrared absorbing layer contains an infrared absorbing dye that absorbs a part of infrared rays and silica.
In the spectral transmittance curve of the infrared cut filter when the incident angles are 0 °, 25 ° and 35 °, the average spectral transmittance at a wavelength of 400 nm to 600 nm is 75% or more.
In the spectral transmittance curves of the infrared reflecting layer and the infrared absorbing layer when the incident angle is 0 °, the wavelength at which the transmittance of the infrared reflecting layer becomes 50% is set to λ _{RT 50%} nm, and the transmission of the infrared absorbing layer is set. When the wavelength at which the rate becomes 50% is λ _AT 50% nm, the infrared reflective layer and the above are satisfied so as to satisfy 630 nm ≤ λ _{RT 50%} ≤ 690 nm, 630 nm ≤ λ _AT 50% ≤ 690 nm and λ _AT 50% <λ _{RT 50%.} An infrared absorbing layer is formed,
The wavelength at which the transmittance is 50% in the spectral transmittance curve of the infrared cut filter when the incident angle is 0 °, and the transmittance is 50 in the spectral transmittance curve of the infrared cut filter when the incident angle is 35 °. When the absolute value of the difference from the wavelength that becomes% is Δλ _T50% , Δλ _T50% <25 nm.
Wherein a thickness of the transparent dielectric substrate is 0.1 mm to 0.3 mm, an infrared cut filter, wherein the Thickness of the infrared-absorbing layer is 0.5μm or more 2.9μm or less.

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