JPWO2013042738A1 - Near-infrared cut filter - Google Patents

Abstract

Provided is a near-infrared cut filter in which the dependence on the incident angle is suppressed and the transmission band in the visible region and the stopbands in the ultraviolet region and the near-infrared region are extended. The near-infrared cut filter is provided on a transparent substrate and at least one main surface of the transparent substrate, and has a refractive index of 2.0 or more and a refractive index of 1.70 or less. And an optical multilayer film having a film. The optical multilayer film has a transmission band in which the average transmittance is 85% or more in the wavelength range of 400 to 700 nm and the average transmittance of 5% on each of the ultraviolet side and near infrared side in the spectral characteristics under normal incidence conditions. It has a stop band that becomes: The optical multilayer film has a transmission band forming part for forming the transmission band and a blocking band forming part for forming the stop band.

Description

  The present invention relates to a near-infrared cut filter, and more particularly to a near-infrared cut filter having an optical multilayer film on a transparent substrate.

The spectral sensitivity of solid-state image sensors such as CCDs and CMOSs used in digital cameras and video cameras has a higher sensitivity to near-infrared light compared to human visual sensitivity characteristics, so spectral correction by a near-infrared cut filter is possible. Necessary. Conventionally, as a near-infrared cut filter, for example, a near-infrared absorption type color glass filter such as fluorophosphate-based glass containing Cu ²⁺ ions as a coloring component has been used. In general, an optical multilayer film having a near-infrared cut characteristic is used in combination because it cannot cut light in the ultraviolet region sufficiently.

  In this case, for example, the half-value wavelength on the ultraviolet side of the transmission band that transmits visible light is determined by the optical multilayer film, and the half-value wavelength on the near infrared side is determined by the color glass filter. This is because the spectral waveform of the optical multilayer film tends to shift to the ultraviolet side as the incident angle increases, and the spectral glass waveform of the colored glass filter having a small incident angle dependency is used as much as possible, and cannot be cut with the colored glass filter. This is because it is reasonable to cut the wavelength region with an optical multilayer film.

  However, as the incident angle becomes wider due to the miniaturization of digital cameras and video cameras, the problem of angle dependency in the band targeted by the optical multilayer film becomes prominent. Specifically, among the transmission bands at 400 to 700 nm required by CCD and CMOS, the rising position of the transmittance from the ultraviolet side stop band to the transmission band formed by the optical multilayer film, and the near infrared side stop band The amount of light in the band that affects the image quality is changed by shifting the rising position of the transmittance from the transmission band to the transmission band.

  Conventionally, it is known that an optical multilayer film has an incident angle dependency in which a spectral waveform moves to the ultraviolet side when the incident angle increases. Incident angle dependence has been a major problem in the field of dichroic mirrors used for prisms and the like, and techniques for reducing the incident angle dependence have been proposed (see, for example, Patent Documents 1 to 3). ).

These make use of the fact that the film having the higher refractive index has less spectral angle dependence. The method disclosed in Patent Document 1 is generally used as an optical multilayer film, but eliminates the SiO ₂ film that increases the angle dependency due to the low refractive index, and eliminates the optical multilayer due to the small refractive index difference between the high refractive index films. A film is formed to suppress the incident angle dependency. The method disclosed in Patent Document 2 uses an Al ₂ O ₃ film having a slightly higher refractive index than a SiO ₂ film as a low refractive index film, and incident at a cut wavelength from the transmission band to the near-infrared stop band. In addition to suppressing the angle dependency, the decrease in the stop band associated with the decrease in the refractive index difference is complemented by a normal optical multilayer film having a cut wavelength on the longer wave side. In the method disclosed in Patent Document 3, the low refractive index film is replaced with an Al ₂ O ₃ film having a larger refractive index than the SiO ₂ film, and the ratio of the high refractive index film such as a TiO ₂ film in the optical film thickness ratio. By increasing the value, the angle dependency is more effectively reduced.

  The basic concept of these methods is to reduce the low refractive index depending on whether the ratio of the high refractive index film is increased or the refractive index of the low refractive index film is increased in the alternating multilayer film of the high refractive index film and the low refractive index film. Basically, the dependence on the incident angle by the rate film is suppressed.

  When the present inventor examined these techniques, it was found to be insufficient for use in a near-infrared cut filter. In the near-infrared cut filter, for example, in combination with a near-infrared absorption type colored glass filter, it has a very wide transmission band in the visible range, and wide stop bands on the ultraviolet side and near-infrared side of this transmission band. It is essential that the incident angle dependence of any of the two cut wavelengths at the rise of the transmittance on the ultraviolet side and the fall of the transmittance on the near infrared side is required.

  In the method of increasing the refractive index of the low refractive index film, if the refractive index is not extremely increased, the incident angle dependency is not sufficiently suppressed, and if the refractive index of the low refractive index film is excessively increased, the high refractive index film While the refractive index difference with the low refractive index film becomes too small and the transmission band becomes too wide, the transmittance of the stop band is not sufficiently low and becomes very narrow, particularly the stop band on the ultraviolet side is sufficiently large Not formed. By increasing the ratio of the high refractive index film in the optical film thickness ratio between the high refractive index film and the low refractive index film without increasing the refractive index of the low refractive index film, the stop band can be sufficiently expanded. The transmission band becomes narrower. In this way, all of the transmission band expansion that is indispensable as a near-infrared cut filter, the suppression of the incident angle dependence of the cut wavelength on the ultraviolet and near infrared sides, and the extension of the stop band on the ultraviolet and near infrared sides are all satisfied. Has not been obtained yet.

Japanese Unexamined Patent Publication No. 7-27907 Japanese Unexamined Patent Publication No. 11-202127 Japanese Unexamined Patent Publication No. 2008-20563

  The present invention has been made in view of the above problems, and an object thereof is to provide a near-infrared cut filter in which the incident angle dependency is suppressed and the transmission band and the ultraviolet and near-infrared stop bands are extended. To do.

  The near-infrared cut filter of the present invention is provided on a transparent substrate and at least one main surface of the transparent substrate, and has two or more kinds of films having a refractive index of 2.0 or more and a refractive index of 1.70. And an optical multilayer film having the following film.

The optical multilayer film has a transmission band having an average transmittance of 85% or more in a wavelength range of 400 to 700 nm in spectral characteristics under a normal incidence condition, and an average transmission on each of an ultraviolet side and a near infrared side of the transmission band. It has a stop band where the rate is 5% or less. The difference between the half-value wavelength on the ultraviolet side and the half-value wavelength on the near infrared side of the transmission band is 200 nm or more. Further, the difference in the half-value wavelength of the transmission band in the spectral characteristics between the normal incidence condition and the 30 ° incidence condition is less than 10 nm for the half-value wavelength on the ultraviolet side and less than 20 nm for the half-value wavelength on the near infrared side. The optical multilayer film is composed of a transmission band constituting part that constitutes a transmission band and a stop band constituting part that constitutes a stop band.
The term “to” indicating the numerical range described above is used to mean that the numerical values described before and after it are used as the lower limit value and the upper limit value, and unless otherwise specified, “to” is the same in the following specification. Used with meaning.

  The transparent substrate is preferably made of a material having absorption in the near infrared wavelength region, for example.

The first form of the transmission band component is a high refractive index film having a refractive index of 2.0 or more, a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film, And a low refractive index film having a refractive index of 1.70 or less. The total number of layers of the high refractive index film, medium refractive index film, and low refractive index film is 50 or more. Further, when the average optical film thickness of the high refractive index film is T _H , the average optical film thickness of the medium refractive index film is T _M , and the average optical film thickness of the low refractive index film is T _L , T _H / _TL is 2 or more and T _M / _TL is 2 or more.

  The medium refractive index film in the transmission band constituent part of the first embodiment is a film having the same refractive index as the high refractive index film in the transmission band constituent part, and the same refractive index as the low refractive index film in the transmission band constituent part. It can be an equivalent film composed of a film having a ratio.

The second form of the transmission band component is a high refractive index film having a refractive index of 2.0 or more and a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film. And a ripple adjusting portion having a low refractive index film having a refractive index of 1.7 or less on the main surface side portion opposite to the transparent substrate side. When the average optical film thickness of the high refractive index film is T _H and the average optical film thickness of the medium refractive index film is T _M , T _H / _TM is 1.2 or more or 0.7 or less. The total number of layers of the high refractive index film, the medium refractive index film, and the low refractive index film is 40 or more.

  The medium refractive index film in the transmission band constituent part of the second form is a film having the same refractive index as the high refractive index film in the transmission band constituent part and the same refractive index as the low refractive index film in the transmission band constituent part. It can be an equivalent film composed of a film having a ratio.

  The stopband component has a transmission band including the transmission band in the spectral characteristics of the optical multilayer film and the transmission band component in the spectral characteristics under normal incidence conditions, and the ultraviolet side in the spectral characteristics of the optical multilayer film and the transmission band component It is preferable to have a half-wavelength on the near infrared side that is 7 nm or more larger than a half-value wavelength on the near infrared side in the spectral characteristics of the optical multilayer film.

  The first form of the blocking band component has a repeating structure of a high refractive index film having a refractive index of 2 or more and a low refractive index film having a refractive index of 1.7 or less.

  The second form of the stopband constituent part has an ultraviolet side stopband constituent part for constituting the ultraviolet side stopband and a near infrared side stopband constituent part for constituting the near infrared side stopband. . The ultraviolet side blocking band constituent part has a repeating structure of a high refractive index film having a refractive index of 2 or more and a low refractive index film having a refractive index of 1.7 or less. The near-infrared-side stopband component includes a high refractive index film having a refractive index of 2.0 or higher, a middle refractive index film having a refractive index of 2.0 or higher and lower than the refractive index of the high refractive index film, and a refractive index. A low refractive index film having a refractive index of 1.70 or less is included. The total number of these high refractive index film, medium refractive index film, and low refractive index film is 30 or more.

  The medium refractive index film in the near-infrared-side stopband constituent part includes a film having the same refractive index as that of the high-refractive-index film in the near-infrared-side stopband constituent part and a low-refractive-index film in the near-infrared-side stopband constituent part. And an equivalent film composed of a film having the same refractive index.

The two or more kinds of films having a refractive index of 2.0 or more and constituting the optical multilayer film are made of, for example, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , or a composite oxide thereof. can do. Further, the film refractive index of 1.70 or less, for _example, may be made of SiO 2, MgF ₂ or the composite oxide thereof.

  The optical multilayer film is formed, for example, by vapor deposition or sputtering.

  According to the present invention, for example, by including an optical multilayer film having a specific transmission band component and a stop band component, the incident angle dependency is suppressed, and the transmission band in the visible region, the ultraviolet region, and the near red region are also included. A near-infrared cut filter with an extended outer band can be provided.

Sectional drawing which shows an example of the near-infrared cut off filter of this invention. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 1 at the time of using a transparent substrate as colorless and transparent glass. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 1 at the time of using a transparent substrate as near-infrared cut glass. The figure which shows the spectral transmittance | permeability of the transmission band structure part of Example 1. FIG. The figure which shows the spectral transmission factor of the stop zone structure part of Example 1. FIG. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 2 at the time of using a transparent substrate as colorless and transparent glass. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 2 at the time of using a transparent substrate as near-infrared cut glass. The figure which shows the spectral transmission factor of the transmission zone structure part of Example 2. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 3 at the time of using a transparent substrate as colorless and transparent glass. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 3 at the time of using a transparent substrate as a near-infrared cut glass. The figure which shows the spectral transmission factor of the transmission zone structure part of Example 3. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 4 at the time of using a transparent substrate as colorless and transparent glass. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 4 at the time of using a transparent substrate as a near-infrared cut glass. The figure which shows the spectral transmittance of the transmission band structure part of Example 4. The figure which shows the spectral transmission factor of the laminated film of Example 5. FIG. The figure which shows the spectral transmission factor of the laminated film of Example 6. The figure which shows the spectral transmission factor of the laminated film of Example 7 ( _TH : _TM : _TL = 1: 1: 4). The figure which shows the spectral transmission factor of the laminated film of Example 7 ( _TH : _TM : _TL = 1: 1: 2). The figure which shows the spectral transmission factor of the laminated film of Example 7 ( _TH : _TM : _TL = 2: 2: 2). The figure which shows the spectral transmittance | permeability of the laminated film of Example 7 ( _TH : _TM : _TL = 4: 4: 2). The figure which shows the spectral transmittance of the laminated film of Example 7 ( _TH : _TM : _TL = 8: 8: 2). The figure which shows the spectral transmission factor of the laminated film of Example 7 ( _TH : _TM : _TL = 8: 5: 2). The figure which shows the spectral transmission factor of the laminated film of Example 7 ( _TH : _TM : _TL = 8: 3: 2). The figure which shows the spectral transmittance | permeability of the laminated film of Example 7 ( _TH : _TM : _TL = 3: 8: 2). The figure which shows the spectral transmission factor of the laminated film (T _H : T _M = 1: 1) of Example 8. The figure which shows the spectral transmission factor of the laminated film of Example 8 ( _TH : _TM = 1.2: 1). The figure which shows the spectral transmittance of the laminated film (T _H : T _M = 2: 1) of Example 8. The figure which shows the spectral transmission factor of the laminated film of Example 8 ( _TH : _TM = 4: 1). The figure which shows the spectral transmission factor of the laminated film (T _H : T _M = 1: 1.5) of Example 8. The figure which shows the spectral transmission factor of the laminated film of Example 8 (T _H : T _M = 1: 1.3). The figure which shows the spectral transmission factor of the laminated film of Example 9. FIG. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 10 at the time of using a transparent substrate as colorless and transparent glass. The figure which shows the spectral transmission factor of the near-infrared cut off filter of Example 10 at the time of using a transparent substrate as a near-infrared cut glass. FIG. 10 is a graph showing the spectral transmittance of the laminated film of Example 11. The figure which shows the spectral transmission factor of the laminated film of Example 12. The figure which shows the spectral transmission factor of the laminated film of Example 13. The figure which shows the spectral transmission factor of the laminated film (T _H : T _L = 1: 1) of Example 14. The figure which shows the spectral transmission factor of the laminated film of Example 14 ( _TH : _TL = 4: 1). The figure which shows the spectral transmittance | permeability of the laminated film of Example 14 ( _TH : _TL = 8: 1). The figure which shows the spectral transmission factor of the laminated film of Example 14 (when T _H : T _L = 8: 1, the short wavelength side is aligned). Sectional drawing which shows an example of the imaging device to which the near-infrared cut off filter of this invention is applied.

Hereinafter, embodiments of the near-infrared cut filter of the present invention will be described.
FIG. 1 is a schematic cross-sectional view showing an embodiment of a near-infrared cut filter.

  The near-infrared cut filter 1 has, for example, a transparent substrate 2 and an optical multilayer film 3 on one main surface thereof. The optical multilayer film 3 may be provided on one main surface of the transparent substrate 2 as shown in FIG. 1 or may be provided separately on each main surface of the transparent substrate 2 although not shown. The optical multilayer film 3 includes at least two kinds of films having a refractive index of 2.0 or more and different refractive indices and a film having a refractive index of 1.70 or less. In addition, the refractive index in this invention means the refractive index with respect to the light of wavelength 550nm unless there is particular notice.

  The optical multilayer film 3 satisfies the following requirements in the spectral characteristics under normal incidence conditions. That is, it has a transmission band with an average transmittance of 85% or more in a wavelength range of 400 to 700 nm, and a blocking band with an average transmittance of 5% or less on each of the ultraviolet side and near infrared side of the transmission band. The difference between the half-value wavelength on the ultraviolet side and the half-value wavelength on the near infrared side of the transmission band is 200 nm or more. Further, the difference in the half-value wavelength of the transmission band in the spectral characteristics between the normal incidence condition and the 30 ° incidence condition is less than 10 nm for the half-value wavelength on the ultraviolet side and less than 20 nm for the half-value wavelength on the near infrared side.

  Note that the optical multilayer film 3 preferably further satisfies the following requirements in terms of spectral characteristics under normal incidence conditions. That is, the difference between the half-value wavelength on the ultraviolet side and the half-value wavelength on the near infrared side of the transmission band is preferably 300 nm or less. The half wavelength on the ultraviolet side is preferably in the range of 390 to 430 nm, and the half wavelength on the near infrared side is preferably in the range of 640 to 720 nm. Further, it is preferable that the wavelength band of the ultraviolet-side stop band is 30 nm or more, and the wavelength band of the near-infrared-side stop band is 250 nm or more.

  Here, the range of the transmission band, that is, the range for obtaining the average transmittance is determined from the wavelength (base point on the ultraviolet side) when the transmittance starts decreasing from the transmission band toward the stop band on the ultraviolet side. To the wavelength (the base point on the near infrared side) when the transmittance starts to decrease toward the stop band on the near infrared side.

  The range of the stop band, that is, the range for obtaining the average transmittance and width is as follows. That is, for the stopband on the ultraviolet side, the transmittance starts from the wavelength at which the transmittance starts from the stopband on the ultraviolet side toward the transmission band (base point on the transmission band side) toward the ultraviolet side. To the wavelength at which the rise starts when it reaches 40% (base point on the ultraviolet side). For the near-infrared stop band, the transmittance from the near-infrared stop band toward the near-infrared side from the wavelength at which the increase in transmittance starts from the near-infrared-side stop band toward the near-infrared side. Up to the wavelength (base point on the near infrared side) at which the rise when 40% is first reached starts.

  The optical multilayer film 3 satisfying such requirements is composed of, for example, a transmission band constituting part that constitutes a transmission band and a stop band constituting part that constitutes a stop band. For example, both of the transmission band component and the blocking band component constituting the optical multilayer film 3 may be provided on one main surface of the transparent substrate 2, or the transmission band configuration may be provided on one main surface of the transparent substrate 2. May be provided, and a blocking band component may be provided on the other main surface. In the case where the transmission band component and the blocking band component are provided on one main surface of the transparent substrate 2, the stacking order from the transparent substrate 2 is not particularly limited.

  In addition, the stop band constituent part can be divided into, for example, an ultraviolet side stop band constituent part and a near infrared side stop band constituent part, and these are all provided on one main surface side of the transparent substrate 2. Alternatively, it may be provided separately on both main surface sides of the transparent substrate 2. When all are provided on one main surface side of the transparent substrate 2, for example, they are provided so as to sandwich the transmission band constituting part. Moreover, when providing separately on both the main surface sides of the transparent substrate 2, any may be provided on any main surface side, and the transparent substrate 2 is provided on the same main surface side as the transmission band component. With respect to the above, there is no particular limitation on the stacking order with the transmission band constituting portion.

(Transparent substrate)
The transparent substrate 2 is not particularly limited as long as it is a material that can transmit at least light in the visible wavelength range. For example, glass, crystal, crystal such as lithium niobate, sapphire, polyethylene terephthalate (PET), polybutylene terephthalate (PBT) Polyester resin such as polyethylene, polypropylene, ethylene vinyl acetate copolymer, etc., acrylic resin such as norbornene resin, polyacrylate, polymethyl methacrylate, urethane resin, vinyl chloride resin, fluorine resin, polycarbonate resin, polyvinyl butyral resin And polyvinyl alcohol resin.

  The transparent substrate 2 is preferably made of a material having absorption in the near infrared wavelength region. By using the transparent substrate 2 having absorption in such a near-infrared wavelength region, it can be made close to human visibility characteristics. The optical multilayer film 3 has an incident angle dependency suppressed and a transmission band expanded, and the characteristics of the transparent substrate 2 having absorption in the near-infrared wavelength region by the expanded transmission band can be obtained. It can be exhibited effectively. That is, in order to effectively exhibit the characteristics of the transparent substrate 2 having absorption in the near-infrared wavelength region, the optical multilayer film 3 has an ultraviolet-side half-value wavelength in the range of 390 to 430 nm, preferably 400 to 420 nm. It is in the range, and the half-value wavelength on the near infrared side is required to be in the range of 640 to 720 nm, preferably in the range of 670 to 710 nm. A conventional optical multilayer film in which high refractive index films and low refractive index films are alternately laminated does not necessarily have a sufficient transmission band width, and it is difficult to obtain such a half-value wavelength. Since a wide transmission band can be formed, such a half-value wavelength can be obtained.

  Examples of the transparent substrate 2 having absorption in the near-infrared wavelength region include near-infrared absorbing glass in which CuO or the like is added to fluorophosphate-based glass or phosphate-based glass. Moreover, what added the absorber which absorbs near infrared rays in the resin material is mentioned. Examples of the absorbent include dyes, pigments, and metal complex compounds, and specifically include phthalocyanine compounds, naphthalocyanine compounds, and dithiol metal complex compounds.

(Transmission band component)
The transmission band forming part forms a transmission band in the spectral characteristics of the optical multilayer film 3, that is, a visible band. Specifically, the transmission band constituent part forms a transmission band in the spectral characteristic of the optical multilayer film 3 by forming a transmission band narrower than the transmission band in the spectral characteristic of the blocking band constituent part. Since the transmission band constituting part suppresses the incident angle dependency and the width (wavelength) of the transmission band is wide, it can suppress the incident angle dependency of the optical multilayer film 3 and can widen the transmission band. Examples of the transmission band component include a first form and a second form as described below.

(Transmission zone component of the first form)
The transmission band constituting part of the first form is a high refractive index film having a refractive index of 2.0 or more, a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film, And a low refractive index film having a refractive index of 1.70 or less. The total number of layers of the high refractive index film, medium refractive index film, and low refractive index film is 50 or more. Further, when the average optical film thickness of the high refractive index film is T _H , the average optical film thickness of the medium refractive index film is T _M , and the average optical film thickness of the low refractive index film is T _L , T _H / _TL is 2 or more and T _M / T _L is 2 or more.

  Here, the optical film thickness is obtained as nd [nm] when the refractive index of the film is n and the physical film thickness is d [nm]. The average optical film thickness is calculated by calculating the optical film thickness nd [nm] for all films of the same type, for example, a high refractive index film, and then adding the total optical film thickness nd [nm] to the layer of the film. It is calculated by dividing by a number.

As the optical multilayer film, a TiO ₂ film that is a high refractive index film and a SiO ₂ film that is a low refractive index film are alternately laminated, and the ratio of the average optical film thickness of the TiO ₂ film in the ratio of these average optical film thicknesses is increased. By doing so, it is possible to suppress the incident angle dependency and to form a sufficiently wide stop band. However, such a thing does not necessarily have a sufficient width of the transmission band, and a transmission band width required for a near-infrared cut filter used for a solid-state imaging device such as a CCD or a CMOS cannot be secured.

According to the transmission band constituting part of the first form, it is composed of a high refractive index film, a medium refractive index film, and a low refractive index film, the total number of layers is 50 or more, and the average optical film thickness is By setting the ratio T _H / T _L to 2 or more and T _M / T _L to 2 or more, a transmission band having a small incident angle dependency and a sufficient width can be formed.

  The number of layers of the transmission band constituting part is not particularly limited as long as it is 50 layers or more, but in order to reduce the influence on the spectral waveform on the color glass side particularly when considering the combined use with a transparent substrate having absorption in the near infrared. In addition, it is better that the rise from the stop band to the transmission band is steep, and from this viewpoint, 60 or more is preferable, and 70 or more is more preferable. Although the upper limit of the number of layers is not particularly limited, generally 150 or less is preferable and 100 or less is more preferable because productivity decreases when the number of layers increases.

The ratios T _H / T _L and T _M / T _L of the average optical film thickness are not particularly limited as long as they are 2 or more, respectively, but a transmission band having a smaller incident angle dependency and a sufficient width is formed. From the viewpoint, T _H / T _L is preferably 2.3 or more, more preferably 2.5 or more, and T _M / T _L is preferably 2.3 or more, more preferably 2.5 or more.

_{Incidentally,} T _H / T _L, but are not necessarily limited on the upper limit value of T M / _{T L,} both preferably 10 or less, 5 or less is more preferable. For example, when T _H / T _L or T _M / T _L is increased, the optical film thickness of the low refractive index film is relatively decreased. However, for a film having a low refractive index such as a low refractive index film, the optical film thickness is reduced. When becomes smaller, it becomes difficult to control the film thickness during film formation. By making T _H / T _L and T _M / T _L preferably 10 or less, more preferably 5 or less, it is possible to achieve excellent productivity.

In view is not particularly limited for T H _/ T _M, it is possible to adjust the size of Murasakisotogawa inhibition zone by varying this ratio, to reduce the incident angle dependence, 1 From the viewpoint of widening the transmission band, it is preferably 3 or less, more preferably 2.5 or less.

The high refractive index film, the medium refractive index film, and the low refractive index film have the following basic units, for example, where H is the high refractive index film, M is the medium refractive index film, and L is the low refractive index film. The layers are laminated so as to have a repeating structure.
Basic unit: [HML]
Basic unit: [LMMHML]

  The transmission band constituting portion does not necessarily have a repeating structure of the basic unit strictly described above. For example, in the case of a film having a low refractive index such as a low refractive index film, it becomes difficult to control the film thickness at the time of film formation if the optical film thickness becomes small. For example, some of the plurality of low refractive index films are omitted. Thus, there may be a portion where a large number of high refractive index films and medium refractive index films are continuous. Since the repeating structure of the basic unit [LMMHML] has a symmetrical shape, a wide transmission band is obtained, which is preferable. On the other hand, the repeating structure of the basic unit [HML] does not necessarily provide a wide transmission band, but is preferable because the degree of freedom of the average optical film thickness of each film is relatively high.

  Note that the repeating structure of the basic unit [LMHMML] can be expressed as [2LMHM] or [LMHM] by considering two L as one L because two L of adjacent basic units are continuous. The average optical film thickness in the invention is calculated based on the final state of the film formed to the last, and a continuous film made of the same material is regarded as one film to determine the physical film thickness and the number of layers. These are used to determine the average optical film thickness.

The high refractive index film and the medium refractive index film are not particularly limited as long as they are made of a material having a refractive index of 2.0 or more. For example, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , or these Preferred are those composed of the above complex oxide. The high refractive index film preferably has a refractive index of 2.3 or higher, and more preferably has a refractive index of 2.4 or higher. As such, the ones made of TiO ₂ (refractive index 2.45), and the like. The medium refractive index film is not particularly limited as long as it is less than the refractive index of the high refractive index film, but preferably has a refractive index of 2 or more and less than 2.3, and more preferably has a refractive index of 2.2 or less. preferable. Such examples include are preferably exemplified those composed of _Ta 2 _{O 5} (refractive index 2.13).

The low refractive index film is not particularly limited as long as it is made of a material having a refractive index of 1.7 or less. For example, a film made of SiO ₂ , MgF ₂ , or a composite oxide thereof is preferably exemplified. .

Since the transmission band component has a large number of layers and a large total film thickness, TiO ₂ and Ta ₂ O as described above are used for various reasons such as the availability of film materials, spectral characteristics, weather resistance, and strength. ₅ , SiO ₂ , MgF _{2 and the} like are preferably used.

  The medium refractive index film in the transmission band component is not necessarily limited to a single film. For example, a film having the same refractive index as that of the high refractive index film and a refractive index identical to that of the low refractive index film are used. It is good also as an equivalent film | membrane comprised from a film | membrane. The equivalent film is preferable because, for example, even when there are two types of film that can be formed in the film forming apparatus, a medium refractive index film can be formed substantially.

  When an equivalent film is used, the number of low refractive index films increases. However, the amount of increase is small, and the number of high refractive index films also increases. Therefore, the incident angle dependency does not substantially increase. When an equivalent film is used, the number of layers increases and the number of layers is so thin that the physical film thickness is 10 nm or less. It is preferable to use it only in a limited case such as when there are two types of film that can be formed in the apparatus.

There are two types of medium refractive index films: those made of LHL and those made of HLH, where H is the high refractive index film and L is the low refractive index film. However, in either case, when the film having the refractive index n _M and the physical film thickness d _M is replaced in the order of the refractive index n _H n _L n _H , the physical film thickness is as follows.
d _H = d _M * q _H
d _L = d _M * q _L

q _H and q _L are coefficients of each film thickness with respect to QWOT (quarter wave optical thickness), and are coefficients calculated from the refractive indexes of the constituent materials of each film, and are constant unless the refractive index is changed. Since the refractive index has wavelength dependency, a representative wavelength is selected, and for example, a Ta ₂ O ₅ film that is a medium refractive index film is formed by a TiO ₂ film and a SiO ₂ film.

When the refractive index of Ta ₂ O ₅ is 2.150331 (wavelength 500 nm), the refractive index of TiO ₂ is 2.50232 (wavelength 500 nm), and the refractive index of SiO ₂ is 1.48155 (wavelength 500 nm), Ta ₂ O ₅ film TiO ₂ film used instead of the ratio of the SiO ₂ film, when one physical thickness of _{the Ta} 2 _{O 5 film, d L: d H: d} L = 0.2348: 0.48876: 0 2348, or d _H : d _L : d _H = 0.39853: 0.1794: 0.39853.

(Transmission band component of the second form)
The transmission band constituting part of the second form includes a high refractive index film having a refractive index of 2.0 or more, a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film, And a ripple adjusting portion having a low refractive index film having a refractive index of 1.7 or less on the main surface side portion opposite to the transparent substrate 2 side. When the average optical film thickness of the high refractive index film is T _H and the average optical film thickness of the medium refractive index film is T _M , T _H / _TM is 1.2 or more or 0.7 or less. The total number of layers of the high refractive index film, the medium refractive index film, and the low refractive index film is 40 or more.

Also in the case of alternately laminating high refractive index films and medium refractive index films, a transmission band having a small incident angle dependency and a sufficient width can be formed. In this case, when the number of the high refractive index film and the middle refractive index film is about 40 layers, the width of the stop band on the near infrared side is sufficient, but T _H / T _M = 1.00 which is a general configuration. On the other hand, the width of the stop band on the ultraviolet side becomes very narrow. If the stop band disappears completely, it is conceivable to use a UV cut filter that is a long pass filter. However, since the stop band on the ultraviolet side is very small, it exists as a stop band. Adjustment method is necessary.

T _H / _T than typical configuration the ratio of _M by shifting about 20%, i.e. _T H / _{T M} 1.2 or more, or by 0.7 or less, the sufficient width to purple outer A stop band can be formed, and the width of the stop band can be adjusted by changing this ratio. As a result, in a structure based on a repetitive structure of a high refractive index film and a medium refractive index film, a blocking band having a sufficient width while forming a transmission band having a small incident angle dependency and a sufficient width. Can be secured. According to the transmission band constituting part of the second embodiment, the repetitive structure is constituted by the high refractive index film and the medium refractive index film, and the repetitive structure basically includes no low refractive index film. The incident angle dependency is easily suppressed as compared with the transmission band constituting portion of the first embodiment. Further, by setting T _H / _TM to 1.2 or more, the ultraviolet-side stop band can be made very clear.

  The number of layers in the transmission band constituting part is not particularly limited as long as it is 40 or more, but is preferably 45 or more, and more preferably 50 or more, from the viewpoint of sufficient width of the blocking band on the ultraviolet side and near infrared side. The upper limit of the number of layers is not particularly limited, but generally, when the number of layers is increased, productivity, spectroscopy, and appearance quality are deteriorated, so 150 or less is preferable, and 100 or less is more preferable.

The average optical film thickness ratio T _H / T _M is not particularly limited as long as it is 1.2 or more, or 0.7 or less, but T _H / T _M that is 1.2 or more is blocked on the ultraviolet side. From the viewpoint of increasing the width of the band, 1.5 or more is preferable, and 2 or more is more preferable. In addition, the upper limit is not necessarily limited, but as it becomes larger, the width of the near-infrared side stop band becomes narrower, and it is necessary to increase the number of layers in order to widen the width of the near-infrared side stop band, 5 or less is preferable and 4 or less is more preferable. On the other hand, for T _H / T _M of 0.7 or less, when T _H / T _M becomes smaller, the width of the stop band on the ultraviolet side becomes wider, but the width of the stop band on the near infrared side becomes narrower. Since it is necessary to increase the number of layers in order to widen the width of the stop band on the near infrared side, 0.3 or more is preferable.

As a high refractive index film and a medium refractive index film, a predetermined effect can be obtained if the refractive index difference is 0.1 or more. However, if the refractive index difference is small, the number of layers must be increased and the productivity is increased. The refractive index difference is preferably 0.2 or more, more preferably 0.3 or more. The high-refractive index film and the medium-refractive index film are not particularly limited as long as the combination has a predetermined refractive index difference. For example, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , or a composite oxide thereof can be used. The thing which becomes is mentioned suitably. The high refractive index film preferably has a refractive index of 2.3 or higher, and more preferably has a refractive index of 2.4 or higher. As such, the ones made of TiO ₂ (refractive index 2.45), and the like. The medium refractive index film is not particularly limited as long as it is less than the refractive index of the high refractive index film, but preferably has a refractive index of 2 or more and less than 2.3, and more preferably has a refractive index of 2.2 or less. preferable. Such examples include are preferably exemplified those composed of _Ta 2 _{O 5} (refractive index 2.13).

  In addition, since the generation of ripples cannot be sufficiently suppressed in the repeated structure of the high refractive index film and the medium refractive index film, the refractive index is 1.7 or less at the main surface side portion opposite to the transparent substrate 2 side. A ripple adjusting unit having a low refractive index film is provided. The ripple adjusting portion has at least one low refractive index film, and is provided on the final layer side (the main surface side opposite to the transparent substrate 2 side, hereinafter also referred to as the outside) of the transmission band constituting portion. It may be a single low refractive index film, a single low refractive index film, a high refractive index film or a medium refractive index film provided on the outside thereof, or these high refractive index film and medium refractive index film, 2 to 9 layers comprising This repetitive structure can have other low refractive index films. The number of layers including the ripple adjusting unit may be 40 or more in the transmission band constituting unit.

  For the purpose of further suppressing the occurrence of ripples, a low refractive index film having a refractive index of 1.7 or less may be provided on the transparent substrate 2 side in the transmission band constituting part. It is preferable that 1 to 9 layers of the low refractive index film for suppressing the generation of the ripples are formed in total including the low refractive index film in the ripple adjusting portion described above.

The low refractive index film is not particularly limited as long as it is made of a material having a refractive index of 1.7 or less. For example, a film made of SiO ₂ , MgF ₂ , or a composite oxide thereof is preferably exemplified.

  The medium refractive index film in the transmission band component is not necessarily limited to a single film. For example, a film having the same refractive index as that of the high refractive index film and a refractive index identical to that of the low refractive index film are used. It is good also as an equivalent film | membrane comprised from a film | membrane. The equivalent film is preferable because, for example, a medium refractive index film can be formed even when there are two types of film that can be formed in the film forming apparatus.

(Stop band component)
The stop band forming part forms a stop band in the spectral characteristics of the optical multilayer film 3, specifically, a stop band on the ultraviolet side and near infrared side. That is, the above-described transmission band constituting part mainly forms the transmission band in the spectral characteristics of the optical multilayer film 3 and the cut-off bands on both sides thereof, and cannot always form a sufficiently wide stop band. The width of the stop band is expanded by the component.

  For example, in the spectral characteristics under the normal incidence condition, the stop band constituting section has a transmission band including the transmission band in the spectral characteristics of the optical multilayer film 3. The stopband component has a half-wavelength on the ultraviolet side that is equal to or less than the half-value wavelength on the ultraviolet side in the spectral characteristics of the optical multilayer film 3 and the transmission band component, and the spectral characteristics of the optical multilayer film and the transmission band component The near-infrared-side half-value wavelength is 7 nm or more larger than the near-infrared-side half-value wavelength.

  By adopting such a configuration, even if the incident angle changes, it is possible to obtain a transmission band including the transmission band formed by the transmission band component, and as a result, the incident angle dependency is improved. In addition to being suppressed, the optical multilayer film 3 in which the transmission band in the visible region and the stopbands in the ultraviolet region and the near infrared region are expanded can be obtained.

  That is, when the incident angle changes, the near-infrared-side half-value wavelength formed by the stopband component is greatly shifted compared to the near-infrared-side half-value wavelength formed by the optical multilayer film 3 or the transmission band component. It's easy to do. In the spectral characteristics under normal incidence conditions, the near-infrared half-value wavelength formed by the stopband component is made 7 nm or more larger than the near-infrared half-value wavelength formed by the optical multilayer film 3 or the transmission band component. Thus, even when the incident angle changes, the near-infrared half-value wavelength formed by the stopband component does not overlap with the near-infrared half-value wavelength formed by the optical multilayer film 3 or the transmission band component. Can be. A preferable upper limit is 50 nm or less, and a more preferable lower limit is 14 nm or more.

  On the other hand, since the half-value wavelength on the ultraviolet side formed by the stopband component does not necessarily change significantly compared to the half-value wavelength on the ultraviolet side formed by the optical multilayer film 3 or the transmission band component, If the spectral characteristics are equal to or less than the half-value wavelength on the ultraviolet side formed by these, even when the incident angle is changed, the half-value wavelength on the ultraviolet side formed by these can be prevented from overlapping.

  Examples of such a blocking band component include a first form and a second form as described below. Note that the form of the blocking band constituent part can be any form regardless of the form of the transmission band constituent part.

(First stop band component)
The stopband constituent part of the first form has a repeating structure of a high refractive index film having a refractive index of 2 or more and a low refractive index film having a refractive index of 1.7 or less. Further, when the average optical film thickness of the high refractive index film is T _H and the average optical film thickness of the low refractive index film is T _L , it is preferable that T _H / _TL is less than 2.

With such a configuration, it is possible to form a transmission band in the spectral characteristics of the optical multilayer film 3, that is, a transmission band including a transmission band in the spectral characteristics of the transmission band constituent part, and the optical multilayer film 3 and the transmission band constituent part. The half-value wavelength on the near infrared side of the spectral characteristics of the optical multilayer film 3 and the transmission band constituting part can be formed at least 7 nm larger than the half-value wavelength on the near infrared side. Wavelength can be formed. That is, when T _H / _TL is 2 or more, the incident angle dependency is easily suppressed, but the transmission band is narrowed. By making T _H / T _L less than 2, the incident angle dependency cannot necessarily be suppressed, but a wide transmission band including the transmission band in the spectral characteristics of the optical multilayer film 3 and the transmission band component can be formed.

  From the viewpoint of obtaining a sufficiently wide transmission band and stop band, and a predetermined half-value wavelength, the number of layers of the stop band constituting part is preferably 20 or more, and more preferably 25 or more. Although the upper limit of the number of layers is not particularly limited, generally 150 or less is preferable and 100 or less is more preferable because productivity decreases when the number of layers increases.

The average optical film thickness ratio T _H / T _L is not particularly limited as long as it is less than 2, but considering the obtaining of a sufficiently wide transmission band and stop band, particularly a wide stop band, when designing the stop band It is preferable to use a general film design method in which the T _H / _TL ratio is about 1 with respect to the design center wavelength. As described above, this is obvious when the increase in T _H / _TL for the purpose of suppressing the dependency on the incident angle causes a decrease in the stop band.

The high refractive index film is not particularly limited as long as it is made of a material having a refractive index of 2.0 or more. For example, it is made of TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , or a composite oxide thereof. The thing which becomes is mentioned suitably. The high refractive index film preferably has a refractive index of 2.3 or higher, and more preferably has a refractive index of 2.4 or higher. As such, the ones made of TiO ₂ (refractive index 2.45), and the like.

The low refractive index film is not particularly limited as long as it is made of a material having a refractive index of 1.7 or less. For example, a film made of SiO ₂ , MgF ₂ , or a composite oxide thereof is preferably exemplified. .

(Second stop band component)
The stopband component of the second embodiment has an ultraviolet stopband component for configuring the ultraviolet stopband and a near infrared stopband component for configuring the near infrared stopband. . The ultraviolet side blocking band constituent part has a repeating structure of a high refractive index film having a refractive index of 2 or more and a low refractive index film having a refractive index of 1.7 or less. The near-infrared-side stopband component includes a high refractive index film having a refractive index of 2.0 or more, a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film, and A low refractive index film having a refractive index of 1.70 or less is included, and the total number of layers of the high refractive index film, the middle refractive index film, and the low refractive index film is 30 or more.

  The transmission band in the spectral characteristic of the optical multilayer film 3, that is, the transmission band including the transmission band in the spectral characteristic of the transmission band component can also be formed in the blocking band constituent part of the second embodiment. The half-value wavelength on the near infrared side, which is 7 nm or more larger than the half-value wavelength on the near-infrared side in the spectral characteristics of the optical multilayer film 3 and the transmission-band composition part. Can be formed.

  In general, the spectral characteristics of the optical multilayer film are preferably such that the near-infrared-side stop band is wide, and the occurrence of ripples in the transmission band when the incident angle increases is small. All of the above-described transmission band components can suppress the occurrence of ripples to some extent because they use a technology that suppresses the incident angle dependence, but ripples still occur in the blocking band components that do not include this technology. Such a ripple cannot always be sufficiently suppressed in the first embodiment of the stopband constituting portion. According to the stopband constituent part of the second embodiment, it is possible to suppress the generation of ripples while sufficiently expanding the width of the transmission band and the stopband.

  As described above, the ultraviolet-side stopband constituent part has a repeating structure of a high refractive index film having a refractive index of 2 or more and a low refractive index film having a refractive index of 1.7 or less.

  From the viewpoint of forming a sufficiently wide ultraviolet-side stop band, the number of layers of the ultraviolet-side stop band constituting part is preferably 15 or more, and more preferably 20 or more. Although the upper limit of the number of layers is not particularly limited, generally 60 or less is preferable and 40 or less is more preferable because productivity decreases when the number of layers increases.

The high refractive index film is not particularly limited as long as it is made of a material having a refractive index of 2.0 or more. For example, it is made of TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , or a composite oxide thereof. The thing which becomes is mentioned suitably. The high refractive index film preferably has a refractive index of 2.3 or higher, and more preferably has a refractive index of 2.4 or higher. As such, the ones made of TiO ₂ (refractive index 2.45), and the like.

The low refractive index film is not particularly limited as long as it is made of a material having a refractive index of 1.7 or less. For example, a film made of SiO ₂ , MgF ₂ , or a composite oxide thereof is preferably exemplified. .

  The near-infrared-side stopband component includes a high refractive index film having a refractive index of 2.0 or higher, a middle refractive index film having a refractive index of 2.0 or higher and lower than the refractive index of the high refractive index film, and a refractive index. A low refractive index film having a refractive index of 1.70 or less is included. The total number of these high refractive index film, medium refractive index film, and low refractive index film is 30 or more.

  The number of layers of the near-infrared-side stopband constituent part is not particularly limited as long as it is 30 or more, but is preferably 40 or more, more preferably 60 or more from the viewpoint of forming a near-infrared-side stopband having a more sufficient width. . Although the upper limit of the number of layers is not particularly limited, generally 150 or less is preferable and 100 or less is more preferable because productivity decreases when the number of layers increases.

The high refractive index film, the medium refractive index film, and the low refractive index film have the following basic units, for example, where H is the high refractive index film, M is the medium refractive index film, and L is the low refractive index film. The layers are laminated so as to have a repeating structure.
Basic unit: [HML]
Basic unit: [LMMHML]

When the above repeating structure is used, the average optical film thickness T _H , the average optical film thickness T _M , and the average optical film thickness T _L are obtained from the viewpoint of obtaining a sufficiently wide stop band. , T _H : T _M : T _L = 1: 1: 1 and around, and the portion having LMHML as a basic unit is a general membrane design with T _H : T _M : T _L = 1: 1: 2 around It is good that the ratio is about. The latter _TL ratio is 2 because the repetition of LMHML overlaps with LL, so the ratio is 2 in the final film design, and the basic idea is T _H : T _It is not different from _M : T _L = 1: 1: 1. Details will be described later. Here, the general ratio is adopted because the blocking band is increased when the ratio of T _{H and} T _M is increased in the incident angle dependency reducing method described in the explanation of the transmission band constituting section of the first embodiment. Since it becomes narrower, it is based on the idea that the optical film thickness ratio is not greatly changed.

  In addition, it is preferable that the stopband forming unit use a general method for extending the stopband by applying two or more design wavelengths to the above-described repetitive structure. In this case, the ratio is set for each designed center wavelength.

  The near-infrared-side stopband component cuts a wide range of near-infrared regions, but it is preferable that the near-infrared cut filter for CCD and CMOS can be cut to a longer wavelength side. Preferably it is 900 nm or more, More preferably, it is 1100 nm or more, More preferably, it is preferable that 1150 nm or more can be cut. When the above method is used, it is possible to suppress the generation of ripples when the incident angle increases while extending the stop band to the longer wave side.

  Note that the near-infrared-side stopband component does not necessarily have a strictly repeating basic unit. For example, in the case of a film having a low refractive index such as a low refractive index film, it becomes difficult to control the film thickness at the time of film formation if the optical film thickness becomes small. For example, some of the plurality of low refractive index films are omitted. Thus, there may be a portion where a large number of high refractive index films and medium refractive index films are continuous.

  In addition, the repeating structure of the basic unit [LMHMML] can be expressed as [2LMHM] because two L's of adjacent basic units are continuous, or two L's are regarded as one L. The average optical film thickness in the invention is calculated based on the final state of the film formed to the last, and a continuous film made of the same material is regarded as one film to determine the physical film thickness and the number of layers. These are used to determine the average optical film thickness.

The high refractive index film and the medium refractive index film are not particularly limited as long as they are made of a material having a refractive index of 2.0 or more. For example, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , or these Preferred are those composed of the above complex oxide. The high refractive index film preferably has a refractive index of 2.3 or higher, and more preferably has a refractive index of 2.4 or higher. As such, the ones made of TiO ₂ (refractive index 2.45), and the like. The medium refractive index film is not particularly limited as long as it is less than the refractive index of the high refractive index film, but preferably has a refractive index of 2 or more and less than 2.3, and more preferably has a refractive index of 2.2 or less. preferable. Such examples include are preferably exemplified those composed of _Ta 2 _{O 5} (refractive index 2.13).

The low refractive index film is not particularly limited as long as it is made of a material having a refractive index of 1.7 or less. For example, a film made of SiO ₂ , MgF ₂ , or a composite oxide thereof is preferably exemplified. .

  The middle refractive index film in the near-infrared-side stopband constituent part is not necessarily limited to a single film. For example, a film having the same refractive index as that of the high refractive index film and the same refractive index as that of the low refractive index film are used. It is good also as an equivalent film | membrane comprised from the film | membrane which has a rate. The equivalent film is preferable because, for example, a medium refractive index film can be formed even when there are two types of film that can be formed in the film forming apparatus.

  The optical multilayer film 3, that is, the transmission band component and the stop band component can be formed by sputtering, vacuum deposition, ion beam, ion plating, or CVD, particularly by sputtering or vacuum deposition. It is preferable to form. The transmission band is a wavelength band used for light reception by a solid-state imaging device such as a CCD or CMOS, and its position accuracy is important. By forming by a sputtering method or a vacuum evaporation method, a wavelength shift can be suppressed and position accuracy can be improved.

  The near-infrared cut filter 1 is used, for example, as a visibility correction filter in an imaging device such as a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, a web camera, or an automatic exposure meter. In an imaging apparatus such as a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, or a web camera, for example, it is disposed between an imaging lens and a solid-state imaging device. In the automatic exposure meter, for example, it is arranged in front of the light receiving element.

  In the imaging apparatus, the near-infrared cut filter 1 may be disposed at a position away from the front surface of the solid-state image sensor, or may be directly attached to the solid-state image sensor or the package of the solid-state image sensor. The near infrared cut filter 1 may be a cover that protects the light. Further, it may be directly attached to a low-pass filter using a crystal such as quartz or lithium niobate for reducing moire and false color.

  FIG. 41 is a cross-sectional view schematically illustrating an embodiment of an imaging apparatus having a solid-state imaging device. The imaging device 50 includes, for example, a solid-state imaging device 51, a cover glass 52, a lens group 53, a diaphragm 54, and a housing 55 that fixes them.

  The lens group 53 is disposed on the imaging surface side of the solid-state imaging device 51, and includes, for example, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. The stop 54 is disposed between the third lens L3 and the fourth lens L4. The cover glass 52 is disposed on the lens group 53 side of the solid-state image sensor 51 and protects the solid-state image sensor 51 from the external environment. The solid-state imaging device 51 is an electronic component that converts light that has passed through the lens group 53 into an electrical signal, and is, for example, a CCD or a CMOS. The solid-state image sensor 51, the cover glass 52, the lens group 53, and the stop 54 are disposed along the optical axis x.

  In the imaging device 50, light incident from the subject side passes through the first lens L 1, the second lens L 2, the third lens L 3, the diaphragm 54, the fourth lens L 4, and the cover glass 52, and the solid-state imaging device. 51 is incident. The solid-state image sensor 51 converts the incident light into an electric signal and outputs it as an image signal.

  The near-infrared cut filter 1 is used as, for example, a cover glass 52 and a lens group 53, that is, a first lens L1, a second lens L2, a third lens L3, or a fourth lens L4. In other words, the optical multilayer film 3 of the near-infrared cut filter 1 is provided on the surface of the transparent substrate 2 using the cover glass or lens group of a conventional imaging device as the transparent substrate 2. By applying the near-infrared cut filter 1 to the cover glass 52 and the lens group 53 of the imaging device 50, the transmission band in the visible region and the stopband in the ultraviolet region and the near-infrared region can be expanded while suppressing the incident angle dependency. , The characteristics can be improved.

Hereinafter, more specific description will be given with reference to examples.
Examples 1 to 4 are examples of the near-infrared cut filter of the present invention. In Examples 5 to 14, the spectral transmittance at each incident angle was obtained by optical simulation for the laminated film having each configuration.

(Example 1)
The near-infrared cut filter has a transmission band constituent part that becomes a part of the optical multilayer film on one main surface of the transparent substrate, and a blocking band constituent part that becomes a part of the optical multilayer film on the other main surface It was. Here, the transparent substrate is colorless and transparent glass (product name: D263, thickness: 0.3 mm) or near infrared cut glass (product name: NF-50T, thickness: 0.26 mm) manufactured by Asahi Glass Co., Ltd. It was.

The transmission band constituting part was the first form of the transmission band constituting part having the structure shown in Table 1. The number of layers in the table is the number of layers from the transparent substrate side. Here, the transmission band component is H for a TiO ₂ film that is a high refractive index film, M for a Ta ₂ O ₅ film that is a medium refractive index film, and L for a SiO ₂ film that is a low refractive index film. and those composed of the basic unit of essentially [LMHML], 84 layers the number of layers, the average optical thickness _{T H} of the TiO ₂ film 119.1Nm, average optical thickness of _{the Ta} 2 _{O 5} film _{T M} Is 138.7 nm, the average optical film thickness T _L of the SiO ₂ film is 45.3 nm, T _H / T _L = 2.6, and T _M / T _L = 3.1.

The blocking band constituting section is a second form of the blocking band constituting section having a configuration as shown in Table 2. Here, as for a stopband structure part, 1-22 layers are ultraviolet side stopband structure parts, and 23-93 layers are near-infrared side stopband structure parts. The ultraviolet-side stopband constituent part is basically composed of a basic unit of [HL], where H is a TiO ₂ film that is a high refractive index film and L is an SiO ₂ film that is a low refractive index film. Yes, the number of layers is 22, the average optical thickness T _H of the TiO ₂ film is 55.4 nm, the average optical thickness T _L of the SiO ₂ film is 117.0 nm, and T _H / T _L = 0.47 It is.

The near-infrared-side stopband component is basically formed when H is a TiO ₂ film that is a high refractive index film, M is a Ta ₂ O ₅ film that is a medium refractive index film, and L is a SiO ₂ film that is a low refractive index film. In particular, it is composed of [LMMHML] basic units, the number of layers is 70, the average optical film thickness T _H of the TiO ₂ film is 119.5 nm, and the average optical film thickness T _M of the Ta ₂ O ₅ film is 95.4 nm, the average optical film thickness T _L of the SiO ₂ film is 224.2 nm, T _H / T _L = 0.5, and T _M / T _L = 0.4.

  For this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 ° and the spectral transmittance when the incident angle θ was 30 ° were determined by optical simulation. FIG. 2 shows the spectral transmittance when colorless transparent glass is used as the transparent substrate, and FIG. 3 shows the spectral transmittance when near infrared cut glass is used as the transparent substrate. FIG. 4 shows the spectral transmittance when only the transmission band constituent part is formed on the colorless transparent glass, and FIG. 5 shows the spectral transmittance when only the blocking band constituent part is formed on the colorless transparent glass.

  Table 3 shows main numerical values in the spectral transmittance of the near-infrared cut filter (using colorless transparent glass as the transparent substrate (FIG. 2)). Tables 4 and 5 show main numerical values in the spectral transmittances (FIGS. 4 and 5) of the transmission band constituent part and the stop band constituent part.

  As is apparent from FIG. 2, the near-infrared cut filter suppresses the incident angle dependence, expands the transmission band, and the ultraviolet and near-infrared stop bands, and increases the incident angle. It is recognized that the generation of ripples during the operation is also suppressed. Since this near-infrared cut filter has a very wide transmission band, it is suitable for combined use with absorptive colored glass such as near-infrared cut glass.

(Example 2)
The near-infrared cut filter has a transmission band component that is a part of the optical multilayer film on one main surface of the transparent substrate, and a blocking band component that is a part of the optical multilayer film on the other main surface. The configuration was as follows. Here, the transparent substrate and the blocking band constituting part were the same as in Example 1.

The transmission band constituting part is the second form of the transmission band constituting part having the structure shown in Table 6. Here, when the TiO ₂ film that is a high refractive index film is H and the Ta ₂ O ₅ film that is a medium refractive index film is M, the transmission band constituting portion is basically composed of basic units of [HM]. Is. Further, the number of layers is 52, the average optical film thickness T _H of the TiO ₂ film is 210.7 nm, the average optical film thickness T _M of the Ta ₂ O ₅ film is 171.4 nm, and the average optical film thickness T _L of the SiO ₂ film. 191.3 nm and T _H / T _M = 1.2.

  For this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 ° and the spectral transmittance when the incident angle θ was 30 ° were determined by optical simulation. FIG. 6 shows the spectral transmittance when colorless transparent glass is used as the transparent substrate, and FIG. 7 shows the spectral transmittance when near infrared cut glass is used as the transparent substrate. Further, FIG. 8 shows the spectral transmittance when only the transmission band constituting part is formed on the colorless transparent glass.

  Table 7 shows the main numerical values in the spectral transmittance of the near-infrared cut filter (using colorless transparent glass as the transparent substrate (FIG. 6)). Table 8 shows the main numerical values in the spectral transmittance (FIG. 8) of the transmission band constituting part.

  As apparent from FIG. 6, the near-infrared cut filter also suppresses the incident angle dependency, expands the visible transmission band and the ultraviolet and near-infrared stop bands, and increases the incident angle. It is recognized that the occurrence of ripples is also suppressed. This near-infrared cut filter is preferable because the dependency on the incident angle is particularly suppressed as compared with Example 1, that is, having the transmission band component of the first embodiment.

(Example 3)
The near-infrared cut filter has a transmission band component that is a part of the optical multilayer film on one main surface of the transparent substrate, and a blocking band component that is a part of the optical multilayer film on the other main surface. The configuration was as follows. Here, the transparent substrate and the blocking band constituting part were the same as in Example 1.

The transmission band constituting part was the first form of the transmission band constituting part having the structure shown in Table 9. Here, the transmission band component is H for a TiO ₂ film that is a high refractive index film, M for a Ta ₂ O ₅ film that is a medium refractive index film, and L for a SiO ₂ film that is a low refractive index film. It is basically composed of basic units of [HML]. Further, the number of layers is 84, the average optical film thickness T _H of the TiO ₂ film is 223.8 nm, the average optical film thickness T _M of the Ta ₂ O ₅ film is 117.5 nm, and the average optical film thickness T _L of the SiO ₂ film. Are 30.4 nm, T _H / T _L = 7.4, and T _M / T _L = 3.9.

  For this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 ° and the spectral transmittance when the incident angle θ was 30 ° were determined by optical simulation. FIG. 9 shows the spectral transmittance when colorless transparent glass is used as the transparent substrate, and FIG. 10 shows the spectral transmittance when near-infrared cut glass is used as the transparent substrate. In addition, FIG. 11 shows the spectral transmittance when only the transmission band constituting part is formed on the colorless transparent glass.

  Table 10 shows main numerical values in the spectral transmittance of the near-infrared cut filter (using colorless transparent glass as the transparent substrate (FIG. 9)). Table 11 shows the main numerical values in the spectral transmittance (FIG. 11) of the transmission band constituting part.

  As is clear from FIG. 9, the near-infrared cut filter also suppresses the incident angle dependency, extends the visible transmission band and the ultraviolet and near-infrared stop bands, and increases the incident angle. It is recognized that the occurrence of ripples is also suppressed. About this near-infrared cut filter, it has the near-infrared cut filter of Example 1, that is, the transmission band constituent part of the first form, and the transmission band constituent part of the first form is a repeating structure of a basic unit of [LMMHML] Although the width of the transmission band is slightly narrower than that having the above, it is preferable because the degree of freedom of the average optical film thickness of each film is high because it is basically composed of basic units of [HML].

(Example 4)
The near-infrared cut filter has a transmission band component that is a part of the optical multilayer film on one main surface of the transparent substrate, and a blocking band component that is a part of the optical multilayer film on the other main surface. The configuration was as follows. Here, the transparent substrate and the blocking band constituting part were the same as in Example 1.

The transmission band constituting part is the second form of the transmission band constituting part having the structure shown in Table 12. Here, in the same manner as in Example 2, when the TiO ₂ film, which is a high refractive index film, is H, and the Ta ₂ O ₅ film, which is a medium refractive index film, is M, the transmission band component is basically [HM]. It consists of basic units. Further, the number of layers is 59, the average optical film thickness T _H of the TiO ₂ film is 245.7 nm, the average optical film thickness T _M of the Ta ₂ O ₅ film is 137.0 nm, and the average optical film thickness T _L of the SiO ₂ film. Is 126.0 nm and T _H / T _M = 1.8.

  For this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 ° and the spectral transmittance when the incident angle θ was 30 ° were determined by optical simulation. FIG. 12 shows the spectral transmittance when colorless transparent glass is used as the transparent substrate, and FIG. 13 shows the spectral transmittance when near infrared cut glass is used as the transparent substrate. In addition, FIG. 14 shows the spectral transmittance when only the transmission band constituting part is formed on the colorless transparent glass.

  Table 13 shows main numerical values in the spectral transmittance of the near-infrared cut filter (using colorless transparent glass as the transparent substrate (FIG. 12)). Table 14 shows the main numerical values in the spectral transmittance (FIG. 14) of the transmission band constituting part.

As is apparent from FIG. 12, the near-infrared cut filter also suppresses the dependence on the incident angle, expands the visible transmission band and the ultraviolet and near-infrared stop bands, and increases the incident angle. It is recognized that the occurrence of ripples is also suppressed. This near-infrared cut filter has a larger T _H / T _M than the near-infrared cut filter of Example 2, that is, a filter having a similar configuration of the transmission band component (transmission band component of the second configuration). Moreover, the width of the stop band on the ultraviolet side becomes wider, and the stop band becomes clearer.

(Example 5)
When the colorless transparent glass as the transparent substrate has only the laminated film having the same configuration as the blocking band component of Example 1 (without the transmission band component), the incident angle θ is 0 °, 30 °, and 40 °. Spectral transmittance was determined by optical simulation. FIG. 15 shows the result.

As already described, in the laminated film, 1 to 22 layers are ultraviolet side stop band constituent parts, and 23 to 93 layers are near infrared side stop band constituent parts. In general, with respect to the stopband component, ripples are likely to occur in the transmission band when the incident angle is increased, and ripples are particularly likely to occur when attempting to widen the stopband on the near infrared side. According to this stopband constituent part, in particular, the near infrared side stopband constituent part, for example, by setting T _H / T _L = 0.5 and T _M / T _L = 0.4, the stop band on the near infrared side The generation of ripples when the incident angle increases can be suppressed.

(Example 6)
With respect to a transparent transparent glass having a laminated film having the structure shown in Table 15 (without a blocking band component), the spectral transmittance when the incident angle θ is 0 ° and the incident angle θ are obtained by optical simulation. The spectral transmittance when the angle is 30 ° was determined.

This laminated film is basically obtained by replacing the middle refractive index film in the transmission band constituting portion of the first form with an equivalent film. The configuration before the replacement with the equivalent film is such that the high refractive index film TiO ₂ film is H, the medium refractive index film Ta ₂ O ₅ film is M, and the low refractive index film SiO ₂ film is L. Basically, it has a configuration of L [LMMHML] ^ 25 ([LMMHML] ^ 25 indicates a configuration in which the basic unit of [LMMHML] is repeated by 25 units), and the average optical film thickness of the TiO ₂ film Is T _H , the average optical film thickness of the Ta ₂ O ₅ film is T _M , and the average optical film thickness of the SiO ₂ film is T _L , T _H : T _M : T _L = 8: 4: 1 It is. When the overlapping portions of LL formed between the basic units are collectively regarded as L, T _H : T _M : T _L = 8: 4: 2.

The replacement with the equivalent film is performed by replacing the Ta ₂ O ₅ film, which is a medium refractive index film, with a TiO ₂ film and a SiO ₂ film, and the configuration after the replacement is 98 layers and the average optical film thickness of the TiO ₂ film. T _H is 144.5 nm, the average optical film thickness T _L of the SiO ₂ film is 47.3 nm, and T _H / T _L = 3.1. FIG. 16 shows the result. Table 16 shows main numerical values in the spectral transmittance.

  If the middle refractive index film of the transmission band constituting part is replaced with an equivalent film, the transmission band becomes somewhat narrower. This is because the equivalent film allocates the film thickness on the premise of the refractive index of a specific wavelength, so the wavelength dependence of the refractive index is ignored, and the ideal type of L [LMMHML] ^ 25 cannot be completely reproduced. . For this reason, if adjustment is performed to widen the transmission band by the optimization process, the number of layers decreases in the process. Nevertheless, the number of layers is increased as compared with the transmission band constituting portion of Example 1, and the number of extremely thin films having a physical film thickness of about 10 nm or less is increased, so that the actual film thickness control becomes very difficult. On the other hand, the effect of suppressing the incident angle dependency is slightly inferior to that of the transmission band constituting portion of Example 1 that does not have an equivalent film, but can be almost within the error range. That is, even when an equivalent film is used, most characteristics including suppression of the incident angle dependency can be reproduced.

(Example 7)
About the thing which has the laminated film of the various structures shown to Tables 17-24 in the colorless transparent glass as a transparent substrate, the spectral transmittance when incident angle (theta) is 0 degree, and incident angle (theta) is 30 degrees by optical simulation. The spectral transmittance at that time was obtained.

Each laminated film basically has a configuration of L [LMMHML] ^ 25, where H is the TiO ₂ film, M is the Ta ₂ O ₅ film, and L is the SiO ₂ film, and TiO ₂ The ratio of the average optical film thickness T _{H of} the film, the average optical film thickness T _M of the Ta ₂ O ₅ film, and the average optical film thickness T _L of the SiO ₂ film is changed, and part of the transmission of the first embodiment It is used as a band component. The results are shown in FIGS. Further, Table 25 collectively shows the shift amount of the wavelength in the vicinity of 10% transmittance of the near red side cut wavelength.

Increasing the ratio of T _H and T _M decreases the incident angle dependency. T _H, when increasing the _{T M} in the same proportion, the calculation that fits to the shift amount of the wavelength of -19nm equal to or more than equal times the _{T L.} However, since it is a very simple configuration that does not perform ripple adjustment etc., PS separation actually occurs when the incident angle increases, and the difference between the high transmittance portion and the low transmittance portion is that of the high transmittance portion. It becomes larger and requires some margin. Accordingly, in consideration of the result of Example 1, both T _H / T _L and T _M / T _L are preferably 2 or more.

There is no need to consider the upper limit from the viewpoint of wavelength shift, but because of the relative decrease in _TL , that is, the film thickness of the SiO ₂ film having a low refractive index is lowered, making it difficult to control the film thickness. Therefore, both T _H / T _L and T _M / T _L are preferably 5 or less. Depending on the ratio, the width of the blocking band on the ultraviolet side is narrowed or the width of the transmission band is slightly changed, but the above range is preferable together with the result of Example 1.

(Example 8)
With respect to a transparent transparent substrate having a laminated film having each of the constitutions shown in Table 26, the optical transmission shows a spectral transmittance when the incident angle θ is 0 °, and a case where the incident angle θ is 30 °. Spectral transmittance was determined.

Each laminated film basically has a configuration of 0.5 L / [MH] ^ 25 / 0.5 L, where TiO ₂ film is H, Ta ₂ O ₅ film is M, and SiO ₂ film is L. Each TiO ₂ film and each Ta ₂ O ₅ film are laminated so as to have basically the same optical film thickness, and the optical film thickness is changed to change the average optical film thickness of the TiO ₂ film. T _H, is obtained by changing the ratio of the average optical thickness T _M of the Ta ₂ O ₅ film, some are made of a transmission band structure of the second embodiment. The results are shown in FIGS. Table 27 summarizes the shift amount in the vicinity of 50% transmittance at the near-red side cut wavelength.

The SiO ₂ films provided in the first layer and the final layer are provided as the ripple adjustment unit, but have almost no influence on the wavelength shift because they are not related to the part that forms the cut wavelength. Note that the wavelength shift is about 50% transmittance of the near-red cut wavelength. This laminated film has a small wavelength shift because it has no SiO ₂ film as a low refractive index film in its basic structure. While better to increase the proportion of T _H is the shift amount is small, since the inhibition zone with near-infrared side ratio be smaller or larger becomes too large decreases, it is necessary to increase the number of layers. _{Incidentally,} T H: when the ratio of _{T H} is large in _{T M, T H: T M} = 1.2: 1, when the ratio of _{T M} is _{large, T H: T M = 1} : 1. When the ratio is larger than 5, the ultraviolet-side stop band becomes clear.

Thus, while increasing the ratio of T _H, although it is preferable that the ratio certain level, one of the film thickness when the ratio is too large between T _H and T _M becomes extremely thin, for example, the near side of the There is a need to increase the number of layers by reducing the stop band. _Thus, although the range of T H / _{T M} is not necessarily limited, when the ratio of _{T H} is large, preferably 1.2 or more, more preferably 1.5 or more, 2.0 or more is more preferable. Moreover, the upper limit is preferably 5.0 or less, and more preferably 4.0 or less. On the other hand, for those ratios of T _M is large, but not necessarily reason to use positively, is sufficiently available, T H _/ T _M is preferably 0.7 or less, preferably 0.3 or more .

(Example 9)
For a transparent transparent substrate having a laminated film having the structure shown in Table 28, spectral transmittance when the incident angle θ is 0 ° and spectral when the incident angle θ is 30 ° are obtained by optical simulation. The transmittance was determined.

This laminated film is basically composed of a basic unit of [HL], where H is a TiO ₂ film that is a high refractive index film and L is an SiO ₂ film that is a low refractive index film. The average optical film thickness T _H of the TiO ₂ film is 109.8 nm, the average optical film thickness T _L of the SiO ₂ film is 41.1 nm, and T _H / T _L is 2.7. The present invention can be applied to an ultraviolet-side stop band constituent part in the stop band constituent part of the form The results are shown in FIG.

According to this laminated film, the ultraviolet band is narrowed. Although not shown, further inhibition zone in the ultraviolet range increasing the ratio of T _H in T H _/ T _L becomes narrower. In the ultraviolet blocking band constituting part of 1 to 22 layers in Example 5, 300 to 400 nm can be cut, but in this laminated film, the cut of 300 to 350 nm is insufficient.

(Example 10)
When one of the main surfaces of the transparent substrate has a laminated film having a structure as shown in Table 29, the optical transmission shows that the spectral transmittance when the incident angle θ is 0 ° and the incident angle θ is 30 °. The spectral transmittance of was determined.

The transparent substrate was the same transparent substrate as in Example 1. The laminated film is basically composed of a basic unit of [HL], where H is a TiO ₂ film that is a high refractive index film and L is an SiO ₂ film that is a low refractive index film. but 50 layers, in which the average optical thickness _{T H} of the TiO ₂ film 185.8Nm, the average optical thickness _{T L} of the SiO ₂ film becomes _197.8Nm, a T _H / T L = 0.9. This laminated film is a comparative example of the near-infrared cut filter of the present invention when formed alone on a transparent substrate. FIG. 32 shows the spectral transmittance when colorless transparent glass is used as the transparent substrate, and FIG. 33 shows the spectral transmittance when near infrared cut glass is used as the transparent substrate. In addition, Table 30 shows main numerical values in spectral transmittance (those using colorless transparent glass as a transparent substrate (FIG. 32)).

  With respect to this laminated film, it was confirmed that the width of the transmission band and the stop band can be sufficiently secured, but the dependency on the incident angle is large and the ripple in the transmission band is also large.

(Example 11)
When one of the main surfaces of the transparent substrate has a laminated film having a structure as shown in Table 31, the optical transmission shows a spectral transmittance when the incident angle θ is 0 ° and an incident angle θ is 30 °. The spectral transmittance of was determined.

The transparent substrate was the same transparent substrate (colorless transparent glass) as in Example 1. The laminated film is basically [LMHMML, where H is a TiO ₂ film that is a high refractive index film, M is a Ta ₂ O ₅ film that is a medium refractive index film, and L is an SiO ₂ film that is a low refractive index film. ] and those composed of a basic unit of 96 layers the number of layers, the average optical thickness _{T H} of the TiO ₂ film is 81.2Nm, average optical thickness _{T M} of _{the Ta} 2 _{O 5} film is 93.5Nm, The average optical film thickness T _L of the SiO ₂ film is 150.4 nm, T _H / T _L = 0.5, and T _M / T _L = 0.6. FIG. 34 shows the spectral transmittance. Table 32 shows main numerical values in the spectral transmittance.

  For this laminated film, the wavelength shift is slightly increased. Further, the P and S separation is large when the incident angle θ is 0 to 30 °, and the influence appears on the near infrared side. For this reason, the shift amount differs between a portion where the transmittance exceeds 50% and a portion where the transmittance does not exceed 50%.

(Example 12)
When one of the main surfaces of the transparent substrate has a laminated film having a structure as shown in Table 33, the optical transmission shows that the incident light angle θ is 0 ° and the incident light angle θ is 30 °. The spectral transmittance of was determined.

The transparent substrate was the same transparent substrate (colorless transparent glass) as in Example 1. The laminated film is basically composed of a basic unit of [HM], where H is a TiO ₂ film that is a high refractive index film and M is a Ta ₂ O ₅ film that is a medium refractive index film. The films have the same optical film thickness, the number of layers is 52, the first layer and the 52nd layer have SiO ₂ films as ripple adjustment films, and the average optical film thickness T _H of the TiO ₂ film. Is 188.6 nm, the average optical film thickness T _M of the Ta ₂ O ₅ film is 185.2 nm, the average optical film thickness T _L of the SiO ₂ film is 107.5 nm, and T _H / T _M = 1. FIG. 35 shows the spectral transmittance. Table 34 shows main numerical values in the spectral transmittance.

  With respect to this laminated film, the width of the transmission band can be widened and the incident angle dependency can be suppressed, but it is recognized that the ultraviolet-side stop band does not sufficiently appear.

(Example 13)
For one having a laminated film having a structure as shown in Table 35 on one main surface of the transparent substrate, the optical transmission shows a spectral transmittance when the incident angle θ is 0 °, and when the incident angle θ is 30 °. The spectral transmittance and the spectral transmittance when the incident angle θ was 40 ° were determined.

The transparent substrate was the same transparent substrate as in Example 1. The laminated film is basically composed of a basic unit of [HL], where H is a TiO ₂ film that is a high refractive index film and L is an SiO ₂ film that is a low refractive index film. The 44th layer, the 1st to the 23rd layers are the near-infrared-side stopband constituent part, and the 23rd and subsequent layers are the ultraviolet-side stopband constituent part. Purple outer zone of inhibition component is to average optical thickness _{T H} of the TiO ₂ film is 223 nm, the average optical thickness _{T L} of SiO ₂ film is _221.1Nm, a T H _{/ T} L = 1. FIG. 36 shows the spectral transmittance. Table 36 shows main numerical values in the spectral transmittance. In addition, about this laminated film, it can be used as a stop band structure part of a 1st form, for example.

  In this laminated film, ripples are slightly increased when the incident angle is increased, but the widths of the transmission band and the stop band can be widened to some extent.

(Example 14)
When one of the main surfaces of the transparent substrate has a laminated film having a structure as shown in Table 37, the optical transmittance shows that the incident angle θ is 0 ° and the incident angle θ is 30 ° by optical simulation. The spectral transmittance of was determined. The wavelength shift was confirmed near 10% transmittance of the near red cut wavelength.

The transparent substrate was the same transparent substrate as in Example 1. Laminated film, a TiO ₂ film is a high refractive index film H, when the SiO ₂ film which is a low refractive index film is L, have a structure essentially [HL], the TiO ₂ A film and each SiO ₂ film are laminated so as to have basically the same optical film thickness, and the number of layers is 53, and T _H / _TL is 1 to 8. 37 to 40 show the spectral transmittance.

For even repeating structure of the SiO ₂ film is TiO ₂ film and a low refractive index film is a high refractive index film, can be suppressed incident angle dependence by increasing the average optical thickness T _H of the TiO ₂ film, The width of the transmission band cannot be secured. That is, FIGS. 37 to 39 have the same cut wavelength position on the near infrared side, but become narrower by about 20 nm when compared with the transmission band of Example 7, for example. If the width of the transmission band is moved to the short wavelength side, it tends to be narrower. FIG. 40 shows the case where the short wavelength side is aligned, but the rise on the long wavelength side is about 650 nm. For example, compared to the case of Example 1, Example 1 has a rise of about 695 nm. It will be about 40 nm narrow.

According to the present invention, it is possible to provide a near-infrared cut filter in which the dependency on the incident angle is suppressed and the transmission band in the visible region and the stopbands in the ultraviolet region and the near-infrared region are extended. This near-infrared cut filter is useful for a solid-state imaging device such as a CCD or CMOS used in a digital camera, a video camera, or the like.
The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2011-206574 filed on September 21, 2011 are incorporated herein as the disclosure of the present invention. .

  DESCRIPTION OF SYMBOLS 1 ... Near-infrared cut filter, 2 ... Transparent substrate, 3 ... Optical multilayer film, 3 are provided. Optical multilayer film 3, 50 ... Imaging device, 51 ... Solid-state imaging device, 52 ... Cover glass, 53 ... Lens group, 54 ... Aperture, 55 ... Housing

Claims (14)

An optical multilayer having a transparent substrate, two or more types of films having a refractive index of 2.0 or more and a film having a refractive index of 1.70 or less, provided on at least one main surface of the transparent substrate A near-infrared cut filter comprising a film,
Spectral characteristics under normal incidence conditions of the optical multilayer film include a transmission band having an average transmittance of 85% or more in a wavelength range of 400 to 700 nm, and an average transmittance on each of the ultraviolet side and near infrared side of the transmission band Having a stop band of 5% or less, the difference between the half-value wavelength on the ultraviolet side and the half-value wavelength on the near-infrared side of the transmission band is 200 nm or more, The difference between the half-value wavelengths of the transmission band is less than 10 nm at the half-value wavelength on the ultraviolet side and less than 20 nm at the half-value wavelength on the near infrared side, and the optical multilayer film includes the transmission band constituting part constituting the transmission band and the stop band. A near-infrared cut filter characterized by having a blocking band constituting part. In the near-infrared cut filter according to claim 1,
The said transparent substrate is a near-infrared cut filter comprised from the material which has absorption in a near-infrared wavelength range. The near-infrared cut filter according to claim 1 or 2,
The transmission band component includes a high refractive index film having a refractive index of 2.0 or more, a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film, and a refractive index. Having a low refractive index film having a refractive index of 1.70 or less, the total number of layers of the high refractive index film, the medium refractive index film, and the low refractive index film is 50 or more, and the average of the high refractive index film When the optical film thickness is T _H , the average optical film thickness of the medium refractive index film is T _M , and the average optical film thickness of the low refractive index film is T _L , T _H / T _L is 2 or more and T _M A near-infrared cut filter having a / _TL of 2 or more. In the near infrared cut filter according to claim 3,
The medium refractive index film is a near infrared cut filter comprising an equivalent film composed of a film having the same refractive index as the high refractive index film and a film having the same refractive index as the low refractive index film. The near-infrared cut filter according to claim 1 or 2,
The transmission band constituting part has a repeating structure of a high refractive index film having a refractive index of 2.0 or more and a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film. And a ripple adjusting portion having a low refractive index film having a refractive index of 1.7 or less on the main surface side portion opposite to the transparent substrate side, and an average optical film thickness of the high refractive index film the _{T H,} when the average optical thickness of the middle refractive index film was _{T M, T} H / _{T M} is 1.2 or more, or 0.7 or less, the high-refractive-index film, the intermediate refractive index layer, And a near-infrared cut filter in which the total number of layers of the low refractive index film is 40 or more. In the near-infrared cut filter according to claim 5,
The medium refractive index film is a near infrared cut filter comprising an equivalent film composed of a film having the same refractive index as the high refractive index film and a film having the same refractive index as the low refractive index film. In the near infrared cut filter according to any one of claims 1 to 6,
The stopband constituent part has a transmission band including a transmission band in the spectral characteristic of the optical multilayer film in the spectral characteristics under normal incidence conditions, and the ultraviolet side in the spectral characteristics of the optical multilayer film and the transmission band constituent part A near-infrared cut filter having an ultraviolet half-value wavelength equal to or less than a half-value wavelength and a near-infrared half-value wavelength that is 7 nm or more larger than a near-infrared half-value wavelength in the spectral characteristics of the optical multilayer film and the transmission band component. The near-infrared cut filter according to claim 7,
The blocking band component is a near infrared cut filter having a repeating structure of a high refractive index film having a refractive index of 2 or more and a low refractive index film having a refractive index of 1.7 or less. The near-infrared cut filter according to claim 7,
The stopband component has an ultraviolet-side stopband component for configuring the ultraviolet-side stopband, and a near-infrared-side stopband component for configuring the near-infrared-side stopband, The ultraviolet side stop band constituent part has a repeating structure of a high refractive index film having a refractive index of 2 or more and a low refractive index film having a refractive index of 1.7 or less, and the near infrared side stop band constituent part Is a high refractive index film having a refractive index of 2.0 or more, a medium refractive index film having a refractive index of 2.0 or more and less than the refractive index of the high refractive index film, and a refractive index of 1.70 or less. A near-infrared cut filter having a low refractive index film, wherein the total number of layers of the high refractive index film, the medium refractive index film, and the low refractive index film is 30 or more. The near-infrared cut filter according to claim 9,
The middle refractive index film in the near-infrared-side stopband component is an equivalent composed of a film having the same refractive index as the high refractive index film and a film having the same refractive index as the low refractive index film. Near-infrared cut filter consisting of a film. In the near-infrared cut filter according to any one of claims 1 to 10,
Two or more kinds of films having a refractive index of 2.0 or more and constituting the optical multilayer film are made of TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , or a composite oxide thereof, and the refractive film rate is 1.70 or _less, the near-infrared cut filter made of SiO 2, MgF ₂ or the composite oxide thereof. The near-infrared cut filter according to any one of claims 1 to 11,
A near-infrared cut filter in which the optical multilayer film is formed by vapor deposition or sputtering.   The near-infrared cut filter according to any one of claims 1 to 12, wherein a half-value wavelength on the ultraviolet side of the transmission band is in a range of 390 to 430 nm, and a half-value wavelength on the near-infrared side of the transmission band is 640-400. Near-infrared cut filter in the range of 720 nm.   The near-infrared cut filter according to any one of claims 1 to 13, wherein a difference between an ultraviolet half-value wavelength and a near-infrared half-value wavelength of the transmission band is 200 nm or more and 300 nm or less. .

Images