JP5973747B2 - Near-infrared cut filter - Google Patents

Description

  The present invention relates to a near-infrared cut filter for correcting visibility used in a solid-state imaging device including a solid-state imaging device such as a CCD or a CMOS.

The spectral sensitivity of CCDs, CMOSs, and other solid-state image sensors used in digital cameras and video cameras has a higher sensitivity in the near infrared region than human visual characteristics, so spectral correction using a near infrared cut filter is required. It becomes. Conventionally, as a near-infrared cut filter, a near-infrared absorption type color glass filter such as a fluorophosphate glass containing Cu ²⁺ ions as a coloring component has been used. However, such a device is relatively expensive and is not always easy to reduce in thickness because it is necessary to maintain spectral characteristics due to absorption.

  For this reason, an interference type near-infrared cut filter in which an optical multilayer film having near-infrared cut characteristics is laminated on silicate glass or the like is also widely used. The interference type near-infrared cut filter uses the interference action to obtain the necessary spectral characteristics, so it is possible to use low-cost and easy-to-handle silicate glass, etc. Although it has many advantages, such as a higher visible light transmittance, it has the following problems in order to use the interference action.

  In general, interference-type near-infrared cut filters have a sharp change in transmittance from the transmission band that transmits visible light to the blocking band that blocks ultraviolet light and infrared light in the spectral characteristics, and human visibility characteristics. A spectral characteristic that is greatly different from that of the first embodiment can be obtained. In addition, since the dependence on the incident angle of light is strong and the spectral waveform moves from the long wavelength side toward the short wavelength side when the incident angle becomes large, a change in color of the image becomes a problem. A technique for solving each problem is known, a technique for smoothing the transmittance change so as to be close to human visibility characteristics (for example, refer to Patent Documents 1 to 3), and a technique for reducing the incident angle dependency. (For example, see Patent Documents 4 to 6).

  Basically, it is preferable to reduce the number of layers of the optical multilayer film in order to smooth the transmittance change, but in order to suppress the incident angle dependency, it is necessary to increase the number of layers of the optical multilayer film. This is preferable because the adjustment width of the design becomes large. However, as described in Patent Document 3 described above, it is not easy to gently change the transmittance with an increased number of layers, and various restrictions are required on the film configuration. In other words, it is difficult for the interference type near-infrared cut filter, like the absorption type colored glass filter, to suppress the incident angle dependency while smoothing the transmittance change, at least within the range investigated by the present inventors. No effective method has been proposed.

  On the other hand, it has been proposed to use the absorption of the film to smooth the transmittance change and suppress the incident angle dependency (see, for example, Patent Document 7). However, a decrease in transmittance is unavoidable due to the use of absorption of the silver film, and silver having a relatively high reactivity is used. Therefore, a decrease in weather resistance under a high temperature and high humidity environment is expected.

JP 2003-29027 A JP 2004-163869 A Japanese Patent No. 3679268 JP-A-7-27907 JP 2004-163741 A JP 2008-20563 A Japanese Patent No. 4404568

  The present invention has been made in view of the above-described situation, and uses an interference action. The transmittance change on the infrared light side is gentle, the incident angle dependency is suppressed, and the absorption type color is reduced. The object is to provide a near-infrared cut filter having spectral characteristics close to those of a glass filter.

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 a high refractive index film having a refractive index of 2.0 or more and a low refractive index having a refractive index of 1.7 or less. And an optical multilayer film having a film.
The optical multilayer film is provided on one main surface of the transparent substrate, and the transmission band defining portion for mainly defining the shape of transparently strip, provided on the other main surface of the transparent substrate, a near-infrared light side mainly and a stopband defining portion for defining a zone of inhibition and ultraviolet light side blocking band shape.
The transmission band defining portion includes a basic portion and an adjustment portion provided on at least one main surface of the basic portion.
The basic part has an alternate laminated structure of a high refractive index film for a basic part having a refractive index of 2.0 or more and a low refractive index film for a basic part having a refractive index of 1.7 or less. The total number of layers of the refractive index film and the basic portion low refractive index film is 10 or more, the average optical film thickness of the basic portion high refractive index film is T _H1 , and the average optical thickness of the basic portion low refractive index film is When the film thickness is T _L1 , T _H1 / T _L1 is 2 or more.
The adjusting portion is provided on one main surface or both main surfaces of the basic portion, and the adjusting portion high refractive index film having a refractive index of 2.0 or more and the adjusting portion low refraction having a refractive index of 1.7 or less. An average optical film of the high refractive index film for the adjustment part, the total number of layers of the high refractive index film for the adjustment part and the low refractive index film for the adjustment part being 10 or more. When the thickness is T _H2 and the average optical film thickness of the low refractive index film for adjusting part is T _L2 , T _H2 / T _L2 is 1.5 or less.
Moreover, the near-infrared cut filter of the present invention has the following spectral characteristics. That is, under normal incidence conditions, a transmission band having a maximum transmittance of 85% or more in at least a part of the wavelength range of 400 to 700 nm, and a minimum transmittance of 1% or less in at least a part of the wavelength range of 750 to 1000 nm. It has a near infrared light side stop band and an ultraviolet light side stop band where the minimum transmittance is 1% or less in at least part of the wavelength range of 350 to 400 nm. Further, under normal incidence conditions, the difference between the half-value wavelength of the ultraviolet light side and the near-infrared light side half-value wavelength of the transmission band is 200 nm or more, and the transmittance between the transmission band and the near-infrared light side stop band is 80%. The difference in absolute value between the wavelength at the time and the wavelength at which the transmittance is 40% is 20 to 100 nm. Further, in the comparison between the normal incidence condition and the 30 degree incidence condition, the average wavelength shift amount at the absolute value of the portion where the transmittance is 20 to 80% between the transmission band and the near infrared light side stop band is 14 nm. It is as follows.

  According to the present invention, the interference action is utilized, the transmittance change on the infrared light side is gentle, the incident angle dependency is suppressed, and the spectral characteristics are close to those of an absorption type colored glass filter. A near-infrared cut filter can be provided.

Sectional drawing which shows one Embodiment of the near-infrared cut off filter of this invention. Sectional drawing which shows an example of the imaging device to which a near-infrared cut filter is applied. The figure which shows the spectral characteristics of the near-infrared cut off filter of Example 1. FIG. 6 is a diagram showing the spectral characteristics of the basic part in the near-infrared cut filter of Example 1. FIG. 6 is a diagram illustrating spectral characteristics of an adjustment unit in the near-infrared cut filter of Example 1. The figure which shows the spectral characteristics of the near-infrared cut off filter of Example 2. FIG. 6 is a diagram showing spectral characteristics of a basic part in the near-infrared cut filter of Example 2. FIG. 10 is a diagram illustrating spectral characteristics of an adjustment unit in the near-infrared cut filter of Example 2. FIG. 6 is a diagram showing spectral characteristics of the near-infrared cut filter of Example 3. FIG. 10 is a diagram showing the spectral characteristics of the basic part in the near-infrared cut filter of Example 3. FIG. 10 is a diagram illustrating spectral characteristics of an adjustment unit in the near-infrared cut filter of Example 3. FIG. 10 is a diagram showing the spectral characteristics of the near-infrared cut filter of Example 4. FIG. 10 is a diagram showing spectral characteristics of a basic part in the near-infrared cut filter of Example 4. The figure which shows the spectral characteristics of the adjustment part (1) in the near-infrared cut off filter of Example 4. FIG. 10 is a diagram illustrating spectral characteristics of an adjustment unit (2) in the near-infrared cut filter of Example 4. FIG. 10 is a diagram showing the spectral characteristics of the near-infrared cut filter of Example 5. FIG. 10 is a diagram showing the spectral characteristics of the basic part in the near-infrared cut filter of Example 5. FIG. 10 is a diagram illustrating spectral characteristics of an adjustment unit in the near-infrared cut filter of Example 5. The figure which shows the spectral characteristics of the near-infrared cut off filter of Example 6. The figure which shows the spectral characteristic of the stop band prescription | regulation part in the near-infrared cut off filter of Example 6. The figure which shows collectively the spectral characteristics of the near-infrared cut off filters of Examples 6 and 9. The figure which shows the spectral characteristics of the near-infrared cut off filter of Example 7. The figure which shows the spectral characteristic of the fundamental part in the near-infrared cut off filter of Example 7. FIG. 10 is a diagram illustrating spectral characteristics of an adjustment unit in the near-infrared cut filter of Example 7. FIG. 10 is a diagram showing the spectral characteristics of the near-infrared cut filter of Example 8. FIG. 10 is a diagram showing the spectral characteristics of the near-infrared cut filter of Example 9.

Hereinafter, embodiments of the near-infrared cut filter of the present invention will be described.
The near-infrared cut filter has, for example, a transparent substrate and an optical multilayer film provided on at least one main surface of the transparent substrate. The optical multilayer film has a high refractive index film having a refractive index of 2.0 or more and a low refractive index film having a refractive index of 1.7 or less. Usually, these high refractive index films and low refractive index films are alternately stacked to form an alternately stacked structure. In addition, the refractive index in this invention means the refractive index with respect to the light of wavelength 500nm unless there is particular notice.

  The near infrared cut filter of the present invention has the following spectral characteristics. That is, under normal incidence conditions, a transmission band having a maximum transmittance of 85% or more in at least a part of the wavelength range of 400 to 700 nm, and a minimum transmittance of 1% or less in at least a part of the wavelength range of 750 to 1000 nm. It has a near infrared light side stop band and an ultraviolet light side stop band where the minimum transmittance is 1% or less in at least part of the wavelength range of 350 to 400 nm.

  Here, the range of the transmission band is from the wavelength (base point on the ultraviolet light side) when the transmittance starts to decrease from the transmission band toward the ultraviolet light blocking band, and from the transmission band to the near infrared light blocking side. Up to the wavelength (base point on the near-infrared light side) when the transmittance starts to decrease toward the band.

  Moreover, the range of the ultraviolet light side stop band is the transmittance from the wavelength (base point on the transmission band side) when the transmittance starts increasing from the ultraviolet light side stop band toward the transmission band toward the ultraviolet light side. Up to the wavelength (base point on the ultraviolet light side) when the rise starts when it first reaches 40%. The range of the near-infrared light side stopband is from the wavelength (base point on the transmission band side) when the transmittance starts from the near-infrared light side stopband toward the transmission band, to the near-infrared light side. Up to the wavelength (base point on the near-infrared light side) when the rise starts when the transmittance first reaches 40%.

  In the following, unless otherwise specified, the transmission band, the near infrared light side stop band, the ultraviolet light side stop band is a transmission band formed by the entire near infrared cut filter, a near infrared light side stop band, Means the ultraviolet light side stopband.

  Further, under normal incidence conditions, the difference between the half-value wavelength of the ultraviolet light side and the near-infrared light side half-value wavelength of the transmission band is 200 nm or more, and the transmittance between the transmission band and the near-infrared light side stop band is 80%. The difference in absolute value between the wavelength at the time and the wavelength at which the transmittance is 40% is 20 to 100 nm.

  The half-value wavelength means the wavelength when the transmittance is 50%. The ultraviolet light side half-value wavelength means the half-value wavelength near the ultraviolet light side of the transmission band, and the near-infrared light side half-value wavelength means the transmission. This means the half-value wavelength near the near infrared light side of the band. In the following description, unless otherwise specified, the ultraviolet light side half-value wavelength and the near-infrared light side half-value wavelength are both assumed to be in a perpendicular incidence condition.

  In addition, in the following, not only the spectral characteristics of the near-infrared cut filter but also the spectral characteristics of each part alone, the difference between the ultraviolet half-wave wavelength and near-infrared half-wave wavelength in the transmission band under normal incidence conditions. Is the absolute value of the wavelength when the transmittance is 80% and the wavelength when the transmittance is 40% between the transmission band and the near-infrared light side stop band under normal incidence conditions. The difference in is “near infrared light side 40-80% wavelength difference”, the wavelength and transmittance is 40% when the transmittance between the transmission band and the ultraviolet light side stop band in the normal incidence condition is 80%. The difference in absolute value with respect to the wavelength when it becomes is described as “40 to 80% wavelength difference on the ultraviolet light side”.

  Further, in the comparison between the normal incidence condition and the 30 degree incidence condition, the average wavelength shift amount at the absolute value of the portion where the transmittance is 20 to 80% between the transmission band and the near infrared light side stop band is 14 nm. It is as follows. Here, the average wavelength shift amount is calculated in steps of 1% transmittance when the transmittance is 20 to 80% in each of the normal incidence condition and the 30 degree incidence condition. Next, the difference in wavelength between the normal incidence condition and the 30 degree incidence condition for each unit transmittance (1%) is calculated. And using these, it calculates | requires by calculating the difference of the wavelength in the unit transmittance | permeability in 20-80% of the transmittance | permeability.

  In the following, not only the spectral characteristics of the near-infrared cut filter, but also the spectral characteristics of each part alone, the transmission band and the near-infrared light side stop band in the comparison between the normal incidence condition and the 30-degree incidence condition The average wavelength shift amount in the absolute value of the portion where the transmittance between 20 and 80% is “near infrared light side average shift amount”, and the transmission band and purple in the comparison between the normal incidence condition and the 30 degree incidence condition The average wavelength shift amount at the absolute value of the portion where the transmittance between the side stop band and 20 to 80% is described as “ultraviolet light side average shift amount”.

  According to such a near-infrared cut filter, since the wavelength difference of 40 to 80% on the near-infrared light side is 20 to 100 nm, a spectral waveform with a gentle change in transmittance can be obtained. Moreover, according to this near-infrared cut filter, since the near-infrared light side average shift amount is 14 nm or less, the incident angle dependency is suppressed. Therefore, according to such a near-infrared cut filter, a spectral characteristic close to that of an absorption type colored glass filter can be obtained.

  The near infrared light side wavelength difference of 40 to 80% is more preferably 30 to 100 nm, and more preferably 35 to 100 nm. Moreover, the near infrared light side average shift amount is preferably 12 nm or less. By setting such an average shift amount on the near infrared light side, it is possible to obtain spectral characteristics closer to those of an absorption type colored glass filter. Further, the ultraviolet light side average shift amount is preferably 10 nm or less, more preferably 7 nm or less. By setting such an ultraviolet light side average shift amount, it is possible to obtain spectral characteristics closer to those of an absorption type colored glass filter. The half-value wavelength difference is not necessarily limited as long as it is 200 nm or more, but 350 nm or less is preferable.

  The near-infrared cut filter preferably further has a near-infrared light half-value wavelength in the range of 600 to 750 nm under normal incidence conditions, and an ultraviolet light-side half-value wavelength in the range of 380 to 430 nm under the same conditions. It is preferable.

  A near-infrared cut filter having such spectral characteristics can be obtained, for example, by adopting the following configuration. FIG. 1 is a schematic cross-sectional view showing an embodiment of a near-infrared cut filter.

  The near-infrared cut filter 1 includes, for example, a transparent substrate 2 and an optical multilayer film 3 provided on both main surfaces of the transparent substrate 2. The optical multilayer film 3 is provided, for example, on one main surface of the transparent substrate 2, and is provided on the other main surface of the transparent substrate 2 and the transmission band defining portion 31 that mainly defines the shape of the transmission band. And a stop band defining portion 32 that mainly defines the shapes of the light side stop band and the ultraviolet light side stop band. The near-infrared cut filter 1 preferably has both a transmission band defining part 31 and a stop band defining part 32 as shown in the figure. However, when a predetermined spectral characteristic is obtained, only the transmission band defining part 31 is provided. It may have.

  The transmission band defining portion 31 is provided on, for example, a basic portion 311 that mainly defines the shape of the transmission band, and at least one main surface of the basic portion 311, and mainly a near-infrared light in the transmission band formed by the basic portion 311. And an adjustment unit 312 that further smoothes the wavelength shift of the transmission band formed by the basic unit 311. Here, the adjustment unit 312 may be provided on both main surfaces of the basic unit 311 as illustrated, or may be provided on one main surface of the basic unit 311 although not illustrated.

  The basic part 311 mainly defines the shape of the transmission band as described above. The adjustment unit 312 smoothes the shape of the vicinity of the near-infrared light mainly in the transmission band formed by the basic unit 311. In other words, the adjustment unit 312 gently changes the transmittance in the portion. As described above together with the basic portion 311, the near infrared light side wavelength difference of 40 to 80% is set to 20 to 100 nm. The adjustment unit 312 further suppresses the wavelength shift of the transmission band formed by the basic unit 311. Specifically, as described above together with the basic unit 311, the near infrared light side average shift amount is set to 14 nm. It is as follows.

  By using the basic unit 311 and the adjustment unit 312 together, the spectral characteristic of the near-infrared cut filter 1 can be made to be a spectral characteristic close to that of an absorption type color glass filter. That is, it is possible to obtain a spectral waveform in which the transmittance change is gentle and the incident angle dependency is suppressed.

(Transparent substrate)
The transparent substrate 2 is not particularly limited as long as it can transmit at least light in the visible wavelength range. For example, crystals such as glass, quartz, 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.

  As the transparent substrate 2, a substrate having absorption in a specific wavelength region such as near infrared or ultraviolet can be used. Examples of the transparent substrate 2 having absorption in the near-infrared wavelength region include absorption glass in which CuO or the like is added to fluorophosphate glass or phosphate 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. By using such a transparent substrate 2 having absorption in a specific wavelength region, the optical characteristics of the near infrared cut filter 1 are a combination of the absorption characteristics of the transparent substrate 2 and the optical characteristics of the optical multilayer film 3. Become. Therefore, by using such a transparent substrate 2, it is possible to improve the optical characteristics of the near-infrared cut filter, reduce the film thickness of the optical multilayer film 3, and the like.

(Transmission band defining part)
The transmission band defining part 31 defines the shape of the transmission band and the vicinity of the ultraviolet light side and near infrared light side thereof. Specifically, the shape of the transmission band by the near-infrared cut filter 1 is defined by forming a transmission band that is included in the transmission band formed by the blocking band defining unit 32 and narrower than this.

  The transmission band defining portion 31 preferably has the following spectral characteristics as a single spectral characteristic. That is, the transmission band by the transmission band defining part 31 and the vicinity of the ultraviolet light side and near infrared light side are the transmission band by the near infrared cut filter 1 and the vicinity of the ultraviolet light side and near infrared light side. The same is preferable.

  Specifically, the half-value wavelength difference is preferably 200 nm or more, more preferably 300 nm or less, and the near infrared light side 40 to 80% wavelength difference is preferably 20 to 100 nm. Further, the near-infrared light side average shift amount is preferably 14 nm or less, more preferably 12 nm or less, and the ultraviolet light side average shift amount is preferably 10 nm or less, more preferably 7 nm or less. Furthermore, the near-infrared light half-value wavelength is preferably 630 to 690 nm, and the ultraviolet light-side half-value wavelength is preferably 395 to 430 nm.

  The transmission band defining portion 31 is provided on at least one main surface of the basic portion 311 that mainly defines the shape of the transmission band, and the transmission band formed by the basic portion 311 mainly on the near infrared light side. An adjustment unit 312 that smoothes the shape of the vicinity and further suppresses the wavelength shift of the transmission band formed by the basic unit 311 is provided. Here, the adjustment unit 312 may be provided separately on both main surfaces of the basic unit 311 as illustrated, or may be provided on only one main surface of the basic unit 311 although not illustrated.

  The transmission band defining unit 31 has a single-side spectral characteristic of the adjustment unit 312 and the basic unit 311 for the normal incidence condition and the 30-degree incidence condition. Are also on the ultraviolet side, and the infrared half-value wavelength of the adjustment unit 312 is on the infrared side of the infrared half-value wavelength of the basic unit 311. Further, the difference between the absolute value of the infrared half-value wavelength of the adjustment unit 312 and the infrared half-value wavelength of the basic unit 312 in the normal incidence condition is 20 nm or more. The upper limit of the difference is not necessarily limited, but is preferably 200 nm or less, more preferably 150 nm or less.

  The basic part 311 forms a rectangular transmission band with a single spectral characteristic, and the transmittance change of the transmission band from the infrared side blocking band is steep near vertical. And it has the characteristic that the difference in the absolute value of the near-infrared-light side half-value wavelength between the normal incidence condition and the 30 degree incidence condition is small.

  As described above, the adjustment unit 312 includes the transmission band of the basic unit 311 and includes a wider transmission band. Further, the spectral change from the transmission band to the stop band is very gentle. And it has the characteristic that the difference in the absolute value of the near-infrared light side half-value wavelength in a normal incidence condition and a 30 degree incidence condition is large.

  The transmission band defining unit 31 can combine the basic unit 311 and the adjusting unit 312 to obtain a smaller infrared-side half-value wavelength shift amount than the infrared-side half-value wavelength shift amount of the basic unit 311 alone. Furthermore, the change in transmittance on the infrared side can be made gentle, and spectral characteristics close to those of an absorption type colored glass filter can be obtained.

  Further, the incident angle characteristic of the transmission band defining portion 31 can reduce the amount of wavelength shift even under an incident condition larger than 30 degrees. As described above, since the spectral change between the vertical incident condition and the oblique incident condition of the adjustment unit 312 is large, the wavelength shift can be apparently reduced by using only this part of the rising on the infrared side. If it is limited to the use of the visibility correction filter in the solid-state imaging device, it is essential that the transmittance change in the wavelength range corresponding to RGB does not occur due to oblique incidence. It is a great advantage that it can be apparently suppressed only by the wavelength shift amount (in particular, R here).

  In order to suppress the wavelength shift under the 45-degree incidence condition, the difference in absolute value between the infrared half-value wavelength of the adjustment unit 312 and the infrared half-value wavelength of the basic unit 312 under the normal incidence condition is 40 nm or more. preferable. The difference in absolute value between the infrared half-value wavelength of the adjusting unit 312 and the infrared half-value wavelength of the basic unit 312 under normal incidence conditions is preferably 200 nm or less, and more preferably 150 nm or less.

  The basic part 311 preferably has the following spectral characteristics as individual spectral characteristics. The difference in absolute value of near-infrared light half-value wavelength under normal incidence conditions and 30 degree incidence condition is preferably 18 nm or less, and the difference in absolute value of ultraviolet light half-value wavelength under the same conditions is preferably 8 nm or less. . By setting it as such a spectral characteristic, the incident angle dependence in the near-infrared cut filter 1 can be suppressed effectively. In the following, the difference in the absolute value of the near-infrared light half-value wavelength under the normal incidence condition and the 30-degree incidence condition is expressed as “near-infrared light half-value wavelength shift amount” and the absolute value of the ultraviolet light half-value wavelength. Is described as “half-value wavelength shift amount on the ultraviolet light side”.

The basic part 311 has, for example, an alternating laminated structure of a high refractive index film for a basic part with a refractive index of 2.0 or more and a low refractive index film for a basic part with a refractive index of 1.7 or less. The total number of layers of the high refractive index film and the basic part low refractive index film is 10 or more, the average optical film thickness of the basic part high refractive index film is T _H1 , and the average optical film thickness of the basic part low refractive index film when was the _{T L1, T} H1 _{/ T L1} is of 2 or more. By setting it as such, the above spectral characteristics can be obtained. That is, in the single spectral characteristic, the transmission band is rectangular, the transmittance change from the stop band on the infrared side to the transmission band is steep near vertical, and near red under normal incidence conditions and 30 degree incidence conditions. A small difference in absolute value of the external light side half-value wavelength is obtained.

The total number of layers is not necessarily limited as long as it is 10 or more, but is preferably 15 or more because it is easy to obtain predetermined spectral characteristics. The total number of layers is preferably as the number of layers basically increases, because it becomes easier to obtain predetermined spectral characteristics, but from the viewpoint of productivity and the like, 100 layers or less is preferable, and 80 layers or less are preferable. Further, T _H1 / T _L1 is not necessarily limited as long as it is 2 or more. However, it is preferably 3 or more and more preferably 4 or more because predetermined spectral characteristics are easily obtained. T _H1 / T _L1 is usually preferably 15 or less, and more preferably 10 or less.

  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]. Further, the average optical film thickness is calculated by calculating the optical film thickness nd [nm] for all of the same type of film in each part, for example, the high refractive index film for the basic part, and then calculating the total optical film thickness nd [nm]. It is calculated by dividing by the number of layers of the film.

  The adjusting unit 312 preferably has the following spectral characteristics alone. That is, in the normal incidence condition and the 30 degree incidence condition, the near-infrared light half-value wavelength is larger than the near-infrared light half-value wavelength of the basic part 311, and the ultraviolet light-side half-value wavelength is the ultraviolet light side half-value wavelength of the basic part 311. Is preferably smaller. With this configuration, when combined with the spectral characteristics of the basic unit 311, the transmittance change of the near-infrared cut filter 1 can be effectively smoothed, and the near-infrared light side average shift amount can be reduced. .

  The adjustment unit 312 needs to have high oblique incidence dependency. This not only smooths the waveform formed by combining with the waveform by the basic unit 311 but also causes the waveform deformation at the time of oblique incidence, so that the apparent wavelength of the combination of the basic unit 311 and the adjusting unit 312 is apparent. This is because it is necessary to reduce the wavelength shift. Specifically, the waveform near the half value on the near infrared side of the adjustment unit 312 is greatly changed with oblique incidence, so that the wavelength shift amount near the half value on the near infrared side of the wavelength combining the basic unit 311 and the adjustment unit 312 is the result. Become smaller. The waveform shift in the vicinity of the near infrared half-value wavelength of the basic unit 311 shifts in parallel with a similar shape, but the waveform shift of the adjustment unit 312 shifts with waveform deformation, that is, in a non-similar shape. Such waveform deformation at the time of oblique incidence of the adjusting unit 312 is caused by a change in the optical film thickness accompanying a change in the incident angle. The difference in the absolute value of the near-infrared light side half-value wavelength between the normal incidence condition and the 30-degree incidence condition (near infrared light side half-value wavelength shift amount) is preferably 25 nm or more, and more preferably 30 nm or more. The upper limit is not necessarily limited, but is preferably 50 nm or less. By having such spectral characteristics, the transmittance change of the near infrared cut filter 1 can be smoothed more effectively.

The adjustment unit 312 has, for example, an alternating stacked structure of an adjustment unit high refractive index film having a refractive index of 2.0 or more and an adjustment unit low refractive index film having a refractive index of 1.7 or less. The total number of layers of the high refractive index film and the adjustment part low refractive index film is 10 or more, the average optical film thickness of the adjustment part high refractive index film is T _H2 , and the average optical film thickness of the adjustment part low refractive index film when was the _{T L2, T} H2 _{/ T L2} is of 1.5 or less. By setting it as such, it can be set as the above-mentioned spectral characteristics. That is, in a single spectral characteristic, a wider transmission band including the transmission band of the basic portion 311 can be formed, and the spectral change from the transmission band to the stop band is very gentle. The difference in the absolute value of the near-infrared light half-value wavelength in the conditions can be large.

The total number of layers is preferably as the number of layers basically increases, because it becomes easier to obtain predetermined spectral characteristics, but from the viewpoint of productivity and the like, 100 layers or less is preferable, and 50 layers or less are preferable. Further, T _H2 / T _L2 is not necessarily limited as long as it is 1.5 or less, but is preferably 1.0 or less and more preferably 0.8 or less because it is easy to obtain predetermined spectral characteristics. T _H2 / T _L2 is usually preferably 0.1 or more, and more preferably 0.3 or more.

  By configuring the transmission band defining unit 31 with the basic unit 311 and the adjusting unit 312, the near-infrared cut filter 1 has a maximum transmittance of 85% or more in at least a part of the wavelength range of 400 to 700 nm. While being able to form a transmission band, the half-value wavelength difference can be 200 nm or more and the near infrared light side 40-80% wavelength difference can be 20-100 nm. Moreover, the near-infrared light side average shift amount can be made 14 nm or less.

The high refractive index film, that is, the high refractive index film for the basic part and the high refractive index film for the adjustment part 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 , Nb ₂ O ₅ , Ta ₂ O ₅ , or a composite oxide thereof is preferable. The refractive index of the high refractive index film is preferably 2.3 or more, and more preferably 2.4 or more. Such as those mentioned as example TiO ₂ (refractive index 2.5) is preferred. The high refractive index film for the basic part and the high refractive index film for the adjustment part may be made of materials having different refractive indexes, and the high refractive index film for the basic part may be made of the high refractive index for the adjustment part. The films may be made of materials having different refractive indexes.

The low refractive index film, that is, the low refractive index film for the basic part and the low refractive index film for the adjustment part are not particularly limited as long as they are made of a material having a refractive index of 1.7 or less. For example, SiO ₂ , MgF ₂ , Al ₂ O ₃ , or a composite oxide thereof is preferable. The low refractive index film for the basic part and the low refractive index film for the adjustment part may be made of materials having different refractive indexes, and the low refractive index film for the basic part may be made of the low refractive index for the adjustment part. The films may be made of materials having different refractive indexes.

Since the transmission band defining portion 31 has a large number of layers and a large total film thickness, for various reasons such as availability of film materials, spectral characteristics, weather resistance, strength, and the like, TiO ₂ , Nb ₂ as described above. O ₅ , Ta ₂ O ₅ , SiO ₂ , MgF ₂ , Al ₂ O _{3 and the} like are preferably used.

(Stop zone regulation part)
The stopband defining unit 32 mainly defines the shapes of the near infrared light side stopband and the ultraviolet light side stopband. That is, the transmission band defining portion 31 mainly defines the shape of the transmission band and the vicinity of the ultraviolet light side and the infrared light side thereof, and the transmission band defining part 31 does not necessarily have a sufficiently wide near infrared light side blocking band or ultraviolet light side. A stopband cannot be formed. By using the stopband defining portion 32 in combination, the width of the near infrared light side stopband and the ultraviolet light side stopband can be expanded.

  The stopband defining part 32 forms a transmission band formed by the optical multilayer film 3, that is, a transmission band wider than the transmission band formed by the transmission band defining part 31, and has an average transmittance of 5 in at least a part of the wavelength range of 350 to 400 nm. It is preferable to form an ultraviolet light side stop band that is not more than% and a near infrared light side stop band that has an average transmittance of not more than 3% in at least part of the wavelength range of 800 to 1000 nm.

“First stopband prescribing section”
The stop band defining portion 32 has, for example, a repeating structure of a high refractive index film for a stop band having a refractive index of 2.0 or more and a low refractive index film for a stop band having a refractive index of 1.7 or less. Further, when the average optical film thickness of the high refractive index film is T _H3 and the average optical film thickness of the low refractive index film is T _L3 , T _H3 / T _L3 is less than 2.

With such a configuration, it is possible to form a transmission band including the transmission band by the optical multilayer film 3, that is, including the transmission band by the transmission band defining portion 31, and an ultraviolet light having a wavelength less than the half-value wavelength on the ultraviolet light side by the optical multilayer film 3. The near-infrared light half-value wavelength that is 7 nm or more larger than the near-infrared light side half-value wavelength by the optical multilayer film 3 can be obtained. That is, when T _H3 / T _L3 is 2 or more, the incident angle dependency is easily suppressed, but the transmission band is narrowed. By making T _H3 / T _L3 less than 2, the incident angle dependency cannot necessarily be suppressed, but a wide transmission band including the transmission band by the optical multilayer film 3, that is, the transmission band defining portion 31, can be formed.

  The number of layers of the stop band defining portion 32 is preferably 40 or more, and more preferably 50 or more, from the viewpoint of obtaining a sufficiently wide transmission band or stop band and a predetermined half-value wavelength. 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.

T _H3 / T _L3 is not particularly limited, but considering that a sufficiently wide transmission band or stop band, particularly a wide stop band is obtained, T _{H3 is} compared to the design center wavelength when the stop band is designed. It is preferable to use a general film design technique with a / _TL3 ratio of about 1. When T _H3 / T _L3 is large, the incident angle dependency can be suppressed, but the width of the stop band decreases.

"Second stopband prescription part"
The stopband defining unit 32 includes an ultraviolet light side stopband defining unit for configuring an ultraviolet light side stopband, and a near infrared light side stopband defining unit for configuring a nearinfrared light side stopband. It may have. The ultraviolet light side stop band defining portion has a repeating structure of a high refractive index film for an ultraviolet light side stop band having a refractive index of 2 or more and a low refractive index film for an ultraviolet light side stop band having a refractive index of 1.7 or less. Have The near-infrared light side stop band defining portion is a high-refractive index film for near-infrared light side stop band having a refractive index of 2.0 or more, a near-infrared light side stop band having a refractive index of 2.0 or more. An intermediate refractive index film for near infrared light side stop band that is less than the refractive index of the high refractive index film for use, and a low refractive index film for near infrared light side stop band that has a refractive index of 1.70 or less, The total number of layers of the high refractive index film for the near infrared light side stop band, the middle refractive index film for the near infrared light side stop band, and the low refractive index film for the near infrared light side stop band is 30 or more. .

  The stop band defining part 32 can also form a transmission band including the transmission band formed by the optical multilayer film 3, that is, the transmission band formed by the transmission band forming part 31, and the ultraviolet light side of the optical multilayer film 3 having an ultraviolet light side half wavelength or less. The near-infrared light side half-value wavelength larger by 7 nm or more than the near-infrared light side half-value wavelength by the optical multilayer film 3 can be formed.

  In general, it is preferable that the optical multilayer film has a wide stop band on the near-infrared light side, and the occurrence of ripples in the transmission band when the incident angle increases is small. The transmission band defining part 31 described above can suppress the occurrence of ripple to some extent because it uses a technique for suppressing the incident angle dependency, but the blocking band defining part 32 that does not include this technique still generates a ripple. . For the first stop band defining portion 32, such a ripple cannot necessarily be sufficiently suppressed. According to the second stop band defining unit 32, it is possible to suppress the occurrence of ripples while sufficiently expanding the width of the transmission band and the stop band.

  As described above, the ultraviolet light side stop band defining portion includes the high refractive index film for the ultraviolet light side stop band having a refractive index of 2 or more and the low refractive index film for the ultraviolet light side stop band having a refractive index of 1.7 or less. And a repeating structure.

  The number of layers of the ultraviolet light side stop band defining portion is preferably 15 or more, and more preferably 20 or more, from the viewpoint of forming a sufficiently wide ultraviolet light side stop band. 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 for the ultraviolet light side stop band is not particularly limited as long as it is made of a material having a refractive index of 2.0 or more. For example, TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , or The thing which consists of these complex oxides is mentioned suitably. The high refractive index film for the ultraviolet light side stop band preferably has a refractive index of 2.3 or higher, more preferably a refractive index of 2.4 or higher. As such, the ones made of TiO ₂ (refractive index 2.5) are preferably exemplified.

The low refractive index film for the ultraviolet light side stop band is not particularly limited as long as it is made of a material having a refractive index of 1.7 or less. For example, SiO ₂ , MgF ₂ , Al ₂ O ₃ , or these Preferred examples include those composed of complex oxides.

  The near-infrared light side stop band defining portion is a high-refractive index film for near-infrared light side stop band having a refractive index of 2.0 or more, and a near-infrared light side stop band having a refractive index of 2.0 or more. A middle refractive index film for near-infrared light side stop band that is less than the refractive index of the high refractive index film for use, and a low refractive index film for near-infrared light side stop band that has a refractive index of 1.70 or less. The total number of these high-refractive-index films for near-infrared light side stopbands, medium-refractive-index films for near-infrared-light side stopbands, and low-refractive-index films for near-infrared-light side stopbands is 30 or more. It is.

  The number of layers of the near-infrared light side stop band defining portion is not particularly limited as long as it is 30 or more, but 40 or more is preferable from the viewpoint of forming a near-infrared light side stop band having a more sufficient width. The above 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.

High refractive index film for near infrared light side stop band, medium refractive index film for near infrared light side stop band, and low refractive index film for near infrared light side stop band are high for near infrared light side stop band. When the refractive index film is H, the near-infrared light side stopband medium refractive index film is M, and the near-infrared light side stopband low-refractive index film is L, for example, the following basic unit repeating structure: It is laminated so that
Basic unit: [HML]
Basic unit: [LMMHML]

When the above repeating structure is used, the average optical film thickness T _H4 , the average optical film thickness T _M4 , and the average optical film thickness T _L4 are obtained from the viewpoint of obtaining a sufficiently wide stop band. , T _H4 : T _M4 : T _L4 = 1: 1: 1, and the portion having LMHML as a basic unit is a general membrane design with T _H4 : T _M4 : T _L4 = 1: 1: 2. The ratio is preferably about. Incidentally, the latter T _L4 ratio becomes 2, repeat the LMHML, in order to overlap with LL, in the final membrane design is because the ratio is 2, the basic idea T _H4: T _M4 : T _L4 = 1: 1: 1. The _{reason why} the general ratio is adopted here is based on the idea that the optical film thickness ratio is not largely changed because the stop band is narrowed when the ratio of T _H4 and T _M4 is increased.

  Further, it is preferable that the stopband defining unit 32 uses a general method for extending the stopband by applying two or more design wavelengths to the repetitive structure. In this case, the ratio is set for each designed center wavelength.

  The near-infrared light side stop band defining part cuts a wide near-infrared region, 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 wavelength side.

  Note that the near-infrared light side stopband defining portion does not necessarily have a strictly repeating basic unit. For example, in the case of a film having a small refractive index such as a near-infrared light side stop band low refractive index film, it becomes difficult to control the film thickness at the time of film formation when the optical film thickness becomes small. A part of the low refractive index film for the outside light blocking band may be omitted, and 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 for the near infrared light side stop band and the middle refractive index film for the near infrared light side stop band are not particularly limited as long as they are made of a material having a refractive index of 2.0 or more. , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , or a composite oxide thereof may be preferably mentioned. As the high refractive index film for the near-infrared light side stop band, those having a refractive index of 2.3 or more are preferred, and those having a refractive index of 2.4 or more are more preferred. As such, the ones made of TiO ₂ (refractive index 2.5) are preferably exemplified. The medium refractive index film for the near infrared light side stop band is not particularly limited as long as it is less than the refractive index of the high refractive index film for the near infrared light side stop band, but the refractive index is 2 or more and less than 2.3. The refractive index is preferably 2.2 or less. Such examples include are preferably exemplified those composed of _Ta 2 _{O 5} (refractive index 2.2).

The low refractive index film for the near-infrared light side stop band is not particularly limited as long as it is made of a material having a refractive index of 1.7 or less. For example, SiO ₂ , MgF ₂ , Al ₂ O ₃ , or The thing which consists of these complex oxides is mentioned suitably.

  The medium refractive index film for the near infrared light side stop band in the near infrared light side stop band defining portion is not necessarily limited to a single film, for example, a high refractive index film for the near infrared light side stop band It is good also as an equivalent film | membrane comprised from the film | membrane which has the same refractive index, and the film | membrane which has the same refractive index as the low-refractive-index film for near-infrared light side stop bands. 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 as described above, that is, the transmission band defining portion 31 and the stop band defining portion 32 can be formed by sputtering, vacuum deposition, ion beam, ion plating, or CVD. It is preferable to form by a sputtering method or a vacuum evaporation method. 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. 2 is a cross-sectional view schematically showing an embodiment of an imaging apparatus having a solid-state imaging element. The imaging device 5 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 5, 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 5, spectral characteristics close to those of an absorption type color glass filter can be obtained.

Hereinafter, more specific description will be given with reference to examples.
Examples 1 to 6 correspond to examples of the near-infrared cut filter of the present invention, and Examples 7 and 8 correspond to comparative examples. Example 9 is a reference example, and shows an ideal near-infrared cut filter (absorption type colored glass filter) using a near-infrared cut glass.

(Example 1)
The near-infrared cut filter was configured to have only a transmission band defining portion as an optical multilayer film on one main surface of the transparent substrate. Here, the transparent base material was colorless and transparent glass (manufactured by Schott, trade name: D263T, thickness: 1 mm). Further, the transmission band defining part has a structure as shown in Table 1. In Table 2, T _H1 , T _L1 , T _H1 / T _L1 of the basic part, T _H2 , T _L2 , and T _H2 / T _L2 of the adjusting part (adjusting part (1) + adjusting part (2)) are shown. Show.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 3 shows the result of the near infrared cut filter. 4 and 5 show the results when only the basic unit and the adjustment unit (adjustment unit (1) + adjustment unit (2)) are provided, respectively. In addition, the ultraviolet light side half-value wavelength shift amount, near-infrared light side half-value wavelength shift amount, and near-infrared light side average shift amount are negative, indicating that they are shifted to the short wavelength side. Those with a plus indicate that they are shifted to the longer wavelength side.

  As shown in FIG. 3, the near-infrared cut filter has a transmittance of 80% in the band between the transmission band and the near-infrared light side stop band when the incident angle θ is 0 degree. Is 612 nm, the wavelength when the transmittance is 40% is 663 nm, and the difference between these absolute values (near infrared light side 40-80% wavelength difference) is 51 nm. Further, the near infrared light side average shift amount is −8.4 nm (8.4 nm on the short wavelength side).

  For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 415 nm, the near-infrared light side half-value wavelength is 654 nm, and the difference between these absolute values (half-value wavelength) Difference) is 239 nm. In addition, for the basic part, the ultraviolet light side half-value wavelength is 422 nm, the ultraviolet light side half-value wavelength shift amount is -7 nm, the near-infrared light side half-value wavelength is 656 nm, and the near-infrared light side half-value wavelength shift amount is -14 nm. For the part 312, the ultraviolet light side half-value wavelength is 418 nm, the ultraviolet light side half-value wavelength shift amount is −16 nm, the near-infrared light side half-value wavelength is 699 nm, and the near-infrared light side half-value wavelength shift amount is −33 nm. Moreover, about this near-infrared cut filter, by using together the stop-band prescription | regulation part, for example, the stop-band prescription | regulation part of Example 6 which is mentioned later, when incident angle (theta) is 0 degree, it is in the wavelength range of 400-700 nm. A transmission band with a maximum transmittance of 85% or more, a near-infrared light blocking band with a minimum transmittance of 1% or less in the wavelength range of 750 to 1000 nm, and a minimum transmission in at least a part of the wavelength range of 350 to 400 nm. An ultraviolet light side stop band having a rate of 1% or less can be formed.

(Example 2)
A near-infrared cut filter similar to Example 1 was used except that the configuration of the transmission band defining portion was changed to the configuration shown in Table 3. In Table 4, T _H1 , T _L1 , T _H1 / T _L1 of the basic part, T _H2 , T _L2 , and T _H2 / T _L2 of the adjusting part (adjusting part (1) + adjusting part (2)) are shown. Show.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 6 shows the result of the near infrared cut filter. 7 and 8 show the results when only the basic part and the adjustment part are provided, respectively.

  As shown in FIG. 6, for this near-infrared cut filter, when the incident angle θ is 0 degree, the transmittance in the band between the transmission band and the near-infrared light side stop band is 80%. Is 614 nm, the wavelength when the transmittance is 40% is 665 nm, and the difference between these absolute values (near infrared light side 40-80% wavelength difference) is 51 nm. Moreover, the near-infrared light side average shift amount is −7.8 nm.

  For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 416 nm, the near-infrared light side half-value wavelength is 653 nm, and the difference between these absolute values (half-value wavelength) Difference) is 237 nm. In addition, for the basic part, the ultraviolet light side half-value wavelength is 421 nm, the ultraviolet light side half-value wavelength shift amount is −7 nm, the near-infrared light side half-value wavelength is 672 nm, and the near-infrared light side half-value wavelength shift amount is −15 nm. For the part 312, the ultraviolet light side half-value wavelength is 405 nm, the ultraviolet light side half-value wavelength shift amount is −13 nm, the near-infrared light side half-value wavelength is 745 nm, and the near-infrared light side half-value wavelength shift amount is −37 nm. Moreover, about this near-infrared cut filter, by using together the stop-band prescription | regulation part, for example, the stop-band prescription | regulation part of Example 6 which is mentioned later, when incident angle (theta) is 0 degree, it is in the wavelength range of 400-700 nm. A transmission band with a maximum transmittance of 85% or more, a near-infrared light blocking band with a minimum transmittance of 1% or less in the wavelength range of 750 to 1000 nm, and a minimum transmission in at least a part of the wavelength range of 350 to 400 nm. An ultraviolet light side stop band having a rate of 1% or less can be formed.

(Example 3)
A near-infrared cut filter similar to Example 1 was used except that the configuration of the transmission band defining portion was changed to the configuration shown in Table 5. In Table 6, T _H1 , T _L1 , T _H1 / T _L1 of the basic part, T _H2 , T _L2 , and T _H2 / T _L2 of the adjusting part (adjusting part (1) + adjusting part (2)) are shown. Show.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 9 shows the result of the near infrared cut filter. 10 and 11 show the results when only the basic unit and the adjustment unit are provided, respectively.

  As shown in FIG. 9, for this near-infrared cut filter, when the incident angle θ is 0 degree, the transmittance in the band between the transmission band and the near-infrared light side stop band is 80%. Is 618 nm, the wavelength when the transmittance is 40% is 667 nm, and the difference between these absolute values (near infrared light side 40-80% wavelength difference) is 49 nm. The near-infrared light side average shift amount is −13.7 nm.

  For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 417 nm, the near-infrared light side half-value wavelength is 657 nm, and the difference between these absolute values (half-value wavelength) The difference is 240 nm. Further, for the basic part, the ultraviolet light side half-value wavelength is 428 nm, the ultraviolet light side half-value wavelength shift amount is -8 nm, the near-infrared light side half-value wavelength is 665 nm, and the near-infrared light side half-value wavelength shift amount is -14 nm. For the part 312, the ultraviolet light side half-value wavelength is 378 nm, the ultraviolet light side half-value wavelength shift amount is −10 nm, the near-infrared light side half-value wavelength is 780 nm, and the near-infrared light side half-value wavelength shift amount is −34 nm. Moreover, about this near-infrared cut filter, by using together the stop-band prescription | regulation part, for example, the stop-band prescription | regulation part of Example 6 which is mentioned later, when incident angle (theta) is 0 degree, it is in the wavelength range of 400-700 nm. A transmission band with a maximum transmittance of 85% or more, a near-infrared light blocking band with a minimum transmittance of 1% or less in the wavelength range of 750 to 1000 nm, and a minimum transmission in at least a part of the wavelength range of 350 to 400 nm. An ultraviolet light side stop band having a rate of 1% or less can be formed.

(Example 4)
A near-infrared cut filter similar to Example 1 was used except that the configuration of the transmission band defining portion was changed to the configuration shown in Table 7. In Table 8, T _H1 , T _L1 , T _H1 / T _L1 of the basic part, T _H2 , T _L2 , and T _H2 / T _L2 of the adjusting part (adjusting part (1) + adjusting part (2)) are shown. Show.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 12 shows the result of the near infrared cut filter. 13 to 15 show the results when only the basic unit, the adjustment unit (1), and the adjustment unit (2) are provided, respectively.

  As shown also in FIG. 12, for this near-infrared cut filter, when the incident angle θ is 0 degree, the transmittance in the band between the transmission band and the near-infrared light side stop band is 80%. Is 609 nm, the wavelength when the transmittance is 40% is 665 nm, and the difference in absolute value thereof (near infrared light side 40-80% wavelength difference) is 56 nm. The near-infrared light side average shift amount is -10.8 nm.

  For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 416 nm, the near-infrared light side half-value wavelength is 655 nm, and the difference between these absolute values (half-value wavelength) Difference) is 239 nm. Further, by using a stop band defining portion, for example, a stop band defining portion of Example 6 as described later, when the incident angle θ is 0 degree, the maximum transmittance is 85% or more in the wavelength range of 400 to 700 nm. A near-infrared light blocking band with a minimum transmittance of 1% or less in the wavelength range of 750 to 1000 nm, and an ultraviolet with a minimum transmittance of 1% or less in at least a part of the wavelength range of 350 to 400 nm. A light side stop band can be formed.

(Example 5)
A near-infrared cut filter similar to Example 1 was used except that the configuration of the transmission band defining portion was changed to the configuration shown in Table 9. In Table 10, T _H1 , T _L1 , T _H1 / T _L1 of the basic part, T _H2 , T _L2 , and T _H2 / T _L2 of the adjusting part (adjusting part (1) + adjusting part (2)) are shown. Show.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 16 shows the result of the near infrared cut filter. 17 and 18 show the results when only the basic unit and the adjustment unit are provided, respectively.

  As shown in FIG. 16, for this near-infrared cut filter, when the incident angle θ is 0 degree, the transmittance in the band between the transmission band and the near-infrared light side stop band is 80%. The wavelength when the transmittance is 620 nm and the transmittance is 40% is 664 nm, and the difference between these absolute values (near infrared light side 40-80% wavelength difference) is 44 nm. Moreover, the near-infrared light side average shift amount is −9.2 nm.

  For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 415 nm, the near-infrared light side half-value wavelength is 656 nm, and the difference between these absolute values (half-value wavelength) Difference) is 241 nm. Further, for the basic part, the ultraviolet light side half-value wavelength is 423 nm, the ultraviolet light side half-value wavelength shift amount is -7 nm, the near-infrared light side half-value wavelength is 656 nm, and the near-infrared light side half-value wavelength shift amount is -14 nm. For the part 312, the ultraviolet light side half value wavelength is 418 nm, the ultraviolet light side half value wavelength shift amount is −16 nm, the near infrared light side half value wavelength is 699 nm, and the near infrared light side half value wavelength shift amount is −32 nm. Moreover, about this near-infrared cut filter, by using together the stop-band prescription | regulation part, for example, the stop-band prescription | regulation part of Example 6 which is mentioned later, when incident angle (theta) is 0 degree, it is in the wavelength range of 400-700 nm. A transmission band with a maximum transmittance of 85% or more, a near-infrared light blocking band with a minimum transmittance of 1% or less in the wavelength range of 750 to 1000 nm, and a minimum transmission in at least a part of the wavelength range of 350 to 400 nm. An ultraviolet light side stop band having a rate of 1% or less can be formed.

  For this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 45 degrees were determined by optical simulation. FIG. 16 also shows the results of this near infrared cut filter. 17 and 18 also show the results when only the basic part and the adjustment part are provided, respectively. In comparison between the spectral transmittances of 0 degrees and 45 degrees, the basic portion is shifted in a relatively similar form, but the spectral transmittance waveform itself of the adjusting portion is greatly deformed. The near-infrared cut filter of Example 5 uses this to suppress a change in transmittance in a specific wavelength region (near 630 nm). That is, by doing so, it is possible to minimize the apparent wavelength shift in the specific wavelength region.

(Example 6)
The near-infrared cut filter has a transmission band defining portion on one main surface of the transparent substrate and a blocking band defining portion on the other main surface. Here, the transparent base material was colorless and transparent glass (manufactured by Schott, trade name: D263T, thickness: 0.3 mm). The configuration of the transmission band defining part was the same as the transmission band defining part of Example 5. The stop band defining portion was configured as shown in Table 11.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 19 shows the result of the near infrared cut filter. FIG. 20 shows the results when only the stop band defining portion is provided. Furthermore, FIG. 21 shows a comparison with the results of Example 9 described later.

  As shown in FIG. 19, for this near-infrared cut filter, when the incident angle θ is 0 degree, the transmittance in the band between the transmission band and the near-infrared light side stop band is 80%. Is 625 nm, the wavelength when the transmittance is 40% is 665 nm, and the difference between these absolute values (near infrared light side 40-80% wavelength difference) is 40 nm. Moreover, the near-infrared light side average shift amount is −9.1 nm. Further, as shown in FIG. 20, for the stopband defining part, when the incident angle θ is 0 degree, the ultraviolet light whose average transmittance is 5% or less in at least a part of the wavelength range of 350 to 400 nm. It has a near-infrared light side stop band in which the average transmittance is 3% or less in at least a part of the side stop band and the wavelength range of 800 to 1000 nm.

  For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 416 nm, the near-infrared light side half-value wavelength is 656 nm, and the difference between these absolute values (half-value wavelength) The difference is 240 nm. Further, when the incident angle θ is 0 degree, the near-infrared light having a maximum transmittance of 85% or more in the wavelength range of 400 to 700 nm and the minimum transmittance of 1% or less in the wavelength range of 750 to 1000 nm. An ultraviolet light side stop band having a minimum transmittance of 1% or less can be formed in at least a part of the side stop band and the wavelength range of 350 to 400 nm.

(Example 7)
A near-infrared cut filter similar to Example 1 was used except that the configuration of the transmission band defining portion was changed to the configuration shown in Table 12. Table 13 shows T _H1 , T _L1 , T _H1 / T _L1 of the basic part, T _H2 , T _L2 , and T _H2 / T _L2 of the adjustment part.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 22 shows the result of the near infrared cut filter. 23 and 24 show the results when only the basic part and the adjustment part are provided, respectively.

  As shown in FIG. 22, the near-infrared cut filter has a transmittance of 80% in the band between the transmission band and the near-infrared light side stop band when the incident angle θ is 0 degree. Is 613 nm, the wavelength when the transmittance is 40% is 669 nm, and the difference between these absolute values (near infrared light side 40-80% wavelength difference) is 56 nm. Moreover, the near-infrared light side average shift amount is -14.4 nm. For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 418 nm, the near-infrared light side half-value wavelength is 657 nm, and the difference between these absolute values (half-value wavelength) Difference) is 239 nm.

(Example 8)
A near-infrared cut filter similar to Example 1 was used except that the configuration of the transmission band defining portion was changed to the configuration shown in Table 14. Table 15 shows the basic parts T _H1 , T _M1 , T _H1 / T _M1 , the adjustment parts T _H2 , T _L2 , and T _H2 / T _L2 . Here, T _M1 is an average optical film thickness of a Ta ₂ O ₅ film (refractive index 2.2) as a medium refractive index film.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 25 shows the result of the near infrared cut filter.

  As shown also in FIG. 25, for this near infrared cut filter, when the incident angle θ is 0 degree, the transmittance in the band between the transmission band and the near infrared light side stop band is 80%. Is 618 nm, the wavelength when the transmittance is 40% is 668 nm, and the difference between these absolute values (near infrared light side 40-80% wavelength difference) is 50 nm. Further, the near infrared light side average shift amount is −16.1 nm. For the transmission band defining portion, when the incident angle θ is 0 degree, the half band wavelength on the ultraviolet side of the transmission band is 416 nm, the half band wavelength on the near infrared side is 659 nm, and the difference between these absolute values (half band wavelength) Difference) is 243 nm.

(Example 9)
The near-infrared cut filter has a transmission band defining portion on one main surface of the transparent substrate and a blocking band defining portion on the other main surface. Here, the transparent base material was near-infrared cut glass (Asahi Glass Co., Ltd., trade name: NF-50T, thickness: 0.26 mm). The transmission band defining portion and the stop band defining portion are configured as shown in Tables 16 and 17, respectively. The near-infrared cut filter uses a transparent substrate that absorbs near-infrared rays, and is provided with an optimal optical multilayer film for such a transparent substrate, which is suitable for a solid-state imaging device. It is an example of what has a characteristic.

  With respect to this near-infrared cut filter, the spectral transmittance when the incident angle θ was 0 degrees and the spectral transmittance when the incident angle θ was 30 degrees were determined by optical simulation. FIG. 26 shows the result of the near infrared cut filter.

  As shown also in FIG. 26, for this near-infrared cut filter, when the incident angle θ is 0 degree, the transmittance in the band between the transmission band and the near-infrared light side stop band is 80%. Is 596 nm, the wavelength when the transmittance is 40% is 662 nm, and the difference in absolute value (near infrared light side 40-80% wavelength difference) is 66 nm. Moreover, the near-infrared light side average shift amount is −5.6 nm. For the near-infrared cut filter, when the incident angle θ is 0 degree, the ultraviolet light side half-value wavelength of the transmission band is 416 nm, the near-infrared light side half-value wavelength is 646 nm, and the difference between these absolute values (half-value wavelength) The difference is 230 nm.

  The results are summarized in Table 18.

  According to the near-infrared cut filters of Examples 1 to 6, the near-infrared light side average shift can be made relatively large, while the near-infrared light side 40 to 80% wavelength difference serving as an index representing the smoothness of the transmittance change can be increased. The amount can be suppressed to a low value such as 14 nm or less. Thereby, it can be set as the characteristic close | similar to an ideal near-infrared cut off filter (absorption type colored glass filter) as shown in Example 9, for example. On the other hand, according to the near-infrared cut filter of Examples 7 and 8, the near-infrared light side 40-80% wavelength difference, which is an index indicating the smoothness of the transmittance change, can be relatively large, but the near-infrared light side The average shift amount exceeds 14 nm.

  DESCRIPTION OF SYMBOLS 1 ... Near-infrared cut filter, 2 ... Transparent substrate, 3 ... Optical multilayer film, 31 ... Transmission band prescription | regulation part, 5 ... Imaging device, 32 ... Stop band prescription | regulation part, 51 ... Solid-state image sensor, 52 ... Cover glass, 53 ... Lens group: 54 ... Aperture, 55 ... Housing, 311 ... Basic part, 312 ... Adjusting part

Claims (4)

A transparent substrate; and an optical multilayer film provided on at least one main surface of the transparent substrate and having a high refractive index film having a refractive index of 2.0 or more and a low refractive index film having a refractive index of 1.7 or less. A near-infrared cut filter,
The optical multilayer film is provided on one main surface of the transparent substrate, and the transmission band defining portion for mainly defining the shape of transparently strip, provided on the other main surface of the transparent substrate, a near-infrared light side the zone of inhibition and ultraviolet light side blocking band shape having a predominantly and stopband defining portion for defining,
The transmission band defining part has a basic part and an adjusting part provided on at least one main surface of the basic part,
The basic part has an alternate laminated structure of a high refractive index film for a basic part having a refractive index of 2.0 or more and a low refractive index film for a basic part having a refractive index of 1.7 or less. The total number of layers of the refractive index film and the basic portion low refractive index film is 10 or more, the average optical film thickness of the basic portion high refractive index film is T _H1 , and the average optical thickness of the basic portion low refractive index film is When the film thickness is T _L1 , T _H1 / T _L1 is 2 or more,
The adjusting portion is provided on one main surface or both main surfaces of the basic portion, and the adjusting portion high refractive index film having a refractive index of 2.0 or more and the adjusting portion low refraction having a refractive index of 1.7 or less. An average optical film of the high refractive index film for the adjustment part, the total number of layers of the high refractive index film for the adjustment part and the low refractive index film for the adjustment part being 10 or more. When the thickness is T _H2 and the average optical film thickness of the low refractive index film for adjusting part is T _L2 , T _H2 / T _L2 is 1.5 or less,
In spectral characteristics under normal incidence conditions, the transmission band has a maximum transmittance of 85% or more in at least part of the wavelength range of 400 to 700 nm, and the minimum transmittance is 1% or less in at least part of the wavelength range of 750 to 1000 nm. A near-infrared light side stop band, and an ultraviolet light side stop band having a minimum transmittance of 1% or less in at least part of the wavelength range of 350 to 400 nm, When the difference between the near-infrared light side half-value wavelength is 200 nm or more and the transmittance between the transmission band and the near-infrared light side stop band is 80% and the transmittance is 40% The difference in absolute value with respect to the wavelength is 20 to 100 nm, and the transmittance between the transmission band and the near-infrared light side stop band is 20 to 20 in comparison of the spectral characteristics between the normal incidence condition and the 30 degree incidence condition. The absolute value of the part that becomes 80% Near infrared cut filter, wherein a mean wavelength shift amount is 14nm or less. The near-infrared cut filter according to claim 1,
The transmission band defining portion is configured such that, in the spectral characteristics under normal incidence conditions and 30 degree incidence conditions, the half-value wavelength on the ultraviolet side of the adjustment unit is closer to the ultraviolet side than the half-value wavelength on the ultraviolet side of the basic unit. The half-value wavelength is on the infrared side than the infrared side half-value wavelength of the basic part,
A near-infrared cut filter in which the difference in absolute value between the infrared half-value wavelength of the adjustment unit and the infrared half-value wavelength of the basic unit is 20 nm or more in the spectral characteristics under normal incidence conditions. The near-infrared cut filter according to claim 1 or 2,
The stopband defining portion has an ultraviolet light side stopband having an average transmittance of 5% or less in at least a part of a wavelength range of 350 to 400 nm and a wavelength range of 800 to 1000 nm in spectral characteristics under normal incidence conditions. A near-infrared cut-off filter having a near-infrared light side blocking band having an average transmittance of 3% or less at least partially. In the near-infrared cut filter according to any one of claims 1 to 3,
The high refractive index film is made of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , or a complex oxide thereof, and the low refractive index film is made of SiO ₂ , MgF ₂ , Al ₂ O ₃ , or these Near-infrared cut filter made of complex oxide.

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