JP6247033B2 - IR cut filter - Google Patents

Description

  The present invention relates to an infrared (IR) cut filter, and more particularly to an IR cut filter formed by an IR cut dielectric multilayer filter layer in which the dependence of the optical characteristics of light rays on the incident angle is reduced.

  Camera modules used in optical devices such as cameras, copiers, and printers are composed of lenses and sensors, and have recently been reduced in height because they are used in smartphones, tablets, and the like.

  FIGS. 1A and 1B are schematic views of a general configuration of this camera module. In FIG. 1B, the camera module 110 shows a case where the camera module 100 shown in FIG. 1A is reduced in height, and the camera modules 100 and 110 include lenses 101 and 111 and an IR cut filter, respectively. 102 and 112 and sensors 103 and 113 are provided. In FIGS. 1 (a) and 1 (b), IR cut filters 102 and 112 are components arranged between lenses 101 and 111 and sensors 103 and 113, respectively, and emit infrared rays that cannot be detected by human eyes. There is an action to block. Without the IR cut filters 102 and 112, light including infrared rays is detected by the sensors 101 and 111 and appears as a red image, and the color reproducibility of the image is impaired.

  A general IR cut filter used for a camera module is created by coating a substrate (glass or resin) with a dielectric multilayer film, and classified as A type or B type as shown below. Is done.

  FIGS. 2A and 2B are schematic diagrams showing the configuration of a general IR cut filter. As shown in FIG. 2 (a), the IR cut filter (A type) 200 is configured by coating IR cut filter layers 202 and 203 on both surfaces of a glass 201, and the IR shown in FIG. 2 (b). The cut filter (B type) 210 is configured by coating an IR cut filter layer 212 on one side of a glass 211 and coating an antireflection (AR) filter layer 213 on the other side of the glass 211. The B type has an effect that the AR surface has an effect of suppressing reflection more than the IR cut filter at a specific wavelength, and is used in a camera module in which harmful effects caused by reflected light are particularly important. Hereinafter, the A type IR cut filter will be described.

  FIG. 3 shows optical characteristics of a general IR cut filter. In FIG. 3, in the optical characteristic 300, the horizontal axis indicates the wavelength of light (unit: nm), and the vertical axis indicates the transmittance (unit:%). The optical characteristic 300 indicates, for each wavelength, what percentage of light passes through the IR filter when the light passes through the IR filter. The optical characteristic 300 shows the characteristic when the incident angle of light is perpendicular to the glass (IR cut filter).

  As an IR cut filter that transmits the visible band and blocks the near-infrared band, a multilayer in which high-refractive index material films and low-refractive index material films are alternately stacked with an optical film thickness that is ¼ of the design center wavelength λ. An IR cut filter having a film configuration is known.

  However, in such an IR cut filter, the 50% transmission wavelength (half-value wavelength) between the transmission band and the stop band tends to shift to the short wavelength side as the incident angle of the light beam increases. In particular, the smaller the apparent refractive index of the entire IR cut filter, the more the half-value wavelength shift amount increases. When such an IR cut filter is used in an optical apparatus, a problem of color unevenness due to a difference in incident angle of light occurs.

  4A and 4B are schematic views of the IR cut filter when the incident angle is changed, and FIG. 5 shows optical characteristics of the IR cut filter when the incident angle is changed. 4A, the IR cut filter 400 schematically shows a case where the incident angle is vertical, and the IR cut filter 410 shown in FIG. 4B schematically shows a case where the incident angle is 45 °. Is shown. As shown in FIG. 5, in a general IR cut filter, the optical characteristic shifts to the short wavelength side when the incident angle is greatly inclined as viewed from the vertical. This shows that the wavelength that should normally be transmitted is not transmitted. In addition, due to the recent reduction in the height of camera modules, the incident angle to the IR cut filter has increased, and this phenomenon has become prominent. Reducing the amount of wavelength shift with respect to the incident angle has led to recent IR cuts. It has become a filter issue.

  In order to solve the above-described problem, there is a method in which alternating layers of a high refractive index material and an intermediate refractive index material are used as a material in the IR cut filter. Such a cut filter is described in Patent Document 1 and Patent Document 2, for example.

JP 2007-183525 A Japanese Patent Laid-Open No. 11-202127

However, in Patent Document 1 and Patent Document 2, an intermediate refractive index material such as Al ₂ O ₃ , ZrO ₂ , and la ₂ O ₃ is used as the material. The intermediate refractive index material and the high refractive index used at this time are used. Depending on the combination of materials, film thickness, film forming method, and the like, there are problems such as the generation of cracks in the film, and it is difficult to stably produce a multilayer film.

  In addition, the film formed with this configuration has a problem that the degree of freedom in design is low because the stop band is determined by the refractive index ratio between the high refractive index material and the intermediate refractive index material.

  Therefore, the object of the present invention is to reduce the half-value wavelength shift when the incident angle of light increases, which is unsolved in the above-mentioned prior art, and uses only a high refractive index material and a low refractive material. An IR cut filter is provided.

In order to solve the above problems, an IR cut filter of the present invention is a transparent substrate and an ultrathin film that is formed on one side of the substrate and has a film thickness of λ / 10 or less of the design center wavelength, and has a wavelength of 550 nm. high refractive index material film having a refractive index of the to light is 2.0 or more, and, a said ultra-thin, 3 of the low refractive index material film having a refractive index of from 1.3 to 1.6 for the wavelength 550nm Alternating layer structure composed of alternating layers of odd or more layers and the above high refractive index material film having a normal film thickness of λ / 2 to λ / 4 of the design center wavelength are alternately stacked. or, alternatively, the above low refractive index material film of the ultra-thin film, comprising the ultra-thin alternating layers of alternately laminated said high refractive index material film having a film thickness of the normal, and the first IR cut filter layer, Formed on the surface of the substrate opposite to the first IR cut filter layer. Characterized in that it comprises the ordinary film thickness the high refractive index material film, and a second IR cut filter layer of alternately laminated said low refractive index material film having a thickness of the normal.

  In addition, the first IR cut filter layer further includes a low-refractive index material film having a normal thickness and a high-refractive index material film having a normal thickness alternately on the glass substrate side of the ultrathin alternating layer. It is good also as a thing further provided with the adjustment layer laminated | stacked on.

  Further, the blocking region of the first IR cut filter layer and the blocking region of the second IR cut filter layer may be overlapped so as to block the infrared region as a whole.

Also includes the high refractive index material is _{TiO 2,} Nb ₂ O 5, either of _Ta 2 _{O 5,} or _{TiO 2,} Nb ₂ O 5, _Ta 2 composite oxide mainly containing any of _{O 5} , the low refractive index material is SiO _2, or may be one containing a composite oxide of SiO _2.

  According to the present invention, the alternating layer of the ultra thin film is composed of three or more odd layers, and when the ultra thin film alternating layer is defined as the ultra thin film alternating layer structure, the ultra thin film alternating layer structure and the normal film thickness By forming an IR cut filter with alternating layers of high refractive index material film, or with alternating layers of ultra-thin low refractive index material film and normal high refractive index material film, It is possible to provide an IR filter with little change in optical characteristics and high surface quality due to a change in angle.

(A), (b) is a schematic diagram of the structure of a general camera module, respectively. (A), (b) is a schematic diagram of the structure of a general IR cut filter, respectively. It is a figure which shows the optical characteristic of a general IR cut filter. (A), (b) is a schematic diagram of the IR cut filter when the incident angle is changed. It is a figure which shows the optical characteristic of IR cut filter when an incident angle is changed. It is a figure which shows the structure of IR cut filter which concerns on one Embodiment of this invention. It is a figure which shows the optical characteristic of the low angle dependence IR cut filter layer of the IR cut filter which concerns on Example 1 of this invention. It is a figure which shows the optical characteristic of the stop area adjustment IR cut filter layer of the IR cut filter which concerns on Example 1 of this invention. It is a figure which shows the optical characteristic of the whole IR cut filter which concerns on Example 1 of this invention. It is a figure which shows the optical characteristic of the low angle dependence IR cut filter layer of the IR cut filter which concerns on Example 2 of this invention. It is a figure which shows the optical characteristic of the stop area adjustment IR cut filter layer of the IR cut filter which concerns on Example 2 of this invention. It is a figure which shows the optical characteristic of the whole IR cut filter which concerns on Example 2 of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 6 is a diagram showing a configuration of an IR cut filter according to an embodiment of the present invention.

  In FIG. 6, the IR cut filter 600 includes a glass substrate 610, a stop band adjusting IR cut filter layer 620 coated on one surface thereof, and a low angle dependent IR cut filter layer 630 coated on the opposite surface thereof. It has. It should be noted that the inhibition zone adjusting IR cut filter layer 620 and the low angle dependent IR cut filter layer 630 have the same effect regardless of which side is disposed with respect to the light source.

  The glass substrate 610 is a substrate made of optical glass such as BK7, and is not limited to glass but can be used as a resin.

  The stop band adjusting IR cut filter layer 620 includes a low refractive index material film 621 having a film thickness of λ / 4 to λ / 2 of a design center wavelength which is a normal film thickness, and a high refractive index material having a normal film thickness. It is composed of alternating layers with the film 622. As can be seen from FIGS. 7, 8, and 9, which will be described later, the stop band adjusting IR cut filter layer 620 is light in the infrared (IR) region (stop band) among the entire optical characteristics of the IR cut filter 600. Has the effect of blocking.

  The low angle-dependent IR cut filter layer 630 includes an adjustment layer 631, an ultrathin film alternate layer 634, and a normal film thickness alternate layer 638 from the glass substrate 610 side. The adjustment layer 631 is composed of alternating layers of a low refractive index material film 632 having a normal film thickness and a high refractive index material film 633 having a normal film thickness. The adjustment layer 631 has an effect of flattening the characteristics in the visible light region out of the entire optical characteristics of the IR cut filter 600.

  The ultra-thin alternating layer 634 includes a plurality of (single) alternating ultra-thin alternating layer structures composed of alternating layers of high-refractive-index material films 637 having a normal film thickness and three or more odd-numbered ultra-thin layers. It is constructed by laminating. The ultra-thin alternating layer structure has three or more layers of an ultra-thin low-refractive index material film 635 and a ultra-thin high-refractive index material film 636 having a film thickness of λ / 10 or less, which is thinner than the normal film thickness. It consists of an odd number of alternating layers. The ultra-thin alternating layer 634 has an effect of reducing the half-wavelength shift when the incident angle of the light beam is increased by the alternating layers of the ultra-thin alternating layer structures 635 and 636 and the high refractive index material 637. Note that the same effect can be obtained by using an ultrathin alternating layer 634 in which an ultrathin low refractive index material film and a normal high refractive index material film are alternately laminated.

  The normal film thickness alternating layer 638 is composed of an alternating layer of a low refractive index material film 639 having a normal film thickness and a high refractive index material film 640 having a normal film thickness.

The high refractive index material includes TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , or a composite oxide containing TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ as a main component. The low refractive index material includes SiO ₂ or a composite oxide of SiO ₂ . Further, the high refractive index material has a refractive index of 2.0 or more for light having a wavelength of 550 nm, and the low refractive index material has a refractive index of 1.3 to 1.6 for a wavelength of 550 nm. The refractive index material has a refractive index in between. Here, the normal film thickness indicates a film thickness from λ / 4 to λ / 2 of the design center wavelength, and the ultrathin film indicates a film thickness of λ / 10 or less of the design center wavelength.

[Example 1]
Next, specific examples will be described.

In the first embodiment, among the configurations of the IR cut filter 600 shown in FIG. 6 described above, the low refractive index materials 621, 632, 635, and 639 are made of SiO ₂ , and the high refractive index materials 622, 633, 636, 637, and 640 are made of TiO 2. _The normal film thickness is set from λ / 4 to λ / 2 of the design center wavelength, and the ultrathin film is set to λ / 10 or less.

  FIG. 7 is a diagram illustrating the optical characteristics of the low-angle-dependent IR cut filter layer 630 of the IR cut filter according to the first embodiment of the present invention, and FIG. 8 is a block diagram of the IR cut filter according to the first embodiment of the present invention. FIG. 9 is a diagram showing optical characteristics of the IR cut filter 600 according to Example 1 of the present invention.

  As can be seen from FIGS. 7, 8, and 9, the low angle-dependent IR cut filter layer 630 has the effect of reducing the half-wavelength shift when the incident angle of the light beam is increased. The layer 620 has an effect of blocking light in the infrared (IR) region (stop region), and as a whole, an IR filter with little change in optical characteristics accompanying a change in incident angle can be provided. Recognize.

[Example 2]
In the second embodiment, among the configurations of the IR cut filter 600 shown in FIG. 6, the low refractive index materials 621, 632, 635, and 639 are made of SiO ₂ , and the high refractive index materials 622, 633, 636, 637, and 640 are made of Nb. ₂ O ₅ , the normal film thickness is set from the design center wavelength λ / 4 to λ / 2, and the ultrathin film is set to λ / 10 or less.

  FIG. 10 is a diagram illustrating optical characteristics of the low-angle-dependent IR cut filter layer 630 of the IR cut filter according to the second embodiment of the present invention, and FIG. 11 is a block diagram of the IR cut filter according to the second embodiment of the present invention. FIG. 12 is a diagram illustrating optical characteristics of the region adjustment IR cut filter layer 620, and FIG. 12 is a diagram illustrating optical characteristics of the entire IR cut filter 600 according to Example 2 of the present invention.

  As can be seen from FIG. 10, FIG. 11, and FIG. 12, the low angle dependent IR cut filter layer 630 has the effect of reducing the half-wavelength shift when the incident angle of the light beam increases, and the stopband adjustment IR cut. The filter layer 620 has an effect of blocking light in the infrared (IR) region (stopping region), and can provide an IR filter that has little change in optical characteristics due to a change in incident angle as a whole. I understand.

  As described above, according to the present invention, when the alternating layers of the ultra-thin layer are composed of three or more odd layers, and the ultra-thin alternating layer is defined as the ultra-thin alternating layer structure, the ultra-thin alternating layer structure And an IR cut filter with alternating layers of high refractive index material with normal film thickness, or with alternating layers of low refractive index material film with ultra-thin film and high refractive index material film with normal film thickness By doing so, it is possible to provide an IR filter with little change in optical characteristics and high surface quality due to change in incident angle.

600 IR cut filter 610 Glass substrate 620 Stop zone adjustment IR cut filter layer 621, 632, 639 Low refractive index material film 622, 633, 637, 640 High refractive index material film 630 Low angle dependent IR cut filter layer 631 Adjustment layer 634 Super Thin film alternating layer 635 Ultra thin film low refractive index material film 636 Ultra thin film high refractive index material film 638 Normal film thickness alternating layer

Claims (4)

A transparent substrate,
Is formed on one surface of the substrate, a super-thin film with a thickness of lambda / 10 or less of the design center wavelength, the high refractive index material film having a refractive index of the wavelength of 550nm to light is 2.0 or more, and, the An ultra-thin film , an ultra-thin alternating layer structure composed of alternating layers of three or more odd layers of a low-refractive index material film having a refractive index with respect to a wavelength of 550 nm of 1.3 to 1.6, and a design center Did the usual film the high refractive index material film having a thickness which is the thickness of lambda / 4 from the lambda / 2 wavelength alternately laminated, or the said low refractive index material film ultrathin, of the normal including ultra-thin alternating layers of alternately laminated said high refractive index material film having a thickness, a first IR cut filter layer,
It is formed on the opposite side of the first IR cut filter layer of the substrate, wherein a normal of the film the high refractive index material layer having a thickness, the thickness of the normal said low refractive index material film alternately An IR cut filter comprising: a laminated second IR cut filter layer. The first IR cut filter layer further wherein said normal membrane the low refractive index material film having a thickness on the glass substrate side of the ultra-thin alternating layers, and the high refractive index material film having a thickness of the normal The IR cut filter according to claim 1, further comprising an adjustment layer in which are alternately stacked.   2. The IR cut according to claim 1, wherein the stop region of the first IR cut filter layer and the stop region of the second IR cut filter layer overlap each other and are set so as to block the infrared region as a whole. filter. The high refractive index material includes TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , or a composite oxide containing TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ as a main component, _2. The IR cut filter according to claim 1, wherein the low refractive index material includes SiO ₂ or a composite oxide of SiO ₂ .

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