JP2020122970A - Optical filter and imaging element using optical filter - Google Patents

Abstract

To provide an optical filter with which a difference between 0° incidence transmittance and high angle incidence transmittance is small and the angular field of view is wide, and which excels in a near-infrared cut rate.SOLUTION: Provided is an optical filter having a transparent substrate and satisfying conditions (i) to (iii) below: (i) T, Tand Tall are 75% or greater, (ii) T>Tand T>Thold true, (iii) X is a numeral in the range 5 to 40, where it is assumed, with respect to one side of the optical filter, that the average transmittance of wavelengths 450-550 nm when measured from the vertical direction is T(%), the average transmittance of wavelengths 450-550 nm when measured from a 45° position from the vertical direction is T(%), and the average transmittance of wavelengths 450-550 nm when measured from an X° position from the vertical direction is T(%).SELECTED DRAWING: Figure 4

Description

The present invention relates to an optical filter. More specifically, the present invention relates to an optical filter having a sufficient viewing angle, which can be suitably used as a visibility correction filter for a solid-state image sensor such as a CCD or a CMOS image sensor, and an image sensor including the optical filter.

CCDs and CMOS image sensors, which are solid-state image pickup devices for color images, are used in video cameras, digital still cameras, mobile phones with camera functions, etc. These solid-state image pickup devices are sensitive to near infrared rays in their light receiving parts. Silicon photodiodes are used. In these solid-state image sensors, it is necessary to perform luminosity correction to make the color look natural to the human eye, and an optical filter that selectively transmits or cuts light rays in a specific wavelength range (for example, near-infrared cutoff). Filter) is often used.

As such an optical filter, those manufactured by various methods have been conventionally used. For example, it is practical to deposit a metal such as silver on the surface of a transparent substrate such as glass to reflect near infrared rays, or to add a near infrared absorbing dye to a transparent resin such as an acrylic resin or a polycarbonate resin. Have been offered to.

In recent years, there has been an increasing demand for thinner optical components, which has been 0.3 mm in the past, but recently, a thinner filter having a thickness of 0.2 mm or less has begun to be used. Along with this, it is required that the transmittance at a high incident angle does not significantly change from the transmittance at a low incident angle in addition to having a sufficient shielding effect even if it is thin.

Patent Document 1 discloses a near-infrared cut filter having a thickness of 0.15 mm, which uses CuO-containing phosphate glass, but the shielding property at a wavelength of 800 to 1200 nm was not sufficient.

Patent Document 2 discloses a near-infrared cut filter that has both thinness and shielding transmittance characteristics at wavelengths of 800 to 1200 nm by providing a dielectric multilayer film on CuO-containing fluorophosphate glass. However, in the near-infrared cut filter of Patent Document 2, although the transmittance measured from the vertical direction (hereinafter also referred to as “0° incident transmittance”) is good, as the incident angle becomes high at 40° to 45°, The transmittance at wavelengths of 450 to 550 nm decreased, and it could not be said that the viewing angle was sufficient.

Further, in Patent Document 3, a transparent resin is used as a base material, and a near-infrared absorbing substrate in which a near-infrared absorbing dye is contained in the transparent resin and a near-infrared reflecting film formed of a dielectric multilayer film are provided. A near infrared cut filter excellent in is disclosed. However, the near-infrared cut filter of Patent Document 3 also has an excellent viewing angle with respect to visible light with a wavelength of 450 to 550 nm, although it has an excellent viewing angle with a wavelength corresponding to red with a wavelength of 560 to 800 nm.

International Publication No. 2011/118724 pamphlet (Patent Document 1) International Publication No. 2014/104370 Pamphlet (Patent Document 2) Japanese Patent No. 5489669 (Patent Document 3)

In view of the above-mentioned conventional technique, the present invention provides an optical filter having a small difference between 0° incident transmittance and high-angle incident transmittance, a wide viewing angle, and an excellent near-infrared ray cutting ability, and an image sensor including the optical filter. The purpose is to provide.

The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have specific optical characteristics, specifically, by using a specific transparent base material or a specific dielectric multilayer film, 0° The present invention has been completed by finding that an optical filter with a small change in optical characteristics can be obtained in the range of up to 45° and the above-mentioned problems can be solved. The example of the aspect of this invention is shown below.

[1] An optical filter having a transparent substrate, wherein one surface of the optical filter has an average transmittance of T ₀ (%) at a wavelength of 450 to 550 nm when measured from the vertical direction, and is 45 from the vertical direction. T ₄₅ (%) is the average transmittance at wavelengths 450 to 550 nm when measured from the position of °, and T _X (%) is the average transmittance at wavelengths 450 to 550 nm when measured from the position of X° from the vertical direction. In the case of, an optical filter satisfying the following conditions (i) to (iii):
(I) All of T ₀ , T ₄₅ and T _X are 75% or more;
(Ii) T _X >T ₀ and T _X >T ₄₅ ;
(Iii) X is a number of 5 or more and 40 or less.

[2] A dielectric layer made of a high refractive index material having a refractive index of 2.0 or more and a dielectric layer made of a low refractive index material having a refractive index of less than 2.0 on at least one surface of the transparent substrate. The optical filter according to item [1], which has a functional film formed of a dielectric multilayer film including:

[3] When the total optical film thickness of the dielectric layer made of the high refractive index material is Hd (nm), and the total optical film thickness of the dielectric layer made of the low refractive index material is Ld (nm) The optical filter according to item [2], wherein Hd/Ld is in a range of 0.900 to 0.998 at a wavelength of 550 nm.

[4] The optical filter according to any one of items [1] to [3], which further satisfies the following conditions (A) to (C):
(A) T ₀ is 80% or more;
(B) In the wavelength region of 800 nm or less, the longest wavelength (Xa) at which the transmittance is 70% when measured from the vertical direction of the optical filter, and in the wavelength region of 580 nm or more, measured from the vertical direction of the optical filter. The absolute value of the difference from the shortest wavelength (Xb) at which the transmittance is 30% is less than 100 nm;
(C) In the wavelength region of 560 to 800 nm, the value of the wavelength (Ya) at which the transmittance is 50% when measured from the vertical direction of the optical filter, and the angle of 30° with respect to the vertical direction of the optical filter In this case, the absolute value of the difference from the wavelength value (Yb) at which the transmittance is 50% is less than 15 nm.

[5] The optical filter according to any one of items [1] to [4], which has an average transmittance of 1% or less at a wavelength of 300 to 380 nm when measured in the vertical direction.

[6] The optical filter according to any one of items [1] to [5], wherein the transparent substrate has a thickness of 40 to 200 μm.

[7] The optical filter according to any one of items [1] to [6], which has the functional film on both surfaces of the transparent substrate.

[8] The transparent substrate contains a transparent resin containing an absorber having an absorption maximum in a wavelength region of 600 to 800 nm, and the transmittance of the transparent substrate is 50% in a wavelength region of 620 to 680 nm. The optical filter according to any one of items [1] to [7].

[9] The transparent substrate contains a near-infrared absorbing glass selected from the group consisting of CuO-containing phosphate glass and CuO-containing fluorophosphate glass, and in the wavelength region of 620 to 680 nm, the transparent substrate The optical filter according to any one of items [1] to [7], wherein the optical filter has a transmittance of 50%.

[10] The optical filter according to item [9], wherein the transparent substrate further contains a transparent resin layer containing an absorber having an absorption maximum in a wavelength region of 600 to 800 nm.

[11] The optical filter according to any one of items [1] to [10], which has an average transmittance of 1% or less at a wavelength of 800 to 1200 nm when measured in the vertical direction.

[12] An image pickup device comprising the optical filter according to any one of items [1] to [11].

According to the present invention, it is possible to provide an optical filter having a wide viewing angle with little change in transmittance at high incident angles.

FIG. 1(a) shows a conventional camera module. FIG. 1B shows an example of a camera module when the optical filter 6'of the present invention is used. FIG. 2 shows a method of measuring the transmittance when measured from the vertical direction of the optical filter. FIG. 3 shows a method for measuring the transmittance when measured from the angle of X° with respect to the vertical direction of the optical filter. FIG. 4 shows the transmittance measurement results when only the functional film (1) formed in Example 1 or the like was provided on silica glass. FIG. 5 shows the transmittance measurement results when only the functional film (2) formed in Comparative Example 1 was provided on silica glass. FIG. 6 shows the transmittance measurement results of the optical filter obtained in Example 1.

Hereinafter, the present invention will be specifically described.

<Optical filter>
The optical filter of the present invention has a transparent base material, and one surface of the optical filter has an average transmittance of T ₀ (%) at a wavelength of 450 to 550 nm when measured from the vertical direction, and is 45 from the vertical direction. T ₄₅ (%) is the average transmittance at wavelengths 450 to 550 nm when measured from the position of °, and T _X (%) is the average transmittance at wavelengths 450 to 550 nm when measured from the position of X° from the vertical direction. In this case, the following conditions (i) to (iii) are satisfied.
(I) All of T ₀ , T ₄₅ , and T _X are 75% or more.
(Ii) T _X >T ₀ and T _X >T ₄₅ .
(Iii) X is a number of 5 or more and 40 or less.

In the present invention, an optical filter having a high transmittance at a wavelength of 450 to 550 nm can be obtained by using a transparent substrate having a high total light transmittance.

When the optical filter is used as a filter for luminosity correction in a lens unit such as a solid-state imaging device or a camera module, the average value of the transmittance at wavelengths of 450 to 550 nm is in the above range and is preferably constant.

It is preferable that the average value of the transmittance is high. When the average value of the transmittance is high, the intensity of light passing through the filter is sufficiently secured, and it can be suitably used for the above-mentioned applications. On the other hand, if the average value of the transmittance is low, the intensity of the light passing through the filter may not be sufficiently secured, and it may not be suitable for the above-mentioned applications.

The above T ₀ is preferably 75% or more, more preferably 80% or more, further preferably 85% or more, and the higher one is suitable.

The T ₄₅ is preferably 75% or more, more preferably 80% or more, still more preferably 85% or more, and the higher the T ₄₅ is, the more preferable.

The above T _X is preferably 75% or more, more preferably 80% or more, further preferably 85% or more, and the higher one is suitable.

X is more preferably 10 or more and 35 or less, further preferably 15 or more and 35 or less, and if X is in this range, the viewing angle becomes extremely wide.

The optical filter of the present invention comprises a dielectric layer made of a high refractive index material having a refractive index of 2.0 or more and a low refractive index material having a refractive index of less than 2.0 on at least one surface of the transparent substrate. It is preferable to have a functional film formed of a dielectric multilayer film including the dielectric layer.

In the functional film, the total optical film thickness of each dielectric layer made of a high refractive index material is Hd (nm), and the total optical film thickness of each dielectric layer made of a low refractive index material is Ld (nm). In such a case, at a wavelength of 550 nm, Hd/Ld is preferably 0.900 to 0.998, more preferably 0.900 to 0.990, and still more preferably 0.900 to 0.980. With such a ratio, the functional film has a small difference between the transmittance of light of 450 to 550 nm incident in the vertical direction and the transmittance of light of 450 to 550 nm incident at a high angle.

By providing the functional film, an optical filter satisfying the conditions (ii) and (iii) can be preferably obtained. By satisfying the conditions (ii) and (iii), it is possible to increase the 0° incident transmittance, the X° incident transmittance, and the 45° incident transmittance. Further, when it is used as an optical filter of an image pickup device, the change in tint corresponding to green when the incident angle is changed is small, and the optical filter has a wide viewing angle.

On the other hand, when a functional film is provided so that T ₀ becomes higher than T _X and T ₄₅ , the transmittance generally decreases as the incident angle becomes higher, and T ₀ >T _X >T ₄₅ . In this case, T ₄₅ is significantly smaller than T ₀ , and when it is used as an optical filter of an image sensor, the change in color becomes large depending on the incident angle and the viewing angle becomes narrow.

The optical filter of the present invention preferably further satisfies the following conditions (A) to (C).

(A) T ₀ is 80% or more, preferably 82% or more, and more preferably 85% or more.

(B) In the wavelength region of 800 nm or less, the longest wavelength (Xa) at which the transmittance is 70% when measured from the vertical direction of the optical filter, and in the wavelength region of 580 nm or more, measured from the vertical direction of the optical filter. In this case, the absolute value of the difference from the shortest wavelength (Xb) at which the transmittance is 30% is less than 100 nm, more preferably 75 nm or less, still more preferably 70 nm or less.

If the absolute value of the difference between (Xa) and (Xb) of the optical filter is within the above range, the transmittance will change abruptly between the wavelengths (Xa) and (Xb) in the vicinity of the near infrared wavelength range. Therefore, when it is used for an image pickup device, it is possible to efficiently cut near infrared rays and efficiently take in light corresponding to red.

(C) In the wavelength range of 560 to 800 nm, the wavelength value (Ya) at which the transmittance is 50% when measured in the vertical direction of the optical filter, and the angle of 30° with respect to the vertical direction of the optical filter In this case, the absolute value of the difference from the wavelength value (Yb) at which the transmittance is 50% is less than 15 nm, more preferably less than 13 nm, further preferably less than 10 nm.

Since the absolute value of the difference between (Ya) and (Yb) of the optical filter is within the above range, when the optical filter is used as an image sensor, a change in tint corresponding to red when the incident angle is changed. And an optical filter with a wide viewing angle can be obtained.

In the present invention, as the transparent substrate, a transparent resin substrate made of a transparent resin containing an absorber having an absorption maximum in the wavelength region of 600 to 850 nm, or a CuO-containing phosphate glass and a CuO-containing fluorophosphate glass is used. An optical filter satisfying the above condition (C) can be obtained by using a near-infrared absorbing glass selected from the group consisting of or a transparent substrate containing a material obtained by combining them. Further, by using such a transparent base material, the transmittance of the transparent base material becomes 50% at any point in the wavelength region of 620 to 680 nm.

In the optical filter of the present invention, the average transmittance at a wavelength of 300 to 380 nm when measured from the vertical direction is preferably 1% or less, more preferably 0.5% or less, still more preferably 0.1% or less. In the present invention, by using a transparent substrate made of a transparent resin containing an ultraviolet absorber that absorbs the ultraviolet rays having a wavelength of 300 to 380 nm, or having a functionality having an optical film thickness that cuts the ultraviolet rays having a wavelength of 300 to 380 nm. By providing the film, an optical filter having an average transmittance at a wavelength of 300 to 380 nm in the above range can be suitably obtained.

Since the average transmittance at wavelengths of 300 to 380 nm is in the above range, when an optical filter is used as an image sensor, the sensor can sufficiently block ultraviolet rays that are invisible to the human eye while reacting, and thus the blue color Suitable for taste.

In the optical filter of the present invention, the thickness of the transparent substrate is preferably 40 to 200 μm, more preferably 40 to 180 μm, still more preferably 40 to 150 μm.

When the thickness of the optical filter is within the above range, the optical filter can be made smaller and lighter, and can be suitably used for various applications such as a solid-state imaging device. Especially when it is used for a lens unit such as a camera module, the height of the lens unit can be reduced.

The optical filter of the present invention preferably has the functional film on both sides of a transparent substrate. By providing the functional films on both surfaces, warpage can be suppressed, and when used in a lens unit such as a camera module, the height of the lens unit can be reduced. Further, since reflection of the optical filter can be reduced, it is possible to suppress ghost when provided in the image pickup device.

In the optical filter of the present invention, the average transmittance at a wavelength of 800 to 1200 nm when measured from the vertical direction is preferably 1% or less, more preferably 0.5% or less, further preferably 0.1% or less. In the present invention, by using a transparent substrate having a near-infrared absorbing glass made of CuO-containing phosphate glass or CuO-containing fluorophosphate glass that absorbs near-infrared rays having the wavelength of 800 to 1200 nm, or By providing a functional film having an optical film thickness that cuts near infrared rays of 800 to 1200 nm, an optical filter having an average transmittance of 800 to 1200 nm in the above range can be suitably obtained.

Since the average transmittance at a wavelength of 800 to 1200 nm is in the above range, when an optical filter is used for an image sensor, the sensor can sufficiently cut near infrared rays that are invisible to the human eye while reacting, and the red Suitable for color.

<Transparent substrate>
The transparent substrate used in the present invention is not particularly limited as long as it does not impair the effects of the present invention, but transparent resin, silicate glass, quartz, alumina glass, sapphire glass, phosphate glass, fluorophosphate glass. Etc. are preferred, and may be a single layer or multiple layers, and a plurality of materials may be combined. As the phosphate glass and the fluorophosphate glass, CuO-containing phosphate glass and CuO-containing fluorophosphate glass are preferable.

The total light transmittance of the transparent substrate at a thickness of 0.1 mm is preferably 75 to 94%, more preferably 78 to 94%, and further preferably 80 to 94%. When the total light transmittance is within such a range, the transparent substrate shows good transparency.

<Transparent resin>
The transparent resin used in the present invention is not particularly limited as long as it does not impair the effects of the present invention. For example, it is possible to secure thermal stability and moldability to a film, and to obtain a vapor deposition temperature of 100°C or higher. A resin having a glass transition temperature (Tg) of preferably 110 to 380° C., more preferably 110 to 370° C., and further preferably 120 to 360° C. in order to obtain a film capable of forming a dielectric multilayer film by high temperature vapor deposition. Can be used. Further, when the glass transition temperature of the transparent resin is preferably 120° C. or higher, more preferably 130° C. or higher, further preferably 140° C. or higher, a film capable of vapor deposition forming a dielectric multilayer film is obtained. To be

Examples of such transparent resin include cyclic olefin resin such as norbornene resin, polyarylate resin (PAR), polysulfone resin (PSF), polyether sulfone resin (PES), polyparaphenylene resin (PPP), Polyarylene ether phosphine oxide resin (PEPO), polyimide resin (PPI), polyetherimide resin (PEI), polyamideimide resin (PAI), (modified) acrylic resin, polycarbonate (PC), polyethylene naphthalate (PEN), Mention may be made of organic-inorganic nanohybrid materials.

<CuO-containing phosphate glass>
The CuO-containing phosphate glass used in the present invention is not particularly limited as long as it does not impair the effects of the present invention, but one having a high visible light transmittance of 400 to 600 nm is preferable. The CuO-containing phosphate glass is made of CuO, P ₂ O ₅ , Al ₂ O ₃ , Na ₂ O, K ₂ O, Sb ₂ O ₃ , BaO, MgO, CaO, SrO, BaO, ZnO, or the like. It is more preferable that they have good light resistance.

<CuO-containing fluorophosphate glass>
The CuO-containing fluorophosphate glass used in the present invention is not particularly limited as long as it does not impair the effects of the present invention, but one having a high visible light transmittance of 400 to 600 nm is preferable. Moreover, what suppressed the Cu(I) ion concentration in glass is more preferable. Such CuO-containing fluorophosphate glass is made of, for example, CuO, P ₂ O ₅ , AlF ₃ , MgF, CaF ₂ , SrF ₂ , BaF ₂ , ZnF ₂ , LiF, NaF, KF and Sb ₂ O _3. Examples include glass.

<Absorbent>
The transparent resin used for the transparent base material preferably contains an absorber having an absorption maximum in the wavelength range of 600 to 800 nm, for example, a dye or pigment absorbing near infrared rays, a metal complex compound or the like. When a transparent substrate containing a material other than a transparent resin, preferably a near infrared absorbing glass selected from the group consisting of CuO-containing phosphate glass and CuO-containing fluorophosphate glass is used, the transparent substrate is It is preferable to contain a transparent resin layer containing an agent.

When the transparent resin contains such an absorbent, it is preferable to use a norbornene-based resin. This is because the dispersibility of the absorbent is good and the processability of the transparent resin substrate containing the absorbent is excellent.

As the absorbent used in the present invention, those having no absorption at a wavelength of 450 to 550 nm are preferable. Further, when the transparent resin contains an absorber having an absorption maximum in the wavelength range of 600 to 800 nm in an amount such that the spectral transmittance at the absorption maximum of the transparent base material is 30%, the transparent substrate has a wavelength of 450 to 550 nm. A compound having a spectral transmittance of 85% or more is more preferable.

When a transparent resin substrate containing such an absorber is provided with a near-infrared reflective film as a functional film made of a dielectric material described later by vapor deposition, etc., the optical characteristics are changed even when the incident angle of incident light is changed. It is possible to obtain an optical filter having a wide viewing angle with little change in

As such an absorber, a metal complex compound, a dye, or a pigment that acts as a dye that absorbs near infrared rays can be used, and examples thereof include a phthalocyanine compound, a naphthalocyanine compound, and a dithiol metal complex compound. it can. Examples of commercially available products, for example, Lumogen IR765, Lumogen IR788 (manufactured by BASF), ABS643, ABS654, ABS667, ABS670T, IRA693N, IRA735 (manufactured by Exciton), SDA3598, SDA6075, SDA8030, SDA8303, SDA8470, SDA3039, SDA3040, SDA3922, SDA7257 (Manufactured by H.W.SANDS), TAP-15, IR-706 (manufactured by Yamada Chemical Industry) SMP54 (manufactured by Hayashibara) and the like. These absorbents may be used alone or in combination of two or more.

In the present invention, the amount of the absorbent used is appropriately selected according to the desired properties, but is usually 0.01 to 10.0 parts by weight, preferably 0.01 to 100 parts by weight with respect to 100 parts by weight of the transparent resin. The amount is 8.0 parts by weight, more preferably 0.01 to 5.0 parts by weight.

When the amount of the absorber used is within the above range, an optical filter having a small incident angle dependency of absorption wavelength, a wide viewing angle, a near infrared ray cutting ability, and excellent transmittance and strength in the range of 450 to 550 nm is obtained. be able to.

When the amount of the absorbent used is more than the above range, it may be possible to obtain an optical filter in which the characteristics of the absorbent are more strongly expressed, but the transmittance in the range of 450 to 550 nm may be lower than a desired value, or The strength of the transparent resin substrate and the optical filter may be reduced. When the amount of the absorbent used is less than the above range, an optical filter having a high transmittance in the range of 450 to 550 nm may be obtained, but the characteristics (properties) of the absorbent are less likely to appear, and the absorption wavelength In some cases, it may be difficult to obtain a transparent resin substrate or an optical filter having a small incident angle dependency and a wide viewing angle.

<Other ingredients>
In the present invention, an additive such as an ultraviolet absorber and an antioxidant can be added to the transparent resin as long as the effect of the present invention is not impaired.

Examples of the ultraviolet absorber include 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone. When an ultraviolet absorber is added, the transmittance of wavelengths of 300 to 380 nm can be suppressed, and when the resulting optical filter is used for an image sensor, the sensor reacts sufficiently to block ultraviolet rays that are invisible to the human eye. And is suitable for a blue tint.

Examples of the antioxidant include 2,6-di-t-butyl-4-methylphenol, 2,2′-dioxy-3,3′-di-t-butyl-5,5′-dimethyldiphenylmethane and tetrakis[ Methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane and the like.

Further, when a transparent resin base material is manufactured by a solution casting method described later, it is possible to easily manufacture the resin base material by adding a leveling agent or an antifoaming agent.

Incidentally, these additives may be mixed with the transparent resin or the like when producing the transparent resin substrate used in the present invention, or may be pre-blended by being added when producing the transparent resin. Good. The addition amount is appropriately selected according to the desired characteristics, but is usually 0.01 to 5.0 parts by weight, preferably 0.05 to 2.0 parts by weight with respect to 100 parts by weight of the transparent resin. Parts by weight.

<Transparent substrate manufacturing method>
The transparent resin substrate containing the absorbent is, for example, a method of melt-forming pellets obtained by melt-kneading the transparent resin and the absorbent, a liquid resin composition containing a transparent resin, an absorbent and a solvent. It can be produced by a method of melt-molding pellets obtained by removing the solvent from the solution or a method of casting (cast molding) the above-mentioned liquid resin composition.

(A) Melt Molding The transparent resin substrate used in the present invention can be manufactured by melt molding a resin composition containing a transparent resin and an absorbent. Examples of the melt molding method include injection molding, melt extrusion molding and blow molding.

(B) Solution Casting The transparent resin substrate used in the present invention is produced by casting a liquid resin composition containing a transparent resin, an absorbent and a solvent on a suitable support to remove the solvent. Can also For example, on a support such as a steel belt, a steel drum, a polyester film or glass, the above liquid resin composition is applied, the solvent is dried, and then the coating film is peeled from the support to obtain a transparent resin. A base material can be obtained.

Further, a transparent substrate having a multi-layer structure containing glass, quartz or transparent plastic can be obtained by coating an optical component made of glass, quartz or transparent plastic with the above liquid resin composition and drying the solvent.

The amount of residual solvent in the transparent substrate obtained by the above method is preferably as small as possible, and is usually 3% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less. When the amount of residual solvent exceeds 3% by weight, the transparent substrate may be deformed or its characteristics may be changed over time, and the desired function may not be exhibited.

<Functional film>
Examples of the functional film used in the present invention include an aluminum vapor deposition film, a noble metal thin film, a resin film in which metal oxide fine particles containing indium oxide or antimony oxide as a main component and containing a small amount of tin oxide are dispersed, and a high refractive index material. A dielectric multilayer film in which dielectric layers (hereinafter also referred to as "high refractive index material layer") and low dielectric index material layers (hereinafter also referred to as "low refractive index material layer") are alternately laminated. Can be used.

In the present invention, the functional film may be provided on one side or both sides of the transparent substrate. When it is provided on one side, it is excellent in manufacturing cost and ease of production, and when it is provided on both sides, an optical filter that is less likely to warp can be obtained, which is suitable for a thinner image pickup element.

Among these functional films, a dielectric multilayer film in which high refractive index material layers and low refractive index material layers are alternately laminated can be preferably used.

<High refractive index material>
As a material forming the high refractive index material layer, a material having a refractive index of 2.0 or more, preferably 2.1 or more, more preferably 2.2 or more, and further preferably 2.3 or more can be used. The upper limit of the refractive index is usually about 2.5.

Examples of such a high refractive index material include titanium oxide, zirconium oxide, tantalum pentoxide, niobium pentoxide, lanthanum oxide, yttrium oxide, zinc oxide, zinc sulfide, and titanium oxide containing tin oxide, indium oxide as a main component, tin oxide, Examples include those containing a small amount of cerium oxide and the like. Among them, titanium oxide, zirconium oxide, tantalum pentoxide, and niobium pentoxide are more preferable because of their high refractive index.

<Low refractive index material>
As the material forming the low refractive index material layer, a material having a refractive index of 2.0 or less, preferably less than 1.8, more preferably less than 1.6, and still more preferably less than 1.5 can be used. The lower limit of the refractive index is usually about 1.2.

Examples of such a low refractive index material include silica, alumina, lanthanum fluoride, magnesium fluoride, sodium aluminum hexafluoride and the like. Of these, silica and magnesium fluoride are more preferable because they have a low refractive index.

<Dielectric multilayer film>
The method of laminating the high refractive index material layer and the low refractive index material layer is not particularly limited as long as a dielectric multilayer film in which these material layers are laminated is formed, but for example, a CVD method, a sputtering method, a vacuum deposition method. By a method or the like, a high-refractive-index material layer and a low-refractive-index material layer are alternately laminated to form a dielectric multilayer film, and this is bonded to a transparent base material with an adhesive, or on the transparent base material, It can be obtained by directly forming a dielectric multilayer film in which high-refractive index material layers and low-refractive index material layers are alternately laminated by a CVD method, a sputtering method, a vacuum deposition method or the like.

The optical film thickness of each of the high-refractive index material layer and the low-refractive index material layer is usually a repetition of the infrared wavelength λ (nm) to be blocked around 0.25λ. However, the three layers and the outermost layer adjacent to the transparent substrate are not limited to this.

In the functional film of the present invention, where Hd (nm) is the total optical film thickness of the high refractive index material layer and Ld is the total optical film thickness of the low refractive index material layer in the functional film, Hd/ Ld=0.900 to 0.998 is preferable, Hd/Ld=0.900 to 0.990 is more preferable, and Hd/Ld=0.900 to 0.980 is further preferable.

The inventors of the present invention shifted the optical film thickness ratio of the high refractive index material and the low refractive index material from a design in which the transmittance becomes highest when incident from an angle of 0° from the vertical direction, so that the specific angle It has been found that the average transmittance of 450 to 550 nm is highest when the light is incident from, and the decrease in the average transmittance of 450 to 550 nm incident from an angle of 45° from the vertical direction can be suppressed.

In addition, the number of laminated layers in the dielectric multilayer film is preferably 5 to 54 layers, and more preferably 16 to 52 layers including both surfaces of the base material. Further, when the substrate warps when the dielectric multilayer film is deposited, in order to solve this, the dielectric multilayer film is deposited on both surfaces of the base material. A method such as irradiating the surface with radiation such as ultraviolet rays can be used. In addition, when irradiating with radiation, it may be irradiated while vapor-depositing the dielectric multilayer film, or may be separately irradiated after vapor deposition.

<Application of optical filter>
The optical filter of the present invention has a wide viewing angle and excellent near-infrared ray cutting ability. Therefore, it is useful for correcting the visibility of a solid-state image sensor such as a CCD or a CMOS image sensor of a camera module. In particular, digital still cameras, mobile phone cameras, digital video cameras, PC cameras, surveillance cameras, automobile cameras, personal digital assistants, personal computers, video game machines, medical devices, USB memories, mobile game machines, fingerprint authentication systems, digital It is useful for music players, toy robots, toys, etc. Further, it is also useful as a heat ray cut filter or the like attached to glass or the like of automobiles or buildings.

Here, a case where the optical filter of the present invention is used in a camera module will be specifically described.

FIG. 1 shows a schematic diagram of a camera module. FIG. 1(a) is a schematic view of the structure of a conventional camera module, and FIG. 1(b) is one of possible camera module structures when the optical filter 6'of the present invention is used. 2 is a schematic diagram showing

In FIG. 1(b), the optical filter 6'of the present invention is used above the lens 5, but the optical filter 6'of the present invention is provided between the lens 5 and the sensor 7 as shown in FIG. 1(a). Can also be used for.

In the conventional camera module, the light needs to enter the optical filter 6 almost perpendicularly. Therefore, the optical filter 6 needs to be arranged between the lens 5 and the sensor 7.

Here, the sensor 7 has a high sensitivity, and since it may not operate correctly when only a dust or dust of about 5 μm is touched, the optical filter 6 used on the upper portion of the sensor 7 is a dust-free one. Therefore, it was necessary to be free of foreign matter. In addition, due to the characteristics of the sensor 7, it is necessary to provide a predetermined space between the optical filter 6 and the sensor 7, which has been a cause of hindering the height reduction of the camera module.

On the other hand, in the optical filter 6'of the present invention, the absolute value of the difference between (Ya) and (Yb) is 15 nm or less. In other words, there is no significant difference in the transmission wavelength between the light incident from the vertical direction of the optical filter 6′ and the light incident from 30° with respect to the vertical direction of the filter 6′ (incident angle dependence of absorption (transmission) wavelength). However, the optical filter 6′ does not need to be arranged between the lens 5 and the sensor 7, and can be arranged on the upper part of the lens.

Therefore, when the optical filter 6'of the present invention is used in a camera module, the camera module is easy to handle, and it is not necessary to provide a predetermined space between the optical filter 6'and the sensor 7. Therefore, it is possible to reduce the height of the camera module.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. In addition, "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified.

The spectral transmittance was measured using a spectrophotometer (U-4100) manufactured by Hitachi, Ltd. As for the transmittance when measured from the vertical direction of the optical filter, the light transmitted perpendicularly to the filter was measured as shown in FIG. In addition, the transmittance when measured from the angle of X° (including 45°) with respect to the vertical direction of the optical filter is the light transmitted at the angle of X° with respect to the vertical direction of the filter as shown in FIG. It was measured.

The viewing angle is based on the "XYZ color system based on the 2-degree field of view" defined in JIS Z 8701, and the three-stimulus at 0° incidence is calculated from the integrated value of the product of the transmittance of each wavelength and the color function of each wavelength. Calculate the tristimulus values X(45), Y(45), and Z(45) at 45° incidence from the values X(0), Y(0), Z(0), and the spectral transmittance at 45° incidence. It was evaluated.

[Example 1]
To 100 parts by weight of JSR's norbornene resin "ARTON G5023", 0.024 parts by weight of an absorber "ABS670T (absorption maximum; 675 nm)" made by EXCITON was added, and toluene was further added to dissolve the solid content to 30 parts. % Solution was obtained. Then, the obtained solution was cast on a smooth glass plate, dried at 60° C. for 8 hours, 100° C. for 8 hours, and further dried under reduced pressure at 100° C. for 8 hours, and then peeled to have a thickness of 0.1 mm and a side of 60 mm. A transparent base material of Then, a functional film (1) [silica (SiO ₂ : refractive index of 550 nm is formed on the obtained transparent substrate by using a vacuum evaporation apparatus, which is a dielectric multilayer film that reflects near infrared rays at an evaporation temperature of 150° C. 1.45, film thickness 31 to 194 nm) and titania (TiO ₂ : 550 nm refractive index 2.45, film thickness 11 to 108 nm) layers alternately laminated, Hd/Ld=0.964, Double-sided laminated number 52] was formed to obtain an optical filter having a thickness of 0.106 mm. Table 2 shows the film thickness design of the functional film (1). The spectral transmittance curve of this optical filter is measured to obtain T ₀ , T ₄₅ , T _X , B [difference between (Xa) and (Xb)], and C [difference between (Ya) and (Yb)]. It was The results are shown in Table 1. The measurement results of the spectral transmittance are shown in FIG.

[Example 2]
35.12 g (0.253 mol) of 2,6-difluorobenzonitrile, 87.60 g (0.250 mol) of 9,9-bis(4-hydroxyphenyl)fluorene, and 41.46 g of potassium carbonate were added to a 3 L four-necked flask. 0.300 mol), N,N-dimethylacetamide (hereinafter also referred to as "DMAc") 443 g, and toluene 111 g were added. Subsequently, a thermometer, a stirrer, a three-way cock with a nitrogen introduction tube, a Dean Stark tube and a cooling tube were attached to the four-necked flask, the inside of the flask was replaced with nitrogen, and the obtained solution was reacted at 140° C. for 3 hours. The generated water was removed from the Dean-Stark tube at any time. When the generation of water was no longer observed, the temperature was gradually raised to 160° C. and the reaction was carried out at that temperature for 6 hours. After cooling to room temperature (25° C.), the produced salt was removed with a filter paper, the filtrate was poured into methanol for reprecipitation, and the filter cake (residue) was isolated by filtration. The obtained filter cake was vacuum dried at 60° C. overnight to obtain a white powder (hereinafter referred to as “resin A”).

To 100 parts by weight of Resin A, 0.05 parts by weight of an absorber "ABS670T (absorption maximum; 675 nm)" manufactured by EXCITON was added, and an ultraviolet absorber "2,6-di-t-butyl-4-methylphenol" was added. 3 parts by weight was added, and DMAc was further added and dissolved to obtain a solution having a solid content of 30%. Then, the obtained solution was applied onto a smooth polyethylene terephthalate (PET) substrate using a doctor blade, dried at 70° C. for 30 minutes, and then dried at 100° C. for 30 minutes to form a film. Peeled off. Then, the film was fixed to a metal frame and further baked at 230° C. for 2 hours to obtain a transparent base material having a thickness of 0.05 mm.

Subsequently, the functional film (1) was formed on the obtained transparent substrate in the same manner as in Example 1 to obtain an optical filter having a thickness of 0.056 mm. The spectral transmittance curve of this optical filter was measured, and T ₀ , T ₄₅ , T _X , B, and C were obtained. The results are shown in Table 1.

[Example 3]
To 100 parts by weight of the resin A, 0.25 parts by weight of an absorbent "ABS670T (absorption maximum; 675 nm)" manufactured by EXCITON was added, and DMAc was further added to dissolve it to obtain a solution having a solid content of 30%. Next, the obtained solution was applied on a smooth plate-shaped silica glass support (thickness 0.1 mm), dried at 70° C. for 30 minutes, and further dried at 100° C. for 30 minutes. Then, the film was fixed to a metal frame and further baked at 230° C. for 2 hours to obtain a transparent substrate made of silica glass and transparent resin having a thickness of 0.11 mm.

Subsequently, the functional film (1) was formed on the obtained transparent substrate in the same manner as in Example 1 to obtain an optical filter having a thickness of 0.116 mm. The spectral transmittance curve of this optical filter was measured and T ₀ , T ₄₅ , T _X , B and C were determined. The results are shown in Table 1.

[Example 4]
41 parts by weight of P ₂ O ₅ , ₅ parts by weight of Al ₂ O ₃ , 24 parts by weight of Na ₂ O, 6 parts by weight of MgO, 6 parts by weight of CaO, 12 parts by weight of BaO, 6 parts by weight of CuO. And mixed. This raw material was put into a platinum crucible and heated and melted at a temperature of 1000°C. After sufficiently stirring and clarifying, the mixture was cast into a mold, gradually cooled, cut and polished to prepare a plate of 50 mm×200 mm×2 mm. This plate was heated near the softening point and stretched to obtain a transparent substrate made of phosphate glass having a thickness of 0.15 mm.

Subsequently, the functional film (1) was formed on the obtained transparent substrate in the same manner as in Example 1 to obtain an optical filter having a thickness of 0.156 mm. The spectral transmittance curve of this optical filter was measured and T ₀ , T ₄₅ , T _X , B and C were determined. The results are shown in Table 1.

[Example 5]
P ₂ O ₅ to 42 parts by weight, 13 parts by weight AlF _3, 5 parts by weight of LiF, 4 parts by weight of NaF, the MgF ₂ 1 part by weight, 9 parts by weight of CaF _2, the SrF ₂ 5 parts by weight, BaF 15 parts by weight of ₂ , 4 parts by weight of CuO, 1 part by weight of Sb ₂ O ₃ and 1 part by weight of LiNO ₃ were weighed and mixed. This raw material mixture was placed in a platinum crucible, covered with a lid, and heated and melted at a temperature of 900° C. in an electric furnace. After sufficiently stirring and clarifying, the mixture was cast into a mold and gradually cooled. Then, cutting and polishing were performed to produce a plate having a size of 50 mm×200 mm×thickness of 2 mm. This plate was heated near the softening point and stretched to obtain a transparent substrate a made of fluorophosphate glass having a thickness of 0.15 mm.

Next, 0.024 parts by weight of an absorbent "ABS670T (absorption maximum; 675 nm)" manufactured by EXCITON was added to 100 parts by weight of a norbornene resin "ARTON G5023" manufactured by JSR, and toluene was further added to dissolve the solid content. To obtain an 8% solution. The obtained solution was cast on a support made of fluorophosphate glass, dried at 60° C. for 8 hours, 100° C. for 8 hours, and further dried under reduced pressure at 100° C. for 8 hours, and then peeled to have a thickness of 0.160 mm and a side of 60 mm. A transparent base material of

Subsequently, the functional film (1) was formed on the obtained transparent substrate in the same manner as in Example 1 to obtain an optical filter having a thickness of 0.166 mm. The spectral transmittance curve of this optical filter was measured and T ₀ , T ₄₅ , T _X , B and C were determined. The results are shown in Table 1.

[Comparative Example 1]
In the same manner as in Example 1, an absorber-containing transparent base material having a thickness of 0.1 mm was obtained. Subsequently, a functional film (2) [silica (SiO ₂ : refractive index of 550 nm is formed on the obtained transparent substrate by using a vacuum evaporation apparatus, which is a dielectric multilayer film that reflects near infrared rays at an evaporation temperature of 150° C. 1.45, film thickness 29 to 185 nm) and titania (TiO ₂ : 550 nm refractive index 2.45, film thickness 11 to 108 nm) layers alternately laminated, Hd/Ld=1.01, Double-sided laminated number 52] was formed to obtain an optical filter having a thickness of 0.106 mm. Table 3 shows the film thickness design of the functional film (2). The spectral transmittance curve of this optical filter was measured, and T ₀ , T ₄₅ , T _X , B, and C were obtained. The results are shown in Table 1 [Comparative Example 2]
In the same manner as in Example 4, a transparent base material made of phosphate glass having a thickness of 0.15 mm was obtained. Then, a functional film (3) [silica (SiO ₂ : refractive index of 550 nm: 1.45) composed of a dielectric multilayer film was formed on both surfaces of the obtained transparent substrate at a vapor deposition temperature of 150° C. using a vacuum vapor deposition apparatus. , Film thickness 5 to 30 nm) and titania (TiO ₂ : 550 nm refractive index 2.45, film thickness 5 to ₂₀ nm ) Layers alternately laminated, double-sided laminated layers 6] were formed to obtain an optical filter having a thickness of 0.15 mm. The spectral transmittance curve of this optical filter was measured, and T ₀ , T ₄₅ , T _X , B, and C were obtained. The results are shown in Table 1.

The “50% transmittance wavelength” in Table 1 is a wavelength at which the transparent substrate has a transmittance of 50% in the wavelength region of 600 to 800 nm.

The "300-380 nm average transmittance" in Table 1 is the average value of the values of 300 to 380 nm measured with a spectrophotometer (U-4100) manufactured by Hitachi, Ltd. according to the measurement of the above-mentioned spectral transmittance. The content of less than 0.0% was evaluated as “◯”, and the content of 1.0% or more was evaluated as “x”.

The “800-1200 nm average transmittance” in Table 1 is an average value of values of 800 to 1200 nm measured by using a spectrophotometer (U-4100) manufactured by Hitachi, Ltd. according to the measurement of the above-mentioned spectral transmittance. The content of less than 0.0% was evaluated as “◯”, and the content of 1.0% or more was evaluated as “x”.

The “viewing angle” in Table 1 is the tristimulus values X(0), Y(0), Z(0), X(45), Y(45), and Z(45) at 0° and 45° incidence. Those satisfying all of the following equations calculated by the above were designated as “◯”, and those not satisfying as “X”.

X(45)/X(0)>0.85
Y(45)/Y(0)>0.92
Z(45)/Z(0)>0.90

The optical filter of the present invention includes a digital still camera, a mobile phone camera, a digital video camera, a PC camera, a surveillance camera, a car camera, a personal digital assistant, a personal computer, a video game, a medical device, a USB memory, a portable game machine, and a fingerprint. It can be suitably used for authentication systems, digital music players, toy robots, toys and the like.

1: Camera module 2: Lens barrel 3: Flexible substrate 4: Hollow package 5: Lens 6: Optical filter 6': Optical filter 7 of the present invention 7: CCD or CMOS image sensor 8: Optical filter 9: Spectrophotometer detector

Claims (7)

An optical filter having a transparent substrate, for one surface of the optical filter,
When the average transmittance at a wavelength of 450 to 550 nm when measured from the vertical direction is T ₀ (%),
The average transmittance at a wavelength of 450 to 550 nm when measured from a position of 45° from the vertical direction is T ₄₅ (%),
When the average transmittance at a wavelength of 450 to 550 nm when measured from the position of X° from the vertical direction is T _X (%),
Satisfy the following conditions (i) to (iii);
At least one surface of the transparent substrate includes a dielectric layer made of a high refractive index material having a refractive index of 2.0 or more and a dielectric layer made of a low refractive index material having a refractive index of less than 2.0. Having a functional film composed of a dielectric multilayer film;
The total optical film thickness of the dielectric layer made of the high refractive index material is Hd (nm),
When the total optical film thickness of the dielectric layer made of the low refractive index material is Ld (nm),
Hd/Ld is in the range of 0.900 to 0.998 at a wavelength of 550 nm;
Optical filter featuring:
(I) All of T ₀ , T ₄₅ and T _X are 75% or more;
(Ii) T _X >T ₀ and T _X >T ₄₅ ;
(Iii) X is 30. The optical filter according to claim 1, further satisfying the following conditions (A) to (C):
(A) T ₀ is 80% or more;
(B) In the wavelength region of 800 nm or less, the longest wavelength (Xa) at which the transmittance is 70% when measured from the vertical direction of the optical filter, and in the wavelength region of 580 nm or more, measured from the vertical direction of the optical filter. The absolute value of the difference from the shortest wavelength (Xb) at which the transmittance is 30% is less than 100 nm;
(C) In the wavelength range of 560 to 800 nm, the wavelength value (Ya) at which the transmittance is 50% when measured from the vertical direction of the optical filter and the angle of 30° with respect to the vertical direction of the optical filter In this case, the absolute value of the difference from the wavelength value (Yb) at which the transmittance is 50% is less than 15 nm. The optical filter according to any one of claims 1 and 2, wherein the average transmittance at a wavelength of 300 to 380 nm when measured from the vertical direction is 1% or less. The optical filter according to any one of claims 1 to 3, wherein the functional film is provided on both surfaces of the transparent substrate. The optical filter according to any one of claims 1 to 4, which has an average transmittance of 1% or less at a wavelength of 800 to 1200 nm when measured from the vertical direction. The optical filter according to any one of claims 1 to 5, wherein the transparent base material has a thickness of 40 to 200 µm. An image pickup device comprising the optical filter according to claim 1.

Images