JP7347145B2 - Optical element and fingerprint detection device - Google Patents

Description

The present invention relates to an optical element and a fingerprint detection device including the optical element.

Optical fingerprint authentication is one of the in-display fingerprint authentication methods for smartphones. For example, an organic thin-film image sensor (CMOS), a near-infrared cut filter, and an organic light-emitting device (OLED) are stacked in this order with an air layer in between, and the outermost surface of the layers is covered with a cover glass. .

In this fingerprint authentication method, when the cover glass surface is pressed with a finger, light with a wavelength of approximately 500 to 600 nm is emitted from the OLED, and this light is reflected by the finger surface. At this time, a difference in reflectance occurs due to the unevenness of the finger surface due to the fingerprint, and the fingerprint is authenticated by detecting this difference using the CMOS.

However, when fingerprint authentication is performed outdoors, for example, light in the near-infrared region, which has a wavelength of about 600 to 1000 nm, from sunlight and other light passes through the finger and becomes noise, making it difficult to improve the accuracy of fingerprint authentication. decreases. Therefore, an optical element such as a near-infrared cut filter is used to selectively cut light with a wavelength of 600 nm or more.

A method of cutting near-infrared light generally uses reflection from a dielectric multilayer film formed on the surface of an optical element.
For example, in Patent Document 1, a dielectric multilayer film (I) consisting of _two layers of SiO and _two layers of TiO is formed on one side of a base material, and _two layers of SiO and _two layers of TiO are formed on the other side. An optical filter is obtained in which a dielectric multilayer film (II) is formed by alternately laminating dielectric multilayer films (II). As a result, the reflectance of the dielectric multilayer film on one surface is over 95%, and the transmission of light in the near-infrared region is suppressed.
Further, in Patent Document 2, an optical filter is manufactured by forming two SiO ₂ layers and two TiO ₂ layers alternately on both sides of a substrate made of a transparent resin. This optical filter has a transmittance (on both sides) of 5% or less in the near-infrared region with a wavelength of 750 to 1000 nm, thereby suppressing the transmission of light in the near-infrared region.
Many of these conventional optical elements that cut light in the near-infrared region are intended to be included in imaging devices such as cameras, as described in Patent Documents 1 and 2.

International Publication No. 2016-158461 Japanese Patent Application Publication No. 2006-30944

In a fingerprint authentication device installed in a display of a smartphone or the like, a flat plate element such as an OLED and an optical element are arranged to face each other. In this case, if the reflectance of the flat plate element is high, multiple reflections will occur between the flat plate element and the optical element, and the multiple reflected light will be scattered between the flat plate element and the optical element and become stray light. . This multiple reflected stray light becomes noise during fingerprint authentication and can be a factor in reducing the accuracy of fingerprint authentication.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical element that suppresses the transmission of light in the near-infrared region and also suppresses the generation of multiple reflected stray light, and a fingerprint authentication device equipped with the optical element.

An optical element according to one aspect of the present invention includes a resin layer having a dye layer having an absorption maximum in a wavelength range of 600 to 800 nm on a base material and at least one main surface of the base material, and a resin layer on both main surfaces of the resin layer. and a reflectance adjustment film formed on the substrate, and satisfies (1) and (2) below.
(1) The maximum value of normal incidence reflectance (R1 _max 700 to 850 nm) of the reflectance adjusting film at a wavelength of 700 to 850 nm is both 98% or less.
(2) The average value of the normal incidence reflectance of the optical element at the wavelength of 700 to 850 nm on the side surface where the average value of the normal incidence reflectance of the reflectance adjustment film at the wavelength of 700 to 850 nm (R1 _{avg 700 to 850 nm} ) is high. The value expressed by (100-R2 _avg700-850nm ) is 3-70% with respect to (R2 _avg700-850nm ).

Further, a fingerprint detection device according to one aspect of the present invention includes the optical element used for fingerprint authentication, an organic light emitting element, and an organic thin film image sensor.

The optical element according to the present invention suppresses transmission of near-infrared light not only by reflection but also by absorption by the dye layer. Therefore, the occurrence of multiple reflected stray light is suppressed, and when used for fingerprint authentication of smartphones, etc., it is possible to maintain high fingerprint authentication accuracy. Therefore, the present invention can also provide a fingerprint detection device with excellent fingerprint authentication accuracy.

FIG. 1 is a schematic cross-sectional view showing one aspect of the configuration of an optical element according to this embodiment. FIG. 2 shows the transmission spectra of the dye layers in the optical elements of Examples 1 to 7. FIG. 3 is a transmission spectrum of the dye layer in the optical element of Example 8. FIG. 4 shows the reflection spectra of the reflectance adjusting films in the optical elements of Examples 1 to 8 and 10.

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be implemented with arbitrary modifications within the scope of the gist of the present invention.
In this specification, reflectance and transmittance mean normal incidence reflectance and normal incidence transmittance, respectively. That is, it means the value when the incident angle of light is 0° and vertical incidence, and shows the value without taking polarization characteristics into consideration. Further, transmittance refers to internal transmittance, and means a value expressed by internal transmittance=transmittance/(100%−reflectance). In addition, "~" indicating a numerical range is used to include the numerical values written before and after it as a lower limit value and an upper limit value.

[Optical element]
As shown in FIG. 1, an optical element 1 according to the present embodiment includes a resin layer 10 having a dye layer 2 having an absorption maximum at a wavelength of 600 to 800 nm on a base material 1 and at least one main surface of the base material 1. and a reflectance adjusting film 20 formed on both main surfaces of the resin layer 10.
Here, the reflectance adjustment film 20 satisfies the following (1), and the optical element 1 satisfies the following (2).
(1) The maximum value of normal incidence reflectance (R1 _{max 700 to 850 nm} ) of the reflectance adjustment film 20 at a wavelength of 700 to 850 nm is both 98% or less.
(2) The average value of the normal incidence reflectance of the optical element 1 at the wavelength of 700 to 850 nm on the side surface where the average value of the normal incidence reflectance of the reflectance adjustment film 20 at the wavelength of 700 to 850 nm (R1 _{avg 700 to 850 nm} ) is high. The value expressed by (100-R2 _avg700-850nm ) is 3-70% with respect to (R2 _avg700-850nm ).

(resin layer)
The resin layer 10 has a dye layer 2 having an absorption maximum at a wavelength of 600 to 800 nm on the base material 1 and at least one main surface of the base material 1.

The base material 1 may be any base material that has a high average value of normal incidence transmittance for light from an organic light emitting device (OLED), for example, a base material that has a high average value of transmittance at a wavelength of 500 to 600 nm is preferable. The average value of such transmittance is preferably 95% or more, more preferably 99% or more.
In addition, from the viewpoint of suppressing yellowing caused by light, a transparent base material that transmits visible light is preferable, and for example, a transparent base material that has a high average value of normal incidence transmittance at a wavelength of 350 to 500 nm is more preferable. More preferably, the average value of transmittance is 90% or more.

The base material may be a resin base material or a glass base material, but a resin base material is preferable because it is difficult to break, is lightweight, can be used in a bent shape, and is easy to process into an external shape.
Conventionally known resins can be used for the resin base material. For example, cycloolefin polymers (COP) or cycloolefin copolymers (COC) such as norbornene resins; polyimide resins (PI); polyamide resins; polycarbonate resins (PC); polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate; polyethylene , polyolefin resins such as polypropylene and ethylene vinyl acetate copolymer; acrylic resins such as polyacrylate and polymethyl methacrylate; epoxy resins, urethane resins, vinyl chloride resins; fluororesins; polyvinyl butyral resins; and polyvinyl alcohol resins.
Among these, the base material is preferably selected from at least one member selected from the group consisting of cycloolefin polymers, cycloolefin copolymers, polyimide resins, polycarbonate resins, and polyester resins such as polyethylene terephthalate.

In addition to the main component resin, the resin base material may contain other resins, adhesion agents, leveling agents, antistatic agents, heat stabilizers, light stabilizers, antioxidants, and dispersants as necessary. , flame retardants, lubricants, plasticizers, and other optional components.

Conventionally known glasses can be used as the glass substrate. For example, absorption type glass (near-infrared absorbing glass) in which CuO or the like is added to fluorophosphate glass, phosphate glass, etc., soda lime glass, borosilicate glass, alkali-free glass, and quartz glass can be used. Among these, absorption-type glass (near-infrared absorption glass), which is made by adding CuO or the like to fluorophosphate glass or phosphate glass, which is used as an infrared absorption filter, or porcelain glass, which is often used for optical purposes. The base material is preferably selected from acid glass and quartz glass.
Note that "phosphate glass" also includes silicophosphate glass in which a part of the glass skeleton is composed of SiO ₂ . Further, the absorption type glass to which CuO is added contains divalent Cu ions.

The base material may be manufactured or a commercially available glass film or resin film may be used. When manufacturing the base material, known manufacturing methods can be applied.
For example, when manufacturing a resin base material, it can be manufactured by melt-extruding a mixture of a main component resin and optional components and molding it into a film.
In addition, a coating liquid prepared by dissolving or dispersing the resin, which is the main component of the base material, in a solvent or dispersion medium together with optional components as necessary is applied to the removable base material for base material production to a desired thickness. After coating, drying, and if necessary curing, the base material can be manufactured by peeling off the releasable base material. The coating liquid may contain a surfactant to improve voids caused by microbubbles, dents caused by adhesion of foreign matter, repellency during the drying process, and the like.
When applying the coating liquid, for example, a dip coating method, a cast coating method, a die coating method, or a spin coating method can be used.

The thickness of the base material is preferably 10 μm or more, more preferably 20 μm or more from the viewpoint of ease of handling during formation of the dye layer and reflectance adjustment layer. Further, from the viewpoint of thinning, the thickness of the substrate is preferably 100 mm or less, more preferably 50 mm or less.

The dye layer 2 is formed on at least one main surface of the base material 1 and has an absorption maximum at a wavelength of 600 to 800 nm. The dye layer is preferably formed on both main surfaces of the base material from the viewpoint of suppressing warpage. When the dye layers are provided on both main surfaces of the base material, the dye layers on both sides may have the same structure or different structures. Further, the dye layer may have a multilayer structure in which two or more layers are laminated on the same main surface. Alternatively, the dye layer 2 may be formed on at least one main surface of the base material 1, and a dye-free layer of a resin that dissolves or disperses the dye compound may be formed on the other main surface.

By absorbing light in the wavelength range of 600 to 800 nm in the dye layer, the transmission of near-infrared light can be suppressed as a whole of the optical element even if the reflectance on the surface of the reflectance adjustment film is reduced. Therefore, even if the optical element is opposed to a flat plate element such as an OLED, multiple reflections are unlikely to occur, and the occurrence of multiple reflection stray light is suppressed.

The dye layer is not particularly limited to the type of dye as long as it has an absorption maximum at a wavelength of 600 to 800 nm, and the number of dyes constituting the dye layer is arbitrary. For example, a dye compound having an absorption maximum at a wavelength of 600 to 750 nm may be used, a dye compound having an absorption maximum at a wavelength of 750 to 800 nm may be used, or these dye compounds may be used in combination. Furthermore, a dye compound having an absorption maximum in another wavelength range, such as a wavelength of 800 to 1000 nm, may also be used in combination.
By appropriately combining these dye compounds, a dye layer having desired optical properties can be designed.

As the dye compound, conventionally known compounds can be used. Specifically, cyanine dyes with extended polymethine skeletons, phthalocyanine dyes with aluminum or zinc as their center, naphthalocyanine compounds, nickel dithiolene complexes with a planar four-coordination structure, squarylium dyes, quinone compounds, diimmonium compounds, azo compounds, immonium dyes, diketopyrrolopyrrole dyes, croconium dyes, and the like.
Among these, examples of dye compounds having maximum absorption in the wavelength range of 600 to 750 nm include squarylium dyes, cyanine dyes, and phthalocyanine dyes.
Examples of dye compounds having an absorption maximum in the wavelength range of 750 to 800 nm include squarylium dyes, cyanine dyes, phthalocyanine dyes, diketopyrrolopyrrole dyes, and croconium dyes.
Examples of dye compounds having an absorption maximum in the wavelength range of 800 to 1000 nm include squarylium dyes, cyanine dyes, immonium dyes, diimmonium dyes, croconium dyes, and phthalocyanine dyes.

The dye layer is a layer in which these dye compounds are uniformly dissolved or dispersed in a resin. As the resin for dissolving or dispersing the dye compound, for example, the resin constituting the base material mentioned above can be used.
The dye layer may further contain an absorbent other than the dye compound. Examples include optional components such as UV absorbers, adhesion agents, color correction pigments, leveling agents, antistatic agents, heat stabilizers, light stabilizers, antioxidants, dispersants, flame retardants, lubricants, and plasticizers. .

Known manufacturing methods can be applied to manufacturing the dye layer.
For example, a dye layer formed into a film can be obtained by extrusion molding a mixture of one or more dye compounds, a resin that dissolves or disperses the dye compound, and optional components as necessary. It will be done. A resin layer is obtained by laminating the obtained film-like dye layer on the main surface of a base material and integrating it by thermocompression bonding or the like.

In addition, a coating liquid prepared by dissolving or dispersing one or more pigment compounds, a resin for dissolving or dispersing the pigment compound, and optional components as necessary in a solvent or dispersion medium, A resin layer containing a pigment layer can also be formed by coating on the main surface of a base material, drying, and curing if necessary. If the above-mentioned base material is a removable base material, after peeling the dye layer from the releasable base material, the resin layer is integrated onto the main surface of the base material by pressure bonding or the like. can get.
The coating liquid may contain a surfactant to improve voids caused by microbubbles, dents caused by adhesion of foreign matter, repellency during the drying process, and the like. When applying the coating liquid, for example, a dip coating method, a cast coating method, a die coating method, an inkjet coating method, a gravure coating method, or a spin coating method can be used.

The thickness of the dye layer is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more from the viewpoint of stability of the coating film thickness. Further, from the viewpoint of suppressing residual solvent after drying, the thickness of the dye layer is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less.

The dye absorption spectroscopy of the resin layer having the base material and the dye layer preferably satisfies at least one of the following (i) and (ii), and more preferably satisfies both.
(i) The average value of normal incidence transmittance at a wavelength of 500 to 600 nm is 85% or more.
(ii) The maximum value of normal incidence transmittance at a wavelength of 700 to 850 nm is 35% or less.

If the above condition (i) is satisfied, the light emitted from the OLED used for fingerprint authentication is not blocked by the dye layer and sufficiently passes through the resin layer. The average value of such transmittance is more preferably 90% or more, and even more preferably 93% or more. The upper limit is not particularly limited as it is more preferable, but it is usually 99% or less.

If the above condition (ii) is satisfied, light in the wavelength range that passes through the finger and causes noise during fingerprint authentication is sufficiently absorbed by the dye layer. That is, it means that the light blocking performance derived from absorption of the dye layer is very good. The maximum value of such transmittance is more preferably 30% or less, and even more preferably 15% or less. The lower limit is not particularly limited as it is more preferable, but it is usually 0.1% or more.

(Reflectance adjustment film)
Reflectance adjustment films having a function of adjusting reflectance are formed on both main surfaces of the resin layer. The maximum value of the normal incidence reflectance (R1 _{max 700 to 850 nm) of both reflectance adjusting films at a wavelength of 700 to 850 nm} is 98% or less.

The function to adjust the reflectance means that wavelength range selectivity can be imparted or the reflectance or transmittance can be set to a desired value depending on the material composing the film and the way in which it is laminated in the case of a multilayer film. means.
Specifically, examples include a reflective film that reflects a specific wavelength range, an antireflection film that prevents reflection of a specific wavelength range, a half mirror or a polarizing film that divides the amount of light into reflection and transmission. More specifically, examples include an infrared reflective film (infrared cut filter), an ultraviolet reflective film (ultraviolet cut filter), a visible light bandpass filter, a visible light antireflection film, and a high reflection film.

The configurations of both reflectance adjustment films may be the same or different.
A conventionally known configuration can be applied to the reflectance adjustment film. For example, it may be a single-layer film or a multilayer film in which two or more layers are laminated. Further, a dielectric film made of an inorganic material may be used, or a film made of an energy-curable resin made of an organic material may be used.

When at least one of the reflectance adjustment films is a multilayer film, the total number of both layers of the reflectance adjustment film is preferably 20 or less layers from the viewpoint of cost and prevention of warping of the base material, and 15 or less layers. More preferably, the number of layers is 10 or less. In this embodiment, since the total number of layers of the reflectance adjustment film is 20 or less, even if the value of R1 _{max 700 to 850 nm} becomes small, the transmission of light in the near-infrared region can be suppressed by absorption in the dye layer. Therefore, the function as an optical element is fully exhibited.
The number of layers per one side of the reflectance adjusting film is preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less.

When the reflectance adjustment film is a multilayer film, desired optical characteristics can be obtained by repeatedly laminating two or more different types of films. For example, a reflective film or an antireflection film can be obtained by alternately stacking films using a low refractive index material (low refractive index film) and films using a high refractive index material (high refractive index film). Furthermore, films using intermediate refractive index materials are also suitably used as antireflection films and the like.

When the reflectance adjustment film is a multilayer film composed of a dielectric film made of an inorganic material, examples of the inorganic material include SiO ₂ , Na ₅ Al ₃ F ₁₄ , Na ₃ AlF ₆ , MgF ₂ , CaF ₂ , ZrO ₂ , _Al2O3 , _{LaF3 , CF3 ,} MgO, _Y2O3 , _TiO2 , _Ta2O5 , _{Nb2O5 , La2O3} , ZnS, _ZnSe , _CeO2 , _LaTiO3 , _SiON , SiN, Examples include HfO ₂ and the like. Among them, it is composed of two or more dielectric films selected from the group consisting of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgF ₂ , TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ and La ₂ O ₃ A dielectric multilayer film is preferred.

It is preferable to select a dielectric multilayer film having a refractive index difference of a certain value or more from the viewpoint of optical properties imparted to the reflectance adjustment film. Among the above materials, it is preferable that a dielectric multilayer film is composed of two or more types of dielectric films containing, for example, SiO ₂ and TiO ₂ , and a dielectric film in which dielectric films of SiO ₂ and TiO ₂ are alternately laminated is used. A multilayer film is more preferred.

A dielectric film or a dielectric multilayer film is generally formed on a resin layer using, for example, a vacuum film forming process such as a CVD method, a sputtering method, or a vacuum evaporation method.

The reflectance adjustment film may be made of not only an inorganic material but also an organic material, such as an energy-curable resin film. An energy-curable resin film is a resin film that is cured by light energy such as visible light, ultraviolet rays, infrared rays, and high frequency, or thermal energy.
The energy-curable resin film may be a resin film, or a film in which the refractive index and the like are adjusted by adding an inorganic material such as SiO ₂ , TiO ₂ , or ZrO ₂ to the resin. Further, it may be a single layer film or a laminated film.

Conventionally known resins can be used as the resin constituting the energy-curable resin. Examples include acrylic resin, methacrylic resin, epoxy resin, and enethiol resin.

Such an energy-curable resin film is produced by dissolving or dispersing the main component resin in a solvent or dispersion medium together with optional components as necessary, and applying a coating solution to the main surface of the pigment layer as desired. It can be formed by coating to a thickness of , drying, and curing by applying energy such as light irradiation or heating.
Further, the above coating solution is applied to a releasable base material to a desired thickness, dried, and cured as necessary to form a film, and then the obtained film is peeled from the releasable base material. However, a film of energy-curable resin may be formed on the main surface of the resin layer by integrating the resin layer by pressure bonding or the like.
The coating liquid may contain a surfactant to improve voids caused by microbubbles, dents caused by adhesion of foreign matter, repellency during the drying process, and the like. Further, when applying the coating liquid, for example, a dip coating method, a cast coating method, a die coating method, an inkjet coating method, a gravure coating method, or a spin coating method can be used.

The reflectance adjustment film satisfies the following optical properties (1).
(1) The maximum value of normal incidence reflectance (R1 _{max 700 to 850 nm) of the reflectance adjustment film at a wavelength of 700 to 850 nm} is both 98% or less.
By lowering the value of R1 _{max 700 to 850 nm} compared to the conventional one, the absolute amount of multiple reflection can be reduced when the optical element is opposed to a flat plate element such as an OLED.
The value of R1 _{max of 700 to 850 nm} of the reflectance adjustment film is preferably 90% or less, more preferably 60% or less. On the other hand, from the viewpoint of suppressing transmission of light in the near-infrared region through the entire optical element, the value of R1 _{max 700 to 850 nm} is preferably 30% or more, more preferably 50% or more.

Furthermore, for the same reason, the average value of normal incidence reflectance (R1 _{avg 700 to 850 nm) of the reflectance adjustment film at a wavelength of 700 to 850} nm is preferably 95% or less on both surfaces, more preferably 90% or less, and 60% or less. is even more preferable. Furthermore, the value of R1 _{avg 700 to 850 nm} is preferably 25% or more, more preferably 45% or more.
The values of R1 _{max 700 to 850 nm} and R1 _{avg 700 to 850 nm} can be adjusted depending on the type of material constituting the reflectance adjustment film, the number of laminated layers, conditions during film formation, etc. Note that the conditions during film formation include, for example, the degree of vacuum during film formation, the heating temperature of the base material, and the energy applied to the material. Furthermore, not only these values but also other optical properties can be adjusted by changing the type of material constituting the reflectance adjustment film, the number of laminated layers, conditions during film formation, etc.

When using optical elements for fingerprint authentication using light from OLEDs, OLEDs do not emit ultraviolet rays, and OLEDs have low ultraviolet transmittance, so they are already sufficiently blocking ultraviolet rays from sunlight, etc. Even if the transmission of light in the ultraviolet region is not suppressed, durability will not be impaired. In order to proactively increase the reflectance in the ultraviolet region, it is necessary to increase the number of layers of the reflection adjustment layer, and from the viewpoint of cost and warpage prevention, the maximum normal incidence reflectance of the reflectance adjustment film at a wavelength of 350 to 400 nm is required. Both values (R1 _{max 350 to 400 nm} ) are preferably at most 60%, more preferably at most 50%, even more preferably at most 40%.

At least one of the reflectance adjustment films preferably has a half value of the maximum value and minimum value of the normal incidence reflectance at a wavelength of 500 to 1000 nm within a wavelength range of 580 to 700 nm, and the half value of both reflectance adjustment films is preferably It is more preferable that the wavelength is within the range of 580 to 700 nm. This is because the cut-off wavelength is within the range of 580 to 700 nm, in which light in the wavelength region lower than half-value is transmitted, and light in the region longer wavelength than half-value is reflected. means selectively reflecting light.

When the optical element is used for fingerprint authentication using light from an OLED, at least one of the reflectance adjustment films has an average value of normal incidence reflectance at a wavelength of 500 to 580 nm (R1 _{avg500 -580 nm} ) is preferably 4% or less, more preferably 2% or less, and even more preferably 1.5% or less. Further, it is more preferable that both the values of R1 _{avg of 500 to 580 nm} of both reflectance adjustment films satisfy the above range.
The lower the value of R1 _{avg 500 to 580 nm} , the more preferable it is, and its lower limit is not particularly limited, but is usually 0.1% or more.

(optical element)
In addition to the resin layer and the reflectance adjustment film, the optical element may further include any layer as long as it does not impede the effects of this embodiment. For example, a hard coat layer may be further provided between the resin layer and the reflectance adjustment film for the purpose of improving the adhesion between the two. In addition, an antistatic layer or the like can also be provided.

The hard coat layer is not particularly limited as long as it does not impair the optical properties of the resin layer or reflectance adjusting film, and any conventionally known hard coat layer can be used. For example, a layer of resin having a glass transition temperature Tg of 170° C. or higher is preferable because it is less likely to be deformed by heat or stress and has excellent adhesion effects. The glass transition temperature is more preferably 200°C or higher, even more preferably 250°C or higher. Although the upper limit of the glass transition temperature is not particularly limited, it is preferably 400° C. or lower from the viewpoint of moldability and the like.

Examples of the resin constituting the hard coat layer include acrylic resin, epoxy resin, enethiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, and polyarylene ether phosphine oxide. Examples include resin, polyimide resin, polyamideimide resin, polyolefin resin, polycycloolefin resin, and polyester resin. Among these, acrylic resin, polyimide resin, and epoxy resin are preferable from the viewpoint of hardness and adhesion with the reflectance adjusting layer.

A known manufacturing method can be applied to the hard coat layer.
For example, a hard coat layer can be obtained by extrusion molding a mixture of a resin constituting the hard coat layer and optional components as required. The obtained film-like hard coat layer is laminated above the resin layer so as to become the outermost layer, and can be integrated by thermocompression bonding or the like.

Further, a coating liquid prepared by dissolving or dispersing the resin constituting the hard coat layer and optional components in a solvent or dispersion medium is applied onto the main surface of the resin layer and dried, A hard coat layer can also be formed by curing as necessary. In addition, when coating is not on the main surface of the resin layer but on a removable base material, after peeling off the hard coat layer from the releasable base material, the outermost layer is placed above the resin layer. A hard coat layer can be formed by laminating them and integrating them by pressure bonding or the like.
The coating liquid may contain a surfactant to improve voids caused by microbubbles, dents caused by adhesion of foreign matter, repellency during the drying process, and the like. When applying the coating liquid, for example, a dip coating method, a cast coating method, a die coating method, an inkjet coating method, a gravure coating method, or a spin coating method can be used.

The optical element according to this embodiment satisfies the following optical property (2). Note that the optical characteristics of the optical element can be adjusted by the configuration of the resin layer including the dye layer and the reflectance adjustment film that constitute the optical element, and the combination thereof.
(2) On the side surface where the average value of the normal incidence reflectance (R1 _{avg700~850 nm) of the reflectance adjustment film at wavelength 700~850 nm} is high, the average value of normal incidence reflectance (R2 avg) at wavelength 700~850 nm of the optical element is high. _{avg700-850 nm} ), the value expressed as (100-R2 _{avg700-850 nm} ) is 3-70%.

When the value expressed by (100-R2 _avg700-850nm ) is 70% or less, in addition to absorption by the dye layer, transmission of near-infrared light is suppressed beyond a certain level by reflection by the reflectance adjustment film. means. The value expressed by (100-R2 _{avg700-850 nm} ) is preferably 60% or less, more preferably 50% or less.
If the value expressed by (100-R2 _avg700-850nm ) is 3% or more, the reflection by the reflectance adjustment film can be suppressed lower than before, and when the optical element is opposed to a flat plate element such as an OLED, The absolute amount of multiple reflections can be reduced. The value expressed by (100-R2 _{avg 700-850 nm} ) is preferably 10% or more, more preferably 30% or more.

Further, it is more preferable that the value expressed by (100-R2 _{avg700-850 nm} ) satisfies the above range in the same manner on the side where the value of R1 _{avg 700-850 nm} is low.

The optical element uses the optical density expressed by the OD value,
(OD_r1+OD_r2+OD_ab)>1, and (OD_r1+OD_r2)<(2.5×OD_ab)
It is preferable that the following relationship is satisfied.
OD_r1 is expressed as -log ₁₀ (100-R1 _{avg700-850nm_1} ) using the average value of normal incidence reflectance (R1 _{avg700-850nm_1} ) of the reflectance adjustment film located on the incident surface side at a wavelength of 700-850nm. This is the light shielding performance derived from reflection.
OD_r2 is expressed as -log ₁₀ (100-R1 _{avg700-850nm_2} ) using the average value of normal incidence reflectance (R1 _{avg700-850nm_2} ) of the reflectance adjustment film located on the exit surface side at a wavelength of 700-850nm. This is the light shielding performance derived from reflection.
OD_ab is the light-shielding performance derived from the absorption of the pigment layer, which is expressed as -log ₁₀ (T3 _{avg 700-850 nm} ) using the average value of normal incidence transmittance of the resin layer at a wavelength of 700-850 nm (T3 _{avg 700-850 nm} ). It is.

In the above, when OD=α, it means that the attenuation rate of light is (1/10 ^α ).
Furthermore, when the optical element is, for example, an organic thin film image sensor (CMOS), an optical element, and an organic light emitting element (OLED), which are stacked in this order with an air layer in between, the OLED side of the optical element is the incident surface side, and the CMOS side is the exit surface. Become a side.

That is, (OD_r1+OD_r2+OD_ab) being more than 1 means that the attenuation rate of light in the wavelength range of 700 to 850 nm is less than ^1/101 , and the transmittance of such light is less than 10%. Thereby, transmission of light in the near-infrared region can be sufficiently suppressed. The value of (OD_r1+OD_r2+OD_ab) is more preferably 1.5 or more, and even more preferably 2 or more.
The upper limit of the value of (OD_r1+OD_r2+OD_ab) is not particularly limited, but is usually 4 or less.

(OD_r1+OD_r2)<(2.5×OD_ab) means that for light in the wavelength range of 700 to 850 nm, the optical density suppresses transmission by reflection by the reflectance adjustment film, and the optical density suppresses transmission by absorption by the dye layer of the resin layer. It means less than 2.5 times the optical density to be suppressed. Thereby, it is possible to sufficiently suppress multiple reflection stray light due to the reflectance adjustment film facing the flat plate element such as an OLED. The value of (OD_r1+OD_r2) is more preferably twice or less than the value of OD_ab, and even more preferably one time or less.
The lower limit of the value of (OD_r1+OD_r2) is preferably 0.3 times or more, and 0.5 times or more of the value of OD_ab, since the reflection of the reflectance adjustment film suppresses the transmission of light in the wavelength range of 700 to 850 nm to some extent. is more preferable.

The optical element according to the present embodiment is preferably used for fingerprint authentication, more preferably used for fingerprint authentication used outdoors where light in the near-infrared region easily enters, and preferably used for fingerprint authentication in a smartphone. is even more preferable.

[Fingerprint detection device]
The fingerprint detection device according to this embodiment includes the optical element described in [Optical Element] above, an organic light emitting element, and an organic thin film imaging element. Preferred embodiments of the optical element are the same as those described in [Optical Element] above.
Conventionally known organic light emitting devices and organic thin film imaging devices can be used. Further, the configurations other than the optical element, the organic light emitting element, and the organic thin film image sensor may be conventionally known configurations.

Next, the present invention will be explained in more detail with reference to Examples. An ultraviolet-visible spectrophotometer (manufactured by Hitachi High-Technologies Co., Ltd., model U-4100) was used to measure the following optical properties.

(Example 1 to Example 8)
A transparent polyimide resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., L-3G30, thickness 30 μm) was used as a base material, and a resin layer was obtained by forming dye layers each having a thickness of 1 μm on both main surfaces thereof. The dye layer consists of five types of dye compounds (A) to (E) shown below and a polyimide resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., C-3G30G) in a mixed solution (solvent or dispersion) of cyclohexanone and γ-butyrolactone. A coating liquid was prepared by dissolving it in a solvent (name of medium). This was applied onto the main surface of the base material, dried, and cured to form a dye layer.
The dye compounds (A) to (E) are compounds with maximum absorption wavelengths λ _max of 707 nm, 753 nm, 772 nm, 809 nm, and 845 nm, respectively. The transmission spectra of the dye layers of Examples 1 to 7 are shown in FIG. 2, and the ratio of the amounts of dye compounds (A) to (E) added is 2.25:1.2:1.2:2.1 in order. :4.2 (mass ratio). Further, the transmission spectrum of the dye layer of Example 8 is shown in FIG. 3, and the ratio of the amounts of dye compounds (A) to (E) added is 1.275:0.66:0.30:1.20: It is 2.10 (mass ratio). Examples 1 to 7 and Example 8 use the same dye compounds, but have different transmission spectra due to differences in the amounts added.
An optical element was obtained by sequentially laminating dielectric films of SiO ₂ and TiO ₂ on both main surfaces of the obtained resin layer to form a reflectance adjustment film of a dielectric multilayer film. Table 1 shows the structure of the reflectance adjustment film and the thickness of each dielectric film.

(Example 9)
An optical element having a resin layer including a base material and a dye layer was obtained in the same manner as in Example 1 except that the reflectance adjustment film was not formed. The transmission spectrum of the dye layer is the same as that of Examples 1 to 7 shown in FIG.
(Example 10)
The same base material as in Example 1 was used, and the resin layer was made without forming a dye layer on its main surface. An optical element was obtained by sequentially laminating dielectric films of SiO ₂ and TiO ₂ on both main surfaces of this resin layer to form a reflectance adjustment film of a dielectric multilayer film. Table 1 shows the structure of the reflectance adjustment film and the thickness of each dielectric film.

FIG. 4 shows the reflection spectra of the reflectance adjusting films in the optical elements of Examples 1 to 10.
In FIG. 4, 3L, 5L, 7L, and 9L mean reflectance adjustment films having three, five, seven, and nine layers, respectively. That is, 3L is the reflection spectrum of the reflectance adjustment film located on the incident surface side in Example 1 and on the exit surface side in Examples 1 and 2. 5L is the reflection spectrum of the reflectance adjustment film located on the incident surface side in Examples 2 and 3 and on the exit surface side in Examples 3 and 4. 7L is the reflection spectrum of the reflectance adjusting film located on the incident surface side in Examples 4, 5, and 8, and on the exit surface side in Examples 5, 6, and 8. 9L is the reflection spectrum of the reflectance adjustment film located on the incident surface side of Examples 6 and 7, and on the exit surface side of Example 7.
Further, in FIG. 4, 13L-1 is the reflection spectrum of the reflectance adjustment film located on the incident surface side in Example 10, in which the number of laminated layers is 13. 13L-2 is the reflection spectrum of the reflectance adjustment film located on the exit surface side of Example 10, in which the number of laminated layers is 13.

In the optical elements of Examples 1 to 10, Table 2 shows the optical properties of the reflectance adjustment film (incidence surface side), Table 3 shows the optical properties of the reflectance adjustment film (output surface side), and optical properties of the resin layer are shown. 4 and Table 5 show the optical properties of the optical elements. Note that Examples 1 to 8 are examples, Example 9 is a reference example, and Example 10 is a comparative example.
In Table 2, R1_max700-850nm represents the maximum value of the normal incidence reflectance in the wavelength range of 700-850nm. R1_avg700-850nm represents the average value of normal incidence reflectance in the wavelength range of 700-850nm. OD_r1 refers to the light-shielding performance derived from reflection, which is expressed as -log ₁₀ (100-R1 _{avg700-850nm_1} ) using the average value of normal incidence reflectance at a wavelength of 700-850nm (R1 _{avg700-850nm_1} ). Represents concentration. R1_max350-400nm represents the maximum value of normal incidence reflectance at a wavelength of 350-400nm. λ_HM (half value) represents the wavelength (nm) at which the normal incidence reflectance is half the maximum value and the minimum value in the wavelength range of 500 to 1000 nm. R1_avg500-580nm represents the average value of normal incidence reflectance in the wavelength range of 500-580nm.
Each notation in Table 3 represents the same thing as the corresponding notation in Table 2.
In Table 4, Tdye_avg500-600nm represents the average value of normal incidence transmittance of the resin layer at a wavelength of 500-600 nm. Tdye_max700-850nm represents the maximum value of normal incidence transmittance of the resin layer at a wavelength of 700-850nm. OD_ab is the light shielding derived from the absorption of the dye layer, which is expressed as -log ₁₀ (T3 _{avg 700-850 nm} ) using the average value of normal incidence transmittance of the resin layer at a wavelength _{of 700-850 nm (T3 avg 700-850 nm} ). Represents optical density, which indicates performance.
In Table 5, OD (A) is an optical density that indicates the light blocking performance of a single optical element, and OD (B) is an optical density that indicates the light blocking performance in a configuration close to that in actual use. The configuration close to actual use is the optical density when flat plates with a reflectance of 50% are opposed to each other with an air layer 0.1 mm thick in between. In addition, durability is an index that takes into consideration factors such as scratch resistance and deterioration of pigments when left in a general environment, and those that are judged to be able to withstand actual use are marked as good, and those that are judged to be able to withstand actual use are marked as good. Items that were determined to be absent were marked with an “×”.

Comparing Examples 1 to 7, the more the near-infrared light is reflected by the reflectance adjustment film, the larger the difference between the light shielding performance OD (A) of the element alone and the light shielding performance OD (B) in the actual usage arrangement becomes. It can be seen that the amount of decrease in light shielding performance increases depending on the usage arrangement. This means that the amount of light passing through to the image sensor side is increasing due to multiple reflections.
Example 9 has a structure in which there is no reflectance adjustment layer made of a dielectric multilayer film on the surface of the dye layer, and most of the light shielding performance is derived from absorption of the dye. In Example 9, there is very little deterioration in the light shielding performance in the actual arrangement, suggesting that suppressing the element reflectance is effective in suppressing multiple reflected stray light. On the other hand, since the dye layer is exposed, the surface of the optical element is easily scratched when manufacturing the optical element, which tends to cause problems in appearance. Furthermore, since the dye layer is exposed, there is a problem that the dye easily deteriorates.
In Example 10, when a dielectric multilayer film is formed without a dye layer and has 10 or more layers on one side and 20 or more layers in total on both sides, most of the near-infrared light is blocked by reflection, but in actual use, Since the reduction rate of light-shielding performance {OD(B)−OD(A)}/OD(A) is 15% or more, it can be seen that the light-shielding performance deteriorates significantly due to multiple reflections.
Furthermore, when comparing Example 3 with Example 8 and Example 10, the light shielding performance OD (A) as an element is approximately 2, but the higher the light shielding performance OD_ab derived from absorption of the dye layer, the better in the actual arrangement. The amount of decrease in light shielding performance and the rate of decrease in light shielding performance are small. This means that multiply reflected stray light can be suppressed by increasing the light-shielding performance through dye absorption.
From the above results, if a resin layer having a dye layer with absorption maximum in the wavelength range of 600 to 800 nm is used, even if the reflection of light in the near-infrared region is suppressed by the reflectance adjustment film, the optical element as a whole will not absorb light in the near-infrared region. It was found that the transmission of light can be sufficiently suppressed. Furthermore, by suppressing reflection by the reflectance adjustment film, the occurrence of multiple reflection stray light can also be suppressed.

The optical element according to the present invention can suppress the occurrence of multiple reflection stray light while suppressing the transmission of light in the near-infrared region to a sufficiently low level. Therefore, the accuracy of fingerprint authentication can be increased, and it is very useful for applications such as fingerprint detection devices installed in smartphones that are used outdoors.

1: Optical element 10: Resin layer 11: Base material 12: Dye layer 20: Reflectance adjustment film

Claims (12)

A resin layer having a dye layer having an absorption maximum at a wavelength of 600 to 800 nm on a base material and at least one main surface of the base material, and a reflectance adjustment film formed on both main surfaces of the resin layer. Prepare,
An optical element that satisfies (1) and (2) below.
(1) The maximum value of normal incidence reflectance (R1 _max 700 to 850 nm) of the reflectance adjusting film at a wavelength of 700 to 850 nm is both 98% or less.
(2) The average value of the normal incidence reflectance of the optical element at the wavelength of 700 to 850 nm on the side surface where the average value of the normal incidence reflectance of the reflectance adjustment film at the wavelength of 700 to 850 nm (R1 _{avg 700 to 850 nm} ) is high. The value expressed by (100-R2 _avg700-850nm ) is 3-70% with respect to (R2 _avg700-850nm ). The optical element according to claim 1, wherein average values (R1 _{avg 700 to 850 nm} ) of normal incidence reflectance of the reflectance adjusting film at the wavelength of 700 to 850 nm are both 95% or less. 3. The optical element according to claim 1, wherein the reflectance adjusting film has a maximum value of normal incidence reflectance (R1 _{max 350 to 400 nm) at a wavelength of 350 to 400 nm} , both of which are 60% or less. According to any one of claims 1 to 3, at least one of the reflectance adjusting films has a half value of a maximum value and a minimum value of the normal incidence reflectance at a wavelength of 500 to 1000 nm within a wavelength range of 580 to 700 nm. The optical element described. Any one of claims 1 to 4, wherein at least one of the reflectance adjusting films is an antireflection film having an average value of normal incidence reflectance (R1 _{avg 500 to 580 nm} ) of 4% or less at a wavelength of 500 to 580 nm. The optical element described in . The optical element according to claim 1, wherein at least one of the reflectance adjusting films is a multilayer film, and the total number of layers of both reflectance adjusting films is 20 or less. The multilayer film is made of two or more dielectric films selected from the group consisting of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgF ₂ , TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , and La ₂ O ₃ The optical element according to claim 6, which is a dielectric multilayer film composed of. The optical element according to claim 1, wherein at least one of the reflectance adjusting films is an energy-curable resin film. The optical element according to any one of claims 1 to 8, wherein the dye absorption spectrum of the resin layer satisfies the following (i) and (ii).
(i) The average value of normal incidence transmittance at a wavelength of 500 to 600 nm is 85% or more.
(ii) The maximum value of normal incidence transmittance at a wavelength of 700 to 850 nm is 35% or less. Reflection expressed as -log ₁₀ (100-R1 _{avg700-850nm_1} ) using the average value of the normal incidence reflectance (R1 _{avg700-850nm_1} ) at a wavelength of 700-850nm of the reflectance adjustment film located on the incident surface side. The original light shielding performance is OD_r1,
Reflection expressed as -log ₁₀ (100-R1 _{avg700-850 nm_2) using the average value of normal incidence reflectance at wavelengths of 700-850 nm (R1 avg700-850 nm_2 )} of the reflectance adjustment film located on the exit surface side. The original light shielding performance is OD_r2,
Using the average value of normal incidence transmittance of the resin layer at a wavelength of 700 to 850 nm (T3 _{avg 700 to 850 nm} ), the light shielding performance derived from absorption of the dye layer expressed as -log ₁₀ (T3 _{avg 700 to 850 nm} ) is expressed as OD_ab In this case,
(OD_r1+OD_r2+OD_ab)>1, and (OD_r1+OD_r2)<(2.5×OD_ab)
The optical element according to any one of claims 1 to 9, which satisfies the following. The optical element according to any one of claims 1 to 10, which is used for fingerprint authentication. A fingerprint detection device comprising the optical element according to claim 11, an organic light emitting element, and an organic thin film imaging element.