JP2018142531A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase luminous efficacy of an optical device.SOLUTION: An optical device comprises: a light reflection film which includes a metal layer and a dielectric layer on the metal layer; and a phosphor layer which is located on the dielectric layer and emits light by being excited by light from a light source. A wavelength at which a reflectivity of light vertically incident on the light reflection film from the phosphor layer is highest is longer than a centroid wavelength of an emission spectrum of the phosphor layer. The dielectric layer has a layered structure where the number of layers is from 2 to 6 inclusive. Refractive indexes of any two adjacent layers in the dielectric layer are different from each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical device.

  In recent years, optical devices using solid-state light sources have attracted attention due to the need for energy saving and long life. Development of highly efficient phosphor devices in which solid-state light sources such as laser diodes (Laser Diodes (LD)) and light emitting diodes (Light Emitting Diodes (LEDs)) and phosphors are combined has been carried out.

  Conventionally, as a method for improving the efficiency of a phosphor device, a reflection-type apparatus has been proposed in which an excitation light source and a phosphor layer are spatially separated to suppress a temperature rise of the phosphor layer. For example, Patent Document 1 discloses such a reflection-type device. The reflective phosphor device includes a reflective layer between the phosphor layer and the substrate. The light emitted from the phosphor layer excited by the excitation light is reflected by the reflection layer and used. In the configuration of Patent Document 1, a flat plate made of aluminum is used as the substrate, and silver is used as the reflective layer. Patent Document 2 discloses a configuration in which a metal film such as silver and aluminum is used as a reflective layer.

JP 2012-64484 A JP 2006-058378 A

  The present disclosure provides a novel technique for increasing the efficiency of an optical device by efficiently reflecting light emitted from a phosphor layer.

  An optical device according to an aspect of the present disclosure is a light reflecting film including a metal layer and a dielectric layer on the metal layer, and a phosphor layer on the dielectric layer, and is excited by light from a light source And a phosphor layer that emits light. The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximum is longer than the barycentric wavelength of the emission spectrum of the phosphor layer, and the dielectric layer is 2 or more and 6 In the laminated structure of the following layers, the refractive indexes of two arbitrary adjacent layers in the dielectric layer are different.

  An optical device according to another aspect of the present disclosure includes a light reflection film including a metal layer and a dielectric layer on the metal layer, and a phosphor layer on the dielectric layer, and is excited by light from a light source. And a phosphor layer that emits light. The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side becomes the maximum is the barycentric wavelength of the light spectrum obtained by combining the emission spectrum of the light source and the emission spectrum of the phosphor layer. The dielectric layer is a laminated structure of 2 or more and 6 or less layers, and the refractive indexes of any two adjacent layers in the dielectric layer are different.

  The comprehensive or specific aspect described above may be implemented by a system, a method, an integrated circuit, a computer program, or a recording medium. Or you may implement | achieve with arbitrary combinations of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

  According to the technique of the present disclosure, the efficiency of the optical device can be increased by efficiently reflecting the light emitted from the phosphor layer.

FIG. 1 is a diagram illustrating a configuration example of an optical device 50 in the present embodiment. FIG. 2 is a diagram schematically showing that light emitted from the phosphor layer 20 enters the dielectric layer 42 and is transmitted or reflected. FIG. 3 is a diagram for explaining the dependence of the amount of light incident on the light reflecting film 40 from the phosphor layer 20 on the incident angle. FIG. 4A shows the reflection spectrum of the light reflecting film 40 at an incident angle of 90 ° and the phosphor layer when the difference (λ ₀ −λ _c ) between the wavelength λ ₀ and the wavelength λ _c is smaller than the wavelength shift amount Δλ. It is a figure which shows 20 emission spectra. FIG. 4B shows the reflection spectrum of the light reflecting film 40 at an incident angle of 90 ° and the phosphor when the difference (λ ₀ −λ _c ) between the wavelength λ ₀ and the wavelength λ _c matches the wavelength shift amount Δλ. FIG. 4 is a diagram showing an emission spectrum of a layer 20. FIG. 4C shows the reflection spectrum of the light reflecting film 40 at an incident angle of 90 ° and the phosphor when the difference (λ ₀ −λ _c ) between the wavelength λ ₀ and the wavelength λ _c is larger than the wavelength shift amount Δλ. FIG. 4 is a diagram showing an emission spectrum of a layer 20. FIG. 5 is a diagram showing a reflection spectrum of the light reflection film 40 at an incident angle of 0 ° and a reflection spectrum of the light reflection film 40 at an incident angle of 90 ° when the wavelengths λ ₀ and λ _c are equal. FIG. 6 shows the reflection spectrum of the light reflection film 40 at an incident angle of 0 ° when the wavelength λ ₀ and the wavelength λ _c coincide with each other (see FIG. 5), and shifted by Δλ _{a to the} longer wavelength side. It is a figure which shows the reflection spectrum of the light reflection film 40 in 90 degrees of incident angles. FIG. 7 shows a light reflecting film 40 (solid line) in which a four-layer dielectric multilayer film is formed on the metal layer 41, and a light reflecting film 40 (dashed line) in which a ten-layer dielectric multilayer film is formed on the metal layer 41. It is a figure which shows the simulation result of the reflectance of the light reflection film 40 in a certain incident angle. FIG. 8 is a diagram showing a simulation result of the reflectance of the light reflecting film 40 in which 60 dielectric multilayer films are formed on the metal layer 41. FIG. 9A is a diagram schematically illustrating an example of a reflection spectrum of the light reflection film 40 and an emission spectrum of the phosphor layer 20 at an incident angle of 0 °. FIG. 9B is a diagram schematically illustrating another example of the reflection spectrum of the light reflection film 40 and the emission spectrum of the phosphor layer 20 at an incident angle of 0 °. FIG. 10 is a diagram showing a reflection spectrum of the light reflecting film 40. FIG. 11 is a diagram showing an emission spectrum of the YAG: Ce phosphor. FIG. 12 is a diagram showing a result of plotting the performance index Z of the optical device calculated by the equation (9) with various λ ₀ varied. FIG. 13 is a diagram showing an emission spectrum of the CaAlSiN ₃ : Eu phosphor. FIG. 14 is a diagram illustrating a result of plotting the performance index Z of the optical device calculated by the equation (9) while changing λ ₀ in various ways. FIG. 15 is a diagram showing an emission spectrum of a phosphor obtained by mixing an SCA: Eu phosphor and a YAG: Ce phosphor. FIG. 16 is a diagram illustrating a result of plotting the performance index Z of the optical device calculated by the equation (9) while changing λ ₀ in various ways. FIG. 17 is a diagram showing an example of the configuration of the light reflecting film. FIG. 18 is a diagram showing a reflection spectrum of a light reflecting film manufactured under the conditions shown in Table 1.

(Knowledge that became the basis of this disclosure)
Prior to describing the embodiments of the present disclosure, the knowledge underlying the present disclosure will be described.

  In this specification, “light” means electromagnetic waves in the range of ultraviolet rays and infrared rays in addition to visible light. More specifically, an electromagnetic wave having a wavelength in the range of approximately 10 nm to 1 mm is referred to as “light”.

  Patent Document 2 discloses a configuration including a metal material as a reflective layer and further including a distributed Bragg reflector (DBR) or an omnidirectional reflector (ODR). However, when DBR is formed on a metal layer, an interference effect appears in the reflection spectrum, and the reflectance is greatly reduced at a certain wavelength. Therefore, it is difficult to make the reflectance about 100% in the entire wavelength region of 400 to 700 nm, and the efficiency of the optical device cannot be increased.

  When a dielectric multilayer film is applied to the reflective layer, the reflection spectrum shifts to the short wavelength side depending on the incident angle, and the reflectance gradually decreases. For this reason, in the optical device of the present disclosure in which a reflective layer is provided immediately below the phosphor layer described later, a dielectric multilayer film is not suitable as the reflective layer.

  When manufacturing a phosphor device, it is common to design so that the center-of-gravity wavelength of the emission spectrum of the phosphor coincides with the wavelength at which the reflection spectrum of light perpendicularly incident on the reflection layer is maximized. The center-of-gravity wavelength is a weighted average of wavelengths with the emission spectrum as a weight. In other words, the center-of-gravity wavelength is obtained by dividing the value obtained by integrating the product of the wavelength of light emitted from the phosphor and the intensity of light of the wavelength over the entire emission wavelength by the value obtained by integrating the intensity of light over the entire emission wavelength. Value. The center-of-gravity wavelength may be referred to as “average wavelength”. When light from an excitation light source (hereinafter also referred to as “excitation light”) is used in addition to the light emitted from the phosphor, the centroid wavelength including the excitation light and the reflection spectrum of vertically incident light are It is common to design so that the maximum wavelength matches. A peak wavelength may be used instead of the centroid wavelength.

  Metals have little angular dependence on reflection characteristics. Therefore, when a metal layer is used as the reflective layer, the efficiency of the phosphor device is maximized by the above design.

  On the other hand, the dielectric layer has an angle dependency on the reflection characteristics. Therefore, when the increased reflection film includes a dielectric layer, the increased reflection film has angle dependency on the reflection characteristics. According to the study by the present inventors, the amount of light incident on the reflecting layer from the phosphor increases as the incident angle increases. For this reason, the reflection characteristics of light incident on the reflection layer at a large angle greatly contribute to the efficiency of the phosphor device. However, the conventional phosphor device has not been designed in consideration of the angle dependency of the reflection characteristics of the dielectric layer. The present inventors have found that in order to increase the efficiency of the phosphor device, it is desirable to design a light reflecting film in consideration of the angle dependency of the reflection characteristics.

  Based on the above findings, the present inventor has conceived each aspect of the present disclosure described below.

  An optical device according to an aspect of the present disclosure is a light reflecting film including a metal layer and a dielectric layer on the metal layer, and a phosphor layer on the dielectric layer, and is excited by light from a light source And a phosphor layer that emits light. The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximum is longer than the barycentric wavelength of the emission spectrum of the phosphor layer, and the dielectric layer is 2 or more and 6 In the laminated structure of the following layers, the refractive indexes of two arbitrary adjacent layers in the dielectric layer are different.

  An optical device according to another aspect of the present disclosure includes a light reflection film including a metal layer and a dielectric layer on the metal layer, and a phosphor layer on the dielectric layer, and is excited by light from a light source. And a phosphor layer that emits light. The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximized is the center wavelength of the light spectrum obtained by combining the emission spectrum of the light source and the emission spectrum of the phosphor layer. The dielectric layer is a laminated structure of 2 or more and 6 or less layers, and any two adjacent layers in the dielectric layer have different refractive indexes.

  With the above configuration, as will be described later, the efficiency of the optical device can be increased.

  Hereinafter, more specific embodiments of the present disclosure will be described. However, more detailed explanation than necessary may be omitted. For example, a detailed description of already well-known matters and a redundant description of substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. The inventor provides the accompanying drawings and the following description in order for those skilled in the art to fully understand the present disclosure, and is not intended to limit the subject matter described in the claims. Absent. In the following description, components having the same or similar functions are denoted by the same reference numerals.

(Embodiment)
The optical device in the present embodiment includes a light reflection film including a metal film and a dielectric layer, and a phosphor layer. The dielectric layer is disposed on the metal film. The phosphor layer is disposed on the dielectric layer. The phosphor layer emits light when excited by light from a light source. The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximum is longer than the barycentric wavelength of the emission spectrum of the phosphor layer. Alternatively, the wavelength at which the reflectance of light perpendicularly incident on the dielectric layer is maximized is longer than the barycentric wavelength of the light spectrum including both the emission spectrum of the light source and the emission spectrum of the phosphor layer. The dielectric layer is a laminated structure of 2 or more and 6 or less layers, and any two adjacent layers in the dielectric layer have different refractive indexes.

  With the above configuration, light emitted from the phosphor layer can be reflected efficiently, and the efficiency of the optical device can be increased.

  FIG. 1 is a diagram illustrating a configuration example of an optical device 50 in the present embodiment. The optical device 50 includes a substrate 30, a light reflecting film 40 on the substrate 30, and a phosphor layer 20. The light reflecting film 40 includes a metal layer 41 and a dielectric layer 42. The substrate 30, the metal layer 41, the dielectric layer 42, and the phosphor layer 20 are laminated in this order. The substrate 30 supports the metal layer 41. The dielectric layer 42 is disposed on the metal layer 41. The phosphor layer 20 is disposed on the dielectric layer 42. The phosphor layer 20 emits light when excited by light from the light source 10.

<Basic structure of light reflecting film>
A basic configuration of the light reflecting film 40 including the metal layer 41 and the dielectric layer 42 will be described. The dielectric layer 42 is a laminated structure of 2 or more and 6 or less layers. The refractive indexes of any two adjacent layers in the dielectric layer 42 are different. Note that the thickness of each layer included in the multilayer structure is at least 3 nm or more. The stacked structure may include a layer having a thickness of less than 3 nm. In that case, the layer does not count as the number of layers of the stacked structure. Unlike the conventional DBR or dielectric multilayer film, the dielectric layer 42 does not have a periodic structure. Therefore, in the dielectric layer 42, Bragg reflection due to the periodic structure does not occur, and reflection due to thin film interference described later occurs. A laminated structure made of a dielectric material generally has a higher reflectance than a uniform medium having the same thickness and the same average refractive index as the laminated structure. Therefore, in the present embodiment, a laminated structure made of a dielectric material is used as the dielectric layer 42. However, in the following description, in order to facilitate formulation, the dielectric layer 42 that is a laminated structure is approximated as a uniform medium.

When the total number of layers of the dielectric layer 42 is N, and the film thickness and refractive index of each layer are d _i , _ni (i = 1, 2,..., N), the total film thickness d _B and the average refractive index. n _B is represented by Formula (1) and Formula (2).

  The reflection characteristics of the light reflecting film 40 can be calculated by taking into account the repetition of thin film interference occurring in the dielectric layer 42.

FIG. 2 is a diagram schematically showing that light emitted from the phosphor layer 20 enters the dielectric layer 42 and is transmitted or reflected. The refractive index of the phosphor layer 20 (medium 1) is n _A , the average refractive index of the dielectric layer 42 (medium 2) is n _B, and the refractive index of the metal layer 41 (medium 3) is n _C. The thickness of the dielectric layer 42 and _{d B.} The incident angle when the light emitted from the phosphor layer 20 is incident on the dielectric layer 42 is θ ₁ and the refraction angle is θ ₂ . Let r _ij (i, j = 1, 2, 3 (i ≠ j)) be the amplitude reflectance and amplitude transmittance when light is incident on the medium j from the medium i. The reflectivity R is expressed by equation (3) using the Fresnel formula.

Δ ₂ is a phase difference generated when light makes one round trip through the dielectric layer 42. Δ ₂ is expressed by equation (4) using the wavelength of light λ.

式（５）は、入射角度θ_１が大きくなるにつれて波長λ_ｒが短波長側にシフトすることを示している。 Assuming that the wavelength at which the reflectance of the light reflecting film 40 takes the maximum value is λ _r , the wavelength λ _r is expressed by the equation (5) from the interference condition (Δ ₂ = π).

Equation (5) indicates that the wavelength λ _r shifts to the short wavelength side as the incident angle θ ₁ increases.

When the light incident angle is 0 °, that is, when the light is vertically incident, the wavelength at which the reflectance of the light reflecting film 40 takes the maximum value is λ ₀ . When the incident angle of light is 90 °, that is, when light is incident horizontally, the wavelength at which the reflectance of the light reflecting film 40 takes the maximum value is λ ₉₀ . Expression (6) and Expression (7) are derived from Expression (5).

<Dependence of incident light amount on incident angle>
FIG. 3 is a diagram for explaining the dependence of the amount of light incident on the light reflecting film 40 from the phosphor layer 20 on the incident angle. The radius of the hemisphere shown in FIG. The phosphor layer 20 emits light in all directions. Therefore, the light emitted from the phosphor layer 20 enters the light reflecting film 40 at any incident angle (0 ° ≦ θ ₁ ≦ 90 °). Assume that light from the phosphor layer 20 is incident on the light reflecting film 40 at an incident angle θ ₁ . This light from the phosphor layer 20 passes through a micro surface having a circumference of 2π sin θ ₁ and a width of dθ ₁ . The area of the minute surface is 2π sin θ ₁ dθ ₁ . When the reflectance of the light reflecting film 40 is R (λ, θ ₁ ), the reflection intensity when the light that has passed through the minute surface is reflected by the light reflecting film 40 is R (λ, θ ₁ ) × 2πsin θ. proportional to _{1 dθ 1.} R (λ, θ ₁₎ a × 2πsinθ ₁ dθ _1, 0 by integrating in a range of _{° ≦ θ 1 ≦ 90 ° (} 0 ≦ θ 1 ≦ π / 2), of the light reflection film 40 in consideration of the angular dependence A reflection intensity Y (λ) is obtained. Y (λ) is expressed by equation (8).

  Expression (8) reflects that the amount of light incident on the light reflecting film 40 increases as the incident angle increases. That is, Expression (8) reflects that the light reflection characteristic at a large incident angle contributes more to the efficiency of the optical device 50 than the light reflection characteristic at a small incident angle. .

λ_ｉ、λ_ｆ（λ_ｉ＜λ_ｆ）は、蛍光体層２０の発光スペクトルの両端の波長を示している。 <Performance index of phosphor device>
The emission spectrum of the phosphor layer 20 is I (λ), and the performance index of the optical device 50 is Z. The performance index Z of the optical device 50 can be calculated by integrating the product of the reflection intensity Y (λ) of the light reflection film 40 in consideration of the angle dependency and the emission spectrum I (λ) of the phosphor layer 20. The performance index Z of the optical device 50 is expressed by Expression (9).

λ _i and λ _f (λ _i <λ _f ) indicate the wavelengths at both ends of the emission spectrum of the phosphor layer 20.

<Principle for improving energy conversion efficiency of optical devices>
The contribution of the reflectance of the light reflecting film 40 at a large incident angle is large in the energy conversion efficiency of the optical device 50. The center-of-gravity wavelength of the emission spectrum of the phosphor layer 20 is λ _c, and the reflectance of the light reflecting film 40 for light having a wavelength λ incident at an incident angle of 90 ° is R ₉₀ (λ). The higher the reflectivity R ₉₀ (λ _c ), the higher the efficiency of the optical device 50.

4A to 4C are diagrams showing examples of the reflection spectrum of the light reflection film 40 and the emission spectrum of the phosphor layer 20 for light incident at an incident angle of 90 °. FIG. 4A shows an example in which the difference (λ ₀ −λ _c ) between the wavelength λ ₀ and the wavelength λ _c is smaller than the wavelength shift amount Δλ (= λ ₀ −λ ₉₀ ). FIG. 4B shows an example in which the difference (λ ₀ −λ _c ) between the wavelength λ ₀ and the wavelength λ _c matches the wavelength shift amount Δλ. FIG. 4C shows an example in which the difference (λ ₀ −λ _c ) between the wavelength λ ₀ and the wavelength λ _c is larger than the wavelength shift amount Δλ.

In the example of FIG. 4B, the wavelengths λ ₉₀ and λ _c coincide (λ ₉₀ = λ _c ). Therefore, R ₉₀ (λ _c ) = R ₉₀ (λ ₉₀ ). On the other hand, in the example of FIG. 4A, the wavelength λ ₉₀ shifts to the shorter wavelength side than the wavelength λ _c , and R ₉₀ (λ _c ) <R ₉₀ (λ ₉₀ ). As a result, the efficiency of the optical device 50 having the characteristics shown in FIG. 4A is smaller than the efficiency of the optical device 50 having the characteristics shown in FIG. 4B. Similarly, in the example of FIG. 4C, the wavelength λ ₉₀ is shifted to the longer wavelength side than the wavelength λ _c and R ₉₀ (λ _c ) <R ₉₀ (λ ₉₀ ). As a result, the efficiency of the optical device 50 having the characteristics shown in FIG. 4C is smaller than the efficiency of the optical device 50 having the characteristics shown in FIG. 4B.

<Conditions for improving luminous efficiency>
FIG. 5 shows an example of the reflection spectrum of the light reflection film 40 at an incident angle of 0 ° and an example of the reflection spectrum of the light reflection film 40 at an incident angle of 90 ° when the wavelengths λ ₀ and λ _c are equal. FIG. In this example, in accordance with the conventional design concept, the wavelength λ ₀ at which the reflectance of the light reflecting film 40 at the incident angle of 0 ° is maximized matches the centroid wavelength λ _c of the emission spectrum of the phosphor layer 20. A body layer 42 is designed. The reflectance R ₉₀ (λ _c ) when light of wavelength λ _c is incident on the light reflecting film 40 at an incident angle of 90 ° is lower than the peak value of the reflectance.

Here, another wavelength at which the reflectance becomes equal to R ₉₀ (λ _c ) is λ _a (λ _a <λ _c ), and the difference between the wavelength λ _c and the wavelength λ _a is Δλ _a (= λ _c −λ _a). ). Assuming that the reflection spectrum of the light reflection film 40 is generally assumed that shifted to the long wavelength side wavelength less than [Delta] [lambda] _a, the reflectance of light of the center of gravity wavelength lambda _c incident on the light reflection film 40 at an incident angle of 90 ° Will improve. For this reason, it can be expected that the overall luminous efficiency is improved. Hereinafter, this point will be described in more detail.

Since the reflectances R _{90 at the} wavelengths λ _a and λ _c are equal, Equation (10) is derived from Equation (3).

Δ _a and Δ _c indicate phase differences at wavelengths λ _a and λ _c , respectively. Expression (11) is derived from Expression (10).

From λ _c = λ ₀ and incident angle θ ₁ = 90 °, Δ _c is expressed by equation (12) from equations (4) and (6).

From the equations (4), (6), (11) and (12), λ _a is expressed by the equation (13).

Wavelength lambda _a is maximum becomes a value within the possible values in the equation (13). Thus, lambda _a is represented by equation (14).

When the difference between the wavelength λ _c and the wavelength λ _a is Δλ _a (= λ _c −λ _a ), Δλ _a is expressed by the equation (15).

When the difference between λ ₉₀ and λ _a is Δλ _b (= λ ₉₀ −λ _a ), Δλ _b is expressed by equation (16) from equations (7) and (14).

6, the example shown in FIG. 5, when the respective reflection spectrum of the light reflection film 40 was shifted to the long wavelength side [Delta] [lambda] _a, the reflection spectrum of the light reflection film 40 at an incident angle of 0 °, the incident angle It is a figure which shows the reflection spectrum of the light reflection film 40 at 90 degrees. FIG. 6 also shows two reflection spectra of the light reflecting film 40 in FIG. 5 for comparison. In this case, the peak wavelength of the reflection spectrum at an incident angle of 0 ° is λ _0m (= λ _c + Δλ _a ). In an actual device, if the wavelength λ ₀ at which the reflectance of light incident at 0 ° reaches a peak is larger than λ _{c and} smaller than the wavelength λ _{0 m, the} luminous efficiency is improved as compared with the example shown in FIG. Can be expected. Therefore, the wavelength λ _{0 m} can be set to the upper limit value of the wavelength λ ₀ . Since λ _0m = Δλ _b + Δλ + λ _c , the wavelength λ _0m is expressed by equation (17) using equations (7) and (16).

From the above, when λ _0m is set as the upper limit value of the wavelength λ ₀ , the possible range of λ ₀ is expressed by the equation (18).

When the wavelength lambda ₀ is a wavelength range represented by the formula (18), the energy conversion efficiency of the optical device 50, same as the case of λ _{c =} λ _0, it is higher than at λ _{c =} λ _0.

式（１９）のλ_０の波長範囲は、式（１８）のλ_０の波長範囲よりも狭い。 Furthermore, if the energy conversion efficiency of the optical device 50 is maximized, i.e. the value of the wavelength lambda ₀ in the case of satisfying the λ _{c =} λ _90, or the upper limit value of the wavelength lambda _0. In that case, the possible range of λ ₀ is expressed by Equation (19).

The wavelength range of λ _{0 in} equation (19) is narrower than the wavelength range of λ _{0 in} equation (18).

The lower limit value of the wavelength λ ₀ may be made larger than λ _c .

For example, as a wavelength lambda ₁₀ at which the reflectance becomes peak at θ ₁ = 10 ° in the case of the wavelength λ ₀ = λ _c, the difference between the lambda ₀ and lambda ₁₀ an (λ ₀ -λ ₁₀₎ on the wavelength lambda _c The added value (2λ _c −λ ₁₀ ) may be set as the lower limit value of the wavelength λ ₀ . In that case, a possible range of λ ₀ is expressed by Expression (20).

Similarly, ₃₀ the wavelength lambda at which the reflectance becomes peak at theta ₁ = 30 ° in the case of the wavelength λ ₀ = λ _c, the wavelength difference between the lambda ₀ and _{λ 30 (λ 0 -λ 30)} λ c The value added to (2λ _c −λ ₃₀ ) may be used as the lower limit value of the wavelength λ ₀ . In that case, the possible range of λ ₀ is expressed by the equation (21).

In the formula (18) or (19), instead of the lower limit lambda _c, may be used lower limit of the formula (20) or (21). In the optical device 50 according to the present embodiment, the dielectric layer 42 can be designed to satisfy, for example, the formula (18) or (19). However, it is not limited to this condition. In the present disclosure, the wavelength λ _{0 at} which the reflectance of light perpendicularly incident on the dielectric layer is maximized should be longer than the centroid wavelength λ _c of the emission spectrum of the phosphor layer 20.

  Next, a case where a conventional dielectric multilayer film having a periodic structure is formed on the metal layer 41 will be described. The dielectric multilayer film is formed, for example, by alternately stacking two layers having different refractive indexes. In that case, the number of layers of the dielectric multilayer film having the period number M is 2M. Hereinafter, a structure having a small number of layers due to a small number of cycles is also referred to as a “dielectric multilayer film”. In the dielectric multilayer film, high reflectivity is obtained in a specific wavelength region by Bragg reflection due to the periodic structure. In other wavelength regions, a reflection peak occurs due to thin film interference (see, for example, FIG. 2) when the entire dielectric multilayer film is a thin film.

  FIG. 7 shows a light reflecting film 40 (solid line) in which a four-layer dielectric multilayer film is formed on the metal layer 41, and a light reflecting film 40 (dashed line) in which a ten-layer dielectric multilayer film is formed on the metal layer 41. It is a figure which shows the simulation result of the reflectance of the light reflection film 40 in the incidence angle 0 degree in FIG. Four layers correspond to two periods, and ten layers correspond to five periods. The light reflection film 40 in which the four-layer dielectric multilayer film is formed on the metal layer 41 has a small number of periods, and the effect of Bragg reflection is small.

  In the light reflecting film 40 (solid line) in which the four dielectric multilayer films are formed on the metal layer 41, the reflectance is 90% or more in the wavelength region of 400 nm to 700 nm. On the other hand, in the light reflection film 40 (broken line) in which the dielectric multilayer film of 10 layers is formed on the metal layer 41, the reflectance is greatly reduced in the vicinity of the wavelength of 600 nm due to the thin film interference. Therefore, in order to suppress a decrease in reflectivity due to thin film interference, it is desirable that the number of stacked layers on the metal layer 41 is small, and in particular, it may be 6 layers or less. The same applies to the dielectric layer 42 having no periodic structure. In this specification, a structure having an extremely small number of periods such as two periods is also defined as the dielectric layer 42 having no periodic structure.

  In order to improve the efficiency of the optical device 50, it is desirable to increase the reflectance in the wavelength region of 400 to 700 nm for all incident angles. Therefore, attention is paid to the dependency of the incident angle of the dielectric multilayer film.

  FIG. 8 is a diagram showing a simulation result of the reflectance of the light reflecting film 40 in which 60 dielectric multilayer films are formed on the metal layer 41. The solid line represents the reflectance at an incident angle of 0 °, and the broken line represents the reflectance at an incident angle of 80 °. The 60 layers correspond to 30 periods. In the 60-layer dielectric multilayer film, significant Bragg reflection occurs.

  When the incident angle is 0 °, the reflectance is about 100% in the wavelength region of approximately 400 nm to 550 nm. The reflectance of about 100% in this specific wavelength region is obtained by Bragg reflection due to the periodic structure. A plurality of reflection peaks in other frequency regions are obtained by thin film interference. On the other hand, when the incident angle is 80 °, the wavelength region where the reflectance is about 100% is shifted to the short wavelength side, and the width of the wavelength region is reduced.

  Therefore, in order to obtain high reflectance in the wavelength region of 400 to 700 nm for all incident angles, the width of the wavelength region of high reflectance at the incident angle of 0 ° is larger than the width of the wavelength region of 400 to 700 nm. However, it must be increased by the sum of the shift amount of the reflectivity and the amount by which the width of the high reflectivity wavelength region is reduced with the shift. The width of the high reflectance wavelength region at an incident angle of 0 ° may be, for example, 500 nm or more. The high reflectivity may not be about 100%, but may be 80% or more.

  The reflection spectrum of the light reflecting film 40 at a large incident angle greatly contributes to the efficiency of the optical device 50. Therefore, in order to increase the efficiency, the peak wavelength of the reflection spectrum at a large incident angle (for example, 80 °) may be made to coincide with the barycentric wavelength of the emission spectrum of the phosphor layer 20. Further, the shift amount of the peak wavelength of the reflection spectrum due to the increase in the incident angle also contributes to the efficiency of the optical device 50.

  FIG. 9A is a diagram schematically illustrating an example of a reflection spectrum of the light reflection film 40 and an emission spectrum of the phosphor layer 20 at an incident angle of 0 °. FIG. 9B is a diagram schematically illustrating another example of the reflection spectrum of the light reflection film 40 and the emission spectrum of the phosphor layer 20 at an incident angle of 0 °. Although not shown in FIGS. 9A and 9B, the peak wavelength of the reflection spectrum of the light reflection film 40 at an incident angle of 80 ° is designed to coincide with the barycentric wavelength of the emission spectrum of the phosphor layer 20. Therefore, the peak wavelength at which the reflectance at the incident angle of 0 ° is maximized is longer than the peak wavelength at which the reflectance at the incident angle of 80 ° is maximized.

  In the example shown in FIG. 9A, the shift amount of the peak wavelength of the reflection spectrum of the light reflection film 40 due to the increase in the incident angle is large, and the overlap integral between the emission spectrum of the phosphor layer 20 and the reflection spectrum of the light reflection film 40 is small. On the other hand, in the example shown in FIG. 9B, the shift amount of the peak wavelength of the reflection spectrum of the light reflection film 40 due to the increase in the incident angle is small, and the overlap integral between the emission spectrum of the phosphor layer 20 and the reflection spectrum of the light reflection film 40 is large.

  In order to improve the efficiency of the optical device, the shift amount of the peak wavelength of the reflection spectrum when the incident angle increases from 0 ° to 90 ° may be reduced. For example, the difference in peak wavelength at incident angles 0 ° and 45 ° is, for example, 70 nm or less, and in an example, 40 nm or less.

  The shift amount of the peak wavelength of the reflection spectrum tends to increase as the thickness of the dielectric layer 42 formed on the metal layer 41 increases. Therefore, the film thickness of the dielectric layer 42 can be set to a small value. The film thickness of the dielectric layer 42 may be, for example, 400 nm or less, or 200 nm or less.

  The efficiency of the optical device 50 in the present embodiment is wide in the wavelength region where the reflectance of the light reflecting film 40 at an incident angle of 0 ° is 80% or more, and the shift amount of the peak wavelength of the reflection spectrum due to the change in the incident angle. Is improved when the number of dielectric layers 42 is small and the thickness of the dielectric layer 42 is small.

<Components of optical device>
Hereinafter, the components of the optical device 50 in FIG. 1 will be described in more detail.

  The light source 10 may be a solid light source that emits light having a wavelength of 450 nm or less, for example. As the light source 10, for example, a light source such as an LD or LED having an emission wavelength in a region from ultraviolet light to blue light can be used. The light source 10 emits excitation light toward the phosphor layer 20. In the example shown in FIG. 1, the excitation light from the light source 10 enters from the surface of the phosphor layer 20 opposite to the dielectric layer 42 (hereinafter referred to as “upper surface”). The light source 10 is disposed away from the phosphor layer 20, the light reflecting film 40, and the substrate 30. This is to prevent the phosphor layer 20 from being heated by the heat generated by the light source 10 to reduce the light emission efficiency. The light source 10 may include one or more lenses that focus the emitted light in addition to a light emitting element such as an LD or an LED.

  A configuration in which excitation light from the light source 10 is incident from the same side of the phosphor layer 20 as the dielectric layer 42 is also possible. Alternatively, a configuration in which excitation light is incident from the side surface of the phosphor layer 20 is also possible. On the other hand, in the configuration in which the excitation light is incident from the upper surface of the phosphor layer 20, it is easy to ensure the distance between the light source 10 and the phosphor layer 20. For this reason, it is easy to suppress that the fluorescence characteristic of the fluorescent substance layer 20 falls with the heat | fever which the light source 10 emits.

  The light source 10 may be a light source including a solid-state laser. For the solid-state laser, a solid material such as crystal or glass doped with transition metal ions or rare earth ions is used. Compared with the LED, the solid-state laser has a high light collecting property. Therefore, if the phosphor layer 20 is excited using a solid-state laser, the emission point of the phosphor layer 20 can be reduced. In order to avoid the influence of heat generation, the solid-state laser light source is arranged as far as possible from the phosphor layer 20.

The phosphor layer 20 receives the excitation light emitted from the light source 10 and emits fluorescence having a wavelength longer than the wavelength of the excitation light. The light emitted from the phosphor layer 20 has at least one peak in a wavelength region of, for example, 400 nm to 800 nm. The phosphor layer 20 may include a plurality of phosphor materials that emit blue light, green light, yellow light, and red light. As a phosphor material that emits blue light, for example, Sr ₅ (PO 4) 3 Cl: Eu ²⁺ (SCA) or BaMgAl ₁₀ O 17: Eu ²⁺ (BAM) can be used. As a phosphor material that emits green light, for example, Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ (LuAG) can be used. As a phosphor material that emits yellow light, for example, a material containing YAG: Ce (cerium-doped yttrium, aluminum, garnet) can be used. Specifically, for example, Y ₃ Al ₅ O ₁₂ : Ce ³⁺ (YAG) or the like can be used. As the phosphor material that emits red light, for example, CaAlSiN ₃ : Eu ²⁺ (CASN), La ₃ Si ₆ N ₁₁ : Ce ³⁺ (LSN), or the like can be used.

  You may implement | achieve light emission of a desired spectrum combining the light which the fluorescent substance layer 20 emits, and the excitation light which the light source 10 emits. For example, white light emission may be realized by combining the light source 10 that emits blue excitation light and the phosphor layer 20 that emits yellow light upon receiving the excitation light.

  As the phosphor layer 20, for example, a phosphor powder dispersed in glass or resin, a glass phosphor in which a luminescent center ion is added to a glass matrix, or phosphor ceramics can be used.

  Although the thickness of the fluorescent substance layer 20 is not specifically limited, For example, it may be designed by 1 micrometer or more and 100 micrometers or less. By setting to such a range, it is possible to suppress heat from being accumulated in the phosphor layer 20. Thereby, a reduction in luminance can be suppressed.

  The light emission surface of the phosphor layer 20, that is, the surface on which the excitation light from the light source 10 is incident, may be subjected to a treatment for preventing reflection of the excitation light as necessary. An antireflection film may be provided on the light emitting surface.

  The substrate 30 can also function as a heat dissipation substrate that releases the heat generated from the phosphor layer 20 to the outside. For this reason, the board | substrate 30 may be comprised with the material which has a high heat conductive characteristic, for example.

  For the metal layer 41, for example, a metal material having a high reflectance in the visible light region can be used. For example, a metal such as Al (aluminum), Ag (silver), or Au (gold), or an alloy of these metals (such as an aluminum alloy, a silver alloy, or a gold alloy) can be used. That is, the metal layer 41 can include at least one of silver, a silver alloy, aluminum, and an aluminum alloy. In particular, in order to increase the reflectance, for example, Ag or an Ag alloy is used.

The dielectric layer 42 includes, for example, a high refractive index material and a low refractive index material including dielectric materials having different refractive indexes. The high refractive index material and the low refractive index material can be alternately laminated a plurality of times. The thickness of each layer of the dielectric thin film constituting the dielectric layer 42 may be, for example, about 1 nm to about 100 nm. The total thickness of the dielectric layer 42 can be, for example, about 50 nm to 400 nm. As the low refractive index material, for example, MgF ₂ (n = 1.38), SiO ₂ (n = 1.46), Al ₂ O ₃ (n = 1.77), or the like can be used. As the high refractive index material, for example, Ta ₂ O ₅ (n = 2.20), TiO ₂ (n = 2.50), Nb ₂ O ₅ (n = 2.35), or the like can be used.

  The light reflecting film 40 includes a metal layer 41 and a dielectric layer 42 disposed on the metal layer 41. The light reflecting film 40 reflects the light emitted from the phosphor layer 20 and the excitation light transmitted through the phosphor layer 20 toward the light emitting surface of the phosphor layer 20. The light reflecting film 40 is disposed between the phosphor layer 20 and the substrate 30. The reflection spectrum of the light reflection film 40 at an incident angle of 0 ° may have at least one peak in a wavelength range of 400 nm to 800 nm, for example. The reflection spectrum may have a peak in another wavelength region.

  FIG. 10 is a diagram illustrating an example of a reflection spectrum of the light reflecting film 40. As shown in FIG. 10, the light reflecting film 40 has an angle dependency in the reflection characteristics. As the incident angle increases, the reflectance peak of the reflection spectrum shifts to the short wavelength side. In the reflection spectrum of the light reflection film 40, the shift amount of the wavelength at which the peak value of the reflection spectrum is changed by an incident angle change from 0 ° to 90 ° can be changed by, for example, about 10 nm or more. In the light reflecting film 40 exhibiting such a wavelength shift, the effect of the embodiment of the present disclosure can be obtained particularly remarkably.

<Comparison with simulation results>
The inventors have confirmed by simulation that the efficiency of the optical device 50 is improved by providing the light reflecting film 40 of the present embodiment. In this simulation, the performance index Z of the optical device represented by Expression (9) was calculated.

The results will be described below. In calculating, the following parameters were set. For the metal layer 41, an Ag alloy (Ag—Pd—Cu) was used. The dielectric layer 42 is composed of three layers of TiO ₂ —SiO ₂ —Al ₂ O ₃ (see FIG. 17). The reflection spectrum of the light reflecting film 40 was calculated by an optical simulation using DiffractMOD, which is a diffractive optical element design / analysis software based on the Rigorous Coupled-Wave Analysis (RCWA) method. In the calculation of the following formulas (18) and (19), n _A = 1.0 and n _B = 2.05 were used.

  First, the results when a YAG: Ce phosphor is used as the phosphor material will be described.

FIG. 11 is a diagram illustrating an example of an emission spectrum of a YAG: Ce phosphor. The center-of-gravity wavelength of the emission spectrum of this YAG: Ce phosphor is λ _c = 565 nm.

FIG. 12 is a diagram showing a result of plotting the performance index Z of the optical device calculated by the equation (9) while variously changing λ ₀ . As shown in FIG. 12, when the wavelength λ ₀ is longer than the center of gravity wavelength of the emission spectrum of the YAG: Ce phosphor, the efficiency of the optical device is increased.

When a YAG: Ce phosphor is used as the phosphor material, the wavelength range of the wavelength λ ₀ in Equation (18) is 565 <λ ₀ ≦ 717 nm. Further, the wavelength range of the wavelength λ ₀ in the equation (19) is 565 <λ ₀ ≦ 653 nm. Further, the wavelength ranges of the wavelength λ ₀ in the equations (20) and (21) are λ ₀ ≧ 567 nm and λ ₀ ≧ 582 nm, respectively.

From the result of the optical simulation shown in FIG. 12, the wavelength range of λ _{0 in which} the efficiency of the optical device 50 is improved is 565 nm to 677 nm (range of the horizontal double-headed arrow in FIG. 12). The optical device has the highest efficiency when λ ₀ = 628 nm (upward arrow in FIG. 12). Therefore, the range of Formula (18) and Formula (19) is satisfy | filled.

Next, the results when using a CaAlSiN ₃ : Eu phosphor as the phosphor material are shown.

FIG. 13 is a diagram showing an emission spectrum of the CaAlSiN ₃ : Eu phosphor. The center-of-gravity wavelength of the emission spectrum of the CaAlSiN ₃ : Eu phosphor is λ _c = 654 nm.

FIG. 14 is a diagram illustrating a result of plotting the performance index Z of the optical device calculated by the equation (9) while changing λ ₀ in various ways. As shown in FIG. 14, when the wavelength λ ₀ is on the longer wavelength side than the barycentric wavelength of the emission spectrum of the CaAlSiN ₃ : Eu phosphor, the efficiency of the optical device is increased.

When a CaAlSiN3: Eu phosphor is used as the phosphor material, the wavelength range of the wavelength λ ₀ in Equation (18) is 654 <λ ₀ ≦ 823 nm. Further, the wavelength range of the wavelength λ ₀ in the equation (19) is 654 <λ ₀ ≦ 749 nm. Furthermore, the wavelength ranges of the wavelength λ ₀ in the equations (20) and (21) are λ ₀ ≧ 656 nm and λ ₀ ≧ 674 nm, respectively.

From the result of the optical simulation shown in FIG. 14, the wavelength range of λ _{0 in which} the efficiency of the optical device is improved is 654 nm to 757 nm (range of the horizontal double arrow in FIG. 14). The efficiency of the optical device is highest when λ ₀ = 697 nm (upward arrow in FIG. 14). Therefore, the range of Formula (18) and Formula (19) is satisfy | filled.

  The phosphor layer 20 may include a plurality of phosphor materials. Hereinafter, the results in the case of using a phosphor obtained by mixing SCA: Eu phosphor and YAG: Ce phosphor as the phosphor material will be shown.

FIG. 15 is a diagram showing an emission spectrum of a phosphor obtained by mixing an SCA: Eu phosphor and a YAG: Ce phosphor. The centroid wavelength of the emission spectrum of the phosphor in which the SCA: Eu phosphor and the YAG: Ce phosphor are mixed is λ _c = 544 nm.

FIG. 16 is a diagram illustrating a result of plotting the performance index Z of the optical device calculated by the equation (9) while changing λ ₀ in various ways. As shown in FIG. 16, when the wavelength λ ₀ is on the longer wavelength side than the barycentric wavelength of the emission spectrum of the phosphor obtained by mixing the SCA: Eu phosphor and the YAG: Ce phosphor, the efficiency of the optical device is Get higher.

When the SCA: Eu phosphor and the YAG: Ce phosphor are mixed as the phosphor material, the wavelength range of the wavelength λ ₀ in the equation (18) is 544 <λ ₀ ≦ 684 nm. Further, the wavelength range of the wavelength λ ₀ in the equation (19) is 544 <λ ₀ ≦ 623 nm. Furthermore, the wavelength ranges of the wavelength λ ₀ in the equations (20) and (21) are λ ₀ ≧ 546 nm and λ ₀ ≧ 560 nm, respectively.

From the result of the optical simulation shown in FIG. 16, the wavelength range of λ _{0 in which} the efficiency of the optical device is improved is 544 nm to 611 nm (range of a double arrow in the horizontal direction in FIG. 16). The efficiency of the optical device is highest when λ ₀ = 584 nm (upward arrow in FIG. 16). Therefore, the range of Formula (18) and Formula (19) is satisfy | filled.

  From the above simulation results, the validity of the ranges shown in Equation (18) and Equation (19) was confirmed.

In the above example, only the emission spectrum of the phosphor layer was considered. This embodiment is also effective when an optical spectrum including both the emission spectrum of the light source and the emission spectrum of the phosphor layer is used. In that case, the centroid wavelength of the light spectrum obtained by combining both the light emission spectrum of the light source and the light emission spectrum of the phosphor layer may be used as λ _c .

  Next, the reason why the result of the optical simulation and the calculation results of the equations (18) and (19) do not match will be examined.

In the calculations of Equation (18) and Equation (19), it is assumed that the efficiency of the optical device depends only on the reflectance R (λ, θ ₁ ) at θ ₁ = 90 ° that contributes the most to the efficiency of the optical device. (See equation (8)). However, the optical simulation, the efficiency of the optical device, as shown in equation (8), also depends on the reflectivity of the outside θ _{1 =} 90 ° as well reflectance at θ _{1 =} 90 °.

  That is, due to the above assumptions in the calculations of Expression (18) and Expression (19), a difference occurs between the result of the optical simulation and the calculation results of Expression (18) and Expression (19). Nevertheless, equations (18) and (19) are valid as a simple estimate of the wavelength range over which the efficiency of the optical device is increased.

<Deposition of light reflecting film>
An embodiment of a method for producing a light reflecting film will be described. The inventors of the present invention produced a light reflection film by the following method.

First, a metal layer was formed on a mirror-finished substrate by sputtering. The material of the metal layer is an Ag alloy (Ag—Pd—Cu). The thickness of the metal layer was 150 nm. Further, Al ₂ O ₃ , SiO ₂ , and TiO ₂ were sequentially formed by a sputtering method, and a dielectric layer was formed on the metal layer. The thickness of the dielectric layer was set to 100 nm to 150 nm. The film formation is not limited to the sputtering method, and a method such as vapor deposition may be used.

<Reflection spectrum of light reflecting film>
An example of the structure of the light reflecting film is shown in FIG. As shown in FIG. 17, an Ag alloy (Ag—Pd—Cu) was used as the metal layer 41, and the thickness of the film was set to 150 nm. The dielectric layer 42 formed on the metal layer 41 was constituted by a laminated structure of Al ₂ O ₃ , SiO ₂ and TiO ₂ .

  Table 1 shows the refractive index and thickness of each dielectric thin film.

In the example of FIG. 17, dielectric thin films of Al ₂ O ₃ , SiO ₂ and TiO ₂ are laminated on the metal layer 41 in this order. In the three-layered dielectric layer 42, the upper layer in contact with the air layer has the highest refractive index, and the middle layer has the lowest refractive index. This is to increase the reflectance of the dielectric layer 42. In general, the greater the difference in refractive index between two adjacent layers, the higher the reflectance of the laminated structure. Among the combinations of Al ₂ O ₃ , SiO ₂ and TiO ₂ in Table 1, when dielectric thin films of Al ₂ O ₃ , SiO ₂ and TiO ₂ are laminated in this order on the metal layer 41, the dielectric layer 42 Has the highest reflectivity.

  In the above example, the dielectric layer 42 having a three-layer structure is used. However, for example, the same effect can be obtained by using the dielectric layer 42 having a five-layer structure.

The average refractive index n _B and the total film thickness d _B of the dielectric layer 42 having a three-layer structure are n _B = 2.05 and d _B = 125 nm, respectively.

FIG. 18 is a diagram showing a reflection spectrum of a light reflecting film manufactured under the conditions shown in Table 1. The reflection spectrum of the light reflecting film 40 shifts to the short wavelength side as the incident angle increases. The wavelength when the reflection spectrum of the light reflection film 40 at the incident angle of 0 ° is maximized is λ ₀ = 620 nm.

Consider the case where YAG: Ce is used as the phosphor of the phosphor layer. The centroid wavelength of the emission spectrum of the YAG: Ce phosphor is λ _c = 565 nm. Therefore, the wavelength range of the wavelength λ ₀ in the equation (18) is 565 <λ ₀ ≦ 711 nm. Further, the wavelength range of the wavelength λ ₀ in the equation (18) is 565 <λ ₀ ≦ 647 nm.

In the light reflection film 40 described above, the wavelength λ ₀ = 628 nm and the wavelength range is 565 ≦ λ ₀ ≦ 647 nm.

  As described above, the present disclosure includes the devices described in the following items.

[Item 1]
A light reflecting film comprising a metal layer and a dielectric layer on the metal layer;
A phosphor layer on the dielectric layer that emits light when excited by light from a light source; and
With
The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximized is longer than the centroid wavelength of the emission spectrum of the phosphor layer,
The dielectric layer is a laminated structure of 2 or more and 6 or less layers, and any two adjacent layers in the dielectric layer have different refractive indexes.
Optical device.

[Item 2]
The width of the wavelength region where the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is 80% or more is 500 nm or more.
Item 4. The optical device according to Item 1.

[Item 3]
The first wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximum is light incident on the light reflecting film from the phosphor layer side at an incident angle of 45 °. Longer than the second wavelength at which the reflectance of the first is the maximum, the difference between the first wavelength and the second wavelength is 70 nm or less,
Item 3. The optical device according to Item 1 or 2.

[Item 4]
The difference between the first wavelength and the second wavelength is 40 nm or less.
Item 3. The optical device according to Item 1 or 2.

[Item 5]
The dielectric layer has a thickness of 400 nm or less.
Item 5. The optical device according to any one of Items 1 to 4.

[Item 6]
The film thickness of the dielectric layer is 200 nm or less.
Item 5. The optical device according to any one of Items 1 to 4.

を満たす、
項目１から６のいずれかに記載の光デバイス。 [Item 7]
The refractive index of the phosphor layer is n _A ,
The average refractive index of the dielectric layer is n _B ,
The wavelength at which the reflectance of light perpendicularly incident on the dielectric layer is maximized is λ ₀ ,
When the center of gravity wavelength of the emission spectrum of the phosphor layer is λ _c ,

Meet,
Item 7. The optical device according to any one of Items 1 to 6.

を満たす、
項目１から６のいずれかに記載の光デバイス。 [Item 8]
The refractive index of the phosphor layer is n _A ,
The average refractive index of the dielectric layer is n _B ,
The wavelength at which the reflectance of light perpendicularly incident on the dielectric layer is maximized is λ ₀ ,
When the center of gravity wavelength of the emission spectrum of the phosphor layer is λ _c ,

Meet,
Item 7. The optical device according to any one of Items 1 to 6.

を満たす、
項目８に記載の光デバイス。 [Item 9]

Meet,
Item 9. The optical device according to Item 8.

を満たす、
項目１から６のいずれかに記載の光デバイス。 [Item 10]
The refractive index of the phosphor layer is n _A ,
The average refractive index of the dielectric layer is n _B ,
The wavelength at which the reflectance of light perpendicularly incident on the dielectric layer is maximized is λ ₀ ,
When the center of gravity wavelength of the emission spectrum of the phosphor layer is λ _c ,

Meet,
Item 7. The optical device according to any one of Items 1 to 6.

[Item 11]
The emission spectrum of the phosphor layer has at least one peak in the range of 400 nm to 800 nm.
Item 11. The optical device according to any one of Items 1 to 10.

[Item 12]
A substrate supporting the metal layer;
Item 12. The optical device according to any one of Items 1 to 11.

[Item 13]
The metal layer includes at least one of silver, a silver alloy, aluminum, and an aluminum alloy.
Item 13. The optical device according to any one of Items 1 to 12.

[Item 14]
The phosphor layer includes cerium-doped yttrium aluminum garnet,
14. The optical device according to any one of items 1 to 13.

[Item 15]
The light source includes a solid state laser,
Item 15. The optical device according to any one of Items 1 to 14.

[Item 16]
The light from the light source is incident from the surface of the phosphor layer opposite to the dielectric layer.
Item 16. The optical device according to any one of Items 1 to 15.

[Item 17]
A light reflecting film comprising a metal layer and a dielectric layer on the metal layer;
A phosphor layer on the dielectric layer that emits light when excited by light from a light source; and
With
The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side becomes the maximum is the barycentric wavelength of the light spectrum obtained by combining the emission spectrum of the light source and the emission spectrum of the phosphor layer. Longer than
The dielectric layer is a laminated structure of 2 or more and 5 or less layers, and any two adjacent layers in the dielectric layer have different refractive indexes.
Optical device.

  The optical device in the embodiment of the present disclosure can be used for applications such as a light emitting device.

DESCRIPTION OF SYMBOLS 1 Incident medium 10 Solid light source 20 Phosphor 30 Substrate 40 Light reflection film 41 Metal layer 42 Dielectric layer 50 Phosphor device

Claims (17)

A light reflecting film comprising a metal layer and a dielectric layer on the metal layer;
A phosphor layer on the dielectric layer that emits light when excited by light from a light source; and
With
The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximized is longer than the centroid wavelength of the emission spectrum of the phosphor layer,
The dielectric layer is a laminated structure of 2 or more and 6 or less layers, and any two adjacent layers in the dielectric layer have different refractive indexes.
Optical device. The width of the wavelength region where the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is 80% or more is 500 nm or more.
The optical device according to claim 1. The first wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side is maximum is light incident on the light reflecting film from the phosphor layer side at an incident angle of 45 °. Longer than the second wavelength at which the reflectance of the first is the maximum, the difference between the first wavelength and the second wavelength is 70 nm or less,
The optical device according to claim 1. The difference between the first wavelength and the second wavelength is 40 nm or less.
The optical device according to claim 1. The dielectric layer has a thickness of 400 nm or less.
The optical device according to claim 1. The film thickness of the dielectric layer is 200 nm or less.
The optical device according to claim 1. The refractive index of the phosphor layer is n _A ,
The average refractive index of the dielectric layer is n _B ,
The wavelength at which the reflectance of light perpendicularly incident on the dielectric layer is maximized is λ ₀ ,
When the center of gravity wavelength of the emission spectrum of the phosphor layer is λ _c ,

Meet,
The optical device according to claim 1. The refractive index of the phosphor layer is n _A ,
The average refractive index of the dielectric layer is n _B ,
The wavelength at which the reflectance of light perpendicularly incident on the dielectric layer is maximized is λ ₀ ,
When the center of gravity wavelength of the emission spectrum of the phosphor layer is λ _c ,

Meet,
The optical device according to claim 1.

Meet,
The optical device according to claim 8. The refractive index of the phosphor layer is n _A ,
The average refractive index of the dielectric layer is n _B ,
The wavelength at which the reflectance of light perpendicularly incident on the dielectric layer is maximized is λ ₀ ,
When the center of gravity wavelength of the emission spectrum of the phosphor layer is λ _c ,

Meet,
The optical device according to claim 1. The emission spectrum of the phosphor layer has at least one peak in the range of 400 nm to 800 nm.
The optical device according to claim 1. A substrate supporting the metal layer;
The optical device according to claim 1. The metal layer includes at least one of silver, a silver alloy, aluminum, and an aluminum alloy.
The optical device according to claim 1. The phosphor layer includes cerium-doped yttrium aluminum garnet,
The optical device according to claim 1. The light source includes a solid state laser,
The optical device according to claim 1. The light from the light source is incident from the surface of the phosphor layer opposite to the dielectric layer.
The optical device according to claim 1. A light reflecting film comprising a metal layer and a dielectric layer on the metal layer;
A phosphor layer on the dielectric layer that emits light when excited by light from a light source; and
With
The wavelength at which the reflectance of light perpendicularly incident on the light reflecting film from the phosphor layer side becomes the maximum is the barycentric wavelength of the light spectrum obtained by combining the emission spectrum of the light source and the emission spectrum of the phosphor layer. Longer than
The dielectric layer is a laminated structure of 2 or more and 5 or less layers, and any two adjacent layers in the dielectric layer have different refractive indexes.
Optical device.

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