JP7377496B2 - Wavelength conversion member for endoscope and endoscope using the same - Google Patents

Description

The present invention relates to a wavelength conversion member for an endoscope that can be used in an illumination optical system of an endoscope, and an endoscope using the same.

Conventionally, as illumination units for endoscopes used in the medical field, etc., illumination units that use laser light guided by an optical fiber as illumination light are known.

Such a lighting unit includes, for example, a light guiding member made of an optical fiber, and illumination light generated by converting the optical characteristics of the light by being placed on the tip surface of the light guiding member, as disclosed in Patent Document 1. A light conversion member that emits light has been proposed. In addition, the light conversion member has a yellow phosphor that excites yellow fluorescence with blue laser light, and by diffusing and emitting the blue laser light and emitting yellow fluorescence, white illumination light can be emitted. It is stated that. This document only describes a structure in which a hemispherical or flat light conversion member in which phosphor particles are dispersed in a base material is disposed on the tip surface of a light guide member.

Further, Patent Document 2 describes a solid-state light source that emits light including blue light and green light, an optical fiber, and a wavelength conversion element that is disposed on the light output side of the optical fiber and includes a red phosphor containing Ce as a light emission center. , a lighting unit has been proposed. In this document, a wavelength conversion element is formed using a powdered crystal of a red phosphor or a layered phosphor that is a sintered body thereof.

Patent No. 6464251 Patent No. 6273637

However, when the phosphor particles are dispersed in the base material as in Patent Document 1, there is a large amount of light scattering, making it difficult to obtain a sufficient amount of wavelength-converted light, and depending on the type of base material. However, there was a problem in that the light resistance and heat resistance against laser light were insufficient.

In addition, in a layered phosphor made by sintering phosphor powder as in Patent Document 2, the excitation light cannot reach the inside or emit light because the phosphor powder scatters a lot of light. There was a problem that the conversion efficiency of

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a wavelength conversion member for an endoscope that has sufficiently high light extraction efficiency and good light resistance and heat resistance, and an endoscope using the same.

The present inventors conducted extensive research to achieve the above objective and found that by dispersing quantum dots in a solution containing metal alkoxide and solidifying it through a sol-gel reaction, a phosphor with good light resistance and heat resistance was created. They discovered that it can be molded into a rod shape and completed the present invention.

That is, the wavelength conversion member for an endoscope of the present invention is a wavelength conversion member for an endoscope for converting the wavelength of excitation light from a light source device of an endoscope system into illumination light including converted light. It is characterized by containing a solid glass containing silica as a main component and quantum dots dispersed in the solid glass, and including a rod-shaped body having a longitudinal length of 3 mm or more.

According to the wavelength conversion member for an endoscope of the present invention, since it contains solid glass mainly composed of silica and quantum dots dispersed in the solid glass, it has good light resistance and heat resistance, and has good light resistance. This results in a wavelength conversion member with less scattering. Moreover, since it can be formed into a rod-shaped body of any length, it is possible to secure a sufficient length along the incident direction while reducing the diameter, making it possible to sufficiently increase the light extraction efficiency. Excitation light from a light source device of a mirror system can be efficiently wavelength-converted to provide illumination light containing sufficient converted light. As described above, the present invention can provide a wavelength conversion member for an endoscope that has sufficiently high light extraction efficiency and good light resistance and heat resistance.

In the above, it is preferable that a reflective layer that reflects at least converted light is provided on the outer circumferential surface of the rod-shaped body along the longitudinal direction. By providing such a reflective layer on the outer circumferential surface, the converted light emitted from the quantum dot toward the outer circumferential surface can be reflected internally, allowing the converted light to be extracted more efficiently to the emission side of the rod-shaped body. be able to.

Further, it is preferable that a converted light reflecting film is provided on the incident side end face of the rod-shaped body, and an excitation light antireflection film is provided on the surface of the converted light reflecting film. By providing a converted light reflecting film on the end face of the incident side of the rod-shaped body, the converted light emitted to the incident side can be reflected inside, and an excitation light antireflection film is provided on the surface of the converted light reflecting film. , the excitation light can be efficiently taken into the rod-shaped body. As a result, the converted light can be more efficiently extracted to the output side of the rod-shaped body.

Further, it is preferable that an excitation light reflecting film and/or a converted light antireflection film be provided on the end face of the rod-shaped body on the exit side. With this configuration, the converted light can be more efficiently extracted to the output side of the rod-shaped body.

The wavelength conversion member for an endoscope is provided with a light guide having a contact portion that contacts at least a part of the outer peripheral surface along the longitudinal direction of the rod-shaped body, and the light guide is configured such that the excitation light is incident on the light guide. It is preferable that the excitation light be provided with an incident surface and a reflective layer that covers an outer surface other than the incident surface and reflects at least the excitation light. With this configuration, the excitation light can be incident from the outer peripheral surface of the rod-shaped body. This increases the distance through which the excitation light passes through the rod-shaped body, increases the rate at which the excitation light hits quantum dots in the rod-shaped body, and increases the efficiency of extracting converted light. In addition, compared to the case where the excitation light is incident from the end face on the input side of the rod-shaped body, the converted light can be extracted at a position closer to the end face on the exit side of the rod-shaped body, so the converted light passes through the inside of the rod-shaped body. Attenuation of light caused by this can be suppressed.

Further, it is preferable that the angle formed between the end surface of the light guide located on the exit side of the rod-shaped body and the contact portion is an acute angle. Thereby, the excitation light traveling parallel to the longitudinal direction of the rod-like body can also be reflected into the inside of the rod-like body and enter the rod-like body, and the extraction efficiency of converted light can be increased.

Furthermore, the outer circumferential surface along the longitudinal direction of the rod-shaped body contacts a contact portion of a core of an optical fiber that guides the excitation light to the rod-shaped body, and the angle formed between the tip of the optical fiber and the contact portion is an acute angle. It is preferable that a reflective layer for reflecting at least the excitation light is provided at the tip of the optical fiber. Thereby, the excitation light can be made to directly enter the inside of the rod-like body from the outer circumferential surface of the rod-like body through the optical fiber. Therefore, the structure can be further simplified and space can be saved.

The wavelength conversion member for an endoscope of the present invention can be obtained, for example, in such a manner that the rod-shaped body has a refractive index of 1.45 to 1.80 at a wavelength of 500 nm. In particular, it is preferable that the rod-shaped body has a smaller refractive index at a wavelength of 500 nm, since reflection at the interface with air can be reduced compared to conventional phosphors.

On the other hand, the endoscope of the present invention includes an insertion section for inserting the distal end into the body, an imaging system that performs imaging or captures an image at the distal end and outputs it to the proximal end side of the insertion section, and a light source side. an illumination optical system including an optical fiber that guides light from the insertion section to near the distal end of the insertion section, the illumination optical system being provided with any of the endoscope wavelength conversion members. characterized by something.

According to the endoscope of the present invention, the wavelength conversion member containing solid glass mainly composed of silica and quantum dots dispersed in the solid glass has good light resistance and heat resistance. light scattering and less light scattering. Moreover, since the wavelength conversion member can be formed into a rod-shaped body of any length, it is possible to secure a sufficient length along the incident direction while reducing the diameter, making it possible to sufficiently increase the light extraction efficiency. The excitation light from the light source device of the endoscope system can be efficiently wavelength-converted to provide illumination light containing sufficient converted light. As described above, the present invention can provide an endoscope in which the wavelength conversion section has sufficiently high light extraction efficiency and good light resistance and heat resistance.

In the above, it is preferable that the wavelength conversion member is provided on the distal end side of the optical fiber, and that an optical window or a diverging lens is provided on the output side of the wavelength conversion member. It is desirable that the insertion section of the endoscope has a small diameter, and the space occupied by the illumination optical system near the tip is also limited, so it is preferable to use a rod-shaped wavelength conversion member with sufficiently high light extraction efficiency as in the present invention. This is particularly effective as an illumination optical system for endoscopes.

Further, it is preferable that the light source is a laser diode that directly emits excitation light to the optical fiber. By using a laser diode as a light source that emits excitation light directly to an optical fiber, there is no need for a complex optical system around the light source, and converted light can be extracted more efficiently by using laser light directly guided from the light source as excitation light. be able to.

Furthermore, the illumination optical system includes a plurality of optical systems, the wavelength conversion member constituting one of the optical systems contains carbon-based quantum dots and/or silicon quantum dots, and the wavelength conversion member constituting the other optical system Preferably, the conversion member contains silicon quantum dots and/or perovskite quantum dots. By containing carbon-based quantum dots and/or silicon quantum dots in the wavelength conversion member constituting any of the optical systems, it is possible to obtain green to yellow converted light for blue light. When the wavelength conversion member constituting the optical system contains silicon quantum dots and/or perovskite quantum dots, it becomes possible to obtain red converted light from blue light. Therefore, by switching the light source, it is possible to switch the illumination light including both converted lights, and it becomes possible to irradiate the illumination light according to the purpose of the imaging system.

1 is a schematic perspective view of an endoscope system having an example of an endoscope according to the present invention. 2 is a schematic configuration diagram showing an example of the configuration of the endoscope system shown in FIG. 1. FIG. 2 is a schematic perspective view showing an example of a main part of an illumination optical system in the endoscope system shown in FIG. 1. FIG. It is a schematic perspective view showing an example of the wavelength conversion member for endoscopes of the present invention. FIG. 1 is a longitudinal cross-sectional view showing an example of the wavelength conversion member for an endoscope according to the present invention. 2 is a graph showing the results of the fluorescence spectrum of the phosphor of Example 1 obtained using graphene quantum dots. 3 is a graph showing the results of the fluorescence spectrum of the phosphor of Example 3 obtained using silicon quantum dots. 7 is a graph showing the results of the fluorescence spectrum of the phosphor of Example 6 obtained using perovskite quantum dots. It is a longitudinal cross-sectional view which shows another Example of the wavelength conversion member for endoscopes of this invention. It is a longitudinal cross-sectional view which shows still another Example of the wavelength conversion member for endoscopes of this invention. It is a longitudinal cross-sectional view which shows still another Example of the wavelength conversion member for endoscopes of this invention. FIG. 12 is an enlarged sectional view of a main part taken along line XII-XII in FIG. 11; FIG. 7 is a graph showing the results of the fluorescence spectrum of the phosphor of Example 7 obtained using chalcopyrite quantum dots. FIG.

<Endoscope of the present invention>
FIG. 1 is a schematic perspective view of an endoscope system 5 including an example of an endoscope 10 of the present invention, and FIG. 2 is a schematic configuration diagram showing an example of the configuration of the endoscope system 5 shown in FIG. . As shown in FIGS. 1 and 2, for example, the endoscope 5 of the present invention includes an insertion section 20 for inserting the distal end into the body, and a proximal end of the insertion section for imaging or capturing an image at the distal end. It includes an imaging system 100 that outputs to the side, and an illumination optical system 50 that includes an optical fiber 51 that guides light from the light source side to near the tip of the insertion section.

The imaging system 100 may be configured using either a transmission method that captures an image at the distal end and sends a signal to the proximal end of the insertion section 20, or an optical method that captures an image at the distal end and sends the image to the proximal end of the insertion section 20. Is possible. In this embodiment, an example of the former is shown.

As shown in FIG. 2, in the endoscope of the present invention, the illumination optical system 50 contains solid glass mainly composed of silica and quantum dots dispersed in the solid glass, and the length in the longitudinal direction is A feature is that a wavelength conversion member 71 including a rod-shaped body of 3 mm or more is provided. In this embodiment, an example is shown in which the wavelength conversion member 71 is provided on the distal end side of the optical fiber 51, and a diverging lens 72 is provided on the output side of the wavelength conversion member 71.

[Endoscope system]
As shown in FIG. 1, the endoscope system 5 includes, for example, an endoscope 10 that illuminates an area to be observed with illumination light and images the area to be observed, and a control device that is detachably connected to the endoscope 10. 14. The part to be observed is, for example, an affected part or a diseased part in a body cavity.

As shown in FIG. 1, the endoscope system 5 includes an image display device 16, which is connected to a control device 14 and is, for example, a monitor, which displays the observed part imaged by the endoscope 10, and an image display device 16 that is detachable from the endoscope 10. It further includes a light source device 18 that is freely connected and detachably connected to the control device 14 .

This endoscope system 5 has an imaging system 100 for imaging the observed part, as shown in FIG. 2, for example. The imaging system 100 includes an imaging unit 101 that images the observed portion, and an image processing unit 103 that processes the image captured by the imaging unit 101. An image captured by the imaging unit 101 is transmitted to the image processing unit 103 via an imaging cable 105. The image processed by the image processing unit 103 is displayed by the image display device 16. The imaging unit 101 is provided in the rigid tip portion 21 , the image processing unit 103 is provided in the control device 14 , and the imaging cable 105 is provided in the endoscope 10 .

[Endoscope]
As shown in FIG. 1, the endoscope 10 includes, for example, a hollow and elongated insertion section 20 that is inserted into a body cavity, and a grip section 30 that is connected to the proximal end of the insertion section 20 and grasped by an operator. In the present invention, as shown in FIG. 2, the optical fiber 51 and the wavelength conversion member 71 are built into the insertion section 20 of the endoscope 10.

As shown in FIG. 1, the insertion section 20 includes, from the distal end side of the insertion section 20 toward the proximal end side of the insertion section 20, a distal rigid section 21, a curved section 23, and a flexible tube section 25. . The proximal end of the rigid tip portion 21 is connected to the distal end of the curved portion 23 , and the proximal end of the curved portion 23 is connected to the distal end of the flexible tube portion 25 .

As shown in FIG. 2 , the imaging unit 101 that is the tip of the imaging system 100 , the tip of the optical fiber 51 that is the tip of the illumination optical system 50 , and the wavelength conversion member 71 are provided in the rigid tip portion 21 .

As shown in FIG. 1, the flexible tube portion 25 extends from the grip portion 30. As shown in FIG. The gripping section 30 includes a bending operation section 37 for bending the bending section 23, a switch section 39 for air/water supply, suction, and photographing, and a universal cord 41 connected to the gripping section 30.

Note that a suction/forceps channel and an air/water supply nozzle can be provided at the distal end of the insertion section 20 of the endoscope 10, and suction operations and treatments using forceps etc. can be performed via the insertion section 20 and the gripping section 30. , air, water, etc.

[Universal code]
As shown in FIG. 1, the universal cord 41 extends from the side surface of the grip part 30. The ends of the universal cord 41 are branched, and each end is provided with a connector 41a. One of the connectors 41a is detachable from the control device 14, and the other connector 41a is detachable from the light source device 18.

[Control device, image display device, and light source device]
The control device 14 controls the endoscope 10, the image display device 16, and the light source device 18. As shown in FIG. 2, the light source device 18 includes a light source unit 91 and a light guide unit 93. Although the light source unit 91 and the light guide unit 93 can be configured by combining various light sources and optical systems such as lenses and mirrors, it is preferable to use a laser diode that directly emits excitation light to the optical fiber 51. Therefore, it is possible to have a simple device configuration (e.g., omitting the light guide unit 93).

[Illumination optical system]
The rigid tip portion 21 includes, for example, a cylindrical holding member that holds the tip of the illumination optical system 50 and a cover member that covers the tip surface (not shown). The holding member has a first hole into which the tip of the optical fiber 51 is inserted (not shown). In the example shown in FIG. 2, only one set of illumination optical systems 50 is provided, but in order to illuminate a wide range, it is preferable to provide two or more sets of illumination optical systems 50. In that case, a plurality of optical windows or diverging lenses are provided at the distal end of the insertion section 20, but the light source unit 91 is configured as one set by separating the light from the light source unit 91 into a plurality of parts. be able to.

In the example shown in FIG. 3, the illumination optical system 50 is composed of a plurality of (three) optical systems, the distal end surface of the optical fiber 51a is arranged on the input side end surface of the wavelength conversion member 71a, and the optical fiber 51a is disposed on the input side end surface of the wavelength conversion member 71a. The end face of the diverging lens 72 is arranged on the incident side end face of the diverging lens 72. The distal end surface of the optical fiber 51b is arranged on the input side end surface of the wavelength conversion member 71b, and the output side end surface of the wavelength conversion member 71b is arranged on the input side end surface of the diverging lens 72. The distal end surface of the optical fiber 51c is arranged at the end surface on the incident side of the diverging lens 72 without intervening the wavelength conversion member 71a. The diverging lens 72 is held by a holding member (not shown) inside the cover member.

In this example, the wavelength conversion member 71a constituting the first optical system contains carbon-based quantum dots and/or silicon quantum dots, and the wavelength conversion member 71b constituting the second optical system contains silicon quantum dots and/or silicon quantum dots. /Or contains perovskite quantum dots.

In any optical system, blue light La, Lb, and Lc are emitted from light sources 91A, 91B, and 91C. The excitation light guided from the optical fiber 51a is wavelength-converted from green to yellow by the wavelength conversion member 71a, and the excitation light guided from the optical fiber 51b is wavelength-converted to red by the wavelength conversion member 71b, and then guided from the optical fiber 51c. The blue light is emitted as it is and enters the diverging lens 72. The diverging lens 72 emits diverging irradiation light L3. Therefore, by switching the light sources 91A, 91B, and 91C, it is possible to switch the irradiation light L3 including each converted light, and it becomes possible to irradiate the irradiation light L3 according to the purpose of the imaging system. Further, by using the light sources 91A, 91B, and 91C at the same time, white light can be irradiated.

Note that the holding member further holds the distal end portion of the imaging system 100. Specifically, the holding member is configured such that the tip of the illumination optical system 50 and the tip of the imaging system 100 are adjacent to each other, the illumination optical system 50 emits illumination light forward, and the imaging system 100 images the front. , the tip of the illumination optical system 50 and the tip of the imaging system 100 are held. For this reason, the holding member 110 further includes a second hole into which the distal end of the imaging system 100 is inserted.

The tip of the illumination optical system 50 is bonded to the first hole with an adhesive (not shown), and the tip of the imaging system 100 is bonded to the second hole 113 with an adhesive (not shown). Note that it is not limited to adhesion, and may be engagement.

The cover member is arranged in front of the tip of the illumination optical system 50 and the tip of the imaging system 100. The cover member is in close contact with the tip and side surfaces of the holding member. The cover member is transparent so that the light emitted from the illumination optical system 50 is transmitted through the cover member, and the light reflected from the observed portion for imaging by the imaging system 100 is transmitted through the cover member.

<Other embodiments of endoscope>
(1) In the previous embodiment, as shown in FIG. 3, an example was shown in which the illumination optical system 50 consisted of a plurality of (three) optical systems, but the light source 91C and the optical fiber 51c were omitted, and two optical systems were used. It is also possible to do this. In that case, the irradiation light L3 can be whitened by increasing the amount of blue light transmitted through each of the wavelength conversion members 71a and 71b by shortening the lengths of the wavelength conversion members 71a and 71b.

(2) In the previous embodiment, as shown in FIG. 3, an example was shown in which the illumination optical system 50 consisted of a plurality of (three) optical systems, but the light source 91B, optical fiber 51b, and wavelength conversion member 71b were omitted. It is also possible to have two optical systems. In that case, the light source 91C and the optical fiber 51c emit blue light, and the light source 91A, the optical fiber 51a, and the wavelength conversion member 71a emit green to yellow light, so that the emitted light L3 can be whitened.

(3) In the previous embodiment, as shown in FIG. 3, an example was shown in which the illumination optical system 50 was composed of a plurality of (three) optical systems. It is also possible to have one optical system. In that case, in addition to the blue light transmitted through the wavelength conversion member 71a, the excitation light guided from the light source 91A and the optical fiber 51a is converted into green to yellow by the wavelength conversion member 71a, thereby whitening the irradiation light L3. I can do it.

(4) In the previous embodiment, an example was shown in which the light sources 91A, 91B, and 91C emit blue light of the same or similar wavelengths, but it is also possible to change the wavelength of some or all of the light sources 91A, 91B, and 91C. be. In that case, it is advantageous to select a wavelength that corresponds to excitation light with high luminous efficiency of the wavelength conversion member. It is also possible to irradiate the light as it is without using a wavelength conversion member, and in that case, it is possible to select the wavelength of the light source depending on the type of light to be irradiated.

[Wavelength conversion member]
The wavelength conversion member for an endoscope according to the present invention is provided for converting the wavelength of excitation light from the light source device of the endoscope system as described above to produce illumination light including the converted light. As shown in FIGS. 4 and 5, the wavelength conversion member 71 for an endoscope of the present invention includes a rod-shaped body 73 having a longitudinal length of 3 mm or more, and this rod-shaped body 73 is a solid material mainly composed of silica. It contains glass and quantum dots dispersed in the solid glass.

In the present invention, a "rod-shaped body" refers to a three-dimensional shape whose length in one direction (longitudinal direction) is longer than the length in any direction perpendicular to that direction. The shapes of rod-shaped bodies include, for example, cylinders, square prisms, etc., which have a constant cross section perpendicular to the longitudinal direction, truncated cones, truncated square pyramids, etc., in which the cross sections perpendicular to the longitudinal direction change regularly, and spindles. It may have any shape, such as a shape in which the cross section changes from a circle to a crescent shape, or a shape in which the cross section perpendicular to the longitudinal direction changes irregularly. Moreover, it may be tubular or hollow. The shape of the rod-like body is preferably a cylinder, a square prism, a hexagonal prism, or the like.

The length in the longitudinal direction of the rod-shaped body 73 is 3 mm or more, preferably 7 mm or more, and more preferably 10 mm or more from the viewpoint of increasing the amount of converted light taken out. Further, from the viewpoint of placement in the insertion section 20 of the endoscope, the length is preferably 20 mm or less, and more preferably 15 mm or less. Further, the major axis or maximum width of the cross section perpendicular to the longitudinal direction of the rod-shaped body 73 is preferably 0.5 to 2 mm, more preferably 1 to 1.5 mm, from the viewpoint of reducing the diameter of the wavelength conversion member. The short axis or minimum width of the cross section perpendicular to the longitudinal direction of the rod-shaped body 73 is preferably 50 to 99%, more preferably 60 to 95%, of the long axis or maximum width.

The rod-shaped body 73 preferably has a refractive index of 1.45 to 1.80 at a wavelength of 500 nm, and preferably 1.45 to 1.70, from the viewpoint of making the reflection at the interface with air smaller than that of conventional phosphors. It is more preferably 1.45 to 1.60.

As shown in FIG. 5, the wavelength conversion member 71 for an endoscope is preferably provided with a reflective layer 74 that reflects at least the converted light L2 on the outer circumferential surface S1 along the longitudinal direction of the rod-shaped body 73. Although the reflective layer 74 is provided on a part or all of the outer peripheral surface S1, it is preferable that the reflective layer 74 covers the entire outer peripheral surface S1. Examples of the reflective layer 74 include metal films such as aluminum and silver, and dielectric multilayer films. The thickness of the reflective layer 74 is approximately 150 to 1000 nm, depending on its material.

The reflective layer 74 can be formed by vapor deposition, sputtering, CVD, plating, coating, or the like. Prior to forming the reflective layer 74, it is preferable to polish and flatten the surface of the rod-shaped body 73. When forming the reflective layer 74, it is preferable to provide a mask material on the incident side end surface S2 and the output side end surface S3 of the rod-shaped body 73, or to polish the end surfaces after processing. The following converted light reflection film 75, excitation light antireflection film 76, etc. can also be formed in the same manner as the reflection layer 74.

It is preferable that a converted light reflecting film 75 is provided on the end surface S2 of the rod-shaped body 73 on the incident side. The converted light reflection film 75 is a dielectric multilayer film whose low refractive index side is made of SiO ₂ , Al ₂ O ₃ or the like, and whose high refractive index side is made of TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ or the like, It is preferable that SiO ₂ is used on the low refractive index side and TiO ₂ is used on the high refractive index side, and the optical film thickness of each layer is designed so as to generally transmit the excitation light L1 and reflect the converted light L2. . Further, it is preferable that an excitation light antireflection film 76 is provided on the surface of the converted light reflection film 75. The excitation light antireflection film 76 preferably has a refractive index between that of the surface of the converted light reflection film 75 and that of air. The thicknesses of the converted light reflection film 75 and the excitation light antireflection film 76 are appropriately determined according to their respective optical characteristics.

It is preferable that an excitation light reflection film 77 and/or a converted light antireflection film 78 be provided on the exit side end surface S3 of the rod-shaped body 73. The excitation light reflecting film 77 is a dielectric multilayer film whose low refractive index side is made of SiO ₂ , Al ₂ O ₃ or the like, and whose high refractive index side is made of TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ or the like, Preferably, SiO ₂ is used on the low refractive index side and TiO ₂ is used on the high refractive index side, and the optical film thickness of each layer is designed so as to reflect the excitation light L1 while transmitting the converted light L2. When the converted light antireflection film 78 is provided alone on the exit side end face S3, it is preferable that the converted light antireflection film 78 has a refractive index between that of the surface of the rod-shaped body 73 and that of air. The thicknesses of the excitation light reflection film 77 and the converted light antireflection film 78 are appropriately determined according to their respective optical characteristics.

<Material of rod-shaped body>
The rod-shaped body contains solid glass mainly composed of silica and quantum dots dispersed in the solid glass. In the present invention, "containing silica as the main component" refers to a case where the content of Si element in the metal component of the glass is 60 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more. ~100 mol%.

(solid glass)
The solid glass containing silica as a main component is preferably silica glass. Silica glass may contain Al, Ca, Cu, Fe, Na, K, Li, Mg, Mn, and Ti as other metal components. However, the content of these metal components in the metal component is preferably 20 mol% or less, preferably 10 mol% or less, and more preferably 0 to 5 mol%.

Silica glass can be broadly classified into fused silica glass, which is obtained by melting natural quartz powder, and synthetic silica glass, which is synthesized from liquid raw materials, and both can be used, but synthetic silica glass is preferable. Synthetic silica glass can be classified into vapor phase synthesis method and liquid phase synthesis method depending on the manufacturing method. Fused silica glass is classified into electric fused silica glass and flame fused silica glass. The former is characterized by a low OH content, and the latter is characterized by a relatively large OH content. All have excellent heat resistance and are relatively inexpensive.

Gas phase synthesis methods include direct method, soot method, and plasma method. The direct method is a method of synthesizing silica glass by hydrolyzing silicon tetrachloride (SiCl ₄ ) in an oxyhydrogen flame and directly depositing and vitrifying it. This type of silica glass contains about 500 to 1500 ppm of OH groups. Optically homogeneous products can be synthesized relatively easily and have excellent UV resistance. Therefore, it is used as an optical material for ultraviolet light.

In the soot method, silica particles are first generated to form a porous body. Next, the amount of OH is controlled by heat treatment in an appropriate atmosphere. Finally, it is turned into transparent glass at high temperature. Since this synthesis method consists of multiple steps, it is easy to control the properties. The plasma method has been used as a method for synthesizing anhydrous silica glass for a longer time than the soot method.

A sol-gel method is a method for synthesizing in a liquid phase. This is a method in which a porous silica body is synthesized by polycondensation of metal alkoxides, and then dried and sintered to vitrify it. Further, as a method for producing a silica glass thin film at a low temperature, there is a liquid phase precipitation (LPD) method.

In the present invention, silica glass obtained by hydrolysis and polycondensation (sol-gel method) of metal alkoxides can be preferably used. When carrying out the sol-gel method, it is preferable to add a polybasic acid from the viewpoint of preventing cracks and chips. For this reason, the solid glass in the present invention preferably contains a polybasic acid and/or its residue component.

(Quantum dot)
Quantum dots refer to nanoscale particles with unique optical properties that comply with quantum chemistry and quantum mechanics.The optical properties can be adjusted depending on the particle size, so they have characteristic luminescent properties that depend on the particle size. have. In the present invention, carbon-based quantum dots, silicon quantum dots, perovskite quantum dots, chalcopyrite quantum dots, etc. can be used depending on the emission wavelength of the converted light. Further, by using a plurality of quantum dots selected from these and adjusting the content of each, a desired emission wavelength can be obtained.

(Carbon-based quantum dots)
Carbon-based quantum dots have luminescent properties that depend on particle size due to π bonds between carbon atoms. Examples of carbon-based quantum dots include graphene quantum dots with a graphene structure, carbon quantum dots without a graphene structure, and chemically modified quantum dots of these. Graphene quantum dots are preferred.

These carbon-based quantum dots are commercially available from Sigma-Aldrich, Fuji Shiki Co., Ltd., GS Alliance Co., Ltd., Funakoshi Co., Ltd., Kishida Kagaku Co., Ltd., etc., and any of these can be used.

The content of carbon-based quantum dots is preferably 0.0001 to 10% by mass in the phosphor composition from the viewpoint of obtaining an appropriate wavelength shift in fluorescence characteristics and obtaining an appropriate luminescence output. , more preferably 0.001 to 5% by mass, and even more preferably 0.01 to 1% by mass.

(Graphene quantum dots)
Graphene quantum dots include non-functionalized graphene quantum dots, functionalized graphene quantum dots, pristine graphene quantum dots, and combinations thereof.

Functionalized graphene quantum dots may be functionalized with one or more functional groups. Functional groups include oxygen groups, carboxyl groups, carbonyl groups, amorphous carbon, hydroxyl groups, alkyl groups, aryl groups, esters, amines, amides, polymers, poly(propylene oxide), and combinations thereof.

Graphene quantum dots also include functionalized graphene quantum dots that are functionalized with one or more alkyl groups. Alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and combinations thereof. In some embodiments, alkyl groups include octyl groups (eg, octylamine).

Graphene quantum dots can also be functionalized with one or more polymer precursors. For example, graphene quantum dots can be functionalized with one or more monomers (eg, vinyl monomers).

Graphene quantum dots can be functionalized with polymer precursors that polymerize to form polymer-functionalized graphene quantum dots. For example, an end-functionalized polyvinyl adduct can be formed by functionalizing the ends with a vinyl monomer that polymerizes.

Graphene quantum dots include functionalized graphene quantum dots that are functionalized with one or more hydrophilic functional groups. Hydrophilic functional groups include carboxyl groups, carbonyl groups, hydroxyl groups, hydroxyalkyl groups, poly(ethylene glycol), poly(vinyl alcohol), poly(acrylic acid), and combinations thereof.

Graphene quantum dots include functionalized graphene quantum dots that are functionalized with one or more hydrophobic functional groups. Hydrophobic functional groups include alkyl groups, aryl groups, and combinations thereof. Hydrophobic functional groups include one or more alkylamides or arylamides.

Graphene quantum dots include edge-functionalized graphene quantum dots. The end-functionalized graphene quantum dots include one or more of the hydrophobic functional groups described above. The edge-functionalized graphene quantum dots include one or more hydrophobic functional groups as described above. The edge-functionalized graphene quantum dots also include one or more hydrophilic functional groups as described above. Edge-functionalized graphene quantum dots include one or more oxygen adducts on their edges. Edge-functionalized graphene quantum dots include adducts of one or more amorphous carbons on their edges.

Graphene quantum dots are end-functionalized with one or more alkyl or aryl groups, such as alkylamides or arylamides. Edge functionalization of graphene quantum dots with alkyl or aryl groups is carried out by reaction of an alkyl or arylamide with a carboxylic acid at the ends of the graphene quantum dots.

Graphene quantum dots include pristine graphene quantum dots. Pristine graphene quantum dots include graphene quantum dots that remain unprocessed after synthesis. Pristine graphene quantum dots include graphene quantum dots that have not undergone any additional surface modification after synthesis.

Graphene quantum dots can be obtained from various sources. For example, graphene quantum dots include coal-derived graphene quantum dots, coke-derived graphene quantum dots, and combinations thereof. Graphene quantum dots include graphene quantum dots derived from coke. Graphene quantum dots include graphene quantum dots derived from coal. Coal includes, but is not limited to, anthracite, bituminous, sub-bituminous, modified bituminous, asphaltenes, asphalt, peat, lignite, boiler coal, petrified oil, carbon black, activated carbon, and combinations thereof. is included. The carbon source is bituminous coal. Carbon includes bituminous coal.

Graphene quantum dots can have various diameters. For example, graphene quantum dots preferably have diameters ranging from about 1 nm to about 100 nm, more preferably from about 1 nm to about 50 nm, and more preferably from about 1 nm to about 20 nm. It is more preferable to have.

Graphene quantum dots can also have various structures. For example, graphene quantum dots may have a crystalline structure, such as a crystalline hexagonal structure. Graphene quantum dots may have a single layer or multiple layers, for example graphene quantum dots have from about two layers to about four layers.

Graphene quantum dots can also have different quantum yields. Preferably, the graphene quantum dots have a quantum yield in the range of about 30-80%. In addition, the fluorescence characteristic of the aqueous dispersion of graphene quantum dots is such that the emission wavelength is preferably 380 nm to 650 nm with respect to at least one wavelength of excitation light of 300 nm to 420 nm.

Graphene quantum dots may be in the form of powder or pellets. Graphene quantum dots may be in a liquid state, a dispersion, a solution, or a molten state.

Various methods can be used to form graphene quantum dots. For example, forming graphene quantum dots can include exposing a carbon source to an oxidizing agent, resulting in the formation of graphene quantum dots. Carbon sources include coal, coke, and combinations thereof.

Oxidizing agents include acids, including sulfuric acid, nitric acid, phosphoric acid, hypophosphorous acid, fuming sulfuric acid, hydrochloric acid, oleum, chlorosulfonic acid, and combinations thereof. Oxidizing agents also include potassium permanganate, sodium permanganate, hypophosphorous acid, nitric acid, sulfuric acid, hydrogen peroxide, and combinations thereof. A preferred oxidizing agent is a mixture of potassium permanganate, sulfuric acid and hypophosphorous acid.

The carbon source is exposed to the oxidizing agent by sonicating the carbon source in the presence of the oxidizing agent. It includes heating the carbon source in the presence of an oxidizing agent. Heating is performed at a temperature of at least about 100°C.

The use of further methods of forming graphene quantum dots can also be envisaged. For example, additional methods of forming graphene quantum dots are disclosed in international patent application PCT/US2014/036604. Further suitable methods for producing graphene quantum dots are also disclosed in the following references: ACS Appl. Mater. Interfaces 2015, 7, 7041-7048; and Nature Commun. 2013, 4:2943, 1- 6.

(carbon quantum dots)
Carbon quantum dots are quantum dots that do not have a ring structure like graphene. It has the property that it is more easily affected by pH value than graphene quantum dots, and its emission intensity and peak position change.

Carbon quantum dots can have various diameters. For example, carbon quantum dots preferably have diameters ranging from about 1 nm to about 100 nm, more preferably from about 1 nm to about 50 nm, and more preferably from about 1 nm to about 30 nm. It is more preferable to have.

Carbon quantum dots can also have varying quantum yields. Preferably, the carbon quantum dots have a quantum yield in the range of about 20-50%. Furthermore, the fluorescence characteristic of the aqueous dispersion of carbon quantum dots is such that the emission wavelength is preferably 380 nm to 600 nm with respect to at least one wavelength of excitation light of 300 nm to 420 nm.

The method for producing carbon quantum dots is not much different from the method for producing graphene quantum dots, and the only difference is whether or not the raw materials used and production conditions facilitate forming a graphene structure.

Therefore, carbon-based quantum dots containing both can be manufactured using, for example, a method of manufacturing a carbon target by laser ablation and then chemical treatment (Japanese Patent Publication No. 2012-501863), or a method of manufacturing from candle soot ( H. Liu, et al., Angew. Chem.Int. Ed. 2007, 46, 6473-6475.), a method for producing graphite oxide by chemical treatment (G. Eda, et al., Adv. Mater. 2010, 22, 505-509.), a method of manufacturing from a chemical reaction using graphite oxide as a precursor (JP 2012-136566), a method of manufacturing from a conversion reaction of fullerene (J. Lu, et al. , Nature Nanotech.2011, 6, 247-252.), and methods to chemically process cheaper carbon raw materials such as carbon fiber and activated carbon (J. Peng, et al., Nano Lett. 2012, 12 , 844-849., Z.A. Qiao, ChemCommun. 2010, 46,8812-8814., Y. Dong, et al., Chem. Mater. 2010, 22, 5895-5899.).

These methods can be broadly classified as top-down methods, but there is also a bottom-up method in which carbon quantum dots are produced from polymerization of organic precursor molecules (G. A. Ozin, et al. al., J. Mater. Chem., 2012, 22, 1265-1269.).

In addition, there is a process of mixing carbon material and hydrogen peroxide, decomposing the carbon with hydrogen peroxide, and preparing a carbon quantum dot generation liquid, and separating carbon quantum dots and hydrogen peroxide in the carbon quantum dot generation liquid. It is also possible to produce carbon quantum dots by a method for producing carbon quantum dots (Japanese Patent Application Laid-open No. 2014-133685), which includes a step of stopping the decomposition reaction and obtaining carbon quantum dots.

(Wavelength conversion characteristics of carbon-based quantum dots)
When using carbon-based quantum dots, the wavelength conversion characteristics (fluorescence characteristics) are such that, from the viewpoint of making it a highly versatile fluorescent material, the emission wavelength (peak wavelength) for at least one of the wavelengths of excitation light from 300 nm to 470 nm. is preferably from 400 nm to 750 nm, more preferably from 450 nm to 650 nm, even more preferably from 500 nm to 600 nm. Such a light emission wavelength is light emission in approximately the same region as that of single crystal YAG/Ce.

Further, it is preferable that the half-width of the emission around the emission peak wavelength is 40 nm to 100 nm, more preferably the emission wavelength is 400 nm to 700 nm, and still more preferably the emission wavelength is 420 nm to 750 nm.

In addition, from the viewpoint of obtaining such fluorescence characteristics, the fluorescence characteristics of the aqueous dispersion of carbon-based quantum dots used as a raw material are determined by the emission wavelength (peak wavelength) for at least one of the wavelengths of excitation light from 300 nm to 420 nm. is preferably from 380 nm to 600 nm, more preferably from 400 nm to 550 nm, even more preferably from 420 nm to 500 nm.

Further, the quantum yield (luminous efficiency) of the phosphor composition is preferably 25% or more, more preferably 50% or more, and particularly preferably 70 to 80%.

(Silicon quantum dot)
When a semiconductor is made into nanoparticles, its band structure changes due to the quantum size effect (confinement effect), and it emits fluorescence of a color depending on the particle size. Silicon quantum dots are typical group IV semiconductor quantum dots.

Etching of silicon wafers is a typical method for synthesizing silicon quantum dots. Nanoparticles can be obtained by refining bulk silicon by electrolytic etching using hydrofluoric acid (HF). At this time, the particle size of the particles obtained can be controlled by controlling the etching time and the like. Particle synthesis by thermal decomposition of silane (SiH ₄ ) is known as a bottom-up synthesis method capable of producing a relatively large amount of particles. Thermal decomposition of silane produces Si atoms, which become supersaturated and generate and grow nuclei to produce particles. Since the particles generated at this time are relatively large in size, the particles are then etched with a mixture of hydrofluoric acid (HF) and nitric acid (HNO ₃ ) to reduce the particle size to a region where the quantum size effect appears. are doing.

A synthesis method using plasma CVD is also known as a method for synthesizing single nanometer particles in one step without going through an etching process. Nanoparticles can be generated by decomposing the precursor silicon tetrabromide (SiBr ₄ ) in an RF plasma field to generate Si atoms, which are then nucleated and grown in a reactor.

Silicon quantum dots are commercially available from GS Alliance Co., Ltd., Sigma-Aldrich, etc., and can be used. Commercially available silicon quantum dots have a size ranging from several angstroms to 10 nm or less, and a quantum yield of about 20 to 30%.

Silicon quantum dots can have an emission wavelength depending on the particle size, and in the present invention, they can be used both as a wavelength conversion member for obtaining green to yellow color or as a wavelength conversion member for obtaining red color. .

In a rod-shaped body in which silicon quantum dots are dispersed in solid glass, when emitting red light in contrast to the wavelength of 400 nm to 470 nm, which is the excitation light of a blue laser diode, the emission wavelength (peak wavelength) is 610 nm to 640 nm. It is preferable that the emission wavelength be 620 nm to 640 nm. Further, when emitting green to yellow light, the emission wavelength (peak wavelength) is preferably 520 nm to 560 nm, more preferably 530 nm to 550 nm.

(Perovskite quantum dot)
Perovskite quantum dots have a perovskite crystal structure. Generally, the perovskite crystal structure is represented by the composition formula ABX ₃ using ions A, ion B, and ion X, with ion A at eight vertices, ion Since ion B is present in , and ion B is relatively smaller than ion A, ion B is easy to move, so that the centers of gravity of positive and negative charges can be separated. In the perovskite quantum dot, ion X is preferably a halogen atom (preferably F, Cl, Br, I), ion A is preferably Cs, and ion B is preferably Pb.

Perovskite quantum dots have the general formula (1): CsPbY _a Z _b (In the above general formula (1), Y and Z each independently represent F, Cl, Br, or I, and a and b each independently represents a real number from 0 to 3, and a+b=3). Further, a material having a composition of CH ₃ NH ₃ PbX ₃ (X=Cl, Br, I) can also be used.

The perovskite quantum dots preferably include at least one type of quantum dot selected from perovskite quantum dots that emit red light. The emission color of light-emitting nanocrystals such as quantum dots depends on the particle size of the quantum dots and the energy gap of the light-emitting nanocrystals, so by adjusting the type of perovskite quantum dots used and their particle size. You can choose the emitting color.

Commercially available perovskite quantum dots are nanocrystallized perovskite compounds, and typical compositions thereof are CH ₃ NH ₃ PbX ₃ and CsPbX ₃ (X=Cl, Br, I). Further, the quantum yield is about 50 to 80%, and the half width is about 18 to 39 nm.

In a rod-shaped body in which perovskite quantum dots are dispersed in solid glass, when emitting red light, the emission wavelength (peak wavelength) is 610 nm to 650 nm, compared to the wavelength of 400 nm to 470 nm, which is the excitation light of a blue laser diode. It is preferable that the emission wavelength be 615 nm to 635 nm.

(chalcopyrite quantum dot)
Chalcopyrite quantum dots are quantum dots made of nanoparticles containing a chalcopyrite semiconductor, and are characterized by being able to change the light absorption range and emission wavelength due to the quantum size effect.
Examples _of chalcopyrite quantum dots include CuInS ₂ , CuAlS ₂ , CuGaS 2 , CuAlSe ₂ , CuGaSe ₂ , AgInS ₂ , AgAlS ₂ , AgGaS ₂ , AgAlSe ₂ , AgGaSe ₂ , AgInSe 2 , AgAlTe ₂ , AgGaTe _{2 ,} AgInTe ₂ , Cu(In, Al)Se ₂ , Cu(In, Ga)(S, Se) ₂ , Ag(In,Ga)Se ₂ , Ag(In, Ga)(S, Se) ₂ , etc., or compounds of these Examples include those in which the ratio of constituent elements differs from the stoichiometry. These can be used alone or in combination of two or more.
Among these, chalcopyrite-type quantum dots made of the three elements copper, indium, and sulfur are preferred because they have low toxicity and a high light absorption coefficient. The Cu/In molar ratio of the chalcopyrite quantum dots may be 0.5 to 3, and the S/In molar ratio may be 0.5 to 3, but preferably the Cu/In molar ratio is 0.5 to 3. CuInS ₂ with a molar ratio of 1. Such chalcopyrite-type quantum dots can be preferably used because the half-width of the emission spectrum is relatively large due to their crystal structure.
Chalcopyrite quantum dots can be used alone, but they can also be used as composite quantum dots through surface modification. Zinc sulfide and the like can be used for surface modification.
Chalcopyrite quantum dots or surface-modified chalcopyrite quantum dots are commercially available from GS Alliance Co., Ltd., and can be used in the present invention. The quantum yield of commercially available CuInS ₂ /ZnS is about 10% to 40%, and the half width is about 60 nm to 130 nm.
The reason why the half-width is wider than other quantum dots is that it largely depends on the variation in particle size, and by separating the particle size using a centrifuge, it is possible to narrow the half-width and increase the quantum yield.

In a rod-shaped body in which chalcopyrite quantum dots are dispersed in solid glass, when emitting red light, the emission wavelength (peak wavelength) is 560 nm to 470 nm, which is the excitation light of a blue laser diode. Preferably it is 660 nm. Further, as a characteristic of the rod-shaped body, it is more preferable that the half width of the emission spectrum is 80 nm to 120 nm.
(Method for manufacturing rod-shaped body)
The rod-shaped body can be obtained by a method in which quantum dots are dispersed during the synthesis of solid glass, or a method in which solid glass obtained by synthesis or the like is finely pulverized, and then quantum dots are dispersed in the pulverized material and solidified.

In the latter method, solid glass finely pulverized to an average particle size of 100 nm to 5000 nm can be used, and a mixture in which quantum dots are dispersed can be solidified by a conventional method at an appropriate temperature and pressure.

In the present invention, from the viewpoint of uniform dispersibility and optical properties of quantum dots, it is preferable to disperse quantum dots during synthesis. It is more preferable to use a manufacturing method in which quantum dots are dispersed. This manufacturing method will be described in detail below.

<Production method using sol-gel method>
The manufacturing method using the sol-gel method includes a dispersion step to obtain a dispersion liquid containing a solid glass precursor containing silica as a main component and quantum dots dispersed in the precursor, and a dispersion step to obtain a dispersion liquid containing a solid glass precursor mainly composed of silica, and a dispersion step to obtain a dispersion liquid containing a solid glass precursor containing silica as a main component. The method includes a reaction step of solidifying by reaction to obtain a phosphor composition containing a solid glass and quantum dots dispersed in the solid glass.

(Dispersion process)
The dispersion step is to obtain a dispersion liquid containing a solid glass precursor containing silica as a main component and quantum dots dispersed in the precursor. The quantum dots may be dispersed by mixing and stirring together with each component of the solid glass precursor. A stirrer, stirring blade, etc. can be used for stirring.

Although the quantum dots described above can be used, it is preferable to use an aqueous dispersion. The concentration of quantum dots in the aqueous dispersion is preferably from 0.01 ppm to 10 ppm, more preferably from 0.5 ppm to 5 ppm, based on mass, from the viewpoint of dispersibility and particle yield upon solidification.

The content of quantum dots should be added to the phosphor composition at 0.0001 to 10% by mass from the viewpoint of obtaining an appropriate wavelength shift in fluorescence characteristics and obtaining an appropriate luminescence output. It is preferably 0.001 to 5% by mass, and even more preferably 0.01 to 1% by mass.

The solid glass precursor preferably contains a metal alkoxide, an alcohol, water, and an acid catalyst. It is also possible to use only alkoxysilanes as metal alkoxides. In the present invention, it is preferable to add a polybasic acid in the dispersion step from the viewpoint of preventing cracks and chips in the obtained phosphor.

Tetraalkoxysilane (Si(OR) ₄ ) is used as the metal alkoxide, and tetraalkoxyzirconium (Zr(OR) ₄ ), tetraalkoxytitanium (Ti(OR) ₄ ), trialkoxyaluminum (Al(OR) ₃ ) etc. are exemplified as arbitrary components.

The above RO is an alkoxy group, preferably a C _1-4 alkoxy group. Specifically, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, tetraethoxyzirconium, tetraisopropoxyzirconium, tetrabutoxyzirconium, tetraethoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium, triethoxyaluminum, triiso Examples include propoxyaluminum and tributoxyaluminum. As the metal alkoxide, one type or two or more types of these metal alkoxides can be used. It is preferable to use tetraalkoxysilane as the metal alkoxide, and tetraethoxysilane is more preferable. When two or more types are mixed, it is preferable to use tetraethoxysilane as the main component (for example, 80 mol% or more).

In the present invention, it is preferable to use a metal alkoxide as a raw material, but if necessary, the general formula:
X _m -Si(OR') _4-m
(In the formula, X represents an aminoalkyl group, a mercaptoalkyl group, etc., R' represents a C1-3 alkyl group, and m = 1, 2 or 3)
An organoalkoxysilane represented by the following may be added. Examples of the organoalkoxysilane include 3-aminopropyltrimethoxysilane (APS) and 3-mercaptopropyltrimethoxysilane (MPS). Usually, the molar ratio of metal alkoxide and organoalkoxysilane may be about 100:0 to 90:10.

Examples of the alcohol used include C _1-4 alcohols such as methanol, ethanol, propanol, isopropanol, and butanol. It is preferable to use an alcohol corresponding to the alkoxide of the metal alkoxide used. For example, when using tetraethoxysilane as the metal alkoxide, ethanol is used as the alcohol.

Examples of the acid catalyst used include hydrochloric acid, acetic acid, and nitric acid. The amount of acid used may be a catalytic amount. The reason why acids are used in the sol-gel method is that under acid conditions, metal alkoxides are rapidly hydrolyzed but the subsequent dehydration reaction is slow. Note that when a base is used, the hydrolysis of the metal alkoxide is slow but the subsequent dehydration reaction is fast, so that gelation progresses rapidly.

The amount of metal alkoxide (if organoalkoxysilane is included, the total of organoalkoxysilane and metal alkoxide), alcohol, and water is in a molar ratio of about 1:0.1 to 2:0.5 to 8. The molar ratio is preferably about 1:0.3 to 1:1 to 4. The acid may be in catalytic amounts as described above.

Examples of polybasic acids include citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, tartaric acid, glutamic acid, sebacic acid, and hexafluorosilicic acid. This polybasic acid can also be added as a hydrate.

The amount of polybasic acid added is preferably 0.00001 to 0.1% by mass, and 0.0001 to 0.05% by mass in the resulting phosphor composition (in solid content). is more preferable, and even more preferably 0.001 to 0.01% by mass.

The details of why the addition of a polybasic acid can suppress cracks and chips in the obtained phosphor are unknown, but it is due to the chelating effect on -SiO bonds and the inactivation of functional groups by reaction with OH groups. Possible causes include denaturation of the gel structure.

As for the order in which the above components are mixed, it is preferable that the metal alkoxide and alcohol are first mixed and mixed completely, and then water, quantum dots, and polybasic acid are added and mixed. Preferably, an acid catalyst is then added to initiate the sol-gel reaction.

The components may be mixed by stirring at about 15 to 80° C. for about 5 minutes to about 1 hour. The temperature during mixing can be appropriately selected depending on the type of metal alkoxide and the like. When mixing two or more metal alkoxides containing tetraalkoxysilane as the main component, add the alcohol of the other metal alkoxide to the hydrolysis solution obtained by adding alcohol, water, and a catalytic amount of acid to the tetraalkoxysilane. Just drop the solution.

(Reaction process)
In the reaction step, the precursor is solidified by a sol-gel reaction to obtain a phosphor composition containing a solid glass and quantum dots dispersed in the solid glass. This reaction can also be carried out in a mold having the desired inner surface shape.

Although the sol-gel reaction can be carried out at room temperature, it is preferably carried out under heated conditions in order to accelerate the reaction. The heating temperature is preferably 25°C to 60°C, more preferably 30°C to 50°C. It is also possible to increase the temperature in stages by changing the heating conditions in two or more stages.

The reaction time is preferably about 3 to 7 days at room temperature, and preferably about 12 to 36 hours when heated, depending on the reaction temperature. By performing the reaction at a higher temperature and for a longer time, a phosphor with greater hardness and specific gravity can be obtained.

Furthermore, the sol-gel reaction may be carried out while removing generated alcohol and water.

Further, the method may include a step of adjusting the pH of the metal alkoxide hydrolysis solution to 5.5 to 8.5. The above hydrolyzed solution is acidic due to the acid catalyst, so when the pH is adjusted to 5.5 to 8.5 using an aqueous alkali (e.g., sodium hydroxide, potassium hydroxide, etc.) solution, it becomes a sol. The dehydration condensation reaction of the hydrolyzed solution will be promoted.

The rod-shaped body in the present invention can be manufactured by performing a sol-gel reaction in a mold having a desired inner surface shape. Note that the rod-shaped body may be obtained by processing the molded product after obtaining it in a mold. Alternatively, it may be formed integrally with other members by insert molding.

Hereinafter, the present invention will be described in detail using Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. Note that the evaluation items in Examples and the like were measured as follows.

(1) Measurement of fluorescence spectrum For liquid samples, a measurement cell is used, and for rod-shaped phosphors, a measurement sample with a reflective layer made of aluminum provided by vapor deposition on the outer peripheral surface along the longitudinal direction is used. The fluorescence spectrum was measured using a fluorescence spectrophotometer (RF-5300PC, manufactured by Shimadzu Corporation). At this time, for each sample, first, the excitation light wavelength at which the excitation light emission intensity was maximum was determined by scanning, and then the fluorescence spectrum of the sample was measured using the excitation light at the determined wavelength.

(2) Measurement of density Using a disk-shaped phosphor produced in the same manner as in Example 1, etc., the volume (3.1 cm ³ ) of the phosphor was determined from the volume of water that overflowed, and the phosphor was measured. It was calculated by dividing the mass (6g) of by the volume.

(3) Quantum yield A phosphor product in which 0.01% by weight of graphene quantum dots were dispersed, which was produced in the same manner as in Example 1, was cut into strips and arranged on a sample holder. -QY Measurement was performed using an absolute PL quantum yield measuring device C11347, and a quantum yield of 58% was obtained at an excitation wavelength of 445 nm.

<Aqueous dispersion 1> (graphene quantum dots)
The fluorescence spectrum of an aqueous dispersion of graphene quantum dots (manufactured by GS Alliance Co., Ltd., graphene quantum dots, quantum yield 70%) was measured using the method described above at an excitation light wavelength of 370 nm. As a result, the peak wavelength of light emission of this water dispersion 1 was 445 nm, and the half width was 75 nm.

<Methanol dispersion 2> (silicon quantum dots, red)
The fluorescence spectrum of a methanol dispersion of silicon quantum dots (manufactured by GS Alliance Co., Ltd., silicon quantum dots, quantum yield 40%) was measured at an excitation light wavelength of 420 nm by the method described above. As a result, the peak wavelength of light emission of this methanol dispersion 2 was 625 nm, and the half width was 60 nm.

<Aqueous dispersion 3> (Perovskite quantum dots)
An organic dispersion of perovskite quantum dots (manufactured by GS Alliance Co., Ltd., perovskite quantum dots, compositional formula CsPbX ₃ (X=Cl, Br, I), quantum yield 60%) was prepared using excitation light using the method described above. Fluorescence spectra were measured at a wavelength of 460 nm. As a result, the peak wavelength of light emission of this organic dispersion was 625 nm, and the half width was 40 nm. Using this organic dispersion, a silane coupling agent and quantum dots were reacted, and then the solvent was replaced to obtain an aqueous dispersion 3 to be used as a raw material.
<Aqueous dispersion 4> (chalcopyrite quantum dots)
Aqueous dispersion 4 was obtained by using commercially available chalcopyrite quantum dots (manufactured by GS Alliance Co., Ltd., CuInS ₂ /ZnS, organic solvent dispersion type) and replacing the solvent with water.

<Example 1> (Graphene quantum dots 2% by mass)
TEOS was placed _{in a polypropylene beaker with} Teflon ₍ (registered trademark) using a measuring pipette, add the measured amount of ethanol using the measuring pipette, stir with a stirrer at room temperature (25 ° C.), mix completely, and then add the aqueous dispersion 1 of graphene quantum dots. Water was added so that the molar ratio of water was 4 (quantum dot concentration was 2% by mass in the phosphor) (total water ratio was 4), and the mixture was further stirred at room temperature (25° C.). At this time, 0.8 mg of citric acid hydrate (C ₆ H ₈ O ₇ ·H ₂ O) was added to 1 mol (208.37 g) of TEOS. 20 ml of 1M nitric acid aqueous solution (HNO ₂ ) as an acid catalyst was added to this solution, and the mixture was stirred until gelation started. After that, it was poured into a container with a rectangular bottom (3 mm x 50 mm) and left at room temperature (25°C) for 60 days to cause reaction and drying. A square prism) phosphor was manufactured. At that time, ethanol was removed as appropriate. This phosphor had graphene quantum dots uniformly dispersed, and there were no cracks or chips.

The fluorescence spectrum of this phosphor was measured using the method described above at an excitation light wavelength of 460 nm, and the results are shown in FIG. The peak wavelength of light emission was 540 nm, and the half width was 75 nm. Thus, compared to the fluorescence characteristics of the aqueous dispersion of graphene quantum dots used, a wavelength shift of nearly 100 nm was observed. Furthermore, when this phosphor was left in an atmospheric furnace at 200° C. for 24 hours and the luminescence intensity before and after heating was compared, it was confirmed that there was no change in the luminescence intensity. In other words, it was confirmed that there was sufficient heat resistance.

<Example 2> (graphene quantum dots 0.1% by mass)
Example 1 except that an aqueous dispersion of graphene quantum dots was mixed into the phosphor at a concentration of 0.1% by mass instead of 2% by mass. Phosphors of the same shape were manufactured under the same conditions. This phosphor had graphene quantum dots uniformly dispersed, and there were no cracks or chips.

The fluorescence spectrum of this phosphor was measured using the excitation light wavelength of 445 nm using the method described above. As a result, the peak wavelength of emission was 515 nm and the half width was 80 nm. As described above, a wavelength shift of 50 nm or more was observed compared to the fluorescence characteristics of the aqueous dispersion of graphene quantum dots used. Further, from comparison with Example 1, it was found that the amount of wavelength shift changes as the concentration of graphene quantum dots changes.

<Example 3> (Silicon quantum dots, red)
In Example 1, instead of using water dispersion 1 of graphene quantum dots, methanol dispersion 2 of silicon quantum dots was used so that the molar ratio of methanol was 2 (quantum dot concentration was 0.5% by mass in the phosphor). A phosphor having the same shape as that of Example 1 was manufactured under the same conditions as in Example 1, except that the phosphor was used. In other words, the raw materials were adjusted so that the molar ratio of Si(OC ₂ H ₅ ) ₄ (TEOS): ethanol (C ₂ H ₅ OH): water (H ₂ O): methanol was 2:1:4:2. It was used. This phosphor had silicon quantum dots uniformly dispersed, and there were no cracks or chips.

The fluorescence spectrum of this phosphor was measured using the method described above at an excitation light wavelength of 420 nm, and the results are shown in FIG. The peak wavelength of light emission was 625 nm, and the half width was 60 nm.

<Example 4> (200°C heating)
In Example 1, the same shape was prepared under the same conditions as in Example 1, except that instead of being left at room temperature (25 °C) for 60 days, it was heated in a heating device at 70 °C for 14 days, and then heated at 200 °C for 20 hours. phosphor was manufactured. This phosphor had graphene quantum dots uniformly dispersed, and there were no cracks or chips.

As a result of measuring the fluorescence spectrum of this phosphor at an excitation light wavelength of 445 nm using the method described above, it was found that it exhibited the same fluorescence characteristics as Example 1. Further, while the phosphor of Example 1 had a density of 2.0 g/cm ³ , the density of the obtained phosphor was 1.8 g/cm ³ .

<Example 5> (No citric acid added)
In Example 1, a phosphor was manufactured under the same conditions as in Example 1 except that citric acid hydrate (C ₆ H ₈ O ₇ .H ₂ O) was not added. At this time, if the shape was the same as in Example 1, cracks would easily occur, so after mixing the raw materials, a small amount of the mixture was used (the composition was the same) to create a thin film phosphor with a thickness of 5 mm. This phosphor had graphene quantum dots uniformly dispersed, and there were no cracks or chips.

As a result of measuring the fluorescence spectrum of this phosphor at an excitation light wavelength of 445 nm using the method described above, it was found that it exhibited the same fluorescence characteristics as Example 1. Further, while the phosphor of Example 1 had a density of 2.0 g/cm ³ , the density of the obtained phosphor was 1.8 g/cm ³ .

<Example 6> (Perovskite quantum dots)
In Example 1, the same conditions as in Example 1 were used, except that instead of using water dispersion 1 of graphene quantum dots, water dispersion 3 of perovskite quantum dots was used so that the molar ratio of water was the same. A phosphor with the same shape was manufactured using the same method. This phosphor had perovskite quantum dots uniformly dispersed therein, and there were no cracks or chips.

The fluorescence spectrum of this phosphor was measured using the method described above at an excitation light wavelength of 460 nm, and the results are shown in FIG. The peak wavelength of light emission was 630 nm, and the half width was 30 nm.
<Example 7> (chalcopyrite quantum dots)
In Example 1, the same as Example 1 except that instead of using water dispersion 1 of graphene quantum dots, water dispersion 4 of chalcopyrite quantum dots was used so that the molar ratio of water was the same. Phosphors of the same shape were manufactured under the same conditions. This phosphor had chalcopyrite quantum dots uniformly dispersed therein, and there were no cracks or chips.

The fluorescence spectrum of this phosphor was measured using the method described above at an excitation light wavelength of 420 nm, and the results are shown in FIG. The peak wavelength of light emission was 620 nm, and the half width was 100 nm.

<Other embodiments of wavelength conversion member>
In the previous embodiment, as shown in FIGS. 4 and 5, a configuration example was shown in which the excitation light L1 is incident from the end surface S2 on the incident side of the rod-shaped body 73. The conversion member 71 is provided with a light guide 81 having a contact portion 82 that contacts at least a part of the outer circumferential surface S1 along the longitudinal direction of the rod-shaped body 73, and the excitation light L1 is transmitted to the rod-shaped body through the light guide 81. The configuration may be such that the light is incident from the outer circumferential surface S1 of the body 73.

(1) As shown in FIG. 9, the wavelength conversion member 71 is provided with a light guide 81 that contacts the entire outer peripheral surface S1 of the rod-shaped body 73. The optical fiber 51 is in contact with or fixed (glued, welded, etc.) to the entrance surface S4, which is the end surface on the entrance side of the light guide 81. Note that, for example, a plurality of optical fibers 51 may be in contact with or fixed to the entrance surface S4 of the light guide 81. Further, the light guide 81 does not need to be in contact with the outer circumferential surface S1 of the rod-shaped body 73 over the entire length, and the light guide 81 may have a structure in which the incident side and/or the output side of the rod-shaped body 73 protrudes from the light guide 81. It's okay. Further, the light guide 81 does not need to cover the entire circumference of the rod-shaped body 73, and the light guide 81 may have a crescent-shaped or triangular cross section perpendicular to the longitudinal direction, for example. In that case, a plurality of light guides 81 may be provided and the excitation light L1 may be input from the optical fibers 51 separately.

The optical fiber 51 is a multimode or single mode optical fiber. The multimode optical fiber preferably has a core diameter of 50 μm to 100 μm, and the single mode optical fiber preferably has a core diameter of 5 μm to 20 μm.

It is preferable that the light guide 81 has a hollow truncated cone shape or a truncated pyramid shape with the incident side as the lower surface, and the shape of the hollow interior is the same as the outer shape of the rod-shaped body 73. With this configuration, the angle Θ1 formed between the end surface S5 of the light guide 81 located on the output side of the rod-shaped body 73 and the contact portion 82 can be made into an acute angle. Thereby, the excitation light L1 traveling parallel to the longitudinal direction of the rod-shaped body 73 can also be reflected into the inside of the rod-shaped body 73 and enter the rod-shaped body 73, and the extraction efficiency of the converted light L2 can be increased. Note that the angle Θ1 formed by the end surface S5 of the light guide 81 and the contact portion 82 is preferably 45° or less.

The light guide 81 is preferably made of silicon dioxide, resin (acrylic, polycarbonate), or the like. Note that in the contact portion 82, the light guide 81 and the rod-shaped body 73 may be fixed (adhesive, welded, etc.). When using an adhesive, from the viewpoint of preventing reflection of the excitation light L1 at the contact portion 82, it is preferable to use an adhesive having the same or similar refractive index as the light guide 81.

It is preferable that a reflective layer 74 that reflects the excitation light L1 and the converted light L2 is provided on the outer surface of the light guide 81 other than the entrance surface S4 and on the end surface S2 of the rod-shaped body 73 on the entrance side. A converted light reflection film 75 and an excitation light antireflection film 76 are provided on the incident surface S4 of the light guide 81, and an excitation light reflection film 77 and a converted light reflection film 76 are provided on the exit side end surface S3 of the rod-shaped body 73. Preferably, a preventive film 78 is provided. The materials, forming methods, etc. of the reflective layer 74, the converted light reflective film 75, the excitation light antireflection film 76, the excitation light reflection film 77, and the converted light antireflection film 78 are as described above.

With this configuration, the excitation light L1 can be made to enter from the outer circumferential surface X1 of the rod-shaped body 73. Thereby, the distance through which the excitation light L1 passes through the inside of the rod-shaped body 73 increases, the rate at which the excitation light L1 hits the quantum dots of the rod-shaped body 73 increases, and the extraction efficiency of the converted light L2 can be increased. Furthermore, compared to the case where the excitation light L1 is incident from the input side end surface S2 of the rod-shaped body 73, the converted light L2 can be extracted at a position closer to the output-side end surface S3 of the rod-shaped body 73, so that the converted light L2 is Attenuation of light due to passing through the inside of the rod-shaped body 73 can be suppressed.

(2) In the wavelength conversion member 71 of (1), as shown in FIG. The excitation light reflection film 77 may be provided on the outer surface of the bar 81 other than the entrance surface S4, and the converted light reflection film 75 may be provided on the outer peripheral surface S1 of the rod-shaped body 73.

(3) The light guide 81 in (1) has a hollow truncated cone shape or a truncated pyramid shape with the incident side as the lower surface, as shown in FIG. For example, as shown in FIG. The configuration may be such that the contact area is in contact with the part.

In this configuration, the end surface S5 of the light guide 81 located on the exit side of the rod-shaped body 73 is inclined. Thereby, the angle Θ1 formed by the end surface S5 of the light guide 81 and the contact portion 82 can be made into an acute angle. Further, a reflective layer 74 is provided on the outer circumferential surface S1 of the rod-shaped body 73 that is not in contact with the contact portion 82. Thereby, the excitation light L1 and the converted light L2 can be prevented from leaking from the outer peripheral surface S1 of the rod-shaped body 73.

Note that when the optical fiber 51 is a multimode optical fiber, the excitation light L1 travels in a zigzag pattern while repeating reflection within the optical fiber 51, and the excitation light L1 from the optical fiber 51 directly reaches the end surface S5 of the light guide 81. , the end surface S5 of the light guide 81 does not need to be inclined.

(4) The wavelength conversion member 71 of (1) is provided with a light guide 81 that contacts the entire outer peripheral surface S1 of the rod-shaped body 73, as shown in FIG. For example, the wavelength conversion member 71 has a configuration in which the core 511 of the optical fiber 51 contacts or is fixed to the outer circumferential surface S1 of the rod-shaped body 73, as shown in FIGS. 11 and 12. It may be configured such that the

In this configuration, a portion of the cladding 512 of the optical fiber 51 is removed from the tip of the optical fiber 51. The cladding 512 of the optical fiber 51 is removed and the exposed core 511 is in contact with the outer peripheral surface S1 of the rod-shaped body 73. Thereby, the excitation light L1 can be made to directly enter the inside of the rod-shaped body 73 from the outer circumferential surface S1 of the rod-shaped body 73 through the optical fiber 51.

Note that, for example, the core 511 and cladding 512 of the optical fiber 51 and the outer circumferential surface S1 of the rod-shaped body 73 may be fixed by adhesive. In that case, from the viewpoint of preventing reflection of the excitation light L1 at the adhesive part, it is preferable to use an adhesive having the same or similar refractive index as the core 511 of the optical fiber 51.

In addition, in this configuration, in order to prevent the excitation light L1 incident from the core 511 of the optical fiber 51 from leaking, the outer periphery of the rod-shaped body 73 except for the core 511 of the optical fiber 51 and the contact portion 513 of the cladding 512 with the rod-shaped body 73. It is preferable that a reflective layer 74 is provided on the surface S1 and the distal end surface S6 of the optical fiber 51. Further, it is preferable that the angle Θ2 formed between the distal end surface S6 of the optical fiber 51 and the contact portion 513 is an acute angle (preferably 45 degrees or less).

Note that the wavelength conversion member 71 and the endoscope 10 are not limited to the configurations of the embodiments described above, nor are they limited to the effects described above. Moreover, it goes without saying that the wavelength conversion member 71 and the endoscope 10 can be modified in various ways without departing from the gist of the present invention. Furthermore, the wavelength conversion member 71 of the above-described embodiment can also be used as a projector light source.

10 Endoscope 20 Insertion part 50 Illumination optical system 51 Optical fiber 71 Wavelength conversion member 72 Diverging lens 73 Rod-shaped body 74 Reflection layer 75 Converted light reflection film 76 Excitation light antireflection film 77 Excitation light reflection film 78 Conversion light antireflection film 81 Light guide 82 Contact part 91 Light source 100 Imaging system L1 Excitation light L2 Converted light L3 Illumination light

Claims (11)

A wavelength conversion member for an endoscope for converting the wavelength of excitation light from a light source device of an endoscope system into illumination light including converted light,
A rod-shaped body containing solid glass mainly composed of silica and quantum dots dispersed in the solid glass, and having a longitudinal length of 3 mm or more,
an outer peripheral surface along the longitudinal direction of the rod-shaped body contacts a contact portion of a core of an optical fiber that guides the excitation light to the rod-shaped body;
A wavelength conversion member for an endoscope, wherein the angle formed between the tip end surface of the optical fiber and the contact portion is an acute angle, and the tip end surface of the optical fiber is provided with a reflective layer that reflects at least the excitation light. The wavelength conversion member for an endoscope according to claim 1, wherein a reflective layer that reflects at least converted light is provided on an outer circumferential surface of the rod-shaped body along the longitudinal direction. 3. The endoscope according to claim 1, wherein a converted light reflecting film is provided on the incident side end surface of the rod-shaped body, and an excitation light antireflection film is provided on the surface of the converted light reflecting film. Wavelength conversion member. The wavelength conversion member for an endoscope according to any one of claims 1 to 3, wherein an excitation light reflection film and/or a converted light antireflection film is provided on the exit side end face of the rod-shaped body. A light guide having a contact portion that contacts at least a part of the outer circumferential surface of the rod-shaped body along the longitudinal direction is provided,
The endoscope according to claim 1, wherein the light guide is provided with an entrance surface into which the excitation light is incident, and a reflective layer that covers an outer surface other than the entrance surface and reflects at least the excitation light. Wavelength conversion material for mirrors. 6. The wavelength conversion member for an endoscope according to claim 5, wherein an angle formed between an end surface of the light guide located on the output side of the rod-shaped body and the contact portion is an acute angle. The wavelength conversion member for an endoscope according to any one of claims 1 to 6, wherein the rod-shaped body has a refractive index of 1.45 to 1.80 at a wavelength of 500 nm. an insertion section for inserting the tip into the body;
an imaging system that performs imaging or captures an image at the distal end and outputs it to the proximal end side of the insertion section;
An endoscope comprising: an illumination optical system including an optical fiber that guides light from the light source side to near the distal end of the insertion section,
An endoscope, wherein the illumination optical system is provided with the endoscope wavelength conversion member according to any one of claims 1 to 7. The endoscope according to claim 8, wherein the wavelength conversion member is provided on the distal end side of the optical fiber, and an optical window or a diverging lens is provided on the output side of the wavelength conversion member. The endoscope according to claim 8 or 9, wherein the light source is a laser diode that directly emits excitation light to the optical fiber. The illumination optical system includes a plurality of optical systems, the wavelength conversion member constituting one of the optical systems contains carbon-based quantum dots and/or silicon quantum dots, and the wavelength conversion member constituting the other optical system. The endoscope according to any one of claims 8 to 10, wherein the endoscope contains silicon quantum dots and/or perovskite quantum dots.