Lens and endoscope member

Abstract

To provide a novel technology that can be applied to a member for image transmission, for example, in an endoscope, and that enables transmission of high-quality images while having excellent bending resistance.SOLUTION: A lens 10 of the present disclosure is a plastic lens for image transmission. The lens 10 has a shape extending linearly in an image transmission direction. The lens 10 includes a core 11 serving as an image transmission part and having a refractive index distribution, and a low refractive index layer 12 disposed around an outer periphery of the core 11 and having a refractive index lower than that of the core 11. The refractive index distribution has a parabolic profile with the refractive index at the center of the core 11 being a maximum value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to lenses and endoscopic members. [Background technology]

[0002] A medical endoscope is an imaging diagnostic instrument that can be inserted into the body from outside to directly observe the inside of a body cavity or the lumen of an internal organ. An endoscope has an insertion section that is inserted into the body, and this insertion section is equipped with an image transmission component that transmits images of the inside of the body.

[0003] An example of an image transmission component mounted on an endoscope is an image fiber, which is formed by bundling a plurality of ultra-fine optical fibers made of glass, as described in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-18329 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with image fibers, one issue is that it is difficult to obtain good image quality, since a single image is transmitted by light propagating through multiple optical fibers.

[0006] An example of an image transmission component that can solve the above-mentioned image quality issues is a graded index (GI) glass lens. Such a GI lens allows incident light rays to travel in a meandering manner within a light propagation region having a refractive index distribution, and propagates while periodically converging, thereby enabling image transmission. Images transmitted by such light propagation can have excellent image quality.

[0007] Furthermore, image transmission components used in the insertion portion of an endoscope are required to not only provide high image quality but also to have bending resistance so as to be less susceptible to breakage due to bending. However, the GI glass lenses described above are weak to bending because they do not have sufficient bending resistance, and for example, bending can cause damage such as cracks, making it difficult to transmit high-quality images.

[0008] The present disclosure aims to provide a new technology that can be applied to components for transmitting images in endoscopes, for example, and that has excellent bending resistance and is capable of transmitting high-quality images. [Means for solving the problem]

[0009] The lens according to the first aspect of the present disclosure is a plastic lens for image transmission, the lens has a shape extending linearly in an image transmission direction, The lens is an image transmission section, the image transmission section including a core having a refractive index profile; a low refractive index layer disposed on the outer periphery of the core and having a refractive index lower than that of the core; Equipped with The refractive index profile has a parabolic profile with the refractive index at the center of the core being the maximum value.

[0010] An endoscope member according to a second aspect of the present disclosure includes the lens according to the first aspect. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a novel technology that can be applied to components for transmitting images in endoscopes, for example, and that has excellent bending resistance and is capable of transmitting high-quality images. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of the cross-sectional structure of a lens according to a first embodiment of the present disclosure. [Figure 2]FIG. 2 is a graph showing an example of a refractive index profile of a lens according to the first embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic diagram showing light rays traveling inside a lens and their periods. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of a manufacturing apparatus that can be used to manufacture the lens shown in FIG. [Figure 5] FIG. 5 is a schematic diagram showing an example of an endoscope device including an endoscope member according to the second embodiment of the present disclosure. [Figure 6] FIG. 6 shows a cross-sectional view of the insert housing the lens and light source therein. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) A lens according to a first embodiment of the present disclosure is a plastic lens for image transmission, and has a shape that extends linearly in the image transmission direction. FIG. 1 is a schematic diagram showing an example of the cross-sectional structure of a lens according to the first embodiment of the present disclosure. As shown in FIG. 1, a lens 10 according to the first embodiment includes a core 11 that is an image transmission section and has a refractive index distribution, and a low-refractive-index layer 12 that is disposed on the outer periphery of the core 11 and has a refractive index lower than that of the core 11. The refractive index distribution of the core 11 has a parabolic profile with the refractive index at the center 11a of the core 11 as a local maximum value.

[0014] In the lens 10 according to the first embodiment, the core 11, which is the image transmission section, has a refractive index distribution. The refractive index distribution has a parabolic profile with the refractive index at the center 11a of the core 11 as a maximum value. In the lens 10 including the core 1 having such a refractive index distribution, incident light rays meander through the core having the refractive index distribution and propagate while periodically converging, thereby transmitting images. Therefore, the lens 10 according to the first embodiment can transmit high-quality images. Furthermore, because the lens 10 according to the first embodiment is made of plastic, it is more flexible and has better bending resistance than a glass lens. Therefore, it is less susceptible to damage such as cracks even when bent. On the other hand, a lens that is highly flexible and has excellent bending resistance is less susceptible to damage due to bending and can transmit images even when bent significantly. However, bending can cause light leakage, resulting in defects such as loss of part of the image. The lens 10 according to the first embodiment includes a low-refractive index layer 12 on the outer periphery of the core 11, thereby preventing light leakage due to bending. As a result, the lens 10 according to the first embodiment is less susceptible to defects such as image loss and can transmit high-quality images even when bent.

[0015] As described above, the lens 10 according to the first embodiment has excellent bending resistance and is capable of transmitting high-quality images. The lens 10 according to the first embodiment having such properties can be suitably used, for example, as an image transmission component for an endoscope.

[0016] The lens according to the first embodiment has a shape that extends linearly in the image transmission direction, and can be considered as a relay lens that transmits an image. Hereinafter, for convenience of explanation, such as to distinguish it from other lenses, the lens according to the first embodiment will be referred to as a relay lens.

[0017] As described above, the relay lens 10 according to the first embodiment has a shape that extends linearly in the image transmission direction, and may be, for example, in the form of a fiber.

[0018] Here, in this specification, the refractive index of the core 11 and the low refractive index layer 12 refers to the refractive index at the wavelength of light propagating through the core 11 to transmit an image. For example, when the relay lens 10 according to the first embodiment is mounted on an endoscope as an image transmission component of the endoscope, the light propagating through the core 11 is reflected light of light irradiated onto an observation object. Therefore, the wavelength in this case is the wavelength of the light source used to irradiate the observation object with light (for example, a wavelength of 300 nm or more and 1000 nm or less).

[0019] 1, the relay lens 10 according to the first embodiment may further include a protective layer 13 disposed on the outer periphery of the low refractive index layer 12 and covering the core 11. The protective layer 13 protects the core 11 and can improve the mechanical strength of the relay lens 10.

[0020] 2 is a graph showing an example of the refractive index profile of the relay lens 10 according to the first embodiment of the present disclosure. As described above, the core 11 has a parabolic profile with the refractive index n0 at the center 11a of the core 11 as a maximum value, and the low refractive index layer 12 has a refractive index n1 lower than the refractive index of the core 11. Note that the refractive index of the core 11 used to specify the refractive index n1 of the low refractive index layer 12 is the refractive index n0 at the outer edge 11b of the core 11. a is.

[0021] In the refractive index profile of the core 11, the refractive index n at a position at a distance r from the center 11a of the core 11 in the radial direction of the core 11 is (r) It is desirable that, for example, the following formula (I) is satisfied.

number

number

[0022] By forming the refractive index profile of core 11 with a refractive index that satisfies the above formula (I), light rays travel sinusoidally within core 11 with a period equal to the pitch, enabling the transmission of higher quality images. Here, the pitch is the minimum distance at which a real image is formed, as shown in Figure 3.

[0023] Refractive index n at the outermost part of the core 11 a and the refractive index n1 of the low refractive index layer 12 (Δn in FIG. 2) is preferably 0.005 or more, more preferably 0.006 or more, even more preferably 0.010 or more, and particularly preferably 0.015 or more. By having the refractive index difference with the core 11 within the above range, the low refractive index layer 12 can more reliably prevent light leakage from the core 11 even when the relay lens 10 is used in a bent state. This makes it possible for the relay lens 10 to more reliably prevent image defects such as image chipping due to bending. The refractive index n a and the refractive index n1 of the low refractive index layer 12 is, for example, 0.02 or less.

[0024] Refractive index n at the outermost part of the core 11 a is not particularly limited, but may be, for example, 1.3 or more and 1.6 or less at a wavelength of 850 nm.

[0025] The refractive index of the low refractive index layer 12 is not particularly limited as long as it is designed according to the refractive index of the outer edge 11b of the core 11. As an example, the refractive index of the low refractive index layer 12 may be, for example, 1.25 or more and 1.34 or less at a wavelength of 850 nm.

[0026] The length of the relay lens 10 (i.e., the length of the relay lens 10 in the image transmission direction) may be, for example, 10 mm or more and 100 mm or less, or 10 mm or more and 50 mm or less. The length of the relay lens 10 can be set to an appropriate length depending on the application.

[0027] The diameter of the core 11 is preferably, for example, 100 μm or more and 250 μm or less. When the core 11 has such a diameter, a high-quality image can be transmitted, and pitch control (i.e., image formation) becomes easier.

[0028] Here, in this specification, the diameter of the core 11 refers to the outer diameter of the core 11. The outer diameter of the core 11 is the diameter at a light intensity of 5% measured by a near-field pattern method (hereinafter referred to as the "NFP method") using light with a wavelength of 650 nm, among methods conforming to IEC 60793-1-20 and IEC 60793-2-40 subcategory A4h. The diameter at a light intensity of 5% refers to the diameter of an approximate circle identified by a point having a light intensity of 5% of the peak light intensity. Furthermore, the point with 100% brightness refers to the point in the core with the highest brightness. The outer edge 11b of the core 11 can be identified by the same method as the core diameter, i.e., the NFP method.

[0029] The outer diameter of the low refractive index layer 12 can also be determined using the NFP method, similar to the core diameter.

[0030] The refractive index of the outermost portion of the core 11 and the refractive index of the low-refractive-index layer 12 can be determined by the following method. Sheet-shaped test pieces are prepared by hot pressing the core material and the material of the low-refractive-index layer. The test pieces are used to determine the refractive indices of the core material and the material of the low-refractive-index layer using the prism coupler method. Next, the aperture angle is measured using the far-field pattern method to determine the refractive index difference between the core and the low-refractive-index layer. Then, the refractive index of the outermost portion of the core 11 and the low-refractive-index layer 12 are calculated by referring to 2.4 of the paper (Mitsuhiro Tachibana, "Method for Measuring the Refractive Index Distribution of Optical Fibers," Applied Physics, Vol. 48, No. 8).

[0031] The outer diameter of the relay lens 10 may be, for example, 100 μm or more and 1000 μm or less. The outer diameter of the relay lens 10 is, for example, preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 350 μm or less, and particularly preferably 250 μm or less. By reducing the outer diameter of the relay lens 10 in this manner, for example, when used as an image transmission component in the insertion section of an endoscope, an endoscope that can obtain high-quality images with less physical strain can be realized. Furthermore, by making the outer diameter of the relay lens 10 500 μm or less, it is possible to achieve both an appropriate amount of light intake and application to, for example, an endoscope.

[0032] As described above, the relay lens 10 according to the first embodiment is made of plastic. That is, the core 11 and the low-refractive index layer 12 are formed of a resin material, and if a protective layer 13 is further provided, the protective layer 13 is also formed of a resin material. Therefore, the relay lens 10 is flexible and has excellent bending resistance. For example, in a bending stress-bending strain curve determined in accordance with the provisions of JIS K 7171:2016, the bending fracture strain of the relay lens 10 according to the first embodiment is preferably 0.0008 or more and 0.023 or less, and more preferably 0.0015 or more and 0.023 or less. Note that instead of the test specimen specified in JIS K 7171:2016, a relay lens having a length of 30 mm is used as the test specimen.

[0033] Each component of the relay lens 10 of the first embodiment will be described in more detail below.

[0034] (Core 11) As described above, the core 11 is a region through which light propagates and corresponds to an image transmission section. As described above, the core 11 has a refractive index distribution, which has a parabolic profile with the refractive index at the center 11a of the core 11 as a maximum value, as shown in FIG. 2. A low-refractive-index layer 12 having a refractive index lower than that of the outer edge 11b of the core 11 is provided on the outer periphery of the core 11. Therefore, when the relay lens 10 is bent, i.e., when the core 11 is bent, the low-refractive-index layer 12 prevents light from leaking from the core 11, and the incident light can be confined within the core 11 and propagated.

[0035] The core 11 is made of a resin material. The core 11 includes, for example, a first resin. The core 11 may include the first resin as a main component. Here, "the core 11 includes the first resin as a main component" means that the component contained in the core 11 in the largest amount by mass is the first resin. The core 11 may include 75% by mass or more, 80% by mass or more, or 85% by mass or more of the first resin.

[0036] The core 11 may further contain an additive in addition to the first resin. The additive is, for example, a refractive index adjuster. That is, the core 11 may be formed of a resin composition containing the first resin and an additive such as a refractive index adjuster. As the refractive index adjuster, for example, a known refractive index adjuster used in the material of the core 11 of the relay lens 10 may be used. The material of the core 11 may contain an additive other than the refractive index adjuster.

[0037] The first resin contained in the core 11 is not particularly limited as long as it is a resin having high transparency. Examples of the first resin include fluorine-containing resins, acrylic resins such as methyl methacrylate, styrene-based resins, and carbonate-based resins.

[0038] The first resin contained in the core 11 may be at least one selected from the group consisting of fully fluorinated resins, partially fluorinated resins, partially chlorinated resins, and partially deuterated resins. The terms partially fluorinated resins, partially chlorinated resins, and partially deuterated resins refer to resins known in the art as core materials for relay lenses, in which some of the hydrogen atoms in C-H bonds have been substituted with fluorine, chlorine, and deuterium, respectively. The term fully fluorinated resin refers to resins known in the art as core materials for relay lenses, in which all of the hydrogen atoms in C-H bonds have been substituted with fluorine. Examples of resins known in the art as core materials include acrylic resins such as methyl methacrylate, styrene-based resins, and carbonate-based resins, as described above. Polymers having an alicyclic structure, such as a polymer having a dioxolane structure, may also be used.

[0039] The first resin is preferably at least one selected from the group consisting of fully fluorinated resins and partially fluorinated resins, that is, the first resin is preferably a fluorine-containing resin.

[0040] The first resin of core 11 is preferably a fluororesin containing a fluoropolymer. Hereinafter, the fluororesin contained in core 11 will be referred to as the first fluororesin, and the fluoropolymer contained in the first fluororesin will be referred to as the first fluoropolymer.

[0041] From the viewpoint of suppressing light absorption due to the stretching energy of C-H bonds, the first fluorine-containing polymer contained in the first fluorine-containing resin preferably contains substantially no hydrogen atoms, and particularly preferably has all hydrogen atoms bonded to carbon atoms substituted with fluorine atoms. That is, the first fluorine-containing polymer preferably contains substantially no hydrogen atoms and is perfluorinated. In this specification, "the fluorine-containing polymer contains substantially no hydrogen atoms" means that the content of hydrogen atoms in the fluorine-containing polymer is 1 mol% or less.

[0042] The first fluorine-containing polymer preferably has a fluorine-containing alicyclic structure. The fluorine-containing alicyclic structure may be contained in the main chain of the fluorine-containing polymer or in a side chain of the first fluorine-containing polymer. The first fluorine-containing polymer has, for example, a structural unit (A) represented by the following formula (1): [ka]

[0043] In formula (1), R ff 1 ~R ff 4 R each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 7 carbon atoms, or a perfluoroalkyl ether group having 1 to 7 carbon atoms. ff 1 and R ff 2 may be linked to form a ring. "Perfluoro" means that all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. In formula (1), the number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1. The perfluoroalkyl group may be linear or branched. Examples of perfluoroalkyl groups include a trifluoromethyl group, a pentafluoroethyl group, and a heptafluoropropyl group.

[0044] In formula (1), the number of carbon atoms in the perfluoroalkyl ether group is preferably 1 to 5, and more preferably 1 to 3. The perfluoroalkyl ether group may be linear or branched. Examples of the perfluoroalkyl ether group include a perfluoromethoxymethyl group.

[0045] R ff 1 and R ff 2When these are linked to form a ring, the ring may be a 5-membered ring or a 6-membered ring. Examples of this ring include a perfluorotetrahydrofuran ring, a perfluorocyclopentane ring, and a perfluorocyclohexane ring.

[0046] Specific examples of the structural unit (A) include structural units represented by the following formulas (A1) to (A8). [ka]

[0047] Of the structural units represented by the above formulas (A1) to (A8), the structural unit (A) is preferably the structural unit (A2), ie, the structural unit represented by the following formula (2). [ka]

[0048] The first fluorine-containing polymer may contain one or more types of structural unit (A). In the first fluorine-containing polymer, the content of the structural unit (A) is preferably 20 mol % or more, more preferably 40 mol % or more, based on the total of all structural units. When the structural unit (A) is contained in an amount of 20 mol % or more, the first fluorine-containing polymer tends to have higher heat resistance. When the structural unit (A) is contained in an amount of 40 mol % or more, the first fluorine-containing polymer tends to have higher transparency and high mechanical strength in addition to high heat resistance. In the first fluorine-containing polymer, the content of the structural unit (A) is preferably 95 mol % or less, more preferably 70 mol % or less, based on the total of all structural units.

[0049] The structural unit (A) is derived from, for example, a compound represented by the following formula (3): ff 1 ~R ff 4is the same as formula (1). The compound represented by formula (3) can be obtained by a known production method, such as the production method disclosed in JP-A-2007-504125. [ka]

[0050] Specific examples of the compound represented by the above formula (3) include compounds represented by the following formulae (M1) to (M8). [ka]

[0051] The fluorine-containing polymer may further contain other structural units in addition to the structural unit (A). Examples of the other structural units include the following structural units (B) to (D).

[0052] The structural unit (B) is represented by the following formula (4). [ka]

[0053] In formula (4), R 1 ~R 3 R each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. 4 represents a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0054] The fluorine-containing polymer may contain one or more types of structural unit (B). In the fluorine-containing polymer, the content of the structural unit (B) is preferably 5 to 10 mol % based on the total of all structural units. The content of the structural unit (B) may be 9 mol % or less, or may be 8 mol % or less.

[0055] The structural unit (B) is derived from, for example, a compound represented by the following formula (5): In formula (5), R 1 ~R 4 is the same as formula (4). The compound represented by formula (5) is a fluorine-containing vinyl ether such as perfluorovinyl ether. [ka]

[0056] The structural unit (C) is represented by the following formula (6). [ka]

[0057] In formula (6), R 5 ~R 8 each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0058] The fluorine-containing polymer may contain one or more types of structural unit (C). In the fluorine-containing polymer, the content of the structural unit (C) is preferably 5 to 10 mol % based on the total of all structural units. The content of the structural unit (C) may be 9 mol % or less, or may be 8 mol % or less.

[0059] The structural unit (C) is derived from, for example, a compound represented by the following formula (7): 5 ~R 8 is the same as formula (6). The compound represented by formula (7) is a fluorine-containing olefin such as tetrafluoroethylene or chlorotrifluoroethylene. [ka]

[0060] The structural unit (D) is represented by the following formula (8). [ka]

[0061] In formula (8), Z is an oxygen atom, a single bond, or —OC(R 19 R 20 )O-, R 9 ~R 20 each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms. s and t each independently represent an integer of 0 to 5, and s+t is an integer of 1 to 6 (provided that Z is -OC(R 19 R 20 )O-, s+t may be 0).

[0062] The structural unit (D) is preferably represented by the following formula (9): The structural unit represented by the following formula (9) is the structural unit represented by the above formula (8) in which Z is an oxygen atom, s is 0, and t is 2. [ka]

[0063] In formula (9), R 141 , R 142 , R 151 , and R 152each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms.

[0064] The fluorine-containing polymer may contain one or more types of structural unit (D). In the fluorine-containing polymer, the content of the structural unit (D) is preferably 30 to 67 mol% based on the total of all structural units. The content of the structural unit (D) is, for example, 35 mol% or more, and may be 60 mol% or less, or may be 55 mol% or less.

[0065] The structural unit (D) is derived from a compound represented by the following formula (10): In formula (10), Z, R 9 ~R 18 , s and t are the same as in formula (8). The compound represented by formula (10) is a fluorine-containing compound which has two or more polymerizable double bonds and is capable of cyclopolymerization. [ka]

[0066] The structural unit (D) is preferably derived from a compound represented by the following formula (11): 141 , R 142 , R 151 , and R 152 is the same as equation (9). [ka]

[0067] Specific examples of the compound represented by formula (10) or formula (11) include the following compounds. CF2=CFOCF2CF=CF2 CF2=CFFOCF(CF3)CF=CF2 CF2=CFOCF2CF2CF=CF2 CF2=CFOCF2CF(CF3)CF=CF2 CF2=CFOCF(CF3)CF2CF=CF2 CF2=CFOCFClCF2CF=CF2 CF2=CFOCCl2CF2CF=CF2 CF2=CFOCF2OCF=CF2 CF2=CFOC(CF3)2OCF=CF2 CF2=CFOCF2CF(OCF3)CF=CF2 CF2=CFCF2CF=CF2 CF2=CFCF2CF2CF=CF2 CF2=CFCF2OCF2CF=CF2 CF2=CFOCF2CFClCF=CF2 CF2=CFOCF2CF2CCl=CF2 CF2=CFOCF2CF2CF=CFCl CF2=CFOCF2CF(CF3)CCl=CF2 CF2=CFOCF2OCF=CF2 CF2=CFOCCl2OCF=CF2 CF2=CClOCF2OCCl=CF2

[0068] The first fluorine-containing polymer may further contain other structural units than the structural units (A) to (D), but preferably does not substantially contain other structural units than the structural units (A) to (D). Here, "the fluorine-containing polymer does not substantially contain other structural units than the structural units (A) to (D)" means that the total of the structural units (A) to (D) is 95 mol % or more, preferably 98 mol % or more, of the total of all structural units in the fluorine-containing polymer.

[0069] The polymerization method for the first fluorine-containing polymer is not particularly limited, and for example, a general polymerization method such as radical polymerization can be used. The polymerization initiator for polymerizing the fluorine-containing polymer may be a perfluorinated compound.

[0070] The first fluorine-containing polymer constitutes a first fluorine-containing resin used as the first resin. The first resin has a first glass transition temperature of, for example, more than 105°C and not more than 140°C, and may be 120°C or higher.

[0071] (Low refractive index layer 12) As described above, the low refractive index layer 12 is disposed on the outer periphery of the core 11. The low refractive index layer 12 preferably covers the core 11 and is preferably provided in contact with the core 11.

[0072] The thickness of the low refractive index layer 12 may be, for example, 1.0 μm or more and 50 μm or less. The thickness of the low refractive index layer 12 can be determined based on the outer diameter of the low refractive index layer 12 and the outer shape of the core 11.

[0073] In the relay lens 10 of this embodiment, the low refractive index layer 12 includes, for example, a second resin. The low refractive index layer 12 may include the second resin as a main component. Here, the low refractive index layer 12 including the second resin as a main component means that the second resin is the component that is contained in the lowest refractive index layer 12 in the largest amount by mass ratio. The low refractive index layer 12 may include 80% by mass or more of the second resin, 90% by mass or more, or 95% by mass or more of the second resin. The low refractive index layer 12 may be composed only of the second resin. The low refractive index layer 12 may further include an additive in addition to the second resin.

[0074] The second resin contained in the low refractive index layer 12 is not particularly limited as long as it is a resin having high transparency. Examples of the second resin are the same as those exemplified as the resin that can be used as the first resin. As with the first resin, a fluorine-containing resin is preferably used as the second resin.

[0075] The second resin of the low refractive index layer 12 is preferably a fluorine-containing resin containing a fluorine-containing polymer. Hereinafter, the fluorine-containing resin contained in the low refractive index layer 12 will be referred to as the second fluorine-containing resin, and the fluorine-containing polymer contained in the second fluorine-containing resin will be referred to as the second fluorine-containing polymer.

[0076] As the second fluorine-containing resin, any of the fluorine-containing resins exemplified as the fluorine-containing resin that can be used as the first fluorine-containing resin can be used.

[0077] As the second fluorine-containing resin, a fluorine-containing resin containing a fluorine-containing polymer having an amorphous structure and further containing a constituent unit (E) represented by the following formula (12), and a fluorine-containing plasticizer may be used. [ka] (In formula (12), Z is an oxygen atom, a single bond, or —OC(R 31 R 32 )O-, R 21 ~R 32 each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. "Perfluoro" means that all hydrogen atoms bonded to carbon atoms have been substituted with fluorine atoms. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms. s and t each independently represent an integer of 0 to 5, and s+t is an integer of 1 to 6 (provided that Z is not -OC(R 31 R 32 ) In the case of O-, s+t may be 0. u and v are each independently 0 or 1.

[0078] The fluorine-containing polymer containing the structural unit (E) may further contain a structural unit (F) represented by the following formula (13). [ka] (In formula (13), R 33 ~R 36each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0079] When the second fluorine-containing polymer is the above copolymer, the ratio of the structural unit (E) to the structural unit (F) is optional and is not particularly limited.

[0080] The second fluorine-containing polymer is preferably, for example, at least one selected from the group consisting of fluorine-containing polymer A and fluorine-containing polymer B shown below.

[0081] The fluorine-containing polymer A contains a structural unit (G) represented by the following formula (14) and a structural unit (H) represented by the following formula (15). 23 , R 24 , R 31 , and R 32 is the same as the above equation (12).

[0082] [ka] [ka] (In formula (15), R 37 ~R 40 each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0083] The fluorine-containing polymer B contains a structural unit (I) represented by the following formula (16): 21 ~R 24 , R27 ~R 30 , R 31 , and R 32 is the same as the above equation (12). [ka]

[0084] The above-mentioned fluorine-containing polymer A and fluorine-containing polymer B have very high transparency and can have a refractive index that is very low compared to the general refractive index of the first fluorine-containing resin used as the material for core 11. Therefore, the second fluorine-containing resin containing at least one selected from the group consisting of fluorine-containing polymer A and fluorine-containing polymer B as the second fluorine-containing polymer can further reduce the refractive index while maintaining the high transparency of low refractive index layer 12. As a result, the difference between the refractive index of core 11 and that of low refractive index layer 12 can be made even larger, which further improves the effect of confining light in core 11 by low refractive index layer 12 and makes it easier to achieve low transmission loss in relay lens 10.

[0085] The second fluorine-containing polymer preferably contains a structural unit (J) represented by the following formula (17). [ka] (In formula (17), m and n are any integers.)

[0086] The fluorine-containing plasticizer is preferably a fluorine-containing polyether, more preferably a perfluoropolyether.

[0087] Specific examples of perfluoropolyethers include organic compounds represented by the following formula (18) or (19): In the following formulas (18) and (19), p1, q1, p2, and q2 each represent an arbitrary integer. CF3-[(O(CF3)CFCF2) p1 -(OCF2) q1 ]OCF3(18) CF3-[(OCF2CF2) p2-(OCF2) q2 ]OCF3(19)

[0088] The second fluorine-containing polymer constitutes a second fluorine-containing resin used as the second resin. The second glass transition temperature Tg2 of the second resin is not particularly limited and may be, for example, higher than 105°C and 170°C or lower, or 125°C or higher.

[0089] (protective layer) Examples of materials for the protective layer 13 include various engineering plastics such as polycarbonate, polyester, cycloolefin polymer, cycloolefin copolymer, polytetrafluoroethylene (PTFE), modified PTFE, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), or copolymers or mixtures thereof.

[0090] (Manufacturing method) The relay lens of this embodiment can be manufactured using, for example, a melt spinning method.

[0091] When preparing a linear molded body made of a core material, a first core material containing a refractive index control agent may be extruded first to form an inner core layer, and then a second core material may be extruded to cover the outer periphery of the inner core layer 2 formed of the first core material. In this case, the refractive index control agent contained in the first core material is diffused toward the outer periphery of the core formed of the second core material, thereby forming a core 11 having a refractive index distribution. To form a desired refractive index distribution, for example, the conditions (e.g., diffusion temperature and diffusion time) for diffusing (e.g., thermal diffusion) the refractive index control agent, the discharge amounts of the first core material and the second core material, etc. may be adjusted.

[0092] FIG. 4 is a schematic cross-sectional view showing an example of a manufacturing apparatus that can be used to manufacture the relay lens 10 shown in FIG.

[0093] The apparatus 1000 shown in FIG. 4 includes a first extrusion device 101a for extruding a first core material, a second extrusion device 101b for extruding a second core material, a third extrusion device 101c for extruding a low refractive index layer material, and a fourth extrusion device 101d for forming a protective layer.

[0094] The first extrusion device 101a has a first storage section 102a that stores the first core material 1a and a first extrusion section 103a that extrudes the first core material 1a stored in the first storage section 102a from the first storage section 102a. The first extrusion device 101a is further provided with a heating section (not shown) so that the first core material 1a can be melted in the first storage section 102a and the molten first core material 1a can be maintained in a molten state until it is molded. A rod-shaped first core material (preform) 1a is inserted into the first storage section 102a through an upper opening and is heated and melted in the first storage section 102a.

[0095] In the first extrusion device 101a, the first core material 1a is extruded by gas extrusion from the first storage section 102a through the first extrusion section 103a to form the inner core layer section 2. The first core material 1a extruded through the first extrusion section 103a to form the inner core layer section 2 then moves vertically downward and is supplied to the first chamber 110.

[0096] The second extrusion device 101b has a second storage section 102b that stores the second core material 1b and a second extrusion section 103b that extrudes the second core material 1b stored in the second storage section 102b from the second storage section 102b. The second extrusion device 101b extrudes the molten second core material so as to cover the outer periphery of the inner core layer section 2 formed from the first core material 1a extruded from the first extrusion device 101a. Specifically, the second core material extruded from the second extrusion device 101b is supplied to a first chamber 110. In the first chamber 110, the inner core layer section 2 formed from the first core material 1a is covered with the second core material, thereby forming an outer core section 3 that covers the outer periphery of the inner core layer section 2. The laminate 4 formed of the inner core layer portion 2 and the outer core portion 3 covering the outer periphery of the inner core layer portion 2 moves from the first chamber 110 to the diffusion tube 120 arranged vertically below the first chamber 110. A heater (not shown) for heating the laminate is arranged in the diffusion tube 120. The diffusion tube 120 diffuses dopants such as a refractive index adjuster contained in the inner core layer portion 2 of the laminate 4 passing through the inside of the diffusion tube 120 toward the outer core portion 3. In other words, the inner core layer portion 2 and the outer core portion 3 ultimately form a core.

[0097] The third extrusion device 101c has a third storage section 102c that stores the low-refractive-index layer material 1c and a third extrusion section 103c that extrudes the low-refractive-index layer material 1c stored in the third storage section 102c from the third storage section 102c. The third extrusion device 101c extrudes the molten low-refractive-index layer material 1c so as to coat the outer periphery of the laminate 4 that has passed through the diffusion tube 120. Specifically, the low-refractive-index layer material 1c extruded from the third extrusion device 101c is supplied to a second chamber 130. In the second chamber 130, the laminate 4 (i.e., the core) is coated with the low-refractive-index layer material 1c, thereby forming a low-refractive-index layer 5 that covers the outer periphery of the core. Hereinafter, the laminate 4 will be referred to as the core 4. The laminate formed of the core 4 and the low-refractive-index layer 5 moves from the second chamber 130 to a third chamber 140 located vertically below the second chamber 130.

[0098] The fourth extrusion device 101d includes a fourth storage section 102d that stores the protective layer material 1d, a screw 104 disposed within the fourth storage section 102d, and a hopper 105 connected to the fourth storage section 102d. In the fourth extrusion device 101d, the protective layer material 1d, for example, in pellet form, is supplied to the fourth storage section 102d through the hopper 105. The protective layer material 1d supplied to the fourth storage section 102d is kneaded by the screw 104 while being heated, thereby softening and becoming fluid. The softened protective layer material 1d is extruded from the fourth storage section 102d by the screw 104.

[0099] The protective layer material 1d extruded from the fourth extrusion device 101d is supplied to the third chamber 140. In the third chamber 140, the surface of the laminate formed of the core 4 and the low refractive index layer 5 is coated with the protective layer material 1d, thereby forming a protective layer 6 that covers the outer periphery of the low refractive index layer 5.

[0100] The laminate 7, in which the core 4, the low refractive index layer 5, and the protective layer 6 are concentrically stacked, flows from the third chamber 140 into the internal flow path through the inlet of the nozzle 150. The laminate 7 is reduced in diameter as it passes through the internal flow path, and is discharged linearly from the outlet of the nozzle 150.

[0101] The laminate 7 discharged linearly from the discharge port of the nozzle 150 flows into the internal space 161 of the cooling pipe 160, is cooled while passing through the internal space 161, and is discharged from the opening to the outside of the cooling pipe 160. The laminate 7 discharged from the cooling pipe 160 passes between two rolls 171 and 172 of the nip roll 170, and further passes through guide rolls 173 to 175 to be taken up by a take-up roll 176 as a relay lens 10. A displacement meter 180 for measuring the outer diameter of the relay lens 10 may be further provided near the take-up roll 176, for example, between the guide roll 175 and the take-up roll 176.

[0102] (Second embodiment) An endoscopic member according to a second embodiment of the present disclosure includes the relay lens according to the first embodiment. For example, the endoscopic member according to the second embodiment may be a member that constitutes a portion of an endoscopic device that is inserted into the interior of an observation target (e.g., the body), i.e., an insertion portion. Because the endoscopic member according to the second embodiment includes the relay lens according to the first embodiment, defects such as image loss are less likely to occur, and high-quality images can be obtained.

[0103] FIG. 5 is a schematic diagram showing an example of an endoscope device including an endoscope member according to the second embodiment of the present disclosure.

[0104] 5 includes, for example, an insertion section 21 that is inserted into the interior of an observation target (e.g., the body), an endoscope main body 22, a reinforcing section 23, and a control box 24. In the endoscope device 20, the insertion section 21 corresponds to the endoscope member of the present disclosure.

[0105] The insertion section 21 includes the relay lens 10 according to the first embodiment and a housing 211 that houses the relay lens 10 therein. The housing 211 may be made of, for example, resin or a metal such as stainless steel. The insertion section 21 may have a bent tip to facilitate insertion into the body, as shown in FIG. 5, for example. Even when the insertion section 21 is bent in this way, the relay lens 10 housed therein can suppress light leakage from the core, thereby enabling the acquisition of high-quality images without defects such as image chipping.

[0106] The insertion section 21 may further include a light source. Fig. 6 shows a cross-sectional view of the insertion section 21 that houses the relay lens 10 and the light source 30 therein. As shown in Fig. 6, the insertion section 21 may include, for example, the relay lens 10 arranged at the center inside the housing 211 and the light source 30 arranged around the relay lens 10.

[0107] The light source 30 may be, for example, a light source optical fiber having a diameter of 500 μm or less. In this case, as shown in FIG. 6, the insertion section 21 may include one relay lens 10 and a plurality of light source optical fibers (light sources 30).

[0108] The relay lens 10 has, for example, a first end 10a that faces the object of observation during use and a second end 10b opposite the first end 10a. As shown in FIG. 5, the insertion section 21 may include a first lens 41 cemented to the first end 10a of the relay lens 10 and a second lens 42 cemented to the second end 10b of the relay lens 10. The numerical apertures of the first lens 41 and the second lens 42 are larger than the numerical aperture of the relay lens 10. The first lens 41 functions as an objective lens, capturing light reflected by the object of observation and its surroundings, converting it into a small image, and directing the light into the relay lens 10. The second lens 42 functions as an eyepiece, magnifying the light propagating through the relay lens 10 into a large image.

[0109] The insertion portion 21 may further be provided with a light-transmitting cap that covers the first lens 41 and the first end 41 of the relay lens 10. This prevents the lens from coming into contact with the body when the insertion portion 21 is inserted into the body, thereby improving safety.

[0110] The endoscope main body 22 is connected to the insertion section 21 via a connector 25. A reinforcing section 23, for example, may be provided at the connection section of the insertion section 21 to prevent the insertion section 21 from breaking at the base of the endoscope main body 22 due to a load. The endoscope main body 22 is provided with, for example, a CMOS or DCC for digitizing received light into an image. The endoscope main body 22 may also be equipped with a light source device for inputting light into a light source fiber (light source 30), a driving power supply, etc.

[0111] The endoscope main body 22 is connected to a control box 24 via, for example, a cable 26. The control box 24 has various functions such as power supply to the endoscope main body 22, light intensity adjustment of the light source, correction and conversion of digital image signals, and image processing.

[0112] [Note] To summarize the above, one aspect of the present disclosure is as follows.

[0113] (1) A plastic lens for image transmission, the lens has a shape extending linearly in an image transmission direction, The lens is an image transmission section, the image transmission section including a core having a refractive index profile; a low refractive index layer disposed on the outer periphery of the core and having a refractive index lower than that of the core; Equipped with the refractive index profile has a parabolic profile with the refractive index at the center of the core being a maximum value; lens.

[0114] (2) In the refractive index profile, the refractive index n at a position at a distance r from the center of the core in the radial direction of the core (r) satisfies the following formula (I): The lens described in (1) above.

number

number

[0115] (3) the difference between the refractive index of the outermost portion of the core and the refractive index of the low refractive index layer is 0.005 or more; The lens according to (1) or (2) above.

[0116] (4) The length of the lens is 10 mm or more and 100 mm or less. A lens according to any one of (1) to (3) above.

[0117] (5) The length of the lens is 10 mm or more and 50 mm or less. The lens described in (4) above.

[0118] (6) The diameter of the core is 100 μm or more and 250 μm or less. A lens according to any one of (1) to (5) above.

[0119] (7) The lens has a bending fracture strain of 0.0008 or more and 0.023 or less in a bending stress-bending strain curve obtained in accordance with the provisions of JIS K 7171:2016. A lens according to any one of (1) to (6) above. However, instead of the test piece specified in JIS K 7171:2016, the above-mentioned lens having a length of 30 mm is used as the test piece.

[0120] (8) A lens according to any one of (1) to (7) above, Endoscopic components.

[0121] (9) Further comprising a metal housing that houses the lens therein. The endoscope member according to (8) above.

[0122] (10) Further equipped with a light source, The endoscope member according to (8) or (9) above.

[0123] (11) The light source is a light source optical fiber having a diameter of 500 μm or less. The endoscope member according to (10) above.

[0124] (12) The endoscope member includes one lens and a plurality of light source optical fibers. The endoscope member according to (11) above.

[0125] (13) the lens has a first end facing an object to be observed in use in the image transmission direction, and a second end opposite the first end, The endoscope member includes: a first lens cemented to the first end of the lens; a second lens cemented to the second end of the lens; Furthermore, the numerical apertures of the first lens and the second lens are greater than the numerical aperture of the lens; An endoscope member according to any one of (8) to (12) above.

[0126] (14) the endoscope member further includes a cap that covers the first lens and the first end of the lens and has translucency; The endoscope member according to (13) above. [Industrial Applicability]

[0127] The lens of the present disclosure has excellent bending resistance and is capable of transmitting high-quality images, and is therefore suitable for use in endoscopes, for example. [Explanation of symbols]

[0128] 1a First core material 1b Second core material 1c Low refractive index layer material 1d protective layer material 2. Core inner layer 3 Core outer periphery 4 Laminate (core) 5 Low refractive index layer 6 Protective layer 7 Laminate 10 Lens (relay lens) 11 cores 11a center 11b outer edge 12 Low refractive index layer 13 Protective layer 20 Endoscopic device 21 Insertion section 22 Endoscope main body 23 Reinforcement 24 Control Box 25 connectors 26 Cable 30 light source 41 First lens 42 Second lens 101a First extrusion device 101b Second extrusion device 101c Third extrusion device 101d Fourth extrusion device 102a First storage section 102b Second storage section 102c Third Storage Unit 102d 4th Storage Unit 103a First extrusion section 103b Second extrusion section 103c Third extrusion section 104 Screw 105 Hopper 110 Room 1 120 Diffusion tube 130 Room 2 140 Room 3 150 nozzles 160 Cooling pipe 161 Interior Space 170 Nip Roll 171,172 rolls 173,174,175 Guide Roll 176 Winding Roll 180 Displacement Meter 211 Case 1000 manufacturing equipment

Claims

1. A plastic lens for image transmission, the lens has a shape extending linearly in an image transmission direction, The lens is an image transmission section, the image transmission section including a core having a refractive index profile; a low refractive index layer disposed on the outer periphery of the core and having a refractive index lower than that of the core; Equipped with the refractive index profile has a parabolic profile with the refractive index at the center of the core being a maximum value; lens.

2. In the refractive index profile, the refractive index n at a position at a distance r from the center of the core in the radial direction of the core (r) satisfies the following formula (I): The lens of claim 1 . [Equation 1] Here, in the above formula (I), n o is the refractive index of the center of the core, and A G is a constant that represents the light-collecting ability and is calculated by the following formula (II). [Equation 2] In the above formula (II), a is the radius of the core, and n a is the refractive index at the outermost part of the core, which is the radial position of the core.

3. a difference between the refractive index of the outermost portion of the core and the refractive index of the low refractive index layer is 0.005 or more; The lens of claim 1 .

4. The length of the lens is 10 mm or more and 100 mm or less. The lens of claim 1 .

5. The length of the lens is 10 mm or more and 50 mm or less. The lens of claim 4.

6. The diameter of the core is 100 μm or more and 250 μm or less. The lens of claim 1 .

7. the lens has a bending fracture strain of 0.0008 or more and 0.023 or less in a bending stress-bending strain curve obtained in accordance with the provisions of JIS K 7171:2016; The lens of claim 1 . However, instead of the test piece specified in JIS K 7171:2016, the above-mentioned lens having a length of 30 mm is used as the test piece.

8. A lens according to any one of claims 1 to 7, Endoscopic components.

9. Further comprising a housing that houses the lens therein. An endoscopic member according to claim 8.

10. Further equipped with a light source, An endoscopic member according to claim 8.

11. The light source is an optical fiber for a light source having a diameter of 500 μm or less. An endoscopic member according to claim 10.

12. The endoscope member includes one lens and a plurality of light source optical fibers. An endoscopic member according to claim 11.

13. the lens has a first end facing an object to be observed in use in the image transmission direction, and a second end opposite the first end, The endoscope member includes: a first lens cemented to the first end of the lens; a second lens cemented to the second end of the lens; Furthermore, the numerical apertures of the first lens and the second lens are greater than the numerical aperture of the lens; An endoscopic member according to claim 8.

14. the endoscope member further includes a cap that covers the first lens and the first end of the lens and has translucency; An endoscopic member according to claim 13.

Images