JP2971626B2 - Image fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The image fiber of the present invention is used as an endoscope in the medical field, measurement field, and industrial field as a fiber, and used for reading characters and objects.

[0002]

2. Description of the Related Art An image fiber is one in which a number of optical fibers are converged and the arrangement at both ends is accurately matched, and light incident on one end is emitted to a corresponding position on the other end surface. In this case, a large number of fibers are fixed only at both end surfaces, and may be free in the middle or fixed along the entire length of the fiber. The former is often practiced with a plastic optical fiber or a glass fiber, in which individual optical fibers are converged as they are, and the converged image guide has a relatively large cross-sectional area. On the other hand, in the case of the latter, individual fibers are arranged in advance, and the fibers are fused or fused as a whole to be integrated and stretched into a fiber shape. Can be captured. This technique is a method often used for quartz fibers, but has disadvantages in that it requires a large number of manufacturing steps and is expensive. As a plastic image fiber attempt, U.S. Pat. No. 3,556,635 has devised a fiber in which a sheath component is made of sea and a core component is made of an island, and a core composed of a large number of islands is arranged in a sheath of sea. ing. JP-A-56-39505 proposes an island having a core-sheath structure and an ocean as a third resin.

[0003]

As for the use of image fibers, those using glass fibers are relatively expensive. In particular, when used as a medical device, there is a demand for the development of an inexpensive fiber which is safest to disposable and is inexpensive in order to prevent virus and bacterial infection. Further, there is a risk that the glass fiber may be broken, and a plastic image fiber that is not broken for medical use, particularly for endoscopic use of blood vessels, is desired. However, there is a disadvantage that the resolution of the plastic fiber is slightly lower than that of the glass fiber. If the core-sheath structure is made into islands and the sea is formed with an opaque third resin in order to improve the resolution, it is possible to prevent light from leaking to the next island, but manufacturing facilities Become a large scale,
By introducing the third resin, only an image fiber having a high transmission loss can be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a plastic image fiber made of two core-sheath materials and having excellent resolution. That is, the present invention is a multi-core plastic waveguide made of a transparent core resin having a high refractive index and filled with a sheath resin having a low refractive index between core fibers so as to separate a large number of small core fibers individually. In the above, the core resin has a melt flow index of 0.5 g / 10 min to 40 g /
When the sum of the structural units of vinylidene fluoride and tetrafluoroethylene exceeds 99 mol% and up to 100 mol%, the vinylidene fluoride structural unit is more than 85 mol%, and 91% or less. Wherein the resin has a melt flow index of 10 g / 10 min or more. Here, the use of a copolymer of vinylidene fluoride and tetrafluoroethylene as the sheath resin is known in plastic optical fibers, and is disclosed in Japanese Patent Application Laid-Open No. 50-20737.
No., JP-A-52-156463, JP-A-52-154
645, etc. In fact, if an image fiber is manufactured with these sheath resin and PMMA resin,
Although a sufficiently practical product can be produced, even better resolution can be obtained when the sheath of the specific composition region of the present invention is used. This is because an image fiber that prevents light from bleeding between the cores can be obtained. Generally, plastic optical fiber sheaths are selected to be more transparent and optical fibers with lower transmission loss are to be obtained.However, image fibers using such sheaths cause light bleeding between pixels. It was found that the interface of the image tended to be slightly blurred. As a result of intensive studies to solve this problem,
When the sheath resin has a sum of structural units of vinylidene fluoride and tetrafluoroethylene exceeding 99 mol% and up to 100 mol%, and a vinylidene fluoride structural unit exceeding 85 mol% and 91% or less, a melt flow index Is particularly preferable to be a resin of 10 g / 10 min or more. When such a sheath is used, the sheath resin alone has crystallinity and is cloudy, and the light transmittance of the sheath resin itself is poor, so that light leakage between pixels is small. On the other hand, there is no significant increase in transmission loss as an optical fiber. It was found that the transmission loss was not so high because PMMA of the core and these sheath resins formed a homogeneous compatible zone at the interface between the core and the sheath. Generally, in plastic optical fibers, copolymers of vinylidene fluoride and tetrafluoroethylene are disclosed in JP-A-52-1546.
According to No. 45, it is said that the area where the vinylidene fluoride is around 80 mol% is the most preferable region. However, in the image fiber, although the transmission loss is somewhat inferior, the vinylidene fluoride structural unit exceeds 85 mol%. And 91
% Area has better resolution,
The present invention has been completed. When the vinylidene fluoride structural unit is 85 mol% or less, the crystallinity of the sheath is relatively low, and the effect of blocking light bleeding between pixels is small. On the other hand, if it exceeds 91%, the transmission loss is disadvantageously increased, which is not preferable.

If these resins are less than 1% in addition to the binary copolymer of vinylidene fluoride and tetrafluoroethylene, the crystallinity of the resin remains even if other copolymer components are present, so that there is no problem. Absent. Examples of such other components include hexafluoropropene, hexafluoroacetone, trifluoroethylene, and chlorotrifluoroethylene. The melt flow index of these sheaths is ASTM-1238, which has a weight of 3.8 kg at 230 ° C and a value of more than 10 g / 10 min. It is preferable because it can be spun without any. Core resin is PM
MA-based resin. Here, the PMMA resin is M
A homopolymer of MA or a copolymer of MMA and another monomer, wherein the copolymerization ratio of MMA is 90 mol% or more. For example, it is a copolymer with methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and the like.

[0006] These resins are well compatible with the sheath resin mainly composed of vinylidene fluoride. The melt flow index of these core resins needs to be 0.5 g / 10 min or more in order to form a smooth core fiber with good fluidity, and 40 g to maintain the mechanical strength of the fiber. / 10 minutes or less. In order to manufacture the image fiber of the present invention, a core resin and a sheath resin are supplied in a molten state to a composite spinning die. The core resin is supplied to the plate, and subsequently the core resin is caused to flow down by a thin tube guide. On the other hand, while supplying the molten sheath resin uniformly around all the thin tubes through which the core resin flows, at the end face of the thin tube,
A method in which the sheath is directly coated around the core is preferable. Thereafter, all the core-sheath structures are integrated, pulled down and drawn to the desired diameter. The thickness of this thread is usually
The diameter is set to be about 0.2 mm to 3 mm, but is not limited to this range. The image fiber may be stretched about 1.0 to 3 times as in the case of a normal plastic optical fiber, or may be subjected to a heat treatment thereafter. The volume ratio of the sheath resin to the total resin is preferably about 20% to 60%. This is because if the sheath resin is small, light leakage between pixels is likely to occur, and if the sheath resin is too large, there is a difficulty in darkening. It is more effective to manufacture an image fiber having excellent resolution with a smaller volume ratio of the sheath resin.

[0007] The multi-core waveguide thus obtained is protectively coated with an antithrombotic material such as ethylene vinyl alcohol resin, Teflon resin, or other fluororesin in addition to polyethylene or PVC resin to obtain a waveguide cable. , Or for medical use in the body.

[0008]

EXAMPLE 1 As a core resin, a homopolymer of MMA having a melt flow index of ASTM-1238, a weight of 3.8 kg at 240.degree. C. and a weight of 1.5 kg / 10 minutes was used, and vinylidene fluoride 85 was used as a sheath resin. A resin of 0.5 mol%, 14.5 mol% of tetrafluoroethylene and a melt flow index of 50 g / 10 min was used. Die temperature 2
40 ° C. A composite spinning die was used in which the core resin was simultaneously extruded from the 3,500 holes provided in the die and the core wire was coated with the sheath resin.

The molten resin was supplied to the composite spinning die from the extruder at a supply rate of the core resin of 600 ml / hr and a supply rate of the sheath resin of 400 ml / hr via the gear pump. Strands having a sea-island structure in which the core coming out of the dice was formed as an island and the sheath was the sea were stretched while cooling to obtain an image fiber having a fiber diameter of 0.5 mm. The transmission loss of this image fiber was 350 dB / km at 650 nm as measured by the 10 m and 1 m cutback methods. 1.5 m of this fiber is taken, and a 0.5 mm selfoc lens ILH0.5Φ-WD is placed at the tip of the fiber.
05 was fixed with a transparent adhesive to form an objective lens, and one end face was magnified 100 times with a microscope.

[0010] Observe USAF test target.
Eight line pairs / mm could be identified.

[0011]

EXAMPLE 2 Vinylidene fluoride 87 was used as a sheath resin.
The same procedure as in Example 1 was carried out except that a resin of mol%, 13 mol% of tetrafluoroethylene and a resin having a melt flow index of 45 g / 10 min were used. Transmission loss is 400 at 650 nm.
It was dB / km. The resolution of this fiber at 1.5 m was 57 line pairs / mm.

[0012]

Example 3 As sheath resin, vinylidene fluoride 90
The resin was used in an amount of 10 mol%, 10 mol% of tetrafluoroethylene, and a melt flow index of 30 g / 10 min. The procedure was the same as in Example 1 except that the temperature of the die was 245 ° C. The transmission loss at 650 nm was 500 dB / km.
The resolution at 1.5 m of this fiber was 50.8 line pairs / mm.

[0013]

Comparative Example 1 Vinylidene fluoride 80 as a sheath resin
The resin used was 20 mol%, 20 mol% of tetrafluoroethylene, and a melt flow index of 30 g / 10 min. The procedure was the same as in Example 1 except that the temperature of the die was 240 ° C. Although the transmission loss was 330 dB / km at 650 nm. The resolution of this fiber at 1.5 m was 45.3 line pairs / mm.

[0014]

Comparative Example 2 Vinylidene fluoride 83 as a sheath resin
The resin used was mol%, tetrafluoroethylene 17 mol%, and a melt flow index of 40 g / 10 min. The procedure was the same as in Example 1 except that the temperature of the die was 240 ° C. Although the transmission loss was 340 dB / km at 650 nm. The resolution of this fiber at 1.5 m was 45.3 line pairs / mm.

[0015]

According to the present invention, there is provided a plastic image fiber composed of a resin having a core and a sheath and having low transmission loss with little light bleeding between pixels.

[Brief description of the drawings]

FIG. 1 is an image fiber of the present invention.

[Explanation of symbols]

 1 sheath (enlarged view of the present invention, image fiber) 2 cores (enlarged view of the present invention, image fiber)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 6/00 391 G02B ^6/ 04-6/06

Claims (1)

(57) [Claims] 1. A multi-core plastic fiber comprising a large number of small core fibers made of a transparent core resin having a high refractive index and filled with a sheath resin having a low refractive index between the core fibers so as to be individually partitioned. In the waveguide, the core resin is a PMMA resin having a melt flow index of 0.5 g / 10 min to 40 g / 10 min, and the sheath resin has a sum of structural units of vinylidene fluoride and tetrafluoroethylene exceeding 99 mol%, 10
0 mol%, and the vinylidene fluoride structural unit is 8
An image fiber characterized by being a resin having a melt flow index of more than 5 mol% and 91% mol% or less and a melt flow index of 10 g / 10 min or more.