JPH0438703B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an ultraviolet irradiation device that irradiates and cures an ultraviolet curable resin composition (hereinafter abbreviated as UV resin) applied to a striated body such as an optical fiber. It is related to.

2. Description of the Related Art An example of a conventional ultraviolet irradiation device used to cure a UV resin coating applied to an optical fiber by irradiating it with ultraviolet rays is shown in FIGS. 2 and 3.
FIG. 2 is a perspective view of this ultraviolet irradiation device, and FIG. 3 is a sectional view.

As can be seen from Fig. 2, this ultraviolet irradiation device has a structure in which an optical fiber 1 coated with UV resin and an ultraviolet lamp 2 are arranged in parallel, and the periphery is surrounded by a cylindrical reflecting mirror 3. There is. These members have a positional relationship shown in the sectional view of FIG. That is, the cross section of the cylindrical reflecting mirror 3 is elliptical, and an optical fiber 1 coated with UV resin is disposed at one focal point, and an ultraviolet lamp 2 is disposed at the other focal point. The ultraviolet rays emitted from the ultraviolet lamp 2 placed at the focal position are reflected on the surface of the elliptical reflecting mirror and condensed at the other focal point, so the optical fiber coated with UV resin placed at that position is highly efficient. It receives good UV irradiation.

In the above-mentioned ultraviolet irradiation device, all the ultraviolet rays emitted from the ultraviolet lamp are irradiated onto the object to be irradiated with ultraviolet rays, which is an optical fiber coated with UV resin. However, the light emitted from an ultraviolet lamp is not only the ultraviolet light necessary for curing the UV resin, but also includes light at wavelengths that are not directly related to this.
Light in a wavelength range unrelated to curing may have an adverse effect on the object to be irradiated with ultraviolet rays. For example, when infrared rays are included, when the object is irradiated with infrared light, the temperature of the object increases. As a result, the irradiated object often undergoes chemical reactions such as decomposition or alteration of properties, producing substances that are undesirable as fiber coatings. Also,
Deformation due to thermal stress also frequently occurs.

In order to remove ultraviolet rays, it is possible to use a cold mirror as a reflector, which has a high reflectance for light with wavelengths shorter than the visible light range and a high transmittance for infrared rays. . However, even using this cold mirror does not solve all the problems in curing UV resin. This is because the cold mirror only transmits infrared light and reflects light in other wavelength ranges, so it is impossible to eliminate the influence of that light on the irradiated object.

For example, although the wavelength of light in the visible light range is not as great as that of infrared rays, irradiation causes the temperature of the irradiated object to rise. Therefore, in order to avoid temperature rise due to light irradiation, it is necessary to transmit not only infrared rays but also visible light.

Furthermore, even if only the ultraviolet rays can be reflected and irradiated, the wavelength of the ultraviolet rays may be harmful to the object to be irradiated, so it is necessary to specify the wavelength of the ultraviolet rays. For example, ultraviolet rays with a wavelength of around 200 nm are UV
It is useful enough to harden the surface of the resin, but
UV does not penetrate inside the resin. Therefore, since the irradiated ultraviolet rays are absorbed only on the surface of the UV resin, there is a problem in that the temperature only on the surface increases significantly.

Problems to be Solved by the Invention As explained above, when the conventional ultraviolet irradiation device is used, various undesirable effects occur because the object to be irradiated is irradiated with light in a wide wavelength range.

Among these, a particularly big problem is the effect of heating. In addition to chemical changes such as decomposition of the irradiated object or chemical reactions that generate substances undesirable as fiber coatings, physical changes such as deformation due to thermal stress also occur.

Cold mirrors have been proposed for the purpose of limiting the wavelength of irradiated light, but they cannot selectively reflect only the ultraviolet light in the wavelength range that is really needed.

When producing optical fibers, it is desirable to produce them at high speed and in large quantities. To this end, it is essential that the UV resin used to coat the optical fiber cure quickly. However, if the above-mentioned problems are not resolved, irradiating UV resin with ultraviolet light of high power to increase speed will only increase the damage.

Therefore, the present invention provides an ultraviolet irradiation device that is equipped with a reflecting mirror that selectively reflects only ultraviolet rays in a useful wavelength range and transmits or absorbs light of other wavelengths, and is capable of effectively curing UV resin. The purpose is to provide

Means for Solving the Problems In order to solve the above problems, the ultraviolet irradiation device of the present invention reflects and condenses ultraviolet rays from an ultraviolet light source, and irradiates a linear ultraviolet irradiated object to cure the reflected ultraviolet rays. In an ultraviolet irradiation device including a mirror, the reflecting mirror is configured to reflect light within a wavelength range of 300 to 450 nm and absorb or transmit light with a wavelength outside the range.

Function UV resin used for coating optical fibers is generally cured by irradiation with ultraviolet light with a wavelength of 450 nm or less. However, when the wavelength of ultraviolet rays becomes short to around 200 nm, the transparency becomes poor, and the irradiated ultraviolet rays are only effective in hardening the surface. Therefore, UV resin can be applied uniformly to the inside, and UV
The wavelength of light that can avoid undesirable effects such as an increase in the temperature of the resin is limited to around 300 to 450 nm.

By using a material in the reflecting mirror that reflects only ultraviolet rays within the wavelength range of 300 to 450 nm and transmits or absorbs light in other wavelength ranges, the UV resin can be effectively cured.

The UV resins to be cured with the apparatus of the present invention include urethane type resins such as urethane acrylate, epoxy type resins such as epoxy acrylate, polyester type resins such as polyester acrylate, polybutadiene type resins such as polybutadiene acrylate, and silicon type resins such as silicone acrylate. It also includes resins and their compounds, or resins that partially contain the above UV resins.

Embodiment FIG. 1 shows an embodiment of the ultraviolet irradiation device according to the present invention. A linear optical fiber 1 coated with UV resin and an ultraviolet lamp 2 are housed in a cylindrical reflecting mirror 3 so as to be parallel to its generatrix. The cylindrical reflecting mirror 3 has an elliptical cross section. An optical fiber 1 and an ultraviolet lamp 2 are placed at each of two focal points. A housing 4 is provided to surround the side surface of the cylindrical reflecting mirror 3.

The reflecting mirror 3 is made of glass, and an interference film is formed on its surface by depositing a non-metallic multilayer thin film.
By controlling the substance to be deposited, the thickness of the deposited film, and the number of layers of the film, only the ultraviolet light with a wavelength of 300 to 450 nm from the ultraviolet lamp 2 is reflected.
Light in other wavelength ranges can be transmitted. However, it is difficult to obtain a film with desired properties because the refractive index of the film greatly depends on the manufacturing conditions, such as the manufacturing method, atmospheric gas, and deposition rate.

As an example, Sb ₂ O ₃ having a small refractive index of 2.04 and a transparent wavelength range of 300 to 1000 nm and cryolite having a small refractive index of 1.35 and a transparent wavelength range of 200 to 1400 nm are alternately deposited on a glass substrate. The number of layers to be deposited is nine each. This multilayer thin film has a maximum reflectance of 95.8% at a dominant wavelength of 320 nm.

The reflecting mirror 3 coated with the above-mentioned multilayer thin film selectively reflects ultraviolet light having a wavelength of 300 to 450 nm, and transmits light in other wavelength ranges. Therefore, a part of the light emitted from the ultraviolet lamp 2 is directly transmitted to the optical fiber 1.
The UV resin coated on the optical fiber 1 is directly irradiated with light, but the wavelength range of the light irradiated onto the UV resin on the optical fiber 1 through the reflecting mirror 3 is limited.

The light transmitted through the reflecting mirror 3 illuminates the inner surface of the casing 4. This housing 4 is made of a material that absorbs the light transmitted through the reflecting mirror 3. In particular, it is desirable to absorb light with wavelengths ranging from the visible region to infrared rays, where the heating effect caused by irradiation is large. A multilayer thin film may be used for light absorption, or the casing 4 may be made of metal and treated with blackening.

For example, if the wavelength of the incident light is λ, then the optical film thickness of MgF ₂ with a refractive index of 1.38 is λ/4 on the glass substrate.
On top of that, ZrO ₂ with a refractive index of 2.1 is evaporated to an optical thickness of λ/2, and on top of that, CeF ₃ with a refractive index of 1.63 is deposited.
A three-layer thin film structure is considered in which the optical film thickness is λ/4. This multilayer thin film can absorb almost all light having wavelengths in the visible light range or longer.

In the case 4, the reflecting mirror 3 is formed by this multilayer thin film processing.
It can absorb the light that passes through it and convert it into heat. This heat can be released to the outside by cooling the housing 4 with air, so it can be transferred to the optical fiber 1 coated with UV resin again by conduction or radiation.
can be prevented from being heated. As a result, even if the UV resin surrounding the optical fiber 1 is irradiated with high-power light, the light in wavelengths other than 300 to 450 nm is significantly reduced, allowing the UV resin to be cured effectively. .

In particular, since light with a wavelength of 450 nm or more is less likely to be reflected by the ultraviolet lamp, it is possible to prevent the temperature of the ultraviolet lamp itself from rising. the result,
It can extend the life of UV lamps.

In addition, it is possible to prevent the concentration of energy on the UV resin surface due to light with a wavelength of 300 nm or less, so it is possible to avoid deterioration of the resin surface and volatilization of the resin composition from the resin surface, making it possible to safely use UV resin. Can be hardened. This is because, if volatilization occurs, the resin composition will adhere to components inside the irradiation device, such as a reflector, which will prevent the UV resin from being irradiated with light, making the curing of the UV resin unstable. It is.

In addition, in the above example, ultraviolet rays in the wavelength range of 300 to 450 nm were reflected, but unless at least light outside the range of 300 to 450 nm is reflected, only part of the wavelength range within the range of 300 to 450 nm is reflected. Even if the reflected light is reflected, the same effect can be achieved as long as the reflected light has sufficient strength.

Effects of the Invention As explained above, when the ultraviolet irradiation device of the present invention is used, wavelengths of 300 to 300, which are effective for curing UV resin,
Since the UV resin can be selectively irradiated with only 450 nm ultraviolet rays, the optical fiber can be well coated with the UV resin.

Furthermore, since the UV resin can be prevented from being excessively heated, there is no need to consider problems caused by heat, such as decomposition, reaction, and deformation. Therefore, the object to be irradiated can be irradiated with intense light, making it possible to cure the UV resin at high speed. This is convenient for high-speed mass production of optical fibers.

[Brief explanation of drawings]

1 is a diagram showing an embodiment of the ultraviolet irradiation device according to the present invention, FIG. 2 is a diagram showing an embodiment of the conventional ultraviolet irradiation device, and FIG. 3 is a diagram showing an embodiment of the conventional ultraviolet irradiation device. FIG. 3 is a plan view of the ultraviolet irradiation device. Main reference numbers: 1... Optical fiber coated with UV resin, 2... Ultraviolet lamp, 3... Reflector, 4... Housing.

Claims (1)

[Scope of Claims] 1. In an ultraviolet irradiation device equipped with a reflecting mirror that condenses ultraviolet rays from an ultraviolet light source and irradiates a linear ultraviolet irradiated object to cure the ultraviolet rays, the reflecting mirror has a wavelength
An ultraviolet irradiation device characterized in that it reflects light within a range of 300 to 450 nm and absorbs or transmits light with a wavelength outside the range. 2. The ultraviolet irradiation device according to claim 1, wherein the reflecting mirror is glass coated with an interference film that reflects light with a wavelength of 300 to 450 nm and transmits light outside that range. . 3. The ultraviolet irradiation device according to claim 2, wherein a light absorber is disposed outside the reflecting mirror to absorb the light transmitted through the reflecting mirror.