JPH0921700A - Optical window member and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical window member made of a resin having an excellent infrared-radiation transmissibity and sufficient strength withstanding external environment by forming a window part transmitting infrared ray and a reinforcing part thicker than the window part as a unitary body by using the resin having the infrared- radiation transmissibity. SOLUTION: The entire body of the optical window member 1 is made of a resin having infrared-radiation as a unitary body. Thick, linear reinforcing parts 11 are arranged at the intermediate parts from the outer surface of a flat plate in a grid pattern. The part surrounded by respective reinforcing parts 11 is made to be a window part 12, which is thinner than the reinforcing part 11 and transmits the infrared rays. In the manufacture of the optical window part 11, any of the following methods is used, that is, an injection method of resin using a metal mold having the irregularities in correspondence with the window part 12 and the reinforcing part 11 from the resin having the infrared-radiation transmissibity, a press molding method for performing press molding of preliminary molded body comprising resin by using a metal mold having the irregularities in correspondence with the window part 12 and the reinforcing part 11 and an after-machining method for removing the resin at a part corresponding to the window part 12 of the preliminary molded body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical window material used for protecting an infrared detecting element in an apparatus using the infrared detecting element such as various sensors.

[0002]

2. Description of the Related Art From various objects such as human bodies, buildings, and plants,
Infrared detection elements that detect infrared radiation emitted according to the surface temperature and detect the temperature and shape of the object in a non-contact manner are, for example, human body detection sensors such as automatic doors and security devices, and fire detection sensors. Or, it is being widely used in various fields such as a temperature detecting sensor such as a microwave oven and a heater.

Along with this, there is a tendency that the demand for an optical window material for protecting the above infrared detecting element from the external environment such as rain, wind, light, dust and the like increases. Conventionally, as the above-mentioned optical window material, for example, those made of an inorganic material excellent in infrared transmissivity such as silicon, barium fluoride, and zinc sulfide have been widely used,
Recently, various studies have been made in order to put into practical use an optical window material made of resin, which is lighter in weight than the above inorganic materials, has excellent moldability and processability, and is inexpensive.

[0004]

As is well known, a resin has a lower mechanical strength than an inorganic material. Therefore, in order to maintain the shape as a molded body and to withstand an external environment, It is necessary to increase the wall thickness. However, the thicker the wall, the lower the transmittance of infrared rays, which makes it difficult to perform sensing by the infrared sensing element.

In order to solve the above-mentioned problems, Japanese Patent Application Laid-Open No. 4-243695 discloses that a window material made of a resin having an infrared transmitting property is reinforced by a reinforcing frame made of metal, for example. However, in order to manufacture the above structure, there is a problem that the manufacturing process becomes complicated because the step of aligning the window member and the reinforcing frame and the step of adhering the two are required.

Further, in the above structure, since the window material and the reinforcing frame are made of different materials, if the expansion and contraction are repeated due to changes in temperature, the reinforcing frame may fall off the window material, The reinforcing frame may be deformed or the window material may be damaged. An object of the present invention is to provide an optical window material made of a resin having excellent infrared ray transparency and having sufficient strength to withstand an external environment, and an efficient manufacturing method thereof.

[0007]

In order to solve the above-mentioned problems, an optical window material of the present invention is a window portion which transmits infrared rays,
It is characterized in that the reinforcing portion having a larger thickness than that is integrally formed of a resin having an infrared transmitting property. Further, the method for manufacturing an optical window material of the present invention includes a resin injection molding method using a mold having irregularities corresponding to the window portion and the reinforcing portion, a preformed body made of the resin, the window portion and the reinforcing portion. Among the press molding method of press molding using a mold having irregularities corresponding to, and the post-processing method of chemically, thermally or mechanically removing the resin at the portion corresponding to the window of the preform The optical window material according to claim 1 is manufactured by at least one of the above methods.

According to the optical window member of the present invention having the above-mentioned structure, the thin window portion ensures the infrared transparency while the thicker reinforcing portion maintains the strength capable of withstanding the external environment. There is. Further, since the window portion and the reinforcing portion are integrally formed of the same resin, they are not deformed or damaged even if they are repeatedly expanded and contracted due to a change in temperature. Therefore, the optical window material of the present invention is made of a resin that is lightweight, and is excellent in moldability and workability and at the same time, is excellent in infrared ray transparency, and has sufficient strength to withstand an external environment. Become.

Further, according to the method of manufacturing an optical window material of the present invention, the above-mentioned optical window material is manufactured by injection molding, press molding,
Alternatively, by using the post-processing method, it is possible to easily and efficiently manufacture.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the optical window material of the present invention will be described below with reference to FIGS. 1 to 3 showing an example thereof. Each of the optical window members 1 in FIGS. 1 and 2 has a flat plate shape, and the optical window member 1 in FIG. 3 has a dome shape. All of these optical window members 1 are integrally formed of a resin having an infrared transmitting property.

Among them, in the optical window member 1 of FIG. 1, thick and linear reinforcing portions 11 are arranged in a lattice pattern on the outer periphery and in the middle of the flat plate, and a portion surrounded by each reinforcing portion 11 is formed. However, the window portion 12 is thinner than the reinforcing portion 11 and transmits infrared rays. In addition, the optical window material 1 of FIG.
A region of more than half of the whole is the thin-plate-like window portion 12, and the remaining region is thicker than the window portion 12 of the reinforcing portion 1.
It is said to be 1.

Comparing these two optical window materials 1, FIG.
Since the reinforcing portions 11 are dispersed and arranged in a grid pattern so as to surround the window portions 12, one window portion 12 is provided.
Has a small area, but has the advantage that the overall strength is almost uniform. On the other hand, in the optical window member 1 of FIG. 2, since the reinforcing portions 11 are arranged in a concentrated manner, the strength thereof has a directionality, but there is an advantage that the area of the window portion 12 can be increased.

The optical window member 1 shown in FIG. 3 has a reinforcing portion 11 so as to project to the outside of a window portion 12 formed in a dome shape.
Is arranged. The reinforcing portion 11 is composed of one that goes around the edge of the dome and two that start from one point of the edge of the dome, pass through the apex of the dome, and then reach the opposite side of the edge of the dome. The reinforcing portion 11 may be arranged inside the dome.

Each of the above-mentioned optical window materials 1 is an injection molding method of resin from a resin having an infrared transmitting property, using a mold having irregularities corresponding to the window portion 12 and the reinforcing portion 11.
A press molding method in which a preform made of a resin is press-formed using a mold having irregularities corresponding to the window portion 12 and the reinforcing portion 11, and a resin at a portion of the preform body corresponding to the window portion 12 Is manufactured by any one of the post-processing methods for removing. Among these post-processing methods, there are a chemical removal method (chemical etching), a thermal removal method (thermal etching), and a mechanical removal method (grinding, engraving, etc.), whichever method is adopted. Good.

Alternatively, two or more of the above manufacturing methods may be used in combination. In the case of the optical window material 1 used in the various sensors described above, as the resin, the wavelength of infrared rays radiated from the surface of the object is mainly 7 μm or more, especially about 8 to 12 μm. It is desirable to have good transparency. Examples of such resins include, but are not limited to, polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyterpenes such as natural rubber and gutta percha; polyamide; butadiene rubber and the like. Among them, polyethylene which is particularly lightweight, excellent in moldability and processability and inexpensive, and also excellent in weather resistance and chemical stability, particularly high-density polyethylene is preferably used.

In the case of the optical window material used in the various sensors described above, the transmittance of infrared rays in the wavelength band of 8 to 12 μm in the window portion 12 is 5 in order to secure sufficient sensitivity of the sensor.
It is preferably 0% or more. If the transmittance is less than 50%, the sensitivity of the sensor may be insufficient. In addition, the transmittance of infrared rays in the above wavelength band in the window portion 12 is preferably as high as possible in consideration of the sensitivity of the sensor,
It is more preferably 70% or more.

However, the transmittance of infrared rays in the window portion 12 is in inverse proportion to the thickness of the window portion 12 as described above, and if the transmittance is too high, the thickness of the window portion 12 becomes small and a defect occurs. It is not easy to form a uniform window portion 12 without any defects, and even if a window portion 12 without defects is formed, it is insufficient in strength and easily damaged by external force. Therefore, there is a possibility that the important function of the window 12 such as protection of the sensor may not be fulfilled.

Therefore, the upper limit of the infrared ray transmittance of the window portion 12 is set in accordance with the minimum thickness at which the window portion 12 can secure sufficient strength. For example, in the case of the above-mentioned olefin resin such as high-density polyethylene,
In order for the window portion 12 to have sufficient strength, its thickness is 0.
It is preferably 1 mm or more, and the wavelength at that time is 8 to 1
The upper limit of the transmittance of infrared rays in the 2 μm band is 90%.

In the case of the above-mentioned olefin resin, in order to achieve the above-mentioned transmittance of 50% or more, the thickness of the window portion 12 is preferably 1 mm or less, more preferably 0.5 mm or less. On the other hand, the thickness of the reinforcing portion 11 may be thicker than the thickness of the window portion 12, but is preferably 1 mm or more and preferably 3 mm or more in order to give the optical window material 1 sufficient strength. Is more preferable and 5 mm
The above is particularly preferable. However, if the thickness of the reinforcing portion 11 is too large, it may be difficult to manufacture the optical window material 1 by a molding method in particular, so the upper limit of the thickness of the reinforcing portion 11 is preferably about 10 mm.

When the reinforcing portions 11 are arranged so as to surround the window portion 12 by arranging the reinforcing portions 11 in a lattice shape as shown in FIG. 1, the area ratio of the window portion 12 is reduced. Fifty
It is preferable to set the ratio of both so as to be 90%. If the area ratio of the window portion 12 is less than the above range, the average transmittance of the infrared rays in the specific wavelength band in the entire optical window material 1 is lowered, and the sensitivity of the sensor when used in various sensors described above, for example. May be insufficient.
In the case of a sensor, the average transmittance is preferably 40% or more in order to secure sufficient sensitivity. In order to achieve such average transmittance, the transmittance and the area ratio of the window portion 12 may be adjusted within the above range.

When the area ratio of the window portion 12 exceeds the above range, the reinforcing portion 11 becomes relatively small,
The reinforcing portion 11 cannot be arranged so as to surround the window portion 12, and the reinforcing effect of the reinforcing portion 11 may be insufficient.

[0022]

The present invention will be described below with reference to examples and comparative examples. Example 1 A plate-shaped preform made of high-density polyethylene [trade name Ace Polyeth HDJ6211 manufactured by Tonen Kagaku Co., Ltd.] was heated to 180 ° C. at a heating rate of 10 ° C./minute, and further heated to 10 ° C. at this temperature. After preheating for 10 minutes, press molding was performed for 10 minutes using a mold having irregularities corresponding to the window portion and the reinforcing portion. Then, the mold was water-cooled in the pressed state, the mold was opened, and the optical window material 1 of Example 1 having the shape shown in FIG. 1 and the dimensions of each part as described below was manufactured.

External dimensions: 100 mm × 100 mm Thickness t _{1 of the} reinforcing portion 11: 5 mm Width w ₁ of the reinforcing portion 11: 4 mm Thickness t _{2 of the} window portion 12: 0.2 mm Length of one side w _{2 of the} window portion 12: 20 mm Area ratio of window 12: 64% Example 2 The same high-density polyethylene as that used in Example 1 except that the size of the mold was changed, and the shape shown in FIG. Then, the optical window material 1 of Example 2 was manufactured in which the dimensions of the respective parts were as follows.

External dimensions: 100 mm × 100 mm Thickness t _{1 of the} reinforcing portion 11: 5 mm Width w ₁ of the reinforcing portion 11: 5.6 mm Thickness t _{2 of the} window portion 12: 0.2 mm Length of one side of the window portion 12 ₂ : 18 mm Area ratio of window portion: 52% Example 3 The same high-density polyethylene as that used in Example 1 was used in the same manner as in Example 1 except that the mold was changed.
In the shape shown in, and the dimensions of each part are as follows,
The optical window material 1 of Example 3 was manufactured.

External dimensions: 100 mm × 100 mm Thickness t _{3 of the} reinforcing portion 11: 5 mm Width w ₃ of the reinforcing portion 11: 20 mm Thickness t _{4 of the} window portion 12: 0.2 mm Width w _{4 of the} window portion 12: 80 mm Window portion 12 Area ratio: 80% Comparative Example 1 A flat plate made of the same high-density polyethylene as that used in Example 1 and having a thickness of 0.2 mm and having no unevenness was used as an optical window material of Comparative Example 1. Comparative Example 2 A flat plate made of the same high-density polyethylene as that used in Example 1 and having a thickness of 0.5 mm and having no unevenness was used as the optical window material of Comparative Example 1. Comparative Example 3 A flat plate having a thickness of 0.8 mm and made of the same high-density polyethylene as that used in Example 1 and having no unevenness was used as an optical window material of Comparative Example 1.

The following tests were conducted on the optical window materials of the above Examples and Comparative Examples to evaluate their characteristics. Measurement of Infrared Transmittance Using a Fourier transform infrared spectroscopic analyzer, the transmittance (%) of infrared rays in the wavelength band of 8 to 12 μm in the optical window materials of Examples and Comparative Examples was measured.

In Examples 1 to 3, the above-mentioned measurement was carried out for each of the window portion 12 and the reinforcing portion 11. Then, the average transmittance (%) of the optical window material 1 as a whole was obtained from the measurement result of the transmittance of both parts and the area ratio (%) of the window portion 12 in each example by the following formula. In the following formula, reference numeral T ₁ is the transmittance (%) of the reinforcing portion 11, T ₂ is the transmittance (%) of the window portion 12, and S is the area ratio (%) of the window portion.

[0028]

[Equation 1]

Strength Measurement Using an Instron tensile tester, the optical window materials of Examples and Comparative Examples were clamped at a gripping tool spacing of 80 mm and a pulling speed of 500.
Breaking strength (k when pulled in the plane direction under the condition of mm / min.
g) was measured. This measurement was performed three times for each of the Examples and Comparative Examples using samples prepared three times, and the average value of each result was obtained. In addition, about Example 3, six samples were created and each of the width direction (W) and the length direction (L) of the reinforcing part 11 was 3 respectively.
The measurement was performed once, and the respective average values in the width direction and the length direction were obtained.

Table 1 shows the above results.

[0031]

[Table 1]

As is clear from the results of Comparative Examples 1 to 3 in Table 1, the flat optical window material having no irregularities has a reduced infrared transmittance when its thickness is increased to obtain sufficient strength. On the contrary, when the thickness was reduced in order to improve the infrared transmittance, the strength decreased. On the other hand, the window 12
It was found that the optical window materials of Examples 1 to 3 provided with and the reinforcing portion 11 can achieve both sufficiently high strength and high infrared transmittance.

Comparing Examples 1 to 3 above, the optical window material of Example 3 in which the reinforcing portions 11 are arranged in a concentrated manner has a directionality in its strength, but the infrared transmittance becomes high, and It was found that the optical window materials of Examples 1 and 2 in which the reinforcing portions 11 were dispersedly arranged so as to surround the window portion 12 had a slightly lower infrared transmittance but a higher strength. . Example 4 From the same high density polyethylene used in Example 1,
The dome-shaped optical window material 1 shown in FIG. 3 was manufactured by injection molding.

The dimensions of each part of the obtained optical window material 1 are as follows. Dome height: 40 mm Diameter of dome bottom: 125 mm Thickness of reinforcing part 11: 3.0 mm Width of reinforcing part 11: 10 mm Thickness of window part 12: 0.2 mm Wavelength 8-12 mm band of the above optical window material 1 The average transmittance (%) of infrared rays of was calculated in the same manner as above, and was 61%.
Met.

[0035]

As described above in detail, the optical window material of the present invention comprises a thin window portion for ensuring infrared transparency and a thick reinforcing portion for maintaining the strength capable of withstanding the external environment. Therefore, the resin is lightweight, is excellent in moldability and workability, and is made of an inexpensive resin. Further, it is excellent in infrared ray transparency and has sufficient strength to withstand an external environment.

Further, according to the method of manufacturing an optical window material of the present invention, it is possible to efficiently manufacture an optical window material excellent in the above characteristics. Therefore, according to the present invention, in a device using an infrared detection element, such as various sensors, it is possible to introduce a lightweight and inexpensive resin into an optical window material for protecting the infrared detection element, which is a unique action. Produce an effect.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an external appearance of an embodiment of an optical window material of the present invention.

FIG. 2 is a perspective view showing the appearance of another embodiment of the optical window material of the present invention.

FIG. 3 is a perspective view showing the external appearance of still another embodiment of the optical window material of the present invention.

[Explanation of symbols]

 1 Optical window material 11 Reinforcing section 12 Window section

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akira Nishimura 1-3-3 Shimaya, Konohana-ku, Osaka Sumitomo Electric Industries, Ltd. Osaka Works

Claims (6)

[Claims] 1. An optical window material, characterized in that a window portion which transmits infrared rays and a reinforcing portion which is thicker than the window portion are integrally formed of a resin having an infrared ray transmitting property. 2. The optical window material according to claim 1, wherein the window has a transmittance of infrared rays in the wavelength band of 8 to 12 μm of 50% or more. 3. The optical window material according to claim 1, wherein the reinforcing portion has a thickness of 1 to 10 mm. 4. The optical window material according to claim 1, wherein the reinforcing portion is arranged so as to surround the window portion. 5. The optical window material according to claim 4, wherein the area ratio of the window portion is 50 to 90%. 6. A resin injection molding method using a mold having projections and depressions corresponding to a window portion and a reinforcement portion, and a preform made of resin, a mold having projections and depressions corresponding to the window portion and the reinforcement portion. By at least one method of a press molding method of press molding using, and a post-processing method of chemically, thermally or mechanically removing the resin at the portion corresponding to the window of the preform, A method of manufacturing an optical window material, comprising manufacturing the optical window material according to claim 1.