JP2013244672A - Ir reflecting laminate and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an IR reflecting laminate which is composed of a combination of a DLC thin film and a silver-based metal film so as to reflect heat rays and allow visible light to transmit efficiently and is usable as a window material; and a DLC thin film manufacturing method which reduces light absorption of the DLC thin film in short wavelengths, prevents the thin film from being tinged with a brown color tone and allows inexpensive production with high mass productivity.SOLUTION: An IR reflecting laminate has a silver-based metal film 16 and a diamond-like carbon film having a light absorption coefficient at a wavelength of 400 nm of ≤3/μm and a thickness of 20-100 nm on a transparent substrate 14 in this order.

Description

  The present invention relates to an infrared reflective laminate using a diamond-like carbon (DLC) thin film excellent in light transmittance and a method for producing the same.

  Specifically, it is a laminate that combines a DLC thin film and a silver-based metal film, and relates to an infrared reflective laminate that can be used as a window material that reflects heat rays and transmits visible light, and an efficient manufacturing method thereof. is there.

  In recent years, attention has been paid to the effects of wear resistance by a DLC thin film and gas barrier properties as a packaging material. The chemical vapor deposition (CVD) method is often used as a method for producing a DLC thin film, and the visible light transmittance is increased by containing hydrogen, and the use as a transparent light-transmitting optical thin film is also expected. .

  By the way, since the DLC thin film absorbs light on the short wavelength side in the visible light region, it tends to have a brown color tone as the film thickness increases. Thus, since the light transmittance of the DLC thin film tends to be lower on the short wavelength side than on the long wavelength side, it has been a problem to improve the light transmittance on the short wavelength side.

  In response to this problem, attempts have been made to make it highly transparent, and certain results have been seen. In sputtering, nitrogen is used as the sputtering gas, nitrogen is mixed into the DLC thin film, and the film is formed at a very slow film formation rate in the low pressure CVD method (Patent Document 1), which is made highly transparent when fired later. And the like (Non-Patent Document 1).

  As described above, in the conventional method, even if a DLC thin film having a high light transmittance is obtained, the sputtering method or the low pressure CVD method is used. Had a productivity problem.

By the way, an infrared reflection laminated body as a window material that reflects heat rays and transmits visible light is made by laminating a reflective film made of a silver-based metal film and a transparent layer having a high refractive index. FIG. 2 shows an example in which a reflective film made of a silver-based metal film and then a transparent layer are formed on a transparent substrate. Further, as shown in FIG. 3, there is a case where a transparent layer, a reflective film made of a silver-based metal film, and a transparent layer are formed on a transparent substrate. As the high refractive index transparent layer, a metal oxide layer such as indium tin oxide (ITO), titanium oxide (TiO ₂ ) or zinc oxide (ZnO) is used. As a manufacturing method, a sputtering method was mainly used. Although the reflective film is formed by a silver-based metal film, the productivity is relatively good because the silver-based metal film is thin and the sputtering speed of the silver-based metal material is high. The deposition rate by the method was low and the productivity was low. There is also a problem that oxygen liberated from the metal oxide layer oxidizes the silver-based reflective film to reduce reliability. In contrast, attempts have been made to prevent deterioration due to oxidation by using a DLC thin film instead of a metal oxide (Non-Patent Document 2), but the deposition rate when sputtering a graphite target is extremely slow, and productivity is reduced. It was greatly lowered. In addition, the visible light transmittance is low, and particularly, since the light on the short wavelength side is absorbed, the color tone tends to be brown, which is not suitable as a window material.

JP 2004-315854 A

S. Yamamoto et al., Diamond & Related Materials 14 (2005) 1112-1115 K. Chiba et al., Applied Surface Science 246 (2005) 48-51

  It is an object of the present invention to provide an infrared reflective laminate that can be used as a window material that can efficiently transmit visible light by reflecting heat rays by combining a DLC thin film and a silver-based metal film. In producing a DLC thin film, the present invention is to provide a production method that reduces the light absorption at a short wavelength of the DLC thin film and avoids a brownish color tone, and is high in mass productivity and inexpensive.

  In order to solve the above problems, the present invention provides a silver-based metal film and a diamond-like carbon film having a light absorption coefficient of 3 / μm or less at a wavelength of 400 nm and a thickness in the range of 20 to 100 nm on a transparent substrate. Provide an infrared reflective laminate laminated in this order.

  In addition, a diamond-like carbon thin film, a silver-based metal film, and a diamond-like carbon thin film are laminated in this order on the transparent substrate, and each diamond-like carbon thin film has an absorption coefficient of light of 3 / μm or less at a wavelength of 400 nm. The infrared reflective laminate is characterized in that the thickness is in the range of 20 to 100 nm.

  Furthermore, as a method for producing a DLC thin film for this purpose, a low-temperature plasma is generated by applying a voltage between opposing electrodes under an atmospheric pressure, and diluted to a concentration of 1 to 40% by volume with nitrogen. And a method of depositing a reaction product by decomposing acetylene, and a method for producing an infrared reflective laminate, comprising laminating a DLC thin film having a light absorption coefficient of 3 / μm or less at a wavelength of 400 nm. .

  The present invention makes it possible to produce a DLC thin film having a high visible light transmittance while maintaining high productivity.

  In addition, when the DLC thin film according to the production method of the present invention is combined with a silver-based metal film reflective film, it has a high light transmittance in visible light while maintaining a high infrared reflectance, and particularly has a high light transmittance on the short wavelength side. Depending on the ratio, it is possible to produce an infrared reflective laminate having no brown coloration with high productivity.

It is an example of the manufacturing apparatus used for this invention. It is the structure of the infrared reflective laminated body to which this invention is applied. It is another structure of the infrared reflective laminated body to which this invention is applied.

  FIG. 1 shows an example of an atmospheric pressure CVD apparatus used in the present invention. The apparatus is placed in atmospheric pressure, and the substrate enters between the counter electrodes 1 and 2 which are continuous spaces from the outside. The counter electrode 1 is grounded, and a high frequency voltage is applied to the counter electrode 2 to form a high electric field with the counter electrode 1 through the dielectric 3 to generate low temperature plasma. The atmospheric gas that is a mixed gas of acetylene and nitrogen supplied from the atmospheric gas supply pipe 5 is turned into plasma, and a DLC thin film is deposited on the substrate 4 placed between the counter electrodes 1 and 2.

  An air curtain that flows in from the atmospheric gas supply pipe 5 and the nitrogen supply pipe 9 and that sucks into the exhaust pipe 8 prevents the surrounding air from flowing into the discharge portion, and is formed between the counter electrodes 1 and 2. The atmosphere gas purity is maintained in the space.

Note that the DLC thin film refers to a carbon thin film in which sp ² bonds and sp ³ bonds, which are hybrid orbitals of carbon atoms, are mixed. As the ratio, the sp ³ bond is in the range of 20 to 85% by the peak area ratio of Raman spectroscopy (“DLC film formation and its application”, Naoto Otake web version 2008, Graduate School of Engineering, Nagoya University).

  A mixed gas with nitrogen containing acetylene is used as the atmospheric gas. An AC or rectangular pulse voltage is applied between the electrodes 1 and 2 to generate a plasma 7 to decompose acetylene.

  Specifically, the atmospheric gas contains acetylene at a ratio of 1 to 40% by volume. In this case, the remaining 99 to 60% by volume is occupied by the nitrogen component.

  Since acetylene has a high carbon ratio in the molecule among hydrocarbons and a high film formation rate, the film formation efficiency is improved by containing acetylene as a raw material gas component in the atmospheric gas. The lower the acetylene gas concentration in the atmospheric gas, the higher the light transmittance on the short wavelength side, but at the same time the film formation efficiency decreases. Conversely, the higher the acetylene concentration, the lower the light transmittance on the short wavelength side, so 40 vol% is the upper limit. From the balance between the film formation speed and the light transmittance, 2 to 15% by volume is desirable.

  The dilution gas of the atmospheric gas is nitrogen. The chemical activity is low so as not to affect the reaction of the raw material gas, and any gas that suppresses arc discharge and lowers the discharge voltage can be used, but especially nitrogen satisfies such conditions and is inexpensive. It is suitable for forming a uniform film by preventing the formation of particles in the formed film and preventing the formation of a porous film. In consideration of these, for further optimization, nitrogen may be mixed with other inert gas such as argon or helium within 30% by volume.

  By adjusting the atmospheric gas in this manner, the light absorption coefficient at a wavelength of 400 nm can be reduced to 3 / μm or less, and the wavelength is 400 nm, which is a typical film thickness of a DLC thin film when used as an infrared reflective laminate intended for the present invention. The light transmittance in can be maintained at 80% or more with the DLC thin film alone. When the absorption coefficient of light at a wavelength of 400 nm exceeds 3 / μm, the light transmittance at a wavelength of 400 nm is lowered and the yellowness is rapidly increased, so that it cannot be used as an infrared reflecting laminate.

  The normal pressure refers to atmospheric pressure or a pressure in the vicinity thereof, and specifically refers to a pressure range of 50 to 150 kPa as an absolute pressure. In this pressure range, a large exhaust system consisting of a vacuum vessel and a vacuum pump is unnecessary. In addition, it is possible to prevent the inflow of outside air to the film forming part by the flow of the atmospheric gas from the film forming part to the outside at atmospheric pressure, and to maintain the purity of the atmospheric gas. In addition, the substrate can be continuously transferred from the outside to the film forming region, and high productivity can be realized. In addition, by having a high molecular density at normal pressure, a large amount of atmospheric gas molecules are decomposed and a high film formation rate can be obtained.

  Low temperature plasma means a state in which part of a gas is ionized by discharge or the like and only electrons are in a high temperature state where energy is high, and gas molecules are in a state equivalent to room temperature. In order to stably generate low-temperature plasma at normal pressure, it is necessary to prevent arc discharge in which discharge is concentrated in some places. Selection of atmospheric gas, that is, atmospheric gas mainly composed of nitrogen, electrode It is important to cover at least one of them with a dielectric, and it is also necessary to pay attention to the waveform of the applied voltage.

  Since a dielectric is used for the electrode part, direct current is not used, but high frequency is used. The high-frequency voltage preferably has a rectangular, sine, or triangular voltage waveform. In order to prevent the occurrence of arc discharge, the rectangular wave specifically includes a frequency of 2 kHz to 20 kHz, a pulse width of 2 to 10 μs, a duty ratio (ratio of time between half cycle of waveform and pulse width). A pulse wave of 01 to 0.2 is preferable. On the other hand, the sine wave or triangular wave may be an intermittent pulse wave having a predetermined pulse width and duty ratio, or may be a continuous wave, but ions and electrons are recombined when there is no electric field. From the viewpoint of maintaining discharge while suppressing the generation of dust due to the operation, a continuous wave with a frequency of 10 kHz to 50 kHz is preferable.

  In FIG. 1, the substrate 4 is placed on one electrode side of the counter electrode, and a film is formed on the side facing the other electrode. When the substrate is thick, a high voltage may be applied by widening the interval between the counter electrodes so that the discharge region is narrowed and the discharge is not hindered.

  The substrate material in the present invention preferably has a high light transmittance in order to make use of the transparency that is the object of the present invention. As the plastic film, polyamide resin such as polyethylene, polypropylene, nylon 66, polyester resin such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin, acrylic resin, etc. may be used. it can. Of these, polyester resins such as polyethylene terephthalate having strength and heat resistance are suitable.

  In addition, as the inorganic material, glass that can be thinned with mass productivity such as boric acid silicate glass and soda lime glass is used.

  In the case of a plastic film, in order to reduce the thermal load at the time of film formation, the film thickness per time may be reduced and the film thickness may be divided into a plurality of times to obtain a desired film thickness. An inorganic material such as glass can be formed without considering the heat problem.

  By combining the method for producing a DLC thin film of the present invention with a reflective film of a silver-based metal film, an infrared reflective laminate having a high visible light transmittance can be produced with high productivity. If the DLC thin film manufactured by the above method is used in place of the metal oxide, which is a high refractive transparent film prepared by sputtering, in the lamination of the silver metal film and the high refractive index transparent film, the manufacturing process Among them, productivity of a high refractive index transparent film, which has been a problem of low film formation speed, is dramatically increased. The silver-based metal film is formed using the sputtering method as in the prior art.

  That is, in the case of the configuration of FIG. 2, after the silver-based metal film 16 is formed on the transparent substrate 14 by sputtering, the DLC thin film 15 according to the present invention is formed. Since the silver-based metal film 16 is covered with the DLC film 15, it is advantageous for reliability, but the order of formation may be reversed depending on the required level of reliability. In the configuration of FIG. 3, after the DLC thin film 15 of the present invention is formed on the transparent substrate 14, the silver-based metal film 16 is formed by sputtering, and the DLC thin film 15 of the present invention is formed thereon.

  Furthermore, in the infrared reflective laminate of the present invention, after laminating these DLC thin films, a protective layer with a hard coat typified by acrylic may be laminated as required by a normal wet coat technique.

  The film thickness of the silver-based metal film 16 is preferably 5 nm or more because it needs to have continuity in a certain region in order to have far infrared reflectivity, and has sufficient far infrared reflectivity. Is more preferably 10 nm or more. Furthermore, 50 nm or less is preferable from the viewpoint of transparency, and 20 nm or less is more preferable for increasing transparency.

  The silver-based metal film may be pure silver, but for the purpose of enhancing chemical stability, it may be used alone or in combination with Au, Pt, Pd, Cu, Bi, Ni, Nd, Mg, Zn, Al, etc. An alloy may be used. The mixing amount may be determined by a balance between the effect and the reduction of the reflectance of silver, but is preferably 5% or less, and preferably 10% or less.

  The film thickness of the DLC thin film 15 needs to be in the range of 20 to 100 nm in order to improve the light transmittance in the visible light region, and more preferably 30 to 90 nm. In the above-described configuration in which the silver-based metal film is sandwiched between the DLC thin films, the thickness of each DLC thin film needs to be in the range of 20 to 100 nm.

  In forming these films, the transparent substrate 14 may be previously formed with an anchor coat or the like for improving adhesion characteristics and durability. Further, a protective coat and a plurality of silver metal films or transparent films for improving optical characteristics may be formed after the silver metal film 16 and the DLC thin film 15 are formed. Reflective characteristics of silver, such as a metal film for preventing oxygen from reaching the silver or a sacrificial layer for preventing oxygen from permeating by oxidizing itself to prevent chemical deterioration above and below the silver-based metal film 16 A thin metal layer of Ti, Sn, Zn, Al, Ni, Cr, or the like that does not deteriorate the thickness may be added.

  This manufacturing method forms a transparent layer with a DLC thin film that absorbs less visible light on the short wavelength side. Therefore, a high-quality infrared reflective laminate that has high light transmittance and is not biased to brown is highly productive. Can be manufactured.

(Condition 1)
The apparatus of FIG. 1 was used. The area of the discharge part of the counter electrodes 1 and ² is 500 cm ² (width (corresponding to the depth in the figure) 500 mm × length 100 mm). The gap between the electrodes was 1.0 mm. A PET film (Toray “Lumirror” T60) having a size of 190 × 300 mm and a thickness of 125 μm was used as the substrate 4 and passed over the electrode 1 at a speed of 3.6 m / min. A mixed gas with nitrogen containing 4% by volume of acetylene was supplied from the atmospheric gas supply pipe 5 and sucked from the exhaust pipe 8 as the atmospheric gas. A rectangular pulse having a voltage of 15 kV and a width of 3 μs was applied between electrodes 1 and 2 at a frequency of 30 kHz to generate plasma 7 to decompose acetylene, thereby obtaining a DLC thin film having a thickness of 40 nm. The film thickness was measured by embedding and reinforcing a sample embedded in an epoxy resin with an ultramicrotome UC-7 manufactured by Leica Microsystems. The acceleration voltage was measured at 5 kV. The film formation time calculated by dividing the length of the electrode by the feed rate was about 2 seconds.
From the light transmittance T, the light reflectance R, the light transmittance T _F of the substrate, the light reflectance R _F , and the thickness d of the DLC thin film measured by a spectrophotometer, the following approximate expression 1 The absorption coefficient a was determined from 2.

In Equation 1, light (100% -R) incident on the DLC thin film obtained by removing the light reflectance R (%) from 100% incident light is absorbed by the thickness d of the DLC film, the absorption coefficient a, and the substrate. As a result of the absorption _AF , the light transmittance T (%) is obtained. Strictly speaking, the light reflectivity R (%) includes light reflected multiple times on the surface of the DLC thin film, the interface between the DLC thin film and the base material, and the back surface of the base material. However, since the region having a high light transmittance is targeted here, the approximation according to Equation 1 is adopted. The absorption A _F by the film is calculated from the measured value of the light transmittance T _F and the light reflectance R _F measured by the base material alone from the relationship of Equation 2. The results are summarized in Table 1 together with the time required for film formation.

Measuring instrument Shimadzu spectrophotometer MPC-3100PC
Measurement conditions Wavelength range: 380 nm to 2500 nm, sampling pitch: 1 nm, scan speed: medium speed, absolute reflection mode

(Conditions 2 and 3)
In condition 1, the same conditions as in Example 1 were applied except that the concentration of acetylene was 35% by volume (condition 2) and 45% by volume (condition 3), and the feed rate was adjusted to match the film thickness.
The absorption coefficients at a wavelength of 400 nm were 2.6 / μm and 3.4 / μm, respectively. The film formation time is as short as in Example 1.

(Condition 4)
The method for producing the DLC thin film was changed as follows.
A base film was set in a chamber of a magnetron sputtering apparatus and evacuated to 1.5 × 10 ⁻⁴ Pa over 70 minutes, and then a sputtering gas in which 4% by volume of hydrogen was introduced into argon gas was allowed to flow to 0.3 Pa. As a pressure, a DLC thin film was formed at a transfer speed of 0.1 m / min by applying DC power of 200 W to a cathode equipped with a graphite target (56 mm × 212 mm × 5 mmt). The absorption coefficient at a wavelength of 400 nm is as large as 4.3 / μm, and the film formation time is long and the productivity is lowered.

Example 1
“Tough Top” C0T0 (100 μm thickness) manufactured by Toray Film Processing Co., Ltd. as an acrylic hard coat film is set in a sputtering device and evacuated to an ultimate pressure of 8 × 10 ⁻³ Pa. The pressure was 0.5 Pa. A direct current power of 210 W is applied to an Ag alloy target (containing 56 mm × 212 mm × 5 mmt: 1 mass% Au), and a silver-based metal film having a thickness of 14 nm is formed on the non-hard coat surface at a conveyance speed of 0.3 m / min. did.
Next, a DLC thin film having a thickness of 40 nm was laminated by the method of Condition 1.
Subsequently, “OPSTAR” Z7535 manufactured by JSR Co., Ltd. as an acrylic hard coat agent was diluted to 7.5% by mass using methyl ethyl ketone as a diluent solvent, and applied using a bar coater (counter No. 10). After drying at 80 ° C. for 3 minutes, UV curing (using a mercury lamp, 670 mJ / cm ² ) was performed. The film thickness of the hard coat layer was 0.6 μm.
Table 1 summarizes the light transmittance at a wavelength of 400 nm and the light reflectance at 2.5 μm, which were measured with a spectrophotometer of the infrared reflective laminate thus prepared. The light transmittance at a wavelength of 400 nm was 59%, which was a high value for this type of application. The light reflectance at 2.5 μm was as high as 80%.

(Example 2)
An infrared reflective laminate was prepared in the same manner as in Example 1 except that a silver-based metal film was formed by the same method as in Example 1 and a DLC thin film was formed under Condition 2.

(Example 3)
A DLC thin film having a film thickness of 40 nm was obtained by the method of Condition 1 on the non-hard coat surface of “Tough Top” C0T0 (100 μm thickness) manufactured by Toray Film Processing Co., Ltd. as a film having an acrylic hard coat. Next, after setting to a sputtering apparatus and evacuating to an ultimate pressure of 8 × 10 ⁻³ Pa, argon gas was flowed to a pressure of 0.5 Pa. A direct current power of 210 W was applied to an Ag alloy target (56 mm × 212 mm × 5 mmt: containing 1 mass% Au) to form a silver-based metal film with a thickness of 14 nm at a transfer speed of 0.3 m / min.
Further, a DLC film having a thickness of 40 nm was obtained by the method of Condition 1.
Subsequently, “OPSTAR” Z7535 manufactured by JSR Co., Ltd. as an acrylic hard coat agent was diluted to 7.5% by mass using methyl ethyl ketone as a diluent solvent, and applied using a bar coater (counter No. 10). After drying at 80 ° C. for 3 minutes, UV curing (using a mercury lamp, 670 mJ / cm ² ) was performed. The film thickness of the hard coat layer was 0.6 μm.
Table 1 summarizes the light transmittance at a wavelength of 400 nm and the light reflectance at 2.5 μm measured by a spectrophotometer. The light transmittance at a wavelength of 400 nm was 55%, which was a high value for this type of application.

Example 4
The same method as in Example 1 except that a silver-based metal film was formed by the same method as in Example 1 and then the DLC thin film was formed twice under the condition 1 to form a DLC thin film of 80 nm. Infrared reflecting laminate was prepared.

(Comparative Example 1)
An infrared reflective laminate was prepared in the same manner as in Example 1 except that a silver-based metal film was formed by the same method as in Example 1 and a DLC thin film was formed by sputtering under Condition 4.
The yellow color of the DLC thin film was strong, and the light transmittance at a wavelength of 400 nm was as low as 31%.

(Comparative Example 2)
An infrared reflective laminate was prepared in the same manner as in Example 1 except that a silver-based metal film was formed by the same method as in Example 1 and a DLC thin film was formed by sputtering under Condition 3.
The yellow color of the DLC thin film was strong, and the light transmittance at a wavelength of 400 nm was insufficient at 43%.

(Comparative Example 3)
Example 1 A silver-based metal film was formed by the same method as in Example 1 and then a DLC thin film was formed at a substrate transport speed of 15 m / min under condition 1 to form a DLC thin film with a thickness of 10 nm. 1 was used to prepare an infrared reflective laminate.
The light transmittance at a wavelength of 400 nm was insufficient at 45%.

(Comparative Example 4)
The same method as in Example 1 except that a silver-based metal film was formed by the same method as in Example 1 and then the DLC thin film was formed four times under the condition 1 to form a 160 nm DLC thin film. Infrared reflecting laminate was prepared.

DESCRIPTION OF SYMBOLS 1, 2 Opposite electrode 3 Dielectric material 4 Base | substrate 5 Atmosphere gas supply piping 6 Atmosphere gas 7 Plasmaization atmosphere gas 8 Exhaust piping 9 Nitrogen supply piping 10 High frequency power supply 11 Atmospheric gas supply device 12 Nitrogen supply device 13 Gas intake device 14 DLC thin film 16 Silver metal film

Claims (3)

An infrared reflective laminate in which a silver-based metal film and a diamond-like carbon film having a light absorption coefficient of 3 / μm or less at a wavelength of 400 nm and a thickness of 20 to 100 nm are laminated in this order on a transparent substrate. A diamond-like carbon thin film, a silver-based metal film, and a diamond-like carbon thin film are laminated in this order on a transparent substrate, and the light absorption coefficient at a wavelength of 400 nm of each diamond-like carbon thin film is 3 / μm or less, and the thickness is An infrared reflective laminate having a thickness in the range of 20 to 100 nm. It is a manufacturing method of the infrared rays reflective laminated body of Claim 1 or 2, Comprising: Under normal-pressure atmosphere, a voltage is applied between the electrodes which oppose, a low-temperature plasma is generated, and 1-40 volume% with nitrogen A method for producing an infrared reflective laminate, comprising laminating a diamond-like carbon film by a method of depositing a reaction product by decomposing acetylene diluted to a concentration.

Images