CN104812810B - Fluorine resin film, its manufacturing method and solar cell module - Google Patents

Abstract

The invention discloses a kind of fluorine resin films, it is will be containing the fluorine resin extrusion molding that Kynoar system resin is principal component, it cools down and is formed in the case where being set as 85~120 DEG C of the cooling temperature of range, by heat flux differential scanning calorimetry, be heated to 200 DEG C from room temperature with 10 DEG C/min of heating rate when the DSC curve (first run) that heats of obtained first round in, the endothermic peak (intrinsic peak) and 1 or more endothermic peak of the low temperature side in the intrinsic peak that have the Kynoar system resin in 150~190 DEG C of range intrinsic.

Description

Fluorine resin film, method for producing same, and solar cell module

technical field

The present invention relates to a novel fluororesin film and its manufacturing method, a solar cell back protection sheet formed using the fluororesin film, and a solar cell module provided with the solar cell back protection sheet.

Background technique

Fluorine resin films are widely used in fields requiring long-term durability due to their excellent weather resistance, heat resistance, stain resistance, chemical resistance, and solvent resistance. In particular, films mainly composed of vinylidene fluoride resins effectively take advantage of the cost advantage obtained by thinning them. As various surface protection materials, they have been widely used in building interior and exterior components. Organic solvent-based container surface materials, solar cell front and back materials, fuel cell components, etc. Furthermore, in recent years, along with a large increase in demand for solar cell modules, they have come to be widely used as solar cell back surface protection sheets (Patent Documents 1 and 2).

The demand for long-term durability for such a solar cell back protection sheet is becoming more and more severe, and use under severe conditions and a longer life are required. Therefore, the present applicant has developed a technology for producing a vinylidene fluoride resin film that has heat resistance, particularly yellowing during heating, by controlling the crystal form of the vinylidene fluoride resin to a specific crystal form (Patent Document 3). That is, after forming a film by extrusion molding, reheating at a temperature of 100° C. or higher, thereby controlling the ratio of the type II crystal component in the film to 90 to 100%, as determined from the absorbance obtained by infrared absorption spectroscopy, wherein When the sum of the type I crystal structure (β crystal) and the type II crystal structure (α crystal) is 100, a fluorine-based resin film with a small degree of yellowing can be obtained. However, with the increase in product life, a fluororesin film with further improved long-term durability is desired.

Patent Document 1: Japanese Patent Laid-Open No. 2011-129672

Patent Document 2: Japanese Patent Laid-Open No. 2008-28294

Patent Document 3: Japanese Patent Laid-Open No. 2006-273980

Contents of the invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluororesin film having improved long-term durability, especially yellowing resistance, compared with conventional films.

Another object of the present invention is to provide a method for producing the above-mentioned fluororesin film, a solar cell backside protection sheet using the above-mentioned fluororesin film, and a solar cell module including the solar cell backside protection sheet.

In Patent Document 3, the ratio of α-crystals in the film obtained from the absorption intensity obtained by infrared absorption spectroscopy is controlled so that the ratio of α-crystals is increased. However, it is known that if the ratio of α-crystals obtained by this method is Its value rises to a certain extent, and sometimes it does not fully reflect the difference in crystal structure. Then, the inventors of the present invention studied the further index of the crystal structure of the resin, and as a result, found that the difference in the crystal structure whose significant difference cannot be judged from the absorption intensity obtained by infrared absorption spectrum can be determined by heat flux differential scanning calorimetry. DSC curve analysis can be performed to clearly identify. Furthermore, the inventors of the present invention conducted intensive studies to obtain a fluororesin film having a higher α-crystal ratio than conventional products using this method, and as a result, unexpectedly found that if the cooling temperature in extrusion molding is set to 85 In the range of -120°C, a fluororesin film with further improved long-term durability, especially yellowing resistance can be obtained.

That is, according to one aspect of the present invention, there is provided a fluororesin film characterized in that a fluororesin composition containing a polyvinylidene fluoride resin as a main component is extruded, and the temperature is set at 85 to It is formed by cooling at a cooling temperature in the range of 120°C, and the DSC curve of the first round of heating is obtained when heating from room temperature to 200°C at a heating rate of 10°C/min by heat flux differential scanning calorimetry In the (first run), there are endothermic peaks (proper peaks) specific to polyvinylidene fluoride-based resins in the range of 150 to 190° C., and one or more endothermic peaks on the low temperature side of the specific peaks.

In the above-mentioned form, the method of extrusion molding is not limited to a specific method as long as the cooling conditions after resin extrusion have a significant influence on the crystallization of the resin, but the present inventors have studied in detail. The best method is the T-die forming method, so the T-die forming method is preferred. In the T-die forming method, the cooling of the extruded resin is implemented by one or more cooling rolls, and the temperature in the first cooling roll of the extruded resin cooling is the cooling temperature in the present invention, which is kept at 85- A certain temperature within the range of 120°C.

In this way, when the cooling temperature during extrusion molding is set at 85 to 120° C., and a film is formed by extrusion molding a fluorine-based resin composition containing a polyvinylidene fluoride-based resin as a main component, the above-mentioned specific properties can be obtained. In the DSC curve (first run) of the first round of heating obtained by heat flux differential scanning calorimetry under the same conditions, there is an endothermic peak (inherent peak) inherent to polyvinylidene fluoride-based resins in the range of 150 to 190°C , a novel film in which one or more endothermic peaks were observed on the low temperature side of the intrinsic peak.

This film is also a film having an α crystal ratio defined by the following formula (1) of 80% or more.

In addition, in the above-mentioned fluororesin film, the above-mentioned fluororesin composition should only be a resin composition containing polyvinylidene fluoride resin as a main component, and may contain arbitrary resins, additives, etc. normally contained in fluororesins. Here, "containing polyvinylidene fluoride resin as a main component" means that the resin composition contains 50% by mass or more, preferably 60% by mass or more, of polyvinylidene fluoride-based resin as a resin component, and includes polyvinylidene fluoride alone. In the case of a vinyl resin, that is, when the polyvinylidene fluoride resin is 100% by mass. Therefore, in one embodiment of the present invention, the fluorine-based resin composition contains only polyvinylidene fluoride-based resin as a resin component. On the other hand, in another embodiment of the present invention, a polymethyl methacrylate resin having excellent compatibility with polyvinylidene fluoride-based resins is blended, mixed and extruded. For example, the extruded resin composition contains 50 to 95% by mass, preferably 60 to 95% by mass of polyvinylidene fluoride resin and 5 to 50% by mass, preferably 5 to 40% by mass of polymethyl methacrylate. ester resin.

Furthermore, in the above-mentioned fluororesin film, the fluororesin composition may contain various additives in addition to the resin component, and in particular, titanium oxide or an ultraviolet absorber is preferably contained for shielding ultraviolet rays. Here, 5 to 40 parts by mass of titanium oxide is added to 100 parts by mass of the resin composition, and 0.1 to 5 parts by mass, preferably 0.3 to 5 parts by mass, of an ultraviolet absorber is added to 100 parts by mass of the resin composition.

In addition, the above-mentioned fluororesin film preferably has a film thickness within a range of 10 to 50 μm.

According to another aspect of the present invention, there is provided a method for producing a fluororesin film that is heated from room temperature to 200° C. at a rate of temperature increase of 10° C./min by heat flux differential scanning calorimetry. In the DSC curve (first run) of the first round of heating obtained at the time, there is an endothermic peak (intrinsic peak) inherent to polyvinylidene fluoride-based resins in the range of 150 to 190°C, and an endothermic peak on the low temperature side of the intrinsic peak. One or more endothermic peaks, the method comprising: extruding a molten resin containing a fluorine-based resin composition containing a polyvinylidene fluoride resin as a main component into a film; and extruding the extruded film-like resin in At a cooling temperature in the range of 85 to 120° C., the step of cooling with a cooling roll set to such a cooling temperature is preferable.

In this production method, the produced fluororesin film also has an α-crystal ratio defined by the formula (1) of 80% or more. In addition, in a preferred embodiment, the above-mentioned fluororesin composition contains 50 to 95% by mass, preferably 60 to 95% by mass of polyvinylidene fluoride resin and 5 to 50% by mass, preferably 5 to 40% by mass. polymethyl methacrylate resin. Furthermore, in the fluororesin composition, it is preferable to contain 5-40 mass parts of titanium oxides or 0.1-5 mass parts of ultraviolet absorbers with respect to 100 mass parts of resin components in total. In addition, the above-mentioned fluororesin film preferably has a film thickness within a range of 10 to 50 μm.

According to another aspect of the present invention, there are provided a solar cell back surface protection sheet formed of the above-mentioned fluororesin film, and a solar cell module formed using the solar cell back surface protection sheet.

The fluororesin film according to the present invention is formed of a fluororesin containing vinylidene fluoride resin as a main component, so it has excellent weather resistance, heat resistance, stain resistance, chemical resistance, solvent resistance, and mechanical properties. And secondary processability, and since it is a resin film having a specific peak pattern in heat flux differential scanning calorimetry, it is excellent in long-term durability, especially yellowing resistance. Moreover, the protective sheet for back surfaces of solar cells and solar cell modules formed using the fluororesin film concerning this invention also have excellent long-term durability, especially anti-yellowing property.

Description of drawings

Fig. 1 shows the fluororesin films formed in Example 1 (cooling roll temperature: 85°C), Example 2 (cooling roll temperature: 100°C) and Example 3 (cooling roll temperature: 120°C). Graph of DSC curves obtained by heat flux differential scanning calorimetry.

Fig. 2 is a graph obtained by plotting the ratio of α crystal obtained by infrared absorption spectrum analysis and the value of Δb obtained by heat and humidity resistance test with respect to the cooling temperature of the cooling roll in T-die forming, showing the effect of cooling temperature on the film. The effect of yellowing phenomenon. The films produced by changing the cooling temperature between 45°C and 75°C are Comparative Examples 3-6, and the films produced by changing the cooling temperature between 85°C and 120°C are Examples 11-14.

FIG. 3 is a spectrogram showing the results of infrared absorption spectroscopic analysis of films produced from fluorine-based resins containing polymethyl methacrylate resin in various amounts. The films prepared by changing the ratio of the polymethylmethacrylate resin in the resin composition from 0 to 50% by mass are Examples 15 to 19, and the films prepared by changing the ratio from 60 to 70% by mass are Comparative Examples 7-8.

4 is a graph showing the results of X-ray diffraction performed on films of Examples 15 to 19 and Comparative Examples 7 to 8. FIG.

FIG. 5 is a graph showing the results of DSC analysis of the films of Examples 15 to 19 and Comparative Examples 7 to 8. FIG.

Detailed ways

Embodiments of the present invention will be described in detail below.

A fluororesin film according to one embodiment of the present invention is formed by extrusion molding of a fluororesin composition containing a polyvinylidene fluoride resin as a main component.

＜Fluorine resin composition＞

The fluororesin composition may contain any resins, additives, and the like generally contained in fluororesins as long as they contain polyvinylidene fluoride resin as the main component. Here, "containing a polyvinylidene fluoride resin as a main component" means that the resin composition contains 50% by mass or more, preferably 60% by mass or more, of a polyvinylidene fluoride resin as a resin component, and includes polyvinylidene fluoride alone. In the case of a vinyl fluoride resin, that is, when the polyvinylidene fluoride resin is 100% by mass.

In addition, "polyvinylidene fluoride-based resin" refers to a crystalline resin mainly composed of vinylidene fluoride monomer and exhibiting various crystal structures such as α-type, β-type, and γ-type, and refers to a homopolymer of vinylidene fluoride. Or a copolymer of vinylidene fluoride and a copolymerizable monomer. Examples of copolymers include vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride-hexafluoropropylene copolymers, and the like. Homopolymers of vinylidene fluoride are preferably used.

The fluorine-based resin composition may contain resin components other than polyvinylidene fluoride-based resins. As such a resin component, in order to exhibit excellent compatibility with vinylidene fluoride-based resins, extrusion molding during film extrusion For effects such as improvement of processability by lowering the temperature and improvement of adhesiveness when laminating with other materials, methacrylate resins are preferable. Here, the methacrylate-based resin includes, in addition to methyl methacrylate homopolymer (polymethyl methacrylate), a methyl methacrylate unit in a predetermined amount, for example, 50 mol % or more, as a constituent unit. and a predetermined amount of, for example, less than 50 mol % of methacrylates other than acrylate and methyl methacrylate, and further examples include mixtures of two or more of these polymers, and the like. Examples of the above-mentioned acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate, and examples of methacrylates other than methyl methacrylate include ethyl methacrylate, methyl methacrylate, and the like. Propyl acrylate, etc. It should be noted that the copolymer is not limited to random copolymers, for example, graft copolymers can also be used, and it is also preferable to use acrylic saturated cross-linked rubber graft polymerization of monomers mainly methyl methacrylate. obtained copolymers. A particularly preferable methacrylate resin is polymethyl methacrylate resin.

Therefore, in one example, the fluororesin composition contains only polyvinylidene fluoride resin as a resin component. In addition, in another example, the fluororesin composition contains a polyvinylidene fluoride resin and a polymethyl methacrylate resin as resin components. In the latter case, as long as the polyvinylidene fluoride resin is the main component, the content of the polymethyl methacrylate resin can be arbitrary. In a preferred embodiment, the fluororesin composition contains 50 to 95% by mass , preferably 60 to 95 mass % of polyvinylidene fluoride resin and 5 to 50 mass %, preferably 5 to 40 mass % of polymethyl methacrylate resin.

Furthermore, in order to impart an ultraviolet shielding effect to the fluororesin composition, it is preferable to contain at least one of a pigment and an ultraviolet absorber. For example, when the film is intended to protect the base material, the pigment may not be added in some cases, but in this case, an ultraviolet absorber is also added. This is because although the weather resistance of the film itself is good, when it is used without adding a pigment, ultraviolet rays reach various substrates, etc. Adhesives and the like used for lamination of materials also deteriorate, and there may be a problem of peeling off from the polyvinylidene fluoride-based resin film.

The pigment used is not particularly limited, and there are any pigments such as inorganic pigments, organic pigments, and pearlescent pigments. From the viewpoint of weather resistance, oxide and composite oxide-based inorganic pigments are preferably used, and titanium oxide is particularly preferred. The addition amount of a pigment, especially titanium oxide, is 5-40 mass parts with respect to 100 mass parts of resins, Preferably it is 10-30 mass parts. When the added amount is less than 5 parts by mass, uniform dispersion in the film may not be possible, and partial color unevenness may appear. On the other hand, when adding more than 40 parts by mass, the dispersibility to the fluorine-based resin is remarkably lowered, and appearance defects may occur.

As long as the ultraviolet absorber is compatible with the vinylidene fluoride resin, for example, benzotriazole-based, oxalic acid-based, benzophenone-based, hindered amine-based and other various ultraviolet absorbers can be used. It is preferable to use a high-molecular-weight type ultraviolet absorber having a molecular weight of 300 or more in order to minimize volatilization during the production process and use as a film. The addition amount of a ultraviolet absorber is 0.1-5 mass parts with respect to 100 mass parts of resins, Preferably it is 0.3-5 mass parts.

In the film of the present invention, in addition to pigments or ultraviolet absorbers, stabilizers, dispersants, antioxidants, matting agents, surfactants, antistatic agents, Various additives such as filler materials such as silica and alumina, fluorine-based surface modifiers, and processing aids.

As a method of mixing pigments, ultraviolet absorbers, and other various additives into the film of the present invention, a method of premixing resins and additives and melt-kneading them using a generally used single-screw extruder can be employed. In addition, by using a high-kneading type twin-screw extruder, using a high-speed rotary type mixer to pre-mix at high temperature and then melt-kneading it with a single-screw extruder, it is possible to obtain a good dispersion state of the additive, Film with excellent appearance quality.

The film thickness of the fluororesin film of the present invention is preferably 50 μm or less, more preferably 10 to 30 μm. When the thickness is less than 10 μm, the handleability is remarkably reduced, and sufficient durability may not be obtained. On the other hand, if it exceeds 50 μm, the cost of raw materials increases, which is disadvantageous in cost. Alternatively, the film of the present invention may be used as a surface layer and a blend of an acrylic resin layer, a vinylidene fluoride resin, and an acrylic resin may be laminated as a back layer to form a film of two or more layers.

＜Manufacture of Fluorine Resin Film＞

The fluororesin film can usually be extrusion-molded by a method of forming a film using a T-die or a method of forming a film using a blow mold. In the present invention, the method of forming a film using a T-die is preferable. The extrusion conditions are not particularly limited, and conventional conditions for forming vinylidene fluoride-based resin films can be used, but in the present invention, the cooling temperature after extrusion must be set to 85 to 120°C, preferably 90 to 120°C. °C, more preferably in the range of 100 to 120 °C. That is, in the case of using a T-die forming machine for film formation, the high-temperature resin extruded from the T-die is cooled and solidified by a metal cooling roll placed under the T-die, and the temperature of the metal cooling roll is set at 85 -120°C, preferably 90-120°C, more preferably 100-120°C. In addition, when a plurality of cooling rolls are arranged in the extrusion molding machine, the temperature of the initial cooling roll (first cooling roll) is set to 85 to 120°C, preferably 90 to 120°C, more preferably It is in the range of 100 to 120°C. In addition, it is customary to arrange a metal cooling roll and a rubber roll in pairs under the T-shaped die, but whether to use a rubber roll and the set temperature of the rubber roll are optional. When the said cooling temperature is set to less than 85 degreeC, the film which has desired long-term durability, especially anti-yellowing property cannot be obtained. On the other hand, when the cooling temperature is set to be higher than 120° C., the film cannot be formed satisfactorily due to poor peeling from the roll.

It should be noted that the supply of raw materials may use a resin composition prepared by melting and kneading each raw material in advance, and various raw materials may be directly supplied to a single-screw or twin-screw extruder, usually at a temperature of 150 to 260°C. Melting is carried out at a temperature, and the film is formed by extruding through a film T-die.

＜Fluorine resin film＞

The fluororesin film obtained by extrusion molding the above-mentioned fluororesin composition under the above-mentioned conditions is a film having an α crystal ratio defined by the above formula (1) of 80% or more, but the α crystal ratio defined by the formula (1) is 80% or more. If the crystal ratio exceeds a certain value, it will be in a saturated state and cannot reflect changes in the crystal structure of the film. However, this state change can be grasped by analysis using heat flux differential scanning calorimetry. That is, for a fluororesin film, regardless of whether the cooling temperature is set in the range of 85 to 120°C, when heated from room temperature to 200°C by heat flux differential scanning calorimetry at a temperature increase rate of 10°C/min. In the DSC curves (first run) of the first round of heating, an endothermic peak inherent to polyvinylidene fluoride-based resins was observed around 170°C. However, in the fluororesin film of the present invention formed by setting the cooling temperature in the range of 85 to 120°C, at least one source of The endothermic peak temperature of α crystal. And, the more prominent the endothermic peak on the low temperature side is, the more the proportion of α crystals increases, and the long-term durability of the film, especially the yellowing resistance is improved. For example, in the fluororesin film of the present invention, the hue b value immediately after the film is about -2.5 to -0.5, there is no significant yellowing after the heat and humidity resistance test described later, and the Δb value before and after the test Suppressed below 2.

It should be noted that in the fluororesin film formed under the conditions of the present invention, the endothermic peak observed on the low temperature side of the endothermic peak inherent in polyvinylidene fluoride resins usually comes from α crystals, but in the cooling process of the present invention When the film is formed under conditions other than the conditions of the present invention, such as a temperature range outside the temperature range, an endothermic peak may be observed on the low temperature side of the endothermic peak inherent to polyvinylidene fluoride resins. However, this endothermic peak is not derived from the α crystal but is derived from the β crystal, and can be confirmed by, for example, X-ray diffraction. Therefore, a fluororesin film showing a desired DSC curve formed under conditions within the scope of the present invention has excellent weather resistance, particularly It is resistant to yellowing.

Example

The present invention will be described more specifically by way of examples below, but the present invention is not limited thereto. In addition, the method of evaluating the characteristics of each sample of the raw material used in the Example and the produced film is as follows.

＜Materials used＞

Vinylidene fluoride resin: Kynar K720 (manufactured by Arkema Corporation), a crystalline polymer, polyvinylidene fluoride resin with a fluorine content of about 59%, and a melting point of about 170°C, MFR (conditions: 230°C, 3.8kg load) 5 ~29(g/10min)

- Methacrylate-based resin: Acrypet IR-S404 (manufactured by Mitsubishi Rayon Corporation), a methacrylate-based resin containing rubber components of butyl acrylate (n-BA) and butyl methacrylate (BMA), MFR (conditions: 230°C, 37.3N) 7.8 (g/10min)

Titanium oxide: Ti-Pure R960 (manufactured by DuPont), (particle size: about 0.35 μm, pure titanium content: about 89%)

＜Evaluation method＞

(1) α crystal ratio

The infrared absorption spectrum was measured by NICOLET380FT-IR (manufactured by Thermo Fisher Scientific Corporation). In the infrared absorption spectrum, the characteristic absorption of polyvinylidene fluoride-based resin β-type crystals exists at a wave number of 840 cm ^-1 , and the characteristic absorption of α-type crystals exists at a wave number of 765 cm ^{-1 .} The intensity was calculated using the following formula (1) to calculate the α-crystal ratio (see Tomomi Hanada, Joy Ando, "Polyphized Vinyliden and Polyacetic Acid Binilo and Polyether Metakurilet Brendo System Ni Okeru Polyfed Vinidon's Crystallization (Polyvinylidene Fluoride and Polyacetic Acid Crystallization of polyvinylidene fluoride in a blend system of vinyl ester and polyethyl methacrylate)", Minutes of Tokyo Keizai Gakuin University, July 1992, No.32, pages 5-12).

(2) Hue after heat and humidity resistance test

The heat-and-moisture resistance test was implemented using Pressure Cooker SPY-4016 (manufactured by ALP Corporation) as a testing machine. For the film sample bonded to EVA, use the color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd. to measure the color difference of the surface bonded to the EVA, put it into the testing machine, and implement the durability test under the following conditions .

Temperature: 125°C

Humidity: 100%

Pressure: 2.3atm

Time: 50hrs

After the test, the color difference measurement of the bonding surface of the film and EVA was performed again, and the Δb value before and after the test was calculated. Evaluation criteria judged that there was little yellowing when the Δb value was 2 or less.

(3) UV transmittance

The UV transmittance of the film at a wavelength of 340 nm was measured using a Hitachi spectrophotometer U-3310 (manufactured by Hitachi-Hightech Fielding Co. Ltd.).

(4) Heat flux differential scanning calorimetry

The measurement was carried out under the following conditions using a differential scanning calorimeter DSC3100SA (manufactured by Bruker AXS Corporation).

Temperature: room temperature→200℃

Heating rate: 10°C/min

Sample mass: 1.5mg

(5) X-ray diffraction

The measurement was carried out under the following conditions using an X-ray diffractometer Ultima IV (Rigaku Corporation).

X-ray source: Cu sealed tube

Applied voltage/current: 40kV/40mA

Detector: High-speed detector D/teX Ultra

<Examples 1-10 and Comparative Examples 1-2>

Vinylidene fluoride resin, polymethyl methacrylate resin, and titanium oxide were mixed according to the ratio of PMMA shown in Table 1 (relative to the total of vinylidene fluoride resin and polymethyl methacrylate resin 100% by mass, polymethyl methacrylate mass % of methyl acrylate resin) and the amount of titanium oxide (with respect to 100 mass parts of resin, mass parts of titanium oxide) were prepared, dropped into φ 65mm single-screw extruder and mixed, extruded from the extruder Extrude through a T-die at a temperature of 240°C, pass through the first cooling roll set at the cooling temperature shown in Table 1, cool and solidify, and perform film molding to obtain the thicknesses shown in Table 1. Examples 1- 10 and the films of Comparative Examples 1-2.

For the produced film, the ratio of α crystals, the hue after the heat-and-moisture resistance test, the UV transmittance, and the heat flux differential scanning calorimetry were evaluated according to the above-mentioned evaluation method. The results are shown in Table 1 together. In addition, the DSC curves obtained by heat flux differential scanning calorimetry for the films of typical Examples 1 to 3 are shown in FIG. 1 . In addition, in Comparative Example 2, the film was not peeled off the cooling roll smoothly, and a film suitable for property evaluation could not be produced.

From the results in Table 1, it can be seen that the films of Examples 1 to 10 have high α crystal ratios, and also have endothermic peaks on the low temperature side of the natural peaks, and the color difference Δb after the heat and humidity resistance test is a sufficiently small value, and the yellowing resistance is excellent. . On the other hand, in Comparative Example 1, it turned out that the α crystal ratio was low, and yellowing resistance deteriorated. It should be noted that although an endothermic peak was observed in Comparative Example 1, it was found by X-ray diffraction that this peak was derived from the β crystal. In addition, as can be seen from the results of FIG. 1, in the fluororesin films of Examples 1 to 3, an endothermic peak was observed on the low temperature side of the intrinsic peak of the polyvinylidene fluoride resin, and as the cooling roll temperature further increased, This endothermic peak becomes conspicuous.

[Table 1]

*Value measured immediately after film production

<Examples 11-14, Comparative Examples 3-6>

In order to study the influence of the setting temperature of the metal cooling roll on the yellowing phenomenon of the film, the PMMA ratio is 25%, the amount of titanium oxide is 22 parts by mass, and the setting cooling temperature of the metal cooling roll is changed to 45°C, 55°C, At 65°C, 75°C, 85°C, 100°C, 110°C, and 120°C, the fluorine-based resin films of Comparative Examples 3-6 and Examples 11-14 were produced. For the obtained film, the α crystal ratio was determined and the Δb value was measured. The results are shown in Figure 2.

It can be seen from Figure 2 that if the cooling temperature is low, the ratio of α crystals is low, and as a result, the yellowing phenomenon becomes significant, but if the cooling temperature increases until the cooling temperature reaches 80°C, the ratio of α crystals also increases, although the yellowing phenomenon Not lowered enough, but slowly lowering. However, if the cooling temperature reaches about 85°C, the α-crystal ratio reaches a saturated state and does not continue to increase, but the yellowing phenomenon still decreases slowly. That is, it can be understood from the experimental results that there is a limit to the reduction method of the yellowing phenomenon based on the analysis of the α crystal ratio based on the infrared absorption spectroscopic analysis.

<Examples 15-19, Comparative Examples 7-8>

In order to study the effect of the PMMA ratio on the crystal structure of the fluororesin film, the set temperature of the metal cooling roll was 85°C, the amount of titanium oxide was 22 parts by mass, and the PMMA ratio was increased from 0 mass % to 10 mass %, 20 mass % %, 30 mass%, 40 mass%, 50 mass%, 60 mass%, and 70 mass%, the fluorine-based resin films of Examples 15-19 and Comparative Examples 7-8 were produced. The crystal structure of the obtained fluororesin film was analyzed by infrared absorption spectroscopy, X-ray diffraction, and heat flux differential scanning calorimetry. The results are shown in FIGS. 3 to 5 . From the analysis results by infrared absorption spectroscopy in FIG. 3 , it can be seen that as the PMMA ratio increases, the peaks derived from α crystals and β crystals become smaller. Moreover, from the analysis result by the X-ray diffraction method of FIG. 4, it turns out that when the ratio of PMMA exceeds 50 mass %, the crystallization of PVDF is suppressed. Furthermore, from the analysis results by heat flux differential scanning calorimetry in FIG. 5 , it can be seen that the melting point Tm gradually decreases from about 170° C. (PMMA ratio: 0% by mass) as the PMMA ratio increases. In addition, when the ratio of PMMA exceeds 50% by mass, the inherent endothermic peak intensity becomes weak, and PVDF and PMMA are compatible.

Claims (7)

1. a kind of fluorine resin film, which is characterized in that its be containing Kynoar system resin for principal component, polymethylacrylic acid Methyl esters is the fluorine resin composition of 0 mass % or Kynoar system resin and 5~50 matter containing 50~95 mass % The plexiglass of amount % is extruded into as the fluorine resin composition of resin component at 150~260 DEG C Type is cooled down in the case where being set as 100~120 DEG C of the cooling temperature of range and is formed, and pass through heat flux differential scanning amount In hot method, the DSC curve of first round heating obtained when being heated to 200 DEG C from room temperature with 10 DEG C/min of heating rate, have Intrinsic endothermic peak, that is, intrinsic the peak of Kynoar system resin in 150~190 DEG C of ranges and in the intrinsic peak 1 or more endothermic peak of low temperature side, fluorine resin composition amount to 100 mass parts relative to resin component, contain 5~40 mass The titanium oxide of part.

2. fluorine resin film according to claim 1, wherein, the α crystalline substances ratio that formula 1 defines is more than 80%,

3. fluorine resin film according to claim 1, wherein, amount to 100 mass parts, fluorine resin relative to resin component Composition contains the ultra-violet absorber of 0.1~5 mass parts.

4. fluorine resin film according to claim 1 or 2, wherein, film thickness is in the range of 10~50 μm.

5. it is a kind of manufacture fluorine resin film method, the fluorine resin film by heat flux differential scanning calorimetry, with 10 DEG C/ In the DSC curve of first round heating that the heating rate of minute obtains when being heated to 200 DEG C from room temperature, have in 150~190 DEG C range the intrinsic endothermic peak, that is, intrinsic peak of Kynoar system resin and 1 of the low temperature side in the intrinsic peak More than endothermic peak, the method have：It is principal component that will contain comprising Kynoar system resin, polymethyl methacrylate is The fluorine resin composition of 0 mass % or Kynoar system resin comprising 50~95 mass % and 5~50 mass % Plexiglass is squeezed out as the molten resin of the fluorine resin composition of resin component at 150~260 DEG C The process of film-like and the process for cooling down the film resin being extruded under the cooling temperature of 100~120 DEG C of range, it is described Fluorine resin composition amounts to 100 mass parts, the titanium oxide containing 5~40 mass parts relative to resin component.

6. a kind of rear surface of solar cell screening glass is as the fluorine resin film described in any one of Claims 1-4 It is formed.

7. a kind of solar cell module is to be formed using the rear surface of solar cell described in claim 6 with screening glass.