Protective film for firing

Abstract

To provide a protective film for baking which can fix a raw chip after dicing, can be conveyed to a baking process while securing traceability, prevents chips from coming into contact with each other during baking, and has little baking residue in a process of manufacturing a ceramic baked body.SOLUTION: The protective film for baking includes a peelable film and a protective layer provided on the peelable film, wherein the protective layer contains a thermoplastic resin and a tackifier, and the protective layer has a maximum weight reduction temperature of 280 °C or less and a maximum weight reduction rate of 3 mass% / °C or more in thermogravimetric measurement.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a protective film for firing that is attached to the surface of a ceramic before firing in the process of producing a fired ceramic body and has a protective layer that is burned away by the heat during firing. [Background technology]

[0002] In recent years, the number of multi-layer ceramic capacitors (MLCCs) used in vehicles has been increasing in the automotive market due to the spread of environmental friendliness and advanced driver assistance systems (ADAS), and with the advancement of electrification, this is expected to increase from the current 6,000 units per vehicle to 8,000-10,000 units per vehicle. As demand for MLCCs for vehicles increases, the miniaturization of electronic components is creating a demand for smaller and more functional chips (MLCCs).

[0003] The manufacturing process for MLCCs involves many steps: (1) manufacturing green sheets, (2) forming internal electrodes, (3) lamination / pressing, (4) dicing / creating raw chips, (5) degreasing / firing, (6) forming external electrodes, (7) baking, and (8) plating.

[0004] In the process of manufacturing sintered ceramics such as MLCCs, dust and foreign matter inside the furnace can adhere to the surface of the ceramic during firing, contaminating the surface of the resulting sintered ceramic body, and these foreign matter can also cause scratches on the surface. For this reason, protective sheets have been proposed that protect the surface of the ceramic during firing by covering it with a surface protective material, allowing the ceramic to be sintered while still covered with the surface protective material.

[0005] Japanese Patent Laid-Open Publication No. 2-107574 (Patent Document 1) describes a ceramic protection tape comprising a heat-resistant substrate and an adhesive layer provided on the substrate, characterized in that the adhesive layer is essentially formed from a resin composition comprising an elastomer and a tackifier resin, and having a maximum weight loss temperature of 400°C or less as measured by a thermobalance device and an ignition residue of 0.05% by weight or less.

[0006] Japanese Patent Laid-Open Publication No. 4-83760 (Patent Document 2) describes an adhesive sheet that comprises a surface protection material for ceramic firing, which is made using a film containing a polymer that thermally decomposes by depolymerization at a temperature lower than the firing temperature of the ceramic molded body, and an adhesive layer that is provided on the surface protection material and thermally decomposes at a temperature lower than the firing temperature of the ceramic molded body, so that the adhesive sheet can be fired while still adhered to the surface of the ceramic molded body via the adhesive layer.

[0007] Japanese Patent Laid-Open No. 4-367570 (Patent Document 3) and Japanese Patent Laid-Open No. 5-139848 (Patent Document 4) describe a protective sheet for firing, which comprises a polymer film that is thermally decomposed and disappears when a ceramic powder compact is fired, and an adhesive layer provided on the polymer film that is thermally decomposed and disappears when the ceramic powder compact is fired. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2-107574 [Patent Document 2] Japanese Patent Application Publication No. 4-83760 [Patent Document 3] Japanese Patent Application Publication No. 4-367570 [Patent Document 4] Japanese Patent Application Publication No. 5-139848 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, the heat-resistant base material shields decomposition gases from the composition forming the adhesive layer, making it easy for firing residues to be generated. In Patent Documents 2 to 4, an adhesive layer is required to adhere to the ceramic before firing, which increases the total thickness of the firing protection sheet, and some of the firing protection sheet remains, causing damage or contamination to the fired body and resulting in poor yield.

[0010] In particular, in recent years, as chips have become smaller, they tend to come apart during the firing process after dicing, making it difficult to determine where the manufactured chips were manufactured and fired, and new problems have arisen where chips collide with each other, causing chips to chip and reducing yield.For this reason, there is a need for a protective film that can fix raw chips after dicing, can transport them to the firing process while ensuring traceability, prevents chips from coming into contact with each other during firing, and leaves little firing residue.

[0011] Therefore, in one embodiment, the object of the present invention is to provide a protective film for firing that can fix raw chips after dicing in the process of manufacturing a fired ceramic body, can transport them to the firing process while ensuring traceability, prevents the chips from coming into contact with each other during firing, and leaves little firing residue. [Means for solving the problem]

[0012] In one embodiment, the present invention relates to a protective film for firing, and more specifically, provides a protective film for firing described in the following [1] to [4]. [1] A protective film for baking, comprising a peelable film and a protective layer provided on the peelable film, the protective layer containing a thermoplastic resin and a tackifier, and the protective layer having a maximum weight loss temperature of 280°C or less and a maximum weight loss rate of 3% by mass / °C or more in thermogravimetric measurement. [2] The protective film for firing according to [1], wherein the protective layer in the protective film for firing has a thickness of 3 to 10 μm and a tack strength of 0.40 N or more. [3] The protective film for firing according to [1] or [2], wherein in the protective layer, the thermoplastic resin is an aliphatic polycarbonate and the tackifier is a benzoic acid-based plasticizer. [4] The protective film for firing according to any one of [1] to [3], wherein the protective layer contains 30 to 55 parts by mass of a tackifier relative to 100 parts by mass of the thermoplastic resin. [Effects of the Invention]

[0013] According to one embodiment of the present invention, in a process for manufacturing a sintered ceramic body such as an MLCC, it is possible to prevent the adhesion of dust, foreign matter, etc. inside the furnace during sintering. In addition, it is possible to fix raw chips after dicing, ensure traceability while transporting them to the sintering process, and provide a protective film that prevents chips from coming into contact with each other during sintering and leaves little sintering residue. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a protective film for firing according to one embodiment of the present invention. [Figure 2] 1 is an example of a thermogravimetric curve of a protective layer in a protective film for firing according to one embodiment of the present invention. [Figure 3] 1 shows a thermogravimetric curve of the resin film in Experimental Example 1. [Figure 4] 10 shows a thermogravimetric curve of the protective layer in Experimental Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail.

[0016] One embodiment of the present invention is a protective film for firing that includes a peelable film and a protective layer provided on the peelable film. Figure 1 is a cross-sectional view that schematically shows an example of a protective film for firing according to one embodiment of the present invention. As shown in Figure 1, the protective film for firing 1 includes a peelable film 2 and a protective layer 3 provided on the peelable film 2.

[0017] A protective film for firing according to one embodiment of the present invention can be applied to cover multiple raw chips cut and separated after dicing in a process for producing a sintered ceramic body such as an MLCC, and the multiple raw chips can be peeled from the dicing film while maintaining their cut positions, allowing them to be transported to the next firing process. The peelable film can be peeled from the protective layer at any time before transport to the firing process or before firing in the firing process, allowing firing to be performed with only the protective layer covering the raw chips, and the protective layer is burned away by the heat during firing.

[0018] In a protective film for baking according to one embodiment of the present invention, the protective layer has a maximum weight loss temperature of 280°C or less and a maximum weight loss rate of 3% by mass / °C or more in thermogravimetry. The maximum weight loss temperature is preferably 280°C or less, and more preferably 250°C or less. The maximum weight loss temperature is preferably 180°C or more, and more preferably 200°C or more. For example, the maximum weight loss temperature is preferably in the range of 180°C to 250°C, and more preferably in the range of 200°C to 250°C. The maximum weight loss rate is preferably 3% by mass / °C or more, and more preferably 5% by mass / °C or more. A higher maximum weight loss rate is preferable, and there is no upper limit. However, in a protective film for baking according to one embodiment of the present invention, the maximum weight loss rate of the protective layer is, for example, 10% by mass / °C or less.

[0019] In this specification, thermogravimetric measurement of the protective layer is performed using a thermogravimetric differential thermal analyzer (TG-DTA) by heating a sample of a predetermined weight (e.g., 10 mg) in a nitrogen gas atmosphere from room temperature (e.g., 20°C) to 650°C at a heating rate of 10°C / min and measuring the change in weight of the sample over time. In the thermogravimetric curve obtained in the thermogravimetric measurement, the temperature at which the weight loss is maximum, i.e., the peak value obtained by first differentiating the thermogravimetric curve with respect to time, is defined as the maximum weight loss temperature (°C), and the absolute value of the slope of the tangent to the thermogravimetric curve at this maximum weight loss temperature is defined as the maximum weight loss rate (mass% / °C). In this specification, thermogravimetric measurement of the resin is performed under the same conditions as the thermogravimetric measurement of the protective layer.

[0020] Figure 2 shows an example of a thermogravimetric curve (TG curve) of a protective layer in a protective film for baking according to one embodiment of the present invention. The vertical axis (TG (%)) of Figure 2 represents the weight loss rate (mass %) of the protective layer, and the horizontal axis (TEMP (°C)) represents temperature (°C). Figure 2 also shows the peak value (maximum weight loss temperature, 238.3°C) obtained by first differentiating the thermogravimetric curve with respect to time, and the slope of the tangent to the thermogravimetric curve at this maximum weight loss temperature.

[0021] In one embodiment of the present invention, the protective layer of the firing protective film has a maximum weight loss temperature of 280°C or less and a maximum weight loss rate of 3 mass% / °C or more in thermogravimetry, so that the protective layer quickly decomposes thermally, preventing the shrinkage of the protective layer due to heat during the firing process and the resulting movement of the individual chips and contact between the chips.

[0022] The peelable film used in the baking protective film according to one embodiment of the present invention is not particularly limited as long as it functions as a support for forming the protective layer and can be peeled off from the protective layer before baking. Examples of films that can be used include films in which a peelable layer such as silicone, fluororesin, or alkyd resin is formed on a resin film such as polyethylene terephthalate (PET), polyimide, or polypropylene, a paper-based substrate such as synthetic paper, or a metal sheet such as aluminum foil.

[0023] In the protective film for firing according to one embodiment of the present invention, the release film is peeled off and removed from the protective layer before firing, so it does not block decomposition gases from the protective layer, etc., and no firing residue is generated. A particularly preferred release film is a resin-based film with appropriate flexibility and strength, taking into consideration workability such as attachment to cut raw chips and peelability from the protective layer. The thickness of the resin-based film is preferably 0.001 mm to 1 mm, and preferably 0.01 mm to 0.1 mm. Furthermore, a protective film for firing using a resin-based film as the release film can be rolled and stored after the protective layer is formed. In such cases, a release layer can be provided on both sides of the resin-based film.

[0024] In one embodiment of the present invention, the protective layer of a protective film for firing contains a thermoplastic resin and a tackifier. The inclusion of a thermoplastic resin and a tackifier allows the protective layer to have appropriate flexibility and adhesiveness. By providing the protective layer with appropriate flexibility and adhesiveness, multiple raw chips cut and separated after dicing can be uniformly attached. The multiple raw chips can be peeled from the dicing film while maintaining their cut positions (in other words, while the raw chips are fixed after dicing), allowing them to be transported to the next firing step while ensuring traceability. Furthermore, since there is no need to form an adhesive layer separate from the protective layer, the amount of organic components lost through pyrolysis can be reduced, preventing damage and contamination of the fired body due to residual substances.

[0025] In the protective film for firing according to one embodiment of the present invention, the thermoplastic resin used in the protective layer can be a plastic, such as an elastomer or synthetic resin, that is thermally decomposed and burned away during the firing process of ceramics. Examples of suitable elastomers include polyvinyl chloride, polystyrene, polyolefin, polyurethane, and polyester thermoplastic elastomers. Examples of suitable synthetic resins include polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer, acrylic resin, and polycarbonate. Particularly preferred thermoplastic resins have a maximum weight loss temperature of 280°C or less in thermogravimetry and a maximum weight loss rate of 3% by mass / °C or more, preferably 5% by mass / °C or more, in thermogravimetry. For the thermoplastic resin, the maximum weight loss temperature is preferably 280°C or less, more preferably 250°C or less. Furthermore, the maximum weight loss temperature is preferably 180°C or more, more preferably 200°C or more. For example, the maximum weight loss temperature is preferably in the range of 180°C to 250°C, more preferably 200°C to 250°C. The maximum weight loss rate is preferably 3% by mass / °C or more, and more preferably 5% by mass / °C or more. The higher the maximum weight loss rate, the better, and there is no upper limit, but the maximum weight loss rate of a thermoplastic resin is, for example, 15% by mass / °C or less.

[0026] In the protective layer of the protective film for firing according to one embodiment of the present invention, the thermoplastic resin is preferably an aliphatic polycarbonate. Aliphatic polycarbonates are polycarbonates that have carbonate ester groups (—O—CO—O—) in their main chains and have aliphatic chains between the carbonate ester groups in the main chains, without containing aromatic rings. Aliphatic polycarbonates are colorless, transparent thermoplastic resins made from carbon dioxide. They undergo rapid thermal decomposition at 200 to 250°C. They are low-decomposition polymers that undergo thermal decomposition well not only in air but also in an inert gas atmosphere such as nitrogen, and can minimize the amount of firing residue after thermal decomposition. Because aliphatic polycarbonates undergo rapid thermal decomposition at relatively low temperatures of 200 to 250°C, they are preferred for rapidly thermally decomposing the protective layer, preventing heat-induced shrinkage of the protective layer during the firing process and the resulting movement of individual chips and contact between chips.

[0027] The tackifier in the protective layer of the baking protective film according to one embodiment of the present invention provides the protective layer with appropriate flexibility and adhesiveness, and is primarily a plasticizer. Various plasticizers, such as phthalic acid-based, adipic acid-based, and phosphoric acid-based plasticizers, can be used as the plasticizer. However, since phthalate esters are considered to pose some risks to human health, non-phthalic acid plasticizers are preferred. Examples of non-phthalic acid plasticizers that can be used include polyester-based plasticizers, ether ester-based plasticizers, and benzoic acid-based plasticizers. Benzoic acid-based plasticizers are preferred, particularly in combination with thermoplastic resins, in terms of the film-forming properties, drying properties, and adhesiveness to raw chips of the protective film.

[0028] The adhesiveness of the protective layer varies depending on the thickness of the protective layer and the content of tackifier. For example, in the process of manufacturing a sintered ceramic body such as an MLCC, a thick protective layer with high adhesiveness is preferable in terms of the strength and adhesiveness required to uniformly attach multiple raw chips cut and separated after dicing, to peel the multiple raw chips from the dicing film while maintaining their cut positions, and to transport them to the next firing step. On the other hand, a thin protective layer is preferable in terms of the ability to sinter the raw chips while only covering them with the protective layer, and the protective layer is burned away by the heat during firing, leaving little sintered residue.

[0029] In a protective film for baking according to one embodiment of the present invention, the thickness of the protective layer is preferably 3 to 10 μm, and more preferably 5 to 10 μm, in consideration of the balance between adhesiveness and baking properties. In a protective film for baking according to one embodiment of the present invention, the content of the tackifier in the protective layer is preferably 30 to 55 parts by mass, and more preferably 45 to 55 parts by mass, per 100 parts by mass of the thermoplastic resin. In a protective film for baking according to one embodiment of the present invention, the content of the thermoplastic resin in the protective layer is preferably 45 to 80% by mass, and more preferably 45 to 70% by mass. In a protective film for baking according to one embodiment of the present invention, from the viewpoint of adhesiveness of the protective layer, the tack strength of the protective layer is preferably 0.40 N or more, more preferably 0.60 N or more, and more preferably 0.80 N or more. The tack strength of the protective layer is preferably 1.2 N or less, and more preferably 1.0 N or less. For example, the tack strength of the protective layer is preferably in the range of 0.40N to 1.2N, and more preferably in the range of 0.40N to 1.0N.

[0030] In this specification, the tack strength of the protective layer is measured using a tack tester (for example, Rhesca TAC1000) in accordance with the probe tack method. Specifically, the tack tester is equipped with a probe, a sample stage, and a stress detector. A sample (herein, a protective film for baking) is placed on the sample stage of the tester, and the probe is brought into contact with the adhesive surface of the sample (herein, the protective layer surface of the protective film for baking) from above the sample at a constant speed, and is held there for a certain period of time with a constant contact load. Immediately after that, the probe is peeled off from the adhesive surface in a direction perpendicular to the adhesive surface at a constant speed. The maximum load required for peeling is determined, and this is taken as the tack strength (unit: N). In this specification, the probe is made of stainless steel (SUS), with a diameter of φ5 mm (probe area 19.63 mm 2 ), the probe speed at the time of contact was 1.0 mm / sec, the contact load was 1.96 N, the retention time after contact was 1.0 second, and the lifting speed when peeling off the probe was 10.0 mm / sec. Measurements using the tacking tester were performed with the sample stage (plate) temperature at 25°C and the probe temperature at 25°C.

[0031] The thicker the protective layer, the better the transfer, but a thicker layer can increase the amount of residue left after baking, so a thickness of 10 μm or less is preferable. The protective layer can be formed on a release film using a volatile coating material in which a thermoplastic resin and a tackifier are dissolved in a solvent, using a coating method such as a die coat or a bar coater, or a printing method such as screen printing. [Example]

[0032] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0033] (Experimental Example 1) Four thermoplastic resins with different TG curves were prepared. Sample No. 1 was a thermoplastic resin (acrylic ester copolymer, Oricox #2004, manufactured by Kyoeisha Chemical Co., Ltd.), Sample No. 2 was a thermoplastic resin (acrylic ester copolymer, Oricox #2810, manufactured by Kyoeisha Chemical Co., Ltd.), Sample No. 3 was a thermoplastic resin (acrylic ester copolymer, Oricox #3000, manufactured by Kyoeisha Chemical Co., Ltd.), and Sample No. 4 was a thermoplastic resin (aliphatic polycarbonate, APC-PHN, manufactured by Sumitomo Seika Chemical Co., Ltd.).

[0034] A 5 μm-thick resin film was screen-printed onto a release film (Fujimori Kogyo Film Bina 38E-0010 DG-2.0, 38 μm thick) using thermoplastic resin. The resin film was then peeled off from the release film. A 10 mg sample of the resin film was placed in a thermogravimetric differential thermal analyzer (TG-DTA, NETZSCH TGDTA2000SA) and heated in a nitrogen gas atmosphere from room temperature (20 °C) to 650 °C at a heating rate of 10 °C / min. The maximum weight loss temperature and maximum weight loss rate were evaluated from the resulting thermogravimetric curve. Additionally, 10 g of the resin film was placed in a sample container (cell) and heated to 650 °C using the TG-DTA for 5 hours. After cooling to room temperature at a rate of 50 °C / hr, the weight was measured and the combustion residue was evaluated. The evaluation results are shown in Figure 3 and Table 1. There was no significant difference in the combustion residues of these thermoplastic resins, even though their TG curves differed.

[0035] [Table 1]

[0036] Figure 3 shows the thermogravimetric curves (TG curves) of the resin films obtained from each resin type. The vertical axis of Figure 3 represents the weight loss rate (mass%) of the resin film, and the horizontal axis represents the temperature (°C).

[0037] (Experimental Example 2) The thermoplastic resins listed in Table 1 were added with the plasticizers listed in Table 2 to evaluate whether they exhibited adhesive properties. A plasticizer-added resin film was formed on a release film in the same manner as in Experimental Example 1, except that a composition containing a thermoplastic resin, a plasticizer, and methyl ethyl ketone (MEK) as a solvent was used instead of the thermoplastic resin. The resin film was evaluated for compatibility between the thermoplastic resin and the plasticizer and adhesive properties. The amount of plasticizer added was determined to be between 25 and 100 parts by mass per 100 parts by mass of thermoplastic resin, while compatibility and adhesive properties were confirmed. Evaluations were based on whether the film was dry poorly, whether film formation was difficult, or whether adhesive properties were not exhibited. Qualities were determined based on whether film formation was possible and adhesive properties were exhibited. Compatibility was evaluated in the film-formed state, and adhesive properties were evaluated simply by touch. The evaluation results are shown in Table 3. While all of the plasticizers listed in Table 2 can be used as tackifiers by appropriately selecting the resin type, the benzoic acid-based plasticizer PB-10 was found to exhibit adhesive properties without any problems in film formation with any thermoplastic resin. From this, it can be said that benzoic acid-based plasticizers are preferred tackifiers because they have a wide range of resin types to choose from.

[0038] [Table 2]

[0039] In Table 2, DINP is an abbreviation for diisononyl phthalate.

[0040] [Table 3]

[0041] In Table 3, "No. 1" to "No. 4" shown in the sample rows correspond to the thermoplastic resins shown in Table 1 as "No. 1" to "No. 4," and the sample columns show the names of the plasticizers shown in Table 2. For example, the evaluation results of a resin film in which plasticizer W-230H was added to the thermoplastic resin of sample No. 1 are shown in the cell where the No. 1 column and W-230H row intersect.

[0042] (Experimental Example 3) A MEK diluted paint (solid content 20% by mass) was prepared by adding 50 parts by mass of PB-10 shown in Table 2 as a tackifier to 100 parts by mass of the thermoplastic resin shown in Table 1, and a protective film to be baked was produced by forming a 5 μm thick protective layer on a release film by screen printing in the same manner as in Experimental Example 1. The protective film to be baked produced here is protective film to be baked 1, which includes a release film 2 and a protective layer 3 provided on the release film 2, as shown in FIG. The laminate of sheets consisting of dielectric and resin was cut on a dicing film to obtain raw chips (chip size 3.2 mm x 1.6 mm, 16 x 7 pieces). The prepared protective film for firing was attached to these raw chips, and the transferability and contact rate were evaluated.

[0043] The transferability was evaluated by attaching a protective film for firing to the raw chip after cutting on the dicing film, and then peeling the protective film for firing and the raw chip from the dicing film. It was visually confirmed whether the raw chip could be transferred to the protective film for firing without falling off. The evaluation criteria were as follows: ○ if the raw chip could be transferred from the dicing film to the protective film for firing without falling off, and × if the raw chip was confirmed to have fallen off.

[0044] The contact rate was evaluated by peeling the release film from the protective layer, baking in a baking furnace at 1300°C, and then cutting the raw chips, and then measuring the ratio of the number of contacting sides to the number of adjacent sides.

[0045] The evaluation results are shown in Table 4. Transferability was unproblematic for all of the baking protective films. However, the contact rate was superior for the baking protective film with a protective layer made of aliphatic polycarbonate as the thermoplastic resin. This is likely due to the fact that the thermoplastic resins used in the other protective layers slowly decompose from around 250°C to around 400°C, and that thermal shrinkage occurs in parallel with the thermal decomposition of the protective layer, resulting in chip contact. In contrast, the protective layer made of aliphatic polycarbonate had a maximum weight loss temperature of 238.3°C and a maximum weight loss rate of 3.76% by mass / °C. Thermal decomposition began rapidly around 200°C, and by around 250°C, more than 90% of the thermal decomposition was complete. This suggests that the short thermal decomposition time and the low shrinkage of the protective layer resulted in a good contact rate.

[0046] [Table 4]

[0047] In Table 4, sample No. 5 shows the evaluation results of a baked protective film having a protective layer made of the thermoplastic resin of sample No. 1 shown in Table 1 to which the benzoic acid-based plasticizer PB-10 shown in Table 2 has been added; sample No. 6 shows the evaluation results of a baked protective film having a protective layer made of the thermoplastic resin of sample No. 2 shown in Table 1 to which the benzoic acid-based plasticizer PB-10 shown in Table 2 has been added; sample No. 7 shows the evaluation results of a baked protective film having a protective layer made of the thermoplastic resin of sample No. 3 shown in Table 1 to which the benzoic acid-based plasticizer PB-10 shown in Table 2 has been added; and sample No. 8 shows the evaluation results of a baked protective film having a protective layer made of the thermoplastic resin of sample No. 4 shown in Table 1 to which the benzoic acid-based plasticizer PB-10 shown in Table 2 has been added.

[0048] (Experimental Example 4) Similar to sample No. 8 in Experimental Example 3, a protective film for baking was prepared having a protective layer in which a specific amount of tackifier (benzoic acid-based plasticizer, PB-10, DIC Corporation) was added to 100 parts by weight of the thermoplastic resin No. 4 (aliphatic polycarbonate, APC-PHN, Sumitomo Seika Chemicals Co., Ltd.) shown in Table 1. However, in Experimental Example 4, the thickness of the protective layer and the amount of plasticizer added were changed, and the adhesion (tack) and transferability depending on the thickness of the protective layer and the amount of plasticizer added were evaluated.

[0049] The adhesiveness was evaluated by measuring the tack strength of the protective layer with a tack tester (TAC1000 manufactured by Rhesca) using the probe tack method.

[0050] The transferability was evaluated by attaching a protective film for firing to the cut green chip and peeling the protective film for firing and the green chip from the dicing film in the same manner as in Experimental Example 3. The evaluation criteria were as follows: ◯ indicates that the green chip could be transferred from the dicing film to the protective film for firing without falling off; △ indicates that the transfer was successful but some of the chip fell off due to impact during transfer; and × indicates that the green chip was confirmed to have fallen off.

[0051] The evaluation results are shown in Table 5. Excellent transferability was obtained when the protective layer was 3 μm or thicker and had a tack strength of 0.30 N or higher. In particular, excellent transferability was stably obtained when the protective layer was 5 μm or thicker and had a tack strength of 0.40 N or higher.

[0052] [Table 5]

[0053] In Table 5, the parts by mass of tackifier is the amount of tackifier added relative to 100 parts by mass of thermoplastic resin.

[0054] (Experimental Example 5) Using an aliphatic polycarbonate (No. 4, APC) as the thermoplastic resin, the difference in thermogravimetric curves with and without the addition of a tackifier (PB-10) was evaluated. 50 parts by mass of the tackifier (PB-10) was added per 100 parts by mass of the thermoplastic resin (APC) (No. 8, APC + PB-10). As in Experimental Example 3, an MEK diluted paint (20% solids) was prepared, and a 5 μm-thick protective layer was formed on a release film by screen printing. The protective layer was then peeled from the release film, and 10 mg of the protective layer was placed in a thermogravimetric differential thermal analyzer (TG-DTA, NETZSCH TGDTA2000SA). It was heated in a nitrogen gas atmosphere from room temperature (20 °C) to 650 °C at a heating rate of 10 °C / min. The maximum weight loss temperature and maximum weight loss rate were evaluated from the resulting thermogravimetric curve. In addition, 10 g of the protective layer was placed in a sample container (cell), heated to 650°C using a TG-DTA, held there for 5 hours, and then cooled to room temperature at a rate of 50°C / hr, after which the weight was measured and the combustion residue was evaluated. The evaluation results are shown in Figure 4 and Table 6. There was no difference in the maximum weight loss temperature between the resin film without tackifier (No. 4, APC) and the protective film with tackifier (No. 8, APC+PB-10). The maximum weight loss rate decreased to 3.76 mass% / °C with the addition of tackifier, but the results of Experimental Example 3 also showed good transferability and contact rate.

[0055] [Table 6]

[0056] In Table 6, Sample No. 4 shows the evaluation results for the resin film obtained from the thermoplastic resin of Sample No. 4 obtained in Experimental Example 1. Sample No. 8 shows the evaluation results for the protective film (No. 8, APC+PB-10) to which a tackifier was added obtained in Experimental Example 5.

[0057] Figure 4 shows the thermogravimetric curve (TG curve, dotted line) of the resin film obtained from the thermoplastic resin of Sample No. 4 obtained in Experimental Example 1, and the thermogravimetric curve (TG curve, solid line) of the protective film (No. 8, APC+PB-10) to which a tackifier was added obtained in Experimental Example 5. The vertical axis of Figure 4 represents the weight loss rate (mass%) of the resin film or protective film, and the horizontal axis represents temperature (°C).

[0058] From the above, it can be seen that the use of a protective film for firing containing a thermoplastic resin and a tackifier and having a protective layer with a maximum weight loss temperature of 280°C or less and a maximum weight loss rate of 3% by mass / °C or more in thermogravimetry can prevent the adhesion of dust and foreign matter inside the furnace during firing in the process of producing a fired ceramic body, and because the film has good transferability, adhesiveness, and adhesion rate, it can fix raw chips after dicing, allowing them to be transported to the firing process while ensuring traceability, and can also prevent chips from contacting each other during firing. Furthermore, it can be seen that the protective film for firing according to one embodiment of the present invention allows the release film to be peeled and removed before firing, and there is no need to provide an adhesive layer separately from the protective layer, thereby reducing firing residue.

[0059] Furthermore, from the viewpoint of forming a protective layer having a maximum weight loss temperature of 280°C or less and a maximum weight loss rate of 3% by mass / °C or more in thermogravimetry, it is preferable to use a thermoplastic resin having a maximum weight loss temperature of 250°C or less and a maximum weight loss rate of 5% by mass / °C or more in thermogravimetry, and from the viewpoint of providing a protective film for firing that has good transferability and contact rate and leaves little combustion residue, it is preferable to use a protective layer having a thickness of 3 to 10 μm and a tack strength of 0.40 N or more. It is also found that for the protective layer, aliphatic polycarbonate is a preferred thermoplastic resin, benzoic acid-based plasticizers are preferred tackifiers, and the amount of tackifier per 100 parts by mass of thermoplastic resin is preferably 30 to 55 parts by mass. [Explanation of symbols]

[0060] 1. Protective film for baking 2 Peelable film 3. Protective layer

Claims

1. A protective film for baking comprising a peelable film and a protective layer provided on the peelable film, the protective layer containing a thermoplastic resin and a tackifier, and the protective layer having a maximum weight loss temperature of 280°C or less and a maximum weight loss rate of 3 mass% / °C or more in thermogravimetric measurement.

2. 2. The protective film for firing according to claim 1, wherein the thickness of the protective layer in the protective film for firing is 3 to 10 μm, and the tack strength of the protective layer is 0.40 N or more.

3. 3. The protective film for firing according to claim 1, wherein in the protective layer, the thermoplastic resin is an aliphatic polycarbonate and the tackifier is a benzoic acid-based plasticizer.

4. The protective film for baking according to claim 1 or 2, wherein the protective layer contains 30 to 55 parts by mass of a tackifier relative to 100 parts by mass of the thermoplastic resin.

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