Stainless steel foil with planarization film

Abstract

Provided is a stainless steel foil with a planarization film that reduces the number of pits present on the surface of the stainless steel foil without generating cracks on the planarization film. The stainless steel foil with a planarization film has a composition comprising a stainless steel component, the remainder consisting of Fe and impurities, and, with respect to the total mass of inclusions having a particle diameter of 2.00 μm or more, Al2O3: 30 mass% or less, MgO: 10 mass% or less, and, among the inclusions having a particle diameter of 2.00 μm or more, inclusions having a particle diameter of greater than 5.00 μm present on the surface are 20 per cm 2 Hereinafter, in a stainless steel foil having a thickness of 5.0 μm or more and 100.0 μm or less, and at least one face of the stainless steel foil, a planarization film having a thickness of 0.3 μm or more and 5.0 μm or less is provided.

Description

Technical Field

[0001] This invention relates to stainless steel foil with a planarization film that can be used in flexible substrates for electronic devices. Background Technology

[0002] For substrate materials used in thin-film electronic devices, such as flexible electronic devices, flatness, reliable insulation, heat resistance, gas barrier properties, and high toughness are required. Resin films or ultra-thin glass are considered as alternative substrate materials; however, resin films have issues with heat resistance and gas barrier properties, while ultra-thin glass suffers from low toughness and reliability problems. On the other hand, stainless steel foil exhibits excellent heat resistance, gas barrier properties, and toughness, but it has issues with flatness and insulation. Therefore, to address these problems, attention has been paid to stainless steel foil with a planarization film formed on at least one side, imparting flatness or insulation. Among these, stainless steel foil with a planarization film covered by a silica-based inorganic-organic composite material with excellent heat resistance is a promising material.

[0003] Stainless steel foil with a silicon dioxide-based inorganic-organic composite material as the film-forming agent is described in patent documents 1 and 2.

[0004] Patent document 1 describes a stainless steel foil covered with an inorganic-organic composite film that exhibits excellent heat resistance, processability, flatness, flexibility, and insulation. This stainless steel foil is obtained by covering one or both sides of a stainless steel foil with an inorganic-organic composite film containing an appropriate amount of organic groups, produced using a sol-gel method.

[0005] Patent Document 2 describes a short-curing planarization film forming coating solution capable of planarizing the surface of a metal foil roll flush with a glass substrate using a roll-to-roll process, a planarization film possessing both heat resistance and moisture resistance, and a metal foil roll planarized therefrom. This metal foil roll is obtained by coating with a planarization film forming coating solution, which is prepared by adding 0.1 to 1 mol of acetic acid and 0.005 to 0.05 mol of organotin as catalysts to an organic solvent containing 1 mol of phenyltrialkoxysilane, hydrolyzing it with 2 to 4 mol of water, and then dissolving the resulting resin, obtained by vacuum distillation to remove the organic solvent at a temperature of 160°C to 210°C, in an aromatic hydrocarbon solvent to obtain a short-curing planarization film forming coating solution.

[0006] On the other hand, even with the planarization film described above, there are still technical problems such as pits on the stainless steel foil surface causing cracks in the planarization film, resulting in low flatness and insulation. The pits on the stainless steel foil surface are caused by inclusions in the stainless steel detaching from the surface of the foil during rolling.

[0007] Various methods for reducing inclusions in stainless steel, the base material for manufacturing stainless steel foil, have been studied. For example, Patent Document 3 discloses a stainless steel sheet suitable for precision instrument components, such as HDD (hard disk drive) parts and semiconductor layer forming substrates, exemplified by thin-film silicon solar cells. The presence of tiny pits distributed on the surface of the stainless steel sheet significantly affects its cleanliness; these pits are caused by inclusions or carbide particles falling off during the rolling process. Patent Document 3 discloses the generation of non-metallic inclusions with Mn(O,S)-SiO2 as the main component, while simultaneously rendering the non-metallic inclusions harmless by adjusting the concentrations of MgO, Al2O3, and Cr2O3 to below a specified level.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2003-247078

[0011] Patent Document 2: International Publication No. 2016 / 076399

[0012] Patent Document 3: Japanese Patent Application Publication No. 2011-202253 Summary of the Invention

[0013] The technical problem that the invention aims to solve

[0014] The purpose of this invention is to provide a stainless steel foil with a planarization film that reduces the number of pits on the surface of the stainless steel foil, which is the cause of cracks in the planarization film, and has excellent flatness and insulation reliability.

[0015] Technical means for solving technical problems

[0016] The inventors of this invention formed a planarization film composed of a phenylsiloxane polymer with a film thickness of 2.0 μm to 4.0 μm on the surface of a stainless steel foil, and prepared a test piece. A liquid with a conductivity of 0.1 S / m to 100 S / m and a cross-sectional area of ​​4 mm² was impregnated with the film. 2 Above 9mm 2 The following electrode is used as the upper electrode, and the stainless steel foil is used as the lower electrode. The surface of the test piece is scanned using the upper electrode, and the leakage current is measured to be 1 μA / mm when 10V is applied between the upper and lower electrodes.2 The number of the above locations. As a result, multiple locations were found for a measurement area of ​​100 cm². 2 It shows 1μA / mm 2 The above current values ​​are located at the positions shown. Observation of this cross-section revealed pits with a width of more than 5 μm perpendicular to the rolling direction on the surface of the stainless steel foil. These pits are the cause of crack formation. Furthermore, it was found that these pits on the surface of the stainless steel foil were caused by the shedding of coarse inclusions with a particle size of more than 5 μm from the stainless steel during the foil rolling process.

[0017] Further research revealed that although the detached inclusions could not be tracked, the greater the number of large, undetached inclusions remaining on the stainless steel foil surface, the greater the number of pits caused by the detachment of inclusions, and the greater the number of cracks generated by the planarization film formed on the stainless steel foil surface.

[0018] Therefore, it was discovered that by suppressing coarse inclusions remaining in the stainless steel foil after foil rolling, the insulation and flatness of the stainless steel foil with a planarization film are significantly improved.

[0019] The inventors focused on Al₂O₃, MgO, SiO₂, CaO, Mn(O, S), and CrS as basic components of inclusions. In the case of inclusions composed of at least one of SiO₂, CaO, Mn(O, S), and CrS, these inclusions are difficult to cluster and are low-melting-point and soft. Therefore, by stretching or breaking them during hot or cold rolling processes, large inclusions can be reduced. (Sometimes SiO₂, CaO, Mn(O, S), and CrS are referred to as soft inclusions.)

[0020] On the other hand, inclusions such as alumina (Al₂O₃) or magnesium-aluminum spinel (MgO·Al₂O₃, hereinafter sometimes referred to as spinel) have high interfacial energy, making them prone to segregation and aggregation during solidification, resulting in larger aggregate sizes. Furthermore, because alumina or spinel inclusions are hard, they are difficult to break up during hot or cold rolling, resulting in larger inclusion particles remaining as inclusions. (Sometimes alumina or magnesium-aluminum spinel is referred to as hard inclusions.)

[0021] Therefore, it was discovered that reducing the proportion of alumina or spinel in the inclusions improves the manufacturing conditions of stainless steel foil, especially the rolling conditions, reduces the number of coarse alumina or spinel inclusions, and disperses soft inclusions into smaller pieces, thereby enabling the production of stainless steel foil with reduced coarse inclusions.

[0022] According to the present invention, the following is provided.

[0023] (1) A stainless steel foil with a planarization film,

[0024] It comprises a stainless steel foil, and at least one side of the stainless steel foil has a planarization film with a thickness of 0.3 μm or more and 5.0 μm or less.

[0025] In the stainless steel foil:

[0026] It has a composition that includes stainless steel components and the remainder consists of Fe and impurities.

[0027] Relative to the total mass of inclusions with a particle size greater than 2.00 μm, Al2O3: less than 30% by mass, MgO: less than 10% by mass.

[0028] Of the inclusions with a particle size of 2.00 μm or larger, the number of inclusions with a particle size of 5.00 μm or larger existing on the surface is 20 per cm. 2 the following,

[0029] The plate thickness is between 5.0 μm and 100.0 μm.

[0030] (2) Stainless steel foil with planarization film as described in (1) above,

[0031] The stainless steel foil is an austenitic stainless steel foil, having the following composition: containing, by mass %

[0032] C: Below 0.150%

[0033] Si: 0.100~2.000%

[0034] Mn: below 0.100% to 10.000%

[0035] P: below 0.045%

[0036] S: less than 0.007%

[0037] Ni: 2,000–15,000%

[0038] Cr: 15,000–20,000% or less

[0039] N: below 0.200%

[0040] Al: below 0.030%

[0041] Mg: less than 0.0005%

[0042] Ca: below 0.0005%,

[0043] The remainder consists of Fe and impurities.

[0044] (3) Stainless steel foil with planarization film as described in (1) above,

[0045] The stainless steel foil is a ferritic stainless steel foil, having the following composition: containing, by mass %

[0046] C: Below 0.120%

[0047] Si: below 2.000%

[0048] Mn: 0.100-1.250% or less

[0049] P: below 0.040%

[0050] S: below 0.030%

[0051] Cr: 16,000–20,000% or less

[0052] N: less than 0.025%

[0053] Al: below 0.030%

[0054] Mg: less than 0.0005%

[0055] Ca: below 0.0005%,

[0056] The remaining portion consists of Fe and impurities.

[0057] (4) Stainless steel foil with planarization film as described in any of (1) to (3) above,

[0058] The planarization film is a silicon dioxide-based organic-inorganic composite film, and the Si core constituting the organic-inorganic composite film contains only T cores and Q cores.

[0059] (5) Stainless steel foil with planarization film as described in (4) above,

[0060] The planarization film is a silica-based organic-inorganic composite film, and the ratio of Q cores to Si cores constituting the organic-inorganic composite film is less than 70%.

[0061] Invention Effects

[0062] It is possible to provide a stainless steel foil with a planarization film, which forms a planarization film on a stainless steel foil with fewer coarse inclusions, thereby improving flatness and insulation reliability. Detailed Implementation

[0063] The stainless steel foil with a planarization film of the present invention will be described. Unless otherwise specified, "%" in relation to composition means % by mass in the steel. Unless otherwise specified, it includes cases where it is not contained (0%).

[0064] The stainless steel foil of the present invention is not particularly limited. For example, it can be an austenitic system such as SUS304, or a ferritic system such as SUS430.

[0065] [Composition of stainless steel foil]

[0066] The stainless steel foil of the present invention, when it is an austenitic stainless steel foil, has the following composition: the stainless steel foil, by mass%, contains C: 0.150% or less, Si: 0.050 to 2.000%, Mn: 0.100 to 10.000%, P: 0.045% or less, S: 0.007% or less, Ni: 2.000 to 15.000%, Cr: 15.000 to 20.000%, N: 0.200% or less, Al: 0.030% or less, Mg: 0.0005% or less, Ca: 0.0005% or less, and the remainder consists of Fe and impurities.

[0067] Ni (Ni) improves corrosion resistance and workability and is a key component used to adjust the coefficient of thermal expansion of stainless steel. From the perspective of improving corrosion resistance, a Ni content of 2.000% or higher is recommended. However, Ni is a high-valence element, and if its content is too high, bainite structure is easily formed in the steel after hot rolling or hot forging. Therefore, the Ni content is set below 15.000%.

[0068] Cr is an alloying element required to improve corrosion resistance; however, if excessive Cr is included, the steel becomes hardened and its machinability deteriorates. Therefore, the Cr content is kept below 20.000%. There is no particular lower limit to the Cr content, but adding Cr at a content of 15.000% or more has a significant effect, hence the requirement of 15.000% or more.

[0069] Carbon (C) may not be specifically present. If C is present in excess, the coefficient of thermal expansion increases, and the amount of Cr-based inclusions precipitating at grain boundaries also increases, contributing to the formation of larger inclusion particles. Therefore, the C content is 0.150% or less, preferably 0.100% or less, and more preferably 0.050% or less.

[0070] Ca dissolves in sulfides, causing them to disperse finely and spherically shape. On the other hand, if a large amount of Ca is present, the Ca not dissolved in the sulfides will form coarse oxides, which may lead to poor etching. Therefore, it is not particularly necessary to contain Ca, and if it is present, the amount of Ca should be 0.0005% or less, preferably 0.0001% or less.

[0071] To avoid spinel formation, Mn is actively used as a deoxidizer, replacing Mg and Al. However, if the Mn content is too high, it segregates to the grain boundaries, promoting grain boundary destruction and reducing resistance to hydrogen embrittlement. Therefore, the Mn content is 10.000% or less, preferably 5.000%, 2.000%, 1.500%, 1.200%, or 1.000%, and more preferably 0.800%, 0.600%, or 0.500%. The lower limit of Mn is not particularly limited. However, if the Mn content is too low, it is difficult to adjust the inclusions to a Mn(O,S)-SiO2 system composition. Therefore, the Mn content is 0.100% or more. Here, Mn(O, S) refers to MnO monomers, MnS monomers, and inclusions composed of MnO and MnS. The ratio of O to S is not constant, and it represents inclusions composed of oxides and sulfides.

[0072] To avoid spinel formation, deoxidation with Mn and Si is actively performed instead of deoxidation with Mg and Al. However, Si increases the coefficient of thermal expansion of stainless steel. Furthermore, the deoxidation product MnO-SiO2 is a vitrified, soft inclusion that extends and fractures during hot rolling, becoming finer. Therefore, resistance to hydrogen embrittlement is improved. On the other hand, if the Si content exceeds 2.000%, the strength becomes excessively high and hardened, requiring more passes to roll to the desired thickness when manufacturing thin sheets in cold working, significantly reducing productivity. Therefore, Si is preferably 2.000% or less, preferably 1.000% or less, 0.500% or less, and more preferably 0.300% or less. The lower limit of Si is not particularly limited, but if it is too low, deoxidation is insufficient, the concentration of Cr2O3 in the inclusions increases, and inclusions that induce processing fracture are easily formed. Therefore, the lower limit of Si is 0.050%, preferably 0.100%.

[0073] Mg is used in the deoxidation of steel. However, if the Mg content exceeds 0.0005%, coarse inclusions may be formed. Furthermore, to avoid the formation of spinel, a lower Mg content is preferred. Therefore, the Mg content is 0.0005% or less, preferably 0.0003% or less, 0.0002% or less, and more preferably 0.0001% or less.

[0074] Al is also used in the deoxidation of steel. However, if the Al content exceeds 0.030%, coarse inclusions may be formed, resulting in poor etching. Furthermore, to avoid the formation of spinel, the Al content is preferably low. Therefore, the Al content is 0.030% or less, preferably 0.020% or less, 0.010% or less, and more preferably 0.005% or less.

[0075] P and S are elements that combine with alloying elements such as Mn in ferrous alloys to form inclusions, and therefore their content is preferably low. Thus, the P content is 0.045% or less, preferably 0.010% or less, 0.007% or less, and more preferably 0.005% or less. The S content is 0.007% or less, and more preferably 0.005% or less.

[0076] Like carbon (C), nitrogen (N) is also a solid solution strengthening element. A high concentration increases toughness by 0.2%, hardening the steel. Conversely, a high concentration significantly deteriorates manufacturability; therefore, the upper limit for N content is 0.200%.

[0077] The remaining portion of the steel composition described above consists of Fe and unavoidable impurities. Here, "unavoidable impurities" refers to components that, during the industrial manufacturing of steel, are introduced due to various reasons from raw materials such as ores or waste, and are considered permissible substances within the scope that do not adversely affect the present invention.

[0078] When the stainless steel foil of the present invention is a ferritic stainless steel foil, the stainless steel foil has the following composition: by mass%, it contains C: 0.120% or less, Si: 0.050 to 2.000%, Mn: 0.100 to 1.250%, P: 0.040% or less, S: 0.030% or less, Cr: 15.000 to 20.000%, N: 0.025% or less, Al: 0.030% or less, Mg: 0.0005% or less, Ca: 0.0005% or less, and the remainder consists of Fe and impurities.

[0079] Cr is an alloying element required to improve corrosion resistance. However, if there is an excess of Cr, the steel will harden and its machinability will deteriorate; therefore, the Cr content should be below 20.000%. There is no particular lower limit to the Cr content, but adding Cr at a content of 15.000% or more has a significant effect, hence the requirement of 15.000% or more.

[0080] C (carbon) may not be specifically present. If C is present in excess, the coefficient of thermal expansion increases, and the amount of Cr-based inclusions precipitated at the grain boundaries increases, leading to the formation of larger inclusion particles. Therefore, the C content is 0.120% or less, preferably 0.100% or less, and more preferably 0.050% or less.

[0081] Ca dissolves in sulfides, causing them to disperse finely and spherically shape. On the other hand, if a large amount of Ca is present, the Ca not dissolved in the sulfides forms coarse oxides, which may result in poor etching. Therefore, it is not necessary to specifically contain Ca, but if it is present, the amount of Ca should be 0.0005% or less, preferably 0.0001% or less.

[0082] To avoid spinel formation, Mn is actively used as a deoxidizer, replacing Mg and Al. However, if the Mn content is too high, it segregates to the grain boundaries, promoting grain boundary damage and reducing resistance to hydrogen embrittlement. Therefore, the Mn content is 1.250% or less. Preferably, it is 0.800% or less, 0.600% or less, and more preferably 0.500% or less. However, if the Mn content is too low, it is difficult to adjust the inclusions to a Mn(O,S)-SiO2 system composition. Therefore, the Mn content is 0.100% or more. Here, Mn(O,S) refers to MnO monomers, MnS monomers, and inclusions composed of MnO and MnS. The ratio of O to S is not fixed, indicating inclusions composed of oxides and sulfides.

[0083] Si is used to actively deoxidize stainless steel, replacing Mg and Al, to avoid spinel formation. However, Si increases the coefficient of thermal expansion of stainless steel. Furthermore, the deoxidation product MnO-SiO2 is a vitrified, soft inclusion that extends and fractures during hot rolling, becoming finer. Therefore, resistance to hydrogen embrittlement is improved. On the other hand, if the Si content exceeds 2.000%, the strength increases, leading to excessive hardening. In cold working, more passes are required to roll thin sheets to the desired thickness, significantly reducing productivity. Therefore, Si content is preferably 2.000% or less, more preferably 1.000% or less, 0.500% or less, and even more preferably 0.300% or less. The lower limit of Si is not particularly limited, but if it is too low, deoxidation is insufficient, the concentration of Cr2O3 in the inclusions increases, and inclusions that induce processing fracture are easily formed. Therefore, the lower limit of Si is 0.050%, preferably 0.100%.

[0084] Mg is used in the deoxidation of steel. However, if the Mg content is higher than 0.0005%, coarse inclusions may be formed. Furthermore, to avoid the formation of spinel, the Mg content is preferably low. Therefore, the Mg content is 0.0005% or less, preferably 0.0003% or less, 0.0002% or less, and more preferably 0.0001% or less.

[0085] Al is also used in the deoxidation of steel. However, if the Al content is higher than 0.030%, coarse inclusions may be formed, resulting in poor etching. Furthermore, to avoid the formation of spinel, the Al content is preferably low. Therefore, the Al content is 0.030% or less, preferably 0.020% or less, 0.010% or less, and more preferably 0.005% or less.

[0086] P and S are elements that combine with alloying elements such as Mn in ferrous alloys to form inclusions, and therefore their content is preferably low. Thus, the P content is 0.040% or less, preferably 0.010% or less, 0.007% or less, and more preferably 0.005% or less. The S content is 0.030% or less, more preferably 0.010% or less, 0.007% or less, and even more preferably 0.005% or less.

[0087] Like carbon, nitrogen (N) is also a solid solution strengthening element. A high concentration increases toughness by 0.2%, hardening the steel. Conversely, a high concentration significantly worsens manufacturability; therefore, the upper limit for N content is 0.025%.

[0088] The remaining portion of the above-mentioned steel composition consists of Fe and impurities. Here, "impurities" refers to components that are mixed into the steel during industrial manufacturing, represented by raw materials such as ores or waste, for various reasons. It refers to substances that are permissible within the scope that do not adversely affect the present invention.

[0089] [Miscellaneous materials]

[0090] Inclusions are preferred to be few, ideally none at all, but they are introduced during manufacturing or generated from the steel composition, making complete absence difficult to achieve. As mentioned earlier, large inclusions on the surface can detach during rolling, easily causing pitting. Therefore, it is important to minimize inclusions with a particle size of 5 μm or larger than the equivalent circle diameter.

[0091] The inventors of this invention focused on the basic components of inclusions: Al₂O₃, MgO, SiO₂, CaO, Mn(O, S), and CrS. It was understood that in the case of soft inclusions such as SiO₂, CaO, Mn(O, S), and CrS, these inclusions are difficult to cluster, are low-melting-point and soft, and therefore tend to stretch or break up during rolling, suppressing coarsening. On the other hand, hard inclusions such as alumina or magnesium-aluminum spinel, due to their high interfacial energy, tend to segregate and agglomerate during solidification, resulting in larger agglomerated particles. Furthermore, it was understood that alumina or spinel inclusions are hard and therefore difficult to stretch or break up during rolling, resulting in larger inclusion particles remaining.

[0092] Based on these insights, it is important to consider that: the generation of soft inclusions should be suppressed, and the generated soft inclusions should be refined by adjusting rolling conditions (e.g., rolling rate). On the other hand, hard inclusions are difficult to refine by rolling, so hard inclusions should not be generated or mixed in, and even if they are generated or mixed in, they should not be agglomerated (or coarsened).

[0093] First, in order to prevent the formation of inclusions regardless of whether it is a soft or hard stainless steel system, and to ensure the mechanical strength of the stainless steel foil, the steel composition can be set as described above.

[0094] To avoid the introduction of inclusions, it is important to re-evaluate the process. For example, re-evaluate the refractory used in molten metal processing and use refractory with less Al or Mg.

[0095] Furthermore, one reason for inclusion aggregation is segregation during solidification of molten metal. Avoiding segregation during solidification is not easy, but methods such as stirring the molten metal can be considered to minimize aggregation. Moreover, this can be achieved by manufacturing steel ingots using processes that do not involve solidification from molten metal, such as HIP (thermal hydrostatic pressing). The manufacturing process will be explained later.

[0096] For measurement purposes, the inclusions contained in the stainless steel foil of the present invention are defined as inclusions with a particle size (equivalent circle diameter) of 2.00 μm or more (hereinafter, unless otherwise specified, they are sometimes referred to as "inclusions"). Coarse inclusions with a particle size greater than 5.00 μm are detrimental and should be minimized as much as possible. Therefore, inclusions with a particle size of 2.00 to 5.00 μm are preferably minimized, but are not necessarily directly detrimental.

[0097] Furthermore, hard inclusions such as alumina or spinel tend to be coarse, so it is best to minimize them. Therefore, relative to the total mass of inclusions with a particle size of 2.00 μm or larger, Al2O3 is 30% by mass or less, and MgO is 10% by mass or less. These hard inclusions are preferably minimal, so the proportion of Al2O3 is preferably 25% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, and more preferably 5% by mass or less, 3% by mass or less, or 1% by mass or less. The proportion of MgO is preferably 8% by mass or less, 6% by mass or less, 5% by mass or less, and more preferably 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less.

[0098] Furthermore, the stainless steel foil of the present invention is characterized in that the number of inclusions with a spherical equivalent particle size greater than 5.00 μm present on the surface of the stainless steel foil is 20 per cm. 2 the following.

[0099] According to the present invention, the proportion of inclusions with a particle size greater than 5.00 μm contained in the stainless steel foil coated with a planarization film needs to be limited to 20 inclusions / cm on the surface of the stainless steel foil. 2The pits on the surface of stainless steel foil are caused by cracks in the planarization film. This is because, during rolling after the plate thickness is reduced to a certain extent and the inclusions are refined to a certain degree, inclusions with a particle size of 5.00 μm or larger existing on the surface of the stainless steel foil detach from the surface, thus creating the pits.

[0100] The particle size of inclusions was determined as follows. Inclusions on the surface of a stainless steel foil were observed using a scanning electron microscope (SEM). For example, a JSM-IT500HR manufactured by Nippon Electronics could be used as the SEM. An example of the SEM setup is shown.

[0101] • Detector: BED-C reflective electron detector

[0102] • Observation magnification: 80x

[0103] Accelerating voltage: 20.0kV

[0104] • Working distance (WD): 10.0mm

[0105] • Irradiation current: 80%

[0106] Furthermore, inclusions are detected in images obtained via SEM using automated inclusion analysis software, and compositional analysis of the inclusions is performed in an energy dispersive X-ray spectrometer (hereinafter, the EDS apparatus). For example, the particle analysis mode of Aztec, manufactured by Oxford Corporation, can be used for automated inclusion analysis software. The EDS apparatus can be, for example, the ULTIM MAX 65, manufactured by Oxford Corporation.

[0107] In the inclusion identification process performed by the automatic inclusion analysis software, an SEM image is first obtained. Next, if the automatic inclusion analysis software detects an equivalent circle diameter of 2.00 μm or larger in the image obtained from the SEM, and detects one or more of the elements Al, Mg, Si, Ca, Mn, and S through EDS, it is identified as an inclusion. The image after EDS analysis is combined with the software and output as a single image. At this time, the equivalent circle diameter and elemental composition of the inclusions identified by the automatic inclusion analysis software are also obtained. The inclusion identification steps described above are repeated until a predetermined area is reached. For example, the measured area of ​​the image is 10 cm². 2 As a measurement unit of 1 field of view, 10 fields of view were measured, totaling 100cm. 2 The area is used as the evaluation area. In addition, the diameter of a circle with the same area as the measured inclusion is taken as the equivalent circle diameter, which is used as the "particle size".

[0108] As mentioned above, the particle size of inclusions is determined by observing the surface of the stainless steel foil. However, it is clear that the particle size of inclusions present on the surface of the stainless steel foil is not significantly different from that of inclusions present in the stainless steel foil.

[0109] The composition of inclusions was calculated for each inclusion identified by the automatic inclusion analysis software as follows: First, the mass percentages of elements Al, Mg, Si, Ca, Mn, Cr, and S obtained through EDS analysis were divided by their atomic weights to obtain the apparent mass of each element. Next, these seven elements were designated as the basic components of the inclusions, i.e., oxides or sulfides. In the inclusions, Al, Mg, Si, and Ca mainly exist as oxides.

[0110] Mn and Cr mainly exist as sulfides, with Mn sometimes also existing as the oxide MnO. Besides the aforementioned sulfide MnS, S sometimes exists as the chromium sulfide CrS. When the apparent mass of S is greater than that of Mn, MnS exists in an amount equal to the apparent mass of Mn; in this case, the amount of CrS is the amount of apparent mass of S minus the apparent mass of Mn. When the apparent mass of S is less than that of Mn, MnS exists in an amount equal to the apparent mass of S; in this case, the amount of MnO is the amount of apparent mass of Mn minus the apparent mass of S. When the apparent mass of Mn and S are completely equal, MnS exists in an amount equal to the mass of both Mn and S.

[0111] Since the inclusions are set as being in the state of oxides or sulfides, the apparent mass of element O (oxygen) or S is assigned according to the stoichiometric ratios of Al:O = 2:3, Mg:O = 1:1, Si:O = 1:2, Ca:O = 1:1, Mn:O = 1:1, Mn:S = 1:1, and S:Cr = 1:1. This mass is then multiplied by the respective molecular weight to derive the equivalent mass of the oxides. The equivalent mass of each oxide is then calculated by dividing the sum of the seven equivalent masses of oxides by the calculated equivalent masses of each of the seven oxides. The equivalent mass percentages of oxides for Al2O3, MgO, SiO2, CaO, MnO, MnS, and CrS (sometimes referred to as "oxides, etc.") are then obtained. The area of ​​the inclusions obtained by the automatic inclusion analysis software is multiplied by the seven equivalent mass percentages of oxides to obtain the inclusion area (μm) of Al2O3, MgO, SiO2, CaO, MnO, MnS, and CrS. 2 ).

[0112] Next, the area of ​​each inclusion identified by the automatic inclusion analysis software was calculated. The areas of each of the seven oxides or sulfides were summed to obtain the total areas of Al₂O₃, MgO, SiO₂, CaO, MnO, MnS, and CrS. This sum of seven areas was taken as the total area of ​​all inclusions. The inclusion composition ratio (mass %) was calculated by dividing the total area of ​​each oxide by the total area of ​​all inclusions.

[0113] The number density of inclusions with a particle size greater than 5.00 μm was set to 20 inclusions / cm³. 2 Therefore, the inclusions that cause pitting on the surface of the stainless steel foil, which are the cause of cracks in the planarization film, are reduced. Inclusions with a particle size greater than 5.00 μm are preferably fewer, preferably 15 per cm. 2 Below, 12 per cm 2 Below, 10 per cm 2 The preferred value is 8 per cm. 2 Below, 6 per cm 2 Below, 5 per cm 2 the following.

[0114] [Plate thickness]

[0115] The stainless steel foil used in this invention has a thickness of 5.0 μm to 100.0 μm. When the thickness exceeds 100.0 μm, flexibility as a foil cannot be expected, and the lightweight advantage, a significant characteristic of foils, is lost. Stainless steel foils thinner than 5.0 μm are very prone to bending or wrinkling during processing, making them difficult to adapt to industrial processes. Simultaneously, the strength of the substrate decreases, leading to reliability issues during use. Furthermore, such thin stainless steel foils are inherently expensive materials from an industrial perspective. In addition, the thickness of the stainless steel foil used in this invention can be measured using a contact micrometer. A thickness of 10.0 μm to 80.0 μm is more preferred in preventing cracks in the planarization film.

[0116] The method for manufacturing the stainless steel foil with a planarization film of the present invention will be described.

[0117] The stainless steel foil of the present invention can be manufactured, for example, in the following manner, but the method shown below is illustrative and is not intended to limit the invention to this method.

[0118] For example, in 10 －1In a vacuum atmosphere below (Torr), raw materials adjusted to a specified composition are vacuum melted to obtain molten metal of the target alloy composition. At this time, in order to deoxidize the molten metal, Mn and Si are added in such a way that the Mn and Si contents of the molten metal after slag removal are respectively specified.

[0119] Next, inert gases such as Ar or N2 are used to atomize (powder) the molten metal through gas spraying. To reduce the viscosity of the molten metal, the temperature of the molten metal during gas spraying is preferably set within the range of +50°C to 200°C from its melting point. Furthermore, the gas flow rate (m³ / s) during gas spraying... 3 The ratio of ( / min) / molten metal flow rate (kg / min) is set to 0.3 (m 3 / kg or above is acceptable. Gas flow rate (m³ / kg) 3 The ratio of ( / min) to molten metal flow rate (kg / min) is less than 0.3 (m 3 When the liquidus rate is reduced to 6 kg / kg, the liquidus rate of the droplets when they collide with the surface of the ingot is too high, resulting in coarser inclusions.

[0120] Therefore, the ratio of gas flow rate to molten metal flow rate is set to 0.3 (m³ / s). 3 The concentration of gas flow rate (m³ / kg) is above 0.5, preferably above 0.7, above 0.9, above 1.0, or above 1.5, and more preferably above 2.0. 3 The upper limit of the ratio of (kg / min) to molten metal flow rate (kg / min) is not specifically limited, but is 5.0 (m³ / min). 3 When the cooling capacity exceeds 5.0 (m³ / kg), the cooling capacity reaches saturation; therefore, the upper limit can be set to 5.0 (m³ / kg). 3 / kg).

[0121] The alloy powder obtained from the atomization process is sintered by hot pressing or HIP (High-Intensity Interval Pressing) to produce steel ingots. The sintering method is not particularly limited; appropriate conditions can be set according to common methods such as hot pressing.

[0122] Smaller alloy powder particles are easier to sinter, but have lower productivity compared to larger particle sizes. On the other hand, larger alloy powder particles are more likely to be contaminated with impurities from the furnace material. Therefore, the particle size of the alloy powder is preferably 300 μm or less, more preferably 250 μm or less, 200 μm or less, 150 μm or less, and even more preferably 100 μm or less.

[0123] The aforementioned atomization (powdering) method can suppress the presence of Al or Mg. Furthermore, if the sintering method is a solid-state treatment, it will not introduce Al or Mg from the refractory as in the solidification method (casting), thus suppressing the formation of coarse inclusions (e.g., larger than 5 μm). For these reasons, the formation of Al2O3 or spinel-based inclusions is ultimately reduced, and the formation of coarse inclusions larger than 5 μm is particularly significantly suppressed.

[0124] Next, the manufactured alloy steel ingot is processed by hot forging, cutting, or grinding to produce steel sheets, which are then rolled to a thickness of 3.0 mm to 200 mm. This rolling can be either hot rolling or cold rolling. The rolled sheet with a thickness of 3.0 mm to 200 mm is repeatedly rolled to form a stainless steel foil with a thickness of 100.0 μm or less. The lower limit of the sheet thickness is 5.0 μm to achieve the desired effect of this invention.

[0125] Annealing processes can also be performed before or after hot rolling, hot forging, or cold rolling of the steel ingot. Furthermore, the temperatures in the annealing, hot forging, and hot rolling processes are lower than the melting point of the iron-based alloy of the present invention to prevent the agglomeration of inclusions. Preferably, these temperatures are set within the range of -500°C or higher and -200°C or lower than the melting point of the iron-based alloy of the present invention.

[0126] Cold rolling can be performed after hot rolling or hot forging. Intermediate annealing can also be carried out during the cold rolling process. Through rolling, inclusions, especially soft inclusions, are extended and broken up, thus refining them. Cold rolling is more effective than hot rolling at refining inclusions, and the thinner the plate, the better. Therefore, based on the plate thickness after hot rolling (the plate thickness before cold rolling), the total rolling ratio of cold rolling can be set to 96.0% or more. Preferably, it can be set to 97.0%, 98.0%, 99.0%, or 99.5% or more. Furthermore, a higher rolling ratio can result in better inclusion refinement; therefore, except for the passes for achieving the target plate thickness and the passes for shape correction, the rolling ratio in each pass can be set to 20.0% or more. By performing cold rolling at such a rolling ratio, soft inclusions can be further refined and dispersed through extension and breakage.

[0127] On the other hand, it is also known that during the final rolling process (final rolling) after the plate thickness is reduced to a certain extent and the inclusions are refined to a certain degree, the refinement of inclusions can lead to the formation of surface irregularities due to inclusion shedding, or the formation of pinholes penetrating the stainless steel foil. Therefore, in the final rolling process (multi-stage rolling) from a plate thickness of 10 to 80 μm thicker than the final plate thickness to the final plate thickness, a gentle rolling process can be set to control the unit rolling load (kN / mm) of each pass within an appropriate range. The unit rolling load is the value obtained by dividing the load applied to the workpiece by the width of the workpiece. For example, the unit rolling load can be set to 0.4 to 1.3 kN / mm, and the cumulative rolling rate can be set to 50.0% or more. If the unit rolling load is less than 0.4 kN / mm, the processing heat generated during rolling is relatively small, reducing the flexibility of the alloy foil as the workpiece. This leads to cracks at the interface between the inclusions and the alloy foil, increasing the likelihood of inclusion detachment. Furthermore, if the load is higher than 1.3 kN / mm, processing heat increases, but the plastic deformation of the alloy foil itself also increases, resulting in cracks at the interface with inclusions and further inclusion detachment. Additionally, if the cumulative rolling percentage at the end of the rolling process is less than 50.0%, the strength of the alloy foil may not be fully realized. While there is no specific upper limit to the cumulative rolling percentage at the end of the rolling process, it is generally acceptable to set it below 98.0% based on the capacity of a typical foil rolling mill.

[0128] Furthermore, in order to suppress the formation of surface irregularities caused by the shedding of inclusions, the final rolling rate for achieving the final plate thickness can be set to 0.2% to 3.0%. Here, the rolling rate, when the plate thickness before rolling is set as t1 and the plate thickness after rolling is set as t2, is expressed by the following formula.

[0129] Rolling rate = (t1 - t2) / t1

[0130] For example, although the cumulative rolling rate of the final rolling is multi-stage, the plate thickness before the final rolling is set as t1, and the plate thickness after the final rolling is set as t2. For the rolling rate of each pass, the plate thickness before each rolling pass is set as t1, and the plate thickness after that rolling pass is set as t2.

[0131] Furthermore, annealing can be performed after final rolling to relieve stress.

[0132] [Composition of the planarization film]

[0133] The planarization film used in the manufacture of the stainless steel foil with planarization film of the present invention is a silicon dioxide-based inorganic-organic composite film.

[0134] [Silica-based inorganic-organic composite membrane]

[0135] Silica-based inorganic-organic composite films typically possess structures based on silicon, containing R₂Si(OR')₂, RSi(OR')₃, or Si(OR')₄. They are obtained by coating a solution hydrolyzed and condensed in a solvent, followed by heat treatment. Here, R represents any organic group, and R' represents an alkyl group. R₂Si(OR')₂, RSi(OR')₃, and Si(OR')₄ correspond to the D (difunctional), T (trifunctional), and Q (tetrafunctional) cores of Si, respectively.

[0136] In silica-based inorganic-organic composite films constituting planarization films, the inclusion of Si (D) cores as constituent elements imparts flexibility to the film. However, during the high-temperature processes in device fabrication, the D cores form and separate into three-membered rings, negatively impacting device characteristics. Therefore, it is desirable for the Si cores constituting the planarization film to be silica-based inorganic-organic composite films composed solely of T and Q cores. When the proportion of Q cores relative to all Si cores exceeds 70%, the density of Si-O bonds in the film becomes excessively high, making the film prone to crack formation and unsuitable. The T cores have only one organic group directly bonded to Si, thus imparting flexibility to the film. A Q core proportion of less than 70% is preferable.

[0137] The organic groups R directly bonded to Si that constitute the silica-based inorganic-organic composite film of the present invention are not particularly limited. For example, from the viewpoint of heat resistance, methyl and phenyl groups are preferred. Methyl and phenyl groups may be contained individually or simultaneously. The type and amount of Si cores in the planarized film can be determined by 29Si-NMR determination. The organic groups directly bonded to Si can be investigated by FTIR or a combination of 13C-NMR and 1H-NMR.

[0138] [Coating solution for forming silica-based inorganic-organic composite films]

[0139] Silica-based inorganic-organic composite films can be fabricated by various methods. In the case of phenyl-modified silica films, they can be fabricated, for example, by a coating solution as shown below. The methods described below are illustrative and are not intended to limit the scope of the method.

[0140] The coating solution is prepared by adding 0.1 to 1 mol of phenyltrialkoxysilane and 0.005 to 0.050 mol of acetic acid as a catalyst to 1 mol of phenyltrialkoxysilane in an organic solvent, followed by hydrolysis with 2.0 to 4.0 mol of water. The organic solvent used in the hydrolysis of phenyltrialkoxysilane, water as a reaction byproduct, and resin obtained by vacuum distillation of ethanol are dissolved in an aromatic hydrocarbon solvent at a temperature of 160°C to 210°C.

[0141] Examples of phenyltrialkoxysilanes used here include phenyltrimethoxysilane, phenyltriethoxysilane, and phenyltripropoxysilane.

[0142] Examples of organic solvents used in the hydrolysis of phenyltrialkoxysilane include methanol, ethanol, and propanol.

[0143] The organic solvents distilled off during vacuum distillation include, in addition to the organic solvents used in the hydrolysis of phenyltrialkoxysilane, ethanol generated from the hydrolysis of phenyltrialkoxysilane. Furthermore, water, sometimes generated from the condensation reaction accompanying the hydrolysis of phenyltrialkoxysilane, may also be present.

[0144] Examples of aromatic hydrocarbon solvents include toluene and xylene. Other organic solvents can also be mixed with aromatic hydrocarbon solvents, provided that their properties are not affected.

[0145] Organotin compounds are catalysts that promote the polycondensation of phenyltrialkoxysilanes and their hydrolysis-condensation products, or phenyl-containing ladder polymers. Examples of organotin compounds include dibutyltin diacetate, bis(acetoxydibutyltin) oxide, diacetylacetone dibutyltin, dibutyltin bismaleate, dioctyltin bismaleate, and bis(lauryl dibutyltin) oxide.

[0146] The silica-based inorganic-organic composite film is formed by coating the above-mentioned coating liquid onto the surface of a stainless steel foil and curing it in an inert gas atmosphere at a heat treatment temperature of 300°C to 450°C, preferably with a film thickness of 0.3 μm to 5.0 μm.

[0147] In the case of a silica-based inorganic-organic composite film, which is a methyl-modified silica film, it can be made, for example, from a coating solution as shown below.

[0148] A coating solution obtained by hydrolyzing and condensing 0.6 mol of methyltriethoxysilane and 0.4 mol of tetramethoxysilane in 12.0 mol of ethanol with 2.0 mol of water and 0.1 mol of acetic acid, with a thickness of 1.0 μm, is applied and then heat-treated at 450 °C for 10 minutes under nitrogen atmosphere to obtain a film. The film exhibits a methyl-bonded T-core ratio of 60% and a Q-core ratio of 40%. Besides tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and colloidal silica can also be used as raw materials for the Q-cores. Methyltrimethoxysilane can also be used in combination with other raw materials.

[0149] Sometimes, due to the heat treatment temperature and the gas atmosphere during the coating process, the organic groups of the organic alkoxysilane in the raw material undergo thermal decomposition in silica-based inorganic-organic composite films, causing Si to transform from T-cores to Q-cores. Therefore, when a coating solution containing 1.0 mole of methyltrimethoxysilane (a raw material for T-cores) is hydrolyzed and condensed in 8.0 moles of methanol using 3.0 moles of water and 0.01 moles of nitric acid, and then coated with a 0.4 μm thick film, a heat treatment of 500°C for 1 minute in nitrogen containing 0.1% oxygen is performed. In the planarized film, the Si content of the T-cores bonded by methyl groups is 98%, while the Si content of the Q-cores after the thermal decomposition of methyl groups is 2%. On the other hand, when the same coating solution is coated with a 0.4 μm thick film onto a stainless steel foil and then heat-treated at 500°C for 1 minute in nitrogen, the Si content of the T-cores bonded by methyl groups becomes 100%.

[0150] The thickness of the silica-based inorganic-organic composite film formed on stainless steel foil is 0.3 μm to 5.0 μm. If the thickness is thinner than 0.3 μm, the surface coverage of the stainless steel foil is insufficient, leading to short circuits between the stainless steel foil and the device. Alternatively, the surface of the silica-based inorganic-organic composite film may not be sufficiently flat, causing delamination of the electrode or semiconductor layers constituting the device, which is unsuitable. If the thickness is greater than 5.0 μm, cracks are prone to form in the film. Cracks are not only prone to form during film fabrication but also when the stainless steel foil covered by the planarization film is bent as a flexible substrate. From the viewpoint of covering the surface of the stainless steel foil and preventing cracks, a film thickness of 0.5 μm to 3.5 μm is more preferable.

[0151] Example

[0152] Next, the present invention will be further described with reference to embodiments. It should be noted that the present invention is not limited to the embodiments shown herein.

[0153] For samples 1 and 2, molten stainless alloys with compositions shown in Table 1 were prepared using a vacuum induction melting furnace and then pulverized via N2-based gas spraying. To reduce the viscosity of the molten metal, the temperature of the molten metal during gas spraying was set within the range of liquidus temperature +50°C to +200°C. Furthermore, the gas flow rate (m³ / s) during gas spraying was... 3 The ratio of ( / min) / molten metal flow rate (kg / min) is adjusted to 1.0~3.0 (m 3 / kg).

[0154] Next, the obtained alloy powder was sealed in a metal container, and steel ingots of samples 1 and 2 were manufactured by the known HIP process.

[0155] For samples 3 and 4, molten metals of stainless alloy composition as shown in Table 1 were prepared by adjusting the composition in a vacuum induction melting furnace. The molten metals were then transferred to a mold and solidified therein to produce steel ingots. During this process, the refractory material flowing into the tundish or inside the mold was the same as that used in normal operation.

[0156] A portion of samples 1 and 2, along with ingots from samples 3 and 4, were hot-forged to produce steel sheets with a cross-section of 80 mm × 80 mm. These sheets were then hot-rolled to a thickness of 3.0 mm and subsequently cold-rolled to obtain a steel plate with a thickness of 0.30 mm. The resulting steel plate was then cold-rolled, with the rolling rate set to at least 20.0% in each pass (except for passes for achieving the target plate thickness or for shape correction) to obtain steel foil with a thickness 50 μm greater than the final plate thickness. The steel foil obtained from samples 1 and 2 was then final-rolled to produce stainless steel foil with thicknesses of 5.0 μm, 10.0 μm, 25.0 μm, 50.0 μm, and 100.0 μm. The steel foil obtained from samples 3 and 4 was then final-rolled to produce a stainless steel foil with a thickness of 50.0 μm. At this point, the unit rolling load was set to 0.4–1.3 kN / mm, and the final rolling rate was set to 0.2–3.0%. In addition, stress annealing is performed to remove the stress caused by cold rolling.

[0157] The stainless steel foils manufactured from Sample 1 were designated as Sample 1-1, 1-2, 1-3, 1-4, and 1-5 in the order of thickness: 5.0 μm, 10.0 μm, 25.0 μm, 50.0 μm, and 100.0 μm. Similarly, the stainless steel foils manufactured from Sample 2 were designated as Sample 2-1, 2-2, 2-3, 2-4, and 2-5. The stainless steel foil manufactured from Sample 3 was designated as Sample 3-1, and the stainless steel foil manufactured from Sample 4 was designated as Sample 4-1.

[0158] A portion of the steel ingots from samples 1 and 2 were hot-forged to produce steel billets with a cross-section of 80 mm × 80 mm. These billets were then hot-rolled to a thickness of 3.0 mm and subsequently cold-rolled to obtain a steel sheet with a thickness of 0.30 mm. The cold-rolled steel sheet, except for passes for achieving the target thickness and for shape correction, had a rolling rate of less than 20.0% in each pass, resulting in a steel foil with a thickness 50.0 μm thicker than the final sheet thickness. This steel foil was then final-rolled to produce a stainless steel foil with a thickness of 50.0 μm. The final rolling rate was set to 5.0%. Furthermore, stress annealing was performed to remove stress caused by cold rolling. The stainless steel foil manufactured from sample 1 was designated as samples 1-6, and the stainless steel foil manufactured from sample 2 was designated as samples 2-6.

[0159] [Table 1]

[0160]

[0161] Prepare a coating solution for forming a phenyl-containing silica-based inorganic-organic composite film. First, prepare the solution in a 1L flask according to the formulation shown in Table 2, mixing the raw materials in a total volume of 0.7L. After mixing, stir and mix the raw materials with a magnetic stirrer for 15 minutes. To promote hydrolysis, reflux at 80°C for 3 hours under a nitrogen atmosphere. Then, using a rotary evaporator with the oil bath set to 80°C, distill the solvent under reduced pressure to obtain the condensation product. Next, add toluene in equal weight to the condensation product to dissolve it. Connect the 1L flask to a reflux reflux unit equipped with a Diane-Stark water separator and heat under reflux. Table 2 shows the oil bath set temperature and reflux time during heating under reflux. After heating and reflux, toluene is added to dilute the solution to a solid content of 30% by mass. A filter with a pore size of 5 μm is used for vacuum filtration to prepare a coating solution for forming a phenyl-containing silica-based inorganic-organic composite membrane.

[0162] [Table 2]

[0163]

[0164] On one side of each manufactured stainless steel foil, a phenyl-containing silica-based inorganic-organic composite film was formed using a die coating machine with film thicknesses of 0.3, 3.0, and 5.0 μm. A 3m long drying oven was used at 100°C, and the foil was transported at a speed of 5 mpm while simultaneously attaching a micro-adhesive protective film (PAC3J-30H). Next, while peeling off the protective film, the foil was transported at 1 mpm through a 6m long hot air drying oven at 400°C under a nitrogen atmosphere, while simultaneously attaching a micro-adhesive protective film (PAC3J-30H), resulting in a stainless steel foil roll with a planarization film. 29Si-NMR confirmed that all Si cores were T cores. FTIR confirmed that the organic groups were phenyl.

[0165] Prepare a coating solution for forming a methyl-containing silica-based organic-inorganic composite film. Hydrolyze and condense 0.5 mol of methyltriethoxysilane and 0.5 mol of tetramethoxysilane in 6.0 mol of 2-ethoxyethanol with 2.0 mol of water and 0.1 mol of acetic acid. Then, add 6.0 mol of MEK and mix to proceed with the synthesis.

[0166] On one side of each manufactured stainless steel foil, a methyl-containing silica-based inorganic-organic composite film was formed to a thickness of 1.0 μm using a die-coating machine. A drying oven with a length of 3 m and a temperature of 150 °C was used, and the foil was transported at a speed of 5 mpm while simultaneously applying a micro-adhesive protective film (PAC3J-30H). Next, while peeling off the protective film, the foil was transported at a speed of 1 mpm through a hot air drying oven with a nitrogen atmosphere and a length of 6 m, at a temperature of 420 °C, while simultaneously applying a micro-adhesive protective film (PAC3J-30H), resulting in a stainless steel foil roll with a planarization film. 29Si-NMR confirmed that the Si cores were 50% T-cores and 50% Q-cores. FTIR confirmed that the organic group was methyl.

[0167] Tables 3, 4, 5, 6, 7, and 8 show the results of the evaluation of inclusions, flatness, and insulation reliability for the stainless steel foil with a planarization film manufactured as described above. Here, the observation of inclusions is performed on the surface of the stainless steel foil without a planarization film, and the flatness or insulation reliability is evaluated on the surface with a planarization film (corresponding to the back side of the stainless steel foil surface on which the inclusion evaluation was performed).

[0168] Inclusions on the surface of stainless steel foil without a planarization film were observed using a SEM (JSM-IT500HR manufactured by Nippon Electronics Corporation). A correlation was observed between the number of inclusions observed on the surface of the stainless steel foil without a planarization film and the number of measurement points for leakage current measured on the surface with a planarization film. The SEM settings are as follows.

[0169] • Detector: BED-C reflective electron detector

[0170] • Observation magnification: 80x

[0171] Accelerating voltage: 20.0kV

[0172] • Working distance (WD): 10.0mm

[0173] • Irradiation current: 80%

[0174] In addition, inclusions were detected in images acquired by SEM using automatic inclusion analysis software (Aztec Particle Analysis Mode manufactured by Oxford), and the composition analysis of inclusions was performed in an EDS device (ULTIM MAX 65 manufactured by Oxford).

[0175] In the inclusion identification process performed by the automatic inclusion analysis software, SEM images used in the software are first acquired. Next, inclusions with an equivalent circle diameter of 2.00 μm or larger are detected in the SEM image by the automatic inclusion analysis software, and at least one of the elements Al, Mg, Si, Ca, Mn, and S is detected by EDS. The images obtained after EDS analysis are combined in the software and output as a single image. At this time, the particle size and elemental composition of the inclusions identified by the automatic inclusion analysis software are also acquired. The evaluation area is set to 100 cm². 2 The equivalent circle diameter is used as the particle size of the inclusions.

[0176] The composition of the inclusions is calculated based on the oxide equivalents of Al2O3, MgO, and [other components] identified by the inclusion automatic analysis software.

[0177] [per 100cm] 2 1μA / mm 2 [Number of leakage current measurement points above]

[0178] A planarization film is formed on the surface of a stainless steel foil to prepare a test piece. A liquid with a conductivity of 0.1 S / m to 100 S / m and a cross-sectional area of ​​1 mm² is impregnated with the film. 2 The above 25mm 2 The electrode below is designated as the upper electrode, and the stainless steel foil is referred to as the lower electrode. The surface of the test piece is scanned through the aforementioned upper electrode, and the leakage current is measured to be 1 μA / mm when 10V is applied between the aforementioned upper electrode and the aforementioned lower electrode. 2 The number of positions listed above.

[0179] Flatness

[0180] The aforementioned test piece was measured to have a flow rate of 1 μA / mm. 2 The locations of the above leakage currents indicate that cracks have formed in the planarization film, and the height difference on the surface of the planarization film caused by the cracks leads to a decrease in planarity.

[0181] With a leakage current of 1μA / mm 2 The above points are at every 100cm 2 If the number of defects is less than 10, the flatness is judged as good "0"; if the number of defects is more than 10, the flatness is judged as unsuitable "×". Since the number of defects increases significantly when the number of defects is more than 10, less than 10 is set as good.

[0182] [Insulation Reliability]

[0183] Measured at 1μA / mm 2If the leakage current is less than 0 to 10 points, the insulation reliability will be rated as good "○"; if it is more than 10 points, the insulation reliability will be rated as unsuitable "×".

[0184] [Table 3]

[0185]

[0186] [Table 4]

[0187]

[0188] [Table 5]

[0189]

[0190] [Table 6]

[0191]

[0192] [Table 7]

[0193]

[0194] [Table 8]

[0195]

[0196] In samples 1-1, 1-2, 1-3, 1-4, 1-5, 2-1, 2-2, 2-3, 2-4, and 2-5, Al2O3 was suppressed to below 28.5% by mass, and MgO was suppressed to below 9.7% by mass. The inclusions that were difficult to refine through rolling, namely Al2O3 and MgO, were reduced, thus the number of inclusions with an equivalent circle diameter greater than 5 μm was suppressed to a low level of 8.8 inclusions / cm. 2 Therefore, it can be known that every 100cm 2 1μA / mm 2 The number of leakage current measurement points is reduced to less than 9.5, thus reducing the occurrence of cracks.

[0197] Furthermore, it is known that the thinner the plate, the finer the inclusions, with a decrease in the mass percentage of Al2O3, the mass percentage of MgO, and the number of inclusions with an equivalent circle diameter greater than 5 μm per 100 cm. 2 1μA / mm 2 The number of measurement points for leakage current has decreased.

[0198] The stainless steel foils in samples 1-6 and 2-6 had a rolling rate of less than 20% in each pass, which was insufficient to refine the inclusions. Therefore, they contained a relatively high amount of Al2O3 (over 43.1% by mass) and a relatively high amount of MgO (over 19.4% by mass). The number of inclusions with an equivalent circle diameter greater than 5 μm was also relatively high, at 30.7 inclusions / cm. 2 That's all. Therefore, for every 100cm 2 1μA / mm 2 The above leakage current was measured at more than 32 points, indicating that a large number of cracks were generated.

[0199] Furthermore, compared with samples 1-6 and 2-6, it can be seen that the rolling rates of samples 1-1, 1-2, 1-3, 1-4, 1-5, 2-1, 2-2, 2-3, 2-4, and 2-5, which were manufactured with changed rolling conditions, were all above 20% in each pass. The inclusions were refined, and the mass percentage of Al2O3, the mass percentage of MgO, and the number of inclusions with an equivalent circle diameter greater than 5 μm were reduced.

[0200] The stainless steel foils of samples 3-1 and 4-1 contained more than 35.1% by mass of Al2O3 and more than 11.3% by mass of MgO. The inclusions, namely Al2O3 and MgO, which are difficult to refine through rolling, were abundant, resulting in an equivalent circle diameter greater than 5 μm of up to 23.4 inclusions / cm. 2 That's all. Therefore, for every 100cm 2 1μA / mm 2 The number of leakage current measurement points is more than 30, indicating that a large number of cracks have been generated.

[0201] The results show that samples 1 and 2 can suppress the presence of Al or Mg, and there is no Al or Mg incorporation from the refractory as in samples 3 and 4. Therefore, Al2O3 or MgO is reduced, and the number of inclusions with equivalent circle diameters higher than 5 μm is reduced.

Claims

1. A stainless steel foil with a planarization film, It comprises a stainless steel foil, and at least one side of the stainless steel foil has a planarization film with a thickness of 0.3 μm or more and 5.0 μm or less. The stainless steel foil is an austenitic stainless steel foil and has the following composition: containing, by mass % C: Below 0.150% Si: 0.050~2.000% Mn: 0.100~10.000% P: below 0.045% S: Below 0.007% Ni: 2.000~15.000% Cr：15.000～20.000%、 N: below 0.200% Al: below 0.030% Mg: less than 0.0005% Ca: below 0.0005%, The remaining part consists of Fe and impurities. In the stainless steel foil: Compared to the total mass of inclusions with a particle size greater than 2.00 μm, Al2O3: less than 30% by mass, MgO: less than 10% by mass. Of the inclusions with a particle size of 2.00 μm or larger, the number of inclusions with a particle size of 5.00 μm or larger existing on the surface is 20 per cm. 2 the following, Furthermore, the stainless steel foil thickness is between 5.0μm and 100.0μm. The planarization film is a silicon dioxide-based organic-inorganic composite film, and the Si core constituting the organic-inorganic composite film is composed of T cores and Q cores.

2. The stainless steel foil with a planarization film according to claim 1, The proportion of Q cores relative to the Si cores constituting the organic-inorganic composite membrane is less than 70%.

3. A stainless steel foil with a planarization film, It comprises a stainless steel foil, and at least one side of the stainless steel foil has a planarization film with a thickness of 0.3 μm or more and 5.0 μm or less. The stainless steel foil is a ferritic stainless steel foil and has the following composition: containing, by mass % C: Below 0.120% Si: 0.050~2.000% Mn: 0.100~1.250%, P: below 0.040% S: Below 0.030% Cr：15.000～20.000%、 N: below 0.025% Al: below 0.030% Mg: less than 0.0005% Ca: below 0.0005%, The remaining part consists of Fe and impurities. In the stainless steel foil: Compared to the total mass of inclusions with a particle size greater than 2.00 μm, Al2O3: less than 30% by mass, MgO: less than 10% by mass. Of the inclusions with a particle size of 2.00 μm or larger, the number of inclusions with a particle size of 5.00 μm or larger existing on the surface is 20 per cm. 2 the following, Furthermore, the stainless steel foil thickness is between 5.0μm and 100.0μm. The planarization film is a silicon dioxide-based organic-inorganic composite film, and the Si core constituting the organic-inorganic composite film is composed of T cores and Q cores.

4. The stainless steel foil with a planarization film according to claim 3, The proportion of Q cores relative to the Si cores constituting the organic-inorganic composite membrane is less than 70%.

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