Multilayer polyimide film and method for manufacturing the same

Abstract

The present invention provides a multilayer polyimide film including a first skin layer and a second skin layer formed on one outer side and the opposite side of the outer side, respectively, of a core layer, the multilayer polyimide film having a thermal expansion coefficient of 2.0 ppm / °C or more and 6.0 ppm / °C or less and a moisture expansion coefficient of 3.0 ppm / RH% or more and 6.0 ppm / RH% or less, and a method for producing the same.

Description

Technical Field

[0001] The present invention relates to a multilayer polyimide film that is excellent in chemical resistance while having excellent dimensional stability. More specifically, it relates to a multilayer polyimide film having high thermal dimensional stability and dimensional stability against moisture, and excellent chemical resistance, and a method for producing the same.

Background Art

[0002] Polyimide (PI) is a polymer material based on an imide ring with a rigid aromatic main chain and extremely excellent chemical stability, and has the highest level of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials.

[0003] Polyimide films have attracted attention as materials for various electronic devices that require the above-described characteristics. Examples of microelectronic components to which polyimide films are applied include thin, flexible circuit boards with high circuit integration to accommodate the weight reduction and miniaturization of electronic products. Polyimide films are particularly widely used as insulating films for thin circuit boards.

[0004] The thin circuit board generally has a structure in which a circuit including a metal foil is formed on an insulating film. Such a thin circuit board is generally referred to as a Flexible Metal Foil Clad Laminate in a broad sense. When a thin copper plate is used as the metal foil, it is sometimes referred to as a Flexible Copper Clad Laminate (FCCL) in a narrower sense. Copper Clad Laminate; FCCL)

[0005] ​Examples of methods for manufacturing flexible metal foil laminates include (i) a casting method in which polyamic acid, a precursor of polyimide, is cast or coated onto a metal foil and then imidized; (ii) a metallizing method in which a metal layer is directly formed on a polyimide film by sputtering; and (iii) a lamination method in which a polyimide film and a metal foil are joined by heat and pressure via a thermoplastic polyimide.

[0006] In particular, the metallizing method is a method for producing flexible metal foil laminates by sputtering a metal such as copper onto a polyimide film with a thickness of 20 to 38 μm, for example, to sequentially deposit tie layers and seed layers. It has advantages in forming ultrafine circuits with a circuit pattern pitch of 35 μm or less, and is widely used in the manufacture of flexible metal foil laminates for COF (chip on film). Polyimide films used in flexible metal foil laminates produced by the metallizing method must possess high dimensional stability. While dimensional stability is typically measured using thermal dimensional stability, expressed as the coefficient of thermal expansion, the importance of dimensional stability with respect to moisture, expressed as the coefficient of hygroscopic expansion, is also steadily increasing, and is no less important than thermal dimensional stability.

[0007] In other words, there is an increasing demand for polyimide films that have excellent thermal dimensional stability and dimensional stability against moisture. However, when designing polyimide films with a low coefficient of thermal expansion and high thermal dimensional stability, the problem of low dimensional stability against moisture arises. Furthermore, polyimide films with high dimensional constraints typically have the problem of reduced chemical resistance (especially alkali resistance). Therefore, it not only has high thermal dimensional stability and high dimensional stability against moisture, There is a pressing need for polyimide films with excellent chemical resistance. The matters described above in the background art are for the purpose of understanding the background of the invention and may include matters that are not prior art and are already known to a person with ordinary skill in the art to which this art belongs. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Republic of Korea Patent Publication No. 10-2012-0133807 [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, the present invention aims to provide a polyimide multilayer film that simultaneously possesses high thermal dimensional stability, high dimensional stability against moisture, and excellent chemical resistance. However, the problems that this invention aims to solve are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0010] To achieve the above objective, one aspect of the present invention includes a first skin layer and a second skin layer formed on one outer surface of the core layer and on the opposite surface of the outer surface, respectively. The coefficient of thermal expansion is 2.0 ppm / °C or higher and 6.0 ppm / °C or lower. The coefficient of moisture absorption and expansion is 3.0 ppm / RH% or higher and 6.0 ppm / RH% or lower. We provide multilayer polyimide films. Another aspect of the present invention includes the multilayer polyimide film and an electrically conductive metal foil. We provide flexible metal foil laminates. A further aspect of the present invention includes the flexible metal foil laminate, We provide electronic components. [Effects of the Invention]

[0011] The present invention provides a polyimide film in which the composition ratio and reaction ratio of dianhydride acid and diamine components are adjusted, thereby providing a polyimide film that is excellent not only in thermal dimensional stability and dimensional stability against moisture, but also in chemical resistance. Such polyimide films are applicable to a variety of fields where polyimide films with excellent dimensional stability and chemical resistance are required, such as flexible metal foil laminates manufactured by metallizing methods or electronic components containing such flexible metal foil laminates. [Modes for carrying out the invention]

[0012] Terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best describe their invention. Therefore, the configurations of the embodiments described herein represent only one of the most preferred embodiments of the present invention and do not represent the entire technical concept of the invention. It should be understood that, at the time of filing, there are various equivalents and modifications that can be substituted for these embodiments.

[0013] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “includes,” “equip,” or “have” are intended to specify the existence of an implemented feature, number, stage, component, or combination thereof, and should be understood not to preemptively exclude the possibility of the existence or addition of one or more other features, numbers, stages, components, or combinations thereof.

[0014] As used herein, "dianhydride acid" is intended to include its precursors or derivatives, which may not technically be dianhydride acids, but nevertheless should react with diamine to form polyamic acid, which is then converted back to polyimide.

[0015] As used herein, "diamine" is intended to include its precursors or derivatives, which may not technically be diamines, but nevertheless should react with dianhydride to form polyamic acid, which is then converted back to polyimide.

[0016] As used herein, when amounts, concentrations, or different values or parameters are given as an enumeration of ranges, preferred ranges or preferred upper and lower limit values, it should be understood that all ranges formed by any pair of limit values or preferred values of any upper range, and limit values or preferred values of any lower range, are specifically disclosed, regardless of whether the range is disclosed separately. When a numerical range is referred to herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. The scope of the present invention is not intended to be limited to the specific values recited when defining the range.

[0017] A multilayer polyimide film according to an embodiment of the present invention includes a first skin layer and a second skin layer formed on one outer surface of a core layer and on the opposite surface of the outer surface, respectively, and has a coefficient of thermal expansion of 2.0 ppm / °C or more and 6.0 ppm / °C or less, and a coefficient of hygroscopic expansion of 3.0 ppm / RH% or more and 6.0 ppm / RH% or less. That is, the multilayer polyimide film may be a three-layer multilayer polyimide film having a core layer and a first skin layer and a second skin layer formed on one outer surface of the core layer and on the opposite surface of the outer surface, respectively, centered on the core layer. The coefficient of thermal expansion may be, for example, 2.0 ppm / °C or more and 5.5 ppm / °C or less. The moisture absorption expansion coefficient may be, for example, 4.0 ppm / RH% or more and 6.0 ppm / RH% or less.

[0018] In one embodiment, the mass loss of the multilayer polyimide film measured after immersing the film in a 15 wt% NaOH aqueous solution at 60°C for 1 hour may be 2 wt% or less. The weight loss of the multilayer polyimide film may be, for example, 1.5 wt% or less, 1.4 wt% or less, or 1.3 wt% or less.

[0019] In one embodiment, the core layer of the multilayer polyimide film is obtained by subjecting a polyamic acid solution containing a dianhydride acid component selected from two or more kinds in a group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA), and a diamine component selected from two or more kinds in a group consisting of paraphenylenediamine (PPD), m-tolidine, and 1,3-bisaminophenoxybenzene (TPE-R) to an imidization reaction. For example, the core layer is obtained by subjecting a polyamic acid solution containing a dianhydride acid component containing biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and a diamine component containing paraphenylenediamine and m-tolidine to an imidization reaction.

[0020] In one embodiment, one or more of the first skin layer and the second skin layer are obtained by imidizing a polyamic acid solution containing a dianhydride acid component comprising one or more selected from the group consisting of biphenyltetracarboxylic dianehydride, pyromeretic dianehydride, oxydiphthalic anhydride, and benzophenone tetracarboxylic dianehydride, and a diamine component comprising one or more selected from the group consisting of paraphenylenediamine, m-tolidine, oxydianiline (ODA), and 1,3-bisaminophenoxybenzene. In other words, the first skin layer and the second skin layer may have the same or different components and composition ratios.

[0021] On the other hand, one or more of the first skin layer and the second skin layer are obtained by imidizing a polyamic acid solution containing one or more dianhydride components selected from the group consisting of biphenyltetracarboxylic dianehydride and pyromellitic dianehydride, and one or more diamine components selected from the group consisting of paraphenylenediamine, m-tolidine, and oxydianiline. For example, one or more of the first skin layer and the second skin layer may use only oxydianiline as the diamine component, or use oxydianiline and paraphenylenediamine together, or use paraphenylenediamine, m-tolidine and oxydianiline together.

[0022] In one embodiment, the core layer may have a content of 40 mol% to 60 mol% of the biphenyltetracarboxylic dianehydride and a content of 40 mol% to 60 mol% of the pyromeretic dianehydride, based on a total content of 100 mol% of the dianhydride acid components, and a content of 50 mol% to 70 mol% of the paraphenylenediamine and a content of 30 mol% to 50 mol% of the m-tolidine, based on a total content of 100 mol% of the diamine components.

[0023] In one embodiment, one or more of the first skin layer and the second skin layer may have a content of 30 mol% or more and 100 mol% or less of biphenyltetracarboxylic dianehydride, a content of 70 mol% or less of pyromeretic dianehydride, a content of 60 mol% or less of paraphenylenediamine, a content of 75 mol% or less of m-tolidine, and a content of 10 mol% or more and 100 mol% or less of oxydianiline, based on a total content of 100 mol% of the diamine components.

[0024] The paraphenylenediamine of the present invention is a rigid monomer, and as the paraphenylenediamine content increases, the synthesized polyimide has a more linear structure, contributing to an improvement in the mechanical properties of the polyimide.

[0025] Furthermore, m-tolidine has a particularly hydrophobic methyl group, which contributes to the low hygroscopic properties related to the dimensional stability of polyimide films against moisture.

[0026] The polyimide chain derived from the biphenyltetracarboxylic dianehydride of the present invention has a structure called a charge transfer complex (CTC), that is, a regular linear structure in which electron donors and electron acceptors are located in close proximity to each other, and intermolecular interactions It will be strengthened. Such a structure has the effect of preventing hydrogen bonding with moisture, thereby reducing the moisture absorption rate and maximizing the effect of reducing the hygroscopicity of the polyimide film, which affects its dimensional stability against moisture.

[0027] Furthermore, pyromeretic dianehydrides are preferable because they are dianhydride acid components with a relatively rigid structure that can impart appropriate elasticity to polyimide films.

[0028] For polyimide films to have excellent dimensional stability, the content ratio of dianhydride acids is important. For example, as the content ratio of biphenyltetracarboxylic dianehydride decreases, it becomes more difficult to expect a low moisture absorption rate due to the CTC structure, and the dimensional stability against moisture also decreases.

[0029] Furthermore, biphenyltetracarboxylic dianehydrides contain two benzene rings corresponding to the aromatic moiety, while pyromeretic dianehydrides contain one benzene ring corresponding to the aromatic moiety.

[0030] An increase in the pyromeretic dianehydride content in the dianhydride acid component can be understood as an increase in the number of imide groups within the molecule, relative to the same molecular weight. This can be understood as an increase in the proportion of imide groups derived from the pyromeretic dianehydride in the polyimide polymer chain compared to the imide groups derived from biphenyltetracarboxylic dianehydride. In other words, an increase in the pyromeretic dianehydride content is seen as a relative increase in imide groups in the polyimide film as a whole, which makes it difficult to expect high dimensional stability against moisture due to a low moisture absorption rate. Conversely, if the pyromeretic dianehydride content decreases, the relatively rigid structural components decrease, which can cause the elasticity of the polyimide film to fall below the desired level.

[0031] For this reason, if the content of biphenyltetracarboxylic dianehydride exceeds the range or the content of pyromellitic dianehydride falls below the range, the dimensional stability of the polyimide film may decrease. Conversely, if the content of biphenyltetracarboxylic dianehydride falls below the range, or if the content of pyromeretic dianehydride exceeds the range, it may also adversely affect the dimensional stability of the polyimide film.

[0032] In the present invention, the production of polyamic acid is, for example, (1) A method of polymerization by placing the entire amount of the diamine component into a solvent, and then adding the dianhydride acid component in a substantially equimolar amount to the diamine component; (2) A method of polymerization by placing the entire amount of the dianhydride acid component into a solvent, and then adding the diamine component in a substantially equimolar amount to the dianhydride acid component; (3) A method of polymerization in which, after adding some of the components of the diamine component to the solvent, some of the components of the dianhydride component are mixed with the reactant in a ratio of approximately 95 to 105 mol%, the remaining diamine component is added, followed by the remaining dianhydride component, until the diamine component and the dianhydride component are substantially equimolar; (4) A method of polymerization in which, after adding the dianhydride acid component to the solvent, a portion of the diamine compound is mixed with the reaction components in a ratio of 95 to 105 mol%, then other dianhydride acid components are added, followed by the addition of the remaining diamine components, so that the diamine components and dianhydride acid components are substantially equimolar; (5) In a solvent, some diamine components and some dianhydride components are reacted in excess to form the first composition, and in another solvent, some diamine A method for polymerizing a second composition is formed by reacting a component with a portion of the dianhydride acid component in such an excess that one of them is present in excess, and then the first and second compositions are mixed to complete the polymerization, wherein, when forming the first composition, if the diamine component is in excess, the dianhydride acid component is made in excess in the second composition, and when the dianhydride acid component is in excess in the first composition, the diamine component is made in excess in the second composition, and the first and second compositions are mixed so that the total amount of diamine component and dianhydride acid component used in these reactions is substantially equimolar, and so on.

[0033] In the present invention, the polymerization method of polyamic acid as described above can be defined as a random polymerization method, and the polyimide film produced from the polyamic acid of the present invention produced by the process described above is preferably applicable in terms of maximizing the effect of the present invention in improving dimensional stability and chemical resistance. However, since the polymerization method described above produces polymers with relatively short repeating units, there may be limitations in exhibiting the excellent properties of the polyimide chains derived from the dianhydride acid component. Therefore, the polymerization method of polyamic acid that is particularly preferable and usable in the present invention is the block polymerization method.

[0034] On the other hand, the solvent used to synthesize polyamic acid is not particularly limited; any solvent that can dissolve polyamic acid can be used, but an amide-based solvent is preferred. Specifically, the organic solvent may be an organic polar solvent, more specifically an aprotic polar solvent, or one or more selected from the group consisting of, for example, N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methylpyrrolidone (NMP), gamma-butyrolactone (GBL), and diglyme, but is not limited thereto, and can be used individually or in combination of two or more as needed. In one example, the organic solvent can be N,N-dimethylformamide or N,N-dimethylacetamide, which are particularly preferred.

[0035] Furthermore, in the manufacturing process of polyamic acid, fillers may be added to improve various properties of the film, such as sliding properties, thermal conductivity, corona resistance, and loop hardness. The added fillers are not particularly limited, but preferred examples include silica, titanium dioxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

[0036] The particle size of the filler is not particularly limited and should be determined by the film characteristics to be modified and the type of filler added. Generally, the average particle size is 0.05 to 100 μm, preferably 0.1 to 75 μm, more preferably 0.1 to 50 μm, and most preferably 0.1 to 25 μm. If the particle size falls below this range, the modification effect becomes less pronounced, and if it exceeds this range, the surface properties may be severely damaged or the mechanical properties may be significantly reduced.

[0037] Furthermore, there are no particular limitations on the amount of filler to be added; it should be determined based on the film characteristics to be modified and the particle size of the filler. Generally, the amount of filler to be added is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight, per 100 parts by weight of polyimide. If the amount of filler added falls below this range, the modification effect of the filler will be less apparent, and if it exceeds this range, the mechanical properties of the film may be severely damaged. The method of adding the filler is not particularly limited, and any known method may be used.

[0038] In the manufacturing method of the present invention, the polyimide film is produced by thermal imidation and chemical imidation. It is manufactured by chemical processes. Alternatively, it may be manufactured by a composite imidation method in which thermal imidation and chemical imidation are carried out in parallel.

[0039] The aforementioned thermal imidation method is a method that eliminates chemical catalysts and induces the imidation reaction using a heat source such as hot air or an infrared dryer. The aforementioned thermal imidation method can imidize the amic acid groups present in the gel film by heat-treating the gel film at a variable temperature in the range of 100 to 600°C, and more specifically, by heat-treating it at 200 to 500°C, and even more specifically, at 300 to 500°C to imidize the amic acid groups present in the gel film. However, even during the gel film formation process, a portion of the amic acid (approximately 0.1 mol% to 10 mol%) is imidized, allowing the polyamic acid composition to be dried at a variable temperature in the range of 50°C to 200°C, which also falls under the category of the thermal imidization method.

[0040] In the case of chemical imidation, polyimide films can be manufactured using a dehydrating agent and an imidizing agent by methods known in the industry.

[0041] As an example of a composite imidation method, a polyimide film can be produced by adding a dehydrating agent and an imidizing agent to a polyamic acid solution, heating it at 80 to 200°C, preferably 100 to 180°C to partially cure and dry it, and then heating it at 200 to 400°C for 5 to 400 seconds.

[0042] On the other hand, the multilayer polyimide film of the present invention described above is manufactured using one or more methods of co-extrusion or coating.

[0043] The co-extrusion method involves filling a storage tank with a polyamic acid solution or a polyimide resin produced by imidizing it, then extruding it in multiple layers onto a casting belt using a co-extrusion die, and finally curing it to produce a multilayer polyimide film. This method offers high productivity and ensures high interfacial adhesion reliability by mixing different types of polyimide resins at the interfaces.

[0044] For example, the method for producing a multilayer polyimide film of the present invention includes a first filling step of filling a first storage tank with a first solution which is a first polyamic acid solution or a first polyimide resin produced by imidizing the first polyamic acid solution; a second filling step of filling a second storage tank with a second solution which is a second polyimide resin produced by imidizing a second polyamic acid solution or a second polyamic acid solution; a co-extrusion step in which a first channel connected to the first storage tank, a second channel and a third channel connected to the second storage tank, respectively, co-extrude the first solution and the second solution through co-extrusion dies formed inside each of them; and a curing step in which the co-extruded first solution and the second solution are cured.

[0045] The first polyamic acid solution is for forming the core layer and is preferably produced by polymerizing a dianhydride acid component containing two or more selected from the group consisting of biphenyltetracarboxylic dianehydride, pyromeretic dianehydride, oxydiphthalic anhydride, and benzophenone tetracarboxylic dianehydride, and a diamine component containing two or more selected from the group consisting of paraphenylenediamine, m-tolidine, oxydianiline, and 1,3-bisaminophenoxybenzene.

[0046] The second polyamic acid solution is for forming the first and second skin layers, and contains biphenyltetracarboxylic dianehydride, pyromeretic dianehydride, oxydiphthalic anhydride, and benzophenone tetracarboxy It is preferable to produce it by polymerizing a dianhydride acid component containing one or more selected from the group consisting of ric dianhydrides and a diamine component containing one or more selected from the group consisting of paraphenylenediamine, m-tolidine, oxydianiline, and 1,3-bisaminophenoxybenzene.

[0047] On the other hand, when the first polyamic acid solution is used as the first solution and the second polyamic acid solution is used as the second solution, it is preferable to further include an imidization step in which the first and second solutions, which are co-extruded, are imidized before the curing step.

[0048] The present invention provides a flexible metal foil laminate comprising the above-described multilayer polyimide film and an electrically conductive metal foil.

[0049] The metal foil used is not particularly limited, but when the flexible metal foil laminate of the present invention is used in electronic or electrical equipment applications, it may include, for example, copper or copper alloys, stainless steel or its alloys, nickel or nickel alloys (including 42 alloys), aluminum or aluminum alloys.

[0050] In general flexible metal foil laminates, rolled copper foil and electrolytic copper foil are commonly used, and these can also be preferably used in the present invention. Furthermore, the surface of these metal foils may be coated with a rust-preventive layer, a heat-resistant layer, or an adhesive layer.

[0051] In the present invention, the thickness of the metal foil is not particularly limited, and any thickness that allows it to perform adequately according to its application is acceptable.

[0052] The flexible metal foil laminate according to the present invention may have a structure in which a metal foil is laminated to at least one surface of the multilayer polyimide film. [Examples]

[0053] The operation and effects of the invention will be described in more detail below through specific manufacturing examples and embodiments. However, these manufacturing examples and embodiments are merely presented as examples of the invention and do not limit the scope of the invention's rights.

[0054] Manufacturing example: Manufacturing of multilayer polyimide film A first polyamic acid solution used in the production of the core layer was prepared by selectively polymerizing dianhydride and diamine components from among biphenyltetracarboxylic dianehydride (BPDA), pyromeretic dianehydride (PMDA), paraphenylenediamine (PPD), m-tolidine (MTD), and oxydianiline (ODA). A second polyamic acid solution used in the production of the first and second skin layers was prepared by selectively polymerizing dianhydride and diamine components from among biphenyltetracarboxylic dianehydride, pyromeretic dianehydride, paraphenylenediamine, m-tolidine, and oxydianiline. By co-extrusion, the previously manufactured first polyamic acid solution and second polyamic acid solution were co-extruded, imidized, and then cured to produce a multilayer polyimide film in which a first skin layer and a second skin layer were formed around the core layer. However, in this case, the core layer was manufactured by co-extruding the first polyamic acid solution, and the first and second skin layers were manufactured by co-extruding the second polyamic acid solution.

[0055] During the production of the aforementioned polyamic acid, the solvent is generally an amide-based solvent, such as an aprotic polar solvent, for example, N,N'-dimethylformamide. N,N'-dimethylacetamide, N-methylpyrrolidone, or a combination thereof can be used. The dianhydride acid and diamine component can be added in powder, lump, or solution form. It is preferable to add them in powder form at the beginning of the reaction to allow the reaction to proceed, and then add them in solution form thereafter to adjust the polymerization viscosity.

[0056] The resulting polyamic acid solution is mixed with an imidation catalyst and a dehydrating agent and then coated onto a support.

[0057] Examples of catalysts used include tertiary amines (e.g., isoquinoline, β-picoline, pyridine, etc.), and examples of dehydrating agents include, but are not limited to, acids anhydride. Examples and Comparative Examples

[0058] As shown in Table 1 below, multilayer polyimide films were produced according to the manufacturing examples by adjusting the content of the dianhydride acid component and the diamine component in Examples 1 to 5 and Comparative Examples 1 to 6. However, Comparative Examples 1-4 correspond to single-layer polyimide films.

[0059] [Table 1]

[0060] The coefficient of thermal expansion (CTE), coefficient of hydroscopic expansion (CHE), and chemical resistance of the manufactured polyimide film were measured and are shown in Table 2 below.

[0061] [Table 2]

[0062] (1) Measurement of the coefficient of thermal expansion The coefficient of thermal expansion (CTE) is measured using a thermomechanical analyzer from TA Corporation. Using the Q400 analyzer model, the manufactured multilayer polyimide film was cut to a width of 4 mm and a length of 20 mm. Under a nitrogen atmosphere, the temperature was raised from 30°C to 400°C at a rate of 10°C / min while applying a tension of 0.05 N, and then the gradient in the range from 50°C to 200°C was measured while cooling again at a rate of 10°C / min.

[0063] (2) Measurement of the coefficient of moisture absorption and expansion The coefficient of moisture absorption and expansion (CHE) was determined by applying a minimum load (approximately 1g for a 25mm x 150mm sample) to the manufactured multilayer polyimide film to prevent it from becoming loose. The humidity was adjusted to 3%RH at 25°C, and the film was allowed to absorb moisture until it was completely saturated. The dimensions were then measured, and after adjusting the humidity to 90%RH and allowing it to absorb moisture again until saturated, the dimensions were measured again. The dimensional change rate was then calculated from the results of both measurements.

[0064] (3) Measurement of chemical resistance The manufactured multilayer polyimide film was immersed in a 15 wt% NaOH aqueous solution at 60°C for 1 hour, and the mass loss of the multilayer polyimide film was measured and expressed as a percentage.

[0065] The measurement results showed that the multilayer polyimide films of Examples 1 to 5 exhibited the following characteristics: a thermal expansion coefficient of 2.0 ppm / °C or higher and 6.0 ppm / °C or lower; a hygroscopic expansion coefficient of 3.0 ppm / RH% or higher and 6.0 ppm / RH% or lower; and a mass loss of 2% by mass or less.

[0066] In contrast, Comparative Example 1, which is a single layer with the same components and composition ratio as the skin layer of the multilayer polyimide film of Example 1, Comparative Example 2, which is a single layer with the same components and composition ratio as the skin layer of the multilayer polyimide film of Example 3, and Comparative Example 3, which is a single layer with the same components and composition ratio as the skin layer of the multilayer polyimide film of Example 4, each had larger thermal expansion coefficients and moisture absorption expansion coefficients compared to the multilayer polyimide films of Examples 1, 3, and 4, and it was confirmed that they had lower dimensional stability.

[0067] Furthermore, Comparative Example 4, which is a single layer with the same components and composition ratio as the core layer of the multilayer polyimide film of Example 1, showed a higher coefficient of thermal expansion and a higher coefficient of moisture absorption and expansion compared to the multilayer polyimide film of Example 1. Although the number of particles was low and dimensional stability was excellent, we were able to confirm that the chemical resistance was significantly reduced.

[0068] On the other hand, in Comparative Example 5, a multilayer polyimide film obtained by adding oxydianiline as a core layer component to the multilayer polyimide film of Example 1 and adjusting the composition ratio by not using m-tolidine to deform the core layer, it was confirmed that the dimensional stability and chemical resistance were all reduced compared to the multilayer polyimide film of Example 1. It was confirmed that the multilayer polyimide film of Comparative Example 5 exhibited lower dimensional stability and chemical resistance compared to the multilayer polyimide film of Example 2, in which the composition ratio of dianhydride acids in the skin layer was adjusted compared to Example 1.

[0069] Furthermore, it was confirmed that the multilayer polyimide film of Comparative Example 6, which was obtained by adding paraphenylenediamine as a skin layer component to the multilayer polyimide film of Example 1 and adjusting its composition ratio to deform the skin layer, exhibited significantly lower chemical resistance compared to the multilayer polyimide film of Example 1. It was confirmed that the multilayer polyimide film of Comparative Example 6 exhibited significantly lower chemical resistance compared to the multilayer polyimide film of Example 2, in which the composition ratio of dianhydride acids in the skin layer was adjusted compared to Example 1.

[0070] Therefore, while the multilayer polyimide films of Examples 1 to 5, manufactured within the appropriate scope of this application, exhibited excellent thermal dimensional stability, dimensional stability against moisture, and chemical resistance, it was confirmed that exceeding the appropriate scope of this application made it difficult to satisfy all of the thermal dimensional stability, dimensional stability against moisture, and chemical resistance requirements of the multilayer polyimide films of this application. Furthermore, it was confirmed that the multilayer polyimide films of Examples 1 to 5, manufactured within the appropriate scope of this application, also possessed elastic modulus and glass transition temperature within an appropriate range applicable to various fields. In other words, we were able to confirm that a multilayer polyimide film that possesses excellent dimensional stability and chemical resistance while satisfying all the diverse conditions applicable to various application fields is a multilayer polyimide film manufactured within the appropriate scope of this application.

[0071] The embodiments of the multilayer polyimide film and method for producing the multilayer polyimide film of the present invention are merely preferred embodiments that enable a person skilled in the art with ordinary skill in the art to easily implement the present invention, and are not limited to the embodiments described above; therefore, the scope of the present invention is not limited by these embodiments. Accordingly, the true scope of technical protection of the present invention must be determined by the technical idea of ​​the appended claims. Furthermore, it is obvious to a person skilled in the art that various substitutions, modifications, and alterations are possible without departing from the technical idea of ​​the present invention, and that parts that can be easily altered by a person skilled in the art are also included in the scope of the present invention. [Industrial applicability]

[0072] The present invention provides a polyimide film in which the composition ratio and reaction ratio of dianhydride acid and diamine components are adjusted, thereby providing a polyimide film that is excellent not only in thermal dimensional stability and dimensional stability against moisture, but also in chemical resistance. Such polyimide films are applicable to a variety of fields where polyimide films with excellent dimensional stability and chemical resistance are required, such as flexible metal foil laminates manufactured by metallizing methods or electronic components containing such flexible metal foil laminates.

Claims

1. A multilayer polyimide film comprising a core layer and a first skin layer and a second skin layer formed on one outer surface of the core layer and on the opposite surface of the outer surface, respectively, The coefficient of thermal expansion is 2.0 ppm / °C or higher and 6.0 ppm / °C or lower. The coefficient of moisture absorption and expansion is 3.0 ppm / RH% or higher and 6.0 ppm / RH% or lower. The resins of the core layer, the first skin layer, and the second skin layer each consist solely of polyimide resin. The mass loss of the multilayer polyimide film measured after immersing it in a 15% by weight NaOH aqueous solution at 60°C for 1 hour was 2% by mass or less. The polyimide of the core layer is obtained by imidizing a polyamic acid solution containing two or more dianhydride acid components selected from the group consisting of biphenyltetracarboxylic dianehydride (BPDA), pyromeretic dianehydride (PMDA), oxydiphthalic anhydride (ODPA), and benzophenone tetracarboxylic dianehydride (BTDA), and two or more diamine components selected from the group consisting of paraphenylenediamine (PPD), m-tolidine, and 1,3-bisaminophenoxybenzene (TPE-R). One or more polyimide resins selected from the group consisting of the first skin layer and the second skin layer are obtained by imidizing a polyamic acid solution containing one or more dianhydride acid components selected from the group consisting of biphenyltetracarboxylic dianehydride, pyromeretic dianehydride, oxydiphthalic anhydride, and benzophenone tetracarboxylic dianehydride, and one or more diamine components selected from the group consisting of paraphenylenediamine, m-tolidine, oxydianiline (ODA), and 1,3-bisaminophenoxybenzene. In the polyimide resin of the core layer, the content of the biphenyltetracarboxylic dianehydride is 40 mol% or more and 60 mol% or less, based on a total content of 100 mol% of the dianhydride components, and the content of the pyromeretic dianehydride is The content is 40 mol% or more and 60 mol% or less, and based on a total content of 100 mol% of the diamine components, the content of paraphenylenediamine is 50 mol% or more and 70 mol% or less, and the content of m-tolidine is 30 mol% or more and 50 mol% or less. In one or more polyimide resins selected from the group consisting of the first skin layer and the second skin layer, the content of the biphenyltetracarboxylic dianehydride is 30 mol% or more and 100 mol% or less, the content of the pyromeretic dianehydride is 70 mol% or less, the content of the paraphenylenediamine is 60 mol% or less, the content of m-tolidine is 75 mol% or less, and the content of the oxydianiline is 10 mol% or more and 100 mol% or less, based on a total content of 100 mol% of the diamine components. Multilayer polyimide film.

2. A flexible metal foil laminate comprising a multilayer polyimide film according to claim 1 and an electrically conductive metal foil.

3. An electronic component comprising a flexible metal foil laminate as described in claim 2.

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