Polyester film for carrier film of circuit board laminate and carrier film for circuit board laminate

Abstract

To provide a polyester film for a carrier film of a circuit board laminate and a carrier film for a circuit board laminate, which achieve reduction in process contamination resulting from oligomer precipitation under heating.SOLUTION: There is provided a polyester film for a carrier film of a circuit board laminate, where the polyester film has a cold crystallization temperature (Tcc) of 150°C or more and less than 165°C, and the polyester film has a haze of 30% or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyester film for a carrier film of a circuit board laminate and a carrier film for a circuit board laminate.

Background Art

[0002] Polyester films are widely used in industrial fields. Specific examples include carrier materials for processes for manufacturing printed wiring boards, flexible printed wiring boards, multilayer printed wiring boards, and green sheets of ceramic multilayer capacitors. Further, it is also used as a protective material for protecting medical tapes, adhesive materials, components for liquid crystal displays, and the like.

[0003] In recent years, due to the diversification of applications of polyester films, the processing of films at high temperatures has increased, and as a result, there is a problem that oligomers precipitate from the polyester film. When the oligomers precipitated from the polyester film adhere to process equipment such as cooling rolls and press dies, there is a problem that the frequency of regular cleaning and replacement of the equipment increases, leading to an increase in production loss.

[0004] In response to the above problems, a method (Patent Document 1) of performing solid-phase polymerization treatment on polyester to reduce the amount of oligomers has been disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, even in the case of a film using a polyester in which oligomer precipitation is suppressed by solid-phase polymerization treatment as disclosed in Patent Document 1, if the surface is matte, the crystallinity of the film is low, oligomers precipitate on the film surface by heat treatment, and there is a problem that the mold gets dirty when press-treated with a mold.

[0007] Therefore, an object of the present invention is to provide a polyester film for a carrier film of a circuit board laminate and a carrier film for a circuit board laminate that suppress process contamination due to oligomer precipitation during heating.

Means for Solving the Problems

[0008] In order to solve the above problems, a preferred embodiment of the present invention has the following configuration. (1) A polyester film for a carrier film of a circuit board laminate, wherein the cold crystallization temperature (Tcc) of the polyester film is 150°C or higher and less than 165°C, and the haze of the polyester film is 30% or higher. (2) The polyester film for a carrier film of a circuit board laminate according to (1), wherein the content of cyclic trimer in the polyester film is 0.01% by mass or more and 1.00% by mass or less. (3) The polyester film for a carrier film of a circuit board laminate according to (1) or (2), wherein the difference ΔHz between the haze of the polyester film and the haze of the film after heating the polyester film at 170°C for 3 hours is less than 2.0%. (4) The number of protrusions with a height exceeding 0.35 μm on at least one surface of the polyester film is 100 pieces / 0.05 mm 2 or more and 10000 pieces / 0.05 mm 2 or less. The polyester film for a carrier film of a circuit board laminate according to any one of (1) to (3). (5) The polyester film for a carrier film of a circuit board laminate according to any one of (1) to (4), wherein the polyester film is composed of at least three layers or more. (6) The polyester film for the carrier film of the circuit board laminate according to any one of (1) to (5), wherein the polyester film contains 40% by mass or more and 100% by mass or less of a recycled polyester raw material. (7) A carrier film for a circuit board laminate process, having the polyester film for the carrier film of the circuit board laminate according to (1) to (6).

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a polyester film for a carrier film of a circuit board laminate that suppresses process contamination due to oligomer precipitation during heating, and a carrier film for a circuit board laminate.

Embodiments for Carrying Out the Invention

[0010] The polyester constituting the film of the present invention is a polyester having dibasic acid and glycol as constituent components. As the aromatic dibasic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenyletherdicarboxylic acid, diphenylketonedicarboxylic acid, phenylindanedicarboxylic acid, sodium sulfoisophthalic acid, dibromoterephthalic acid, etc. can be used. As the alicyclic dibasic acid, oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, etc. can be used. As the glycol, as the aliphatic diol, ethylene glycol, propylene glycol, tetramethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, etc. can be used, and as the aromatic diol, naphthalenediol, 2,2-bis(4-hydroxydiphenyl)propane, 2,2-bis(4-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, hydroquinone, etc. can be used, and as the alicyclic diol, cyclohexanedimethanol, cyclohexanediol, etc. can be used. Among them, it is preferable that the film of the present invention contains 90% by mass or more of polyethylene terephthalate in which the terephthalic acid component is 95 mol% or more as the dicarboxylic acid component and the ethylene glycol component is 95 mol% or more as the glycol component in 100% by mass of the film.

[0011] In the polyester constituting the film of the present invention, other dibasic acid components or diol components may be partially copolymerized, but the amount of the copolymerized component is preferably 20 mol% or less. Further, the polyester constituting the film of the present invention may be used alone or as a polymer blend of two or more kinds.

[0012] The film of the present invention is required to have a cold crystallization temperature (Tcc) of 150°C or higher and less than 165°C. The cold crystallization temperature refers to the crystallization peak of the 2ndRun obtained by differential scanning calorimetry described below. By setting the cold crystallization temperature (Tcc) to less than 165°C, heating crystallization can be carried out prior to the precipitation of oligomers during heating, preventing the oligomers from adhering to process equipment such as cooling rolls and press dies and floating to the surface, thereby suppressing the contamination of the process. However, when the cold crystallization temperature (Tcc) is less than 150°C, thermal crystallization proceeds rapidly during heating, and oligomers that could only exist in the amorphous part precipitate, adhering to process equipment such as cooling rolls and press dies, and tending to be easily contaminated. When the cold crystallization temperature (Tcc) is 165°C or higher, the glossiness of the film after heating tends to deteriorate, and oligomers are likely to precipitate prior to heating crystallization, easily contaminating the process. From the same perspective as above, the cold crystallization temperature (Tcc) is more preferably 153°C or higher and 157°C or lower.

[0013] In the present invention, for the cold crystallization temperature, 5 mg of a polyester sample is weighed with an electronic balance, sandwiched between aluminum packings, and measured using a Seiko Instruments Inc. robot DSC-RDC220 thermal differential scanning calorimeter. Data analysis is performed using the company's disk session SSC / 5200 in accordance with JIS-K-7121 (1987). Specifically, as the measurement conditions, the temperature is raised from 25°C to 300°C at 20°C / min, then rapidly cooled to 25°C, and when the temperature is raised again to 300°C at 20°C / min (2ndRun), the crystallization peak temperature (Tcc) in the 2ndRun is determined as the peak temperature at the apex of the crystallization peak. When multiple crystallization peaks are observed in the 2ndRun, the crystallization peak apex temperature indicating the maximum peak area obtained by JIS-K-7122 (2012) is taken as the crystallization peak temperature (Tcc).

[0014] As a means for setting the cold crystallization temperature (Tcc) to 150°C or higher and lower than 165°C, for example, a method of adjusting the average molecular weight, particle content, and cyclic trimer content of the polyester resin used for the film is mentioned as a preferable method. As a result of investigations by the present inventors, if the weight average molecular weight is small (if there are few polymers with long molecular chains), the crystallinity of the film tends to be high and the cold crystallization temperature (Tcc) tends to decrease. Conversely, if the weight average molecular weight is large (if there are many polymers with long molecular chains), the crystallinity of the film tends to be low and the cold crystallization temperature (Tcc) tends to increase.

[0015] Also, it is considered that the cold crystallization temperature (Tcc) also changes depending on the content of particles present in the polyester resin used for the film of the present invention. For example, if the particle content increases, the particles serve as nuclei and the crystallization of the film progresses, so the cold crystallization temperature (Tcc) of the polyester resin becomes lower. On the other hand, if the particle content decreases, the crystallization of the film is also suppressed, so it is considered that the cold crystallization temperature (Tcc) tends to be high. Regarding cyclic trimers, when the content is low, there are fewer components that inhibit the orientation crystallization of the polymer molecular chains, so it is easy to crystallize at a low temperature and the cold crystallization temperature (Tcc) tends to be low. On the other hand, when the cyclic trimer content is high, there are more components that inhibit the orientation crystallization of the polymer molecular chains, so it is difficult to crystallize and the cold crystallization temperature (Tcc) tends to be high. However, it is considered that the influence of the average molecular weight and particle content of the polyester resin is greater. As a means for adjusting cyclic trimers, for example, there is solid-phase polymerization. When performing solid-phase polymerization, although the weight average molecular weight increases, the amount of cyclic trimers decreases. Therefore, it is desirable to adjust the degree of solid-phase polymerization to obtain an appropriate weight average molecular weight and amount of cyclic trimers. In addition, since contamination by oligomers affects not only the surface layer but also the inner layer of the film, it is preferable to adopt the same achievement means as above as much as possible for the average molecular weight, particle content, and cyclic trimer content in each layer of the film.

[0016] The film of the present invention preferably has a haze difference ΔHz of less than 2.0% between after heating at 170°C for 3 hours and before heating, more preferably 1.0% or less, and even more preferably 0.5% or less. By setting the ΔHz value to less than 2.0%, temperature rise crystallization is caused prior to the precipitation of oligomers, and by suppressing oligomer precipitation, it is possible to prevent the oligomers from adhering to process equipment such as cooling rolls and press dies and contaminating the process. When the ΔHz value is 2.0% or more, oligomer precipitation cannot be suppressed, and there is a possibility that it may adhere to and contaminate process equipment such as cooling rolls and press dies.

[0017] The film of the present invention preferably has a haze value of 30% or more. When the haze value is less than 30%, there may be a case where a high-class metallic texture cannot be obtained due to low light diffusibility. The haze value is more preferably 50% or more. Conversely, from the viewpoint of impairing the high-class feeling when the haze is too high, the haze value is preferably less than 90%.

[0018] The film of the present invention preferably has a glossiness of 50% or less. The glossiness referred to in the present invention is obtained by the measurement method described later. By setting the glossiness to 50% or less, an excellent matte appearance can be achieved. When the glossiness is greater than 50%, the matte tone becomes insufficient and the design property may be inferior. The glossiness is more preferably 40% or less, and even more preferably 30% or less.

[0019] The film of the present invention is composed of at least three layers, having an outermost layer and layers other than the outermost layer. It is preferable to form a three-layer laminate with the A layer and the C layer of the A layer / B layer / C layer as the outermost layers and the B layer as any layer other than the outermost layer, i.e., the intermediate layer. Also, it may be a configuration of four or more layers with the A layer and the C layer of the A layer / B1 layer / B2 layer / C layer as the outermost layers and including two or more layers such as the B1 layer and the B2 layer as any layer other than the outermost layer. Further, the C layer may be a layer having the same composition and the same thickness as the A layer, and may be A layer / B layer / A layer or A layer / B1 layer / B2 layer / A layer. By adopting a laminate structure of three or more layers, it becomes possible to have a structure in which the layer other than the outermost layer has a reduced particle content, maintaining the mechanical strength of the film and enhancing the film-forming property and processability. The laminate structure is more preferably a laminate structure of three or more layers with both surface layers being the A layer, and particularly preferably a three-layer structure with both surface layers being the A layer. At this time, the A layers on both surface layers do not necessarily need to be A layers composed of the same polyester resin composition, and A layer / B layer / A' layer is also cited as a preferable embodiment.

[0020] In the laminating method, each layer may be a separate sheet and they may be laminated using an adhesive or plasma discharge treatment. However, when the thickness is thin, since each layer becomes a thin film, if it is a laminating method, the handleability is poor and wrinkles may occur during processing. Therefore, coextrusion lamination is preferable. Also, in the coextrusion method, since the film of the present invention is a thin film, it is preferably provided with a certain strength and is preferably oriented using stretching. The preferred manufacturing method will be described later. Note that on the release laminate polyester film of the present invention, other functional layers such as a release layer having release properties such as a coating layer, an undercoat layer considering the coatability of the release layer, and an antistatic layer for preventing adhesion of dust may be provided.

[0021] On at least one outermost side constituting the outermost layer of the film of the present invention, it is preferable to contain particles having an average particle diameter of 2 to 5 μm, and the content of the particles is preferably 1% by mass or more and 10% by mass or less with respect to the entire polyester resin composition constituting the A layer. By containing the above particles in the layer constituting at least one outermost layer, the haze of the film can be increased and a matte appearance can be achieved.

[0022] Further, from the viewpoint of suppressing uneven appearance spots, the particles used in the present invention preferably have an average particle diameter of 2 μm or more and 5 μm or less, and more preferably 2.5 μm or more and 4.5 μm or less. The average particle diameter in the present invention refers to the number average particle diameter D represented by D = ΣDi / N (Di: equivalent circle diameter of the particle, N: number of particles) obtained by the measurement method described later.

[0023] In addition, in order to achieve a matte appearance (high haze), the film of the present invention preferably contains 1.0% by mass or more and 10% by mass or less of particles with respect to the entire layer in at least one outermost layer constituting the outermost layer. From the viewpoints of matte appearance (low glossiness), film formability, and processability, the content of the particles is preferably 1.5% by mass or more and 8.0% by mass or less, and more preferably 2.0% by mass or more and 6.0% by mass or less.

[0024] In addition, from the viewpoints of achieving a matte appearance (high haze) and suppressing process contamination due to oligomer precipitation during heating, the film of the present invention preferably contains 1.5% by mass or more and 8.5% by mass or less of particles with respect to the entire film. From the viewpoints of matte appearance (low glossiness), film formability, and processability, it is preferably contained in an amount of 3.0% by mass or more and 8.0% by mass or less, and more preferably 4.0% by mass or more and 7.5% by mass or less.

[0025] The particles used in the present invention are not particularly limited, and inorganic particles and organic particles can be used. Examples of the inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, calcium carbonate, calcium phosphate, aluminum oxide, and the like. Examples of the organic particles include particles composed of styrene, silicone, acrylic acids, methacrylic acids, polyesters, divinyl compounds, and the like. Among them, inorganic particles such as wet and dry silica, colloidal silica, and aluminum silicate, and organic particles composed of styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene, and the like are preferable. From the viewpoints of matte appearance and economy, wet and dry silica, colloidal silica, and aluminum silicate are particularly preferably used. Note that two or more of these particles may be used in combination.

[0026] From the viewpoint of imparting appropriate slipperiness and better light diffusibility, the film of the present invention preferably has a center plane average roughness SRa of 100 nm or more and 1000 nm or less. By setting the center plane average roughness SRa to 100 nm or more and 1000 nm or less, the releasability as a process paper can be improved. If the center plane average roughness SRa is less than 100 nm, the slipperiness during film production may decrease, and wrinkles different from the streaks of the present invention may easily occur on the film. Further, if the center plane average roughness SRa is greater than 1000 nm, surface defects of the object to be released may easily occur due to the rough surface. More preferably, the center plane average roughness SRa is 200 nm or more and 900 nm or less.

[0027] The film of the present invention preferably has the number of protrusions exceeding 0.35 μm on at least one surface of 100 pieces / 0.05 mm 2 or more and 10000 pieces / 0.05 mm 2 or less. If the number of protrusions with a protrusion height exceeding 0.35 μm is less than 100 pieces / 0.05 mm 2 , the running property during the manufacturing process may decrease and wrinkles may easily occur. Further, 10000 pieces / 0.05 mm 2When it exceeds this value, the matte finish becomes insufficient and the designability may be inferior. The number of protrusions exceeding 0.35 μm is preferably 200 or less per 0.05 mm 2 or more, and 80,000 or less per 0.05 mm 2 more preferably 300 or less per 0.05 mm 2 or more, and 5,000 or less per 0.05 mm 2 and less.

[0028] The intrinsic viscosity of the polyester resin constituting each layer of the film of the present invention is preferably in the range of 0.45 dl / g or more and 0.90 dl / g or less in order to maintain good flatness and film-forming stability during production and breaking strength during processing. When the intrinsic viscosity of the polyester resin constituting the polyester film is less than 0.45 dl / g, thickness unevenness is likely to occur in the film during film production, and thickness unevenness of the target object is likely to be caused. Further, when the intrinsic viscosity of the polyester resin constituting the polyester film exceeds 0.90 dl / g, the viscosity in the molten state is high, which places a burden on the extruder during film production, making stable discharge difficult and likely to cause thickness unevenness. In addition, when the draw ratio is increased to suppress breakage during processing, there are many film breaks, the film-forming stability is inferior, and the productivity tends to deteriorate.

[0029] At this time, within a range that does not adversely affect the surface characteristics of the film, the recycled raw materials of the edge portions generated in the film-forming process, or the recycled raw materials of other film-forming processes, etc. can be mixed and used in a timely manner, which can reduce the consumption of petroleum resources and obtain cost advantages.

[0030] In the polyester film of the present invention, recycled polyester raw materials can be used for each layer. Preferably, for each layer, 40% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more and 100% by mass of recycled polyester raw materials can be used. In particular, it is easy to use in layers that are not located on the surface layer such as a three-layer structure of the film configuration. The polyester film of the present invention can contain 40% by mass or more of recycled polyester raw materials with respect to the entire film. Preferably, it is 50% by mass or more, more preferably 80% by mass or more, and still more preferably 100% by mass.

[0031] Among them, from the viewpoints of mechanical properties and dimensional stability, polyesters selected from polyethylene terephthalate (PET) and its copolymers, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, and further polyhexamethylene terephthalate and its copolymers and polyhexamethylene naphthalate and its copolymers are preferably used.

[0032] The recovered polyester resin generated in the film manufacturing process is processed by the method described in JP-A-2016-175066. Flakes crushed by a crusher are compressed and cut by a granulator to form pellets (for example, cylindrical molded articles with a height of 30 mm or less), or the flakes crushed by a crusher are melt-kneaded by an extruder, and after filtering out coarse particles and foreign substances with a filter, they are discharged in a strand shape from a die and cut while cooling to form chips. By appropriately mixing with virgin polyester resin, it can be recycled into a recycled polyester raw material. However, since these recycled polyester raw materials have undergone a thermal history and have been depolymerized into low molecules, it is inevitable that the intrinsic viscosity IV decreases each time the recycled polyester raw material is repeatedly used in film manufacturing with a self-circulation rate of 100%. However, by adding virgin polyester resin and / or recycled polyester raw material of used film and adjusting the content ratio of each resin with respect to the total mass of the polyester resin constituting the film, a polyester film with a preferable range of intrinsic viscosity IV can be manufactured.

[0033] Note that the recycled polyester raw material may contain a polycondensation reaction catalyst, additives, stabilizers, and alkali metal phosphates similar to the above virgin polyester resin, and may also contain particles as long as they do not affect the properties and design of the film.

[0034] A used film refers to a film that has been used for a specific purpose as a product. By recycling the film that has lost its product performance as a result of being used for a specific purpose and is originally intended to be discarded, it becomes possible to reduce the environmental impact. Examples of used films include a hard coat layer typified by a functional layer of an optical film, a refractive index adjustment layer, an easy adhesion layer that facilitates bonding to other members, and in the case of a release film, the base material of an adhesive tape after use, the release paper of the adhesive tape, and films for product manufacturing processes. Among these, films for product manufacturing processes, particularly release films for manufacturing multilayer ceramic capacitors and polarizing films, are preferred in recent years because their usage has been increasing, and recycling can reduce the amount of waste and lead to a reduction in the environmental impact.

[0035] As methods for recycling used films and PET bottles, chemical recycling and mechanical recycling are known. The chemical recycling method chemically decomposes a used film to return it to a crude raw material (monomer) and repolymerize the polyester, making it possible to obtain a recycled polyester resin that is indistinguishable from virgin polyester resin. However, there is a problem that the process is longer and the cost is higher than producing virgin polyester resin. The mechanical recycling method is, for example, the method described in Japanese Patent Application Laid-Open No. 2023-81479. The film obtained by crushing the used film into flakes is washed with water to remove the film residue and alkali components that remain in trace amounts after removing the coating (impurities) from the surface using an aqueous alkali solution. Next, it is dried to volatilize the moisture, melt-kneaded with an extruder, the coarse particles and foreign matter are filtered out with a filter, then extruded from a die in a strand shape, and cut into chips while cooling, making it possible to obtain a recycled polyester resin at a lower cost than the chemical recycling method.

[0036] When washing, the concentration of the alkaline aqueous solution used is preferably 0.5% by mass or more and 6.0% by mass or less. If it is less than 0.5% by mass, the peelability of the coating decreases, and it may take a long time to peel. If it exceeds 6.0% by mass, it may cause a decrease in the molecular weight and IV of the polyester support due to the promotion of hydrolysis.

[0037] It is preferable to contain a surfactant in the alkaline aqueous solution. The content is preferably 0.01% by mass or more and 0.10% by mass or less based on the total amount of the alkaline aqueous solution. By adding a surfactant, the permeability of the alkaline aqueous solution to the interface between the polyester support and the coating increases, which promotes peeling and has the effect of suppressing the reattachment of the peeled coating to the polyester support. Examples of the type of surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, etc., and preferably nonionic and anionic surfactants. Examples of nonionic surfactants include polyethylene glycol ether-based, particularly polyethylene glycol ethers of higher alcohols, polyethylene glycol ethers of alkylphenols, etc. Examples of anionic surfactants include alkylbenzene sulfonates and alkyl sulfate esters. In order to prevent the precipitation of the surfactant in the alkaline aqueous solution and the reattachment of impurities insoluble in the alkali, it is advisable to perform stirring and washing in a washing tank equipped with a stirring blade.

[0038] The temperature of the alkaline aqueous solution is preferably 60°C or more and 98°C or less. If it is less than 60°C, the peelability of the coating laminated on the polyester support decreases, and it may take a long time to peel. If it exceeds 98°C, since it becomes a temperature near the boiling point, a pressure-type washing tank is required, and hydrolysis or dissolution of the polyester support due to heating may occur.

[0039] When treating by stirring and washing, when the washing concentration is 10% by mass or less (the mass part of the alkaline aqueous solution containing the surfactant is 9 or more with 1 mass part of the object to be washed), the time is preferably 15 minutes or more and 30 minutes or less. By setting it within the above range, the coating can be efficiently removed from the polyester support.

[0040] After washing with an aqueous alkali solution, it is preferable to wash with water. The water washing removes the residue of the film that remains in trace amounts on the polyester support and removes the adhering alkali components. Similar to the alkali washing, a washing tank equipped with a stirring blade can be used. From the viewpoints of washing time and cost, it is preferable to carry out the washing in one step. Further, for both the alkali washing and the water washing, the stirring rotation speed is preferably in the range of 100 rpm or more and 300 rpm or less, and the time for treatment by stirring washing is preferably 15 minutes or more and 30 minutes. By setting the range as described above, the film can be efficiently removed from the polyester support. After the water washing, it is preferable to carry out vacuum drying at 60°C or more and 200°C or less. More preferably, it is 90°C or more and 120°C or less.

[0041] The polyester support dried to volatilize moisture is melt-kneaded with an extruder, and after filtering out coarse particles and foreign matters with a filter, it is discharged in a strand shape from a die and cut while being cooled, whereby a recycled polyester raw material can be obtained.

[0042] From the viewpoints of cost reduction and reduction of environmental load with respect to the polyester resin constituting the film, it is preferable to increase the content of the recovered polyester resin, but it is advisable to determine the upper limit of the content of the recycled polyester raw material within a range that does not impair the required characteristics for each film application such as mechanical properties, dimensional stability, and surface smoothness.

[0043] Furthermore, in the film of the present invention, various additives, for example, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, etc. may be added to such an extent that their properties are not deteriorated.

[0044] From the viewpoints of heat resistance, handleability, and economy, the film thickness of the film of the present invention is preferably 10 μm or more and 150 μm or less, more preferably 15 μm or more and 100 μm or less, and most preferably 20 μm or more and 75 μm or less.

[0045] Next, an example of a specific manufacturing method of the film of the present invention will be described, but the present invention is not construed as being limited to such an example.

[0046] When using a three-layer laminated polyester film having an A layer forming the outermost two layers and a B layer forming the inner layer, first, as the polyester A used for the A layer, polyethylene terephthalate resin (a) and polyethylene terephthalate resin (a) containing silica particles with an average particle diameter of 3.8 μm are weighed at a predetermined ratio. Also, as the polyester B used for the B layer, polyethylene terephthalate resin (a) is used.

[0047] It is preferable to produce the polyester film by laminating polyester A and polyester B by a coextrusion method.

[0048] First, melt polyester A with an extruder and then filter it as it is with a filter. Also, melt polyester B with another extruder, filter it with another filter, then guide them to a feed block respectively, and compound and laminate them in a molten state. The ratio of the laminated thickness of polyester A and polyester B can be adjusted to a desired laminated thickness ratio by adjusting the extrusion amounts of the extruders for each layer. At this time, it is preferable to control the resin temperature at 265°C to 295°C. Then, through the filter and gear pump, foreign matter removal and extrusion amount equalization are performed respectively, and it is discharged in a sheet form onto a cooling drum from a T-die. At this time, an electrostatic printing method of closely adhering the cooling drum and the resin with static electricity using an electrode applied with a high voltage, a casting method of providing a water film between the casting drum and the extruded polymer sheet, a method of adhering the extruded polymer by setting the casting drum temperature to the glass transition point of the polyester resin to (glass transition point - 20°C), or a method of combining a plurality of these methods is used to closely adhere the sheet-shaped polymer to the casting drum, cool and solidify it, and obtain an unstretched film. Among these casting methods, when using polyester, from the viewpoints of productivity and flatness, the method of applying static electricity is preferably used.

[0049] The film of the present invention is preferably a biaxially oriented film from the viewpoints of heat resistance and dimensional stability. The biaxially oriented film can be obtained by a sequential biaxial stretching method in which an unstretched film is stretched in the longitudinal direction and then in the width direction, or in the width direction and then in the longitudinal direction, or by a simultaneous biaxial stretching method in which the longitudinal and width directions of the film are stretched substantially simultaneously.

[0050] As the stretching ratio in such a stretching method, a ratio of 2.8 times or more and 3.4 times or less, more preferably 2.9 times or more and 3.3 times or less, is adopted in the longitudinal direction. Also, the stretching speed is desirably 1,000% / min or more and 200,000% / min or less. Further, the stretching temperature in the longitudinal direction is preferably 70°C or more and 100°C or less. Also, the stretching in the longitudinal direction is preferably performed using stretching rolls and stretching nip rolls, and the nip pressure between the stretching roll and the stretching nip roll is preferably 0.1 to 0.5 MPa. As the stretching ratio in the width direction, a ratio of preferably 2.8 times or more and 3.8 times or less, more preferably 3.0 times or more and 3.6 times or less, is adopted. The stretching speed in the width direction is desirably 1,000% / min or more and 200,000% / min or less. Further, in order to achieve high tear strength, a method in which the stretching temperature in the width direction is increased in the order of the first half of stretching temperature of 90°C or more and 120°C or less, the middle stage of stretching temperature of 100°C or more and 130°C or less, and the latter half of stretching temperature of 110°C or more and 150°C or less is preferably adopted.

[0051] Furthermore, the film is heat-treated after biaxial stretching. The heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. This heat treatment is performed at a temperature of 120°C or higher and below the crystal melting peak temperature of the polyester. However, in order to achieve high tear strength, the temperature in the first half of the heat treatment is preferably 180°C or higher and less than 220°C, the temperature in the middle of the heat treatment is preferably 220°C or higher and 240°C or lower, and the temperature in the second half of the heat treatment is preferably 210°C or higher and 220°C or lower. Furthermore, in order to reduce the heat shrinkage rate, it is also preferable to perform slow cooling at 140°C or higher and less than 180°C after the heat treatment. The heat treatment time can be arbitrary within a range that does not deteriorate the characteristics, and is preferably 5 seconds or more and 60 seconds or less, more preferably 10 seconds or more and 40 seconds or less, and most preferably 15 seconds or more and 30 seconds or less. Furthermore, when used for applications where mold release properties are required, in order to ensure stable mold release properties, a mold release layer can also be coated inline. As a method of providing the coating layer inline in the film manufacturing process, a method of uniformly applying a dispersion of the coating layer composition in water on a film that has been at least uniaxially stretched using a metering ring bar or a gravure roll and drying the coating agent while stretching is preferable. At this time, the thickness of the mold release layer is preferably 0.02 μm or more and 0.10 μm or less. In addition, various additives such as antioxidants, heat stabilizers, ultraviolet absorbers, infrared absorbers, pigments, dyes, organic or inorganic particles, antistatic agents, and nucleating agents may be added to the mold release layer.

[0052] The film of the present invention is excellent in the performance of suppressing process contamination due to oligomer precipitation during heating, and thus can be suitably used as a carrier film for circuit board laminates. In particular, it can be more suitably used for a carrier film for circuit board laminates that is heated to a heating temperature of 165°C or higher, and even more suitably used for a carrier film for circuit board laminates that is heated to a heating temperature of 165°C or higher and has a pressing pressure of 1.5 MPa or higher.

Examples

[0053] The measurement methods for the characteristics and the evaluation methods for the effects in the present invention are as follows.

[0054] (1) Cold crystallization temperature (Tcc) Weigh 5 mg of the film using an electronic balance, sandwich it with aluminum packing, and measure it using a Seiko Instruments Inc. robot DSC-RDC220 differential scanning calorimeter. Data analysis was performed using the company's disk session SSC / 5200 in accordance with JIS-K-7121 (1987). As the measurement conditions, the temperature was raised from 25°C to 300°C at a rate of 20°C / min, then rapidly cooled to 25°C, and then heated again to 300°C at a rate of 20°C / min (2nd Run). From the 2nd Run, the crystallization peak temperature (Tcc) was determined as the peak temperature at the apex of the crystallization peak. When multiple crystallization peaks are observed in the 2nd Run, the crystallization peak apex temperature indicating the maximum peak area determined by JIS-K-7122 (2012) is used.

[0055] (2) Content of cyclic trimer Using 20 mg of the film piece before heating as a sample, dissolve it in OCP (o-chlorophenol) at 150°C for 30 minutes and cool it to room temperature. Then, after adding 1,4-diphenylbenzene as an internal standard, add 2 ml of methanol and separate the polymer using a high-speed centrifuge. The liquid layer was measured using a high-performance liquid chromatograph ("LC-10ADvp" manufactured by Shimadzu Corporation).

[0056] (3) Haze Using a 5 cm square film as a sample, measure the haze before heating and after heating and cooling after being heated in an oven set at 170°C for 3 hours using a haze meter based on JIS-K-7105 (1985). (Using "HZ-V3" manufactured by Suga Test Instruments Co., Ltd.) Prepare 3 samples for each measurement sample, and use the average as the haze value, and obtain ΔHz from the difference.

[0057] (4) Glossiness In accordance with the method specified in JIS-Z-8741 (1997), using a digital variable-angle gloss meter UGV-5D manufactured by Suga Test Instruments Co., Ltd., measure the 60° specular glossiness on both sides of the film (I side / II side) at 18 points every 50 mm in the film width direction. The average value of these 18 points was used as the glossiness.

[0058] (5) Average particle diameter of the particles From the polyester film, the polyester is removed by the plasma low-temperature ashing treatment method (PR-503 type manufactured by Yamato Scientific Co., Ltd.) to expose the particles. These are observed with a transmission electron microscope (TEM H7100 manufactured by Hitachi, Ltd.), and the image of the particles (the light shading formed by the particles) is linked to an image analyzer (QTM900 manufactured by Cambridge Instruments). The following numerical processing is performed with 5000 or more particles while changing the observation location, and the number average diameter D obtained thereby is taken as the average particle diameter. D = ΣDi / N Here, Di is the equivalent circle diameter of the particle, and N is the number of particles.

[0059] (6) Content of the particles 1 g of the polymer is put into 200 ml of a 1N-KOH methanol solution and heated under reflux to dissolve the polymer. After the dissolution is complete, 200 ml of water is added to the solution, and then the liquid is centrifuged to precipitate the particles, and the supernatant is removed. Water is further added to the particles for washing, and centrifugation is repeated twice. The particles thus obtained are dried, and the content of the particles is calculated by weighing their mass.

[0060] (7) Center plane average roughness (SRa value) of the film surface Measurement was carried out using a three-dimensional fine surface shape measuring instrument (ET-350K manufactured by Kosaka Laboratory Ltd.), and from the obtained surface profile curve, the center plane average roughness SRa value, which is a three-dimensional parameter conforming to JIS-B0601 (1994), was determined. (Measurement conditions) Measurement length in the X direction: 0.5 mm, Feed rate in the X direction: 0.1 mm / second. Feed pitch in the Y direction: 5 μm, Number of lines in the Y direction: 40 lines. Cutoff: 0.25 mm. Stylus pressure: 0.02 mN. Magnification in the height (Z direction): 50,000 times.

[0061] (8) Number of protrusions on the film surface (number / 0.05 mm 2 ) Cut the film into a 7 cm square, and for one surface of the obtained sample, use a 3D roughness meter Bird Scan (VertScan 2.0 manufactured by Rhika System Co., Ltd.) to determine the number of protrusions (number / 0.05 mm 2 ). The objective lens is 10 times, the internal lens is 0.5 times, the Wave mode, and the measurement area is 0.0497 mm 2 . Measure the number of protrusions a in an arbitrary area of the measurement sample. From the bearing analysis (height histogram data) of the Bird Scan measurement, confirm the number of protrusions calculated every 0.01 μm in protrusion height, and count the number of protrusions a exceeding 0.35 μm. To convert the measurement area from 0.0497 mm 2 to 0.05 mm 2 , calculate (number of protrusions a) × 0.05 / 0.0497 to obtain the number of protrusions b per 0.05 mm 2 . Using the same sample, repeat 90 times as an arbitrary area on the same surface, and obtain the average value of the number of protrusions b. <Measurement conditions> Objective lens: 50 times Internal lens: 0.5 times Measurement mode: Phase mode Scan range: +10, -20 Wavelength filter: 530 Filter: Gaussian cut-off value 50 μm Interpolation: Complete Approximation surface: Polynomial approximation 4th order.

[0062] (9) Intrinsic viscosity of polyester According to JIS K7367 (2000), dissolve the polyester resin or polyester film in 100 mL of orthochlorophenol (solution concentration C = 1.2 g / mL), and measure the viscosity of the solution at 25°C using an Ostwald viscometer. Also, measure the viscosity of the solvent in the same way. Using the obtained solution viscosity and solvent viscosity, calculate [η] by the following formula (C), and use the obtained value as the intrinsic viscosity. ηsp / C = [η] + K[η] 2 ·C (Here, ηsp = (solution viscosity / solvent viscosity) - 1, and K is the Huggins constant (assumed to be 0.343 ) is.

[0063] (10) Film thickness, each layer thickness The film was embedded in an epoxy resin, and a film cross-section was cut out with a microtome. The cross-section was observed with a transmission electron microscope (TEM H7100 manufactured by Hitachi, Ltd.) at a magnification of 5000 times to determine the film thickness and the thickness of each polyester layer.

[0064] (11) Process contamination suppression The biaxially oriented polyester film was cut into a rectangular sample with a width of 10 mm and a length of 150 mm, and was heat-pressed on a rubber plate with a width of 10 cm, a length of 10 cm, and a thickness of 1 cm using an air press at a temperature of 180 °C, a pressure of 1.5 MPa, and a press time of 10 minutes. The generation of foreign substances due to oligomers adhering to the rubber plate after the heat press treatment was calculated by the following formula as the ratio of the area of the oligomers adhering to the rubber plate to the area of any 1 cm × 1 cm area on the surface of the rubber plate. This evaluation was performed 20 times (n = 20) and judged according to the following criteria. Process contamination = (Area of oligomers adhering to the rubber plate / Area of 1 cm × 1 cm on the rubber plate) × 100 (%) ◎: Less than 10% 〇: 10% or more and less than 20% △: 20% or more and less than 50% ×: 50% or more.

[0065] (12) Release property A hard coat layer (UF-TCI-1 manufactured by Kyoeisha Chemical Co., Ltd.) was applied to a biaxially oriented polyester film using an applicator so that the dried thickness would be 40 μm, and it was dried at 80°C for 10 minutes. Then, it was cut into a rectangular sample with a width of 10 mm and a length of 150 mm. Using this laminate, a press machine heated to a temperature of 160°C for both the upper and lower mold temperatures was used, and an aluminum plate with a thickness of 0.2 mm / a polyimide film with a thickness of 0.125 mm ("Kapton" (registered trademark) 500H / V manufactured by Toray DuPont) / biaxially oriented polyester film / hard coat layer / polyimide film with a thickness of 0.125 mm ("Kapton" (registered trademark) 500H / V manufactured by Toray DuPont) / an aluminum plate with a thickness of 0.2 mm was heated and pressed under the condition of 1.5 MPa for 1 hour. After the heat pressing, it was cooled to 25°C, the biaxially oriented polyester film / hard coat layer was taken out, and 2 irradiated with ultraviolet rays having an illuminance of 2000 mJ / cm ◎: Ten release tests were conducted, and film breakage and adhesion did not occur in all ten times. 〇: Ten release tests were conducted, and film breakage or adhesion occurred once. ×: Ten release tests were conducted, and film breakage or adhesion occurred two or more times.

[0066] (13) Content of recycled polyester raw material It was calculated from the total content and layer thickness of the recycled polyester raw materials A to C used in each example and comparative example, and rounded up to an integer by rounding off one digit or more after the decimal point.

[0067] (Manufacture of polyester) The polyester resin used for film formation was prepared as follows.

[0068] (Polyester resin A) A polyethylene terephthalate resin (intrinsic viscosity 0.45 dl / g) with 100 mol% terephthalic acid component as the dicarboxylic acid component and 100 mol% ethylene glycol component as the glycol component was used as polyester resin A.

[0069] (Polyester resin B) A polyethylene terephthalate resin (intrinsic viscosity 0.45 dl / g) with 100 mol% terephthalic acid component as the dicarboxylic acid component and 100 mol% ethylene glycol component as the glycol component was used as polyester A. Then, a polyethylene terephthalate resin with an intrinsic viscosity of 0.65 dl / g obtained by solid-phase polymerization was used as polyester resin B.

[0070] (Polyester resin C) A polyethylene terephthalate resin (intrinsic viscosity 0.75 dl / g) with 100 mol% terephthalic acid component as the dicarboxylic acid component and 100 mol% ethylene glycol component as the glycol component was used as polyester E. Then, a polyethylene terephthalate resin with an intrinsic viscosity of 0.90 dl / g obtained by solid-phase polymerization was used as polyester resin C.

[0071] (Polyester resin D) "Hytrel" (registered trademark) manufactured by Toray DuPont Co., Ltd., which is a copolymer of polybutylene terephthalate and polytetramethylene glycol, was used as polyester resin D.

[0072] (Recycled polyester raw material A) A film obtained by biaxially stretching and molding only polyester resin B as a raw material by a conventional method was wound up to obtain a film roll. Next, this film was compressed and cut by a granulator and pelletized into a cylindrical shape of Φ5 mm × 20 mm to be used as recycled polyester raw material A. The obtained recycled polyester raw material A had an intrinsic viscosity of 0.60 dl / g.

[0073] (Recycled polyester raw material B) The film obtained in Example 1 described below was cut with a crusher having a screen diameter of Φ5 mm, and then the cut used film was added to a washing tank equipped with stirring blades. A 4.0 mass% aqueous sodium hydroxide solution was added so that the washing concentration became 10 mass%. Further, polyoxyethylene octyl phenyl ether corresponding to 0.02 mass% was added to the added aqueous sodium hydroxide solution. The washing tank was heated to 85°C and washed for 20 minutes while stirring at a stirrer rotation speed of 200 rpm, and then washed with pure water. Further, a polyester support dried in vacuo at 120°C was melt-kneaded with an extruder, coarse particles and foreign matters were filtered off with a filter having a mesh size of 5 μm, and then discharged in a strand shape from a die and cut while cooling to form chips to obtain a recycled polyester raw material. This was designated as recycled polyester raw material B. The entire film of Example 1 contained 4.0 mass% of silica particles having an average particle diameter of 2.2 μm, and these were used as the particles contained in recycled polyester raw material B.

[0074] (Recycled polyester raw material C) A recycled polyester raw material was obtained in the same manner as recycled polyester raw material B except that the film produced in Example 9 described below was used. This was designated as recycled polyester raw material C. The entire film of Example 9 contained 2.8 mass% of silica particles having an average particle diameter of 4.7 μm, and these were used as the particles contained in recycled polyester raw material C.

[0075] (Particle master raw material A) A polyethylene terephthalate particle master (intrinsic viscosity 0.65 dl / g) containing aggregated silica particles having a number average particle diameter of 2.2 μm in polyester B at a particle concentration of 10 mass% was used as particle master raw material A.

[0076] (Particle master raw material B) A polyethylene terephthalate particle master (intrinsic viscosity 0.65 dl / g) containing aggregated silica particles having a number average particle diameter of 4.7 μm in polyester B at a particle concentration of 10 mass% was used as particle master raw material B.

[0077] (Particle master raw material C) A polyethylene terephthalate particle masterbatch (intrinsic viscosity 0.65 dl / g) containing aggregated silica particles with a number average particle diameter of 4.7 μm at a particle concentration of 20% by mass in polyester B was used as the particle masterbatch raw material C.

[0078] (Example 1) The raw materials were supplied to separate single-screw extruders with an oxygen concentration of 0.2% by volume so that the composition and layer structure were as shown in the table. The cylinder temperature of the A-layer extruder was melted at 270 °C, the cylinder temperature of the B-layer extruder was melted at 270 °C, the short tube temperature after the A-layer and B-layer merged was set at 275 °C, and the die temperature was set at 280 °C. At a resin temperature of 280 °C, it was discharged in a sheet form onto a cooling drum with temperature control at 25 °C from a T-die. At that time, electrostatic application was performed using a wire-shaped electrode with a diameter of 0.1 mm and adhered to the cooling drum to obtain an unstretched sheet. Next, before stretching in the longitudinal direction, the film temperature was raised with a heating roll, and using a stretching roll and a stretching nip roll, the nip pressure between the stretching roll and the stretching nip roll was 0.3 MPa, and it was stretched 3.0 times in the longitudinal direction at a stretching temperature of 83 °C, and immediately cooled with a metal roll with temperature control at 40 °C. Next, it was stretched 3.4 times in the width direction with a tenter-type transverse stretching machine at a stretching first half temperature of 95 °C, a stretching middle stage temperature of 110 °C, and a stretching second half temperature of 140 °C. As it was, heat treatment was performed in the tenter at a heat treatment first half temperature of 200 °C and a heat treatment middle stage temperature of 230 °C, and heat treatment was performed at a slow cooling temperature of 170 °C while applying a 5% relaxation in the width direction to obtain a biaxially oriented polyester film with a three-layer structure of A-layer / B-layer / A-layer with a film thickness of 12 μm. The obtained biaxially oriented polyester film was excellent in both process contamination suppression and releasability.

[0079] (Examples 2 to 4) A biaxially oriented polyester film with a film thickness of 12 μm was obtained in the same manner as in Example 1 except that the composition and layer structure were changed as shown in the table. The obtained biaxially oriented polyester film was excellent in both process contamination suppression and releasability.

[0080] (Examples 5 to 7) A biaxially oriented polyester film with a film thickness of 50 μm was obtained in the same manner as in Example 1, except that the composition and layer structure were changed as shown in the table. The obtained biaxially oriented polyester film was excellent in both process contamination suppression and releasability.

[0081] (Examples 8 - 10) A biaxially oriented polyester film with a film thickness of 125 μm was obtained in the same manner as in Example 1, except that the composition and layer structure were changed as shown in the table. The obtained biaxially oriented polyester film was excellent in both process contamination suppression and releasability.

[0082] (Examples 11 - 13) Biaxially oriented polyester films with a film thickness of 12 μm were obtained in the same manner as in Example 1, except that the composition was changed as shown in the table. The obtained biaxially oriented polyester films were excellent in both process contamination suppression and releasability.

[0083] (Example 14) A biaxially oriented polyester film with a film thickness of 50 μm was obtained in the same manner as in Example 5, except that the composition was changed as shown in the table. The obtained biaxially oriented polyester film was excellent in both process contamination suppression and releasability.

[0084] (Example 15) A biaxially oriented polyester film with a film thickness of 125 μm was obtained in the same manner as in Example 9, except that the composition was changed as shown in the table. The obtained biaxially oriented polyester film was excellent in both process contamination suppression and releasability.

[0085] (Comparative Examples 1 - 2) A biaxially oriented polyester film with a film thickness of 12 μm was obtained in the same manner as in Example 1, except that the composition and layer structure were changed as shown in the table. The obtained biaxially oriented polyester film was excellent in releasability, but poor in both process contamination suppression.

[0086] (Comparative Example 3) A biaxially oriented polyester film with a film thickness of 50 μm was obtained in the same manner as in Example 1, except that the composition and layer structure were changed as shown in the table. The obtained biaxially oriented polyester film was excellent in releasability, but had poor process contamination suppression performance.

[0087] (Comparative Example 4) A biaxially oriented polyester film with a film thickness of 125 μm was obtained in the same manner as in Example 15, except that the composition was changed as shown in the table. The obtained biaxially oriented polyester film was excellent in releasability, but had poor process contamination suppression performance.

[0088] [Table 1]

[0089] [Table 2]

[0090] [Table 3] [Industrial Applicability]

[0091] According to the present invention, it is possible to provide a polyester film for a carrier film of a circuit board laminate and a carrier film for a circuit board laminate that suppress process contamination due to oligomer precipitation during heating.

Claims

1. A polyester film for use as a carrier film in a circuit board laminate, the polyester film having a cold crystallization temperature (Tcc) of 150° C. or higher and lower than 165° C. and a haze of 30% or higher.

2. The polyester film for a carrier film of a circuit board laminate according to claim 1 , wherein the content of a cyclic trimer in the polyester film is 0.01% by mass or more and 1.00% by mass or less.

3. 2. The polyester film for a carrier film of a circuit board laminate according to claim 1, wherein the difference ΔHz between the haze of the polyester film and the haze of the film after heating the polyester film at 170° C. for 3 hours is less than 2.0%.

4. The number of protrusions having a height exceeding 0.35 μm on at least one surface of the polyester film is 100 / 0.05 mm ２ More than 10,000 pieces / 0.05mm ２ 2. The polyester film for use as a carrier film in a circuit board laminate according to claim 1, which is:

5. 2. The polyester film for use as a carrier film in a circuit board laminate according to claim 1, wherein the polyester film comprises at least three layers.

6. 2. The polyester film for use as a carrier film for circuit board laminate according to claim 1, wherein the polyester film contains 40% by mass or more and 100% by mass or less of recycled polyester raw materials.

7. A carrier film for a circuit board lamination process, comprising the polyester film for a circuit board lamination carrier film according to claim 1 .

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