JP3150902B2 - Polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film, and more particularly to a polyester film used for a support layer of a photoresist film having excellent substrate shape followability and resolution.

[0002]

2. Description of the Related Art Conventionally, photoresist films have been widely used in the production of printed wiring circuit boards and the like.
The photoresist film is usually a laminated structure composed of a support layer / photoresist layer / protective layer. As the support layer, a polyester film excellent in mechanical properties, optical properties, chemical resistance, dimensional stability, flatness and the like is mainly used. The photoresist layer is a layer made of a photosensitive resin, and a polyethylene film or a polyester film is used as a protective layer.

[0003] The method of using a photoresist film will be briefly described. First, the protective layer is peeled off, and the exposed photoresist layer is brought into close contact with a conductive substrate adhered to a base. The conductive substrate is generally a copper plate. Next, a glass plate on which a circuit is printed is brought into close contact with the support layer side of the photoresist film, and light is irradiated from the glass plate side. Light passes through the transparent portion of the circuit image printed on the glass plate, and the photosensitive resin of the photoresist layer reacts only in the exposed portion. Next, the glass plate and the support layer are removed, and the unexposed portions of the photoresist layer are removed using a suitable solvent or the like. Further, if etching is performed using an acid or the like, the photoresist layer is removed and the exposed conductive base portion is removed. Thereafter, by removing the exposed and reacted photoresist layer by an appropriate method, a conductive substrate layer is formed as a circuit on the substrate.

[0004]

However, recently, an insulating layer is provided on an existing circuit of a conductive base layer formed on a base, and another conductive base layer is further formed on the insulating layer. (Lamination of circuits) is frequently performed. This circuit lamination is performed by laminating an insulating layer / conductive substrate layer on a substrate on which an existing circuit is formed, and further attaching a photoresist layer / support layer on the conductive substrate layer. Then, another circuit of the conductive base material layer is formed by the above-described method. However, when the circuit is laminated, the surface of the laminated insulating layer / conductive substrate layer has an uneven shape influenced by the unevenness of the existing circuit, and the photoresist layer / If the support layer is not adhered in a shape following the uneven shape, there arises a problem that a newly provided circuit is partially missing.

In recent years, the circuit of the conductive base material has become thinner and the interval between the circuits has become narrower, so that reproducibility of image formation and high resolution are required. For this reason, high quality has been required for the polyester film used as the support layer. That is, it is necessary that the polyester film used as the support layer has high transparency and low film haze. When exposing the photoresist layer in the photoresist film, light passes through the support layer as described above.
Therefore, if the transparency of the support layer is low, problems such as insufficient exposure of the photoresist layer and deterioration of resolution due to light scattering occur.

[0006]

The present inventors have made intensive studies to develop a film for a support layer of a photoresist film capable of solving the above-mentioned problems. It has been found that a polyester film having a plane orientation coefficient of 1) has excellent properties, and the present invention has been completed.

That is, the present invention relates to a copolymer of 99 to 55% by weight mainly composed of polyethylene terephthalate having a melting point of 210 to 250 ° C., and a polybutylene terephthalate or a polybutylene terephthalate having a melting point of 180 to 223 ° C. Copolyester 1-4
5% by weight, containing a lubricant having an average particle diameter of 2.5 μm or less, and having a film plane orientation coefficient of 0.08 to 0.16.
A polyester film used for a support layer of a photoresist film. Hereinafter, the present invention will be described in more detail.

[Polyester] The copolymerized polyester mainly composed of polyethylene terephthalate used in the present invention may be an acid component or a glycol component. As the acid component, isophthalic acid, phthalic acid, aromatic dibasic acids such as naphthalenedicarboxylic acid, etc.
Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid and the like, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and the like, and glycol components such as butanediol and hexanediol can be used. Examples thereof include alicyclic diols such as diols and cyclohexanedimethanol. These can be used alone or in combination of two or more.

The proportion of the copolymer component of the copolymerized polyester mainly composed of polyethylene terephthalate depends on the kind thereof, but as a result, the melting point of the polymer is from 210 to 250 ° C.
The ratio is preferably in the range of 215 to 235 ° C.
When the melting point of the polymer is less than 210 ° C., the crystallinity of the polymer is so small that the obtained film causes blocking and is not suitable for production, and the mechanical strength of the film is also poor. On the other hand, if the melting point of the polymer exceeds 250 ° C., the crystallinity of the polymer is too large, and the followability of the substrate shape when used in a photoresist film is impaired.

[0010] On the other hand, the copolymerized polyester mainly composed of polybutylene terephthalate used in the present invention may be an acid component or a glycol component. As the acid component, isophthalic acid, phthalic acid,
Aromatic dicarboxylic acids such as aromatic dibasic acids such as naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, etc., and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be exemplified. Examples thereof include aliphatic diols such as ethylene glycol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more.

The proportion of the copolymer component of the copolymerized polyester mainly composed of polybutylene terephthalate depends on the kind thereof, but as a result, the melting point of the polymer is from 180 to 223 ° C.
Preferably it is 200-223 degreeC, More preferably, it is 210-200.
This is a ratio in the range of 223 ° C. Polymer melting point 18
If the temperature is lower than 0 ° C., the crystallinity of the polymer is too small, resulting in blocking of the resulting film, which is not suitable for production, and the mechanical strength of the film is also poor. The melting point of polybutylene terephthalate homopolymer is 223 ° C., and it is difficult to obtain a copolyester having a higher melting point.

Here, the melting point of polyester is measured by Du.
Pont Instruments 910 DSC
And determining a melting peak at a heating rate of 20 ° C./min. The sample amount is about 20 mg.

The copolymer polyester mainly composed of polyethylene terephthalate and the copolymer polyester mainly composed of polybutylene terephthalate or polybutylene terephthalate used in the present invention are not limited by the production method. For example, in the case of a copolymer polyester mainly composed of polyethylene terephthalate,
Terephthalic acid, a method of subjecting ethylene glycol and a copolymer component to an esterification reaction, and then subjecting the resulting reaction product to a polycondensation reaction to form a copolymerized polyester, or a method of subjecting dimethyl terephthalate, ethylene glycol and a copolymer component to a transesterification reaction, Then, the obtained reaction product is subjected to a polycondensation reaction to give a copolymerized polyester,
Is preferably used. In the production of each copolymerized polyester and polybutylene terephthalate, if necessary, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent and the like can be added.

The polyester film of the present invention is mainly composed of polyethylene terephthalate and has a melting point of 210 to 25.
It must be composed of 99 to 55% by weight of a copolymerized polyester at 0 ° C and 1 to 45% by weight of a polybutylene terephthalate or 1 to 45% by weight of a copolymerized polyester mainly composed of polybutylene terephthalate and having a melting point of 180 to 223 ° C. For a film containing less than 1% by weight of polybutylene terephthalate or a copolymerized polyester mainly composed of polybutylene terephthalate and more than 99% by weight of a copolymerized polyester mainly composed of polyethylene terephthalate, a fine base when used in a photoresist film. Poor shape followability.

When the content of polybutylene terephthalate or the copolymerized polyester mainly composed of polybutylene terephthalate exceeds 45% by weight and the content of the copolymerized polyester mainly composed of polyethylene terephthalate is less than 55% by weight, the mechanical strength of the film is reduced. Insufficient, pinholes occur when pasted on a substrate with uneven surface.

[Lubricant] The polyester in the present invention comprises:
Contains a lubricant having an average particle size of 2.5 μm or less. The lubricant may be inorganic or organic, but is preferably inorganic. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, barium sulfate and the like, and examples of the organic lubricant include crosslinked polystyrene particles and silicone particles. All have an average particle size of 2.5μ
m or less. The average particle size of the lubricant is 2.5μ
If it exceeds m, the transparency of the film will be impaired, causing problems such as insufficient exposure of the photoresist and a reduction in resolution.

The amount of the lubricant in the polyester may be determined depending on the winding property in the film production process. For example, the amount is 0.001 to 0.5% by weight in the polyester, but the preferred amount varies depending on the average particle size of the lubricant used. . Generally, it is preferable to add a small amount of a lubricant having a large particle size and a large amount of a small lubricant. For example, it is preferable to add about 0.05% by weight in the case of silica having an average particle diameter of 2.0 μm, and about 0.3% by weight in the case of titanium dioxide having an average particle diameter of 0.3 μm.

[Polyester Film] The polyester film of the present invention is prepared by blending a predetermined amount of the above-mentioned copolymerized polyester mainly composed of polyethylene terephthalate and a copolymerized polyester mainly composed of polybutylene terephthalate or polybutylene terephthalate, respectively. It can be manufactured by melt-extrusion, forming into a film, biaxial stretching, and heat setting. At this time, the above-mentioned lubricant, for example, a spherical monodispersed lubricant, is contained in the copolymerized polyester mainly composed of polyethylene terephthalate and / or the copolymerized polyester mainly composed of polybutylene terephthalate or polybutylene terephthalate, or both, during polymerization. Or may be added and mixed during melt extrusion.

The polyester film of the present invention is obtained by melting the above-mentioned lubricant-containing polyester, discharging it from a die, forming it into a film, biaxially stretching and heat setting.
The polyester film of the present invention needs to have a plane orientation coefficient of 0.08 to 0.16. More preferably, the plane orientation coefficient of the film is 0.10 to 0.15.

When the plane orientation coefficient of the film is less than 0.08, the mechanical strength of the film is insufficient, and a pinhole is generated when the film is attached to a substrate having an uneven surface. on the other hand,
If the plane orientation coefficient exceeds 0.16, the film base shape followability is inferior, and a defect occurs in the circuit.

Here, the plane orientation coefficient is defined by the following equation.

[0022]

F = [(nx + ny) / 2] -nz

In the above equation, f is the plane orientation coefficient, nx,
ny and nz are the refractive indexes in the horizontal, vertical and thickness directions of the film, respectively.

The refractive index is measured by attaching a polarizing plate analyzer to the eyepiece side of the Abbe refractometer and using a monochromatic NaD line. The mounting solution uses methylene iodide, and the measurement temperature is 25 ° C.

In order to obtain a film having the above-mentioned plane orientation coefficient, for example, the polyester of the present invention is melt-extruded into a sheet and quenched to produce an unstretched film. 85 to 14
5 ° C., stretching ratio in the longitudinal and transverse directions is 2.6 to 4.0.
And if necessary, the film after biaxial stretching
It can be obtained by heat setting at 0 to 210 ° C.

The above-mentioned biaxial stretching is carried out by a sequential biaxial stretching method in which an unstretched film is stretched in a machine direction or a transverse direction to form a uniaxially stretched film, and then the uniaxially stretched film is stretched in a transverse direction or a machine direction. Or a simultaneous biaxial stretching method in which an unstretched film is simultaneously stretched in the machine direction and the transverse direction. The biaxially stretched film can be further stretched in the machine direction and / or the transverse direction as required.

Further, the polyester film of the present invention comprises:
The L5 values in the vertical and horizontal directions of the film are 1 to 1, respectively.
It is preferably 55 g / mm, and more preferably the average value of L5 values in the vertical and horizontal directions is 1 to 45 g / mm. When the L5 value in the vertical direction and the horizontal direction of the film is within the above range, the photoresist film adheres in a shape following the uneven shape of the existing circuit when laminating the circuits. It is preferable because partial omission does not occur.

The above L5 value is obtained by conducting a tensile test of a film (a strip-shaped sample having a width of 10 mm) at 100 ° C. under the conditions of a chuck interval of 10 cm and a pulling speed of 10 cm / min. It is a value (g / mm) obtained by dividing the load at the time of application by the width of the sample.

The film having the above L5 value can be obtained under the same stretching conditions as the biaxially stretched film having the above-mentioned plane orientation coefficient. In particular, the unstretched film made of the polyester of the present invention is biaxially stretched. At this time, the stretching temperature is 100 to 145 ° C, the stretching ratio in the longitudinal direction and the transverse direction is 3.0 to 3.6 times, and the film after biaxial stretching is heat-set at 170 to 190 ° C as needed, It can be obtained by setting the thickness of the stretched film to 5 to 50 μm, particularly 10 to 30 μm.

The thickness of the polyester film of the present invention is preferably 3 to 75 μm. 5 to 75μ
m, particularly preferably 5 to 50 μm. Thickness 3
If it is less than μm, breakage or the like is likely to occur during processing, while 7
Those exceeding 5 μm are excessive quality and uneconomical.

[Coating Layer] The polyester film of the present invention may be provided with a coating layer for the purpose of adjusting the adhesiveness with the photoresist layer. Such a coating layer may be provided in the film manufacturing process, or may be applied after the film is manufactured. In particular, from the viewpoint of the uniformity of the thickness of the coating layer and the production efficiency, it is preferable to apply the film after the longitudinal stretching in the film manufacturing process and before the horizontal stretching process. Examples of coating agents include polyester, polyamide, polystyrene,
Examples include, but are not limited to, resins such as polyacrylate, polycarbonate, polyarylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, polyurethane, and copolymers and mixtures of these resins. Do not mean.
In the present invention, about 1% by weight or less of another polymer (for example, polyethylene, polystyrene, polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) can be contained based on the total amount of polyester used for film formation. If necessary, additives such as an antioxidant, a heat stabilizer, an antistatic agent, a lubricant, a dye, and a pigment may be added.

[0032]

The present invention will be further described with reference to the following examples.

Examples 1 to 6 and Comparative Examples 1 to 10 Spherical monodispersed silica having an average particle size of 1.5 μm (particle size ratio 1.07,
0.1% by weight relative standard deviation 0.1)
(Hereinafter referred to as “copolymerized PE”).
T ") and polybutylene terephthalate (hereinafter abbreviated as" PBT ") or a copolymerized polyester mainly composed of polybutylene terephthalate obtained by copolymerizing the components shown in Table 1 (hereinafter abbreviated as" copolymerized PBT ") Do)
Are blended in the proportions shown in Table 1 and melt-extruded at 280 ° C.
It was quenched and solidified to obtain an unstretched film.

Next, this unstretched film was stretched in the machine direction under the conditions shown in Table 2, then stretched in the transverse direction, and then heat-set at 180 ° C. to obtain the thickness and plane orientation coefficient shown in Table 2. An axially oriented film was obtained. Table 3 shows the characteristics of the film and the results of the practical evaluation of the photoresist film.

Example 7 The procedure was carried out except that 0.3% by weight of titanium dioxide having an average particle diameter of 0.3 μm was added instead of adding 0.1% by weight of spherical monodispersed silica having an average particle diameter of 1.5 μm. In the same manner as in Example 5, the thickness was 10 μm, and the plane orientation coefficient was 0.1.
088 biaxially oriented film was obtained. Table 3 shows the characteristics of the film and the results of the practical evaluation of the photoresist film.

[Comparative Example 11] The procedure was carried out except that 0.1% by weight of spherical monodispersed silica having an average particle size of 1.5 μm was added and 0.05% by weight of bulk silica having an average particle size of 2.7 μm was added. In the same manner as in Example 5, a biaxially oriented film having a thickness of 10 μm and a plane orientation coefficient of 0.089 was obtained. Table 3 shows the characteristics of the film and the results of the practical evaluation of the photoresist film.

[Examples 8 to 10 and Comparative Example 12] Table 4
Using the polyester shown in Table 1, the thickness of the unstretched film was changed according to the conditions of melt extrusion, and the film was stretched under the stretching conditions shown in Table 5. An oriented film was obtained. Table 6 shows the characteristics of this film and the results of the practical evaluation of the photoresist film.
Shown in

Various measurements and evaluations were carried out in the following examples.

1. Plane Orientation Coefficient Attach a polarizing plate analyzer to the eyepiece side of Abbe's refractometer, use methylene iodide as the mounting liquid, and measure at a measurement temperature of 25.
The lateral refractive index of the film (n
x), longitudinal refractive index (ny) and thickness refractive index (n
z) The refractive index was measured, and the plane orientation coefficient (f) was determined by the following equation.

[0040]

F = [(nx + ny) / 2] -nz

2. L5 value Toyo Baldwin Co., Ltd. Tensillon universal tensile tester with a thermostat attached at 100 ° C.
mm width strip type sample) tensile test
m, the tensile speed was 10 cm / min, and the load obtained when the sample showed 5% elongation divided by the width of the sample was L.
Five values (g / mm) were used.

[Evaluation of Followability of Base Shape and Resistance to Pinholes] A film was prepared with a width of 50 μm, a depth of 15 μm, and a length of 5 μm.
mm grooves are cut in parallel at intervals of 20 μm.
The film was laminated on the surface of a copper plate heated to 0 ° C., and the following observations were made on the copper plate on which the film was laminated by a microscope, and each was evaluated according to the following criteria.

3. Substrate shape followability ：: The distance (“floating”) from the bottom surface of the groove cut in the copper plate to the surface of the film on the copper plate side is 0.1 μm or less. X: The distance (“floating”) from the bottom surface of the groove cut in the copper plate to the surface of the film on the copper plate side exceeds 0.1 μm. (Failure to follow substrate shape)

4. Pinhole resistance ○: The film covering the groove of the copper plate has a diameter of 0.
No pinhole of 1 μm or more is observed. (Good pinhole resistance) ×: The film covering the groove of the copper plate has a diameter of 0.
Pinholes of 1 μm or more are observed. (Poor pinhole resistance)

[Evaluation of practicality of photoresist film]
A photoresist layer was provided on one side of the film, and a polyethylene film was laminated thereon as a protective layer to produce a photoresist film. A printed circuit was manufactured using the obtained photoresist film. That is, on a copper plate provided on a glass fiber-containing epoxy resin base,
The surface of the photoresist layer of the photoresist film from which the protective layer was peeled off was brought into close contact. Next, a glass plate on which a circuit was printed was brought into close contact with the photoresist film, and ultraviolet light was exposed from the glass plate side. Thereafter, the photoresist film was peeled off, and a series of developing operations such as washing and etching were performed to form a circuit. The circuit thus obtained was observed visually or using a microscope, and the practicality of the photoresist film was evaluated according to the following criteria based on the result.

5. Resolution ：: Extremely high resolution, and a clear circuit was recognized. (Good resolution) ×: Poor resolution, cannot be used for high-density circuits.
(Defective resolution)

6 Defect resistance of the circuit 欠: No lack is found in the circuit. (Good defect resistance of the circuit) Δ: Occasionally, the circuit is missing. (Slightly good defect resistance of circuit) ×: The circuit is missing and there is a problem in practical use. (Defective defect resistance of circuit) Tables 3 and 6 show the above evaluation results.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

[0051]

[Table 4]

[0052]

[Table 5]

[0053]

[Table 6]

As is clear from the results shown in Tables 3 and 6, the films of the examples are excellent in all of the substrate shape followability, the pinhole resistance, the resolution, and the defect resistance of the circuit.

[0055]

According to the present invention, when the polyester film of the present invention is used as a support layer of a photoresist film for providing a circuit on a substrate having fine irregularities, it exhibits excellent substrate followability to the irregularities, and The occurrence of circuit defects can be prevented, and its industrial value is very large.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazutaka Masaoka 4-13-1, Higashicho, Hitachi City, Ibaraki Prefecture (72) Inventor Yoji Tanaka 4-13-1, Higashicho, Hitachi City, Ibaraki Prefecture (72) Inventor Kimura Hakuse 4- 13-1, Higashi-cho, Hitachi City, Ibaraki Prefecture (56) References JP-A-5-186612 (JP, A) JP-A-5-222216 (JP, A) JP-A-5-186613 (JP, A) JP-A-3-86729 (JP, A) JP-A-2-305727 (JP, A) JP-A-3-83625 (JP, A) JP-A-61-80236 (JP, A) JP-A-1- 96641 (JP, A) JP-A-7-96544 (JP, A) JP-A-9-302114 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 7/004 512 G03F 7/09 501 C08J 5/18 CFD C08L 67/02 H05K 3/06

Claims (2)

(57) [Claims] 1. A copolymer polyester mainly composed of polyethylene terephthalate and having a melting point of 210 to 250 ° C.
55% by weight, having a melting point of 180 to 2 mainly composed of polybutylene terephthalate or polybutylene terephthalate.
A photopolymer comprising 1 to 45% by weight of a copolymerized polyester at 23 ° C., containing a lubricant having an average particle diameter of 2.5 μm or less, and having a film plane orientation coefficient of 0.08 to 0.16. Polyester film used for the support layer of the resist film. 2. The polyester film according to claim 1, wherein the L5 value in the longitudinal direction and the L5 value in the lateral direction of the film are each 1 to 55 g / mm.