JP3364380B2 - 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 as a support layer of a photoresist film having excellent substrate shape conformability 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 / a photoresist layer / a protective layer. As the support layer, a polyester film having excellent mechanical properties, optical properties, chemical resistance, dimensional stability and flatness 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 the protective layer.

The method of using the photoresist film will be briefly described. First, the protective layer is peeled off, and the exposed photoresist layer is brought into close contact with the conductive substrate attached to the substrate. 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 image of the circuit printed on the glass plate, and the photosensitive resin of the photoresist layer reacts only on the exposed portion. Then, the glass plate and the support layer are removed, and the unexposed portion of the photoresist layer is 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 material portion is removed. After that, if the exposed and reacted photoresist layer is removed by an appropriate method, a conductive base material 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 material layer formed on a substrate, and another conductive base material layer is further provided on the insulating layer. Forming circuits (so-called circuit stacking) is frequently performed. This circuit is laminated by laminating an insulating layer / conductive substrate layer on a substrate on which an existing circuit is formed, and further adhering a photoresist layer / support layer on this conductive substrate layer. Then, another circuit of the conductive base material layer is formed by the method described above. However, when the circuits are laminated, the surface of the laminated insulating layer / conductive base material layer has an uneven shape influenced by the unevenness of the existing circuit, and the photoresist layer / If the support layer does not adhere in a shape that follows this uneven shape, there will be a problem that a newly provided circuit will be partially omitted.

In addition, recently, the circuit of the conductive base material has become thinner and the interval between them has become narrower, so that reproducibility of image formation and high resolution are required. Therefore, the polyester film used as the support layer is also required to have high quality. That is, the polyester film used as the support layer is required to have high transparency and low film haze. When exposing a photoresist layer in a photoresist film, light will pass through the support layer as described above.
Therefore, if the transparency of the support layer is low, the photoresist layer may not be sufficiently exposed, and the resolution may deteriorate due to light scattering.

[0006]

Means for Solving the Problems The inventors of the present invention have earnestly studied to develop a film for a support layer of a photoresist film which can solve the above problems, and as a result, have identified a specific polyester compounded with a specific lubricant. It was found that the polyester film having the above-mentioned plane orientation coefficient has excellent properties, and has completed the present invention.

That is, according to the present invention, the average particle size is 2.5 μm.
m or less lubricant, polymer melting point 210-250
℃ , the proportion of isophthalic acid as a copolymerization component is 3-18 m
A film made of a copolymerized polyester of 10 % by weight,
A polyester film used for a support layer of a photoresist film, wherein the film has a plane orientation coefficient of 0.09 to 0.16. The present invention will be described in more detail below.

[0008] The copolymerized polyester in the [copolyesters present invention, the melting point of the polymer consists of an acid component and a glycol component is a copolymer component of 210 to 250 ° C.
It is a copolymerized polyethylene terephthalate containing 3 to 18 mol% of isophthalic acid . The copolymerization component other than isophthalic acid of the copolymerization polyethylene terephthalate may be an acid component or a glycol component. Examples of the acid component off Tal acid,
Aromatic dibasic acids such as naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, etc., and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, etc. can be exemplified, and glycol component Examples thereof include aliphatic diols such as butanediol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These may be used alone or in combination of two or more.

[0009] proportion of the copolymerizable component, the type depending on the results as a polymer melting point of 210 to 250 ° C., a ratio preferably comprised within the range of two hundred fifteen to two hundred and thirty-five ° C., the copolymerization synthesis
The proportion of isophthalic acid, which is the amount, is in the range of 3 to 18 mol% . If the melting point of the polymer is less than 210 ° C., the crystallinity of the polymer is too small and the obtained film causes blocking and is not suitable for production, and the mechanical strength of the film is poor. On the other hand, when the melting point of the polymer exceeds 245 ° C., the crystallinity of the polymer is too large, and the followability of the photoresist film to the substrate shape is impaired.

Here, the melting point of the copolymerized polyester is measured by Du Pont Instruments 910.
According to a method of determining a melting peak at a temperature rising rate of 20 ° C./minute using DSC. The sample amount was about 20 mg.

The copolymerized polyester used in the present invention is not limited by its production method. For example, a method in which terephthalic acid, ethylene glycol and a copolymerization component are subjected to an esterification reaction, and then the resulting reaction product is subjected to a polycondensation reaction to obtain a copolymerized polyester, or dimethyl terephthalate, ethylene glycol and a copolymerization component are transesterified. A method of reacting and then subjecting the obtained reaction product to a polycondensation reaction to obtain a copolyester is preferably used. In the production of the copolyester, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber and an antistatic agent may be added if necessary.

[Lubricant] The copolyester of the present invention contains a lubricant having an average particle size of 2.5 μm or less. This lubricant may be inorganic or organic, but is preferably inorganic. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, barium sulfate, etc., and examples of the organic lubricant include crosslinked polystyrene particles,
Examples thereof include silicone particles. Both require that the average particle size is 2.5 μm or less. If the average particle size of the lubricant exceeds 2.5 μm, the transparency of the film is impaired, and problems such as insufficient exposure of the photoresist layer and deterioration of resolution occur.

The amount of the lubricant in the copolyester may be determined depending on the winding property in the film manufacturing process. For example, it is 0.001 to 0.5% by weight in the copolyester, but it depends on the average particle size of the lubricant used. Preferred amounts will vary. 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 size of 2.0 μm and about 0.3% by weight in the case of titanium dioxide having an average particle size of 0.3 μm.

[Polyester Film] The polyester film of the present invention is obtained by melting the above-mentioned copolymerized polyester containing a lubricant, discharging it from a die to form a film, biaxially stretching and heat-setting. The polyester film of the present invention needs to have a plane orientation coefficient of 0.09 to 0.16. It is more preferable that the film have a plane orientation coefficient of 0.10 to 0.15.

If the surface orientation coefficient of the film is less than 0.09, the mechanical strength of the film is insufficient and pinholes are formed when the film is attached to a substrate having irregularities on the surface. on the other hand,
When the plane orientation coefficient exceeds 0.16, the film substrate conformability is poor and a defect occurs in the circuit.

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

[0017]

## EQU1 ## f = [(nx + ny) / 2] -nz

In the above equation, f is the plane orientation coefficient, nx,
ny and nz are the refractive indices in the lateral direction, the longitudinal direction and the thickness direction of the film, respectively.

Regarding the refractive index, a polarizing plate analyzer is attached to the eyepiece side of Abbe's refractometer, and each refractive index is measured with a monochromatic light NaD line. Methylene iodide was used as the mount solution, and the measurement temperature was 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 rapidly cooled to prepare an unstretched film, and the stretching temperature is set when the unstretched film is biaxially stretched. 85 to 14
Stretching ratio in the longitudinal and transverse directions of 2.6 to 4.0 at 5 ° C.
Double the film and, if necessary, biaxially stretch the film to 15
It can be obtained by heat setting at 0 to 210 ° C.

The above-mentioned biaxial stretching is a sequential biaxial stretching method in which an unstretched film is stretched in the machine direction or the transverse direction to obtain a uniaxially stretched film, and then this uniaxially stretched film is stretched in the transverse direction or the machine direction. Alternatively, it may be a simultaneous biaxial stretching method in which the 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, if necessary.

Further, the polyester film of the present invention is
The L5 value in the vertical and horizontal directions of the film is 1 to
It is preferably 65 g / mm, and more preferably the average value of L5 values in the longitudinal direction and the lateral direction is 1 to 55 g / mm. If the L5 values in the vertical direction and the horizontal direction of the film are within the above ranges, the photoresist film adheres in a shape that follows the uneven shape of the existing circuit when stacking the circuits, so that the newly provided circuit This is preferable because there is no partial omission.

With respect to the above L5 value, a tensile test of a film (10 mm wide strip type sample) was conducted at 100 ° C. under conditions of a chuck interval of 10 cm and a tensile speed of 10 cm / min, and the sample showed an elongation of 5%. 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, but especially the unstretched film made of the polyester of the present invention is biaxially stretched. At that time, the stretching temperature was 100 to 145 ° C., the stretching ratio in the machine direction and the transverse direction was 3.0 to 3.6 times, and the film after biaxial stretching was heat set at 170 to 190 ° C., if necessary. It can be obtained by adjusting the thickness of the film after stretching 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. 5-75μ
m, particularly preferably 10 to 50 μm. If the thickness is less than 3 μm, breakage or the like is likely to occur during processing, while if it exceeds 75 μm, it is uneconomical because of excessive quality.

[Coating Layer] The polyester film of the present invention may be provided with a coating layer for the purpose of adjusting the adhesiveness to the photoresist layer. Such a coating layer may be provided in the film manufacturing process or may be applied after the film is manufactured. Particularly, from the viewpoint of the uniformity of the thickness of the coating layer and the production efficiency, a method of coating after the longitudinal stretching in the film manufacturing process and before entering the lateral stretching step is preferable. Examples of coating agents include polyester, polyamide, polystyrene,
Examples thereof include resins such as polyacrylate, polycarbonate, polyarylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, polyurethane, and copolymers and mixtures of these resins, but are not limited thereto. Do not mean.
In addition, 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 with respect to the total amount of polyester used for film formation. If necessary, additives such as antioxidants, heat stabilizers, antistatic agents, lubricants, dyes and pigments may be added.

[0027]

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

Examples 1 to 4 and Comparative Examples 1 to 3 Spherical monodisperse silica having an average particle size of 1.5 μm (particle size ratio 1.0
7, containing 0.1% by weight of relative standard deviation 0.1),
Copolymerized polyethylene terephthalate (intrinsic viscosity 0.60) obtained by copolymerizing the components shown in Table 1 was melt extruded at the temperature shown in Table 2 and rapidly solidified to obtain an unstretched film.

Next, this unstretched film was longitudinally and laterally stretched under the conditions shown in Table 2 and then heat set at 180 ° C. to obtain a biaxially oriented film having a thickness of 25 μm. The characteristics of this film are shown in Table 3.

[Example 5 and Comparative Example 4] 12 mol% of isophthalic acid copolymerized polyethylene terephthalate containing a lubricant shown in Table 2 (intrinsic viscosity 0.6)
0) is melt-extruded at 280 ° C. and rapidly solidified to give an unstretched film, and then the unstretched film is stretched at a longitudinal stretching temperature of 110.
Biaxially oriented film was obtained in the same manner as in Example 1 except that the film was sequentially biaxially stretched at a temperature of 180 ° C., a longitudinal stretching ratio of 3.0 times, a lateral stretching temperature of 120 ° C., and a lateral stretching ratio of 3.0 times, and then heat-set at 180 ° C. Got The characteristics of this film are shown in Table 3.

[Comparative Examples 5 to 6] Spherical monodisperse silica having an average particle size of 1.5 μm (particle size ratio 1.07, relative standard deviation 0.
1) 12 mol% isophthalic acid copolymerized polyethylene terephthalate containing 0.1% by weight (melting point 228
C., intrinsic viscosity 0.60) was melt extruded at 280.degree. C. and rapidly solidified to obtain an unstretched film. Next, this unstretched film was longitudinally stretched and laterally stretched under the conditions shown in Table 2, and subsequently heat-set at 180 ° C. to obtain a biaxially oriented film. The characteristics of this film are shown in Table 3.

[Examples 6 to 10 and Comparative Example 7] Using the copolymerized polyesters shown in Table 4, the thickness of the unstretched film was changed according to the melt extrusion conditions, and the stretching was carried out under the stretching conditions shown in Table 5. In the same manner as in Example 1, a biaxially oriented film having the thickness and the plane orientation coefficient shown in Table 5 was obtained. Table 6 shows the characteristics of the film and the results of the practical evaluation of the photoresist film.

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

1. A polarizing plate analyzer was attached to the eyepiece side of the refractometer with a plane orientation coefficient Abbe, and methylene iodide was used as the mount solution.
The refractive index of the film in the lateral direction (n
x), the longitudinal refractive index (ny) and the thickness refractive index (n
z) The refractive index was measured, and the plane orientation coefficient (f) was calculated by the following formula.

[0035]

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

2. L5 value manufactured by Toyo Baldwin Co., Ltd.
Attach a constant temperature bath to the Tensilon universal tensile tester, and
The tensile test of the film (10 mm wide strip sample) was performed at 0 ° C. under the conditions of a chuck interval of 10 cm and a tensile speed of 10 cm / min, and the load when the sample showed 5% elongation was divided by the width of the sample. The obtained value was defined as the L5 value (g / mm).

[Evaluation of substrate shape conformability and pinhole resistance] A film having a width of 100 μm, a depth of 15 μm and a length of 5 mm is carved in parallel at intervals of 20 μm.
The copper plate laminated on the surface of a copper plate heated to 00 ° C. was subjected to the following observations with a microscope and evaluated according to the following criteria.

3. Substrate shape conformability ○: The distance from the bottom of the groove carved in the copper plate to the surface of the film on the copper plate side (“lifting”) is 0.1 μm or less. (Flat substrate shape conformability) X: The distance from the bottom of the groove carved in the copper plate to the surface of the film on the copper plate side (“lifting”) exceeds 0.1 μm. (Poor substrate conformability)

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) x: The film covering the groove of the copper plate has a diameter of 0.
Pinholes of 1 μm or more are recognized. (Poor pinhole resistance)

[Practicality Evaluation of Photoresist Film]
A photoresist layer was provided on one side of the film, and a polyethylene film was laminated as a protective layer on the photoresist layer to prepare 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 substrate,
The photoresist layer surface of the photoresist film from which the protective layer was peeled off was adhered. Next, a glass plate on which a circuit was printed was brought into close contact with the photoresist film, and UV exposure was performed 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 produce a circuit. The circuit thus obtained was observed visually or using a microscope, and the practicability of the photoresist film was evaluated based on the results based on the following criteria.

5. Resolution ◯: It has a very high resolution and a clear circuit is recognized. (Good resolution) x: Poor resolution and cannot be used for high-density circuits.
(Poor resolution)

6. Circuit defect resistance ◯: No defects are found in the circuit. (Good circuit defect resistance) Δ: The circuit is rarely found missing. (Slightly good resistance to defects in the circuit) ×: There is a defect in the circuit and there is a practical problem. (Defective Fault Tolerance of Circuit) The above evaluation results are shown in Tables 3 and 6.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

[Table 6]

From the results shown in Tables 3 and 6, it can be seen that the films of Examples are excellent in all of substrate shape followability, pinhole resistance, resolution, and circuit defect resistance.

[0050]

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 extremely excellent substrate followability with respect to the irregularities, and The occurrence of circuit defects can be prevented, and its industrial value is extremely high.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI // H05K 3/06 H05K 3/06 J B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 C08L 67:02 C08L 67:02 (72) Inventor Kazutaka Masaoka 4-13-1 Higashimachi, Hitachi City, Ibaraki Prefecture (72) Inventor Youji Tanaka 4-13-1 Higashimachi, Hitachi City, Ibaraki Prefecture (72) Inventor Kiyo Kimura Ibaraki Prefecture 4-13-1, Higashimachi, Hitachi City (56) Reference JP-A-1-96640 (JP, A) JP-A 64-40400 (JP, A) JP-A 1-96641 (JP, A) JP-A 2-305827 (JP, A) JP-A-3-86729 (JP, A) JP-A-4-50852 (JP, A) JP-A-5-297595 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 G03F 7 / 09,7 / 11 C08G 63/00-63/91

Claims (2)

(57) [Claims] 1. A copolymer component containing a lubricant having an average particle size of 2.5 μm or less, a polymer melting point of 210 to 250 ° C.
A film of a copolyester having a proportion of isophthalic acid of 3 to 18 mol% , wherein the film has a plane orientation coefficient of 0.09 to 0.16. Polyester film used for. 2. The polyester film according to claim 1, wherein the L5 values in the machine direction and the transverse direction of the film are 1 to 65 g / mm, respectively.