JP3932074B2 - Polyester film for photoresist - Google Patents

Description

【００３８】
【表２】

【００３９】
【発明の効果】
以上説明したように、本発明のフォトレジスト用ポリエステルフイルムによれば、フォトレジストの際に基材フイルムといて使用される積層ポリエステルフイルムのヘイズ、両面の表面粗さ、厚さ方向の屈折率をそれぞれ特定の範囲に規定したので、フォトレジストにおける解像度、基材フイルム剥離の際の劈開や伸び、基材フイルム自身の巻き性の全てに優れたフォトレジスト用ポリエステルフイルムを得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film for photoresist, and more particularly to a laminated polyester film used as a base film when a photosensitive resin composition is laminated on one side and used for a photoresist.
[0002]
[Prior art]
In the case of a photoresist, particularly a dry film photoresist, a photosensitive resin composition is laminated on one side of a light-transmitting base film, and a cover film made of polyethylene or the like is provided thereon. When the photoresist is used, the cover film is first removed, and the exposed photosensitive resin composition surface is adhered onto an object such as a printed wiring board manufacturing substrate. In this state, the negative film is brought into close contact with the base film, and an active ray such as ultraviolet rays is irradiated from the negative film side so as to transmit the base film, thereby exposing the photosensitive resin composition to a predetermined pattern. After exposure, the negative film is removed, the substrate film is peeled off, and the uncured unexposed portion of the photosensitive resin composition is removed with a solvent or the like to form a target pattern on the substrate. The
[0003]
In such a dry photoresist, in recent years, higher resolution has been demanded due to miniaturization of printed circuit boards. Further, in order to achieve the above-described high resolution at the time of exposure, it is required that the light-transmitting substrate film be made as thin as possible while providing necessary self-shape retention. However, when the film thickness is reduced, there is a problem that when the base film is peeled off, the film is easily broken. In order to increase the strength of the film, it is usually effective to increase the orientation degree of the stretched film. However, in this case, since a force acts in the thickness direction at the time of peeling, the orientation degree is reduced. If it is too high, it will be easy to cleave if the degree of orientation in the thickness direction is too low. On the other hand, if the degree of orientation, particularly the degree of orientation in the thickness direction, is too high, the film itself tends to be stretched, and the film is not peeled cleanly when the film is peeled off due to the elongation of the film.
[0004]
On the other hand, from the viewpoint of the production of the base film, not only the film forming property but also the winding property at the time of winding on a take-up roll which is a form when shipped from a film manufacturing manufacturer is important. If the rollability is inferior, wrinkles are generated in the film, which is a fatal defect for a photoresist base film.
[0005]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to pay attention to the above-mentioned problems relating to the substrate film for photoresist, and to ensure the transparency required for the photoresist, while being excellent in resolution in the photoresist, and when peeling the substrate film. An object of the present invention is to provide a polyester film for photoresists which can prevent troubles such as elongation and cleavage of the film and has good rollability of the base film itself.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a polyester film for a photoresist of the present invention is a laminated polyester film having a thickness of 16 to 20 μm, which is formed by a co-extrusion method having an A layer, a B layer, and a C layer made of polyester. When the haze of the laminated polyester film is 0.05% or more and 10% or less, the center line surface roughness of the A layer is ARa, and the center line surface roughness of the C layer is CRa,
0.005 μm ≦ ARa ≦ 0.05 μm
0.005 μm ≦ CRa ≦ 0.05 μm
And the refractive index in the thickness direction of the laminated polyester film is 1.490 or more and 1.505 or less.
[0007]
In this polyester film for photoresist,
ARa ≦ CRa
Is preferably satisfied.
Here, the A layer is the photosensitive resin composition lamination side.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail together with preferred embodiments.
The polyester film for photoresists according to the present invention comprises at least three layers of laminated polyester film compositely formed by a coextrusion method having an A layer, a B layer, and a C layer made of polyester. By adopting a three-layer structure in this way, the inner layer B layer is a highly transparent layer while controlling the surface of the layer A (surface A) and the surface of the layer C (surface C) to the optimum surface roughness. The translucency of the laminated film as a whole can be easily ensured. Therefore, the A layer and the C layer may be thinner than the B layer. For example, it is preferable that the total thickness of the A layer and the C layer is smaller than the thickness of the B layer.
[0009]
The polyester constituting the A layer, the B layer, and the C layer may be the same or different polyesters. The polyester constituting the biaxially oriented polyester film used in the present invention includes, as an acid component, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, Aliphatic dicarboxylic acids such as decanedicarboxylic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used, and alcohol components include aliphatic diols such as ethylene glycol, diethylene glycol, butanediol, hexanediol, cyclohexanedimethanol, etc. Can be used.
[0010]
Also known additives in this polyester, such as heat stabilizers, oxidation stabilizers, weathering stabilizers, UV absorbers, organic lubricants, pigments, dyes, fillers, antistatic agents, nucleating agents, etc. May be blended. The intrinsic viscosity (measured in 25 ° C. orthochlorophenol) of the polyester as described above is preferably 0.40 to 1.20, more preferably 0.50 to 0.80, still more preferably 0.55 to 0.00. The range is 75 dl / g.
[0011]
The particles contained in the biaxially oriented polyester film used in the present invention include particles, aggregates, silicon dioxide particles, calcium carbonate particles, alumina particles, titanium oxide particles, and barium sulfate particles generated during polymerization using various nucleating agents. Typical examples thereof include inorganic particles such as crosslinked particles, organic particles such as crosslinked polystyrene particles, acrylic particles, and imide particles, or mixtures thereof.
[0012]
The diameter of the particles to be used is not particularly limited. Usually, those having an average particle diameter measured by a sedimentation method or a light scattering method of 0.05 to 8.0 μm, preferably 0.1 to 4.0 μm are representative. Can be mentioned.
[0013]
The lamination of the A layer, the B layer, and the C layer in the laminated polyester film according to the present invention can be performed by a laminating method or the like, but in order to prevent cleavage in a photoresist application, etc., before being melt-extruded into a sheet shape. In other words, it is necessary to laminate by coextrusion.
[0014]
Further, the haze of the laminated polyester film according to the present invention needs to be 0.05% or more and 10% or less from the viewpoint of ensuring the translucency required for the photoresist. Films having a haze of less than 0.05% are practically very difficult to form, and considering the inclusion of particles described later, it is difficult to achieve a haze of less than 0.05%. On the other hand, if the haze exceeds 10%, the translucency for the photoresist is insufficient, the exposure is incomplete, and a high resolution cannot be obtained.
[0015]
Moreover, in the laminated polyester film according to the present invention, when the surface roughness of the A layer is ARa and the surface roughness of the C layer is CRa,
0.005 μm ≦ ARa ≦ 0.05 μm
0.005 μm ≦ CRa ≦ 0.05 μm
Need to be satisfied. Below this range, good rollability as the film itself cannot be obtained, and wrinkles or the like may occur. Moreover, when it exceeds this range, it becomes difficult to obtain a desired haze. That is, in order to increase the surface roughness, the amount of particles contained in the surface layer is generally increased. However, in that case, the haze exceeds 10%, and as a result, it becomes difficult to achieve the above-mentioned haze of 10% or less.
[0016]
Regarding the surface roughness, when the A-side is the photosensitive resin composition laminate side,
ARa ≦ CRa
Is preferably satisfied. This is for improving the adhesiveness with the photosensitive resin composition on the A surface side and improving the slipperiness on the C surface side to ensure good winding properties.
[0017]
As described above, in order to obtain the desired surface roughness for both the A and C planes, it is preferable that the A layer and the C layer each contain particles. The surface roughness of each surface can be controlled to a desired value by appropriately controlling the particle size and content of the particles.
[0018]
Furthermore, in the laminated polyester film according to the present invention, the refractive index in the thickness direction needs to be 1.490 or more and 1.505 or less. This refractive index serves as an index of the peelability of the base film after the exposure of the dry film photoresist film. If the refractive index is less than 1.490, it is peeled off as a base film for photoresist. It becomes easier to cleave. On the other hand, if the refractive index exceeds 1.505, the film is stretched at the time of peeling, which tends to cause a peeling failure.
[0019]
【Example】
Specific examples of the present invention will be described below. First, a method for measuring each characteristic used in the definition and description of the present invention will be described.
[0020]
(1) Surface roughness The center line average roughness Ra was measured according to JIS-B-0601.
[0021]
(2) Haze The haze of the film was measured according to JIS-K-7105.
[0022]
(3) Refractive index The refractive index in the thickness direction of the film was measured according to JIS-K-7105.
[0023]
(4) The film was slit to a winding width of 1000 mm and a length of 4000 m, wound on a paper core having a length of 1200 mm, an inner diameter of 6 inches, and a wall thickness of 12 mm, and the winding state was observed, and judged according to the following criteria.
Wrapped with no defects such as wrinkles: ○
Those with defects such as wrinkles: ×
[0024]
(5) Elongation After laminating a film coated with a known photosensitive resin to a thickness of 45 μm on a copper-clad laminate, the film was exposed to light and peeled off due to elongation when the film was peeled off.
No elongation: ○
Elongation: ×
[0025]
(6) Cleavage After laminating a film coated with a known photosensitive resin to a thickness of 45 μm on a copper-clad laminate, the film was exposed and cleaved when the film was peeled off, and judged according to the following criteria.
No cleavage: ○
With cleavage: ×
[0026]
(7) Resolution After laminating a film coated with a known photosensitive resin to a thickness of 45 μm on a copper-clad laminate, a negative film for evaluation of resolution (STOUFFER GRAPHIC ARTS EQUIIPMENT, 21STEP, SENSITIVITY GUIDE, # T2115) is provided. The film was removed by exposure. Next, using a 1.0 wt% sodium carbonate aqueous solution at 30 ° C, spraying is performed for 60 seconds at a spray pressure of 1.0 kg / cm ² to remove unexposed portions, and the number of steps of the step tablet of the photocured film on the copper-clad laminate Was measured and judged according to the following criteria. The larger the number of steps, the better the resolution.
Stage number 8.0 or more: Resolution ○
Number of steps less than 8.0: Resolution ×
[0027]
Example 1
Polyethylene terephthalate (PET) having an intrinsic viscosity of 0.60 was used as the A layer resin and the C layer resin, and PET having an intrinsic viscosity of 0.58 was used as the B layer resin. As shown in Table 1, the agglomerated silica having an average particle size of 1.1 μm was added to the raw material for the A layer during polymerization, and the raw material for the C layer was added to the agglomerated silica having an average particle size of 1.0 μm during polymerization. After each raw material was dried to a moisture content of 200 ppm, it was extruded at 290 ° C. into a three-layer laminate sheet composed of A layer, B layer, and C layer, and rapidly cooled and solidified on a cooling roll whose surface temperature was controlled at 30 ° C. . This unstretched laminated sheet was stretched in the longitudinal direction at a stretching temperature of 115 ° C. and a stretching ratio of 3.8 times, then stretched in the width direction at a stretching temperature of 120 ° C. and a stretching ratio of 3.7 times, and then at 215 ° C. A biaxially oriented laminated polyester film having a total thickness of 20 μm with a thickness ratio A / B / C of 1/18/1 (μm) of the A layer, B layer, and C layer is obtained by heat treatment at a relaxation rate of 5.0%. It was.
[0028]
The surface roughness, haze, and refractive index in the thickness direction of the A layer and C layer of this film were measured. Further, a known photosensitive resin solution was applied to the A side of the above film and dried at 100 ° C. for 8 minutes, and the film thickness of the photosensitive resin after drying was set to 45 μm. This film was heated to 90 ° C. and laminated on a printing substrate in which a copper plate was pasted on a glass epoxy plate heated to 60 ° C. Then, a negative film for resolution evaluation (STOUFFER GRAPHIC ARTS EQUIIPMENT, 21STEP, SENSITIVITY GUIDE, # T2115) was provided on this film, and exposure was performed at 110 mJ / cm ² with a high-pressure mercury lamp. After the exposure, the polyester film on the substrate was peeled off, and cleavage and elongation were evaluated. Furthermore, the substrate from which the polyester film was peeled was sprayed with a 1% by weight sodium carbonate aqueous solution at 30 ° C. for 60 seconds at a spray pressure of 1.0 kg / cm ² to remove unexposed portions, and a photocured film on a copper-clad laminate. The resolution was measured from the number of steps of the step tablet. The results are shown in Table 1.
[0029]
Example 2
As the raw material for layer A, the amount of particles added was changed as compared with Example 1, and the film was formed in the same manner as in Example 1 to evaluate each characteristic. The results are shown in Table 1.
[0030]
Example 3
As the raw material for the B layer, the amount of particles added was changed as compared with Example 1, and the film was formed in the same manner as in Example 1 to evaluate each characteristic. The results are shown in Table 1.
[0031]
Example 4
As the raw material for the A layer and the raw material for the B layer, the amount of particles added was changed as compared with Example 1, and the film was formed in the same manner as in Example 1 to evaluate each characteristic. The results are shown in Table 1.
[0032]
Examples 5 and 6
Compared to Example 1, the particle size and the amount of particles added as the raw material for the A layer and the material for the C layer, the amount of added particles as the raw material for the B layer were changed, and the thickness ratio was further changed. Similarly, the film was formed and each characteristic was evaluated. The results are shown in Table 1.
[0033]
Comparative Example 1
Compared to Example 1, the particle size and the amount of particles added as the raw material for the A layer and the material for the C layer, the amount of added particles as the raw material for the B layer were changed, and the thickness ratio was further changed. Similarly, the film was formed and each characteristic was evaluated. The results are shown in Table 2.
[0034]
Comparative Examples 2 and 3
As the raw material for the A layer, the raw material for the B layer, and the raw material for the C layer, the amount of particles added was changed as compared with Example 1, and the film was formed in the same manner as in Example 1 to evaluate each characteristic. The results are shown in Table 2.
[0035]
Comparative Example 4
As the raw material for the A layer and the raw material for the B layer, the amount of particles added was changed, and the draw ratio was changed, and the film was formed in the same manner as in Example 1 to evaluate each characteristic. The results are shown in Table 2.
[0036]
Comparative Example 5
Compared to Example 1, the intrinsic viscosity is changed as the raw material for the A layer, the raw material for the B layer, the raw material for the C layer, the addition amount of the particles is changed as the raw material for the B layer, and the draw ratio is changed. Each of the properties was evaluated. The results are shown in Table 2.
[0037]
[Table 1]

[0038]
[Table 2]

[0039]
【The invention's effect】
As described above, according to the polyester film for photoresist of the present invention, the haze, the surface roughness of both surfaces, and the refractive index in the thickness direction of the laminated polyester film used as the base film in the case of the photoresist are obtained. Since each of the specific ranges is specified, a polyester film for a photoresist excellent in all of the resolution in the photoresist, the cleavage and elongation when the base film is peeled off, and the rollability of the base film itself can be obtained.

Claims (4)

It is composed of a laminated polyester film having a thickness of 16 to 20 μm and formed into a composite film by a co-extrusion method having A layer, B layer, and C layer made of polyester, and the haze of the laminated polyester film is 0.05% or more and 10% or less. When the center line surface roughness of the A layer is ARa and the center line surface roughness of the C layer is CRa,
0.005 μm ≦ ARa ≦ 0.05 μm
0.005 μm ≦ CRa ≦ 0.05 μm
And a refractive index in the thickness direction of the laminated polyester film is 1.490 or more and 1.505 or less, a polyester film for photoresists. further,
ARa ≦ CRa
The polyester film for photoresists according to claim 1 satisfying
Here, the A layer is the photosensitive resin composition lamination side.   The polyester film for photoresists according to claim 1 or 2, wherein particles are contained in at least the A layer and the C layer.   The polyester film for photoresists according to any one of claims 1 to 3, wherein the total thickness of the A layer and the C layer is smaller than the thickness of the B layer.