JP2012175053A - Novel white cover lay film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cover lay film with a white resin layer, which has at least one kind or more of advantages, such as no process contamination, high flexibility, high whiteness, high reflectance, excellent flame retardancy, no bleeding-out during hot pressing, and reduced reflectance-hue change after irradiation with light, and to provide a printed wiring board.SOLUTION: There is provided a white cover lay film comprising at least a white thermosetting resin composition layer and a polyimide film, the white thermosetting resin composition layer containing (A) a thermosetting resin substantially containing no silicon in a molecule, (B) a white coloring agent and (C) a filler-type flame retardant.

Description

  The present invention relates to a white coverlay film, a printed wiring board, a light emitting device using them, and the like.

  2. Description of the Related Art In recent years, electronic devices have been rapidly improved in performance, function, and size, and accordingly, there is an increasing demand for downsizing and weight reduction of electronic components used in electronic devices. In response to the above requirements, the flexible printed wiring board is flexible and can withstand repeated bending, so it can be mounted in three-dimensional high density in a narrow space, and functions as a wiring, cable, or connector for electronic devices. Its use as a composite part with the

  Under such circumstances, polyimide resins are widely used in electronic parts used in electronic devices because of their excellent heat resistance, electrical insulation reliability, chemical resistance, and mechanical properties. For example, it is used for base materials and surface protection materials such as insulating films on semiconductor devices, flexible circuit boards and integrated circuits.

  In particular, when used as a surface protection material for flexible circuit boards, coverlay films obtained by applying an adhesive to a molded body such as a polyimide film are widely used because of its ease of use and durability. .

  On the other hand, a solder resist or the like may be used as a surface protective material for a circuit board. As this surface protective solder resist, a resin composition mainly composed of an epoxy resin or the like is used, but this solder resist is excellent in electrical insulation reliability as an insulating material, but has poor mechanical properties such as flexibility, Since the curing shrinkage is large, when it is laminated on a thin and flexible circuit board such as a flexible circuit board, there is a problem that the warpage of the board becomes large and it is difficult to use for a flexible circuit board. In addition, it has poor flame retardancy, and when a flame retardant is added for the purpose of imparting flame retardancy, contact failure and process contamination due to bleed out that the flame retardant exudes from the cured film is a problem .

  By the way, in recent years, light emitting diodes (LEDs) can be applied to backlights and lighting devices of liquid crystal displays such as portable devices, personal computers, and televisions in that they can have low power consumption, long life, miniaturization, thinning, and weight reduction. The printed wiring board on which the LED chip is mounted has whiteness and high reflectivity in the coverlay film, which is an insulating protective film of the printed wiring board, in order to efficiently use the light from the LED chip. Is required.

  As such a white and highly reflective surface protection material for circuit boards, it has coating properties, solder heat resistance, adhesion, electrical insulation, etc., and suppresses coloration due to deterioration and deterioration of reflectance over time. In addition, a solder resist composition having a high reflectance has been proposed (see, for example, Patent Document 1).

  In addition, when exposed to high temperatures during solder reflow or when irradiated with light, it is difficult to change color from white, and the reflectance is not easily lowered, and siloxane polymer, white filler, acid anhydride group or carboxyl group A resist material containing a resin having an unsaturated double bond has been proposed (see, for example, Patent Document 2).

JP 2009-149879 A International Publication No. 2009/090867

  In the said patent document, the various method which solves the subject of a soldering resist is proposed. However, although the solder resist composition described in Patent Document 1 contains rutile-type titanium oxide, it has a high reflectivity, and the coloration due to deterioration and deterioration of reflectivity over time is suppressed. Due to poor flexibility and large shrinkage during curing, when used as an insulating protective film for flexible printed wiring boards, there is a problem of poor flame resistance and breakage resistance and large warpage. Since the resist material described in Patent Document 2 contains a siloxane polymer, a white filler, an acid anhydride group or a carboxyl group, and a resin having an unsaturated double bond, it is exposed to high temperatures during solder reflow. When it is used as an insulating protective film for flexible printed wiring boards, it is difficult to change its color from white when exposed to light or when irradiated with light. There are problems of contact failure due to bleed-out, as well as problems of poor flame resistance and breakage resistance and large warpage.

  As a result of diligent research to solve the above problems, the present inventors have at least (A) a thermosetting resin substantially free of silicon in the molecule, (B) a white colorant, and (C) a filler type difficulty. From white thermosetting resin composition layer containing flame retardant and white coverlay film including polyimide film, no process contamination, high flexibility, high whiteness and reflectivity, excellent flame retardancy, during hot press Obtained the knowledge that white coverlay film and printed wiring board with at least one effect such as no bleeding, low reflectance and hue change after light irradiation, etc. are obtained, based on these findings, The present invention has been achieved. The present invention can solve the above problems with a white coverlay film in which a layer made of a white thermosetting resin composition having the following novel structure is provided on at least one surface of a polyimide film.

  That is, the present invention provides a white thermosetting resin composition containing at least (A) a thermosetting resin substantially free of silicon in the molecule, (B) a white colorant, and (C) a filler-type flame retardant. A white coverlay film comprising a layer and a polyimide film.

  Moreover, in the white thermosetting resin composition concerning this invention, it is preferable that the said (C) filler type flame retardant contains a phosphinic acid salt.

  Moreover, in the white thermosetting resin composition concerning this invention, it is preferable that the said (A) thermosetting resin contains a urethane bond at least after hardening.

  Moreover, in the white thermosetting resin composition concerning this invention, it is preferable that the said (B) white colorant contains a titanium oxide.

  Moreover, the flexible printed wiring board concerning this invention is obtained by coat | covering the circuit with the white coverlay film with an adhesive layer which provided the adhesive bond layer in the polyimide film surface of the said white coverlay film.

  Moreover, the light-emitting device which mounted LED concerning this invention is obtained by mounting LED in the said flexible printed wiring board.

  The white coverlay film of the present invention has at least (A) a thermosetting resin containing substantially no silicon in the molecule, (B) a white colorant, and (C) a filler-type flame retardant. Since it is a conductive resin composition layer and polyimide film, there is no process contamination, high flexibility, high whiteness and reflectivity, excellent flame retardancy, no oozing during heating press, reflection after light irradiation There are at least one effect such as a small rate and hue change. Therefore, the multilayer film of the present invention can be used as a protective film for various circuit boards and exhibits excellent effects.

  Hereinafter, the present invention will be described in detail in the order of (I) white thermosetting resin composition, (II) polyimide film, (III) white coverlay film, and (IV) white coverlay film.

(I) White thermosetting resin composition The white thermosetting resin composition of the present invention is at least (A) a thermosetting resin substantially free of silicon in the molecule, (B) a white colorant, And (C) a filler-type flame retardant. Here, the thermosetting resin of the present invention may be any resin that has a reaction point that reacts irreversibly by heating and exhibits insulating properties after curing. This irreversible reaction point may be incorporated into a polymer chain having a large number of repeating units or may be contained in a monomer composed of one kind of structural unit. Further, the thermosetting resin in the present invention may be one kind or a combination of plural kinds.

  The fact that (A) of the present invention contains substantially no silicon in the molecule basically means that no silicon is contained in the molecule, but it is desorbed during thermosetting and disappears from the resin composition. It may contain about the protecting group etc. which do. Examples of the thermosetting resin that substantially does not contain silicon in the molecule (A) include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, polyglycol type epoxy resin, aliphatic epoxy resin, and alicyclic epoxy. Resin, cyclopentadiene type epoxy resin, dicyclopentadiene type epoxy resin, triazine skeleton-containing epoxy resin, aliphatic diisocyanate compound, aliphatic polyisocyanate compound, alicyclic diisocyanate compound, alicyclic polyisocyanate compound, and block of these isocyanate compounds Body, melamine resin, melamine formaldehyde resin and the like are preferred, but not limited thereto. Particularly in the present invention, an epoxy compound and an isocyanate compound are preferably used, and more preferably an isocyanate compound is used from the viewpoint of imparting flexibility. Further, when an isocyanate compound is used, it can be used in combination with a resin containing a carboxyl group, an amino group, a thiol group, or a hydroxyl group having a reactive site with these compounds and containing substantially no silicon. Among these, it is preferable to use a hydroxyl group-containing resin from the viewpoint of reactivity and ease of handling, and when these are used, the white thermosetting resin layer should have flexibility by having a urethane bond after thermosetting. Is more preferable because In addition, a resin having a urethane bond in advance and having a reaction point that reacts with the epoxy resin or isocyanate resin can be used. Furthermore, metals can be used as the catalyst, and tertiary amines can also be used. Thus, in this invention, it is preferable that (A) thermosetting resin contains a urethane bond at least after hardening.

  Next, (B) white colorant will be described. The white colorant of the present invention has a function of coloring the resin white, and the white thermosetting resin composition layer after thermosetting only needs to be colored white. In the present invention, it is preferable to use a single or a combination of inorganic pigments such as metal oxides and metal nitrides and / or surface treatments thereof with organic matter, glass or the like. In the present invention, it is more preferable that (B) contains titanium oxide. By containing titanium oxide, it is possible to efficiently absorb ultraviolet rays and prevent resin deterioration and coloring due to ultraviolet rays. Moreover, 1-200 wt% is preferable with respect to the said thermosetting resin component, and, as for the addition amount of the white colorant in this invention, it is more preferable to add 50-150 wt%.

  Next, (C) filler type flame retardant will be described. The filler-type flame retardant of the present invention is a component in which the flame retardant effect is not dissolved in the white thermosetting resin composition layer, and the particulate flame retardant component is dispersed in the white thermosetting resin composition. It means that it exists. In particular, in the present invention, the filler-type flame retardant preferably contains a phosphinate from the viewpoints of flame retardancy and high heat resistance. Said phosphinic acid salt can be used individually by 1 type or in combination of 2 or more types. Moreover, the said phosphinic acid salt can also be purchased as a commercial item, for example, EXOLIT OP 930, EXOLIT OP 935, EXOLIT OP 940 (all are the brand names made by Clariant) can also be used. In particular, from the viewpoint of bending resistance, it is preferable to use a product obtained by pulverizing the commercially available phosphinate using a bead mill or the like. Moreover, 1-50 wt% is preferable with respect to the said thermosetting resin component, and, as for the addition amount of the filler type flame retardant in this invention, it is more preferable to add 5-30 wt%.

  Moreover, you may use various additives for the white thermosetting resin composition as described in this invention as needed. Examples of additives include antioxidants, ultraviolet absorbers, light stabilizers, and the like. Any of these commercially available additives can be used alone or in combination. Antioxidants include phenolic antioxidants such as ADK STAB AO-60 (manufactured by ADEKA) and IRGANOX 1010 (manufactured by BASF), phosphorus antioxidants such as ADK STAB HP-10, and thiol oxidations such as ADK STAB AO-503. An inhibitor etc. can be illustrated. Examples of ultraviolet absorbers include benzotriazole types such as ADK STAB LA-31, benzophenone types such as ADK STAB 1413, and triazine types such as ADK STAB LA-46. Examples of the light stabilizer include hindered amines such as ADK STAB LA-81. These additives may be used in a range that does not impair the properties of the white resin composition, but are generally used in a range of 0.01 wt% to 10 wt% with respect to the resin composition.

(II) Polyimide film Next, the polyimide film in this invention is demonstrated. The polyimide film according to the present invention can be usually produced using polyamic acid as a precursor thereof. Any known method can be used for producing the polyamic acid. Usually, an aromatic acid dianhydride and an aromatic diamine can be dissolved and reacted in an organic solvent so as to have a substantially equimolar amount to obtain a polyamic acid organic solvent solution.

  Moreover, as a manufacturing method of the polyimide film which concerns on this invention, all well-known methods can be used. In particular, from the viewpoint of productivity, a method of adding an imidization accelerator such as acetic anhydride to the polyamic acid solution and imidizing by heating and baking is preferable.

  The polyimide film concerning this invention can also be purchased as a commercial item, and what has been used as a coverlay film by itself, such as Apical NPI (a Kaneka company make, brand name), can be used.

  The polyimide film used in the present invention may be subjected to a surface treatment for the purpose of improving the adhesiveness with the white thermosetting resin layer or the adhesive when used as a coverlay film. Examples of surface treatment methods include, but are not limited to, corona treatment and plasma treatment.

  Although the thickness of the polyimide film used by this invention is not specifically limited, 5-50 micrometers is preferable from a softness | flexibility and a bendable viewpoint, and 5-30 micrometers is more preferable.

(III) White coverlay film The white coverlay film according to the present invention is characterized in that the white thermosetting resin layer is provided on one surface of a polyimide film. The method of providing the white thermosetting resin layer on the polyimide film is not particularly limited, but a method of applying an uncured white thermosetting resin solution onto the polyimide and drying and curing by heating is preferable from the viewpoint of productivity. Any conventionally known method can be used as the coating method, but a reverse coater or a die coater is preferably used because it contains a large amount of powder.

(IV) Utilization Method of White Coverlay Film A utilization method of the white coverlay film according to the present invention will be described. As described above, an adhesive layer is provided on the other side of the film provided with the white thermosetting resin layer on one side of the polyimide film, that is, on the side opposite to the white thermosetting resin layer. A flexible printed wiring board having a white color and flame retardancy can be obtained by covering a flexible wiring board having a circuit formed through an agent layer.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

<Preparation of white thermosetting resin composition>
(A) As thermosetting resin substantially free of silicon in the molecule, 40.0 g of acrylic polyol UH-2041 manufactured by Toagosei Co., Ltd. having a hydroxyl group and Duranate TPA-B80E manufactured by Asahi Kasei Chemicals Co., Ltd. having an isocyanate group 26.1 g was dissolved in 60 g of 2-butanone as a solvent. TPA-B80E is a block-type isocyanate, and when heated, the block-type protective group is removed, and a hydroxyl group and a urethane bond can be formed. Next, (B) 60 g of rutile titanium oxide CR-60 manufactured by Ishihara Sangyo Co., Ltd. as a white colorant component, 10 g of Exolit OP-935 manufactured by Clariant, which is a phosphinic acid salt as a filler type flame retardant, as an antioxidant 0.15 g of Irganox 1010 manufactured by BASF was put in a bead mill manufactured by AIMEX, and mixed and stirred at 760 rpm. Next, zirconia beads having a particle diameter of 1 mm were added so as to have a filling rate of 70%, and after stirring and dispersing at 1000 rpm, the zirconia beads were separated by filtration to obtain a white thermosetting resin composition solution of the present invention. The following evaluation was carried out by completely defoaming the foam in the solution with a defoaming device. The evaluation results are shown in Table 1.

<Preparation of coating film on polyimide film>
The white thermosetting resin composition was cast on an area of 300 mm × 200 mm on a 25 μm polyimide film (manufactured by Kaneka Corporation: product name 25 NPI) using a Baker type applicator so that the final dry thickness was 16 μm. After applying and drying at 80 ° C. for 2 minutes, a cured film of a white thermosetting resin composition was prepared on a polyimide film by heating and curing in an oven at 180 ° C. for 30 minutes.

<Evaluation of cured film>
(I) Evaluation of flexibility A cured film laminated film of a white thermosetting resin composition is cut into a 50 mm × 10 mm strip and bent at 180 ° at 25 mm with the cured film of the white thermosetting resin composition facing outward. Then, after applying a load of 5 kg to the bent portion for 3 seconds, the load was removed, and the vertex of the bent portion was observed with a microscope. After microscopic observation, the bent portion was opened, and a 5 kg load was again applied for 3 seconds, and then the load was removed to completely open the cured film laminated film. The above operation was repeated, and the number of occurrences of cracks in the bent portion was defined as the number of bending times.
A: The cured film has no cracks after being bent five times.
Δ: The cured film has no cracks after being bent three times.
X: A crack occurs in the cured film at the first folding.

(Ii) Warpage Cut the cured film laminated film into an area of 50 mm x 50 mm and place it on a smooth base so that the coating film is on the upper surface, and measure the maximum height of the warp at the end of the film as the amount of warpage . The smaller the amount of warpage on the polyimide film surface, the smaller the stress on the surface of the printed wiring board and the lower the amount of warping of the printed wiring board. The warp amount is preferably 5 mm or less. In addition, when rounding cylindrically, it was set as x.

(Iii) Combustibility The cured film laminated film is cut into a dimension: 50 mm width × 200 mm length × 41 μm thickness (including the thickness of the polyimide film), a marked line is put in a 125 mm portion, and it is rolled into a cylindrical shape having a diameter of about 13 mm, PI tape was affixed so that there was no gap at the overlapping part (75 mm) above the marked line and at the top, and 20 flammability test tubes were prepared. Of these, 10 were treated at (1) 23 ° C./50% relative humidity / 48 hours, and the remaining 10 were treated at (2) 70 ° C. for 168 hours and then cooled in a desiccator containing anhydrous calcium chloride for 4 hours or more. The upper part of these samples is clamped and fixed vertically, and a burner flame is brought close to the lower part of the sample for 3 seconds to ignite. After 3 seconds, move the burner flame away and measure how many seconds after the sample flame or burning disappears.
○: For each condition ((1), (2)), the flame and combustion stopped within 10 seconds on average (average of 10) after the flame of the burner was moved away from the sample, and self-extinguishment within 10 seconds at maximum However, it has not burned to the rating line.
×: Even one sample does not extinguish within 10 seconds, or the flame rises above the rating line and burns.

(Iv) Bleeding during heating press The cured film laminated film is cut out into 50 mm x 50 mm, sandwiched between two polyimide films, sandwiched between two SUS plates with a thickness of 2 mm, and a pressure of 3 MPa is applied at 180 ° C for 30 minutes. The treated test piece was observed, and minute swelling on the surface of the test piece, exudation of oily substances, and the like were observed.
○: No abnormalities such as swelling and exudation on the surface of the specimen ×: No abnormalities such as swelling and exudation on the surface of the specimen

(V) Initial reflectance Using the cured film laminated film, the initial reflectance of the white thermosetting resin composition cured film layer was measured by the following method, and the measured value at 450 nm was defined as the initial reflectance.
Equipment used: UV-visible spectrophotometer V-650 manufactured by JASCO Corporation
Measurement wavelength region: 300 to 800 nm
Standard white board: Spectralon TM manufactured by Labsphere.

(Vi) L, a, and b values of the white thermosetting resin composition cured film layer were measured with the following apparatus using the initial hue cured film laminated film. L represents lightness, a represents reddishness, and b represents yellowishness.
Device used: Nippon Denshoku Industries Co., Ltd. Handy color difference meter NR-3000.

(Vii) Reflectance change after light irradiation The cured film laminated film used in the above (v) measurement of the initial reflectance was irradiated with 100 J / cm ² of UV under the following conditions, and (v) the same as the initial reflectance measurement method. The reflectance was measured by the method.
Equipment used: Conveyor type UV irradiator manufactured by Iwasaki Electric Co., Ltd. Output: 120 W / cm
Lamp: Metal halide lamp, 6 kW, 2 lamp irradiator: Cold mirror Condensation type The change rate from the initial reflectance before the light irradiation to the reflectance after the light irradiation was calculated.
A: The rate of change in reflectance is less than 5%.
Δ: The reflectance change rate is 5% or more and less than 10%.
X: The rate of change in reflectance is 10% or more.

(Viii) Hue change after light irradiation (vi) The cured film laminated film used for the measurement of initial hue is irradiated with 100 J / cm ² of UV under the same conditions as (vii) reflectance change after light irradiation, (Vi) L, a, and b values were measured by the same method as the initial hue measurement method.
○: L value is 80 or more, a value is less than 1, and b value is less than 1.
Δ: L value is 80 or more, a value is less than 2, and b value is less than 2.
X: L value is 80 or less, a value is 2 or more, b value is 2 or more.

  From the above evaluation results, the white coverlay in the present invention does not substantially contain silicon, so there is no process contamination, high flexibility, high whiteness and reflectance, excellent flame retardancy, and exudation during hot press. It can be seen that this is a coverlay film with a white resin layer that does not occur and has at least one effect such as little change in reflectance and hue after light irradiation.

Claims (6)

  At least (A) a thermosetting resin substantially free of silicon in the molecule, (B) a white colorant, and (C) a white thermosetting resin composition layer and a polyimide film containing a filler-type flame retardant. Including white coverlay film.   The white coverlay film according to claim 1, wherein the (C) filler-type flame retardant contains a phosphinate.   The white coverlay film according to claim 1 or 2, wherein the (A) thermosetting resin contains a urethane bond at least after curing.   The white coverlay film according to any one of claims 1 to 3, wherein the (B) white colorant contains titanium oxide.   A flexible printed wiring, wherein a circuit is coated with a white coverlay film with an adhesive layer in which an adhesive layer is provided on a polyimide film surface of the white coverlay film according to any one of claims 1 to 4. Board.   A light emitting device in which an LED is mounted on the flexible printed wiring board according to claim 5.