阅读说明：本技术 电子基板以及光固化性组合物 (Electronic substrate and photocurable composition ) 是由 爱泽眸 于 2020-06-09 设计创作，主要内容包括：提供一种具有柔软性和硬度均衡优异的挠性部位的电子基板。一种电子基板(10),具有刚性基板(12)、从所述刚性基板(12)的端部延伸并以能够导通的方式连接的挠性基板(14)以及从所述刚性基板(12)至所述挠性基板(14)的配线,所述挠性基板(14)具有弯折部(16),所述弯折部(16)从所述刚性基板(12)端部突出并朝向所述刚性基板(12)的一面侧弯折,电子基板(10)的特征在于,在从所述刚性基板(12)的端部至所述弯折部(16)的所述刚性基板(12)与所述挠性基板(14)的分界部分,在所述挠性基板(14)的至少一面上设置有弹性保护构件(18),所述弹性保护构件(18)通过纳米压痕试验测量的马氏硬度为0.35～3.0N/mm～(2),拉伸断裂伸长率为100％以上。(Provided is an electronic substrate having a flexible portion excellent in balance between flexibility and hardness. An electronic substrate (10) has a rigid substrate (12), and a flexible substrate (14) that extends from an end of the rigid substrate (12) and is conductively connected theretoAnd wiring from the rigid substrate (12) to the flexible substrate (14), the flexible substrate (14) having a bent portion (16), the bent portion (16) protruding from an end of the rigid substrate (12) and being bent toward one surface side of the rigid substrate (12), the electronic substrate (10) being characterized in that an elastic protection member (18) is provided on at least one surface of the flexible substrate (14) at a boundary portion between the rigid substrate (12) and the flexible substrate (14) from the end of the rigid substrate (12) to the bent portion (16), the elastic protection member (18) having a March's hardness of 0.35 to 3.0N/mm as measured by a nanoindentation test 2 The tensile elongation at break is 100% or more.)

1. An electronic substrate, comprising:

a rigid substrate having a plurality of conductive layers,

a flexible substrate extending from an end of the rigid substrate and conductively connected, an

Wiring from the rigid substrate to the flexible substrate,

the flexible substrate has a bent portion that protrudes from an end of the rigid substrate and is bent toward one surface side of the rigid substrate,

the electronic substrate is characterized in that,

an elastic protection member is provided on at least one surface of the flexible substrate at a boundary portion between the rigid substrate and the flexible substrate from an end portion of the rigid substrate to the bent portion,

the elastic protection component has the Martensitic hardness of 0.35-3.0N/mm measured by a nano indentation test²The tensile elongation at break is 100% or more.

2. The electronic substrate of claim 1,

the elastic protection member covers at least a part of an end surface of the rigid substrate intersecting a contact surface of the rigid substrate and the flexible substrate.

3. The electronic substrate according to claim 1 or 2,

the flexible substrate located on the opposite side of the rigid substrate is bent by approximately 180 degrees with respect to the rigid substrate via the bent portion.

4. The electronic substrate according to any one of claims 1 to 3,

the flexible substrate is a resin film having a thickness of 15 to 200 μm,

when the flexible substrate is bent, the elastic protection member is arranged on the bent inner surface of the flexible substrate.

5. A photocurable composition for forming an elastic protective member by applying the composition on an electronic substrate and then curing the composition by irradiation with light,

comprising a monofunctional alicyclic (meth) acrylate monomer, a monofunctional aliphatic (meth) acrylate monomer, a thermoplastic elastomer, and a radical polymerization initiator,

the cured body after curing has a Martensitic hardness of 0.35 to 3.0N/mm as measured by a nanoindentation test²The tensile elongation at break is 100% or more.

6. The photocurable composition according to claim 5, wherein the photocurable composition,

the viscosity of the uncured resin composition is in the range of 10 to 5000 mPas.

Technical Field

The present invention relates to an electronic substrate having a flexible portion with excellent bending resistance and a photocurable composition with excellent flexibility and bending resistance.

Background

In an electronic substrate having a flexible portion having flexibility, a flexible substrate (including a flexible circuit board (hereinafter also referred to as a "flexible substrate")) is generally used as the flexible portion. A flexible substrate is generally known as a bendable substrate, in which a metal conductor circuit such as a copper foil is formed on a film such as a polyimide resin or a polyester resin, and a cover film such as a polyimide resin or a polyester resin is provided thereon as a protective layer. For example, in japanese patent application laid-open No. 7-106728 (patent document 1), a resin composition is used as a protective member for a connection portion between a rigid portion and a flexible portion in a substrate having the rigid portion and the flexible portion.

In addition, electronic substrates having a rigid substrate and a flexible substrate provided at an end portion of the rigid substrate are also used in image display devices such as liquid crystal display devices, plasma display devices, organic EL display devices, and RGB inorganic LED-mounted display devices. In these image display devices, a panel, which is an image display portion, is used as a rigid substrate, and a flexible substrate electrically connected to an end portion of the panel is provided in order to apply a voltage or a signal to the panel. Here, an anisotropic conductive film is generally used for connection between the panel and the flexible substrate, and a protective member for insulation protection and adhesion reinforcement of the connection portion is coated thereon. The other end of the flexible substrate is electrically connected to a circuit board (e.g., a motherboard). Generally, since the circuit board is disposed on the back surface of the panel, the flexible board extending from the panel is bent and connected to the circuit board. In recent years, there has been an increasing demand for smaller size and narrower frame of image display devices, and in order to save space for non-image display portions, a Chip on film (Chip on film) structure in which a driver IC is mounted on a flexible substrate has been adopted instead of a conventional structure mounted on a panel.

In order to control the flexibility of the flexible substrate, japanese patent application laid-open No. 2008-26528 (patent document 2) discloses an image display device including a panel having an electrode lead-out portion, a flexible substrate connected to the electrode lead-out portion, and a protective layer covering a connection portion between the flexible substrate and the electrode lead-out portion, in which wettability to a resin material on the flexible substrate is changed. With the above configuration, when the resin material is applied to the flexible substrate, a region where the resin material stably forms the protective layer and a region where the resin material repels the resin material and the protective layer is not stably formed are generated, and as a result, the flexible substrate is bent with the tip of the protective layer in the flexible substrate on which the protective layer is formed as a starting point, and therefore, the region on which the protective layer is formed can be controlled within a predetermined width. This makes it possible to control the projecting width of the bent portion of the flexible substrate projecting outward from the panel end to be small.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 7-106728

Patent document 2: japanese laid-open patent publication No. 2008-26528

Disclosure of Invention

Problems to be solved by the invention

Further, further downsizing and frame narrowing are desired for image display devices, and there is a strong demand for further reducing the projecting width of the bent portion in a flexible substrate bent at an end portion of a rigid substrate constituting an image display device or the like. However, if the protruding width is forcibly reduced, the wiring is bent excessively, and if the adhesion of the connection portion of the wiring is insufficient, the wiring may peel off. In addition, the flexible substrate is sharply bent near the rigid substrate, and stress is concentrated at a boundary portion between the flexible substrate and the rigid substrate, which may cause a break in wiring.

It is also known that the flexural modulus of the resin composition used as the protective member is 880kg/mm in the technique described in Japanese patent application laid-open No. 7-106728 (patent document 1)²In the case of 8630MPa (example), the wiring is hard and can be prevented from being broken at the boundary between the rigid substrate and the flexible substrate, but the flexible substrate is sharply bent at the boundary between the portion where the protective member is formed and the portion where the protective member is not formed, and the wiring is easily broken.

The present invention has been made to solve the above problems. That is, an object of the present invention is to provide an electronic substrate having a flexible portion with excellent durability, and a photocurable composition used in the flexible portion and having excellent flexibility and bending resistance.

Means for solving the problems

The electronic substrate and the photocurable composition of the present invention for achieving the above object are as follows.

The electronic substrate of the present invention includes: the electronic substrate is characterized in that an elastic protection member is arranged on at least one surface of the flexible substrate at a boundary part between the rigid substrate and the flexible substrate from the end part of the rigid substrate to the bent part, and the Martensis hardness of the elastic protection member measured by a nano indentation test is 0.35-3.0N/mm²The tensile elongation at break is 100% or more.

The electronic substrate has: a rigid substrate, a flexible substrate extending from an end of the rigid substrate and conductively connected, and a wiring from the rigid substrate to the flexible substrate, the flexible substrate having a bent portion extending from the rigid substrateThe electronic substrate is configured in such a manner that an elastic protection member is provided on at least one surface of the flexible substrate at a boundary portion between the rigid substrate and the flexible substrate from an end portion of the rigid substrate to the bent portion, and the elastic protection member has a Martensitic hardness of 0.35 to 3.0N/mm as measured by a nanoindentation test²Since the tensile breaking elongation is 100% or more, the wiring is less likely to be broken at the boundary between the rigid substrate and the bent flexible substrate and at the boundary between the portion where the elastic protection member is formed and the portion where the elastic protection member is not formed, and the reliability of conduction can be improved.

The elastic protection component has the Martensitic hardness of 0.35-3.0N/mm measured by a nano indentation test²Therefore, the elastic protection member has flexibility from the end of the rigid substrate to the flexible substrate and has a predetermined hardness, and the bending radius of the flexible substrate when it is bent can be made smaller than that of the conventional one without being made too small. Accordingly, the protruding width of the bent portion of the flexible substrate protruding outward from the end portion of the rigid substrate (i.e., the protruding amount of the flexible substrate from the end portion of the rigid substrate) can be made smaller than that of the conventional one, and sharp bending of the boundary portion between the rigid substrate and the flexible substrate and the boundary portion between the portion where the elastic protection member is formed and the portion where the elastic protection member is not formed can be avoided.

The elastic protection member has a tensile elongation at break of 100% or more, and therefore has a tensile property from the end of the rigid substrate to the flexible substrate, and can follow the deformation when the flexible substrate is bent, thereby avoiding extreme bending of the flexible substrate, and can prevent peeling of the elastic protection member when bent, and is excellent in durability.

The elastic protection member may have a Young's modulus of 40 to 250 MPa. When the young's modulus is 40 to 250MPa, the flexible substrate has appropriate flexibility, and thus the bending radius of the flexible substrate can be made smaller than that of the conventional substrate without being too small. As a result, the projecting width of the bent portion of the flexible substrate projecting outward from the end portion of the rigid substrate can be made smaller than that of the conventional one, and the boundary portion between the rigid substrate and the flexible substrate and the boundary portion between the portion where the protective member is formed and the portion where the protective member is not formed can be prevented from being bent extremely.

Further, since the elastic protection member is provided at the boundary portion between the rigid substrate and the flexible substrate, the elastic protection member is in close contact with both the rigid substrate and the flexible substrate, so that peeling of the rigid substrate and the flexible substrate can be prevented, and intrusion of moisture or foreign matter into the boundary between the rigid substrate and the flexible substrate can be prevented.

In the electronic board according to the present invention, the elastic protection member may cover at least a part of an end surface of the rigid board intersecting a contact surface between the rigid board and the flexible board. Since the elastic protection member covers at least a part of the end face of the rigid substrate intersecting the contact surface between the rigid substrate and the flexible substrate, the adhesion between the elastic protection member and the rigid substrate can be improved, and the elastic protection member is less likely to be peeled off from the rigid substrate.

In the electronic substrate according to the present invention, the flexible substrate located on the opposite side of the rigid substrate may be bent by approximately 180 degrees with respect to the rigid substrate via the bent portion. Since the flexible substrate located on the opposite side of the rigid substrate is bent by approximately 180 degrees with respect to the rigid substrate via the bent portion, the flexible substrate can be disposed in the vicinity of the rigid substrate, and the flexible substrate can be compactly housed.

The flexible substrate may be a resin film having a thickness of 15 to 200 μm, and the elastic protection member may be provided on a bent inner surface of the flexible substrate when the flexible substrate is bent. Even if the thickness of the resin film of the flexible substrate is 15 to 200 μm, the protruding width of the bent portion of the flexible substrate can be made smaller than that of the conventional one without becoming too small. Further, since the elastic protection member is provided on the bending inner surface of the flexible substrate, it is possible to suppress damage to the wiring when bending so as to reduce the bending radius.

The present invention can also be configured as a photocurable composition for forming an elastic protective member by applying the composition to an electronic substrate and then curing the composition by irradiation with light, the photocurable composition comprising a monofunctional alicyclic (meth) acrylate monomer, a monofunctional aliphatic (meth) acrylate monomer, a thermoplastic elastomer, and a radical polymerization initiator, wherein the cured product after curing has a mohs hardness of 0.35 to 3.0N/mm as measured by the nanoindentation test²The tensile elongation at break is 100% or more.

The photocurable composition of the present invention is applied to an electronic substrate and then cured by irradiation with light to form an elastic protective member, and the photocurable composition comprises a monofunctional alicyclic (meth) acrylate monomer, a monofunctional aliphatic (meth) acrylate monomer, a thermoplastic elastomer, and a radical polymerization initiator, and the cured product after curing has a Martin hardness of 0.35 to 3.0N/mm as measured by a nanoindentation test²Since the tensile elongation at break is 100% or more, the cured body provided on the flexible substrate does not interfere with the bending of the flexible substrate, and the flexible substrate can be bent with a small bending radius and not more than a small bending radius. In addition, since the cured body has stretchability and can follow deformation when the flexible substrate is bent, the flexible substrate can be prevented from being bent extremely, and peeling during bending can be prevented. And excellent in durability.

The present invention can be configured as a photocurable composition further containing a highly polar monomer. The photocurable composition containing a highly polar monomer has high adhesion to a flexible substrate, and improves the following property to deformation of the flexible substrate.

The photocurable composition of the present invention can be configured such that the viscosity thereof is 10 to 5000 mPas when uncured. Since the viscosity of the uncured resin composition is in the range of 10 to 5000 mPas, the coating amount on the electronic substrate can be easily and precisely controlled, and the coating workability is excellent. As a result, the possibility of excessive coating on the electronic substrate is low.

ADVANTAGEOUS EFFECTS OF INVENTION

The electronic substrate of the invention can prevent the wire from breaking at the boundary part of the rigid substrate and the flexible substrate and the boundary part of the part formed with the elastic protection member and the part not formed with the elastic protection member. The photocurable composition of the present invention has a low viscosity when uncured, is easy to apply, and has excellent workability, and the cured product after curing can exhibit desired hardness, bending resistance, and appropriate flexibility.

Drawings

Fig. 1 is a perspective view of an electronic substrate in an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of an electronic substrate in an embodiment of the invention.

FIG. 3 is an explanatory view for explaining a test method.

Detailed Description

The electronic substrate 10 of the present invention will be described in detail based on the embodiments. As shown in fig. 1, the electronic substrate 10 includes a rigid substrate 12 and a flexible substrate 14 extending from an end of the rigid substrate 12 and conductively connected to each other, and the rigid substrate 12 to the flexible substrate 14 include wiring (not shown) disposed on the substrates 12 and 14. As shown in fig. 2, the flexible substrate 14 has a bent portion 16, the bent portion 16 protrudes from an end of the rigid substrate 12 and is bent toward one surface side (lower side in fig. 2) of the rigid substrate 12, and an elastic protection member 18 is provided on at least one surface from the end of the rigid substrate 12 to the bent portion 16. The bent portion 16 protrudes from the rigid substrate 12 by a protrusion width 40.

As shown in an enlarged portion of fig. 2, the rigid substrate 12 can be, for example, a liquid crystal display panel or an LED-mounted panel in which various functional layers are laminated on a glass substrate. More specifically, in the case of a liquid crystal display panel, the rigid substrate 12 is configured by sequentially laminating: a polarizing plate 12 a; a glass substrate 12b with a first transparent electrode; a glass substrate 12d with a second transparent electrode; a liquid crystal layer 12c sandwiched by the first glass substrate 12b and the second glass substrate 12 d; a sealing material (not shown) for sealing the liquid crystal; a polarizing plate 12e disposed on the rear surface of the second glass substrate 12 d; and a backlight unit 12 f.

Further, the structure of the electronic substrate 10 is not limited to the above structure, and may be any structure as long as the rigid substrate 12 is a hard substrate compared to the flexible substrate 14. For example, a glass epoxy substrate, a phenol resin substrate, a silicon substrate, a ceramic substrate, or the like can be used. In the case of a TFT (Thin Film Transistor) liquid crystal display, the glass substrate 12b with the first transparent electrode is a glass substrate with the first transparent electrode and the color filter, and the glass substrate 12d with the second transparent electrode is a glass substrate with the second transparent electrode and the TFT. The wiring disposed on the glass substrate 12d and the wiring disposed on the flexible substrate 14 are connected by an anisotropic conductive adhesive 15.

At the boundary between the rigid substrate 12 and the flexible substrate 14, a photocurable composition, which will be described later, is applied to at least one of the inner side and the outer side of the bent portion 16, and cured by ultraviolet rays or the like to form the elastic protection member 18. It is preferable that the elastic protection member 18 covers at least a part of the end surface 12g of the rigid substrate 12, and the end surface 12g intersects with the contact surface between the rigid substrate 12 and the flexible substrate 14.

The flexible substrate 14 is a substrate made of a resin film such as a polyimide film or a mylar film, and usually has at least wiring formed on the surface of the resin film. In the present invention, it is preferable that the polyimide film is provided with wiring. Further, the thickness of the flexible substrate 14 is more preferably 15 to 200 μm. When the thickness is smaller than 15 μm, the film itself is easily bent, and there is a possibility that the film is bent at an acute angle rather than a moderate curve. On the other hand, if the thickness is larger than 200 μm, the bent peak side is excessively stretched and the valley side is excessively compressed, so that it becomes difficult to protect the wiring.

The flexible substrate 14 may have a resist layer (not shown) in addition to the wiring. Further, the present invention may be a so-called chip on film mounted with electronic components. In this case, the electronic component is preferably disposed so as to avoid a portion of the bent portion where bending is largest.

The elastic protection member 18 is provided from the end of the rigid substrate 12 to the flexible substrate 14 to protect the wiring, and is configured by curing a photocurable composition described later. The elastic protection member 18 has elongation and compression properties in addition to excellent flexibility, thereby preventing the flexible substrate 14 from being bent at a large angle. More specifically, when the elastic protection member 18 is disposed inside the flexible substrate 14, the bending radius can be reduced by compressing the elastic protection member 18 during bending, but the bending radius is not too small. On the other hand, in the case where the elastic protection member 18 is disposed outside the flexible substrate 14, the bending radius can be reduced without being excessively reduced by the elastic protection member 18 being stretched by a weak stress at the time of bending.

The elastic protection member 18 has a Martensitic hardness of 0.35 to 3.0N/mm as measured by a nanoindentation test²Preferably 0.4 to 2.5N/mm². The elastic protection member 18 has a Martensitic hardness of 0.35 to 3.0N/mm²The tensile breaking elongation is also set to a predetermined range, and the wiring can be prevented from breaking at the boundary between the rigid substrate 12 and the flexible substrate 14 and at the boundary between the portion where the elastic protection member is formed and the portion where the elastic protection member is not formed. On the other hand, the Martensitic hardness is less than 0.35N/mm²The elastic protection member 18 is too soft, and if it exceeds 3.0N/mm²It is too hard to sufficiently protect the wiring in any case.

The Young's modulus of the elastic protection member 18 may be 40 to 250MPa, preferably 60 to 200 MPa. When the young's modulus of the elastic protection member 18 is within the range of 40 to 250MPa, the mahalanobis hardness and the tensile elongation at break are easily brought within predetermined ranges, and the wiring can be prevented from breaking at the boundary portion between the rigid substrate 14 and the flexible substrate 16 and the boundary portion between the portion where the elastic protection member is formed and the portion where the elastic protection member is not formed.

The young's modulus is somewhat related to, but not necessarily proportional to, the mahalanobis hardness. More specifically, the young's modulus represents the property of the hardness of the entire cured product when it is stretched, and the mahalanobis hardness is a value that can be said to reflect the influence of the hardness when the surface of the cured product is compressed. In the bending resistance of the flexible substrate connected to the rigid substrate, the influence of the hardness when the cured product is compressed is more important, and therefore, the present invention places more importance on the mahalanobis hardness. On the other hand, when the mohs hardness is the same, a cured product having a small young's modulus is preferable. This is because the surface curability is more excellent, and the flexibility and the surface durability are more excellent.

The elastic protection member 18 has a tensile elongation at break of 100% or more. By setting the tensile breaking elongation of the elastic protection member 18 to 100% or more and setting the mahalanobis hardness to a predetermined range, it is possible to prevent the wiring from breaking at the boundary portion between the rigid substrate 14 and the flexible substrate 16 and at the boundary portion between the portion where the elastic protection member is formed and the portion where the elastic protection member is not formed. On the other hand, if the tensile elongation at break is less than 100%, it is difficult to follow the deformation of the flexible substrate, and the wiring cannot be sufficiently protected.

The elastic protective member 18 is formed by applying a photocurable composition containing a monofunctional alicyclic (meth) acrylate monomer, a monofunctional aliphatic (meth) acrylate monomer, a thermoplastic elastomer, and a radical polymerization initiator to the substrates 12 and 14, and then irradiating light and curing the composition. And as a property of the cured body, a Martensitic hardness measured by a nanoindentation test of 0.35 to 3.0N/mm²The tensile elongation at break is 100% or more. The cured product of the photocurable composition is also simply referred to as a cured product.

Herein, the "monofunctional alicyclic (meth) acrylate monomer" is meant to include both monofunctional alicyclic acrylate monomers as well as monofunctional alicyclic methacrylate monomers. By "monofunctional aliphatic (meth) acrylate monomer" is meant to include monofunctional aliphatic acrylate monomers as well as monofunctional aliphatic methacrylate monomers. Likewise, "highly polar monomer" is meant to include an acrylate monomer containing a polar group (meth), a monomer having an acrylamide group, or a monomer having a maleimide group.

From the viewpoint of coatability, the uncured viscosity of the photocurable composition at 23 ℃ is in the range of 10 to 5000 mPas, preferably in the range of 50 to 2000 mPas, and more preferably in the range of 90 to 1000 mPas. In particular, when the photocurable composition is applied to a predetermined region of an object to be coated having irregularities to have a predetermined thickness using a non-contact type application device such as a spray dispenser, the viscosity is preferably set to 90 to 1000mPa · s in order to control the application amount with high accuracy.

The photocurable composition contains the above components and has the viscosity in the uncured state in the above range, so that the photocurable composition is easy to apply and excellent in handling properties, and the cured product has the above-mentioned predetermined properties and thus has appropriate hardness, flexibility and bending resistance, and can be used as the elastic protective member 18 of the electronic substrate 10.

Next, the components contained in the photocurable composition will be described.

Monofunctional alicyclic (meth) acrylate monomer: the monofunctional alicyclic (meth) acrylate monomer is a liquid composition and is a component for dissolving the thermoplastic elastomer. Further, by blending a monofunctional alicyclic (meth) acrylate monomer, the adhesion of the cured product after curing of the photocurable composition can be improved, and the amount of smear can be reduced when the cured product is peeled off from an adherend. In addition, it has an effect of making the cured body tough and thereby increasing the Young's modulus. Further, if the ratio of the component is increased, the moisture resistance can be improved.

Specific examples of the monofunctional alicyclic (meth) Acrylate monomer include isobornyl Acrylate, cyclohexyl Acrylate, dicyclopentyl Acrylate, 3, 5-trimethylcyclohexyl Acrylate, and 4-tert-Butylcyclohexyl Acrylate (4-tert-Butylcyclohexyl Acrylate).

Monofunctional aliphatic (meth) acrylate monomer: the monofunctional aliphatic (meth) acrylate monomer is a liquid composition, and is a component for dissolving the thermoplastic elastomer together with the monofunctional alicyclic (meth) acrylate monomer. By blending a monofunctional aliphatic (meth) acrylate monomer, the flexibility of a cured product obtained after curing the photocurable composition can be improved, and the young's modulus can be reduced.

Specific examples of the monofunctional aliphatic (meth) acrylate monomer include aliphatic ether (meth) acrylate monomers such as ethoxydiglycol acrylate, 2-Ethylhexyl diglycol acrylate, butoxyethyl acrylate, and the like, and aliphatic hydrocarbon (meth) acrylate monomers such as lauryl acrylate, stearyl acrylate, isostearyl acrylate, decyl acrylate, isodecyl acrylate, isononyl acrylate, and n-octyl acrylate. By using the aliphatic hydrocarbon (meth) acrylate monomer, the compatibility with the soft segment of the thermoplastic elastomer can be improved, and the viscosity of the photocurable composition can be reduced.

The mixing ratio (% by mass) of the monofunctional aliphatic (meth) acrylate monomer to the monofunctional alicyclic (meth) acrylate monomer is preferably 15: 85-20: 80. if the mixing ratio of the monofunctional aliphatic (meth) acrylate monomer is less than 15 mass%, the elastic protective member 18 becomes too hard, and there is a possibility that the rubber elasticity is impaired. On the other hand, if the mixing ratio of the monofunctional aliphatic (meth) acrylate monomer exceeds 20 mass%, the elastic protective member 18 may become excessively soft.

The photocurable composition of the present invention may further contain a polyfunctional aliphatic (meth) acrylate monomer, a highly polar monomer, or the like as appropriate.

Specific examples of the polyfunctional aliphatic (meth) acrylate monomer include a bifunctional aliphatic (meth) acrylate monomer. Examples of the bifunctional aliphatic (meth) acrylate monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, glycerin di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methyl-1, 5-pentanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, and 1, 10-decanediol di (meth) acrylate. From the viewpoint of relatively high compatibility with the soft segment of the thermoplastic elastomer, a bifunctional aliphatic hydrocarbon di (meth) acrylate monomer having a reactive group at both ends is preferred.

Examples of the high-polar monomer include a multifunctional high-polar monomer and a monofunctional high-polar monomer. As the multifunctional highly polar monomer, a (meth) acrylate monomer having a polar group and bismaleimide are included. Specifically, examples of the (meth) acrylate monomer having a polar group include ethoxylated isocyanuric acid di/tri (meth) acrylate, and epsilon-caprolactone-modified tris (2-acryloyloxyethyl) isocyanurate. From the viewpoint of improving the close adhesion, a tris (2-hydroxyethyl) isocyanurate-based (meth) acrylate monomer is preferable.

Specific examples of bismaleimides include 4,4 '-diphenylmethane bismaleimide, 4-methyl-1, 3-phenylene bismaleimide, 2-bis [4- (4-maleimidophenoxy) phenyl ] propane, bis (3-ethyl-5-methyl-4) -maleimidophenyl) methane, 1, 6-bis (maleimide) hexane, and 1,6' -bismaleimide- (2,2, 4-trimethyl) hexane. Among them, aliphatic bismaleimides such as 1, 6-bis (maleimide) hexane and 1,6' -bismaleimide- (2,2, 4-trimethyl) hexane are preferable in terms of difficulty in suppressing the compatibility and photocurability of the photocurable composition.

Specifically, examples of the monofunctional highly polar monomer include a hydroxyl group-containing (meth) acrylate monomer, a glycidyl group-containing (meth) acrylate monomer, an acrylamide group-containing monomer, a tertiary amine group-containing (meth) acrylate monomer, and an imide group-containing (meth) acrylate monomer. From the viewpoint of improving storage stability and adhesion in the photocurable composition, nitrogen-containing monomers such as an acrylamide group-containing monomer, a tertiary amine group-containing (meth) acrylate monomer, and an imide group-containing (meth) acrylate monomer are preferable. Examples thereof include acryloylmorpholine, dimethylaminoethyl (meth) acrylate, and N-acryloyloxyethylhexahydrophthalimide. In addition, when polyimide is used as the flexible substrate, it is particularly preferable to use an acrylic imide typified by N-acryloyloxyethylhexahydrophthalimide.

Thermoplastic elastomer: examples of the thermoplastic elastomer include styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, ester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, amide-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, fluororesin-based thermoplastic elastomers, and ionomer-based thermoplastic elastomers. As the thermoplastic elastomer in the present invention, a styrene-based thermoplastic elastomer is preferable.

In the photocurable composition, the styrenic thermoplastic elastomer is dissolved in any one of the monofunctional alicyclic (meth) acrylate monomer, the monofunctional aliphatic (meth) acrylate monomer, and the monofunctional highly polar monomer. The styrene-based thermoplastic elastomer can reduce the amount of scum when a cured product formed by curing the monofunctional alicyclic (meth) acrylate monomer, the monofunctional aliphatic (meth) acrylate monomer, and the monofunctional high-polarity monomer is peeled off, and can reduce the moisture permeability. The styrene-based thermoplastic elastomer is a component that is dissolved in any one of the monofunctional alicyclic (meth) acrylate monomer, the monofunctional aliphatic (meth) acrylate monomer, and the monofunctional highly polar monomer and imparts rubber elasticity (flexibility and elongation) to a cured product. In the present invention, the dissolved state may be a state in which the whole is in a uniform liquid state, and may be a white turbid state or a turbid state of another color, other than a colorless transparent state.

The styrene-based thermoplastic elastomer alone is solid and therefore has no adhesiveness at normal temperature, but can be contained as one component of a photocurable composition having adhesion by being dissolved in any one of the monofunctional alicyclic (meth) acrylate monomer, the monofunctional aliphatic (meth) acrylate monomer, and the monofunctional highly polar monomer to be uniformly dispersed in the photocurable composition and a cured product thereof.

The amount of the styrenic thermoplastic elastomer added to the photocurable composition is preferably 5 to 35% by mass, more preferably 10 to 20% by mass. When the amount of the styrene-based elastomer is less than 10% by mass, the moisture permeability is low, and the rubber elasticity may be impaired. On the other hand, if it exceeds 35 mass%, the viscosity of the photocurable composition increases, and coating may become difficult. When the content is 20% by mass or less, the fluidity is suitable and the coating is easy.

Specific examples of the styrene-based thermoplastic elastomer include a styrene-butadiene-styrene block copolymer (SBS), a styrene-isoprene-styrene block copolymer (SIS), a styrene-ethylene-butylene-styrene block copolymer (SEBS), a styrene-ethylene-propylene-styrene block copolymer (SEPS), a styrene-isobutylene-styrene block copolymer (SIBS), a styrene-ethylene-propylene-styrene block copolymer (SEEPS), and modifications thereof. Among these, the use of SEBS, SEPS, SIBS, or SEEPS having no unsaturated bond in the soft segment is preferable because the cured product of the photocurable composition has excellent weather resistance.

In the present specification, the weight average molecular weight of the styrenic thermoplastic elastomer is measured using a GPC method (Gel Permeation Chromatography; Gel Permeation Chromatography) with reference to a calibration curve (calibration curve) measured according to a standard polystyrene. In the present invention, in terms of easy adjustment to a viscosity suitable for coating, it is preferable to use a styrene-based thermoplastic elastomer having a weight average molecular weight of less than 20 ten thousand.

Radical polymerization initiator: as the radical polymerization initiator, specifically, for example, a photo radical polymerization initiator which is cured by photoreaction of a monofunctional aliphatic (meth) acrylate monomer, a monofunctional alicyclic (meth) acrylate monomer, and a monofunctional highly polar monomer by light is preferable. By adding a photo-radical polymerization initiator to the photocurable composition and irradiating the photocurable composition with light, for example, the photocurable composition applied to an object to be coated can be photocured to form a coating film. Examples of the photo radical polymerization initiator include photopolymerization initiators such as benzophenones, thioxanthones, acetophenones, acylphosphines, oxime esters, and alkylbenzophenones. The amount of the photo radical polymerization initiator added is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the total amount of all the monomers including the monofunctional and polyfunctional monomers.

When curing is performed by an LED light source, an alkylbenzophenone-based photo radical polymerization initiator that absorbs a wavelength of 300nm or more is preferable. Among them, an alkylbenzophenone-based photo radical polymerization initiator having a morpholine skeleton is particularly preferably used because the curing rate and the film curability can be improved.

Other components: the photocurable composition of the present invention may further contain other components such as various additives as appropriate within the scope not departing from the gist of the present invention. Examples thereof include thixotropy imparting agents such as silica and alumina, plasticizers such as olefin oils and paraffin oils, silane coupling agents, polymerization inhibitors, defoaming agents, light stabilizers, antioxidants, antistatic agents, and fillers.

The above embodiments are examples of the present invention, and the embodiments may be modified, or known techniques may be added or combined without departing from the scope of the present invention, and these techniques are also included in the scope of the present invention.

Examples

Next, the present invention will be described in further detail based on examples (comparative examples). The photocurable compositions and cured products thereof of the following samples 1 to 19 were prepared and evaluated by the following evaluation methods.

< preparation of sample >

Samples were prepared as follows.

Sample 1: lauryl acrylate was prepared as a monofunctional aliphatic (meth) acrylate monomer, isobornyl acrylate was prepared as a monofunctional alicyclic (meth) acrylate monomer, N-acryloyloxyethylhexahydrophthalimide was prepared as a monofunctional high-polarity monomer, and 1, 9-nonanediol diacrylate was prepared as a multifunctional aliphatic (meth) acrylate monomer. Next, elastomer a (trade name "SIBSTAR 062T", SIBS (styrene-isobutylene-styrene block copolymer), manufactured by KANEKA corporation) as a thermoplastic elastomer was added to the above-mentioned monomer and stirred for 24 hours, thereby dissolving the thermoplastic elastomer in the above-mentioned monomer. The mixing ratio in this case is shown in Table 1, for example. When the "resin component" composed of the above monomer and the thermoplastic elastomer was defined as 100 parts by mass, 2-hydroxy-2-methylphenylacetone, which is a photo radical polymerization initiator, was added in an amount of 4.0 parts by mass to obtain a photocurable composition of sample 1.

In order to measure various characteristics or perform various tests described later, the obtained photocurable composition of sample 1 was applied to a predetermined substrate, and irradiated with ultraviolet light under the conditions described later, to form an elastic protective member which is a cured product of sample 1.

Sample 2-19: photocurable compositions of samples 2 to 19 were prepared in the same manner as in sample 1, except that the thermoplastic elastomer, the monomers, and the like of sample 1 were changed to the types and the compounding (mass portion) shown in table 1 and table 2 below. The photocurable compositions of samples 2 to 19 were irradiated with ultraviolet rays in the same manner as in sample 1 to form the elastic protective members of samples 2 to 19.

[ Table 1]

[ Table 2]

[ combination ]:

the details of the raw materials shown in tables 1 to 2 are as follows, except for the already described contents.

Ethoxylated isocyanuric acid di/tri (meth) acrylate is used as the multifunctional highly polar monomer.

The thermoplastic elastomer is as follows.

An elastomer B: SEPS (styrene-ethylene-propylene-styrene block copolymer) having a trade name of "SEPTON 2002", manufactured by Coli,

an elastomer C: SEEPS (styrene-ethylene-propylene-styrene block copolymer), trade name "SEPTON 4055", manufactured by KOLEI.

As the photo radical polymerization initiator, in addition to 2-hydroxy-2-methylphenylacetone, 2-dimethylamino-2- (4-methylbenzyl) -1- (4-morpholinophenyl) -1-butanone can be used.

For comparison, a polyfunctional polymer was used as an alternative ingredient to the thermoplastic elastomer, as described below.

Polymer A: polybutadiene having a terminal methacrylic group introduced thereinto (acrylic acid equivalent: 2000) is available under the trade name "TE-2000", manufactured by Nippon Kabushiki Kaisha,

polymer B: the terminal methacrylic group was introduced into hydrogenated polybutadiene (acrylic acid equivalent: 1400) having a trade name of "TEAI-1000", manufactured by Nippon Cao Kabushiki Kaisha.

For comparison, sample 19 used a completely different composition than the other samples, and therefore the matching column for sample 19 is labeled as # 1. Specifically, a product having a trade name of "Loctite 3523" manufactured by Henkel Japan Ltd., Japan, and the like, which is a photocurable composition mainly composed of a urethane methacrylate resin and a (meth) acrylic monomer, and does not contain a thermoplastic elastomer, is used.

[ characteristics ]:

in tables 1 to 2, various characteristics of the elastic protection member and the photocurable composition of each of the obtained samples are also described. The details of the characteristics shown in each table are as follows.

Ma hardness (N/mm)²)：

A nanoindentation test of the cured body was performed using a nanoindenter (manufactured by ELIONIX, ENT-2100). The following cured products were used for the test pieces: a photocurable composition was applied to a polyimide film having a thickness of 50 μm to form a film having a thickness of 100 μm, and an LED having a wavelength of 365nm was used to irradiate light at a rate of 200mW/cm²The cured product was produced by irradiating the cured product with ultraviolet light for 15 seconds. Then, the Martensitic hardness of the cured body was measured by the nanoindenter under conditions of a maximum pushing load of 0.1mN and a pushing speed of 0.01 mN/sec.

Tensile elongation at break (%), tensile strength (MPa), tensile stress at 100% elongation (MPa), and young's modulus (MPa):

mechanical strength of the cured body was obtained by mixing JISK 6251: part 2010 is modified and implemented. A1 mm thick photocurable composition was coated on a polyester film on which silicone release treatment was completed, using an LED having a wavelength of 365nm at 200mW/cm²The photocurable composition was cured by irradiating with ultraviolet light for 15 seconds, the obtained cured body was punched out with a dumbbell 8-shaped die, and marks were added to the bar-shaped portions of the dumbbell-shaped samples at intervals of 16mm to prepare test pieces. A tensile test was conducted at a speed of 200 mm/min, and the tensile elongation at break (elongation at cut), tensile strength (maximum tensile stress), 100% tensile stress, Young's modulus (modulus of elasticity) were measured. At this time, since the thickness of sample 6 was 1mm and the curing was insufficient, the thickness was changed to 100 μm, and the same measurement was performed. The tensile elongation at break, tensile strength and 100% elongation stress were calculated by applying the following formulas (1), (2) and (3), respectively. The Young's modulus was determined by dividing the tensile stress within the limit of the tensile ratio by the strain.

TS ═ Fm/S ·, formula (1),

Eb ═ L1-L0/L0X 100. cndot. formula (2),

TS100 ═ F100/S · formula (3),

TS: tensile strength (MPa),

Fm: maximum tensile force (N),

S: initial load bearing (mm) of test piece²)、

Eb: tensile elongation at break (%),

L0: initial inter-line distance (mm),

L1: the distance (mm) between the standard lines when the fracture occurs,

TS 100: tensile stress at 100% elongation (MPa),

F100: tensile force (N) at 100% elongation.

Peeling force (N/m):

the weight ratio of JISK 6852-2: 1999 the 180 degree peel test method was partially modified to perform the measurements. A1 mm thick photocurable composition was applied to a polyimide film having a thickness of 50 μm or a glass having a thickness of 1mm, and an LED having a wavelength of 365nm was used at 20 deg.C0mW/cm²The cured product was cured by irradiating with ultraviolet light for 15 seconds, and then cut into a width of 25mm, and peeled at a peeling speed of 300 mm/min and a peeling angle of 180 degrees, thereby measuring the peeling force (adhesive strength). At this time, since the thickness of sample 6 was 1mm and the curing was insufficient, the thickness was changed to 100 μm, and the measurement was performed in the same manner.

Moisture permeability (g/m)²·24h)：

According to JISZ 0208: 1976 coating a resin composition having a thickness of 100 μm on a polyester film subjected to a silicone release treatment using an LED having a wavelength of 365nm at 200mW/cm²The cured product was cured by irradiation with ultraviolet light for 15 seconds, and the moisture permeability (water vapor transmission rate) of the cured product was measured at a temperature of 40 ℃ and a relative humidity of 90% RH. In the measurement of moisture permeability, in the case where the weight of the sample is reduced, the reduced portion is corrected.

Viscosity (mPa · s):

the viscosity of the photocurable composition was measured when it was uncured. The viscosity at 23 ℃ and 107rpm was measured using a rotary Viscometer (manufactured by Bohlin instruments, Bohlin V88Viscometer, cone plate "CP 5 °/30").

Storage stability:

the storage stability shows the properties of the photocurable composition when left standing at 25 ℃ for 2 weeks. By visual observation, the case where no precipitation or separation was confirmed was denoted by "a", and the case where precipitation or separation was confirmed was denoted by "B".

[ test ]:

in tables 1 to 2, the elastic protective member of each of the obtained samples was subjected to various tests as described below. The results are shown in the tables.

Bending resistance test (wiring):

in order to examine the protection state of the elastic protection member provided at the connection portion between the flexible substrate and the rigid substrate with respect to the wiring, the following bending resistance test was performed. As shown in fig. 2, the length of the boundary between the flexible substrate and the rigid substrate in the depth direction of the portion protruding from the front end of the rigid substrate is 400 to 800 μm, and the boundary covers the rigid substrateCoating a photocurable composition on the end face of the tip with a spray dispenser in a height range of 50-100 μm, and applying a 200mW/cm LED with a wavelength of 365nm²The photocurable composition was cured by irradiation with ultraviolet light for 15 seconds. The portions that could not be coated by the jet dispenser were coated in the same manner using a pneumatic dispenser. Thus, a test piece for bending resistance test was produced. In addition, 10 copper wirings having a line width of 10 μm formed in the depth direction of the flexible substrate coated with the photocurable composition were evaluated.

Next, as shown in fig. 3, an operation of holding the rigid substrate side by a holding member H and bending it by 180 degrees and then returning it to the original state is performed so that the cured body is positioned inside by attaching a weight W to the tip 200g of the flexible substrate, and when the operation is set to 1 cycle, the wiring after 100 cycles is observed.

Then, the case where a break was observed in any of the wirings was evaluated as "B", and the case where no break was observed in the wirings was evaluated as "a".

Bending resistance test (material):

in order to investigate the bending resistance of the elastic protection member, a bending resistance test was performed. A photocurable composition was applied to a polyimide film having a thickness of 50 μm to a thickness of 100 μm, and an LED having a wavelength of 365nm was used at a rate of 200mW/cm²The ultraviolet rays were irradiated for 15 seconds, thereby curing it. Each cured polyimide film was cut into 20mm × 100mm, bent at a bending angle of 180 degrees and a bending radius of 1mm or less so that the cured body was located inside, then bent at a bending angle of 180 degrees and a bending radius of 1mm or less so that the cured body was located outside to the opposite side, and the bent portion after 10 cycles was visually observed with the state after bending being set to 1 cycle.

Then, the case where the elastic protection member was not peeled from the polyimide film and no fracture was generated in the elastic protection member was evaluated as "a", the case where the elastic protection member was peeled from the polyimide film but no fracture was observed was evaluated as "B", and the case where peeling was generated and fracture was observed was evaluated as "C".

UV-LED curing test:

a photocurable composition was applied to a polyimide film having a thickness of 50 μm to form a film having a thickness of 100. mu.m, and an LED having a wavelength of 365nm was used at a rate of 200mW/cm²Ultraviolet rays were irradiated for 15 seconds, thereby curing it. The case where no transfer was observed when the surface on the atmospheric side of the cured body was touched with a finger was evaluated as "a", and the case where no transfer was observed was evaluated as "B".

Spray dispenser coating test:

coating of the photocurable composition by a jet dispenser was examined for rationality and evaluated. The coating rationality (coatability) when the photocurable composition of each sample was coated at a nozzle temperature of 40 ℃ was confirmed by using a spray dispenser PicoPulse manufactured by NordsonEFD, and evaluated.

The case where the coating could be performed by the jet dispenser was evaluated as "a", and the case where the coating could not be performed was evaluated as "B".

And (4) reworking test:

the ease of peeling from the substrate of the elastic protection member was evaluated. When the above-mentioned "peeling force" was measured, the peeling of the elastic protective member from the polyimide film was confirmed and evaluated.

The elastic protective member was evaluated as "a" when peeled from the polyimide film without breaking, and as "B" when broken.

And (3) insulation reliability test:

whether or not the elastic protection member can stably protect the wiring is evaluated based on whether or not migration (migration) occurs in the wiring protected by the elastic protection member and whether or not discoloration occurs in the wiring.

A photocurable composition was applied to a glass epoxy substrate having copper wiring with a wiring width of 0.318mm and a wiring interval of 0.318mm on the surface thereof to a thickness of 100 μm, and an LED with a wavelength of 365nm was used at a wavelength of 200mW/cm²The ultraviolet rays were irradiated for 15 seconds, thereby curing it. A voltage of 50V was applied at 85 ℃ and 85% RH, and the presence or absence of migration after 300 hours was confirmed.

The case where no migration or discoloration occurred on the wiring was evaluated as "a", the case where no migration or discoloration occurred was evaluated as "B", and the case where migration occurred was evaluated as "C".

< investigation of test results >

From the results of the bending resistance test (wiring), the wiring was not broken and evaluated as "a" in samples 1 to 6, while the wiring was broken and evaluated as "B" in samples 7 to 19. The evaluation results of all other tests, i.e., the bending resistance test (material), the UV-LED curing test, the spray dispenser coating test, the rework test, and the insulation reliability test, were "a" for samples 1 to 6 in which no wire breakage occurred. On the other hand, some of samples 7 to 19 in which the wiring was broken were also evaluated as "B" or "C" in the other tests.

As for samples 1 to 6, it is understood that the Ma hardness of any 1 of the samples is 0.35 to 3.0N/mm²In the range of (1), the tensile elongation at break is 100% or more.

Description of the reference numerals

10: an electronic substrate,

12: a rigid substrate,

12 a: a polarizing plate,

12 b: a glass substrate with a first transparent electrode,

12 c: a liquid crystal layer,

12 d: a glass substrate with a second transparent electrode,

12 e: a polarizing plate,

12 f: a backlight unit,

12 g: end face,

14: a flexible substrate,

15: an anisotropic conductive adhesive,

16: a bent part,

18: an elastic protection component,

40: the projecting width,

W: a hammer,

H: a holding member.