KR102440212B1 - Electronic substrates and photocurable compositions - Google Patents

Abstract

An electronic substrate having a flexible portion having an excellent balance between flexibility and hardness is provided. A rigid substrate (12), a flexible substrate (14) extending from an end portion of the rigid substrate (12) and connected so as to be conductive, and a wiring from the rigid substrate (12) to the flexible substrate (14) In the electronic substrate 10 having a bent portion 16 protruding from the end of the rigid substrate 12 and bent toward one side of the rigid substrate 12 in the flexible substrate 14 , an elastic protective member on at least one surface of the flexible substrate 14 at the boundary between the rigid substrate 12 and the flexible substrate 14 from the end of the rigid substrate 12 to the bent portion 16 . (18) is installed, the Martens hardness measured by the nano-indentation test of the elastic protective member 18 is 0.35 to 3.0 N/mm ² , and the tensile elongation at break is 100% or more ( 10) was made.

Description

Electronic substrates and photocurable compositions

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

BACKGROUND ART In an electronic substrate having a flexible portion having flexibility, a flexible substrate (including flexible printed circuits (hereinafter, also referred to as "flexible substrate")) is generally used as the flexible portion. In a flexible substrate, a metal conductor circuit such as copper foil is usually formed on a film such as polyimide resin or polyester resin, and a cover film such as polyimide resin or polyester resin is provided as a protective layer. known as possible substrates. For example, in Japanese Patent Laid-Open No. 7-106728 (Patent Document 1), in a substrate having a rigid portion and a flexible portion, a resin composition is used as a protective member for the connection portion between the rigid portion and the flexible portion. are doing

Further, the electronic substrate having a rigid substrate and a flexible substrate provided at the end of the rigid substrate is, for example, a liquid crystal monitor device, a plasma display device, an organic EL display device, an RGB inorganic LED mounted display device, etc. It is also used in image display devices of In this image display apparatus, the panel which is an image display site|part is used as a rigid board|substrate, and in order to apply a voltage or a signal to the panel, the flexible board|substrate electrically connected to the edge part of the panel is provided. Here, an anisotropic conductive film is generally used for the connection between the panel and the flexible substrate, and a protective member for insulation protection or adhesion reinforcement of the connection portion is applied. And the other end of the said flexible board|substrate is electrically connected to an electronic circuit board (motherboard etc.). Generally, since an electronic circuit board is arrange|positioned on the back surface of a panel, the flexible board|substrate extended from a panel is bent and connected to an electronic circuit board. In addition, in recent years, there has been a growing demand for downsizing and narrowing the frame of image display devices, and in order to save space in non-image display parts, a chip-on-film in which driver ICs are mounted on a flexible substrate instead of on a conventional panel. Rescue, etc. are also employed.

Here, in order to control the bendability of a flexible substrate, in Unexamined-Japanese-Patent No. 2008-26528 (patent document 2), the panel which has an electrode lead-out part, the flexible substrate connected to the said electrode lead-out part, the said flexible substrate, In an image display device having a protective layer covering a connecting portion of the electrode lead-out portion, it is disclosed to change the wettability to a resin material on the flexible substrate. With the above configuration, when the resin material is applied to the flexible substrate, a region in which the resin material is stably formed with a protective layer and a region in which the protective layer is not stably formed by repelling the resin material are created, as a result, the protection Since the flexible substrate is bent from the tip of the protective layer in the layered flexible substrate as a starting point, the region in which the protective layer is formed can be controlled to a predetermined width. Thereby, the protrusion width of the bent part of the flexible board|substrate which protrudes outward from the panel edge part can be controlled small.

Japanese Patent Laid-Open No. 7-106728 Japanese Laid-Open Patent Publication No. 2008-26528

However, new miniaturization and narrower frames are expected for image display devices, and there is a strong demand for further reducing the protrusion width of the bent portion for a flexible substrate bent at the end of a rigid substrate constituting an image display device or the like. However, if the protrusion width is forcibly reduced, it may be bent excessively, and if the adhesive force of the connecting portion of the wiring is insufficient, there is a risk of peeling. Further, the flexible substrate is bent abruptly in the vicinity of the rigid substrate, stress is concentrated at the boundary portion between the flexible substrate and the rigid substrate, and there is a fear that the wiring may break.

In addition, in the technique described in Japanese Patent Application Laid-Open No. 7-106728 (Patent Document 1), the flexural modulus of the resin composition of the protective member used is 880 kg/mm ² (=8630 MPa) (Example), which is hard because, Breakage of wiring can be prevented at the boundary between the rigid substrate and the flexible substrate, but at the boundary between the portion where the protection member is formed and the portion where the protection member is not formed, the flexible substrate is abruptly bent and the wiring is broken. I found it easy too.

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

The electronic board|substrate of this invention which achieves the said objective, and a photocurable composition are as follows.

An electronic substrate of the present invention includes a rigid substrate, a flexible substrate extending from an end of the rigid substrate and connected so as to be electrically conductive, and wiring from the rigid substrate to the flexible substrate, wherein the flexible substrate includes: With respect to an electronic substrate having a bent portion protruding from the end of the rigid substrate and bent toward one side of the rigid substrate, at the boundary between the rigid substrate and the flexible substrate from the end of the rigid substrate to the bent portion, among the flexible substrates An elastic protective member is installed on at least one surface, and the elastic protective member has a Martens hardness measured by a nanoindentation test of 0.35 to 3.0 N/mm ² , and a tensile rupture elongation ( It is an electronic substrate, characterized in that tensile breaking elongation) is 100% or more.

A rigid substrate, a flexible substrate extending from an end of the rigid substrate and connected in a conductive manner, and a wiring extending from the rigid substrate to the flexible substrate, the flexible substrate protruding from the end of the rigid substrate and extending from the rigid substrate An electronic substrate having a bent portion bent toward one side of the substrate has an elastic protective member on at least one surface of the flexible substrate at a boundary between the rigid substrate and the flexible substrate extending from the end of the rigid substrate to the bent portion installed, and the elastic protective member has a Martens hardness measured by a nanoindentation test of 0.35 to 3.0 N/mm ² and a tensile rupture elongation of 100% or more, so that of a rigid substrate and a bent flexible substrate Disconnection of wiring does not easily occur at the boundary portion 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, so that the reliability of conduction can be improved.

The elastic protective member has a Martens hardness measured by the nanoindentation test of 0.35 to 3.0 N/mm ² It becomes a thing with hardness of , and it can make it small compared with the prior art, and the bending radius at the time of bending a flexible board|substrate, it can be made not to become small too much. Thereby, while making the protrusion width of the bent portion of the flexible substrate protruding outward from the end of the rigid substrate (that is, the amount of protrusion of the flexible substrate from the end of the rigid substrate) smaller than that of the prior art, the boundary between the rigid substrate and the flexible substrate It is possible to avoid extreme bending of the portion and the boundary portion between the portion in which the elastic protective member is formed and the portion in which the elastic protective member is not formed.

Since the elastic protective member has a tensile rupture elongation of 100% or more, the elastic protective member has extensibility from the end of the rigid substrate to the flexible substrate and can follow the deformation when the flexible substrate is bent, so it is flexible Since it is possible to avoid extreme bending of the substrate and to prevent peeling of the elastic protective member at the time of bending, it is excellent in durability.

In addition, the Young's modulus of the elastic protective member may be 40 to 250 MPa. When the Young's modulus is set to 40 to 250 MPa, adequate flexibility is obtained, and thus, the bending radius of the flexible substrate can be reduced compared to the prior art, but not too small. As a result, while the protrusion width of the bent portion of the flexible substrate protruding outward from the end of the rigid substrate is made smaller than in the prior art, the boundary portion between the rigid substrate and the flexible substrate and the portion where the protection member is formed and the protection member Extreme bending of the boundary portion of the unformed portion can be avoided.

And, 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 to prevent peeling of the rigid substrate and the flexible substrate, It is possible to prevent moisture or foreign substances from entering the boundary between the substrate and the flexible substrate.

The present invention can be an electronic substrate in which the elastic protection member covers at least a part of an end surface of the rigid substrate that intersects the contact surfaces of the rigid substrate and the flexible substrate. Since the elastic protection member covers at least a part of an end surface of the rigid substrate that intersects the contact surfaces of the rigid substrate and the flexible substrate, the elastic protection member improves the adhesion of the rigid substrate to the rigid substrate, and the elastic protection member can be made difficult to peel from the rigid substrate.

The present invention can be an electronic substrate in which the flexible substrate positioned on the opposite side to the rigid substrate is bent by approximately 180 degrees with respect to the rigid substrate by sandwiching the bent portion. Since the flexible substrate positioned on the opposite side to the rigid substrate by holding the bent portion is bent by approximately 180 degrees with respect to the rigid substrate, it is possible to arrange the flexible substrate in the vicinity of the rigid substrate, thereby making the flexible substrate compact can be accepted

The flexible substrate is a resin film having a thickness of 15 to 200 μm, and when the flexible substrate is bent, the elastic protection member is provided on the bent inner surface of the flexible substrate. Even if the thickness of the resin film of the said flexible board|substrate is 15-200 micrometers, the protrusion width of the said flexible board|substrate bending part can be made small compared with the prior art, and it can be made not to become small too much. Further, since the elastic protection member is provided on the bent inner surface of the flexible substrate, damage to the wiring can be suppressed when bent so as to reduce the bending radius.

In addition, the present invention is a photocurable composition for forming an elastic protective member by curing by irradiating light after application to an electronic substrate, a monofunctional alicyclic (meth)acrylic acid ester monomer, and a monofunctional aliphatic (meth) An acrylic acid ester monomer, a thermoplastic elastomer, and a radical polymerization initiator, wherein the cured product after curing has a Martens hardness measured by a nanoindentation test of 0.35 to 3.0 N/mm ² and a tensile elongation at break of 100% It can be comprised as the above photocurable composition.

The photocurable composition of the present invention is a photocurable composition that forms an elastic protective member by curing it by irradiating light after application to an electronic substrate, and includes a monofunctional alicyclic (meth)acrylic acid ester monomer and a monofunctional aliphatic (meth) An acrylic acid ester monomer, a thermoplastic elastomer, and a radical polymerization initiator, wherein the cured product after curing has a Martens hardness measured by a nanoindentation test of 0.35 to 3.0 N/mm ² and a tensile elongation at break of 100% or more Therefore, there is no fear that the cured body provided on the flexible substrate interferes with the bending of the flexible substrate, and the flexible substrate can be bent with a small bending radius but not too small. Moreover, since a hardening body has extensibility and can follow the deformation|transformation at the time of bending a flexible substrate, it can avoid extreme bending of a flexible substrate, and also can prevent peeling at the time of bending. It also has excellent durability.

The present invention can also be made into a photocurable composition containing an amount polar monomer. Moreover, the photocurable composition containing a high polarity monomer has high adhesiveness to a flexible substrate, and the followability|trackability with respect to the deformation|transformation of a flexible substrate becomes high.

The present invention can be a photocurable composition having a viscosity in the uncured range of 10 to 5000 mPa·s. Since the viscosity at the time of uncuring is the range of 10-5000 mPa*s, it is easy to precisely control the amount of application to an electronic board|substrate, and it is excellent in the workability|operativity of application|coating. As a result, there is a low possibility that it is applied excessively to the electronic substrate.

The electronic board of the present invention can prevent breakage of wiring in the boundary portion between the rigid substrate and the flexible substrate and the boundary portion between the portion in which the elastic protection member is formed and the portion in which the elastic protection member is not formed. In addition, since the photocurable composition of the present invention has a low viscosity when uncured, it is easy to apply and has excellent workability, and the cured body after curing can exhibit desired hardness, flex resistance, and appropriate flexibility.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view of the electronic board|substrate in one Embodiment of this invention.
Fig. 2 is a schematic cross-sectional view of an electronic substrate according to an embodiment of the present invention.
It is explanatory drawing explaining one of the test methods.

The electronic board 10 of this invention is demonstrated in detail based on embodiment. 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 connected so as to be conductive, the rigid substrate 12 . The flexible substrate 14 has wirings (not shown) arranged on these substrates 12 and 14 . As shown in Fig. 2, the flexible substrate 14 has a bent portion 16 that protrudes from the end of the rigid substrate 12 and is bent toward one side side (lower side in Fig. 2) of the rigid substrate 12, , from the end of the rigid substrate 12 to the bent portion 16 , an elastic protection member 18 is provided on at least one surface thereof. The bent portion 16 protrudes from the rigid substrate 12 with a protruding width 40 .

As shown in the enlarged part of FIG. 2, the rigid substrate 12 can be set as the liquid crystal monitor panel or LED mounting panel which laminated|stacked various functional layers on the glass substrate, for example. More specifically, in the case of a liquid crystal monitor panel, the rigid substrate 12 includes a polarizing plate 12a, a first glass substrate 12b with a transparent electrode, a glass substrate 12d with a second transparent electrode, A liquid crystal layer 12c sandwiched between the (1) glass substrate 12b and the (2) glass substrate 12d, a sealing material (not shown) for sealing the liquid crystal; 2 A polarizing plate 12e and a backlight unit 12f disposed on the rear surface of the glass substrate 12d are sequentially stacked.

In addition, the structure of the electronic board|substrate 10 is not limited to the structure mentioned above, As long as the rigid board|substrate 12 is a board|substrate which is hard compared with the flexible board|substrate 14, any structure may be sufficient. If an example is shown, a glass epoxy resin board|substrate, a phenol resin board|substrate, a silicon board|substrate, a ceramic board|substrate etc. may be sufficient, for example. In addition, in the case of a TFT liquid crystal monitor, the 1st glass substrate 12b with a transparent electrode becomes a 1st transparent electrode and a glass substrate with a color filter, The 2nd glass substrate 12d with a transparent electrode is a 2nd transparent electrode and a glass substrate with TFT. The wiring arranged on the glass substrate 12d and the wiring arranged on the flexible substrate 14 are connected by an anisotropic conductive adhesive 15 .

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

The flexible substrate 14 is a board|substrate used as resin films, such as a polyimide film and a polyester film, Usually, wiring is formed in the surface of a resin film at least. In this invention, it is preferable that wiring is provided on a polyimide film. Moreover, as for the thickness of the flexible substrate 14, it is more preferable that it is 15-200 micrometers. When it is thinner than 15 micrometers, the film itself is easy to bend|fold, and there exists a possibility that acute-angle bending may arise instead of the bending which drew an appropriate curve. On the other hand, when the thickness is greater than 200 μm, the bent mountain side is stretched excessively and the valley side is excessively reduced, making it difficult to protect the wiring.

In addition, the said flexible board|substrate 14 can be provided with a resist layer (not shown) in addition to wiring. Furthermore, it is good also as a so-called chip-on film in which an electronic element is implemented. In that case, it is preferable to arrange|position the said electronic element avoiding the most curved part of a bending part.

The elastic protection member 18 protects wiring by providing it from the edge part of the rigid board|substrate 12 to the flexible board|substrate 14, It hardens|cures the photocurable composition mentioned later. The elastic protective member 18 is preventing the flexible substrate 14 from bending at an acute angle by having extensibility and compressibility in addition to excellent flexibility. More specifically, when the elastic protective member 18 is disposed inside the flexible substrate 14, the bending radius can be reduced by compressing the elastic protective member 18 when bent, but it is not too small. On the other hand, when the elastic protective member 18 is disposed on the outside of the flexible substrate 14, when the elastic protective member 18 is bent with a relatively weak stress, the bending radius can be reduced, but it is not too small. .

The elastic protective member 18 has a Martens hardness measured by the nanoindentation test in the range of 0.35 to 3.0 N/mm ² , and preferably 0.4 to 2.5 N/mm ² . The boundary portion between the rigid substrate 12 and the flexible substrate 14 and the elastic protection member by setting the Martens hardness of the elastic protective member 18 in the range of 0.35 to 3.0 N/mm ² and the tensile rupture elongation in a predetermined range. It is possible to prevent breakage of the wiring at the boundary between the portion in which is formed and the portion in which is not formed. On the other hand, when the Martens hardness is smaller than 0.35 N/mm ² , the elastic protective member 18 becomes too soft, and when it is larger than 3.0 N/mm ² , it becomes too hard, and the protection of the wiring becomes insufficient in any case.

The Young's modulus of the elastic protective member 18 can be 40 to 250 MPa, preferably 60 to 200 MPa. When the Young's modulus of the elastic protective member 18 is in the range of 40 to 250 MPa, it is easy to set the Martens hardness and tensile elongation at break within a predetermined range, and the boundary portion between the rigid substrate 14 and the flexible substrate 16 and the elasticity It is possible to prevent breakage of the wiring at the boundary between the portion in which the protection member is formed and the portion in which the protection member is not formed.

The Young's modulus has a certain correlation with the Martens hardness, but is not necessarily proportional. More specifically, it can be said that the Young's modulus represents the property of hardness when the entire cured product is stretched, and the Martens hardness is a value that more reflects the effect of hardness when the surface of the cured product is compressed. About the bending resistance of the flexible board|substrate connected to a rigid board|substrate, since the influence of the hardness at the time of compression of hardened|cured material is more important, in this invention, the Martens hardness is considered as important. On the other hand, in the case of the same Martens hardness, it is preferable that the cured product has a small Young's modulus. This is because the surface hardenability is excellent, and the flexibility and durability of the surface are excellent.

The tensile rupture elongation of the elastic protective member 18 is 100% or more. By setting the tensile breaking elongation of the elastic protection member 18 to 100% or more and the Martens hardness to a predetermined range, the boundary portion between the rigid substrate 14 and the flexible substrate 16 and the portion where the elastic protection member is formed and formed It is possible to prevent breakage of the wiring at the boundary of the unfinished part. On the other hand, when the tensile rupture elongation is less than 100%, it is difficult to follow the deformation of the flexible substrate, and the protection of the wiring becomes insufficient.

The photocurable composition is a photocurable composition that forms the elastic protective member 18 by irradiating light after being applied to the substrates 12 and 14 and curing it, and includes a monofunctional alicyclic (meth)acrylic acid ester monomer and a monofunctional It contains an aliphatic (meth)acrylic acid ester monomer, a thermoplastic elastomer, and a radical polymerization initiator. And, as a property of the hardened body, the Martens hardness measured by the nanoindentation test is 0.35 to 3.0 N/mm ² , and the tensile elongation at break is 100% or more. In addition, the hardening body of this photocurable composition is also simply called a hardening body.

Here, "monofunctional alicyclic (meth)acrylic acid ester monomer" is a meaning including a monofunctional alicyclic acrylic acid ester monomer and a monofunctional alicyclic methacrylic acid ester monomer. "Monofunctional aliphatic (meth)acrylic acid ester monomer" is a meaning including a monofunctional aliphatic acrylic acid ester monomer and a monofunctional aliphatic methacrylic acid ester monomer. Similarly, a "high polarity monomer" is a meaning including the (meth)acrylic acid ester monomer containing a polar group, the monomer which has an acrylamide group, and the monomer which has a maleimide group.

From the viewpoint of applicability of the photocurable composition, the uncured viscosity at 23°C is in the range of 10 to 5000 mPa·s, preferably 50 to 2000 mPa·s, and more preferably 90 to 1000 mPa·s. It is the range of s. In particular, when the photocurable composition is applied to a predetermined area of an application target having irregularities to a predetermined thickness using a non-contact application apparatus such as a jet dispenser, the viscosity is set to 90 to 1000 mPa in order to control the application amount with high precision. It is preferable to set it as s.

The photocurable composition contains each of the components described above, and by having an uncured viscosity within the above range, it is easy to apply and has excellent workability. It has flexibility and bending resistance, and can be used as the elastic protection member 18 of the electronic board 10.

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

Monofunctional alicyclic (meth)acrylic acid ester monomer: A monofunctional alicyclic (meth)acrylic acid ester monomer is a liquid composition, and is a component which melt|dissolves a thermoplastic elastomer. In addition, by blending a monofunctional alicyclic (meth)acrylic acid ester monomer, the adhesive strength of the cured product after curing of the photocurable composition is increased, and the adhesive remains when the cured product is peeled from the adherend. can In addition, there is an effect of increasing the Young's modulus by making the hardening body tough. In addition, when the ratio of this component is increased, moisture resistance can be improved.

Specific examples of the monofunctional alicyclic (meth)acrylic acid ester monomer include isobornyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, and 4-tert-butylcyclo hexyl acrylate and the like.

Monofunctional aliphatic (meth)acrylic acid ester monomer: The monofunctional aliphatic (meth)acrylic acid ester monomer is a liquid composition, and is a component for dissolving the thermoplastic elastomer together with the aforementioned monofunctional alicyclic (meth)acrylic acid ester monomer. By mix|blending a monofunctional aliphatic (meth)acrylic acid ester monomer, the flexibility of the hardening body obtained after hardening of a photocurable composition can be improved, and a Young's modulus can be low.

As a monofunctional aliphatic (meth)acrylic acid ester monomer, specifically, aliphatic ether-type (meth)acrylic acid ester monomers, such as ethoxydiethylene glycol acrylate, 2-ethylhexyl diglycol acrylate, butoxyethyl acrylate, and lauryl and aliphatic hydrocarbon-based (meth)acrylic acid ester monomers such as acrylate, stearyl acrylate, isostearyl acrylate, decyl acrylate, isodecyl acrylate, isononyl acrylate, and n-octyl acrylate. . By using the aliphatic hydrocarbon-based (meth)acrylic acid ester monomer, compatibility with the soft segment of the thermoplastic elastomer can be improved, and the viscosity of the photocurable composition can be lowered.

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

The photocurable composition of this invention may also contain suitably a polyfunctional aliphatic (meth)acrylic acid ester monomer, a highly polar monomer, etc. further.

Specific examples of the polyfunctional aliphatic (meth)acrylic acid ester monomer include a bifunctional aliphatic (meth)acrylic acid ester monomer. Examples of the bifunctional aliphatic (meth)acrylic acid ester 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, 1,10-decanedioldi(meth)acrylate, etc. have. Since compatibility with the soft segment of the thermoplastic elastomer is relatively high, a difunctional aliphatic hydrocarbon-based di(meth)acrylic acid ester monomer having reactive groups at both terminals is preferable.

Examples of the high polarity monomer include a polyfunctional high polarity monomer and a monofunctional high polarity monomer. As said polyfunctional highly polar monomer, the (meth)acrylic acid ester monomer and bismaleimide which have a polar group are contained. Specific examples of the (meth)acrylic acid ester monomer having a polar group include ethoxylated isocyanuric acid di/tri(meth)acrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, and the like. can be heard From a viewpoint of an adhesive improvement, a tris (2-hydroxyethyl) isocyanurate type (meth)acrylic acid ester monomer is preferable.

Further, specific examples of the bismaleimide include 4,4'-diphenylmethanebismaleimide, 4-methyl-1,3-phenylenebismaleimide, and 2,2-bis[4-(4-maleimidephenoxy). Cy)phenyl]propane, bis(3-ethyl-5-methyl-4-maleimidephenyl)methane, 1,6-bis(maleimide)hexane, 1,6'-bismaleimide-(2,2,4 -trimethyl)hexane is exemplified. Among these, from the viewpoint of difficulty in inhibiting the compatibility and photocurability of the photocurable composition, 1,6-bis(maleimide)hexane, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, etc. Aliphatic bismaleimides are preferred.

Specifically, as the monofunctional high polarity monomer, hydroxyl group-containing (meth)acrylic acid ester monomer, glycidyl group-containing (meth)acrylic acid ester monomer, acrylamide group-containing monomer, tertiary amino group-containing (meth)acrylic acid ester monomer , an imide group-containing (meth)acrylic acid ester monomer. Nitrogen-containing monomers such as acrylamide group-containing monomers, tertiary amino group-containing (meth)acrylic acid ester monomers, and imide group-containing (meth)acrylic acid ester monomers are preferable from the viewpoint of storage stability and adhesion improvement in the photocurable composition. For example, acryloylmorpholine, dimethylaminoethyl(meth)acrylate, and N-acryloyloxyethylhexahydrophthalimide are exemplified. Moreover, when using a polyimide as a flexible substrate, it is especially preferable to use the imide acrylate represented by N-acryloyloxyethyl hexahydrophthalimide.

Thermoplastic elastomer: Examples of the thermoplastic elastomer include styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, ester-based thermoplastic elastomer, urethane-based thermoplastic elastomer, amide-based thermoplastic elastomer, vinyl chloride thermoplastic elastomer, fluororesin-based thermoplastic elastomer, ion-crosslinked thermoplastic elastomer, and the like. can be heard As the thermoplastic elastomer in the present invention, a styrenic thermoplastic elastomer is preferable.

The styrenic thermoplastic elastomer is dissolved in any one of the monofunctional alicyclic (meth)acrylic acid ester monomer, the monofunctional aliphatic (meth)acrylic acid ester monomer, and the monofunctional high polarity monomer in the photocurable composition. And, in the styrenic thermoplastic elastomer, the monofunctional alicyclic (meth)acrylic acid ester monomer, the monofunctional aliphatic (meth)acrylic acid ester monomer, and the monofunctional high polarity monomer are cured. The adhesive remains when the cured product is peeled off. You can do less and also lower the moisture permeability. In addition, the styrenic thermoplastic elastomer is dissolved in any one of the monofunctional alicyclic (meth)acrylic acid ester monomer, the monofunctional aliphatic (meth)acrylic acid ester monomer, and the monofunctional high polarity monomer, and the rubber elastic ( It is a component that provides flexibility and extensibility). In addition, in this invention, what is necessary is just to be the state which has become a uniform liquid state as a whole, and it shall be clouded by cloudiness or another color except the case where it is colorless and transparent.

Since the styrenic thermoplastic elastomer alone is a solid, it does not have adhesion at room temperature, but the monofunctional alicyclic (meth)acrylic acid ester monomer, the monofunctional aliphatic (meth)acrylic acid ester monomer, and the monofunctional high polarity monomer By dissolving in any one, it can be contained as one component of the photocurable composition which has adhesiveness by disperse|distributing uniformly in the photocurable composition and its hardening body.

It is preferable that it is 5-35 mass % in the photocurable composition, and, as for the addition amount of a styrenic thermoplastic elastomer, it is more preferable that it is 10-20 mass %. When the mixing|blending of a styrene-type elastomer is less than 10 mass %, moisture permeability is low and there exists a possibility that rubber elasticity may also be impaired. On the other hand, when it exceeds 35 mass %, the viscosity of a photocurable composition may become high, and there exists a possibility that application|coating may become difficult. If it is 20 mass % or less, fluidity|liquidity is preferable and it is easy to apply|coat.

Specific examples of the styrene-based thermoplastic elastomer include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene -propylene-styrene block copolymer (SEPS), styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), and these modified products are mentioned. . Among these, it is preferable to use SEBS, SEPS, SIBS, or SEEPS which do not have an unsaturated bond in the soft segment, since the cured body of the photocurable composition has excellent weather resistance.

In the present specification, the weight average molecular weight of the styrenic thermoplastic elastomer was measured using the GPC method (Gel Permeation Chromatography), and based on a calibration curve (calibration curve) measured with standard polystyrene. In the present invention, it is preferable to use a styrenic thermoplastic elastomer having a weight average molecular weight of less than 200,000 from the viewpoint of easy adjustment to a viscosity suitable for application.

Radical polymerization initiator: As a radical polymerization initiator, specifically, a monofunctional aliphatic (meth)acrylic acid ester monomer, a monofunctional alicyclic (meth)acrylic acid ester monomer, and a monofunctional high polarity monomer are photoreacted with light, for example. A radical photopolymerization initiator, which is cured by making it, is preferable. When the photocurable composition contains a radical photopolymerization initiator, by irradiating the photocurable composition with a light beam, for example, the photocurable composition applied on the coating film formation object can be photocured to form a coating film. As a radical photopolymerization initiator, photoinitiators, such as a benzophenone type, a thioxanthone type, an acetophenone type, an acyl phosphine type, an oxime ester type, an alkylphenone type, are mentioned. 0.1-15 mass parts is preferable with respect to 100 mass parts of total amounts of all the monomers in which monofunctionality and polyfunctionality were included, and, as for the addition amount of a radical photopolymerization initiator, 0.5-10 mass parts is more preferable.

In the case of curing with an LED light source, an alkylphenone-based radical photopolymerization initiator having absorption at a wavelength of 300 nm or more is preferable. Moreover, among these, it is especially preferable to use the alkylphenone-type radical photopolymerization initiator which has a morpholine backbone since the improvement of a curing rate and thin film curability can be improved.

Other components: The photocurable composition of this invention can mix|blend other components, such as various additives, as appropriate in the range which does not deviate from the meaning of this invention. For example, thixotropy imparting agents such as silica and aluminum oxide, plasticizers such as olefinic oils and paraffinic oils, silane coupling agents and polymerization inhibitors, antifoaming agents, light stabilizers, antioxidants, electrification ( There are anti-corrosion agents and fillers.

The above embodiment is an illustration of the present invention, and changes in the embodiment or addition or combination of known techniques can be made without departing from the spirit of the present invention, and these techniques are also included in the scope of the present invention. will become

Example

Next, based on an Example (comparative example), this invention is demonstrated in more detail. The photocurable composition of the following Samples 1 - Sample 19 and its hardening body were produced, and the evaluation method shown below evaluated.

<Production of sample>

As shown below, the sample was produced.

Sample 1: Lauryl acrylate as a monofunctional aliphatic (meth)acrylic acid ester monomer, isobornyl acrylate as a monofunctional alicyclic (meth)acrylic acid ester monomer, and N-acryloyloxyethyl as a monofunctional high polarity monomer 1,9-nonanediol diacrylate was prepared for hexahydrophthalimide as a polyfunctional aliphatic (meth)acrylic acid ester monomer. Next, to the above-mentioned monomer, elastomer A (trade name "Sibstar 062T", SIBS (styrene-isobutylene-styrene block copolymer), manufactured by Ganeka Corporation) as a thermoplastic elastomer was added and stirred for 24 hours. , the thermoplastic elastomer was dissolved in the above-mentioned monomer. The compounding ratio at this time is as showing in Table 1. Then, when the "resin component" consisting of the above-mentioned monomer and thermoplastic elastomer was 100 parts by mass, 4.0 parts by mass of 2-hydroxy-2-methylpropiophenone, which is a radical photopolymerization initiator, was added to prepare the photocurable composition of Sample 1 got it

The obtained photocurable composition of Sample 1 is applied to a predetermined substrate in order to measure various properties or perform various tests to be described later, and irradiated with ultraviolet rays under the conditions described below to obtain an elastic protective member that is the cured body of Sample 1 has formed

Samples 2 to 19: Examples of Samples 2 to 19 in the same manner as in Sample 1 except that the thermoplastic elastomer and each monomer of Sample 1 were changed to the types and formulations (parts by mass) shown in Tables 1 and 2 shown below. A chemical composition was prepared. The photocurable compositions of Samples 2 to 19 were also irradiated with ultraviolet rays in the same manner as in Sample 1 to form elastic protective members of Samples 2 to 19.

[Table 1]

[Table 2]

[Furtherance]:

The details of the raw materials shown in Tables 1 to 2 are shown below except for those already described.

As the polyfunctional and highly polar monomer, ethoxylated isocyanuric acid di/tri(meth)acrylate was used.

The thermoplastic elastomer is as follows.

Elastomer B: SEPS (styrene-ethylene-propylene-styrene block copolymer), trade name "Septon 2002", manufactured by Crayon Corporation

Elastomer C: SEEPS (styrene-ethylene-ethylene-propylene-styrene block copolymer), trade name "Septon 4055", manufactured by CRALE Corporation

As the radical photopolymerization initiator, in addition to 2-hydroxy-2-methylpropiophenone, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholinophenyl)-butan-1-one is used. did.

The polyfunctional polymer was used as an alternative component of the thermoplastic elastomer for comparison, and is as follows.

Polymer A: polybutadiene introduced with a terminal methacrylic group (acrylic equivalent 2000), trade name "TE-2000", manufactured by Nippon Soda Co., Ltd.

Polymer B: Hydrogenated polybutadiene introduced with a terminal methacrylic group (acrylic equivalent 1400), trade name "TEAI-1000", manufactured by Nippon Soda Co., Ltd.

Incidentally, for sample 19, for comparison, a sample having a completely different composition from that of the other samples was used. Specifically, the brand name "Loctite3523" manufactured by Henkel Japan Co., Ltd., which is a photocurable composition mainly containing a polyurethane methacrylate resin and a (meth)acrylic monomer without containing a thermoplastic elastomer, was used.

[characteristic]:

In Tables 1 to 2, various properties of the elastic protective member or the photocurable composition of each obtained sample were also described. Details of the properties shown in each table are as follows.

Martens hardness (N/mm ² :

The nanoindentation test of the hardened body was implemented using the nanoindenter (the ELIONIX make, ENT-2100). For the test piece, a photocurable composition was applied to a polyimide film having a thickness of 50 μm to a thickness of 100 μm, and a cured product prepared by curing by irradiating an ultraviolet ray with an illuminance of 200 mW/cm ² for 15 seconds using an LED having a wavelength of 365 nm was used. . Then, with the nanoindenter, the Martens hardness of the cured body was measured under the conditions of a maximum indentation load of 0.1 mN and an indentation rate of 0.01 mN/sec.

Tensile Elongation at Break (%), Tensile Strength (MPa), 100% Elongation Tensile Stress (MPa) and Young’s Modulus (MPa):

The mechanical strength of the hardening body was implemented by changing a part of JISK6251:2010. A photocurable composition is applied to a thickness of 1 mm on a silicone release-treated polyester film, and the photocurable composition is cured by UV irradiation at 200 mW/cm ² using an LED having a wavelength of 365 nm for 15 seconds. It punched out by dumbbell type No. 8 type|mold, and the marked line (marked line) was provided with the space|interval of 16 mm in the bar-shaped part of a dumbbell type sample, and the test piece was produced. A tensile test was performed at a speed of 200 mm/min, and the tensile elongation at break (elongation at cut), tensile strength (maximum tensile stress), 100% elongation tensile stress, and Young's modulus (modulus of elasticity) were measured. At this time, since the sample 6 had insufficient curing at a thickness of 1 mm, it was changed to a thickness of 100 µm and measured in the same manner. Tensile breaking elongation, tensile strength, and 100% tensile tensile stress were calculated by applying the following formulas (1), (2), and (3), respectively. The Young's modulus was obtained by dividing the tensile stress within the tensile proportionality limit by the deviation.

TS=Fm/S… Formula (1)

Eb=(L1-L0)/L0×100… Equation (2)

TS100=F100/S… Equation (3)

TS: Tensile strength (MPa)

Fm: Maximum tensile force (N)

S: Initial cross-sectional area of the specimen (mm ²

Eb: Elongation at break (%)

L0: Initial distance between display lines (mm)

L1: Distance between marks at break (mm)

TS100: 100% tensile stress (MPa)

F100: 100% tensile tensile force (N)

Peel force (N/m):

It was measured by partially changing the 180 degree peeling test method of JISK6852-2:1999. A polyimide film having a thickness of 50 μm, or a photocurable composition having a thickness of 1 mm is applied on a glass having a thickness of 1 mm, and cured by UV irradiation at 200 mW/cm ² using an LED having a wavelength of 365 nm for 15 seconds, and then cut to a width of 25 mm, Peeling force (adhesive strength) was measured by peeling at a peeling rate of 300 mm/min and a peeling angle of 180 degrees. At this time, since the sample 6 had insufficient curing at a thickness of 1 mm, it was changed to a thickness of 100 µm and measured in the same manner.

Water vapor permeability (g/m ² ·24hr):

According to JIS Z0208: 1976, a resin composition with a thickness of 100 μm is applied on a polyester film subjected to silicone release treatment, and using an LED having a wavelength of 365 nm, UV light is irradiated at 200 mW/cm ² for 15 seconds. ) was measured at a temperature of 40°C and a relative humidity of 90%RH. When there was a decrease in the weight of the sample during the measurement of the water vapor transmission rate, the decrease was corrected.

Viscosity (mPa s):

The viscosity of the photocurable composition at the time of non-hardening was measured.

Viscosity in 23 degreeC and 107 rpm was measured using the rotational viscometer (The Bohlin Instruments make, Bohlin V88 Viscometer, cone plate "CP5°/30").

Storage stability:

Storage stability shows the properties when the photocurable composition is left still for 2 weeks in an environment of 25°C. Those in which precipitation or separation could not be confirmed by visual observation were denoted by "A", and those in which precipitation or separation could be confirmed were denoted by "B", respectively.

[exam]:

In the said Tables 1 - 2, various tests demonstrated below about the elastic protection member of each obtained sample were done. And the results are shown in each table.

Bend resistance test (wiring):

In order to investigate the protection state of the wiring by the elastic protection member provided in the connection part of a flexible board|substrate and a rigid board|substrate, the following bending resistance test was done. As shown in Fig. 2, at the boundary portion between the flexible substrate and the rigid substrate, the length of the portion protruding from the tip of the rigid substrate in the depth direction is 400 to 800 μm, and the height of 50 to 100 μm covering the end face of the tip of the rigid substrate is 50 to 100 μm. The photocurable composition was applied with a jet dispenser in the range of , and the photocurable composition was cured by UV irradiation at 200mW/cm ² for 15 seconds using an LED having a wavelength of 365nm. Those that could not be applied with a jet dispenser were similarly applied using an air dispenser. In this way, the test piece for a bending resistance test was produced. And 10 copper wirings with a line|wire width of 10 micrometers formed in the said depth direction of the flexible board|substrate which apply|coated the photocurable composition were made into evaluation object.

Next, as shown in FIG. 3, attach a 200 g weight (W) to the tip of the flexible substrate, hold the rigid substrate side with a holding member (H) so that the hardening body is inside, and bend it 180 degrees, then return to the original state A reversing operation was performed, and when this was set to 1 cycle, the appearance of the wiring after 100 cycles was observed.

And the case where a fracture|rupture was seen in any one wiring was evaluated as "B", and the case where the fracture|rupture formed in the wiring was not seen was evaluated as "A", respectively.

Flexural Resistance Test (Material):

In order to investigate the bending resistance of the elastic protective member, a bending resistance test was conducted. The photocurable composition was apply|coated to the polyimide film of thickness 50 micrometers so that it might become 100 micrometers in thickness, and it hardened by UV irradiation at 200 mW/cm< ² > for 15 second using the LED of wavelength 365nm. For each polyimide film, the cured body is cut to 20 mm × 100 mm, the cured body is inside, and the bending angle is 180 degrees and the bending radius is 1 mm or less, and then bent to the opposite side so that the cured body is outward, 180 degrees bending angle, 1 mm bending radius The state bent below was made into 1 cycle, and the state of the bending part after 10 cycles was observed visually.

The case where the elastic protective member did not peel from the polyimide film and breakage did not occur in the elastic protective member was “A”; Each case was evaluated as "C".

UV-LED Curing Test:

The photocurable composition was apply|coated to the polyimide film of thickness 50 micrometers so that it might become 100 micrometers thick, and it hardened by UV irradiation at 200 mW/cm< ² > for 15 second using the LED of wavelength 365nm. The case where the surface on the atmospheric side of the hardening body was touched with a finger and a transition material could not be confirmed was evaluated as "A", and the case where the transition material was recognized was evaluated as "B", respectively.

Jet Dispenser Application Test:

The application titration by a jet dispenser of the photocurable composition was investigated and evaluated. Using the jet dispenser Pico Pulse manufactured by Nordson EFD, the application|coating titration (applicability) at the time of apply|coating the photocurable composition of each sample at the nozzle temperature of 40 degreeC was confirmed and evaluated.

The case where it could apply|coat with this jet dispenser was evaluated as "A", and the case where it could not apply|coat was evaluated as "B", respectively.

Rework Test:

Ease of peeling of the elastic protective member from the substrate was evaluated. At the time of the measurement of the said "peel force", the mode that an elastic protective member peels from a polyimide film was confirmed and evaluated.

The case where the elastic protective member was peeled from the polyimide film without breaking into pieces was evaluated as "A", and the case where the elastic protective member broke into pieces was evaluated as "B", respectively.

Insulation Reliability Test:

Whether or not the elastic protective member can stably protect the wiring was evaluated from the presence or absence of migration occurring in the wiring protected by the elastic protection member and the presence or absence of discoloration occurring in the wiring.

By applying a photocurable composition to a thickness of 100 μm on a glass epoxy substrate having copper wires having a wiring width of 0.318 mm and a wiring spacing of 0.318 mm on the surface, and irradiating with ultraviolet rays at 200 mW/cm ² for 15 seconds using an LED having a wavelength of 365 nm. hardened. 50V was applied at 85 degreeC and 85%RH, and the presence or absence of migration was confirmed after 300 hours.

The case where there was no migration and no discoloration in the wiring was evaluated as "A", the case where there was no migration but discoloration occurred was evaluated as "B", and the case where migration occurred was evaluated as "C", respectively.

<Consideration of test results>

From the results of the bending resistance test (wiring), no breakage occurred in the wiring for Samples 1 to 6, and for the sample 7 to Sample 19, the wiring did not break, and the evaluation was "A". It was B. In addition, for Samples 1 to 6 in which no breakage occurred in the wiring, all other tests, i.e., bending resistance test (material), UV-LED curing test, jet dispenser coating test, rework test, and insulation reliability test were all evaluated. It became "A". On the other hand, for some of Samples 7 to 19 in which the wiring was broken, evaluations of "B" or "C" were made for other tests as well.

For Samples 1 to 6, it was found that all of them were in the range of 0.35 to 3.0 N/mm ² in Martens hardness and 100% or more in tensile elongation at break.

10: electronic board
12: Rigid substrate
12a: polarizer
12b: Glass substrate with 1st transparent electrode
12c: liquid crystal layer
12d: Glass substrate with 2nd transparent electrode
12e: polarizer
12f: backlight unit
12g: single side
14: flexible substrate
15: anisotropic conductive adhesive
16: bend
18: elastic protection member
40: protrusion width
W: weight
H: no gripping

Claims (6)

a rigid substrate;
a flexible substrate extending from an end of the rigid substrate and connected so as to be conductive;
A wiring from the rigid substrate to the flexible substrate is provided;
The flexible substrate is an electronic substrate having a bent portion that protrudes from an end of the rigid substrate and is bent toward one side of the rigid substrate,
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 extending from the end of the rigid substrate to the bent portion,
The elastic protective member has a Martens hardness measured by a nanoindentation test of 0.35 to 3.0 N/mm ² , and a tensile breaking elongation of 100% or more, an electronic substrate . According to claim 1,
The electronic substrate, wherein the elastic protection member covers at least a part of an end surface of the rigid substrate intersecting the contact surfaces of the rigid substrate and the flexible substrate. According to claim 1,
The electronic substrate, wherein the flexible substrate positioned on the opposite side to the rigid substrate is bent by 180 degrees with respect to the rigid substrate, sandwiching the bent portion. According to claim 1,
The flexible substrate is a resin film having a thickness of 15 to 200 μm,
The electronic board with which the said elastic protection member is provided in the curved inner surface of the said flexible board|substrate when the said flexible board|substrate is bent. A photocurable composition for forming an elastic protective member by curing by irradiating light after application to an electronic substrate, the photocurable composition comprising:
A monofunctional alicyclic (meth)acrylic acid ester monomer, a monofunctional aliphatic (meth)acrylic acid ester monomer, a thermoplastic elastomer, and a radical polymerization initiator,
The cured body after curing has a Martens hardness measured by a nanoindentation test of 0.35 to 3.0 N/mm ² , and a tensile elongation at break of 100% or more, a photocurable composition. 6. The method of claim 5,
The photocurable composition whose viscosity at the time of uncuring is the range of 10-5000 mPa*s.

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