CN110616054A

CN110616054A - Assembly layer based on organic silicon modified acrylate, preparation method thereof and laminate

Info

Publication number: CN110616054A
Application number: CN201910929870.XA
Authority: CN
Inventors: 方龙
Original assignee: XINLUN TECHNOLOGY (CHANGZHOU) Co Ltd
Current assignee: XINLUN TECHNOLOGY (CHANGZHOU) Co Ltd
Priority date: 2019-09-29
Filing date: 2019-09-29
Publication date: 2019-12-27

Abstract

The invention belongs to the field of flexible assembly layers, and particularly relates to an assembly layer based on organic silicon modified acrylate, a preparation method of the assembly layer and a laminate. Wherein the silicone-modified acrylate-based assembly layer is derived from a precursor comprising: a (methyl) acrylate monomer, an organic silicon modified (methyl) acrylate monomer and a free radical initiator. By utilizing the flexibility and the bending resistance of the organic silicon modified (methyl) acrylate monomer, an organic silicon structure is introduced into a side chain of the (methyl) acrylate monomer, the creep recovery performance and the stress relaxation performance of the component layer can be effectively improved, and the requirements of the static folding performance and the dynamic folding performance of the foldable display equipment are met.

Description

Assembly layer based on organic silicon modified acrylate, preparation method thereof and laminate

Technical Field

The invention relates to a flexible assembly layer, in particular to an assembly layer based on organic silicon modified acrylate, a preparation method thereof and a laminate.

Background

With the advent of flexible electronic displays, there is an increasing demand for adhesives, and in particular Optically Clear Adhesives (OCAs), to be used as an assembly layer or gap-fill layer between an outer cover lens or sheet (based on glass, PET, PC, PMMA, polyimide, PEN, cyclic olefin copolymers, etc.) and a display module underneath an electronic display assembly to improve the performance of the display by improving brightness and contrast. In a flexible assembly, the OCA may also absorb most of the stress generated by the fold to prevent damage to fragile components of the display panel and to protect the electronic components from breaking under the folding stress. The OCA layer may also be used to locate and maintain the neutral bending axis at or at least near fragile components of the display, such as barrier layers, drive electrodes, or thin film transistors of an Organic Light Emitting Display (OLED).

Due to the different mechanical requirements for flexible display assemblies, OCAs face new requirements and challenges, such as bendability and foldability, in addition to the conventional performance requirements, such as optical transparency, adhesion, and durability. Conventional OCAs are viscoelastic in nature and are intended to provide durability over a range of environmental exposure conditions and high frequency loads, maintaining a high level of adhesion and viscoelastic properties to achieve good pressure sensitive behavior. However, these characteristics cannot meet the practical application requirements of the current flexible foldable display device, such as static bending and dynamic bending performance.

Disclosure of Invention

The invention aims to provide an assembly layer based on organic silicon modified acrylate, a preparation method thereof and a laminate.

In order to solve the above technical problem, the present invention provides a silicone-modified acrylate-based assembly layer derived from a precursor comprising: a (methyl) acrylate monomer, an organic silicon modified (methyl) acrylate monomer and a free radical initiator.

Further, the shear storage modulus of the component layer is between 10 at a frequency of 1Hz in a temperature range of-40 ℃ to 150 DEG C⁴～10⁶Pa; and after 5 seconds of stress action at 95KPa, the strain recovery of the component layer is not less than 90% within 1 minute; and the groupThe glass transition temperature of the layer does not exceed-40 ℃.

Further, the silicone-modified (meth) acrylate monomer includes an organosiloxane terminated at one end by a (meth) acrylate.

Further, the molecular weight of the organosiloxane does not exceed 300. Further, the radical initiator includes at least one of a thermal radical initiator and a UV photo radical initiator.

Further, the UV photo radical initiator includes at least one of a cleavable radical initiator, a hydrogen abstraction type radical initiator.

Further, the assembly layer further comprises one or more of a chain transfer agent, a tackifying resin, a stabilizer, a cross-linking agent and a coupling agent.

Further, the number of carbon atoms of the (meth) acrylate monomer is not more than 20. Further, the (meth) acrylate monomer includes a soft monomer and a functional monomer; the functional monomer comprises at least one of hydroxyl modified acrylate monomer, carboxyl modified acrylate monomer and amino modified acrylate monomer.

In yet another aspect, the present invention also provides a method of making an assembly layer suitable for formation by polymerization of a precursor as hereinbefore described.

In another aspect, the present invention also provides a laminate comprising: the flexible printed circuit board comprises a first flexible substrate, a second flexible substrate and a component layer between the first flexible substrate and the second flexible substrate.

Further, both flexible substrates are optically transparent.

Further, the adhesive force of the assembly layer and each flexible substrate is not lower than 1000g/25 mm.

Further, the laminate appeared to fail when subjected to about 100,000 dynamic fold tests at room temperature with a radius of curvature of less than 10 mm.

The assembly layer based on the organic silicon modified acrylate, the preparation method thereof and the laminate have the advantages that the flexibility and the bending resistance of the organic silicon modified (methyl) acrylate monomer are utilized, the organic silicon structure is introduced into the main chain of the (methyl) acrylate monomer, the creep recovery performance and the stress relaxation performance of the assembly layer can be effectively improved, and the requirements of static and dynamic folding test performance of foldable display equipment are met.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof.

In order to make the aforementioned and other objects, features and advantages of the invention more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to better understand the technical solution of the present invention, some materials or terms appearing in the examples are explained as shown in table 1.

Table 1 partial material or noun interpretation

Example 1

The silicone-based component layer of example 1, which was derived from precursors comprising: a (methyl) acrylate monomer, an organic silicon modified (methyl) acrylate monomer and a free radical initiator.

Specifically, theThe components in the precursor can form the component layer by means of UV photopolymerization or thermal polymerization; and the shear storage modulus of the component layer is between 10 at a frequency of 1Hz in the temperature range of-40 ℃ to 150 DEG C⁴～10⁶Pa, strain recovery of not less than 90% within 1 minute after stress action of 95KPa for 5 seconds, and glass transition temperature of not more than-40 deg.C.

Optionally, the repeating unit of the formula after polymerization of the precursor is:

wherein

m and n are respectively the carbon atom number of the alcohol chain of the soft monomer and the functional monomer, and x is the silicon atom number of the organosilicon siloxane.

Optionally, the assembly layer is optically clear with a haze of no more than 1%, optionally no more than 0.5% or no more than 0.2%.

As an alternative embodiment of the silicone-modified (meth) acrylate monomer.

The organic silicon modified (methyl) acrylate monomer is not limited to organic siloxane with one end capped by acrylate, the organic silicon modified (methyl) acrylate has an acrylate active functional group, can be copolymerized with other acrylates, and has dimethyl siloxane groups on a polymer side chain, which is helpful for improving the bending resistance and the high temperature resistance of the polymer, but common organic siloxane does not have the property.

Optionally, the structural formulas of the organosilicon modified (meth) acrylate monomers are two, as follows:

optionally, the organosiloxane has a molecular weight of no more than 300. On one hand, the high molecular weight organosilicone is weak in polarity and poor in compatibility with acrylate, and on the other hand, the high molecular weight organosilicone is weak in reaction activity and cannot be effectively copolymerized with acrylate. Therefore, too large a molecular weight of the organosiloxane lowers the reactivity, and the copolymerization cannot be efficiently performed.

As an alternative embodiment of the free-radical initiator.

The radical initiator is not limited to at least one of thermal radical initiator, UV photo radical initiator. Wherein, the UV photo-free radical initiator is not limited to at least one of a cleavage type free radical initiator and a hydrogen abstraction type free radical initiator.

Alternatively, specific classes of thermal radical initiators include, but are not limited to: azodiisobutyronitrile, azodiisoheptonitrile, azodiisobutyronitrile dimethyl ester, azoisobutyryl cyano formamide, dibenzoyl peroxide, tert-butyl peroxybenzoate and cumyl hydroperoxide.

Alternatively, specific classes of UV photo radical initiators include, but are not limited to: 1-hydroxycyclohexyl phenyl ketone (photoinitiator 184), 2-methyl-1- [ 4-methylthiophenyl ] -2-morpholinyl-1-propanone (photoinitiator 907), 2-hydroxy-methylphenylpropane-1-one (photoinitiator 1173), 2, 4, 6-trimethylbenzoyl-diphenylphosphine oxide (photoinitiator TPO), phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide (photoinitiator 819), 2-phenylbenzyl-2-dimethylamine-1- [ 4-morpholinylbenzylphenyl ] -butanone (photoinitiator 369), alpha, any one or more of alpha-dimethoxy-alpha-phenylacetophenone (photoinitiator 651), benzophenone (photoinitiator BP) and methyl benzoylformate (photoinitiator MBF).

Alternatively, aliphatic mercaptans and dodecyl mercaptan are often used as chain transfer agents for radical polymerization, and in addition, polyfunctional mercaptan compounds are suitable for preparing polymers having a broad molecular weight distribution, such as PE1 developed by Showa and electrician, because of their high activity and good chain transfer effect.

Optionally, in the development of the pressure-sensitive adhesive formula, the tackifying resin can effectively improve the initial tack and the adhesive force, and is an indispensable important component. In general, tackifying resins can be classified into natural series resins and synthetic series resins. Natural series resins include rosins (gum rosin, tall oil rosin, wood rosin), rosin derivatives (hydrogenated rosin, disproportionated rosin, polymerized rosin, esterified rosin, maleated rosin), and terpene resins (alpha-terpene resins, beta-terpene resins, terpene phenolic resins); synthetic series resins include polymeric resins C5, C9 and C5/C9 petroleum resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins, styrene series resins and condensation resins (alkyl phenol resins, xylene resins).

Alternatively, the stabilizers can be divided into heat stabilizers and light stabilizers, the primary function of which is to improve the long-term stability of the component layers under heat and light conditions. Light stabilizers are particularly important for clear optical adhesives. Two types of light stabilizers commonly used today are ultraviolet light absorbers and hindered amine light stabilizers.

Alternatively, the main function of the crosslinker is to increase the crosslinking density of the system, and is generally a difunctional acrylate monomer, such as 1, 4-butanediol di (meth) acrylate, 1, 5-pentanediol (meth) diacrylate, 1, 6-hexanediol di (meth) acrylate, triethylene glycol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and the like.

Alternatively, the main function of the coupling agent is, on the one hand, to further increase the cohesion of the system and, on the other hand, to increase the adhesion to the substrate. Generally, silane coupling agents having an amphiphilic structure with a siloxane group at one end and an acrylate or epoxy group at the other end are commonly used, such as 3-glycidoxypropyltrimethoxysilane (KBM403), 3-methacrylonitrile propylmethyldimethoxysilane (KBM502), 3-methacrylonitrile propyltrimethoxysilane (KBM503), 3-acryloxypropyltrimethoxysilane (KBM5103), and the like, in Beacon chemistry.

As an alternative embodiment of the (meth) acrylate monomer.

The number of carbon atoms of the (meth) acrylate ester monomer is no more than 20, optionally no more than 15 or no more than 10. Examples of suitable (meth) acrylate monomers include, but are not limited to: 2-ethylhexyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, pentyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, one or more of hexyl (meth) acrylate, n-nonyl (meth) acrylate, isoamyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, isostearyl acrylate, and 2-methylbutyl (meth) acrylate.

Optionally, the (meth) acrylate monomers include, but are not limited to, soft monomers and functional monomers; the functional monomer comprises at least one of hydroxyl modified acrylate monomer, carboxyl modified acrylate monomer and amino modified acrylate monomer. Suitable functional monomers include, but are not limited to: one or more of (methyl) acrylamide, N-morpholino (methyl) acrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, 2-hydroxyethyl (methyl) acrylate, 2-hydroxy-propyl (methyl) acrylate and 4-hydroxybutyl (methyl) acrylate.

Example 2

This example 2 also provides, on the basis of example 1, a method for the preparation of an assembly layer suitable for being formed by polymerization of a precursor as described previously.

Alternatively, the components of the precursor may be polymerized by UV or thermal polymerization to form the assembly layer.

For the component content and the specific implementation process of the component layer, reference is made to the relevant discussion in example 1, and the details are not repeated here.

Example 3

On the basis of examples 1 and 2, the laminate of example 3 comprises: the flexible printed circuit board comprises a first flexible substrate, a second flexible substrate and a component layer between the first flexible substrate and the second flexible substrate.

Optionally, each flexible substrate is optically transparent; the adhesive force between the component layer and the two flexible substrates is not lower than 1000g/25 mm; and the laminate exhibits no failure when subjected to about 100,000 dynamic folding tests at room temperature with a radius of curvature of less than 10 mm.

For the component content and the specific implementation process of the component layer, reference is made to the relevant discussion in examples 1-2, which is not repeated here.

Example 4

In this example 4, the precursor of different embodiments is polymerized by UV polymerization or thermal polymerization, and then a crosslinking monomer and a photoinitiator are added to form a device layer, and in combination with the comparative embodiment (i.e., a conventional or existing device layer), dynamic mechanical analysis, creep test, static folding test, dynamic folding test, adhesion test and other detection items are performed to detect and obtain the maximum strain, strain recovery, static folding test result, dynamic folding test result, adhesion data and the like of the device layer. Wherein the component content of the precursor and the existing module layer of the different embodiments before UV polymerization is shown in table 2, and the content ratio of the subsequently added components (i.e. crosslinking monomer and photoinitiator) is shown in table 3.

TABLE 2 comparison of the component content before polymerization of the precursors

The unit of each component in table 2 is part by weight.

TABLE 3 comparison of the contents of the subsequently added components

The unit of each component in table 3 is part by weight.

In example 4, the precursors of embodiments 1 to 6 and the device layer formed by polymerization of the comparative embodiment were tested, and the test results are shown in table 4. The assembly layer based on the organic silicon introduces an organic silicon structure into a main chain of a (methyl) acrylate monomer, so that the flexibility and the bending resistance of the organic silicon modified (methyl) acrylate monomer can be fully utilized, the creep recovery performance and the dynamic and static folding test performance of the assembly layer are effectively improved, the maximum strain and the strain recovery of the assembly layer are more than or equal to those of the conventional assembly layer, the static folding test and the dynamic folding test are passed, and the creep recovery performance and the stress relaxation performance requirements of the foldable display device can be met.

TABLE 4 comparison of the Properties of the component layers

The specific operation steps of dynamic mechanical analysis, creep test, static folding test, dynamic folding test and adhesion test are as follows:

(1) dynamic mechanical analysis

Dynamic shear modulus and glass transition temperature were tested using dynamic mechanical analysis. The sample size was 8mm diameter and about 1mm thick and the rheometer used was a DHR type parallel plate rheometer from TA corporation, usa. The temperature scanning interval is-40-150 ℃, the heating rate is 5 ℃/min, the frequency is 1Hz, and the strain is 0.1%. The shear storage modulus (G') is recorded at a particular temperature selected and the loss tangent versus peak in the temperature curve is defined as the glass transition temperature (T;)_g)。

(2) Creep test

The assembly layer samples were subjected to creep testing by placing an 8mm diameter x 0.5mm thick disk in a DHR parallel plate rheometer and applying a shear stress of 95kPa for 5 seconds, at which point the applied stress was removed and the sample allowed to recover in the fixture for 60 seconds. The peak shear strain at 5 seconds and the amount of strain recovery after 60 seconds were recorded. The shear creep compliance J at any time after the application of stress is defined as the ratio of the shear strain at that time divided by the applied stress. To ensure sufficient compliance within the assembly layer, it is preferred that the peak shear strain after application of a load in the above test be greater than about 200%. Further, to allow material creep within the flexible assembly, it is preferred that the material recover greater than about 50% strain 60 seconds after the applied stress is removed. The percent recoverable strain is defined as ((S1-S2)/S1) × 100, where S1 is the shear strain at the peak recorded 5 seconds after the applied stress and S2 is the shear strain measured 60 seconds after the applied stress is removed.

(3) Static folding test

A 25um thick assembly layer was laminated between 50um sheets of Polyimide (PI) to form a 3 layer construction, then cut into 10cm lengths. In addition, a 5-layer construction consisting of PI/OCA/PI/OCA/PI is also prepared in a similar manner with 25um thick assembly layers and 50um PI. Laminate constructions were also prepared in a similar manner using 100um and 150um thick assembly layers between the PI layers. The sample was then bent to a radius of curvature of approximately 3mm and held in this position for 24 hours. After 24 hours, the sample was observed to have passed the static hold test if the adhesive did not exhibit buckling or delamination.

(4) Dynamic fold test

A 25um thick assembly layer was laminated between 50um sheets of Polyimide (PI) to form a 3 layer construction, and the laminate was then cut into 5cm lengths by 1cm widths. In addition, a 5-layer construction consisting of PI/OCA/PI/OCA/PI is also prepared in a similar manner with 25um thick assembly layers and 50um PI. The sample was mounted in a dynamic folding apparatus with two folding stages that rotated from 180 degrees (sample not bent) to 0 degrees (sample folded) and was subjected to 100,000 cycles at a test rate of about 40 cycles/minute. The 5mm bend radius is determined by the gap between the two rigid plates in the closed state (0 degrees). No mandrel is used to guide the curvature (i.e., free-form bending is used), and the folding is performed at room temperature.

(5) Adhesion test

An approximately 25um thick assembly layer was laminated between two primed polyester layers having a thickness of 75 um. Strips 25mm wide by 10cm long were cut from the laminate for testing. The end of each sliver was placed in the tensile jig of a tensile machine (STB-1225S Model). The peel was then taken off at a rate of 300mm/min while measuring the force of peel strength in grams. Three peel tests were performed per sample and the resulting peel forces were averaged.

In summary, the silicone-based assembly layer, the preparation method thereof and the laminate thereof utilize flexibility and bending resistance of the silicone-modified (meth) acrylate monomer to introduce the silicone structure into the main chain of the (meth) acrylate monomer, can effectively improve creep recovery performance and stress relaxation performance of the assembly layer, and meet the requirements of static and dynamic bending performance of the foldable display device.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.

Claims

1. A silicone-based component layer, the component layer being derived from a precursor,

the precursor comprises: a (methyl) acrylate monomer, an organic silicon modified (methyl) acrylate monomer and a free radical initiator.

2. The component layer according to claim 1,

the shear storage modulus of the component layer is between 10 at a frequency of 1Hz in a temperature range of-40 ℃ ~ 150 DEG C⁴~10⁶Pa; and is

After 5 seconds of stress at 95KPa, the component layer has a strain recovery of no less than 90% in 1 minute; and

the glass transition temperature of the assembly layer does not exceed-40 ℃.

3. The component layer according to claim 1,

the silicone-modified (meth) acrylate monomer comprises an organosiloxane terminated at one end by a (meth) acrylate; wherein

The molecular weight of the organosiloxane does not exceed 300.

4. The component layer according to claim 1,

the free radical initiator comprises at least one of a thermal free radical initiator and a UV photo free radical initiator.

5. The component layer according to claim 4,

the UV light free radical initiator comprises at least one of a cracking free radical initiator and a hydrogen abstraction type free radical initiator.

6. The component layer according to claim 4,

the component layer also comprises one or more of a chain transfer agent, tackifying resin, a stabilizer, a cross-linking agent and a coupling agent.

7. The component layer according to claim 1,

the number of carbon atoms of the (meth) acrylate ester monomer is not more than 20.

8. The component layer according to claim 1 or 7,

the (meth) acrylate monomer includes a soft monomer and a functional monomer; wherein

The functional monomer comprises at least one of hydroxyl modified acrylate monomer, carboxyl modified acrylate monomer and amino modified acrylate monomer.

9. A method for producing an assembly layer,

the assembly layer is adapted to be formed by polymerization of the precursor of claim 1.

10. A laminate, comprising:

the flexible printed circuit board comprises a first flexible substrate, a second flexible substrate and a component layer between the first flexible substrate and the second flexible substrate.

11. The laminate of claim 10,

both flexible substrates are optically transparent.

12. The laminate of claim 10,

the adhesive force of the component layer and each flexible substrate is not lower than 1000g/25 mm.

13. The laminate of claim 10,

the laminate appeared to be non-failure by performing about 100,000 dynamic fold tests at room temperature with a radius of curvature of less than 10 mm.