THEREFOR

Technical Field

The present invention relates to an antistatic device. More particularly, the present invention relates to a multilayer structure adhesive tape having a carbon nanotube antistatic layer, and a preparation method therefor.

Background

Optical films with antistatic layers are widely applied to, for example, surfaces of electronic equipment and electronic apparatuses, such as surfaces of OLED liquid crystal displays, to protect the surfaces of electronic equipment during processing and to prevent damage to electronic circuits due to static electricity. It is generally desirable for such optical films to have both outstanding antistatic performance and optical performance (at least excellent optical transparency) without deterioration over time due to conditions such as ultraviolet exposure, oxidation, humidity or high temperature.

At present, two types of traditional coatings are typically used to impart antistatic performance to the film surfaces. One type is coatings based on ionic liquid materials, and the other is coatings based on a conductive polymers. Each of these two coatings has advantages and limitations. Most of ionic liquids are colorless, and therefore have good optical transparency and relatively stable performance that do not easily deteriorate. However, carriers of ionic liquids are ions, and thus it is rather difficult to achieve high conductivity or low surface resistance, but a sufficient antistatic effect cannot be provided if surface resistance is relatively high. A conductive polymer has p electrons as carriers, and the conductivity depends on the conjugated structure of the polymer. Therefore, compared with ionic liquids, conductive polymers can exhibit lower surface resistance and higher conductivity, and thus provide excellent antistatic ability. For comparison, ionic liquids with a mass concentration of up to 1% can usually only achieve surface resistance of 10 ^L 9 ohm/sq, while conductive polymers can usually achieve surface resistance of 10 ^L 3 ohm/sq. However, conductive polymers are relatively sensitive to ultraviolet light, oxygen or high temperature, and their physicochemical properties easily deteriorate.

In contrast, carbon nanomaterials (e.g., carbon nanotubes, and graphene) combine the advantages of the above two materials, that is, they have outstanding conductivity and stable physicochemical properties based on the conjugated structure. Therefore, carbon nanomaterials are naturally one of the ideal choices for eliminating static electricity. At present, the challenges of using carbon nanomaterials in applications such as OLED liquid crystal displays mainly lie in how to uniformly disperse carbon nanomaterials in a certain solvent, how to apply a coating uniformly, and how to minimize the impact of the dark color of the carbon nanomaterials themselves on the optical performance. The present invention aims to overcome the challenges existing in the prior art, by applying a carbon nanomaterial to an antistatic optical fdm on the surface of electronic equipment.

Summary

An object of the present invention is to provide a multilayer structure adhesive tape having both excellent antistatic ability and optical performance, which has stable performance and does not easily deteriorate. Another objective of the present invention is to overcome the above challenges in the application of carbon nanomaterials to antistatic optical films, in the prior art.

According to one aspect of the present invention, a multilayer structure adhesive tape is provided, the adhesive tape comprising an adhesive tape substrate layer, and an antistatic layer and an adhesive layer located on opposite sides of the adhesive tape substrate layer, where the antistatic layer comprises single-walled or double-walled carbon nanotubes.

Carbon nanotubes have low surface resistance and stable physicochemical properties, resulting in excellent and stable antistatic ability. Furthermore, unlike multi-walled carbon nanotubes, single-walled or double-walled carbon nanotubes can minimize the impact of the color of the carbon nanotubes themselves on the optical performance of the multilayer structure adhesive tape while ensuring excellent antistatic ability.

In one embodiment, the antistatic layer is formed by applying an aqueous dispersion solution comprising single-walled or double-walled carbon nanotubes and a water-soluble or water-dispersible binder onto one side of the adhesive tape substrate layer and drying. The water-soluble or water-dispersible binder facilitates uniform dispersion of the carbon nanotubes in the aqueous dispersion solution.

In one embodiment, a thickness of the antistatic layer is less than 80 nm, to ensure excellent optical performance.

In one embodiment, the adhesive layer comprises a polyurethane adhesive.

In one embodiment, a peeling force of the adhesive layer is less than 15 g/inch. A lower peeling force can protect the surface to which the multilayer structure adhesive tape is adhered (e.g., the surface of an OLED liquid crystal display), and protect the multilayer structure adhesive tape itself from being damaged during peeling.

In one embodiment, the adhesive layer comprises a plasticizer. The addition of the plasticizer can further reduce the peeling force of the adhesive layer, to achieve the desired viscosity.

In one embodiment, the multilayer structure adhesive tape further comprises a release fdm covering the adhesive layer, to protect the adhesive layer prior to use.

According to another aspect of the present invention, a method for preparing a multilayer structure adhesive tape comprising an adhesive tape substrate layer, is provided. The method comprises: preparing an adhesive solution; preparing an aqueous dispersion solution comprising single-walled or double-walled carbon nanotubes; applying the aqueous dispersion solution onto one side of the adhesive tape substrate layer and drying to form an antistatic layer; applying the adhesive solution onto the other side of the adhesive tape substrate layer, drying and curing to form an adhesive layer; and subjecting the adhesive layer to post-curing treatment.

In one embodiment, the aqueous dispersion solution comprises a water-soluble or water-dispersible binder.

In one embodiment, the antistatic layer is formed to have a thickness of less than 80 nm.

In one embodiment, the adhesive layer is formed by using a polyurethane adhesive.

In one embodiment, the adhesive layer is formed to have a peeling force of less than 15 g/inch.

In one embodiment, lamination of a release fdm on the adhesive layer is further comprised.

As mentioned above, the present invention achieves a multilayer structure adhesive tape having both excellent antistatic ability and optical performance, and has stable performance and does not easily deteriorate, by forming an antistatic layer comprising single-walled or double-walled carbon nanotubes, and obtains performance superior to traditional ionic liquid antistatic layers and conductive polymer antistatic layers. In addition, in the present invention, by forming the antistatic layer via the method of application of an aqueous dispersion solution, the carbon nanotubes can be uniformly dispersed and applied, thereby forming a uniform antistatic layer.

Brief Description of the Drawings

Embodiments of the present invention are described below, by way of examples only, with reference to the accompanying drawings. In the drawings, the same features or members are designated by the same reference numbers, and the figures are not necessarily drawn to scale. In the accompanying drawings:

FIG. 1 shows a schematic cross-sectional view of a multilayer structure adhesive tape according to the present invention. FIG. 2 shows a schematic cross-sectional view of a multilayer structure adhesive tape having a release film according to the present invention.

FIG. 3 shows a schematic flow diagram of a method for preparing a multilayer structure adhesive tape according to the present invention.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the invention and its applications and uses. It should be understood that, similar reference numbers refer to the same or similar parts and features throughout the drawings. The accompanying drawings illustratively show the idea and principles of the embodiments of the present invention, but do not necessarily show specific size of each embodiment of the present invention and the scale thereof. In specific parts of specific accompanying drawings, related details or structures of the embodiments of the present invention may be illustrated in an exaggerated manner.

In the description of the various embodiments of the present invention, the orientation terms used in relation to “upper,” “lower,” “left” and “right” are described using upper, lower, left and right positions of the views shown in the accompanying drawings. In the actual application process, the positional relationship of “upper,” “lower,” “left” and “right” used can be defined according to the actual situation, and such relationships can be reversed.

The performance indicators such as “optical transparency,” “haze,” “peeling force” and “surface resistance” described herein conform to the general definitions in the art and can be measured by the testing techniques commonly used in the art.

FIG. 1 shows a schematic cross-sectional view of a multilayer structure adhesive tape according to the present invention. According to FIG. 1, the multilayer structure adhesive tape 1 comprises an adhesive tape substrate layer 10, and an antistatic layer 20 and an adhesive layer 30 located respectively on opposite sides of the adhesive tape substrate layer 10. Where, the adhesive tape substrate layer 10 may be a PET film or any other suitable optical film, with a thickness of typically 50-75 pm; the antistatic layer 20 is a coating formed by applying an aqueous solution comprising single-walled or double-walled carbon nanotubes; and the adhesive layer 30 is used to adhere to surfaces of electronic equipment, such as surfaces of OLED liquid crystal displays.

The antistatic layer 20 comprises single-walled or double-walled carbon nanotubes. The single-walled or double-walled structure avoids the adverse impact the dark color of multi-walled carbon nanotubes can have on the color, transparency, and other optical performance of the adhesive tape. Exemplarily and non-restrictively, the single-walled carbon nanotubes may be JCST-75-1.5-20 produced by Nanjing Jicang Nanotechnology Co., Ltd., with an average length of about 75 nm and an average diameter of about 1.5 nm; and double-walled carbon nanotubes may be JCST-60-3-50 produced by Nanjing Jicang Nanotechnology Co., Ltd., with an average length of about 60 nm and an average diameter of about 3 nm. The antistatic layer 20 further comprises a water-soluble or water-dispersible binder, for example, the DSM986 binder produced by DSM Company, to uniformly disperse the carbon nanotubes in the aqueous solution and uniformly apply the carbon nanotubes during the process of forming the antistatic layer 20. A premix of commercially available carbon nanotubes and a binder, such as JCGMT-999-11-30-COOH produced by Nanjing Jicang Nanotechnology Co., Ltd., may also be used directly. A thickness of the antistatic layer 20 is preferably less than 80 nm, to ensure good optical performance. The particular preparation process is described below in detail.

The adhesive layer 30 preferably adopts a low-viscosity adhesive, such as a polyurethane adhesive, so as to avoid damage to the OLED liquid crystal display and the multilayer structure adhesive tape 1 during the process of peeling the multilayer structure adhesive tape 1 from the OLED liquid crystal display. A preferred viscosity is a viscosity having a peeling force less than 15 g/inch. Commercially available polyurethane adhesives include, for example, CYABINE SP205 produced by Toyo Ink Company and PA-67-2 produced by Xinzong Chemical Company, etc. The polyurethane adhesive is mixed with a suitable crosslinker and an organic solvent, so as to be applied onto one side of the adhesive tape substrate layer 10. The adhesive layer 30 further comprises an antistatic ionic liquid, for example, a product HQ115 from 3M Company, to provide the adhesive layer 30 with a certain antistatic function. Optionally, the adhesive layer 30 may further comprise a plasticizer or the like to further reduce the viscosity.

As shown in FIG. 2, in other embodiments, the outer surface of the adhesive layer 30 may also be covered with a peelable release film 40, to protect the adhesive layer 30 prior to use. The release film 40 may also be made of a PET film.

Next, the preparation method for the multilayer structure adhesive tape 1 is described in detail with reference to FIG. 3.

In Step SI, an adhesive solution is prepared. In this embodiment, a polyurethane adhesive, an organic solvent (e.g., methyl ethyl ketone), and an antistatic ionic liquid are mixed in an appropriate proportion. Optionally, a suitable plasticizer may be added depending on the desired target viscosity. Where, a preferred viscosity is a viscosity having a peeling force less than 15 g/inch.

In Step S2, an aqueous dispersion solution of single-walled or double-walled carbon nanotubes is prepared. The single-walled or double-walled carbon nanotubes and the water-soluble or water-dispersible binder are mixed and dispersed in deionized water in an appropriate proportion, to form an aqueous dispersion solution. The mass concentration of the aqueous dispersion solution is, for example, about 1%. An appropriate amount of carboxyl groups or similar functional groups may be added to the carbon nanotube aqueous dispersion solution, so as to improve the hydrophilicity of the carbon nanotubes and make it easier for the carbon nanotubes to disperse uniformly in the aqueous solution.

In Step S3, the antistatic layer 20 is formed by the aqueous dispersion solution of single-walled or double-walled carbon nanotubes prepared in Step S2. The carbon nanotube aqueous dispersion solution is uniformly applied onto one side of the adhesive tape substrate layer 10 by a mesh roller, and the carbon nanotube aqueous dispersion solution is dried by natural air drying or oven-drying in an oven, to form the antistatic layer 20. The thickness of the coating after drying is calculated by the weight and mass concentration of the applied carbon nanotube aqueous dispersion solution is preferably less than 80 nm, to ensure good optical performance. The temperature and time of natural air drying or oven-drying depend on the weight and mass concentration of the applied carbon nanotube aqueous dispersion solution. For example, in this embodiment, the coating is heated in an oven at a temperature of 100°C for 5 min, to form the antistatic layer 20.

In Step S4, the adhesive layer 30 is formed by the adhesive solution prepared in Step S 1. The polyurethane adhesive solution is uniformly applied to the other side of the adhesive tape substrate layer 10 to form a coating with a thickness of about 20-25 pm, and the adhesive tape substrate layer 10 carrying the coating is heated in an oven, to dry the polyurethane adhesive solution and cure the polyurethane adhesive. The drying and curing time and temperature depend on the composition and coating thickness of the polyurethane adhesive solution, for example, in this embodiment, the adhesive layer 30 is heated in an oven at a temperature of 100°C for 10 min.

Optionally, in Step S5, the PET release film 40 is laminated on the formed adhesive layer 30. A thickness of the release film 40 may generally be about 50 pm.

In Step S6, post-curing treatment is performed. In this embodiment, the multilayer structure adhesive tape 1 formed by the above steps is kept in an oven at 60°C for 2 days, to complete the post-curing of the adhesive layer 30. The time and temperature of the post-curing treatment can be adaptively adjusted according to the composition and thickness of the adhesive layer 30.

The orders of some of the above steps may be interchanged if the order of operations is not expressly or implicitly stated. For example, Steps SI and S2 of pre-preparing the adhesive solution or the carbon nanotube aqueous dispersion solution can obviously be performed in an interchanged order or simultaneously, and Steps S3 and S4 of forming the antistatic layer 20 and the adhesive layer 30 respectively by coating and drying can also be interchanged in the order.

Via the above preparation method, the multilayer structure adhesive tape 1 having excellent optical transparency, excellent and stable antistatic performance and low viscosity can be formed. The use of single-walled or double-walled carbon nanotubes instead of multi-walled carbon nanotubes can provide the antistatic layer 20 with a clear and only slightly black appearance, as well as excellent optical transparency and haze. For example, the optical transparency can reach 86% or higher and the haze may be less than 4.5%. Meanwhile, the antistatic layer 20 containing single-walled or double-walled carbon nanotubes can achieve a surface resistance of the order of 10 ^L 6 ohm/sq, and can still maintain a surface resistance of the order of 10 ^L 6 ohm/sq after long-term exposure to ultraviolet light, which means that the antistatic layer 20 has excellent antistatic performance that does not easily deteriorate. Dispersing carbon nanotubes in an aqueous solution via a water-soluble or water-dispersible binder can form a uniform carbon nanotube aqueous dispersion solution, thereby facilitating the uniform application of carbon nanotubes onto the adhesive tape substrate layer 10. Using a low-viscosity adhesive to form the adhesive layer 30 having a peeling force of less than 15 g/inch can protect the OLED liquid crystal display and the multilayer structure adhesive tape 1 from being damaged during the peeling process.

The exemplary embodiments of the multilayer structure adhesive tape having a carbon nanotube antistatic layer and a preparation method therefor according to the present invention have been described in detail above, but it should be understood that, the present invention is not limited to the particular embodiments described and shown in detail above. Those skilled in the art can make various variations and variants for the present invention without departing from the gist and scope of the present invention. All these variations and variants fall within the scope of the present invention. In addition, all members described here can be replaced with other technically equivalent members.