CN112080099A

CN112080099A - QLED device, composite material and application thereof

Info

Publication number: CN112080099A
Application number: CN202010994867.9A
Authority: CN
Inventors: 完亮亮; 龙能文; 管子豪
Original assignee: Hefei Funa Technology Co ltd
Current assignee: Hefei Funa Technology Co ltd
Priority date: 2020-09-21
Filing date: 2020-09-21
Publication date: 2020-12-15

Abstract

A QLED device, a composite material and application thereof belong to the field of light emitting diodes. The composite material comprises a carrier and a functional substance which are mixed uniformly, and the functional substance is present in an amount capable of forming a network-like structure in the carrier. Wherein the carrier comprises a matrix resin; wherein the functional substance comprises water-absorbing resin and heat-conducting material. The composite material has high heat dissipation performance, and can absorb and retain water, so that the composite material can be used in a plurality of environments with the requirement.

Description

QLED device, composite material and application thereof

Technical Field

The application relates to the field of light emitting diodes, in particular to a QLED device, a composite material and application thereof.

Background

There are many factors affecting the lifetime of a quantum dot light emitting diode device, and therefore, increasing the lifetime of a QLED device has been a major challenge in large-scale industrialization.

Generally, the decay mechanism of the lifetime of a QLED device includes internal and external factors.

The internal factors are mainly determined by the characteristics of the material itself, and therefore, it is usually necessary to find more stable materials and better material combinations to improve the device lifetime.

The external factors mainly include impurities introduced by environmental pollution, migration of metal elements, heat dissipation of devices, water molecule residues and the like.

Disclosure of Invention

The application provides a QLED device, a composite material and application thereof, which aim to improve or even solve the problem of short service life of the QLED device.

The application is realized as follows:

in a first aspect, examples of the present application provide a composite material comprising a carrier and a functional substance blended together; wherein the carrier comprises a matrix resin; wherein the functional substance comprises water-absorbing resin and heat-conducting material.

According to some examples of the application, the thermally conductive material is present in an amount capable of forming a network-like structure within the carrier.

Optionally, the content of the heat conductive material in the composite material is more than 30 wt%;

optionally, the thermally conductive material is present in the composite material in an amount of 30 wt% to 60 wt%.

According to some examples of the present application, in the composite material, the water absorbent resin is contained in an amount of 20 wt% to 50 wt%, and the thermally conductive material is contained in an amount of 30 wt% to 60 wt%.

Optionally, the mass ratio of the water-absorbing resin to the heat-conducting material is 1:3 to 5: 3.

According to some examples of the present application, the content of the functional substance in the composite material is above 80 wt%.

According to some examples of the present application, the water absorbent resin is a water-soluble high molecular polymer having a hydrophilic group and a crosslinked structure.

According to some examples of the present application, the water absorbent resin includes a combination of any one or more of a polyvinyl alcohol-based water absorbent resin, a polyacrylate-based water absorbent resin, a starch graft acrylate-based water absorbent resin, a starch graft acrylamide-based water absorbent resin, and a cellulose-based water absorbent resin.

According to some examples of the application, the thermally conductive material comprises a combination of any one or more of graphite, carbon black, pitch-based carbon fibers, polyacrylonitrile, carbon nanotubes, graphene, diamond, silicon carbide, magnesium oxide, boron nitride, aluminum nitride, silicon nitride, and aluminum oxide.

According to some examples of the present application, the composite material is a viscous slurry and is capable of being cured;

optionally, the matrix resin comprises 95-98 wt% of organic silicon resin, 1-4 wt% of curing agent and 0.1-1 wt% of catalyst.

In a second aspect, the present application example proposes the application of the above composite material as an encapsulation material to achieve heat dissipation, water absorption and water retention in the fabrication of QLED devices.

According to some examples of the present application, a QLED device has a substrate and a cover plate, wherein the substrate is attached to the cover plate by frame bonding and the composite material is attached to an inner surface of the cover plate.

In a third aspect, the present application illustrates a QLED device comprising an encapsulant, and the encapsulant is made from the above-described composite material.

According to some examples of the present application, the encapsulation material is located on an inner surface of a cover glass of the QLED device.

In the implementation process, the composite material provided by the embodiment of the application has the characteristics of high heat conductivity coefficient, water absorption and water retention, so that the composite material can play a role in heat dissipation and blocking water transfer, can play a certain protection role in waterproof and electronic components which are not suitable for working in a high-temperature environment, and further prolongs the service life of the composite material. In composite materials, the carrier provides structural strength and provides containment space for other primary functional materials. The water-absorbing resin has the functions of absorbing and retaining water, and the heat-conducting material can improve the heat-conducting coefficient so as to be beneficial to heat dissipation. In addition, due to the water absorbing effect of the water absorbent resin, when it absorbs water and retains water, the water absorbent resin and the water retained therein can collectively lower the temperature, thereby having a synergistic heat dissipating effect.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

Fig. 1 is a schematic structural diagram of a QLED device in an example of the present application.

Icon: 101-a substrate; 102-packaging glue; 103-a back plate; 104-a composite material; 105-a thermally conductive material; 106-water-absorbent resin; 107-light emitting chip; 108-cathode.

Detailed Description

Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The following is a detailed description of a QLED device, a composite material and applications thereof according to embodiments of the present application:

the lifetime of QLED devices is adversely affected to a considerable extent by water, temperature, and the like. For example, the attack of water and oxygen on the device can lead to degradation of the device and shortening of the device. It is important to reduce the temperature while protecting the core (QLED, as distinguished from its package) of the device from water.

In some studies, it has been selected to use a desiccant to adsorb moisture remaining in the device after packaging when the device is packaged. For example, some of the commonly used drying agents for devices include metal oxides such as soda lime, calcium oxide, and barium oxide. The metal oxides absorb water and then generate OH-ions, if the metal oxides contact a cathode electrode (such as Al) to generate chemical reaction, on one hand, cathode corrosion is caused, and on the other hand, the chemical reaction generated by water, oxygen and aluminum releases trace gas to cause the separation of the metal cathode and a contact layer, so that the QLED display effect is reduced and the service life is shortened.

In addition, at present, an organic or (and) inorganic water absorption layer is directly spin-coated or evaporated on the surface of the device to isolate water and oxygen and absorb residual water, but due to the fact that thermal expansion coefficients of different materials are different, the method can cause stress to be generated on a device function layer, black spots are generated, and the device fails.

In view of this problem, the present application proposes a composite material that can be used for manufacturing a QLED device to reduce the temperature thereof, prevent water erosion, and improve the service life thereof.

When applied to a QLED device, the method can be implemented as follows:

referring to fig. 1, a substrate 101 and a back plate 103 of the QLED device are combined by a packaging adhesive 102 to form an enclosed space, and a light emitting chip 107 is mounted in the enclosed space. The above-mentioned composite material 104, which includes a heat conductive material 105 and a water absorbent resin 106, is attached to the inner surface of the back sheet 103.

In the QLED device, a layer of water-absorbing and heat-conducting polymer resin (composite material) is coated on the inner surface of the back plate, and the substrate and the back plate are connected by frame bonding. Because the base plate and the cover plate are connected in a frame pasting mode, a reserved space can be reserved for water absorption and expansion of the water absorption macromolecules. When the water-absorbing material is directly coated on the surface of a device, the water-absorbing expansion can cause uneven stress on a functional layer of the device, and further, point discharge and black spot problems are caused. In addition, the composite material in the example of the application does not contain alkaline substances, and even if the water-absorbing polymer is directly contacted with the cathode 108 after being expanded, the cathode 108 (such as Al) can be prevented from being damaged, and the service life of the device is further prolonged.

The composite material has the characteristics of high thermal conductivity and at the same time is capable of absorbing and retaining water (the characteristic of not losing water under certain heating and pressurizing conditions). Furthermore, therefore, the composite material provided in the present application example can be applied to other fields having thermal conductivity requirement or water blocking requirement, such as making it a heat dissipation layer, a water retention layer, etc., besides being suitable for the QLED device described above.

When the composite material is applied to a QLED device, it may be applied to the inner surface of a cover glass of the QLED device in general. In these examples, the QLED device can be cured by using an ultraviolet curing encapsulant (e.g., epoxy) and mounting a cover glass, by irradiation with an ultraviolet lamp. Whereas the composite material in the present example was applied to the inner surface of the cover glass, i.e. arranged facing the QLED core. That is, the composite material can act as an encapsulation material to plug potential gaps in the cover glass to inhibit water penetration and to avoid heat build up in the QLED core.

The composite material in the examples of the present application is explained in detail below.

The composite material comprises a carrier and a functional substance, and the carrier and the functional substance are mixed uniformly.

In particular, in the composite material, the functional substance forms a network-like structure within the carrier (mainly constituted by the heat conductive material/heat conductive particles in the functional substance mentioned later, in which the heat conductive material may also be referred to as a filler), so that the heat conductivity of the composite material can be made larger (compared to the case where the functional substance does not form a network structure).

In practice, the inventors have found that the mass fraction content of the thermally conductive material in the composite material has a considerable influence on whether the above-mentioned network structure can be formed in the composite material.

The concrete expression is as follows:

when the amount of the heat conductive material is small, the particles of the heat conductive material are wrapped by the polymer matrix. Thus, a "sea-island two-phase system" structure similar to that in polymer blend systems, i.e. appearing in the form of approximately islands.

When the mass fraction of the particles of the heat conduction material reaches a certain critical value, the particles of the heat conduction material are contacted with each other to form a heat conduction network chain, and the heat conduction chain or the heat conduction network can be mutually connected and penetrated along with the continuous increase of the mass fraction of the particles of the heat conduction material, so that the heat conduction performance of the composite material is obviously improved.

When the loading of particles of the thermally conductive material (mass fraction, thermally conductive material mass/composite mass) is less than a critical value for the loading required to form the chain of thermally conductive mesh, the thermal conduction of the composite material is similar to the series manner of current flow in a circuit. In this case, since the polymer is a poor conductor of heat (functions as a thermal resistance), it results in a small increase in the thermal conductivity of the composite material.

When the loading of the particles of the thermally conductive material is above the threshold loading required to form the thermally conductive network chains, the thermal conduction of the composite material is similar to the parallel manner of current flow in a circuit. Thus, the heat flow is preferentially transferred from the path of greater thermal conductivity, so the increase in thermal conductivity of the composite material is significant.

Wherein the carrier comprises a matrix resin. Thus, the matrix resin is essentially present as a load bearing structure for the other materials in the composite and is capable of providing the mechanical properties (e.g., cohesiveness, compressive strength, bending strength, etc.) for which the composite is intended.

Generally, to facilitate the mixing of the carrier and functional substance and the use as a heat-dissipating, water-absorbing and water-retaining material, the carrier may be selected to be a liquid material, and in some cases, to be a solid by the selection of specific components that can be cured by an appropriate means (e.g., light or heat) for the convenience of application in a specific environment.

In the present example, the carrier is mainly composed of a silicone resin. Further, for curing, the carrier may also contain a curing agent (typically a phenolic or anhydride species) corresponding to the silicone resin, or further include a catalyst (which may be N, N-dimethylethanolamine, for example). Illustratively, other materials besides silicone resins, such as epoxy resins, may also be included in the carrier. Since the carrier is a silicone resin, the silicone resin is liquid at normal temperature. Thus, in the support solution comprising mainly silicone resins, it is possible to obtain composites based thereon in the form of viscous slurries. And can be cured by having a curing agent.

When the carrier simultaneously contains organic silicon resin, a curing agent and a catalyst, the matrix resin comprises 95-98 wt% of organic silicon resin, 1-4 wt% of curing agent and 0.1-1 wt% of catalyst.

Wherein the functional substance provides a primary source of the function of the composite material. Namely, the heat dissipation, water absorption and water retention of the composite material are mainly from functional substances. Also in the present application, the functional substance is a composition which mainly comprises two substances. Therefore, the above-mentioned heat dissipation and water absorption and retention properties are derived independently from the above-mentioned two substances, and further the enhancement of the upper function (heat dissipation) is synergistically promoted by the mixed presence of both (for example, the water absorbed by the water absorbent resin may exert a certain heat conduction effect or suppress a sharp rise in temperature).

In the present example, the functional substance includes a water-absorbent resin and a heat conductive material. As the name suggests, the water-absorbent resin has the performance of absorbing and retaining water. The heat conduction material can improve the heat conduction coefficient of the composite material, so that the composite material is endowed with heat dissipation performance. In addition, the water-absorbent resin can absorb heat energy even after absorbing water, thereby suppressing a rapid temperature rise to some extent, contributing to gradual heat release, and achieving heat dissipation.

In an example, the functional substance content in the composite material is above 80 wt%. Further, when the functional substance is present in the above-mentioned mass content, the ratio of the two substances in the functional substance may also be defined.

For example, the water absorbent resin is contained in the composite material in an amount of 20 wt% to 50 wt% (may be 22 wt%, 25 wt%, 34 wt%, 38 wt%, 43 wt%, or 49 wt%, etc.).

For example, in the composite material, the content of the heat conductive material may be 30 wt% or more, and further, it may be 30 wt% to 60 wt% (may be 33 wt%, 37 wt%, 41 wt%, 46 wt%, 54 wt%, 56 wt%, or 59 wt%, etc.). When the content of the heat conduction material is lower than 30 wt%, the heat conduction performance of the composite material is poor; and when the content of the heat conduction material is higher than 60 wt%, the heat conduction effect of the composite material is better. The inventor speculates that the heat conduction effect is poor because the heat conduction material cannot form a parallel structure when the content of the heat conduction material is lower than 30 wt%, so that the heat is relatively difficult to transfer.

As a specific alternative example, the mass ratio of the water-absorbent resin and the heat-conductive material is 1:3 to 5:3, such as 2:3, 3:3, or 4:3, and so on. Among them, especially in the case where the mass ratio of the water-absorbent resin to the heat conductive material is 1:1, the composite material can exhibit a balanced improvement in performance.

The water-absorbent resin is generally a substance having a strong hydrophilic group such as a carboxyl group and a hydroxyl group, and is capable of absorbing and retaining water. In particular, the water-absorbent resin may have a certain degree of crosslinking, thereby improving its water-absorbing and water-retaining properties. The cross-linked structure can also improve the combination of the heat conduction material and the cross-linked structure, so that the combination is firmer and tighter. Meanwhile, the water-absorbing resin is water-soluble, which is more beneficial to the preparation of composite materials.

As an example, the water-absorbent resin may be a synthetic polymeric water-absorbent resin such as polyvinyl alcohols, polyacrylates, and the like. Alternatively, the water-absorbent resin can also be starch-based super-absorbent resin, such as starch grafted acrylate, starch grafted acrylamide, and starch grafted various monomer synthesis. Alternatively, the water-absorbent resin may be a cellulose-based super absorbent resin. Of course, the water absorbent resin may also be a combination of a plurality (e.g., two, three, four, or even more) of the above-described various components.

Alternatively, the heat conducting material may be an organic heat conducting material, an inorganic heat conducting material, or a mixture of an organic heat conducting material and an inorganic heat conducting material.

Illustratively, the thermally conductive material includes a combination of any one or more of graphite, carbon black, pitch-based carbon fibers, polyacrylonitrile, carbon nanotubes, graphene, diamond, silicon carbide, magnesium oxide, boron nitride, aluminum nitride, silicon nitride, and aluminum oxide. For example, the thermally conductive material is a combination of graphite and carbon black; alternatively, the thermally conductive material is a combination of pitch-based carbon fiber, polyacrylonitrile, and silicon carbide; alternatively, the thermally conductive material is a combination of diamond, silicon carbide and magnesium oxide.

A QLED device, a composite material and its use of the present application are described in further detail below with reference to examples.

Example 1

A composite material includes thermally conductive particles, a water absorbent resin, and a matrix resin mixed in a weight ratio of 4:4: 2.

Wherein the heat conducting particles are graphene; the water-absorbing resin is starch grafted acrylate; the matrix resin consists of 95 percent of organic silicon resin, 4 percent of curing agent (phthalic anhydride) and 1 percent of catalyst (N, N-dimethylethanolamine).

The manufacturing method of the composite material comprises the following steps: adding the heat conducting particles, the water-absorbing resin and the matrix resin into a container, and uniformly mixing by stirring.

Examples 2 to 5 were carried out according to the method of example 1 described above to obtain a plurality of composite materials. The difference between the embodiments is the ratio of the water absorbent resin and the thermally conductive particles.

In addition, the matrix resin, the water absorbent resin and the matrix resin, the thermally conductive particles and the matrix resin in example 1 described above were mixed to form comparative materials of three comparative examples (comparative example 1 to comparative example 5), respectively.

Test example 1

Using the materials of examples 1 to 5 and comparative examples 1 to 5 and the same quantum dots, a test device (QD-LED, quantum dot light emitting diode) was obtained by encapsulating with an encapsulating adhesive, and a lifetime test was performed thereon, with the results as shown in table 1 below.

TABLE 1

Note that: the lifetime T95 is the time when the luminance decreases to 95% of the maximum luminance.

As can be seen from the data in table 1, the QD-LED device T95 has a service life of only 6 hours without adding the heat conductive material and the water absorbent resin, and the service life is slightly improved due to the addition of the water absorbent resin without adding the heat conductive material, because the material has good water absorption performance but poor heat dissipation; only adding heat conduction materials instead of water absorption materials reduces the service life, and the reason for the service life is that the sealing effect of matrix resin is influenced due to excessive heat conduction materials; proper heat conduction material and water-absorbing resin are added, the service life of the QD-LED device can be prolonged by about 3-8 times, wherein the heat conduction material is as follows: water-absorbent resin: the matrix resin has excellent performance of 4:4:2, and the service life of the QD-LED is prolonged by 733 percent.

Test example 2

Test devices (QD-LED, quantum dot light emitting diode) were obtained by encapsulating with an encapsulating adhesive according to the embodiment of example 1 described above (examples 6 to 10), and life test was performed thereon, and the material selection and life test results of each example other than example 1 are shown in table 2 below.

TABLE 2

Test example 3

This experiment investigated the effect of the proportion by mass (mass fraction) of the thermally conductive particles in the mixed composite material on the thermal conductivity of the composite material, as shown in table 3.

Wherein the mixed material refers to a mixture of matrix resin, water-absorbent resin and conductive particles. Firstly, uniformly mixing matrix resin (95% of organic silicon resin, 4% of curing agent and 1% of catalyst) with the same mass with water-absorbing resin (starch grafted acrylate), and adding heat-conducting particles (graphene) with different mass fractions.

TABLE 3

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The composite material is characterized by comprising a uniformly mixed carrier and a functional substance;

wherein the carrier comprises a matrix resin;

wherein the functional substance comprises water-absorbing resin and heat-conducting material.

2. The composite material of claim 1, wherein the thermally conductive material is present in an amount capable of forming a network-like structure within the carrier;

3. The composite material according to claim 1, wherein the composite material contains the water-absorbent resin in an amount of 20 to 50 wt% and the thermally conductive material in an amount of 30 to 60 wt%;

4. Composite material according to any of claims 1 to 3, characterized in that the content of functional substances in the composite material is above 80 wt%.

5. The composite material according to claim 1, wherein the water absorbent resin is a water-soluble high molecular polymer having a hydrophilic group and a crosslinked structure;

optionally, the water-absorbing resin comprises one or more of polyvinyl alcohol water-absorbing resin, polyacrylate water-absorbing resin, starch grafted acrylate water-absorbing resin, starch grafted acrylamide water-absorbing resin and cellulose water-absorbing resin;

optionally, the thermally conductive material comprises a combination of any one or more of graphite, carbon black, pitch-based carbon fibers, polyacrylonitrile, carbon nanotubes, graphene, diamond, silicon carbide, magnesium oxide, boron nitride, aluminum nitride, silicon nitride, and aluminum oxide.

6. The composite material of claim 1, wherein the composite material is a viscous slurry and is capable of being cured;

7. Use of the composite material of any one of claims 1 to 6 as an encapsulation material for heat dissipation, water absorption and retention in the manufacture of QLED devices.

8. The use of claim 7, the QLED device having a substrate and a cover plate, wherein the QLED device is frame-mounted to the substrate and the cover plate, and the composite material is adhered to the inner surface of the cover plate.

9. A QLED device comprising an encapsulant made from the composite material of any of claims 1 to 7.

10. A QLED device according to claim 9, wherein the encapsulant is on an inner surface of a cover glass of the QLED device.