TW201815564A - Graphene stack and method for producing same - Google Patents
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本發明係有關於石墨烯層合體及其製造方法，更詳而言之，係有關於一種適用於熱擴散片之顯示良好的熱傳導性的石墨烯層合體及廉價之其製造方法。 The present invention relates to a graphene laminate and a method for manufacturing the same. More specifically, the present invention relates to a graphene laminate suitable for a thermal diffusion sheet and exhibiting good thermal conductivity and an inexpensive method for manufacturing the same.
自智慧型手機普及以來，為了讓使用者使用得更得心應手，每當開發新產品時，往往會追求軟體處理速度的提升。其中，近年來多核心型中央處理單元(中央處理器，下稱CPU)逐漸普及。單一CPU進行程式中的多項處理時係細分利用時間並依序予以分配來進行處理，而多核心型CPU則可同時並列地進行多項處理，而加快處理速度，從而成為CPU形態之主流。 Since the popularization of smart phones, in order to make users more comfortable to use, whenever a new product is developed, it often pursues the improvement of software processing speed. Among them, in recent years, a multi-core central processing unit (central processing unit, hereinafter referred to as a CPU) has gradually spread. A single CPU performs multiple processing in the program by subdividing the use of time and allocating them sequentially for processing, while a multi-core CPU can perform multiple processings in parallel at the same time to speed up the processing speed, thus becoming the mainstream of the CPU form.
然而，將一CPU之處理能力較高者作成多核心時，耗電量必然會增加，隨之發熱量亦增加。此由CPU所產生的熱，為了防止高溫導致CPU本身的故障及防止使用者的燙傷，必須適切地由CPU去除熱而放熱，此已成智慧型手機的開發中最重要的課題之一。 However, when a CPU with a higher processing capacity is made into a multi-core, the power consumption will inevitably increase, and the heat generation will increase accordingly. The heat generated by the CPU must be properly removed by the CPU to release heat in order to prevent the CPU itself from malfunctioning due to the high temperature and to prevent burns from the user. This has become one of the most important issues in the development of smart phones.
作為由發熱體使熱放熱的方法，有傳導、對流、放射此三種。傳導為透過物質傳導熱的現象；對流為 藉由液體或氣體的流動而傳導熱的現象；放射則是藉由從物體放射電磁波而傳導熱的現象。此等當中，放熱性能係依對流、傳導、放射之順序逐漸增高。 There are three methods of heat release from a heating element: conduction, convection, and radiation. Conduction is the phenomenon of conducting heat through matter; convection is the phenomenon of conducting heat by the flow of liquid or gas; radiation is the phenomenon of conducting heat by radiating electromagnetic waves from an object. Among these, the exothermic performance gradually increases in the order of convection, conduction, and radiation.
作為利用對流的放熱構件之實例可舉出熱管。熱管係於內部具有液體，接近發熱部的部位呈高溫，內部的液體沸騰，於相反側冷卻而凝結，藉此循環而達到放熱。 An example of a heat release member using convection is a heat pipe. The heat pipe has a liquid inside, and the portion close to the heat generating portion becomes high temperature. The internal liquid boils, cools and condenses on the opposite side, and circulates to achieve heat release.
然而，如智慧型手機之薄型機器，由於未有可導入能實現充分之熱輸送的量之液體的空間，便利用放熱性能高為次於對流之使用傳導機構的薄片狀構件所致之熱傳導作為放熱手段。特別是將使在CPU等產生的熱，使用薄片狀構件朝面內方向放熱的構件稱為熱擴散片。此熱擴散片為具有較高熱傳導率的構件，若為數十μm左右的厚度，則可導入於薄型機器之智慧型手機等，而且可放熱而壓低CPU的發熱所致之局部溫度上昇。 However, thin devices such as smartphones do not have room to introduce liquids in sufficient quantities to achieve sufficient heat transfer. It is convenient to use the heat conduction caused by sheet-like members with high heat release performance that is inferior to convection. Exothermic means. In particular, a member that radiates heat generated in a CPU or the like in a plane direction using a sheet-like member is referred to as a heat diffusion sheet. This thermal diffusion sheet is a member having a high thermal conductivity, and if it has a thickness of about several tens of μm, it can be introduced into a smart phone or the like of a thin device, and it can release heat and reduce the local temperature rise caused by the heat generated by the CPU.
實際上，熱擴散片所使用的放熱構件係使用數百W/(m‧K)以上的高熱傳導者，其中有熱傳導率分別為236W/(m‧K)、401W/(m‧K)的鋁箔或銅箔等金屬箔、與數百W/(m‧K)至最高約2000W/(m‧K)的石墨薄片等。 In fact, the heat radiating members used in the thermal diffusion sheet use hundreds of W / (m‧K) or higher heat conductors, among which the thermal conductivity is 236W / (m‧K), 401W / (m‧K) Metal foils such as aluminum foil and copper foil, and graphite flakes with hundreds of W / (m‧K) up to about 2000W / (m‧K).
擔負上述金屬箔或石墨薄片之熱傳遞的載子分別主要為自由電子、與源自於晶格振動的聲子(phonon)。金屬箔的高熱傳導性係源自於金屬所具有的自由電子。在石墨薄片中則為聲子，即晶格振動為熱傳遞 的主要載子。就石墨而言，如碳的較輕元素在面內、二維方向會被共價鍵強力地束縛，因此，認為晶格振動的傳遞較快，薄片面內的熱傳導性較高。 Carriers responsible for the heat transfer of the metal foil or graphite sheet are mainly free electrons and phonons derived from lattice vibration, respectively. The high thermal conductivity of metal foil is derived from the free electrons that metal has. In the graphite sheet, there are phonons, that is, lattice vibration is the main carrier of heat transfer. As for graphite, lighter elements such as carbon are strongly constrained by covalent bonds in the plane and in two dimensions. Therefore, it is considered that the transmission of lattice vibration is faster and the thermal conductivity in the plane of the sheet is higher.
如上所述，金屬箔與石墨薄片之主要的熱傳導載子為自由電子與聲子而不同；惟，任一種材料皆具有導電性。如前述，金屬材料係主要藉由自由電子傳熱，因此熱傳導性與導電性有關，理當具有導電性。石墨薄片藉由聲子所致的熱傳導，係石墨的共價鍵結晶愈大則愈高；而石墨的共價鍵結晶愈大，則石墨的π共軛系統也愈大，因此，產生藉由π電子所致之導電性，此亦為具有導電性的薄片。 As mentioned above, the main thermally conductive carriers of metal foil and graphite flake are different from free electrons and phonons; however, any material is conductive. As mentioned above, metal materials mainly transfer heat through free electrons, so thermal conductivity is related to conductivity, and it should be conductive. The thermal conduction caused by phonons of graphite flakes, the larger the covalent bond crystals of the graphite, the higher the graphite; the larger the crystals of the covalent bonds of the graphite, the larger the π conjugate system of the graphite. The conductivity due to π electrons is also a thin sheet with conductivity.
從而，由於使用於熱擴散片的金屬箔或石墨薄片等的高熱傳導構件皆具有導電性，以CPU等電子零件的放熱為目的而於智慧型手機內部設置熱擴散片時，為了防止熱擴散片與電子零件接觸而造成短路，一般係對放熱層層合PET薄膜等的絕緣層來使用。亦即，在智慧型手機的熱擴散用途使用具有高熱傳導性的構件時，必然會構成為層合絕緣層來使用具有高熱傳導性但具有導電性的構件。 Therefore, since highly thermally conductive members such as metal foils and graphite sheets used in thermal diffusion sheets are electrically conductive, when a thermal diffusion sheet is installed inside a smartphone for the purpose of exothermic electronic components such as a CPU, it is necessary to prevent the thermal diffusion sheet. Contact with electronic parts to cause a short circuit is generally used for laminating heat insulation layers such as PET films. That is, when a member having high thermal conductivity is used for the thermal diffusion application of a smartphone, it is inevitably constituted by laminating an insulating layer to use a member having high thermal conductivity but having electrical conductivity.
再者，近年來隨著CPU的性能提升之發熱量增加，從而要求熱傳導性更高的薄片，以3000℃附近的超高溫熱處理製作聚醯亞胺等的高分子薄膜之高熱傳導性的石墨薄片逐漸普及。有人報導一種以高分子薄膜為原料加熱至3000℃附近，可維持薄片狀態同時將高分子組成物石 墨化，由碳-碳再結合使石墨結晶增大並提升配向性，藉此具有最高接近2000W/(m‧K)的熱傳導率之熱擴散片。 In addition, in recent years, with the improvement of the performance of the CPU, the amount of heat generation has increased, and thus a sheet with higher thermal conductivity is required. The ultra-high temperature heat treatment near 3000 ° C is used to produce a graphite sheet with high thermal conductivity such as polyimide Gradually spread. It has been reported that a polymer film is used as a raw material to heat it to around 3000 ° C, and the polymer composition can be graphitized while maintaining the sheet state. The carbon-carbon recombination can increase the graphite crystals and improve the alignment, thereby having a maximum close to 2000W. / (m‧K) thermal diffusion sheet.
然而，3000℃附近的熱處理極為耗電，而且，必須採取針對加熱器或隔熱材的劣化、冷卻設備的建構及安全面之方策，而為非屬簡便且需要大量能量的手法。亦即，近年來不可或缺的熱傳導薄片，由於為熱傳導性更高的構件，會在非簡便且需要大量能量所製成的薄片產生導電性，因而設計成在後續步驟中貼合絕緣層之構成。 However, the heat treatment near 3000 ° C consumes a lot of power, and it is necessary to take measures against the deterioration of heaters or heat insulators, the construction of cooling equipment, and safety aspects. It is a simple and energy-intensive method. That is, the indispensable heat conductive sheet in recent years, because it is a member with higher thermal conductivity, will conduct electricity in a sheet that is not simple and requires a lot of energy, so it is designed to be bonded to the insulating layer in the subsequent steps Make up.
此種製法理當難以視為最佳者，理所當然地向來便有人想要以微小的碳材料粒子為原料來製作大面積的放熱薄片，實際上市場上已有將石墨粉末使用壓力與熱作成薄片狀的放熱材料販售。然而，現況在於僅單純將粉末固化，只能形成數百W/(m‧K)者。亦即，一直以來公認不易以碳材料微粒子為原料以低成本製作如數百W/(m‧K)至超過1000W/(m‧K)之高熱傳導性的石墨薄片。 Such a method is difficult to be regarded as the best. Of course, there have always been people who want to use large carbon material particles as raw materials to make large-area exothermic flakes. In fact, graphite powder has been made into flakes using pressure and heat on the market. Exothermic material for sale. However, the status quo is that the powder can be solidified only to form hundreds of W / (m · K). That is, it has been recognized that it is not easy to produce graphite flakes with high thermal conductivity, such as hundreds of W / (m‧K) to more than 1000W / (m‧K), at low cost by using carbon material fine particles as raw materials.
就最新潮流而言，跳脫如石墨粉末之破碎型粒子，作為用來更簡便地製作高熱傳導性的薄片之材料，石墨烯材料備受矚目。石墨烯係指石墨經一片片剝離之狀態者，亦有人報導單層石墨烯的熱傳導率為2000~5000W/(m‧K)，因此，只要以此石墨烯為原料來製作薄片，則極有可能能達到高熱傳導，從而諸多研究者、技 術者為了加以實現而進行研究。 In terms of the latest trend, graphene materials have attracted attention as a material that breaks down broken particles such as graphite powder to make flakes with high thermal conductivity more easily. Graphene refers to the state where graphite is peeled off piece by piece. It has also been reported that the thermal conductivity of single-layer graphene is 2000 ~ 5000W / (m‧K). Therefore, as long as graphene is used as a raw material to make thin sheets, it is extremely useful. It is possible to achieve high heat conduction, so that many researchers and technicians carry out research in order to achieve it.
要使用石墨烯成形薄片等，一般而言可藉由將石墨烯分散於水或有機溶媒等，予以成膜後，去除溶媒來製作。惟，石墨烯對水或有機溶媒僅能以極低濃度分散，因此，一般而言若為奈米級厚度之薄片則可製作之。 To form a graphene sheet or the like, it is generally produced by dispersing graphene in water or an organic solvent, forming a film, and removing the solvent. However, graphene can only be dispersed at a very low concentration in water or organic solvents, so in general, it can be made if it is a nano-thickness sheet.
然而，屬實際熱擴散性能的熱輸送量，不僅與熱傳導率，亦與其成形品的體積成正比，因此，若為奈米級的厚度則熱輸送量不足，而無法發揮高放熱性能。為了確保熱輸送量，而欲由石墨烯製作厚度數十μm的石墨烯薄片時，由其低濃度的分散性而言則需要極大量的溶媒，於工業上難以達成。作為其他的方法，只要使用分散劑等，則可製作更高濃度的石墨烯分散物，但由於分散劑會妨害熱傳導性，而非屬適於熱擴散片用途之方法。 However, the heat transfer amount, which is the actual heat diffusion performance, is not only proportional to the thermal conductivity, but also the volume of the molded product. Therefore, if the thickness is nanometer, the heat transfer amount is insufficient, and high heat release performance cannot be exhibited. In order to ensure a heat transfer amount, when a graphene sheet having a thickness of several tens of μm is to be produced from graphene, an extremely large amount of solvent is required in terms of its low concentration dispersibility, which is difficult to achieve industrially. As another method, if a dispersant or the like is used, a graphene dispersion having a higher concentration can be produced. However, the dispersant interferes with thermal conductivity and is not a method suitable for the use of a thermal diffusion sheet.
因此，作為能以更高濃度分散於溶媒的石墨烯材料，氧化石墨烯備受矚目。氧化石墨烯係一種藉由將石墨以過錳酸鉀、硫酸等強氧化劑氧化，對構成石墨之石墨烯的面內賦予羥基、環氧基、羰基及羧基等含氧基，而使其對水或一部分有機溶媒的分散性顯著提升的石墨烯材料。藉由將氧化石墨烯分散物成膜並去除溶媒，可製作厚度數十μm的氧化石墨烯薄片。 Therefore, graphene oxide has attracted attention as a graphene material capable of being dispersed in a solvent at a higher concentration. Graphene oxide is a kind of oxidizing graphite with strong oxidizing agents such as potassium permanganate and sulfuric acid to give hydroxyl groups, epoxy groups, carbonyl groups, and carboxyl groups to the in-plane of graphene constituting graphite to make it resistant to water. Or a graphene material in which the dispersibility of a part of the organic solvent is significantly improved. By forming a graphene oxide dispersion and removing a solvent, a graphene oxide sheet having a thickness of several tens of μm can be produced.
惟，氧化石墨烯會因對石墨烯面內導入官能基而喪失石墨烯的共價鍵結晶結構，與石墨烯相比熱傳導性減少。因此，為達到高熱傳導則須再度使其回復至石墨烯結構。此外，以下將由氧化石墨烯去除含氧基而再次使 其回復至石墨烯之處理稱為還原。 However, graphene oxide loses the covalent bond crystal structure of graphene due to the introduction of functional groups into the graphene plane, and its thermal conductivity is reduced compared to graphene. Therefore, in order to achieve high thermal conductivity, it must be restored to the graphene structure again. The process of removing oxygen-containing groups from graphene oxide and returning them to graphene is hereinafter referred to as reduction.
氧化石墨烯之還原方法當中受到最多人探討的是藉由熱處理所致之還原(例如參照專利文獻1)。已知藉由對氧化石墨烯進行熱處理，經由脫水或去氧，去除氧化石墨烯中的含氧基，可作成石墨烯結構。 Among the reduction methods of graphene oxide, the reduction by heat treatment is the most widely discussed method (for example, refer to Patent Document 1). It is known that graphene oxide can be made into a graphene structure by heat-treating graphene oxide and dehydrating or deoxidizing to remove oxygen-containing groups in graphene oxide.
惟，熱處理雖為可對整個膜均勻地施加能量之方法，但必須使整個爐內空間為高溫，由此而言會發生能量損失，而非屬有效率的方法。再者，氧化石墨烯的石墨烯化所需之熱處理溫度，雖能達成比前述之由高分子薄膜製作石墨薄片時的熱處理溫度更低的溫度，但仍需要高溫。從而，便要求一種比熱處理的能量損失較少、更廉價且為高熱傳導性的熱擴散片。 However, although heat treatment is a method that can uniformly apply energy to the entire film, it is necessary to make the entire furnace space high temperature, so that energy loss occurs instead of being an efficient method. In addition, although the heat treatment temperature required for the grapheneization of graphene oxide can reach a lower temperature than the heat treatment temperature when the graphite thin film is made of the polymer film described above, it still needs a high temperature. Therefore, there is a need for a thermal diffusion sheet that has less energy loss than heat treatment, is cheaper, and has high thermal conductivity.
[專利文獻1]日本特表2015-536900號公報 [Patent Document 1] Japanese Patent Publication No. 2015-536900
本發明係有鑑於上述問題、狀況而完成者，其欲解決之課題在於提供一種適用於熱擴散片之顯示良好的熱傳導性的石墨烯層合體。又，在於提供一種廉價之其製造方法。 The present invention has been made in view of the above-mentioned problems and situations, and a problem to be solved is to provide a graphene laminate that exhibits good thermal conductivity and is suitable for a thermal diffusion sheet. Another object is to provide an inexpensive manufacturing method.
本案發明人為解決上述課題，而在針對上述問題的原因等加以研究的過程中發現，藉由對氧化石墨烯薄片施加僅數V左右的電場，會發生氧化石墨烯的還原反應，可形成氧化石墨烯層與石墨烯層、及於此之間形成具有含氧比率的濃度梯度之混合層，終至完成本發明。 In order to solve the above-mentioned problems, the inventors of the present case have studied the causes of the above-mentioned problems, and found that by applying an electric field of only a few V to the graphene oxide sheet, a reduction reaction of graphene oxide occurs, and graphite oxide can be formed The ene layer and the graphene layer, and a mixed layer having a concentration gradient having an oxygen-containing ratio therebetween, have finally completed the present invention.
亦即，本發明之上述課題可藉由以下手段來解決。 That is, the above-mentioned subject of the present invention can be solved by the following means.
1.一種石墨烯層合體，其係具有含氧化石墨烯的層與含石墨烯的層之石墨烯層合體，其特徵為在前述含氧化石墨烯的層與前述含石墨烯的層之間，具有顯示從前述含氧化石墨烯的層側向前述含石墨烯的層側沿厚度方向含氧比率(原子%)連續地減少的濃度梯度之混合層。 A graphene laminate comprising a graphene laminate including a graphene oxide-containing layer and a graphene-containing layer, wherein the graphene laminate is between the graphene oxide-containing layer and the graphene-containing layer, A mixed layer having a concentration gradient showing a continuous decrease in the oxygen content ratio (atomic%) in the thickness direction from the graphene oxide-containing layer side to the graphene-containing layer side.
2.如第1項之石墨烯層合體，其中前述混合層的厚度為0.2~5μm的範圍內。 2. The graphene laminate according to item 1, wherein the thickness of the mixed layer is in a range of 0.2 to 5 μm.
3.如第1項或第2項之石墨烯層合體，其中前述含石墨烯的層的厚度與含氧比率分別為10~60μm、0.1~15原子%的範圍內，前述含氧化石墨烯的層的厚度與含氧比率分別為0.5~10μm、24~50原子%的範圍內。 3. The graphene laminate according to item 1 or 2, wherein the thickness and oxygen ratio of the graphene-containing layer are in the range of 10 to 60 μm and 0.1 to 15 atomic%, respectively. The thickness and oxygen content of the layer are in the range of 0.5 to 10 μm and 24 to 50 atomic%, respectively.
4.如第3項之石墨烯層合體，其中前述含石墨烯的層的含氧比率為0.1~10原子%的範圍內。 4. The graphene laminate according to item 3, wherein the oxygen content ratio of the graphene-containing layer is within a range of 0.1 to 10 atomic%.
5.如第3項之石墨烯層合體，其中前述含石墨烯的層的含氧比率為0.1~3原子%的範圍內。 5. The graphene laminate according to item 3, wherein the oxygen content ratio of the graphene-containing layer is in a range of 0.1 to 3 atomic%.
6.如第1項至第5項中任一項之石墨烯層合體， 其中具有前述含氧化石墨烯的層的面之表面電阻率為1×104~1×109Ω/sq的範圍內。 6. The graphene laminate according to any one of items 1 to 5, wherein a surface resistivity of a surface having the aforementioned graphene oxide-containing layer is in a range of 1 × 10 4 to 1 × 10 9 Ω / sq Inside.
7.如第1項至第6項中任一項之石墨烯層合體，其中前述含石墨烯的層為氧化石墨烯薄片之厚度方向的部分還原體。 7. The graphene laminate according to any one of items 1 to 6, wherein the graphene-containing layer is a partially reduced body in the thickness direction of the graphene oxide sheet.
8.一種石墨烯層合體之製造方法，其係製造如第1項至第7項中任一項之石墨烯層合體的石墨烯層合體之製造方法，其特徵為藉由從氧化石墨烯薄片的兩面施加電壓，而於該氧化石墨烯薄片的厚度方向，將氧化石墨烯部分地還原，而形成由含石墨烯的層、石墨烯與氧化石墨烯的混合層、及含氧化石墨烯的層所構成之層合體，而且，該混合層係控制成具有從前述含氧化石墨烯的層側向前述含石墨烯的層側沿厚度方向含氧比率(原子%)連續地減少的濃度梯度。 8. A method for producing a graphene laminate, which is a method for producing a graphene laminate according to any one of items 1 to 7, which is characterized by using graphene oxide flakes When voltage is applied to both sides of the graphene, the graphene oxide sheet is partially reduced in its thickness direction to form a graphene-containing layer, a mixed layer of graphene and graphene oxide, and a graphene oxide-containing layer. The laminated body is constituted, and the mixed layer is controlled to have a concentration gradient in which the oxygen content ratio (atomic%) in the thickness direction continuously decreases from the graphene oxide-containing layer side to the graphene-containing layer side.
根據本發明之上述手段，可提供一種適用於熱擴散片之顯示良好的熱傳導性的石墨烯層合體。又，可提供一種廉價之其製造方法。 According to the above-mentioned means of the present invention, it is possible to provide a graphene laminate which exhibits good thermal conductivity and is suitable for a thermal diffusion sheet. In addition, an inexpensive manufacturing method can be provided.
就本發明之效果的展現機構或作用機構，仍尚不明確，惟可如下推測。 The effect display mechanism or action mechanism of the present invention is still unclear, but it can be speculated as follows.
吾人推測，對氧化石墨烯薄片施加電場，則可有效率地作成氧化石墨烯分子之激發態，由此激發態，存在於氧化石墨烯中的含氧基以脫水或去氧的形式，自陰 極側有效率地進行還原反應所致。 I speculate that by applying an electric field to the graphene oxide sheet, the excited state of the graphene oxide molecule can be efficiently formed. From this excited state, the oxygen-containing oxygen present in the graphene oxide is dehydrated or deoxygenated from the cathode. Side due to efficient reduction reaction.
1‧‧‧石墨烯層合體 1‧‧‧graphene laminate
2‧‧‧含石墨烯的層 2‧‧‧ graphene-containing layer
3‧‧‧含氧化石墨烯的層 3‧‧‧ Graphene oxide-containing layer
4‧‧‧放熱之方向 4‧‧‧ Direction of heat release
5‧‧‧混合層 5‧‧‧ mixed layer
6‧‧‧氧化石墨烯薄片 6‧‧‧graphene oxide flakes
H‧‧‧熱源(電子零件) H‧‧‧ heat source (electronic parts)
A‧‧‧陰極與氧化石墨烯之LUMO的能階差 A‧‧‧ Lumen energy difference between cathode and graphene oxide
B‧‧‧陽極與氧化石墨烯之HOMO的能階差 B‧‧‧ Energy step difference between HOMO of anode and graphene oxide
第1圖為本發明之石墨烯層合體的剖面圖的一例 FIG. 1 is an example of a cross-sectional view of a graphene laminate of the present invention.
第2A圖為表示熱傳導的示意圖 Figure 2A is a schematic diagram showing heat conduction
第2B圖為表示熱傳導的示意圖 Figure 2B is a schematic diagram showing heat conduction
第3圖為電極與氧化石墨烯薄片之能階的示意圖 Figure 3 is a schematic diagram of the energy levels of an electrode and a graphene oxide sheet
第4圖為表示在氧化石墨烯薄片之陽極側生成電洞的示意圖 FIG. 4 is a schematic diagram showing generation of holes on the anode side of a graphene oxide sheet.
第5圖為表示自由基陽離子從陽極側向陰極側移動之過程的示意圖 Figure 5 is a schematic diagram showing the process of radical cations moving from the anode side to the cathode side
第6圖為表示對氧化石墨烯薄片之陰極側的LUMO能階注入電子的示意圖 FIG. 6 is a schematic diagram showing injection of electrons into the LUMO level of the cathode side of the graphene oxide sheet.
第7圖為表示藉由載子再結合而形成激發態，並由此激發態還原之情形的示意圖 FIG. 7 is a schematic diagram showing a state where an excited state is formed by carrier recombination, and the excited state is reduced.
第8圖為表示經還原的石墨烯層作為電極，進一步使次一層反應，而進行還原反應之情形的示意圖 FIG. 8 is a schematic diagram showing a case where a reduced graphene layer is used as an electrode, and the next layer is further reacted to perform a reduction reaction.
第9A圖為本發明之石墨烯層合體與比較例之層合體的熱擴散性評定結果 FIG. 9A is a thermal diffusion evaluation result of the graphene laminate of the present invention and the laminate of the comparative example.
第9B圖為本發明之石墨烯層合體與比較例之層合體的熱擴散性評定結果 FIG. 9B is a thermal diffusion evaluation result of the graphene laminate of the present invention and the laminate of the comparative example.
第9C圖為本發明之石墨烯層合體與比較例之層合體的熱擴散性評定結果 FIG. 9C shows the results of thermal diffusion evaluation of the graphene laminate of the present invention and the laminate of the comparative example.
本發明之石墨烯層合體為一種具有含氧化石墨烯的層與含石墨烯的層之石墨烯層合體，其特徵為在前述含氧化石墨烯的層與前述含石墨烯的層之間，具有顯示從前述含氧化石墨烯的層側向前述含石墨烯的層側沿厚度方向含氧比率(原子%)連續地減少的濃度梯度之混合層。此特徵為各請求項之發明所共有的技術特徵。 The graphene laminate of the present invention is a graphene laminate having a graphene oxide-containing layer and a graphene-containing layer, and is characterized in that between the graphene oxide-containing layer and the graphene-containing layer, there is A mixed layer showing a concentration gradient in which the oxygen content ratio (atomic%) in the thickness direction continuously decreases from the side of the graphene-containing layer to the side of the graphene-containing layer. This feature is a technical feature common to the invention of each claim.
就本發明之實施形態，基於展現本發明之效果的觀點，前述混合層的厚度較佳為0.2~5μm的範圍內。 In the embodiment of the present invention, from the viewpoint of exhibiting the effects of the present invention, the thickness of the mixed layer is preferably in a range of 0.2 to 5 μm.
基於超過廣用性優良之高熱傳導金屬的鋁的熱傳導率、及熱輸送量的觀點，以及高電阻性的觀點，較佳的是前述含石墨烯的層的厚度與含氧比率分別為10~60μm、0.1~15原子%的範圍內，前述含氧化石墨烯的層的厚度與含氧比率分別為0.5~10μm、24~50原子%的範圍內。 Based on the viewpoint of the thermal conductivity and heat transfer capacity of aluminum exceeding the highly heat-conductive metal with excellent versatility, and the viewpoint of high electrical resistance, the thickness and oxygen-containing ratio of the graphene-containing layer are preferably 10 to In the range of 60 μm and 0.1 to 15 atomic%, the thickness and oxygen content ratio of the graphene oxide-containing layer are in the range of 0.5 to 10 μm and 24 to 50 atomic%, respectively.
前述含石墨烯的層的含氧比率為0.1~10原子%的範圍內，由於超過廣用性較高之高熱傳導金屬的銅的熱傳導率而於產業上有其價值。 The graphene-containing layer has an oxygen content in the range of 0.1 to 10 atomic%, and has industrial value due to the thermal conductivity of copper, which is higher than that of a highly thermally conductive metal having high versatility.
前述含石墨烯的層的含氧比率為0.1~3原子%的範圍內，由於具有超過1000W/(m‧K)之極高的熱傳導性，於產業上特別有價值。 The graphene-containing layer has an oxygen content ratio in the range of 0.1 to 3 atomic%, and has extremely high thermal conductivity exceeding 1000 W / (m · K), which is particularly valuable in the industry.
再者，於本發明中，基於在作為針對電子零 件之熱擴散片使用時防止短路的觀點，較佳的是具有前述含氧化石墨烯的層的面之表面電阻率為1×104~1×109Ω/sq的範圍內。 Furthermore, in the present invention, from the viewpoint of preventing short circuits when used as a thermal diffusion sheet for electronic parts, it is preferable that the surface resistivity of the surface having the graphene oxide-containing layer is 1 × 10 4 to 1 × 10 9 Ω / sq.
又，前述含石墨烯的層較佳為氧化石墨烯薄片之厚度方向的部分還原體。 The graphene-containing layer is preferably a partially reduced body in the thickness direction of the graphene oxide sheet.
就製造本發明之石墨烯層合體的石墨烯層合體之製造方法而言，此製造方法之形態為藉由從氧化石墨烯薄片的兩面施加電壓，而於該氧化石墨烯薄片的厚度方向，將氧化石墨烯部分地還原，而形成由含石墨烯的層、石墨烯與氧化石墨烯的混合層、及含氧化石墨烯的層所構成之層合體，而且，該混合層係控制成具有從前述含氧化石墨烯的層側向前述含石墨烯的層側沿厚度方向含氧比率(原子%)連續地減少的濃度梯度，由於能以較少能量且廉價地製造而較佳。 As for the manufacturing method of the graphene laminated body of the graphene laminated body of the present invention, the form of this manufacturing method is to apply a voltage from both sides of the graphene oxide sheet and apply a voltage in the thickness direction of the graphene oxide sheet. The graphene oxide is partially reduced to form a laminate composed of a graphene-containing layer, a mixed layer of graphene and graphene, and a graphene-oxide-containing layer, and the mixed layer is controlled so as to have The concentration gradient in which the oxygen-containing ratio (atomic%) of the graphene-containing layer side continuously decreases in the thickness direction toward the graphene-containing layer side is preferable because it can be manufactured with less energy and inexpensively.
以下，就本發明與其構成要素、及實施本發明之形態、態樣進行詳細說明。此外，於本案中，「~」係以包含其前後所記載之數值作為下限值及上限值的意義使用。 Hereinafter, the present invention and its constituent elements, and the forms and aspects of implementing the present invention will be described in detail. In addition, in this case, "~" is used in the meaning including the numerical value described before and after it as a lower limit and an upper limit.
此外，於本發明中含氧比率(原子%)係將氧原子相對於氧原子與碳原子的和之原子比率(O/(C+O))以%表示者。 In addition, in the present invention, the oxygen content ratio (atomic%) refers to an atomic ratio (O / (C + O)) of an oxygen atom with respect to a sum of an oxygen atom and a carbon atom in%.
《石墨烯層合體之概述》 "Overview of Graphene Laminates"
本發明之石墨烯層合體1為具有含氧化石墨烯的層3與 含石墨烯的層2之石墨烯層合體，其特徵為在前述含氧化石墨烯的層3與前述含石墨烯的層2之間具有混合層5(參照第1圖)，該混合層5具有從前述含氧化石墨烯的層側向含石墨烯的層側沿厚度方向含氧比率(原子%)連續地減少的濃度梯度。 The graphene laminate 1 of the present invention is a graphene laminate having a graphene oxide-containing layer 3 and a graphene-containing layer 2, and is characterized in that the graphene oxide-containing layer 3 and the graphene-containing layer 2 are There is a mixed layer 5 (see FIG. 1) therebetween, which has a concentration gradient in which the oxygen content ratio (atomic%) in the thickness direction continuously decreases from the graphene oxide-containing layer side to the graphene-containing layer side in the thickness direction. .
此混合層5由於具有從前述含氧化石墨烯的層3向前述含石墨烯的層2沿厚度方向含氧比率(原子%)連續地減少的濃度梯度，在經還原之含石墨烯的層與未還原之含氧化石墨烯的層之間不存在明確的界面，因此密接性優良，放熱性能優異。一般而言，用於電子零件的熱擴散片，在電子零件上有絕緣層等的高電阻層，並於其上配置熱傳導層。因此，電子零件所產生的熱便通過高電阻層而滲透至熱傳導層，認為高電阻層與熱傳導層之間的界面熱阻會對熱擴散片的實際放熱性能造成影響。 This mixed layer 5 has a concentration gradient in which the oxygen content ratio (atomic%) in the thickness direction continuously decreases from the graphene oxide-containing layer 3 to the graphene-containing layer 2 in the thickness direction. There is no clear interface between the unreduced graphene oxide-containing layers, so the adhesiveness is excellent and the heat release performance is excellent. Generally, a heat diffusion sheet used for electronic parts has a high-resistance layer such as an insulating layer on the electronic part, and a heat conductive layer is disposed thereon. Therefore, the heat generated by the electronic parts penetrates into the heat-conducting layer through the high-resistance layer. It is considered that the interface thermal resistance between the high-resistance layer and the heat-conducting layer will affect the actual heat dissipation performance of the heat diffusion sheet.
第2A圖及第2B圖為表示熱傳導的示意圖。電子零件H所產生的熱係朝白箭號所示之放熱方向4釋放。此時，若使用不存在明確的界面的本發明之石墨烯層合體時(參照第2A圖)，由於從含氧化石墨烯的層3至含石墨烯的層2，含氧比率連續地減少而不存在明確的界面，認為密接性優良而能夠從含氧化石墨烯的層3向含石墨烯的層2有效地傳熱。另一方面，存在界面時(參照第2B圖)，與不存在明確的界面的情形相比，認為無法有效地傳熱。 2A and 2B are schematic diagrams showing heat conduction. The heat generated by the electronic component H is released in the heat radiation direction 4 indicated by the white arrow. At this time, if the graphene laminate of the present invention is used without a clear interface (see FIG. 2A), since the graphene oxide-containing layer 3 to the graphene-containing layer 2 are continuously reduced, There is no clear interface, and it is considered that the adhesiveness is excellent and heat can be efficiently transferred from the graphene-containing layer 3 to the graphene-containing layer 2. On the other hand, when there is an interface (refer to FIG. 2B), it is considered that the heat cannot be efficiently transferred compared to the case where there is no clear interface.
藉由施加電場製作本發明之石墨烯層合體時，氧化石墨烯薄片係從陰極側進行還原反應。從陽極側 則注入電洞，亦即取出電子，而常時呈現氧化狀態，因此與陽極相接之面的氧化石墨烯未被還原，結果，若從氧化石墨烯薄片的兩面施加電場，除了具有高熱傳導性之含石墨烯的層之外，具有高電阻的氧化石墨烯層亦殘留，以一次的處理即可廉價地製造適於具有熱傳導層與高電阻層的熱擴散片之構成的石墨烯層合體。 When the graphene laminate of the present invention is produced by applying an electric field, the graphene oxide flakes undergo a reduction reaction from the cathode side. Holes are injected from the anode side, that is, electrons are taken out, and they are always in an oxidized state. Therefore, graphene oxide on the surface contacting the anode is not reduced. As a result, if an electric field is applied from both sides of the graphene oxide sheet, in addition to having a high In addition to the thermally conductive graphene-containing layer, a high-resistance graphene oxide layer remains, and a graphene layer suitable for the structure of a thermal diffusion sheet having a thermally conductive layer and a high-resistance layer can be manufactured inexpensively in one treatment. Fit.
《氧化石墨烯》 "Graphene oxide"
於本發明中，氧化石墨烯係指石墨烯經羧基、羰基、羥基及環氧基等含氧基修飾而成者。就本發明所使用的氧化石墨烯不特別限定，具有羧基、羰基、羥基或環氧基等含氧基之氧化石墨烯的含氧比率(原子%)較佳為24~50原子%的範圍內。若為24原子%以上，上述含氧基會以高於特定量的量鍵結而使π共軛被切斷，使氧化石墨烯的電阻增高而較佳。又，若為50原子%以下則可有效地促進還原反應而較佳。氧化石墨烯係以氧化石墨烯薄片形態使用。 In the present invention, graphene oxide means that graphene is modified by oxy groups such as carboxyl, carbonyl, hydroxyl, and epoxy groups. The graphene oxide used in the present invention is not particularly limited, and the oxygen-containing ratio (atomic%) of the oxygen-containing graphene oxide having a carboxyl group, a carbonyl group, a hydroxyl group, or an epoxy group is preferably in a range of 24 to 50 atomic%. . If it is 24 atomic% or more, the above-mentioned oxygen-containing group is bonded in an amount higher than a specific amount, and the π conjugate is cut off, and the resistance of graphene oxide is increased, which is preferable. Moreover, if it is 50 atomic% or less, it is effective in accelerating a reduction reaction, and it is preferable. Graphene oxide is used in the form of graphene oxide flakes.
<氧化石墨烯的面方向直徑> <Plane diameter of graphene oxide>
氧化石墨烯為藉由對石墨進行氧化處理，使構成石墨的石墨烯剝離、氧化而成的層狀粒子。此層狀粒子的面方向直徑愈大，以熱傳導性觀點而言愈佳。這是因為，由於薄片內部之層狀粒子間的界面為妨礙熱傳導的主因，層的面方向直徑愈大，則界面愈少，以熱傳導性觀點而言係較 佳。以高熱傳導性觀點而言，層的面方向直徑較佳為1μm以上，更佳為5μm以上，以氧化石墨烯溶媒分散體的分散狀態不會發生問題的範圍而言，再更佳為10μm以上。 Graphene oxide is a layered particle obtained by oxidizing graphite to peel and oxidize graphene constituting graphite. The larger the planar diameter of the layered particles, the better it is from the viewpoint of thermal conductivity. This is because the interface between the layered particles inside the sheet is the main cause of hindering heat conduction. The larger the diameter of the layer in the plane direction, the smaller the interface, which is better from the viewpoint of thermal conductivity. From the viewpoint of high thermal conductivity, the surface direction diameter of the layer is preferably 1 μm or more, more preferably 5 μm or more, and in a range in which the dispersion state of the graphene oxide solvent dispersion does not cause a problem, it is more preferably 10 μm or more. .
《氧化石墨烯薄片的還原》 《Reduction of Graphene Oxide Sheets》
氧化石墨烯薄片的還原係存在於氧化石墨烯中的含氧基以脫水或去氧的形式持續脫離的化學反應。因此，要有效率地引起化學反應，重要的是如何能夠將分子有效率地激發而使其呈高能量狀態。一般而言，要藉由熱產生足以使化學反應進行的激發分子，則需要數千度至一萬度以上的溫度；實際上，如前述，要將聚醯亞胺薄膜或氧化石墨烯薄片以熱方式轉換成石墨、石墨烯薄片，需要2000℃至3000℃附近的溫度。 The reduction of graphene oxide flakes is a chemical reaction in which the oxygen groups present in graphene oxide are continuously desorbed in the form of dehydration or deoxygenation. Therefore, in order to cause a chemical reaction efficiently, it is important how to efficiently excite the molecule to a high energy state. Generally speaking, to generate excited molecules sufficient for chemical reactions by heat, temperatures of thousands to 10,000 degrees or more are needed; in fact, as mentioned above, polyimide films or graphene oxide sheets need to be Thermal conversion to graphite and graphene flakes requires temperatures around 2000 ° C to 3000 ° C.
因此，作為有效率地形成激發態的技術之實例，可舉出施加電場時會發光的半導體元件、有機電致發光(有機EL)元件等。 Therefore, examples of a technique for efficiently forming an excited state include a semiconductor element that emits light when an electric field is applied, an organic electroluminescence (organic EL) element, and the like.
在有機EL元件中，藉由對層狀的元件施加電場，位於陽極側元件之最高佔有分子軌域(HOMO)能階的電子便朝陽極移動，而生成自由基陽離子。自由基陽離子係以相鄰電子埋覆陽離子的形式，以陽離子朝陰極側移動。另一方面，在陰極則電子注入至元件之最低未佔有分子軌域(LUMO)，生成自由基陰離子，持續朝陽極側跳躍移動。藉由移動之自由基陽離子與自由基陰離子再結合，便形成激發態。 In an organic EL device, by applying an electric field to a layered device, electrons located at the highest occupied molecular orbital (HOMO) level of the anode-side device move toward the anode to generate radical cations. Free radical cations move to the cathode side as cations buried in adjacent electrons. On the other hand, at the cathode, electrons are injected into the lowest unoccupied molecular orbital region (LUMO) of the device, generating radical anions, which continue to jump toward the anode side. By moving the free radical cation and free radical anion together, an excited state is formed.
此激發態，以僅數V即可使其生成，就作成激發態之手段而言可謂低能量。實際上，在有機EL元件中，係將由此激發態失活時所放出的能量以光形式利用；例如，白熾燈等係藉由對燈絲通電，至2000℃以上使其發熱，作成激發態而使其發光，相對於此，藉由自由基陽離子與自由基陰離子的再結合所致之激發態的生成可謂低能量。實際上，白熾燈與LED照明、有機EL照明的能量效率據稱有約10倍的差。 This excited state can be generated with only a few V, and it can be said to be low-energy in terms of the means to create the excited state. In fact, in the organic EL element, the energy released when the excited state is deactivated is used in the form of light; for example, incandescent lamps are heated by heating the filament above 2000 ° C. to form an excited state. To make it emit light, in contrast, the generation of an excited state by the recombination of a radical cation and a radical anion can be described as low energy. In fact, the energy efficiency of incandescent lamps, LED lighting, and organic EL lighting is said to be about 10 times worse.
於此，透過利用有機EL的機構與氧化石墨烯的特性，認為可能可使氧化石墨烯有效率地轉變為石墨烯。 Here, by utilizing the mechanism of the organic EL and the characteristics of graphene oxide, it is considered that it is possible to efficiently convert graphene oxide into graphene.
對石墨烯或石墨施加電場時，會與金屬材料同樣地遵守歐姆定律，僅電流流經電阻體，並無法有效率地形成分子的激發態。 When an electric field is applied to graphene or graphite, it obeys Ohm's law in the same way as metal materials. Only the current flows through the resistor and cannot form an excited state of the molecule efficiently.
另一方面，氧化石墨烯實際上作成薄片，若測定HOMO-LUMO能階，則HOMO能階測量為約5.7eV，由吸收光譜的解析LUMO能階推算為約3.1eV。再者，若以金屬電極包夾氧化石墨烯薄片，則電極與氧化石墨烯薄片6之能階的示意圖係如第3圖所示，透過以此構成施加電場，於氧化石墨烯內部形成由電荷再結合所產生的激發態，認為能有效率地使其轉變為石墨烯。 On the other hand, graphene oxide is actually made into a thin sheet. When the HOMO-LUMO energy level is measured, the HOMO energy level is measured to be about 5.7 eV, and the LUMO energy level analyzed from the absorption spectrum is estimated to be about 3.1 eV. In addition, if a graphene oxide sheet is sandwiched by a metal electrode, the schematic diagram of the energy levels of the electrode and the graphene oxide sheet 6 is shown in FIG. 3, and an electric field is applied through this structure to form a charge in the graphene oxide. Combined with the excited state generated, it is thought that it can be efficiently transformed into graphene.
以下更詳細地說明沿此氧化石墨烯薄片6的厚度方向施加電場而發生還原的推定機制。第4圖為表示在氧化石墨烯薄片6之陽極側生成電洞的示意圖。 In the following, the mechanism for estimating the reduction by applying an electric field in the thickness direction of the graphene oxide sheet 6 will be described in more detail. FIG. 4 is a schematic view showing generation of holes on the anode side of the graphene oxide sheet 6.
首先，若對氧化石墨烯薄片6施加電場，由於氧化石墨烯之HOMO與陽極的能階差B較小，而由陽極發生載子的注入。換言之，由氧化石墨烯向陽極注入電子。亦即，由陽極注入電洞(自由基陽離子)。 First, if an electric field is applied to the graphene oxide sheet 6, since the energy step difference B between the HOMO of the graphene oxide and the anode is small, carrier injection occurs from the anode. In other words, electrons are injected into the anode from graphene oxide. That is, holes (radical cations) are injected from the anode.
當陽極及陰極與氧化石墨烯的能階處於如第4圖之左圖的位置關係時，由於陰極與氧化石墨烯的LUMO能階差A，比陽極與氧化石墨烯之HOMO能階的差B更大，因此，認為在由電極(陰極)向LUMO能階發生電子注入前，自由基陽離子會持續擴散至陰極附近。 When the energy levels of the anode and cathode and graphene oxide are in the positional relationship as shown in the left figure of Figure 4, the difference between the LUMO energy level A of the cathode and graphene oxide is A, and the HOMO energy level difference B between the anode and graphene oxide is B. Larger, therefore, it is thought that free radical cations will continue to diffuse near the cathode before electron injection from the electrode (cathode) to the LUMO energy level.
在陽極側附近生成的自由基陽離子(電洞)，藉由從直流電源施加的電壓，於圖中持續由右方向(陽極側)向左方向(陰極側)移動(參照第5圖)。 The radical cations (holes) generated near the anode side continuously move from the right direction (anode side) to the left direction (cathode side) in the figure by a voltage applied from a DC power source (see FIG. 5).
理當在陰極，藉由施加高於電極(陰極)之能階與氧化石墨烯之LUMO的能階差的電壓，也會使電子注入至氧化石墨烯之陰極側的LUMO能階(參照第6圖)。 It should be at the cathode. By applying a voltage higher than the energy level difference between the energy level of the electrode (cathode) and the LUMO energy level of graphene oxide, electrons are also injected into the LUMO energy level of the cathode side of graphene oxide (see Figure 6). ).
此時，如先前所說明，由於連陰極附近亦存在有自由基陽離子，於此部位發生載子(自由基陰離子與自由基陽離子)的再結合，形成激發態，認為此激發態會持續有效率地向氧化石墨烯的還原反應使用(參照第7圖)。此外，於以下圖中為了簡化而省略混合層。 At this time, as previously explained, since there is also a radical cation near the cathode, a recombination of carriers (radical anions and radical cations) occurs at this position to form an excited state, and it is believed that this excited state will continue to be efficient It is used for the reduction of graphene oxide (see Figure 7). In addition, in the following figures, the hybrid layer is omitted for simplicity.
換言之，在具有如示意圖所示之能階的氧化石墨烯中，於陰極側首先發生載子再結合，形成激發態，由此氧化石墨烯被還原而形成石墨烯，茲認為形成含石墨 烯的層2與含氧化石墨烯的層3。 In other words, in graphene oxide having an energy level as shown in the schematic diagram, carriers first recombine on the cathode side to form an excited state, whereby graphene oxide is reduced to form graphene, and it is considered that graphene-containing Layer 2 and layer 3 containing graphene oxide.
如此，由陰極側持續形成石墨烯，惟，如前述，由於石墨烯為遵守歐姆定律的導電體，如第8圖所示含有通電而隨時間經過被還原的石墨烯之含石墨烯的層2作為電極，繼而使次一層反應，還原便持續朝陽極側進行。對於陰極側，導電性之含石墨烯的層2緩緩地增厚。 In this way, graphene is continuously formed on the cathode side. However, as described above, since graphene is an electrical conductor that complies with Ohm's law, as shown in FIG. 8, the graphene-containing layer 2 contains graphene that is reduced and passes with time as time passes. As an electrode, the next layer is reacted, and the reduction continues to the anode side. On the cathode side, the conductive graphene-containing layer 2 is gradually thickened.
此方式之特徵在於，即使施加電場，由於在陽極也會持續產出電子(持續由陽極注入電洞)，與陽極相接之含有氧化石墨烯的含氧化石墨烯的層3因而時常呈現氧化狀態，不會被還原成為石墨烯。換言之，與陽極相接的一側殘留有高電阻層，含有經還原之石墨烯的含石墨烯的層2、與含有未還原之氧化石墨烯的含氧化石墨烯的層3即形成於同一薄片。 This method is characterized in that even if an electric field is applied, since the anode will continue to produce electrons (the holes are continuously injected from the anode), the graphene oxide-containing graphene-containing layer 3 which is in contact with the anode often shows an oxidation state. , Will not be reduced to graphene. In other words, the high-resistance layer remains on the side that is in contact with the anode. The graphene-containing layer 2 containing reduced graphene and the graphene-oxide-containing layer 3 containing unreduced graphene are formed on the same sheet. .
利用此種藉由電荷再結合所致之激發能量的還原，其最大好處在於，由電極能階與氧化石墨烯之LUMO能階的電位差來看，頂多以數伏特至十數伏特左右便會進行還原；為了利用載子再結合方式，與如3000℃加熱之習知燃燒方式相比能以約10分之1左右的能量使用量加以製造。 The greatest advantage of using the reduction of excitation energy caused by charge recombination is that from the potential difference between the electrode energy level and the LUMO energy level of graphene oxide, it will be at most several volts to ten volts or so. The reduction is carried out; in order to use the carrier recombination method, it can be manufactured with an energy usage amount of about 1/10 compared with a conventional combustion method such as heating at 3000 ° C.
又，以此方式製作的石墨烯層合體，由其製法上的特異性，與陽極相接、或存在於陽極附近的氧化石墨烯層未被還原，因此，電阻較高的氧化石墨烯層可與熱傳導性較高的石墨烯層同時形成係屬先進者，而為劃時代的組成物。 In addition, the graphene laminate produced in this way has a graphene oxide layer that is in contact with the anode or that exists near the anode is not reduced due to its specificity in the manufacturing method. Therefore, a graphene oxide layer with a high resistance can be used. It is an epoch-making composition when it is formed simultaneously with a graphene layer having high thermal conductivity.
以往的石墨薄片等的熱擴散片，為了製作具有石墨結構或石墨烯結構的薄片狀組成物，而須對聚醯亞胺薄膜或氧化石墨烯薄片實施高溫熱處理，而且為使其具絕緣性，須於後續步驟中貼合樹脂薄膜等，而不需要此種耗費成本之操作於產業利用上亦屬理想者。 In order to produce a flake-like composition having a graphite structure or a graphene structure, a conventional thermal diffusion sheet such as a graphite sheet requires high-temperature heat treatment of a polyimide film or a graphene oxide sheet, and in order to make it insulating, Resin films and the like must be laminated in subsequent steps, and such costly operations are also ideal for industrial use.
<含石墨烯的層> <Graphene-containing layer>
藉由施加電場，可去除氧化石墨烯中的環氧基、羥基、羰基及羧基等含氧基，隨之，氧化石墨烯形成雙鍵、π共軛系統，而生成石墨烯結構。設想含氧基的去除係以去氧、脫水、或去羧的形式進行。茲將此種反應於本發明中稱為還原；將藉由施加電場進行還原反應，使氧化石墨烯還原所形成的層稱為含石墨烯的層。於本發明中，含石墨烯的層係指含氧比率(原子%)為15原子%以下的層。 By applying an electric field, the oxygen-containing groups such as epoxy groups, hydroxyl groups, carbonyl groups, and carboxyl groups in the graphene oxide can be removed. Then, the graphene oxide forms a double bond and a π-conjugated system to generate a graphene structure. It is envisaged that the oxygen-containing removal is performed in the form of deoxygenation, dehydration, or decarboxylation. Such a reaction is referred to as reduction in the present invention; a layer formed by reducing graphene oxide by applying a reduction reaction by applying an electric field is referred to as a graphene-containing layer. In the present invention, the graphene-containing layer means a layer having an oxygen content ratio (atomic%) of 15 atomic% or less.
此外，於本說明書中，含石墨烯的層係包含單層的石墨烯或2層以上100層以下的多層石墨烯。單層石墨烯係指具π鍵之單原子層的碳分子薄片。又，氧化石墨烯係指上述石墨烯經氧化的化合物。 In addition, in this specification, the graphene-containing layer system includes a single layer of graphene or a multilayer graphene of two or more layers and 100 or less layers. Single-layer graphene refers to a monoatomic layer of carbon molecular flakes with a π bond. The graphene oxide refers to a compound in which the graphene is oxidized.
又，將氧化石墨烯還原而形成石墨烯時，氧化石墨烯所含的氧並非全部脫離，而是一部分的氧殘留於石墨烯中。當石墨烯含有氧時，氧的比例，以XPS(X-ray Photoelectron Spectroscopy)測定時石墨烯層合體中的含氧比率為0.1~15原子%的範圍內，較佳為0.1~10原子%，更佳為0.1~3原子%以下的範圍內。含氧比率若為15原 子%以下，則高於廣用性較高之高熱傳導金屬的鋁的熱傳導率；若為10原子%以下，則高於廣用性較高之高熱傳導金屬當中熱傳導性最高的銅之性能；若為3原子%以下，則超過1000W/(m‧K)，能以低能量製作，而於產業上特別有價值。 When graphene oxide is reduced to form graphene, not all the oxygen contained in the graphene oxide is released, but a part of the oxygen remains in the graphene. When graphene contains oxygen, the oxygen ratio in the graphene laminate when measured by XPS (X-ray Photoelectron Spectroscopy) is in the range of 0.1 to 15 atomic%, preferably 0.1 to 10 atomic%. It is more preferably within a range of 0.1 to 3 atomic%. If the oxygen content is 15 atomic% or less, the thermal conductivity of aluminum is higher than that of high-heat-conducting metals with higher versatility; if it is 10 atomic% or less, the thermal conductivity is higher than that of high-heat-conducting metals with higher versatility The highest copper performance; if it is less than 3 atomic%, it exceeds 1000W / (m‧K), which can be produced with low energy, and is particularly valuable in the industry.
殘留於含石墨烯的層中的氧量可依施加之電壓、反應時間等來調整。施加之電壓較佳為2~15V的範圍內。含石墨烯的層係發揮作為良好的熱傳導層之機能。 The amount of oxygen remaining in the graphene-containing layer can be adjusted according to the applied voltage, reaction time, and the like. The applied voltage is preferably in the range of 2 to 15V. The graphene-containing layer system functions as a good heat conductive layer.
含石墨烯的層的厚度，基於熱輸送量觀點較佳為10μm以上。實際的熱擴散性能，由於係與熱傳導率及膜厚成正比，故較佳存在10μm以上之一定的厚度。基於近年來在智慧型手機或平板電腦用途中節省空間下的熱擴散用途觀點，較佳為60μm以下的薄膜。 The thickness of the graphene-containing layer is preferably 10 μm or more from the viewpoint of a heat transfer amount. The actual thermal diffusion performance is proportional to the thermal conductivity and film thickness, so it is preferable to have a certain thickness of 10 μm or more. From the viewpoint of thermal diffusion use in space-saving applications in smartphones and tablet computers in recent years, a film having a thickness of 60 μm or less is preferred.
<含氧化石墨烯的層> <Graphene oxide-containing layer>
含氧化石墨烯的層為含有因氧化石墨烯薄片的還原反應而殘留於陽極側之未還原的氧化石墨烯的層。於本發明中，含氧化石墨烯的層係指含氧比率(原子%)為24原子%以上的層。 The graphene oxide-containing layer is a layer containing unreduced graphene oxide remaining on the anode side due to the reduction reaction of the graphene oxide sheet. In the present invention, the graphene oxide-containing layer refers to a layer having an oxygen content ratio (atomic%) of 24 atomic% or more.
對氧化石墨烯薄片施加電壓來製作石墨烯層合體之際，在陽極側部分會殘留未必被還原的氧化石墨烯層。與能以施加低能量來製作石墨烯層合體的同時，形成高電阻的氧化石墨烯層，同時可使高電阻層於同一薄片內形成，以超過鋁(236W/(m‧K))或銅(401W/(m‧K))的性能之 高熱傳導，於同一層合體內包含高電阻層之構成於產業上有其價值，以1000W/(m‧K)以上之高熱傳導於同一層合體內包含高電阻層之構成，於產業上更有價值。 When a voltage is applied to a graphene oxide sheet to produce a graphene laminate, a graphene oxide layer that is not necessarily reduced remains on the anode side portion. At the same time that a low-energy graphene laminate can be made, a high-resistance graphene oxide layer can be formed, and a high-resistance layer can be formed in the same sheet to exceed aluminum (236W / (m‧K)) or copper. (401W / (m‧K)) high heat conduction performance, including the high-resistance layer in the same laminated body has industrial value, with a high heat conduction of 1000W / (m‧K) or more in the same laminated body Including the structure of high resistance layer is more valuable in the industry.
(高電阻層) (High resistance layer)
藉由在其中一面殘留高電阻之未還原的氧化石墨烯層，在與此層相接的面，不易發生電子零件的短路所引起的問題。 With the high-resistance unreduced graphene oxide layer remaining on one side, problems caused by short-circuiting of electronic components are less likely to occur on the side in contact with this layer.
理當可視用途而定進一步貼合絕緣層，此時，存在氧化石墨烯層，較能減薄絕緣層的厚度，而於產業上有其價值。 It is reasonable to further attach the insulation layer depending on the application. At this time, the existence of the graphene oxide layer can reduce the thickness of the insulation layer, and has industrial value.
<混合層> <Mixed layer>
混合層為具有從前述含氧化石墨烯的層側向前述含石墨烯的層側沿厚度方向含氧比率(原子%)連續地減少的濃度梯度之混合層。從未達24原子%至超過15原子%的區域為止連續地具有濃度梯度。透過具有此種濃度梯度，如前述，與含氧化石墨烯的層與含石墨烯的層具有界面的情形相比，界面熱阻減少，可使熱傳導性成為良好。 The mixed layer is a mixed layer having a concentration gradient in which the oxygen content ratio (atomic%) in the thickness direction continuously decreases from the graphene oxide-containing layer side to the graphene-containing layer side in the thickness direction. It has a concentration gradient continuously from a region from 24 atomic% to more than 15 atomic%. By having such a concentration gradient, as described above, compared with the case where the graphene oxide-containing layer and the graphene-containing layer have an interface, the thermal resistance at the interface is reduced, and the thermal conductivity can be improved.
其斜率較佳為以按每0.1μm，含氧比率為0.15~25.0原子%的範圍內之減少率，從含氧比率為24~50原子%的含氧化石墨烯的層之區域至含氧比率為0.1~15原子%的含石墨烯的層之區域為止連續地減少的區域。此斜率可例如由從石墨烯層合體之含氧化石墨烯的層，視需求按 每0.1μm厚持續剝離時之含氧比率(原子%)的測定來求得。 The slope is preferably a reduction rate in the range of 0.15 to 25.0 atomic% per 0.1 μm, from the region of the graphene oxide-containing layer having an oxygen content of 24 to 50 atomic% to the oxygen content. It is a region continuously decreasing up to the region of the graphene-containing layer of 0.1 to 15 atomic%. This slope can be obtained, for example, from the graphene oxide-containing layer of the graphene laminate by measuring the oxygen content ratio (atomic%) at the time of continuous peeling per 0.1 m thickness as required.
混合層的厚度較佳為0.2~5μm的範圍內。 The thickness of the mixed layer is preferably in a range of 0.2 to 5 μm.
藉由施加電壓而製作之石墨烯薄片的厚度方向的含氧比率(原子%)之分布可藉由將石墨烯薄片用膠帶持續撕裂、剝離，隨時以XPS測量含氧比率與此時的厚度而明瞭。根據電壓或施加時間，雖有濃度梯度差，但氧化石墨烯之經還原的層、與未還原的層並未明確地有界線，而緩緩地變化。依此狀態，電子零件的發熱朝厚度方向傳遞時的界面熱阻較少，認為放熱性優良的材料。 The distribution of the oxygen content ratio (atomic%) in the thickness direction of the graphene sheet produced by applying a voltage can be continued by tearing and peeling off the graphene sheet with an adhesive tape. Be clear. Although there is a difference in concentration gradient depending on the voltage or the application time, the reduced layer and the unreduced layer of graphene oxide do not have a clear boundary line, but change slowly. In this state, the interface thermal resistance when the heat of the electronic component is transmitted in the thickness direction is small, and the material is considered to be excellent in heat release.
含氧比率的測定可如以下方式進行。 The measurement of the oxygen content ratio can be performed as follows.
<含氧比率與各層之厚度的測定> <Measurement of oxygen content ratio and thickness of each layer>
石墨烯層合體的含氧比率(原子%)為可藉由X-ray Photoelectron Spectroscopy(下稱XPS)來測定，以O/(C+O)原子%表示的值。本發明之實施例所使用之氧化石墨烯的含氧比率為約24、50原子%，惟亦可視用途，而於分散狀態不會發生問題的範圍內改變氧化反應的條件，而調整含氧比率。 The oxygen content ratio (atomic%) of the graphene laminate is a value that can be measured by X-ray Photoelectron Spectroscopy (hereinafter referred to as XPS) and is expressed as O / (C + O) atomic%. The oxygen content of the graphene oxide used in the examples of the present invention is about 24, 50 atomic%, but depending on the application, the conditions of the oxidation reaction can be changed within the range where no problem occurs in the dispersed state, and the oxygen content can be adjusted. .
可透過使用膠帶，從陽極側按每1μm厚持續剝離，隨時以XPS測量含氧比率與此時的厚度，而由以厚度為橫軸、含氧比率為縱軸之含氧比率(原子%)的XPS曲線來讀取之。又，可按每0.1μm予以剝離，並隨時測定含氧比率，而正確地求出混合層的厚度。 Through the use of adhesive tape, it can be continuously peeled from the anode side every 1 μm thickness, and the oxygen content ratio and the thickness at this time can be measured by XPS at any time. XPS curve to read it. The thickness of the mixed layer can be accurately determined by peeling it off every 0.1 μm and measuring the oxygen content ratio at any time.
具體而言，含氧化石墨烯的層的含氧比率可藉由從陽極按每1μm剝離時，由含氧比率達24%為止的厚度、與迄此之含氧比率的算術平均值來算出。 Specifically, the oxygen content ratio of the graphene oxide-containing layer can be calculated from the thickness at which the oxygen content ratio reaches 24% when peeled from the anode per 1 μm, and the arithmetic average value of the oxygen content ratio thus far.
含石墨烯的層亦同樣地可藉由按每1μm剝離時，含氧比率減少至15%後，達到與陰極相接的面為止的厚度來求得。 Similarly, the graphene-containing layer can also be obtained by reducing the thickness of the graphene-containing layer to 15% after peeling it at 1 μm, and then reaching the thickness of the surface contacting the cathode.
混合層可作為如上述方式所測得之含氧化石墨烯的層與含石墨烯的層之中間層來求出其厚度。 The thickness of the mixed layer can be determined as the intermediate layer between the graphene oxide-containing layer and the graphene-containing layer measured as described above.
於本發明中，各層的含氧比率係設為如上述方式求得之每1μm的含氧比率的算術平均值。當層的厚度為2μm以下時，含氧比率可基於按每0.1μm持續剝離時測定藉由XPS所得之含氧比率(原子%)的數據來求出層的含氧比率。 In the present invention, the oxygen content ratio of each layer is the arithmetic average value of the oxygen content ratio per 1 μm obtained as described above. When the thickness of the layer is 2 μm or less, the oxygen content ratio of the layer can be determined based on the data of the oxygen content ratio (atomic%) obtained by XPS when the peeling is continued per 0.1 μm.
<電極> <Electrode>
作為電極，較佳使用以金屬、合金、導電性化合物及此等之混合物為電極物質者。作為此類電極物質之具體例，可舉出銅、鋁、銀、鉑、金、鐵、鎂等金屬、不鏽鋼、黃銅等合金、石墨等的碳材料、或銦錫氧化物等的無機半導體材料等。 As the electrode, a metal, an alloy, a conductive compound, and a mixture of these are preferably used as the electrode substance. Specific examples of such an electrode substance include metals such as copper, aluminum, silver, platinum, gold, iron, magnesium, alloys such as stainless steel, brass, carbon materials such as graphite, and inorganic semiconductors such as indium tin oxide. Materials, etc.
《石墨烯層合體的物性》 "Physical Properties of Graphene Laminates"
<熱傳導率> <Thermal conductivity>
作為表示放熱性能的物理量，有熱傳導率。熱傳導率 (W/(m‧K))係以熱擴散率(m2/s)、比熱容量(J/kg‧K)、密度(kg/m3)的積表示。藉由分別測定熱擴散率、比熱容量、密度，可算出熱傳導率。 As a physical quantity showing heat release performance, there is a thermal conductivity. Thermal conductivity (W / (m‧K)) is expressed as the product of thermal diffusivity (m 2 / s), specific heat capacity (J / kg‧K), and density (kg / m 3 ). By measuring the thermal diffusivity, specific heat capacity, and density separately, the thermal conductivity can be calculated.
<放熱性能> <Exothermic performance>
具高熱傳導率之廣用性的金屬的性能，係鋁在300K的溫度下為236W/(m‧K)、銅為401W/(m‧K)。因此，只要具有超過鋁或銅的熱傳導率，並且可廉價地製作，則於產業上有其價值。再者，為了提供具有1000W/(m‧K)以上之熱傳導率的構件，現況在於僅能藉由約3000℃附近的燒結來製作石墨薄片；而本發明之能以低能量製作，且具有1000W/(m‧K)以上之熱傳導率的構件於產業上特別有價值。 The properties of widely used metals with high thermal conductivity are 236W / (m‧K) for aluminum at 300K and 401W / (m‧K) for copper. Therefore, as long as it has a thermal conductivity higher than that of aluminum or copper and can be produced inexpensively, it has industrial value. Furthermore, in order to provide a member having a thermal conductivity of more than 1000 W / (m‧K), the current situation is that graphite flakes can be made only by sintering at about 3000 ° C; and the present invention can be made with low energy and has 1000 W Components with a thermal conductivity above / (m‧K) are particularly valuable in the industry.
<熱擴散片性能> <Heat diffusion sheet performance>
於各電子零件中，對於作動時的最高發熱量，存在有用來避免電子零件故障的應放熱之熱量。按每單位長度有1℃的溫度梯度時，熱傳導率為通過單位剖面積的熱量，因此，薄片的面積若為一定，則實際上輸送的熱量與熱傳導率及厚度成正比。藉由調整含石墨烯的層的熱傳導率與厚度，可進行用來避免電子零件故障的適當放熱。 In each electronic component, there is a heat quantity that should be radiated to avoid the failure of the electronic component with respect to the maximum heat generation amount during operation. When there is a temperature gradient of 1 ° C per unit length, the thermal conductivity is the amount of heat passing through the unit cross-sectional area. Therefore, if the area of the sheet is constant, the actual heat transferred is directly proportional to the thermal conductivity and thickness. By adjusting the thermal conductivity and thickness of the graphene-containing layer, appropriate heat release can be performed to avoid failure of electronic parts.
《製造方法》 "Production method"
製造本發明之石墨烯層合體的石墨烯層合體之製造方 法，其特徵為藉由從氧化石墨烯薄片的兩面施加電壓，而於該氧化石墨烯薄片的厚度方向，將氧化石墨烯部分地還原，而形成由含石墨烯的層、石墨烯與氧化石墨烯的混合層、及含氧化石墨烯的層所構成之層合體，而且，該混合層係控制成具有從前述含氧化石墨烯的層側向前述含石墨烯的層側沿厚度方向含氧比率(原子%)連續地減少的濃度梯度。 The method for producing a graphene laminate of the graphene laminate of the present invention is characterized in that by applying a voltage from both sides of the graphene oxide sheet, the graphene oxide sheet is partially reduced in its thickness direction. A layered body composed of a graphene-containing layer, a mixed layer of graphene and graphene oxide, and a graphene oxide-containing layer is formed, and the mixed layer system is controlled to have a layer from the aforementioned graphene oxide-containing layer. A concentration gradient in which the oxygen content ratio (atomic%) in the thickness direction continuously decreases laterally to the aforementioned graphene-containing layer side.
<氧化石墨烯溶媒分散體> <Graphene oxide solvent dispersion>
氧化石墨烯可藉由將石墨、或多層石墨烯以強氧化劑氧化，在石墨烯粒子的面上或邊緣賦予環氧基、羥基、羰基及羧基等含氧基，而使其具有製作薄片所需的溶媒分散性。氧化石墨烯溶媒分散物能以Hummers法、或將其改良之Modified Hummers法，基於周知文獻來製作。就溶媒而言，基於氧化石墨烯的分散性觀點，水為最廣用者；而關於氧化石墨烯的凝聚、或製作之薄片的膜質，亦可於不發生問題的範圍內使用有機溶媒。作為製作氧化石墨烯之周知文獻，可舉出例如W.S.Hummers.,Journal of American Chemistry(1958)1339、M.Hirata.,Carbon 42(2004)2929等。 Graphene oxide can be used to oxidize graphite or multi-layer graphene with a strong oxidizing agent to give epoxy groups, hydroxyl groups, carbonyl groups, and carboxyl groups to the surface or edges of graphene particles, so that it has the necessary flakes. Solvent dispersibility. The graphene oxide vehicle dispersion can be produced based on a well-known literature by the Hummers method or a modified Hummers method. In terms of solvents, from the viewpoint of graphene oxide's dispersibility, water is the most widely used. Regarding the aggregation of graphene oxide or the film quality of the thin films produced, organic solvents can also be used within the range where no problems occur. Examples of well-known documents for preparing graphene oxide include W.S. Hummers., Journal of American Chemistry (1958) 1339, M. Hirata., Carbon 42 (2004) 2929, and the like.
<氧化石墨烯薄片的製作> <Production of Graphene Oxide Sheet>
氧化石墨烯薄片可藉由塗佈氧化石墨烯溶媒分散體成某一定的厚度，並使溶媒乾燥來製作。只要可塗佈成一定 的厚度並使其乾燥，則可於膜質不發生問題的範圍內採用任何塗佈方法。例如，除本發明之實施例中的澆鑄製膜外，尚有過濾製膜、浸漬塗佈、旋轉塗佈、噴霧塗佈等。又，氧化石墨烯薄片可藉由塗佈於玻璃基板或樹脂基材而予以剝離。在可剝離氧化石墨烯薄片的範圍內，基板或基材可使用任何材料。 Graphene oxide flakes can be produced by coating a graphene oxide solvent dispersion to a certain thickness and drying the solvent. As long as it can be applied to a certain thickness and allowed to dry, any coating method can be used as long as there is no problem with the film quality. For example, in addition to the casting film formation in the embodiment of the present invention, there are also filtration film formation, dip coating, spin coating, spray coating, and the like. In addition, the graphene oxide sheet can be peeled off by being coated on a glass substrate or a resin substrate. Any material can be used for the substrate or the substrate within the range of the peelable graphene oxide sheet.
氧化石墨烯薄片的厚度，基於保持供耐受從基板剝離時所產生之張力的強度觀點，較佳為10μm以上。又，藉由增加氧化石墨烯溶媒分散體的濃度、或製膜時之氧化石墨烯溶媒分散體的厚度，可增大氧化石墨烯薄片的厚度；基於提高濃度所引起之氧化石墨烯的凝聚、或薄片之膜面的平滑性的觀點，通常較佳為100μm以下的範圍內。又，氧化石墨烯薄片中之氧化石墨烯的含量較佳為80~100質量%。較佳的是氧化石墨烯薄片僅由氧化石墨烯所構成。 The thickness of the graphene oxide sheet is preferably 10 μm or more from the viewpoint of maintaining the strength to withstand the tension generated when peeling from the substrate. In addition, by increasing the concentration of the graphene oxide solvent dispersion or the thickness of the graphene oxide solvent dispersion at the time of film formation, the thickness of the graphene oxide sheet can be increased; Or from the viewpoint of the smoothness of the film surface of the sheet, it is usually preferably within a range of 100 μm or less. The content of graphene oxide in the graphene oxide sheet is preferably 80 to 100% by mass. It is preferred that the graphene oxide sheet is composed of graphene oxide only.
<添加物> <Additives>
以進一步降低還原反應的活化能為目的，亦可將周知之還原劑添加於氧化石墨烯薄片中。可舉出例如周知文獻(C.K.Chua.,Chemical Society Reviews 43(2014)291)所記載的還原劑等。添加物可例如藉由在氧化石墨烯溶媒分散體之階段摻混並製作成膜，而添加於氧化石墨烯薄片中。又，亦可於分散狀態不發生問題的範圍內，對氧化石墨烯溶媒分散體添加還原劑，並藉由攪拌、適當地 加熱、調整反應時間，而以分散體之狀態調整氧化石墨烯的含氧比率。 For the purpose of further reducing the activation energy of the reduction reaction, a known reducing agent may be added to the graphene oxide sheet. Examples thereof include a reducing agent described in a well-known document (C.K. Chua., Chemical Society Reviews 43 (2014) 291). The additive can be added to the graphene oxide sheet by blending and forming a film at the stage of the graphene oxide solvent dispersion, for example. In addition, it is also possible to add a reducing agent to the graphene oxide solvent dispersion within a range where no problem occurs in the dispersed state, and adjust the content of the graphene oxide in the state of the dispersion by stirring, appropriately heating, and adjusting the reaction time. Oxygen ratio.
<施加電場> <Applied electric field>
藉由對剝離之氧化石墨烯薄片以電極包夾其兩面，可對膜全體施加電場。只要可沿膜壓方向以電極予以包夾，則電極可為任何形態。例如，可單純以金屬板予以包夾而施加電場，亦可準備二個滾筒狀電極，將薄片壓接於滾筒電極間，一邊運送一邊施加電場。又，電極除金屬或合金外，亦可為ITO等無機氧化物、碳材料等，只要石墨烯化不發生問題，則可使用任何電極材料。 An electric field can be applied to the entire film by sandwiching both surfaces of the peeled graphene oxide sheet with electrodes. As long as the electrodes can be sandwiched along the film pressing direction, the electrodes can be in any shape. For example, an electric field may be applied simply by sandwiching a metal plate, or two roll-shaped electrodes may be prepared, and a sheet may be crimped between the roll electrodes, and an electric field may be applied while being conveyed. In addition, the electrode may be an inorganic oxide such as ITO, a carbon material, etc. in addition to a metal or an alloy, and any electrode material may be used as long as grapheneization does not cause a problem.
《用途》 "Use"
本發明之石墨烯層合體，僅以低能量、施加電場1次即具有高熱傳導層與高電阻層，而且高熱傳導層與高電阻層的界線非為明確的界面而是具有濃度梯度，故可有效地傳導由電子零件等所產生的熱。又，可廉價地製造，而能夠較佳地適用於熱擴散片。 The graphene laminate of the present invention has a high heat conduction layer and a high resistance layer only with low energy and once applied an electric field, and the boundary between the high heat conduction layer and the high resistance layer is not a clear interface but has a concentration gradient, so it can be Effectively conducts heat generated by electronic parts and the like. In addition, it can be manufactured at low cost, and can be suitably used for a heat diffusion sheet.
以下，舉出實施例對本發明具體地加以說明，惟本發明非限定於此等。 Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited thereto.
〔實施例1〕 [Example 1]
《石墨烯層合體的製作》 "Production of Graphene Laminates"
〈石墨烯層合體1的製作〉 <Production of Graphene Laminate 1>
(氧化石墨烯水分散體1的調製) (Preparation of graphene oxide aqueous dispersion 1)
將東京化成工業(股)之石墨烯奈米薄板(厚度6~8nm、寬5μm)10g、硝酸鈉7.5g裝入燒瓶中，對其添加濃硫酸621g。將燒瓶浸漬於冰浴中，一邊攪拌，以溶液溫度不超過20℃的方式逐次少量添加過錳酸鉀45g。其後，回升至室溫，攪拌5天後，對其添加1L的5質量%硫酸並攪拌1小時。進而，對其添加30質量%的過氧化氫水30g，攪拌1小時。添加硫酸的濃度調整成3質量%、過氧化氫水的濃度調整成0.5質量%的混合溶液1L加以稀釋。將此溶液進行離心分離(5000rpm、15分鐘)，去除上澄液，添加同樣的混合溶液，重複進行離心分離10次。以純水進行同樣的離心分離10次，於第10次捨棄上澄液後，添加250mL的純水而製成氧化石墨烯水分散體1。 10 g of graphene nano sheet (thickness 6-8 nm, width 5 μm) and 7.5 g of sodium nitrate from Tokyo Chemical Industry Co., Ltd. were charged into the flask, and 621 g of concentrated sulfuric acid was added thereto. The flask was immersed in an ice bath, and while stirring, 45 g of potassium permanganate was successively added so that the solution temperature did not exceed 20 ° C. Thereafter, the temperature was returned to room temperature, and after stirring for 5 days, 1 L of 5 mass% sulfuric acid was added thereto, followed by stirring for 1 hour. Furthermore, 30 g of 30 mass% hydrogen peroxide water was added to this, and it stirred for 1 hour. The mixed solution was adjusted to have a concentration of 3% by mass and the concentration of hydrogen peroxide water was adjusted to 0.5% by mass to dilute 1 L of the mixed solution. This solution was centrifuged (5000 rpm, 15 minutes), the supernatant liquid was removed, the same mixed solution was added, and centrifugation was repeated 10 times. The same centrifugation was performed 10 times with pure water, and the supernatant was discarded at the 10th time, and then 250 mL of pure water was added to prepare a graphene oxide aqueous dispersion 1.
(氧化石墨烯水分散體2的調製) (Preparation of graphene oxide aqueous dispersion 2)
除添加過錳酸鉀後攪拌14天以外，係與氧化石墨烯水分散體1同樣地製作。 The system was produced in the same manner as in the graphene oxide aqueous dispersion 1 except that potassium permanganate was added and stirred for 14 days.
(氧化石墨烯薄片的製作) (Production of graphene oxide sheet)
將4g的氧化石墨烯水分散體1以調整成0.75mm之間隙的塗佈器塗佈於黏貼於玻璃基板的25μm之PET(聚對苯二甲酸乙二酯)薄膜上。於50℃使其乾燥10小時後，由PET 薄膜剝離，而得到厚度20.7μm的氧化石墨烯薄片。 4 g of the graphene oxide aqueous dispersion 1 was applied to a 25 μm PET (polyethylene terephthalate) film adhered to a glass substrate with an applicator adjusted to a gap of 0.75 mm. After drying at 50 ° C. for 10 hours, the PET film was peeled off to obtain a graphene oxide sheet having a thickness of 20.7 μm.
(氧化石墨烯薄片的部分還原) (Partial reduction of graphene oxide flakes)
以2片100μm銅箔板包夾此氧化石墨烯薄片，一邊用壓機施予10MPa的壓力，一邊在2片銅箔板間施加12V的電壓1小時，而製成石墨烯層合體1。 This graphene oxide sheet was sandwiched between two 100 μm copper foil plates, and a pressure of 10 MPa was applied with a press, and a voltage of 12 V was applied between the two copper foil plates for 1 hour to prepare a graphene laminate 1.
〈石墨烯層合體2~8的製作〉 <Production of Graphene Laminates 2 to 8>
除變更表1所記載之電壓與施加時間以外，係與石墨烯層合體1同樣地製作，而得到石墨烯層合體2~8。 Except that the voltage and application time described in Table 1 were changed, it was produced in the same manner as the graphene laminate 1 to obtain graphene laminates 2 to 8.
〈石墨烯層合體9~16的製作〉 <Production of Graphene Laminates 9-16>
除將塗佈氧化石墨烯水分散體1時之塗佈器的間隙變更為1.5mm，並將電壓、施加時間變更為表1所記載之條件以外係與石墨烯層合體1同樣地製作，而得到石墨烯層合體9~16。 Except that the gap of the applicator when applying the graphene oxide aqueous dispersion 1 was changed to 1.5 mm, and the voltage and application time were changed to the conditions described in Table 1, it was produced in the same manner as the graphene laminate 1 and Graphene laminates 9 to 16 were obtained.
〈石墨烯層合體17~24的製作〉 <Production of Graphene Laminates 17-24>
除將塗佈氧化石墨烯水分散體1時之塗佈器的間隙變更為2.25mm，並將電壓、施加時間變更為表1所記載之條件以外係與石墨烯層合體1同樣地製作，而得到石墨烯層合體17~24。 Except that the gap of the applicator when applying the graphene oxide aqueous dispersion 1 was changed to 2.25 mm, and the voltage and application time were changed to the conditions described in Table 1, it was produced in the same manner as the graphene laminate 1 and Graphene laminates 17 to 24 were obtained.
〈石墨烯層合體25~32的製作〉 <Production of Graphene Laminates 25 to 32>
除使用氧化石墨烯水分散體2，並將電壓、施加時間變更為表2所記載之條件以外係與石墨烯層合體1同樣地製作，而得到石墨烯層合體25~32。 Except that the graphene oxide aqueous dispersion 2 was used and the voltage and application time were changed to the conditions described in Table 2, it was produced in the same manner as the graphene laminate 1 to obtain graphene laminates 25 to 32.
〈石墨烯層合體33~40的製作〉 <Production of graphene laminates 33 to 40>
除使用氧化石墨烯水分散體2，將塗佈氧化石墨烯水分散體2時之塗佈器的間隙變更為1.5mm，並將電壓、施加時間變更為表2所記載之條件以外係與石墨烯層合體1同樣地製作，而得到石墨烯層合體33~40。 Except that the graphene oxide aqueous dispersion 2 was used, the gap between the applicator when applying the graphene oxide aqueous dispersion 2 was changed to 1.5 mm, and the voltage and application time were changed to the conditions described in Table 2. The olefin layered product 1 was produced in the same manner, and graphene layered products 33 to 40 were obtained.
〈石墨烯層合體41~48的製作〉 <Production of Graphene Laminates 41 to 48>
除使用氧化石墨烯水分散體2，將塗佈氧化石墨烯水分散體2時之塗佈器的間隙變更為2.25mm，並將電壓、施加時間變更為表2所記載之條件以外係與石墨烯層合體1同樣地製作，而得到石墨烯層合體41~48。 Except that the graphene oxide aqueous dispersion 2 was used, the gap between the applicator when applying the graphene oxide aqueous dispersion 2 was changed to 2.25 mm, and the voltage and application time were changed to the conditions described in Table 2. The olefin layered product 1 was produced in the same manner, and graphene layered products 41 to 48 were obtained.
〈石墨烯層合體的含氧比率(原子%)的測定〉 <Measurement of the oxygen content ratio (atomic%) of the graphene laminate>
依以下所述方法測定所得石墨烯層合體1之含石墨烯的層的含氧比率(原子%)的結果，含氧比率由24.6原子%減少至1.2原子%，確認進行還原。又，以XPS同樣地測定含氧化石墨烯的層的結果，含氧比率為24.7原子%而確認未進行還原。 As a result of measuring the oxygen content ratio (atomic%) of the graphene-containing layer of the obtained graphene laminate 1 by the method described below, the oxygen content ratio was reduced from 24.6 atomic% to 1.2 atomic%, and reduction was confirmed. In addition, when the graphene oxide-containing layer was measured in the same manner as XPS, the oxygen content ratio was 24.7 atomic%, and it was confirmed that the reduction was not performed.
將石墨烯層合體1藉由膠帶(3M，Scotch膠帶)，從與陽極相接的面按每1μm持續撕裂、剝離，以 XPS進行測定，求出含氧比率達24.0%為止的厚度，將其作為含氧化石墨烯的層的厚度。同樣地進行撕裂、剝離，將含氧比率減少至15%後，達到與陰極相接的面為止的厚度作為含石墨烯的層。又，由各自之每1μm之XPS測定值的含氧比率的算術平均值求出含氧化石墨烯的層及含石墨烯的層的含氧比率。 The graphene laminate 1 was continuously torn and peeled at 1 μm from the surface in contact with the anode with a tape (3M, Scotch tape), and measured by XPS to determine the thickness until the oxygen content ratio reached 24.0%. It serves as the thickness of the graphene oxide-containing layer. Tearing and peeling were performed in the same manner, and after reducing the oxygen content ratio to 15%, the thickness until the surface contacting the cathode was used as the graphene-containing layer. The oxygen content ratios of the graphene oxide-containing layer and the graphene-containing layer were calculated from the arithmetic average of the oxygen content ratios of the XPS measurement values per 1 μm.
當層的厚度為2μm以下時，含氧比率係基於按每0.1μm持續剝離時藉由XPS測定含氧比率(原子%)所得的數據來求出層的含氧比率。 When the thickness of the layer is 2 μm or less, the oxygen content ratio of the layer is determined based on data obtained by measuring the oxygen content ratio (atomic%) by XPS when the peeling is continued per 0.1 μm.
又，在混合層、與含石墨烯的層或含氧化石墨烯的層的邊界部分，按每0.1μm持續剝離時藉由XPS持續測定含氧比率(原子%)，來測定各層的厚度。 In addition, the thickness of each layer was measured by continuously measuring the oxygen content ratio (atomic%) by XPS at the time of continuous peeling per 0.1 μm at the boundary portion of the mixed layer, the graphene-containing layer, or the graphene-oxide-containing layer.
對石墨烯層合體2~48同樣地予以撕裂、剝離，在表1及表2所記載之混合層各者的整個厚度範圍，確認由含氧化石墨烯的層的含氧比率減少至含石墨烯的層的含氧比率。 The graphene laminates 2 to 48 were similarly torn and peeled, and it was confirmed that the oxygen content ratio of the graphene oxide-containing layer was reduced to graphite in the entire thickness range of each of the mixed layers described in Tables 1 and 2. Oxygen ratio of the ene layer.
又，XPS測定條件如下。 The XPS measurement conditions are as follows.
使用ULVAC-PHI股份有限公司製QuanteraSXM來進行測定。就測定條件，作為X射線源係使用經單色化之Al-Kα射線，分光器係以如測定經清潔過的銀之Ag3d5/2峰時的峰半高寬為0.5eV以下之條件設定，來進行測定。分光器的校正係依循ISO15472來進行。 The measurement was performed using QuanteraSXM manufactured by ULVAC-PHI Co., Ltd. Regarding the measurement conditions, monochromatic Al-Kα rays were used as the X-ray source, and the spectroscope was such that the peak full width at half maximum when the Ag 3 d 5/2 peak of the cleaned silver was measured was 0.5 eV or less. The conditions are set for measurement. The calibration of the spectroscope is performed in accordance with ISO15472.
〈表面電阻率的測定〉 <Measurement of surface resistivity>
將石墨烯層合體1~48在23℃相對濕度55%的環境下靜置24小時後，以電阻率計測器(Mitsubishi Chemical Analytech公司製，Hiresta-UP MCP-HT450)測定含氧化石墨烯的層側的表面電阻率。將其結果示於表1及表2。就石墨烯層合體1~48，確認殘留高電阻層。 After the graphene laminates 1 to 48 were allowed to stand in an environment of 23 ° C and 55% relative humidity for 24 hours, the resistivity meter (Mitsubishi Chemical Analytech, Hiresta-UP MCP-HT450) was used to measure the graphene-containing layer. Surface resistivity on the side. The results are shown in Tables 1 and 2. Regarding the graphene laminates 1 to 48, it was confirmed that a high-resistance layer remained.
〈熱傳導率的測定〉 <Measurement of thermal conductivity>
在上述製作之石墨烯層合體1~48，將含氧化石墨烯的層、混合層以膠帶持續剝離、去除，並測定石墨烯層的熱傳導率。如前述，熱傳導率係以下式表示，可藉由分別測定熱擴散率、比熱容量、密度而算出。 In the graphene laminates 1 to 48 prepared as described above, the graphene oxide-containing layer and the mixed layer were continuously peeled and removed with an adhesive tape, and the thermal conductivity of the graphene layer was measured. As described above, the thermal conductivity is expressed by the following formula, and can be calculated by measuring the thermal diffusivity, specific heat capacity, and density, respectively.
熱傳導率=熱擴散率×比熱容量×密度 Thermal conductivity = thermal diffusivity × specific heat capacity × density
熱擴散率係以ADVANCE RIKO(股)之Laser Pit，比熱容量係以示差掃描式熱量計(DSC6220：Hitachi High-Technologies(股)製)，密度係測定薄片的質量與體積，算出溫度23℃下的熱傳導率。 The thermal diffusivity is based on Laser Pit of ADVANCE RIKO, and the specific heat capacity is based on a differential scanning calorimeter (DSC6220: Hitachi High-Technologies). The density is based on the mass and volume of the sheet. Thermal conductivity.
〈厚度的測定〉 <Measurement of thickness>
層的厚度係以Nikon公司製DIGIMICRO MH-15M測定。 The thickness of the layer was measured with DIGIMICRO MH-15M manufactured by Nikon Corporation.
將以上之結果示於表1及表2。 The above results are shown in Tables 1 and 2.
〔實施例2〕 [Example 2]
〈比較層合體1~48的製作〉 〈Comparative production of laminated bodies 1 ~ 48〉
將石墨烯層合體1~48分別以膠帶持續剝離，去除含氧化石墨烯的層、混合層，對剩餘之含石墨烯的層，將氧化石墨烯水分散體以表3所記載之倍率稀釋，將塗佈器的間隙設為0.75mm而進行塗佈，於50℃使其乾燥10小時，而設置與本發明之各石墨烯層合體1~48之含氧化石墨烯的層相同厚度的含氧化石墨烯的層。將此層合體作為比較層合體1~48。此外，比較層合體1~24的製作係使用氧化石墨烯水分散體1；比較層合體25~48則是使用氧化石墨烯水分散體2。 The graphene laminates 1 to 48 were continuously peeled off with adhesive tape to remove the graphene oxide-containing layer and the mixed layer. For the remaining graphene-containing layers, the graphene oxide aqueous dispersion was diluted at the rates listed in Table 3. The gap of the applicator was set to 0.75 mm, and the coating was dried at 50 ° C for 10 hours. An oxidation-containing layer having the same thickness as the graphene-oxide-containing layer of each of the graphene laminates 1 to 48 of the present invention was provided. Graphene layer. This laminated body was made into comparative laminated bodies 1-48. In addition, the production of the comparative laminates 1 to 24 uses the graphene oxide aqueous dispersion 1; the comparative laminates 25 to 48 use the graphene oxide aqueous dispersion 2.
〈熱擴散性的評定〉 <Evaluation of thermal diffusivity>
其次，如下評定本發明之石墨烯層合體的熱擴散性。將石墨烯層合體1~48切成長1cm、寬3cm，在試片一端長1cm、寬1cm之區域，將含氧化石墨烯的層側的面經由熱傳導片(Taica(股)，αGEL，COH-4000LVC，1mm)黏貼於加熱板。使加熱板昇溫至80℃，1分鐘後，對試片之與加熱器相接的區域之相反側的另一端長1cm、寬1cm之區域的中心部，由含石墨烯的層側，利用非接觸溫度計測定溫度，來評定本發明之石墨烯層合體1~48的熱擴散性。又，與上述同樣地評定比較層合體1~48的熱擴散性。 Next, the thermal diffusivity of the graphene laminate of the present invention was evaluated as follows. The graphene laminate was cut from 1 to 48 cm long and 3 cm wide. In the area of 1 cm long and 1 cm wide at one end of the test piece, the surface on the side of the graphene oxide-containing layer was passed through a thermally conductive sheet (Taica, αGEL, COH- 4000LVC, 1mm) adhered to the heating plate. The heating plate was heated to 80 ° C. After 1 minute, the other end of the test piece opposite to the area where the heater was in contact with the heater was 1cm in length and 1cm in width from the center of the graphene-containing layer side. The temperature was measured with a contact thermometer to evaluate the thermal diffusivity of the graphene laminates 1 to 48 of the present invention. The thermal diffusivity of the laminates 1 to 48 was evaluated and compared in the same manner as described above.
將其結果示於第9A圖~第9C圖。黑色之長條圖、反白之長條圖分別為本發明、比較例。橫軸的編號分別為對應本發明之石墨烯層合體1~48、比較層合體1~48之層合體的編號。如第9A圖~第9C圖所示，與對含石墨烯的層單純層合塗佈氧化石墨烯層之比較層合體的測定溫度相比，本發明之石墨烯層合體，即使在遠離與加熱器相接之處的位置溫度亦較高，可傳導更多加熱器的熱，可知熱擴散性能較高。 The results are shown in Figs. 9A to 9C. The black bar graph and the reverse bar graph are the present invention and a comparative example, respectively. The numbers on the horizontal axis are the numbers corresponding to the graphene laminates 1 to 48 of the present invention, and the laminates of the comparative laminates 1 to 48, respectively. As shown in Figs. 9A to 9C, the graphene laminate of the present invention is compared with the measured temperature of a comparative laminate in which a graphene-containing layer is simply laminated and coated with a graphene oxide layer. The temperature of the location where the heaters meet is also higher, which can conduct more heat from the heater, which shows that the heat diffusion performance is higher.
以上，總結此等結果，具有高熱傳導性之含石墨烯的層、高電阻性之含氧化石墨烯的層，且於此之間從前述含氧化石墨烯的層至含石墨烯的層含氧比率連續地減少的混合層的本發明之石墨烯層合體為適宜作為熱擴散 片之形態，具有高放熱性。再者，藉由朝氧化石墨烯薄片膜厚方向施加電場，能以一次的處理製作之，而能夠簡便地以低能量製作。 In the above, the results are summarized. The graphene-containing layer having high thermal conductivity and the graphene-oxide-containing layer having high electrical resistance, and the graphene-containing layer to the graphene-containing layer in the foregoing range contain oxygen. The graphene laminate of the present invention in a mixed layer in which the ratio is continuously reduced is in a form suitable as a heat diffusion sheet and has a high exothermic property. Furthermore, by applying an electric field to the thickness direction of the graphene oxide sheet, it can be produced in a single process, and it can be produced easily with low energy.
本發明之石墨烯層合體可較佳地適用於顯示良好的熱傳導性，有效地放熱由電子零件等所產生的熱之熱擴散片。又，可廉價地製造。 The graphene laminate of the present invention can be preferably applied to a thermal diffusion sheet that exhibits good thermal conductivity and effectively radiates heat generated from electronic parts and the like. Moreover, it can be manufactured cheaply.
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