KR20190050298A - External housing structure and method of fabricating the same - Google Patents

Abstract

The present invention relates to an outer housing structure of a portable electronic device and a method for manufacturing the same. According to an embodiment of the present invention, provided is an outer housing structure of a portable electronic device, which is a zirconium structure, comprises a fired body in which a plurality of green sheets including zirconium oxide stacked and fired together, wherein the fired stacked body has a 3-point flexural strength of 1200 MPa or greater.

Description

[0001] The present invention relates to an external housing structure and a manufacturing method thereof,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a technique for manufacturing an external housing of an electronic product, and more particularly, to an external housing structure of a portable electronic device.

Among the portable electronic devices, smart phones have been added to new functions as personalized small computers that go beyond simple communication functions with advances in communication technology and semiconductor manufacturing technology. In the recent smartphone market, competition among manufacturers has been increasing not only in terms of technology competition for adding new functions, but also in design competition. As consumers' response to new functions has weakened, market competition is rather focused on design competition .

Generally, development of an exterior housing of a portable electronic device is important because it has a dominant influence on the aesthetics of the appearance through the material and the texture of the surface of the exterior housing. Since the smartphone is a portable electronic device and is an electronic device most frequently carried by an individual, the external housing for a smart phone has a performance such that the smartphone can not be damaged due to scratches or falling due to carelessness during its use, In terms of aspect, it is necessary to secure impact resistance and scratch resistance along with aesthetic appearance.

On the other hand, an outer housing structure using zirconium has recently been produced, but the structure produced by a general process is not sufficiently excellent in strength and impact resistance, and its manufacturing cost is too high, and thus improvement is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an external housing structure capable of providing an exterior housing of a high-grade portable electronic device while maintaining an excellent appearance and texture and ensuring impact resistance and scratch resistance.

According to another aspect of the present invention, there is provided a housing structure for a portable electronic device, the housing structure comprising: a zirconium structure including a plurality of green sheets including zirconium oxide stacked and fired, The 3-point flexural strength of the fired laminate may be more than 1200 MPa.

In one embodiment, the plurality of green sheets are formed by tape casting, and the thickness of the fired laminate may be 100 to 1000 mu m.

In another embodiment, the surface roughness of the fired laminate may be 1 to 50 nm.

In another embodiment, the surface hardness (Vicker's Hardness) of the fired laminated body may be 11 GPa or more.

In another embodiment, the weight average molecular weight of the resinous binder may be from 3,000 g / mol to 100,000 g / mol.

In another embodiment, the green sheet may comprise an additional oxide in the range of 0.05 mol% to 10 mol% capable of stabilizing the zirconium oxide powder. The additional oxides may be selected from the group consisting of calcium oxide (CaO), magnesium oxide (MgO), scandium oxide (Sc ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), erbium oxide (ErO ₂ ), cerium oxide (CeO ₂ ) Oxide (Y ₂ O ₃ ).

In another embodiment, the thickness of the thick film of the green sheet formed by the thick film method may be in the range of 40 mu m to 300 mu m.

In another embodiment, the plurality of green sheets may comprise first green sheets comprising a colorless zirconium oxide and second green sheets comprising a zirconium oxide having a specific color by a pigment or colorant . The second green sheets may be located on top of the first green sheets.

The total thickness of the second green sheets may range from 5% to 50% of the total thickness of the plurality of green sheets.

According to the embodiment of the present invention, the zirconium oxide is used as a main material to provide a beautiful appearance based on deep color such as ceramics, while ensuring the impact resistance and scratch resistance by the multilayer laminate structure in which a plurality of zirconium oxide layers are fired At the same time, an external housing structure excellent in moldability in various shapes can be provided.

Further, according to another embodiment of the present invention, a portable electronic device using the external housing structure having the above advantages can be provided.

FIG. 1A is a perspective view showing an outer housing structure according to an embodiment of the present invention, and FIG. 1B is a sectional view of an outer housing structure taken along line IB-IB 'in FIG. 1A.
FIG. 2A is a flow chart for explaining a method of manufacturing an outer housing structure according to an embodiment of the present invention, and FIG. 2B is a perspective view illustrating intermediate structures formed during manufacture of the outer housing structure according to an embodiment of the present invention .
3A is a view for explaining a molding method of an outer housing structure according to an embodiment of the present invention.
FIG. 3B is a view for explaining a general method of forming a zirconium sheathing housing structure in comparison with the embodiment of the present invention.
4 is a view for explaining a method of manufacturing a color sheathing housing structure according to an embodiment of the present invention.
5 is optical images of an exterior housing structure of a portable electronic device having various colors according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In the drawings, the thickness and size of each layer are exaggerated for convenience and clarity of description, and the same reference numerals refer to the same elements in the drawings. As used herein, the term " and / or " includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise " and / or " comprising " when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Although the terms first, second, etc. are used herein to describe various elements, components, regions, and / or portions, these elements, components, regions, and / or portions should not be limited by these terms. It is self-evident. These terms are only used to distinguish one member, component, region or portion from another region or portion. Accordingly, the first member, component, region or portion described below may refer to a second member, component, region or portion without departing from the teachings of the present invention.

Embodiments of the present invention will now be described with reference to the drawings schematically illustrating ideal embodiments of the present invention. In the drawings, for example, the size and shape of the members may be exaggerated for convenience and clarity of explanation, and in actual implementation, variations of the illustrated shape may be expected. Accordingly, the embodiments of the present invention should not be construed as being limited to the specific shapes of members or regions illustrated herein.

FIG. 1A is a perspective view showing an outer housing structure 100 according to an embodiment of the present invention, and FIG. 1B is a sectional view of an outer housing structure 100 taken along line IB-IB 'in FIG. 1A.

Referring to FIG. 1A, the external housing structure 100 exemplifies a back cover of a smart phone, which is a part of an external housing of a portable electronic device, and has a display unit or a front cover on the front surface thereof. The exterior housing structure 100 may have at least a portion formed therein and may have various shapes, and may have a body portion 100P having a flat main surface as shown in FIG. 1A and a rounded edge portion 100E. However, this is exemplary, and the outer housing structure 100 may be molded into bending, bending, planarizing, embossing, patterning, or a combination of these, depending on the application specifications.

Referring to FIG. 1B, the cross-sectional structure of the outer housing structure 100 is a structure in which a green sheet layer including zirconium oxide having a sheet shape, rather than a sintered body or a composite of different materials having a uniform structure in the thickness direction, Bonded plastic laminate. Since the interlaminarly fused cross-sectional structure has a discontinuous structure of a plurality of interlayer interfacial surfaces extended two-dimensionally in the depth direction, the impact transmitted from the outside is not uniformly propagated into the interior of the exterior housing structure 100, Cracks are prevented from being developed due to sequential blocking at the interlayer interface formed, whereby the impact resistance can be secured according to the embodiment of the present invention.

It is preferable that the impact resistance of the outer housing structure is able to withstand a height of 1.5 m or more when a load of 190 g is applied in the measurement through the impact drop inspecting weight drop test. In the case of a typical external housing structure, when a load of 190 g is applied, it is broken even at a height of less than 1 m, and thus the internal product such as a portable electronic device can not be effectively protected.

The interlayer interface does not become apparent after firing, but may be such that it is tracked by traces as shown in FIG. 1B. The zirconium oxide constituting the outer housing structure 100 is a refractory material having a high melting temperature of about 2,700 DEG C and is chemically stable and has a low coefficient of thermal expansion, high strength and high hardness (Mohs hardness of about 8.0 or more), and brittleness ), The strength can be improved by the discontinuity in the depth direction according to the embodiment of the present invention.

The strength is preferably 1200 MPa or more when measured by a 3-point flexural strength measurement method, which is a general strength measurement standard. The higher the value, the better the effect. Concretely, 1200 MPa to 1800 MPa is exemplified, but the strength of the fired laminated body according to the present invention is not limited to the above example.

In addition, the zirconium ceramic material has an advantage of being resistant to discoloration while having scratch resistance peculiar to ceramics. Therefore, according to the embodiment of the present invention, it is possible to secure not only the above-mentioned impact resistance but also the scratch resistance which is not possessed by the conventional polymer-based material, and the scratch resistance of the external housing structure according to this embodiment of the present invention Performance is a next-generation exterior material that can replace conventional gorilla glass.

Specifically, the front surface roughness of the external housing structure is preferably 1 to 50 nm.

In one embodiment, the outer housing structure 100 may have a white or beige color that is expressed from the inherent hue of the zirconium oxide. In another embodiment, the outer housing structure 100 may be colored to have other colors such as blue, pink, red, or black. To this end, the fired laminate for obtaining the outer housing structure 100 can impart color to only a part of the green sheet layers including the outermost green sheet constituting the outer appearance, thereby enhancing the esthetics by color without reducing the impact resistance. This will be described later in detail with reference to FIG.

FIG. 2A is a flow chart for explaining a method of manufacturing an outer housing structure according to an embodiment of the present invention, and FIG. 2B is a perspective view illustrating intermediate structures formed during manufacture of the outer housing structure according to an embodiment of the present invention .

2A, a slurry or paste for a green sheet containing a zirconium oxide powder, a resin binder and a solvent is first formed (S10) in order to produce an outer housing structure. The binder may be dissolved. The solvent and the resin binder may be removed through a drying and a heat treatment process for a green sheet laminate to be described later.

The solvent may be any solvent capable of stably dispersing the zirconium oxide powder and dissolving the solvent. For example, the solvent may be distilled water, but not limited thereto, and alcohol-based solvents such as ethanol or other organic solvents such as toluene or xylene may be used.

In some embodiments, a dispersant may be further added to the solvent. The dispersant may be, for example, an organic dispersant such as partially saponified polyvinyl alcohol, polyacrylate, polyvinylpyrrolidone, carboxymethylcellulose or methylcellulose, magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, phosphoric acid Inorganic dispersants such as magnesium, magnesium carbonate, and magnesium oxide, or a mixture thereof. Preferably, an inorganic dispersant applicable in water can be used. In some embodiments, with the dispersing agent, a surfactant may be further added. For example, as the surfactant, sodium dodecylbenzenesulfonate or sodium alpha -olefin sulfonate may be used, and various known surfactants may be applied.

The zirconium oxide powder is a powder having an average diameter of 100 nm to 20 mu m. The zirconium oxide powder may include stabilized zirconium oxide powder by addition oxides within the range of 0.05 mol% to 10 mol%. The additional oxide is calcium oxide (CaO), magnesium oxide (MgO), scandium oxide (Sc ₂ O _3), aluminum oxide (Al ₂ O _3), erbium oxide (ErO _2), cerium oxide (CeO _2), and And yttrium oxide (Y ₂ O ₃ ), and may preferably include yttrium oxide. The stabilized zirconium oxide powder may be formed by various known synthetic methods such as hydrothermal synthesis, coprecipitation, sol-gel synthesis, sintering, or a combination thereof as a material having no volume change at the time of transition between tetragonal and monoclinic. But is not limited thereto.

In some embodiments, the zirconium oxide powder may be colored by a colorant. The coloring material may include a coloring oxide which is added and preprocessed in preparing the zirconium oxide powder. For example, the colored oxide may include an iron oxide (Fe ₂ O ₃ ), an elvania, a polonium oxide (PoO), a cobalt oxide (CoO or Co ₃ O ₄ ). In another embodiment, a pigment mixed with the zirconium oxide powder may be added to form a slurry for the green sheet. The pigment may be an inorganic pigment that can be implemented in various colors such as black, green, blue, yellow, red, magenta, or black, as a non-limiting example, titanium oxide (TiO _2), aluminum oxide (Al ₂ O _3), or silicon oxide (SiO ₂₎ may be.

The resin binder may be, for example, an acrylic binder resin. The acrylic binder resin may be at least one selected from the group consisting of polybenzyl methacrylate, (meth) acrylic acid / benzyl methacrylate copolymer, (meth) acrylic acid / benzyl methacrylate / styrene copolymer, (meth) acrylic acid / benzyl methacrylate / 2- Hydroxyethyl methacrylate copolymer or a (meth) acrylic acid / benzyl methacrylate / styrene / 2-hydroxyethyl methacrylate copolymer, and the present invention is not limited thereto, Or more may be used in combination.

When the weight average molecular weight of the acrylic binder resin is within the above range, the viscosity of the slurry for green sheets to be formed is suitable, and when the weight average molecular weight of the acrylic binder resin is within the above range, The adhesion with the handle substrate is secured. If the weight-average molecular weight is out of the above range, adhesion with the handle substrate may be deteriorated, thereby causing problems in alignment during stacking of the substrate, or inferiority in the processing step. The acid value of the resin binder may be, for example, 15 mgKOH / g to 100 mgKOH / g, such as 30 mgKOH / g to 50 mgKOH / g, and the present invention is not limited thereto. The content of the zirconium oxide powder and resin binder contained in the solvent may be 5 wt% to 20 wt%.

A green sheet containing zirconium oxide is formed from the green sheet slurry or paste (S20). The green sheet is a thick film of zirconium oxide. The thickness of the green sheet thick film may be in the range of 40 to 300 mu m. When the thickness of the green sheet thick film is 300 탆 or more, as described later, when the green sheet slurry or paste formed on the handle substrate during the treatment through tape casting is dried or gelled, Stress may be generated between the substrate and the coating layer of the thick film, thereby causing defects such as cracks in the coating layer. When the thickness of the thick film is more than 300 占 퐉, the number of interlayer interfaces is reduced, and the propagation of the impact due to the interlayer interface is not effectively restricted, so that the impact resistance can also be weakened.

On the other hand, when the thickness of the green sheet thick film is less than 40 탆, a large number of green sheets must be laminated when forming a green sheet laminate of a predetermined thickness. Therefore, So that it is difficult to improve the impact resistance in the final formed plastic laminate.

In one embodiment, the green sheet thick film can be formed by coating the green sheet slurry or paste on the handle substrate and drying or gelling. The handle substrate may be a substrate for a support for tape casting to form the green sheet thick film. In one embodiment, the handle substrate may be a flexible resin-based film. The flexible resin film may be, for example, polyethylene terephthalate (PET) or polypropylene, but the present invention is not limited thereto. For example, it may be any resin-based material that can easily peel off the green sheet from the surface, or may be a composite layer of two or more. In addition, the handle substrate may include any material that facilitates drying or gelation of the green sheet thick film, or may even be a ceramic substrate.

In one embodiment, the green sheet thick film may be coated on the handle substrate by a roller coating, a bar coating, a spray coating, a spin coating, a doctor blade coating, a sol-gel method, a dipping method or a combination thereof. However, this is merely exemplary and the present invention is not limited thereto. In another embodiment, a green sheet thick film may be formed on the handle substrate through a process for obtaining a high density green density such as an electrochemical method, an electrophoresis method or a hydrothermal synthesis method.

In one embodiment, the coating may be performed by a roll-to-roll process. To this end, the handle substrate may be formed of a flexible material, as described above, and the slurry or paste for the green sheet may be successively formed on the surface of the handle substrate exposed while the handle substrate wound on the take- Can be coated. Thereafter, the coating layer may be dried or gelled on the handle substrate to form the green sheet.

In some embodiments, the formed green sheet may be cut to a predetermined size in consideration of the shrinkage ratio of the fired laminate described later. The cutting of the green sheet may be performed in a state of being coated on the handle substrate or peeled off from the handle substrate, but the present invention is not limited thereto. FIG. 2B illustrates green sheets 10G formed on the handle substrate 10S, respectively.

2A and 2B, the green sheet 10G is laminated at least twice to form a green sheet laminate 100G (S30). When the green sheet is subjected to tape casting through a continuous process such as the roll-to-roll process as described above, the green sheet 10G can be cut to a predetermined size and then laminated. In another embodiment, the green sheet may be folded without overlap and overlapped, but the present invention is not limited thereto. The green sheet laminate 100G can be cut to a suitable size in consideration of the size of the housing for the final portable electronic device.

The green sheet laminate 100G may be formed by laminating 3 to 30 sheets of green sheets, and the thickness of the green sheet laminate 100G may be within a range of 50 to 2,000 mu m. In one embodiment, the green sheet laminate can be subjected to an integrated treatment to remove unwanted air between adjacent green sheets in the green sheet laminate under pressure, preferably under pressure, in a vacuum atmosphere. The integrated structure further densifies the structure inside the green sheet and increases the density after firing

For example, the green sheet laminate is placed in a sealable polymer container, the polymer container is evacuated, the polymer container is brought into close contact with the green sheet laminate, the polymer container is placed in water having a temperature of about 80 캜, The green sheet laminate 100G can be integrated by pressurizing with water pressure of 400 atmospheres for about 20 minutes. Such integrated green sheet laminate may also be referred to herein as a green body.

The green sheet laminate 100G can be cut to an appropriate size in consideration of the shrinkage ratio of the subsequent firing step and the size of the final product. The cutting process of the green sheet laminate 100G may be performed before or after the above-described integration process, but the present invention is not limited thereto.

Thereafter, the green sheet laminate 100G is sintered to form a fired laminate 100S (S40). The sintering can be carried out at a suitable temperature and for a time so that not only the individual green sheets but also adjacent green sheets are sintered to each other to form an interlayer fired bonded plastic laminated body. The calcined zirconium oxide may include tetragonal or cubic, and the present invention is not limited thereto.

In one embodiment, the sintering may be performed by a first heat treatment step to allow complete removal of the resinous binder added during the manufacture of the green sheet and a second heat treatment step to cause sintering between the zirconium oxide particles to occur. The first heat treatment step may be performed at a temperature within a range of 100 ° C to 900 ° C and the second heat treatment step may be performed at a temperature higher than 1,000 ° C to 1,700 ° C higher than the first heat treatment step. The temperature profile of each heat treatment step may be variously designed so as to have a constant or an interval in which the temperature gradually increases or decreases. The shrinkage ratio in the thickness direction after firing is in the range of 20% to 40%, which can be suitably adjusted through the composition ratio of the green sheet.

On the other hand, the thickness of the fired laminated body obtained through the sintering is preferably 100 to 1000 mu m. When the thickness of the fired laminated body is less than 100 탆, the interlayer interfacial surface formed in the depth direction is not sufficient and the impact can not be sufficiently absorbed, so that the impact resistance is lower than a generally required level.

When the thickness of the fired laminated body is 1000 mu m or more, the weight of the external housing itself becomes too heavy, which makes it difficult to carry, and curved surface processing becomes difficult.

In one embodiment, when a plurality of green sheets are fired and bonded to each other by sintering, the outer diameter machining and polishing of the fired laminate can be performed to meet specifications of the outer housing structure as the final product. Through the above polishing, planarization with respect to the outer surface of the fired laminate can be performed, and luster can be imparted. The polishing may be carried out mechanically or mechanically and chemically in parallel, but the present invention is not limited thereto.

On the other hand, it is preferable to control the front surface roughness of the fired laminate through the above polishing to 1 to 50 nm, more preferably 5 to 10 nm. In order to set the front illuminance to 1 nm or less, an extremely high processing is required and the economical efficiency is low. On the other hand, when the front illuminance is 50 nm or more, the luster of the exterior housing is lowered. Since the surface is uneven, the whole surface may not have a uniform color, so that the color expression may not be expressed as desired.

The surface hardness of the fired laminated body subjected to sintering and surface processing is preferably 11 Gpa or more, more preferably 13 Gpa or more. When the hardness is less than 11 Gpa, it is difficult to expect sufficient abrasion resistance, and scratches may occur on the surface when strong friction is applied to the surface.

3A is a view for explaining a molding method of an outer housing structure according to an embodiment of the present invention.

In order to manufacture the outer housing structure of various shapes, the fired laminate may be molded by various methods such as bending, bending, or patterning. In one embodiment, the molding of the fired laminate can be performed by a mold assembly including a lower mold and an upper mold, as shown in FIG. 3A. When the fired laminated body 100S is placed on the lower mold and pressure is applied to the fired laminated body by the upper mold, molding of the fired laminated body can be performed in the same manner as the interface shape of the upper mold and the lower mold. Fig. 3 exemplifies the edge forming of the fired laminate 100S. In one embodiment, the forming of the fired laminate 100S may be hot forming, wherein the heating temperature may be in the range of 500 ° C to 1,500 ° C.

FIG. 3B is a view for explaining a general method of forming a zirconium sheathing housing structure in comparison with the embodiment of the present invention.

The process of fabricating a typical zirconia sheathing housing structure may proceed as follows. First, zirconium powder is charged into a mold having a certain standard, and the mold is vibrated. Thereafter, after the upper surface is planarized, the zirconium powder is charged again and the mold is vibrated. After repeating the above process, if a certain amount of zirconium powder is accumulated in the mold, a zirconium plate is produced by applying pressure through a press molding machine.

Thereafter, the manufactured zirconium plate is cut by a CNC machining process to align its outer diameter, and then the outer surface is subjected to optical polishing and finishing.

4 is a view for explaining a method of manufacturing a color sheathing housing structure according to an embodiment of the present invention. Reference may be made to the foregoing disclosure with respect to the elements having the same reference numerals as the above-described elements among the illustrated elements.

Referring to Fig. 4, a color sheath housing structure may also be produced by superimposing the individual green sheets 10CG and 10G to form a green sheet laminate 100G ', similar to that described with reference to Figs. 2A and 2B, To form a fired laminated body 100S '.

First, a slurry or paste for a first green sheet containing a zirconium oxide powder, a resin binder and a solvent is formed. The zirconium oxide powder may be dispersed in the solvent and the resin binder may be dissolved.

Further, a slurry or paste for a second green sheet in which an inorganic pigment is further added as a coloring agent for coloring with the zirconium oxide powder is formed. The content of the inorganic pigment may be several wt% to several tens wt% with respect to the total amount of the zirconium oxide powder and the pigment, and the present invention is not limited thereto. For example, the inorganic pigment may be mixed with 0.5 wt% to 30 wt%. As the content of the inorganic pigment added to the slurry for the second green sheet is increased, the impact resistance after firing is weakened. The above-mentioned disclosure can be referred to regarding the binder, the solvent and the dispersant applied to the slurry for the first and second green sheets.

A first green sheet 10G containing zirconium oxide is formed from the slurry or paste for the first green sheet. A second green sheet 10CG colored from the slurry or paste for the second green sheet is formed. The first and second green sheets 10G and 10CG are thick films of zirconium oxide having a thickness of 40 to 300 mu m.

In one embodiment, the first and second green sheet thick films may be formed by coating the slurry or slurry for the green sheet on the handle substrate 10S, respectively, and drying or gelling them. As a non-limiting example, the green sheet thick film may be coated on the handle substrate by a roller coating, a bar coating, a spray coating, a spin coating, a doctor blade coating, a sol-gel method, a dipping method or a combination thereof. Further, a green sheet thick film may be formed through a process by a film forming process to obtain a high green density such as an electrochemical method, an electrophoresis method or a hydrothermal synthesis method.

The formed first and second green sheets 10G and 10CG may be cut to a predetermined size in consideration of the shrinkage ratio of the plastic laminated body 100S 'described later. The cutting of the green sheet can be cut in a state of being coated on the handle substrate or peeled off from the handle substrate, but the present invention is not limited thereto. Fig. 4 illustrates first and second green sheets 10CG and 10G respectively formed on a handle substrate.

Thereafter, the formed green sheet is laminated at least twice to form a green sheet laminate 100G '. In the upper portion of the green sheet laminate 100G ', second to 10th layers of second green sheets 10CG are laminated for coloring, and on the bottom of the second green sheets 10CG, The first green sheets 10G are stacked in a number larger than the number of the first green sheets 10G. The strength after firing of the second green sheet 10CG is weaker than the strength after firing of the first green sheet 10G due to the coloring agent or pigment for colorization. Therefore, for the color implementation, the second green sheet 10CG for coloring is applied only to some layers including the outermost layer exposed to the outside, and the bottom of the second green sheet 10CG is provided with the first The green sheet 10G is applied.

The lamination thickness of the second green sheet 10CG for coloring may be within 5% to 50% of the thickness of the entire green sheet laminate 100G '. If the lamination thickness of the second green sheet 10CG is less than 5%, it may be difficult to achieve a uniform color, or the abrasion of the aesthetics may easily occur due to the exposure of the first green sheet 10G at the time of scratching. If the lamination thickness of the second green sheet 10CG exceeds 50%, deterioration of the impact resistance may occur.

5 is optical images of exterior housing structures 100A, 100B, and 100C of portable electronic devices of various colors in accordance with an embodiment of the present invention.

Referring to Figure 5, the exterior housing structures 100A, 100B, and 100C illustrate a back cover as an exterior housing of a smartphone. The exterior housing structures 100A, 100B, and 100C may include, but are not limited to, blue, black, or white The illustrated exterior housing structures 100A, 100B, and 100C may include a first green sheet 10G and a second green sheet 10CG having a thickness of 100 mu m in accordance with the manufacturing method disclosed with reference to Fig. A sixth green sheet 10CG is superimposed on the first green sheet 10CG and a second green sheet 10CG having three colors is laminated thereon to form a green sheet laminate 100G having a total thickness of 900 mu m, And pressing it in a vacuum environment to carry out an integrated process, and firing the same.

The firing is achieved by removing the binder through the low temperature heat treatment in the first step and densifying the high temperature heat treatment in the second step. Since the shrinkage in the thickness direction reached about 30% by the above firing, the thickness of the final fired laminate was about 630 탆. Thereafter, outer diameter machining and double-side grinding were carried out in accordance with the specification of the product, and about 60 to 70 탆 was polished in the thickness direction of both sides of the sintered body to produce a flat plate having a thickness of 500 탆. In the finished product, the thickness of the color layer is about 140 μm, which accounts for about 28% of the total thickness.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the examples.

≪ Example 1 >

Adding a zirconium oxide in a solvent composed of distilled water and adding calcium oxide (CaO) in a proportion of 5 mol% of the zirconium oxide and adding 40 wt% of the zirconium oxide to a polybenzyl methacrylate having a molecular weight of 10.000 g / To prepare a green sheet slurry.

A green sheet slurry (5 g) prepared as described above was coated on a handle substrate and dried to form 10 sheets of green sheets having a width of 50 mm, a length of 100 mm and a thickness of 90 to 100 μm Lt; / RTI >

The ten green sheet thick films were placed in a polymer bag, the polymer bag was vacuumed to adhere the polymer container to the green sheet laminate, the polymer container was placed in water having a temperature of about 80 DEG C, For 20 minutes to remove unnecessary air between adjacent green sheets in the green sheet laminate, and the green sheet laminate was integrated.

Thereafter, after a first heat treatment step at a temperature of 500 캜, a sintering process was carried out at a temperature of 1300 캜 through a second heat treatment to produce a fired laminated body having a thickness of 630 탆.

Thereafter, the outer diameter of the fired laminate was processed and polished to finally produce an outer housing structure having a thickness of 500 mu m.

≪ Example 2 >

Of the ten green sheet thick films of Example 1, three green sheet thick films were prepared by adding 10 wt% of pigment to zirconium oxide to prepare a colored green sheet thick film, And the laminate was placed on top of the remaining seven green sheet thick films to carry out the unification of the laminate, thereby manufacturing an external housing structure.

≪ Comparative Example 1 &

As a general process for manufacturing an external housing structure using zirconia oxide, zirconium powder is charged into a mold having a width of 50 mm, a length of 100 mm and a thickness of 2000 탆, and the mold is vibrated. Thereafter, after the upper surface is planarized, the zirconium powder is charged again and the mold is vibrated. After repeating the above process, when zirconium powder having a thickness of 1000 μm or more was accumulated, a zirconium plate having a thickness of about 630 μm was produced by applying pressure through a press molding machine.

The zirconia plate was cut through a central portion by CNC machining to adjust the outer diameter of the zirconia plate, and the outer surface was subjected to optical polishing and finishing to finally produce an outer housing structure of 500 탆.

Table 1 below is a table showing the test results of the impact resistance of the outer housing structure manufactured according to the embodiment of the present invention.

For impact resistance measurement, a 130 g steel ball drop test was used to evaluate the impact resistance performance by examining whether cracks were generated in the samples. All of the samples were found to have good performance in all five drop tests.

The following Table 2 shows the data of Comparative Example 1, which is an external housing structure manufactured by a general method, by measuring the strength, impact resistance and surface hardness of Example 1 above.

In the above measurement, the strength was measured by a 3-point flexural strength method, which is a general strength measurement method, and a shock drop test (weight drop test) was conducted. When a load of 190 g was applied, To be able to withstand without being damaged. The surface hardness was measured based on Vicker's Hardness.

As a result of the measurement, the strength of the external housing structure of Example 1 was measured to be 1200 Mpa, the height not damaged in the impact resistance test was 1.5 m, and the surface hardness was 13 Gpa.

On the other hand, the strength of the external housing structure of Comparative Example 1 was measured to be 900 Mpa, the height not damaged in the impact resistance test was 1.0 m, and the surface hardness was 10 Gpa.

Impact resistance test 20 cm 25 cm 30 cm 35 cm Example 1 Good for 5 times Good for 5 times Good for 5 times Good for 5 times Example 2 Good for 5 times Good for 5 times Good for 5 times Good for 5 times

Property test burglar Impact resistance Surface hardness Example 1 1200Mpa 1.6m 13 Gpa Comparative Example 1 900Mpa 1.0m 10 Gpa

As shown in the above table, the outer housing structure of the present invention has excellent impact resistance, and has a strength of about 33%, an impact resistance of about 50%, a surface hardness of about 30% It can be confirmed that it is improved. Such excellent strength and surface hardness can prevent the outer housing structure from being damaged due to external impacts or scratches on the surface thereof. Further, it is possible to effectively protect electronic devices that are likely to be damaged by an external impact through high impact resistance .

In addition, the process yield can be maintained at 70 to 80% when manufactured through the technique of the present invention, so that the outer housing structure can be made much more economically than the yield of about 20% in Comparative Example 1 manufactured by a general process .

In addition, the external housing structure of the present invention is particularly useful when used as an external housing structure such as a portable electronic device, because it is possible to add a color representing the above-mentioned individual physical properties and excellent aesthetics.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be clear to those who have knowledge.

Claims (9)

A zirconium structure comprising a plurality of green sheets containing zirconium oxide laminated and fired bonded to each other,
Wherein the plastic laminate has a 3-point flexural strength of 1200 MPa or more.
The method according to claim 1,
Wherein the plurality of green sheets are formed by tape casting, and the thickness of the plastic laminate is 100 to 1000 占 퐉.
The method according to claim 1,
Wherein the fired laminate has a surface roughness of 1 to 50 nm.
The method according to claim 1,
And the surface hardness (Vicker's Hardness) of the plastic laminated body is 11 GPa or more.
The method according to claim 1,
Wherein the green sheet comprises a resinous binder,
Wherein the resinous binder has a weight average molecular weight of from 3,000 g / mol to 100,000 g / mol.
The green sheet according to claim 1, wherein the green sheet comprises an additive oxide in a range of 0.05 mol% to 10 mol% capable of stabilizing the zirconium oxide powder;
The additional oxides may be selected from the group consisting of calcium oxide (CaO), magnesium oxide (MgO), scandium oxide (Sc ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), erbium oxide (ErO ₂ ), cerium oxide (CeO ₂ ) oxide (Y ₂ O ₃₎ exterior casing structure of a portable electronic device including at least one of a.
The external housing structure of a portable electronic device according to claim 2, wherein the thickness of the thick film of the green sheet formed by the thick film method is in a range of 40 mu m to 300 mu m.
The method according to claim 1,
The plurality of green sheets comprises first green sheets comprising a colorless zirconium oxide and second green sheets comprising a zirconium oxide having a specific color by a pigment or a colorant;
And the second green sheets are located on top of the first green sheets.
9. The enclosure housing structure of a portable electronic device according to claim 8, wherein the total thickness of the second green sheets has a range of 5% to 50% of the total thickness of the plurality of green sheets.

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