WO2020091116A1 - Exterior housing structure and method for producing same - Google Patents

Abstract

The present invention relates to: an exterior housing structure for a portable electronic device; and a method for producing same. According to one embodiment of the present invention, provided is an exterior housing structure for a portable electronic device, the structure being a zirconium structure comprising a fired laminate obtained by laminating, sintering, and combining a plurality of green sheets including zirconium oxides, wherein the fired laminate has a 3-point flexural strength of 1200 MPa or greater.

Description

[Correction by Rule 26.12.2018] Exterior housing structure and manufacturing method thereof

The present invention relates to a technology for manufacturing an outer housing of an electronic product, and more particularly, to an outer housing structure of a portable electronic device.

Among portable electronic devices, smart phones have been added as new personalized computers as well as simple communication functions due to the development of communication technology and semiconductor manufacturing technology. Recently, in the smartphone market, competition among manufacturers is sharpening not only technology competition for the addition of new functions, but also design competition, and as consumer response to new functions weakens, market competition tends to concentrate on design competition. .

In general, the exterior housing of a portable electronic device has a dominant effect on the aesthetics of the exterior through the material or texture of the surface, so its development is important. Since a smart phone is a portable electronic device and is an electronic device that is most frequently carried by an individual, the external housing for the smartphone is capable of preventing the product from being damaged or aesthetics easily damaged by scratches or falls due to carelessness during its use. In addition to the aesthetic sense of the exterior, impact and scratch resistance must be secured.

On the other hand, an exterior housing structure using zirconium has been recently produced, but the structure produced by a general process is not sufficiently excellent in strength and impact resistance and needs to be improved because its manufacturing cost is too high.

The problem to be solved by the present invention is to provide an exterior housing structure capable of providing an exterior housing of an advanced portable electronic device by securing a shock resistance and scratch resistance while having a beautiful appearance and texture.

An external housing structure of a portable electronic device according to an embodiment of the present invention for solving the above-described problem is a zirconium structure, and includes a plastic laminate in which a plurality of green sheets containing zirconium oxide are stacked and plastically bonded. The plastic laminate may have a 3-point flexural strength of 1200 MPa or more.

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

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

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

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

In another embodiment, the green sheet may include an additional oxide in the range of 0.05 mol% to 10 mol% that can stabilize the zirconium oxide powder. The addition 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 yttrium It may include at least one of oxides (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 μm to 300 μm.

In another embodiment, the plurality of green sheets may include first green sheets including a colorless zirconium oxide and second green sheets including 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 an embodiment of the present invention, while providing a beautiful appearance based on a deep color sense, such as porcelain, using zirconium oxide as a main material, a plurality of zirconium oxide layers are plastically bonded to secure impact resistance and scratch resistance by a multilayered laminate structure, At the same time, an outer housing structure excellent in formability in various shapes can be provided.

In addition, according to another embodiment of the present invention, a portable electronic device to which an exterior housing structure having the above-described advantages is applied can be provided.

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

2A is a flowchart illustrating a method of manufacturing an exterior housing structure according to an embodiment of the present invention, and FIG. 2B is a perspective view showing intermediate structures formed during manufacture of an exterior housing structure according to an embodiment of the present invention .

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

3B is a view for explaining a molding method of a typical zirconium exterior housing structure as compared with an embodiment of the present invention.

4 is a view for explaining a method of manufacturing a color exterior housing structure according to an embodiment of the present invention.

5 is optical images of an external housing structure of a portable electronic device having various colors according to an embodiment of the present invention. It is a blue, black and white exterior housing structure in turn from the left.

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 provided to more fully describe the present invention to those of ordinary skill in the art, and the following embodiments can be modified in various other forms, and the scope of the present invention is as follows. It is not limited to the Examples. Rather, these examples are provided to make the present disclosure more faithful and complete, and to fully convey the spirit of the present invention to those skilled in the art.

In addition, the thickness or size of each layer in the drawings is exaggerated for convenience and clarity of description, and the same reference numerals in the drawings refer to the same elements. 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 used to describe a specific embodiment and is not intended to limit the present invention. As used herein, singular forms may include plural forms unless the context clearly indicates otherwise. Also, as used herein, “comprise” and / or “comprising” specifies the shapes, numbers, steps, actions, elements, elements and / or the presence of these groups. And does not exclude the presence or addition of one or more other shapes, numbers, actions, elements, elements and / or groups.

Although the terms first, second, etc. are used herein to describe various members, parts, regions, and / or parts, these members, parts, regions, and / or parts should not be limited by these terms. Is self-explanatory. These terms are only used to distinguish one member, part, region or part from another region or part. Accordingly, the first member, part, region, or part described below may refer to the second member, part, region, or part without departing from the teachings of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the drawings, for example, the size and shape of members may be exaggerated for convenience and clarity of description, and in actual implementation, deformations of the illustrated shape can be expected. Accordingly, embodiments of the present invention should not be construed as limited to the specific shapes of the members or regions shown herein.

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

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

Referring to FIG. 1B, the cross-sectional structure of the exterior housing structure 100 is not a composite of a sintered body or a heterogeneous material having a uniform structure in a thickness direction, but a green sheet layer containing zirconium oxide having a sheet shape is adjacent to each other and fired between layers. It is a combined fired laminate. Since the interlayer plastically coupled cross-sectional structure has a discontinuous structure called a plurality of interlayer interfaces that extend in two dimensions in the depth direction, the impact transmitted from the outside does not propagate uniformly into the interior of the exterior housing structure 100, but rather in the depth direction. Crack development is suppressed while being sequentially blocked at the formed interlayer interface, whereby impact resistance can be secured according to an embodiment of the present invention.

It is preferable that the impact resistance of the exterior 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 resistance test weight drop test. In the case of a general exterior housing structure, when a load of 190 g is applied, it is damaged even at a height of less than 1 m, and thus does not effectively protect internal items such as portable electronic devices.

The interlayer interface is not apparent after firing, and may be traced by traces as shown in FIG. 1B. The zirconium oxide constituting the exterior housing structure 100 is a heat-resistant material having a high melting temperature of about 2,700 ° C. and is chemically stable, and has low thermal expansion coefficient, high strength and high hardness (Moss hardness of about 8.0 or more) and brittleness Although it is a typical ceramic material having), according to an embodiment of the present invention, the strength can be improved by discontinuity in the depth direction.

When the strength is measured through a 3-point flexural strength measurement method, which is a general strength measurement standard, it is preferable that it is 1200 Mpa or more. The higher the value, the better the effect. Specifically, 1200Mpa to 1800Mpa can be exemplified, but the strength of the fired laminate according to the present invention is not limited to the above example.

In addition, the zirconium ceramic material has an advantage of not being discolored while having scratch resistance peculiar to ceramic. Therefore, according to the embodiment of the present invention, it is possible to secure not only the above-described impact resistance, but also scratch resistance that a conventional polymer-based material does not have, such as scratch resistance of the exterior housing structure according to the embodiment of the present invention Performance is a next-generation exterior material that can replace conventional gorilla glass.

Specifically, it is preferable that the front surface roughness of the exterior housing structure is 1 to 50 nm.

In one embodiment, the exterior housing structure 100 may have a white or beige color expressed from the native color of zirconium oxide. In other embodiments, the exterior housing structure 100 can be colored to have other colors such as blue, pink, red or black. To this end, the fired laminate for obtaining the exterior housing structure 100 may impart color to only some of the green sheet layers including the outermost green sheet constituting the exterior to enhance aesthetic sense due to color without reducing impact resistance. This will be described later in detail with reference to FIG. 5.

2A is a flowchart illustrating a method of manufacturing an exterior housing structure according to an embodiment of the present invention, and FIG. 2B is a perspective view showing intermediate structures formed during manufacture of an exterior housing structure according to an embodiment of the present invention .

Referring to Figure 2a, in order to manufacture the exterior housing structure, first, to form a slurry or paste for a green sheet comprising a zirconium oxide powder, a resin-based binder and a solvent (S10). Zirconium oxide powder is dispersed in the solvent and resin-based The binder can be dissolved. The solvent and the resin-based binder may be removed through a drying and heat treatment process for the green sheet laminate, which will 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 is not limited thereto, and an alcohol-based alcohol such as ethanol or another organic solvent such as toluene or xylene may be used.

In some embodiments, a dispersant may be further added to the solvent. The dispersant is, for example, partially saponified polyvinyl alcohol, polyacrylic acid salt, polyvinylpyrrolidone, carboxymethylcellulose, or an organic dispersant such as methylcellulose, magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, phosphoric acid Inorganic dispersants such as magnesium, magnesium carbonate, and magnesium oxide or mixtures thereof. Preferably, an inorganic dispersant applicable in an aqueous system can be used. In some embodiments, a surfactant may be further added along with the dispersant. For example, as the surfactant, sodium dodecylbenzenesulfonate or α-olefinsulfonate 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 μm. The zirconium oxide powder may include stabilized zirconium oxide powder by addition oxides in the range of 0.05 mol% to 10 mol%. The addition 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 It may include at least one of yttrium oxide (Y ₂ O ₃ ), preferably it may include yttrium oxide. The stabilized zirconium oxide powder is a material having no volume change during transition between a tetragonal crystal and a monoclinic crystal, and may be formed by various known synthetic methods such as hydrothermal synthesis, coprecipitation, sol-gel synthesis, sintering, or a combination thereof, and the present invention It is not limited.

In some embodiments, the zirconium oxide powder can be colored with a colorant. The colored body may include a colored oxide which is added during the preparation of the zirconium oxide powder and pre-treated. For example, the colored oxide may include iron oxide (Fe ₂ O ₃ ), elbia, polonium oxide (PoO), and cobalt oxide (CoO or Co ₃ O ₄ ). In another embodiment, a pigment for mixing with the zirconium oxide powder may be added to form a slurry for green sheets. The pigment may be an inorganic pigment capable of realizing various colors such as black, green, blue, yellow, red, magenta, or black, and as a non-limiting example, titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), or silicon oxide (SiO ₂ ).

The resin-based binder may be, for example, an acrylic-based binder resin. The acrylic binder resin, polybenzyl methacrylate, (meth) acrylic acid / benzyl methacrylate copolymer, (meth) acrylic acid / benzyl methacrylate / styrene copolymer, (meth) acrylic acid / benzyl methacrylate / 2- It may be a hydroxyethyl methacrylate copolymer, or (meth) acrylic acid / benzyl methacrylate / styrene / 2-hydroxyethylmethacrylate copolymer, and the present invention is not limited thereto, and these may be used alone or in combination of two or more. The above can also be used in combination.

The weight average molecular weight of the resin-based binder may be 3,000 g / mol to 100,000 g / mol, and when the weight-average molecular weight of the acrylic binder resin is within the above range, the viscosity of the slurry for the green sheet to be formed is appropriate, and when thick film casting is performed. Adhesion with the handle substrate is secured. When the weight average molecular weight is out of the above range, the adhesion with the handle substrate is poor, which may cause alignment problems when stacking the substrate, or may increase the defect rate in the processing process. The acid value of the resin-based 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 the resin-based binder contained in the solvent may be 5 wt% to 20 wt%.

A green sheet including 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 μm. When the thickness of the green sheet thick film is 300 µm or more, as described later, the handle for shrinkage occurs when the slurry or paste for the green sheet formed on the handle substrate is dried or gelled during processing through tape casting. Stress may be generated between the substrate and the coating layer of the thick film, and thus defects such as cracks may occur in the coating layer. In addition, when the thickness of the thick film exceeds 300 μm, the number of interlayer interfaces is reduced, so that the propagation of impact by the interlayer interface is not effectively limited, and impact resistance can also be weakened.

On the other hand, when the thickness of the green sheet thick film is less than 40 μm, a large number of green sheets must be stacked when forming a green sheet laminate having a predetermined thickness, and thus defects at the interface in the subsequent firing process as the number of interlayer interfaces increases. Easily generated, it may be difficult to improve the impact resistance in the final formed fired laminate.

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

In one embodiment, the green sheet thick film may be coated on the handle substrate by roller coating, bar coating, spray coating, spin coating, doctor blade coating, sol-gel method, dipping method, or a combination thereof. However, this is only an example, 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 can 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 is continuously on the surface of the handle substrate exposed as the handle substrate wound on the winding roll is drawn out. 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 rate of the plastic laminate described later. The cutting of the green sheet may be performed in a state coated on the handle substrate or in a state peeled from the handle substrate, and the present invention is not limited thereto. 2B, green sheets 10G respectively formed on the handle substrate 10S are illustrated.

Subsequently, referring to FIG. 2B together with FIG. 2A, the formed green sheet 10G is stacked at least twice or more to form a green sheet stack 100G (S30). When the green sheet is subjected to a tape casting process through a continuous process as in the roll-to-roll process as described above, the green sheet 10G may be cut to a predetermined size and then laminated. In other embodiments, the green sheets may be folded and overlapped without cutting, and the present invention is not limited thereto. The green sheet laminate 100G may 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 stacking 3 to 30 layers of green sheets, and the thickness of the green sheet laminate 100G may be in a range of 50 μm to 2,000 μm. In one embodiment, an unifying process may be performed to remove unnecessary air between adjacent green sheets in the green sheet stack by pressing, preferably, purified water pressure in a vacuum atmosphere against the green sheet stack. The integration process also increases the density of the internal structure of the green sheet, thereby increasing the density after firing.

For example, the green sheet laminate is placed in a sealable polymer container, the polymer container is evacuated to adhere the polymer container to the green sheet laminate, and the polymer container is placed in water having a temperature of about 80 ° C. to 200 to By pressing for about 20 minutes at a water pressure of 400 atm, the integration of the green sheet laminate 100G may be performed. The green sheet laminate integrated as described above may be referred to herein as a green body.

The green sheet laminate 100G may be cut to an appropriate size in consideration of the shrinkage rate 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 the above-described integration process or after the integration process, and the present invention is not limited thereto.

Thereafter, the green sheet laminate 100G is sintered to form the fired laminate 100S (S40). The sintering may be performed for a suitable temperature and time such that the green sheets adjacent to each other as well as within the individual green sheets are sintered with each other to form an interlayer plastically bonded plastic laminate. 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 completely remove the resin-based binder added during production of the green sheet and a second heat treatment step to cause sintering between zirconium oxide particles. The first heat treatment step may be performed at a temperature within the range of 100 ° C to 900 ° C, and the second heat treatment step may be performed within a range of 1,000 ° C to 1,700 ° C higher than the first heat treatment step. The temperature profile of each heat treatment step may be constant or variously designed to have a section where the temperature is gradually increased or decreased. The shrinkage rate in the thickness direction after firing is in the range of 20% to 40%, which can be appropriately adjusted through the component ratio of the green sheet.

On the other hand, the thickness of the fired laminate obtained through the sintering is preferably 100 to 1000㎛. When the thickness of the fired laminate is less than 100 µm, the interlayer interface formed in the depth direction is not sufficient, so that the impact cannot be sufficiently absorbed, and the impact resistance is lower than the generally required level.

In addition, when the thickness of the fired laminate is 1000 µm or more, the weight of the exterior housing itself becomes too heavy, so there is a disadvantage that it is difficult to carry, and the surface processing is difficult.

In one embodiment, when a plastic laminate in which a plurality of green sheets are plastically bonded by sintering is formed, outer diameter processing and polishing of the plastic laminate may be performed to meet specifications of a final product exterior housing structure. Through the polishing, flattening is performed on the outer surface of the fired laminate, and gloss may be imparted. The polishing may be performed mechanically or in combination with mechanical and chemical polishing, and the present invention is not limited thereto.

On the other hand, it is preferable to adjust the front roughness of the fired laminate to 1 to 50 nm, more preferably 5 to 10 nm through the polishing. In order to make the front roughness to 1 nm or less, excessively high processing is required, and thus economic efficiency is poor. On the other hand, when the front roughness is 50 nm or more, the gloss of the exterior housing deteriorates, and because the surface is uneven, the entire surface does not have a uniform color, so the color expression may not be as smoothly expressed as desired.

Further, it is preferable that the surface hardness of the fired laminate subjected to sintering and surface treatment is 11 Gpa or more, more preferably 13 Gpa or more. If it has a hardness of less than 11Gpa, 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 method of forming an exterior housing structure according to an embodiment of the present invention.

In order to manufacture various types of exterior housing structures, the fired laminate may be molded in various ways such as bending, bending or patterning treatment. In one embodiment, forming of the fired laminate may be performed by a mold assembly including a lower mold and an upper mold, as shown in FIG. 3A. When the fired laminate 100S is placed on the lower mold and pressure is applied to the fired laminate by the upper mold, molding of the fired laminate may be performed in the same manner as the interface between the upper mold and the lower mold. In FIG. 3, bending molding of the edge of the fired laminate 100S is illustrated. In one embodiment, the molding 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.

3B is a view for explaining a molding method of a typical zirconium exterior housing structure as compared with an embodiment of the present invention.

The process of manufacturing a general zirconium exterior housing structure can be performed as follows. First, zirconium powder is filled into a mold having a certain standard, and the mold is vibrated. After this, after the planarization of the upper surface, the zirconium powder is filled again, and the mold is vibrated. After repeating the above process, when a certain amount of zirconium powder is accumulated in the mold, a zirconium plate is manufactured by applying pressure through a press molding machine.

Thereafter, the produced zirconium plate may be processed by CNC machining to dig the central portion and match the outer diameter, and then proceed to the process of photopolishing and finishing the outer surface.

4 is a view for explaining a method of manufacturing a color exterior housing structure according to an embodiment of the present invention. Among the illustrated components, the aforementioned disclosure may be referred to with respect to a component having the same reference number as the aforementioned component.

Referring to FIG. 4, a colored exterior housing structure diagram, similar to that described with reference to FIGS. 2A and 2B, overlaps individual green sheets 10CG and 10G to form a green sheet laminate 100G 'and fires it It can be produced by forming a fired laminate (100S ').

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

Further, a zirconium oxide powder and a second green sheet slurry or paste to which an inorganic pigment is further added as a colorant for coloring are formed. The content of the inorganic pigment may be several wt% to tens of 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 by 0.5 wt% to 30 wt%. As the content of the inorganic pigment added to the second green sheet slurry increases, impact resistance after firing is weakened. The contents of the binder, solvent, and dispersant applied to the first and second green sheet slurries may be referred to the aforementioned disclosure.

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

In one embodiment, the first and second green sheet thick films may be formed by coating and drying or gelling the green sheet slurry or slurry on the handle substrate 10S, respectively. As a non-limiting example, the green sheet thick film may be coated on the handle substrate by roller coating, bar coating, spray coating, spin coating, doctor blade coating, sol-gel method, dipping method, or a combination thereof. In addition, 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.

Thereafter, the formed first and second green sheets 10G and 10CG may be cut to a predetermined size in consideration of the shrinkage of the fired laminate 100S 'described later. The cutting of the green sheet may be cut in a state coated on the handle substrate or peeled from the handle substrate, and the present invention is not limited thereto. 4, first and second green sheets 10CG and 10G respectively formed on the handle substrate are illustrated.

Thereafter, the formed green sheet is laminated at least two times to form a green sheet laminate (100G '). On the top of the green sheet stack 100G ', second green sheets 10CG of one to ten layers are stacked for colorization, and second green sheets ( More than the number of 10CG), the first green sheets 10G are stacked. 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 a colorant or pigment for colorization. Therefore, for color realization, the second green sheet 10CG for colorization is applied only to some layers including the outermost layer exposed to the outside, and the first for strengthening the impact resistance on the lower surface of the second green sheet 10CG. Green sheet 10G is applied.

The stacking thickness of the second green sheet 10CG for colorization may be within 5% to 50% of the thickness of the entire green sheet stack 100G '. When the stacking thickness of the second green sheet 10CG is less than 5%, it is difficult to implement a uniform color or damage to the aesthetic sensation may easily occur due to exposure of the first green sheet 10G of the lower limb when scratching. When the layer thickness of the second green sheet 10CG exceeds 50%, deterioration of impact resistance may occur.

5 is optical images of external housing structures 100A, 100B, and 100C of a portable electronic device having various colors according to an embodiment of the present invention.

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, 100C are non-limiting examples of blue, black, or white. The illustrated exterior housing structures 100A, 100B, 100C may include a first green sheet 10G and a second green sheet 10CG having a thickness of 100 μm according to the manufacturing method disclosed with reference to FIG. 4. To form, overlapping the six first green sheets 10CG and stacking the second green sheet 10CG having three colors thereon to form a green sheet laminate 100G having a total thickness of 900 μm, It is manufactured by pressurizing it in a vacuum environment to perform an integration process and firing it.

The firing is achieved by removing the binder through the low temperature heat treatment in the first step and densifying it through the high temperature heat treatment in the second step. Since the shrinkage in the thickness direction reached about 30% by the firing, the thickness of the final fired laminate was approximately 630 μm. Subsequently, outer diameter processing and double-sided polishing were performed to meet the specifications of the product, and about 60 to 70 μm was polished in the thickness direction of both surfaces of the fired body to produce a 500 μm thick flat plate. The thickness of the color layer in this finished product is about 140 μm and accounts for about 28% of the total thickness.

Hereinafter, specific examples are provided to help understanding of the present invention. However, the following examples are provided only to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

<Example 1>

Under a solvent composed of distilled water, zirconium oxide is added, calcium oxide (CaO) is added at a ratio of 5 mol% of the zirconium oxide, and polybenzyl methacrylate having a molecular weight of 10.000 g / mol is 40 wt% of the zirconium oxide. A green sheet slurry was prepared by mixing.

10 green sheet thick films each having a width of 50 mm, a length of 100 mm, and a thickness of 90 to 100 μm, respectively, through a tape casting method of coating and drying about 5 g of the green sheet slurry prepared as above. Produced.

The ten green sheet thick films were put in a polymer bag, the polymer bag was evacuated to adhere the polymer container to the green sheet laminate, and the polymer container was placed in water having a temperature of about 80 ° C., and a water pressure of 200 to 400 atmospheres was applied. By pressing for about 20 minutes to remove unnecessary air between adjacent green sheets in the green sheet laminate, and at the same time, integration of the green sheet laminate was performed.

Subsequently, after passing through the first heat treatment step at a temperature of 500 ° C., a sintering process through a second heat treatment at 1300 ° C. was performed to prepare a fired laminate of 630 μm.

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

<Example 2>

Of the ten green sheet thick films of Example 1, in preparing three green sheet thick films, an additional 10 wt% of pigment was added to zirconium oxide to prepare a colored green sheet thick film, and the three colored green sheet thick films were prepared. The exterior housing structure was manufactured in the same manner as in Example 1, except that the other seven green sheet thick films were placed on top of each other to perform integration of the laminate.

<Comparative Example 1>

As a general process of manufacturing an exterior housing structure using zirconia oxide, a zirconium powder is filled into a mold having a width of 50 mm, a length of 100 mm, and a thickness of 2000 µm, and the mold is vibrated. After this, after the planarization of the upper surface, the zirconium powder is filled again, and the mold is vibrated. After repeating the above process, when the zirconium powder having a thickness of 1000 µm or more was accumulated, a pressure was applied through a press molding machine to produce a zirconium plate having a thickness of about 630 µm.

After dividing the central portion of the zirconia plate through CNC machining and aligning the outer diameter, the outer housing structure of 500 µm was finally manufactured through light polishing and finishing treatment on the outer surface.

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

In order to measure the impact resistance, the impact resistance performance was evaluated through the presence or absence of cracks in the samples through a 130 g steel ball drop test. All of the samples were found to have good performance in all 5 drop tests.

Table 2 below is data compared with Comparative Example 1, which is an exterior housing structure manufactured by a general method by measuring the strength, impact resistance, and surface hardness of Example 1.

In the above measurement, the strength was a three-point flexural strength method, which is a general strength measurement method, and the impact resistance test was carried out by a weight drop test, and when a load of 190 g was applied, several meters were applied. Until it was measured whether it can withstand without breaking. In addition, the surface hardness was measured based on Vicker's Hardness.

As a result of the measurement, the strength of the exterior housing structure of Example 1 was measured to be 1200 Mpa, a height that did not break in the impact resistance test, and a surface hardness of 13 Gpa.

On the other hand, the strength of the exterior housing structure of Comparative Example 1 was measured to be 900 Mpa, a height that did not break in the impact resistance test, and a surface hardness of 10 Gpa.

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

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

As described in the table above, the case of the outer casing structure of the present invention has excellent impact resistance, and compared to a commonly used outer casing structure, the strength is about 33%, the impact resistance is about 50%, and the surface hardness is about 30%. You can see the improvement. Due to such excellent strength and surface hardness, the exterior housing structure can be prevented from being damaged or scratched on the surface by an external impact, and also, through high impact resistance, to effectively protect electronic devices that are susceptible to external impact. In addition, in the case of manufacturing through the technique of the present invention, the process yield can be maintained at 70 to 80%, so that the housing structure of the housing is much more economical than the yield of about 20% in Comparative Example 1 produced by a general process. The outer housing structure of the present invention was particularly used as an outer housing structure, such as a portable electronic device, because it is possible to add a color that exhibits a unique aesthetic and excellent physical properties as described above. This is especially useful when.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope of the technical spirit of the present invention. It will be clear to those who have knowledge.

Claims (9)

1. As a zirconium structure, a plurality of green sheets containing zirconium oxide are laminated to include a plastically bonded plastic laminate,

   The casing structure of the portable electronic device having a three-point flexural strength of 1200 MPa or more of the fired laminate.
2. According to claim 1,

   The plurality of green sheets are formed by a tape casting method, and the outer housing structure of the portable electronic device having a thickness of the fired laminate is 100 to 1000 μm.
3. According to claim 1,

   The outer housing structure of the portable electronic device having a front roughness of 1 to 50 nm of the fired laminate.
4. According to claim 1,

   An outer housing structure of a portable electronic device having a Vicker's Hardness of 11 GPa or more.
5. According to claim 1,

   The green sheet includes a resin-based binder,

   The resin-based binder has a weight average molecular weight of 3,000 g / mol to 100,000 g / mol, an external housing structure of a portable electronic device.
6. The method according to claim 1, wherein the green sheet comprises an additional oxide in the range of 0.05 mol% to 10 mol% capable of stabilizing the zirconium oxide powder;

   The addition 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 yttrium An exterior housing structure of a portable electronic device comprising at least one of oxides (Y ₂ O ₃ ).
7. The outer housing structure of a portable electronic device according to claim 2, wherein a thickness of the thick film of the green sheet formed by the thick film method is within a range of 40 μm to 300 μm.
8. According to claim 1,

   The plurality of green sheets include 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 are external housing structures of the portable electronic device positioned above the first green sheets.
9. The outer 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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