WO2006129972A1

WO2006129972A1 - Method of processing visually hologramed mark in the surface of metal parts by laser marking device and metal parts processed thereby

Info

Publication number: WO2006129972A1
Application number: PCT/KR2006/002101
Authority: WO
Inventors: Jin Duck Kim
Original assignee: Kwang Sung Electronics Co., Ltd.
Priority date: 2005-06-03
Filing date: 2006-06-01
Publication date: 2006-12-07
Also published as: KR100612609B1

Abstract

A method of processing a visually hologramed mark on a surface of a metal part .using, a Laser marker includes, (a) pr.epar.ing, the, metal part, (b) adjusting a focal point of a laser beam such that a process surface of the metal part is located at a point selected from a range of 0.2 mm - 7.0 mm in a direction separated from a focus lens and a range of 0.2 mm - 7.0 mm in a direction approaching the focus lens based on a focal length from the focus lens to a focal point at which the size of the focal point that is the diameter of a laser beam is between 1 mm - 60 mm, (c) processing a mark having a predetermined shape to be visually hologramed by a thermal change and dispersion of light on a surface of the metal part by emitting a laser beam to form- the mark- on- the process surface of the- metal- part to-be indented to a predetermined depth. A mark such as a character or logo is processed using a laser marker in intaglio on the surface of the metal part of an external case of a mobile communications terminal such as a mobile phone, as a visually hologramed mark which has an effect that is visually similar to a general hologram mark and exhibits superior durability and anti-abrasion feature without deformation so as to be environment-friendly and provide a super productivity.

Description

[DESCRIPTION]

[Invention Title]

METHOD OF PROCESSING VISUALLY HOLOGRAMED MARK IN.THE, SURFACE QF METAL PARTS

BY LASER MARKING DEVICE AND METAL PARTS PROCESSED THEREBY

[Technical Field]

The present invention relates to a method of processing visually

hologramed mark on a surface of a metal part using a laser marker and a metal

part processed thereby, and more particularly, to a method of processing

visually hologramed mark on a surface of a metal part using a laser marker

which can process a mark such as a character or logo on an external case of a

metal part, for example, a mobile communications terminal such as a mobile

phone, as- a visually hologramed mark showing an effect^■■ similar to -a real

hologram mark, using a laser marker, and a metal part processed by the method.

[Background Art]

In general, a laser machine is used to cut an object to be processed or

make a groove indented to a desired depth without cutting the same by

adjusting a voltage and the pressure of nitrogen gas that is injected.

Typically, when the depth of a groove is not more than 0.1 mm, the groove is

called as a marking.

A laser marker is very reliable because it can permanently mark a company name, specifications, or a sign on an important part of an

electric/electronic part, a car plate, a stereo operation panel, or a tool,

without being affected by a production process. .Since the laser marking uses

an effect of selectively vaporizing part of a surface using a feature of a

laser beam, that is, a high energy density, when the laser beam is emitted to

an object, a local marking is possible on a limited surface. Also, the laser

marking is a non-contact processing method so that a work can be done at high

speed, the result of work is fine, and reproduction is possible by computer

control. Also, since a desired shape can be obtained as a surface is

vaporized, pre-treatment and post-treatment are not needed. Further, since

the laser marking is easy to electrically control, it is very effectively

used for a line wh-kh- -requires automation such as continuous- manufacture

serial numbers or barcodes. In addition, since the laser marker is capable

of performing a work in a small area for a short time in a non-contact manner,

the tool does not wear out and deformation of a product due to heat is

prevented so that a process can be performed without a damage to parts.

The principle of laser marking is that a laser beam is emitted to an

objected to be processed using the feature of a laser beam having a high

energy density in a small area to enable a surface process using a phenomenon

of heating, melting, and vaporizing or generating chemical reactions so that demerits of the conventional printing or carving methods can be compensated.

Thus, the laser marking is widely used together with laser cutting and

punching techniques, in a laser application field.

A silver rectangular sticker adheres to most credit cards and a picture

on the sticker is displayed in 3 dimensions by turning the credit cards in

different directions. Such a picture is referred to as a hologram and a

hologram mark on credit cards is used to prevent forgery of the credit cards.

The hologram is a film on which information about the wave surface of

light emitted from an object is recorded and a technology therefor is

referred to as holography. The word "holo" is a Greek which means the whole

while the word "gram" is a Greek which means a message or information.

The hologram, like a photo film, records and- reproduces an- image of an

object using a silver photo film. It is the only difference that the

resolution of a film for hologram is relatively higher than that of a photo

film such that a fine part of the object can be recorded. However, the photo

film cannot reproduce an object in 3 dimensions because it merely records

bright and dark shapes of the object, not the position of the object, that is,

the distances from eyes of a human to various parts of the object. A degree

of brightness and darkness of the object is indicated by amplitude while the

position of the object is indicated by phase. When the amplitude and the phase both are recorded, an image in 3 dimensions can be represented.

A rainbow embossing hologram is currently widely used for credit cards

where hologram marks are attached. The rainbow, embossing hologram can be

mass produced by printing using a rainbow hologram as master. In the general

manufacture of embossing holograms, a hologram having an uneven surface is

made using photoresist as a photosensitive material. The depth of unevenness

is not greater than 0.4 mm. Since the surface of photoresist is not strong,

mass printing is not available so that a metal mold needs to be made using

the unevenness. The metal mold is typically made of nickel. To make a

nickel mold, gold or silver is deposited on a developed photoresist to

provide electric conductivity and nickel plate is applied to a depth of 200

mm - 300 mm and a nickel plate is ripped- off. The- embossing hologram is

printed while applying heat to thermoplastic using the nickel mold. Although

the plating step can be omitted by using photopolymer instead of the

photoresist to thereby make the step simple, the number of prints is reduced

to one tenth compared to the nickel mold. The photopolymer that is a

photosensitive polymer does not need development because it is hardened when

exposed to blue light over a predetermined degree. The hologram is

classified into dichromatic gelatin and thermoplastic according to the type

of a photosensitive material. Recently, to attract customers interests and improve image of a

manufacturer, a mark such as a character, logo, or emblem is attached in form

of a hologram, on an external case of a product such as.. a mobiIa,phone. As a

related technique, Korean Patent Registration No. 10-0376248 discloses a

technique about a method for manufacturing a window plate where a hologram

character is formed to promote the image of a company by forming a hologram

character to display the brand of a manufacturing company on a window plate

attached to various electronic products such as communication devices, TVs,

VCRs, or washing machine. According to the patent, the method includes steps

of forming a deposition layer by vacuum .depositing metal on a hard coated

plate, performing a silk printing on the surface of the deposition layer

where the metal is deposited, removing a window portion- and- a character

portion from the deposition layer, washing the window plate after the

deposition layer is removed, drying the washed window plate, processing the

dried window plate to have a shape appropriate to an electronic product,

forming a hologram character on the character portion of the window plate

that is processed to a predetermined shape (a hot stamping step), and forming

an adhesive layer on the surface thereof after the hologram character is

formed by hot stamping.

However, in the conventional method of forming a hologram on a metal part such as an external case of a mobile communications terminal, since the

hologram cannot be formed directly on the metal part, the hologram is printed

on a thermoplastic using, a nickel mold, by applying heat, thereto and attached

to the metal part, or a hologram character is formed on a transparent acrylic

plate using hot stamping and the transparent acrylic plate is attached to the

metal part, the manufacturing process is complicated and productivity is

lowered so that the method is not appropriate for mass production. The

hologram mark formed in the conventional method has demerits in that

durability and anti-abrasion feature are deteriorate, for example, a hologram

mark portion is easily deformed or damaged unless . a protective tape is

attached thereon.

[Disclosure]

[Technical Problem]

To solve the above and/or other problems, the present invention

provides a method of processing visually hologramed mark on a surface of a

metal part using a laser marker which can process a mark such as a character

or logo in intaglio on the surface of the metal part of an external case of a

mobile communications terminal such as a mobile phone, as a visually

hologramed mark which shows an effect that is visually similar to a general

hologram mark and exhibits superior durability and anti-abrasion feature without deformation than the general hologram mark so as to be environment-

friendly and have a superior productivity, and a metal part processed by the

above method.

[Technical Solution]

According to an aspect of the present invention, a method of processing

a visually hologramed mark on a surface of a metal part using a laser marker,

the method comprising the steps of (a) preparing the metal part, (b)

adjusting a focal point of a laser beam such that a process surface of the

metal part is located at a point selected from a range of 0.2 mm - 7.0 mm in

a direction separated from a focus lens and a range of 0.2 mm - 7.0 mm in a

direction approaching the focus lens based on a focal length from the focus

lens to a focal point at which the size of the focal point that is the

diameter of a laser beam is between 1 mm - 60 mm, (c) processing a mark

having a predetermined shape to be visually hologramed by a thermal change

and dispersion of light on a surface of the metal part by emitting a laser

beam to form the mark on the process surface of the metal part to be indented

to a predetermined depth.

The step (a) comprises mirror surface finishing of the process surface

of the metal part.

The surface of the metal part that is mirror surface finished has a surface roughness of 0.2 mm - 5.0 mm.

In the step (c), a frequency is set to one selected from a range of 50

kHz - 120 kHz.

The diameter of the focus lens is substantially between 160 mm - 416 mm.

In the step (c) power, speed, and frequency to adjust the laser beam

are maintained constant.

The laser beam is a single mode beam and the size of a focal point is

obtained by an equation that ⁷^ , wherein "λ" is the wavelength of laser

light, "f" is the focal length of a lens, "R" is the radius of a beam of a

lens, and "r" is the radius of a beam at the focal point.

The metal part is an external case of a mobile communications terminal,

the external case being made of stainless steel.

According to another aspect of the present invention, a metal part

manufactured in the above-described method.

[Advantageous Effects]

According to the present invention, a mark such as a character or logo

is processed using a laser marker in intaglio on the. surface of the metal

part of an external case of a mobile communications terminal such as a mobile

phone, as a visually hologramed mark which has an effect that is visually similar to a general hologram mark and exhibits superior durability and anti-

abrasion feature without deformation so as to be environment-friendly and

provide a superior productivity.

[Description of Drawings]

FIG. 1 is a flow chart for explaining a method of processing a visually

hologramed mark on the surface of a metal part using a laser marker according

to an embodiment of the present invention;

FIG. 2 is a view showing a state of processing a visually hologramed

mark on the surface of a metal part using a laser marker according to an

embodiment of the present invention!

FIG. 3 is a conceptual view showing the focusing state of FIG. 2 in

which the size of a focus of a laser beam is exaggeFated-ly shown!

FIG. 4 is a view for explaining a general property of focusing of a

laser beam!

FIG. 5 is a table containing basic variables of a laser set during the

process of FIG. 2;

FIG. 6 is a conceptual view showing the focusing state of processing a

visually hologramed mark on the surface of a metal part using a laser marker

according to another embodiment of the present invention, in which the size

of a focus of a laser beam is exaggeratedly shown; and FIG. 7 is an image of the surface of the metal part on which a visually

hologramed mark is processed using a laser marker according to a method of

processing, according, to the present invention.

[Best Mode]

The attached drawings for illustrating preferred embodiments of the

present invention are referred to in order to gain a sufficient understanding

of the present invention, the merits thereof, and the objectives accomplished

by the implementation of the present invention.

Hereinafter, the present invention will be described in detail by

explaining- preferred embodiments of the invention . with reference . to the

attached drawings. Like reference numerals in the drawings denote like

elements.

The present invention can be applied to various metal parts such as an

external case of a mobile phone, where the external case is made of stainless

steel, a metal external case of a PDA made of stainless steel, and a metal

frame of a display device. However, in the follow description, a metal

external case of a mobile phone, in particular, an external case of a mobile

phone, where the external case is made of a stainless steel, for the

convenience of explanation.

FIG. 1 is a flow chart for explaining a method of processing a visually hologramed mark on the surface of a metal part using a laser marker according

to an embodiment of the present invention. FIG. 2 is a view showing a state

of processing a visually hologramed mark on the surface of a metal part using

a laser marker according to an embodiment of the present invention. FIG. 3

is a conceptual view showing the focusing state of FIG. 2 in which the size

of a focus of a laser beam is exaggeratedly shown. FIG. 4 is a view for

explaining a general property of focusing of a laser beam. FIG. 5 is a table

containing basic variables of a laser set during the process of FIG.2.

Referring to FIG. 1, a metal external case of a mobile phone is

provided in mechanical processing (SlOO). A process surface αf the external

case of a mobile phone where a character or logo is indicated is mirror

surface finished to provide a high glossy surface (S200). It is preferable

to process the surface to have a surface roughness Ra of about 0.2 mm - 5.0

mm. The reason for processing the surface in the mirror surface finishing is

that a hologram effect becomes superior when the processing method of the

present invention is applied to a high glossy surface rather than a rough

surface.

As shown in FIG. 3, the focal point of a laser beam is adjusted such

that the process surface of an external case of a mobile phone is located at

a point selected from a range between 0.2 mm (Ll) - 7.0 mm (L2) in a direction separated from a focus lens, that is, downwardly, based on a focal

distance from the focus lens to a focal point at which the size of a focal

point that is the diameter of a laser beam is between 1 mm - 6Q,im,(S300).

The focusing of a laser beam in a laser marker is described below with

reference to FIG. 4. For a laser marking process, focusing using a single

lens or multiple lens is generally needed. This is to greatly increase a

laser energy intensity on a process surface through focusing. The energy

intensity is defined as in the following equation.

Power [W)

Energy Intensity (WI cm ) =

Area of focalpoint portionfcm²)

[Equation 1]

As the size of the focal point of a laser beam that is focused becomes

smaller, more precise processing of laser marking is possible. For example,

for a single mode beam, focusing is possible to a very small size, that is, 1

mm - 50 mm.

The size of a focal point of a single mode laser beam can be defined as

in the following equation.

πR [Equation 2]

Here, "λ" is the wavelength of laser light, "f" is the focal length of a lens, "R" is the radius of a beam of a lens, and "r" is the radius of a

beam at the focal point.

In the present invention, unlike the laser marking., the focal point of

a laser beam is adjusted such that the process surface of a metal part is

located at a point selected from a range of 0.2 mm (Ll) - 7.0 mm (L2) in a

direction separated from a focus lens, that is, downwardly, and a range of

0.2 mm (L3) - 7.0 mm (L4) in a direction approaching the focus lens, that is,

upwardly, based on a focal length from the focus lens to a focal point at

which the size of the focal point that is the diameter of a laser beam is

between 1 mm - 60 mm, and the laser beam is emitted to process a mark having

a predetermined shape (S400).

When the laser beam is emitted by making the focal- point uncl-ear as

above, the size of the focal point of the laser beam varies during the laser

marking. Thus, a sopt of the laser beam is overlapped due to the size of the

focal point, that is, the size of the spot of the laser beam so that the

surface of a metal part is processed. As a result, a visually hologramed

mark is processed due to the thermal change and the dispersion of light on

the surface of the metal part. That is, when the marking process is

performed in a focused state during the laser marking, the material itself is

ripped off. However, when the process surface of a metal part is located at a point selected from a range of 0.2 mm - 7.0 mm in a direction separated

from the focus lens, that is, downwardly, and a range of 0.2 mm - 7.0 mm in a

direction approaching,, the. focus,.lens, that*, i.s,,.,.upwardly,, Light is dispersed.

Referring to FIG. 2, in a process of emitting a laser beam to the

process surface of an external case of a mobile phone, a laser beam 10 is

emitted by a beam expander 20. The laser beam 10 is reflected by an X Galbo

mirror 30 and a Y Galbo mirror 40, passes through a focus lens 50, and

arrives at a process surface 60 to process a mark 70. The diameter of the

focus lens 50 is normally 160 mm, 254 mm, or 416 mm, in particular, in the

present embodiment, 254 mm. , .

In the present embodiment, as shown in FIG. 3, the focal point of a

laser beam is adjusted- such th-at the process- surface of- a metal part, for

example, an external case of a mobile phone, is located at a point selected

from a range of 0.2 mm (Ll) - 7.0 mm (L2) in a direction separated from a

focus lens, that is, downwardly, based on a focal length from the focus lens

to a focal point at which the size of the focal point that is the diameter of

a laser beam is between 1 mm - 60 mm, and the laser beam is emitted to the

process surface so as to process a mark having a predetermined shape.

Accordingly, the mark is hologramed on the process surface by the thermal

change of the metal itself and the dispersion of light. The laser power, speed, and frequency can be set as shown in the table

of FIG. 5. The ranges in the table of FIG. 5 signify that the optimal value

in each range Ls, set , according, tc the. condition,.. When , a..-mark having „a

predetermined shape is processed by emitting a laser beam to the process

surface, it is preferable to maintain the laser power, speed, and frequency

constant. For example, a laser beam can be set to a power of 30 W, a speed

of 350 m/s, and a frequency of 90 kHz to process the process surface of an

external case of a mobile phone, where the external case is made of stainless

steel. Referring to FIG. 5, as the laser power increases, the speed and

frequency need to constantly increase to process a visually hologramed mark.

The frequency is set to one selected from a range of 50 kHz - 120 kHz. It is

^■preferable that the visually hologramed mark can- be obtained^ only when the

frequency is over 50 kHz.

FIG. 6 is a conceptual view showing the focusing state of processing a

visually hologramed mark on the surface of a metal part using a laser marker

according to another embodiment of the present invention, in which the size

of a focus of a laser beam is exaggeratedly shown. As shown in FIG. 6,

according to another embodiment of the present invention, the focal point of

a laser beam is adjusted such that the process surface of a metal part, that

is, an external case of a mobile phone, is located at a point selected from a range of 0.2 mm (L3) - 7.0 mm (L4) in a direction approaching the focus lens,

that is, upwardly, based on a focal length from the focus lens to a focal

point at which the size of the focal* point that is, the diameter of a laser

beam is between 1 mm - 60 mm, and the laser beam is emitted to process a mark

having a predetermined shape. According to an actual processing result, the

effect of hologram of a visually hologramed mark is more apparent in the

previously described embodiment rather than the present embodiment.

FIG.7 is an image of the surface of the metal part on which a visually

hologramed mark is processed using a laser marker according to a method of

processing according to the present invention. As shown in FIG. 7, when the

surface of a metal part is directly processed using a laser marker according

to the processing method of the present invention, a visually holgoramed mark

can be obtained which has an effect visually similar to a general hologram

mark.

In the above-described embodiments, although the metal part is an

external case of a mobile phone, where the external case is made of stainless

steel, the present invention can be applied to a variety of products made of

various metal materials such as aluminum. Also, in the above-described

embodiments, although the process surface of a metal part is mirror surface

finished, the process surface of a metal part may not be mirror surface finished if a visually hologramed mark to a desired degree can be obtained

without mirror surface finishing.

While this invention has been particularly shown-. and, described with

reference to preferred embodiments thereof, it will be understood by those

skilled in the art that various changes in form and details may be made

therein without departing from the spirit and scope of the invention as

defined by the appended claims.

[Industrial Applicability]

As described above, according to the present invention, a mark such as

.a character αr logo is processed using, a laser marker in. intaglio on the

surface of the metal part of an external case of a mobile communications

^■terminal sueh as a mobile phone, as a visually hologramed mark which--has an

effect that is visually similar to a general hologram mark and exhibits

superior durability and anti-abrasion feature without deformation so as to be

environment-friendly and provide a superior productivity.

Claims

[CLAIMS]

[Claim 1]

A method of processing, a visually hologramed mark „011 ,a,, surface of a

metal part using a laser marker, the method comprising the steps of:

(a) preparing the metal part;

(b) adjusting a focal point of a laser beam such that a process surface

of the metal part is located at a point selected from a range of 0.2 mm - 7.0

mm in a direction separated from a focus lens and a range of 0.2 mm - 7.0 mm

in a direction approaching the focus lens based on a focal length from the

focus lens to a focal point at which the size of the focal point, that is the

diameter of a laser beam is between 1 mm - 60 mm;

(c) processing a mark having a predetermined shape^ to- be -visually

hologramed by a thermal change and dispersion of light on a surface of the

metal part by emitting a laser beam to form the mark on the process surface

of the metal part to be indented to a predetermined depth.

[Claim 2]

The method of claim 1, wherein the step (a) comprises mirror surface

finishing of the process surface of the metal part.

[Claim 3]

The method of claim 2, wherein the surface of the metal part that is mirror surface finished has a surface roughness of 0.2 mm - 5.0 mm.

[Claim 4]

The method of claim. L, wherein in. the step (c) a. frequency is set to

one selected from a range of 50 kHz - 120 kHz.

[Claim 5]

The method of claim 1, wherein the diameter of the focus lens is

substantially between 160 mm - 416 mm.

[Claim 6]

The method of claim 1, wherein in the step (c) power, speed, and

frequency to adjust the laser beam are maintained constant.

[Claim 7]

The method of claim 1, wherein the laser beam is a si-ng-1-e mode beam and

the size of a focal point is obtained by an equation that

⁷^ , wherein "λ" is the wavelength of laser light, "f" is the focal

length of a lens, "R" is the radius of a beam of a lens, and "r" is the

radius of a beam at the focal point.

[Claim 8]

The method of claim 1, wherein the metal part is an external case of a

mobile communications terminal, the external case being made of stainless steel .

[Claim 9]

A metal part .manufactured in a method .according* t.α one .of claims 1

through 8.