Typesetting fixing method, display plate and timepiece

A typesetting fixing method includes: disposing a typesetting member on a front surface of a dial plate, the dial plate being made of a transparent or semitransparent resin and the typesetting member being made of an opaque or semitransparent resin having a laser absorbing property; irradiating the dial plate with a laser beam from a rear side of the dial plate while the dial plate is uniformly applied a pressure by a heat-resistant jig; and welding the typesetting member on the dial plate by absorbing the laser beam at an interface of the typesetting member and by melting at least one of the typesetting member and the dial plate by heat.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority based on Japanese Patent Application No. 2014-134435, filed on Jun. 30, 2014, the entire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a typesetting fixing method, a display plate and a timepiece.

2. Description of the Related Art

On a dial plate for a timepiece, there are numbers or characters representing time and the like, indicators (so-called hour characters) to replace them, various scale marks, symbols, or the like, to be disposed.

These hour characters and the like may be two-dimensionally formed by printing. However, in order to make a high-quality finish, it is preferable to three-dimensionally express them. A “typesetting” method of forming a typesetting member as a separate member and disposing and fixing the typesetting member on a dial plate is widely used.

In the related art, it is general to make a typesetting member of a metal material, and in order to fix a typesetting member, mechanical swaging or bonding is often used.

That is, for example, a typesetting member is fixed by providing a leg on the rear side of the typesetting member, and forming a hole for inserting the leg in a dial plate made of a metal material or a resin material, and disposing the typesetting member on the dial plate, and then fixing the leg on the rear side of the dial plate by mechanical swaging, bonding using an adhesive, or the like.

In this regard, according to recent evolution of a molding technology, it has become possible to make typesetting members which are fine components of resin materials.

In a case of making both of a dial plate and a typesetting member of resin materials, it is possible to fix the typesetting member on the dial plate by various methods of joining resins.

Examples of the methods of joining resins include fixing using an adhesive, thermo compression bonding, and ultrasonic joining.

However, it takes a lot of trouble to fix a fine component by an adhesive, and due to some reason such as extrusion of the adhesive, it may be impossible to make a beautiful finish.

In JP-A-2001-198982, there has been disclosed a method of welding resins by a laser welding technique.

However, a typesetting member is a fine component to be disposed on a dial plate, and on the dial plate of a timepiece, slight flaws such as deformation and burns due to heat and dirt are easy to notice. Therefore, product quality decreases.

In this regard, the method of the related art as described above has an issue that, since fine heat control is impossible, it is difficult to perform stable welding in a fine area of a fine component. And, it is especially difficult to perform welding of a component strongly required to eliminate influence of heat on the external appearance, like a typesetting member of a timepiece.

SUMMARY OF THE INVENTION

The present invention was made in view of the above described circumstances, and an object of the present invention is to provide a typesetting fixing method, a display plate, and a timepiece capable of precisely fixing a typesetting member which is a fine component made of a resin on a dial plate made of a resin.

In order to achieve the above described object, according to an aspect of the present invention, a typesetting fixing method includes: disposing a typesetting member on a front surface of a dial plate, the dial plate being made of a transparent or semitransparent resin and the typesetting member being made of an opaque or semitransparent resin having a laser absorbing property; irradiating the dial plate with a laser beam from a rear side of the dial plate while the dial plate is uniformly applied a pressure by a heat-resistant jig; and welding the typesetting member on the dial plate by absorbing the laser beam at an interface of the typesetting member and by melting at least one of the typesetting member and the dial plate by heat.

In order to achieve the above described object, according to another aspect of the present invention, a display plate includes a dial plate and a typesetting member. The dial plate is made of a transparent or semitransparent resin. The typesetting member is disposed on a front surface of the dial plate and is made of an opaque or semitransparent resin having a laser absorbing property. The dial plate is irradiated with a laser beam from a rear side of the dial plate while the dial plate is uniformly applied a pressure by a heat-resistant jig, the laser beam is absorbed at an interface of the typesetting member. At least one of the typesetting member and the dial plate is melted by heat, whereby the typesetting member is welded on the dial plate.

In order to achieve the above described object, according to another aspect of the present invention, a timepiece includes a display plate. The display plate includes a dial plate and a typesetting member. The dial plate is made of a transparent or semitransparent resin. The typesetting member is disposed on a front surface of the dial plate and is made of an opaque or semitransparent resin having a laser absorbing property. The dial plate is irradiated with a laser beam from a rear side of the dial plate while the dial plate is uniformly applied a pressure by a heat-resistant jig. The laser beam is absorbed at an interface of the typesetting member. At least one of the typesetting member and the dial plate is melted by heat. The typesetting member is welded on the dial plate, whereby the display plate is formed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of a typesetting fixing method, a display plate, and a timepiece according to the present embodiment will be described with reference toFIGS. 1 to 8.

Also, although the after-mentioned embodiments are provided with various technically preferred limitations to perform the present invention, the scope of the present invention is not limited to the following embodiments and illustrated examples.

FIG. 1is a plan view of a display plate of a timepiece according to the present embodiment.

As shown inFIG. 1, the display plate of the present embodiment has a dial plate1and typesetting members2.

In the present embodiment, the dial plate1is made of a transparent or semitransparent resin.

The material which forms the dial plate1is specifically acrylic resin (methacrylic resin, or PMMA such as polymethyl methacrylic acid or polymethyl methacrylate) or polycarbonate resin (PC), for example. And, it is preferable that its light transmittance is 20% or more.

Also, the typesetting members2are disposed on the front surface of the dial plate1, and are indicated, for example, by hands3. The typesetting members2include typesetting members2aand typesetting members2b. The typesetting members2aindicates hour characters which three-dimensionally express numbers or characters representing time and the like, indicators (so-called hour characters) to replace them, and the like. The typesetting members2bindicates decoration which three-dimensionally express a ring, scale marks, symbols, and the like to be provided around a small display section4for displaying various information and at other positions.

The typesetting members2are made of an opaque or semitransparent resin having a laser absorbing property.

It is preferable that the material which forms the typesetting members2may be an opaque material having relatively excellent heat resistance and absorbing visible light, specifically, for example, polycarbonate resin (PC) or ABS resin. It is preferable that its light transmittance may be 20% or less.

FIG. 2Ais an enlarged view of a typesetting member shown inFIG. 1and the surrounding dial plate, andFIG. 2Bis a front view of the typesetting member as seen from an arrow b direction ofFIG. 2A, andFIG. 2Cis a side view of the typesetting member as seen from an arrow c direction ofFIG. 2A.

Also,FIGS. 3A, 4A, and 5Aare enlarged views of modifications of the typesetting member and the surrounding dial plates, andFIGS. 3B, 4B, and 5Bare front views of the typesetting members as seen from arrow b directions ofFIGS. 3A, 4A, and 5A, respectively.

As shown inFIGS. 2A to 2C, a typesetting member2consists of a main body portion21, and a leg22which is provided on the rear side of the main body portion21.

Also, the shapes and number of legs22are not limited to the illustrated examples.

Also, it is not essential for the typesetting member2to have the leg22, and the leg22may not be provided.

In a case where the typesetting member2has the leg22, in the dial plate1, a hole for fitting the leg22is formed.

Also, the hole may be a through-hole, or may be a recess which does not penetrating through the dial plate.

Since the leg22is provided on the typesetting member2and the hole for fitting the leg22is formed in the dial plate1, positioning of the typesetting member2becomes easy.

Also, on the top surface of a typesetting member2aof the present embodiment, a crest line23is provided along a longitudinal direction, and thus the typesetting member2ahas an inverted V shape as seen in a front view (seeFIG. 2B).

Here, the crest line23means a portion where surfaces intersect with each other and which is higher than the other portion.

Also, in the present embodiment, not only a portion where inclined surfaces intersect with each other as shown inFIG. 2Bor the like, but also a portion where an inclined surface and a flat surface intersect with each other, for example, as shown inFIGS. 3B and 4Bare defined as crest lines23.

Also, in a case where there is a point higher than the other portion as shown inFIGS. 5A and 5B, the corresponding point is defined as an apex24.

FIG. 6is a cross-sectional view of a main portion for explaining a typesetting fixing method according to the present embodiment, and roughly shows a device configuration for realizing a display plate of the present embodiment.

A device for realizing the typesetting fixing method according to the present embodiment specifically includes a support member51, a pressing member52and a pressure uniformizing jig53as shown inFIG. 6. The support member51supports the dial plate1and the typesetting members2. The pressing member52presses the dial plate1and the typesetting members2. The pressure uniformizing jig53uniformizes a pressure to be applied by the pressing member52.

The pressure uniformizing jig53needs to be able to transmit a laser beam L and withstand heat which is generated during laser welding. For example, flat-plate-like transparent heat-resistant glass can be applied.

By applying a pressure through the pressure uniformizing jig53, it is possible to press the dial plate1and the typesetting members2in a plane, and it is possible to perform laser welding while applying a uniform pressure to the typesetting members2.

Here, it is preferable that the uniform pressure may be a pressure with a uniformity ratio of 80% or more. It is preferable that its power may be 0.1 N to 5 N.

On the occasion of fixing the typesetting members2on the dial plate1, the typesetting members2are disposed on the front surface of the dial plate1, and a protective sheet54is disposed on the typesetting members2positioned on the front side of the dial plate1and to be fixed. The protective sheet54protects the front surfaces of the dial plate1and the typesetting members2.

Further, a cushioning member55is disposed on the front side of the typesetting members2, and a pressure is applied through the cushioning member55by the pressing member52.

As the cushioning member55, for example, silicon rubber can be used.

In the present embodiment, the dial plate is irradiated with a laser beam L from the rear side of the dial plate1while the dial plate is uniformly applied a pressure by the heat-resistant jig as described above, whereby the laser beam L is absorbed at the interfaces of the typesetting members2. The typesetting members2or/and the dial plate1are melted by heat, whereby the typesetting members2are welded on the dial plate1.

In the present embodiment, it is preferable that the irradiation condition (output condition) of the laser beam L may be set such that its wavelength is 390 nm to 1200 nm, and its power is 0.1 W to 10.0 W (more preferably, 5.0 W to 8.0 W), its repetition frequency is 1 kHz to 500 kH, and its scan speed is about 1 mm/s to 100 mm/s.

Also, it is preferable that the beam shape of the laser beam L may be a beam shape with a uniform distribution having no peak, not a general Gaussian distribution shape having a peak at a central portion.

FIGS. 7A and 8Aare views of examples of a beam having no peak as seen from the above, andFIGS. 7B and 8Bare views of the beams shown inFIGS. 7A and 8Aas seen three-dimensionally.

It is preferable to use a beam having a small shape with a high uniformity ratio, for example, like a top hat shape shown inFIGS. 7A and 7Bor a ring shape shown inFIGS. 8A and 8B, as the beam shape of the laser beam L.

The beam shape of the laser beam L is determined by adjusting the structure of a resonator (cavity) which is included in a laser generating device (not shown) and where a laser oscillates, and beam diffraction (for example, the size of a beam output terminal and a wavelength).

In a case of irradiation with the laser beam L, it is necessary to prevent an influence of heat which is generated by absorption of the laser beam L from exhibiting on the viewable side of the typesetting members2(that is, the front surfaces of the typesetting members2), to the utmost. And, to that end, it is preferable to secure a distance from the interfaces of the typesetting members2to be melted by the laser beam L to the front surfaces of the typesetting members2, in the irradiation direction of the laser beam L, as much as possible.

For example, in a case where the typesetting members2has a thick portion, it is preferable to set the thick portion as a position to be irradiated with the laser beam L.

In the present embodiment, a thick portion means a portion thick in the irradiation direction of the laser beam L.

For example, in a case where a typesetting member2has a leg22extending in the longitudinal direction as shown inFIG. 4A, the portion where there is the leg22is a thick portion thick in the typesetting members2(thick in the irradiation direction of the laser beam L).

It is preferable that irradiation with the laser beam L may be performed along the leg22.

Also, even in a case where the leg22is thin as shown inFIG. 2A, in a case where it is possible to fix the typesetting member2only by melting the corresponding portion, spot welding may be performed by irradiating the corresponding leg22with the laser beam L.

Also, in a case where it is possible to provide a thick portion other than a leg22as design of a typesetting member2, the corresponding thick portion is irradiated with the laser beam L.

Also, in a case where a typesetting member2has a crest line23as shown inFIGS. 2A and 3A, or in a case where a typesetting member2has an apex24as shown inFIG. 5A, it is preferable that the crest line23or the apex24may be irradiated with the laser beam L.

Since a portion where the crest line23or the apex24is provided is the highest portion of the corresponding typesetting member2, if this portion is irradiated with the laser beam L, it is possible to secure the irradiation distance of the laser beam L.

InFIGS. 2A, 3A, 4A, and 5A, portions which are melted by irradiation with the laser beam L are shown by diagonal meshes.

In a case where two crest lines23are provided as shown inFIG. 3A, the laser beam L may be reciprocated with respect to each crest line23, or each crest line23and a portion connected to the corresponding crest line may be scanned in a U shape with the laser beam L.

In the case of performing scan in a U shape with the laser beam L, with respect to a portion connected to each crest line23, it is preferable to minimize a portion to be melted, for example, by increasing the movement speed of the scan or decreasing the power of the laser beam L.

Also, in the case where two crest lines23are provided, it is preferable to change an irradiation angle when each crest line23is irradiated with the laser beam L, thereby performing irradiation from the obliquely lower direction, as shown inFIG. 3B.

By doing this, it is possible to further secure the irradiation distance to each crest line23.

InFIGS. 2B and 2C, a heat diffusion state in a typesetting member2in a case of irradiating the crest line23with the laser beam L is shown by arrows.

As shown inFIGS. 2B and 2C, in the case of irradiating the crest line23with the laser beam L, heat diffuses around the crest line23which is a relatively thick portion, and thus it is possible to suppress thermal influence from exhibiting on the front surface of the typesetting member2.

Next, the typesetting fixing method according to the present embodiment will be described.

In the present embodiment, in a case of fixing the typesetting members2on the dial plate1, as shown inFIG. 6, heat-resistant glass or the like which is the pressure uniformizing jig53is mounted on the support member51, and on it, the dial plate1having the typesetting members2mounted thereon is mounted.

Thereafter, on the typesetting members2positioned on the front side of the dial plate1and to be fixed, the protective sheet54for protecting the front surfaces of the dial plate1and the typesetting members2is disposed, and the cushioning member55is disposed on the front side of the typesetting members2, and pressing is performed through the cushioning member55by the pressing member52.

A laser radiation device (not shown) adjusts the beam shape of a laser beam L to be radiated to a shape having no peak, and radiates the laser beam L onto thick portions of the typesetting members2such as portions where the crest lines23or the apexes24or the legs22are provided.

As a result, in a state where a pressure is uniformly applied, irradiation with the laser beam L from the rear side of the dial plate1is performed, whereby the laser beam L is absorbed at the interfaces of the typesetting members2, and the typesetting members2or/and the dial plate1are melted by heat, whereby the typesetting members2are welded on the dial plate1.

In this case, heat generated by the laser welding diffuses in the relatively thick portions of the typesetting members2, and thus the influence of the heat on the front surfaces of the typesetting members2is suppressed.

As described above, according to the present embodiment, the typesetting members2made of an opaque or semitransparent resin having a laser absorbing property are disposed on the front surface of the dial plate1made of a transparent or semitransparent resin, the dial plate1is irradiated with a laser beam L from the rear side of the dial plate1while the dial plate1is uniformly applied a pressure by the pressure uniformizing jig53which is a heat-resistant jig.

As a result, the laser beam L is absorbed at the interfaces of the typesetting members2, and the typesetting members2or/and the dial plate1are melted by heat, whereby the typesetting members2are welded on the dial plate1.

Like this, since laser welding is performed in a state where a pressure is uniformly applied, it is possible to uniformly disperse the influence of heat generated by the laser welding, and it is possible to prevent an influence of the heat on the front surfaces (that is, the viewable side) of the typesetting members2, and form the dial plate1having the high-quality typesetting members2(upright indexes).

Also, since the typesetting members2are fixed by thermal welding using irradiation with a laser beam L, it is possible to remarkably improve impact resistant performance as compared to any other fixing method such as fixing using an adhesive.

Also, portions which are thick in the typesetting members2and where there are the legs22, the crest lines23, or the apexes24are irradiated with the laser beam L.

Therefore, it is possible to secure the irradiation distance of the laser beam L, and it is possible to suppress an influence of heat which is generated by laser welding from exhibiting on the front surfaces (that is, viewable side) of the typesetting members2.

Also, in a case where the typesetting members2have crest lines23or apexes24, even if dirt or the like exhibits due to an influence of heat caused by irradiation with the laser beam L, the dirt or the like is inconspicuous as compared to a case of forming the front surfaces of the typesetting members2flat, and it is possible to realize typesetting excellent in designability.

Further, since the beam shape of the laser beam L is adjusted to a top hat shape having no peak at a center portion, or the like, as compared to a case of using a laser beam L having a Gaussian distribution shape, it becomes difficult for the influence of heat caused by the irradiation with the laser beam L to be focused on one point, and thus it is possible to further reduce the influence of the heat on the front surfaces (that is, viewable side) of the typesetting members2.

Also, although the embodiment of the present invention has been described, it goes without saying that the present invention is not limited to such embodiment and various modifications can be made without departing from the scope of the present invention.

For example, in the present embodiment, a case of performing irradiation with the laser beam L from the side directly below the typesetting members2has been exemplified. However, the irradiation direction of the laser beam L is not limited thereto.

For example, in a case of radiating the laser beam L toward the leg22of a typesetting member2, as shown inFIGS. 9A to 9C, irradiation with the laser beam L from the obliquely lower side of the leg22may be performed.

In a case of performing irradiation with the laser beam L from the obliquely lower side as described above, it is possible to secure a longer distance to the front surface of the typesetting member2as compared to a case of performing irradiation with the laser beam L from the side directly below the typesetting member, and it is possible to suppress an influence of heat on the front surface of the typesetting member2.

Also, in this case, as shown inFIG. 9C, a portion to be irradiated with the laser beam L (inFIG. 9C, the leg22of the typesetting member2) may be cut obliquely according to the irradiation angle of the laser beam L.

If the incident angle of the laser beam L to an irradiation target is set to a substantially right angle, it is possible to efficiently diffuse heat.

Also, for example, in a case where it is desired to fix a typesetting member2designed to have a recess at the central portion on the dial plate1as shown inFIG. 10A, in a thin portion, a cavity may be formed in the typesetting member2, whereby an air layer25may be provided.

Like this, since the air layer25is provided inside the typesetting member2, it is possible to suppress transmission of heat caused by irradiation with the laser beam L, and it is possible to suppress dirt and burns attributable to influence of heat from exhibiting on the front surface (viewable side) of the typesetting member2.

Also, since the heat insulation structure is provided inside the typesetting member2, it has no influence on the external appearance of the typesetting member2.

Also, for example, as shown inFIG. 10B, slits26may be formed in the side portions of the lower side of a typesetting member2.

In some cases such as a case where the width of a typesetting member2is narrow, it is feared that the thermal influence of the laser beam L may exhibit at the side portions of the typesetting member2.

In this regard, in a case of forming slits26in the side portions of the typesetting member2, in these portions, heat insulating layers are formed by air. Therefore, it is possible to suppress heat transmission, and it is possible to suppress dirt and burns attributable to influence of heat from exhibiting on the front surface (viewable side) of the typesetting member2.

Also, even in this case, since the heat insulation structures are provided in internal portions of the typesetting member2hidden by the dial plate1, they have no influence on the external appearance of the typesetting member2.

Also, in the present embodiment, an example using a laser beam L having a beam shape having no peak in the center portion has been described. However, the beam shape of the laser beam L is not limited thereto.

For example, in a case where an irradiation distance to the front surface of a typesetting member2is sufficiently secured, or in a case of providing a heat insulation structure inside a typesetting member2, the beam shape of the laser beam L may be set to a general Gaussian distribution shape.

Also, in the present embodiment, as the pressure uniformizing jig53, heat-resistant glass which transmits a laser beam L is used. However, the pressure uniformizing jig53is not limited thereto.

For example, even a member which does not transmit a laser beam L can be applied as the pressure uniformizing jig if a hole is formed on the route of the laser beam L.

Though several embodiments of the present invention have been described above, the scope of the present invention is not limited to the above embodiments, and includes the scope of inventions, which is described in the scope of claims, and the scope equivalent thereof.