Patent Description:
<CIT> discloses a plastic container mainly made of crystalline resin. The plastic container has different optical properties in different crystal structures of the crystalline resin and produces vivid colors, dark and glossy colors, which are different from chemically produced colors. Such a plastic container has an advantage in recycling.

<CIT> discloses a method of making a blow molded article from a preform including: a) providing a preform of a thermoplastic material having a plurality of effect structures each having an effect surface having a normal with an orientation, the preform having a body with one or more walls and an opening, wherein at least a portion of the one or more walls of the preform has a three-dimensional pattern of cavities and/or protrusions thereon; and b) blow molding the preform to form a blow molded article, wherein the step of blow molding the preform changes the orientation of the normal of at least some of the effect surfaces of the effect structures to create a visual effect in at least one wall of the blow molded article.

<CIT> discloses a method for the preferential heating of a thermoplastic hollow body having at least one portion to be heated and another to be superheated, the portion that is to be superheated initially having a radiation absorption coefficient substantially identical to that of the portion to be heated. The method includes, in succession: a first step of marking the portions of the hollow body that are to be superheated, during which step isolated marks are made in the thickness of the wall of the portion that is to be superheated so as to increase its absorption coefficient; a second step of preferential heating of the hollow body by uniform exposure of the portions that are to be heated and of the portions that are to be superheated to the heating electromagnetic radiation. Also disclosed is a preform marked in accordance with the first step of the method.

<CIT> discloses a device for molding plastic preforms into plastic containers, comprising a movable support, on which a plurality of molding stations are arranged that are suitable for and designed to mold the plastic preforms into the plastic containers by supplying a flowable medium; at least one transport device, which transports the plastic preforms to the molding stations along a specified transport path; and at least one second transport device, which further transports the molded plastic containers after the molding process. According to the invention, the device has a marking device which is arranged upstream of the molding stations in the transport direction of the plastic preforms and provides at least some of the plastic preforms with a marking, and a container inspection device, which is arranged downstream of the molding stations in the transport direction of the plastic containers and is suitable for and designed to inspect at least one part of the marking generated by the marking device.

<CIT> discloses a polyethylene terephthalate container having a laser-formed area, wherein the laser-formed area is modified in response to radiation energy. In some embodiments, the laser-formed area of the container permitting localized contouring to permit or otherwise generally prevent flexural response to vacuum and/or loading forces. In some embodiments, the laser-formed area of the container comprises visible indicia formed to permit labelless containers.

In view of the above circumstances, embodiments of the present invention aim at providing a laser processing method to form a mark or to mark a concave on the surface of a preform.

The invention is set out in appended claim <NUM>.

According to the embodiments of the present invention, the laser processing method to form the mark or to mark the concave on the surface of the preform is provided.

The accompanying drawings are intended to depict embodiments and comparative examples. The invention is in accordance with claim <NUM>, which is the only valid definition of the present invention. The main characteristics of the invention are best depicted by <FIG>.

However, the disclosure of this specification is not intended to be limited to the specific terminology so selected.

In the description of the drawings, the same components are denoted by the same reference numerals, and overlapping description will be omitted.

<FIG> is a flowchart of a laser processing method according to the present embodiment.

In <FIG>, a preform is formed (S1), a mark is made on the preform by laser processing (S2), and a molded product is formed by blow molding (S3). In the laser processing, laser light (laser beam) is emitted to the preform.

A laser processing method includes: marking multiple concaves on a surface of a preform before blow molding.

A preform has the multiple concaves formed by the laser processing method.

<FIG> are diagrams of a basic configuration according to the present embodiment. <FIG> is an example of the preform <NUM>, and <FIG> is an example of the molded product <NUM>. Specifically, the preform or the molded product includes a plastic container, a plastic bottle, or a polyethylene terephthalate (PET) bottle.

In the present embodiment, the mark <NUM> is formed on the preform <NUM> before blow molding, and the molded product <NUM> after blow molding still includes the mark <NUM>. In other words, the mark <NUM> is formed by expanding the mark <NUM> on the preform <NUM> in the blow molding.

In the region of the mark <NUM>, the preform (i.e., the material of the preform) is deformed or modified by a reaction such as melting, vaporization, or foaming caused by laser light emission. Such a reaction forms a minute concave and convex on the surface of the preform or a minute foam in the vicinity of the surface of the preform as the marking. The minute concave and convex, or foam increases the scattering coefficient of light and becomes hazy or whitish. Such a phenomenon is equivalent to the microfacet theory in computer graphics. Since the surface of the preform is flat and transparent, the contrast between the preform and the mark that is hazy or whitish is generated, and the mark102 is visually recognizable.

Since the mark <NUM> of the preform <NUM> is smaller than the mark <NUM> of the molded product <NUM>, the region of the laser processing of the mark <NUM> is also smaller. If the mark <NUM> on the molded produce is formed by the laser processing, the productivity of the mark <NUM> is decreased as compared with that of the mark <NUM>. Thus, the productivity increases.

The mark <NUM> formed on the preform before blow molding may be visually unrecognizable, but the mark <NUM> on the molded product <NUM> after blow molding is visually recognizable.

<FIG> are diagrams of steps of the laser processing method as a comparative example. <FIG> is a diagram of the laser emission process. In the laser emission process, the laser light <NUM> is emitted to the preform <NUM>. <FIG> is a diagram of the mark <NUM> formed on the surface of the preform <NUM> by a thermal reaction or a chemical reaction caused by the laser emission. <FIG> is a diagram of the heating process. In the heating process, the preform is heated, and the mold <NUM> for blow molding is arranged in the vicinity of the preform <NUM>. <FIG> is a diagram of the blow molding process. In the blow molding process, gas is injected into the preform <NUM>, and the preform expands. The surface of the preform <NUM> is pressed to the mold <NUM>. When the surface of the preform <NUM> is pressed to the mold <NUM>, the mark <NUM> is also pressed to the mold <NUM>, and the shape of the mark <NUM> is deformed. <FIG> is diagram of the molded product <NUM> having the deformed mark <NUM> after blow molding. The mark <NUM> is unintentionally deformed and formed as the deformed mark <NUM>.

<FIG> is a diagram of an example of the marking formed on the preform in the present embodiment. <FIG> is an enlarged and cross-sectional view of the marking on the preform in <FIG>.

As illustrated in <FIG>, the mark <NUM> is formed on the preform <NUM>. In <FIG>, an enlarged view <NUM> and a cross-sectional view <NUM> by cutting line <NUM> of the mark <NUM> on the preform <NUM> are illustrated. In the cross-sectional view <NUM> of the preform <NUM>, the mark <NUM> has a marking surface <NUM> having a concave shape formed with respect to the preform surface <NUM> of the preform <NUM>. The mark may have a V-shape surface.

<FIG> are diagrams of the laser processing method according to the present embodiment. <FIG> is a laser emission process. In the laser emission process, the laser light <NUM> is emitted to the preform <NUM>. The laser light <NUM> may be condensed by using the condensing lens <NUM>. <FIG> is a diagram of a mark <NUM> formed by the laser processing. The shape of the mark <NUM> is a concave shape (concave). <FIG> is a diagram of the heating process. In the heating process, the preform is heated, and the mold <NUM> for the blow molding is arranged in the vicinity of the preform <NUM>. <FIG> is a diagram of the blow molding process. In the blow molding process, gas is injected into the preform <NUM>, and the preform expands. The surface of the preform <NUM> is pressed to the mold <NUM>. When the surface of the preform <NUM> is pressed to the mold <NUM>, the mark <NUM> is not in contact with the mold <NUM> because the shape of the mark <NUM> is concave. <FIG> is diagram of the molded product <NUM> having the mark <NUM> after blow molding. Since the mark <NUM> formed on the molded product <NUM> is not in contact with the mold, the mark <NUM> maintains its shape and is visually recognizable.

The mark <NUM> may also be formed by coloring of a thermal reaction or a photochemical reaction in the laser processing (i.e., coloring method), or a chemical reaction of pigment addition (i.e., pigment method). The mark <NUM> may also be in combination with the coloring method or the pigment method and the laser processing method illustrated in <FIG> (i.e., combination marking). In the case of the combination marking, preferably, the wavelength of the laser light used for the laser processing is <NUM> to <NUM> because the pigment can be selectively reacted.

<FIG> is a diagram of the marking according to the first modification of the present embodiment. In the first modification, the marking has a U-shaped cross section (i.e., U-shaped marking). The U-shaped marking has an inner surface <NUM> steeper than the marking surface <NUM> illustrated in <FIG>.

In the laser processing method, each of the multiple concaves has a U-shaped cross section.

Herein, the U-shaped marking is determined by the angle formed by the preform surface <NUM> and the inner surface <NUM>. Preferably, the angle is from <NUM>° to <NUM>°, more preferably, from <NUM>° to <NUM>°. Preferably, the U-shaped marking is formed by the top hat laser beam rather than the gaussian beam. The top hat laser beam is formed by adjusting the shape of the laser beam or the scanning condition of the laser beam to widen the angle described above.

Since the shape of the marking is U-shaped, the boundary between the preform surface <NUM> and the marking surface <NUM>, which are adjacent each other, becomes clear. At the same time, the marking surface <NUM> is not in contact with the mold <NUM>.

<FIG> are diagrams of the U-shaped marking as a specific example according to the first modification illustrated in <FIG>.

A preferable condition for forming the marking will be described with reference to <FIG>. In the present embodiment, the marking formed on the molded product after blow molding does not affect the mechanical strength and function of the molded product. <FIG> is the diagram of the preform <NUM> having a length L_a1 in a direction A and a length L_b1 in a direction B. The direction A and the direction B are orthogonal each other and denoted by L_a1 and L_b1, respectively. <FIG> is a diagram of the molded product <NUM> having a length L_a2 in the direction A and a length L_b2 in the direction B. The directions A and B, and the lengths L_a2 and L_b2 are similarly to those of the preform. Herein, a value obtained by dividing L_a1 by L_a2, and a value obtained by dividing L_b1 by L_b2 are referred to as enlargement ratios. The enlargement ratio is different between the direction A and the direction B. In other words, the enlargement ratio has anisotropy. The larger value of these two enlargement ratios is defined as the maximum enlargement ratio. In <FIG>, an enlarged view and a cross-sectional view by cutting line <NUM> of the mark <NUM> on the preform <NUM> are illustrated. In the cross-sectional view, the marking depth <NUM> and the preform thickness <NUM> are denoted.

In the laser processing method, the first direction is orthogonal to the second direction. Herein, for example, the first direction is the direction A, and the second direction is the direction B.

The amount of the marking depth <NUM> does not exceed the value in which the preform thickness <NUM> is divided by the maximum enlargement ratio. As a result, even the preform <NUM> is expanded and the wall surface of the preform <NUM> is stretched, a hole is not formed in the molded product <NUM> by the marking.

<FIG> is a diagram of the mark according to the second modification of the present embodiment. The mark <NUM> is formed by multiple minute concaves <NUM>. In the mark <NUM>, the multiple minute concaves <NUM> are overlapped each other. Herein, the minute concave <NUM> has the circular shape on the surface of the preform and the concave shape in the cross section. As a result, the entire mark is less likely to be deformed in blow molding.

In the laser processing method, the marking forms at least two concaves of the multiple concaves partially overlapped with each other.

<FIG> is a diagram of the mark <NUM> including multiple minute concaves <NUM>. Herein, the minute concave <NUM> has the circular shape on the surface of the preform and the concave shape in the cross section. In the mark <NUM>, a distance between two adjacent concaves <NUM> in the direction A is referred to as a space <NUM> and a distance between two adjacent concaves <NUM> in the direction B is referred to as a space <NUM>. The direction A and the direction B is orthogonal to each other. The space <NUM> and the space <NUM> are substantially the same.

In the laser processing method, the marking forms at least two concaves of the multiple concaves separated with each other.

<FIG> is a diagram the preform surface <NUM> of the preform having the mark <NUM> illustrated in <FIG> (i.e., before blow molding). <FIG> is a diagram of the surface <NUM> of the molded product expanded by the blow molding (i.e., after blow molding) from the preform in <FIG>. The molded product has the mark <NUM> expanded by the blow molding. The preform and the molded product have multiple line-shaped mark. In the preform, the multiple line-shaped mark are regularly arranged, but there is an irregularity in terms of the space (interval), which is small and is not recognizable. The line-shaped mark including the irregularity are expanded by blow molding, and the irregularity become recognizable in the molded product.

The irregularity <NUM> (i.e., wider space) is a portion excluding the concaves and unrecognizable in the preform. But, the irregularity <NUM> becomes recognizable as a mark deformation in the molded product,.

<FIG> is a diagram of the mark according to the third modification. In <FIG>, since two concaves formed among multiple concaves <NUM> are formed adjacent to each other, there is no unprocessed region, which is flat (flat region), between the concaves. Herein, unprocessed region is a cause of irregularity. Accordingly, when the preform is expanded by blow molding, the irregularity of the mark is less likely to generate. Herein, the concave <NUM> has a circular shape on the surface of the preform and a concave shape in the cross section. The processed region and the unprocessed region will be described in detail below.

In a case where the concaves are adjacent, and the expansion ratio of the preform in blow molding is larger, only the concave is expanded, and the unprocessed portion (i.e., the flat region) is not generated. By contrast, in a case where there is a unprocessed region between concaves, the flat region between the concaves, which is transparent of darker, is expanded. When the flat region is present in the mark whitened and is visually recognized, the flat region stands out and is a cause of "mark deformation". Since the concaves are adjacent to each other, the mark uniformly whitened without the flat region is formed. Herein, the concaves may contact or overlap each other.

In <FIG>, the concave is further adjacent to other concaves in multiple directions. Since the concave is adjacent to the other concaves in at least two directions, the mark deformation is not generated in the two expanded directions. The expanded direction by blow molding typically has anisotropy. In a case where the concave is adjacent to the other concaves only in one direction, a slit-like flat region is generated in a direction perpendicular to the one direction. Preferably, the concave is adjacent to other concaves in at least two directions substantially perpendicular to each other to prevent the mark deformation. Accordingly, if the preform is anisotropically expanded by blow molding, the mark is not deformed.

In <FIG>, one concave is adjacent to all concaves around the one concave. As a result, if the preform is expanded in any directions, the mark is not deformed.

In the laser processing method, the marking forms one concave of the multiple concaves adjacent to other of the multiple concaves surrounding the one concave.

When the flat region (i.e., the unprocessed region) has a width of <NUM> or more, the flat region becomes visually recognizable as the mark deformation. Preferably, the distance between the concaves on the preform before expanding by blow molding is determined by inversely calculating the expansion ratio.

In the laser processing method, the marking continuously forms at least two concaves of the multiple concaves, and an unprocessed region between said two concaves is <NUM> or less on the preform before blow molding.

<FIG> is a diagram of the mark <NUM> having the processed region and the unprocessed region <NUM>. The unprocessed region <NUM> has a width <NUM> (Lcw) in the direction A and a width <NUM> (Lch) in the direction B. Preferably, conditional expressions (<NUM>) and (<NUM>) below are satisfied:.

where Am and Bm are the expansion ratios in the directions A and B, respectively, in the blow-molding process. As a result, the visibility of the mark satisfying the conditional expressions (<NUM>) and (<NUM>) is improved.

<FIG> are diagrams of the preform, the molded product, and the marks according to the fourth modification. In the fourth modification illustrated in <FIG>, the visibility is further improved as compared with the mark <NUM> illustrated in <FIG>.

Specifically, in <FIG>, there are unprocessed regions between the concaves. Since the unprocessed regions are not processed in the laser processing process, the operation rate and the cost for processing are reduced. However, depending on the arrangement of the unprocessed region, the visibility of the mark is reduced. In particular, the mark nonuniformly whitened affects the sensory evaluation.

The preform <NUM> illustrated in <FIG> has a length L_a1 in the direction A and a length L_b1 in the direction B. The direction A and the direction B are orthogonal each other. The opening of the preform <NUM> is parallel to the direction A. The preform (i.e., its size) is expanded by blow molding. <FIG> is a diagram of the molded product having a length L_a2 in the direction A and a length L_b2 in the direction B, in which the directions A and B are the same with the directions for the preform in <FIG>. Herein, a value obtained by dividing L_a1 by L_a2 and a value obtained by dividing L_b1 by L_b2 are expansion ratios. The expansion ratios are different in the direction A and the direction B. In other words, the expansion ratio is anisotropic. <FIG> is the diagram of a mark including the concaves <NUM> arrayed on the preform <NUM>. The space between the two concaves in the direction A is smaller than that between the two concaves in the direction B. <FIG> is the diagram of another mark including the concaves <NUM> marked on the preform <NUM>. The space between the two concaves in the direction B is smaller than that between the two concaves in the direction A.

In the laser processing method, the marking forms one concave of the multiple concaves adjacent to other of the multiple concaves in multiple directions.

In the preform <NUM> according to the present modification, a first center-to-center distance between two concaves <NUM> in a first direction having a first expansion ratio of the preform is narrower than a second center-to-center distance between two concaves <NUM> in a second direction having a second expansion ratio of the preform. The first expansion ratio is higher than the second expansion ratio. As a result, in the molded product <NUM> after blow molding, the first center-to-center distance and the second center-to-center distance are the same. Thus, the mark uniformly whitened is formed. Thus, the visibility of the mark is improved.

In the laser processing method, the marking continuously forms at least two concaves of the multiple concaves, and a first center-to-center distance between the two concaves in a first direction having a first expansion ratio of the preform is narrower than a second center-to-center distance between the two concaves in a second direction having a second expansion ratio of the preform. The first expansion ratio is higher than the second expansion ratio. The first expansion ratio and the second expansion ratio are determined by expanding the preform by blow molding.

Since increasing the density of the concave on the preform increases energy of laser emission, the direction in which the density of the concave array is higher is selected depending on the forming condition. Accordingly, the information is added to the molded product with decreasing the workload on the laser processing apparatus.

<FIG> is a micrograph of the concave array of the fourth modification.

Since the mark (the concave array) of the present embodiment is formed by laser emission, the mark is formed by appropriately scanning the surface of the preform with the laser light. In the forming the concave array, the laser light may be pulsed light or continuous light, and is not limited thereto. The mark may be formed by single laser light or multiple laser light.

In <FIG>, the shape of the concave on the surface of the preform is circular, but is not limited thereto. For example, the shape of the concave on the surface of the preform may be elliptic, linear, or rectangular. These shapes are formed by changing the scanning method of laser light.

<FIG> are diagrams of the preform, the molded product, and the marks according to the fourth modification. <FIG> is a diagram of the preform <NUM>. The preform <NUM> illustrated in <FIG> has a length L_a1 in the direction A and a length L_b1 in the direction B. The direction A and the direction B are orthogonal each other. The opening of the preform <NUM> is parallel to the direction A. The preform (i.e., its size) is expanded by blow molding. <FIG> is a diagram of the molded product having a length L_a2 in the direction A and a length L_b2 in the direction B, in which the directions A and B are the same with the directions for the preform in <FIG>. Herein, a value obtained by dividing L_a1 by L_a2 and a value obtained by dividing L_b1 by L_b2 are expansion ratios. The expansion ratios are different in the direction A and the direction B. In other words, the expansion ratio is anisotropic. <FIG> is a diagram of the mark including rows of the concave on the surface of the preform <NUM>. The shape of the concave on surface of the preform <NUM> is an elliptical shape elongated in the direction A. <FIG> is a diagram of mark including columns of the concave on the surface of the preforms <NUM>. The shape of the concave on the surface of the preform <NUM> is an elliptical shape elongated in the direction B.

In the preform of the present modification, the concave is formed in an elliptical shape so that the length of the concave in the direction in which the expansion ratio is larger is longer than the length of the concave in the direction in which the expansion ratio is smaller when the preform is expanded to the molded product. Effects similar to those of the fourth modification is obtained.

<FIG> are diagrams of the mark formed on the preform <NUM> according to the sixth modification. <FIG> is a diagram of the preform <NUM> according to the sixth modification. In <FIG>, an enlarged view <NUM> and a cross-sectional view <NUM> by cutting line <NUM> of the mark <NUM> on the preform <NUM> are illustrated. In <FIG>, a convex-adjacent-concave <NUM> and a convex <NUM> of the mark are illustrated. In the cross-sectional view, the concave surface <NUM> and the convex surface <NUM> are illustrated.

In the present embodiment, the convex <NUM> are provided on the surface of the preform adjacent to the convex-adjacent-concave <NUM>. By providing the convex, the concave is harder to contact with the mold at the time of blow molding. The material of the preform is melted by the laser emission (i.e., melted material), and the convex <NUM> is formed by deposition of the melted material on the wall of the preform adjacent to the convex-adjacent-concave <NUM>. Herein, the melted material is flowed by, for example, Marangoni convection. Accordingly, since the surface of the convex <NUM> formed by cooling the melted material is smooth, the diffusive reflectance of the convex <NUM> is lower than that of the convex-adjacent-concave <NUM>. If the convex <NUM> comes into contact with the mold at the time of blow molding and expands in the in-plane direction of the preform, it is not confused with a mark error.

<FIG> are diagrams of the preform according to the seventh modification. <FIG> is a diagram of the preform <NUM> according to the seventh modification. In <FIG>, an enlarged view <NUM> and a cross-sectional view <NUM> by cutting line <NUM> of the mark <NUM> on the preform <NUM> are illustrated. In the mark <NUM>, multiple circular-concaves <NUM> and multiple circular-convexes <NUM> are arranged, and each of multiple circular-convexes <NUM> is formed around the corresponding multiple circular-concaves <NUM>. In the cross-sectional view <NUM>, the concave surface <NUM> and the convex surface <NUM> are illustrated.

In the laser processing method, the marking forms a convex in a periphery of each of the multiple concaves.

<FIG> is a perspective view of an electron micrograph of the mark according to a seventh modification. <FIG> is a cross-sectional view of an electron micrograph of the mark according to the seventh modification. The circular-convex <NUM> is formed around the circular-concave <NUM>. The cross-sectional view in <FIG>, the concave depth <NUM> is represented as a distance from the bottom <NUM> of the concave to the preform surface <NUM>.

<FIG> are diagrams of a laser processing method according to the seventh modification. <FIG> is a laser emission process. In the laser emission process, the laser light <NUM> is emitted to the preform <NUM>. The laser light <NUM> may be condensed by using the condensing lens <NUM>. <FIG> is a diagram of a mark <NUM> formed by the laser processing. The shape of the mark <NUM> is the concave shape and the convex shape. <FIG> is a diagram of the heating process. In the heating process, the preform is heated, and the mold <NUM> is arranged in the vicinity of the preform <NUM> for the blow molding. <FIG> is a diagram of the blow molding process. In the blow molding process, gas is injected into the preform <NUM>, and the preform expands. The surface of the preform <NUM> is pressed to the mold <NUM>. When the surface of the preform <NUM> is pressed to the mold <NUM>, the mark <NUM> is not in contact with the mold <NUM> because the shape of the mark <NUM> is concave. Further, the concave is less likely to come into contact with the mold because there is convex around the concave. <FIG> is a molded product <NUM> after blow molding. Since the mark <NUM> formed on the molded product <NUM> is not in contact with the mold, the mark <NUM> maintaining the shape of the concave is visually recognized.

<FIG> is a flowchart of a laser processing method according to an eighth modification. In the laser emission to the preform, since a region of the preform emitted by the laser is locally heated according to the amount of the laser emission, the temperature distribution of the region on the preform during blow molding becomes non-uniform, the expansion ratio also becomes non-uniform, and unintended molding occurs. As illustrated in <FIG>, in order to uniformize the temperature distribution of the preform during blow molding, it is preferable that the preform is cooled to a temperature at which the glass transition point of the preform material is lowest by heat dissipation after laser emission. The laser processing method according to the present modification is substantially equivalent to a process using a cold parison, which is considered to be compatible with the present embodiment.

<FIG> is a flowchart of a laser processing method according to the ninth modification. In the ninth modification, the preform is expanded to the molded product without cooling and solidifying while maintaining the temperature molding the preform. Accordingly, thermal energy in the processing is less likely to waste. Preferably, the conditions of the laser emission in the ninth modification is optimized to reduce the influence of the temperature change caused by the laser emission. Specifically, a pulse laser having a picosecond-order pulse that has less thermal influence in laser processing is used. Preferably, the condition of the pulse laser is of a pulse of <NUM> picoseconds or shorter.

<FIG> is a flowchart of a laser processing method according to the tenth modification. The preform is expanded to the molded product by blow molding. The mark formed on the preform is expanded proportional to the expansion ratio, and the area of the mark on the molded product becomes larger. When the mark to be formed, for example, a log of a brand, has a larger area, the marking is formed on the preform before blow molding (S41). When the mark to be formed, for example, ingredients, has a smaller area, the mark is formed on molded product after blow molding (S44).

In the laser processing method further includes: marking multiple concaves on the surface of the preform after the blow molding.

As described above, since the mark having a large area is formed in the preform before blow molding (S42), the mark is formed at a higher speed as compared with a case where the mark is formed on the molded product after the blow molding. By contrast, since the smaller mark is formed on the molded product after blow molding (S44), the mark is formed more finely than when the mark is formed on the preform before blow molding. The laser processing is performed on the preform and the molded product in two separate steps. Thus, the laser processing at both higher precision and higher speed is achieved. In addition, if the laser processing is performed after blow molding, the amount of fine information is smaller. Thus, the workload is not increased.

Preferably, a finer mark is formed on the preform. A laser light having a shorter wavelength has an advantage in forming a smaller focus due to the diffraction limit. Preferably, UV laser light is used as the laser light. Furthermore, when the wavelength is <NUM> to <NUM>, it is preferable for forming a finer mark, and such a wavelength is absorbable in many resin materials. Thus, the base material is easy to modify.

<FIG> is a preform having a mark of the bar code according to the present embodiment. A bar code includes indispensable information adding to the label-less product and is effective to spread to other than e-commerce. For example, in a case of a Japanese Article Number (JAN) code, the size of a module which is a minimum unit constituting a bar code is about <NUM> per module (i.e., mm/module) as a standard size. Since the mark formed on the preform is a reduced scale (larger size is preferable), and it is <NUM>/module in consideration of the maximum allowable expansion ratio of <NUM> of the JAN code.

In the beverage industry, label-free bottles are spreading to use. For example, the size of the cap attachment portion of a plastic bottle of <NUM> is about <NUM> in diameter, which may be equivalent to the diameter of the preform, and the diameter of the molded product is from <NUM> to <NUM>. Thus, the expansion ratio is from <NUM> to <NUM>.

In consideration of the expansion ratio, the mark is reduced to be formed on the preform. When the expansion ratio is <NUM> and the size of the module is <NUM>, one module to be formed on the preform is <NUM> (<NUM>) or less. The beam size of the laser light is also <NUM> or less. Preferably, the printing amount is smaller. In consideration of the JAN code allowable minimum magnification of <NUM>%, the size of the JAN code is <NUM>. Preferably, the laser emission region is also <NUM> or less.

When the mark is formed by arranging multiple minute concaves by forming the pulse laser, preferably, the area of the laser processing is smaller as long as there is no reading error on the code. In a case where multiple columns including circular concaves is formed to align, the width of the one module is, for example, <NUM> for two columns, <NUM> for three columns, <NUM> for four columns, and <NUM> for five columns.

In the present embodiment, the beam diameter of the laser light is <NUM> to <NUM>. When the size of preform is <NUM> in diameter (the cap size is <NUM> in common), and the size of PET bottle (i.e., the molded product) is from <NUM> to <NUM> in diameter, the enlargement ratio is from <NUM> to <NUM>.

When the JAN code is written as the original size(i.e., <NUM>%), the module-width is <NUM>. Thus, the size of the single module formed on the preform is <NUM> (i.e., <NUM>/<NUM> = <NUM>) in width.

By setting the beam width of the laser light to <NUM> or less, a barcode is easy to form on the preform as a versatile manner. In addition, when the beam diameter is <NUM> or more, the beam is focused with a simple lens configuration without exceeding the diffraction limit, and a long working distance is obtained, so that the manufacturing cost is reduced.

<FIG> is a diagram of a laser processing method as an example in the present embodiment. In the laser emission to the preform, the space between the preform and the laser light source may be wider due to the layout such as the holding.

In particular, when the laser scanning is used to form the mark, a mark area is widened by taking a distance from a lens longer. As illustrated in <FIG>, one scanning laser light (i.e., single laser light scanning) forms the marks on the multiple preforms by taking the distance from the lens longer and by using the maximum lens performance. As a result, productivity is increased. The single laser light scanning reduces the number of the light source.

<FIG> is a diagram of a laser processing method as an example in the present embodiment. One laser processing apparatus (laser marking apparatus) forms the marks on multiple preforms of multiple production lines. Accordingly, the number of the laser marking apparatus per production line and the laser light source per production line are reduced.

<FIG> is a diagram of a laser processing method as an example in the present embodiment. In a case where multiple production lines of the laser processing, preferably the laser light is visible light recognizable by an ordinary camera for safety. Preferably, a visible laser light source that emits pulse light having a nanosecond-order pulse is used to process resin material. Specifically, when the laser light has a wavelengths of <NUM> to <NUM> and a pulse width of <NUM> microsecond (ms) or less, the laser processing is performed, and a normal camera recognizes the laser light as illustrated in <FIG>.

<FIG> is a diagram of a laser processing method as an example in the present embodiment. When the laser scanning system for the laser processing scans a wider area than the mark in a case where the distance between the laser scanning system and the preform is longer, the laser light <NUM> is likely to hit the cap portion <NUM> of the preform <NUM> because the mark and the cap portion <NUM> is closer. If the laser light processes the cap portion <NUM>, the cap does not work properly after blow molding to form the molded product. In the present embodiment, the shield <NUM> is arranged in the vicinity of the cap portion <NUM> to prevent the laser light <NUM> from hitting the cap portion in the laser processing. Thus, the cap portion of the molded product after blow molding works properly.

<FIG> is a diagram of a laser processing method as an example in the present embodiment. In the marking by laser emission, backwash such as gas generated by vaporization of the preform is generated and flows into the inside of the preform As illustrated in <FIG>, the mark is formed with the opening of the preform tilted against the gravity to prevent the backwash from flowing into the inside of the preform. The arrangement of the opening of the preform illustrated in <FIG> is not limited thereto as long as the opening is tilted to the direction of the gravity from the horizontal.

In the present embodiment and modifications, the preform is not limited to being transparent. For example, the preform may be opaque as long as the contrast of the marking is developed. In the present embodiment and the modifications, the opaque preform develops the contrast because the marking includes the concave.

As described above, the laser processing method according to present embodiments forms the mark including the concave on the preform. Accordingly, the shape of the mark formed on the preform is maintained in the molded product.

In the first aspect, a laser processing method includes: marking multiple concaves on a surface of a preform before blow molding.

According to the second aspect, the entire mark is less likely to be deformed in blow molding.

In the second aspect, in the laser processing method according to the first aspect, the marking forms a convex in a periphery of each of the multiple concaves.

According to the first aspect, the laser processing method, in which the shape of the mark formed on the preform before blow molding is surely maintained in the molded product after blow molding is provided.

In the third aspect, in the laser processing method according to the first aspect or the second aspect, the marking forms at least two concaves of the multiple concaves separated with each other.

In the fourth aspect, in the laser processing method according to the first aspect or the second aspect, the marking forms at least two concaves of the multiple concaves partially overlapped with each other.

According to the third aspect, the laser processing method that forms uniformly whitened mark is provided.

In the fifth aspect, in the laser processing method according to any one of the first aspect to the third aspect, the marking continuously forms at least two concaves of the multiple concaves, and a first center-to-center distance between the two concaves in a first direction having a first expansion ratio of the preform is narrower than a second center-to-center distance between the two concaves in a second direction having a second expansion ratio of the preform. The first expansion ratio is higher than the second expansion ratio. The first expansion ratio and the second expansion ratio are determined by expanding the preform by blow molding.

According to the fifth aspect, the laser processing method provides that the molded product in which the marking is uniformly whitened in the directions having different expansion ratios is provided.

In the sixth aspect, in the laser processing method according to the fifth aspect, the first direction is orthogonal to the second direction.

In the seventh aspect, in the laser processing method according to any one of the first aspect to the sixth aspect, the marking forms one concave of the multiple concaves adjacent to other of the multiple concaves in multiple directions.

According to the seventh aspect, the laser processing method provides the molded product in which the marking is uniformly whitened in multiple directions.

In the eighth aspect, in the laser processing method according to any one of the first aspect to the seventh aspect, the marking forms on concave of the multiple concaves adjacent to other of the multiple concaves surrounding the one concave.

According to the eight aspect, the laser processing method provides the molded product in which the marking is uniformly whitened in any directions.

In the ninth aspect, in the laser processing method according to any one of the first aspect to the eighth aspect, the marking continuously forms at least two concaves of the multiple concaves, and an unprocessed region between said two concave is <NUM> or less on the preform before blow molding.

According to the ninth aspect, the laser processing method provides the molded product in which the marking is uniformly whitened.

n the tenth aspect, in the laser processing method according to any one of the first aspect to the ninth aspect, each of the multiple concaves has a U-shaped cross section.

According to the tenth aspect, the boundary between the preform surface and the marking surface adjacent each other is clear, and the marking surface is not in contact with the mold. Thus, the shape of the marking formed on the preform is maintained in the molded product.

In the eleventh aspect, the laser processing method according to any one of the first aspect to the ninth aspect further includes marking multiple concaves on the surface of the preform after blow molding.

According to the eleventh aspect, a laser processing method that achieves a finer marking forming at higher speed and productivity is provided.

Claim 1:
A laser processing method comprising:
marking multiple concaves (<NUM>) on a surface (<NUM>) of a preform (<NUM>) using a laser before blow molding to form a first mark,
characterized by
marking multiple concaves (<NUM>) on the surface of the molded product using a laser after the blow molding to form a second mark, wherein the second mark formed after the blow molding is smaller than the first mark formed before the blow molding.