JPH10329832A - Easily openable can lid with excellent openability and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damages from occurring to a gilt layer and resin-coated layers while stably reducing force required for opening of a can by a method wherein a first stage opening groove and a second stage opening groove each having specified front-end radius and groove width are formed in continuity. SOLUTION: Opening grooves 2 are formed respectively on the surface 1a and the reverse side 1b of a can lid 1 made of surface-treated steel plate with resin-coated layers formed on both sides thereof. The opening groove 2 is a two-stage groove that is formed in continuity of the first stage opening groove 2a and the second stage opening groove 2b. The depth D1 and the front-end radius ρ1 of the first stage opening groove 2a, the depth D2 and the front-end radius ρ2 of the second stage opening groove 2b and the thickness t of the can lid 1 shall be such that satisfies the relations represented by formulae I, II, III and IV. Therefor, corrosion resistance can be ensured without damaging resin coating while reducing force required for opening the can.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easy-open can lid used for beverage cans and food cans, which has a structure in which the opening groove formed in the can lid of the can body is broken to open the can. And a method of manufacturing the same.

[0002]

2. Description of the Related Art As a can lid for cans containing various beverages such as beer, juice and coffee, an easy-open can lid is widely used in which an opening groove formed in a panel of the can lid is broken by a finger and opened. ing. The easy-open can lid is roughly classified into a partial-open type can lid mainly used for beverage cans and a full-open type can lid mainly used for food cans.

[0003] Partial open type can lids are broadly classified into pull-top tab type can lids and stay-on tab type can lids. FIG. 7 is a schematic plan view showing an example of a pull-top tab type can lid. As shown in FIG. 7, the opening of the pull-top tab type can lid is performed as follows. That is, the tab 5 fixed to the center of the central panel portion 3 of the can lid 1 made of a metal plate such as steel or aluminum by the rivet mechanism 4 is pulled up, so that the opening groove 6 formed in the central panel portion 3 is raised. Of the tab 5 is pushed down by leverage. As a result, the opening groove 6 is broken, and the broken opening piece is completely separated from the can lid 1 by further pulling the tab 5.

FIG. 8 is a schematic plan view showing an example of a canion tub type can lid. As shown in FIG. 8, the opening of the stay-on tub type can lid is performed as follows. That is, by pulling up the tab 5 fixed to the center of the central panel portion 3 of the can lid 1 by the rivet mechanism 4, the opening groove 6 formed in the central panel portion 3 is moved to the working end of the tab 5, Push down by leverage. As a result, the opening groove 6 is broken, and further, the breaking is advanced by pulling up the raising end of the tab 5,
A part of the broken opening piece generated at that time is pushed into the can while being connected to the can lid 1.

A full-open type can lid has an opening groove engraved along the outer peripheral edge of the can lid, and pulls up a tab fixed to a panel portion near the outer peripheral edge of the can lid, thereby pulling a top. As in the case of the type, the opening piece is separated from the can lid.

[0006] A typical conventional method for forming the opening groove in the above-mentioned easy-open can lid is as follows.
It is as follows. That is, as shown in FIG. 9, a machining tool 7 having a sharp edge-shaped projection with a predetermined opening contour is formed.
The working tool 7 is pressed against the can lid from the surface side of the can lid by a press to form an opening groove 8 having a V-shaped cross section. The formation of the opening groove 8 reduces the tab pulling force at the time of opening the can, and increases the depth of the can lid 1 to a depth equal to or more than half the thickness of the can lid 1 so that the can can be easily opened with a fingertip. This is performed by pressing a sharp edge with a load.

[0007]

As described above, since the formation of the opening groove is performed by press-forming with a high load by a press using a working tool, the plating layer formed on the surface of the can lid, There is a problem that the resin coating layer is damaged and the corrosion resistance is deteriorated. In order to prevent the above-mentioned deterioration of corrosion resistance, repair painting had to be performed after press molding, which required much labor and cost. Therefore, most of the beverage can lids are made of aluminum that does not rust even if the plating layer or resin layer is damaged,
The use of such aluminum increases costs and poses a problem in terms of recycling.

As a countermeasure against the above-mentioned problem that occurs when forming a groove for opening in a can lid by pressing a processing tool having a sharp cutting edge-like projection, it is necessary to reduce the opening force and repair the can lid. For this purpose, the following means have been proposed.

Japanese Patent Laid-Open No. 2-179329: A trapezoidal anvil is arranged on the back side of a V-shaped groove on the surface of a can lid, and a processing tool having a blade-shaped projection is pressed from the front side of the can lid (hereinafter, referred to as a “tool”). , Referred to as Prior Art 1).

Japanese Patent Publication No. 3-5890: Prior to pressing a processing tool having a blade-shaped projection from the front surface side of a can lid, a relatively shallow groove having an arc-shaped cross section is formed on one of the front side and the back side of the can lid. (Hereinafter referred to as prior art 2).

JP-A-6-115546, JP-A-6-115546
JP-A-115547 and JP-A-6-115548: By forming an opening groove by composite extrusion, the resin coating layer is not damaged, and repair painting of the inner and outer surfaces becomes unnecessary (hereinafter referred to as prior art 3). ).

JP-A-8-99140: Using an upper and lower mold having a shoulder radius of 0.1 to 1.0 mm, press-forming the opening groove without damaging the resin coating of the can lid by warm working ( Hereinafter, this is referred to as prior art 4).

[0013] Japanese Utility Model Publication No. Sho 63-40439: Finger insertion recess for the purpose of widening the gap between the center panel portion of the can lid and the finger hook holding portion of the dove in order to facilitate finger insertion and finger hook holding portion. Is formed on the central panel portion below the dove finger-holding portion (hereinafter referred to as Prior Art 5).

Japanese Utility Model Laid-Open No. 5-40133: The central axis of the dub is shifted from the central axis of the break opening,
Riveting the tab to the extent that it can be rotated to the openable position where the center axis of the dove coincides with the center axis of the break opening,
While the tab moves from the non-openable position to the openable position,
By lifting the finger hook and pinch portion of the tab with a tapered projection provided on the center panel portion located between the rivet and the finger hook and pinch portion of the dove, to the gap between the central panel portion of the can lid and the finger hook and pinch portion of the tab (See Prior Art 6).
).

However, in the methods of Prior Art 1 and Prior Art 2, repair on the back side of the can lid is said to be unnecessary, but it is necessary to press a tool having a sharp cutting edge to form a guide groove. Repair of the can lid surface side is required. According to the method of Prior Art 3, since the opening groove is formed by composite extrusion, it is said that the resin coating layer is not damaged and repair painting is not necessary. However, the processing conditions and groove shape of the composite extrusion are considered. Details are unknown, and stable formation of the opening groove is questionable.

Further, since the radius of curvature of the groove formed by the method of Prior Art 4 is in the range of 0.1 to 1.0 mm, the radius of curvature formed by pressing with a processing tool having a sharp edge-like projection is small. Compared to the groove of about 0.05mm,
It is considered that the groove has a radius of curvature that is two orders of magnitude larger, and the opening force cannot be reduced due to the strain concentration effect of the groove.

Further, in the prior arts 5 and 6, since the finger insertion concave portion or the tapered protrusion is formed, compared with the case where these are not formed,
Insertion of fingers into the gap between the center panel of the can lid and the finger-holding portion of the tab, and finger-holding on the finger-holding portion become easy, but the lifting force at the time of opening the can does not change. The power has not been reduced.

[0018] Accordingly, an object of the present invention is to solve the above-mentioned problem, and to damage a plating layer and a resin coating layer formed on both sides of a can lid made of a surface-treated steel sheet having a resin coating layer formed on both sides. An object of the present invention is to provide an easy-open can lid with excellent can-opening properties, which can form an opening groove without performing the opening operation and can stably reduce the can-opening force, and a method of manufacturing the same.

[0019]

According to the first aspect of the present invention, an opening groove is formed on each side of a can lid made of a surface-treated steel sheet having an organic resin layer having a thickness of 5 to 100 μm formed on both sides. In the easy-open can lid having a structure formed to open the can by breaking the opening groove, the opening groove is formed by continuously forming a first-stage opening groove and a second-stage opening groove. The depth of each of the first-stage opening groove and the second-stage opening groove and the tip radius thereof are:
It is characterized by satisfying the following expressions (1) to (4).

0.25t ≦ D1 + D2 ≦ 0.4tmm (1) 0.2 ≦ D1 / (D1 + D2) ≦ 0.6 (2) ρ1 ≧ D1 + D2 (1 + 0.5 (D2 / D1)) mm (3) 0.02 ≦ ρ2 ≦ 0.05 mm (4) where D1: one step Groove depth for eye opening, D2: Groove depth for second stage opening, ρ1: Radius tip radius for first stage opening, ρ2: 2
Radius of groove end for step opening, t: can lid plate thickness.

According to a second aspect of the present invention, there is provided an opening comprising a two-stage groove in which a first-stage opening groove and a second-stage opening groove are continuously formed. With grooves for
And the tab is a can lid rotatably attached to the openable position from the unopenable position to the openable position around the tab fastening, and the center position of the tab fastening is from the center of the can lid to the opening opposite to the following ( 5) is shifted by the distance a shown in the equation,
The length S between the center of the tab and the finger-holding portion of the tab is within the range of the following expression (6), and the angle θ between the tab center line at the opening impossible position and the tab center line at the opening position is In the range of the following expression (7), and at the position where the opening is possible, the lifting means capable of setting the finger-holding portion of the tab outside the outer periphery of the can lid and higher than the periphery of the can lid is provided by a can lid. Is characterized in that it is provided in (M−m) / 2 <a <m / 2−w (5) m−w>S> m / 2−a (6) −1 <Cos θ <1 / (2 × a × S) × {(m / 2) ² − (S ² + a ² )} (7) where a: the center of the tab from the center of the can lid Deviation distance, S: length between the center of the tab fastening and the tab finger holder, w: length between the center of the tab fastening and the tab action part, θ: at the tab center line at the opening impossible position and at the opening possible position Angle between tab center line, m: inner diameter of can lid, M: outer diameter of can lid.

The method according to the third aspect of the present invention is directed to the first aspect.
Or a can lid material for producing an easy-open can lid having an opening groove composed of a two-step groove in which a first-step opening groove and a second-step opening groove are continuously formed. First, a second-stage opening groove is formed, and then a first-stage opening groove is formed.

The method according to the fourth aspect of the present invention is the method according to the first aspect.
Or a can lid material for producing an easy-open can lid having an opening groove composed of a two-step groove in which a first-step opening groove and a second-step opening groove are continuously formed. The process of forming the groove for the opening is performed by a method according to claim 3 using a liquid or solid lubricant.

The method according to the fifth aspect of the present invention is directed to the first aspect.
Or a can lid material for producing an easy-open can lid having an opening groove composed of a two-step groove in which a first-step opening groove and a second-step opening groove are continuously formed. Forming the first opening groove using a liquid or solid lubricant, and then forming the second opening groove. is there.

The method of the present invention described in claim 6 is the method of claim 1
Or a can lid material for producing an easy-open can lid having an opening groove composed of a two-step groove in which a first-step opening groove and a second-step opening groove are continuously formed. The formation of the groove for the opening is performed by the method of claim 3, 4 or 5 under a temperature condition of not less than the glass transition point of the resin and not more than (melting point −20 ° C.).

The method of the invention described in claim 7 is the method of claim 1
Or a can lid material for producing an easy-open can lid having an opening groove composed of a two-step groove in which a first-step opening groove and a second-step opening groove are continuously formed. Forming the first-stage opening groove and then forming the second-stage opening groove in accordance with a temperature condition not lower than the glass transition point of the resin and not higher than (melting point −20 ° C.). It is characterized in that it is performed by:

[0027]

Next, an easy-open can lid according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a cut portion for opening formed in a can lid panel of a can body, showing one embodiment of an easy-open can lid of the present invention. As shown in FIG. 1, a front surface 1a and a back surface 1 of a can lid 1 made of a surface-treated steel sheet having a resin coating layer formed on both sides.
Opening grooves 2 and 2 are formed in each of b. Each of the opening grooves 2 and 2 includes a first-stage opening groove 2a having a depth D1.
Continuous 2 comprising a second-stage opening groove 2b having a depth D2
It consists of a step groove. Such first stage opening groove 2a
The continuous two-stage opening grooves 2 and 2 composed of the second-stage opening groove 2b can be formed by double pressing.

In order to secure the corrosion resistance without damaging the resin film and at the same time to reduce the opening force, the depth of the first-stage opening groove 2a should be D1 and that of the second-stage opening groove 2b. D for depth
2, when the tip radius of the first-stage opening groove 2a is ρ1, the tip radius of the second-stage opening groove 2b is ρ2, and the plate thickness of the can lid 1 is t, the first-stage opening groove and 2 It is necessary that the depth of the step opening groove and the tip radius thereof satisfy the following expressions (1) to (4).

0.25t ≦ D1 + D2 ≦ 0.4tmm (1) 0.2 ≦ D1 / (D1 + D2) ≦ 0.6 (2) ρ1 ≧ D1 + D2 (1 + 0.5 (D2 / D1)) mm (3) 0.02 ≦ ρ2 ≦ 0.05 mm (4) FIG. (D1 + D2) = 0.6, ρ1 ≧ D1 + D2 (1 + 0.5
FIG. 4 is a diagram showing the relationship between the depth of each of the opening grooves 2 and 2 and the can opening characteristics under the conditions of (D2 / D1)) mm and ρ2 = 0.05 mm. As shown in FIG. 2, when the depth [(D1 + D2) / t] of each of the opening grooves 2 and 2 is less than 0.25 t and is shallow, there is a great difference between the conventional V-groove shape and the can opening force. However, the deeper the opening grooves 2 are, the more effective it is in reducing the can opening force.

However, if the depth [(D1 + D2) / t] of each of the opening grooves 2 and 2 exceeds 0.40 t and becomes too deep, there is a possibility that the can is broken by an external impact. Therefore, the depth (D1 + D2) of each of the opening grooves 2 and 2 needs to satisfy the following expression (1). 0.25t ≦ D1 + D2 ≦ 0.4tmm (1) FIG. 3 shows (D1 + D2) /t=0.25, ρ1 ≧ D1 + D2 (1 + 0.5)
(D2 / D1)) mm, ρ2 = 0.05 mm, the depth [D1 / (D1 + D2)] of the first-stage opening groove 2a and the can opening force (two-step guide groove / V-shaped groove) It is a figure showing a relation. As shown in FIG. 3, the depth [D1 / D1
(D1 + D2)] is equal to or less than 0.6, which is equal to or less than the can opening force in the case of the conventional V-groove shape. On the other hand, if the depth of the first-stage opening groove 2a is less than 0.2, a problem occurs in the corrosion resistance as described later. Therefore, the depth [D1 / (D1 + D2)] of the first-stage opening groove 2a needs to satisfy the following expression (2). 0.2 ≦ D1 / (D1 + D2) ≦ 0.6 (2) FIG. 4 shows (D1 + D2) /t=0.25, D1 / (D1 + D2) = 0.6, ρ
Under the condition of 1 ≧ D1 + D2 (1 + 0.5 (D2 / D1)) mm, 2
It is the figure which showed the relationship between the front-end | tip radius (rho) 2 of the groove | channel 2b for step openings, and can open force (two steps guide groove / V-shaped groove). As shown in FIG. 4, the sharper the tip radius ρ2 of the second-stage opening groove 2b is, the more effective the reduction of the can opening force is. And there is no big difference in can opening force. Accordingly, the tip radius ρ2 of the second-stage opening groove 2b is
In consideration of the corrosion resistance described below, it is necessary that the following formula (4) is satisfied. 0.02 ≦ ρ2 ≦ 0.05 mm (4) FIG. 5 shows the depth [D1 / (D1 + D) of the first-stage opening groove 2a.
2)] and a diagram showing the relationship between the tip radius ρ2 of the second-stage opening groove 2b and the corrosion resistance of the resin film. The corrosion resistance of the resin coating was evaluated by a salt spray test. Using a can lid sample in which grooves for opening were formed on the front and back surfaces by double pressing, a 5% saline solution was sprayed in a sample chamber at 35 ° C. It was visually observed and observed with a microscope, and evaluated according to the following. ○: no rust even after 24 hours from the start of the salt spray test, x: red rust within 24 hours from the start of the salt spray test.

From FIG. 5, the depth of the first-stage opening groove 2a [D
1 / (D1 + D2)] is equal to or greater than 0.2 and the tip radius ρ2 of the second-stage opening groove 2b is equal to or greater than 0.02 mm.
It was recognized that there was no problem in corrosion resistance.

The tip radius ρ1 of the first-stage opening groove 2a needs to satisfy the following expression (3) within the above-mentioned limit range, whereby good can opening force and corrosion resistance can be obtained. ρ1 ≧ D1 + D2 (1 + 0.5 (D2 / D1)) mm (3) An opening composed of a two-step groove in which the above-described first-step opening groove and the second-step opening groove are continuously formed. When manufacturing an easy-open can lid with a groove for use, first add 2
The step opening groove 2b is formed, and then the first step opening groove 2b is formed.
Preferably, a is formed. In this manner, if the first-stage opening groove 2a is formed after the second-stage opening groove 2b is formed, the acting force generated when the first-stage opening groove 2a is formed causes the second-stage opening groove 2b to be formed. The tip of the shape is sharper,
The opening force can be stably reduced.

It is preferable that the opening groove is formed on the can lid material by using a liquid or solid lubricant. By processing using a lubricant in this way, the relative slip between the mold and the resin film is improved, and the safety against corrosion resistance can be further improved. When forming the opening groove using a lubricant, as described above, after forming the second-stage opening groove 2b, the first-stage opening groove 2a is formed. The same effect can be obtained by forming the second-stage opening groove 2b after forming the opening groove 2a.

If the forming process of the opening groove on the surface-treated steel sheet having the organic resin layers formed on both surfaces is performed at a temperature equal to or higher than the glass transition point of the resin of the resin layers formed on both surfaces, the resin is softened. Thus, damage to the resin layer due to a load received during processing or friction with a tool can be suppressed. On the other hand, when the processing temperature exceeds (the melting point of the resin −20 ° C.) and approaches the melting point of the resin, the softening of the resin proceeds, the fluidity increases, and the resin in the processed portion becomes too thin, resulting in deterioration of corrosion resistance. . Therefore, it is preferable that the forming temperature of the opening groove is not less than the glass transition point of the resin and not more than (the melting point of the resin−20 ° C.).

By forming the opening groove under such a temperature condition, the processed resin layer can be made in a sound state with less damage, and good corrosion resistance can be stably maintained with respect to the inner and outer surfaces. Can be obtained.

When forming the opening groove on the can lid material under the temperature condition of not less than the glass transition point of the resin and not more than (melting point −20 ° C.), the second opening groove is formed as described above. The same effect can be obtained by forming the first-stage opening groove 2a after forming the second-stage opening 2b or by forming the second-stage opening groove 2b after forming the first-stage opening groove 2a. .

Further, when the opening groove is formed in the can lid material by using a lubricant and under a temperature condition not less than the glass transition point of the resin and not more than (melting point−20 ° C.), A better effect is exhibited.

The thickness of the resin coating layer of a can lid made of a surface-treated steel sheet having a resin coating layer formed on both surfaces is 5 to 100.
It should be limited to the range of μm. If the thickness of the resin coating layer is less than 5 μm, the corrosion resistance of the portion becomes insufficient even if the opening groove is formed by the method of the present invention. On the other hand, when the thickness of the resin coating layer exceeds 100 μm, the resin coating layer is not easily broken at the time of opening.

As the resin coating layer formed on both surfaces of the surface-treated steel sheet, a resin generally used for a can, such as a thermoplastic laminated film, can be used. You can choose.

FIG. 6 is a schematic plan view showing an embodiment of the easy-open can lid according to the second aspect. In FIG. 6, a indicates the distance between the center position of the tab and the center of the can lid 1, S indicates the length from the center of the rivet to the tip of the tab 5, and w indicates the center of the tab. Indicates the length between the tab center line at the opening impossible position and the tab center line at the opening possible position, and m indicates the inner diameter of the can lid 1. , And
M indicates the outer diameter of the can lid 1.

In the present invention, by setting the length S from the center of the rivet to the tip of the tab 5 within the range of the following equation (6) and making it longer than before, the distance between the fulcrum and the fulcrum caused by the leverage action is increased. Is increased, thereby increasing the force generated at the point of action as compared with the conventional case. m−w>S> m / 2−a (6) Further, the center position of the tab fastening is shifted from the center of the can lid to the opposite side of the opening within the range of the following expression (5). , (M−m) / 2 <a <m / 2−w (5) Around the center of the tab 5 around the tab fastening center, θ obtained by the following equation (7) is obtained.
Rotated by minutes. −1 <cos θ <1 / (2 × a × S) × {(m / 2) ² − (S ² + a ² )} (7) Open the center position of the tab fastening from the center of the can lid. The reason for shifting to the opposite side of the part within the range of the above equation (5) is as follows. That is, in the case where the center of the can lid is to be dubbed, if the length from the center of the rivet to the tip of the tab 5 is increased, the entire tab cannot be accommodated on the central panel 3, and the stackability, storage property and can The transportability is significantly impaired, while the distance between the rivet and the finger-hanging end is set to keep the tab 5 within the tightening portion and to secure a space for inserting a finger between the tab end and the tightening portion. Is S <m / 2-5mm
Is restricted to In contrast, according to the present invention,
As described above, the center position of the tab fastening is shifted by a,
Then, the entire tab can be placed on the central panel 3 by rotating the tab by θ.

Further, at the time of opening the can, the tab is rotated from the unopenable position to the openable position around the tab fastening. However, simply rotating the tab ends in the middle of the rotation causes the tab end to hit the tightened portion around the can lid, and further rotation is impossible. Therefore, it is possible to rotate the tab 5 to a position where the tab 5 can be opened by forming a slope-shaped projection on the center panel 3 and lifting the tab end to a height equal to or higher than the height of the tightening portion.

When the tab 5 is rotated to the opening-possible position in this manner, the tab-raising side end is located outside the outer periphery of the can lid (outer periphery of the tightening portion).
This makes it easy to pinch a finger.

In FIG. 6, a rivet is shown as a means for stopping the tab 5 so that the tab 5 can be moved angularly. However, the present invention is not limited to this, and a tab fastening member having the same structure is fixed to the central panel portion by another adhesive means. You may. As for the shape of the tab 5, it is desirable to raise the side surface of the tab so that the corner can be easily moved, and to improve the finger grip. In FIG. 6,
Although a stion tab type can lid has been shown, the present invention is not limited to this, and the pull top tab
It can also be applied to types of can lids.

The fact that the opening grooves are formed on each of the front and back surfaces of the can lid is that the depth of each opening groove is shallower than that of the conventional single-side opening groove only on the front surface. It is easier to process and has less tool wear, and has better impact resistance to external impact than the single-sided opening groove.

[0046]

Next, the present invention will be further described with reference to examples and comparative examples. [Example 1] Hardness (HR30T) with a plate thickness of 0.25 mm
Is formed on the surface of a thin steel plate having a thickness of 2.8 g / m ² , an electrotin plating layer in an amount of 2.8 g / m ² , and a metal chromium layer in an amount of 12 mg / m ² by chromate treatment on the electrotin plating layer; On the both surfaces of a tin-plated steel sheet having a chromium hydrated oxide layer formed thereon in an amount of 10 mg / m ^{2 in} terms of metal chromium, a thickness of 25 μm
m of a heat-sealing type polyester film was laminated.

In the tin-plated steel sheet laminated with the polyester film in this manner, a groove composed of the first-stage opening groove and the second-stage opening groove within the scope of the present invention shown in Table 1 was formed. , Pull-top tab type easy-open can lid specimen (hereinafter referred to as the specimen of the present invention) No.
1-3 were prepared. For comparison, a pull-top / tab-type easy-open can lid specimen (hereinafter referred to as a comparative specimen) No. 1 having an opening groove outside the scope of the present invention shown in Table 1 was formed. ~ 3 were prepared.

[0048]

[Table 1]

Example 2 A 120 mg / m ² metal chromium layer was formed on the surface of a thin steel sheet having a thickness of 0.25 mm and a hardness (HR30T) of 61 by chromate treatment, and a metal chromium layer A heat-fusible polyester film having a thickness of 25 μm was laminated on both surfaces of the tin-free steel on which a chromium hydrated oxide layer was formed in an amount of 15 mg / m ^{2 in} terms of conversion.

On the surface-treated steel sheet laminated with the polyester film as described above, a groove composed of a first-stage opening groove and a second-stage opening groove within the scope of the present invention shown in Table 2 was formed. Nos. 4 to 6 of the present invention as easy-open can lids of the Stion tub type were prepared. For comparison, comparative specimens Nos. 4 to 6 were prepared for easy-open can lids of the Stion tub type in which the opening grooves outside the range of the present invention also shown in Table 2 were formed.

[0051]

[Table 2]

An opening groove was formed on the surface of the tin-plated steel sheet on which the polyester film was laminated, which was used in the specimens Nos. 1 to 3 of the present invention, by using a conventional mold having an inverted trapezoidal blade. Specimen No. 7 consisting of an easy-open can lid of the Stion tub type, the tin-free steel laminated with the polyester film used in Specimens Nos. 4-6 of the present invention, and a comparative specimen No. . For each of the comparative sample No. 8 consisting of a stion tub type easy-open can lid with a groove for opening formed in the same manner as in No. 7, the evaluation of the openness and corrosion resistance and the overall evaluation were performed as follows. Table 3 shows the results.

[0053]

[Table 3]

[Evaluation of Opening Property]
For the test specimens Nos. 1 to 6 and Comparative Sample Nos. 1 to 8, the load W when the opening groove was broken at the time of opening was measured, and
As an index of the easy opening property, the ratio (W / W8) to the opening load W8 of the comparative sample No. 8 which is a general prior art was calculated, and the opening property was evaluated by this.

As is clear from Table 3, the specimen N of the present invention
o. 1 to 6 have an opening property evaluation (W / W8) of 0.5 to
0.9, all of which were excellent in opening properties. On the other hand, the comparative specimens Nos. 1, 4, and 7 were evaluated for openability (W
/ W8) was 1 or more, and the opening properties were poor.
Comparative specimens Nos. 3 and 6 were evaluated for openness (W /
W8) was about 0.1 in each case, and the opening load was too small. Therefore, there was a high possibility that an accident such as breakage would occur during the conveyance, and it could not be put to practical use.

[Evaluation of Corrosion Resistance] Each of the test specimens Nos. 1 to 6 of the present invention and the test specimens Nos. 1 to 8 was subjected to a salt spray test to evaluate the external corrosion resistance. Twenty-four hours later, the appearance of the specimen was visually observed and observed with a microscope, and its corrosion resistance was evaluated as described below.印: No rust was generated even after 24 hours from the start of the salt spray test. X: Red rust was generated within 24 hours after the start of the salt spray test. Specimens No. 1 to 6 and Comparative Specimens No. 1 and No. 4 were all excellent in corrosion resistance. On the other hand, the comparative specimens Nos. 2, 3 and Nos. 5 to 8 had poor corrosion resistance.

The test pieces Nos. 1 to 6 of the present invention
To evaluate the inner corrosion resistance, a commercially available canned body was filled with a commercially available carbonated beverage (Coca-Cola), sealed with each specimen, stored at 38 ° C., and stored for 1 month. Was analyzed for the amount of iron eluted. As a result, the specimen N of the present invention
o. In each of 1 to 6, the iron concentration in the solution was 0.1.
It was less than 1 ppm, and it was confirmed that the corrosion resistance to the internal environment was sufficient.

[Comprehensive Evaluation] The specimens Nos. 1 to 6 of the present invention and the comparative specimens Nos. 1 to 8 were evaluated in terms of openness and corrosion resistance as follows.印: excellent in both openability and corrosion resistance ×: poor in one or both of openness and corrosion resistance As is clear from Table 3, the specimens of the present invention Nos. 1 to 6
While the overall evaluation was excellent, the comparative specimen N
o. 1 to 8 had poor one or both of the opening property and the corrosion resistance.

[0059]

As described above, according to the easy-open type can lid of the present invention, both sides of the can lid made of a surface-treated steel sheet having a resin coating layer having a thickness of 5 to 100 μm formed on both sides. Since the two-step opening groove is formed, an industrially useful effect is brought about such that the opening force is stably reduced and the repair coating of the resin layer becomes unnecessary.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an opening cut portion formed in a can lid panel of a can body, showing one embodiment of an easy-open can lid of the present invention.

FIG. 2 is a diagram showing a relationship between each depth of an opening groove and can opening characteristics.

FIG. 3 is a diagram showing a relationship between a depth of a first-stage opening groove and a can opening force.

FIG. 4 is a diagram showing a relationship between a tip radius of a second-stage opening groove and a can opening force.

FIG. 5 is a diagram showing the relationship between the depth of the first-stage opening groove and the tip radius of the second-stage opening groove, and the corrosion resistance of the resin film.

FIG. 6 is a schematic plan view showing another embodiment of the easy-open can lid of the present invention.

FIG. 7 is a schematic plan view showing an example of a pull-top tab type can lid.

FIG. 8 is a schematic plan view showing an example of a canion tab type can lid.

FIG. 9 is an explanatory view showing the shape of an opening groove formed by a conventional processing tool having a sharp cutting edge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Can lid 2 Opening groove 2a First-stage opening groove 2b Second-stage opening groove 3 Central panel part 4 Riveting mechanism 5 Tab 6 Opening groove 7 Processing tool 8 V-shaped opening groove

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuji Yamazaki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Yoshinori Yomura 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Reiko Sugihara 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd.

Claims (7)

[Claims] An opening groove is formed on each of both surfaces of a can lid made of a surface-treated steel sheet having an organic resin layer having a thickness of 5 to 100 μm formed on both surfaces, and the opening groove is broken to open the can. In the easy-open can lid having the structure described above, the opening groove is formed of a two-step groove in which a first-step opening groove and a second-step opening groove are continuously formed, and
The depth of each of the first-stage opening groove and the second-stage opening groove and the tip radius thereof satisfy the following formulas (1) to (4). Excellent easy open can lid. 0.25t ≦ D1 + D2 ≦ 0.4tmm (1) 0.2 ≦ D1 / (D1 + D2) ≦ 0.6 (2) ρ1 ≧ D1 + D2 ( 1 + 0.5 (D2 / D1)) mm (3) 0.02 ≦ ρ2 ≦ 0.05 mm (4) where D1 is for the first stage opening Groove depth, D2: Groove depth for the second stage opening, ρ1: Radius tip radius for the first stage opening, ρ2: 2
Radius of groove end for step opening, t: can lid plate thickness. 2. An opening groove comprising a two-step groove in which a first-step opening groove and a second-step opening groove satisfying the condition of claim 1 are formed, and The tab is a can lid which is rotatably attached to the opening possible position from a position where opening is impossible to a position where opening is possible around the tab fastening, and the center position of the tab fastening is the following (5) ), The length S between the center of the tab fastening and the finger-holding portion of the tab is within the range of the following equation (6), and the tab center line and the opening position at the opening impossible position The angle θ between the tab and the center line is within the range of the following expression (7), and at the openable position, the finger-clamping portion of the tab is positioned outside the outer periphery of the can lid and higher than the periphery of the can lid. Lifting means capable of being lifted can be provided on the lid of the can. Easy-open can lid was. (M−m) / 2 <a <m / 2−w (5) m−w>S> m / 2−a (6) −1 <Cos θ <1 / (2 × a × S) × {(m / 2) ² − (S ² + a ² )} (7) where a: the center of the tab from the center of the can lid Deviation distance, S: length between the center of the tab fastening and the tab finger holder, w: length between the center of the tab fastening and the tab action part, θ: at the tab center line at the opening impossible position and at the opening possible position Angle between tab center line, m: inner diameter of can lid, M: outer diameter of can lid. 3. An easy-open can lid having an opening groove comprising a two-step groove in which the first-step opening groove and the second-step opening groove according to claim 1 or 2 are formed. In manufacturing the first, first form a groove for the second stage opening in the can lid material,
Next, a first-stage opening groove is formed,
A method for manufacturing an easy-open can lid with excellent openability. 4. An easy-open can lid having an opening groove comprising a two-step groove in which the first-step opening groove and the second-step opening groove according to claim 1 or 2 are continuously formed. The manufacturing process of the opening groove in the can lid material is performed using a liquid or solid lubricant when manufacturing the can.
4. The method for producing an easy-open can lid having excellent can-opening properties according to item 1. 5. An easy-open can lid having an opening groove comprising a two-step groove in which the first-step opening groove and the second-step opening groove are continuously formed, according to claim 1 or 2. When manufacturing the opening groove, the opening groove is formed on the can lid material by using a liquid or solid lubricant, first forming the first opening groove, and then forming the second opening groove. A method for producing an easy-open can lid having excellent can-opening properties. 6. An easy-open can lid having an opening groove comprising a two-step groove in which the first-step opening groove and the second-step opening groove according to claim 1 or 2 are formed. 6. The can according to claim 3, wherein, when manufacturing the can, the forming process of the opening groove in the can lid material is performed under a temperature condition not lower than the glass transition point of the resin and not higher than (melting point −20 ° C.). Method for manufacturing easy-open can lids with excellent properties. 7. An easy-open can lid having an opening groove formed of a two-step groove in which the first-step opening groove and the second-step opening groove according to claim 1 or 2 are formed. When manufacturing the opening lid, the opening groove is formed on the can lid material by first forming a first-stage opening groove and then forming a second-stage opening groove under a temperature condition of not less than the glass transition point of the resin and not more than (melting point −20 ° C.). A method for producing an easy-open can lid having excellent can-opening properties, wherein the method is performed by forming an eye opening groove.