JP2002154281A - Screen printing plate and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve screen printing characteristics under the state that the printing surface of an object to be printed is uneven. SOLUTION: In a screen printing plate, the tension measured with a dial dype STG 75 tension gate of a screen stretched on the frame of which is set to be 2.0 to 5.0 mm and in particular the elastic modulus of the stock of the screen employed in which is set to be 200 to 1,000 N/mm2. The screen printing characteristics are improved by using the above screen printing plate under the conditions that a pressure applying to a squeegee is set to be 0.3 MPa or higher and the hardness of the tip part of the squeegee is set to be 50 to 90.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen printing plate used for screen (silk screen) printing and a printing method using the screen printing plate, and more particularly to a cassette or cartridge containing a magnetic recording medium such as a magnetic tape or a magnetic disk. Printing of designs and the like on the surface of cartridges containing optical recording media such as optical disks and magneto-optical disks, other cartridges for recording media, and storage cases for storing and protecting these cassettes and cartridges by screen printing. The technology to be applied.

[0002]

2. Description of the Related Art The surface of a cartridge or a storage case is provided with a portion one step lower than the surface of the cartridge or the storage case, such as a label recess for attaching a label. When printing across the step of the label recess,
There were problems such as printing being interrupted at the stepped portion and ink bleeding. There are the following proposals for such a problem. SUMMARY OF THE INVENTION The present invention relates to a printing method in which a printing layer is provided on a recording medium having a step portion on the surface, wherein the step portion is constituted by an inclined surface so that the front and back of the step portion are connected as smoothly as possible, and an ink layer is formed. The printing layer is prevented from being interrupted at the step by applying thermal pressure by applying pressure and heat to the thermal transfer foil having the above-mentioned method, or by performing printing using a pad printing method. Patent Document 1: Japanese Patent Application Laid-Open No. 2000-11600 This relates to a printing method in which a printing layer is provided on a recording medium having a step portion on the surface similarly to the above-mentioned document, and at least a part of the step portion is constituted by an inclined surface, and a portion having an inclined surface Is matched with the direction of travel of the squeegee in screen printing, so that it is possible to provide a print layer with little bleeding or the like while leaving a step portion formed of a vertical surface.

[0003]

The above proposals exhibit desired effects, but have other disadvantages. In the thermal transfer printing method, a printing layer is transferred to an object by applying heat and pressure, and the object is subjected to heating and compression. In such a recording medium mainly composed of a thermoplastic resin, it is necessary to prevent thermal deformation due to heating. Further, since the pad printing method does not require heating, troubles due to heat can be avoided, but the compressive force acts directly on the entire object. At this time, it seems that at first glance the whole object is compressed uniformly, but in actuality, the object containing the recording medium inside has a structure in which the upper and lower main surfaces are supported by the side walls of the peripheral edge. That is, since it has a hollow structure,
Even if the pressure is uniformly applied, the central portion is more deformed by compression than the peripheral portion, and it is difficult to adjust the balance between the printing on the stepped portion and the deformation. As described above, the thermal transfer printing method and the pad printing method are not suitable for a cartridge or the like for a high-density recording medium, which is mainly composed of a thermoplastic resin and particularly requires high dimensional accuracy.

In the above proposal, since a screen printing method is used, troubles due to heat and problems due to pressurization can be avoided. However, in this proposal, it is possible to print on an inclined surface that matches the traveling direction of the squeegee. However, in a step portion formed by a vertical surface other than the inclined surface, the screen (shape) of the screen printing plate and the vertical surface When a gap is left between the target object and the target object, ink bleeding occurs, and a desired print quality cannot be obtained as a whole object. Furthermore, even if this proposed screen printing method is used, it is still insufficient to achieve high print quality on inclined surfaces. This is because the screen used in the screen printing method is strongly attached to the holding frame, and cannot sufficiently cope with printing on an uneven surface including an inclined surface. It has been found that this is thought to be because the conventional screen printing plate is set to a tension suitable for printing a flat surface.

To explain this point more concretely, FIG. 7 first shows the principle of screen printing.
(B) and (c) show the sequential steps of printing in this order. Frame 4
A sliding block that slides on the screen is provided above the screen 1 stretched on the screen, and a sliding block (not shown) for spreading ink on the screen and a doctor 2 are provided. Squeegees 3 for allowing ink to pass through the mesh of the screen and reach the target are provided individually vertically movably. The squeegee 3 and the doctor 2 are arranged in parallel. A printing object (work) 6 is arranged below the screen 1 and is sent one by one horizontally to a printing position as printing proceeds. First, as shown in FIG. 7A, the sliding block moves from one end (left side in the figure) of the screen 1 to the other side (right side in the figure) with the doctor 2 lowered and the squeegee 3 raised. At this time, the doctor 5 spreads the ink 5 over the entire screen. Next, as shown in FIG. 7B, the sliding block moves from the other end of the screen 1 with the doctor 2 raised at one end and the squeegee 3 lowered. At this time, the screen 1 is brought into close contact with the object by the squeegee 3, and the ink 5 spread over the entire surface of the screen 1 is transferred to the object while passing through the mesh of the screen 1 (FIG. 7).
(C)). That is, when the screen 1 is squeezed by the squeegee 3, the ink on the screen 1 is pushed out. At this time, as the hardness of the squeegee 3 is lower (softer), the tip of the squeegee penetrates deeper into the mesh of the screen and pushes out a larger amount of ink (a larger discharge amount), so that the ink layer of the object becomes thicker. Conversely, the higher the hardness (harder) of the squeegee 3, the smaller the amount of ejection, and the thinner the ink layer. When the sliding block has been moved to one end, the squeegee 3 is raised and the doctor 2 is lowered, the next work is sent to the printing position, and the process shown in FIG. 7A is repeated.

On the other hand, in a magneto-optical disk cartridge 6 in which a cartridge to be printed, for example, a magneto-optical disk (not shown) to which the present invention is applied as shown in FIG. As mentioned above with respect to the example, as shown in FIGS. 1 and 2, the inclined surface 9 is provided at the step portion at the boundary between the concave portion 7 and the flat surface 8 constituting the label sticking surface.

When screen printing is performed on the object having the above structure using a screen printing frame in which a screen 1 stretched with a conventional standard tension is stretched over a frame 4 in FIG. 7 (FIG. 7B). (Corresponding to the step (c))), and the sequential steps as shown by arrows in FIG. FIG. 6A is an enlarged view of the squeegee on the inclined surface. At this time, if a conventionally used screen stretched with a standard tension is used, the tip of the squeegee 3 cannot make the screen 1 sufficiently contact the inclined surface of the object. This is because the distance between the point A where the squeegee 3 is in contact with the screen 1 and the vertex B of the inclined surface 9 is short due to insufficient deflection of the screen and the inclined surface 9 and the screen 1
It was found that a gap was formed between the ink and the ink, resulting in insufficient transfer of the ink. When the squeegee 3 is further advanced past the lowermost point C of the inclined surface, the screen 1 comes into sufficient contact with the object again.

[0008] The deflection of the screen when pressed by the squeegee does not have a relationship like the deflection of a single string. It was found that only the area immediately bends greatly locally. It is understood that the reason for the insufficient transfer of the ink between the concave portion 7 and the inclined surface 9 is that the vertex B hinders the screen from being recessed and the local recess cannot be sufficiently performed. Was. It was also found that good printing was again performed on the concave side because the distance from the vertex B became large even with the same pressing force, so that the local dent of the squeegee was not hindered. In other words, the present invention makes it possible to increase the overall squeegee compliance by reducing the tension of the screen, and at the same time, to increase the local indentation by selecting the elasticity of the material of the screen. Is what is possible.

[0009]

SUMMARY OF THE INVENTION The present inventor has proposed a method for performing screen printing on an object having a concave and convex portion including an inclined surface such as a label concave portion as a whole.
We thought that it would be important to apply appropriate pressure with a squeegee of appropriate hardness using a screen that could flexibly follow the uneven shape of the object. This idea deviates from the idea of setting the screen tension with the plane part considered conventionally in screen printing as a standard.However, even if the screen tension is loosened to some extent and it is adapted to printing on inclined surfaces, the printing of the plane part also The inventor has found that it can be implemented without problems. By doing so, the degree of local indentation of the screen can be increased in combination with the selection of a flexible screen material having a relatively small elastic modulus, and excellent printing results can be obtained.

[0010] That is, the present invention relates to a screen printing plate used for screen printing, wherein the tension measured by a dial gauge type STG75 tension gauge described later is 2.0 mm to 5.0 mm. Provide a screen printing plate featuring. In the above printing plate, the elastic modulus of the screen material is 200 to 1
It is preferable to use 000 N / mm ² , more preferably 300 to 750 N / mm ² , and particularly a resin for synthetic fibers can be suitably used. The present invention also uses the above screen printing plate, and the hardness of the squeegee tip is JIS-
Using a squeegee having an A hardness of 50 to 90, at least 0.3 MPa or more is applied to the squeegee.
A method of performing screen printing on a printing surface while applying a pressure of about MPa. In the above screen printing method, the surface to be printed has a step formed of an inclined surface, and a printing layer is also provided on the surface including the step. The angle of the inclined surface of the step portion (with respect to the horizontal plane) is 45 degrees, preferably 3
It has been found that up to 0 degrees can be sufficiently handled. In this case, the dimensions of the screen printing plate were not so related, and it was found that the tension and the elastic modulus were dominant.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention provides the following: (1) The tension of a screen (gauze) at the time of attaching to a plate frame is lower than that of the prior art so that it can flexibly follow the uneven shape of an object. Specifically, the measured value of the dial type tension gauge is set to 2.0 to 5.0 mm. This value is considerably looser than the set value of conventional flat printing of 1.0 to 1.5 mm.

At this time, the tension is measured by Toprotec Co., Ltd. (located in Setagaya-ku, Tokyo) which is common in the industry.
(Digital tension gauge STG-75)
Even in the mold tension gauge, only the read portion is digitized, and the same value is obtained within an error range.) The larger the measured value, the smaller the tension applied to the screen and the looser the tension.

The procedure for attaching the screen to the plate frame is as follows. First, it is big enough (wide) than the frame
Pull the screen back and forth, left and right, and apply the frame from under the screen. In this state, the tension state is adjusted while a tension gauge is placed on the tension gauge to check the value (temporary setting). Next, the tension gauge and the plate frame are removed, and the plate frame coated with the adhesive is applied to the screen again. After the adhesive has hardened, a tension gauge is mounted again to confirm that the desired tension is obtained.

In the screen plate of the present invention, (2) In order to obtain a screen having good followability, a resin material having high elasticity is selected from materials generally used as a material of the screen. Specifically, polyester,
Nylon or the like can be used, but a metal such as stainless steel or a combination of a metal thread and a synthetic resin thread lacks flexibility and is not suitable. The selection criteria for such a material are to set the elastic modulus at the used tension to 200 to 1000 N / mm ^2.
And A more preferred value is 300 to 750 N / mm ² . Nylon about 200~600N / mm ^2, the polyester is about 400~1000N / mm ^2. On the other hand, the elastic modulus of stainless steel is about 2000 to 3000 N / mm ² . The elastic modulus is the ratio of tensile stress to strain,
Specifically, it can be determined from the data of a tensile test as shown as an example in FIG.

Further, in the screen printing method of the present invention, (3) the screen printing plate is used, and the pressure applied to the squeegee is 0.3 MPa (3.0 kg / m ² ) or more. If the pressure is 0.3 MPa or more, it is possible to follow the uneven shape of the object, but if the pressure is too high, the screen is strongly wrung and the durability of the plate is reduced.
The upper limit is 1.2 MPa, more practically 0.7 MPa
(7.0 kg / m ² ) or less is preferable.

Also, the present invention relates to a squeegee used for screen printing, wherein (4) the hardness of the squeegee tip is 50 to 90 (JIS-K
6301). If it is less than 50, the ink layer applied to the object becomes thick, and the drying (curing) time becomes long, which is not practical. If it exceeds 90, the ink layer applied to the object becomes thin, and there is a case where the ink layer is blurred at a step portion or the like. We have already explained that the reason is due to the screen printing mechanism.

Regarding the inclination angle between the inclined surface 9 of the object 6 and the screen facing the object, if the angle is 15 degrees or less, printing can be performed on the inclined surface by the conventional method. Is not practical. If the inclined surface is 45 degrees or less, the screen printing plate of the present invention and the method of the present invention can perform good printing even on the inclined surface and can obtain a sufficiently wide concave portion. If it exceeds 45 degrees, it will be in a state close to the case of the step formed by the above-described vertical plane,
Good printing is also difficult with the method of the present invention. A preferred range is 15 to 30 degrees. On the other hand, if the depth (step) of the concave portion 7 is too deep, the concave of the screen cannot catch up, so if the inclination angle of the inclined surface 9 is large, it should be shallow.
If less, it may be deeper.

The method of the present invention is shown in FIG. The progress of printing is the same as in the conventional example of FIG. The state when the squeegee has reached the inclined portion 9 is shown in FIG. In the present invention, since the tension of the screen 1 on the frame 4 of the printing plate is loose and the elasticity of the screen material is low, there is no gap between the screen and the object 6 even at the lowest point C of the inclined surface 9, It can also be seen that beautiful printing is performed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An object to be printed was an MD (mini disc) cartridge. The upper shell surface 8 is provided with a rectangular label recess 7 as shown in FIG. The depth of the label recess (H in FIG. 2) was 0.2 mm at the maximum at the step. Regarding the angle (α in FIG. 4) of the inclined surface of the step portion, three sides of the four sides of the rectangle are 30 degrees, and the remaining one side is 10 degrees. If the angle is 45 degrees or less, almost satisfactory printing is possible. Preferably, the angle is about 15 to 30 degrees. FIG. 3 shows a screen printing plate. The screen is set in a square frame. The material of the screen is nylon thread (6,6-nylon, elasticity 324N /
mm ² , but as a value at a tension of 3 mm). In another embodiment, a polyester yarn (polyethylene terephthalate, 710 N / mm ² ,
mm), and a stainless steel thread (347
5 N / mm ² , but with a tension of 3 mm)
It was used. The number of screen meshes is nylon # 330, polyester # 300, stainless steel # 300.
It was used. The size of the screen plate used is 300 × 260 mm in the outer size and 250 × 210 mm in the inner size in consideration of the size of the object, equipment, member costs and the like. The squeegee has a size corresponding to the above frame and a length of 150
× width 30 × thickness 6 mm. The ink used is a UV-curable ink. The printing press can use the screen plate and has a UV curing device. The printing procedure was as follows. (Refer to FIG. 4 and FIG. 7) (1) Bring the screen printing plate closer to a slightly distant object. Thereafter, the ink is spread by the doctor. (2) Squeeze the screen with a squeegee so that the ink passes through the mesh. (3) The ink is transmitted through the screen and transferred to the object according to the transmission / non-transmission of the screen.

(1) Experiment on Tension and Material The screen plate tension was measured when the material of the screen was nylon, and the measured value of the tension gauge was 2.3 to 5.0 mm as an example, and 1.3 mm as a comparative example. 5.5 mm. In the case of polyester, 3.0 mm and 5.0 mm as another example, and 1.3 as another comparative example.
mm was used. In the case of stainless steel, 3.0 mm was used as still another comparative example. Table 1 shows the measurement results when the tension was changed. In the printing results in the table, x indicates poor printing on the inclined surface, Δ indicates good quality, and o indicates high quality. When nylon is used from Table 1, the tension is 2.3 to 5.0.
When the polyester was used, the tension was 3.0 mm and 5.0 mm.
Stainless steel was bad. In the table, the tension is the value measured by the tension gauge, the pressure is the pressure applied to the squeegee, the hardness is the hardness of the tip of the squeegee, the angle is the inclination angle of the squeegee (θ in FIG. 4), and the distance is no pressure applied to the plate. The distance between the object in the state and the plate (W in FIG. 4) is shown in Table 2 below.
The same applies to Tables 5 to 5.

[0021]

[Table 1]

(2) Experiment on Squeegee Pressure The squeegee pressure was 0.3 to 1.2 MPa as an embodiment.
a, 0.2 MPa was used as a comparative example. Table 2 shows the results when the pressure of the squeegee was varied. In the case of nylon, it was preferable that the squeegee pressure be 0.3 MPa or more. In consideration of the durability of the plate, the maximum value should be 0.7 MPa or less. The same applies to polyester.

[0023]

[Table 2]

(3) Experiment on Hardness of Squeegee Tip The hardness of the squeegee tip used was 50 to 90 as an example, and 40 and 100 as comparative examples. Table 3 shows the results. In the case of nylon, it was good in the range of 50 to 90.

[0025]

[Table 3]

(4) Experiment on squeegee angle Squeegee angle (angle from normal to squeegee moving direction)
Used 10 to 30 degrees as an example and 5 degrees as a comparative example. Table 4 shows the results. If it is 10 degrees or more, there is no problem, and it can be appropriately selected and used.

[0027]

[Table 4]

(5) Experiment on distance between screen and object The distance between the screen and the object is 0.5 to 0.5 as an embodiment.
2.5 mm, and 3.0 mm as a comparative example. Table 5 shows the results. It can be seen that there is no problem if it is less than 3 mm.

[0029]

[Table 5]

[0030]

In the embodiment of the present invention, since the screen tension is low and the material has high elasticity, the screen can flexibly expand and contract (within a minute range) and follow the irregularities of the object. Also, the pressure and hardness of the squeegee should be adjusted in the same range as in the case of the conventional high tension, that is, in a range where it is not necessary to perform special remodeling etc. on the printing press or prepare rubber with a special hardness. By adjusting, it is possible to more reliably follow and improve the productivity. In the related art, since the tension of the screen is high and the elasticity of the material is low, a portion where the screen cannot follow the unevenness of the object is generated, and it is difficult to improve the print quality. Also, if you try to compensate for the lack of followability by the pressure and hardness of the squeegee, increasing the pressure will damage the screen itself, and decreasing the hardness will increase the thickness of the ink layer in areas other than the steps, causing drying (curing). Troubles, such as a long time, and the productivity is reduced. In the embodiment of the present invention, the object is reliably followed, so that high-quality printing can be performed over the entire printing range. The conventional one has a problem that the ink is not transferred onto the object or the ink bleeds partially, particularly at the step. The object to be printed is not limited to the MD cartridge of the above embodiment, and is effective when printing is performed on an object provided with a concave portion having a stepped portion formed by an inclined surface, in a state of straddling the stepped portion. . Also, the depth of the recess is
The present invention is not limited to the maximum of 0.2 mm in the above-described embodiment, and it is possible to efficiently perform high-quality printing by implementing the present invention not only in a shallow case but also in a deep case. Further, the size of the screen plate or the squeegee can be appropriately set in consideration of the conditions of the target object and the facilities. Furthermore, the ink used is not limited to the UV curable type, and there is no particular limitation as long as it can be used for screen printing.

As described above, the tension applied to the plate frame is adjusted to 2.0 to 5.0 mm, which is lower than before, and other conditions (screen material, squeegee pressure, hardness) are made special. No good printing is possible. Significant changes in the screen printing machine, even if the surface of the cartridge or storage case has a step formed by an inclined surface with a depth about the same as the label recess, even if the target is not a flat, uneven surface as a whole It is possible to realize appropriate printing conditions within a range of adjustment that does not require the printing, and perform printing over the entire surface of the target object including the inclined surface of the step portion.

[Brief description of the drawings]

FIG. 1 is a plan view showing a rectangular label recess on the surface of an upper shell of an MD (mini disc) cartridge.

FIG. 2 is a sectional view taken along the line AA in FIG. 1 including a label recess.

FIG. 3 is a screen printing plate.

FIG. 4 is a schematic view of a printing process according to the present invention.

FIG. 5 is a schematic view of a conventional printing process.

6 (a) is an enlarged view of a main part of FIG. 5 (conventional example),
(B) is an enlarged view of the main part of FIG. 4 (the present invention).

FIG. 7 is a diagram showing the principle of the screen printing method (a).
(C) shows an order process.

FIG. 8 is a graph showing the relationship between the tensile strength and the elongation of the screen material used in Examples and Comparative Examples of the present invention.

[Explanation of symbols]

 Reference Signs List 1 screen 2 doctor 3 squeegee 4 screen printing plate frame 5 ink 7 concave part of object 8 flat surface of object 9 inclined surface of step

Claims (5)

[Claims] 1. A screen printing plate used for screen printing, wherein a tension of a screen stretched on a frame of the screen printing plate measured by a dial gauge type STG75 tension gauge is 2.0 mm to 5.0 mm. Features a screen printing version. 2. The screen material according to claim 1, wherein said screen material has an elastic modulus of 200.
~ 1000N / mm ^TwoThe screen according to claim 1, which is
Printing plate. 3. The screen printing plate according to claim 1, wherein the screen is made of a resin. 4. Using the screen printing plate according to claim 1, at least a pressure applied to the squeegee is 0.3 MPa or more, and JIS-JIS at the squeegee tip.
A screen printing method, wherein A hardness is 50 to 90. 5. The screen printing method according to claim 4, wherein the surface of the object to be printed has a step formed of an inclined surface, and a printing layer is provided on the surface.