WO2023223827A1

WO2023223827A1 - Pressure sensitive adhesive sheet

Info

Publication number: WO2023223827A1
Application number: PCT/JP2023/017070
Authority: WO
Inventors: 寛三清水
Original assignee: 日榮新化株式会社
Priority date: 2022-05-20
Filing date: 2023-05-01
Publication date: 2023-11-23
Also published as: JP7461690B1; JPWO2023223827A1

Abstract

A pressure sensitive adhesive sheet 10 is provided with a pressure sensitive adhesive agent layer 3 and a print part 5 formed on at least one surface of the pressure sensitive adhesive agent layer 3. The print part 5 is formed by an ink cured product, and is provided on at least one print region that is set on the pressure sensitive adhesive agent layer 3 as a printing range. In the print region, the loop tackiness value of the pressure sensitive adhesive agent layer 3 with respect to a SUS steel sheet is less than 1.0 N/25 mm. In the print region, the adhesive force of the pressure sensitive adhesive agent layer 3 with respect to a SUS steel sheet at 23°C and at a peel angle of 180 degrees and a relative humidity of 50% when a load of 2 kg was used for pasting the same and after 24 hours has elapsed is 0.05 N/25 mm or more.

Description

adhesive sheet

The technology disclosed in this specification relates to a pressure-sensitive adhesive sheet in which a printed portion is provided on at least one surface of the pressure-sensitive adhesive layer.

Adhesive sheets equipped with an adhesive layer are used in a variety of fields, such as for fixing components of electronic devices, screen protection sheets, wallpaper and other construction materials, printed materials and laminated sheets for printed materials, and various tapes. Depending on the use of the pressure-sensitive adhesive sheet, there are cases where it is desired that the adhesive sheet stick firmly to the adherend and not be easily peeled off, and cases where it is desired that it be easy to reapply when pasting.

The specification of Japanese Patent Publication No. 2003-531253 (Patent Document 1) discloses that a graphic adhesive sheet that is easy to reapply is created by forming a non-adhesive polymer having a predetermined pattern on the adhesive surface of the adhesive layer. It describes what you can do.

Special table 2003-531253

By the way, in some cases, the adhesive force of the adhesive sheet to the adherend is better to be stronger, and in other cases, it is better to be weaker. There is a great demand for adhesive sheets that are easy to reapply and are difficult to peel off after pasting, but other properties may be required.

Here, in the adhesive sheet described in Patent Document 1, a non-adhesive polymer is formed not only to facilitate reattachment but also to remove air remaining between the adhesive layer and the adherend. . For this reason, the non-stick polymer is provided evenly over the entire adhesive surface of the sheet. As a result, it is difficult for the pressure-sensitive adhesive sheet described in Patent Document 1 to respond flexibly to cases where a plurality of different properties are desired.

An object of the present invention is to provide a pressure-sensitive adhesive sheet having a structure in which properties such as adhesive strength and ease of pasting and peeling can be easily controlled.

An example of the adhesive sheet disclosed in this specification includes an adhesive layer and a printed portion formed on at least one surface of the adhesive layer. The printing part is formed of a cured ink product, and is provided on one or more printing areas set in the adhesive layer as a printing range, and the printing part is formed of an ink cured product, and is provided on one or more printing areas set in the adhesive layer as a printing area, and the printing part is formed of the adhesive layer in the printing area with respect to the SUS steel plate. The loop tack value was less than 1.0 N/25 mm, and the adhesive layer was applied to the SUS steel plate in the printing area after 24 hours at 23°C, a load of 2 kg during lamination, a relative humidity of 50%, and a peeling angle of 180 degrees. The adhesive force at this time is 0.05 N/25 mm or more.

According to the adhesive sheet disclosed in this specification, properties such as adhesive strength and ease of application and peeling can be easily controlled by appropriately changing the thickness of the adhesive layer, the thickness of the printed part, etc.

FIG. 1 is a cross-sectional view showing an example of a pressure-sensitive adhesive sheet according to an embodiment of the present disclosure. FIG. 2 is a plan view of the adhesive sheet shown in FIG. 1 when viewed from the printing section side. FIG. 3 is a photographic diagram showing an enlarged printing section in area A shown in FIG. 2. FIG. FIG. 4 is a sectional view showing a pressure-sensitive adhesive sheet according to a first modification of the present disclosure. FIG. 5 is a plan view schematically showing a method of printing a pressure-sensitive adhesive sheet according to a second modification of the present disclosure. FIG. 6 is a diagram showing microscopic photographs of the adhesive sheets of Examples 1 to 3 in which the thickness of the printed part is 2 μm (ink amount K10%), and the measurement results of the number of dots and dot size in the printed part.

In the process of investigating various means to solve the above-mentioned problems without significantly increasing manufacturing costs, the inventors of the present application discovered that adhesive components may seep out from the printed area formed on the adhesive layer using an inkjet method. I also noticed that when a load was applied to the printing part, the amount of adhesive component seeping out tended to increase. After further investigation, they discovered that by changing the thickness of the printed part, etc., the degree of reduction in tack and adhesive strength can be easily adjusted compared to when no printed part is provided, and they came up with the present invention. Ta.

[Configuration of adhesive sheet]
FIG. 1 is a sectional view showing an adhesive sheet 10, which is an example of an embodiment disclosed in this specification, and FIG. 2 is a plan view of the adhesive sheet 10 of this embodiment when viewed from the printing unit 5 side It is a diagram. FIG. 3 is a photographic diagram showing an enlarged printing section in area A shown in FIG. 2. FIG.

As shown in FIG. 1, the adhesive sheet 10 of this embodiment is formed on an adhesive layer 3 and at least one surface of the adhesive layer 3, and an adhesive component that is a component of the adhesive layer 3 oozes out. It is equipped with a printing section 5. In the adhesive sheet 10 of this embodiment, the sheet-like base material 1 is provided on the surface of the adhesive layer 3 that is opposite to the surface on which the printed portion 5 is provided. A release liner 7 may be provided on the surface of the adhesive layer 3 on which the printed portion 5 is formed, with the printed portion 5 interposed therebetween. By protecting the adhesive surface of the adhesive layer 3 on which the printed portion 5 is provided by the release liner 7, it is possible to store it not only in a roll shape but also in a planar state. A known release liner can be used as the release liner 7, and a release agent layer containing a silicone release agent or a fluorine release agent may be provided on the side in contact with the adhesive layer 3.

However, since the adhesive sheet 10 of this embodiment has very little tack when no load is applied, it can be stored in a roll even when the release liner 7 is not provided. When the release liner 7 is not provided, there are advantages such as saving resources and reducing the diameter of the roll.

In the printing area 12 of the adhesive sheet 10 of this embodiment, by providing the printing part 5, the loop tack value of the adhesive layer 3 with respect to the stainless steel (SUS) plate can be made less than 1.0 N/25 mm. Can be done. On the other hand, the adhesive force of the adhesive layer 3 to the SUS steel plate after 24 hours at 23°C, a load of 2 kg during bonding, a relative humidity of 50%, and a peeling angle of 180 degrees is 0.05 N/25 mm or more. good.

Therefore, it is easy to reapply the adhesive sheet 10 in the printing area 12, and once the attachment position is determined, the adhesive sheet 10 can be fixed by applying a load to the sheet. This makes the pasting process easy. In addition, since the adhesive surface has minute irregularities before pasting, air bubbles are less likely to enter during pasting, and air remaining between the adhesive and the adherend after crimping can be easily expelled.

According to the adhesive sheet 10 of this embodiment, by changing the thickness of the printed portion 5, etc., it is possible to adjust the tack value and adhesive force to desired values even when using the same adhesive. Become. For example, it becomes possible to produce a slightly adhesive sheet using an inexpensive strong adhesive type adhesive instead of using a relatively expensive slightly adhesive type adhesive.

In the adhesive sheet 10 of the present embodiment, by applying a load after bringing the adhesive layer 3 into contact with an adherend, seepage of the constituent components (adhesive components) of the adhesive layer 3 can be promoted. In addition, by leaving it in a state where it is peeled off from the adherend, the adhesive component that has once oozed out can be quickly restored to its pre-pressing state by its elastic force. Therefore, the adhesive sheet 10 can be used repeatedly. The adhesive sheet 10 can also be used, for example, as a temporary fixing sheet such as a sticky note.

In the adhesive sheet 10, the first tack value for the SUS steel plate of the adhesive layer 3 occurs in the printing area 12 immediately after applying a load of 300 g/cm ² for 10 seconds using the pressing means, and after applying the load, the first tack value is generated from the pressing means. When two minutes have elapsed since the film was peeled off, either the tack on the PET film may disappear, or a second tack value smaller than the first tack value may remain. Alternatively, in the printing area 12 immediately after applying a load of 2000 g/cm ² for 10 seconds using a pressing means, the third tack value for the SUS steel plate of the adhesive layer 3 occurs, and the adhesive layer 3 peels off from the pressing means after the application of the load. After 3 minutes have elapsed, either the tack on the PET film may disappear, or a fourth tack value smaller than the third tack value may remain.

In the adhesive sheet 10 of the present embodiment, the storage elastic modulus G' of the adhesive layer 3 at 23° C. and a frequency of 1 Hz may be 1.0×10 ⁴ Pa or more and 5.0×10 ⁶ Pa or less, and 9 It may be .0×10 ⁴ Pa or more and 2.0×10 ⁶ Pa or less. The storage modulus represents the hardness of the adhesive layer 3, and the inventors of the present invention have found that as the storage modulus decreases, the adhesive layer 3 tends to flow more easily, and the adhesive component tends to ooze out from the printed area 5. I know it will happen. When the storage modulus is 5.0×10 ⁶ Pa or less, the tack can be kept small and the adhesive strength can be exerted to the extent that it does not easily peel off after being attached to an adherend. Moreover, if the storage elastic modulus of the adhesive layer 3 is 1.0×10 ⁴ Pa or more, the adhesive component can be exuded by making the printed part 5 have an appropriate thickness, and the storage elastic modulus is 9. When the pressure is 0×10 ⁴ Pa or more, it is easy to restore the state to a state with small tack after applying a load to cause tack, and therefore it becomes easy to use repeatedly. If the storage elastic modulus of the adhesive layer 3 is 1.5×10 ⁵ Pa or more, the holding power of the adhesive layer 3 described later can be improved.

When the storage modulus of the adhesive layer 3 is large, it is easier to reduce the loop tack value even if the thickness of the printed part 5 is kept the same, compared to when the storage modulus of the adhesive layer 3 is small.

The glass transition temperature (Tg) of the adhesive layer 3 may be −50° C. or higher. In this case, when the pressure-sensitive adhesive sheet 10 is used at room temperature, the pressure-sensitive adhesive layer 3 has appropriate fluidity, so that the constituent components of the pressure-sensitive adhesive layer 3 are likely to ooze out from the printed area 5.

In the printing area 12 of the adhesive sheet 10 of this embodiment, the holding force duration at 40°C may be 1000 seconds or more, and the amount of deviation (mm /50,000 seconds) is preferably 1 mm or less. If the adhesive sheet 10 has excellent holding power, it will be less likely to peel off or fall off from an adherend when used, for example, as a label, a graphic sheet, or the like. The holding power of the adhesive sheet 10 can be fully demonstrated by applying appropriate pressure by hand, roller, etc. after bonding it to an adherend. This is because the amount of adhesive component seeping out from the printing section 5 increases due to pressurization. When the adhesive component oozes out from the printed area 5, the amount of displacement of the adhesive sheet 10 becomes smaller as the adhesive layer 3 has a stronger cohesive force.

The printing section 5 is formed of a cured ink and is provided on one or more printing areas 12 set on the adhesive layer 3 as a printing range. In the example shown in FIG. 2, the entire adhesive surface of the adhesive layer 3 serves as the printing area 12, and the printed portion 5 is also formed on the entire adhesive surface.

As shown in FIG. 3, the printing section 5 is composed of a large number of dots 15 made of cured ink. The diameter of the dots 15 is not particularly limited, but may be, for example, 0.1 μm or more and 100 μm or less, 0.1 μm or more and 50 μm or less, or 1 μm or more and 30 μm or less. The diameter of the dots 15 depends on the printing press used. If the dot diameter is 50 μm or less, it becomes easier to precisely control the tack and adhesive force of the adhesive sheet 10. The diameters of the dots 15 may be uniform, but may also have moderate variations. The printing section 5 may include an average of five or more dots 15 per 0.5 mm square. The larger the dot diameter, the easier it is to reduce the loop tack value even if the density (number density) of the dots 15 is small.

The height of the dots 15 increases as the dot diameter increases, and may be, for example, 0.05 μm or more and 50 μm or less. When the surface tension of the adhesive surface is low and the difference in surface tension from the ink is large, the dots 15 are difficult to spread, and the height of the dots 15 relative to the dot diameter tends to be high. Generally, the adhesive layer 3 formed using a silicone adhesive has lower polarity than the adhesive layer 3 formed using an acrylic adhesive, so the surface tension of the adhesive surface is lower. There is a tendency. For this reason, in the dots 15 provided on the adhesive layer 3 made using a silicone adhesive, the value of dot height/dot diameter is often about 0.1 or more and 0.6 or less. On the other hand, in the dots 15 provided on the adhesive layer 3 made using an acrylic adhesive, the value of dot height/dot diameter is often about 0.01 or more and 0.3 or less. .

When the density of the dots 15 is low to some extent, gaps exist between the dots 15, allowing the components of the adhesive layer 3 to seep out. Due to this oozing of the adhesive component, the adhesive sheet 10 of the present embodiment tucks to some extent when pressure is applied, and when attached to an adherend, the adhesive sheet 10 maintains its attached state.

As the density of the dots 15 increases, the gap between the dots 15 decreases and the number of overlapping areas of the dots 15 increases, making it difficult to measure the density of the dots 15. component) decreases. Therefore, although it varies depending on the type of adhesive used, the average thickness of the printed portion 5 may be approximately 0.1 μm or more and 20 μm or less, preferably 1 μm or more and 6 μm or less. If the average thickness of the printed area 5 is less than 0.1 μm, the gaps between the dots 15 will become large, and a large amount of adhesive component will easily seep out from these gaps, which will reduce the tack strength and adhesive force of the adhesive sheet 10. This is almost the same as the case where dots 15 are not provided. If the thickness of the printed portion 5 exceeds 20 μm, the amount of components of the adhesive layer 3 that seep out may become small, making it difficult to attach it to an adherend. By setting the average thickness of the printed portion 5 to 6 μm or less, the types of adhesives that can be used as the main ingredient of the adhesive layer 3 can be further expanded.

Note that when the average thickness of the printed portion 5 is as thin as 6 μm or less, the total light transmittance of the adhesive sheet 10 will be 50% or more even if black ink or color ink is used to form the printed portion 5. It is semi-transparent. However, by making the thickness of the printing section 5 greater than 6 μm and less than 20 μm, it becomes possible to form a desired image with the printing section 5 while keeping the loop tack value less than 1.0 N/25 mm.

In the printing area 12, the dots 15 may be arranged regularly or irregularly. When the printing section 5 is formed by an inkjet printer to be described later, the dots 15 are arranged irregularly. Further, the sizes of the dots 15 constituting the printing section 5 may be the same, but may also be non-uniform.　

The ink used to form the printed portion 5 is not limited, and one or more types of ink selected from photo-curable ink, electron beam-curable ink, and solvent-based ink can be used; If it is a photo-curable ink or electron beam-curable ink that is cured by UV) or visible light, the ink can be difficult to diffuse into the adhesive layer 3 when forming the printed part 5, and the thickness required for the printed part 5 can be reduced. This is preferable because it is easier to secure. Furthermore, since UV curable ink and electron beam curable ink can be cured instantly after printing, the production time of the adhesive sheet 10 can be reduced by using these inks compared to the case where solvent-based ink is used. Can be shortened.

The color of the ink used to form the printing section 5 is not particularly limited, and may be only black (K), for example, cyan (C), magenta (M), yellow (Y), and black (K). , white (W), gray, light cyan, light magenta, red, and transparent, or a combination of a plurality of colors may be used. When using multiple colors of ink, the thickness of the printed portion 5 may be the same as when using one color of ink.

The printing section 5 can be formed by a printing method in which ink is ejected using a known inkjet printer or the like. On the other hand, if the printed portion 5 is formed by solid printing such as offset printing, gravure printing, or silk screen printing, the adhesive layer 3 will be covered without any gaps, and the adhesive component will not be able to seep out. Even if halftone dots with a diameter of 0.1 μm or more and 50 μm or less, which is about the same as the dots 15, are formed in the printing area 12 by offset printing or gravure printing, the components in the adhesive layer 3 cannot be realized. It is possible. However, unlike offset printing, gravure printing, etc., which require expensive plates, using an inkjet printer eliminates the need to create plates, allowing you to freely change the density and formation position of the dots 15 in a short time. can do.

In the adhesive sheet 10, the surface roughness (Ra) of the printed portion 5 may be 0.3 μm or more and 10 μm or less. Since the printing section 5 is composed of a large number of dots 15, when the printing section 5 is not provided, the surface roughness is greater than when a printing section is provided by offset printing or silk screen printing.

Since the adhesive force of the adhesive sheet 10 is smaller than the adhesive force of the adhesive layer 3 when the printed part 5 is not provided, the adhesive used for forming the adhesive layer 3 is a medium adhesive type or a strong adhesive type. By using a pressure-sensitive adhesive, it is possible to produce a pressure-sensitive adhesive sheet 10 that exhibits a wide range of adhesive strength. For example, when using a strong adhesive type adhesive, by setting the printed area 5 thicker, it is possible to create an adhesive sheet 10 that exhibits slight adhesiveness in the printed area 12, and by reducing the thickness of the printed area 5, It also becomes possible to produce a pressure-sensitive adhesive sheet 10 that exhibits tackiness.

The adhesive used to form the adhesive layer 3 is not particularly limited, but includes, for example, acrylic adhesive, acrylic-urethane adhesive, urethane adhesive, silicone adhesive, polyester adhesive, and rubber adhesive. It may be one kind or a mixture of two or more kinds selected from these agents. As the adhesive used, water-based adhesives, solvent-based adhesives, solvent-free adhesives, etc. can be used.

The thickness of the adhesive layer 3 is not particularly limited, but may be about 10.0 times or less the average thickness of the printed portion 5. The thickness of the adhesive layer 3 may be, for example, 0.5 μm or more and 100 μm or less, or 2 μm or more and 50 μm or less. If the thickness of the adhesive layer 3 is within this range, it becomes easy to set the loop tack value and adhesive force within the desired range in the printing area 12 as well.

When the average thickness of the printed portion 5 is the same, the loop tack value and adhesive strength increase as the thickness of the adhesive layer 3 increases. This is thought to be because the thicker the adhesive layer 3 is, the more easily the adhesive component oozes out from the printed area 5 due to the pressure applied during bonding after the printed area 5 is formed.

In addition to using an appropriate curing agent during production, the adhesive layer 3 may contain additives such as a tackifier, an antistatic agent, a coloring agent, and a filler, if necessary. At least one of the adhesive and the additive for forming the adhesive layer 3 may contain a biological component. For example, the adhesive layer 3 may contain about 10% by mass or more and 50% by mass or less of a terpene-based or rosin-based tackifier. The biomass degree of the adhesive layer 3 may be, for example, about 10% or more and 50% or less.

As the base material 1, known materials such as resin sheets, synthetic paper, paper, nonwoven fabrics, woven fabrics, etc., and laminates thereof can be used. Examples of the constituent materials of the resin sheet include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyimide (PI), etc. can be used.

The thickness of the base material 1 is not particularly limited, but may be, for example, about 2 μm or more and 300 μm or less, or 5 μm or more and 250 μm or less. At least one surface of the base material 1 may be provided with an easily adhesive layer or an antistatic layer, if necessary.

As the base material 1, a biomass material or a recycled material may be used partially or entirely in order to reduce the environmental load. In addition, it is preferable to manufacture the adhesive sheet 10 using materials, including the base material 1, that emit as little CO ₂ as possible during manufacture.

[Modified example of adhesive sheet]
FIG. 4 is a cross-sectional view showing an adhesive sheet 20 according to a first modification of the present disclosure. As shown in the figure, the adhesive sheet 20 according to the present modification includes an adhesive layer 3 and a printed portion 5 formed on at least one surface of the adhesive layer 3, from which constituent components of the adhesive layer 3 seep out. It is equipped with The adhesive sheet 20 according to this modification differs from the adhesive sheet 10 shown in FIG. 1 in that the base material 1 is not provided. A release liner 7 is bonded to the surface of the adhesive layer 3 on which the printed portion 5 is provided, and a second release liner 17 is bonded to the other surface of the adhesive layer 3. The peeling force required to peel off the release liner 7 and the peeling force required to peel off the second release liner 17 may be approximately the same, but it is possible to make a difference between them and use the release liner on the light release side. It may be made so that it can be easily peeled off. The other configurations of the adhesive sheet 20 are basically the same as those of the adhesive sheet 10.

When producing the adhesive sheet 20 according to this modification, as shown in FIG. The printed portion 5 may be formed after manufacturing and pasting the adhesive layer 3 on the adherend.

In the adhesive sheet 20 according to this modification, the adhesive strength of the surface (first surface) on the side where the printed portion 5 of the adhesive layer 3 is provided is the same as that of the surface (second surface) on the opposite side to the same adherend. The adhesive force is smaller than that of . Further, the loop tack value of the first surface of the adhesive layer 3 is smaller than the loop tack value of the second surface. Therefore, it is possible to realize a double-sided adhesive sheet having different adhesive strengths on one side and the other side of the adhesive layer 3. The adhesive used in the adhesive sheet 20 according to this modification is not particularly limited.

On the side where the printed portion 5 is provided, the area of the adherend that is substantially in contact with the adhesive component is smaller than on the opposite side, so that the adherend is less likely to be contaminated by the adhesive. The adhesive sheet 20, like the adhesive sheet 10, can be used in various fields.

For example, the adhesive sheet 20 using a removable adhesive that causes less contamination of the adherend can be used as a fixing adhesive sheet for a graphic sheet or the like. For general double-sided adhesive sheets, if you select an adhesive with strong adhesive strength, the adhesion to the adherend will become stronger, and the adhesive layer tends to remain on the adherend when the graphic sheet is peeled off. . For this reason, as a fixing adhesive sheet, a removable type adhesive layer is often provided on one side (adherent side) of the core material, and a strong adhesive type adhesive layer is provided on the other side. On the other hand, according to the adhesive sheet 20 according to this modification, the adhesive force and tack value can be changed between one surface and the other surface at a relatively low cost.

Although not shown, it is also possible to produce a pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layers are provided on both sides of a core material, and a printed portion is provided on at least one pressure-sensitive adhesive layer.

FIG. 5 is a plan view schematically showing a method of printing a pressure-sensitive adhesive sheet 30 according to a second modification of the present disclosure. As shown in the figure, the adhesive sheet 30 according to this modification differs from the adhesive sheet 10 shown in FIG. 1 in that a plurality of printing areas are provided on the adhesive layer 3 within the sheet. In the example shown in FIG. 5, a first print area 12A and a second print area 12B are formed on the adhesive layer 3 provided on one surface of the base material 1. A first printing section 5A formed of a cured ink is provided on the first printing area 12A, and a second printing section 5B is provided on the second printing area 12B. The average thickness of the first printed portion 5A and the second average thickness may be the same or different. Moreover, as shown in FIG. 5, a part of the adhesive layer 3 may not be covered by the printed part and may be exposed.

In the example shown in FIG. 5, two print areas are formed within the adhesive sheet, but three or more print areas may be formed. The total area of the printing area may be 1% or more and 100% or less of at least one surface of the adhesive layer 3. If the print area is less than 1%, the adhesive strength and loop tack value of the adhesive sheet as a whole will be approximately the same as those without the print area, so the effect of forming the print area will be weakened.

The planar shape of the first printing area 12A and the second printing area 12B may be a strip shape in which the flow direction (coating progress direction) is longer than the width direction, as shown in FIG. 5, or may be in any other shape. There may be. Further, the size of each printing area is not particularly limited.

The thickness of the first printed part 5A on the first printed area 12A and the thickness of the second printed part 5B on the second printed area 12B do not need to be constant, and may differ partially. You can leave it there. For example, the thickness of the first printed portion 5A and the second printed portion 5B may decrease in a gradation pattern from the outside to the inside in the width direction. Thereby, in the first printing area 12A and the second printing area 12B, it is possible to design the adhesive force to become stronger as it goes inward from the end.

When forming a plurality of printed parts on one surface of the adhesive layer 3, for example, a known line inkjet printer can be used. After forming the adhesive layer 3 on one side of the base material 1 using a coating machine and drying it, for example, UV curing is applied to the exposed surface of the adhesive layer 3 from the head 23 of a line inkjet printer extending in the width direction. The first printing section 5A and the second printing section 5B are formed by ejecting ink and then UV irradiation. Note that if a long printing time is acceptable, the printing section may be formed using a serial head type inkjet printer. After forming the printed portion, the adhesive sheet 30 may be aged at 40° C. for about 3 days, or aging may be performed in advance before forming the printed portion. Alternatively, the printed portion may be formed after cutting the adhesive sheet to a desired size using a slitter before forming the printed portion.

When forming a strip-shaped first printing area 12A and a second printing area 12B extending parallel to each other on one surface of the adhesive layer 3, a slitter is used to cut the adhesive sheet 30 in the machine direction. By separating the adhesive sheet into three areas: a printing area 12A, a second printing area 12B, and an area where no printing area is provided, it becomes possible to produce three types of adhesive sheets with one coating. Thereafter, by cutting the produced adhesive sheet in the width direction, a lithographic pressure-sensitive adhesive sheet of a desired size can be produced.

Alternatively, when forming a highly adhesive adhesive layer 3, by cutting the adhesive sheet 30 made to a predetermined length in the width direction, the adhesive strength at both ends in the width direction is equal to that of the central part. A pressure-sensitive adhesive sheet with weaker adhesive force can be produced. With this adhesive sheet, if it becomes necessary to peel off the adhesive sheet after it has been pasted on an adherend, it can be easily peeled off from the adherend by peeling from the end where the adhesive strength is weak. . By using an inkjet printer, it is possible to arbitrarily adjust the thickness and formation position of the printed area without creating a plate.

Note that in the case of the pressure-sensitive adhesive sheet 10 of the present embodiment shown in FIG. 1 and the pressure-sensitive adhesive sheets 20 and 30 according to its modified examples, the pressure-sensitive adhesive sheets without printed parts are stored and when an order is received from a customer. In addition, printing parts that exhibit tack and adhesive strength according to customer requests can be formed on demand, reducing the amount of product inventory compared to storing adhesive sheets with different tack and adhesive strengths. can be significantly reduced.

The adhesive sheet 10 of the present embodiment and the adhesive sheets 20 and 30 according to the modified examples described above are examples of the present invention, and the constituent materials and thickness of the base material 1, adhesive layer 3, printed part 5, etc. The shape, formation position, etc. can be changed as appropriate without departing from the spirit of the present invention.

The present invention will be explained in more detail below based on Examples, but the present invention is not limited to these Examples.

[Preparation of adhesive sheet]
By adding and mixing appropriate amounts of curing agents to five types of commercially available adhesives, acrylic adhesive compositions A and E, acrylic-urethane adhesive composition B, and both silicone adhesive compositions were prepared. Products C and D were produced. Here, since adhesive composition A contains a rosin-based tackifier corresponding to 15% by mass of the adhesive layer weight after drying, the biomass content of the adhesive layer formed is 15%. It has become. The biomass degree of the adhesive layer formed by adhesive composition E is estimated to be about 10%.

Next, adhesive compositions A and B were coated onto the release agent layer of a commercially available release liner having a PET film having a thickness of 50 μm and on which a release agent layer containing a silicone release agent was formed using a known comma-type coater. , E was applied and dried to form an adhesive layer. The thickness of the adhesive layer formed using adhesive compositions A and B was 10 μm and 20 μm, and the thickness of the adhesive layer formed using adhesive composition E was 10 μm. Next, the coated side of the release liner was bonded to one side of the base material to transfer the adhesive layer onto the base material, and then aged at 40° C. for about 3 days to form a pressure-sensitive adhesive sheet. As the base material, a 50 μm thick PET film (manufactured by Toyobo Co., Ltd., trade name: Cosmoshine (registered trademark) A4360) on which adhesive layers were formed on both sides was used. Here, Comparative Examples 1 to 4 are various pressure-sensitive adhesive sheets without a printed part. For adhesive compositions C and D, adhesive sheets with adhesive layer thicknesses of 10 μm, 20 μm, and 30 μm were coated directly onto the substrate using a comma-type coater in Comparative Examples 5 to 10. It was created as

Next, in the prepared adhesive sheet, printing was performed by discharging and curing UV curable ink using a UV inkjet printer (“UJF-6042MkII” manufactured by Mimaki Engineering Co., Ltd.) on the entire exposed surface of the adhesive layer. The division was formed. As the UV curing ink, black ink "LH-100" manufactured by Mimaki Engineering Co., Ltd. was used. The ink amounts were set to K10%, K20%, K30%, K40%, and K50%. The structures of the pressure-sensitive adhesive sheets produced as Examples 1 to 21 and Comparative Examples 1 to 14 are listed in Tables 2 to 8 shown below.

[Measuring method]
<Measurement of storage modulus G', loss modulus G'', loss tangent (tan δ), and glass transition temperature Tg of adhesive layer>
The storage modulus G', loss modulus G'', and loss tangent of the adhesive layer of the adhesive sheet were measured by the following methods. First, a base material-less tape having an adhesive layer with a thickness of 50 μm was produced using each of the prepared adhesive compositions A to E. Next, this base material-less tape was aged at 40° C. for 72 hours. Next, only the adhesive layer was laminated to a total thickness of 1 mm, and then punched out to a size of 8 mm in diameter to produce a tablet. This tablet was placed between the plates of a rheometer (product name: AR2000ex), and the storage modulus G' and loss modulus G'' were measured at a frequency of 1 Hz, a strain amount of 0.05%, and a measurement temperature of -40 to 100°C. was measured. Moreover, the value of loss elastic modulus G''/storage elastic modulus G' was calculated as a loss tangent. The temperature at which the loss tangent was maximum was read as the glass transition temperature of the adhesive layer.

<Measurement of thickness of printed part>
On a PET film with a thickness of 50 μm, ink amounts were set to K10%, K20%, K30%, K40%, and K50% using a UV inkjet printer (“UJF-6042MkII” manufactured by Mimaki Engineering Co., Ltd.). A printed part was formed. The total thickness of each sheet sample was measured using a constant pressure thickness measuring device, and the thickness of each printed portion was calculated by subtracting the thickness of the PET film (50 μm) from the measured value.

As a result of the measurement, the thickness of the printed area (ink thickness) is approximately 2 μm at 10% K, the thickness of the printed area is approximately 3 to 4 μm at 20% K, the thickness of the printed area is approximately 5 μm at 30% K, and the thickness of the printed area is approximately 5 μm at 40% K. The thickness of the printed part was about 7 μm, K was 50%, and the thickness of the printed part was about 10 μm.

<Counting the number of dots and checking the dot size>
Photographs of the surfaces of the adhesive sheet samples prepared in Examples 1 to 3 on the printed side were taken using a microscope and magnified 200 times. The number of dots was counted by arbitrarily selecting three 0.5 mm square areas of this micrograph, and the average value was taken as the counted value of the number of dots. Furthermore, the range of the diameter of the dots was measured from this micrograph.

<Measurement of adhesive strength against SUS>
The adhesive sheet whose adhesive surface was exposed by peeling off the release liner was attached to a SUS steel plate polished with 360 degree waterproof paper by a method conforming to JIS Z 0237, and the adhesive force was measured. Specifically, a test piece of an adhesive sheet cut to a width of 25 mm was pasted on a SUS steel plate as an adherend, and then pressed with a 2 kg roller twice in a reciprocating manner, and then heated at 23°C and a relative humidity of 50% for 20 minutes or It was left standing for 24 hours. The adhesive force (N/25 mm) was measured as the force required to peel these test pieces from the SUS steel plate using a universal material testing machine under conditions of a peel angle of 180° and a peel rate of 300 mm/min.

<Measurement of loop tack value>
After cutting out a test piece with a width of 25 mm and a length of 150 mm from the adhesive sheet, the release liner is peeled off and the release liner is divided into two pieces. The divided release liners each having a width of 25 mm were attached to each other so as to cover only 25 mm from both ends of the exposed surface of the adhesive layer (100 mm of the adhesive layer of the test piece was left exposed). The test piece was set in a loop shape on the upper grip part of the tensile testing machine so that the adhesive side was facing outside. After setting the SUS steel plate on the lower grip part of the tensile testing machine, the upper grip part is lowered at a speed of 300 mm/min until the height from the lower grip part is 20 mm, and the adhesive surface of the test piece and the SUS It was brought into contact with a steel plate. Immediately after contact, the upper grip part was raised to its original position at a speed of 300 mm/min, and the maximum value of the tensile load required to peel off the test piece from the SUS steel plate was measured. The measurement was repeated three times, and the average of the measurements was recorded as the loop tack value. The measurements were performed under conditions of 23° C. and 50% relative humidity.

<Restoration test>
The adhesive sheet from which the release liner had been removed was placed on an electronic balance, and the bottom surface of a stainless steel cylinder (pressing means) was pressed against the adhesive surface on which the printed portion was formed. After applying a predetermined load for 10 seconds to confirm the presence or absence of tack, a PET film was attached to the adhesive surface after a period of time. The loads due to the cylinders were 300 g/cm ² , 1000 g/cm ² , and 2000 g/cm ² , respectively. In each case, the time from peeling off the cylinder until the PET film no longer stuck to the adhesive surface was measured.

<Measurement of holding force and holding force duration>
A test piece with a width of 25 mm and a length of 100 mm was cut out from the adhesive sheet, and a square portion of 25 mm x 25 mm at one end of this test piece was attached to a SUS steel plate. The square portion attached to the SUS steel plate was strongly crimped with uniform force using a squeegee.

Next, the SUS steel plate was held vertically so that the square part of the adhesive sheet was located above, and in this state, a 1 kg weight was suspended from the other end of the adhesive sheet located below. In this state, the time until the adhesive sheet was completely peeled off was measured as the retention force duration. In addition, the amount of displacement of the adhesive sheet (unit: mm) after 50,000 seconds had elapsed from the start of the measurement was measured as a value representing the holding force. Note that the measurement was performed at 40°C.

[Measurement result]
Table 1 shows the storage modulus, loss modulus, loss tangent, and glass transition temperature of the adhesive compositions A to E after curing that form the adhesive layer.

Regarding the storage modulus and loss modulus, the order from the smallest was adhesive composition E, adhesive composition A, adhesive composition B, adhesive composition C, and adhesive composition D. Regarding glass transition temperature, adhesive composition E, adhesive composition A, adhesive composition B, adhesive composition C, and adhesive composition D were ordered from the lowest to lowest.

Tables 2 to 8 show the measurement results of the adhesive strength, loop tack value, and holding power of the adhesive sheets of Examples 1 to 21 and Comparative Examples 1 to 14.

In Comparative Examples 1 to 10 without a printing section, the loop tack values were all 1.0 N/25 mm or more, whereas in Examples 1 to 21, in which a printing section was provided, the loop tack values were 1.0 N/25 mm. It was confirmed that the tack value was significantly smaller by providing the printing section. When a printed part is provided, from the results of Examples 10 to 12 and Examples 13 to 15, if the thickness of the adhesive layer is the same, as the thickness of the printed part becomes thicker, the tack becomes smaller and the adhesive force also becomes smaller. It was found that there is a tendency to From a comparison of Examples 1 to 3, 21 and Comparative Example 14, even when the storage modulus is low, the tack can be reduced by increasing the thickness of the printed part within an appropriate range, and the adhesive force can be increased to 0.05 N/25 mm or more. It turns out that it can be adjusted to

From the comparison between Example 1 and Comparative Example 11 and the comparison between Example 2 and Comparative Example 12, when the thickness of the printed part is the same and the same adhesive composition is used, the thinner the adhesive layer is, the more the loop is It was confirmed that both the tack value and adhesive strength could be reduced. Furthermore, it was confirmed that the higher the storage modulus of the adhesive composition, the stronger the holding power tended to be.

Tables 9 to 12 show the results of the tack restoration test.

As a result of the restoration tests shown in Tables 9 to 11, even when tack occurred when a load of 300 g/cm ² was applied for 10 seconds, the adhesive sheets produced in Examples 1, 3 to 9, 11 to 15, 17, and 20 It was confirmed that the state returned to a state with small tack or no tack within 2 minutes. It was confirmed that even if tack occurred when a load of 2000 g/cm ² was applied for 10 seconds, these pressure-sensitive adhesive sheets returned to a state with little tack or no tack within 3 minutes. As the load was increased, the time until the tack disappeared tended to become longer.

FIG. 6 shows the measurement results and micrographs of the number of dots and dot size (dot diameter) in the printed part of the adhesive sheet where the printed part thickness is 2 μm.

As shown in FIG. 6, when the ink amount was K10% (the thickness of the printed area was about 2 μm), it was confirmed that the printed area was composed of many dots of various sizes. Here, the K value expressed as a percentage is a value indicating the amount of ink, and is a term used in the dedicated software of the UV inkjet printer used this time. It was confirmed that the average number of dots of different sizes included in a 0.5 mm square area was 5 or more for all test pieces. The dot diameter was approximately 23 μm to 30 μm for large dots and approximately 14 μm to 18 μm for small dots. Note that it is thought that the density of dots increases as the amount of ink increases, but when the amount of ink exceeds K30%, the overlap between dots increases, making it difficult to count the number of dots.

The adhesive sheet disclosed in this specification can be used in various fields as a label or graphic sheet, a member fixing sheet, various protective sheets, a temporary fixing sheet for articles, etc.

1 Base material 3 Adhesive layer 5 Printing section 5A First printing section 5B Second printing section 7 Release liner 10, 20, 30 Adhesive sheet 12 Print area 15 Dots 17 Second release liner 20 Adhesive sheet 23 Head

Claims

an adhesive layer;
a printed portion formed on at least one surface of the adhesive layer,
The printing part is formed of a cured ink product, and is provided on one or more printing areas set on the adhesive layer as a printing range,
A loop tack value of the adhesive layer with respect to the SUS steel plate in the printing area is less than 1.0 N/25 mm,
The adhesive force of the adhesive layer in the printing area to the SUS steel plate after 24 hours at 23° C., a load of 2 kg during lamination, a relative humidity of 50%, and a peeling angle of 180 degrees is 0.05 N/25 mm or more. adhesive sheet.
The adhesive sheet according to claim 1,
Immediately after applying a load of 300 g/cm 2 for 10 seconds using a pressing means, a first tack value of the adhesive layer with respect to the SUS steel plate occurs in the printing area,
After the application of the load, when 2 minutes elapse after the film is peeled off from the pressing means, either the tack on the PET film disappears or a second tack value smaller than the first tack value remains. An adhesive sheet.
The adhesive sheet according to claim 1,
Immediately after applying a load of 2000 g/cm 2 for 10 seconds using a pressing means, a third tack value of the adhesive layer with respect to the SUS steel plate occurs in the printing area,
After the application of the load, when 3 minutes have passed since the film is peeled off from the pressing means, either the tack on the PET film disappears or a fourth tack value smaller than the third tack value remains. Adhesive sheet.
The adhesive sheet according to claim 1,
In the printing section, a pressure-sensitive adhesive sheet is used in which constituent components of the pressure-sensitive adhesive layer ooze out when a load is applied.
The adhesive sheet according to claim 1,
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a storage modulus of 1.0×10 4 Pa or more and 5.0×10 6 Pa or less at 23° C. and a frequency of 1 Hz.
The adhesive sheet according to claim 1,
An adhesive sheet having a deviation amount of 1 mm or less after 50,000 seconds at 40° C. in the printing area.
The adhesive sheet according to claim 1,
The adhesive sheet has an average thickness of the printed portion of 0.1 μm or more and 20 μm or less.
The adhesive sheet according to claim 1,
A pressure-sensitive adhesive sheet in which the total area of the printing area occupies 1% or more and 100% or less of at least one surface of the pressure-sensitive adhesive layer.
The adhesive sheet according to claim 1,
The printing section is an adhesive sheet made of a cured ink material and including dots irregularly arranged on the printing area.
The adhesive sheet according to claim 9,
The printed portion includes an average of 5 or more dots per 0.5 mm square,
A pressure-sensitive adhesive sheet in which the dots have a diameter of 0.1 μm or more and 50 μm or less.
In the adhesive sheet according to any one of claims 1 to 10,
The printing portion is a pressure-sensitive adhesive sheet formed of a cured product of photocurable ink or electron beam curing ink.
The adhesive sheet according to claim 1,
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a glass transition temperature of -50°C or higher.
The adhesive sheet according to claim 1,
The printed part is formed on one side of the adhesive layer,
The pressure-sensitive adhesive sheet further includes a sheet-like base material provided on a surface of the pressure-sensitive adhesive layer opposite to the surface on which the printed portion is provided.
The adhesive sheet according to claim 1,
A pressure-sensitive adhesive sheet that does not include a base material and has both surfaces of the pressure-sensitive adhesive layer serving as adhesive surfaces for an adherend.
The adhesive sheet according to claim 1,
The printing part is an adhesive sheet formed by curing ink applied by an inkjet method.