JP2023088639A - Adhesive sheet - Google Patents

Abstract

To provide an adhesive sheet capable of easily controlling properties such as adhesive force and easiness of application/removal.SOLUTION: A adhesive sheet 10 includes an adhesive layer 3 having a storage modulus at 23°C and 1 Hz frequency of 5.0×104 Pa or more and 3.5×105 Pa or less, and a print part 5 which is formed at least on one surface of the adhesive layer 3 and from which components of the adhesive layer 3 seeps out. The print part 5 is formed of an ink hardened material and is provided in one or more printing regions which have been defined on the adhesive layer 3 as a print range(s).SELECTED DRAWING: Figure 1

Description

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

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer is used in various fields, such as fixing members of electronic devices, screen protection sheets, building materials such as wallpaper, printed matter, laminate sheets for printed matter, and various tapes. Depending on the application of the pressure-sensitive adhesive sheet, there are cases where it is desired that the pressure-sensitive adhesive sheet adheres strongly to the adherend and is not easily peeled off, and there are cases where it is desired that the pressure-sensitive adhesive sheet can be easily reapplied.

In the specification of Japanese National Publication of International Patent Application No. 2003-531253 (Patent Document 1), a non-adhesive polymer having a predetermined pattern is formed on the adhesive surface of the adhesive layer to produce an adhesive sheet for graphics that can be easily reapplied. It states what you can do.

Special table 2003-531253

By the way, the adhesive strength of the pressure-sensitive adhesive sheet to the adherend may be better if it is strong, or if it is weak. Although there is a great demand for adhesive sheets that are easy to re-stick when stuck and are hard to peel off after sticking, there are cases where other properties are required.

Here, in the adhesive sheet described in Patent Document 1, a non-adhesive polymer is formed not only for ease of reattachment but also for removing air remaining between the adhesive layer and the adherend. . Therefore, the non-adhesive 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 Literature 1 to flexibly cope with the demand for a plurality of different properties.

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 peeling can be easily controlled.

An example of the pressure-sensitive adhesive sheet disclosed in the present specification includes a pressure-sensitive adhesive layer having a storage modulus of 5.0×10 ⁴ Pa or more and 3.5×10 ⁵ Pa or less at 23° C. and a frequency of 1 Hz; and a printed portion formed on at least one surface of the layer and through which constituent components of the pressure-sensitive adhesive layer ooze out. The printing portion is formed of a cured ink and provided on one or more printing areas set on the pressure-sensitive adhesive layer as a printing area.

According to the pressure-sensitive adhesive sheet disclosed in the present specification, properties such as adhesive strength and ease of peeling can be easily controlled by appropriately changing the thickness of the pressure-sensitive adhesive layer, the thickness of the printed portion, and the like.

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 view showing an enlarged print portion in the area A shown in FIG. FIG. 4 is a cross-sectional view showing an adhesive sheet according to a first modified example of the present disclosure; FIG. 5 is a plan view schematically showing a method of printing an adhesive sheet according to the second modified example of the present disclosure. FIG. 6 shows micrographs of pressure-sensitive adhesive sheets of Examples and Comparative Examples in which the thickness of the printed portion is 2 μm (ink amount K 10%), and the measurement results of the number of dots and the dot size in the printed portion.

In the process of variously examining means for solving the above-described problems without greatly increasing the manufacturing cost, the inventors of the present application found that the adhesive component may seep out from the printed portion formed on the adhesive layer by the inkjet method. In addition, it was found that the lower the storage elastic modulus of the adhesive layer, the larger the amount of the adhesive component oozing out. After further studies, it was found that by changing the thickness of the printed portion, etc., it was possible to easily adjust the degree of decrease in tackiness and adhesive force compared to the case where the printed portion was not provided, and the inventors arrived at the present invention. rice field.

[Structure of Adhesive Sheet]
FIG. 1 is a cross-sectional view showing an adhesive sheet 10, which is an example of the embodiment disclosed in this specification, and FIG. It is a diagram. FIG. 3 is a photographic view showing an enlarged print portion in the area A shown in FIG.

As shown in FIG. 1, the pressure-sensitive adhesive sheet 10 of the present embodiment is formed on the pressure-sensitive adhesive layer 3 and at least one surface of the pressure-sensitive adhesive layer 3. and a printing unit 5 . In the pressure-sensitive adhesive sheet 10 of the present embodiment, the sheet-like base material 1 is provided on the surface of the pressure-sensitive adhesive layer 3 opposite to the surface on which the printed portion 5 is provided. A release liner 7 may be provided on the surface of the pressure-sensitive 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 provided with the printed portion 5 with the release liner 7, it is possible to store not only a roll but also a planographic plate. A known release liner 7 can be used, and a release layer containing a silicone-based release agent or a fluorine-based release agent may be provided on the side in contact with the pressure-sensitive adhesive layer 3 .

In the printed region 12 of the adhesive sheet 10 of the present embodiment, the printed portion 5 is provided, so that the loop tack value of the adhesive layer 3 against a stainless steel (SUS) steel plate is 0.01 N/25 mm or more and 20 N/25 mm. You can: Therefore, in the printing area 12, the adhesive sheet 10 can be easily reapplied, and the adhesive sheet 10 can be temporarily fixed so that the adhesive sheet 10 does not move from the fixed position. It makes work easier.

According to the pressure-sensitive adhesive sheet 10 of the present embodiment, by changing the thickness of the printed portion 5 or the like, it is possible to adjust the tack value and the adhesive force to desired values even when the same pressure-sensitive adhesive is used. Become. For example, it is possible to produce a slightly tacky sheet by using an inexpensive strong tackiness type adhesive without using a relatively expensive tackiness type adhesive.

In the printed region 12 of the pressure-sensitive adhesive sheet 10 of the present embodiment, the holding force duration at 40° C. may be 1000 seconds or more, and in the holding force measurement test described later, the amount of deviation (mm /50,000 seconds) is preferably 1 mm or less. If the pressure-sensitive adhesive sheet 10 has excellent holding power, it is less likely to be peeled off or come off from an adherend when used as a label, graphic sheet, or the like. The holding power of the pressure-sensitive adhesive sheet 10 can be fully exhibited by applying an appropriate amount of pressure with a hand, roller, or the like after bonding it to the adherend. This is because the amount of adhesive component oozing out from the printing section 5 increases due to the application of pressure. When the adhesive component oozes out from the printed portion 5, the amount of displacement of the adhesive sheet 10 becomes smaller as the cohesive force of the adhesive layer 3 is stronger.

The printing portion 5 is formed of a cured ink and is provided on one or more printing regions 12 set in the pressure-sensitive adhesive layer 3 as a printing range. In the example shown in FIG. 2, the entire adhesive surface of the adhesive layer 3 is the printed 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. Although the diameter of the dots 15 is not particularly limited, it may be, for example, 0.1 μm or more and 50 μm or less, or 1 μm or more and 30 μm or less. The diameter of dot 15 depends on the printer 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 diameter of the dots 15 may be uniform, but may have moderate variations. The printing portion 5 may include an average of 5 or more dots 15 per 0.5 mm square.

When the density of the dots 15 is low to some extent, there are gaps between the dots 15, which allows the components of the pressure-sensitive adhesive layer 3 to seep out. Due to the oozing of the adhesive component, the adhesive sheet 10 of the present embodiment has a certain degree of tackiness without applying pressure, and can be easily peeled off by applying pressure after being attached to the adherend. Adhesive force to the extent that it does not occur can be exhibited.

As the density of the dots 15 increases, the gaps between the dots 15 decrease, and the overlap between the dots 15 also increases. component) is reduced. For this reason, the average thickness of the printed portion 5 may be approximately 0.1 μm or more and 20 μm or less, and preferably 1 μm or more and 6 μm or less, depending on the type of adhesive used. When the average thickness of the printed portion 5 is less than 0.1 μm, the gaps between the dots 15 become large, and a large amount of the adhesive component tends to seep out from the gaps. It is almost the same as when the dot 15 is not provided. If the thickness of the printed portion 5 exceeds 20 μm, the amount of the components of the pressure-sensitive adhesive layer 3 oozes out, which may make it difficult to attach the adhesive layer 5 to the adherend. By setting the average thickness of the printed portion 5 to 6 μm or less, it is possible to further expand the types of adhesives that can be used as the main agent of the adhesive layer 3 .

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 is 50% or more even when black ink or color ink is used to form the printed portion 5. It is translucent. However, by setting the thickness of the printing portion 5 to be more than 6 μm and 20 μm or less, it is possible to form a desired image with the printing portion 5 while keeping the loop tack value within a desired range.

In the print area 12, the dots 15 may be arranged regularly or may be arranged irregularly. When the printing portion 5 is formed by an inkjet printer, which will be described later, the dots 15 are arranged irregularly. Further, the sizes of the dots 15 forming the printing portion 5 may be the same, but they may be non-uniform.
The ink used to form the printed portion 5 is not limited, and one or more inks selected from photocurable inks, electron beam curable inks, and solvent-based inks can be used. UV) or photocurable ink or electron beam curable ink that cures with visible light or the like can make it difficult for the ink to diffuse into the adhesive layer 3 when forming the printed portion 5, and the thickness required for the printed portion 5 can be reduced. It is preferable because it becomes easier to secure. In addition, since the UV curable ink and electron beam curable ink can be cured immediately after printing, the use of these inks reduces the production time of the pressure-sensitive adhesive sheet 10 compared to the case of using solvent-based inks. can be shortened.

The color of the ink used to form the printing portion 5 is not particularly limited, and may be black (K) only, or 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. When using inks of multiple colors, the thickness of the printing portion 5 should be the same as when using inks of one color.

The printing unit 5 can be formed by a printing method that ejects ink using a known inkjet printer or the like. On the other hand, if the printed portion 5 is formed by offset printing, gravure printing, silk screen printing, or the like, the adhesive layer 3 will be covered without gaps, and the adhesive component will not seep out. Even if halftone dots of 0.1 μm or more and 50 μm or less, which are the same as the dots 15, are formed in the printing area 12 by offset printing or gravure printing, it is possible to realize the bleeding of the components in the pressure-sensitive adhesive layer 3. However, while offset printing and gravure printing require expensive plates, using an inkjet printer eliminates the need to prepare a plate, so the density and formation position of the dots 15 can be freely changed in a short period of time. can do.

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

In the pressure-sensitive adhesive sheet 10 of the present embodiment, the storage elastic modulus G′ of the pressure-sensitive adhesive layer 3 at 23° C. and a frequency of 1 Hz may be 5.0×10 ⁴ Pa or more and 3.5×10 ⁵ Pa or less. .5×10 ⁴ Pa or more and 3.0×10 ⁵ Pa or less may be used. The storage elastic modulus represents the hardness of the adhesive layer 3, and according to the study of the inventors of the present application, the lower the storage elastic modulus, the easier the adhesive layer 3 will flow, and the easier the adhesive component will seep out from the printed portion 5. I know it will be If the storage elastic modulus is 3.5×10 ⁵ Pa or less, the adhesive component oozing out from the printed portion 5 produces an appropriate level of tackiness, and the adhesiveness is such that it does not come off easily after being attached to the adherend. can exert power. Moreover, when the storage elastic modulus of the pressure-sensitive adhesive layer 3 is 5.0×10 ⁴ Pa or more, it becomes easy to balance physical properties.

When the storage elastic modulus of the adhesive layer 3 is low, it is easier to secure a certain level of loop tack and adhesive strength even if the thickness of the printed portion 5 is increased, compared to when the storage elastic modulus of the adhesive layer 3 is high.

The glass transition temperature (Tg) of the adhesive layer 3 may be 10°C or lower. In this case, when the adhesive sheet 10 is used at normal temperature, the pressure-sensitive adhesive layer 3 has appropriate fluidity, so that the constituent components of the pressure-sensitive adhesive layer 3 tend to seep out from the printed portion 5 .

In the printed area 12, the adhesive force of the adhesive layer 3 to the adherend may be appropriately set according to the application. In this case, the adhesive strength 24 hours after attachment to the SUS steel plate may be, for example, about 0.01 N/25 mm or more and 20 N/25 mm or less. Since the adhesive strength of the adhesive sheet 10 is smaller than the adhesive strength of the adhesive layer 3 in the case where the printed portion 5 is not provided, the adhesive used to form the adhesive layer 3 may be a medium adhesive type or a strong adhesive type. By using an adhesive, it is possible to produce the adhesive sheet 10 exhibiting a wide range of adhesive strength. For example, when a strong adhesive type adhesive is used, by setting the printed portion 5 to be thicker, the adhesive sheet 10 that exhibits slightly adhesiveness in the printed area 12 can be produced, and by reducing the thickness of the printed portion 5, the adhesive sheet 10 can be produced. It is also possible to produce an adhesive sheet 10 exhibiting adhesiveness.

The adhesive used to form the adhesive layer 3 is not particularly limited, but is selected from, for example, an acrylic adhesive, an acrylic-urethane adhesive, a urethane adhesive, a silicone adhesive, and a rubber adhesive. It may be one or a mixture of two or more. As the adhesive to be used, a water-based adhesive, a solvent-based adhesive, a non-solvent type adhesive, or the like can be used.

Although the thickness of the pressure-sensitive adhesive layer 3 is not particularly limited, it 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 may be 2 μm or more and 50 μm or less. If the thickness of the pressure-sensitive adhesive layer 3 is within this range, it becomes easier to set the loop tack value and the adhesive strength in the desired ranges even in the printed area 12 .

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 probably because the thicker the pressure-sensitive adhesive layer 3, the more easily the adhesive component seeps out from the printed portion 5 due to the pressure applied during bonding after the formation of the printed portion 5. FIG.

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

As the substrate 1, known materials such as resin sheets, synthetic papers, papers, non-woven fabrics, woven fabrics, etc., and laminates thereof can be used. Materials constituting the resin sheet include, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyimide (PI), and the like. can be used.

Although the thickness of the base material 1 is not particularly limited, it may be, for example, about 2 μm or more and 300 μm or less, or may be 5 μm or more and 250 μm or less. At least one surface of the substrate 1 may be provided with an easy-adhesion layer or an antistatic layer, if necessary.

As the base material 1, a biomass material or a recycled material may be used partially or wholly in order to reduce the environmental load. In addition, it is preferable to manufacture the pressure-sensitive adhesive sheet 10 using materials, including the substrate 1, which emit as little CO ₂ as possible for manufacturing.

[Modified example of adhesive sheet]
FIG. 4 is a cross-sectional view showing an adhesive sheet 20 according to the first modified example of the present disclosure. As shown in the figure, the pressure-sensitive adhesive sheet 20 according to this modification is formed on at least one surface of the pressure-sensitive adhesive layer 3 and the pressure-sensitive adhesive layer 3. and 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 attached to the surface of the adhesive layer 3 on which the printed portion 5 is provided, and a second release liner 17 is attached to the other surface of the adhesive layer 3 . The release force required to release the release liner 7 and the release force required to release the second release liner 17 may be approximately the same, but the release liner on the light release side may be used with a difference between the two. You may make it peelable easily. Other configurations of the adhesive sheet 20 are basically the same as those of the adhesive sheet 10 .

In the adhesive sheet 20 according to this modification, the adhesive force of the surface (first surface) of the adhesive layer 3 on which the printed portion 5 is provided is is smaller than the adhesive force of Also, the loop tack value of the first surface of the pressure-sensitive adhesive layer 3 is smaller than the loop tack value of the second surface. Therefore, it is possible to realize a double-sided pressure-sensitive adhesive sheet having different adhesive strengths on one side and the other side of the pressure-sensitive adhesive layer 3 . The adhesive used in the adhesive sheet 20 according to this modified example is not particularly limited.

Since the area of the adherend substantially in contact with the adhesive component is smaller on the surface on which the printed portion 5 is provided than on the opposite surface, contamination of the adherend by the adhesive is less likely to occur. Like the adhesive sheet 10, the adhesive sheet 20 can be used in various fields.

For example, the pressure-sensitive adhesive sheet 20 using a re-peelable pressure-sensitive adhesive that causes little contamination to the adherend can be used as a pressure-sensitive adhesive sheet for fixing a graphic sheet or the like. For general double-sided adhesive sheets, if an adhesive with strong adhesive strength is selected, the adhesive layer tends to remain on the adherend when the graphic sheet is peeled off because the adhesion to the adherend becomes stronger. . Therefore, as a fixing adhesive sheet, a removable adhesive layer is provided on one side (adherend side) of the core material, and a strong adhesive type adhesive layer is provided on the other side in many cases. On the other hand, according to the pressure-sensitive adhesive sheet 20 according to this modified example, it is possible to change the adhesive force and the tack value between one surface and the other surface at a relatively low cost.

FIG. 5 is a plan view schematically showing a printing method for the adhesive sheet 30 according to the second modified example of the present disclosure. As shown in FIG. 1, the adhesive sheet 30 according to this modification differs from the adhesive sheet 10 shown in FIG. 1 in that a plurality of print areas are provided on the adhesive layer 3 in the sheet. In the example shown in FIG. 5 , a first printed area 12A and a second printed area 12B are formed on the pressure-sensitive adhesive layer 3 provided on one surface of the base material 1 . A first printed portion 5A formed of a cured ink material is provided on the first printed area 12A, and a second printed portion 5B is provided on the second printed 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 be exposed without being covered with the printed portion.

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

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

Both the thickness of the first printed portion 5A on the first printed area 12A and the thickness of the second printed portion 5B on the second printed area 12B may not be constant, and the thickness may be partially different. may be For example, the thickness of the first printed portion 5A and the second printed portion 5B may decrease in a gradation from the outside to the inside in the width direction. Thereby, in 12A of 1st printing areas, and 2nd printing area 12B, it can design so that adhesive strength may become strong as it goes inward from an edge part.

When forming a plurality of printed portions on one surface of the pressure-sensitive 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, the exposed surface of the adhesive layer 3 is coated with, for example, UV curing from the head 23 of a line inkjet printer extending in the width direction. The first printed portion 5A and the second printed portion 5B are formed by ejecting ink and then UV irradiation. If a long printing time is acceptable, the printing unit 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 may be aged in advance before forming the printed portion. Alternatively, the printed portion may be formed after cutting the pressure-sensitive adhesive sheet before forming the printed portion into a desired size with a slitter.

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

Alternatively, when the strongly adhesive adhesive layer 3 is formed, the adhesive sheet 30 manufactured to have a predetermined length is cut in the width direction so that the adhesive strength of both ends in the width direction is reduced to that of the central portion. A pressure-sensitive adhesive sheet with weaker adhesive force can be produced. With this pressure-sensitive adhesive sheet, when it becomes necessary to peel off the pressure-sensitive adhesive sheet after it has been attached to an adherend, it can be easily peeled off from the adherend by peeling it off from the end with the weaker adhesive strength. . By using an inkjet printer, it is possible to arbitrarily adjust the thickness and formation position of the printing portion without preparing a plate.

In addition, in the adhesive sheet 10 of the present embodiment shown in FIG. 1 and the adhesive sheets 20 and 30 according to the modified examples thereof, the adhesive sheet is stored in a state in which the printing portion is not formed, and when an order is received from a customer, the adhesive sheet is stored. In addition, since it is possible to form printed parts on demand that exhibit tackiness and adhesiveness according to the customer's request, the amount of product inventory can be reduced compared to storing adhesive sheets with different tackiness and adhesiveness. can be significantly reduced.

The pressure-sensitive adhesive sheet 10 of the present embodiment and the pressure-sensitive adhesive sheets 20 and 30 according to the modifications described above are examples of the present invention. The shape, formation position, etc. can be changed as appropriate without departing from the gist of the present invention.

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

[Production of adhesive sheet]
By adding an appropriate amount of a curing agent to each of four types of commercially available adhesives and mixing them, an acrylic adhesive composition A, an acrylic-urethane adhesive composition B, and a silicone adhesive composition C are prepared. And a pressure-sensitive adhesive composition D was produced. Here, since the pressure-sensitive adhesive composition A contains a rosin-based tackifier corresponding to 15% by mass of the weight of the pressure-sensitive adhesive layer after drying, the pressure-sensitive adhesive layer formed has a biomass degree of 15%. It's becoming

Next, PSA compositions A and B were coated on the release layer of a commercially available release liner having a PET film having a release layer containing a silicone-based release agent and having a thickness of 50 μm, using a known comma-type coater. was applied to a predetermined thickness after drying. The thickness of the adhesive layer was 10 μm, 20 μm, and 30 μm. Next, the coated surface of the release liner was adhered to one surface of the base material to transfer the pressure-sensitive 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 PET film (manufactured by Toyobo Co., Ltd., trade name: Cosmoshine (registered trademark) A4360) having easy adhesion layers formed on both sides with a thickness of 50 μm was used. Here, various pressure-sensitive adhesive sheets having no printed portion were designated as Comparative Examples 1-6. As for the adhesive compositions C and D, adhesive sheets having adhesive layer thicknesses of 10 μm, 20 μm, and 30 μm were produced by directly coating the base material using a comma-type coater in Comparative Examples 7 to 12. was made as

Next, on the prepared pressure-sensitive adhesive sheet, a UV ink jet printer ("UJF-6042MkII" manufactured by Mimaki Engineering Co., Ltd.) is used to print on the entire exposed surface of the pressure-sensitive adhesive layer by discharging and curing UV curable ink. formed a department. As the UV curable ink, black ink "LH-100" manufactured by Mimaki Engineering Co., Ltd. was used. The ink amounts were set to K10%, K20%, and K30%. Using the adhesive compositions A and B, pressure-sensitive adhesive sheets having printed portions formed as described above were produced as Examples 1 to 14. Further, using the adhesive compositions C and D, pressure-sensitive adhesive sheets having printed portions formed as described above were produced as Comparative Examples 13 to 28. The configurations of the pressure-sensitive adhesive sheets according to Examples and Comparative Examples are described in Tables 2 to 9 below.

[Measuring method]
<Measurement of Storage Elastic Modulus G′, Loss Elastic Modulus G″, Loss Tangent (tan δ) and Glass Transition Temperature Tg of PSA Layer>
The storage elastic modulus G′, loss elastic modulus G″ and loss tangent of the adhesive layer of the adhesive sheet were measured by the following methods. First, each of the prepared pressure-sensitive adhesive compositions A to D was used to prepare a baseless tape having a pressure-sensitive adhesive layer with a thickness of 50 μm. Then, this baseless tape was aged at 40° C. for 72 hours. Next, only the pressure-sensitive adhesive layer was laminated to a total thickness of 1 mm, and then punched into a size of 8 mm in diameter to prepare a tablet. This tablet was sandwiched between the plates of a rheometer (product name: AR2000ex), and the storage elastic modulus G' and the loss elastic modulus G'' were measured under the conditions of a frequency of 1 Hz, a strain amount of 0.05%, and a measurement temperature of -40 to 100 ° C. was measured. Also, the value of loss elastic modulus G''/storage elastic modulus G' was calculated as the loss tangent. The temperature at which the loss tangent was maximized was read as the glass transition temperature of the pressure-sensitive adhesive layer.

<Thickness measurement of printed part>
On a PET film having a thickness of 50 μm, a UV inkjet printer ("UJF-6042MkII" manufactured by Mimaki Engineering Co., Ltd.) was used to set the ink amount to K10%, 20%, and 30%, respectively, to form a printed portion. . The total thickness of each sheet sample was measured using a constant pressure measuring instrument, and the thickness of each printed portion was calculated by subtracting the thickness (50 μm) of the PET film from the measured value.

As a result of measurement, the thickness of the printed portion (ink thickness) was about 2 μm with 10% K, about 3 to 4 μm with 20% K, and about 5 μm with 30% K.

<Counting the number of dots and confirming the dot size>
Using a microscope, a 200-fold photograph was taken of the print side surface of each pressure-sensitive adhesive sheet sample. Three 0.5 mm square regions were arbitrarily selected from the photomicrograph, the number of dots was counted, and the average value was taken as the count value of the number of dots. Also from this micrograph, the range of dot diameters was measured.

<Measurement of adhesive strength to SUS>
The adhesive sheet was peeled off from the release liner to expose the adhesive surface, and was attached to a SUS steel plate that had been polished with 360-degree water-resistant 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 attached to a SUS steel plate as an adherend, and then crimped by two reciprocations with a 2 kg roller, 23 ° C., 50% relative humidity for 20 minutes or It was allowed to stand for 24 hours. The adhesive strength (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 the conditions of a peel angle of 180° and a peel speed of 300 mm/min.

<Measurement of loop tack value>
After cutting out a test piece having a width of 25 mm and a length of 150 mm from the pressure-sensitive adhesive sheet, the release liner is peeled off and divided into two. Separated release liners each having a width of 25 mm were laminated so as to cover only 25 mm from both ends of the exposed surface of the pressure-sensitive adhesive layer (100 mm of the pressure-sensitive adhesive layer of the test piece was exposed). The test piece was set in a loop on the upper grip of the tensile tester so that the sticky side was on the outside. After setting the SUS steel plate on the lower grip part of the tensile tester, the upper grip part is lowered at a speed of 300 mm / min until the height from the lower grip part becomes 20 mm, and the adhesive surface of the test piece and the SUS made contact with the steel plate. Immediately after the contact, the upper grip part was raised to the 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 measured values was recorded as the loop tack value. The measurement was performed under the conditions of 23° C. and 50% relative humidity.

<Measurement of holding force and holding force duration>
A test piece having 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×25 mm at one end of the test piece was attached to a SUS steel plate. Using a squeegee, the square portion attached to the SUS steel plate was strongly crimped with a uniform force.

Next, the SUS steel plate was placed vertically so that the square portion of the pressure-sensitive adhesive sheet was positioned upward, and in this state, a weight of 1 kg was hung from the other end of the pressure-sensitive adhesive sheet positioned below. In this state, the time until the adhesive sheet was completely peeled off was measured as the holding power duration. In addition, the displacement amount (unit: mm) of the adhesive sheet after 50,000 seconds passed from the start of the measurement was measured as a value representing the holding power. In addition, the measurement was performed at 40 degreeC.

[Measurement result]
Table 1 shows the storage elastic modulus, loss elastic modulus, loss tangent and glass transition temperature of the cured adhesive compositions A to D forming the adhesive layer.

貯蔵弾性率と損失弾性率については、小さい方から粘着剤組成物Ａ、粘着剤組成物Ｂ、粘着剤組成物Ｃ、粘着剤組成物Ｄの順となっていた。ガラス転移温度については、低い方から粘着剤組成物Ａ、粘着剤組成物Ｂ、粘着剤組成物Ｃ、粘着剤組成物Ｄの順となっていた。

The storage elastic modulus and the loss elastic modulus were in order of the adhesive composition A, the adhesive composition B, the adhesive composition C, and the adhesive composition D from the smallest. Regarding the glass transition temperature, the adhesive composition A, the adhesive composition B, the adhesive composition C, and the adhesive composition D were in order from the lowest.

Tables 2 to 9 show the measurement results of adhesive strength, loop tack value and holding power of the adhesive sheets according to Examples 1 to 14 and Comparative Examples 1 to 28.

印刷部を設けない比較例１～３と、印刷部を設けた実施例１～３、７～９、１２、１３との比較から、多少のばらつきはあるものの、組成が同じ粘着剤層を使用する場合、粘着剤層の厚みが大きくなる程粘着力及びループタック値が大きくなること、印刷部の平均厚みが大きくなるにつれて粘着力及びループタック値が小さくなる傾向にあることが確認できた。

From the comparison of Comparative Examples 1 to 3 without a printed portion and Examples 1 to 3, 7 to 9, 12, and 13 with a printed portion, adhesive layers with the same composition are used, although there are some variations. In this case, it was confirmed that the greater the thickness of the adhesive layer, the greater the adhesive force and loop tack value, and that the greater the average thickness of the printed portion, the smaller the adhesive force and loop tack value.

The tendency for both the adhesive strength and the loop tack to decrease as the thickness of the printed portion increased was similarly observed in the adhesive sheets produced using any of the adhesive compositions B, C, and D. From this, it was found that by adjusting the thickness of the printed portion, it is possible to control the adhesive strength and the loop tack value so that they fall within the desired ranges.

In addition, the adhesive sheets according to Examples 1 to 14, which were produced using the adhesive compositions A and B having a storage modulus of 5.0×10 ⁴ Pa or more and 3.5×10 ⁵ Pa or less, had a loop tack value of was 0.01 N/25 mm or more and 20 N/25 mm or less.

On the other hand, the pressure-sensitive adhesive sheets using the pressure-sensitive adhesive compositions C and D having a storage modulus of more than 3.5×10 ⁵ Pa (Comparative Examples 13 to 28) do not stick to the adherend, so the loop tack values are comparable. Not measurable except for Example 15. However, these pressure-sensitive adhesive sheets could be attached to adherends by being strongly pressed. A pressure-sensitive adhesive sheet whose loop tack value could not be measured cannot be temporarily fixed when it is applied to a wall surface or the like, and therefore it is considered that the workability of the application work is not good.

FIG. 6 shows the measurement results of the number of dots and the dot size (dot diameter) in the printed portion of the pressure-sensitive adhesive sheet having a printed portion thickness of 2 μm, and a micrograph.

As shown in FIG. 6, it was confirmed that when the ink amount was K10% (the thickness of the printed portion was about 2 μm), the printed portion was composed of many large and small dots. It was confirmed that the average number of large and small dots included in the 0.5 mm square area was 5 or more for all test pieces. The dot diameter was about 23 μm to 36 μm for large dots and about 14 μm to 23 μm for small dots. It is thought that the density of dots increases as the amount of ink increases. However, when the amount of ink exceeds K30%, overlapping between dots increases, making it difficult to count the number of dots.

The pressure-sensitive adhesive sheet disclosed in the present specification can be used in various fields as a label, graphic sheet, member-fixing sheet, various protective sheets, and the like.

1 Base material 3 Adhesive layer 5 Printed part 5A First printed part 5B Second printed part 7 Release liners 10, 20, 30 Adhesive sheet 12 Printed area 15 Dots 17 Second release liner 20 Adhesive sheet 23 Head

As shown in FIG. 6, it was confirmed that when the ink amount was K10% (the thickness of the printed portion was about 2 μm), the printed portion was composed of many large and small dots. It was confirmed that the average number of large and small dots included in the 0.5 mm square area was 5 or more for all test pieces. The dot diameter was about 23 μm to 36 μm for large dots and about 14 μm to 23 μm for small dots. It is thought that the density of dots increases as the amount of ink increases. However, when the amount of ink exceeds K30%, overlapping between dots increases, making it difficult to count the number of dots.

Claims (13)

a pressure-sensitive adhesive layer having a storage modulus of 5.0×10 ⁴ Pa or more and 3.5×10 ⁵ Pa or less at 23° C. and a frequency of 1 Hz;
a printed portion formed on at least one surface of the pressure-sensitive adhesive layer and through which constituent components of the pressure-sensitive adhesive layer ooze;
The adhesive sheet, wherein the printed portion is formed of a cured ink and is provided on one or more print areas set on the adhesive layer as a print area. In the pressure-sensitive adhesive sheet according to claim 1,
A pressure-sensitive adhesive sheet, wherein the loop tack value of the pressure-sensitive adhesive layer to a SUS steel plate in the printed area is 0.01 N/25 mm or more and 20 N/25 mm or less. In the pressure-sensitive adhesive sheet according to claim 1 or 2,
The pressure-sensitive adhesive sheet, wherein the printed portion has an average thickness of 0.1 μm or more and 20 μm or less. In the adhesive sheet according to any one of claims 1 to 3,
The pressure-sensitive adhesive sheet, wherein the total area of the printed regions occupies 1% or more and 100% or less of at least one surface of the pressure-sensitive adhesive layer. In the adhesive sheet according to any one of claims 1 to 4,
The pressure-sensitive adhesive sheet, wherein the printed portion has a surface roughness Ra of 0.3 μm or more and 10 μm or less. In the adhesive sheet according to any one of claims 1 to 5,
The pressure-sensitive adhesive sheet, wherein the printed portion is made of a cured ink and includes dots arranged irregularly on the printed area. In the adhesive sheet according to claim 6,
The printing unit includes an average of 5 or more dots per 0.5 mm square,
The pressure-sensitive adhesive sheet, wherein 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 7,
The printed portion is a pressure-sensitive adhesive sheet formed of a cured product of photocurable ink or electron beam curable ink. In the adhesive sheet according to any one of claims 1 to 8,
The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a glass transition temperature of 10°C or less. In the adhesive sheet according to any one of claims 1 to 9,
The printed portion is formed on one surface of the adhesive layer,
A pressure-sensitive adhesive sheet further comprising a sheet-like substrate provided on a surface of the pressure-sensitive adhesive layer opposite to the surface provided with the printed portion. In the adhesive sheet according to any one of claims 1 to 10,
A pressure-sensitive adhesive sheet having a holding force duration of 1000 seconds or more at 40° C. in the printed area. In the adhesive sheet according to any one of claims 1 to 11,
The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a biomass content of 10% or more and 50% or less. In the adhesive sheet according to any one of claims 1 to 12,
The pressure-sensitive adhesive sheet, wherein the printed portion is formed by curing ink applied by an inkjet method.

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