TW201716211A - Embossing tool and method for preparation thereof - Google Patents

Abstract

An embossing tool is prepared by: forming a mold (51, 52) having a non-planar mold surface defining the external form of the embossing tool; depositing a layer (53) of gold or an alloy thereof over the mold surface; depositing a base metal (54) over the layer (53) of gold or alloy thereof to form a layer of base metal having a substantially flat surface remote from the mold surface; and removing the mold (51, 52) from the layers (53, 54) of gold or alloy thereof and base metal to form an embossing tool having a three-dimensional structure on one side and a substantially flat surface on the other.

Description

Embossing tool and preparation method thereof

The present invention relates to an embossing tool, an assembly for preparing such an embossing tool, and a method for preparing such an embossing tool.

Embossing tools are typically made of nickel, copper, alloy or other types of composite materials. Nickel is the most widely used material for the manufacture of embossing machines.

There are some problems associated with currently available embossing tools, particularly the incomplete release of embossed cured material or hot embossed material from the embossing tool.

There are a number of methods for modifying the surface of an embossing tool to reduce the adhesion between the surface of the embossing tool and the cured or hot embossed material. These methods may include decane coating, decane resin coating, PTFE (polytetrafluoroethylene) coating or nickel-PTFE composite plating. Unfortunately, none of them can achieve satisfactory results.

The decane resin and PTFE can be applied to the surface of the embossing tool via wet coating. However, after drying and curing, the thickness uniformity of the coating on the microstructured surface is poor, which may change the shape of the microstructure obtained on the embossing tool.

When the microstructure on the surface of the embossing tool has a high aspect ratio, the PTFE coating via physical vapor deposition (PVD) or chemical vapor deposition (CVD) has exhibited a throwing power (throwning power) ) Poor, also showing uneven coverage. In addition, the durability and mechanical strength of the PTFE coating are an additional concern, especially if the embossing tool needs to be widely used in mass production.

The nickel-PTFE composite coating can be applied to the surface of the embossing tool by electroplating or electro-less plating. However, the minimum coating thickness is typically a few microns. Therefore, if the embossing tool has a small-sized microstructure on its surface, especially a narrow groove, such a coating may completely change the contour and aspect ratio of the microstructure, making the embossing work much more difficult.

U.S. Patent Application Serial No. 2016/0059442 and the Japanese Application No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. No. Publication No. The tool is prepared by first forming a microstructure using conventional photolithographic techniques and then coating the microstructures with a noble metal or precious metal alloy. The present invention relates to variations of the method for forming an embossing tool, and to structures prepared during the process.

Accordingly, the present invention provides a method for preparing an embossing tool, the method comprising: a) forming a mold having a non-planar mold surface defining the contour of the embossing tool; b) coating the surface of the mold Gold or its alloy layer; c) plating a base metal on the gold or alloy layer thereof to form a base metal layer having a substantially flat surface away from the surface of the mold; and d) from the gold or alloy layer thereof The mold is removed from the base metal layer to form an embossing tool having a three-dimensional structure on one side and a substantially flat surface on the other side. In one embodiment, the embossing tool prepared in step d) is subsequently wrapped on a drum. The mold can be formed by coating a photoresist material on a substrate, exposing the photoresist material to radiation, and removing exposed or unexposed regions of the photoresist.

The present invention also provides an assembly for preparing an embossing tool, the assembly comprising: a mold having a non-planar mold surface; a gold or alloy layer disposed on the mold surface and conforming to the mold surface And a base metal layer on the opposite side of the gold or alloy layer thereof away from the mold surface, the base metal layer having a three-dimensional structure in contact with the gold or alloy layer thereof, and at a distance therefrom A substantially flat surface on one side of the gold or its alloy layer.

11‧‧‧ embossing tools

12‧‧‧curable embossing composition or heat embossable material

21‧‧‧embossing roller or sleeve

22‧‧‧Photosensitive materials

23‧‧‧Light source

24‧‧‧Photomask

25‧‧‧ patterned photosensitive materials

26‧‧‧ plating materials

31‧‧‧ precious metals or alloys thereof

41‧‧‧Substrate layer or substrate

42‧‧‧Photosensitive materials

43‧‧‧Electrical seed layer

44‧‧‧Metal or alloy, plated material, sheet metal

51‧‧‧Substrate

52‧‧‧Photosensitive materials

53‧‧‧ Gold or its alloy layer, gold or alloy coating

54‧‧‧ Plated materials, metal sheets

1A and 1B show a general embossing method.

Figure 2 illustrates a prior art method for forming a microstructure on the surface of an embossing tool.

Figure 3 is a cross section through an embossing tool of the prior art described in the above-mentioned US 2016/0059442, which has a three-dimensional microstructure and a precious metal (e.g., gold) plated on its surface.

Figure 4 illustrates a method for forming an embossing tool as described in the aforementioned US 2016/0059442.

Figure 5 illustrates a method of forming an embossing tool of the present invention.

Figure 6A is a photograph showing the surface of an object manufactured by an embossing process using a conventional embossing tool.

Figure 6B is a photograph showing the surface of an object manufactured by an embossing process using the embossing tool of the present invention.

Figures 1A and 1B show an embossing process using an embossing tool (11) having a three-dimensional microstructure (circled) on the surface of the embossing tool (11). As shown in Figure 1B, the embossing tool (11) is applied to the curable embossed composition or the heat embossable material (12), and the embossed composition is cured (e.g., by radiation) or hot compressible After the flower material becomes embossed by heat and pressure, the cured or hot embossed material is released from the embossing tool (see Figure 1B). However, when conventional embossing tools are used, the cured or hot embossed material sometimes cannot be completely released from the tool due to the undesired strong adhesion between the cured or hot embossed material and the surface of the embossing tool. In this case, there may be some cured or hot embossed material that is transferred to the surface of the embossing tool or to the surface of the embossing tool, leaving an uneven surface on the object formed by the method.

This problem is even more pronounced if the object is formed on a support layer such as a transparent conductive layer or a polymer layer. If the adhesion between the cured or hot embossed material and the support layer is weaker than the adhesion between the cured or hot embossed material and the surface of the embossing tool, then curing The release of the hot or embossed material from the embossing tool may result in the separation of the object from the support layer.

In some cases, an object may be formed on the stacked layer, in which case if the adhesion between any two adjacent layers is between the cured or hot embossed material and the surface of the embossing tool The adhesion is weaker, and the process of releasing the cured or hot embossed material from the embossing tool can result in splitting between the two layers.

These problems described above are particularly a concern when the cured embossed composition or the hot embossed material does not adhere well to certain support layers. For example, if the support layer is a polymer layer, the adhesion between the polymer layer and the cured or hot embossed embossing composition is weak in the case where one of them is hydrophilic and the other is hydrophobic. Therefore, it is preferred that both the embossing composition and the support layer are hydrophobic or both are hydrophilic.

As an example, a suitable hydrophobic composition for forming an embossed layer or a support layer can include a thermoplastic material, a thermoset material, or a precursor thereof. Examples of thermoplastic or thermoset precursors can be multifunctional acrylates or methacrylates, polyfunctional vinyl ethers, polyfunctional epoxides, and oligomers or polymers thereof.

Suitable hydrophilic compositions for forming the embossed layer or support layer can include polar oligomers or polymeric materials. Such a polar oligomer or polymeric material may be selected from the group consisting of having at least one such as a nitro group (-NO ₂ ), a hydroxyl group (-OH), a carboxyl group, as described in U.S. Patent No. 7,880,958. (-COO), alkoxy (-OR, wherein R is alkyl), halogen (such as fluorine, chlorine, bromine or iodine), cyano (-CN) and sultanate (-SO ₃ ), etc. The oligomer or polymer of the group. The glass transition temperature of the polar polymeric material is preferably below about 100 °C, and more preferably below about 60 °C. Specific examples of suitable polar oligomers or polymeric materials can include, but are not limited to, polyvinyl alcohol, polyacrylic acid, poly(2-hydroxyethyl methacrylate), polyhydroxy-functional polyester acrylate (such as BOE) 1025, Bomar Specialties Co, Winsted, CT) or alkoxylated acrylates such as ethoxylated nonylphenol acrylate (eg SR504, Sartomer Company), ethoxylated trimethylolpropane triacrylate ( For example, SR9035, Sartomer Company) or ethoxylated pentaerythritol tetraacrylate (for example, SR494 from Sartomer Company).

method 1:

Figure 2 illustrates a prior art method for forming microstructures on the surface of an embossing tool.

The term "embossing tool" as used herein may be an embossing sleeve, an embossing drum, or other form of embossing tool. Although only the preparation of the embossing sleeve is shown in Figure 2, the method can also be used to prepare an embossing cylinder. The term "embossing" drum or sleeve refers to a drum or sleeve having a three-dimensional microstructure on its outer surface. The term "embossing cylinder" is used to distinguish it from a plain drum that does not have a three-dimensional microstructure on the outer surface.

The embossing cylinder can be used directly as an embossing tool. When an embossing sleeve is used for embossing, it is typically mounted on a smoothing cylinder to allow the embossing sleeve to rotate.

The embossing cylinder or sleeve (21) is typically formed from a conductive material such as a metal (eg, aluminum, copper, zinc, nickel, chromium, iron, titanium, or cobalt, etc.), from any of the foregoing metals The resulting alloy, or stainless steel. Different materials can be used to form the drum or sleeve. For example, the center of the drum or sleeve may be formed of stainless steel and sandwich the nickel layer between the stainless steel and the outermost layer, and the outermost layer may be a copper layer.

Alternatively the embossing cylinder or sleeve (21) may be formed from a non-conductive material having a conductive coating or a conductive seed layer on its outer surface.

Prior to coating the photosensitive material (22) on the outer surface of the drum or sleeve (21), as shown in step B of Figure 2, precision grinding and polishing can be used to ensure the smoothness of the outer surface of the drum or sleeve.

In step B, a photosensitive material (22), such as a photoresist, is coated on the outer surface of the drum or sleeve (21). The photosensitive material may be a positive tone, a negative tone, or a dual tone. The photosensitive material may also be a chemically amplified photoresist. Coating can be carried out using dip coating, spray coating or ring coating. After drying and/or baking, the photosensitive material is exposed to a source of radiation as shown in step C.

Alternatively, the photosensitive material (22) may be a dry film photoresist (which is typically commercially available) that is laminated to the outer surface of the drum or sleeve (21). When a dry film is used, it can also be exposed to a radiation source as described below.

In step C, a suitable light source (23), such as IR, UV, electron beam or laser, is applied to the roller or sleeve (21). The photosensitive material or the dry film photoresist (22) laminated on the drum or sleeve (21) is exposed. The light source can be continuous light or pulsed light. A photomask (24) is optionally used to define a three-dimensional microstructure to be formed. Depending on the microstructure, the exposure can be stepwise, continuous, or a combination thereof.

The photosensitive material (22) may undergo post-exposure treatment, such as baking, prior to development after exposure. The exposed or unexposed areas are removed by using a developer depending on the type of the photosensitive material. A roller or sleeve having a patterned photosensitive material (25) on its outer surface prior to deposition (eg, electroplating, electroless plating, physical vapor deposition, chemical vapor deposition, or sputter deposition) after development (as in step D) Show) can undergo baking or full exposure. The thickness of the patterned photosensitive material is preferably greater than the depth or height of the three-dimensional microstructure to be formed.

A metal or alloy (e.g., nickel, cobalt, chromium, copper, zinc, or an alloy derived from any of the foregoing metals) may be plated and/or electroless plated onto the drum or sleeve. The plating material (26) is deposited on the outer surface of the drum or sleeve in a region that is not covered by the patterned photosensitive material. The deposited thickness is preferably less than the thickness of the photosensitive material as shown in step E. The deposit can be deposited throughout the plating conditions by adjusting the plating conditions, such as the distance between the anode and the cathode (ie, the drum or sleeve) (if plating is used), the rotational speed of the drum or sleeve, and/or the circulation of the plating solution. The thickness variation on the drum or sleeve area is controlled to be less than 1%.

Alternatively, where electroplating is used to deposit the plating material (26), the deposit can be controlled by inserting a non-conductive thickness uniformer between the cathode (ie, the drum or sleeve) and the anode. The thickness variation on the entire surface of the drum or sleeve is as described in U.S. Patent No. 8,114,262.

After plating, the patterned photosensitive material (25) can be peeled off by a release agent such as an organic solvent or an aqueous solution. Precision polishing can optionally be employed to ensure acceptable thickness variations and roughness of the deposit (26) over the entire drum or sleeve.

Step F of Figure 2 shows a cross section through an embossing cylinder or sleeve having a three-dimensional pattern microstructure formed thereon.

As described in the above-mentioned US 2016/0059442, it has been found that if the surface of the embossing tool is coated with a noble metal or an alloy thereof, the embossing tool can have improved release properties. In other words, as a post-processing step after forming a three-dimensional microstructure on the surface of the embossing tool, a noble metal or alloy thereof (31) can be applied to the entire surface of the embossing tool, as shown in FIG.

The term "noble metal" may include gold, silver, platinum, palladium, and other less common metals such as ruthenium, osmium, iridium or osmium. Among these precious metals, the inventors have found that gold and its alloys are most effective in reducing the adhesion between the cured or hot embossed material and the surface of the embossing tool. This advantage is especially pronounced when the cured or hot embossed material has one or more of the following ingredients: polyacrylate, polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), polycarbonate Fat (PC), polyvinyl chloride (PVC), polystyrene (PS), polyester, polyamide, polyurethane, polyolefin, polyvinyl butyral and copolymers thereof. Among these cured or heat-embossed materials, polymers based on acrylate or methacrylate are particularly preferred.

In the present invention, an alloy of one or more noble metals and non-precious metals may also be used. Suitable non-precious metals in the alloy may include But not limited to, copper, tin, cobalt, nickel, iron, indium, zinc or molybdenum. More than one precious metal and/or more than one non-noble metal may also be present in the alloy. The total weight percentage of non-noble metals in the alloy may range from 0.001% to 50%, preferably from 0.001% to 10%.

Coating of the noble metal or alloy can be achieved by electroplating, chemical deposition, sputter coating or vapor deposition. In one embodiment, cyanide-based neutral gold, acid hard gold or gold strike plating electrolytes may be used at a temperature of 30-70 ° C and a pH range of 3-8. Platinum and palladium may be plated with an acid chloride electrolyte at a temperature of 40-70 ° C and a pH range of 0.1-3. Alkaline electrolytes of some precious metals or alloys thereof are commercially available and can also be used in the present invention.

The noble metal or alloy thereof on the surface preferably has a sub-micron thickness so that it does not result in any significant change in the profile of the microstructure. The thickness of the noble metal or alloy thereof may range from 0.001 to 10 microns, preferably from 0.001 to 3 microns.

Method 2:

Alternatively, as described in the above-referenced US 2016/0059442, a three-dimensional microstructure can be formed on a flat substrate, as shown in FIG.

In step A of Fig. 4, a photosensitive material (42) is applied onto a substrate layer (41) (e.g., a glass substrate). As described above, the photosensitive material may be of a positive type, a negative type or a double type. The photosensitive material may also be a chemically amplified photoresist. Coating can be carried out using dip coating, spray coating, slot die coating or spin coating. After drying and/or baking, the photosensitive material is exposed to a suitable light source (not shown) by a photomask (not shown).

Alternatively, the photosensitive material (42) may be a dry film photoresist (which is generally commercially available) laminated to a substrate (41). The dry film can also be exposed to a light source as described above.

In step B, after exposure, depending on the type of photosensitive material, the exposed or unexposed areas of the photosensitive material are removed by using a developer. Prior to development, prior to step C, the substrate layer (41) having the remaining photosensitive material (42) may undergo baking or full exposure. The thickness of the remaining photosensitive material should be the same as the depth or height of the three-dimensional microstructure to be formed.

In step C, a conductive seed layer (43) is applied to the remaining photosensitive material (42) and to the substrate (41) in a region not occupied by the photosensitive material. The conductive seed layer is typically formed of silver.

In step D, a metal or alloy (44) (eg, nickel, cobalt, chromium, copper, zinc, or an alloy derived from any of the foregoing metals) is electroplated and/or electrolessly plated over the layer of conductive seed layer On the surface, and a plating process is performed until there is sufficient plating material thickness (h) on the patterned photosensitive material. The thickness (h) in Fig. 4 is preferably from 25 to 5000 μm, and more preferably from 25 to 1000 μm.

After plating, the plated material (44) is separated from the exfoliated substrate layer (41). The photosensitive material (42) is removed along with the conductive seed layer (43). The photosensitive material can be removed by a stripper such as an organic solvent or an aqueous solution. The conductive seed layer (43) can be removed by an acidic solution (e.g., a sulfur/nitrogen-containing mixture) or a commercially available chemical stripper, leaving only a metal sheet having a three-dimensional structure on one side and a flattened side on the other side ( 44).

Precision polishing can be applied to the metal sheet (44), after which a smooth shim can be used directly for embossing. Alternatively, it can be mounted (e.g., wrapped) on a roller having a three-dimensional microstructure on the outer surface to form an embossing tool.

As described above, the noble metal or its alloy is finally coated on the entire surface of the embossing tool. As mentioned above, gold or its alloys are preferred over other precious metals and alloys.

Method 3:

Figure 5 illustrates the method of the invention. This method is similar to the method of Figure 4, but is simplified. Steps A and B of FIG. 5 are the same as the corresponding steps of FIG. However, in step C of FIG. 5, gold or its alloy layer (53) is coated instead of a conductive seed layer such as silver.

Thus, in step E of Figure 5, after the plated material (54) is separated from the substrate (51), only the photosensitive material (52) needs to be removed, the gold or alloy coating (53) and A metal sheet (54) having a three-dimensional structure on the side and a flat surface on the other side remains together.

Metal sheets can be used directly for embossing. Alternatively, it can be mounted on a drum. In this method of the invention, there is no need for a separate coating step to form a gold or alloy layer on the surface of the embossing tool.

The embossing tool of the present invention is suitable for use in the microembossing process as described in U.S. Patent No. 6,930,818. The microembossing method produces cup-shaped microcells separated by partition walls, such as MICROCUPS (registered trademark). These micelles may be filled with an electrophoretic fluid comprising charged particles dispersed in a solvent or solvent mixture. Filled micro The cells form an electrophoretic display membrane. When sandwiched between the electrode layers, the electrophoretic display film forms an electrophoretic device.

Example

Example 1

In this embodiment, two embossing tools (i.e., male molds) were prepared. These molds are formed from nickel in accordance with one of the methods described above.

The surface of one of these nickel molds was untreated. The other nickel mold formed was further electroplated with a cyanide-based gold plating electrolyte at a temperature of 50 ° C and pH 5 to obtain a gold coating having a thickness of 0.5 μm on the surface thereof.

To test the two embossing dies, a water-based polymer layer fluid and an embossing composition were prepared. The polymer layer fluid is prepared according to U.S. Patent No. 7,880,958, which has polyvinyl alcohol as a main component. The embossing composition is prepared according to U.S. Patent No. 7,470,386, which has a polyfunctional acrylate as a main component.

The polymer fluid was first coated onto a PET (polyethylene terephthalate) substrate using a No. 3 Meyer drawdown bar. The dried polymer layer has a thickness of 0.5 microns.

The embossed composition was diluted with methyl ethyl ketone (MEK) and then applied to the polymer layer side of the PET substrate with a target dry thickness of 25 microns.

Using these two embossing dies, the UV exposure (0.068 J/cm ² , Fusion UV, D lamp) through the back of the PET substrate was applied separately at 160 °F (71 ° C) under a pressure of 50 psi (350 kPa). The layers are dried and embossed.

Figure 6A is a photomicrograph of the surface of a film prepared by using a nickel embossing mold. It can be seen that due to the strong adhesion between the cured material and the nickel metal, some of the cured material on the resulting film has been transferred to the nickel mold or adhered to the nickel mold, leaving unevenness on the resulting film. surface.

When a gold plated nickel mold is used, the cured embossed material is completely separated from the gold metal surface leaving a smooth surface on the resulting film, as shown in Figure 6B. This is due to the fact that the gold-plated surface reduces the adhesion between the mold surface and the cured material, making the mold easier to release from the cured material.

Example 2

In this embodiment, several embossing tools (i.e., male molds) were prepared. These molds are formed from nickel according to one of the methods described above. One of the formed nickel molds was further plated with 0.5 μm gold in the same electrolyte bath as the electrolytic bath used in Example 1.

Three of the formed nickel molds were further subjected to a decane surface treatment. For the decane treatment, polydimethyl methoxyoxane (Gelest, Inc.) was added to a mixture of 95% n-propanol and 5% DI water, and the mixture was previously adjusted to pH 4.5 with acetic acid. Three concentrations of polydimethyloxane solution were prepared at 0.25%, 1%, and 2% by weight, respectively. The nickel molds were separately immersed in different concentrations of decane solution for 10 minutes and then baked at 100 ° C overnight to obtain a decane coating on the surface of the microstructure.

The embossing test materials and conditions were the same as those of the user in Example 1. All cured embossed materials when using gold-plated nickel molds Completely separated from the gold metal surface. However, regardless of the concentration of polydimethyl siloxane in the treatment solution, more than about 50% of the cured embossed material on the resulting film has been transferred to the surface of the decane-treated nickel mold or to the decane. The surface of the treated nickel mold.

This example shows that the cured material is more easily released from the gold plated surface than from the decane treated surface.

Claims (17)

A method for preparing an embossing tool, the method comprising: a) forming a mold having a non-planar mold surface defining an outer shape of the embossing tool; b) depositing a layer of gold or an alloy thereof on the surface of the mold; c) depositing a base metal on the gold or alloy layer thereof to form a base metal layer having a substantially flat surface away from the surface of the mold; and d) from the gold or alloy layer thereof and the base metal The layer removes the mold to form an embossing tool having a three-dimensional structure on one side and a substantially flat surface on the other side. The method of claim 1 wherein the embossing tool prepared in step d) is then wrapped on a drum. The method of claim 1, wherein the mold is formed by coating a photoresist material on a substrate, exposing the photoresist material to radiation, and removing an exposed region of the photoresist or Unexposed area. The method of claim 1, wherein the gold alloy comprises one or more of gold and the following: copper, tin, cobalt, nickel, iron, indium, zinc, and molybdenum. The method of claim 4, wherein the total weight of the non-noble metals in the alloy is in the range of 0.001-50%. The method of claim 4, wherein the total weight of the non-noble metals in the alloy is in the range of 0.001 to 10%. The method of claim 1 wherein the gold or alloy layer thereof has a thickness of from 0.001 to 10 microns. The method of claim 1, wherein the gold or alloy layer thereof has a thickness of 0.001-3 microns. The method of claim 1, wherein the base metal comprises any one or more of nickel, cobalt, chromium, copper, and zinc. The method of claim 1 wherein the base metal layer has a minimum thickness in the range of 25-5000 microns. The method of claim 1 wherein the base metal layer has a minimum thickness in the range of 25-1000 microns. An assembly for preparing an embossing tool, the assembly comprising: a mold having a non-planar mold surface; a layer of gold or an alloy thereof disposed on the surface of the mold and attached to the surface of the mold; And a base metal layer remote from the mold surface and on the opposite side of the gold or alloy layer thereof, the base metal layer having a three-dimensional structure in contact with the gold or alloy layer thereof and having a distance away from the A substantially flat surface on one side of the gold or its alloy layer. The assembly of claim 12, wherein the gold alloy comprises one or more of gold and the following: copper, tin, cobalt, nickel, iron, indium, zinc, and molybdenum. The assembly of claim 12, wherein the total weight of the non-noble metals in the alloy is in the range of 0.001-50%. The assembly of claim 12, wherein the gold or alloy layer thereof has a thickness in the range of 0.001 to 10 microns. The assembly of claim 12, wherein the base metal comprises any one or more of nickel, cobalt, chromium, copper, and zinc. The assembly of claim 1 wherein the base metal layer has a minimum thickness in the range of 25-5000 microns.