TWI620651B - Embossing tool and method for preparation thereof - Google Patents

Abstract

An embossing tool prepared by: forming a mold having a non-planar mold surface defining an outer shape of the embossing tool; depositing gold or an alloy layer thereof on the mold surface; on the gold or alloy layer thereof Depositing base metal to form a base metal layer having a substantially flat surface away from the mold surface; and removing the die from the gold or its alloy layer and the base metal layer to form a three-dimensional surface An embossing tool with a structure that has a substantially flat surface on the other side.

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 usually made of nickel, copper, alloys or other types of composite materials. Nickel is the most widely used material for embossing machine manufacture.

There are some problems associated with the currently available embossing tools, especially the incomplete release of embossed or cured materials from embossing tools.

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

Siloxane 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 surface of the microstructure 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 already exhibited a throwing power ) Poor, and also showed uneven coverage. In addition, poor durability and mechanical strength of the PTFE coating are additional concerns, especially if the embossing tool needs to be widely used for 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 usually a few microns. Therefore, if the embossing tool has small-sized microstructures on its surface, especially narrow grooves, this coating may completely change the microstructure's contour and aspect ratio, making the embossing work much more difficult.

Published U.S. Patent Application No. 2016/0059442 and Taiwan Application No. 104129779 describe an embossing tool having a microstructure on its surface such that the surface of the microstructure is coated with a precious metal or precious metal alloy. The tool is prepared by first forming microstructures using conventional photolithographic techniques and then coating these microstructures with a noble metal or noble metal alloy. The invention relates to a variant of the method for forming an embossing tool, and to a structure prepared during the method.

Therefore, the present invention provides a method for preparing an embossing tool, the method comprising: a) forming a mold having a non-planar mold surface that defines the outer shape of the embossing tool; b) coating on the mold surface Gold or its alloy layer; c) plating a base metal on said gold or its alloy layer to form a base metal layer having a substantially flat surface away from the mold surface; and d) from said gold or its alloy layer And the base metal layer to remove the mold 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 may be formed by coating a photoresist material on a substrate, exposing the photoresist material to radiation, and removing exposed or unexposed areas 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; and 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 its alloy layer away from the mold surface, the base metal layer having a three-dimensional structure in contact with the gold or its alloy layer, and away from the A substantially flat surface on one side of a layer of gold or its alloy.

11‧‧‧ Embossing tools

12‧‧‧ Curable embossing composition or heat embossing material

21‧‧‧Embossed roller or sleeve

22‧‧‧Photosensitive material, dry film photoresist

23‧‧‧light source

24‧‧‧Mask

25‧‧‧ patterned photosensitive material

26‧‧‧Plating materials, deposits

31‧‧‧Precious metals or their alloys

41‧‧‧ substrate layer or substrate

42‧‧‧Photosensitive material

43‧‧‧Conductive seed layer

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

51‧‧‧ substrate

52‧‧‧Photosensitive materials

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

54‧‧‧Plating material, metal sheet

1A and 1B illustrate a general embossing method.

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

Fig. 3 is a cross section through an embossing tool of the conventional technique described in the aforementioned US 2016/0059442, said embossing tool having a three-dimensional microstructure and a precious metal (e.g. gold) plated on its surface.

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

Fig. 5 shows a method for forming an embossing tool according to the present invention.

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

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

Figures 1A and 1B show an embossing process using an embossing tool (11) with a three-dimensional microstructure (circled) on the surface of the embossing tool (11). As shown in FIG. 1B, the embossing tool (11) is applied to a curable embossing composition or a heat embossable material (12), and the embossing composition is cured (e.g., by radiation) or heat embossable After the embossing material becomes embossed by heat and pressure, the cured or heat embossed material is released from the embossing tool (see Figure 1B). However, when using conventional embossing tools, the cured or hot embossed material sometimes cannot be completely released from the tool due to the undesirably strong adhesion between the cured or hot embossed material and the surface of the embossed tool. In this case, there may be some cured or hot embossed material that is transferred to the surface of the embossing tool or stuck to the surface of the embossing tool, leaving an uneven surface on the object formed by this 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 heat embossed material and the support layer is weaker than the adhesion between the cured or heat embossed material and the surface of the embossing tool, then cure The release of hot or embossed material from the embossing tool may cause the object to separate from the support layer.

In some cases, objects may be formed on stacked layers, and in this case, if the adhesion between any two adjacent layers is greater than The adhesion is weaker, so the process of releasing the cured or hot embossed material from the embossing tool can cause splitting between the two layers.

These issues described above are particularly a concern when the cured embossed composition or heat embossed material does not adhere well to certain support layers. For example, if the support layer is a polymer layer, in the case where one of them is hydrophilic and the other is hydrophobic, the adhesion between the polymer layer and the cured or heat-embossed embossed composition is weak. Therefore, it is preferred that both the embossed 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 may include a thermoplastic material, a thermosetting material, or a precursor thereof. Examples of the thermoplastic or thermosetting material precursors may be polyfunctional acrylates or methacrylates, polyfunctional vinyl ethers, polyfunctional epoxides, and oligomers or polymers thereof.

A suitable hydrophilic composition for forming the embossed layer or support layer may include a polar oligomer or a polymer material. As described in US Patent No. 7,880,958, such a polar oligomer or polymer material may be selected from the group consisting of having at least one such as a nitro (-NO ₂ ), a hydroxyl (-OH), a carboxyl group (-COO), alkoxy (-OR, where R is alkyl), halogen (e.g. fluorine, chlorine, bromine or iodine), cyano (-CN), and sultanate (-SO ₃ ), etc. Group of oligomers or polymers. The glass transition temperature of the polar polymer material is preferably about 100 ° C or lower, and more preferably about 60 ° C or lower. Specific examples of suitable polar oligomers or polymer materials may include, but are not limited to, polyvinyl alcohol, polyacrylic acid, poly (2-hydroxyethyl methacrylate), polyhydroxy-functional polyester acrylates 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 (eg, SR494 from Sartomer Company).

method 1:

Figure 2 illustrates a method of a conventional technique 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 Fig. 2, this method can also be used to prepare an embossing cylinder. The term "embossed" drum or sleeve refers to a drum or sleeve having a three-dimensional microstructure on its outer surface. The term "embossing drum" 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 usually mounted on a smooth drum to allow the embossing sleeve to rotate.

The embossing roller or sleeve (21) is generally formed of a conductive material such as a metal (e.g., aluminum, copper, zinc, nickel, chromium, iron, titanium, or cobalt, etc.), or any of the foregoing metals The obtained 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 with a nickel layer sandwiched between the stainless steel and the outermost layer, and the outermost layer may be a copper layer.

Alternatively, the embossing roller or sleeve (21) may be formed of a non-conductive material having a conductive coating or a conductive seed layer on an outer surface thereof.

Before coating the photosensitive material (22) on the outer surface of the drum or sleeve (21), as shown in step B of FIG. 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 a roller or sleeve (21). The photosensitive material may be a positive tone, a negative tone, or a dual tone. The photosensitive material may be a chemically amplified photoresist. Coating can be performed using dip coating, spray coating, or ring coating. After drying and / or baking, the photosensitive material undergoes exposure to a radiation source, as shown in step C.

Alternatively, the photosensitive material (22) may be a dry film photoresist (which is usually commercially available), which 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 used to coat the roller or sleeve (21). Light-sensitive material or dry film photoresist (22) laminated on a roller or sleeve (21) for exposure. The light source may be continuous light or pulsed light. A photomask (24) is optionally used to define the three-dimensional microstructure to be formed. Depending on the microstructure, the exposure can be stepwise, continuous, or a combination thereof.

Prior to development after exposure, the photosensitive material (22) may undergo post-exposure processing, such as baking. Depending on the type of photosensitive material, exposed areas or unexposed areas are removed by using a developer. A roller or sleeve having a patterned photosensitive material (25) on its outer surface (as described in step D) before development (e.g., electroplating, electroless plating, physical vapor deposition, chemical vapor deposition or sputtering deposition) (Shown) 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.

Metals or alloys (for example, nickel, cobalt, chromium, copper, zinc, or alloys derived from any of the above metals) can be electroplated and / or electrolessly plated on a drum or sleeve. A plating material (26) is deposited in an area on the outer surface of the drum or sleeve that is not covered by the patterned photosensitive material. The deposition thickness is preferably smaller than the thickness of the photosensitive material, as shown in step E. By adjusting the plating conditions, such as the distance between the anode and the cathode (i.e. drum or sleeve) (if electroplating is used), the speed of rotation 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 less than 1%.

Alternatively, in the case of using electroplating to deposit the plating material (26), by inserting a non-conductive thickness uniformer between the cathode (i.e., the drum or the sleeve) and the anode, the deposit can be controlled at The thickness of the roller or sleeve over the entire surface is as described in US Patent No. 8,114,262.

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

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

As described in the aforementioned US 2016/0059442, it has been found that if the surface of an embossing tool is coated with a precious metal or an alloy thereof, the embossing tool may have improved release properties. In other words, as a post-processing step after the three-dimensional microstructure is formed on the surface of the embossing tool, a noble metal or its alloy (31) may be coated on the entire surface of the embossing tool, as shown in FIG. 3.

The term "precious metal" may include gold, silver, platinum, palladium, and other less common metals, such as ruthenium, rhodium, osmium, or iridium. Among these precious metals, the present inventors have found that gold and its alloys are most effective in reducing the adhesion between the solidified or hot-embossed material and the surface of the embossing tool. This advantage is particularly evident when the cured or heat embossed material has one or more of the following ingredients: polyacrylate, polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), polycarbonate Grease (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 acrylates or methacrylates are particularly preferred.

In the present invention, alloys of one or more noble metals and non-noble metals can also be used. Suitable non-noble metals in the alloy may include Without limitation, copper, tin, cobalt, nickel, iron, indium, zinc, or molybdenum. In alloys, there may also be more than one noble metal and / or more than one non-noble metal. The total weight percentage of non-noble metals in the alloy may be in the range of 0.001% -50%, and preferably in the range of 0.001% -10%.

Coating of precious metals or alloys 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 can be plated with acid chloride electrolytes at a temperature of 40-70 ° C and a pH range of 0.1-3. Alkaline electrolytes of some precious metals or their alloys are commercially available and can also be used in the present invention.

The noble metal or its alloy on the surface preferably has a thickness of the sub-micron order, so it does not cause any significant change to the profile of the microstructure. The thickness of the noble metal or its alloy may be in the range of 0.001-10 microns, and preferably in the range of 0.001-3 microns.

Method 2:

Alternatively, as described in the aforementioned US 2016/0059442, a three-dimensional microstructure may be formed on a flat substrate, as shown in FIG. 4.

In step A of FIG. 4, a photosensitive material (42) is applied on a substrate layer (41) (for example, a glass substrate). As described above, the photosensitive material may be a positive type, a negative type, or a dual type. The photosensitive material may be a chemically amplified photoresist. Coating can be performed 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) through a photomask (not shown).

Alternatively, the photosensitive material (42) may be a dry film photoresist (which is generally commercially available) laminated on 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. After development, before step C, the substrate layer (41) with 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 on the remaining photosensitive material (42) and on the substrate (41) in a region not occupied by the photosensitive material. The conductive seed layer is usually formed of silver.

In step D, a metal or alloy (44) (e.g., nickel, cobalt, chromium, copper, zinc, or an alloy obtained from any of the above metals) is electroplated and / or electrolessly plated on the surface covered by the conductive seed layer Surface, and a plating process is performed until there is a sufficient thickness of the plated material (h) on the patterned photosensitive material. The thickness (h) in FIG. 4 is preferably 25-5000 microns, and more preferably 25-1000 microns.

After plating, the plated material (44) is separated from the peeled substrate layer (41). The photosensitive material (42) is removed together with the conductive seed layer (43). The photosensitive material may be removed by a release agent 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-containing / nitrogen-containing mixture) or a commercially available chemical stripper, leaving only a metal sheet with a three-dimensional structure on one side and a flat surface on the other 44).

Precision polishing can be applied to the metal sheet (44), after which smooth shims 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 precious 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 shows the method of the invention. This method is similar to the method of FIG. 4 but simplified. Steps A and B of FIG. 5 are the same as the corresponding steps of FIG. 4. However, in step C of FIG. 5, a gold or alloy layer (53) thereof is applied instead of a conductive seed layer such as silver.

Therefore, in step E of FIG. 5, after separating the plated material (54) from the substrate (51), only the photosensitive material (52) needs to be removed, and the gold or alloy coating (53) is The metal sheet (54) with a three-dimensional structure on one 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 the method of the present 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 a micro-embossing method as described in US Patent No. 6,930,818. The micro-embossing method manufactures cup-shaped microcells separated by partition walls, such as MICROCUPS (registered trademark). These cells can be filled with an electrophoretic fluid containing charged particles dispersed in a solvent or solvent mixture. Filled micro The cells form an electrophoretic display film. When sandwiched between the electrode layers, the electrophoretic display film forms an electrophoretic device.

Examples

Example 1

In this example, two embossing tools (ie, male molds) were prepared. These molds are formed from nickel according to one of the methods described above.

The surface of one of these nickel molds is untreated. At a temperature of 50 ° C. and a pH of 5, the other nickel molds formed were further plated with a cyanide-based gold plating electrolyte to obtain a gold coating layer having a thickness of 0.5 μm on the surface thereof.

To test both embossing dies, a water-based polymer layer fluid and embossing composition were prepared. The polymer layer fluid was prepared according to US Patent No. 7,880,958, and it had polyvinyl alcohol as a main component. The embossed composition was prepared according to US Patent No. 7,470,386, and it had a polyfunctional acrylate as a main ingredient.

The polymer fluid was first coated on 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 coated on the polymer layer side of the PET substrate to a target dry thickness of 25 microns.

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

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

When using a gold-plated nickel mold, the solidified 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 example, several embossing tools (ie, male molds) were prepared. These molds are formed from nickel according to one of the methods described above. One of the nickel molds formed was further plated with 0.5 micron gold using the same electrolyte bath as the electrolyte bath used in Example 1.

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

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

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

Claims (15)

A method for preparing an embossing tool, the method comprising: a) forming a mold having a non-planar mold surface defining an outline of the embossing tool; b) depositing a gold alloy layer on the mold surface, wherein the The gold alloy includes gold and one or more non-noble metals, and the total weight of the one or more non-noble metals in the gold alloy is in the range of 0.001-50%; c) depositing a base metal on the gold alloy layer to Forming a base metal layer having a substantially flat surface away from the mold surface; and d) removing the die from the gold alloy layer and the base metal layer to form a three-dimensional structure on one side and the other side Embossing tool with a substantially flat surface. The method according to 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 the exposed area of the photoresist or Unexposed area. The method of claim 1, wherein the one or more non-noble metals are selected from the group consisting of copper, tin, cobalt, nickel, iron, indium, zinc, and molybdenum. The method of claim 1, wherein the total weight of the non-noble metal in the alloy is in the range of 0.001-10%. The method of claim 1, wherein the gold alloy layer has a thickness of 0.001 to 10 micrometers. The method of claim 1, wherein the gold alloy layer has a thickness of 0.001 to 3 micrometers. The method of claim 1, wherein the base metal includes any one or more of nickel, cobalt, chromium, copper, and zinc. The method of claim 1, wherein the minimum thickness of the base metal layer is in a range of 25-5000 microns. The method of claim 1, wherein the minimum thickness of the base metal layer is in a range of 25-1000 microns. An assembly for preparing an embossing tool, the assembly comprising: a mold having a non-planar mold surface; a gold alloy layer disposed on the mold surface and conforming to the mold surface, wherein the The gold alloy contains gold and one or more non-noble metals, and the total weight of the one or more non-noble metals in the gold alloy is in the range of 0.001-50%; and A base metal layer on the opposite side, the base metal layer having a three-dimensional structure in contact with the gold alloy layer and having a substantially flat surface on its side remote from the gold alloy layer. The assembly according to claim 11, wherein the one or more non-precious metals are selected from the group consisting of copper, tin, cobalt, nickel, iron, indium, zinc, and molybdenum. The assembly according to claim 11, wherein the gold alloy layer has a thickness in a range of 0.001 to 10 micrometers. The assembly of claim 11, wherein the base metal comprises any one or more of nickel, cobalt, chromium, copper, and zinc. The assembly according to claim 11, wherein the minimum thickness of the base metal layer is in a range of 25-5000 microns.