This invention relates to photochemical etching to form cavities on a substrate.
Photochemical etching commonly involves placing a mask over an etchable substrate that has been coated with a layer of photoresist material and then exposing the photoresist material. If negative photoresist is used, the exposed areas of the photoresist become cured and resistant to chemical etchant. Areas of the photoresist that are not exposed are washed away using a solvent leaving a portion of the underlying substrate uncovered and ready for etching. If positive photoresist is used, then exposed areas are weakened and are easily washed away.
Once the photoresist mask has been applied, chemical etchant is applied to the substrate to create a cavity in the uncovered areas of the substrate. Often applications, such as the creation of microhook molds for hook fasteners, seek to create very small molds that have complex shapes. U.S. Pat. No. 5,900,350 describes a method for creating microhook molds for hook fasteners and is fully incorporated herein by reference.
In one aspect, the invention features a method of forming a cavity on a substrate (e.g., a microhook mold plate, semiconductor die, optical lens plate, etc.) that includes forming on the substrate a layer of photoresist material that includes a pattern of etchant-passing and etchant-blocking regions. Chemical etchant is applied to the substrate such that etchant passed through the etchant-passing regions undercuts the etchant-blocking regions to form a single contiguous cavity on the substrate in the area beneath the pattern of etchant-passing and etchant-blocking regions.
In some configurations, forming the patterned layer of photoresist material on the first mold plate includes applying photoresist material to at least one side of the substrate, placing over the photoresist material a mask having a shaded region adapted to partially block exposure of photoresist material disposed beneath the shaded region, and exposing the photoresist material to light through the mask. If negative photoresist material is used, the unexposed areas are removed to create the layer of photoresist material having a pattern of etchant-passing and etchant-blocking regions. If positive photoresist material is used, exposed areas are removed to create the patterned layer. The etchant-passing regions of the photoresist in some configurations may include apertures bounded by etchant-blocking regions, and the etchant-blocking regions may include discrete, bounded areas of photoresist material surrounded by etchant-passing regions void of photoresist material. The pattern of the etchant-passing and etchant-blocking regions may be uniform to form a cavity having a substantially uniform depth or may be non-uniform to form a cavity having a variable depth. In some configurations the pattern of etchant-passing and etchant-blocking regions may be selected to form a cavity that extends completely through the substrate when etchant is applied.
In some configurations, the substrate may be a mold plate adapted to be assembled with one or more additional plates to define a mold for a hook or stem on a hook component of a touch fastener.
In another aspect, the invention features a method of forming a cavity on a substrate that includes applying a photoresist material to the substrate, placing over the photoresist material a mask that has a shaded region adapted to partially block exposure of photoresist material disposed beneath the shaded region, exposing the photoresist material to light through the mask, and applying a chemical etchant to the plate such that a single contiguous cavity is formed on the substrate in the area corresponding to the shaded region of the mask.
In another aspect, the invention features a method of forming a sheet-form product having an array of projections extending from a broad surface that includes forming a cavity on a first mold plate by forming a layer of photoresist material that includes a pattern of etchant-passing and etchant-blocking regions on at least one side of the first mold plate. Chemical etchant is applied to the plate such that the etchant undercuts the etchant-blocking regions to form a single contiguous cavity on the plate in an area beneath the pattern of etchant-passing and etchant-blocking regions. The first mold plate is assembled with one or more additional plates to form a mold, the cavity cooperating with a surface of an adjacent plate to at least partially define one of an array of mold cavities extending inward from a surface of the mold. Resin is applied to the surface of the mold and forcing some of the resin into the mold cavities to form an array of projections extending integrally from a layer of resin formed on the mold surface.
In some configurations, the formation of the patterned layer of photoresist material on the first mold plate includes applying photoresist material to at least one side of the plate, placing over the photoresist material a mask having a shaded region adapted to partially block exposure of photoresist material disposed beneath the shaded region, and exposing the photoresist material to light through the mask. If negative photoresist material is used, the unexposed areas are removed to create the layer of photoresist material having a pattern of etchant-passing and etchant-blocking regions. If positive photoresist material is used, exposed areas are removed to create the patterned layer. The etchant-passing regions of the photoresist in some configurations may include apertures bounded by etchant-blocking regions, and the etchant-blocking regions may include discrete, bounded areas of photoresist material surrounded by etchant-passing regions void of photoresist material. The pattern of the etchant-passing and etchant-blocking regions may be uniform to form a cavity having a substantially uniform depth or may be non-uniform to form a cavity having a variable depth.
In some configurations, the cavity formed on the first mold plate is in the shape of a hook or a stem for use in a hook component of a touch fastener.
In another aspect, the invention features a method of forming a mold form for making a sheet-form product having an array of projections extending from a broad surface that includes applying a photoresist material to at least one side of a first mold plate, placing over the photoresist material a mask having a shaded region adapted to partially block exposure of the photoresist material disposed beneath the shaded region, and exposing the photoresist material to light through the mask. Chemical etchant is applied to the plate such that a single contiguous cavity is formed on the plate in the area corresponding to the shaded region of the mask. The first mold plate is assembled with one or more additional mold plates to form a mold such that the cavity cooperates with a surface of an adjacent plate to at least partially define one or an array of mold cavities extending inward from a surface of the mold.
In some configurations, the shaded region of the mask includes a pattern of light-blocking regions and light-passing regions (e.g., apertures bounded by light-blocking regions or discrete, bounded areas of mask material surrounded by light-passing regions void of mask material) printed on a non-opaque sheet (e.g., Mylar® film) using a high-resolution plotter or printer. The shaded region of the mask may include an area having a uniform exposure density such application of the chemical etchant to the plate results in a cavity having an approximately uniform depth in an area corresponding to the shaded region of the mask having a uniform exposure density. The shaded region may include an area having a non-uniform exposure density such that application of the chemical etchant to the plate results in a cavity having a variable depth in the area corresponding to the shaded region of the mask having a non-uniform exposure density. The mask may also include a second region adapted to completely block exposure of the photoresist material disposed beneath the second region.
In some configurations, the etchable plate defines a perimeter having some cross-sectional shape (e.g., circular, rectangular, etc) and the cavities are etched along the perimeter of the plate. The cavity formed in the plate may have a hook shape such as one that includes a base and a tip and a cross-sectional area that tapers from the base of the cavity to the tip. The cavity may also have hook shape that includes a pedestal portion contiguous to a crook portion and at least one barb protruding from either the pedestal portion or the crook portion. In other configurations, the cavity may have a stem shape.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
Referring to
Referring to
In one implementation, there are approximately 24 hook members per lineal inch (9.44 hook members per lineal centimeter). The hook members are preferably spaced apart laterally (i.e., in the cross-machine direction) a distance 36 of about 0.008 inches (0.203 millimeters), and the pedestals 12 have a maximum thickness, W2, of about 0.006 inches (0.152 millimeters). This yields a density in the cross-machine direction of approximately 71 hook members per inch (27.95 members per linear centimeter). Hence, there are on the order of 1700 hook members per square inch (263.5 members per square centimeter) in this implementation.
As shown in
Referring to
The mold cavities 10 are formed along the periphery of the tool rings by a chemical etch process. In one implementation, a tool ring formed of 17-7 PH stainless steel or other material susceptible to chemical etchant is coated with a layer of negative photoresist material. A mask, shown in
As shown in
Similarly, as shown in
In one implementation, the shaded mask, such as mask 60 shown in
The use of a shaded photoresist mask in a photo-etching process provides a cost effective technique for creating hooks with a wide variety of shapes and features. For example, as shown in
Similarly, as shown in
Because the crook portion of a hook is often substantially narrower than its base, a mold cavity etched with a uniformly shaded mask (e.g., a completely blacked-out mask) will often be shallower at the tip than at the base, thus creating a hook that is narrower at its tip than at its base. This etching difference can be compensated using a mask, such as mask 104 shown in
Referring to
As shown in
Shaded masks may be used to fabricate mold plates for a hook component of a touch fastener that employs stems and stem-like hooks described in U.S. application Ser. No. 10/455,240 filed Jun. 4, 2003, entitled “Hook and Loop Fastener” to Mark A. Clarner, George A. Provost, and William L. Huber, which is fully incorporated herein by reference. For example, as shown in
As shown in
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, in each of the above examples negative photoresist is used. While negative photoresist is currently preferred from a cost perspective, positive photoresist may also be used. When positive photoresist is used, areas that are exposed are weakened and become soluble and thus easily removed and the remaining portion of the photoresist (i.e., the area covered by a mask) remains on the plate. Therefore, masks adapted for use with positive photoresist will be the negative image of a mask adapted for use with negative photoresist.
As explained in detail in U.S. Pat. No. 5,900,350, hooks formed from mold rolls, such as roll 42 shown in
Additionally, the mold cavities need not be formed on a tool ring adapted to produce hook fasteners by passing molten resin into a nip formed between a cooled molding roll and a pressure-applying roll as illustrated in
Moreover, the techniques described for fabricating a microhook mold cavity may be extended to a wide variety of other photochemical etching applications in which a cavity is etched on a substrate, such as forming a lens from a glass substrate, fabricating a tapered disk drive data head from a metallic substrate, or fabricating an integrated circuit from a semiconductor substrate.
Accordingly, other embodiments are within the scope of the following claims.