JP7794222B2 - Patterned films and articles - Google Patents

Description

The present invention relates to a patterned film.

Various methods have been reported for forming patterned films, including those using active energy rays such as ultraviolet rays or electron beams, and those using self-assembling materials such as block copolymers.

JP 2009-260330 A Japanese Patent Application Laid-Open No. 2016-197176

The objective of the present invention is to provide a patterned film with a special structure.

According to a first aspect of the present invention, there is provided a patterned film including a plurality of portions having different pattern densities, one or more of which are porous, and one or more of which have a lower pattern density and porosity than one of the porous portions.

According to a second aspect of the present invention, there is provided an article comprising the pattern film according to the first aspect and a substrate supporting the pattern film.

The present invention provides a patterned film with a special structure.

1 is a cross-sectional view schematically illustrating a portion of an article according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view schematically illustrating another portion of the article according to the first embodiment of the present invention. FIG. 1 is a cross-sectional view schematically illustrating an example of a state in which a film made of an emulsion is formed on a substrate. FIG. 10 is a cross-sectional view schematically illustrating an example of a state in which a particulate layer made of a hardened product of dispersed particles is formed in an area irradiated with ultraviolet light by patterned irradiation of ultraviolet light. 10A and 10B are cross-sectional views illustrating an example of a state in which coalescence of dispersed particles occurs in non-irradiated areas by initiating removal of the second liquid from the film. FIG. 10 is a cross-sectional view schematically illustrating an example of a state in which coalescence of dispersed particles further progresses in a non-irradiated region, and the coalesced dispersed particles penetrate and diffuse into a granular layer made of a hardened product of the dispersed particles. FIG. 10 is a cross-sectional view schematically illustrating an example of a state in which removal of the second liquid has been completed and the coalescence of dispersed particles has completely moved to the granular layer. FIG. 10 is a cross-sectional view schematically illustrating an example of a state in which the uncured first liquid is cured by irradiating the entire surface with ultraviolet rays. FIG. 4 is a cross-sectional view schematically illustrating a portion of an article according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view schematically illustrating another portion of the article according to the second embodiment of the present invention. FIG. 10 is a cross-sectional view schematically illustrating a portion of an article according to a third embodiment of the present invention. FIG. 10 is a cross-sectional view schematically illustrating another portion of the article according to the third embodiment of the present invention. Graph showing particle size distributions of the first to third emulsions prepared in the examples. 10 is a scanning electron microscope photograph showing a cross section of a line and space pattern formed using the first emulsion with varying line widths and space widths. 10 is a scanning electron microscope photograph showing a cross section of a line and space pattern formed using the second emulsion with varying line and space widths. 10 is a scanning electron microscope photograph showing a cross section of a line and space pattern formed using the third emulsion with varying line and space widths. 16 is a graph showing a concentration distribution obtained by image analysis of a part of the photograph of FIG. 15 . 17 is a graph showing the influence of the ratio of line width to space width on the standard deviation of the concentration distribution obtained by image analysis of the photographs of FIGS. 14 to 16 . 10 is an optical microscope photograph showing the top surface of a line portion of a line and space pattern formed using the first to third emulsions with different line widths and space widths. 20 is a graph showing the effect of the ratio of line width to space width on the average density obtained by image analysis of the photograph of FIG. 19 . 20 is a graph showing the relationship between the standard deviation of the density distribution obtained by image analysis of the photographs of FIGS. 14 to 16 and the average density value obtained by image analysis of the photograph of FIG. 19 .

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below embody one of the above aspects in more detail. Elements having the same or similar functions will be given the same reference numerals, and duplicate descriptions will be omitted.

[First embodiment]
Fig. 1 is a cross-sectional view schematically showing a part of an article according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view schematically showing another part of the article according to the first embodiment of the present invention.

The article shown in FIGS. 1 and 2 includes a substrate 1 and a patterned film 2 .
The material and shape of the substrate 1 are not limited. The substrate 1 preferably has a smooth surface. For example, a film or a sheet can be used as the substrate 1.

The pattern film 2 is supported by the substrate 1. In the example shown in Figures 1 and 2, the pattern film 2 forms a line and space pattern. The pattern film 2 may also form a pattern other than a line and space pattern.

The pattern film 2 includes a plurality of portions with different pattern densities. Here, the term "pattern density" means the ratio of the area of the region where the pattern film 2 is located to the area of the region where the pattern film 2 and its openings are located. For example, when the pattern film 2 forms a line and space pattern, the pattern density of a certain portion is the ratio W _L /(W L +W S ) of the width W _L of the line portion to the sum W _L +W _S of the width W _L of the line _portion and the width W _S of the _space portion in this portion.

Among the multiple portions included in the pattern film 2, one or more are porous. Figure 2 illustrates an example of such a portion. The portion in Figure 2 has a larger ratio W _L /(W _L +W _S ) than the portion in Figure 1. That is, the portion in Figure 2 has a higher pattern density than the portion in Figure 1.

Of the multiple portions included in the patterned film 2, one or more have a lower pattern density and porosity than one of the porous portions. Such portions may be porous or non-porous. Figure 1 illustrates an example of a non-porous portion.

The pattern film 2 may include three or more portions with different pattern densities. In this case, one or more portions may be porous and two or more portions may be non-porous. Alternatively, two or more portions may be porous and one or more portions may be non-porous. In this case, of these three or more portions, the portion with the lower pattern density preferably has a porosity equal to or less than that of the portion with the higher pattern density. According to one example, the portion with a pattern density of 0.5 or less is non-porous, and the portion with a pattern density of 0.6 or more is porous.

This porosity correlates with the standard deviation of the concentration distribution obtained by image analysis of the cross section of the pattern film 2. The standard deviation of the concentration distribution obtained by image analysis of the cross section of a portion of the pattern film 2 where the pattern density is 0.6 or more is preferably 5 or more, and more preferably 10 or more.

The ratio of the maximum to minimum standard deviations obtained for multiple areas with different pattern densities is preferably 4.3 or greater, and more preferably 20.3 or greater. If this ratio is small, the difference in porosity is also small. There is no upper limit to this ratio, but it is usually 30.0 or less.

This image analysis uses the image processing software Image J. Specifically, in each image of the cross section of the patterned film, an area that does not contain areas that would result in contrast noise, such as fractures, is selected. Then, for each selected area, the standard deviation of the density distribution in a 256-level grayscale is extracted as a feature. If there are no pores (gaps between particles) in the selected area, the standard deviation will be small; the more pores there are, i.e., the higher the porosity, the larger the standard deviation. Therefore, the above ratio serves as an indicator of the porosity ratio.

The porosity of each portion of the pattern film 2 correlates with the light scattering properties of that portion. The porosity of each portion of the pattern film 2 also correlates with the pattern density of that portion. Therefore, the light scattering properties of each portion of the pattern film 2 correlate with the pattern density of that portion. Specifically, for multiple portions with different pattern densities, the average value of the concentration distribution obtained by image analysis of their surfaces has a positive correlation with the pattern density of those portions. This image analysis is performed using the same method as described above.

For multiple areas with different pattern densities, the average value of the concentration distribution obtained by image analysis of the surfaces is positively correlated with the light scattering properties of those areas. The light scattering properties of each area of the pattern film 2 are positively correlated with the porosity of that area. Therefore, for multiple areas with different pattern densities, the standard deviation of the concentration distribution obtained by image analysis of the cross sections of those areas is positively correlated with the average value of the concentration distribution obtained by image analysis of their surfaces. This image analysis is performed using the same method as described above.

The pattern film 2 contains a cured product of dispersed particles 21b1, which will be described later, and a polymerized phase 21b2.

The hardened dispersed particles (21b1) form a particulate layer (21b). The particulate layer (21b) is a porous layer.

The polymerized phase 21b2 is located in the gaps between the particles contained in the granular layer 21b. In areas of the pattern film 2 with lower pattern density, more of these gaps are filled with the polymerized phase 21b2 than in areas with higher pattern density. On the other hand, in areas of the pattern film 2 with higher pattern density, more of these gaps remain unfilled with the polymerized phase 21b2 than in areas with lower pattern density. This results in the difference in porosity described above.

The pattern film 2 is made of, for example, a polymer material. Furthermore, the pattern film 2 is made of, for example, the same material throughout. According to one example, the cured material 21b1 and the polymerized phase 21b2 are made of the same polymer material. In this case, the cured material 21b1 and the polymerized phase 21b2 may have the same degree of polymerization or different degrees of polymerization. In the latter case, the cured material 21b1 may have a higher degree of polymerization than the polymerized phase 21b2.

Note that in Figures 1 and 2, the polymerized phase 21b2 is not present in the openings of the pattern made of the granular layer 21b. The polymerized phase 21b2 may be present in the openings of the pattern made of the granular layer 21b in the form of a layer thinner than the granular layer 21b.

This pattern film 2 can be formed by, for example, the method described below (called the Emulsion Transforming Method for Patterning (ET method)).
<Preparation of emulsion>
First, an emulsion is prepared that contains dispersed particles containing a first liquid that is cured by irradiation with active energy rays, and a dispersion medium that contains a second liquid that is not cured by irradiation with active energy rays.

The emulsion may be an oil-in-water (O/W) emulsion or a water-in-oil (W/O) emulsion.

The dispersed particles contain a first liquid that hardens when exposed to active energy rays. Examples of active energy rays include visible light, ultraviolet light, electron beams, and X-rays. The first liquid can be, for example, an acrylic monomer or oligomer, a methacrylic monomer or oligomer, an epoxy monomer or oligomer, or a mixture containing one or more of these. Due to the advantages of a wide range of options and the flexibility to adjust physical properties, it is preferable to use an acrylic monomer or oligomer, or a methacrylic monomer or oligomer as the first liquid. For example, trimethylolpropane triacrylate can be used as the first liquid. The proportion of the monomer and oligomer in the first liquid is, for example, 30 to 100% by mass.

Furthermore, there are more lipophilic liquids that harden when exposed to active energy rays than hydrophilic ones. Therefore, O/W emulsions offer greater freedom in material selection than W/O emulsions.

The dispersion medium contains a second liquid that does not harden when exposed to actinic energy rays. If the first liquid is lipophilic, the second liquid can be a hydrophilic liquid, such as water, a lower alcohol such as methanol or ethanol, or a mixture thereof. On the other hand, if the first liquid is hydrophilic, the second liquid can be a lipophilic liquid, such as an isoparaffin solvent or mineral spirits.

The size of the dispersed particles depends on the size of the pattern to be formed, but it is preferable for them to have an average particle size of 0.5 μm to 0.5 mm. Here, "average particle size" refers to the weight-average diameter obtained by particle size distribution measurement using a laser diffraction/scattering method. If the dispersed particles have this size, the uncured first liquid can efficiently penetrate into the gaps between the particles in a later process.

The proportion of dispersed particles in the emulsion is preferably 25% by mass or more. When the dispersed particles occupy this proportion in the emulsion, the temperature of the area irradiated with active energy rays can be increased by effectively utilizing the heat of polymerization, thereby destabilizing the dispersion state of the dispersed particles containing the first liquid and simultaneously forming an aggregate layer. The upper limit of the proportion of dispersed particles in the emulsion is not particularly limited, as long as it is within a range that does not cause phase inversion of the emulsion. According to one example, this proportion is 70 to 80% by mass or less.

The first liquid may further contain a photopolymerization initiator. As the photopolymerization initiator, a known photopolymerization initiator, such as an alkylphenone-based photopolymerization initiator, can be used. An example of an alkylphenone-based photopolymerization initiator is 1-hydroxycyclohexyl phenyl ketone. The first liquid may contain the photopolymerization initiator in an amount of, for example, 0.1 to 10 parts by mass per 100 parts by mass of the total amount of the monomer and oligomer.

When the emulsion is, for example, an O/W type, the dispersed particles may contain a hydrophobe in addition to the first liquid. Examples of hydrophobes include higher alcohols with low solubility in water, such as cetyl alcohol, hexadecane, polymerizable monomers with relatively large hydrocarbon chain molecular weights, such as lauryl methacrylate and stearyl methacrylate, hydrophobic dyes, and polymers, such as polymethyl methacrylate and polystyrene. The hydrophobe serves to stabilize the emulsion. The hydrophobe can be included in an amount of, for example, 0.1 to 10 parts by weight per 100 parts by weight of the first liquid.

The dispersion medium may further contain a surfactant. Examples of surfactants that can be used include those commercially available for use in emulsion polymerization. Examples of surfactants that can be used include sulfosuccinate surfactants such as dioctyl sodium sulfosuccinate. The emulsion may contain the surfactant in an amount of, for example, 0.1 to 5.0% by mass, based on the total mass of the emulsion.

In the case of O/W emulsions, the dispersion medium generally contains a surfactant to ensure emulsification and the stability of the dispersed particles. Furthermore, O/W emulsions can also contain water-soluble polymers, cellulose nanofibers, etc. in the dispersion medium to improve the emulsion's long-term storage stability. Furthermore, O/W emulsions can also contain viscosity modifiers and antifoaming agents in the dispersion medium, if necessary.

On the other hand, in the case of W/O type emulsions, in order to prepare stable emulsions, the dispersion medium can contain a nonionic surfactant or a polymeric dispersion stabilizer with an appropriate hydrophilic-lipophilic balance (HLB) value. If necessary, it is also effective for W/O type emulsions to contain an ionic surfactant in the dispersion medium.

Emulsions can be prepared using known emulsification and dispersion techniques, such as paint shakers, ultrasonic homogenizers, colloid mills, homogenizers, and membrane emulsification methods.

<Film formation>
Next, a film made of the emulsion is formed on a substrate. Hereinafter, the "film made of emulsion" is also referred to as a liquid film. Specifically, the liquid film can be formed on the substrate by applying the emulsion onto the substrate. Any substrate can be used as the substrate, and for example, a film or a sheet can be used.

The coating method is not particularly limited, but an appropriate coating method, such as die coating, comma coating, or curtain coating, can be selected depending on the thickness of the liquid film. The thickness of the liquid film can be, for example, 10 to 3,000 μm. Furthermore, when applying a small amount of emulsion to form a liquid film over a small area, a dispenser or the like can be used as needed.

Figure 3 shows a schematic diagram of an example of a film made of an emulsion formed on a substrate. In Figure 3, a film 2a made of an emulsion consisting of dispersed particles 21a and a dispersion medium 22 is formed on a substrate 1.

<Irradiation with active energy rays>
Next, the formed film is irradiated with active energy rays in a pattern such that the patterned film 2 finally obtained contains a plurality of portions with different pattern densities.

As mentioned above, examples of active energy rays include ultraviolet rays, electron beams, and X-rays. Pattern irradiation can be carried out, for example, by selectively irradiating the active energy rays through a mask or by selectively irradiating the laser beam.

By irradiating the active energy rays in a pattern, the first liquid contained in the dispersed particles is polymerized and hardened in the areas irradiated with the active energy rays (hereinafter also referred to as the irradiated areas). This allows the formation of a granular layer made of hardened dispersed particles.

Figure 4 shows a schematic example of a state in which a granular layer made of hardened dispersed particles is formed in the area irradiated with ultraviolet light through patterned irradiation.

As shown in Figure 4, in the area irradiated with ultraviolet light, the first liquid contained in the dispersed particles 21a is polymerized and hardened, and the dispersed particles 21a become hardened dispersed particle material 21b1. The hardened dispersed particle material 21b1 aggregates and stacks, resulting in the formation of a granular layer 21b made of hardened dispersed particle material 21b1. The pattern made of this granular layer 21b includes multiple portions with different pattern densities, just like the final pattern film 2.

In the areas irradiated with ultraviolet light, the second liquid contained in the dispersion medium 22 does not harden, so the dispersion medium 22 exists within the granular layer 21b, specifically in the gaps between the hardened particles 21b1. On the other hand, in the areas not irradiated with ultraviolet light (hereinafter also referred to as non-irradiated areas) in Figure 4, the first liquid contained in the dispersion particles 21a remains unhardened.

The inventors believe the reason for the aggregation mechanism of the cured material 21b1 in the irradiated area is as follows.

When exposed to active energy rays, the dispersed particles 21a generate heat as they polymerize, causing the temperature of the irradiated area to rise. This temperature rise causes the surfactant that had been adsorbed to the surface of the dispersed particles 21a and stabilized the dispersion of the dispersed particles 21a to desorb. This reduces the surface potential of the dispersed particles 21a as polymerization progresses. As a result, the dispersion of the dispersed particles 21a or their cured product 21b1 becomes unstable, promoting particle aggregation. Furthermore, as the particles aggregate and come into contact with each other, polymerization crosslinking may occur between the particles.

Furthermore, this aggregation is completed before the surfactant that has been released due to the temperature rise caused by the heat of polymerization is re-adsorbed onto the particles. As a result, the aggregated particles maintain their aggregated state without being re-dispersed.

Aggregation of the cured material 21b1 in the irradiated area may be promoted by incorporating a crosslinking agent into the dispersion medium in advance. This facilitates crosslinking between particles upon irradiation with active energy rays, thereby promoting particle aggregation.

<Removal of second liquid>
After irradiation with active energy rays, at least a portion of the second liquid is removed from the film. In this step, it is sufficient to remove at least a portion of the second liquid, but it is also possible to remove all of the second liquid. Removal of the second liquid can be carried out, for example, by drying the film. Drying is preferably carried out until the amount of the second liquid is 30% by mass or less, more preferably 5% by mass or less, of the amount of the second liquid immediately after forming the liquid film. Removal of the second liquid can be carried out by leaving the film at room temperature, but is preferably carried out by heating and drying the film. Heat drying can be carried out, for example, by heating the film at a temperature in the range of 40 to 100°C for 0.1 to 1 hour. Removal of the second liquid can move at least a portion of the uncured first liquid from the region not irradiated with active energy rays to the granular layer consisting of the cured product of the dispersed particles.

In this process, the removal of the second liquid causes at least a portion of the uncured first liquid to migrate from the non-irradiated area to the granular layer consisting of the cured dispersed particles. The migration of the uncured first liquid from the non-irradiated area to the granular layer may be carried out so that all of it migrates to the granular layer, or so that only a portion of it migrates to the granular layer.

In this method, there is no need to perform a development step after irradiation with active energy rays, i.e., to remove the uncured first liquid using a developer.

Figures 5 to 7 show schematic examples of changes in the state of the film caused by the removal of the second liquid. Figure 5 shows a schematic example of a state in which coalescence of dispersed particles occurs in non-irradiated areas as the removal of the second liquid from the film begins. Figure 6 shows a schematic example of a state in which coalescence of dispersed particles progresses further in non-irradiated areas, and the coalesced dispersed particles penetrate and diffuse into the granular layer made of hardened dispersed particles. Figure 7 shows a schematic example of a state in which the removal of the second liquid is complete and the coalesced dispersed particles have completely migrated into the granular layer.

When a portion of the second liquid contained in the dispersion medium 22 is removed from the film 2a, as shown in Figure 5, the second liquid that filled the gaps between particles in the granular layer 21b decreases in the irradiated area, while in the non-irradiated area, as the second liquid decreases, the dispersed particles 21a coalesce, forming coalescence 21a'. Then, as shown in Figure 6, the uncured first liquid that forms these coalescences 21a' penetrates into the gaps in the granular layer 21b and diffuses into the granular layer 21b. This penetration and diffusion is thought to occur due to capillary force.

Once the removal of the second liquid is complete, the migration of the uncured first liquid from the non-irradiated areas to the granular layer 21b is complete. As a result, for example, the structure shown in Figure 7 is obtained. Note that when the second liquid is completely removed from the film, the only liquid remaining in the film is, for example, the liquid that makes up the dispersed particles 21a or their combined particles 21a'.

As described above, the pattern formed by the granular layer 21b includes multiple areas with different pattern densities, similar to the final pattern film 2. As explained below, the amount of the first liquid that penetrates into the gaps within the granular layer 21b differs between areas with lower pattern density and areas with higher pattern density.

That is, around areas with lower pattern density, there is a larger non-irradiated area, and therefore a larger amount of the first liquid. On the other hand, around areas with higher pattern density, there is a smaller non-irradiated area, and therefore a smaller amount of the first liquid.

As a result, in areas with lower pattern density, a larger amount of the first liquid penetrates into the gaps in the granular layer 21b. For example, the entire gap is filled with the first liquid.

On the other hand, in areas with higher pattern density, a smaller amount of the first liquid penetrates into the gaps in the granular layer 21b. For example, only a portion of the gaps is filled with the first liquid.

<Establishing the pattern>
Finally, the uncured first liquid contained in the film from which the second liquid has been removed is cured. The uncured first liquid can be cured, for example, by irradiating the entire film with active energy rays. This forms a patterned film.

Figure 8 shows a schematic diagram of an example of the state in which the uncured first liquid has been cured by irradiating the entire surface with ultraviolet light. As shown in Figure 8, when the entire film is irradiated with ultraviolet light, the uncured first liquid is cured by polymerization. As a result, a polymerized phase 21b2 is formed. Furthermore, in the cured material 21b1 that constitutes the particulate layer 21b, further polymerization progresses due to ultraviolet light irradiation. As a result, a patterned film 2 consisting of the cured material 21b1 of the dispersed particles and the polymerized phase 21b2 is formed.

As described above, before full-surface irradiation with ultraviolet light, in the granular layer 21b, the gaps in the areas with lower pattern density are entirely filled with the first liquid, while in the areas with higher pattern density, only some of the gaps are filled with the first liquid. Therefore, in the pattern film 2 obtained by full-surface irradiation with ultraviolet light, the areas with higher pattern density have a higher porosity than the areas with lower pattern density.

As mentioned above, the uncured first liquid can be cured after all of the uncured first liquid present in the non-irradiated area has migrated from this area to the granular layer. Alternatively, the uncured first liquid can be cured when only a portion of the uncured first liquid present in the non-irradiated area has migrated from this area to the granular layer. For example, the entire film can be irradiated with active energy rays before the second liquid is completely removed from the film (i.e., at a stage in the middle of the first liquid in the non-irradiated area penetrating and diffusing into the granular layer), such as at the stage shown in Figure 6. In this way, a patterned film can be obtained in which the non-irradiated area has a thickness and the irradiated area is thicker than the non-irradiated area.

<Effects>
As described above, the pattern film 2 includes a plurality of portions with different pattern densities. Of these portions, one or more are porous, and the other one or more have lower pattern densities and porosities. Therefore, in an article including the pattern film 2, the regions corresponding to the portions with higher pattern densities have higher light scattering properties than the regions corresponding to the portions with lower pattern densities. Therefore, this article can display, for example, images or patterns by utilizing the difference in light scattering properties.

Furthermore, this pattern film 2 can be formed in a self-organizing manner by simply irradiating the emulsion film with active energy rays in a pattern and then removing the second liquid. This method does not require a guide pattern to be formed on the substrate in advance, nor does it require a development process. Therefore, this pattern film 2 can be produced using a simple method.

While conventional technology has only been able to achieve pattern sizes of, for example, a line width of several nanometers to several hundred micrometers and a height difference of several nanometers to several hundred micrometers, the above method makes it possible to achieve a wide range of pattern sizes. For example, the above method makes it possible to form pattern films with large line widths and height differences, such as line widths on the order of micrometers to millimeters and height differences on the order of micrometers to millimeters. As an example, the above method can form pattern films with line widths in the range of 10 micrometers to 5 mm and height differences in the range of 10 micrometers to 2 mm.

Furthermore, the above method allows for excellent control over the shape and size of patterns, making it possible to form patterned films of various shapes and sizes.

Second Embodiment
Fig. 9 is a cross-sectional view schematically showing a part of an article according to a second embodiment of the present invention, and Fig. 10 is a cross-sectional view schematically showing another part of an article according to the second embodiment of the present invention.

The article according to the second embodiment is similar to the article according to the first embodiment, except for the following points. That is, the article according to the second embodiment further includes a layer 3 attached to the substrate 1 with the pattern film 2 sandwiched therebetween, as shown in Figures 9 and 10. The layer 3 may have a single-layer structure or a multi-layer structure. According to one example, the layer 3 serves as a protective layer that protects the pattern film 2 from damage.

Layer 3 is attached to substrate 1 and pattern film 2 by adhesive layer 4. Adhesive layer 4 is made of an adhesive or pressure-sensitive adhesive. Adhesive layer 4 fills the gaps in pattern film 2. Typically, adhesive layer 4 has a different refractive index from pattern film 2, so this article also exhibits the same optical effect as the article according to the first embodiment.

The adhesive layer 4 does not have to fill the gaps in the pattern film 2. An article having such a structure also exhibits the same optical effects as the article according to the first embodiment.

Furthermore, in this article, the ease with which layer 3 peels off may differ between locations corresponding to areas with higher pattern density and locations corresponding to areas with lower pattern density. For example, the adhesive strength to layer 3 may differ between areas with higher pattern density and areas with lower pattern density due to differences in their structures. Furthermore, the ease with which brittle fracture may occur may differ between areas with higher pattern density and areas with lower pattern density due to differences in their structures. Therefore, this article can also be used, for example, as a brittle label, in which one of the layers will undergo brittle fracture when an attempt is made to peel it off from another article to which it is attached.

Instead of attaching layer 3 via adhesive layer 4, a coating liquid may be applied to substrate 1 and pattern film 2, and the coating may then be cured. The layer obtained in this manner can also be used, for example, as a protective layer.

[Third embodiment]
Fig. 11 is a cross-sectional view schematically showing a part of an article according to a third embodiment of the present invention, and Fig. 12 is a cross-sectional view schematically showing another part of the article according to the third embodiment of the present invention.

The article according to the third embodiment is similar to the article according to the first embodiment, except for the following points. That is, the article according to the third embodiment further includes a colorant 5 carried on the pattern film 2, as shown in Figures 11 and 12. The colorant 5 is, for example, a dye, a pigment, or a combination thereof.

A portion of the pattern film 2 with a higher pattern density carries a larger amount of colorant 5 than a portion with a lower pattern density. Therefore, in this article, the areas corresponding to the higher pattern density are more intensely colored than the areas corresponding to the lower pattern density. Therefore, this article can display, for example, a colored image or a colored pattern such as a wood grain pattern. The surface of the substrate 1 may or may not carry colorant 5.

This article is produced, for example, by the following method.
First, an article according to the first embodiment is manufactured. Next, a colorant 5 is supplied to this article, and excess colorant 5 is removed. Alternatively, a solution or dispersion containing the colorant 5 is supplied to this article, and the solvent or dispersion medium is removed.

As described above, the portions of the pattern film 2 with higher pattern density have higher porosity than the portions with lower pattern density. Therefore, the former have higher adsorption capacity than the latter. Therefore, this method makes it possible to obtain an article in which the amount of colorant 5 carried differs between the portions with higher pattern density and the portions with lower pattern density.

[Fourth embodiment]
The coloring method described in the third embodiment can also be applied to security technology, for example, as will be described below.

In the article according to the first embodiment, the regions corresponding to the higher pattern density have higher light scattering properties than the regions corresponding to the lower pattern density. Therefore, when the substrate 1 is colored, the regions corresponding to the higher pattern density appear white, for example, while the regions corresponding to the lower pattern density appear the color of the substrate 1 or a color close to it, and the regions corresponding to the openings in the pattern film 2 appear the color of the substrate 1. Furthermore, when the substrate 1 is colorless and transparent and the background of the article is colored, the regions corresponding to the higher pattern density appear white, for example, while the regions corresponding to the lower pattern density appear the color of the background or a color close to it, and the regions corresponding to the openings in the pattern film 2 appear the color of the background.

In contrast, if the substrate 1 is white, or if the substrate 1 is colorless and transparent and has a white background, the areas corresponding to the higher pattern density, the areas corresponding to the lower pattern density, and the areas corresponding to the openings in the pattern film 2 all appear white. That is, in this case, the pattern film 2 forms a latent image that is visualized by coloring it using the method described in the third embodiment. Therefore, when this article is used as a security element with a recorded latent image, authenticity can be determined by visualizing the latent image using the coloring method described in the third embodiment and confirming this visualized image.

<Preparation of First Emulsion>
An O/W emulsion was prepared using the following ingredients:
Monomer or oligomer: Trimethylolpropane triacrylate (Light Acrylate (registered trademark) TMP-A, manufactured by Kyoeisha Chemical Co., Ltd.)
Photopolymerization initiator: 1-benzoylcyclohexanol (Lunacure® 200, commercially available from DKSH Japan Co., Ltd.)
Surfactant: Dioctyl sodium sulfosuccinate (Sunmorin (registered trademark) OT-70, manufactured by Sanyo Chemical Industries, Ltd.)
Second liquid: distilled water First, 0.375 g of Lunacure (registered trademark) 200, 0.259 g of Sunmorin (registered trademark) OT-70, and 7.5 g of Light Acrylate (registered trademark) TMP-A were placed in this order into a 50 mL brown vial, and the mixture was subjected to a rotary mixing process on a ball mill roll. Next, 9 g of distilled water was further placed into the vial, and the mixture was subjected to an emulsification/dispersion process. The emulsification/dispersion process was carried out by propeller stirring. The propeller rotation speed was 738 rpm, and the stirring time was 10 minutes. The vial was then subjected to rotary mixing for 2 hours. In this manner, a first emulsion was prepared.

<Preparation of Second Emulsion>
The second emulsion was prepared in the same manner as described above for the first emulsion, except that the emulsification and dispersion treatment was carried out using a paint shaker (Paint Shaker PC1171 manufactured by Asada Iron Works Co., Ltd.), and shaking with the paint shaker was carried out for 30 seconds.

<Preparation of third emulsion>
The third emulsion was prepared in the same manner as described above for the first emulsion, except that the emulsification and dispersion process was carried out by hand shaking, which was carried out 10 times.

<Measurement of particle size distribution>
The particle size distribution and average particle size of each of the first to third emulsions were measured. For these measurements, a measurement system consisting of a Nikkiso Microtrac MT3300EXII particle size distribution analyzer equipped with a Nikkiso Microtrac USVR liquid circulation pump was used, and the weight-average diameter was determined as the average particle size. The resulting emulsions were composed of dispersed particles (hereinafter also referred to as emulsion droplets) containing the first liquid and a dispersion medium containing the second liquid. The average particle sizes of the first to third emulsions are summarized in Table 1 below. The particle size distributions of the first to third emulsions are also shown in Figure 13.

<Film formation>
Using each of the first to third emulsions, multiple films were formed by the following method. First, five layers of 20 mm wide, 80 μm thick masking tape (manufactured by 3M) were attached to the surface of a microscope slide. The center of this five-layer laminate was cut out into a rectangular shape, thereby creating a cell (hereinafter referred to as a liquid-reservoir cell) with a depth of 400 μm and an opening measuring 10 mm × 30 mm.

Next, 112 μL of emulsion was collected using a micropipette and spread and filled into a liquid storage cell, forming a film (i.e., liquid film) made of emulsion with a thickness of approximately 375 μm, calculated taking into account the specific gravity.

<UV irradiation>
A copper mask having a thickness of 0.25 mm and having stripe-shaped openings was placed on the liquid film via a 1 mm-thick aluminum spacer so as not to come into contact with the liquid surface. Here, multiple copper masks were used, each having stripe-shaped openings corresponding to the line and space pattern and with different widths of the line and space portions.

Next, using a UV parallel light exposure device (UVC-2502S manufactured by SAN-EI ELECTRONIC Corporation), ultraviolet light at an illuminance of 4.6 mW/ ^cm2 was irradiated from above the mask for 8 seconds, thereby exposing each liquid film to an integrated light dose of 36.8 mJ/ ^cm2 . This caused the first liquid to polymerize in the areas irradiated with ultraviolet light, forming a granular layer made of a cured product of the dispersed particles.

<Drying the film>
Next, the film after UV exposure was air-dried at room temperature (22°C, 49% RH) for 90 minutes, thereby removing water from the film.

<Establishing the pattern>
Finally, the entire surface of the dried film was exposed to ultraviolet light with an integrated light intensity of 414 mJ/cm ² (=4.6 mW/cm ² ×90 seconds), thereby fixing the pattern. In this way, a patterned film was formed.

<Imaging the surface of a patterned film>
The surface of each patterned film was photographed using a digital camera (L-835 manufactured by HOZAN Corp.) equipped with a zoom lens (L-815 manufactured by HOZAN Corp.). Some of the images thus obtained are shown in Figure 19. Photographs of the patterned films were taken by placing a piece of black paper behind the slide glass on which the pattern was formed.

<Imaging the cross section of a patterned film>
First, each pattern film was peeled off from the slide glass using tweezers. Next, each pattern film was folded to create a fracture surface. For highly porous and brittle pattern films, a cross section was created using a razor. Next, each pattern film with a cross section was fixed to a sample stage for cross-section observation with double-sided carbon conductive tape, and gold was sputtered onto the tape. In this manner, samples for observation with a scanning electron microscope (SEM) were prepared. Then, the cross sections of each sample were photographed with the SEM. The images obtained in this manner are shown in Figures 14 to 16.

Figure 14 is a scanning electron microscope photograph showing the cross section of a line and space pattern formed using the first emulsion with varying line and space widths. Figure 15 is a scanning electron microscope photograph showing the cross section of a line and space pattern formed using the second emulsion with varying line and space widths. Figure 16 is a scanning electron microscope photograph showing the cross section of a line and space pattern formed using the third emulsion with varying line and space widths.

<Image analysis>
Image analysis was performed using the image processing software Image J.
Specifically, in each image of the cross section of the patterned film, a region that did not contain any contrast noise, such as fractured portions, was selected. Then, for each selected region, the standard deviation of the density distribution in a 256-level grayscale was extracted as a feature. Note that if there are no pores (gaps between particles) in the selected region, the standard deviation is small; however, the more pores there are, i.e., the higher the porosity, the larger the standard deviation.

Furthermore, for each image of the pattern film surface, the standard deviation of the density distribution in the 256-level grayscale was determined using the same method as above. Furthermore, the average density value was calculated from this density distribution, and this was used as an index of the whiteness of the pattern film surface.

<Result 1>
14 to 16, the patterned film becomes porous when the ratio of line width to space width (L/S ratio) is set to 1 to 1.5 or more, and this tendency does not depend on the average particle size of the emulsion.

Figure 17 shows the density distribution obtained by image analysis of a portion of the photograph in Figure 15. As shown in Figure 17, when the ratio of line width to space width is small (L/S ratio = 1), the density, i.e., brightness, of the image of the cross section of the pattern film is distributed over a relatively narrow range. In contrast, when the ratio of line width to space width is large (L/S ratio = 3), the density of the image of the cross section of the pattern film is distributed over a relatively wide range.

Table 2 shows the standard deviation of the concentration distribution obtained by image analysis of the photographs in Figures 14 to 16. Figure 18 also shows the effect of the ratio of line width to space width on the standard deviation of the concentration distribution obtained by image analysis of the photographs in Figures 14 to 16.

As shown in Table 2 and Figure 18, regardless of which of the first to third emulsions is used, the larger the ratio of line width to space width (L/S ratio), the larger the standard deviation of the density distribution obtained for the image of the cross section of the pattern film. Furthermore, the smaller the average particle size of the emulsion, the greater the effect of the L/S ratio on the standard deviation.

Comparing Figures 14 to 16 with Figure 18, it can be seen that there is a positive correlation between the porosity of the patterned film and the standard deviation of the concentration distribution obtained from the image of the cross section of the patterned film. From the above, it can be seen that the standard deviation of the concentration distribution obtained from the image of the cross section of the patterned film can be an indirect indicator of the porosity of the patterned film.

<Result 2>
Table 3 shows the average density values obtained by image analysis of the photograph in Fig. 19. Also, Fig. 20 shows the effect of the ratio of line width to space width on the average density values obtained by image analysis of the photograph in Fig. 19.

As shown in Table 3 and Figure 20, regardless of which of the first to third emulsions is used, the greater the ratio of line width to space width (L/S ratio), the greater the average density obtained for the image of the pattern film surface. In other words, the greater the L/S ratio, the higher the light scattering properties of the pattern film. Furthermore, the smaller the average particle size of the emulsion, the greater the average density obtained for the image of the pattern film surface.

Comparing Figures 19 and 20, it can be seen that there is a positive correlation between the whiteness of the pattern film and the average density obtained for the image of the pattern film surface.

Tables 4 to 6 show the standard deviation of the concentration distribution obtained by image analysis of the photographs in Figures 14 to 16, and the average concentration obtained by image analysis of the photograph in Figure 19. Also, Figure 21 shows the relationship between the standard deviation of the concentration distribution obtained by image analysis of the photographs in Figures 14 to 16 and the average concentration obtained by image analysis of the photograph in Figure 19.

As shown in Tables 4 to 6 and FIG. 21, there is a positive correlation between the standard deviation of the density distribution obtained from the image of the cross section of the patterned film and the average density obtained from the image of the surface of the patterned film.
The invention as originally claimed is set forth below.
[1]
A patterned film comprising a plurality of portions with different pattern densities, one or more of the plurality of portions being porous, and one or more of the other portions having a lower pattern density and porosity compared to one of the one or more porous portions.
[2]
Item 2. The patterned film according to item 1, wherein among the plurality of portions, portions with lower pattern density have a porosity equal to or lower than that of portions with higher pattern density.
[3]
Item 3. The patterned film according to Item 1 or 2, wherein one or more of the plurality of portions is non-porous.
[4]
Item 4. The patterned film according to any one of Items 1 to 3, wherein the line width is in the range of 10 μm to 5 mm.
[5]
Item 5. The patterned film according to any one of items 1 to 4, wherein the height difference is in the range of 10 μm to 2 mm.
[6]
Item 6. An article comprising the patterned film according to any one of items 1 to 5 and a substrate supporting the patterned film.
[7]
Item 7. The article according to item 6, further comprising layers attached to the substrate with the patterned film sandwiched therebetween.
[8]
Item 8. The article according to item 6 or 7, further comprising a colorant carried on the patterned film.

1...substrate, 2...patterned film, 2a...film made of emulsion, 3...layer, 4...adhesive layer, 5...colorant, 21a...dispersed particles, 21a'...combined, 21b...granular layer, 21b1...cured dispersed particles, 21b2...polymerized phase, 22...dispersion medium.

Claims (7)

A patterned film comprising multiple portions with different pattern densities, one or more of which are porous, and one or more of which have a lower pattern density and porosity compared to one of the porous portions. The patterned film of claim 1 , wherein one or more of the plurality of portions is non-porous. 3. The patterned film according to claim 1, wherein the line width is in the range of 10 [mu]m to 5 mm. 4. The patterned film according to claim 1 , wherein the height difference is in the range of 10 μm to 2 mm. An article comprising the patterned film according to any one of claims 1 to 4 and a substrate supporting the patterned film. 6. The article of claim 5 , further comprising a layer attached to the substrate with the patterned film sandwiched therebetween. The article according to claim 5 or 6 , further comprising a colorant carried on the patterned film.