TW202003603A - Flakes, method for producing same, and paint - Google Patents

Abstract

To provide flakes of which the reflected color is clearly visible in both a frontal direction and an inclined direction of a layer containing the flakes. (Solution) Flakes containing crushed pieces of a layer of a resin having cholesteric regularity, the layer of resin containing alignment defects in which the cholesteric regularity is impaired, and the haze of the layer of resin being 10-60%.

Description

Flakes, manufacturing method and paint

The present invention relates to flakes, their manufacturing methods and paints.

In the field of security inks, special pigments are sometimes used for the purpose of preventing counterfeiting. As one of such special pigments, it is known to use a resin having cholesterol regularity (hereinafter referred to as “cholesterol resin” as appropriate.) (refer to Patent Document 1).

"Patent Literature" "Patent Document 1": Japanese Patent Publication No. 2007-141117

The inventors focused on a sheet containing cholesterol resin as the aforementioned special pigment. In the case of printing an anti-counterfeiting ink containing the sheet to form an optical layer containing the sheet, the reflection color of the sheet seen through the observation of the optical layer generally varies depending on the viewing angle. Here, the observation angle of a certain layer means the angle between the observation direction and the thickness direction of this layer. According to this, for example, the reflection color observed in the front direction of the optical layer (the direction with an observation angle of 0°) and the oblique direction in the optical layer (the observation angle is a direction greater than 0° and less than 90°) ) Most of the reflection colors observed are different. Therefore, it is conceivable to use the specificity such that the reflection color differs depending on the viewing angle, and use a sheet containing cholesterol resin as a special pigment.

In other words, as printed materials printed with anti-counterfeiting inks containing special pigments, there are various types such as tax stamps, securities, banknotes, and cards. Also, the environment for viewing these printed materials may be bright or dark. Furthermore, the illumination in the aforementioned environment may have illumination with a wide light distribution angle, and may also have illumination with a narrow light distribution angle. As such, the environment in which anti-counterfeiting inks containing special pigments can be applied is diverse. Therefore, for the aforementioned special pigments, it is required that the reflected color can be clearly seen under various lighting environments.

However, the conventional sheet material containing cholesterol resin is difficult to clearly see the reflection color in both the front direction and the oblique direction. In particular, even in an environment where the reflection color can be clearly seen by observation in the frontal direction, there are many cases where the reflection color cannot be clearly seen in the oblique direction.

The present invention was initiated in view of the foregoing problems, and its object is to provide a sheet-like object in which the reflection color can be clearly seen in both the frontal direction and the oblique direction of the layered body including the sheet-like object, a method for manufacturing the same, and including the aforementioned Flake paint.

The inventor has made intensive studies to solve the aforementioned problems. As a result, the present inventors found that a sheet-like material containing a crushed sheet of a cholesterol resin layer can solve the aforementioned problems, and completed the present invention. The cholesterol resin layer has a specified range of fog due to light scattering due to orientation defects degree. That is, the present invention includes the following.

[1] A flake comprising a crushed piece of resin layer with regularity of cholesterol, The aforementioned resin layer contains orientation defects with impaired regularity of cholesterol, The haze of the aforementioned resin layer is 10% or more and 60% or less.

[2] The sheet-like article according to [1], wherein the sheet-like article has one or more reflection bands including a visible light region.

[3] The sheet-like object described in [2], wherein the bandwidth of each of the aforementioned reflection bands is 100 nm or more.

[4] The sheet-like article according to any one of [1] to [3], wherein the average particle diameter of the sheet-like article is 1 μm or more and 500 μm or less.

[5] A method for manufacturing a sheet-shaped article, which is a method for manufacturing a sheet-shaped article as described in any one of [1] to [4], including: The process of forming a resin layer with cholesterol regularity, and The step of pulverizing the resin layer.

[6] A paint comprising: the flakes and the dispersion medium as described in any one of [1] to [4].

According to the present invention, it is possible to provide a sheet-like article in which the reflection color can be clearly seen in both the front direction and the oblique direction of the layered body including the sheet-like article, a method for producing the sheet-like article, and a coating material including the aforementioned sheet-like article.

The embodiments and examples are disclosed below to explain the present invention in detail. However, the present invention is not limited to the embodiments and examples described below, and can be arbitrarily changed and implemented without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, the front direction of a certain layer means a direction parallel to the thickness direction of a certain layer unless otherwise noted. In addition, unless otherwise noted, the inclination direction of a certain layer means a direction that is neither parallel nor perpendicular to the thickness direction of a certain layer.

[1. Structure of flakes]

A sheet-like object related to an embodiment of the present invention includes a crushed piece of cholesterol resin layer. The cholesterol resin refers to a resin having cholesterol regularity as described above.

The so-called regularity of cholesterol is like "the molecular axis is arranged in a fixed direction on a certain plane, but the direction of the molecular axis on the plane below it is slightly offset by the angle, and the angle is more staggered on the next plane." A structure that staggers (twists) the angles of the molecular axes in the plane as it progresses through the overlapping planes in sequence. That is, when the molecules in the layered body of a certain resin have cholesterol regularity, the molecules are arranged on a first plane inside the layered body so that the molecular axis becomes a fixed direction. On the second plane that overlaps the first plane inside the layer body, the direction of the molecular axis is slightly offset from the direction of the molecular axis in the first plane. On a third plane that further overlaps with the second plane, the direction of the molecular axis is more staggered from the direction of the molecular axis in the second plane. In this way, in the plane of the overlapping arrangement, the angles of the molecular axes in the plane are sequentially shifted (twisted). Such a structure in which the direction of the molecular axis is gradually twisted is usually a spiral structure, but an optical palm structure.

In the present embodiment, the one containing the orientation defect is used as the cholesterol resin layer. The so-called orientation defect refers to the part of cholesterol resin whose cholesterol regularity is impaired. In such orientation defects, the molecules are usually oriented in a direction different from the surrounding molecules. Therefore, in such directional defects, optical phenomena such as refraction, reflection, and diffraction generally occur. According to this, the cholesterol resin containing orientation defects has a scattering property that scatters light.

The cholesterol resin layer has a specific range of haze through scattering due to directional defects. The specific haze range of the cholesterol resin layer is usually 10% or more, preferably 15% or more, preferably 20% or more, and usually 60% or less, preferably 55% or less, and 50% or less good. When the haze of the cholesterol resin layer is equal to or higher than the lower limit of the aforementioned range, the visibility of the reflected color of the sheet can be improved in both the front direction and the oblique direction of the optical layer including the sheet. In addition, when the haze of the cholesterol resin layer is below the upper limit of the aforementioned range, the degree of blue shift can be increased, so that the reflection corresponding to the "observation angle of the optical layer containing the sheet" can be increased Color difference.

The haze of the cholesterol resin layer can be adjusted by, for example, a method of adjusting the conditions of the orientation treatment included in the method of manufacturing the cholesterol resin layer; a method of adjusting the thickness of the cholesterol resin layer; and the like. Specifically, as the orientation temperature is lower during orientation treatment, orientation defects are more likely to occur, so that haze can be increased. In addition, the thicker the cholesterol resin is, the easier it is to cause orientation defects, so the haze can be improved.

The haze of the cholesterol resin layer can be measured with a haze meter using the cholesterol resin layer before crushing. The specific measurement method can adopt the method described in the embodiment.

The cholesterol resin layer usually has a circularly polarized light separation function. That is, the cholesterol resin layer can function as a circularly polarized light separation film that transmits one of right-handed circularly polarized light and left-handed circularly polarized light and transmits part or all of the other circularly polarized light The nature of reflection. The reflection in the cholesterol resin reflects circular polarized light while maintaining its palm properties. In the following description, the wavelength range that exerts the circular polarization separation function in this manner is sometimes referred to as a "reflection band." By adjusting this reflection band, the sheet can reflect circularly polarized light corresponding to the color of this reflection band. Accordingly, by adjusting the reflection band, the reflection color of the sheet can be adjusted.

The specific wavelength that performs the function of separating circularly polarized light generally depends on the pitch of the spiral structure in the cholesterol resin layer. The pitch of the so-called spiral structure is the distance between the direction of the molecular axis in the spiral structure as it penetrates into the plane, and then returns to the normal direction of the plane to the original molecular axis again. By changing the size of the pitch of this spiral structure, the wavelength that performs the function of separating circular polarized light can be changed.

For example, in a cholesterol resin layer formed using a liquid crystal compound, when the "spiral axis representing the rotation axis when the molecular axis of the spiral structure is twisted" is parallel to the "normal line of the cholesterol resin layer", the spiral structure The distance p and the wavelength λ of the circularly polarized light reflected usually have the relationship of formula (X) and formula (Y).

Formula (X): λ _c = n×p×cosθ Formula (Y): n _o ×p×cosθ≦λ≦n _e ×p×cosθ

In formula (X) and formula (Y), λ _c represents the center wavelength of the reflection band (hereinafter sometimes referred to as “reflection center wavelength”), n _o represents the refractive index in the short axis direction of the liquid crystal compound, and n _e represents the longitudinal direction of the refractive index of the liquid crystal compound, n represents the _{(n e + n o) /} 2, p represents the pitch of the helical structure, θ represents (an angle subtended between the surface and the normal) angle of incidence of light.

Therefore, the reflection center wavelength λ _c depends on the pitch p of the spiral structure of the polymer in the cholesterol resin layer. By changing the pitch p of this spiral structure, the reflection band can be changed. Accordingly, the pitch p of the spiral structure is preferably set according to the wavelength of the circularly polarized light to be reflected by the cholesterol resin layer. As a method of adjusting the pitch p, for example, the method described in Japanese Patent Publication No. 2009-300662 can be used. To cite specific examples, a method of adjusting the type of palm-based agent or the amount of palm-based agent in the cholesterol liquid crystal composition can be cited.

In addition, from the aforementioned formula (X) and formula (Y), it can be seen that the reflection band changes according to the incident angle of light. According to this, a phenomenon called "blue shift" usually occurs in the cholesterol resin layer, "the larger the incident angle becomes, the more the reflection band shifts to the lower wavelength side."

Examples of the cholesterol resin layer include (i) a cholesterol resin layer that changes the size of the pitch of the spiral structure stepwise and (ii) a cholesterol resin layer that continuously changes the size of the pitch of the spiral structure.

(I) A cholesterol resin layer in which the pitch between the spiral structures is changed stepwise, for example, can be obtained by stacking a plurality of cholesterol resin layers with different pitches between the spiral structures. The stacking can be performed by fixing a plurality of cholesterol resin layers with different distances between the spiral structures in advance, and then fixing the adhesive or bonding agent in each layer. Alternatively, stacking can also be performed by forming a cholesterol resin layer and then sequentially forming another cholesterol resin layer.

(Ii) For the cholesterol resin layer that continuously changes the pitch of the spiral structure, for example, the liquid crystal composition layer may be subjected to irradiation treatment including active energy rays and/or heating treatment at least once to widen the bandwidth After the treatment, this liquid crystal composition layer is cured and obtained. According to the aforementioned broadband processing, since the pitch of the spiral structure can be continuously changed in the thickness direction, the reflection band of the cholesterol resin layer can be expanded, so it is called broadband processing.

The cholesterol resin layer may be a single-layer structure composed of only one layer, or a multilayer structure including two or more layers. The number of layers included in the cholesterol resin layer is preferably from 1 layer to 100 layers, and preferably from 1 layer to 20 layers from the viewpoint of ease of production.

The refractive index anisotropy Δn of the cholesterol resin layer can be appropriately selected according to the reflection band of the produced sheet. For example, when making a sheet with a narrow reflection band and high color purity, it is preferable to use a cholesterol resin layer having a refractive index anisotropy Δn of 0.2 or less. In addition, in the case of producing a sheet material having a reflection band in a mixed color or multi-color even in the entire visible light region, a cholesterol resin layer having a large refractive index anisotropy Δn of 0.2 or more is preferable. However, from the viewpoint of thinning the necessary thickness in order to ensure reflectivity and making it easy to adjust the haze of the cholesterol resin layer due to the thickness, the refractive index anisotropy Δn of the cholesterol resin layer is preferably 0.05 or more. If the refractive index anisotropy Δn is 0.30 or more, although the absorption end of the long-wavelength side of the ultraviolet absorption spectrum may be in the visible region, as long as the absorption end of the spectrum is in the visible region, the desired optical performance will not be affected. Negative impact, that is, it can be used. Here, the refractive index anisotropy Δn has to be measured by the Senamon method. The upper limit of the refractive index anisotropy Δn is, for example, 0.25 or less.

The sheet material related to this embodiment is included in the above-mentioned crushed piece of cholesterol resin layer, so the sheet material usually contains a cholesterol resin layer. In the following description, the cholesterol resin layer before pulverization is sometimes referred to as a "cholesterol original layer", and the cholesterol resin layer after pulverization included in a sheet is referred to as a "cholesterol pulverization layer".

Because it contains a crushed layer of cholesterol, the flakes usually have a single or different reflection bands. Among them, the sheet-like object preferably has one or more reflection bands including visible light regions. The visible light region generally refers to a wavelength range from 400 nm to 800 nm. In addition, the reflection band includes a visible light region, which means that the reflection band includes at least a part of the visible light region. In addition, the specific wavelength range of the reflection band can be measured as the wavelength range corresponding to the half-height width of the reflection peak in the reflection spectrum measured using a spectroscope (such as Japan Spectroscopy Co., Ltd. "V570") (also That is, the intensity is in the wavelength range where the peak intensity is 50% or more). The aforementioned measurement is usually performed under the measurement conditions of an incident angle of light of 5° and a detection angle of 0°. In this way, the sheet-like object having the reflection band in the visible light region can be reflected by the naked eye. According to this, this kind of sheet can be used in a wide range of applications.

When the sheet-like object has a reflection band in the visible light region, the number of reflection bands located in the visible light region may be one, or may be two or more. For example, a sheet having only one reflective band with a narrow bandwidth in the visible light region can obtain the reflected light corresponding to the monochromatic (eg, red, green, blue, etc.) of the reflective band. Moreover, for example, a sheet having only one reflective band wide enough to cover the entire visible light region in the visible light region can obtain reflected light corresponding to the mixed color (usually silver) of the reflective band. Furthermore, for example, a sheet having two or more reflection bands in the visible light region can obtain reflected light of a mixed color corresponding to the colors of these reflection bands, respectively.

The bandwidth of each of the aforementioned reflection bands is preferably above 100 nm, preferably above 200 nm, and more preferably above 400 nm. In particular, the sheet-like object preferably has a "reflection band having the aforementioned bandwidth" in the visible light region. With this, the amount of light reflected by a single sheet can be increased, and a paint with excellent designability and visibility can be obtained. The upper limit of the bandwidth of each reflection band should be 300 nm or less.

The bandwidth of the reflection band can be measured using a spectroscope (such as Japan Spectroscopy Co., Ltd. "V570") and the reflection spectrum can be calculated based on this reflection spectrum. More specifically, the value of the half-height width of the reflection peak in the measured reflection spectrum can be determined as the value of the bandwidth of the reflection band. The aforementioned measurement is usually performed under the measurement conditions of an incident angle of light of 5° and a detection angle of 0°.

As mentioned above, in the cholesterol crushing layer containing cholesterol resin, blue shift usually occurs. Accordingly, when observing a sheet-like object, different reflection colors are usually seen depending on the viewing angle. Generally speaking, the color seen when the viewing angle is small will gradually change to the color on the short wavelength side as the viewing angle becomes larger. For example, when you see green when the viewing angle is small, you will see blue as the viewing angle becomes larger. However, in the case where the blue region and the infrared region have flakes with reflection bands, a color change called red shift can occur opposite to the blue shift. In such a redshift, for example, blue is seen when the viewing angle is small, but red is seen as the viewing angle becomes larger.

The flakes may further comprise any layer combination in the cholesterol crushing layer. For example, when a multilayer film composed of a combination of an original layer of cholesterol and an arbitrary layer is crushed to produce a sheet, the sheet may include a crushed layer of cholesterol and an arbitrary layer.

The flakes usually have a flake shape because they contain crushed pieces that have crushed the original layer of cholesterol. Such a sheet-like sheet-like object has the following tendency: in the case of applying a coating material containing the sheet-like object to obtain a layered body, the layer plane of the layered body and the cholesterol pulverized layer will pass through the shearing force at the time of coating. The layer planes are oriented in a parallel manner.

The average particle size of the flakes is preferably 1 μm or more from the viewpoint of improving the visibility of the reflection color of the flakes, and from the viewpoint of optimizing the coating property of the coating, it is preferably 500 μm or less, 100 μm or less is preferable.

The average particle size of the flakes can be measured by the method described in the examples.

[2. Manufacturing method of flakes]

The sheet related to this embodiment can be generally manufactured by a manufacturing method including: a process of forming an original layer of cholesterol; and a process of pulverizing the original layer of cholesterol;

In the process of forming the original cholesterol layer, for example, a layer of cholesterol liquid crystal composition is provided on a suitable support for forming the original cholesterol layer, and the aforementioned layer is cured to obtain the original cholesterol layer. The material cheaply called "liquid crystal composition" includes not only a material made of a mixture of two or more substances, but also a material made of a single substance. In addition, the cholesterol liquid crystal composition refers to a composition in which the liquid crystal compound can exhibit a liquid crystal phase (cholesteric liquid crystal phase) having cholesterol regularity when the liquid crystal compound included in the liquid crystal composition is aligned.

As the cholesterol liquid crystal composition, a liquid crystal composition containing a liquid crystal compound and optionally containing any components can be used. As the liquid crystal compound, a liquid crystal compound which is a polymer compound and a polymerizable liquid crystal compound can be used. In order to obtain high thermal stability, it is preferable to use a polymerizable liquid crystal compound. By polymerizing the polymerizable liquid crystal compound in a state exhibiting cholesterol regularity, the layered body of the cholesterol liquid crystal composition can be cured to obtain a non-liquid crystallinity cholesterol resin layer cured in the state exhibiting cholesterol regularity. As the cholesterol liquid crystal composition, for example, those described in International Patent Publication No. 2016/002765 can be used.

As the support, any member having a flat support surface can be generally used, and the flat support surface can support the layered body of the cholesterol liquid crystal composition. Generally, a resin film is used as such a support. In addition, the support surface of the support may be subjected to treatment for imparting orientation restricting force in order to promote the orientation of the liquid crystal compound in the layer of the cholesterol liquid crystal composition. Here, the orientation restricting force of a certain surface refers to the "property of this surface" that allows the liquid crystal compound in the cholesterol liquid crystal composition to be oriented. Examples of the aforementioned treatment for imparting an orientation restricting force to the support surface include rubbing treatment, orientation film formation treatment, stretching treatment, and ion beam orientation treatment.

The layered body of cholesterol liquid crystal composition is usually provided by applying the cholesterol liquid crystal composition to the support surface of the support. The thickness of the layer of cholesterol liquid crystal composition is determined by the thickness of the original layer of cholesterol that should be targeted. In addition, the thickness of the layer of the cholesterol liquid crystal composition is preferably set in accordance with the haze of the original layer of cholesterol. In general, the thicker the layer of cholesterol liquid crystal composition, the thicker the original layer of cholesterol can be obtained. Moreover, the thicker the original layer of cholesterol, the higher the haze of the original layer of cholesterol. Therefore, by adjusting the thickness of the layer of cholesterol liquid crystal composition formed on the supporting surface, the haze of the original layer of cholesterol can be adjusted.

The method of applying the cholesterol liquid crystal composition is arbitrary. Examples of the coating method include curtain coating method, extrusion coating method, roll coating method, spin coating method, dip coating method, bar coating method, spray coating method, inclined plate coating method, printing coating method, gravure coating method, Die coating method, gap coating method and dipping method.

After the layered body of the cholesterol liquid crystal composition is set, the layered body of the cholesterol liquid crystal composition can also be subjected to orientation treatment according to requirements. Orientation treatment can usually be performed by heating the layer of cholesterol liquid crystal composition to a specified orientation temperature. By applying such an orientation treatment, the liquid crystal compound contained in the cholesterol liquid crystal composition is oriented and becomes a state of regularity of cholesterol.

The orientation temperature can be arbitrarily set within the range in which the liquid crystal compound is oriented. However, the directional temperature is preferably set according to the haze of the original layer of cholesterol. Generally speaking, the lower the directional temperature, the higher the haze of the original layer of cholesterol. Therefore, by adjusting the directional temperature, the haze of the original layer of cholesterol can be adjusted. The specific orientation temperature can be adjusted according to the composition of the cholesterol liquid crystal composition, for example, in a range of 50°C to 150°C so as to obtain a desired value of haze.

In the alignment process, the layer of cholesterol liquid crystal composition is usually heated at the aforementioned alignment temperature for as long as specified. The treatment time at this time can be arbitrarily set in the range in which the alignment of the liquid crystal compound is performed, and it is, for example, 0.5 minutes to 10 minutes.

However, the orientation of the liquid crystal compound included in the cholesterol liquid crystal composition may sometimes be directly achieved by coating the cholesterol liquid crystal composition. Therefore, it is not necessary to apply orientation treatment to the layer of cholesterol liquid crystal composition.

After aligning the liquid crystalline compound, the layer of cholesterol liquid crystal composition is cured to obtain an original layer of cholesterol. In this step, polymerizable components such as a polymerizable liquid crystal compound contained in the cholesterol liquid crystal composition are generally polymerized to cure the layer of the cholesterol liquid crystal composition. As a polymerization method, a method suitable for the properties of the components contained in the cholesterol liquid crystal composition may be selected. Examples of the polymerization method include a method of irradiating active energy rays and a thermal polymerization method. Among them, since the polymerization reaction can be carried out at room temperature without heating, a method of irradiating active energy rays is preferred. Here, the active energy rays to be irradiated may include any energy rays such as visible light, ultraviolet rays and infrared rays, and electron beams. In addition, when the layer of the cholesterol liquid crystal composition is cured by irradiation with active energy rays, the intensity of the irradiated active energy rays is, for example, 50 mJ/cm ² to 10,000 mJ/cm ² .

In addition, after the alignment of the liquid crystal compound, the layer of cholesterol liquid crystal composition may be subjected to a broadband treatment before the layer of cholesterol liquid crystal composition is cured. Such a broadbanding treatment can be performed by a combination of, for example, one or more active energy ray irradiation treatments and heat treatments. The irradiation treatment in the broadbandization treatment can be performed by irradiating light with a wavelength of 200 nm to 500 nm for 0.01 seconds to 3 minutes, for example. At this time, the energy of the irradiated light is set to, for example, 0.01 mJ/cm ² to 50 mJ/cm ² . In addition, the heat treatment can be performed by heating to, for example, preferably 40° C. or higher, preferably 50° C. or higher, more preferably 200° C. or lower, and 140° C. or lower. The heating time at this time is preferably 1 second or more, preferably 5 seconds or more, and usually 3 minutes or less, and preferably 120 seconds or less. By performing such a widening process, the distance between the spiral structures can be greatly changed in continuity, and a wide reflection band can be obtained.

The irradiation of the aforementioned active energy rays may be performed under air, or a part or all of this process may be performed under a gas environment in which the oxygen concentration has been controlled (for example, under a nitrogen environment).

The steps of applying and curing the cholesterol liquid crystal composition are not limited to one, and the coating and curing may be repeated multiple times. Thereby, a cholesterol resin layer including two or more thick layers can be obtained.

In the case of manufacturing the original layer of cholesterol by the aforementioned method, the twisting direction in the regularity of cholesterol can be appropriately selected according to the structure of the palmitant used. For example, in the case where the twist is to be turned to the right, the cholesterol liquid crystal composition containing the palmitate imparting right-handedness is used, and in the case where the twisted direction is to the left, the composition containing the left-handedness is used Cholesterol liquid crystal composition.

In order to obtain sufficient reflectivity, the thickness of the original layer of cholesterol is preferably 0.1 μm or more, and more preferably 1 μm or more. In addition, in obtaining the transparency of the original cholesterol layer, it is preferably 20 μm or less, and more preferably 10 μm or less.

According to the aforementioned procedure, the original layer of cholesterol can usually be obtained on the support. Therefore, before the step of pulverizing the original layer of cholesterol, the step of peeling the support may be performed as required. The peeling method is arbitrary, and for example, the method described in Japanese Patent Publication No. 2015-27743 can be used.

After preparing the original layer of cholesterol, a process of crushing the original layer of cholesterol is performed. By pulverizing the original layer of cholesterol, a sheet containing "the pulverized cholesterol layer as a pulverized tablet of the original layer of cholesterol" can be obtained. The crushing method is arbitrary. Examples of the crushing device include hammer crushers, cutting and grinding machines, hammer mills, bead mills, vibratory mills, planetary ball mills, sand mills, ball mills, roll mills, and three-roll mills. , Jet mill, high-speed rotary crusher, micro crusher-demolition granulator, nano jet crusher, etc.

The method for manufacturing the sheet-shaped object described above may further include any steps. As an arbitrary process, the process of classifying a sheet-like object etc. are mentioned, for example.

[3. Paint]

The flakes described above can be used as pigments for paints, for example. This coating is a fluid material containing the aforementioned sheet. Here, the so-called fluid state includes not only a liquid state of low viscosity but also a gel state of high viscosity. The specific viscosity of the paint should be adjusted appropriately according to the application of the paint. The flakes contained in the paint may be one kind or two or more kinds.

Usually the coating contains a dispersion medium combined with flakes. In this coating, the flakes are usually dispersed into the aforementioned dispersion medium. As the dispersion medium, an inorganic solvent such as water can be used, but an organic solvent is usually used. Examples of organic solvents include organic solvents such as ketone compounds, halogenated alkane compounds, amide compounds, sulfonate compounds, heterocyclic compounds, hydrocarbon compounds, ester compounds, and ether compounds. Among these, ketone compounds are preferred in consideration of environmental load. In addition, one type of dispersion medium may be used alone, or two or more types may be used in combination at any ratio.

The amount of the dispersion medium is preferably 40 parts by weight or more, preferably 60 parts by weight or more, more preferably 80 parts by weight or more, and 1000 parts by weight or less with respect to 100 parts by weight of the sheet. 800 parts by weight or less is preferred, and 600 parts by weight or less is particularly preferred. By setting the amount of the dispersion medium to the aforementioned range, the coatability of the coating can be optimized.

Moreover, the coating may also contain a binder for bonding the sheets after the dispersion medium is dried. As the binder, a polymer is usually used. Examples of such polymers include polyester-based polymers, acrylic-based polymers, polystyrene-based polymers, polyamide-based polymers, polyurethane-based polymers, polyolefin-based polymers, Polycarbonate polymer, polyethylene polymer, etc. The adhesive can be used alone or in combination of two or more at any ratio.

The amount of the binder is preferably 20 parts by weight or more, preferably 40 parts by weight or more, more preferably 60 parts by weight or more, and 1000 parts by weight or less with respect to 100 parts by weight of the sheet. 800 parts by weight or less is preferred, and 600 parts by weight or less is particularly preferred. By setting the amount of the binder within the aforementioned range, the coatability of the coating can be optimized. Moreover, the sheet-like substance can be stably bonded after the dispersion medium is dried.

Furthermore, the aforementioned coating may also contain monomers of the polymer instead of the polymer as a binder, or be combined with the polymer. In this case, the optical layer containing the sheet-like material and the adhesive can be manufactured by applying a coating to a suitable part and then drying and polymerizing the monomer. Furthermore, it is preferable that the paint containing the monomer further contains a polymerization initiator.

The paint can contain arbitrary components other than flakes, dispersion media and adhesives. Examples of optional components include antioxidants, ultraviolet absorbers, light stabilizers, and bluing agents. In addition, one of these may be used alone, or two or more may be used in combination at an arbitrary ratio.

[4. Use method and effect of flakes]

The aforementioned sheet is generally used for the production of an optical layer containing the sheet. Such an optical layer can be manufactured by applying a coating to a suitable part and curing the coating layer formed by coating. The curing of the paint layer can be achieved, for example, by drying the paint layer and polymerizing the monomers contained in the paint layer.

This optical layer includes the aforementioned sheet. According to this, if light is irradiated to the optical layer, the circular polarized light of the reflection band of the cholesterol resin corresponding to the circular polarized light separation function will be reflected by the sheet. Therefore, the observer can see the reflection color "corresponding to the wavelength of the circularly polarized light reflected as described above". In particular, in the case of using the sheet related to the above-described embodiment, the reflected color can be clearly seen by the observer in both the front direction and the oblique direction of the optical layer.

As described above, the mechanism that can achieve high visibility in both the frontal direction and the oblique direction is supposed to be as follows by the inventors. However, the mechanism described below does not limit the technical scope of the present invention.

1 to 3 are schematic cross-sectional views of an example of an optical layer 10 including a sheet 100 according to an embodiment of the present invention.

As shown in FIGS. 1 to 3, consider an example of the optical layer 10 including the sheet 100 and the adhesive 200. In the example shown here, the sheet 100 is oriented parallel to the layer plane of the optical layer 10. Therefore, the layer plane of the cholesterol crushing layer 110 included in the sheet 100 is parallel to the layer plane of the optical layer 10. In addition, the cholesterol crushing layer 110 is obtained by crushing a cholesterol original layer (not shown) having a haze in a specific range as described above, and includes orientation defects 120. When light is incident on such a sheet 100, the circularly polarized light of the reflection band of the cholesterol resin corresponding to the circularly polarized light separation function will be reflected on the cholesterol crushing layer 110.

As shown in FIGS. 1 and 2, the amount of light received by the sheet 100 generally varies depending on the angle of incidence of light. Accordingly, as shown in FIG. 1, the sheet-like object 100 tends to receive the light A1 in the frontal direction with a small incident angle at a relatively large amount of light. On the other hand, as shown in FIG. 2, the sheet 100 tends to receive the ray A2 in the oblique direction with a large incident angle at a relatively small amount of light. Therefore, assuming that there is no orientation defect 120, a large amount of light reflection will be generated in the front direction of the optical layer 10, and a small amount of light reflection will be generated in the oblique direction of the optical layer 10. According to this, when a conventional sheet-like object is used, it is difficult to see the reflection color of the sheet-like object viewed from an oblique direction.

In contrast, if the sheet 100 includes the directional defect 120 as in this embodiment, as shown in FIG. 3, the directional defect 120 generates light scattering. According to this, a part of the ray A1 incident in the front direction changes the direction of travel due to the scattering effect, and then exits in the oblique direction after being reflected. Therefore, since the amount of light visible to the observer in the oblique direction can be increased, the visibility of the reflected color in the oblique direction can be improved. Therefore, in both the front direction and the oblique direction of the optical layer 10, the observer can clearly see the reflected color.

In FIG. 3, although an example in which the light scattered by the directional defect 120 is reflected by the sheet 100 including the directional defect 120, the light scattered by the directional defect 120 may be different from the directional defect. 120 flakes (not shown) of 100 flakes 100 are reflected. In addition, in FIG. 3, although the scattering of the directional defect 120 is shown, the traveling direction of the light A1 is changed before being reflected by the sheet 100, but after the reflection of the sheet 100 is taken as The circularly polarized light A1 may also be changed due to the scattering of the directional defect 120.

Furthermore, it is conceivable that when the layer plane of the cholesterol crushing layer 110 included in the sheet 100 is not parallel to the layer plane of the optical layer 10, the effect can also be obtained by the same mechanism as described above. That is, according to the effect of scattering, the variation in the amount of light due to the traveling direction of light can be suppressed, so the observer can clearly see the reflected color without depending on the observation angle.

In the optical layer, generally speaking, the whole sheet is oriented in a certain direction. According to this, the layer plane of the cholesterol crushing layer contained in the sheet is generally oriented in a certain direction as a whole. In most cases, the sheet is oriented parallel to the layer plane of the optical layer. Therefore, the layer plane of the cholesterol crushing layer is also mostly parallel to the layer plane of the optical layer. In the case where such a whole sheet is oriented in a certain direction, an observer who observes the optical layer can see the reflection color of the uniform sheet in the entire optical layer.

In addition, the reflection color of a sheet-like object can change due to the influence of blue shift. Therefore, the reflection color seen by observing an optical layer containing the sheet-like object can usually change according to the observation angle with respect to the optical layer. In general, the oblique direction with the larger observation angle tends to be closer to the blue reflection color than the oblique direction with the observation angle of 0° with respect to the thickness direction of the optical layer.

[5. Use]

The flakes and coatings described above can be used as security products to prevent counterfeiting, for example.

For example, the optical layer formed using the aforementioned sheet or paint is as described above, and the reflected color seen changes depending on the viewing angle. According to this, when an optical layer is formed on an article by printing or the like, the optical layer is observed, and if the color of the pigment changes according to the observation angle, the article can be judged to be authentic.

In addition, for example, the circular polarized light separation function of the cholesterol crushing layer included in the sheet may be used to determine the authenticity. The flake usually reflects only one of right-handed circularly polarized light and left-handed circularly polarized light. According to this, the optical layer containing the sheet-like object will see different images in the case of using a right-handed circular polarizing plate and the case of using a left-handing circular polarizing plate. According to this, if the image observed using the right-handed circular polarizing plate is different from the image observed using the left-handed circular polarizing plate, it can be determined that the article on which the optical layer is formed is real.

The target as the target for forming the optical layer as described above is not limited, and a wide range of objects can be used. Examples of the target include: cloth products such as clothing; leather products such as leather bags and shoes; metal products such as screws; paper products such as price tags; rubber products such as tires; but the target is not limited to these examples . In addition, in order to impart designability or information, the aforementioned optical layer may also be formed into a designated planar shape like patterns, numbers, symbols, identifiers (barcodes, etc.).

『Examples』

The following examples are disclosed to specifically illustrate the present invention. However, the present invention is not limited to the embodiments described below, and can be arbitrarily changed and implemented without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, "%" and "parts" indicating the amount are based on weight unless otherwise noted. In addition, unless otherwise noted, the operations described below are performed under normal temperature and pressure conditions.

[Evaluation method]

[Measurement method of haze]

Corona treatment is applied to one side of the flat glass plate. Moreover, the surface of the cholesterol original layer manufactured in the Example or the comparative example was subjected to corona treatment. The corona-treated surface of the glass plate was brought into contact with the corona-treated surface of the original layer of cholesterol, and then pressed and bonded at a pressure of 5 MPa at a temperature of 40°C. After that, the support was peeled off to obtain a sample having a layer structure of "glass plate/cholesterol original layer". Using this sample, a haze meter ("NDH-5000" manufactured by Nippon Denshoku Co., Ltd.) was used to measure the haze of the original layer of cholesterol.

[Measurement method of average particle size of flakes]

The average particle size of the flakes is measured by the following method. First, using a plurality of sieves with different mesh openings, the proportion of flakes passing through the mesh with mesh openings is measured. Then, from the ratio of the size of the sieve opening to the lamellae passing through the sieve having the sieve opening, the particle size distribution of the lamellae is expressed as a cumulative weight percentage. In this particle size distribution, the particle size whose cumulative value of weight is 50% is used as the average particle size.

[Measurement method of wavelength range and bandwidth of reflection band]

Using the sample prepared in the aforementioned [Haze Measurement Method], the reflectance spectrum of the original layer of cholesterol was measured using a spectrometer ("V570" of Japan Spectroscopy Co., Ltd.). The aforementioned measurement is performed under the measurement conditions of the incident angle of light of 5° and the detection angle of 0°. In the measured reflection spectrum, a reflection peak with a reflectance of 30% or more is specified as a reflection peak indicating a reflection band. The wavelength range corresponding to the half-height width of this reflection peak is obtained as the reflection band. In addition, the value of the half-height width of the reflection peak is obtained as the value of the bandwidth of the reflection band.

[Evaluation method of reflection color of flakes]

The optical layer manufactured in the example or the comparative example was visually observed. This observation was carried out under (1) white fluorescent lighting and (2) car interior lighting. Furthermore, the aforementioned observations were made in (i) the front direction of the optical layer and (ii) the oblique direction of the optical layer. According to the reflection color of the observed sheet, the evaluation was performed according to the following criteria. "A": A clear reflection color can be clearly recognized. "B": Although it is not clear, the reflection color itself can be recognized. "C": The reflection color can be barely recognized. "D": The reflection color cannot be recognized.

[Evaluation method of color change]

Under the illumination of a white fluorescent lamp, the optical layer manufactured in the example or the comparative example was visually observed. This visual observation is carried out first (i) in the frontal direction of the optical layer, and thereafter, the observation angle is increased (ii) in the oblique direction of the optical layer. According to the color change (blue shift) of the reflection color that occurs when the observation direction is changed from the front direction to the oblique direction of the optical layer in this way, the evaluation is performed according to the following criteria. "A": It can be recognized that the reflection color changes sharply and obviously due to the larger observation angle. "B": It can be recognized that the reflection color changes significantly but not sharply due to the increased viewing angle. "C": Can barely recognize the change in reflection color due to the increased viewing angle. "D": Even if the viewing angle is increased, the change in the reflected color is still slow, and the color change cannot be recognized.

[Example 1]

(1-1. Manufacture of cholesterol liquid crystal composition)

25.5 parts of a compound having a refractive index anisotropy Δn 0.24 represented by the following formula (X1), 11 parts of a polymerizable liquid crystal compound represented by the following formula (Y1), and a palming agent (manufactured by BASF) LC756”) 2.3 parts, polymerization initiator (“Irgacure OXE02” manufactured by Ciba Specialty Chemicals) 1.2 parts, surfactant (“FTERGENT 209F” manufactured by NEOS) 0.04 parts, and 60 parts of cyclopentanone as a solvent to prepare cholesterol Liquid crystal composition.

『Chem 1』

『Chem 2』

The compound represented by the aforementioned formula (X1) is manufactured using the method described in Japanese Patent No. 5365519. In addition, the compound represented by the aforementioned formula (Y1) is produced using a method described in Japanese Patent No. 4053392.

(1-2. Manufacture of circular polarized light separation membrane)

A polyester film ("COSMOSHINE A4100" manufactured by Toyobo, with a thickness of 100 μm) on one side is prepared as a support. The surface of the support body on the side opposite to the easy-to-join processing surface is subjected to friction treatment. After that, on this rubbed surface, the cholesterol liquid crystal composition was coated with a #12 wire rod to form a layered body of the liquid crystal composition.

The layered body of the liquid crystal composition was subjected to orientation treatment by heating at 80°C for 5 minutes. Thereafter, the layered body of the liquid crystal composition was subjected to a broadband treatment consisting of "UV irradiation treatment with 20.7 mJ/cm ² of weak ultraviolet rays" and "heating treatment followed by heating at 100°C for 1 minute". After that, 800 mJ/cm ² of ultraviolet light was irradiated to the layered body of the liquid crystal composition to cure it. In this way, an original layer of cholesterol as a circularly polarized light separation membrane with a thickness of 5.2 μm and a reflection band with a bandwidth of 250 nm in the wavelength range of 450 nm to 700 nm is obtained on the support. The haze of the original layer of cholesterol was measured by the measurement method described above.

(1-3. Manufacturing of flakes)

By spraying the water flow, the original layer of cholesterol is peeled off from the support. The original layer of cholesterol was pulverized using a reverse jet mill to obtain flakes with an average particle diameter of 20 μm as a phosphor flake filler.

(1-4. Manufacturing of paint)

20 parts by weight of the aforementioned sheet-like material, 80 parts by weight of urethane acrylate ultraviolet curing resin ("UNIDIC 17-806" manufactured by Dainippon Ink Chemical Industry Co., Ltd.), and an ultraviolet polymerization initiator (manufactured by Ciba Specialty Chemicals) "Irgacure 187") 2 parts by weight are dispersed in toluene to produce a paint with a solid content concentration of 20% by weight.

(1-5. Manufacturing of optical layer)

On a 100 μm thick resin film (“ZeonorFilm ZF14-100” manufactured by Nippon Reion Co., Ltd.) formed of a resin based on norbornene, apply the above coating with a coater, dry it, and further heat at 100°C for 2 minutes. Form a coating film. Then, using an ultraviolet irradiator ("UVC321AM1" manufactured by Ushiwang Electric Co., Ltd.), the coating film was irradiated with ultraviolet light of 50 mW/cm ² × 1 second to cure the coating film to obtain an optical layer with a thickness of 50 μm. Observing the obtained optical layer, the color tone of the optical layer will change according to the observation angle.

The optical layer thus obtained was evaluated in accordance with the evaluation method described above.

[Example 2]

Except that the thickness specification of the wire rod was changed to #8, the optical layer was manufactured and evaluated by the same operation as in Example 1. In this Example 2, the obtained cholesterol original layer had a thickness of 3.7 μm and had 2 reflection bands. One of the reflection bands has a bandwidth of 100 nm in the wavelength range of 400 nm to 500 nm. The other reflection band has a bandwidth of 100 nm in the wavelength range of 550 nm to 650 nm.

[Example 3]

Except that the thickness specification of the wire rod was changed to #18, the optical layer was manufactured and evaluated by the same operation as in Example 1. In this Example 3, the thickness of the obtained cholesterol original layer is 8.6 μm, and it has a reflection band with a bandwidth of 200 nm in the wavelength range of 450 nm to 650 nm.

[Example 4]

The optical layer was manufactured and evaluated by the same operation as in Example 2 except that the broadband treatment was not performed. In this Example 4, the obtained cholesterol original layer has a reflection band with a bandwidth of 150 nm in the wavelength range of 500 nm to 650 nm.

[Comparative Example 1]

Except that the temperature of the orientation treatment was changed to 130° C., the optical layer was manufactured and evaluated by the same operation as in Example 2. In this Comparative Example 1, the obtained cholesterol original layer had a thickness of 3.6 μm and had 2 reflection bands. One of the reflection bands has a bandwidth of 100 nm in the wavelength range of 400 nm to 500 nm. The other reflection band has a bandwidth of 100 nm in the wavelength range of 550 nm to 650 nm.

[Comparative Example 2]

The optical layer was manufactured and evaluated by the same operation as in Example 1, except that the surface of the support opposite to the easy-to-bond surface was not rubbed. The liquid crystal compound contained in the cholesterol original layer obtained in Comparative Example 2 is not oriented in the entire layer body, but is oriented in units of small segments. According to this, the original cholesterol layer obtained in Comparative Example 2 becomes a collection of the aforementioned segments, and the whole layer body has no cholesterol regularity, and a plurality of orientation defects are generated. Moreover, the original layer of cholesterol did not show a clear reflection band, and the whole was cloudy.

[result]

The results of the foregoing examples and comparative examples are disclosed in Table 1 below.

"Table 1" [Table 1. Results of Examples and Comparative Examples]

10‧‧‧Optical layer 100‧‧‧flakes 110‧‧‧Cholesterol Crushing Layer 120‧‧‧Directional defects 200‧‧‧Binder

<FIG. 1> FIG. 1 is a schematic cross-sectional view showing an example of an optical layer including a sheet-like object according to an embodiment of the present invention.

<FIG. 2> FIG. 2 is a schematic cross-sectional view showing an example of an optical layer including a sheet-like object according to an embodiment of the present invention.

<FIG. 3> FIG. 3 is a schematic cross-sectional view showing an example of an optical layer including a sheet-like object according to an embodiment of the present invention.

10‧‧‧Optical layer

100‧‧‧flakes

110‧‧‧Cholesterol Crushing Layer

120‧‧‧Directional defects

200‧‧‧Binder

A1‧‧‧Light

Claims (6)

A sheet-like article comprising a crushed piece of a resin layer having cholesterol regularity, the resin layer containing orientation defects with impaired cholesterol regularity, and a haze of the resin layer of 10% or more and 60% or less. The sheet-like article according to claim 1, wherein the sheet-like article has one or more reflection bands including a visible light region. The sheet according to claim 2, wherein the bandwidth of each of the aforementioned reflection bands is 100 nm or more. The sheet-like article according to any one of claims 1 to 3, wherein the average particle diameter of the aforementioned sheet-like article is 1 μm or more and 500 μm or less. A method of manufacturing a sheet-like article, which is a method of manufacturing a sheet-like article according to any one of claims 1 to 4, comprising: a step of forming a resin layer having cholesterol regularity, and a step of pulverizing the resin layer . A paint comprising: the flakes according to any one of claims 1 to 4 and a dispersion medium.

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