JP7367246B2 - Fingerprint resistance evaluation method - Google Patents

Description

The present invention relates to a method for evaluating fingerprint resistance, a laminate, a method for manufacturing the same, and a display device.

2. Description of the Related Art In recent years, there have been an increasing number of opportunities to operate various electronic devices by actually touching a display device such as a touch panel display with a finger. Such display devices are required to have fingerprint resistance in order to prevent deterioration of display image performance due to fingerprints.

In addition, various treatments such as anti-glare treatment, low-reflection treatment, and anti-fingerprint treatment are usually applied to the surface of in-vehicle display devices in order to suppress the effects of reflections caused by sunlight, etc. Such processing may make fingerprints more noticeable and reduce fingerprint resistance.

As a method for evaluating fingerprint resistance, Patent Document 1 discloses simultaneous photometric spectroscopic chromaticity defined by CIE1976L ^* a ^* b ^* display system before and after applying a diluted oleic acid solution to the surface of an object to be evaluated. Discloses a technique that uses lightness L ^* measured with a meter as an index.

JP2020-34416A

When a display device is used in a vehicle, such as an in-vehicle display device, the evaluation results obtained by the evaluation method described in Patent Document 1 may deviate from the results of sensory evaluation by humans inside the vehicle. In some cases, the evaluation method itself was unable to reproduce the actual in-vehicle environment. Here, if there are fingerprints or the like on the display screen, users usually wipe the display screen before use. Development of evaluation methods is also very important.

Therefore, the objects of the present invention are: a method for evaluating fingerprint resistance based on wipeability that can also be applied to in-vehicle display devices, a laminate with excellent fingerprint resistance that satisfies the evaluation criteria by the evaluation method, a method for manufacturing the same, and An object of the present invention is to provide a display device having the laminate.

The present invention provides a method for evaluating fingerprint resistance, a laminate, a method for manufacturing the same, and a display device having the following configurations [1] to [12].
[1] A method for evaluating the fingerprint resistance of the surface of an object, which includes a variable angle colorimeter measuring the area on the surface of the object where the artificial fingerprint liquid has been transferred and then wiped off, and the area where it has not been transferred. A method for evaluating fingerprint resistance characterized by using the measured value difference ΔL ^* (θ) obtained from the following formula (1):
Formula (1)
ΔL ^* (θ) = L of the area to be wiped off after transferring the artificial fingerprint liquid ^* - L of the area where the artificial fingerprint liquid has not been transferred ^*
However, the light incident angle is -70° with respect to the normal to the object surface, and the measurement angle is -5° with respect to the normal to the object surface.
[2] The method for transferring the artificial fingerprint liquid includes attaching the artificial fingerprint liquid to a transfer base material by a spin coating method to prepare a transfer foil having a haze value of 7±2%, and applying a pseudo finger to the transfer foil. The evaluation method according to [1], wherein the pseudo finger is pressed against the surface of the object for 2 seconds with a load of 60N after pressing the surface of the object with a load of 60N.
[3] The evaluation method according to [1] or [2], wherein the amount of squalene attached to the surface of the object is further used when evaluating the fingerprint resistance of the surface of the object.
[4] After the artificial fingerprint liquid has been transferred, the measured value difference ΔL ^* (θ) obtained from the following formula (1) using a variable angle colorimeter between the area where it has been wiped off and the area where it has not been transferred is 0. A laminate characterized by having a surface of 1 or less:
Formula (1)
ΔL ^* (θ) = L of the area to be wiped off after transferring the artificial fingerprint liquid ^* - L of the area where the artificial fingerprint liquid has not been transferred ^*
However, the light incident angle is -70° with respect to the normal to the surface of the object to be measured, and the measurement angle is -5° with respect to the normal to the surface of the object to be measured.
[5] A base material, a predetermined layer disposed on the base material, and an outermost layer disposed on the predetermined layer,
The predetermined layer includes a first predetermined layer on the base material side and a second predetermined layer on the outermost layer side,
The laminate according to [4], wherein the first predetermined layer has a refractive index of 2.00 or less.
[6] A base material, a predetermined layer disposed on the base material, and an outermost layer disposed on the predetermined layer,
The predetermined layer includes a first predetermined layer on the base material side and a second predetermined layer on the outermost layer side,
The laminate according to [4] or [5], wherein the second predetermined layer has a refractive index of 1.43 or more and 1.49 or less.
[7] On the surface of the laminate, the angular dependence of ΔL ^* (θ) at the light incidence angle of −70° has a negative peak in the specular reflection area and a positive peak at angles other than the specular reflection area. have
The laminate according to any one of [4] to [6], wherein the amount of squalene attached to the surface of the laminate after the artificial fingerprint liquid is transferred and before wiping is less than 40 μg.
[8] On the surface of the laminate, the angular dependence of ΔL ^* (θ) at the light incidence angle of −70° does not have a positive peak at angles other than the specular reflection region, [4] to [6] The laminate according to any of the above.
[9] The laminate according to [8], wherein the outermost layer is disposed on the second predetermined layer, and the distance from the surface of the outermost layer to the second predetermined layer is 60 nm or less.
[10] The artificial fingerprint liquid transfer method includes attaching the artificial fingerprint liquid to a transfer base material by spin coating to produce a transfer foil having a haze value of 7±2%, and applying a pseudo finger to the transfer foil. The laminate according to any one of [4] to [9], wherein the pseudo finger is pressed against the surface of the laminate for 2 seconds with a load of 60N after pressing the surface of the laminate with a load of 60N.
[11] A display device comprising the laminate according to any one of [4] to [10].
[12] On the surface of the laminate, the measurement value difference ΔL between the area where the artificial fingerprint liquid has been transferred and once wiped off and the area where it has not been transferred is determined by the following formula (1) using a variable angle colorimeter ^.* A method for manufacturing a laminate, characterized in that the laminate is manufactured so that (θ) is 0.1 or less:
Formula (1)
ΔL ^* (θ) = L of the area to be wiped off after transferring the artificial fingerprint liquid ^* - L of the area where the artificial fingerprint liquid has not been transferred ^*
However, the light incident angle is -70° with respect to the normal to the surface of the object to be measured, and the measurement angle is -5° with respect to the normal to the surface of the object to be measured.

The present invention provides a method for evaluating fingerprint resistance based on wiping properties that can also be applied to in-vehicle display devices, a laminate with excellent fingerprint resistance that satisfies evaluation criteria by the evaluation method, a method for producing the same, and the laminate. A display device having the following can be provided.

(a) is a schematic plan view showing how sunlight is irradiated onto the display device from outside the vehicle directly or through glass, etc., and (b) is a schematic plan view showing the incident angle and measurement angle of sunlight on the display device. FIG. It is a graph showing an example of the correlation between the ΔL ^* (θ) value and the sensory evaluation result by the user. It is a graph showing an example of the correlation between the ΔL ^* (SCI) value and the sensory evaluation result by the user. 2 is a graph showing an example of the angular dependence of ΔL ^* (θ) at a light incident angle of −70° after transfer of an artificial fingerprint liquid and before a wiping operation in a laminate. 12 is a graph showing another example of the angular dependence of ΔL ^* (θ) at a light incident angle of −70° after transfer of the artificial fingerprint liquid and before the wiping operation in the laminate.

In the evaluation method described in Patent Document 1, the resistance of the object to be evaluated is evaluated using the lightness L ^* defined by the CIE1976L ^* a ^* b ^* display system on the surface of the object to be evaluated before and after applying the diluted oleic acid solution as an index. Fingerprint properties are being evaluated. Furthermore, in Patent Document 1, a simultaneous photometric spectrophotometer is used to measure the lightness L ^* , and furthermore, in order to evaluate the accuracy of the evaluation method, a sensory evaluation under a three-wavelength fluorescent lamp is used. are doing. However, under these conditions, since the incident angle and the measurement angle are not determined, it is not possible to evaluate the fingerprint resistance of the display device in the environment inside the vehicle, and the evaluation results obtained by the method of Patent Document 1 and There were cases where the results of the sensory evaluation in the actual vehicle differed from each other.
Furthermore, in the evaluation method described in Patent Document 1, an oleic acid diluted solution in which oleic acid is dissolved in ethanol is used to evaluate fingerprint resistance. There were cases where it was different. In particular, for display devices equipped with an oil-repellent coating, it has sometimes been difficult to accurately evaluate fingerprint resistance due to droplet repelling of the diluted oleic acid solution.
Furthermore, in the evaluation method described in Patent Document 1, fingerprint resistance is evaluated by attaching a diluted oleic acid solution using a finger cot, but in this method, a pseudo fingerprint is attached with good reproducibility. There were times when it was not possible.

On the other hand, the fingerprint resistance evaluation method of the present invention uses the brightness L ^* defined by CIE1976L ^* a ^* b ^* display system, similar to the method described in Patent Document 1, but as a measuring device, the Rather than a photometric spectrophotometer, we use a variable angle colorimeter that applies a specific light incident angle and measurement angle. In this way, in the present invention, the measurement conditions of the variable angle colorimeter are changed to the incident angle by assuming the environment inside a car and taking into account the position of the sun, the position of the display device, and the viewpoint of the user such as the driver. The amount of change in the angular lightness L ^* (θ) before and after adhesion of the artificial fingerprint liquid is taken as an index of fingerprint resistance, taking into consideration the wiping property when the measurement angle is set to -70° and the measurement angle is -5°. Therefore, the present invention can provide a highly accurate fingerprint resistance (fingerprint conspicuousness) evaluation method that can obtain evaluation results equivalent to the sensory evaluation results in an actual vehicle.
Furthermore, in the present invention, for example, a conventionally known artificial fingerprint liquid can be used for evaluation instead of the oleic acid diluted liquid. Some artificial fingerprint liquids take solid components such as dust and sebum into account, and by using these artificial fingerprint liquids, evaluations that take into account actual fingerprint adhesion can be performed more accurately than with oleic acid diluted liquids. can. Further, by using an artificial fingerprint liquid containing such a solid component, the fingerprint resistance evaluation method of the present invention can be easily applied to a display device equipped with an oil-repellent coating.
Furthermore, in the present invention, the fingerprint resistance can be evaluated after the artificial fingerprint liquid has been applied and wiped off using a specific transfer method, so the evaluation can be performed under conditions that more closely reflect the actual vehicle environment. It can be carried out.

The present invention will be explained in detail below. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings are simplified as appropriate. In the following description, "~" indicating a numerical range means that the numerical values written before and after it are included as a lower limit value and an upper limit value. Moreover, (meth)acrylic acid means either one or both of methacrylic acid and acrylic acid.

<Evaluation method of fingerprint resistance>
The fingerprint resistance evaluation method of the present invention (hereinafter sometimes referred to as the present evaluation method) is a method for evaluating fingerprint resistance after wiping the surface of an object (measurement object). The measurement value difference ΔL ^* (θ) obtained from the following equation (1) between the area where the fingerprint liquid has been transferred and once wiped off and the area where the fingerprint liquid has not been transferred is used using a variable angle colorimeter. Note that various members can be used to wipe off the surface of the object, but for example, Scotchbrite No. 5000 (trade name, manufactured by 3M Japan) can be used.
Formula (1)
ΔL ^* (θ) = L of the area to be wiped off after transferring the artificial fingerprint liquid ^* - L of the area where the artificial fingerprint liquid has not been transferred ^*
However, the light incident angle is -70° with respect to the normal to the object surface, and the measurement angle is -5° with respect to the normal to the object surface.

In this evaluation method, as shown in FIG. 1(a), light from a light source 1 such as the sun is transmitted into the vehicle either directly from outside the vehicle or through a light-transmitting object 2 such as glass of the vehicle. This is to evaluate the conspicuousness of fingerprints after wiping (fingerprint resistance) when the surface of the display device 3 mounted on the vehicle is irradiated with the light and the user visually observes the display device in the vehicle environment. Furthermore, it is expected that the fingerprint resistance under such circumstances will be greatly affected by light irradiated through the windshield or side glass at an angle of 45° or more with respect to the normal to the surface of the display device. In this evaluation method, as shown in FIG. 1(b), in particular, light from a light source 1 such as the sun is irradiated at an incident angle of −70° with respect to the normal N of the surface of the display device 3, and the normal This test evaluates the fingerprint resistance after wiping when visually observed by the user at an angle of -5° (measurement angle), which better reflects the fingerprint resistance of the display device after wiping in a vehicle environment. Evaluation results are obtained.

In this evaluation method, from the viewpoint of obtaining excellent fingerprint resistance after wiping, the above ΔL ^* (θ) is preferably 0.1 or less, more preferably 0.10 or less, and 0.0 or less. It is more preferable that Furthermore, the smaller ΔL ^* (θ) is, the more preferable it is. In addition, ΔL ^* (θ) is 0, which means that the measurement value with a variable angle colorimeter of the area on the object surface where the artificial fingerprint liquid was transferred and then wiped off and the area where it was not transferred is It means that they are the same (there is no difference). Therefore, it can be said that the closer ΔL ^* (θ) is to 0, the more preferable it is. Therefore, the fingerprint wiping property does not refer to the physical removability of fingerprints, but to the fact that they are optically invisible (optical invisibility). A detailed method for measuring ΔL ^* (θ) will be described later.

As the artificial fingerprint liquid used in this evaluation method, conventionally known ones can be used as appropriate, but as mentioned above, it is more preferable to use one that takes solid components such as dust and sebum into consideration. Note that a fingerprint is mainly composed of water and sebum components, and the proportion of sebum components increases as the water evaporates. Therefore, in many cases, it is safe to assume that fingerprints are sebum. Components constituting sebum include, for example, fatty acids, glycerolipids, fatty acid esters, wax esters, cholesterol derivatives, squalene, and the like.
Examples of the fatty acids include oleic acid, stearic acid, linolenic acid, palmitic acid, nonanoic acid, adipic acid, tridecanoic acid, myristoleic acid, tetradecanoic acid, and palmitoleic acid.
Examples of the glycerolipid include monoolein, trimyristin, monocaprylin, triolein, monolaurin, monopalmitin, monostearin, tristearin, tripalmitin, and tricaproin.
Examples of the fatty acid ester include n-butyl octoate, benzyl octoate, isobutyl decanoate, ethyl undecanoate, ethyl stearate, ethyl palmitate, ethyl pentadecanoate, benzyl laurate, amyl n-octanoate, and myristic acid. Butyl is mentioned.
Examples of the wax ester include dodecyl stearate, decyl decanoate, hexadecyl palmitate, 3-isoamyl-6-methyl-2-heptyl myristate, myricyl palmitate, cecyl palmitate, and myricyl cerotate.
Examples of the cholesterol derivatives include cholesterol, 7-dehydrocholesterol, vitamin D, cholic acid, chenodeoxycholic acid, deoxycholic acid, lithocholic acid, progesterone, aldosterone, and cortisol.
Furthermore, the artificial fingerprint liquid contains inorganic particles such as silica particles, alumina particles, iron oxide particles, keratin particles, chitin particles, chitosan particles, acrylic particles, styrene particles, divinylbenzene particles, polyamide particles, etc. It can contain one or more types of particulate matter selected from organic particulates such as polyimide-based particulates, polyurethane-based particulates, and melamine-based particulates. Further, the artificial fingerprint liquid can also contain Kanto loam (JIS test powder 1) as particulate matter. The average particle size of the particulate matter can be set as appropriate and is not particularly limited, but for example, the average particle size can be set to 0.05 μm or more and 100 μm or less. In addition, thickeners such as carrageenan and gum arabic, and surfactants such as quaternary ammonium salts and alkylbenzene sulfonates can also be added to the artificial fingerprint liquid. The blending ratio of each component constituting the artificial fingerprint liquid can be appropriately set within a range that provides the effects of the present invention, and is not particularly limited.
In addition, the artificial fingerprint liquid used in this evaluation method can be diluted with an organic solvent as appropriate when preparing a thin film (transfer film). As the organic solvent, conventionally known ones can be used as appropriate, such as isopropyl alcohol, methyl ethyl ketone, methoxypropanol, and ethanol.

As the artificial fingerprint liquid, for example, one having the following formulation can be used.
- Artificial fingerprint liquid obtained by adding 1.0 g of triolein to 10 g of methoxypropanol as a diluent, and further adding 400 mg of Kanto loam of test powder 1 class 11 specified in JIS Z8901 and stirring.
・Add 200 mg of triolein to 5 g of methoxypropanol as a diluent, and further add 200 mg of keratin (derived from human epithelium, manufactured by Wako Pure Chemical Industries, Ltd.), stir, shake vigorously, and let stand for 10 seconds. Then, the artificial fingerprint liquid obtained by gently collecting the supernatant, which does not contain large particle size keratin.

Here, as the artificial fingerprint liquid, it is preferable to appropriately use one that can reproduce the above-mentioned fingerprint components. Specifically, in the present invention, it is preferable to use an artificial fingerprint liquid that is solid at a temperature of 20°C and becomes a dispersed system at a temperature of 40°C. For example, by adding a substance with a melting point higher than room temperature (for example, among the components constituting the sebum mentioned above) to the above-mentioned artificial fingerprint liquid, an artificial fingerprint becomes solid at a temperature of 20°C and becomes a dispersed system at a temperature of 40°C. liquid can be prepared. Artificial fingerprint fluids with these properties adhere to coated surfaces more easily than conventional diluted oleic acid solutions that use oleic acid alone, and can be used for evaluations that take into account actual fingerprint adhesion, improving adhesion and evaluation reproducibility. Excellent in

Note that when evaluating the squalene adhesion amount, the squalene content in the artificial fingerprint liquid is preferably 10 to 15% by mass from the viewpoint of performing the evaluation appropriately.

Here, it is known that the components constituting sebum and their ratios vary from person to person and with age. However, the refractive index of sebum should be between the minimum and maximum values of the refractive index of the components contained in sebum. Among the sebum components, the substance with the smallest refractive index is n-butyl octoate, which has a refractive index of 1.42. Furthermore, among these sebum components, the substance with the highest refractive index is benzyl octoate, which has a refractive index of 1.49. Therefore, the refractive index of a fingerprint is considered to be in the range of 1.42 to 1.49.

Although conventionally known methods can be applied to transfer the artificial fingerprint liquid, it is preferable to use the following method. That is, a transfer foil having a haze value of 7±2% was prepared by attaching the artificial fingerprint liquid to a transfer base material by spin coating, and after pressing a pseudo finger against the transfer foil with a load of 60N, It is preferable to use a method in which a pseudo finger is pressed against the surface of the object for 2 seconds with a load of 60 N. In this method, artificial fingerprint liquid is dripped onto a rotating transfer substrate using a spin coating method, and a uniform thin film can be formed by centrifugal force, making it possible to transfer artificial fingerprint liquid with good reproducibility. can. Here, as the transfer base material, conventionally known materials can be used as appropriate, and for example, a polycarbonate plate can be used. Further, as the pseudo finger, conventionally known ones can be used as appropriate, and for example, natural rubber (rubber hardness: Shore E60, Shore E70 according to JIS K 6253 standard) can be used. Further, as described above, it is preferable to use an artificial fingerprint liquid that is solid at a temperature of 20°C and becomes a dispersion system at a temperature of 40°C.

In addition, in this evaluation method, a luminance meter (for example, product name: SR-UL1R, TOPCON TECHNO HOUSE It is possible to use the measured value difference Δ luminance obtained by the following formula (2) by the company (manufactured by Co., Ltd.).
Formula (2)
ΔBrightness = Brightness of the wiped area after transferring the artificial fingerprint liquid - Brightness of the area not transferred with the artificial fingerprint liquid However, the light incident angle is 85° above the normal to the surface of the measurement sample, and the measurement angle is the normal to the surface of the measurement sample. The angle is 25° upward and 30° to the right, the measurement distance is 650 mm, and the measurement range is 0.2° (solid angle). Further, the wiping member and wiping conditions can be the same as those used when measuring ΔL ^* (θ) above. However, it is difficult to measure brightness in a specified environment due to problems with the installation angle and external light, and the evaluation method of the present invention using a variable angle colorimeter is used because the reproducibility is not high. Alternatively, it is desirable to use both the evaluation based on brightness and the evaluation according to the present invention.

In this evaluation method, the Δ brightness is preferably 0.1 [cd/m ² ] or less from the viewpoint of obtaining excellent fingerprint resistance after wiping. There is a certain correlation between ΔBrightness and ΔL ^* (θ), and by setting both ΔBrightness and ΔL ^* (θ) to good values, better fingerprint resistance after wiping can be imparted. be able to.

When evaluating the fingerprint resistance after wiping the surface of the object, it is possible to further use the amount of squalene adhesion (amount of fingerprint component adhesion) on the surface of the object (for example, assuming that a fingerprint is attached). preferable. Particularly when the surface of the object is oil-repellent, if the amount of squalene attached is less than 40 μg, fingerprints will be less noticeable and fingerprint resistance will be excellent. Note that a detailed method for measuring the amount of squalene attached will be described later.

<Laminated body>
The laminate of the present invention (hereinafter sometimes referred to as the present laminate) has a surface with a measured value difference ΔL ^* (θ) of 0.1 or less in the above-mentioned present evaluation method, so it is resistant to fingerprints after wiping. It has excellent properties and can make fingerprints attached to the surface less noticeable. Note that the transfer method of the artificial fingerprint liquid used for evaluation is preferably the transfer method using the spin coating method described above.
Further, the present laminate can include a base material, a predetermined layer disposed on the base material, and an outermost layer disposed on the predetermined layer. Further, the predetermined layer may include a first predetermined layer on the base material side and a second predetermined layer on the outermost layer side. Further, other materials may be added between the base material and the first predetermined layer, between the first predetermined layer and the second predetermined layer, between the outermost layer and the second predetermined layer, etc. within the range where the effects of the present invention can be obtained. It may have a layer (intermediate layer). Examples of the intermediate layer include a desired functional layer, an adhesive layer, an ultraviolet absorbing layer, an infrared absorbing layer, an antireflection layer, a soft (impact resistant) layer, a hard coat layer, a conductive layer, an antistatic layer, a heat insulating layer, and a reflective layer. Each layer can be used, such as a layer, a primer layer, etc. Note that the outermost layer is placed in a situation where it is touched by human hands during use. The outermost layer may include, for example, an oil-repellent coating layer or a lipophilic coating layer, which will be described later. The present laminate may be used for an operation surface of a touch panel, or a protective member such as a display surface of a display panel or a cover panel covering the display surface. However, the uses of this laminate are not limited to these.

Here, the refractive index of the first predetermined layer is preferably more than 1.49, more preferably 1.60 or more, from the viewpoint of providing excellent fingerprint resistance after wiping. It is preferably 00 or less, and more preferably 1.80 or less.
Further, the refractive index of the second predetermined layer is preferably 1.43 or more, more preferably 1.45 or more, from the viewpoint of providing excellent fingerprint resistance after wiping. It is preferably 49 or less, more preferably 1.47 or less. In addition, since the refractive index of a fingerprint is considered to be 1.42 to 1.49 as described above, it is more preferable that the refractive index of the second predetermined layer is close to the average value of 1.46. . If the refractive index of the second predetermined layer is 1.43 to 1.49, the interface reflectance between the fingerprint and the surface of the laminate will be small, and the difference between the fingerprint-attached part and the other parts will be small; Fingerprints become less noticeable.
Here, the refractive index of the base material can be set as appropriate; for example, a base material with a refractive index of 1.50 can be used. Note that the refractive index of each layer can be measured using an ellipsometer or the like.

The material constituting the base material is not particularly limited, and conventionally known materials can be used as appropriate. For example, the base material may be a transparent resin film made of TAC (triacetyl cellulose), PMMA (polymethyl methacrylate), PC (polycarbonate), PET (polyethylene terephthalate), etc., or a laminated film (laminate plate) of these materials, that is, a resin substrate. It may be wood. Further, as the base material, a conventionally known glass base material (glass base material) may be used.

Further, the materials constituting the first predetermined layer, the second predetermined layer, and the outermost layer are not particularly limited. Each of them may be composed of a thin film obtained by, for example, vacuum deposition, sputtering, or wet coating of ZrO ₂ , Al ₂ O ₃ , SiO ₂ ), or the like. These layers can be given different properties depending on the additives and resins they contain.

In addition, in this laminate, the angular dependence of ΔL ^* (θ) at a light incidence angle of -70° has a negative peak in the specular reflection region and a positive peak at angles other than the specular reflection region, and has oil repellency. When the coating is on the surface (the outermost layer), the amount of squalene attached to the surface of the laminate after the artificial fingerprint liquid is transferred and before wiping (that is, assuming that the fingerprint is attached) is less than 40 μg. It is preferable that there be. For example, the angular dependence of ΔL ^* (θ) can be measured by setting the light incident angle to −70° and the measurement angle from −60° to +85° and calculating ΔL ^* (θ) for each angle. By satisfying such conditions, ΔL*(θ) due to fingerprint adhesion can be reduced, and fingerprints can be made less noticeable. When the outermost layer has oil repellency, its refractive index can be, for example, 1.30 to 1.50. Note that the specular reflection area at a light incidence angle of -70° is +70±10°. Here, FIG. 4 is a graph showing an example of the angular dependence of ΔL ^* (θ) at a light incidence angle of −70° after transfer of artificial fingerprint liquid and before wiping operation in a laminate having an oleophobic coating on the surface. shows. In the graph shown in FIG. 4, the angular dependence of ΔL ^* (θ) at a light incidence angle of −70° has a negative peak in the specular reflection region (+70±10°). Further, in the graph, there are positive (plus) peaks at angles other than the specular reflection region. Note that having a negative peak in the specular reflection region means that the angle (°) at the apex of the negative peak is within the range of the specular reflection region (70° in FIG. 4). Can be interpreted. Also, having a positive peak at an angle other than the specular reflection area means that the angle (°) at the apex of the positive peak is within the range other than the specular reflection area (55° in Figure 4). It can also be interpreted to mean.

In addition, in this laminate, the angular dependence of ΔL ^* (θ) at a light incidence angle of -70° has a lipophilic coating on the surface (the outermost layer) that does not have a positive peak at angles other than the specular reflection region. It is also preferable. Note that the lipophilic coating can have a positive peak only in the specular reflection region in the angular dependence of ΔL ^* (θ) at a light incidence angle of −70°. By having such a lipophilic coating surface, ΔL ^* (θ) due to fingerprint adhesion can be reduced, and fingerprints can be made less noticeable. Although specular reflection increases with lipophilic coating, the conspicuousness of fingerprints can be easily suppressed by bringing the refractive index of the second predetermined layer closer to the refractive index of the fingerprint component. When the outermost layer has lipophilicity, its refractive index can be, for example, 1.30 to 1.50. Here, FIG. 5 is a graph showing an example of the angular dependence of ΔL ^* (θ) at a light incident angle of -70° after transfer of artificial fingerprint liquid and before wiping operation in a laminate having a lipophilic coating on the surface. shows. In the graph shown in Figure 5, the angular dependence of ΔL ^* (θ) at a light incidence angle of -70° does not have a positive peak at angles other than the specular reflection region (+70 ± 10°), and only in the specular reflection region. It has a positive peak. The angle (°) of the position at the apex of the positive peak is within the range of the specular reflection region (70° in FIG. 5).
Note that the wipeability of the surface of the laminate does not depend on the properties of the outermost layer (for example, oil repellency or lipophilicity). Furthermore, the above-mentioned angular dependence of the bending angle ΔL ^* (θ) is not limited to the light incidence angle of -70°, and similar behavior is observed even when the light incidence angle is -30°, for example.

In the present laminate having the lipophilic coating, the distance from the surface of the outermost layer disposed on the second predetermined layer to the second predetermined layer is preferably 60 nm or less. If the distance is 60 nm or less, optical interference due to the difference between the refractive index of the lipophilic outermost layer and the refractive index of fingerprints (sebum) attached to the surface can be suppressed, and fingerprints can be made less noticeable. . In addition, when the lipophilic outermost layer is directly laminated on the second predetermined layer, the thickness of the outermost layer is preferably 60 nm or less. Further, when another layer is disposed between the outermost layer and the second predetermined layer, the total thickness of the outermost layer and the other layer is preferably 60 nm or less. By doing so, it is possible to maintain the lipophilicity of the surface of the outermost layer while reducing the optical influence due to its refractive index. In other words, it can be considered that the fingerprint is substantially directly attached to the second predetermined layer.

In this laminate, from the viewpoint of imparting excellent fingerprint resistance after wiping, it is preferable that the Δ brightness on the surface calculated from the above-mentioned formula (2) is 0.1 [cd/m ² ] or less.

Note that each numerical value mentioned above is based on simulation results by the inventors. The simulations are performed under various conditions in which the refractive index (including the refractive index of air) and thickness of each member of the laminate are changed as appropriate, and a desired numerical range is determined based on the results. For example, in the present laminate having a lipophilic coating, in a simulation in which the distance from the surface of the outermost layer disposed on the second predetermined layer to the second predetermined layer was determined to be 60 nm or less, the lipophilicity of the laminate was determined to be 60 nm or less. Only the thickness of the outermost layer was changed. Furthermore, although the thickness of a fingerprint is usually 10 to several hundred nm in actual measurements, 50 nm was used as a representative value in this simulation. Note that the optical interference ΔY in the simulation is expressed as ΔY=∫photopic luminous efficiency function×D65 light source function×(R _A −R _B )dλ. Here, R _A is the intensity reflectance on the surface of the laminate, and R _B is the intensity reflectance of the fingerprint attached to the surface of the laminate. Since Y is in a proportional relationship with lightness L ^* , when ΔY becomes a small value, ΔL ^* (θ) also becomes a small value.

In the simulation, the intensity reflectance Rm is given by the following formula I.

In Formula I, ηa is the refractive index of air, ηs is the refractive index of the base material, and m is the component of the characteristic matrix [M]. The characteristic matrix [M] is expressed by the following formula II.

In Formula II, n: number of layers stacked on the base material, j: order of each layer stacked on the base material from the outermost layer (top layer), η: optical admittance, φ: optical path length. . Note that if a fingerprint is attached to the surface of the laminate, it is assumed that the fingerprint is on the outermost layer of the laminate. Further, η is represented by the following formula III, and φ is represented by the following formula IV.

In Formula III and Formula IV, N: refractive index of each layer, φ: angle of incidence on each layer. Further, in Formula IV, d: thickness of each layer, λ: wavelength of light.

In this embodiment, the distance from the surface of the laminate to the second predetermined layer, the refractive index of each layer, etc. can be measured non-destructively using an ellipsometer. Alternatively, the laminate may be cut, and the cut surface may be observed or analyzed after being subjected to ion milling or FIB (Focused Ion Beam) processing. For example, elements and structures may be identified by performing qualitative analysis using XPS (X-ray photoelectron spectroscopy) or the like. Further, the number of layers and film thickness may be confirmed using an electron microscope. It is also possible to confirm the structure with higher accuracy by comparing the measurement results with the ellipsometer and other observation or analysis results.

<Method for manufacturing laminate>
In the method for manufacturing a laminate of the present invention (hereinafter sometimes referred to as the present manufacturing method), the laminate is manufactured so that the above-mentioned ΔL ^* (θ) is 0.1 or less on the surface of the laminate. The laminate obtained by this manufacturing method can have excellent fingerprint resistance in consideration of wipeability. In this manufacturing method, the surface of the laminate can also be surface-treated so that ΔL ^* (θ) is 0.1 or less. The surface treatment method is not particularly limited as long as the effects of the present invention can be obtained, and conventionally known methods can be used. For example, an AG (Anti-Glare) coating can be applied to the surface of the base material. AG coating can diffuse reflected light and suppress reflections and reflections by creating very fine irregularities on the surface of the base material.

The laminate of the present invention can be manufactured, for example, by the following procedure.
First, a coating solution containing an active energy ray-curable resin is applied onto a base material such as a resin base material or a glass base material using a bar coater or the like, and heated as necessary (e.g., 80°C). (for 90 seconds) to dry. Thereafter, active energy ray curing is performed in an inert gas (eg, nitrogen gas) atmosphere to form a hard coat film with a predetermined thickness (eg, 5 μm).

The active energy ray-curable resin contains a polymerizable compound that can undergo a curing reaction and form a cured product upon irradiation with active energy rays. As the polymerizable compound, monofunctional monomers, polyfunctional monomers, oligomers and polymers having a vinyl group or (meth)acryloyl group can be used.

Examples of monofunctional monomers include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, ( Isobutyl meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, (meth)acrylic acid Cetyl, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, tricyclodecyl (meth)acrylate, benzyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dicyclopentenyloxy (meth)acrylate Ethyl, dicyclopentanyl (meth)acrylate, pentamethylpiperidyl (meth)acrylate, ethyl (meth)acrylate hexahydrophthalate, ethyl (meth)acrylate 2-hydroxypropylphthalate, (meth)acrylic acid 2-Hydroxybutyl, butoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, etc. meth)acrylic acid esters, styrene, α-methylstyrene, p-methoxystyrene, m-methoxystyrene, di-t-butyl fumarate, di-n-butyl fumarate, diethyl fumarate, mono(di)methyl itaconate, Mono(di)ethyl itaconate, N-isopropylacrylamide, N-vinyl-2-pyrrolidone, and the like can be used.

Examples of the polyfunctional monomer include polyfunctional polymerizable compounds containing two or more (meth)acryloyl groups, such as esterified products of polyhydric alcohol and (meth)acrylic acid, and urethane-modified acrylates. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, propanediol, butanediol, pentanediol, Dihydric alcohols such as hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, 2,2'-thiodiethanol, 1,4-cyclohexanedimethanol; trimethylolpropane, glycerol, pentaerythritol, Examples include trihydric or higher alcohols such as glycerol, dipentaerythritol, and ditrimethylolpropane.

Urethane-modified acrylate can be obtained by a urethane reaction between an organic isocyanate having a plurality of isocyanate groups in one molecule and a (meth)acrylic acid derivative having a hydroxyl group. Examples of organic isocyanates having multiple isocyanate groups in one molecule include hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, diphenylmethane diisocyanate, xylyline diisocyanate, and dicyclohexylmethane diisocyanate. Examples thereof include organic isocyanates having three isocyanate groups in one molecule, which are obtained by isocyanurate modification, adduct modification, and biuret modification of these organic isocyanates.

Examples of oligomers having vinyl groups or (meth)acryloyl groups include polyester oligomers, epoxy oligomers, urethane oligomers, polyether oligomers, alkyd oligomers, polybutadiene oligomers, polythiol polyene oligomers, and spiroacetal oligomers, and polyfunctional alcohols. Examples include oligomers made of (meth)acrylic esters to which vinyl groups and (meth)acryloyl groups are added. Examples of the polymer having a vinyl group or (meth)acryloyl group include the above-mentioned oligomer type having a vinyl group or (meth)acryloyl group.

In addition, the coating solution may contain diluting solvents, beads, fillers, photolytic or thermally decomposable polymerization initiators, metal oxides, surfactants, ultraviolet absorbers, infrared absorbers, antioxidants, etc., as necessary. Additives such as agents, photosensitizers, photostabilizers, and silane coupling agents can be added.

Examples of diluent solvents include toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, ethyl cellosolve acetate, methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, acetone, methyl ethyl ketone, methyl Examples include isobutyl ketone, cyclohexanone, hexane, heptane, octane, decane, dodecane, propylene glycol monomethyl ether, and 3-methoxybutanol.

Examples of the polymerization initiator include benzophenones, acetophenones, α-amyloxime ester, Michler benzoyl benzoate, tetramethylthuram monosulfide, and thioxanthone, and specifically, 1-hydroxycyclohexylphenyl ketone, 2-Hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morphelinopropan-1-one, 1-[4-(2- hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, benzoin, 2,2-dimethoxy-1,2-diphenylethan-1-one, benzophenone, [4-(methylphenylthio) ) phenyl] phenylmethanone, 4-hydroxybenzophenone, 4-phenylbenzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, Examples include α-amyloxime ester, Michler benzoyl benzoate, and tetramethylthuram monosulfide.

Examples of metal oxides include silica, hollow silica, aluminum oxide (alumina), titanium oxide, antimony oxide, zinc oxide, tin oxide, and zirconium oxide.

Surfactants are used for the purpose of compatibilization when blending various raw materials and for the purpose of improving the smoothness of the coating, and include, but are not limited to, acrylic copolymers (ionic and nonionic). , methacrylic copolymers, leveling agents for solvent-based paints, polysiloxane compounds, and the like.

As the photosensitizer, the above-mentioned known compounds for polymerization initiators are used, such as tributylamine, triethylamine, polyethyleneimine, poly-n-butylphosophine, p-dimethylaminobenzoic acid ethyl ester, p-dimethyl Examples include tertiary amines such as aminobenzoic acid isoamyl ester.

The blending proportions of these various components can be appropriately set within the range in which the effects of the present invention can be obtained, and are not particularly limited.
By appropriately blending these various components, various properties such as optical properties, coating film properties, and durability of the produced laminate can be adjusted. Furthermore, for the active energy ray and its irradiation amount, conventionally known conditions can be used as appropriate; for example, a metal halide lamp can be used.

Next, the obtained hard coat coating film is subjected to plasma treatment, and vacuum evaporation is performed to form the first predetermined layer (high refractive index layer) and the second predetermined layer (low refractive index layer). Reflection) coating films are formed respectively.
Here, the constituent material of each layer can be appropriately selected depending on the desired refractive index and reflectance, and the number of layers, thickness, etc. can also be appropriately set. For example, the first predetermined layer and the second predetermined layer may each be formed one layer at a time, or may be a laminate in which a plurality of layers are alternately stacked. Moreover, the thickness of the first predetermined layer and the second predetermined layer can be, for example, each 1 nm or more and 200 nm or less.
Furthermore, each layer may be formed by a sputtering method, a wet coating method, or the like.

The first predetermined layer includes niobium pentoxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), tungsten oxide (WO ₃ ), cerium oxide (CeO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), and zinc oxide ( ZnO), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), hafnium oxide (HfO ₂ ), indium tin oxide (ITO), zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), oxide Antimony (Sb ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), zinc sulfide (ZnS), etc. can be used. Further, if it is desired to impart conductive properties to the first predetermined layer, for example, ITO, indium zinc oxide (IZO) can be used. Further, in the first predetermined layer, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, amino alkyd resin, melamine-urea cocondensation resin, silicon resin, polyester resin, etc. Thermosetting resins such as siloxane resins may also be used. In this case, the first predetermined layer can also contain an inorganic material such as silica, alumina, zirconia, and titania, or an organic material such as acrylic resin.

From the viewpoint of availability and cost, the second predetermined layer preferably contains an oxide of Si, and is preferably a layer mainly composed of SiO ₂ (an oxide of Si) or the like. Here, the term "main component" refers to the component with the highest content among the components contained in the target (here, the second predetermined layer). The second predetermined layer can contain, in addition to SiO ₂ , elements such as Na for the purpose of improving durability, Zr, Al, and N for the purpose of improving hardness, and Zr and Al for the purpose of improving alkali resistance. . The second predetermined layer contains, for example, magnesium fluoride (MgF ₂ ), sodium fluoride (NaF), cryolite (Na ₃ AlF ₆ ), thiolite (Na ₅ Al ₃ F ₁₄ ), lithium fluoride (LiF), Also contains aluminum fluoride (AlF ₃ ), calcium fluoride (CaF ₂ ), styrontium fluoride (SrF ₂ ), zirconium fluoride (ZrF ₄ ), barium fluoride (BaF ₂ ), yttrium fluoride (YF ₃ ), etc. can.

More specifically, for example, as the first predetermined layer, an AR coating film (for example, film thickness: 150 nm) having a refractive index of 1.70 is formed by vacuum evaporation using raw materials: ZrO ₂ /Al ₂ O ₃ . can be formed. Furthermore, for example, as a second predetermined layer, an AR coating film (e.g., film thickness: 90 nm) having a refractive index of 1.46 is formed on the first predetermined layer by vacuum evaporation using SiO ₂ as a raw material. Can be formed.

Subsequently, a silane coupling agent (e.g., perfluoropolyether-based silane coupling agent) is applied onto the second predetermined layer by a spray method, and then heated at high temperature and high humidity (e.g., temperature 50°C, relative humidity 90%). ) It is cured in an environment for a predetermined time (for example, 12 hours) to form an AF (Anti-Fingerprint) coating film with a predetermined thickness (for example, 10 nm) as the outermost layer.
As described above, the laminate of the present invention can be obtained.

The outermost layer is formed using a fluorine compound having at least one functional group selected from the group consisting of a fluoroalkyl group, a fluorooxyalkyl group, a fluoroalkenyl group, a fluoroalkanediyl group, and a fluorooxyalkanediyl group. An oil-repellent coating layer can be used. Some of these functional groups may have --H groups remaining, or all H groups may be replaced with fluorine (-F) groups. Further, there may be branches in the structure, and a plurality of branches may be connected to form a dimer, trimer, oligomer, or polymer structure. In addition, the fluorine compound has reactive properties such as silyl ether groups, alkoxysilyl groups, silanol groups obtained by hydrolyzing alkoxysilyl groups, carboxyl groups, hydroxyl groups, epoxy groups, vinyl groups, allyl groups, acryloyl groups, methacryloyl groups, etc. It may have a group.

As the fluorine compound, for example, a compound represented by the following general formula (A) can be used.
R ^f1 -R ² -D ¹ ...General formula (A)
(R ^f1 is a moiety containing a fluoroalkyl group, a fluorooxyalkyl group, a fluoroalkenyl group, a fluoroalkanediyl group, a fluorooxyalkanediyl group, and ^R2 is an alkanediyl group, an alkantriyl group, and a moiety derived therefrom. ester structure, urethane structure, ether structure, triazine structure, and ^D1 indicates a reactive site).

Examples of the compound represented by general formula (A) include the following. 2,2,2-trifluoroethyl acrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2-perfluorobutyl ethyl acrylate, 3-perfluorobutyl-2-hydroxypropyl acrylate, 2-perfluorobutyl acrylate Fluorohexylethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 2-perfluorooctyl ethyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 2-perfluorodecylethyl acrylate, 2-perfluoro- 3-Methylbutylethyl acrylate, 3-perfluoro-3-methoxybutyl-2-hydroxypropyl acrylate, 2-perfluoro-5-methylhexylethyl acrylate, 3-perfluoro-5-methylhexyl-2-hydroxypropyl acrylate , 2-perfluoro-7-methyloctyl-2-hydroxypropyl acrylate, tetrafluoropropyl acrylate, octafluoropentyl acrylate, dodecafluoroheptyl acrylate, hexadecafluorononyl acrylate, hexafluorobutyl acrylate, 2,2,2-tri Fluoroethyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2-perfluorobutylethyl methacrylate, 3-perfluorobutyl-2-hydroxypropyl methacrylate, 2-perfluorooctylethyl methacrylate, 3-perfluorobutyl ethyl methacrylate Fluorooctyl-2-hydroxypropyl methacrylate, 2-perfluorodecylethyl methacrylate, 2-perfluoro-3-methylbutylethyl methacrylate, 3-perfluoro-3-methylbutyl-2-hydroxypropyl methacrylate, 2-perfluoro-5 -Methylhexylethyl methacrylate, 3-perfluoro-5-methylhexyl-2-hydroxypropyl methacrylate, 2-perfluoro-7-methyloctylethyl methacrylate, 3-perfluoro-7-methyloctylethyl methacrylate, tetrafluoropropyl methacrylate , octafluoropentyl methacrylate, octafluoropentyl methacrylate, dodecafluoroheptyl methacrylate, hexadecafluorononyl methacrylate, 1-trifluoromethyltrifluoroethyl methacrylate, hexafluorobutyl methacrylate, triacryloyl-heptadecafluorononenyl-pentaerythritol, etc. Can be mentioned.
In addition to these, a conventionally known oil-repellent coating layer can be used as the outermost layer.

Further, as the outermost layer, for example, a lipophilic coating layer using a hydrolyzable organosilane compound (for example, one containing a hindered ester group) or a hydrolyzed condensate thereof can be used. The organosilane compound can contain a hindered ester group having excellent lipophilicity and heat resistance, and a hydrolyzable silyl group (for example, an alkoxysilyl group) or a hydroxyl group-containing silyl group. As the lipophilic coating layer, conventionally known ones can be used, and for example, organosilane compounds described in JP-A-2020-203838 can be used.

<Display device>
The display device of the present invention (hereinafter sometimes referred to as the present display device) is not particularly limited as long as it includes the present laminate, and any conventionally known display device can be appropriately applied. Since the present display device having the present laminate has excellent fingerprint resistance, it can be suitably used in various electronic devices such as display devices equipped with touch panels, display panels, and the like.

The present invention will be explained in more detail below using Examples, but the present invention is not limited to these Examples. Note that Examples 1 to 15, which will be described later, are examples for evaluating the fingerprint resistance evaluation method of the present invention, and Examples 16 to 30 are examples for evaluating the conventional evaluation method.

(Confirmation of correlation between ΔL ^* (θ) value and sensory evaluation results)
(1) Preparation of measurement sample First, 2.0 g of artificial fingerprint liquid was dropped onto a colorless and transparent polycarbonate plate with an external diameter of 115 mm x 90 mm and a thickness of 2.0 mm, and by spin coating, a HAZE value of 7 ± 2% was obtained. We created a transfer foil for artificial fingerprint liquid. The HAZE value was measured using a haze meter (product name: NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.), and was determined by HAZE value (%) = diffuse transmittance ÷ total light transmittance. The artificial fingerprint liquid used had the property of being solid at a temperature of 20°C and becoming a dispersion system at a temperature of 40°C.
Next, a natural rubber pad (natural rubber, rubber hardness: Shore E70) with a diameter of 20 mm and a thickness of 2 mm is pressed against the transfer foil of the artificial fingerprint liquid for 2 seconds with a force of 60 N, and then the natural rubber pad to which the artificial fingerprint liquid has been transferred is pressed. A measurement sample was prepared by pressing the sample against the sample with a force of 60 N for 2 seconds to transfer the artificial fingerprint liquid onto the sample. In addition, since the purpose of this example is to verify the correlation between ΔL ^* (θ) and the sensory evaluation results, detailed explanation of each sample will be omitted, but for example, the sample in the example below I'm using the following: Example 1: A first layer with a refractive index of 2.33 and a second layer with a refractive index of 1.46 were formed on a glass substrate whose surface was coated with AG, and the surface was coated with an oil repellent coating (reflectance: 0. 3%). Example 2 and Example 3 (Example 3 and Example 17 are the same sample): The glass base material of Example 1 was changed to a film base material and a resin plate, respectively (reflectance: 0.3% for both). Example 4 (same sample as Example 16): A resin plate whose surface was coated with AG was used as the base material, and the surface was coated with lipophilic coating (reflectance: 4.5%). Example 5: A first layer with a refractive index of 2.33 and a second layer with a refractive index of 1.46 were formed on a resin plate whose surface was coated with AG (reflectance: 0.4%).

(2) Measurement of Diffuse Reflection Fingerprint Resistance ΔL ^* (θ) In the above measurement sample obtained, the area where the artificial fingerprint liquid was transferred and then wiped once, and the area where the artificial fingerprint liquid was not transferred, that is, the area where the artificial fingerprint liquid was transferred. Using a variable angle colorimeter (product name: VC-2, manufactured by Suga Test Instruments Co., Ltd.), we measured CIE 1976L ^* a ^* b ^* on the area where the wiping was performed after adhesion and the area where it was not adhered. The variable angle lightness L ^* defined by the display system was measured. Then, the difference between the measured values ΔL ^* (θ) was calculated according to the following equation (1).
Formula (1)
ΔL ^* (θ) = L of the area to be wiped off after transferring the artificial fingerprint liquid ^* - L of the area where the artificial fingerprint liquid has not been transferred ^*
However, the light incident angle was -70° with respect to the normal to the surface of the measurement sample, and the measurement angle was -5° with respect to the normal to the surface of the measurement sample. Also, as a wiping member, Scotchbrite No. 5000 (trade name, manufactured by 3M Japan), 40 mm x 70 mm, and a load of 500 g, the area to which the artificial fingerprint liquid was applied was once passed through to be wiped off.

(3) Implementation of sensory evaluation For the obtained measurement sample, we constructed an evaluation environment that reproduced the incident angle of sunlight and the positional relationship between the display device and the user in the actual vehicle environment, and based on the following sensory evaluation criteria. , a sensory evaluation was conducted by humans. Specifically, artificial sunlight lighting was used as sunlight, the illuminance was 30,000 to 60,000 lux, the incident angle of the artificial sunlight lighting was -70°, and the observation angle by the user was -5°.
- Sensory evaluation criteria 3: Can be wiped off.
2: Cannot be wiped off and a little remains.
1: Cannot be wiped off.

According to the above procedure, the ΔL ^* (θ) value was measured and the sensory evaluation by the user was performed for 15 measurement samples 1 to 15, and the correlation between the ΔL ^* (θ) value and the sensory evaluation result was confirmed. . Table 1 below shows the results of each measurement sample, and FIG. 2 shows a graph showing the correlation of each measurement sample.

As shown in FIG. 2, it was confirmed that there was a certain correlation between the ΔL ^* (θ) value and the sensory evaluation results. Furthermore, when ΔL ^* (θ) was 0.1 or less, the sensory evaluation result was 3, indicating that the film had excellent fingerprint resistance after wiping.

(Confirmation of correlation between conventional fingerprint resistance evaluation method and sensory evaluation results)
(1) Preparation of measurement sample Eight sheets of gauze were spread, one drop of oleic acid was added, and the mixture was left for 10 seconds. Next, silicone rubber was placed on the part where oleic acid was dropped, a load of 500 g was applied, and the product was left at rest for 2 seconds. Then, the silicone rubber was placed on eight new sheets of gauze, a load of 500 g was applied, and the gauze was left at rest for 2 seconds. Subsequently, the silicone rubber was transferred onto the sample, a load of 500 g was applied, and the sample was held at rest for 2 seconds to transfer the oleic acid to the sample, thereby preparing a sample for measurement.

(2) Measurement of ΔL ^* (SCI) In the obtained measurement sample, the parts to which oleic acid is transferred and the parts to which it is not transferred, that is, the parts to which oleic acid is attached and the parts to which oleic acid is not attached. The lightness L ^* defined by the CIE1976L ^* a ^* b ^* display system was measured using a color difference meter (trade name: CM-5, manufactured by Konica Minolta). Then, the difference between the measured values ΔL ^* (SCI) was calculated according to the following equation (3).
Formula (3)
ΔL ^* (SCI) = L ^* of oleic acid transferred area - L ^* of oleic acid non-transferred area

(3) Implementation of sensory evaluation Human sensory evaluation was performed on the obtained measurement sample using the sensory evaluation method described above. According to the above procedure, the ΔL ^* (SCI) value was measured and the sensory evaluation by the user was performed for 15 measurement samples 16 to 30, and the correlation between the ΔL ^* (SCI) value and the sensory evaluation result was confirmed. . The following sensory evaluation criteria were used.
- Sensory evaluation criteria 5: Fingerprint marks are not visible.
4: Fingerprint marks are hardly visible.
3: Fingerprint marks are slightly visible.
2: Fingerprint marks are visible.
1: Fingerprint marks are clearly visible.

Subsequently, Table 2 below shows the results of each measurement sample, and FIG. 3 shows a graph showing the correlation of each measurement sample. Although ΔL ^* (SCI) is not the value after wiping, it can be seen from FIG. 3 that the conventional evaluation method does not provide a result that reflects the actual sensory evaluation under the vehicle environment.

As mentioned above, the optical index ΔL ^* (SCI), which indicates the reflection intensity at all angles integrated by an integrating sphere, has been conventionally used as an evaluation index for fingerprint resistance, regardless of whether it is wiped off or not. It turned out that it is difficult to properly evaluate the Furthermore, in the conventional transfer method described above, oleic acid may remain on the gauze or droplet repelling may occur, and oleic acid may not be transferred to the sample with good reproducibility.

(Measurement of squalene adhesion amount)
Assuming a laminate with fingerprints attached, after transferring the artificial fingerprint liquid to the surface of the measurement sample and before the wiping operation, the artificial fingerprint liquid adhering to the surface of the measurement sample is cleaned with a solvent to remove the adhering oil. Normal hexane was impregnated into quartz wool, and the surface was scrubbed and rinsed with normal hexane, and the washing liquid was collected in a 40 mL container. Then, after putting the quartz wool used in the container, the container was sealed tightly, and 50 mL of the solution subjected to ultrasonic extraction for 5 minutes was weighed out and subjected to a measuring device to measure the amount of squalene. The calibration curve used to measure the amount of squalene was prepared by applying a standard solution that had been diluted stepwise with n-hexane to the measuring device, and using the adjusted concentration and the area value obtained from the measurement results. The squalene content in the artificial fingerprint liquid used was 13% by mass.
・Measurement device Gas chromatography (GC): Agilent Technologies 7890B (product name)
Mass spectrometer (MS): JEOL JMS-Q1500GC (product name)
・GC conditions Inlet temperature: 280℃
Introduction method: splitless method Introduction amount: 2 μL (using autosampler)
Analytical column: Agilent Technologies (trade name) 5% phenyl-95% methylsiloxane Carrier gas: Helium Head pressure: 64.50 kPa (constant pressure)
Oven conditions: 60℃(3min)-20℃/min-300℃
・MS conditions Ionization method: EI
Measurement method: Scan measurement using electron ionization method Measurement mass range: m/Z = 40 to 425
Ionization voltage: 70eV
Ion source temperature: 200℃
Interface temperature: 250℃

The above measurement sample was a display device equipped with an oleophobic coating, specifically, the angular dependence of ΔL ^* (θ) at a light incident angle of -70° had a negative peak in the specular reflection region (70 ± 10°). , and a positive peak at angles other than the specular reflection region was used. The angular dependence of ΔL ^* (θ) was determined by using the same method as the above-mentioned method for measuring the diffuse reflection resistance ΔL ^* (θ), with the measurement angle set from -60° to +85°, and ΔL ^* for each angle. (θ). Below, the amount of squalene adhering to the measurement sample after the transfer of the artificial fingerprint liquid and before the wiping operation (assuming that a fingerprint is attached), and the amount of ΔL ^* (θ) after the transfer of the artificial fingerprint liquid and after the wiping operation are shown below. The relationship is shown in Table 3 below.

As shown in Table 3 above, in a display device equipped with an oleophobic coating, if the amount of squalene attached to the surface after transferring the artificial fingerprint liquid (assuming that a fingerprint is attached) is less than 40 μg, the ΔL after wiping ^is (θ) is 0.1 or less, indicating that it has excellent fingerprint resistance. In addition, in a display device equipped with an oleophilic coating in which the angular dependence of ΔL ^* (θ) at a light incidence angle of -70° does not have a positive peak in areas other than the specular reflection region, fingerprint components adhere to the oleophilic surface. Therefore, ΔL ^* (θ) is not affected by the amount of squalene attached and has excellent fingerprint resistance (for example, even if the amount of squalene attached exceeds 100 μg, ΔL ^* (θ) is - 0.09).

From the above, it can be seen that the fingerprint resistance evaluation method of the present invention is an excellent evaluation method that can also be applied to in-vehicle display devices. Note that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit.

1 Light source 2 Light-transmitting object 3 Display device N Normal line

Claims (3)

A method for evaluating fingerprint resistance of a surface of an object, the method comprising:
After the artificial fingerprint liquid has been transferred on the surface of the object, the measured value difference ΔL ^* (θ) between the area where it has been wiped off and the area where it has not been transferred is determined by the angle colorimeter using the following formula (1). Fingerprint resistance evaluation method characterized by using:
Formula (1)
ΔL ^* (θ) = L of the area to be wiped off after transferring the artificial fingerprint liquid ^* - L of the area where the artificial fingerprint liquid has not been transferred ^*
However, the light incident angle is -70° with respect to the normal to the object surface, and the measurement angle is -5° with respect to the normal to the object surface. The method for transferring the artificial fingerprint liquid includes attaching the artificial fingerprint liquid to a transfer base material by a spin coating method to prepare a transfer foil having a haze value of 7±2%, and applying a pseudo finger to the transfer foil with a load of 60N. 2. The evaluation method according to claim 1, wherein the pseudo finger is pressed against the surface of the object for 2 seconds with a load of 60 N. The evaluation method according to claim 1, further comprising using the amount of squalene attached to the surface of the object when evaluating the fingerprint resistance of the surface of the object.