JP2017185691A - Light-shielding film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-shielding film capable of obtaining sufficient light-shielding properties.SOLUTION: A light-shielding film includes a base material 2 made of a plastic film and a plurality of printing ink layers 3 laminated respectively in multiple layers on both sides of the base material 2. The plurality of printing ink layers 3 laminated on a single surface of the base material 2 have an optical density of 3.5 or more. The number of generated pin holes is less than 1.0 per 625 mm, the pin holes appearing on all the printing ink layers 3 arranged on both sides of the base material 2 and allowing light to pass in a thickness direction of the base material 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light-shielding film.

Some conventional light-shielding films have a printing ink layer superimposed on one or both sides of a base film.
Patent Document 1 discloses a light-shielding film in which a printing ink layer is overlaid on both sides of a base film, and an aluminum foil is overlaid on one printing ink layer that overlaps one side of the base film.
Patent Document 2 discloses that a plurality of printing ink layers (light-shielding layers) of a light-shielding film are formed by printing and laminating ink on a base film (resin film) a plurality of times by gravure printing. Yes. By printing the ink a plurality of times, the effect of filling the pinhole generated in the lower printing ink layer with the upper printing ink layer can be expected.

JP 2006-231619 A Japanese Patent No. 5217170

By the way, when the light-shielding film is used in an electrical product such as a liquid crystal display, the light-shielding film is required to have electrical insulation. For this reason, in the light-shielding film of patent document 1 containing an aluminum foil, the use will be limited, ie, there exists a problem that versatility is low.
Further, as in Patent Document 1, if the printing ink layers are simply overlapped one by one on both surfaces of the base film, there is a high possibility that pinholes generated in both printing ink layers overlap each other. For this reason, there is a high possibility that light leaks through the overlapping pinholes and a sufficient light shielding property cannot be obtained.

  Conventionally, in order to suppress the occurrence of pinholes, it is conceivable to form a plurality of printing ink layers on the same surface of a substrate film by gravure printing as in Patent Document 2. However, if printing is simply performed a plurality of times, a phenomenon (back trap) occurs in which a part of the lower printing ink layer is taken on the printing plate on which the upper printing ink layer is printed in the second and subsequent printings. Resulting in. Since the occurrence of back traps causes the generation of pinholes, there is a high possibility that sufficient light shielding properties cannot still be obtained in the light shielding film.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a light-shielding film capable of obtaining a sufficient light-shielding property.

One aspect of the present invention includes a base material made of a plastic film, and a plurality of printing ink layers that overlap each other on both sides of the base material, and the plurality of printing ink layers stacked on the same surface of the base material The optical density is 3.5 or more, and appears in all the printing ink layers arranged on both sides of the base material, and the number of pinholes through which light is transmitted in the thickness direction of the base material, The light-shielding film is less than 1.0 per 625 mm ² .

  The plurality of printing ink layers stacked on the same surface of the substrate may have an optical density of 5.3 or less.

  Of the plurality of printing ink layers stacked on the same surface of the substrate, the lowermost printing ink layer in contact with the substrate may include a polyurethane-based resin.

  Of the plurality of printing ink layers stacked on the same surface of the substrate, the thickness of the lowermost printing ink layer in contact with the substrate and the thicknesses of the other printing ink layers may be different from each other.

  The thickness of the lowermost printing ink layer may be larger than the thickness of the other printing layer.

  The uppermost printing ink layer among the plurality of printing ink layers stacked on the same surface of the substrate may include a polyester resin or an acrylic resin.

  Of the plurality of printing ink layers stacked on the same surface of the substrate, the uppermost printing ink layer may include a filler having an average particle diameter of 5 μm or more.

According to the present invention, the optical density of the plurality of printing ink layers stacked on the same surface of the substrate is 3.5 or more, and the number of pinholes is less than 1.0 / 625 mm ^2. Sufficient light shielding properties can be obtained.

It is a schematic sectional drawing which shows the light-shielding film which concerns on one Embodiment of this invention. It is a schematic sectional drawing which shows the light-shielding film which concerns on other embodiment of this invention. It is a schematic sectional drawing which shows the light-shielding film which concerns on other embodiment of this invention.

  As shown in FIG. 1, the light-shielding film 1 according to this embodiment includes a base material 2 and a plurality of printing ink layers 3.

The base material 2 consists of a plastic film. As the plastic film, a polyethylene terephthalate (PET) film, a polybutylene terephthalate (PBT) film, a polyethylene naphthalate (PEN) film, a polyamide (PA) film, a polyolefin film such as polyethylene (PE) or polypropylene (PP) is used. be able to. Although the thickness of the base material 2 may be arbitrary, it may be about 2.0-12.0 micrometers, for example.
The base material 2 may be formed, for example, so as to be colored and difficult to transmit light.

A plurality of printing ink layers 3 are overlapped on both surfaces 2a and 2b (first surface 2a and second surface 2b) of the substrate 2, respectively. That is, the number of the printing ink layers 3 overlapping the same surface (first surface 2a, second surface 2b) of the base material 2 may be at least two. In the light-shielding film 1 of the present embodiment, two printing ink layers 3 (3A, 3B) overlap the first surface 2a and the second surface 2b of the base material 2, respectively.
The printing ink layer 3 can be formed by printing by a method such as gravure printing, flexographic printing, or screen printing. Moreover, you may form by application | coating methods, such as a gravure coat, a roll coat, a curtain coat, and a die coat.

In the light-shielding film 1 of the present embodiment, the total optical density of the plurality of printing ink layers 3A and 3B stacked on the same surface of the substrate 2 is 3.5 or more. Further, the total optical density of the plurality of printing ink layers 3A and 3B superimposed on the same surface of the substrate 2 may be, for example, 5.3 or less.
In the light-shielding film 1 of the present embodiment, in order to measure the optical density of the plurality of printing ink layers 3A and 3B superimposed on one surface (first surface 2a or second surface 2b) of the substrate 2, For example, the plurality of printing ink layers 3A and 3B overlaid on the other surface (second surface 2b or first surface 2a) of the substrate 2 may be removed with a solvent or the like.

If the optical density of the plurality of printing ink layers 3A, 3B overlapping one side of the substrate 2 is 3.5 or more, the light source arranged on one side of the substrate 2 is a strong light such as an LED (for example, Even when 8000 cd / mm ² or more is emitted, the light source can be prevented from being visually recognized from the other surface side of the substrate 2. That is, it is possible to sufficiently obtain the light shielding performance (hereinafter referred to as the light shielding performance) that is exhibited according to the optical density of the printing ink layers 3A and 3B.
Further, even if the optical density of the plurality of printing ink layers 3A and 3B overlapping one surface of the substrate 2 is 5.3 or less, a light source that emits strong light is visible from the other surface side of the substrate 2. Can be sufficiently prevented. That is, sufficient light shielding performance can be obtained.

Moreover, in the light-shielding film 1 of the present embodiment, the number of pinholes that appear in all the printing ink layers 3 superimposed on both surfaces of the substrate 2 and through which light passes in the thickness direction of the substrate 2 is 625 mm. Less than 1.0 per ² .

  In order to obtain the characteristics of the light-shielding film 1 described above, the printing ink layer 3 is preferably set as follows, for example.

  The printing ink layer 3 preferably contains, for example, a dark pigment or dye. The printing ink layer 3 is preferably made black by containing, for example, carbon black. When the printing ink layer 3 contains carbon black, it is possible to improve the light shielding performance (increase in optical density) in the light shielding film 1.

  In order to set the optical density of the plurality of printing ink layers 3A and 3B superimposed on the same surface of the substrate 2 to 3.5 or more, for example, a plurality of printing ink layers 3A stacked on the same surface of the substrate 2 is used. , 3B is preferably set to 1.8 μm or more and 2.5 μm or less.

Of the plurality of printing ink layers 3A and 3B stacked on the same surface of the substrate 2, the thickness of the lower printing ink layer 3A (lowermost printing ink layer) in contact with the substrate 2 and the upper printing ink layer 3B ( The thickness of the other printing ink layer) may be the same or different, for example.
However, the thickness of the lower printing ink layer 3A and the thickness of the upper printing ink layer 3B are preferably different from each other. In the light-shielding film 1 of the present embodiment, the thickness of the lower printing ink layer 3A is larger than the thickness of the upper printing ink layer 3B.

  The lower printing ink layer 3A preferably contains a polyurethane resin as a binder resin, for example. In this case, adhesion between the substrate 2 and the lower printing ink layer 3A can be secured. Thereby, when the upper printing ink layer 3B is formed, the occurrence of back traps can be suppressed, and the number of pinholes generated in the lower printing ink layer 3A can be reduced.

  The upper printing ink layer 3B (uppermost printing ink layer) is preferably harder than the lower printing ink layer 3A. The upper printing ink layer 3B preferably contains, for example, a polyester resin or an acrylic resin as a binder resin.

Further, the hardness of the upper printing ink layer 3B is preferably, for example, 150 N / mm ² or more in terms of Martens hardness.
Martens hardness can be measured by a dynamic ultra-micro hardness meter manufactured by Shimadzu Corporation, and is standardized by standard ISO 14577-1.

Martens hardness is calculated | required by the following formula | equation.
HM (N / mm ² ) = F / As (h)
F: Maximum test load As (h): Indenter surface area at depth (h)

In order to set the Martens hardness of the upper printing ink layer 3B to 150 N / mm ² or more, a binder resin contained in the printing ink layer 3 may be appropriately selected and used. Examples of the selected binder resin include various curable resins using techniques such as two-component curing, heat curing, energy beam curing with an electron beam or ultraviolet rays. As the binder resin, a polyester resin, an acrylic resin, an epoxy resin, or the like can be suitably used. Examples of the curing agent include isocyanate curing agents. When an isocyanate curing agent is used, polyester polyol or acrylic polyol can be used as the main agent. A polyester urethane polyol that has been chain-extended by reacting one or more of the isocyanate compounds may be used. The isocyanate used as the curing agent may be aliphatic isocyanate or aromatic isocyanate, but aliphatic isocyanate is preferred. The aliphatic isocyanate curing agent is a bifunctional or higher functional isocyanate compound having no aromatic ring. By not having an aromatic ring, the benzene ring is not quinoidized by ultraviolet rays, and yellowing can be suppressed.

  Moreover, in the light-shielding film 1 of this embodiment, each printing ink layer 3 may contain a granular filler, for example. In this case, when the printing ink layer 3 is formed by printing, the ink forming the printing ink layer 3 is easily peeled off from the plate surface. That is, the printing ink layer 3 can be suitably formed on the surface of the substrate 2. The filler may be, for example, a silica filler or an acrylic filler. The average particle size of the filler is preferably 3 μm or more, for example. Moreover, the average particle diameter of the filler contained in upper printing ink layer 3B is good in it being 5 micrometers or more, for example.

According to the light-shielding film 1 of the present embodiment, a plurality of printing ink layers 3 are overlapped on both surfaces of the substrate 2. In addition, the optical density of the plurality of printing ink layers 3A and 3B superimposed on the same surface of the substrate 2 is 3.5 or more, and the number of pinholes generated in the light-shielding film 1 is less than 1.0 / 625 mm. ² . For this reason, sufficient light-shielding property can be obtained.
Moreover, in the light-shielding film 1 of this embodiment, sufficient light-shielding property is ensured by making the optical density of several printing ink layer 3A, 3B piled up on the same surface of the base material 2 into 5.3 or less. However, the thickness of the printing ink layers 3A and 3B can be set thin.

  Further, according to the light-shielding film 1 of the present embodiment, the thickness of the lower printing ink layer 3A (lowermost printing ink layer) and the thickness of the upper printing ink layer 3B (other printing ink layers) are: They are different from each other. For this reason, compared with the case where the lower printing ink layer 3A and the upper printing ink layer 3B have the same thickness, the pins generated in the plurality of printing ink layers 3A and 3B stacked on the same surface of the substrate 2 The number of holes can be reduced. That is, the light-shielding film 1 with few pinhole defects can be provided.

  Moreover, according to the light-shielding film 1 of the present embodiment, the thickness of the lower printing ink layer 3A (lowermost printing ink layer) is larger than the thickness of the upper printing ink layer 3B (other printing ink layers). . For this reason, the adhesive force of the lower printing ink layer 3A with respect to the base material 2 is thereby increased, and a back trap is hardly generated when the upper printing ink layer 3B is printed. As a result, the number of pinholes generated in the plurality of printing ink layers 3A and 3B stacked on the same surface of the substrate 2 can be further reduced. That is, the light-shielding film 1 with further fewer pinhole defects can be provided.

  In the light-shielding film 1 of the present embodiment, the upper printing ink layer 3B (uppermost printing ink layer) contains a polyester resin or an acrylic resin, and the upper ink layer 3B has an average particle diameter of 5 μm or more. When the filler is contained, the following effects are obtained. That is, even if the light-shielding films 1 are wound up in a roll shape and the light-shielding films 1 are overlapped with each other, the light-shielding films 1 are prevented from sticking (blocking), and the overlapping light-shielding films 1 are relatively Easy to peel off. Therefore, even if the long light-shielding film 1 is wound into a roll, it can be easily fed out.

  Hereinafter, although the effect of this embodiment mentioned above is explained more concretely by an example, the present invention is not limited by the following statements.

≪Measurement of optical density and evaluation of shading performance≫
For the light-shielding films of the four types of samples shown in Table 1 (Examples 1 to 3, Comparative Example 1), the optical density (OD value) was measured and the light-shielding performance was evaluated.

<About the sample in Table 1>
In Table 1, the light-shielding films of all samples (Examples 1 to 3 and Comparative Example 1) are all made of a colorless and transparent PET film having a thickness of 4.5 μm (visible light transmittance of about 85%). Two printing ink layers are stacked on the same surface. Each printing ink layer is formed by gravure printing.

In each sample of Table 1, the lower printing ink layer in contact with the base material among the two printing ink layers overlapping on the same surface of the base material both contains a polyurethane-based resin as a binder resin, and carbon black as a pigment. Ink containing was used. Further, 5 wt% of silica filler having an average particle diameter of 3 μm was added to the ink forming the lower printing ink layer.
On the other hand, in the upper printing ink layer overlapping the lower printing ink layer, an ink containing a polyester resin as a binder resin and carbon black as a pigment was used. Further, 5 wt% of silica filler having an average particle diameter of 7 μm was added to the ink constituting the upper printing ink layer.

  In each sample of Table 1, a configuration in which two printing ink layers are stacked on only one side (first side) of the base material (“single side printing” in Table 1), and both sides of the base material (first side and first side) A configuration (two-sided printing in Table 1) was prepared in which two printing ink layers were superimposed on each other.

  In Examples 1 to 3 and Comparative Example 1 in Table 1, the total thicknesses of the two printing ink layers overlapping the same surface of the substrate are different from each other. The total thickness of the two printing ink layers that overlap the same surface of the substrate is 1.5 μm in Comparative Example 1, 1.8 μm in Example 1, 2.0 μm in Example 2, and 2.5 μm in Example 3. ing. The thickness of each printing ink layer shown in Table 1 is the thickness after drying. The thickness of each printing ink layer was adjusted by changing the number of lines of a plate (Helio plate) used in gravure printing.

<Measurement method of optical density>
The optical density (OD value) was measured with respect to “single-sided printing” of each sample in Table 1 using a portable transmission densitometer 341 manufactured by x-rite.

<Evaluation method of shading performance>
Regarding the evaluation of the light shielding performance, the light shielding performance was subjected to sensory evaluation with respect to “single-sided printing” and “double-sided printing” of each sample in Table 1 using an LED light table of 8800 cd / m ² as a light source under dark room conditions. Specifically, in a dark room, an LED light table as a light source was arranged on one surface side of the substrate, and it was evaluated whether or not the light source could be seen through from the other surface side of the substrate. According to the sensory evaluation, when the light was completely shielded (when the light source was not visible), it was “◯ (passed)”, and when the light source was seen through even a little, it was “× (failed)”.

  As shown in Table 1, in Comparative Example 1 in which the total thickness of the two printing ink layers overlapping on one side of the substrate was 1.5 μm, the optical density in single-sided printing was 3.0. In Comparative Example 1, the light shielding performance was unacceptable for both single-sided printing and double-sided printing. That is, in Comparative Example 1, sufficient light shielding performance cannot be obtained even for double-sided printing.

  On the other hand, in Examples 1 to 3, in which the total thickness of the two printing ink layers overlapping on one side of the substrate was 1.8 μm or more, the optical density in single-sided printing was 3.5. Moreover, in Examples 1-3, although the light-shielding performance failed in the case of single-sided printing, it passed in the case of double-sided printing. In other words, the optical density of the two printing ink layers that overlap one side of the substrate is set to 3.5 or more, and the two printing ink layers that have an optical density of 3.5 or more are overlapped on both sides of the substrate to block light. As a conductive film, sufficient light shielding performance can be obtained. Moreover, the optical density of two printing ink layers which overlap the single side | surface of a base material can be 3.5 or more because the total thickness of the two printing ink layers which overlap the single side | surface of a base material shall be 1.8 micrometers or more. .

  Moreover, when the optical density in single-sided printing is 5.3 or less as in Examples 1 to 3, the total thickness of the two printing ink layers that overlap one side of the substrate is set to be relatively thin, 2.5 μm or less. Is possible. Since thinning of the light-shielding film is regarded as important in a liquid crystal display, it is effective to reduce the thickness of the light-shielding film by setting the optical density in single-sided printing to 5.3 or less.

≪Measure the number of pinholes≫
About the light-shielding film of three types of samples (Examples 4-6) shown in Table 2, the number of pinholes was measured.

<About the sample in Table 2>
In Table 2, the light-shielding films of all samples (Examples 4 to 6) are the same as the samples in Table 1 except for the thickness of the upper printing ink layer and the thickness of the lower printing ink layer.
In each sample of Table 2, similarly to the sample of Table 1, a configuration in which two printing ink layers are stacked only on one side (first side) of the substrate (“single-sided printing” in Table 2), and a substrate A configuration (two-sided printing in Table 2) was prepared in which two printing ink layers were superimposed on both sides (first side and second side).

  In each sample of Table 2, each printing ink layer is formed so that the total thickness of the two printing ink layers overlapping on the same surface of the substrate is 2.0 μm after drying. In the sample of Table 2, an error of ± 0.1 μm occurs in the total thickness of the two actually measured printing ink layers with respect to the target value of 2.0 μm. This error is an error based on a printing apparatus that forms a printing ink layer by printing, and is acceptable when measuring pinholes.

  In each sample of Table 2, the total thickness of the two printing ink layers overlapping one side of the substrate is 1.8 μm or more. For this reason, in each sample of Table 2, the optical density of the two printing ink layers overlapping on one side of the substrate is 3.5 or more. Moreover, in each sample of Table 2, sufficient light-shielding performance as a light-shielding film can be obtained by stacking two printing ink layers having an optical density of 3.5 or more on both surfaces of the substrate.

  In Examples 4 to 6 in Table 2, the relationship between the thickness of the lower printing ink layer and the thickness of the upper printing ink layer is different from each other. In Example 4, the thicknesses of the lower and upper printing ink layers are the same. In Example 5, the thickness of the lower printing ink layer is smaller than the thickness of the upper printing ink layer. In Example 6, the thickness of the lower printing ink layer is larger than the thickness of the upper printing ink layer. The thickness of each printing ink layer in each sample was adjusted by changing the number of lines of a plate (Helio plate) used in gravure printing.

<Measurement method of pinhole number>
For the measurement of the number of pinholes, an LED light table of 8800 cd / m ² as a light source under darkroom conditions was used for “single-sided printing” and “double-sided printing” of each sample in Table 2 as in the evaluation of the light shielding performance described above. The number of pinholes was counted visually. Specifically, in a dark room, an LED light table of 8800 cd / m ² is arranged as a light source on one surface side of the substrate, and the area within 25 mm × 25 mm (625 mm ² ) when viewed from the other surface side of the substrate. The number of visible pinholes was counted. The size of the pinhole to be counted is not limited. The number of pinholes in Table 2 is obtained by calculating an average value of the number of pinholes measured at 10 locations randomly selected in the same sample.

As shown in Table 2, in Examples 4 to 6, the number of pinholes in double-sided printing is much smaller than the number of pinholes in single-sided printing. This means that even if there are many pinholes in the printing ink layer on one side of the substrate, many of the pinholes in the printing ink layer on one side of the substrate are printed on the other side of the substrate. This is because it is covered by the ink layer.
In each of Examples 4 to 6, the number of pinholes in double-sided printing is all less than 1.0 / 625 mm ² . Furthermore, in Examples 4 to 6, as described above, since the optical density of the two printing ink layers overlapping on one side of the base material is 3.5 or more, both have sufficient light shielding properties as a light shielding film. Can be obtained.

As shown in Table 2, in Examples 5 and 6 in which the thickness of the lower printing ink layer and the thickness of the upper printing ink layer are different from each other, the thicknesses of the lower printing ink layer and the upper printing ink layer are the same as in Example 4 There are few pinholes.
In Example 4, since the thickness of the lower printing ink layer is the same, the pinhole generated in the lower printing ink layer is difficult to cover with the upper printing ink layer, and the upper printing ink layer is printed. It is thought that back traps are likely to occur when For this reason, in Example 4, it is thought that many pinholes will generate | occur | produce.

On the other hand, in Example 5, it is considered that the upper printing ink layer is thicker than the lower printing ink layer, so that pinholes generated in the lower printing ink layer are easily covered with the upper printing ink layer. Thereby, in Example 5, it is thought that the number of pinholes can be suppressed smaller than Example 4.
In Example 6, since the lower printing ink layer is thicker than the upper printing ink layer, the adhesion of the lower printing ink layer to the substrate is increased, and a back trap is generated when the upper printing ink layer is printed. It will be difficult to do. Thereby, in Example 6, it is thought that the number of pinholes can be suppressed smaller than Example 4.

  Moreover, as shown in Table 2, in Example 6 where the thickness of the lower printing ink layer is larger than the thickness of the upper printing ink layer, the thickness of the lower printing ink layer is smaller than the thickness of the upper printing ink layer. The number of pinholes is smaller than in the fifth embodiment. This means that the number of pinholes can be effectively reduced by suppressing the occurrence of back traps, rather than covering the pinholes of the lower printing ink layer with the upper printing ink layer. That is, in order to reduce the number of pinholes, it is more effective to make the thickness of the lower printing ink layer larger than the thickness of the upper printing ink layer.

Moreover, as shown in Table 2, the number of pinholes in double-sided printing is 0.0 / 625 mm by setting the number of pinholes in single-sided printing to less than 10.0 / 625 mm ² as in Example 6. ² can be used. That is, it is possible to provide a light-shielding film free from pinhole defects.

≪Evaluation of blocking≫
About the light-shielding film of 6 types of samples (Examples 7-12) shown in Table 3, blocking (adhesion) of the light-shielding films after overlapping two light-shielding films was evaluated.

<About the sample in Table 3>
In Table 3, all of the light-shielding films of the samples (Examples 7 to 12) are obtained by superimposing two printing ink layers on both surfaces of the substrate by gravure printing.
In all samples, the base material of the light-shielding film is the same as the samples in Tables 1 and 2. The lower printing ink layer is the same as the samples in Tables 1 and 2 except for the thickness. Moreover, in all the samples, the two printing ink layers overlapping on one side of the substrate are both formed so that the thickness after drying is 1.0 μm. That is, the total thickness of the two printing ink layers overlapping on one side of the substrate is set to 2.0 μm in any sample after drying.

  In Examples 7 to 12 in Table 3, the type of the binder resin contained in the upper printing ink layer, the presence or absence of the silica filler in the upper printing ink layer, and the average particle diameter of the silica filler contained in the upper printing ink layer Are different from each other.

In the light-shielding film of Example 7, the upper printing ink layer contains an acrylic resin. Further, 5 wt% of silica filler having an average particle diameter of 7 μm is added to the upper printing ink layer in Example 7.
In the light-shielding film of Example 8, the upper printing ink layer contains a polyester resin. In the upper printing ink layer in Example 8, 5 wt% of silica filler having an average particle diameter of 7 μm is added.
In the light-shielding film of Example 9, the upper printing ink layer contains a polyester resin. In the upper printing ink layer in Example 9, 5 wt% of silica filler having an average particle diameter of 5 μm is added.
In the light-shielding film of Example 10, the upper printing ink layer contains a polyester resin. In the upper printing ink layer in Example 10, 5 wt% of silica filler having an average particle diameter of 3 μm is added.
In the light-shielding film of Example 11, the upper printing ink layer contains a polyester resin. No silica filler is added to the upper printing ink layer in Example 10.
In the light-shielding film of Example 12, the upper printing ink layer contains the same polyurethane-based resin as the lower printing ink layer. In the upper printing ink layer in Example 12, 5 wt% of silica filler having an average particle diameter of 7 μm is added.

In each sample of Table 3, the total thickness of the two printing ink layers overlapping one side of the substrate is 1.8 μm or more. For this reason, in each sample of Table 3, the optical density of two printing ink layers which overlap on one side of a substrate is 3.5 or more. Moreover, in each sample of Table 3, since two printing ink layers with an optical density of 3.5 or more overlap on both surfaces of the base material, sufficient light shielding performance as a light shielding film can be obtained.
Moreover, when the number of pinholes similar to that described above was measured for each sample in Table 3, the number of pinholes was less than 1.0 / 625 mm ² . For this reason, in each sample of Table 3, sufficient light-shielding properties can be obtained.

<Blocking evaluation method>
The evaluation of blocking for each sample in Table 3 was carried out by superposing two light-shielding films and applying a load of 30 kg / cm ² from these superposition directions to the two light-shielding films by a blocking tester. After leaving for 48 hours in an environment of 0 ° C., the two light-shielding films were peeled off from each other with the hands of the operator.
The evaluation of blocking is a feeling that an operator feels when the light-shielding film is peeled off by hand, that is, a sensory evaluation by the operator. The evaluation criteria were as follows, and the evaluation was “Pass” when the evaluation was “Δ”, “◯”, “◎”.
X: It sticks and does not peel off.
▲: Peeling but resistance (large).
Δ: peeling but resistance (medium)
○: Peeled but has resistance (small).
(Double-circle): It peels without resistance.

As shown in Table 3, in Example 11 in which the upper printing ink layer does not contain a filler, and in Example 12 in which the upper printing ink layer contains a filler having an average particle diameter of 7 μm, a polyurethane resin is included as a binder resin. The light-shielding films are no longer peeled off.
In Example 11, since the upper printing ink layer does not contain a filler, unevenness was not sufficiently formed on the surface of the light-shielding film, so that the light-shielding films were not peeled off.
In Example 12, the polyurethane resin of the upper printing ink layer is relatively soft, so that the unevenness of the surface of the light shielding film based on the filler of the upper printing ink layer cannot be maintained in a state where the two light shielding films are overlaid. For this reason, it is considered that the light-shielding films are no longer peeled off.

Further, although the upper printing ink layer contains a polyester resin harder than the polyurethane resin, in Example 10 where the average particle diameter of the filler contained in the upper printing ink layer is 3 μm, the light shielding films are very close to each other. It became difficult to peel off. In Example 10, since the average particle diameter of the filler contained in the upper printing ink layer was as small as 3 μm, unevenness was not sufficiently formed on the surface of the light-shielding film, so that the light-shielding films were very difficult to peel off. It is thought.
In the light-shielding films of Examples 10 to 12 described above, the light-shielding films cannot be peeled off from each other or are very difficult to peel off, so that it is difficult to wind and store the long light-shielding film in a roll shape.

  On the other hand, in Examples 7 to 9 in which the upper printing ink layer contains a polyester resin or an acrylic resin and contains a filler having an average particle diameter of 5 μm or more, the light shielding films are peeled relatively easily. Can do. For this reason, even if it winds up a long light-shielding film in roll shape, it can be easily drawn out. That is, a long light-shielding film can be wound into a roll and stored.

  Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  In the light-shielding film of the present invention, for example, as shown in FIG. 2, three printing ink layers 3 (3C, 3D, 3E) may be overlapped on the same surface of the substrate 2, for example, four or more printings The ink layers may overlap.

  In the light-shielding film of the present invention, for example, as shown in FIG. 3, the number of printing ink layers 3 overlapping the same surface of the substrate 2 may be different from each other on both surfaces of the substrate 2. In the light-shielding film illustrated in FIG. 3, three printing ink layers 3 (3C, 3D, 3E) overlap the first surface 2 a of the base material 2, and two printings are performed on the second surface 2 b of the base material 2. The ink layer 3 (3F, 3G) is overlapped.

DESCRIPTION OF SYMBOLS 1 Light-shielding film 2 Base material 2a 1st surface 2b 2nd surface 3, 3A, 3B, 3C, 3D, 3E, 3F, 3G Printing ink layer 3A Lower layer printing ink layer (lowermost layer printing ink layer)
3B Upper printing ink layer (top printing ink layer, other printing ink layers)

Claims (7)

A substrate made of plastic film;
A plurality of printing ink layers respectively overlapping on both sides of the substrate;
The optical density of the plurality of printing ink layers stacked on the same surface of the substrate is 3.5 or more,
And,
The number of pinholes that appear in all the printing ink layers arranged on both sides of the substrate and through which light passes in the thickness direction of the substrate is less than 1.0 per 625 mm ² the film.   The light-shielding film according to claim 1, wherein an optical density of the plurality of printing ink layers stacked on the same surface of the substrate is 5.3 or less.   The light-shielding film according to claim 1 or 2, wherein a lowermost printing ink layer in contact with the substrate among the plurality of printing ink layers stacked on the same surface of the substrate contains a polyurethane resin.   The thickness of the lowermost printing ink layer in contact with the substrate among the plurality of printing ink layers stacked on the same surface of the substrate and the thicknesses of the other printing ink layers are different from each other. The light-shielding film according to claim 3.   The light-shielding film according to claim 4, wherein a thickness of the lowermost printing ink layer is larger than a thickness of the other printing ink layer.   The uppermost printing ink layer among a plurality of the printing ink layers stacked on the same surface of the substrate includes a polyester-based resin or an acrylic-based resin. Light-shielding film.   The light-shielding film according to claim 6, wherein the uppermost printing ink layer among the plurality of printing ink layers stacked on the same surface of the substrate contains a filler having an average particle diameter of 5 μm or more.

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