Liquid paper container base material, and liquid paper container

Abstract

The present invention provides a liquid paper container substrate and a liquid paper container that achieve both light-shielding properties and storage stability. [Solution] A liquid paper container substrate 100 comprises a paper substrate layer 110, a first polyethylene layer 112 provided on one side of the paper substrate layer 110, a light-shielding printing layer 114 provided on the other side of the paper substrate layer 110, a barrier layer 116 provided on the light-shielding printing layer 114, and a second polyethylene layer 118 provided on the barrier layer 116, wherein the light-shielding printing layer 114 is made of a urethane resin containing carbon black. A liquid paper container 1 is made using the liquid paper container substrate 100.

Description

[Technical Field]

[0001] This invention relates to a liquid paper container substrate and a liquid paper container. [Background technology]

[0002] Paper containers are widely used for filling and storing liquids such as beverages. Liquid paper containers are generally made from laminated packaging materials, which consist of a main component of paper, a liquid-impermeable resin such as polyethylene, polypropylene, or polyvinyl chloride, and other materials as needed. For example, a gable-top container is obtained by cutting the laminated packaging material into a predetermined shape, joining (sealing) the blanks in the longitudinal direction of the container, sealing the bottom of the blanks in a filling machine, filling the liquid contents through the top opening, and then sealing the top.

[0003] Furthermore, rectangular brick-shaped, polygonal prism-shaped, and tetrahedral containers are obtained by forming laminated packaging material into a tube shape by longitudinal line sealing, filling the tube with liquid contents through the top opening, applying transverse line sealing in the transverse direction of the tube to form the primary shape, then cutting and folding each individual container to form the final shape such as a rectangular parallelepiped.

[0004] However, because paper containers cannot prevent light from passing through, when used as containers for liquids such as beverages, there is a problem in that the quality of the contents, such as taste and aroma, deteriorates as the storage period lengthens.

[0005] To solve these problems, for example, Patent Document 1 below describes a light-shielding laminated packaging material having, in order from the outer surface of the packaging, a first resin layer, a first paper layer, a second resin layer, a second paper layer, and a third resin layer, and having a light-shielding ink layer in at least one of the spaces between the second resin layer and the second paper layer, and between the second paper layer and the third resin layer. Patent Document 1 describes black ink as the ink that forms the light-shielding ink layer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-200708 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in recent years, there has been a demand for further improvement in light-shielding properties to prevent deterioration of the quality of the contents inside the paper container. Furthermore, when forming a liquid paper container using the light-shielding laminated packaging material described in Patent Document 1, the light-shielding laminated packaging material is folded to form the container. However, when folded, the ink layer which has light-shielding properties may partially break, resulting in a loss of continuity in the ink layer and a decrease in light-shielding properties. Alternatively, gas and water vapor may leak more easily, leading to a decrease in light-shielding properties and storage stability.

[0008] This invention has been made in view of these circumstances, and aims to provide a liquid paper container substrate and a liquid paper container that achieve both light-shielding properties and storage stability. [Means for solving the problem]

[0009] This invention was made to solve the above-mentioned problems, and the present invention was completed by finding that the problems of the present invention can be solved by forming a light-shielding printing layer using a specific material. The gist of the present invention is as follows. [1] A liquid paper container substrate comprising a paper substrate layer, a first polyethylene layer provided on one side of the paper substrate layer, a light-shielding printing layer provided on the other side of the paper substrate layer, a barrier layer provided on the light-shielding printing layer, and a second polyethylene layer provided on the barrier layer, wherein the light-shielding printing layer is made of a urethane resin containing carbon black. [2] The liquid paper container substrate according to [1], wherein the light-shielding printing layer contains metal powder. [3] The liquid paper container substrate according to [2], wherein the metal powder is aluminum powder. [4] The liquid paper container base material according to any one of [1] to [3], wherein the carbon black is contained in the urethane resin composition for forming the light-shielding printing layer at 5 to 30% by mass. [5] The liquid paper container base material according to any one of [1] to [4], wherein the barrier layer is a barrier layer having a metal oxide vapor deposition layer. [6] The liquid paper container base material according to any one of [1] to [5], wherein the color difference (ΔE) before and after storage of a liquid stored at normal temperature for one month using the liquid paper container made of the liquid paper container base material is 1 or less. [7] A liquid paper container made using the liquid paper container base material according to any one of [1] to [6]. [8] The liquid paper container according to [7], wherein the first polyethylene layer side is the outside of the container and the second polyethylene layer side is the inside of the container. [9] The liquid paper container according to [7] or [8], wherein the light-shielding printing layer is provided so as to cover at least the entire inner surface of the liquid paper container formed using the liquid paper container base material. [Effect of the Invention]

[0010] According to the present invention, it is possible to provide a liquid paper container base material and a liquid paper container that achieve both light-shielding properties and storage stability. [Brief Description of the Drawings]

[0011] [Figure 1] It is a conceptual diagram showing the layer structure of the liquid paper container base material of the present invention. [Figure 2] It is a perspective view showing an example of the liquid container paper container of the present invention. [Figure 3] It is a plan view seen from the back side of the carton blank sheet for forming the liquid paper container of FIG. 2. [Embodiments for Carrying out the Invention]

[0012] <> Hereinafter, the liquid paper container base material and the liquid paper container according to the present invention will be described with reference to the accompanying drawings.

[0013] [Paper substrate for liquid paper containers] FIG. 1 is a conceptual diagram showing the layer structure of the paper substrate 100 for liquid paper containers of the present invention. The paper substrate 100 for liquid paper containers of the present invention includes a paper substrate layer 110, a first polyethylene layer 112 provided on one surface of the paper substrate layer 110, a light-shielding printing layer 114 provided on the other surface of the paper substrate layer 110, a barrier layer 116 provided on the light-shielding printing layer 114, and a second polyethylene layer 118 provided on the barrier layer 116. The light-shielding printing layer 114 is composed of a urethane resin containing carbon black. In the paper substrate 1 for liquid paper containers of the present invention, the side of the second polyethylene layer 18 is the inner surface side of the paper substrate for liquid paper containers, and the side of the first polyethylene layer 12 is the surface side.

[0014] [Paper substrate layer] The paper substrate constituting the paper substrate layer 110 is not particularly limited as long as it does not inhibit the object of the present invention, and known paper substrates used for liquid paper containers and packaging products are used. Specifically, it may be acid paper manufactured using pulp or recycled pulp and having a papermaking pH in the acidic range, pseudo-neutral paper having a papermaking pH in the pseudo-neutral range, neutral paper having a papermaking pH in the neutral range, or alkaline paper having a papermaking pH in the alkaline range. In the present invention, among these, it is preferable to use acid paper because it reduces residual hydrogen peroxide during packaging material sterilization.

[0015] The basis weight of the paper substrate is preferably in the range of 100 to 500 g / m<(0000106)>, <(0000005)>, <(0000104)>, <(0000105)>, <(0000003)>, <(0000004)>, <(0000103)>, <(0000002)>When the basis weight is 100 g / m<(0000002)>or more, the stiffness is sufficient and there is no concern about molding defects. On the other hand, when it is 500 g / m<(0000003)>or less, the stiffness is not too high and molding is easy. From the above viewpoints, the basis weight of the paper substrate is more preferably in the range of 150 to 400 g / m<(0000004)>and even more preferably in the range of 200 to 300 g / m<(0000005)>. <(0000103)><(0000104)><(0000105)>[First polyethylene layer]<(0000106)>The liquid paper container base material 100 of the present invention has a first polyethylene layer 112 on one side (surface side) of the paper base material layer 110. The resin forming the first polyethylene layer 112 may be polyethylene derived from fossil fuels, polyethylene derived from biomass, or a mixture thereof.

[0017] In the production of biomass-derived ethylene, it is preferable to use biomass-derived fermented ethanol obtained from plant materials as a raw material. Examples of plant materials include, but are not limited to, corn, sugarcane, and beets. Furthermore, the method for polymerizing monomers containing biomass-derived ethylene is not particularly limited and can be carried out by known methods.

[0018] The polyethylene constituting the first polyethylene layer 112 preferably contains low-density polyethylene (LDPE) with a biomass content of 70% or more. A biomass content of 70% or more significantly reduces the amount of fossil fuels used, thereby reducing the environmental burden and contributing to measures against global warming and the creation of a circular economy. From this perspective, a biomass content of 80% or more is more preferable, 90% or more is even more preferable, and 100% is also acceptable.

[0019] Furthermore, if there is an odor originating from the biomass, it is preferable to include a deodorant in the biomass polyethylene layer. Examples of deodorants include porous materials, metal oxides, and chemical adsorbents having acidic or basic groups. Note that biomass content is only found in materials of biological origin. 14 It can be identified by measuring C.

[0020] The thickness of the first polyethylene layer 112 is preferably in the range of 1 to 30 μm. If the thickness of the first polyethylene layer 12 is 1 μm or more, the heat sealability is sufficient, and if it is 30 μm or less, the rebound is not strong and molding is easy. From the above viewpoint, the thickness of the polyethylene layer is more preferably in the range of 5 to 20 μm, and even more preferably in the range of 10 to 15 μm. Furthermore, the melt flow rate (hereinafter sometimes referred to as "MFR") of the polyethylene forming the first polyethylene layer 112 is preferably 0.8 to 10 g / 10 min. When the MFR is within this range, sufficient strength and good film-forming properties can be obtained. The melt flow rate can be measured in accordance with ASTM D1238, and the value obtained was measured at a temperature of 190°C and a load of 2.16 kg.

[0021] <Light-shielding printing layer> The liquid paper container substrate 100 of the present invention has a light-shielding printing layer 114 on the other side (inside) of the paper substrate layer 110. The light-shielding printing layer 114 is a layer that prevents the transmission of external light from outside the liquid paper container and prevents the quality of the contents from deteriorating.

[0022] A urethane-based resin is used as the resin constituting the light-shielding printing layer 114. By using a urethane-based resin, flexibility can be imparted to the light-shielding printing layer, so that when forming the liquid paper container, cracks do not form in the light-shielding printing layer 114, preventing external light from passing through or gases such as oxygen and water vapor from passing through, thereby preventing a deterioration in the quality of the contents.

[0023] Carbon black is used as the light-blocking colorant to impart light-blocking properties to the light-blocking printing layer 114. By incorporating carbon black, the total light transmittance at wavelengths of 300 to 800 nm can be suppressed, preventing a deterioration in the quality of the contents. It is preferable that carbon black be contained in the resin composition for forming the light-blocking printing layer 114 at a concentration of 5 to 30% by mass, and more preferably at a concentration of 15 to 25% by mass. By setting the carbon black content to 5% by mass or more, the total light transmittance of external light passing through the liquid paper container can be reduced. Furthermore, even when the carbon black content exceeds 30% by mass, no significant difference is observed in the effect of reducing the total light transmittance.

[0024] Furthermore, the light-shielding printing layer 114 may contain metal powder. By incorporating metal powder, the light-shielding properties of the liquid paper container base material 100 can be improved, and the quality of the contents can be prevented from deteriorating. As the metal powder, aluminum powder or the like can be used.

[0025] <Barrier layer> The liquid paper container substrate 100 of the present invention has a barrier layer 116 on a light-shielding printing layer 114. The barrier layer 116 is a layer that prevents the quality of the contents from deteriorating due to oxidation or the like. The barrier layer 116 can be a resin film having a metal oxide vapor deposition layer. Examples of metal oxides include aluminum oxide (alumina) and silicon oxide. Furthermore, examples of resins used in resin films on which metal oxides are deposited include polyethylene terephthalate (hereinafter also referred to as "PET"). By making the barrier layer 116 a PET film having a metal oxide vapor deposition layer, it can be recycled in the same way as milk cartons and the like.

[0026] Furthermore, by including recycled PET as a material for PET, an even more environmentally friendly liquid paper container base material can be created. As for PET, recycled PET and virgin PET can be mixed and used, and from an environmental standpoint, the recycled PET content is preferably 5% or more, more preferably 80% or more, and recycled PET may be 100%.

[0027] In the liquid paper container substrate 100 of the present invention, a known vapor-deposited film can also be used as the barrier layer 116, which is a film substrate made of PET with aluminum oxide and / or silicon oxide deposited on one side. In particular, a vapor-deposited film in which aluminum oxide and silicon oxide are deposited in two dimensions is preferred. Such a vapor-deposited film has high gas barrier properties and excellent flexibility. The deposition method is not particularly limited, and methods such as vacuum deposition, sputtering, physical deposition, or chemical deposition can be used.

[0028] The thickness of the barrier layer 116 is preferably in the range of 1 to 30 μm. If the thickness of the barrier layer 116 is 1 μm or more, sufficient barrier properties are obtained, and if it is 30 μm or less, the repulsion does not become strong and molding becomes easy. From the above viewpoint, the thickness of the barrier layer is more preferably in the range of 5 to 20 μm, and even more preferably in the range of 9 to 15 μm.

[0029] <Second polyethylene layer> The liquid paper container substrate 100 of the present invention has a second polyethylene layer 118 on a barrier layer 116. As the resin forming the second polyethylene layer 118, linear low-density polyethylene resin (LLDPE) or a mixed resin of linear low-density polyethylene resin and low-density polyethylene resin is used. When low-density polyethylene resin is used, the content is 30% by mass or less of the total resin constituting the second polyethylene layer 118. By including linear low-density polyethylene resin, the heat sealability when manufacturing liquid paper containers can be improved, and liquid paper containers can be easily manufactured. By setting the content of low-density polyethylene resin to 30% by mass or less of the total resin, the blocking phenomenon (the phenomenon of the second polyethylene layers sticking together) can be suppressed, and the molding of liquid paper containers can be easily performed. The content of low-density polyethylene resin is preferably 10% by mass or more and 30% by mass or less.

[0030] The polyethylene MFR for forming the second polyethylene layer 118 is preferably 0.8 to 10 g / 10 min. When the MFR is within this range, sufficient strength and good film-forming properties can be obtained.

[0031] The thickness of the second polyethylene layer 118 is preferably in the range of 10 μm to 40 μm. By setting the thickness of the second polyethylene layer 18 within the above range, sufficient heat sealability can be achieved, and since the rebound is not strong, the molding of the liquid paper container can be easily performed. The thickness of the second polyethylene layer 18 is more preferably 20 μm to 35 μm, and even more preferably 25 μm to 35 μm.

[0032] The polyethylene constituting the second polyethylene layer 118 may also be fossil-derived polyethylene, biomass-derived polyethylene, or a mixture thereof, similar to the first polyethylene layer 12. From the perspective of sufficiently reducing the environmental load to meet measures against global warming and the construction of a recycling-oriented society, it is preferable that the biomass content is 70% or more, more preferably 80% or more, still more preferably 90% or more, and it may even be 100%.

[0033] <Design printing layer> The liquid paper container base material 100 of the present invention may have a design printing layer (not shown) on the first polyethylene layer 112. The design printing layer is a layer for printing a design representing the appearance, product name, product information, etc. when used as a liquid paper container.

[0034] According to the liquid paper container base material 100 of the present invention, since it has a light-shielding printing layer 114 that blocks the transmission of external light and a barrier layer 116 that prevents the transmission of water vapor, oxygen, etc., it is possible to suppress the browning (color difference) of the contents during normal temperature storage of the paper container base material formed using the liquid paper container base material 100. It is preferable that the browning of the contents satisfies ΔE obtained by measuring the Lab values of the contents before and after storage and using the following formula is 1 or less. ΔE = [(ΔL) 2 +(Δa) 2 +(Δb) 2 1 / 2 Note that Δ indicates the difference in each numerical value.

[0035] [Liquid paper container] The liquid paper container of the present invention is formed according to a known molding process using the above-described liquid paper container base material of the present invention. For example, the manufacturing process of a liquid paper container for containing liquid beverages such as milk and juice usually consists of steps of base material preparation, printing, ruling, punching (blank creation), pasting, content filling, and sealing.

[0036] ​Hereinafter, an example of the liquid paper container of the present invention will be described in detail with reference to the drawings. Figure 2 is a perspective view showing an example of the liquid paper container according to the present invention, and Figure 3 is a plan view of the carton blank sheet forming the liquid paper container of Figure 2, viewed from the back side (inner side).

[0037] The liquid paper container 1 of this embodiment consists of a rectangular cylindrical body 6 comprising a front panel 2, a right side panel 3, a back panel 4, and a left side panel 5, a container body 9 comprising a bottom 7 that seals the lower opening of the body 6, and a flat top 8 that seals the upper opening of the body 6, and a spout 10 provided on the top 8. In this example, the container body 9 is formed from a single blank sheet as shown in Figure 3.

[0038] The plug 10 provided on the top 8 is positioned close to the first top corner 11(A), which is one of the four top corners 11 on the top 8, and is formed by the top edge 2a of the front panel 2 and the top edges 3a, 5a of either the right side panel 3 or the left side panel 5. In this example, it is formed by the top edge 2a of the front panel 2 and the top edge 5a of the left side panel 5. The close position here refers to a position that is closer to the first top corner 11(A) from the center of the top 8, and the closer the position is to the first top corner 11(A), the better.

[0039] The blank sheet 30 for forming the liquid paper container shown in Figure 2 is made from the liquid paper container base material of the present invention. As shown in Figure 3, the blank sheet 30 has a front panel 2, a right side panel 3, a back panel 4, and a left side panel 5 connected via vertical fold lines 31, 32, and 33 to form the body 6.

[0040] At the upper ends of the front panel 2 and the rear panel 4, a pair of opposing top panels 36 and 37 are connected via top horizontal fold lines 34 and 35 to form a top 8. At the upper ends of the right side panel 3 and the left side panel 5, a pair of opposing folded panels 40 and 41 are connected via top horizontal fold lines 38 and 39 to form a top 8. The folded panels 40 and 41 are provided with top diagonal fold lines 42 and 43. In addition, sealing panels 48, 49, 50, and 51 are connected to the upper ends of the top panels 36 and 37 and the folded panels 40 and 41 via sealing section horizontal fold lines 44, 45, 46, and 47.

[0041] At the lower ends of the front panel 2 and the rear panel 4, a pair of opposing bottom panels 54 and 55 are connected via bottom horizontal fold lines 52 and 53 to form the bottom 7. At the lower ends of the right side panel 3 and the left side panel 5, a pair of opposing inner panels 58 and 59 are connected via bottom horizontal fold lines 56 and 57 to form the bottom 7. Furthermore, a side seal panel 61 is connected to one open edge of the blank sheet 30 via a side seal vertical fold line 60 to seal to the other open edge of the blank sheet 30.

[0042] In the top panel 36 of the blank sheet 30, which is connected to the upper end of the front panel 2, a plug attachment opening 64 is formed at a position close to the intersection 63 of the top horizontal fold line 34 of the front panel 2 and the top vertical fold line 62 that is located between the top panel 36 and the folded panel 40, which constitutes the first top corner 11(A).

[0043] As described above, the liquid paper container substrate 100 of the present invention has a light-shielding printing layer 114 on the inner surface side of the paper substrate layer 110. When the liquid paper container 1 is formed from the liquid paper container substrate 100, the light-shielding printing layer 114 does not need to be provided on the entire back surface of the blank sheet 30, as long as it is provided so as to cover at least the entire inner surface of the formed liquid paper container 1.

[0044] For example, in Figure 3, when manufacturing a liquid paper container, the folded panels 40 and 41 are bonded together with sealing panels 50 and 51 facing each other, then folded outwards along the top horizontal fold lines 38 and 39, and bonded to the right side panel 3 and left side panel 5. Therefore, if the right side panel 3 and left side panel 5 are provided with a light-shielding printing layer, it is not necessary to form a light-shielding printing layer on the folded panels 40 and 41. Regarding the top portion 8, a light-shielding printed layer is formed on the inner surface of the top portion 8 by providing a light-shielding printed layer on the top panels 36 and 37.

[0045] The bottom portion 7 is formed by folding a pair of inner panels 58 and 59 inward along the bottom horizontal fold lines 56 and 57, and then overlapping and sealing a bottom panel 55, which is folded inward from above the inner panels 58 and 59 along the bottom horizontal fold line 53, and a bottom panel 54, which is folded inward from above the bottom panel 55 along the bottom horizontal fold line 52. Therefore, for the bottom panels 54 and 55 and the inner panels 58 and 59, a light-shielding printing layer is provided in the areas where the respective bottom panels 54 and 55 and inner panels 58 and 59 do not overlap, and for the overlapping areas, it is sufficient that a light-shielding printing layer is provided on at least one of the laminated portions. For example, as shown in Figure 3, a light-shielding printing layer can be provided on the inner surface of the bottom 7 by forming a light-shielding printing layer in a triangular region on each bottom panel 54, 55 and inner panel 58, 59, with the bottom horizontal fold lines 52, 53, 56, 57 as the base of a triangle, the opposite side of the bottom horizontal fold lines 52, 53, 56, 57 as the vertices, and each bottom horizontal fold line 52, 53, 56, 57 and the ends of each bottom horizontal fold line 52, 53, 56, 57 from the vertices as the sides.

[0046] Furthermore, the liquid paper container of the present invention is not limited to the paper container with a spout shown in Figures 2 and 3, but can be applied to various types of liquid paper containers, such as cable-top containers with a gable roof shape and rectangular brick-shaped containers. [Examples]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0048] (Example 1) A liquid paper container substrate having the following configuration was formed. (1) First polyethylene layer: LDPE layer (thickness 12 μm), manufactured by Nippon Polyethylene Co., Ltd. (2) Paper base layer: Clay coated paper (basis weight 226 g / m²) 2 ) (3) Light-shielding printing layer: Formed by applying and drying the following inks (thickness 0.5 μm). Ink: Hydric FCF794 Black (carbon black-containing urethane resin-based ink, manufactured by Dainichi Seika Kogyo Co., Ltd.) As shown in Figure 3, the light-shielding printing layer was provided so as to be formed on the entire inner surface when the liquid paper container was formed. (4) Barrier layer: Aluminum oxide vapor-deposited PET film (12 μm thick), manufactured by Toray Film Processing Co., Ltd.; product name "SBR2" (5) Second polyethylene layer: LLDPE layer (thickness 37 μm), manufactured by Nippon Polyethylene Co., Ltd.

[0049] (Comparative Example 1) Except for not providing the light-shielding printing layer (3) in Example 1, the liquid paper container substrate was formed in the same manner as in Example 1.

[0050] (Comparative Example 2) Except for not providing the light-shielding printing layer (3) in Example 1, and using "aluminum foil (7 μm thick)" as the barrier layer (4), a liquid paper container substrate was formed in the same manner as in Example 1.

[0051] The oxygen permeability and total light transmittance were measured for the liquid paper container substrates obtained in Example 1 and Comparative Examples 1 and 2 described above. The results are shown in Table 1. Oxygen permeability was measured using a MOCON OX-TRAN10 / 50A. The unit is cc / m³. 2 It is / day. Furthermore, total light transmittance was measured using a Shimadzu UV-3100PC self-recording spectrophotometer equipped with a LISR-3100 large integrating sphere attachment (150 mmφ).

[0052] [Table 1]

[0053] Furthermore, using the liquid paper container substrates of Example 1, Comparative Examples 1 and 2 described above, liquid paper containers were formed, filled to their maximum capacity (270 ml) with the following green tea beverages, left in the following environments (after 1 week and 1 month), and then the contents were opened to check for any changes in the color of the beverages. Filling: Green tea beverage (aqueous solution containing approximately 0.1% vitamin C and approximately 0.3% green tea powder) Vitamin C: Manufactured by Kanto Chemical Co., Ltd., ascorbic acid Green tea powder: Manufactured by Ito En Co., Ltd., powdered tea. Storage environment: Darkroom (room temperature (approx. 20°C, approx. 14 hours / day)) + under illumination (approx. 1,000 Lux, approx. 37°C, approx. 10 hours / day)

[0054] The change in the color of the beverage was measured using a spectrophotometer (eXact (x-rite)), and the Lab value of the beverage was measured. The difference between the Lab value immediately after filling, the Lab value after one week of storage, and the Lab value after one month of storage was used to calculate ΔE using the following formula. ΔE=[(ΔL) 2 +(Δa) 2 +(Δb) 2 ] 1 / 2 Note that Δ represents the difference between each value. The results are shown in Table 1.

[0055] [Table 2]

[0056] As shown in Table 2, Example 1, which has a light-shielding printing layer, was able to suppress the color change ΔE to 1 or less, and was able to suppress color change even when stored for one month. [Industrial applicability]

[0057] The present invention provides a light-shielding printing layer on the inner surface of a liquid paper container substrate, which improves light shielding from external light and suppresses gas permeability such as water vapor and oxygen, thereby preventing deterioration of the quality inside the container, without affecting the external design. Therefore, it can be suitably used as a paper container substrate and paper container for liquids such as milk and juice. [Explanation of symbols]

[0058] 1. Liquid paper container 2. Front Panel 2a top 3 Right side panel 3a top 4. Rear panel 5. Left side panel 5a Top 6 Torso 7 Bottom 8 Top 9. Container body 10 spouts 11 Top corner 11(A) First apex corner 30 Blank Sheets 31, 32, 33 Vertical fold lines on the torso 34,35 Top horizontal fold line 36,37 Top panel 38,39 Top horizontal fold line 40, 41 Folding Panel 42,43 Top diagonal fold line 44, 45, 46, 47 Transverse fold lines of the sealing portion 48, 49, 50, 51 Sealing Panels 52,53 Bottom horizontal fold line 54, 55 Bottom panel 56,57 Bottom transverse fold line 58, 59 Inner panel 60 Side seal vertical fold line 61 Side seal panel 62 Vertical fold line at the top 63 intersection 100 Liquid paper container base material 110 Paper base layer 112 First polyethylene layer 114 Light-shielding printing layer 116 Barrier layer 118 Second polyethylene layer

Claims

1. It comprises a paper substrate layer, a first polyethylene layer provided on one side of the paper substrate layer, a light-shielding printing layer provided on the other side of the paper substrate layer, a barrier layer provided on the light-shielding printing layer, and a second polyethylene layer provided on the barrier layer. The aforementioned light-shielding printing layer is made of a urethane resin containing carbon black, and is a liquid paper container substrate.

2. The liquid paper container substrate according to claim 1, wherein the light-shielding printing layer contains metal powder.

3. The liquid paper container substrate according to claim 2, wherein the metal powder is aluminum powder.

4. The liquid paper container substrate according to any one of claims 1 to 3, wherein the carbon black is contained in 5 to 30% by mass in the urethane resin composition forming the light-shielding printing layer.

5. The liquid paper container substrate according to any one of claims 1 to 3, wherein the barrier layer is a barrier layer having a metal oxide vapor deposition layer.

6. A liquid paper container substrate according to any one of claims 1 to 3, wherein the color difference (ΔE) of a liquid stored at room temperature for one month using a liquid paper container made of the liquid paper container substrate is 1 or less.

7. A liquid paper container made using the liquid paper container substrate described in any one of claims 1 to 3.

8. The liquid paper container according to claim 7, wherein the first polyethylene layer side is on the outside of the container and the second polyethylene layer side is on the inside of the container.

9. The light-shielding printing layer is provided so as to cover at least the entire inner surface of the liquid paper container formed using the liquid paper container substrate, according to claim 7.

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