JP2003127312A - Laminated polylactic biaxially-oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polylactic biaxially-oriented film with heat sealing property and excellent transparency. SOLUTION: The laminated polylactic biaxially-oriented film is a laminated film formed by laminating a heat sealing layer on at least one side of a polylactic biaxially-oriented film. The heat sealing layer is formed of at least one kind of resin selected from aliphatic polyester resin, aliphatic-aromatic copolymerization ester resin and polyester carbonate resin, and the haze value of the laminated film is 35% or less.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polylactic acid-based biaxially stretched film having a heat-sealing layer laminated thereon. More specifically, it relates to a laminated polylactic acid-based biaxially stretched film having excellent transparency.

[0002]

2. Description of the Related Art Polylactic acid biaxially stretched film is a so-called biodegradable material that can be easily decomposed into water and carbon dioxide in soil or by composting equipment. As a material for solving problems and environmental load, it has been attracting attention as a packaging film material.

However, when the polylactic acid-based biaxially stretched film is used as a packaging material, the adhesiveness between the films is not practically sufficient, so that its use is limited.

As a method for improving the adhesiveness of a polylactic acid-based biaxially stretched film, JP-A-8-323946 discloses a film having a polylactic acid-based polymer or a composition containing the polylactic acid-based polymer as a main component. And, at least one outermost layer is a multilayer biodegradable plastic film is a biodegradable plastic film, the melting temperature of the biodegradable plastic film forming the outermost layer, the polylactic acid-based polymer or this Disclosed is a technique relating to a multilayer biodegradable plastic, which is lower than the melting temperature of a film made of a composition containing the main component by 10 ° C. or more.

Further, in Japanese Patent Laid-Open No. 10-100353, a polylactic acid-based polymer and a polylactic acid-based polymer are provided on at least one side of a stretched film made of a polylactic acid-based polymer or a composition containing the polylactic acid-based polymer as a main component. Disclosed is a technique relating to a biodegradable laminated film, which is provided with an unstretched film containing a biodegradable aliphatic polyester different from the coalescence.

However, in these methods, as shown in the examples of JP-A-10-100353, a biodegradable aliphatic polyester alone or a polylactic acid-based polymer considered to be advantageous in adhesiveness is used. In a film in which an unstretched film having a high content of a biodegradable aliphatic polyester different from the above was laminated, the use of the obtained film was significantly limited due to insufficient transparency.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems and provide a laminated polylactic acid-based biaxially stretched film having heat sealability and excellent transparency.

[0008]

Means for Solving the Problems The inventors of the present invention have made extensive studies on a method for forming a heat-sealing layer, and as a result, by laminating a specific resin layer formed under specific conditions,
The present inventors have found that a polylactic acid-based biaxially stretched film having a heat-sealing layer having a practically sufficient transparency can be obtained, and completed the present invention. That is, the present invention is a laminated film in which a heat seal layer is laminated on at least one surface of a polylactic acid-based biaxially stretched film, wherein the heat seal layer is an aliphatic polyester resin, an aliphatic-aromatic copolyester resin, Alternatively, the gist of the present invention is a laminated polylactic acid-based biaxially stretched film which is formed of at least one resin selected from polyester carbonate resins and has a haze value of 35% or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In the present invention, the polylactic acid resin constituting the polylactic acid biaxially stretched film has a structural unit of lactic acid of L
-Poly L-lactic acid which is lactic acid, poly D-lactic acid whose structural unit is D-lactic acid, poly DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid, or a mixture thereof.
Further, a small amount of hydroxycarboxylic acid other than lactic acid may be contained as a copolymerization component. Further, the number average molecular weight of the polylactic acid resin is preferably in the range of 50,000 to 300,000, more preferably 80,000 to 150,000. If the number average molecular weight is less than 50,000, the mechanical strength of the obtained film will be insufficient. On the other hand, when the number average molecular weight is more than 300,000, the fluidity at the time of melting becomes poor, and the film formability deteriorates. Further, the polylactic acid resin may contain known additives such as stabilizers, antioxidants, fillers, lubricants, antistatic agents, antiblocking agents, and colorants.

In the present invention, the heat seal layer is required to be formed of at least one resin selected from aliphatic polyester resins, aliphatic-aromatic copolymer polyester resins, and polyester carbonate resins.

As the aliphatic polyester resin, lactic acid,
Glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,
3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid,
Homopolymers or copolymers of hydroxycarboxylic acids such as 2-hydroxyvaleric acid, 2-methyllactic acid and 2-hydroxyacetic acid, polyethylene succinate, polyethylene adipate, polyethylene suberate, polyethylene sebacate, polyethylene decanedicarboxylate, poly Butylene succinate, polybutylene adipate, polybutylene sebacate and their copolymers and blends,
Further, copolymerization with the above-mentioned hydroxycarboxylic acid, blending with a homopolymer or copolymer of hydroxycarboxylic acid, and the like can be mentioned. Among them, polybutylene succinate and polybutylene succinate adipate copolymer are preferably used. Further, a urethane bond, an amide bond, an ether bond or the like can be introduced into the aliphatic polyester resin as long as the biodegradability is not affected.

The aliphatic-aromatic copolyester resin may be any one whose polymer is composed of an aliphatic component and an aromatic component, such as lactic acid, glycolic acid, hydroxybutyric acid and hydroxycapron. Hydroxycarboxylic acids such as acids, cyclic lactones such as caprolactone, butyrolactone, lactide and glycolide, diols such as ethylene glycol, butanediol, cyclohexanedimethanol, bis-hydroxymethylbenzene and toluenediol, succinic acid, adipic acid, suberin Acid, sebacic acid, terephthalic acid, isophthalic acid,
Examples thereof include copolymers containing dicarboxylic acids such as naphthalenedicarboxylic acid, cyclic acid anhydrides, and oxiranes as components and having an aliphatic component and an aromatic component. As an aliphatic component, succinic acid, adipic acid, ethylene glycol and 1,
A copolymerized polyester having 4-butanediol as an aromatic component and having terephthalic acid or isophthalic acid is preferable. Further, a urethane bond, an amide bond, an ether bond or the like may be introduced into these as long as the biodegradability is not affected.

As the polyester carbonate resin, a number average molecular weight of 10,0 obtained by reacting an aliphatic dibasic acid and / or its derivative, an aliphatic dihydroxy compound and / or a hydroxycarboxylic acid compound
Examples thereof include polymers having a carbonate unit of at least 5 mol% and a weight average molecular weight of at least 100,000, which are obtained by reacting an aliphatic polyester oligomer of 00 or less with a carbonate compound.

The heat seal layer is formed from at least one resin selected from the above aliphatic polyester resin, aliphatic-aromatic copolyester resin, or polyester carbonate resin. Polylactic acid resin is added to these resins. You may add. The addition of the polylactic acid-based resin improves the blocking property of the film, and imparts rigidity to improve the processability. As the polylactic acid-based resin, the structural unit of lactic acid is L-
Examples thereof include poly L-lactic acid which is lactic acid, poly D-lactic acid whose structural unit is D-lactic acid, poly DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid, or a mixture thereof. The molar ratio of L-lactic acid to D-lactic acid of the polylactic acid resin (L-lactic acid / D-lactic acid) is 70/30 to 96/4, or 4/96.
It is preferably -30/70. Further, a small amount of hydroxycarboxylic acid other than lactic acid may be contained as a copolymerization component. The number average molecular weight of the polylactic acid resin is preferably in the range of 50,000 to 300,000, and 80,000 to 1
More preferably, it is 50,000. If the number average molecular weight is less than 50,000, the mechanical strength of the obtained film will be insufficient. On the other hand, when the number average molecular weight is more than 300,000, the fluidity at the time of melting becomes poor, and the film formability deteriorates.

In the heat seal layer, the content of the polylactic acid resin is preferably 50% by mass or less, more preferably 40% by mass or less. When the content of the polylactic acid resin is more than 50% by mass, the heat seal layer cannot have sufficient heat sealability. The method of mixing the polylactic acid-based resin with the resin is not particularly limited, but after blending the respective raw material chips in a predetermined mass ratio, a method of melt mixing with an extruder, each raw material with a separate extruder Examples include a method of melting and mixing in a molten state.

The heat-sealing layer may contain a stabilizer, an antioxidant, a filler, a lubricant, an antistatic agent, an antiblocking agent, a coloring agent, a plasticizer, etc. within a range that does not impair the effects of the present invention. Good.

The laminated polylactic acid biaxially stretched film of the present invention is a polylactic acid biaxially stretched film having a heat seal layer laminated on at least one surface thereof. As a method for laminating the heat seal layer on the polylactic acid-based biaxially stretched film, a resin for the heat seal layer is melted, and a T-die method,
A film is formed by an air-cooled inflation method, a water-cooled inflation method, etc., and the obtained sheet is laminated on one side or both sides of a polylactic acid-based biaxially stretched film via an adhesive layer, a resin for a melted heat-sealing layer By a T-die method, optionally via an adhesive layer, to form a sheet on a polylactic acid-based biaxially stretched film, and further,
The polylactic acid-based resin and the resin for the heat-sealing layer are melted by separate extruders, and the heat-sealing layer is applied to one or both sides of the polylactic acid-based resin layer by T-die method, air-cooling inflation method, water-cooling inflation method, etc. There is a method of forming a sheet by extruding from a die outlet in a laminated state by a coextrusion method so as to be formed, and biaxially stretching the sheet to obtain a film. If an adhesive layer is required, the adhesive is melt-extruded from another extruder to obtain a sheet having an adhesive layer between the polylactic acid-based resin layer and the heat-sealing layer. A method of axially stretching is included.

The adhesive used in the present invention is not particularly limited, but vinyl-based, acrylic-based, polyamide-based,
In addition to adhesives such as polyester, rubber and urethane,
Polysaccharides such as starch, amylose and amylopectin, which have biodegradability, proteins and polypeptides such as glue, gelatin, casein and collagen, natural materials such as unvulcanized natural rubber, aliphatic polyester, aliphatic-aromatic Preferred adhesives include group-copolymerized polyesters, aliphatic polyurethanes, and aliphatic polyester-modified polyvinyl alcohol vinyl acetate copolymers.

The haze value of the biaxially oriented laminated polylactic acid film thus obtained is 35% or less, more preferably 30% or less. If the haze value exceeds 35%, it cannot be applied to applications requiring transparency, and the applications are significantly limited.

In order to obtain a laminated film having excellent transparency in the present invention, any method of film formation such as T-die method, air-cooled inflation method, water-cooled inflation method, etc. may be used when forming the heat-sealing layer. Also, it is preferable that the molten resin is rapidly cooled and molded into a sheet. T-
In the case of the die method, a method in which a sheet is formed by bringing it into close contact with an electrostatic pinning method on a cooling roll cooled to 10 ° C. or less can be mentioned. Further, in the case of the air-cooled inflation method, a method of applying a cold air cooled to 10 ° C. or less to the outside of the tube to form a film by cooling is mentioned. However, a water-cooled inflation method is preferable as a method for obtaining a heat-sealing layer that is stable and economically excellent in transparency.

In the water-cooled inflation method, a sheet for heat-sealing layer melt-extruded, a laminated sheet of a polylactic acid-based resin layer and a heat-sealing layer, or a laminated sheet in which an adhesive layer is further laminated, if necessary. After being extruded from the tubular die, it is cooled in a liquid cooling medium such as water. The temperature of this liquid cooling medium is preferably 20 ° C. or lower, more preferably 15 ° C. or lower. When the temperature of the liquid cooling medium exceeds 20 ° C., a laminated polylactic acid-based biaxially stretched film having good transparency cannot be obtained. The passage time of the inflation tube extruded from the tubular die in the cooling medium is preferably 1 second or longer, more preferably 2 seconds or longer. If the passage time is shorter than 1 second, the cooling effect becomes insufficient, and a laminated polylactic acid-based biaxially stretched film having good transparency cannot be obtained.

In the present invention, the extrusion temperature of the polylactic acid resin is a cylinder temperature of 180 ° C to 240 ° C.
However, the temperature of the T-die or the inflation die is preferably 200 to 240 ° C. Further, the extrusion temperature of the resin for the heat seal layer is a cylinder temperature of 150 ° C to 2 ° C.
10 ° C., and the temperature of the T-die or the inflation die is preferably 170 ° C. to 210 ° C. Further, the temperature of the T-die or the inflation die in the case of melt-forming a laminated sheet comprising a polylactic acid-based resin layer, a heat-sealing layer, and optionally an adhesive layer is 200 to
240 ° C is preferred.

In the present invention, as a stretching method for obtaining a polylactic acid-based biaxially stretched film, either a tenter simultaneous biaxial stretching method, a tubular simultaneous biaxial stretching method, or a sequential biaxial stretching method using a roll and a tenter can be used. Either method can be used. Further, as a method for stretching a laminated sheet comprising a polylactic acid resin layer, a heat seal layer, and optionally an adhesive layer, when a sheet is obtained by a T-die method, a tenter simultaneous biaxial stretching is used. Any of the methods, or a sequential biaxial stretching method using a roll and a tenter can be used. When a laminated sheet is obtained by an air-cooled inflation method or a water-cooled inflation method, a method by a tubular stretching method of introducing air into the tube while heating the obtained tube so that a predetermined magnification is obtained, or a folded sheet The two sheets obtained by cutting both ends can be stretched by either a tenter simultaneous biaxial stretching method or a sequential biaxial stretching method using a roll and a tenter. Regarding the stretching temperature, the glass transition temperature (Tg) to Tg of the polylactic acid resin
The range of + 50 ° C is preferred. After stretching, 100 ° C-150
It is preferable to perform a heat treatment at a temperature of ° C and a heat relaxation treatment under the condition of a relaxation rate of 2 to 8%.

Although the thickness of each layer of the laminated film of the present invention is not particularly limited, it is 5 to 250 μm, preferably 10 to 100 μm as the polylactic acid biaxially stretched film layer, and 10 to 100 μm, further 10 as the heat seal layer.
˜50 μm is preferred. When an adhesive layer is formed between both layers, its thickness is preferably 0.01 to 5 μm.

[0025]

EXAMPLES Next, the present invention will be specifically described with reference to examples. The evaluation methods used for evaluation of the examples and comparative examples are as follows. Haze (Hz): Measured according to ASTM D1003 using a fully automatic haze meter manufactured by Tokyo Denshoku. Heat-sealing strength: Two strip-shaped films having a width of 15 mm and a length of 100 mm are stacked so that the heat-sealing layers are on the inner side, and set so that a heat-sealing bar having a width of 20 mm is orthogonal to the long side of the film, Temperature 130
It was heat-sealed for 2 seconds at a temperature of 0.2 MPa and a pressure of 0.2 MPa. The heat-sealed film was peeled at a peeling rate of 30 according to JIS K-6854 using an autograph manufactured by Shimadzu Corporation.
Peeling was performed at 0 mm / min, and the peak value of the measured values was taken as the heat seal strength. The heat seal strength of 7 N / cm or more was evaluated as ◯, and the heat seal strength of less than 7 N / cm was evaluated as x.

Example 1 Polylactic acid type resin (Nature Works manufactured by Cargill Dow Polymer Co., L-lactic acid / D-lactic acid = 98.5 / 1.5
(Molar ratio), number average molecular weight 107,000, MFR5.
7/10 minutes (210 ° C)) is melted at 230 ° C using a 65 mmΦ extruder, and coat hanger type width 60
It was extruded from a 0 mm T-die and cooled and solidified into a sheet on a cooling roll to form an unstretched sheet having a thickness of 250 μm. Next, this sheet is supplied to a tenter type simultaneous biaxial stretching machine, both ends are gripped by clips, and the biaxial stretching is carried out simultaneously at a stretching temperature of 80 ° C. at a longitudinal stretching ratio of 3.0 times and a transverse stretching ratio of 3.3 times. I went. Subsequently, while being heat-treated at 120 ° C., a relaxation treatment of 5% was performed in the TD direction to obtain a biaxially stretched film having a thickness of 25 μm (film A).

Next, an aliphatic polyester resin (Bionore # 3001 manufactured by Showa High Polymer Co., Ltd.) was melted at 170 ° C. using an extruder having a diameter of 65 mm and extruded downward using a circular die having a die diameter of 200 mm, and then at 15 ° C. Inflation film formation was performed at a blow ratio of 2.5 while passing through the cooling tank having water of 2 seconds for 2 seconds to obtain a film having a thickness of 40 μm (film B).

To the film A, 1 part of an aliphatic polyester-based adhesive (Polysol OLX-07527 manufactured by Showa High Polymer Co., Ltd.)
After being applied at a thickness of μm and dried at 80 ° C., the film B is pressure-bonded with a heating roll at 90 ° C. and further at 40 ° C. for 3 minutes.
It was aged for a day to obtain a laminated film.

Comparative Example 1 Aliphatic polyester resin (Bionore # manufactured by Showa High Polymer Co., Ltd.
3001) was melted at 170 ° C. using a 65 mmΦ extruder, and an upward air cooling inflation method (air cooling temperature 25
Inflation film formation was carried out at a blow ratio of 2.5 by (° C.) to obtain a film having a thickness of 40 μm (film C).
A laminated film was obtained from the film A and the film C in the same manner as in Example 1.

Example 2 Polylactic acid type resin (Nature Works manufactured by Cargill Dow Polymer Co., L-lactic acid / D-lactic acid = 96/4 (molar ratio), number average molecular weight 95,000, MFR 6.0 / 10
A laminated film was obtained in the same manner as in Example 1 except that the temperature (210 ° C.) was used.

Example 3 Polylactic acid type resin (Nature Works manufactured by Cargill Dow Polymer Co., L-lactic acid / D-lactic acid = 98.5 / 1.5
(Molar ratio), number average molecular weight 107,000, MFR5.
7/10 minutes (210 ° C)) and an aliphatic polyester resin (Bionore # 3001 manufactured by Showa High Polymer Co., Ltd.) are melted by separate extruders, respectively, and the die diameter is adjusted so that the aliphatic polyester resin layer is formed on the outer surface. Using a 200 mm two-layer circular die, the film was extruded downward and passed through a cooling tank containing water at 15 ° C. for 2 seconds to carry out inflation film formation at a blow ratio of 2.5 to obtain a thickness of 650 μm.
I got a film of. The thickness of each layer is 250 μm for the polylactic acid-based resin layer and 40 for the aliphatic polyester resin layer.
It was 0 μm. While heating this tube at 85 ° C., air was introduced into the tube, and the longitudinal stretching ratio was 3.0 times.
Tubular simultaneous biaxial stretching was performed at a lateral stretching ratio of 3.3 times. Trimming both ends of the folded tubular sheet, heat-treating with a tenter type heat treatment machine at 120 ° C., while performing 5% relaxation treatment in the TD direction to obtain a thickness of 6
A laminated biaxially stretched film of 5 μm was obtained. In this laminated film, the polylactic acid resin layer had a thickness of 25 μm, and the aliphatic polyester resin layer had a thickness of 40 μm.

Comparative Example 2 Polylactic acid type resin (Nature Works manufactured by Cargill Dow Polymer Co., L-lactic acid / D-lactic acid = 98.5 / 1.5
(Molar ratio), number average molecular weight 107,000, MFR5.
7/10 minutes (210 ° C)) and an aliphatic polyester resin (Bionore # 3001 manufactured by Showa High Polymer Co., Ltd.) are melted by separate extruders, respectively, and the die is formed so that the aliphatic polyester resin layer is formed on the outer surface. Using a two-layer circular die having a diameter of 200 mm, an inflation film was formed by an upward air-cooling inflation method (air-cooling temperature 25 ° C.) with a blow ratio of 2.5 to obtain a film having a thickness of 650 μm. The thickness of each layer is 250 for the polylactic acid resin layer.
μm, and the aliphatic polyester resin layer was 400 μm. While heating this tube at 85 ° C., air was introduced into the tube, and the longitudinal stretching ratio was 3.0 times and the lateral stretching ratio was 3.
Tubular simultaneous biaxial stretching was performed 3 times. Trimming both ends of the folded tubular sheet and heat treating at 120 ° C with a tenter heat treatment machine,
A 5% relaxation treatment was performed in the direction to obtain a laminated biaxially stretched film having a thickness of 65 μm. In this laminated film, the polylactic acid resin layer had a thickness of 25 μm, and the aliphatic polyester resin layer had a thickness of 40 μm.

Example 4 Aliphatic polyester resin (Bionore # manufactured by Showa High Polymer Co., Ltd.
3001) 80 parts by mass of polylactic acid type resin (Nature Works manufactured by Cargill Dow Polymer, L-lactic acid / D-
20 parts by mass of lactic acid = 90/10 (molar ratio) are chip-blended, melted at 200 ° C. using a 65 mmΦ extruder, and extruded downward using a circular die having a die diameter of 200 mm, and water at 15 ° C. Inflation film formation was carried out at a blow ratio of 2.5 while passing through a cooling tank having the above for 2 seconds to obtain a film having a thickness of 40 μm (film D). A laminated film was obtained from the film A and the film D in the same manner as in Example 1.

Examples 5-8, Comparative Examples 3-4 Instead of the aliphatic polyester resin used in Examples 1-4 and Comparative Examples 1-2, an aliphatic-aromatic copolyester resin (Ecoflex manufactured by BASF Corporation) was used. It carried out like each Example and a comparative example except having used -F).

Examples 9 to 12 and Comparative Examples 5 to 6 Instead of the aliphatic polyester resin used in Examples 1 to 4 and Comparative Examples 1 and 2, a polyester carbonate resin (IUPEC550 manufactured by Mitsubishi Gas Chemical Co., Inc.) was used. Except for the above, the same procedure as in each of Examples and Comparative Examples was performed.

Example 13 Polylactic acid type resin (Nature Works manufactured by Cargill Dow Polymer Co., L-lactic acid / D-lactic acid = 98.5 / 1.5
(Molar ratio), number average molecular weight 107,000, MFR5.
7/10 minutes (210 ° C)), polyester carbonate resin (IUPEC550 manufactured by Mitsubishi Chemical Co., Ltd.), and polylactic acid resin (Nature Works manufactured by Cargill Dow Polymer Co., L-lactic acid / D-lactic acid) as an adhesive layer resin. = 9
0/10 (molar ratio)) and polyester carbonate resin (IUPEC550 manufactured by Mitsubishi Chemical Co., Ltd.) are melted in different extruders respectively, and the die diameter is adjusted so that the polyester carbonate resin layer is formed on the outer surface. 200 m
Using a 3-layer circular die of m, the film was extruded downward and passed through a cooling tank containing water at 15 ° C. for 2 seconds to carry out inflation film formation at a blow ratio of 2.5 to obtain a film having a thickness of 660 μm. It was The thickness of each layer is 250 μm for the polylactic acid resin layer, 400 μm for the polyester carbonate resin layer, and 10 μ for the adhesive resin layer.
It was m. While heating the tube at 85 ° C., air was introduced into the tube to perform tubular simultaneous biaxial stretching at a longitudinal stretching ratio of 3.0 times and a lateral stretching ratio of 3.3 times.
Both ends of the folded tubular sheet were trimmed and subjected to a relaxation treatment of 5% in the TD direction while being heat-treated at 120 ° C. by a tenter type heat treatment machine to obtain a laminated biaxially stretched film having a thickness of 65 μm. In this laminated film, the polylactic acid-based resin layer had a thickness of 25 μm, the polyester carbonate resin layer had a thickness of 40 μm, and the adhesive resin layer had a thickness of 1 μm. Table 1 shows the haze value and heat seal strength of the laminated films obtained in Examples and Comparative Examples.

[0037]

[Table 1]

[0038]

According to the present invention, a laminated polylactic acid biaxially stretched film having excellent transparency and heat sealability can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4F100 AK41A AK41B AK41G AK45B                       BA02 EJ38A JN30 YY00                 4F210 AA24 AA28 AE10 AG01 AR06                       AR11 QA01 QK33

Claims (3)

[Claims] 1. A laminated film in which a heat seal layer is laminated on at least one surface of a polylactic acid-based biaxially stretched film, wherein the heat seal layer is an aliphatic polyester resin,
A laminated polylactic acid-based biaxially stretched film, which is formed from at least one resin selected from an aliphatic-aromatic copolyester resin or a polyester carbonate resin and has a haze value of 35% or less. 2. The laminated polylactic acid-based biaxially stretched film according to claim 1, wherein the heat-sealing layer is formed by a water-cooled inflation method. 3. The water-cooled inflation method is carried out under the condition that the temperature of the liquid cooling medium is 20 ° C. or lower and the passage time of the inflation tube in the cooling medium is 1 second or longer. A method for producing the laminated polylactic acid-based biaxially stretched film described.