JP2001219939A - Styrene resin film for envelope window - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a styrene resin film for an envelope window which is beautiful in finish, less in damages of the film and free from any wrinkles or positional deviation in a rapid window sticking operation associated with the rapid traveling of the film. SOLUTION: In an oriented film for the envelope window, a coating film is formed of a surface finishing agent containing at least (A) particles having the inner surface area of the number average grain size of 1-7 μm on both sides of the film with the surface density of 0.2-2.5 mg/m2, (B) a surfactant which is a liquid antistatic at normal temperature (20 deg.C) on both sides of the film with the surface density of 2-15 mg/m2, and (C) a water soluble polymer resin on both sides of the film with the surface density of 0.5-6 mg/m2 on both sides of the styrene resin film with the center line average height of the surface roughness parameter being 0.4 to 2.2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched film mainly composed of a styrene resin used for an envelope window, and an object thereof is to provide a film having improved suitability for high-speed running in an envelope window pasting machine. .

[0002]

2. Description of the Related Art Stretched styrene films are the most widely used resin films for envelope windows, because of their rigidity and good transparency. An envelope with a window is made by using a window sticking machine to suck a film cut to a predetermined size into a metal vacuum drum having fine vacuum holes, and then sticking the film to an opening of the envelope. In recent years, the tendency of the pasting speed to increase due to the progress of window pasting machines has become remarkable. That is, a window pasting machine having a pasting speed of about 400 to 600 sheets / min but a pasting speed of more than 1000 sheets has been introduced, and the running speed of the film has been increased.

[0003] With such an increase in the attaching speed, the required quality characteristics of the film are also increasing.
A styrene-based stretched film for an envelope window is disclosed in
Japanese Patent Application Laid-Open No. 1-19978 discloses a film in which an antistatic treatment is less likely to cause clogging due to sticking of the film in a machine and poor sticking due to meandering of the film. The film described in Japanese Patent Application Laid-Open No. H10-119978, if attention is paid only to electrostatic troubles,
Although it is true that the film has reduced such troubles, no consideration has been given to preventing damage to the film, and wrinkles and misalignment of the film after pasting have not been completely eliminated.

On the other hand, JP-A-2-72050 discloses a styrene-based film containing a waxy anti-flecking agent, and JP-A-2-72051 discloses a styrene-based film containing a granular anti-flecking agent. Although the films disclosed in these publications are provided with slipperiness, the film is less damaged, but still has a problem that electrostatic trouble is likely to occur. Under such circumstances, that is, sufficient results have not been obtained only by improving either the antistatic property or the slip property, it can be considered that by realizing both of them at the same time, the suitability for high-speed running is enhanced. However, the provision of antistatic properties disclosed in JP-A-10-11978 and JP-A-2-72050 or JP-A-2
It is practically difficult to simultaneously impart the slipperiness disclosed in JP-A-72051. This is because each of them is an improvement technique relating to the surface characteristics, and the application of different improvement techniques will reduce or eliminate the effect of imparting antistatic properties and the effect of imparting slipperiness, which are their own characteristics. Therefore, in the pasting of a styrene-based film in a beautiful state in which wrinkles and misalignments have been eliminated with little damage, it has not yet been realized in the pasting with high-speed running.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a styrene-based film for an envelope window which can achieve a beautiful finish with less damage to the film and less wrinkles and misalignment in high-speed window application with high-speed running of the film. The purpose is to provide.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor (or the like) has conducted intensive studies on the surface characteristics of a film suitable for high-speed running in a window laminator, and has accomplished the present invention. That is, the present invention relates to a film mainly composed of a styrene-based resin, wherein at least the following (A) and (B) are provided on both surfaces of the film having a center line average value of the surface roughness parameter of 0.4 to 2.2 μm. , And (C)
A styrene-based resin stretched film for an envelope window, wherein a coating film is formed by a surface treatment agent containing (A) A surface treatment agent containing 0.2 to 2.5 mg of fine particles having an internal surface area having a number average particle diameter of 1 to 7 μm per unit area (m ² ) on both surfaces of the film. (B) A surface treatment agent which is a liquid antistatic agent at room temperature (20 ° C.) and has a surface treatment agent of ^{2 to} 15 mg per unit area (m ² ) on both surfaces of the film. (C) 0.5 to 6 mg of a water-soluble polymer resin per unit area (m ² ) on both sides of the film.

The present invention will be specifically described below.
The film of the present invention is mainly composed of a styrene resin, that is, the resin composition constituting the film contains 50% by weight or more of the styrene resin. Styrene resin is a homopolymer of vinyl aromatic hydrocarbon, a copolymer of a monomer copolymerizable with the vinyl aromatic hydrocarbon, and a so-called rubber in which a soft component is dispersed in the vinyl aromatic hydrocarbon. Modified polystyrene resins, block copolymers of vinyl aromatic hydrocarbons and conjugated dienes, and the like, but it is preferable to mainly use general-purpose polystyrene (GPPS).

In the present invention, the average value of the center line of the surface roughness parameter (hereinafter abbreviated as the surface roughness parameter) is determined by a surface shape analyzer (SAS-2010 manufactured by Meishin Koki Co., Ltd.).
Is measured by extracting a roughness curve on a specific straight line on the film surface, and calculating the area of a portion surrounded by a 1 mm-length roughness curve and its center line in each of the longitudinal and lateral directions of the film. The average deviation obtained by dividing by 1 mm which is the measurement length is obtained, and the values in the vertical and horizontal cases are averaged.

The film of the present invention must have a surface roughness parameter of 0.4 to 2.2 μm, preferably 0.42 to 2.0 μm. In the present invention,
The surface properties of the film are improved with a surface treatment agent that is a new composition, and with regard to imparting slipperiness, it can be improved by adding fine particles having a specific range of diameter and a specific range of application amount to the surface treatment agent. However, it has been found that it is effective to have not only the unevenness of the fine particles dispersed in the shape of protrusions but also the relatively smooth unevenness of the film itself under conditions of high-speed running, and the surface, which is a measure of the unevenness of the film itself, has been found. The roughness parameter has been reached within the specific range described above.

If the surface roughness parameter is smaller than 0.4 μm, the surface becomes smooth and a lot of abrasions due to metal rolls and the like remain during high-speed running. Also, since the slipperiness is slightly inferior, the film is sucked during high-speed window application. Film is likely to be wrinkled on a vacuum drum. In addition, even if the surface of the film is too large, the slipperiness is poor, that is, if the surface roughness parameter is larger than 2.2 μm, wrinkles and misalignment are likely to occur. Generally, the slipperiness is evaluated by a coefficient of kinetic friction. However, the slipperiness in high-speed window sticking or high-speed running cannot be said to be sufficient when measured at a speed of less than 10 m / min conventionally measured. The high-speed dynamic friction coefficient measured between the film and the metal (stainless steel metal on the mirror surface) at a high speed per minute is 0.2 to 0.3.
5 is used as a reference value for the search. Particularly, when the surface roughness parameter exceeds 2.2 μm, the tendency that the dynamic friction coefficient increases becomes apparent at this high-speed dynamic friction coefficient. However, the evaluation criterion in the present invention is based on the evaluation in an envelope window pasting machine, and it is not always essential that the high-speed dynamic friction coefficient is within the above range.

The surface roughness parameter can be adjusted to the above-mentioned specific range by appropriately mixing a rubber-modified polystyrene resin, which is a styrene resin, into the resin composition. Although it depends on the particle size of the rubber in the polystyrene resin, it is generally 3
A rubber-modified polystyrene resin content of 24% by weight is preferred. In addition, a component dispersed in the form of particles in the rubber-modified styrene-based resin composition, such as a block copolymer of vinyl aromatic hydrocarbon and a conjugated diene, or organic or inorganic fine particles not corresponding to styrene-based resins, is blended. Can also be adjusted. In the case of blending the fine particles, the blending is preferably about 10% by weight or less, although it varies depending on the diameter of the fine particles and the resin composition constituting the fine particles.
The presence of particulate components in the film affects the film surface due to the biaxial stretching as well as the above-mentioned blending, and is compared with the unevenness caused by adding fine particles to the surface treatment agent. Smooth irregularities are formed. The measurement of the surface roughness parameter is performed on the film before the coating film is formed by the surface treatment agent.

The film of the present invention contains conventionally known additives such as a heat stabilizer, an antioxidant, and an ultraviolet absorber in addition to the above-mentioned resin and fine particles as long as the requirements and characteristics of the present invention are not impaired. It is possible to Stretching of a film is performed by a conventionally known method such as an inflation method or a tenter stretching method. However, it is necessary to perform biaxial stretching, and in the case of the tenter method, it is preferable to carry out in combination with roll stretching or the like. The stretching ratio is 3 to 17 times in each of the longitudinal direction and the transverse direction. From the viewpoint of reinforcing the film strength by imparting the orientation and uniform stretching, particularly 4
A range of up to 12 times is preferred. The film thickness after stretching is
It is preferably in the range of 10 to 70 μm, and more preferably 15 to 50 μm, but is not particularly limited in the present invention.

Next, the surface treating agent used in the present invention will be described. The number average particle diameter of the fine particles (A) blended in the surface treatment agent is 1 to 7 μm. 1.2μm to 5μ
More preferably, the particle diameter is m. Fine particles (A) are semi-fixed to the film surface (although they are held by other surface treatment agents, ie, surfactant (B) and water-soluble polymer resin (C), they are completely fixed to the surface) In this case, the effect of reducing the friction due to the rolling of the particles during high-speed running is given, and the film is hardly completely separated from the film surface, so that the film is unlikely to be damaged. In other words, damage due to a large difference in speed between the stationary fine particles and the film running at high speed, which occurs when the film completely separates, is unlikely to occur. When the particle diameter is less than 1 μm, the fine particles protruding on the film surface are excessively small compared to the surface roughness of the film itself, and are directed to a portion of a window sticking machine (metal roll or vacuum drum) where the film is rubbed. The chance of contact is reduced, and the effect of adding fine particles is reduced. 7 μm
If it is larger, the slipperiness is inferior as in the case where the surface roughness parameter is too large, and wrinkles and misalignment are likely to occur.

Further, the fine particles (A) need to have an internal surface area, and on the surface of the particles or in the vicinity thereof, another surface treating agent, that is, a surfactant (B) and a water-soluble polymer resin (C) are used. The increased contact area reinforces retaining the particles on the film surface.
In the case of particles having no internal surface area, the particles are likely to separate from the film surface and cause abrasion with the film. Particles having an internal surface area have various conventionally known production methods depending on the material constituting the particles. For example, one of the production methods of synthetic silica (silicon dioxide fine particles) is to prepare primary particles formed by polymerization of a silica sol. Further, there is a method of forming secondary particles having pores (that is, having an internal surface area) by agglomeration or baking of primary particles as in the method of agglomerating into sol.

Further, the amount of the fine particles (A) may be in the range of 0.2 to 2.0 per unit area (m ² ) on both sides of the film.
A coating film is formed to be 5 mg, preferably 0.3 mg.
-2.0 mg, more preferably 0.3-1.8 mg. If it is less than 0.2 mg per unit area (m ² ),
Due to the small number of fine particles, the effect of adding fine particles, that is, the effect of improving the slipperiness by dispersing in the form of protrusions and the effect of reducing the friction due to rolling, cannot be sufficiently exhibited, resulting in increased damage to the film and window. Wrinkles and misalignment are likely to occur after sticking. 2.5 m per unit area (m ² )
When the value exceeds g, the number of fine particles detached from the film increases, and in this case also, the film is damaged.

Examples of the fine particles (A) include silicon dioxide fine particles, silicate-based fine particles, synthetic zeolite fine particles, calcium carbonate fine particles, magnesium carbonate fine particles, and the like, but are not limited to these examples. It is important to select among those having an average particle size and an internal surface area. Next, the surfactant (B) incorporated in the surface treatment agent is a surfactant having a liquid antistatic effect at room temperature (20 ° C.), and has a surface area of ² μm per unit area (m ² ) on both sides of the film. A coating film is formed so as to be 15 mg, preferably 3 to 12 mg.
By being in a liquid state, the fine particles (A) can be held in a semi-fixed state, so that the effects of the fine particle blending in the present invention can be sufficiently exhibited. The surfactant (B)
Anionic ones such as alkyl sulfonates, alkylbenzene sulfonates, alkyl sulfates and alkyl phosphates, cationic ones such as quaternary ammonium salts, amphoteric ones such as alkyl betaine type and imidazoline type, and polyoxyethylene Nonionic surfactants such as alkylamine, fatty acid ester of polyoxyethylene alkylamine, glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene fatty alcohol ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene sorbitan fatty acid ester Any of them can be used and a combination of two or more kinds may be used. However, an amphoteric or nonionic surfactant is preferable because it exhibits stable antistatic performance.

When the amount of the surfactant (B) is less than 2 mg per unit area (m ² ), the antistatic effect is inferior, wrinkles and misregistration due to static electricity of the film easily occur in a window pasting machine, and fine particles ( The effect of retaining A) is weakened. If the amount exceeds 15 mg, the proportion of the fine particles (A) that are buried in the surfactant coating layer, that is, the entire surface of the fine particles are coated with the surfactant is considered to increase, but in this case also, In this case, wrinkles and misalignment of the film easily occur.

The improvement of the antistatic performance by adding the surfactant (B) was confirmed by reducing the half-life of the decay of the charged voltage. In the research process of the present invention, the condition of 20 ° C. and 25% relative humidity was used. The half-life of 90 seconds or less was used as an evaluation scale for the required antistatic performance. However, in the present invention, the evaluation in high-speed window sticking with high-speed running is used as a reference, and it is not always necessary that the half-life is within the above range.

Next, a coating film is formed on the water-soluble polymer resin (C) to be mixed with the surface treating agent so that the coating amount is 0.5 to 6 mg per unit area (m ² ) on both sides of the film. 0.5 to 4 mg. The water-soluble polymer resin (C) is compounded with a surfactant for the purpose of holding the fine particles (A) on the film surface.
The surfactant alone does not have a sufficient retention ability, and thus plays a role as a so-called adhesion reinforcing agent for further strengthening. Therefore, 0.5 m per unit area (m ² )
If less than g, the effect of retaining the fine particles (A) is weakened,
Abrasion due to separation of the fine particles from the film surface is likely to occur. On the other hand, if the amount exceeds 6 mg, the antistatic performance of the surfactant (B) is impaired, and at the same time, the tackiness on the film surface is increased and the sliding performance is reduced.

Examples of the water-soluble polymer resin (C) include, but are not limited to, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, and sodium polystyrenesulfonate. As a preferable mixing ratio of the fine particles (A), the surfactant (B), and the water-soluble polymer resin (C) to be mixed in the surface treatment agent, the weight ratio is (A) :( B) :( C) = 0.05 ~
The ratio is 0.5: 1: 0.1 to 1.

The formation of the coating film by the surface treating agent is performed by applying a surface treating agent diluted with a solvent such as water to the surface of the film after stretching and forming the film, followed by drying. As a coating method, a conventionally known method such as a spray coater, a roll coater, and an air knife coater is employed. The method of coating the film of the present invention on both surfaces is preferable because the coating film needs to be formed on both surfaces. However, before the film is completely dried after the surface treatment agent diluted with a solvent is applied to one surface (completely). (Before the solvent is removed), the film may be wound into a roll, and the surface treatment agent may be transferred to the opposite surface by winding tension to form a coating film on both surfaces. In addition, it is preferable to apply a corona treatment to both surfaces of the film before coating so as to increase the surface tension of the film, since a coating film having a uniform thickness can be easily formed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to examples and comparative examples. First, the evaluation methods of the films used in the examples and comparative examples are described below. (1) Center line average value of surface roughness parameter: using a surface shape analyzer (SAS-2010 manufactured by Meishin Koki Co., Ltd.)
Measurements were made at any three points in the vertical and horizontal directions by the method described above, and the average value was expressed as μm
Calculate as significant figures from the decimal to the second place in the unit of. (2) Dynamic friction coefficient between film and metal: Measured at a speed of 30 m / min with a stainless steel rider on the mirror surface using a high-speed friction coefficient measuring device (AB-410 manufactured by Tester Sangyo Co., Ltd.) Hereinafter, the first two digits are calculated as significant figures. (3) Half-life of decay of charged voltage: Using a static honestometer (H-0110 manufactured by Shisido Electrostatic Co., Ltd.)
It is measured in an atmosphere of 0 ° C. and 25% relative humidity under the conditions of an applied voltage of 10 kv and a distance between the electrode and the sample of 20 mm.

(4) Evaluation on Envelope Window Attaching Machine: Window Attaching Machine (WINKLER + DUNNEBIER HELI
OS202), using a vinyl copolymer type paste (Sibinol FB-403 manufactured by Seiden Chemical Co., Ltd.)
12000 envelopes were attached to a 50 × 90 window frame of a 5 × 235 mm envelope at a speed of 1200 sheets / min, and evaluated in the following manner. (4-1) Evaluation of misalignment: 1000 immediately before the end of window application
100 envelopes are randomly extracted from the sheets, and one point whose deviation from a predetermined attaching position is less than 0.5 mm is one point.
A score of 0.5 to 1.0 mm is regarded as 0.5 point, a score exceeding 1.0 mm is regarded as 0 point, 、 when the total score of 100 sheets is 100 points, Δ when 98 to 99.5 points, and 95-9
The case of 7.5 points was judged as Δ, and the score of less than 95 points was judged as ×. (4-2) Evaluation of wrinkles: 100 envelopes were randomly extracted from 1,000 sheets immediately before the end of the window application, and no wrinkles were observed in all cases. The case where it was recognized in the envelope was evaluated as Δ, the case where the degree of wrinkles or the frequency of occurrence was slightly larger than the judgment of Δ, and the case where the degree of wrinkles or the frequency of occurrence was large and had a serious problem in practice was evaluated as ×. (4-3) Scratchability: 10 envelopes were randomly extracted from 1000 sheets immediately before the end of the window application, and the haze value of the film after the window application (the total average of the haze values of the 10 surfaces on both sides). Is less than 1% with respect to the haze value of the film before window application (the value obtained by calculating the total average of both surfaces at any five positions before the film is applied to the window application machine). When less than 5% is Δ, when 1.5% or more and less than 2.5% is Δ, 2.5%
The above case was determined as x. The haze value is AST
It was measured according to MD1003.

In the following Examples and Comparative Examples, the resins and additives used were the mixtures shown in Table 1, and acrylate heat stabilizers (Sumilyzer GM manufactured by Sumitomo Chemical Co., Ltd.) were used as heat stabilizers. 0. for the mixture.
2 parts by weight were added. As a method of stretching a film in Examples and Comparative Examples, a single-screw extruder is used to extrude a film from a die having an annular slit, and a bubble chamber is formed by inflation so that the center of the bubble is at 117 to 122 ° C. The film was stretched 7.1 times in the vertical direction and 7.9 times in the horizontal direction while adjusting the temperature in the above to obtain a film having a thickness of 30 μm.
In addition, the outer surface when the bubble is formed is the surface of the film,
The inside surface was the back surface.

In Examples and Comparative Examples, the fine particles mixed with the surface treating agent are shown in Table 2, the surfactant is shown in Table 3, and the water-soluble polymer is shown in Table 4. As a method of applying the surface treating agent in the examples and comparative examples, first, the surface to be applied is subjected to corona treatment so that the surface tension becomes 48 dyn / cm, and the concentration of the surface treating agent becomes 0.4% by weight. Was applied by a spray coat, and then water was removed by hot air drying at 90 ° C. The coating amount was adjusted under the conditions of spray coating (air pressure and line speed), but the coating amount described in Examples and Comparative Examples was calculated by converting the weight increase of the film after forming the coating. did.

[0026]

Example 1 The resin composition and the surface treating agent were as shown in Table 5 for NO. Was used. In addition, each NO. That is, the resin composition NO. , Fine particle NO. , Surfactant NO. ,
And water-soluble polymer NO. Are specifically described in Tables 1 to 4, respectively. The film of Example 1 falls within the range of the specific surface roughness parameter, which is a requirement of the present invention, contains the essential surface treatment agent, and the amount of the coating film falls within the specific range. As shown in Table 5, very excellent evaluation results were obtained with an envelope window mounting machine.

[0027]

Example 2 and Comparative Examples 1 to 6 Example 2 and Comparative Examples 1 to 6
Table 5 shows the resin composition and surface treatment agent, the results of surface property evaluation, and the results of evaluation on an envelope window mounting machine. Example 2 is a film that satisfies the requirements of the present invention, whereas Comparative Examples 1 to 4 are those in which any of the surface treatment agents (A) to (C) is omitted, and are provided with an envelope window. From the results of evaluation on the press, it can be seen that the surface treatment agents (A) to (C) are all essential components. In Comparative Examples 5 and 6, the coating film was formed only on one surface, and the slipperiness and antistatic property of the surface on which the coating film was not formed were inferior. Is not obtained, indicating that it is necessary to form a coating film on both surfaces.

[0028]

Examples 3 to 7 and Comparative Examples 7 to 9 Table 6 shows the resin compositions and surface treatment agents of Examples 3 to 7 and Comparative Examples 7 to 9, evaluation results of surface properties, and evaluation results of an envelope window mounting machine. .
The surface treatment agents of Examples 3 to 7 and Comparative Examples 7 to 9 are all the same and satisfy the requirements of the present invention, but the types of resin compositions are different, and Comparative Examples 7 to 9 are different.
The film of No. 9 has a surface roughness parameter outside the range specified in the present invention. Comparative Example 7 has a rough parameter smaller than the specified range and is slightly inferior in the evaluation of wrinkles and scratches. Comparative Examples 8 and 9 have a rough parameter larger than the specified range and is slightly inferior in the evaluation of displacement and wrinkles.

Examples 3 and 4 are films whose surface roughness parameters are close to the lower and upper limits of the range specified in the present invention, and have a slightly higher dynamic friction coefficient than those of Examples 5 to 7; Although the evaluation results in the above are practically excellent, the evaluations of the scratching property and the wrinkle are only judged as Δ.

[0030]

Examples 8 and 9 and Comparative Examples 10 to 15 Table 7 shows resin compositions and surface treatment agents of Examples 8 and 9 and Comparative Examples 10 to 15, evaluation results of surface characteristics, and evaluation results of an envelope window mounting machine.
Shown in The resin compositions of Examples 8 and 9 and Comparative Examples 10 to 15 are all the same and satisfy the requirements of the present invention, but the types and amounts of the surface treatment agents are different.

The films of Example 8 all satisfied the requirements of the present invention, and as shown in Table 7, extremely excellent evaluation results were obtained on an envelope window mounting machine. On the other hand, in the film of Example 9, the amount of the water-soluble polymer resin is 6 mg / m ² which is the upper limit of the specific range defined in the present invention,
This is probably due to the slightly higher adhesiveness of the surface, but the evaluation of wrinkles was only 〇. In the films of Comparative Examples 10 and 11, the diameter of the fine particles in the surface treatment agent was out of the specific range of 1 to 7 μm required in the present invention, and in the film of Comparative Example 12, the fine particles were required in the present invention. The film of Comparative Example 13 is not a fine particle having an internal surface area, and the surfactant is a solid surfactant that is not liquid at normal temperature, which is a requirement of the present invention. Inferior to the films of Examples 8 or 9.

The film of Comparative Example 14 had an amount of fine particles in the coating film of 0.2 to 2.5 m, which is a requirement of the present invention.
g, which is 3 mg / m ² , which is inferior to the evaluation of the scratch resistance. The film of Comparative Example 15 shows that the amount of the surfactant in the coating film is 2 which is a requirement of the present invention. ~ 15
It is 18 mg / m ² , exceeding the mg range, which is inferior in the evaluation of displacement and wrinkles.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

[Table 7]

[0040]

The film of the present invention has a surface roughness within a specified range, forms a coating film with a novel composition of a surface treating agent, and improves the surface characteristics to enable high-speed running of the film. Provided is a styrene-based resin film for an envelope window, which realizes a beautiful finish with less damage to the film and less wrinkles and misalignment in high-speed window application at more than 1000 sheets / minute.

Claims (3)

[Claims] 1. A film mainly composed of a styrene resin, wherein a center line average value of a surface roughness parameter is 0.1.
An envelope window, wherein a coating film is formed on both surfaces of the film having a thickness of 4 to 2.2 μm with a surface treatment agent containing at least the following (A), (B), and (C). Styrene-based resin stretched film. (A) A surface treatment agent containing 0.2 to 2.5 mg of fine particles having an internal surface area having a number average particle diameter of 1 to 7 μm per unit area (m ² ) on both surfaces of the film. (B) A surface treatment agent containing a surfactant, which is a liquid antistatic agent at room temperature (20 ° C.), in an amount of ^{2 to} 15 mg per unit area (m ² ) on each side of the film. (C) A surface treatment agent containing 0.5 to 6 mg of a water-soluble polymer resin per unit area (m ² ) on both sides of the film. 2. The stretched film according to claim 1, wherein a coating film formed by a surface treatment agent is formed after both surfaces of the film are subjected to corona treatment. 3. The film has a dynamic friction coefficient of 0.2 to 0.35 between the film and the metal measured at 30 m / min in each measurement of both sides of the film, and halves the charge decay at 20 ° C. and 25% relative humidity. The time is less than 90 seconds.
The stretched film according to 1.