JPH04128026A - Polyester film for printing display body - Google Patents

Abstract

PURPOSE:To contrive modification of flatting and transparency, by a method wherein since the title film is a biaxially oriented laminated polyester film comprised of at least two layers and satisfies general formulas 1-8 at the same time. CONSTITUTION:Polyester raw materials obtained by performing mixing and adding of fine particles such as kaolin or silica along with an additive agent such as a stabilizer or a coloring agent or a defoaming agent or an organic lubricant or polyalkylene glycol at need and polyester raw materials prepared separately are dried independently. They are extruded by separate extruding machines, two kinds of raw materials are made complex so that they becomes surface layers each other, cooled and solidified on a casting drum and unoriented polyester sheet comprised of two layers is formed. The obtained sheet is oriented secondly in the first axial direction, ordinarily in a longitudinal direction. Then although the obtained biaxially oriented film is fixed thermally for 1sec. to 10min. at 200-250 deg.C, it is important to slacken the film in the direction of a width of the film in a thermally fixing zone. With this construction, a film for printing display body having excellent transparency, flatting and dazzle preventive properties can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a film for printed displays that has excellent transparency and matte properties.

[Prior art and problems to be solved by the invention] Conventionally, display bodies printed on vinyl chloride film have been widely used, but vinyl chloride film has excellent transparency, mechanical properties, heat resistance, and weather resistance. Since it is inferior to polyester film in this respect, it has been desired to switch to polyester film.

However, although conventional polyester films have excellent transparency, they do not have matte properties, so they cannot be used particularly when used outdoors.

For this reason, attempts have been made to impart matte properties to the film, and for example, methods have been proposed to increase the unevenness of the film surface. I can't do it.

In addition, it has been difficult to improve the two mutually exclusive properties of polyester film, such as transparency and transparency.

[Means to solve the problem]

As a result of intensive testing to solve the above problems, the present inventors discovered that a composite polyester film having a specific configuration is useful as a film for printed displays, and completed the present invention.

That is, the gist of the present invention is a biaxially oriented laminated polyester film consisting of at least two layers, comprising the following [1] to [
8] A polyester film for printed displays is characterized in that it satisfies the following formulas:

0,005≦RaA≦0.030 −・・■0
．． 020; Ra■≦0.300...[2]12
0≦GsA≦250 ,,,■80≦Gs
Corridor≦200 ・・・■0.002≦RaB
-Ra＾≦0.300 ・・・■l≦GsA -Gs
Dew ≦80 ・・・■0.5≦H≦20
...■0, 002≦d, /d≦0.3
...■ The present invention will be explained in detail below.

The biaxially oriented laminated film referred to in the present invention is not particularly limited as long as it satisfies the gist of the present invention, and those obtained by an in-line coating method, a lamination method, a coextrusion method, etc. can be used. However, those obtained by coextrusion are preferred.

That is, the laminated film of the present invention is preferably extruded by a co-extrusion method in which all layers are co-melt extruded from a die, biaxially stretched and heat-set. Although a layered film will be described, in the present invention, the number of layers to be composited is not limited to two layers, but may be more than two layers.

In the present invention, the raw material polyesters constituting each layer include terephthalic acid, isophthalic acid, naphthalene-2,
Examples include polymers obtained by polycondensing aromatic dicarboxylic acids such as 6-dicarboxylic acid or esters thereof with glycols such as ethylene glycol, diethylene glycol, tetramethylene glycol, and neopentyl glycol.

Such polyesters can be obtained by directly polycondensing aromatic dicarboxylic acids and glycols, or by polycondensing aromatic dicarboxylic acid dialkyl esters and glycols after transesterification. It can also be obtained by a method such as polycondensation of diglycol ester. Typical examples of such polymers include polyethylene terephthalate and polyethylene terephthalate.
Examples include 2°6-naphthalene dicarboxylate.

The polymer may be a non-copolymerized homopolymer, with up to 15 mole percent of the dicarboxylic acid component and/or 15 mole percent of the diol component.
A copolymerized polyester having a diol component other than aliphatic glycol in an amount of mol % or less may be used. Furthermore, a polymer blend of these polyesters and other polymers may be used. Examples of other polymers that can be blended include polyamide, polyolefin, and various other polyesters (including polycarbonate).

Further, the polyester may contain additives such as stabilizers, colorants, antioxidants, antifoaming agents, etc., if necessary.

In the present invention, such polyesters are preferably composited by co-melt extrusion, but both layers to be composited usually contain fine particles. The fine particles to be contained include lithium fluoride, kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, calcium phosphate, titanium oxide, and other elements from Groups 1, 2, and 2 of the periodic table. Inert particles made of salts or oxides containing elements selected from group Ⅰ and others, high melting point organic compounds that are insoluble during melt film formation of polyester resin, inert particles such as crosslinked polymers (these are not added externally). (particles that occur are called external particles)
Alternatively, particles formed inside the polymer during polyester production (particles formed during polyester production are referred to as internal particles) by metal compound catalysts used during polyester synthesis, such as alkali metal compounds, alkaline earth metal compounds, etc. It will be done.

These inert external particles, internal particles can be used alone or in combination with
More than one species can be used in combination.

The average particle diameter of these particles is preferably in the range of 0.01 to 3.5 μm, and the amount of fine particles contained in the film is 0. The content is preferably in the range of 0.03 to 0.9% by weight, and in the layer constituting the smooth surface (side A), 0.005 to 0.1% by weight.

In the present invention, in order to obtain better effects, the additive particles are preferably particles that have a refractive index comparable to that of polyethylene terephthalate and that are less likely to form voids during film stretching. As such particles, particles of amorphous silica are particularly suitable. When using amorphous silica particles, they may be used alone or in combination with other particles, but the most preferable form in the layer constituting the smooth surface (A side) is a combination of large particles and small particles. Modal system, specifically average particle size 0. A bimodal system consisting of small particles with an average particle size of 0.8 to 0.8 μm and large particles with an average particle size of 0.8 to 1.5 μm, both of which are made of amorphous silica, can be mentioned. In this case, the content of large particles in the film is between 0.003 and 0.
．． 015% by weight, the content of small particles is preferably less than 0.05% by weight, the average particle size of the added large particles is 0.
．． If it is less than 8 μm, its contribution to the slipperiness of the film is extremely small, and if it exceeds 1.5 μm, band-like unevenness will occur on the film surface, which is not preferable. Furthermore, if the content of large particles is less than 0.003% by weight, the resulting film will have low slipperiness, while if the content of O, OI exceeds 5% by weight, the transparency may deteriorate.

In the present invention, in addition to the above-mentioned fine particles, it is also a preferable method to include an organic lubricant in one or two exposed layers of the film in order to improve the slipperiness of the film. The type of organic lubricant is not particularly limited, but aliphatic compounds, fatty acid esters, alkylene bis aliphatics, aromatic amides, and the like are preferred. As the aliphatic compound, those having a large number of carbon atoms such as montanic acid are preferred. Moreover, examples of aliphatic esters include montanic acid ethylene glycol ester and the like.

Examples of the alkylene bis aliphatic and/or aromatic amides include hexamethylene bis behenamide, hexamethylene bis stearyl amide, N N'-distearine terephthalamide, and the like.

The content of these organic lubricants in the film is usually less than 500 ppm, preferably less than 200 ppm. If a large amount of these lubricants are mixed in, it is not preferable because the adhesion will be lowered when the film is subjected to treatments such as vapor deposition or coating, and the color of the film will become too yellowish.

Furthermore, for the purpose of improving the printability of the film and the adhesion during vapor deposition, it is also suitable to include polyalkylene glycols in the two layers constituting the exposed surface of the film. Examples of the polyalkylene glycol include polyethylene glycol, polytetramethylene glycol, polypropylene glycol, and the like. Methods for incorporating these polyalkylene glycols into the film include adding them to the reaction system during transesterification or polymerization,
Any method may be used, such as blending a polymer copolymerized with polyalkylene glycol or kneading the polyester during drying or extrusion.

However, in order not to impair the transparency of the film of the present invention, the polyalkylene glycol usually has a molecular weight of 1.
0000 or less, preferably 8000 or less,
Further, the content in the film is usually 1% by weight or less, preferably 0.5% by weight or less.

In the present invention, the centerline average roughness (R
a') is in the range of 0.005 to 0.030, preferably in the range of o, o o s to 0.025.

A film with a smooth surface Ra' exceeding 0.030 is unsuitable due to poor transparency. On the other hand, a film having Ra^ of less than 0.005 is unsuitable because of poor running properties even if the easily slippery surface (B side) is roughened. Easy sliding surface (B
The center line average roughness (Ra”) of the surface is 0.02 [1] ~
[8]. 300, preferably 0.03[1
] ~ [8]. 200, more preferably 0.04 [1]
~[8]. The range is 150.

The difference in Ra between A side and B side (Ra"-Ra^) is 0°002
~0.300, preferably 0°01-0
．． 200. More preferably, it is in the range of 0.02 to 0.100. If the difference in Ra is less than 0.002, it is unsuitable because it is inferior in transparency and slipperiness, which is the objective of the present invention. On the other hand, if the difference in Ra exceeds 0.300, the haze of the easily slippery surface becomes too high to be of practical use.

The glossiness (GsA) of the A side of the film of the present invention is 120~
250, preferably 140-200. If the GsA is less than 120, the transparency will be poor and it will be inappropriate. On the other hand, if the GsA exceeds 250, the running properties of the film are extremely poor, which is not preferred. B-side gloss level GS! l is in the range of 80 to 200, preferably 100 to 190, more preferably 120 to 17
It is in the range of 0.

The difference in glossiness between side A and side B [GsA-Gs”) is 1 to
80, preferably 2-50, more preferably 2-30. (GsA-Gs”) is 1
If it is less than that, it is not possible to satisfy both transparency and matte property (or anti-glare property).

On the other hand, when (GsA-Gs'') exceeds 80, the film base becomes too high, which is not preferable.

The film of the present invention has a film base (H) of 0.5 to
The number is in the range of 20, preferably 2 to 15, more preferably 5 to 12. If the film base is less than 0.5, the running properties will be poor, and if it is more than 20, the transparency will be poor and it will be unsuitable as a film for printed displays.

The thickness (da) of the layer constituting the smooth surface (B side) of the film of the present invention is O,OO2 with respect to the total film thickness (d).
-0.3, preferably 0.002-0.2
0, more preferably in the range of 0.002 to 0.15. When d and /d are less than 0.002, the thickness of the layer constituting the B side becomes uneven, which is undesirable, and when it exceeds 0.3, the film base becomes too high, which is inappropriate.

The thickness of the polyester film of the present invention is not particularly limited, but is usually 1 m at 25 to 250°C, preferably 1 m to 250°C.
The range is 200 μm.

Next, the method for forming the polyester film of the present invention will be specifically explained, but the film of the present invention is not limited to the following production examples.

Polyester raw materials mixed and added with fine particles such as kaolin and silica, and additives such as stabilizers, colorants, antifoaming agents, organic lubricants, and polyalkylene glycols (
1) and a separately prepared polyester raw material (II),
Each is dried separately and extruded using a separate extruder, and by coextrusion method, raw materials (1) and (II) are combined so that they form a surface layer, and are cooled and solidified on a casting drum to form an unstretched two-layered product. Form a polyester sheet. At this time, it is preferable to use a conventional electrostatic application cooling method.

The resulting sheet is then stretched in a first axial direction, usually in the machine direction. At that time, the stretching temperature is preferably in the range of 75 to 130°C. As the roll used for stretching, hard chrome rolls, ceramic rolls, elastomer rolls such as Teflon rolls, etc. can be used as appropriate, but in particular, hard chrome rolls are used and the stretching temperature is set at 80 to 80°C.
Preferably, the temperature is 90°C and the stretching is performed in -steps.

The uniaxially stretched film stretched in the first axis direction in this way is
Then, it is stretched in the second axial direction. The second axial stretching is carried out by cooling the -axially stretched film to below the glass transition point or without cooling, for example at 90-150°C.
This is carried out by preheating to a temperature of , and further stretching 3.0 to 5 times in the second axial direction at approximately the same temperature. If the stretching ratio in the second axis direction is less than 30 times, thickness unevenness in the second axis direction will be amplified, which is not preferable. The stretching ratio in the second axis direction is preferably in the range of 3.2 to 4.5 times, more preferably 3.2 to 4.0 times.

Then, the obtained biaxially stretched film has a molecular weight of 200 to 250
℃ for 1 second to 10 minutes, but in the present invention, in the heat setting zone, 1 to 1 seconds to 10 minutes at 200℃ or higher.
It is important to relax the film by 15% in the width direction.

It is particularly preferable that the relaxation treatment is carried out in the width direction in the maximum heat setting temperature range of the heat setting zone. Further, it is also preferable to relax in the longitudinal direction within a range that does not deteriorate the flatness.

In the present invention, in order to further improve the transparency and slipperiness of the resulting film, the temperature is increased to 200°C.
It is also preferable to employ so-called two-stage heat-setting, in which after heat-setting as described above, the material is once cooled to 120° C. or lower, and then heat-set again at 200° C. or higher.

In order to further improve the heat resistance of the film thus obtained, it is also preferable to perform off-line relaxation treatment under low tension.

The smooth surface (side A) of the thus obtained film is subjected to an undercoating treatment to facilitate adhesion, if necessary, and printed according to various formulations. It is particularly compatible with inkjet printing.

The film of the present invention is not particularly limited as long as it is used for printed displays. For example, it can be used as image receiving paper for thermal transfer, but it can also be used for color printing and outdoor use (for example, advertising printing mark sheets on the side of trucks, It can be preferably used for information boards on expressways, etc.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

In addition, the evaluation method of film characteristics in Examples and Comparative Examples is as shown below.

(1) Surface roughness (Ra) The center line average roughness Ra (μm) was defined as the surface roughness.

■Using a surface roughness measuring machine (SE3F) manufactured by Koita Research Institute,
A reference length L (
2.5an) is extracted, and the roughness curve y=f is drawn with the center line of this extracted portion as the y-axis and the direction of vertical magnification as the y-axis.
When expressed as (x), the value given by the following formula is Cμm
], and the center line average roughness is 1 from the sample film surface.
Zero cross-sectional curves were determined, and the average value of the center line average roughness of the sampled portion determined from these cross-sectional curves was expressed.

The tip radius of the stylus was 2 μm, the load was 30 mm, and the cutoff value was 0.08 mm.

(2) Film glossiness (Gs) Using a Nippon Denshoku Kogyo Co., Ltd. VGS-1001DP type gloss meter, measure the 60 degree specular glossiness cs (60') using the JIS standard.
Measured according to Z8741. That is, the reflectance of the sample was determined based on the reflectance of a black standard plate at an incident angle and a reflection angle of 60 degrees, and was defined as the glossiness.

(3) Film haze The turbidity of the film was measured according to JIS K6714 using a sphere-splitting turbidity meter NDH-20D manufactured by Nippon Heavy Industries, Ltd.

(4) Film thickness and layer thickness A cross section of the film was cut and measurements were taken from a photograph of the cross section.

Example 1 Polyester (Bl) containing 2000 ppwl of thyroids with an average particle size of 1.4 μm and an average particle size of 0.7 μm
of ion exchange resin with 240 ppI++ and average particle size 1°4
Polyester containing 4 oppm of μm thyroid (A1
) were dried separately, and the raw material (A1) and the raw material (B, ) were made into surface layers of each other using a separate melt extruder with a diameter of 90 mm, and a two-layer composite was prepared with a thickness ratio of B, /A, -10/178. An unstretched sheet was produced.

This sheet was first heated with an IR heater, stretched 3.3 times in the longitudinal direction at 85°C with a hard chrome mirror-finish roll, and after setting Δn to 0.090, stretched it in the transverse direction at 120°C. It was stretched 3.5 times. Next, heat setting was performed at 240''C, and relaxation treatment in the width direction was performed at a relaxation rate of 10% during heat setting to obtain a two-wheel stretched film with a thickness of 188 μm.

Example 2 A polyester (B2) containing 11,000 ppm of thyroids with an average particle size of 1.4 μm and a polyester (A2) containing 240 ppa+ of ion exchange resin with an average particle size of 0.7 μm and 40 ppm of thyroids with an average particle size of 1°4 μm were carried out. A two-wheel stretched film having a thickness of 188 μm was obtained by forming a film in the same manner as in Example 1.

Comparative Example 1 A two-wheel stretched film with a thickness of 188 μm was obtained in the same manner as in Example 1, except that polyester containing 1 wt% of siloids with an average particle size of 2.3 μm was used instead of (B,).

Comparative Example 2 A 188 μm film was obtained using only the polyester (Bl) of Example 1.

Comparative Example 3 A 188 μm film was obtained using only the polyester (AI) of Example 1.

The properties of the film thus obtained are shown in Table 1 below.

After providing an undercoat layer on the smooth surface side of the film of Example 1.2 to prevent easy electrification, the film was color printed and used outdoors as a mark sheet and display, and the results were very good. On the other hand, the film of Comparative Example 1.2 had a high haze and was unsuitable, and the film of Comparative Example 2 had a printed surface that reflected diffusely, making it impossible to confirm the displayed content.

〔Effect of the invention〕

The film of the present invention has excellent transparency, matte properties and anti-glare properties, is useful as a film for printed displays, and has high industrial value.

Applicant: Diafoil Co., Ltd.

Claims (1)

[Claims] (1) A biaxially oriented laminated polyester film consisting of at least two layers, characterized in that it satisfies the following formulas [1] to [8] at the same time: 0.005≦Ra^A≦ 0.030…[1] 0.020≦Ra＾B≦0.300…[2] 120≦Gs＾A≦250…[3] 80≦Gs＾B≦200…[4] 0.002≦Ra＾ B-Ra＾A≦0.300…[5] 1≦Gs＾A-Gs＾B≦80…[6] 0.5≦H≦20…[7] 0.002≦d_B/d≦0.3 ...[8] However, in the above formula, Ra^A and Ra^B are exposed 2
Center line average roughness (μm) of surfaces (A surface and B surface), Gs
^A and Gs^B are the glossiness of the A side and B side, H is the film haze (%), d is the total film thickness (μm), d
_B represents the thickness (μm) of the layer constituting the B side