JPH091648A - Polyester film and light reflecting sheet composed thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance reflectivity and abrasion resistance such that particles do not fall off even by surface rubbing by specifying the surface glossiness of at least the single surface of a polyester film, the concn. of particles in the surface layer thereof and the refractive index in the thickness direction of the polyester film. SOLUTION: The surface glossiness of at least the single surface of a polyester film is set to 5-80% and the concn. of particles in the surface layer thereof is set to 0.5wt.% or less and the refractive index in the thickness direction of the polyester film is set to 1.46-1.54. Therefore, pellets of high speed crystallizing polyester A are dried to be supplied to a known melt extruder. Then, polyester A is laminated to at least the single surface of polyester B by using a two-or three-layered manifold or confluent block and a two-or three-layered sheet is extruded from a slit like cap and the extrudate is cooled by a casting roll to form a non-stretched film which is, in turn, heat-treated to be stretched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film suitable for a reflector, particularly a light reflector used for the inside of a liquid crystal display (hereinafter LCD), a road sign, and the like.

[0002]

2. Description of the Related Art Known polyester films include a particle addition method (for example, Japanese Patent Publication No. 63-2779) and a film having surface projections formed by polyester crystals (for example, Japanese Patent Laid-Open No. 5-131600).

[0003]

However, the above-mentioned conventional polyester film has a problem that its reflectivity, that is, the reflection intensity in the normal direction when light incident from various angles is reflected, is insufficient. was there.
In addition, when a large amount of particles are added to form the surface with irregularities to impart reflectivity, the surface is rubbed by the transport roll in the step of vapor depositing metal, etc., and the particles fall off, which affects the process and product performance. There was a problem of becoming trouble.

The present invention solves the above problems and provides a film having excellent reflectivity and in which particles do not fall off even when the surface is rubbed, that is, excellent in abrasion resistance, and a reflector using the film. Is an issue.

[0005]

According to the present invention, the surface glossiness of at least one surface is 5 to 80%, the surface layer particle concentration is 0.5% by weight or less, and the refractive index in the thickness direction is 1. 46
It is a polyester film having a range of from 1.54 to 1.54 and a reflector using the polyester film as a support.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester film of the present invention must have a surface glossiness of at least one surface of 5 to 80%, preferably 7 to 70%, more preferably 10 to 60%. If the glossiness is less than the above range, the intensity of the reflected light will be low (dark), and if it is high, the reflectivity will be poor. Further, it is necessary that the surface layer particle concentration of the surface having a glossiness in the above range is 0.5% by weight or less, preferably 0.4% by weight or less, and more preferably 0.3% by weight or less. If the surface layer particle concentration is higher than the above range, the protrusions produced by it and the particles fall off remarkably, resulting in poor wear resistance.

The film of the present invention has a refractive index in the thickness direction of 1.46 to 1.54, preferably 1 as measured by the principle of total reflection by allowing light to enter from the surface having a glossiness in the range of 5 to 80%. .47 to 1.53, more preferably 1.50 to 1.3.
It should be in the range of 53. If the refractive index in the thickness direction is smaller than the above range, both the reflectivity and the abrasion resistance will be poor, and conversely if it is large, the reflectivity will be poor, such being undesirable.

The center line average roughness Ra of the surface having a glossiness of 5 to 80% is 30 nm or more and 300 nm or less, preferably 40 nm or more and 250 nm or less, and more preferably 50 nm.
The thickness is preferably not less than 200 nm and not more than 200 nm. The protrusion spacing Sm on the surface is 20 μm or less, preferably 17 μm.
It is preferably m or less, and more preferably 15 μm or less. If the center line average roughness is less than 30 nm or the protrusion spacing is more than 20 μm, diffuse reflection is small and reflectivity tends to be poor, which is not preferable. If the center line average roughness is larger than 300 nm, too much diffusion occurs on the surface and the reflectivity tends to be poor, which is not preferable.

The film of the present invention has a surface gloss of 5
Ratio of average surface roughness Ra to maximum height Rt of -80%, R
It is preferable that t / Ra is 10 or less, preferably 9 or less, and more preferably 8 or less. If Rt / Ra is larger than the above range, the reflectivity tends to be poor.

The film of the present invention has a crystallization index of 10 to 60 ° C., preferably 15 to 5 on at least one side of polyester.
It is a film obtained by laminating high-speed crystallized polyester in the range of 5 ° C., and more preferably 20 to 50 ° C., and the glossiness of the surface of the high-speed crystallized polyester is within the range of the present invention in terms of abrasion resistance. Especially desirable. The polyester used in this laminated portion is rapidly crystallized when magnesium acetate, a phosphorus compound containing a phenyl ring, or antimony oxide (or germanium oxide) is present as a catalyst / heat stabilizer during transesterification or polymerization. It is desirable because it is easily obtained and the surface morphology of the present invention is easily obtained. Further, it is effective to add a small amount of a flexible movable component or copolymerize the polyester used in the laminated portion to obtain the surface of the present invention. Here, the movable component refers to a component having a long flexible chain in the main chain and having high affinity or copolymerization with polyester, such as long-chain aliphatic dicarboxylic acid, long-chain aliphatic diol, and polyalkylene glycol. It is particularly effective to use a polyalkylene glycol such as polyethylene glycol and hexamethylene glycol. Especially, the number average molecular weight is 200 or more and 50000 or less, preferably 1000 or more 4
0000 or less, more preferably 2000 or more and 3000
0.01 to 15% by weight, preferably 0.1 to 13% by weight, and more preferably 1 to 0% by weight of polyethylene glycol based on polyester.
It is desirable to use in the range of not less than 10% by weight and not more than 10% by weight.

The laminated thickness is 0.5 to 8 μm, 1 to 7 μm, and 1 to 5 μm at the product stage.
When it is in the range of m, the reflectivity is further improved, which is desirable.

The film of the present invention is preferably a biaxially oriented film. A uniaxial or non-oriented film is not preferable because it has poor reflectivity and friction coefficient.
The degree of this orientation is not particularly limited, but it is desirable that the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 200 kg / mm ² or more in both the longitudinal direction and the lateral direction because the reflectivity is further improved. Especially, Young's modulus in the vertical direction is 2
When it is 50 kg / mm ² or more, the reflectivity is further improved, which is extremely desirable. The upper limit of the Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, but the production limit is usually about 1500 kg / mm ² .

In the film of the present invention, when the center line average surface roughness Ra of both surfaces is different, the center line average surface roughness Ra of one surface is 2 nm or more, preferably 5 or more than that of the other surface.
A dual surface having a size larger than or equal to nm, and more preferably greater than or equal to 50 nm is desirable because the reflectivity is further improved. In this case, it is desirable to use the surface with the larger Ra for reflection.

The total thickness of the film of the present invention is 25 to 500 μm.
When it is m, preferably 30 to 400 μm, the reflectivity, the shape retention as a reflection plate and the like are further improved, which is desirable.

Further, the film of the present invention has a gloss of 5 to 80.
% Metal having a metal vapor deposited on the surface can be used as a reflector having excellent reflectivity. In particular, when the metal is aluminum or silver, especially aluminum, the surface morphology and the size of the vapor deposition particles are well matched, and therefore, the metal has excellent reflectivity and is particularly suitable as a reflector.

The polyester constituting the present invention is not particularly limited, but ethylene terephthalate, ethylene 2,6-naphthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate. When at least one structural unit selected from the group consisting of ethylene terephthalate is used as a main constituent, ethylene terephthalate is used as a repeating unit.
A polyester containing 5 mol% or more is desirable because the reflectivity is further improved. The above polyester is
At the time of transesterification and polymerization, it is effective to allow lithium acetate, magnesium acetate, potassium acetate, phosphorous acid, phosphonic acid, phosphinic acid or their derivatives, antimony oxide, and germanium oxide to be present. A particularly desirable combination is magnesium acetate and phosphonic acid (or a derivative thereof) and antimony oxide, and desirable examples of the phosphonic acid (or a derivative thereof) include phenylphosphonic acid, dimethylphenylphosphonate and the like. In addition, as described above, it is effective to add or copolymerize a small amount of a flexible movable component to obtain the surface of the present invention.

The film of the present invention contains the above-mentioned composition as a main component, but may be blended with other polymers within a range not impairing the object of the present invention, and may also contain an antioxidant, a heat stabilizer, a lubricant, Additives such as an ultraviolet absorber and an antistatic agent may be added.

Next, a method for producing the film of the present invention will be described. The point of achieving the surface morphology of the present invention is not mainly to form the surface by conventional particle addition, but to crystallize the polyester and generate its spherulites, and biaxially stretch it to add particles to the surface. The purpose is to form fine irregularities that cannot be achieved with. From that point of view and from the viewpoint of improving wear resistance due to particles falling off, the point is to keep the content of particles within the range of the present invention.

The raw polyester is extruded into a sheet form from a slit-shaped die by a known melt extruder and cooled by a casting roll to prepare an unstretched film.

Next, the unstretched film is heat treated.
The method of heat treatment is not particularly limited, the roll non-contact surface with the above casting roll, hot air heating,
Radiant heating, steam heating, or the temperature of the casting roll may be adjusted to slow cooling conditions, or before longitudinal stretching or after fine stretching in the range of 1.01 to 2 times. The heat treatment may be carried out by the above heating method or heating on a roll. Especially desirable for the diffusion plate is a method of making the roll non-contact surface with a casting roll that is hard to cause optical unevenness, hot air heating, radiant heating, steam heating, or a method of gradually cooling the temperature of the casting roll to adjust to slow cooling conditions. is there. As the heat treatment condition, the surface temperature of the film facing the heat source is 120 to 230 ° C., preferably,
130-220 ° C., more preferably 140-220
Treatment at 0.1 ° C. for 0.1 to 10 seconds, preferably 0.2 to 8 seconds is effective for obtaining the surface morphology within the scope of the present invention.

In this case, it is preferable to control the heat source temperature of the non-contact surface of the roll and the roll temperature of the contact surface so that the temperature of the front and back of the film has a difference of 5 ° C. or more. It is effective in obtaining the Ra difference.

Next, the heat-treated film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used.
However, it is effective to obtain a film of the present invention by using a sequential biaxial stretching method in which the film is stretched in the longitudinal direction first and then in the width direction and stretched 3 to 6 times in two stages in the longitudinal direction.
The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generally stated. However, stretching at a temperature higher than usual by 15 ° C. or more above the glass transition point is effective for obtaining the film of the present invention. The longitudinal stretching speed is 5
The range of 000 to 50,000% / min is suitable. As a stretching method in the width direction, a method using a stenter is generally used. A suitable stretch ratio is in the range of 3 to 7 times. At this time, it is effective to obtain a desired Young's modulus of the present invention by making the stretching ratio in the width direction larger than that in the longitudinal direction. Further, the stretching speed in the width direction is preferably 1000 to 20000% / min, and the temperature is preferably 80 to 160 ° C. Further, the film once biaxially stretched may be further stretched in at least one direction. The stretched film is then heat treated again. It is effective that the heat treatment temperature in this case is higher than the previous heat treatment temperature, particularly 170 to 200 ° C., especially 17
The range of 0 to 190 ° C. and the time of 0.5 to 60 seconds are suitable.

Next, a more desirable production method is to obtain the film of the present invention in a laminated constitution. In this case, pellets of the rapidly crystallized polyester A are dried and then fed to a known melt extruder 1, Crystallization index is 1 more than that
Polyester B having a temperature of 0 ° C. or more is fed to the extruder 2 and 2
Alternatively, by using a manifold or a merging block having three or more layers, polyester A is laminated on at least one surface of polyester B, and a sheet having two or more layers is extruded from a slit-shaped die and cooled by a casting roll to be unstretched. Make a film. In this case, a method of stacking by using a merging block having a rectangular merging cross section is effective for stably obtaining the surface morphology of the present invention. This is extruded into a sheet from a slit-shaped die and cooled with a casting roll to prepare an unstretched film. The subsequent manufacturing method is the same as that described above.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows.

(1) Centerline average roughness Ra and protrusion spacing S
m, maximum height Rt The center line average surface roughness Ra, the maximum height Rt, and the protrusion spacing Sm were measured using a high-precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was determined as the average value of 20 measurements.

-Stylus tip radius: 0.5 μm-Stylus load: 5 mg-Measurement length: 1 mm-Cut-off value: 0.08 mm Note that the definitions of Ra, Sm, Rt, etc. are, for example, written by Jiro Nara, "Surface". Roughness measurement / evaluation method "(General Technology Center, 1983).

(2) Surface layer particle concentration The concentration of particles that form protrusions on the surface layer is defined as follows. That is, the surface layer is separated by peeling only the laminated portion or uniformly scraping the surface. Using this sample, a solvent in which polyester was dissolved and particles were not dissolved was selected, the particles were centrifuged from the polyester, and the surface layer particle concentration was defined as the weight percentage of the particles.

(3) Thickness of Laminated Portion Generally, a method of observing a cross section of a film with an electron microscope such as a transmission electron microscope and recognizing an interface from the difference in contrast to obtain the laminated thickness, However, the present invention is not limited to this, and after the laminated portion is peeled off, the laminated thickness can be obtained using a thin film step measuring machine.

(4) Young's modulus According to the method specified in JIS-Z-1702,
Using an Instron type tensile tester, 25
It measured at 65 degreeC and 65% RH.

(5) Surface Glossiness According to the method specified in JIS-K-7105,
The 60-degree specular glossiness was measured using a Suga Test Instruments digital variable angle gloss meter UGV-5D.

(6) Refractive index in the thickness direction In accordance with the method specified in JIS-K-7105,
The measurement was carried out using an Abbe refractometer with sodium D line (wavelength 589 nm) as a light source. The mount solution was methylene iodide, and the measurement was performed at 25 ° C. and 65% RH.

(7) Reflectivity The reflected light intensity (glossiness indication value) at an incident angle of 45 degrees and a detection angle of 0 degree of the vapor-deposited film was measured using a digital variable angle gloss meter UGV-5D manufactured by Suga Test Instruments. did. The larger this value is, the higher the reflection performance for enhancing the brightness in the vertical direction is. When the value is 5% or more, the reflectance is excellent, 4% or more 5
% Less than reflectivity: good, 3% or more and less than 4% reflectivity:
Acceptable when less than 3%: Poor. The reflectivity is preferably excellent or good, but even if it is acceptable, it is practically durable.

The measurement was carried out by calibrating using a light source and a diaphragm of the light receiver for 45 degree specular gloss.

(8) Abrasion resistance A film obtained by slitting a film into a tape having a width of 1/2 inch is loaded with a load of 100 g using a tape low-speed running tester, and a commercially available razor single-edged blade (FA Feather Safety Razor Co., Ltd. FA
S-10) is pressed against the running surface for 1 mm to run (running speed 250 m / min, running distance 100 mm, running times 1
Times). At this time, the adhesion width of the shavings adhering to the razor single blade is observed with a microscope. When the adhesion width of the shavings is less than 40 μm, wear resistance is excellent. If the thickness is less than 60 μm, the wear resistance is acceptable. If the thickness is 60 μm or more, the wear resistance is poor. The model test using the single edge of the razor well reflects the abrasion resistance when traveling on the transport roll in the processing process, and excellent or good is desirable, but even good ones can withstand use. is there.

(9) Crystallization Index The crystallization index was measured using DSC (Differential Scanning Calorimeter) Model II manufactured by Parking Elma. The measurement conditions of DSC are as follows. That is, 10 mg of a sample is set in a DSC device,
After melting at a temperature of 300 ° C. for 5 minutes, it is quenched in liquid nitrogen. This sample is heated at a rate of 10 ° C./minute to obtain a glass transition point T
g is detected. The temperature is further raised, and the crystallization exothermic peak temperature from the glass state is set as the cold crystallization temperature Tcc. Here, the difference between Tcc and Tg (Tcc-Tg) is defined as the crystallization index. As the sample, raw material pellets before film formation may be used, or 10 mg of powder obtained by scraping off the surface layer portion of the film after film formation with a razor blade may be used.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments.

Example 1 A transesterification catalyst was 0.1% by weight of magnesium acetate, a polymerization catalyst was 0.03% by weight of antimony trioxide, and a heat stabilizer was 0.35% by weight of dimethylphenylphosphonate. Polyethylene terephthalate (PET) containing 10% by weight of polyethylene glycol and having substantially no particles and a crystallization index of 50 ° C.
Was manufactured. The intrinsic viscosity was 0.65.

The chips were dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours, then melted at 290 ° C. by an extruder, extruded into a sheet, and undrawn while cooling one side on a cast roll having a surface temperature of 45 ° C. I got a film. At this time, in order to keep the surface on the opposite side of the roll warm, the surface was covered with a chamber, and hot air was blown into the chamber to control the temperature therein to 45 ° C. The time for the film to pass through the area covered by the chamber was 8 seconds.

This film was stretched 4.0 times in two steps in the longitudinal direction at a temperature of 80 ° C. This stretching was performed at a peripheral speed difference between two sets of rolls. This uniaxially stretched film was stretched 4.5 times in the width direction at 100 ° C. at a stretching speed of 5000% / min using a stenter, and then heat-treated at 200 ° C. for 5 seconds under a constant length, and biaxially oriented with a thickness of 120 μm. A polyester film was obtained.

Aluminum is applied to this film to a thickness of about 50.
A reflector was made by vapor deposition at nm.

As shown in Tables 1 and 2, the surface properties of the film satisfied the requirements of the present invention, and therefore, the reflectivity when used as a reflector was excellent.

Examples 2 to 6 and Comparative Examples 1 to 3 As polyester A, transesterification catalyst was 0.1% by weight of magnesium acetate, and polymerization catalyst was antimony trioxide 0.
Polyethylene terephthalate (PE) having a crystallizing index of 35 to 50 ° C., containing 0.3% by weight of a heat stabilizer and 0.35% by weight of dimethylphenylphosphonate as a heat stabilizer, and containing substantially no particles.
T) was produced. Adjusting the crystallization index reduces the intrinsic viscosity to 0.6
The change was performed in the range of 0 to 0.65. As the polyester B, an intrinsic viscosity of 0.65 to 0.
PET with a crystallization index of 75 to 80 ° C. of 8, crystallization index of 10
PEN at 0 ° C was made.

These polymers were used for the laminated part (polyester A) and the base layer part (polyester B), and each of 18 parts
Dry under reduced pressure (3 Torr) at 0 ° C. for 3 hours, feed each to two extruders and melt at 290 ° C.
Combined and laminated with a rectangular confluent block (feed block) for 2 or 3 layers, extruded into a sheet shape using an electrostatic cast method, cooled and solidified on a cast roll whose surface temperature is changed, and the laminated thickness is predetermined. An unstretched film having a 2-3 layer structure was prepared. At this time, as in Example 1, the temperature and flow rate of the hot air sent into the chamber were changed and the temperature inside the chamber was controlled to independently control the temperature history of the front and back of the unstretched film.

These unstretched films were stretched 4.0 times in the longitudinal direction in two steps at a temperature of 80 ° C. This stretching was performed at a peripheral speed difference between two sets of rolls. This uniaxially stretched film was stretched 4.5 times in the width direction at 100 ° C. at a stretching speed of 5000% / min using a stenter, and then heat-treated at 200 ° C. for 5 seconds under a constant length, and biaxially oriented with a thickness of 120 μm. A polyester film was obtained. Aluminum, silver, or iron was vapor-deposited on this film to a thickness of about 50 nm to form a reflector.

The surface properties of these films are shown in Tables 1 to 4
When the requirements of the present invention are satisfied,
It can be seen that a film excellent in reflectivity can be obtained when it is used as a reflector, but a reflector excellent in reflectivity cannot be obtained in other cases.

Examples 7 to 10 A biaxially oriented polyester film having a thickness of 120 μm was prepared in the same manner as in Example 1 except that as the polyester A, a flexible movable component as shown in the note of Table 1 was added. Got Aluminum with a thickness of about 50 nm
I made a reflector by vapor deposition. The surface texture of the film satisfies the requirements of the present invention as shown in Tables 1 and 2,
Therefore, the reflectivity when used as a reflector was also excellent.

[0047]

[Table 1]

[Table 2] Note to Table 1 and Table 2: 1) "Polymer" Example 1 PET: 10% by weight of polyethylene glycol (molecular weight 20,000) was added to polyethylene terephthalate during polymerization Examples 2 to 6 and Comparative Examples 1 to 2 PET: polyethylene terephthalate PEN: Polyethylene naphthalate Example 7 PET: 13% by weight of polyethylene glycol (molecular weight 1500) added to polyethylene terephthalate during polymerization Example 8 PET: 15% by weight of polyethylene glycol (molecular weight 400) added to polyethylene terephthalate Example 9 PET: Polyethylene terephthalate with polypropylene glycol (molecular weight 4000) added at 10 wt% during polymerization Example 10 PET: Polyethylene terephthalate with polypropylene glycol (molecular weight 4000) added at 15 wt% during polymerization Added 2) "processing temperature on the casting roll" Temperature I: cast roll surface temperature Temperature II: chamber - the inner temperature

[Table 3]

[Table 4]

[0048]

INDUSTRIAL APPLICABILITY According to the present invention, by the special stretching after crystallization,
A biaxially oriented polyester film with a refractive index in the thickness direction in a specific range, and a combination of surface morphologies that cannot be achieved by ordinary methods. The board has been completed.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G02B 5/08 G02B 5/08 Z G02F 1/1335 520 G02F 1/1335 520 G09F 9/00 333 7426-5H G09F 9/00 333A // B29K 67:00 B29L 9:00 11:00 C08L 67:00

Claims (13)

[Claims] 1. The surface glossiness of at least one surface is 5 to 80.
%, And the surface layer particle concentration on the surface is 0.5% by weight or less,
A polyester film having a refractive index in the thickness direction of 1.46 to 1.54. 2. The center line average roughness Ra of the surface having a glossiness of 5 to 80% is 30 nm or more and 300 nm or less, and the protrusion spacing Sm of the surface is 20 μm or less. The polyester film described in 1. 3. The polyester film according to claim 1, wherein the ratio Rt / Ra of the center line average roughness Ra of the surface having a glossiness of 5 to 80% and the maximum height Rt is 10 or less. 4. The polyester film according to claim 1, wherein the polyester having a crystallization index of 10 to 60 ° C. is laminated on at least one surface of the polyester. 5. The polyester film according to claim 1, wherein the average surface roughness Ra of one surface is larger than that of the other surface by 2 nm or more. 6. The polyester film according to claim 1, wherein the polyester contains 85 mol% or more of ethylene terephthalate as a repeating unit. 7. The polyester comprises 0.0 or more flexible movable components.
The biaxially oriented polyester film according to any one of claims 1 to 6, wherein the biaxially oriented polyester film is composed of a polyester containing 1% by weight or more and 15% by weight or less. 8. The flexible movable component has a number average molecular weight of 200.
The biaxially oriented polyester film according to claim 7, which is a polyalkylene glycol of 50000 or less. 9. The Young's modulus in the machine direction of the film is 250 k.
The polyester film according to claim 1, which has a g / mm ² or more. 10. The polyester film according to claim 1, wherein the film thickness is in the range of 25 to 500 μm. 11. The polyester film according to claim 1, which has a gloss of 5 to 8 as a support.
A light reflection plate having a metal layer on the surface of 0%. 12. The light reflection plate according to claim 11, wherein the metal is silver or aluminum. 13. The metal according to claim 1, which is aluminum.
1. The light reflecting plate according to 1.