JPH1044355A - Polyester film for cathode ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily provide a biaxially oriented polyester film for a cathode ray tube which has excellent productivity, transparency, and adhesive properties with a hard coating layer and can largely rationalize the cathode ray tube manufacturing process. SOLUTION: A coating layer is provided at least on one side surface of a biaxially oriented polyester film which simultaneously satisfies following formulae: Ht<=2.0%, 0.5%<=Hs<=1.5%, and Hi<=0.5% where Ht is a film haze, Hs is a surface haze of the film, and Hi is an inner haze of the film. The polyester for constituting the film contains ethylene terephthalate unit, ethylene-2,6- naphthalate unit or 1,4-cyclohexane terephthalate in 80% or more of its repeated structural unit. The ultimate viscosity of such polyester is normally 0.45 to 1.0, preferably 0.50 to 1.0 or further preferably 0.52 to 0.80.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film for a cathode ray tube, which is excellent in productivity and transparency and excellent in adhesion to a hard coat layer and an adhesive layer of a glass panel.

[0002]

2. Description of the Related Art In recent years, cathode ray tubes, particularly color cathode ray tubes, have been mass-produced for general household televisions, industrial televisions, computer displays, and the like. These glass panels for cathode ray tubes are produced by molding molten glass in a mold.However, the surface of the panel glass during molding is uneven, so the panel glass surface is polished before use. It is.

[0003] A polishing step is indispensable to obtain a panel glass surface of a cathode ray tube which is as smooth as required. In the cathode ray tube manufacturing process, the time and cost occupied by this step are 20 to 30% of the panel cost. In order to respond to the demand for reduction of the cathode ray tube manufacturing cost, the polishing process must be rationalized. It is important. A method for simplifying the process of manufacturing a cathode ray tube by adhering a biaxially stretched polyester film having excellent properties in mechanical strength, flatness, heat resistance, chemical resistance, transparency, etc. to the face surface of the cathode ray tube. Can be considered.

[0004] When a biaxially stretched polyester film is used for the face surface of a cathode ray tube, higher transparency than before is required. However, in order to obtain a highly transparent film, it is necessary to reduce the number of fine particles for securing the slipperiness and to reduce voids generated between the fine particles and the polymer. There is a problem that scratches are generated in the longitudinal stretching step. Thus, it is not easy for a polyester film to have both characteristics of high transparency and easy sliding.

Another problem common to plastic films is that the surface hardness is lower than that of inorganic materials such as glass, and the surface is easily scratched. For example, it is common to perform a hard coat treatment to prevent scratches on the polyester film surface, but when the adhesion with the hard coat layer is insufficient or when the polyester film is adhered to the glass surface via an adhesive In some cases, the adhesion to the glass surface is insufficient, and this has not always been achieved sufficiently.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a biaxially oriented polyester for a cathode ray tube, which is excellent in productivity and transparency, has excellent adhesion to a hard coat layer, and can greatly streamline the process of producing a brass tube. It is an object of the present invention to provide a film easily.

[0007]

Means for Solving the Problems As a result of intensive studies on the above-mentioned problems, the present inventors have found that a polyester film having specific optical properties can solve the above-mentioned problems. Reached. That is, the gist of the present invention resides in a polyester film for a cathode ray tube, which has a coating layer on at least one surface of a biaxially oriented polyester film that satisfies the following formulas (1) to (3) at the same time.

[0008]

Ht ≦ 2.0% (1) 0.5% ≦ Hs ≦ 1.5% (2) Hi ≦ 0.5% (3) Ht is the film haze, Hs is the surface haze of the film, and Hi is the internal haze of the film.)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester constituting the film of the present invention is a polyester obtained by using an aromatic dicarboxylic acid or an ester thereof and a glycol as main starting materials. For example, 80% or more of the repeating structural units are ethylene terephthalate units or ethylene-2, Refers to a polyester having 6-naphthalate units or 1,4-cyclohexane terephthalate. Then, other conditions may be contained as long as the conditions do not deviate from the above range.

As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxy) Benzoic acid and the like can be used. As the glycol component, other than ethylene glycol, for example, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol,
One or more of neopentyl glycol and the like can be used.

The intrinsic viscosity of such a polyester is usually 0.1.
It is 45 to 1.0, preferably 0.50 to 1.0, and more preferably 0.52 to 0.80. Intrinsic viscosity is 0.4
If it is less than 5, productivity during film production may be reduced, or mechanical strength of the film may be reduced. If the intrinsic viscosity exceeds 1.0, the melt extrusion stability of the polymer tends to be poor.

The film haze (Ht) of the biaxially oriented polyester film of the present invention has a value measured at a film thickness of 188 μm of 2.0% or less, preferably 1.5% or less.
More preferably, it is 1.0% or less. The surface haze (Hs) of the film is 0.5 to 1.5%, preferably 0.6 to 1.0%. Ht exceeds 2.0 or H
When s exceeds 1.5%, a so-called shimofuri pattern or an iridescent pattern is formed on the film surface, and when the film is closely attached to a glass panel to form a cathode ray tube, the resolution on the screen is undesirably reduced. On the other hand, if Hs is less than 0.5%, abrasion is likely to occur in the film production process, particularly in the longitudinal stretching process, which is not preferable. The internal haze (Hi) of the film is 0.5% or less, preferably 0.4% or less, more preferably 0.3% or less. If Hi exceeds 0.5%, when the film is brought into close contact with a glass panel to form a cathode ray tube, the sharpness of the screen deteriorates, which is not preferable.

The polyester film of the present invention preferably contains particles in the polyester to form appropriate protrusions on the film surface for the purpose of imparting slipperiness to the film and improving handleability. Examples of the particles used in the present invention include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide, and crosslinked polymers. particle,
Organic particles such as calcium oxalate, and precipitated particles generated during the polymerization of polyester can be mentioned,
In order to obtain a film having high transparency and good slipperiness (workability), which is the most important feature of the present invention, silica among the above particles,
Kaolin, crosslinked polymer particles and precipitated particles are preferably used. In the present invention, the average particle diameter of the particles contained in the film is usually 3.0 μm or less, preferably 2.mu.m.
It is 5 μm or less, more preferably 2.0 μm or less.
When the average particle size exceeds 3.0 μm, the film surface tends to be roughened, and the transparency tends to decrease.

The content of particles in the polyester is usually 1.0% by weight or less, preferably 0.1% by weight or less,
More preferably, the content is 0.01% by weight or less. If the particle content exceeds 1.0% by weight, the transparency of the film may be impaired. In the film, two or more kinds of the above particles may be blended, or the same kind of particles having different particle diameters may be blended. In any case, it is preferable that the average particle diameter of all the particles contained in the film and the total content satisfy the above-mentioned range.

In the production of polyester containing particles,
The particles may be added during the polyester synthesis reaction or may be added directly to the polyester. When it is added during the synthesis reaction, a method in which the particles are added as a slurry in which the particles are dispersed in ethylene glycol or the like at an arbitrary stage of polyester synthesis is preferable. On the other hand, when it is directly added to the polyester, it is used as dried particles or water or a compound having a boiling point of 2%.
As a slurry dispersed in an organic solvent at a temperature of
A method of adding and mixing with polyester using a shaft kneading extruder is preferred. In addition, the particles to be added may be subjected to processing such as crushing, dispersion, classification, and filtration as needed.

As a method of adjusting the content of particles, a master material containing particles at a high concentration is prepared in advance by the above-described method, and is diluted with a material substantially containing no particles at the time of film formation. A method of adjusting the particle content is effective. In addition, as additives other than the above-mentioned projection-forming agent, as necessary, an antistatic agent, a stabilizer, a lubricant, a crosslinking agent, an antiblocking agent, an antioxidant, a coloring agent (dye, pigment),
It may contain a light-blocking agent, an ultraviolet absorber and the like.

In order to use the film of the present invention as a polyester film for a cathode ray tube, it is necessary to provide a coating layer on at least one side of the film, and such a coating layer is a layer having good adhesion to a panel glass and a hard coat layer. Is preferred. The coating layer forming agent is not particularly limited, and may be a water-soluble or water-dispersible polyester composition, polyurethane composition, polyacryl composition, styrene-butadiene copolymer and acrylonitrile-butadiene copolymer. And the like.

Further, the coating layer of the film of the present invention preferably has an antistatic function. That is, the workability may be reduced due to sticking due to the charging of the film, or a problem such as an ignition accident due to spark discharge may occur. It is also important to prevent the attachment of dust. As a method of imparting antistatic properties, a low molecular weight anionic surfactant such as an organic sulfonic acid metal salt, for example, an antistatic agent such as polystyrene sulfonic acid sodium salt is blended with the above-mentioned coating agent, and applied in-line. Is preferred. Further, a high molecular weight cationic antistatic agent may be used as an antistatic agent, or a polymer containing a resin having phosphoric acid or a phosphate group, or a polymer having an ionized nitrogen element in the main chain may be used as a compounding agent. This is the preferred method.

When a coating layer is provided on the film of the present invention,
It is preferable that sticking between the films, that is, so-called blocking is small. If there is blocking, the film sticks when winding and slitting after film formation, and in extreme cases, the film may be broken. A cross-linking agent may be contained for the purpose of improving the blocking properties, water resistance, solvent resistance and mechanical strength of the coating layer. Crosslinking agents include methylolated or alkylolated urea-based, melamine, guanamine-based, alkylamide-based, polyamide-based compounds, epoxy compounds, oxazoline compounds, aziridine compounds, blocked isocyanate compounds, silane coupling agents, dialcohol aluminates Examples thereof include a coupling agent, a zircoaluminate coupling agent, a peroxide, a thermally or photoreactive vinyl compound, and a photosensitive resin.

The coating solution for obtaining the coating layer of the present invention may contain particles for improving the slipperiness of the coating layer.
Examples of the particles include inert inorganic particles such as colloidal silica, alumina, calcium carbonate, and titanium dioxide, and fine particles obtained from a polystyrene-based resin, a polyacryl-based resin, and a polyvinyl-based resin, or organic particles represented by crosslinked particles thereof. Is done.

The coating liquid for obtaining the coating layer of the present invention may be, if necessary, a defoaming agent, a coating improver, a thickener, a low-molecular antistatic agent, an organic lubricant, an antioxidant, and an ultraviolet ray. It may contain an absorbent, a foaming agent, a dye, a pigment and the like. Further, the coating solution for obtaining the coating layer of the present invention may contain a small amount of an organic solvent for the purpose of improving dispersion in water or improving film forming performance, as long as water is the main medium. Good. When the organic solvent is used by mixing with water as a main medium, it is necessary to use the organic solvent within a range that dissolves in water. Examples of the organic solvent include aliphatic or alicyclic alcohols such as n-butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol, and methyl alcohol; glycols such as ethylene glycol, propylene glycol, and diethylene glycol; and n-butyl. Glycol derivatives such as cellosolve, ethyl cellosolve, methyl cellosolve, propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and amyl acetate, ketones such as methyl ethyl ketone and acetone, N
Amides such as -methylpyrrolidone, but are not limited thereto. These organic solvents may be used alone or in combination of two or more as necessary.

The thickness of the coating layer of the film of the present invention is usually from 0.02 to 0.5 μm, preferably from 0.01 to 0.3 μm, more preferably from 0.0 to 0.5 μm, after the final drying.
3 to 0.2 μm. When the thickness of the coating layer is more than 0.5 μm, the films are likely to block each other, and particularly when the stretched coated film is redrawn for the purpose of increasing the strength of the film, the film adheres to the roll during the process. Tends to be easier. If the thickness of the coating layer is less than 0.02 μm, the effect of improving the adhesiveness tends to be small.

The film may be subjected to a chemical treatment or a discharge treatment before application in order to improve the coating property and adhesion of the coating agent to the film. Further, in order to improve the surface characteristics of the coating layer of the biaxially stretched film of the present invention, the surface of the coating layer may be subjected to a discharge treatment after the formation of the coating layer. As a method of forming the coating layer, there are a method of forming the biaxially stretched film at the time of manufacturing the film and a method of forming the film after the biaxial stretching, and the former is more preferable. As a specific example of the former, for example, after a thin film forming liquid is applied to the surface of an unstretched film, the film is stretched by a biaxial method. Alternatively, a method of applying a thin film-forming liquid to the surface of a uniaxially stretched film and then stretching the film in the perpendicular direction may be mentioned, but a method of using these in combination is also suitable.

If the stretching treatment is not performed after the coating, the adhesion between the coating layer to be formed and the base film tends to be weak, and the adhesiveness suitable for practical use may not be obtained. In order to achieve these industrially advantageously, it is preferable to apply in the manufacturing process of the biaxially stretched film, but it is not limited thereto. As a method of applying the above-described coating liquid to a polyester film, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or the like described in “Coating System”, written by Yuji Harasaki, Maki Shoten, 1979, can be used. .

Next, the production method of the film of the present invention will be described more specifically, but it is not particularly limited to the following examples as long as the constitutional requirements of the present invention are satisfied. The polyester raw material is supplied to an extruder, melt-extruded at a temperature equal to or higher than the melting point of the polyester, and extruded as a molten sheet from a slit die. Next, the molten sheet is quenched and solidified on a rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature, thereby obtaining a substantially amorphous unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

In the present invention, the sheet thus obtained is biaxially stretched to form a film. When the stretching conditions are specifically described, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinally uniaxially stretched film, and then a coating liquid is applied to at least one surface of the film. Is subjected to appropriate drying or undried and stretched 2 to 6 times in the transverse direction at 90 to 160 ° C.
The heat treatment is preferably performed at 50 to 250 ° C. for 1 to 600 seconds. At this time, after a relaxation treatment of 10% or less, preferably 5% or less in the lateral direction in or after the heat treatment step,
A method such as a method of stretching by 0.1 to 5% in the longitudinal direction can also be adopted, particularly in order to keep the heat shrinkage in the transverse direction and the longitudinal direction within a suitable range.

[0027]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example is as follows. In Examples and Comparative Examples, “parts” means “parts by weight”. (1) Intrinsic viscosity of polymer 1 g of polymer is phenol / tetrachloroethane = 50
/ 50 (weight ratio) in 100 ml of a mixed solvent.
Measured in ° C.

(2) Average particle size: Centrifugal sedimentation type particle size distribution analyzer SA- manufactured by Shimadzu Corporation
The particle size was measured using a CP3 type by the sedimentation method based on Stokes' resistance law. The average particle size was determined using a value of 50% of the integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement.

(3) Film haze The turbidity of the film was measured with an integrating sphere turbidity meter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS-K7105. Using a 188 μm film, the measured value of the film haze was defined as Ht, and the measured value of the haze after applying liquid paraffin to the film surface was defined as the internal haze Hi. The surface haze Hs was calculated by the following equation.

[0030]

Hs = Ht-Hi

(4) Surface resistivity The inner electrode 5 of Yokogawa-Hewlett-Packard Co., Ltd.
0 mm diameter, outer electrode 70 mm diameter concentric electrode 1
The sample was placed in 6008A (trade name) under an atmosphere of 23 ° C. and 50% RH, a voltage of 100 V was applied, and the surface resistivity of the sample was measured with 4329A (trade name), a high resistance meter of the same.

(5) Film Scratches An area of 10 m ² was visually observed under a halogen lamp, and the number of scratches having a length of 5 mm or more was measured and evaluated according to the following criteria. ：: the number of scratches <10 Δ: 10 ≦ the number of scratches ≦ 30 ×: the number of scratches> 30

(6) Adhesion to Hard Coat Layer A hard coat agent having the following composition was applied to the polyester film surface using a # 20 bar, dried at 90 ° C. for 1 minute to remove the solvent, and then dried with a high-pressure mercury lamp for 120 watts. / Cm, an irradiation distance of 15 cm, and a 9 μm hard coat layer were formed under the conditions of 10 m / min. A cross cut was made on the hard coat layer of the obtained film so as to have 100 grids in a width of 1 inch, and a peel test was performed by a 90-degree drawing method (tensile speed: 2 inches / minute) to measure the adhesiveness. Was evaluated according to the following criteria. ：: Peeling of grid pattern <5 pieces Δ: 5 pieces ≦ peeling of grid pattern ≦ 20 pieces ×: Peeling of grid pattern> 20 pieces

[Hard Coating Agent Composition] 30 parts Seika Beam EXY-26 (S) (manufactured by Dainichi Seika Kogyo Co., Ltd.) 35 parts methyl ethyl ketone 35 parts toluene 35 parts

(7) State of Screen The panel glass to which the polyester sheet was adhered was visually observed and judged according to the following criteria. ：: No abnormality is observed on the surface of the panel glass. △: Irregular rainbow is observed on the surface of the panel glass. ×: Scratch is conspicuous on the surface of the panel glass. (Adjustment of coating agent) Was adjusted.

[0036]

[Table 1] * Solid concentration

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 containing 0.0025 parts of crosslinked organic particles having an average particle diameter of 1.2 μm was dried by a conventional method, supplied to an extruder, melted at 290 ° C. The sheet was extruded into a sheet and quenched on a cooling roll using an electrostatic application contact method to obtain an amorphous sheet having a sheet thickness of 2566 μm. The obtained unstretched sheet was stretched 2.5 times at 85 ° C. in the machine direction by a roll stretching method, and further stretched 1.3 times at 95 ° C. The production speed at this time was 50.0 m / min. Before the obtained uniaxially stretched film is transversely stretched by a tenter, an aqueous paint shown in Table 1 above is applied, and the film is guided to a tenter, and then 4.2 ° at 120 ° C. in a transverse direction.
After stretching twice and performing heat treatment at 225 ° C, 2%
After relaxation, the film was wound up into a roll to obtain a biaxially stretched polyester film having a film thickness of 188 μm. The intrinsic viscosity of the obtained film was 0.583.

Examples 2-3 and Comparative Examples 1-5 The particle size and content of the silica particles in Example 1 are shown in Table 2 below.
A biaxially stretched polyester film having a film thickness of 188 μm was obtained in the same manner as in Example 1 except that the composition was changed to the composition shown in Example 1.

Comparative Example 6 A film thickness of 18 was obtained in the same manner as in Example 1 except that the aqueous coating was not applied after the longitudinal stretching and before the transverse stretching.
An 8 μm biaxially stretched polyester film was obtained. The properties of the obtained biaxially stretched polyester film are summarized in Tables 2 and 3 below.

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

The film of the present invention can stably produce a biaxially oriented polyester film for a cathode ray tube which is excellent in productivity and transparency and excellent in adhesion to a hard coat layer, and greatly increases the production process of a cathode ray tube. Rationalized, its industrial value is extremely high.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 9:00

Claims (1)

[Claims] 1. A polyester film for a cathode ray tube, characterized by having a coating layer on at least one surface of a biaxially oriented polyester film satisfying the following formulas (1) to (3) at the same time. Ht ≦ 2.0% (1) 0.5% ≦ Hs ≦
1.5% (2) Hi ≦ 0.5% (3) (In the above formula, Ht represents the film haze, Hs represents the surface haze of the film, and Hi represents the internal haze of the film.)