KR20040046344A - A manufacturing method of polyethersulfone film for display panel - Google Patents

Abstract

PURPOSE: Provided is a method for making a polyethersulfone film for a display panel, which is environment-friendly and is amenable to a continuous process to give a high productivity and to reduce optical anisotropic phase contrast significantly. CONSTITUTION: The method for making a polyethersulfone film comprises the steps of: (a) melting a polyethersulfone resin in an extruder; (b) extruding the melted polyethersulfone resin through a die into a film having a predetermined thickness and width; (c) annealing and cooling the extruded film; and (d) heat-treating the cooled film by irradiating the film with NIR(Near Infrared). Particularly, in step (c), the extruded film is annealed by passing it through a first roller under 130-200 deg.C, a second roller under 130-200 deg.C and a third roller under 180-240 deg.C, successively, and then cooled to room temperature.

Description

A manufacturing method of polyethersulfone film for display panel

The present invention relates to a method for producing a polyether sulfone film used in various display panels, and more particularly, it can be applied to an environmentally friendly and continuous process, which not only increases productivity but also greatly increases the optical anisotropy retardation of the film without deteriorating other physical properties. A method for producing a polyethersulfone film useful for a display panel which can be reduced.

Display panels are widely used in display devices such as electronic calculators, electronic clocks, car navigation systems, office automation devices, mobile phones, laptop computers, and information communication terminals. For example, liquid crystal displays have transparent electrodes and alignment layers formed therein. The liquid crystal is injected between the opposing upper panel and the lower panel.

Conventionally, such a display panel uses a panel made of glass. However, the glass panel is insufficient in impact resistance due to the nature of the glass is not easily damaged by impact and thinning, as well as the weight per unit volume is limited to light weight. Therefore, in recent years, a panel made of a plastic film that is excellent in impact resistance and lightweight can gradually replace glass panels.

Such plastic films for display panels have excellent optical properties such as polycarbonate (PC), polyimide (PI), polyethersulfone (PES), polyarylate (PAR), and polyethylene naphthalate ( It can be made of thermoplastic resins such as polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) and thermosetting resins such as epoxy and unsaturated polyester. Resin is known as the most useful raw material resin.

As a method for producing a display film using a polyether sulfone resin, which is a thermoplastic resin, there are a solvent casting method, a blow molding method, a melt extrusion method, and the like, but a solvent casting method is mainly used.

The solvent casting method is a batch process method in which a polyethersulfone resin is dissolved in a solvent to prepare a solution, and then applied to a caster and the solvent is evaporated to form a film or sheet. In addition to the inconvenience in the process, there is a problem that environmental pollution occurs by the evaporated solvent. In addition, there is a disadvantage that the production cost is very high because the productivity is not high because of the batch process.

Therefore, a melt extrusion method is preferred in which a die such as a T-die or a coat hanger die is mounted on an extruder to extrude the molten polyether sulfone resin onto a sheet (film), and then pass through a roller to anneal and cool. . This method can be manufactured in a continuous process without the trouble of the process or the environmental pollution caused by the solvent to remove the solvent, which is pointed out as a disadvantage of the solvent casting method, it can significantly lower the production cost.

However, the polyethersulfone film produced by the conventional melt extrusion method has a large optical anisotropy retardation and thus poor performance as a display panel, which causes shear stress on the resin melt inside the die during extrusion and passes through the roller for annealing. This is because the birefringence is also increased due to the stretching orientation caused by the drawing of the roller. In particular, the performance of the film for display panel mainly used between the polarizing plate is greatly influenced by such optical anisotropy retardation, it is very important to minimize it.

Accordingly, there is an urgent need to develop a method for manufacturing a polyether sulfone film for a display panel which overcomes the disadvantages of the melt extrusion method and minimizes optical anisotropy retardation.

The technical problem to be achieved by the present invention can be applied to an environmentally friendly and continuous process to solve the above problems is not only high productivity, but also useful for display panels, which can greatly reduce the optical anisotropy phase difference of the film without deteriorating other physical properties. It is to provide a method for producing a polyether sulfone film.

The present invention to achieve the above technical problem, (a) melting the polyether sulfone resin in an extruder; (b) extruding the molten polyethersulfone resin into a film having a predetermined thickness and width through a die; (c) annealing and cooling the extruded film; And (d) irradiating NIR (Near Infrared) to the cooled film and heat-treating it. The method of manufacturing a polyethersulfone film for a display panel comprising a;

In the manufacturing method according to the present invention, step (c) is annealed through a first roller of 130 ~ 200 ℃, a second roller of 130 ~ 200 ℃ and a third roller of 180 ~ 240 ℃ sequentially and then annealed to room temperature It is preferable to cool, and the surface temperature of the film at the time of heat treatment by NIR (Near Infrared) irradiation in step (d) is preferably such that it is 90 ~ 170 ℃.

Hereinafter, a method of manufacturing a polyether sulfone film for display panel according to the present invention will be described in more detail.

The polyethersulfone film produced by a conventional melt extrusion method has a large optical anisotropy retardation, and thus poor performance as a display panel. This is because the shear stress acts on the molten resin in the die during extrusion, and the birefringence is increased due to the stretching orientation caused by the drawing of the roller even when passing through the roller for annealing. In particular, when the polyether sulfone film is brought into contact with a roller having a predetermined temperature for annealing, a low orientation of the roller causes stretching orientation, and too high roller temperature causes fine cooling wrinkles on the cooling roll, resulting in optical nonuniformity. . Due to the nature of the rollers, it is not easy to precisely control the annealing atmosphere to such an extent that this optical non-uniformity of the film can be eliminated.

In the present invention, this problem is solved by additionally adopting a continuous post-process of irradiating and heat-treating NIR (NearInfrared) on the polyether sulfone film prepared by melt extrusion. In other words, when the NIR (approximately 800 to 1300 nm), which is a hot wire, is irradiated on the surface of the film, the temperature inside the film is increased instantaneously, thereby alleviating the stress inherent in the film, The optical anisotropy retardation of the film is minimized without effect. The heat treatment temperature by NIR irradiation can be easily adjusted by changing the distance between the film surface and the NIR lamp, the speed of the line, and this post process can be easily applied to the conventional melt extrusion process. The ether sulfone film can be mass-produced.

Referring to the manufacturing method of the polyether sulfone film for display panel of the present invention in detail as follows, this manufacturing method is possible in a continuous process.

First, the polyether sulfone resin in a chip state is dried and then melted in an extruder, and then extruded into a film having a predetermined thickness (for example, 100 to 500 μm) and an appropriate width through a T-die or the like mounted on the extruder. The extruded film is then annealed and cooled, preferably through the first roller at 130-200 ° C., the second roller at 130-200 ° C. and the third roller at 180-240 ° C. sequentially. . As a result of the experiment, it was confirmed that the optically anisotropic retardation was further reduced by selectively passing the film through a tertiary roller maintained at a temperature of at least T _g of the polyether sulfone resin.

Then, the NIR (Near Infrared) is irradiated to the polyether sulfone film cooled to room temperature through an annealing process and heat-treated. The heat treatment temperature by NIR (Near Infrared) irradiation is preferably adjusted so that the surface temperature of the film is 90 to 170 ° C. When the surface temperature of the film is adjusted to this temperature range, cooling of the film does not occur without the occurrence of cooling wrinkles. The optical anisotropy retardation can be minimized the most.

The polyethersulfone film for display panel manufactured as described above has excellent light transmittance and small optical anisotropy retardation, thereby satisfying all of the properties as an optical film for display, and also having excellent physical properties such as surface smoothness, mechanical strength and thickness variation. . In particular, the polyethersulfone film having a thickness of 100-500 µm prepared according to the manufacturing method of the present invention exhibited excellent optical and physical properties of light transmittance of 90% or more, retardation of 15 nm or less, and thickness variation of 1% or less.

Hereinafter, examples will be described in detail to help understand the present invention. However, embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example 1

The polyethersulfone resin chip was dried and then put into an extruder, heated to 417 ° C. to be melted, and extruded into a film having a thickness of 200 μm and a width of 1450 mm through a T-die mounted on the extruder. The extruded film was then passed sequentially through the first roller, the second roller and the third roller at a rate of 50 mm / s maintained at temperatures of 143 ° C., 165 ° C. and 195 ° C., respectively.

Then, the film passing through the roller is spaced apart from the third roller at a predetermined interval (the film surface temperature just before the NIR lamp barrel is about 40 ° C.) under the installed NIR (Near Infrared) lamp (the distance between the film and the lamp is 50 mm The polyether sulfone film was prepared by passing NIR.

Examples 2-4

A polyether sulfone film was prepared in the same manner as in Example 1, except that the production conditions of the polyether sulfone film were changed as shown in Table 1 below.

Comparative Example 1

It was prepared in the same manner as in Example 1 except that NIR was not examined.

The light transmittance and optical anisotropy retardation of the film produced by the method described above were measured and shown in Table 1 below. Optical anisotropy retardation was measured at 633 nm using a PCT-2000 automatic birefringence meter (Germany instrument system), and the light transmittance was measured with a UV-VIS spectrophotometer (HP, Agilent8453).

Distance between NIR lamp and film (mm) Line speed (mm / s) Film surface temperature (℃) Phase difference value (nm) % Light transmittance Example 1 50 50 93 15 90.3 Example 2 50 16 120 12 90.3 Example 3 40 33 143 10 90.2 Example 4 40 16 155 7 90.3 Comparative Example 1 - 50 - 18 90.3

Referring to Table 1, compared to the retardation value of the polyether sulfone film of Comparative Example 1 which did not irradiate NIR according to the production method of the present invention, the polyether sulfones of Examples 1 to 4 which passed the post-process of irradiating NIR It can be seen that the retardation value of the film is reduced. In particular, polyethersulfone films (Examples 3 and 4) treated with NIR so as to have a film surface temperature of 143 ° C. or more were minimized to 10 nm or less. Meanwhile, light of a polyethersulfone film irradiated with NIR according to the present invention The transmittance did not change, and although not shown in Table 1, other physical properties did not deteriorate.

As such, the manufacturing method according to the present invention can be applied to an environment-friendly and continuous process not only high productivity, but also greatly reduce the optical anisotropy retardation of the film through the heat treatment step by NIR irradiation without deterioration of other physical properties. Therefore, the polyether sulfone film produced by the method of the present invention can be usefully used for display panels because it has excellent light transmittance and small optical anisotropy retardation to satisfy all properties as an optical film.

Claims (3)

(a) melting the polyethersulfone resin in an extruder; (b) extruding the molten polyethersulfone resin into a film having a predetermined thickness and width through a die; (c) annealing and cooling the extruded film; And (d) irradiating the NIR (Near Infrared) to the cooled film and heat-treating the manufacturing method of the polyether sulfone film for a display panel. The method of claim 1, wherein the step (c) passes through the first roller at 130 to 200 ° C, the second roller at 130 to 200 ° C, and the third roller at 180 to 240 ° C, followed by annealing and cooling to room temperature. The manufacturing method of the polyether sulfone film for display panels characterized by the above-mentioned. The method according to claim 1, wherein the surface temperature of the film during heat treatment by NIR (Near Infrared) irradiation in step (d) is 90 to 170 ° C.