KR20220033413A - Manufacturing method of Window cover for display device and window cover - Google Patents

Abstract

According to the present invention, in a method for manufacturing a window cover for a display device, the window cover is manufactured by injection compression molding, wherein an injection material has a melt index of 30 to 50 cm^3/10min and an impact strength of 50 to 60 kJ/m^2. Accordingly, the present invention can reduce the overall retardation value while reducing generation of dust. The plane-side retardation value of the window cover manufactured by the manufacturing method of the present invention is 50 nm or less, and the 45°-side retardation value thereof is 270 nm or less.

Description

Method of manufacturing a window cover for a display device and a window cover for a display device {Manufacturing method of Window cover for display device and window cover}

The present invention relates to a method of manufacturing a window cover for a display device and to a window cover for a display device.

Various display devices are used in a vehicle to deliver necessary information while driving or to deliver content that provides convenience in the vehicle. Among them, the Center Information Display (CID) is placed in front of the vehicle to deliver necessary information to the driver.

On the other hand, the window cover for the display device serves to protect the display panel of the display device. Glass has been conventionally used as a material for the window cover, but is being replaced with a plastic material due to the demand for light weight and impact resistance. The window cover for the display device is located on the upper layer of the display panel, and optical properties having high transparency and low retardation value are required to prevent distorted transmission of information displayed on the display to the driver or passengers.

However, the resin forming the window cover may generate dust during transportation or processing, and when such dust is introduced into the mold and molded, it is not melted or carbonized dust during plasticization creates defects in the window cover. Appearance may deteriorate. When a resin having high impact strength is used, the generation of dust can be reduced, but in this case, there is a problem in that the birefringence value is lowered due to residual stress.

Accordingly, there is a need for a method of manufacturing a window cover having a good appearance and good birefringence performance without distorting information displayed on a display device or reducing visibility by improving optical properties. In addition, there is a need to develop a method for manufacturing a window cover for a display device capable of minimizing the generation of dust during the manufacturing process of the window cover.

Patent Laid-Open No. 10-2007-0120484 (Name: Non-birefringent optical resin material and optical member)

An object of the present invention is to provide a method of manufacturing a window cover for a display device having improved birefringence and good visibility.

An object of the present invention is to provide a method of manufacturing a window cover for a display device having fewer defects by reducing the generation of dust.

A method of manufacturing a window cover for a display device according to an embodiment of the present invention includes the steps of mounting an insert film on an upper mold, positioning the lower mold at a predetermined distance from the upper mold, injecting an injection material into the mold, and compression pressing the core. The melt index (MI) of the injection material may be 30-50 cm ³ /10min at 300°C.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the impact strength of the injection material may be 50 to 60 kJ/m ² .

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the average particle diameter of the injection material may be 2-3 mm.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the temperature of the injection material may be 270 to 320°C.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the injection material may be PC or PMMA.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, in the step of injecting the injection material into the mold, the injection speed may be controlled for each of four stroke sections.

In the method for manufacturing a window cover for a display device according to an embodiment of the present invention, the stroke section has a position of the tip of the nozzle of 0 mm, and the positions of the tip of the screw are 33 to 37 mm, 23 to 27 mm, 10 to 14 mm, and 5 to 9 mm. It can be divided into 1 section, 2 section, 3 section, and 4 section based on the in position.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the injection speed in the second section may be greater than the injection speed in the first section.

In the method for manufacturing a window cover for a display device according to an embodiment of the present invention, the injection speed is 40-50 mm/s in section 1, 75-85 mm/s in section 2, 75-85 mm/s in section 3, and in section 4 It can be 65~75mm/s.

The method of manufacturing a window cover for a display device according to an embodiment of the present invention may further include the step of preforming the insert film before the step of mounting the insert film on the upper mold.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the temperatures of the upper mold and the lower mold may be 70 to 95°C.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the temperature of the gate for injecting the injection material may be 20 to 40 ℃.

In the method for manufacturing a window cover for a display device according to an embodiment of the present invention, the temperature of the compression core may be 80 to 105°C.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the temperature of the compression core is greater than the temperature of the upper mold, and the temperature difference between the upper mold and the compression core may be 10° C. or more.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the compression holding time in the step of pressing the compression core may be 8 to 10 seconds.

In the method of manufacturing a window cover for a display device according to an embodiment of the present invention, the clamping force may be 250 to 600 tons in the step of pressing the compression core.

A window cover for a display device according to an embodiment of the present invention may be manufactured by the method of manufacturing a window cover for a display device of the present invention.

In the window cover for a display device according to an embodiment of the present invention, the plane-side average retardation value may be 50 nm or less.

In the window cover for a display device according to an embodiment of the present invention, an average retardation value at an incident angle of 45° may be 270 nm or less.

In the window cover for a display device according to an embodiment of the present invention, an average retardation deviation value according to an incident angle may be 20 nm or less.

A window cover for a display device according to an embodiment of the present invention may have a flatness of 0.8 or less.

According to an embodiment of the present invention, the window cover for a display device can reduce retardation by optimizing the MI value and impact strength of the injection material, and thus has excellent optical performance.

In addition, since the amount of dust is reduced, it is possible to manufacture a window cover for a display device with few defects.

1 is a view showing a schematic structure of a window cover for a display device of the present invention.
2 is a view schematically showing the configuration of the film layer of the present invention.
3 is a schematic configuration diagram of a film layer.
4 is a schematic configuration diagram of a film layer according to another embodiment.
5 is a diagram schematically illustrating a window cover of the present invention.
6 is a schematic AA cross-sectional view of the window cover shown in FIG.
7 is a configuration diagram schematically illustrating technical characteristics of the detailed configuration of the window cover shown in FIG. 5 .
FIG. 8 is a configuration diagram schematically illustrating technical characteristics of a gate region of a film layer in the window cover shown in FIG. 7 .
9 is a configuration diagram schematically illustrating an embodiment of a mold and an injection material discharging device for implementing a method of manufacturing a window cover.
10 is a configuration diagram schematically illustrating a preforming film mounted on a mold.
11 is a flowchart illustrating a method of manufacturing a window cover for a display device according to an embodiment of the present invention.
12 and 13 are diagrams schematically showing a specific example for implementing the insert film upper mold mounting step.
14 is a configuration diagram schematically illustrating a specific example for implementing the injection material discharging step.
15 is a schematic usage state diagram of the injection material discharging step shown in FIG. 14 .
16 is a configuration diagram schematically showing a specific example for implementing the step of pressing the lower mold.
17 is a flowchart illustrating a method of manufacturing a window cover for a display device according to a second embodiment of the present invention.
18 is a flowchart illustrating a method of manufacturing a window cover for a display device according to a third embodiment of the present invention.
19 is a view illustrating a compression gap (G) in a method of manufacturing a window cover for a display device according to an embodiment of the present invention.
20 is a diagram illustrating a compression rate in a method of manufacturing a window cover for a display device according to an embodiment of the present invention.
21 is a view illustrating a stroke section in a method of manufacturing a window cover for a display device according to an embodiment of the present invention.
22 is a schematic diagram illustrating that resin flows into a cylinder. FIG. 23 is a diagram illustrating a state in which a bending phenomenon occurs in the window cover during the manufacturing process of the window cover for a display device.
24 is a view showing a plurality of measurement positions for measuring flatness.
25 is a view showing a film layer in a window cover for a display device according to an embodiment of the present invention.
26 is a view illustrating a first area and a second area in a window cover for a display device according to an embodiment of the present invention.
27 is a view showing the flow of injection material in the step of forming the base layer of the window cover for a display device according to an embodiment of the present invention.
28 is a view showing the results of visual evaluation of birefringence performance in the first region and the second region in the window cover for a display device according to the present invention.
29 is a view showing a flow mark in the window cover for a display device of the present invention.
30 is a diagram illustrating a first area and a second area in a window cover for a display device according to an embodiment of the present invention.
31 is a diagram illustrating a first area and a second area in a window cover for a display device according to an embodiment of the present invention.
32 is a diagram illustrating a flow mark in a window cover for a display device according to an embodiment of the present invention.
33 is a flowchart schematically illustrating a method for manufacturing a window cover material according to a sixth embodiment of the present invention.
34 is a configuration diagram schematically illustrating an embodiment of a suction device for implementing the method for manufacturing a window cover material shown in FIG. 31 .
35 is a configuration diagram schematically showing a specific example for implementing the insert film suction step.
36 is a configuration diagram schematically illustrating a window covering material according to a sixth embodiment of the present invention.
37 is a configuration diagram schematically illustrating a window cover for a display device according to an embodiment of the present invention.
FIG. 38 is a schematic BB cross-sectional view of the window cover for the display device shown in FIG. 37 .

Since the present invention can apply various transformations and can have various embodiments, specific embodiments will be illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as 'comprising' or 'having' are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, and one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that in the accompanying drawings, the same components are denoted by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings.

The window cover is a component that protects the panel of the display device, and excellent optical properties are required. As a material of the window cover, conventionally, glass is being replaced by a plastic material. The plastic window cover has the advantage of being lightweight and strong against impact.

Window covers are generally manufactured by injection molding. Injection molding refers to molding by injecting a resin or the like between the upper and lower molds and pressurizing them. However, in injection molding, high pressure is applied to the cavity, and as the molded window cover contracts due to a large temperature change, a large residual stress is left in the window cover. The residual stress leads to deterioration of optical properties such as an increase in the birefringence value of the manufactured window cover.

Accordingly, the present invention uses an injection compression molding (ICM) process to minimize residual stress during molding of the window cover. Injection compression molding can control the pressure in the cavity to be low and uniform, and by reducing the cavity volume itself through compression, the effect of molding shrinkage of the resin can be minimized.

Injection compression molding partially injects the injection material into the cavity before the mold is completely closed in the filling stage, and the clamping device works until the mold is completely closed, and the injection material enters the cavity by the cavity surface compression and the filling is completed. have a process of becoming

In the present invention, a separate compression core is installed in the mold to compress the cavity with the compression core. In a state where the upper and lower molds are closed, only the compression core is partially opened, the injection material is partially injected, the compression core is closed, and the final molding is completed by applying compression to the injection material. In the injection compression molding process, a compressive force is uniformly applied to the entire surface of the window cover to obtain a product with uniform physical properties, and since the residual stress is low, optical problems such as birefringence can be greatly reduced.

1 is a view showing the schematic structure of a window cover for a display device of the present invention, Figure 2 is a view schematically showing the configuration of the film layer of the present invention, Figure 3 is a schematic configuration diagram of the film layer, 4 is a schematic configuration diagram of a film layer according to another embodiment, FIG. 5 is a diagram schematically showing a window cover of the present invention, and FIG. 6 is a schematic AA cross-sectional view of the window cover shown in FIG. 7 is a configuration diagram schematically illustrating technical characteristics of the detailed configuration of the window cover shown in FIG. 5, and FIG. 8 is a schematic diagram showing technical characteristics of a gate region of a film layer in the window cover shown in FIG. It is one configuration.

As shown in FIG. 1 , the window cover 1000 for a display device includes a base layer 1100 and a film layer 1200 . The window cover 1000 for the display device serves to protect the panel of the display device.

The base layer 1100 is a layer that provides rigidity to the window cover and protects the display panel. The base layer 1100 may be formed of a material such as PC (PolyCarbonate), PMMA (PolyMethyl Methacrylate), or polyacrylate. PC is a thermoplastic plastic and has excellent heat resistance, visibility, transparency, electrical insulation, and durability. PMMA has the advantage of being excellent in visibility, transparency, weather resistance, colorability, and the like. However, the material of the base layer is not limited thereto, and any material having optical transparency may be used as the base layer.

The base layer 1100 may be formed to a thickness of 1500-2500㎛. When the base layer 1100 is formed to be less than 1500 μm, it is difficult to secure the minimum surface hardness, the probability of non-molding during injection is high, and deviation and warpage due to thickness non-uniformity may occur. When the base layer 1100 exceeds 2500 μm, cracks may occur due to an external impact, and sensitivity may decrease when the display touches the rear surface.

The film layer 1200 is disposed on the base layer 1100 . The film layer 1200 may be formed of a material such as PC or PMMA. The film layer 1200 may be formed of a single layer of PC or PMMA, but a two-layer co-extrusion sheet in which the PC and PMMA layers are simultaneously formed may be used. If necessary, a 3-layer sheet in which PMMA, PC, and PMMA layers are sequentially stacked may be used. The film layer 1200 may hard-coat a PC or PMMA material film to improve the surface hardness, scratch resistance, and weather resistance of the window cover.

The film layer 1200 may have a thickness of 100 to 500 μm, preferably 180 to 220 μm.

In this embodiment, after hard coating for scratch resistance on a 2-layer sheet of PC/PMMA, an anti-reflection coating layer (LR coating layer) and an antifouling functional coating layer (AF coating layer) are formed, thereby forming a film layer 1200. In the film layer 1200 of this embodiment, the thickness of the 2-layer sheet of PC/PMMA is 200 μm, the thickness of the hard coating layer is 3 μm, and the thickness of the LR/AF coating layer is 0.2 μm.

The film layer 1200 may be integrally molded with an injection material during injection compression molding of the base layer 1100 .

Meanwhile, in the film layer 1200 , a gate region 1250 that can be mounted on the injection material injection hole 31 is provided for molding the window cover 1000 . 2 and 3 , a gate region 1250 is formed in the film layer 1200 . The gate region 1250 serves as the gate region G of the film layer into which the injection material is introduced when the injection material is discharged to the rear surface of the film layer 1200 . In addition, the gate region 1250 simultaneously serves as a film hanger (F) for fixing the film layer 1200 during the injection compression process.

To this end, the injection material injection device 30 includes an injection material injection hole 31 through which injection material is discharged, and an end of the injection material injection hole 31 is formed to correspond to the gate region 1250 . The injection material injection hole 31 passes through the front surface (FS) gate region 1250 of the film layer 1200 and injects the injection material into the rear surface RS of the film layer 1200 to the rear surface of the film layer 1200 ( A base layer 1100 is formed on RS).

At this time, the gate region 1250 is mounted on the injection material injection hole 31 and serves as a film hook portion F for fixing the film layer 1200 during injection.

In the present invention, the gate region 1250 fixes the film layer 1200 without a separate fixing member for fixing the film layer 1200 in the step of injecting the injection material to the rear surface of the film layer 1200 during the injection compression process. By acting as a hook, the process becomes simpler.

Here, the gate region 1250 of the film layer 1200 may be formed in the buttonhole region of the film layer 1200 corresponding to the buttonhole region of the window cover for a display device. The buttonhole area means a hole area corresponding to the button part of the display apparatus when the window cover for the display apparatus is coupled to the display apparatus.

In another embodiment, as shown in FIG. 4 , a gate region 1250 ′ may be formed in the film layer 1200 ′. The gate region 1250 ′ serves as the gate G when the injection material is discharged to the film layer 1200 ′. In addition, the gate region 1250 ′ simultaneously functions as a hook portion F for fixing the film layer during the injection compression process. In the present embodiment, the gate area 1250' is formed in the outer area 1200b' extending from the display area 1200a' of the display apparatus when the window cover for the display apparatus is coupled to the display apparatus. That is, the gate region 1250 is finally removed from the manufactured window cover.

More specifically, the film layer 1200 may be formed of a preformed In Mold Label (IML) film. The film layer 1200 may include a transparent part 1260 and a light blocking part 1270 so that the window cover 1000 is implemented as a window cover for a display device. That is, the transparent portion 1260 is formed to correspond to the display area, and the light blocking portion 1270 is formed to surround the outer periphery of the transparent portion 1260 .

In addition, a film layer gate region 1271 and a film layer buttonhole region 1272 are formed in the light blocking portion 1270 . The film layer gate region 1271 is a gate region for injecting the injection material onto the film layer 1200 . That is, the film layer gate region 1271 is a gate region through which the injection material flows. At the same time, the film layer gate region 1271 also serves as a film hanger for fixing the film layer during the injection compression process.

5 to 8 show, as an example of a position where the film layer gate region 1271 is formed, the film layer gate region 1271 is formed in the film layer buttonhole region 1272 .

The film layer buttonhole region 1272 may be formed to protrude in a direction in which the base layer 1100 is positioned with respect to the film layer 1200 . This is for the base layer buttonhole area 1272 to be performed as a hook area when the injection material is supplied. That is, the hook region is formed as a step portion with respect to one surface of the film layer.

In addition, the base layer 1100 is combined with the film layer 1200 . To this end, the base layer 1100 is formed while the injection material is injected and compressed to the rear surface of the IML film, which is the film layer 1200 , and the base layer 1100 is combined with the film layer 1200 .

In addition, a base layer gate region 1160 corresponding to the film layer gate region 1271 of the film layer 1200 is formed in the base layer 1100 , and a base layer buttonhole region corresponding to the film layer buttonhole region 1272 . 1170 is formed.

Hereinafter, the detailed configuration and shape of the film layer gate region and the film layer buttonhole region will be described in more detail with reference to FIGS. 7 to 8 .

7, the film layer 1200 of the window cover 1000 has a first center line C1 in the uniaxial (X-axis) direction and a second center line C2 in the other axis (Y-axis) direction. It has a side that includes The first center line C1 is an imaginary line that passes through the midpoint of the finally manufactured window cover and is parallel to the Y-axis direction, and the second center line C2 is an imaginary center line on the window cover, which is the midpoint of the finally manufactured window cover. It is a line parallel to the X-axis direction. That is, in the X-axis direction, the film layer 1200 has the same distance D1 from the first center line C1 to both ends, and the film layer 1200 in the Y-axis direction extends from the second center line C2 to both ends. have the same distance D2.

The film layer gate region 1271 and the film layer buttonhole region 1272 of the film layer 1200 may be positioned on one side with respect to the second center line C2 . For example, the film layer gate region 1271 and the film layer buttonhole region 1272 of the film layer 1200 may be positioned below the second center line C2 . This is in consideration of the fact that the film layer gate region 1271 is formed on one side so that when the injection material is discharged to the film layer 1200 , it flows from one side to the other without obstruction.

In addition, in the display device, as the button portion is formed under the display portion, it is considered that the film layer buttonhole region 1272 is formed on one side.

In addition, the base layer buttonhole region 1170 and the base layer gate region 1160 are also positioned below the second center line C2 .

More specifically, the film layer gate region 1271 is positioned on the first center line C1 .

In addition, it is preferable that the separation distance D3 of the gate region of the film layer, which may be formed to be spaced apart from the first center line C1, is 10% or less of the total distance D4 of the window cover.

In this case, the insert film and the base layer may be formed in a symmetrical shape with respect to the first center line.

When the film layer gate region 1271 serves as a gate through which the injection material flows during injection molding, when the allowable separation distance from the center line is within 10% as described above, the effect of improving optical performance due to the symmetry of birefringence is obtained. can be obtained

In addition, the base layer gate region 1160 is also located on the first center line C1, and the base layer gate region 1160 is spaced apart from the first center line C1 so that the separation distance of the base layer gate region is the window cover. It is preferable to form 10% or less of the total distance D4.

9 is a configuration diagram schematically illustrating an embodiment of a mold and an injection material discharging apparatus for implementing a method of manufacturing a window cover, and FIG. 10 is a configuration diagram schematically illustrating a preforming film mounted on a mold.

A mold and an injection material discharging device for manufacturing the window cover will be described.

As shown in FIG. 9 , the mold 100 includes an upper mold 110 and a lower mold 120 . An upper mold buttonhole hook 111 , a hot runner 112 , and an upper mold gate step 113 are formed in the upper mold 110 .

More specifically, the upper mold buttonhole hook 111 is formed of a protrusion corresponding to the film layer buttonhole region so that the film layer buttonhole region of the insert film is inserted and supported. The hot runner 112 is formed in the upper mold buttonhole hook 111 to communicate with the upper mold gate step 113 .

The upper mold gate step 113 has a protruding shape for mounting the film layer gate region 1271 of the film layer 1200 . Accordingly, it is possible to provide the injection material in a state in which the film layer 1200 is more accurately constrained to the upper mold.

The lower mold 120 has a groove 121 corresponding to the upper mold buttonhole hook 111 of the upper mold 110 is formed. As the outer shape of the upper mold 110 and the outer shape of the lower mold 120 are formed to correspond to each other, the insert film in contact with the upper mold and the injection material in contact with the lower mold have the same shape.

Meanwhile, as another embodiment, a hot runner may be formed in the lower mold and the ejection nozzle may be inserted through the lower mold to provide the injection material.

As shown in FIG. 10 , the insert film, which is the film layer 1200 of the injection-molded film, includes a transparent part 1260 and a light blocking part 1270 . In addition, a film layer gate region 1270 and a film layer buttonhole region 1272 are formed in the light blocking portion 1270 .

The film layer gate region 1270 of the insert film layer 1200 is implemented as a gate for providing the injection material to the insert film layer 1200 .

In addition, the insert film layer 1200 for injection molding is different from the insert film layer 1200 of the window cover 1000 shown in FIG. 10 , the film layer buttonhole region 1272 and the film layer gate region 1271 are positioned to face upwards.

This is to mount the insert film through the film layer buttonhole region 1272 when the injection material is supplied through the film layer gate region 1271 .

11 is a flowchart illustrating a method of manufacturing a window cover for a display device according to an embodiment of the present invention, and FIGS. 12 and 13 are schematic diagrams showing a specific example implementing the insert film upper mold mounting step, 14 is a configuration diagram schematically showing a specific example of implementing the injection material discharging step, FIG. 15 is a schematic usage state diagram of the injection material discharging step shown in FIG. 14, and FIG. 16 is a lower mold pressing step It is a configuration diagram schematically showing a specific embodiment, and FIG. 17 is a flowchart illustrating a method of manufacturing a window cover for a display device according to a second embodiment of the present invention, and FIG. 18 is a display according to a third embodiment of the present invention It is a flowchart showing a method of manufacturing a window cover for a device, Figure 19 is a view showing a compression gap (G) in the method of manufacturing a window cover for a display device according to an embodiment of the present invention, Figure 20 is an embodiment of the present invention It is a view showing a compression speed in a method of manufacturing a window cover for a display device according to the present invention, and FIG. 21 is a view showing a stroke section in a method of manufacturing a window cover for a display device according to an embodiment of the present invention.

Next, a method of manufacturing the window cover 1000 for a display device of the present invention will be described.

11, in order to manufacture the window cover according to the first embodiment of the present invention, the insert film is preformed (S1110). The insert film may form an optical coating layer to satisfy the optical properties required to form the film layer. Through the insert film preforming step, a gate region for injecting an injection material and a buttonhole region for mounting the insert film may be formed on the insert film. The gate region may be formed within the region of the final window cover, or located outside the final window cover region, and may be removed after injection and curing of the injection molding material.

Next, the insert film is mounted on the upper mold (S1120). Make sure that the gate area and the buttonhole area of the insert film are positioned at the corresponding positions of the upper mold. The gate region of the insert film is positioned to face the hot runner of the upper mold.

Specifically, as shown in FIG. 12, the film layer buttonhole region 1272 is mounted on the upper mold gate step 113 so that the insert film layer 1200 is supported on the upper mold 110, and the upper mold button The film layer buttonhole region 1272 of the insert film layer 1200 is mounted on the hole hook portion 111 .

In addition, when the film layer buttonhole region 1272 is mounted on the upper mold gate step 113 , the film layer gate region 1271 is positioned to face the hot runner 112 .

The film layer buttonhole region 1272 and the film layer buttonhole region 1272 of the insert film layer 1200 are formed with the upper mold gate step 113 and the upper mold buttonhole hook portion 111 of the upper mold 110, respectively. As the insert film layer 1200 is mounted on the upper mold 110 in a manner of inserting the film into the film, it is possible to fix the film for injection molding without a separate film hanger.

Accordingly, it is possible to apply the injection material to the other surface of the insert film layer 1200 in which one surface is in contact with the upper mold 110 .

The lower mold is positioned so that the lower mold is spaced apart from the upper mold by a predetermined distance (S1130). The lower mold is moved toward the upper mold to form a cavity of a predetermined volume in the mold.

The injection material is injected into the mold (S1140). The injection material is sprayed to the back of the film by a hot runner. The injection material may be a PC or PMMA material. The injection material is cured to form the base layer 1100 . The temperature of the injection material may be 270 ~ 320 ℃, preferably 280 ℃.

Specifically, the injection material is provided on the other surface of the insert film through a hot runner in a state in which one surface of the insert film is placed in contact with the upper mold. Accordingly, the injection material is coupled to the insert film.

14 , the injection material is discharged through the film layer gate region 1121 of the insert film layer 1100 through the hot runner 112 . At this time, the flow in the ejection direction of the injection material is limited by the lower mold 120 and flows in the lower direction.

More specifically, as shown in FIG. 15 , the flow of the injection material includes a first flow flow F1 , a second flow flow F2 , and a third flow flow F3 .

The first flow F1 defines the flow of the injection material discharged through the film layer gate region 1121, which is the gate of the injection material, the second flow F2 defines the flow of the injection material in the horizontal direction, 3 The flow F3 defines the vertical flow of the injection material according to the flow pressure of the injection material.

In addition, the vertical flow of the injection material may correspond to the direction of gravity.

As described above, as the injection material flows in the first flow flow F1, the second flow flow F2, and the third flow flow F3, the reverse flow of the injection material and the formation of the melt line are reduced. .

Press the compression core (S1150). When a predetermined amount of injection material is filled in the mold, the compression core is pressed to compress the cavity surface. As the compression core is pressed, the volume of the cavity is reduced, and the base layer is bonded to the molding and film layer while the injection material is compressed and flows in the cavity. In addition, the thickness of the injection material bonded to the insert film is adjusted by the compression core pressing step. The compression holding time may be 8 to 10 seconds, preferably 9 seconds. In addition, the clamping force for pressing the compression core may be 250 to 600 tons.

Meanwhile, the method of manufacturing the window cover may further include the step of forming the gate region of the base layer. In the base layer gate region forming step, after the injection material is supplied to the insert film, a base layer gate region forming bar is inserted from the upper mold through the film layer gate region of the insert film to form the base layer gate region to form the base layer gate region. can be

In other embodiments, the lower mold rather than the compression core may be moved. As shown in FIG. 16 , the lower mold 120 is moved while the injection material is discharged between the upper mold 110 and the lower mold 120 .

That is, the discharging material is discharged between the upper mold 110 and the lower mold 120 so as to be less than the specified amount, and the lower mold 120 is moved to the upper mold 110 . Accordingly, a sudden change in the flow of the injection material is prevented due to the initial discharge pressure, the injection material flows stably, and the thickness of the injection material can be adjusted by adjusting the interval between the upper mold 110 and the lower mold 120 .

In the second embodiment according to the present invention, the step of checking the upper and lower mold temperatures may be further included. The same content as in the previous embodiment will be briefly described.

17, in order to manufacture the window cover according to the present invention, the insert film is preformed (S1210). The insert film may form an optical coating layer to satisfy optical properties required to form a film layer, or may form a gate region and a buttonhole region for mounting an insert film to inject an injection material.

The insert film is mounted on the upper mold (S1220). Make sure that the gate area and the buttonhole area of the insert film are positioned at the corresponding positions of the upper mold. The gate region of the insert film is positioned to face the hot runner of the upper mold.

Next, the lower mold is positioned so that the lower mold is spaced apart from the upper mold by a predetermined distance (S1230). The lower mold is moved toward the upper mold to form a cavity of a predetermined volume in the mold.

Check the temperature of the upper mold and the lower mold (S1240). The temperature of the upper and lower molds affects the flow and residual stress of the injection material. Therefore, the upper and lower molds must be maintained at a temperature within a predetermined range. The temperature of the upper and lower molds is maintained by a fluid at a predetermined temperature. The temperature of the mold can be checked by checking the flow rate of the fluid, and a temperature sensor can be provided in the mold to check the temperature.

The temperature of the upper mold and the lower mold may be 70 ~ 95 ℃, preferably 80 ℃. When the upper and lower mold temperatures are lower than 70° C., there is a problem in that the flow resistance of the injection material increases and the residual stress increases. As the temperature of the upper and lower molds increases, the shear stress of the resin and the residual stress of the product are reduced during injection compression, and the birefringence property can be improved. there is. In particular, if the temperature of the upper and lower molds is 105° C. or higher, the mold may be damaged, and the mold may be damaged or scaling may occur. In general, water is used as a constant temperature medium for controlling the temperature of the mold, but due to the boiling point of water, mold damage and scaling problems occur near 100°C. However, it was confirmed through the experiment that there was no difficulty in operating the injection molding machine up to 105°C without major damage because the constant temperature medium was not placed under 1 atm pressure and circulated inside the mold. The above results are valid when water is used as a medium, and when a medium with a high boiling point is used as a constant temperature medium, the numerical value may be changed.

The temperature of the gate for injecting the injection material may be 20 to 40 ℃, preferably 30 ℃. The temperature of the compression core may be 80 to 105 °C, preferably 90 °C.

In this embodiment, the temperatures of the upper mold and the lower mold are checked, but in another embodiment, the temperatures of the compression core and the gate in addition to the upper mold and the lower mold can be further checked. The temperature of the compression core is set higher than the temperature of the upper and lower molds, and the temperature difference between the upper and lower molds and the compression core may be at least 10°C or more.

When the temperature difference between the upper and lower mold temperatures and the compression core is 10° C. or less, there is a problem that compression burrs and burrs (silver) are generated in the parting line. Specifically, the coefficient of thermal expansion should be different between the molds. When the temperature of the compression core is lowered, the expansion of the mold becomes smaller compared to the upper/lower side, and the pressure of the parting line during injection is reduced. may occur. If production continues in a state where the temperature of the compression core is low, burrs are continuously generated in the product produced by the burrs generated in the compression parting line, and the mold parting line collapses, which may increase the defect rate of the product.

Injection material is injected into the mold (S1250). The injection material is sprayed to the back of the film by a hot runner. The injection material may be a PC or PMMA material. The injection material is cured to form the base layer 1100 . The temperature of the injection material may be 270 ~ 320 ℃, preferably 280 ℃.

Press the compression core (S1260). When a predetermined amount of injection material is filled in the mold, the compression core is pressed to compress the cavity surface. As the compression core is pressed, the volume of the cavity is reduced, and the base layer is bonded to the molding and film layer while the injection material is compressed and flows in the cavity. The compression holding time may be 8 to 10 seconds, preferably 9 seconds. In addition, the clamping force for pressing the compression core may be 250 to 600 tons.

In the third embodiment according to the present invention, the compression speed can be controlled in multiple stages in the compression step. The same content as in the previous embodiment will be briefly described.

18, in order to manufacture the window cover according to the present invention, the insert film is preformed (S1310). The insert film may form an optical coating layer to satisfy the optical properties required to form the film layer, or may form a gate region and a buttonhole region on which the insert film can be mounted to inject an injection material.

The insert film is mounted on the upper mold (S1320). Make sure that the gate area and the buttonhole area of the insert film are positioned at the corresponding positions of the upper mold. The gate region of the insert film is positioned to face the hot runner of the upper mold.

The lower mold is positioned so that the lower mold is spaced apart from the upper mold by a predetermined distance (S1330). The lower mold is moved toward the upper mold to form a cavity of a predetermined volume in the mold.

The injection material is injected into the mold (S1340). The injection material 1100a is injected to the rear side of the film by a hot runner. The injection material 1100a may be a PC or PMMA material. The injection material 1100a is cured to form the base layer 1100 . The temperature of the injection material 1100a may be 270 to 320 °C, preferably 280 °C.

The compression core is pressed by controlling the compression speed in two stages (S1350). When a predetermined amount of the injection material 1100a is filled in the mold, the compression core 130 is pressed to compress the inside of the cavity. As the compression core 130 is pressed, the volume of the cavity is reduced, and as the injection material 1100a compresses and flows within the cavity, the base layer 1100 is coupled to the molding and film layer 1200 .

19 and 20, the compression speed is controlled in two stages based on the compression gap (G). Compression speed is the speed at which the compression core moves. The compression gap (G) means a compression distance, and the compression speed is divided into a first section (G1) and a second section (G2) based on a 1/2 point of the compression gap and is controlled in two stages.

The first section G1 is a first half section in which the compression core 130 moves toward the upper mold 110 , and refers to a point from an initial position of the compression core 130 to a point 1/2 of the compression gap. Section 2 (G2) is a second half section in which the compression core 130 moves toward the upper mold 110, and refers to a point from a point 1/2 of the compression gap to a point where the compression core 130 is finally moved. For example, if the compression gap is 1 mm and the initial position of the compression core is 0, the first section (G1) is a section from 0 to -0.5 mm, and the second section (G2) is from -0.5 mm to -1 mm. means section.

The compression speed in the first section G1 is constant, and the compression speed in the second section G2 may increase linearly. That is, the compression speed in the second section may have an equivalent acceleration. In section 2, compression marks are generated in the injection material and the shear stress of the injection material increases. Therefore, the compression speed is increased to perform compression before the flow of the injection material decreases.

In an embodiment of the present invention, the compression speed is 1.8 to 2.2 mm/s in the first section (G1), the acceleration 1.8 to 2.2 mm/s2 in the second section (G2), preferably 2 mm/s in the first section (G1), In the second section (G2), the acceleration can be set to 2 mm/s ² . That is, the speed in section 2 has an acceleration of 1.8 to 2.2 mm/s ² with the speed in section 1 as the initial speed. If the compression rate of the first section is lower than 1.8 mm/s, the resin stagnates and the solidified layer increases.

As the compression gap increases, the compression rate may also increase. On the other hand, the compression holding time may be 8 to 10 seconds, preferably 9 seconds. In addition, the clamping force for pressing the compression core may be 250 to 600 tons.

In the fourth embodiment according to the present invention, the injection speed may be controlled for each stroke section. The same content as in the previous embodiment will be briefly described.

In order to manufacture the window cover according to the present invention, the insert film is preformed (S1110). The insert film may form an optical coating layer to satisfy optical properties required to form a film layer, or may form a gate region and a buttonhole region for mounting an insert film to inject an injection material.

The insert film is mounted on the upper mold (S1320). Make sure that the gate area and the buttonhole area of the insert film are positioned at the corresponding positions of the upper mold. The gate region of the insert film is positioned to face the hot runner of the upper mold.

The lower mold is positioned so that the lower mold is spaced apart from the upper mold by a predetermined distance (S1130). The lower mold is moved toward the upper mold to form a cavity of a predetermined volume in the mold. The temperature of the upper mold and the lower mold may be 70 ~ 95 ℃, the temperature of the gate is 20 ~ 40 ℃, the temperature of the compression core may be 80 ~ 105 ℃.

The injection material is injected into the mold (S1140). The injection material is sprayed to the back of the film by a hot runner. The injection material may be a PC or PMMA material. The injection material is cured to form the base layer 1100 . The temperature of the injection material may be 270 ~ 320 ℃, preferably 280 ℃.

The injection speed is the speed at which the injection material is injected, and means the amount of the injection material being filled in the mold per unit time. As the injection speed increases, the flow distance of the injection material increases. By dividing the stroke section, the injection speed can be adjusted for each section. As shown in FIG. 21 , the stroke section is defined according to the position of the tip of the screw in the longitudinal direction of the cylinder with the position of the tip of the nozzle being 0 mm. The stroke section can be adjusted according to the shape of the mold.

In the process of injecting the injection material, the flow resistance of the mold may occur. The flow resistance of the mold causes surface defects such as jetting, flow marks, and weld lines. The flow resistance may vary depending on the shape of the mold, and the point at which the injection speed is controlled may vary depending on the shape of the mold. The stroke section may be divided based on, for example, points where the screw tip is located at 33 to 37 mm, 23 to 27 mm, 10 to 14 mm, and 5 to 9 mm. In this embodiment, the stroke section is divided into 4 sections based on the positions of the screw tip positions of 35mm, 25mm, 12mm, and 7mm, and the 35~25mm point among the sections in which the screw moves toward the nozzle tip is 1 section (S ₄ - S ₃ ), 25-12mm in 2 sections (S ₃ -S ₂ ), 12-7mm in 3 sections (S ₂ -S ₁ ), 7-0mm in 4 sections (S ₁ -S ₀₎ ) is defined as The injection speed is controlled in section 1, section 2, section 3, and section 4, respectively.

The injection speed is 40-50 mm/s in section 1, 75-85 mm/s in section 2, 75-85 mm/s in section 3, 65-75 mm/s in section 4, preferably 45 mm/s in section 1, 2 80 mm/s in section 3, 80 mm/s in section 3, and 70 mm/s in section 4. The speed of sections 2 and 3 has a large effect on birefringence, and when the speed of sections 2 and 3 increases compared to section 1, the birefringence can be improved. That is, the injection speed in section 2 and section 3 is set to be greater than the injection speed in section 1.

Press the compression core (S1350). When a predetermined amount of injection material is filled in the mold, the compression core is pressed to compress the cavity surface. As the compression core is pressed, the volume of the cavity is reduced, and the base layer is bonded to the molding and film layer while the injection material is compressed and flows in the cavity. On the other hand, the compression holding time may be 8 to 10 seconds, preferably 9 seconds. In addition, the clamping force for pressing the compression core may be 250 to 600 tons.

The compression speed is controlled in two stages based on the compression gap. As the compression gap increases, the compression rate may increase. The compression gap may be 40-50% of the thickness of the window cover for the display device, which is the final molded product.

In the fifth embodiment according to the present invention, the compression gap may be set to 0.8 to 1.2 mm. The same content as in the previous embodiment will be briefly described.

In order to manufacture the window cover according to the present invention, the insert film is preformed (S1310). The insert film may form an optical coating layer to satisfy the optical properties required to form the film layer, or may form a gate region and a buttonhole region on which the insert film can be mounted to inject an injection material.

The insert film is mounted on the upper mold (S1320). Make sure that the gate area and the buttonhole area of the insert film are positioned at the corresponding positions of the upper mold. The gate region of the insert film is positioned to face the hot runner of the upper mold.

The lower mold is positioned so that the lower mold is spaced apart from the upper mold by a predetermined distance (S1330). The lower mold is moved toward the upper mold to form a cavity of a predetermined volume in the mold. The temperature of the upper mold and the lower mold may be 70 ~ 95 ℃, the temperature of the gate is 20 ~ 40 ℃, the temperature of the compression core may be 80 ~ 105 ℃.

The injection material is injected into the mold (S1340). The injection material is sprayed to the back of the film by a hot runner. The injection material may be a PC or PMMA material. The injection material is cured to form the base layer 1100 . The temperature of the injection material may be 270 ~ 320 ℃, preferably 280 ℃.

The injection speed can be adjusted for each section by dividing the stroke section. The stroke section can be divided into 4 sections based on the positions where the screw tip position (S) is 35mm, 25mm, 12mm, and 7mm.

Press the compression core (S1350). When a predetermined amount of injection material is filled in the mold, the compression core is pressed to compress the cavity surface. As the compression core is pressed, the volume of the cavity is reduced, and the base layer is bonded to the molding and film layer while the injection material is compressed and flows in the cavity.

The compression gap refers to the compression distance at which the injection material is compressed, and the timing of the injection material stagnation time is affected according to the compression gap. The smaller the compression gap, the faster the overall stress transfer, resulting in an increase in the retardation value of the entire area. As the compression gap increases, stress relaxation after filling and an increase in stress due to the solidified layer occur together, and retardation is concentrated in the compression position. In this embodiment, the compression gap is 0.8 to 1.2 mm, preferably 1 mm. When the compression gap is less than 0.8 mm, the stress transfer is accelerated, the birefringence property deteriorates, and a compression burr may occur in the parting line. When the compression gap is 1.2mm or more, the injection material may stagnate and compression marks may occur. The compression gap is preferably set to 40-50% of the thickness of the window cover.

As the compression gap increases, the compression rate may increase. The compression holding time may be 8 to 10 seconds, preferably 9 seconds. In addition, the clamping force for pressing the compression core may be 250 to 600 tons.

On the other hand, factors affecting the optical properties of the injection-compression-molded window cover during the manufacturing process of the window cover include mold temperature, compression speed, injection speed, compression gap, impact strength of the resin, melt index (MI) of the resin, etc. there is.

In the present invention, the mold temperature condition defines the temperatures of the upper mold, the lower mold, the compression core, and the gate. The mold temperature affects the flow state and residual stress of the injection material.

In one embodiment of the present invention, PC was used as the injection material, and in the case of PC, the mold temperature is in the range of 70 to 95 ℃, 80 to 105 ℃, 20 to 40 ℃, respectively, the temperature of the upper and lower mold, compression core, and gate, preferably can be injection-compression-molded under the conditions of 80 ℃, 90 ℃, 30 ℃. If the temperatures of the upper and lower molds, compression core, and gate are lower than 70°C, 80°C, and 20°C, respectively, there is a problem in that the flow resistance of the injection material increases and the residual stress increases. As the temperature of the upper and lower molds, compression cores, and gates increases, the shear stress of the resin and the residual stress of the product during injection compression are reduced, so that the birefringence property can be improved. . In particular, when the temperature of the upper and lower molds or the compression core is 105° C. or higher, the mold itself may be too strained, and the upper and lower molds or the compression core may be damaged or scaling may occur. In general, water is used as a constant temperature medium for controlling the temperature of the mold, but due to the boiling point of water, mold damage and scaling problems occur near 100°C. However, it was confirmed through the experiment that there was no difficulty in operating the injection molding machine up to 105°C without major damage because the constant temperature medium was not placed under 1 atm pressure and circulated inside the mold. The above results are valid when water is used as a medium, and when a medium with a high boiling point is used as a constant temperature medium, the numerical value may be changed.

Meanwhile, the injection material injected into the upper and lower molds is compressed by the compression core, and the injection material disposed on the compression surface of the compression core receives a greater pressure than the injection material disposed inside the upper mold. Therefore, in order to reduce the residual stress on the compression core side, it is preferable that the temperature of the compression core is higher than the temperature of the upper mold. The temperature difference between the upper and lower molds and the compression core can be at least 10℃ or more.

When the temperature difference between the upper and lower mold temperatures and the compression core is 10° C. or less, there is a problem that compression burrs and burrs (silver) are generated in the parting line. Specifically, the coefficient of thermal expansion should be different between the molds. When the temperature of the compression core is lowered, the expansion of the mold becomes smaller compared to the upper/lower side, and the pressure of the parting line during injection is reduced. may occur. If production continues at a low temperature of the compression core, burrs are continuously generated in the product produced by the burrs generated in the compression parting line, and the mold parting line collapses, increasing the defective rate of the product.

The compression speed defines the speed at which the compression core moves, and is divided into 1 section and 2 sections based on 1/2 section of the compression gap and controlled in two stages.

Section 1 is the first half section in which the compression core moves toward the upper mold, and refers to a point from the initial position of the compression core to a point 1/2 of the compression gap. Section 2 is the second half section in which the compression core moves toward the upper mold side, and refers to the point from 1/2 of the compression gap to the point where the compression core finally moves. For example, when the compression gap is 1 mm, if the initial position of the compression core is 0, section 1 means a section from 0 to -0.5 mm, and section 2 means a section from -0.5 mm to -1 mm.

The compression speed in the first section is constant, and the compression speed in the second section may have an equivalent acceleration that increases linearly. As for the compression speed in the second section, a predetermined acceleration may be added to the speed in the first section. In section 2, compression marks are generated in the injection material and the shear stress of the injection material increases. Therefore, the compression speed is increased to perform compression before the flow of the injection material decreases.

In an embodiment of the present invention, the compression speed is 1.8 to 2.2 mm/s in the first section, 1.8 to 2.2 mm/s ² in the second section, preferably 2 mm/s in the first section, and 2 mm/s ² in the second section. can That is, the speed in section 2 has an acceleration of 1.8 to 2.2 mm/s2 using the speed in section 1 as the initial speed. If the compression rate of the first section is lower than 1.8 mm/s, the resin stagnates and the solidified layer increases.

The injection speed is the speed at which the injection material is injected, and means the amount of the injection material being filled in the mold per unit time. As the injection speed increases, the flow distance of the injection material increases.

The injection speed can be controlled depending on where the screw is positioned. That is, the injection speed can be adjusted for each section by dividing the stroke section. In the process of injecting the injection material, the flow resistance of the mold may occur. The flow resistance of the mold causes surface defects such as jetting, flow marks, and weld lines. The flow resistance may vary depending on the shape of the mold, and the point at which the injection speed is controlled may vary depending on the shape of the mold. The stroke section is defined according to the position of the screw tip in the longitudinal direction of the cylinder with the nozzle tip position being 0 mm. The stroke section can be divided into a plurality of sections depending on the shape of the mold. can

In one embodiment of the present invention, the stroke section is divided into 4 sections based on the positions where the tip positions (S) of the screw are 35mm, 25mm, 12mm, and 7mm, and 35~25mm of the section in which the screw moves toward the nozzle tip. 1 section (S ₄ -S ₃ ), 2 sections (S ₃ -S ₂ ) for the 25~12mm point, 3 section (S ₂ -S ₁ ) for the 12~7mm point, 4 the 7~0mm point It is defined as a section (S ₁ -S ₀ ). The injection speed is controlled in section 1, section 2, section 3, and section 4, respectively.

The injection speed is 40-50 mm/s in section 1, 75-85 mm/s in section 2, 75-85 mm/s in section 3, 65-75 mm/s in section 4, preferably 45 mm/s in section 1, 2 80 mm/s in section 3, 80 mm/s in section 3, and 70 mm/s in section 4. The speed of sections 2 and 3 has a large effect on birefringence, and when the speed of sections 2 and 3 increases compared to section 1, the birefringence can be improved.

The compression gap refers to the compression distance, and depending on the compression gap, the injection material stagnation time is affected. The smaller the compression gap, the faster the overall stress transfer, resulting in an increase in the retardation value of the entire area. As the compression gap increases, stress relaxation after filling and an increase in stress due to the solidified layer occur together, and retardation is concentrated in the compression position. In this embodiment, the compression gap is 0.8 to 1.2 mm, preferably 1 mm. When the compression gap is less than 0.8 mm, the stress transfer is accelerated, the birefringence property deteriorates, and a compression burr may occur in the parting line. When the compression gap is 1.2mm or more, the injection material may stagnate and compression marks may occur. The compression gap is preferably set to 40-50% of the thickness of the window cover.

The compression force acts as a compressive force after injection of the injection material so that the injection material flows and fills the unfilled area. In addition, by compressing the injection material in consideration of the amount of shrinkage of the injection material, it is possible to remove the stress caused by the contraction after molding.

Retardation refers to a phase difference between polarization elements passing through a window cover. In the present invention, a plane-side retardation value and a retardation value at an incident angle of 45° are measured. The retardation deviation value means a difference in the retardation value according to the incident angle.

On the other hand, in order to manufacture a window cover with few defects and reduced retardation, conditions of the injection material may be prescribed.

As an injection material for manufacturing the window cover, a PC or PMMA material, which is a transparent material, is used. It is preferable to use a resin having a heat deflection temperature (HDT) that satisfies heat resistance of 120° C. or higher in order to prevent post-deformation in order to be used as an automobile interior material. In addition, since the window cover protects the display panel and transmits an image implemented on the display panel, it is required to be strong in impact, have fewer defects, and have excellent birefringence performance.

In order to supply the injection material into the mold, as shown in FIG. 22 , the resin particles are supplied into the cylinder 1510 through the hopper 1530 . The resin may be a resin in a pellet state. Depending on the shape and size of the product to be manufactured, the amount of the resin may be adjusted. The average particle diameter of the injected resin particles may be 2-3 mm. The resin in the form of pellets flows into the cylinder 1510 by a fixed amount through the hopper 1530, melts in the cylinder 1510, and is sprayed by a nozzle.

A screw 1520 is positioned coaxially with the cylinder 1510 inside the cylinder 1510 , and a heating device (not shown) capable of heating the inside of the cylinder 1510 is provided. The resin particles in the cylinder are melted by the heating device, and the melted injection material advances toward the tip of the nozzle by the rotation of the screw 1520 . Since the temperature of the cylinder 1510 greatly affects the fluidity of the injection material, it is controlled to maintain a constant temperature during molding. The injection cylinder 1540 and the hydraulic motor 1550 advance the screw 1520 and generate injection pressure, injection speed, and back pressure.

When the resin, which is a raw material of the injection material, is put into the injection machine, dust may be generated due to friction, impact, etc. during the processing or transport of the resin. In particular, when the impact strength of the resin is low, there is a problem that the amount of generated dust increases. The dust may have the form of fine resin powder, fine chips in the form of chips, or the like. Dust may be introduced into the mold together with the injection material and carbonized during processing, and may cause problems such as surface defects and microcracks of the manufactured window cover.

In order to manufacture a good window cover, it is preferable that the amount of dust generated is 120 ppm or less per 25 kg of injection material, preferably 100 ppm or less per 25 kg. In order to satisfy 100ppm or less of 100ppm per 25kg of dust generated in the process of processing or transporting the resin, it is required that the impact strength of the resin be 50-60kJ/m ² , preferably 55kJ/m ² . When the impact strength is 50 kJ/m ² or less, the amount of dust generated increases and the quality of the final product is deteriorated, such as defects on the surface. In the case of PC, it is difficult to have an impact strength exceeding 60 kJ/m ² , and when a filler such as glass fiber is added to the PC to increase the impact strength, the transparency of the manufactured product is reduced and there is a problem that it cannot be used for optics. In this example, PC was used as the resin, and the impact strength of the resin was measured by making a notch in a 3 mm thick specimen at 23° C. according to the ISO 179 standard.

Meanwhile, it is important to adjust a melt index (MI) value in order to reduce defects and improve birefringence performance. The melt index is the flow rate when the thermoplastic polymer melt is extruded from the piston at the load and temperature specified for each specific resin, and is an index indicating the ease of flow of the melt and is related to the molecular weight. The higher the molecular weight, the lower the melt index.

The melt index (MI) is measured by measuring the amount released when the resin is pushed out at a constant speed in a sufficiently melted state above the melting point (Tm). It is calculated as the weight or volume of the sample flowed out over 10 minutes, and the unit is g/10min or cm ³ /10min. In this example, PC was used as the resin, and the melt index was measured with an MI measuring device.

If the melt index is low, the fluidity is poor, and the birefringence performance of the manufactured window cover is deteriorated. If the melt index is high, the birefringence performance is good, but if the fluidity is excessively high, the weight of the final product changes and the injection reproducibility is not good.

In the sixth embodiment of the present invention, the MI value of the resin is 30-50 cm ³ /10 min at 300° C., preferably 35 cm ³ /10 min. When the melt index is less than 30 cm ³ /10min, the retardation value has a value of 100 nm or more based on the front surface and 300 nm or more based on 45°, so the birefringence performance is not good. When the MI value exceeds 50 cm ³ /10min, injection reproducibility is poor, fluidity is high, so a check ring change is required, and the injection condition change is limited. In addition, in general, when the MI value is high, since the impact strength is low, the possibility of dust generation is high. A high MI value means that the resin has a low molecular weight. A low molecular weight resin improves workability, but reduces rigidity and stress resistance, which may cause crazing, resulting in fine cracks during reliability testing.

Examples and comparative examples for each compression factor value with respect to the retardation value will be described.

In the manufacturing process of the window cover, factors affecting the optical properties of the injection compression window cover are mold temperature, compression speed, injection speed, compression gap, impact strength of the resin, melt index (MI) of the resin, and the like. In order to derive the optimal conditions for each factor with respect to these compression factors, the following experiments were performed for each factor. Conditions excluding factors for comparison may be different depending on the order of the experiment. In each experiment, the comparison target factor conditions of Examples and Comparative Examples were applied differently to derive the optimum value of the corresponding compression factor. PC (L1225 ZL 100M by Teijin Corporation) was used as an injection material, and a 2-layer sheet of PC/PMMA was used for the film.

<Mold Temperature>

Among the compression factors, we look at the optimum value for the mold temperature.

The window cover was molded at an injection temperature of 300°C, compression time of V/P switching point, compression holding time of 3 seconds, and clamping force of 250 tons. The mold temperature indicates the temperature of the upper and lower molds, element core, and gate.

The mold temperature conditions of Examples and Comparative Examples are as follows.

mold temperature Example 1 95/105/30 Example 2 80/90/30 Comparative Example 1 70/80/30 Comparative Example 2 110/120/30

Visual evaluation and measurement of the retardation value were performed on the retardation value of the window cover molded under each condition. Visual evaluation and measurement of retardation values were performed using a birefringence checking device and a birefringence measuring instrument WPA-200, respectively. In the case of visual evaluation, the evaluation was made based on the maximum value visually based on the Levy chart. In the case of visual measurement, the light source was measured after a 200-500 lux surface light source was spaced 0.3 to 1 m apart, and in this example, a 300 lux surface light source was 0.3 m apart. and measured. The retardation value was evaluated based on the average value for a specific area.

mold temperature Visual evaluation Planar-side retardation value (nm) 45˚ side retardation value (nm) Retardation deviation value (nm, flat side/45˚ side) Example 1

45 200 12/59 Example 2

50 270 13/62 Comparative Example 1

97 411 19/99 Comparative Example 2

68 285 17/67

As the mold temperature increased, it was confirmed that the shear stress of the resin and the residual stress of the window cover decreased during compression injection, thereby improving the birefringence performance and decreasing the retardation value. Example 1 showed the best birefringence performance with a plane-side retardation value of 45 nm and a 45°-side retardation value of 200 nm. The plane-side retardation value of Example 2 was measured to be 50 nm, and the 45°-side retardation value was measured to be 270 nm. The retardation value on the plane side of Comparative Example 2 was 68 nm, the retardation value on the 45° side was 285 nm, and the retardation value of Comparative Example 1 (the plane side retardation value was The retardation values on the 97nm and 45˚ side showed excellent birefringence performance compared to 411nm), but the variation in the compression gap increased due to the change in resin flow, resulting in poor reproducibility. The compression core is operated by hydraulic pressure. If the mold temperature is higher than 105℃, when the mold expands as the mold temperature rises, it also affects the hydraulic pressure in the mold. and the reproducibility of the product is not good due to this difference. As a result, dimensional differences due to mass differences occurred in the final product. In addition, in the case of Comparative Example 2, as the temperature of the upper mold and the lower mold and the temperature of the compression core exceed 105° C., the mold may be damaged, which is not preferable.

Therefore, considering that reproducibility is reduced when the temperature of the mold is increased, the mold temperature condition of Example 2, 80/90/30°C, is preferable.

<Compression speed>

Among the compression factors, the optimum value for the compression speed is examined.

The window cover was molded with an injection temperature of 300°C, compression time of V/P switching point, compression holding time of 9 seconds, and clamping force of 250 tons.

The compression speed was controlled in two steps in a stepwise fashion, and the compression speed increased linearly until the 1/2 section of the compression gap was a constant speed, and after the 1/2 section of the compression gap.

The compression rate conditions and results of Examples and Comparative Examples are as follows.

2 division speed (mm/s ² )
(Plane side retardation value (nm)/ 45˚ side retardation value (nm)/ of retardation value
Deviation) One 2 3 4 1 division speed
(mm/s) One

98/425/99

98/425/99

68/338/69

75/368/73

78/372/70 2

67/342/70

55/327/75

72/367/73

79/382/88 4

69/345/71

70/346/70

72/365/86

73/363/84 8

70/350/68

72/357/67

77/369/77

81/385/86

In the case of the comparative example in which the speed of section 1 is 1 mm/s, the compression marks are severe, which is because the resin stagnated due to the low initial speed. When the speed of the second section is large, it can be confirmed that the compression rate is high and the shear stress is increased, thereby deteriorating the birefringence property.

When the compression speed of section 1 and section 2 is 2-2 mm/s, it can be seen that the plane-side retardation value is 55 nm, and the 45°-side retardation value is 327 nm, which has an optimal value. That is, the optimum value of the compression speed condition is 2 mm/s in section 1 and acceleration 2 mm/s ² in section 2.

<Injection speed>

Among the compression factors, we look at the optimum value for the injection speed.

The window cover was molded at an injection temperature of 290°C, compression time of V/P switching point, compression holding time of 9 seconds, and clamping force of 250 tons.

The injection speed had a different speed profile for each section, and the speed was controlled by dividing it into 4 sections. The injection speed is controlled based on the stroke positions of 35mm, 25mm, 12mm and 7mm.

In order to check the effect of the injection speed in sections 2 and 3, a window cover was manufactured under the same conditions as the injection speed in other sections except for the corresponding section. Sections 1 and 4 were excluded because they did not significantly affect the birefringence performance as they were the time point at which the injection material started to be discharged and the last section where it was discharged.

Injection speed conditions of Comparative Examples 1 to 6 are as follows.

Injection speed (mm/s) 1 section Section 2 Section 3 4 sections Comparative Example 1 20 20 60 80 Comparative Example 2 20 40 60 80 Comparative Example 3 20 60 60 80 Comparative Example 4 10 20 20 60 Comparative Example 5 10 20 40 60 Comparative Example 6 10 20 60 60

Visual evaluation and measurement of the retardation value were performed for the retardation value of the window cover molded under each condition.

Visual evaluation Comparison of speed change in 2 sections (20/40/60)

378Comparative Example 1

378 Comparative Example 2

382 Comparative Example 3

376 Speed change in 3 sections (20/40/60) Comparative Example 4

386 Comparative Example 5

364 Comparative Example 6

356

It was confirmed that the change width of the birefringence performance according to the speed change in the second section was small, 4 to 6 nm. In section 3, the width of the change in birefringence performance according to the speed is 8 to 20 nm, and it can be confirmed that the birefringence performance is better as the speed increases. It can be seen that the higher the speed of the central part, the greater the influence on the flow of the injection material and the greater the stress control during compression.

The birefringence performance according to the speed in sections 3 and 4 was compared.

injection speed 1 section
(mm/s) Section 2
(mm/s) Section 3
(mm/s) 4 sections
(mm/s) Planar retardation value (nm) / 45˚ retardation value (nm) / Deviation of retardation value Example 45 80 80 70

55/280/68

55/280/68 Comparative Example 1 40 60 60 60

64/354/73 Comparative Example 2 20 60 60 20

63/356/75 Comparative Example 3 20 40 40 40

85/423/98

When the injection speed is 45mm/s in section 1, 80mm/s in section 2, 80mm/s in section 3, and 70mm/s in section 4, the flat-side retardation value is 55nm and the 45˚ side retardation value is 280nm. It can be confirmed that it has an optimal value.

<compression gap>

Among the compression factors, the optimum value for the compression gap is examined.

The window cover was molded at an injection temperature of 300°C, compression time of V/P switching point, compression holding time of 3 seconds, and clamping force of 250 tons.

The compression gaps of Examples and Comparative Examples are as follows.

Compression gap (mm) Comparative Example 1 0.2 Comparative Example 2 0.5 Example One Comparative Example 3 1.5 Comparative Example 4 2

Visual evaluation and measurement of the retardation value were performed on the retardation value of the window cover molded under each condition.

compression gap Visual evaluation Planar-side retardation value (nm) 45˚ side retardation value (nm) Retardation deviation value (nm) Comparative Example 1

310 328 79 Comparative Example 2

290 301 77 Example

276 290 65 Comparative Example 3

357 398 89 Comparative Example 4

400 412 97

When the compression gap was 1 mm, the plane-side retardation value was 276 nm and the 45°-side retardation value was 290 nm, confirming the best birefringence performance.

In order to derive an appropriate range of impact strength and melt index values, look at the following experimental results for impact strength and melt index values.

MI (cm ³ /10 min)
impact strength
(kJ/m ² )
over 50
30-50
less than 30 50 to 60 Birefringence: OK
Injection reproducibility: NG
Appearance: OK Birefringence: OK
Injection reproducibility: OK
Appearance: OK Birefringence: NG
Injection reproducibility: OK
Appearance: OK less than 50 Birefringence: OK
Injection reproducibility: NG
Appearance: NG Birefringence: OK
Injection reproducibility: OK
Appearance: NG Birefringence: NG
Injection reproducibility: OK
Appearance: NG

In the case of PC, the impact strength is difficult to exceed 60 kJ/m ² , and in order for the impact strength of the resin to exceed 60 kJ/m ² , a filler such as glass fiber must be added to the PC. In this case, since the transparency of the manufactured product is reduced and cannot be used for optical purposes, the range where the impact strength exceeds 60 kJ/m ² is excluded.

In the range where the melt index of the resin exceeds 50 cm ³ /10min and the impact strength is 50 to 60 kJ/m ² , the resin has high fluidity and high impact strength, so it has good birefringence performance and good appearance, but with excessively high fluidity. As a result, injection reproducibility is not good. On the other hand, when the melt index of the resin is less than 30 cm ³ /10 min and the impact strength is 50 to 60 kJ/m ² , the resin has low fluidity and high impact strength, so injection reproducibility and appearance are good, but fluidity is reduced As a result, the residual stress increases and the birefringence performance is not good.

The melt index of the resin is 30-50 cm ³ /10min and the impact strength is 50-60 kJ/m ² In the range, the impact strength is high and fluidity is high, so the appearance of the product is good, injection reproducibility and birefringence performance are good.

Next, in the range where the impact strength of the resin is less than 50 kJ/m ² , a large amount of dust is generated and the appearance of the product is not good. In the range where the melt index of the resin exceeds 50 cm ³ /10 min and the impact strength is less than 50 kJ/m ² , the resin has good fluidity but low impact strength, good birefringence performance, but poor injection reproducibility and defects in appearance.

In the range where the melt index of the resin is 30-50 cm ³ /10min and the impact strength is less than 50 kJ/m ² , the fluidity is good but the impact strength is low.

In the range where the melt index of the resin is less than 30 cm ³ /10 min and the impact strength is less than 50 kJ/m ² , the resin has low fluidity and low impact strength, so injection reproducibility is good, but residual stress increases due to fluidity deterioration and birefringence performance This is not good, and the appearance of the product is also not good.

On the other hand, the above-mentioned ranges are values when the resin is PC, and when other materials such as PMMA are used, the ranges of desirable impact strength and melt index may vary.

Based on the above-described ranges, examples and comparative examples for the MI value and impact strength value of the resin will be described.

The present invention stipulates the MI value and impact strength value of the resin in order to reduce defects of the injection-compressed window cover and improve optical properties such as birefringence during the manufacturing process of the window cover. In order to derive the optimal conditions for each factor with respect to the MI value and impact strength value of the resin, the following experiments were performed for each factor. Conditions excluding factors for comparison may be different depending on the order of the experiment. In each experiment, the comparison target factor conditions of Examples and Comparative Examples were applied differently to derive the optimum value of the corresponding compression factor. PC (L1225 ZL 100M by Teijin Corporation) was used as an injection material, and a 2-layer sheet of PC/PMMA was used for the film.

Among the compression factors, the optimum values for the MI value and impact strength of the resin will be examined.

The temperature of the injection material is 300℃, the injection pressure is 800~1500bar, the temperature of the upper and lower molds is 80℃, the temperature of the compression core is 90℃, the compression point is the V/P switching point, the compression holding time is 9 seconds, the clamping force is 250ton was molded.

MI values and impact strength values of Examples and Comparative Examples are as follows.

MI (cm ³ /10 min) Impact strength (kJ/m ² ) Example 35 55 comparative example 24 35

Visual evaluation and measurement of the retardation value were performed on the retardation value of the window cover molded under each condition. Visual evaluation and measurement of retardation values were performed using a birefringence checking device and a birefringence measuring instrument WPA-200, respectively. In the case of visual evaluation, the visual maximum value was evaluated based on the Levy chart, and the retardation value was evaluated based on the average value for a specific area.

Planar-side retardation value (nm) 45˚ side retardation value (nm) Example

66

66

270 comparative example

142

477

When the melt index was 35 cm ³ /10 min (300 ° C) and the impact strength value was 55 kJ/m ² (Example), the appearance was good and the birefringence pattern was also good when viewed with the naked eye, and the plane-side retardation value was 66 nm, It was confirmed that the 45˚ side retardation value was 270 nm.

When the melt index was 24 cm ³ /10min (300° C.) and the impact strength value was 35 kJ/m ² (comparative example), a bright color pattern and a rainbow color pattern occurred when viewed with the naked eye, and a black color at the lower center part It was confirmed that the defects of In addition, as for the retardation value, the plane-side retardation value was 142 nm, and the 45°-side retardation value was measured as high as 477 nm. It can be seen that when the melt index is low, the fluidity of the resin is not good and the residual stress is large, and thus the birefringence performance is deteriorated. In addition, it can be seen that a lot of dust is generated due to the low impact strength, which deteriorates the appearance quality of the product.

As a result, the window cover according to the present invention has a mold temperature of 80/90/30℃, a compression gap of 1mm, a V/P switching point at the compression point, a compression speed of 2-2mm/s, and injection The retardation value is minimized when the speed is 45-80-80-70mm/s, the compression holding time is 3 seconds, the melt index of the injection material is 35cm ³ /10min (300℃), and the impact strength value is 55kJ/m ² .

The average retardation value of the window cover molded under the above conditions is 50 nm or less in a plane and 270 nm or less at a 45° angle.

A plurality of compression factors may influence each other, and birefringence may be alleviated by mutually controlling the plurality of factors. For example, when the compression gap becomes large, the compression rate can be increased to prevent the resin from stagnation.

The optimal conditions for injection compression molding may vary depending on the type of resin, and the Examples and Comparative Examples show the conditions when the material of the injection material is PC.

23 is a view showing a state in which a bending phenomenon occurs in the window cover during the manufacturing process of the window cover for a display device, and FIG. 24 is a view showing a plurality of measurement positions for measuring flatness

Meanwhile, the temperature difference between the upper mold and the lower mold among the compression factors affects the flatness of the manufactured window cover.

The window cover 1000 ′ is formed by mounting the insert film 200 on an upper mold, injecting an injection material into the mold, and then pressing the compression core. The injection material is integrally combined with the insert film 200 to form the base layer 100 . The temperature of the injection material injected into the mold is 270~320℃. The lower the temperature of the injection material, the smaller the heat transfer amount deviation, and the temperature of the injection material may be preferably 280°C. The injection material forms the base layer 100 while cooling after the pressing step. However, the injection material has a difference in cooling rate in the thickness direction. While the insert film 200 acts as a heat insulating material, the injection material is gradually cooled in the upper portion of the base layer 100 , and the injection material is cooled faster in the lower portion of the base layer 100 disposed on the lower mold side. That is, based on the middle point in the thickness direction of the base layer 100 , the upper temperature gradient is smaller than the lower temperature gradient. That is, the heat transfer rate of the upper part is smaller than the heat transfer rate of the lower part. Due to the difference in the cooling rate of the injection material, the window cover 1000 ′ is bent so that the insert film 200 is convex. This is because the insert film 200 is shrunk while the opposite side is cured first. Therefore, in order to prevent the window cover from being bent during the cooling process, it is necessary to make the heat transfer rates of the upper and lower portions of the base layer similar. In the present invention, the difference between the upper and lower heat transfer rates of the base layer is reduced by controlling the temperature of the upper mold.

In the seventh to ninth embodiments of the present invention, the flatness of the window cover is improved by adjusting the temperature difference between the upper mold and the lower mold, clamping force, and hydraulic core pressure conditions.

In order to manufacture the window cover 1000 according to the seventh embodiment of the present invention, an insert film is preformed (S1310). The insert film may form an optical coating layer to satisfy the optical properties required to form the film layer. The present invention can provide black masking and a functional surface by applying an In Mold Label (IML) method.

The insert film may include a gate region for injecting the injection material and a buttonhole region for mounting the insert film. The gate region may be formed within the region of the final window cover, or located outside the final window cover region, and may be removed after injection and curing of the injection molding material.

The insert film has a different heat transfer rate from the injection material, and lowers the cooling rate of the adjacent injection material. As the thickness of the insert film increases, the heat transfer deviation along the thickness direction of the injection material increases, and accordingly, the difference in cooling rate in the thickness direction of the injection material increases. The thickness of the insert film may be 0.15-0.3-mm, preferably 0.2mm. When the thickness of the insert film is greater than 0.3 mm, the difference in the cooling rate in the thickness direction of the injection material increases, so that the flatness of the manufactured window cover is deteriorated. If the thickness of the insert film is less than 0.15 mm, the physical strength of the insert film may be weakened. The heat transfer rate of the insert film may be 0.23 w/mk or more. When the heat transfer rate of the insert film is less than 0.23w/mk, the thermal insulation effect is better and the cooling rate is slowed down. Accordingly, the deviation of the cooling rate in the thickness direction of the injection material may increase and warpage may occur. The shrinkage rate of the insert film may be 1.4% or less based on JIS K7133, 160 °C, 30 min. As the shrinkage rate of the insert film is lower, the amount of shrinkage during cooling of the injection material decreases, thereby reducing the effect on flatness.

Next, the insert film is mounted on the upper mold (S1320). Make sure that the gate area and the buttonhole area of the insert film are positioned at the corresponding positions of the upper mold. The gate region of the insert film is positioned to face the hot runner of the upper mold.

The lower mold is positioned so that the lower mold is spaced apart from the upper mold by a predetermined distance (S1330). The lower mold is moved toward the upper mold to form a cavity of a predetermined volume in the mold. The clamping force acting on the upper mold and the lower mold may be 250 to 600 tons.

The temperature of the upper and lower molds affects the flow and residual stress of the injection material. Therefore, the upper and lower molds must be maintained at a temperature within a predetermined range. The temperature of the upper and lower molds is maintained by a fluid at a predetermined temperature. However, when the temperature of the injection material is too high or a film layer is formed, heat distribution is different in the thickness direction of the injection material, which causes a difference in the cooling rate of the injection material. The temperature of the upper mold and the lower mold is adjusted so that the deviation of the heat transfer rate in the thickness direction of the injection material is minimized. The temperature of the upper mold may be 70 ~ 95 ℃, preferably 90 ℃. The temperature of the lower mold is set lower than the temperature of the upper mold, and the temperature difference between the upper mold and the lower mold may be 10° C. or more. As the temperature difference between the upper mold and the lower mold increases, the flatness may be improved. When the temperature difference between the upper mold and the lower mold decreases during the manufacturing process, the clamping force can be increased to suppress warpage. When the clamping force is increased, the density of the injection material increases and the shrinkage rate can be reduced.

The injection material is injected into the mold (S1340). The injection material is sprayed to the back of the film by a hot runner. The injection material may be a PC or PMMA material. The injection material is cured to form the base layer 1100 . As the temperature of the injection material increases, the variation in the amount of heat transfer in the thickness direction of the injection material may increase. Therefore, in order to improve the flatness, the lower the temperature of the injection material is, the better. However, when the temperature of the injection material is lowered, the residual stress of the injection material increases, so that the birefringence performance of the manufactured window cover may be deteriorated. In this embodiment, the flatness can be improved while maintaining the birefringence performance by setting the temperature of the injection material to 270 to 320°C. The temperature of the injection material may be preferably 280 ℃. The heat transfer rate of the injection material may be 0.2 w/mk or more. When the heat transfer rate of the injection material is less than 0.2 w/mk, the cooling time increases and productivity decreases. As the difference between the heat transfer rate of the injection material and the heat transfer rate of the insert film is small, the flatness is improved.

Press the compression core (S1350). When a predetermined amount of injection material is filled in the mold, the compression core is pressed to compress the cavity surface. As the compression core is pressed, the volume of the cavity is reduced, and the base layer is molded while the injection material is compressed and flows in the cavity. The base layer bonds with the insert film. The thickness of the injection material bonded to the insert film is adjusted by the compression core pressing step.

On the other hand, the temperature difference between the upper mold and the lower mold affects the cooling rate of the injection material injected into the mold. Since the upper part of the injection material injected into the mold is in contact with the insert film, the heat transfer rate is reduced due to the insulating action of the film. On the other hand, the lower portion of the injection material has a higher heat transfer rate than the injection material located on the upper portion. Therefore, it is necessary to minimize the difference in the heat transfer rate. In order to minimize the difference in heat transfer rate, the temperature of the upper mold may be set higher than the temperature of the lower mold. In this embodiment, the temperature of the upper mold may be 70 ~ 95 ℃, preferably 90 ℃. The temperature of the lower mold may be 70 ~ 85 ℃, preferably 80 ℃. The temperature difference between the upper mold and the lower mold may be 10°C or more.

The compression holding time of the compressed core may be 8 to 10 seconds, preferably 9 seconds. In addition, the clamping force acting on the upper mold and the lower mold may be 250 to 600 tons. After the compression core pressing step, the hydraulic core pressure may be maintained at 70-80%. This is to minimize the shrinkage of the injection material in the mold by changing the pressure acting on the lower mold.

The final thickness of the manufactured window cover may be 1.5 to 3 mm, preferably 2.5 mm. The thicker the final product, the less warpage.

The temperature difference between the upper mold and the lower mold, clamping force, and hydraulic core output will be described in detail as compression factor conditions for manufacturing a window cover with improved flatness.

The present invention minimizes the variation in the amount of heat transfer in the thickness direction of the window cover to prevent warping.

In the seventh embodiment of the present invention, the temperatures of the upper mold and the lower mold are defined. As the difference in heat transfer rate between the upper side and the lower side of the window cover is small, the flatness is improved. However, an insert film is disposed on the upper side of the window cover, and the heat transfer rate is reduced by inhibiting cooling of the upper side of the window cover. On the other hand, the lower side of the window cover has a higher heat transfer rate than the upper side. That is, the temperature distribution is asymmetrically formed in the thickness direction of the window cover. In order to reduce the difference in heat transfer rate, the temperature of the upper mold is preferably higher than that of the lower mold. In this embodiment, by increasing the temperature of the upper mold, it is possible to reduce the difference in the heat transfer rate of the injection material disposed on the upper side and the lower side of the window cover, respectively. The greater the temperature difference between the upper mold and the lower mold, the better the flatness.

The temperature of the upper mold may be 70 ~ 95 ℃, preferably 90 ℃, the temperature of the lower mold may be 70 ~ 85 ℃, preferably 80 ℃.

When the temperatures of the upper mold and the lower mold are respectively lower than 70° C., there is a problem in that the flow resistance of the injection material increases and the residual stress increases. On the other hand, when the temperature of the upper and lower molds increases, the shear stress of the resin and the residual stress of the product are reduced during injection compression, so that the birefringence property can be improved. not. The temperatures of the upper mold and the lower mold are preferably 95°C and 85°C or less, respectively.

The temperature difference between the upper mold and the lower mold can be at least 10℃ or more.

If the temperature difference between the upper mold and the lower mold is more than 20°C, there may be a problem that compression burrs and burrs are generated in the parting line in addition to a decrease in flatness. Specifically, the coefficient of thermal expansion should be different between the molds. When the temperature of the lower mold is low, the expansion of the mold becomes smaller compared to the upper/lower side, and the pressure of the parting line during injection is reduced. may occur. If production continues at a low temperature of the lower mold, burrs are continuously generated in the product produced by the burrs generated on the compression parting line, and the mold parting line collapses, increasing the defective rate of the product.

In the eighth embodiment, in order to prevent bending of the window cover, a clamping force is defined.

The clamping force refers to the force that fastens the upper and lower molds, and the necessary clamping force is related to the material or quantity of injection material, and the size or number of gates. In this embodiment, PC was used as the injection material, and the clamping force may be 250 to 600 tons, preferably 450 tons. When the clamping force is 250 to 600 t, the amount of shrinkage due to cooling of the injection material can be suppressed.

In order to reduce the temperature deviation depending on the location of the injection material, the temperature difference between the upper mold and the lower mold is defined, but when the temperature difference between the upper mold and the lower mold becomes small during the manufacturing process, the clamping force can be increased to suppress the bending phenomenon.

In the ninth embodiment, in order to prevent the window cover from bending, a holding pressure output is defined.

The holding pressure output is a force for pressing the compressed core, and the output of the force acting on the compressed core in the cooling step after the compression core pressing step may be maintained at 70 to 80%. While the injection material is cooling, the force for pressing the injection material can be kept to a minimum to prevent the injection material from bending while cooling. If the holding pressure output exceeds 80%, overload in the injection machine may cause strain on the mold, etc.

In another embodiment, the final thickness of the window cover, the thickness of the insert film, and the like may be defined. The final thickness of the window cover may be 1.5 to 3 mm, preferably 2.5 mm. The insert film thickness may be 0.15 to 0.3 mm, preferably 0.2 mm.

Examples and comparative examples for compression factors related to flatness improvement will be described.

Flatness was measured in each Example and Comparative Example. The flatness refers to the degree to which the window cover is bent. The flatness is calculated as a difference between a maximum value and a minimum value by measuring z-values at a plurality of points on the window cover.

In this embodiment, flatness is measured in the following way. A plurality of virtual points are set on the window cover surface to be measured. The point made by the intersection of the lines connecting the four origin points on the left/right/top and bottom of the measurement target is taken as the measurement origin. Set the midpoint of the line connecting neighboring Origin Points among the four Origin Points on the left/right/top and bottom of the measurement target as the measurement point. A plurality of virtual points including the Origin Point are referred to as P1, P2, P3, P4, P5, P6, P7, P8, and P9 from the top and left, respectively. In FIG. 24 , P1, P3, P7, and P9 are four origin points, and P5 is an origin. The midpoint of the line connecting neighboring Origin Points among the four Origin Points is set to P2, P4, P6, and P8, respectively, and the flatness is calculated with the z-values of the origins P5, P2, P4, P6, and P8.

Dimensions are measured at a plurality of points on the window cover to be measured. Dimensions are measured using a 3D measuring machine. The 3D measuring device used is a vision inspection type, and the flatness is also focused using a camera to measure the z value. In the case of fascia, since the flatness measurement part is the A/A part, the flatness of the transparent part is measured by setting the mesh. The measured values of P2, P4, P5, P6, and P8 are used to calculate the flatness.

The flatness can be obtained by the following equation.

Flatness=Zmax- Zmin (Equation 1)

(Zmax = maximum value of z value, Zmin = minimum value of z value)

Calculate the maximum and minimum values among the measured z values of P2, P4, P5, P6, and P8, and find the difference between the maximum and minimum values. In the present embodiment, measurement values of points corresponding to P2, P4, P5, P6, and P8 in FIG. 24 are used, but in another embodiment, measurement values of a plurality of arbitrary points other than the corresponding points may be used.

In order to derive the optimal conditions for each factor, the following experiments were performed for each factor. Conditions excluding factors for comparison may be different depending on the order of the experiment. In each experiment, the comparison target factor conditions of Examples and Comparative Examples were applied differently, and the optimum value of the corresponding flatness factor was derived. PC (Ai2217 of covrstro) was used as an injection material, and a 2-layer sheet of PC/PMMA was used for the film.

<Upper mold temperature>

Among the factors related to flatness, the optimum value for the upper mold temperature is examined.

The temperature of the lower mold was 80°C, the temperature of the injection material was 280°C, the holding pressure output was 80%, and the clamping force was 450t, and the window cover was molded.

The upper mold temperature conditions of Examples and Comparative Examples are as follows.

Upper mold temperature (℃) Example 90 Comparative Example 1 70 Comparative Example 2 60

The flatness measurement results of Examples and Comparative Examples are as follows.

P2 P4 P5 P6 P8 flatness Example 0.09 0.16 0.03 0.14 -0.63 0.79 Comparative Example 1 0.12 -0.49 -0.82 -0.44 -0.93 1.05 Comparative Example 2 -0.13 -0.26 -0.94 -0.1 -1.33 1.23

In the case of Examples, the flatness was measured to be 0.79 by the measurement of points P2 to P8, Comparative Example 1 having an upper mold temperature of 70°C had a flatness value of 1.05, and Comparative Example 2 having an upper mold temperature of 60°C had flatness The value was determined to be 1.23. As the upper mold temperature decreases, it can be seen that the flatness value increases, that is, the flatness decreases. It can be seen that when the temperature of the upper mold is 90° C. (Example), the best flatness is obtained.

<crystal force>

Among the factors related to flatness, the optimal value for clamping force will be examined.

The window cover was molded with an upper mold temperature of 90°C, a lower mold temperature of 80°C, an injection material temperature of 280°C, and a holding pressure output of 80%.

Clamping force conditions of Examples and Comparative Examples are as follows.

clamp force (t) Example 450 Comparative Example 1 350 Comparative Example 2 250

The flatness measurement results of Examples and Comparative Examples are as follows.

P2 P4 P5 P6 P8 flatness Example 0.09 0.16 0.03 0.14 -0.63 0.79 Comparative Example 1 0.19 0.04 -0.21 0.05 -0.95 1.14 Comparative Example 2 0.24 -0.04 0.41 0.11 -1.25 1.66

In the case of Examples, the flatness value was measured to be 0.79 by the measurement of points P2 to P8, Comparative Example 1 had a flatness value of 1.14, and Comparative Example 2 had a flatness value of 1.66. It can be seen that the flatness value increases as the clamping force decreases. It can be seen that the embodiment having a clamping force of 450t has the best flatness.

<holding pressure output>

Among the factors related to flatness, the optimum value for the holding pressure output is examined.

The window cover was molded with an upper mold temperature of 90°C, a lower mold temperature of 80°C, an injection material temperature of 280°C, and a clamping force of 450t.

The holding pressure output conditions of Examples and Comparative Examples are as follows.

Holding pressure output (%) Example 80 Comparative Example 1 60 Comparative Example 2 30

The flatness measurement results of Examples and Comparative Examples are as follows.

P2 P4 P5 P6 P8 flatness Example 0.09 0.16 0.03 0.14 -0.63 0.79 Comparative Example 1 0.34 -0.02 0.52 0.16 -1.72 2.24 Comparative Example 2 0.54 -0.14 0.62 0.21 -1.93 2.55

In the case of Examples, the flatness value was measured to be 0.79 by the measurement of points P2 to P8, Comparative Example 1 had a flatness value of 2.24, and Comparative Example 2 had a flatness value of 2.55. It can be seen that as the holding pressure output increases, the flatness value decreases, that is, the warpage is reduced. It can be seen that the embodiment in which the holding pressure output is 80% has the best flatness.

Optimal conditions for injection compression molding may vary depending on the type of resin, and the examples and comparative examples show a case where the material of the injection material is PC.

<Injection thickness>

Among the factors related to flatness, the optimum value for injection thickness will be examined.

The window cover was molded with an upper mold temperature of 90 °C, a lower mold temperature of 80 °C, an injection material temperature of 280 °C, a film thickness of 0.2 mm, and a clamping force of 450 tons.

Injection thickness conditions of Examples and Comparative Examples are as follows.

Injection thickness (mm) Example 3.0 Comparative Example 1 2.8 Comparative Example 2 2.5 Comparative Example 3 2.2

The flatness measurement results of Examples and Comparative Examples are as follows.

P2 P4 P5 P6 P8 flatness Example 0.02 0.11 0.01 0.11 -0.50 0.61 Comparative Example 1 0.04 0.13 0.02 0.12 -0.56 0.69 Comparative Example 2 0.06 0.15 0.03 0.11 -0.61 0.74 Comparative Example 3 0.09 0.16 0.03 0.14 -0.63 0.79

In the case of Example, the flatness was 0.61 by the measurement of the points P2 to P8, showing good results. Comparative Example 1 had a flatness value of 0.69, and Comparative Example 2 had a flatness value of 0.74. Comparative Example 3 had a flatness value of 0.79. It can be seen that the thicker the injection thickness, the better the flatness. It can be seen that when the injection thickness is 3.0 mm, it has the best flatness. However, when the injection thickness is 2.5 mm or more, the touch sensitivity is lowered during use, and the injection thickness may be determined in consideration of other conditions.

<Film thickness>

Among the factors related to flatness, the optimum value for the film thickness will be examined.

The window cover was molded with an upper mold temperature of 90°C, a lower mold temperature of 80°C, an injection material temperature of 280°C, and a clamping force of 450t.

Film thickness conditions of Examples and Comparative Examples are as follows.

Film thickness (mm) Example 0.2 Comparative Example 1 0.25 Comparative Example 2 0.3

The flatness measurement results of Examples and Comparative Examples are as follows.

P2 P4 P5 P6 P8 flatness Example 0.09 0.16 0.03 0.14 -0.63 0.79 Comparative Example 1 0.13 0.19 0.04 0.17 -1.10 1.29 Comparative Example 2 0.22 0.24 0.07 0.21 -1.56 1.80

In the case of Example, the flatness was 0.79 by the measurement of the points P2 to P8, showing good results. Comparative Example 1 had a flatness value of 1.29, and Comparative Example 2 had a flatness value of 1.80. It can be seen that the thinner the film thickness, the better the flatness. It can be seen that when the film thickness is 0.2 mm, it has the best flatness.

<Film shrinkage rate>

Among the factors related to flatness, the optimum value for film shrinkage will be examined.

The window cover was molded with an upper mold temperature of 90°C, a lower mold temperature of 80°C, an injection material temperature of 280°C, and a clamping force of 450t.

Film shrinkage conditions of Examples and Comparative Examples are as follows. Shrinkage is the result of measurement in the MD direction after 30 min at 160°C.

Film shrinkage (%) Example 1.4 Comparative Example 1 2.7 Comparative Example 2 3.4 Comparative Example 3 4.2

The flatness measurement results of Examples and Comparative Examples are as follows.

P2 P4 P5 P6 P8 flatness Example 0.09 0.16 0.03 0.14 -0.63 0.79 Comparative Example 1 0.12 0.30 0.05 0.19 -1.22 1.52 Comparative Example 2 0.18 0.30 0.07 0.22 -1.54 1.84 Comparative Example 3 0.25 0.52 0.09 0.33 -1.70 2.22

In the case of Example, the flatness was 0.79 by the measurement of the points P2 to P8, showing good results. Comparative Example 1 had a flatness value of 1.52, Comparative Example 2 had a flatness value of 1.84, and Comparative Example 3 had a flatness value of 2.22. It can be seen that the lower the film shrinkage, the better the flatness. It can be seen that the film has the best flatness when the shrinkage rate is 1.4%.

As a result, the window cover according to the present invention is flat when the temperature of the upper mold is 90°C, the clamping force is 450t, the holding pressure output is 80%, the injection thickness is 3.0mm, the film thickness is 0.2mm, and the film shrinkage rate is 1.4%. The degree value is lowered and the warpage phenomenon is suppressed.

The flatness of the window cover molded under the above conditions is 0.8 or less.

Optimal conditions for injection compression molding may vary depending on the type of resin, and the examples and comparative examples show a case in which the material of the injection material is PC.

On the other hand, the present invention uses a compression injection method to minimize the residual stress after molding of an injection material that appears in a general injection process, and the birefringence performance of the manufactured window cover is superior to that of the window cover by the general injection process.

The retardation values of the window cover according to the above-described exemplary embodiment and the window cover manufactured by the general injection process are compared as follows.

Example: Injection Compression Process

<condition>

Melt index of resin: 30-50cm ³ /10min,

Injection temperature: 300℃,

Mold temperature: 80/90/30℃,

Compression gap: 1mm;

Compression point: V/P switching point,

Compression speed: 2-2mm/s;

Injection speed: 45-80-80-70mm/s,

Compression holding time: 3 seconds

Clamping force: 250ton

Comparative example: general injection process

<condition>

Melt index of resin: 30-50cm ³ /10min,

Injection temperature: 300℃,

Mold temperature: 80/90/30℃,

Injection speed: 45-80-80-70mm/s,

Injection pressure (packing pressure): 10 bar

Clamping force: 250ton

Visual evaluation (side) Planar-side retardation value (nm, mean/deviation) 45˚ side retardation value (nm, average/deviation) Example (Window Cover Manufactured by Compression Injection Process)

50/13 270/62 Comparative example (window cover manufactured by general injection process)

180/110 473/164

In the case of the window cover manufactured by the general injection process, the plane-side retardation value was 180 nm and the 45˚-side retardation value was 473 nm, whereas in the case of the window cover manufactured by the injection compression process according to the present invention, the plane-side retardation value was The 50nm and 45˚ side retardation values are 270nm, and it can be seen that the retardation values are significantly reduced. In addition, in the case of the window cover manufactured by the injection compression process according to the present invention, it can be seen that the retardation deviation values on the plane side and the 45° side are also reduced.

25 is a view showing a film layer in a window cover for a display device according to an embodiment of the present invention.

Meanwhile, the film layer 1200 may include a film, a hard coating layer for protecting the film, and various optical coating layers. The film layer 1200 may include at least one of an anti-glare (AG) coating layer, an anti-reflective (AR) coating layer, and an anti-finger (AF) coating layer as an optical coating layer. AG (Anti-Glare) coating is to prevent glare and blocks light refraction by inducing diffuse reflection by forming irregularities on the film surface. AR (Anti-Reflective) coating is to prevent light from being reflected off the surface, and it lowers the refractive index to further improve the transparency by lowering the reflectance. AF (Anti-Finger) coating is to prevent fingerprints from being left on the surface.

23 , the film layer 1200 may include two coating layers. A hard coating layer 1220 may be formed on the film 1210 , and an optical coating layer 1230 may be formed on the hard coating layer 1220 . The hard coating layer 1220 protects the film surface and improves scratch resistance. The optical coating layer 1220 may include at least one of an anti-glare (AG) coating layer, an anti-reflective (AR) coating layer, and an anti-finger (AF) coating layer.

The hard coating layer can be coated with AG treatment at the same time, and silica is used for the AG coating. LR coating, which is a wet coating, can be applied on the AG coating layer, and hollow silica is used for LR coating. Multi-layer coating can be realized through simultaneous coating treatment by adding -F group additive capable of AF function during coating treatment. The thickness of the hard coating layer 1220 is 2 to 5 μm, the thickness 1230 of the optical coating layer is 0.1 to 0.5 μm, preferably the thickness of the hard coating layer 1220 is 3 μm, and the thickness 1230 of the optical coating layer is 0.2 μm. can be

The optical coating layer may be formed using a micro gravure coating method, a slot die coating method, a spray coating method, or a flow coating method, but is not limited thereto.

The film layer 1200 may include a light blocking area and a transparent area. The transparent area corresponds to an area in which information is displayed, and the light blocking area is disposed to surround the transparent area. The light blocking area corresponds to a non-display area called a so-called bezel area in the display apparatus, and is an area in which an image generated by the display apparatus is not viewed. The light blocking area may have a color and/or a pattern. For example, the light blocking area may be viewed as black. The light transmitting area induces diffuse reflection of external light such as sunlight, thereby reducing the surface reflectance of external light and increasing visibility of an image produced by the display device.

26 is a view showing a first area and a second area in the window cover for a display device according to an embodiment of the present invention, and FIG. 27 is injection molding in the base layer forming step of the window cover for a display device according to the embodiment of the present invention It is a view showing the flow of ash, and FIG. 28 is a view showing the results of visual evaluation of the birefringence performance in the first region and the second region in the window cover for a display device according to the present invention.

During injection molding of the window cover 1000, molecular orientation is solidified in the flow direction of the injection material due to shear flow, and residual stress remains inside the material after molding is completed, causing birefringence. In order to minimize birefringence, the residual stress generated in the material after molding should be minimized. However, from the viewpoint of manufacturing efficiency, it is necessary to optimize the birefringence value in consideration of manufacturing cost and required time. The present invention optimizes the birefringence value of the window cover according to the above-described manufacturing conditions. The average retardation value in the plane of the window cover manufactured by the above-described manufacturing method has a value of 60 nm or less, and may preferably be 50 nm or less. The average retardation value at an incident angle of 45° of the manufactured window cover is 280 nm or less, and may preferably be 270 nm or less.

Meanwhile, the retardation value may be different for each area of the window cover. The window cover of the present invention is manufactured through compression flow while the injection material is injected into the gate region located on the center line C1 of the film material, and stress due to the solidification of the injection material occurs. Accordingly, the retardation value may increase toward the outside of the window cover 1000 .

26 , the window cover 1000 may include a first area 1110 and a second area 1120 . The first area 1110 and the second area 1120 may be divided into inner and outer sides by an arbitrary line on the window cover. The arbitrary line may be a line connecting points that bisect a line connecting the outer portion of the window cover from the midpoint of the window cover in a 1:1 ratio. Here, the outer portion means an outer end of the rectangular window cover. On the window cover, that is, the first region 1110 and the second region 1120 are divided by an imaginary line connecting intermediate points of a line connecting arbitrary points of the outer film layer at the midpoint of the film layer. The inner region including the midpoint of the window cover 1000 may be the first region 1110 , and the outer region including the outer portion of the window cover may be the second region 1120 .

The average of the plane-side retardation values of the first region 1110 may be 60 nm or less, and preferably 50 nm or less. The average of the plane-side retardation values of the second region 1120 is different from the plane-side retardation value of the first region 1110 . The plane-side retardation value of the second region 1120 may be 50 nm or less, and may be smaller than the plane-side retardation value of the first region 1110 . The difference in the retardation value for each region is due to the difference in the shear rate of the injection material.

As shown in FIG. 27 , the injection material injected into the gate region flows in the mold. At this time, the shear rate value of the injection material is generated at a maximum value in the first region and injection is performed. Accordingly, a large amount of residual stress is present in the first region of the window cover, so that the retardation value of the first region 1110 may be large. there is. Relatively, the retardation value of the second region 1120 may be smaller than that of the first region 1110 .

The difference between the plane-side average retardation values of the first region 1110 and the second region 1120 may be 10 nm or less, and the difference between the retardation deviation values may be 3 nm or less.

As shown in FIG. 28 , a visual evaluation result in which retardation values of the first region and the second region are different can be confirmed. 26 is a diagram of a retardation value according to a contour line; It is a distribution diagram, and the distribution of retardation values is shown based on 0 to 300 nm. Looking at the distribution diagram of the retardation, it can be seen that the retardation value of the first region 1110 is greater than the retardation value of the second region 1120 .

Meanwhile, when the incident angle is 45°, the retardation value of the first region 1110 may be 280 nm or less, preferably 270 nm or less. The retardation value of the second region 1120 is different from the retardation value of the first region 1110 . The retardation value of the second region 1120 may be 270 nm or less, and may be smaller than the retardation value of the first region 1110 . The difference between the average retardation values on the 45 degree side of the first region 1110 and the second region 1120 may be 15 nm or less, and the difference between the retardation deviation values may be 5 nm.

In another embodiment, retardation deviation values in the first area 1110 and the second area 1120 of the window cover 1000 may be different. The first area 1110 and the second area 1120 may be divided into inner and outer sides of the window cover 1000 . The inner region may be the first region 1110 , and the outer region may be the second region 1120 . The average retardation deviation value according to the incident angle of the first region 1110 may be 20 nm or less, and preferably, 10 nm or less. The retardation deviation value of the second region 1120 may be different from the retardation deviation value of the first region 1110 . The retardation deviation value of the second region 1120 may be 15 nm or less, and may have a smaller value than the retardation deviation value of the first region 1110 .

29 is a view showing a flow mark in a window cover for a display device of the present invention, FIG. 30 is a view showing a first area and a second area in a window cover for a display device according to an embodiment of the present invention, and FIG. 31 is It is a view showing a first area and a second area in a window cover for a display device according to an embodiment of the present invention, and FIG. 32 is a view showing a flow mark in the window cover for a display device according to an embodiment of the present invention.

In the present invention, the base layer is formed while the injection material is compressed and flows in the cavity. The injection material is injected into the gate region located on the center line C1 of the film material, and a part of the injected injection material flows horizontally to the left and right in the vicinity of the gate region, and a part flows downward. By shear flow, the molecular orientation of the injection material is solidified in the flow direction, and such flow traces form flow marks. The flow mark defines one characteristic of the window cover.

In the process of manufacturing the base layer 1100 of the window cover 1000 , various types of flow marks 1300 may be formed. The flow mark 1300 can be confirmed during visual evaluation, and is divided into a visually distinguishable flow line area. In the case of visual measurement, the light source was measured after a 200-500 lux surface light source was separated by 0.3 to 1 m, and in this example, a 300 lux surface light source was measured by 0.3 m apart.

A flow mark 1300 is formed on the base layer 1100 . The base layer 1100 is molded by injecting and compressing an injection material between the upper mold and the lower mold. As shown in FIG. 5 , a part of the injection material discharged to the gate region flows in the horizontal direction to the left and right in the vicinity of the gate region, and a part flows downward. The injection material forms a main flow line and a main flow line on the base layer 1100 while moving downward of the mold and left and right with respect to the main flow line.

As shown in FIG. 27 , the flow mark 1300 is formed in a shape in which a plurality of main flow lines and sub flow lines are formed downward from the upper gate region side of the base layer 1100, and the width of the flow mark 1300 spreads downward toward the bottom. That is, the flow mark 1300 may be symmetrically formed with respect to the first center line C1 of the window cover 1000 , and the overall outline may be formed in a sectoral shape. In this case, the birefringence characteristic may be symmetrically formed.

The retardation value of the window cover may be formed substantially symmetrically with respect to the virtual center line of the window cover 1000 . In an embodiment, the window cover 1000 includes a first area 1110 ′ and a second area 1120 ′. As shown in FIG. 28 , the first area 1110 ′ and the second area 1120 ′ may be divided left and right based on the first center line C1 . The first center line C1 is an imaginary line passing through the midpoint of the finally manufactured window cover and parallel to the Y-axis direction.

In the window cover of the present invention, the injection material is injected into the gate region located on the center line C1 of the film material, and the injected injection material flows in compression within the cavity. The flow flow of the injection material may be defined in a vertical direction and a horizontal direction, and a distribution of retardation values along the center line C1 of the film material is formed substantially symmetrically.

That is, the plane-side average retardation value of the first region 1110 ′ and the second region 1120 ′ is 60 nm or less, preferably 50 nm or less, and the retardation distribution based on the first center line C1 is It has a substantially symmetrical aspect.

Meanwhile, the distribution of the retardation values at the 45° angle of incidence of the first region 1110 ′ and the second region 1120 ′ of the window cover 1000 is also substantially symmetrical with respect to the first center line C1 . has The retardation values of the first region 1110 ′ and the second region 1120 ′ at an incident angle of 45° are 220 nm or less, and preferably have a value of 200 nm or less. The difference in the plane-side average retardation values may be 10 nm or less, and the difference in the retardation deviation values may be 3 nm or less.

29 , in another embodiment, the first area 1110 ″ and the second region 1120 ″ may be divided vertically based on the second center line C2 . The second center line C2 is a virtual center line on the window cover, passes through the midpoint of the finally manufactured window cover, and is parallel to the X-axis direction. The lower region of the second center line C2 may be the first region 1110 ″, and the upper region may be the second region 1120 ″.

The average of the plane-side retardation values of the first region 1110″ and the second region 1120″ is 60 nm or less, preferably 50 nm or less, and the distribution of each retardation value is the second center line (C2) has a symmetrical aspect based on

Meanwhile, the distribution of the retardation values at the 45° angle of incidence of the first region 1110 ″ and the second region 1120 ″ of the window cover 1000 also has a symmetrical pattern with respect to the second center line C2. . The retardation values at the 45° angle of incidence of the first region 1110″ and the second region 1120″ are 220 nm or less, preferably 200 nm or less, and the distribution of the respective retardation values is the second center line It has a symmetrical aspect with reference to (C2). The difference between the average retardation values on the 45 degree side of the first region 1110 and the second region 1120 may be 15 nm or less, and the difference between the retardation deviation values may be 5 nm.

In another embodiment, retardation deviation values may be defined in the first area 1110 ′ and the second area 1120 ′ of the window cover 1000 .

The first region 1110 ′ and the second region 1120 ′ may be divided left and right based on the first center line C1 . The average retardation deviation value according to the incident angle of the first region 1110 ′ is 20 nm or less, and may preferably be 10 nm or less. The distribution of the retardation deviation value of the second region 1120 ′ is symmetrical with the distribution of the retardation deviation value of the first region 1110 ′.

In another embodiment, the first region 1110 ″ and the second region 1120 ″ may be divided vertically based on the second center line C2 . The lower region may be the first region 1110 ″, and the upper region may be the second region 1120 ″.

The average retardation deviation value according to the incident angle of the first region 1110" is 20 nm or less, and preferably, 10 nm or less. The distribution of the retardation deviation value of the second region 1120" is the first region 1110". It may be symmetrical with respect to the distribution of the retardation deviation value of , and the second center line C2 .

The shape of the flow mark may vary depending on injection compression conditions, the position of the gate, and the size and shape of the window cover. For example, when the length in the longitudinal direction of the product is increased, the length of the flow mark is changed, and when the length in the width direction is increased, the flow mark can be widened. In addition, when the mold temperature is low or the injection speed is slow, the flow mark may be conspicuous due to the cooling of the injection material.

Meanwhile, from the shape of the flow mark 1300 , a position at which the injection material is injected, the number of gate regions, an injection speed, molding conditions, and the like may be estimated. For example, as shown in FIG. 27 , the aspect in which the flow mark 1300 is developed is developed in a short and narrow sector shape downward based on one main flow line, and between the sub flow lines of the flow mark 1300 . If the interval of is formed to be larger at the bottom than at the top, it can be assumed that the gate region exists inside the window cover and that the gate region is located on the center line C1 of the window cover 1000 .

As shown in FIG. 30, the aspect in which the flow mark 1300 is developed is developed in a fan-shaped downward direction based on one main flow line, and if the downward flow mark 1300 is long and wide, the injection The gate region of ash exists outside the final window cover region, and it can be estimated that the gate region is located on the center line C1 of the window cover 1000 .

The area in which the flow mark 1300 is formed is preferably 60% or less of the total area of the window cover 1000 . If the area in which the flow mark 1300 is formed exceeds 60% of the total area of the window cover, the overall retardation value of the window cover may increase and optical properties may be deteriorated. The width of the flow mark 1300 in the horizontal direction is preferably 80% or less of the width of the window cover 1000 .

33 is a flowchart schematically illustrating a method for manufacturing a window cover material according to a sixth embodiment of the present invention, and FIG. 34 is a schematic diagram of an embodiment of a suction device for implementing the method for manufacturing a window cover material shown in FIG. 32 Fig. 35 is a configuration diagram schematically showing a specific example for implementing the insert film suction step, and Fig. 36 is a configuration diagram schematically showing a window cover material according to a tenth embodiment of the present invention. am.

Next, a method of manufacturing a window cover according to a tenth embodiment of the present invention will be described.

As shown in FIG. 33 , the method for manufacturing a window cover according to the sixth embodiment further includes an insert film suction step as compared to the previous embodiment.

More specifically, the window cover manufacturing method (S2000) includes an insert film preforming step (S2100), an insert film upper mold mounting step (S2200), an insert film suction step (S2300), an injection material discharging step (S2400), and a lower mold It includes a pressing step (S2500).

In addition, the insert film preforming step (S2100) and the insert film upper mold mounting step (S2200) are the insert film preforming step (S1100) and the insert film upper mold mounting step of the window cover manufacturing method (S1000) according to the first embodiment It is the same as (S1200).

Next, the insert film suction step (S2300) is a step of fixing the insert film to the upper mold by providing a suction force to the insert film through the suction unit. Accordingly, the insert film mounted on the upper mold is maintained in a state of being adsorbed to the upper mold by the suction force.

As the insert film is adsorbed to the upper mold as described above, when the injection material is supplied to the insert film in the injection material discharging step, more stable support of the insert film is possible.

Next, the injection material discharging step (S2400) and the lower mold pressing step (S2500) are the same as the injection material discharging step (S1300) and the lower mold pressing step (S1400) of the window cover manufacturing method (S1000) according to the first embodiment and a detailed description thereof as described above will be omitted.

As shown in FIG. 34 , the suction unit 200 may be coupled to the upper mold 110 to extend to the upper mold buttonhole hook 111 .

In addition, when a suction force is provided to the insert film, the film layer buttonhole region 1122 is in close contact with the upper mold buttonhole hook part 111 of the upper mold 110 so that the adhesion area S is formed in a large area. The fixing efficiency is increased (FIG. 33).

As described above, the insert film can be sucked in the injection material discharging step to be more effectively fixed to the upper mold, and the insert film is pushed as the injection material is discharged to the insert film while the insert film is in close contact. This phenomenon is prevented in advance, and efficient application is possible.

As shown in FIG. 36 , the window cover 2000 has no gate area formed in the buttonhole area compared to the window cover 1000 shown in FIG. 35 .

More specifically, the window cover 2000 includes a film layer 2100 and a base layer (not shown).

The film layer 2100 may be formed of a preformed In Mold Label (IML) film. The film layer 2100 includes a transparent part 2110 and a light blocking part 2120 so that the window cover 2000 is implemented as a window cover.

In addition, a film layer buttonhole region 2111 and a gate region 2112 are formed in the transparent portion 2110 . The gate region 2112 is implemented as a gate for supplying an injection material to the insert film during an injection process.

As described above, the film layer buttonhole region 2111 is formed to protrude from one surface on which the transparent part 2110 is formed to the other surface direction.

The film layer buttonhole region 2111 serves as an upper mold buttonhole hanger in the manufacturing step of the window cover, and a detailed description thereof will be omitted as described above.

In addition, the base layer (not shown) is coupled to the film layer 2100 by injection-molding an injection material on the rear surface of the film layer 2100 . And in the base layer (not shown), a base layer buttonhole region (not shown) and a base layer gate region (not shown) corresponding to the film layer buttonhole region 2111 and the film layer gate region 2112 of the film layer 2100, respectively. city) is formed.

In addition, the film layer gate region 2112 and the base layer gate region are formed in an extension portion extending outwardly of the light blocking portion 2120 .

In addition to this, the film layer has a first center line (shown as C1 in FIG. 7 ) in the uniaxial direction (shown as C1 in FIG. 7 ) and a second center line (as C2 in FIG. 7 ) in the other axial direction excluding the extension for forming the film layer gate region 2112 . shown), and the film layer buttonhole region of the film layer, and the base layer buttonhole region are located below the second center line. The first center line C1 is an imaginary line that passes through the midpoint of the finally manufactured window cover and is parallel to the Y-axis direction, and the second center line C2 is an imaginary center line on the window cover, which is the midpoint of the finally manufactured window cover. It is a line parallel to the X-axis direction.

Since the window cover according to the tenth embodiment of the present invention is made as described above, the productivity is improved as injection molding is implemented with the insert film mounted by the film layer buttonhole region.

37 is a configuration diagram schematically showing a window cover for a display device according to an embodiment of the present invention, and FIG. 38 is a schematic B-B cross-sectional view of the window cover for a display device shown in FIG. 37 .

As shown in FIG. 37 , the window cover 3000 for the display device is formed as a through part by cutting the film layer buttonhole area and the ejection part buttonhole area compared to the window cover 1000 shown in FIG. 5 .

More specifically, the window cover 3000 for a display device includes a film layer 3100 and a base layer 3200 .

More specifically, the film layer 3100 may be formed of a preformed In Mold Label (IML) film. The film layer 3100 may include a transparent part 3110 and a light blocking part 3120 . That is, the transparent portion 3110 is formed to correspond to the display area, and the light blocking portion 3120 is formed to surround the outer periphery of the transparent portion 3110 .

In addition, a penetrating film layer buttonhole region 3121 is formed in the light blocking portion 3120 .

In addition, the base layer 3200 is coupled to the film layer 3100 . The injection material is injection-molded on the back surface of the IML film, which is the film layer 3100 , to form the base layer 3200 , and the base layer 3200 is coupled to the film layer 3100 .

And the base layer buttonhole region 3210 corresponding to the film layer buttonhole region 3121 is formed in the base layer 3200 .

In addition, in the window cover 3000 for the display device, as described above through the window cover 1000 , the gate region through which the injection material flows out is formed inside the film layer buttonhole region 3121 , so that the film layer gate which is a hook portion The flow of the injection material forming the base layer 3200 in a state where the film layer is mounted through the region (shown as 1271 in FIG. 5 ) is directed from the base layer buttonhole region 3210 to the outer periphery of the base layer 3200 can confirm.

In addition, the flow flow of the injection material forming the base layer 3200 in the window cover 3000 for a display device can be confirmed through Moldex3D and the Optic Module.

In the above, an embodiment of the present invention has been described, but those of ordinary skill in the art can add, change, delete or add components within the scope that does not depart from the spirit of the present invention described in the claims. The present invention may be variously modified and changed by, etc., and this will also be included within the scope of the present invention.

1000: window cover 1100: base layer
1110, 1110', 1110": first area
1120, 1120', 1120": second area
1200: film layer 1250: gate region
1271: film layer gate region 1272: film layer buttonhole region
1300: flow mark

Claims (21)

In the method for manufacturing a window cover for a display device with improved defect reduction and birefringence performance,
Mounting the insert film on the upper mold;
positioning the lower mold at a predetermined distance from the upper mold;
injecting an injection material having a melt index (MI) of 30-50 cm ³ /10min at 300° C. into the mold;
A method of manufacturing a window cover for a display device comprising the; pressing the compression core. According to claim 1,
The impact strength of the injection material is 50 ~ 60kJ / m ² Method of manufacturing a window cover for a display device, characterized in that. According to claim 1,
The method of manufacturing a window cover for a display device, characterized in that the average particle diameter of the injection material is 2-3mm. According to claim 1,
The method of manufacturing a window cover for a display device, characterized in that the temperature of the injection material is 270 ~ 320 ℃. According to claim 1,
The method for manufacturing a window cover for a display device, characterized in that the injection material is PC or PMMA. According to claim 1,
In the step of injecting the injection material into the mold,
A method of manufacturing a window cover for a display device, characterized in that the injection speed is controlled for each of the four stroke sections. According to claim 1,
When the position of the nozzle tip is 0mm, the stroke section is 1 section, 2 section, 3 section and 4 section based on the position of the screw tip of 33~37mm, 23~27mm, 10~14mm, 5~9mm. A method of manufacturing a window cover for a display device, characterized in that divided into. 14. The method of claim 13,
The injection speed is a method of manufacturing a window cover for a display device, characterized in that the injection speed in the second section is greater than the injection speed in the first section. 14. The method of claim 13,
The injection speed is 40-50mm/s in section 1, 75-85mm/s in section 2, 75-85mm/s in section 3, 65-75mm/s in section 4 of the window cover for a display device, characterized in that manufacturing method. The method of claim 1,
Before the step of mounting the insert film on the upper mold
Method of manufacturing a window cover for a display device, characterized in that it further comprises the step of preforming the insert film. According to claim 1,
The method of manufacturing a window cover for a display device, characterized in that the temperature of the upper mold and the lower mold is 70 ~ 95 ℃. According to claim 1,
The method of manufacturing a window cover for a display device, characterized in that the temperature of the gate for injecting the injection material is 20 ~ 40 ℃. According to claim 1,
The temperature of the compression core is a method of manufacturing a window cover for a display device, characterized in that 80 ~ 105 ℃. According to claim 1,
The temperature of the compression core is greater than the temperature of the upper mold, and the temperature difference between the upper mold and the compression core is 10° C. or more. The method of claim 1,
A method of manufacturing a window cover for a display device, characterized in that in the step of pressing the compression core, the compression holding time is 8 to 10 seconds. According to claim 1,
A method of manufacturing a window cover for a display device, characterized in that in the step of pressing the compression core, the clamping force is 250 to 600 t. A window cover for a display device, comprising:
A window cover for a display device manufactured by the method for manufacturing the window cover for a display device according to any one of claims 1 to 16. 18. The method of claim 17,
A window cover for a display device, characterized in that the plane-side average retardation value is 50 nm or less. 18. The method of claim 17,
A window cover for a display device, characterized in that the average retardation value at an incident angle of 45° is 270 nm or less. 18. The method of claim 17,
A window cover for a display device, characterized in that the average retardation deviation value according to the incident angle is 20 nm or less. 21. The method of claim 20,
A window cover for a display device, characterized in that the flatness is 0.8 or less.

Images