WO2021154057A1 - Ultra-thin glass for protecting surface of flexible display - Google Patents

Abstract

The present invention provides an ultra-thin glass for protecting the surface of a flexible display used for a display of an in-folding type smartphone, wherein the thickness of the ultra-thin glass is 15-65 ㎛, and the ultra-thin glass is enhanced through a temperature-raising step, an aging step, and a cooling step, so that an optimized thermal treatment process for improving the properties of the ultra-thin glass can be secured in order to protect the surface of a flexible display used as a screen of a smartphone by using an ultra-thin glass having a thickness of 15-70 ㎛.

Description

Ultra-thin glass to protect the flexible display surface

The present invention relates to an ultra-thin glass that protects the surface of a flexible display, and chemically polishes a relatively thin glass of about 70-400 μm produced for smartphones to have a thickness of 15-70 μm. It relates to an ultra-thin glass that protects the surface of a flexible display to be made of a protective glass that protects the flexible display after being made of thin glass, UTG) and then subjected to heat treatment to strengthen the ultra-thin glass.

Since 2019, global smartphone manufacturers have started developing and mass-producing foldable phones in earnest, and interest in companies that supply parts related to foldable phones is growing. Therefore, domestic and foreign companies are preparing parts for foldable smartphones, and there are currently many companies that use transparent polyimide (Colorless PI, CPI) rather than glass for the cover that protects the display surface due to the nature of the foldable. In the case of glass, the elastic limit is low, so the current technology is not suitable as a cover for a foldable display. In fact, metal and glass show a low elastic limit of less than 0.5%, but in the case of plastic film, it is 5%, showing an elastic limit 10 times that of metal and glass.

However, in order to produce a CPI film with film characteristics, a hard coating operation is required on the base film. However, even after hard coating, as long as the matrix is a film, there are limitations no matter how good the CPI film is.

Of course, in Korean Patent Registration No. 10-1557307, "In the display cover glass; it consists of tempered glass and a printed film bonded to the tempered glass, wherein the printed film is attached to the tempered glass through a glass adhesive layer, and the The printing film forms a printing layer on the edge of the opposite side of the glass adhesive layer by printing, and a printing release paper is attached to the upper surface of the printing layer. It provides a display cover glass, characterized in that it forms a screen projection area to cut and remove the inner edge of the print layer, and is formed of a print release paper adhered by a print adhesive layer on the upper surface of the print layer.

In addition, in Korean Patent Laid-Open No. 10-2015-0131550, "Glass that forms the exterior of a touch screen panel; an adhesive layer that is transparent and has adhesive properties, one side of which is attached to the surface of the glass 500; the other side of the adhesive layer A printed layer attached to some areas and printed with letters, numbers, patterns, or patterns, and the remaining areas to which the printed layer is not attached are filled with the adhesive layer, so that the area to which the printed layer is attached and the area to which the printed layer is not attached Provides a touch screen panel equipped with a thermal transfer adhesive layer, characterized in that there is no step difference at the boundary between the printed layer and the adhesive layer due to the uniform thickness of the panel.

However, all of the above techniques are related to the glass protecting the surface of the conventional flat smart phone display, and thus the above technique cannot be applied to the flexible display.

However, since a product for applying a flexible display to a smartphone has already been released, the development of glass for protecting the surface of the flexible display for a smartphone is urgently needed.

Patent Literature:

Cited Document 1: Republic of Korea Patent No. 10-1557307, registration date (September 25, 2015)

Cited Document 2: Korea Patent Publication No. 10-2015-0131550, publication date (November 25, 2015)

An object of the present invention is to provide a glass for protecting the surface of the flexible display in a smart phone employing a flexible display. This is to provide an ultra-thin glass capable of protecting the surface of the flexible display by going through a processing process such as heat treatment to have it as a result.

The object is, in the ultra-thin glass to protect the surface of a flexible display equipped with a digitizer used for the display of the in-folding method smart phone, the thickness of the ultra-thin glass is 15 ~ 70 ㎛, the ultra-thin glass is achieved by strengthening the temperature raising step, the aging step, and the cooling step.

And, the stress of the ultra-thin glass is characterized in that 400 Mpa ~ 800 Mpa, the elastic limit of the ultra-thin glass is 1.5% to 5%.

In addition, when the side surface of the ultra-thin glass is etched at the boundary of the ultra-thin glass when the edge is processed, let L be the distance at which the ultra-thin glass is etched, and let the thickness of the ultra-thin glass be T, the ratio between the L value and the T value is

1/6 ≤ L/T ≤ 1/2.

In addition, the thickness of the coating to be coated to strengthen the surface of the ultra-thin glass is

1/30 ≤ T1 (thickness of reinforcing coating)/T (thickness of ultra-thin glass) ≤ 15/30

am.

Meanwhile, in the heat treatment process to strengthen the ultra-thin glass, the cooling rate is from 7.5°C per minute to 25°C per minute.

As another embodiment of the present invention, an input device unit is provided between the flexible display unit and the ultra-thin glass, and the input unit unit is provided with a touch panel layer and a digitizer layer, and a touch panel layer and a touch panel layer inside the input unit unit When the digitizer layer is provided, the touch panel layer is positioned above the digitizer layer.

In addition, the display unit includes a TFT layer and an encaps layer, the touch panel layer includes a touch panel electrode layer 52c, the digitizer layer includes a digitizer electrode 52a layer, and the touch panel electrode layer When the inner insulating layer 52b is present between the layer 52c and the digitizer electrode 52a, the thickness of the inner insulating layer 52b is smaller than the thickness of the encap.

In addition, a camera hole through which light can pass is provided in a fixed substrate that supports the flexible display to be folded and unfolded, and when an SUS layer or an alloy metal layer is present in the flexible display, the SUS layer or alloy metal layer of light A camera hole through which transmission is possible is provided.

According to the present invention, the ultra-thin glass having a thickness of 15 to 65 μm is used to protect the surface of a flexible display equipped with a digitizer used as a smartphone screen, an optimized heat treatment process in which the properties of the ultra-thin glass are improved this will be secured.

1 is a view of an embodiment showing a method of folding a flexible glass,

FIG. 2 is a diagram of another embodiment of FIG. 1A .

3 is a view of another embodiment when the ultra-thin glass is folded.

4 is a diagram of an embodiment showing a heat treatment step.

5 is a view of an embodiment showing the side processing of the ultra-thin glass.

6 is a view of an embodiment showing a reliability test method in the folding and unfolding process.

7 is a view showing an ultra-thin glass having a multilayer structure.

8 is a diagram of an embodiment showing a practical application example of the present invention.

9 is a view of an embodiment showing the extent to which the ultra-thin glass is stretched.

10 and 11 are views showing the method of the embodiment of precipitating the ultra-thin glass in the reinforcing solution.

12 to 14 are diagrams of an embodiment showing a method in which a digitizer is provided.

15 is a diagram of an embodiment showing a method in which a camera is formed on a flexible display.

16 is a view of an embodiment showing the surface roughness of the ultra-thin glass.

17 and 18 are diagrams of an embodiment showing the thickness condition occupied by the ultra-thin glass in the entire flexible display.

19 is a diagram of an embodiment showing a criterion for adhesive force.

20 to 22 are views showing the digitizer layer and the electrode structure provided in the present invention.

23 is a diagram of an embodiment showing how a digitizer layer is provided under the TFT layer.

23 is a diagram of an embodiment showing how a digitizer layer is provided under the TFT layer.

24 to 27 are diagrams of another embodiment of the present invention.

Explanation of symbols

10: ultra-thin glass 20: fixed substrate

20: camera hole 26: SUS

25: base film 52: input device unit

52a: digitizer layer 52b: inner insulating layer

52c: touch layer 52d: outer insulating layer

50: display unit 50a: TFT layer

50b: encap 70: test board

71: test projections 10-1, 10-2: first and second second thin glass

20-1, 20-2 1st and 2nd fixed substrate 15: Adhesive

55: camera 52a-1: upper substrate

52a-2: lower substrate 52a-3: upper electrode

52a-4: lower electrode 52a-5: insulating film

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings. The configuration of the present invention and the effects thereof will be clearly understood through the following detailed description.

In addition, a detailed description of the known technical configuration may be omitted.

Meanwhile, in order to obtain the result of the present invention, some of the methods of performing chemical etching or heat treatment may follow conventional general methods.

1 is a view of an embodiment showing a method of folding a flexible glass,

As shown in the figure, in order for the flexible display applied to the in-folding method to be folded, the folding and unfolding operations of the flexible display are performed while the flexible display is relatively fixed to the fixed substrate 20 . will wake up

In addition, the ultra-thin glass of the present invention, which protects the surface of the flexible display applied to the in-folding method, is also fixed to the fixed substrate 20 (a substrate fixed without bending of a metal or plastic material) so that folding and unfolding operations occur. it can only be

Therefore, experiments such as measuring the radius of curvature of the ultra-thin glass 10 developed in the present invention and some reliability tests were carried out by the method of the embodiment of FIG. 1 .

And, the value of the gap G between the substrates shown in FIG. 1A is determined according to the radius of curvature of the ultra-thin glass 10 . That is, as shown in FIGS. 1 (B) and 1 (C), the two fixed substrates 20 are rotated and moved to be folded, and the ultra-thin film attached to the two fixed substrates 20 The glass 10 is also folded together.

However, in the ultra-thin glass 10, since one substrate is folded, the G value exists because the radius of curvature must exist at least.

That is, even in the process in which the ultra-thin glass 10 is completely folded, there is a region that maintains a flat state as it is, and there is a folded region, where the distance of the folded region of the ultra-thin glass 10 is the G value.

FIG. 2 is a diagram of another embodiment of FIG. 1 ;

1 (A) is an embodiment in which the interval between the two fixed substrates 20 is spaced apart by G, but FIG. 2 is an embodiment in which the two fixed substrates 20 are in contact with each other. However, the gap G also exists in FIG. 2 .

That is, when the two fixed substrates 20 are in contact with each other, the fixed region and the non-fixed region by the interval G exist. In the fixed area shown in FIG. 2, the ultra-thin glass 10 is fixed to the fixed substrate 20 by an adhesive or fixing means, but in the non-fixed area (gap G) shown in FIG. 2, the ultra-thin glass 10 is fixed. It is not fixed to the substrate 20 (or is not adhered), but only in a state of being placed on it.

And, in the embodiment of Fig. 2, as in Figs. 1 (B) and (C), when the two fixed substrates 20 are rotated and folded, the ultra-thin glass 10 provided on the fixed substrate 20. will also be folded.

On the other hand, if the two fixed substrates 20 are spaced apart from each other by a distance less than the G value, the ultra-thin glass 10 and the fixed substrate 20 are fixed to each other in the region existing within the G value. It is not attached (not glued).

3 is a view of another embodiment when the ultra-thin glass is folded.

In order for the ultra-thin glass 10 of the present invention to be used in an actual flexible display, the ultra-thin glass 10 is placed on the display unit 50 to be used.

In this case, the display unit 50 shown in FIG. 3 of the present invention means a foldable flexible display and an input device (touch panel) provided thereon.

And, when the two fixed substrates 20 are rotated and folded in the embodiment of FIG. 3 as in the embodiment of FIG. 1 , the ultra-thin glass 10 and the display unit 50 are also folded together.

On the other hand, since the achieved R value is 5.0 or 4.6 in the case of an in-folding flexible display that has already been commercialized and released, the R value of the ultra-thin glass 10 developed in the present invention must also be at least 5.0 or 4.6 or less.

In addition, in the embodiment of Fig. 3, the fixed substrate 20 can be set as the example of the embodiment of Fig. 2, and in this case, the adhesive is not coated between the display unit 50 and the fixed substrate 20 in the non-fixed area. do.

- Manufacture of ultra-thin glass -

Although the thickness of the glass sold by companies that produce glass used to protect the surface of the smartphone display is generally about 400 μm, recently, it is produced and sold to 200 μm or less or even 70 μm.

However, the glass having the above thickness does not serve as a glass that protects the surface of the flexible display. Therefore, it is necessary to manufacture the ultra-thin glass 10 having a desired thickness through an additional polishing process.

For the polishing process, physical polishing is also used, and although physical polishing is a very difficult and laborious task, it is a technique that can be performed by a company that has been in our processing industry for a long time.

On the other hand, a polishing process mainly used to make ultra-thin glass is a method of chemical etching using a hydrofluoric acid solution, which is a process generally used in the prior art. Accordingly, it is possible to make the glass having a thickness of 400 μm, 200 μm, or 70 μm into ultra-thin glass having a desired thickness by a conventional chemical polishing method.

However, in order to protect the surface of the flexible display while the ultra-thin glass has plastic properties and is folded to an R value of 5.0 R or 4.6 R or less or less, the etched and polished ultra-thin glass must be strengthened. .

- Reinforcement process of ultra-thin glass -

The conventionally generally known strengthening process of ultra-thin glass is a process of precipitating ultra-thin glass processed to a desired thickness in a reinforcing solution, and then performing heat treatment in 5 minutes.

As the fortifying solution, sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ) are mainly used, _{and a small amount of silicic acid (H 2} SiO ₃ ), etc. is added and used. And, the time for immersing the ultra-thin glass in the reinforcing solution, that is, precipitation, is within 2 to 3 hours.

4 is a diagram of an embodiment showing a heat treatment step.

As shown in FIG. 4 , the heat treatment process is divided into three steps: a temperature increase process, an aging process, and a cooling process. And, since this process is a conventional process, in the present invention, a method of a new temperature condition is found to improve the properties of the ultra-thin glass.

Through various trials and errors in the past, the optimized heat treatment conditions were found for 2 hours of heating time, 2 hours of aging at 400 °C, and cooling within 30 minutes. And, in the present invention, in order to drastically reduce the number of experiments, an appropriate R value and an appropriate thickness are determined in advance to manufacture an ultra-thin glass 10 having a suitable thickness, and the manufactured ultra-thin glass can have an appropriate R value. A method of developing process conditions for heat treatment was used.

An appropriate thickness of the ultra-thin glass 10 was set to 30 μm, and an appropriate R value was set to 2. The predetermined value of 30 μm is a value determined in consideration of the thickness of the protective film used in the flexible display, and the predetermined 2 R value is a commercially available R value of 5, 0 or 4.6, so An appropriate R value was determined.

On the other hand, with the sold glass having a thickness of 100 μm or more, a polishing process is performed using a hydrofluoric acid solution, and the ultra-thin glass having a thickness of 30 μm is manufactured by repeatedly performing several times.

At this time, as described above, the optimized heat treatment temperature and aging time conditions are as follows.

- Time of temperature increase step: 2 hours

- Aging temperature: 2 hours at 400 ℃

- Time of cooling phase: 30 minutes to room temperature (25℃)

That is, the temperature increase rate in the temperature raising step is 3.13 °C per minute, and the cooling rate per minute in the cooling stage is 12.5 °C.

On the other hand, the environment of the heat-treated paper oven is an environment in which a vacuum or an inert gas is present.

- Reinforcement Experiment -

After immersing 30 μm thick ultra-thin glass in the reinforcing solution, heat treatment of 30 μm-thick ultra-thin glass under the above temperature conditions, and then folding it to a value of 2 R, cracked and failed.

The settling time in the fortifying solution is between 2 and 4 hours.

In order to overcome the failure, I thought of quenching the iron, and eventually came to think of a method of repeated heat treatment.

And, by repeating the heat treatment process from 1 to n times, the ultra-thin glass was found to be folded without cracking even at a value of 2R.

1) After cutting the ultra-thin glass having a thickness of 30 μm into 10 cm and 15 cm in width and length, respectively, a heat treatment process is performed.

2) After performing the heat treatment process once, the ultra-thin glass was folded to a value of 2R, but cracks occurred,

3) After repeating the experiment 2) 5 times, the ultra-thin glass was folded to a value of 2 R, and as a result, the ultra-thin glass was folded to a value of 2 R.

That is, as a result of performing the heat treatment process 5 times with the ultra-thin glass having a thickness of 30 μm, the result of folding the ultra-thin glass to a value of 2 R was obtained.

When repeated 6 times, more stable folding results were obtained, but no significant problems were observed even after repeated 5 times.

4) The aging temperature may vary depending on the conditions for n repeated experiments. And the aging temperature is not necessarily limited to the 400 ℃, that is, the temperature for one heat treatment may be 450 ℃, the second heat treatment temperature may be 390 ℃. And from the third time, the heat treatment temperature can be set to 400°C, and can be changed based on 400°C.

- How to get the optimized thickness -

1) Ultra-thin glass with a thickness of 65 μm:

As a result of performing the heat treatment process 8 times, it was successful in folding to a value of 4.6R,

2) Ultra-thin glass with a thickness of 50 μm

As a result of performing the heat treatment process 7 times, it was successful in folding to a value of 4.6R.

3) Ultra-thin glass with a thickness of 40 μm

As a result of performing the heat treatment process 6 times, it was successful in folding to a value of 3.5R.

3) Ultra-thin glass with a thickness of 20 μm

As a result of performing the heat treatment process 6 times, it was successful in folding to a value of 2.0R.

3) Ultra-thin glass having a thickness of 15 μm

As a result of performing the heat treatment process 7 times, it was successful in folding to a value of 2.0R.

4) Ultra-thin glass with a thickness of 10 μm

Even when the heat treatment process was tested up to 8 times, cracks occurred in the process of folding to a value of 2.0R.

5) Ultra-thin glass with a thickness of 70 μm

As a result of performing the heat treatment process 8 times, it was successful in folding to a value of 4.6R. The precipitation time in the reinforcing solution was longer by about 20 to 30 minutes than the condition of the ultra-thin glass having a thickness of only 65 μm.

However, the 70 μm thickness can be seen as the limit thickness for commercialization, and it was determined that there is a problem in commercialization to make it thicker, so that the experiment was carried out only up to a thickness of 70 μm.

Therefore, when the ultra-thin glass (thickness of 15 μm to 70 μm) is heat treated in the above method to have a value of 2 R or less than 5,0 R or 4.6 R, which has already been commercialized as a flexible display, the above-mentioned R value is was found to be achievable.

On the other hand, in the case of the substrate capable of 2R, it was only folded up to 2R in consideration of stability, and when it was folded stably in 2R, it was stably folded even at 1.5 R.

- Various temperature conditions -

When the heat treatment temperature of ultra-thin glass with a thickness of 30 μm was 400° C., the cooling rate was changed.

The temperature increase rate in the temperature increasing step used in the heat treatment process in the previous embodiment of the present invention is 3.13 °C per minute, and the cooling rate per minute in the cooling step is 12.5 °C. And the aging temperature was 2 hours at 400 degreeC.

The temperature at which the glass is heat treated is not necessarily limited to 400°C, and the temperature could be achieved from 250°C to 450°C.

1) In the previous embodiment of the present invention, the aging temperature was 400°C. And, the cooling time reached from 400°C to 25°C was changed to 40 minutes. When the cooling time was changed to 40 minutes, the cooling rate was 9.4°C per minute.

And, when the cooling rate is 9.4°C per minute and the other heat treatment is performed under the same conditions, the temperature raising step, the aging step, and the cooling step are 1 cycle, and the 1 cycle is repeated 7 times. As a result, the thickness of 30 μm It was possible to fold the excitation ultra-thin glass to 2R.

2) The cooling time from 400°C to 25°C was changed to 50 minutes. When the cooling time was changed to 50 minutes, the cooling rate was 7.5° C. per minute.

In addition, when the cooling rate is 7.5° C. per minute and other heat treatments are performed under the same conditions, the temperature raising step, aging step, and cooling step are 1 cycle, and as a result of repeating the 1 cycle 10 times, the thickness of 30 μm It was possible to fold the excitation ultra-thin glass to 2R.

However, repeating up to 10 times is reasonable, considering that there is a problem with practicality. However, it can be said that folding with 2 R was successful.

3) The cooling time from 400°C to 25°C was changed to 20 minutes. When the cooling time was changed to 20 minutes, the cooling rate was 18.75° C. per minute.

And, when the cooling rate is 18.75° C. per minute and other heat treatment is performed under the same conditions, the temperature rising step, aging step, and cooling step are 1 cycle, and the result of repeating the 1 cycle 4 times is 30 μm thick. It was possible to fold the excitation ultra-thin glass to 2R.

3) The cooling time from 400°C to 25°C was changed to 15 minutes. In this case, the cooling rate was 25.0° C. per minute.

And, when the cooling rate is 25.0° C. per minute and other heat treatment is performed under the same conditions, the temperature raising step, aging step, and cooling step are 1 cycle, and the result of repeating the 1 cycle 3 times is 2 R. it was possible But soon cracks arose. However, folding with 2 R can be said to have been successful.

4) The cooling time from 400°C to 25°C was changed to 10 minutes. In this case, the ultra-thin glass was cracked. The cooling rate was 37.0° C. per minute.

As a result, after performing the aging process in the present invention, the cooling rate for cooling was appropriate at 7.5°C to 25°C per minute. And it can be expressed as follows.

7.5°C per minute ≤ Cooling rate ≤ 25°C per minute

On the other hand, in the case of the substrate capable of 2R, it was only folded up to 2R in consideration of stability, and when it was folded stably in 2R, it was stably folded even at 1.5 R.

In addition, in the present invention, the experiment was conducted under the condition that the cooling rate at which the temperature decreases in the cooling stage floats faster than the temperature increase rate, which is the rate at which the temperature rises in the temperature increasing stage. That is, in the graph of FIG. 4 , “the slope of the curve in which the temperature decreases in the cooling step” is greater than the “slope of the curve in which the temperature increases in the temperature increase step” in the graph of FIG. 4 .

However, various heat treatment methods can be performed by changing the temperature conditions, so “the slope of the curve in which the temperature decreases in the cooling step (assuming that it is the A slope)” Assumption)” is not limited to the condition of being greater than the

That is, “slope of A” and “slope of B” may be the same, and “slope of A” may be smaller than “slope of B”.

5 is a view of an embodiment showing the side processing of the ultra-thin glass.

In order to prevent cracking of the glass, it is also one of the important issues to process the edge of the glass side.

Edge processing on the side of the glass will also use a conventional general method. That is, the etching is performed using the hydrofluoric acid solution, but the portion that does not require etching is masked so that the etching is not performed.

Patent In this case, instead of using only one glass, 10 or 20 ultra-thin glasses are stacked, and then the side part is immersed in hydrofluoric acid solution to be etched.

As shown in FIG. 5 , when the thickness of the ultra-thin glass 10 is T and the distance L is etched at the boundary of the ultra-thin glass, the correlation ratio is important.

When the thickness of the glass is 30 μm, the value of the distance L is preferably 10 μm. Therefore, the value of L/T becomes 1/3.

However, when the side surface of the ultra-thin glass is actually processed, errors in the machining process exist, and thus, these errors can be considered and the level of the degree to which the problem caused by the edges of the ultra-thin glass is eliminated. That is, even if the L value was 5 μm, there was no problem in actual use, and even 15 μm was not obtained at a level that was too unreasonable.

No problem above means that folding from 2R (or 1.5R) to 5R does not cause cracking. Cracks are the biggest cause of breakage in the process of folding ultra-thin glass, and even very small micro-cracks can cause breakage.

Accordingly, the range of the L value is 5 µm to 15 µm.

As a result, in the processing of the side edge of the ultra-thin glass, when the thickness of the ultra-thin glass is T and the distance at which the etching is performed at the boundary of the ultra-thin glass is L, the value of the ratio of the T value and the L value is as follows same.

1/6 ≤ L/T ≤ 1/2 (L/T value is greater than or equal to 1/6 and less than or equal to 1/2)

Conventionally, the reason for processing the side of the glass is to soften the edge to improve handling, but the reason for processing the side of the ultra-thin glass in the present invention is to prevent cracking of the glass. That is, if the corner of the ultra-thin glass is rounded, it has an effect of preventing breakage when bending or applying an impact to the ultra-thin glass.

6 is a view of an embodiment showing a reliability test method in the folding and unfolding process.

A reliability test may be performed by actually applying the ultra-thin glass of the present invention to a smart phone employing a flexible display, but since it may be difficult in reality, the reliability test may be performed by imitating the structure when applied to a flexible display.

That is, the drawing of FIG. 6 is a diagram of an embodiment showing a reliability test method manufactured by imitating the structure of a folding smartphone that is actually folded and unfolded.

Two test boards 70 that can be folded and unfolded by rotating 180 degrees and 0 degrees are provided, and on the test board, the ultra-thin glass 10 is mounted as in the embodiment of FIG. 1 (or the embodiment of FIG. 2 ) do.

And, as shown in FIG. 6 , the test protrusion 71 is mounted on the boundary of the test substrate 70 . The test protrusion 71 is a protrusion protruding to a certain height, therefore, due to the test protrusion 71 . As in the embodiment of FIG. 1(C) or the embodiment of FIG. 2(C), the ultra-thin glass 10 is folded with a predetermined value of curvature. In addition, the height value of the test protrusion 71 is adjustable,

In addition, the presence of the second protrusion 72 prevents the folded ultra-thin glass 10 from contacting each other.

As a result, the second protrusion 72 is formed to be higher than the ultra-thin glass 10, and the first protrusion 71 is formed to be higher than the second protrusion.

The ultra-thin glass 10 of the present invention is mounted (attached with a thermoplastic resin) to the device of the embodiment of FIG. 6 . Therefore, when heat is applied, the ultra-thin glass 10 can be easily separated from the test substrate 70 . ), and by connecting the electric device to the test board 70 and repeating folding and unfolding operations, it is possible to determine reliability.

At this time, considering the process of the operation of actually opening and closing the flexible display user, the time taken to fold and unfold the unfolded ultra-thin glass 10 was set to 1.5 seconds, and a reliability test was conducted.

On the other hand, assuming that it is opened and closed 20 times a day and used for 3 years, reliability can be secured by repeating the folding and unfolding operations up to 20,000 times in the method shown in the embodiment of FIG. 6 . And, it takes 8.33 hours to repeat the folding and unfolding action 20,000 times within 1.5 seconds.

And, the experiment of the present invention is to fold continuously for 20,000, and thus, in the folding process, in a state in which the vibration energy generated when folding before is not zero, that is, in a state in which the vibration energy remaining when previously folded exists. The vibrational energy that is generated will be generated again. Therefore, it can be said that the continuous test of 20,000 times shows reliability when folded 40,000 times (more than twice as much as 20,000 times) in actual use. Of course, continuous numerical experiments will be necessary for this.

- Characteristic values of ultra-thin glass -

1) Stress value

The stress value of the glass that protects the conventional smartphone display was requested by the set company at 650 Mpa and 800 Mpa, respectively. However, the stress value of the ultra-thin glass that protects the flexible display cannot be as high as the stress value that protects the conventional smartphone display.

In the present invention, as a result of testing as an ultra-thin glass having 30 μm, it had a stress value of 450 Mpa, and as a result of testing the operation of folding and unfolding by the method of the embodiment of FIG. 6 (based on 3 R), the folding and unfolding operation 20,000 rounds were possible.

Therefore, the stress value of the ultra-thin glass 10 for protecting the flexible display is preferably 250 Mpa or more. However, the maximum value can be said to be 800 Mpa because it does not need to be greater than the stress value that protects the conventional smartphone display screen.

As a result, it can be said that the stress value of the ultra-thin glass presented in the present invention is 450 Mpa to 800 Mpa.

For the measurement of the stress value, a measuring device manufactured by RIHARA (Surface Stress Merer) of Japan is generally used, and the same is true in the present invention.

2) DOL value

The DOL value is the strengthening depth, and the longer the immersion time in the strengthening solution, the thicker the DOL layer. In the present invention, it took time to settle in the strengthening solution within 2 to 3 hours.

In the present invention, the DOL value was also measured. And the measured values for each thickness were as follows.

15 µm: 5 to 7. 20 µm: 6 to 8, 30 µm: 7 to 10, 40 µm: 9 to 13, 50 µm: 10 to 15, 65 to 70 µm: 14 to 17

Therefore, the range of the DOL value in the present invention is 5 to 17 when the range of the ultra-thin glass is 15 µm to 65 µm.

2) Elastic limit

Glass generally shows a low elastic limit of less than 0.5%, but in the case of a plastic film, it shows an elastic limit 10 times that of glass at 5%. Therefore, even if the elastic limit of the ultra-thin glass 10 manufactured in the present invention is not as high as the plastic film, it should be at a level exceeding the range of the elastic limit of the conventional glass.

As a result of measuring the elastic limit of the 30 μm thick ultra-thin glass prepared in the present invention, it was found that the value was increased to 1.5%, and folded and unfolded up to 20,000 times in the experiment by the method of the example of FIG. 6 . was possible.

And, the heat treatment process used in the previous embodiment of the present invention was performed more than 5 times. That is, as a result of repeated experiments up to 10 times, the elastic limit was increased to 2.5%.

As a result, it was found that the properties of the ultra-thin glass were improved by repeating the heat treatment process.

On the other hand, since the elastic limit of the glass cannot go beyond the level of the plastic film, in the present invention, it can be said that the elastic limit value of the ultra-thin glass protecting the flexible display surface is from 1.5% to 5%.

- Surface coating -

Since the glass that protects the display surface in the smartphone is exposed to the outside as it is, the glass should be coated on the surface.

As the type of coating, a protective film may be present to protect consumers when the ultra-thin glass ruptures, AF coating, etc. may be applied, and a reinforcing coating may also be applied.

On the other hand, the level of the reinforced coating thickness of the conventional smartphone was 20 μm to 45 μm. However, since the thickness of the ultra-thin glass protecting the flexible display is thin, the thickness of the reinforcing coating cannot be used as it is.

Reinforcement coating was applied with ultra-thin glass having a thickness of 30 μm. 2 When folded at the R level, the range was set to a level where there was no uniformity, and the range was set to be reinforced.

The thickness of the reinforcing coating was coated at a level of 1 μm, and the coating was performed in 2 μm steps from 2 μm to 16 μm, and then it was judged whether cracks occurred when folded at the 2 R level.

When the thickness of the reinforcing coating was varied from 2 μm to 12 μm, cracks did not occur when folded at the 2 R level, but cracks occurred when coated with 16 μm. Naturally, even at the time of 1 μm coating, it was folded to the level of 2 R.

Therefore, in the present invention, when the thickness of the reinforcing coating was from 1 μm to 15 μm, an ultra-thin glass that protects the surface of the flexible display was possible.

As a result, the range of the thickness for applying the reinforcing coating is as follows.

1/30 ≤ T1 (thickness of reinforcing coating)/T (thickness of ultra-thin glass) ≤ 15/30

In this case, the coating may be a film attached to the ultra-thin glass. That is, various types of transparent films may be used, and for example, a CPI film may also be used.

On the other hand, if another functional layer is additionally present on the ultra-thin glass, the coating may be present on the other functional layer. Accordingly, in this case, the coating is a coating positioned on the top of the flexible display.

That is, there is not only a hard coating on the top of the ultra-thin glass, that is, an anti-fingerprint function may exist. Also, a PET layer may be present between the hard coating layer and the ultra-thin glass layer, and an optical adhesive material (OCA) layer used to minimize light loss or reflection may also be present.

7 is a view showing an ultra-thin glass having a multilayer structure.

A common common knowledge known to those who study film layers is that "even if the total thickness is the same, the tensile strength is better when two or three films are used and overlapped rather than one film".

In the present invention, an attempt was also made for this.

That is, as in FIG. 7 , the first ultra-thin glass 10-1 and the second ultra-thin glass 10-2 are provided, and the first ultra-thin glass 10-1 and the second ultra-thin glass 10 are provided. The adhesive layer 15 is formed between -2).

In addition, another resin film layer may be present in the adhesive layer.

At this time, in the present invention, it is an object to manufacture an ultra-thin glass for protecting the flexible display surface, and thus, the ultra-thin glass 10 (10-1) (10-2) of the present invention is also folded. Accordingly, in the ultra-thin glass 10, 10-1, and 10-2 of the present invention, there are a folded region (non-fixed region) and an unfolded region (fixed region).

And, in FIG. 7 , the folded area (non-fixed area) is a section marked with G shown in the embodiment of FIG. 1 .

Naturally, the adhesive must also show a difference in adhesive strength in the folded area (non-fixed area) and the non-folded area (fixed area). That is, it can be expressed as

Adhesive force of the adhesive in the folded area (non-fixed area) < Adhesive force of the adhesive in the unfolded area (fixed area)

That is, the “adhesive force of the adhesive in the folded region (non-fixed region)” is weaker than the “adhesive force of the adhesive in the unfolded region (fixed region)”.

On the other hand, when actually coating the adhesive, it becomes difficult to accurately distinguish and coat the boundary between the folded region (non-fixed region) and the non-folded region (fixed region). Visible does not mean exactly dividing boundaries. That is, it will be understood that the adhesive force of the adhesive mainly coated on the folded region (non-fixed region) is weaker.

8 is a diagram of an embodiment showing a practical application example of the present invention.

Attaching the ultra-thin glass 10 (or the ultra-thin glass 10-1, 10-2) having multiple layers of the present invention to the display unit 50 (the part including the display and the input device) of the flexible display will do

At this time, as in the embodiment of FIG. 7 , there are a fixed region and a non-fixed region, and even at this time, the adhesive force of the adhesive used in the non-fixed region is weaker as in the embodiment of FIG. 7 .

9 is a view of an embodiment showing the extent to which the ultra-thin glass is stretched.

If R is 1.5 and the thickness of the ultra-thin glass is 30 μm, the length of the ultra-thin glass on the outer surface is compared to the distance between the inner surface of the ultra-thin glass and the outer ultra-thin glass. should be increased by 4% compared to the length of the ultra-thin glass present on the inner surface,

In addition, when R is 5 and the thickness of the ultra-thin glass is 65 μm, when comparing the distance between the surface of the ultra-thin glass existing inside and the ultra-thin glass existing on the outside, the The length should be increased by 2.6% over the length of the ultra-thin glass present on the inner surface,

As a result, in the present invention, the outer surface should be increased by 2.6% to 4% than the inner surface as it is folded.

10 and 11 are views showing the method of the embodiment of precipitating the ultra-thin glass in the reinforcing solution.

In general, during the strengthening process of the ultra-thin glass 10, there is a process of precipitating the ultra-thin glass 10 in a reinforcing solution, and in this case, a method of horizontally positioning the thinly processed ultra-thin glass is used.

However, when the strengthening process is performed by horizontally positioning the thinly processed ultra-thin glass, a defect occurs in that the ultra-thin glass 10 is bent and the flat shape cannot be maintained.

Therefore, in order to solve this problem, as in the embodiment of FIG. 10 , a method of placing a plurality of ultra-thin glasses 10 in a vertical direction and then depositing the reinforcement liquid 90 in the reinforcement liquid container 100 containing the used

And, although omitted in the embodiment of Figure 10, the upper portion of each of the ultra-thin glass 10 is fixed.

11 is a view showing the depth in which the ultra-thin glass 10 is immersed in the strengthening liquid. 1 to 3 of the present invention, there is a distance G of the area in which the ultra-thin glass is folded. That is, only the region (region G in FIGS. 1 to 3 ) of the ultra-thin glass 10 positioned at the foldable portion of the flexible display may be strengthened.

Therefore, even in the embodiment of FIG. 10 , when the ultra-thin glass 10 is immersed in the reinforcing solution, the G region may be immersed in the reinforcing solution 90 . That is, it is not necessary that all of the first film glass 10 be immersed in the reinforcing solution 90 .

That is, the following relationship exists.

SL ≥ GT/2 + G/2

SL: the length of the depth at which the ultra-thin glass 10 is immersed in the reinforcing solution 90

GT: the total length of the ultra-thin glass 10

G: The length of the region in which the ultra-thin film glass 10 is folded.

On the other hand, due to the above conditions, when the ultra-thin glass is strengthened by the method of the embodiment of FIG. be different".

That is, in FIG. 11 , the stress values or DOL values of the A zone and the B zone, which are side edges of the ultra-thin glass 10 based on the folded center, are different from each other.

On the other hand, a commercialized smart phone employing a flexible display cannot employ a digitizer function. This is because, in order to use the digitizer, a pen must be used, and as the pen is used, the surface of the flexible display made of the resin film is worn.

However, since the ultra-thin glass is used in the present invention, the smartphone using the ultra-thin glass 10 of the present invention does not wear the flexible display surface even if the digitizer function is employed.

Accordingly, the embodiments of FIGS. 12 to 14 are diagrams of an embodiment showing a method of employing a digitizer in a flexible display.

That is, FIGS. 12 to 14 are diagrams of an embodiment showing a method in which a digitizer is provided.

12 is a diagram of an embodiment showing a cross-sectional structure of a commercially available flexible display. That is, the two fixed substrates 20-1 and 20-2 support the foldable and unfoldable flexible display, the base film 25 exists under the flexible display unit 50, and the input device is on the flexible display. The part 52 is present, and the ultra-thin glass 10 of the present invention is present on the input device part 52 .

And, FIG. 13 is a diagram showing the layered structure three-dimensionally by separating it.

On the other hand, in the case of a conventionally commercialized flexible display, the input device unit 52 includes a touch panel function. And, in order to minimize the layer structure of the flexible display, when the touch panel layer is provided on the top of the flexible display unit 50 conventionally, it is provided as a coating layer instead of as a separate layer.

Accordingly, by manufacturing the touch panel layer as a coating layer rather than as a separate layer, the thickness of the touch panel layer is formed within 30 μm. In this case, the touch panel layer includes a conductive film layer and an insulating resin film layer.

14 is a diagram of an embodiment showing the input device unit 52 in detail. Based on the base film 25 layer, a TFT layer 50a is formed over the base film 25 layer. The TFT layer 50a includes a display pixel connection electrode wiring, an OLED layer, and the like.

And an encap 50b layer is formed on the TFT layer 50a. The encaps 50b layer protects the TFT layer 50a over the TFT layer 50a. Therefore, an insulating function should be provided to the TFT layer by coating with an organic layer, but the breathability (property through which moisture or oxygen, etc.) of the organic layer should be blocked by coating the inorganic layer. And "SiN _X " is generally used as an inorganic layer. In addition, when the encaps 50b layer is formed, a multilayer structure may be formed in the order of organic coating, inorganic coating, and organic coating.

Then, the input device 52 is formed on the encaps 50b layer. 14 , the input device 52 includes a digitizer electrode layer 52a, an inner insulating layer 52b, a touch panel electrode layer 52c, and an outer insulating layer 52d.

In addition, in the present invention, in order to minimize the structure of the flexible display layer, when the digitizer electrode layer 52a and the internal insulating layer 52b are further formed, it is formed as a coating layer instead of a separate layer.

That is, the thickness of the inner insulating layer 52b serving to insulate the upper digitizer electrode layer 52a and the touch panel electrode layer 52c is made thinner than that of the encaps layer 50b, and the thickness is also set to within 30 μm. In addition, as the inner insulating layer 52b, only one layer from an organic layer and an inorganic layer may be used. This is because the insulating function is sufficient.

Then, an external insulating layer 52d is formed on the touch panel electrode layer 52c. The outer insulating layer 52d is formed to be thicker than the inner insulating layer 52b because reliability is also required.

15 is a diagram of an embodiment showing a method in which a camera is formed on a flexible display.

The weights of the multiple layers present on both sides of the TFT layer 50a as seen in the structures of FIGS. 12 to 14 should be balanced with each other. Accordingly, SUS is used as the base film layer.

Since the glass weighs more than the resin and the ultra-thin glass 10 is used in the present invention, a material heavier than the resin should be used on the opposite side of the TFT layer 50a, and the material that can be used is an alloy metal or It becomes SUS.

In fact, a dummy layer (in the previous technical description of the present invention, since the dummy layer is a prior art, an additional amplification of the dummy layer is omitted.) is added and used to the base film 25, and SUS is used as the dummy layer and alloy metals are used.

On the other hand, in order to mount the camera inside the flexible display, a camera hole is required, and a view showing the camera hole is shown in FIG. 15 .

Since light has to reach the camera in the region where the camera is located, a camera hole 20a that allows light to pass through must be formed in the fixed substrates 20-1 and 20-2, and SUS (or A camera hole 26a for allowing light to pass through the alloy metal 26 should also be formed.

In addition, a transparent resin is filled inside the camera holes 20a and 26a.

Meanwhile, in the present invention, the camera holes 20a and 26a mean that the cutout is formed so that light is transmitted through the camera (image element), and does not necessarily mean the shape of the hole (circular sphere).

16 is a view of an embodiment showing the surface roughness of the ultra-thin glass.

From an empirical point of view of performing a polishing process to manufacture an ultra-thin glass, it is found that the greater the surface roughness, the greater the degree of damage to the ultra-thin glass 10 due to an external impact.

For example, if a ball drop test (an experiment in which an iron ball having a weight of 1 g is dropped on the surface of ultra-thin glass is conducted), the above phenomenon can be clearly discovered.

On the other hand, the surface roughness can be measured using a normal roughness meter or a non-contact type roughness meter.

As shown in the drawing of the embodiment of FIG. 16 , when the height of the largest mountain is RL and the height of the ultra-thin glass is T, whether the ball drop test passes or not is determined according to the value. The ball drop test is an experiment in which a 1 g iron ball is dropped from a height of 50 cm.

- When the thickness T is 20 μm,

: If the height RL of the largest mountain is 5 μm, the Ball Drop test did not pass.

: If the height RL of the largest mountain is 3 μm, it partially passed the Ball Drop test.

: If the height RL of the largest mountain is 2 μm, it passed the Ball Drop test.

- When the thickness T is 30 μm,

: If the height RL of the largest mountain is 8 μm, the Ball Drop test did not pass.

: If the height RL of the largest mountain is 5 μm, the Ball Drop test has passed.

- When the thickness T is 40 μm,

: If the height RL of the largest mountain is 10 μm, the Ball Drop test did not pass.

: If the height RL of the largest mountain is 8 μm, it did not pass the Ball Drop test.

: If the height RL of the largest mountain is 6 μm, it passed the Ball Drop test.

- When the thickness T is 50 μm,

: If the height RL of the largest mountain is 10 μm, the Ball Drop test did not pass.

: If the height RL of the largest mountain is 8 μm, the Ball Drop test has passed.

: If the height RL of the largest mountain is 7 μm, the Ball Drop test has passed.

- When the thickness T is 60 μm,

: If the height RL of the largest mountain is 12 μm, the Ball Drop test did not pass.

: If the height RL of the largest mountain is 10 μm, the Ball Drop test has passed.

: If the height RL of the largest mountain is 8 μm, the Ball Drop test has passed.

According to the above experiment, it can be seen that if the height of RL is within 17% of the height of T when T is 30 μm, the ball drop test is passed.

And, it can be seen that the ball drop test is passed when the height of RL is within 17% of the height of T when T is 60 μm.

As a result, it can be seen that the ball drop test is passed when RL/T has a roughness of 0.17 or more. This is an experiment in which an iron ball of g is dropped from a height of 50 cm.)

On the other hand, in the present invention, the meaning of the highest mountain height means the highest value in the normal distribution value, that is, when the x-axis is the frequency of mountains and the y-axis is the height of the mountain in a normal xy coordinate, y The largest value on the axis is the height of the largest mountain illustrated in Fig. 15 of the present invention. (In this case, the frequency of the mountains means the number. For example, 5 μm may have 10 heights, and 6 μm may have 8 mountains in 1 cm square.)

17 and 18 are diagrams of an embodiment showing the thickness condition occupied by the ultra-thin glass in the entire flexible display.

The TFT layer 50a present in the flexible display is preferably located at the center of gravity in the flexible display.

As shown in FIG. 17 , in the flexible display, a base film 25 layer and a dummy film 27 exist under the TFT layer 50a, and the encap 50b, the input device unit 52, and the polarization layer are on the TFT layer. (28), the ultra-thin glass 10 is present.

The TFT 50a includes an electrode wiring and an OLED layer, and the base film 25 layer is a coating film on which the TFT layer is mounted, and is a resin material or inorganic material that also functions to planarize the surface, and the dummy film 27 is a thickness control. It is a film that is additionally attached, such as, and in some cases, the base film 25 and the dummy film 27 may be integrated.

In addition, the encap (50b) layer is coated with an organic layer to provide an insulating function to the TFT layer, but by coating an inorganic layer, the air permeability (property through which moisture or oxygen, etc.) As the inorganic layer, "SiN _X " is generally used. In addition, when the encaps 50b layer is formed, a multilayer structure may be formed in the order of organic coating, inorganic coating, and organic coating.

In addition, the input device unit 52 is a layer that functions as a touch panel or a digitizer, and thus, the input device unit 52 includes a plurality of layers, such as an electrode layer and an insulating layer.

In addition, the polarization layer 28 is a layer having a normal polarization function, and a plurality of layers are included here as well.

On the other hand, the ultra-thin glass 10 of the present invention is coated on the outermost part of the flexible display. Of course, the ultra-thin glass 10 may have a coating layer or a film preventing scattering of the ultra-thin glass 10 .

At this time, a plurality of layers (encap 50b, input device 52, polarization layer 28, ultra-thin glass 10, etc.) existing on the TFT layer are included, and on the TFT layer 52a in the flexible display. It means a plurality of layers that exist.) The thickness is called "UL",

of a plurality of layers existing under the TFT layer (including a base film 25 layer, a dummy film 27, and the like, meaning a plurality of layers existing under the TFT layer 52a in the flexible display.) When the thickness is "LL",

The thickness of the "LL" should be greater than the thickness of the "UL".

And, the basis for "the thickness of the LL must be greater than the thickness of the UL" is as follows.

- In order for the flexible display to perform a stable operation in which the flexible display is folded and unfolded, the TFT layer 52a in the flexible display must exist at the center of gravity.

- The weight of the "UL layer" and the weight of the "LL layer" must be the same or similar within the error range.

- The density of tempered glass is 2.54 (2.76 for other types)), and the general density of resin is 0.915 to 0.925, so the density of tempered glass is 2.76 times or 3 times higher than that of resin on average. Therefore, "the thickness of the LL must be greater than the thickness of the UL" is established.

- Accurate thickness range -

If the thickness of the ultra-thin glass 10 is T in the thickness of UL,

Even if the thickness of "LL" becomes "thickness of UL - T X (2/3)", when the weight is considered, the weight of "LL" and the weight of "UL" become similar.

This formula is made on the assumption that ultra-thin glass has three times the density of resin. Also, the reason why they are similar is because there are variables when the weight is considered due to the existence of various layers.

That is, when the “thickness of UL” is 200 μm and the thickness of the ultra-thin glass is 50 μm,

By calculation of "200 - 50 X 2/3 = 166.7", the "thickness of LL" may be 166.7 mu m.

As a result, if the thickness of the ultra-thin glass is T,

A value of "UL - T x 2/3" becomes an appropriate thickness of "LL". However, since there are multiple layers and an adhesive electrode layer, and there is a range for the values of resin and ultra-thin glass, the error range must be considered, and when this point is taken into account, "(UL - T x 2/3") ± 33.3 %" will be the thickness range of "LL".

This can be generalized and expressed as an expression as follows.

"(UL - T + T X K1) ± 33.3 %" is the thickness range of "LL".

K1 = density of ultra-thin glass/density of resin,

18 is a diagram of an embodiment in which SUS is used as a dummy film.

The density of SUS is 7.75 to 7.93. The average density of SUS is 7,84, and the average density of ultra-thin glass is 2.65. Therefore, the weight of SUS becomes heavier than that of ultra-thin glass (average density of resin 0.92).

Therefore, based on the basis described in FIG. 13, when the SUS layer 26 is used as the dummy film and ultra-thin glass is used as the flexible display protection material,

"Thickness of UL" becomes thicker than "Thickness of LL".

In a sense, the thickness of the SUS (or metal alloy or metal) layer 26 may be made thinner than the thickness of the ultra-thin film. This is because the density of SUS (or metal alloy or metal) is lower than that of super-film glass, and it is natural that the high-density layer is made to be low in order to balance the weight.

"The weight of SUS is heavier than UTG, and consequently, the thickness of UL becomes thicker than that of LL." , and the value obtained by subtracting the thickness of SUS from LL is called LL1, and the thickness of the SUS layer can be called S. Then, it also means that the value of “T-S” may be larger than the value of “UL1 - LL1”.

- Setting the range of "thickness of UL" and "thickness of LL" when the SUS layer 26 is used as the dummy film.

The density of SUS is 8.52 times greater than that of resin, and the density of ultra-thin glass is 2.88 times greater than that of resin.

Taking this into account, the following formula is established,

UL - T + T X 2.88 = LL - S + S X 8.52 (S is the thickness of the SUS layer.)

However, an error range of 33.3% may be considered in the above equation. Multiple layers, adhesives, electrode etching, etc. may be considered. This is because the densities of glass, resin, and SUS may also be different from the above-mentioned average values.

Therefore, if the error range is set to 33.3%, "UL - T + TX 2.88" can be larger than "LL - S + SX 8.52" within 33.3%, and conversely, "LL - S + SX 8.52" becomes "UL - T" + It can be larger than TX 2.88" within 33.3%.

This can be expressed as a generalized expression as follows.

UL - T + T X K1 = LL - S + S X K2

K1 = Density of ultra-thin glass/density of resin

K2 = density of SUS/density of resin

And, considering the margin of error,

"UL - T + TX K1" may be greater than "LL - S + SX K2" within 33.3 %, and conversely, "LL - S + SX K2" may be greater than "UL - T + TX K1" within 33.3 %. can be

The plurality of layers included in the LL and UL shown in FIGS. 17 and 18 are only representative layers necessary for the description of the present invention. Therefore, it goes without saying that, in addition to the layers shown in Figs. 17 and 18, more functional layers may be included, and even with several additional layers that function (layers not shown in Figs. 17 and 18, but which may be present), TFT If it is above the layer, it is included in the UL, and if it is below the TFT layer, it is included in the LL.

On the other hand, in general, in a flexible display, in addition to the above-mentioned layers of the present invention, PSA (Pressure Sensitive Adhesive Application) layer, transparent polyimide (PI) layer, Cushion Film (layer), PET (Optical axis Control Film) layer , a black matrix layer, etc. may be further present, and as mentioned above, if above the TFT layer, it is included in the UL, and if it is below the TFT layer, it is included in the LL.

19 is a diagram of an embodiment showing a criterion for adhesive force.

19(A) is a view showing a state in which the ultra-thin glass 10 and the polarizing layer 28 or the input device unit 52 are adhered with an adhesive, and FIG. 19(B) is a base film 25 and It is a view showing a state in which the dummy film 27 (or it may be a SUS layer) is adhered with an adhesive.

Since the flexible display repeats the pressing and unfolding operations, an adhesive is used when attaching the layers to each other.

Also, as seen in the drawing of FIG. 18 , since the flexible display is folded with the top inside, the folding radius is small at the top and large at the bottom as seen in FIG. 18 .

Accordingly, the pressure-sensitive adhesive used in (A) of FIG. 19 has a small turning radius, and the pressure-sensitive adhesive used in FIG. 19(B) has a large turning radius. Therefore, the adhesive force of the pressure-sensitive adhesive used in FIG. 19(B) should be smaller than that of the pressure-sensitive adhesive used in FIG. 19(A).

However, since ultra-thin glass having a density three times higher is used, this part is taken into consideration, and consequently, "adhesive force of the adhesive used in FIG. 19(B)" and "adhesion of the adhesive used in FIG. 19(A)" are should be similar to each other. Of course, there is also an error range here, so it should be similar within ±33.3%.

On the other hand, as the pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, a cold release type pressure-sensitive adhesive, a UV pressure-sensitive adhesive, etc. are used, and the antistatic agent is added in a small amount.

The silicone pressure-sensitive adhesive includes an alkenyl group-containing polydiorganosiloxane, a hydrocarbon group, a polyorganosiloxane copolymer, a polyorganosiloxane, a platinum group catalyst compound, and an antistatic agent.

The platinum group catalyst compound is selected from those consisting of platinum black, chloroplatinic acid, chloroplatinic acid-olefin complex, chloroplatinic acid-alcohol coordination compound, rhodium, and rhodium-olefin complex;

The UV adhesive includes an elastomer, an ultraviolet crosslinking resin, an adhesion imparting agent, a polymerization initiator, and a polymerization inhibitor.

The antistatic agent consists of an inorganic salt consisting of a metal cation and an anion, or an onium cation and an anion.

20 to 22 are views showing the digitizer layer and the electrode structure provided in the present invention.

That is, FIG. 20 is a detailed view of the digitizer layer 52a shown in FIG. 14 .

In the digitizer layer 52a, an upper substrate 52a-1, an upper electrode 52a-3 and a lower substrate 52a-2 provided on the upper substrate 52a-1, and the lower substrate 52a-2 are provided. a lower electrode 52a-4 provided in

21 is a diagram illustrating an electrode structure, and is a diagram illustrating shapes of electrodes provided on an upper substrate and a lower substrate, respectively. In this case, the upper substrate may be the lower substrate depending on the electrode design method, and the upper substrate may be the lower substrate.

The pattern electrode of the digitizer is provided as if a plurality of electrode lines 17b of the embodiment of FIG. 21 were formed, and each electrode line 17b is made using a printing method, and for printing, silver (Ag) use paste,

At this time, in the present invention, it is characterized in that the electrode line 17b is made thin so as not to be observed by the eye. In addition, it is preferable that the thickness of the electrode line 17b does not exceed 10 μm.

On the other hand, the interval between the electrode line (17b) and the electrode line (17b) is suitable within 1mm to 10mm,

On the other hand, the content of silver (Ag) in the silver (Ag) paste is 70 to 90% by weight, and an epoxy-based resin or a thermosetting resin is used as the resin in the silver (Ag) paste.

That is, a lower electrode 52a-4 is formed on the lower substrate 52a-2 by a printing method, an insulating film 52a-5 is formed on the lower electrode 52a-4 by a coating method, and again An upper electrode 52a-3 is formed on the insulating film 52a-5 by a printing method, and an upper substrate 52a-1 is formed on the upper electrode 52a-3 by a coating method.

In addition, in FIG. 21 , the active area (digitizer sensor area) 17d and the driving connection unit 17c connected to the digitizer driving unit are also shown.

22 is a method of another embodiment in which an electrode layer is positioned. In a flexible display, there are a plurality of layers, so it may be important to use a method to reduce the number of layers.

That is, the digitizer layer 52a has a structure in which the upper substrate 52a-1 and the lower substrate 52a-1 are omitted. Accordingly, the lower electrode 52a-4 is formed on the encap 50b (refer to the description of FIGS. 14 and 14) by a printing method, and the insulating film 52a-5 is formed by a coating method on the lower electrode 52a-4. ) is formed, and an internal insulating layer 52b (refer to the description of FIGS. 14 and 14) is formed on the insulating film 52a-5 by printing again.

Then, a touch electrode (an electrode present in the touch layer described with reference to FIG. 14) is formed on the inner insulating layer 52b.

23 is a diagram of an embodiment showing how a digitizer layer is provided under the TFT layer.

Finding a method for increasing the transmittance of a portable display device is also one of the important factors. Accordingly, if the digitizer layer is positioned under the TFT layer 50a that emits light, it is possible to compensate for the disadvantage that the transmittance is reduced by the digitizer layer 52a.

Accordingly, a lower electrode 52a-4 is formed on the encap 50b, an insulating film 52a-5 is formed on the lower electrode 52a-4 by a coating method, and again on the insulating film 52a-5. An upper electrode 52a-3 is formed by a printing method, and an intermediate insulating film 52e is formed on the upper electrode 52a-3 by a coating method.

On the other hand, in the present invention, a conventional insulating film used for manufacturing a flexible display is used as the insulating film, that is, the material of the insulating film is listed below.

Meanwhile, the insulating film may be, for example, an organic insulating film. Examples of such organic insulating films include acrylic polymers such as polymethyl methacrylate (PMMA), polystyrene (PS), polymer derivatives having phenol groups, imide polymers, arylether polymers, amide polymers, fluorine polymers, and p-xylene polymers. Polymers, vinyl alcohol-based polymers, and mixtures thereof may be included.

It may be formed of an acrylic organic material or BCB (Benzocyclobutene).

It may be formed of an inorganic material such as silicon oxide, silicon nitride or silicon oxynitride.

It may be formed in a single layer or in multiple layers of a material such as silicon oxide or silicon nitride.

It may be formed of various materials, such as a plastic material such as polyethylen terephthalate (PET), polyethylen naphthalate (PEN), or polyimide.

In this case, in the present invention, the transmittance and thickness of the insulating film may be specified.

In the digitizer layer 52a, an insulating film 52a-5 is formed between the upper electrode 52a-3 and the lower electrode 52a-4, and the transmittance of the insulating film should be 90% or more, and 97% is sufficient. It is more preferable to maintain more than 98% in

Meanwhile, the thickness of the insulating layer 52a - 5 should be determined in consideration of the entire flexible display, and a range of 0.1 μm to 5 μm or 10 μm is suitable. In addition, the thickness of the insulating layer 52a - 5 should be smaller than the thickness of the encap 50b.

In addition, the transmittance and thickness of the upper substrate 52a-1 and the lower substrate 52a-2 in the digitizer layer 52a are manufactured according to the transmittance and thickness of the insulating layer 52a-5. That is, the transmittances of the upper substrate 52a-1 and the lower substrate 52a-2 should be 90% or more, and it is more preferable to maintain 97% to 98% or more to be sufficient. In addition, the thickness of the upper substrate 52a-1 and the lower substrate 52a-2 is preferably 0.1 μm to 5 μm or 10 μm. In addition, the thickness of the insulating layer 52a - 5 should be smaller than the thickness of the encap 50b.

24 to 27 are diagrams of another embodiment of the present invention.

24 and 25, the flexible display 50' is wound on two rolls 100-1 and 100-2.

At this time, the display 50' shown in FIGS. 24 to 26 means a flexible display 50' to which all films having various functions and ultra-thin glass are integrally attached.

The first roll 100-1 and the second roll 100-2 form a pair, and the flexible display 50' wound on the first roll 100-1 is formed by the second roll 100-2. ), and the flexible display 50 ′ wound on the second roll 100 - 2 may be transferred to the first roll 100 - 1 .

In this case, the rolls 100-1 and 100-2 may have a cylindrical shape and may wind the flexible display 50', which is a film having a constant width.

In addition, on the other hand, as the direction indicated by the arrow shown in FIG. 25 , the distance between the first roll 100-1 and the second roll 100-2 is made close to each other, and the first and second rolls are flexible. The display 50' may be wound.

At this time, there is a method in which the distance between the first roll 100-1 and the second roll 100-2 approaches or moves away from each other, and in this case, the first roll 100-1 and the second roll 100-2. Among them, there is a method of moving only one roll, and there is a method of moving both the first roll 100-1 and the second roll 100-2.

In addition, as the distance approaches, the flexible display 50' may be wound or unwound on both the first roll 100-1 and the second roll 100-2, and the first roll 100-1 and the first roll 100-1 may be unwound. ) and the second roll 100 - 2 , the flexible display 50 ′ may be wound or unwound on only one roll.

26 is a view illustrating a method in which the flexible display 50' is wound on at least one of the first roll 100-1 and the second roll 100-2. The diameters of the first and second rolls 100-1 and 100-2 are referred to as D2, and the flexible display 50' is maximally wound (the first and second rolls 100-1 and 100-2). 2) The diameter of the state in which the distance between them is closest) is referred to as D1 (the value of the sum of the thicknesses of the multiple layers of the flexible display wound up to the maximum and the diameters of the rolls 100-1 and 100-2), and the flexible display Let the thickness of (50') be T.

27 is a view showing a plan view of a flexible display wound on a roll. The left view of FIG. 27 is a view of a state in which the distance between the first roll and the second roll 100-1 and 100-2 is the closest, and the right view of FIG. 27 is the first roll and the second roll 100- 1) The distance between (100-2) is the farthest.

Let L1 be the length of the width of the flexible display unfolded when the two rolls 100-1 and 100-2 are closest to each other, and the flexible display unfolded when the two rolls 100-1 and 100-2 are most distant from each other is referred to as L1. The length of the width of the display may be referred to as L2.

Then, according to Figs. 26 and 27, the following equation is established.

L2 - L1 = 2π(D/2) + 2π(D/2 + T) + 2π(D/2 + 2T) + - - - + 2π(D/2 + nT)

T is the flexible display thickness.

At this time, the value of the L1 and L2 should be taken into account of the actual width of the smartphone, and when the length of the width of the smartphone is large, it may be 100 mm, and thus the value of L2 may be set to 200 mm, and The value of L1 can be set to 20mm, which is 1/5 of the width of the smartphone. Therefore, the maximum value of L2 - L1 is 180m.

On the other hand, it is assumed that the minimum value of L2 - L1 is increased by two times the width of the smartphone by the rollable effect, and the width of the smartphone is also 5 cm instead of 10 cm. Assuming that the size of is only doubled, the minimum value of L2 - L1 is 50 mm,

Therefore, 50 mm and 180 mm can be substituted into the above equations.

And the R value of the ultra-thin glass 10 used in the present invention is 1.5, and in consideration of the realistic structure, the value of D2 may be 2 mm. Of course, considering the thickness of the smartphone device, the D2 value can be set to 20mm.

Then the above formula becomes:

180 = L2 - L1 = 2π(D/2) + 2π(D/2 + T) + 2π(D/2 + 2T) + - - - + 2π(D/2 + nT) = 2π(D/2) + 2π n (D/2) + 2π((n+1)n/2) -- (1)

50 = L2 - L1 = 2π(D/2) + 2π(D/2 + T) + 2π(D/2 + 2T) + - - - + 2π(D/2 + nT) = 2π(D/2) + 2π n (D/2) + 2π((n+1)n/2) -----(2)

In other words. The range of the value of n exists between the value of n obtained in Equation (1) above and the value of n obtained in Equation (2) above. And n is the range of the number of times the flexible display 50' is wound around the first roll 100-1 or the second roll 100-2.

For reference, the thickness of the rolls 100-1 and 100-2 can be actually used from 2 mm to 20 mm, and by reflecting the thickness of the rolls 100-1 and 100-2 used, the formula (1) ) (2), the range of n values is obtained.

That is, when the thickness of the rolls 100-1 and 100-2 is 2 mm, the range of n is obtained by substituting a value of 2 into the equations (1) and (2) above. And, when the thickness of the rolls 100-1 and 100-2 is 20 mm, it means that the value is obtained by substituting a value of 20 into the equations (1) and (2). As a result, the number n of the number of times the flexible display 50' is wound around the rolls 100-1 and 100-2 is determined by the diameter values of the rolls 100-1 and 100-2.

Claims (11)

In the ultra-thin glass that protects the surface of the flexible display equipped with the digitizer used for the display of the in-folding method smartphone, The thickness of the ultra-thin glass is 15 μm to 70 μm, The ultra-thin glass is an ultra-thin glass for protecting the surface of a flexible display, characterized in that it is strengthened by a temperature raising step, an aging step, and a cooling step. The ultra-thin glass for protecting the flexible display surface according to claim 1, wherein the stress of the ultra-thin glass is 450 Mpa to 800 Mpa. The ultra-thin glass for protecting the flexible display surface according to claim 1, wherein the elastic limit of the ultra-thin glass is 1.5% to 5%. According to claim 1, When processing the edge of the ultra-thin glass side, When the etched distance at the boundary of the ultra-thin glass is L and the thickness of the ultra-thin glass is T, the ratio between the L value and the T value is 1/6 ≤ L/T ≤ 1/2 Ultra-thin glass to protect the surface of the flexible display, characterized in that. According to claim 1, wherein the thickness of the coating coating the surface of the ultra-thin glass is 1/30 ≤ T1 (thickness of coating)/T (thickness of ultra-thin glass) ≤ 15/30 Ultra-thin glass to protect the surface of the flexible display, characterized in that. The ultra-thin glass for protecting the flexible display surface according to claim 1, wherein, in the heat treatment process to strengthen the ultra-thin glass, the cooling rate is from 7.5°C per minute to 25°C per minute. . The ultra-thin glass for protecting the flexible display surface according to claim 1, wherein an input device is provided between the flexible display and the ultra-thin glass, and a touch panel layer and a digitizer layer are provided in the input device. . The ultra-thin glass of claim 7, wherein the touch panel layer is positioned above the digitizer layer when the touch panel layer and the digitizer layer are provided inside the input device unit. The method according to claim 8, wherein a TFT layer and an encap layer are present in the display unit, The touch panel layer includes a touch panel electrode layer 52c, the digitizer layer includes a digitizer electrode 52a layer, and an internal insulating layer between the touch panel electrode layer 52c and the digitizer electrode 52a layer When (52b) is present, The thickness of the inner insulating layer (52b) is an ultra-thin glass for protecting the surface of the flexible display, characterized in that thinner than the thickness of the encap. The ultra-thin glass of claim 1, wherein a camera hole through which light can pass is provided in a fixed substrate that supports the flexible display to be folded and unfolded. The ultra-thin glass of claim 1, wherein when the SUS layer or the alloy metal layer is present in the flexible display, a camera hole through which light can pass is provided in the SUS layer or the alloy metal layer.

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