CN110675755B - Foldable display device - Google Patents
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- CN110675755B CN110675755B CN201910967944.9A CN201910967944A CN110675755B CN 110675755 B CN110675755 B CN 110675755B CN 201910967944 A CN201910967944 A CN 201910967944A CN 110675755 B CN110675755 B CN 110675755B
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
- G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
- G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0412—Digitisers structurally integrated in a display
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- Physics & Mathematics (AREA)
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- General Engineering & Computer Science (AREA)
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- Devices For Indicating Variable Information By Combining Individual Elements (AREA)
- Electroluminescent Light Sources (AREA)
Abstract
The embodiment of the invention provides a foldable display deviceThe utility model relates to a show technical field for provide a mode of measuring collapsible display device's ability of buckling. The foldable display device comprises P film layers which are arranged in a stacked mode; bending capability phi of foldable display device
Positive correlation; wherein k is1Is a coefficient, MiThe interfacial bonding ability of the ith and (i + 1) th membrane layers; s is the elongation at break of the film layer with the minimum elongation at break among the P film layers, h is the distance between the central plane of the film layer with the minimum elongation at break among the P film layers and the first surface of the 1 st film layer, wherein the first surface is the surface of the 1 st film layer away from the 2 nd film layer; t is the thickness of the film layer with the smallest elongation at break among the P film layers, yNIs the distance between the neutral plane of the foldable display device and the first surface of the 1 st film layer.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of display, in particular to a foldable display device.
[ background of the invention ]
With the continuous development of display technology, various display products with different characteristics are produced to meet different use requirements. A foldable display device is a novel display product with flexibility. When the foldable display device is used, a user can fold the foldable display device according to needs so as to reduce the size of the display device and improve the portability of the display device. Alternatively, the foldable display device may be unfolded to obtain a large display screen. At present, how to improve the performance of the foldable display device has become a focus of attention of researchers.
[ summary of the invention ]
In view of the above, embodiments of the present invention provide a foldable display device, which provides a way to measure the bending resistance of the foldable display device, and in the design of the foldable display device, the film layers in the foldable display device can be selected based on this, and the stacking sequence of the film layers in the foldable display device can be designed reasonably, so that the bending resistance of the designed foldable display device can meet the use requirement.
In one aspect, embodiments of the present invention provide a foldable display device, which includes P film layers stacked one on another;
bending capability phi of the foldable display device and
positive correlation;
wherein k is1Is a coefficient, MiThe interfacial binding capacity of the ith and (i + 1) th membrane layers; s is the elongation at break of the P film layers with the minimum elongation at break, h is the distance between the central plane of the P film layers with the minimum elongation at break and the first surface of the 1 st film layer, wherein the first surface is the surface of the 1 st film layer away from the 2 nd film layer; t is the thickness of P film layers with the minimum breaking elongation, yNIs the distance between the neutral plane of the foldable display device and the first surface of the 1 st film layer.
Optionally, a plurality of the film layers comprise:
a flexible display panel;
the functional film layer is positioned on one side of the flexible display panel;
the glue material is positioned between the flexible display panel and the functional film layer;
the interface bonding capacity M between the rubber material and the functional film layer meets the following requirements:
M＝k2E1 log(tanδ×E2)≥50；
wherein k is2Is a coefficient; e1The interfacial energy between the adhesive material and the functional film layer; e2The elastic modulus of the rubber material is shown; tan delta is the loss factor of the glue.
Optionally, k is more than or equal to 0.52≤1.5。
Optionally, E1≥30mJ/m2。
Optionally, at-50 deg.C to 100 deg.C, tan delta satisfies 0.1 ≤ tan delta ≤ 2.
Optionally, E is more than or equal to 0.1GPa2≤5GPa。
Optionally, the interface bonding capability M between the adhesive material and the functional film layer and the thickness x of the adhesive material satisfy:
m ═ alnx, where a is a coefficient.
Optionally, a is more than or equal to 1 and less than or equal to 5.
Optionally, x is more than or equal to 20 μm and less than or equal to 1000 μm.
Optionally, the functional film layer includes a touch layer, a polarizer, a first protection layer and a second protection layer, which are stacked;
the touch layer is positioned on the light emitting side of the flexible display panel, the polarizer is positioned on one side of the touch layer, which is far away from the flexible display panel, and the second protective layer is positioned on one side of the polarizer, which is far away from the flexible display panel; the first protective layer is positioned on the backlight side of the flexible display panel;
the glue material comprises:
the first glue material is positioned between the flexible display panel and the first protective layer;
the second adhesive material is positioned between the flexible display panel and the touch layer;
and the third adhesive material is positioned between the polarizer and the second protective layer.
Alternatively to this, the first and second parts may,
wherein,
Eithe elastic modulus of the ith film layer; h isiIs the distance between the central plane of the ith film layer and the first surface of the 1 st film layer; t is tiIs the thickness of the ith film layer.
The invention makes the bending capability phi of the foldable display device equal to
Positive correlationI.e. to make the bending ability phi inversely related to the distance between the film layer with the smallest elongation at break and the neutral plane of the foldable display device. Can be reduced by designing the foldable display device
That is, the distance between the film layer with the smallest elongation at break and the neutral plane is reduced, and the film layer with the smallest elongation at break is arranged as close to the neutral plane as possible, so as to reduce the stress applied to the film layer with the smallest elongation at break during the bending process, thereby improving the bending capability of the film layer with the smallest elongation at break, and further improving the bending capability of the foldable display device including the film layer with the smallest elongation at break.
Moreover, in the way of measuring the bending ability Φ provided by the embodiment of the present invention, the sum of the bending ability Φ and the interface bonding ability between any two adjacent film layers in the foldable display device is further made
And (4) positively correlating. When the foldable display device is designed, the size of the foldable display device can be increased
Namely, the interfacial bonding capability between two adjacent film layers is increased to improve the bending capability of the foldable display device.
When the foldable display device is designed, the film layer with the smallest elongation at break (namely the most fragile film layer) in the foldable display device is placed on a neutral surface according to the mode of measuring the bending capability phi of the foldable display device provided by the invention, and the interface bonding capability between the film layer and the adhesive material is improved by arranging the adhesive material for bonding the film layer in the foldable display device and combining the film layer and the adhesive material, so that the bending capability of the whole foldable display device is improved.
[ description of the drawings ]
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Figure 1 is a schematic view of a prior art foldable display device,
fig. 2 is a schematic diagram of a foldable display device according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another foldable display device provided in an embodiment of the present invention;
FIG. 4 is a schematic view of another foldable display device provided in accordance with an embodiment of the present invention;
FIG. 5 is a schematic view of the foldable display device shown in FIG. 3 after being folded;
fig. 6 is a schematic view of the foldable display device shown in fig. 4 after being folded.
[ detailed description ] embodiments
For better understanding of the technical solutions of the present invention, the following detailed descriptions of the embodiments of the present invention are provided with reference to the accompanying drawings.
It should be understood that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be understood that although the terms first, second, etc. may be used to describe the glue in embodiments of the present invention, the glue should not be limited to these terms. These terms are only used to distinguish the individual glue materials from each other. For example, the first rubber material may also be referred to as a second rubber material, and similarly, the second rubber material may also be referred to as a first rubber material without departing from the scope of the embodiments of the present invention.
As shown in fig. 1, fig. 1 is a schematic diagram of a foldable display device in the prior art, wherein the foldable display device includes a flexible display panel 1 ', and in particular, the flexible display panel 1 ' includes a substrate 10 ', a pixel circuit layer 11 ', a light emitting device layer 12 ' and an encapsulation layer 13 ' formed on one side of the substrate 10 '.
In addition to the image display function, in order to enrich the use function of the foldable display device, a plurality of functional film layers having different functions are further provided in the foldable display device. For example:
in order to make the foldable display device have a touch function, so that a user can use the foldable display device more conveniently through touch operation, a touch layer 2 'is generally disposed on the light-emitting side of the flexible display panel 1'.
In order to increase the image display contrast of the foldable display device and reduce the reflection of ambient light by the foldable display device, a polarizer 3 'is usually further disposed on the light exit side of the flexible display panel 1'.
In order to protect the foldable display device, a protective layer may be further disposed on the outermost side of the foldable display device, and specifically, a first protective layer 41 'and a second protective layer 42' for protecting the foldable display device may be disposed on the light emitting side and the backlight side of the foldable display device, respectively.
In order to enhance the stability of the functional film layer in the foldable display device and prevent the functional film layer from falling off and moving, a glue material is generally used to bond the functional film layer and other film layers located above and below the functional film layer. Exemplarily, as shown in fig. 1, the substrate 10 ' and the first protective layer 41 ' are bonded by a first adhesive 51 ', the encapsulation layer 13 ' and the touch layer 2 ' are bonded by a second adhesive 52 ', and the polarizer 3 ' and the second protective layer 42 ' are bonded by a third adhesive 53 '.
In the process of implementing the present invention, the inventors have studied and found that, in the foldable display device in the prior art, since stress is repeatedly applied to each film layer therein during use, the foldable display device is easily subjected to bending failure. Moreover, two failure modes often occur when the foldable display device is bent: one is failure due to sliding separation of adjacent membrane layers. For example, as shown in fig. 1, a degumming phenomenon is easily occurred between the second protection layer 42 'and the third glue material 53', that is, a separation phenomenon of the third glue material 53 'and the second protection layer 42' occurring during the process of bending the third glue material 53 'and the second protection layer 42' along with the folding of the foldable display device. Another is failure due to cracking of one or more of the film layers of the foldable display device. For example, the second protective layer 42 'and the polarizer 3' shown in fig. 1 are cracked by bending. The former situation arises because: because the interface between two adjacent film layers is subjected to tensile stress or compressive stress in the bending process, if the tensile stress or the compressive stress is greater than the interface bonding force between the two adjacent film layers, the two adjacent film layers can be separated. The latter occurs because the external forces applied during bending exceed the maximum stress that some of the film layers in the foldable display device can withstand.
Based on this, an embodiment of the present invention provides a foldable display device, as shown in fig. 2, fig. 2 is a schematic diagram of a foldable display device provided in an embodiment of the present invention, where the foldable display device includes P film layers stacked together: f1、F2、……、Fp-1、Fp。
The embodiment of the invention provides that the folding capability phi of the foldable display device comprising the P film layers is equal to that of the foldable display device
And (4) positively correlating. Wherein k is1Are coefficients. And t is the thickness of the film layer with the smallest breaking elongation in the P film layers. MiIs the ith film layer FiAnd the (i + 1) th film layer Fi+1I-1, 2, … …, P-1, e.g. M1Is the 1 st film layer F1And 2 nd film layer F2The interfacial binding ability of (a). s is the elongation at break of the film with the smallest elongation at break of the P films. h is the central plane of the film layer with the minimum elongation at break in the P film layers and the 1 st film layer F1Of the first surface 11. y isNIs the neutral plane of the foldable display device and the 1 st film layer F1Of the first surface 11. As shown in FIG. 2, the first surface 11 is the 1 st film layer F1Away from the 2 nd film layer F2Of (2) is provided.
It will be appreciated that for a bendable object, when bent, there is a neutral plane, which is stressed to 0 during bending, and which has the same length during bending as in the unfolded state. The film layer on the convex side of the neutral plane is subjected to tensile stress when bent, and the length of the film layer is increased compared with that in the unfolded state. The film on the concave side of the neutral plane is subjected to compressive stress when bent, and the length of the film is reduced compared with that in the unfolded state. And the film layer with different distance from the neutral surface is also subjected to different magnitude of compressive stress or tensile stress.
In designing a foldable display device, in P film layers: f1、F2、……、Fp-1、FpGiven the circumstances, the different arrangement of the P film layers may affect the bending capability of the foldable display device including the P film layers. Also, the elongation at break may be different due to different film layers. And the elongation at break of the film layer affects the bending ability of the film layer. Specifically, the greater the elongation at break of the film layer, the greater its ability to bend. The smaller the elongation at break of the film layer, the poorer the bending ability thereof. Therefore, the film layer with a smaller elongation at break is more likely to cause failure at break than the film layer with a larger elongation at break under the same external force. Therefore, in the way of measuring the bending capability Φ of the foldable display device provided by the embodiment of the inventionBy making the bending capability of the foldable display device phi and
positive correlation, in which the denominator is
Representing the distance between the film layer with the smallest elongation at break and the neutral plane of the foldable display device. That is, in the way of measuring the bending ability Φ provided by the embodiment of the present invention, the bending ability Φ is inversely related to the distance between the film layer having the smallest breaking elongation and the neutral plane of the foldable display device. Can be reduced by designing the foldable display device
That is, the distance between the film layer with the smallest elongation at break and the neutral plane is reduced, and the film layer with the smallest elongation at break is arranged as close to the neutral plane as possible, so as to reduce the stress applied to the film layer with the smallest elongation at break during the bending process, thereby improving the bending capability of the film layer with the smallest elongation at break, and further improving the bending capability of the foldable display device including the film layer with the smallest elongation at break.
Moreover, in the way of measuring the bending ability Φ provided by the embodiment of the present invention, the sum of the bending ability Φ and the interface bonding ability between any two adjacent film layers in the foldable display device is further made
And (4) positively correlating. When the foldable display device is designed, the size of the foldable display device can be increased
Namely, the interfacial bonding ability between two adjacent film layers is increased to improve the bending ability of the foldable display device.
When designing the foldable display device, the film layer with the smallest elongation at break (i.e., the most brittle film layer) in the foldable display device is placed on the neutral plane according to the method for measuring the bending capability Φ of the foldable display device provided by the embodiment of the invention, and the adhesive material for bonding the film layer is arranged in the foldable display device, so that the interface bonding capability between the film layer and the adhesive material is improved through the combination of the film layer and the adhesive material, and the bending capability of the whole foldable display device is improved.
For example, when designing the foldable display device, the quantitative criteria of the bending capability of the foldable display device can be selected according to different use conditions and use requirements of the foldable display device. For example, in the embodiment of the present invention, the bending capability Φ can be set to Φ ≧ 225, which ensures that the films in the foldable display device will not crack and separate from each other during and after bending.
Specifically, in the embodiment of the present invention, bending tests are performed on three different foldable display devices, and the results are shown in table 1, where table 1 is bending test data of the foldable display devices. Wherein the test result OK indicates that the foldable display device has not failed to be bent. The test result NG indicates that the foldable display device has failed to bend.
Table 1 bending test data of foldable display device
As can be seen from table 1, the results of the bending tests of the four foldable display devices represented by the control group 0 and the experimental groups 1-2, 2-1, and 3-1 are OK, and the results of the bending tests of the three foldable display devices represented by the experimental groups 1-1, 2-2, and 3-2 are NG. And, parameters representing the properties of each film layer in the four foldable display devices represented by the control group 0 and the experimental groups 1-2, 2-1, and 3-1 were substituted
The calculated bending capability phi of the foldable display device is 225, 450, 900 and 250 respectively, and the requirement that the bending capability phi is more than or equal to 225 in the embodiment of the invention is met. ComputingThe obtained foldable display devices represented by experimental groups 1-1, 2-2 and 3-2 have bending capacities Φ of 69, 135 and 125, respectively, which do not satisfy the requirement of making the bending capacity Φ larger than or equal to 225 according to the embodiment of the present invention. It has thus also been proven that the way of measuring the bending ability Φ of a foldable display device proposed by the embodiments of the present invention is effectively feasible. When designing the foldable display device, the design can be as follows
According to the method, each film layer in the foldable display device is selected, and the stacking sequence of each film layer in the foldable display device is reasonably designed, so that the bending capacity of the designed foldable display device meets the use requirement.
In addition, as can be seen by comparing the data of the experimental groups 1-1, 1-2 and the control group 0, the distance between the film layer having the smallest elongation at break and the neutral plane was increased, that is, the distance between the film layer having the smallest elongation at break and the neutral plane was increased, based on the control group 0
Then, the foldable display device suffers from a bending failure. By reducing
Then, the foldable display device is not subjected to bending failure. Thus illustrating that the bending ability of the foldable display device decreases with increasing distance between the film layer with the lowest elongation at break and the neutral plane.
As can be seen by comparing the data of the experimental groups 2-1, 2-2 and the control group 0, on the basis of the control group 0, the foldable display device is not bent to fail by increasing the elongation at break of the film layer having the smallest elongation at break, and is bent by decreasing the elongation at break of the film layer having the smallest elongation at break. It is thus demonstrated that the ability of a foldable display device to bend increases with the increase in elongation at break of the film layer with the smallest elongation at break (i.e. the most brittle layer in a foldable display device).
As can be seen by comparing the data of the experimental groups 3-1, 3-2 and the control group 0, in the controlGroup 0 by increasing the sum of the interfacial binding capacities
The foldable display device has no bending failure, and the sum of the interface bonding capacity is reduced
The foldable display device is bent. Thus illustrating the bending capability of the foldable display device as a function of the combined interface capabilities
Is increased.
For example, the position of the neutral plane in the foldable display device can be determined by equation (1):
wherein E isiIs the ith film layer FiThe modulus of elasticity of (a). h isiIs the ith film layer FiWith the 1 st film layer F1Of the first surface 11. t is tiIs the ith film layer FiIs measured. P film layers F included in the foldable display device1、F2、……、Fp-1、FpFor a given situation, the modulus of elasticity as well as the thickness of the respective film layer is determined. Therefore, by changing different stacking modes, the ith film layer F is changediWith the 1 st film layer F1Is arranged at a distance h from the first surface 11iThe neutral plane can be located at different positions. Furthermore, after the position of the neutral plane is determined, according to the mode for measuring the bending capability of the foldable display device provided by the embodiment of the invention, the position of the film layer with the minimum elastic modulus can be reasonably set, so that the foldable display device meeting the requirement of the bending capability is designed.
For example, the plurality of film layers may include a flexible display panel and a plurality of functional film layers, and a glue material between the flexible display panel and the functional film layers for bonding the flexible display panel and the functional film layers. The flexible display panel comprises a flexible substrate, a pixel circuit layer, a flexible display layer and an encapsulation layer, wherein the flexible substrate, the pixel circuit layer, the flexible display layer and the encapsulation layer are stacked, and the flexible display layer is provided with a plurality of pixels to display pictures.
In the foldable display device, if the glue material is separated from the functional film layer, the performance of the foldable display device is greatly affected. Therefore, in the embodiment of the invention, the interface bonding capability M between the adhesive material and the functional film layer is larger than or equal to 50, and the functional film layer and the adhesive material are ensured not to be separated in the bending process and after the foldable display device is bent.
For example, the interfacial bonding capability M between the adhesive material and the functional film layer in the foldable display device can be determined by formula (2):
M＝k2E1 log(tanδ×E2) (2)
wherein k is2Is a coefficient; e1The interface energy between the glue material and the functional film layer; e2The elastic modulus of the rubber material; tan delta is the loss factor of the glue.
Illustratively, 0.5 ≦ k2Less than or equal to 1.5. Alternatively, k may be2Is set to 1.
Illustratively, the above E may be added at room temperature1Is set to E1≥30mJ/m2So that the interface between the glue material and the functional film layer is as large as possible, and the interface bonding capability between the glue material and the functional film layer is improved.
Illustratively, tan delta satisfies 0.1. ltoreq. tan delta. ltoreq.2 at-50 ℃ to 100 ℃. Alternatively, tan δ may be set to satisfy 0.12 ≦ tan δ ≦ 1.8.
Illustratively, the loss factor tan δ is G "/G ' as described above, where G" is the loss modulus, G ' is the storage modulus, and G ' and tan δ are parameters describing the viscoelasticity of the viscoelastic material. After the material of the glue and the environmental conditions are determined, the values of these three parameters can be determined. Alternatively, the loss factor tan δ may be measured by a viscoelasticity measuring apparatus.
Illustratively, the elastic modulus E of the above rubber material2Satisfies the following conditions: e is more than or equal to 0.1GPa2Less than or equal to 5 GPa. Modulus of elasticity E2The determination of (2) can be obtained by a stress-strain curve measured by a tensile test of a rubber material by a tensile testing machine under the conditions of room temperature of 25 ℃ and a strain rate of 0.0525 (1/s). Optionally, E can be2Set to 0.35 GPa.
In the embodiment of the present invention, bending tests are performed on six different adhesive materials and functional film layers, and the results are shown in table 2, where table 2 shows bending test data of the adhesive materials and the functional film layers. Wherein, the test result OK indicates that the glue material and the functional film layer are not separated. The test result NG indicates that the glue was separated from the functional film layer.
Table 2 bending test data of glue and functional film
As can be seen from table 2, in the three cases represented by the experimental groups 1-1, 2-2, and 3-2, the separation of the functional film layer and the adhesive material occurred, the bending test result was NG, the four cases represented by the control group 0 and the experimental groups 1-2, 2-1, and 3-1 did not occur, and the bending test result was OK. And, parameters indicating properties of the functional film layer and the adhesive material in the seven test examples indicated in the control group and the experimental group were substituted into k2E1 log(tanδ×E2) In, let k2The calculated interfacial bonding capacities M between the adhesive and the functional film layer represented by experimental groups 1-1, 2-2, and 3-2 were 47, and 46, respectively, which do not satisfy the requirement of making the interfacial bonding capacity M be greater than or equal to 50 as proposed in the embodiment of the present invention. The calculated interface binding capacities M between the glue material and the functional film layer represented by the control group 0 and the experimental groups 1-2, 2-1 and 3-1 are 57, 76, 59 and 77 respectively, and the requirement that the interface binding capacity M is more than or equal to 50 provided by the embodiment of the invention is met. It is thus also confirmed that the method for measuring the interfacial bonding capability M between the adhesive and the functional film layer in the foldable display device according to the embodiment of the present invention is effectively feasible. When designing the foldable display device, canWith k2E1 log(tanδ×E2) The functional film layer and the adhesive material in the foldable display device are selected according to the selection, so that the functional film layer and the adhesive material are not separated, and the bending capability of the foldable display device comprising the functional film layer and the adhesive material meets the use requirement.
In addition, as can be seen by comparing the data of the experimental groups 1-1, 1-2 and the control group 0, the interfacial energy E between the adhesive material and the functional film layer is increased on the basis of the control group 01The functional film layer and the adhesive material are not separated. By reducing the interfacial energy E between the glue and the functional film layer1The functional film layer and the glue material are separated. Thus illustrating that the interfacial bonding ability increases with the increase of the interfacial energy between the glue and the functional film layer.
As can be seen by comparing the data of the experimental groups 2-1, 2-2 and the control group 0, the elastic modulus E of the rubber material is increased on the basis of the control group 02The functional film layer and the adhesive material are not separated. By reducing the modulus of elasticity E of the rubber material2The functional film layer and the glue material are separated. Thus illustrating the interfacial bonding ability along with the elastic modulus E of the glue2Is increased.
As can be seen by comparing the data of the experimental groups 3-1, 3-2 and the control group 0, the functional film layer and the glue material are not separated by increasing the loss factor tan delta of the glue material on the basis of the control group 0. By reducing the loss factor tan delta of the glue, the functional film layer and the glue are separated. Thus illustrating that the interfacial bonding ability increases with the increase in the loss factor tan δ of the glue.
Illustratively, the embodiment of the present invention further provides another way to measure the interfacial bonding capability M between the adhesive material and the functional film layer, where M and the thickness x of the adhesive material satisfy:
M＝alnx (3)
wherein a is a coefficient. Illustratively, 1 ≦ a ≦ 5.
Optionally, the thickness x of the adhesive material satisfies that x is more than or equal to 20 μm and less than or equal to 1000 μm. If the thickness of the adhesive material is too small, since the microstructure of the surface of the functional film layer is uneven, the excessively thin adhesive material may not fill the unevenness of the surface of the functional film layer, resulting in poor adhesion between the adhesive material and the functional film layer to which the adhesive material is adhered. After the glue material has been filled with the irregularities of the surface of the functional film layer, if the thickness of the glue material is designed to be excessively large, an unnecessary increase in the thickness of the foldable display device will result. Illustratively, the thickness x of the glue material can be set to satisfy 20 μm ≦ x ≦ 300 μm.
For example, the functional film layer may include one or more of a touch layer, a polarizer and a protective layer, which is not limited in the embodiment of the present invention. As shown in fig. 2, the flexible display panel may be other than F1And FPAny one of the other P-2 membrane layers.
Illustratively, the protective layer may include a first protective layer and a second protective layer. The first protective layer is located on the backlight side of the flexible display panel, and the second protective layer is located on the light emergent side of the flexible display panel. The structure of the foldable display device will be described by taking P as 11, that is, an example in which the foldable display device includes eleven film layers stacked one on another. The functional film layer comprises a touch layer, a polarizer, a first protective layer and a second protective layer which are arranged in a stacked mode. The glue material comprises a first glue material, a second glue material and a third glue material. Optionally, the Adhesive material may be Optical Clear Adhesive (OCA) to ensure a display effect of the foldable display device.
The stacking order of most functional film layers is basically fixed based on the role of each functional film layer in the foldable display device. For example, in order to better protect the foldable display device, it is necessary to dispose the protective layer at the outermost side of the foldable display device, e.g., dispose the first protective layer at the outermost side of the light exit side of the foldable display device and dispose the second protective layer at the outermost side of the backlight side of the foldable display device. Also, in order to improve the display effect of the foldable display device, it is necessary to have a polarizer on the light emitting side of the light emitting device. In order to facilitate the touch operation of the user, the touch layer needs to be disposed on the light emitting side of the light emitting device. Specifically, as shown in FIG. 3, FIG. 3 illustrates the practice of the present inventionAnother schematic view of a foldable display device is provided, wherein a first film layer F1The first protective layer Back Film is located on the backlight side of the flexible display panel.
Second film layer F2Is the first glue material OCA 1.
Third film layer F3Is a flexible substrate. The flexible substrate may be made of an insulating material having flexibility, and for example, the flexible substrate may be made of a Polymer material such as Polyimide (PI), Polycarbonate (PC), Polyethersulfone (PES), Polyethylene terephthalate (PET), Polyethylene Naphthalate (PEN), or Cyclic Olefin Polymer (COP).
Fourth film layer F4The pixel circuit layer includes a plurality of pixel circuits arranged in an array, and the pixel circuits may be provided with a corresponding number of Thin Film Transistors (TFTs), storage capacitors, and other electronic components according to display requirements.
The fifth film layer F5The flexible display layer includes a plurality of Organic Light Emitting Diodes (OLEDs) arranged in an array, and the Organic Light Emitting diodes are connected to the pixel circuits in a one-to-one correspondence.
The sixth film layer F6For the Encapsulation layer, the Encapsulation layer may be, for example, a Thin Film Encapsulation layer (TFE) in which an inorganic Encapsulation layer and an organic Encapsulation layer are stacked to protect the organic light emitting device from water and oxygen in the external environment.
Seventh film layer F4Is the second glue material OCA 2.
The eighth film layer F8Is a touch layer TP. The touch layer TP is bonded to the package layer through the second adhesive OCA 2. The touch layer may be a touch grid pattern formed by a conductive material, for example, the conductive material may be a metal, a metal oxide, graphene, or the like.
Ninth film layer F9Is a polarizer POL. The polarizer POL may be, for example, a circular polarizer, so as to reduce reflection of ambient light by metal electrodes and the like in the foldable display device, and improve contrast of a display screen of the foldable display device.
The tenth film layer F10Is the third glue material OCA 3.
Eleventh individual film layer F11Is a second protective layer Cover Film. When the foldable display device is damaged by external force impact and the like, the first protective layer and the second protective layer can protect each film layer positioned between the first protective layer and the second protective layer.
Exemplarily, the side where the touch layer TP is located is the light emitting side of the flexible display layer OLED. The side where the first protection layer Back Film is located is the backlight side of the flexible display panel. Optionally, the relative positions of the polarizer POL and the touch layer TP may be adjusted, and by adjusting the relative positions of the polarizer POL and the touch layer TP, the distance between the touch layer TP and the finger of the user may be set within a range that meets the touch requirement, so as to optimize the touch performance of the foldable display device. For example, as shown in fig. 3, the polarizer POL may be disposed on a side of the touch layer TP away from the flexible display layer OLED, and the second protection layer may be disposed on a side of the polarizer away from the flexible display panel. Alternatively, the touch layer TP may be disposed on a side of the polarizer POL away from the flexible display layer OLED, which is not limited in the embodiment of the present invention.
After the stacking sequence of each film layer in the foldable display device is determined, the quantitative standard of the interface bonding capability of two adjacent film layers in the foldable display device is selected according to different use conditions and use requirements of the foldable display device, for example, the interface bonding capability M is larger than or equal to 50, and the formula (2) is combined, so that the materials of the film layers and the rubber materials in the foldable display device can be selected, the interface bonding capability between the two adjacent film layers and the rubber materials can meet the requirements, and the two adjacent film layers can be ensured not to be separated in the bending process and after the foldable display device is bent.
After the material of the film layers is determined, the elongation at break of the respective film layer can be determined, corresponding to the most brittle layer (i.e. the layer at break)The film layer having the smallest elongation) can also be determined. And after the material and stacking sequence of each film layer are determined, the thickness t of each film layer can be selected according to the thickness requirement of the foldable display device, and then the elastic modulus and the thickness of each film layer, and the 1 st film layer F of each film layer and the foldable display device can be determined1That is, the distance h between the first surfaces 11 of the first protective layers BackFilm shown in fig. 3 is substituted into the above formula (1) to calculate the position of the neutral plane of the foldable display device. Based on the structure of the foldable display device shown in fig. 3, taking the calculated position of the neutral plane at the flexible display layer OLED as an example, the distance h between the central plane of the flexible display layer OLED and the first surface 11 of the first protective layer Back Film at this time is5＝yN。
Then according to
And the value of the calculated binding capacity M, the elongation at break s of the film layer with the minimum elongation at break, the thickness t of the film layer with the minimum elongation at break, and the neutral plane and the 1 st film layer F of the foldable display device1Of the first surface 11, yNThe bending capability Φ of the foldable display device can be calculated. The calculated ability to bend Φ can then be compared to a predetermined criteria (e.g., a predetermined criteria of 225 can be selected), if the calculated ability to bend Φ is less than the predetermined criteria. The position of the neutral plane of the foldable display device can be adjusted by changing the elastic modulus E of the corresponding film layer by replacing the material of the functional film layer, and the bending capability phi of the foldable display device is increased by changing the position of the neutral plane close to the film layer with the minimum breaking elongation.
For example, taking the polarizer POL as an example of a Film layer with the smallest breaking elongation in a foldable display device, the embodiments of the present invention may change the materials of the first protective layer Back Film and the second protective layer Cover Film, and after the materials are changed, the elastic modulus E of the first protective layer Back Film and the second protective layer Cover Film may change, combining the formula:
after the elastic modulus E of the first protective layer Back Film and the second protective layer Cover Film is changed, the position of the neutral plane of the foldable display device may be changed. Taking as an example that before and after the materials of the first protective layer Back Film and the second protective layer Cover Film are changed, the position of the neutral plane is adjusted from the central plane of the flexible display layer OLED shown in fig. 3 to the position of the polarizer POL shown in fig. 4. In the structure shown in fig. 3, the distance between the film layer having the smallest elongation at break and the neutral plane of the foldable display device is the distance (h) between the polarizer POL and the flexible display layer OLED9-h5). In the structure shown in fig. 4, the neutral plane of the foldable display device is adjusted to the layer where the polarizer POL is located, and the distance between the film layer having the smallest elongation at break and the neutral plane of the foldable display device is approximately 0.
After folding the foldable display device of the type shown in fig. 3, as shown in fig. 5, fig. 5 is a schematic view of the foldable display device shown in fig. 3 after being folded, wherein the polarizer POL may have cracks L1 and L2, which may cause failure of folding. After the foldable display device shown in fig. 4 is folded, as shown in fig. 6, fig. 6 is a schematic diagram of the foldable display device shown in fig. 4 after being folded, wherein each film layer in the foldable display device including the polarizer POL has no crack, and no separation phenomenon occurs between two adjacent film layers, which indicates that the foldable display device is reliable.
It should be noted that, since the thickness of the film layer affects the total thickness of the formed foldable display device, the embodiment of the present invention may not select the method for adjusting the thickness of the film layer when adjusting the position of the neutral plane. Moreover, since the interfacial bonding ability M between the adhesive material and the adjacent film layer is changed after the adhesive material is changed, the material of the adhesive material is not changed after the adhesive material satisfying the required interfacial bonding ability is selected.
The above is only one idea of designing the structure of the foldable display device by using the above formula for measuring the bending capability of the foldable display device, and those skilled in the art can adjust different parameters related thereto according to different requirements, for example, the position of the neutral plane can be adjusted by adding a buffer layer with a smaller elastic modulus in the foldable display device, which is not limited in this invention.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (11)
1. A foldable display device, comprising P film layers arranged in a stack;
bending capability phi of the foldable display device and
positive correlation;
wherein k is1Is a coefficient, MiThe interfacial binding capacity of the ith and (i + 1) th membrane layers; s is the elongation at break of the P film layers with the minimum elongation at break, h is the distance between the central plane of the P film layers with the minimum elongation at break and the first surface of the 1 st film layer, wherein the first surface is the surface of the 1 st film layer away from the 2 nd film layer; t is the thickness of P film layers with the minimum breaking elongation, yNIs the distance between the neutral plane of the foldable display device and the first surface of the 1 st film layer.
2. The foldable display device of claim 1, wherein the plurality of film layers comprises:
a flexible display panel;
the functional film layer is positioned on one side of the flexible display panel;
the glue material is positioned between the flexible display panel and the functional film layer;
the interface bonding capacity M between the rubber material and the functional film layer meets the following requirements:
M＝k2E1 log(tanδ×E2)≥50；
wherein k is2Is a coefficient; e1The interfacial energy between the adhesive material and the functional film layer; e2The elastic modulus of the rubber material is shown; tan delta is the loss factor of the glue.
3. The foldable display device of claim 2,
0.5≤k2≤1.5。
4. the foldable display device of claim 2,
E1≥30mJ/m2。
5. the foldable display device of claim 2,
at the temperature of between 50 ℃ below zero and 100 ℃, the tan delta is more than or equal to 0.1 and less than or equal to 2.
6. The foldable display device of claim 2,
0.1GPa≤E2≤5GPa。
7. the foldable display device of claim 2,
the interface bonding capacity M between the adhesive material and the functional film layer and the thickness x of the adhesive material meet the following requirements:
m ═ alnx, where a is a coefficient.
8. The foldable display device of claim 7,
1≤a≤5。
9. the foldable display device of claim 7,
20μm≤x≤1000μm。
10. the foldable display device of claim 2,
the functional film layer comprises a touch layer, a polaroid, a first protective layer and a second protective layer which are arranged in a stacked mode;
the touch layer is positioned on the light emitting side of the flexible display panel, the polarizer is positioned on one side of the touch layer, which is far away from the flexible display panel, and the second protective layer is positioned on one side of the polarizer, which is far away from the flexible display panel; the first protective layer is positioned on the backlight side of the flexible display panel;
the glue material comprises:
the first glue material is positioned between the flexible display panel and the first protective layer;
the second adhesive material is positioned between the flexible display panel and the touch layer;
and the third adhesive material is positioned between the polarizer and the second protective layer.
11. The foldable display device of claim 1,
Eithe elastic modulus of the ith film layer; h isiIs the distance between the central plane of the ith film layer and the first surface of the 1 st film layer; t is tiIs the thickness of the ith film layer.
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| CN113936550B (en) * | 2020-06-29 | 2023-02-14 | 华为技术有限公司 | Inner folding screen electronic equipment |
| CN111816077B (en) | 2020-07-13 | 2022-04-26 | 武汉华星光电半导体显示技术有限公司 | Foldable display module |
| CN115188332A (en) | 2020-07-30 | 2022-10-14 | 华为技术有限公司 | Display module assembly and electronic equipment |
| CN114220342B (en) * | 2021-10-27 | 2023-11-17 | 京东方科技集团股份有限公司 | Flexible display module and display device |
| CN116847619A (en) * | 2022-03-25 | 2023-10-03 | 华为技术有限公司 | Display assembly and electronic equipment |
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