Detailed Description
In the following detailed description, certain embodiments of the invention are shown and described, simply by way of illustration. As will be appreciated by those skilled in the art, the embodiments described herein may be modified in numerous ways without departing from the spirit or scope of the present invention.
In the drawings, the thickness of layers, films, plates, areas, etc. may be exaggerated for clarity and for better understanding and ease of description. In addition, unless explicitly described to the contrary, the word "comprise" and variations such as "comprises" or "comprising" will be understood to imply the inclusion of stated elements but not the exclusion of other elements. Further, in the specification, the word "on … …" means placed above or below the subject portion, and does not necessarily mean placed on the upper side of the subject portion based on the direction of gravity.
It will be understood that, although the terms "first," "second," etc. may be used herein to describe various components, these components should not be limited by these terms. These components are used only for zoning one component and another.
When a display device with a visual angle display effect is arranged, a plurality of liquid crystal regulating layers are arranged in the display device, and when 2D display or 3D display is needed, liquid crystals in the liquid crystal regulating layers are regulated and controlled, so that the purpose of visual angle conversion is achieved. However, the liquid crystal regulating layer has a complex preparation process, and the corresponding display effect is not ideal when different display modes of the display device are switched, so that the further use requirement of people cannot be met.
The embodiment of the application provides a display device. The film layer in the display device is improved, so that the structure of the display device is simplified, and the display effect of the display device in different display modes is improved.
Fig. 1 is a schematic diagram of a film structure of a display device according to an embodiment of the application. The display device includes: a display substrate 100, a viewing angle conversion layer 107, and a second substrate 383.
Specifically, the display substrate 100 includes a first substrate 101, a light emitting device 102, a first planarization layer 103, a first isolation layer 104, a first electrode layer 105, and a first alignment layer 106. In the embodiment of the present application, a plurality of pixel units are disposed in the display substrate 100, and the pixel units emit light to realize the display. The light emitting component 102 is disposed on the first substrate 101, the first planarization layer 103 is disposed on a side of the light emitting component 102 away from the first substrate 101, the first isolation layer 104 is disposed on a side of the first planarization layer 103 away from the first substrate 101, and the first electrode layer 105 is disposed on a side of the first isolation layer 104 away from the first substrate 101.
In the embodiment of the present application, the first substrate 101 is configured as a driving circuit substrate, and a driving circuit for driving the light emitting component 102 to work is disposed in the first substrate 101, and when the display device works, the first substrate 101 provides a control signal to the light emitting component 102 and controls the light emitting display of the light emitting component 102. In the embodiment of the present application, the first substrate 101 may be configured as an array substrate, and a plurality of thin film transistors are disposed in the array substrate, and control signals are provided to the corresponding light emitting components 102 through the thin film transistors, and the light emitting components 102 are driven to emit light.
Further, the first substrate 101 may be configured as a driving circuit substrate with other structures, and the driving circuit in the driving circuit substrate is used to drive the light emitting component 102, and the driving circuit substrate with other structures is within the scope of the present application.
Further, the light emitting device 102 is mainly used for providing display light for the display device, and thus, in an embodiment of the present application, the light emitting device 102 may include any light source device capable of emitting light autonomously or passively. Such as light emitting assembly 102 is provided as a light emitting diode (LIGHT EMITTING LED), microLED, or the like. In the embodiment of the present application, the light emitting component 102 is illustrated as an LED. When in setting, the first substrate 101 is provided with a positive electrode and a negative electrode, the positive electrode is electrically connected with the positive electrode pin of the LED, and the negative electrode is electrically connected with the negative electrode pin of the LED, so that a large number of LEDs are transferred or mounted on the first substrate 101.
Fig. 2 is a schematic structural diagram of a light emitting device according to an embodiment of the application. In connection with the structure of the display device in fig. 1, in the embodiment of the present application, when the light emitting assembly 102 is disposed, the light emitting assembly 102 is arranged in an array on the first substrate 101, thereby forming the light emitting pixels 201 of the display device. When the light emitting element 102 forms the light emitting pixel 201, the corresponding light emitting pixel 201 may include a plurality of pixel units 2011 disposed in an array, and each pixel unit 2011 includes a plurality of LEDs with different colors: red LED251, blue LED252, and green LED253. The LEDs with different colors can be arranged according to different panel requirements, so that the color display effect is realized.
Specifically, the pixel unit 2011 includes a red LED251, a blue LED252, and a green LED253 sequentially arranged therein. And a first black matrix layer 301 is disposed between two adjacent LEDs of different colors. The problem of optical crosstalk between two adjacent LEDs of different colors is avoided by the first black matrix layer 301, and the display effect is improved. In the embodiment of the present application, the width of the first black matrix layer 301 between two adjacent LEDs may be set according to the size of the reserved space of the display device, for example, the widths of the first black matrix layers 301 at different positions are the same, or they are differently set, so as to meet the use requirements of different display devices.
Further, in the embodiment of the present application, the first planarization layer 103 is correspondingly disposed on the light emitting component 102. The first planarization layer 103 is arranged to level the light-emitting component 102, so that the flatness of the surface of the light-emitting side of the light-emitting component 102 is improved, and the preparation effect of other film layers is ensured. Optionally, the first planarization layer 103 is made of an organic material, which has good leveling property, and the thickness of the first planarization layer 103 is 8um to 15um.
In the embodiment of the present application, a first isolation layer 104 is disposed on the first planarization layer 103. The first insulating layer 104 includes a metal oxide material, such as an Al2O3 material. In the preparation process, an Al2O3 metal oxide layer with the thickness of 5-50 nm is formed on the first planarization layer 103 by utilizing a physical or chemical vapor deposition process. The first insulating layer 104 has a good function of insulating water vapor, and can prevent external water vapor from entering the light-emitting component at the bottom through the first insulating layer 104, and can make transition for the preparation of the subsequent metal electrode through setting a transitional Al2O3 layer in the middle, so that the preparation effect of the subsequent metal film layer is improved.
Further, in the embodiment of the present application, a first electrode layer 105 is further disposed on the first insulating layer 104. The first electrode layer 105 may be formed as an indium tin oxide electrode, and the entire surface of the indium tin oxide material is disposed on the first insulating layer 104, and etched to form the first electrode layer 105 of the present application. The thickness of the film layer of the first electrode layer 105 is set to 50nm to 200nm.
Further, a first alignment layer 106 is further provided on the first electrode layer 105. The first alignment layer 106 is provided as a polyimide material. When a driving voltage is applied to the first electrode layer 105, the first alignment layer 106 aligns the viewing angle conversion layer under the action of the driving voltage, thereby controlling the propagation path of light. Specifically, the first alignment layer 106 may be prepared by an inkjet printing or transfer printing process, and the thickness of the first alignment layer 106 is 60nm to 150nm.
As shown in fig. 3, fig. 3 is a schematic view of a part of a film layer structure of a display device according to an embodiment of the present application. In connection with the structure in fig. 1, in forming the display device provided in the present application, a first substrate 101 is provided, and a light emitting element 102, a first planarization layer 103, a first insulating layer 104, a first electrode layer 105, and a first alignment layer 106 are sequentially prepared on the first substrate 101. Thereby laying a foundation for the subsequent preparation of other film layers.
Referring to fig. 1, a viewing angle conversion layer 107 is further provided on the first alignment layer 106. In the embodiment of the application, the viewing angle conversion layer 107 is used to realize the 2D and 3D display modes of the display device. Specifically, the refractive index of the material in the viewing angle conversion layer 107 is controlled, and the refractive index of the viewing angle conversion layer 107 is changed, so that switching between the 2D display mode and the 3D display mode is realized.
Specifically, in the present application, the viewing angle conversion layer 107 includes at least the refractive medium 1071 and the light emitting portion 1072. The refractive medium 1071 is provided between the light emitting portion 1072 and the pixel. Specifically, the refractive medium 1071 is disposed on a side near the first alignment layer 106.
In embodiments of the present application in which the refractive medium 1071 is a birefringent material, in the following embodiments, the refractive medium 1071 is configured as a liquid crystal, such as any one of nematic liquid crystal, cholesteric liquid crystal, or other birefringent material. When the LED emits light, the light propagates to the refraction medium 1071, and is acted on again by the refraction medium 1071, so as to control the emitted light and obtain the required deflection effect.
In the present application, when the light-emitting portion 1072 is provided, the light-emitting portion 1072 is provided in a curved surface, such as an arc-shaped curved surface, in the light-emitting direction of the display substrate 100. The light-emitting portion 1072 further includes a groove 1073, and the groove 1073 is disposed opposite to the first alignment layer 106 and defines a receiving cavity 1074. The accommodating chamber 1074 has an accommodating space, wherein the refraction medium 1071 or the liquid crystal is correspondingly disposed in the accommodating space formed by the accommodating chamber 1074. When the display device is in operation, the first alignment layer 106 controls the deflection of the liquid crystal under the action of an electric field or voltage.
In the embodiment of the present application, the groove 1073 of the light-emitting portion 1072 has an arc surface 401, and the arc surface 401 can form a curved surface structure of the light-emitting portion 1072. The arc surface 401 is an inner wall of the accommodating cavity 1074 corresponding to the light emitting portion 1072. In an embodiment, as shown in fig. 1, the opening of the arc surface 401 is disposed towards one side of the pixel, so that the arc surface 401 protrudes outwards relative to the first alignment layer 106, that is, the arc surface 401 and the light-emitting portion 1072 form a lens structure, and at this time, the light-emitting portion 1072 is recessed relative to the concave lens structure, so that light enters the light-emitting portion 1072 from the accommodating cavity 1074 as a concave lens.
In another embodiment, the opening of the arc surface 401 may also be changed, for example, the opening of the arc surface 401 is disposed away from the pixel side. In this way, the light-emitting portion 1072 corresponding to the arc surface 401 protrudes outwards relative to the first alignment layer 106, that is, the light-emitting portion 1072 forms a convex lens structure, and light enters the light-emitting portion 1072 from the accommodating cavity 1074 to act as a convex lens, so as to achieve different light regulation effects, and the different types of lens structures are all within the protection scope of the present application.
Meanwhile, in the present application, the 2D and 3D display modes are realized by controlling the refractive index of the refractive medium 1071 at the light emitting portion.
As shown in fig. 3, the refractive medium 1071 has a refractive index n1, and for a liquid crystal, the liquid crystal has an ordinary refractive index n0 and an extraordinary refractive index ne, and the refractive index n1 in the present application may be an average refractive index value corresponding to the ordinary refractive index n0 and the extraordinary refractive index ne.
Correspondingly, the light-emitting portion 1072 has a refractive index n2. The light-emitting portion 1072 has a groove 1073, and the groove 1073 and the first alignment layer 106 opposite thereto form a receiving cavity 1074. Meanwhile, in the present application, the inner wall of the light-emitting portion 1072 corresponding to the groove 1073 is provided with the arc surface 401, and the refractive medium 1071, such as nematic liquid crystal, is provided in the accommodating cavity 1074.
Meanwhile, a second alignment layer 206 is further disposed on the inner wall of the light-emitting portion 1072 corresponding to the groove 1073. The second alignment layer 206 is attached to the inner wall of the light-emitting portion 1072, and optionally, the second alignment layer 206 is made of polyimide alignment material, and the thickness of the second alignment layer is 60 nm-150 nm.
Further, the first alignment layer 106 and the second alignment layer 206 are made of the same material, and the thickness of the layers may be set as required. When the display device is in operation, the first alignment layer 106 and the second alignment layer 206 can align the liquid crystal in the accommodating cavity 1074.
In one embodiment, the opening of the arcuate surface 401 is disposed toward the side of the light emitting pixel 201, and forms a concave lens structure. When the bottom pixel emits light, the emitted light will propagate to the refraction medium 1071 in the accommodating cavity 1074, and after being acted by the refraction medium 1071, will continue to propagate to the arc surface 401 of the light emitting portion 1072, and be acted by the arc surface 401 to change the propagation path of the light, and then be emitted from the light emitting surface of the light emitting portion 1072. In the present application, the refractive medium 1071 and the light emitting portion 1072 have different refractive indices, and the combined action of the refractive medium 1071 and the light emitting portion 1072 achieves the 2D and 3D display effects.
In connection with the light propagation path in fig. 3, in the convex lens structure, the first viewing angle mode is a 2D planar display mode. At this time, the refractive medium 1071 is not energized, and an electric field is not applied in the accommodation chamber 1074, and the refractive index of the refractive medium 1071 is the same as the refractive index of the light emitting portion 1072. After the light passes through the refraction medium 1071 and the light-emitting portion 1072, the light can directly enter the light-emitting portion 1072 from the arc-shaped surface 401, and the viewing angle is not changed, so that the 2D display is correspondingly performed.
And when in the second viewing angle mode, for example, the second viewing angle mode is a 3D display mode. At this time, a voltage is applied to the viewing angle conversion layer 107, and the refractive medium 1071 deflects due to the electric field applied to both the accommodating chamber 1074 and the refractive medium 1071, so that the refractive index of the refractive medium 1071 is smaller than the refractive index of the light emitting portion 1072, and the incident light is refracted and deflected at the arc surface 401, so that the light emitting angle of the emitted light is changed, and a 3D display mode is realized.
Conversely, when the viewing angle conversion layer 107 is disposed, the opening of the arcuate surface 401 in the recess 1073 may also be disposed away from the side of the light emitting pixel 201, and the accommodating cavity 1074 and the arcuate surface 401 form a concave lens structure. At this time, when the bottom light propagates upward, the light changes its optical path at the interface of the refractive medium 1071 and the arc surface 401 corresponding to the light exit portion 1072.
Specifically, when the light-emitting portion 1072 corresponding to the viewing angle conversion layer 107 forms a convex lens structure, in contrast to the concave lens structure, in the 2D mode corresponding to the first viewing angle mode, the viewing angle conversion layer 107 applies a voltage action, and at this time, the refractive index of the refractive medium 1071 is regulated and controlled, so that the refractive index of the refractive medium 1071 is the same as that of the light-emitting portion 1072, and light is not refracted and is directly transmitted from the viewing angle conversion layer 107, thereby realizing the 2D display mode.
In the 3D mode corresponding to the second viewing angle mode, no voltage is applied to the viewing angle conversion layer 107, and the refractive index of the refractive medium 1071 is larger than the refractive index of the light emitting portion 1072, so that the incident light is refracted at the arc surface 401, thereby realizing the 3D display mode.
In the embodiment of the present application, when the viewing angle conversion layer 107 corresponds to a concave lens structure, the liquid crystal corresponding to the refractive medium 1071 may be any one of Twisted Nematic (TN) mode liquid crystal and in-plane switching (IPS) mode liquid crystal. In order to ensure the mutual matching effect of the liquid crystal and the light emitting portion 1072, the refractive index of the refractive medium 1071 may be set to 1.1-2.0 when the refractive medium 1071 is set, and optionally, the refractive index of the refractive medium 1071 may be 1.4, 1.8 or any value between 1.5-1.8.
The refractive index difference Δn of the extraordinary refractive index ne of the ordinary refractive index n0 of the liquid crystal corresponding to the refractive medium 1071 is not less than 0.15. Such as an setting of 0.15, 0.3. The light ray control effect of the refractive medium 1071 is improved by controlling the refractive index difference of the refractive medium.
In detail, referring to fig. 3, when the viewing angle conversion layer 107 is disposed, the height of the corresponding accommodating cavity 1074 in the viewing angle conversion layer 107 is set to 10um to 30um. Meanwhile, the corresponding pitch is set to 100um to 400um, and in the present application, the pitch is understood as the width of the accommodating cavity 1074. Meanwhile, when the height and pitch of the viewing angle conversion layer 107 are set, the viewing angle conversion layer 107 with different sizes and shapes can be set according to the requirements of different products, and the viewing angle conversion layer 107 with different sizes and shapes is within the protection scope of the application.
Further, in the embodiment of the present application, in the area where the viewing angle conversion layer 107 is opposite to the light emitting pixel 201, the projection of the light emitting pixel 201 is located in the projection area of the viewing angle conversion layer 107 by orthographic projection on the same plane. And the pixel unit 2011 is correspondingly disposed at an edge position of the viewing angle conversion layer 107.
Specifically, when configured, the pixel unit 2011 includes a first pixel unit 2012 and a second pixel unit 2013. Wherein each pixel unit 2011 includes a red LED251, a blue LED252, and a green LED253, and a first black matrix layer 301 disposed between two adjacent different color LEDs.
Wherein the first pixel unit 2012 is disposed at an edge position of one side of the viewing angle conversion layer 107 and the second pixel unit 2013 is disposed at an edge position of the other side opposite to the viewing angle conversion layer 107. Optionally, the first pixel unit 2012 and the second pixel unit 2013 may be symmetrically disposed with respect to the central axis MM of the viewing angle conversion layer 107, so that the first pixel unit 2012 and the second pixel unit 2013 below the viewing angle conversion layer 107 are symmetrically arranged, thereby ensuring uniformity of light effects in different regions.
Further, a second black matrix layer 302 is further disposed between the first pixel unit 2012 and the second pixel unit 2013. The second black matrix layer 302 can effectively avoid the color mixing problem of the first pixel unit 2012 and the second pixel unit 2013. In one or more embodiments, the width of the second black matrix layer 302 is greater than the width of the first black matrix layer 301, and the pixel units 2013 correspond to the areas of the accommodation cavities 1074 in the viewing angle conversion layer 107, i.e. the first pixel units 2012 and the second pixel units 2013 are located in the forward projection areas of the accommodation cavities 1074. When different pixel units emit light, the emitted light can enter the accommodating cavity 1074 and be acted by the refraction medium 1071 and the light emitting part 1072 in the accommodating cavity 1074, so that a 2D or 3D display mode is realized. Further, in the present application, the first pixel unit 2012 and the second pixel unit 2013 can be symmetrically distributed with respect to the second black matrix layer 302, so as to ensure that the light emitted from the first pixel unit 2012 and the second pixel unit 2013 have the same light emitting effect in the upper viewing angle conversion layer 107.
In detail, as shown in fig. 3, two different pixel units on two sides emit light, the light emitted by the first pixel unit 2012 is deflected to the right side of the central axis MM of the viewing angle conversion layer 107 after the light passes through the refraction medium 1071 and the light emitting portion 1072, and the light emitted by the second pixel unit 2013 is deflected to the left side of the central axis MM of the viewing angle conversion layer 107 after the light passes through the refraction medium and the light emitting portion 1072. In this way, when the user observes from different external perspectives, different effects can appear, and then a 3D display mode is formed.
In the present application, the first pixel unit 2012 and the second pixel unit 2013 are disposed at different positions on two sides of the viewing angle conversion layer 107, and the pixel units at two different positions are combined with the viewing angle conversion layer 107 on the light emitting side, so that the light emitting angle of the outgoing light can be effectively regulated and controlled, and the display effect in the 3D display mode is further improved. In detail, referring to fig. 3, in the 3D display mode, the refractive index of the refractive medium 1071 is smaller than the refractive index of the light emitting portion 1072.
As shown in fig. 4, fig. 4 is a schematic illustration of a light emitting effect in a 2D display mode according to an embodiment of the present application. In the present application, with reference to the structures shown in fig. 2 to 3, a certain voltage is applied to two sides of the viewing angle conversion layer 107, under the voltage, the liquid crystal in the viewing angle conversion layer 107 is deflected, for example, from a horizontal state to a vertical state, and when the light emitted from the pixel unit at the bottom propagates onto the refraction medium 1071, the light can be directly transmitted from the refraction medium 1071, the arc-shaped surface 401 and the light emitting portion 1072, and when a user observes from the outside, the user can observe the picture displayed by the display device normally, thereby realizing the 2D display mode. In the embodiment of the present application, in the 2D display mode, two different pixel units are correspondingly disposed below the viewing angle conversion layer 107, and both the two different pixel units normally emit light, so that the number of pixel units of the display device is increased, and the display effect of the display device is improved.
Further, in the embodiment of the present application, a transition layer 381 and a second electrode layer 382 are further disposed on the viewing angle conversion layer 107 as shown in fig. 1. The second electrode layer 382 is disposed on a side of the transition layer 381 remote from the viewing angle conversion layer 107. The second electrode layer 382 and the first electrode layer 105 may apply a desired voltage, so that a corresponding electric field is formed between the first electrode layer 105 and the second electrode layer 382, thereby controlling the refractive medium 1071 in the viewing angle conversion layer 107, and thus achieving different display modes. The second electrode layer 382 is made of the same material and disposed in the same manner as the first electrode layer 105, and may have a thickness of 50nm to 200nm.
The transition layer 381 may provide a transition for the preparation of other film layers. For example, the viewing angle conversion layer 107 needs to be prepared later, and since the viewing angle conversion layer 107 is directly prepared on the second electrode layer 382, the surface wettability of the second electrode layer 382 is not good, and the material of the viewing angle conversion layer 107 is usually an organic material, such as ultraviolet glue, the appearance of the viewing angle conversion layer 107 is easily uneven during preparation, and the design specification is not met. Therefore, it is necessary to form the transition layer 381 on the surface of the second electrode layer 382, and the wettability of the subsequent viewing angle conversion layer 107 is improved by the transition layer 381, so that the film accuracy of the viewing angle conversion layer 107 is improved, and the display effect of the display device is ensured. In the present application, the material of the transition layer 381 includes SiNx or other materials with high wettability.
Meanwhile, a second substrate 383 is further disposed on the second electrode layer 382, where the second substrate 383 is used to protect or seal the display device and ensure that other film layers in the display device work normally. The second substrate 383 can be paired with the first substrate 101 and the corresponding film layer through a sealant to form a box, and finally form the display device in the application. In the present application, the material of the second substrate 383 may be a glass substrate or other organic or inorganic material with high transparency.
As shown in fig. 5 to 10, fig. 5 to 10 are film structures in the manufacturing process of the display device according to the embodiment of the application. In connection with the structures of fig. 1-4, in the preparation of the display device, it may be manufactured by dividing it into a plurality of different parts, and after each part is prepared, it is paired to form a box, and finally the display device of the present application is formed.
Specifically, referring to fig. 5 in detail, a first substrate 101 is provided, and a light emitting device 102, a first planarization layer 103, and a first isolation layer 104 provided in the above embodiment of the present application are sequentially formed on the first substrate 101. The structure and characteristics of each film layer are referred to above and will not be further described herein.
In detail, as shown in fig. 6, the first electrode layer 105 and the first alignment layer 106 are further formed on the first isolation layer 104. Meanwhile, support columns 666 are prepared on first alignment layer 106. And a refractive medium 1071 is disposed on the first alignment layer 106, wherein the support beams 666 are opposite to the accommodation cavity 1074 of the viewing angle conversion layer 107 in the present application, and the light emitting portion 1072 and the accommodation cavity 1074 are supported by the support beams 666, so that the reliability of the viewing angle conversion layer 107 is ensured.
Referring to fig. 7, other part of the film layer of the display device is prepared. At this time, a second substrate 383 is provided, and a second electrode layer 382 and a transition layer 381 provided in the embodiment of the present application are sequentially formed on the second substrate 383. After the film layer is prepared, the light-emitting portion 1072 of the viewing angle conversion layer 107 is prepared on the transition layer 381. In fig. 7, a layer of uv glue is deposited directly over the entire surface of the transition layer 381. The ultraviolet glue is processed by the subsequent process, and finally forms the light emergent part 1072 in the application.
In detail, referring to fig. 8, specifically, the deposited ultraviolet glue is transferred, a required mold is selected in the transfer process, the mold is stamped, then the mold is removed, ultraviolet and high-temperature curing are performed after the ultraviolet glue is removed, and a structure corresponding to the light emergent portion 1072 in fig. 7 is formed. The light emergent portion 1072 is embossed to form an arc surface 401, a groove 1073 and a receiving cavity 1074. So as to be paired with the film layer in fig. 5.
In fig. 9, the second alignment layer 206 is deposited on the curved surface 401 corresponding to the light-emitting portion 1072. Further, the structure prepared in fig. 9 was paired with the film layer in fig. 6 to form a cartridge. And the first substrate 101 is sealed with the second substrate 383, to finally obtain the display device in fig. 10. When the display device is operated, the voltage between the first electrode layer 105 and the second electrode layer 382 is adjusted, thereby realizing different display modes of 2D and 3D.
Further, in the embodiment of the application, the viewing angle conversion layer is arranged in the display device, so that the display effect of the display device in different 2D and 3D display modes is improved, and the comprehensive performance of the display device is improved. The display device may be any product or component with display, fingerprint identification or other functions, such as a mobile phone, a computer, an electronic paper, a display, wearing glasses, etc., and the specific type of the product or component is not particularly limited.
In summary, the foregoing has described in detail a display device provided by an embodiment of the present invention, and specific examples are applied to illustrate the principles and embodiments of the present invention, where the foregoing description of the embodiment is only for helping to understand the technical solution and core idea of the present invention; although the present invention has been described with reference to the preferred embodiments, it should be understood that the invention is not limited to the particular embodiments described, but can be modified and altered by persons skilled in the art without departing from the spirit and scope of the invention.