LED lamp bead, preparation method thereof and display screen

Abstract

The invention discloses an LED lamp bead, a preparation method of the LED lamp bead and a display screen. The LED lamp bead comprises an LED chip set and a packaging adhesive layer. The LED chip set comprises a glass substrate and a light-emitting chip. Wherein the glass substrate is provided with an upper surface, a lower surface, a first side surface and a second side surface, the lower surface of the glass substrate is provided with a pin area, and the upper surface, the first side surface and the second side surface of the glass substrate are respectively provided with a first die bonding area, a second die bonding area and a third die bonding area; and the plurality of light-emitting chips are respectively arranged on the first die bonding area, the second die bonding area and the third die bonding area. And the packaging adhesive layer at least covers the light-emitting chip. According to the invention, the size of the LED lamp bead can be reduced, and the reliability of the LED lamp bead can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and in particular to an LED lamp bead and a preparation method thereof, and a display screen. Background Art

[0002] Existing small-pitch LED devices use a flat BT substrate as a bracket. The substrate is divided into a front line, a back line and a base material. The front line is used to bind the light-emitting chip and realize electrical interconnection. The back line is used to weld with the LED display module PCB. The front line and the back line are connected and conducted through through holes. During preparation, light-emitting chips of different colors are laid out flatly, and a certain interval needs to be maintained between multiple light-emitting chips. In addition, sufficient space needs to be reserved for the arrangement of wires and pads, which makes it difficult to meet the requirements of miniaturization of LED devices.

[0003] Two-in-one LED lamp beads are two LED lamp beads combined together, that is, multiple light-emitting chips (two groups of light-emitting chips) are packaged on the same substrate, which will inevitably lead to an increase in leads and ink coverage area. Due to the poor bonding between the encapsulation glue and the bonding wires and ink, during use, water vapor in nature can easily enter the interior of the LED lamp beads, causing failed dead lamps, and ultimately leading to display problems such as caterpillars on the LED screen, affecting the display effect. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an LED lamp bead and a preparation method thereof, and a display screen, so as to reduce the size of the LED lamp bead and improve the reliability of the LED lamp bead.

[0005] In order to solve the above problems, the present invention discloses an LED lamp bead, including an LED chipset and a packaging glue layer;

[0006] The LED chipset includes a glass substrate and a light-emitting chip;

[0007] The glass substrate has an upper surface, a lower surface, a first side surface and a second side surface, the lower surface of the glass substrate is provided with a pin area, and the upper surface, the first side surface and the second side surface of the glass substrate are respectively provided with a first crystal-bonding area, a second crystal-bonding area and a third crystal-bonding area;

[0008] The plurality of light emitting chips are respectively arranged on the first solid crystal region, the second solid crystal region and the third solid crystal region.

[0009] The packaging glue layer at least covers the light-emitting chip.

[0010] As an improvement of the above technical solution, the first solid crystal region includes a first pad region and a second pad region arranged at intervals, the second solid crystal region includes a third pad region and a fourth pad region arranged at intervals, and the third solid crystal region includes a fifth pad region and a sixth pad region arranged at intervals;

[0011] The pin area includes a first function pin, a second function pin, a third function pin and a fourth function pin which are arranged at intervals.

[0012] As an improvement of the above technical solution, the first pad area, the third pad area and the fifth pad area are connected to each other and electrically connected to the first functional pin;

[0013] The second pad area is electrically connected to the fourth functional pin;

[0014] The fourth pad area is electrically connected to the second functional pin;

[0015] The sixth pad area is electrically connected to the third functional pin.

[0016] As an improvement of the above technical solution, the first pad area and the second pad area are both provided with through holes penetrating the upper surface and the lower surface of the glass substrate in the projection area of ​​the glass substrate, and the through holes are filled with a conductive medium; the first pad area is electrically connected to the first functional pin through the conductive medium; the second pad area is electrically connected to the fourth functional pin through the conductive medium;

[0017] The fourth pad area is electrically connected to the second functional pin via a lead;

[0018] The sixth pad area is electrically connected to the third functional pin through a lead.

[0019] As an improvement of the above technical solution, the light-emitting chip includes a first light-emitting chip, a second light-emitting chip and a third light-emitting chip, and the first light-emitting chip, the second light-emitting chip and the third light-emitting chip are one of a red light chip, a green light chip and a blue light chip;

[0020] The first light-emitting chip, the second light-emitting chip and the third light-emitting chip are all flip-chip structures; the positive and negative electrodes of the first light-emitting chip are electrically connected to the first pad area and the second pad area, respectively, the positive and negative electrodes of the second light-emitting chip are electrically connected to the third pad area and the fourth pad area, respectively, and the positive and negative electrodes of the third light-emitting chip are electrically connected to the fifth pad area and the sixth pad area, respectively.

[0021] As an improvement of the above technical solution, a side wall of the through hole and the lower surface of the glass substrate have a preset angle; the preset angle is 55° to 85°.

[0022] As an improvement of the above technical solution, the side wall of the through hole has a first wall surface, a second wall surface and a third wall surface, the first wall surface and the upper surface of the glass substrate have a preset angle, the third wall surface and the lower surface of the glass substrate have a preset angle, the first wall surface, the second wall surface and the third wall surface are connected to form a convex structure toward the center of the through hole; the preset angle is 55° to 85°.

[0023] As an improvement of the above technical solution, the LED lamp bead includes a packaging glue layer and at least two LED chip groups, the LED chip groups are arranged at a preset distance, and the packaging glue layer at least covers the light-emitting chip.

[0024] Correspondingly, the present invention also discloses a method for preparing an LED lamp bead, which is used to prepare the above-mentioned LED lamp bead, comprising the following steps:

[0025] Providing a glass substrate, and forming a pin area on the lower surface of the glass substrate;

[0026] Forming a first crystal-bonding region, a second crystal-bonding region and a third crystal-bonding region on the upper surface, the first side surface and the second side surface of the glass substrate respectively;

[0027] The pin region is electrically connected to the first die-bonding region, the second die-bonding region and the third die-bonding region respectively;

[0028] Fixing light-emitting chips on the first solid crystal region, the second solid crystal region and the third solid crystal region and forming electrical connections to obtain an LED chip group;

[0029] A packaging adhesive layer is formed on the LED chip group to obtain the LED lamp bead.

[0030] Correspondingly, the present invention also discloses a display screen, comprising the above-mentioned LED lamp beads.

[0031] The implementation of the present invention has the following beneficial effects:

[0032] The present invention arranges the first solid crystal area, the second solid crystal area and the third solid crystal area on different surfaces of the glass substrate respectively, and forms an electrical connection with the light-emitting chip, so that the light-emitting chips originally arranged in a flat pattern are arranged on different surfaces of the glass substrate, and the arrangement of the light-emitting chips is transformed from a planar structure to a three-dimensional structure, which significantly saves the layout space of the LED chipset, eliminates the conventional BT substrate structure, and reduces the thickness of the LED lamp beads. In addition, the present invention effectively reduces the use of leads, and at the same time, the packaging glue has good bonding with the glass substrate, thereby improving the airtightness of the LED lamp beads, and the reliability of the LED lamp beads is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of an LED lamp bead provided in an embodiment of the present invention;

[0034] Figure 2 is a schematic structural diagram of an LED chipset provided by an embodiment of the present invention;

[0035] Figure 3 is a top view of an LED chipset provided by an embodiment of the present invention;

[0036] Figure 4 is a left view of an LED chipset provided by an embodiment of the present invention;

[0037] Figure 5 is a right side view of the LED chipset provided by an embodiment of the present invention;

[0038] Figure 6 is a bottom view of an LED chipset provided by an embodiment of the present invention;

[0039] Figure 7 is a schematic structural diagram of a glass substrate provided by an embodiment of the present invention;

[0040] Figure 8 is a top view of a glass substrate provided by an embodiment of the present invention;

[0041] Fig. 9 is a left side view of a glass substrate provided by an embodiment of the present invention;

[0042] Fig.10 is a right side view of a glass substrate provided by an embodiment of the present invention;

[0043] Fig.11 is a bottom view of a glass substrate provided by an embodiment of the present invention;

[0044] Fig.12 is a schematic structural diagram of a through hole provided by an embodiment of the present invention;

[0045] Fig.13 is a schematic structural diagram of a through hole provided by another embodiment of the present invention;

[0046] Fig.14 is a schematic diagram of the structure of an LED lamp bead provided by another embodiment of the present invention;

[0047] Fig.15 is a top view of an LED lamp bead provided by an embodiment of the present invention;

[0048] Fig.16 It is a bottom view of the LED lamp bead provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0050] See also Figure 1 to Figure 6 The present invention provides an LED lamp bead, which includes an LED chipset 100 and a packaging glue layer 200. The LED chipset 100 includes a glass substrate 1 and a light-emitting chip 2. The glass substrate has an upper surface 11, a lower surface 12, a first side surface 13 and a second side surface 14. The lower surface 12 of the glass substrate 1 is provided with a pin area 121, and the upper surface 11, the first side surface 13 and the second side surface 14 of the glass substrate 1 are respectively provided with a first solid crystal area 111, a second solid crystal area 131 and a third solid crystal area 141.

[0051] The plurality of light emitting chips 2 are respectively disposed on the first crystal-bonding area 111 , the second crystal-bonding area 131 and the third crystal-bonding area 141 .

[0052] The packaging adhesive layer 200 at least covers the light emitting chip 2 .

[0053] It can be understood that the upper surface, the first side surface and the second side surface of the glass substrate are respectively provided with a solid crystal area that can fix the chip, that is, the glass substrate has a certain thickness. In one embodiment, the glass substrate is in the shape of a rectangular parallelepiped, and the thickness and width are greater than the width of the light-emitting chip, and the length is greater than the length of the light-emitting chip. Compared with the conventional layered substrate, the side utilization rate of the glass substrate is increased, so that the light-emitting chip can be fixed on different sides of the glass substrate to form a three-dimensional structure. Compared with arranging the light-emitting chips flat on the same surface, the three-dimensional structure of the present invention does not require a large interval in the horizontal direction for multiple light-emitting chips, thereby significantly reducing the area of ​​a single LED chip group, which can be reduced by 1 / 5 to 1 / 3 compared with the conventional structure, thereby saving the layout space of the LED chip group, and the present invention also cancels the conventional BT substrate structure to reduce the thickness of the LED lamp beads produced later.

[0054] like Figure 7 to Figure 11 As shown, in one embodiment, the first solid crystal area 111 includes a first pad area 111a and a second pad area 111b arranged at intervals, the second solid crystal area 131 includes a third pad area 131a and a fourth pad area 131b arranged at intervals, the third solid crystal area 141 includes a fifth pad area 141a and a sixth pad area 141b arranged at intervals; the pin area 121 includes a first function pin 121a, a second function pin 121b, a third function pin 121c and a fourth function pin 121d arranged at intervals.

[0055] Specifically, the first pad area 111a, the third pad area 131a and the fifth pad area 141a are connected to each other to form a common pad, and are electrically connected to the first functional pin 121a;

[0056] The second pad area 111b is electrically connected to the fourth functional pin 121d;

[0057] The fourth pad area 131b is electrically connected to the second functional pin 121b;

[0058] The sixth pad area 141 b is electrically connected to the third functional pin 121 c.

[0059] In a preferred embodiment, the first pad area 111a and the second pad area 111b are both provided with a through hole 15 penetrating the upper surface 11 and the lower surface 12 of the glass substrate 1 in the projection area of ​​the glass substrate 1, and the through hole 15 is filled with a conductive medium, which is generally Cu, or other metals or alloys with excellent thermal and electrical conductivity, which are not specifically limited here. The first pad area 111a is electrically connected to the first functional pin 121a through a conductive medium; the second pad area 111b is electrically connected to the fourth functional pin 121d through a conductive medium, and the first pad area 111a, the third pad area 131a and the fifth pad area 141a are interconnected through a lead 16;

[0060] The fourth pad area 131b is electrically connected to the second functional pin 121b through the lead 16;

[0061] The sixth pad area 141 b is electrically connected to the third functional pin 121 c through a lead 16 .

[0062] In traditional small-pitch LED lamp beads, through holes are generally set at the four corners of the BT substrate to form a connection between the front circuit and the back circuit of the substrate. The through holes of the BT substrate are usually obtained by mechanical drilling, and the aperture is generally 0.1mm~0.3mm. After subsequent cutting, they are exposed to the outside, which will form more water vapor channels. Although the ink layer can block part of the water vapor, the bonding between the ink and the packaging glue is relatively poor, which will also form certain water vapor channels. With the structure of the present invention, the fourth pad area located on the first side and the sixth pad area located on the second side can be directly electrically connected to the corresponding functional pins through the lead wire, and the first pad area and the second pad area located on the upper surface are respectively electrically connected through the through holes that penetrate the glass substrate. Under the joint action of the processing technology and structure, the aperture of the through hole can be significantly reduced, and can usually be set to 0.01mm~0.06mm, reducing the number and aperture of the through holes, thereby reducing the channels for water vapor to enter.

[0063] In one embodiment, Figure 2 to Figure 5As shown, the light emitting chip 2 includes a first light emitting chip 2a, a second light emitting chip 2b and a third light emitting chip 2c, and the first light emitting chip 2a, the second light emitting chip 2b and the third light emitting chip 2c are one of a red light chip, a green light chip and a blue light chip.

[0064] Preferably, the first light-emitting chip 2a, the second light-emitting chip 2b and the third light-emitting chip 2c are all flip-chip structures, and accordingly, the positive and negative electrodes of the first light-emitting chip 2a are electrically connected to the first pad area 111a and the second pad area 111b, respectively, the positive and negative electrodes of the second light-emitting chip 2b are electrically connected to the third pad area 131a and the fourth pad area 131b, respectively, and the positive and negative electrodes of the third light-emitting chip 2c are electrically connected to the fifth pad area 141a and the sixth pad area 141b, respectively. The use of flip-chips can directly form an electrical connection between the electrodes of the light-emitting chip and the corresponding pad areas, thereby reducing the range of the solid crystal area, reducing the use of bonding wires, and further improving airtightness. More preferably, the first light-emitting chip 2a is a red light flip-chip, the second light-emitting chip 2b is a blue light flip-chip, and the third light-emitting chip 2c is a green light flip-chip, to achieve the best light efficiency.

[0065] It is understandable that the electrical connection between the light-emitting chip and the corresponding pad area can be achieved through solder paste. In a preferred embodiment, solder pastes with different curing temperatures are used to solder different light-emitting chips in steps. Since the materials, voltage and current characteristics of different chips are different, the step-by-step use of solder pastes with different curing temperatures can improve the thermal, electrical, mechanical and process compatibility in multi-chip packaging, thereby improving the performance consistency, reliability and life of LED lamp beads.

[0066] Compared with BT substrates, glass substrates have a smaller thermal expansion coefficient, generally about 4ppm / ℃, which is much different from the thermal expansion coefficient of conventional metal media (such as Cu with a thermal expansion coefficient of 17ppm / ℃). When experiencing temperature changes, it will cause interface stress, which may cause cracking or peeling of the metal medium. In addition, conventional through holes are straight through holes, and the side walls of the through holes are approximately at right angles to the upper and / or lower surfaces of the glass substrate, with sharp edges, which further increases the problem of metal medium fracture and uneven distribution of the metal medium in the through holes, ultimately leading to unstable product performance. Therefore, in a preferred embodiment, if Fig.12 As shown, the side wall of the through hole 15 has a preset angle α with the lower surface 11 of the glass substrate 1; the preset angle α is 55° to 85°. By providing a through hole with an inclined side wall, it is possible to increase the difficulty of water vapor entering the LED lamp bead along the through hole, while slowing down the angle of the metal medium transitioning from the upper surface to the side wall of the through hole, thereby reducing the probability of the metal medium breaking.

[0067] In a preferred embodiment, Fig.13As shown, the side wall of the through hole 15 has a first wall surface 151, a second wall surface 152 and a third wall surface 153, the first wall surface 151 and the upper surface 11 of the glass substrate 1 have a preset angle β, the third wall surface 153 and the lower surface 12 of the glass substrate 1 have a preset angle α, the first wall surface 151, the second wall surface 152 and the third wall surface 153 are connected to form a convex structure toward the center of the through hole 15, wherein the first wall surface 151, the second wall surface 152 and the third wall surface 153 can be a plane or an arc surface, which is not specifically limited here; the preset angle α is 55° to 85°, and the preset angle β is 55° to 85°. The upper and lower openings of the through hole have a larger aperture, and the aperture of the middle part is smaller, which can improve the conductivity and heat dissipation performance without increasing the amount of metal medium used.

[0068] In one embodiment, if Figure 1 As shown, the LED lamp bead includes an LED chip group 100 and a packaging glue layer 200, and the packaging glue layer 200 at least covers the light-emitting chip 2. In one embodiment, as Figure 14 to Figure 16 As shown, the LED lamp bead includes two LED chip groups 100 and a packaging glue layer 200, the LED chip groups 100 are arranged at a preset distance, and the packaging glue layer 200 at least covers the light-emitting chip 2. It can be understood that there is no specific limitation on the number of LED chip groups 100. When the number of LED chip groups is two, the two LED chip groups 100 are arranged in a straight line, and when the number of LED chip groups 100 is four, the four LED chip groups 100 are arranged in a field shape. Specifically, the preset distance between adjacent LED chip groups 100 can be selected according to actual conditions, but compared with conventional two-in-one or multi-in-one LED lamp beads, the preset distance between the two LED chip groups of the present invention can be significantly shortened. Compared with conventional structures, the preset distance of the present invention can be shortened by 30% to 50%.

[0069] Correspondingly, the present invention also provides a method for preparing an LED lamp bead, which is used to prepare the above-mentioned LED lamp bead, comprising the following steps:

[0070] S1. Provide a glass substrate and form a pin area on the lower surface of the glass substrate.

[0071] S2. Forming a first crystal-bonding region, a second crystal-bonding region, and a third crystal-bonding region on the upper surface, the first side surface, and the second side surface of the glass substrate, respectively.

[0072] Specifically, the pin region, the first crystal-bonding region, the second crystal-bonding region and the third crystal-bonding region can be prepared by an etching process.

[0073] S3, electrically connecting the pin region to the first die-bonding region, the second die-bonding region, and the third die-bonding region respectively.

[0074] In one embodiment, the first crystal-bonding area includes a first pad area and a second pad area that are spaced apart, the second crystal-bonding area includes a third pad area and a fourth pad area that are spaced apart, the third crystal-bonding area includes a fifth pad area and a sixth pad area that are spaced apart; the pin area includes a first function pin, a second function pin, a third function pin and a fourth function pin that are spaced apart.

[0075] Specifically, the first pad area, the third pad area and the fifth pad area are connected to each other to form a common pad, and are electrically connected to the first functional pin;

[0076] The second pad area is electrically connected to the fourth functional pin;

[0077] The fourth pad area is electrically connected to the second functional pin;

[0078] The sixth pad area is electrically connected to the third functional pin.

[0079] S4, fixing the light-emitting chip on the first crystal-bonding area, the second crystal-bonding area and the third crystal-bonding area and forming an electrical connection to obtain an LED chip group.

[0080] In one embodiment, the electrodes of the light-emitting chip are electrically connected to the corresponding pad areas through solder paste.

[0081] S5. Forming a packaging adhesive layer on the LED chipset to obtain the LED lamp beads.

[0082] In one embodiment, the encapsulation adhesive layer is formed by molding, and the encapsulation adhesive layer covers the light-emitting chip and the upper surface, the first side surface and the second side surface of the glass substrate. Preferably, the boundary shape of the LED lamp bead is rectangular, and the structure is regular, which is more conducive to subsequent layout.

[0083] In one embodiment, when the number of LED chip groups is at least two, the LED chip groups are arranged at a preset distance, and a packaging adhesive layer is formed on the LED chip groups to obtain the LED lamp bead. Specifically, the packaging adhesive layer is formed by molding, and the packaging adhesive layer covers the upper surface, the first side surface, and the second side surface of the light-emitting chip and the glass substrate, and connects multiple LED chip groups into a whole.

[0084] It is understandable that after the encapsulation glue layer is formed by molding, it is then processed through molding and cutting processes to finally form the LED lamp beads.

[0085] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. An LED lamp bead, characterized in that: Including LED chipset and encapsulation glue layer; The LED chipset includes a glass substrate and a light-emitting chip; The glass substrate has an upper surface, a lower surface, a first side surface and a second side surface, the lower surface of the glass substrate is provided with a pin area, and the upper surface, the first side surface and the second side surface of the glass substrate are respectively provided with a first crystal-bonding area, a second crystal-bonding area and a third crystal-bonding area; The plurality of light emitting chips are respectively arranged on the first solid crystal region, the second solid crystal region and the third solid crystal region. The packaging glue layer at least covers the light-emitting chip.

2. The LED lamp bead according to claim 1, characterized in that: The first crystal-bonding area includes a first pad area and a second pad area that are spaced apart, the second crystal-bonding area includes a third pad area and a fourth pad area that are spaced apart, and the third crystal-bonding area includes a fifth pad area and a sixth pad area that are spaced apart; The pin area includes a first function pin, a second function pin, a third function pin and a fourth function pin which are arranged at intervals.

3. The LED lamp bead as claimed in claim 2, characterized in that: The first pad area, the third pad area and the fifth pad area are connected to each other and electrically connected to the first functional pin; The second pad area is electrically connected to the fourth functional pin; The fourth pad area is electrically connected to the second functional pin; The sixth pad area is electrically connected to the third functional pin.

4. The LED lamp bead as claimed in claim 3, characterized in that: The first pad area and the second pad area are both provided with through holes penetrating the upper surface and the lower surface of the glass substrate in the projection area of ​​the glass substrate, and the through holes are filled with a conductive medium; the first pad area is electrically connected to the first functional pin through the conductive medium; the second pad area is electrically connected to the fourth functional pin through the conductive medium; The fourth pad area is electrically connected to the second functional pin via a lead; The sixth pad area is electrically connected to the third functional pin through a lead.

5. The LED lamp bead as claimed in claim 2, characterized in that: The light-emitting chip comprises a first light-emitting chip, a second light-emitting chip and a third light-emitting chip, wherein the first light-emitting chip, the second light-emitting chip and the third light-emitting chip are one of a red light chip, a green light chip and a blue light chip; The first light-emitting chip, the second light-emitting chip and the third light-emitting chip are all flip-chip structures; the positive and negative electrodes of the first light-emitting chip are electrically connected to the first pad area and the second pad area, respectively, the positive and negative electrodes of the second light-emitting chip are electrically connected to the third pad area and the fourth pad area, respectively, and the positive and negative electrodes of the third light-emitting chip are electrically connected to the fifth pad area and the sixth pad area, respectively.

6. The LED lamp bead according to claim 1, characterized in that: A preset angle is formed between the side wall of the through hole and the lower surface of the glass substrate; the preset angle is 55° to 85°.

7. The LED lamp bead as claimed in claim 6, characterized in that: The side wall of the through hole has a first wall surface, a second wall surface and a third wall surface, the first wall surface and the upper surface of the glass substrate have a preset angle, the third wall surface and the lower surface of the glass substrate have a preset angle, the first wall surface, the second wall surface and the third wall surface are connected to form a convex structure facing the center of the through hole; the preset angle is 55° to 85°.

8. The LED lamp bead according to claim 1, characterized in that: The LED lamp bead comprises a packaging glue layer and at least two LED chip groups, the LED chip groups are arranged at a preset distance, and the packaging glue layer at least covers the light-emitting chip.

9. A method for preparing an LED lamp bead, used for preparing the LED lamp bead as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: Providing a glass substrate, and forming a pin area on the lower surface of the glass substrate; Forming a first crystal-bonding region, a second crystal-bonding region and a third crystal-bonding region on the upper surface, the first side surface and the second side surface of the glass substrate respectively; The pin region is electrically connected to the first die-bonding region, the second die-bonding region and the third die-bonding region respectively; Fixing light-emitting chips on the first solid crystal region, the second solid crystal region and the third solid crystal region and forming electrical connections to obtain an LED chip group; A packaging adhesive layer is formed on the LED chip group to obtain the LED lamp bead.

10. A display screen, characterized in that: It comprises the LED lamp bead as claimed in any one of claims 1 to 8.

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