JPWO2007138709A1 - Plasma display panel and manufacturing method thereof - Google Patents

Abstract

In the plasma display panel (1), a sealing material in which peripheral portions of the front plate (10) and the rear plate (20) are arranged in a frame shape with a width of 3.0 to 6.0 mm and surrounding the discharge gas space ( 35). The sealing material (35) is a fired body of a glass paste (35a) having a thixo value of 3.0 to 7.0 according to the viscosity characteristics depending on the shear rate, and has a density of 5 to 40 pieces / cm <2>. Contains spacers (71, 72, 74, 75).

Description

  The present invention relates to a plasma display panel (PDP) and a manufacturing method thereof, and more particularly to a configuration of a joint portion between a front plate and a back plate.

  The plasma display panel is composed of a front plate and a back plate both larger than the screen. The front plate and the back plate are joined by a frame-shaped sealing material located outside the screen, and constitute a flat device that seals the discharge gas space. The main material of the front plate and the back plate is a glass substrate, and the sealing material is a sintered body of low-melting glass.

  The main processes in the manufacture of the plasma display panel are the process of manufacturing each of the front plate and the back plate, the step of bonding the peripheral parts of the front plate and the back plate with the sealing material, and the residual in the internal space formed by the bonding A process of exhausting the gas to be discharged, and a process of filling the internal space cleaned by the exhaust with the discharge gas.

  The joint portion between the front plate and the back plate may be in a so-called submerged state at the exhaust stage of manufacture through these steps. In the exhaust process, the sealing material is easily deformed because it is heated to about 400 ° C. together with the front plate and the back plate. Therefore, when the pressure in the internal space decreases due to exhaust, the sealing material may be crushed by the external air pressure that presses the front plate and the back plate. When the sealing material is crushed, the facing gap between the front plate and the back plate at the joint portion becomes smaller than the set value. This condition is called subduction.

  The sinking causes poor adhesion between the front plate and the back plate in the peripheral portion of the screen. The adhesion failure causes abnormal noise during the display operation. Anomalous noise is generated when periodic electrostatic attraction accompanying application of a high-frequency driving voltage for display causes the glass substrate to vibrate locally. The generation of abnormal noise impairs display quality.

In general, in order to prevent sinking, measures are taken to make the width of each side of the sealing material arranged in a rectangular frame shape a sufficiently large value exceeding 10 mm so as to withstand the pressing force during exhaust. Yes. As another countermeasure, Japanese Patent Laid-Open No. 2001-236896 proposes that a sealing material contains beads as a spacer. However, the publication does not specifically describe the width of the sealing material and the density of the spacer. In addition, as an improvement of measures using beads, JP-A-2006-49265 describes that non-porous beads are contained in a sealing material. In this publication, a glass paste having a nonporous bead content of 0.05 to 2 wt% is applied in a frame shape having a width of 3 to 5 mm and fired, thereby sealing with a width of 8 to 12 mm. Specific examples of providing the material are disclosed.
JP 2001-236896 A JP 2006-49265 A

In flat panel displays including plasma display panels,
The product value is increased when the outer dimensions are close to the screen size. In other words, if there are two similar flat panel displays with the same external dimensions but different screen sizes, the larger screen size is generally preferred, and there are two similar flat panel displays with the same external dimensions but different external dimensions. In general, a smaller outer dimension is preferred.

  In the design of a new plasma display panel, if the screen size is made larger than the existing size while maintaining the existing dimensions, the inevitably the annular peripheral part surrounding the screen in the inner space of the plasma display panel. The width narrows. The surrounding portion is an important ventilation path in the exhaust process for manufacturing, and is deeply related to the quality of the purification of the internal space. When this peripheral portion is narrowed, the exhaust conductance is lowered, so that an impurity gas such as water or carbon dioxide tends to remain in the internal space, and there is a risk that display characteristics vary or the change with time becomes remarkable. In particular, the more complicated the structure in the screen for high definition and high brightness, the more the impurity gas is deposited and the more difficult the impurity gas flows from the screen to the surrounding area. desirable.

  It is effective to make the frame-shaped sealing material as thin as possible in order to enlarge the screen while suppressing an increase in the outer dimensions and to secure a sufficient exhaust conductance. The exhaust passage (the above-mentioned surrounding portion in the internal space) is expanded by the amount of the sealing material that becomes thinner.

  However, when the sealing material is made thin, the compressive strength is lowered due to the decrease in the volume of the sealing material. Therefore, in order to prevent the occurrence of subsidence, it is necessary to find the added amount of beads suitable for a narrow sealing material.

  Further, in order to make the sealing material thinner, it is necessary to apply a glass paste, which is a sealing material, at the time of manufacture thinner than before by dispenser or screen printing. The coating layer must be sufficiently thicker than the sealing material obtained by subsequent firing (for example, twice the thickness). For this reason, it is necessary to find a viscosity of a paste suitable for forming a coating layer having a thin and high coating section having a large aspect ratio.

  An object of the present invention is to provide a plasma display panel having a sealing structure that does not cause subsidence and can improve exhaust conductance. Another object is to provide a method of manufacturing a plasma display panel having the above sealing structure.

In the plasma display panel that achieves the above object, the peripheral portions of the front plate and the back plate are joined by a frame-shaped sealing material that surrounds the discharge gas space with a width of 3.0 to 6.0 mm, The bonding material contains bead spacers at a density of 5 to 40 pieces / cm ² .

  The manufacturing method for achieving the above object includes a bead spacer as a sealing material for joining the front plate and the back plate, and a thixo value defined by the following formula (1) is 3.0 to 7. A glass paste of 0 is used.

Thixo value = η _0.3 / η ₁₇ (1)
However, η _0.3 in the formula is the viscosity when the shear rate is _{0.3 s} ⁻¹ corresponding to the leveling immediately after coating. η ₁₇ is the viscosity when the shear rate is 17 s ⁻¹ corresponding to the time when the nozzle is ejected during coating or the time when the screen passes.

It is a front view which shows schematic structure of a plasma display panel. It is sectional drawing which shows schematic structure of a plasma display panel. It is a disassembled perspective view which shows the typical cell structure of a plasma display panel. It is a figure which shows the positional relationship of a sealing material and a screen, and the path | route of exhaust. It is a figure which shows the cross-section of the peripheral part of a plasma display panel. It is a figure which shows an example of the coating method of the paste for sealing. It is a figure which shows typically the process of joining with a front board and a backplate. It is a figure which shows the viscosity characteristic of the paste for sealing.

A schematic configuration of the plasma display panel is shown in FIGS. The plasma display panel 1 includes a front plate 10 and a back plate 20 and has a screen 60 composed of discharge cells arranged vertically and horizontally. Both the front plate 10 and the rear plate 20 are structures in which electrodes and other components are fixed to a glass substrate having a thickness of about 3 mm larger than the screen 60. The front plate 10 and the back plate 20 are arranged to face each other so as to overlap each other, and are joined by a sealing material 35 having a frame shape in a plan view at the periphery of the overlapping region. The front plate 10 projects about 5 mm to the left and right of the figure with respect to the back plate 20, and the back plate 20 projects about 5 mm to the top and bottom of the drawing with respect to the front plate 10. A flexible wiring board for conductive connection with the drive unit is joined to the end portions of the front plate 10 and the back plate 20 that protrude in this manner. For example, when the size of the screen 60 is 42 inches diagonal, the plasma display panel 1 has a size of approximately 994 mm × 585 mm. The internal space 30 sealed by the front plate 10, the back plate 20, and the sealing material 35 is filled with a discharge gas in which neon and xenon are mixed.

  The screen 60 of the plasma display panel 1 has a cell structure shown in FIG. In FIG. 3, the front plate 10 and the back plate 20 are drawn separately to facilitate understanding of the internal structure.

  The front plate 10 includes a glass substrate 11, a first row electrode X, a second row electrode Y, a dielectric layer 17, and a protective film 18. The back plate 20 includes a glass substrate 21, a column electrode A, a dielectric layer 24, a plurality of partition walls 23, a red (R) phosphor 24, a green (G) phosphor 25, and a blue (B) phosphor 26. Is provided.

  The row electrode X and the row electrode Y are alternately arranged on the inner surface of the glass substrate 11 as an electrode for generating a surface discharge. Each of these electrodes consists of a patterned transparent conductive film 12 and metal film 13. The dielectric layer 17 extends over the entire screen and covers the row electrodes X and Y. The protective film 18 prevents sputtering of the dielectric layer 17.

  As shown in FIG. 4, the annular peripheral portion 31 surrounding the screen 60 in the internal space surrounded by the sealing material 35 is formed in the vent hole 90 for exhaust and gas filling provided in the back plate 20. It is connected. In the exhaust process of manufacturing the plasma display panel 1, the peripheral portion 31 becomes an important exhaust path. The impurity gas in the screen 60 flows to the outside through the peripheral portion 31 and the vent hole 90. The larger the width W31 of the peripheral portion 31 to be discharged, the larger the exhaust conductance. When the substrate size and the screen size are determined, the narrower the sealing material 35, that is, the smaller the width W35 of the sealing material 35, the greater the width W31 of the peripheral portion 31.

  FIG. 5 shows a cross-sectional structure of the periphery of the front plate and the back plate. In FIG. 5, the thickness of the element between the glass substrates is enlarged to make the structure easy to understand.

  The partition wall 23 arranged on the back plate 20 prevents discharge interference between adjacent rows and also functions as a spacer. That is, the thickness of the internal space in the screen 60 is defined by the partition wall 23 and is substantially equal to the height H of the partition wall 23. The height H is optimized according to the cell size, and is generally selected to be a value within the range of 130 μm to 200 μm.

  A characteristic component in the plasma display panel 1 is a sealing material 35 that integrates the front plate 10 and the back plate 20. The sealing material 35 is a fired body of a low-melting glass paste and includes a sufficient amount of bead spacers 71 and 72 for preventing sinking in the plasma display panel 1 and equalizing the thickness of the peripheral portion. The sealing material 35 has a width W35 of about 3.0 to 6.0 mm. The distance between the inner end of the sealing material 35 and the partition wall 23, that is, the width W31 of the peripheral portion 31 of the internal space is about 20 mm. The bead spacers 71 and 72 have a relatively broad particle size distribution including a particle size of about 5/6 times the design thickness of the sealing material 35 and a particle size of about 1.5 times.

FIG. 6 shows an example of a method for applying a sealing paste. In the manufacture of the plasma display panel 1, after the front plate 10 and the back plate 20 are separately manufactured, a sealing low melting point glass paste (hereinafter referred to as a seal) containing bead spacers on one or both of the front plate 10 and the back plate 20 is used. Apply a paste). In FIG. 6, a seal paste 35a is applied by a dispenser to two back plates 20 that are collectively manufactured using a mother glass 210 that is a material of a glass substrate. The application is performed by simultaneously moving the two nozzles 86 relative to the back plate 20 so as to draw a square. For example, by using a nozzle 86 having an inner diameter of 3 mm and applying a seal paste 35a having a viscosity of 40 to 50 Pa · s under the conditions of a discharge pressure of 1.0 to 2.0 kgf / cm ² and a moving speed of 100 mm / s, a width of 1. A paste layer having a thickness of 5 to 3.0 mm and a thickness of 450 μm or more can be obtained. The application width of the seal paste 35a must be controlled so that the finished width after baking is about 3.0 to 6.0 mm. In consideration of leakage resistance at the time of sealing, which will be described later, it is necessary that the coating width be 1.5 mm or more, and it is desirable that the coating width be 3.0 mm or less in order to ensure air permeability during exhaust.

  As shown in FIG. 7A, it is necessary to apply the seal paste 35 a sufficiently higher than the partition wall 23. For example, when the height H of the partition wall 23 is 200 μm, the coating thickness Ha of the seal paste 35a is set to about 400 to 450 μm. In this case, a gap having a dimension D of about 200 to 250 μm is provided between the partition wall 23 and the front plate 10 in a state where the front plate 10 is overlapped with the back plate 20 to which the seal paste 35a is applied so as to sandwich the seal paste 35a. 30a exists.

  In the exhaust process, the overlapped front plate 10 and back plate 20 are heated to about 400 ° C., and the inside is exhausted through a tip tube 95 that is attached to the outer surface of the back plate 10 in advance so as to communicate with the vent hole 90. . At this time, a gap 30a between the front plate 10 and the partition wall 23 becomes an exhaust path. The larger the dimension D of the gap 30a, the faster the impurity gas in the screen area can be discharged.

  As the internal pressure decreases due to exhaust, the front plate 10 and the back plate 20 approach each other, and accordingly, the seal paste 35a spreads along the substrate surface, and the width of 1.5 mm to 3.0 mm is 3.0 mm to 6.mm. It becomes about 0 mm. After the front plate 10 and the partition wall 23 come into contact with each other, the peripheral portion of the internal space becomes the main exhaust passage as described with reference to FIG. And bead spacers 71, 72, 74, and 75 contained in seal paste 35a prevent sinking.

Here, when the sealing width is 3.0 to 6.0 mm, the content of the bead spacers contained in the seal paste 35a must be a value at which the density becomes 5 pieces / cm ² or more after firing. . When the density is less than 5 / cm ² , the bead spacers 71, 72, 74, and 75 are deformed due to the pressure difference between the inside and outside during exhaust, and sinking occurs. On the other hand, the content of the bead spacers 71, 72, 74, and 75 is considered in consideration of the viscosity characteristics, the increase in material cost due to the addition of beads, and the probability of the generation of excessive particles that cause electrode disconnection (bonding between beads). It is desirable to limit the density after firing to 40 pieces / cm ² or less.

  FIG. 7B shows a state in which the seal paste 35 a is baked to become the sealing material 35, and the front plate 10 and the back plate 20 are joined by the sealing material 35. After joining, the discharge gas is filled through the tip tube 95, and then the inner space is sealed by melting the tip tube 95.

  In such a manufacturing process, it is desirable in terms of exhaust efficiency that the coating thickness Ha of the seal paste 35a is large. On the other hand, it is desirable that the coating width W35a of the seal paste 35a is smaller within a range in which necessary leak resistance can be obtained. That is, it is necessary to apply the seal paste 35a so that a cross section with a larger aspect ratio (Ha / W35a) can be obtained. To achieve the desired application, the viscosity characteristics of the seal paste 35a must be appropriate. Appropriate viscosity characteristics are characteristics in which the viscosity when discharging from the nozzle 86 in the case of using a dispenser or passing through the screen in the case of using screen printing is small, and the viscosity immediately after application is reasonably large.

FIG. 8 shows an example of a viscosity straight line of the seal paste 35a. The viscosity when the seal paste 35a flows inside the nozzle 86 or passes through the printing screen is a viscosity in a high shear region where the shear rate is 17 s ⁻¹ , and the viscosity at the time of leveling immediately after application is shear. Viscosity in the low shear region with a speed of 0.3 s ⁻¹ . Here, in order to obtain a coating thickness of 450 μm or more with a coating width of 3.0 mm or less at the time of coating, the coating flow rate is relatively increased, and the flow in the coating width direction during leveling is suppressed. It is essential. Given this, as shown in FIG. 8, the ratio of the viscosity eta _0.3 and a shear rate when the shear rate is 0.3 s ^-1 is the viscosity eta ₁₇ when the 17s ^-1, i.e. diagram of the slope of the line ( The appropriate range of the thixo value: η _0.3 / η ₁₇ ) is 3.0 to 7.0. The thixo value of the comparative example in the figure is less than 3.0. If the thixo value is less than 3.0, the viscosity immediately after coating is too small, so that it spreads after coating and the coating width increases and the coating thickness decreases, or the viscosity at the time of ejection is excessive. Application is difficult. If it is greater than 7.0, the viscosity immediately after coating is excessive, so that leveling after coating becomes insufficient, and noticeable uneven coating thickness tends to occur.

  The present invention is useful for realizing a plasma display panel having a small difference in size between the outer shape and the screen, and contributes to improving the display quality and reliability of such a plasma display panel.

Claims (4)

A plasma display panel comprising a front plate and a back plate facing each other across a discharge gas space,
The peripheral portions of the front plate and the back plate are joined by a frame-shaped sealing material that surrounds the discharge gas space with a width of 3.0 to 6.0 mm,
The plasma display panel, wherein the sealing material contains bead spacers at a density of 5 to 40 pieces / cm ² . The plasma display panel according to claim 1, wherein a diameter dimension of the bead spacer is 5/6 to 9/6 times a design value of a facing distance in a peripheral portion of the front plate and the back plate. A method of manufacturing a plasma display panel comprising a front plate and a back plate joined by a frame-shaped sealing material,
Producing the front plate and the back plate separately,
A glass paste for sealing containing a bead spacer and having a thixo value of 3.0 to 7.0 defined by the following formula is applied in a frame shape to the periphery of the front plate or the periphery of the back plate And
Thixo value = η _0.3 / η ₁₇
Where η _0.3 is the viscosity when the shear rate is _{0.3 s} ⁻¹ , and η ₁₇ is the viscosity when the shear rate is 17 s ⁻¹ ,
The front plate and the back plate are overlapped so as to sandwich the frame-shaped glass paste layer formed by coating,
The method for producing a plasma display panel, comprising firing the frame-shaped glass paste layer in a state where a facing gap between the front plate and the back plate is reduced in pressure. The method for manufacturing a plasma display panel according to claim 3, wherein the glass paste is applied in a frame shape including a band portion having a width of 1.5 to 3.0 mm or less.