JP2008076588A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a matrix electron source display using a thin-film electron source generates an afterimage phenomenon right after a display gradation is greatly switched. <P>SOLUTION: The afterimage phenomenon is reduced by applying additional pulses, having the same polarity as that during electron discharging, within a one-field period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image display device that displays an image using electron-emitting devices and phosphors arranged in a matrix.

  A matrix electron source display uses a crossing point of electrodes orthogonal to each other as a pixel, an electron emitting element is provided in each pixel, and the amount of emitted electrons is adjusted by adjusting the voltage or pulse width applied to each electron emitting element. The emitted electrons are accelerated in a vacuum, and then irradiated onto the phosphor, causing the irradiated phosphor to emit light. As an electron-emitting device, one using a field emission cathode, one using a MIM (Metal-Insulator-Metal) type electron source, one using a carbon nanotube cathode, one using a diamond cathode, one using a surface conduction electron-emitting device, Some use a ballistic surface electron source. Thus, the matrix electron source display refers to an electron beam excitation type flat display in which an electron emitting element and a phosphor are combined.

  As an electron-emitting device used for a matrix electron source display, there is a thin film electron source. A thin-film electron source has a structure in which an upper electrode, an electron acceleration layer, and a lower electrode are stacked. The MIM (Metal-Insulator-Metal) type electron source, MOS (Metal-oxide Semiconductor) type electron source, ballistic surface Includes electron sources. The MOS type electron source uses a semiconductor-insulator laminated film as an electron acceleration layer. For example, Japanese Journal of Applied Physics, Vol. 36, Part 2, No. 7B, pp. L939 to L941 (1997) (Non-Patent Document 1). The ballistic surface electron source uses a porous silicon or the like for the electron acceleration layer. For example, Japanese Journal of Applied Physics, Vol. 34, Part 2, No. 6A, pp. L705 to L707 (1995) (Non-Patent Document 2). A thin-film electron source emits electrons accelerated in an electron acceleration layer into a vacuum.

  FIG. 2 is an energy band diagram showing the operating principle of the thin film electron source. The lower electrode 13, the electron acceleration layer 12, and the upper electrode 11 are stacked, and the state when a positive voltage is applied to the upper electrode 11 is illustrated. In the case of the MIM type electron source, an insulator is used as the electron acceleration layer 12. An electric field is generated in the electron acceleration layer 12 by a voltage applied between the upper electrode and the lower electrode. Due to this electric field, electrons flow from the lower electrode 13 into the electron acceleration layer 12 by a tunnel phenomenon. The electrons are accelerated by the electric field in the electron acceleration layer 12 and become hot electrons. When the hot electrons pass through the upper electrode 11, some electrons lose energy due to inelastic scattering or the like. When reaching the upper electrode 11-vacuum interface (that is, the surface of the upper electrode), electrons having a kinetic energy larger than the work function Φ of the surface are emitted from the surface of the upper electrode 11 into the vacuum 10. In the present specification, the current flowing between the lower electrode 13 and the upper electrode 11 due to the hot electrons is referred to as a diode current Jd, and the current released into the vacuum is referred to as an emission current Je. The ratio α between the emission current Je and the diode current Jd (emission ratio α = Je / Jd) is about 0.01% to 10%.

  Compared to field emission cathodes, thin-film electron sources are more resistant to surface contamination, and the emission electron beam has a smaller spread, so that a high-definition display device can be realized. The operating voltage is low and the driver circuit driver is low. It has the characteristics suitable for the display device.

JP 2004-363075 A Japanese Journal of Applied Physics, Vol.36, Part 2, No.7B, pp. L939 to L941 (1997) Japanese Journal of Applied Physics, Vol.34, Part 2, No.6A, pp. L705 ~ L707 (1995) IEEE Transactions on Electron Devices, vol. 49, No. 6, pp. 1059-1065 (2002).

  In a matrix electron source display using a thin-film electron source as an electron-emitting device, there is a problem that right luminance (gradation) is not displayed immediately after the display luminance is largely changed, and an afterimage remains.

  The present invention provides an image display device that reduces this afterimage.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
A lower electrode, an upper electrode, and an electron acceleration layer sandwiched between the lower electrode and the upper electrode; by applying a voltage between the lower electrode and the upper electrode, A plurality of thin film electron sources emitting electrons;
A plurality of scan electrodes parallel to each other and a plurality of data electrodes parallel to each other, and the thin film electron source is disposed at an intersection of the scan electrodes and the data electrodes,
A display panel having a phosphor screen having a phosphor screen formed with a phosphor that emits light when excited by the electrons;
In an image display device having a first driving means connected to the plurality of scanning electrodes and outputting a scanning pulse, and a second driving means connected to the plurality of data electrodes,
One field period is divided into a display period in which scan pulses are sequentially output and a non-display period other than that.
An image display device, wherein the upper electrode applies one or more additional pulses having a positive voltage with respect to the lower electrode during the non-display period.

A lower electrode, an upper electrode, and an electron acceleration layer sandwiched between the lower electrode and the upper electrode; by applying a voltage between the lower electrode and the upper electrode, A plurality of thin film electron sources emitting electrons;
A plurality of scan electrodes parallel to each other and a plurality of data electrodes parallel to each other, and the thin film electron source is disposed at an intersection of the scan electrodes and the data electrodes,
A display panel having a phosphor screen having a phosphor screen formed with a phosphor that emits light when excited by the electrons;
In an image display device having a first driving means connected to the plurality of scanning electrodes and outputting a scanning pulse, and a second driving means connected to the plurality of data electrodes,
In addition to applying the scanning pulse within one field period, the upper electrode applies an additional pulse having a positive voltage to the lower electrode one or more times,
The voltage applied between the upper electrode and the lower electrode by the additional pulse is larger than the difference between the maximum value and the minimum value of the voltage applied to the data electrode.

  An afterimage is a phenomenon in which an image before gradation change remains slightly after the gradation (luminance) of the display image has changed greatly. As an example, let us consider a case where a rectangular (window-like) pattern 802 is displayed on a part of the display screen 801 of the image display device as shown in FIG. The pattern 802 has peak luminance (maximum gradation (for example, 255 levels)), and other areas have average luminance (for example, gradation 64). Then, consider the case where the same gradation (for example, gradation 64 level) is displayed on the entire screen (FIG. 3B). For a while after switching the gradation, the area where the pattern 802 is displayed becomes slightly darker than the other areas. After a certain period of time, the area 802 has the same luminance as the other areas. This is an afterimage.

  In order to describe the afterimage phenomenon in more detail, it will be described with reference to FIG. FIG. 4 is a diagram schematically showing temporal changes in the input signal (gradation signal) and the actually displayed luminance in the region 802. At time t1, the input signal is changed from the gradation level GS2 to GS1. At time t2, the input signal is changed from the gradation level GS1 to GS2. The gradation level is arbitrary, but as an example, GS1 is 255 gradations corresponding to the peak luminance, and GS2 is 64 gradations. The display brightness corresponding to the gradation level GS1 is L1, and the display brightness corresponding to the gradation level GS2 is L2.

  At time t1, the luminance increases from L2 to L1, but then changes to luminance level L1-ΔL1 after a certain time. At time t2, the luminance is expected to change to L2, but actually, the luminance is once lower than L2 (L2-ΔL2), and thereafter reaches luminance level L2 after a certain time. Due to the behavior at time t2, an afterimage phenomenon as shown in FIG. 3B occurs on the display screen.

  In FIG. 4, the time required for the luminance to reach the expected value L2 after switching the input signal at time t2 is referred to as “afterimage time”.

  In order to improve the quality of the displayed image, it is important to shorten the afterimage time. For example, if the afterimage time is 0.1 seconds or less, the afterimage is hardly detected due to human visual characteristics. However, when the afterimage time is 10 seconds, the image quality is degraded because it is clearly detected visually.

  In general, there are (a) voltage amplitude modulation method (PAM) and (b) pulse width modulation method (PWM) as typical methods of gradation display of an image display device. PAM adjusts the luminance by changing the applied voltage amplitude, whereas PWM adjusts the luminance by changing the applied pulse width.

  The above-mentioned afterimage phenomenon appears in both PAM and PWM gradation display methods, but the inventors have found that PAM (voltage amplitude modulation method) causes more afterimages. Therefore, in an image display apparatus that performs gradation display using PAM, it is particularly necessary to take measures against afterimages.

  Conventionally, in an image display device using a thin film electron source, when gradation display is performed by PAM (voltage amplitude modulation method), the afterimage time is about several tens of seconds to several hundreds of seconds, and the image quality of the display image is deteriorated. It was a factor.

  The present inventor has intensively studied the cause of the afterimage phenomenon described with reference to FIGS. 3 and 4 in the image display device using the thin film electron source, and has found that the cause is as follows. First, when the afterimage phenomenon occurs, the electron emission ratio (= Je / Jd) of the thin film electron source is found to be constant. That is, the afterimage phenomenon occurs because the diode current temporarily deviates from the assumed current value.

  The inventors have found that the cause of the temporary deviation of the diode current is that the current-voltage characteristics of the thin film electron source change. FIG. 5 is a diagram schematically showing the relationship between the diode current (Jd) and the diode voltage (Vd) of the thin film electron source. Here, the diode current Jd is a current flowing between the upper electrode and the lower electrode, and the diode voltage Vd is a voltage applied between the upper electrode and the lower electrode, and the upper electrode voltage is measured with reference to the lower electrode potential. It is a thing. In FIG. 5, the diode current Jd is plotted on a logarithmic scale.

  In FIG. 5, a Jd-Vd characteristic 805 is a characteristic at the luminance level GS2, and a Jd-Vd characteristic 806 is a characteristic at the luminance level GS1. The Jd-Vd characteristic 806 when driving in GS1 with a high luminance level (that is, a region where the diode current is large) is shifted to a higher voltage side than the characteristic 805. This is because the amount of charge accumulated in the electron acceleration layer constituting the thin film electron source increases as the diode current increases (at the luminance level GS1). This will be described with reference to FIG.

  FIG. 6 schematically shows an electron energy band diagram of the thin film electron source. When there is no accumulated charge in the electron acceleration layer (FIG. 6A), the electric field formed by the externally applied voltage becomes the internal electric field. Since this internal electric field is applied to the interface between the lower electrode and the electron acceleration layer electric field, electrons are emitted from the lower electrode to the electron acceleration layer, resulting in a diode current Jd. On the other hand, FIG. 6B shows a case where negative charges are accumulated in the electron acceleration layer. In this case, the internal electric field is reduced because the electric field formed by the accumulated charge works in a direction to cancel the external electric field. For this reason, even if the same external voltage Vd is applied, the diode field Jd becomes small because the internal electric field is small. In other words, the Jd-Vd characteristic is shifted to the high voltage side.

  As an example, in the configuration described in the following embodiment, the operating voltage is about 8V, but the Jd-Vd characteristic (806 in FIG. 5) when GS1 = 255 level and the Jd-Vd characteristic when GS2 = 64 level. The threshold voltage difference ΔVth from (805) was 15 mV.

  The current-voltage characteristics in FIG. 5 and the afterimage characteristics in FIG. 4 will be described in association with each other. In FIG. 4, immediately before time t2, the Jd-Vd characteristic is the characteristic 806 in FIG. At time t2, the input signal becomes smaller corresponding to GS2, but the accumulated charge amount in the thin film electron source does not change instantaneously, so the Jd-Vd characteristic remains at 806. Thereafter, the Jd-Vd characteristic shifts to the characteristic 805 corresponding to the decrease in the input signal. When the original Jd-Vd characteristic 805 is reached, the luminance value also becomes the original value L2.

  As described above, the process of changing the amount of stored charge in the electron acceleration layer of the thin film electron source is the afterimage recovery process. Therefore, if the change in the accumulated charge amount is accelerated, the afterimage recovery is accelerated and the afterimage can be reduced.

  The cause of the afterimage phenomenon in the image display device using the thin film electron source is the shift of the Jd-Vd characteristic as described above. Therefore, when the thin film electron source is driven by a constant current circuit and a driving method (constant current driving method) in which the diode current is set to a predetermined value in terms of a circuit is used, the afterimage phenomenon does not matter. This is because in the constant current driving method, the diode current value corresponding to the desired gradation level is controlled by an external circuit, so that the desired current value Jd flows even if the Jd-Vd characteristic changes. That is, the present invention solves a problem that occurs in an image display device that uses a driving method that controls gradation according to a voltage value.

  In the present invention, by applying an additional pulse, the change in the amount of accumulated charge in the electron acceleration layer of the thin film electron source is accelerated, and the afterimage is reduced. The specific method and action mechanism will be described in accordance with specific examples.

  As described above, according to the present invention, in an image display apparatus using a thin film electron source, it is possible to reduce an afterimage that has occurred immediately after the display gradation (brightness) is greatly changed.

  In this manner, the image display device according to the present invention can realize an image display device that displays an image with higher quality than before.

  The image display apparatus according to the present invention will be described below in more detail with reference to embodiments of the invention according to some examples shown in the drawings.

  A first embodiment using the present invention will be described. In this embodiment, a MIM (Metal-Insulator-Metal, metal-insulator-metal) electron source is used as the thin film electron source 301.

  FIG. 7 is a plan view of the display panel used in this embodiment. 8 is a cross-sectional view taken along the line AB in FIG. In FIG. 8, only the scanning electrode 310 is extracted from the components of the cathode plate 601 and described.

  The inside surrounded by the cathode plate 601, the fluorescent plate 602, and the frame member 603 is in a vacuum. A spacer 60 is disposed in the vacuum region to resist atmospheric pressure. The shape, number and arrangement of the spacers 60 are arbitrary. In FIG. 7, the thickness of the spacer 60 is drawn to be larger than the width of the scan electrode 310, but this is for ease of viewing the drawing, and the thickness of the spacer 60 is actually thinner than the width of the scan electrode 310. On the cathode plate 601, the scanning electrode 310 is disposed in the horizontal direction, and the data electrode 311 is disposed orthogonally thereto. An intersection between the scan electrode 310 and the data electrode 311 corresponds to a pixel. Here, the pixel corresponds to a sub-pixel in the case of a color image display device.

  Although only 14 scanning electrodes 310 are shown in FIG. 7, the actual display has hundreds to thousands. There are hundreds to thousands of data electrodes 311 in an actual image display device. A thin film electron source 301 is disposed at the intersection of the scan electrode 310 and the data electrode 311.

  FIG. 9 is a plan view showing a part (four sub-pixels) of the cathode plate 601 in FIG. FIG. 10 is a cross-sectional view of a part of the cathode plate 601 corresponding to FIG. 10A is a cross-sectional view taken along a line AB in FIG. 9, and FIG. 10B is a cross-sectional view taken along a line C-D in FIG. FIG. 9 is a plan view with the upper electrode 11 removed. Actually, as can be seen from the sectional view of FIG. 10, the upper electrode 11 is formed on the entire surface.

  A triple rectangle is arranged in a corresponding portion of each sub-pixel. The innermost rectangular region indicates the electron emission region 35, which corresponds to the inner periphery of the taper portion (inclined region portion) of the first interlayer insulating film 15. The outer rectangle corresponds to the outer periphery of the taper film of the first interlayer insulating film 15. The outside (re-periphery) is an opening of the second interlayer insulating layer 51.

  In this embodiment, the scanning electrode 310 is constituted by the bus electrode 32. In this embodiment, the spacer 60 is provided on the scan electrode 310. The spacers 60 do not have to be installed on all the scan electrodes, and may be installed for every several scan electrodes.

  The spacer 60 is electrically connected to the scanning electrode 310 and functions to flow a current flowing from the accelerating electrode 122 of the fluorescent plate 602 through the spacer 60 and to flow a charged charge to the spacer 60.

  In this embodiment, a thin film electron source is used as the thin film electron source 301. As shown in FIG. 10, the lower electrode 13, the tunnel insulating layer 12, and the upper electrode 11 are the basic configuration of the thin film electron source. The electron emission region 35 in FIG. 9 is a place corresponding to the tunnel insulating layer 12. Electrons are emitted from the surface of the upper electrode 11 in the electron emission region 35 into a vacuum.

  In this embodiment, a part of the data line 311 (a region in contact with the tunnel insulating layer 12) is the lower electrode 13. In this specification, a portion of the data line 311 that is in contact with the tunnel insulating layer 12 is referred to as a lower electrode 13.

  The configuration of the cathode plate 601 is as follows. A thin film electron source 301 (thin film electron source 301 in this embodiment) composed of the lower electrode 13, the insulating layer 12, and the upper electrode 11 is formed on an insulating substrate 14 such as glass. The bus electrode 32 is electrically connected to the upper electrode 11 through the contact electrode 55. The bus electrode 32 serves as a power supply line to the upper electrode 11. In other words, it serves to carry current from the drive circuit to the position of this sub-pixel. In this embodiment, the bus electrode 32 functions as the scan electrode 310.

  In FIG. 10, the scale in the height direction is arbitrary. That is, the lower electrode 13 and the upper electrode have a thickness of several μm or less, but the distance between the substrate 14 and the face plate 110 is about 1 to 3 mm.

  A method for producing the cathode plate 601 will be described with reference to FIGS. FIGS. 11 to 19 show a process for manufacturing a thin film electron source on the substrate 14. In these drawings, a thin film electron source corresponding to 2 × 2 sub-pixels is described. (A) of each figure is a top view, The sectional view between AB is shown in (b), and the sectional view between CD is shown in (c).

  On the insulating substrate 14 such as glass, an Al alloy is formed to a thickness of, for example, 300 nm as a material for the lower electrode 13 (data line 311). Here, an Al—Nd alloy was used. For example, sputtering or resistance heating vapor deposition is used to form the Al alloy film. Next, the Al alloy film is processed into a stripe shape by resist formation by photolithography and subsequent etching to form the lower electrode 13. The resist used here only needs to be suitable for etching, and can be either wet etching or dry etching.

  Next, a resist is applied and exposed to ultraviolet light for patterning to form a resist pattern 501 in FIG. As the resist, for example, a quinonediazide positive resist is used. Next, with the resist pattern 501 attached, anodization is performed to form the first interlayer insulating layer 15. In this embodiment, the anodic oxidation is performed at a formation voltage of about 100 V, and the film thickness of the first interlayer insulating layer 15 is about 140 nm. Thereafter, the resist pattern 501 is peeled off. This is the state of FIG.

  Next, the surface of the lower electrode 13 covered with the resist 501 is anodized to form the insulating layer 12. In this example, the formation voltage was set to 6 V, and the insulating layer thickness was 10.6 nm. This is the state of FIG. A region where the insulating layer 12 is formed becomes an electron emission region 35. That is, the region surrounded by the first interlayer insulating layer 15 is the electron emission region 35.

  It has been conventionally reported that the thickness d of the anodized insulating film obtained by anodizing aluminum has a relationship of d (nm) = 13.6 × VAO with the formation voltage VAO. According to recent studies by the inventors, it is shown that the relationship d (nm) = 13.6 × (VAO + 1.8) is established when the film thickness is thinner than about 20 nm (IEEE Transactions on Electron). Devices, vol. 49, No. 6, pp. 1059-1065, 2002. [Non-patent Document 3]). The above values (formation voltage 6V, insulating layer thickness 10.6 nm) are values obtained from this latest relational expression.

  Next, the second interlayer insulating layer 51 and the electron emission region protective layer 52 are formed by the following procedure (FIG. 14). The pattern of the second interlayer insulating layer 51 is formed in the intersection region between the bus electrode 32 and the data electrode 311 and the electron emission region 35 is exposed. However, in the process step of FIG. 14, the electron emission region 35 is covered with the electron emission region protective layer 52. The second interlayer insulating layer 51 and the electron emission region protection layer 52 are patterned by etching after silicon nitride SiNx, silicon oxide SiOx, or the like is formed. In this embodiment, a silicon nitride film having a thickness of 100 nm is used. Etching is performed by dry etching using an etchant mainly composed of CF4 or SF6, for example. The second interlayer insulating layer 51 is formed in order to improve the insulation between the scan electrode and the data electrode. The electron emission region protection layer 52 is for protecting a portion that becomes the electron emission region 35 (that is, the insulating layer 12) from process damage in a subsequent process, and is removed in a subsequent process as will be described later. In this embodiment, the second interlayer insulating layer 51 and the electron emission region protection layer 52 are formed by the same material and in the same process.

  Next, the materials constituting the contact electrode 55, the bus electrode 32, and the bus electrode upper layer 34 are formed in this order (FIG. 15). In this embodiment, the contact electrode 55 is made of chromium (Cr) 100 nm thick, the bus electrode 32 is made of aluminum (Al) 2 μm thick, and the bus electrode upper layer 34 is made of chromium (Cr) 200 nm thick. These electrodes were formed by sputtering. As the material of the bus electrode 32, it is preferable to use a material having high conductivity because the wiring resistance is reduced and the voltage drop at the electrode can be reduced.

  Next, the bus electrode upper layer 34 and the bus electrode 32 are patterned by etching and exposed so that the upper electrode 11 can be connected to the contact electrode 55 later, thereby forming the bus electrode 32 (FIG. 16).

  Next, the contact electrode 55 is patterned by etching (FIG. 17). The patterning of the contact electrode 55 here determines the power supply state from the contact electrode 55 to the electron emission region 35.

  As shown in FIG. 17A, the contact electrode 55 has a pattern along three sides of the four sides of the electron emission region 35. As described above, the power supply capability is improved by adopting such a three-side power supply structure.

  As shown by the arrow in the cross-sectional view of FIG. 17B, one side of the contact electrode 55 (the part indicated by the arrow in the figure) forms an undercut with respect to the bus electrode 32, and the upper electrode is formed in a later process. A ridge for electrically separating 13 is formed. Due to the presence of the undercut, the upper electrodes of the sub-pixels connected to the adjacent scanning lines are electrically insulated (separated) from each other. This is called “pixel separation”.

  The undercut amount of the contact electrode 55 is controlled as follows.

  In the portion where the undercut is to be formed, the contact electrode 55 is etched using the side of the bus electrode 32 as a photomask. Therefore, the contact electrode 55 is undercut with respect to the bus electrode 32. On the other hand, if the undercut amount is too large, the bus electrode 32 collapses, the bus electrode 32 and the second interlayer insulating layer 51 come into contact, and wrinkles disappear. Therefore, in order to prevent excessive undercut formation, a material having a standard electrode potential nobler than the bus electrode 32 material is used as the material of the contact electrode 55. That is, a material having a higher standard electrode potential than the material of the bus electrode 32 is used as the contact electrode 55. When the bus electrode is made of aluminum, examples of such a material include chromium (Cr), molybdenum (Mo), or a Cr alloy, and an alloy containing these as components, such as a molybdenum-chromium-nickel alloy. Examples of alloys include Mo-Cr-Ni alloys. In this case, the side etching of the contact electrode 55 stops halfway due to the local battery action, so that it is possible to prevent the undercut amount from increasing excessively. Further, by controlling the exposed area of the bus electrode, which is a material having a low (low) standard electrode potential, to the etching solution, the local battery action is controlled and the side etch stop position (that is, the amount of undercut) of the contact electrode 55 is controlled. ) Can be controlled. For this purpose, a bus electrode upper layer 34 made of chromium (Cr) is formed.

  As can be seen from the above description, it is preferable that the material of the contact electrode 55 is a noble (higher) standard electrode potential than the material of the bus electrode 32.

  Next, the electron emission region protective layer 52 is removed by dry etching or the like (FIG. 18).

  Next, the upper electrode 11 is formed to complete the cathode plate 601 (FIG. 19). In this embodiment, a laminated film of iridium (Ir), platinum (Pt), and gold (Au) is used as the upper electrode 11. The upper electrode 11 was formed by sputtering film formation. Actually, the upper electrode 11 is formed on the entire surface, but for the purpose of making the configuration easy to understand, FIG. 19A shows a diagram in which the upper electrode is removed. The position of the data line 311 is indicated by a dotted line.

  As shown in FIG. 19, current is supplied from the bus electrode 32, which is a power supply line, to the upper electrode 11 in the electron emission region 35 via the contact electrode 55. On the other hand, as described above, since an appropriate amount of undercut is formed in the contact electrode 55, the adjacent scan electrodes 310 are electrically insulated from each other.

  The configuration of the fluorescent plate 602 is as follows. As shown in FIG. 10, a black matrix 120 is formed on a translucent face plate 110 such as glass, and a phosphor 114 is formed at a position facing each electron emission region. In the case of a color image display device, a red phosphor, a green phosphor, and a blue phosphor are separately applied as the phosphor 114. Further, an acceleration electrode 122 is formed. The acceleration electrode 122 is formed of an aluminum film having a film thickness of about 70 nm to 100 nm, and electrons emitted from the thin film electron source 301 are accelerated by an acceleration voltage applied to the acceleration electrode 122 and then incident on the acceleration electrode 122. Then, it passes through the accelerating electrode and collides with the phosphor 114, causing the phosphor to emit light.

  Details of the method for producing the fluorescent screen 602 are described in, for example, Japanese Patent Application Laid-Open No. 2001-83907.

  An appropriate number of spacers 60 are arranged between the cathode plate 601 and the fluorescent plate 602. As shown in FIG. 7, the cathode plate 601 and the fluorescent plate 602 are sealed with a frame member 603 interposed therebetween. Further, the space surrounded by the cathode plate 601, the fluorescent plate 602, and the frame member 603 is evacuated to a vacuum.

  The display panel is completed by the above procedure.

  FIG. 20 is a connection diagram to the drive circuit of the display panel 100 manufactured as described above. Scan electrode 310 is connected to scan electrode drive circuit 41, and data electrode 311 is connected to data electrode drive circuit 42. The acceleration electrode 122 is connected to the acceleration electrode driving circuit 43 via the resistor 130. The dot at the intersection of the nth scan electrode 310Rn and the mth data electrode 311Cm is represented by (n, m).

  The resistance value of the resistor 130 was set as follows. For example, in a display device having a diagonal size of 51 cm (20 inches), the display area is 1240 cm 2. When the distance between the acceleration electrode 122 and the cathode is set to 2 mm, the electrostatic capacitance Cg between the acceleration electrode 122 and the cathode is about 550 pF. In order to set the time constant sufficiently longer than the generation time of vacuum discharge (about 20 nanoseconds), for example, 500 nanoseconds, the resistance value Rs of the resistor 130 may be set to 900Ω or more. In this example, it was set to 18 KΩ (time constant 10 μs). Thus, by inserting a resistor having a resistance value satisfying the time constant Rs × Cg> 20 ns between the accelerating electrode 122 and the accelerating electrode driving circuit 43, there is an effect of suppressing the occurrence of vacuum discharge in the display panel. .

  FIG. 21 shows the waveform of the voltage generated by each drive circuit. Although not shown in FIG. 21, a voltage (phosphor screen voltage Va) of about 3 to 10 KV is applied to the acceleration electrode 122.

  At time t0, since no voltage is applied to any electrode, no electrons are emitted, and therefore the phosphor 114 does not emit light.

At time t1, a scan pulse 750 having a voltage V _R1 is applied to the scan electrode 310R1, and a data pulse 751 having a voltage −V _C1 is applied to the data electrodes 311C1 and C2. Since a voltage of (V _C1 + V _R1 ) is applied between the lower electrode 13 and the upper electrode of the dots (1, 1) and (1, 2), (V _C1 + V _R1 ) is higher than the electron emission start voltage. In this case, electrons are emitted into the vacuum 10 from the thin film electron source of these two dots. In this embodiment, V _R1 = + 5V and −V _C1 = −4V. The emitted electrons are accelerated by the voltage applied to the accelerating electrode 122 and then collide with the phosphor 114 to cause the phosphor 114 to emit light.

At time t2, when the voltage V _R1 is applied to the scan electrode 310R2 and the voltage −V _C1 is applied to the data electrode 311C1, the dot (2, 1) is similarly lit. Thus, when the voltage waveform of FIG. 21 is applied, only the hatched dots of FIG. 20 are lit.

In this manner, a desired image or information can be displayed by changing a signal applied to the data electrode 311. In addition, by changing the magnitude (voltage amplitude) of the voltage −V _C1 applied to the data electrode 311 as appropriate according to the image signal, it is possible to display an image with gradation.

  One field period constituting an image of one screen includes a “display period” and a “non-display period”. Referring to FIG. 21, the period from t1 to t4 is a period in which the scan pulse 750 is sequentially applied and an image is displayed in combination with the data pulse 751, so the period from t1 to t4 is the “display period”. Call it. On the other hand, the period from t4 to t7 is called “non-display period” because it does not directly contribute to the display image. That is, the period in which the scan pulse is sequentially applied to the scan electrode and the data pulse 751 corresponding to the image signal is applied to the data electrode is the “display period”, and the period in which the data pulse is not output is the “non-display period”. is there.

The drive waveform during this non-display period will be described. As shown in FIG. 21, a voltage of −V _R2 is applied to all the scan electrodes 310 at time t4. In this embodiment, −V _R2 = −5V. At this time, since the voltage applied to all the data electrodes 311 is 0 V, a voltage of −V _R2 = −5 V is applied to the thin film electron source 301. In this way, by applying a voltage (inversion pulse 754) having a polarity opposite to that at the time of electron emission, the charge accumulated in the trap in the insulating layer 12 is released, and the life characteristics of the thin film electron source can be improved.

  During the period from t5 to t6, an additional pulse 755 is applied to all the scan electrodes 310. The additional pulse 755 causes the voltage polarity applied to the thin film electron source 401 to be the same as when the scanning pulse 750 is applied. That is, a voltage that has a forward polarity is applied. That is, a voltage is applied so that the potential of the upper electrode becomes a positive voltage with respect to the lower electrode. The appropriate voltage and appropriate pulse width of the additional pulse 755 will be described in detail later.

  As described above, the inversion pulse 754 and the additional pulse 755 are applied during the non-display period (t4 to t7, t10 to t13 in FIG. 21). If the vertical blanking period of the video signal is used as the non-display period, it is preferable because the consistency with the video signal is good.

  In the description of FIGS. 20 and 21, the example of 3 × 3 dots has been described for the sake of simplicity. However, in an actual image display apparatus, the number of scanning electrodes is several hundred to several thousand, and the number of data electrodes is several hundred to several. There are thousands.

  Next, the appropriate drive waveform of the additional pulse is described.

  The drive voltage of the image display device created in this example is as follows: The drive voltage (diode voltage Vd) at the brightness signal 255 level (GS2 = 255 in FIG. 4) corresponding to the peak brightness is 8.8V, The drive voltage at 64 levels of the luminance signal corresponding to the average luminance (GS2 = 64 in FIG. 4) was 8.0V.

  FIG. 22 shows the afterimage time when the voltage amplitude Vad of the additional pulse 755 is 8.0 V and the pulse width is 80 μs. The figure also shows the results of the conventional driving method for comparison. The conventional driving method is a case where Vad = 0, that is, a case where the additional pulse 755 is not applied. Further, the afterimage time shown in FIG. 22 is the time until the display brightness is restored to 90% of the correct brightness after the transition from the peak brightness level to the average brightness level GS2. That is, in FIG. 4, it is the time for (L2−ΔL2) to reach L2 × 0.9.

  As shown in FIG. 22, the afterimage time is 1 second when there is no additional pulse. However, when the additional pulse is applied, the afterimage time is reduced to 1/6 second (0.16 second), which is below the detection of the human eye. Become.

  A mechanism for improving the afterimage by applying the additional pulse will be described. As described above, the afterimage is caused by the change of the internal electric field due to the electric charge accumulated in the electron acceleration layer as shown in FIG. When the additional pulse 755 is applied, an electric field is generated in the insulating layer, and charges accumulated in the trap in the electron acceleration layer are detrapped by the electric field (charge is released from the trap). As a result, the accumulated charge amount in the electron acceleration layer is eliminated in a shorter time. Therefore, the afterimage time is shortened by the mechanism described with reference to FIGS. That is, the transition to the original luminance value corresponding to the input signal is promptly performed.

  Since the mechanism for improving the afterimage by the additional pulse is the accumulated charge detrapping by the internal electric field, it is necessary to apply a voltage of a certain level or more as the additional pulse. When detrapping, even a small amount of current needs to flow. On the other hand, in matrix driving, the absolute value | Vc | of the voltage amplitude of the data pulse 751 applied to the data electrode 311 is set so that no current flows even at the maximum amplitude. This is because unintentional light emission (crosstalk light emission) occurs when the current flows only by applying the data pulse when the scan pulse 750 is not applied to the scan electrode 310, and the screen contrast is lowered. It is because it will do. Therefore, the voltage amplitude of the additional pulse is preferably set to a value larger than the maximum amplitude of the data pulse 751 (that is, the difference between the maximum voltage and the minimum voltage of the data pulse) in order to obtain an afterimage reduction effect.

  Since the additional pulse applies a voltage having the same polarity as the scanning pulse, electron emission may occur depending on conditions such as the applied voltage and pulse width, and an unintended pixel may emit light. In this specification, such unintentional light emission is referred to as “unnecessary light emission”.

  FIG. 23 shows the result of measuring the pulse width that gives the same afterimage time when the voltage Vad of the additional pulse is changed. FIG. 23A shows the actually measured required pulse width and the current density Jd at each voltage value. FIG. 23 (b) plots the amount of charge flowing from one additional pulse period calculated from (a), that is, (current density) × (pulse width). As expected from the above mechanism, if the additional pulse voltage Vad is reduced to reduce the current density, the required pulse width increases. However, as can be seen from FIG. 23B, the amount of charge necessary to obtain the same afterimage time is not constant, and the amount of necessary charge can be reduced as the voltage Vad decreases.

FIG. 24A shows the relationship between the additional pulse voltage V _ad and the electron emission ratio. As the additional pulse voltage V _ad decreases, the electron emission ratio also decreases. When the applied voltage V _ad was 9 V, 8 V, and 6 V, the electron emission efficiency was 4.3%, 3.6%, and 0.3%, respectively. Combined with the effects of FIG. 23B and FIG. 24A, the emission current amount, that is, the light emission amount becomes smaller as Vad becomes smaller. FIG. 24 (b) shows the result. When the additional pulse voltage V _ad = 6V, the unnecessary light emission amount is reduced to 1/300 compared to the case of V _ad = 8V.

As can be seen from this result, it is preferable to make the width of the additional pulse wider than the width of the scanning pulse, and to reduce the voltage V _{ad of the} additional pulse accordingly, because unnecessary light emission is reduced.

  Further, it is preferable to insert an additional pulse within the vertical blanking period in order to match the video signal. Therefore, it is preferable to make the width of the additional pulse approximately the same as the width of the vertical baseline period and to reduce the additional pulse voltage accordingly, because unnecessary light emission is reduced. Specifically, it is preferable to apply an additional pulse having a time width of ½ or more of the vertical blanking period in the vertical blanking period.

  Although the width of the vertical blanking period varies depending on the video signal standard, it is approximately 1 ms, so the pulse width of the additional pulse is preferably set to 500 μs or more.

  As can be seen from the result of FIG. 24B, although the required pulse width is reduced when the additional pulse voltage is increased, the amount of unnecessary light emission is not preferable. Therefore, the magnitude of the additional pulse voltage is preferably set smaller than the voltage applied to the thin film electron source at the time of displaying the maximum luminance.

  FIG. 1 shows driving waveforms in an image display device having M rows × N columns of pixels. Here, “pixels” correspond to individual “subpixels” of red, green, and blue in the case of a color display image device. In a normal image display device, N = several hundreds to thousands of rows and M = several hundreds to thousands of columns.

  One field period of the video signal (1 field period = 16.67 ms in the case of NTSC standard, 20 ms in the PAL standard) is divided into a display period and a non-display period. In the display period, a scan pulse 750 is sequentially applied to each of the N scan electrodes 310R1 to R (N), and a data pulse 751 having a voltage amplitude corresponding to the display image is applied to the data electrodes 311C1 to C (M). Apply. As described above, an image having a desired gradation is displayed in the display period of one field period. Thus, an image is displayed using the line sequential driving method.

  In the display period, the voltage of the scan electrode during a period in which the scan pulse is not applied is Vr0. The voltage of the data electrode 311 when no voltage is applied to the data electrode is set to Vc0. In this embodiment, Vr0 = 0V and Vc0 = 0V were set. Vr0 and Vc0 may be set to voltages other than 0V.

  The non-display period is a period during which no scan pulse is applied in one field period. If the non-display period is set equal to the vertical blanking period of the video signal, the consistency with the video signal is good.

  An inversion pulse 754 and an additional pulse 755 are applied in the non-display period.

  When the inversion pulse 754 is applied for each field, the charge accumulated in the trap in the insulating layer is reduced, so that the afterimage characteristics are further improved as compared with the case where only the additional pulse is applied.

  Even if the additional pulse 755 is applied during the display period, it has the effect of improving the afterimage characteristics. However, the application of the additional pulse 755 during the non-display period has the following advantages. During the non-display period, the potential of the data electrode 311 is set to a constant value (= Vc0) regardless of the display image. Therefore, if the voltage applied to the scan electrode when the additional pulse is applied is Vradd, the voltage applied to the thin film electron source is Vad = Vradd−Vc0. Thus, the constant additional pulse voltage Vad can be applied to the thin film electron source regardless of the display image.

  Although FIG. 1 shows an example in which the pulse width of the additional pulse 755 is set to ½ or more of the non-display period, a plurality of additional pulses may be applied instead of increasing the pulse width. FIG. 25 shows specific drive waveforms. In this example, three additional pulses are applied during the non-display period.

  FIG. 26 shows drive waveforms in another embodiment. In this embodiment, the additional pulse is applied to both the scanning electrode 310 and the data electrode 311. When an additional pulse is applied, a voltage Vradd is applied to the scan electrode, and a voltage Vcadd is applied to the data electrode. Therefore, the additional pulse voltage applied to the thin film electron source is Vad = Vradd−Vcadd. In this way, the respective output voltage ranges of the scanning drive circuit 41 and the data drive circuit 42 are reduced, so that there is an advantage that the circuit can be easily made.

In particular, if Vradd is set equal to the applied voltage VR1 of the scan pulse 750, the scan drive circuit 41 only needs to output three types of voltages, V _R1 , Vr0, and the inverted pulse voltage, so that the configuration of the drive circuit is improved. There is an advantage that it is greatly simplified.

  In order to determine whether or not a certain display image causes an afterimage, it is necessary to add a signal processing circuit and compare image data between screens, so that an expensive signal processing circuit is required. Therefore, it is preferable that the presence or absence of the output of the additional pulse 755 or the voltage amplitude is set to a constant value regardless of the display image because such a signal processing circuit is unnecessary.

  A second embodiment using the present invention will be described with reference to FIG. The structure and manufacturing method of the display panel used in this embodiment are the same as those in the first embodiment.

  In this embodiment, as shown in FIG. 27, the additional pulse 755 is applied during the non-display period, and the voltage (phosphor screen voltage) Va applied to the phosphor screen during this period is reduced from the voltage Va1 during the display period to Va2. This reduces unnecessary light emission due to electrons emitted when the additional pulse 755 is applied. In this embodiment, Va1 = 7 KV and Va2 = 4 KV. When the phosphor screen voltage is reduced from 7 KV to 4 KV, the phosphor screen luminous efficiency is reduced to 1/3. Since the phosphor screen irradiation energy when the same current is applied to the phosphor screen is reduced to Va2 / Va1, the light emission amount is 1/3 * (4KV / 7KV) = 0.19. That is, unnecessary light emission is reduced to 1/5 or less.

  Thus, when the phosphor screen luminous efficiency at the phosphor screen voltage Va1 in the display period is η1, and the phosphor screen luminous efficiency at the phosphor screen voltage Va2 in the non-display period is η2, the product (η2 / η1) * (Va2 / It is preferable to set Va2 so that Va1) is 1/5 or less because unnecessary light emission is sufficiently reduced.

  If the vertical blanking period of the video signal is used as the non-display period, the signal consistency is good and more preferable.

  A third embodiment using the present invention will be described with reference to FIGS. 28, 29, and 30. FIG.

  FIG. 28 schematically shows a cross-sectional view of the display panel used in this embodiment. The structure of the cathode plate 601 is basically the same as that of the first embodiment. In this embodiment, a common electrode 630 is provided between the thin film electron source 301 and the acceleration electrode 122. The common electrode 630 has a hole 632 in a portion corresponding to the thin-film electron source 301, and electrons emitted from the thin-film electron source 301 pass through the hole 632 and irradiate the accelerating electrode 122 to form a phosphor (not shown in FIG. 28). (Omitted). The common electrode 630 is supported and fixed in the panel by a support body 635.

  FIG. 29A is a plan view showing a phosphor pattern of the phosphor plate 602 of the display panel used in this embodiment. A cross-sectional view of the fluorescent screen is as shown in FIG. A black matrix 120 and a phosphor 114 are formed on the phosphor plate. In FIG. 29 (a), the acceleration electrode 122 is not shown. As shown in FIG. 29 (b), the phosphor pattern may be formed as a “striped pattern” in which the same color phosphors in the same column are formed in the same column pattern. A “dot pattern” (FIG. 29A) in which the phosphor pattern is separated for each row was used.

  FIG. 30 is a diagram showing a driving voltage waveform to the display panel in this embodiment. The driving waveform of the cathode is basically the same as in the first embodiment. In this embodiment, the additional pulse 755 is applied to the electron source during the non-display period. Then, the voltage Vcom applied to the common electrode is changed from Vcom1 to Vcom2 during the non-display period. In this way, the electrons emitted from the thin film electron source 301 change the trajectory until they pass through the hole 632 and reach the acceleration electrode 122, and irradiate the phosphor coating portion (114 in FIG. 29 (a)). The amount is reduced during the non-display period. As a result, unnecessary light emission due to application of the additional pulse 755 was reduced.

The applied voltage of the common electrode 630 is set as follows. The distance between the fluorescent plate 602 and the thin film electron source 301 is d (AK), and the vertical distance between the thin film electron source 301 and the common electrode 630 is d (com-K). The applied voltage Vcom1 to the common electrode during the display period is:
Vcom1 = Va * d (com-K) / d (AK)
Set to. When Vcom1 is set in this way, an equal electric field space is formed between the thin-film electron source 301 and the acceleration electrode 122, so that the electron beam goes straight and irradiates the phosphor 114.

  An operation when the voltage Vcom applied to the common electrode 630 is changed to Vcom2 (≠ Vcom1) in the non-display period will be described. In this case, the electric field distribution around the hole 632 becomes a non-uniform electric field, and an electron lens is formed. This electron lens effect changes the trajectory of the electron beam. For this reason, a part of the electron beam is irradiated to the area of the black matrix 120 without irradiating the phosphor 114. Since light is not emitted even when the black matrix 120 is irradiated with electrons, light emission during unnecessary periods (unnecessary light emission) is reduced.

  In this embodiment, when the dot pattern shown in FIG. 29A is used as the pattern of the phosphor 114, the light emission reduction effect due to the change in the trajectory of the electron beam is larger than that of the stripe pattern. Even more preferred.

  Alternatively, the voltage Vcom2 applied to the common electrode 630 during the non-display period may be set to be sufficiently higher than Vcom1, so that electrons emitted from the thin film electron source 301 are irradiated to the common electrode 360. In this case, since the electrons do not reach the fluorescent screen 114, unnecessary light emission does not occur.

  If the vertical blanking period of the video signal is used as the non-display period, the signal consistency is good and more preferable.

  A fourth embodiment using the present invention will be described with reference to FIG. The display panel used in this embodiment is the same as that in the first embodiment. This embodiment is characterized in that the additional pulse is applied during the display period.

  In this embodiment, the additional pulse 757 is applied within the display period. As can be seen from FIGS. 23 and 24, the amount of unnecessary light emission decreases as the pulse width (or number of pulses) of the additional pulse is increased and the additional pulse voltage is lowered. If the additional pulse 757 is applied also in the display period, the width (or the number of pulses) of the additional pulse can be increased, and there is an advantage that unnecessary light emission can be reduced.

  On the other hand, since the voltage of the data electrode varies depending on the display image within the display period, there is a demerit that a desired voltage is not always applied to the thin film electron source. In consideration of the fact that a data pulse is applied to the data electrode in the display period, the voltage of the additional pulse 757 applied to the scan electrode is set to a voltage smaller than that applied in the non-display period.

  The additional pulse 757 is always applied regardless of the display image.

  In addition, since it is necessary to add a signal processing circuit to determine whether a certain display image causes an afterimage during the display operation, if the voltage amplitude of the additional pulse 757 is set to a constant value regardless of the display image. Such a signal processing circuit is unnecessary and preferable.

  As described above, the voltage applied to the thin film electron source when the additional pulse 757 is applied is set to a value larger than the maximum amplitude of the data pulse 751 (that is, the difference between the maximum voltage and the minimum voltage of the data pulse). This is preferable for obtaining an afterimage reduction effect.

The figure which shows an example of the drive voltage waveform of the image display apparatus which concerns on this invention. The figure for demonstrating the electron emission mechanism of a thin film electron source. The figure for demonstrating the afterimage phenomenon. The figure for demonstrating the afterimage phenomenon. The figure which showed the current-voltage characteristic of the thin film electron source. The figure which shows the mechanism of the change of an electric current-voltage characteristic. The top view which shows the structure of the display panel of the image display apparatus which concerns on this invention. Sectional drawing which shows the structure of the display panel of the image display apparatus which concerns on this invention. 1 is a plan view showing a part of a cathode plate of a first embodiment of an image display device according to the present invention. 1 is a cross-sectional view showing a part of a cathode plate of a first embodiment of an image display device according to the present invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure for demonstrating the creation process of the cathode plate of the 1st Example of the image display apparatus which concerns on this invention. The figure which shows the connection of the display panel and drive circuit of 1st Example of the image display apparatus which concerns on this invention. The figure which shows the drive method of the 1st Example of the image display apparatus which concerns on this invention. The graph which shows the afterimage time in the 1st Example of the image display apparatus which concerns on this invention. The graph which shows the relationship between the voltage of an additional pulse, and required pulse width. The graph which shows the relationship between the voltage of an additional pulse, and the intensity | strength of unnecessary light emission. . The figure which shows an example of the drive voltage waveform of the image display apparatus which concerns on this invention. The figure which shows an example of the drive voltage waveform of the image display apparatus which concerns on this invention. The figure which shows the drive voltage waveform in the 2nd Example of the image display apparatus which concerns on this invention. Sectional drawing of the display panel in the 3rd Example of the image display apparatus which concerns on this invention. The figure which shows the top view of the fluorescent screen in the 3rd Example of the image display apparatus which concerns on this invention. The figure which shows the drive voltage waveform in the 3rd Example of the image display apparatus which concerns on this invention. The figure which shows the drive voltage waveform in the 4th Example of the image display apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Upper electrode, 12 ... Tunnel insulating layer, 13 ... Lower electrode, 14 ... Substrate, 15 ... First interlayer insulating layer, 32 ... Bus electrode, 34 ... Bus electrode upper layer, 35 ... Electron emission region, 41... Scanning drive circuit, 42... Data drive circuit, 43... Acceleration electrode drive circuit, 51... Second interlayer insulating layer, 52. , 60 ... spacer, 100 ... display panel, 110 ... face plate, 114 ... phosphor, 120 ... black matrix, 122 ... acceleration electrode, 130 ... resistor, 301 ... thin film electron source, 310 ... scanning Electrodes, 311... Data electrodes,
601 ... Cathode plate, 602 ... Fluorescent plate, 603 ... Frame member, 630 ... Common electrode, 632 ... Hole,
750 ... Scanning pulse, 751 ... Data pulse, 754 ... Inverted pulse, 755 ... Additional pulse.

Claims (20)

An electron acceleration layer is provided between the lower electrode, the upper electrode, and the lower electrode and the upper electrode, and electrons are emitted from the upper electrode side by applying a voltage between the lower electrode and the upper electrode. A plurality of thin film electron sources,
A plurality of scan electrodes parallel to each other and a plurality of data electrodes parallel to each other, and the thin film electron source is disposed at an intersection of the scan electrodes and the data electrodes,
A display panel having a phosphor screen having a phosphor screen formed with a phosphor that emits light when excited by the electrons;
In an image display device having a first driving means connected to the plurality of scanning electrodes and outputting a scanning pulse, and a second driving means connected to the plurality of data electrodes,
One field period is divided into a display period in which scan pulses are sequentially output and a non-display period other than that.
An image display device, wherein the upper electrode applies one or more additional pulses having a positive voltage with respect to the lower electrode during the non-display period.   The image display apparatus according to claim 1, wherein an image is displayed by a line sequential driving method.   The image display apparatus according to claim 1, wherein the additional pulse is applied regardless of an image signal to be displayed.   3. The image display device according to claim 1, wherein the voltage of the additional pulse is constant regardless of an image signal to be displayed.   5. The image display device according to claim 1, wherein the non-display period corresponds to a vertical blanking period of the image signal.   The voltage applied between the upper electrode and the lower electrode by the additional pulse is smaller than the maximum value of the voltage applied between the upper electrode and the lower electrode when the scan pulse is applied. 5. The image display device according to 1 to 4.   7. The image display device according to claim 1, wherein a pulse width of the additional pulse is wider than a pulse width of the scanning pulse.   8. The image according to claim 1, wherein a pulse width of the additional pulse is applied as a single pulse or a plurality of pulses over a period of ½ or more of a time width of the vertical blanking period. Display device.   9. The image display device according to claim 1, wherein the gradation of the display image is controlled by a voltage amplitude applied to the data electrode when the scan pulse is applied.   The image according to claim 9, wherein a voltage applied between the upper electrode and the lower electrode by the additional pulse is larger than a difference between a maximum value and a minimum value of the voltage applied to the data electrode. Display device. 11. The image display device according to claim 1, wherein the voltage of the additional pulse is distributed to a voltage applied to the scan electrode and a voltage applied to the data electrode and applied to the thin film electron source.
  The image display device according to claim 11, wherein a voltage applied to the scan electrode when applying the additional pulse is equal to a voltage of the scan pulse.   The image display device according to claim 1, wherein when the additional pulse is applied, an applied voltage of the phosphor screen is decreased.   The phosphor screen voltage during the display period is Va1, the phosphor screen voltage during the application of the additional pulse is Va2, the phosphor screen luminous efficiency is η1 when the phosphor screen voltage is Va1, and the phosphor screen is when the phosphor screen voltage is Va2. 14. The image display device according to claim 13, wherein when the luminous efficiency is η2, the phosphor screen voltage Va2 is set so that (η2 / η1) * (Va2 / Va1) is 1/5 or less. . A common electrode is provided between the thin film electron source and the phosphor screen,
The image display device according to claim 1, wherein when the additional pulse is applied, a voltage of the common electrode is changed.   The image display device according to claim 15, wherein the phosphor pattern on the phosphor screen is a dot pattern.   17. The image display device according to claim 1, wherein a voltage is applied so that the upper electrode becomes a negative voltage with respect to the lower electrode within one field period. An electron acceleration layer is provided between the lower electrode, the upper electrode, and the lower electrode and the upper electrode, and electrons are emitted from the upper electrode side by applying a voltage between the lower electrode and the upper electrode. A plurality of thin film electron sources,
A plurality of scan electrodes parallel to each other and a plurality of data electrodes parallel to each other, and the thin film electron source is disposed at an intersection of the scan electrodes and the data electrodes,
A display panel having a phosphor screen having a phosphor screen formed with a phosphor that emits light when excited by the electrons;
In an image display device having a first driving means connected to the plurality of scanning electrodes and outputting a scanning pulse, and a second driving means connected to the plurality of data electrodes,
In addition to applying the scanning pulse within one field period, the upper electrode applies an additional pulse having a positive voltage to the lower electrode one or more times,
The voltage applied between the upper electrode and the lower electrode by the additional pulse is larger than the difference between the maximum value and the minimum value of the voltage applied to the data electrode.   The image display device according to claim 18, wherein the additional pulse is applied regardless of an image signal to be displayed. The image display device according to claim 18, wherein the voltage of the additional pulse is constant regardless of an image signal to be displayed.

Images