JP2014048303A - Method for inspecting electro-optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting an electro-optical device, by which the product life of the device can be ensured in a highly accurate manner.SOLUTION: A method for inspecting an electro-optical device comprises: displaying an inspection image with an intermediate gradation on a display screen 200 by using a polarity inversion drive; measuring flicker values FLK of the inspection image at k number of measurement points (k is an integer of 2 or greater) of places on the display screen; calculating direct current component potentials Vfrom the flicker values FLK; and inspecting whether a first statistically processed result of the k number of the direct current component potentials Vsatisfies a first prescribed condition or not. In this way, a slight electrical asymmetry present in the electro-optical device is quantitatively evaluated. Accordingly, it is possible to provide an inspection method that is able to ensure the product life of the electro-optical device in a highly accurate manner.

Description

  The present invention relates to an inspection method for an electro-optical device.

  The projector is an electronic device that irradiates a transmissive electro-optical device or a reflective electro-optical device with light and projects transmitted light or reflected light modulated by these electro-optical devices onto a screen. This is configured so that light emitted from a light source is condensed and incident on an electro-optical device, and transmitted light or reflected light modulated according to an electric signal is enlarged and projected onto a screen through a projection lens. It has the advantage of displaying a large screen. A liquid crystal device is known as an electro-optical device used in such an electronic apparatus, and an image is formed by using dielectric anisotropy of liquid crystal and optical rotation of light in a liquid crystal layer.

  A liquid crystal device has a configuration in which a liquid crystal layer is sandwiched between substrates, but it is known that display defects occur if ionic impurities are present in the liquid crystal layer. For this reason, grasping the density of ionic impurities contained in the liquid crystal device is important in assuring product quality and product life. As a method for estimating the density of ionic impurities, for example, as described in Patent Document 1, a rectangular wave having a low frequency of about 1 Hz is applied to observe flicker, and the amplitude or area of the observed flicker Therefore, the ion density in the liquid crystal device was estimated using a calibration curve.

JP 2001-4971 A

  However, the measurement method described in Patent Document 1 has a problem that it is difficult to detect trace ions. Even if a very small amount of ionic impurities that cannot be detected by the measurement method described in Patent Document 1 are present in the liquid crystal layer, the liquid crystal device may deteriorate over time. In other words, even if good display quality is shown immediately after manufacturing, ionic impurities may locally accumulate in the liquid crystal layer during long-term use, resulting in display defects such as spots and unevenness. there were. In other words, the conventional measuring method has a problem that it is difficult to guarantee the product life of the electro-optical device with high accuracy.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

この構成によれば、電気光学装置に存在する僅かな電気的非対称性を定量的に評価するので、電気光学装置の製品寿命を高精度に保証し得る検査方法を提供する事ができる。 In the inspection method of the electro-optical device according to this application example, an intermediate gradation inspection image is displayed on the display surface using polarity inversion driving, and the flicker value FLK of the inspection image is k places (k is 2 or more on the display surface). (V) is an integer) measurement point, and k DC component potentials V _DC from each of the flicker values FLK measured at k measurement points are V ₀ which is a coefficient corresponding to the polarity of the flicker value FLK. It is calculated according to Formula 1 including α and β, and it is characterized in that it is checked whether or not the first statistical processing result of k DC component potentials V _DC satisfies the first specified condition.

According to this configuration, since a slight electrical asymmetry existing in the electro-optical device is quantitatively evaluated, it is possible to provide an inspection method that can guarantee the product life of the electro-optical device with high accuracy.

In the inspection method of the electro-optical device according to the application example, the first statistical processing result is a difference between the maximum value and the minimum value of the k DC component potentials V _DC , and the first specified condition is 0.12 V or less. Something is preferable.
According to this configuration, it is possible to determine whether a small amount of ionic impurities present in the electro-optical device will adversely affect display quality in the future.

In the inspection method of the electro-optical device according to the application example, the first statistical processing result is the maximum value among the differences in the DC component potential V _DC between adjacent measurement points, and the first specified condition is 0.023 V or less. Something is preferable.
According to this configuration, it is possible to determine whether a small amount of ionic impurities present in the electro-optical device will adversely affect display quality in the future.

この構成によれば、電気光学装置に存在する僅かな電気的非対称性を定量的に評価するので、電気光学装置の製品寿命を高精度に保証し得る検査方法を提供する事ができる。 In the inspection method of the electro-optical device according to this application example, an intermediate gradation inspection image is displayed on the display surface using polarity inversion driving, and the flicker value FLK of the inspection image is k places (k is 2 or more on the display surface). (V) is an integer) measurement point, and k DC component potentials V _DC from each of the flicker values FLK measured at k measurement points are V ₀ which is a coefficient corresponding to the polarity of the flicker value FLK. It is calculated according to equation 2 including the α and beta, or first statistics processing result of the k DC component voltage V _DC meets a first specified condition, and the second statistics of k DC component voltage V _DC It is characterized in that whether the processing result satisfies the second specified condition is inspected.

According to this configuration, since a slight electrical asymmetry existing in the electro-optical device is quantitatively evaluated, it is possible to provide an inspection method that can guarantee the product life of the electro-optical device with high accuracy.

In the inspection method of the electro-optical device according to the application example, the first statistical processing result is a difference between the maximum value and the minimum value of the k DC component potentials V _DC , and the first specified condition is 0.12 V or less. Yes, the second statistical processing result is the maximum value in the difference between the DC component potentials V _DC of adjacent measurement points, and the second specified condition is preferably 0.023 V or less.
According to this configuration, it is possible to determine whether a small amount of ionic impurities present in the electro-optical device will adversely affect display quality in the future.

In the inspection method of the electro-optical device according to the application example, when the flicker value FLK is positive, V ₀ = + 1 V, α = 7.9477, β = 1.0223, and the flicker value FLK is negative. In this case, it is preferable that V ₀ = −1V, α = 8.3538, and β = 1.3294.
According to this configuration, the DC component potential V _DC can be calculated from the flicker value FLK.

In the inspection method of the electro-optical device according to the application example, the electro-optical device has a pixel electrode and a common electrode, and the auxiliary flicker value FLKA of the inspection image is k places (k is an integer of 2 or more) on the display surface. The potential of the common electrode when the auxiliary flicker value FLKA is measured is higher than the potential of the common electrode when the flicker value FLK is measured, and the flicker value FLK is higher than the auxiliary flicker value FLKA. If the flicker value FLK is not larger than the auxiliary flicker value FLKA, the flicker value FLK is preferably negative.
According to this configuration, since it can be determined whether the flicker value FLK is positive or negative, the DC component potential V _DC can be calculated from the flicker value FLK.

FIG. 3 is a schematic diagram illustrating a configuration of a liquid crystal device as an electro-optical device. FIG. 3 is an equivalent circuit diagram illustrating an electrical configuration of the liquid crystal device. The top view which shows the structure of the three-plate-type projector as an electronic device. FIG. 3 is a diagram illustrating an apparatus that performs the inspection method according to the first embodiment. FIG. 3 is a diagram illustrating an inspection method according to the first embodiment. 6A and 6B illustrate a voltage applied to a liquid crystal, a luminance of a displayed image, and a flicker size. The figure explaining an example of a flicker value. The figure which shows an example of the flicker value measured at each measurement point. The figure explaining the relationship between a flicker value and DC component potential. The figure which shows an example of the direct-current component electric potential measured at each measurement point. FIG. 6 is a diagram for explaining a result of an inspection method for an electro-optical device according to a second embodiment. The figure explaining the apparatus which enforces the test | inspection method concerning the modification 1. FIG. The figure explaining the apparatus which enforces the test | inspection method concerning the modification 1. FIG. The figure explaining the apparatus which enforces the test | inspection method concerning the modification 1. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each layer and each member is made different from the actual scale so that each layer and each member can be recognized.

(Embodiment 1)
"Outline of electro-optical device"
1A and 1B are schematic views showing a configuration of a liquid crystal device as an electro-optical device, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line HH ′ in FIG. In addition, in the following forms, when “on XX” is described, when placed on XX, or placed on XX via other components Or, when a part is arranged on OO and a part is arranged through another component, it represents.

  First, the liquid crystal device 100 will be described with reference to FIG. As shown in FIGS. 1A and 1B, a liquid crystal device 100 according to the present embodiment includes an element substrate 110 and a counter substrate 120 that are disposed to face each other, and a liquid crystal layer 150 that is sandwiched between the pair of substrates. . For the base material 110s of the element substrate 110 and the base material 120s of the counter substrate 120, a transparent substrate such as a quartz substrate or a glass substrate is used.

  The element substrate 110 is slightly larger than the counter substrate 120, and both the substrates are bonded together via a sealant 140 disposed along the outer periphery of the counter substrate 120, and has positive or negative dielectric anisotropy in the gap. Liquid crystal is sealed to form a liquid crystal layer 150. As the sealing material 140, for example, an adhesive such as a thermosetting or ultraviolet curable epoxy resin is employed. Spacers (not shown) are mixed in the sealing material 140 to keep the distance between the pair of substrates constant.

  A parting part 121 is provided inside the sealing material 140. The parting part 121 is made of, for example, a light-shielding metal or metal oxide, and the inside of the parting part 121 is a pixel region E. In the pixel region E, a plurality of pixels P are arranged in a matrix.

  The pixel region E may include a plurality of dummy pixels arranged so as to surround a plurality of effective pixels P that contribute to display. Although not shown in FIG. 1, also in the pixel region E, light shielding portions that divide a plurality of pixels P in a plane are provided on the element substrate 110 and the counter substrate 120, respectively.

  A signal line drive circuit 101 is provided between the sealing material 140 along the first side of the element substrate 110 and the first side. An inspection circuit 103 is provided on the inner side of the sealing material 140 along the second side facing the first side. Further, the scanning line driving circuit 102 is provided inside the sealing material 140 along the third and fourth sides that are orthogonal to the first side and face each other. A plurality of wirings 105 that connect the two scanning line driving circuits 102 are provided inside the sealing material 140 on the second side. Wirings connected to the signal line driving circuit 101 and the scanning line driving circuit 102 are connected to a plurality of external connection terminals 104 arranged along the first side. Near the center of the first side, an opening Op where no sealant 140 is disposed is provided, and liquid crystal is injected between the element substrate 110 and the counter substrate 120 from the opening Op. A sealing material 122 is provided outside the opening Op, and seals the opening Op after liquid crystal injection. Hereinafter, the direction along the first side will be referred to as the X direction, and the directions along the third and fourth sides perpendicular to the first side and facing each other will be described as the Y direction.

  As shown in FIG. 1B, on the surface of the base 110s on the liquid crystal layer 150 side, a light-transmissive pixel electrode 115 provided for each pixel P and a thin film transistor (TFT; Thin Film) as a switching element. A transistor (hereinafter referred to as TFT) 130, a signal wiring (not shown), and an alignment film 118 that covers the plurality of pixel electrodes 115 are formed. Further, a light shielding structure is employed that prevents light from entering a semiconductor layer in the TFT 130 and causing a light leakage current to flow, resulting in an inappropriate switching operation. That is, the element substrate 110 in this embodiment includes at least the base material 110s, the pixel electrode 115, the TFT 130, the signal wiring, and the alignment film 118.

  On the surface of the substrate 120s on the liquid crystal layer 150 side, the parting part 121, the planarization layer 123 formed so as to cover the parting part 121, and the planarization layer 123 covering at least the pixel region E are covered. A provided common electrode 124 and an alignment film 125 covering the common electrode 124 are provided. That is, the counter substrate 120 in this embodiment includes at least the base material 120 s, the light blocking part 121, the planarization layer 123, the common electrode 124, and the alignment film 125.

  As shown in FIG. 1A, the parting part 121 is provided in a position overlapping the scanning line driving circuit 102 and the inspection circuit 103 in a plane. Thus, the light incident from the counter substrate 120 side is shielded, and the malfunction of the peripheral circuits including these drive circuits due to light is played. Further, unnecessary stray light is shielded from entering the pixel region E, and high contrast in the display of the pixel region E is ensured.

  The planarization layer 123 is made of an inorganic material such as silicon oxide, for example, and is provided so as to cover the parting portion 121 with light transmittance. That is, the flattening layer 123 relaxes the unevenness generated on the base material 120s by the parting portion 121. As a method for forming such a planarization layer 123, for example, a method of forming a film using a plasma CVD method or the like can be given.

  The common electrode 124 is made of, for example, a transparent conductive film such as ITO, and covers the planarization layer 123. As shown in FIG. 1A, the common electrode 124 is provided on the element substrate 110 side by the vertical conduction portions 106 provided at the four corners of the counter substrate 120. It is electrically connected to the wiring.

  The alignment film 118 covering the pixel electrode 115 and the alignment film 125 covering the common electrode 124 are selected based on the optical design of the liquid crystal device 100. For example, an organic material such as polyimide is formed, and the surface thereof is rubbed so that liquid crystal molecules having positive dielectric anisotropy are subjected to a substantially horizontal alignment treatment, or SiOx (silicon oxide) Inorganic materials such as those described above are formed by vapor deposition, and liquid crystal molecules having negative dielectric anisotropy are subjected to a substantially vertical alignment treatment.

  Such a liquid crystal device 100 is a transmissive type, and in the present embodiment, a normally black mode optical design is employed in which the pixel P is darkly displayed when not driven. When the liquid crystal device 100 is driven based on the image signal, the illumination light can be modulated and the display light can be emitted.

"Circuit configuration"
FIG. 2 is an equivalent circuit diagram showing an electrical configuration of the liquid crystal device. Hereinafter, the electrical configuration of the liquid crystal device 100 will be described with reference to FIG.

  As illustrated in FIG. 2, the liquid crystal device 100 includes a plurality of pixels P that form a pixel region E. In each pixel P, a pixel electrode 115 is disposed. A TFT 130 is formed on the pixel P.

  The TFT 130 is a pixel switching element that controls energization of the pixel electrode 115. A signal line 17 is electrically connected to the source side of the TFT 130. Each signal line 17 is supplied with image signals S1, S2,..., Sn from the signal line drive circuit 101, for example.

  Further, the scanning line 16 is electrically connected to the gate side of the TFT 130. For example, scanning signals G1, G2,..., Gm are supplied to the scanning lines 16 in a pulsed manner at a predetermined timing from the scanning line driving circuit 102. Further, the pixel electrode 115 is electrically connected to the drain side of the TFT 130.

  The scanning signals G1, G2,..., Gm supplied from the scanning line 16 are selection potentials for the pixel switching elements. The pixel switching elements become conductive when a selection potential is applied, and when a non-selection potential is applied. It becomes a non-conductive state. That is, the TFT 130 which is a switching element is turned on for a certain period of time when the selection potential is supplied, so that the image signals S1, S2,..., Sn supplied from the signal line 17 are supplied to the pixel P through the pixel electrode 115. Are written at a predetermined timing.

  Image signals S 1, S 2,..., Sn written at a predetermined potential in the pixel P are held for a certain period by a liquid crystal capacitor formed between the pixel electrode 115 and the common electrode 124. Note that a storage capacitor 48 is formed by the pixel electrode 115 and the capacitor line 47 in order to suppress a decrease in the potential of the stored image signals S1, S2,..., Sn due to leakage current.

  When a voltage signal is applied to the liquid crystal layer 150, the alignment state of the liquid crystal molecules changes according to the applied voltage level. Thereby, the light incident on the liquid crystal layer 150 is modulated to generate image light. When an image is displayed in the pixel area E, polarity inversion driving is employed to suppress display problems such as flicker and burn-in of the displayed image. This is a display method in which the direction of the electric field applied between the pixel electrode 115 and the common electrode 124 is reversed every predetermined period with reference to the potential of the common electrode 124. For example, the polarity of the voltage of the image signal written to the pixel electrode 115 is inverted with respect to the potential of the common electrode 124 for each image (frame). In this case, if the direction of the electric field applied to the liquid crystal layer 150 in the first image (first frame) is from the pixel electrode 115 toward the common electrode 124, the first image (first frame) continues. In the second image (second frame), the direction of the electric field applied to the liquid crystal layer 150 is from the common electrode 124 to the pixel electrode 115. The predetermined period for reversing the direction of the electric field may be a frame period (frame inversion driving), a scanning line 16 selection period (scanning line inversion driving), or a signal line 17 selection period. In some cases (pixel inversion driving), 60 Hz frame inversion driving is employed in this embodiment. That is, the first frame and the second frame whose polarity is inverted with respect to the first frame are displayed within 1/60 seconds.

"Electronics"
FIG. 3 is a plan view showing a configuration of a three-plate projector as an electronic apparatus. Next, a projector will be described with reference to FIG. 3 as an example of the electronic apparatus according to the present embodiment.

  In the projector 2100, light emitted from a light source 2102 configured by an ultrahigh pressure mercury lamp is red (R), green (G), and blue by three mirrors 2106 and two dichroic mirrors 2108 arranged inside. The light is separated into the three primary colors (B) and guided to the liquid crystal devices 100R, 100G, and 100B corresponding to the primary colors. Since blue light has a longer optical path than other red and green colors, the blue light is guided through a relay lens system 2121 including an incident lens 2122, a relay lens 2123, and an exit lens 2124 in order to prevent the loss. .

  The liquid crystal devices 100R, 100G, and 100B have the above-described configuration and are driven by image signals corresponding to red, green, and blue colors supplied from an external device (not shown).

  The light modulated by the liquid crystal devices 100R, 100G, and 100B is incident on the dichroic prism 2112 from three directions. In the dichroic prism 2112, red and blue light is refracted at 90 degrees, while green light travels straight. The light representing the color image synthesized by the dichroic prism 2112 is enlarged and projected by the lens unit 2114, and a full color image is displayed on the screen 2120.

  The transmitted images of the liquid crystal devices 100R and 100B are projected after being reflected by the dichroic prism 2112, whereas the transmitted image of the liquid crystal device 100G is projected as it is, so that the images formed by the liquid crystal devices 100R and 100B and The image formed by the liquid crystal device 100G is set so as to have a horizontally reversed relationship.

"Inspection device configuration"
FIG. 4 is a diagram illustrating an apparatus for performing the inspection method according to the first embodiment. Next, the configuration of the inspection apparatus will be described with reference to FIG.

  The inspection device inspects the illuminance of the image formed by the electro-optical device. When the electronic apparatus is the projector 2100 as in the present embodiment, the product quality of the liquid crystal device 100 is inspected by analyzing the projected image. In this case, the area on the screen 2120 where the image is projected is the display surface 200. In the case of a direct-view type electro-optical device, the pixel region E corresponds to the display surface 200.

  K optical sensors 210 (k is an integer of 2 or more) are arranged on the display surface 200. A point where one optical sensor 210 is arranged is one measurement point. In FIG. 4, for the convenience of explanation, eight photosensors 210 are illustrated, but for example, 13 photosensors 210 may be arranged on the display surface 200. The photosensors 210 are arranged in a substantially straight line, and are arranged in a line along the y direction near the center of the display surface 200 in the x direction. The vicinity of the center in the x direction of the display surface 200 is a place corresponding to the opening Op of the liquid crystal device 100 as described with reference to FIG. In the liquid crystal device 100, since there is a high possibility that ionic impurities are mixed into the liquid crystal layer 150 from the opening Op, a straight line is formed on a concentric circle that becomes larger at equal intervals from the reference point, with a location corresponding to the opening Op as a reference point. The optical sensor 210 is disposed so as to be almost mounted on the surface. That is, the photosensors 210 are regularly arranged so that the intervals between the adjacent photosensors 210 are substantially the same. In the present embodiment, the photosensors 210 are arranged at equal intervals with respect to the y coordinate, and the x coordinate is arranged in a zigzag manner on the left and right for each one. Although such a zigzag arrangement is obtained due to the shape of the optical sensor 210, it is ideal to arrange the optical sensor 210 so that the x-coordinates of the optical sensor 210 substantially coincide.

  The k photosensors 210 (k is an integer of 2 or more) are controlled by one photosensor control device 220. The illuminance is input from the optical sensor 210 to the logger 230 as an analog signal (the illuminance analog signal ANG, see FIG. 7), and the logger 230 transfers the illuminance analog signals ANG of all the optical sensors 210 to the computer 240 at once. The computer 240 analyzes the illuminance analog signal ANG and calculates the flicker value of the optical sensor 210. Note that the fluctuation of the illuminance with respect to time is flicker, which will be described later.

"Inspection method"
FIG. 5 is a diagram for explaining an inspection method according to the first embodiment. FIG. 6 is a diagram for explaining the voltage applied to the liquid crystal, the brightness of the displayed image, and the size of the flicker. FIG. 7 is a diagram for explaining an example of the flicker value. FIG. 8 is a diagram showing an example of the flicker value measured at each measurement point. FIG. 9 is a diagram for explaining the relationship between the flicker value and the DC component potential. FIG. 9A shows the case where the flicker value is positive, and FIG. 9B shows the case where the flicker value is negative. FIG. 10 is a diagram illustrating an example of the DC component potential measured at each measurement point. Next, an inspection method will be described with reference to FIGS.

  As shown in FIG. 5, when the inspection is started, an intermediate gradation inspection image is displayed on the display surface 200 using polarity inversion driving (S1). The inspection image is a still image of the same gradation at all the pixels P. The polarity inversion driving cycle is suitably 60 Hz, 120 Hz, or 240 Hz, and may be 50 Hz or more. As described above, in this embodiment, frame inversion driving is performed at 60 Hz.

The still image that forms the inspection image has an intermediate gradation in which the brightness is approximately 50% of the maximum value. That is, the voltage applied between the pixel electrode 115 and the common electrode 124 of the liquid crystal device 100 is set to a voltage at which the luminance is approximately 50% of the maximum luminance. As shown in FIG. 6, the slope of the curve (VT characteristic curve) indicating the relationship between the voltage (V) applied to the liquid crystal and the luminance (T) of the image (voltage differential curve of the VT characteristic curve) is the maximum. This is because the point where the luminance becomes 50% of the maximum luminance. As shown in FIG. 6, the luminance amplitude due to flicker is maximized at the point where the voltage differential curve of the VT characteristic curve takes the maximum value. That is, flicker can be measured with the highest sensitivity by displaying an intermediate gradation in which the luminance is approximately 50% of the maximum luminance. Strictly speaking, the point at which the luminance is approximately 50% of the maximum luminance can vary for each liquid crystal device 100. For example, as shown in FIG. 6, in this embodiment, the absolute value of the voltage V _LC applied to the liquid crystal is about 3.1 V and the luminance is 50% of the maximum luminance. It can be about 2.9V. Since it is difficult to say that it is efficient to change the inspection condition for each liquid crystal device 100, in consideration of the design of the liquid crystal device 100, the inspection is performed with a voltage value of an intermediate gray level having a luminance of about 50%. In the present embodiment, the absolute value of the voltage V _LC applied to the liquid crystal is set to 3.0 V as the voltage at which the luminance is approximately 50% of the maximum luminance. As described above, when an inspection is performed by incorporating the liquid crystal device 100 into the three liquid crystal devices 100, the liquid crystal device 100 to be inspected displays an intermediate gradation, and the liquid crystal device not to be inspected displays black. And The relationship between the voltage V _LC applied to the liquid crystal, the potential V _px of the pixel electrode 115 and the potential V _com of the common electrode 124 is V _LC = V _px −V _com , and the pixel electrode 115 and the common electrode 124 Is a voltage V _LC applied to the liquid crystal (see FIG. 7).

As described with reference to FIG. 4, the display surface 200 is provided with k measurement points (k is an integer of 2 or more), and the flicker value FLK of the inspection image is measured for each measurement point (FIG. 4). 5 S2). FIG. 7 illustrates the potential V _px of the pixel electrode 115 and an example of the illuminance analog signal ANG. The potential V _px of the pixel electrode 115 is a rectangular wave of 60 Hz, and the time average value of the potential V _px of the pixel electrode 115 in operation substantially matches the potential V _{com of the} common electrode 124. Therefore, the voltage V _LC applied to the liquid crystal layer 150 is a rectangular wave of 60 Hz, and the polarity is inverted between the first half cycle and the second half cycle. In the present embodiment, the potential of the common electrode 124 is set to 6.63 V, and an amplitude of ± 3.0 V is given to the common electrode 124 to form a rectangular wave that becomes the potential V _px of the pixel electrode 115. That is, the highest value of the potential V _px of the pixel electrode 115 is 9.63V, and the lowest value is 3.63V. Along with this, the illuminance analog signal ANG has also changed. The illuminance analog signal ANG is extracted as a voltage signal, and the horizontal axis in FIG. 7 represents time. The difference in illuminance V ₁ appearing between the first half cycle and the second half cycle within one cycle of polarity inversion drive is caused by an electrical asymmetry in the liquid crystal layer 150, so that a DC electric field remains in the liquid crystal layer 150. It shows that you are doing. On the other hand, the illuminance fluctuation V ₂ that appears in the half cycle of the polarity inversion drive reflects the amount of ionic impurities in the liquid crystal layer 150, and indicates that the ionic impurities migrate through the liquid crystal layer 150 in the half cycle. ing. When the time average value of illuminance is V _A , the flicker value FLK is expressed by Equation 3.

  As shown in Equation 3, the flicker value FLK is a natural value obtained by dividing the difference in illuminance appearing between the first half cycle and the second half cycle within one cycle of polarity inversion drive by the time average value of illuminance. Logarithmic. The unit of the flicker value FLK is decibel (dB). In this way, the flicker value FLK of the inspection image is measured at each measurement point (S2 in FIG. 5). FIG. 8 shows an example of the flicker value FLK measured at 13 measurement points in this way, the vertical axis is the flicker value FLK, and the horizontal axis is the measurement point. The flicker value FLK is drawn for the three liquid crystal devices (sample A, sample B, and sample C).

Next, the auxiliary flicker value FLKA of the inspection image is measured at k measurement points (k is an integer of 2 or more) on the display surface 200 (S3 in FIG. 5). The method of measuring the auxiliary flicker value FLKA is the same as the measurement of the flicker value FLK described above, but the potential of the common electrode 124 when measured is higher than the potential of the common electrode 124 when measuring the flicker value FLK. Is set. As an example, when measuring the auxiliary flicker value FLKA, the potential of the common electrode 124 is made 30 millivolts (mV) higher than the potential of the common electrode 124 when the flicker value FLK is measured. Therefore, in the present embodiment, the potential of the common electrode 124 when measuring the auxiliary flicker value FLKA is 6.66V, the maximum value of the potential V _px of the pixel electrode 115 is 9.66V, and the minimum value is 3.66V. there were.

  When the auxiliary flicker value FLKA is obtained, this value is compared with the previously obtained flicker value FLK (S4 in FIG. 5). When the flicker value FLK is larger than the auxiliary flicker value FLKA, the flicker value FLK is positive. On the other hand, when the flicker value FLK is not larger than the auxiliary flicker value FLKA, the flicker value FLK is negative.

Next, the DC component potential V _DC is calculated from the flicker value FLK according to Equation 4 (S5-1 and S5-2 in FIG. 5).

When the flicker value FLK is positive (S5-1 in FIG. 5) during the calculation of Equation 4, the positive coefficient (V ₀ = + 1 V, α = 7.9477, β = 1.0223) is calculated. When the flicker value FLK is negative (S5-2 in FIG. 5), the negative coefficient (V ₀ = −1V, α = 8.3538, β = 1.3294) is used. When the flicker value FLK is compared with the auxiliary flicker value FLKA (S4 in FIG. 5), it can be determined whether the flicker value FLK is positive polarity or negative polarity, so that the DC component potential V _DC can be determined from the flicker value FLK. Can be calculated accurately.

According to the earnest study by the present inventor, as shown in FIG. 9, the correlation shown in Formula 5 is established between the flicker value FKL and the DC component potential V _DC .

FIG. 9A shows a case where the flicker value is positive and the positive coefficient is applied, and FIG. 9B shows a case where the flicker value is negative and the negative coefficient is applied. When the flicker value in FIG. 9A is positive, the correlation coefficient R ² = 0.9635, and when the flicker value in FIG. 9B is negative, the correlation coefficient R ² = 0. 9226. By solving Equation 5 in reverse, Equation 4 is obtained, so that the DC component potential V _DC can be accurately calculated from the flicker value FLK. FIG. 10 shows the result of converting the flicker value FLK shown in FIG. 8 into the DC component potential V _DC by the above-described method.

Next, the first statistical processing is performed on the k DC component potentials V _DC thus obtained (S6 in FIG. 5), and it is checked whether the first statistical processing result satisfies the first prescribed condition (FIG. 5). S7). Here, the first statistical processing result is a difference between the maximum value and the minimum value of the k DC component potentials V _DC (this difference is named Global). The first specified condition is a condition for determining whether or not the difference (Global) is 0.12 V or less. When Global does not satisfy the first specified condition (when Global ≧ 0.12 V), the inspection is terminated as a global failure (E1 in FIG. 5).

When Global satisfies the first specified condition (when Global <0.12V), the second statistical processing is then performed on k DC component potentials V _DC (S8 in FIG. 5), and the second statistical processing result is It is inspected whether the second specified condition is satisfied (S9 in FIG. 5). Here, the second statistical processing result is the maximum value in the difference between the DC component potentials V _DC at adjacent measurement points (this difference is named Local). The second specified condition is a condition for determining whether or not the difference (Local) is 0.023V or less. When Local does not satisfy the second specified condition (when Local ≧ 0.023V), the inspection ends as a Local failure (E2 in FIG. 5). On the other hand, when Local satisfies the second specified condition (when Local <0.023V), the inspection ends with the liquid crystal device 100 as a non-defective product (E3 in FIG. 5). Since the second statistical processing result compares the difference in DC component potential V _DC between adjacent measurement points, it is preferable that k measurement points are arranged at equal intervals from the viewpoint of improving measurement accuracy.

  The first specified condition (Global <0.12V) and the second specified condition (Local <0.023V) are the results of repeated repetitions of the above-described inspection and accelerated durability test for the liquid crystal device 100 by the inventor of the present application. Obtained as a result of experiments. When both of these conditions are satisfied, the probability of occurrence of defects such as spots and unevenness derived from ionic impurities in the future decreases, and the liquid crystal device 100 can be determined as a non-defective product. That is, it is possible to quickly estimate the product quality reliability of the electro-optical device and the electronic device by the above-described inspection method. In short, it is possible to determine whether a small amount of ionic impurities present in the electro-optical device will adversely affect the display quality in the future, and quantitatively evaluate the slight electrical asymmetry present in the electro-optical device. Therefore, it is possible to provide an inspection method that can guarantee the product life of the electro-optical device with high accuracy.

In this embodiment, two types of inspections were performed: whether the first statistical processing result satisfies the first specified condition and whether the second statistical processing result satisfies the second specified condition. This may be either one. That is, the first statistical processing result may be determined as a difference between the maximum value and the minimum value of the k DC component potentials V _DC and the first specified condition may be 0.12V or less, or The first statistical processing result may be set to the maximum value among the differences between the DC component potentials V _DC of adjacent measurement points, and the first specified condition may be determined to be 0.023V or less.

  In the present embodiment, the electronic device is the projector described with reference to FIG. 3, but in addition to this, the electronic device can be a rear projection television, a direct-view television, a mobile phone, a portable audio device, a personal computer, It may be a computer, a video camera monitor, a car navigation device, a pager, an electronic notebook, a calculator, a word processor, a workstation, a video phone, a POS terminal, a digital still camera, or the like. The inspection method described in detail in this embodiment can also be applied to these electronic devices and electro-optical devices.

(Embodiment 2)
"Inspection method using a variation V ₂ of illumination"
11A and 11B are diagrams for explaining the results of the electro-optical device inspection method according to the second embodiment. FIG. 11A shows a non-defective product and FIG. 11B shows a defective product. Hereinafter, an inspection method for the electro-optical device according to the present embodiment will be described with reference to FIG. In addition, about the component same as Embodiment 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

In the first embodiment, as shown in Formula 3, the inspection is performed using the illuminance difference V ₁ (see FIG. 7) that appears between the first half cycle and the second half cycle within one cycle of polarity inversion driving. I was going. On the other hand, in the present embodiment, the inspection is performed using the illuminance fluctuation V ₂ that appears in the half cycle of the polarity inversion driving. The illuminance variation V ₂ that appears in the half cycle of polarity inversion driving shown in FIG. 7 reflects the amount of ionic impurities in the liquid crystal layer 150, and the ionic impurities migrate through the liquid crystal layer 150 in the half cycle. It shows that there is. Therefore, when the time average value of illuminance is V _A , the ionic flicker value IFLK is defined by Equation 6.

  As shown in Equation 6, the ionic flicker value IFLK is a value obtained by dividing the change in illuminance appearing in the half cycle of polarity inversion driving by the time average value of illuminance. A measurement example of the ionic flicker value IFLK thus obtained is shown in FIG. As a result of repeating the above-described inspection and accelerated durability test on many liquid crystal devices 100 by the inventors of the present application, as shown in FIG. 11A, the ionic flicker value IFLK is 0.006 (0. In the case of less than 6%) (IFLK <0.006), it was rare that spots and unevenness derived from ionic impurities were expressed in the accelerated durability test. On the other hand, as shown in FIG. 11B, when the ionic flicker value IFLK is 0.006 (0.6%) or more (IFLK ≧ 0.006), it is derived from ionic impurities in the accelerated durability test. The appearance of spots and unevenness was often observed. Therefore, when the liquid crystal device 100 is inspected on the condition that the ionic flicker value IFLK is less than 0.006 (0.6%) (IFLK <0.006), the reliability of the product quality is improved early. You can estimate.

  Variations in illuminance that appear within a half cycle of polarity inversion drive are caused by light leakage current of the TFT 130 in addition to electrophoresis of ionic impurities. Therefore, the above-described inspection method produces a particularly effective effect in an electro-optical device having excellent light shielding properties such that light leakage current hardly occurs in the TFT 130. In particular, it is preferable to apply the inspection method of this embodiment to the reflective liquid crystal device 100 using metal for the pixel electrode 115.

  The present invention is not limited to the above-described embodiment, and various changes and improvements can be added to the above-described embodiment. A modification will be described below.

(Modification 1)
"Form with different arrangement of measurement points"
12 to 14 are diagrams illustrating an apparatus for performing the inspection method according to the first modification. Next, an inspection method according to this modification will be described with reference to FIGS. In addition, about the component same as Embodiment 1 thru | or 2, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  This modified example is different from the first and second embodiments in the arrangement of the optical sensor 210. That is, the arrangement of measurement points on the display surface 200 is different. Other configurations are substantially the same as those in the first and second embodiments. In the first and second embodiments, as shown in FIG. 4, the optical sensors 210 are arranged in a vertical row. The arrangement of the optical sensor 210 is not limited to this, and various arrangements are possible. For example, as shown in FIG. 12, the optical sensors 210 may be arranged in a horizontal row with respect to the display surface 200. FIG. 12 also shows positions corresponding to the sealing material 140 and the opening Op in the liquid crystal device 100 for reference. If the photosensors 210 are arranged in a horizontal row in the vicinity of the portion corresponding to the opening Op, it is possible to determine whether or not ionic impurities are mixed during liquid crystal injection or after sealing.

  In addition, as shown in FIG. 13, the optical sensor 210 may be disposed obliquely with respect to the display surface 200. FIG. 13 also shows positions corresponding to the sealing material 140 and the opening Op in the liquid crystal device 100 for reference. Alternatively, as shown in FIG. 14, the optical sensor 210 may be arranged in a ring shape with respect to the center of the display surface 200. For reference, FIG. 14 also shows a position corresponding to the sealing material 140 in the liquid crystal device 100. When assembling the liquid crystal device 100, a manufacturing method may be employed in which after the sealing material 140 is disposed in a frame shape on the element substrate 110, liquid crystal is dropped on the central portion of the element substrate 110, and then the counter substrate 120 is bonded. is there. In such a case, as shown in FIG. 14, if the center of the display surface 200 is the center of the circle and the optical sensors 210 are arranged at equal intervals on this arc, whether or not ionic impurities are mixed when the liquid crystal is dropped is determined. You will be able to judge.

  DESCRIPTION OF SYMBOLS 100 ... Liquid crystal device, 110 ... Element substrate, 115 ... Pixel electrode, 120 ... Counter substrate, 122 ... Sealing material, 124 ... Common electrode, 130 ... TFT, 140 ... Sealing material, 150 ... Liquid crystal layer, 200 ... Display surface, 210 ... light sensor, 220 ... light sensor control device, 230 ... logger, 240 ... computer, 2100 ... projector, 2120 ... screen.

Claims (7)

An inspection image of intermediate gradation is displayed on the display surface using polarity inversion driving,
Flicker value FLK of the inspection image is measured at k measurement points (k is an integer of 2 or more) on the display surface,
A mathematical expression including k 0, DC component potentials V _DC from each of the flicker values FLK measured at the k measurement points, and V ₀ , α, and β, which are coefficients corresponding to the polarity of the flicker value FLK. Calculated according to 1,
An inspection method for an electro-optical device, wherein whether or not the first statistical processing result of the k DC component potentials V _DC satisfies a first specified condition is inspected.

2. The first statistical processing result is a difference between a maximum value and a minimum value of k DC component potentials V _DC , and the first specified condition is 0.12 V or less. Inspection method for electro-optical device. The first statistical processing result is a maximum value among the differences in DC component potential V _DC between the adjacent measurement points, and the first specified condition is 0.023 V or less. The inspection method of the electro-optical device according to claim. An inspection image of intermediate gradation is displayed on the display surface using polarity inversion driving,
Flicker value FLK of the inspection image is measured at k measurement points (k is an integer of 2 or more) on the display surface,
A mathematical expression including k 0, DC component potentials V _DC from each of the flicker values FLK measured at the k measurement points, and V ₀ , α, and β, which are coefficients corresponding to the polarity of the flicker value FLK. Calculated according to 2,
Whether the first statistical processing result of the k DC component potentials V _DC satisfies the first specified condition, and the second statistical processing result of the k DC component potentials V _DC satisfies the second specified condition An inspection method for an electro-optical device, characterized by

The first statistical processing result is a difference between a maximum value and a minimum value of k DC component potentials V _DC , and the first specified condition is 0.12 V or less,
5. The second statistical processing result is a maximum value in a difference between DC component potentials V _DC at adjacent measurement points, and the second specified condition is 0.023 V or less. The inspection method of the electro-optical device according to claim. When the flicker value FLK is positive, V ₀ = + 1 V, α = 7.9477, β = 1.0223,
6. The electricity according to claim 1, wherein when the flicker value FLK is negative polarity, V ₀ = −1V, α = 8.3538, and β = 1.3294. 6. Inspection method for optical devices. The electro-optical device has a pixel electrode and a common electrode,
On the display surface, the auxiliary flicker value FLKA of the inspection image is measured at the k measurement points (k is an integer of 2 or more),
The potential of the common electrode when the auxiliary flicker value FLKA is measured is higher than the potential of the common electrode when the flicker value FLK is measured,
When the flicker value FLK is larger than the auxiliary flicker value FLKA, the flicker value FLK is the positive polarity,
7. The electro-optical device inspection method according to claim 6, wherein when the flicker value FLK is not larger than the auxiliary flicker value FLKA, the flicker value FLK has the negative polarity.

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