JP4415549B2 - Display panel color prediction apparatus, color prediction method, and color prediction program - Google Patents

Description

【００３８】
図３（ｃ）を参照するとわかるように、ＲＧＢ各色とも、分光特性の積Ｓ（ｎ，λ）は基本的にステップＳ１で入力された各データの積である。なお、式（１）において“１／３”を乗算しているのは、液晶表示パネル１００のセル構造がストライプ型であり、各色のセルの面積は１画素の面積の１／３に相当するからである。図５に、式１により計算した、各駆動レベル（階調）毎の赤色セルの分光特性変化を示す。
【００３９】
式（１）から理解されるように、Ｒセルにおける分光特性の積Ｓ_Ｒ（ｎ，λ）、緑色（Ｇ）セル（以下、「Ｇセル」とも呼ぶ。）における分光特性の積Ｓ_Ｇ（ｎ，λ）及び青色（Ｂ）セル（以下、「Ｂセル」とも呼ぶ。）における分光特性の積Ｓ_Ｂ（ｎ，λ）は、カラーフィルタの分光特性が各色で異なる以外は同じ計算により得られる。
【００４０】
（単色ＲＧＢのＸＹＺ計算：ステップＳ３）
次にステップＳ２で計算した分光特性の積を用いて、各セルの駆動による三刺激値を計算する。例えば駆動レベルをｎとすると、ＲＧＢ各セルのＸ値、Ｙ値、Ｚ値はそれぞれ以下の式（２）で得られる。
【００４１】
【数２】

【００４２】
なお、式（２）の定数ｋは放射輝度から輝度への換算定数６８３であり、この定数ｋを乗算することにより、Ｙ_Ｒ（ｎ）〜Ｙ_Ｂ（ｎ）は輝度［ｃｄ／ｍ^２］として得られることになる。また、ｘ（λ）、ｙ（λ）、ｚ（λ）は等色関数と呼ばれ、三刺激値ＸＹＺを得るための人間の目の感度関数に相当するものである。よって、セル毎の分光特性の積に等色関数を乗算し、波長で積分することにより、三刺激値ＸＹＺが求められる。
【００４３】
さて、こうしてＲＧＢ各色の三刺激値が得られるが、これらだけでは正確な単色ＲＧＢの色予測を行うためには十分ではない。その理由は、例えば赤（Ｒ）単色の予測を行う場合、ＧセルとＢセルからの漏れ光を考慮する必要があるからである。
【００４４】
図６に漏れ光発生の様子を模式的に示す。図６において、カラーフィルタ３の赤色領域を３Ｒ、緑色領域を３Ｇ、青色領域を３Ｂとする。液晶表示パネルは、照明光を液晶の配向によるシャッター機能により部分的に通過させ又は遮断することにより表示を実現している。例えば、液晶表示パネルにより赤色単色を表示する場合、図６の下方から照射される照明光が、カラーフィルタ３の赤色領域３Ｒを通過し、かつ、緑色領域３Ｇ及び青色領域３Ｂを通過しないように駆動電圧を印加して液晶分子の配向を制御する。これにより、赤色領域３Ｒを通過した光のみが観察者に至り、緑色領域３Ｇ及び青色領域３Ｂでは照明光が通過しない。その結果、観察者は赤色のみの表示を認識することになる。
【００４５】
しかし、実際には、液晶表示パネルの駆動レベルを「０」としても、液晶によるシャッター機能は完全ではなく、図６に模式的に示すように無視できない程度の漏れ光が発生する。この漏れ光が、観察者が実際に認識する色に影響を与える。その結果、単純に液晶表示パネルの各構成要素の分光特性の積を計算して色予測を行っても、その結果は実測値とは一致しない。
【００４６】
そこで、本発明では、この漏れ光の影響を考慮した演算を実行する。具体的には、図６のような場合、ＧセルとＢセルからの漏れ光の影響を考慮すると、ＲセルのＸ値Ｘ_Ｒ（ｎ）は次式（３）により補正され、補正後のＸ値はＸ’_Ｒ（ｎ）として得られる。また、他の色及びＹ、Ｚ値も同様に得られる。
【００４７】
【数３】

【００４８】
これらの値が最終的な単色の三刺激値となる。
【００４９】
なお、式（３）によれば、ＲＧＢ全てのセルがオフの場合、即ち表示データが黒の場合のＸＹＺ各値はＲＧＢの全てのセルで等しくなり、次式のように表せる（ＲＧＢで等しくなるため、あらためてＸ’（０）、Ｙ’（０）、Ｚ’（０）、として表す）。
【００５０】
【数４】

【００５１】
図７に、式（３）に従って単色ＲＧＢのＸＹＺ値を予測し、ｘｙ色度上にプロットした結果を示す。駆動レベルが変わるとき、単色のｘｙ色度が内側にシフトしていくことが確認できる。内側にシフトしているのは、漏れ光を考慮したためである。
【００５２】
（単色ＲＧＢのＸＹＺの補間計算：ステップＳ４）
分光特性及び開口率の入力の欄で述べたが、本実施形態の色予測処理では液晶表示パネルの駆動レベルとして１６駆動レベルを入力し、後で２５６駆動レベル（即ち２５６階調）分計算することとしている。よって、ステップＳ３で三刺激値の計算が終了した後、２５６階調分のＸＹＺ値を得るための補間計算を行う。これは、次式により求められる。
【００５３】
【数５】

【００５４】
ここで、式（５）における変数ｍは、液晶表示パネル１００に供給される２５６階調のデータとなる。
【００５５】
図８に補間計算のフローチャートを示し、図９に補間計算課過程の階調特性のグラフを示す。基準となる階調特性に従ってデータ補間を行うため、まず、基準階調特性（γ２．２：データと輝度が指数２．２として表される特性など）を入力する（ステップＳ１０）。続いて、補間元データとして、先に得られた１６階調分のＸＹＺ値を入力し、正規化を行う（ステップＳ１１）。
【００５６】
次に、ステップＳ１２〜Ｓ１４により構成されるループでは、補間元データが基準階調特性のどの位置に該当するかを決定する。具体的には、補間元データに最も近い基準階調特性上の値を探索し（ステップＳ１２）、探索により得られた値に近いデータをその階調レベルに対応する値として記録する（ステップＳ１３）。これを全ての補間元データについて実行する（ステップＳ１４）。なお、ステップＳ１２〜Ｓ１５の処理は、液晶表示パネルの各駆動レベルが基準階調特性のどこに該当するかを決定しているので、ＲＧＢのＸＹＺ値のいずれか１つを利用してこの対応付けを行い、他についてはその決定された対応付けを利用すればよい。図９の例は、Ｇセルの輝度Ｙ’_Ｇ（ｎ）を用いて、液晶駆動レベルの対応付けを行っている。
【００５７】
次に、ステップＳ１５及びＳ１６により構成されるループでは、隣接データ間の補間を行う。即ち、ステップＳ１３で得られた複数のデータのうち、隣接するデータ間を基準階調特性に沿って補間して値を記録し（ステップＳ１５）、これをステップＳ１３で得られた全てのデータについて実行する（ステップＳ１６）。こうして、１６駆動レベル（階調レベル）分の入力データを補間して２５６階調分のデータを得ることができる。
【００５８】
（混色計算：ステップＳ５）
次に、補間計算によって求めた単色ＲＧＢのＸＹＺ値を用いて、単色以外の色を計算する。基本的には加法混色とするが、このとき黒のオフセット分を重ねて加算しないようにする。具体的には、液晶表示パネルへ供給するデータを（ｍ_Ｒ，ｍ_Ｇ，ｍ_Ｂ）とするとき、式（４）と式（５）を用いて、黒のオフセット分が重複しないように加法混色を行う式を以下に示す。
【００５９】
【数６】

【００６０】
以上の計算によって、液晶表示パネルの各構成要素の分光特性や開口率などに基づいて、色予測が行える。特に、ここで予測した三刺激値のＹは輝度であるため、データが（ｍ_Ｒ，ｍ_Ｇ，ｍ_Ｂ）＝（２５５，２５５，２５５）のときの輝度Ｙ’’’（２５５，２５５，２５５）については、バックライト単体の輝度に対する比率を計算することによって、透過率の予測も行うことができる。
【００６１】
［本色予測方法の評価］
以上説明した本発明の色予測方法によれば、液晶表示パネルの各構成要素の分光特性の積を単純に計算するのみでなく、液晶表示パネルの構造上不可避である漏れ光の影響を考慮して予測を行っているので、実測値に近い高精度の色予測が可能である。一例では、従来の分光特性の単純な積による予測による色予測精度がΔＥ_９４平均が８．０８程度だったのに対し、本実施形態の色予測手法による色予測精度はΔＥ_９４平均が３．９２程度であり、色予測精度が大幅に改善された。なお、ΔＥ_９４は予測値と実測値との差である色差を示す。
【００６２】
このように高精度で色予測を行うことができるので、液晶表示パネルの試作を行わずに液晶カラーフィルタの設計することが可能となる。従来からカラーフィルタ設計時に液晶表示パネルの色予測は行われていたが、試作なしで設計を行えるほどに高い予測精度は得られていなかった。本発明の色予測手法により、試作なしでも最適なカラーフィルタの設計が可能となる。
【００６３】
［変形例］
なお、ここで示した液晶表示パネルの構造は一例であり、例えばカラーフィルタが下側ガラス基板側に配置されるなど、各層や膜の配置が異なるタイプの液晶表示パネルに対しても本発明は適用可能である。また、ＴＦＤ駆動方式の透過型液晶表示パネルを例示したが、本発明の色予測方法は、ＴＦＴ駆動方式の液晶表示パネルや、半透過反射型液晶表示パネルなどにも適用が可能である。
【００６４】
また、液晶表示パネルに限らず、エレクトロルミネッセンスパネル、無機エレクトロルミネッセンスパネル、プラズマディスプレイパネル、電気泳動表示パネル、電界放出表示パネル、ＬＥＤ（ライトエミッティングダイオード）表示パネルなどの電気光学パネルにおいても本発明を同様に適用することが可能である。
【００６５】
さらに、上記の色予測処理では、ＲＧＢをカラーの構成要素色とする液晶表示パネルについて説明を行ったが、例えば、▲１▼ＣＭＹの減法混色によるカラー液晶表示パネル、▲２▼ＲＧＢに加えてオレンジ・紫等を設けた多色（マルチカラー）液晶表示パネル、など、カラーの構成要素色がＲＧＢ以外からなる液晶表示用パネルにも、本発明の色予測方法は適用が可能である。
【００６６】
上記の色予測処理は、データ入力部と演算部を備える色予測装置により実行される。また、上記の色予測処理を色予測プログラムとして構成し、データ入力部とＣＰＵなどの演算部を備えるコンピュータにより色予測プログラムを実行することも可能である。
【００６７】
［応用例］
近年では、各種表示装置間で同一の色を表示すべきとの要求が大きくなっており、そのためには各表示装置の色特性をデータとして求める必要がある。各種表示装置の色特性を記述するためのファイルのフォーマットはＩＣＣ（International Color Consortium）で定められており、各種情報機器ではＩＣＣプロファイルを利用したカラーマネージメントシステムが導入されている。また、色特性データから、ＩＣＣプロファイルを作成するソフトウェアも開発され、市販されている。よって、そのようなソフトウェアを利用すれば、本発明の色予測方法により得られた色特性データからＩＣＣプロファイルを作成することが可能である。
【図面の簡単な説明】
【図１】 透過型液晶表示パネルの概略構成を示す。
【図２】 色予測処理のフローチャートである。
【図３】 色予測処理における入出力データを示す。
【図４】 色予測処理で入力される特性例を示す。
【図５】 赤色（Ｒ）セルの駆動レベル毎の分光特性を示す。
【図６】 セルからの漏れ光の様子を模式的に示す。
【図７】 単色ＲＧＢのＸＹＺ予測時のｘｙ色度図である。
【図８】 単色ＲＧＢの補間計算のフローチャートである。
【図９】 補間計算過程における階調特性例を示す。
【符号の説明】
１、１１ 偏光板、 ２、１０ ガラス基板、３ カラーフィルタ、
４ 保護膜、 ５ 対向電極、 ６、８ 配向膜、 ７ 液晶層、 ９ 画素電極、
１２ バックライト、 １４ 集光フィルム、 １６ 信号線、
１７ ＴＦＤ素子 １００ 液晶表示パネル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display panel design technique, and more particularly to a color prediction method for a color filter.
[0002]
[Background]
In a color display panel, for example, necessary electrodes and protective layers are formed between two transparent substrates sandwiching an electro-optical element, and a color filter is disposed. In the case of a transmissive display panel, illumination light from a light source such as a backlight passes through each component of the display panel including a color filter and reaches the viewer's eyes. Therefore, the color characteristics of the color display panel are affected by the spectral characteristics of each component of the display panel.
[0003]
A method has been proposed in which the color reproduction characteristics are controlled by determining the area ratio of the openings of the electro-optic cells of each color in consideration of the spectral characteristics of the backlight and color filters that are constituent elements of the display device (Patent Document 1). See). In addition, it has been reported that the spectral characteristics of the entire display panel are determined by the product of the spectral characteristics of each component constituting the display panel (see Non-Patent Document 1).
[0004]
Note that an additive color mixing technique is often used when controlling the color design and color reproducibility of the display panel (see Patent Document 2, Non-Patent Document 2, etc.).
[0005]
[Patent Document 1]
JP-A-8-84347
[Patent Document 2]
JP 2002-131131 A
[Non-Patent Document 1]
Tatsumi Takahashi, “Color Filter”, Journal of the Imaging Society of Japan, Vol. 41, No. 1 (2002)
[Non-Patent Document 2]
Nobuhiko Tamura and two others, “Calibration of color reproduction characteristics of liquid crystal displays considering channel interaction”, Journal of the Institute of Image Information and Television Engineers Vol.56, No.8, pp.1315-1320 (2002)
[0006]
[Problems to be solved by the invention]
Therefore, as a method of predicting the color characteristics of the display panel, a method of calculating a product of spectral characteristics of each component of the display panel can be considered. However, it is known that simply calculating the product of the spectral characteristics of each component of the display panel does not match the actual measured values of the color characteristics of the display panel, and sufficient prediction accuracy cannot be obtained. .
[0007]
The present invention has been made in view of the above points, and an object thereof is to perform color prediction of a display panel with high accuracy based on the spectral characteristics of each component.
[0008]
[Means for Solving the Problems]
In one aspect of the present invention, when a color prediction device for a display panel that predicts a color displayed by a display panel performs color prediction of one of the component colors constituting the color, the predetermined color of the one color is determined. The predicted color of the one color is determined based on the predicted color at the drive level and the predicted color at the non-drive level of the other element colors.
[0009]
The color prediction device predicts the color of each element color when the display panel is driven at a predetermined drive level by calculation, and generates predicted color data. For example, R (red), G (green), and B (blue) are representative element colors, but C (cyan), M (magenta), Y (yellow), and RGB by subtractive color mixing are representative. It may be multicolored by adding purple to the color. Here, for example, in the case of a color display panel composed of RGB three colors, the predicted color when a certain color region is driven at a predetermined drive level is adjacent to the color component of the color itself due to light. Color components due to leakage light when the other two colors are at the non-driving level. This is because one pixel of the display panel is composed of adjacent regions of RGB three colors, and even when only one color is driven and the other two colors are not driven, the shutter function of the electro-optical element is not perfect. This is because the other two colors of leakage light are mixed. Therefore, in consideration of the occurrence of such leakage light, the predicted color of the one color is determined in consideration of predicted colors at the other two non-driving levels, so that the predicted color with high accuracy close to the actually measured value is obtained. Can be obtained.
[0010]
  In another aspect of the invention,A color predicting device for a liquid crystal display panel that predicts a color displayed by a liquid crystal display panel having a plurality of components including a light source, a liquid crystal layer, and a color filter is provided with a driving level of a plurality of element colors constituting the display color. Monochromatic data is calculated for each drive level of the display panel for one element color based on characteristics including luminance characteristics of the light source, spectral characteristics of the liquid crystal layer, and spectral characteristics of a color filter corresponding to the element colors. Monochromatic data generation means, correction data at non-driving levels of element colors other than the one element color among the plurality of element colors, luminance characteristics of the light source, spectral characteristics of the liquid crystal layer, and the other element colors Based on characteristics including spectral characteristics of a color filter corresponding to the plurality of element colors other than the one element color, and the single color for the one element color It is added separately over data and a correction means for correcting the monochromatic data.
[0011]
  In another aspect of the invention,A color prediction method for a liquid crystal display panel for predicting a color displayed by a liquid crystal display panel having a plurality of constituent elements including a light source, a liquid crystal layer, and a color filter is a driving level of a plurality of element colors constituting a display color. Monochromatic data is calculated for each drive level of the display panel for one element color based on characteristics including luminance characteristics of the light source, spectral characteristics of the liquid crystal layer, and spectral characteristics of a color filter corresponding to the element colors. Correction data at a non-driving level of an element color other than the one element color among the plurality of element colors, a luminance characteristic of the light source, a spectral characteristic of the liquid crystal layer, and the other element color; Based on characteristics including spectral characteristics of a color filter corresponding to the plurality of element colors other than the one element color, and the single color for the one element color It is added separately over data, and a correction step of performing correction of the monochrome data.
[0012]
According to the above color prediction apparatus, for example, when RGB three colors are used as element colors, first, single color data when each of the RGB colors is at a predetermined drive level is calculated based on characteristics of a plurality of components constituting the display panel. To do. Then, in consideration of the influence of leakage light of the other two adjacent colors, correction is performed by adding the single color data at the non-driving level of the other two colors to the obtained single color data. Thereby, highly accurate color data close to the actual measurement value can be obtained.
[0014]
One aspect of the color predicting apparatus further includes means for generating monochrome data corresponding to the number of gradations of the display panel by interpolating the corrected monochrome data according to predetermined reference gradation characteristics.
[0015]
When the number of gradations of the display panel is large, if monochrome data is generated for each drive level, the burden of input of characteristics and calculation processing increases. Therefore, the monochrome data is generated by generating monochrome data with a predetermined number of drive levels (for example, 16) and performing interpolation according to the reference gradation characteristics, so that the monochrome corresponding to the actual number of gradations (for example, 256) of the display panel is obtained. Generate data. Thereby, it is possible to prevent an excessive calculation processing burden or the like.
[0016]
One aspect of the above color prediction apparatus is the addition data obtained by adding the corrected single color data for the component colors constituting the color, and the single color data when all the component colors are in the non-driven state. Based on this, color mixing data generation means for generating color mixing data is further provided. In the embodiment, the color mixture data generation means subtracts twice the single color data when all the element colors are in the non-driven state from the addition data. Thereby, not only RGB single color data but also color mixture data can be obtained. At this time, since the color components at the non-driving level of the other two colors are included in the single color data of each color by correcting the single color data, accurate color mixture data from which the offset is removed is obtained by subtracting that amount. be able to.
[0017]
In one aspect of the above color prediction apparatus, it may further comprise means for generating an ICC profile based on the single color data and the mixed color data. Thus, an ICC profile corresponding to the display panel can be created using the predicted color data.
[0018]
  In another aspect of the invention,A color prediction program for a liquid crystal display panel that is executed by a computer and predicts a color displayed by a liquid crystal display panel having a plurality of components including a light source, a liquid crystal layer, and a color filter is provided for a plurality of component colors that constitute a display color. For one element color of the drive level, for each drive level of the display panel, based on characteristics including luminance characteristics of the light source, spectral characteristics of the liquid crystal layer, and spectral characteristics of a color filter corresponding to the element color Monochromatic data generating means for calculating monochromatic data, correction data at a non-driving level of an element color other than the one element color among the plurality of element colors, luminance characteristics of the light source, spectral characteristics of the liquid crystal layer, and the Based on characteristics including spectral characteristics of color filters corresponding to other element colors, individually calculated for a plurality of element colors other than the one element color, Correcting means for serial by adding separately to the monochrome data for one element color corrects the monochrome data, causes the computer to function as.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[0020]
In the present invention, a liquid crystal display panel is used as the display panel, and in the color prediction of the liquid crystal display panel, elements that affect the color characteristics due to the structure of the liquid crystal display panel, specifically, leakage light from the cell is considered. And color prediction is performed.
[0021]
[LCD panel structure]
FIG. 1 shows a schematic configuration of a transmissive liquid crystal display panel 100. As shown in the figure, the liquid crystal display panel 100 has a liquid crystal layer 7 sandwiched between two glass substrates 2 and 10. In the drawing, a color filter 3 and a protective film 4 are provided on the inner surface of the upper glass substrate 2, that is, the surface on the liquid crystal layer 7 side, and a counter electrode 5 is formed on the lower side by ITO (Indium-Tin Oxide). . Further, an alignment film 6 is provided below the counter electrode 5. On the other hand, a TFD (Thin Film Diode) element, which is a driving element, is provided for each pixel on the inner surface of the lower glass substrate 10 in the figure, and a pixel electrode 9 and a signal line 16 are formed of ITO. An alignment film 8 is provided.
[0022]
A polarizing plate 1 is disposed on the outer surface (upper surface in the drawing) of the upper glass substrate 2, and a polarizing plate 11 is disposed on the outer surface (lower surface in the drawing) of the lower glass substrate 10. The A condensing film 14 is attached under the polarizing plate 11. The condensing film 14 has a function of increasing the gain of illumination light from the light source without changing the spectral characteristics.
[0023]
The liquid crystal display panel 100 configured as described above is irradiated with illumination light from the backlight 12. The backlight 12 includes, for example, a predetermined number of LEDs and a light guide plate that diffuses light from the LEDs and guides the light toward the liquid crystal display panel 100. Illumination light from the backlight 12 passes through each layer of the liquid crystal display panel 100 and reaches the eyes 18 of the observer.
[0024]
[Color prediction]
Next, a color prediction method for a liquid crystal display panel according to the present invention will be described. First, the outline will be described. In the color prediction method of the present invention, the spectral characteristic of the liquid crystal display panel is calculated for each cell based on the spectral characteristic of each component of the liquid crystal display panel. At that time, the influence of light leaked from the cell is considered. Then, after predicting a single color of each RGB color by calculation, color prediction of a color other than a single color (mixed color) is performed.
[0025]
In the embodiment described below, the glass substrates 2 and 10 and the alignment films 6 and 8 are not considered among the components of the liquid crystal display panel 100 shown in FIG. This is because the glass substrate and the alignment film have spectral characteristics of a substantially flat shape at the wavelength of visible light, and hardly affect color prediction. However, these can be added to the color prediction calculation as well as other components. In that case, spectral characteristics may be obtained for each glass substrate or alignment film, and may be added to the calculation as an independent component similar to each component included in the calculation in this embodiment. The characteristic can be calculated as a part of various transparent films included in the calculation in this embodiment.
[0026]
FIG. 2 shows a flowchart of the color prediction process according to this embodiment.
[0027]
Prior to the start of processing, the spectral characteristics and the aperture ratio of the liquid crystal display panel for each component constituting the liquid crystal display panel are determined in advance by measurement or the like and prepared as input data. When the process is started, first, the spectral characteristics and the aperture ratio of each component are input (step S1). A “cell” refers to an area of each color of RGB included in an area constituting one pixel.
[0028]
Next, a product of spectral characteristics of each component is calculated for each cell of the liquid crystal display panel based on the input data (step S2). Next, tristimulus values (X, Y, Z) for each color of R, G, B constituting each cell are calculated (step S3). In this step, a calculation that takes into account the leakage light from the cell, which is a feature of the present invention, is performed.
[0029]
Next, the obtained tristimulus values are made into data for the number of gradations of the liquid crystal display panel by interpolation calculation (step S4). Next, calculation is performed for mixed colors other than a single color using X, Y, and Z of RGB single colors obtained by the interpolation calculation (step S5). And the obtained result is output (step S6) and a process is complete | finished.
[0030]
Next, each step will be described in detail.
[0031]
(Input of spectral characteristics, aperture ratio, etc .: Step S1)
First, in step S1, spectral characteristics and an aperture ratio of each component of the liquid crystal display panel 100 are input in order to perform color prediction. Specifically, each data shown in FIG. Of the input data shown in FIG. 3A, “liquid crystal drive” is spectral characteristic data of the liquid crystal layer 7 and the polarizing plates 1 and 11, and an example of the characteristic is shown in FIG. The liquid crystal layer 7 and the polarizing plates 1 and 11 are hereinafter also referred to as “liquid crystal driving unit”. The example of FIG. 4A is spectral characteristic data of the liquid crystal drive unit when the drive level (corresponding to the number of gradations) of the liquid crystal display panel is 16 (that is, n = 0,..., 15). It can be seen that the spectral characteristics change for each gradation. Note that when the input data to the liquid crystal display panel 100 is 8 bits = 256 gradations, it is possible to input spectral characteristics of 256 drive levels, but in this case, the amount of spectral characteristic data to be input is large. Become. For this reason, in this embodiment, 16 drive levels are input, and data for 256 gradations is created by interpolation calculation described later.
[0032]
“Color filter” in the input data is spectral characteristic data of the color filter 3, and an example of the characteristic is shown in FIG. Since the color filter is composed of R, G, and B color regions, the spectral characteristics are defined for each of R, G, and B.
[0033]
“Various transparent films” are spectral characteristic data of each component of the protective film 4, the counter electrode 5, and the pixel electrode 9, and an example of the characteristic is shown in FIG. In the example of FIG. 4C, the spectral characteristics of the protective film 4 and the electrodes 5 and 9 formed of ITO are shown. “Backlight” is characteristic data of the backlight 12, and is actually characteristic data of radiance of illumination light emitted from the backlight as shown in FIG. Therefore, the horizontal axis is the wavelength, and the vertical axis is the radiance.
[0034]
The “aperture ratio” is a value indicating the ratio of the image display area in each cell of the liquid crystal display panel 100, and depends on the arrangement of electrodes, drive elements, various electrodes, etc. on the liquid crystal display panel. It is a determined value. The “condensing film increase rate” corresponds to the amplification factor of illumination light by the condensing film 14. Since the light collecting film increases only the brightness of the illumination light without affecting the spectral characteristics, the light collecting film increase rate is a constant value independent of the wavelength.
[0035]
These input data will be described by the function or constant shown in FIG. That is, the spectral characteristic of the liquid crystal drive unit is denoted by LC (n, λ), and the spectral characteristic of the color filter is CF for each color of R, G, B._R(Λ), CF_G(Λ), CF_BDenote by (λ). Various transparent films have the spectral characteristics of the protective film 4 set to FL.₁(Λ) and the spectral characteristic of the counter electrode 5 is FL₂(Λ) and the spectral characteristic of the pixel electrode 9 is FL₃Denote by (λ). Also, the radiance characteristic of the backlight is indicated by BL (λ), and the aperture ratio is A₁The increase rate of the condensing film is A₂With
[0036]
(Calculation of spectral characteristic product in cell unit: Step S2)
When the input of the characteristic data of each component is completed, the product of spectral characteristics is calculated for each cell. For example, in a red (R) cell (hereinafter also referred to as “R cell”), the product of spectral characteristics at drive level n and wavelength λ is calculated by the following equation (1) (ratio from percentage (0 to 100)) The conversion term to (0-1) was omitted).
[0037]
[Expression 1]

[0038]
As can be seen from FIG. 3C, the spectral characteristic product S (n, λ) is basically the product of the data input in step S1 for each of the RGB colors. Note that “1/3” is multiplied in equation (1) because the cell structure of the liquid crystal display panel 100 is a stripe type, and the area of each color cell corresponds to 1/3 of the area of one pixel. Because. FIG. 5 shows changes in the spectral characteristics of the red cell for each drive level (gradation) calculated by Equation (1).
[0039]
As understood from the equation (1), the product S of spectral characteristics in the R cell_RThe product S of spectral characteristics in (n, λ), green (G) cell (hereinafter also referred to as “G cell”)._GThe product S of spectral characteristics in (n, λ) and blue (B) cell (hereinafter also referred to as “B cell”)._B(N, λ) is obtained by the same calculation except that the spectral characteristics of the color filter are different for each color.
[0040]
(Monochromatic RGB XYZ Calculation: Step S3)
Next, the tristimulus value by driving each cell is calculated using the product of the spectral characteristics calculated in step S2. For example, when the drive level is n, the X value, Y value, and Z value of each RGB cell can be obtained by the following equation (2).
[0041]
[Expression 2]

[0042]
Note that the constant k in Equation (2) is a radiance-to-luminance conversion constant 683, and by multiplying this constant k, Y_R(N) to Y_B(N) is the luminance [cd / m²] Will be obtained. Further, x (λ), y (λ), and z (λ) are called color matching functions and correspond to the sensitivity function of the human eye for obtaining tristimulus values XYZ. Therefore, the tristimulus value XYZ is obtained by multiplying the product of the spectral characteristics for each cell by the color matching function and integrating with the wavelength.
[0043]
Now, tristimulus values for each color of RGB can be obtained in this way, but these alone are not sufficient for accurate color prediction of monochromatic RGB. The reason is that, for example, when prediction of red (R) single color is performed, it is necessary to consider leakage light from the G cell and the B cell.
[0044]
FIG. 6 schematically shows how light leaks. In FIG. 6, the red region of the color filter 3 is 3R, the green region is 3G, and the blue region is 3B. The liquid crystal display panel realizes display by partially passing or blocking illumination light by a shutter function based on the orientation of liquid crystal. For example, when displaying a single red color on the liquid crystal display panel, the illumination light irradiated from below in FIG. 6 passes through the red region 3R of the color filter 3 and does not pass through the green region 3G and the blue region 3B. A driving voltage is applied to control the alignment of liquid crystal molecules. Thereby, only the light that has passed through the red region 3R reaches the observer, and the illumination light does not pass through the green region 3G and the blue region 3B. As a result, the observer recognizes the display of only red.
[0045]
However, actually, even if the drive level of the liquid crystal display panel is set to “0”, the shutter function by the liquid crystal is not perfect, and leak light that cannot be ignored is generated as schematically shown in FIG. This leaked light affects the color that the observer actually recognizes. As a result, even if color prediction is performed by simply calculating the product of spectral characteristics of each component of the liquid crystal display panel, the result does not match the actual measurement value.
[0046]
Therefore, in the present invention, a calculation considering the influence of this leakage light is executed. Specifically, in the case shown in FIG. 6, the X value X of the R cell X is taken into consideration when the influence of leakage light from the G cell and the B cell is considered._R(N) is corrected by the following equation (3), and the corrected X value is X ′_RObtained as (n). Further, other colors and Y and Z values are obtained in the same manner.
[0047]
[Equation 3]

[0048]
These values are the final monochromatic tristimulus values.
[0049]
According to the equation (3), when all the RGB cells are off, that is, when the display data is black, the XYZ values are equal in all the RGB cells and can be expressed as the following equation (equal in RGB) Therefore, it is again expressed as X ′ (0), Y ′ (0), Z ′ (0)).
[0050]
[Expression 4]

[0051]
FIG. 7 shows the result of predicting the XYZ values of monochromatic RGB according to the equation (3) and plotting them on the xy chromaticity. When the drive level changes, it can be confirmed that the monochromatic xy chromaticity shifts inward. The reason for shifting to the inside is that leakage light is taken into consideration.
[0052]
(Monochromatic RGB XYZ Interpolation Calculation: Step S4)
As described in the column of spectral characteristics and aperture ratio input, in the color prediction process of this embodiment, 16 drive levels are input as the drive level of the liquid crystal display panel, and 256 drive levels (that is, 256 gradations) are calculated later. I am going to do that. Therefore, after the calculation of the tristimulus values is completed in step S3, interpolation calculation for obtaining XYZ values for 256 gradations is performed. This is obtained by the following equation.
[0053]
[Equation 5]

[0054]
Here, the variable m in the equation (5) is 256 gradation data supplied to the liquid crystal display panel 100.
[0055]
FIG. 8 shows a flowchart of the interpolation calculation, and FIG. 9 shows a graph of gradation characteristics in the interpolation calculation section process. In order to perform data interpolation according to the reference gradation characteristic, first, a reference gradation characteristic (γ2.2: a characteristic in which data and luminance are expressed as an exponent 2.2) is input (step S10). Subsequently, the XYZ values for 16 gradations obtained previously are input as interpolation source data, and normalization is performed (step S11).
[0056]
Next, in the loop constituted by steps S12 to S14, it is determined which position of the reference gradation characteristics the interpolation source data corresponds to. Specifically, a value on the reference gradation characteristic closest to the interpolation source data is searched (step S12), and data close to the value obtained by the search is recorded as a value corresponding to the gradation level (step S13). ). This is executed for all the interpolation source data (step S14). In addition, since the processing of steps S12 to S15 determines where each drive level of the liquid crystal display panel corresponds to the reference gradation characteristic, this association is performed using any one of RGB XYZ values. It is sufficient to use the determined correspondence for others. The example of FIG. 9 shows the luminance Y ′ of the G cell._G(N) is used to associate liquid crystal drive levels.
[0057]
Next, in a loop constituted by steps S15 and S16, interpolation between adjacent data is performed. That is, among the plurality of data obtained in step S13, values are recorded by interpolating between adjacent data along the reference gradation characteristics (step S15), and this is applied to all the data obtained in step S13. Execute (step S16). Thus, data for 256 gradations can be obtained by interpolating input data for 16 drive levels (gradation levels).
[0058]
(Mixed color calculation: Step S5)
Next, colors other than the single color are calculated using the XYZ values of the single color RGB obtained by the interpolation calculation. Basically, additive color mixture is used, but at this time, the black offset is not overlapped and added. Specifically, the data supplied to the liquid crystal display panel is (m_R, M_G, M_B), An equation for performing additive color mixing using Equation (4) and Equation (5) so that the black offset does not overlap is shown below.
[0059]
[Formula 6]

[0060]
With the above calculation, color prediction can be performed based on the spectral characteristics and aperture ratio of each component of the liquid crystal display panel. In particular, since the Y of the tristimulus value predicted here is the luminance, the data is (m_R, M_G, M_B) = (255, 255, 255) For the luminance Y ″ ″ (255, 255, 255), the transmittance can also be predicted by calculating the ratio of the backlight alone to the luminance.
[0061]
[Evaluation of true color prediction method]
According to the color prediction method of the present invention described above, not only the product of spectral characteristics of each component of the liquid crystal display panel is simply calculated, but also the influence of leakage light that is unavoidable due to the structure of the liquid crystal display panel is taken into consideration. Therefore, color prediction with high accuracy close to actual measurement values is possible. In one example, the color prediction accuracy based on the prediction based on a simple product of the conventional spectral characteristics is ΔE.₉₄Whereas the average was about 8.08, the color prediction accuracy according to the color prediction method of this embodiment is ΔE.₉₄The average was about 3.92, and the color prediction accuracy was greatly improved. ΔE₉₄Indicates a color difference which is the difference between the predicted value and the actually measured value.
[0062]
Since color prediction can be performed with high accuracy in this way, a liquid crystal color filter can be designed without trial manufacture of a liquid crystal display panel. Conventionally, color prediction of a liquid crystal display panel has been performed at the time of designing a color filter, but high prediction accuracy has not been obtained so that the design can be performed without trial manufacture. With the color prediction method of the present invention, an optimum color filter can be designed without trial production.
[0063]
[Modification]
In addition, the structure of the liquid crystal display panel shown here is an example. For example, the present invention is applied to a liquid crystal display panel of a type in which the arrangement of each layer and film is different, for example, a color filter is arranged on the lower glass substrate side Applicable. Further, although the TFD driving type transmissive liquid crystal display panel is illustrated, the color prediction method of the present invention can be applied to a TFT driving type liquid crystal display panel, a transflective liquid crystal display panel, and the like.
[0064]
Further, the present invention is not limited to a liquid crystal display panel, but also in an electro-optical panel such as an electroluminescence panel, an inorganic electroluminescence panel, a plasma display panel, an electrophoretic display panel, a field emission display panel, and an LED (light emitting diode) display panel. Can be applied as well.
[0065]
Further, in the above color prediction processing, a liquid crystal display panel having RGB as a color component color has been described. For example, (1) a color liquid crystal display panel by subtractive color mixing of CMY, and (2) in addition to RGB The color prediction method of the present invention can also be applied to a liquid crystal display panel whose color component color is other than RGB, such as a multi-color liquid crystal display panel provided with orange and purple.
[0066]
The color prediction process is executed by a color prediction device that includes a data input unit and a calculation unit. Further, the above color prediction process can be configured as a color prediction program, and the color prediction program can be executed by a computer including a data input unit and a calculation unit such as a CPU.
[0067]
[Application example]
In recent years, there is a growing demand for the same color to be displayed between various display devices, and for this purpose, it is necessary to obtain the color characteristics of each display device as data. The format of a file for describing the color characteristics of various display devices is defined by the ICC (International Color Consortium), and a color management system using an ICC profile is introduced in various information devices. Software for creating an ICC profile from color characteristic data has also been developed and is commercially available. Therefore, by using such software, it is possible to create an ICC profile from the color characteristic data obtained by the color prediction method of the present invention.
[Brief description of the drawings]
FIG. 1 shows a schematic configuration of a transmissive liquid crystal display panel.
FIG. 2 is a flowchart of color prediction processing.
FIG. 3 shows input / output data in color prediction processing.
FIG. 4 shows an example of characteristics input in color prediction processing.
FIG. 5 shows spectral characteristics for each drive level of a red (R) cell.
FIG. 6 schematically shows the state of light leaking from a cell.
FIG. 7 is an xy chromaticity diagram at the time of XYZ prediction of monochromatic RGB.
FIG. 8 is a flowchart of monochrome RGB interpolation calculation.
FIG. 9 shows an example of gradation characteristics in the interpolation calculation process.
[Explanation of symbols]
1, 11 Polarizing plate, 2, 10 Glass substrate, 3 Color filter,
4 protective film, 5 counter electrode, 6, 8 alignment film, 7 liquid crystal layer, 9 pixel electrode,
12 backlight, 14 light collecting film, 16 signal line,
17 TFD element 100 liquid crystal display panel

Claims (7)

In a color prediction device for a liquid crystal display panel that predicts a color displayed by a liquid crystal display panel having a plurality of components including a light source, a liquid crystal layer, and a color filter,
Based on a characteristic including a luminance characteristic of the light source, a spectral characteristic of the liquid crystal layer, and a spectral characteristic of a color filter corresponding to the element color for one element color of a driving level among a plurality of element colors constituting the display color. Monochrome data generation means for calculating monochrome data for each drive level of the display panel;
Correction data at a non-driving level of an element color other than the one element color among the plurality of element colors is used as a luminance filter of the light source, a spectral characteristic of the liquid crystal layer, and a color filter corresponding to the other element color. A correction for individually calculating a plurality of element colors other than the one element color based on characteristics including spectral characteristics and individually adding to the single color data for the one element color to correct the single color data Means,
A color prediction apparatus comprising:   2. The color prediction apparatus according to claim 1, further comprising means for interpolating the corrected monochrome data according to a predetermined reference gradation characteristic to generate monochrome data corresponding to the number of gradations of the display panel. .   Color mixing data for generating color mixing data based on the addition data obtained by adding the corrected single color data for the component colors constituting the color and the single color data when all the element colors are in the non-driven state The color prediction apparatus according to claim 1, further comprising a generation unit.   4. The color prediction apparatus according to claim 3, wherein the color mixture data generation unit subtracts twice the single color data when all the element colors are in the non-driven state from the addition data.   5. The color prediction apparatus according to claim 3, further comprising means for generating an ICC profile based on the single color data and the mixed color data. In a color prediction method for a liquid crystal display panel for predicting a color displayed by a liquid crystal display panel having a plurality of components including a light source, a liquid crystal layer, and a color filter,
Based on a characteristic including a luminance characteristic of the light source, a spectral characteristic of the liquid crystal layer, and a spectral characteristic of a color filter corresponding to the element color for one element color of a driving level among a plurality of element colors constituting the display color. A monochrome data generation step for calculating monochrome data for each drive level of the display panel;
Correction data at a non-driving level of an element color other than the one element color among the plurality of element colors is used as a luminance filter of the light source, a spectral characteristic of the liquid crystal layer, and a color filter corresponding to the other element color. A correction for individually calculating a plurality of element colors other than the one element color based on characteristics including spectral characteristics and individually adding to the single color data for the one element color to correct the single color data Process,
A color prediction method characterized by comprising: In a color prediction program for a liquid crystal display panel, which is executed by a computer and predicts a color displayed by a liquid crystal display panel having a plurality of components including a light source, a liquid crystal layer, and a color filter,
Based on a characteristic including a luminance characteristic of the light source, a spectral characteristic of the liquid crystal layer, and a spectral characteristic of a color filter corresponding to the element color for one element color of a driving level among a plurality of element colors constituting the display color. Monochrome data generation means for calculating monochrome data for each drive level of the display panel,
Correction data at a non-driving level of an element color other than the one element color among the plurality of element colors is used as a luminance filter of the light source, a spectral characteristic of the liquid crystal layer, and a color filter corresponding to the other element color. A correction for individually calculating a plurality of element colors other than the one element color based on characteristics including spectral characteristics and individually adding to the single color data for the one element color to correct the single color data A color prediction program which causes the computer to function as means.

Images